title: Tissue protective effect of xanthine oxidase inhibitor, polymer conjugate of (styrene-maleic acid copolymer) and (4-amino-6-hydroxypyrazolo[3,4-d]pyrimidine), on hepatic ischemia-reperfusion injury.
abstract: The detrimental role of superoxide anion (O(2)(-)) has been well documented in the pathogenesis of ischemia-reperfusion (I/R) injury. Our and other studies suggested that one critical source of O(2)(-) generation may be xanthine oxidase (XO). We thus hypothesized that I/R injury could be protected by inhibiting XO activity, which would reduce the amount of O(2)(-) and hence reduce pathogenic consequences. Among various XO inhibitors, we previously found 4-amino-6-hydroxypyrazolo[3,4-d]pyrimidine (AHPP) exhibited potent XO inhibitory activity. Here, we report that the covalent conjugate of AHPP with amphipathic styrene-maleic acid copolymer (SMA-AHPP) showed protective effect against I/R-induced injury in a rat hepatic I/R model. Liver ischemia was induced by occluding both the portal vein and the hepatic artery for 30 min, and followed by reperfusion. SMA-AHPP was administered via the tail vein two hours before ischemia was initiated. A remarkable increase of liver enzymes in plasma (aspartate aminotransferase, AST; alanine aminotransferase, ALT and lactate dehydrogenase, LDH) was detected three hours after reperfusion, whereas prior injection of SMA-AHPP greatly suppressed this increase of AST, ALT and LDH. Moreover, induction of inflammatory cytokines, i.e. tumor necrosis factor-alpha (TNF-alpha), interleukin-12 (IL-12) and monocyte chemotactic protein-1 (MCP-1) by I/R were significantly inhibited by SMA-AHPP treatment. Accordingly, cytotoxic effect or apoptosis in the liver caused by I/R was clearly reduced by SMA-AHPP pretreatment. Furthermore, thiobarbituric acid-reactive substance assay showed a significant decrease of lipid peroxidation in rat liver after the administration of SMA-AHPP, which is parallel with the decreased XO activity after SMA-AHPP treatment, indicating the involvement of reactive oxygen species generated by XO. In addition, SMA-AHPP was found to bind to albumin, thus to exhibit prolonged in vivo (plasma) half-life. These results suggest that SMA-AHPP exerted a potent cytoprotective effect against I/R injury in rat liver, by inhibiting XO activity and the subsequent generation of O(2)(-).
authors.affiliation: Laboratory of Microbiology & Oncology, Faculty of Pharmaceutical Sciences, Sojo University, Kumamoto 860-0082, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Fang
authors.forename: Takahiro
authors.initials: T
authors.lastname: Seki
authors.forename: Haibo
authors.initials: H
authors.lastname: Qin
authors.forename: Gahininath Y
authors.initials: GY
authors.lastname: Bharate
authors.forename: Arun K
authors.initials: AK
authors.lastname: Iyer
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maeda
mesh_terms: D000418:Albumins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016207:Cytokines / Q000097:blood; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D051547:Heme Oxygenase-1 / Q000378:metabolism; D008099:Liver / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D008298:Maleates / Q000737:chemistry / Q000494:pharmacology*; D008970:Molecular Weight; D010117:Oxypurinol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D011137:Polystyrenes / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D013481:Superoxides / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014018:Tissue Distribution; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: C548914:4-amino-6-hydroxypyrazolo(3,4-d)pyrimidine; D000418:Albumins; D016207:Cytokines; D004791:Enzyme Inhibitors; D008298:Maleates; D011137:Polystyrenes; D017392:Thiobarbituric Acid Reactive Substances; D013481:Superoxides; C024074:styrene-maleic acid polymer; D051547:Heme Oxygenase-1; D014969:Xanthine Oxidase; D010117:Oxypurinol