tetrahydroneopterin and Ischemia

Tetrahydrobiopterin has been shown to efficiently abrogate ischemia reperfusion injury (IRI). However, it is unclear, whether its beneficial action relies on cofactor activity of one of the five known tetrahydrobiopterin-dependent reactions or on its antioxidative capacity. We therefore compared tetrahydrobiopterin with the pterin derivate tetrahydroneopterin (similar biochemical properties, but no nitric oxide synthase cofactor activity) and the antioxidants vitamin C and 5-methyltetrahydrofolate. Donor mice were pretreated with tetrahydrobiopterin, tetrahydroneopterin, vitamin C, or 5-methyltetrahydrofolate. Pancreatic grafts were subjected to 16-h cold ischemia time and implanted in syngeneic recipients. Untreated and nontransplanted animals served as controls. Following 2-h reperfusion, microcirculation was analyzed by intravital fluorescence microscopy. Graft damage was assessed by histology and nitrotyrosine immunostaining, and tetrahydrobiopterin levels were determined by HPLC. Recipient survival served as ultimate readout. Prolonged cold ischemia time resulted in microcirculatory breakdown. Only tetrahydrobiopterin pretreatment succeeded to preserve the capillary net, whereas all other compounds showed no beneficial effects. Along with increased intragraft tetrahydrobiopterin levels during recovery and implantation, only tetrahydrobiopterin pretreatment led to significant reduction of IRI-related parenchymal damage enabling recipient survival. These results show a striking superiority of tetrahydrobiopterin in preventing lethal IRI compared with related compounds and suggest nitric oxide synthases as treatment target.

Topics: Animals; Antioxidants; Ascorbic Acid; Biopterins; Cold Ischemia; Immunohistochemistry; Ischemia; Liver; Male; Mice; Mice, Inbred C57BL; Microcirculation; Microscopy, Confocal; Nitric Oxide; Organ Preservation; Pancreas; Pancreas Transplantation; Reperfusion Injury; Tetrahydrofolates; Time Factors

The therapeutic potency of 5,6,7,8-tetrahydroneopterin (NPH4) was investigated in ischemic paw edema, Adriamycin (ADR)-induced cardiotoxicity, and endotoxin [lipopolysaccharide (LPS)]- and carbon tetrachloride (CCl4)-induced hepatotoxicity in mice. Ischemic paw edema was completely suppressed by pre-administration of NPH4. ADR-induced cardiotoxicity and LPS-induced hepatotoxicity were significantly decreased by post-administration of NPH4. Furthermore, NPH4 ameliorated CCl4-induced hepatotoxicity. These results suggest that NPH4 may be useful for the treatment of free radical, especially superoxide radical, -related tissue injury.

Topics: Animals; Biopterins; Carbon Tetrachloride; Chemical and Drug Induced Liver Injury; Doxorubicin; Edema; Foot; Foot Diseases; Forelimb; Free Radical Scavengers; Free Radicals; Hindlimb; Ischemia; Lipopolysaccharides; Liver Diseases; Male; Mice; Mice, Inbred ICR; Mice, Inbred Strains; Myocardial Ischemia; Superoxides