Role of SIRT1/FoxO3α signaling pathway in berberine pretreatment-induced reduction of hypoxia/reoxygenation-caused injury to hepatic parenchymal cells

Objective To evaluate the role of silent information regulator factor 2-related enzyme 1(SIRT1)/Forkhead Box O3(FoxO3a)signaling pathway in berberine pretreatment-induced reduction of hypoxia/reoxygenation(H/R)-caused injury to hepatic parenchymal cells. Methods Hepatic parenchymal cells obtained from AML12 mice were cultured and seeded in 6-well plates(2 ml/well)and in 96-well plates(200 μl/well)at the density of 1×106 cells/ml.The cells were divided into 4 groups(n=36 each)using a random number table: control group(group C), group H/R, berberine pretreatment group(group BP)and SIRT1-siRNA group(group SS). The cells were cultured in normal culture atmosphere(5% CO2-21% O2-74% N2)in group C. In H/R, BP and SS groups, the cells were exposed to hypoxic air(5% CO2-1% O2-94% N2)for 12 h, followed by 6 h reoxygenation in normal culture atmosphere(5% CO2-21% O2-74% N2). In group SS, small interference RNA targeting SIRT1(SIRT1-siRNA)was added to the culture medium at 24 h prior to hypoxia.Berberine(final concentration 5 μmol/L)was added at 2 h prior to hypoxia in BP and SS groups.At the end of reoxygenation, the cell viability was measured by methyl thiazolyl tetrazolium assay, the malondialdehyde(MDA)content and superoxide dismutase(SOD)activity were determined using enzyme-linked immunosorbent assay, cell apoptosis was detected by flow cytometry, the expression of SIRT1 and FoxO3α was detected by Western blot, and the acetylation of FoxO3α was measured by using immunoprecipitation.Apoptotic rate was calculated. Results Compared with group C, the cell viability was significantly decreased, the MDA content was increased, the SOD activity was decreased, apoptotic rate was increased, the expression of SIRT1 and ratio of FoxO3α expression in nucleus/in cytoplasma were increased, and the acetylation of FoxO3α in the nucleus was increased in H/R, BP and SS groups(P<0.05). Compared with group H/R, the cell viability was significantly increased, the MDA content was decreased, the SOD activity was increased, apoptotic rate was decreased, the expression of SIRT1 and ratio of FoxO3α expression in nucleus/in cytoplasma were increased, and the acetylation of FoxO3α in the nucleus was increased in group BP(P<0.05). Compared with group BP, the cell viability was significantly decreased, the MDA content was increased, the SOD activity was decreased, apoptotic rate was increased, the expression of SIRT1 and ratio of FoxO3α expression in nucleus/in cytoplasma were decreased, and the acetylation of FoxO3α in the nucleus was decreased in group SS(P<0.05). Conclusion The mechanism by which berberine pretreatment attenuates H/R-caused injury to hepatic parenchymal cells is related to promotion of SIRT1 expression in cells and inhibition of FoxO3α acetylation in the nucleus. Key words: Berberine; Liver; Reperfusion injury; Sirtuins; Apoptosis