The Regulatory Role Of Mcl-1 In Apoptosis Of Mouse Peritoneal Macrophage Infected With M. Tuberculosis Strains That Differ In Virulence

Purpose: Myeloid cell leukaemia-1 (Mcl-1) is a valuable target in tumour treatments. However, several reports have suggested that Mcl-1 may play a role in tuberculosis infection. Therefore, we investigated the function of Mcl-1 in tuberculosis infection and the underlying regulatory mechanism. Methods: Mcl-1-shRNA was used to down-regulate Mcl-1 expression in BCG-, H37Ra-, H37Rv- and XJ-MTB-infected mouse peritoneal macrophages. TUNEL staining detected macrophage apoptosis. The colony-forming units (CFUs) were determined to assess the Mycobacterium tuberculosis (MTB) clearance after down-regulating Mcl-1. Immunohistochemical analysis of Mcl-1 expression in mouse peritoneal macrophages was performed. Haematoxylin and eosin staining detected pathologic damage of the liver, spleen, lung, and kidney in mice. Real-time PCR and Western blotting determined the expression of cytochrome-c in Mcl-1-shRNA-treated mouse peritoneal macrophages infected with MTB strains that differ in virulence. Results: Mcl-1-shRNA significantly promoted host macrophage apoptosis and cytochrome-c induction, and the apoptotic induction of the XJ-MTB and H37Rv strains was stronger than the H37Ra and BCG strains (P<0.05). Apoptotic protein cytochrome-c levels continued to increase in mouse peritoneal macrophages infected MTB before and after treatment, Caspase-8 levels only slightly increased after Mcl-1-shRNA-treated (P<0.05), but the increase of Cytochrome-c have no significant differences compared with Caspase-8 levels (P>0.05). Conclusion: Mcl-1-shRNA intervention effectively down-regulated Mcl-1 expression, significantly increased host macrophage apoptosis, and induced cytochrome-c expression in mouse peritoneal macrophages infected with MTB strains of different virulence, and these changes were influenced by the virulence of the MTB strains. The mitochondria-mediated intrinsic apoptotic pathway play an important role before Mcl-1-shRNA-trated, and then with the extrinsic apoptotic pathway co-regulate host macrophage apoptosis.