[J774A.1 cell apoptosis induced by Leptospira interrogans and effects of caspase-3, -6 activation on apoptosis].

OBJECTIVE:To investigate the apoptosis of J774A.1 cells induced by Leptospira interrogans and the effect of caspase-3, -6 activation on the apoptosis. METHODS:Mouse monocyte-macrophage like cell line J774A.1 was infected by L.interrogans serogroup Icterohaemorrhagiae serovar icterohaemorrhagiae Lai strain 56601. The apoptosis or necrosis of infected cells was examined by flow cytometry using fluorescein labeling FITC-Annexin V/PI. The activity of caspase-3, -6, and their cleaved substrates PARP and Lamin A/C were measured by fluorometry and Western Blotting, respectively. RESULT:L. interrogans strain Lai was able to induce apoptosis of J774A.1 cells and the maximal apoptotic rate was(48.81+/-5.95)% when microbe: cell ratio was 100: 1. The maximal activities of caspase-3 and -6 in the infected J774A.1 cells were (1453.41+/-36.07) and (618.65+/-39.82) FU, respectively, which were 16.38- and 9.98-fold of those uninfected cells. PARP and Lamin A/C in the infected cells were detected. Caspase-3 and -6 inhibitors remarkably blocked the L. interrogans-induced apoptosis in J774A.1 cells. CONCLUSION:L. interrogans is able to induce the apoptosis of J774A.1 cells and intracellular caspase-3 and -6 are closely associated with the apoptosis.