Protection of tubular epithelial cells during renal injury via post-transcriptional control of BMP7

Cross-talk between microRNA-let7c and transforming growth factor-β2 during epithelial-to-mesenchymal transition of retinal pigment epithelial cells

AIM

To explore the roles of microRNA-let7c (miR-let7c) and transforming growth factor-β2 (TGF-β2) and cellular signaling during epithelial-to-mesenchymal transition (EMT) of retinal pigment epithelial cells.

METHODS

Retinal pigment epithelial (ARPE-19) cells were cultured with no serum for 12h, and then with recombinant human TGF-β2 for different lengths of time. ARPE-19 cells were transfected with 1×10⁶ TU/mL miR-let7c mimcs (miR-let7cM), miR-let7c mimcs negative control (miR-let7cMNC) and miR-let7c inhibitor (miR-let7cI) using the transfection reagent. The expression of keratin-18, vimentin, N-cadherin, IKB alpha, p65 were detected by Western blot, quantitative polymerase chain reaction and immunofluorescence.

RESULTS

The expression of miR-let7c was dramatically reduced and the nuclear factor-kappa B (NF-κB) signaling pathway was activated after induction by TGF-β2 (P<0.05). In turn, overexpressed miR-let7c significantly inhibited TGF-β2-induced EMT (P<0.05). However, miR-let7c was unable to inhibit TGF-β2-induced EMT when the NF-κB signaling pathway was inhibited by BAY11-7082 (P<0.01).

CONCLUSION

The miR-let7c regulates TGF-β2-induced EMT through the NF-κB signaling pathway in ARPE-19 cells.

Emerging role of miRNAs in renal fibrosis

As one type of the most common endogenous short noncoding RNAs (ncRNAs), microRNAs (miRNAs) act as posttranscriptional regulators of gene expression and have great potential biological functions in the physiological and pathological processes of various diseases. The role of miRNAs in renal fibrosis has also attracted great attention in the previous 20 years, and new therapeutic strategies targeting miRNAs appear to be promising. Some researchers have previously reviewed the roles of miRNA in renal fibrosis disease, but numerous studies have emerged over the recent 5 years. It is necessary to update and summarize research progress in miRNAs in renal fibrosis. Thus, in this review, we summarize progress in miRNA-mediated renal fibrosis over the last 5 years and evaluate the biological functions of some miRNAs in different stages of renal fibrosis. Furthermore, we also expound the recent clinical applications of these miRNAs to provide new insights into the treatment of renal fibrosis disease.

Renal Inflammation and Fibrosis: A Double-edged Sword

Renal tissue injury initiates inflammatory and fibrotic processes that occur to promote regeneration and repair. After renal injury, damaged tissue releases cytokines and chemokines, which stimulate activation and infiltration of inflammatory cells to the kidney. Normal tissue repair processes occur simultaneously with activation of myofibroblasts, collagen deposition, and wound healing responses; however, prolonged activation of pro-inflammatory and pro-fibrotic cell types causes excess extracellular matrix deposition. This review focuses on the physiological and pathophysiological roles of specialized cell types, cytokines/chemokines, and growth factors, and their implications in recovery or exacerbation of acute kidney injury.

Kidney microRNA profile in pregnant mice reveals molecular insights into kidney adaptation to pregnancy: A pilot study

The maternal kidneys undergo numerous physiological changes during pregnancy to maintain a healthy pregnancy for mother and child. Over the past decade, interest in microRNAs (miRNAs) for regulating gene expression during pregnancy has expanded. However, the role of miRNAs in modulating kidney physiology during pregnancy has not been extensively investigated. In this study, miRNome profiling suggested differential expression of 163 miRNAs (of 887 miRNAs detected) in the kidneys from pregnant mice at 6.5 days gestation when compared to non-pregnant female mice, of which 35 and 128 miRNAs were potentially down- and up-regulated, respectively. We performed network and pathway analyses of the >1700 potential mRNA targets of the differentially expressed miRNAs using MiRNet, Gene Ontology, Reactome and KEGG analyses. The mRNA targets were over-represented in numerous cellular signalling pathways, including cellular protective responses. In addition, we explored 13 and 29 potential differentially expressed miRNAs to have putative binding sites in the Slc13a1 and Slc26a1 sulfate transporter mRNAs, respectively, and that decreased levels of mir-466k may potentially explain the increased expression of these sulfate transporters in early mouse gestation. Collectively, this study suggests altered expression levels of miRNAs during mouse gestation, which provides pilot data for future investigations into the molecular events that modulate kidney adaptsation to pregnancy.

Febuxostat inhibits TGF‑β1‑induced epithelial‑mesenchymal transition via downregulation of USAG‑1 expression in Madin‑Darby canine kidney cells in vitro

Our previous study demonstrated that febuxostat, a xanthine oxidase inhibitor, can alleviate kidney dysfunction and ameliorate renal tubulointerstitial fibrosis in a rat unilateral ureteral obstruction (UUO) model; however, the underlying mechanisms remain unknown. Increasing evidence has revealed that epithelial-mesenchymal transition (EMT) is one of the key mechanisms mediating the progression of renal tubulointerstitial fibrosis in chronic kidney disease (CKD). Uterine sensitization-associated gene-1 (USAG-1), a kidney-specific bone morphogenetic protein antagonist, is involved in the development of numerous types of CKDs. The present study aimed to investigate the role of febuxostat in the process of EMT in Madin-Darby canine kidney (MDCK) cells in vitro. Western blotting, reverse transcription-semiquantitative polymerase chain reaction analysis and immunofluorescence staining were used to evaluate the expression levels of bone morphogenetic protein 7, USAG-1, α-smooth muscle actin (α-SMA) and E-cadherin, respectively. The results demonstrated that the expression of USAG-1 and α-SMA increased, and that of E-cadherin decreased significantly in MDCK cells following treatment with transforming growth factor-β1 (TGF-β1). The application of small interfering RNA-USAG-1 potently inhibited TGF-β1-induced EMT. Subsequently, the effects of febuxostat on TGF-β1-induced EMT was investigated. The results demonstrated that febuxostat downregulated the expression of USAG-1, and reversed TGF-β1-induced EMT in MDCK cells. Furthermore, pretreatment with febuxostat significantly restored the decreased expression levels of phosphorylated Smad1/5/8 induced by TGF-β1 in MDCK cells. The results of the present study suggested that USAG-1 may be involved in the EMT process of MDCK cells induced by TGF-β1, and febuxostat inhibited EMT by activating the Smad1/5/8 signaling pathway via downregulating the expression of USAG-1 in MDCK cells.