Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2026 Mar 12.
Published in final edited form as: Hypertension. 2026 Feb 5;83(6):e25795. doi: 10.1161/HYPERTENSIONAHA.125.25795

Sex-Specific Blood Pressure and Brain Microvascular Traits in a Model of Low Renin Hypertension

T Michael De Silva 1,4,5,*, Rasna Sabharwal 1,2,*, Thomas D Gerhold 1, Cynthia Lynch 1, Gary L Baumbach 3, Frank M Faraci 1,2
PMCID: PMC12977921  NIHMSID: NIHMS2139689  PMID: 41641533

Abstract

Background.

Hypertension is a leading risk factor for negative health outcomes due to end-organ effects that include small vessel disease (SVD) in brain. Low renin hypertension is understudied at the blood pressure (BP), microvascular, and mechanistic level, and in relation to biological sex. This study examined effects of low renin hypertension, produced by activation of the brain renin-angiotensin system (RAS) in a deoxycorticosterone acetate (DOCA) salt model.

Methods.

C57BL/6J mice were treated with DOCA (or sham) and given tap H2O and H2O with 0.15 mol/L NaCl for 3–4 weeks followed by assessment of the microvasculature. Mean arterial pressure (MAP) and BP variability (BPV) were measured using radiotelemetry.

Results.

Baseline and diurnal changes in MAP, increases in MAP and BPV during DOCA-salt, were greater in male than female mice. Compared to sham-treatment, endothelial function of cerebral arterioles in vivo was reduced by >70% by DOCA-salt in males, dysfunction that could be reversed by local inhibition of angiotensin II type 1 (AT1R) or mineralocorticoid (MR) receptors or Rho kinase. DOCA-salt increased arteriolar cross-sectional area and wall stiffness in male, but not female mice. In males (but not females), performance on a novel object recognition test was selectively impaired.

Conclusions.

Activation of the central RAS has sex-specific effects on BP, diurnal changes in BP, BPV, arteriolar structure and stiffness. Marked endothelial dysfunction was present in males (with several contributing mechanisms). These findings provide new insight into BP- and SVD-related phenotypes, mechanisms that contribute to endothelial dysfunction, and sex-specific differences in BP traits in a preclinical model of low renin hypertension.

Keywords: small vessel disease, angiotensin II, endothelium, nitric oxide, Rho kinase, aldosterone

Introduction

Hypertension is among the 10 most common risk factors for negative health outcomes in individuals below 50 years of age, increasing to number one for ages 50 years and above.1 At the end-organ level, chronically increased blood pressure (BP) and BP variability (BPV) are leading risk factors for cerebrovascular disease, stroke, and negative effects on brain health.1–3 Early onset hypertension is a risk factor for cognitive decline later in life and young-onset dementia.1,4 While many neurological disorders have a vascular component,5 the nature of the phenotypes and underlying mechanisms are not fully defined. Relevant sites of vascular disease include cerebral arteries and the microvasculature (eg, cerebral small vessel disease, SVD).5 Both absolute BP levels and BPV may affect endothelial function, loss of which plays a prominent role in large vessel disease, and may be equally (or even more) important in SVD.3,5–7

There are many preclinical models of hypertension. Low renin models are one subtype with relevance for human hypertension. Reductions in circulating renin are relatively common in humans with essential hypertension.8 That percentage is increased in groups that include the elderly, Blacks, and resistant hypertension.8,9 Activation of the brain renin-angiotensin system (RAS) with deoxycorticosterone acetate (DOCA)-salt is one model of low renin hypertension.7,10,11 Variations of the model have been used on numerous occasions to study effects of DOCA-salt on BP and the vasculature (eg, mainly aorta or peripheral arteries). In contrast, studies of the cerebral circulation using DOCA-salt models are much less common, with even fewer focusing on the microcirculation (cerebral small vessels).7 In addition, quantification of BP, diurnal patterns in BP, and BPV in the same study, in both biological sexes, has not been done previously to our knowledge.

Considering this background, the current study had several goals using a DOCA-salt model. First, we obtained more complete quantification of BP traits using radiotelemetry. Second, we determined if endothelial dysfunction was present in small cerebral arterioles in vivo, examining underlying mechanisms. Third, we quantified changes in arteriolar structure and distensibility. Fourth, we determined if an index of cognition was altered. Most experiments were performed in both sexes. The data obtained support the concepts that baseline BP, diurnal changes in BP, and BPV during DOCA-salt treatment were greater in males than females. Substantial endothelial dysfunction was present, with several contributing mechanisms. Changes in microvascular structure and stiffness and an index of cognition were also observed, but only in male mice. Thus, the current findings fill several knowledge gaps in these areas.

Materials and Methods

The data that support the findings of this study are available from the corresponding author on reasonable request.

Experimental animals.

Animal protocols were approved by the University of Iowa Animal Care and Use Committee and the La Trobe University Animal Ethics Committee. We used male and female C57BL/6J mice (Jackson Laboratories) or Animal Resource Centre, Canning Vale, WA, Australia) (#000664). Mice were fed standard chow (Teklad 7913: 0.135 mEq Na/g) and water (H2O) ad libitum prior to surgery. Age was not significantly different between males and females, averaging 22.6±0.9 wks. Body weight was less in females compared to males, respectively [(25.3±0.6 versus 29.0±0.3 grams, P<0.001 based on an unpaired t-test)]. Husbandry met the standards set forth by the National Institutes of Health for the care and use of experimental animals. The study included 4 areas of investigation: BP traits; arteriolar endothelial function; arteriolar structure and mechanics; and cognitive testing. Details regarding experimental procedures are in the text and the on-line Materials and Methods.7,12–20

Statistical analysis.

Data were evaluated using Prism 8 or 9 software and expressed as mean±SE. Statistical significance was accepted at P<0.05. The ‘n’ represents the number of mice studied, each mouse represented by an n of 1. A total of 226 mice were used. We obtained data from 216 mice. No data was collected from 10 mice, due to equipment issues (eg, servo-null, telemetry) or animals that died after surgery (eg, did not recover from anesthesia) or during the protocol to reduce BP to obtain pressure-diameter curves. One mouse scheduled for cognitive testing was euthanized due to skin wounds. No data was excluded based on the values obtained. Details regarding statistical analyses and numbers in each group are provided in the text or Figure Legends.

Results

Systemic arterial BP.

An example of BP recordings in mice is shown in Figure S1. Prior and during sham or DOCA-salt treatment, MAP and systolic BP in awake, freely moving mice were significantly higher in males compared to females (Figure S2A, S2B). With sham treatment, both variables were stable over the course of the experiments (Figure S2). During DOCA-salt treatment, MAP increased, becoming statistically significant from baseline on days 8–9 in both sexes (Figure 1A). MAP continued to increase for the duration of the treatment (Figure 1A). Values for MAP during DOCA-salt treatment were greater in males than in females (Figure 1A).

Figure 1. Effects of DOCA-salt treatment on 24 hr MAP and diurnal changes in MAP.

Figure 1.

Open in a new tab

A) With DOCA-salt treatment, MAP began to increase, becoming statistically significant (based on 2-way ANOVA) from baseline on days 8–9 in both sexes (P=0.0156 for females; P=0.0351 for males). MAP continued to increase during the treatment, reaching P values of <0.0001 in both sexes. When the entire data set is compared, values for MAP were greater in males than in females (average difference of 9.4±0.5 mmHg with DOCA-salt) (P=0.0185), n=6 per group. B) Based on 2-way ANOVA, MAP was significantly altered depending on time of day in female (P=0.0004) and male (P<0.0001) mice (upper panels). This variation during the day was not affected by sham treatment (P=0.1822 and P=0.6340 in females and males, respectively). With DOCA-salt, MAP increased in both sexes, but to higher levels in males than in females (P=0.0241), n=6 per group.

Diurnal variations in BP were present in both sexes, with MAP being greater at night (the active phase) than during the day (when mice normally sleep or are relatively inactive) (Figure 1B, upper panels). MAP was significantly altered depending on time of day in both female and male mice (Figure 1B). The variation in BP during the day was not affected by sham treatment in either sex (Figure 1B). With DOCA-salt, MAP was increased in both sexes, but to higher levels in males than in females (Figure 1B, lower panels). The diurnal pattern in MAP was largely absent in males during DOCA-salt treatment (Figure 1B). For example, the night-minus-day difference in MAP was 22.9±3.8 and 6.8±1.3 mmHg in sham versus DOCA-salt treated male mice (P=0.0005).

BPV was not significantly different in female versus male mice under baseline or sham conditions (Figure 2). BPV was also similar at baseline versus sham treatment in both sexes (Figure 2). DOCA-salt significantly increased BPV vs the sham group in males, but not females (Figure 2). In sham-treated mice, BPV tended to be higher in males compared to female mice, but the difference was not statistically significant. BPV was significantly higher in male DOCA-salt treated mice compared to females with the same treatment (Figure 2).

Figure 2. Sex-dependent effects on BPV.

Figure 2.

Open in a new tab

Baseline values and effects of sham or DOCA-salt treatment on BPV are shown for female (A) and male (B) mice. Based on ANOVA, BPV was higher in male mice than in females (P<0.0001). Using Sidak’s multiple comparison test, baseline and sham values were not significantly different in female vs male mice, respectively (P>0.05). DOCA-salt treatment significantly increased BPV compared to shams in male mice (P<0.0001), but not female mice (P=0.7560). BPV was also significantly higher in male compared to female mice treated with DOCA-salt (P<0.0001) (n=6 mice per group).

Endothelial function in vivo.

Because female mice did not develop endothelial dysfunction during DOCA-salt treatment in our previous study,7 we performed the following experiments using only male mice. Under anesthesia, MAP was greater in DOCA-salt mice compared to sham controls (Figure 3A). Baseline diameter of cerebral arterioles with spontaneous tone was similar following sham or DOCA-salt treatment (Figure 3B). Vasodilation to acetylcholine is dependent on production of nitric oxide (NO) by endothelial NO synthase (eNOS).19,21 Compared to sham mice, the response was impaired by >70% during DOCA-salt treatment (Figure 3C). In contrast, vasodilation to nitroprusside (an NO donor) or nifedipine (a dihydropyridine Ca2+ channel inhibitor) were not significantly affected (Figure 3C).

Figure 3. Effects of DOCA-salt treatment on vasodilator responses of cerebral arterioles.

Figure 3.

Open in a new tab

Mean arterial pressure (MAP) (A), baseline diameter of arterioles (B), and vasodilation to acetylcholine, nitroprusside and nifedipine (C) in sham and DOCA-salt treated mice. The analysis in (A) and (B) were based on unpaired t-tests [n=7–10, P = 0.0005 for (A); n=64–68, P = 0.9867 for (B)]. Baseline diameter (B) and the acetylcholine panel represent a grand mean for all groups tested. In (C), a two-way ANOVA with Bonferroni’s post hoc test revealed effects of acetylcholine were reduced by DOCA-salt (P<0.0001, n=64–68) compared to sham controls. These inhibitory effects were significant at each concentration of acetylcholine (P<0.0001). The same ANOVA test revealed DOCA-salt had no significant effect on vasodilation to nitroprusside (P = 0.3186, n=10–11) or nifedipine (P = 0.8117, n=8–11). *P<0.05 vs sham.

Mechanisms of endothelial dysfunction.

Baseline arteriolar diameter was not significantly affected by treatment with inhibitors within the cranial window (Figures 4, S3, S4). In a previous study, losartan (an AT1R antagonist) improved endothelial function of basilar arteries from DOCA-salt treated mice studied in vitro.7 In the current experiments, losartan (1 µmol/L) had no significant effect on acetylcholine-induced vasodilation in sham mice, but restored responses to normal in DOCA-salt mice (Figure 4A). Thus, DOCA-salt-induced endothelial dysfunction requires activation of the AT1R, but is acutely reversible. Because Ang II, aldosterone, and their receptors can interact,22 we tested effects of an MR antagonist. Eplerenone (5 µmol/L) had no significant effect on acetylcholine-induced vasodilation in sham mice, but significantly improved responses during DOCA-salt treatment (Figure 4B).

Figure 4. Losartan or eplerenone increased endothelial function in DOCA-salt treated mice.

Figure 4.

Open in a new tab

Vasodilation of arterioles to acetylcholine in sham and DOCA-salt treated mice in the presence of vehicle and during treatment with losartan (A) or eplerenone (B). A two-way ANOVA with Bonferroni’s post hoc tests indicated responses to acetylcholine were impaired at each concentration by DOCA-salt, but were significantly increased by losartan after DOCA-salt (P<0.0001, n=8–9) (A). The P values were 0.0034 and <0.0001 for 1 and 10 µmol/L acetylcholine, respectively. Losartan had no effect on acetylcholine-induced vasodilation in sham mice (P=0.9585). In the presence of losartan, vasodilation in the DOCA-salt group was not significantly different from the respective sham group for 1–10 µmol/L acetylcholine (P >0.05). Losartan did not alter baseline diameter in sham (34.8±1.3 vs 34.8±1.3) or DOCA-salt treated mice (32.9±1.2 vs 32.7±1.4). For eplerenone (B), the same statistical analysis revealed responses were increased after DOCA-salt (P=0.0002, n=6). P values were 0.0178, 0.0009, and 0.0034 for 0.1–10 µmol/L acetylcholine, respectively. Eplerenone had no effect in sham mice (P=0.3417) (B). With eplerenone, vasodilation in the DOCA-salt group was not significantly different from the respective sham group for 0.1–10 µmol/L acetylcholine (P >0.05). Eplerenone did not alter baseline diameter in sham (33.7±1.3 vs 33.8±1.5) or DOCA-salt treated mice (33.0±2.0 vs 33.0±1.9). *P<0.05 vs control.

Endothelial function can be impaired by activation of Rho kinase (ROCK).23 Thus, we tested effects of two inhibitors of ROCK (Y-27632, 1 µmol/L) and SLX-2119 (1 µmol/L). Neither inhibitor had significant effects on arteriolar acetylcholine responses in sham mice, but each improved vasodilation in DOCA-salt treated mice (Figure S3A, S3B). In some models, Ang II impairs endothelial function by increasing production of endothelin-1 (ET1).24 In the current model, an inhibitor of ETA receptors (BQ-123, 1 µmol/L) produced a small increase in the effect of acetylcholine in DOCA-salt mice (but only at the lowest concentration) (Figure S4).

Arteriolar structure and mechanics.

Very little is known regarding changes in microvascular structure or mechanics during low renin hypertension, and whether any changes are sex-dependent. Control diameter of arterioles with basal tone was similar in male, female, sham- and DOCA-salt treated mice (Figure 5A). Arteriolar diameter increased about 45% during maximal vasodilation with ethylenediaminetetraacetic acid in both sexes (Figure 5A), indicating substantial resting tone in vivo.

Figure 5. Effects of DOCA-salt treatment on structure and mechanics of small cerebral arterioles in vivo.

Figure 5.

Open in a new tab

Diameter of arterioles under baseline (Control) conditions and after treatment with EGTA (Passive) in mice treated with DOCA-salt or sham controls (A). Based on one-way ANOVA, there were significant differences between control and passive diameter in sham and DOCA-salt groups (P<0.0001). With Tukey’s multiple comparison test, there were no differences between baseline diameter in male, female, sham, or DOCA-salt mice. Passive diameter increased to a similar extent in each group (A). Arteriolar CSA (B), W:L ratio (C), WT (D), and ET vs stress (E) are shown for DOCA-salt and sham groups. The difference in CSA (C) with DOCA-salt was significant in males using a one-tailed unpaired t-test (P=0.0425, n=10–11). Although CSA data was normally distributed (Shapiro-Wilk test), we also performed a non-parametric analysis (Mann Whitney test, two-tailed test), which makes no assumptions regarding normality, variance, and so forth. A significant difference in CSA was obtained (P=0.0430) (P<0.05) with that analysis. There were no differences in CSA in females using a one-tailed unpaired t-test (P=0.4410, n=10), and no differences in the W:L ratio in females (one-tailed unpaired t-test, P=0.1653, n=10) or males (P=0.2022, n=10–11) (C). Similarly, there were no differences in WT in females (one-tailed unpaired t-test, P=0.1653, n=10) or males (P=0.2022, n=10–11) (D). Using a one-tailed unpaired t-test, there was an increase in ET vs stress in male (P=0.0459, n=9–10), but not female mice (P=0.1087, n=6–8) (E).

Arteriolar cross-sectional area (CSA) increased with DOCA-salt treatment in male, but not female, mice (Figure 5B), but had no significant effect on wall thickness or the wall:lumen ratio) (Figure 5C, 5D). Tangential elastic modulus (ET) vs stress increased in male mice (Figure 5E). In both sexes, there were no significant shift in pressure-diameter curves (Figure 6A). In contrast, arteriolar stress-strain curves shifted significantly to the left with DOCA-salt treatment in males (Figure 6B).

Figure 6. DOCA-salt treatment shifted the stress-stain curve of small cerebral arterioles in male mice.

Figure 6.

Open in a new tab

Based on two-way ANOVA (A), there was no significant shift in pressure-diameter curves following DOCA-salt treatment in female (n=6–10) or male (n=9–11) mice (P=0.727 and P=0.0516, respectively). In females, the stress-strain curve was not affected by DOCA-salt treatment (B) (P=0.5156, n=6–10). With the same analysis, the stress-strain curve was shifted to the left in males following DOCA-salt (P=0.0259, n=9–11). *P<0.05 vs sham.

Cognitive and behavioral function.

Treatment with DOCA-salt for 3 weeks did not alter locomotor activity (Figure S5A) or the time spent in the inner zone in the open field test (an index of anxiety) (Figure S5B). Both sham and DOCA-salt treated female mice and sham treated male mice explored the novel object about 60% of the time (Figure S5C, left and right). In contrast, male DOCA-salt mice explored the novel object 50% of the time, suggesting some impairment of working memory (Figure S5C, right). Heat maps for the different tests are also shown (Figure S5B and S5C, bottom). Changes of similar magnitude are described in other models of cognitive impairment.11,25

Discussion

As a result of the four goals described above, there are several major findings in this study. First, baseline BP, increases in MAP during the active phase of the diurnal cycle, and increases in MAP and BPV with DOCA-salt treatment were all greater in male than in female mice. Second, treatment with DOCA-salt produced substantial impairment of endothelium-dependent vasodilation in cerebral arterioles in male mice in vivo, with several mechanisms contributed to this dysfunction. Third, DOCA-salt produced an increase in CSA and a shift in the stress-strain curves of passive arterioles, changes that were detected only in males. Lastly, the changes in BP traits and in the microcirculation in males were associated with impairment of an index of memory. Overall, these experiments provide new insight into sex-specific differences in BP and BPV under baseline conditions and during DOCA-salt treatment. They help fill knowledge gaps related to phenotypic changes in brain small vessel biology and underlying mechanisms in a model of low renin hypertension. Preclinical models of hypertension can vary in their BP characteristics and vascular phenotypes. Depending on specific hypotheses or phenotypes of interest, the DOCA-salt model has relevant traits.

Changes in arterial pressure.

Hypertension is a major risk factor for cerebrovascular disease.1,3,26 Despite the potential relevance for human hypertension,8,9,27 there are few preclinical models of low renin hypertension (the DOCA-salt model being one).10,28 Collective findings from our laboratory and others provided multiple lines of evidence that DOCA-salt activates the brain RAS, with phenotypes consistent with low renin hypertension in humans. For example, DOCA-salt increased expression of brain angiotensinogen and the Ang II AT1 receptor (Agt and Agtr1a mRNA), elevated concentrations of Ang II in brain and cerebrospinal fluid (CSF), enhanced central angiotensinergic signaling, resulting in neurohumoral activation, volume expansion, and increased BP.7,10,11 DOCA-salt also increased mRNA expression for Agt and Ace (angiotensin converting enzyme) in cerebral arteries,7 as well as vascular expression of GFP driven by the Agtr1a promoter, an effect consistent with increased transcription.7 Central effects of RAS activation in the model were inhibited by intracerebroventricular administration of an AT1 receptor antagonist.10

While DOCA-salt activates the brain RAS, simultaneous suppression of the peripheral RAS occurs, with phenotypes that include decreased renal Ren1 mRNA expression and reduced Ang II levels in plasma.7,10,11,24 While multiple studies quantified changes in renin expression during DOCA-salt treatment,7,10,11 a limitation for the field as a whole is that quantification of renin levels or activity in both sexes has been extremely rare. Reports that are available present data consistent with significant reductions in renin in both males and females in response to DOCA-salt.29,30

In the current study, we quantified multiple experimental endpoints in both sexes. Because we used the same model as in our previous study,7 we did not repeat the quantification of renin, a potential limitation. The current findings related to effects of DOCA-salt on BP in male and female mice are consistent with previous studies in mice and rats.31–33 That is, both sexes become hypertensive, but the levels of BP are higher in males. To our knowledge, other BP traits that were quantified in both sexes in the current study were not measured in previous studies.

In relation to low renin hypertension, DOCA-salt increased 24-hr MAP, peak levels of MAP during the diurnal cycle, and BPV - all to a greater extent in male mice compared to females. The use of radiotelemetry to measure BP in rodents is much more accurate with fewer limitations than more commonly used tail-cuff methodology.26 In relation to scientific rigor of previous work in this area, there are few studies that included both sexes using telemetry-based measurements of BP.31–33 The previous reports used DOCA-salt in rodents (mice or rats) with unilateral nephrectomy and saline in the drinking water (regular tap water was not available). Similar to the current findings, DOCA-salt progressively increased MAP in both sexes, with larger increases in males compared to females. In contrast to the current study, diurnal changes in MAP and BPV were not quantified.31–33

BP normally exhibits diurnal variations.26 In humans, BP typically falls during sleep, then rises early in the morning.26 Because mice are nocturnal, BP is higher at night (compared to the light phase) when they are awake and active,26 a pattern observed in the current experiments. In contrast to sham treatment, DOCA-salt increased absolute levels of MAP and largely eliminated the diurnal pattern in MAP in male mice.

In clinical studies, increased BPV has been associated with increased cerebral SVD, decreased cerebral blood flow (CBF), and increased risk for cognitive impairment and dementia.34–36 Such effects can be observed even when MAP is relatively well controlled.36 Some data suggest the impact of increased BPV may be greater than increased systolic BP or MAP.37 Collectively, such data support the emerging concept that BPV may be a stronger predictor or determinant of end-organ damage,36 including overt or covert neurovascular events during hypertension.

Endothelial dysfunction during hypertension.

Vasodilation to acetylcholine requires functional endothelial cells.19,21 In addition to being an experimental tool in preclinical models and humans, acetylcholine is an important neurotransmitter in brain. With DOCA-salt treatment, dilation of cerebral arteries or parenchymal arterioles to acetylcholine was substantially impaired in vitro, an effect seen in males, but not females.7 The current data extend those observations to brain the microcirculation in vivo. In contrast, vasodilation to nitroprusside and nifedipine were not affected, indicating changes were specific for endothelium. In other studies, DOCA-salt impaired acetylcholine-induced increases in local CBF.11,38 Responses of parenchymal arterioles to acetylcholine from nephrectomized rats given DOCA-salt were also impaired in vitro.39 These previous studies provided limited insight into underlying mechanisms,38,39 although recent evidence suggest IL-17 may also play a role in endothelial dysfunction.11 That endothelial function is markedly impaired in brain by DOCA-salt (present study and previous reports7,11,38) is consistent with observations in other models of hypertension.40,41 It is interesting that despite substantial endothelial dysfunction in brain, the current DOCA-salt model produced no such change in small mesenteric arteries.7

Quantitative measurements revealed that resting CBF is not altered in mice treated with DOCA-salt, but neurovascular coupling and the CBF response to acetylcholine were both significantly reduced.11 Thus, while baseline arteriolar diameter (current study) and CBF11 may not be reduced at this stage of the disease, the microvasculature exhibits disease-related phenotypes in a low renin model. A mismatch between cellular activity, exposure to a key neurotransmitter, and vasodilation - if present chronically - may be detrimental to brain function long term.11,42 In this context, we are not aware of studies of endothelial function in intracranial vessels in hypertensive humans.

The current findings provide new insight into underlying mechanisms in the microcirculation in a low renin model of hypertension. Losartan restored endothelial function of cerebral arterioles in DOCA-salt treated mice, suggesting impaired responses require local activation of the AT1R. Ang II interacts with the MR,22 a potential contributor to endothelial dysfunction. Thus, we tested effects of an MR antagonist, which improved endothelial function during DOCA-salt treatment. Ang II-induced endothelial dysfunction requires ROCK activity in some models.23 Both isoforms of ROCK are expressed in the cerebral circulation.23 Y-27632 inhibits both isoforms,23 but SLX-2119 is highly selective for ROCK2.23 Both inhibitors improved acetylcholine-induced vasodilation after DOCA-salt, supporting the concept that ROCK contributes to endothelial dysfunction in low renin hypertension. Lastly, activation of the central RAS can increase production of ET1.24 Inhibition of ETA receptors produced a small increase in endothelium-dependent vasodilation in DOCA-salt mice. Thus, several mechanisms contribute to endothelial dysfunction during low renin hypertension.

The decision to only study male mice in this portion of the study was based on several issues. With DOCA-salt treatment in males, substantial endothelial dysfunction was present in all vascular zones - cerebral arteries, pial and parenchymal arterioles (present and previous study).7 Thus, it seemed unlikely pial arterioles in females would exhibit impaired responses to acetylcholine, when cerebral arteries from females did not.7 Other issues were the additional resources that would be needed to perform such experiments and the concept of ‘reduction’ related to animal usage. The latter seemed relevant for this circumstance. For the other areas of investigation (listed above), no previous data was available in both sexes, so males and females were studied. A limitation of this approach is that we cannot exclude the possibility that endothelial dysfunction was present in pial arterioles in female mice treated with DOCA-salt.

Microvascular structure and mechanics.

Hypertension is associated with changes in cerebrovascular structure and mechanics.43,44 For example, systemic infusion of a pressor dose of Ang II rapidly increases arteriolar CSA in mice.16 Similar changes occur in other models of hypertension and in hypertensive humans.43–45 Previous experiments in this area have predominantly used male animals. In the current study, DOCA-salt increased arteriolar CSA in male, but not female mice. We also observed a shift in the stress-strain curve, indicating a stiffer arteriolar wall. Increased stiffness of large cerebral arteries has been described during hypertension.39,46 In other models of hypertension, cerebral arterioles exhibited either no change or a reduction in vascular stiffness during hypertension.16,39,43,46 Thus, the increase in arteriolar stiffness in the current study may be a unique feature of activation of the central RAS and low renin hypertension. While some morphological data for cerebral arteries or arterioles are available in humans,44,47 we are not aware of studies that quantified structure and mechanics of passive cerebral arterioles from humans with hypertension.

Despite marked endothelial dysfunction, we detected no significant or moderate changes in relation to arteriolar structure in the DOCA-salt model. This result differs from systemic Ang II-dependent models of hypertension, which exhibit significant increases in arteriolar CSA, inward remodeling, and increased arteriolar distensibility.16 One interpretation would be that endothelial dysfunction is not a major contributor to increased arteriolar stiffness or inward remodeling. This conclusion is supported by data from Nos3 deficient mice which do not exhibit either phenotype.13 In contrast, increases in CSA are present in Nos3 deficient mice,13 suggesting loss of eNOS function may contribute to that microvascular change with DOCA-salt.

Perspectives.

Endothelial cells have emerged as a major determinant of vascular health and disease.48,49 Hypertension is a leading risk factor for large vessel and SVD.2,4,42,50 Features of cerebral SVD were observed in the current study, including endothelial dysfunction, increased CSA, and increased stiffness of arterioles. The present findings provide new insight into hemodynamics (BP traits), SVD phenotypes, and underlying mechanisms, in low renin hypertension, an understudied preclinical model. The majority of this work included testing for differences due to biological sex. While endothelial dysfunction has been described in peripheral arteries and resistance vessels from humans with essential hypertension,51 we are not aware of studies that quantified endothelial function in cerebral arterioles in hypertensive humans.

In this report, we studied hypertension in adult mice, not hypertension combined with aging. The majority of studies in these areas have not combined aging and hypertension. Because aging itself has significant effects on function, structure, and mechanics of cerebral blood vessels and activates the brain RAS,52 quantifying effects of DOCA-salt on microvascular biology in adult mice was a logical initial step. A study with combined risk factors would require a different design if both groups exhibited vascular phenotypes at baseline. Early onset hypertension is increasingly being detected, and may be a risk factor for vascular disease and loss of brain health later in life.53 Thus, defining SVD at early and later stages of life are arguable both important. We also acknowledge the current approach was not based on a model of life-long hypertension.

Hypertension is a well-established risk factor for the development of SVD, cognitive deficits, and dementia.2,50 Previous studies reported a decline in cognitive function in Ang II infusion models of hypertension.54,55 In the present study, DOCA-salt treatment was associated with a reduction in an index of working memory in male mice. It is interesting that female mice did not exhibit a similar decline. While female mice treated with DOCA-salt were hypertensive, changes in MAP, diurnal variations in BP, vascular stiffness, and BPV were all significantly less than in male mice. In addition, a previous study found no evidence for endothelial dysfunction in females using the same model.7 Such sex-specific observations raise multiple questions. For example, what is the relative impact of increased BPV versus average BP in relation to cognitive dysfunction? Do variables such as diurnal BP patterns or arteriolar stiffness influence cognitive function, and if so, is this impact dependent on endothelial cells?

The current findings help fill several knowledge gaps related to effects of DOCA-salt on BP traits and the brain microvasculature. Like many studies, new findings raise additional questions. For example, questions related to the potential role of border-associated macrophages in DOCA-salt induced microvascular phenotypes, including effects on brain endothelial cells and sites of production of Ang II.11

Lastly, activation of sympathetic nerves is a relatively common feature of human hypertension. The potential impact of sympathetic nerves on microvascular or endothelial cell phenotypes is not entirely clear. Previous studies provided evidence that in contrast to Ang II-dependent hypertension, activation of sympathetic nerves or adrenergic receptors may have little effect on endothelial or neurovascular function.56,57 Additional studies to define possible sex-specific changes in RAS components and RAS-dependent phenotypes that impact microvascular biology, with a possible contribution of sympathetic nerves are needed. However, such lines of exploration will very likely require approaches that are distinct from those used in the current experiments.

Supplementary Material

Supplemental Materials and Methods

Novelty and Relevance.

1. What Is New?

  • Using a low renin model and radiotelemetry, male mice exhibited higher BP at baseline and during the active phase of the diurnal cycle. Compared to females, male mice had greater increases in BP and BPV during DOCA-salt treatment.

  • DOCA-salt produced substantial endothelial dysfunction in cerebral arterioles in male mice in vivo, with several contributing mechanisms (eg, AT1R, MR, and ROCK).

  • Low renin hypertension increased CSA and stiffness of passive cerebral arterioles, changes that were only present in males.

  • Functional, structural, and mechanical arteriolar changes in males, along with differences in BP traits, were associated with impairment of an index of memory.

  • These data provide new insight into sex-specific differences in BP and BPV, changes in small vessel biology, and underlying mechanisms in a model of low renin hypertension.

2. What Is Relevant?

  • Hypertension is the leading modifiable risk factor for vascular disease and negative health outcomes due to end-organs effects that include SVD and reductions in brain health.

  • Despite being a common subtype in humans, low renin hypertension is understudied at the BP, microvascular, and mechanistic level. Potential sex-specific phenotypes are poorly defined.

  • At the end-organ level, chronically increased BP and BPV are leading risk factors for cerebrovascular disease, stroke, with negative effects on brain function.

  • In relation to scientific rigor of previous work in this area, very few studies included both sexes when defining changes related to cerebral SVD during hypertension. To our knowledge, quantification of absolute BP levels, diurnal changes in BP, and BPV have not been performed previously in both sexes in a single study.

3. Pathophysiological Implications

Our findings support the concepts that activation of the central RAS has sex-specific effects on BP, diurnal changes in BP, and BPV. Marked effects on cerebral arteriolar endothelial function were present in males (with mechanistic contributions from AT1R, MR, and ROCK). In addition, changes in arteriolar structure and stiffness as well as an index of memory were observed, but were also sex-dependent. These findings provide new insight into SVD-related phenotypes and mechanisms, including sex-specific differences in components of BP and the brain microcirculation in an understudied preclinical model of hypertension.

Sources of Funding

Conduction of this study and preparation of this manuscript was supported by the National Institutes of Health (NS-096465, NS-108409, HL-149677, AG-070188), and the Leducq Foundation (International Network of Excellence, 22CVD01).

Nonstandard Abbreviations and Acronyms

Ang II

angiotensin II

AT1R

angiotensin II type 1 receptor

BP

blood pressure

BPV

blood pressure variability

DOCA

deoxycorticosterone acetate

eNOS

endothelial nitric oxide synthase

ET1

endothelin-1

MAP

mean arterial pressure

MR

mineralocorticoid receptor

NO

nitric oxide

RAS

renin-angiotensin system

ROCK

Rho kinase

References

  • 1.Collaborators GBDRF. Global burden and strength of evidence for 88 risk factors in 204 countries and 811 subnational locations, 1990–2021: A systematic analysis for the Global Burden of Disease Study 2021. Lancet. 2024;403:2162–2203. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Gottesman RF, Schneider AL, Albert M, Alonso A, Bandeen-Roche K, Coker L, Coresh J, Knopman D, Power MC, Rawlings A, et al. Midlife hypertension and 20-year cognitive change: the atherosclerosis risk in communities neurocognitive study. JAMA Neurol. 2014;71:1218–1227. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Martin SS, Aday AW, Almarzooq ZI, Anderson CAM, Arora P, Avery CL, Baker-Smith CM, Barone Gibbs B, Beaton AZ, Boehme AK, et al. 2024 Heart disease and stroke statistics: A report of US and global data from the American Heart Association. Circulation. 2024;149:e347–e913. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Levine DA, Springer MV, Brodtmann A. Blood pressure and vascular cognitive impairment. Stroke. 2022;53:1104–1113. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Markus HS, Joutel A. The pathogenesis of cerebral small vessel disease and vascular cognitive impairment. Physiol Rev. 2025;105:1075–1171. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Qiu C, Fratiglioni L. A major role for cardiovascular burden in age-related cognitive decline. Nat Rev Cardiol. 2015;12:267–277. [DOI] [PubMed] [Google Scholar]
  • 7.De Silva TM, Modrick ML, Grobe JL, Faraci FM. Activation of the central renin-angiotensin system causes local cerebrovascular dysfunction. Stroke. 2021;52:2404–2413. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Alderman MH, Madhavan S, Ooi WL, Cohen H, Sealey JE, Laragh JH. Association of the renin-sodium profile with the risk of myocardial infarction in patients with hypertension. New Engl J Med. 1991;324:1098–1104. [DOI] [PubMed] [Google Scholar]
  • 9.Carey RM, Calhoun DA, Bakris GL, Brook RD, Daugherty SL, Dennison-Himmelfarb CR, Egan BM, Flack JM, Gidding SS, Judd E, et al. Resistant hypertension: Detection, evaluation, and management: A scientific statement from the American Heart Association. Hypertension. 2018;72:e53–e90. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Grobe JL, Buehrer BA, Hilzendeger AM, Liu X, Davis DR, Xu D, Sigmund CD. Angiotensinergic signaling in the brain mediates metabolic effects of deoxycorticosterone (DOCA)-salt in C57 mice. Hypertension. 2011;57:600–607. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Santisteban MM, Schaeffer S, Anfray A, Faraco G, Brea D, Wang G, Sobanko MJ, Sciortino R, Racchumi G, Waisman A, et al. Meningeal interleukin-17-producing T cells mediate cognitive impairment in a mouse model of salt-sensitive hypertension. Nature Neurosc. 2024;27:63–77. [Google Scholar]
  • 12.Baumbach GL, Heistad DD, Siems JE. Effect of sympathetic nerves on composition and distensibility of cerebral arterioles in rats. J Physiol. 1989;416:123–140. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Baumbach GL, Sigmund CD, Faraci FM. Structure of cerebral arterioles in mice deficient in expression of the gene for endothelial nitric oxide synthase. Circulation Res. 2004;95:822–829. [DOI] [PubMed] [Google Scholar]
  • 14.Chillon JM, Baumbach GL. Effects of chronic nitric oxide synthase inhibition on cerebral arterioles in Wistar-Kyoto rats. J Hypertension. 2004;22:529–534. [Google Scholar]
  • 15.Leger M, Quiedeville A, Bouet V, Haelewyn B, Boulouard M, Schumann-Bard P, Freret T. Object recognition test in mice. Nature Protoc. 2013;8:2531–2537. [DOI] [PubMed] [Google Scholar]
  • 16.Sabharwal R, Chapleau MW, Gerhold TD, Baumbach GL, Faraci FM. Plasticity of cerebral microvascular structure and mechanics during hypertension and following recovery of arterial pressure. Am J Physiol. 2022;323:H1108–H1117. [Google Scholar]
  • 17.Sabharwal R, Zhang Z, Lu Y, Abboud FM, Russo AF, Chapleau MW. Receptor activity-modifying protein 1 increases baroreflex sensitivity and attenuates angiotensin-induced hypertension. Hypertension. 2010;55:627–635. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Seibenhener ML, Wooten MC. Use of the open field maze to measure locomotor and anxiety-like behavior in mice. J Vis Exp. 2015:e52434. [Google Scholar]
  • 19.Sobey CG, Faraci FM. Effects of a novel inhibitor of guanylyl cyclase on dilator responses of mouse cerebral arterioles. Stroke. 1997;28:837–842. [DOI] [PubMed] [Google Scholar]
  • 20.Zhang Y, Ye Y, Tang X, Wang H, Tanaka T, Tian R, Yang X, Wang L, Xiao Y, Hu X, et al. CCL17 acts as a novel therapeutic target in pathological cardiac hypertrophy and heart failure. J Exp Med. 2022;219. [Google Scholar]
  • 21.Faraci FM, Heistad DD. Regulation of the cerebral circulation: Role of endothelium and potassium channels. Physiol Reviews. 1998;78:53–97. [Google Scholar]
  • 22.Forrester SJ, Booz GW, Sigmund CD, Coffman TM, Kawai T, Rizzo V, Scalia R, Eguchi S. Angiotensin II signal transduction: An update on mechanisms of physiology and pathophysiology. Physiol Rev. 2018;98:1627–1738. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.De Silva TM, Kinzenbaw DA, Modrick ML, Reinhardt LD, Faraci FM. Heterogeneous impact of ROCK2 on carotid and cerebrovascular function. Hypertension. 2016;68:809–817. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Basting T, Lazartigues E. DOCA-salt hypertension: An update. Curr Hypertens Rep. 2017;19:32. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Whittaker DS, Akhmetova L, Carlin D, Romero H, Welsh DK, Colwell CS, Desplats P. Circadian modulation by time-restricted feeding rescues brain pathology and improves memory in mouse models of Alzheimer’s disease. Cell Metabol. 2023;35:1704–1721. [Google Scholar]
  • 26.Faraci FM, Scheer F. Hypertension: Causes and consequences of circadian rhythms in blood pressure. Circulation Res. 2024;134:810–832. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Maraboto C, Ferdinand KC. Update on hypertension in African-Americans. Progress Cardiovasc Dis. 2020;63:33–39. [Google Scholar]
  • 28.Lerman LO, Kurtz TW, Touyz RM, Ellison DH, Chade AR, Crowley SD, Mattson DL, Mullins JJ, Osborn J, Eirin A, et al. Animal models of hypertension: A scientific statement from the American Heart Association. Hypertension. 2019;73:e87–e120. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29.Murray RD, Cho KW, Malvin RL. Deoxycorticosterone acetate-induced renin suppression in the absence of antidiuretic hormone. Proc Soc Exp Biol Med. 1980;165:137–140. [DOI] [PubMed] [Google Scholar]
  • 30.Shade RE, Grim CE. Suppression of renin and aldosterone by small amounts of DOCA in normal man. J Clin Endocrinol Metab. 1975;40:652–658. [DOI] [PubMed] [Google Scholar]
  • 31.Belanger KM, Crislip GR, Gillis EE, Abdelbary M, Musall JB, Mohamed R, Baban B, Elmarakby A, Brands MW, Sullivan JC. Greater T regulatory cells in females attenuate DOCA-salt-induced increases in blood pressure versus males. Hypertension. 2020;75:1615–1623. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Giachini FR, Sullivan JC, Lima VV, Carneiro FS, Fortes ZB, Pollock DM, Carvalho MH, Webb RC, Tostes RC. Extracellular signal-regulated kinase 1/2 activation, via downregulation of mitogen-activated protein kinase phosphatase 1, mediates sex differences in desoxycorticosterone acetate-salt hypertension vascular reactivity. Hypertension. 2010;55:172–179. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 33.Karatas A, Hegner B, de Windt LJ, Luft FC, Schubert C, Gross V, Akashi YJ, Gurgen D, Kintscher U, da Costa Goncalves AC, et al. Deoxycorticosterone acetate-salt mice exhibit blood pressure-independent sexual dimorphism. Hypertension. 2008;51:1177–1183. [DOI] [PubMed] [Google Scholar]
  • 34.Lohman T, Sible I, Kapoor A, Engstrom AC, Shenasa F, Alitin JPM, Gaubert A, Rodgers KE, Bradford D, Mather M, et al. Blood pressure variability, central autonomic network dysfunction, and cerebral small-vessel disease in APOE4 carriers. J Amer Heart Assoc. 2024:e034116. [Google Scholar]
  • 35.Sible IJ, Nation DA. Blood pressure variability and cerebral perfusion decline: A post hoc analysis of the SPRINT MIND trial. J Amer Heart Assoc. 2023;12:e029797. [Google Scholar]
  • 36.Sible IJ, Nation DA. 24-Hour blood pressure variability via ambulatory monitoring and risk for probable dementia in the SPRINT trial. J Prev Alzheimers Dis. 2024;11:684–692. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37.Mahinrad S, Bennett DA, Sorond FA, Gorelick PB. Blood pressure variability, dementia, and role of antihypertensive medications in older adults. Alzheimers Dement. 2023;19:2966–2974. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 38.Faraco G, Park L, Zhou P, Luo W, Paul SM, Anrather J, Iadecola C. Hypertension enhances Aß-induced neurovascular dysfunction, promotes ß-secretase activity, and leads to amyloidogenic processing of APP. J Cerebral Blood Flow Metabol. 2016;36:241–252. [Google Scholar]
  • 39.Matin N, Pires PW, Garver H, Jackson WF, Dorrance AM. DOCA-salt hypertension impairs artery function in rat middle cerebral artery and parenchymal arterioles. Microcirculation. 2016;23:571–579. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40.Faraci FM, Lamping KG, Modrick ML, Ryan MJ, Sigmund CD, Didion SP. Cerebral vascular effects of angiotensin II: New insights from genetic models. J Cerebral Blood Flow Metabol. 2006;26:449–455. [Google Scholar]
  • 41.Johnson AW, Kinzenbaw DA, Modrick ML, Faraci FM. Small-molecule inhibitors of signal transducer and activator of transcription 3 protect against angiotensin II–induced vascular dysfunction and hypertension. Hypertension. 2013;61:437–442. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Hachinski V, Einhaupl K, Ganten D, Alladi S, Brayne C, Stephan BCM, Sweeney MD, Zlokovic B, Iturria-Medina Y, Iadecola C, et al. Special topic section: Linkages among cerebrovascular, cardiovascular, and cognitive disorders: Preventing dementia by preventing stroke: The Berlin Manifesto. Internat J Stroke. 2019:1747493019871915. [Google Scholar]
  • 43.Baumbach GL, Heistad DD. Remodeling of cerebral arterioles in chronic hypertension. Hypertension. 1989;13:968–972. [DOI] [PubMed] [Google Scholar]
  • 44.Rosenberg EF. The brain in malignant hypertension - A clinicopathologic study. Arch Intern Med. 1940;65:545–586. [Google Scholar]
  • 45.Pires PW, Jackson WF, Dorrance AM. Regulation of myogenic tone and structure of parenchymal arterioles by hypertension and the mineralocorticoid receptor. Am J Physiol. 2015;309:H127–36. [Google Scholar]
  • 46.Hajdu MA, Baumbach GL. Mechanics of large and small cerebral arteries in chronic hypertension. Am J Physiol. 1994;266:H1027–1033. [DOI] [PubMed] [Google Scholar]
  • 47.Rizzoni D, De Ciuceis C, Porteri E, Paiardi S, Boari GE, Mortini P, Cornali C, Cenzato M, Rodella LF, Borsani E, et al. Altered structure of small cerebral arteries in patients with essential hypertension. J Hypertension. 2009;27:838–845. [Google Scholar]
  • 48.De Silva TM, Faraci FM. Contributions of aging to cerebral small vessel disease. Annu Rev Physiol. 2020;82:275–295. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 49.Kremer R, Williams A, Wardlaw J. Endothelial cells as key players in cerebral small vessel disease. Nat Rev Neurosci. 2025;26:179–188. [DOI] [PubMed] [Google Scholar]
  • 50.Santisteban MM, Iadecola C, Carnevale D. Hypertension, neurovascular dysfunction, and cognitive impairment. Hypertension. 2023;80:22–34. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 51.Taddei S, Virdis A, Mattei P, Salvetti A. Vasodilation to acetylcholine in primary and secondary forms of human hypertension. Hypertension. 1993;21:929–933. [DOI] [PubMed] [Google Scholar]
  • 52.Fan LM, Geng L, Cahill-Smith S, Liu F, Douglas G, McKenzie CA, Smith C, Brooks G, Channon KM, Li JM. Nox2 contributes to age-related oxidative damage to neurons and the cerebral vasculature. J Clin Invest. 2019;129:3374–3386. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 53.Suvila K, Lima JAC, Yano Y, Tan ZS, Cheng S, Niiranen TJ. Early-but not late-onset hypertension is related to midlife cognitive function. Hypertension. 2021;77:972–979. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 54.Diaz-Otero JM, Yen TC, Fisher C, Bota D, Jackson WF, Dorrance AM. Mineralocorticoid receptor antagonism improves parenchymal arteriole dilation via a TRPV4-dependent mechanism and prevents cognitive dysfunction in hypertension. Am J Physiol. 2018;315:H1304–H1315. [Google Scholar]
  • 55.Foulquier S, Namsolleck P, Van Hagen BT, Milanova I, Post MJ, Blankesteijn WM, Rutten BP, Prickaerts J, Van Oostenbrugge RJ, Unger T. Hypertension-induced cognitive impairment: Insights from prolonged angiotensin II infusion in mice. Hypertension Res. 2018;41:817–827. [Google Scholar]
  • 56.Kazama K, Wang G, Frys K, Anrather J, Iadecola C. Angiotensin II attenuates functional hyperemia in the mouse somatosensory cortex. Am J Physiol. 2003;285:H1890–1899. [Google Scholar]
  • 57.Rajagopalan S, Kurz S, Munzel T, Tarpey M, Freeman BA, Griendling KK, Harrison DG. Angiotensin II-mediated hypertension in the rat increases vascular superoxide production via membrane NADH/NADPH oxidase activation. Contribution to alterations of vasomotor tone. J Clin Invest. 1996;97:1916–1923. [DOI] [PMC free article] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplemental Materials and Methods
NIHMS2139689-supplement-Supplemental_Materials_and_Methods.docx (22.5MB, docx)

RESOURCES