Fragment C of tetanus toxin, more than a carrier. Novel perspectives in non-viral ALS gene therapy

The non-toxic carboxy-terminal fragment of tetanus toxin heavy chain (TTC) has been implicated in the activation of cascades responsible for trophic actions and neuroprotection by inhibition of apoptosis. Previous in vitro studies have described signalling pathways that underlie the administration of TTC to neurons. We investigated whether these properties were maintained in a mouse model of neurodegenerative disease. Naked DNA encoding for TTC was injected intramuscularly and neuromuscular function and clinical behaviour were monitored until endstage in the transgenic SOD1 G93A mouse model that expresses a mutant variant of human superoxide dismutase 1 (SOD1). Our results indicate that TTC treatment ameliorated the decline of hindlimb muscle innervation, significantly delayed the onset of symptoms and functional deficits, improved spinal motor neuron survival, and prolonged lifespan. Furthermore, we found that caspase-1 and caspase-3 proapoptotic genes were down-regulated in the spinal cord of treated mice. Western blot analysis showed that the active form of caspase-3 was also down-regulated after TTC treatment and survival signals, such as the significant phosphorylation of serine/threonine protein kinase Akt, were also detected. These results suggest that fragment C of tetanus toxin, TTC, provides a potential therapy for neurodegenerative diseases.