Exogenous H2S exerts biphasic effects on porcine mammary epithelial cells proliferation through PI3K/Akt-mTOR signaling pathway

This study aimed to investigate the effects of exogenous H2S on the proliferation of porcine mammary gland epithelial cells (PMECs) and explore the underlying mechanisms. We found that exposure of PMECs to NaHS, at concentrations ranging from 10 to 200 mu M, stimulated cell proliferation. However, high concentration of NaHS (600 mu M) inhibited PMECs proliferation. Accordingly, 10 mu M NaHS significantly increased the percentage of cells undergoing DNA replication, elevated the mRNA and/or protein expression of Cyclin A2, Cyclin D1/3, Cyclin E2 and PCNA, and decreased p21 mRNA expression. In contrast, 600 mu M NaHS elicited the opposite effects to that of 10 mu M NaHS. In addition, PI3K/Akt and mTOR signaling pathways were activated or inhibited in response to 10 or 600 mu M NaHS, respectively. Furthermore, the promotion of PMECs proliferation, the change of proliferative genes expression, and the activation of mTOR signaling pathway induced by 10 mu M NaHS were effectively blocked by PI3K inhibitor Wortmannin. Similarly, inhibition of mTOR with Rapamycin totally abolished the 10 mu M NaHS-induced stimulation of PMECs proliferation and alteration of proliferative genes expression, with no influence on PI3K/Akt signaling pathway. Moreover, constitutive activation of Akt pathway via transfection of Akt-CA completely eliminated the inhibition of PMECs proliferation and mTOR signaling pathway, and the change of proliferative genes expression induced by 600 mu M NaHS. In conclusion, our findings provided evidence that exogenous H2S supplied by NaHS exerted biphasic effects on PMECs proliferation, with stimulation at lower doses and suppression at high dose, through the intracellular PI3K/Akt-mTOR signaling pathway.