[Cordyceps sinensis protects HK2 cells from ischemia-reperfusion injury through Sirt1 pathway]

To investigate the effects of Cordyceps sinensis (CS) on cellular apoptosis and Sirt1 expression in HK2 cells followed by ischemia-reperfusion (I/R).
 Methods: HK2 cells were incubated with different concentrations of CS (10, 20, 40, 80, 160, 320 mg/L) for 24 hours, and the optimal concentration of CS was selected by measuring cell proliferation. The confluent HK2 cells were incubated with 0.01 μmol/L antimycin A for 2 hours to induce ischemia in vitro, and then the reperfusion was achieved by incubating cells with glucose-replete complete growth medium for 24 hours. HK2 cells were divided into 4 groups: a control group, an I/R group, an I/R+CS (160 mg/L) group, and an I/R+CS (160 mg/L)+Sirtinol (25 μmol/L) group. Twenty-four hours later, total RNA and protein were collected. The cell proliferation was evaluated by MTT assay; the mRNA and protein expression of Sirt1 and the cleaved caspase-3 were measured by qRT-PCR and Western blot, respectively. The cellular apoptosis rate was determined by Annexin V-FITC/PI double staining and flow cytometry.
 Results: Certain concentrations (10-160 mg/L) of CS did not show effect on the proliferation of HK2 cells (P>0.05), while 320 mg/L of CS inhibited cell proliferation significantly (P<0.01); compared with the control group, the mRNA and protein expressions of Sirt1 and the cleaved caspase-3 in the I/R group were up-regulated (P<0.01) and the apoptosis rate was extremely high; compared with the I/R group, CS significantly up-regulated Sirt1 mRNA and protein expression (P<0.01) while down-regulated cleaved caspase-3 mRNA and protein levels (P<0.01), and reduced apoptosis rate (P<0.05). The effects of CS were blocked in the presence of sirtinol, an inhibitor of CS.
 Conclusion: CS protects HK2 cells from I/R injury through activation of Sirt1 pathway.