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.

Dependence on O2- generation by xanthine oxidase of pathogenesis of influenza virus infection in mice.

Abstract: We evaluated various biochemical parameters in influenza virus-infected mice and focused on adenosine catabolism in the supernatant of bronchoalveolar lavage fluid (s-BALF), lung tissue, and serum (plasma). The activities of adenosine deaminase (ADA) and xanthine oxidase (XO), which generates O2-, were elevated in the s-BALF, lung tissue homogenate, and serum (plasma). The elevations were most remarkable in s-BALF and in lung tissue: We found a 170-fold increase in ADA activity and a 400-fold increase in XO activity as measured per volume of alveolar lavage fluid. The ratio of activity of XO to activity of xanthine dehydrogenase in s-BALF increased from 0.15 +/- 0.05 (control; no infection) to 1.06 +/- 0.13 on day 6 after viral infection. Increased levels of various adenosine catabolites (i.e., inosine, hypoxanthine, xanthine, and uric acid) in serum and s-BALF were confirmed. We also identified O2- generation from XO in s-BALF obtained on days 6 and 8 after infection, and the generation of O2- was enhanced remarkably in the presence of adenosine. Lastly, treatment with allopurinol (an inhibitor of XO) and with chemically modified superoxide dismutase (a scavenger of O2-) improved the survival rate of influenza virus-infected mice. These results indicate that generation of oxygen-free radicals by XO, coupled with catabolic supply of hypoxanthine from adenosine catabolism, is a pathogenic principle in influenza virus infection in mice and that a therapeutic approach by elimination of oxygen radicals thus seems possible.

Reactive oxygen disrupts mitochondria in MA-10 tumor Leydig cells and inhibits steroidogenic acute regulatory (StAR) protein and steroidogenesis.

Abstract: Reactive oxygen species (ROS) are involved in a variety of pathophysiological conditions of the testis, and oxidative stress is known to inhibit ovarian and testicular steroidogenesis The site of ROS-mediated inhibition of steroidogenesis in the corpus luteum and MA-10 tumor Leydig cells was shown to be the hormone-sensitive mitochondrial cholesterol transfer step The purpose of this study was to examine the effects of ROS on steroidogenic acute regulatory (StAR) protein in MA-10 cells and determine the extent to which MA-10 cell mitochondria are sensitive to oxidative stress cAMP-stimulated progesterone production was inhibited in a dose-dependent manner in MA-10 cells exposed to H(2)O(2) StAR protein, but not mRNA levels, was decreased in parallel to changes in progesterone production Even at the highest concentrations of H(2)O(2) tested, there was no effect on P450 side-chain cleavage enzyme protein levels Oxidative stress from exposure to exogenous xanthine oxidase and xanthine resulted in the inhibition of both progesterone production and StAR protein expression The mature 30- and 32-kDa intramitochondrial forms of StAR were decreased relative to the 37-kDa extramitochondrial precursor form of StAR, indicating that the ROS-mediated inhibition of StAR protein was due, in part, to the inhibition of mitochondrial import and processing Vital staining with the fluorescent dye tetramethylrhodamine ethyl ester was used to visualize changes in the mitochondrial electrochemical gradient-dependent membrane potential (Deltapsim) ROS caused a significant dissipation of Deltapsi(m) and time-dependent loss of tetramethylrhodamine ethyl ester fluorescence The inhibitory effects of H(2)O(2) were transient There was no evidence for ROS-induced cell death, and following H(2)O(2) removal in the presence of continuous treatment with 8-bromo-cAMP, StAR protein levels and progesterone production were restored In addition, there was no loss of cell viability following treatment with H(2)O(2) or xanthine/xanthine oxidase as determined by trypan blue exclusion H(2)O(2) did not cause a significant decrease in total cellular ATP levels These data indicate that oxidative stress-mediated perturbation of the mitochondria and dissipation of Deltapsi(m) results in the inhibition of StAR protein expression and its import, processing, and cholesterol transfer activity These findings confirm earlier studies demonstrating the requirement for maintenance of an intact Deltapsi(m) for StAR protein function in cholesterol transport The significant reduction in the 32- to 30-kDa mature forms of StAR, cessation of cholesterol transport, and loss of Deltapsi(m) are consistent with mitochondrial perturbation because of oxidative stress This mechanism likely contributes to a host of pathophysiological events evident in testicular disorders such as infection, reperfusion injury, aging, cryptorchidism, and varicocele