Isorhamnetin protects zearalenone-induced damage via the PI3K/Akt signaling pathway in porcine ovarian granulosa cells

Zearalenone (ZEA) is widely derived from moldy cereal grain, which has adverse effects on animal reproduction. In particular, pigs are more sensitive to ZEA-induced toxicity than other animals. Isorhamnetin has extensive pharmacological activity. However, the role of isorhamnetin in ZEA-induced cytotoxicity remains unclear. This study was designed to investigate the therapeutic effect of isorhamnetin on ZEA-induced damage in porcine ovarian granulosa cells and elucidate its molecular mechanism. Two experiments were conducted, where a minimum of 3 biological replicates were used for each treatment. In Exp. 1, ovarian granulosa cells were treated with different concentrations of isorhamnetin (1, 5, 10, 20 and 30 μmol/L) and ZEA (0, 10, 30, 60, 90 and 120 μmol/L) for 24 h. Our results indicated that 60 μmol/L ZEA (half-maximal inhibitory concentration value) and 20 μmol/L isorhamnetin (the most effective concentration against ZEA-induced cytotoxicity) were optimum concentrations. In Exp. 2, ovarian granulosa cells were treated with isorhamnetin (20 μmol/L) for 2 h, before treatment with ZEA (60 μmol/L) for 24 h. Apoptosis, endoplasmic reticulum stress, oxidative stress, proliferation and hormone secretion of ovarian granulosa cells were detected. Our findings showed that isorhamnetin suppressed (P < 0.05) ZEA-induced apoptosis by altering mitochondrial membrane potential and apoptosis-related proteins (B-cell lymphoma-2 [Bcl-2], Bcl2-associated x [Bax] and cleaved caspase-3 [C-Casp3]). Changes in intracellular Ca(2+) levels and C/EBP homologous protein (CHOP), recombinant activating transcription factor 6 (ATF6), glucose regulated protein78 kD (GRP78) indicated that isorhamnetin rescued (P < 0.05) ZEA-induced endoplasmic reticulum stress. Furthermore, isorhamnetin prevented (P < 0.05) ZEA-induced oxidative stress via the mitogen-activated protein kinase (P38) signaling pathway. Mechanistically, isorhamnetin stimulated (P < 0.05) the expression of proliferating cell nuclear antigen (PCNA) and cyclin D, thereby increasing the ratio of S phase cells in response to ZEA-induced apoptosis via phosphatidylinositol 3 kinase/protein kinase B (PI3K/Akt) signaling pathway. Isorhamnetin also recovered (P < 0.05) ZEA-induced steroidogenesis disorder by regulating steroidogenic enzyme gene and proteins (follicle-stimulating hormone receptor [FSHR] and cytochrome P450 family 19 subfamily a member 1 [CYP19A1]). Collectively, these findings show that isorhamnetin protects ovarian granulosa cells from ZEA-induced damage, which promotes proliferation, alleviates apoptosis, endoplasmic reticulum stress, oxidative stress, and steroidogenesis disorder.