Review article: the role of tumor necrosis factor in renal ischemia-reperfusion injury

MnTMPyP, a superoxide dismutase/catalase mimetic, decreases inflammatory indices in ischemic acute kidney injury

OBJECTIVE

This study investigates the effect of a superoxide dismutase mimetic, MnTMPyP, on pro- and anti-inflammatory cytokines in acute renal ischemia-reperfusion (IR).

MATERIALS AND TREATMENT

Male Sprague-Dawley rats underwent bilateral clamping of the renal arteries for 45 min followed by 1, 4, or 24 h of reperfusion. A subset of animals was treated with MnTMPyP (5 mg/kg, i.p.) or saline. Porcine proximal tubular epithelial cells were ATP-depleted for 4 h followed by recovery for 2 h.

METHODS

Cytokines were analyzed by ELISA, and ED1(+) macrophages and CD8(+) T lymphocytes by immunohistochemistry. Statistical analysis was performed using ANOVA.

RESULTS

MnTMPyP attenuated the IR-mediated increase in serum creatinine and circulating levels of interleukin (IL)-2 following 24 h of reperfusion. Furthermore, treatment attenuated increases in tissue levels of tumor necrosis factor (TNF)-α, IL-2, IL-4, and IL-13. MnTMPyP partially prevented the IR-induced infiltration of ED1(+) macrophages and CD8(+) T lymphocytes in the kidney. ATP depletion-recovery of porcine proximal tubular epithelial cells resulted in decreased IL-6 and IL-10 levels, and MnTMPyP partially restored these cytokines.

CONCLUSIONS

These results show that MnTMPyP is partially effective in reducing inflammation associated with renal IR and that reactive oxygen species play a role in modulating both pro- and anti-inflammatory pathways in acute kidney injury.

Protective effects of pentoxifylline on cigarette smoking-induced renal tissue damage in rats

In this study, we investigated the protective effect of pentoxifilline (PTX) on smoking-induced damage in rat kidney tissues. Twenty-seven male Wistar rats were used in the study. Animals were divided into three equal groups as follows: Group 1: control group with only normal saline (NS; 0.9% NaCl) injection for 8 weeks; Group 2: cigarette smoking and NS injection for 8 weeks; and Group 3: cigarette smoking and PTX injection for 8 weeks. The rats were sacrificed after 8 weeks and their kidneys were excised for histopathological analysis. Serial paraffin sections (5 µm) of the kidneys were cut and stained with hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS). The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) method was used to assess apoptosis. Glomerular diameters, glomerular cell number and proximal tubule cell numbers were compared between the groups. Our results showed that PTX treatment prevented negative effects of smoking in rat kidneys. There was a statistically significant difference in all assessed parameters between Group 2 and other groups (p < 0.05). In conclusion, our study shows that PTX treatment is effective in preventing the negative effects of cigarette smoking on kidneys by inhibiting cell damage with its antioxidant properties.

Isoflurane activates intestinal sphingosine kinase to protect against bilateral nephrectomy-induced liver and intestine dysfunction

Acute kidney injury (AKI) frequently leads to systemic inflammation and extrarenal organ dysfunction. Volatile anesthetics are potent anti-inflammatory agents and protect against renal ischemia-reperfusion injury. Here, we sought to determine whether isoflurane, a commonly used volatile anesthetic, protects against AKI-induced liver and intestinal injury, the mechanisms involved in this protection, and whether this protection was independent of the degree of renal injury. Bilateral nephrectomy-induced AKI under pentobarbital sodium anesthesia led to severe hepatic and intestinal injury with periportal hepatocyte vacuolization, small intestinal necrosis, apoptosis, and proinflammatory mRNA upregulation. In contrast, isoflurane anesthesia reduced hepatic and intestinal injury after bilateral nephrectomy. Mechanistically, isoflurane anesthesia upregulated and induced small intestinal crypt sphingosine kinase-1 (SK1) as SK1 mRNA, protein, and enzyme activity increased with isoflurane treatment. Furthermore, isoflurane failed to protect mice treated with a selective SK inhibitor (SKI-II) or mice deficient in the SK1 enzyme against hepatic and intestinal dysfunction after bilateral nephrectomy, demonstrating the key role of SK1. Therefore, in addition to its potent anesthetic properties, isoflurane protects against AKI-induced liver and intestine injury via activation of small intestinal SK1 independently of the effects on the kidney. These findings may help to elucidate the cellular signaling pathways underlying volatile anesthetic-mediated hepatic and intestinal protection and result in novel clinical applications of volatile anesthetics to attenuate perioperative complications arising from AKI.

TNF superfamily: a growing saga of kidney injury modulators

Members of the TNF superfamily participate in kidney disease. Tumor necrosis factor (TNF) and Fas ligand regulate renal cell survival and inflammation, and therapeutic targeting improves the outcome of experimental renal injury. TNF-related apoptosis-inducing ligand (TRAIL and its potential decoy receptor osteoprotegerin are the two most upregulated death-related genes in human diabetic nephropathy. TRAIL activates NF-kappaB in tubular cells and promotes apoptosis in tubular cells and podocytes, especially in a high-glucose environment. By contrast, osteoprotegerin plays a protective role against TRAIL-induced apoptosis. Another family member, TNF-like weak inducer of apoptosis (TWEAK induces inflammation and tubular cell death or proliferation, depending on the microenvironment. While TNF only activates canonical NF-kappaB signaling, TWEAK promotes both canonical and noncanonical NF-kappaB activation in tubular cells, regulating different inflammatory responses. TWEAK promotes the secretion of MCP-1 and RANTES through NF-kappaB RelA-containing complexes and upregulates CCl21 and CCL19 expression through NF-kappaB inducing kinase (NIK-) dependent RelB/NF-kappaB2 complexes. In vivo TWEAK promotes postnephrectomy compensatory renal cell proliferation in a noninflammatory milieu. However, in the inflammatory milieu of acute kidney injury, TWEAK promotes tubular cell death and inflammation. Therapeutic targeting of TNF superfamily cytokines, including multipronged approaches targeting several cytokines should be further explored.

Neutralization of the extracellular HMGB1 released by ischaemic damaged renal cells protects against renal ischaemia-reperfusion injury

BACKGROUND

Graft quality, comprised of ischaemia-reperfusion injury (IRI) and surgical manipulation, is one of the major factors influencing transplant rejection. High-mobility group box 1 (HMGB1), a known activator of innate immunity, has been associated with tissue-generated immunological 'danger' signals; however, its role in renal IRI is not clear.

METHODS

Renal IRI was induced by clamping the left renal pedicle for 60 min in uninephrectomized BALB/c mice. Rabbit anti-mouse HMGB1 antibody was given intraperitoneally 24 h and 30 min before renal ischaemia. Renal HMGB1 expression was assessed by immunohistochemistry and western blot. The therapeutic effect of HMGB1 neutralizing antibody on IRI was evaluated in terms of renal function, histological and immunopathologic examination and terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick end labelling assays.

RESULTS

Ischaemia alone was associated with release of HMGB1, which after reperfusion appeared to induce localization of HMGB1 to renal tubules, peritubular capillaries and glomeruli where the renal cells might be more susceptible to ischaemic insult. Administration of blocking antibody to HMGB1 was associated with reduction in tubular apoptosis and inflammation (TNF-α expression) in situ and in vivo with preservation of renal function.

CONCLUSIONS

These data suggest that released HMGB1 by ischaemic renal parenchyma cells may act as an essential early mediator in delayed inflammatory response during IRI, and targeting HMGB1 may represent a potential approach in the prevention of clinical IRI associated with kidney transplantation.

Novel insights for systemic inflammation in sepsis and hemorrhage

The inflammatory responses in sepsis and hemorrhage remain a major cause of death. Clinically, it is generally accepted that shock in sepsis or hemorrhage differs in its mechanisms. However, the recognition of inflammatory cytokines as a common lethal pathway has become consent. Proinflammatory cytokines such as tumor necrosis factor (TNF) or high-mobility group box1 (HMGB1) are fanatically released and cause lethal multiorgan dysfunction. Inhibition of these cytokines can prevent the inflammatory responses and organ damage. In seeking potential anti-inflammatory strategies, we reported that ethyl pyruvate and alpha7 nicotinic acetylcholine receptor (alpha7nAChR) agonists effectively restrained cytokine production to provide therapeutic benefits in both experimental sepsis and hemorrhage. Here, we review the inflammatory responses and the anti-inflammatory strategies in experimental models of sepsis and hemorrhage, as they may have a consistent inflammatory pathway in spite of their different pathophysiological processes.

Sirolimus in kidney transplant donors and clinical and histologic improvement in recipients: rat model

BACKGROUND

Ischemia-reperfusion (I/R) injury is one of the risk factors for delayed graft function, acute rejection episodes, and impaired long-term allograft survival after kidney transplantation. This antigen-independent inflammatory process produces tissue damage. Isogeneic transplantation in a rat model is a useful method for study of nonimmunologic risk factors for kidney damage.

OBJECTIVE

To study the effect of sirolimus on I/R injury using only 1 dose of the drug in the donor.

MATERIALS AND METHODS

Eighteen rats were allocated to 3 groups of 6 rats each: sham group, control group, and rapamycin group.

RESULTS

Improved renal function and systemic inflammatory response were observed in the rapamycin group compared with the control group (Deltaurea, Deltacreatinine, and DeltaC3, all P < .01). The number of apoptotic nuclei in the renal medulla in the control group was higher than in the rapamycin group (P < .01). Tubular damage was less severe in the rapamycin group compared with the control group (P < .01). Complement 3 and tumor necrosis factor-alpha expression in the kidney samples were significantly decreased when rapamycin was given to the donor rats (P > .01). Bcl-2 protein was upregulated in the rapamycin group compared with the control group (P < .01).

CONCLUSION

Administration of rapamycin in donors attenuates the I/R injury process after kidney transplantation in a rat model.

Icariin attenuates LPS-induced acute inflammatory responses: involvement of PI3K/Akt and NF-kappaB signaling pathway

This study aimed to investigate the mechanism underlying the attenuation of LPS-induced lung inflammation by icariin in vivo and in vitro. The anti-inflammatory effects of icariin on LPS-induced acute inflammatory and the molecular mechanism were investigated. Pretreatment with icarrin (20mg/kg) could attenuate acute lung inflammation by inhibiting mRNA expressions of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), metalloproteinase cycloxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) in the lung of LPS-treated mice. In addition, icariin suppressed the secretion of TNF-alpha, prostaglandin E2 (PGE(2)) and nitric oxide (NO) as well as NF-kappaB p65 activation. Furthermore, decreased myeloperoxidase (MPO) activity was observed in the lung tissue and LPS-induced cytotoxicity in the RAW 264.7 macrophages cells was also markedly attenuated by icariin. Western blotting analysis and confocal microscopy showed that icariin pretreatment reduced the nucleus transportation and constant level of NF-kappaB p65 in the RAW 264.7 macrophage cells. However, the protective effects of icariin were reversed by a PI3K/Akt inhibitor (wortmannin). Our in vitro and in vivo results suggested that activation of the PI3K/Akt pathway and the inhibition of NF-kappaB were involved in the protective effects of icariin on LPS-induced acute inflammatory responses.

JNK signalling in human and experimental renal ischaemia/reperfusion injury

BACKGROUND

Ischaemia/reperfusion (I/R) is an important factor in delayed graft function in renal transplantation and is a determinant of long-term graft outcome. This study examined the role of c-Jun N-terminal kinase (JNK) signalling in human and experimental renal I/R injury.

METHODS

Biopsies obtained 15-20 min after reperfusion of human renal allografts were examined for JNK signalling by immunostaining for phospho-c-Jun. To examine the pathologic role of JNK signalling, a selective JNK inhibitor (CC-401) was administered to rats before or after the induction of a 30-min period of bilateral renal ischaemia followed by reperfusion. Renal function and tubular damage were analysed.

RESULTS

Substantial JNK activation was evident in tubular epithelial cells in kidneys from deceased donors (n = 30) which was less prominent in kidneys from live donors (n = 7) (44.6 +/- 24.8% vs 29.1 +/- 20% p-c-Jun+, respectively; P < 0.05), whereas biopsies of thin basement membrane disease exhibited little, or no, p-c-Jun staining. The degree of p-c-Jun staining correlated with ischaemic time in deceased donor allografts, but not with graft function. Administration of CC-401 to rats prior to bilateral renal I/R prevented acute renal failure and largely prevented tubular damage, leucocyte infiltration and upregulation of pro-inflammatory molecules. However, delaying CC-401 treatment until 1 h after reperfusion (after the peak of JNK activation) had no protective effect.

CONCLUSIONS

We have identified acute activation of the JNK signalling pathway following I/R in human kidney allografts. Experimental studies indicate that blockade of JNK signalling, commenced prior to this activation, can prevent acute tubular necrosis and renal dysfunction secondary to I/R injury.

Cytoprotective Actions of FTY720 Modulate Severe Preservation Reperfusion Injury in Rat Renal Transplants

BACKGROUND

Fingolimod (FTY720) is a potent agonist of sphingosine 1 phosphate receptors and thereby interferes with lymphocyte trafficking. We previously showed that FTY720 protects from mild preservation reperfusion injury induced by 4 hr of cold ischemia. The purpose of this study was to explore the role of FTY720 in ischemic injury and regeneration using a clinically relevant rat renal transplant model with 24 hr of cold ischemia.

METHODS

Donor kidneys were cold stored in the University of Wisconsin solution for 24 hr before transplantation into bilaterally nephrectomized syngeneic recipients (n=6 per group), which received 0.5 mg/kg/d FTY720 or vehicle through oral gavage. Grafts were harvested 2 or 7 days posttransplantation. Renal tissue was examined histologically, stained for apoptosis, proliferation, inflammatory cell infiltrates, and studied for transforming growth factor-beta, and tumor necrosis factor-alpha expression. Rat proximal tubular cells were incubated with 0.1 to 30 micromol/L of phosphorylated FTY720 to test for in vitro cytopathic effects.

RESULTS

FTY720 induced peripheral lymphopenia and significantly reduced intragraft CD3 and ED1 infiltrates. Acute tubular damage scores and graft function were not influenced by FTY720. Tubular apoptosis was significantly reduced, whereas the number of proliferating cell nuclear antigen-positive tubular cells were markedly increased. FTY720 attenuated renal tumor necrosis factor-alpha and transforming growth factor-beta expression. In vitro, pharmacologic concentrations up to 1 micromol/L of phosphorylated FTY720 did not affect tubular cell viability.

CONCLUSION

FTY720 confers tubular epithelial protection in the presence of severe preservation reperfusion injury. Beneficial effects may in part be due to reduction in cell-mediated immune mechanisms. Furthermore, FTY720 could be helpful in patients with delayed graft function.

Effects of metalloproteinase inhibition in a murine model of renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a leading cause of acute tubular necrosis (ATN) and delayed graft function in transplanted organs. Up-regulation of matrix metalloproteinases (MMPs) propagates the microinflammatory response that drives IRI. This study sought to determine the specific effects of Marimastat (Vernalis, BB-2516), a broad spectrum MMP and TNF-alpha-converting enzyme inhibitor, on IRI-induced ATN. Mice were pretreated with Marimastat or methylcellulose vehicle for 4 d before surgery. Renal pedicles were bilaterally occluded for 30 min and allowed to reperfuse for 24 h. Baseline creatinine levels were consistent between experimental groups; however, post-IRI creatinine levels were 4-fold higher in control mice (p < 0.0001). The mean difference between the post-IRI histology grades of Marimastat-treated and control kidneys was 1.57 (p = 0.003), demonstrating more severe damage to control kidneys. Post-IRI mean (+/-SEM) MMP-2 activity rose from baseline levels in control mice (3.62 +/- 0.99); however, pretreated mice presented only a slight increase in mean MMP-2 activity (1.57 +/- 0.72) (p < 0.001). In conclusion, these data demonstrate that MMP inhibition is associated with a reduction of IRI in a murine model.

Evaluation of early macrophage activation and NF-kappaB activity in pulmonary injury caused by deep hypothermia circulatory arrest: an experimental study

This study aimed to analyze changes in nuclear factor-kappa B (NF-kappaB), inflammation factors, and macrophages in pulmonary tissue under deep hypothermia circulatory arrest (DHCA) at different time points, which can be used to infer the role of early macrophage activation and NF-kappaB activity in pulmonary injury. The possible pathogenic mechanisms of DHCA-induced pulmonary injury were investigated in this study to provide an experimental basis for clinical lung protective strategies. Piglets (n = 12) were randomly divided into 2 groups, with 6 piglets in each group. The control group had ambient temperature cardiopulmonary bypass (CPB), and the experimental group had DHCA. Both groups had conventional CPB with 30 min of parallel circulation. Changes in NF-kappaB and inflammatory factors were examined in each group at 6 different time points. At 0.5 h after ischemia-reperfusion, NF-kappaB expression in the nucleus of pulmonary tissue reached its peak, and brown-stained nuclei were mainly polymorphonuclear antibodies. At 1 h after ischemia-reperfusion, plasma tumor-necrosis factor (TNF)-alpha in the experimental group was significantly increased compared with that before reperfusion (P < 0.05). The plasma levels of interleukin (IL)-8 and IL-6 in the experimental group were significantly increased at 1.5 h after ischemia-reperfusion compared with the levels before reperfusion (P < 0.05). Early activation of NF-kappaB under DHCA might play an important role in DHCA-induced pulmonary injury.

Atorvastatin prevents gentamicin-induced renal damage in rats through the inhibition of p38-MAPK and NF-kappaB pathways

BACKGROUND AND AIMS

Gentamicin (GM) is still considered to be an important antibiotic against life-threatening, gram-negative bacterial infections despite its known nephrotoxic effects. We aimed to evaluate the potential protective effect of atorvastatin (ATO) against GM-induced nephrotoxicity in rats.

MATERIALS AND METHODS

The rats were randomly divided into five groups of six animals each: control, GM (100 mg/kg/day), ATO (10 mg/kg/day), GM + ATO, and GM + Vehicle. Kidney function tests, tissue oxidative stress parameters, and histopathological and immunohistochemical studies clarified GM nephrotoxicity.

RESULTS

GM caused a marked reduction in renal functions and increased oxidative stress parameters. Histopathological examination revealed tubular necrosis especially in the renal cortex in GM rats. On immunohistochemical evaluation, GM rat showed more intense expressions of mitogen-activated protein kinase (MAPK), nuclear factor kappa B (NF-kappaB), and inducible nitric oxide synthase (iNOS) compared with control. Kidney function tests and tissue oxidative stress parameters were normalized in the GM + ATO group. Histopathological and immunohistochemical pictures were also greatly ameliorated.

CONCLUSIONS

ATO acts in the kidney as a potent scavenger of free radicals to prevent the toxic effects of GM via the inhibition of MAPK and NF-kappaB signaling pathways and iNOS expression.

Effects of pomegranate juice on hyperoxaluria-induced oxidative stress in the rat kidneys

To evaluate the role of the inducible nitric oxide synthase (iNOS), selective nuclear factor-kB (NF-kB), and p38-mitogene-activated protein kinase (p38-MAPK) on hyperoxaluria-induced oxidative stress and stone formation in rat kidneys. The rats were divided into five groups: group 1, control group; group 2: ethylene glycol (EG) group; group 3: EG + pomegranate juice (PJ)-low group; group 4: EG + PJ-middle group; group 5: EG + PJ-high group. Rats were sacrificed on 7, 15, and 45 days. The iNOS expression, p65-NF-kB and p38-MAPK activity, and oxidative stress markers were evaluated in the kidney. Crystal depositions were evident on day 7, and mild and severe crystallization were observed on day 15 and 45 in EG group, respectively. There was limited or no crystal formation in rats in both middle- and high-dose PJ groups when compared to low-dose PJ group. Crystal depositions, iNOS, p38-MAPK and p65-NF-kB activity, and oxidative stress markers were found to be decreased by middle- and high-dose PJ treatment. PJ was found to have inhibitory effects on renal tubular cell injury and oxidative stress caused by oxalate crystals by reducing ROS, iNOS, p38-MAPK, and NF-kB expression.

High renal ischemia temperature increases neutrophil chemoattractant production and tissue injury during reperfusion without an identifiable role for CD4 T cells in the injury

Various leukocyte populations, including neutrophils and CD4 T cells, have been implicated as mediators of acute renal ischemic injury. The influence of ischemic temperature on molecular and cellular mechanisms mediating this injury was tested in a mouse model. Wild-type C57BL/6, B6.CD4(-/-), B6.CD8(-/-), and B6.RAG-1(-/-) mice subjected to bilateral renal pedicle occlusion for 30 min at a higher (37 degrees C) but not a lower (32 degrees C) ischemic maintenance temperature had clear evidence of renal dysfunction and histopathology. Ischemia imposed at the higher temperature also increased CXCL1/KC and CXCL2/MIP-2 levels and neutrophils, but not T cells or macrophages, infiltrating into the ischemic kidneys. Depletion of neutrophils but not T cells attenuated the acute ischemic injury. These results indicate the influence of ischemic temperature and time on the production of neutrophil chemoattractants and subsequent neutrophil infiltration to mediate acute ischemic injury but fail to identify a role for adaptive immune components in this injury.

Prostacyclin-induced peroxisome proliferator-activated receptor-alpha translocation attenuates NF-kappaB and TNF-alpha activation after renal ischemia-reperfusion injury

Prostacyclin and peroxisome proliferator-activated receptors (PPAR) protect against ischemia-reperfusion (I/R) injury by the induction of an anti-inflammatory pathway. In this study, we examined the prostacyclin-enhanced protective effect of PPARalpha in I/R-induced kidney injury. PPAR-alpha reduced the NF-kappaB-induced overexpression of TNF-alpha and apoptosis in cultured kidney cells. In a murine model, pretreating wild-type (WT) mice with a PPAR-alpha activator, docosahexaenoic acid (DHA), significantly reduced I/R-induced renal dysfunction (lowered serum creatinine and urea nitrogen levels), apoptotic responses (decreased apoptotic cell number and caspase-3, -8 activation), and NF-kappaB activation. By comparison, I/R-induced injury was exacerbated in PPAR-alpha knockout mice. This indicated that PPAR-alpha attenuated renal I/R injury via NF-kappaB-induced TNF-alpha overexpression. Overexpression of prostacyclin using an adenovirus could also induce PPAR-alpha translocation from the cytosol into the nucleus to inhibit caspase-3 activation. This prostacyclin/PPAR-alpha pathway attenuated TNF-alpha promoter activity by binding to NF-kappaB. Using a cAMP inhibitor (CAY10441) and a prostacyclin receptor antibody, we also found that there was another prostacyclin/IP receptor/cAMP pathway that could inhibit TNF-alpha production. Taken together, our results demonstrate for the first time that prostacyclin induces the translocation of PPAR-alpha from the cytosol into the nucleus and attenuates NF-kappaB-induced TNF-alpha activation following renal I/R injury. Treatments that can augment prostacyclin, PPAR-alpha, or the associated signaling pathways may ameliorate conditions associated with renal I/R injury.

Amelioration of renal ischaemia-reperfusion injury by synthetic oligopeptides related to human chorionic gonadotropin

BACKGROUND

We have previously reported that small synthetic oligopeptides related to human beta-chorionic gonadotropin (beta-hCG) can reduce inflammation. Here we investigated whether such oligopeptides can reduce renal ischaemia-reperfusion injury in the mouse.

METHODS

Ten different oligopeptides were administered 1 min before induction of renal ischaemia and 1 min before reperfusion.

RESULTS

Survival at 72 h post-reperfusion was significantly higher in mice treated with oligopeptides MTRV, LQG, VLPALPQ or AQGV as compared to placebo-treated mice. Some oligopeptides were more effective than others. AQGV completely prevented mortality and best preserved kidney function. Next, AQGV was tested in a dose-escalating study in a range of 0.3-30 mg/kg. A survival gain was observed with all doses. Improvement of kidney function was observed from 1 mg/kg. Highest survival and best preserved kidney function were observed at 3 and 10 mg/kg. Upon treatment with AQGV, a significantly lower influx of neutrophils was found, apoptosis was decreased, whereas tubular epithelial cell proliferation was significantly increased at 24 h post-reperfusion. Serum levels of TNF-alpha, INF-gamma, IL-6 and IL-10 were significantly decreased at 24 h post-reperfusion. E-selectin mRNA levels in kidneys were significantly decreased at 6 h post-reperfusion. AQGV did not reduce mortality when treatment was started after reperfusion.

CONCLUSIONS

This study shows that small oligopeptides related to the primary structure of beta-hCG, especially AQGV, are promising potential drugs for preventing the development of renal ischaemia-reperfusion injury.

Influence of nephron mass and a phosphorylated 38 mitogen-activated protein kinase inhibitor on the development of early and long-term injury after renal warm ischaemia

BACKGROUND

Renal ischaemia is accompanied by acute and chronic complications. Tumour necrosis factor (TNF) alpha production via p38 mitogen-activated protein kinase (MAPK) is one of the pivotal mechanisms linking ischaemia to inflammation and could be a therapeutic target. FR167653 (FR), an inhibitor of p38 MAPK and TNF-alpha production, may ameliorate renal damage through its effects on TNF-alpha.

METHODS

Warm ischaemia (WI) was induced in male pigs by bilateral clamping of the renal pedicle for 60 min or unilateral renal clamping after contralateral nephrectomy. FR was administered before and during WI, and continuously for 3 h during reperfusion in pigs exposed to the same WI conditions. Experimental groups were compared with sham-operated pigs and those subjected to unilateral nephrectomy without renal ischaemia. Renal function, fibrosis and inflammation were evaluated, and expression of monocyte chemoattractant protein 1, transforming growth factor beta and TNF-alpha was determined after 12 weeks.

RESULTS

FR significantly reduced renal failure in groups subjected to unilateral nephrectomy and bilateral renal ischaemia. Proteinuria was significantly reduced, and inflammation and expression of proinjury proteins were diminished, accompanied by a reduction in renal fibrosis.

CONCLUSION

Control of TNF-alpha production and activity prevents renal damage after prolonged WI.

Pretreatment of sildenafil attenuates ischemia-reperfusion renal injury in rats

Sildenafil was the first selective inhibitor of phosphodiesterase-5 (PDE5) to be widely used for treating erectile dysfunction. Many recent studies have investigated the cardioprotective role of sildenafil in animal models. We evaluated the protective effects of sildenafil in experimental renal ischemia-reperfusion (IR) injury in two studies. In study 1, male Sprague-Dawley rats were divided into four groups: sham, sildenafil-treated sham, vehicle-treated IR, and sildenafil-treated IR groups. In study 2, we divided the rats into two groups: sildenafil-treated IR rats and PD98059 (ERK inhibitor)+sildenafil-treated IR rats. Functional parameters of the kidney were evaluated at the molecular and structural levels. Blood urea nitrogen (BUN) and serum creatinine levels were lower in sildenafil-treated IR rats than in vehicle-treated IR rats. The expression of inducible (iNOS) and endothelial nitric oxide synthase (eNOS) proteins in sildenafil-treated IR rats was significantly higher than in vehicle-treated IR rats. Pretreatment with sildenafil in IR rats increased ERK phosphorylation and reduced the renal Bax/Bcl-2 ratio, renal caspase-3 activity, and terminal dUTP nick end-labeling-positive apoptotic cells. In contrast, PD98059 treatment increased BUN and serum creatinine levels and attenuated the sildenafil-induced expression of pERK, iNOS, eNOS, and Bcl-2. PD98059 also increased caspase-3 activity but did not decrease the sildenafil-induced accumulation of cGMP. In conclusion, this study suggests that sildenafil has antiapoptotic effects in experimental IR renal injury via ERK phosphorylation, induction of iNOS and eNOS production, and a decrease in the Bax/Bcl-2 ratio.

Ischemic preconditioning improves rat kidney allograft function after ischemia/reperfusion injury: the role of tumor necrosis factor-alpha

OBJECTIVE

The aim of this study was to investigate the early protection of ischemic preconditioning (IPC) and its mechanisms in transplanted rat kidneys.

MATERIALS AND METHODS

Thirty-six male Sprague-Dawley (SD) rat donors and recipients were randomly divided into the following groups: sham-operated group (A; n = 6); untreated transplantation group (B; n = 6); and treatment group (C; n = 6). Group A was subjected to exploratory laparotomy. Group B received orthotopic transplantation. Group C underwent a 15-minute period of ischemia followed by a 10-minute reperfusion before orthotopic transplantation. We assessed the serum creatinine (SCr), blood urea nitrogen (BUN), and to evaluate the degree of kidney graft ischemia/reperfusion injury: tumor necrosis factor-alpha (TNF-alpha), IkappaB kinase-beta (IKK-beta), and nuclear factor-kappa B (NF-kappaB) P65 subunit mRNA expressions.

RESULTS

The levels of SCr and BUN in groups C and B were greater than in the sham-operated group (P < .01), but there was no significant difference between the C and B groups at 24 hours after transplantation (P > .05). The degree of renal graft tubular injury in group C was significantly less compared with group B (P < .01). TNF-alpha transcription levels at 24 hours after transplantation were significantly less compared with the non-IPC group (P < .01). However, no significant difference was observed in IKK-beta mRNA and P65 mRNA expressions between groups C and B (P > .05).

CONCLUSIONS

A 1-cycle schedule of preconditioning (15 min/10 min) attenuated renal graft ischemia/reperfusion injury in the early phase. IPC can improve rat kidney allograft function after ischemia/reperfusion injury. The inhibitory effects on TNF-alpha and on positive feedback signaling of TNF-alpha/NF-kappaB pathways may play important roles in renal graft protection in the early stage.

Effects of everolimus on cytokines, oxidative stress, and renal histology in ischemia-reperfusion injury of the kidney

BACKGROUND

To evaluate the effects of everolimus on renal ischemia-reperfusion injury (IRI).

METHODS

Wistar albino rats were divided into control, ischemia-reperfusion (IR), and ischemia-reperfusion/everolimus (IR/eve) groups. Everolimus was administered for seven consecutive days to the IR/eve group prior to injury. IR and IR/eve groups underwent forty-five minutes ischemia followed by the application of reperfusion at 2 and 24 hours. Blood samples and kidneys were taken from all animals.

RESULTS

. Serum blood urea nitrogen and creatinine levels increased at two hours of reperfusion in the IR and IR/eve groups, and decreased at 24 hours of reperfusion in the IR group. In the IR/eve group, we detected significantly high interleukin-6 levels and low tumor necrosis factor-alpha and malondialdehyde levels at 24 hours. Myeloperoxidase levels increased at two hours of reperfusion in the IR/eve group, but decreased significantly at 24 hours. Everolimus did not improve renal tubular and interstitial injuries in renal IRI.

CONCLUSIONS

It has been demonstrated that pretreatment with everolimus has beneficial effects on cytokines and oxidative stress in renal IRI. However, these effects are insufficient for the correction of histopathological changes and restoration of normal kidney function.

Activation and clinical significance of p38 MAPK signaling pathway in patients with severe trauma

BACKGROUND

Organ dysfunction or multiple organ dysfunction syndrome caused by developing immunological dysfunction and subsequent sepsis or the systemic inflammatory response syndrome after trauma is the leading cause of death in trauma patient. It is believed that mitogen-activated protein kinase) (p38MAPK) is one of the most important kinases in inflammatory signaling. In this study, the change of p38 MAPK signaling pathway in trauma patient with different severity and its clinical significance in trauma inflammation were investigated.

METHODS

One hundred fifty major trauma patients were included in the study and divided into three groups according to injury severity score (ISS). All data required to calculate ISS and determine organ function were registered on admission and during the ICU-stay. Peripheral blood samples were collected from trauma patients 6 h, 1 d, 3 d, 5 d, and 7 d after injury. RQ-PCR and Western blot was used to examine the changes in gene expression, protein expression, and activation level of leukocyte p38 MAPK. Plasma IL-6 and TNFalpha were assayed by ELISA.

RESULTS

Organ dysfunction in 33 trauma patients developed and eight deaths occurred after 24 h in ICU. The causes of death included severe ARDS, MODS, and irreversible brain injury. Incidence of organ dysfunction was related to the increase of injury severity (P < 0.01). Compared with healthy control, the gene expression of p38 MAPK in trauma patients increased significantly 6 h after injury (P < 0.05), and reached a maximum in 1 d (P < 0.01). The expression maintained a high level for 7 d (P < 0.05). One day after injury, significant elevation was observed in protein expression and activation level of p38 MAPK (P < 0.05), as well as the plasma TNFalpha and IL-6 level (P < 0.01). Further investigation found that the gene expression, protein expression, and activation levels of p38 MAPK increased with higher ISS (P < 0.05), and the elevation of plasma TNFalpha and IL-6 level was associated with the increase of activated p38 MAPK and ISS (P < 0.05).

CONCLUSION

p38 MAPK signal pathway was activated in trauma patients. The severity of trauma had highly positive correlation with the expression and activation of p38 MAPK, as well as the elevation of plasma TNFalpha and IL-6 expression. These findings indicate that p38 MAPK signaling pathway plays an important role in the pathological mechanism of trauma.

NK cells induce apoptosis in tubular epithelial cells and contribute to renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) can result in acute renal failure with mortality rates of 50% in severe cases. NK cells are important participants in early-stage innate immune responses. However, their role in renal tubular epithelial cell (TEC) injury in IRI is currently unknown. Our data indicate that NK cells can kill syngeneic TEC in vitro. Apoptotic death of TEC in vitro is associated with TEC expression of the NK cell ligand Rae-1, as well as NKG2D on NK cells. In vivo following IRI, there was increased expression of Rae-1 on TEC. FACS analyses of kidney cell preparations indicated a quantitative increase in NKG2D-bearing NK cells within the kidney following IRI. NK cell depletion in wild-type C57BL/6 mice was protective, while adoptive transfer of NK cells worsened injury in NK, T, and B cell-null Rag2(-/-)gamma(c)(-/-) mice with IRI. NK cell-mediated kidney injury was perforin (PFN)-dependent as PFN(-/-) NK cells had minimal capacity to kill TEC in vitro compared with NK cells from wild-type, FasL-deficient (gld), or IFN-gamma(-/-) mice. Taken together, these results demonstrate for the first time that NK cells can directly kill TEC and that NK cells contribute substantially to kidney IRI. NK cell killing may represent an important underrecognized mechanism of kidney injury in diverse forms of inflammation, including transplantation.

The A20 gene protects kidneys from ischaemia/reperfusion injury by suppressing pro-inflammatory activation

Ischaemia followed by reperfusion (I/R) can induce inflammation and injury and is a risk factor for delayed graft function and rejection of transplanted kidneys. Inflammation is regulated by NF-kappaB transcription factors which induce pro-inflammatory molecules in endothelial cells (EC). We examined whether A20, a negative regulator of NF-kappaB, can protect kidneys from I/R injury. To mimic the fluctuations in endothelial oxygenation that occur during I/R we exposed cultured human umbilical vein EC (HUVEC) to hypoxia (1% O(2) for 4 h) followed by re-oxygenation (21% O(2) for 1 h-24 h). We observed transient expression of pro-inflammatory molecules (E-selectin, VCAM-1 and IL-8) and sustained expression of A20 in HUVEC exposed to hypoxia/re-oxygenation. The effect of A20 on endothelial responses to hypoxia/re-oxygenation was assessed. We observed that pre-treatment of HUVEC with an adenovirus containing A20 (Ad-A20) suppressed activation of NF-kappaB and induction of pro-inflammatory molecules by hypoxia/re-oxygenation, whereas a control adenovirus had little or no effect. Thus the induction of A20 may form a negative feedback loop in pro-inflammatory signalling in cells exposed to hypoxia/re-oxygenation. To validate our cell culture experiments we examined the role of A20 in renal responses to I/R. We observed that A20 was induced in rat kidneys exposed to I/R. Moreover, pre-treatment of animals with Ad-A20 significantly reduced acute tubular necrosis, renal expression of VCAM-1 and NF-kappaB activation in response to I/R, whereas pre-treatment with control adenovirus did not. Our observations suggest that A20 maintains physiological homeostasis in kidneys exposed to I/R by protecting them from inflammation and injury.

Complement 5a receptor inhibition improves renal allograft survival

Complement activation plays a key role in mediating apoptosis, inflammation, and transplant rejection. In this study, the role of the complement 5a receptor (C5aR) was examined in human renal allografts and in an allogenic mouse model of renal transplant rejection. In human kidney transplants with acute rejection, C5aR expression was increased in renal tissue and in cells infiltrating the tubulointerstitium. Similar findings were observed in mice. When recipient mice were treated once daily with a C5aR antagonist before transplantation, long-term renal allograft survival was markedly improved compared with vehicle-treatment (75 versus 0%), and apoptosis was reduced. Furthermore, treatment with a C5aR antagonist significantly attenuated monocyte/macrophage infiltration, perhaps a result of reduced levels of monocyte chemoattractant protein 1 and the intercellular adhesion molecule 1. In vitro, C5aR antagonism inhibited intercellular adhesion molecule 1 upregulation in primary mouse aortic endothelial cells and reduced adhesion of peripheral blood mononuclear cells. Furthermore, C5aR blockade markedly reduced alloreactive T cell priming. These results demonstrate that C5aR plays an important role in mediating acute kidney allograft rejection, suggesting that pharmaceutical targeting of C5aR may have potential in transplantation medicine.

Importance and limits of ischemia in renal partial surgery: experimental and clinical research

Introduction. The objective is to determine the clinical and experimental evidences of the renal responses to warm and cold ischemia, kidney tolerability, and available practical techniques of protecting the kidney during nephron-sparing surgery. Materials and methods. Review of the English and non-English literature using MEDLINE, MD Consult, and urology textbooks. Results and discussion. There are three main mechanisms of ischemic renal injury, including persistent vasoconstriction with an abnormal endothelial cell compensatory response, tubular obstruction with backflow of urine, and reperfusion injury. Controversy persists on the maximal kidney tolerability to warm ischemia (WI), which can be influenced by surgical technique, patient age, presence of collateral vascularization, indemnity of the arterial bed, and so forth. Conclusions. When WI time is expected to exceed from 20 to 30 minutes, especially in patients whose baseline medical characteristics put them at potentially higher, though unproven, risks of ischemic damage, local renal hypothermia should be used.

Apolipoprotein A-I attenuates renal ischemia/reperfusion injury in rats

Apolipoprotein A-I (ApoA-I), the major protein component of serum high-density lipoprotein (HDL), exhibits its anti-inflammatory activity in inflammatory responses. As renal inflammation plays an important role in ischemia/reperfusion (I/R) injury of the kidney, the aim of this study was to investigate the beneficial effect of ApoA-I on renal I/R injury in rats and the underlined mechanism. Using rats subjected to renal I/R by occlusion of bilateral renal pedicles, we found that administration of ApoA-I significantly reduced serum creatinine levels, serum TNF-alpha and IL-1beta levels as well as tissue myeloperoxidase (MPO) activity, compared with I/R controls. Moreover, ApoA-I treatment suppresses the expression of intercellular adhesion molecules-1 (ICAM-1) and P-selectin on endothelium, thus diminishing neutrophil adherence and the subsequent tissue injury. These results showed that ApoA-I reduced I/R-induced inflammatory responses, decreased renal microscopic damage and improved renal function. It seems likely that ApoA-I protects kidney from I/R injury by inhibiting inflammatory cytokines release and neutrophil infiltration and activation.

Systemic gene therapy with interleukin-13 attenuates renal ischemia-reperfusion injury

Ischemia-reperfusion injury is a leading cause of acute renal failure and a major determinant in the outcome of kidney transplantation. Here we explored systemic gene therapy with a modified adenovirus expressing Interleukin (IL)-13, a cytokine with strong anti-inflammatory and cytoprotective properties. When ischemia was induced we found that the IL-13 receptor is expressed in both the normal and experimental kidneys. Prior to the induction of ischemia, rats received adenovirus-IL-13, control adenovirus or saline. IL-13 plasma levels increased more than 50-fold in adenovirus-IL-13 treated animals, confirming successful IL-13 gene delivery. Histological analysis showed decreased tubular epithelial cell damage with adenovirus-IL-13 therapy, accompanied by reduced kidney injury molecule-1 expression. Interstitial infiltration by neutrophils and macrophages was reduced by half as was interstitial fibrosis and expression of alpha-smooth muscle actin. IL-13 treatment significantly diminished the expression of E-selectin, IL-8, MIP-2, TNF-alpha and MCP-1 mRNA. These results suggest that the use of systemic IL-13 gene therapy may be useful in reducing renal tubulointerstitial damage and inflammation caused by ischemia-reperfusion.

Testosterone exacerbates obstructive renal injury by stimulating TNF-alpha production and increasing proapoptotic and profibrotic signaling

Upper urinary tract obstruction is a common cause of renal dysfunction in children and adults. While there is clinical evidence of an increased male incidence and mortality rate with acute renal failure, the effect of gender and testosterone on obstructive renal injury has not previously been evaluated. We hypothesized that testosterone exacerbates proinflammatory TNF-alpha production and proapoptotic and profibrotic signaling during renal obstruction, resulting in increased apoptotic cell death and tubulointerstitial fibrosis. To study this, male, female, castrated male, and testosterone-treated oophorectomized female rats were subjected to sham operation or 3 days of unilateral ureteral obstruction (UUO). Renal cortical tissue was then analyzed for TNF-alpha production; proapoptotic caspase-8, -9, and -3 activity; apoptotic cell death; profibrotic transforming growth factor-beta1 production; and alpha-smooth muscle actin expression. In a separate arm, glomerular filtration rate (inulin clearance) was measured in rats pre- and post-UUO. Male and testosterone-treated oophorectomized female rats demonstrated a significant increase in TNF-alpha production, caspase activity, apoptotic cell death, tubulointerstitial fibrosis, and renal dysfunction during UUO compared with castrated males and normal female rats subjected to the same time course of obstruction. These results demonstrate that endogenous testosterone production in normal male rats and testosterone exogenously administered to oophorectomized females significantly increases TNF production and proapoptotic and profibrotic signaling during renal obstruction, resulting in increased apoptotic cell death, tubulointerstitial fibrosis, and renal dysfunction.

Ozone oxidative preconditioning inhibits inflammation and apoptosis in a rat model of renal ischemia/reperfusion injury

Ischemia/reperfusion injury, which is commonly seen in the field of renal surgery or transplantation, is a major cause of acute renal failure. Previous studies showed that ozone oxidative preconditioning (OzoneOP) attenuated renal ischemia/reperfusion injury. The objective of this study was to examine the role of the OzoneOP in modulating inflammation and apoptosis after renal ischemia/reperfusion injury. Rats were subjected to 45 min of renal ischemia, with or without treatment with OzoneOP (1 mg/kg). Renal function, inflammation and apoptosis were compared at 24 h after renal injury. OzoneOP improved the renal dysfunction and reduced inflammation and apoptosis after ischemia/reperfusion injury. In conclusion, OzoneOP has potent anti-apoptotic and anti-inflammatory properties. These findings may have major implications in the treatment of human ischemic acute renal failure.

Renal protection by delayed ischaemic preconditioning is associated with inhibition of the inflammatory response and NF-kappaB activation

Brief and sublethal ischaemia renders an organ tolerant to subsequent prolonged ischaemia, which is called ischaemic preconditioning (IPC). In regard to the beneficial effects and endogenous mechanisms of renal delayed IPC, few data are available. In this study, we aim at determining reno-protective effects of delayed IPC against ischaemia-reperfusion (I/R) injury, and illustrating whether these effects are associated with suppressing inflammation and nuclear factor-kappaB (NF-kappaB) activation. I/R injury was induced by clamping both renal pedicles for 40 min, followed by 24 h of reperfusion. The rats were subjected to ischaemia for 20 min (preconditioning) or sham surgery (non- preconditioning) at day 4 before I/R. Functional and morphological parameters were evaluated at 24 h after reperfusion. At the same time, macrophage (ED-1(+)) infiltration, and the expression of intercellular adhesion molecule-1 (ICAM-1) and tumor necrosis factor-alpha (TNF-alpha) were assessed by immunohistochemistry. Moreover, I kappa B-alpha degradation and NF-kappaB/DNA binding activity were analyzed. Compared with rats exposed to I/R injury, preconditioned rats had a significant decrease in levels of serum creatinine (Scr, 384.3 +/- 21.8 micromol/L vs. 52.5 +/- 21.7 micromol/L; p<0.001), blood urea nitrogen (BUN, 40.4 +/- 2.7 mmol/L vs. 15.9 +/- 4.2 mmol/L; p<0.001) and serum aspartate aminotransferase (AST, 486.7 +/- 58.6 IU/L vs. 267.3 +/- 43.9 IU/L; p<0.001). Parallel to the above changes, preconditioned rats preserved structural integrity and decreased tubulointerstitial damage scores (3.4 +/- 0.3 vs. 0.2 +/- 0.05; p<0.001) and ED-1(+) cell infiltration (25.3 +/- 3.5 vs. 6.2 +/- 1.2 cells/HPF, p<0.01). Furthermore, our results showed that the expression of ICAM-1 and TNF-alpha, the degree of I kappa B-alpha degradation, and NF-kappaB/DNA binding activity were reduced by IPC. Taken together, our results demonstrated that delayed IPC offered both functional and histological protection, which may be related to suppression of inflammation in preconditioned kidneys.

Decreased peripheral nerve damage after ischemia-reperfusion injury in mice lacking TNF-alpha

We sought to explore the role of tumor necrosis factor-alpha (TNF-alpha) in the pathogenesis of peripheral nerve ischemia-reperfusion (IR) injury. We established an ischemia-reperfusion model in wild type (WT) and TNF-alpha knockout (KO) mice. Electrophysiology, behavioral score and morphological indices (edema and ischemic fiber degeneration [IFD]) were examined to determine the influence of TNF-alpha on peripheral nerve structure and function following ischemia followed by reperfusion. TNF-alpha and nuclear factor-kappa B (NF-kappaB) expression were evaluated using immunohistochemistry. TNF-alpha KO mice, compared to WT had, in sciatic nerve, marked improvement in nerve pathology. This is a region subject to moderate ischemia-reperfusion injury. There was also a significant improvement in electrophysiological and some behavioral indices. TNF-alpha and NF-kappaB expression were abundant in sciatic-tibial nerves of WT mice subjected to IR, but there was less, or complete lack of, expression in ischemic nerve of TNF-alpha KO mice. We conclude that TNF-alpha plays an essential role in the pathogenesis of peripheral nerve ischemia-reperfusion injury, possibly partly through the activation of NF-kappaB.

Functions of TNF and its receptors in renal disease: distinct roles in inflammatory tissue injury and immune regulation

Tumor necrosis factor (TNF) alpha is a potent proinflammatory cytokine and important mediator of inflammatory tissue damage. In addition, it has important immune-regulatory functions. Many experimental studies and clinical observations support a role for TNF in the pathogenesis of acute and chronic renal disease. However, given its dual functions in inflammation and immune regulation, TNF may mediate both proinflammatory as well as immunosuppressive effects, particularly in chronic kidney diseases and systemic autoimmunity. Blockade of TNF in human rheumatoid arthritis or Crohn's disease led to the development of autoantibodies, lupus-like syndrome, and glomerulonephritis in some patients. These data raise concern about using TNF-blocking therapies in renal disease because the kidney may be especially vulnerable to the manifestation of autoimmune processes. Interestingly, recent experimental evidence suggests distinct roles for the 2 TNF receptors in mediating local inflammatory injury in the kidney and systemic immune-regulatory functions. In this review the biologic properties of TNF and its receptors, TNF receptors 1 and 2, relevant to kidney disease are summarized followed by a review of the available experimental and clinical data on the pathogenic role of the TNF system in nonimmune and immune renal diseases. Experimental evidence also is reviewed that supports a rationale for specifically blocking TNF receptor 2 versus anti-TNF therapies in some nephropathies, including immune complex-mediated glomerulonephritis.

Pulmonary macrophage inhibition and inhaled nitric oxide attenuate lung ischemia-reperfusion injury

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) is postulated to occur biphasically. Donor pulmonary macrophages mediate early injury, and neutrophil-dependent injury predominates in the later phase of LIRI. We hypothesized that the biphasic response to LIRI would be attenuated by the administration of gadolinium, a known pulmonary macrophage inhibitor, and inhaled nitric oxide (NO), a pulmonary vasodilator that also interferes with neutrophil chemotaxis.

METHODS

Using our isolated, ventilated, blood-perfused rabbit lung model, study groups (n = 10 per group) underwent two hours of reperfusion after 18 hours of cold ischemia (4 degrees C). Lungs received gadolinium alone, or inhaled NO in the presence or absence of macrophage inhibition with gadolinium.

RESULTS

Compared with control animals, pulmonary macrophage inhibition with the concurrent administration of inhaled NO increased lung compliance (p < 0.01) and oxygenation (p = 0.03), while also decreasing pulmonary artery pressure (p < 0.01), myeloperoxidase content by 63% (p < 0.01), wet to dry ratios by 23% (p < 0.01), and lung tissue (p < 0.01) and bronchoalveolar lavage tumor necrosis factor-alpha (TNF-alpha) protein levels (p < 0.01).

CONCLUSIONS

The severity of LIRI was most significantly reduced by the inhibition of pulmonary macrophages and the concomitant use of inhaled NO. Pulmonary macrophages, likely through the elaboration of proinflammatory cytokines such as TNF-alpha, not only cause early injury themselves but also prime cells such as neutrophils to injure lungs in the later stages of LIRI. The LIRI was effectively blunted by the reduction of macrophage-dependent injury by gadolinium while inhaled NO also attenuated injury by reducing pulmonary hypertension and minimizing neutrophil sequestration.

Effect of atrial natriuretic peptide on ischemia-reperfusion injury in a porcine total hepatic vascular exclusion model

AIM: To evaluate the effect of ANP on warm I/R injury in a porcine THVE model.

METHODS: Miniature pigs (mini-pigs) weighing 16-24 kg were observed for 120 min after reperfusion following 120 min of THVE. The animals were divided into two groups. ANP (0.1 μg/kg per min) was administered to the ANP group (n = 7), and vehicle was administered to the control group (n = 7). Either vehicle or ANP was intravenously administered from 30 min before the THVE to the end of the experiment. Arterial blood was collected to measure AST, LDH, and TNF-α. Hepatic tissue blood flow (HTBF) was also measured. Liver specimens were harvested for p38 MAPK analysis and histological study. Those results were compared between the two groups.

RESULTS: The AST and LDH levels were lower in the ANP group than in the control group; the AST levels were significantly different between the two groups (60 min: 568.7 ± 113.3 vs 321.6 ± 60.1, P = 0.038 < 0.05, 120 min: 673.6 ± 148.2 vs 281.1 ± 44.8, P = 0.004 < 0.01). No significant difference was observed in the TNF-α levels between the two groups. HTBF was higher in the ANP group, but the difference was not significant. A significantly higher level of phosphorylated p38 MAPK was observed in the ANP group compared to the control group (0 min: 2.92 ± 1.1 vs 6.38 ± 1.1, P = 0.011 < 0.05). Histological tissue damage was milder in the ANP group than in the control group.

CONCLUSION: Our results show that ANP has a protective role in I/R injury with p38 MAPK activation in a porcine THVE model.

Differential expression of cytoprotective and apoptotic genes in an ischaemia-reperfusion isolated organ perfusion model of the transplanted kidney

The optimal kidney preservation system and methods to ameliorate reperfusion injury are major factors in accomplishing successful graft function following transplantation. Ischaemia and reperfusion lead to cellular stress and the adaptive response may include the activation of genes involved in cellular protection and/or cell death by apoptosis. We investigated the expression of cytoprotective heme oxygenase-1 (HO-1), anti-apoptotic Bcl-2 and pro-apoptotic Bax after 6 h isolated organ perfusion in porcine kidneys that had been given 10 and 40 min warm ischaemic time. The level of HO-1 was shown to be significantly higher in the 10-min warm ischaemic group compared with 40-min group (0.90 +/- 0.03 vs. 0.83 +/- 0.03; P = 0.002). The levels of HO-1 showed a significant positive correlated with parameters of renal function, creatinine clearance, and renal blood flow and urine output (AUC; r = 0.8042, P = 0.03; r = 0.6028, P = 0.04; r = 0.6055, P = 0.04), demonstrating a possible protective role of this gene in this model of renal transplantation.

Cell adhesion molecules in chemically-induced renal injury

Cell adhesion molecules are integral cell-membrane proteins that maintain cell-cell and cell-substrate adhesion and in some cases act as regulators of intracellular signaling cascades. In the kidney, cell adhesion molecules, such as the cadherins, the catenins, the zonula occludens protein-1 (ZO-1), occludin and the claudins are essential for maintaining the epithelial polarity and barrier integrity that are necessary for the normal absorption/excretion of fluid and solutes. A growing volume of evidence indicates that these cell adhesion molecules are important early targets for a variety of nephrotoxic substances including metals, drugs, and venom components. In addition, it is now widely appreciated that molecules, such as intracellular adhesion molecule-1 (ICAM-1), integrins, and selectins play important roles in the recruitment of leukocytes and inflammatory responses that are associated with nephrotoxic injury. This review summarizes the results of recent in vitro and in vivo studies indicating that these cell adhesion molecules may be primary molecular targets in many types of chemically-induced renal injury. Some of the specific agents that are discussed include cadmium (Cd), mercury (Hg), bismuth (Bi), cisplatin, aminoglycoside antibiotics, S-(1,2-dichlorovinyl)-l-cysteine (DCVC), and various venom toxins. This review also includes a discussion of the various mechanisms, by which these substances can affect cell adhesion molecules in the kidney.

Resident dendritic cells are the predominant TNF-secreting cell in early renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) rapidly induces production of inflammatory mediators including, and in particular, tumor necrosis factor (TNF). Possible sources include resident parenchymal and bone marrow-derived cells as well as recruited leukocytes. Cell suspensions from kidneys subjected to IRI were examined by cell separation followed by in vitro culture and enzyme-linked immunosorbent assay (ELISA), immunoperoxidase and immunofluorescence microscopy, and multicolor flow cytometry to determine the contribution of dendritic cells (DCs) to early production of TNF and other inflammatory mediators. Secretion of TNF, interleukin (IL-6), monocyte chemoattractant protein-1 (MCP-1), and regulated on activation normal T cell expressed and secreted (RANTES) was increased in cell suspensions from IRI compared with control kidneys and was higher in DC-enriched preparations. Immunostaining identified TNF(+ve) cells that coexpressed the DC marker CD11c. Flow cytometry of bone marrow-derived (CD45(+ve)) cell populations at 24 h post-IRI demonstrated that F4/80(+ve)/CD11c(+ve) DCs remained proportionately stable and exhibit higher levels of DC maturation markers, whereas the proportion of F4/80(-ve) DCs, monocytes, neutrophils, and T cells increased. Intracellular staining for TNF confirmed that F4/80(+ve) DCs were the predominant TNF(+ve) cell and expressed higher levels than other TNF(+ve) cells. In vivo depletion of DCs from the kidney substantially attenuated TNF secretion by total and CD45(+ve) cells following IRI. The results uncover a role for resident F4/80(+ve) DCs as the predominant secretors of TNF within 24 h of IRI.

Liver cytokine production and ICAM-1 expression following bone fracture, tissue trauma, and hemorrhage in middle-aged mice

Although studies have indicated that hemorrhagic shock and resuscitation produces hepatic damage by mechanisms involving adhesion molecules in endothelial cells and hepatocytes, it is not known if there is any difference in the extent of hepatic damage following bone fracture, soft tissue trauma, and hemorrhage (Fx-TH) between young and middle-aged animals. To study this, young (6-8 wk) and middle-aged (approximately 12 mo) C3H/HeN male mice were subjected to a right lower leg fracture, soft tissue trauma, (i.e., midline laparotomy), and hemorrhage (blood withdrawal to decrease the blood pressure to 35 +/- 5 mmHg for 90 min) followed by resuscitation with four times the shed blood volume in the form of lactated Ringer solution. Mice were euthanized 24 h later, and liver tissues were harvested. Total bilirubin levels in the hepatocyte extract increased markedly following Fx-TH in both groups of mice; however, the increase in middle-aged mice was significantly higher compared with young mice. TNF-alpha and IL-6 levels in the hepatocyte extract following Fx-TH increased significantly in middle-aged mice but remained unchanged in young mice. IL-10 levels significantly decreased in middle-aged mice following Fx-TH but remained unchanged in young mice. Kupffer cells from middle-aged mice produced significantly higher IL-6 and IL-10 levels compared with young mice. Protein levels and mRNA expression of ICAM-1 in hepatocytes were also significantly higher in middle-aged mice compared with young mice following Fx-TH. These results collectively suggest that the extent of hepatic damage following Fx-TH is dependent on the age of the subject.

Increasing resistance of tubular epithelial cells to apoptosis by shRNA therapy ameliorates renal ischemia-reperfusion injury

Renal tubular epithelial cells (TEC) die by apoptosis or necrosis in renal ischemia-reperfusion injury (IRI). Fas/Fas ligand-dependent fratricide is critical in TEC apoptosis, and Fas promotes renal IRI. Therefore, targeting Fas or caspase-8 may have therapeutic potential for renal injury in kidney transplant or failure. RNA silencing by short hairpin RNA (shRNA) is a novel strategy to down-regulate protein expression. Using this approach, silencing of Fas or caspase-8 by shRNA to prevent TEC apoptosis and IRI was evaluated. IRI was induced by renal artery clamping for 45 or 60 min at 32 degrees C in uninephrectomized C57BL/6 mice. Here, we showed that Fas or pro-caspase-8 expression was significantly knocked down in TEC by stable expression of shRNA, resulting in resistance to apoptosis induced by superoxide, IFN-gamma/TNF-alpha and anti-Fas antibody. Inferior vena cava delivery of pHEX-small interfering RNA targeting Fas or pro-caspase-8 resulted in protection of kidney from IRI, indicated by reduction of renal tubular injury (necrosis and apoptosis) and serum creatinine or blood urea nitrogen. Our data suggest that shRNA-based therapy targeting Fas and caspase-8 in renal cells can lead to protection of kidney from IRI. Attenuation of pro-apoptotic proteins using genetic manipulation strategies such as shRNA might represent a novel strategy to promote kidney allograft survival from rejection or failure.

Discovering erythropoietin's extra-hematopoietic functions: Biology and clinical promise

A greatly expanded understanding of the biology of endogenous erythropoietin (EPO) has emerged since the early 1990s. Originally viewed as the renal hormone dedicated to erythrocyte production, it is now clear that EPO is produced locally by many other tissues in response to physical or metabolic stress. In its autocrine-paracrine roles, EPO mediates preconditioning (ischemic tolerance) and specifically limits the destructive potential of tumor necrosis factor alpha and other proinflammatory cytokines in the brain, heart, kidney, and other tissues. As local production of EPO is generally suppressed following injury, administration of exogenous EPO has been a successful therapeutic approach in preclinical and clinical studies, for example, following ischemia-reperfusion and toxin-induced renal injuries, and in human stroke. The therapeutic time window of tissue protection by EPO is typically very wide in experimental models, showing effectiveness when administered before, during, or after an insult and raising optimism for a high clinical potential. Although there is progress in understanding the signaling pathways responsible for EPO's tissue-protective actions that are similar to, but not as redundant as, those employed for erythrocyte maturation, much work remains to be carried out. Experimental observations also suggest the existence of EPO receptor (EPOR) isoforms mediating EPO's diverse biological activities and have identified a tissue-protective receptor complex consisting of the EPOR and the beta common receptor (CD131) subunit that is also employed by granulocyte-macrophage colony-stimulating factor, interleukin-3 and interleukin-5. Successfully engineered analogues of EPO that selectively activate tissue protection without stimulating hematopoiesis confirm the concept of a tissue-protective receptor and have significant potential utility in the investigational and therapeutic arenas.