Friday, 10 May 2013

Sirtuin another target for myelin repair

Rafalski VA, Ho PP, Brett JO, Ucar D, Dugas JC, Pollina EA, Chow LM, Ibrahim A, Baker SJ, Barres BA, Steinman L, Brunet A.
Expansion of oligodendrocyte progenitor cells following SIRT1 inactivation in the adult brain. Nat Cell Biol. 2013 May 5. doi: 10.1038/ncb2735. [Epub ahead of print]

Oligodendrocytes-the myelin-forming cells of the central nervous system-can be regenerated during adulthood. In adults, new oligodendrocytes originate from oligodendrocyte progenitor cells (OPCs), but also from neural stem cells (NSCs). Although several factors supporting oligodendrocyte production have been characterized, the mechanisms underlying the generation of adult oligodendrocytes are largely unknown. 

Here we show that genetic inactivation of SIRT1, a protein deacetylase implicated in energy metabolism, increases the production of new OPCs in the adult mouse brain, in part by acting in NSCs. New OPCs produced following SIRT1 inactivation differentiate normally, generating fully myelinating oligodendrocytes. Remarkably, SIRT1 inactivation ameliorates remyelination and delays paralysis in mouse models of demyelinating injuries. SIRT1 inactivation leads to the upregulation of genes involved in cell metabolism and growth factor signalling, in particular PDGF receptor α (PDGFRα). Oligodendrocyte expansion following SIRT1 inactivation is mediated at least in part by AKT and p38 MAPK-signalling molecules downstream of PDGFRα. The identification of drug-targetable enzymes that regulate oligodendrocyte regeneration in adults could facilitate the development of therapies for demyelinating injuries and diseases, such as multiple sclerosis.

Sirtuin 1, also known as NAD-dependent deacetylase sirtuin-1, is a protein SIRT1 stands for sirtuin (silent mating type information regulation 2 homolog) 1 (S. cerevisiae = YEAST), SIRT1 is an enzyme that deacetylates proteins that contribute to cellular regulation (reaction to stressors, longevity). This study they report that SIRT facilitates the production of myelinating cultures which is good news as the target may be drugable. As to the animal models of MS, blocking the SIRT1 slowed the development of disability by a few days, and suppossedly stoped remyelination, how would this equate to human benefit of disease over years. As ever more work is needed

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