Musante Luca, Bruschi Maurizio, Candiano Giovanni, Petretto Andrea, Dimasi Nazzareno, Del Boccio Piero, Urbani Andrea, Rialdi Giovanni, Ghiggeri Gian Marco
Laboratory on Pathophysiology of Uremia, G. Gaslini Children Hospital, Genoa, Italy.
Biochem Biophys Res Commun. 2006 Oct 20;349(2):668-73. doi: 10.1016/j.bbrc.2006.08.079. Epub 2006 Aug 23.
Anti-oxidants are paradoxically much lower in plasma than inside cells even blood is comparably exposed to the oxidative stress. 'In vitro' models suggest a critical role of albumin as substitutive anti-oxidant in plasma but no proof for this role is available 'in vivo.' Herein, we demonstrate by LC/MS/MS that plasma albumin undergoes massive oxidation in primary nephrotic syndrome, involving stable sulphonation SO3- of the free SH of Cys 34 with +48Da increase in exact mass of the protein (ESI-MS) and formation of a fast moving isoform in the pH range between 5 and 7. Physical-chemical experiments with DSC and fluorescence spectra indicate a thermal stabilization of the structure upon oxidation. This is the first demonstration of massive oxidation of albumin 'in vivo' that reflects a functional role of the protein. Free radicals should be implicated in the pathogenesis of proteinuria in human FSGS.
矛盾的是，即使血液同样暴露于氧化应激之下，血浆中的抗氧化剂含量也比细胞内低得多。“体外”模型表明白蛋白在血浆中作为替代性抗氧化剂起关键作用，但“体内”尚无此作用的证据。在此，我们通过液相色谱/串联质谱法证明，原发性肾病综合征患者的血浆白蛋白会发生大量氧化，涉及半胱氨酸34游离巯基的稳定磺化（SO3-），蛋白质精确质量增加48Da（电喷雾质谱），并在pH值5至7范围内形成一种快速移动的异构体。差示扫描量热法和荧光光谱的物理化学实验表明，氧化后结构发生热稳定。这是首次在“体内”证明白蛋白大量氧化，反映了该蛋白质的功能作用。自由基应与人类局灶节段性肾小球硬化症蛋白尿的发病机制有关。
