Development of lentiviral vectors targeted to P38MAPK inhibition and Akt activation in motor neurons of a mouse model of familial amyotrophic lateral sclerosis

Peviani, Marco (2010). Development of lentiviral vectors targeted to P38MAPK inhibition and Akt activation in motor neurons of a mouse model of familial amyotrophic lateral sclerosis. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.000100a4

Abstract

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterised by progressive loss of motor neurons in the cortex, brainstem and spinal cord. This leads to weakness and muscular atrophy that evolves to paralysis and death. Studies on patients and animal models of ALS suggest that the pathology is the consequence of the unbalance between pro-degenerative (p38MAPK) and pro-survival (Akt) pathways in motor neurons. In order to re-equilibrate this complex interplay, the major objective of this study was to develop a gene-based approach to target, in vivo, these two intracellular signaling proteins.
We demonstrated for the first time that a construct derived from Hb9 promoter can be used in lentivectors to restrict transgene expression to motor neurons in vivo; moreover we found that induction of Akt pathway, through expression of constitutively activated Akt3 in motor neurons, prevents neuronal loss in SOD1G93A mice, although it does not influence their premature death. On the other hand, we used RNAi to downregulate p38MAPKalpha in a mouse model of ALS. We revealed that expression of p38MAPK-targeted shRNA in the spinal cord of presymptomatic mice reduces motor neuronal loss in the early phases of the pathology, but then it is not able to sustain neuronal survival during disease progression, eventually resulting in worsening of symptoms and shortening of life span. We found preliminary evidences that hyperactivation of microglial cells may be responsible for this more aggressive phenotype, suggesting that a fine tuning of microglial reactivity may be important to avoid pro-degenerative effects.
Overall these data support the hypothesis that modulation of pro-degenerative and pro-survival pathways may help counteracting motor neuronal degeneration, and strengthen the evidence that preservation of neuronal perikaria is not sufficient to ameliorate disease progression in ALS. The peripheral compartment (axons, muscles) should be regarded as an additional target for potential therapeutic approaches.