Endothelial dysfunction and enhanced contractility in microvessels from ovariectomised rats: roles of oxidative stress and perivascular adipose tissue

Abstract

Ovarian hormone loss increases reactive oxidative species (ROS), endothelial dysfunction and cardiovascular disease. Since perivascular adipose tissue (PVAT) regulates endothelial function, we hypothesized that ROS in PVAT mediate adverse microvascular effects of ovarian hormone deficiency. Rats were ovariectomized (OVX) or sham-operated (SHAM) and given vehicle or tempol for 6 weeks. Mesenteric resistance arterioles from OVX compared to SHAM rats had dysfunctional responses to acetylcholine (ACh) including: decreased ACh induced endothelium-dependent relaxation; (50±6 vs 72±2%) and endothelium-dependent relaxation factor (EDRF; 17±4 vs 37±2%) and increased endothelium-dependent contracting factor (EDCF; 27±5 vs 9±3%). OVX rat mesenteric arterioles had increased contractions to the thromboxane/prostanoid receptor (TP-R) agonist U-46,619 (58±3 vs 40±5%) and increased of ROS (tempo-9-AC fluorescence) with U-46,619 (0.65±0.17 vs 0.14±0.06 units) or ACh (0.49±0.09 vs 0.09±0.05 units) and increased p22^phox protein expression (0.89±0.05 vs 0.18±0.04 units) while nitric oxide (NO) activity (DAF-FM fluorescence) with ACh was reduced (0.39±0.1 vs 0.70±0.10 units). No differences were found in endothelium-dependent hyperpolarizing factor (EDHF) or contractile responses to phenylephrine (PE). PVAT enhanced ACh induced relaxation, EDRF and NO only in SHAM rats. Tempol prevented OVX-induced endothelial dysfunction and restored the enhancing effects of PVAT on ACh induced relaxation, EDRF and NO in OVX rat vessels but both tempol and PVAT were required to normalize the enhanced U-46,619 contractions after OVX. In conclusion, ovariectomy redirects endothelial responses from relaxation to contraction by reducing vascular NO, augmenting TP-R signaling and attenuating the vasodilatory effects of PVAT, all of which were dependent on ROS.

Introduction

Ovarian hormone loss in women is associated with increased vascular reactive oxygen species (ROS), reduced endothelial nitric oxide synthase (NOS) expression and NO, increased endothelial dysfunction^{1, 2} and risk of cardiovascular disease (CVD).² Similar findings have been reported in ovariectomized (OVX) animal models.^{3, 4}

Endothelial dysfunction entails both impaired relaxation and an endothelium dependent contracting factor (EDCF) generated by ROS.⁵ The EDCF is a prostaglandin (PG) or thromboxane (Tx) product of cyclooxygenase (COX) and/or thromboxane A₂ (TxA₂) synthase that vasoconstricts vascular smooth muscle cells (VSMCs) by activating thromboxane-prostanoid receptors (TP-Rs).⁵ OVX leads to a COX-dependent EDCF response in rat mesenteric arteries⁶ and in pig coronary arteries.⁷ Furthermore, endothelial dysfunction in cutaneous blood vessels of postmenopausal women was mediated by COX-2.⁸ However, the effects of OVX on ROS and TP-R signaling in microvessels remains poorly understood.

Obesity is an independent CVD risk factor⁹ whose incidence is increased in women with ovarian hormone loss,¹⁰ or animal models of ovarian hormone deficiency.¹¹ Perivascular adipose tissue (PVAT) improves vascular function¹² through generation of NO,¹³ hydrogen perioxide (H₂O₂).¹² hydrogen sulphide¹⁴ and/or poorly characterized adipokine pathways.^{14, 15} ROS inhibit these protective effects of PVAT in hypertensive models¹⁵ and contribute to endothelial dysfunction in animal models¹⁶ and in patients with obesity and the metabolic syndrome.¹⁷

We tested the hypothesis that OVX impairs PVAT-induced microvascular NO-dependent relaxation and enhances endothelium-dependent contractions through ROS and enhanced TP-R signaling. We reduced ROS using tempol which is a redox cycling nitroxide¹⁸ and activated TP-Rs with the stable agonist U-46,619.¹⁹ These experiments are clinically significant because restoration of endothelial function and NO, and abrogation of EDCF and enhanced TP-R signaling, could attenuate the enhanced CVD risk after ovarian hormone deficiency but it is unclear if the microvessels and/or the surrounding PVAT should be the preferred therapeutic target.

Methods

Animal preparation and protocols

Female Sprague Dawley rats (200–220 gm; Taconics Lab, Germantown, NY) maintained on tap water and standard chow (Na⁺ 0.3g · 100g⁻¹) under conditions approved by the Institutional Animal Care and Use Committee of Georgetown University underwent ovariectomy (OVX) or sham surgery (SHAM)²⁰ and received oral tempol (2 mmol·l⁻¹) or vehicle in the drinking water for 6 weeks.⁵ After euthanasia by exsanguination, the second branch mesenteric resistance arterioles were isolated with the surrounding PVAT intact (PVAT+) or removed (PVAT−) and mounted in a four chamber myograph or snap frozen and stored at −80°C for analysis of p22^phox protein.²¹

Vascular ACh-induced endothelial responses, NO, ROS activities and contractions

The media and lumen cross-sectional areas of mesenteric arterioles were measured.²² For the first series, mesenteric arterioles were preconstricted with 10⁻⁵ mol·l⁻¹ norepinephrine (NE) to study: ACh induced relaxation (endothelium dependent relaxation, EDR); endothelium dependent relaxation factor (EDRF; change in EDR after 10⁻⁵ mol·l⁻¹-L-N^G-nitroarginine methylester, L-NAME); endothelium dependent hyperpolarizing factor (EDHF; change in EDRF after 10⁻⁶ mol·l⁻¹ apamin (AP) and 10⁻⁵ mol·l⁻¹ charabdotoxin (Chx) to block small and medium conductance calcium activated potassium channels); and endothelium independent responses (EIR; relaxation to sodium nitroprusside, SNP). To study ACh-induced nitric oxide (NO), arterioles were loaded with 5×10⁻⁵ mol·l⁻¹ 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAFFM-DA). The change of fluorescence (ΔF₁/F₀) with 10⁻⁵ mol·l⁻¹ ACh quantitated vascular NO.⁵

For the second series, endothelium dependent contraction factor (EDCF) was measured in arterioles under spontaneous tone with relaxation pathways blocked by L-NAME + AP + Chx and contracted with ACh. Other vessels prepared similarly, were loaded with tempo-9-AC and the change of fluorescence with 10⁻⁴ mol·l⁻¹ ACh determined to quantitate vascular ROS.⁵

For the third series, vessels were contracted with phenylephrine (PE) or U-46,619. ROS generation with 10⁻⁶ mol·l⁻¹ U-46,619 was quantitated by tempo-9-AC fluorescence.

Expression of p22^phox

The protein expression of the NADPH oxidase regulatory subunit p22^phox in lysates of mesenteric arterioles was measured by Western blot²¹ and normalized to β-actin.

Statistics

Data are expressed as mean±SEM calculated from 6 rats per group. The concentration-response relationships were analyzed by two-way, repeated measures ANOVA to assess the effects of OVX, PVAT and the interaction (effects of PVAT on responses to OVX) followed, where appropriate, by Bonferroni tests. Separate analyses were undertaken in the groups given tempol. Significance was defined as P < 0.05.

Results

Body weight (BWt), vascular structure and p22^phox protein expression

OVX increased BWt by 16% whereas tempol reduced it by a similar degree (Table 1). OVX almost doubled the MRA media area without changing the lumen area resulting in a doubling of the ratio of media to lumen (M/L). The p22^phox protein expression was increased by 400% in OVX rat vessels (Fig.1). These effects of OVX were prevented by tempol.

Table 1.

Effect of ovariectomy and tempol on body weight and mesenteric arteriole (MRA) structure and p22^phox expression

Variable	Sham	ovx	Sham+Tempol	OVX + tempol	By ANOVA, effect of:
					OVX	Tempol	Interaction
Body weight (g)	251±11	287±9	219±5	246±6	P<0.001	P<0.001	NS
MRA media area (M; μm2)	48±5	91±7	51±5	48±6	P<0.01	P<0.01	P<0.01
MRA lumen area (L; μm2)	187±12	170±6	178±14	193±5	NS	NS	NS
MRA M/L ratio (cross section area, μm2/μm2)	1.54±0.29	3.43±0.38*	1.53±0.24	1.63±0.19	P<0.05	P<0.05	P<0.05
MRA p22phox expression (relative to β- actin)	0.18±0.04	0.89±0.05**	0.28±0.11	0.26±0.14	P<0.01	P<0.05	P<0.001

Mean ± SEM value (n=6 per group). Compared to SHAM:

^*P<0.05.

^**P<0.01

Fig. 1.

Effect of ovariectomy and tempol on p22^phox protein expression. Mean± SEM values normalized to β-actin in mesenteric arterioles from SHAM (open bar) or OVX (hatched bar) rats after 6 weeks of vehicle or tempol treatment (n=6 per group). Top panel, Representative Western blot used to quantitate p22^phox expression.

Effects of OVX and PVAT on endothelial relaxation and generation of NO

The maximum ACh- induced relaxation and EDRF responses in preconstricted mesenteric arterioles from OVX rats were reduced by 30 ±3% and 53±3% (P<0.05), respectively (Fig. 2A, 2B) but the EDHF and EIR responses were maintained (Table 2-I). Vascular NO activity with ACh was reduced in mesenteric arterioles from OVX rats by ≈2-fold (P<0.001; Table 2-I; Figure 3A).

Fig. 2.

Effect of perivascular adipose tissue and ovariectomy on ACh induced relaxation (ACh), EDRF and EDCF responses after 6 weeks of vehicle or tempol administration. Mean± SEM (n=6 per group) values for ACh induced relaxation (A&D), EDRF (B&E), and EDCF (C&F) in mesenteric arterioles with PVAT (solid symbol) or without PVAT (open symbol) from SHAM (circles) or OVX (squares) rats after 6 weeks of vehicle (A–C) or tempol (D–F). Comparing PVAT+ vs – in same treatment groups: *P<0.05; **, P<0.01. Comparing SHAM vs OVX in same treatment groups: ‡, P<0.01; ‡‡‡, P<0.005.

Table 2.

Effect of ovariectomy and PVAT on maximum vascular reactivity, NO and ROS in mesenteric artenoles.

I. After vehicle
	SHAM:		OVX:		By ANOVA, effect of:
Responses	PVAT−	PVAT+	PVAT−	PVAT+	OVX	PVAT	Interaction
ACh (%)	71.9±2.1	89.5±4.4†	50.1±6.2**	56.7±6.4**	P<0.01	P<0.05	P<0.05
EDRF (%)	37.1±3.5	52.0±3.3†††	17.0±1.3***	19.8±5.6***	P<0.05	P<0.001	P<0.01
EDHF (%)	27.9±5.2	31.2±2.4	25.3±4.9	29.3±2.8	NS	NS	NS
SNP (%)	96.3±2.1	98.1±4.1	93.6±2.8	91.6±3.8	NS	NS	NS
EDCF (%)	8.7±2.9	7.5±2.7	26.7±2.9**	17.4±2.7**†	P<0.001	P<0.05	NS
PE (%)	67.0±5.3	55.7±8.1	65.6±6.1	55.9±9.3	NS	NS	NS
U46,619(%)	39.6±5.7	10.0±2.4†††	57.5±3.4*	35.4±8.5**†††	P<0.05	P<0.001	NS
ACh-NO (Δunit)	0.69±0.07	1.17±0.07†††	0.39±0.08*	0.55±0.11*†††	P<0.001	P<0.001	P<0.01
EDCF-ROS(Δunit)	0.09±0.05	0.07±0.06	0.49±0.09***	0.42±0.07***	P<0.001	NS	NS
U46,619-ROS(Δunit)	0.14±0.06	0.11±0.05	0.65±0.17***	0.45±0.14*†	P<0.01	P<0.05	P<0.05

II. After tempol
	SHAM:		OVX:		By ANOVA, effect of:
Responses	PVAT−	PVAT+	PVAT−	PVAT+	OVX	PVAT	Interaction
ACh (%)	71.1±2.6	86.5±2.1†	72.5±1.8	87.0±2.3†	NS	P<0.001	NS
EDRF (%)	31.3±4.2	51.2±4.2††	30.7±4.0	51.4±4.5††	NS	P<0.001	NS
EDHF (%)	33.6±1.6	27.4±2.5	36.1±2.4	30.1±2.5	NS	NS	NS
EDCF (%)	6.7±2.1	5.1±1.8	11.5±3.1	9.4±1.8	NS	NS	NS
PE (%)	66.5±4.9	47.9±6.9	76.9±7.3	61.2±6.8	NS	NS	NS
U-46,619 (%)	37.9±3.9	8.9±3.6††	51.9±5.1†	16.8±3.8†††	P<0.05	P<0.01	NS
ACh-NO (Δunit)	0.67±0.09	1.14±0.10††	0.62±0.11	0.96±0.12†	NS	P<0.01	NS
EDCF-ROS(Δunit)	0.08±0.04	0.06±0.03	0.12±0.06	0.09±0.02	NS	NS	NS
U-46,619-ROS(Δunit)	0.13±0.07	0.10±0.06	0.27±0.12	0.24±0.11	NS	NS	NS

Data were obtained from experiments described in figure 2, 3 and 4. Compared to SHAM,

^*P<0.05,

^**P<0.01,

^***P<0.001.

Compared PVAT-:

^†P<0.005,

^††P<0.001,

^†††P<0.001.

Fig. 3.

Effects of perivascular adipose tissue and ovariectomy on NO and ROS generation in mesenteric resistant arterioles with 10⁻⁴ mol.l⁻¹ of acetylcholine or 10⁻⁶ mol.l⁻¹ of U-46,619. Comparing SHAM vs OVX in same treatment groups: *, P<0.05; **, P<0.01; ***, P<0.005. Comparing tempol vs vehicle in same treatment groups: ‡, P<0.05; ‡ ‡, P<0.01; ‡ ‡ ‡, P<0.005.

The presence of PVAT around mesenteric arterioles from SHAM rats increased their ACh induced relaxation and EDRF response by 20±4% and 29±3%, respectively (P<0.05; Fig. 2A, 2B) and increased their vascular NO activity with ACh by 41±4% (P<0.001; fig.3A) without changing their EDHF or EIR responses (table 2-I). However, these effects were lost in OVX rat vessels.

EDCF contractions were increased by 200% in vessels from OVX rats (Fig.2C), accompanied by a 500% (P< 0.001) increase in vascular ROS activity (Table 2-I; Fig.3C). PVAT reduced the EDCF responses in OVX rats (P<0.01) without reducing the associated vascular ROS generation.

Contractions with PE were unchanged in mesenteric arterioles from OVX rats but contractions with U-46,619 were increased by 45% (P<0.05; Table 2-I; Fig. 4B) accompanied by a 350% increase in vascular ROS (P< 0.001; Fig.3E). PVAT moderated the contractions with U-46,619 in both SHAM and OVX rat vessels and moderated the accompanying ROS generation in vessels from OVX rats. Nevertheless, both the vascular contractions and the ROS generation with U-46,619 in OVX rat vessels with PVAT remained >3 fold higher than in vessels from SHAM rats despite the moderating effects of PVAT (Table 2-I).

Fig.4.

Effect of perivascular adipose tissue and ovariectomy on contractions to phenylephrine and U-46,619 in mesenteric arterioles with PVAT (solid symbols) or without PVAT (open symbols) from SHAM (circles) or OVX (squares) rats after 6 weeks of vehicle or tempol. Comparing PVAT+ vs – in same treatment groups: *P<0.05; **, P<0.01. Comparing SHAM vs OVX in same treatment groups: ‡, P<0.05.

Effects of tempol on endothelial function, contractility and generation of NO and ROS

Tempol did not affect the vascular responses or NO generation of vessels from SHAM rats. However, it improved these responses in OVX rat vessels and prevented the enhanced EDCF responses (Table 2-II; Fig.2F) and ROS generation (Table 2-II; Fig.3D). However, although tempol prevented the enhanced vascular ROS generation with U-46,619 in OVX rat vessels without PVAT, the enhanced contractions to U-46,619 persisted.

Tempol administration OVX rats without PVAT restored EIR and EDRF and attenuated EDCF responses (Table 2-II; Fig.2D–F). However, the enhanced contractions to U-46,619 were not significantly moderated by tempol (Fig.4D), despite prevention of the enhanced generation of ROS. This indicated that there was a ROS-independent vascular effect of OVX to enhance U-46,619 contractions.

PVAT reduced the contractions to U-46,619 in OVX rat vessels by 40% (Table 2-I; Fig. 4B) but after tempol, PVAT reduced the contractions by 70% (Table 2-II; Fig.4D). The U-46,619 contractions in vessels from OVX rats given tempol was 17±4% with PVAT which was similar to the value of 10±2% in vessels with PVAT from SHAM rats (P=NS). Thus tempol +PVAT normalized the enhanced contraction to U-46,619 in vessels from OVX rats. Again, the effects of PVAT to moderate U-46,619 contraction after tempol occurred independent of ROS which was effectively suppressed by tempol in vessels without PVAT. Thus, neither PVAT, nor tempol alone were sufficient to prevent enhanced contractions to U-46,619, but the contractions were normalized by their combination. This suggests that OVX enhanced contractions to U-46,619 by independent effects of enhanced ROS and diminished blunting by PVAT. Thus, a primary effect of tempol on OVX rat vessels was to restore normal signaling from PVAT which blunted the response to U-46,619 in the adjacent blood vessels.

Discussion

This study confirms previous findings that OVX or ovarian hormone deficiency lead to endothelial dysfunction and enhanced vascular oxidative stress.^{3, 4, 23–25} The main new findings are that defects in endothelium dependent relaxation in OVX rat vessels were specific for EDRF since they did not impact EDHF and were accompanied by reduced NO generation. OVX rat vessels had an enhanced expression of p22^phox which is a critical regulatory component of NADPH oxidase.²¹ Indeed, these vessels developed enhanced ACh-and U-46,619-induced ROS generation and contractions.

The main new findings related to PVAT signaling are summarized in fig.5. The presence of PVAT surrounding the mesenteric arterioles from SHAM rats enhanced their EDRF responses and NO generation and diminished their contractions to U-46,619 substantially without modifying the modest vascular ROS generation or contractions to PE. In contrast, PVAT surrounding OVX rat vessels failed to enhance EDRF responses or to restore NO generation. Furthermore, PVAT was less effective in moderating the contractions to U-46,619 after OVX and failed to prevent the associated ROS generation.

Fig. 5.

Flow diagram outlining pathways intrinsic to blood vessels or that originate in PVAT that may modulate vasodilator and vasoconstrictor pathways. OVX, ovariectomy; PVAT. perivasvular adipose tissue; ROS, reactive oxygen species; TP-R, thromboxane prostanoid receptor; ACh, acetylcholine.

As in prior studies,^{5, 18, 19} tempol did not affect relaxation or contraction responses or NO generation of SHAM vessels, implying that ROS have little effect on normal vascular function. The main new findings related to tempol in OVX rat vessels are that it prevented all of the endothelial dysfunction and diminished NO generation, and prevented the augmented EDCF contractions and ACh-induced ROS generation. Moreover, tempol given to OVX rats restored the effects of PVAT to enhance endothelial function. In contrast, tempol failed to prevent the enhanced contractions to U-46,619 despite preventing the excessive ROS generation.²⁶ In fact, a combination of PVAT and tempol was required to reduce U-46,619 contractions in OVX rat vessels to SHAM levels.

In contrast, incubation of canine coronary arteries with bradykinin released an adipokine that reduced vascular ROS, yet inhibited vasodilation. Another apparently paradoxical effect of tempol was to reduce bradykinin-induced relaxations. There are important differences in the functions of PVAT between vessels and experimental circumstances.²⁶ After OVX, tempol enhanced both the intrinsic relaxation to ACh (in vessels without PVAT) and the relaxations mediated by PVAT, while reducing ROS generation consistent with many other reports that tempol moderated ROS and contractility and enhanced relaxation during oxidative stress.¹⁸

Of interest was the finding that OVX increased weight gain similar to the menopause.¹⁰ However, tempol reduced the weight gain in both OVX and SHAM rats. Tempol given to fat-fed mice also prevented weight gain²⁷ which was attributed to alteration in the microbiome and signaling via intestinal farnesoid x in receptors.

Thus, oxidative stress in microvessels from OVX rats redirected endothelial function from NO-dependent vasorelaxation to ROS-dependent vasoconstriction. About one half of these changes related to effects of ROS mediated by PVAT. The endothelial dysfunction is analogous to the effects on prolonged Ang II-infusion in rabbits¹⁹ and rats⁵ which also enhanced p22^phox expression. EDCF requires vascular ROS generation after endothelial activation by shear stress,²⁸ ACh,^{5, 19} Ang II¹⁹ or endothelin-1.²⁹ Vascular ROS generate vasoconstrictor PGs and TxA₂ from endothelial COX-1 or -2 and TxA₂ synthase that activate TP-Rs on adjacent VSMCs to mediate EDCF responses.¹⁹ A second effect of vascular ROS is to enhance TP-R responsiveness of VSMCs¹⁹ by reducing the recycling of TP-Rs.³⁰ The enhanced TP-R responsiveness of mesenteric arterioles from OVX rats confirms a prior study.⁶ However, an enhanced microvascular TP-R responsiveness is an incomplete explanation for the enhanced EDCF responses of mesenteric arterioles from OVX rats since tempol prevented the enhanced EDCF responses without fully correcting the enhanced responses to U-46,619. Apparently, by an ROS in PVAT change the release or responsiveness of an adipokine acting on TP-Rs or their signaling in adjacent VSMCs. The moderation of EDCF responses by PVAT in OVX rat vessels cannot be ascribed to upregulation of counterveiling endothelial vasodilation since this was blocked by L-NAME, apamin and charybdatoxin.

OVX rats had a similar increase in vascular ROS generation with TP-R activation as with ACh yet neither was prevented by PVAT alone and required co-administration of tempol. Thus, although PVAT enhanced ACh induced NO generation in OVX rat vessels, it did not restore EDRF responses or abrogate EDCF or U-46,619 contractions without first preventing ROS generation with tempol. This extends findings at the whole animal³¹ or cellular level³² that TP-R activation is a cause of oxidative stress, rather than just its consequence.

EDRF responses of normal rodent mesenteric arterioles depend on NO but not on PGs.¹⁹ The reduced EDRF responses and NO generation after OVX, and their restoration by tempol, implies a ROS-dependent bio-inactivation of NO or oxidation of the NOS cofactor, tetrahydrobiopterin.³³ The maintenance of EDHF responses is consistent since EDHF does not normally depend on NO. PVAT enhanced EDRF responses and NO only in mesenteric arterioles from SHAM rats but an enhancing effect of PVAT in OVX rats was restored by tempol administration. This implies that ROS in PVAT surrounding OVX rat vessels impaired the adipokine signaling that normally enhanced NO generation and EDRF responses or that ROS in blood vessels prevented the signaling effects of the adipokine. Thus, ROS in PVAT were implicated in both enhancing the EDCF responses and reducing the EDRF/NO responses in vessels from OVX rats.

This study has some limitations. It was confined to mesenteric arterioles. However, their function parallels that of renal afferent arterioles and systemic vessels.^{5, 31} We did not test the effects of ovarian hormone replacement in OVX rats. However, prior studies have reported that concomitant 17β-estradiol replacement at the time of OVX prevents endothelial dysfunction and enhanced TP-R signaling.⁶ The adipokine(s) released from PVAT was not identified. However, these studies suggest it was not hydrogen sulfide, which activates vascular ATP-dependent K⁺ channels and leads to hyperpolarization of VSMCs since we did not detect any effect of PVAT on EDHF responses.

Perspective

TP-R signaling not only mediates EDCF responses but also contributes to hypertension, vascular remodeling, renal vasoconstriction, oxidative stress and platelet aggregation, as observed during angiotensin³¹ or Goldblatt renovascular hypertension.^{34, 35} Thus, enhanced TP-R signaling may contribute to the microvascular remodeling, endothelial dysfunction and oxidative stress observed in OVX rat vessels and also to the loss of protection from CVD observed in women with ovarian hormone deficiency. The finding that microvessels from OVX rats have defects in endothelial relaxation, an EDCF response and enhanced TP-R signaling that were mediated by adverse ROS-dependent signaling in the vessels and the surrounding PVAT suggests that full restoration of the beneficial signaling from PVAT would be a valuable therapeutic approach for reducing CVD risk in women with ovarian hormone deficiency.

Novelty and Significance.

What is New?

Microvascular endothelial dysfunction and reduced NO in this model of ovarian hormone deficiency derives from ROS and impaired relaxant signaling from PVAT. Correction of oxidative stress and presence of PVAT are both required to normalize the greatly enhanced TP-R responses.

What is Relevant?

Correction of vascular ROS alone is insufficient to correct microvascular dysfunction in full. Vascular TP-Rs and PVAT are novel targets to correct menopausal microvascular dysfunction.

Summary

Microvascular endothelial dysfunction and enhanced TP-R signaling after ovariectomy originates from interactive effects of oxidative stress in blood vessel and adverse adipokine signaling from PVAT.