Human Renal Disease Research Articles

Natural killers: the bad guys in fibrosis?

Immune cells infiltrating the tubulointerstitium critically contribute to the progression of chronic kidney disease. In this issue of Kidney international, Law etal. provide first evidence for a role of natural killer cells in the perpetuation of tubulointerstitial fibrosis in human renal disease. By detailed flow cytometric characterization of leukocytes isolated from kidney biopsies of chronic kidney disease patients, they define accumulation of natural killer cells as a feature of fibrotic kidney tissue and provide insight into potential mechanisms of how these cells might promote chronic kidney inflammation.

The G-protein-coupled bile acid receptor Gpbar1 (TGR5) protects against renal inflammation and renal cancer cell proliferation and migration through antagonizing NF-κB and STAT3 signaling pathways.

Gpbar1 (TGR5), a G-protein-coupled bile acid membrane receptor, is well known for its roles in regulation of glucose metabolism and energy homeostasis. In the current work, we found that TGR5 activation by its ligand suppressed lipopolysaccharide (LPS)-induced proinflammatory gene expression in wild-type (WT) but not TGR5−/− mouse kidney. Furthermore, we found that TGR5 is a suppressor of kidney cancer cell proliferation and migration. We show that TGR5 activation antagonized NF-κB and STAT3 signaling pathways through suppressing the phosphorylation of IκBα, the translocation of p65 and the phosphorylation of STAT3. TGR5 overexpression with ligand treatment inhibited gene expression mediated by NF-κB and STAT3. These results suggest that TGR5 antagonizes kidney inflammation and kidney cancer cell proliferation and migration at least in part by inhibiting NF-κB and STAT3 signaling. These findings identify TGR5 may serve as an attractive therapeutic tool for human renal inflammation related diseases and cancer.

Proximal Tubular Expression Patterns of Megalin and Cubilin in Proteinuric Nephropathies

IntroductionReceptor-mediated endocytosis is responsible for protein reabsorption in the proximal tubules. For albumin this process involves at least 2 interacting receptors, megalin and cubilin. Albumin is not usually present in the urine, indicating a highly efficient tubular reuptake under physiological conditions. However, early appearance of albuminuria may mean that the tubular system is overwhelmed by large quantities of albumin or that the function is impaired.MethodsTo better understand the physiological role of megalin and cubilin in human renal disease, renal biopsies from 15 patients with a range of albuminuria and 3 healthy living donors were analyzed for proximal tubular expression of megalin and cubilin using immunohistochemistry (IHC) and semiquantitative immune-electron microscopy. Their expression in proteinuric zebrafish was also studied.ResultsMegalin and cubilin were expressed in brush border and cytoplasmic vesicles. Patients with microalbuminuric IgA nephropathy and thin membrane disease had significantly higher megalin in proximal tubules, whereas those with macro- or nephrotic-range albuminuria had unchanged levels. Cubilin expression was significantly higher in all patients. In a proteinuric zebrafish nphs2 knockdown model, we found a dose-dependent increase in the expression of tubular megalin and cubilin in response to tubular protein uptake.DiscussionMegalin and cubilin show different expression patterns in different human diseases, which indicates that the 2 tubular proteins differently cooperate in cleaning up plasma proteins in kidney tubules.

Sepsis in frail patient

Frailty is defined as a clinical syndrome in which three or more of the following criteria are present: unintentional weight loss, self-reported exhaustion, weakness (grip strength), slow walking speed and low physical activity. Sepsis is defined as an inflammatory response to infection, with severe sepsis and septic shock being the most severe forms. The incidence of severe sepsis increases with older age and several studies have shown that there are many risk factors that predispose the elderly to a higher incidence of sepsis. Pre-existing co-morbidities such as cancer, diabetes, obesity, human immunodeficiency virus, and renal or pulmonary disease can cause sepsis, but other factors including poor lifestyle habits (i.e., smoking, drug or alcohol abuse), malnutrition, and endocrine deficiencies, which are frequent in the elderly, may also predispose to severe infections. Other risk factors for sepsis include recurrent hospitalization, especially in the Intensive Care Unit, and nursing home residence, where interventions such as urinary catheterization or multiple drug use are quite frequent and many studies reported that people above 65 years of age are three times more likely to be admitted to hospital than those aged 16-64 years, and have a higher risk of prolonged hospital stays, institutionalization and death. Clinical evaluation of the frail patient with sepsis poses some challenges. The immune response becomes progressively less efficient with increasing age thereby causing an altered response to infection and it is important to know that the clinical evaluation of the so-called fragile patient with severe infection should take into account the sometimes unusual signs and symptoms that, if identified, can lead to early diagnosis. Laboratory diagnostics can also be of great help in this setting. The treatment of sepsis in the fragile patient can be empirical or based on microbiological culture. Moreover, frail patient population presents many clinical problems with numerous comorbidities, therefore anti-infective treatment is difficult, so the physician’s armamentarium must include many antibiotic drugs, of which there are far more available for the treatment of sepsis caused by Gram-positive bacteria than for sepsis caused by Gram-negative ones or fungi.

APOL1-G1 in Nephrocytes Induces Hypertrophy and Accelerates Cell Death.

People of African ancestry carrying certain APOL1 mutant alleles are at elevated risk of developing renal diseases. However, the mechanisms underlying APOL1-associated renal diseases are unknown. Because the APOL1 gene is unique to humans and some primates, new animal models are needed to understand the function of APOL1 in vivo We generated transgenic Drosophila fly lines expressing the human APOL1 wild type allele (G0) or the predominant APOL1 risk allele (G1) in different tissues. Ubiquitous expression of APOL1 G0 or G1 in Drosophila induced lethal phenotypes, and G1 was more toxic than was G0. Selective expression of the APOL1 G0 or G1 transgene in nephrocytes, fly cells homologous to mammalian podocytes, induced increased endocytic activity and accumulation of hemolymph proteins, dextran particles, and silver nitrate. As transgenic flies with either allele aged, nephrocyte function declined, cell size increased, and nephrocytes died prematurely. Compared with G0-expressing cells, however, G1-expressing cells showed more dramatic phenotypes, resembling those observed in cultured mammalian podocytes overexpressing APOL1-G1. Expressing the G0 or G1 APOL1 transgene in nephrocytes also impaired the acidification of organelles. We conclude that expression of an APOL1 transgene initially enhances nephrocyte function, causing hypertrophy and subsequent cell death. This new Drosophila model uncovers a novel mechanism by which upregulated expression of APOL1-G1 could precipitate renal disease in humans. Furthermore, this model may facilitate the identification of APOL1-interacting molecules that could serve as new drug targets to treat APOL1-associated renal diseases.

Donor and recipient genetic variants in NLRP3 associate with early acute rejection following kidney transplantation.

NLRP3 (NOD-like receptor family, pyrin domain containing 3) is a member of the inflammasome family and is of special interest in renal disease. Experimental studies have shown that Nlrp3 plays a significant role in the induction of renal damage and dysfunction in acute and chronic renal injury. However, the role of NLRP3 in human renal disease is completely unknown. From a retrospective cohort study, we determined in 1271 matching donor and recipient samples if several NLRP3 single nucelotide polymorphisms (SNPs) were associated with primary non-function (PNF), delayed graft function (DGF), biopsy-proven acute rejection (BPAR) and death-censored graft and patient survival. NLRP3 gain-of-function SNP (rs35829419) in donors was associated with an increased risk of BPAR while NLRP3 loss-of-function SNP (rs6672995) in the recipient was associated with a decreased risk of BPAR in the first year following renal transplantation (HR 1.91, 95% CI 1.38–2.64, P < 0.001 and HR 0.73, 95% CI 0.55–0.97, P = 0.03 resp.). NLRP3 SNPs in both donor and recipient were not associated with PNF, DGF, graft survival or patient survival. We conclude that genetic variants in the NLRP3 gene affect the risk of acute rejection following kidney transplantation.

Modulation of endogenous antioxidant defense and the progression of kidney disease in multi-heritage groups of patients with type 2 diabetes: PRospective EValuation of Early Nephropathy and its Treatment (PREVENT).

BackgroundDiabetes is the western world’s leading cause of end-stage renal disease. Glucose-dependent, oxidative stress is linked to the development of renal inflammation and sclerosis, which, in animal models of diabetes, can be prevented by anti-oxidative treatment. Patients of non-Caucasian heritage have low activity of the selenoprotein, antioxidant enzyme, glutathione peroxidase (GPx) and its co-factor vitamin E, which may be linked to their increased propensity to developing end-stage renal disease.Research design and methodsWe have designed a double-blind, randomized, placebo controlled study with selenium and/or vitamin E versus placebo as the interventions for patients with type 2 diabetes and chronic kidney disease (CKD) stages 1–3. A 2 × 2 factorial design will allow a balanced representation of the heritage groups exposed to each intervention. The primary biochemical outcome is change in GPx activity, and clinical outcome measure is the actual, rate of—and/or percentage change in estimated glomerular filtration rate (eGFR) from baseline. Analysis will be with a marginal model for longitudinal data using Generalized Estimating Equations corrected for measures of baseline serum antioxidant enzyme activities (GPx, superoxide dismutase and catalase), micronutrient levels (vitamins E and C), measures of inflammation (interleukin 6, c-reactive protein and monocyte chemoattractant protein-1) and markers of oxidative damage (plasma 8-isoprostaglandin F2α and urinary 8-hydroxydeoxyguanosine).Expected resultsThe study will assess the relationship between GPx activity, oxidative stress, inflammation and eGFR. It will test the null hypothesis that antioxidant therapy does not influence the activity of GPx or other antioxidant enzymes and/or alter the rate of change in eGFR in these patient groups.ConclusionsOutcome data on the effect of antioxidants in human diabetic renal disease is limited. Previous post hoc analyses have not shown a beneficial effect of vitamin E on renal function. A recent trial of a pharmaceutical antioxidant agent, improved eGFR, but in patients with advanced diabetes-related chronic kidney disease its use was associated with an increased incidence of cardiovascular events. We will explore whether the nutritional antioxidants, vitamin E and selenium alone, or in combination in patients at high risk of renal disease progression, forestalls a reduction in eGFR. The study will describe whether endogenous antioxidant enzyme defenses can be safely modified by this intervention and how this is associated with changes in markers of oxidative stress.Trial registration ISRCTN 97358113. Registered 21st September 2009

Short-chain fatty acids induce effector T helper cells and cause inflammatory responses in the renal system.

Abstract Short-chain fatty acids (SCFAs) are major products of gut microbial fermentation and profoundly affect host health and disease. SCFAs generate IL-10+ regulatory T cells, which may promote immune tolerance. SCFAs can also induce Th1 and Th17 cells during active immune responses and, therefore, have the potential to induce inflammatory responses. However, the potential function of SCFAs in induction of tissue inflammation has not been documented to date. We investigated, in depth, the impact of elevated SCFA levels on T cells and tissue inflammation in mice. Orally administered SCFAs induced effector (Th1 and Th17) and regulatory T cells in ureter and kidney tissues, and induced T-cell mediated ureteritis leading to kidney hydronephrosis (hereafter called C2RD). Kidney hydronephrosis in C2RD was caused by ureteral obstruction, which was, in turn, induced by SCFA-induced inflammation in the ureteropelvic junction (UPJ) and proximal ureter. Oral administration of all major SCFAs, such as acetate, propionate, and butyrate, induced the disease. We found that C2RD development is dependent on mTOR activation, T cell-derived inflammatory cytokines such as IFNg and IL-17, and gut microbiota. In a manner similar to many types of chronic renal diseases in humans, young or male animals were more susceptible than old or female animals respectively. However, SCFA receptor (GPR41 or GPR43) deficiency did not affect C2RD development. Our study provide evidence for the first time that SCFAs can cause dysregulated T cell responses and tissue inflammation in a specific organ in the body. We believe that our results have significant ramifications in therapeutic applications of SCFAs.

Nephrin Tyrosine Phosphorylation Is Required to Stabilize and Restore Podocyte Foot Process Architecture.

Podocytes are specialized epithelial cells of the kidney blood filtration barrier that contribute to permselectivity via a series of interdigitating actin-rich foot processes. Positioned between adjacent projections is a unique cell junction known as the slit diaphragm, which is physically connected to the actin cytoskeleton via the transmembrane protein nephrin. Evidence indicates that tyrosine phosphorylation of the intracellular tail of nephrin initiates signaling events, including recruitment of cytoplasmic adaptor proteins Nck1 and Nck2 that regulate actin cytoskeletal dynamics. Nephrin tyrosine phosphorylation is altered in human and experimental renal diseases characterized by pathologic foot process remodeling, prompting the hypothesis that phosphonephrin signaling directly influences podocyte morphology. To explore this possibility, we generated and analyzed knockin mice with mutations that disrupt nephrin tyrosine phosphorylation and Nck1/2 binding (nephrin(Y3F/Y3F) mice). Homozygous nephrin(Y3F/Y3F) mice developed progressive proteinuria accompanied by structural changes in the filtration barrier, including podocyte foot process effacement, irregular thickening of the glomerular basement membrane, and dilated capillary loops, with a similar but later onset phenotype in heterozygous animals. Furthermore, compared with wild-type mice, nephrin(Y3F/Y3F) mice displayed delayed recovery in podocyte injury models. Profiling of nephrin tyrosine phosphorylation dynamics in wild-type mice subjected to podocyte injury indicated site-specific differences in phosphorylation at baseline, injury, and recovery, which correlated with loss of nephrin-Nck1/2 association during foot process effacement. Our results define an essential requirement for nephrin tyrosine phosphorylation in stabilizing podocyte morphology and suggest a model in which dynamic changes in phosphotyrosine-based signaling confer plasticity to the podocyte actin cytoskeleton.

Biochemical and biophysical analyses of tight junction permeability made of claudin-16 and claudin-19 dimerization.

The molecular nature of tight junction architecture and permeability is a long-standing mystery. Here, by comprehensive biochemical, biophysical, genetic, and electron microscopic analyses of claudin-16 and -19 interactions--two claudins that play key polygenic roles in fatal human renal disease, FHHNC--we found that 1) claudin-16 and -19 form a stable dimer through cis association of transmembrane domains 3 and 4; 2) mutations disrupting the claudin-16 and -19 cis interaction increase tight junction ultrastructural complexity but reduce tight junction permeability; and 3) no claudin hemichannel or heterotypic channel made of claudin-16 and -19 trans interaction can exist. These principles can be used to artificially alter tight junction permeabilities in various epithelia by manipulating selective claudin interactions. Our study also emphasizes the use of a novel recording approach based on scanning ion conductance microscopy to resolve tight junction permeabilities with submicrometer precision.

Nephron Patterning: Lessons from Xenopus, Zebrafish, and Mouse Studies.

The nephron is the basic structural and functional unit of the vertebrate kidney. To ensure kidney functions, the nephrons possess a highly segmental organization where each segment is specialized for the secretion and reabsorption of particular solutes. During embryogenesis, nephron progenitors undergo a mesenchymal-to-epithelial transition (MET) and acquire different segment-specific cell fates along the proximo-distal axis of the nephron. Even if the morphological changes occurring during nephrogenesis are characterized, the regulatory networks driving nephron segmentation are still poorly understood. Interestingly, several studies have shown that the pronephric nephrons in Xenopus and zebrafish are segmented in a similar fashion as the mouse metanephric nephrons. Here we review functional and molecular aspects of nephron segmentation with a particular interest on the signaling molecules and transcription factors recently implicated in kidney development in these three different vertebrate model organisms. A complete understanding of the mechanisms underlying nephrogenesis in different model organisms will provide novel insights on the etiology of several human renal diseases.

Albuminuria Is Associated with Traditional Cardiovascular Risk Factors and Viral Load in HIV-Infected Patients in Rural South Africa.

ContextAs life expectancy improves among Human Immunodeficiency Virus (HIV) patients, renal and cardiovascular diseases are increasingly prevalent in this population. Renal and cardiovascular disease are mutual risk factors and are characterized by albuminuria. Understanding the interactions between HIV, cardiovascular risk factors and renal disease is the first step in tackling this new therapeutic frontier in HIV.MethodsIn a rural primary health care centre, 903 HIV-infected adult patients were randomly selected and data on HIV-infection and cardiovascular risk factors were collected. Glomerular filtration rate (eGFR) was estimated. Albuminuria was defined as an Albumin-Creatinine-Ratio above 30 mg/g. Multivariate logistic regression analysis was used to analyse albuminuria and demographic, clinical and HIV-associated variables.ResultsThe study population consisted of 903 HIV-infected patients, with a median age of 40 years (Inter-Quartile Range (IQR) 34–48 years), and included 625 (69%) women. The median duration since HIV diagnosis was 26 months (IQR 12–58 months) and 787 (87%) received antiretroviral therapy. Thirty-six (4%) of the subjects were shown to have diabetes and 205 (23%) hypertension. In the cohort, 21% had albuminuria and 2% an eGFR <60 mL/min/1.73m2. Albuminuria was associated with hypertension (adjusted odds ratio (aOR) 1.59; 95% confidence interval (CI) 1.05–2.41; p<0.05), total cholesterol (aOR 1.31; 95% CI 1.11–1.54; p<0.05), eGFR (aOR 0.98; 95% CI 0.97–0.99; p<0.001) and detectable viral load (aOR 2.74; 95% CI 1.56–4.79; p<0.001). Hypertension was undertreated: 78% were not receiving treatment, while another 11% were inadequately treated. No patients were receiving lipid-lowering medication.ConclusionGlomerular filtration rate was well conserved, while albuminuria was common amongst HIV-infected patients in rural South Africa. Both cardiovascular and HIV-specific variables were associated with albuminuria. Improved cardiovascular risk prevention as well as adequate virus suppression might be the key to escape the vicious circle of renal failure and cardiovascular disease and improve the long-term prognosis of HIV-infected patients.

Endothelial nitric oxide synthase gene intron 4 variable number tandem repeat polymorphism in β-thalassemia major: relation to cardiovascular complications.

Endothelial nitric oxide synthase (eNOS), an enzyme that generates nitric oxide, is a major determinant of endothelial function. Several eNOS gene polymorphisms have been reported as 'susceptibility genes' in various human diseases states, including cardiovascular, pulmonary and renal diseases. We studied the 27-base pair tandem repeat polymorphism in intron 4 of eNOS gene in 60 β-thalassemia major (β-TM) patients compared with 60 healthy controls and assessed its role in subclinical atherosclerosis and vascular complications. Patients were evaluated stressing on transfusion history, splenectomy, thrombotic events, echocardiography and carotid intima-media thickness (CIMT). Analysis of eNOS intron 4 gene polymorphism was performed by PCR. No significant difference was found between β-TM patients and controls with regard to the distribution of eNOS4 alleles or genotypes. The frequency of eNOS4a allele (aa and ab genotypes) was significantly higher in β-TM patients with pulmonary hypertension or cardiomyopathy. Logistic regression analysis revealed that eNOS4a allele was an independent risk factor for pulmonary hypertension in β-TM patients [odds ratio (OR) 2.2, 95% confidence interval (95% CI) 1.19-5.6; P < 0.001]. We suggest that eNOS intron 4 gene polymorphism is related to endothelial dysfunction and subclinical atherosclerosis and could be a possible genetic marker for prediction of increased susceptibility to cardiovascular complications.

Gremlin regulates renal inflammation via the vascular endothelial growth factor receptor 2 pathway.

Inflammation is a main feature of progressive kidney disease. Gremlin binds to bone morphogenetic proteins (BMPs), acting as an antagonist and regulating nephrogenesis and fibrosis among other processes. Gremlin also binds to vascular endothelial growth factor receptor-2 (VEGFR2) in endothelial cells to induce angiogenesis. In renal cells, gremlin regulates proliferation and fibrosis, but there are no data about inflammatory-related events. We have investigated the direct effects of gremlin in the kidney, evaluating whether VEGFR2 is a functional gremlin receptor. Administration of recombinant gremlin to murine kidneys induced rapid and sustained activation of VEGFR2 signalling, located in proximal tubular epithelial cells. Gremlin bound to VEGFR2 in these cells in vitro, activating this signalling pathway independently of its action as an antagonist of BMPs. In vivo, gremlin caused early renal damage, characterized by activation of the nuclear factor (NF)-κB pathway linked to up-regulation of pro-inflammatory factors and infiltration of immune inflammatory cells. VEGFR2 blockade diminished gremlin-induced renal inflammatory responses. The link between gremlin/VEGFR2 and NF-κB/inflammation was confirmed in vitro. Gremlin overexpression was associated with VEGFR2 activation in human renal disease and in the unilateral ureteral obstruction experimental model, where VEGFR2 kinase inhibition diminished renal inflammation. Our data show that a gremlin/VEGFR2 axis participates in renal inflammation and could be a novel target for kidney disease.

Role of tubulointerstitial plasmin in the progression of IgA nephropathy.

Plasmin has recently been reported to be associated with renal fibrosis in experimental models, but its role in human renal diseases is unclear. Fifty-seven patients with IgA nephropathy (IgAN) were evaluated retrospectively. Plasmin in their renal biopsy tissues was assessed by in situ zymography using a plasmin-sensitive synthetic peptide, and the relationships between patients' histologic or clinical parameters and their renal plasmin activity [assessed semiquantitatively by calculating the positively stained percentage of the total tubulointerstitial (TI) area] were evaluated. Plasmin activity was observed almost exclusively in the TI space (mainly in the interstitium and partly in the tubular epithelial cells) and was significantly stronger in patients with TI lesion (tubular atrophy/interstitial fibrosis and tubulointerstitial inflammation) than in those without TI lesion. It was significantly and positively correlated with the global glomerulosclerosis rate and significantly and negatively correlated with estimated glomerular filtration rate not only at the time of renal biopsy but also at the end of the follow-up period. Double stainings for plasmin activity and inflammatory cells, cytokeratin, or α-smooth muscle actin (α-SMA) in selected patients revealed TI infiltration of inflammatory cells, attenuated tubular epithelial expression of cytokeratin, and augmented interstitial expression of α-SMA close to upregulated plasmin activity in the TI space. These data suggest that TI plasmin is associated with TI inflammation leading to renal fibrosis, and can cause the decline in renal function seen in patients with IgAN. Reducing plasmin in situ may therefore be a promising therapeutic approach slowing renal fibrogenesis and improving renal function.

The Research Progress of PDGF-C/PDGFR-α Signaling Pathway in Renal Fibrosis and its Traditional Chinese Medicine Intervention

Traditional Chinese Medicine (TCM) is a valuable heritage of human experience [1]. Salvia (dan shen) is one of the most widely used herbs in TCM for treating kidney diseases. Whereas, Salvianolic acid A, B and C are Salvia’s important component. The component compatibility of them for renal fibrosis is a doable and innovative proposition. The literature describing intervention effect of compatibility of Salvia miltiorrhiza water-soluble active components on PDGF-C/PDGFR-α signaling pathway in renal fibrosis. The summary of renal fibrosis, the etiology and pathogenesis of PDGF-C/PDGFR-α signaling pathway and the development in the research of TCM intervention were all examined. PDGF-C and PDGFR-α contribute to the formation of the renal cortical interstitium. Almost all experimental and human renal diseases are characterized by altered expression of the PDGF-C/PDGFR-α signaling pathway. Accordingly, component compatibility of TCM is an effective treatment for renal fibrosis, which is a most innovative application. It can improve renal function, renal tubular function and kidney pathology both in animal experiments and cell culture. Accordingly, it probably has a certain protective effect to the kidney.

Sodium‐independent Dietary Effects on Renal Immune Cell Infiltration in Salt‐sensitive Hypertension

The Dahl SS rat is a well-established model of human salt-sensitive hypertension and renal disease. Recently, sodium-independent effects of diet, particularly during gestation, were shown to be important in the development of this disease phenotype. Dahl SS/JrHsdMcwiCrl (SS/Crl) rats fed a grain-based diet (Teklad 5L2F) were less susceptible to salt-induced blood pressure elevation and renal damage compared to SS/JrHsdMcwi (SS/Mcw) rats fed a casein-based diet (AIN-76A). With the known role of the immune system in hypertension, the present study characterized the immune cells infiltrating the kidney in both SS/Mcw and SS/Crl rats. Following a 3 week high salt (4.0% NaCl) challenge, SS/Crl rats displayed significantly less CD45+ leukocyte infiltration in the kidney than SS/Mcw (47.3% reduction, n=6-7). Specifically, there were respective decreases in infiltrating CD3+ T cells, CD45R+ B cells, and CD11b/c+ antigen presenting cells by 52.4%, 77.7%, and 45.9%, in SS/Crl versus SS/Mcw. The SS/Crl immune system appears to be less activated, as demonstrated by a respective 44.8% and 66.8% reduction in CD4+CD25+ and CD8+CD25+ T cells, as well as a 54.9% decrease in CD4+CD25+FoxP3+ regulatory T cells. SS/Crl rats were also protected from salt-induced kidney damage, indicated by attenuated urinary albumin (20±2 vs 99±16 mg/day) and protein (73±4 vs 173±32 mg/day) excretion compared to SS/Mcw (n=6). These differences between SS/Mcw and SS/Crl show that sodium-independent dietary effects may influence the immune response and infiltration of immune cells in the kidney, ultimately impacting susceptibility to salt-induced hypertension and renal damage. Support: DK96859, HL116264, 5T32HL007792.

Effects of losartan on expression of monocyte chemoattractant protein-1 (MCP-1) in hyperuricemic nephropathy rats

The monocyte chemoattractant protein-1 (MCP-1) plays an important role in the pathogenesis of progression of renal failure. This is based on the observations done both in various animal models of renal damage and in different types of human renal disease. During the development of non-infectious kidney stones, crystals are formed and deposited on the kidneys and the kidneys are surrounded by monocytes/macrophages. We have proposed that in response to crystal exposure, renal epithelial cells produce chemokines, which attract the monocytes/macrophages to the sites of crystal deposition. In this study, we investigated the expression of MCP-1 protein by SD rats exposed to oxonic acid (OA). Our study showed that hyperuricemia accelerates renal progression via a mechanism linked to high MCP-1 which may mediate the inflammation reaction of renal diseases induced by hyperuricemia. Losartan may retard the progression of advanced renal dysfunction, and the mechanism was partly due to blocking of renal inflammation induced by the uric acid. Because the number of experiments performed here is very few, results must be confirmed by more extensive studies with a larger sample size.

Mutation of SH2B3 (LNK), a genome-wide association study candidate for hypertension, attenuates Dahl salt-sensitive hypertension via inflammatory modulation.

Human genome-wide association studies have linked SH2B adaptor protein 3 (SH2B3, LNK) to hypertension and renal disease, although little experimental investigation has been performed to verify a role for SH2B3 in these pathologies. SH2B3, a member of the SH2B adaptor protein family, is an intracellular adaptor protein that functions as a negative regulator in many signaling pathways, including inflammatory signaling processes. To explore a mechanistic link between SH2B3 and hypertension, we targeted the SH2B3 gene for mutation on the Dahl salt-sensitive (SS) rat genetic background with zinc-finger nucleases. The resulting mutation was a 6-bp, in-frame deletion within a highly conserved region of the Src homology 2 (SH2) domain of SH2B3. This mutation significantly attenuated Dahl SS hypertension and renal disease. Also, infiltration of leukocytes into the kidneys, a key mediator of Dahl SS pathology, was significantly blunted in the Sh2b3(em1Mcwi) mutant rats. To determine whether this was because of differences in immune signaling, bone marrow transplant studies were performed in which Dahl SS and Sh2b3(em1Mcwi) mutants underwent total body irradiation and were then transplanted with Dahl SS or Sh2b3(em1Mcwi) mutant bone marrow. Rats that received Sh2b3(em1Mcwi) mutant bone marrow had a significant reduction in mean arterial pressure and kidney injury when placed on a high salt diet (4% NaCl). These data further support a role for the immune system as a modulator of disease severity in the pathogenesis of hypertension and provide insight into inflammatory mechanisms at play in human hypertension and renal disease.

The protective effect of MCP-1 -2518 A>G promoter polymorphism in Turkish chronic renal failure patients requiring long-term hemodialysis.

Monocyte chemoattractant protein-1 (MCP-1) plays a major role in the pathogenesis and progression of different types of human renal disease. Therefore, in this study, we aimed to investigate the effect of MCP-1 gene -2518 A>G promoter polymorphism in chronic renal failure (CRF) patients requiring long-term hemodialysis. The study population consisted of 201 adult CRF patients requiring long-term hemodialysis and 194 healthy controls. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used for genotyping of MCP-1 -2518 A>G polymorphism in the CRF patients and healthy controls. There were statistically significant differences in terms of genotypic (χ (2) = 12.69, p = 0.02) and allelic (χ (2) = 5.72, p = 0.02) frequencies of MCP-1 -2518 A>G between CRF patients and control subjects. According to our results, in the patient group MCP-1 -2518 AA genotype frequency was significantly higher than that of control group. On the other hand, heterozygous AG genotype frequency in the control group was significantly higher than that of the study group. Three different main disease subgroups of CRF (hypertension, diabetes mellitus, and atherosclerosis) patients were also evaluated, and significant associations were found between hypertension (genotype: χ (2) = 9.28, p = 0.01; allele: χ (2) = 6.00, p = 0.01), atherosclerosis (genotype: χ (2) = 5.37, p = 0.02; allele: χ (2) = 4.13, p = 0.04), and distributions of MCP-1 -2518 A>G genotypes and alleles. However, no significant association was found between diabetes mellitus and distributions of MCP-1 -2518 A>G genotype and allele frequencies (genotype: χ (2) = 2.37, p = 0.3; allele: χ (2) = 1.88, p = 0.17). Current data show that MCP-1 -2518 AA genotype may cause susceptibility to CRF, while G allele may have a protective effect against development of CRF. In addition, MCP-1 -2518 AA genotype seems to associate with CRF originated from hypertension and atherosclerosis in our study population.