Protective effect of L‑carnitine against oxidative stress injury in human ovarian granulosa cells

Granulosa cells (GCs) are important for supporting and nourishing oocytes during follicular development and maturation. Oxidative stress (OS) injury of GCs can lead to decreased responsiveness of follicles to follicular stimulating hormone (FSH), which will accelerate ovarian senescence and adversely affect oocyte and embryo quality. Since L-carnitine has been previously reported to exert strong antioxidant activity, the present study aimed to explore the possible effects of L-carnitine on OS injury and FSH receptor (FSHR) expression in ovarian GCs, results of which may be of significance for GCs protection. In the present study, OS was induced in vitro in KGN cells by treatment with H(2)O(2). KGN cells were cultured and divided into the following four groups: Blank, OS, and 40 and 80 µmol/l L-carnitine pre-treatment groups. In the OS group, cells showed nuclear pyknosis, mitochondria swelled irregularly whilst featuring fractured cristae. In addition, cell viability, ROS levels, superoxide dismutase levels, glutathione levels, malondialdehyde levels, the mitochondrial membrane potential and FSHR expression, as determined by Cell Counting Kit-8 (CCK-8), 2,7-dichloro-dihydrofluorescein diacetate, spectrophotometry, ELISA, spectrophotometry, JC-1 and western blot analyses, respectively, were all significantly different in the OS group compared with those in the control group. However, malonaldehyde levels, reactive oxygen species levels and the apoptosis rate according to flow cytometry were all significantly increased compared with those in the control. Compared with those in the OS group, the morphology of cells and mitochondria in the L-carnitine pre-treatment groups were improved, whilst cell viability and the expression of FSHR were significantly increased but oxidative stress injury was decreased. The present results suggest that L-carnitine can protect the cells from OS damage induced by H(2)O(2), enhance antioxidant activity whilst suppressing the apoptosis of GCs, in addition to preserving FSHR expression in GCs under OS. Therefore, the present study revealed that the introduction of L-carnitine in clinical medicine or dietary supplement may protect GCs, improve follicular quality and female reproductive function.