Topic
Xanthine
About: Xanthine is a research topic. Over the lifetime, 4046 publications have been published within this topic receiving 129820 citations. The topic is also known as: Xanthine.
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TL;DR: The substrate specificity and other characteristic properties of xanthine oxidase have been determined and it is found that among all methylated uric acids, which are formed after administration of methylated xanthines to animals, only the l-methyl derivative can be produced by direct action of X0.
105 citations
TL;DR: An inhibition of enzymes involved in signaling rather than a scavenging of superoxide anion radicals dominates in fMet-Leu-Phe-stimulated neutrophils exposed to flavonols.
105 citations
TL;DR: CSF hypoxanthine, xanthine and uric acid levels appear superior to lactate in reflecting glutamate-mediated excitotoxicity in neurological patients, which is likely related to preserved glial and neuronal uptake mechanisms.
105 citations
TL;DR: Higher doses of caffeine can cause an increase in A 1 agonist binding without a corresponding change in A1 mRNA or in A2A antagonist binding, suggesting that the adaptive changes seen upon prolonged caffeine treatment may be in sites different from A1 receptors.
105 citations
TL;DR: Endothelial XO and XDH expression are strongly dependent on H2O2 and calcium, and Stimulation of XDH conversion to XO may represent a feed-forward mechanism whereby H2 O2 can stimulate further production of ROS.
Abstract: Objective— We have previously demonstrated that endothelial xanthine oxidase (XO) levels are dependent on the NADPH oxidase. We postulated that H 2 O 2 may modulate the irreversible conversion of xanthine dehydrogenase (XDH) to XO and sought to examine mechanisms involved. Methods and Results— H 2 O 2 (100 μmol/L) decreased bovine aortic endothelial cell (BAEC) XDH protein expression, and metabolic labeling studies indicated that H 2 O 2 stimulated conversion of XDH to XO. The decline in XDH was mimicked by the reactive oxygen species (ROS) generating compounds SIN-1 and Menadione, as well as by stimulating BAECs with angiotensin II (200 nmol/L). BAPTA-AM prevented the decline in XDH by H 2 O 2 , indicating that it was calcium-dependent. In keeping with calcium acting downstream of H 2 O 2 , the calcium ionophore A23187 (1 μmol/L) caused XDH-to-XO conversion, and this was not prevented by the antioxidants. In addition, XDH-to-XO conversion was blocked by 2-APB and NO donors and induced by thapsigargin and M-3M3FBS, implicating phospholipase C and endoplasmic reticulum calcium stores in this process. Conclusions— Endothelial XO and XDH expression are strongly dependent on H 2 O 2 and calcium. Stimulation of XDH conversion to XO may represent a feed-forward mechanism whereby H 2 O 2 can stimulate further production of ROS.
104 citations