Inhibition of JAK2 by AG490 promotes TNF-α-induced apoptosis by inhibiting autophagy in MC3T3-E1 cells.

Tumor necrosis factor-alpha (TNF-α), one of the pro-inflammatory factors in osteoporosis, has a strong enhancement effect on osteoclastogenesis and disruption of osteoblast survival and function. JAK2 participates in a wide range of biological processes, including bone homeostasis, but its function in osteoblast survival in inflammatory environments remains unknown. In this study, flow cytometry and immunofluorescence staining of LC3B were performed under TNF-α stimulation in MC3T3-E1 cells. Apoptosis-related protein Cleaved PARP and autophagy-related protein LC3 were upregulated, meanwhile, p62 was downregulated by TNF-α. JAK2 signaling was also activated in the process. AG490 was used to inhibit JAK2 signaling, which promoted apoptosis and attenuated autophagy induced by TNF-α. Enhancement of autophagy by rapamycin reversed the promotional effect of AG490 on apoptosis, and the autophagy inhibitor chloroquine further enhanced apoptosis. Western blot analysis showed that the STAT3, Akt, and Erk signaling pathways are involved in AG490 treatment. This study demonstrated for the first time that JAK2 inhibition by AG490 may play a crucial role in TNF-α-induced apoptosis by inhibiting autophagy and inhibiting the STAT3, Akt, and Erk signaling pathways.