Shedding light on Multiple Sclerosis: Neutrophils, Sunlight and Vitamin D

Background

Multiple sclerosis (MS) is a chronic autoimmune disease without known cure that affects the central nervous system and is the primary cause of non-traumatic disability in young adults. In MS, demyelination affecting nerves in the brain and spinal cord is driven by dysregulated immune cells. Risk factors for developing MS include viral infection, genetic and environmental factors including reduced sun exposure [1]. MS incidence varies by geographical location with higher incidence rates at greater distance from the equator. Scotland has amongst the highest rates of MS in the world with 1 in 500 people affected. Sunlight results in production of vitamin D (vitD) by the body. VitD acts as immunomodulator that binds the nuclear vitD receptor (VDR) and controls gene transcription of innate and adaptive immune cells. A correlation exists between vitD deficiency and MS development/progression, yet findings to date suggest that vitD supplementation does not conclusively impact MS progression. Rather, sunlight drives vitD-dependent and -independent immune pathways and both appear to be important in MS [2]. 

Neutrophils are short-lived, highly abundant circulating immune cells in humans that are key to host damage in autoimmunity [3]. Neutrophils infiltrate active lesions in MS and in its mouse model, EAE [e.g. 4]. Inhibiting neutrophil infiltration into new lesions reduced disease onset in EAE. Genetic experiments with mice have identified that neutrophils contribute to neurodegeneration in EAE, for example by employing neutrophil extracellular traps that weaken the brain blood barrier and drive demyelination and also by undergoing changes that permit them to engage in cross-talk with B and T cells [4 and others]. Neutrophils isolated from MS patients are characterized by changes in their proteome, suggesting that functional and transcriptional changes in neutrophils occur also in MS. Neutrophils express VDR, and reports in the literature suggest vitD to have immunomodulatory, anti-inflammatory functions. However, neutrophils were only recently recognized as transcriptionally active, and their vitD (or indeed sunlight)-induced transcriptional changes have not yet been analysed in any depth. This contrasts with monocytes, B and T cells, which have already been shown to be regulated transcriptioinally by sunlight in a vitD-dependent and -independent fashion [2; unpublished results, Weller laboratory]. 

This project will address the hypothesis that neutrophils are important drivers of inflammation in MS, and that vitD/sunlight exerts important immunomodulatory functions by regulating  neutrophil transcription, and thereby also MS development and progression.

Aims

This project will 

1. examine how sunlight-driven vitD-dependent and -independent pathways regulate neutrophil transcription and functionality,
2. elucidate differentially expressed genes in MS patient neutrophils, and
3. validate key findings and integrate the data obtained to look for correlations. 

Training outcomes

This project will combine experimentation and data analysis. To examine how vitD and sunlight regulate transcription, neutrophils will be isolated from healthy Scottish volunteers in winter when sunlight is insufficient to generate vitD. Blood will be taken on three occasions (at baseline; after 4 weeks vitD supplement; after 4 weeks controlled sunbed, allowing us to differentiate between changes induced by vitD and any other effects of sunlight). Analysis of the neutrophil (bulk) transcriptome under the three conditions will be performed. In parallel, MS patient neutrophils will be analysed, comparing their transcriptome with that of neutrophils from healthy controls, complemented by some analysis of serum to ascertain vitD, and markers of neutrophil activation/inflammation. Once transcriptome analysis has been completed, experiments will be designed to validate findings (e.g., validating RNA expression on a protein level). In this way, this project provide in-depth training of a PhD student, generate novel insights and build a platform for potential future improved treatment of MS patients.

References

1. Filippi et al (2018) Multiple Sclerosis. Nat Rev Disease Primers DOI: 10.1007/s00415-021-10663-x
2. Ostkamp et al (2020) Sunlight exposure exerts immunomodulatory effects to reduce MS severity. PNAS DOI: 10.1073/pnas.2018457118
3. Bissenova et al (2022) Neutrophils in autoimmunity: when the hero becomes the villain. Clin Exp Immunol DOI: 10.1093/cei/uxac093
4. Rumble et al (2015) Neutrophil-related factors as biomarkers in EAE and MS. J Exp Med DOI: 10.1084/jem.20141015