RESUMO
Exposure to decreasing oxygen tensions progressively increased xanthine dehydrogenase (XD) and xanthine oxidase (XO) activities over 48 hr in cultured pulmonary artery endothelial cells (EC) without altering XD/XO ratios. Increases in XD and XO activity in EC induced by hypoxia were associated upon reoxygenation with increased (P less than 0.05) extracellular superoxide anion (O2-.) levels that were inhibited by treatment with XO inhibitors (tungsten, allopurinol) or an anion-channel blocker (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid). EC monolayers subjected to hypoxia/reoxygenation also leaked more preloaded 51Cr, were more adherent to neutrophils, and permitted greater albumin transit than control monolayers. Treatment with tungsten, allopurinol, and/or superoxide dismutase decreased (P less than 0.05) 51Cr release, neutrophil adherence, and albumin transit in EC monolayers exposed to hypoxia/reoxygenation. We conclude that prolonged hypoxia increases both XO and XD activity in EC and may predispose the endothelium to oxidative and inflammatory damage.
Assuntos
Adesão Celular , Hipóxia Celular/fisiologia , Endotélio Vascular/fisiologia , Neutrófilos/fisiologia , Superóxidos/metabolismo , Xantina Desidrogenase/metabolismo , Xantina Oxidase/metabolismo , Ácido 4,4'-Di-Isotiocianoestilbeno-2,2'-Dissulfônico , Ácido 4-Acetamido-4'-isotiocianatostilbeno-2,2'-dissulfônico/análogos & derivados , Ácido 4-Acetamido-4'-isotiocianatostilbeno-2,2'-dissulfônico/farmacologia , Análise de Variância , Animais , Bovinos , Células Cultivadas , Cromo/metabolismo , Técnicas de Cultura/métodos , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/enzimologia , Sequestradores de Radicais Livres , Cinética , Oxigênio/farmacologia , Artéria Pulmonar , Fatores de TempoRESUMO
Exposure to recombinant human tumor necrosis factor-alpha (TNF-alpha) or calcium ionophore (A23187) for 4 h increased (P less than 0.05) lactate dehydrogenase (LDH) release from cultured bovine brain endothelial cells (EC). In contrast, treatment with endotoxin or interleukin-1 did not increase (P greater than 0.05). LDH release from brain EC. Pretreatment with tungsten decreased (P less than 0.05) xanthine oxidase activity in brain EC and decreased (P less than 0.05) LDH release from brain EC following exposure to TNF. Our results suggest that TNF-alpha injures brain microvascular EC and that this effect may be mediated by xanthine oxidase.
Assuntos
Encéfalo/efeitos dos fármacos , Endotélio Vascular/efeitos dos fármacos , Fator de Necrose Tumoral alfa/antagonistas & inibidores , Tungstênio/uso terapêutico , Animais , Encéfalo/metabolismo , Bovinos , Células Cultivadas , L-Lactato Desidrogenase/metabolismo , Xantina Desidrogenase/metabolismo , Xantina Oxidase/metabolismoRESUMO
Bovine brain endothelial cells (EC) that were isolated and propagated in pure culture had increased (greater than 20-fold) levels of xanthine oxidase and xanthine dehydrogenase activity compared to whole brain homogenate. Brain EC also released superoxide anion (O2-) into the extracellular medium. Treatment of EC with tungsten decreased (P less than 0.05) both XO activity and O2- release. XO appears to be highly concentrated in cerebral vascular endothelium and may be an important source of O2-.
Assuntos
Encéfalo/irrigação sanguínea , Endotélio Vascular/enzimologia , Superóxidos/metabolismo , Xantina Oxidase/metabolismo , Animais , Encéfalo/enzimologia , Capilares/enzimologia , Bovinos , Células Cultivadas , Endotélio Vascular/citologia , Xantina Desidrogenase/metabolismoRESUMO
The mechanism of xanthine oxidase (XO) inactivation by hydrogen peroxide (H2O2) and its biologic significance are unclear. We found that addition of increasing concentrations of H2O2 progressively decreased xanthine oxidase activity in the presence but not the absence of xanthine in vitro. Inactivation of XO by H2O2 was also enhanced by anaerobic reduction of XO by xanthine. Inactivation of XO by H2O2 was accompanied by production of hydroxyl radical (.OH), measured as formation of formaldehyde from dimethylsulfoxide (DMSO). In contrast, addition of H2O2 to deflavo XO did not produce .OH. Inactivation of XO by H2O2 was decreased by simultaneous addition of the .OH scavenger, DMSO. However, inactivation of XO by H2O2 and formation of .OH were not decreased following addition of the metal chelator. DETAPAC, and/or the O2 scavenger, superoxide dismutase. The results suggest that inactivation of XO by H2O2 occurs by production of .OH following direct reduction of H2O2 by XO at the flavin site.
Assuntos
Peróxido de Hidrogênio/farmacologia , Hidróxidos/metabolismo , Xantina Oxidase/metabolismo , Dimetil Sulfóxido/farmacologia , Ativação Enzimática/efeitos dos fármacos , Formaldeído/metabolismo , Sequestradores de Radicais Livres , Radical Hidroxila , Ácido Pentético/farmacologia , Especificidade por Substrato , Superóxido Dismutase/farmacologiaRESUMO
This is a case report of an athletic, middle-aged man with a remote history of penetrating right leg trauma who developed a pulmonary embolism, thrombosis of the popliteal vein, a mass in the popliteal fossa, and acute ischemia of the right lower leg. At operation a thrombosed pseudoaneurysm was found arising from a defect in the popliteal vein with extrinsic compression of the popliteal artery. The defect was patched with autogenous vein and the long-term result was excellent. Pseudoaneurysm of the popliteal vein is a previously unreported entity. Popliteal venous aneurysms usually begin with phlebitic or pulmonary thromboembolic manifestations and present a diagnostic challenge. Venous aneurysms in general are uncommon pathologic entities with a diverse etiology; the current etiologic concepts and classification are briefly discussed in the text. A new differential diagnosis for masses in the popliteal fossa is introduced by this report.
