2-phenyl-4-4-5-5-tetramethylimidazoline-1-oxyl-3-oxide and Reperfusion-Injury

Cystathionine-beta-synthase (CBS) catalyzes the rate-limiting step in the transsulfuration pathway for the metabolism of homocysteine (Hcy) in the kidney. Our recent study demonstrates that ischemia-reperfusion reduces the activity of CBS leading to Hcy accumulation in the kidney, which in turn contributes to renal injury. CBS is also capable of catalyzing the reaction of cysteine with Hcy to produce hydrogen sulfide (H(2)S), a gaseous molecule that plays an important role in many physiological and pathological processes. The aim of the present study was to examine the effect of ischemia-reperfusion on CBS-mediated H(2)S production in the kidney and to determine whether changes in the endogenous H(2)S generation had any impact on renal ischemia-reperfusion injury. The left kidney of Sprague-Dawley rat was subjected to 45-min ischemia followed by 6-h reperfusion. The ischemia-reperfusion caused lipid peroxidation and cell death in the kidney. The CBS-mediated H(2)S production was decreased, leading to a significant reduction in the renal H(2)S level. The activity of cystathionine-gamma-lyase, another enzyme responsible for endogenous H(2)S generation, was not significantly altered in the kidney upon ischemia-reperfusion. Partial restoration of CBS activity by intraperitoneal injection of the nitric oxide scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide not only increased renal H(2)S levels but also alleviated ischemia-reperfusion-induced lipid peroxidation and reduced cell damage in the kidney tissue. Furthermore, administration of an exogenous H(2)S donor, NaHS (100 microg/kg), improved renal function. Taken together, these results suggest that maintenance of tissue H(2)S level may offer a renal protective effect against ischemia-reperfusion injury.

Topics: Animals; Apoptosis; Cyclic N-Oxides; Cystathionine beta-Synthase; Cystathionine gamma-Lyase; Disease Models, Animal; Free Radical Scavengers; Homeostasis; Homocysteine; Hydrogen Sulfide; Imidazoles; Kidney; Male; Nitric Oxide; Rats; Rats, Sprague-Dawley; Reperfusion Injury

Our recent study (Prathapasinghe GA, Siow YL, O K. Am J Physiol Renal Physiol 292: F1354-F1363, 2007) indicates that homocysteine (Hcy) plays a detrimental role in ischemia-reperfusion-induced renal injury. Elevation of renal Hcy concentration during ischemia-reperfusion is attributed to reduced activity of cystathionine-beta-synthase (CBS) that catalyzes the rate-limiting step in the transsulfuration pathway for the metabolism of the majority of Hcy in the kidney. However, the mechanisms of impaired CBS activity in the kidney are unknown. The aim of this study was to investigate the effects of pH and nitric oxide (NO) on the CBS activity in the kidney during ischemia-reperfusion. The left kidney of a Sprague-Dawley rat was subjected to ischemia-reperfusion. The CBS activity was significantly reduced in kidneys subjected to ischemia alone (15-60 min) or subjected to ischemia followed by reperfusion for 1-24 h. The pH was markedly reduced in kidneys upon ischemia. Injection of alkaline solution into the kidney partially restored the CBS activity during ischemia. Further analysis revealed that reduction of CBS activity during reperfusion was accompanied by an elevation of NO metabolites (nitrate and nitrite) in the kidney tissue. Injection of a NO scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), restored the CBS activity in the kidneys subjected to ischemia-reperfusion. Treatment with PTIO could abolish ischemia-reperfusion-induced lipid peroxidation and prevent cell death in the kidney. These results suggested that metabolic acidosis during ischemia and accumulation of NO metabolites during reperfusion contributed, in part, to reduced CBS activity leading to an elevation of renal Hcy levels, which in turn, played a detrimental role in the kidney.

Topics: Acidosis; Animals; Apoptosis; Cyclic N-Oxides; Cystathionine beta-Synthase; Enzyme Activation; Enzyme Inhibitors; Free Radical Scavengers; Homocysteine; Hydrogen-Ion Concentration; Imidazoles; Kidney; Lipid Peroxidation; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reperfusion Injury