Carbamazepine disrupts the hypothalamic-pituitary-testicular axis and induces hormonal imbalances and sperm damage through activating GABBR2 to inhibit AC/cAMP/PKA pathway.

Carbamazepine (CBZ), a widely prescribed antiepileptic drug, is known to cause male reproductive toxicity, yet the underlying biological pathways remain poorly characterized. This study comprehensively investigated the impact of CBZ on the hypothalamic-pituitary-testicular (HPT) axis using integrated in vivo and in vitro models to decipher the precise molecular mechanisms involved. Rats subjected to long-term exposure (12 weeks) to CBZ at doses of 100, 200, and 400 mg/kg showed structural damage in the hypothalamus, pituitary, and testes. Concurrently, serum levels of gonadotropin-releasing hormone (GnRH), follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone were reduced, indicating impairment of the HPT axis function. In-depth mechanistic studies demonstrated that CBZ suppressed the adenylyl cyclase (AC)/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway by upregulating the expression of gamma-aminobutyric acid type B receptor subunit 2 (GABBR2) protein, thereby triggering apoptosis of hypothalamic GnRH neurons. When GABBR2 was knocked down in GT1-7 cells (an immortalized mouse hypothalamic GnRH neuronal cell line), the AC/cAMP/PKA inhibition induced by CBZ was significantly attenuated, apoptosis was reduced, and GnRH secretion was partially restored. These findings indicate that activation of GABBR2, by repressing the AC/cAMP/PKA pathway, plays a pivotal role in CBZ-induced apoptosis of hypothalamic neurons, reduction of GnRH levels, and disruption of the HPT axis. This provides a new perspective for understanding CBZ-induced male reproductive toxicity.