Polymorphisms in MT1a gene coding region are associated with longevity in Italian Central female population

Catia Cipriano Æ Marco Malavolta Æ Laura Costarelli Æ Robertina Giacconi Æ Elisa Muti Æ Nazzarena Gasparini Æ Maurizio Cardelli Æ Daniela Monti Æ Erminia Mariani Æ Eugenio Mocchegiani

Abstract Metallothioneins (MTs) play a pivotal role in zinc-related cell homeostasis because of their high affinity for zinc, which is in turn fun- damental for immune response and antioxidant activity. MTs regulate zinc homeostasis by bind- ing zinc and releasing zinc at the occurrence for immune response. The zinc release by MT is very limited in chronic inflammation and ageing. Some polymorphisms of MTs gene, in particular MT1a sub-isoform, may affect this release that is a problem still unresolved in ageing. The screening

MT1a gene has revealed for the first time that the polymorphism corresponding to a A/C (Asp/Thr) transition at 647 nt position in the Mt1a coding region is the more involved in the longevity, at least in old women, rather than the other corre- sponding to A/G (Lys/Arg) transition at 1,245 nt position. Concomitantly, for the +647 MT1a polymorphism, old and very old female with Asp/ Asp genotype (called C-carriers) display higher zinc release by MT (detected by Zinpyr-1 fluo- rescent probe in presence of NO donor), low MT levels and reduced IL-6 plasma concentrations, suggesting its involvement in longevity and in lower inflammatory status. This fact is confirmed by the analysis of haplotypes in which the allele Asp is more involved in longevity. Therefore the +647 MT1a polymorphism more affects MTs induction and zinc release, which are indis- pensable to undertake the inflammatory status under control and subsequently to reach healthy longevity.

Presented at the ZincAge Conference, Madrid, February 10–13, 2006.

C. Cipriano Æ M. Malavolta Æ L. Costarelli Æ R. Giacconi Æ E. Muti Æ N. Gasparini Æ E. Mocchegiani (&) Immunology Ctr. (Section: Nutrition and Immunosenescence), Res. Dept. INRCA, Via Birarelli

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Ancona, Italy e-mail: e.mocchegiani@inrca.it

Introduction

Metallothioneins (MTs), a group of low-molecu- lar-weight metal-binding proteins rich in cysteine

Immunology and Genetic Lab., Istituto di Ricerca Codivilla Putti, IOR, Bologna, Italy

dysregulation of the immune function that accompanies ageing may be due to some poly- morphisms in MT genes. A polymorphism of MTs, such as –209 A/G MT2A, is in fact corre- lated with chronic inflammation (high plasma levels of IL-6) and marked zinc deficiency in old type-2 diabetes-atherosclerotic patients (Giacconi et al. 2005). Some polymorphisms also exist for MT1a gene, in particular those in position +647 and +1245 are relevant because both involved in aminoacid transition. For the first one, Adenine/ Cytosine (A/C) substitution results in aminoacid transition from asparagine to threonine in posi- tion 27 of the protein (PubMed Reference rs 8052394). For the second one, Adenine/Guano- sine (A/G) substitution results in aminoacid transition from Lysine to Arginine in position 51 of the protein (PubMed Reference rs 11640851).

isoforms and play a pivotal role in metal-related cell homeostasis because of their affinity for metals, in particular zinc and copper. The zinc/ cysteine interactions form two metal thiolate clusters forming mercaptide bonds (Kagi and Schaffer 1988). Human MT genes are clustered at a single locus on chromosome 16 (16q13) and at least 10 of the 17 genes so far identified, are functional (West et al. 1990; Stennard et al. 1994). Among them, MT1a gene is the more functional (Richards et al. 1984), expressed in human lymphocytes and up-regulated by zinc (Vandeghinste et al. 2000), with a task of anti- oxidant agent because zinc–sulphur clusters are sensitive to changes in cellular redox state and oxidizing sites, inducing transfer of zinc by MTs to other proteins, such as antioxidant enzymes (Maret and Vallee 1998). Since high MT gene expression in lymphocytes is associated with zinc deficiency in ageing (Mocchegiani et al. 2003), this transfer may be very limited in ageing leading to suggest a different role of MT: from protective as antioxidant agent in young adult-age (Kelly et al. 1996), to a dangerous role in ageing because of the inability of zinc release by MT (Mocchegiani et al. 2002). Indeed, a lack of zinc ion bioavailability in ageing allows a derangement of the immune response as well as impaired antioxidant activity (Mocchegiani et al. 1998). Because MT induction and expression are also under the control of IL-6 (Jacob et al. 1999), this phenomenon of the limited zinc release by MT in ageing is strictly related to the chronic inflam- matory status due to high circulating levels of IL- 6 (Mocchegiani et al. 2003). On the other hand,