The place of environmental factors in multiple sclerosis: Genes, environment and the interactions thereof in the etiology of multiple sclerosis

Climate change impacts the symptomology and healthcare of multiple sclerosis patients through fatigue and heat sensitivity - A systematic review

BACKGROUND

Climate change, in terms of global warming and heat waves, might negatively impact people with neurological diseases. Patients with Multiple Sclerosis (MS), which is characterized by heat sensitivity, may therefore have an increased vulnerability. Subsequently, we aimed to specifically investigate the state of knowledge on climate change and MS.

METHODS

We conducted a literature search in the Pub Med database during 2022-2024 using the search terms "multiple sclerosis" AND "climate ", "climate change", "global warming", "heat waves", and "seasonal variations". A total of 773 scientifical papers were retrieved and scrutinized according to the inclusion/exclusion criteria. Finally, 24 publications were manually selected based on their relevance to the intended topic, covering climate change related heat sensitivity in MS patients, associated healthcare burden, and treatment strategies.

RESULTS

Only few publications focused on climate change and its effect on MS. The search yielded 24 articles on effects of climate/environmental heat and seasonal variations on MS. There was both evidence of worsened clinical symptoms as well as negative studies. However, the majority of selected papers, 16/24 (67 %) revealed an impact on MS symptoms/hospitalization from environmental heat.

CONCLUSIONS

So far there has been limited interest in the vulnerability of MS patients to climate change. The future perspective of increased temperature and heat waves should be highlighted so that authorities prepare health systems to apply to this new, but logical and intuitive, scientific knowledge. As heat sensitivity also seems to affect neurological disorders beyond MS, further research is needed to develop general care strategies in the future.

Stem cell therapy for cuprizone model of multiple sclerosis focusing on the effectiveness of different injection methods and cell labeling

Multiple Sclerosis (MS) is a chronic and autoimmune disease of the central nervous system that causes inflammation in the brain and spinal cord, progressive degeneration of central nervous system tissue, damage to neuronal axons, and loss of function of central nervous system neurons. Experimental encephalomyelitis is an alternative animal model of MS that can simulate the symptoms of this disease. Cuprizone is one of the factors creating this model. Various researchers are testing the use of different cells to reduce the symptoms of cuprizone-demyelinated mice. The different injection methods explained in this article include intracerebral, intraperitoneal, intravenous, and intranasal. The intracerebral method, in contrast to the intranasal method, was widely employed by researchers. In each technique, the researchers try to inject a specific type of stem cell (SC) and monitor their efficiency. For monitoring SCs various labeling procedures are available, however, there is an upward trend in using magnetic resonance imaging (MRI). Two main barriers to using this method are high cost and complexity. In the current review, we try to make review cell therapy in the cuprizone model of MS.

Toxic Air Pollutants and Their Effect on Multiple Sclerosis: A Review Study

Toxic air pollutants are one of the main factors that have the effect of synergism to increase the incidence of multiple sclerosis (MS). This review aims to investigate the effects of toxic air pollutants on the occurrence of multiple sclerosis (MS). A narrative review of the literature was done from 2000 to 2022 based on various databases such as Google Scholar, Web of Science, Springer, PubMed, and Science Direct. In this study, according to the databases, three hundred and sixty articles were retrieved. Of these, 28 studies were screened after review and 14 full-text articles entered into the analysis process. Finally, 9 articles were selected in this study. According to the finding of this study, toxic air pollutants including polycyclic aromatic hydrocarbons (PAHs), heavy metals (HM), volatile organic compounds (VOCs), particulate matter (PM), and gases are the main agents that cause the development and spread of chronic diseases such as respiratory and cardiovascular diseases, chronic obstructive pulmonary disease (COPD), and multiple sclerosis. The result of this study showed that the main sources of emission of toxic air pollutants include industries, cars, power plants, and the excessive consumption of fossil fuels. In general, the inhalation of high concentration of toxic air pollutants can increase the risk of chronic diseases and multiple sclerosis.

Prevention of MS Requires Intervention on the Causes of the Disease: Reconciling Genes, Epigenetics, and Epstein Barr Virus

Prevention of multiple sclerosis requires intervention on modifiable causes of the condition making it necessary to establish what those causes are. MS is often stated to be a polygenic disease, with causal contributions from environmental factors and gene-environment interactions, implying an additive and independent relationship of these factors. Mechanistically there are no independent contributions of genes or environmental factors to traits. This model is unrealistic but still useful and underlies the concept of heritability, a foundational parameter in population genetics. However, it perpetuates a debate on an irreconcilable dichotomy about whether MS is primarily genetic or environmental. In particular, epidemiological evidence now exists for a causal, possibly even necessary, role for Epstein Barr Virus in MS. The additive model makes it unintuitive to reconcile MS as a genetic disease but also independently a viral illness. In this perspective it is argued that starting from a realistic interaction only model, based on broadly accepted biological premises, and working forward to explain why the classical additive model gives useful results, there is actually no paradox. An integrated approach using population genetic studies, immunology and molecular virology offers a particularly promising route to establish the elusive role of EBV in MS pathology, as EBV is a large and complex virus and its latency, dysregulated in most EBV-related pathologies, is hard to study in vivo. This approach may offer a route to prevention of MS altogether.

Immune gene network of neurological diseases: Multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD)

Neurological diseases, such as MS, AD, PD and HD, are a major health concern of the elderly population, but still therapeutic options are limited. Recent advances in genomic sequencing and bioinformatics, present an opportunity to understand mechanisms of these diseases for identification of therapeutic targets. Several studies have shown association of immune dysfunction with immune system mediated neurological disease, MS, as well as neurodegenerative diseases (AD, PD and HD). However, similarities and differences in role of the immune system, immune pathways and immune cell types in these diseases remains unknown. In this study, immune cell type signature genes in gene networks associated with neurological diseases, MS, AD, PD and HD was investigated using meta-analysis and bioinformatics methods. Application of Weighted Gene Co-expression Network Analysis (WGCNA) on publicly available gene expression datasets (microarray and RNA-seq) revealed a ModArray_04 module (microarray) or ModRNAseq_06 module (RNA-seq), significantly associated with MS, AD, PD and HD. Hypergeometric enrichment test revealed significant enrichment of immune cell type genes in these neurological disease modules. This study demonstrates that immune system mediated neurological disease, MS and neurodegenerative diseases (AD, PD and HD), share a common gene network characterized by immune cell type signature genes (microglia, monocytes and macrophages) and are probable targets for therapeutic intervention. In summary, this work shows a connection between MS, a disease where the role of the immune system and inflammation is established, and neurodegenerative diseases (AD, PD and HD) where the role of inflammation is still a hypothesis.

Gut Microbiota Changes in Experimental Autoimmune Encephalomyelitis and Cuprizone Mice Models

Multiple sclerosis (MS) is a chronic and neurodegenerative disease of the central nervous system (CNS) characterized by the immune mediated attack on axons and the subsequent demyelination. There is growing evidence that the gut microbiota of MS patients is altered; however, the connection between demyelination events and changes in the gut microbiota has not been determined. The objective of the current work was to characterize the microbial dysbiosis in two murine demyelinating models and to study the correlation between them. Concurrently, their suitability as predictors of microbial changes in MS patients was assessed. To this purpose, experimental autoimmune encephalomyelitis (EAE) and cuprizone (CPZ) models were induced in C57BL/6 mice that were monitored for 4 and 9 weeks, respectively. Fecal samples were collected during disease progression. Motor skill performance was evaluated by EAE scale measurement in EAE mice and demyelination by magnetic resonance imaging (MRI) in CPZ ones. EAE and CPZ mice revealed drastic microbial changes according to disease progression, adding a new layer of complexity to the understanding of demyelination and remyelination processes. Besides, the reported microbial changes replicate most of the characteristics that define the potential dysbiosis in MS patients. The controlled environment and stable diet that animals have in research centers offer an exceptional scenario to modify animal's microbiota and provide opportunities to study host microbiota interplay with restrained conditions not achievable in human studies. Nevertheless the slight differences from murine model's and patient's microbiota should be considered in the design of studies aiming to modulate the microbiota.

Viral infections and their relationship to neurological disorders

The chronic dysfunction of neuronal cells, both central and peripheral, a characteristic of neurological disorders, may be caused by irreversible damage and cell death. In 2016, more than 276 million cases of neurological disorders were reported worldwide. Moreover, neurological disorders are the second leading cause of death. Generally, the etiology of neurological diseases is not fully understood. Recent studies have related the onset of neurological disorders to viral infections, which may cause neurological symptoms or lead to immune responses that trigger these pathological signs. Currently, this relationship is mostly based on epidemiological data on infections and seroprevalence of patients who present with neurological disorders. The number of studies aiming to elucidate the mechanism of action by which viral infections may directly or indirectly contribute to the development of neurological disorders has been increasing over the years but these studies are still scarce. Comprehending the pathogenesis of these diseases and exploring novel theories may favor the development of new strategies for diagnosis and therapy in the future. Therefore, the objective of the present study was to review the main pieces of evidence for the relationship between viral infection and neurological disorders such as Alzheimer's disease, Parkinson's disease, Guillain-Barré syndrome, multiple sclerosis, and epilepsy. Viruses belonging to the families Herpesviridae, Orthomyxoviridae, Flaviviridae, and Retroviridae have been reported to be involved in one or more of these conditions. Also, neurological symptoms and the future impact of infection with SARS-CoV-2, a member of the family Coronaviridae that is responsible for the COVID-19 pandemic that started in late 2019, are reported and discussed.

High birth weight and risk of multiple sclerosis: A multicentre study in Argentina

BACKGROUND

Multiple sclerosis (MS) is now recognized as a multifactorial disease in which genetic and environmental factors intervene. Considerable efforts have been made to identify external risk factors present in childhood, adolescence and youth, though only a few perinatal risk factors have been positively associated with MS. Previously, we found an association between high birth weight and MS in male patients in a small study in Argentina. The present research was designed to further assess the association between high birth weight and MS in a larger sample of patients, using an extensive and validated general population database as control.

METHODS

We present an analytical observational, multicentre, population-based, and case-control study. A total of 637 patients (cases) with confirmed MS diagnosis attending five MS specialized centres in Argentina were included. Birth weight (BW) data was recalled by the patient's mother, which is a validated approach. A two-way comparison was performed. First, we used the standard categories of high, adequate and low BW in grams. Then, we applied the weight percentile distribution to provide reproducible results for further research. For a proper assessment and comparison of variables, we adopted the guidelines of the American Academy of Pediatrics for neonate classification according to gestational weeks and to BW in grams. The neonate's BW distribution of the general population was used as control. For the purposes of the study, we adapted Urquía's et al. curves, which are based on an extensive database of all the live births registered in the country from 2003 to 2007. To measure the magnitude of the proportional differences between low, adequate and high BW, the odds ratio (OR) and their 95% confidence interval (CI) were estimated. The mean BW and percentile values for each sex were compared using a z-Normal test. The respective MS patients and general population BW distribution curves by sex were compared between each other.

RESULTS

Cases and controls were comparable in their demographic, geographic and environmental characteristics. Males showed higher BW than females both in the MS patients and the general population groups. When we applied the sex stratified analysis separately, we found that males in the MS group showed an almost seven times higher risk of high birth weight than males from the general population (OR 6.58 [95% CI 4.81-8.99]). Female patients showed an almost five times higher risk of high BW than their respective controls (OR 4.5 [95% CI 3.06-6.58]). The comparison based on the BW percentile distribution confirmed that MS patients showed higher BW than the general population. This result reached statistical significance from the 75^th percentile onwards for both sexes.

CONCLUSION

In summary, our findings suggested that high BW could be one of the earliest risk factors for MS in life. If this results were reproduced in other centres, high birth weight would emerge as a novel and very early risk factor, potentially modifiable in utero or immediately postpartum, representing a unique opportunity to prevent the disease in future generations.

Disentangling the molecular mechanisms of multiple sclerosis: The contribution of twin studies

Twin studies of disease concordance are useful to weight the relative contribution of genetic and environmental factors to the cause of common complex disorders. In multiple sclerosis (MS) different twinning rates from geographic areas at different prevalence suggested that heritable and non-heritable factors contribute in different proportions and ways to MS risk in diverse populations. This concept prompted genome-wide association studies, and the implementation of the co-twin control design, that allows stringent experimental approaches in MS-discordant identical pairs, controlling for genetic influences and many other known and unknown factors. The co-twin control design provided important clues on MS molecular model. These studies will be reviewed, focusing on those showing significant differences between affected and healthy co-twins. In some cases, differences that emerged in non-twin patients compared to matched controls were not confirmed in identical MS-discordant pairs, suggesting an 'MS subclinical trait'. Early patterns of magnetic resonance imaging and predictive biomarkers that characterize 'healthy' co-twins may be useful for the identification of a prodromal reversible phase of the disease.