Novel insights into renal fibrosis

Endophilin A2 protects against renal fibrosis by targeting TGF-β/Smad signaling

Renal fibrosis underlies all forms of end-stage kidney disease. Endophilin A2 (EndoA2) plays a role in nephrotic syndrome; however, its effect on renal fibrosis remains unknown. Here, we demonstrate that EndoA2 protects against kidney interstitial fibrosis via the transforming growth factor-β (TGF-β)/Smad signaling pathway. Mouse kidneys with fibrosis or kidney biopsy specimens from patients with fibrotic nephropathy had lower levels of EndoA2 protein expression than that in kidneys without fibrosis. In vivo overexpression of EndoA2 with the endophilin A2 transgene (EndoA2^Tg ) notably prevented renal fibrosis, decreased the protein expression of profibrotic molecules, suppressed tubular injury, and reduced apoptotic tubular cells in the obstructed kidney cortex of mice with unilateral ureteral obstruction (UUO). In vivo and in vitro overexpression of EndoA2 markedly inhibited UUO- or TGF-β1-induced phosphorylation of Smad2/3 and tubular epithelial cells dedifferentiation. Furthermore, EndoA2 was co-immunoprecipitated with the type II TGF-β receptor (TβRII), thus inhibiting the binding of the type I TGF-β receptor (TβRI) to TβRII. These findings indicate that EndoA2 mitigates renal fibrosis, at least partially, via modulating the TGF-β/Smad signaling. Targeting EndoA2 may be a new potential therapeutic strategy for treatment of renal fibrosis.

The Role of Platelets in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is among the most common microvascular complications in patients with diabetes, and it currently accounts for the majority of end-stage kidney disease cases worldwide. The pathogenesis of DKD is complex and multifactorial, including systemic and intra-renal inflammatory and coagulation processes. Activated platelets play a pivotal role in inflammation, coagulation, and fibrosis. Mounting evidence shows that platelets play a role in the pathogenesis and progression of DKD. The potentially beneficial effects of antiplatelet agents in preventing progression of DKD has been studied in animal models and clinical trials. This review summarizes the current knowledge on the role of platelets in DKD, including the potential therapeutic effects of antiplatelet therapies.

Cellular and molecular mechanisms of kidney fibrosis

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. It is considered as the underlying pathological process of chronic kidney disease (CKD), which affects more than 10% of world population and for which treatment options are limited. Renal fibrosis is defined by excessive deposition of extracellular matrix, which disrupts and replaces the functional parenchyma that leads to organ failure. Kidney's histological structure can be divided into three main compartments, all of which can be affected by fibrosis, specifically termed glomerulosclerosis in glomeruli, interstitial fibrosis in tubulointerstitium and arteriosclerosis and perivascular fibrosis in vasculature. In this review, we summarized the different appearance, cellular origin and major emerging processes and mediators of fibrosis in each compartment. We also depicted and discussed the challenges in translation of anti-fibrotic treatment to clinical practice and discuss possible solutions and future directions.

Role of Sirolimus in renal tubular apoptosis in response to unilateral ureteral obstruction

Renal tubule cell apoptosis plays a pivotal role in the progression of chronic renal diseases. The previous study indicates that Sirolimus is effective on unilateral ureteral obstruction (UUO)-induced renal fibrosis. However, the role of Sirolimus in renal tubular apoptosis induced by UUO has not yet been addressed. The aim of this study was to determine the role of Sirolimus in renal tubular apoptosis induced by UUO. Male Sprague-Dawley rats were divided into three groups, sham-operated rats, and after which unilateral ureteral obstruction (UUO) was performed: non-treated and sirolimus-treated (1mg/kg). After 4, 7 and 14 d, animals were sacrificed and blood, kidney tissue samples were collected for analyses. Histologic changes and interstitial collagen were determined microscopically following HE and Masson's trichrome staining. The expression of PCNA was investigated using immunohistochemistry and the expression of Bcl-2, Bax, caspase-9, and caspase-3 were investigated using Western blot in each group. Tubular apoptotic cell deaths were assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. Sirolimus administration resulted in a significant reduction in tubulointerstitial fibrosis scores. After UUO, there was an increase in tubular and interstitial apoptosis in untreated controls as compared to Sirolimus treatment rats (P<0.05). In addition, the expression of PCNA, Bcl-2, Bax, caspase-9, and caspase-3 in obstructed kidney was characterized by immunohistochemistry and Western blot analyses demonstrating that sirolimus treatment significantly reduced PCNA, Bax, caspase-9 and cleaved caspase-3 expression compared to those observed in controls (P<0.05), whereas, Bcl-2 in the obstructed kidney were decreased in untreated controls compared to Sirolimus treatment rats subjected to the same time course of obstruction (P<0.05). We demonstrated a marked renoprotective effect of sirolimus by inhibition of UUO-induced renal tubular apoptosis in vivo.

Antioxidant activity of Inonotus obliquus polysaccharide and its amelioration for chronic pancreatitis in mice

Inonotus obliquus polysaccharide (IOP) was extracted by water with a yield of 9.83% and purified by an anion-exchange DEAE cellulose column and Sephadex G-200 gel with a polysaccharide content of 98.6%. The scavenging activities for 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and hydroxyl radicals of IOP were 82.3% and 81.3% respectively at a concentration of 5 mg/mL. IOP was composed of Man, Rha, Glu, Gal, Xyl and Ara in a molar ratio of 9.81:3.6：29.1：20.5：21.6：5.4 respectively. The gel permeation chromatography indicated that IOP was a homogeneous polysaccharide with molecular weight of 32.5 kDa. IOP helped to alleviate pancreatic acinar atrophy and weight loss for chronic pancreatitis (CP) mice induced by Diethyldithiocarbamate (DDC). The SOD level was increased most by IOP-H treatment (400 mg/kg body weight). MDA, IL-1β and LDH were significantly decreased by IOP treatment, especially hydroxyproline, IFN-γ and AMS levels were decreased 39.18%, 37.82% and 41.57% by IOP-H treatment respectively compared to MC group. In conclusion, IOP possessed strong antioxidant activity for scavenging free radicals in vitro and vivo which could be propitious to CP therapy in mice.

Mesenchymal stem cell-derived microparticles ameliorate peritubular capillary rarefaction via inhibition of endothelial-mesenchymal transition and decrease tubulointerstitial fibrosis in unilateral ureteral obstruction

Introduction

Microparticles (MPs) derived from kidney-derived mesenchymal stem cells (KMSCs) have recently been reported to ameliorate rarefaction of peritubular capillaries (PTC) in ischemic kidneys via delivery of proangiogenic effectors. This study aimed to investigate whether KMSC-derived MPs show anti-fibrotic effects by ameliorating endothelial-to-mesenchymal transition (EndoMT) in human umbilical vein endothelial cells (HUVEC) in vitro and by preserving PTC in kidneys with unilateral ureteral obstruction (UUO) in vivo.

Methods

MPs isolated from the supernatants of KMSC were co-cultured with HUVEC to assess their in vitro biologic effects on endothelial cells. Mice were treated with MPs via the tail vein after UUO injury to assess their anti-fibrotic and PTC sparing effects. Renal tubulointerstitial damage and inflammatory cell infiltration were examined with Masson’s trichrome, F4/80 and α-smooth muscle actin (α-SMA) staining and PTC rarefaction index was determined by CD31 staining.

Results

KMSC-derived MPs significantly ameliorated EndoMT and improved in vitro proliferation of TGF-β1 treated HUVEC. In vivo administration of KMSC-derived MPs significantly inhibited EndoMT of PTC endothelial cells and improved PTC rarefaction in UUO kidneys. Furthermore, administration of KMSC-derived MPs inhibited inflammatory cell infiltration as well as tubulointerstitial fibrosis in UUO mice as demonstrated by decreased F4/80 and α-SMA-positive cells and Masson’s trichrome staining, respectively.

Conclusions

Our results suggest that KMSC-derived MPs ameliorate PTC rarefaction via inhibition of EndoMT and protect against progression of renal damage by inhibiting tubulointerstitial fibrosis.

Targeting the epithelial to mesenchymal transition in glioblastoma: the emerging role of MET signaling

Glioblastoma multiforme (GBM) is the most common human primary brain malignancy and has a dismal prognosis. Aggressive treatments using maximal surgical resection, radiotherapy, and temozolomide result in median survival of only 14.6 months in patients with GBM. Numerous clinical approaches using small molecule inhibitors have shown disappointing results because of the genetic heterogeneity of GBM. The epithelial to mesenchymal transition (EMT) is a crucial biological process occurring in the early development stages of many species. However, cancer cells often obtain the ability to invade and metastasize through the EMT, which triggers the scattering of cells. The hepatocyte growth factor (HGF)/MET signaling pathway is indicative of the EMT during both embryogenesis and the invasive growth of tumors, because HGF potently induces mesenchymal transition in epithelial-driven cells. Activation of MET signaling or co-overexpression of HGF and MET frequently represents aggressive growth and poor prognosis of various cancers, including GBM. Thus, efforts to treat cancers by inhibiting MET signaling using neutralizing antibodies or small molecule inhibitors have progressed during the last decade. In this review, we discuss HGF/MET signaling in the development of diseases, including cancers, as well as updates on MET inhibition therapy.

Protection from renal fibrosis, putative role of TRIB3 gene silencing

BACKGROUND

Renal fibrosis is thought to be the common pathway in most cases of chronic kidney disease. Recently, TRIB3 was found to play an important role in progression of cardiac fibrosis in an insulin-resistant state. We investigated whether TRIB3 might participate in the pathogenesis of renal fibrosis in insulin-resistant rats.

METHODS

We randomly separated 40 male Sprague-Dawley into 4 groups for treatment (n = 10 each): control and high-fat diet (HFD) with TRIB3 siRNA adenovirus transfection, vehicle transfection or HFD alone. Insulin resistance markers were measured. Renal tissues were stained with hematoxylin and eosin, Masson's trichrome and periodic acid-Schiff.

RESULTS

Rats with HFD showed insulin resistance and TRIB3 overexpression. Upregulated TRIB3 expression could induce renal fibrosis accompanied by increased phosphorylation of extracellular signal-regulated kinase (ERK). Also, TRIB3 siRNA knockdown could ameliorate renal fibrosis, which was accompanied by decreased phosphorylation of ERK.

CONCLUSIONS

TRIB3 gene silencing can attenuate renal fibrosis for beneficial effect on the development of renal fibrosis in chronic kidney disease in rat.

Antifibrotic role of chemokine CXCL9 in experimental chronic pancreatitis induced by trinitrobenzene sulfonic acid in rats

Chemokines have been shown to play an important role in the pathogenesis of pancreatitis, but the role of chemokine CXCL9 in pancreatitis is poorly understood. The aim of this study was to investigate whether CXCL9 was a modulating factor in chronic pancreatitis. Chronic pancreatitis was induced in Sprague-Dawley rats by intraductal infusion of trinitrobenzene sulfonic acid (TNBS) and CXCL9 expression was assessed by immunohistochemistry, Western blot analysis and enzyme linked immunosorbent assay (ELISA). Recombinant human CXCL9 protein (rCXCL9), neutralizing antibody and normal saline (NS) were administered to rats with chronic pancreatitis by subcutaneous injection. The severity of fibrosis was determined by measuring hydroxyproline in pancreatic tissues and histological grading. The effect of rCXCL9 on activated pancreatic stellate cells (PSCs) in vitro was examined and collagen 1α1, TGF-β1 and CXCR3 expression was assessed by Western blot analysis in isolated rat PSCs. Chronic pancreatic injury in rats was induced after TNBS treatment and CXCL9 protein was markedly upregulated during TNBS-induced chronic pancreatitis. Although parenchymal injury in the pancreas was not obviously affected after rCXCL9 and neutralizing antibody administration, rCXCL9 could attenuate fibrogenesis in TNBS-induced chronic pancreatitis in vivo and exerted antifibrotic effects in vitro, suppressing collagen production in activated PSCs. In conclusion, CXCL9 is involved in the modulation of pancreatic fibrogenesis in TNBS-induced chronic pancreatitis in rats, and may be a therapeutic target in pancreatic fibrosis.

Effect of Chinese herbs on immunoglobulin A nephropathy: a randomized controlled trial

OBJECTIVE

The accumulation of extracellular matrix (ECM) is one of the main causes of renal fibrosis. Emerging evidence suggests that the metabolic enzyme of ECM is associated with renal fibrosis. In this study, we applied randomly controlled trial to check the curative effect of Chinese herbs on patients with immunoglobulin A nephropathy (IgAN).

METHODS

Twenty-six patients were randomly divided into group A (control group) treated with Western Medicine and group B (treatment group) treated with combination of Traditional Chinese Medicine (TCM) and Western Medicine. Blood and urine tests were done before treatment and after 8-week treatment.

RESULTS

The levels of the main composition of extracellular matrix (MC-ECM), the metabolic enzyme of ECM (ME-ECM) and some cytokines in group B decreased more obviously than those in group A after 8-week treatment. So did the level of 24-hour urine protein. However, Metal matrix protease (MMP)-2 and vascular endothelial growth factor in group B increased more obviously than those in group A after 8-week treatment. No effects on the renal function were found in both groups.

CONCLUSION

Our study provided important information on using the combination of TCM with Western Medicine to inhibit the progression of renal fibrosis in patients with IgAN.

Renal fibrosis

Renal fibrosis, characterized by tubulointerstitial fibrosis and glomerulosclerosis, is the final manifestation of chronic kidney disease. Renal fibrosis is characterized by an excessive accumulation and deposition of extracellular matrix components. This pathologic result usually originates from both underlying complicated cellular activities such as epithelial-to-mesenchymal transition, fibroblast activation, monocyte/macrophage infiltration, and cellular apoptosis and the activation of signaling molecules such as transforming growth factor beta and angiotensin II. However, because the pathogenesis of renal fibrosis is extremely complicated and our knowledge regarding this condition is still limited, further studies are needed.

Postobstructive regeneration of kidney is derailed when surge in renal stem cells during course of unilateral ureteral obstruction is halted

Unilateral ureteral obstruction (UUO), a model of tubulointerstitial scarring (TIS), has a propensity toward regeneration of renal parenchyma after release of obstruction (RUUO). No information exists on the contribution of stem cells to this process. We performed UUO in FVB/N mice, reversed it after 10 days, and examined kidneys 3 wk after RUUO. UUO resulted in attenuation of renal parenchyma. FACS analysis of endothelial progenitor (EPC), mesenchymal stem (MSC) and hematopoietic stem (HSC) cells obtained from UUO kidneys by collagenase-dispersed single-cell suspension showed significant increase in EPC, MSC, and HSC compared with control. After RUUO cortical parenchyma was nearly restored, and TIS score improved by 3 wk. This reversal process was associated with return of stem cells toward baseline level. When animals were chronically treated with nitric oxide synthase (NOS) inhibitor at a dose that did not induce hypertension but resulted in endothelial dysfunction, TIS scores were not different from control UUO, but EPC number in the kidney decreased significantly; however, parenchymal regeneration in these mice was similar to control. Blockade of CXCR4-mediated engraftment resulted in dramatic worsening of UUO and RUUO. Similar results were obtained in caveolin-1-deficient but not -overexpressing mice, reflecting the fact that activation of CXCR4 occurs in caveolae. The present data show increase in EPC, HSC, and MSC population during UUO and a tendency for these cells to decrease to control level during RUUO. These processes are minimally affected by chronic NOS inhibition. Blockade of CXCR4-stromal cell-derived factor-1 (SDF-1) interaction by AMD3100 or caveolin-1 deficiency significantly reduced the UUO-associated surge in stem cells and prevented parenchymal regeneration after RUUO. We conclude that the surge in stem cell accumulation during UUO is a prerequisite for regeneration of renal parenchyma.

Indolent course of tubulointerstitial disease in a mouse model of subpressor, low-dose nitric oxide synthase inhibition

Deficiency of nitric oxide (NO) represents a consistent manifestation of endothelial dysfunction (ECD), and the accumulation of asymmetric dimethylarginine occurs early in renal disease. Here, we confirmed in vitro and in vivo the previous finding that a fragment of collagen XVIII, endostatin, was upregulated by chronic inhibition of NO production and sought to support a hypothesis that primary ECD contributes to nephrosclerosis in the absence of other profibrotic factors. To emulate more closely the indolent course of ECD, the study was expanded to an in vivo model with N(G)-monomethyl-L-arginine (L-NMMA; mimics effects of asymmetric dimethylarginine) administered to mice in the drinking water at subpressor doses of 0.3 and 0.8 mg/ml for 3-6 mo. This resulted in subtle but significant morphological alterations detected in kidneys of mice chronically treated with L-NMMA: 1) consistent perivascular expansion of interstitial matrix components at the inner stripe of the outer medulla and 2) collagen XVIII/endostatin abundance. Ultrastructural abnormalities were detected in L-NMMA-treated mice: 1) increased activity of the interstitial fibroblasts; 2) occasional detachment of endothelial cells from the basement membrane; 3) splitting of the vascular basement membrane; 4) focal fibrosis; and 5) accumulation of lipofuscin by interstitial fibroblasts. Preembedding labeling of microvasculature with anti-CD31 antibodies showed infiltrating leukocytes and agglomerating platelets attaching to the visibly intact or denuded capillaries. Collectively, the data indicate that the mouse model of subpressor chronic administration of L-NMMA is not a robust one (endothelial pathology visible only ultrastructurally), and yet it closely resembles the natural progression of endothelial dysfunction, microvascular abnormalities, and associated tubulointerstitial scarring.

Interleukin-6 gene polymorphism and faster progression to end-stage renal failure in chronic glomerulonephritis

Interleukin-6 (IL-6) is a multifunctional cytokine produced by different cell types, including monocytes, lymphocytes, endothelial and mesangial cells. Deregulated production of IL-6 was found to be involved in mesangial proliferative glomerulonephritis. We investigated whether the single nucleotide polymorphism (SNP) in the promoter region of the IL-6 gene is associated with a development of chronic glomerulonephritis (CGN). The study group consisted of 541 patients with CGN. Of those 338 already progressed to ESRD. The control group involved 253 healthy individuals. All subjects were genotyped for the -634 C/G polymorphism of the IL-6 gene by polymerase chain reaction (PCR). PCR product was digested with BsrBI restriction endonuclease and analyzed on 3% agarose. The allele and genotype frequencies were similar between CGN patients in a pre-dialysis stage and control subjects. Significantly increased frequency of the G allele was observed in the ESRD patients (13% vs. 6% in pre-dialysis stage, P < 0.01). After dividing ESRD patients according to time from reported disease onset to ESRD, those with time < or =5 years showed even higher G allele frequency (21% vs. 13% in entire ESRD group). Interestingly, most of the GG homozygotes were in this faster progressing group. Both subgroups were comparable for sex, age, BMI, total cholesterol and serum creatinine. The multivariate logistic regression analysis revealed that the IL-6 genotype with the G allele was an independent risk factor of progression to ESRD (P < 0.001). Our results indicate that the IL-6 -634 G/C polymorphism may be a possible risk factor for faster progression of chronic glomerulonephritis to ESRD. It is also possible that this polymorphism is in linkage disequilibrium with another functional polymorphism in the II-6 gene or its vicinity.

Chronic NOS inhibition actuates endothelial-mesenchymal transformation

Chronic kidney diseases are accompanied by the accumulation of substances like asymmetric dimethylarginine, phenylacetic acid, homocysteine, and advanced glycation end products, known to either inhibit endothelial nitric oxide synthase (eNOS) or uncouple it, consequently limiting the amount of available nitric oxide (NO). Reduced bioavailability of NO induces endothelial dysfunction. An early loss of peritubular capillaries in tubulointerstitial fibrotic areas and injury to endothelial cells have been linked to progressive renal disease. Screening endothelial genes in cells treated with NOS inhibitors showed upregulation of collagen XVIII, a precursor of a potent antiangiogenic substance, endostatin. This finding was confirmed at the level of mRNA and protein expression. Tie-2 promoter-driven green fluorescent protein mice treated with nonhypertensinogenic doses of a NOS inhibitor exhibited upregulation of collagen XVIII/endostatin and rarefaction of capillary profiles. This was accompanied by the increased expression of transforming growth factor-β and connective tissue growth factor in the kidney. Occasional endothelial cells expressed both the marker of endothelial lineage (green fluorescent protein) and mesenchymal marker (α-smooth muscle actin or calponin). In vitro studies of endothelial cells treated with asymmetric dimethylarginine showed decreased expression of eNOS and Flk-1 and enhanced expression of calponin and fibronectin, additional markers of smooth muscle and mesenchymal cells. These cells overexpressed transforming growth factor-β and connective tissue growth factor, as well as endostatin. In conclusion, data presented here 1) ascribe to NO deficiency in endothelial cells the function of a profibrotic stimulus associated with the expression of an antiangiogenic fragment of collagen XVIII (endostatin) and 2) provide evidence of endothelial-mesenchymal transdifferentiation in the course of inhibition of NOS by a pathophysiologically important antagonist, asymmetric dimethylarginine. Both mechanisms may account for microvascular rarefaction.

Application of antibody array technology in the analysis of urinary cytokine profiles in patients with chronic kidney disease

AIMS

Emerging evidence suggests that the urinary excretion of cytokines is associated with the progression of chronic kidney disease (CKD). However, detection of urinary cytokines in high throughput is still a problem in clinical practice. In this cross-sectional study, we applied a novel proteomic technology, antibody array, to analyze urinary cytokine profiles in patients with CKD.

METHODS

A total of 10 subjects including 7 CKD patients and 3 normal controls were studied. These patients with CKD were divided into two groups according to the levels of estimated glomerular filtration rate (eGFR): group A (eGFR >or=80 ml/min/1.73 m(2), n = 3) and group B (eGFR <or=40 ml/min/1.73 m(2), n = 4). Urine samples taken from age and gender-matched healthy volunteers (n = 3) served as control. Differential excretion of urinary cytokines was determined by human cytokine antibody array (Raybiotech, Norcross, Ga., USA). A 2-fold change in spot intensity compared to controls was considered as significant. In order to check the reliability of the data obtained by antibody array, urinary monocyte chemoattractant protein (MCP) 1 and tumor necrosis factor (TNF) alpha were determined by using enzyme-linked immunosorbent assay.

RESULTS

A total of 15 cytokines varied significantly in urinary samples obtained from patients with CKD compared with normal controls. It was shown that the levels of MCP-1, RANTES, tissue inhibitor of metalloproteinase (TIMP) 1, TNF-alpha, vascular endothelial growth factor (VEGF), E-selectin, Fas, intercellular adhesion molecule 1, interleukin 2, matrix metalloproteinase (MMP) 2 and transforming growth factor beta in patients with CKD at stage 1-2 (group A) were 2- to 5-fold higher than those in normal controls, while the excretion of MCP-1, RANTES, TIMP-1, TNF-alpha and VEGF was further increased in the patients with renal insufficiency (group B). However, a lower excretion of urinary vascular cell adhesion molecule 1 and platelet-derived growth factor was found in patients with CKD compared with normal controls. Impressively, the urinary MMP-9 excretion was 492-fold higher in group A and 198-fold higher in group B than that in normal controls. The levels of MCP-1 and TNF-alpha correlated well with the relative n-fold change seen in the antibody array experiments. The rank correlation coefficients (r values) were 0.976 (p < 0.001) and 0.939 (p < 0.001) for MCP-1and TNF-alpha, respectively.

CONCLUSION

Antibody array could serve as a fast, high-throughput and sensitive tool for detecting the excretion of urinary cytokines. Our study is the first to provide an important information regarding the utility of antibody array in evaluating the role of cytokines in the initiation and progression of CKD.

The renal antifibrotic effects of angiotensin-converting enzyme inhibition involve bradykinin B2 receptor activation in angiotensin II-dependent hypertension

OBJECTIVE

The renoprotective action of angiotensin I-converting enzyme inhibitors (ACE-Is) is well established, but the role played by bradykinin (BK) remains unclear. We therefore investigated whether an enhanced BK effect on B2 receptor subtype mediated the antifibrotic effect of ACE-Is and whether neutral endopeptidase (NEP) inhibition, which can blunt BK degradation more effectively than ACE inhibition, provided further renoprotection in a rat model of angiotensin (Ang) II-dependent renal damage.

METHODS

Five-week-old Ren-2 transgenic rats (TGRen2) received, for 8 weeks, a placebo, ramipril (5 mg/kg body weight) or the dual ACE + NEP inhibitor MDL 100,240 (MDL) (40 mg/kg body weight). After 4 weeks, the B2 receptor antagonist icatibant (0.5 mg/kg body weight) was administered on top of active treatment for 4 weeks to 50% of the TGRen2 rats. Blood pressure was measured weekly by a tail-cuff method and, after sacrifice, kidney weight, glomerular volume, density of glomerular profiles were measured; tubulo-interstitial fibrosis, glomerular and perivascular fibrosis were quantified by histomorphometry.

RESULTS

The development of hypertension and tubulo-interstitial fibrosis was prevented by both ramipril and MDL (P = 0.0001 versus placebo); icatibant annulled the latter effect. Glomerular and perivascular fibrosis were unaffected by either ramipril or MDL alone; however, combined treatment with icatibant enhanced glomerular fibrosis (P = 0.0001 versus placebo).

CONCLUSION

Enhanced BK effect on B2 subtype receptors is essential for the prevention of tubulo-interstitial fibrosis with ACE or dual ACE + NEP inhibition in TGRen2 rats.

Protective role of selectin ligand inhibition in a large animal model of kidney ischemia-reperfusion injury

Experiments in rodents have demonstrated an important role for selectins in kidney ischemia-reperfusion injury (IRI). However, the relevance of this in larger mammals, as well as the impact on long-term structure and function is unknown. We tested the hypothesis that small molecule selectin ligand inhibition attenuates IRI, cellular inflammation, and long-term effects on renal interstitial fibrosis. We used a porcine model of kidney IRI and used Texas Biotechnology Corporation (TBC)-1269, a selectin ligand inhibitor. Renal function, tissue inflammation, and tubulointerstitial fibrosis development were evaluated up to 16 weeks. Both warm and cold ischemia models were studied for relevance to native and transplant kidney injury. Pigs treated with TBC-1269 during 45 min of warm ischemia (WI) showed significantly increased glomerular filtration rate compared to control animals. In pigs with severe IRI (WI for 60 min), TBC-1269 treatment during IRI significantly increased renal recovery. Cellular inflammation was strongly reduced, particularly influx of CD4 cells. Quantitative measurement of fibrosis by picrosirius red staining showed strong reduction in TBC-1269-treated groups. TBC-1269 also reduced cold IRI, inflammation, and fibrosis in kidneys preserved for 24 h at 4 degrees C and autotransplanted. The selectin ligand inhibitor TBC-1269 provides a novel and effective approach to attenuate IRI in both warm and cold ischemia in large mammals, in both short and long terms. Selectin ligand inhibition is an attractive strategy for evaluation in human kidney IRI.

Adrenomedullin impairs the profibrotic effects of transforming growth factor-beta1 through recruiting Smad6 protein in human renal tubular cells

Adrenomedullin (AM) was originally identified as a vasodilator peptide, and has recently been shown to be an antiproliferative factor in renal mesangial cells, suggesting that adrenomedullin may impair the progression of glomerulosclerosis. This study was to investigate the effect of adrenomedullin on transforming growth factor-beta1 (TGF-beta1)-stimulated cell growth, synthesis of extracellular matrix (ECM) components and the related molecular mechanism in a human tubular epithelial cell line HK-2. TGF-beta1 inhibited cell proliferation induced by fetal bovine serum, but neither AM itself affectted cell proliferation, nor did AM influence TGF-beta1-caused cell growth arrest. However, AM beginning at 10(-8) M alleviated the action of TGF-beta1-stimulated cellular collagen synthesis and secretion of fibronectin into cell culture supernatant. Activation of Smad proteins is known to be the key signaling pathway of the profibrotic effect of TGF-beta1, AM at 10(-8) M exerted no effect on TGF-beta1-induced Smad2 phosphorylation, but prevented the suppression of the inhibitory Smad6 protein by TGF-beta1 and restored Smad2-Samd6 complex formation. Our results suggest that AM can attenuate TGF-beta1-mediated renal tubulointerstitial ECM turnover via an antagonistic mechanism of inhibitory Smad in TGF-beta1-elicited signaling.

Influence of cytokine gene polymorphisms on focal segmental glomerulosclerosis

BACKGROUND

Recently, polymorphisms of cytokine genes have been associated with modified gene expression and increased cytokine production. We evaluated the influence of TGF-beta(1) gene Arg(25)-->Pro, TNF alpha gene G-308A and IL-6 gene G-174C polymorphisms on the clinical manifestations of focal segmental glomerulosclerosis (FSGS).

METHODS

The clinical course of 71 patients with biopsy-proven primary FSGS followed up for 6.0 +/- 4.4 years was studied. Patients were classified according to the slope of reciprocal serum creatinine into slow (n = 49) and fast (n = 22) progressors. One hundred healthy volunteers were analysed as controls. Genetic polymorphisms were determined by PCR amplification.

RESULTS

The genotype distribution of the studied polymorphisms was similar in patients and controls (n.s.). Age, initial renal function, proteinuria and blood pressure did not differ significantly between patients with different genotypes (n.s.). The investigated polymorphisms were not associated with the progression of FSGS as shown by the similar genotype frequencies among slow and fast progressors (n.s.) and the renal survival in the Kaplan-Meier analysis (n.s.).

CONCLUSION

Our results indicate that TGF-beta(1) gene Arg(25)-->Pro, TNF alpha gene G-308A and IL-6 gene G-174C polymorphisms are not risk factors or markers of progression in focal segmental glomerulosclerosis.

Epithelial–mesenchymal transitions in development and pathologies

The epithelial-mesenchymal transition (EMT) is a fundamental process governing morphogenesis in multicellular organisms. This process is also reactivated in a variety of diseases including fibrosis and in the progression of carcinoma. The molecular mechanisms of EMT were primarily studied in epithelial cell lines, leading to the discovery of transduction pathways involved in the loss of epithelial cell polarity and the acquisition of a variety of mesenchymal phenotypic traits. Similar mechanisms have also been uncovered in vivo in different species, showing that EMT is controlled by remarkably well-conserved mechanisms. Current studies further emphasise the critical importance of EMT and provide a better molecular and functional definition of mesenchymal cells and how they emerged >500 million years ago as a key event in evolution.