Bacterial endotoxin (LPS) is responsible for much of the widespread inflammatory response seen in sepsis, a condition often accompanied by acute renal failure (ARF). In this work we report that mice deficient in TNFR1 (TNFR1−/−) were resistant to LPS-induced renal failure. Compared with TNFR1+/+ controls, TNFR1−/− mice had less apoptosis in renal cells and fewer neutrophils infiltrating the kidney following LPS administration, supporting these as mediators of ARF. TNFR1+/+ kidneys transplanted into TNFR1−/− mice sustained severe ARF after LPS injection, which was not the case with TNFR1−/− kidneys transplanted into TNFR1+/+ mice. Therefore, TNF is a key mediator of LPS-induced ARF, acting through its receptor TNFR1 in the kidney.

Ischemia-reperfusion injury (IRI) is a complex and incompletely understood process involving a cascade of events that culminates in apoptotic and/or necrotic cell death. Natural IgM antibodies and complement have been implicated in the pathogenesis of IRI in a variety of organ systems as have T lymphocytes in renal IRI. To investigate the role of Ig and T lymphocytes in renal IRI, recombination-activating gene (RAG)-1-deficient mice were studied. RAG-1(−/−) mice were not protected from acute renal failure induced by 27.5 min of bilateral renal ischemia and subsequent reperfusion [serum urea nitrogen levels 30 h after reperfusion, 155.2 ± 5.6 and 152.8 ± 11.4 mg/dl in RAG-1(−/−) and wild-type mice, respectively; n = 13 each]. Histological examination showed acute tubular necrosis and neutrophilic infiltration with no significant differences between groups. In contrast with other organ systems, Igs were not found in kidneys at time points ranging from 1 min to 30 h after ischemia. Thus Igs and mature T lymphocytes do not appear to play a significant role in the pathogenesis of IRI in the kidney.

To investigate the role of complement in lupus nephritis, we used MRL/lpr mice and a transgene overexpressing a soluble complement regulator, soluble CR1-related gene/protein y (sCrry), both systemically and in kidney. Production of sCrry in sera led to significant complement inhibition in Crry-transgenic mice relative to littermate transgene negative controls. This complement inhibition with sCrry conferred a survival advantage to MRL/lpr mice. In a total of 154 animals, 42.5% transgene-negative animals had impaired renal function (blood urea nitrogen > 50 mg/dl) compared with 16.4% mice with the sCrry-producing transgene (p < 0.001). In those animals that died spontaneously, MRL/lpr mice with the sCrry-producing transgene did not die of renal failure, while those without the transgene did (blood urea nitrogen values of 46.6 ± 9 and 122 ± 29 mg/dl in transgene-positive and transgene-negative animals, respectively; p < 0.001). Albuminuria was reduced in those transgenic animals in which sCrry expression was maximally stimulated (urinary albumin/creatinine = 12.4 ± 4.3 and 36.9 ± 7.7 in transgene-positive and transgene-negative animals, respectively; p < 0.001). As expected in the setting of chronic complement inhibition, there was less C3 deposition in glomeruli of sCrry-producing transgenic mice compared with transgene-negative animals. In contrast, there was no effect on glomerular IgG deposition, levels of anti-dsDNA Ab and rheumatoid factor, or spleen weights between the two groups. Thus, long-term complement inhibition reduces renal disease in MRL/lpr mice, which translates into improved survival. MRL/lpr mice in which complement is inhibited still have spontaneous mortality, yet this is not from renal disease.

Abstract. The complex pathogenesis of ischemia reperfusion injury (IRI) includes endothelial expression of adhesion molecules, leukocyte recruitment and activation, reactive oxygen species production, and apoptotic and necrotic cell death. A role for complement in IRI of different organs, including kidney, has been proposed on the basis of results of experiments that used pharmacologic inhibitors as well as animals that were deficient in individual complement proteins. Here, renal IRI in mice was examined. Animals that were deficient in C3 had partial protection from IRI induced by 27.5 min of bilateral renal ischemia, followed by 20 h of reperfusion (blood urea nitrogen [BUN] values, 46.6 ± 6.9 and 68.4 ± 7.9 mg/dl in C3 -/- and C3 +/+ mice; n = 7 and 8, respectively; P = 0.033). Given the reduction in IRI in C3 -/- mice, it was investigated, by use of the rodent C3 convertase inhibitor CR1-related gene/protein y-Ig (Crry-Ig), whether exogenous administration of a complement inhibitor could lessen renal injury. Despite the use of Crry-Ig in high doses, there was no significant reduction of injury induced by 20 to 30 min of ischemia followed by up to 30 h of reperfusion. Histologic examination revealed acute tubular necrosis and neutrophilic infiltration, both of which correlated significantly with BUN values (P < 0.001). Of interest, C3 deposition around renal tubules was significantly less in animals with IRI, compared with that in unmanipulated controls (P < 0.001). In Crry-Ig—treated animals, C3 deposition was inversely proportional to BUN values (r = -0.63; P < 0.001), which presumably indicates that severe vascular IRI allowed access of the 160 kD Crry-Ig to the interstitium. Thus, renal IRI in mice may have a partial complement dependence, yet pharmacologic inhibition of the complement system does not seem to be effective, likely because of the presence of other mediator systems that operate in parallel.