Abstract-Blockade of angiotensin (Ang) II is efficient in various renal diseases. Although interest has focused on the hemodynamic changes and reduction of proteinuria, recent studies emphasize the nonhemodynamic effects of Ang II on kidney injury. The aim of this study was to clarify the mechanisms of Ang II on the immune system that alter the balance of helper T-cell (Th) subsets. We used a continuous, Ang II infusion model of rats that develop hypertension, proteinuria, and tubulointerstitial damage, including de novo expression of ␣-smooth muscle actin and loss of endothelial cells. We isolated T cells from the spleen and measured cytokine levels by ELISA systems. Ang II-infused rats showed an increase in the Th1 cytokine ␥-interferon and a decrease in the Th2 cytokine interleukin-4. The same change in cytokine mRNA expression in the spleen and kidney was confirmed by quantitative polymerase chain reaction analysis. Our ELISPOT assay showed an increase in the number of ␥-interferon-secreting T cells by Ang II. To investigate whether these changes were specific effects of Ang II, we treated the model rats with the Ang II receptor blocker (ARB) olmesartan or the nonspecific vessel dilator hydralazine. Administration of the ARB ameliorated disease manifestations and the imbalance in Th subsets, whereas hydralazine did not, despite comparable effects on blood pressure. These results demonstrate a direct role of Ang II in the modification of Th balance. T he renin-angiotensin system has been a target for research on hypertension for a long time. This system plays a crucial role in regulating a variety of renal functions, such as blood pressure (BP) and electrolyte and water homeostasis.

Renal ischemia-reperfusion injury (IRI) is a feature of ischemic acute renal failure and it impacts both short- and long-term graft survival after kidney transplantation. Complement activation has been implicated in renal IRI, but its mechanism of action is uncertain and the determinants of complement activation during IRI remain poorly understood. We engineered mice deficient in two membrane complement regulatory proteins, CD55 and CD59, and used them to investigate the role of these endogenous complement inhibitors in renal IRI. CD55-deficient (CD55−/−), but not CD59-deficient (CD59−/−), mice exhibited increased renal IRI as indicated by significantly elevated blood urea nitrogen levels, histological scores, and neutrophil infiltration. Remarkably, although CD59 deficiency alone was inconsequential, CD55/CD59 double deficiency greatly exacerbated IRI. Severe IRI in CD55−/−CD59−/− mice was accompanied by endothelial deposition of C3 and the membrane attack complex (MAC) and medullary capillary thrombosis. Complement depletion in CD55−/−CD59−/− mice with cobra venom factor prevented these effects. Thus, CD55 and CD59 act synergistically to inhibit complement-mediated renal IRI, and abrogation of their function leads to MAC-induced microvascular injury and dysfunction that may exacerbate the initial ischemic assault. Our findings suggest a rationale for anti-complement therapies aimed at preventing microvascular injury during ischemia reperfusion, and the CD55−/−CD59−/− mouse provides a useful animal model in this regard.

RNA interference by short interfering RNAs (siRNAs) holds promise as a therapeutic strategy, but use of siRNAs in vivo remains limited. Here, we developed a system to target delivery of siRNAs to glomeruli via poly(ethylene glycol)-poly(L-lysine)-based vehicles. The siRNA/nanocarrier complex was approximately 10 to 20 nm in diameter, a size that would allow it to move across the fenestrated endothelium to access to the mesangium. After intraperitoneal injection of fluorescence-labeled siRNA/nanocarrier complexes, we detected siRNAs in the blood circulation for a prolonged time. Repeated intraperitoneal administration of a mitogen-activated protein kinase 1 (MAPK1) siRNA/nanocarrier complex suppressed glomerular MAPK1 mRNA and protein expression in a mouse model of glomerulonephritis; this improved kidney function, reduced proteinuria, and ameliorated glomerular sclerosis. Furthermore, this therapy reduced the expression of the profibrotic markers TGF-␤1, plasminogen activator inhibitor-1, and fibronectin. In conclusion, we successfully silenced intraglomerular genes with siRNA using nanocarriers. This technique could aid the investigation of molecular mechanisms of renal disease and has potential as a molecular therapy of glomerular diseases.

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