The role of apoptosis in in vitro and in vivo models of amyotrophic lateral sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease leading to motor neurons death. Although many studies were performed, the aetiology and the features of cellular death occurring in ALS are poorly understood, and studies carried out from autoptic samples do not allow to clarify early events occurring in ALS. To understand the basic mechanisms leading to motor neuronal death in ALS and to detect the different steps involved in motor neuron degeneration, alternative models are required. The wobbler mouse is one of the most reliable models of human motor neurodegenerative diseases. In the wobbler mouse neuromuscular deficits that are related to a selective vulnerability of cervical spinal cord motor neurons have an early onset and progress rapidly. In my project of thesis I first characterized apoptosis in primary cultures of motor neurons exposed to detrimental stimuli, and then I evaluated the possible involvement of apoptosis in the cervical spinal cord neurons of early symptomatic wobbler mice. In primary cultures of motor neurons I found that: I) BDNF deprivation produced apoptotic cell death, II) AMPA and kainate induced apoptotic or non apoptotic cell death depending on the experimental conditions utilized, III) EPO selectively protected motor neurons committed to dye apoptically. In wobbler mice I found that: I) mitochondrial activity is reduced but caspase9 -mediated apoptosis does not seem involved, II) glutamate induced excitotoxicity does not seem involved in motor neuron degeneration, III) markers of neuroinflammation, such as activated microglia and TNF-a, appeared highly increased in the cervical region of early symptomatic wobbler mice but this process does not seem to induce the activation of caspase 8-mediated apoptosis. Pharmacological treatments confirmed that an antiglutamatergic agent (RPR 119990) and an antiapoptotic agent (EPO) were ineffective, while riluzole showed protective effects. Although alternative cell death pathways should be investigated, my study excludes apoptosis as the mechanism of death in cervical motor neurons of wobbler mice.