A vitamin D analog down-regulates proinflammatory chemokine production by pancreatic islets inhibiting T cell recruitment and type 1 diabetes development

Paricalcitol inhibits renal inflammation by promoting vitamin D receptor-mediated sequestration of NF-kappaB signaling

Inflammation is a pathologic feature of a variety of chronic kidney diseases. Several lines of evidence suggest a potential anti-inflammatory role for vitamin D in chronic kidney disease, but the underlying mechanism remains unknown. Here, the effect of the synthetic vitamin D analogue paricalcitol on renal inflammation was investigated in a mouse model of obstructive nephropathy. Paricalcitol reduced infiltration of T cells and macrophages in the obstructed kidney. This inhibition of inflammatory cell infiltration was accompanied by a decreased expression of RANTES and TNF-alpha. Induction of RANTES was localized primarily to the tubular epithelium, underscoring a role for tubular cells in renal inflammation. In a human proximal tubular cell line (HKC-8), paricalcitol inhibited RANTES mRNA and protein expression and abolished the ability of tubular cells to recruit lymphocytes and monocytes after TNF-alpha stimulation. Although RANTES induction depended on NF-kappaB signaling, paricalcitol affected neither TNF-alpha-mediated IkappaB alpha phosphorylation and degradation nor p65 NF-kappaB activation and nuclear translocation. Instead, chromatin immunoprecipitation assay showed that paricalcitol abolished the binding of p65 to its cognate cis-acting element in the RANTES promoter. The vitamin D receptor (VDR) and p65 formed a complex in tubular cells after paricalcitol treatment, which inhibited the ability of p65 to trans-activate gene transcription. In vivo, paricalcitol did not block NF-kappaB nuclear translocation after obstructive injury but did increase the expression and nuclear distribution of VDR. These results suggest that paricalcitol inhibits renal inflammatory infiltration and RANTES expression by promoting VDR-mediated sequestration of NF-kappaB signaling.

Dendritic cells in islets of Langerhans constitutively present beta cell-derived peptides bound to their class II MHC molecules

Islets of Langerhans from normal mice contained dendritic cells (DCs) in the range of 8-10 per islet. DCs were found in several mouse strains, including those from lymphocyte-deficient mice. DCs were absent in islets from colony stimulating factor-1 deficient mice and this absence correlated with small size islets. Most DCs were found next to blood vessels and resided in islets for several days. Some DCs contained insulin-like granules, and most expressed peptide-MHC complexes derived from beta cell proteins. Islet DCs were highly effective in presenting beta cell antigens to CD4 T cells ex vivo. Presentation of beta cell-derived peptide-MHC complexes by DCs neither depended on islet inflammation nor correlated with the extent of spontaneous beta cell death. Periislet stroma DCs did not contain beta cell peptide-MHC complexes; however, 50% of DCs in pancreatic node were positive. Hence, presentation of high levels of beta cell antigens normally takes place by islet DCs, a finding that has to be placed in the perspective of autoimmune diabetes.

Islet expression of M3 uncovers a key role for chemokines in the development and recruitment of diabetogenic cells in NOD mice

OBJECTIVE

Type 1 diabetes is an autoimmune disease characterized by a local inflammatory reaction in and around islets followed by selective destruction of insulin-secreting beta-cells. We tested the hypothesis that chemokines affect different mechanisms responsible for the development of diabetes in NOD mice.

RESEARCH DESIGN AND METHODS

We examined chemokine expression in islets of NOD mice and tested their functional relevance to development of diabetes using transgenic mice expressing the mouse herpesvirus 68-encoded chemokine decoy receptor M3 (NOD-M3 mice) in insulin-secreting beta-cells.

RESULTS

Multiple chemokines were expressed in pancreatic islets of NOD mice before development of diabetes. Islet-specific expression of the pan-chemokine inhibitor M3 dramatically reduced leukocyte infiltration and islet destruction and completely blocked development of diabetes in NOD-M3 mice. M3 blocked diabetes by inhibiting the priming of diabetogenic cells in the pancreatic lymph nodes and their recruitment into the islets. This effect was specific to the pancreatic islets because M3 expression did not affect other ongoing autoimmune processes.

CONCLUSIONS

These results demonstrate that chemokines mediate afferent and efferent immunity in type 1 diabetes and suggest that broad chemokine blockade may represent a viable strategy to prevent insulitis and islet destruction.

IL4 gene delivery to the CNS recruits regulatory T cells and induces clinical recovery in mouse models of multiple sclerosis

Central nervous system (CNS) delivery of anti-inflammatory cytokines, such as interleukin 4 (IL4), holds promise as treatment for multiple sclerosis (MS). We have previously shown that short-term herpes simplex virus type 1-mediated IL4 gene therapy is able to inhibit experimental autoimmune encephalomyelitis (EAE), an animal model of MS, in mice and non-human primates. Here, we show that a single administration of an IL4-expressing helper-dependent adenoviral vector (HD-Ad) into the cerebrospinal fluid (CSF) circulation of immunocompetent mice allows persistent transduction of neuroepithelial cells and long-term (up to 5 months) CNS transgene expression without toxicity. Mice affected by chronic and relapsing EAE display clinical and neurophysiological recovery from the disease once injected with the IL4-expressing HD-Ad vector. The therapeutic effect is due to the ability of IL4 to increase, in inflamed CNS areas, chemokines (CCL1, CCL17 and CCL22) capable of recruiting regulatory T cells (CD4+CD69-CD25+Foxp3+) with suppressant functions. CSF delivery of HD-Ad vectors expressing anti-inflammatory molecules might represent a valuable therapeutic option for CNS inflammatory disorders.

Family-based analysis of vitamin D receptor gene polymorphisms and type 1 diabetes in the population of South Croatia

Type 1 diabetes mellitus (T1DM) is a disease characterised by the autoimmune destruction of insulin-producing pancreatic beta cells. Vitamin D is a known immune system modulator and its effects are exerted via the vitamin D receptor (VDR). Several VDR gene single nucleotide polymorphisms (SNPs) have been commonly studied in relation to T1DM. The aim of this study was to evaluate the role of VDR gene variation in T1DM susceptibility by genotyping four SNPs (FokI-rs10735810, TaqI-rs731236, BsmI-rs1544410, and Tru9I-rs757343) in 160 case-parent trio samples from the population of South Croatia. We observed overtransmission of Tru9I allele G and undertransmission of the Tru9I-BsmI A-A haplotype from parents to affected children (P = 0.032, P = 0.002, respectively). These results indicate a possible role of the VDR gene in T1DM aetiology. In conclusion, this family-based study presents some evidence of association of specific VDR gene variants with T1DM in the population of South Croatia.

Vitamin D receptor agonists in the treatment of autoimmune diseases: selective targeting of myeloid but not plasmacytoid dendritic cells

Vitamin D receptor (VDR) agonists are well known for their capacity to control calcium and bone metabolism and to regulate growth and differentiation of many cell types. More recently, it has become clear that VDR agonists possess immunoregulatory properties and, in particular, pronounced protolerogenic activities. These agents have been shown to be effective in several models of autoimmune diseases and are the most used topical agents in the treatment of psoriasis, a Th1 and Th17 cell-mediated autoimmune disease of the skin, indicating their potential applicability in the treatment of a variety of autoimmune diseases. VDR agonists can act directly on T cells, but dendritic cells (DCs) seem to be their primary targets. A potentially very important activity of VDR agonists is their capacity to induce in vitro and in vivo tolerogenic DCs able to enhance CD4(+)CD25(+) suppressor T cells that, in turn, inhibit effector T-cell responses. Novel data now show that VDR agonists selectively modulate tolerogenic properties in blood myeloid but not plasmacytoid DCs, shedding new light on the multifaceted immunoregulatory properties of these agents.

CYP2R1 (vitamin D 25-hydroxylase) gene is associated with susceptibility to type 1 diabetes and vitamin D levels in Germans

BACKGROUND

The vitamin D system has been implicated in type 1 diabetes by epidemiological and immune intervention studies as well as by polymorphisms of the vitamin D binding protein (DBP) and CYP27B1 genes. CYP2R1, a cytochrome P450 enzyme, catalyzes the formation of vitamin D3 to 25-hydroxyvitamin D3 (25(OH)D3), the main circulating vitamin D metabolite.

METHODS

Two hundred and three simplex type 1 German diabetes families (609 subjects) were genotyped for the rs10741657 and for the rs12794714 polymorphisms. 25(OH)D3 levels were measured and correlated with CYP2R1 polymorphisms in 133 type 1 diabetes patients as well as its mRNA expression from peripheral blood mononuclear cells (PBMCs) in 58 type 1 diabetes patients. Frequencies and genotypes of the CYP2R1 polymorphisms were analyzed using Haploview software version 3.2. The correlation between 25(OH)D3 and CYP2R1mRNA with the genotypes of the rs10741657 and rs12794714 polymorphism was evaluated by Wilcoxon-Mann-Whitney- and ANOVA test using Bias Statistical package 7.01.

RESULTS

Whereas the rs12794714 polymorphism was not associated with type 1 diabetes the variant 'G' of the rs10741657 polymorphism was more often transmitted to affected offspring (61% vs 39% P = 0.004) and was also more frequent in cases than in controls (46.1% vs 35.7%, P = 0.03). Patients carrying the genotype 'GG' or 'GA' of the rs10741657 polymorphism possessed, on average, lower levels of 25(OH)D3 compared to those with the genotype 'AA' (P = 0.003, Pc = 0.01 and P = 0.01, Pc = 0.04, respectively).

CONCLUSION

Thus, our findings reveal a novel association of CYP2R1 polymorphisms in patients with type 1 diabetes and with their circulating levels of 25(OH)D3.

Evidence for association between vitamin D receptor BsmI polymorphism and type 1 diabetes in Japanese

Type 1 diabetes is considered to be T-helper 1 (Th1) type autoimmune disease. Because the vitamin D receptor is expressed on CD4+T cells and is known to affect cytokine responses, several groups have investigated the association between the vitamin D receptor gene BsmI polymorphism and type 1 diabetes. However, this issue is still controversial; therefore, we examined this gene polymorphism in a large number of type 1 diabetic patients as a multi-center collaborative study in Japan. A total of 1,373 subjects, including 774 cases and 599 control subjects of Japanese origin, were studied. The frequency of carriers of the BB genotype in type 1 diabetic patients was significantly higher than that in controls (p<0.01, odds ratio 3.65). Moreover, IFN-gamma production upon anti-CD3 stimulation in the BB genotype group was significantly higher than that in the Bb and bb genotype groups (p<0.05), suggesting that the polyclonal T cell response in BB genotype patients is Th1 dominant. Based upon these results, we propose that it may be worthwhile to focus on subjects with the BB genotype of this gene polymorphism as having high risk for type 1 diabetes.

Effect of 1,25-(OH)2D3 (a vitamin D analogue) on passively sensitized human airway smooth muscle cells

BACKGROUND AND OBJECTIVES

In asthma, airway smooth muscle cell (ASMC) hyperplasia plays an important role in airway remodelling. Increased expression of matrix metalloproteinases-9 (MMP-9), a disintegrin and metalloprotease 33 (ADAM33) in ASMCs are also relevant to asthmatic airway remodelling. 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) has potent antiproliferative properties in vitro in various cell types; however, its role in ASMCs is not well understood. This study investigated the effect of 1,25-(OH)(2)D(3) on passively sensitized human bronchial (airway) smooth muscle cell (HASMC) proliferation and MMP-9 and ADAM33 expressions.

METHODS

The effect of 1,25-(OH)(2)D(3) on cell proliferation was examined by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium-bromide colorimetry assay; cell cycle analysis by flow cytometry; and immunocytochemical staining for proliferating cell nuclear antigen (PCNA). The expression of MMP-9 and ADAM33 in HASMCs was investigated by real-time quantitative PCR and Western Blot analysis.

RESULTS

1,25-(OH)(2)D(3) effectively suppressed passively sensitized HASMC proliferation, proliferating cell nuclear antigen expression and G(1)/S transition in HASMCs passively sensitized with asthmatic serum. Further analysis showed that 1,25-(OH)(2)D(3) significantly down-regulated the expressions of protein for MMP-9 and ADAM33, as well as their mRNA levels in passively sensitized HASMCs.

CONCLUSIONS

1,25-(OH)(2)D(3) has direct inhibitory effects on passively sensitized HASMCs in vitro, including inhibition of cell proliferation and expression of MMP-9 and ADAM33, suggesting a possible beneficial role for 1,25-(OH)(2)D(3) in preventing and treating asthmatic airway remodelling.

Modulatory effects of 1,25-dihydroxyvitamin D3 on human B cell differentiation

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) can modulate immune responses, but whether it directly affects B cell function is unknown. Patients with systemic lupus erythematosus, especially those with antinuclear Abs and increased disease activity, had decreased 1,25(OH)(2)D(3) levels, suggesting that vitamin D might play a role in regulating autoantibody production. To address this, we examined the effects of 1,25(OH)(2)D(3) on B cell responses and found that it inhibited the ongoing proliferation of activated B cells and induced their apoptosis, whereas initial cell division was unimpeded. The generation of plasma cells and postswitch memory B cells was significantly inhibited by 1,25(OH)(2)D(3), although the up-regulation of genetic programs involved in B cell differentiation was only modestly affected. B cells expressed mRNAs for proteins involved in vitamin D activity, including 1 alpha-hydroxylase, 24-hydroxylase, and the vitamin D receptor, each of which was regulated by 1,25(OH)(2)D(3) and/or activation. Importantly, 1,25(OH)(2)D(3) up-regulated the expression of p27, but not of p18 and p21, which may be important in regulating the proliferation of activated B cells and their subsequent differentiation. These results indicate that 1,25(OH)(2)D(3) may play an important role in the maintenance of B cell homeostasis and that the correction of vitamin D deficiency may be useful in the treatment of B cell-mediated autoimmune disorders.

Elevated phosphorus modulates vitamin D receptor-mediated gene expression in human vascular smooth muscle cells

Clinical observations show that an increase in serum inorganic phosphorus (Pi) is linked to higher cardiovascular (CV) mortality, while vitamin D receptor (VDR) agonist therapy is associated with survival benefit in stage 5 chronic kidney disease. Smooth muscle cells (SMCs) play an important role in CV pathophysiology, but the interaction between Pi and the VDR signaling pathway in SMCs is not known. Real-time RT-PCR studies revealed that elevated Pi (2.06 mM) modulated VDR-mediated regulation of a panel of genes including thrombomodulin and osteopontin in SMCs. DNA microarray results demonstrated that increasing Pi from 0.9 to 2.06 mM exerted a widespread modulating effect on VDR-mediated gene expression. A total of 325 target genes were affected by paricalcitol at 0.9 mM Pi, with 195 up- and 130 downregulated. The number of target genes affected by paricalcitol at 2.06 mM Pi decreased to 86, with 55 up- and 31 downregulated. VDR-mediated gene expression in As4.1 cells (a juxtaglomerular cell-like cell line derived from kidney tumors in SV40 T-antigen transgenic mice) and peroxisome proliferator-activated receptor (PPAR)gamma-mediated gene expression in SMCs were also altered by elevated Pi, suggesting that the observation is not unique to VDR in SMCs. Mechanism analysis showed that elevated Pi had no significant effect on VDR or PPARgamma protein level but altered the cytosolic vs. nuclear distribution of NF-kappaB or nuclear receptor corepressor 1 (NCoR1). Our results demonstrate for the first time that elevated Pi affects VDR-mediated gene expression in human coronary artery SMCs and the effect is not limited to VDR in SMCs.

1,25-Dihydroxyvitamin D3 targeting of NF-kappaB suppresses high glucose-induced MCP-1 expression in mesangial cells

Macrophages accumulate in kidney glomeruli and interstitium of patients with diabetic nephropathy in response to monocyte chemoattractant protein-1 (MCP-1); a chemokine produced by both tubular epithelial and mesangial cells (MCs). Vitamin D and its analogs have been shown to have renoprotective effects; however, there are few studies involving diabetic nephropathy. We explored mechanisms by which 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) can be renoprotective by measuring MCP-1 expression in MCs. Using a luciferase reporter assay, we found that high glucose (HG)-induced MCP-1 transcription and that this induction is blocked by 1,25(OH)2D3. Electrophoretic mobility shift and chromatin immunoprecipitation assays showed that HG increased the p65/p50 binding to the two NF-kappaB sites within the promoter. This was suppressed by 1,25(OH)2D3, but this decrease was reversed by overexpression of p65. 1,25(OH)2D3 was found to stabilize IkappaBalpha leading to an inhibition of p65 translocation to the nucleus and subsequent reduction of NF-kappaB binding. In primary MCs prepared from vitamin D receptor knockout animals, basal MCP-1 levels were elevated but not affected by 1,25(OH)2D3. The analog paricalcitol inhibited the induction and activity of MCP-1 while ameliorating glomerulosclerosis in streptozotocin-diabetic mice. Our results suggest that 1,25(OH)2D3 might block hyperglycemia-induced renal injury by blunting NF-kappaB activation.

Quantification of chemokines by real-time reverse transcriptase PCR: applications in type 1 diabetes

Type 1 diabetes is a T-cell mediated autoimmune disease, characterized by the destruction of insulin-producing pancreatic beta-cells. This review will discuss the role of chemokines in the recruitment of immune cells leading to the pathology of this disease. There will be a focus on the quantification of chemokines and chemokine receptors by the recently developed real-time reverse transcriptase PCR technique. Today, this technique is in widespread use for analysis of chemokines in cells, tissues and tissue biopsies. The minute amount of tissue needed for analysis, as well as the very high sensitivity of this method, make it the method of choice for analysis of chemokines, which are often expressed at very low levels in target tissues. However, validation and optimization of the technique is of crucial importance for obtaining reliable results.

NF-kappa B as a therapeutic target in autoimmune disease

NF-kappaB transmits signals from the cell surface to the nucleus. Signaling through cell surface receptors to activate NF-kappaB and mitogen-activated protein kinases through adaptor molecules is of critical importance to survival and activation of all cells in the body, including those regulating innate and adaptive immunity. As such, NF-kappaB is a key signaling component in autoimmunity and an attractive target for autoimmune disease therapy. However, given its global importance, targeting NF-kappaB tends to be immunosuppressive. In this review, the authors discuss the roles played by NF-kappaB in autoimmunity, drugs which target it, and complexities which need to be addressed to improve the use of NF-kappaB as a target. Finally, the authors highlight some novel approaches that are likely to be important in the next generation of NF-kappaB therapies.

1,25-Dihydroxyvitamin D3 selectively modulates tolerogenic properties in myeloid but not plasmacytoid dendritic cells

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is an immunomodulatory agent inducing dendritic cells (DCs) to become tolerogenic. To further understand its mechanisms of action, we have examined the effects of 1,25(OH)(2)D(3) on tolerogenic properties of blood myeloid (M-DCs) and plasmacytoid (P-DCs) human DC subsets. Exposure of M-DCs to 1,25(OH)(2)D(3) up-regulated production of CCL22, a chemokine attracting regulatory T cells, whereas production of CCL17, the other CCR4 ligand, was reduced. 1,25(OH)(2)D(3) also decreased IL-12p75 production by M-DCs, as expected, and inhibited CCR7 expression. 1,25(OH)(2)D(3) treatment markedly increased CD4(+) suppressor T cell activity while decreasing the capacity of M-DCs to induce Th1 cell development. Surprisingly, 1,25(OH)(2)D(3) did not exert any discernible effect on tolerogenic properties of P-DCs, and even their high production of IFN-alpha was not modulated. In particular, the intrinsically high capacity of P-DCs to induce CD4(+) suppressor T cells was unaffected by 1,25(OH)(2)D(3). Both DC subsets expressed similar levels of the vitamin D receptor, and its ligation by 1,25(OH)(2)D(3) similarly activated the primary response gene cyp24. Interestingly, 1,25(OH)(2)D(3) inhibited NF-kappaB p65 phosphorylation and nuclear translocation in M-DCs but not P-DCs, suggesting a mechanism for the inability of 1,25(OH)(2)D(3) to modulate tolerogenic properties in P-DCs.

Inhibition of prostate growth and inflammation by the vitamin D receptor agonist BXL-628 (elocalcitol)

The prostate is a target organ of vitamin D receptor (VDR) agonists and represents an extra-renal site of 1,25-dihydroxyvitamin D(3) synthesis, but its capacity to respond to VDR agonists has, so far, been almost exclusively probed for the treatment of prostate cancer. We have analyzed the capacity of VDR agonists to treat benign prostatic hyperplasia (BPH), a complex syndrome characterized by a static component related to prostate overgrowth, a dynamic one responsible for urinary irritative symptoms, and an inflammatory component. Preclinical data demonstrate that VDR agonists, and notably BXL-628 (elocalcitol), reduce the static component of BPH by inhibiting the activity of intra-prostatic growth factors downstream of the androgen receptor, and the dynamic component by targeting bladder cells. In addition, BXL-628 inhibits production of proinflammatory cytokines and chemokines by human BPH cells. These data have led to a proof-of-concept clinical study that has successfully shown arrest of prostate growth in BPH patients treated with BXL-628, with excellent safety. We have documented the anti-inflammatory effects of BXL-628 also in animal models of autoimmune prostatitis, observing a significant reduction of intra-prostatic cell infiltrate following administration of this VDR agonist, at normocalcemic doses, in mice with already established disease. These data extend the potential use of VDR agonists to novel indications that represent important unmet medical needs, and provide a sound rationale for further clinical testing.

Involvement of the vitamin D receptor in the regulation of NF-kappaB activity in fibroblasts

We have used mouse embryonic fibroblasts (MEFs) derived from VDR(+/-) and VDR(-/-) mice to determine whether the nuclear vitamin D receptor (VDR) is directly involved in the regulation of NF-kappaB activation. We found that the basal IkappaBalpha protein level was markedly decreased in VDR(-/-) MEFs compared to VDR(+/-) MEFs; however, degradation of IkappaBalpha and its phosphorylation were not altered in VDR(-/-) cells, neither were the levels of IKKalpha and IKKbeta proteins. Consistently, p65 nuclear translocation was increased in unstimulated VDR(-/-) cells. The physical interaction between VDR and p65 was absent in VDR(-/-) MEFs, which may free p65 and increase its activity. Consequently, these alterations combined led to a marked increase in NF-kappaB transcriptional activity. Consistently, induction of IL-6 by TNFalpha or IL-1beta was much more robust in VDR(-/-) than in VDR(+/-) cells, indicating that VDR(-/-) cells are more susceptible to inflammatory stimulation. Therefore, fibroblasts lacking VDR appear to be more pro-inflammatory due to the intrinsic high NF-kappaB activity. The reduction of IkappaBalpha in VDR(-/-) MEFs may be partially explained by the lack of VDR-mediated stabilization of IkappaBalpha by 1,25(OH)(2)D(3). These data suggest that VDR plays an inhibitory role in the regulation of NF-kappaB activation.

The direct action of 1α,25(OH)2-vitamin D3 on purified mouse Langerhans cells

The action of vitamin D(3) on Langerhans cells (LCs) is not well understood. Using highly purified murine LCs (>95%), we investigated the direct action of 1alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) on their functions. 1,25(OH)(2)D(3) inhibited the expression of cell surface molecules including I-A(d), CD40, CD80, and CD86, leading to impaired ability of LCs to stimulate allogenic T cells in the mixed leukocyte reaction. Furthermore, this reagent inhibited chemotaxis of LCs to CCL21 and their survival. Interestingly, 1,25(OH)(2)D(3) reduced the IL-10 production by LCs, whereas the production of IL-6 and IL-12p40 upon activation by CD40 ligation was enhanced. With regard to inflammatory cytokines and chemokines, 1,25(OH)(2)D(3) upregulated the production of IL-1beta, CCL3, CCL4, and CCL5. The production of Th2-type chemokines, represented by CL17 and CCL22, was inhibited, whereas IFN-gamma-triggered production of Th1-type chemokines, represented by CXCL9, CXCL10, and CXCL11, was augmented. These data indicate that the mode of regulation of cytokine and chemokine production in association with 1,25(OH)(2)D(3) treatment seems to be another characteristic discriminating LCs from classical myeloid dendritic cells.

Treatment of experimental autoimmune prostatitis in nonobese diabetic mice by the vitamin D receptor agonist elocalcitol

On the basis of on the marked inhibitory activity of the vitamin D receptor agonist Elocalcitol on basal and growth factor-induced proliferation of human prostate cells and on its potent anti-inflammatory properties, we have tested its capacity to treat experimental autoimmune prostatitis (EAP) induced by injection of prostate homogenate-CFA in nonobese diabetic (NOD) mice. Administration of Elocalcitol, at normocalcemic doses, for 2 wk in already established EAP significantly inhibits the intraprostatic cell infiltrate, leading to a profound reduction in the number of CD4(+) and CD8(+) T cells, B cells, macrophages, dendritic cells, and I-A(g7)-positive cells. Immunohistological analysis demonstrates reduced cell proliferation and increased apoptosis of resident and infiltrating cells. Significantly decreased production of the proinflammatory cytokines IFN-gamma and IL-17 is observed in prostate-draining lymph node T cells from Elocalcitol-treated NOD mice stimulated by TCR ligation. In addition, Elocalcitol treatment reduces IFN-gamma production by prostate-infiltrating CD4(+) T cells and draining lymph node T cells specific for an immunodominant peptide naturally processed from prostate steroid-binding protein, a prostate-specific autoantigen. Finally, CD4(+) splenic T cells from Elocalcitol-treated NOD mice show decreased ability, upon adoptive transfer into NOD.SCID recipients, to induce autoimmune prostatitis, paralleled by a reduced capacity to produce IFN-gamma in response to prostate steroid-binding protein. The results indicate that Elocalcitol is able to interfere with key pathogenic events in already established EAP in the NOD mouse. These data show a novel indication for vitamin D receptor agonists and indicate that treatment with Elocalcitol may inhibit the intraprostatic inflammatory response in chronic prostatitis/chronic pelvic pain syndrome patients.

The chemokine decoy receptor M3 blocks CC chemokine ligand 2 and CXC chemokine ligand 13 function in vivo

Chemokines and their receptors play a key role in immune homeostasis regulating leukocyte migration, differentiation, and function. Viruses have acquired and optimized molecules that interact with the chemokine system. These virus-encoded molecules promote cell entry, facilitate dissemination of infected cells, and enable the virus to evade the immune response. One such molecule in the murine gammaherpesvirus 68 genome is the M3 gene, which encodes a secreted 44-kDa protein that binds with high affinity to certain murine and human chemokines and blocks chemokine signaling in vitro. To test the hypothesis that M3 directly interferes with diverse chemokines in vivo, we examined the interaction of M3 with CCL2 and CXCL13 expressed in the pancreas of transgenic mice. CCL2 expression in the pancreas promoted recruitment of monocytes and dendritic cells; CXCL13 promoted recruitment of B and T lymphocytes. Coexpression of M3 in the pancreas blocked cellular recruitment induced by both CCL2 and CXCL13. These results define M3 as multichemokine blocker and demonstrate its use as a powerful tool to analyze chemokine biology.

Animal models of spontaneous autoimmune disease: type 1 diabetes in the nonobese diabetic mouse

The nonobese diabetic (NOD) mouse represents probably the best spontaneous model for a human autoimmune disease. It has provided not only essential information on type 1 diabetes (T1D) pathogenesis, but also valuable insights into mechanisms of immunoregulation and tolerance. Importantly, it allows testing of immunointervention strategies potentially applicable to man. The fact that T1D incidence in the NOD mouse is sensitive to environmental conditions, and responds, sometimes dramatically, to immunomanipulation, does not represent a limit of the model, but is likely to render it even more similar to its human counterpart. In both cases, macrophages, dendritic cells, CD4+, CD8+, and B cells are present in the diseased islets. T1D is a polygenic disease, but, both in human and in NOD mouse T1D, the primary susceptibility gene is located within the MHC. On the other hand, T1D incidence is significantly higher in NOD females, although insulitis is similar in both sexes, whereas in humans, T1D occurs with about equal frequency in males and females. In addition, NOD mice have a more widespread autoimmune disorder, which is not the case in the majority of human T1D cases. Despite these differences, the NOD mouse remains the most representative model of human T1D, with similarities also in the putative target autoantigens, including glutamic acid decarboxylase IA-2, and insulin.

Lower levels of plasma 25-hydroxyvitamin D among young adults at diagnosis of autoimmune type 1 diabetes compared with control subjects: results from the nationwide Diabetes Incidence Study in Sweden (DISS)

AIMS/HYPOTHESIS

Low plasma vitamin D concentrations may promote the development of type 1 diabetes. To test this hypothesis, we measured plasma 25-hydroxyvitamin D (25OHD) in young adults with type 1 diabetes.

METHODS

The nationwide Diabetes Incidence Study in Sweden (DISS) covers 15- to 34-year-old people with newly diagnosed diabetes. Blood samples at diagnosis were collected during the 2-year period 1987/1988. Patients with islet antibodies (islet cell antibodies, GAD antibodies or tyrosine phosphatase-like protein antibodies) were defined as having autoimmune type 1 diabetes. Plasma 25OHD was measured in samples taken from 459 patients at the time of diagnosis, and in 138 of these subjects 8 years later. The results were compared with age- and sex-matched control subjects (n=208).

RESULTS

At diagnosis, plasma 25OHD levels were significantly lower in patients with type 1 diabetes than in control subjects (82.5+/-1.3 vs 96.7+/-2.0 nmol/l; p<0.0001). Eight years later, plasma 25OHD had decreased in patients (81.5+/-2.6 nmol/l; p=0.04). Plasma 25OHD levels were significantly lower in diabetic men than in diabetic women at diagnosis (77.9+/-1.4 vs 90.1+/-2.4 nmol/l; p<0.0001) and at follow-up (77.1+/-2.8 nmol/l vs 87.2+/-4.5 nmol/l; p=0.048).

CONCLUSIONS/INTERPRETATION

The plasma 25OHD level was lower at diagnosis of autoimmune type 1 diabetes than in control subjects, and may have a role in the development of type 1 diabetes. Plasma 25OHD levels were lower in men than in women with type 1 diabetes. This difference may be relevant to the high incidence of type 1 diabetes among young adult men.

Meta-analysis of vitamin D receptor polymorphisms and type 1 diabetes: a HuGE review of genetic association studies

Several polymorphisms in the vitamin D receptor (VDR) gene have been reported to be associated with the risk of developing type 1 diabetes, yet published findings have been conflicting. In this study, the authors attempted to evaluate the evidence regarding the association. They searched all relevant reports from original papers published from 1997 to December 2005. Predefined criteria were used to identify 1) case-control association studies examining the FokI (11 studies), BsmI (13 studies), ApaI (9 studies), and TaqI (7 studies) polymorphisms and 2) a few family-transmission studies with analysis of these four polymorphisms. In random-effects modeling, the 95% confidence intervals of the summary odds ratios for all four polymorphisms included 1, indicating no effect. Except for FokI, no heterogeneity was found. The 95% confidence intervals of the transmission proportions all included 0.5, indicating no effect. Thus, the authors found no evidence for an association between VDR gene polymorphisms and type 1 diabetes risk in either case-control studies or family-transmission studies. In fact, a reanalysis of previously published data (McDermott et al., Diabetologia 1997;40:971-5) indicated no evidence of an association as reported.

Increased NF-kappaB activity in fibroblasts lacking the vitamin D receptor

1,25-Dihydroxyvitamin D [1,25(OH)2D3] is known to have anti-inflammatory activity; however, the molecular mechanism remains poorly defined. Here we show that the nuclear vitamin D receptor (VDR) is directly involved in the regulation of NF-kappaB activation, a pathway essential for inflammatory response. In mouse embryonic fibroblasts (MEFs) derived from VDR-/- mice, the basal level of kappaB inhibitor (IkappaB) alpha protein was markedly decreased compared with VDR+/- MEFs; however, degradation of IkappaBalpha and its phosphorylation in response to TNF-alpha treatment or Salmonella infection were not altered in VDR-/- cells, neither were the levels of IkappaB kinase-alpha and IkappaB kinase-beta proteins. Consistent with IkappaBalpha reduction, p65 accumulation in the nucleus was markedly increased in unstimulated VDR-/- cells. In addition, the physical interaction between VDR and p65 was absent in VDR-/- MEFs, which may free p65 and increase its activity. Consequently, these alterations combined led to a marked increase in nuclear p65 DNA binding and NF-kappaB transcriptional activity; consistently, induction of IL-6 by TNF-alpha or IL-1beta was much more robust in VDR-/- than in VDR+/- cells, indicating that VDR-/- cells are more susceptible to inflammatory stimulation. Therefore, cells lacking VDR appear to be more proinflammatory due to the intrinsic high NF-kappaB activity. The reduction of IkappaBalpha in VDR-/- MEFs may be partially explained by the lack of VDR-mediated stabilization of IkappaBalpha by 1,25(OH)2D3. This is supported by the observation that IkappaBalpha degradation induced by TNF-alpha was inhibited by 1,25(OH)2D3 in VDR+/- cells, but not in VDR-/- cells. Taken together, these data suggest that VDR plays an inhibitory role in the regulation of NF-kappaB activation.

Pre-clinical evidence and clinical translation of benign prostatic hyperplasia treatment by the vitamin D receptor agonist BXL-628 (Elocalcitol)

The active form of vitamin D, 1,25-dihydroxyvitamin D3, is a secosteroid hormone that binds to the vitamin D receptor (VDR), a member of the superfamily of nuclear receptors, and exerts a number of diverse biological functions. The natural hormone and synthetic VDR agonists are well known for their capacity to control calcium and bone metabolism, but they also regulate proliferation and differentiation of many cell types, and possess exquisite immunoregulatory properties, mostly by targeting dendritic cells (DC) and T cells. These properties have been clinically exploited in the treatment of different diseases, from secondary hyperparathyroidism to osteoporosis to psoriasis. The VDR is expressed by most cell types, including cells of the urogenital system such as prostate and bladder cells. In particular, the prostate has been recognized as a target organ of VDR agonists and represents an extra-renal synthesis site of 1,25-dihydroxyvitamin D3, but its capacity to respond to VDR agonists has, so far, been probed only for the treatment of prostate cancer. We have taken a different approach, and have analysed the capacity of VDR agonists to treat benign prostatic hyperplasia (BPH), a complex syndrome characterized by a static component related to prostate overgrowth, a dynamic component responsible for urinary irritative symptoms, and a possible inflammatory component. Pre-clinical data reviewed here demonstrate that VDR agonists, and notably BXL-628 (Elocalcitol), reduce the static component of BPH by inhibiting the activity of intra-prostatic growth factors downstream of the androgen receptor, and the dynamic component by targeting bladder cells. These data have led to a proof-of-concept clinical study that has successfully shown arrest of prostate growth in BPH patients treated with BXL-628. Ongoing clinical studies will assess the capacity of this VDR agonist to reduce symptoms and ameliorate flow parameters in BPH-affected individuals. The pronounced effects of BXL-628 on bladder smooth muscle cells and its anti-inflammatory properties indeed anticipate beneficial effects also on BPH-related lower urinary tract symptoms.

Regulatory T cells: How do they find their space in the immunological arena?

After more of a decade of controversy, the concept of suppressor T cells initially promoted by Gershon, has now become an established paradigm. Current knowledge withholds that populations of suppressor or regulatory T cells (Treg cells) constitute a pivotal mechanism of immunological tolerance. Diverse types of Treg cells, with distinct origins, disparate and multiple functions have been described. However, despite the recognized importance of Treg cells in regulating immune responses, our understanding of their significance, mechanism of action and interplay with other means of immunological tolerance is still in its infancy. Increased comprehension of how Treg cells exert their function holds the promise for therapeutic intervention by manipulating one of the most sophisticated features of immunity to either boost responses in cancer and microbial diseases or suppresses those unwanted in autoimmunity and transplantation. Here, I will discuss new findings and open questions related to CD25(+)Treg cells in an attempt to cover some of the most puzzling aspects in the functioning of these cells.

Vitamin D decreases NFkappaB activity by increasing IkappaBalpha levels

BACKGROUND

In a previous study we demonstrated the inhibitory effect of 1,25-dihydroxyvitamin D (1,25(OH)(2)D(3)) and its less calcaemic analog 1,24(OH)(2)D(2) on the production of tumour necrosis factor alpha (TNFalpha) by human peritoneal macrophages. The aim of the present study is to examine whether this vitamin D inhibition of TNFalpha is mediated by its major transcription factor, nuclear factor-kappaB (NFkappaB).

METHODS

Murine macrophage cells (P388D1) were incubated with 10(-7) M 1,25(OH)(2)D(3) or 1,24(OH)(2)D(2) and then stimulated with lipopolysaccharide. NFkappaB activity was assayed using a reporter gene and by electrophoretic mobility shift assay (EMSA). In addition, we evaluated mRNA and protein levels of NFkappaB-p65 and of IkappaBalpha, a potent NFkappaB inhibitor, and phosphorylated IkappaBalpha.

RESULTS

Both 1,25(OH)(2)D(3) and 1,24(OH)(2)D(2) induced a 60% reduction of TNFalpha secretion. By using a reporter gene and EMSA we found that vitamin D markedly reduced NFkappaB activity. 1,25(OH)(2)D(3) or 1,24(OH)(2)D(2) decreased NFkappaB-p65 levels in the nucleus and increased NFkappaB-p65 levels in the cytosol; no changes were observed in the total levels of NFkappaB-p65 protein and mRNA. Concurrently, vitamin D induced a significant increase in mRNA and protein levels of IkappaBalpha (approximately 6.5- and 4.5-fold, respectively). Elevated levels of IkappaBalpha can be explained by the vitamin D-induced prolongation of IkappaBalpha-mRNA half-life from 110 to 190 min and by the decrease in IkappaBalpha phosphorylation.

CONCLUSIONS

Vitamin D up-regulates IkappaBalpha levels by increasing mRNA stability and decreasing IkappaBalpha phosphorylation. The increase in IkappaBalpha levels reduces nuclear translocation of NFkappaB and thereby downgrades its activity. Since NFkappaB is a major transcription factor of inflammatory mediators, these findings suggest that the less-calcaemic analog, 1,24(OH)(2)D(2) may be effective as an anti-inflammatory therapeutic agent.

Prevention of chronic allograft rejection by Vitamin D receptor agonists

While immunosuppressive drugs now permit a good control of acute allograft rejection, chronic rejection remains an important unmet medical problem. We propose that Vitamin D receptor (VDR) agonists, secosteroid hormones that control cell proliferation and differentiation and exert immunoregulatory activities, in addition to regulate calcium and bone metabolism, have the potential to contribute to the management of chronic allograft rejection. Recent advances in understanding the immunomodulatory and growth-regulating properties of VDR agonists indicate the clinical applicability of these hormones in transplantation, with the aim of facilitating tolerance induction and preventing chronic graft rejection.

Therapeutic synergism of gemcitabine and CpG-oligodeoxynucleotides in an orthotopic human pancreatic carcinoma xenograft

CpG-oligodeoxynucleotides (CpG-ODN) exhibit potent immunostimulatory activity by binding with Toll-like receptor 9 (TLR9). Based on the finding that TLR9 is highly expressed and functional in pancreatic tissue, we evaluated the antitumor effects of chemotherapy combined with CpG-ODNs in the orthotopic mouse model of a human pancreatic tumor xenograft. Chemotherapy consisted of the maximum tolerated dose of gemcitabine (i.v., 100 mg/kg, q3dx4). CpG-ODNs were delivered (i.p., 20 microg/mouse), weekly, after the end of chemotherapy. CpG-ODNs alone had little effect on tumor growth, whereas gemcitabine alone significantly delayed the median time of disease onset (palpable i.p. tumor) and of bulky disease development (extensive peritoneal tumor burden), but did not enhance survival time. When the gemcitabine regimen was followed by administration of the immunostimulator, development of bulky disease was delayed, survival time was significantly improved (median survival time, 106 days; P < 0.02 versus gemcitabine-treated mice). Autoptic examination showed that tumor spread in the peritoneal cavity was reduced to a greater extent than with gemcitabine alone. All treatment regimens were well-tolerated. The use of nude mice excluded a T cell-mediated immune response, whereas the high pancreatic expression of TLR9 might have contributed to the tumor response. The clear improvement of survival observed in an orthotopic murine model of human pancreatic cancer by the combined use of CpG-ODNs with chemotherapy suggests the promise of this therapeutic regimen in the clinical setting.

Expression of the inhibitory receptor ILT3 on dendritic cells is dispensable for induction of CD4+Foxp3+ regulatory T cells by 1,25-dihydroxyvitamin D3

1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is a secosteroid hormone that renders dendritic cells (DCs) tolerogenic, favoring the induction of regulatory T cells. Induction of DCs with tolerogenic properties by 1,25(OH)(2)D(3) is associated with increased selective expression of immunoglobulin-like transcript 3 (ILT3), suggesting its involvement in the immunoregulatory properties of this hormone. Here we show an in vivo correlate of the increased ILT3 expression on DCs in healing psoriatic lesions following topical treatment with the 1,25(OH)(2)D(3) analog calcipotriol. Analysis of DC subsets reveals a differential regulation of ILT3 expression by 1,25(OH)(2)D(3), with a marked up-regulation in myeloid DCs but no effect on its expression by plasmacytoid DCs. A regulatory role for ILT3 expressed on DCs is indicated by the increased interferon-gamma (IFN-gamma) secretion promoted by anti-ILT3 addition to cultures of DCs and T cells, but this effect is blunted in 1,25(OH)(2)D(3)-treated DCs, suggesting ILT3-independent mechanisms able to regulate T-cell activation. Although ILT3 expression by DCs is required for induction of regulatory T cells, DC pretreatment with 1,25(OH)(2)D(3) leads to induction of CD4(+)Foxp3(+) cells with suppressive activity irrespective of the presence of neutralizing anti-ILT3 monoclonal antibody (mAb), indicating that ILT3 expression is dispensable for the capacity of 1,25(OH)(2)D(3)-treated DCs to induce regulatory T cells.

Manipulating dendritic cells to induce regulatory T cells

Dendritic cells (DCs) induce and regulate T-cell responses, and tolerogenic DCs can promote the development of regulatory T cells with suppressive activity. The possibility of manipulating DCs using different pharmacological or biological agents, enabling them to exert tolerogenic activities, could be exploited to better control a variety of chronic inflammatory conditions, from autoimmune diseases to allograft rejection.

T cell costimulation by chemokine receptors

Signals mediated by chemokine receptors may compete with T cell receptor stop signals and determine the duration of T cell-antigen-presenting cell interactions. Here we show that during T cell stimulation by antigen-presenting cells, T cell chemokine receptors coupled to G(q) and/or G(11) protein were recruited to the immunological synapse by a G(i)-independent mechanism. When chemokine receptors were sequestered at the immunological synapse, T cells became insensitive to chemotactic gradients, formed more stable conjugates and finally responded with enhanced proliferation and cytokine production. We suggest that chemokine receptor trapping at the immunological synapse enhances T cell activation by improving T cell-antigen-presenting cell attraction and impeding the 'distraction' of successfully engaged T cells by other chemokine sources.

1,25-Dihydroxyvitamin D3 modulates expression of chemokines and cytokines in pancreatic islets: implications for prevention of diabetes in nonobese diabetic mice

1,25-Dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) is an immune modulator that prevents experimental autoimmune diseases. Receptors for 1,25-(OH)(2)D(3) are present in pancreatic beta-cells, the target of an autoimmune assault in nonobese diabetic (NOD) mice. The aim of this study was to investigate the in vivo and in vitro effects of 1,25-(OH)(2)D(3) on beta-cell gene expression and death and correlate these findings to in vivo diabetes development in NOD mice. When female NOD mice were treated with 1,25-(OH)(2)D(3) (5 microg/kg per 2 d), there was a decrease in islet cytokine and chemokine expression, which was accompanied by less insulitis. Complementing these findings, we observed that exposure to 1,25-(OH)(2)D(3) in three cell systems INS-1(E) cell line, fluorescence-activated cell sorting purified rat beta-cells, and NOD-severe combined immunodeficient islets) suppressed IP-10 and IL-15 expression in the beta-cell itself but did not prevent cytokine-induced beta-cell death. This 1,25-(OH)(2)D(3)-induced inhibition of chemokine expression in beta-cells was associated with a decreased diabetes incidence in some treatment windows targeting early insulitis. Thus, although a short and early intervention with 1,25-(OH)(2)D(3) (3-14 wk of age) reduced diabetes incidence (35 vs. 58%, P < or = 0.05), a late intervention (from 14 wk of age, when insulitis is present) failed to prevent disease. Of note, only early and long-term treatment (3-28 wk of age) prevented disease to a major extent (more than 30% decrease in diabetes incidence). We conclude that 1,25-(OH)(2)D(3) monotherapy is most effective in preventing diabetes in NOD mice when applied early. This beneficial effect of 1,25-(OH)(2)D(3) is associated with decreased chemokine and cytokine expression by the pancreatic islets.

Intervention in autoimmunity: The potential of vitamin D receptor agonists

Vitamin D receptor (VDR) agonists are well known for their capacity to control calcium metabolism and to regulate growth and differentiation of many cell types. More recently, it has become clear that VDR agonists possess immunoregulatory properties and, in particular, pronounced pro-tolerogenic activities. VDR agonists can act directly on T cells, but DCs appear to be their primary targets. The capacity of VDR agonists to modulate DC and T cell functions is mediated by VDR expression in both cell types and by the presence of common targets in their signal transduction pathways, such as the nuclear factor NF-kappaB that is downregulated by VDR agonists in APCs and in T cells. A potentially very important activity of VDR agonists is their capacity to induce in vitro and in vivo tolerogenic DCs able to enhance CD4+CD25+ suppressor T cells that, in turn, inhibit Th1 cell responses. These mechanisms of action can explain some of the immunoregulatory properties of VDR agonists in the treatment of Th1-mediated autoimmune diseases, but may also represent a physiologic element in the VDR-mediated regulation of innate and adaptive immune responses.