Effect of apoptosis of rVvhA on J774A.1 and the related mechanism
Objective To investigate the activity of recombinant Vibrio vulnificus hemolysin (rVvhA) on the apoptosis of J774A.1 cells and the related mechanism. Methods The cytotoxic effect of rVvhA on the growth of J774A.1 cells was identified by MTT, celluar and mitochondrial morphology were observed by transmission electron microscopy, apoptosis or necrosis and mitochondrial membrane potential in J774A.1 cells were measured by flow cytometry, activities of caspase-3 ,-8,-9 were detected by spectrophotometry. Results The viability of J774A.1 cells exposed to rVvhA was inhibited, and it is dependent on dose. Celluar and mitochondrial uhrastructure both occurred to change obviously observed by transmission electron microscopy in J774A.1 treated by 2.0 HU/ml and 3.0 HU/ml rVvhA after 8 hours; and 3.0 HU/ml rVvhA group had a better cytotoxic effect on J774A.1 than that of 3.0 HU/ml rVvhA group. The percentage of apoptosis is (7.80±0.62)%, (12.33±0.12)%, respectively. Besides, the mitochondriai membrane potential also reduced, because the rate of fluorescence which is green increase 1.0% (normal) to 9.8% (2.0 HU/ml rVvhA) and 39.2% (3.0 HU/ml rVvhA). At the same time, the caspase-3, -9 activity increased gradually, but caspase-8 remained unchanging. In J774A.1 cells treated by 3.0 HU/ml rV-vhA + caspase-3 inhibitor(Ac-DEVD-FMK) or caspase-9 inhibitor(Ac-LEHD-FMK), The apoptosis of was reduced to(6.23±3.95)% ,(9.60±3.14)%, and the activity of caspase-3, -9 reduced, too. Conclusion The rVvhA has cytotoxic effect on J774A.1. Mitochondria-mediated apoptosis pathway which is dependent on caspase may be related to apoptosis induced by rVvhA in J774A.1. 
 
Key words: 
Vibrio vulnificus;  Cytolysin;  J774A.1;  Apoptosis;  Mitochondria