Orexin-A/OX1 Receptor Regulates Autophagy, Mitochondrial Autophagy, and Cortisol Secretion in Human Adrenocortical Cells Through the mTORC1/P70s6k1 Signaling Pathway

Orexin-A is a neuropeptide responsible for many physiological activities in the central nervous system and peripheral tissues. We found that orexin-A regulates proliferation and apoptosis in human adrenocortical cells, but its effects on autophagy and mitochondrial autophagy remain unclear. We aimed to investigate the effects of orexin-A/orexin type 1 receptor (OX1R) on cortisol secretion, autophagy, and mitochondrial autophagy in human adrenocortical cells. Transmission electron microscopy and immunofluorescence were used to detect autophagosomes. The levels of expression of LC3II/LC3I, beclin-1, P62, TOM20, HSP60, mTORC1, and p70s6k1 were determined by western blotting. The levels of secreted cortisol were measured using an enzyme-linked immunosorbent assay. Our findings showed that orexin-A inhibited autophagy and mitochondrial autophagy, whereas increased cortisol secretion. Phosphorylation of mTORC1 and p70s6k1 was increased by orexin-A, whereas the OX1R antagonist abolished these effects. Antagonists for mTORC1 and p70s6k1 partially blocked the orexin-A-mediated inhibition of autophagy, mitochondrial autophagy, and increase in cortisol secretion. Treatment of cells with the autophagy inhibitor 3MA and orexin-A led to a further increase in cortisol secretion. In summary, our findings showed that orexin-A/OX1R inhibits autophagy and mitochondrial autophagy and increases cortisol secretion through the mTORC1/ p70s6k1 signaling.