肌肽对激素诱导晶状体α-晶状体蛋白修饰的作用

目的：研究肌肽对糖皮质激素诱导的α-晶状体蛋白修饰和分子伴侣功能降低的保护作用，以及肌肽与糖皮质激素的直接反应。 方法：采用SephacryIS-300HR凝胶柱分离牛αL-晶状体蛋白。αL-晶状体蛋白分别与不同浓度的泼尼松龙-21-半琥珀酸（P-21-H）及肌肽孵育不同时间。以α1-晶状体蛋白对热凝聚的抑制作为分子伴侣活性指标。采用SDS-聚丙烯酰胺凝胶电泳和荧光光度仪来监测被修饰的αL-晶状体蛋白，并观察肌肽和泼尼松龙-21-半琥珀酸作用后的光谱变化。 结果：泼尼松龙-21-半琥珀酸可导致浓度和时间依赖性αL-晶状体蛋白分子伴侣活性的降低，但是肌肽加剧了这种效应。被泼尼松龙-21-半琥珀酸修饰后的较未被修饰的αL-晶状体蛋白色氨酸荧光强度显著降低，但是其非色氨酸荧光强度向较长波长移位，并呈现时间一剂量依赖的增强，提示有新的荧光色素物的形成。SDS-聚丙烯酰胺凝胶电泳结果显示肌肽能与泼尼松龙-21-半琥珀酸迅速反应，从而抑制激素诱导的蛋白质修饰。时间依赖性的光吸收强度增加提示肌肽与泼尼松龙-21-半琥珀酸反应可能形成了新的加合物。 结论：肌肽能够与泼尼松龙-21-半琥珀酸直接反应，肌肽具有潜在的抗糖皮质激素作用。

Effect of carnosine on steroid-induced modification of lens α-crystallin

AIM: To explore whether carnosine can protect α -crys-tallin modification and decreased chaperone by a steroid,and whether carnosine could directly react with a steroid.METHODS: Bovine lens α L-crystallin was separated by size-exclusion chromatography on a Sephacyl S-300 HR column. α L-Crystallin was incubated with different concentrations of prednisolone-21-hemisuccinate (P-21-H)with or without carnosine for different times. The chaperone activity of α L-crystallin was monitored using the prevention thermal aggregation of α L-crystallin. The modified α L-crystallinwas examined by SDS-PAGE and fluorescence measurements. The absorbance spectra of solutions of carnosine and P-21-H were investigated.RESULTS: P-21-H decreased the chaperone activity ofα L-crystallin in a concentration- and time-dependent fashion. Carnosine only worsened this effect. The tryptophan fluorescence intensity of α L-crystallin modified by P-21-H was significantly decreased compared to unmodified crystallin, whereas its non-tryptophan fluorescence was increased with a shift to longer wavelengths in a time- and dose-dependent manner, suggesting that new fluorophores are possibly formed. Carnosine readily reacted with P-21-H thereby inhibiting steroid-mediated protein modification as revealed electrophoretically. The increased absorbance was time-dependent, suggesting adducts may be formed between carnosine and P-21-H.CONCLUSION: Carnosine reacts with P-21-H, which suggests carnosine's potential as a possible anti-seroid agent.