Activation transcription factor-3 activation and the development of spinal cord degeneration in a rat model of amyotrophic lateral sclerosis

It has been reported that an early activation of glial fibrillary acid protein (GFAP) in astroglial cells occurs simultaneously in peripheral nerves and spinal cord from the G93A SOD1 mouse model of amyotrophic lateral sclerosis (ALS), an invariably fatal neurodegenerative disorder. In ALS, the contribute to the pathological process of different cell types varies according to the disease stage, with a florid immune response in spinal cord at end stage disease. In this study, we have mapped in different anatomical sites the process of disease-induced functional perturbation from a pre-symptomatic stage using a marker of cellular distress expressed in neurons and glial cells, the activating transcription factor 3 (ATF-3), and applied large-scale gene expression analysis to define the pattern or transcriptional changes occurring in spinal cord from the G93A SOD1 rat model of ALS in parallel with ATF-3 neuronal activation. From the disease onset onward, transgenic lumbar spinal cord displayed ATF-3 transcriptional regulation and motor cells immunostaining in association with the over-expression of genes promoting cell growth, the functional integrity of cell organelles and involved in the modulation of immune responses. While spinal cord from the pre-symptomatic rat showed no detectable ATF-3 transcriptional regulation, ATF-3 activation was appreciated in large size neurofilament-rich, small size non-peptidergic and parvalbumin-positive neurons within the dorsal root ganglia (DRG), and in ventral roots Schwann cells alongside macrophages infiltration. This pattern of peripheral ATF-3 activation remained detectable throughout the disease process. In the G93A SOD1 rat model of ALS, signs of roots and nerves subtle distress preceded overt clinical-pathological changes, involving both glial cells and neurons that function as receptors of peripheral sensory stimuli from the muscle. In addition, factors previously described to be linked to ATF-3 activation under various experimental conditions of stress, become switched on in spinal cord from the end-stage transgenic rat model of ALS.