Community Engagement and Psychometric Methods in Aboriginal and Torres Strait Islander Patient-Reported Outcome Measures and Surveys-A Scoping Review and Critical Analysis.

(1) Background: In healthcare settings, patient-reported outcome measures (PROMs) and surveys are accepted, patient-centered measures that provide qualitative information on dimensions of health and wellbeing. The level of psychometric assessment and engagement with end users for their design can vary significantly. This scoping review describes the psychometric and community engagement processes for PROMs and surveys developed for Aboriginal and Torres Strait Islander communities. (2) Methods: The PRISMA ScR guidelines for scoping reviews were followed, aimed at those PROMs and surveys that underwent psychometric assessment. The Aboriginal and Torres Strait Islander Quality Appraisal Tool and a narrative synthesis approach were used. (3) Results: Of 1080 articles, 14 were eligible for review. Most articles focused on a validity assessment of PROMs and surveys, with reliability being less common. Face validity with Aboriginal and Torres Strait Islander communities was reported in most studies, with construct validity through exploratory factor analyses. Methodological design risks were identified in the majority of studies, notably the absence of explicit Indigenous knowledges. Variability existed in the development of PROMs and surveys for Aboriginal and Torres Strait Islander communities. (4) Conclusions: Improvement in inclusion of Indigenous knowledges and research approaches is needed to ensure relevance and appropriate PROM structures. We provide suggestions for research teams to assist in future design.

Multiple Sclerosis: Lipids, Lymphocytes, and Vitamin D.

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. We review the two core MS features, myelin instability, fragmentation, and remyelination failure, and dominance of pathogenic CD4+ Th17 cells over protective CD4+ Treg cells. To better understand myelin pathology, we describe myelin biosynthesis, structure, and function, then highlight stearoyl-CoA desaturase (SCD) in nervonic acid biosynthesis and nervonic acid's contribution to myelin stability. Noting that vitamin D deficiency decreases SCD in the periphery, we propose it also decreases SCD in oligodendrocytes, disrupting the nervonic acid supply and causing myelin instability and fragmentation. To better understand the distorted Th17/Treg cell balance, we summarize Th17 cell contributions to MS pathogenesis, then highlight how 1,25-dihydroxyvitamin D3 signaling from microglia to CD4+ T cells restores Treg cell dominance. This signaling rapidly increases flux through the methionine cycle, removing homocysteine, replenishing S-adenosyl-methionine, and improving epigenetic marking. Noting that DNA hypomethylation and inappropriate DRB1*1501 expression were observed in MS patient CD4+ T cells, we propose that vitamin D deficiency thwarts epigenetic downregulation of DRB1*1501 and Th17 cell signature genes, and upregulation of Treg cell signature genes, causing dysregulation within the CD4+ T cell compartment. We explain how obesity reduces vitamin D status, and how estrogen and vitamin D collaborate to promote Treg cell dominance in females. Finally, we discuss the implications of this new knowledge concerning myelin and the Th17/Treg cell balance, and advocate for efforts to address the global epidemics of obesity and vitamin D deficiency in the expectation of reducing the impact of MS.

Resetting the Narrative in Australian Aboriginal and Torres Strait Islander Nutrition Research.

As the oldest continuous living civilizations in the world, Aboriginal and Torres Strait Islander peoples have strength, tenacity, and resilience. Initial colonization of the landscape included violent dispossession and removal of people from Country to expand European land tenure and production systems, loss of knowledge holders through frontier violence, and formal government policies of segregation and assimilation designed to destroy ontological relationships with Country and kin. The ongoing manifestations of colonialism continue to affect food systems and food knowledges of Aboriginal peoples, and have led to severe health inequities and disproportionate rates of nutrition-related health conditions. There is an urgent need to collaborate with Aboriginal and Torres Strait Islander peoples to address nutrition and its underlying determinants in a way that integrates Aboriginal and Torres Strait Islander peoples' understandings of food and food systems, health, healing, and well-being. We use the existing literature to discuss current ways that Australian Aboriginal and Torres Strait Islander peoples are portrayed in the literature in relation to nutrition, identify knowledge gaps that require further research, and propose a new way forward.

Vitamin D3-mediated resistance to a multiple sclerosis model disease depends on myeloid cell 1,25-dihydroxyvitamin D3 synthesis and correlates with increased CD4+ T cell CTLA-4 expression.

Microglial cell activation is the earliest biomarker of the inflammatory processes that cause central nervous system (CNS) lesions in multiple sclerosis. We hypothesized that 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) production by activated microglia and macrophages in the CNS inhibits these inflammatory processes. To test this hypothesis, we targeted the Cyp27b1 gene specifically in myeloid cells, then analyzed the influence of disrupted myeloid cell 1,25-(OH)2D3 synthesis on vitamin D3-mediated resistance to experimental autoimmune encephalomyelitis (EAE). Myeloid cell 1,25-(OH)2D3 synthesis was essential for vitamin D3-mediated EAE resistance. Increased CTLA-4 expression in the CNS-infiltrating CD4+ Tconv and Treg cells and decreased splenic B cell CD86 expression correlated with resistance. These new data provide solid support for the view that vitamin D3 reduces MS risk in part through a mechanism involving myeloid cell 1,25-(OH)2D3 production and CTLA-4 upregulation in CNS-infiltrating CD4+ T cells. We suggest that CTLA-4 serves as a vitamin D3-regulated immunological checkpoint in multiple sclerosis prevention.

1,25-Dihydroxyvitamin D3 increases the methionine cycle, CD4+ T cell DNA methylation and Helios+Foxp3+ T regulatory cells to reverse autoimmune neurodegenerative disease.

We investigated how one calcitriol dose plus vitamin D3 reverses experimental autoimmune encephalomyelitis (EAE), a multiple sclerosis model. This protocol rapidly increased CD4+ T cell Ikzf2 transcripts, Helios protein, and CD4+Helios+FoxP3+ T regulatory cells. It also rapidly increased CD4+ T cell Bhmt1 transcripts, betaine:homocysteine methyltransferase-1 (BHMT1) enzyme activity, and global DNA methylation. BHMT1 transmethylates homocysteine to replenish methionine. Targeting the Vdr gene in T cells decreased Ikzf2 and Bhmt1 gene expression, reduced DNA methylation, and elevated systemic homocysteine in mice with EAE. We hypothesize that calcitriol drives a transition from encephalitogenic CD4+ T cell to Treg cell dominance by upregulating Ikzf2 and Bhmt1, recycling homocysteine to methionine, reducing homocysteine toxicity, maintaining DNA methylation, and stabilizing CD4+Helios+FoxP3+Tregulatory cells. Conserved vitamin D-responsive element (VDRE)-type sequences in the Bhmt1 and Ikzf2 promoters, the universal need for methionine in epigenetic regulation, and betaine's protective effects in MTHFR-deficiency suggest similar regulatory mechanisms exist in humans.

Vitamin D3 alters microglia immune activation by an IL-10 dependent SOCS3 mechanism.

Microglia become activated immune cells during infection or disease in the central nervous system (CNS). However, the mechanisms that downregulate activated microglia to prevent immune-mediated damage are not completely understood. Vitamin D3 has been suggested to have immunomodulatory affects, and high levels of vitamin D3 have been correlated with a decreased risk for developing some neurological diseases. Recent studies have demonstrated the synthesis of active vitamin D3, 1,25-dihydroxyvitamin D3, within the CNS, but its cellular source and neuroprotective actions remain unknown. Therefore, we wanted to determine whether microglia can respond to vitamin D3 and whether vitamin D3 alters immune activation of microglia. We have previously shown that microglia become activated by IFNγ or LPS or by infection with virus to express pro-inflammatory cytokines, chemokines, and effector molecules. In this study, activated microglia increased the expression of the vitamin D receptor and Cyp27b1, which encodes the enzyme for converting vitamin D3 into its active form, thereby enhancing their responsiveness to vitamin D3. Most importantly, the activated microglia exposed to vitamin D3 had reduced expression of pro-inflammatory cytokines, IL-6, IL-12, and TNFα, and increased expression of IL-10. The reduction in pro-inflammatory cytokines was dependent on IL-10 induction of suppressor of cytokine signaling-3 (SOCS3). Therefore, vitamin D3 increases the expression of IL-10 creating a feedback loop via SOCS3 that downregulates the pro-inflammatory immune response by activated microglia which would likewise prevent immune mediated damage in the CNS.

Vitamin D and estrogen synergy in Vdr-expressing CD4(+) T cells is essential to induce Helios(+)FoxP3(+) T cells and prevent autoimmune demyelinating disease.

Multiple sclerosis (MS) is a neurodegenerative disease resulting from an autoimmune attack on the axon-myelin unit. A female MS bias becomes evident after puberty and female incidence has tripled in the last half-century, implicating a female sex hormone interacting with a modifiable environmental factor. These aspects of MS suggest that many female MS cases may be preventable. Mechanistic knowledge of this hormone-environment interaction is needed to devise strategies to reduce female MS risk. We previously demonstrated that vitamin D3 (D3) deficiency increases and D3 supplementation decreases experimental autoimmune encephalomyelitis (EAE) risk in a female-biased manner. We also showed that D3 acts in an estrogen (E2)-dependent manner, since ovariectomy eliminated and E2 restored D3-mediated EAE protection. Here we probed the hypothesis that E2 and D3 interact synergistically within CD4(+) T cells to control T cell fate and prevent demyelinating disease. The E2 increased EAE resistance in wild-type (WT) but not T-Vdr(0) mice lacking Vdr gene function in CD4(+) T cells, so E2 action depended entirely on Vdr(+)CD4(+) T cells. The E2 levels were higher in WT than T-Vdr(0) mice, suggesting the Vdr(+)CD4(+) T cells produced E2 or stimulated its production. The E2 decreased Cyp24a1 and increased Vdr transcripts in T cells, prolonging the calcitriol half-life and increasing calcitriol responsiveness. The E2 also increased CD4(+)Helios(+)FoxP3(+) T regulatory (Treg) cells in a Vdr-dependent manner. Thus, CD4(+) T cells have a cooperative amplification loop involving E2 and calcitriol that promotes CD4(+)Helios(+)FoxP3(+) Treg cell development and is disrupted when the D3 pathway is impaired. The global decline in population D3 status may be undermining a similar cooperative E2-D3 interaction controlling Treg cell differentiation in women, causing a breakdown in T cell self tolerance and a rise in MS incidence.

Vitamin D Actions on CD4(+) T Cells in Autoimmune Disease.

This review summarizes and integrates research on vitamin D and CD4(+) T-lymphocyte biology to develop new mechanistic insights into the molecular etiology of autoimmune disease. A deep understanding of molecular mechanisms relevant to gene-environment interactions is needed to deliver etiology-based autoimmune disease prevention and treatment strategies. Evidence linking sunlight, vitamin D, and the risk of multiple sclerosis and type 1 diabetes is summarized to develop the thesis that vitamin D is the environmental factor that most strongly influences autoimmune disease development. Evidence for CD4(+) T-cell involvement in autoimmune disease pathogenesis and for paracrine calcitriol signaling to CD4(+) T lymphocytes is summarized to support the thesis that calcitriol is sunlight's main protective signal transducer in autoimmune disease risk. Animal modeling and human mechanistic data are summarized to support the view that vitamin D probably influences thymic negative selection, effector Th1 and Th17 pathogenesis and responsiveness to extrinsic cell death signals, FoxP3(+)CD4(+) T-regulatory cell and CD4(+) T-regulatory cell type 1 (Tr1) cell functions, and a Th1-Tr1 switch. The proposed Th1-Tr1 switch appears to bridge two stable, self-reinforcing immune states, pro- and anti-inflammatory, each with a characteristic gene regulatory network. The bi-stable switch would enable T cells to integrate signals from pathogens, hormones, cell-cell interactions, and soluble mediators and respond in a biologically appropriate manner. Finally, unanswered questions and potentially informative future research directions are highlighted to speed delivery of etiology-based strategies to reduce autoimmune disease.

One calcitriol dose transiently increases Helios+ FoxP3+ T cells and ameliorates autoimmune demyelinating disease.

Multiple sclerosis (MS) is an incurable inflammatory demyelinating disease. We investigated one calcitriol dose plus vitamin D3 (calcitriol/+D) as a demyelinating disease treatment in experimental autoimmune encephalomyelitis (EAE). Evidence that calcitriol-vitamin D receptor pathway deficits may promote MS, and data showing calcitriol enhancement of autoimmune T cell apoptosis provided the rationale. Whereas vitamin D3 alone was ineffective, calcitriol/+D transiently increased central nervous system (CNS) Helios(+)FoxP3(+) T cells and sustainably decreased CNS T cells, pathology, and neurological deficits in mice with EAE. Calcitriol/+D, which was more effective than methylprednisolone, has potential for reversing inflammatory demyelinating disease safely and cost-effectively.

The Ifng gene is essential for Vdr gene expression and vitamin D3-mediated reduction of the pathogenic T cell burden in the central nervous system in experimental autoimmune encephalomyelitis, a multiple sclerosis model.

Compelling evidence suggests that vitamin D3 insufficiency may contribute causally to multiple sclerosis (MS) risk. Experimental autoimmune encephalomyelitis (EAE) research firmly supports this hypothesis. Vitamin D3 supports 1,25-dihydroxyvitamin D3 (1,25-[OH]2D3) synthesis in the CNS, initiating biological processes that reduce pathogenic CD4+ T cell longevity. MS is prevalent in Sardinia despite high ambient UV irradiation, challenging the vitamin D-MS hypothesis. Sardinian MS patients frequently carry a low Ifng expresser allele, suggesting that inadequate IFN-γ may undermine vitamin D3-mediated inhibition of demyelinating disease. Testing this hypothesis, we found vitamin D3 failed to inhibit EAE in female Ifng knockout (GKO) mice, unlike wild-type mice. The two strains did not differ in Cyp27b1 and Cyp24a1 gene expression, implying equivalent vitamin D3 metabolism in the CNS. The 1,25-(OH)2D3 inhibited EAE in both strains, but 2-fold more 1,25-(OH)2D3 was needed in GKO mice, causing hypercalcemic toxicity. Unexpectedly, GKO mice had very low Vdr gene expression in the CNS. Injecting IFN-γ intracranially into adult mice did not increase Vdr gene expression. Correlating with low Vdr expression, GKO mice had more numerous pathogenic Th1 and Th17 cells in the CNS, and 1,25-(OH)2D3 reduced these cells in GKO and wild-type mice without altering Foxp3+ regulatory T cells. Thus, the Ifng gene was needed for CNS Vdr gene expression and vitamin D3-dependent mechanisms that inhibit EAE. Individuals with inadequate Ifng expression may have increased MS risk despite high ambient UV irradiation because of low Vdr gene expression and a high encephalitogenic T cell burden in the CNS.

1,25-Dihydroxyvitamin D3 acts directly on the T lymphocyte vitamin D receptor to inhibit experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is an incurable autoimmune neurodegenerative disease. Environmental factors may be key to MS prevention and treatment. MS prevalence and severity decrease with increasing sunlight exposure and vitamin D(3) supplies, supporting our hypothesis that the sunlight-dependent hormone, 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2) D(3) ), inhibits autoimmune T-cell responses in MS. Moreover, 1,25-(OH)(2) D(3) inhibits and reverses experimental autoimmune encephalomyelitis (EAE), an MS model. Here, we investigated whether 1,25-(OH)(2) D(3) inhibits EAE via the vitamin D receptor (VDR) in T lymphocytes. Using bone marrow chimeric mice with a disrupted VDR only in radio-sensitive hematopoietic cells or radio-resistant non-hematopoietic cells, we found that hematopoietic cell VDR function was necessary for 1,25-(OH)(2) D(3) to inhibit EAE. Furthermore, conditional targeting experiments showed that VDR function in T cells was necessary. Neither 1,25-(OH)(2) D(3) nor T-cell-specific VDR targeting influenced CD4(+) Foxp3(+) T-cell proportions in the periphery or the CNS in these studies. These data support a model wherein 1,25-(OH)(2) D(3) acts directly on pathogenic CD4(+) T cells to inhibit EAE.

Murine BAFF-receptor residues 168-175 are essential for optimal CD21/35 expression but dispensable for B cell survival.

BAFF-R (B cell-activating factor belonging to the tumor necrosis factor family receptor) regulates B lymphocyte survival, maturation, homeostasis, and self-tolerance through signaling mechanisms that are not completely understood. A spontaneous BAFF-R mutation, Bcmd-1, disrupts BAFF-R signaling. However, it is not clear why the Bcmd-1-encoded BAFF-R fails to adequately support B cell survival, optimal CD21/35 expression, and B-cell tolerance to dsDNA, since it is 95% identical to the wild-type (wt) BAFF-R and retains the only known signaling motif. A retrotransposon insertion in A/WySnJ strain mice generated the Bcmd-1 allele, replacing the eight C-terminal BAFF-R residues with 21 retrotransposon-encoded residues. New data reported here show that the displaced residues, previously thought to have no signaling role, are essential for optimal CD21/35 expression but contribute little to B cell survival signaling. Analysis of wt Baffr or Bcmd-1 homozygous (A/WySnJ X B6.BCL2)F2 mice confirmed that BCL2 complemented Bcmd-1 for B cell survival but not CD21/35 expression. Through in vivo retroviral transduction experiments, we show that Baffr complemented Bcmd-1 for B cell survival but not CD21/35 expression, whereas the BaffrDelta103-175 deletion mutant lacking the BAFF-R cytoplasmic domain failed to support these functions. Importantly, we show that the BaffrDelta168-175 deletion mutant lacking the retrotransposon-displaced residues, and a BaffrT170A mutant lacking a critical threonine, supported B cell survival but failed to support optimal CD21/35 expression. These data provide the first evidence for a possible bifurcation at the receptor level in the BAFF-R signaling pathway. We suggest that discrete BAFF-R cytoplasmic domains may interact with distinct downstream pathways to provide fine control over B cell survival, maturation, and tolerance induction.

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.

Altered BAFF-receptor signaling and additional modifier loci contribute to systemic autoimmunity in A/WySnJ mice.

Systemic lupus erythematosus pathology reflects autoantibody-mediated damage due to a failure of B-lymphocyte tolerance. We previously reported that B-lymphopenic A/WySnJ mice develop a lupus-like syndrome and linked this syndrome to the B-cell maturation defect-1 (Bcmd-1) mutant allele of the B-cell-activating factor belonging to the TNF family-receptor (Baffr) gene. Here, we further evaluate the genetic basis for autoimmunity in A/WySnJ mice. We produced B6.Bcmd-1 and AW.Baffr(-/-) congenic mice (N5), and compared them with B6.Baffr(-/-) and A/WySnJ mice with respect to B-lymphocyte development. Bcmd-1-expressing mice had more B cells with greater maturity than Baffr(-/-) mice regardless of genetic background, indicating that Bcmd-1 encodes a partially functional BAFF-R. We also compared these mice for lupus phenotypes to determine whether Bcmd-1 is necessary and sufficient for disease, or whether the Baffr(-/-) (-) allele can also cause autoimmunity. The Baffr(-/-) allele did not lead to autoimmunity on either genetic background. In contrast, the Bcmd-1 allele was necessary and sufficient for development of low levels of IgM autoantibodies in B6.Bcmd-1 mice. However, Bcmd-1 plus unidentified A/WySnJ modifier genes were necessary for development of IgG autoantibodies and renal pathology. We propose that in A/WySnJ mice an excess of BAFF per B cell rescues self-reactive B cells through a partially functional BAFF-R in a B-lymphopenic environment.

A unifying multiple sclerosis etiology linking virus infection, sunlight, and vitamin D, through viral interleukin-10.

Multiple sclerosis (MS) is a neurodegenerative disease of uncertain etiology. In MS, neurodegeneration is thought to be secondary to autoimmune-mediated damage. However, no cohesive explanation yet exists as to how environmental factors interact to induce a neurodegenerative autoimmune response. Insufficient sunlight exposure and chronic viral infections have been proposed as unrelated environmental risk factors for MS. We suggest that these risk factors may act synergistically to enable the pathogenic autoimmune response. Low ultraviolet light (UVL) exposure depletes vitamin D3 stores, and low vitamin D3 levels correlate strongly with high MS risk. The central nervous system converts vitamin D3 into 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D3), a biologically active hormone with anti-inflammatory and neuro-protective functions that depend on IL-10-producing regulatory lymphocytes. Herpesvirus infection also correlates with MS risk. Some herpesviruses like Epstein-Barr virus produce an IL-10-like cytokine termed vIL-10. We hypothesize that vIL-10 may induce a dysfunction of IL-10-producing regulatory lymphocytes, thereby undermining the protective functions of sunlight, vitamin D3, and 1,25-(OH)2 D3. The vIL-10 could elicit a host immune response capable of neutralizing or depleting IL-10, or the vIL-10 could compete with IL-10 but fail to perform an essential IL-10 function. In either case, the lack of sunlight exposure and the herpes virus infection might synergize to induce a defect in IL-10-producing regulatory lymphocyte function that undermines self-tolerance mechanisms and enables a pathogenic autoimmune response to neural proteins.

Systemic autoimmunity in BAFF-R-mutant A/WySnJ strain mice.

Systemic lupus erythematosis is an autoimmune disease of unknown etiology. Lupus pathology is thought to reflect autoantibody-mediated damage due to a failure of B lymphocyte tolerance. Since excessive B cell-activating factor belonging to the TNF family (BAFF) expression correlates with human and murine lupus, and BAFF signals B cell survival through BAFF-R, it is believed that excessive BAFF-R signaling can subvert B cell tolerance and facilitate lupus development. Here we report the unexpected finding that BAFF-R-mutant A/WySnJ mice develop a lupus-like syndrome. These mice carry the B cell maturation defect-1 (Bcmd-1) mutant allele of the Baffr gene. Bcmd-1 causes premature B cell death and profound B cell deficiency. Despite having 90% fewer splenic B cells than normal mice, A/WySnJ mice had an 18-fold increased frequency of splenocytes secreting IgM antibodies to dsDNA, and increased amounts of circulating IgM and IgG to dsDNA by 9 months of age. By age 11 months, most A/WySnJ mice displayed renal pathology characteristic of lupus, including proteinuria as well as periodic acid-Schiff-positive deposits and glomerular capillary bed destruction. Importantly, we genetically linked this autoimmunity to Bcmd-1, since congenic AW.Baffr(+/+) mice carrying a wild-type allele developed none of these phenotypes. Our data provide the first evidence linking altered BAFF-R signaling to the development of B cell-mediated autoimmunity.

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.

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.