Neurosteroidogenesis and progesterone anti-inflammatory/ neuroprotective effects

Abstract

Progesterone shows anti-inflammatory and promyelinating effects in mice with autoimmune experimental encephalomyelitis (EAE), a commonly used model for multiple sclerosis (MS). Since neurosteroids have been implicated as protective factors for MS and EAE, we analyzed the expression of neurosteroidogenic enzymes in the compromised spinal cord of EAE mice. EAE was induced in female C57Bl6 mice and killed on day 16 after induction. Progesterone was given by pellet implantation 1 week before EAE induction. Untreated EAE mice showed decreased mRNAs for the steroidogenic acute regulatory protein (Star), voltage-dependent anion channel (VDAC), cholesterol side-chain cleavage (P450scc), 5α-reductase, 3α-hydroxysteroid dehydrogenase (3α-HSOR) and aromatase, whereas changes of 3β-hydroxysteroid dehydrogenase (3β-HSD) were not significant. mRNA of 18 Kd translocator protein (TSPO) was elevated, concomitantly with a reactive microgliosis. EAE mice also showed abnormal mitochondrial ultrastructure in axons and neuronal bodies, and reduced expression of fission and fusion protein mRNAs. Progesterone pretreatment before EAE induction increased Star,VDAC, P450scc, 5α-reductase type I, 3α-HSOR and aromatase mRNAs and did not modify 3β-HSD. TSPO mRNA was decreased, possibly due to reversal of microgliosis. Progesterone pretreatment also improved mitochondrial ultrastructure and increased fission/fusion protein mRNAs. These mitochondrial effects may be part of progesterone recovery of neurosteroidogenesis. The enzymes 3β-HSD, 3α-HSOR and 5α-reductase are also responsible for the formation of androgens. Since MS patients and EAE rodents show changes of central androgen levels, it is likely that together with progestins and estrogens, neuroandrogens afford neuroprotection for EAE and MS. Data reviewed in this paper suggest that enhanced synthesis of neurosteroids contributes in an auto/paracrine manner to reinforce the neuroprotective and anti-inflammatory effects of exogenous progesterone given to EAE mice.

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