N-homocysteinylation of tau and MAP1 is increased in autopsy specimens of Alzheimer's disease and vascular dementia.

The pathomechanisms that associate a deficit in folate and/or vitamin B12 and the subsequent hyperhomocysteinemia with pathological brain ageing are unclear. We investigated the homocysteinylation of microtubule-associated proteins (MAPs) in brains of patients with Alzheimer's disease or vascular dementia, and in rats depleted in folate and vitamin B12, Cd320 KO mice with selective B12 brain deficiency and H19-7 neuroprogenitors lacking folate. Compared with controls, N-homocysteinylated tau and MAP1 were increased and accumulated in protein aggregates and tangles in the cortex, hippocampus and cerebellum of patients and animals. N-homocysteinylation dissociated tau and MAPs from ß-tubulin, and MS analysis showed that it targets lysine residues critical for their binding to ß-tubulin. N-homocysteinylation increased in rats exposed to vitamin B12 and folate deficit during gestation and lactation and remained significantly higher when they became 450 days-old, despite returning to normal diet at weaning, compared with controls. It was correlated with plasma homocysteine (Hcy) and brain expression of methionine tRNAsynthetase (MARS), the enzyme required for the synthesis of Hcy-thiolactone, the substrate of N-homocysteinylation. Experimental inactivation of MARS prevented the N-homocysteinylation of tau and MAP1, and the dissociation of tau and MAP1 from ß-tubulin and PSD95 in cultured neuroprogenitors. In conclusion, increased N-homocysteinylation of tau and MAP1 is a mechanism of brain ageing that depends on Hcy concentration and expression of MARS enzyme. Its irreversibility and cumulative occurrence throughout life may explain why B12 and folate supplementation of the elderly has limited effects, if any, to prevent pathological brain ageing and cognitive decline. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Systems medicine approaches for the definition of complex phenotypes in chronic diseases and ageing. From concept to implementation and policies.

Chronic diseases are diseases of long duration and slow progression. Major NCDs (cardiovascular diseases, cancer, chronic respiratory diseases, diabetes, rheumatologic diseases and mental health) represent the predominant health problem of the Century. The prevention and control of NCDs are the priority of the World Health Organization 2008 Action Plan, the United Nations 2010 Resolution and the European Union 2010 Council. The novel trend for the management of NCDs is evolving towards integrative, holistic approaches. NCDs are intertwined with ageing. The European Innovation Partnership on Active and Healthy Ageing (EIP on AHA) has prioritised NCDs. To tackle them in their totality in order to reduce their burden and societal impact, it is proposed that NCDs should be considered as a single expression of disease with different risk factors and entities. An innovative integrated health system built around systems medicine and strategic partnerships is proposed to combat NCDs. It includes (i) understanding the social, economic, environmental, genetic determinants, as well as the molecular and cellular mechanisms underlying NCDs; (ii) primary care and practice-based interprofessional collaboration; (iii) carefully phenotyped patients; (iv) development of unbiased and accurate biomarkers for comorbidities, severity and follow up of patients; (v) socio-economic science; (vi) development of guidelines; (vii) training; and (viii) policy decisions. The results could be applicable to all countries and adapted to local needs, economy and health systems. This paper reviews the complexity of NCDs intertwined with ageing. It gives an overview of the problem and proposes two practical examples of systems medicine (MeDALL) applied to allergy and to NCD co-morbidities (MACVIA-LR, Reference Site of the European Innovation Partnership on Active and Healthy Ageing).

Oligomeric-induced activity by thienyl pyrimidine compounds traps prion infectivity.

Accumulation of PrP(Sc), an abnormal form of cellular prion protein (PrP), in the brain of animals and humans leads to fatal neurodegenerative disorders known as prion diseases. Limited protease digestion of PrP(Sc) produces a truncated form called PrP(27-30) that retains prion infectivity and is the main marker of disease targeted in most diagnostic tests. In the search for new anti-prion molecules, drug-screening assays on prion-infected murine cells have been oriented toward decreasing levels of PrP(27-30). In contrast, we screened for drugs promoting multimers of PrP(27-30), illustrating a possible stabilization of mouse PrP(Sc) species, because recent studies aiming to characterize the conformational stability of various prion strains showed that stable recombinant amyloids produced more stable prion strain, leading to longest incubation time. We identified a family of thienyl pyrimidine derivatives that induce SDS-resistant dimers and trimers of PrP(27-30). Bioassays performed on mice brain homogenates treated with these compounds showed that these thienyl pyrimidine derivatives diminished prion infectivity in vivo. Oligomeric-induced activity by thienyl pyrimidine compounds is a promising approach not only to understanding the pathogenesis of prions but also for prion diagnostics. This approach could be extended to other neurodegenerative "prionopathies," such as Alzheimer's, Huntington, or Parkinson's diseases.

Anti-PrP antibodies block PrPSc replication in prion-infected cell cultures by accelerating PrPC degradation.

The use of anti-PrP antibodies represents one of the most promising strategies for the treatment of prion diseases. In the present study, we screened various anti-PrP antibodies with the aim of identifying those that would block PrP(Sc) replication in prion-infected cell culture. Two antibodies, SAF34 recognizing the flexible octarepeats region on HuPrP protein, and SAF61 directed against PrP amino acid residues (144-152), not only inhibited PrP(Sc) formation in prion-infected neuroblastoma cells but also decreased the PrP(C) levels in non-infected N2a cells. In addition, treatment with both SAF34 and SAF61 antibodies decreased PrP(C) and PrP(Sc) levels in the cells synergistically. In the presence of both antibodies, our results showed that the mode of action which leads to the disappearance of PrP(Sc) in cells is directly coupled to PrP(C) degradation by reducing the half-life of the PrP(C) protein.