Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hypoxia and reoxygenation (H/R) generate oxygen free radicals that result in renal cell injury. We tested the roles of calcium and calmodulin in mediating xanthine oxidase-derived oxygen free radical production during H/R. Lowering extracellular Ca2+ attenuated lethal cell injury. H/R increased superoxide radical production over basal levels, whereas removing extracellular Ca2+ before hypoxia decreased superoxide radical production to basal levels. Pretreatment with either 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride or thapsigargin, to inhibit release or deplete stores of intracellular Ca2+, did not affect injury following H/R. Ionomycin increased lactate dehydrogenase release during H/R but did not increase superoxide radical to levels greater than that observed for H/R alone. The calmodulin inhibitors trifluoperazine, calmidazolium, or N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide decreased cell injury to varying degrees. Trifluoperazine also decreased superoxide radical production during H/R and was shown to inhibit the conversion of xanthine dehydrogenase to xanthine oxidase. Cell injury and superoxide radical production correlated with cytosolic free Ca2+ during H/R as determined with the Ca(2+)-sensitive fluoroprobe indo 1. Cytosolic free Ca2+ increased slightly during hypoxia and showed a dramatic increase as soon as cells were reoxygenated. Cells incubated in a Ca(2+)-free medium actually showed a small decrease in intracellular Ca2+ despite H/R. In summary, Ca2+ derived from extracellular sources promoted superoxide radical production and renal cell injury by a calmodulin-dependent conversion of xanthine dehydrogenase to xanthine oxidase, a major source of oxygen free radicals during H/R.
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PMID:Calcium and free radicals in hypoxia/reoxygenation injury of renal epithelial cells. 830 79