Oxidative stress and autophagic alteration in brainstem of SOD1-G93A mouse model of ALS.

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease involving both upper and lower motor neurons. The mechanism of motor neuron degeneration is still unknown. Although many studies have been performed on spinal motor neurons, few have been reported on brainstem and its motor nuclei. The aim of this study was to investigate oxidative stress and autophagic changes in the brainstem and representative motor nuclei of superoxide dismutase 1 (SOD1)-G93A mouse model of ALS. The expression levels of cluster of differentiation molecule 11b (CD11b), glial fibrillary acidic protein, glutamate-cysteine ligase catalytic subunit, heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, voltage-dependent anion-selective channel protein 1, Sequestosome 1/p62 (p62), microtubule-associated protein 1 light chain 3B (LC3), and SOD1 proteins in brainstem were examined by Western blot analysis. Immunohistochemistry and immunofluorescence were performed to identify the cellular localization of SOD1, p62, and LC3B, respectively. The results showed that there were progressive asctrocytic proliferation and microglial activation, induction of antioxidant proteins, and increased p62 and LC3II expression in brainstem of SOD1-G93A mice. Additionally, SOD1 and p62 accumulated in hypoglossal, facial, and red nuclei, but not in oculomotor nucleus. Furthermore, electron microscope showed increased autophagic vacuoles in affected brainstem motor nuclei. Our results indicate that brainstem share similar gliosis, oxidative stress, and autophagic changes as the spinal cord in SOD1-G93A mice. Thus, SOD1 accumulation in astrocytes and neurons, oxidative stress, and altered autophagy are involved in motor neuron degeneration in the brainstem, similar to the motor neurons in spinal cord. Therefore, therapeutic trials in the SOD1G93A mice need to target the brainstem in addition to the spinal cord.

The modest impact of transcription factor Nrf2 on the course of disease in an ALS animal model.

Oxidative stress is associated with the pathogenesis of amyotrophic lateral sclerosis (ALS). Nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway is one of the major cellular defense mechanisms against oxidative stress. However, the role of Nrf2-mediated neuroprotection (antioxidant defense) in the disease development of ALS remains unclear. To further investigate the role of Nrf2 in ALS, we genetically eliminate the Nrf2 gene from SOD1-G93A mice, a commonly used ALS mouse model, by generating a double mutant (Nrf2-/- SOD1-G93A mice). We found that it only had a modest impact on the course of disease by knocking out Nrf2 gene in these mice. Further studies demonstrated that, among previously known Nrf2-regulated phase II enzymes, only NAD(P)H: quinone oxidoreductase 1 induction was significantly affected by the elimination of Nrf2 gene in SOD1-G93A mice. Taken together, our data suggested that Nrf2 is not the sole mediator for the induction of antioxidant genes in SOD1-G93A mice, and Nrf2-mediated neuroprotection is not the key protective mechanism against neurodegeneration in those mice.

Food restriction-induced autophagy modulates degradation of mutant SOD1 in an amyotrophic lateral sclerosis mouse model.

Autophagy dysregulation has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). The expression of LC3II and sequestosome 1 (P62) was progressively increased in the lumbar spinal cord of ALS mice. However, whether autophagy is activated or inhibited is still unclear. By treating mice with food restriction, a well-recognized way to induce autophagy, we found that 48 h of food restriction significantly reduced p62 and mutated SOD1 expressions at onset stage but not at pre-end stage in the spinal cord of SOD1-G93A mice. These data indicate that activating autophagy at a certain disease stage may have potential protective effects on ALS.

HO-1 induction in motor cortex and intestinal dysfunction in TDP-43 A315T transgenic mice.

TAR DNA-binding protein 43 (TDP-43) has been found to be related to the pathogenesis of amyotrophic lateral sclerosis (ALS). TDP-43 A315T transgenic mice develop degeneration of specific motor neurons, and accumulation of ubiquitinated proteins has been observed in the pyramidal cells of motor cortex of these mice. In this study, we found stress-responsive HO-1 induction and no autophagic alteration in motor cortex of TDP-43 A315T transgenic mice. Glial activation, especially astrocytic proliferation, occurred in cortical layer 5 and sub-meningeal region. Interestingly, we noticed that progressively thinned colon, swollen small intestine and reduced food intake, rather than severe muscle weakness, contributed to the death of TDP-43 A315T transgenic mice. Increased TDP-43 accumulation in the myenteric nerve plexus and increased thickness of muscular layer of colon were related to the intestinal dysfunction.