The mechanism of NF-κB-TERT feedback regulation of granulosa cell apoptosis in PCOS rats with follicular development disorder

Background The aim of this study is to investigate whether TERT mediates chronic inflammation and induces granulosa cell apoptosis by participating in the regulation of the NF-κB signaling pathway. Methods Letrozole combined with high-fat diet was used to establish a PCOS rat model, which was divided into Ctrl group and PCOS group. The expressions of inflammatory factors (NF-κB, IL-6,TNF-α), apoptotic factors (NF-κB, IL-6,TNF-α) and telomerase gene TERT in the ovaries were detected by IHC, qRT-PCR and WB. The serum testosterone level was detected by radioimmunoassay. Quantitative PCR was performed to measure relative telomere length. KGN cells were cultured in vitro and divided into blank control group, LPS treatment group, LPS + NF-kB inhibitor group and LPS + TERT inhibitor group. The cell function was analyzed. Results: Most of the rats in the PCOS group were in the estrus phase, indicating that the estrus cycle was disordered in the PCOS group. Body weight and serum testosterone levels were significantly increased in PCOS rats. HE staining showed that PCOS rats had a significant increase in ovarian cystic follicles and thinning of the granulosa cell layer. The expression levels of NF-κB and its downstream inflammatory factors, telomerase TERT and pro-apoptotic factors in the ovary of PCOS rats are significantly increased, while the expression levels of anti-apoptotic factors are significantly decreased. Telomere length in PCOS rats was also significantly higher than that in Ctrl rats. By correlation analysis, NF-κB and its downstream inflammatory factors and TERT were significantly correlated with apoptosis-related factors, and positively correlated with pro-apoptotic factors, and negatively correlated with anti-apoptotic factors. At the cellular level, the expression levels of NF-κB and its downstream inflammatory factors, telomerase TERT and pro-apoptotic factors were significantly increased, while the expression levels of anti-apoptotic factors were significantly decreased after LPS treatment, which were restored in the LPS + NF-kB inhibitor group and LPS + TERT inhibitor group. Conclusion TERT may participate in the regulation of NF-κB signaling pathway and activate the downstream inflammatory factors IL-6 and TNF-α to mediate the chronic inflammatory response and induce ovarian granulosa cell apoptosis in PCOS.