Inhibition of integrin-linked kinase blocks podocyte epithelial-mesenchymal transition and ameliorates proteinuria.

Proteinuria is a primary clinical symptom of a large number of glomerular diseases that progress to end-stage renal failure. Podocyte dysfunctions play a fundamental role in defective glomerular filtration in many common forms of proteinuric kidney disorders. Since binding of these cells to the basement membrane is mediated by integrins, we determined the role of integrin-linked kinase (ILK) in podocyte dysfunction and proteinuria. ILK expression was induced in mouse podocytes by various injurious stimuli known to cause proteinuria including TGF-beta1, adriamycin, puromycin, and high ambient glucose. Podocyte ILK was also found to be upregulated in human proteinuric glomerular diseases. Ectopic expression of ILK in podocytes decreased levels of the epithelial markers nephrin and ZO-1, induced mesenchymal markers such as desmin, fibronectin, matrix metalloproteinase-9 (MMP-9), and alpha-smooth muscle actin (alpha-SMA), promoted cell migration, and increased the paracellular albumin flux across podocyte monolayers. ILK also induced Snail, a key transcription factor mediating epithelial-mesenchymal transition (EMT). Blockade of ILK activity with a highly selective small molecule inhibitor reduced Snail induction and preserved podocyte phenotypes following TGF-beta1 or adriamycin stimulation. In vivo, this ILK inhibitor ameliorated albuminuria, repressed glomerular induction of MMP-9 and alpha-SMA, and preserved nephrin expression in murine adriamycin nephropathy. Our results show that upregulation of ILK is a convergent pathway leading to podocyte EMT, migration, and dysfunction. ILK may be an attractive target for therapeutic intervention of proteinuric kidney diseases.

Wnt/beta-catenin signaling promotes podocyte dysfunction and albuminuria.

Podocyte dysfunction, one of the major causes of proteinuria, leads to glomerulosclerosis and end stage renal disease, but its underlying mechanism remains poorly understood. Here we show that Wnt/beta-catenin signaling plays a critical role in podocyte injury and proteinuria. Treatment with adriamycin induced Wnt and activated beta-catenin in mouse podocytes. Overexpression of Wnt1 in vivo activated glomerular beta-catenin and aggravated albuminuria and adriamycin-induced suppression of nephrin expression, whereas blockade of Wnt signaling with Dickkopf-1 ameliorated podocyte lesions. Podocyte-specific knockout of beta-catenin protected against development of albuminuria after injury. Moreover, pharmacologic activation of beta-catenin induced albuminuria in wild-type mice but not in beta-catenin-knockout littermates. In human proteinuric kidney diseases such as diabetic nephropathy and focal segmental glomerulosclerosis, we observed upregulation of Wnt1 and active beta-catenin in podocytes. Ectopic expression of either Wnt1 or stabilized beta-catenin in vitro induced the transcription factor Snail and suppressed nephrin expression, leading to podocyte dysfunction. These results suggest that targeting hyperactive Wnt/beta-catenin signaling may represent a novel therapeutic strategy for proteinuric kidney diseases.

A rare case of perianal apocrine adenocarcinoma.

Apocrine adenocarcinoma is a rare primary cutaneous malignancy that arises from areas with high apocrine gland density, most frequently described in the axilla. There have only been three previously reported cases of apocrine adenocarcinoma in the anal/perianal region. A 72-year-old female presented for evaluation of a perianal lesion with persistent drainage that she had noticed for over a year. The patient proceeded with surgical excision of the perianal nodule. Diagnosis was made based on pathology demonstrating areas of mixed solid and trabecular areas with large nuclei and many prominent mitotic figures, which stained positive for periodic acid-Schiff-diastase, cytokeratin 7 and gross cystic disease fluid protein 15. We are reporting just the fourth such case of apocrine adenocarcinoma in the anal/perianal region. It is important to consider apocrine adenocarcinoma in our differential, because though apocrine adenocarcinoma has a benign clinical presentation, it can have a high incidence of lymph invasion on presentation.

Antineutrophil cytoplasmic antibody-positive pauci-immune glomerulonephritis associated with mantle cell lymphoma.

Renal involvement in non-Hodgkin lymphoma, especially mantle cell lymphoma (MCL) is rare. A 77-year-old man presented with acute kidney injury (AKI), which rapidly progressed to dialysis dependence. Kidney biopsy revealed patchy B-cell lymphocytic aggregates in the interstitium, which were positive for cyclin D1, consistent with atypical CD5-negative MCL as confirmed by the detection of translocation t(11;14) by FISH. Crescents were noted in 3 of 26 glomeruli; while PR-3 antineutrophil cytoplasmic antibody (ANCA) positivity and negative immunofluorescence suggested an additional pauci-immune (rapidly progressive) glomerulonephritis pattern of injury. Patient received chemotherapy (cyclophosphamide, vincristine, and prednisone), which improved his renal function and allowed for discontinuation of hemodialysis. However, he died from pulmonary hemorrhage 8 months after initial presentation. This is the first reported case of a patient with coexistence of renal MCL infiltration and ANCA-positive pauci-immune glomerulonephritis.

Renal biopsy findings predicting outcome in scleroderma renal crisis.

Scleroderma renal crisis is irreversible in some patients despite aggressive treatment. This study was designed to identify pathologic prognostic features in scleroderma renal crisis. We retrospectively reviewed the pathology and the clinical records of 17 patients who underwent kidney biopsies during scleroderma renal crisis (group A, recovered renal function [n = 7]; group B, remained in renal failure or died [n = 10]). Multiple histologic features were assessed semiquantitatively (0-3) or as percentages. C4d staining of peritubular capillaries and small vessels was assessed semiquantitatively (0-3) in patients with scleroderma (n = 11), normotensive (n = 10), and hypertensive (n = 12) nonscleroderma native kidney controls. The percentage of thrombosed vessels (25.1 +/- 21.0 versus 5.6 +/- 12.3, P = .045) and the severity of glomerular ischemic collapse (2.9 +/- 0.3 versus 1.4 +/- 0.8, P = .001) were significantly higher in group B than in group A. Also, group B patients tended to have more severe acute tubular injury and vascular fibrinoid changes. The peritubular capillary C4d score in patients with scleroderma, normotensive controls, and hypertensive controls were 1.1 +/- 0.9, 0.3 +/- 0.7, and 0.3 +/- 0.5, respectively (P = .018, scleroderma versus other controls). Small vessel C4d score was higher in scleroderma compared to normotensive but not hypertensive controls. Within scleroderma samples, a significantly higher peritubular capillary C4d score (1.6 +/- 0.7 versus 0.3 +/- 0.5, P = .024) but not small vessel score was found in group B compared to group A. This tended to be associated with peritubular capillary leukocyte margination. Vascular thrombosis, severe glomerular ischemic collapse, and peritubular capillary C4d deposits in scleroderma renal crisis kidney biopsies correlated with increased risk of failure to recover renal function.

Smad ubiquitination regulatory factor-2 in the fibrotic kidney: regulation, target specificity, and functional implication.

Smad ubiquitination regulatory factor-2 (Smurf2) is an E3 ubiqutin ligase that plays a pivotal role in regulating TGF-beta signaling via selectively targeting key components of the Smad pathway for degradation. In this study, we have investigated the regulation of Smurf2 expression, its target specificity, and the functional implication of its induction in the fibrotic kidney. Immunohistochemical staining revealed that Smurf2 was upregulated specifically in renal tubules of kidney biopsies from patients with various nephropathies. In vitro, Smurf2 mRNA and protein were induced in human proximal tubular epithelial cells (HKC-8) upon TGF-beta1 stimulation. Ectopic expression of Smurf2 was sufficient to reduce the steady-state levels of Smad2, but not Smad1, Smad3, Smad4, and Smad7, in HKC-8 cells. Interestingly, Smurf2 was also able to downregulate the Smad transcriptional corepressors Ski, SnoN, and TG-interacting factor. Inhibition of the proteasomal pathway prevented Smurf2-mediated downregulation of Smad2 and Smad corepressors. Functionally, overexpression of Smurf2 enhanced the transcription of the TGF-beta-responsive promoter and augmented TGF-beta1-mediated E-cadherin suppression, as well as fibronectin and type I collagen induction in HKC-8 cells. These results indicate that Smurf2 specifically targets both positive and negative Smad regulators for destruction in tubular epithelial cells, thereby providing a complex fine-tuning of TGF-beta signaling. It appears that dysregulation of Smurf2 could contribute to an aberrant TGF-beta/Smad signaling in the pathogenesis of kidney fibrosis.

Epithelial-to-mesenchymal transition is a potential pathway leading to podocyte dysfunction and proteinuria.

Podocyte dysfunction plays an essential role in the pathogenesis of proteinuria and glomerulosclerosis. However, the mechanism underlying podocyte dysfunction in many common forms of chronic kidney diseases remains poorly understood. Here we tested the hypothesis that podocytes may undergo epithelial-to-mesenchymal transition after injury. Conditionally immortalized mouse podocytes were incubated with transforming growth factor (TGF)-beta1, a potent fibrogenic cytokine that is up-regulated in the diseased kidney. TGF-beta1 suppressed the slit diaphragm-associated protein P-cadherin, zonula occludens-1, and nephrin, a change consistent with loss of the epithelial feature. Meanwhile, TGF-beta1 induced the expression of the intermediate filament protein desmin and interstitial matrix components fibronectin and collagen I. Furthermore, TGF-beta1 promoted the expression and secretion of matrix metalloproteinase-9 by podocytes. Functionally, TGF-beta1 increased albumin permeability across podocyte monolayers, as demonstrated by a paracellular albumin influx assay. The expression of Snail, a key transcriptional factor that has been implicated in initiating epithelial-to-mesenchymal transition, was induced by TGF-beta1, and ectopic expression of Snail suppressed P-cadherin and nephrin in podocytes. In vivo, in addition to loss of nephrin and zonula occludens-1, mesenchymal markers such as desmin, fibroblast-specific protein-1, and matrix metalloproteinase-9 could be observed in glomerular podocytes of diabetic nephropathy. These results suggest that podocyte dedifferentiation and mesenchymal transition could be a potential pathway leading to their dysfunction, thereby playing a role in the genesis of proteinuria.