Alpha-melanocyte-stimulating hormone inhibits renal injury in the absence of neutrophils

Melanocortin System in Kidney Homeostasis and Disease: Novel Therapeutic Opportunities

Melanocortin peptides, melanocortin receptors, melanocortin receptor accessory proteins, and endogenous antagonists of melanocortin receptors are the key components constituting the melanocortin hormone system, one of the most complex and important hormonal systems in our body. A plethora of evidence suggests that melanocortins possess a protective activity in a variety of kidney diseases in both rodent models and human patients. In particular, the steroidogenic melanocortin peptide adrenocorticotropic hormone (ACTH), has been shown to exert a beneficial effect in a number of kidney diseases, possibly via a mechanism independent of its steroidogenic activity. In patients with steroid-resistant nephrotic glomerulopathy, ACTH monotherapy is still effective in inducing proteinuria remission. This has inspired research on potential implications of the melanocortin system in glomerular diseases. However, our understanding of the role of the melanocortinergic pathway in kidney disease is very limited, and there are still huge unknowns to be explored. The most controversial among these is the identification of effector cells in the kidney as well as the melanocortin receptors responsible for conveying the renoprotective action. This review article introduces the melanocortin hormone system, summarizes the existing evidence for the expression of melanocortin receptors in the kidney, and evaluates the potential strategy of melanocortin therapy for kidney disease.

Melanocortin Regulation of Inflammation

Adrenocorticotropic hormone (ACTH), and α-, β-, and γ-melanocyte-stimulating hormones (α-, β-, γ-MSH), collectively known as melanocortins, together with their receptors (melanocortin receptors), are components of an ancient modulatory system. The clinical use of ACTH in the treatment of rheumatoid arthritis started in 1949, originally thought that the anti-inflammatory action was through hypothalamus-pituitary-adrenal axis and glucocorticoid-dependent. Subsequent decades have witnessed extensive attempts in unraveling the physiology and pharmacology of the melanocortin system. It is now known that ACTH, together with α-, β-, and γ-MSHs, also possess glucocorticoid-independent anti-inflammatory and immunomodulatory effects by activating the melanocortin receptors expressed in the brain or peripheral immune cells. This review will briefly introduce the melanocortin system and highlight the action of melanocortins in the regulation of immune functions from in vitro, in vivo, preclinical, and clinical studies. The potential therapeutic use of melanocortins are also summarized.

ABT-719 for the Prevention of Acute Kidney Injury in Patients Undergoing High-Risk Cardiac Surgery: A Randomized Phase 2b Clinical Trial

Background

Patients undergoing cardiac surgeries with cardiopulmonary bypass (on‐pump) have a high risk for acute kidney injury (AKI). We tested ABT‐719, a novel α‐melanocyte‐stimulating hormone analog, for prevention of AKI in postoperative cardiac surgery patients.

Methods and Results

This phase 2b randomized, double‐blind, placebo‐controlled trial included adult patients with stable renal function undergoing high‐risk on‐pump cardiac surgery in the United States and Denmark. Participants received placebo (n=61) or cumulative ABT‐719 doses of 800 (n=59), 1600 (n=61), or 2100 μg/kg (n=59). Primary outcome was development of AKI based on Acute Kidney Injury Network (AKIN) criteria, measured utilizing preoperative creatinine value and maximum value within 48 hours and urine output within the first 42 hours postsurgery. Secondary outcomes included incidence of AKI based on maximal changes from baseline in novel AKI biomarkers over a 72‐hour period after clamp release and length of intensive care unit stays through 90 days postsurgery. A total of 65.5%, 62.7%, and 69.6% of patients in the 800‐, 1600‐, and 2100‐μg/kg groups, respectively, developed AKI (stages 1, 2, and 3 combined) versus 65.5% in the placebo group (for each pair‐wise comparison with placebo, P=0.966, 0.815, and 0.605, respectively). Adverse events occurred at a similar rate in all treatment groups.

Conclusions

ABT‐719 treatment did not lower AKI incidence using AKIN criteria, influence the elevations of novel biomarkers, or change 90‐day outcomes in patients after cardiac surgery.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique Identifier: NCT01777165.

Mitochondria-Targeted Antioxidants: Future Perspectives in Kidney Ischemia Reperfusion Injury

Kidney ischemia/reperfusion injury emerges in various clinical settings as a great problem complicating the course and outcome. Ischemia/reperfusion injury is still an unsolved puzzle with a great diversity of investigational approaches, putting the focus on oxidative stress and mitochondria. Mitochondria are both sources and targets of ROS. They participate in initiation and progression of kidney ischemia/reperfusion injury linking oxidative stress, inflammation, and cell death. The dependence of kidney proximal tubule cells on oxidative mitochondrial metabolism makes them particularly prone to harmful effects of mitochondrial damage. The administration of antioxidants has been used as a way to prevent and treat kidney ischemia/reperfusion injury for a long time. Recently a new method based on mitochondria-targeted antioxidants has become the focus of interest. Here we review the current status of results achieved in numerous studies investigating these novel compounds in ischemia/reperfusion injury which specifically target mitochondria such as MitoQ, Szeto-Schiller (SS) peptides (Bendavia), SkQ1 and SkQR1, and superoxide dismutase mimics. Based on the favorable results obtained in the studies that have examined myocardial ischemia/reperfusion injury, ongoing clinical trials investigate the efficacy of some novel therapeutics in preventing myocardial infarct. This also implies future strategies in preventing kidney ischemia/reperfusion injury.

Renoprotective approaches and strategies in acute kidney injury

Acute kidney injury (AKI) is a major renal disease associated with high mortality rate and increasing prevalence. Decades of research have suggested numerous chemical and biological agents with beneficial effects in AKI. In addition, cell therapy and molecular targeting have been explored for reducing kidney tissue damage and promoting kidney repair or recovery from AKI. Mechanistically, these approaches may mitigate oxidative stress, inflammation, cell death, and mitochondrial and other organellar damage, or activate cytoprotective mechanisms such as autophagy and pro-survival factors. However, none of these findings has been successfully translated into clinical treatment of AKI. In this review, we analyze these findings and propose experimental strategies for the identification of renoprotective agents or methods with clinical potential. Moreover, we propose the consideration of combination therapy by targeting multiple targets in AKI.

α-Melanocyte stimulating hormone treatment in pigs does not improve early graft function in kidney transplants from brain dead donors

Delayed graft function and primary non-function are serious complications following transplantation of kidneys derived from deceased brain dead (DBD) donors. α-melanocyte stimulating hormone (α-MSH) is a pleiotropic neuropeptide and its renoprotective effects have been demonstrated in models of acute kidney injury. We hypothesized that α-MSH treatment of the recipient improves early graft function and reduces inflammation following DBD kidney transplantation. Eight Danish landrace pigs served as DBD donors. After four hours of brain death both kidneys were removed and stored for 18 hours at 4°C in Custodiol preservation solution. Sixteen recipients were randomized in a paired design into two treatment groups, transplanted simultaneously. α-MSH or a vehicle was administered at start of surgery, during reperfusion and two hours post-reperfusion. The recipients were observed for ten hours following reperfusion. Blood, urine and kidney tissue samples were collected during and at the end of follow-up. α-MSH treatment reduced urine flow and impaired recovery of glomerular filtration rate (GFR) compared to controls. After each dose of α-MSH, a trend towards reduced mean arterial blood pressure and increased heart rate was observed. α-MSH did not affect expression of inflammatory markers. Surprisingly, α-MSH impaired recovery of renal function in the first ten hours following DBD kidney transplantation possibly due to hemodynamic changes. Thus, in a porcine experimental model α-MSH did not reduce renal inflammation and did not improve short-term graft function following DBD kidney transplantation.

Remifentanil temporarily improves renal function in adult patients with chronic kidney disease undergoing orthopedic surgery

PURPOSE

The objective of this study was to confirm the renal protective effect of remifentanil-based anesthesia in perioperative adult patients with chronic kidney disease (CKD).

METHODS

A total of 90 non-dialysis perioperative adult patients with CKD, with preoperative estimated glomerular filtration rate from creatinine (eGFRcreat) values of lower than 50 ml/min/1.73 m(2), who had undergone orthopedic surgery under general anesthesia were retrospectively selected. The subjects were divided into two groups according to whether or not remifentanil was used for anesthesia management: group R, in which remifentanil was used for anesthesia management (n = 45), and group NR, in which remifentanil was not used for anesthesia (n = 45). eGFRcreat was measured pre-surgery (pre), 7 days after surgery (day-7), and 14 days after surgery (day-14).

RESULTS

In group R, both day-7 eGFRcreat (52.2 ± 17.0 ml/min/1.73 m(2)) and day-14 eGFRcreat (49.7 ± 15.5 ml/min/1.73 m(2)) were significantly higher than the pre eGFRcreat (40.7 ± 7.5 ml/min/1.73 m(2)) (day-7: p < 0.01; day-14: p < 0.01). In group NR, on the other hand, pre eGFRcreat (37.8 ± 7.6 ml/min/1.73 m(2)), day-7 eGFRcreat (41.2 ± 10.9 ml/min/1.73 m(2)), and day-14 eGFRcreat (40.2 ± 10.5 ml/min/1.73 m(2)) values were similar. Furthermore, both day-7 eGFRcreat and day-14 eGFRcreat were significantly higher in group R than in group NR (day-7: p < 0.01; day-14: p < 0.01).

CONCLUSIONS

Our findings suggest that anesthesia management using remifentanil may have a renal protective effect in perioperative adult CKD patients undergoing orthopedic surgery.

Adrenocorticotropic hormone ameliorates acute kidney injury by steroidogenic-dependent and -independent mechanisms

Adrenocorticotropic hormone (ACTH) has a renoprotective effect in chronic kidney disease; however, its effect on acute kidney injury (AKI) remains unknown. In a rat model of tumor necrosis factor (TNF)–induced AKI, we found that ACTH gel prevented kidney injury, corrected acute renal dysfunction, and improved survival. Morphologically, ACTH gel ameliorated TNF-induced acute tubular necrosis, associated with a reduction in tubular apoptosis. While the steroidogenic response to ACTH gel plateaued, the kidney-protective effect continued to increase at even higher doses, suggesting steroid-independent mechanisms. Of note, ACTH also acts as a key agonist of the melanocortin system, with its cognate melanocortin 1 receptor (MC1R) abundantly expressed in renal tubules. In TNF-injured tubular epithelial cells in vitro, ACTH reinstated cellular viability and eliminated apoptosis. This beneficial effect was blunted in MC1R-silenced cells, suggesting that this receptor mediates the anti-apoptotic signaling of ACTH. Moreover, ACTH gel protected mice against cecal ligation puncture–induced septic AKI better than α-melanocyte-stimulating hormone: a protein equal in biological activity to ACTH except for steroidogenesis. Thus, ACTH has additive renoprotective actions achieved by both steroid-dependent mechanisms and MC1R-directed anti-apoptosis. ACTH may represent a novel therapeutic strategy to prevent or treat AKI.

Effects of α-MSH on ischemia/reperfusion injury in the rat sciatic nerve

Background:

Ischemia/reperfusion (I/R) causes the production of toxic free radicals and leads to pathological changes in nerve tissue. We investigated the effect of alpha-melanocyte stimulating hormone (α-MSH) in a rat model for sciatic nerve I/R and discuss the possible cytoprotective and antioxidant mechanism of α-MSH against ischemic fiber degeneration.

Methods:

Experiments were performed using 42 adult male Wistar rats. Rats were divided into six experimental groups: control group, ischemia group, I/R groups, and α-MSH treated groups. Ischemia was produced by clamping of the femoral vessels. Immediately after ischemia that lasted 3 h, 75 μg/kg of α-MSH was administered subcutaneously before reperfusion and the tissue malondialdehyde (MDA) level was evaluated as an indicator of lipid peroxidation in groups with different reperfusion periods.

Results:

The reperfusion injury did not begin in the first hour of reperfusion after 3 h of ischemia, and MDA levels increased on the first day of reperfusion. During the first day, blood MDA levels were decreased in the α-MSH group compared to the control group. The tissue from animals pre-treated with α-MSH showed fewer morphological alterations. Myelin breakdown was significantly diminished after treatment with α-MSH, and the ultrastructural features of axons showed remarkable improvement. Two-way analysis of variance was used for comparing three or more groups. When a significant difference existed, the post-hoc multiple-comparison test was applied to demonstrate the differences.

Conclusions:

The results confirm that pre-treatment with α-MSH after ischemia protected the peripheral nerves against I/R injury.

Mediators of inflammation in acute kidney injury

Acute kidney injury (AKI) remains to be an independent risk factor for mortality and morbidity. Inflammation is now believed to play a major role in the pathopathophysiology of AKI. It is hypothesized that in ischemia, sepsis and nephrotoxic models that the initial insult results in morphological and/or functional changes in vascular endothelial cells and/or in tubular epithelium. Then, leukocytes including neutrophils, macrophages, natural killer cells, and lymphocytes infiltrate into the injured kidneys. The injury induces the generation of inflammatory mediators like cytokines and chemokines by tubular and endothelial cells which contribute to the recruiting of leukocytes into the kidneys. Thus, inflammation has an important role in the initiation and extension phases of AKI. This review will focus on the mediators of inflammation contributing to the pathogenesis of AKI.

The peptide NDP-MSH induces phenotype changes in the heart that resemble ischemic preconditioning

alpha-Melanocyte-stimulating hormone (alpha-MSH) is a pro-opiomelanocortin (POMC)-derived peptide that exerts multiple protective effects on host cells. Previous investigations showed that treatment with alpha-MSH or synthetic melanocortin agonists reduces heart damage in reperfusion injury and transplantation. The aim of this preclinical research was to determine whether melanocortin treatment induces preconditioning-like cardioprotection. In particular, the plan was to assess whether melanocortin administration causes phenotype changes similar to those induced by repetitive ischemic events. The idea was conceived because both ischemic preconditioning and melanocortin signaling largely depend on cAMP response element binding protein (CREB) phosphorylation. Rats received single i.v. injections of 750microg/kg of the alpha-MSH analogue Nle(4),DPhe(7)-alpha-MSH (NDP-MSH) or saline and were sacrificed at 0.5, 1, 3, or 5h. Western blot analysis showed that rat hearts expressed melanocortin 1 receptor (MC1R) protein. Treatment with NDP-MSH was associated with early and marked increase in interleukin 6 (IL-6) mRNA. This was followed by signal transducer and activator of transcription 3 (STAT3) phosphorylation and induction of suppressor of cytokine signaling 3 (SOCS3). There were no changes in expression of other cytokines of the IL-6 family. Expression of IL-10, IL-1beta, and TNF-alpha was likewise unaltered. In hearts of rats treated with NDP-MSH there was increased expression of the orphan nuclear receptor Nur77. The data indicate that NDP-MSH induces phenotype changes that closely resemble ischemic preconditioning and likely contribute to its established protection against reperfusion injury. In addition, the increased expression of Nur77 and SOCS3 could be part of a broader anti-inflammatory effect.

Change of melanocortin receptor expression in rat kidney ischemia-reperfusion injury

OBJECTIVES

alpha-Melanocyte stimulating hormone (alpha-MSH) may ameliorate renal ischemia-reperfusion (I/R) injury. Recent data suggest that melanocortin receptors may be related to the anti-inflammatory and immunomodulating action for alpha-MSH. We designed this experiment to determine the renal distribution of alpha-MSH receptors; melanocortin-1 receptor (MC-1R) and melanocortin-3 receptor (MC-3R).

METHODS

Sprague-Dawley male rats (n = 24) were randomly divided into 2 groups: the sham (n = 2) and the operation groups with warm ischemia (n = 12). Animals in the operation group were subjected to 40 minutes of warm renal ischemia. Western blotting analyses and immunohistochemistry were employed to determine expression of MC-1R and MC-3R.

RESULTS

Expression of MC-1R and MC-3R was decreased on 1 day after reperfusion. Immunohistochemical study confirmed the findings of Western blot analysis.

CONCLUSIONS

The present study demonstrated novel renal expression of MC-1R and MC-3R, especially in the outer medulla, representative of the renal I/R injury. Our current study suggested that the mechanisms of action of alpha-MSH may significantly attenuate the renal I/R injury by specific kidney-targeted effects via MC-Receptors as well as by systemic cytokine effects.

The innate immune response in ischemic acute kidney injury

Kidney ischemia reperfusion injury is a major cause of morbidity in both allograft and native kidneys. Ischemia reperfusion-induced acute kidney injury is characterized by early, alloantigen-independent inflammation. Major components of the innate immune system are activated and participate in the pathogenesis of acute kidney injury, plus prime the allograft kidney for rejection. Soluble members of innate immunity implicated in acute kidney injury include the complement system, cytokines, and chemokines. Toll-like receptors (TLRs) are also important contributors. Effector cells that participate in acute kidney injury include the classic innate immune cells, neutrophils and macrophages. Recent data has unexpectedly identified lymphocytes as participants of early acute kidney injury responses. In this review, we will focus on immune mediators that participate in the pathogenesis of ischemic acute kidney injury.

Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo, and future perspectives for the treatment of immune-mediated inflammatory diseases

Alpha-MSH is a tridecapeptide derived from proopiomelanocortin. Many studies over the last few years have provided evidence that alpha-MSH has potent protective and antiinflammatory effects. These effects can be elicited via centrally expressed melanocortin receptors that orchestrate descending neurogenic antiinflammatory pathways. alpha-MSH can also exert antiinflammatory and protective effects on cells of the immune system and on peripheral nonimmune cell types expressing melanocortin receptors. At the molecular level, alpha-MSH affects various pathways implicated in regulation of inflammation and protection, i.e., nuclear factor-kappaB activation, expression of adhesion molecules and chemokine receptors, production of proinflammatory cytokines and mediators, IL-10 synthesis, T cell proliferation and activity, inflammatory cell migration, expression of antioxidative enzymes, and apoptosis. The antiinflammatory effects of alpha-MSH have been validated in animal models of experimentally induced fever; irritant and allergic contact dermatitis, vasculitis, and fibrosis; ocular, gastrointestinal, brain, and allergic airway inflammation; and arthritis, but also in models of organ injury. One obstacle limiting the use of alpha-MSH in inflammatory disorders is its pigmentary effect. Due to its preserved antiinflammatory effect but lack of pigmentary action, the C-terminal tripeptide of alpha-MSH, KPV, has been delineated as an alternative for antiinflammatory therapy. KdPT, a derivative of KPV corresponding to amino acids 193-195 of IL-1beta, is also emerging as a tripeptide with antiinflammatory effects. The physiochemical properties and expected low costs of production render both agents suitable for the future treatment of immune-mediated inflammatory skin and bowel disease, fibrosis, allergic and inflammatory lung disease, ocular inflammation, and arthritis.

Renal repair and recovery

OBJECTIVE

To review the cellular and molecular mechanisms of renal repair and recovery after acute kidney injury (AKI).

DATA SOURCE

The data were summarized from published research articles.

RESULTS

In AKI, there is an acute inflammatory response, epithelial cell necrosis and apoptosis, and shedding of epithelial cells into the tubular lumen. Recent work demonstrates that repopulation of damaged renal tubules occurs primarily from proliferation of tubular epithelial cells and resident renal-specific stem cells, with some contribution of paracrine factors from bone marrow-derived mesenchymal stem cells. In addition, growth factors seem to play a critical role in the repair process in animal models of renal injury. However, attempts to use growth factors in the clinical setting to attenuate human AKI or accelerate renal repair have not yet been successful. The endothelium also plays a critical role in the pathogenesis of AKI. Lastly, in human studies, the effect of dialysis on renal recovery remains poorly understood.

CONCLUSIONS

Experimental animal models of AKI demonstrate that renal recovery and repair involves proliferation of tubular epithelial cells and stem cell populations and the coordinated contribution of multiple growth factors. Future efforts to improve recovery from AKI and improve patient outcomes may include novel therapies based on manipulation of populations of stem cells and augmenting repopulation of renal tubules.

AP214, an analogue of alpha-melanocyte-stimulating hormone, ameliorates sepsis-induced acute kidney injury and mortality

Sepsis remains a serious problem in critically ill patients with the mortality increasing to over half when there is attendant acute kidney injury. alpha-Melanocyte-stimulating hormone is a potent anti-inflammatory cytokine that inhibits many forms of inflammation including that with acute kidney injury. We tested whether a new alpha-melanocyte-stimulating hormone analogue (AP214), which has increased binding affinity to melanocortin receptors, improves sepsis-induced kidney injury and mortality using a cecal ligation and puncture mouse model. In the lethal cecal ligation-puncture model of sepsis, severe hypotension and bradycardia resulted and AP214 attenuated acute kidney injury of the lethal model with a bell-shaped dose-response curve. An optimum AP214 dose reduced acute kidney injury even when it was administered 6 h after surgery and it significantly improved blood pressure and heart rate. AP214 reduced serum TNF-alpha and IL-10 levels with a bell-shaped dose-response curve. Additionally; NF-kappaB activation in the kidney and spleen, and splenocyte apoptosis were decreased by the treatment. AP214 significantly improved survival in both lethal and sublethal models. We have shown that AP214 improves hemodynamic failure, acute kidney injury, mortality and splenocyte apoptosis attenuating pro- and anti-inflammatory actions due to sepsis.

Blocking the immune response in ischemic acute kidney injury: the role of adenosine 2A agonists

Acute kidney injury (AKI) is associated with a high degree of morbidity and mortality and its incidence is increasing. These factors, together with a lack of successful clinical trials, necessitate a comprehensive evaluation of the pathogenesis of AKI and trial design. The progress that has been made in elucidating the pathogenesis of AKI has defined inflammation as an early event and therefore a potential target for therapeutic intervention. This Review summarizes recent advances in our understanding of the role of inflammation in AKI as well as our approach to limiting inflammation using compounds that stimulate adenosine 2A receptors (A(2A)Rs). A(2A)Rs are members of a family of guanine nucleotide-binding proteins that have become a focus of interest primarily because of their ability to broadly inactivate the inflammatory cascade. An A(2A) agonist-ATL146 ester (ATL146e)-is currently being tested in a phase III clinical trial as a pharmacological stress agent in cardiac perfusion imaging studies. This study, together with extensively published preclinical data, will facilitate testing of ATL146e in human trials of AKI.

Disruption of renal peritubular blood flow in lipopolysaccharide-induced renal failure: role of nitric oxide and caspases

Acute renal failure (ARF) is a frequent and serious complication of endotoxemia caused by lipopolysaccharide (LPS) and contributes significantly to mortality. The present studies were undertaken to examine the roles of nitric oxide (NO) and caspase activation on renal peritubular blood flow and apoptosis in a murine model of LPS-induced ARF. Male C57BL/6 mice treated with LPS ( Escherichia coli) at a dose of 10 mg/kg developed ARF at 18 h. Renal failure was associated with a significant decrease in peritubular capillary perfusion. Vessels with no flow increased from 7 ± 3% in the saline group to 30 ± 4% in the LPS group ( P < 0.01). Both the inducible NO synthase inhibitor l- N6-1-iminoethyl-lysine (l-NIL) and the nonselective caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone (Z-VAD) prevented renal failure and reversed perfusion deficits. Renal failure was also associated with an increase in renal caspase-3 activity and an increase in renal apoptosis. Both l-NIL and Z-VAD prevented these changes. LPS caused an increase in NO production that was blocked by l-NIL but not by Z-VAD. Taken together, these data suggest NO-mediated activation of renal caspases and the resulting disruption in peritubular blood flow are an important mechanism of LPS-induced ARF.

alpha-MSH prevents impairment in renal function and dysregulation of AQPs and Na-K-ATPase in rats with bilateral ureteral obstruction

The purpose of this study was to evaluate the effects of the anti-inflammatory hormone alpha-melanocyte-stimulating hormone (alpha-MSH) treatment on renal function and expression of aquaporins (AQPs) and Na-K-ATPase in the kidney in response to 24 h of bilateral ureteral obstruction (BUO) or release of BUO (BUO-R). In rats with 24-h BUO, immunoblotting revealed that downregulation of AQP2 and AQP3 was attenuated (AQP2: 38 +/- 5 vs. 13 +/- 4%; AQP3: 44 +/- 3 vs. 19 +/- 4% of sham levels; P < 0.05), whereas downregulation of Na-K-ATPase was prevented by alpha-MSH treatment (Na-K-ATPase: 94 +/- 7 vs. 35 +/- 5% of sham levels; P < 0.05). Immunocytochemistry confirmed the changes in AQP1 and Na-K-ATPase expression. Renal tubular cell apoptosis was confirmed in BUO kidneys, and alpha-MSH treatment virtually completely abolished apoptosis. Furthermore, we measured glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), respectively. Forty-eight hours after BUO-R demonstrated that alpha-MSH treatment almost completely prevented the decrease in GFR (nontreated: 271 +/- 50; alpha-MSH: 706 +/- 85; sham: 841 +/- 105 microl x min(-1).100 g body wt(-1), P < 0.05) and ERPF (nontreated: 1,139 +/- 217; alpha-MSH: 2,598 +/- 129; sham: 2,633 +/- 457 microl x min(-1).100 g body wt(-1), P < 0.05). alpha-MSH treatment also partly prevented the downregulation of AQP1 and Na-K-ATPase expression in rats after BUO-R for 48 h. In conclusion, alpha-MSH treatment significantly prevents impairment in renal function and also prevents downregulation of AQP2, AQP3, and Na-K-ATPase during BUO or AQP1 and Na-K-ATPase after BUO-R, demonstrating a marked renoprotective effect of alpha-MSH treatment in conditions with urinary tract obstruction.

Inflammatory cells in ischemic acute renal failure

Ischemic acute renal failure (ARF) is increasingly recognized as involving a complex cascade of mechanisms with both acute and chronic consequences. Attention to nontraditional mediators of ARF such as inflammatory pathways and microvascular events has yielded new paradigms and avenues of research. The initiation phase of renal ischemia/reperfusion (I/R) injury damage involves microvascular hemodynamic changes characterized by red blood cell sludging with platelets and leukocytes. Blocking leukocyte-endothelial interactions has yielded significant protection from renal I/R injury in experimental models. However, experiments focusing on the role of the neutrophil have led to a modest expectation of its role in ARF. Recent studies have found that T cells directly mediate renal injury in experimental I/R injury. The CD4+ T cell, working both via interferon-gamma (IFN-gamma) and costimulatory molecules appears to be an important modulator of ARF. The B cell has recently been implicated in ARF. Little is known about the role for the macrophage. Finally, resident kidney cells likely contribute to the inflammatory pathogenesis of I/R damage and protection/repair, but how, and to what extent they are involved is not known. New tools to modulate inflammatory cells, particularly mononuclear leukocytes, hold promise for clinical trials in ARF.

Gamma-MSH, sodium metabolism, and salt-sensitive hypertension

Alpha-, beta-, and gamma-melanocyte stimulating hormones (MSHs) are melanotropin peptides that are derived from the ACTH/beta-endorphin prohormone proopiomelanocortin (POMC). They have been highly conserved through evolutionary development, although their functions in mammals have remained obscure. The identification in the last decade of a family of five membrane-spanning melanocortin receptors (MC-Rs), for which the melanotropins are the natural ligands, has permitted the characterization of a number of important actions of these peptides, although the physiological function(s) of gamma-MSH have remained elusive. Much evidence indicates that gamma-MSH stimulates sympathetic outflow and raises blood pressure through a central mechanism. However, this review focuses on newer cardiovascular and renal actions of the peptide, acting in most cases through the MC3-R. In rodents, a high-sodium diet (HSD) increases the pituitary abundance of POMC mRNA and of gamma-MSH content and results in a doubling of plasma gamma-MSH concentration. The peptide is natriuretic and acts through renal MC3-Rs, which are also upregulated by the HSD. Thus the system appears designed to participate in the integrated response to dietary sodium excess. Genetic or pharmacologic induction of gamma-MSH deficiency results in marked salt-sensitive hypertension that is corrected by the administration of the peptide, probably through a central site of action. Deletion of the MC3-R also produces salt-sensitive hypertension, which, however, is not corrected by infusion of the hormone. These observations in aggregate suggest the operation of a hormonal system important in blood pressure control and in the regulation of sodium excretion. The relationship of these two actions to each other and the significance of this system in humans are important questions for future research.

Targeting Melanocortin Receptors as a Novel Strategy to Control Inflammation

Adrenocorticotropic hormone and alpha-, beta-, and gamma-melanocyte-stimulating hormones, collectively called melanocortin peptides, exert multiple effects upon the host. These effects range from modulation of fever and inflammation to control of food intake, autonomic functions, and exocrine secretions. Recognition and cloning of five melanocortin receptors (MCRs) has greatly improved understanding of peptide-target cell interactions. Preclinical investigations indicate that activation of certain MCR subtypes, primarily MC1R and MC3R, could be a novel strategy to control inflammatory disorders. As a consequence of reduced translocation of the nuclear factor kappaB to the nucleus, MCR activation causes a collective reduction of the major molecules involved in the inflammatory process. Therefore, anti-inflammatory influences are broad and are not restricted to a specific mediator. Short half-life and lack of selectivity could be an obstacle to the use of the natural melanocortins. However, design and synthesis of new MCR ligands with selective chemical properties are already in progress. This review examines how marshaling MCR could control inflammation.

Alpha-melanocyte-stimulating hormone inhibits lung injury after renal ischemia/reperfusion

Combined acute renal and pulmonary failure has a very high mortality. In animals, lung injury develops after shock or visceral or renal ischemia. Alpha-melanocyte-stimulating hormone (alpha-MSH) is an antiinflammatory cytokine, which inhibits inflammatory, apoptotic, and cytotoxic pathways implicated in acute renal injury. We sought to determine if alpha-MSH inhibits acute lung injury after renal ischemia and to determine the early mechanisms of alpha-MSH action. Mice were subjected to renal ischemia treated with vehicle or alpha-MSH. At early time points, we measured organ histology, leukocyte accumulation, myeloperoxidase activity, activation of nuclear factor-kappaB, p38 mitogen-activated protein kinase, c-Jun, and activator protein-1 pathways, in addition to messenger RNA for intracellular adhesion molecule-1 and tumor necrosis factor-alpha. Renal ischemia rapidly activated kidney and lung nuclear factor-kappaB, p38 mitogen-activated protein kinase, c-Jun, and activator protein-1 pathways, and distant lung injury. Alpha-MSH administration immediately before reperfusion significantly decreased kidney and lung injury and prevented activation of kidney and lung transcription factors and stress response genes, and lung intracellular adhesion molecule-1 and tumor necrosis factor-alpha at early time points after renal ischemia/reperfusion. We conclude that distant lung injury occurs rapidly after renal ischemia. alpha-MSH protects against both kidney and lung damage after renal ischemia, in part, by inhibiting activation of transcription factors and stress genes early after renal injury.

Leukocyte recruitment and acute renal failure

Despite advances in medical technology, acute renal failure (ARF) still represents a major challenge in clinical medicine, as morbidity and mortality have remained unchanged over the past two decades. The pathophysiology of ARF is highly complex and only poorly understood; new insights into the pathophysiology of ARF are therefore of utmost importance to develop better understanding and therapies. Acute tubular necrosis (ATN) is the predominant cause of ARF and often arises as a consequence of septic, toxic, or ischemic insults. The recruitment of leukocytes into the kidney has recently emerged as a key event in the development of experimental ischemic and septic ARF. A few descriptive clinical studies support this idea. However, the clinical relevance of various animal models remains unclear, as does the importance of different leukocyte subsets, and even methodological aspects as how to quantify renal leukocyte recruitment. This review summarizes and critically evaluates experimental findings that provide insight into the role of leukocytes and their recruitment during ARF. We aim to provide a valid description of ARF, illustrate animal models of ARF, review qualitative and quantitative methods to assess renal leukocyte recruitment, and discuss the components of the leukocyte recruitment cascade and their role in ARF.

The role of adhesion molecules and T cells in ischemic renal injury

PURPOSE OF REVIEW

The pathophysiology of ischemic acute renal failure is complex, incompletely understood and there are no specific therapies. Descriptive observations in human acute renal failure, as well as mechanistic studies in animals, have demonstrated an important pathophysiological role for leukocytes and leukocyte adhesion molecules. The purpose of this review is to summarize and interpret the recent advances on the role of T cells and leukocyte adhesion molecules in ischemic acute renal failure.

RECENT FINDINGS

Emerging data suggest that the T cell is involved in modulating the outcome of ischemic acute renal failure, as well as ischemic injury to other organs. These new data build on the established role of inflammation in acute renal failure, and identify novel therapeutic targets. In addition, identification of the role of the T cell in the immediate injury response extends current immunological models of T cell function. Studies on leukocyte adhesion in acute renal failure have now identified the selectins and their ligands as important components of the inflammatory response to ischemic injury.

SUMMARY

The identification of T cells and new adhesion molecule pathways as modulators of ischemic acute renal failure offers novel and feasible therapeutic opportunities for both native and transplant acute renal failure. Rigorous clinical trials are required to translate these basic findings to the bedside. In addition, mechanistic studies are needed to elucidate the molecular mechanisms by which these pathways modulate kidney injury. The identification of T cell engagement in ischemic renal injury can also help explain long-standing observations linking alloantigen-independent and alloantigen-dependent renal damage.

Mycophenolate mofetil attenuates renal ischemia/reperfusion injury

Immunosuppressive agents may have an impact on ischemia/reperfusion (I/R) injury. The immunosuppressant mycophenolate mofetil (MMF) presents properties that can attenuate such injury. This study investigated the effects of MMF on renal I/R injury. Male Wistar rats received MMF (20 mg/kg per d) or vehicle by gavage beginning 2 d before ischemia and maintained during the entire study. Ischemic injury was induced by bilateral renal arteries occlusion for 60 min. Control rats received MMF and underwent sham operation. At days 1, 2, and 14, post-ischemia renal function was assessed and kidneys were removed for histologic and immunohistochemical studies. MMF given to nonischemic rats did not alter renal function. There was no functional protection at 24 h post-ischemia with MMF. At 2 d, post-ischemia rats pretreated with MMF presented higher inulin clearance compared with untreated rats (0.42 +/- 0.04 versus 0.15 +/- 0.02 ml/min per 100 g; P < 0.001) and attenuated renal blood flow decrease (5.23 +/- 0.28 versus 3.24 +/- 0.37 ml/min; P < 0.01). The immunostaining for intercellular adhesion molecule-1 (ICAM-1) was less intense in rats pretreated with MMF. These rats also presented an earlier decreased infiltrating macrophages/lymphocytes and cell proliferation at day 1 post-ischemia. The functional and immunohistochemical analyses performed at day 14 post-ischemia returned to values similar to controls in both groups of rats. To determine whether mycophenolic acid (MPA) could induce cytoprotection, the effects of MPA on normoxic and hypoxic/reoxygenated (H/R) isolated tubule suspensions were also investigated. MPA was not deleterious to normoxic tubules and it was not protective against H/R tubules. In conclusion, pretreatment with MMF attenuates I/R injury in rats and does not limit the recovery from ischemia. The protective effect of MMF by reducing inflammation precedes the hemodynamic changes and tubular injury.

The T cell as a bridge between innate and adaptive immune systems: implications for the kidney

The T cell as a bridge between innate and adaptive immune systems: Implications for the kidney. The immune system is classically divided into innate and adaptive components with distinct roles and functions. T cells are major components of the adaptive immune system. T cells are firmly established to mediate various immune-mediated kidney diseases and are current targets for therapy. Ischemic acute renal failure, a major cause of native kidney and allograft dysfunction, is mediated in part by inflammatory components of the innate immune system. However, recent data from experimental models in kidney as well as liver, intestine, brain and heart implicate T cells as important mediators of ischemia reperfusion injury. These data reveal new insights into the pathogenesis of ischemic acute renal failure, as well as identify novel and feasible therapeutic approaches. Furthermore, the identification of T cells as a mediator of early alloantigen-independent tissue injury demonstrates that the functional capacity of T cells spreads beyond adaptive immunity into the realm of the innate immune response.

Alpha-melanocyte-stimulating hormone protects against mesenteric ischemia-reperfusion injury

Mesenteric ischemia-reperfusion (I/R) injury to the intestine is a common and often devastating clinical occurrence for which there are few therapeutic options. alpha-Melanocyte-stimulating hormone (alpha-MSH) is a tridecapeptide released by the pituitary gland and immunocompetent cells that exerts anti-inflammatory actions and abrogates postischemic injury to the kidneys and brainstem of rodents. To test the hypothesis that alpha-MSH would afford similar protection in the postischemic small intestine, we analyzed the effects of this peptide on intestinal transit, histology, myeloperoxidase activity, and nuclear factor-kappaB (NF-kappaB) activation after 45 min of superior mesenteric artery occlusion and <or=6 h of reperfusion. Rats subjected to I/R exhibited markedly depressed intestinal transit, histological evidence of severe injury to the ileum, increased myeloperoxidase activity in ileal cytoplasmic extracts, and biphasic activation of NF-kappaB in ileal nuclear extracts. In contrast, rats treated with alpha-MSH before I/R exhibited intestinal transit and histological injury scores comparable to those of sham-operated controls. In addition, the alpha-MSH-treated rats demonstrated less I/R-induced activation of intestinal NF-kappaB and myeloperoxidase activity after prolonged (6 h) reperfusion. We conclude that alpha-MSH significantly limits postischemic injury to the rat small intestine.

A(2A) adenosine receptor: a novel therapeutic target in renal disease

Present strategies in the treatment of inflammatory renal injury have focused on developing agents that specifically target individual mechanisms thought to contribute toward the pathogenesis of the disease. Such an approach is hindered by redundancies in the inflammatory cascade, rendering intervention suboptimal. The A(2A) adenosine receptor (A(2A)-AR) is a member of the family of guanine nucleotide binding proteins and has become a focus of major interest primarily because of its ability to broadly inactivate the inflammatory cascade. This review summarizes our present knowledge regarding the molecular biology and pharmacology of A(2A)-ARs as well as the physiological effects of activation of A(2A)-ARs in the kidney. We also review our recent experience in targeting this receptor subtype in abrogating the inflammatory cascade in ischemia-reperfusion injury.

Interleukin-10 inhibits ischemic and cisplatin-induced acute renal injury

BACKGROUND

Acute renal failure (ARF) is caused by ischemic and nephrotoxic insults acting alone or in combination. Anti-inflammatory agents have been shown to decrease renal ischemia-reperfusion and cisplatin-induced injury and leukocyte infiltration. Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine that inhibits inflammatory and cytotoxic pathways implicated in acute renal injury. Therefore, we sought to determine if IL-10 inhibits acute renal injury.

METHODS

The effects of IL-10 were studied in mice following cisplatin administration and bilateral renal ischemia-reperfusion, in a rat model of renal transplantation, and in cultured mouse cortical tubule cells.

RESULTS

IL-10 significantly decreased renal injury following cisplatin administration and following renal ischemia/reperfusion. Delay of IL-10 treatment for one hour after cisplatin also significantly inhibited renal damage. IL-10 and alpha-melanocyte stimulating hormone (alpha-MSH) increased recovery following transplantation of a kidney subjected to warm ischemia. To explore the mechanism of action of IL-10, its effects were measured on mediators of leukocyte trafficking and inducible nitric oxide synthase (NOS-II). IL-10 inhibited cisplatin and ischemia-induced increases in mRNA for tumor necrosis factor-alpha (TNF-alpha), intercellular adhesion molecule-1 (ICAM-1), and NOS-II. IL-10 also inhibited staining for markers of apoptosis and cell cycle activity following cisplatin administration, and nitric oxide production in cultured mouse cortical tubules.

CONCLUSIONS

IL-10 protects against renal ischemic and cisplatin-induced injury. IL-10 may act, in part, by inhibiting the maladaptive activation of genes that cause leukocyte activation and adhesion, and induction of iNOS.

Postoperative renal insufficiency

The poor clinical outcomes associated with postoperative HARI necessitate increased vigilance for HARI detection and intervention to minimize the progression to dialysis dependency. Patient survival significantly worsens if HARI requires the initiation of dialysis. Postoperative changes, including intravascular volume expansion, SIRS, and reduced lean body mass, frequently confound the detection of HARI. Serum creatinine levels frequently do not reflect the decreased renal function because creatinine production rate is decreased with reduced lean body mass, and the serum creatinine concentration is reduced by increased intravascular volume expansion and increased volume of distribution associated with anasarca. Additional indices of renal function must be used postoperatively, including urine output, net volume status, urinalysis with microscopic examination of the spun pellet, and corrected estimations of creatinine clearance. Few therapeutic interventions currently exist to reverse HARI other than optimization of renal perfusion and limitation of nephrotoxin exposure. Dialysis remains a cornerstone of maintenance therapy for refractory and severe HARI. Selection of dialysis modality continues to be based on modality availability and patient stability.

Pathophysiologic Features and Prevention of Human and Experimental Acute Tubular Necrosis

Abstract.Acute renal failure (ARF) remains a common and potentially devastating disorder that affects as many as 5% of all hospitalized patients, with a higher prevalence in patients in critical care units. The focus of this article is on categorizing recent pathophysiologic and clinically relevant developments in the field. The vascular and tubular factors in the pathogenesis of ARF, together with the potential mechanisms of recovery and repair of the injured kidney, are discussed. A number of experimental and clinical interventions to prevent. ARF are summarized. Although the clinical treatment of these patients is still largely supportive and many recent clinical trials showed rather negative results, it is hoped that basic research will provide therapeutic tools to improve the grim prognosis of this disease in the future.

New pharmacologic options for renal preservation

The understanding of the cause and pathophysiology of renal failure has guided the rational development of pharmacologic renoprotective strategies. Although traditionally anesthesiologists have focused on renal hemodynamic derangements, newer information suggests that cellular interactions amplify and perpetuate the insult. Consequently, the potential renoprotective armamentarium not only encompasses the more traditional vasoactive agents but also therapeutic approaches that may modify the cellular response to injury. Although few of these agents have reached the clinical arena, preliminary work suggests that this new approach to renal injury and protection may be promising.

A(2A) adenosine receptor-mediated inhibition of renal injury and neutrophil adhesion

We sought to determine the mechanisms responsible for the reduced renal tissue injury by agonists of A(2A) adenosine receptors (A(2A)-ARs) in models of ischemia-reperfusion (I/R) injury. DWH-146e, a selective A(2A)-AR agonist, was administered subcutaneously to Sprague-Dawley rats and C57BL/6 mice via osmotic minipumps, and animals were subjected to I/R. I/R led to an increase in plasma creatinine and kidney neutrophil infiltration. Infusion of DWH-146e at 10 ng. kg(-1). min(-1) produced a 70% reduction in plasma creatinine as well as a decrease in neutrophil density in outer medulla and cortex and myeloperoxidase activity in the reperfused kidney. Myeloperoxidase activity in kidney correlated with the degree of renal injury. P-selectin and intercellular adhesion molecule 1 (ICAM-1) immunoreactivity were most prominent in endothelial cells of peritubular capillaries and interlobular arteries of cortex and outer and inner medulla of vehicle-treated mice whose kidneys were subjected to I/R. DWH-146e treatment led to a pronounced decrease in P-selectin- and ICAM-1-like immunoreactivity. These data are consistent with our hypothesis that A(2A)-AR agonists limit I/R injury due to an inhibitory effect on neutrophil adhesion.

Inhibition of poly(ADP-ribose) polymerase attenuates ischemic renal injury in rats

The enzyme, poly(ADP-ribose) polymerase (PARP), effects repair of DNA after ischemia-reperfusion (I/R) injury to cells in nerve and muscle tissue. However, its activation in severely damaged cells can lead to ATP depletion and death. We show that PARP expression is enhanced in damaged renal proximal tubules beginning at 6-12 h after I/R injury. Intraperitoneal administration of PARP inhibitors, benzamide or 3-amino benzamide, after I/R injury accelerates the recovery of normal renal function, as assessed by monitoring the levels of plasma creatinine and blood urea nitrogen during 6 days postischemia. PARP inhibition leads to increased cell proliferation at 1 day postinjury as assessed by proliferating cell nuclear antigen and improves the histopathological appearance of kidneys examined at 7 days postinjury. Furthermore, inhibition of PARP increases levels of ATP measured at 24 h postischemia compared with those in vehicle-treated animals. Our data indicate that PARP activation is a part of the cascade of molecular events that occurs after I/R injury in the kidney. Although caution is advised, transient inhibition of PARP postischemia may constitute a novel therapy for acute renal failure.

Identification and kinetics of leukocytes after severe ischaemia/reperfusion renal injury

BACKGROUND

Leukocyte adhesion/infiltration in response to renal ischaemia/reperfusion (I/R) injury is a well-known but poorly understood phenomenon. The identification, kinetics, and exact role of these inflammatory cells in I/R injury and regeneration are still matters of debate.

METHODS

Uninephrectomized rats were submitted to 60 min renal ischaemia by clamping of renal vessels.

RESULTS

Severe acute renal failure was observed, with maximum functional impairment on day 2. By 12 h after the ischaemic event, up to 80% of proximal tubular cells in the outer stripe of outer medulla (OSOM) were already severely damaged. Proliferation (proliferating cell nuclear antigen (PCNA) staining) started after 24 h, reaching maximum activity on day 3. Regeneration of tubular morphology started on the 3rd day, and after 10 days 50% of tubules had regenerated completely. Interstitial leukocytes (OX-1 immunohistochemical staining) were already prominent at day 1, thereafter gradually increasing with time. The so-called neutrophil-specific identification methods (myeloperoxidase (MPO), chloroacetate esterase, mAb HIS-48) proved to be non-specific, since they also stained for macrophages, as demonstrated by flow cytometry and the combination of these stainings with the macrophage-specific ED-1 staining. MPO activity was already significantly increased at 1 h post-I/R (439+/-34%, P<0.005), reaching its maximum activity after 12 h of I/R (1159+/-138%, P<0.0005), declining thereafter. On the other hand, neutrophil presence investigated by H&E staining revealed only a few neutrophils in glomeruli, medullary rays, and OSOM at 24 h after the ischaemic event (4.7+/-4.2 cells/mm(2) vs controls=2.3+/-2.0 cells/mm(2) (n.s.)), and remained unchanged over the next 10 days. In contrast, significant monocyte/macrophage adhesion/infiltration (ED-1 staining) occurred at the OSOM at 24 h post-ischaemia (at 24 h, 120+/-46 cells/mm(2) vs. sham=18+/-4 cells/mm(2) (P<0.05)), became prominent at day 5 (1034+/-161 cells/mm(2) vs sham=18+/-18 cells/mm(2) (P<0.05)), and almost disappeared after 10 days. CD4(+) cells (W3/25) gradually increased from day 5, reaching a maximum at day 10. A few CD8(+) cells (OX-8) were apparent from days 3 until 10, but no B-cells (OX-33) were observed.

CONCLUSIONS

After severe warm I/R renal injury, a pronounced acute tubular necrosis occurs during the first 12-24 h in the absence of a marked cellular infiltrate, but with an important renal MPO activity, reflecting the activation of the adhering inflammatory cells (polymorphonuclear cells (PMNs) and mainly monocytes/macrophages). Only later at the time and site (OSOM) of regeneration a sequential accumulation of monocytes/macrophages and T cells becomes prominent, in contrast with the low number of neutrophils found in the kidney during the 10-day post-ischaemic period. The non-specificity of the so-called neutrophil-specific identification methods (MPO activity, naphthol AS-D chloroacetate esterase, or mAb HIS-48 staining), cross-reacting with monocytes/macrophages, explains the controversy in literature concerning the number of PMNs in post-ischaemic injury.

alpha-MSH inhibits induction of C/EBPbeta-DNA binding activity and NOS2 gene transcription in macrophages

BACKGROUND

alpha-Melanocyte-stimulating hormone (alpha-MSH) is an endogenous tridecapeptide that exerts anti-inflammatory actions and abrogates postischemic renal injury in rodents. alpha-MSH inhibits lipopolysaccharide (LPS)-induced gene expression of several cytokines, chemokines, and nitric oxide synthase-2 (NOS2), but the molecular mechanisms underlying these effects have not been clearly defined. To test the hypothesis that alpha-MSH inhibits the expression of inducible trans-activating factors involved in NOS2 regulation, we used RAW 264.7 macrophage cells to examine the effects of alpha-MSH on the activation of nuclear factor-kappaB (NF-kappaB) and CCAAT/enhancer binding protein-beta (C/EBPbeta), trans-acting factors known to be involved in LPS + interferon (IFN)-gamma induction of the NOS2 gene.

METHODS

Gel shift assays were performed to identify NF-kappaB and C/EBP DNA binding activities in LPS + IFN-gamma-treated RAW 264.7 cells in the presence and absence of alpha-MSH. NOS2 promoter assays were conducted to identify the effects of alpha-MSH on LPS + IFN-gamma-mediated induction of NOS2 transcription.

RESULTS

Gel shift assays demonstrated LPS + IFN-gamma induction of NF-kappaB and C/EBP family protein-DNA complexes in nuclei harvested from the cells. Supershift assays revealed that the C/EBP complexes were comprised of C/EBPbeta, but not C/EBPalpha, C/EBPdelta, or C/EBPepsilon. alpha-MSH (100 nmol/L) inhibited the LPS + IFN-gamma-mediated induction of nuclear DNA binding activity of C/EBPbeta, but not that of NF-kappaB (in contrast to reports in other cell types), as well as the activity of a murine NOS2 promoter-luciferase construct. In contrast, alpha-MSH (100 nmol/L) had no effect on the induction of NOS2 promoter-luciferase genes harboring deletion or mutation of the C/EBP box.

CONCLUSIONS

These data indicate that alpha-MSH inhibits the induction of C/EBPbeta DNA binding activity and that this effect is a major mechanism by which alpha-MSH inhibits the transcription of the NOS2 gene. The inability of alpha-MSH to inhibit LPS + IFN-gamma induction of NF-kappaB in murine macrophage cells, which contrasts with inhibitory effects of the neuropeptide in other cell types, suggests that cell-type-specific mechanisms are involved.

Treatment of acute renal failure

Acute renal failure is a life threatening illness whose mortality has remained high since the introduction of hemodialysis 25 years ago, despite advances in supportive care. Acute renal failure is an extremely morbid and costly disorder with a significant proportion of patients progressing to end-stage renal disease requiring dialysis. To the nephrologist, acute renal failure remains an extremely frustrating disease, because the pathophysiology is not well understood and the limited therapeutic options force the nephrologist to sit on the sidelines and wait for renal function to return. For example, dialysis remains the only FDA-approved treatment for acute renal failure, but dialysis may also cause renal injury that prolongs renal failure. The purpose of this perspective is to understand the results of the recent, largely negative, clinical trials in view of recent advances in the epidemiology of ARF. This review will also discuss diagnostic tools, strategies for improved design of clinical trials, and other therapeutic interventions that will be needed to properly treat acute renal failure in the 21st century.