Macrophages Regulate Unilateral Ureteral Obstruction-Induced Renal Lymphangiogenesis through C-C Motif Chemokine Receptor 2-Dependent Phosphatidylinositol 3-Kinase-AKT-Mechanistic Target of Rapamycin Signaling and Hypoxia-Inducible Factor-1α/Vascular Endothelial Growth Factor-C Expression.

Lymphangiogenesis occurs during renal fibrosis in patients with chronic kidney diseases and vascular endothelial growth factor (VEGF)-C is required for the formation of lymphatic vessels; however, the underlying mechanisms remain unclear. We demonstrate that macrophages can regulate unilateral ureteral obstruction (UUO)-induced renal lymphangiogenesis by expressing high levels of VEGF-C by C-C motif chemokine receptor 2 (CCR2)-mediated signaling. Mice deficient in Ccr2 manifested repressed lymphangiogenesis along with attenuated renal injury and fibrosis after UUO induction. The infiltrated macrophages after UUO induction generated a microenvironment in favor of lymphangiogenesis, which likely depended on Ccr2 expression. Mechanistic studies revealed that CCR2 is required for macrophages to activate phosphatidylinositol 3-kinase (PI3K)-AKT-mechanistic target of rapamycin (mTOR) signaling in response to its ligand monocyte chemoattractant protein 1 stimulation, whereas hypoxia-inducible factor (HIF)-1α is downstream of PI3K-AKT-mTOR signaling. HIF-1α directly bound to the VEGF-C promoter to drive its expression to enhance lymphangiogenesis. Collectively, we characterized a novel regulatory network in macrophages, in which CCR2 activates PI3K-AKT-mTOR signaling to mediate HIF-1α expression, which then drives VEGF-C expression to promote lymphangiogenesis.

Erbin interacts with Sema4C and inhibits Sema4C-induced epithelial-mesenchymal transition in HK2 cells.

Erbin, a member of Leucine-rich repeat and PDZ-containing protein family, was found to inhibit TGF-ß-induced epithelial-mesenchymal transition (EMT) in our previous study. However, the mechanism of Erbin in regulating EMT is unclear. Semaphorin protein Sema4C, with PDZ binding site at C-terminal has been recognized as a positive regulator of EMT. Here, we aimed to examine the interaction between Erbin and Sema4C. HK2 cells were treated with TGF-ß1, or transfected with Erbin and (or) Sema4C. Interaction of Erbin and Sema4C was identified by immunoprecipitation. RT-PCR was used to detect the expression of Erbin and Sema4C at mRNA level after transfection. The expression levels of Erbin, Sema4C, and markers of EMT were measured by using Western blotting or ELISA. After HK2 cells were stimulated with 10 ng/mL TGF-ß1 for 72 h, the protein expression levels of Erbin and Sema4C were both up-regulated, and immunoprecipitation results showed Erbin interacted with Sema4C in HK2 cells both at endogenous and exogenous levels. Furthermore, overexpression of Sema4C suppressed E-cadherin, induced vimentin and promoted fibronectin secretion, indicating Sema4C promotes the process of EMT. However, HK2 cells overexpressing Erbin were resistant to Sema4C-induced EMT. In contrast, Erbin specific siRNA promoted EMT induced by Sema4C. Taken together, these results suggest that Erbin can interact with Sema4C, and co-expression of Erbin blocks the process of Sema4C-induced EMT.

Interleukin-7 Is Associated with Clinical and Pathological Activities in Immunoglobulin A Nephropathy and Protects the Renal Proximal Tubule Epithelium from Cellular Fibrosis.

OBJECTIVE: Diagnosis of immunoglobulin A nephropathy (IgAN) requires the evaluation of renal biopsy specimens. However, renal biopsy is an invasive procedure and is not frequently performed for various reasons. Thus, recognized noninvasive biomarkers for predicting IgAN progression are urgently needed. METHODS: In the present study, we included 86 IgAN patients with renal biopsy from June 2015 to May 2016 and had their plasma interleukin-7 (IL-7) level measured with ELISA. The association between the plasma IL-7 level and clinico-pathological characteristics was analyzed. Immunohistochemical staining was used to assay the in situ expression of IL-7 in vivo. Western blotting was performed to examine the production of extracellular matrix, p-mTOR and the markers of autophagy under the treatment of IL-7 after TGF-ß1 stimulation in renal tubular epithelial cells. RESULTS: IL-7 was significantly decreased in patients with IgAN compared to healthy subjects (2.3077 vs. 8.6294 pg/mL, P<0.0001). There was a significant difference in the plasma IL-7 level between tubular atrophy/interstitial fibrosis T0 and T2 classes (P=0.0064). A lower plasma IL-7 value in patients at the time of biopsy indicated a poor renal outcome. In addition, IL-7 was over-expressed in renal tubular epithelial cells and significantly attenuated transforming growth factor ßl-induced extracellular matrix production by suppression of cellular autophagy via activation of mTOR1 signaling. CONCLUSION: These results suggested that IL-7 might be a noninvasive biomarker for predicating IgAN. It protected renal proximal tubular epithelial cells from cellular fibrosis by inhibiting autophagy via mTORl signaling.

Soluble Urokinase Receptor Levels Are Correlated with Focal Segmental Glomerulosclerosis Lesions in IgA Nephropathy: A Cohort Study from China.

BACKGROUND: Soluble urokinase receptor (suPAR) may be involved in the pathological mechanisms of focal segmental glomerulosclerosis (FSGS) changes. However, it remains unclear whether suPAR is correlated with the FSGS-like lesions in IgA nephropathy (IgAN). METHODS: We measured the plasma suPAR levels in 138 patients with IgAN, and then their clinical and pathological relationships were analyzed. RESULTS: We found that the plasma suPAR levels were significantly correlated with age and renal function by both univariate and multivariate analysis in our IgAN patient cohort. Female had higher plasma suPAR levels and no significant correlation was observed between plasma suPAR levels and 24-h urine protein and highly sensitive C-reaction protein with multivariate analysis. In our cohort, sixty of these IgAN patients could be diagnosed with a type of FSGS lesions. The plasma suPAR levels were higher in the IgAN patients with FSGS lesions than in the IgAN patients without FSGS lesions by univariate (P < 0.0001) and multivariate (P < 0.001) analysis adjusting for other predictor variables, which might be helpful to differentiate the pathological changes with and without FSGS lesions. And the optimal cutoff value was 1806 pg/ml in this study. The plasma suPAR concentrations were also associated with the degree of tubular atrophy/interstitial fibrosis in both univariate and multivariate analysis. In multivariate analysis, the plasma suPAR levels were correlated with the percentage of crescents, not global sclerosis and arterial lesions. CONCLUSIONS: Our study suggested that the plasma suPAR levels were associated with age, gender, renal function, the degree of tubular atrophy/interstitial fibrosis and the percentage of crescent formation. The plasma suPAR might be a potential predictor for the presence of FSGS pathological lesions in Chinese patients with IgAN.