The von Hippel-Lindau gene product inhibits renal cell apoptosis via Bcl-2-dependent pathways

Previous studies have reported a protective role for the von Hippel-Lindau (VHL) gene products against proapoptotic cellular stresses, but the mechani sms remain unclear. In this study, we examined the role of VHL in renal cel ls subjected to chemical hypoxia, using four VHL-negative and two VHL-posit ive cell lines. VHL-negative renal carcinoma cells underwent apoptosis foll owing chemical hypoxia (short-term glucose deprivation and antimycin treatm ent), as evidenced by morphologic changes and internucleosomal DNA cleavage . Reintroduction of VHL expression prevented this apoptosis. VHL-negative c ells displayed a significant (greater than 5-fold) activation of caspase 9 and release of cytochrome c into the cytosol following chemical hypoxia. In contrast, VHL-positive cells showed minimal caspase 9 activation, and abse nce of cytochrome c release under the same conditions. Caspase 8 was only m inimally activated in both VHL-negative and -positive cells. In addition, V HL-positive cells displayed a striking up-regulation of Bcl-2 expression (5 -fold) following chemical hypoxia. Antisense oligonucleotides to Bcl-2 sign ificantly down-regulated Bcl-2 protein expression in VHL-positive cells and rendered them sensitive to apoptosis. Overexpression of Bcl-2 in VHL-negat ive cells conferred resistance to apoptosis. Our results suggest that VHL p rotects renal cells from apoptosis via Bcl-2-dependent pathways.