Suppression of experimental autoimmune encephalomyelitis by 300-315nm ultraviolet light

Infections and Autoimmunity-The Immune System and Vitamin D: A Systematic Review

Both 25-autoimmunity and(25(OH)D: calcifediol) and its active form, 1,25-dihydroxyvitamin D (1,25(OH)2D: calcitriol), play critical roles in protecting humans from invasive pathogens, reducing risks of autoimmunity, and maintaining health. Conversely, low 25(OH)D status increases susceptibility to infections and developing autoimmunity. This systematic review examines vitamin D's mechanisms and effects on enhancing innate and acquired immunity against microbes and preventing autoimmunity. The study evaluated the quality of evidence regarding biology, physiology, and aspects of human health on vitamin D related to infections and autoimmunity in peer-reviewed journal articles published in English. The search and analyses followed PRISMA guidelines. Data strongly suggested that maintaining serum 25(OH)D concentrations of more than 50 ng/mL is associated with significant risk reduction from viral and bacterial infections, sepsis, and autoimmunity. Most adequately powered, well-designed, randomized controlled trials with sufficient duration supported substantial benefits of vitamin D. Virtually all studies that failed to conclude benefits or were ambiguous had major study design errors. Treatment of vitamin D deficiency costs less than 0.01% of the cost of investigation of worsening comorbidities associated with hypovitaminosis D. Despite cost-benefits, the prevalence of vitamin D deficiency remains high worldwide. This was clear among those who died from COVID-19 in 2020/21-most had severe vitamin D deficiency. Yet, the lack of direction from health agencies and insurance companies on using vitamin D as an adjunct therapy is astonishing. Data confirmed that keeping an individual's serum 25(OH)D concentrations above 50 ng/mL (125 nmol/L) (and above 40 ng/mL in the population) reduces risks from community outbreaks, sepsis, and autoimmune disorders. Maintaining such concentrations in 97.5% of people is achievable through daily safe sun exposure (except in countries far from the equator during winter) or taking between 5000 and 8000 IU vitamin D supplements daily (average dose, for non-obese adults, ~70 to 90 IU/kg body weight). Those with gastrointestinal malabsorption, obesity, or on medications that increase the catabolism of vitamin D and a few other specific disorders require much higher intake. This systematic review evaluates non-classical actions of vitamin D, with particular emphasis on infection and autoimmunity related to the immune system.

Efficacy of ultraviolet B radiation versus vitamin D3 on postural control and cognitive functions in relapsing-remitting multiple sclerosis: A randomized controlled study

BACKGROUND

The relapsing-remitting multiple sclerosis (RRMS) is the most common type of MS with prevalence rate 20-60 patients/100.000 individuals in Egypt. Poor postural control and cognitive dysfunctions are well-established complications of RRMS without potent remedy yet. The latest evidence highlighted the potential and independent immune-modulating effects of vitamin D3 and ultraviolet radiation in the management of RRMS.

OBJECTIVE

To investigate the efficacy of broadband ultraviolet B radiation (UVBR) versus moderate loading dose of vitamin D3 supplementation in improving postural control and cognitive functions.

DESIGN

Pretest-posttest randomized controlled study.

SETTING

Multiple sclerosis outpatient unit of Kasr Al-Ainy Hospital.

PARTICIPANTS

Forty-seven patients with RRMS were recruited from both genders, yet only 40 completed the study.

INTERVENTIONS

Patients were randomized into two groups: UVBR group involved 24 patients, received sessions for 4 weeks and vitamin D3 group involved 23 patients, took vitamin D3 supplementation (50 000 IU/week) for 12 weeks.

MAIN OUTCOME MEASURES

Overall balance system index (OSI) and symbol digit modalities test (SDMT).

RESULTS

Highly significant decrease (P < 0.001) of the OSI in both groups post-treatment, indicating improved postural control. Moreover, highly significant improvement in the SDMT scores was noted, indicating information processing speed enhancement. Nonetheless, no statistically significant (P ≥ 0.05) differences were evident between the two groups post-treatment in all tested measures.

CONCLUSION

Both therapeutic programs were statistically equal in improving postural control and cognitive functions. However, clinically, UVBR therapy was more convenient owing to its shorter treatment time and higher percentage of change for all tested measures.

Exposure to Systemic Immunosuppressive Ultraviolet Radiation Alters T Cell Recirculation through Sphingosine-1-Phosphate

Systemic suppression of adaptive immune responses is a major way in which UV radiation contributes to skin cancer development. Immune suppression is also likely to explain how UV protects from some autoimmune diseases, such as multiple sclerosis. However, the mechanisms underlying UV-mediated systemic immune suppression are not well understood. Exposure of C57BL/6 mice to doses of UV known to suppress systemic autoimmunity led to the accumulation of cells within the skin-draining lymph nodes and away from non-skin-draining lymph nodes. Transfer of CD45.1⁺ cells from nonirradiated donors into CD45.2⁺ UV-irradiated recipients resulted in preferential accumulation of donor naive T cells and a decrease in activated T cells within skin-draining lymph nodes. A single dose of immune-suppressive UV was all that was required to cause a redistribution of naive and central memory T cells from peripheral blood to the skin-draining lymph nodes. Specifically, CD69-independent increases in sphingosine-1-phosphate (S1P) receptor 1-negative naive and central memory T cells occurred in these lymph nodes. Mass spectrometry analysis showed UV-mediated activation of sphingosine kinase 1 activity, resulting in an increase in S1P levels within the lymph nodes. Topical application of a sphingosine kinase inhibitor on the skin prior to UV irradiation eliminated the UV-induced increase in lymph node S1P and T cell numbers. Thus, exposure to immunosuppressive UV disrupts T cell recirculation by manipulating the S1P pathway.

UV light suppression of EAE (a mouse model of multiple sclerosis) is independent of vitamin D and its receptor

Vitamin D and sunlight have each been reported to protect against the development of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS). To date, the contribution of each has been unclear as ultra violet (UV) exposure also causes the generation of vitamin D in the skin. To examine whether the UV based suppression of EAE results, at least, in part from the production of vitamin D, we studied the effect of UV light on EAE in mice unable to produce 7-dehydroxycholesterol (7-DHC), the required precursor of vitamin D. Furthermore, we examined UV suppression of EAE in mice devoid of the vitamin D receptor (VDR). Our results demonstrate that UV light suppression of EAE occurs in the absence of vitamin D production and in the absence of VDR. Future investigations will focus on identifying the pathway responsible for the protective action of UV in EAE and presumably human MS.

Lifetime exposure to ultraviolet radiation and the risk of multiple sclerosis in the US radiologic technologists cohort study

BACKGROUND

Low exposure to ultraviolet radiation (UVR) from sunlight may be a risk factor for developing multiple sclerosis (MS). Possible pathways may be related to effects on immune system function or vitamin D insufficiency, as UVR plays a role in the production of the active form of vitamin D in the body.

OBJECTIVE

This study examined whether lower levels of residential UVR exposure from sunlight were associated with increased MS risk in a cohort of radiologic technologists.

METHODS

Participants in the third and fourth surveys of the US Radiologic Technologists (USRT) Cohort Study eligible (N = 39,801) for analysis provided complete residential histories and reported MS diagnoses. MS-specialized neurologists conducted medical record reviews and confirmed 148 cases. Residential locations throughout life were matched to satellite data from NASA's Total Ozone Mapping Spectrometer (TOMS) project to estimate UVR dose.

RESULTS

Findings indicate that MS risk increased as average lifetime levels of UVR exposures in winter decreased. The effects were consistent across age groups <40 years. There was little indication that low exposures during summer or at older ages were related to MS risk.

CONCLUSION

Our findings are consistent with the hypothesis that UVR exposure reduces MS risk and may ultimately suggest prevention strategies.

Latitude, Vitamin D, Melatonin, and Gut Microbiota Act in Concert to Initiate Multiple Sclerosis: A New Mechanistic Pathway

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). While the etiology of MS is still largely unknown, scientists believe that the interaction of several endogenous and exogenous factors may be involved in this disease. Epidemiologists have seen an increased prevalence of MS in countries at high latitudes, where the sunlight is limited and where the populations have vitamin D deficiency and high melatonin levels. Although the functions and synthesis of vitamin D and melatonin are contrary to each other, both are involved in the immune system. While melatonin synthesis is affected by light, vitamin D deficiency may be involved in melatonin secretion. On the other hand, vitamin D deficiency reduces intestinal calcium absorption leading to gut stasis and subsequently increasing gut permeability. The latter allows gut microbiota to transfer more endotoxins such as lipopolysaccharides (LPS) into the blood. LPS stimulates the production of inflammatory cytokines within the CNS, especially the pineal gland. This review summarizes the current findings on the correlation between latitude, sunlight and vitamin D, and details their effects on intestinal calcium absorption, gut microbiota and neuroinflammatory mediators in MS. We also propose a new mechanistic pathway for the initiation of MS.

Sex-Specific Gene-by-Vitamin D Interactions Regulate Susceptibility to Central Nervous System Autoimmunity

Vitamin D3 (VitD) insufficiency is postulated to represent a major modifiable risk factor for multiple sclerosis (MS). While low VitD levels strongly correlate with higher MS risk in white populations, this is not the case for other ethnic groups, suggesting the existence of a genetic component. Moreover, VitD supplementation studies in MS so far have not shown a consistent benefit. We sought to determine whether direct manipulation of VitD levels modulates central nervous system autoimmune disease in a sex-by-genotype-dependent manner. To this end, we used a dietary model of VitD modulation, together with the autoimmune animal model of MS, experimental autoimmune encephalomyelitis (EAE). To assess the impact of genotype-by-VitD interactions on EAE susceptibility, we utilized a chromosome substitution (consomic) mouse model that incorporates the genetic diversity of wild-derived PWD/PhJ mice. High VitD was protective in EAE in female, but not male C57BL/6J (B6) mice, and had no effect in EAE-resistant PWD/PhJ (PWD) mice. EAE protection was accompanied by sex- and genotype-specific suppression of proinflammatory transcriptional programs in CD4 T effector cells, but not CD4 regulatory T cells. Decreased expression of proinflammatory genes was observed with high VitD in female CD4 T effector cells, specifically implicating a key role of MHC class II genes, interferon gamma, and Th1 cell-mediated neuroinflammation. In consomic strains, effects of VitD on EAE were also sex- and genotype dependent, whereby high VitD: (1) was protective, (2) had no effect, and (3) unexpectedly had disease-exacerbating effects. Systemic levels of 25(OH)D differed across consomic strains, with higher levels associated with EAE protection only in females. Analysis of expression of key known VitD metabolism genes between B6 and PWD mice revealed that their expression is genetically determined and sex specific and implicated Cyp27b1 and Vdr as candidate genes responsible for differential EAE responses to VitD modulation. Taken together, our results support the observation that the association between VitD status and MS susceptibility is genotype dependent and suggest that the outcome of VitD status in MS is determined by gene-by-sex interactions.

Are the protective benefits of vitamin D in neurodegenerative disease dependent on route of administration? A systematic review

Background: The clinical and preclinical exploration of the therapeutic properties of vitamin D have significantly increased in the past decade, owing to the growing associative evidence suggesting vitamin D is neuroprotective. However, whether depletion of vitamin D contributes to the onset of neurological disorders or is a symptom of neurological disease has yet to be defined. Much remains unclear about the causal role of vitamin D and the method of use and forms of vitamin D.Objectives: We sought to quantitatively assess if neuroprotective benefits from vitamin D in neurodegenerative diseases are dependent on route of administration: comparing the effect of endogenously sourced vitamin D from UV exposure to exogenously derived vitamin D through synthetic supplementation.Design: We systematically searched PubMed, Embase and PsycInfo databases which included both pre-clinical and clinical studies investigating vitamin D in neurodegenerative diseases. Articles were subject to strict inclusion criteria and objectively assessed for quality. Additionally, Medline data was analysed to identify trends in topic publications and linguistic characteristics of papers.Results: From a total of 231 screened articles, we identified 73 appropriate for review based on inclusion criteria: original studies that investigated vitamin D levels or levels of vitamin D supplementation in neurodegenerative diseases or investigated past/present sun exposure in disease cohorts. Results indicate there is insufficient evidence to comprehensively reflect on a potential neuroprotective role for vitamin D and if this was dependent on route of administration. The majority of current data supporting neuroprotective benefits from vitamin D are based on pre-clinical and observational studies. Solid evidence is lacking to support the current hypothesis that the beneficial effect of UV exposure results from the synthesis of vitamin D. Sun exposure, independent of vitamin D production, may be protective against multiple Sclerosis, Parkinson's disease and Alzheimer's disease. Yet, further research is required to elucidate the beneficial mechanism of actions of UV exposure. The literature of vitamin D and amyotrophic lateral sclerosis was limited, and no conclusions were drawn. Therefore, in cases where UV-derived vitamin D was hypothesized to be the beneficial mediator in the neuroprotective effects of sun exposure, we propose results are based only on associative evidence.Conclusion: On the basis of this systematic review, strong recommendations regarding therapeutic benefits of vitamin D in neurodegenerative disease cannot be made. It is unclear if vitamin D mediates a protective benefit in neurodegenerative disease or whether it is an associative marker of UV exposure, which may contribute to as of yet unidentified neuroprotective factors.

Salate derivatives found in sunscreens block experimental autoimmune encephalomyelitis in mice

UV light suppresses experimental autoimmune encephalomyelitis (EAE), a widely used animal model of MS, in mice and may be responsible for the decreased incidence of MS in equatorial regions. To test this concept further, we applied commercially available sunblock preparations to mice before exposing them to UV radiation. Surprisingly, some of the sunblock preparations blocked EAE without UV radiation. Furthermore, various sunblock preparations had variable ability to suppress EAE. By examining the components of the most effective agents, we identified homosalate and octisalate as the components responsible for suppressing EAE. Thus, salates may be useful in stopping the progression of MS, and may provide new insight into mechanisms of controlling autoimmune disease.

Suppression of experimental autoimmune encephalomyelitis by ultraviolet light is not mediated by isomerization of urocanic acid

Background

Ultraviolet B irradiation confers strong resistance against experimental autoimmune encephalomyelitis, a model of multiple sclerosis. This protection by ultraviolet B is independent of vitamin D production but causes isomerization of urocanic acid, a naturally occurring immunosuppressant.

Methods

To determine whether UCA isomerization from trans to cis is responsible for the protection against experimental autoimmune encephalomyelitis afforded by ultraviolet B, trans- or cis-urocanic acid was administered to animals and their disease progression was monitored.

Results

Disease incidence was reduced by 74% in animals exposed to ultraviolet B, and skin cis-urocanic acid levels increased greater than 30%. However, increasing skin cis-urocanic acid levels independent of ultraviolet B was unable to alter disease onset or progression.

Conclusions

It is unlikely that urocanic acid isomerization is responsible for the ultraviolet B-mediated suppression of experimental autoimmune encephalomyelitis. Additional work is needed to investigate alternative mechanisms by which UVB suppresses disease.

UVB radiation, vitamin D and multiple sclerosis

Achesonet al.(1960) observed an inverse relationship between sunlight exposure and the incidence of Multiple Sclerosis (MS).

The absence of 25-hydroxyvitamin D3-1α-hydroxylase potentiates the suppression of EAE in mice by ultraviolet light

Ultraviolet B (UVB) light suppresses the development of multiple sclerosis (MS) in patients and experimental autoimmune encephalomyelitis (EAE) in mice. Although vitamin D3 is produced by ultraviolet light, the suppression of EAE by narrow band UVB (NBUVB) is independent of vitamin D3. However, it is possible that the NBUVB suppression of EAE can be further influenced by 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). We used NBUVB lamps (10KJ/m(2)) to irradiate both wild type (WT) and 1α-hydroxylase knockout mice (CYP27B1 KO) that were then induced to develop EAE. There was a complete elimination of EAE development by NBUVB in the KO mice. On the other hand, the NBUVB treatment of WT mice reduced but did not eliminate the severity or incidence of EAE. This suggests that the presence of 1,25-dihydroxyvitamin D3 actually counteracts the suppressive effect of NBUVB. In support of this concept, cytokines (IFN-γ, IL-10) and chemokine (CCL-5) mRNA in spinal cord were reduced in wild type or eliminated in the KO mice by the NBUVB. Cytokine mRNA levels in the spinal cord correlated with clinical scores in both WT and KO mice.

Prevention and Mitigation of Experimental Autoimmune Encephalomyelitis by Murine β-Defensins via Induction of Regulatory T Cells

The antimicrobial peptide murine β-defensin-14 (mBD14) was found to exert, in addition to its antimicrobial activity, the capacity to induce regulatory T cells as demonstrated in the model of contact hypersensitivity. Because it is induced by ultraviolet radiation, mBD14 may contribute to the antigen-specific immunosuppression by ultraviolet radiation. To prove whether this applies also for other immunologic models and because ultraviolet radiation appears to have beneficial effects on multiple sclerosis, we utilized the model of experimental autoimmune encephalomyelitis. Injection of mBD14 into mice before immunization with myelin oligodendrocyte glycoprotein caused amelioration of the disease with less central nervous system inflammation and decreased levels of proinflammatory cytokines and cytotoxic T cells. The beneficial effect was due to Foxp3(+) regulatory T cells because it was lost on in vivo depletion of regulatory T cells. mBD14, however, also acts in a therapeutic setting, because injection of mBD14 into mice with clinical features of experimental autoimmune encephalomyelitis reduced the clinical score significantly. Human β-defensin-3, the human orthologue of mBD14, induced in vitro regulatory T cell-specific markers in CD4(+)CD25(-) T cells, shifting these nonregulatory cells into a regulatory phenotype with suppressive features. Thus, defensins may represent candidates worth being further pursued for the therapy of multiple sclerosis.

Farming, Foreign Holidays, and Vitamin D in Orkney

Orkney, north of mainland Scotland, has the world's highest prevalence of multiple sclerosis (MS); vitamin D deficiency, a marker of low UV exposure, is also common in Scotland. Strong associations have been identified between vitamin D deficiency and MS, and between UV exposure and MS independent of vitamin D, although causal relationships remain to be confirmed. We aimed to compare plasma 25-hydroxyvitamin D levels in Orkney and mainland Scotland, and establish the determinants of vitamin D status in Orkney. We compared mean vitamin D and prevalence of deficiency in cross-sectional study data from participants in the Orkney Complex Disease Study (ORCADES) and controls in the Scottish Colorectal Cancer Study (SOCCS). We used multivariable regression to identify factors associated with vitamin D levels in Orkney. Mean (standard deviation) vitamin D was significantly higher among ORCADES than SOCCS participants (35.3 (18.0) and 31.7 (21.2), respectively). Prevalence of severe vitamin D deficiency was lower in ORCADES than SOCCS participants (6.6% to 16.2% p = 1.1 x 10(-15)). Older age, farming occupations and foreign holidays were significantly associated with higher vitamin D in Orkney. Although mean vitamin D levels are higher in Orkney than mainland Scotland, this masks variation within the Orkney population which may influence MS risk.

CYP2R1 Mutations Impair Generation of 25-hydroxyvitamin D and Cause an Atypical Form of Vitamin D Deficiency

CONTEXT

Production of the active vitamin D hormone 1,25-dihydroxyvitamin D requires hepatic 25-hydroxylation of vitamin D. The CYP2R1 gene encodes the principal vitamin D 25-hydroxylase in humans.

OBJECTIVE

This study aimed to determine the prevalence of CYP2R1 mutations in Nigerian children with familial rickets and vitamin D deficiency and assess the functional effect on 25-hydroxylase activity.

DESIGN AND PARTICIPANTS

We sequenced the CYP2R1 gene in subjects with sporadic rickets and affected subjects from families in which more than one member had rickets.

MAIN OUTCOME MEASURES

Function of mutant CYP2R1 genes as assessed in vivo by serum 25-hydroxyvitamin D values after administration of vitamin D and in vitro by analysis of mutant forms of the CYP2R1.

RESULTS

CYP2R1 sequences were normal in 27 children with sporadic rickets, but missense mutations were identified in affected members of 2 of 12 families, a previously identified L99P, and a novel K242N. In silico analyses predicted that both substitutions would have deleterious effects on the variant proteins, and in vitro studies showed that K242N and L99P had markedly reduced or complete loss of 25-hydroxylase activity, respectively. Heterozygous subjects were less affected than homozygous subjects, and oral administration of vitamin D led to significantly lower increases in serum 25-hydroxyvitamin D in heterozygous than in control subjects, whereas homozygous subjects showed negligible increases.

CONCLUSION

These studies confirm that CYP2R1 is the principal 25-hydroxylase in humans and demonstrate that CYP2R1 alleles have dosage-dependent effects on vitamin D homeostasis. CYP2R1 mutations cause a novel form of genetic vitamin D deficiency with semidominant inheritance.

Increasing ultraviolet light exposure is associated with reduced mortality from Clostridium difficile infection

BACKGROUND

Clostridium difficile infection (CDI) is an increasingly common cause of inpatient mortality. Vitamin D deficiency is associated with more aggressive CDI. We aimed to determine if average annual ultraviolet light (UV) exposure was associated with mortality in patients with CDI.

METHODS

We used the US National Inpatient Sample (NIS) from 2004-2011 to assess the mortality risk in patients with a diagnosis of CDI (as per ICD-9CM 008.45). Annual average state UV exposure was assigned to each hospitalization. Logistic regression was used to determine the effects of UV exposure on mortality, controlling for age, gender, race and other comorbidities.

RESULTS

During the study period, there were 2.61 million hospitalizations with a diagnosis of CDI. The mortality rate was 9.0%. In univariate analysis, the odds ratio (OR) of inpatient mortality for the UV index was 0.97 (95% CI 0.95-0.99; p = 0.008) per unit of UV exposure. In a multivariable model adjusting for age, gender, race, Charlson-Deyo index, season and coexisting inflammatory bowel disease, the UV index remained a protective predictor, with an OR of 0.94 (95% CI 0.92-0.96; p < 0.001). In the multivariate model, a seasonal effect was also present, with the highest risk of inpatient mortality in the period from January to March (OR 1.11; 95% CI 1.08-1.14) and the lowest risk, from July to September (OR 0.95; 95% CI 0.92-0.98).

CONCLUSIONS

An increase in UV exposure index is associated with a reduced risk of inpatient mortality in patients with CDI. A seasonal effect is also present, with the highest risk of death during winter months. Further studies exploring the role of UV light in CDI are necessary.

Is there more to learn about functional vitamin D metabolism?

The state of information on the enzymes responsible for the conversion of vitamin D3 to 1α,25-dhydroxyvitamin D3 (1,25-(OH)2D3), the metabolic active form responsible for the well-known function of vitamin D on calcium metabolism and bone mineralization has been briefly reviewed. There remains an unidentified enzyme responsible for 25% of the 25-hydroxylation of vitamin D3, while 75% of serum 25-hydroxyvitamin D3 (25-OH-D3) arises from CYP2R1. The well-established suppression of multiple sclerosis (MS) by sunlight has been confirmed using the mouse model, experimental autoimmune encephalomyelitis (EAE). This suppression results from a narrow band of ultraviolet light (300-315nm) that does not increase serum 25-OH-D3. Thus, UV light suppresses EAE by a mechanism not involving vitamin D. Vitamin D deficiency unexpectedly suppresses the development of EAE. Further, vitamin D receptor knockout in susceptible mice also prevents the development of EAE. On the other hand, deletion of CYP2R1 and the 1α-hydroxylase, CYP27B1, does not impair the development of EAE. Thus, either vitamin D itself or a heretofore-unknown metabolite is needed for the development of a component of the immune system necessary for development of EAE. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Cholecalciferol or 25-hydroxycholecalciferol neither prevents nor treats adenomas in a rat model of familial colon cancer

BACKGROUND

Epidemiologic studies in humans have shown associations between greater sunlight exposure, higher serum 25-hydroxycholecalciferol [25(OH)D3] concentrations, and reduced colon cancer risk. However, results from a limited number of vitamin D supplementation trials in humans have not shown a protective effect.

OBJECTIVE

We sought to determine whether adding to the diet increasing amounts of either 25(OH)D3, the stable metabolite measured in serum and associated with cancer risk, or cholecalciferol (vitamin D3), the compound commonly used for supplementation in humans, could reduce emergent adenomas (chemoprevention) or decrease the growth of existing adenomas (treatment) in the colons of vitamin D-sufficient rats carrying a truncation mutation of adenomatous polyposis coli (Apc), a model of early intestinal cancer.

METHODS

Apc(Pirc/+) rats were supplemented with either vitamin D3 over a range of 4 doses [6-1500 μg/(kg body weight · d)] or with 25(OH)D3 over a range of 6 doses [60-4500 μg/(kg body weight · d)] beginning after weaning. Rats underwent colonoscopy every other week to assess effects on adenoma number and size. At termination (140 d of age), the number of tumors in the small intestine and colon and the size of tumors in the colon were determined, and serum calcium and 25(OH)D3 measurements were obtained.

RESULTS

At lower doses (those that did not affect body weight), neither of the vitamin D compounds reduced the number of existing or emergent colonic tumors (P-trend > 0.24). By contrast, supplementation at higher doses (those that caused a suppression in body weight gain) with either 25(OH)D3 or vitamin D3 caused a dose-dependent increase in colonic tumor number in both males and females (P-trend < 0.003).

CONCLUSIONS

No evidence for protection against colon tumor development was seen with lower dose supplementation with either cholecalciferol or 25-hydroxycholecalciferol. Thus, the association between sunlight exposure and the incidence of colon cancer may involve factors other than vitamin D concentrations. Alternative hypotheses warrant investigation. Furthermore, this study provides preliminary evidence for the need for caution regarding vitamin D supplementation of humans at higher doses, especially in individuals with sufficient serum 25(OH)D3 concentrations.

Vitamin D and inflammation

Several studies found an inverse relationship between 25-hydroxyvitamin D [25(OH)D] and markers of inflammation. A controversy exists as to whether vitamin D lowers inflammation or whether inflammation lowers 25(OH)D concentrations. Certainly 25(OH)D concentrations fall after major surgery. However, is this due to inflammation lowering 25(OH)D or is 25(OH)D being metabolically cleared by the body to quell inflammation. We searched the literature and found 39 randomized controlled trials (RCT) of vitamin D and markers of inflammation. Seventeen found significantly reduced inflammatory markers, 19 did not, one was mixed and one showed adverse results. With few exceptions, studies in normal subjects, obesity, type 2 diabetics, and stable cardiovascular disease did not find significant beneficial effects. However, we found that 6 out of 7 RCTS of vitamin D3 in highly inflammatory conditions (acute infantile congestive heart failure, multiple sclerosis, inflammatory bowel disease, cystic fibrosis, SLE, active TB and evolving myocardial infarction) found significant reductions. We found baseline and final 25(OH)D predicted RCTs with significant reduction in inflammatory markers. Vitamin D tends to modestly lower markers of inflammation in highly inflammatory conditions, when baseline 25(OH)D levels were low and when achieved 25(OH)D levels were higher. Future inquiries should: recruit subjects with low baseline 25(OH)D levels, subjects with elevated markers of inflammation, subjects with inflammatory conditions, achieve adequate final 25(OH)D levels, and use physiological doses of vitamin D. We attempted to identify all extant randomized controlled trials (RCTs) of vitamin D that used inflammatory markers as primary or secondary endpoints.

Photoimmunology and Multiple Sclerosis

The ultraviolet (UV) radiation contained in sunlight is a powerful immune suppressant. While exposure to UV is best known for its ability to cause skin cancer, it is also associated with protection against a range of autoimmune diseases, particularly multiple sclerosis (MS). Although the precise mechanism by which sunlight affords protection from MS remains to be determined, some have hypothesised that UV immunosuppression explains the "latitude-gradient effect" associated with MS. By stimulating the release of soluble factors in exposed skin, UV activates immune suppressive pathways that culminate in the induction of regulatory cells in distant tissues. Each and every one of the immune suppressive cells and molecules activated by UV exposure are potential targets for treating and preventing MS. A thorough understanding of the mechanisms involved is therefore required if we are to realise the therapeutic potential of photoimmunology.

UV light selectively inhibits spinal cord inflammation and demyelination in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS). The incidence of MS is inversely related to sun light exposure or ultraviolet radiation (UVR). UVR was found to suppress experimental autoimmune encephalomyelitis (EAE), an animal model of MS, independent of vitamin D production. The mechanism of this suppression remains to be elucidated. To this end, several elements of an immune response in the spinal cord, spleen and skin during development of EAE were studied. As expected, UVR (10kJ/m(2)) inhibits inflammation and demyelination of the spinal cord. Most significant, UVR dramatically reduced spinal cord chemokine CCL5 mRNA and protein levels. UVR also suppressed IL-10 in skin and spleen but not the spinal cord. As expected from the UVR action on skin, macrophage population and IFN-γ levels are increased in that organ. UVR had no effect on lymphocyte proliferation and IFN-γ in spleen. From these measurements, we suggest that UVR suppression of EAE prevents the migration of inflammatory cells into the CNS by a focal inhibition of chemokine CCL-5 in the CNS and a systemic elevation of immunosuppressive IL-10.

[Role of vitamin D in the physiopathology of neurodegenerative diseases]

The involvement of vitamin D in brain function has been discovered in the past 25 years by epidemiological and fundamental studies. Research on neurodegenerative diseases and their animal or cellular models unveiled converging lines of evidence indicating that hypovitaminosis D is not just an effect of the progression of neurodegenerative diseases, but truly an aggravating co-factor, sometimes very closely related to their physiopathology. Vitamin D is a steroid hormone capable of regulating the expression of hundreds of genes through both genetic and epigenetic mechanisms. This reflects the highly pleiotropic nature of its action in its conventional bone and phosphocalcic metabolism targets. Its role in the central nervous system and neurodegenerative diseases makes no exception to this rule. Here we focus on the identified role and mechanisms of vitamin D in multiple sclerosis, Alzheimer's disease and Parkinson's disease. The important prevalence of hypovitaminosis D under our latitudes in general and in at-risk groups in particular, its easy evaluation and correction, and the results of early clinical studies, suggest that vitamin D supplementation could usefully complement our therapeutic armory to fight these diseases.

Phototherapy with artificial light suppresses dextran sulfate sodium-induced colitis in a mouse model

BACKGROUND AND AIM

Medical treatment for inflammatory bowel disease (IBD) requires chronic administration and causes side effects. Recently, anti-inflammatory effects of phototherapy were reported in animal models. The present study evaluated whether phototherapy improves dextran sulfate sodium (DSS)-induced colitis in a mouse model of IBD.

METHODS

Mice were divided into four equal groups: Control, DSS, DSS + light low (LL), and DSS + light high (LH) groups. Normal fluorescent light intensity in the Control and DSS groups was 200 lux. Artificial light intensities were as follows: DSS + LL group, 1000 lux; DSS + LH group, 2500 lux. After administering phototherapy for 7 days, we evaluated disease activity index (DAI), histological score, colon length/weight, serum 1,25-dihydroxyvitamin D(3) level, and serum and colonic cytokines in the mice.

RESULTS

DAI and histological scores were significantly lower in the DSS + LL group than in the DSS group (both, P < 0.05). Colon length and weight were significantly higher in the DSS + LL group than in the DSS group (both, P < 0.05). Serum interleukin (IL)-6, TNF-α, and IL-17 in the DSS + LL group were significantly lower, and serum and colonic IL-10 were significantly higher in the DSS + LL group than in the DSS group (all, P < 0.05). Serum 1,25-dihydroxyvitamin D(3) levels in the DSS + LH group were significantly increased compared with those in the DSS + LL and DSS groups.

CONCLUSION

Artificial light phototherapy suppressed DSS-induced colitis in mice by suppression of pro-inflammatory cytokines and promotion of anti-inflammatory cytokines.

Triennial Growth Symposium--Vitamin D: bones and beyond

The exploration of vitamin D metabolism and function has led to the discovery of active forms of vitamin D that find great usefulness in treating patients with bone disease or renal failure and also perhaps in topical application for the treatment of skin disorders, such as psoriasis. It may also be effective in some types of autoimmune disease. This warrants our attention to maintaining an adequate vitamin D level in our blood to assure that the expected functions of vitamin D take place. However, we must not get so overenthusiastic as to expect vitamin D to be effective in treating or preventing many diverse diseases and especially caution is urged in considering that vitamin D compounds might be used to suppress cancerous growth.