High Fat Diet Induces Kidney Injury via Stimulating Wnt/ß-Catenin Signaling.

High fat diet could cause kidney injury, and the underlying mechanism remains incompletely understood. In this study, we investigated the role of Wnt signaling in this process. Mice were fed with high-fat diet in vivo, and podocytes were stimulated with palmitate in vitro. In mice fed with high-fat diet, renal function was impaired, accompanied by induction of various proinflammatory cytokines and proteinuria. Renal expression of Wnt ligands was also significantly induced, with Wnt1 and Wnt3a being the most pronounced, in high-fat diet mice, compared with normal diet controls. Intervention with ICG-001, a small molecule Wnt/ß-catenin inhibitor, improved renal function, inhibited proinflammatory cytokines expression, reduced proteinuria and alleviated podocyte injury. In palmitate-treated podocytes, intracellular lipid deposition was increased, Wnt1 and Wnt3a expression was up-regulated, which was accompanied by an increased proinflammatory cytokines expression and podocyte injury. These lesions caused by palmitate were largely alleviated by ICG-001. Furthermore, ICG-001 also restored the expression of phosphorylated AMPK repressed by palmitate in podocytes or a high-fat diet in mice. These studies suggest that Wnt/ß-catenin signaling is involved in the pathogenesis of high-fat diet-induced kidney injury. Targeting this signaling may be a potential therapeutic strategy for alleviating obesity-related nephropathy.

CXCR4 induces podocyte injury and proteinuria by activating ß-catenin signaling.

Background: C-X-C chemokine receptor type 4 (CXCR4) plays a crucial role in mediating podocyte dysfunction, proteinuria and glomerulosclerosis. However, the underlying mechanism remains poorly understood. Here we studied the role of ß-catenin in mediating CXCR4-triggered podocyte injury. Methods: Mouse models of proteinuric kidney diseases were used to assess CXCR4 and ß-catenin expression. We utilized cultured podocytes and glomeruli to delineate the signal pathways involved. Conditional knockout mice with podocyte-specific deletion of CXCR4 were generated and used to corroborate a role of CXCR4/ß-catenin in podocyte injury and proteinuria. Results: Both CXCR4 and ß-catenin were induced and colocalized in the glomerular podocytes in several models of proteinuric kidney diseases. Activation of CXCR4 by its ligand SDF-1α stimulated ß-catenin activation but did not affect the expression of Wnt ligands in vitro. Blockade of ß-catenin signaling by ICG-001 preserved podocyte signature proteins and inhibited Snail1 and MMP-7 expression in vitro and ex vivo. Mechanistically, activation of CXCR4 by SDF-1α caused the formation of CXCR4/ß-arrestin-1/Src signalosome in podocytes, which led to sequential phosphorylation of Src, EGFR, ERK1/2 and GSK-3ß and ultimately ß-catenin stabilization and activation. Silencing ß-arrestin-1 abolished this cascade of events and inhibited ß-catenin in response to CXCR4 stimulation. Podocyte-specific knockout of CXCR4 in mice abolished ß-catenin activation, preserved podocyte integrity, reduced proteinuria and ameliorated glomerulosclerosis after Adriamycin injury. Conclusion: These results suggest that CXCR4 promotes podocyte dysfunction and proteinuria by assembling CXCR4/ß-arrestin-1/Src signalosome, which triggers a cascade of signal events leading to ß-catenin activation.

Sonic hedgehog selectively promotes lymphangiogenesis after kidney injury through noncanonical pathway.

Kidney fibrosis is associated with an increased lymphangiogenesis, characterized by the formation and expansion of new lymphatic vessels. However, the trigger and underlying mechanism responsible for the growth of lymphatic vessels in diseased kidney remain poorly defined. Here, we report that tubule-derived sonic hedgehog (Shh) ligand is a novel lymphangiogenic factor that plays a crucial role in mediating lymphatic endothelial cell proliferation and expansion. Shh was induced in renal tubular epithelium in various models of fibrotic chronic kidney disease, and this was accompanied by an expansion of lymphatic vessels in adjacent areas. In vitro, Shh selectively promoted the proliferation of human dermal lymphatic endothelial cells (HDLECs) but not human umbilical vein endothelial cells, as assessed by cell counting, MTT assay, and bromodeoxyuridine incorporation. Shh also induced the expression of vascular endothelial growth factor receptor-3, cyclin D1, and proliferating cell nuclear antigen in HDLECs. Shh did not affect the expression of Gli1, the downstream target and readout of canonical hedgehog signaling, but activated ERK-1/2 in HDLECs. Inhibition of Smoothened with small-molecule inhibitor or blockade of ERK-1/2 activation abolished the lymphatic endothelial cell proliferation induced by Shh. In vivo, inhibition of Smoothened also repressed lymphangiogenesis and attenuated renal fibrosis. This study identifies Shh as a novel mitogen that selectively promotes lymphatic, but not vascular, endothelial cell proliferation and suggests that tubule-derived Shh plays an essential role in mediating lymphangiogenesis after kidney injury.

Association of miR-100 expression with clinicopathological features and prognosis of patients with lung cancer.

The expression of microRNA (miR)-100 in non-small cell lung cancer (NSCLC) and its association with clinicopathological features and poor prognosis were investigated. A total of 283 patients with NSCLC were enrolled in The First Hospital of Jiaxing from February 2013 to April 2015. Total RNA was extracted from cancer tissues and corresponding adjacent normal tissues. The expression of miR-100 was detected by RT-qPCR. Association between the expression level of miR-100 with clinicopathological features and prognosis of NSCLC were analyzed. The expression level of miR-100 in NSCLC tissues was lower than that in the normal tissues (P<0.05). According to the median expression level of miR-100 in cancer tissue, patients were divided into the high expression and low expression groups. Cross-tabulation analysis showed that the expression level of miR-100 was significantly associated with patients' age, TNM stage, metastasis and histological type (P<0.05), but not with sex (P>0.05). The proportion of patients with low miR-100 expression was higher in patients who died than in those who survived (P<0.05). Univariate prognostic analysis showed that miR-100 expression, age, TNM staging, and metastasis may be risk factors for poor prognosis in patients with NSCLC. Cox multivariate regression analysis showed that the downregulated miR-100 expression, advanced TNM stage, and metastasis were independent risk factors for poor prognosis of NSCLC. The relatively low expression level of miR-100 in NSCLC is associated with poor prognosis of patients. Therefore, miR-100 shows potential as a prognostic marker for NSCLC.

Fibroblast-Specific ß-Catenin Signaling Dictates the Outcome of AKI.

AKI is a devastating condition with high morbidity and mortality. The pathologic features of AKI are characterized by tubular injury, inflammation, and vascular impairment. Whether fibroblasts in the renal interstitium have a role in the pathogenesis of AKI is unknown. In this study, we investigated the role of fibroblast-specific ß-catenin signaling in dictating the outcome of AKI, using conditional knockout mice in which ß-catenin was specifically ablated in fibroblasts (Gli1-ß-cat-/-). After ischemia-reperfusion injury (IRI), Gli1-ß-cat-/- mice had lower serum creatinine levels and less morphologic injury than Gli1-ß-cat+/+ littermate controls. Moreover, we detected fewer apoptotic cells, as well as decreased cytochrome C release; reduced expression of Bax, FasL, and p53; and increased phosphorylation of Akt, in the Gli1-ß-cat-/- kidneys. Gli1-ß-cat-/- kidneys also exhibited upregulated expression of proliferating cell nuclear antigen and Ki-67, which are markers of cell proliferation. Furthermore, Gli1-ß-cat-/- kidneys displayed suppressed NF-κB signaling and cytokine expression and reduced infiltration of inflammatory cells. Notably, loss of ß-catenin in fibroblasts induced renal expression of hepatocyte growth factor (HGF) and augmented the tyrosine phosphorylation of c-met receptor after IRI. In vitro, treatment with Wnt ligands or ectopic expression of active ß-catenin inhibited HGF mRNA and protein expression and repressed HGF promoter activity. Collectively, these results suggest that fibroblast-specific ß-catenin signaling can control tubular injury and repair in AKI by modulating HGF expression. Our studies uncover a previously unrecognized role for interstitial fibroblasts in the pathogenesis of AKI.

C-X-C Chemokine Receptor Type 4 Plays a Crucial Role in Mediating Oxidative Stress-Induced Podocyte Injury.

AIMS: Oxidative stress plays a role in mediating podocyte injury and proteinuria. However, the underlying mechanism remains poorly understood. In this study, we investigated the potential role of C-X-C chemokine receptor type 4 (CXCR4), the receptor for stromal cell-derived factor 1α (SDF-1α), in mediating oxidative stress-induced podocyte injury. RESULTS: In mouse model of adriamycin nephropathy (ADR), CXCR4 expression was significantly induced in podocytes as early as 3 days. This was accompanied by an increased upregulation of oxidative stress in podocyte, as demonstrated by malondialdehyde assay, nitrotyrosine staining and secretion of 8-hydroxy-2'-deoxyguanosine in urine, and induction of NOX2 and NOX4, major subunits of NADPH oxidase. CXCR4 was also induced in human kidney biopsies with proteinuric kidney diseases and colocalized with advanced oxidation protein products (AOPPs), an established oxidative stress trigger. Using cultured podocytes and mouse model, we found that AOPPs induced significant loss of podocyte marker Wilms tumor 1 (WT1), nephrin, and podocalyxin, accompanied by upregulation of desmin both in vitro and in vivo. Furthermore, AOPPs worsened proteinuria and aggravated glomerulosclerosis in ADR. These effects were associated with marked activation of SDF-1α/CXCR4 axis in podocytes. Administration of AMD3100, a specific inhibitor of CXCR4, reduced proteinuria and ameliorated podocyte dysfunction and renal fibrosis triggered by AOPPs in mice. In glomerular miniorgan culture, AOPPs also induced CXCR4 expression and downregulated nephrin and WT1. Innovation and Conclusion: These results suggest that chemokine receptor CXCR4 plays a crucial role in mediating oxidative stress-induced podocyte injury, proteinuria, and renal fibrosis. CXCR4 could be a new target for mitigating podocyte injury, proteinuria, and glomerular sclerosis in proteinuric chronic kidney disease. Antioxid. Redox Signal. 27, 345-362.

Klotho Ameliorates Kidney Injury and Fibrosis and Normalizes Blood Pressure by Targeting the Renin-Angiotensin System.

Loss of Klotho and activation of the renin-angiotensin system (RAS) are common pathological findings in chronic kidney diseases. However, whether these two events are intricately connected is poorly understood. We hypothesized that Klotho might protect kidneys by targeted inhibition of RAS activation in diseased kidneys. To test this hypothesis, mouse models of remnant kidney, as well as adriamycin nephropathy and unilateral ureteral obstruction, were utilized. At 6 weeks after 5/6 nephrectomy, kidney injury was evident, characterized by elevated albuminuria and serum creatinine levels, and excessive deposition of interstitial matrix proteins. These lesions were accompanied by loss of renal Klotho expression, up-regulation of RAS components, and development of hypertension. In vivo expression of exogenous Klotho through hydrodynamic-based gene delivery abolished the induction of multiple RAS proteins, including angiotensinogen, renin, angiotensin-converting enzyme, and angiotensin II type 1 receptor, and normalized blood pressure. Klotho also inhibited ß-catenin activation and ameliorated renal fibrotic lesions. Similar results were obtained in mouse models of adriamycin and obstructive nephropathy. In cultured kidney tubular epithelial cells, Klotho dose-dependently blocked Wnt1-triggered RAS activation. Taken together, these results demonstrate that Klotho exerts its renal protection by targeted inhibition of RAS, a pathogenic pathway known to play a key role in the evolution and progression of hypertension and chronic kidney disorders.