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Abstract: Elevated plasma fibrinogen is a prothrombotic risk factor for cardiovascular disease (CVD). Recent small studies report that fibrinogen oxidative modifications, specifically tyrosine residue nitration, can occur in inflammatory states and may modify fibrinogen function. HDL cholesterol is inversely related to CVD and suggested to reduce the oxidation of LDL cholesterol, but whether these antioxidant functions extend to fibrinogen modifications is unknown. We used a recently validated ELISA to quantify nitrated fibrinogen during experimental human endotoxemia (N =23) and in a cohort of healthy adults (N =361) who were characterized for inflammatory and HDL parameters as well as subclinical atherosclerosis measures, carotid artery intima-medial thickness (IMT) and coronary artery calcification (CAC). Fibrinogen nitration increased following endotoxemia and directly correlated with accelerated ex vivo plasma clotting velocity. In the observational cohort, nitrated fibrinogen was associated with levels of CRP and serum amyloid A. Nitrated fibrinogen levels were not lower with increasing HDL cholesterol and did not associate with IMT and CAC. In humans, fibrinogen nitration was induced during inflammation and was correlated with markers of inflammation and clotting function but not HDL cholesterol or subclinical atherosclerosis in our modest sample. Inflammation-induced fibrinogen nitration may be a risk factor for promoting CVD events. [Copyright &y& Elsevier]

Elevated levels of circulating fibrinogen are associated with an increased risk of atherothrombotic diseases although a causative correlation between high levels of fibrinogen and cardiovascular complications has not been established. We hypothesized that a potential mechanism for an increased prothrombotic state is the post-translational modification of fibrinogen by tyrosine nitration. Mass spectrometry identified tyrosine residues 292 and 422 at the carboxyl terminus of the β-chain as the principal sites of fibrinogen nitration in vivo. Immunoelectron microscopy confirmed the incorporation of nitrated fibrinogen molecules in fibrin fibers. The nitration of fibrinogen in vivo resulted in four distinct functional consequences: increased initial velocity of fibrin clot formation, altered fibrin clot architecture, increased fibrin clot stiffness, and reduced rate of clot lysis. The rate of fibrin clot formation and clot architecture was restored upon depletion of the tyrosine-nitrated fibrinogen molecules. An enhanced response to the knob "B" mimetic peptides Gly-His-Arg-Proam and Ala-His-Arg-Proam suggests that incorporation of nitrated fibrinogen molecules accelerates fibrin lateral aggregation. The data provide a novel biochemical risk factor that could explain epidemiological associations of oxidative stress and inflammation with thrombotic complications. [ABSTRACT FROM AUTHOR]

The mechanisms that govern the formation of α-synuclein (α-syn) aggregates are not well understood but are considered a central event in the pathogenesis of Parkinson's disease (PD). A critically important modulator of α-syn aggregation in vitro is dopamine and other catechols, which can prevent the formation of α-syn aggregates in cell-free and cellular model systems. Despite the profound importance of this interaction for the pathogenesis of PD, the processes by which catechols alter α-syn aggregation are unclear. Molecular and biochemical approaches were employed to evaluate the mechanism of catechol-α-syn interactions and the effect on inclusion formation. The data show that the intracellular inhibition of α-syn aggregation requires the oxidation of catechols and the specific noncovalent interaction of the oxidized catechols with residues 125YEMPS129 in the C-terminal region of the protein. Cell-free studies using novel near infrared fluorescence methodology for the detection of covalent protein-orthoquinone adducts showed that although covalent modification of α-syn occurs, this does not affect α-syn fibril formation. In addition, oxidized catechols are unable to prevent both thermal and acid-induced protein aggregation as well as fibrils formed from a protein that lacks a YEMPS amino acid sequence, suggesting a specific effect for α-syn. These results suggest that inappropriate C-terminal cleavage of α-syn, which is known to occur in vivo in PD brain or a decline of intracellular catechol levels might affect disease progression, resulting in accelerated α-syn inclusion formation and dopaminergic neurodegeneration. [ABSTRACT FROM AUTHOR]