Mouse metallothionein-1 and metallothionein-2 are not biologically interchangeable in an animal model of multiple sclerosis, EAE

Abstract

Mouse metallothionein-1 and 2 (MT1 and MT2) are often considered physiologically equivalent, because they are normally regulated coordinately by a wide range of stimuli, and it is assumed that in vivo they will be normally fully loaded with zinc(II) (Zn₇-MT1/2), although other metal ions, such as copper(I), may be eventually found as well. However, mouse MT2, in contrast to MT1, exhibits a preference for Zn(II) coordination in comparison to that for Cu(I), which might underlie putatively different biological functions for these two mammalian isoforms. We have characterized the effects of exogenously administered mouse MT1 and MT2, and of transgenic Mt1 overexpression, in an animal model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE), by active immunization with MOG_35–55 peptide. Mice treated daily with MT2 showed a significant amelioration of the clinical course, with decreased peak and cumulative scores and delayed onset of EAE. In contrast, treatment with MT1 or its transgenic overexpression only caused a non-significant trend. MT2 treatment preserved better the myelin of the spinal cord, and the pattern of leukocyte infiltrates and gene expression are compatible with an inhibitory effect on neuroinflammation. Splenocytes from these animals in culture responded adequately to MOG_35–55 peptide, but a bias for a Th2 profile seemed to be present in the MT2-treated mice. Interestingly, MT1 but not MT2 decreased the number of cytokines in the serum. The present results indicate that mouse MT1 and MT2 are not biologically interchangeable in the EAE model.