Gopala K. Rangan

Disruption of E-Cadherin by Matrix Metalloproteinase Directly Mediates Epithelial-Mesenchymal Transition Downstream of Transforming Growth Factor-β1 in Renal Tubular Epithelial Cells

Epithelial-mesenchymal transition (EMT) plays an important role in organ fibrosis, including that of the kidney. Loss of E-cadherin expression is a hallmark of EMT; however, whether the loss of E-cadherin is a consequence or a cause of EMT remains unknown, especially in the renal system. In this study, we show that transforming growth factor (TGF)-beta1-induced EMT in renal tubular epithelial cells is dependent on proteolysis. Matrix metalloproteinase-mediated E-cadherin disruption led directly to tubular epithelial cell EMT via Slug. TGF-beta1 induced the proteolytic shedding of E-cadherin, which caused the nuclear translocation of beta-catenin, the transcriptional induction of Slug, and the repression of E-cadherin transcription in tubular epithelial cells. These findings reveal a direct role for E-cadherin and for matrix metalloproteinases in causing EMT downstream of TGF-beta1 in fibrotic disease. Specific inhibition rather than activation of matrix metalloproteinases may offer a novel approach for treatment of fibrotic disease.

Quantification of renal pathology by image analysis (Methods in Renal Research)

SUMMARY:  Recent advances in computer image analysis techniques allow more accurate quantification of kidney pathological lesions, which are identified by histological staining or immunohistochemistry. This article provides a detailed description of the basic techniques for quantifying these lesions in digital images of light microscopy using Image J software, which is freely available over the Internet. The methods discussed include calibrating measurements, applying scales to images, assessment of object size and thickness, cell counting and point counting, and analysis of area stained. Our explanations indicate how these methods can be used to evaluate glomerular hypertrophy, tubular and vascular injury, accumulation of inflammatory cells and myofibroblasts, deposition of extracellular matrix, and the development of renal scarring.

Effects of uric acid-lowering therapy on renal outcomes: a systematic review and meta-analysis.

BACKGROUND Non-randomized studies suggest an association between serum uric acid levels and progression of chronic kidney disease (CKD). The aim of this systematic review is to summarize evidence from randomized controlled trials (RCTs) concerning the benefits and risks of uric acid-lowering therapy on renal outcomes. METHODS Medline, Excerpta Medical Database and Cochrane Central Register of Controlled Trials were searched with English language restriction for RCTs comparing the effect of uric acid-lowering therapy with placebo/no treatment on renal outcomes. Treatment effects were summarized using random-effects meta-analysis. RESULTS Eight trials (476 participants) evaluating allopurinol treatment were eligible for inclusion. There was substantial heterogeneity in baseline kidney function, cause of CKD and duration of follow-up across these studies. In five trials, there was no significant difference in change in glomerular filtration rate from baseline between the allopurinol and control arms [mean difference (MD) 3.1 mL/min/1.73 m2, 95% confidence intervals (CI) -0.9, 7.1; heterogeneity χ2=1.9, I2=0%, P=0.75]. In three trials, allopurinol treatment abrogated increases in serum creatinine from baseline (MD -0.4 mg/dL, 95% CI -0.8, -0.0 mg/dL; heterogeneity χ2=3, I2=34%, P=0.22). Allopurinol had no effect on proteinuria and blood pressure. Data for effects of allopurinol therapy on progression to end-stage kidney disease and death were scant. Allopurinol had uncertain effects on the risks of adverse events. CONCLUSIONS Uric acid-lowering therapy with allopurinol may retard the progression of CKD. However, adequately powered randomized trials are required to evaluate the benefits and risks of uric acid-lowering therapy in CKD.

Inhibition of NFκB activation with antioxidants is correlated with reduced cytokine transcription in PTC

We recently reported that inhibition of the transcription factor nuclear factor-κB (NFκB) with pyrrolidinedithiocarbamate (PDTC) reduced interstitial monocyte infiltration in rats with proteinuric tubulointerstitial disease, whereas N-acetylcysteine (NAC) was not effective. Here we investigate the effects of antioxidants (PDTC, NAC, and quercetin) on NFκB activation and cytokine transcription in primary cultured rat proximal tubular epithelial cells (PTC) stimulated with lipopolysaccharide. Antioxidant-mediated inhibition of NFκB activation (PDTC, 20-100 μM; NAC, 100 mM; and quercetin, 50 μM) diminished the induction of both pro- [interleukin (IL)-1β, tumor necrosis factor-α, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1α, and MIP-2] and anti-inflammatory (IL-10, transforming growth factor-β1) cytokine transcription in PTC (RT-PCR analysis). PDTC and quercetin did not affect PTC viability, but NAC (100 mM) caused a threefold increase in lactate dehydrogenase leakage ( P < 0.001). We conclude that NAC is unable to suppress NFκB activation in PTC at subtoxic and physiologically relevant concentrations. Furthermore, antioxidant-mediated inhibition of NFκB is correlated with the nonselective reduction of cytokine transcription in activated tubular cells. These data might explain the protective effects of PDTC-mediated NFκB inhibition in tubulointerstitial disease in vivo.

Temporal relationship between renal cyst development, hypertension and cardiac hypertrophy in a new rat model of autosomal recessive polycystic kidney disease

Background/Methods: We have examined the hypothesis that cyst formation is key in the pathogenesis of cardiovascular disease in a Lewis polycystic kidney (LPK) model of autosomal-recessive polycystic kidney disease (ARPKD), by determining the relationship between cyst development and indices of renal function and cardiovascular disease. Results: In the LPK (n = 35), cysts appear at week 3 (1.1 ± 0.1 mm) increasing to week 24 (2.8 ± 2 mm). Immunostaining for nephron-specific segments indicate cysts develop predominantly from the collecting duct. Cyst formation preceded hypertension (160 ± 22 vs. Lewis control 105 ± 20 mm Hg systolic blood pressure (BP), n = 12) at week 6, elevated creatinine (109 ± 63 vs. 59 ± 6 µmol/l, n = 16) and cardiac mass (0.7 vs. 0.4% bodyweight, n = 15) at week 12, and left ventricular hypertrophy (2,898 ± 207 vs. 1,808 ± 192 µm, n = 14) at week 24 (all p ≤ 0.05). Plasma-renin activity and angiotensin II were reduced in 10- to 12-week LPK (2.2 ± 2.9 vs. Lewis 11.9 ± 4.9 ng/ml/h, and 25.0 ± 19.1 vs. 94.9 ± 64.4 pg/ml, respectively, n = 26, p ≤ 0.05). Ganglionic blockade (hexamethonium 3.3 mg/kg) significantly reduced mean BP in the LPK (52 vs. Lewis 4%, n = 9, p ≤ 0.05). Conclusion: Cyst formation is a key event in the genesis of hypertension while the sympathetic nervous system is important in the maintenance of hypertension in this model of ARPKD.

NF-kappaB signalling in chronic kidney disease.

The mammalian NF-kappaB signalling pathway is an important intracellular transcription factor system that is induced in response to diverse extracellular stimuli. The hallmark of NF-kappaB activation is the nuclear translocation of dimeric Rel protein transcription factors, which regulate hundreds of kappaB-dependent genes that are involved in inflammation, immunity, apoptosis, cell proliferation and differentiation. In addition, cell-surface receptors (TNFR, Toll-like and angiotensin II, type 1 receptors), inhibitory kappaB kinases (IKK proteins), I kappaB proteins and factors regulating the post-translational modification of the Rel proteins (acetylation, phosphorylation), are other intracellular components that regulate NF-kappaB activation. Over the last decade, in vitro studies, animal models and human studies have provided evidence that upregulation of the canonical (RelA/p50) NF- kappaB isoform (in tubular epithelial cells, podocytes, mesangial cells, macrophages) has a pathogenic role in mediating chronic inflammation in chronic kidney disease (CKD). This review will examine current evidence regarding NF- kappaB isoforms and their potential role in the treatment of kidney failure due to CKD.

Sirolimus-associated proteinuria and renal dysfunction.

Sirolimus is a novel immunosuppressant with potent antiproliferative actions through its ability to inhibit the raptor-containing mammalian target of rapamycin protein kinase. Sirolimus represents a major therapeutic advance in the prevention of acute renal allograft rejection and chronic allograft nephropathy. Its role in the therapy of glomerulonephritis, autoimmunity, cystic renal diseases and renal cancer is under investigation. Because sirolimus does not share the vasomotor renal adverse effects exhibited by calcineurin inhibitors, it has been designated a ‘non-nephrotoxic drug’. However, clinical reports suggest that, under some circumstances, sirolimus is associated with proteinuria and acute renal dysfunction. A common risk factor appears to be presence of pre-existing chronic renal damage. The mechanisms of sirolimus-associated proteinuria are multifactorial and may be due to an increase in glomerular capillary pressure following calcineurin inhibitor withdrawal. It has also been suggested that sirolimus directly causes increased glomerular permeability/injury, but evidence for this mechanism is currently inconclusive. The acute renal dysfunction associated with sirolimus (such as in delayed graft function) may be due to suppression of compensatory renal cell proliferation and survival/repair processes. Although these adverse effects occur in some patients, their occurrence could be minimised by knowledge of the molecular effects of sirolimus on the kidney, the use of sirolimus in appropriate patient populations, close monitoring of proteinuria and renal function, use of angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers if proteinuria occurs and withdrawal if needed. Further long-term analysis of renal allograft studies using sirolimus as de novo immunosuppression along with clinical and laboratory studies will refine these issues in the future.

Role of interstitial inflammation in the pathogenesis of polycystic kidney disease

Interstitial infiltrates, consisting of macrophages and other inflammatory cells, have been consistently reported in human and animal models of polycystic kidney diseases (PKD). However, the mechanisms underlying this inflammation are not well defined. Evidence suggests that interstitial inflammation in PKD is driven by pro‐inflammatory chemoattractants such as monocyte chemoattractant protein‐1 (MCP‐1), and cytokines such as tumour necrosis factor (TNF)‐α. Putative upregulated inflammatory pathways include JAK‐STAT and nuclear factor (NF)‐κB signalling. In addition, the genetic mutations of PKD may further complicate the relationship between inflammation and cystic disease, by increasing the susceptibility to inflammatory injury, and facilitating interactions between the genetically determined cystoproteins and biological mediators of inflammation. Moreover, the roles of interstitial inflammation in promoting cyst growth and progression to kidney failure in PKD are not clearly understood. Although anti‐inflammatory therapies have attenuated cystogenesis in animal models, inflammatory cells may also have reparative actions. Thus, in developing therapies for PKD, it is prudent to consider the potential negative outcomes of ablating inflammation, and whether it is more viable to target certain inflammatory pathways over others.

PARTIAL DEPLETION OF MACROPHAGES BY ED7 REDUCES RENAL INJURY IN ADRIAMYCIN NEPHROPATHY

Background:  Because macrophages are considered to be possible effectors of disease in Adriamycin (ADR) nephrosis, we hypothesized that depletion of macrophages might protect against the initiation of renal injury. In the present study, a monoclonal antibody (ED7) directed against CD11b/CD18 integrin, which is expressed by macrophages, was used to investigate the pathogenetic effects of macrophages in ADR nephropathy.

DNA Vaccination with CCL2 DNA Modified by the Addition of an Adjuvant Epitope Protects against "Nonimmune" Toxic Renal Injury

CC-chemokine-encoding DNA vaccine has been reported to be capable of inducing immunologic memory to corresponding pathogenic self CC-chemokines in animal models of autoimmune disease. This study investigated whether introduction of a foreign T helper epitope into monocyte chemoattractant protein 1 (CCL2) DNA vaccine could boost its immunogenicity by inducing strong neutralizing autoantibody against the pathogenic chemokine CCL2 sufficiently to be protective in a classically nonimmune model of disease, Adriamycin nephropathy (AN). Modification of the CCL2 DNA vaccine by replacing a surface loop region of CCL2 sequence with tetanus toxoid T helper epitope P30 elicited a strong self-specific CCL2 autoantibody production, as well as an IFN-gamma-producing T cell cellular response. The increased immunogenicity of modified CCL2 DNA vaccination but not unmodified CCL2 DNA vaccination was protective against functional and structural renal injury in rat AN. The protective effect of the modified CCL2 DNA vaccine was associated with blockade of glomerular and interstitial macrophage recruitment by neutralizing autoantibody against CCL2, which plays a critical role in eliciting renal injury in AN. Therefore, modification with a foreign T helper epitope breaks self-tolerance by inducing a cellular and humoral response against self-protein and provides a strategy to increase the potency of DNA vaccination sufficiently to afford protection in toxin-induced chronic renal disease.