Abstract: Han Changxu, Dang Erle, Jin Liang, Li Bing, Zhang Nan, Wang Gang. Department of Dermatology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China Corresponding author: Wang Gang, Email: xjwgang@fmmu.edu.cn 【Abstract】 Objective To investigate the effects of narrow-band ultraviolet B （NB-UVB） on the expression of keratin 17 （K17） in the human keratinocyte cell line HaCaT. Methods Cultured HaCaT cells were irradiated with different doses （0, 50, 100, 200, 400 mJ/cm2） of NB-UVB followed by additional culture for 6, 12 and 24 hours respectively. To explore the mechanisms underlying the effects of NB-UVB on K17 expression, some HaCaT cells were pretreated with PD98059 （an inhibitor of mitogen-activated protein kinase kinase） followed by UVB radiation and additional culture as described above. Cell counting kit-8 （CCK 8） was used to evaluate the proliferation of, real time PCR to measure the mRNA expressions of K17 in, and Western blot to determine the protein expression of K17, Erk1/2 and phosphorylated Erk1/2 in, HaCaT cells. Results Both the proliferation of and K17 expression in HaCaT cells were promoted by NB-UVB radiation at low doses （50, 100 mJ/cm2）, but inhibited by NB-UVB radiation at high doses （200, 400 mJ/cm2）. Significant differences were observed for the proliferative activity between HaCaT cells irradiated with NB-UVB at 100 or 400 mJ/cm2 and unirradiated HaCaT cells at 12 and 24 hours （P < 0.01 or 0.05）. The phosphorylation of Erk1/2 was upregulated by NB-UVB radiation at 100 mJ/cm2, but downregulated by that at 400 mJ/cm2, and the upregulation induced by low dose NB-UVB could be suppressed by blocking the Erk 1/2 pathway. Conclusion The effects of NB-UVB radiation on K17 expression may be modulated by the Erk 1/2 pathway.

Key words: Ultraviolet rays, Keratinocytes, Keratin-17, Cell proliferation, Phosphorylases