Zinc dyshomeostasis, ageing and neurodegeneration: implications of A2M and inflammatory gene polymorphisms

Zinc maintains brain functions because involved in glutaminergic transmission, in antioxidant response and in conferring biological activity to brain enzymes and growth factors. Zinc turnover is mediated by Metallothioneins (MT) which regulate the intracellular free zinc ions [Zn](i). Alterations in zinc homeostasis are associated to various brain dysfunctions, including brain inflammatory status, but little is known about its implication in the aging brain and neurodegeneration. Literature data in experimental animals suggest that zinc dyshomeostasis may occur in aging associated to a decline in brain functions. One of the causes may be an altered homeostasis of MT and other zinc-binding proteins, such as alpha2 macroglobulin (A2M), which are of protection against stress and inflammation during young/adult age but turn into being harmful in aging. In fact, despite total brain zinc content is unchanged in the brain of aged animals, with respect to the young/adult, the activity of some zinc dependent enzymes is impaired and large amount of zinc has been found in the core of Alzheimer's disease senile plaques. The role played by MT and A2M is reported in ageing and Alzheimer's disease and on some polymorphisms of A2M and inflammatory genes (cytokines and their receptors) because some of them may be affected by zinc, via MT homeostasis.