miR-155 facilitates calcium oxalate crystal-induced HK-2 cell injury via targeting PI3K associated autophagy.

Nephrolithiasis is one of the most common and highly recurrent diseases worldwide. Accumulating evidence revealed the elevated miR-155 levels both in serum and urine of nephrolithiasis patients. The aim of our research was to explore the role of miR-155 in CaOx-induced apoptosis in HK-2 cells. The expression levels of miR-155 in serum and renal tissues were quantified in 20 patients with nephrolithiasis using qRT-PCR assay. ELISA was performed to determine urinary levels of interleukin (IL)-1ß, IL-6 and tumor necrosis factor-alpha (TNF-α). Renal tubular cell model of CaOx nephrolithiasis was established to investigate the role and molelular mechanism of miR-155. Cell viability and apoptosis were assessed by MTT and flow cytometry, respectively. Immunofluoresent staining of LC3 autophagosome and western blotting were performed to evaluate the autophagic activity. Luciferase reporter assay was employed to verify the interaction between miR-155 and PI3KCA/Rheb. PI3K/Akt/mTOR signaling was further examined by western blotting. Serum and renal levels of miR-155 and inflammatory factors were significantly elevated in nephrolithiasis patients than in controls. CaOx treatment caused up-regulation of miR-155 and induced autophagy in renal tubular epithelial cells, while silencing miR-155 or inhibition of autophagy by 3-metheladenine (3-MA) ameliorated CaOx crystal-induced cell injury. PI3KCA and Rheb was identified as downstream targets of miR-155. Moreover, miR-155 activates autophagy and promotes cell injury through repressing PI3K/Akt/mTOR signaling pathway. Taken together, these findings demonstrated that miR-155 facilitates CaOx crystal-induced renal tubular epithelial cell injury via PI3K/Akt/mTOR-mediated autophagy, providing therapeutic targets for ameliorating cellular damage by CaOx crystals.

Inhibition of miR-155 Ameliorates Acute Kidney Injury by Apoptosis Involving the Regulation on TCF4/Wnt/ß-Catenin Pathway.

BACKGROUND: Acute kidney injury (AKI) is a complex clinical disorder with sudden decay in renal function. Ischemia-reperfusion injury (IRI) has been regarded as the main etiology for the occurrence of AKI. MicroRNAs have been consistently shown to be involved AKI. OBJECTIVES: We aimed to investigate the role of miR-155 in AKI and its underlying mechanism. METHODS: Ischemia-reperfusion (I/R)-induced AKI rat model and hypoxia-reoxygeneration (H/R)-induced NRK-52E cell model were established. The concentrations of serum creatinine and blood urea nitrogen were measured to evaluate renal function. Hematoxylin and eosin staining and TUNEL assay were performed to assess the severity of kidney injury. Additionally, quantitative real-time-PCR and western blot analysis were subjected to determine the expression of miR-155, TCF4, and apoptosis-related proteins, respectively. Moreover, cell proliferation and apoptosis were evaluated by Cell Counting Kit-8, bromodeoxyuridine, and flow cytometry analyses, respectively. Luciferase reporter assay was used to validate the direct targeting of TCF4 with miR-155. The protein levels of TCF4 and its downstream proteins in cells were measured by western blot. RESULTS: The expression level of miR-155 was upregulated in both I/R-induced AKI rat model and H/R-treated NRK-52E cells. Moreover, overexpression of miR-155 promoted H/R-induced NRK-52E cells apoptosis and suppressed cell proliferation, while inhibition of miR-155 expression exerted opposite effects. Additionally, TCF4 was identified as a target of miR-155, of which expression was downregulated both in vivo and in vitro. Furthermore, the activity of Wnt/ß-catenin signaling pathway was promoted following overexpression of TCF4 in NRK-52E cells, and this effect was attenuated by the increasing miR-155 expression. CONCLUSION: We demonstrated that miR-155 exacerbated AKI involving the targeting and regulation of TCF4/Wnt/ß-catenin signaling pathway, indicating a novel regulatory network and elucidating a potential target for IRI-induced AKI treatment.