Liver Soluble Epoxide Hydrolase Regulates Behavioral and Cellular Effects of Chronic Stress

Summary: Major depression is a serious global health concern; however, the pathophysiology underlying this condition remains unclear. While numerous studies have focused on brain-specific mechanisms, few have evaluated the role of peripheral organs in depression. Here, we show that the liver activates an intrinsic metabolic pathway that can modulate depressive-like behavior. We find that chronic stress specifically increases the protein levels of monomeric and oligomeric soluble epoxide hydrolase (sEH), a key enzyme in epoxyeicosatrienoic acid (EET) signaling, in the liver. Hepatic deletion of Ephx2 (which encodes sEH) results in antidepressant-like effects, while the hepatic overexpression of sEH induces depressive phenotypes. The activity of sEH in hepatocytes modulates the plasma levels of 14,15-EET, which then interacts with astrocytes in the medial prefrontal cortex to mediate the effects of hepatic Ephx2 deletion. These results suggest that targeting mechanisms underlying the hepatic response to stress would increase our therapeutic options for the treatment of depression. : Qin et al. show that the expression levels of hepatic sEH increase following CMS. Deletion of hepatic Ephx2 produces antidepressant-like effects, while the overexpression of Ephx2 induces depressive phenotypes. Collectively, data demonstrate that the liver is able to modulate depression. Keywords: major depressive disorder, liver, soluble epoxide hydrolase, oligomerization, 14,15-epoxyeicosatrienoic acid, 14,15-EET, biomarkers, therapy