Adenovirus-mediated expression of a dominant negative mutant of p65/RelA inhibits proinflammatory gene expression in endothelial cells without sensitizing to apoptosis

Abstract

We hypothesized that blocking the induction of proinflammatory genes associated with endothelial cell (EC) activation, by inhibiting the transcription factor nuclear factor kappaB (NF-kappaB), would prolong survival of vascularized xenografts. Our previous studies have shown that inhibition of NF-kappaB by adenovirus-mediated overexpression of I kappaB alpha suppresses the induction of proinflammatory genes in EC. However, I kappaB alpha sensitizes EC to TNF-alpha-mediated apoptosis, presumably by suppressing the induction of the NF-kappaB-dependent anti-apoptotic genes A20, A1, manganese superoxide dismutase (MnSOD), and cellular inhibitor of apoptosis 2. We report here that adenovirus mediated expression of a dominant negative C-terminal truncation mutant of p65/RelA (p65RHD) inhibits the induction of proinflammatory genes, such as E-selectin, ICAM-1, VCAM-1, IL-8, and inducible nitric oxide synthase, in EC as efficiently as does I kappaB alpha. However, contrary to I kappaB alpha, p65RHD does not sensitize EC to TNF-alpha-mediated apoptosis although both inhibitors suppressed the induction of the anti-apoptotic genes A20, A1, and MnSOD equally well. We present evidence that this difference in sensitization of EC to apoptosis is due to the ability of p65RHD, but not I kappaB alpha, to inhibit the constitutive expression of c-myc, a gene involved in the regulation of TNF-alpha-mediated apoptosis. These data demonstrate that it is possible to block the expression of proinflammatory genes during EC activation by targeting NF-kappaB, without sensitizing EC to apoptosis and establishes the role of c-myc in controlling induction of apoptosis during EC activation. Finally, these data provide the basis for a potential approach to suppress EC activation in vivo in transgenic pigs to be used as donors for xenotransplantation.