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 IFN-'y 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-affi, tumor necrosis factor-a, interleukin-i 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-"y markedly increases the level of the 5.0-kb XDH/XO mRNA in LMVC. 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-'y to rats. Intraperitoneal administration leads to an increased XDH/XO activity and XDH/XO mRNA level in rat lungs. In sum, IFN-'y is a potent and biologically relevant inducer of XDH/XO expression; the major site of upregulation occurs at the transcriptional level. (J. Clin. Invest. 1992. 89:197-202.)

Sequential activation of JAKs, STATs and xanthine dehydrogenase/oxidase by hypoxia in lung microvascular endothelial cells

“…We found that hypoxia-mediated XDH/XO activation is dependent on the JAK/ STAT pathway in primary cultures of LMVEC. We demonstrated that the XDH/XO activity significantly increased by hypoxia, consistent with the increased phosphorylation or activation of XDH/XO in response to hypoxia in other cells (Terada et al, 1992;Dupont et al, 1992;Kayyali et al, 2001;Mervaala et al, 2001;Terada et al, 1997;Poss et al, 1996;Sohn et al, 2003;Kang et al, 2006). Interestingly, our data demonstrated that XDH/XO activation induced by could be inhibited by either depletion of IL6 using IL6 antibodies, pretreatment with the JAK2 inhibitor AG490 or transient expression of the JAK-STAT pathway blocker SOCS3 and their inhibitory effect on the XDH/XO activation was at a similar magnitude.…”

“…It has been demonstrated that hypoxia activates XDH/XO, an important source of reactive oxygen species (ROS) (Terada et al, 1992;Dupont et al, 1992;Kayyali et al, 2001;Mervaala et al, 2001;Terada et al, 1997;Poss et al, 1996;Sohn et al, 2003;Kang et al, 2006). However, the molecular mechanism underlying the hypoxia-mediated activation of XDH/XO remains largely unknown.…”

Oxygen radical inhibition of nitric oxide-dependent vascular function in sickle cell disease

“…The immunohistochemical localization of increased XO in the vessel wall of SCD mice could be a manifestation of either the binding and uptake of circulating XO by vascular endothelial cells (33,50,51) or the increased expression of XOR by activated vascular endothelium (52). Considering the high association constant of XO for binding to vascular endothelium (K d ϭ 6 nM; ref.…”

Reactive Oxygen Species in Inflammation and Tissue Injury

“…The activity of XDH/XO is specifically induced by IFN-c in lung microvascular endothelial cells and the pulmonary artery endothelial cells. In contrast, IFN-a/b, TNF-a, IL-1 or -6, LPS, and PMA have no effect on the activity of XDH/XO (104). The activity of XO is up-regulated in the airway inflammatory disorders, ischemia reperfusion injury, atherosclerosis, diabetes, and autoimmune disorders such as rheumatoid arthritis (332).…”