Reactive oxygen species in chronic allograft dysfunction:

Effect of a novel nuclear factor-κB activation inhibitor on renal ischemia-reperfusion injury

BACKGROUND

In kidney transplantation, the relationship between prolonged warm or cold ischemic storage of kidneys and a higher incidence of delayed graft function is previously known, and delayed graft function has been known to aggravate poor long-term graft survival. We investigated the effect of a novel nuclear factor-κB activation inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on renal ischemia-reperfusion (I/R) injury.

METHODS

DHMEQ was administered to Lewis rats once just before renal artery clamping (DHMEQ pretreatment group), and the effect on I/R injury was investigated.

RESULTS

In the DHMEQ pretreatment group, the 24-hr urine volume on days 1 to 3 after I/R was significantly larger, and the protein concentration of the urine on days 2 to 7 was significantly smaller than in the untreated group. The serum creatinine level was significantly improved, and significantly lower levels of the inflammatory cells and inflammatory cytokines were present in the kidneys on day 1. The relative ratio of nuclear to cytoplasmic nuclear factor-κB and oxidative stress of kidney tissue on day 1 were significantly decreased.

CONCLUSIONS

Treatment with DHMEQ before renal artery clamping may therefore be useful for renal I/R injury and application to renal transplantation is expected.

Lecithinized superoxide dismutase reduces cold ischemia-induced chronic allograft dysfunction

BACKGROUND

Chronic renal allograft failure (CAF) is influenced by both allo-dependent and independent factors and is a major cause of graft loss in clinical renal transplantation. We evaluated a novel membrane-bound free radical scavenger, lecithinized superoxide dismutase (lec-SOD), to determine its potential in limiting the harmful effects of ischemia/reperfusion injury on CAF.

METHODS

Fisher rat kidneys were stored for either 1 hour or 18 hours in cold Marshall's preservation solution either with or without lec-SOD and transplanted into Lewis recipients.

RESULTS

Within 3 days of transplantation, an early inflammatory response involving granulocytes and macrophages was detected in renal allografts exposed to 18 hours cold ischemia that was significantly reduced by preservation with lec-SOD. By 24 weeks post-transplantation, elevated proteinuria and detection of apoptotic cells was observed in kidneys exposed to 18 hours of cold ischemia, that was attenuated by preservation with lec-SOD (P < 0.05). However, up-regulated expression of intracellular adhesion molecule-1 (ICAM-1) and major histocompatibility complex (MHC) Class II together with a T lymphocyte infiltration were observed at 24 weeks that was not prevented by preservation with lec-SOD.

CONCLUSIONS

These results demonstrate that ischemia/reperfusion injury, apoptotic cell death and allo-immune responses may be exacerbated by cold ischemia and accelerate the development of CAF. Preservation with lec-SOD may protect against the early damage induced by cold ischemia and reperfusion injury.

The endothelium in clinical cardiac transplantation

Cardiac transplantation is the most successful therapy for refractory heart failure, but clinical transplantation is still confronted with the problems of acute rejection and acute pump failure. The limiting factor in achieving prolonged survival remains cardiac allograft vasculopathy. In recent years it has become apparent that from brain death onward, the cardiac endothelium plays a key role in these acute and chronic events. Brain death is associated with an inflammatory response that primes the endothelium for cumulative injury during the subsequent stages of ischemic cold storage, reperfusion and allorecognition. As a structural and functional interface, the endothelium is the site at which inflammatory cells move from the bloodstream through the vessel wall into the parenchyma. The endothelium interacts with the complement system, the coagulation and inflammatory cascades, circulating leukocytes, the immune system, the smooth muscle in the vessel wall, and the surrounding matrix and cardiomyocytes. A better understanding of its many roles may lead to expansion of our therapeutic possibilities and better outcomes overall. This article reviews the possible roles of the endothelium in relation to cardiac transplantation, and discusses the diagnostic and therapeutic modalities that are available to date.

Endothelial cell protection against ischemia/reperfusion injury by lecithinized superoxide dismutase

BACKGROUND

Organs used for transplantation may experience long periods of cold ischemic preservation and consequently oxygen free radical-mediated damage following reperfusion. Lecithinized superoxide dismutase (lec-SOD) is a novel free radical scavenger that has been shown to bind with high affinity to cell membranes. The aim of this study was to determine whether lec-SOD bound to endothelial cells under organ preservation conditions to mediate direct antioxidant activity at the endothelial cell surface and thus offer protection against the harmful effects of ischemia/reperfusion injury.

METHODS

An in vitro study was performed on large vessel endothelial cells (HUVEC) and a human microvascular endothelial cell line HMEC-1, to investigate the potential therapeutic benefits of incorporating lec-SOD into organ preservation solution. A cold hypoxia/reoxygenation system was developed to examine lec-SOD binding affinity to endothelial cells, protection against hypoxia/reoxygenation-induced cell death, and neutrophil adhesion.

RESULTS

Lec-SOD bound to endothelial cells with higher affinity than unmodified recombinant human superoxide dismutase (rhSOD) and significantly protected both HUVEC and HMEC-1 from cell death following 27 hours of cold hypoxia (P < 0.01). Furthermore, neutrophil adhesion to the endothelium stimulated by hypoxia and reoxygenation was significantly inhibited by treatment with lec-SOD but not by lecithin or rhSOD (P < 0.01). Analysis by flow cytometry demonstrated that E-selectin and ICAM-1 were up-regulated by hypoxia/reoxygenation that was inhibited in part by lec-SOD.

CONCLUSIONS

The results from this study suggest that incorporation of lec-SOD into organ preservation solutions provides effective protection to endothelial cells against cold ischemia and reperfusion injury following transplantation.