Oxidative Stress Alters the Morphology and Toxicity of Aortic Medial Amyloid

Abstract

The aggregation and fibril deposition of amyloid proteins have been implicated in a range of neurodegenerative and vascular diseases, and yet the underlying molecular mechanisms are poorly understood. Here, we use a combination of cell-based assays, biophysical analysis, and atomic force microscopy to investigate the potential involvement of oxidative stress in aortic medial amyloid (AMA) pathogenesis and deposition. We show that medin, the main constituent of AMA, can induce an environment rich in oxidative species, increasing superoxide and reducing bioavailable nitric oxide in human cells. We investigate the role that this oxidative environment may play in altering the aggregation process of medin and identify potential posttranslational modification sites where site-specific modification and interaction can be unambiguously demonstrated. In an oxidizing environment, medin is nitrated at tyrosine and tryptophan residues, with resultant effects on morphology that lead to longer fibrils with increased toxicity. This provides further motivation to investigate the role of oxidative stress in AMA pathogenicity.

Probing Medin Monomer Structure and its Amyloid Nucleation Using 13C-Direct Detection NMR in Combination with Structural Bioinformatics

“…5)), and could assist in driving the extension of the C-terminal β-strand as indicated in Figs 4 and 5. In addition, we recently showed that medin can be nitrated at positions Y16 and W11/W22 with subsequent alterations in aggregation properties38. The model proposed here is consistent with all of these sites being accessible for modification altering the ability of the protein to assemble through intermolecular facial β-sheet interactions (Fig.…”

Age‐associated proteomic alterations in human aortic media

“…However, hyperglycemia was not observed in the older-aged subjects examined in the present study, suggesting that the stronger expression of CML in the older-aged group was associated with oxidative damage. These findings might be associated with arterial stiffness of older-aged individuals, as reported by Semba et al 23 As deposition of medin caused injury of SMC, 17 and SMC in the aortic media were decreased with aging, 1,24 it is consistent with the decrease of α-actin, a marker protein of SMC, in older-aged aortic media. It is known that remodeling of the extracellular matrix, such as elastin, collagen and glycosaminoglycan, was caused by aging.…”

“…c,d) and CML (Fig. e,f), were examined . Few regions of SMC nuclei were stained positive for 8‐OHdG in young individuals, whereas most nuclei were positive in older‐aged individuals (Fig.…”

“…Medin was also reported to cause oxidative stress through the production of superoxide radicals and the reduction of nitric oxide. 17 Accordingly, the elevation of MFGE8, and subsequently the increase of medin in older-aged aortic media, would bring about oxidative damage. In the present study, oxidative damage markers, such as 8-OHdG, 4-HNE and CML, were stained strongly in older-aged media.…”

Monosialoganglioside‐Containing Nanoliposomes Restore Endothelial Function Impaired by AL Amyloidosis Light Chain Proteins

“…Second, we report for the first time that the mechanism, or one of the mechanisms, by which NLGM1 protects against LC endothelial injury is through Nrf‐2–mediated upregulation of antioxidant stress responses (HO‐1 and NQO1), leading to reduced oxidative and nitrative stress and increased NO bioavailability. Because we previously demonstrated that oxidative and nitrative stress underlie microvascular injury induced by amyloid proteins (LC in AL, β‐amyloid in Alzheimer's disease, and medin in aortic medial amyloidosis), the induction of an antioxidant stress response by NLGM1 may have potential clinical relevance not only to AL but also to other amyloid diseases.…”