Regulation of xanthine dehydrogenase and xanthine oxidase activity and gene expression in cultured rat pulmonary endothelial cells

Abstract

The central importance of xanthine dehydrogenase (XDH) and xanthine oxidase (XO) in the pathobiochemistry of a number of clinical disorders underscores the need for a comprehensive understanding of the regulation of their expression. This study was undertaken to examine the effects of cytokines on XDH/ XO activity and gene expression in pulmonary endothelial cells. The results indicate that IFNγ-7 is a potent inducer of XDH/XO activity in rat lung endothelial cells derived from both the microvasculature (LMVC) and the pulmonary artery. In contrast Interferon-α/β tumor necrosis factor-α interleukin-1 or -6 lipopolysaccharide and phorbol myristate acetate have no demonstrable effect. The increase in XDH/XO activity requires new protein synthesis. By Northern analysis IFN-γ markedly increases the level of the 5.0-kb XDH/XO mRNA in IMVC. The increase is due in part to increased transcription rate of the XDH/XO gene. Transcriptional activation does not require new protein synthesis. The physiologic relevance of these observations was evaluated by administering IFN-γ to rats. Intraperitoneal administration leads to an increased XDH/XO activity and XDH/XO mRNA level in rat lungs. In sum IFN-γ is a potent and biologically relevant inducer of NDH/XO expression; the major site of upregulation occurs at the transcriptional level.