Abstract: Objective To study the effects of the IL-1 receptor antagonist (IL-1Ra) on matrix metalloproteinase 1 (MMP-1) expression in UV-irradiated fibroblasts. Methods Simulating the impact of environmental ultraviolet (UV) light on human skin, UVA-irradiated human fibroblasts were cultured in medium obtained from UVB-irradiated HaCaT cells. MMP-1 was detected by ELISA in the culture medium of fibroblasts. After treatment with IL-1Ra, the mRNA expression levels of C-Jun, C-Fos and GAPDH (internal control) of fibroblasts were measured by real-time fluorescent quantitative RT-PCR. Results Production of MMP-1 by UVA (10 J/cm²)-irradiated fibroblasts was increased in culture medium from UVB-irradiated HaCaT cells. The fibroblasts produced significantly higher levels of MMP-1 in culture medium from HaCaT cells treated without UVB than those with 15 mJ/cm² UVB (t=8.413,P=0.014). However, IL-1Ra inhibited MMP-1 production of fibroblasts in a dose-dependent manner. Standard curves of real-time fluorescent quantitative RT-PCR showed a linear correlation between the copy number and the threshold cycle (Tc). Melting curves confirmed the specificity of PCR products. The original copy numbers of C-Jun and C-Fos as well as the ratios of the numbers to the GAPDH copy number showed that IL-1Ra inhibited the C-Jun mRNA expression of fibroblasts in a dose-dependent manner but had no significant effects on C-Fos mRNA expression. Conclusions The culture medium from UVB-irradiated HaCaT cells can promote MMP-1 production by UVA-irradiated fibroblasts. IL-1Ra reduces MMP-1 production via inhibition of C-Jun mRNA expression.

Key words: Interstitial collagenase, Ultraviolet rays, Fibroblasts, IL-1 receptor antagonist