Induction of heme oxygenase-1 by phenylarsine oxide. Studies in cultured primary liver cells

Heme oxygenase-1, the major inducible isoform of heme oxygenase (HO), can b e induced by heme and numerous other physical and chemical factors, many of which cause cellular stress. This has led to the realization that HO-1 is a major highly conserved stress or heat shock protein. Recent work has impl icated activation of mitogen-activated protein kinases and other kinases in the mechanism of induction of HO-1, and suggested that signal transduction pathways through tyrosine kinases are involved in induction of HO-1 gene e xpression by stress inducers. We hypothesized that phenylarsine oxide (PAO) , an inhibitor of protein tyrosine phosphatases (PTPs), might up-regulate t he HO-1 gene. Here, we show that a remarkably brief (1-15 min) exposure of normal hepatocytes to low concentrations (0.5-3 muM) of PAO produces a mark ed increase in mRNA and protein of HO-1. This increase is comparable to the level obtained by addition of heme (20 muM), and occurs without producing changes in cellular glutathione levels or stabilization of HO-1 message. Pr eincubation of cells with inhibitors of protein synthesis decreased the abi lity of PAO to increase levels of HO-1 mRNA, suggesting that the inductive effect requires de novo protein synthesis. Addition of thiol donors abrogat ed the PAO-mediated induction of HO-1 in a dose dependent fashion. Addition of genistein, a tyrosine kinase inhibitor, blunted the induction produced by both PAO and heme. After brief incubations with PAO or heme, cell extrac ts showed comparable increases in levels of protein tyrosine phosphorylatio n in general, and specifically in ZAP70 kinase. Our results are consistent with the proposition that induction of HO-1 by PAO involves inhibition of s pecific PTP(s), and that the mechanisms of induction of HO-1 by PAO and by heme may share some common pathways.