Effects of sirolimus on autophagy in HaCaT human keratinocytes irradiated by ultraviolet B

Abstract

Objective To investigate whether sirolimus increases the autophagy level in HaCaT human keratinocytes induced by ultraviolet B (UVB) irradiation.Methods HaCaT cells were irradiated by UVB of O,25 and 50 mJ/cm2 respectively.After additional 6-hour culture,monodansylcadaverin (MDC) staining was canied out to detect autophagosomes in HaCaT cells.Then,some HaCaT cells were classified into 4 groups to be irradiated with UVB (25 and 50 mJ/cm2 respectively) alone or followed by sirolimus (10 nmol/L) treatment,those remaining untreated served as the blank control group,and those treated by dimethyl sulfoxide (DMSO)served as the DMSO group.The level of autophagy in these groups was determined by monodansylcadaverin (MDC) staining.Results Autophagy was detected in HaCaT cells after UVB irradiation.Significant differences were observed in the percentage of autophagosome-positive cells irradiated by UVB at 0,25 and 50mJ/cm2 (1.07％± 1.85％ vs.9.37％± 1.14％ vs.16.29％± 3.03％,F = 37.34,P ＜ 0.01).The percentage of autophagosome-positive cells was 0.56％± 0.79％,1.61％± 2.27％,10.00％ ± 0.47％,21.18％± 3.03％,15.82％ ± 4.13％ and 29.45％ ± 1.24％ in the blank control group,DMSO group,25 mJ/cm2 UVB group,25mJ/cm2 UVB + sirolimus group,50 mJ/cm2 UVB group,50 mJ/cm2 UVB + sirolimus group,respectively (F =45.23,P ＜ 0.01). Sirolimus significantly elevated the level of autophagy in HaCaT cells irradiated by UVB of 50 and 25 mJ/cm2.Conclusions Autophagosomes are observed in HaCaT cells irradiated by UVB.And sirolimus may upregulate the autophagy level in UVB-induced HaCaT cells. Key words: Keratinocytes; Autophagy; Sirolimus; Ultraviolet rays