• ALS
• microglia
• motor cortex
• motor neurons
• serotonin
• SOD1G93A
• striatum
• Trimetazidine

Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease characterized by the degeneration of motor neurons in the brain, brainstem and spinal cord. The degeneration of motor neurons is accompanied by a marked activation of microglial cells, the main cells of the innate immune system of the central nervous system. Microglia have the ability to adapt their function, gene expression and metabolism in response to various environmental stimuli; their activation is also reflected in their morphology. Furthermore, among the various regulators of microglial function, a potential immunomodulatory role for the neurotransmitter serotonin has also emerged from the literature. However, a clear correlation between serotonin-induced microglia activation and the influence that this regulatory mechanism might have in ALS is still lacking. The first aim of this thesis project was to examine the involvement of microglia at the brain level compared to their clear activation at the spinal cord level, which have already been reported in the literature. For this purpose, the superoxide dismutase 1 G93A (SOD1G93A) transgenic mouse was used as an ALS model, and fluorescence immunohistochemistry analyses were performed on brain sections of wild-type and SOD1G93A transgenic mice, with associated confocal microscopy and Sholl analyses to study in detail the morphology of microglial cells. Being the modulation of microglia is associated with metabolic variations of these cells, we also evaluated the efficacy of the metabolic modulator Trimetazidine (TMZ) on microglia activation, by Sholl analyses. Our data showed that in the cortex of SOD1G93A mice there is a reduction of microglial complexity, similarly to what was observed in the spinal cord, although to a less marked extent. This minor variation could suggest a type of activation that is not only more attenuated, but also probably distinct. TMZ treatment showed a positive effect in mitigating microglia morphological changes in SOD1G93A transgenic mice. This effect is particularly interesting since it suggests that metabolic modulation could represent an effective strategy in slowing down the progression of the disease. TMZ could in fact potentially stimulate the anti-inflammatory microglial phenotype, generally associated with a more oxidative metabolism, compared to the more glycolytic pro-inflammatory phenotype. Moreover, in order to be able to analyze the details the mechanism of action of TMZ, we decided to take advantage of the zebrafish larva model in which the motor neurons are clearly visible in vivo. In this thesis, as an experiment preliminary to such an analysis, we demonstrated that TMZ is able to act on zebrafish larvae where it induces a significant increase of motility.Finally, here we started evaluating the role of serotonin in this pathology, by analyzing the expression of serotonin receptors by qPCR on lysates of cortex, striatum, cerebellum, and spinal cord of SOD1G93A transgenic mice compared to wild-type mice. Whereas an increased expression of the 5HT-2B receptor was observed in spinal cord microglia, as already reported in the literature, the expression of 5HT-2B, 5HT-2A, 5HT-2C and 5HT-6 receptors, did not show significant variations in the investigated areas. Further research will be necessary to explore the molecular pathways involved in this pathological context and to clarify the underlying molecular mechanisms and the efficacy of the drug used.