Role of HIF-1α/BNIP3 signaling pathway in regulating macrophage autophagy induced by BCG infection

Abstract:

[Background] Hypoxia-inducible factor 1-alpha (HIF-1α) is a key factor in response to cellular hypoxia and plays an important role in erythropoiesis, angiogenesis, energy metabolism and regulation of host immune metabolism.[Objective] To investigate the effects of HIF-1α/Bcl-2-adenovirus E1B 19-kDa interacting protein 3 (BNIP3) signaling pathway on the BCG infection-induced autophagy of macrophage RAW 264.7 cells. [Methods] Small interfering RNA of HIF-1α, siHIF-1α, was constructed, and after the transfection of siHIF-1α and/or Bacillus Calmette-Guerin (BCG) infection of RAW 264.7 cells, the autophagy rate of the cells was detected by flow cytometer. Western blotting or immunofluorescence technique was employed to determine the protein levels of HIF-1α, BNIP3, LC3, Beclin 1, Rheb and mTOR.[Results] BCG infection up-regulated the expression of LC3 and HIF-1α in RAW 264.7 cells. The transfection of siHIF-1α down-regulated the levels of HIF-1α, BNIP3, LC3, and Beclin 1 and decreased the autophagy rate of the macrophages after BCG infection. Moreover, siHIF-1α promoted the expression of Rheb and p-mTOR.[Conclusion] Our results indicated that the knockdown of HIF-1α inhibited the HIF-1α/BNIP3 signaling pathway, thereby activating the mTOR pathway and inhibiting autophagy in RAW 264.7 cells after BCG infection.