Lipotoxicity-induced ER-mitochondrial hypercoupling activates the mtDNA-cGAS-STING-NF-κB axis to drive follicular arrest in metabolically compromised PCOS

Abstract

Polycystic ovary syndrome (PCOS) represents a major cause of anovulatory infertility worldwide, yet the mechanistic nexus linking metabolic perturbations to follicular microenvironment deterioration remains elusive. This study uncovers a novel pathogenic axis wherein lipotoxicity in metabolically compromised PCOS (M-PCOS) patients—irrespective of hyperandrogenemia status—disrupts organelle homeostasis to drive follicular arrest. Integrated analyses of human follicular samples and functional validation in palmitic acid (PA)-treated granulosa cells reveal that lipotoxic stress induces endoplasmic reticulum (ER) stress, triggering ER-mitochondrial hypercoupling and pathological calcium flux. This cascade culminates in mitochondrial permeability transition pore (mPTP)-dependent release of mitochondrial DNA (mtDNA) into the cytosol, where it serves as a potent damage-associated molecular pattern (DAMP) that activates the cGAS-STING-NF-κB inflammatory pathway. Critically, we establish that this pathway operates independently of hyperandrogenemia and represents a core mechanism of granulosa cell dysfunction in M-PCOS. Genetic or pharmacological inhibition of mtDNA release (cyclosporine A), STING signaling (C-176), or ER stress (TUDCA) effectively suppressed the inflammatory cascade and restored cellular homeostasis. Most significantly, melatonin emerged as a superior therapeutic candidate, preserving organelle architecture, preventing calcium dysregulation, blocking mtDNA release, and attenuating inflammation both in vitro and in a PCOS mouse model. These findings redefine our understanding of M-PCOS pathogenesis by establishing lipotoxicity-induced organelle dysfunction as a central driver of follicular arrest, and position melatonin as a clinically translatable therapeutic agent for rescuing follicular development in metabolic PCOS—a population with notoriously poor response to conventional ovulation induction therapies.