Study On The Mechanism Of HIV - 1 Infection In Monocytes And Macrophages

Objective Acquired immune deficiency syndrome (AIDS) causes serious damage to human health and life. How to eliminate the HIV cellular reservoirs has been the focus of AIDS research, and monocyte-macrophage is one of the important HIV-1cellular reservoirs, because it would resist to apoptosis induced by HIV-1. To provide theoretical and application basis for eradication of HIV-1monocyte-macrophages reservoirs, our study explore the mechanism of apoptosis of HIV-1infectded monocyte-macrophages.Methods In this study, THP1monocytes and THP1monocyte-derived macrophages are used as the cell model. Cells were infected by HIV-1(R5-tropic), and then stained by PE-Annexin-V and7-AAD to assay the rate of cell apoptosis by flow cytometry to confirme the anti-apoptotic effect of THP1derived macrophages infected by HIV-1. To confirme the relationship between pro-or anti-apoptotic molecules and the anti-apoptotic effect of macrophages infected by HIV-1, the expression of pro-and anti-apoptotic molecules of Bcl-2family in HIV-1infected macrophages was assayed by western blotting. In order to eliminate HIV-1-infected macrophages, we used classical apoptosis inducers to induce HIV-1-infected macrophage apoptosis. Then, galectin-3-induced HIV-1-infected macrophage apoptosis was analyzed by Annexin-V/7-AAD staining and detection of loss of mitochondrial membrane potential. Besides we verified this result in the rhesus monkey model of AIDS.Based on our previous observations, we go deep into study the mechanism of apoptosis. We used different caspase inhibitors, detection of caspase-3substrate PARP and activity of caspase-3to analyze the caspase apoptosis pathway. We detected the expression of pro-apoptotic and anti-apoptotic molecules, cytochrome C, AIF and Endo G in HIV-1-infected macrophages induced by galectin-3.In addition, in order to clarify the impact of90K/Mac-2BP in the apoptosis of HIV-1infected monocyte-macrophage, we knocked down the90K/Mac-2BP gene in human monocyte-macrophage cell line U937by gene silencing.Results We confirmed the anti-apoptotic effect of THP1derived macrophages infected by HIV-1, namely the cell death rate of HIV-1infected monocytes is:con (6.99±0.54)%, infected (28.82±1.03)%, they showed significant differences, and the cell death of HIV-1-infected-THP1derived macrophages were:con (5.42±0.47)%, infected (7.91±0.49)%, they showed no significant differences. Our study found that galectin-3could induce monocytes apoptosis, cell death rates were:con (6.13±0.70)%, galectin-3(20.46±0.62)%. Interestingly, we found that galectin-3could induce HIV-1-infected macrophage apoptosis, the cell death rates of macrophages were:con (5.31±0.18)%, galectin-3(11.2±0.32)%. Cell death rates of HIV-1-infected macrophage were:con (15.56±1.56)%, galectin-3(29.78±1.94)%, there existed significant difference between the two groups.On these basis, we firstly confirmed that galectin-3induced the apoptosis of monocyte (THP1) and HIV-1-infected-macrophages (THP1-MACs HIV-1+) is distict from classical death pathways triggered by FasL or TRAIL, which is caspase independent. We also observed that the apoptosis of monocytes (THP1) and HIV-1-infected-macrophages (THP1-MACs HIV-1+) induced by galectin-3have nothing to do with pro-apoptotic proteins (Bax), anti-apoptotic proteins (Mcl-1, Bcl-2, Bcl-xL), also have nothing to do with mitochondrial associated event:cytochrome C (Cyto C) and apoptosis inducing factor (AIF), but closely related to the nuclear transferation of endonuclease G (Endo G).Furthermore, we found that the percentages of Annexin V+cells without90K/Mac-2BP knock-down were (16.27±0.30)%by HIV-1infection. The percentages of them with90K/Mac-2BP knock-down were (31.26±0.35)%,(25.76±0.30)%,(23.69±0.33)%respectively. The increase of cell apoptosis rate for HIV-1-infected U937cells by90K/Mac-2BP siRNA transfection was significantly greater than that for HIV-1-infected untreated cells.Conclusion Our study found that galectin-3could induce HIV-1infected monocyte-macrophage apoptosis and its mechanism was associated with Endo G nuclear transfer, also observed that90K/Mac-2BP as a ligand of galectin-3could increase the apoptosis of HIV-1-infected-monocyte-macrophages when it is silenced. These results put forward a new theory to eradication of HIV-1monocyte-macrophage reserviors, and provide new clues for the development of AIDS treatment drugs from the perspective of the eradication of HIV-1reserviors.