The impact of free radical-mediated reperfusion injury on acute and chronic rejection events following cadaveric renal transplantation.

In a prospective, randomized, double-blind, placebo-controlled trial, rhSOD was given to cadaveric renal allograft recipients intravenously in a dose of 200 mg during surgery, and its effect on both acute and chronic rejection was investigated. The results showed that rhSOD exerts a beneficial effect on acute rejection episodes as indicated by a statistically significant reduction of first acute rejection episodes to 18.5% compared with 33.3% in controls, and a reduction in early irreversible acute rejection to 3.7% compared with 12.5% in controls. With regard to longterm results, there was a statistically significant improvement in the actual 5-year graft survival rate for rhSOD-treated patients to 68% (with a corresponding 13-year half-life) compared with 50% in controls (with a corresponding 6-year half-life). The incidence of acute rejection episodes did not prove to be a risk factor for long-term graft outcome. Rather only the combination of acute rejection episodes and the presence of uninfluenced reperfusion injury appeared to have a detrimental effect on long-term prognosis. The beneficial effect of rhSOD observed in this trial is not well understood, although one can assume that the effect is brought about by interference of rhSOD with ischemia or reperfusion injury to the allograft by oxygen-free radicals. In this sense, rhSOD may mitigate increased MHC expression and presentation, cytokine-adhesion molecule expression, and APC activation induced by reperfusion injury. In addition, in accordance with the "response-to-injury" hypothesis to explain the pathogenesis of arteriosclerosis, rhSOD may mitigate acceleration of chronic obliterative rejection or arterio-/arteriolosclerosis induced by reperfusion injury. In this sense, rhSOD may act indirectly by reducing acute rejection-mediated endothelial injury, or directly, by ablation of reperfusion-mediated acute endothelial injury.