17β-estradiol protects nucleus pulposus cells from serum deprivation-induced apoptosis and regulates expression of MMP-3 and MMP-13 through promotion of autophagy

Serum deprivation is a likely contributor to intervertebral disc (IVD) degeneration (IVDD).17β-estradiol (E2) have been noted to protect nucleus pulposus cells (NPCs) against apoptosis. Autophagy and apoptosis play a paramount role in maintaining the homeostasis of IVD. So far, little research has been published on whether autophagy plays a role for the E2 mediated protection of NPCs. The aim of this study is to understand whether autophagy is involved in the protective effect of E2 against serum deprivation-induced cell apoptosis and expression of matrix metalloproteinase (MMP)-3 and MMP-13. mCherry-GFP-LC3-adenovirus transfection is used to monitor autophagy detection. The expression levels of autophagy-related proteins were measured by Western blotting, Apoptosis and MMPs were detected by flow cytometry and Western blotting. Accordingly, Autophagy and apoptosis was detected in NP cells under serum deprivation conditions, the autophagy incidence began to reached a peak value at 48 h, the apoptosis and MMPs incidence began reached a minimum value treat with E2 (10−7 M). Whereas the combined use of E2 and 3-MA led to a dramatic decrease in autophagy, while aberrantly elevated expression levels of apoptotic and MMPs. These data suggest that serum deprivation-induced apoptosis and MMP-3, MMP-13, which was efficiently suppressed by the E2 through promoting autophagy in rat NPCs.