Caratterizzazione di un modello di encefalomielite autoimmune sperimentale e ruolo neuroprotettivo del progesterone

Studies concerning the role of neuroactive steroids in chronic models of Experimental Autoimmune Encephalomyelitis (EAE) are still scarce. First we considered different pathological targets in Dark Agouti (DA) rats affected by EAE in order to well characterize this chronic model of Multiple Sclerosis (MS) which well reflects the relapsing-remitting form of MS. We analyzed neuroinflammatory profile, assonopathy and neuroactive steroid levels in the spinal cord of DA rats affected by EAE. Data obtained at 14 dpi (i.e. days post induction) showed that acute neurological signs were associated with infiltrating T cells (CD3+) and macrophages (ED1+) and with microglial activation (MHC-II+ cells) which were accompanied by an increased expression of pro- and anti-inflammatory cytokines in the spinal cord. We immunolocalized a few damaged axons (SMI-32+) in the spinal cord white matter, moreover we identified a general decrease in the level of most neuroactive steroids analyzed. At 45 dpi we observed a decrease of inflammatory infiltration, of microglial cell activation and of cytokine gene expression respect to EAE rats at 14dpi. Assonopathy was exacerbated as demonstrated by the increase in SMI-32 immunoreactivity and by the decreased Na+,K+-ATPase activity. Changes in the neuroactive steroid level observed at 14dpi were maintained or reverted at 45dpi. Interestingly, the level of progesterone (PROG) significantly decreased only at 45dpi suggesting a possible role of this neuroactive steroid in the chronicization of EAE. Basing on this evidence, we performed a second study aimed to evaluate the possible neuroprotective properties of PROG treatment in DA rats affected by EAE. Data obtained at 45 dpi showed that PROG was able to improve EAE course by reducing the spinal cord neuroinflammation and microglia activation. Moreover PROG treatment was able to promote a functional recover of axons and to counteract the MBP protein reduction observed in EAE rats. Finally an increase in the levels of dihydroprogesterone and isopregnanolone (i.e. two PROG metabolites) was also observed in the spinal cord after PROG treatment providing evidence on PROG metabolic profile. Taken together these results indicate that PROG may have a role in the pathogenesis of EAE and that it is effective in reducing the severity of EAE in DA rats. Consequently our data may represent an interesting background for future treatments of MS based on synthetic analogous of PROG.