Robert A. Star

Bone marrow stromal cells attenuate sepsis via prostaglandin E 2 –dependent reprogramming of host macrophages to increase their interleukin-10 production

Sepsis causes over 200,000 deaths yearly in the US; better treatments are urgently needed. Administering bone marrow stromal cells (BMSCs—also known as mesenchymal stem cells) to mice before or shortly after inducing sepsis by cecal ligation and puncture reduced mortality and improved organ function. The beneficial effect of BMSCs was eliminated by macrophage depletion or pretreatment with antibodies specific for interleukin-10 (IL-10) or IL-10 receptor. Monocytes and/or macrophages from septic lungs made more IL-10 when prepared from mice treated with BMSCs versus untreated mice. Lipopolysaccharide (LPS)-stimulated macrophages produced more IL-10 when cultured with BMSCs, but this effect was eliminated if the BMSCs lacked the genes encoding Toll-like receptor 4, myeloid differentiation primary response gene-88, tumor necrosis factor (TNF) receptor-1a or cyclooxygenase-2. Our results suggest that BMSCs (activated by LPS or TNF-α) reprogram macrophages by releasing prostaglandin E2 that acts on the macrophages through the prostaglandin EP2 and EP4 receptors. Because BMSCs have been successfully given to humans and can easily be cultured and might be used without human leukocyte antigen matching, we suggest that cultured, banked human BMSCs may be effective in treating sepsis in high-risk patient groups.

Intensity of renal support in critically ill patients with acute kidney injury.

BACKGROUND The optimal intensity of renal-replacement therapy in critically ill patients with acute kidney injury is controversial. METHODS We randomly assigned critically ill patients with acute kidney injury and failure of at least one nonrenal organ or sepsis to receive intensive or less intensive renal-replacement therapy. The primary end point was death from any cause by day 60. In both study groups, hemodynamically stable patients underwent intermittent hemodialysis, and hemodynamically unstable patients underwent continuous venovenous hemodiafiltration or sustained low-efficiency dialysis. Patients receiving the intensive treatment strategy underwent intermittent hemodialysis and sustained low-efficiency dialysis six times per week and continuous venovenous hemodiafiltration at 35 ml per kilogram of body weight per hour; for patients receiving the less-intensive treatment strategy, the corresponding treatments were provided thrice weekly and at 20 ml per kilogram per hour. RESULTS Baseline characteristics of the 1124 patients in the two groups were similar. The rate of death from any cause by day 60 was 53.6% with intensive therapy and 51.5% with less-intensive therapy (odds ratio, 1.09; 95% confidence interval, 0.86 to 1.40; P=0.47). There was no significant difference between the two groups in the duration of renal-replacement therapy or the rate of recovery of kidney function or nonrenal organ failure. Hypotension during intermittent dialysis occurred in more patients randomly assigned to receive intensive therapy, although the frequency of hemodialysis sessions complicated by hypotension was similar in the two groups. CONCLUSIONS Intensive renal support in critically ill patients with acute kidney injury did not decrease mortality, improve recovery of kidney function, or reduce the rate of nonrenal organ failure as compared with less-intensive therapy involving a defined dose of intermittent hemodialysis three times per week and continuous renal-replacement therapy at 20 ml per kilogram per hour. (ClinicalTrials.gov number, NCT00076219.)

In-center hemodialysis six times per week versus three times per week

BACKGROUND In this randomized clinical trial, we aimed to determine whether increasing the frequency of in-center hemodialysis would result in beneficial changes in left ventricular mass, self-reported physical health, and other intermediate outcomes among patients undergoing maintenance hemodialysis. METHODS Patients were randomly assigned to undergo hemodialysis six times per week (frequent hemodialysis, 125 patients) or three times per week (conventional hemodialysis, 120 patients) for 12 months. The two coprimary composite outcomes were death or change (from baseline to 12 months) in left ventricular mass, as assessed by cardiac magnetic resonance imaging, and death or change in the physical-health composite score of the RAND 36-item health survey. Secondary outcomes included cognitive performance; self-reported depression; laboratory markers of nutrition, mineral metabolism, and anemia; blood pressure; and rates of hospitalization and of interventions related to vascular access. RESULTS Patients in the frequent-hemodialysis group averaged 5.2 sessions per week; the weekly standard Kt/V(urea) (the product of the urea clearance and the duration of the dialysis session normalized to the volume of distribution of urea) was significantly higher in the frequent-hemodialysis group than in the conventional-hemodialysis group (3.54±0.56 vs. 2.49±0.27). Frequent hemodialysis was associated with significant benefits with respect to both coprimary composite outcomes (hazard ratio for death or increase in left ventricular mass, 0.61; 95% confidence interval [CI], 0.46 to 0.82; hazard ratio for death or a decrease in the physical-health composite score, 0.70; 95% CI, 0.53 to 0.92). Patients randomly assigned to frequent hemodialysis were more likely to undergo interventions related to vascular access than were patients assigned to conventional hemodialysis (hazard ratio, 1.71; 95% CI, 1.08 to 2.73). Frequent hemodialysis was associated with improved control of hypertension and hyperphosphatemia. There were no significant effects of frequent hemodialysis on cognitive performance, self-reported depression, serum albumin concentration, or use of erythropoiesis-stimulating agents. CONCLUSIONS Frequent hemodialysis, as compared with conventional hemodialysis, was associated with favorable results with respect to the composite outcomes of death or change in left ventricular mass and death or change in a physical-health composite score but prompted more frequent interventions related to vascular access. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; ClinicalTrials.gov number, NCT00264758.).

Incidence and Mortality of Acute Renal Failure in Medicare Beneficiaries, 1992 to 2001

This studys objective was to determine the incidence and mortality of acute renal failure (ARF) in Medicare beneficiaries. Data were from hospitalized Medicare beneficiaries (5,403,015 discharges) between 1992 and 2001 from the 5% sample of Medicare claims. For 1992 to 2001, the overall incidence rate of ARF was 23.8 cases per 1000 discharges, with rates increasing by approximately 11% per year. Older age, male gender, and black race were strongly associated (P < 0.0001) with ARF. The overall in-hospital death rate was 4.6% in discharges without ARF, 15.2% in discharges with ARF coded as the principal diagnosis, and 32.6% in discharges with ARF as a secondary diagnosis. In-hospital death rates were 32.9% in discharges with ARF that required renal dialysis and 27.5% in those with ARF that did not require dialysis. Death within 90 d after hospital admission was 13.1% in discharges without ARF, 34.5% in discharges with ARF coded as the principal diagnosis, and 48.6% in discharges with ARF as a secondary diagnosis. Discharges with ARF were more (P < 0.0001) likely to have intensive care and other acute organ dysfunction than those without ARF. For discharges both with and without ARF, rates for death within 90 d after hospital admission showed a declining trend. In conclusion, the incidence rate of ARF in Medicare beneficiaries has been increasing. Those of older age, male gender, and black race are more likely to have ARF. These data show ARF to be a major contributor to morbidity and mortality in hospitalized patients.

Acute Kidney Injury and Chronic Kidney Disease as Interconnected Syndromes

For more than 40 years, nephrologists have classified diminished kidney function as two distinct syndromes — acute and chronic kidney failure. Whereas chronic kidney disease was recognized in the 19th century, acute renal dysfunction became evident during the London Blitz of World War II, with the realization that crush injuries could cause dramatic but often reversible cessation of renal function. The disease states and stages of both acute and chronic renal syndromes are delineated according to the serum creatinine concentration or the glomerular filtration rate (GFR), functional markers that were identified in the early 20th century. 1 Advanced renal impairment in both syndromes is treated with dialysis. During the past decade, separate conceptual models for chronic kidney disease 2 and acute kidney injury 3 were developed to facilitate organized approaches to clinical research and trials. However, recent epidemiologic and mechanistic studies suggest that the two syndromes are not distinct entities but rather are closely interconnected — chronic kidney disease is a risk factor for acute kidney injury, acute kidney injury is a risk factor for the development of chronic kidney disease, and both acute kidney injury and chronic kidney disease are risk factors for cardiovascular disease (Fig. 1). 4

Large-Scale Proteomics and Phosphoproteomics of Urinary Exosomes

Normal human urine contains large numbers of exosomes, which are 40- to 100-nm vesicles that originate as the internal vesicles in multivesicular bodies from every renal epithelial cell type facing the urinary space. Here, we used LC-MS/MS to profile the proteome of human urinary exosomes. Overall, the analysis identified 1132 proteins unambiguously, including 177 that are represented on the Online Mendelian Inheritance in Man database of disease-related genes, suggesting that exosome analysis is a potential approach to discover urinary biomarkers. We extended the proteomic analysis to phosphoproteomic profiling using neutral loss scanning, and this yielded multiple novel phosphorylation sites, including serine-811 in the thiazide-sensitive Na-Cl co-transporter, NCC. To demonstrate the potential use of exosome analysis to identify a genetic renal disease, we carried out immunoblotting of exosomes from urine samples of patients with a clinical diagnosis of Bartter syndrome type I, showing an absence of the sodium-potassium-chloride co-transporter 2, NKCC2. The proteomic data are publicly accessible at http://dir.nhlbi.nih.gov/papers/lkem/exosome/.

Exosomes from human saliva as a source of microRNA biomarkers

OBJECTIVE The aim of this study was to examine the presence of microRNAs (miRNAs) within exosomes isolated from human saliva and to optimize and test methods for successful downstream applications. DESIGN Exosomes isolated from fresh and frozen glandular and whole human saliva were used as a source of miRNAs. The presence of miRNAs was validated with TaqMan quantitative PCR and miRNA microarrays. RESULTS We successfully isolated exosomes from human saliva from healthy controls and a patient with Sjögrens syndrome. microRNAs extracted from the exosomal fraction were sufficient for quantitative PCR and microarray profiling. CONCLUSIONS The isolation of miRNAs from easily and non-invasively obtained salivary exosomes with subsequent characterization of the miRNA expression patterns is promising for the development of future biomarkers of the diagnosis and prognosis of various salivary gland pathologies.

The effects of frequent nocturnal home hemodialysis: the Frequent Hemodialysis Network Nocturnal Trial

Prior small studies have shown multiple benefits of frequent nocturnal hemodialysis compared to conventional three times per week treatments. To study this further, we randomized 87 patients to three times per week conventional hemodialysis or to nocturnal hemodialysis six times per week, all with single-use high-flux dialyzers. The 45 patients in the frequent nocturnal arm had a 1.82-fold higher mean weekly stdKt/V(urea), a 1.74-fold higher average number of treatments per week, and a 2.45-fold higher average weekly treatment time than the 42 patients in the conventional arm. We did not find a significant effect of nocturnal hemodialysis for either of the two coprimary outcomes (death or left ventricular mass (measured by MRI) with a hazard ratio of 0.68, or of death or RAND Physical Health Composite with a hazard ratio of 0.91). Possible explanations for the left ventricular mass result include limited sample size and patient characteristics. Secondary outcomes included cognitive performance, self-reported depression, laboratory markers of nutrition, mineral metabolism and anemia, blood pressure and rates of hospitalization, and vascular access interventions. Patients in the nocturnal arm had improved control of hyperphosphatemia and hypertension, but no significant benefit among the other main secondary outcomes. There was a trend for increased vascular access events in the nocturnal arm. Thus, we were unable to demonstrate a definitive benefit of more frequent nocturnal hemodialysis for either coprimary outcome.

Animal models of sepsis and sepsis-induced kidney injury

Sepsis is characterized by a severe inflammatory response to infection, and its complications, including acute kidney injury, can be fatal. Animal models that correctly mimic human disease are extremely valuable because they hasten the development of clinically useful therapeutics. Too often, however, animal models do not properly mimic human disease. In this Review, we outline a bedside-to-bench-to-bedside approach that has resulted in improved animal models for the study of sepsis - a complex disease for which preventive and therapeutic strategies are unfortunately lacking. We also highlight a few of the promising avenues for therapeutic advances and biomarkers for sepsis and sepsis-induced acute kidney injury. Finally, we review how the study of drug targets and biomarkers are affected by and in turn have influenced these evolving animal models.

Alpha-melanocyte-stimulating hormone protects against renal injury after ischemia in mice and rats.

Reperfusion after ischemia induces cytokines, chemoattractant chemokines, adhesion molecules, and nitric oxide (NO). The resultant neutrophil adherence and NO potentiates renal injury. alpha-Melanocyte-stimulating hormone (alpha-MSH) is a potent anti-inflammatory agent that inhibits neutrophil migration and production of neutrophil chemokines and NO. Since neutrophils and NO promote renal ischemic injury, we sought to determine if alpha-MSH inhibits renal injury in a model of bilateral renal ischemia. alpha-MSH significantly reduced ischemia-induced renal damage, measured by changes in renal histology and plasma blood urea nitrogen and creatinine in mice. alpha-MSH significantly decreased tubule necrosis, neutrophil plugging, and capillary congestion. Delay of alpha-MSH treatment for 6 h after ischemia also significantly inhibited renal damage. alpha-MSH also significantly inhibited ischemic damage in rats. To begin to determine the mechanism of action of alpha-MSH, we measured its effects on mediators of neutrophil trafficking and induction of the inducible isoform of NO synthase-II. alpha-MSH inhibited ischemia-induced increases in mRNA for the murine neutrophil chemokine KC/IL-8. alpha-MSH also inhibited induction of mRNA for the adhesion molecule ICAM-1, which is known to be critical in renal ischemic injury. alpha-MSH inhibited nitration of kidney proteins and induction of NO synthase-II. We conclude: (a) alpha-MSH protects against renal ischemia/reperfusion injury; and (b) it may act, in part, by inhibiting the maladaptive activation of genes that cause neutrophil activation and adhesion, and induction of NO synthase.