Role of epoxy fatty acids - soluble epoxide hydrolase axis in intestinal mucosal barrier defense - Overarching objective of this project is to elucidate whether and how cytochrome p450 (CYP)-derived epoxy fatty acid metabolites (EpFAs) and soluble epoxide hydrolase (sEH)-hydrolyzed EpFAs metabolites (called diol oxylipins) in sustaining gastrointestinal (GI) mucosa barrier homeostasis and to develop the efficient therapeutic approach against GI mucosa barrier damage. More than 80% polyunsaturated fatty acids (PUFA)/eicosanoids are metabolized through CYP pathway and GI mucosa has the highest expression levels of CYP epoxygenase and sEH. We found that sEH inhibition or knockout against nonsterol anti-inflammatory drugs (NSAIDs) or aflatoxin B1 (AFB)-induced GI mucosa damage via strengthening mucosa barrier defense and preserving levels of EpFAs to limit inflammation in vivo. We have developed novel sEH inhibitors with excellent pharmacokinetics and low toxicity, including the IND approved inhibitor EC5026. This sEH inhibitor has a strong effect on blocking inflammation, eicosanoid/cytokine storms, and NSAIDs or aflatoxin B1-induced GI mucosa damage or ulcer. PPARγ’s anti-inflammatory activities are well-known, and EpFAs are PPARγ agonist or PPARγ is a possible EpFAs-binding receptor. Our hypothesis is that enhancement of EpFAs via sEH inhibition is crucial in sustaining Gl mucosa barrier for their defense and restitution to mucosa damage, and mechanistically EpFAs block NSAIDs or AFB-induced GI mucosa injury through its binding protein/receptor - PPARγ and its mediated signaling pathway/s to i) enhance the GI mucosa barrier defense by increasing goblet cell mucin production and enterocyte tight junction and by enhancing mucosa restitution/regeneration by activating enterocyte progenitor cell proliferation/migration/regeneration process, and ii) inhibit endoplasmic reticulum (ER)/mitochondrial stress, and iii) inhibit eicosanoid/cytokine storms and inflammatory activity. We have established and used numerous novel genetically engineered mouse models and in vitro intestinal organoids, and showed a critical role of sEH knockout in epithelial regeneration. We proposed the following three aims: 1) to determine the independent roles of sEH specific cell-lineage knockout compared to global sEH inhibition in strengthening intestinal mucosa barrier defense and restitution against NSAIDS/toxin-induced GI mucosal injury using powerful Villin-Cre/sEHfl/fl, Cdh5- Cre/sEHfl/fl and LysM-Cre/sEHfl/fl mouse models that have specific sEH knockout in intestinal epithelium, endothelium, and macrophages, respectively; 2) to determine how sEH inhibition/knockout or EpFAs enhances intestinal mucosa restitution/regeneration process responded to injury via activating the PPARγ-mediated signals and regulating the key related transcriptome profile in intestinal epithelium using our novel 3xTg-iEAP intestinal epithelial injury-healing mouse model and in vitro intestinal crypt organoids; and 3) to determine whether the key EpFAs-binding protein - PPARγ is a central player for EpFAs or sEH inhibition to block NSAIDs/toxin-induced GI mucosa damage and strengthen intestinal mucosal barrier defense and restitution using both powerful PPARγ knockout mice and in vitro intestinal organoids and molecular biology approaches.
