Protective effects of melatonin against hypoxia-induced TM3 cell damage via suppression of the TGF-β pathway

This study aimed to explore whether melatonin protects TM3 Leydig cells from cobalt (II) chloride (CoCl₂)-induced hypoxia through the transforming growth factor beta (TGF-β) signaling pathway. Cells were divided into four groups: a control group without treatment (Group 1), a melatonin group (10.00 ng mL^-1; Group 2), a group treated with CoCl₂ (100 µM) to induce hypoxia (Group 3), and a melatonin + CoCl₂ group (Group 4). After 96 hr of incubation, cell viability was assessed using the MTT assay, and transforming growth factor beta 1, activin receptor-like kinase-5, and bone morphogenetic protein 4 gene and protein expressions were measured through RT‑PCR and western blotting. The CoCl₂ and melatonin + CoCl₂ groups exhibited significantly diminished cell viability compared to the control. However, melatonin treatment enhanced survival in the CoCl₂-exposed cells. Notably, transforming growth factor beta 1 expression was elevated in all groups. Activin receptor-like kinase-5 (gene and protein expression increased in CoCl₂-treated groups but was lower in the melatonin + CoCl₂ group. Melatonin treatment reduced bone morphogenetic protein 4 expression compared to the control, while CoCl₂ groups showed increased bone morphogenetic protein 4 levels. These findings suggest melatonin's potential as a therapeutic agent against oxidative stress and hypoxia in TM3 cells through its antioxidant properties.