Therapeutic effect of combination vitamin D3 and siponimod on remyelination and modulate microglia activation in cuprizone mouse model of multiple sclerosis

Technical Assessment of Motor and Behavioral Tests in Rodent Models of Multiple Sclerosis

BACKGROUND

Multiple sclerosis (MS) is a neurodegenerative disorder characterized by progressive motor and cognitive impairments, affecting millions worldwide. It significantly reduces patients' quality of life and imposes a burden on health systems. Despite advances in understanding MS, there is no cure, highlighting the need for effective therapeutic strategies. Preclinical animal models are critical for gaining insights into MS pathophysiology and treatments. However, these models fail to fully replicate the complexity of human MS, making it essential to choose appropriate models and behavioral tests to evaluate their efficacy.

PURPOSE

This review examines various motor and cognitive behavioral tests used in preclinical MS models, discussing their strengths and limitations. The goal is to guide researchers in selecting the most appropriate tests for their models, while providing insights into how these tests are performed and analyzed.

METHODS

We reviewed motor and cognitive behavioral tests used in MS models, detailing test procedures and evaluating their advantages and disadvantages.

RESULTS

This review offers a comprehensive overview that aids researchers in choosing the most suitable tests for their studies, improving the accuracy and reliability of preclinical MS research.

CONCLUSIONS

Understanding the strengths and limitations of these tests is crucial for making informed decisions, leading to better experimental designs and, ultimately, more effective therapeutic interventions for MS.

Siponimod supports remyelination in the non-supportive environment

Inflammatory demyelination, a hallmark of multiple sclerosis (MS) lesions, leads to functional impairments and progressive axonal loss over time. Although remyelination is thought to protect axons, endogenous regenerative processes are often incomplete or fail entirely in many MS patients. While the precise reasons for remyelination failure remain unclear, repeated demyelination in previously affected white matter regions is a recognized contributing factor. In a previous study, we demonstrated that the sphingosine-1-phosphate modulator Siponimod ameliorates metabolic oligodendrocyte injury in an MS animal model. In this study, we explored the potential of Siponimod to enhance remyelination in a non-supportive environment. To this end, male mice were subjected to Cuprizone intoxication for seven weeks. From the onset of the fifth week, when oligodendrocyte progenitor cells begin to differentiate, mice were administered either a vehicle or Siponimod solution. Post-treatment, brain specimens were processed for (immune-) histochemical analyses. After four weeks of Cuprizone intoxication, staining intensities for various myelination markers, were significantly reduced. At the end of week seven, loss of myelin staining intensities was still pronounced, but anti-myelin basic protein (MBP) and myelin-associated glycoprotein (MAG) expression was significantly higher in Siponimod- versus vehicle-treated mice. Consistent with this finding, densities of OLIG2+ oligodendrocytes significantly recovered in Siponimod-treated but not in vehicle-treated mice. This enhanced recovery was paralleled by the trend of lower densities of Ki67+ proliferating oligodendrocyte progenitor cells. Our findings suggest that Siponimod has modest pro-regenerative capacities, partly explaining the amelioration of disease progression in secondary progressive MS patients.

Neurotherapeutic impact of vanillic acid and ibudilast on the cuprizone model of multiple sclerosis

Multiple sclerosis (MS) affects 2.8 million people worldwide. Although the cause is unknown, various risk factors might be involved. MS involves the immune system attacking the central nervous system's myelin sheath, leading to neuron damage. This study used a cuprizone (CPZ)-intoxicated mouse model to simulate MS's demyelination/remyelination process. It evaluated the molecular, histological, and behavioral effects of vanillic acid (VA), a natural phenolic acid, alone and with Ibudilast (IBD), a clinically tested MS medication. Mice were divided into a control group (regular chow) and a CPZ group (0.3% cuprizone chow for 5 consecutive weeks). During remyelination, the CPZ group was split into four groups: no therapy, 10 mg/kg of IBD, 30 mg/kg of VA, and combined, each treated for 4 weeks. Behavioral, biochemical, molecular, and histopathological tests occurred in the 5th week (demyelination), 7th (early remyelination), and 9th (late remyelination). Cognitive assessments were at weeks 5 and 9. VA enhanced motor, coordination, and cognitive impairments in CPZ-intoxicated mice and improved histopathological, molecular, and biochemical features during early remyelination. IBD improved behavioral abnormalities across all tests, but combined therapy showed no significant difference from single therapies. Further investigations are necessary to understand VA's mechanisms and potential as an MS treatment.

Understanding Multiple Sclerosis Pathophysiology and Current Disease-Modifying Therapies: A Review of Unaddressed Aspects

Multiple sclerosis (MS) is a complex autoimmune disorder of the central nervous system (CNS) with an unknown etiology and pathophysiology that is not completely understood. Although great strides have been made in developing disease-modifying therapies (DMTs) that have significantly improved the quality of life for MS patients, these treatments do not entirely prevent disease progression or relapse. Identifying the unaddressed pathophysiological aspects of MS and developing targeted therapies to fill in these gaps are essential in providing long-term relief for patients. Recent research has uncovered some aspects of MS that remain outside the scope of available DMTs, and as such, yield only limited benefits. Despite most MS pathophysiology being targeted by DMTs, many patients still experience disease progression or relapse, indicating that a more detailed understanding is necessary. Thus, this literature review seeks to explore the known aspects of MS pathophysiology, identify the gaps in present DMTs, and explain why current treatments cannot entirely arrest MS progression.

Vitamin D: The crucial neuroprotective factor for nerve cells

Vitamin D is well known for its role in regulating the absorption and utilization of calcium and phosphorus as well as bone formation, and a growing number of studies have shown that vitamin D also has important roles in the nervous system, such as maintaining neurological homeostasis and protecting normal brain function, and that neurons and glial cells may be the targets of these effects. Most reviews of vitamin D's effects on the nervous system have focused on its overall effects, without distinguishing the contributors to these effects. In this review, we mainly focus on the cells of the central nervous system, summarizing the effects of vitamin D on them and the related pathways. With this review, we hope to elucidate the role of vitamin D in the nervous system at the cellular level and provide new insights into the prevention and treatment of neurodegenerative diseases in the direction of neuroprotection, myelin regeneration, and so on.

Microglial Neuroinflammation-Independent Reversal of Demyelination of Corpus Callosum by Arsenic in a Cuprizone-Induced Demyelinating Mouse Model

Demyelination is the loss of myelin in CNS, resulting in damaged myelin sheath. Oxidative stress and neuroinflammation play a key role in inducing demyelinating diseases like MS; hence, controlling oxidative stress and neuroinflammation is important. Cuprizone (CPZ), a copper chelator, generates oxidative stress and neuroinflammation, thereby inducing demyelination. Therefore, the CPZ-induced demyelinating mouse model (CPZ model) is widely used in research. The present study was intended to unravel a mechanism of inhibition of demyelination by arsenic in a CPZ model, which is otherwise known for its toxicity. We investigated an alternative mechanism of inhibition of demyelination by arsenic through the reversal of SOD1 activity employing in silico analysis, analytical chemistry techniques, and in vitro and in vivo experiments. In vivo experiments showed protection of body weight, survivability, and myelination of the corpus callosum in CPZ and arsenic-co-exposed animals, where neuroinflammation was apparently not involved. In vitro experiments revealed that arsenic-mediated reversal of impaired SOD1 activity leads to reduced cellular ROS levels and better viability of primary oligodendrocytes. Reversal of SOD1 activity was also observed in the corpus callosum tissue isolated from experimental animals. In silico and analytical chemistry studies revealed that similar to copper, arsenic can potentially bind to CPZ and thereby make the copper freely available for SOD1 activity. Suitable neurobehavior tests further validated the protective effect of arsenic. Taken together, the present study revealed that arsenic protects oligodendrocytes and demyelination of corpus callosum by reversing CPZ-induced impaired SOD1 activity.

Vitamin D Supplementation: Effect on Cytokine Profile in Multiple Sclerosis

Vitamin D is known for its role in modulating calcium and phosphate homeostasis and is implicated both in bone mineralization and immune system regulation. The immune-modulatory role of vitamin D and its impact on multiple sclerosis (MS) courses are still debated. The aim of this review was to check the effect of vitamin D supplementation on cytokine profile regulation in people with MS. A significant increase in serum concentrations of interleukin (IL)-10 and Transforming growth factor (TGF)-β1 after vitamin D supplementation was demonstrated in most studies, with some of them reporting a reduction in disability scores after vitamin D supplementation and an inverse correlation between IL-10 levels and disability. The effect of vitamin D on the serum levels of IL-17 and IL-6 was controversial; different results across studies could be explained by a variability in the treatment duration, route, and frequency of administration, as well as the dosage of vitamin D supplementation, responses to vitamin D treatment and the serum levels reached with supplementation, including the methods used for cytokine analysis and the different cell types investigated, the MS phenotype, the disease phase (active vs. non-active) and duration, and concomitant treatment with disease-modifying therapies. Nevertheless, the significant increase in the serum concentrations of IL-10 and TGF-β1, demonstrated in most studies, suggests an anti-inflammatory effect of vitamin D supplementation.