Soluble epoxide hydrolase (sEH) is an emerging therapeutic target in a number of diseases that have inflammation as a common underlying cause. sEH limits tissue levels of cytochrome P450 (CYP) epoxides derived from omega-6 and omega-3 polyunsaturated fatty acids (PUFA) by converting these antiinflammatory mediators into their less active diols. Here, we explored the metabolic effects of a sEH inhibitor (t-TUCB) in fat-1 mice with transgenic expression of an omega-3 desaturase capable of enriching tissues with endogenous omega-3 PUFA. These mice exhibited increased CYP1A1, CYP2E1, and CYP2U1 expression and abundant levels of the omega-3-derived epoxides 17,18-epoxyeicosatetraenoic acid (17, in insulinsensitive tissues, especially liver, as determined by LC-ESI-MS/MS. In obese fat-1 mice, t-TUCB raised hepatic 17,18-EEQ and 19,20-EDP levels and reinforced the omega-3-dependent reduction observed in tissue inflammation and lipid peroxidation. t-TUCB also produced a more intense antisteatotic action in obese fat-1 mice, as revealed by magnetic resonance spectroscopy. Notably, t-TUCB skewed macrophage polarization toward an antiinflammatory M2 phenotype and expanded the interscapular brown adipose tissue volume. Moreover, t-TUCB restored hepatic levels of Atg12-Atg5 and LC3-II conjugates and reduced p62 expression, indicating up-regulation of hepatic autophagy. t-TUCB consistently reduced endoplasmic reticulum stress demonstrated by the attenuation of IRE-1α and eIF2α phosphorylation. These actions were recapitulated in vitro in palmitate-primed hepatocytes and adipocytes incubated with 19,20-EDP or 17,18-EEQ. Relatively similar but less pronounced actions were observed with the omega-6 epoxide, 14,15-EET, and nonoxidized DHA. Together, these findings identify omega-3 epoxides as important regulators of inflammation and autophagy in insulin-sensitive tissues and postulate sEH as a druggable target in metabolic diseases.obesity | inflammation | autophagy | omega-3-derived epoxides | soluble epoxide hydrolase C ytochrome P450 (CYP) epoxygenases represent the third branch of polyunsaturated fatty acid (PUFA) metabolism (1). CYP epoxygenases add oxygen across one of the four double bonds of PUFA to generate three-membered ethers known as epoxides (1). In the case of arachidonic acid, CYP epoxygenases convert this omega-6 PUFA into epoxyeicosatrienoic acids (EETs), which act as autocrine or paracrine factors in the regulation of vascular tone, inflammation, hyperalgesia, and organ and tissue regeneration (2, 3). In addition to omega-6s, CYP epoxygenases also convert the omega-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into novel epoxyeicosatetraenoic (EEQs) and epoxydocosapentaenoic (EDPs) acids, respectively (4, 5). These omega-3-derived epoxides also exert salutary actions and are even more effective and potent than omega-6-derived EETs (4-8).Because the predicted in vivo half-lives of fatty acid epoxides (EpFA) are in the order of seconds (9), drugs that stabilize their levels by targeting the en...

Background & Aim A key feature in the pathogenesis of liver fibrosis is fibrillar collagen-I deposition; yet, mediators that could be key therapeutic targets remain elusive. We hypothesized that osteopontin (OPN), an extracellular matrix (ECM) cytokine expressed in hepatic stellate cells (HSC), could drive fibrogenesis by modulating the HSC profibrogenic phenotype and collagen-I expression. Results rOPN up-regulated collagen-I protein in primary HSC in a TGFβ-independent fashion whereas it down-regulated matrix metalloprotease-13 (MMP13) thus favoring scarring. rOPN activated primary HSC -confirmed by increased α-smooth muscle actin (α-SMA) expression- and enhanced their invasive and wound-healing potential. HSC isolated from wild type (WT) mice were more profibrogenic than those from Opn-/- mice and infection of primary HSC with an Ad-OPN increased collagen-I, indicating correlation between both proteins. The OPN induction of collagen-I occurred via integrin αvβ3 engagement and activation of the PI3K-pAkt-NFκB signaling pathway, while CD44-binding and mTOR-p70S6K were not involved. Neutralization of integrin αvβ3 prevented the OPN-mediated activation of the PI3K-pAkt-NFκB signaling cascade and collagen-I up-regulation. Likewise, inhibition of PI3K and NFκB blocked the OPN-mediated collagen-I increase. HCV-cirrhotic patients showed co-induction of collagen-I and cleaved OPN compared to healthy individuals. Acute and chronic liver injury by carbon tetrachloride (CCl4)-injection or thioacetamide (TAA)-treatment elevated OPN expression. Reactive oxygen species up-regulated OPN in vitro and in vivo and antioxidants prevented this effect. OpnHEP Tg mice developed spontaneous liver fibrosis compared to WT mice. Lastly, chronic CCl4-injection and TAA-treatment caused more liver fibrosis to WT than to Opn-/- mice and the reverse occurred in OpnHEP Tg mice. Conclusion OPN emerges as a cytokine within the ECM protein network driving the increase in collagen-I protein contributing to scarring and liver fibrosis.

We conclude with a brief description of how epigenetics, an evolving field, can regulate the behavior of MF and of how new "omics" tools may advance our understanding of the mechanisms by which the fibrogenic response to liver injury occurs.

OPN emerges as a key matricellular protein driving DR and contributing to scarring and liver fibrosis via TGF-β.

ObjectiveLiver fibrosis is associated with significant collagen-I deposition largely produced by activated hepatic stellate cells (HSCs); yet, the link between hepatocyte damage and the HSC profibrogenic response remains unclear. Here we show significant induction of osteopontin (OPN) and high-mobility group box-1 (HMGB1) in liver fibrosis. Since OPN was identified as upstream of HMGB1, we hypothesised that OPN could participate in the pathogenesis of liver fibrosis by increasing HMGB1 to upregulate collagen-I expression.Design and resultsPatients with long-term hepatitis C virus (HCV) progressing in disease stage displayed enhanced hepatic OPN and HMGB1 immunostaining, which correlated with fibrosis stage, whereas it remained similar in non-progressors. Hepatocyte cytoplasmic OPN and HMGB1 expression was significant while loss of nuclear HMGB1 occurred in patients with HCV-induced fibrosis compared with healthy explants. Well-established liver fibrosis along with marked induction of HMGB1 occurred in CCl4-injected OpnHep transgenic yet it was less in wild type and almost absent in Opn−/− mice. Hmgb1 ablation in hepatocytes (Hmgb1ΔHep) protected mice from CCl4-induced liver fibrosis. Coculture with hepatocytes that secrete OPN plus HMGB1 and challenge with recombinant OPN (rOPN) or HMGB1 (rHMGB1) enhanced collagen-I expression in HSCs, which was blunted by neutralising antibodies (Abs) and by Opn or Hmgb1 ablation. rOPN induced acetylation of HMGB1 in HSCs due to increased NADPH oxidase activity and the associated decrease in histone deacetylases 1/2 leading to upregulation of collagen-I. Last, rHMGB1 signalled via receptor for advanced glycation end-products and activated the PI3K–pAkt1/2/3 pathway to upregulate collagen-I.ConclusionsDuring liver fibrosis, the increase in OPN induces HMGB1, which acts as a downstream alarmin driving collagen-I synthesis in HSCs.