EETs Reduction Contributes to Granulosa Cell Senescence and Endometriosis-Associated Infertility via the PI3K/AKT/mTOR Signaling Pathway

We aimed to examine abnormal oxidative lipid levels and their related mechanisms in EM-associated infertility. Through liquid chromatography tandem mass spectrometry analysis, decreased levels of epoxyeicosatrienoic acids (EETs), which have antioxidant and anti-senescence effects are observed, in EM patient follicular fluid samples. EET levels are positively correlated with in vitro fertilization outcomes. Lower 14, 15-EET concentrations led to a decreased GC antioxidant capacity, reduced ATP production, Reactive Oxygen Species (ROS) accumulation in oocytes, and abnormal cumulus-oocyte complex (COC) expansion, ultimately resulting in decreased fertility. Elevated soluble Epoxide Hydrolase (EPHX2) expression in EM-GCs is the main reason for EET reduction in EM follicular fluid. Inhibiting EPHX2 in vivo or in vitro can reverse these observed abnormalities by upregulating EETs. 14, 15-EET treatment alleviated GC senescence and improved fertility by inhibiting excessive PI3K/Akt/mTOR signaling pathway activation in EM-GCs, with BEZ-235-mediated inhibition of this pathway significantly alleviating ROS-induced cell senescence and abnormal COC expansion. Oxidative stress-induced decreased EZH2/H3K27Me3 histone methylation led to elevated EPHX2 expression patterns in EM-GCs. Decreased 14, 15-EET levels resulted in ROS accumulation, reduced EZH2 enzymatic activity, less EPHX2/H3K27Me3 histone methylation, and increased EPHX2 protein expression levels, which further reduced 14, 15-EET levels in a vicious feedback loop.