ABSTRACT
Objective:To investigate the effect of autophagy inhibitor 3-methyladenine (3-MA) on uric acid (UA)-induced apoptosis of renal tubular epithelial cells.Methods:(1) Totally 24 SD rats were randomly divided into 4 groups: control group, treatment with 3-MA group, hyperuricemic nephropathy (HN) group, and HN+3-MA group, with 6 rats in each group. According to the body weight of the rats, adenine (100 mg/kg) and potassium oxonate (1 500 mg/kg) were mixed with distilled water to make a suspension, and the rats were given intragastrically once daily for consecutive 21 days to establish HN rat model. The control group and the 3-MA treatment group were fed an equivalent amount of distilled water. At the same time, the 3-MA treatment group and the HN+3-MA group were intraperitoneally injected with 3-MA (15 mg/kg), and the control group and HN group were intraperitoneally injected with an equal volume of saline once daily for 21 consecutive days. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) was used to observe renal cell apoptosis. Western blotting was used to detect the expression levels of cleaved caspase-3 and Bax, and immunofluorescence staining was used to detect the expression and localization of cleaved caspase-3 in renal tissue. (2) Human renal tubular epithelial cells (HK-2) were stimulated with UA (800 μmol/L), and cells were administrated with different concentrations of 3-MA or Beclin-1 small interfering RNA (siRNA). The apoptosis of renal tubular epithelial cells was detected by Western blotting and immunofluorescence staining.Results:Compared with the normal rats, the apoptosis of renal tubular epithelial cells in the HN group was significantly increased ( P<0.01), and the expression levels of cleaved caspase-3 and Bax were significantly up-regulated (both P<0.05). Compared with the HN group, the apoptosis of renal tubular epithelial cells in the HN+3-MA group was significantly decreased ( P<0.01). In addition, high level of uric acid could significantly increase the levels of apoptosis associated proteins in HK-2 cells (all P<0.05), and using different concentrations of 3-MA or transfecting with Beclin-1 siRNA could significantly reduce the expression of cleaved caspase-3 and Bax (all P<0.05). Conclusion:Autophagy plays an important role in uric acid-induced apoptosis of renal tubular epithelial cells. Inhibiting the excessive activation of autophagy may be a new strategy to prevent the progression of HN.
ABSTRACT
Objective:To investigate the role and mechanism of (histone deacetylase 6, HDAC6) in the epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells and the activation of renal interstitial fibroblasts.Methods:Human renal tubular epithelial cells (HK-2) and rat renal interstitial fibroblast (NRK-49F) were cultured in vitro, and divided into 4 groups: control group, Tubastatin A (TA) group (treated with 10 μmol/L HDAC6 inhibitor TA for 36 h), transforming growth factor-β1 (TGF-β1) group (10 ng/ml TGF-β1 for 36 h), and TGF-β1+TA group (treated with 10 ng/ml TGF-β1 and 10 μmol/L TA for 36 h). The expression levels of fibronectin, α-smooth muscle actin (α-SMA), collagen I, E-cadherin, HDAC6, acetyl histone H3, histone H3, acetyl α-tubulin, α-tubulin, TGF-β receptor (TGF-βR) 1, p-Smad3, Smad3, connective tissue growth factor (CTGF), epidermal growth factor receptor (EGFR) and p-EGFR in HK-2 and NRK-49F cell samples were detected by Western blotting, and quantitative analysis was performed according to gray level. Results:(1) In HK-2 cells stimulated by TGF-β1, TA decreased the expression of fibronectin, α-SMA, collagen I, and increased the expression of epithelial cell marker E-cadherin. Meanwhile, TA decreased the expression of HDAC6 and increased the expression levels of acetyl histone H3 and acetyl α-tubulin (all P<0.05). (2) Compared with the TGF-β1 group, the expressions of TGF-βR1, p-Smad3, CTGF and p-EGFR in TGF-β1+TA group were decreased (all P<0.05), while the total protein levels of Smad3 and EGFR were not significantly different (both P>0.05). (3) In NRK-49F cells stimulated by TGF-β1, TA decreased the expressions of fibronectin, α-SMA, collagen I, TGF-βR1 and p-Smad3 (all P<0.05). Conclusions:Blockade of HDAC6 by TA may inhibit the EMT of renal tubular epithelial cells and the activation of renal interstitial fibroblasts via regulating multiple signaling pathways including TGF-β/Smad3, CTGF and EGFR.