LukS-PV induces apoptosis in acute myeloid leukemia cells mediated by C5a receptor.

LukS-PV is one of the two components of Panton-Valentine leucocidin (PVL). Our previous study showed that LukS-PV can induce apoptosis in human acute myeloid leukemia (AML) THP-1 and HL-60 cells. C5aR (C5a receptor) is the receptor for PVL, but whether C5aR plays a key role in LukS-PV induced apoptosis is unclear. The aim of this study was to establish whether C5aR plays a physiological role in apoptosis of leukemia cells induced by LukS-PV. We investigated the role of C5aR in leukemia cell apoptosis induced by LukS-PV by pretreatment of THP-1 and HL-60 cells with C5aR antagonist and transfection to knockdown C5aR in THP-1 cells or overexpress C5aR in Jurkat cells before treatment with LukS-PV. Cell apoptosis was analyzed by staining with Annexin V/propidium iodide or Annexin V-PE/7-AAD. Mitochondrial membrane potential (MMP) was determined using JC-1 dye. The expression of apoptosis-associated genes and proteins was identified by qRT-polymerase chain reaction and Western blotting analysis, respectively. As the C5aR antagonist concentration increased, the rate of apoptosis induced by LukS-PV decreased, the MMP increased, and expression of pro-apoptotic Bax and Bak genes and proteins was downregulated while that of anti-apoptotic Bcl-2 and Bcl-x genes and proteins was upregulated. Knockdown of C5aR also decreased LukS-PV-induced THP-1 cell apoptosis. LukS-PV did not induce apoptosis of Jurkat cells, which have no endogenous C5aR expression; however, LukS-PV did induce apoptosis in Jurkat cells after overexpression of C5aR. Correspondingly, the MMP decreased and Bax and Bak were upregulated while Bcl-2 and Bcl-x were downregulated. LukS-PV can induce apoptosis in AML cells by targeting C5aR. C5aR may be a potential therapeutic target for AML and LukS-PV is a candidate targeted drug for the treatment of AML.