Abstract: JIANG Yan-ling*, ZHAO Ming, LIANG Gong-ping, WANG Li-tao, SU Yu-wen. *Department of Dermatology, Hunan Children′s Hospital, Changsha 410007, China Corresponding author: ZHAO Ming, Email: xyyleyy@126.com 【Abstract】 Objective To estimate the influence of 1, 25（OH）2D3 on the proliferative ability of and methylation levels of genomic DNA and proliferation-associated gene promoter in human HaCaT keratinocytes. Methods Some cultured HaCaT cells were treated with 1, 25（OH）2D3 of 10-6, 10-7 and 10-8 mol/L for 24 hours, then, methyl thiazolyl tetrazolium （MTT） assay was carried out to evaluate the proliferative activity of cells, and a global DNA methylation quantification kit was used to determine the global DNA methylation level. Real-time PCR was conducted to quantify the mRNA expression of DNA methyl transferases （DNMTs） and methyl-DNA binding domain （MBD） proteins, and methylation-specific PCR （MS-PCR） to evaluate the methylation status of promoter region in the programmed cell death 5 （PDCD5） and tissue inhibitor of metalloproteinase 2 （TIMP2） genes, in HaCaT cells after 24-hour treatment with 1, 25（OH）2D3 of 10-6 mol/L. The HaCaT cells receiving no treatment served as the control. Results Compared with the untreated HaCaT cells, those treated with 1,25（OH）2D3 of 10-6 mol/L showed significantly down-regulated proliferative activity （0.152 ± 0.027 vs. 0.290 ± 0.017, P < 0.01）, global DNA methylation level （0.187 ± 0.071 vs. 0.316 ± 0.049, P < 0.05）, DNMT3a and DNMT3b mRNA expression levels （P < 0.01 or 0.05）, but markedly upregulated mRNA expression levels of MECP2, MBD2, PDCD5 and TIMP2（P < 0.01 or 0.05）. Moreover, the DNA methylation levels within the promoter region of PDCD5 and TIMP2 genes were significantly lower in HaCaT cells treated with 1, 25（OH）2D3 of 10-6 mol/L than in the control cells（0.38 ± 0.135 vs. 0.72 ± 0.121, 0.46 ± 0.172 vs. 0.68 ± 0.133, both P < 0.05）. Conclusions 1, 25（OH）2D3 may down-regulate the global genomic DNA methylation level of, and modulate the expression of DNA methylation-modifying genes in, HaCaT cells. Furthermore, 1, 25（OH）2D3 can decrease the promoter methylation levels but induce the overexpression of PDCD5 and TIMP2 genes, and decelerate the proliferation of HaCaT cells. 【Key words】 Calcitriol; Keratinocytes; DNA methylation

Key words: DNA methylation