A novel immunosuppressive 1alpha,25-dihydroxyvitamin D3 analog with reduced hypercalcemic activity

Reviewing the Significance of Vitamin D Substitution in Monoclonal Gammopathies

Vitamin D is a steroid hormone that is essential for bone mineral metabolism and it has several other effects in the body, including anti-cancer actions. Vitamin D causes a reduction in cell growth by interrupting the cell cycle. Moreover, the active form of vitamin D, i.e., 1,25-dihydroxyvitamin D, exerts various effects via its interaction with the vitamin D receptor on the innate and adaptive immune system, which could be relevant in the onset of tumors. Multiple myeloma is a treatable but incurable malignancy characterized by the growth of clonal plasma cells in protective niches in the bone marrow. In patients affected by multiple myeloma, vitamin D deficiency is commonly correlated with an advanced stage of the disease, greater risk of progression, the development of pathological fractures, and a worse prognosis. Changes in the vitamin D receptor often contribute to the occurrence and progress of deficiencies, which can be overcome by supplementation with vitamin D or analogues. However, in spite of the findings available in the literature, there is no clear standard of care and clinical practice varies. Further research is needed to better understand how vitamin D influences outcomes in patients with monoclonal gammopathies.

Immunomodulation by vitamin D

Vitamin D exerts several immunological functions in addition to its homeostatic functions on calcium and bone metabolism. Current data show that relative vitamin D deficiency (< 75 nmol/l 25-hydroxyvitamin D) as well as acquired seasonal vitamin D deficiency (< 50 nmol/l) are frequent in Germany. As confirmed by our own data, UV exposure plays a major role for maintenance of vitamin D status, e.g., in patients with UV-triggered diseases, vitamin D deficiency is more frequent, even throughout the year. The beneficial impact of vitamin D on immune functions is highlighted by epidemiologic, genetic, and experimental evidence. In the past years, numerous publications have presented associations between vitamin D deficiency, on the one hand, and severity and prevalence of allergic asthma in children and adults, on the other hand.

Hypertrophic Scars: Are Vitamins and Inflammatory Biomarkers Related with the Pathophysiology of Wound Healing?

BACKGROUND

Hypertrophic scars are a consequence of wound healing.

OBJECTIVE

The objective of the present study is to evaluate vitamin D and inflammatory biomarker plasma levels during wound healing.

METHODS

A prospective study was performed in patients (n = 63) submitted to body contouring surgery. Blood samples were collected before (t ₀) and 5 days after surgery (t ₅). Blood cell count, protein inflammatory biomarkers, and circulating plasma levels of 25(OH)D, vitamin A and vitamin E were quantified. Six months after surgery, scars were evaluated and classified as normal or hypertrophic.

RESULTS

At the end of the study, 73% of the patients developed a normal scar (control group, n = 46) and 27% of the patients presented hypertrophic scars (HT group, n = 17). The patients in the HT group presented higher eosinophil (0.145 × 10⁹ /L vs. 0.104 × 10⁹ /L, p = 0.028) and basophil count (0.031 × 10⁹ /L vs. 0.22 × 10⁹ /L, p = 0.049) and C-reactive protein levels (6.12 mg/L vs. 2.30 mg/L, p = 0.015) in t ₀ than the patients in the control group. At t ₅, the patients in the HT group showed a decrease in neutrophil (3.144 × 10^9/L vs. 4.03 × 10⁹/L, p = 0.031) and an increase in basophil (0.024 × 10⁹/L vs. 0.015 × 10⁹/L, p = 0.005) and lymphocyte count (1.836 × 10⁹ /L vs. 1.557 × 10⁹/L; p = 0.028). Before surgery, vitamin D plasma levels were found to be decreased by almost 50% (23.52 ng/mL vs. 15.46 ng/mL, p = 0.031) in the patients who developed hypertrophic scars. Thirty-one percent of the patients submitted to bariatric surgery had more hypertrophic scars, versus 24% of the patients with no previous bariatric surgery.

CONCLUSION

There is a different systemic inflammatory profile response in the patients during the formation of hypertrophic scars. Vitamin D plasma levels are marked reduced in these patients. Considering the powerful anti-inflammatory effect of vitamin D, these findings could be related.

Inhibitors for the Vitamin D Receptor-Coregulator Interaction

The vitamin D receptor (VDR) belongs to the superfamily of nuclear receptors and is activated by the endogenous ligand 1,25-dihydroxyvitamin D3. The genomic effects mediated by VDR consist of the activation and repression of gene transcription, which includes the formation of multiprotein complexes with coregulator proteins. Coregulators bind many nuclear receptors and can be categorized according to their role as coactivators (gene activation) or corepressors (gene repression). Herein, different approaches to develop compounds that modulate the interaction between VDR and coregulators are summarized. This includes coregulator peptides that were identified by creating phage display libraries. Subsequent modification of these peptides including the introduction of a tether or nonhydrolyzable bonds resulted in the first direct VDR-coregulator inhibitors. Later, small molecules that inhibit VDR-coregulator inhibitors were identified using rational drug design and high-throughput screening. Early on, allosteric inhibition of VDR-coregulator interactions was achieved with VDR antagonists that change the conformation of VDR and modulate the interactions with coregulators. A detailed discussion of their dual agonist/antagonist effects is given as well as a summary of their biological effects in cell-based assays and in vivo studies.

Matrix metalloproteinases in inflammatory bowel disease: an update

Matrix metalloproteinases (MMPs) are known to be upregulated in inflammatory bowel disease (IBD) and other inflammatory conditions, but while their involvement is clear, their role in many settings has yet to be determined. Studies of the involvement of MMPs in IBD since 2006 have revealed an array of immune and stromal cells which release the proteases in response to inflammatory cytokines and growth factors. Through digestion of the extracellular matrix and cleavage of bioactive proteins, a huge diversity of roles have been revealed for the MMPs in IBD, where they have been shown to regulate epithelial barrier function, immune response, angiogenesis, fibrosis, and wound healing. For this reason, MMPs have been recognised as potential biomarkers for disease activity in IBD and inhibition remains a huge area of interest. This review describes new roles of MMPs in the pathophysiology of IBD and suggests future directions for the development of treatment strategies in this condition.

Role of vitamin D derivatives in intestinal tissue of patients with inflammatory bowel diseases

BACKGROUND AND AIM

The adhesion molecule expression and matrix metalloproteinases (MMPs) are proposed to be major factors for intestinal injury mediated by T cells in (IBD) and are up-regulated in intestinal mucosa of IBD patients. To investigate the effect of vitamin D derivatives on adhesion molecules and MMPs in colonic biopsies of IBD patients.

METHODS

Biopsies from inflamed and non-inflamed tract of terminal ileum and colon and PBMC from the same IBD patients were cultured with or without vitamin D derivatives. MMP activity and adhesion molecule levels were determined.

RESULTS

1,25(OH)2D3 and ZK 191784 significantly decrease ICAM-1 protein levels in the biopsies obtained only from the inflamed region of intestine of UC patients, while MAdCAM-1 levels decrease in the presence of 1,25(OH)2D3 in the non-inflamed region, and, in the presence of ZK, in the inflamed one. In CD patients 1,25(OH)2D3 and ZK decrease ICAM-1 and MAdCAM-1 in the biopsies obtained from the non-inflamed and inflamed regions, with the exception of ICAM-1 in the inflamed region in the presence of 1,25(OH)2D3. The expression of MMP-9, MMP-2, and MMP-3 decreases in the presence of vitamin D derivatives in UC and CD with the exception of 1,25(OH)2D3 that does not affect the levels of MMP-9 and MMP-2 in CD. Vitamin D derivatives always affect MMP-9, MMP-2 and ICAM-1 in PBMC of UC and CD patients.

CONCLUSIONS

Based on the increased expression of ICAM-1, MAdCAM-1 and MMP-2,-9,-3 in IBD, our study suggests that vitamin D derivatives may be effective in the management of these diseases.

1α,25-dihydroxycholecalciferol induces nitric oxide production in cultured endothelial cells

BACKGROUND

Recently, 1α,25-dihydroxycholecalciferol (vitD) has received increasing interest for its effects on many tissues and organs other than bone. A number of experimental studies have shown that vitD may have an important role in modifying risk for cardiovascular disease.

AIMS

This study was planned to test the effects of vitD on endothelial nitric oxide (NO) production and to study the intracellular pathways leading to NO release.

METHODS

In human umbilical vein endothelial cells (HUVEC) cultures the effects of vitD on NO production and p38, Akt, ERK and eNOS phosphorylations were examined in absence or in presence of the NO synthase inhibitor L-NAME and protein kinases specific inhibitors SB203580, wortmannin and UO126.

RESULTS

VitD caused a concentration-dependent increase in NO production. The maximum effect was observed at a concentration of 1 nM and the optimal time of stimulation was 1 min. Effects induced by vitD were abolished by L-NAME and by pre-treatment with protein kinases inhibitors. To verify the effective involvement of vitD receptor (VDR) in the action mechanism of vitD, experiments were repeated in presence of the specific VDR ligands ZK159222 and ZK191784.

CONCLUSIONS

The results of this study demonstrate that vitD can induce a significant increase in endothelial NO production. VitD interaction with VDR caused the phosphorylation of p38, AKT and ERK leading to eNOS activation.

Targeting the vitamin D receptor inhibits the B cell-dependent allergic immune response

BACKGROUND

1α,25-dihydroxyvitamin D(3) (calcitriol), the biologically active form of vitamin D, is an immunomodulatory hormone, e.g. it inhibits IgE synthesis in B cells. As its clinical application is limited by hypercalcemia, synthetic vitamin D receptor (VDR) agonists that mediate immunomodulatory activities without adverse hypercalcemic effects are of great interest. This study aimed to investigate the impact of a low-calcemic VDR agonist on the IgE immune response in vitro and in vivo.

METHODS

Human peripheral B cells were cultured under IgE inducing conditions in the presence of VDR ligands. B cells were analyzed by quantitative RT-PCR, enzyme-linked immunosorbent assays, enzyme-linked immunospot technique, and flow cytometry. BALB/c mice were sensitized with ovalbumin (OVA)/alum followed by the therapeutic VDR agonist treatment and analyzed regarding the humoral immunoglobulin profile.

RESULTS

The natural VDR ligand calcitriol, but also a low-calcemic VDR agonist, profoundly suppressed IgE production by human peripheral B cells by 63.9 ± 5.9%. The potential mechanisms involved are the reduction of the transcript for activation-induced deaminase (AID) and the reduction of IgE immunoglobulin-secreting cells by 68.1 ± 12.7%. By using an in vivo approach, we finally demonstrate that the humoral IgE response in a type I allergy mouse model was impaired by the VDR agonist.

CONCLUSION

Our results show that targeting the VDR modulates the humoral immune response including IgE. Whether it might be useful for clinical applications has to be determined in appropriate clinical trials.

Inhibition of the IL-2-inducible tyrosine kinase (Itk) activity: a new concept for the therapy of inflammatory skin diseases

T-cell-mediated processes play an essential role in the pathogenesis of several inflammatory skin diseases such as atopic dermatitis, allergic contact dermatitis and psoriasis. The aim of this study was to investigate the role of the IL-2-inducible tyrosine kinase (Itk), an enzyme acting downstream of the T-cell receptor (TCR), in T-cell-dependent skin inflammation using three approaches. Itk knockout mice display significantly reduced inflammatory symptoms in mouse models of acute and subacute contact hypersensitivity (CHS) reactions. Systemic administration of a novel small molecule Itk inhibitor, Compound 44, created by chemical optimization of an initial high-throughput screening hit, inhibited Itk's activity with an IC50 in the nanomolar range. Compound 44 substantially reduced proinflammatory immune responses in vitro and in vivo after systemic administration in two acute CHS models. In addition, our data reveal that human Itk, comparable to its murine homologue, is expressed mainly in T cells and is increased in lesional skin from patients with atopic dermatitis and allergic contact dermatitis. Finally, silencing of Itk by RNA interference in primary human T cells efficiently blocks TCR-induced lymphokine secretion. In conclusion, Itk represents an interesting new target for the therapy of T-cell-mediated inflammatory skin diseases.

Control of cutaneous antimicrobial peptides by vitamin D3

Constant exposure to a wide variety of microbial pathogens represents a major challenge for our skin. Antimicrobial peptides (AMPs) are mediators of cutaneous innate immunity and protect primarily against microbial infections. Cathelicidins were among the first AMPs identified in human skin and recent evidence suggests that they exert a dual role in innate immune defense: At first, due to their antimicrobial activity they kill pathogens directly. In addition, these peptides initiate a potent host response to infection resulting in cytokine release, inflammation and a cellular response. Disturbed cathelicidin expression and function was observed in several common inflammatory skin diseases, such as psoriasis where cathelicidin peptide converts inert self-DNA and self-RNA into an autoimmune stimulus. In atopic dermatitis decreased levels of cathelicidin facilitating microbial superinfections have been discussed. Furthermore, abnormally processed cathelicidin peptides induce inflammation and a vascular response in rosacea. Until recently, the molecular mechanisms underlying cathelicidin regulation were unknown. Recently, the vitamin D3 pathway was identified as the major regulator of cathelicidin expression. Consequently, vitamin D3 entered the spotlight as an immune modulator with impact on both innate and adaptive immunity. Therapies targeting vitamin D3 signaling may provide new approaches for infectious and inflammatory skin diseases by affecting both innate and adaptive immune functions.

Vitamin D controls T cell antigen receptor signaling and activation of human T cells

Phospholipase C (PLC) isozymes are key signaling proteins downstream of many extracellular stimuli. Here we show that naive human T cells had very low expression of PLC-gamma1 and that this correlated with low T cell antigen receptor (TCR) responsiveness in naive T cells. However, TCR triggering led to an upregulation of approximately 75-fold in PLC-gamma1 expression, which correlated with greater TCR responsiveness. Induction of PLC-gamma1 was dependent on vitamin D and expression of the vitamin D receptor (VDR). Naive T cells did not express VDR, but VDR expression was induced by TCR signaling via the alternative mitogen-activated protein kinase p38 pathway. Thus, initial TCR signaling via p38 leads to successive induction of VDR and PLC-gamma1, which are required for subsequent classical TCR signaling and T cell activation.

The role of mitogen-activated protein kinase-activated protein kinase 2 in the p38/TNF-alpha pathway of systemic and cutaneous inflammation

Mitogen-activated protein kinase-activated protein kinase 2 (MK2) is a downstream molecule of p38, involved in the production of TNF-alpha, a key cytokine, and an established drug target for many inflammatory diseases. We investigated the role of MK2 in skin inflammation to determine its drug target potential. MK2 deficiency significantly decreased plasma TNF-alpha levels after systemic endotoxin application. Deficient mice showed decreased skin edema formation in chronic 2-O-tetradecanoylphorbol-13-acetate (TPA)-induced irritative dermatitis and in subacute 2,4-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity. Surprisingly, MK2 deficiency did not inhibit edema formation in subacute 2,4-dinitrochlorobenzene (DNCB)-induced contact allergy and even increased TNF-alpha and IL-1beta levels as well as granulocyte infiltration in diseased ears. Ear inflammation in this model, however, was inhibited by TNF-alpha neutralization as it was in the subacute DNFB model. MK2 deficiency also did not show anti-inflammatory effects in acute DNFB-induced contact hypersensitivity, whereas the p38 inhibitor, SB203580, ameliorated skin inflammation supporting a pathophysiological role of p38. When evaluating possible mechanisms, we found that TNF-alpha production in MK2-deficient spleen cells was strongly diminished after TLR stimulation but less affected after T-cell receptor stimulation. Our data suggest that MK2, in contrast to its downstream effector molecule, TNF-alpha, has a rather elusive role in T-cell-dependent cutaneous inflammation.

Vitamin D analogs differentially control antimicrobial peptide/"alarmin" expression in psoriasis

Antimicrobial peptides (AMPs) are strongly expressed in lesional skin in psoriasis and play an important role as proinflammatory "alarmins" in this chronic skin disease. Vitamin D analogs like calcipotriol have antipsoriatic effects and might mediate this effect by changing AMP expression. In this study, keratinocytes in lesional psoriatic plaques showed decreased expression of the AMPs beta-defensin (HBD) 2 and HBD3 after topical treatment with calcipotriol. At the same time, calcipotriol normalized the proinflammatory cytokine milieu and decreased interleukin (IL)-17A, IL-17F and IL-8 transcript abundance in lesional psoriatic skin. In contrast, cathelicidin antimicrobial peptide expression was increased by calcipotriol while psoriasin expression remained unchanged. In cultured human epidermal keratinocytes the effect of different vitamin D analogs on the expression of AMPs was further analyzed. All vitamin D analogs tested blocked IL-17A induced HBD2 expression by increasing IkappaB-alpha protein and inhibition of NF-kappaB signaling. At the same time vitamin D analogs induced cathelicidin through activation of the vitamin D receptor and MEK/ERK signaling. These studies suggest that vitamin D analogs differentially alter AMP expression in lesional psoriatic skin and cultured keratinocytes. Balancing AMP "alarmin" expression might be a novel goal in treatment of chronic inflammatory skin diseases.

Characterization of ZK 245186, a novel, selective glucocorticoid receptor agonist for the topical treatment of inflammatory skin diseases

BACKGROUND AND PURPOSE

Glucocorticoids are highly effective in the therapy of inflammatory diseases. Their value, however, is limited by side effects. The discovery of the molecular mechanisms of the glucocorticoid receptor and the recognition that activation and repression of gene expression could be addressed separately opened the possibility of achieving improved safety profiles by the identification of ligands that predominantly induce repression. Here we report on ZK 245186, a novel, non-steroidal, low-molecular-weight, glucocorticoid receptor-selective agonist for the topical treatment of inflammatory dermatoses.

EXPERIMENTAL APPROACH

Pharmacological properties of ZK 245186 and reference compounds were studied in terms of their potential anti-inflammatory and side effects in functional bioassays in vitro and in rodent models in vivo.

KEY RESULTS

Anti-inflammatory activity of ZK 245186 was demonstrated in in vitro assays for inhibition of cytokine secretion and T cell proliferation. In vivo, using irritant contact dermatitis and T cell-mediated contact allergy models in mice and rats, ZK 245186 showed anti-inflammatory efficacy after topical application similar to the classical glucocorticoids, mometasone furoate and methylprednisolone aceponate. ZK 245186, however, exhibits a better safety profile with regard to growth inhibition and induction of skin atrophy after long-term topical application, thymocyte apoptosis, hyperglycaemia and hepatic tyrosine aminotransferase activity.

CONCLUSIONS AND IMPLICATIONS

ZK 245186 is a potent anti-inflammatory compound with a lower potential for side effects, compared with classical glucocorticoids. It represents a promising drug candidate and is currently in clinical trials.

Osteopontin: a fibrosis-related marker molecule in cardiac remodeling of enterovirus myocarditis in the susceptible host

The characteristics of dilated cardiomyopathy (DCM) resulting from chronic viral myocarditis are remodeling processes of the extracellular matrix. Based on our findings of enhanced osteopontin (OPN) expression in inflamed human hearts, we further investigated in the murine model of acute and chronic coxsackievirus (CV)B3-myocarditis the role of OPN regarding its involvement in resolution of cardiac virus infection and fibrosis. In hearts of A.BY/SnJ mice susceptible to chronic CVB3-myocarditis, a pronounced increase of OPN expression levels was detected by microarray analysis and quantitative RT-PCR during acute stages of myocarditis. Combined immunohistochemistry and in situ hybridization identified infiltrating macrophages as main OPN producers. In contrast to resistant C57BL/6 and OPN gene-deficient mice, transcription levels of matrix metalloproteinase-3, TIMP1 (tissue inhibitor of metalloproteinases-1), uPA (urokinase-type plasminogen activator), and transforming growth factor beta1 were elevated in susceptible mice, and as a consequence, procollagen-1alpha mRNA expression and fibrosis was considerably enhanced. Treatment of infected susceptible mice with the vitamin D analog ZK 191784 led to decreased myocardial expression levels of OPN, metalloproteinase-3, TIMP1, uPA, and procollagen-1alpha and subsequently to reduced fibrosis. Concurrently, the fibrosis-relevant signaling molecules pERK (phosphorylated extracellular signal-regulated kinase) and pAkt (phosphorylated Akt), increased in A.BY/SnJ mice, were diminished in ZK 191784-treated mice. Here, we show that high expression levels of OPN in acute myocarditis are associated with consecutive development of extensive fibrosis that can be reduced by treatment with a vitamin D analog. Thus, OPN may serve as a diagnostic tool as well as a potential therapeutic target to limit cardiac remodeling in chronic myocarditis.

Immunomodulation by a novel, dissociated Vitamin D analogue

The biologically active metabolite of vitamin D3, 1alpha,25-dihydroxyvitamin D3, has potent immunomodulatory activity; however, its clinical use is limited because of its hypercalcaemic activity in anti-inflammatory active doses. Here, we present ZK203278, a novel, structurally different vitamin D3 analogue with profound immunomodulatory activities. It potently inhibits lymphocyte proliferation in the mixed lymphocyte reaction, and release of cytokines that are central in inflammation, such as TNFalpha and IL-12 in the low nanomolar range. Similarly, expression of cell-surface molecules involved in cell adhesion and antigen presentation, e.g. to T cells, is down-regulated on human monocytes by low nanomolar concentrations of ZK203278. Potent anti-inflammatory activity has been demonstrated also in vivo in rodent disease models. ZK203278 inhibited allergic contact dermatitis in rodents after oral administration in doses approximately two orders of magnitude below the hypercalcaemic threshold dose. Moreover, ZK203278 significantly prolonged skin allograft survival in rats in well-tolerated doses. Altogether ZK203278, in contrast to 1alpha,25-dihydroxyvitamin D3, exerts considerable immunomodulatory activity at non-hypercalcaemic dosages and may have therapeutic potential for immune disorders or transplant rejection.

The complex role of vitamin D in autoimmune diseases

Vitamin D, besides having well-known control functions of calcium and phosphorus metabolism, bone formation and mineralization, also has a role in the maintenance of immune-homeostasis. The immune-regulatory role of vitamin D affects both the innate and adaptive immune system contributing to the immune-tolerance of self-structures. Impaired vitamin D supply/regulation, amongst other factors, leads to the development of autoimmune processes in animal models of various autoimmune diseases. The administration of vitamin D in these animals leads to improvement of immune-mediated symptoms. Moreover, in human autoimmune diseases, such as multiple sclerosis, or rheumatoid arthritis the pathogenic role of vitamin D has been described. The review aims at describing the complex immune-regulatory role of vitamin D from the cellular level through autoimmune animal models and depicting the known contribution of vitamin D in the pathogenesis of human autoimmune diseases.

Vitamin D derivatives induce apoptosis and downregulate ICAM-1 levels in peripheral blood mononuclear cells of inflammatory bowel disease patients

BACKGROUND

Lymphocytes are crucial in the pathogenesis of inflammatory bowel disease (IBD) and are an important target for drug development. Our aim was to verify whether 2 vitamin D derivatives, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and EB 1089, could induce cell apoptosis and affect cell-cell interaction by regulating adhesion molecule levels.

METHODS

Peripheral blood mononuclear cell (PBMC) proliferation was studied by [3H]thymidine incorporation and apoptosis was determined using an enzyme-linked immunosorbent assay (ELISA) kit. (Poly(ADP-ribose)polymerase (PARP) cleavage, caspase-3, and ICAM-1 protein levels were determined by Western blot analysis.

RESULTS

Our results indicate that 1,25(OH)2D3 or EB 1089 or anti-TNF-alpha (infliximab) induce apoptosis in PBMC obtained from healthy subjects. In IBD patients apoptosis is induced by vitamin D derivatives and by anti-TNF-alpha only in CD patients. Caspase-3 activation and PARP cleavage are registered when PBMC were treated with vitamin D derivatives. ICAM-1 levels remarkably increase when PBMC was incubated with lipopolysaccharide (LPS) or TNF-alpha. The treatment with the vitamin D derivatives, alone or in combination with LPS or TNF-alpha, significantly decreases ICAM-1 levels both in healthy subjects and IBD patients. In HUVEC cocultured with PBMC, previously incubated with LPS or TNF-alpha associated with 1,25(OH)2D3, ICAM-1 levels decrease both in healthy subjects and IBD patients.

CONCLUSIONS

1,25(OH)2D3 and EB 1089 inhibit PBMC proliferation, induce apoptosis in PBMC of healthy subjects and IBD patients, and affect ICAM-1 expression on PBMC and on HUVEC cocultured with PBMC, suggesting that the ICAM-1 downregulation could provide a new target for controlling the recruitment of leukocytes at the sites of inflammation in IBD.

Calcitriol analog ZK191784 ameliorates acute and chronic dextran sodium sulfate-induced colitis by modulation of intestinal dendritic cell numbers and phenotype

AIM: To investigate the effects of ZK1916784, a low calcemic analog of calcitriol on intestinal inflammation.

METHODS: Acute and chronic colitis was induced by dextran sodium sulfate (DSS) according to standard procedures. Mice were treated intraperitoneally with ZK1916784 or placebo and colonic inflammation was evaluated. Cytokine production by mesenterial lymph node (MLN) cells was measured by ELISA. Immunohistochemistry was performed to detect intestinal dendritic cells (DCs) within the colonic tissue, and the effect of the calcitriol analog on DCs was investigated.

RESULTS: Treatment with ZK191784 resulted in significant amelioration of disease with a reduced histological score in acute and chronic intestinal inflammation. In animals with acute DSS colitis, down-regulation of colonic inflammation was associated with a dramatic reduction in the secretion of the proinflammatory cytokine interferon (IFN)-γ and a significant increase in intereleukin (IL)-10 by MLN cells. Similarly, in chronic colitis, IL-10 expression in colonic tissue increased 1.4-fold when mice were treated with ZK191784, whereas expression of the Th1-specific transcription factor T-beta decreased by 81.6%. Lower numbers of infiltrating activated CD11c⁺ DCs were found in the colon in ZK191784-treated mice with acute DSS colitis, and secretion of proinflammatory cytokines by primary mucosal DCs was inhibited in the presence of the calcitriol analog.

CONCLUSION: The calcitriol analog ZK191784 demonstrated significant anti-inflammatory properties in experimental colitis that were at least partially mediated by the immunosuppressive effects of the derivate on mucosal DCs.

Differential regulation of apolipoprotein A-I gene expression by vitamin D receptor modulators

We have found that 1,25-dihydroxy-cholecalciferol (1,25-(OH)(2)D(3)) represses the expression of the apolipoprotein A-I (apo A-I) gene in hepatocytes. In this manuscript we examined the effects of the vitamin D receptor (VDR) modulators EB1089 (EB) and ZK191784 (ZK) on expression of the apo A-I gene in liver (HepG2) and in intestinal (Caco-2) cells. In HepG2 cells, EB and ZK induced apo A-I secretion and gene promoter activity in a dose-dependent manner. This induction did not require the VDR since antisense-mediated inhibition of VDR had no appreciable effect on apo A-I promoter activity in cells treated with EB or ZK. Although repression of apo A-I gene expression by 1,25-(OH)(2)D(3) in hepatocytes required nuclear receptor binding to site A in the promoter, this cis-element was insufficient for induction of apo-AI by EB and ZK. In Caco-2 cells, treatment with 1,25-(OH)(2)D(3) had no effect on apo A-I protein secretion or promoter activity while EB induced and ZK inhibited apo A-I gene expression. Gel shift assays showed that none of the treatments resulted in a change in site A binding activity. These results indicate that VDR modulators in hepatocytes and intestinal cells differentially regulate expression of the apo A-I gene.

The new low calcemic vitamin D analog 22-ene-25-oxa-vitamin D prominently ameliorates T helper cell type 1-mediated colitis in mice

In addition to its well defined role as a key regulator of calcium and bone metabolism, 1,25-dihydroxyvitamin D(3) (calcitriol) has been established as a potent modulator of immune cell function. Still, because of the hypercalcemic toxicity occurring after systemic application of the parent compound, its clinical application as an immunosuppressant has been hampered. Recently, we described 22-ene-25-oxa-vitamin D (ZK156979) as a representative of a novel class of low calcemic vitamin D analogs with well preserved immunosuppressive activity in vitro. Here, in vivo colitis was induced by applying a rectal enema of 2,4,6-trinitrobenzene sulfonic acid (TNBS) to male BALB/c mice, and calcitriol (0.2 microg/kg) or ZK156979 (0.1-2.0 microg/kg) was given i.p. from days 0 to 3 or 3 to 5. Body mass and clinical activity score of colitis were recorded daily. Colon tissue was analyzed macroscopically and microscopically, myeloperoxidase activity and cytokine levels [tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-10, and IL-4] were determined by enzyme-linked immunosorbent assay, and T-box transcription factor (T-bet) expression was determined by immunoblot analysis. We found that treatment with ZK156979 clearly reduced the severity of TNBS-induced colitis without exhibiting calcemic effects. Both early and late treatment abrogated body weight loss, diarrhea, and macroscopic intestinal inflammation with a potency comparable with that of calcitriol. The therapeutic effect of ZK156979 was accompanied by a down-regulation of myeloperoxidase activity, TNF-alpha, IFN-gamma, and T-bet expression decreased, whereas local tissue IL-10 and IL-4 protein levels increased. To conclude, our data provide the first clear evidence that ZK156979 exhibits a beneficial prophylactic as well as therapeutic profile in T helper cell type 1-like experimental colitis, offering new therapeutic options for the treatment of human inflammatory bowel diseases.

Interaction among vitamin D(3) analogue KH 1060, TNF-alpha, and vitamin D receptor protein in peripheral blood mononuclear cells of inflammatory bowel disease patients

BACKGROUND

The active form of vitamin D, 1,25(OH)(2)D(3), exerts important effects on proliferation and differentiation of many cell types, and immunoregulatory activities in particular on T cell-mediated immunity.

AIM

The aim of this study was to investigate whether KH 1060, a vitamin D analogue, could decrease tumor necrosis factor-alpha (TNF-alpha) levels in patients with inflammatory bowel disease (IBD).

METHODS

PBMC proliferation was determined by [(3)H]thymidine incorporation. TNF-alpha levels were measured by ELISA kit; VDR, Bcl-2 and Bax protein levels with Western blot analysis.

RESULTS

KH 1060 inhibited PBMC proliferation and decreased TNF-alpha levels in IBD patients and this effect was synergistic with anti-TNF-alpha. VDR protein levels were significantly increased by PBMC treatment with KH 1060 or anti-TNF-alpha or their combination in ulcerative colitis (UC) patients, and decreased in Crohn's disease (CD) patients, treating the cells with KH 1060. In UC patients an increase in Bcl-2 and Bax levels was observed incubating, PBMC with KH 1060 or anti-TNF-alpha or their combination. In CD patients a slight decrease in Bcl-2 levels was registered when anti-TNF alone or in association with KH 1060 was used. Bax protein levels were slightly increased in the presence of KH 1060 alone or in combination with anti-TNF.

CONCLUSION

This study shows that KH 1060 acts as an immunomodulator on PBMC, acting as TNF-alpha inhibitor. This finding provides strong evidence that vitamin D status could be an important regulator of immunity IBD.

22-ene-25-oxa-vitamin D: a new vitamin D analogue with profound immunosuppressive capacities

BACKGROUND

The biologic role of 1,25-dihydroxyvitamin D(3), such as anti-inflammatory functions, reduction of cytokine production by T cells and immunoglobulin production by B cells, is well established. However, its clinical use as an immunosuppressive agent is limited because of the hypercalcemic toxicity occurring after systemic application. The purpose of this study was to investigate the immunmodulatory effects of 22-ene-25-oxa-vitamin D (ZK156979), a novel low calcemic vitamin D analogue.

MATERIALS AND METHODS

Human peripheral blood mononuclear cells (PBMCs) from healthy donors were isolated using the Ficoll Hypaque technique, cultured for 24 h and treated with different concentrations of ZK156979 ranging from 10(-5) to 10(-10) mol L(-1) compared with 1,25-dihydroxyvitamin D(3)[10(-5)-10(-10) mol L(-1)] following phytohaemagglutinin (PHA) stimulation. Interferon gamma (IFNgamma), tumour necrosis factor alpha (TNFalpha), interleukin 1 beta (IL-1beta), interleukin 10 (IL-10) and interleukin 4 (IL-4) secretion in supernatants were measured by ELISA.

RESULTS

ZK156979 inhibited the PHA-induced Th1-response (IFNgamma and TNFalpha levels) and the macrophage-product IL-1beta in a concentration-dependent manner (10(-10)-10(-5) mol L(-1)) with the efficiency on cytokine expression compared with 1,25-dihydroxyvitamin D(3) being slightly reduced. In contrast, ZK156979 and 1,25-dihydroxyvitamin D(3) both affected the Th2 response, leading to significantly increased IL-10- and IL-4 secretion.

CONCLUSIONS

ZK156979 is a member of novel vitamin D analogues revealing prominent immunomodulatory and suppressive characteristics with distinctive inhibition of Th1-cytokines whereas the Th2 compartment is augmented, thus providing a considerable therapeutic potential in T-cell -mediated diseases.

The Vitamin D3 Pathway in Human Skin and its Role for Regulation of Biological Processes

The skin is the only tissue yet known in which the complete ultraviolet-B (UV-B)-induced pathway from 7-dehydrocholesterol to hormonally active calcitriol (1alpha,25-dihydroxyvitamin D(3)) occurs under physiological conditions. Epidermal synthesis of calcitriol could be of fundamental relevance because calcitriol regulates important cellular functions in keratinocytes and immunocompetent cells. Because of their antiproliferative and prodifferentiating effects, calcitriol and other vitamin D analogs are highly efficient in the treatment of psoriasis vulgaris. The known antipsoriatic effect of UV-B light could, at least in part, be mediated via UV-B-induced synthesis of calcitriol. In addition, mounting evidence indicates that cutaneous vitamin D(3) synthesis is of high importance for the prevention of a broad variety of diseases, including various malignancies. New but controversially discussed sun-protection guidelines were established for the prevention of internal cancers. A better understanding of the metabolism of vitamin D in the skin opens new perspectives for therapeutic applications of vitamin D analogs.

Vitamin D and skin: new aspects for dermatology

It has been shown that epidermal keratinocytes have the capacity for the UVB-induced photochemical conversion of 7-dehydrocholesterol to vitamin D3, and also for the enzymatically controlled hydroxylation of the photolysis product. This metabolic loop results in the formation of the biologically active final product 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3, calcitriol). The epidermal synthesis of calcitriol is of fundamental relevance because calcitriol regulates important cellular functions in keratinocytes and immunocompetent cells. Because of their anti-proliferative and prodifferentiating effects, calcitriol and other vitamin D analogs are highly efficient in the treatment of psoriasis vulgaris. In addition, the known therapeutic effect of UVB light therapy in the treatment of psoriasis may, at least in part, be mediated via UVB-induced synthesis of calcitriol. Increasing evidence now indicates that cutaneous vitamin D synthesis is of great importance for the prevention of a broad variety of diseases, including various malignancies. It has been postulated that cancer mortality could be reduced via careful UV exposure or, more safely, via oral substitution with vitamin D. These new findings must be taken into account when establishing new sun protection guidelines for the prevention of skin cancer. In addition, better understanding of the metabolism of vitamin D in the skin has opened up new perspectives for the therapeutic application of vitamin D analogs, e.g. in inflammatory skin diseases.

[Topical treatment of psoriasis: a systematic update]

Classical topical treatment regimens in psoriasis including dithranol and corticosteroids are widely used and have been supplemented in recent years by topical vitamin D preparations, by vitamin D analogues and topical retinoids. The combination of these preparations with each other, with UV light or with systemic drugs often lead to improved effectiveness and tolerability when compared with the respective monotherapy. In private offices, the combination of calcipotriol with various corticosteroids is very commonly prescribed for patients with mild to moderate psoriasis. This combination can be sequentially applied twice daily or--in a newly introduced fixed preparation--once daily. In severe psoriasis requiring systemic treatment a concomitant effective topical treatment regimen can greatly improve the overall longtime management in affected patients.