The role of Toll-like receptors in renal diseases

Treatment with lecinoxoids attenuates focal and segmental glomerulosclerosis development in nephrectomized rats

Focal segmental glomerulosclerosis (FSGS) is a scarring process associated with chronic low‐grade inflammation ascribed to toll‐like receptor (TLR) activation and monocyte migration. We developed synthetic, small‐molecule lecinoxoids, VB‐201 and VB‐703, that differentially inhibit TLR‐2‐ and TLR‐4‐mediated activation and monocyte migration. The efficacy of anti‐inflammatory lecinoxoid treatment on FSGS development was explored using a 5/6 nephrectomy rat model. Five‐sixths of nephrectomized rats were treated with lecinoxoids VB‐201, VB‐703 or PBS, for 7 weeks. Upon sacrifice, albumin/creatinine ratio, glomerulosclerosis, fibrosis‐related gene expression and the number of glomerular and interstitial monocyte were evaluated. Treatment of nephrectomized rats with lecinoxoids ameliorated glomerulosclerosis. The percentage of damaged glomeruli, glomerular sclerosis and glomeruli fibrotic score was significantly reduced following VB‐201 and VB‐703 treatment. VB‐703 attenuated the expression of fibrosis hallmark genes collagen, fibronectin (FN) and transforming growth factor β (TGF‐β) in kidneys and improved albumin/creatinine ratio with higher efficacy than did VB‐201, but only VB‐201 significantly reduced the number of glomerular and interstitial monocytes. These results indicate that treatment with TLR‐2, and more prominently, TLR‐4 antagonizing lecinoxioids, is sufficient to significantly inhibit FSGS. Moreover, inhibiting monocyte migration can also contribute to treatment of FSGS. Our data demonstrate that targeting TLR‐2‐TLR‐4 and/or monocyte migration directly affects the priming phase of fibrosis and may consequently perturb disease parthogenesis.

Antinatriuretic phenomena seen in children with acute pyelonephritis may be related to the activation of intrarenal RAAS

We investigated whether antinatriuretic phenomena [decreases in urinary sodium (uNa) and fractional excretion of sodium (FENa)] seen in children with acute pyelonephritis (APN) are associated with the renin-angiotensin-aldosterone system (RAAS).We examined 114 children experiencing their first episode of febrile urinary tract infection (fUTI) consecutively admitted to our hospital from July 2012 to June 2014. Blood tests [C-reactive protein, white blood cell count, erythrocyte sedimentation rate, and aldosterone (Aldo)] and urine tests [uNa, urine potassium (uK) and FENa] were performed upon admission. All enrolled children underwent a 99m-dimercaptosuccinic acid renal scanning (DMSA) at admission. Areas with cortical defects (AreaCD) and uptake counts (UptakeCD) on their DMSA scans were calculated. Data were compared between children with positive DMSA results (APN), lower urinary tract infection (L-UTI), and controls; and between children with high and low Aldo levels.uNa, uNa/K, and FENa negatively correlated with AreaCD%, UptakeCD, and Aldo; were significantly lower in APN patients than in LUTIs and controls regardless of Aldo level; were lower in the high Aldo group than in the low Aldo group. However, there is no difference in AreaCD% and UptakeCD between APN children with the high and low Aldo level.Decreases in uNa, uNa/K, and FENa in children with APN may result from an antinatriuretic effect of RAAS and be related to the activation of the intrarenal RAAS.

Kidney Proximal Tubular TLR9 Exacerbates Ischemic Acute Kidney Injury

The role for kidney TLR9 in ischemic acute kidney injury (AKI) remains unclear. In this study, we tested the hypothesis that renal proximal tubular TLR9 activation exacerbates ischemic AKI by promoting renal tubular epithelial apoptosis and inflammation. To test this hypothesis, we generated mice lacking TLR9 in renal proximal tubules (TLR9^fl/fl PEPCK Cre mice). Contrasting previous studies in global TLR9 knockout mice, mice lacking renal proximal tubular TLR9 were protected against renal ischemia/reperfusion (IR) injury, with reduced renal tubular necrosis, inflammation (decreased proinflammatory cytokine synthesis and neutrophil infiltration), and apoptosis (decreased DNA fragmentation and caspase activation) when compared with wild-type (TLR9^fl/fl) mice. Consistent with this, a selective TLR9 agonist oligonucleotide 1668 exacerbated renal IR injury in TLR9^fl/fl mice but not in renal proximal tubular TLR9-null mice. Furthermore, in cultured human and mouse proximal tubule cells, TLR9-selective ligands induced NF-κB activation, proinflammatory cytokine mRNA synthesis, as well as caspase activation. We further confirm in the present study that global TLR9 deficiency had no impact on murine ischemic AKI. Taken together, our studies show that renal proximal tubular TLR9 activation exacerbates ischemic AKI by promoting renal tubular inflammation, apoptosis as well as necrosis, after IR via NF-κB and caspase activation. Our studies further suggest the complex nature of TLR9 activation, as renal tubular epithelial TLR9 promotes cell injury and death whereas TLR9 signaling in other cell types may promote cytoprotective effects.

Pharmacological Inhibition of Macrophage Toll-like Receptor 4/Nuclear Factor-kappa B Alleviates Rhabdomyolysis-induced Acute Kidney Injury

Background:

Acute kidney injury (AKI) is the most common and life-threatening systemic complication of rhabdomyolysis. Inflammation plays an important role in the development of rhabdomyolysis-induced AKI. This study aimed to investigate the kidney model of AKI caused by rhabdomyolysis to verify the role of macrophage Toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-κB) signaling pathway.

Methods:

C57BL/6 mice were injected with a 50% glycerin solution at bilateral back limbs to induce rhabdomyolysis, and CLI-095 or pyrrolidine dithiocarbamate (PDTC) was intraperitoneally injected at 0.5 h before molding. Serum creatinine levels, creatine kinase, the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, and hematoxylin and eosin stainings of kidney tissues were tested. The infiltration of macrophage, mRNA levels, and protein expression of TLR4 and NF-κB were investigated by immunofluorescence double-staining techniques, reverse transcriptase-quantitative polymerase chain reaction, and Western blotting, respectively. In vitro, macrophage RAW264.7 was stimulated by ferrous myoglobin; the cytokines, TLR4 and NF-κB expressions were also detected.

Results:

In an in vivo study, using CLI-095 or PDTC to block TLR4/NF-κB, functional and histologic results showed that the inhibition of TLR4 or NF-κB alleviated glycerol-induced renal damages (P < 0.01). CLI-095 or PDTC administration suppressed proinflammatory cytokine (TNF-α, IL-6, and IL-1β) production and macrophage infiltration into the kidney (P < 0.01). Moreover, in an in vitro study, CLI-095 or PDTC suppressed myoglobin-induced expression of TLR4, NF-κB, and proinflammatory cytokine levels in macrophage RAW264.7 cells (P < 0.01).

Conclusion:

The pharmacological inhibition of TLR4/NF-κB exhibited protective effects on rhabdomyolysis-induced AKI by the regulation of proinflammatory cytokine production and macrophage infiltration.

Atorvastatin attenuates experimental contrast-induced acute kidney injury: a role for TLR4/MyD88 signaling pathway

Objectives: To investigate the protective effect of different atorvastatin doses on contrast-induced acute kidney injury and the related mechanism.

Methods: Healthy male Sprague–Dawley (SD) rats were randomly divided into the blank control group, experimental control group and different-dose atorvastatin groups. A rat model of contrast-induced acute kidney injury was established. We detected changes in serum creatinine (Scr) and blood urea nitrogen (BUN) before and after model establishment, observed and scored renal tubular injury, analyzed rat renal cell apoptosis, and measure the expression of signal pathway proteins and downstream inflammatory factors.

Results: After contrast agent injection, the Scr and BUN levels of the experimental control group were significantly increased, the different doses applied in the atorvastatin group significantly reduced the Scr and BUN levels (p < .05) and ameliorated the contrast-induced acute kidney injury (p < .05) and significantly reduced Toll-like receptor 4 (TLR4), Myeloid differentiation factor 88 (Myd88), and Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) protein expression and relative mRNA expression levels (p < .05) and significantly decreased expression levels of downstream inflammatory factors (p < .05).

Conclusion: Different atorvastatin doses have protective effects on contrast-induced acute renal tubular injury in rats, possibly by targeting TLR4, suppressing TLR4 expression, regulating the TLR4/Myd88 signaling pathway, and inhibiting the expression of downstream inflammatory factors.

Viral-host interaction in kidney reveals strategies to escape host immunity and persistently shed virus to the urine

Hepatitis A virus is one of five types of hepatotropic viruses that cause human liver disease. A similar liver disease is also identified in ducks caused by Duck Hepatitis A virus (DHAV). Notably, many types of hepatotropic viruses can be detected in urine. However, how those viruses enter into the urine is largely unexplored. To elucidate the potential mechanism, we used the avian hepatotropic virus to investigate replication strategies and immune responses in kidney until 280 days after infection. Immunohistochemistry and qPCR were used to detect viral distribution and copies in the kidney. Double staining of CD4+ or CD8+ T cells and virus and qPCR were used to investigate T cell immune responses and expression levels of cytokines. Histopathology was detected by standard HE staining. In this study, viruses were persistently located at scattered renal tubules. No CD4+ or CD8+ T cells were recruited to the kidney, which was only accompanied by transient cytokine storms. In conclusion, the extremely scattered infection was the viral strategy to escape host immunity and may persistently shed virus into urine. The deletion of Th or Tc cell responses and transient cytokine storms indeed provide an advantageous renal environment for their persistent survival.

Inflammation and Peritoneal Dialysis

Inflammation is one of the well-recognized nontraditional risk factors that contributes to the excessive cardiovascular mortality in peritoneal dialysis (PD) patients. Serum C-reactive protein and interleukin-6 levels are common surrogate markers used to measure inflammatory burden and predict adverse clinical outcomes in PD patients. Causes of inflammation are complex and can be categorized into factors related to a decrease in renal function and factors related to dialysis. They interact with each other and finally result in systemic and intraperitoneal inflammation. This review discusses the various causes and clinical implications of inflammation in PD patients. More importantly, potential therapeutic options that target the underlying pathogenic mechanisms are explored.

C5aR1 promotes acute pyelonephritis induced by uropathogenic E. coli

C5a receptor 1 (C5aR1) is a G protein-coupled receptor for C5a and also an N-linked glycosylated protein. In addition to myeloid cells, C5aR1 is expressed on epithelial cells. In this study, we examined the role of C5aR1 in bacterial adhesion/colonization of renal tubular epithelium and addressed the underlying mechanisms of this role. We show that acute kidney infection was significantly reduced in mice with genetic deletion or through pharmacologic inhibition of C5aR1 following bladder inoculation with uropathogenic E. coli (UPEC). This was associated with reduced expression of terminal α-mannosyl residues (Man; a ligand for type 1 fimbriae of E. coli) on the luminal surface of renal tubular epithelium and reduction of early UPEC colonization in these mice. Confocal microscopy demonstrated that UPEC bind to Man on the luminal surface of renal tubular epithelium. In vitro analyses showed that C5a stimulation enhances Man expression in renal tubular epithelial cells and subsequent bacterial adhesion, which, at least in part, is dependent on TNF-α driven by C5aR1-mediated intracellular signaling. Our findings demonstrate a previously unknown pathogenic role for C5aR1 in acute pyelonephritis, proposing a potentially novel mechanism by which C5a/C5aR1 signaling mediates upregulation of carbohydrate ligands on renal tubules to facilitate UPEC adhesion.

Blockade of Inflammation and Apoptosis Pathways by siRNA Prolongs Cold Preservation Time and Protects Donor Hearts in a Porcine Model

In donor hearts from mini pigs, overtime cold preservation and ischemia-reperfusion injury cause poor graft quality and impaired heart function. Blockage of complement, apoptosis, and inflammation is considered a strategy for attenuating ischemia-reperfusion injury and protecting cardiac function. Minipig donor hearts were perfused and preserved in Celsior solution or transfection reagent containing Celsior solution with scramble siRNA or siRNAs targeting complement 3, caspase-8, caspase-3, and nuclear factor κB-p65 genes at 4°C and subsequently hemo-reperfused ex vivo (38°C) or transplanted into recipients. The protective effect of the siRNA solution was evaluated by measuring cell apoptosis, structural alteration, protein markers for tissue damage and oxidative stress, and cardiac function. We found a reduction in cell apoptosis, myocardial damage, and tissue inflammation by reduced biochemistry and markers and protein expression of proinflammatory cytokines and improvement in cardiac function, as shown by the improved hemodynamic indices in 12-hr-preserved siRNA-treated hearts of both ex vivo and orthotopic transplantation models. These findings demonstrate that blockade of inflammation and apoptosis pathways using siRNA can prolong cold preservation time and better protect donor heart function in cardiac transplantation of large animals, which may be beneficial for human heart preservation.

Characterizing the Association Between Toll-like Receptor Subtypes and Nephrolithiasis With Renal Inflammation in an Animal Model

OBJECTIVE

To show experimentally induced renal stone disease and to evaluate secondary inflammatory responses in vivo, and to characterize changes in the expression of Toll-like receptor (TLR) subtypes in this model.

METHODS

Twenty 5- to 6-week-old male Wistar rats were divided into control and hyperoxaluria groups (n = 10 per group) and were supplied with normal water or 1% ethylene glycol, respectively, for 16 weeks. The animals were then placed in metabolic cages, and urine was collected for a 24-hour urine oxalate level evaluation. Following sacrifice, rats were subjected to bilateral nephrectomy and both kidneys were histopathologically evaluated. A 1-mm³ biopsy section from the right kidney of each rat was subjected to real-time polymerase chain reaction of the TLR expression.

RESULTS

At the end of week 16, the hyperoxaluria group had a higher mean 24-hour urine oxalate level (1.91) than the control group (0.29) (P <.05) and a remarkably increased deposition of renal CaOx crystals (15/20) than the control group (0/20) (P <.05), which was universally accompanied by inflammation (15/15). Twelve and no rats in the hyperoxaluria and control groups, respectively, had macroscopically visible renal pelvic stones (P <.05). Quantitative real-time polymerase chain reaction revealed significant decreases in the expression of several TLRs, particularly TLR11 and TLR7. Decreases in TLR1, TLR3, and TLR6 expressions and an increase in the TLR2 expression did not differ significantly between the groups.

CONCLUSION

We believe that is the first evaluation of TLR expression associated with renal stone formation in an animal model of inflammation. These results might lead to novel TLR-based treatments for nephrolithiasis and related inflammatory renal damage.

The optimal duration of ischemic preconditioning for renal ischemia-reperfusion injury in mice

Purpose

The aim of the present study was to investigate the protective effects of ischemic preconditioning for different periods of time and to elucidate the optimal safe ischemic preconditioning time for renal ischemia-reperfusion (I/R) injury in mice.

Methods

A total of 25 male C57BL/6 mice were randomly divided into 5 groups (sham, I/R, ischemic preconditioning [IP]-3, IP-5, and IP-7 groups), in which the kidney was preconditioned with IP of various durations and then subjected to I/R injury (the last 3 groups). To induce renal ischemia, the left renal pedicle was occluded with a nontraumatic microaneurysm clamp for 30 minutes followed by reperfusion for 24 hours. The effects of IP on renal I/R injury were evaluated in terms of renal function, tubular necrosis, apoptotic cell death and inflammatory cytokines.

Results

Results indicated that BUN and creatinine (Cr) levels increased significantly in the I/R group, but the elevations were significantly lower in IP groups, especially in the IP-5 group. Histological analysis revealed that kidney injury was markedly decreased in the IP-5 group compared with the I/R group, as evidenced by reduced renal necrosis/apoptosis. In addition, IP significantly inhibited gene expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) and chemokines (monocyte chemoattractant protein-1). Western blot analysis indicated that the expression levels of Toll-like receptor 4 (TLR4) and nuclear factor-kappa B (NF-κB) were upregulated in the I/R group, while expression was inhibited in the IP groups.

Conclusion

Five-minute IP had the greatest protective effect against I/R injury.

Toll-like Receptor 4 Signaling Pathway in the Protective Effect of Pioglitazone on Experimental Immunoglobulin A Nephropathy

Background:

In vitro experiments have revealed that toll-like receptor 4 (TLR4) pathway is involved in the progression of immunoglobulin A nephropathy (IgAN) by induction of proinflammatory cytokines. Evidence showed that, in other disease models, peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists have been shown to exert anti-inflammatory effects through suppression of the expression and activity of TLR4. However, the interaction between PPAR-γ and TLR4 in IgAN has not been fully studied both in vitro and in vivo. In this study, we explored whether TLR4 pathway attributed to the progression of IgAN in experimental rats.

Methods:

Bovine gamma globulin was used to establish IgAN model. Fifty-four Lewis rats were randomly divided into six groups: Control_TAK242, IgAN_TAK242, toll-like receptor 4 inhibitor (TAK242) groups (rats were administrated with TLR4 inhibitor, TAK242) and Control_Pio, IgAN_Pio, Pio groups (rats were administrated with PPAR-γ agonist, pioglitazone). Urinary albumin-to-creatinine ratio (ACR), serum creatinine, and blood urea nitrogen were detected by automatic biochemical analyzer. Renal histopathological changes were observed after hematoxylin-eosin staining, and the IgA deposition in glomeruli was measured by immunofluorescence staining. Real-time polymerase chain reaction and Western blotting were used to detect TLR4 and interleukin-1 beta (IL-1β) message ribonucleic acid (mRNA) and protein expression in renal tissues. Results were presented as mean ± standard deviation. Differences between groups were analyzed by one-way analysis of variance.

Results:

Compared to normal rats, experimental rats showed higher ACR (4.45 ± 1.33 mg/mmol vs. 2.89 ± 0.96 mg/mmol, P < 0.05), obvious IgA deposition with mesangial hypercellularity, hyperplasia of mesangial matrix accompanied by increased serum IL-1β (48.28 ± 13.49 pg/ml vs. 35.56 ± 7.41pg/ml, P < 0.05), and renal expression of IL-1β and TLR4. The biochemical parameters and renal pathological injury were relieved in both TAK242 group and Pio group. The expressions of renal tissue TLR4, IL-1β, and serum IL-1β were decreased in rats treated with TAK242, and the expression of TLR4 mRNA and protein was significantly reduced in Pio group compared to IgAN_Pio group (1.22 ± 0.28 vs. 1.72 ± 0.45, P < 0.01, and 0.12 ± 0.03 vs. 0.21 ± 0.05, P < 0.01).

Conclusions:

Our study proves that inflammation mediated by TLR4 signaling pathway is involved in the progression of IgAN in rat models. Moreover, pioglitazone can inhibit the expression of TLR4 in IgAN.

Dendritic Cell Dysfunction in Patients with End-stage Renal Disease

End-stage renal disease (ESRD) with immune disorder involves complex interactions between the innate and adaptive immune responses. ESRD is associated with various alterations in immune function such as a reduction in polymorphonuclear leukocyte bactericidal activity, a suppression of lymphocyte proliferative response to stimuli, and a malfunction of cell-mediated immunity at the molecular level. ESRD also increases patients' propensity for infections and malignancies as well as causing a diminished response to vaccination. Several factors influence the immunodeficiency in patients with ESRD, including uremic toxins, malnutrition, chronic inflammation, and the therapeutic dialysis modality. The alteration of T-cell function in ESRD has been considered to be a major factor underlying the impaired adaptive cellular immunity in these patients. However, cumulative evidence has suggested that the immune defect in ESRD can be caused by an Ag-presenting dendritic cell (DC) dysfunction in addition to a T-cell defect. It has been reported that ESRD has a deleterious effect on DCs both in terms of their number and function, although the precise mechanism by which DC function becomes altered in these patients is unclear. In this review, we discuss the effects of ESRD on the number and function of DCs and propose a possible molecular mechanism for DC dysfunction. We also address therapeutic approaches to improve immune function by optimally activating DCs in patients with ESRD.

Toll-Like Receptor 4 Deficiency Improves Short-term Renal Function but not Long-term Graft Survival in a Fully MHC-Mismatched Murine Model of Renal Allograft Transplantation

BACKGROUND

We have previously demonstrated that absence of myeloid differentiation primary response gene 88 (MyD88) induced donor-specific kidney allograft tolerance. The upstream pathways of MyD88 that mediate this process, however, remain unclear. Toll-like receptor 4 (TLR4) is an innate immune receptor that is dependent upon MyD88 for activity of its dominant signaling pathway. Here, we investigated the role of TLR4 in kidney allograft rejection using a fully major histocompatibility complex-mismatched, life-sustaining, murine model of renal allograft rejection.

METHODS

Donor (BALB/c) and recipient (C57BL/6) mice either both deficient or sufficient for TLR4 underwent heterotopic renal allograft transplantation, with an additional group of mice receiving renal isografts as controls. Survival was assessed up to 100 days posttransplantation. Animals were also sacrificed 14 days posttransplantation for assessment of the acute allograft rejection response.

RESULTS

Both wild-type (WT) and TLR4 allografts showed inferior survival compared to isografts, with no difference in survival between the allograft groups. Serum creatinine was lower in TLR4 allografts at day 14 posttransplantation compared with WT allografts, but this was not sustained by day 100. At day 14 posttransplant, increased CD11c dendritic cell accumulation, expression of IL-2 and indoleamine 2,3-dioxygenase were evident in TLR4 compared with WT allografts, whereas expression of inducible nitric oxide synthase was decreased.

CONCLUSIONS

Acute kidney allograft rejection was modestly attenuated in TLR4 mice; however, long-term allograft survival and function were not affected in our model. Protection against acute rejection may involve increased accumulation of CD11c cells and indoleamine 2,3-dioxygenase expression.

Fibroblast growth factor 23, iron and inflammation - are they related in early stages of chronic kidney disease?

INTRODUCTION

Fibroblast growth factor 23 (FGF-23) levels are elevated in impaired renal function. Inflammation and iron are potential regulators of FGF-23. The aim of the study was to evaluate the association between FGF-23 concentration, novel iron status biomarkers and inflammatory parameters among patients with early stages of chronic kidney disease (CKD).

MATERIAL AND METHODS

The study population included 84 patients with CKD in the early stage. Serum hemoglobin, fibrinogen, creatinine, iron, transferrin saturation and ferritin levels were measured using standard laboratory methods. Commercially available kits were used to measure: intact FGF-23, hepcidin, soluble transferrin receptor (sTfR), interleukin 6 (IL-6) and high-sensitivity C-reactive protein (hsCRP).

RESULTS

In patients with CKD no differences in FGF-23 concentration according to iron status were observed. Lower iron concentration was associated with higher concentrations of hsCRP, IL-6 and fibrinogen. In univariate and multivariate analysis FGF-23 correlated with fibrinogen (r = -0.23, p < 0.05) and eGFR (r = -0.36, p < 0.05).

CONCLUSIONS

FGF-23 is affected by kidney function and fibrinogen but not iron status parameters in the early stages of CKD. Our data are paving the way for further studies on the role of FGF-23 in iron metabolism, especially in early stages of CKD.

Urinary calprotectin, kidney injury molecule-1, and neutrophil gelatinase-associated lipocalin for the prediction of adverse outcome in pediatric acute kidney injury

Early identification of patients with acute kidney injury (AKI) being at high risk for adverse outcome can influence medical treatment. This study compares urinary calprotectin, kidney injury molecule-1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) for their performance in predicting mortality and need for renal replacement therapy (RRT) in pediatric AKI patients. Urinary biomarker concentrations were assessed prospectively in 141 subjects aged 0-18 years including 55 patients with established AKI according to pediatric Risk, Injury, Failure, Loss, and End-stage kidney disease (pRIFLE) criteria, 27 patients without AKI, and 59 healthy children. Within the AKI group, receiver operating characteristic (ROC) curve analysis revealed moderate to poor performance of calprotectin and KIM-1 in the prediction of 30-day mortality (calprotectin area under the curve (AUC) 0.55; KIM-1 AUC 0.55) and 3-month mortality (calprotectin AUC 0.61; KIM-1 AUC 0.60) and fair performance in the prediction of RRT requirement (calprotectin AUC 0.72; KIM-1 AUC 0.71). Urinary NGAL showed good performance in predicting 30-day (AUC 0.79) and 3-month (AUC 0.81) mortality and moderate performance in predicting RRT (AUC 0.61).

CONCLUSIONS

Whereas urinary calprotectin and KIM-1 can be useful for the prediction of RRT, urinary NGAL has a good diagnostic performance in predicting mortality in pediatric patients with AKI of heterogeneous etiology. What is known: • There is increasing evidence that urinary biomarkers like neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) are valuable for the prediction of adverse outcome in adult acute kidney injury (AKI), whereas data on pediatric AKI is scarce. What is new: • Urinary calprotectin and KIM-1 do not predict mortality in our heterogeneous pediatric AKI cohort, but they show moderate performance in the prediction of dialysis. • Urinary NGAL is a good predictor of mortality performing better than pRIFLE stage, eGFR, or creatinine, but it shows moderate performance in the prediction of dialysis.

Physiological aspects of Toll-like receptor 4 activation in sepsis-induced acute kidney injury

Sepsis‐induced acute kidney injury (SI‐AKI) is common and associated with high mortality. Survivors are at increased risk of chronic kidney disease. The precise mechanism underlying SI‐AKI is unknown, and no curative treatment exists. Toll‐like receptor 4 (TLR4) activates the innate immune system in response to exogenous microbial products. The result is an inflammatory reaction aimed at clearing a potential infection. However, the consequence may also be organ dysfunction as the immune response can cause collateral damage to host tissue. The purpose of this review is to describe the basis for how ligand binding to TLR4 has the potential to cause renal dysfunction and the mechanisms by which this may take place in gram‐negative sepsis. In addition, we highlight areas for future research that can further our knowledge of the pathogenesis of SI‐AKI in relation to TLR4 activation. TLR4 is expressed in the kidney. Activation of TLR4 causes cytokine and chemokine release as well as renal leucocyte infiltration. It also results in endothelial and tubular dysfunction in addition to altered renal metabolism and circulation. From a physiological standpoint, inhibiting TLR4 in large animal experimental SI‐AKI significantly improves renal function. Thus, current evidence indicates that TLR4 has the ability to mediate SI‐AKI by a number of mechanisms. The strong experimental evidence supporting a role of TLR4 in the pathogenesis of SI‐AKI in combination with the availability of pharmacological tools to target TLR4 warrants future human studies.

Endoplasmic reticulum stress inhibition attenuates hypertensive chronic kidney disease through reduction in proteinuria

Endoplasmic reticulum (ER) stress is implicated in chronic kidney disease (CKD) development in patients and in animal models. Here we show that ER stress inhibition through 4-phenylbutyric acid (4-PBA) administration decreases blood pressure, albuminuria, and tubular casts in an angiotensin II/deoxycorticosterone acetate/salt murine model of CKD. Lower albuminuria in 4-PBA-treated mice was associated with higher levels of cubilin protein in renal tissue membrane fractions. 4-PBA decreased renal interstitial fibrosis, renal CD3⁺ T-cell and macrophage infiltration, mRNA expression of TGFβ1, Wnt signaling molecules, and ER stress-induced pro-inflammatory genes. CHOP deficient mice that underwent this model of CKD developed hypertension comparable to wild type mice, but had less albuminuria and tubular casts. CHOP deficiency resulted in higher nephrin levels and decreased glomerulosclerosis compared to wild type mice; this effect was accompanied by lower macrophage infiltration and fibrosis. Our findings portray ER stress inhibition as a means to alleviate hypertensive CKD by preserving glomerular barrier integrity and tubular function. These results demonstrate ER stress modulation as a novel target for preserving renal function in hypertensive CKD.

Could "calprotectin" and "endocan" serve as "Troponin of Nephrologists"?

AKI, a serious, common and occasionally under-recognized condition, which is a significant contributor to the growing incidence of CKD and end-stage renal disease (ESRD). To date, the diagnosis of AKI is made by serial measurement of Cr and BUN which are late and imprecise markers of kidney injury. "Calprotectin" and "endocan" are two biomarkers that could reflect renal tubular injury and glomerular/endothelial-vascular damage, respectively. Measurement of urinary calprotectin could help the physicians to diagnose tubular degradation and differentiate prerenal AKI from intrinsic AKI. Serum level of endocan could signify endothelial damage. Herein it is hypothesized that calprotectin and endocan may help the clinicians to diagnose intrinsic AKI, earlier than rise of serum creatinine, differentiate AKI from acute presentation of CKD and also discriminate tubular injury from glomerular/vascular-endothelial injury, assess the prognosis and extent of renal damage and plan for appropriate therapy which may render these biomarkers as potentially applicable equivalents of Troponin in the field of nephrology.

Urinary biomarkers for the differentiation of prerenal and intrinsic pediatric acute kidney injury

BACKGROUND

Urinary calprotectin and neutrophil gelatinase-associated lipocalin (NGAL) have recently been identified as promising biomarkers for the differentiation of prerenal and intrinsic acute kidney injury (AKI) in adults. In the study reported here we examined the diagnostic accuracy of calprotectin, NGAL, and kidney injury molecule 1 (KIM-1) in pediatric patients.

METHODS

Urinary calprotectin, NGAL, and KIM-1 concentrations were assessed in a study population of 139 pediatric subjects including 39 patients with intrinsic AKI, 14 with prerenal AKI, and 86 non-AKI subjects.

RESULTS

Median urinary calprotectin and NGAL concentrations were higher in patients with intrinsic AKI than in those with prerenal AKI (calprotectin by 22-fold, NGAL by 9-fold). Receiver operating characteristic (ROC) curve analyses for the differentiation of intrinsic and prerenal AKI resulted in an area under the curve (AUC) of 0.90 [95 % confidence interval (CI) 0.81-0.98] for calprotectin and 0.73 (95 % CI 0.58-0.87) for NGAL. Median urinary KIM-1 concentrations were not significantly different between patients with prerenal AKI and those with intrinsic disease (P = 0.98; AUC 0.50, 95 % CI, 0.35-0.65). The AUC for the fractional excretion of sodium (FE_Na) and proteinuria was 0.78 (95 % CI 0.63-0.92) and 0.77 (CI 0.65-0.90), respectively.

CONCLUSIONS

Urinary calprotectin outperforms NGAL, KIM-1, FE_Na, and proteinuria as a biomarker for the differentiation of prerenal and intrinsic AKI in pediatric patients with a high diagnostic accuracy.

The role of toll-like receptors (TLRs) in urinary tract infections (UTIs)

Introduction

Urinary Tract Infections (UTIs) are caused by different types of microbial agents such as uropathogenic Escherichia coli (UPEC) and Candida albicans. The presence of strong physical barriers may prevent the breach of pathogens into the urinary tract. However, sometimes the pathogenic microorganisms may pass through the barriers and stimulate the innate and adaptive responses. Among a variety of innate immune responses, Toll-Like Receptors (TLRs) are one of the most unique and interesting molecules regarding UTIs. Thus, the authors have focused their attention on the role of TLRs in urinary tract defense against pathogenic microbial agents such as UPEC and C.albicans through this literature review.

Material and methods

Several papers regarding UTIs and TLRs including original and review articles were searched by PubMed and Google Scholar. They were studied and the most important aspects in association with the role of TLRs in UTIs were extracted. Additionally, this paper was prepared using the experience of the authors.

Results

The TLRs 2, 4 and 5 are the most functional molecules that contribute to urinary tract defense system and UTIs. It is incredible that TLRs are able to detect and recognize different parts of microbial components relating to the same pathogen. Besides, the flexibility of the TLR molecules may lead to identification of different types of microorganisms with different signaling pathways.

Conclusions

Our knowledge associated with TLRs and their activities against microbial causative agents of UTIs may help us to prevent, control and treat UTIs at a higher quality level.

Selenium Plays a Protective Role in Staphylococcus aureus-Induced Endometritis in the Uterine Tissue of Rats

The essential trace element selenium (Se) modulates the functions of many regulatory proteins in signal transduction, conferring benefits in inflammatory diseases. Endometritis is a reproductive obstacle disease both in humans and animals. Staphylococcus aureus is the major pathogen that causes endometritis. The present study analyzes the protection and mechanism of Se-methylselenocysteine (MSC) and methylseleninic acid (MSA) on S. aureus-induced endometritis. An atomic fluorescence spectrophotometry study showed that the uterine Se content increased with the addition of MSC and MSA. Histopathology observation and TUNEL detection showed that Se supplementation displayed a greater defense against uterine inflammatory damage. The quantitative PCR (qPCR) and ELISA analyses showed that the expressions of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) increased with S. aureus infection and decreased with the addition of MSC and MSA. The Toll-like receptor 2 (TLR2) expression showed the same status as the inflammatory cytokines. The Western blot results showed that the increased phosphorylation of IκBα and NF-κB p65 was also reduced by the addition of MSC and MSA. The qPCR and Western blot results also showed that the transcription expressions and the protein dissociation of caspase-9, caspase-3, caspase-7, caspase-6, and poly(ADP-ribose) polymerase (PARP), which were increased by S. aureus infection, were inhibited by Se supplementation. All of the results displayed that the protection conferred by MSC was stronger than MSA. The present study indicated the Se supplementation might be a potential prevention and control measure for S. aureus-induced endometritis.

HMGB1 facilitates hypoxia-induced vWF upregulation through TLR2-MYD88-SP1 pathway

Increased plasma level of von Willebrand Factor (vWF) is associated with major cardiovascular diseases. We previously reported that multimeric vWF binds to NO synthase and inhibits insulin-induced production of NO, thus promoting insulin resistance during acute hypoxia (AH). However, the transcriptional regulation of vWF during AH is not clearly understood. Here, we investigated the mechanisms underlying the upregulation of vwf in mice. AH significantly upregulates the tlr2, tlr3, myd88, and vwf expression and phosphorylation of specificity protein 1 (SP1). Furthermore, AH significantly upregulates high mobility group box-1 (HMGB1) in a time-dependent manner. Moreover, a TLR2 agonist upregulates vWF but a TLR3 agonist does not. Pretreatment with an HMGB1 inhibitor, TLR2-immunoneutralizing antibody, or SP1 inhibitor significantly inhibits vWF expression. Furthermore, Tlr2 silencing completely inhibited MYD88, vWF expression, and SP1 phosphorylation. However, pretreatment with glycyrrhizic acid or silencing of Tlr2 completely blocks binding of Sp1 to the Vwf promoter, thus inhibiting its expression, and enhances insulin resistance during AH. Patients with type 2 diabetes mellitus also showed significantly elevated levels of HMGB1, TLR2, SP1, and vWF, thereby supporting the results of the murine model of AH. Taken together, HMGB1 upregulates vWF in vivo through the TLR2-MYD88-SP1 pathway in mice.

TLR4-mediated inflammation is a key pathogenic event leading to kidney damage and fibrosis in cyclosporine nephrotoxicity

Cyclosporine A (CsA) successfully prevents allograft rejection, but nephrotoxicity is still a dose-limiting adverse effect. TLR4 activation promotes kidney damage but whether this innate immunity receptor mediates CsA nephrotoxicity is unknown. The in vivo role of TLR4 during CsA nephrotoxicity was studied in mice co-treated with CsA and the TLR4 inhibitor TAK242 and also in TLR4^-/- mice. CsA-induced renal TLR4 expression in wild-type mice. Pharmacological or genetic targeting of TLR4 reduced the activation of proinflammatory signaling, including JNK/c-jun, JAK2/STAT3, IRE1α and NF-κB and the expression of Fn14. Expression of proinflammatory factors and cytokines was also decreased, and kidney monocyte and lymphocyte influx was prevented. TLR4 inhibition also reduced tubular damage and drastically prevented the development of kidney fibrosis. In vivo and in vitro CsA promoted secretion of the TLR ligand HMGB1 by tubular cells upstream of TLR4 activation, and prevention of HMGB1 secretion significantly reduced CsA-induced synthesis of MCP-1, suggesting that HMGB1 may be one of the mediators of CsA-induced TLR4 activation. These results suggest that TLR4 is a potential pharmacological target in CsA nephrotoxicity.

Taking a Toll on Self-Renewal: TLR-Mediated Innate Immune Signaling in Stem Cells

Innate immunity has evolved as the front-line cellular defense mechanism to acutely sense and decisively respond to microenvironmental alterations. The Toll-like receptor (TLR) family activates signaling pathways in response to stimuli and is well-characterized in both resident and infiltrating immune cells during neural inflammation, injury, and degeneration. Innate immune signaling has also been observed in neural cells during development and disease, including in the stem and progenitor cells that build the brain and are responsible for its homeostasis. Recently, the activation of developmental programs in malignant brain tumors has emerged as a driver for growth via cancer stem cells. In this review we discuss how innate immune signaling interfaces with stem cell maintenance in the normal and neoplastic brain.

The Nucleotide Oligomerization Domain-Like Receptors in Kidney Injury

BACKGROUND

Inflammation is a hallmark of almost all forms of renal injury and the activation of the innate immune system is of importance in the development of many kidney diseases. Pattern recognition receptors (PRRs) act as sensors of the innate immune system to detect pathogen- or damage-associated molecular patterns, which initiate immune responses to resolve infections and repair damaged tissues. Abnormalities in PRR activation will lead to excessive inflammation.

SUMMARY

Nucleotide oligomerization domain (NOD)-like receptors (NLRs) are recently identified intracellular PRRs that are essential to innate immune responses and tissue homeostasis. A better understanding of the function of NLRs will provide unexpected opportunities to develop new therapies for kidney diseases by modulation of the innate immune system.

KEY MESSAGES

NLRs are constitutively expressed in the kidney and emerging evidence has shown that activation of NLRs plays an important role in the pathogenesis of renal injury. Among NLRs, NOD2 and NLRP3 inflammasome are the best characterized members in the kidney. In this review, we summarize current knowledge about the pathological mechanisms that are related to NOD2 and NLRP3 inflammasome in various kidney diseases by their canonical and non-canonical effects and discuss the opportunities of pharmacological targeting of NLR-mediated signaling pathways at multiple levels for the treatment of renal disease.

The Complex Relationship of Extracorporeal Membrane Oxygenation and Acute Kidney Injury: Causation or Association?

Extracorporeal membrane oxygenation (ECMO) is a modified cardiopulmonary bypass (CPB) circuit capable of providing prolonged cardiorespiratory support. Recent advancement in ECMO technology has resulted in increased utilisation and clinical application. It can be used as a bridge-to-recovery, bridge-to-bridge, bridge-to-transplant, or bridge-to-decision. ECMO can restitute physiology in critically ill patients, which may minimise the risk of progressive multiorgan dysfunction. Alternatively, iatrogenic complications of ECMO clearly contribute to worse outcomes. These factors affect the risk : benefit ratio of ECMO which ultimately influence commencement/timing of ECMO. The complex interplay of pre-ECMO, ECMO, and post-ECMO pathophysiological processes are responsible for the substantial increased incidence of ECMO-associated acute kidney injury (EAKI). The development of EAKI significantly contributes to morbidity and mortality; however, there is a lack of evidence defining a potential benefit or causative link between ECMO and AKI. This area warrants investigation as further research will delineate the mechanisms involved and subsequent strategies to minimise the risk of EAKI. This review summarizes the current literature of ECMO and AKI, considers the possible benefits and risks of ECMO on renal function, outlines the related pathophysiology, highlights relevant investigative tools, and ultimately suggests an approach for future research into this under investigated area of critical care.

SIGIRR participates in negative regulation of LPS response and tolerance in human bladder epithelial cells

Background

The innate immune response of urinary tract is critically important in the defense to microbial attack. Toll-like receptor 4 (TLR4) controls initial mucosal response to uropathogenic Escherichia coli (UPEC). However, excessive and dysfunctional TLR signaling may result in severe inflammation and inappropriate tissue damage. Previous studies have demonstrated that single immunoglobulin IL-1R-related receptor/Toll IL-1 receptor 8 (SIGIRR/TIR8) is a member of the toll-interleukin-1 receptor (TIR) family that can negatively modulate TLR4 mediated signaling, but its role in the innate immunity of urinary tract infection remains incompletely defined. In this study, we investigated its cellular distribution and mechanisms involved within the human bladder epithelial cells after LPS stimulation.

Results

Immunostaining, reverse transcription PCR and Western blot results showed that SIGIRR was constitutively expressed in the human bladder epithelial cell lines and was downregulated after LPS stimulation. To further define the role of SIGIRR, cells were transiently transfected with SIGIRR siRNA and stimulated with LPS. SIGIRR gene silencing augmented chemokine expression in response to LPS, as indicated by increased levels of IL-6 and IL-8 secretions in the supernatants compared with negative control siRNA. Furthermore, LPS tolerance, a protective mechanism against second LPS stimulation, was significantly reduced in SIGIRR siRNA transfected cells. Moreover, transient gene silencing augmented LPS-induced NF-κB and MAPK activation.

Conclusions

In conclusion, our results suggest that SIGIRR plays an important role in the negative regulation of LPS response and tolerance in human bladder epithelial cells, possibly through its impact on TLR-mediated signaling.

DC-SIGN expression on podocytes and its role in inflammatory immune response of lupus nephritis

Podocytes, the main target of immune complex, participate actively in the development of glomerular injury as immune cells. Dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) is an innate immune molecular that has an immune recognition function, and is involved in mediation of cell adhesion and immunoregulation. Here we explored the expression of DC-SIGN on podocytes and its role in immune and inflammatory responses in lupus nephritis (LN). Expression of DC-SIGN and immunoglobulin (Ig)G1 was observed in glomeruli of LN patients. DC-SIGN was co-expressed with nephrin on podocytes. Accompanied by increased proteinuria of LN mice, DC-SIGN and IgG1 expressions were observed in the glomeruli from 20 weeks, and the renal function deteriorated up to 24 weeks. Mice with anti-DC-SIGN antibody showed reduced proteinuria and remission of renal function. After the podocytes were stimulated by serum of LN mice in vitro, the expression of DC-SIGN, major histocompatibility complex (MHC) class II and CD80 was up-regulated, stimulation of T cell proliferation was enhanced and the interferon (IFN)-γ/interleukin (IL)-4 ratio increased. However, anti-DC-SIGN antibody treatment reversed these events. These results suggested that podocytes in LN can exert DC-like function through their expression of DC-SIGN, which may be involved in immune and inflammatory responses of renal tissues. However, blockage of DC-SIGN can inhibit immune functions of podocytes, which may have preventive and therapeutic effects.

Dexmedetomidine Inhibits TLR4/NF-κB Activation and Reduces Acute Kidney Injury after Orthotopic Autologous Liver Transplantation in Rats

Patients who undergo orthotopic liver transplantation often sustain acute kidney injury(AKI). The toll-like receptor 4(TLR4)/Nuclear factor-кB(NF-кB) pathway plays a role in AKI. Dexmedetomidine(Dex) has been shown to attenuate AKI. The current study aimed to determine whether liver transplantation-induced AKI is associated with inflammatory response, and to assess the effects of dexmedetomidine pretreatment on kidneys in rats following orthotopic autologous liver transplantation(OALT). Seventy-seven adult male rats were randomized into 11 groups. Kidney tissue histopathology and levels of blood urea nitrogen(BUN) and serum creatinine(SCr) were evaluated. Levels of TLR4, NF-κB, tumor necrosis factor-α, and interleukin-1β levels were measured in kidney tissues. OALT resulted in significant kidney functional impairment and tissue injury. Pre-treatment with dexmedetomidine decreased BUN and SCr levels and reduced kidney pathological injury, TLR4 expression, translocation of NF-κB, and cytokine production. The effects of dexmedetomidine were reversed by pre-treatment with atipamezole and BRL44408, but not ARC239. These results were confirmed by using α_2A-adrenergic receptor siRNA which reversed the protective effect of dexmedetomidine on attenuating NRK-52E cells injury induced by hypoxia reoxygenation. In conclusion, Dexmedetomidine-pretreatment attenuates OALT-induced AKI in rats which may be contributable to its inhibition of TLR4/MyD88/NF-κB pathway activation. The renoprotective effects are related to α_2A-adrenergic receptor subtypes.

Toll-Like Receptor Family Polymorphisms Are Associated with Primary Renal Diseases but Not with Renal Outcomes Following Kidney Transplantation

Toll-like receptors (TLRs) play a crucial role in innate- and adaptive immunity. The TLR pathways were shown to play key functional roles in experimental acute and chronic kidney injury, including the allo-immune response after experimental renal transplantation. Data about the precise impact of TLRs and their negative regulators on human renal transplant outcomes however are limited and contradictory. We studied twelve non-synonymous single nucleotide polymorphisms (SNPs) of which eleven in TLR1-8 and one in SIGIRR in a final cohort comprising 1116 matching donors and recipients. TLR3 p.Leu412Phe and SIGIRR p.Gln312Arg significantly deviated from Hardy-Weinberg equilibrium and were excluded. The frequency distribution of the minor alleles of the remaining 10 TLR variants were compared between patients with end-stage renal disease (recipients) and controls (kidney donors) in a case-control study. Secondly, the associations between the minor allele frequency of the TLR variants and delayed graft function, biopsy-proven acute rejection and death-censored graft failure after transplantation were investigated with Cox regression. Carrier frequencies of the minor alleles of TLR1 p.His305Leu (OR = 4.79, 95% CI = 2.35–9.75, P = 0.0002), TLR1 p.Asn248Ser (OR = 1.26, 95% CI = 1.07–1.47, P = 0.04) and TLR8 p.Met1Val (OR = 1.37, 95% CI = 1.14–1.64, P = 0.008) were significantly higher in patients with ESRD, with little specificity for the underlying renal disease entity (adjusted for age, gender and donor-recipient relatedness). The minor allele frequency of none of the TLR variants significantly associated with the surrogate and definite outcomes, even when multivariable models were created that could account for TLR gene redundancy. In conclusion, genetic variants in TLR genes were associated with the prevalence of ESRD but not renal transplant outcomes. Therefore, our data suggests that specific TLR signaling routes might play a role in the final common pathway of primary renal injury. A role for TLR signaling in the context of renal transplantation is probably limited.

Dioscin attenuates renal ischemia/reperfusion injury by inhibiting the TLR4/MyD88 signaling pathway via up-regulation of HSP70

We previously reported the effect of dioscin against hepatic ischemia/reperfusion injury (IRI) in rats. However, little is known concerning the role of dioscin in renal IRI. In the present study, rats were subjected to IRI and dioscin was intragastrically administered for seven consecutive days before surgery. In vitro models of hypoxia/reoxygenation were developed in NRK-52E and HK-2 cells, which were prophylactically treated with or without dioscin. The results showed that dioscin significantly decreased serum BUN and Cr levels, and markedly attenuated cell injury. Mechanistic studies showed that dioscin significantly increased HSP70 levels, decreased the levels of TLR4, MyD88, TRAF6, COX-2, JNK, ERK and p38 MAPK phosphorylation, suppressed the nuclear translocation of NF-κB and HMGB1, and subsequently decreased the mRNA levels of IL-1β, IL-6, TNF-α, ICAM-1 and IFN-γ. Moreover, HSP70 siRNA or TLR4 DNA reversed the nephroprotective effects of dioscin, while dioscin still significantly down-regulated the TLR4 signaling pathway. Furthermore, by inhibiting MyD88 with ST2825 (a MyD88 inhibitor), renal IRI was significantly attenuated, suggesting that the effect of dioscin against renal IRI depended on MyD88. Our results suggested that dioscin had a potent effect against renal IRI through suppressing the TLR4/MyD88 signaling pathway by up-regulating HSP70. These data provide new insights for investigating the natural product with the nephroprotective effect against IRI, which should be developed as a new therapeutic agent for the treatment of acute kidney injury in the future.

Toll-like receptor 4 gene polymorphisms and susceptibility to colorectal cancer: a meta-analysis and review

INTRODUCTION

Many case-control studies have investigated the association between toll-like receptor 4 (TLR4) Asp299Gly and Thr399Ile polymorphisms and risk of colorectal cancer (CRC). However, published data are still conflicting.

MATERIAL AND METHODS

A systematic search was conducted in the electronic databases of PubMed, MEDLINE, EMBASE, Web of Science and CNKI between 2000 and 2014. The associations between TLR4 polymorphisms and CRC susceptibility were assessed by pooled odds ratios (ORs) and 95% confidence intervals (95% CI) in fixed or random effects models.

RESULTS

In total nine case-control studies were identified in this meta-analysis. For TLR4 Asp299Gly polymorphism, 9 studies included 1198 cases and 1290 controls. The GG genotype carriers had higher risk for developing CRC than AA + GA genotype carriers (OR = 1.95, 95% CI: 1.00-3.77, p = 0.05). No association was found in other genetic models (p > 0.05). Analysis stratified by ethnicity showed no association in any genetic models among the Asian or Caucasian population. For TLR4 Thr399Ile polymorphism, 6 studies contained 619 cases and 632 controls. The overall analysis showed significantly increased risk in TT homozygote carriers compared to CC homozygote (OR = 4.99, 95% CI: 1.41-17.65, p = 0.01) and C carriers (TC + CC) (OR = 4.50, 95% CI: 1.27-15.87, p = 0.02). In terms of analyses stratified by race, a significant association was found in each genetic model among the Asian population, rather than the Caucasian group.

CONCLUSIONS

The GG homozygote carriers of TLR4 Asp299Gly and TT homozygote carriers of TLR4 Thr399Ile polymorphisms might be correlated with an increased risk of CRC, suggesting they may serve as genetic risk factors for CRC.

High-mobility group box 1 inhibits HCO(3)(-) absorption in medullary thick ascending limb through a basolateral receptor for advanced glycation end products pathway

High-mobility group box 1 (HMGB1) is a damage-associated molecule implicated in mediating kidney dysfunction in sepsis and sterile inflammatory disorders. HMGB1 is a nuclear protein released extracellularly in response to infection or injury, where it interacts with Toll-like receptor 4 (TLR4) and other receptors to mediate inflammation. Previously, we demonstrated that LPS inhibits HCO(3)(-) absorption in the medullary thick ascending limb (MTAL) through a basolateral TLR4-ERK pathway (Watts BA III, George T, Sherwood ER, Good DW. Am J Physiol Cell Physiol 301: C1296-C1306, 2011). Here, we examined whether HMGB1 could inhibit HCO(3)(-) absorption through the same pathway. Adding HMGB1 to the bath decreased HCO(3)(-) absorption by 24% in isolated, perfused rat and mouse MTALs. In contrast to LPS, inhibition by HMGB1 was preserved in MTALs from TLR4(-/-) mice and was unaffected by ERK inhibitors. Inhibition by HMGB1 was eliminated by the receptor for advanced glycation end products (RAGE) antagonist FPS-ZM1 and by neutralizing anti-RAGE antibody. Confocal immunofluorescence showed expression of RAGE in the basolateral membrane domain. Inhibition of HCO(3)(-) absorption by HMGB1 through RAGE was additive to inhibition by LPS through TLR4 and to inhibition by Gram-positive bacterial molecules through TLR2. Bath amiloride, which selectively prevents inhibition of MTAL HCO(3)(-) absorption mediated through Na⁺/H⁺ exchanger 1 (NHE1), eliminated inhibition by HMGB1. We conclude that HMGB1 inhibits MTAL HCO(3)(-) absorption through a RAGE-dependent pathway distinct from TLR4-mediated inhibition by LPS. These studies provide new evidence that HMGB1-RAGE signaling acts directly to impair the transport function of renal tubules. They reveal a novel paradigm for sepsis-induced renal tubule dysfunction, whereby exogenous pathogen-associated molecules and endogenous damage-associated molecules act directly and independently to inhibit MTAL HCO(3)(-) absorption through different receptor signaling pathways.

Reduction of Tubular Flow Rate as a Mechanism of Oliguria in the Early Phase of Endotoxemia Revealed by Intravital Imaging

Urine output is widely used as a criterion for the diagnosis of AKI. Although several potential mechanisms of septic AKI have been identified, regulation of urine flow after glomerular filtration has not been evaluated. This study evaluated changes in urine flow in mice with septic AKI. The intratubular urine flow rate was monitored in real time by intravital imaging using two-photon laser microscopy. The tubular flow rate, as measured by freely filtered dye (FITC-inulin or Lucifer yellow), time-dependently declined after LPS injection. At 2 hours, the tubular flow rate was slower in mice injected with LPS than in mice injected with saline, whereas BP and GFR were similar in the two groups. Importantly, fluorophore-conjugated LPS selectively accumulated in the proximal tubules that showed reduced tubular flow at 2 hours and luminal obstruction with cell swelling at 24 hours. Delipidation of LPS or deletion of Toll-like receptor 4 in mice abolished these effects, whereas neutralization of TNF-α had little effect on LPS-induced tubular flow retention. Rapid intravenous fluid resuscitation within 6 hours improved the tubular flow rate only when accompanied by the dilation of obstructed proximal tubules with accumulated LPS. These findings suggest that LPS reduces the intratubular urine flow rate during early phases of endotoxemia through a Toll-like receptor 4-dependent mechanism, and that the efficacy of fluid resuscitation may depend on the response of tubules with LPS accumulation.

Statin intolerance - an attempt at a unified definition. Position paper from an International Lipid Expert Panel

Statins are one of the most commonly prescribed drugs in clinical practice. They are usually well tolerated and effectively prevent cardiovascular events. Most adverse effects associated with statin therapy are muscle-related. The recent statement of the European Atherosclerosis Society (EAS) has focused on statin associated muscle symptoms (SAMS), and avoided the use of the term 'statin intolerance'. Although muscle syndromes are the most common adverse effects observed after statin therapy, excluding other side effects might underestimate the number of patients with statin intolerance, which might be observed in 10-15% of patients. In clinical practice, statin intolerance limits effective treatment of patients at risk of, or with, cardiovascular disease. Knowledge of the most common adverse effects of statin therapy that might cause statin intolerance and the clear definition of this phenomenon is crucial to effectively treat patients with lipid disorders. Therefore, the aim of this position paper was to suggest a unified definition of statin intolerance, and to complement the recent EAS statement on SAMS, where the pathophysiology, diagnosis and the management were comprehensively presented.

Overexpression of toll-like receptor 2 in glomerular endothelial cells and podocytes in septic acute kidney injury mouse model

Acute kidney injury (AKI) is one of the most common complications in patients with severe sepsis. The development of septic AKI increases patients' mobility and even mortality. Toll-like receptor 2 (TLR2), as a membrane surface receptor for bacterial, fungal, viral and certain endogenous substances, has been described to contribute to the development of septic AKI; however, the renal cell types associating TLR2 overactivation in septic AKI has not been described. In the current study, we investigated the TLR2 activation patterns in the kidney of lipopolysaccharide-induced septic AKI mice. Our results demonstrated that mRNA level of TLR2 significantly increased in the kidney of lipopolysaccharide-treated mice. Immunohistochemistry revealed the overactivation of TLR2 in the glomeruli. Double immunofluorescence analysis shows the precise distribution of TLR2 by showing the colocalization of TLR2 in glomeruli with synaptopodin, a podocyte marker, and Tie2, an endothelial marker. In addition, proapoptotic molecules Bax and Caspase-3 were increased in the glomeruli of lipopolysaccharide-treated mice. Together, the current study indicates that TLR2 is overactivated in the glomerular endothelial cells and podocytes in septic AKI mice, while the abundance of Bax and Caspase-3 were increased in the glomeruli of these mice, it may supply a clue that TLR2 induced these cell apoptosis in AKI. This finding provides an alternative mechanism to understand AKI development and potential targets for treatment.

Collecting duct intercalated cell function and regulation

Intercalated cells are kidney tubule epithelial cells with important roles in the regulation of acid-base homeostasis. However, in recent years the understanding of the function of the intercalated cell has become greatly enhanced and has shaped a new model for how the distal segments of the kidney tubule integrate salt and water reabsorption, potassium homeostasis, and acid-base status. These cells appear in the late distal convoluted tubule or in the connecting segment, depending on the species. They are most abundant in the collecting duct, where they can be detected all the way from the cortex to the initial part of the inner medulla. Intercalated cells are interspersed among the more numerous segment-specific principal cells. There are three types of intercalated cells, each having distinct structures and expressing different ensembles of transport proteins that translate into very different functions in the processing of the urine. This review includes recent findings on how intercalated cells regulate their intracellular milieu and contribute to acid-base regulation and sodium, chloride, and potassium homeostasis, thus highlighting their potential role as targets for the treatment of hypertension. Their novel regulation by paracrine signals in the collecting duct is also discussed. Finally, this article addresses their role as part of the innate immune system of the kidney tubule.

Differential membrane expression of Toll-like receptors and intracellular cytokine induction in peripheral blood monocytes of patients with chronic kidney disease and diabetic nephropathy

BACKGROUND

Toll-like receptors (TLRs) are key players in the innate immune system whose activation leads to an inflammatory response. Inflammation plays an important role in the pathogenesis of chronic kidney disease (CKD) and diabetes mellitus. The aim of our study was to assess the proinflammatory state of nondialysis CKD patients by evaluating the membrane expression of TLR2 and TLR4 and the intracellular IL-1β and IL-6 production in response to the ligand Pam3Cys-Ser-(Lys)4 (Pam3CSK4).

METHODS

85 nondialysis CKD patients [mean estimated glomerular filtration rate: 34 (17-90) ml/min/1.73 m(2)] were divided in 2 groups: 55 nondiabetic CKD patients (CKD group) and 30 patients with diabetic nephropathy (DN group). The two groups were compared with 36 healthy subjects (control group). TLR2 and TLR4 membrane expression in monocytes and Pam3CSK4-induced intracellular production of IL-1β and IL-6 were assessed by flow cytometry.

RESULTS

Both patient groups showed increased TLR2 membrane expression compared with the control group, both at baseline (p < 0.05 for both) and after Pam3CSK4 stimulation (p < 0.05 for both). The DN group exhibited significantly higher TLR4 expression at baseline compared to the CKD and control groups (p < 0.04 and p < 0.02, respectively). Intracellular IL-1β and IL-6 levels at baseline were significantly lower in CKD patients compared to the DN and control groups. After Pam3CSK4 stimulation, intracellular IL-1β and IL-6 increased in all groups, but were lower in the CKD group versus the control group or DN group, which exhibited higher levels than the controls.

CONCLUSIONS

Nondialysis CKD patients showed significant alterations in TLR2 and TLR4 membrane expression, and impaired Pam3CSK4-induced cytokine production in monocytes, a phenomenon that is markedly influenced by the presence of diabetes.

How the Innate Immune System Senses Trouble and Causes Trouble

The innate immune system is the first line of defense in response to nonself and danger signals from microbial invasion or tissue injury. It is increasingly recognized that each organ uses unique sets of cells and molecules that orchestrate regional innate immunity. The cells that execute the task of innate immunity are many and consist of not only "professional" immune cells but also nonimmune cells, such as renal epithelial cells. Despite a high level of sophistication, deregulated innate immunity is common and contributes to a wide range of renal diseases, such as sepsis-induced kidney injury, GN, and allograft dysfunction. This review discusses how the innate immune system recognizes and responds to nonself and danger signals. In particular, the roles of renal epithelial cells that make them an integral part of the innate immune apparatus of the kidney are highlighted.

Toll-like receptor activation: from renal inflammation to fibrosis

Toll-like receptors (TLRs) are a conserved family of pattern recognition receptors that play a fundamental role in the innate immune system by triggering proinflammatory signaling pathways in response to microbial pathogens through exogenous pathogen-associated molecular patterns or tissue injury through endogenous danger-associated molecular patterns. In the kidney, TLRs are widely expressed in a variety of cell types. Emerging evidence demonstrates the participation of TLRs in the activation of these cells during renal fibrosis. This review highlights the role of TLRs and their endogenous ligands in the pathogenesis of renal fibrosis using ureteral obstruction and diabetic nephropathy as models of chronic kidney disease.