Etiopathology of chronic tubular, glomerular and renovascular nephropathies: clinical implications

ALK1-Smad1/5 signaling pathway in fibrosis development: friend or foe?

Fibrosis is a common phenomenon associated with several pathologies, characterized by an excessive extracellular matrix deposition that leads to a progressive organ dysfunction. Thus fibrosis has a relevant role in chronic diseases affecting the kidney, the liver, lung, skin (scleroderma) and joints (arthritis), among others. The pathogenesis of fibrosis in different organs share numerous similarities, being one of them the presence of activated fibroblasts, denominated myofibroblast, which act as the main source of extracellular matrix proteins. Transforming growth factor beta-1 (TGF-β1) is a profibrotic cytokine that plays a pivotal role in fibrosis. The TGF-β1/ALK5/Smad3 signaling pathway has been studied in fibrosis extensively. However, an increasing number of studies involving the ALK1/Smad1 pathway in the fibrotic process exist. In this review we offer a perspective of the function of ALK1/Smad1 pathway in renal fibrosis, liver fibrosis, scleroderma and osteoarthritis, suggesting this pathway as a powerful therapeutical target. We also propose several strategies to modulate the activity of this pathway and its consequences in the fibrotic process.

Premature senescence and cellular phenotype transformation of mesangial cells induced by TGF-B1

BACKGROUND

Transforming growth factor-β1 (TGF-β1) is a polypeptide member of the transforming growth factor β superfamily of cytokines and performs many cellular functions. Its overexpression may lead to renal fibrosis.

AIM

This study planed to investigate the effects of TGF-β1 on the cell cycle and phenotype of mesangial cells.

METHODS

Rat mesangial cells were cultured together with different concentrations (0, 1, 2, 5, and 10 ng/mL) of TGF-β1 for specified times from 0 min to 72 h. 0 ng/mL TGF-β1 and 0 min served as controls. Cell cycles were assessed by flow cytometry and α-smooth muscle actin expression (α-SMA) protein expression by western blot analysis. All data were presented as Mean ± SD. Statistical analysis was performed by using one-way analysis of variance and correlation analysis. Results were considered significant at p < 0.05.

RESULTS

After 15 min of co-culture with different concentrations of TGF-β1, the percentage of mesangial cells in G0/G1 phase was significantly elevated compared to the control (p < 0.05). 12 h co-culture induced cell hyperplasia, 24 h co-culture obvious up-regulation of α-SMA (p < 0.01) and one or two cells' myofibroblast phenotype transition, and 36 h co-culture several cells' phenotype transition. Correlation analysis prompted that the TGF-β1-induced premature aging was time-dependent (p < 0.01).

CONCLUSION

TGF-β1 may induce mesangial cells' premature senescence and myofibroblast-like phenotype transformation time-dependently, which may contribute to the development of early stage of glomerulosclerosis.

In vitro self-assembly of human pericyte-supported endothelial microvessels in three-dimensional coculture: a simple model for interrogating endothelial-pericyte interactions

We describe a method for coculture of macro- or microvascular human endothelial cells (ECs) and pericytes (PCs) within a 3-dimensional (3-D) protein matrix resulting in lumenized EC cords invested by PCs. To prevent apoptotic cell death of ECs in 3-D culture, human umbilical vein or dermal microvascular ECs were transduced to express the antiapoptotic protein Bcl-2. To prevent PC-mediated gel contraction, the collagen-fibronectin gel was polymerized within a polyglycolic acid nonwoven matrix. Over the first 24-48 h, EC-only gels spontaneously formed cords that developed lumens via vacuolization; such vascular networks were maintained for up to 7 days. In EC-PC cocultures, PCs were recruited to the EC networks. PC investment of EC cords both limited the lumen diameter and increased the degree of vascular network arborization. Peg and socket junctions formed between ECs and PCs in this system, but dye transfer, indicative of gap junction formation, was not observed. This simple system can be used to analyze bidirectional signals between ECs and PCs in a 3-D geometry.

Paeoniflorin of Paeonia lactiflora prevents renal interstitial fibrosis induced by unilateral ureteral obstruction in mice

Paeoniflorin (PF), the major active constituent of Paeonia lactiflora Pallas, has previously been reported to alleviate hepatic fibrosis. Whether and how it affects renal fibrosis was evaluated in the present study. The experimental renal fibrosis was induced by unilateral ureteral obstruction (UUO) operation in mice, and PF was orally administered for consecutive 7 days. Renal interstitial destruction and fibrosis degree were evaluated by histopathological examination and hydroxyproline assay. It was shown that PF treatment markedly ameliorated renal interstitial fibrotic lesions, attenuated synthesis of collagen and plasminogen activator inhibitor-1 (PAI-1), an important inhibitor of extracellular matrix degrading enzymes, in UUO mice. PF also suppressed epithelial-mesenchymal transition (EMT) by down-regulating TGF-β1 expression and maintaining BMP-7 mRNA expression, and inhibited Smad2/3 activation in fibrotic kidneys induced by UUO. These observations suggest that PF can effectively prevent renal interstitial fibrosis, and the underlying mechanisms are, at least in part, through blocking EMT via BMP-7 recovery and TGF-β/Smad signaling inhibition.

Lyme nephritis

OBJECTIVE

To review what is known and highlight knowledge gaps regarding Lyme nephritis (LN).

DATA SOURCES

Publications identified via PubMed using the keywords "Borrelia burgdorferi," "Borreliosis," "glomerulonephritis," "protein-losing nephropathy," "autoimmunity," and "retriever," and as generated by investigators working in the fields of Borreliosis and immune-mediated glomerulonephritis.

HUMAN DATA SYNTHESIS

Postborrelial immune-mediated glomerulonephritis was described recently in 6 people; 3 responded to antimicrobials/steroids, 1 to antimicrobials/angiotensin-converting enzyme inhibitor/warfarin, 1 required hemodialysis but became hemodialysis independent after 5 months and treatment with antimicrobials, steroids, plasmapheresis, immunoglobulin, and 1 did not respond to steroids and angiotensin-converting enzyme inhibitor and still requires hemodialysis.

VETERINARY DATA SYNTHESIS

Lyme nephritis is seen in <1-2% of Lyme seropositive dogs, with an average onset at 5-6 years. Labrador and Golden Retrievers are predisposed to this condition. Prior or concurrent lameness is described in 9-28% cases. Historical presentations include acute progressive protein-losing nephropathy with membranoproliferative glomerulonephritis, tubular necrosis/regeneration, and interstitial nephritis, but possibly milder forms exist. Complications include thromboembolic events, hypertension, effusive disease, and oliguric/anuric renal failure. Diagnostic tests help stage disease and rule out other causes. Renal biopsy is advocated early, when intervention may help, and to prove if immune-complex disease exists. Treatment includes standard therapy for protein-losing nephropathy, long-term antimicrobials, and perhaps immunosuppressive therapy.

CONCLUSIONS

There is no experimental model of LN to study predisposing factors, pathogenesis, onset, progression, treatment, or prevention. There are no predictive tests to identify the few individuals at highest risk, therefore all seropositive dogs should be screened and monitored for proteinuria. Lyme nephritis mimics other forms of protein-losing nephropathy and sometimes Leptospirosis. Renal biopsy helps show if immune-complex disease exists, but may not prove LN specifically. More studies are warranted on dogs with Lyme-specific immune-complex deposition to evaluate risk factors, understand pathogenesis, variability of expression, and to validate treatment and prevention protocols.

The effect of allopurinol on lowering blood pressure in hemodialysis patients with hyperuricemia

BACKGROUND

Hyperuricemia has been associated with the development of high blood pressure (BP). We studied the effects of allopurinol therapy in hyperuricemic hemodialysis (HD) patients with high BP.

MATERIALS AND METHODS

This single-blind, randomized cross-over clinical study involved 55 HD patients with serum uric acid level > 6.5 (men) and > 5.5 mg/dL (women). They were randomly divided in two groups, each of which went through two phases. Group-1 in phase-1 received 100 mg/day orally of allopurinol for three months; while Group-2 was given whatever medication they received prior to the study. After two months of washing period, the groups were crossed-over. The BP levels were measured before and after HD during the eight months study period.

RESULTS

Fifty-three patients completed the study (33 men and 20 women, with mean age of 55.8 years). Uric acid levels decreased significantly during the12 weeks of allopurinol therapy (7.71 ± 1.53 to 5.2 ± 1.2 P < 0.005). Overall, after the 12 weeks of allopurinol therapy, systolic and diastolic BP also significantly decreased in allopurinol group, 15.8% (139 to 117, P < 0.0005) and 8.6% (81 to 74, P <.0005), respectively. There were not significant changes in body mass index, blood urea nitrogen, creatinine, albumin, cholesterol, triglyceride, hemoglobin, liver enzymes and serum electrolytes level after treatment. Patients treated with allopurinol had a significant increase in the quality of dialysis (KT/V) (P: 0.043).

CONCLUSIONS

In HD patients, allopurinol treatment reduced BP. The results indicate a new potential therapeutic approach for controlling BP in HD patients.

Chronic kidney disease: highlights for the general pediatrician

Chronic kidney disease in the pediatric population has been increasing. Early detection and treatment can slow down the progression of kidney disease and help prevent the development of end stage renal disease. In addition, as the kidney function declines, there are many pathophysiologic interactions with other organ systems that need to be monitored and treated. In particular, because of impaired vitamin D metabolism, calcium and phosphorus homeostasis is dysregulated and results in secondary bone disease. Anemia is common due to a number of factors including impaired erythropoietin production. Growth is often impacted by chronic kidney disease but can be improved by proper treatment. Complications of chronic kidney disease can be minimized by proper monitoring and treatment of these parameters. The general pediatrician plays a critical role in this process.

Role of TWEAK in lupus nephritis: a bench-to-bedside review

There is significant unmet need in the treatment of lupus nephritis (LN) patients. In this review, we highlight the role of the TWEAK/Fn14 pathway in mediating key pathologic processes underlying LN involving both glomerular and tubular injury, and thus the potential for renal protection via blockade of this pathway. The specific pathological mechanisms of TWEAK - namely promoting inflammation, renal cell proliferation and apoptosis, vascular activation and fibrosis - are described, with supporting data from animal models and in vitro systems. Furthermore, we detail the translational relevance of these mechanisms to clinical readouts in human LN. We present the opportunity for an anti-TWEAK therapeutic as a renal protective agent to improve efficacy relative to current standard of care treatments hopefully without increased safety risk, and highlight a phase II trial with BIIB023, an anti-TWEAK neutralizing antibody, designed to assess efficacy in LN patients. Taken together, targeting the TWEAK/Fn14 axis represents a potential new therapeutic paradigm for achieving renal protection in LN patients.

Human apolipoprotein L1 (ApoL1) in cancer and chronic kidney disease

Human apolipoprotein L1 (ApoL1) possesses both extra- and intra-cellular functions crucial in host defense and cellular homeostatic mechanisms. Alterations in ApoL1 function due to genetic, environmental, and lifestyle factors have been associated with African sleeping sickness, atherosclerosis, lipid disorders, obesity, schizophrenia, cancer, and chronic kidney disease (CKD). Importantly, two alleles of APOL1 carrying three coding-sequence variants have been linked to CKD, particularly in Sub-Saharan Africans and African Americans. Intracellularly, elevated ApoL1 can induce autophagy and autophagy-associated cell death, which may be critical in the maintenance of cellular homeostasis in the kidney. Similarly, ApoL1 may protect kidney cells against renal cell carcinoma (RCC). We summarize the role of ApoL1 in RCC and CKD, highlighting the critical function of ApoL1 in autophagy.

Role of TGF-β in chronic kidney disease: an integration of tubular, glomerular and vascular effects

Transforming growth factor beta (TGF-β) has been recognized as an important mediator in the genesis of chronic kidney diseases (CKD), which are characterized by the accumulation of extracellular matrix (ECM) components in the glomeruli (glomerular fibrosis, glomerulosclerosis) and the tubular interstitium (tubulointerstitial fibrosis). Glomerulosclerosis is a major cause of glomerular filtration rate reduction in CKD and all three major glomerular cell types (podocytes or visceral epithelial cells, mesangial cells and endothelial cells) participate in the fibrotic process. TGF-β induces (1) podocytopenia caused by podocyte apoptosis and detachment from the glomerular basement membrane; (2) mesangial expansion caused by mesangial cell hypertrophy, proliferation (and eventually apoptosis) and ECM synthesis; (3) endothelial to mesenchymal transition giving rise to glomerular myofibroblasts, a major source of ECM. TGF-β has been shown to mediate several key tubular pathological events during CKD progression, namely fibroblast proliferation, epithelial to mesenchymal transition, tubular and fibroblast ECM production and epithelial cell death leading to tubular cell deletion and interstitial fibrosis. In this review, we re-examine the mechanisms involved in glomerulosclerosis and tubulointerstitial fibrosis and the way that TGF-β participates in renal fibrosis, renal parenchyma degeneration and loss of function associated with CKD.

Long-term outcomes of percutaneous nephrolithotomy in 177 patients with chronic kidney disease: a single center experience

PURPOSE

We evaluated the long-term outcomes of percutaneous nephrolithotomy in patients with chronic kidney disease.

MATERIALS AND METHODS

Data on 1,904 patients who underwent percutaneous nephrolithotomy between 2002 and 2011 were retrospectively collected. The estimated glomerular filtration rate for each patient was retrospectively calculated using a 4-variable modification of diet in renal disease equation. Patients were staged for chronic kidney disease by National Kidney Foundation guidelines.

RESULTS

A total of 242 patients (12.7%) had a preoperative glomerular filtration rate of less than 60 ml per minute/1.73 m(2). Those monitored a minimum of 1 year were included in analysis. The study included 177 patients with a mean ± SD age of 54.3 ± 12.1 years. Perioperative and postoperative complications were noted in 15.2% of patients. At a mean followup of 43.4 ± 22.7 months renal function in 29.4% of patients had improved but it remained the same or deteriorated in 54.2% and 16.4%, respectively. On multivariate regression analysis diabetes and preoperative or postoperative complications predicted renal function. The stone-free rate 3 months postoperatively was 80.2% (142 of 177 cases). Stones recurred during long-term followup in 36 of these patients (25.3%). Spontaneous stone passage was detected in 12 of the 35 patients (34.2%) with residual stones but 8 (22.8%) with residual stones experienced an increase in stone size.

CONCLUSIONS

At long-term followup renal function was maintained or improved in greater than 80% of patients with chronic kidney disease who underwent percutaneous nephrolithotomy. Stones recurred or residual stones grew in approximately 25% of these patients.