Septin4 regulates endoplasmic reticulum stress and apoptosis in melatonin‑induced osteoblasts.

Idiopathic scoliosis (IS) is a spinal 3‑dimensional deformity with an unknown cause. Melatonin is secreted by the pineal body and contributes to the occurrence and progression of IS. In our previous preliminary study, it was reported that high concentrations of melatonin can induce osteoblast apoptosis, thus acting as an IS treatment, but the mechanism of action is unknown. Therefore, the present study was performed to further investigate the possible mechanism underlying the efficacy of melatonin as a treatment for IS. The present results indicated that high concentrations of melatonin mediate endoplasmic reticulum stress (ERS)‑induced apoptosis in hFOB 1.19 cells, and this resulted in a significant and dose‑dependent increase in the expression of Septin4, as well as the expression levels of glucose‑regulated protein (GRP)78, GRP94 and cleaved caspase‑3. Furthermore, osteoblasts were overexpressed with Septin4 and the mechanism via which melatonin induces osteoblast ERS was demonstrated to be via the regulation of Septin4. In addition, it was indicated that cytoskeleton destruction, cell morphology changes and the decrease in the number of cells were aggravated after osteoblasts were overexpressed with Septin4, as indicated by phalloidin and DAPI staining. Collectively, the present results suggest that the Septin4 protein may be a target of ERS in melatonin‑induced osteoblast apoptosis, which is involved in bone metabolism diseases, thus providing novel evidence for clinical melatonin treatment of IS.