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)-1 beta, IL-6 and tumor necrosis factor-alpha (TNF-alpha). 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.