A novel molecular mechanism for nitrated alpha-synuclein-induced cell death

Although previous studies have demonstrated the involvement of nitrated alpha-synuclein in neurodegenerative disorders (synucleinopathies), the effects of nitrated alpha-synuclein and the molecular mechanisms underlying its toxicity are still unclear. In the present study, nitrated alpha-synuclein with four 3-nitrotyrosines (Tyr(39), Tyr(125), Tyr(133), and Tyr(136)) was obtained non-enzymatically by incubation with nitrite. The nitrated protein existed as a mixture of monomers, dimers, and polymers in solution. The nitrated alpha-synuclein could induce cell death in a time-and concentration-dependent manner when SH-SY5Y cells (a human neuroblastoma cell line) were incubated with the dimers and polymers. Treatment with anti-integrin alpha 5 beta 1 antibody partially rescued the SH-SY5Y cells from the cell death. Dot blotting and immunoprecipitation revealed that the nitrated protein bound to integrin on the cell membranes. Level of nitric oxide (NO) and calcium-independent inducible NO synthase (iNOS) activity increased during the initial stages of the treatment. The expression of phosphorylated focal adhesion kinase (FAK) decreased in the cells. Subsequently, an increase in caspase 3 activity was observed in SH-SY5Y cells. Our results demonstrate that activation of iNOS and inhibition of FAK may both be responsible for the cell death induced by nitrated alpha-synuclein. These data suggest that the cytotoxicity of nitrated alpha-synuclein is mediated via an integrin-iNOS/-FAK signaling pathway, and that the nitration of alpha-synuclein plays a role in neuronal degeneration

Reactive carbonyl compounds (RCCs) cause aggregation and dysfunction of fibrinogen

Fibrinogen is a key protein involved in coagulation and its deposition on blood vessel walls plays an important role in the pathology of atherosclerosis. Although the causes of fibrinogen (fibrin) deposition have been studied in depth, little is known about the relationship between fibrinogen deposition and reactive carbonyl compounds (RCCs), compounds which are produced and released into the blood and react with plasma protein especially under conditions of oxidative stress and inflammation. Here, we investigated the effect of glycolaldehyde on the activity and deposition of fibrinogen compared with the common RCCs acrolein, methylglyoxal, glyoxal and malondialdehyde. At the same concentration (1 mmol/L), glycolaldehyde and acrolein had a stronger suppressive effect on fibrinogen activation than the other three RCCs. Fibrinogen aggregated when it was respectively incubated with glycolaldehyde and the other RCCs, as demonstrated by SDS-PAGE, electron microscopy and intrinsic fluorescence intensity measurements. Staining with Congo Red showed that glycolaldehyde-and acrolein-fibrinogen distinctly formed amyloid-like aggregations. Furthermore, the five RCCs, particularly glycolaldehyde and acrolein, delayed human plasma coagulation. Only glycolaldehyde showed a markedly suppressive effect on fibrinogenesis, none did the other four RCCs when their physiological blood concentrations were employyed, respectively. Taken together, it is glycolaldehyde that suppresses fibrinogenesis and induces protein aggregation most effectively, suggesting a putative pathological process for fibrinogen (fibrin) deposition in the blood

Formaldehyde induces hyperphosphorylation and polymerization of Tau protein both in vitro and in vivo

Background Chronic formaldehyde exposure leads to memory impairment and abnormal elevation of endogenous formaldehyde has been found in the brains of Alzheimer's disease (AD) patients. Hyperphosphorylated Tau protein with subsequent aggregates as neurofibrillary tangles (NFTs) is one of the typical pathological characteristics in AD brains. The mechanism underlying abnormally elevated concentrations of endogenous formaldehyde that induce Tau hyperphosphorylation is unknown. Methods N2a cells and mice were treated with formaldehyde for different time points, then Western blotting and immunocytochemistry were utilized to determine the phosphorylation and polymerization of Tau protein. HPLC was used to detect the concentration of formaldehyde in cell media. Results Under formaldehyde stress, Tau became hyperphosphorylated, not only in the cytoplasm, but also in the nucleus of neuroblastoma (N2a) cells, and mouse brains. Polymers of cellular phospho-Tau were also detected. Significant accumulation of glycogen synthase kinase-3β (GSK-3β) in the nucleus of N2a and mouse brain cells, and elevation of its phosphorylation at Y216, was observed under formaldehyde stress. Formaldehyde-induced Tau hyperphosphorylation was blocked in the presence of LiCl and CT99021, inhibitors of GSK-3β, and by RNAi interference. Conclusions Formaldehyde, which may cause age-related memory loss, can act as a factor triggering Tau hyperphosphorylation via GSK-3β catalysis and induces polymerization of Tau. General significance Investigation of formaldehyde-induced Tau hyperphosphorylation may provide novel insights into mechanisms underlying tauopathies

D-ribose in glycation and protein aggregation

Background: D-ribose is a naturally occurring pentose monosaccharide present in all living cells and their microenvironments and is a key component of numerous biomolecules involved in many important metabolic pathways. It also participates in the glycation of proteins producing advanced glycation end products (AGEs) that lead to cell dysfunction and death. As recent studies show, ribosylation, a rapid process, causes protein aggregation in vitro and in vivo

Urine formaldehyde level is inversely correlated to mini mental state examination scores in senile dementia

It is widely known that exogenous formaldehyde exposure induces human cognitive impairment and animal memory loss; and recent studies show that formaldehyde at pathological levels induces A beta deposition and misfolding of tau protein to form globular amyloid-like aggregates. Endogenous formaldehyde may be a marker for progressive senile dementia