α7 Nicotinic acetylcholine receptor activation rescues mitochondrial dysfunction in gestational diabetes mellitus by competing with p66Shc for VDAC1 binding

Gestational diabetes mellitus (GDM) is associated with placental hormone-induced insulin resistance; however, the mechanisms connecting hyperglycaemia to mitochondrial dysfunction remain incompletely understood. This study aimed to investigate the role of the α7 nicotinic acetylcholine receptor (α7nAChR) in regulating mitochondrial Ca²⁺ homeostasis in trophoblasts under hyperglycaemic stress, and to explore whether its dysregulation contributes to placental mitochondrial pathology in GDM.

Clinical placental samples from GDM pregnancies were analysed to assess α7nAChR expression, mitochondrial morphology and Ca²⁺ signalling pathways. Complementary in vitro and murine models of hyperglycaemia were employed to examine molecular interactions involving α7nAChR, voltage-dependent anion channel 1 (VDAC1) and p66Shc. Mitochondrial-associated endoplasmic reticulum membranes were studied to evaluate pathological Ca²⁺ transfer mechanisms. Pharmacological activation of α7nAChR was performed using PNU-282987 (PNU) or GTS-21, and RNA-seq was conducted to analyse downstream transcriptional changes related to mitochondrial dysfunction and cellular senescence.

Clinical analysis revealed reduced α7nAChR expression, mitochondrial vacuolisation and dysregulated Ca²⁺ signalling pathways in GDM placentas. Under hyperglycaemic conditions, disrupted α7nAChR-VDAC1 interactions facilitated competitive binding of the pro-oxidant p66Shc to VDAC1, promoting pathological Ca²⁺ transfer from the endoplasmic reticulum to mitochondria via mitochondrial-associated endoplasmic reticulum membranes. This led to mitochondrial permeability transition pore overactivation, loss of mitochondrial membrane potential and induction of cellular senescence. Pharmacological activation of α7nAChR with PNU or GTS-21 restored α7nAChR-VDAC1 coupling, attenuated p66Shc-mediated oxidative stress and reversed mitochondrial Ca²⁺ overload. RNA-seq confirmed that PNU treatment normalised gene expression profiles associated with endoplasmic reticulum stress and cellular senescence.

This study identifies a non-canonical role for α7nAChR in maintaining mitochondrial Ca²⁺ homeostasis by competitively regulating VDAC1-p66Shc interactions under hyperglycaemic conditions. The findings reveal a mechanistic link between α7nAChR dysfunction, mitochondrial Ca²⁺ overload and cellular senescence in GDM placentas. Targeting α7nAChR with pharmacological agents such as GTS-21 may offer a novel therapeutic approach to ameliorate mitochondrial dysfunction and placental pathology in GDM by restoring Ca²⁺ dynamics.