Leptin increases the proliferation of human HaCaT keratinocytes through activation of STAT3 pathway

Objective To estimate the biological effects of leptin on human HaCaT keratinocytes and explore their molecular mechanisms.Methods Cell counting kit-8 (CCK-8) was used to evaluate the proliferation of cultured HaCaT cells treated with different concentrations of leptin for 24 and 48 hours.Some HaCaT cells were classified into four groups to remain untreated,be treated with leptin (100 μg/L) and piceatannol (a specific inhibitor of STAT3 phosphorylation) alone or in combination for 24 hours,respectively,followed by the evaluation of cell proliferation using CCK-8 kit.Flow cytometry was performed to assess cell cycle of HaCaT cells treated with leptin of 100 μg/L,Western blot to determine the phosphorylation level of Erk1/2 and STAT3 in HaCaT cells treated with leptin of 100 μg/L for different durations.Statistical analysis was done by Student's t-test for unpaired data using GraphPad Prism 5 software.Results The proliferation of HaCaT cells was accelerated to different degrees after treatment with leptin of 50 and 100 μg/L for 24 and 48 hours,and the accelerating effect was in a dose-dependent manner within 24 hours (r =0.9989,P ＜ 0.05).Piceatannol apparently inhibited the promotive effect of leptin on the proliferation of HaCaT cells.There was an obvious elevation in the percentage of cells at S phase ((57.70 ± 5.88)％ vs.(42.50 ± 7.55)％,P ＞ 0.05),but a significant decrease in that at G0/G1 phase ((39.70 ± 1.57)％ vs.(45.20 ± 1.44)％,P ＜ 0.05),with a significant increase in proliferation index (0.603 ±0.0157 vs.0.564 ± 0.0144,P ＜ 0.05) in HaCaT cells treated with leptin of 100 μg/L for 24 hours compared with the untreated controls.Western blot showed that leptin of 100 μg/L markedly enhanced the phosphorylation level of STAT3 in HaCaT cells.Conclusion Leptin may upregulate the proliferation of HaCaT cells through activation of STAT3 pathway.