Luteinizing hormone regulates testosterone biosynthesis via the cAMP/PKA-CREB pathway in Leydig cells of Tibetan...

Luteinizing hormone (LH), a pivotal gonadotropin, governs the physiological functions of Leydig cells (LCs) and testicular testosterone biosynthesis, and plays an indispensable role in regulating reproductive capacity and gonadal function in male animals. Tibetan sheep are domestic animals endemic to the Qinghai-Tibet Plateau. Improving testosterone biosynthesis in rams is critical for sustaining their reproductive performance. Nevertheless, the molecular mechanism by which LH regulates steroid hormone synthesis in Tibetan sheep LCs remains unclear. In this study, primary LCs isolated from Tibetan sheep were cultured and treated with LH for different durations. We subsequently detected testosterone secretion, the expression of key steroidogenic enzymes, cell proliferation and apoptosis, as well as the levels of molecules related to the cAMP (cyclic adenosine monophosphate)/PKA (protein kinase A) signaling pathway. The experimental results revealed that LH could promote testosterone secretion in LCs, with the optimal effect observed at 24 h. Alongside elevated testosterone biosynthesis, the expression levels of key steroidogenic proteins were significantly upregulated. These findings verified that LH activates the androgen biosynthetic pathway in LCs, facilitates LCs proliferation and suppresses cellular apoptosis. In addition, LH activates the cAMP/PKA-CREB (cAMP response element-binding protein) signaling pathway to facilitate testosterone biosynthesis. Collectively, LH regulates testosterone production in Tibetan sheep LCs through the cAMP/PKA-CREB cascade. This study lays a theoretical foundation for enhancing ram reproductive performance and provides strategies to optimize Tibetan sheep reproductive cycles.