Polychlorinated biphenyls activate caspase-3-like death protease in vitro but not in vivo

We prove here that serum albumin inhibits apoptosis induced by polychlorina ted biphenyls (PCBs), confirming that serum albumin binds to PCB, and that the albumin-PCB complexes inhibit apoptosis in HL-60 cells. We found that P CB (50 muM) increased the activity of caspase-3-like protease when HL-60 ce lls, as well as splenocytes, were cultured in "serum-free medium." Benzylox ycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk) inhibited apoptosis in cells cultured in the serum-free medium containing 50 muM PCB. To elucidat e whether or not PCBs induce apoptosis in vivo, we examined apoptosis of sp lenocytes by administering PCB to ICR mice (100, 500, 1000 mg.kg(-1).d(-1)) for 5d and characterizing splenocytes. Interestingly, splenocytes treated with PCB did not show any changes characteristic of apoptosis. These result s demonstrate that PCB activates the caspase-3-like death protease in vitro in serum-free medium, but does not induce apoptosis of splenocytes in vivo , suggesting that blood serum may mask the apoptosis induced by PCB.