4种食源性肽改善SD大鼠光老化皮肤弹性及机理的比较分析

Comparative Analysis of Elasticity Enhancement and Mechanism of Four Kinds of Food-Derived Bioactive Peptides on Photoaged Skin in SD Rats

为评价4种食源性肽口服后对SD大鼠光老化皮肤弹性的改善效果并探讨其力学机制,将健康成年雌性SD大鼠随机分为空白对照组、紫外线(ultraviolet,UV)辐照模型组、4种活性肽摄取组,空白组不施行UV辐照,模型组及肽组均行UVA+UVB联合辐照,4种活性肽分别配制成0.3、0.9、1.5 g/L的含肽水溶液口服,脱毛后连续UV辐照18周至光老化模型建立,测定皮肤弹性后将动物处死,取其背部皮肤制备匀浆,生化法测定羟脯氨酸和透明质酸含量,酶联免疫吸附法检测Ⅰ型胶原蛋白(collagen Ⅰ,Col Ⅰ)、Ⅲ型胶原蛋白(Col Ⅲ)含量及基质金属蛋白酶-1(matrix metalloproteinase-1,MMP-1)活力,另取部分皮肤组织进行石蜡包埋、切片后进行苏木精-伊红染色观察。结果表明,与空白组相比,模型组大鼠皮肤弹性,Col Ⅰ、羟脯氨酸、透明质酸含量显著降低(P<0.05),而Col III含量及MMP-1活力显著升高(P<0.05),组织化学显示皮肤表皮增生,真皮层胶原纤维排列紊乱、且断裂呈片段化聚集扭曲,基底膜溶解呈扁平化。与模型组相比,4种活性肽口服后均能改善皮肤弹性,且样品2效果最显著,其皮肤组织中Col I、羟脯氨酸、透明质酸含量显著升高(P<0.05),而Col III含量及MMP-1活力显著降低(P<0.05)。组织化学显示样品2摄食组大鼠表皮增生明显改善,真皮层增厚、胶原纤维增加,排列趋向均匀化致密分布,不同程度上恢复到空白组波浪状规律排列,提示样品2提高光老化SD大鼠皮肤弹性的机理在于促进了胞外基质(extracellular matrix,ECM)的生物合成,抑制了ECM降解酶MMP-1活力,修复了受损皮肤的力学结构。

In order to evaluate the effect of oral supplementation of four kinds of food-derived bioactive peptides on improving the elasticity of photoaged skin in SD rats and to explore the underlying mechanical mechanism,healthy adult female SD rats were randomly divided into normal control group,ultraviolet(UV)exposure group and four bioactive peptide administration groups.All animals except those in the normal control group were exposed to UVA radiation in combination with UVB.Water solutions of each bioactive peptide were prepared in at concentrations of 0.3,0.9,and 1.5 g/L for the low,middle and high-dose peptide treatment groups,respectively.The model and peptide treatment groups were exposed to UV irradiation thrice weekly for 18 consecutive weeks until the photoaging model was established.The elasticity of dorsal skin in each animal group was detected with a skin analyzer and then the rats were sacrificed.Approximately 1 g of dorsal skin samples were mixed into 10 mL of buffer solution and homogenized,and then the homogenate was prepared for biochemical measurements.The contents of hydroxyproline and hyaluronic acid(HA)were determined by biochemical assays,and the contents of type I and III collagen,and the activity of matrix metalloproteinase-1(MMP-1)were determined by enzyme-linked immunosorbent assay.Paraffin-embedded sections of skin tissue were prepared and stained with hematoxylin and eosin for histochemical observation.Results showed that skin elasticity and the contents of collagen I,hydroxyproline and HA in rat skin from the model group were significantly decreased when compared with the normal group,while the content of collagen III and the activity of MMP-1 were significantly increased.Histochemical assays showed epidermal hyperplasia and disorderly arrangement of collagen fibers in the dermis which were broken into fragments aggregated and distorted,together with solubilization and flattening of the basement membrane.In comparison with the model group,skin elasticity in all peptide supplementation groups was improved to some different degrees,with elastinderived peptide showing the best effect,which significantly increased the contents of collagen I,hydroxyproline and HA and significantly decreased the content of collagen III and the activity of MMP-1(P<0.05).Histochemical assays demonstrated that elastin-derived peptide markedly improved epidermal hyperplasia,increased the thickness of the dermis and the amount of collagen fibers and restored collagen fibers to the uniform compact wave-like arrangement of the blank control,suggesting that the mechanism of action of elastin-derived peptide was enhancing the biosynthesis of extracellular matrix(ECM)and inhibiting the degradation of ECM by MMP-1 as well as restoring the mechanical structure of photodamaged skin.