Transgenic mice rich in endogenous omega-3 fatty acids are protected from colitis

Abstract

Omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFA) are the precursors of potent lipid mediators and play an important role in regulation of inflammation. Generally, n-6 PUFA promote inflammation whereas n-3 PUFA have antiinflammatory properties, traditionally attributed to their ability to inhibit the formation of n-6 PUFA-derived proinflammatory eicosanoids. Newly discovered resolvins and protectins are potent antiinflammatory lipid mediators derived directly from n-3 PUFA with distinct pathways of action. However, the role of the n-3 PUFA tissue status in the formation of these antiinflammatory mediators has not been addressed. Here we show that an increased n-3 PUFA tissue status in transgenic mice that endogenously biosynthesize n-3 PUFA from n-6 PUFA leads to significant formation of antiinflammatory resolvins and effective reduction in inflammation and tissue injury in colitis. The endogenous increase in n-3 PUFA and related products did not decrease n-6 PUFA-derived lipid mediators such as leukotriene B4 and prostaglandin E2. The observed inflammation protection might result from decreased NF-κB activity and expression of TNFα, inducible NO synthase, and IL-1β, with enhanced mucoprotection probably because of the higher expression of trefoil factor 3, Toll-interacting protein, and zonula occludens-1. These results thus establish the fat-1 transgenic mouse as a new experimental model for the study of n-3 PUFA-derived lipid mediators. They add insight into the molecular mechanisms of inflammation protection afforded by n-3 PUFA through formation of resolvins and protectins other than inhibition of n-6 PUFA-derived eicosanoid formation.

The epithelial surface of the gut is the largest mucosal surface in mammals and is particularly exposed to microbial attacks and trauma. The inflammatory bowel diseases (IBD) Crohn’s disease and ulcerative colitis are characterized by idiopathic relapses and remitting chronic inflammation. Modulating the formation of proinflammatory mediators and/or antiinflammatory molecules is useful in the treatment of IBD (1).

The omega-3 (n-3) fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are implicated in treating IBD (2–4), whereas the eicosanoids derived from the omega-6 (n-6) fatty acid arachidonic acid, such as prostaglandin E2 (PGE₂) and leukotriene B4 (LTB₄), are potent proinflammatory mediators (5–7). The increased incidence of IBD in humans correlates with an increased dietary content of n-6 fatty acids (8, 9). In most Westerners the amounts of tissue n-3 fatty acids appear to be low, whereas the levels of n-6 fatty acids are high, with an n-6/n-3 ratio ranging from 10:1 to 20:1 (10).

Newly identified lipid mediators produced from n-6 and n-3 polyunsaturated fatty acids (PUFA), the aspirin-triggered lipoxins (11, 12) and their stable analogues (13), as well as the resolvin E1 (RvE1) generated from EPA, have inflammation-dampening effects in models of inflammation (14). In light of these findings the direct contribution of n-3 fatty acid status itself to chronic disease progression such as in IBD and to the generation of local inflammatory mediators remains of interest.

Transgenic fat-1 mice, engineered to express the Caenorhabditis elegans fat-1 gene encoding an n-3 fatty acid desaturase, are capable of producing n-3 PUFA from n-6 PUFA and thereby have a low or balanced ratio of n-6/n-3 fatty acids in their tissues and organs without the need of dietary interventions (15). This model allows carefully controlled studies to be performed in the absence of restricted diets, which can create confounding factors that limit studies of this nature. Therefore, the transgenic mice offer the opportunity to address the molecular events underlying the beneficial impact of n-3 fatty acids.

Dextran sodium sulfate (DSS)-induced colitis is a well established experimental model of IBD used to study cytokine-triggered inflammation and injury in the colon (16, 17) as well as other mechanisms of colitis such as thrombin-triggered pathways of inflammation (18). DSS colitis is characterized histologically by infiltration of inflammatory cells into the lamina propria, with lymphoid hyperplasia, focal crypt damage, and epithelial ulceration (16–19). These pathological changes are thought to develop as a result of a barrier-destructive effect of DSS on the epithelium, subsequent phagocytosis of lamina propria cells, and production of cytokines (16–19). Although the relationship of murine DSS-induced colitis to the human disease remains to be established, this widely used IBD model has a number of advantages, including simplicity, high degree of uniformity of the lesions, and leukocyte infiltration (19). In the present report we used this model to examine the impact of enhanced n-3 PUFA tissue status on the development of colitis in the fat-1 transgenic mice and relationship to resolvins and protectins.

Results

Fatty Acid Profiles of Colon Tissues.

Both WT and fat-1 transgenic littermates born to the same mother were maintained on a diet (10% safflower oil) high in n-6 and low in n-3 PUFA (n-6/n-3 > 20). During this dietary regime, fat-1 transgenic mice had significantly higher amounts of n-3 PUFA, such as EPA, DPA, and DHA, in all organs and tissues including the colon compared with WT mice (Fig. 1 and Table 1). The ratio of the long-chain n-6 PUFA (20:4 n-6, 22:4 n-6, and 22:5 n-6) to the long-chain n-3 PUFA (20:5 n-3, 22:5 n-3, and 22:6 n-3) was 1.7 in fat-1 transgenics and 30.1 in WT mice. Apparently, although both WT and fat-1 eat the same diet, their body fatty acid profiles are distinct.

Fig. 1.

Differential fatty acid profiles in WT and fat-1 transgenic mice. Whereas high levels of n-6 fatty acids characterize WT samples (A), n-3 fatty acids are nearly absent. In contrast, an abundance of EPA (20:5 n-3), docosapentaenoic acid (22:5 n-3), and DHA (22:6 n-3) can be found in fat-1 transgenic mice (B). The n-3 PUFA are marked with asterisks.

Table 1.

PUFA profiles of colons from WT and fat-1 mice

PUFA	WT(n = 3)	fat-1(n = 4)
n-6 (%)
AA (20:4 n-6)	12.66 ± 2.94	12.47 ± 1.94
DTA (22:4 n-6)	3.02 ± 0.33	2.17 ± 0.38
DPA (22:5 n-6)	2.95 ± 1.13	0.57 ± 0.22
Total	18.62 ± 4.85	15.21 ± 2.22
n-3 (%)
EPA (20:5 n-3)	0.06 ± 0.08	2.03 ± 0.47
DPA (22:5 n-3)	0.12 ± 0.15	2.45 ± 0.55
DHA (22:6 n-3)	0.43 ± 0.08	4.68 ± 0.36
Total	0.62 ± 0.15	9.86 ± 1.17
n-6/n-3 (of total fractions)	30.13	1.66

DTA, docosatetraenoic acid; DPA, docosapentaenoic acid; AA, arachidonic acid.

fat-1 Transgenic Mice Are Protected Against DSS-Induced Colitis.

Induction of colitis resulted in significant changes in body weight, stool consistence, appearance of fecal blood, and general status, typically associated with human and experimental DSS colitis. fat-1 mice showed significantly less body weight loss (Fig. 2D) and a delayed progression of diarrhea but no apparent change in fecal bleeding. Interestingly, fat-1 transgenic mice showed a recovery beginning from the second day after stop of DSS exposure whereas WT mice exhibited a continued loss of body weight during the 3 days after cessation of DSS (Fig. 2D). These clinical manifestations were reflected in the macroscopic pathological changes. Multiple adhesions, strictures, and a massive thickening of the colon were observed in WT mice but not in fat-1 animals (Fig. 2A). Furthermore, colon shortening amounted to 35% in WT mice but only 15% in fat-1 transgenic mice when compared with that of untreated control mice (Fig. 2B). Microscopic assessment of the distal part of the colon revealed that severity and thickness of the inflammatory infiltrate as well as the extent of epithelial damage were significantly alleviated in fat-1 mice (Fig. 2A). All hallmarks of colitis were reduced in fat-1 mice except for minor punctate erosions and few ulcerations. In contrast, WT mice showed a massive fibrinous exudate on the luminal surface and marked epithelial infiltrate of leukocytes, as well as severe submucosal edema and diffuse ulcerations of the mucosa (Fig. 2C). These findings indicate that fat-1 transgenic mice, rich in n-3 fatty acids, are protected from inflammation.

Fig. 2.

Colon inflammation activity in WT and fat-1 transgenic mice. (A) Macroscopic view (Upper) and microscopic hematoxylin and eosin staining (Lower) of the distal colon in WT control mice (Left), DSS-treated WT nontransgenic littermates (Center), and fat-1 mice (Right). (B) Colon shortening as a hallmark of DSS-induced colonic damage is reduced in fat-1 mice. ∗, P < 0.01 versus WT DSS-treated animals. (C) Histopathological scores for colonic inflammatory infiltration and epithelial damage in WT and fat-1 mice. ∗, P < 0.01 versus WT DSS. (D) Body weight change from 100% baseline over 8 days in fat-1 mice and WT littermates (n = 6 for each group), 5 days of DSS treatment and 3 days of normal drinking water. ∗, P < 0.05 versus WT DSS; ∗∗, P < 0.01 versus WT DSS. Mice were killed on day 8 (arrow), and samples were taken for further analysis.

Formation of n-3-Derived Antiinflammatory Mediators.

Newly identified potent n-3 fatty acid-derived mediators such as the resolvins, including RvE1 and resolvin D3 (RvD3), and protectins, i.e., neuroprotectin D1 (NPD1)/protectin D1 (PD1), are antiinflammatory (20, 21). We assessed both n-6 and n-3 PUFA-derived mediators from colons using liquid chromatography–UV–tandem MS mediator informatics to determine whether the difference in DSS-induced colitis observed between WT and fat-1 mice was associated with these pathways. The n-3-derived mediators, including RvE1, RvD3, and NPD1/PD1, were identified in physiologically active levels within colons of fat-1 transgenics (Fig. 3). These mediators were not found in the WT colons. Also, both 17-hydroxy-DHA and 14-hydroxy-DHA as pathway markers of DHA utilization (22) were identified in fat-1 mice. In addition to the resolvin lipid mediators, significant amounts of n-3 PUFA-derived prostaglandin E3 (PGE₃) and leukotriene B5 (LTB₅) were formed in fat-1 mice. There were no significant differences in the levels of LTB₄, a potent chemoattractant, and the proinflammatory PGE₂. Similarly, there was no significant difference in the formation of 15-hydroxyeicosatetraenoic acid, the precursor for the n-6 PUFA-derived antiinflammatory lipoxin A4, between WT and fat-1 mice.

Fig. 3.

LC–UV–tandem MS profiles of n-3 PUFA-derived lipid mediators. (A) DHA-derived resolvins and protectins (main pathway products identified were RvD3 and PD1/NPD1). (B) EPA-derived bioactive lipid mediators (identified mediators include RvE1, PGE₃, and LTB₅). (C) Arachidonic acid-derived bioactive mediators [PGE₂, LTB₄, and 15-hydroxyeicosatetraenoic acid (15-HETE) as precursor for the n-6 PUFA-derived lipoxin A4 (LXA₄)]. (D) Presence of different lipid mediators in colon samples of fat-1 transgenic mice (n = 6) and WT animals (n = 6). ∗∗, P < 0.01; ∗, P < 0.05. Note the different scale for 15-HETE and PGE₂ (on the right).

Expression of Genes Involved in Inflammation and Colitis Pathogenesis.

We next examined whether the protection from colitis observed in fat-1 transgenics had an impact on inflammation-related gene expression. TNFα plays a critical role in IBD, and its overexpression is associated with an IBD-like phenotype in mice (23). Concordant with the protective action of the increased n-3 PUFA status was a decrease in NF-κB protein activity, as determined by activated p65 protein (Fig. 4A) as well as in TNFα mRNA levels (Fig. 4B). In addition, transcription of other prominent inflammatory markers, such as inducible NO synthase and IL-1β (24), was dampened in the transgenic fat-1 mice (Fig. 4 C and D).

Fig. 4.

Markers of inflammation and mucoprotection. (A) NF-κB activation reflected in p65 ELISA activity shows significant differences in control baselines and in disease between WT and fat-1 mice. ∗, P < 0.05 versus WT DSS; ∗∗, P < 0.05 versus WT control. (B–F) Semiquantitative real-time PCR analysis of mRNA expression levels of inflammatory mediators TNFα, inducible NO synthase (iNOS), and IL-1β (B–D) and mucoprotective factors Tollip and TFF3 (E and F) in colons from WT and fat-1 mice after DSS exposure and fat-1 control mice, normalized as fold increase to the baseline of WT controls (dashed line). ∗, P < 0.05 versus WT DSS; ∗∗, P < 0.01 versus WT DSS. (G) ZO-1 expression profile. Compared with WT mice without treatment (Left), ZO-1 expression is down-regulated on the luminal epithelial surface in WT mice on day 4 (Center), whereas luminal continuity of expression is sustained in fat-1 mice (Right).

In addition, we observed that the mRNA levels of intestinal trefoil factor 3 (TFF3), a factor important in maintenance and repair of the intestinal mucosa (25), was increased in the colons of fat-1 mice (Fig. 4F). The intercellular tight junction protein zonula occludens 1 (ZO-1), which is important in epithelial integrity (26), was also sustained in fat-1 transgenic animals (Fig. 4G). Furthermore, mRNA levels of Toll-interacting protein (Tollip), a downstream inhibitor of the Toll-like receptor pathway that mediates inflammatory response (27), were higher in fat-1 transgenic mice (Fig. 4E). These results suggest an enhanced defense status in the fat-1 mice.

Discussion

The results presented here clearly show that the inflammation of colon induced by DSS, in terms of both clinical manifestation and pathology, is significantly less severe in fat-1 transgenic mice than that in WT littermates. The protection from colitis in fat-1 mice is correlated with the formation of antiinflammatory derivates of n-3 fatty acids, down-regulation of proinflammatory cytokines, and up-regulation of mucoprotective factors in the colons of these animals. These findings suggest a role played by an increased tissue status of n-3 fatty acids in protection against colitis through alterations of gene expression mediated, probably, by antiinflammatory lipid mediators of the n-3 fatty acids.

Although a number of previous studies have examined the effectiveness of n-3 fatty acids in prevention and treatment of colitis (2–4), the outcomes were inconsistent or conflicting. The discrepancy may be caused by the confounding factors of diet or n-3 fatty acid supplements. In fact, many variables can arise from the diets and the feeding procedure, including the impurity or unwanted components of the oils used (e.g., fish oil versus corn oil), flavor, sensitivity to oxidation, diet storage, duration of diet change, etc., which can impose confounding effects on the fatty acid ratio. In contrast, the genetic approach using the fat-1 gene, as presented here, only modifies the n-6/n-3 fatty acid ratio (converts n-6 to n-3) endogenously and thereby allows experimental animals (i.e., WT and transgenic littermates) to be fed with a single diet. Therefore, the results obtained by using this model are more reliable.

The n-3 fatty acids may exert an antiinflammatory effect via competitive inhibition of the n-6 (arachidonic acid)-derived proinflammatory eicosanoids, most notably LTB₄ and PGE₂, and this has been the mechanism mostly proposed in the past to explain the biological effectiveness of n-3 fatty acids (28). In this study we found no significant differences in the content of arachidonic acid, LTB₄, and PGE₂ between fat-1 transgenic and WT mice. There was a remarkable difference in the amounts of n-3 fatty acids (EPA, DHA, and precursors) and their potent bioactive products, the resolvins and protectins (RvE1, RvD3, and PD1/NPD1), as well as the n-3 PUFA-derived LTB₅ and PGE₃ (Fig. 3). It is possible that LTB₅ and PGE₃ could exert an antiinflammatory effect through competition with LTB₄ and PGE₂. However, given the much higher absolute concentrations of LTB₄ and PGE₂ present in the fat-1 mice this may not be the major underlying mechanism.

The newly identified n-3-derived resolvins and protectins are potent antiinflammatory mediators in various settings, including trinitrobenzene sulfonate colitis and periodontitis (20, 21, 29, 30). These lipid mediators have been shown to decrease formation of inflammatory cytokines such as TNFα, IL-6, and others (31, 32). Our data confirm decreased levels of cytokines, which may be due to the documented lower NF-κB activity in fat-1 mice shown here. Indeed, RvE1 has been shown to inhibit NF-κB activation through its specific G protein-coupled receptor, ChemR23 (14). Our data are consistent with this mechanism of action. In view of these results the n-3 fatty acid-derived mediators documented in the fat-1 transgenic mice might link an enhanced n-3 PUFA status to inflammation dampening.

Although the pathogenesis of DSS colitis appears to be T cell-independent (33), cytokine production plays a key role in the development of colitis in this model (16, 17). In fact, cytokines are important mediators of inflammation (34). Increased production of proinflammatory cytokines such as TNFα, IL-1β, IL-12, and IFN-γ are found in inflamed colons from patients with IBD (35) as well as DSS colitis animals (16, 17). Further evidence for the involvement of these cytokines came from the observations that antibodies against TNFα and IL-12 reduced the severity of the disease in the animal model of DSS-induced colitis (36, 37) as well as patients with Crohn’s disease (38). Thus, reduction in the production of proinflammatory cytokines appears to be an effective approach to the prevention and treatment of IBD. In the present study, the colons of fat-1 mice, rich in n-3 fatty acids, exhibited significantly lower amounts of the proinflammatory cytokines TNFα and IL-1β than those from WT animals and were protected from DSS-induced colitis. Along these lines, earlier animal and human results showed that dietary supplementation with n-3 fatty acids reduced the production of cytokines, including TNFα and IL-1 (39). This finding suggests that the inflammation protection observed in fat-1 mice may be, in part, the result of the reduction in cytokine production and action by n-3-derived resolvins.

The results of the present study also support a role for n-3 fatty acids in the maintenance of intestinal integrity, as demonstrated by higher levels of the mucosal protective factors Tollip, TFF3, and ZO-1 in the colon tissues of fat-1 transgenic mice. The innate immune system maintains a steady state of physiologic inflammation in coexistence with the luminal commensal bacteria. Toll-like receptors sense components of these microorganisms (e.g., LPS) and lead to a delicately regulated downstream signaling cascade that balances an appropriate mucosal response by production of protective factors (40) or inflammatory mediators (41). In the uninflamed colon a state of reduced sensitivity to bacterial products like LPS inhibits an exaggerated activation of the transcriptional factor NF-κB and the consecutive proinflammatory stimuli (27). A dysregulation of this balancing system may contribute to the severity and chronification of intestinal inflammation. It is possible that n-3 fatty acids may preserve this system, because our results showed that the inhibitory Tollip, a downstream regulator of the Toll-like receptor pathway, was markedly reduced in WT mice but sustained in fat-1 transgenic mice. Intestinal TFF3 is secreted by goblet cells throughout the entire colon onto the luminal surface in physiologic conditions. Under disease conditions TFF3 promotes epithelial cell migration into damaged areas to subserve the reestablishment of mucosal integrity. In this context, mice lacking intestinal trefoil factor may suffer from an impaired epithelial defense and are more vulnerable to inflammatory injury. Our results show a favorable effect of n-3 fatty acids on this system, as evidenced by the up-regulation of TFF3 in fat-1 transgenic mice. Thus, it seems that up-regulation or maintenance of mucoprotective factors (TFF3 and Tollip) in the n-3 PUFA-enriched tissues may be one of the underlying mechanisms for the observed protection against colitis in fat-1 mice. However, the molecular mechanisms remain for further study.

In short, the present results demonstrate that colon tissue with an increased n-3 PUFA status generates higher levels of bioactive n-3 PUFA-derived lipid mediators (resolvins and protectins), which may, on one hand, suppress the inflammatory response and, on the other hand, enhance mucoprotection (defense of intestinal mucosa) and is thereby protected against inflammation and injury.

Methods

Mice.

Transgenic fat-1 mice were created as in ref. 15 and subsequently backcrossed onto a C57BL background. Generations of heterozygous fat-1 mice were then mated to obtain WT and heterozygous/homozygous transgenic mice. In this study, all transgenic fat-1 mice used were heterozygous. Animals were kept under specific pathogen-free conditions in standard cages and were fed a special diet (10% safflower oil) high in n-6 and low in n-3 fatty acids until the desired age (9–10 weeks) and weight (19–21 g). Each cage housed two weight-matched female mice, combining one WT and one fat-1 transgenic mouse. All studies were approved by the Massachusetts General Hospital Subcommittee on Research Animal Care.

Induction of Colitis.

Colitis was induced in both WT and transgenic mice by addition of 3% (wt/vol) DSS (molecular weight 35,000–40,000; ICN Biomedicals) to sterile drinking water. On day 5, DSS supplementation was discontinued, and mice were killed on day 8 (3 days after cessation of DSS administration). Clinical assessment of all DSS-treated animals for body weight, stool consistency, rectal bleeding, and general appearance was performed daily. Mice were weighed twice at designated time points each day. Mice were killed on day 8. Colons were excised, and their length and thickening were documented. Histological examination was performed in a blinded manner, and the degree of inflammation and epithelial damage on microscopic cross-sections of the colon was graded by an experienced pathologist. The inflammation score is a combined score of (i) severity of inflammation (0 = no inflammation, 1 = mild, 2 = moderate, and 3 = severe) and (ii) thickness of inflammatory involvement (0 = no inflammation, 1 = mucosa, 2 = mucosa plus submucosa, and 3 = transmural); epithelial damage score consists of character (0 = intact epithelium, 1 = disruption of architectural structure, 2 = erosion, and 3 = ulceration) and extent of lesions (0 = no lesions, 1 = punctuate, 2 = multifocal, and 3 = diffuse).

Immunofluorescence.

Colon tissue was fresh-frozen in OCT medium, and sections were cut at 4-μm thickness. After air-drying, they were incubated with ZO-1 primary antibody (1:100 dilution; Zymed) for 30 min at room temperature in a moist chamber, rinsed with PBS, and incubated with an Alexa Fluor 488 FITC-conjugated secondary antibody (1:50 dilution; Molecular Probes) in the same manner. Sections were mounted with Glycergel mounting medium (Dako) and evaluated with a Zeiss LSM 5 Pascal confocal microscope.

Semiquantitative Real-Time PCR.

Total RNA was isolated from whole colon tissue using TRIzol reagent (Invitrogen Life Technologies) following the manufacturer’s instructions. RNA concentrations and purity were determined spectrometrically by their absorbance at 260 nm in relation to the absorbance at 280 nm. Reverse transcription of mRNA was performed by using random hexamer primers. Real-time PCR was carried out by using SYBR Green in a PRISM 9000 Light Cycler (Applied Biosystems) following the manufacturer’s protocol. All samples were processed in triplicate, and means were standardized to GAPDH values. Results are expressed as a fold induction of the WT controls.

NF-κB Activation.

To quantify the activated p65/RelA protein, TransAM NF-κB p65 Activation Assay (Active Motif) was performed according to the manufacturer’s instructions. Nuclear extracts from whole colon tissues were collected by using NE-PER (Pierce), and protein concentrations were determined by using a Coomassie Plus Assay. Lysates (13 μg of total protein) were incubated at room temperature for 1 h in 96-well dishes containing immobilized oligonucleotides that comprise the NF-κB consensus DNA binding site (5′-GGGACTTTCC-3′). Consecutively, the primary antibody against p65 and the horseradish peroxidase-conjugated secondary antibody were incubated in the same manner, separated by washing steps. The reaction was developed for 5 min at room temperature, and its intensity was measured immediately at 450 nm by using a microplate reader.

Analysis of PUFA and Lipid Mediators.

Fatty acid profiles were analyzed by using gas chromatography as described previously (42). Briefly, fresh colon tissues were grounded to powder under liquid nitrogen and subjected to extraction of total lipids and fatty acid methylation by heating at 100°C for 1 h under 14% boron trifluoride–methanol reagent. Fatty acid methyl esters were analyzed by gas chromatography using a fully automated HP5890 system equipped with a flame-ionization detector. Peaks of resolved fatty acids were identified by comparison with fatty acid standards (Nu Chek Prep, Elysian, MN), and area percentage for all resolved peaks was analyzed by using a PerkinElmer M1 integrator.

Lipid mediators from n-3 and n-6 fatty acids were measured by using LC–tandem MS methods as in ref. 14. Samples were extracted with 2 ml of cold methanol and analyzed by LC–UV–tandem MS using a Finnigan LCQ liquid chromatography ion trap tandem mass spectrometer equipped with a LUNA C18–2 (100 × 2 mm × 5 μm) column and UV diode array detector using mobile phase (methanol:water:acetate at 65:35:0.01) with a 0.2 ml/min flow rate.

Statistical Analysis.

Data analysis was performed with Prism 3.02 software (GraphPad). Comparison was made by using the Student t test. All values are presented as the mean ± SEM or as indicated. Statistical significance was set at P < 0.05.

Abbreviations

n-3

omega-3

n-6

omega-6

PUFA

polyunsaturated fatty acids

EPA

eicosapentaenoic acid

DHA

docosahexaenoic acid

IBD

inflammatory bowel disease

RvE1

resolvin E1

RvD3

resolvin D3

NPD1

neuroprotectin D1

PD1

protectin D1

LTB₄

leukotriene B4

LTB₅

leukotriene B5

PGE₃

prostaglandin E3

PGE₂

prostaglandin E2

TFF3

trefoil factor 3

Tollip

Toll-interacting protein

ZO-1

zonula occludens-1

DSS

dextran sodium sulfate.