Acute renal failure in endotoxemia is caused by TNF acting directly on TNF receptor-1 in kidney

Kidney and heart interactions during cardiorenal syndrome: a molecular and clinical pathogenic framework

The heart and kidney are physiologically interconnected. Cardiorenal syndrome (CRS) is a pathological disorder where acute or chronic dysfunction in one organ may induce dysfunction in the other one. Although classical studies have proposed a role for hypertension, dyslipidemia and endothelial dysfunction, CRS should be considered as a complex molecular interplay of neurohumoral pathway activation including the sympathetic nervous system, the renin angiotensin aldosterone axis, the endothelin system and the arginine vasopressin system. This activation may induce vascular inflammation, oxidative stress, accelerated atherosclerosis, cardiac hypertrophy and both myocardial and intrarenal fibrosis with progression of CRS treatment. More recently, epigenetics has opened new pathogenic molecular routes for CRS. This will lead to a more rapid development of novel, safe and effective clinical therapies.

Cardio-renal syndromes: from foggy bottoms to sunny hills

"Cardio-renal syndromes" (CRS) are disorders of the heart and kidneys whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction of the other. The current definition has been expanded into five subtypes whose etymology reflects the primary and secondary pathology, the time-frame and simultaneous cardiac and renal co-dysfunction secondary to systemic disease: CRS type I: acute worsening of heart function (AHF-ACS) leading to kidney injury and/or dysfunction. CRS type II: chronic abnormalities in heart function (CHF-CHD) leading to kidney injury or dysfunction. CRS type III: acute worsening of kidney function (AKI) leading to heart injury and/or dysfunction. CRS type IV: chronic kidney disease (CKD) leading to heart injury, disease and/or dysfunction. CRS type V: systemic conditions leading to simultaneous injury and/or dysfunction of heart and kidney. These different subtypes may have a different pathophysiological mechanism and they may represent separate entities in terms of prevention and therapy.

Management of obesity-induced kidney disease: a critical review of the literature

It is well established that obesity is a risk factor for the development of chronic kidney disease (CKD) and may promote the progression to end stage renal disease (ESRD). Therefore, it is strongly suggested that reduction of body weight can be an important intervention in order to reduce the prevalence of renal impairment. The current article describes extensively the already published trials which have studied the association between weight loss and kidney disease. The weight management programs include surgical and non-surgical interventions (low-calorie diet, aerobic exercise, drug-induced weight loss, combination treatment). The focus has been placed on the following renal function markers: albuminuria, proteinuria, glomerular filtration rate (GFR), and creatinine clearance. This review also aims to clarify challenges that clinicians have to deal with in everyday practice regarding the management of obesity-induced kidney disease (degree of weight loss, duration of the weight loss program, early initiation of the intervention).

Oxidants as important determinants of renal apoptosis during pneumoperitoneum: a study in an isolated perfused rat kidney model

INTRODUCTION

Pneumoperitoneum-associated ischemia-reperfusion (IR) may initiate renal dysfunction. Whether oxidants are responsible for renal structural damage, such as cell apoptosis, has not yet been evaluated. We investigated such eventuality in an isolated rat kidney model.

METHODS

Thirty-five rat kidneys with their vessels and ureter were harvested and perfused within a closed environment at flow of 15 ml min(-1). After stabilization, kidneys were assigned to one of five groups (n = 7 per group): CO(2)-induced intrachamber pressure of 8, 12, or 0 mmHg (control), and 8 or 12 mmHg pressure applied to kidneys from rats treated pre-experimentally with tungsten for 14 days. Pressurization lasted 60 min.

RESULTS

Organ perfusion pressure raised as intrachamber pressure increased. Urinary output decreased in the two pressurized nonpretreated groups. Intrachamber pressure was directly associated with an increase in postexperimental xanthine oxidase tissue levels. Twofold apoptosis was documented (p < 0.05) in cortex of nonpretreated kidney in the 12 mmHg group compared with the 8 or 0 mmHg groups. Tungsten pretreatment significantly (p < 0.05) attenuated the abnormalities documented in the 12 mmHg group, but less so in the 8 mmHg pressurized nontreated counterparts.

CONCLUSIONS

Pneumoperitoneal pressure applied to isolated perfused kidney is associated with renal apoptosis. This rapidly induced structural renal damage is oxidant dependent and can be attenuated by antioxidants. Further studies may shed more light on the role of antioxidants in preventing pneumoperitoneum-induced kidney dysfunction.

Extracorporeal therapies in sepsis

The treatment of sepsis is an ongoing challenge for clinicians; despite the wide choice of effective antibiotics to treat infection, sepsis remains the leading cause of morbidity and mortality for patients admitted to an intensive care unit. Dysregulation of the immune response is now recognized to be a key factor in multiple organ dysfunction, yet our therapy for inflammation remains ineffective. It has been advocated for more than a decade that cytokine reduction in blood compartment could lead to a reduction in mortality in sepsis. Over the years, multiple extracorporeal techniques have evolved, with the intent of influencing the circulating levels of inflammatory mediators like cytokines and chemokines, the complement system, as well as factors of the coagulation system. These include high-volume hemofiltration, use of high cutoff membranes, and systems based on adsorption, such as coupled plasma filtration adsorption and the polymyxin-B column. In addition, new experimental systems that utilize human phagocytic cells and immobilized antibodies for targeted immunomodulation have emerged. In the context of limited resources and growing expansion in the availability of technologies, a better understanding of these therapies is required before they can be properly integrated into standard clinical practice in the hope of influencing major clinical outcomes. In this article, we will provide a concise overview of selected extracorporeal modalities currently in clinical use and briefly introduce some new promising techniques for sepsis.

PGC-1α promotes recovery after acute kidney injury during systemic inflammation in mice

Sepsis-associated acute kidney injury (AKI) is a common and morbid condition that is distinguishable from typical ischemic renal injury by its paucity of tubular cell death. The mechanisms underlying renal dysfunction in individuals with sepsis-associated AKI are therefore less clear. Here we have shown that endotoxemia reduces oxygen delivery to the kidney, without changing tissue oxygen levels, suggesting reduced oxygen consumption by the kidney cells. Tubular mitochondria were swollen, and their function was impaired. Expression profiling showed that oxidative phosphorylation genes were selectively suppressed during sepsis-associated AKI and reactivated when global function was normalized. PPARγ coactivator-1α (PGC-1α), a major regulator of mitochondrial biogenesis and metabolism, not only followed this pattern but was proportionally suppressed with the degree of renal impairment. Furthermore, tubular cells had reduced PGC-1α expression and oxygen consumption in response to TNF-α; however, excess PGC-1α reversed the latter effect. Both global and tubule-specific PGC-1α-knockout mice had normal basal renal function but suffered persistent injury following endotoxemia. Our results demonstrate what we believe to be a novel mechanism for sepsis-associated AKI and suggest that PGC-1α induction may be necessary for recovery from this disorder, identifying a potential new target for future therapeutic studies.

Preactivation of AMPK by metformin may ameliorate the epithelial cell damage caused by renal ischemia

Alterations in epithelial cell polarity and in the subcellular distributions of epithelial ion transport proteins are key molecular consequences of acute kidney injury and intracellular energy depletion. AMP-activated protein kinase (AMPK), a cellular energy sensor, is rapidly activated in response to renal ischemia, and we demonstrate that its activity is upregulated by energy depletion in Madin-Darby canine kidney (MDCK) cells. We hypothesized that AMPK activity may influence the maintenance or recovery of epithelial cell organization in mammalian renal epithelial cells subjected to energy depletion. MDCK cells were ATP depleted through a 1-h incubation with antimycin A and 2-deoxyglucose. Immunofluoresence localization demonstrated that this regimen induces mislocalization of the Na-K-ATPase from its normal residence at the basolateral plasma membrane to intracellular vesicular compartments. When cells were pretreated with the AMPK activator metformin before energy depletion, basolateral localization of Na-K-ATPase was preserved. In MDCK cells in which AMPK expression was stably knocked down with short hairpin RNA, preactivation of AMPK with metformin did not prevent Na-K-ATPase redistribution in response to energy depletion. In vivo studies demonstrate that metformin activated renal AMPK and that treatment with metformin before renal ischemia preserved cellular integrity, preserved Na-K-ATPase localization, and led to reduced levels of neutrophil gelatinase-associated lipocalin, a biomarker of tubular injury. Thus AMPK may play a role in preserving the functional integrity of epithelial plasma membrane domains in the face of energy depletion. Furthermore, pretreatment with an AMPK activator before ischemia may attenuate the severity of renal tubular injury in the context of acute kidney injury.

Bench-to-bedside review: Ventilation-induced renal injury through systemic mediator release--just theory or a causal relationship?

We review the current literature on the molecular mechanisms involved in the pathogenesis of acute kidney injury induced by plasma mediators released by mechanical ventilation. A comprehensive literature search in the PubMed database was performed and articles were identified that showed increased plasma levels of mediators where the increase was solely attributable to mechanical ventilation. A subsequent search revealed articles delineating the potential effects of each mediator on the kidney or kidney cells. Limited research has focused specifically on the relationship between mechanical ventilation and acute kidney injury. Only a limited number of plasma mediators has been implicated in mechanical ventilation-associated acute kidney injury. The number of mediators released during mechanical ventilation is far greater and includes pro- and anti-inflammatory mediators, but also mediators involved in coagulation, fibrinolysis, cell adhesion, apoptosis and cell growth. The potential effects of these mediators is pleiotropic and include effects on inflammation, cell recruitment, adhesion and infiltration, apoptosis and necrosis, vasoactivity, cell proliferation, coagulation and fibrinolysis, transporter regulation, lipid metabolism and cell signaling. Most research has focused on inflammatory and chemotactic mediators. There is a great disparity of knowledge of potential effects on the kidney between different mediators. From a theoretical point of view, the systemic release of several mediators induced by mechanical ventilation may play an important role in the pathophysiology of acute kidney injury. However, evidence supporting a causal relationship is lacking for the studied mediators.

Endotoxin uptake by S1 proximal tubular segment causes oxidative stress in the downstream S2 segment

Gram-negative sepsis carries high morbidity and mortality, especially when complicated by acute kidney injury (AKI). The mechanisms of AKI in sepsis remain poorly understood. Here we used intravital two-photon fluorescence microscopy to investigate the possibility of direct interactions between filtered endotoxin and tubular cells as a possible mechanism of AKI in sepsis. Using wild-type (WT), TLR4-knockout, and bone marrow chimeric mice, we found that endotoxin is readily filtered and internalized by S1 proximal tubules through local TLR4 receptors and through fluid-phase endocytosis. Only receptor-mediated interactions between endotoxin and S1 caused oxidative stress in neighboring S2 tubules. Despite significant endotoxin uptake, S1 segments showed no oxidative stress, possibly as a result of the upregulation of cytoprotective heme oxygenase-1 and sirtuin-1 (SIRT1). Conversely, S2 segments did not upregulate SIRT1 and exhibited severe structural and functional peroxisomal damage. Taken together, these data suggest that the S1 segment acts as a sensor of filtered endotoxin, which it takes up. Although this may limit the amount of endotoxin in the systemic circulation and the kidney, it results in severe secondary damage to the neighboring S2 segments.

Renal HIV expression is unaffected by serum LPS levels in an HIV transgenic mouse model of LPS induced kidney injury

Acute kidney injury (AKI) is associated with increased rates of mortality. For unknown reasons, HIV infected individuals have a higher risk of AKI than uninfected persons. We tested our hypothesis that increased circulating LPS increases renal expression of HIV and that HIV transgenic (Tg26) mice have increased susceptibility to AKI. Tg26 mice harbor an HIV transgene encoding all HIV genes except gag and pol, and develop a phenotype analogous to HIVAN. Mice were used at 4-6 weeks of age before the onset of gross renal disease. Mice were injected i.p. with LPS or sterile saline. Renal function, tubular injury, cytokine expression, and HIV transcription were evaluated in Tg26 and wild type (WT) mice. LPS injection induced a median 60.1-fold increase in HIV expression in spleen but no change in kidney. There was no significant difference in renal function, cytokine expression, or tubular injury scores at baseline or 24 hours after LPS injection. HIV transcription was also analyzed in vitro using a human renal tubular epithelial cell (RTEC) line. HIV transcription increased minimally in human RTEC, by 1.47 fold, 48 hours after LPS exposure. We conclude that Tg26 mice do not increase HIV expression or have increased susceptibility to LPS induced AKI. The increased risk of AKI in HIV infected patients is not mediated via increased renal expression of HIV in the setting of sepsis. Moreover, renal regulation of HIV transcription is different to that in the spleen.

New roles for innate immune response in acute and chronic kidney injuries

The innate immune system plays an important role as a first response to tissue injury. This first response is carried out via germline-encoded receptors. They can recognize exogenous Pathogen-Associated Molecular Patterns and endogenous Dangers-Associated Molecular Patterns. The Toll-Like Receptor (TLR) family is well-studied, but more recently another family in the cytoplasmic compartment, called nod-like receptor (NLR), was discovered. In addition to being present in inflammatory cells, these receptors are widely distributed in various cell types, including renal tissue, where these receptors have an important role in triggering the inflammatory response during renal diseases. This review summarizes the present data regarding the role of TLRs and NLRs in the course and development of various kidney pathologies.

Sepsis and acute kidney injury

Sepsis is a severe and dysregulated inflammatory response to infection characterized by end-organ dysfunction distant from the primary site of infection. Development of acute kidney injury (AKI) during sepsis increases patient morbidity, predicts higher mortality, has a significant effect on multiple organ functions, is associated with an increased length of stay in the intensive care unit, and hence consumes considerable healthcare resources. When compared with AKI of nonseptic origin, septic AKI is characterized by a distinct pathophysiology and therefore requires a different approach. Despite impressive advances in several fields of medicine, the pathophysiology, diagnostic procedures, and appropriate therapeutic interventions in sepsis are still highly debatable. Numerous immunomodulatory agents showing promise in preclinical studies fail to reduce the overwhelmingly high mortality rate of sepsis and provoke AKI when compared with other critically ill patients. Major impediments to progress in understanding, early diagnosis, and application of appropriate therapeutic modalities in sepsis-induced AKI include limited histopathologic information, few animal models that closely mimic human sepsis, and a relative shortage of specific diagnostic tools. Here we discuss the most recent advances in understanding the fundamental mechanisms of sepsis-induced AKI, characteristics of relevant animal models available, and potential therapies.

Tumor necrosis factor-alpha is an endogenous inhibitor of Na+-K+-2Cl- cotransporter (NKCC2) isoform A in the thick ascending limb

The effects of TNF gene deletion on renal Na(+)-K(+)-2Cl(-) cotransporter (NKCC2) expression and activity were determined. Outer medulla from TNF(-/-) mice exhibited a twofold increase in total NKCC2 protein expression compared with wild-type (WT) mice. This increase was not observed in TNF(-/-) mice treated with recombinant human TNF (hTNF) for 7 days. Administration of hTNF had no effect on total NKCC2 expression in WT mice. A fourfold increase in NKCC2A mRNA accumulation was observed in outer medulla from TNF(-/-) compared with WT mice; NKCC2F and NKCC2B mRNA accumulation was similar between genotypes. The increase in NKCC2A mRNA accumulation was attenuated when TNF(-/-) mice were treated with hTNF. Bumetanide-sensitive O(2) consumption, an in vitro correlate of NKCC2 activity, was 2.8 ± 0.2 nmol·min(-1)·mg(-1) in medullary thick ascending limb tubules from WT, representing ∼40% of total O(2) consumption, whereas, in medullary thick ascending limb tubules from TNF(-/-) mice, it was 5.6 ± 0.3 nmol·min(-1)·mg(-1), representing ∼60% of total O(2) consumption. Administration of hTNF to TNF(-/-) mice restored the bumetanide-sensitive component to ∼30% of total O(2) consumption. Ambient urine osmolality was higher in TNF(-/-) compared with WT mice (2,072 ± 104 vs. 1,696 ± 153 mosmol/kgH(2)O, P < 0.05). The diluting ability of the kidney, assessed by measuring urine osmolality before and after 1 h of water loading also was greater in TNF(-/-) compared with WT mice (174 ± 38 and 465 ± 81 mosmol/kgH(2)O, respectively, P < 0.01). Collectively, these findings suggest that TNF plays a role as an endogenous inhibitor of NKCC2 expression and function.

Mortality in Patients With Septic Shock Correlates With Anti-Inflammatory But not Proinflammatory Immunomodulatory Molecules

Background: Mortality in patients with septic shock remains unacceptably high and the attempts to antagonize certain proinflammatory cytokines based on the results of animal model studies have failed to improve survival rates. The objective of this article is to examine the pro-/anti-inflammatory cytokine balance in patients with septic shock and its connection with mortality. Methods: Serum levels of proinflammatory cytokines (tumor necrosis factor-α [TNF-α], interleukin 1β [IL-1β], interferonγ [IFN-γ], and IL-6) and soluble cytokine antagonists (soluble TNF receptor I [sTNF-RI], sTNF-RII, and IL-1Ra) were determined on admission to the intensive care unit (ICU) and 3, 7, 14, and 28 days later in 52 patients with septic shock and in 36 healthy controls. Specific sandwich enzyme-linked immunosorbent assay (ELISA) was used for all determinations. Results: Serum levels of most of the pro- and anti-inflammatory molecules examined (TNF-α, IL-6, sTNF-RI, sTNF-RII, and IL-1 receptor agonist [IL-1Ra]) were significantly elevated on admission and during the 28-day observation period in patients when compared to controls. Notably, the anti-inflammatory mediators sTNF-RI, sTNF-RII, and IL-1Ra were better predictors of mortality. Receiver-operating characteristic (ROC) analysis revealed that sTNF-RI or sTNF-RII concentrations over 2767 or 4619 pg/mL, respectively, determined a high risk of death (sensitivity: 100%-100%, specificity: 57.1%-71.4%, area under the curve [AUC] 0.759-0.841, respectively), whereas IL-1Ra concentrations below 7033 pg/mL determined a high probability of survival (sensitivity: 60%, specificity: 100%, AUC 0.724). In addition, IFN-γ levels were significantly higher in survivors than in controls during the initial 2 weeks of observation. Conclusions: Our data show that serum cytokine disturbance patterns have prognostic significance in patients with septic shock admitted to the ICU. The pattern, defined by an early response to continuously elevated anti-inflammatory cytokine serum levels, is associated with an enhanced risk of a fatal outcome for patients.

Peptide nanofibers preconditioned with stem cell secretome are renoprotective

Stem cells may contribute to renal recovery following acute kidney injury, and this may occur through their secretion of cytokines, chemokines, and growth factors. Here, we developed an acellular, nanofiber-based preparation of self-assembled peptides to deliver the secretome of embryonic stem cells (ESCs). Using an integrated in vitro and in vivo approach, we found that nanofibers preconditioned with ESCs could reverse cell hyperpermeability and apoptosis in vitro and protect against lipopolysaccharide-induced acute kidney injury in vivo. The renoprotective effect of preconditioned nanofibers associated with an attenuation of Rho kinase activation. We also observed that the combined presence of follistatin, adiponectin, and secretory leukoprotease during preconditioning was essential to the renoprotective properties of the nanofibers. In summary, we developed a designer-peptide nanofiber that can serve as a delivery platform for the beneficial effects of stem cells without the problems of teratoma formation or limited cell engraftment and viability.

Erythropoietin does not attenuate renal dysfunction or inflammation in a porcine model of endotoxemia

BACKGROUND

Erythropoietin (EPO) is a multifunctional cytokine with anti-apoptotic, anti-inflammatory, and organ protective effects. EPO protects against ischemia-reperfusion injuries, and recent reports suggest that EPO also prevents organ dysfunction in experimental sepsis. The aims of this study were to determine whether EPO prevents endotoxemia-induced organ dysfunction in a porcine model and to characterize the immunomodulatory and anti-apoptotic effects of EPO.

METHODS

Twenty-eight pigs were randomly assigned to three groups: (1) endotoxemia treated with EPO 5000 IU/kg, (2) endotoxemia treated with placebo, and (3) a sham group anesthetized and submitted to sham operation without treatment. A laparotomy was performed, and a flow probe was placed around the left renal artery, which allowed renal blood flow (RBF) measurements. Endotoxemia was induced by an infusion of lipopolysaccharide. After 2 h, the infusion was reduced to a maintenance dose and the animals were fluid resuscitated. The glomerular filtration rate (GFR), RBF, renal oxygen consumption, and plasma cytokines [interleukin (IL)-1β, IL-6, IL-8, IL-10, and tumor necrosis factor-alpha] were analyzed. Renal biopsies were analyzed for cytokine content and apoptosis.

RESULTS

Endotoxemia elicited impaired renal function, estimated as GFR, and increased the levels of renal apoptotic cells, with no modifying effect of EPO. Furthermore, EPO had no effect on RBF, renal oxygen consumption, or the systemic hemodynamic response to endotoxemia. EPO did not modify the inflammatory response, measured as changes in cytokine levels in plasma and organs.

CONCLUSION

EPO did not confer renal protection in this fluid-resuscitated porcine model of endotoxemia, and EPO did not modify the inflammatory response.

Cardiorenal syndrome and heart failure

PURPOSE OF REVIEW

Concomitant anemia, heart failure, and renal disease can be seen in a large proportion of patients with heart failure. The purpose of this review is to discuss the current definitions and mechanisms involved in this pathophysiological relationship, as well as the potential management and treatment options available for these patients.

RECENT FINDING

Dysfunctional heart can promote the dysfunction of the kidneys through a variety of pathophysiological mechanism, the reciprocal holds true as well. Heart failure has been considered as the most common type of cardiovascular complication seen in patients with renal failure. Central to this relationship lies anemia, which can be the result or the cause of either heart or kidney disease.

SUMMARY

Cardiorenal syndrome is a complex condition, which requires the collaboration and resources from cardiology, cardiac surgery, nephrology, and critical care. Of great importance is recognizing the presence of cardiorenal syndrome and appreciating the impact it can play on treatment options and survival.

Low-protein diet supplemented with ketoacids reduces the severity of renal disease in 5/6 nephrectomized rats: a role for KLF15

Dietary protein restriction is an important treatment for chronic kidney disease. Herein, we tested the effect of low-protein or low-protein plus ketoacids (KA) diet in a remnant kidney model. Rats with a remnant kidney were randomized to receive normal protein diet (22%), low-protein (6%) diet (LPD), or low-protein (5%) plus KA (1%) diet for 6 months. Protein restriction prevented proteinuria, decreased blood urea nitrogen levels, and renal lesions; however, the LPD retarded growth and decreased serum albumin levels. Supplementation with KA corrected these abnormalities and provided superior renal protection compared with protein restriction alone. The levels of Kruppel-like factor-15 (KLF15), a transcription factor shown to reduce cardiac fibrosis, were decreased in remnant kidneys. Protein restriction, which increased KLF15 levels in the normal kidney, partially recovered the levels of KLF15 in remnant kidney. The expression of KLF15 in mesangial cells was repressed by oxidative stress, transforming growth factor-β, and tumor necrosis factor (TNF)-α. The suppressive effect of TNF-α on KLF15 expression was mediated by TNF receptor-1 and nuclear factor-κB. Overexpression of KLF15 in mesangial and HEK293 cells significantly decreased fibronectin and type IV collagen mRNA levels. Furthermore, KLF15 knockout mice developed glomerulosclerosis following uninephrectomy. Thus, KLF15 may be an antifibrotic factor in the kidney, and its decreased expression may contribute to the progression of kidney disease.

Surgical sepsis and organ crosstalk: the role of the kidney

Acute kidney injury (AKI) is a common complication of hospitalized patients, and clinical outcomes remain poor despite advances in renal replacement therapy. The accepted pathophysiology of AKI in the setting of sepsis has evolved from one of simple decreased renal blood flow to one that involves a more complex interaction of intra-glomerular microcirculatory vasodilation combined with the local release of inflammatory mediators and apoptosis. Evidence from preclinical AKI models suggests that crosstalk occurs between kidneys and other organ systems via soluble and cellular inflammatory mediators and that this involves both the innate and adaptive immune systems. These interactions are reflected by genomic changes and abnormal rates of cellular apoptosis in distant organs including the lungs, heart, gut, liver, and central nervous system. The purpose of this article is to review the influence of AKI, particularly sepsis-associated AKI, on inter-organ crosstalk in the context of systemic inflammation and multiple organ failure (MOF).

Intravital Two-Photon Microscopy Assessment of Renal Protection Efficacy of siRNA for p53 in Experimental Rat Kidney Transplantation Models

Renal ischemia-reperfusion (I/R) injury, which is unavoidable in renal transplantation, frequently influences both short- and long-term allograft survival. Despite decades of laboratory and clinical investigations, and the advent of renal replacement therapy, the overall mortality rate due to acute tubular injury has changed little. I/R-induced DNA damage results in p53 activation in proximal tubule cells (PTC), leading to their apoptosis. Therefore, we examined the therapeutic effect of temporary p53 inhibition in two rat renal transplantation models on structural and functional aspects of injury using intravital two-photon microscopy. Nephrectomized Sprague-Dawley rats received syngeneic left kidney transplantation either after 40 min of intentional warm ischemia or after combined 5-h cold and 30-min warm ischemia of the graft. Intravenously administrated siRNA for p53 (siP53) has previously been shown to be filtered and reabsorbed by proximal tubular epithelial cells following the warm ischemia/reperfusion injury in a renal clamp model. Here, we showed that it was also taken up by PTC following 5 h of cold ischemia. Compared to saline-treated recipients, treatment with siP53 resulted in conservation of renal function and significantly suppressed the I/R-induced increase in serum creatinine in both kidney transplantation models. Intravital two-photon microscopy revealed that siP53 significantly ameliorated structural and functional damage to the kidney assessed by quantification of tubular cast formation and the number of apoptotic and necrotic tubular cells and by evaluation of blood flow rate. In conclusion, systemic administration of siRNA for p53 is a promising new approach to protect kidneys from I/R injury in renal transplantation.

Mechanisms of Cisplatin nephrotoxicity

Cisplatin is a widely used and highly effective cancer chemotherapeutic agent. One of the limiting side effects of cisplatin use is nephrotoxicity. Research over the past 10 years has uncovered many of the cellular mechanisms which underlie cisplatin-induced renal cell death. It has also become apparent that inflammation provoked by injury to renal epithelial cells serves to amplify kidney injury and dysfunction in vivo. This review summarizes recent advances in our understanding of cisplatin nephrotoxicity and discusses how these advances might lead to more effective prevention.

Proinflammatory gene expression and renal lipogenesis are modulated by dietary protein content in obese Zucker fa/fa rats

Obesity is a risk factor for the development of chronic kidney disease (CKD) and end-stage renal disease. It is not clear whether the adoption of a high-protein diet in obese patients affects renal lipid metabolism or kidney function. Thus the aims of this study were to assess in obese Zuckerfa/fa rats the effects of different types and amounts of dietary protein on the expression of lipogenic and inflammatory genes, as well as renal lipid concentration and biochemical parameters of kidney function. Rats were fed different concentrations of soy protein or casein (20, 30, 45%) for 2 mo. Independent of the type of protein ingested, higher dietary protein intake led to higher serum triglycerides (TG) than rats fed adequate concentrations of protein. Additionally, the soy protein diet significantly increased serum TG compared with the casein diet. However, rats fed soy protein had significantly decreased serum cholesterol concentrations compared with those fed a casein diet. No significant differences in renal TG and cholesterol concentrations were observed between rats fed with either protein diets. Renal expression of sterol-regulatory element binding protein 2 (SREBP-2) and its target gene HMG-CoA reductase was significantly increased as the concentration of dietary protein increased. The highest protein diets were associated with greater expression of proinflammatory cytokines in the kidney, independent of the type of dietary protein. These results indicate that high soy or casein protein diets upregulate the expression of lipogenic and proinflammatory genes in the kidney.

Histopathology of septic shock induced acute kidney injury: apoptosis and leukocytic infiltration

PURPOSE

Septic shock is one of the leading causes of acute kidney injury. The mechanisms of this injury remain mostly unknown notably because of the lack of data on renal histological lesions in humans.

METHODS

Kidney biopsy was performed immediately post-mortem in consecutive patients who died of septic shock. Comparisons were made with specimens from eight patients who died of trauma on scene and nine ICU patients that died of non-septic causes.

RESULTS

Nineteen septic patients were included, 11 were male, and age was 72 +/- 12 years. Anuria occurred in all patients 2.2 +/- 1.4 days before death. Seven patients had disseminated intravascular coagulation. In all patients we observed (1) acute tubular lesions whose intensity correlated with blood lactate concentration; (2) intense infiltration by leukocytes, mainly monocytic, in glomeruli and interstitial capillaries as compared to controls; (3) presence of tubular cell apoptosis proved by the presence of apoptotic bodies (2.9% of tubular cells) significantly more frequently than in controls and confirmed by TUNEL and activated caspase-3 staining. Arteriolar/arterial thromboses were observed in only 4 of 19 patients, without any association with presence of disseminated intravascular coagulation.

CONCLUSIONS

Kidney lesions in septic shock go beyond those associated with simple acute tubular injury, notably capillary leukocytic infiltration and apoptosis. Vascular thrombosis, however, did not appear to play a major role in the majority of patients. The extent to which these lesions are specific to sepsis or are common to all multi-organ failure independent of its cause is yet to be elucidated. Electronic supplementary material The online version of this article (doi:10.1007/s00134-009-1723-x) contains supplementary material, which is available to authorized users.

The role of Toll-like receptors in renal diseases

Toll-like receptors (TLRs) have a key role in innate immunity. These receptors recognize both pathogen-associated molecular patterns and molecules that are released from damaged tissue. TLRs mediate signal transduction pathways through the activation of transcription factors that regulate the expression of proinflammatory cytokines and chemokines and are required for the development of adaptive immune responses. TLRs might have an important role in the pathogenesis of renal diseases: their exaggerated activation is associated with ischemic kidney damage, acute kidney injury, end-stage renal failure, acute tubulointerstitial nephritis, acute renal transplant rejection and delayed allograft function. As the results of previous studies concerning the role of TLRs in renal diseases are conflicting, further work is needed to determine the exact role of these receptors and to evaluate strategies to prevent TLR-mediated local inflammation. This Review discusses the evidence supporting a role for TLRs in contrasting bacterial infections and in causing or aggravating renal conditions when TLR activation leads to a harmful inflammatory response.

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.

Protective effect of resin adsorption on septic plasma-induced tubular injury

Introduction

A pro-apoptotic effect of circulating mediators on renal tubular epithelial cells has been involved in the pathogenesis of sepsis-associated acute kidney injury (AKI). Adsorption techniques have been showed to efficiently remove inflammatory cytokines from plasma. The aim of this study was to evaluate the efficiency of the hydrophobic resin Amberchrom CG161 M to adsorb from septic plasma soluble mediators involved in tubular injury.

Methods

We enrolled in the study 10 critically ill patients with sepsis-associated AKI and we evaluated the effects of their plasma on granulocyte adhesion, apoptosis and functional alterations of cultured human kidney tubular epithelial cells. We established an in vitro model of plasma adsorption and we studied the protective effect of unselective removal of soluble mediators by the Amberchrom CG161 M resin on septic plasma-induced tubular cell injury.

Results

Plasma from septic patients induced granulocyte adhesion, apoptosis and altered polarity in tubular cells. Plasma adsorption significantly decreased these effects and abated the concentrations of several soluble mediators. The inhibition of granulocyte adhesion to tubular cells was associated with the down-regulation of ICAM-1 and CD40. Resin adsorption inhibited tubular cell apoptosis induced by septic plasma by down-regulating the activation of caspase-3, 8, 9 and of Fas/death receptor-mediated signalling pathways. The alteration of cell polarity, morphogenesis, protein reabsorption and the down-regulation of the tight junction molecule ZO-1, of the sodium transporter NHE3, of the glucose transporter GLUT-2 and of the endocytic receptor megalin all induced by septic plasma were significantly reduced by resin adsorption.

Conclusions

Septic plasma induced a direct injury of tubular cells by favouring granulocyte adhesion, by inducing cell apoptosis and by altering cell polarity and function. All these biological effects are related to the presence of circulating inflammatory mediators that can be efficiently removed by resin adsorption with a consequent limitation of tubular cell injury.

Nitro-oleic acid protects against endotoxin-induced endotoxemia and multiorgan injury in mice

Nitroalkene derivatives of nitro-oleic acid (OA-NO2) are endogenous lipid products with potent anti-inflammatory properties in vitro. The present study was undertaken to evaluate the in vivo anti-inflammatory effect of OA-NO2 in mice given LPS. Two days before LPS administration, C57BL/6J mice were chronically infused with vehicle (LPS vehicle) or OA-NO2 (LPS OA-NO2) at 200 microg x kg(-1) x day(-1) via osmotic minipumps; LPS was administered via a single intraperitoneal (ip) injection (10 mg/kg in saline). A third group received an ip injection of saline without LPS or OA-NO2 and served as controls. At 18 h of LPS administration, LPS vehicle mice displayed multiorgan dysfunction as evidenced by elevated plasma urea and creatinine (kidney), aspartate aminotransferase (AST) and alanine aminotransferase (ALT; liver), and lactate dehydrogenase (LDH) and reduced ejection fraction (heart). In contrast, the severity of multiorgan dysfunction was less in LPS OA-NO2 animals. The levels of circulating TNF-alpha and renal TNF-alpha mRNA expression, together with renal mRNA expression of monocyte chemoattractant protein-1, ICAM-1, and VCAM-1, and with renal mRNA and protein expression of inducible nitric oxide synthase and cyclooxygenase 2, and renal cGMP and PGE2 contents, were greater in LPS vehicle vs. control mice, but were attenuated in LPS OA-NO2 animals. Similar patterns of changes in the expression of inflammatory mediators were observed in the liver. Together, pretreatment with OA-NO2 ameliorated the inflammatory response and multiorgan injury in endotoxin-induced endotoxemia in mice.

Acute kidney injury in non-severe pneumonia is associated with an increased immune response and lower survival

While sepsis is a leading cause of acute kidney injury in critically ill patients, the relationship between immune response and acute kidney injury in less severely ill patients with infection is not known. Here we studied the epidemiology, 1-year mortality, and immune response associated with acute kidney injury in 1836 hospitalized patients with community-acquired severe and non-severe pneumonia. Acute kidney injury developed in 631 patients of whom 329 had severe and 302 had non-severe sepsis. Depending on the subgroup classification, 16-25% of the patients with non-severe pneumonia also developed acute kidney injury. In general, patients with acute kidney injury were older, had more comorbidity, and had higher biomarker concentrations (interleukin-6, tumor necrosis factor, D-dimer) even among patients without severe sepsis. The risk of death associated with acute kidney injury varied when assessed by Gray's survival model and after adjusting for differences in age, gender, ethnicity, and comorbidity. This risk was significantly higher immediately after hospitalization but gradually fell over time in the overall cohort and in those with non-severe pneumonia. A significantly higher risk of death (hazard ratio 1.29) was also present in those never admitted to an intensive care unit. Hence acute kidney injury is common even among patients with non-severe pneumonia and is associated with higher immune response and an increased risk of death.

Cardiorenal syndromes

PURPOSE OF REVIEW

The purpose of the present review is to identify the mechanisms involved in the syndrome related to combined heart-kidney dysfunction.

RECENT FINDINGS

The bidirectionality of the syndrome and the various time frames involved in the different clinical pictures have induced to generate a new definition of the cardiorenal syndrome, focusing on five specific subtypes (acute cardiorenal syndrome, type 1; chronic cardiorenal syndrome, type 2; acute renocardiac syndrome, type 3; chronic renocardiac syndrome, type 4; and secondary cardiorenal syndrome, type 5).

SUMMARY

The new definition allows to characterize the various clinical scenarios and to identify patients with different subtypes in which the primary disorder and the sequelae are clearly described. Biomarkers for early diagnosis of heart and kidney dysfunction may further contribute to a clearer definition of the disorder. The new classification will allow to test diagnostic tools and prevention strategies as well as therapeutic measures that in the past might not have been applied properly due to the lack of a consistent classification of the syndrome.

Renal FcRn reclaims albumin but facilitates elimination of IgG

The widely distributed neonatal Fc receptor (FcRn) contributes to maintaining serum levels of albumin and IgG in adults. In the kidney, FcRn is expressed on the podocytes and the brush border of the proximal tubular epithelium. Here, we evaluated the role of renal FcRn in albumin and IgG metabolism. Compared with wild-type controls, FcRn(-/-) mice had a lower t((1/2)) for albumin (28.7 versus 39.9 h) and IgG (29.5 versus 66.1 h). Renal loss of albumin could account for the former, suggested by the progressive development of hypoalbuminemia in wild-type mice transplanted with FcRn-deficient kidneys. Furthermore, serum albumin levels returned to normal in FcRn(-/-) recipients of wild-type kidneys after removing the native FcRn-deficient kidneys. In contrast, renal loss could not account for the enhanced elimination of IgG in FcRn(-/-) mice. These mice had minimal urinary excretion of native and labeled IgG, which increased to wild-type levels in FcRn(-/-) recipients of a single FcRn-sufficient kidney (t((1/2)) of IgG was 21.7 h). Taken together, these data suggest that renal FcRn reclaims albumin, thereby maintaining the serum concentration of albumin, but facilitates the loss of IgG from plasma protein pools.

siRNA targeted to p53 attenuates ischemic and cisplatin-induced acute kidney injury

Proximal tubule cells (PTCs), which are the primary site of kidney injury associated with ischemia or nephrotoxicity, are the site of oligonucleotide reabsorption within the kidney. We exploited this property to test the efficacy of siRNA targeted to p53, a pivotal protein in the apoptotic pathway, to prevent kidney injury. Naked synthetic siRNA to p53 injected intravenously 4 h after ischemic injury maximally protected both PTCs and kidney function. PTCs were the primary site for siRNA uptake within the kidney and body. Following glomerular filtration, endocytic uptake of Cy3-siRNA by PTCs was rapid and extensive, and significantly reduced ischemia-induced p53 upregulation. The duration of the siRNA effect in PTCs was 24 to 48 h, determined by levels of p53 mRNA and protein expression. Both Cy3 fluorescence and in situ hybridization of siRNA corroborated a short t(1/2) for siRNA. The extent of renoprotection, decrease in cellular p53 and attenuation of p53-mediated apoptosis by siRNA were dose- and time-dependent. Analysis of renal histology and apoptosis revealed improved injury scores in both cortical and corticomedullary regions. siRNA to p53 was also effective in a model of cisplatin-induced kidney injury. Taken together, these data indicate that rapid delivery of siRNA to proximal tubule cells follows intravenous administration. Targeting siRNA to p53 leads to a dose-dependent attenuation of apoptotic signaling, suggesting potential therapeutic benefit for ischemic and nephrotoxic kidney injury.

Ghrelin protects mice against endotoxemia-induced acute kidney injury

Acute kidney injury (AKI) in septic patients drastically increases the mortality to 50-80%. Sepsis is characterized by hemodynamic perturbations as well as overwhelming induction of proinflammatory cytokines. Since ghrelin has been shown to have anti-inflammatory properties, we hypothesized that ghrelin may afford renal protection during endotoxemia-induced AKI. Studies were conducted in a normotensive endotoxemia-induced AKI model in mice by intraperitoneal injection of 3.5 mg/kg LPS. Serum ghrelin levels were increased during endotoxemia accompanied by increased ghrelin receptor (GHSR-1a) protein expression in the kidney. Ghrelin administration (1.0 mg/kg sc 6 h and 30 min before and 14 h after LPS) significantly decreased serum cytokine levels (TNF-alpha, IL-1beta, and IL-6) and serum endothelin-1 levels which had been induced by LPS. The elevated serum nitric oxide (NO) levels and renal inducible NO synthase expression were also decreased by ghrelin. Renal TNF-alpha levels were also increased significantly in response to LPS and ghrelin significantly attenuated this increase. When administrated before LPS, ghrelin protected against the fall in glomerular filtration rate at 16 h (172.9 +/- 14.7 vs. 90.6 +/- 15.2 microl/min, P < 0.001) and 24 h (147.2 +/- 20.3 vs. 59.4 +/- 20.7 microl/min, P < 0.05) as well as renal blood flow at 16 h (1.65 +/- 0.07 vs. 1.47 +/- 0.04 ml/min, P < 0.01) and 24 h (1.56 +/- 0.08 vs. 1.22 +/- 0.03 ml/min, P < 0.05) after LPS administration without affecting mean arterial pressure. Ghrelin remained renal protective even when it was given after LPS. In summary, ghrelin offered significant protection against endotoxemia-induced AKI. The renal protective effect of ghrelin was associated with an inhibition of the proinflammatory cytokines. Of particular importance was the suppression of TNF-alpha both in the circulation and kidney tissues. Thus, ghrelin may be a promising peptide in managing endotoxemia-induced AKI.

The protein C pathway and pathologic processes

Alterations in expression of protein C (PC) pathway components have been identified in patients with active inflammatory disease states. While the PC pathway plays a pivotal role in regulating coagulation and fibrinolysis, activated PC (aPC) also exhibits cytoprotective properties. For example, PC-deficient mice challenged in septic/endotoxemic models exhibit phenotypes that include hypotension, disseminated intravascular coagulation, elevated inflammatory mediators, neutrophil adhesion to the microvascular endothelium, and loss of protective endothelial and epithelial cell barriers. Further, inflammatory bowel disease has been correlated with diminished endothelial PC receptor and thrombomodulin levels in the intestinal mucosa. Downregulated expression of the cofactor, protein S, as well as PC, is also associated with ischemic stroke. Studies to elucidate further the structural elements that differentiate the various functions of PC will serve to identify novel therapeutic approaches toward regulating these and other diseases.

Hypercytokinemia-induced metabolic encephalopathy in a multiple myeloma patient on hemodialysis undergoing autologous stem cell transplantation: clinical response after plasma exchange

We report here a 50-years old female with multiple myeloma-associated chronic renal failure who underwent high-dose chemotherapy supported by autologous hematopoietic stem cell transplantation. She developed progressive encephalopathy on day 5 progressing to coma despite hemodialysis and no obvious organ failure. She finally recovered after a single 1-liter plasma exchange. The final diagnosis was metabolic encephalopathy due to hypercytokinemia, particularly high serum TNF levels. We discuss here the pathogenesis and raise an alert for monitoring cytokine levels in patients with renal failure undergoing high-dose chemotherapy.

Inhibiting glycogen synthase kinase-3 reduces endotoxaemic acute renal failure by down-regulating inflammation and renal cell apoptosis

BACKGROUND AND PURPOSE

Excessive inflammation and apoptosis are pathological features of endotoxaemic acute renal failure. Activation of glycogen synthase kinase-3 (GSK-3) is involved in inflammation and apoptosis. We investigated the effects of inhibiting GSK-3 on lipopolysaccharide (LPS)-induced acute renal failure, nuclear factor-kappaB (NF-kappaB), inflammation and apoptosis.

EXPERIMENTAL APPROACH

The effects of inhibiting GSK-3 with inhibitors, including lithium chloride (LiCl) and 6-bromo-indirubin-3'-oxime (BIO), on LPS-treated (15 mg x kg(-1)) C3H/HeN mice (LiCl, 40 mg x kg(-1) and BIO, 2 mg x kg(-1)) and LPS-treated (1 microg x mL(-1)) renal epithelial cells (LiCl, 20 mM and BIO, 5 microM) were studied. Mouse survival was monitored and renal function was analysed by histological and serological examination. Cytokine and chemokine production, and cell apoptosis were measured by enzyme-linked immunosorbent assay and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling staining, respectively. Activation of NF-kappaB and GSK-3 was determined by immunostaining and Western blotting, respectively.

KEY RESULTS

Mice treated with GSK-3 inhibitors showed decreased mortality, renal tubular dilatation, vacuolization and sloughing, blood urea nitrogen, creatinine and renal cell apoptosis in response to endotoxaemia. Inhibiting GSK-3 reduced LPS-induced tumour necrosis factor-alpha (TNF-alpha) and CCL5/RANTES (released upon activation of normal T-cells) in vivo in mice and in vitro in murine kidney cortical collecting duct epithelial M1 cells. Inhibiting GSK-3 did not block TNF-alpha-induced cytotoxicity in rat kidney proximal tubular epithelial NRK52E or in M1 cells.

CONCLUSIONS AND IMPLICATIONS

These results suggest that GSK-3 inhibition protects against endotoxaemic acute renal failure mainly by down-regulating pro-inflammatory TNF-alpha and RANTES.

Searching for genes that matter in acute kidney injury: a systematic review

BACKGROUND AND OBJECTIVES

Identifying patients who may develop acute kidney injury (AKI) remains challenging, as clinical determinants explain only a portion of individual risk. Another factor that likely affects risk is intrinsic genetic variability. Therefore, a systematic review of studies was performed that related the development or prognosis of AKI to genetic variation.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

MEDLINE, EMBASE, HuGEnet, SCOPUS, and Web of Science were searched for articles from 1950 to Dec 2007. Two independent researchers screened articles using predetermined criteria. Studies were assessed for methodological quality via an aggregate scoring system.

RESULTS

The 16 included studies were of cohort or case-cohort design and investigated 35 polymorphisms in 21 genes in association with AKI. Fifteen gene-gene interactions were also investigated in four separate studies. Study populations were primarily premature infants or adults who were critically ill or postcardiac bypass patients. Among the studies, five different definitions of AKI were used. Only one polymorphism, APO E e2/e3/e4, had greater than one study showing a significant impact (P < 0.05) on AKI incidence. The mean quality score of 5.8/10 (range four to nine), heterogeneity in the studies, and the dearth of studies precluded additional meta-analysis of the results.

CONCLUSIONS

Current association studies are unable to provide definitive evidence linking genetic variation to AKI. Future success will require a narrow consensus definition of AKI, rigorous epidemiologic techniques, and a shift from a priori hypothesis-driven to genome-wide association studies.

TNF induces caspase-dependent inflammation in renal endothelial cells through a Rho- and myosin light chain kinase-dependent mechanism

The pathogenesis of LPS-induced acute kidney injury (AKI) requires signaling through tumor necrosis factor-alpha (TNF) receptor 1 (TNFR1), which within the kidney is primarily located in the endothelium. We showed previously that caspase inhibition protected mice against LPS-induced AKI and in parallel significantly inhibited LPS-induced renal inflammation. Therefore we hypothesized that caspase activation amplifies TNF-induced inflammation in renal endothelial cells (ECs). In cultured renal ECs, TNF induced apoptosis through a caspase-8-dependent pathway. TNF caused translocation of the p65 subunit of NF-kappaB to the nucleus, resulting in upregulation of inflammatory markers such as adhesion molecules ICAM-1 and VCAM-1. However, the broad-spectrum caspase inhibitor Boc-d-fmk reduced NF-kB activation as assessed by gel shift assay, reduced phosphorylation of subunit IkappaBalpha, and significantly inhibited TNF-induced expression of ICAM-1 and VCAM-1 as assessed by both real-time PCR and flow cytometry. Broad-spectrum caspase inhibition markedly inhibited neutrophil adherence to the TNF-activated endothelial monolayer, supporting the functional significance of this effect. Specific inhibitors of caspases-8 and -3, but not of caspase-1, reduced TNF-induced NF-kappaB activation. Caspase inhibition also reduced TNF-induced myosin light chain (MLC)-2 phosphorylation, and activation of upstream regulator RhoA. Consistent with this, MLC kinase (MLCK) inhibitor ML-7 reduced TNF-induced NF-kappaB activation. Thus caspase activation influences NF-kappaB signaling via its affect on cytoskeletal changes occurring through RhoA and MLCK pathways. These cell culture experiments support a role for caspase activation in TNF-induced inflammation in the renal endothelium, a key event in LPS-induced AKI.

Cardiorenal syndrome

The term cardiorenal syndrome (CRS) increasingly has been used without a consistent or well-accepted definition. To include the vast array of interrelated derangements, and to stress the bidirectional nature of heart-kidney interactions, we present a new classification of the CRS with 5 subtypes that reflect the pathophysiology, the time-frame, and the nature of concomitant cardiac and renal dysfunction. CRS can be generally defined as a pathophysiologic disorder of the heart and kidneys whereby acute or chronic dysfunction of 1 organ may induce acute or chronic dysfunction of the other. Type 1 CRS reflects an abrupt worsening of cardiac function (e.g., acute cardiogenic shock or decompensated congestive heart failure) leading to acute kidney injury. Type 2 CRS comprises chronic abnormalities in cardiac function (e.g., chronic congestive heart failure) causing progressive chronic kidney disease. Type 3 CRS consists of an abrupt worsening of renal function (e.g., acute kidney ischemia or glomerulonephritis) causing acute cardiac dysfunction (e.g., heart failure, arrhythmia, ischemia). Type 4 CRS describes a state of chronic kidney disease (e.g., chronic glomerular disease) contributing to decreased cardiac function, cardiac hypertrophy, and/or increased risk of adverse cardiovascular events. Type 5 CRS reflects a systemic condition (e.g., sepsis) causing both cardiac and renal dysfunction. Biomarkers can contribute to an early diagnosis of CRS and to a timely therapeutic intervention. The use of this classification can help physicians characterize groups of patients, provides the rationale for specific management strategies, and allows the design of future clinical trials with more accurate selection and stratification of the population under investigation.

The endothelin receptor antagonist tezosentan improves renal microcirculation in a porcine model of endotoxemic shock

BACKGROUND

Impaired renal microcirculation has been suggested as a factor contributing to the development of renal dysfunction in sepsis. This study was conducted to elucidate the role of endothelin-1 (ET-1)in mediating reductions in renal microcirculatory blood flow during endotoxemic shock.

METHODS

A prospective, randomized, and experimental study was performed with 16 anesthetized and mechanically ventilated pigs. After 2 h of lipopolysaccaride-induced endotoxemia, eight animals received a bolus dose of the dual endothelin receptor antagonist tezosentan (1 mg/kg), followed by a continuous infusion of 1 mg/kg/h throughout the experiment. Eight animals served as the control group. Renal microcirculation, total renal blood flow, plasma creatinine levels, cardiac index, and mean arterial pressure were measured. Plasma samples were collected for the measurement of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-10 (IL-10), ET-1, angiotensin II, and aldosterone.

RESULTS

Endotoxin infusion resulted in a state of circulatory shock with impairment of renal microcirculation. An increase in the plasma levels of TNF-alpha, IL-6, IL-10, ET-1, angiotensin II, and aldosterone was also observed. Tezosentan attenuated the decrease in renal microcirculation and renal blood flow, and attenuated the increase in plasma creatinine. Treatment with tezosentan did not significantly affect the plasma cytokine, angiotensin II, or aldosterone response to endotoxemia.

CONCLUSION

These results indicate that treatment with the dual endothelin receptor tezosentan in endotoxemic shock attenuates the reduction of renal microcirculation and total renal blood flow independently of plasma changes in the renin-angiotensin-aldosterone system or early plasma cytokine response.

Meprin A metalloproteases enhance renal damage and bladder inflammation after LPS challenge

Meprin metalloproteases, composed of alpha and/or beta subunits, consist of membrane-bound and secreted forms that are abundantly expressed in proximal tubules of the kidney as well as secreted into the urinary tract. Previous studies indicated that meprin metalloproteases play a role in pathological conditions such as ischemic acute renal failure and urinary tract infection. The aim of this work was to examine the role of meprins in endotoxemic acute renal failure using meprin alpha knockout (alphaKO), meprin beta knockout (betaKO), and wild-type (WT) mice. Differences among the responses of the genotypes were observed as early as 1 h after challenge with 2.5 mg/kg ip Escherichia coli LPS, establishing roles for meprins in the endotoxemic response. Meprin alphaKO mice displayed lower blood urea nitrogen levels and decreased nitric oxide levels, indicative of a decreased systemic response to LPS compared with WT and meprin betaKO mice. Serum cytokine profiles showed lower levels of IL-1beta and TNF-alpha in the meprin alphaKO mice within 3 h after LPS challenge and confirmed a role for meprins in the early phases of the host response. Meprin alphaKO mice were also hyporesponsive to LPS administered to the bladder, exhibiting significantly less bladder edema, leukocyte infiltration, and bladder permeability than WT mice. These data indicate that meprin A contributes to the renal and urogenital pathogenesis of endotoxicity.