Posttreatment with Aminoguanidine Attenuates Renal Ischemia/Reperfusion Injury in Rats

Acute renal failure secondary to ischemia/reperfusion (I/R) injury is associated with significant mortality and morbidity. Aminoguanidine (AG), an inducible nitric oxide synthase inhibitor with antioxidant properties, has been reported beneficial in renal I/R injury. The aim of the present study was to investigate the effect of AG on renal I/R injury and compare the effectiveness of different AG treatment modalities. Sprague-Dawley rats were randomly assigned to one of four groups. The control group (n?=?6) received sham operation. The I/R group (n?=?6), AG-I group (n?=?8), and AG-II group (n?=?8) received bilateral renal ischemia for 45 min followed by 24 hours of reperfusion. The AG-I group received AG (50 mg/kg) intraperitoneally four hours and 10 minutes before the induction of ischemia. The AG-II group received AG (50 mg/kg) intraperitoneally four hours and 10 minutes after the initiation of reperfusion. Serum urea and creatinine levels increased significantly in the I/R and AG-I groups compared to the control group. Kidney samples from rats in the I/R and AG-I groups revealed severe tubular damage at histopathological examination. Posttreatment with AG significantly reduced serum urea and creatinine levels and improved histopathological lesions compared with the I/R group. Although pretreatment with AG failed to protect kidneys against I/R injury in this experimental model, posttreatment with AG attenuated renal dysfunction and histopathological changes after I/R injury.     

P2X7 Deficiency Attenuates Renal Injury in Experimental Glomerulonephritis

The P2X₇ receptor is a ligand-gated cation channel that is normally expressed by a variety of immune cells, including macrophages and lymphocytes. Because it leads to membrane blebbing, release of IL-1β, and cell death by apoptosis or necrosis, it is a potential therapeutic target for a variety of inflammatory diseases. Although the P2X₇ receptor is usually not detectable in normal renal tissue, we previously reported increased expression of both mRNA and protein in mesangial cells and macrophages infiltrating the glomeruli in animal models of antibody-mediated glomerulonephritis. In this study, we used P2X₇-knockout mice in the same experimental model of glomerulonephritis and found that P2X₇ deficiency was significantly renoprotective compared with wild-type controls, evidenced by better renal function, a striking reduction in proteinuria, and decreased histologic glomerular injury. In addition, the selective P2X₇ antagonist A-438079 prevented the development of antibody-mediated glomerulonephritis in rats. These results support a proinflammatory role for P2X₇ in immune-mediated renal injury and suggest that the P2X₇ receptor is a potential therapeutic target.Glomerulonephritis (GN) is a major cause of end-stage kidney disease; current therapy usually involves relatively nonspecific immunosuppression with often serious adverse effects.¹ Glomerular deposition of antibodies directed against exogenous antigens or autoantigens, leading to immune complex–mediated inflammation and tissue injury, has been well documented in both experimental and clinical forms of GN.²The rat model of nephrotoxic nephritis (NTN) has demonstrated the importance of IL-1β in GN; renal levels of IL-1β are increased in this form of GN, and IL-1β has been shown to play an important role in glomerular crescent formation and in subsequent tubulointerstitial injury.³ Moreover, early and late treatment with an IL-1 receptor antagonist prevents the progression of crescentic GN.^4,5 Crescentic GN is also less severe in IL-1β^−/− or IL-18^−/− mice, and treatment with caspase inhibitors reduces renal inflammation and apoptosis—all consistent with a central role for IL-1β in this experimental model of GN.^6–8The ATP-sensitive P2X₇ receptor is a cation channel activated by high concentrations of extracellular ATP.⁹ Stimulation of this receptor is proinflammatory, causing release of inflammatory cytokines such as IL-1β and IL-18 from macrophages, changes in plasma membrane lipid distribution, and cell death by necrosis or apoptosis.^10,11 A central role for P2X₇ in IL-1β secretion via the Nacht Domain-, Leucine-Rich Repeat-, and PYD-Containing Protein 3 (NALP3) inflammasome has been shown in P2X₇-deficient mice.^12,13 This receptor also has significant prothrombotic effects,¹⁴ causing release of tissue factor–bearing microparticles.¹⁵ Indeed, P2X₇ is already considered to be a possible therapeutic target in inflammation, and antagonists are currently in Phase II clinical trials for the treatment of rheumatoid arthritis and chronic obstructive pulmonary disease; however, the role of this receptor in renal disease or injury is still unclear.¹⁶We previously reported an increase in glomerular expression of the P2X₇ receptor (at the mRNA and protein levels) in rats and mice with NTN induced by nephrotoxic globulin (NTG)—an established model of immune complex–mediated GN characterized by proteinuria, glomerular thrombosis, and tubulointerstitial injury—as well as in renal biopsy tissue from patients with lupus nephritis.^17,18 In this study, we used P2X₇-deficient mice and the selective P2X₇ antagonist A-438079 to examine in more detail the role of P2X₇ in the NTN model of GN.     

蛋白激酶C激活在兔内毒素休克诱发急性肾损伤中的作用

目的:探讨蛋白激酶C(PKC)在兔内毒素休克诱发急性肾损伤中的作用及其可能作用机制。方法:健康清洁级雄性新西兰大白兔40只,采取随机数字表法分为对照组(CON组)、内毒素休克致急性肾损伤组(AKI组)、PKC-α阻断剂-白屈菜赤碱加AKI组(CHA)、PKC-α激活剂-佛波酯加AKI组(PMA)。PMA组经兔耳缘静脉注射佛波酯5μg/kg,CHA组静脉注射白屈菜赤碱5 mg/kg,CON组与AKI组注射各自溶媒1%DMSO 0.5 m L。30 min后,AKI组、PMA组及CHA组静脉注射脂多糖(LPS)5 mg/kg(溶于2 m L生理盐水),CON组给予等容量生理盐水。静脉注射LPS或生理盐水6 h时,采集动脉血,检测血清尿素氮(BUN)和肌酐(Cr)浓度,处死动物后取肾组织,进行病理学观察及肾损伤评分,测定肾组织PKC-α蛋白、HO-1蛋白、Nrf2核蛋白及总蛋白的表达水平。结果:与CON组比较,AKI组、CHA组及PMA组血清BUN、Cr浓度升高,肾组织病理学评分升高,PKC-α蛋白(1.37±0.26)、HO-1蛋白(0.89±0.11)、Nrf2核蛋白(0.97±0.26)及总蛋白的表达均上调(P0.05);与AKI组比较,PMA组血清BUN、Cr浓度降低,肾组织病理学评分降低,PKC-α蛋白、HO-1蛋白、Nrf2核蛋白及总蛋白的表达均上调(P0.05),CHA组血清BUN、Cr浓度升高,肾组织病理学评分(9.8±3.9)升高,PKC-α蛋白、HO-1蛋白、Nrf2核蛋白及总蛋白的表达均下调(P0.05)。结论:PKC-α激活是内毒素休克诱发急性肾损伤时机体的适应性调节反应机制之一,其机制可能与激活Nrf2/ARE通路、上调HO-1的表达有关。     

Apigenin Attenuates Inflammation in Experimentally Induced Acute Pancreatitis-Associated Lung Injury

Background: Acute pancreatitis is associated with acute lung injury. The aim of the present study is to evaluate alterations of lungs in an experimental model of acute pancreatitis (AP) following both bilio-pancreatic duct obstruction close to the duodenum. Acute pancreatitis is a common disease with significant mortality. This situation makes the need of finding protective factors for the lung parenchyma, imperative. In the present study there is an effort to clarify the role of apigenin, a substance which is well known for its antioxidant and anti-inflammatory effects, on lung injury, following acute pancreatitis in rats. Materials and methods: In the present study, 126 male Wistar-type rats 3–4 months old and 220–350 g weight were used. At time 0 we randomly assigned the following groups: Group Sham: Rats were subjected to virtual surgery. Group Control: Rats were subjected to surgery for induction of acute pancreatitis. Group Apigenin: Rats were subjected to surgery for induction of acute pancreatitis and enteral feeding with apigenin. Immunochemistry for TNF-α and IL-6 as well as MPO activity were measured at predetermined time intervals 6, 12, 24, 48, and 72 h, in order to evaluate architectural disturbances of the lung tissue. Results: From the pathological reports we realized that comparing the control group with the apigenin group, there is an improvement of lung tissue damage following apigenin administration, with statistical significance. Apigenin reduces most histopathological alterations of the pulmonary tissue, reduces MPO and TNF-α activity at 48 hours and, furthermore, reduces IL-6 activity at 72 hours post-administration. Conclusions: Oral Apigenin administration in rats, following experimental induced acute pancreatitis, seems to be protective on the lung tissue. Apigenin administration to humans could potentially ameliorate acute lung injuries. However, special caution is required for humans' use, as more detailed studies are needed.     

Acute Renal Failure Secondary to Leukocyte-Mediated Acute Glomerular Injury

Acute glomemlonephritis can cause acute renal failure. Activated neutrophils and monocytes are major eflectors of glomerulonephritic renal failure. Adhesion molecules, granule enzymes, reactive oxygen radicals, lipid metabolites, and cytokines of activated neutrophils and monocytes mediate glomerular capillary constriction, occlusion, and destruction. Injurious products and biologically active mediators released by activated leukocytes have profound fictional eflects on mesangial cells and endothelial cells, which in turn participate in the disturbance of glomerularfinc-tion, for example, by altering capillary diameter and surface area. f i e glomerular injlammatory events result in decreased glomerular capillary ultrajiltraton coefl-cient and glomerular jiltration rate, as well as other functional perturbations.     

3-Aminobenzamide,a Poly ADP Ribose Polymerase Inhibitor,Attenuates Renal Ischemia/Reperfusion Injury

Introduction. This study was designed to investigate whether 3-amino benzamide (3-AB), a poly (ADP-ribose) polymerase (PARP) inhibitor, has a protective effect on kidney injury induced by renal ischemia/reperfusion (I/R) by decreasing oxidative and nitrosative stress on renal dysfunction and injury. Materials and Methods. Thirty-two male Sprague-Dawley rats were divided into four groups: sham-operated, sham-operated + 3-AB, I/R, I/R + 3-AB. Rats were given 3-AB (100 mg/kg/day ip) 14 days prior to I/R. I/R and I/R + 3-AB groups underwent 60 min of bilateral renal ischemia followed by 6 h of reperfusion. After reperfusion, kidneys and blood were obtained for evaluation. Superoxide dismutase, glutathione peroxidase, malondialdehide, protein carbonyl content, and nitrite/nitrate level (NO_x) were determined in the renal tissue. Serum creatinine (S_Cr), blood urea nitrogen (BUN), and aspartate aminotransferase (AST) were determined in the blood. Additionally, renal sections were used for histological grade of renal injury. Results. 3-AB significantly reduced the I/R-induced increases in S_Cr, BUN, and AST. In addition, 3-AB markedly reduced elevated oxidative stress product, restored decreased antioxidant enzymes, and attenuated histological alterations. Moreover, 3-AB attenuated the tissue NO_x levels, indicating reduced NO production. Conclusions. 3-AB has beneficial effect on renal glomerular and tubular dysfunction in rats' kidneys subjected to I/R injury. Moreover, 3-AB has ameliorating effect on both oxidative stress and nitrosative stress of the kidneys, which correlated with histopathological evaluation.     

Acute Ischemia/Reperfusion Injury After Isogeneic Kidney Transplantation Is Mitigated in a Rat Model of Chronic Renal Failure

The influence of chronic renal failure on renal susceptibility to an acute ischemic insult was evaluated. Recipient Lewis rats were randomly assigned to undergo 5/6 nephrectomy (chronic renal failure, CRF) or sham operation (normal renal function, NRF). After 11 weeks, normal kidneys of Lewis donor rats were transplanted in the recipients. The outcome of the isografts was assessed. Filtration capacity of the isografts in the CRF rats was preserved to approximately one-quarter of its normal capacity on the 1st day post-transplantation, whereas it fell to 0 in the NRF rats. This was reflected by a significantly higher increase in serum creatinine in the latter group. The isografts in the CRF rats had a significantly lower degree of acute tubular necrosis and no increase in the number of macrophages and T lymphocytes in the first 24 h in contrast to the NRF rats. Epithelial regeneration and repair started earlier in the CRF group. In conclusion, the present study indicated that CRF blunted ischemia/reperfusion injury of a transplanted kidney, and that its regeneration capacity was certainly not hampered by the presence of chronic uremia. These results will be the basis for studies on modulation of early leukocyte-endothelial interactions resulting from immunological disturbances inherent to the uremic environment.     

IL-2/Anti-IL-2 Complex Attenuates Renal Ischemia-Reperfusion Injury through Expansion of Regulatory T Cells

Regulatory T cells (Tregs) can suppress immunologic damage in renal ischemia-reperfusion injury (IRI), but the isolation and ex vivo expansion of these cells for clinical application remains challenging. Here, we investigated whether the IL-2/anti-IL-2 complex (IL-2C), a mediator of Treg expansion, can attenuate renal IRI in mice. IL-2C administered before bilateral renal IRI induced Treg expansion in both spleen and kidney, improved renal function, and attenuated histologic renal injury and apoptosis after IRI. Furthermore, IL-2C administration reduced the expression of inflammatory cytokines and attenuated the infiltration of neutrophils and macrophages in renal tissue. Depletion of Tregs with anti-CD25 antibodies abrogated the beneficial effects of IL-2C. However, IL-2C–mediated renal protection was not dependent on either IL-10 or TGF-β. Notably, IL-2C administered after IRI also enhanced Treg expansion in spleen and kidney, increased tubular cell proliferation, improved renal function, and reduced renal fibrosis. In conclusion, these results indicate that IL-2C–induced Treg expansion attenuates acute renal damage and improves renal recovery in vivo, suggesting that IL-2C may be a therapeutic strategy for renal IRI.AKI is associated with high morbidity and mortality, and patients with AKI are at high risk for progression to CKD.^1,2 Renal ischemia-reperfusion injury (IRI) is one of the major causes of AKI, and is an important cause of delayed graft function after kidney transplantation. However, clinical management of AKI including IRI remains largely supportive.Inflammation is shown to be mainly involved in the pathogenesis of renal IRI, and renal IRI is now regarded as an acute inflammatory process. Both innate and adaptive immune cells participate in renal IRI.^3,4 Foxp3⁺CD4⁺ regulatory T cells (Tregs) play a critical role in suppression of both adaptive and innate immune responses.⁵ Tregs have also been reported to attenuate renal IRI.^6,7 However, clinical application of Tregs is practically hard, because isolation and expansion of rare Tregs are not easy, and there is also a risk for contamination.Recently, a particular form of IL-2 mAbs (JES6-1) was reported to prevent interaction of IL-2 with IL-2 receptor β-chain without affecting binding to IL-2 receptor α-chain (CD25); thus, complex (IL-2C) of IL-2 and JES6-1 is reported to expand Tregs preferentially up to 4-fold without a significant effect on natural killer cells and “memory phenotype” CD8⁺ T cells.^8,9 IL-2C treatment suppressed islet allograft rejection¹⁰ by inducing Tregs without significant side effects. Furthermore, the IL-2C treatment showed its therapeutic potential in adriamycin nephropathy, a form of CKD.¹¹ However, there has been no study for the effect of the IL-2C on AKI. Here, we investigated whether the IL-2C can attenuate renal IRI by inducing Tregs using murine models.First, we measured Tregs after renal IRI. We administered IL-2C or PBS for 3 consecutive days from 5 days before IRI, because a previous study showed that Treg expansion reached a peak on day 5 after IL-2C treatment.¹⁰ IL-2C induced significant expansion of Foxp3⁺CD4⁺ Tregs in both spleen and kidney (IL-2C versus PBS, P<0.001 on day 1 and P=0.001 on day 5 for spleen, Figure 1, A and B; P<0.001 on both day 1 and day 5 for kidney, Figure 1, A and E). Absolute numbers of Foxp3⁺CD4⁺ Tregs were also increased by 3- to 5-fold in the IL-2C group (IL-2C versus PBS, P=0.001 on day 1 for spleen, Figure 1C; P<0.001 on day 1 and P=0.01 on day 5 for kidney, Figure 1F). Foxp3⁻CD4⁺ T cells were also increased after IL-2C treatment in kidney, but not in spleen (Figure 1, D and G); however, the balance between Tregs and non-Tregs was still skewed toward Tregs, because expansion of Tregs by IL-2C was more vigorous (Figure 1E). There was no significant increase in either memory CD8⁺ or natural killer cells after IL-2C (Figure 1, H and I). When anti-CD25 antibodies (PC61) were administered shortly after injection of IL-2C, expansion of Tregs in both spleen and kidney was completely abrogated (Figure 1, B and C).Open in a separate windowFigure 1.Expansion of Tregs in both spleen and kidney after renal IRI by IL-2C treatment. IL-2C treatment significantly increases proportions of Foxp3⁺CD4⁺ Tregs among CD4⁺ T cells in both spleen (A and B) and kidney (A and E), compared with the PBS control. Depletion of Tregs by PC61 treatment (IL-2C/PC-61) abrogates expansion of Tregs by IL-2C treatment. Absolute count of Foxp3⁺CD4⁺ Tregs is significantly increased in both spleen (C) and kidney (F) by IL-2C treatment. Foxp3⁻CD4⁺ T cells are also increased after IL-2C treatment in kidney (G), but not in spleen (D). (H and I) However, either memory CD8⁺ (CD8⁺CD44⁺ cells) or natural killer cells (CD3⁻CD49b⁺ cells) are not increased by IL-2C treatment (the proportion is shown in H; the absolute number is shown in I). n=6–9 per group. *P<0.05 for IL-2C versus PBS; ^#P<0.05 for IL-2C versus IL-2C/PC-61.When renal functions were assessed after IRI, renal functions were significantly lower in the IL-2C group than in the PBS group (P=0.001 for BUN on day 1, P=0.001 for creatinine on day 1, P<0.05 for creatinine on day 3, Figure 2). As expected based on its ability to abolish IL-2C–mediated Treg expansion, PC61 treatment abrogated beneficial effects of IL-2C on renal function after IRI. Both serum BUN and creatinine were significantly higher in the PC61 group than those in the IL-2C group (P=0.014 for BUN, Figure 2A; P=0.02 for creatinine, Figure 2B). Abrogation of beneficial effects of IL-2C by PC61 supports that expansion of Tregs was the main mechanism of beneficial effects of IL-2C on renal IRI.Open in a separate windowFigure 2.Attenuation of renal functional impairment after IRI by IL-2C treatment. When IL-2C is administered before bilateral IRI, the levels of BUN (A and C) and creatinine (Cr) (B and D) are significantly decreased by IL-2C treatment during the early injury phase (day 1 and day 3). Treg depletion by PC61 treatment (IL-2C/PC-61) abrogates protective effects of IL-2C treatment on renal function after IRI (BUN is shown in A; creatinine is shown in B). n=9–10 per group. *P<0.05 for IL-2C versus PBS; ^#P<0.05 for IL-2C versus IL-2C/PC-61.IRI induced significant tubular injury in renal tissue 1 day after IRI. IL-2C treatment protected renal tissue injury, and tubular injury score was lower in the IL-2C group than in the PBS group (P=0.003, Figure 3A). IL-2C attenuated apoptosis in renal tissue 1 day after IRI (P<0.001, Figure 3B). When renal regeneration was assessed 3 and 10 days after IRI, the number of proliferating tubular cells was significantly higher in IL-2C group on day 3 (P=0.02, Figure 3C).Open in a separate windowFigure 3.Attenuation of renal tissue injury and infiltration of inflammatory cells after IRI by IL-2C treatment. (A and B) IL-2C treatment significantly attenuates histologic tubular injury that is assessed by tubular injury score (A), and renal apoptosis (B). (C) Proliferation of renal tubular cells is also significantly increased on day 3 by IL-2C treatment. (D and E) IL-2C treatment significantly suppressed infiltration of Ly6G⁺ neutrophil (D) and F4/80⁺ macrophages (E) into renal tissues. n=9–10 per group. *P<0.05 for IL-2C versus PBS. PCNA, proliferating cell nuclear antigen. Original magnification, ×200 in A, B, D, and E; ×40 in C.We also assessed renal inflammation by means of immunohistochemical staining and tissue cytokine measurement. Neutrophils and macrophages are the predominant infiltrates in the injury phase of renal IRI, and Treg depletion significantly increased their infiltration.⁶ Immunohistochemical study demonstrated that IRI increased infiltration of both neutrophils and macrophages into renal tissues 1 day after renal IRI, and that IL-2C significantly attenuated the infiltration of these cells after IRI (P<0.001 for neutrophils, Figure 3D; P=0.03 for macrophages, Figure 3E). Increased infiltration of CD4⁺ T cells in the IL-2C group was attributed to the increased infiltration of both Foxp3⁺ and Foxp3^- cells (Figure 1, F and G, and Supplemental Figure 1A). Foxp3⁺CD4⁺ Tregs were mainly observed in the corticomedullary junction in the IL-2C group (Supplemental Figure 1C). However, there was no difference in infiltration of CD8⁺ T cells (Supplemental Figure 1B), and there was very low infiltration of B cells in both the PBS and IL-2C groups (data not shown). The role of the innate immune response in IRI has been well established. Depletion of neutrophils or macrophages showed a protective effect in IRI.^12–16 Tregs can suppress innate immune cells directly as well as indirectly by suppressing T cells.^17,18 Our data suggest that expanded Tregs by IL-2C attenuated renal IRI mainly through suppression of innate immune responses. These results were in parallel with a recent report that demonstrated that depletion of Tregs resulted in infiltration of more innate immune cells, and higher expression of innate cytokines in the kidney without significant effect on T cells or B cells.⁶When cytokines in renal tissue were measured 1 day after IRI, IRI increased IL-6 and CCL2. IL-2C treatment significantly decreased expression of both IL-6 and CCL2 (P=0.04 and P<0.05 for IL-6 and CCL2, respectively, Supplemental Figure 2, A and B). PC61 treatment abrogated beneficial effects of IL-2C on expression of both IL-6 and CCL2 (Supplemental Figure 2, A and B). There was a discrepancy among the previous studies regarding the levels of TNF-α and IFN-γ after IRI according to the experimental settings including methods of cytokine measurement.^19–21 Levels of these cytokines in this study were not different between IL-2C and the control groups, consistent with a previous study that used the multiplex-bead array (Supplemental Figure 2, C and D).²¹ IL-10 was not increased by IL-2C (Supplemental Figure 2E). Taken together, IL-2C treatment attenuated renal inflammation by decreasing infiltration of innate immune cells and expression of IL-6/CCL2.A previous study reported that Tregs from IL-10 knockout mice have defects in protection of renal IRI.⁶ In order to assess the role of IL-10 in IL-2C–mediated renal protection from IRI, we administered IL-2C in IL-10 knockout mice. IL-2C induced expansion of Tregs in IL-10 knockout mice as well as wild-type mice (Supplemental Figure 3, A and B). Although renal injury was more prominent in IL-10 knockout mice, IL-2C attenuated renal impairment in IL-10 knockout mice as well as wild-type mice (Supplemental Figure 3C). These data suggested that IL-10 is dispensable in the IL-2C–mediated expansion of Tregs and protective effects for IRI. Several differences in experimental settings such as mouse strain, number of Tregs, number of effector T cells, and method of Treg potentiation might contribute to the apparent discrepancy. Although the suppressive activity of IL-10⁻ Tregs on a per cell basis could be weaker, the much higher number of IL-10⁻ Tregs in IL-10 knockout mice might be sufficient to control IRI in response to IL-2C, whereas the small number of adoptive-transferred IL-10⁻ Tregs was insufficient to control IRI in the previous study.⁶ Next, we investigated whether TGF-β plays the crucial role in IL-2C–mediated protection from IRI, and found that neutralizing anti-TGF-β treatment did not abrogate beneficial effects of IL-2C (PBS versus IL-2C/anti-TGF-β, P=0.004; IL-2C/anti-TGF-β versus IL-2C/isotype control, P=0.57, Supplemental Figure 3D). Overall, these data suggest that renal protection by IL-2C–induced Tregs might not be dependent on a single mechanism of suppression. Tregs can suppress target cells through various mechanisms including contact-mediated regulation as well as soluble factor-mediated regulation according to the environmental context.^22,23 Further studies are needed to elucidate the detailed mechanisms of IL-2C–mediated renal protection from IRI.We performed additional experiments to determine the therapeutic potential of IL-2C during the recovery phase after renal IRI. As seen with the above prophylactic approach, IL-2C treatment after IRI also induced significant expansion of Foxp3⁺CD4⁺ Tregs in both spleen and kidney (Figure 4, A and B). Renal function in the IL-2C group was slightly improved on day 5 in the bilateral IRI model (P=0.01 for BUN, Figure 4C; P=0.002 for creatinine, Figure 4D). In addition, renal tubular cell proliferation significantly increased on day 5 (P=0.04, Figure 4E), and renal fibrosis also significantly decreased on day 28 after IL-2C treatment in the unilateral model (P=0.01 for Masson trichrome staining, Figure 4F; P<0.001 for type IV collagen; P=0.04 for fibronectin, Figure 4G), suggesting that IL-2C contributes to improving renal recovery.Open in a separate windowFigure 4.Beneficial effects of IL-2C treatment on the recovery phase after renal IRI. (A and B) When IL-2C is administered after bilateral or unilateral IRI for 3 consecutive days, IL-2C significantly increases proportions of Foxp3⁺CD4⁺ Tregs in both spleen and kidney compared with the PBS. (C and D) IL-2C treatment significantly improves the levels of BUN and creatinine on day 5 after bilateral IRI. n=9–10 per group. (E–G) IL-2C treatment after unilateral IRI also increases renal tubular cell proliferation (PCNA) on day 5 (E), and reduces renal fibrosis on day 28 (F), which is associated with reduced expression of type IV collagen and fibronectin in kidney (G). n=5–8 per group. *P<0.05 for IL-2C versus PBS. PCNA, proliferating cell nuclear antigen.In conclusion, IL-2C can attenuate acute renal damage, and improve renal recovery in IRI by expanding Tregs. Considering its convenience of manipulation and safety, IL-2C is promising for clinical application to renal IRI.     

Renal Transplantation for Chronic Renal Failure in Acute Porphyria

A woman with acute intermittent porphyria and a man with variegateporphyria developed chronic renal failure in middle age. Afterperiods on haemodialysis, both received successful cadavericrenal transplants. On the basis of animal porphyrinogenicitystudies prednisolone and azathioprine were used in preferenceto cyclosporin as immunosuppressive agents. Neither of the patientsshowed any evidence of activation of their porphyria during,or following, transplantation. The findings in these two patientsand a review of two previous reports indicate that acute porphyriais not a contraindication to renal transplantation.     

Activation of Nrf2 Pathway by Dimethyl Fumarate Attenuates Renal Ischemia-Reperfusion Injury

BackgroundDimethyl fumarate (DMF) is a novel antioxidant that selectively reduces hydroxyl radicals. This study aimed to investigate the potential role of DMF in the pathogenesis of renal ischemia-reperfusion injury (IRI) and the mechanisms involved.MethodsC57BL/6 wild-type mice were treated with DMF or a vehicle. Subsequently, renal IRI was induced in mice by a model of right kidney nephrectomy and left renal ischemia for 30 minutes followed by reperfusion for 24 hours. Sham operation and phosphate-buffered saline were used as controls. Serum and renal tissues were collected at 24 hours after IRI to evaluate the influence of DMF on the recovery of renal function after IRI. Blood urea nitrogen and serum creatinine levels were measured. Kidney cell apoptosis was evaluated using terminal deoxynucleotidyl transferase dUTP nick end labeling-positive staining. Interleukin 6 and tumor necrosis factor α cytokines in the kidney tissues were measured. Indicators of oxidative stress in the kidneys were detected. Finally, Nrf2-deficient mice were used to determine the protective role of the nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) and NAD(P)H dehydrogenase quinone 1 (NQO1) signaling pathways induced by DMF using western blot assay.ResultsDMF significantly attenuated renal dysfunction in mice and showed reductions in the severity of renal tubular injury, cell necrosis, and apoptosis. Moreover, DMF significantly reduced the amount of key inflammatory mediators. Additionally, DMF attenuated the malondialdehyde levels 24 hours after IRI but upregulated the superoxide dismutase activities. Western blot assay showed that DMF significantly increased the protein levels of Nrf2, HO-1, and NQO-1. Importantly, these DMF-mediated beneficial effects were not observed in Nrf2-deficient mice.ConclusionsDMF attenuates renal IRI by reducing inflammation and upregulating the antioxidant capacity, which may be through Nrf2/HO-1and NQO1 signaling pathway.     

TLR4 Promotes Fibrosis but Attenuates Tubular Damage in Progressive Renal Injury

Toll-like receptors (TLRs) can orchestrate an inflammatory response upon activation by pathogen-associated motifs and release of endogenous stress ligands during tissue injury. The kidney constitutively expresses most TLRs, including TLR4. The function of TLR4 during the inflammation, tubular atrophy, and fibrosis that accompany progressive renal injury is unknown. Here, we subjected wild-type (WT) and TLR4-deficient mice to unilateral ureteral obstruction and observed elevated levels of TLR4 mRNA in the kidney after obstruction. One day after unilateral ureteral obstruction, TLR4-deficient mice had fewer proliferating tubular epithelial cells and more tubular damage than WT mice; however, TLR4-deficient mice developed considerably less renal fibrosis despite decreased matrix metalloproteinase activity and without significant differences in myofibroblast accumulation. In vitro, TLR4-deficient primary tubular epithelial cells and myofibroblasts produced significantly less type I collagen mRNA after TGF-β stimulation than WT cells. The reduced fibrosis in TLR4-deficient mice associated with an upregulation of Bambi, a negative regulator of TGF-β signaling. In conclusion, TLR4 attenuates tubular damage but promotes renal fibrosis by modulating the susceptibility of renal cells to TGF-β. These data suggest that TLR4 signaling may be a therapeutic target for the prevention of renal fibrosis.Fibroproliferative diseases, including progressive renal disease, are a leading cause of morbidity and mortality worldwide.¹ Renal tubular damage, inflammation, and interstitial fibrosis are main predictors for the risk for progression toward end-stage renal failure.² Progression of renal fibrosis involves a cascade of pathophysiologic processes, including disruption of tubular integrity, a robust inflammatory response, accumulation of (myo)fibroblasts, tubular atrophy, and an increased deposition of extracellular matrix (ECM) components, resulting in fibrogenesis.^3–5The group of Toll-like receptors (TLRs) may be one of the receptor families that orchestrate this cascade of inflammation, myofibroblast accumulation, and fibrosis in the kidney. TLRs can initiate an inflammatory response upon recognition of specific pathogen-associated molecular patterns. It is widely accepted that not only pathogen-associated molecular patterns can trigger TLR-mediated immune responses but endogenous danger molecules that are released upon tissue or cell injury as well.^6–11 We already found that several of these endogenous ligands that can potentially activate both TLR2 and TLR4^9,11–13 are strongly upregulated in murine kidneys after unilateral ureteral obstruction (UUO).^14,15 We demonstrated that TLR2 does not play a role in the development of fibrosis or injury after UUO.¹⁴ Until now, the role of TLR4 in progressive renal injury and fibrosis has remained unknown. In a model of hepatic fibrogenesis, it was demonstrated that TLR4 can enhance TGF-β signaling and myofibroblast activation, suggesting that TLR4 can function as a molecular link between proinflammatory and profibrogenic signals in liver tissue.¹⁶ Interestingly, TLR4 is widely and constitutively expressed in the kidney (e.g., on tubular epithelial cells [TECs]).^17,18 We and others have shown that renal-associated TLR2 and TLR4 can induce an exaggerated inflammatory response in the kidney upon acute ischemic renal injury with subsequent detrimental effects on renal histology and function.^19–21 To study the role of TLR4 in progressive renal injury and renal fibrosis, we subjected wild-type (WT) and TLR4−/− mice to UUO.     

Renal Dendritic Cells Ameliorate Nephrotoxic Acute Kidney Injury

Inflammation contributes to the pathogenesis of acute kidney injury. Dendritic cells (DCs) are immune sentinels with the ability to induce immunity or tolerance, but whether they mediate acute kidney injury is unknown. Here, we studied the distribution of DCs within the kidney and the role of DCs in cisplatin-induced acute kidney injury using a mouse model in which DCs express both green fluorescence protein and the diphtheria toxin receptor. DCs were present throughout the tubulointerstitium but not in glomeruli. We used diphtheria toxin to deplete DCs to study their functional significance in cisplatin nephrotoxicity. Mice depleted of DCs before or coincident with cisplatin treatment but not at later stages experienced more severe renal dysfunction, tubular injury, neutrophil infiltration and greater mortality than nondepleted mice. We used bone marrow chimeric mice to confirm that the depletion of CD11c-expressing hematopoietic cells was responsible for the enhanced renal injury. Finally, mixed bone marrow chimeras demonstrated that the worsening of cisplatin nephrotoxicity in DC-depleted mice was not a result of the dying or dead DCs themselves. After cisplatin treatment, expression of MHC class II decreased and expression of inducible co-stimulator ligand increased on renal DCs. These data demonstrate that resident DCs reduce cisplatin nephrotoxicity and its associated inflammation.Innate immune responses are pathogenic in both ischemic and toxic acute renal failure. In response to renal injury, inflammatory chemokines and cytokines are produced both by renal parenchymal cells, such as proximal tubule epithelial cells, and resident or infiltrating leukocytes.^1–4 The elaborated chemokines and cytokines, including TNF-α, IL-18, keratinocyte-derived chemokine, and monocyte chemoattractant protein 1, subsequently recruit additional immune cells to the kidney, such as neutrophils, T cells, monocytes, and inflammatory dendritic cells (DCs), which may cause further injury through pathways that are not fully defined.^2,5–12 DCs are sentinels of the immune system and under steady-state conditions induce tolerance by various mechanisms, including production of TGF-β, IL-10, or indoleamine 2,3-dioxygenase^13–16; expression of PDL-1, PDL-2, or FcγR2B^17,18; clonal deletion of autoreactive T cells¹⁹; and induction of T regulatory cells via the inducible co-stimulator (ICOS) pathway.^20–23 In response to pathogens or products of tissue injury, DCs mature and initiate immunity or inflammatory diseases.^24,25 Monocytes recruited to inflamed tissue can also differentiate into inflammatory DCs and mediate defense against pathogens or contribute to inflammatory tissue responses.^12,26–28Although DCs represent a major population of immune cells in the kidney,²⁹ their role in renal disease is poorly defined. Liposomal clodronate has been used to study the pathophysiologic role of phagocytic cells, which include DCs and macrophages.^3,30–32 An alternative DC-specific approach uses expression of the simian diphtheria toxin receptor (DTR) driven by the CD11c promoter to target DCs for DT-mediated cell death.²⁴ This model has been used extensively to study the role of DCs in various physiologic and pathophysiologic contexts^32,33; however, its application in kidney disease has been limited to recent studies of immune complex–mediated glomerulonephritis.^12,23We have reported that inflammation plays an important role in the pathogenesis of cisplatin-induced acute kidney injury (AKI).^1,4,5,34 Given the dearth of information regarding the role of renal DCs in AKI, this study examined the renal DC population and the impact of its depletion on cisplatin nephrotoxicity. We show that DCs are the most abundant population of renal resident leukocytes and form a dense network throughout the tubulointerstitium. Renal DCs displayed surface markers that distinguished them from splenic DCs. Using a conditional DC depletion model, we determined that DC ablation markedly exacerbates cisplatin-induced renal dysfunction, structural injury, and infiltration of neutrophils.     

Ulinastatin Ameliorates Acute Ischemic Renal Injury in Rats

Effects of ulinastatin (a Kunitz-type proteinase inhibitor) administration was examined in a model of acute ischemic renal injury induced by bilateral renal artery occlusion in rats. Compared with rats administered vehicle, rats administered ulinastatin (150,000 U/kg body weight) intravenously 30 min preischemia had significantly lower serum creatinine and blood urea nitrogen, and much less injury evident by examination of kidney histologies over the course of 48 h postreperfusion. We conclude that ulinastatin exerts a protective effect against ischemic renal injury.     

Vancomycin Nephrotoxicity Causing Renal Transplant Acute Kidney Injury

Nephrotoxicity is a rather frequent side effect of vancomycin treatment. Attributes of vancomycin nephrotoxicity (VN) are well documented, including its clinical manifestations and renal morphologic changes. However, VN has not been emphasized as the cause of acute kidney injury (AKI) in the renal transplant setting. We report the first 3 such cases. In each of these cases, AKI developed concurrently with vancomycin treatment and resolved after its cessation. As compared with the general population, VN in the renal transplant setting displayed some unusual clinical behaviors. Its development was rather capricious, being noted in some but not every episode of vancomycin treatment, even in the same individual. AKI developed gradually in conjunction with protracted vancomycin treatment, in contrast to a precipitous course in the nontransplant setting. However, renal transplant biopsies showed typical features of VN in each case. VN is an unusual but now well-documented cause of AKI in renal transplant recipients. VN in this setting may display some atypical features, setting it apart from that in the general population. However, renal transplant biopsy changes are characteristic and are amenable to a definitive diagnosis.