The Effects And The Preliminary Mechanistic Study Of PM2.5 Treatment Combined With UVB On The Survial Of HaCaT Cells

BackgroundWith the focus on the environmental pollution,atmospheric particulate matter(particulate matter,PM)has become an important indicator of environmental quality monitoring.PM is a complex mixture of tiny particles and droplets composed of acids,organic chemicals,metals,and dust particles.Fine particles refers to the ambient air aerodynamic equivalent diameter less than or equal to 2.5?m particles,also known as PM2.5.The number of particles and the total surface area increase exponentially with the decrease of the diameter of the particles in the environment.This indicates that it is easy to accumulate metal ions,bacterial viruses,organic substances and acidic oxides because of the small particle size and relatively large surface areain,which is more likely to affect human health.It has been reported that exposured to PM2.5 can cause specific dermatitis,exacerbate inflammatory skin diseases such as acne and eczema,and promote skin aging and so on.As a result,PM2.5 is a great risk for human health.Ultraviolet in sunlight,especially UV B,is one of the most common environmental factors that cause skin damage.Keratinocyte is one of the most important part of skin eidermis.It accounts for 90%of eidermal cells,and it is the main target cell of UVB radiation.UVB can cause oxidative stress,DNA damage and apoptosis in keratinocytes,and even skin cancer.The human skin exposured to the external environment is highly suscebtible to the combined effects of the two environental injury factors.The purpose of this study is to explore the initial effect of PM2.5 combined with UVB on the human keratino cytes HaCaT,and to provide evidence for further clarifying the mechanism of two factors acting on HaCaT cells.Methods?The PM2.5 in the air was collected and the mental ingredients were analysed by ICP-MS.?The cells were divided into four groups:negetive control group(group NC),PM2.5 treatment group with the concentration of IC50(group PM2.5),UVB irradiation group with the dose of 30mJ/cm2(UVB group),PM2.5 treatment combined with UVB group(combined treatment group).The effects of different treatments on cell viability were measured by MTT assay.?The flow cytometry was used to detect the changes of the apoptosis rate and the cell cycle arrest of different treatments on HaCaT cells.?The expressions of PARP and LC3 protein were detected by Western blot.?Expression of mRNA14-3-3? was detected by qPCR..Results?The metal components in PM2.5 samples had Ca,Zn,Ba,Al,,Cu,Pb,etc.? After the treatment of PM2.5 on HaCaT cells,we conclued that the 50%concentra tion of inhibition(IC50)is about 300 ?g/ml.Among different groups,the inhibitory effect on cell viability increased significantly(P<0.001),the viability of the combined group was the lowest(P<0.001).?Flow cytometry analysis showed that compared with the group NC,the apoptosis rate of PM2.5(P<0.01),UVB(P<0.01)and the combined treatment group(P<0.01)increased,but the apoptosis rate of the combined treatment group was higher than group of PM2.5(P<0.05),lower than the group of UVB(P<0.01).Compared with group NC,the proportion of S phase cells increased in group UVB(P<0.01),and the proportion of G2/M phase cells increased in combined treatment group(P<0.05).?Western blot showed that the level of LC3-? and PARP in another three groups was higher than the NC group,PARP in combined treatment group was lower than that in the UVB group,LC3-? increased compared with PM2.5 and UVB group.The expressions of p-Cdc2,p-Chkl and 14-3-3? were higher than those in NC group,and the highest in UVB treatment group.? The expression of mRNA 14-3-3? in group PM2.5,UVB and combined treatment was higher than the group NC,and the combined treatment group was high in the group of UVB.ConclusionPM2.5 can increase the damage of UVB on HaCaT cells,the main way may be through increased autophagy,rather than apoptosis.PM2.5 combined with UVB can cause cell cycle arrest.