Comparative analysis of the time-dependent functional and molecular changes in spinal cord degeneration induced by the G93A SOD1 gene mutation and by mechanical compression

All-in-one wearable drug efficacy assessment systems for bulbar muscle function using amyotrophic lateral sclerosis animal models

Preclinical studies are crucial for developing amyotrophic lateral sclerosis drugs. Current FDA-approved drugs have been created by monitoring limb muscle function and histological analysis of amyotrophic lateral sclerosis model animals. Drug candidates for this disease have yet to be tested for bulbar-onset type due to the limitations of traditional preclinical tools: excessive animal use and discrete detection of disease progress. Here, our study introduces an all-in-one, wireless, integrated wearable system for facilitating continuous drug efficacy assessment of dysphagia-related muscles in animals during natural eating behaviors. By incorporating a kirigami-based strain-isolation mechanism, this device mounted on the skin of animals mitigates electromyography signal contamination caused by unpredictable animal movements. Our findings indicate this system, measuring the progression of motor neuron denervation, offers high precision in monitoring drug effects on dysphagia-responsible bulbar muscles. This study paves the way for more humane and efficient approaches to developing treatment solutions for degenerative neuromuscular diseases.

Role of NLRP3 Inflammasome in Post-Spinal-Cord-Injury Anxiety and Depression: Molecular Mechanisms and Therapeutic Implications

The majority of research on the long-term effects of spinal cord injury (SCI) has primarily focused on neuropathic pain (NP), psychological issues, and sensorimotor impairments. Among SCI patients, mood disorders, such as anxiety and depression, have been extensively studied. It has been found that chronic stress and NP have negative consequences and reduce the quality of life for individuals living with SCI. Our review examined both human and experimental evidence to explore the connection between mood changes following SCI and inflammatory pathways, with a specific focus on NLRP3 inflammasome signaling. We observed increased proinflammatory factors in the blood, as well as in the brain and spinal cord tissues of SCI models. The NLRP3 inflammasome plays a crucial role in various diseases by controlling the release of proinflammatory molecules like interleukin 1β (IL-1β) and IL-18. Dysregulation of the NLRP3 inflammasome in key brain regions associated with pain processing, such as the prefrontal cortex and hippocampus, contributes to the development of mood disorders following SCI. In this review, we summarized recent research on the expression and regulation of components related to NLRP3 inflammasome signaling in mood disorders following SCI. Finally, we discussed potential therapeutic approaches that target the NLRP3 inflammasome and regulate proinflammatory cytokines as a way to treat mood disorders following SCI.

Nutritional interventions for spinal cord injury: preclinical efficacy and molecular mechanisms

Spinal cord injury (SCI) is a debilitating condition that leads to motor, sensory, and autonomic impairments. Its intrinsic pathophysiological complexity has hindered the establishment of effective treatments for decades. Nutritional interventions (NIs) for SCI have been proposed as a route to circumvent some of the problems associated with this condition. Results obtained in animal models point to a more holistic effect, rather than to specific modulation, of several relevant SCI pathophysiological processes. Indeed, published data have shown NI improves energetic imbalance, oxidative damage, and inflammation, which are promoters of improved proteostasis and neurotrophic signaling, leading ultimately to neuroprotection and neuroplasticity. This review focuses on the most well-documented Nis. The mechanistic implications and their translational potential for SCI are discussed.

Inflammation is increased with anxiety- and depression-like signs in a rat model of spinal cord injury

Spinal cord injury (SCI) leads to increased anxiety and depression in as many as 60% of patients. Yet, despite extensive clinical research focused on understanding the variables influencing psychological well-being following SCI, risk factors that decrease it remain unclear. We hypothesized that excitation of the immune system, inherent to SCI, may contribute to the decrease in psychological well-being. To test this hypothesis, we used a battery of established behavioral tests to assess depression and anxiety in spinally contused rats. The behavioral tests, and subsequent statistical analyses, revealed three cohorts of subjects that displayed behavioral characteristics of (1) depression, (2) depression and anxiety, or (3) no signs of decreased psychological well-being. Subsequent molecular analyses demonstrated that the psychological cohorts differed not only in behavioral symptoms, but also in peripheral (serum) and central (hippocampi and spinal cord) levels of pro-inflammatory cytokines. Subjects exhibiting a purely depression-like profile showed higher levels of pro-inflammatory cytokines peripherally, whereas subjects exhibiting a depression- and anxiety-like profile showed higher levels of pro-inflammatory cytokines centrally (hippocampi and spinal cord). These changes in inflammation were not associated with injury severity; suggesting that the association between inflammation and the expression of behaviors characteristic of decreased psychological well-being was not confounded by differential impairments in motor ability. These data support the hypothesis that inflammatory changes are associated with decreased psychological well-being following SCI.

Morphologic features and glial activation in rat oxaliplatin-dependent neuropathic pain

Neurotoxicity is the limiting side effect of the anticancer agent oxaliplatin. A tangled panel of symptoms, sensory loss, paresthesia, dysesthesia, and pain may be disabling for patients and adversely affect their quality of life. To elucidate the morphologic and molecular alterations that occur in the nervous system during neuropathy, rats were daily injected with 2.4 mg kg(-1) oxaliplatin intraperitoneally. A progressive decrease in the pain threshold and hypersensitivity to noxious and nonnoxious stimuli were evidenced during the treatment (7, 14, 21 days). On day 21, morphometric alterations were detectable exclusively in the dorsal root ganglia, whereas the activating transcription factor 3 and neurofilament (heavy-chain) expression changed dramatically in both the nerves and ganglia. Inflammatory features were not highlighted. Interestingly, satellite cells exhibited signs of activation. Glial modulation was characterized in the spinal cord and brain areas involved in pain signaling. On the 21st day, spinal astrocytes increased numerically whereas the microglial population was unaltered. The number of glial cells in the brain differed according to the zone and treatment time points. In particular, on day 21, a significant astrocyte increase was measured in the anterior cingulate cortex, somatosensory area 1, neostriatum, ventrolateral periaqueductal gray, and nucleus raphe magnus.

PERSPECTIVES

These data highlight the relevance of glial cells in chemotherapy-induced neurotoxicity as part of the investigation of the role that specific brain areas play in neuropathy.

A hydrogen sulfide-releasing cyclooxygenase inhibitor markedly accelerates recovery from experimental spinal cord injury

Spinal cord trauma causes loss of motor function that is in part due to the ensuing inflammatory response. Hydrogen sulfide (H2S) is a potent, endogenous anti-inflammatory and neuroprotective substance that has been explored for use in the design of novel nonsteroidal anti-inflammatory drugs. In the current study, we evaluated the potential beneficial effects of ATB-346 [2-(6-methoxynapthalen- 2-yl)-propionic acid 4-thiocarbamoyl-phenyl ester], an H2S-releasing derivative of naproxen, in a murine model of spinal cord injury (SCI). SCI was induced in mice by spinal cord compression, produced through the application of vascular clips to the dura via a T5 to T8 laminectomy. ATB-346, naproxen (both at 30 μmol/kg), or vehicle was orally administered to the mice 1 and 6 h after SCI and once daily thereafter for 10 d. Motor function [Basso Mouse Scale (BMS) of locomotion] improved gradually in the mice treated with naproxen. However, those treated with ATB-346 exhibited a significantly more rapid and sustained recovery of motor function, achieving greater than double the increase in locomotion score of the naproxen group by the 10th day of treatment. ATB-346 also significantly reduced the severity of inflammation (proinflammatory cytokines, apoptosis of neural tissue, and nitrosative stress) that characterized the secondary effects of SCI. Again, the effects of ATB-346 were superior to those of naproxen for several parameters. These results showed marked beneficial effects of an H2S-releasing derivative of naproxen in an animal model of SCI, significantly enhancing recovery of motor function, possibly by reducing the secondary inflammation and tissue injury that characterizes this model. The combination of inhibition of cyclooxygenase and delivery of H2S may offer a promising alternative to existing therapies for traumatic injury.

Gene expression profile of SOD1-G93A mouse spinal cord, blood and muscle

The exact pathway leading to neuron death and muscle atrophy in amyotrophic lateral sclerosis (ALS) has not yet been elucidated. Gene expression profile of spinal cord, blood and muscle could provide signalling pathways and systemic alterations useful for future biomarker development. In our study we compared whole genome expression profiles of lumbar spinal cord with peripheral blood and tibialis anterior muscle in 16 mutant SOD1-G93A mice and 15 wild-type littermates. In SOD1-G93A mice, 11 genes were significantly differentially expressed in spinal cord, and 16 genes in blood, while much larger transcriptional changes were noted in muscle (1745 genes significant; six overlapping with spinal cord (0.3%)) probably due to muscle atrophy. Overlap with spinal cord was enriched for significant genes in blood (six of 16 overlapping with spinal cord (37.5%)). Three genes were significantly down-regulated in all three tissues, and were closely related to mitochondrial function. Furthermore, clustering the significant genes in spinal cord and in blood, but not in muscle, could identify the SOD1-G93A mice. We conclude that blood gene expression profile overlapped with profile of spinal cord, allowing differentiation of SOD1-G93A mice from wild-type littermates. Blood gene expression profiling may be a promising biomarker for ALS patients.

Spinal cord trauma and the molecular point of no return

A mechanical trauma to the spinal cord can be followed by the development of irreversible and progressive neurodegeneration, as opposed to a temporary or partially reversible neurological damage. An increasing body of experimental and clinical evidence from humans and animal models indicates that spinal cord injury may set in motion the development of disabling and at times fatal neuromuscular disorders, whose occurrence is not normally associated with any major environmental event. This outcome appears to be dependent on the co-occurrence of a particular form of mechanical stress and of a genetically-determined vulnerability. This increased vulnerability to spinal cord injury may depend on a change of the nature and of the timing of activation of a number of neuroprotective and neurodestructive molecular signals in the injured cord. Among the main determinants, we could mention an altered homeostasis of lipids and neurofilaments, an earlier inflammatory response and the failure of the damaged tissue to rein in oxidative damage and apoptotic cell death. These changes could force injured tissue beyond a point of no return and precipitate an irreversible neurodegenerative process. A better knowledge of the molecular signals activated in a state of increased vulnerability to trauma can inform future treatment strategies and the prediction of the neurological outcome after spinal cord injury.

The human G93A-SOD1 mutation in a pre-symptomatic rat model of amyotrophic lateral sclerosis increases the vulnerability to a mild spinal cord compression

Background

Traumatic injuries can undermine neurological functions and act as risk factors for the development of irreversible and fatal neurodegenerative disorders like amyotrophic lateral sclerosis (ALS). In this study, we have investigated how a mutation of the superoxide dismutase 1 (SOD1) gene, linked to the development of ALS, modifies the acute response to a gentle mechanical compression of the spinal cord. In a 7-day post-injury time period, we have performed a comparative ontological analysis of the gene expression profiles of injured spinal cords obtained from pre-symptomatic rats over-expressing the G93A-SOD1 gene mutation and from wild type (WT) littermates.

Results

The steady post-injury functional recovery observed in WT rats was accompanied by the early activation at the epicenter of injury of several growth-promoting signals and by the down-regulation of intermediate neurofilaments and of genes involved in the regulation of ion currents at the 7 day post-injury time point. The poor functional recovery observed in G93A-SOD1 transgenic animals was accompanied by the induction of fewer pro-survival signals, by an early activation of inflammatory markers, of several pro-apoptotic genes involved in cytochrome-C release and by the persistent up-regulation of the heavy neurofilament subunits and of genes involved in membrane excitability. These molecular changes occurred along with a pronounced atrophy of spinal cord motor neurones in the G93A-SOD1 rats compared to WT littermates after compression injury.

Conclusions

In an experimental paradigm of mild mechanical trauma which causes no major tissue damage, the G93A-SOD1 gene mutation alters the balance between pro-apoptotic and pro-survival molecular signals in the spinal cord tissue from the pre-symptomatic rat, leading to a premature activation of molecular pathways implicated in the natural development of ALS.

Differential histone deacetylase mRNA expression patterns in amyotrophic lateral sclerosis

Histone deacetylases (HDACs) are important regulators of gene expression and cell differentiation. The HDAC inhibitors have recently been considered as potential novel neuroprotective drugs for the treatment of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). A major limitation, however, lies in the broad spectrum of action of currently available HDAC inhibitors that may cause a variety of toxic side effects. The mRNA expression levels of the HDAC isoforms HDACs 1 to 11 have previously been characterized in rat brain but have not been studied in human tissue. Using in situ hybridization histochemistry and immunohistochemistry we assessed the distribution and expression levels of HDACs 1to 11 in postmortem ALS and control brain and spinal cord specimens (n = 6 cases each) to determine alterations in the mRNA expression pattern that could provide a basis for disease-specific therapies. We found a reduction of HDAC 11 mRNA and increased HDAC 2 levels in ALS brain and spinal cord compared with controls. A more precise knowledge of the disease-related expression pattern could lead to the development of more specific pharmacotherapeutic approaches.

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.