Alterations of peroxisomal function in ischemia-reperfusion injury of rat kidney

We have previously demonstrated that ischemic injury results in the loss of peroxisomal functions (e.g., inhibition of catalase activity and fatty-acid beta-oxidation activity). To understand the molecular mechanism leading to the loss of peroxisomal beta-oxidation in ischemic tissue, we examined the levels of individual enzyme activities and proteins of the peroxisomal beta-oxidation system and overall fatty-acid oxidation in peroxisomes isolated from kidney exposed to ischemia-reperfusion injury. The peroxisomal beta-oxidation decreased with an increase in time of ischemic injury (53% and 43% of the control in kidneys exposed to 60 and 90 min ischemia, respectively). In vivo inactivation of catalase with aminotriazole and exposure of isolated peroxisomes to H2O2 resulted in inhibition of peroxisomal beta-oxidation system suggesting that this enzyme system is labile to excessive H2O2 produced during ischemic injury. The enzyme activities of lignoceroyl-CoA ligase, acyl-CoA oxidase, bifunctional enzymes and acyl-CoA thiolase (individual peroxisomal beta-oxidation enzymes) after 90 min of ischemia were 87, 80, 87 and 85% of the control, respectively. This decrease in enzyme activities was more pronounced following reperfusion (28, 11, 23 and 35% of the control, respectively). Immunoblot analysis of these enzymes indicated that the major loss of these enzyme activities during ischemia was due to their inactivation, whereas during reperfusion, proteolysis also contributed toward the observed loss of these activities. In summary, these results demonstrated that loss of peroxisomal beta-oxidation in ischemia-reperfusion injury was due to inactivation and proteolysis of beta-oxidation enzymes. Acyl-CoA oxidase was more sensitive to ischemia-reperfusion injury compared to other enzymes, and the overall loss of peroxisomal beta-oxidation may be a reflection of the loss of acyl-CoA oxidase activity, a rate-limiting enzyme.