Andreozzi Giovanni B, Pacella Alessandro, Corazzari Ingrid, Tomatis Maura, Turci Francesco
Dipartimento di Scienze della Terra, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185, Roma, Italy.
CNR-IGG, U.O. Roma, c/o Dipartimento di Scienze della Terra, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185, Roma, Italy.
Sci Rep. 2017 Oct 31;7(1):14696. doi: 10.1038/s41598-017-14480-z.
Among asbestos minerals, fibrous riebeckite (crocidolite) and tremolite share the amphibole structure but largely differ in terms of their iron content and oxidation state. In asbestos toxicology, iron-generated free radicals are largely held as one of the causes of asbestos malignant effect. With the aim of clarifying i) the relationship between Fe occurrence and asbestos surface reactivity, and ii) how free-radical generation is modulated by surface modifications of the minerals, UICC crocidolite and fibrous tremolite from Maryland were leached from 1 day to 1 month in an oxidative medium buffered at pH 7.4 to induce redox alterations and surface rearrangements that may occur in body fluids. Structural and chemical modifications and free radical generation were monitored by HR-TEM/EDS and spin trapping/EPR spectroscopy, respectively. Free radical yield resulted to be dependent on few specific Fe and Fe surface sites rather than total Fe content. The evolution of reactivity with time highlighted that low-coordinated Fe ions primarily contribute to the overall reactivity of the fibre. Current findings contribute to explain the causes of the severe asbestos-induced oxidative stress at molecular level also for iron-poor amphiboles, and demonstrate that asbestos have a sustained surface radical activity even when highly altered by oxidative leaching.
在石棉矿物中，纤维状钠闪石（青石棉）和透闪石具有角闪石结构，但铁含量和氧化态差异很大。在石棉毒理学中，铁产生的自由基在很大程度上被认为是石棉产生恶性效应的原因之一。为了阐明：i）铁的存在与石棉表面反应性之间的关系，以及ii）矿物表面改性如何调节自由基的产生，将国际癌症研究机构（UICC）的青石棉和来自马里兰州的纤维状透闪石在pH 7.4缓冲的氧化介质中浸出1天至1个月，以诱导可能在体液中发生的氧化还原变化和表面重排。分别通过高分辨率透射电子显微镜/能谱仪（HR-TEM/EDS）和自旋捕集/电子顺磁共振光谱法（spin trapping/EPR spectroscopy）监测结构和化学修饰以及自由基的产生。自由基产率取决于少数特定的铁和铁表面位点，而不是总铁含量。反应性随时间的演变表明，低配位铁离子对纤维的整体反应性起主要作用。目前的研究结果有助于在分子水平上解释贫铁角闪石引起严重石棉诱导的氧化应激的原因，并表明即使经过氧化浸出高度改变，石棉仍具有持续的表面自由基活性。
