In vivo transfection of NF-kappaB decoy oligodeoxynucleotides attenuate renal ischemia/reperfusion injury in rats

Effects of alpha-lipoic acid on ischemia-reperfusion-induced renal dysfunction in rats

We investigated whether alpha-lipoic acid (alpha-LA), an antioxidant, attenuates the ischemia-reperfusion (I/R)-induced dysregulation of these transporters. Both renal pedicles of male Sprague-Dawley rats were clamped for 40 min. alpha-LA (80 mg/kg) was administered intraperitoneally before and immediately after induction of ischemia. After 2 days, the expression of aquaporins (AQPs), sodium transporters, and nitric oxide synthases (NOS) was determined in the kidney by immunoblotting and immunohistochemistry. The expression of endothelin-1 (ET-1) mRNA was determined by real-time PCR. Activities of adenylyl cyclase and guanylyl cyclase were measured by stimulated generation of cAMP and cGMP, respectively. The expression of AQP1-3 as well as that of the alpha(1)-subunit of Na-K-ATPase, type 3 Na/H exchanger, Na-K-2Cl cotransporter, and Na-Cl cotransporter was markedly decreased in response to I/R. The expression of type VI adenylyl cyclase was decreased in I/R-injured rats, which was counteracted by the treatment of alpha-LA. AVP-stimulated cAMP generation was blunted in I/R rats and was then ameliorated by alpha-LA treatment. alpha-LA treatment attenuated the downregulation of AQPs and sodium transporters. The expression of endothelial NOS was decreased in I/R rats, which was prevented by alpha-LA. The cGMP generation in response to sodium nitroprusside was blunted in I/R rats, which was also significantly prevented by alpha-LA. The mRNA expression of ET-1 was increased, which was recovered to the control level by alpha-LA treatment. In conclusion, alpha-LA treatment prevents I/R-induced dysregulation of AQPs and sodium transporters in the kidney, possibly through preserving normal activities of local AVP/cAMP, nitric oxide/cGMP, and ET systems.

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.

Novel pharmacological approaches to the treatment of renal ischemia-reperfusion injury: a comprehensive review

Renal ischemia-reperfusion (I-R) contributes to the development of ischemic acute renal failure (ARF). Multi-factorial processes are involved in the development and progression of renal I-R injury with the generation of reactive oxygen species, nitric oxide and peroxynitrite, and the decline of antioxidant protection playing major roles, leading to dysfunction, injury, and death of the cells of the kidney. Renal inflammation, involving cytokine/adhesion molecule cascades with recruitment, activation, and diapedesis of circulating leukocytes is also implicated. Clinically, renal I-R occurs in a variety of medical and surgical settings and is responsible for the development of acute tubular necrosis (a characteristic feature of ischemic ARF), e.g., in renal transplantation where I-R of the kidney directly influences graft and patient survival. The cellular mechanisms involved in the development of renal I-R injury have been targeted by several pharmacological interventions. However, although showing promise in experimental models of renal I-R injury and ischemic ARF, they have not proved successful in the clinical setting (e.g., atrial natriuretic peptide, low-dose dopamine). This review highlights recent pharmacological developments, which have shown particular promise against experimental renal I-R injury and ischemic ARF, including novel antioxidants and antioxidant enzyme mimetics, nitric oxide and nitric oxide synthase inhibitors, erythropoietin, peroxisome-proliferator-activated receptor agonists, inhibitors of poly(ADP-ribose) polymerase, carbon monoxide-releasing molecules, statins, and adenosine. Novel approaches such as recent research involving combination therapies and the potential of non-pharmacological strategies are also considered.

Renal inflammation is modulated by potassium in chronic kidney disease: possible role of Smad7

High-potassium diets have been shown to be beneficial in cardiovascular disease partly because of a blood pressure-lowering effect. The effect of potassium on inflammation has not been studied. We investigated the influence of potassium supplementation on the degree of renal inflammation and the intracellular signaling mechanisms that could mediate inflammation in chronic kidney disease (CKD). CKD was created in male Sprague-Dawley rats by subtotal nephrectomy. Two groups of CKD rats were pair fed with diets containing 2.1% potassium (potassium-supplemented diet) or 0.4% potassium (basal diet). Body weight, blood pressure, and blood and urine electrolytes were measured biweekly. The animals were euthanized at week 8, and the remnant kidneys were analyzed by histology, immunohistochemistry, Western blotting, and real-time quantitative PCR. In the CKD pair-fed groups, blood potassium concentration did not differ significantly, but blood pressure was lower in the potassium-supplemented group. Compared with the basal diet, potassium supplementation decreased renal tubulointerstitial injury and suppressed renal inflammation as evidenced by decreased macrophage infiltration, lower expression of inflammatory cytokines, and decreased NF-kappaB activation. These renoprotective effects were associated with downregulation of renal transforming growth facto-beta, upregulation of renal Smad7, and lower blood pressure. Our results show that potassium supplementation can reduce renal inflammation and hence, could modulate the progression of kidney injury in CKD.

ANCA-associated vasculitis: new options beyond steroids and cytotoxic drugs

Small vessel vasculitic syndromes--Wegener's granulomatosis, microscopic polyangiitis and renal limited vasculitis (which are associated with circulating antineutrophil cytoplasmic autoantibodies)--are an important cause of renal failure. Present immunosuppressive regimens that are based on cyclophosphamide have significantly increased survival rates. However, these treatments are toxic, increase the risk of infection and do not cure disease. Therefore, newer approaches are required. Understanding disease pathogenesis has allowed rational use for newer therapies such as rituximab, which depletes B cells. Unfortunately, blockade of promising targets such as TNF-alpha, which was thought to be a pivotal cytokine in inflammation, has not shown benefit in a randomised controlled trial. Better understanding of the pathogenesis of the disease is the key to the development of novel targeted therapies, which are urgently required to improve patient prognosis. Gene therapy with targeted delivery of specific proteins is an exciting future prospect.

Cell death in NF-kappaB-dependent tumour cell lines as a result of NF-kappaB trapping by linker-modified hairpin decoy oligonucleotide

The transcription factor NF-kappaB is frequently activated in cancer, and is therefore a valuable target for cancer therapy. Decoy oligodeoxynucleotides (ODNs) inhibit NF-kappaB by preventing its binding to the promoter region of target genes. Few studies have used NF-kappaB-targeting with ODNs in cancer. Using a hairpin NF-kappaB-decoy ODN we found that it induced growth inhibition and cell death in NF-kappaB-dependent tumour cell lines. The ODN colocalized with the p50 subunit of NF-kappaB in cells and directly interacted with it in nuclear extracts. In TNFalpha-treated cells the ODN and the p50 subunit were found in the cytoplasm suggesting that the complex did not translocate to the nucleus. Transcriptional activity of NF-kappaB was efficiently inhibited by the ODN, whereas a scrambled ODN was without effect on transcription. Thus, ODN-mediated inhibition of NF-kappaB can efficiently promote cell death in cancer cells providing a potentially powerful approach to tumour growth inhibition.

Triggers of inflammation after renal ischemia/reperfusion

Renal ischemia/reperfusion (I/R) is a common cause of acute renal failure (ARF). Ischemic ARF is associated with tubulointerstitial inflammation, and studies using animal models have demonstrated that the inflammatory response to I/R exacerbates the resultant renal injury. Ischemic ARF involves complement activation, the generation of cytokines and chemokines within the kidney, and infiltration of the kidney by leukocytes. Recent work has revealed some of the events and signals that trigger the inflammatory response to aseptic, hypoxic injury of the kidney. In many ways, the inflammatory reaction to this injury resembles that seen during ascending urinary infection, and it may represent a general response of the tubular epithelial cells (TECs) to stress or injury. A greater understanding of the signals that trigger the inflammatory response may permit the development of effective therapies to ameliorate ischemic ARF.

Heat preconditioning attenuates renal injury in ischemic ARF in rats: role of heat-shock protein 70 on NF-kappaB-mediated inflammation and on tubular cell injury

Although heat preconditioning has been known to be protective in various types of injury, the precise molecular mechanism for this is unclear. Recent observations that indicate that previous heat shock has an anti-inflammatory, antiapoptotic effect led to this investigation of the in vivo effect of heat preconditioning on NF-kappaB activation and inflammation and also on tubular cell injury in ischemic acute renal failure (ARF). Heat preconditioning provided marked functional protection and also reduced histologic evidence of tubular necrosis. Ischemia/reperfusion-induced NF-kappaB activation was suppressed by heat preconditioning with a subsequent decrease in monocyte chemoattractant protein-1 expression and inflammatory cell infiltration. Heat preconditioning also suppressed the accumulation of phosphorylated inhibitory kappaBalpha (IkappaBalpha) with a resultant depletion of cytoplasmic IkappaBalpha, indicating that heat preconditioning blocked the activation of the IkappaB kinase complex. Tubular cell apoptosis, determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, also was decreased by heat preconditioning, and this was accompanied by decreased caspase 3 activation. Among several heat-shock proteins (HSP), HSP-70 was induced primarily by heat preconditioning. Inhibition of HSP-70 by quercetin almost completely reversed the functional protection that was provided by heat preconditioning. These data provide evidence that HSP-70 affords protection via inhibition of NF-kappaB-mediated inflammation and also inhibition of the cell death pathway in ischemic ARF. Further elucidation of the cytoprotective mechanism of stress proteins could facilitate new target or drug development in the treatment of ARF.

Influence of bradykinin B1 and B2 receptors in the immune response triggered by renal ischemia-reperfusion injury

Bradykinin B1 receptors are exclusively expressed in inflamed tissues. For this reason, they have been related with the outcomes of several pathologies. Ischemia-reperfusion injury is caused by the activation of inflammatory and cytoprotective genes, such as macrophage chemoattractant protein-1 and heme oxygenase-1, respectively. This study was aimed to analyze the involvement of bradykinin B1 and B2 receptors (B1R and B2R) in tissue response after renal ischemia-reperfusion injury. For that, B1R (B1-/-), B2R (B2-/-) knockout animals and its control (wild-type mice, B1B2+/+) were subjected to renal bilateral ischemia, followed by 24, 48 and 120 h of reperfusion. At these time points, blood serum samples were collected for creatinine and urea dosages. Kidneys were harvested for histology and molecular analyses by real-time PCR. At 24 and 48 h of reperfusion, B1-/- group resulted in the lowest serum creatinine and urea levels, indicating less renal damage, which was proved by renal histology. Renal protection associated with B1-/- mice was also related with higher expression of HO-1 and lower expression of MCP-1. In conclusion, the absence of B1R had a protective role against inflammatory responses developed after renal ischemia-reperfusion injury.

Signal transduction of MEK/ERK and PI3K/Akt activation by hypoxia/reoxygenation in renal epithelial cells

The extracellular signal-regulated kinase (ERK) and Akt have been reported to be activated by ischemia/reperfusion in vivo. However, the signaling pathways involved in activation of these kinases and their potential roles were not fully understood in the postischemic kidney. In the present study, we observed that these kinases are activated by hypoxia/reoxygenation (H/R), an in vitro model of ischemia/reperfusion, in opossum kidney (OK) cells and elucidated the signaling pathways of these kinases. ERK and Akt were transiently activated during the early phase of reoxygenation following 4-12h of hypoxia. The ERK activation was inhibited by U0126, a specific inhibitor of ERK upstream MAPK/ERK kinase (MEK), but not by LY294002, a specific inhibitor of phosphoinositide 3-kinase (PI3K), whereas Akt activation was blocked by LY294002, but not by U0126. Inhibitors of epidermal growth factor receptor (EGFR) (AG 1478), Ras and Raf, as well as antioxidants inhibited activation of ERK and Akt, while the Src inhibitor PP2 had no effect. PI3K/Akt activation was shown to be associated with up-regulation of X chromosome-linked inhibitor of apoptosis (XIAP), but not survivin. Reoxygenation following 4-h hypoxia-stimulated cell proliferation, which was dependent on ERK and Akt activation and was also inhibited by antioxidants and AG 1478. Taken together, these results suggest that H/R induces activation of MEK/ERK and PI3K/Akt/XIAP survival signaling pathways through the reactive oxygen species-dependent EGFR/Ras/Raf cascade. Activation of these kinases may be involved in the repair process during ischemia/reperfusion.

Endothelin-1-mediated inflammation in acute renal failure

Acute renal failure presents a serious and life-threatening problem in hospitalized patients. Current therapies address the systemic alterations in renal failure. Cellular changes also occur. These changes affect the glomerular filtration rate and the integrity of the glomerular membrane. ET-1, the most potent vasoconstrictor known, has a negative effect on both the rate of filtration and the integrity of the filtering membrane in renal failure. Using ET-1 antagonists along with the current therapies may prove useful in patients.

Influence of TH1/TH2 Switched Immune Response on Renal Ischemia-Reperfusion Injury

BACKGROUND/AIMS

Recent evidence shows a critical role of the CD4+ T cell with the Th1/Th2 paradigm as a possible effector mechanism in ischemia and reperfusion injury. We hypothesize that a polarized Th1 activation response may negatively influence the renal IRI through its relationship with chemokine production (MCP-1) and with a protective tissue response (HO-1).

METHODS

We subjected mice to renal ischemia for 45 min using IL-4 and IL-12 knockout C57BL/6. We then measured serum urea levels, performed histomorphometric analysis for tubular necrosis and regeneration, and evaluated the mRNA expression of HO-1, t-bet, Gata-3 and MCP-1 by real-time PCR at 24, 48 and 120 h after surgery.

RESULTS/CONCLUSIONS

The IL-4 knockout mice had a statistically significant rise in serum urea levels post IRI compared with control animals. The IL-12-deficient mice were not affected. The IL-4-deficient mice had a statistically significant increase in tubular injury and impairment in cell regeneration. The IRI in IL-4-deficient mice was accompanied by higher levels of HO-1, t-bet and later up-regulation of MCP-1. These findings suggest that the deleterious effects of the Th1 cell involve increased production of chemokines such as MCP-1.

NF-kappa B activation as a pathological mechanism of septic shock and inflammation

The pathophysiology of sepsis and septic shock involves complex cytokine and inflammatory mediator networks. NF-kappaB activation is a central event leading to the activation of these networks. The role of NF-kappaB in septic pathophysiology and the signal transduction pathways leading to NF-kappaB activation during sepsis have been an area of intensive investigation. NF-kappaB is activated by a variety of pathogens known to cause septic shock syndrome. NF-kappaB activity is markedly increased in every organ studied, both in animal models of septic shock and in human subjects with sepsis. Greater levels of NF-kappaB activity are associated with a higher rate of mortality and worse clinical outcome. NF-kappaB mediates the transcription of exceptional large number of genes, the products of which are known to play important roles in septic pathophysiology. Mice deficient in those NF-kappaB-dependent genes are resistant to the development of septic shock and to septic lethality. More importantly, blockade of NF-kappaB pathway corrects septic abnormalities. Inhibition of NF-kappaB activation restores systemic hypotension, ameliorates septic myocardial dysfunction and vascular derangement, inhibits multiple proinflammatory gene expression, diminishes intravascular coagulation, reduces tissue neutrophil influx, and prevents microvascular endothelial leakage. Inhibition of NF-kappaB activation prevents multiple organ injury and improves survival in rodent models of septic shock. Thus NF-kappaB activation plays a central role in the pathophysiology of septic shock.

Fenoldopam Inhibits Nuclear Translocation of Nuclear Factor Kappa B in a Rat Model of Surgical Ischemic Acute Renal Failure

OBJECTIVE

Vasoactive compounds are known to modulate gene transcription, including nuclear factor kappa B (NF-kappaB), in renal tissues, but the molecular effects of fenoldopam in this setting are not known. The authors used a rat model of surgical acute ischemic nephropathy to test the hypothesis that fenoldopam attenuates ischemia/reperfusion (I/R)-induced NF-kappaB-mediated inflammation.

DESIGN

Prospective, single-blind, randomized, controlled animal study.

SETTING

Academic Department of Anesthesiology laboratory.

SUBJECTS

Twenty-four male Sprague-Dawley rats.

INTERVENTIONS

Rats were anesthetized by intraperitoneal administration of 50 mg/kg of urethane and randomly allocated into 4 groups (n = 6 each): sham operation, sham operation with infusion of 0.1 microg/kg/min of fenoldopam, unilateral renal ischemia (1 hour, left renal artery cross-clamping) followed by 4 hours of reperfusion, and unilateral renal I/R with fenoldopam infusion.

MEASUREMENTS AND MAIN RESULTS

Kidney samples were used to measure NF-kappaB DNA-binding activity with an electrophoretic mobility shift assay. NF-kappaB signaling-dependent gene transcription was assessed with microarray analysis, and validated with reverse transcriptase polymerase chain reaction (RT-PCR). Expression of insulin-like growth factor-1 and nitric oxide synthetase-3 messenger RNA (not included in the array) was studied with RT-PCR. NF-kappaB DNA binding activity was significantly higher (p < 0.001) after I/R injury. Of the 96 genes analyzed, 75 were induced and another 8 were suppressed completely (2-fold or greater change v control) after I/R. Treatment with fenoldopam prevented activation of NF-kappaB DNA binding activity (p < 0.001) and attenuated 72 of 75 I/R-induced genes and 3 of 8 I/R-suppressed genes.

CONCLUSION

Data from this rat model of renal I/R suggest that the mechanism by which fenoldopam attenuates I/R-induced inflammation appears to involve inhibition of NF-kappaB translocation and signal transduction.

MCP-1 is up-regulated in unstressed and stressed HO-1 knockout mice: Pathophysiologic correlates

BACKGROUND

Up-regulation of heme oxygenase-1 (HO-1) occurs in, and often confers protection to, the injured kidney. Up-regulation of monocyte chemoattractant protein-1 (MCP-1) promotes not only acute and chronic nephritides but also acute ischemic and nephrotoxic injury. The present study was stimulated by the hypothesis that expression of MCP-1 is suppressed by HO-1, and analyzed the effect of HO-1 on the expression of MCP-1 in stressed and unstressed conditions.

METHODS

Expression of MCP-1 and pathophysiologic correlates were examined in HO-1 knockout (HO-1-/-) and wild-type (HO-1+/+) mice in the unstressed state in young and aged mice, and following nephrotoxic and ischemic insults.

RESULTS

In unstressed HO-1-/- mice, plasma levels of MCP-1 protein were elevated, and MCP-1 mRNA expression was increased in circulating leukocytes and in the kidney. Such early and heightened up-regulation of MCP-1 was eventually accompanied by phenotypic changes in the aged kidney consistent with MCP-1, namely, proliferative changes in glomeruli, tubulointerstitial disease, and up-regulation of transforming growth factor-beta1 (TGF-beta1) and collagens I, III, and IV. In response to a nephrotoxic insult such as hemoglobin, MCP-1 mRNA was up-regulated in a markedly sustained manner in HO-1-/- mice. In response to a duration of ischemia that exerted little effect in HO-1+/+ mice, HO-1-/- mice exhibited higher expression of MCP-1 mRNA, enhanced activation of nuclear factor-kappaB (NF-kappaB) (the transcription factor that regulates MCP-1), markedly greater functional and structural renal injury, increased caspase-3 expression, and increased mortality.

CONCLUSION

In the absence of HO-1, expression of MCP-1 is significantly and consistently enhanced in unstressed and stressed conditions. We speculate that the protective effects of HO-1 in injured tissue may involve, at least in part, the capacity of HO-1 to restrain up-regulation of MCP-1.

Prevention of neutrophil extravasation by hepatocyte growth factor leads to attenuations of tubular apoptosis and renal dysfunction in mouse ischemic kidneys

Ischemia and reperfusion (I/R) injuries occur in numerous organs under pathophysiological conditions. In this process, neutrophils play important roles in eliciting parenchymal injuries. Using a murine model of renal I/R, we show that hepatocyte growth factor (HGF) is a natural ligand that inhibits endothelial injuries and neutrophil extravasation. In mice after renal I/R, plasma HGF levels increased, along with c-Met/HGF receptor phosphorylation in the vascular endothelium. However, this c-Met activation was transient, associated with a decrease in endogenous HGF level, and followed by neutrophil infiltration and renal dysfunction. Suppression of endothelial c-Met phosphorylation by anti-HGF IgG led to rapid progressions of neutrophil extravasation, tubular apoptosis, and renal dysfunction. Inversely, enhancement of the c-Met activation by exogenous HGF blocked endothelial/tubular apoptotic injuries and acute renal failure. In this process, HGF prevented endothelial nuclear factor kappaB activation and inhibited induction of an adhesion molecule (ICAM-1), resulting in attenuated vascular edema and neutrophil infiltration. Thus, we conclude that 1) the HGF/c-Met system of endothelial cells confers an initial barrier to block neutrophil infiltration, and 2) transient and insufficient HGF production allows manifestation of postischemic renal failure. Our study provides a rationale for why HGF supplementation elicits therapeutic effects in ischemic kidneys.

Inhibitors of calpain activation (PD150606 and E-64) and renal ischemia-reperfusion injury

Calpain activation has been implicated in the development of ischemia-reperfusion (I-R) injury. Here we investigate the effects of two inhibitors of calpain activity, PD150606 and E-64, on the renal dysfunction and injury caused by I-R of rat kidneys in vivo. Male Wistar rats were administered PD150606 or E-64 (3mg/kg i.p.) or vehicle (10%, v/v, DMSO) 30min prior to I-R. Rats were subjected to bilateral renal ischemia (45min) followed by reperfusion (6h). Serum and urinary biochemical indicators of renal dysfunction and injury were measured; serum creatinine (for glomerular dysfunction), fractional excretion of Na(+) (FE(Na), for tubular dysfunction) and urinary N-acetyl-beta-d-glucosaminidase (NAG, for tubular injury). Additionally, kidney tissues were used for histological analysis of renal injury, immunohistochemical analysis of intercellular adhesion molecule-1 (ICAM-1) expression and nitrotyrosine formation. Renal myeloperoxidase (MPO) activity (for polymorphonuclear leukocyte infiltration) and malondialdehyde (MDA) levels (for tissue lipid peroxidation) were determined. Both PD150606 and E-64 significantly reduced the increases in serum creatinine, FE(Na) and NAG caused by renal I-R, indicating attenuation of renal dysfunction and injury and reduced histological evidence of renal damage caused by I-R. Both PD150606 and E-64 markedly reduced the evidence of oxidative stress (ICAM-1 expression, MPO activity, MDA levels) and nitrosative stress (nitrotyrosine formation) in rat kidneys subjected to I-R. These findings provide the first evidence that calpain inhibitors can reduce the renal dysfunction and injury caused by I-R of the kidney and may be useful in enhancing the tolerance of the kidney against renal injury associated with aortovascular surgery or renal transplantation.

Future strategies in the treatment of acute renal failure: growth factors, stem cells, and other novel therapies

PURPOSE OF REVIEW

Acute renal failure remains a significant cause of morbidity and mortality in adults and children. Despite advances in understanding the pathophysiology of acute renal failure, little progress has been made in its treatment. This review assesses the recent data on current and promising new therapies for acute renal failure.

RECENT FINDINGS

The first section of the review describes the recent therapies that have been used in humans, all of whom have been adults. The second section evaluates the use of agents given in experimental animal models during or after the onset of acute renal failure. The third section describes the many animal studies using therapies before the onset of experimental renal failure. The final section discusses how the emerging field of stem cell research might be used to treat acute renal failure.

SUMMARY

Among the recent studies in humans, the most intriguing have been the use of atrial natriuretic peptide in patients with nonoliguric renal failure and isotonic sodium bicarbonate infusions to prevent radiocontrast medium-induced renal failure. Among the agents used in animal studies, those with the greatest potential were hepatocyte growth factor and ethyl pyruvate, because they seem to protect against or accelerate recovery from acute renal failure after the renal insult. Finally, stem cell therapy may someday offer the best option for recovery from acute renal failure.

Renal ischemia-reperfusion injury and adenosine 2A receptor-mediated tissue protection: role of macrophages

The role of monocytes/macrophages in the pathogenesis of ischemia-reperfusion injury (IRI) is unknown. We sought to determine whether activation of macrophage adenosine 2A (A(2A)) receptors (A(2A)Rs) mediates tissue protection. We subjected C57Bl/6 mice infused with clodronate [dichloromethylene bisphosphonate (Cl(2)MBP)] to IRI (32 min of ischemia followed by 24 h of reperfusion) to deplete them of macrophages. IRI induced an elevation of plasma creatinine that was reduced with Cl(2)MBP (26% of control). Adoptive transfer of murine RAW 264.7 cells reconstituted injury, an effect blocked significantly by A(2A) agonists (27% of plasma creatinine from mice reconstituted with macrophages). Macrophages subjected to A(2A) knockout by small interfering RNA were adoptively transferred to macrophage-depleted mice and reconstituted injury (110% of control mice); however, the increase in plasma creatinine was blocked by A(2A) agonists (20% of vehicle treatment). Finally, the A(2A) agonist effect on IRI was blocked in macrophage-depleted A(2A)-knockout mice reconstituted with wild-type RAW 264.7 cells. RNase protection assays 24 h after IRI demonstrated that macrophages are required for IL-6 and TGF-beta mRNA induction. However, A(2A) agonist-mediated tissue protection is independent of IL-6 and TGF-beta mRNA. We conclude that the full extent of IRI requires macrophages and that A(2A) agonist-mediated tissue protection is independent of activation of macrophage A(2A)Rs.