Menter J M, Cornelison L M, Cannick L, Patta A M, Dowdy J C, Sayre R M, Abukhalaf I K, Silvestrov N S, Willis I
Department of Medicine, Morehouse School of Medicine, Atlanta, GA, USA.
Photodermatol Photoimmunol Photomed. 2003 Feb;19(1):28-34. doi: 10.1034/j.1600-0781.2003.00004.x.
BACKGROUND/PURPOSE: Photoaging of the skin is a result of chronic exposure to environmental ultraviolet radiation (UV). The milieu provided by the extracellular matrix, which significantly influences the behaviour of resident fibroblasts, depends critically on the supermolecular collagen structure. We ask whether direct photochemical treatment of type I collagen with solar wavelengths capable of reaching the dermis can modify the substrate's susceptibility to collagenase in a model in vitro system.
Acid- extracted Skh-1 hairless mouse collagen samples were irradiated with 0-140 J/cm2 of radiation from bank of filtered FS lamp (UVB/UVA = 0.33, fluence rate = 0.81 mW/cm2). Subsequent to UV irradiation, collagen samples were coupled with fluorescein isothiocyanate (FITC) and assayed for susceptibility to bacterial collagenase by monitoring the appearance of supernatant FITC fluorescence (a measure of lysed collagen) over time of incubation. As a 'reference', unirradiated commercial FITC-labelled citrate-soluble collagen (Elastin Products, Owensville, MO 65066, USA) was similarly analysed.
Unirradiated mouse collagen had a lower rate of cleavage than did the calfskin sample. Irradiation of unlabelled mouse collagen for 0-48 h (0-140 J/cm2 total UV) rendered the sample more soluble, with concomitant chain degradation, cross-linking and loss of intrinsic collagen fluorescence. At irradiation time's >/= 4 h (>/=11.7 J/cm2), the irradiated collagen was significantly more susceptible to bacterial collagenase digestion.
It appears that the rate of cleavage depends on the superstructure of the collagen, since the kinetics of collagen cleavage differ for two collagen samples having essentially the same primary structure. Cleavage kinetics may depend on the 'maturity' (solubility) of the collagen. The observation that UV-damaged mouse collagen is a better substrate for collagenase than the intact sample may be illustrative of a mechanism whereby damaged collagen targets itself for selective attack by collagenase.
背景/目的：皮肤光老化是长期暴露于环境紫外线辐射（UV）的结果。细胞外基质所提供的环境对驻留成纤维细胞的行为有显著影响，而这关键取决于超分子胶原蛋白结构。我们探讨在体外模型系统中，用能够穿透真皮的太阳波长对I型胶原蛋白进行直接光化学处理，是否会改变底物对胶原酶的敏感性。
用来自一组过滤后的FS灯（UVB/UVA = 0.33，通量率 = 0.81 mW/cm²）的0 - 140 J/cm²辐射照射酸提取的Skh - 1无毛小鼠胶原蛋白样品。紫外线照射后，胶原蛋白样品与异硫氰酸荧光素（FITC）偶联，并通过监测孵育过程中上清液FITC荧光（裂解胶原蛋白的一种度量）的出现来测定对细菌胶原酶的敏感性。作为“对照”，对未辐照的市售FITC标记的柠檬酸盐可溶性胶原蛋白（美国密苏里州欧文斯维尔市Elastin Products公司，邮编65066）进行类似分析。
未辐照的小鼠胶原蛋白的裂解速率低于小牛皮样品。对未标记的小鼠胶原蛋白进行0 - 48小时（总紫外线0 - 140 J/cm²）照射，使样品更易溶解，同时伴有链降解、交联和固有胶原蛋白荧光的丧失。在照射时间≥4小时（≥11.7 J/cm²）时，辐照后的胶原蛋白对细菌胶原酶消化的敏感性显著更高。
似乎裂解速率取决于胶原蛋白的超结构，因为对于两种一级结构基本相同的胶原蛋白样品，胶原裂解动力学不同。裂解动力学可能取决于胶原蛋白的“成熟度”（溶解度）。紫外线损伤的小鼠胶原蛋白比完整样品更易被胶原酶作用这一观察结果，可能说明了受损胶原蛋白将自身作为胶原酶选择性攻击目标的一种机制。
