Vitamin D3Confers Protection from Autoimmune Encephalomyelitis Only in Female Mice

Vitamin D and the immune system: new perspectives on an old theme

Interaction with the immune system is one of the most well-established nonclassic effects of vitamin D. For many years this was considered to be a manifestation of granulomatous diseases such sarcoidosis, in which synthesis of active 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is known to be dysregulated. However, recent reports have supported a role for 1,25(OH)(2)D(3) in mediating normal function of the innate and adaptive immune systems. Crucially, these effects seem to be mediated via localized autocrine or paracrine synthesis of 1,25(OH)(2)D(3) from precursor 25-hydroxyvitamin D(3), the main circulating metabolite of vitamin D. The ability of vitamin D to influence normal human immunity is highly dependent on the vitamin D status of individuals, and may lead to aberrant response to infection or autoimmunity in those who are lacking vitamin D. The potential health significance of this has been underlined by increasing awareness of impaired vitamin D status in populations across the globe. This article describes some of the recent developments with respect to vitamin D and the immune system, and possible clinical implications.

Oral administration of probiotic bacteria, Lactobacillus casei and Bifidobacterium breve, does not exacerbate neurological symptoms in experimental autoimmune encephalomyelitis

To evaluate the safety of two probiotic bacterial strains, Lactobacillus casei strain Shirota (LcS) and Bifidobacterium breve strain Yakult (BbY), these probiotics were orally administered to Lewis rats with experimental autoimmune encephalomyelitis (EAE), the experimental model of human multiple sclerosis. We examined three experimental designs by combining different antigen types and probiotic administration periods: (1) EAE was induced with a homogenate of guinea pig spinal cord as the sensitizing antigen, and LcS was orally administered from one week before this sensitization until the end of the experiment; (2) EAE was induced using guinea pig originated myelin basic protein (MBP) as the sensitizing antigen, and LcS was orally administered from one week before this sensitization to the end of the experiment; (3) EAE was induced using guinea pig MBP as the sensitizing antigen, and the probiotic strains (LcS and BbY) were administered starting in infancy (two weeks old) and continued until the end of the experiment. In experiment 1, oral administration of LcS tended to suppress the development of neurological symptoms. Differences in neurological symptoms between the control group and the administration groups did not reach statistical significance in experiments 2 and 3. These results support the notion that neither LcS nor BbY exacerbates autoimmune disease.

Environmental factors and their timing in adult-onset multiple sclerosis

Multiple sclerosis (MS) is a common, complex neurological disease. Epidemiological data implicate both genetic and environmental factors in the etiology of MS, with various factors interacting with one another. Environmental exposures might occur long before the disease becomes clinically evident, as suggested by the wide range in onset age. In this Review, we examine the key time periods during which the environment might contribute to MS susceptibility, as well as the potential environmental factors involved. Understanding the nature of environmental influences in MS is highly relevant to the development of public health measures that are aimed at preventing this debilitating disease.

Vitamin D, a neuro-immunomodulator: implications for neurodegenerative and autoimmune diseases

It has been known for more than 20 years that vitamin D exerts marked effects on immune and neural cells. These non-classical actions of vitamin D have recently gained a renewed attention since it has been shown that diminished levels of vitamin D induce immune-mediated symptoms in animal models of autoimmune diseases and is a risk factor for various brain diseases. For example, it has been demonstrated that vitamin D (i) modulates the production of several neurotrophins, (ii) up-regulates Interleukin-4 and (iii) inhibits the differentiation and survival of dendritic cells, resulting in impaired allo-reactive T cell activation. Not surprisingly, vitamin D has been found to be a strong candidate risk-modifying factor for Multiple Sclerosis (MS), the most prevalent neurological and inflammatory disease in the young adult population. Vitamin D is a seco-steroid hormone, produced photochemically in the animal epidermis. The action of ultraviolet light (UVB) on 7-dehydrocholesterol results in the production of pre-vitamin D which, after thermo-conversion and two separate hydroxylations, gives rise to the active 1,25-dihydroxyvitamin D. Vitamin D acts through two types of receptors: (i) the vitamin D receptor (VDR), a member of the steroid/thyroid hormone superfamily of transcription factors, and (ii) the MARRS (membrane associated, rapid response steroid binding) receptor, also known as Erp57/Grp58. In this article, we review some of the mechanisms that may underlie the role of vitamin D in various brain diseases. We then assess how vitamin D imbalance may lay the foundation for a range of adult disorders, including brain pathologies (Parkinson's disease, epilepsy, depression) and immune-mediated disorders (rheumatoid arthritis, type I diabetes mellitus, systemic lupus erythematosus or inflammatory bowel diseases). Multidisciplinary scientific collaborations are now required to fully appreciate the complex role of vitamin D in mammal metabolism.

Body size and risk of MS in two cohorts of US women

OBJECTIVE

To examine whether obesity during childhood, adolescence, or adulthood is associated with an increased risk of multiple sclerosis (MS).

METHODS

Women in the Nurses' Health Study (n = 121,700) and Nurses' Health Study II (n = 116,671) provided information on weight at age 18 and weight and height at baseline, from which body mass index was derived. Women also selected silhouettes representing their body size at ages 5, 10, and 20. Over the total 40 years of follow-up in both cohorts combined, we confirmed 593 cases of MS. Cox proportional hazards models, adjusting for age, latitude of residence, ethnicity, and cigarette smoking, were used to estimate the rate ratios and 95% confidence intervals (CI).

RESULTS

Obesity at age 18 (body mass index > or =30 kg/m(2)) was associated with a greater than twofold increased risk of MS (multivariate relative risk(pooled) = 2.25, 95% CI: 1.50-3.37, p trend <0.001). After adjusting for body size at age 20, having a large body size at ages 5 or 10 was not associated with risk of MS, whereas a large body size at age 20 was associated with a 96% increased risk of MS (95% CI: 1.33-2.89, p trend = 0.009). No significant association was found between adult body mass and MS risk.

CONCLUSIONS

Obese adolescents have an increased risk of developing multiple sclerosis (MS). Although the mechanisms of this association remain uncertain, this result suggests that prevention of adolescent obesity may contribute to reduced MS risk.

25-Hydroxyvitamin D in cerebrospinal fluid during relapse and remission of multiple sclerosis

Hypovitaminosis D may play a role in multiple sclerosis (MS), but little is known about intrathecal vitamin D. 25-Hydroxyvitamin D was measured in cerebrospinal fluid and sera from 36 patients with relapsing-remitting MS, 20 patients with other inflammatory neurological diseases and 18 patients with non-inflammatory neurological diseases with liquid chromatography-mass spectrometry. There were no significant differences in cerebrospinal fluid concentrations of 25-hydroxyvitamin D, but the cerebrospinal fluid:serum ratio was significantly lower in MS compared with other inflammatory neurological diseases (p=0.0012) and non-inflammatory neurological diseases (p=0.041) patients. The concentrations of 25-hydroxyvitamin D in cerebrospinal fluid and serum were positively correlated and their ratio was similar to that of albumin. Neither the concentrations of 25-hydroxyvitamin D in cerebrospinal fluid or serum nor their ratio were associated with the presence of relapses or gadolinium-enhanced lesions. These results do not support that 25-hydroxyvitamin D is actively transported to the cerebrospinal fluid, or that the cerebrospinal fluid or serum levels or their ratio exert a major impact on MS activity.

Estrogen controls vitamin D3-mediated resistance to experimental autoimmune encephalomyelitis by controlling vitamin D3 metabolism and receptor expression

Multiple sclerosis (MS) is an autoimmune, neurodegenerative disease with a rapidly increasing female gender bias. MS prevalence decreases with increasing sunlight exposure, supporting our hypothesis that the sunlight-dependent hormone 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) is a natural inhibitor of autoimmune T cell responses in MS. We found that vitamin D(3) inhibited experimental autoimmune encephalomyelitis (EAE) in intact female mice, but not in ovariectomized females or males. To learn whether 17beta-estradiol (E(2)) is essential for vitamin D(3)-mediated protection, ovariectomized female mice were given E(2) or placebo and evaluated for vitamin D(3)-mediated EAE resistance. Diestrus-level E(2) implants alone provided no benefit, but they restored vitamin D(3)-mediated EAE resistance in the ovariectomized females. Synergy between E(2) and vitamin D(3) occurred through vitamin D(3)-mediated enhancement of E(2) synthesis, as well as E(2)-mediated enhancement of vitamin D receptor expression in the inflamed CNS. In males, E(2) implants did not enable vitamin D(3) to inhibit EAE. The finding that vitamin D(3)-mediated protection in EAE is female-specific and E(2)-dependent suggests that declining vitamin D(3) supplies due to sun avoidance might be contributing to the rapidly increasing female gender bias in MS. Moreover, declining E(2) synthesis and vitamin D(3)-mediated protection with increasing age might be contributing to MS disease progression in older women.

Gender differences in multiple sclerosis: cytokines and vitamin D

The disproportional increase of the female:male ratio in relapse-onset (relapsing remitting (RR) and secondary progressive (SP)) multiple sclerosis (MS) patients in the last 20 years has further raised scientific interest in gender difference in MS. It has been suggested that the immune system, especially cytokines, plays an important role in the gender issue, as can also be seen in other autoimmune diseases. The immune system is influenced by different factors including hormones and seasonal fluctuations (vitamin D). This overview will highlight the gender differences in MS, with emphasis on the cytokines and vitamin D.

Vitamin D treatment in multiple sclerosis

Multiple sclerosis is an immune-mediated disease of the central nervous system caused by a complex interplay between several different genetic as well as environmental factors. Vitamin D is one of the most attractive candidates among various environmental factors suggested to be involved in the development of the disease. Epidemiological evidence combined with clinical and laboratory analyses, and experimental animal models, suggest a possible influence of vitamin D on MS susceptibility as well as clinical disease activity. Supplement with vitamin D may reduce the risk of developing MS. An intervention may also reduce the risk of conversion from a first clinical event suggestive of MS to clinical definite MS, as well as reduce the relapse rate among patients with relapsing remitting MS. More studies are, however, needed to determine optimal dose and serum level for vitamin D, as well as target populations and optimal timing for intervention.

Antioxidant therapy in multiple sclerosis

Reactive oxygen species (ROS) play an important role in various events underlying multiple sclerosis pathology. In the initial phase of lesion formation, ROS are known to mediate the transendothelial migration of monocytes and induce a dysfunction in the blood-brain barrier. Although the pathogenesis of MS is not completely understood, various studies suggest that reactive oxygen species contribute to the formation and persistence of multiple sclerosis lesions by acting on distinct pathological processes. The detrimental effects of ROS in the central nervous system are endowed with a protective mechanism consisting of enzymatic and non-enzymatic antioxidant. Antioxidant therapy may therefore represent an attractive treatment of MS. Several studies have shown that antioxidant therapy is beneficial in vitro and in vivo in animal models for MS. Since oxidative damage has been known to be involved in inflammatory and autoimmune-mediated tissue destruction in which, modulation of oxygen free radical production represents a new approach to the treatment of inflammatory and autoimmune diseases. Several experimental studies have been performed to see whether dietary intake of several antioxidants can prevent and or reduce the progression of EAE or not. Although a few antioxidants showed some efficacy in these studies, little information is available on the effect of treatments with such compounds in patients with MS. In this review, our aim is to clarify the therapeutic efficacy of antioxidants in MS disease.

Clinical implications of a possible role of vitamin D in multiple sclerosis

Hypovitaminosis D is currently one of the most studied environmental risk factors for multiple sclerosis (MS) and is potentially the most promising in terms of new clinical implications. These practical consequences, which could be applied to MS patients without further delay, constitute the main purpose of this review. Vitamin D is involved in a number of important general actions, which were not even suspected until quite recently. In particular, this vitamin could play an immunomodulatory role in the central nervous system. Many and varied arguments support a significant role for vitamin D in MS. In animal studies, vitamin D prevents and improves experimental autoimmune encephalomyelitis. Epidemiologically, latitude, past exposure to sun and the serum level of vitamin D influence the risk of MS, with, furthermore, significant links existing between these different factors. Clinically, most MS patients have low serum levels of vitamin D and are in a state of insufficiency or even deficiency compared to the international norm, which has been established on a metabolic basis. Large therapeutic trials using vitamin D are still lacking but the first results of phase I/II studies are promising. In the meantime, while awaiting the results of future therapeutic trials, it can no longer be ignored that many MS patients have a lack of vitamin D, which could be detected by a serum titration and corrected using an appropriate vitamin D supplementation in order to restore their serum level to within the normal range. From a purely medical point of view, vitamin D supplementation appears in this light to be unavoidable in order to improve the general state of these patients. Furthermore, it cannot currently be ruled out that this supplementation could also be neurologically beneficial.

The causal cascade to multiple sclerosis: a model for MS pathogenesis

BACKGROUND

MS pathogenesis seems to involve both genetic susceptibility and environmental risk factors. Three sequential factors are implicated in the environmental risk. The first acts near birth, the second acts during childhood, and the third acts long thereafter. Two candidate factors (vitamin D deficiency and Epstein-Barr viral infection) seem well suited to the first two environmental events.

METHODOLOGY/PRINCIPAL FINDINGS

A mathematical Model for MS pathogenesis is developed, incorporating these environmental and genetic factors into a causal scheme that can explain some of the recent changes in MS-epidemiology (e.g., increasing disease prevalence, a changing sex-ratio, and regional variations in monozygotic twin concordance rates).

CONCLUSIONS/SIGNIFICANCE

This Model suggests that genetic susceptibility is overwhelmingly the most important determinant of MS pathogenesis. Indeed, over 99% of individuals seem genetically incapable of developing MS, regardless of what environmental exposures they experience. Nevertheless, the contribution of specific genes to MS-susceptibility seems only modest. Thus, despite HLA DRB1*1501 being the most consistently identified genetic marker of MS-susceptibility (being present in over 50% of northern MS patient populations), only about 1% of individuals with this allele are even genetically susceptible to getting MS. Moreover, because genetic susceptibility seems so similar throughout North America and Europe, environmental differences principally determine the regional variations in disease characteristics. Additionally, despite 75% of MS-patients being women, men are 60% more likely to be genetically-susceptible than women. Also, men develop MS at lower levels of environmental exposure than women. Nevertheless, women are more responsive to the recent changes in environmental-exposure (whatever these have been). This explains both the changing sex-ratio and the increasing disease prevalence (which has increased by a minimum of 32% in Canada over the past 35 years). As noted, environmental risk seems to result from three sequential components of environmental exposure. The potential importance of this Model for MS pathogenesis is that, if correct, a therapeutic strategy, designed to interrupt one or more of these sequential factors, has the potential to markedly reduce or eliminate disease prevalence in the future.

Vitamin D and multiple sclerosis

Vitamin D is a principal regulator of calcium homeostasis. However, recent evidence has indicated that vitamin D can have numerous other physiological functions including inhibition of proliferation of a number of malignant cells including breast and prostate cancer cells and protection against certain immune mediated disorders including multiple sclerosis (MS). The geographic incidence of MS indicates an increase in MS with a decrease in sunlight exposure. Since vitamin D is produced in the skin by solar or UV irradiation and high serum levels of 25-hydroxyvitamin D (25(OH)D) have been reported to correlate with a reduced risk of MS, a protective role of vitamin D is suggested. Mechanisms whereby the active form of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) may act to mediate this protective effect are reviewed. Due to its immunosuppressive actions, it has been suggested that 1,25(OH)(2)D(3) may prevent the induction of MS.

Novel therapeutic strategies for multiple sclerosis--a multifaceted adversary

Therapeutic strategies for multiple sclerosis have radically changed in the past 15 years. Five regulatory-approved immunomodulatory agents are reasonably effective in the treatment of relapsing-remitting multiple sclerosis, and appear to delay the time to progression to disabling stages. Inhibiting disease progression remains the central challenge for the development of improved therapies. As understanding of the immunopathogenesis of multiple sclerosis has advanced, a number of novel potential therapeutics have been identified, and are discussed here. It has also become apparent that traditional views of multiple sclerosis simply as a CD4+ T-cell-mediated disease of the central nervous system are incomplete. The pathogenic role of other immune components such as the innate immune system, regulatory T cells, T helper 17 cells and B cells is reaching centre stage, opening up exciting avenues and novel potential targets to affect the natural course of multiple sclerosis.

Vitamin D and human health: lessons from vitamin D receptor null mice

The vitamin D endocrine system is essential for calcium and bone homeostasis. The precise mode of action and the full spectrum of activities of the vitamin D hormone, 1,25-dihydroxyvitamin D [1,25-(OH)(2)D], can now be better evaluated by critical analysis of mice with engineered deletion of the vitamin D receptor (VDR). Absence of a functional VDR or the key activating enzyme, 25-OHD-1alpha-hydroxylase (CYP27B1), in mice creates a bone and growth plate phenotype that mimics humans with the same congenital disease or severe vitamin D deficiency. The intestine is the key target for the VDR because high calcium intake, or selective VDR rescue in the intestine, restores a normal bone and growth plate phenotype. The VDR is nearly ubiquitously expressed, and almost all cells respond to 1,25-(OH)(2)D exposure; about 3% of the mouse or human genome is regulated, directly and/or indirectly, by the vitamin D endocrine system, suggesting a more widespread function. VDR-deficient mice, but not vitamin D- or 1alpha-hydroxylase-deficient mice, and man develop total alopecia, indicating that the function of the VDR and its ligand is not fully overlapping. The immune system of VDR- or vitamin D-deficient mice is grossly normal but shows increased sensitivity to autoimmune diseases such as inflammatory bowel disease or type 1 diabetes after exposure to predisposing factors. VDR-deficient mice do not have a spontaneous increase in cancer but are more prone to oncogene- or chemocarcinogen-induced tumors. They also develop high renin hypertension, cardiac hypertrophy, and increased thrombogenicity. Vitamin D deficiency in humans is associated with increased prevalence of diseases, as predicted by the VDR null phenotype. Prospective vitamin D supplementation studies with multiple noncalcemic endpoints are needed to define the benefits of an optimal vitamin D status.

Higher levels of 25-hydroxyvitamin D are associated with a lower incidence of multiple sclerosis only in women

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory disease with an as yet not fully understood etiological background. The geographical distribution of MS is striking with a prevalence that increases with latitude. For this reason, vitamin D deficiency is considered a possible pathogenic co-factor in MS.

MATERIALS AND METHODS

To study the role of the vitamin D metabolism in MS, blood samples were taken twice (summer and winter) from 103 patients with MS and 110 healthy controls. Serum concentrations of 25-hydroxyvitamin D (25(OH) D) and 1,25-dihydroxyvitamin D (1,25(OH)(2)D) were measured, and detailed information on disease characteristics and environmental factors that might influence the vitamin D metabolite levels was collected.

RESULTS

Mean serum 25(OH)D and 1,25(OH)(2)D concentrations were significantly higher in summer compared to winter in both patients and controls. Using logistic regression methods, we found that in women for every 10 nmol/L increase of serum 25(OH)D level the odds of MS was reduced by 19% (odds ratio 0.81; 95% confidence interval: 0.69-0.95), suggesting a "protective" effect of higher 25(OH)D serum levels. In addition, also restricted to women, a negative correlation was found between Expanded Disability Status Scale and 25(OH)D levels (r = -0.29, P = 0.020).

CONCLUSIONS

Our data suggest that higher circulating levels of 25(OH)D are associated with a lower incidence of MS and MS-related disability in women. This may imply clues to the pathogenesis of the sex difference in risk and to the nature of the environmental factors involved in MS.

Association of vitamin D metabolite levels with relapse rate and disability in multiple sclerosis

BACKGROUND

Multiple Sclerosis is associated with low serum levels of 25-hydroxyvitamin D (25(OH)D). We investigated the association between serum levels of 25(OH)D and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active metabolite, and clinical MS severity as expressed by EDSS-score and relapse rate.

STUDY-DESIGN

Cross-sectional study.

PATIENTS AND METHODS

Serum samples from 267 MS patients were collected for 25(OH)D and 1,25(OH)2D measurement. Clinical MS parameters at the date of serum sampling were determined.

RESULTS

Both metabolite levels were significantly lower in the progressive forms compared to the relapsing remitting (RR)MS phenotype. In RRMS patients (disease course < or = 5 years), high 25(OH)D levels were associated with a high chance of remaining relapse-free. Low 25(OH)D levels were associated with high EDSS-scores. 1,25(OH)2D was not directly associated with relapse rate or EDSS-score, and was dependent of age and 25(OH)D level.

CONCLUSION

Serum levels of 25(OH)D were associated with both relapse rate and disability in MS patients. These results are suggestive for a disease modulating effect of the serum concentrations of 25(OH)D on MS. The low circulating 1,25(OH)2D levels in progressive MS are due to older age and lower 25(OH)D levels. The potential consequences for vitamin D supplementation in MS will be discussed.

Multiple Sclerosis disease distribution and potential impact of environmental air pollutants in Georgia

Multiple Sclerosis (MS) is one of the most common diseases of the central nervous system. Although the disease has been associated with some genetic and environmental factors, it has neither clear causes nor clear temporality with respect to exposure. The purpose of this study was to explore potential relationships between MS and outdoor air pollutants in GA. This study used cross-sectional data from the member's list of the Multiple Sclerosis Society's GA chapter (MSS-GA), the US Census, and a database of county-level Toxic Release Inventory data (emissions across identified, reporting sources to outdoor air, as a surrogate indicator of potential exposure to a criteria pollutant subject to regulation or to chemical toxicants). The final study population was 9,072,576 people, including 6247 self-reported MS cases from MSS-GA. Cases were stratified by gender and transformed into county-level, self-reported prevalence rates using 2005 US Census estimates. County-level prevalence was displayed using a Geographic Information System. Linear regression was conducted to investigate potential relationships between self-reported MS prevalence rates, census data, and environmental outdoor air pollutant indicators. MS prevalence tended to be clustered within the largest metropolitan statistical area (MSA) in Georgia, around Atlanta (Fulton County). The best predictive models for the MS prevalence in GA included both per capita income and PM-10 for females, but only per capita income only for males. The clustering of prevalence of MS in the largest MSA of Georgia, after controlling for population distribution, suggested that urban attributes may be associated with MS. The results of this study further suggested a potential role of PM-10 in the etiology of MS in females, perhaps due to the influence of PM-10 on systemic immune response and inflammation. Based on this initial exploratory study, we recommend more basic and clinical exposure research to understand environmental influences on MS. In particular, outdoor air pollutants like particles, and attached chemicals and metals, which have other known adverse cardiopulmonary health outcomes and are subject to federal and state regulations, could be examined using routinely collected outdoor air monitoring station data and/or modeling.

1,25-dihydroxyvitamin D3 reverses experimental autoimmune encephalomyelitis by inhibiting chemokine synthesis and monocyte trafficking

Multiple sclerosis (MS) is a complex neurodegenerative disease whose pathogenesis involves genetic and environmental risk factors leading to an aberrant, neuroantigen-specific, CD4+ T cell-mediated autoimmune response. In support of the hypothesis that vitamin D3 may reduce MS risk and severity, we found that vitamin D3 and 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) inhibited induction of experimental autoimmune encephalomyelitis (EAE), an MS model. To investigate how 1,25-(OH)2D3 could carry out anti-inflammatory functions, we administered 1,25-(OH)2D3 or a placebo to mice with EAE, and subsequently analyzed clinical disease, chemokines, inducible nitric oxide synthase (iNOS), and recruitment of dye-labeled monocytes. The 1,25-(OH)2D3 treatment significantly reduced clinical EAE severity within 3 days. Sharp declines in chemokines, inducible iNOS, and CD11b+ monocyte recruitment into the central nervous system (CNS) preceded this clinical disease abatement in the 1,25-(OH)2D3-treated animals. The 1,25-(OH)2D3 did not directly and rapidly inhibit chemokine synthesis in vivo or in vitro. Rather, the 1,25-(OH)2D3 rapidly stimulated activated CD4+ T cell apoptosis in the CNS and spleen. Collectively, these results support a model wherein inflammation stimulates a natural anti-inflammatory feedback loop. The activated inflammatory cells produce 1,25-(OH)2D3, and this hormone subsequently enhances the apoptotic death of inflammatory CD4+ T cells, removing the driving force for continued inflammation. In this way, the sunlight-derived hormone could reduce the risk of chronic CNS inflammation and autoimmune-mediated neurodegenerative disease.

Experimental allergic encephalomyelitis in connexin 43-heterozygous mice

Alterations in the expression of gap junction proteins (connexins) have previously been observed in experimental allergic encephalomyelitis (EAE). Demyelinating lesions have significantly decreased Cx43, while recovering lesions have greatly increased Cx43 and increased glial fibrillary acidic protein-expressing astrocytes. This suggests an important role for gap-junctional intercellular communication in astrocytes in the recovery from CNS inflammation. To study the effects of decreased Cx43 expression during acute disease (21 days post-immunization) and in recovering spinal cord tissue (55 days post-immunization) we induced EAE in Cx43 heterozygous and wild-type mice. Mice showed signs of disease by day 10, and signs of recovery by day 25. There were no clinical or pathological differences between heterozygous and wild-type mice in the acute disease stage, except that wild-type male mice had fewer clinical signs of disease. Male mice that were heterozygous for Cx43, and therefore had decreased expression of Cx43, had increased EAE disease severity. All demyelinating lesions had reduced numbers of reactive astrocytes and a significant decrease in Cx43 expression. In the 55-day study, all heterozygous and wild-type mice were clinically improved, showed decreased pathological signs, and showed increased laminin expression, indicative of CNS recovery. Furthermore, all heterozygous mice showed a striking increase in Cx43 expression during recovery, suggesting that the regulatory factors affecting Cx43 expression are still present in mice that have only one wild-type Cx43 allele.

Environmental risk factors for multiple sclerosis. Part II: Noninfectious factors

As discussed in Part I of this review, the geographic distribution of multiple sclerosis (MS) and the change in risk among migrants provide compelling evidence for the existence of strong environmental determinants of MS, where "environmental" is broadly defined to include differences in diet and other behaviors. As we did for infections, we focus here primarily on those factors that may contribute to explain the geographic variations in MS prevalence and the change in risk among migrants. Among these, sunlight exposure emerges as being the most likely candidate. Because the effects of sun exposure may be mediated by vitamin D, we also examine the evidence linking vitamin D intake or status to MS risk. Furthermore, we review the evidence on cigarette smoking, which cannot explain the geographic variations in MS risk, but may contribute to the recently reported increases in the female/male ratio in MS incidence. Other proposed risk factors for MS are mentioned only briefly; although we recognize that some of these might be genuine, evidence is usually sparse and unpersuasive.

Assessment of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D3 concentrations in male and female multiple sclerosis patients and control volunteers

Populations with insufficient ultraviolet exposure and who consume diets low in vitamin D have low vitamin D status (plasma 25-hydroxyvitamin D (25(OH)D) concentrations) and a reported higher incidence of multiple sclerosis (MS). The active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), is an effective anti-inflammatory molecule. No research to date has assessed 1,25(OH)2D3 concentrations in individuals with MS. In this study, plasma concentrations of 25(OH)D, 1,25(OH)2D3 and parathyroid hormone (PTH) were measured in 29 individuals with MS and 22 age- and sex-matched control volunteers. There were no significant differences in plasma PTH, 25(OH)D and 1,25(OH)2D3 concentrations between individuals with MS and control volunteers. Women with MS had significantly higher 25(OH)D and 1,25(OH)2D3 concentrations than men with MS (79.1+/-45.4 versus 50.2+/-15.3 nmol/L, P=0.019 and 103.8+/-36.8 versus 70.4+/-28.7 pmol/L, P=0.019, respectively). There was a significant positive correlation between 25(OH)D and 1,25(OH)2D3 concentrations in all subjects (r=0.564, P=0.000), but secondary analysis revealed that the correlation was driven by women with MS (r=0.677, P=0.001). Significant sex differences in vitamin D metabolism were observed and were most marked in individuals with MS, suggesting that vitamin D requirements may differ between the sexes, as well as by underlying disease state.

Studies of associations between disability in multiple sclerosis, skin type, gender and ultraviolet radiation

Recent studies suggest ultraviolet radiation (UVR)/vitamin D is protective against the development of multiple sclerosis (MS). We determined if outcome in MS is associated with the surrogate for host pigmentation, skin type, and parameters of UVR exposure. We used a validated questionnaire to determine skin type and UVR exposure during childhood (0-16 years), and early adult life (17-40 years), in 448 Caucasians with MS. Outcome was assessed using the Kurtzke Expanded Disability Status Score (EDSS) and Multiple Sclerosis Severity Scale (MSSS). We studied the association of skin type and exposure with dichotomized values of EDSS (< and ≥6) and MSSS (continuous variable) using logistic and linear regression analyses, respectively. Sex, onset age and MS duration were significantly associated with outcome in all patients. In 169 females with established disease (≥10 years), sun sensitive skin types 1 and 2 were associated with reduced risk of EDSS ≥6 (odds ratio =0.50; 95% CI = 0.26-0.97), and higher MSSS values (coefficient = -0.86; 95% CI = -1.67 to -0.05). Parameters of UVR exposure were not significantly associated with outcome. These preliminary data show an association between skin type and disability in female MS patients. They are compatible with independent studies suggesting that exposure mediates MS pathogenesis via vitamin D. Further studies are required to properly assess these potentially important findings. Multiple Sclerosis 2007; 13: 369-375. http://msj.sagepub.com

The effects on human health from stratospheric ozone depletion and its interactions with climate change

Ozone depletion leads to an increase in the ultraviolet-B (UV-B) component (280-315 nm) of solar ultraviolet radiation (UVR) reaching the surface of the Earth with important consequences for human health. Solar UVR has many harmful and some beneficial effects on individuals and, in this review, information mainly published since the previous report in 2003 (F. R. de Gruijl, J. Longstreth, M. Norval, A. P. Cullen, H. Slaper, M. L. Kripke, Y. Takizawa and J. C. van der Leun, Photochem. Photobiol. Sci., 2003, 2, pp. 16-28) is discussed. The eye is exposed directly to sunlight and this can result in acute or long-term damage. Studying how UV-B interacts with the surface and internal structures of the eye has led to a further understanding of the location and pathogenesis of a number of ocular diseases, including pterygium and cataract. The skin is also exposed directly to solar UVR, and the development of skin cancer is the main adverse health outcome of excessive UVR exposure. Skin cancer is the most common form of malignancy amongst fair-skinned people, and its incidence has increased markedly in recent decades. Projections consistently indicate a further doubling in the next ten years. It is recognised that genetic factors in addition to those controlling pigment variation can modulate the response of an individual to UVR. Several of the genetic factors affecting susceptibility to the development of squamous cell carcinoma, basal cell carcinoma and melanoma have been identified. Exposure to solar UVR down-regulates immune responses, in the skin and systemically, by a combination of mechanisms including the generation of particularly potent subsets of T regulatory cells. Such immunosuppression is known to be a crucial factor in the generation of skin cancers. Apart from a detrimental effect on infections caused by some members of the herpesvirus and papillomavirus families, the impact of UV-induced immunosuppression on other microbial diseases and vaccination efficacy is not clear. One important beneficial effect of solar UV-B is its contribution to the cutaneous synthesis of vitamin D, recognised to be a crucial hormone for bone health and for other aspects of general health. There is accumulating evidence that UVR exposure, either directly or via stimulation of vitamin D production, has protective effects on the development of some autoimmune diseases, including multiple sclerosis and type 1 diabetes. Adequate vitamin D may also be protective for the development of several internal cancers and infections. Difficulties associated with balancing the positive effects of vitamin D with the negative effects of too much exposure to solar UV-B are considered. Various strategies that can be adopted by the individual to protect against excessive exposure of the eye or the skin to sunlight are suggested. Finally, possible interactions between ozone depletion and climate warming are outlined briefly, as well as how these might influence human behaviour with regard to sun exposure.

IL-10 signaling is essential for 1,25-dihydroxyvitamin D3-mediated inhibition of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) results from an aberrant, neuroantigen-specific, T cell-mediated autoimmune response. Because MS prevalence and severity decrease sharply with increasing sunlight exposure, and sunlight supports vitamin D(3) synthesis, we proposed that vitamin D(3) and 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) may protect against MS. In support of this hypothesis, 1,25-(OH)(2)D(3) strongly inhibited experimental autoimmune encephalomyelitis (EAE). This inhibition required lymphocytes other than the encephalitogenic T cells. In this study, we tested the hypothesis that 1,25-(OH)(2)D(3) might inhibit EAE through the action of IL-10-producing regulatory lymphocytes. We report that vitamin D(3) and 1,25-(OH)(2)D(3) strongly inhibited myelin oligodendrocyte peptide (MOG(35-55))-induced EAE in C57BL/6 mice, but completely failed to inhibit EAE in mice with a disrupted IL-10 or IL-10R gene. Thus, a functional IL-10-IL-10R pathway was essential for 1,25-(OH)(2)D(3) to inhibit EAE. The 1,25-(OH)(2)D(3) also failed to inhibit EAE in reciprocal, mixed bone marrow chimeras constructed by transferring IL-10-deficient bone marrow into irradiated wild-type mice and vice versa. Thus, 1,25-(OH)(2)D(3) may be enhancing an anti-inflammatory loop involving hemopoietic cell-produced IL-10 acting on brain parenchymal cells and vice versa. If this interpretation is correct, and humans have a similar bidirectional IL-10-dependent loop, then an IL-10-IL-10R pathway defect could abrogate the anti-inflammatory and neuro-protective functions of sunlight and vitamin D(3). In this way, a genetic IL-10-IL-10R pathway defect could interact with an environmental risk factor, vitamin D(3) insufficiency, to increase MS risk and severity.

Vitamin D3-mediated alterations to myeloid dendritic cell trafficking in vivo expand the scope of their antigen presenting properties

The mucosal immune system provides the host with a first line of adaptive immune defense against invasion by many species of pathogenic microorganisms and their secreted products. Calcitriol, the active form of Vitamin D3 (VD3), promotes the induction of mucosal immunity in mice when added to subcutaneously administered vaccine formulations. Dendritic cells (DCs) activated at vaccination sites where VD3 is present gain the capacity to bypass sequestration in the draining lymph node and traffic to the Peyer's Patches (PP) of immunized animals. By employing protocols that allow the effective tracking of endogenous or adoptively transferred myeloid DCs in vivo, we found that VD3 influences on the trafficking of fully differentiated immature DCs were temporary, and occur without negative effects to antigen processing or peptide presentation to CD4+ T cells. In contrast, DCs differentiated from hematopoietic precursors in the presence of VD3 (conditioned DCs), were markedly compromised in their antigen presenting properties, while manifesting clear alterations to their trafficking properties in vivo. Similar to the recent finding of VD3-mediated enhancement of innate immune protection, our findings suggest that VD3 could also play an important role in controlling the types of immune effector responses elicited subsequent to either infection or vaccination.