TPPU alleviates hepatic ischemia–reperfusion injury by regulating macrophage polarization

Hepatic ischemia-reperfusion injury (IRI) represents a major challenge in liver surgery and transplantation, with macrophage polarization imbalance being a key contributing factor. This study investigated the protective effects and mechanisms of the soluble epoxide hydrolase (sEH) inhibitor 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) and 14,15-epoxyeicosatrienoic acid (14,15-EET) against hepatic IRI. In a murine model of 70% hepatic IRI, pretreatment with TPPU or administration of 14,15-EET during reperfusion significantly alleviated liver injury. TPPU reduced serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, mitigated hepatic congestion and necrosis, and decreased hepatocyte apoptosis. It also downregulated pro-inflammatory cytokines and chemokines, suppressed neutrophil infiltration, and attenuated oxidative stress by reducing malondialdehyde levels while enhancing superoxide dismutase activity. Mechanistically, TPPU promoted the polarization of hepatic macrophages toward the anti-inflammatory M2 phenotype by upregulating M2 markers and downregulating M1 markers. In vitro experiments confirmed that TPPU reduced inflammatory and oxidative responses in macrophages and protected hepatocytes from apoptosis in a co-culture system. Crucially, co-administration of the EET receptor antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EE-5(Z)-E) with TPPU markedly reversed TPPU-mediated protection. This confirms that the protective effect of TPPU is specifically mediated through 14,15-EET and its associated signaling pathway. In conclusion, TPPU inhibits sEH to elevate endogenous 14,15-EET levels, thereby regulating macrophage polarization to mitigate inflammation, oxidative stress, and apoptosis in hepatic IRI. This study not only identifies a potential therapeutic target but also pharmacologically validates the central role of the sEH-EET axis in this process.