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Vitamin D and the immune system: Do we need more?
S22
Abstracts
tion of oxidative response genes may be related to disease mechanism in some PDB patients. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. doi:10.1016/j.bone.2012.02.048
IS27 NF-κB signaling and bone resorption Y. Abu-Amer⁎ Orthopedics and Cell Biology & Physiology, Washington University School of Medicine, Saint Louis, MO, USA Learning Outcome 1: Overview of NF-kB signal transduction classical and alternative pathways. Learning Outcome 2: Overview of the role of NF-kB signaling in osteoclastogenesis and bone metabolism. Learning Outcome 3: The role of IKK2 in osteoclastogenesis and skeletal development and its pathologic implications. Abstract: The transcription factor NF-kB family consists of the upstream kinase IKK2 and NEMO that direct activation of classical (p50/p65) and IKK1 that regulates activation of the alternative (p52/RelB) pathway. It is well-accepted that NF-kB is crucial for bone metabolism in health and disease and is central mediator of inflammatory responses. In the bone, whereas combined deletion of P50/P52 subunits led to complete arrest of osteoclast differentiation and osteopetrosis, deletion of other NF-kB subunits and proximal kinases affected osteoclasts and bone development to varying degrees. We have investigated the role of IKK2 in the myeloid compartment and found that deletion of this kinase affects osteoclast differentiation and survival. Further molecular analysis of the role of IKK2 in osteoclastogenesis led to the surprising discovery that constitutively active IKK2 (IKK2SSEE), in which serine residues were substituted with glutamic acid, was sufficient to induce osteoclastogenesis. In this regard, introduction of IKK2SSEE but not WT-IKK2 into monocytes stimulates differentiation of bona-fide osteoclasts in the absence of RANK Ligand. This phenomenon is independent of upstream signals, since IKK2SSEE induced the development of bone-resorbing osteoclasts from RANK-, IKK1-, and NEMO-deficient monocytes. Inflammatory autocrine signaling by TNFα and IL-1 was dispensable for the spontaneous osteoclastogenesis driven by IKK2SSEE. More importantly, adenoviral gene transfer of IKK2SSEE induced osteoclasts and osteolysis in calvariae and knees of mice. To determine the physiological significance of this finding, we examined its role in vivo through expression of constitutively active IKK2 in a tissue-specific manner. Specifically, we employed the R26StopIkk2SSEE mice in which a cDNA encoding IKK2 containing two serine to glutamate substitutions in the activation loop of the kinase domain, preceded by a loxP-flanked STOP cassette, into the ubiquitously expressed ROSA26 locus. We crossed mice carrying this allele with the CD11b-cre mice in order to express IKK2SSEE exclusively in myeloid cells, inclusive of osteoclast progenitors. Phenotypic assessment revealed that expression of IKK2SSEE in the myeloid compartment induces significant bone loss in vivo. This observation was supported by dramatic increase in the number and size of osteoclasts in trabecular regions, elevated levels of circulating TRACP-5b, and reduced bone volume. Mechanistically, we surprisingly observed that IKK2SSEE induced high expression of not only p65 but p52 and RelB, the latter two molecules are considered exclusive members of the alternative NF-kB pathway. Even more surprisingly, RelB and P52 are both required to mediate the osteoclastogenic effect of IKK2SSEE and co-expression of these two proteins is sufficient to recapitulate osteoclastogenesis in the absence of RANKL or IKK2SSEE. In summary, molecular activation of IKK2 may play a role in conditions of pathologic bone destruction which maybe refractory to therapeutic interventions targeting the proximal RANKL signal. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared.
doi:10.1016/j.bone.2012.02.049
IS28 NF-κB signaling and bone formation C.-Y. Wang⁎ University of California, Los Angeles, Los Angeles, USA Learning Outcome 1: 1) NF-κB plays an important role in inhibition of bone formation in inflammatory and metabolic bone diseases. Learning Outcome 2: NF-κB regulates osteoblast functions. Learning Outcome 3: NF-κB regulates the differentiation of mesenchymal stem cells. Abstract: NF-κB is a family of transcription factors involved in the immune system and many other tissues. Although it has been well studied in osteoclasts, the role of NF-
κB in osteoblasts and bone formation is less defined. In this workshop, I will discuss how NF-κB activation affects osteoblast function and bone formation in osteoporosis and inflammatory bone diseases. In particular, I describe experiments using IKK inhibitors in osteoblasts that showed that a reduction of NF-κB activity in osteoblasts results in an increase in bone formation via an increase in JNK activity, which regulates Fra-1 expression. I will show our recent work on regulation of mesenchymal stem cell differentiation by NF-κB. Considering the well-established role of NF-κB in inflammation and infection, our results suggest that targeting NF-κB may have dual benefits in enhancing bone formation and repair and inhibiting inflammation. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. doi:10.1016/j.bone.2012.02.050
IS29 Vitamin D and the immune system: Do we need more? C. Mathieu⁎ Katholieke Universiteit Leuven, Leuven, Belgium Learning Outcome 1: Basic understanding of the immune system. Learning Outcome 2: Understanding how vitamin D can influence the immune system. Learning Outcome 3: Understanding the limitations with present literature. Abstract: In recent years great attention has been given to the pleiotropic effect of vitamin D, a vitamin well known from its role in bone and calcium homeostasis. Also in the immune system, modulating effects by vitamin D have been described. Receptors for vitamin D are present in cells throughout the immune system and a central role for the antigen presenting dendritic cell and the macrophage in the effect of vitamin D in the immune system is described. The latter cells not only carry receptors, but also contain the machinery to produce themselves the activated form of vitamin D, 1,25dihydroxyvitamin D3. Finally also other immune cells, like T lymphocytes carry receptors for vitamin D. These data suggest a physiological role for vitamin D as an immune modulator. Epidemiology confirms this possible role, indicating correlations between vitamin D deficiency and adverse immune outcomes (more infections, more autoimmune diseases). Animal models confirm this detrimental effect of vitamin D deficiency on immune function and even point towards the possibility of exploiting these effects of vitamin D in a pharmacological way, using analogues of vitamin D as immune modulators or treating immune cells ex vivo. The place for vitamin D in a healthy immune system for clinicians will be discussed. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared.
doi:10.1016/j.bone.2012.02.051
IS30 Vitamin D and cardiovascular disease M.D. Witham⁎ Ageing and Health, University of Dundee, Dundee, UK Learning Outcome 1: The mechanisms by which vitamin D may affect vascular health. Learning Outcome 2: Current observational and interventional evidence regarding vitamin D and vascular health. Learning Outcome 3: The limitations of existing evidence and areas where further research is needed. Abstract: Low circulating 25-hydroxyvitamin D (25OHD) levels are associated with a wide range of vascular disease states, including hypertension, diabetes mellitus, stroke, myocardial infarction and heart failure. These associations have been confirmed by large cross-sectional studies, and evidence from longitudinal cohort studies suggests that low 25OHD levels are an independent predictor of future cardiovascular events and incident hypertension. A range of biological mechanisms exists that might explain these findings, including effects on the renin–angiotensin system, alterations in calcium handling, suppression of pro-inflammatory cytokines involved in atherosclerosis and effects on other vasculotoxic mediators, including parathyroid hormone. Observational data in this area is dogged by confounding and reverse causality however; thus evidence from intervention studies is necessary to elucidate whether low vitamin D levels are a cause of cardiovascular disease. Current evidence suggests weak effects on blood pressure reduction in selected groups, beneficial effects on markers of vascular health in selected groups of patients, but little effect on metabolic control in patients with diabetes. The optimum dose, duration of therapy and target populations for intervention with vitamin D to reduce cardiovascular disease are not known, and large-scale trials of vitamin D designed specifically to reduce cardiovascular events have not been conducted to date. Metaanalyses from osteoporosis trials to date have not found evidence for significant reductions in cardiovascular events, but are dogged by cointervention with calcium.
Abstracts
tion of oxidative response genes may be related to disease mechanism in some PDB patients. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. doi:10.1016/j.bone.2012.02.048
IS27 NF-κB signaling and bone resorption Y. Abu-Amer⁎ Orthopedics and Cell Biology & Physiology, Washington University School of Medicine, Saint Louis, MO, USA Learning Outcome 1: Overview of NF-kB signal transduction classical and alternative pathways. Learning Outcome 2: Overview of the role of NF-kB signaling in osteoclastogenesis and bone metabolism. Learning Outcome 3: The role of IKK2 in osteoclastogenesis and skeletal development and its pathologic implications. Abstract: The transcription factor NF-kB family consists of the upstream kinase IKK2 and NEMO that direct activation of classical (p50/p65) and IKK1 that regulates activation of the alternative (p52/RelB) pathway. It is well-accepted that NF-kB is crucial for bone metabolism in health and disease and is central mediator of inflammatory responses. In the bone, whereas combined deletion of P50/P52 subunits led to complete arrest of osteoclast differentiation and osteopetrosis, deletion of other NF-kB subunits and proximal kinases affected osteoclasts and bone development to varying degrees. We have investigated the role of IKK2 in the myeloid compartment and found that deletion of this kinase affects osteoclast differentiation and survival. Further molecular analysis of the role of IKK2 in osteoclastogenesis led to the surprising discovery that constitutively active IKK2 (IKK2SSEE), in which serine residues were substituted with glutamic acid, was sufficient to induce osteoclastogenesis. In this regard, introduction of IKK2SSEE but not WT-IKK2 into monocytes stimulates differentiation of bona-fide osteoclasts in the absence of RANK Ligand. This phenomenon is independent of upstream signals, since IKK2SSEE induced the development of bone-resorbing osteoclasts from RANK-, IKK1-, and NEMO-deficient monocytes. Inflammatory autocrine signaling by TNFα and IL-1 was dispensable for the spontaneous osteoclastogenesis driven by IKK2SSEE. More importantly, adenoviral gene transfer of IKK2SSEE induced osteoclasts and osteolysis in calvariae and knees of mice. To determine the physiological significance of this finding, we examined its role in vivo through expression of constitutively active IKK2 in a tissue-specific manner. Specifically, we employed the R26StopIkk2SSEE mice in which a cDNA encoding IKK2 containing two serine to glutamate substitutions in the activation loop of the kinase domain, preceded by a loxP-flanked STOP cassette, into the ubiquitously expressed ROSA26 locus. We crossed mice carrying this allele with the CD11b-cre mice in order to express IKK2SSEE exclusively in myeloid cells, inclusive of osteoclast progenitors. Phenotypic assessment revealed that expression of IKK2SSEE in the myeloid compartment induces significant bone loss in vivo. This observation was supported by dramatic increase in the number and size of osteoclasts in trabecular regions, elevated levels of circulating TRACP-5b, and reduced bone volume. Mechanistically, we surprisingly observed that IKK2SSEE induced high expression of not only p65 but p52 and RelB, the latter two molecules are considered exclusive members of the alternative NF-kB pathway. Even more surprisingly, RelB and P52 are both required to mediate the osteoclastogenic effect of IKK2SSEE and co-expression of these two proteins is sufficient to recapitulate osteoclastogenesis in the absence of RANKL or IKK2SSEE. In summary, molecular activation of IKK2 may play a role in conditions of pathologic bone destruction which maybe refractory to therapeutic interventions targeting the proximal RANKL signal. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared.
doi:10.1016/j.bone.2012.02.049
IS28 NF-κB signaling and bone formation C.-Y. Wang⁎ University of California, Los Angeles, Los Angeles, USA Learning Outcome 1: 1) NF-κB plays an important role in inhibition of bone formation in inflammatory and metabolic bone diseases. Learning Outcome 2: NF-κB regulates osteoblast functions. Learning Outcome 3: NF-κB regulates the differentiation of mesenchymal stem cells. Abstract: NF-κB is a family of transcription factors involved in the immune system and many other tissues. Although it has been well studied in osteoclasts, the role of NF-
κB in osteoblasts and bone formation is less defined. In this workshop, I will discuss how NF-κB activation affects osteoblast function and bone formation in osteoporosis and inflammatory bone diseases. In particular, I describe experiments using IKK inhibitors in osteoblasts that showed that a reduction of NF-κB activity in osteoblasts results in an increase in bone formation via an increase in JNK activity, which regulates Fra-1 expression. I will show our recent work on regulation of mesenchymal stem cell differentiation by NF-κB. Considering the well-established role of NF-κB in inflammation and infection, our results suggest that targeting NF-κB may have dual benefits in enhancing bone formation and repair and inhibiting inflammation. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. doi:10.1016/j.bone.2012.02.050
IS29 Vitamin D and the immune system: Do we need more? C. Mathieu⁎ Katholieke Universiteit Leuven, Leuven, Belgium Learning Outcome 1: Basic understanding of the immune system. Learning Outcome 2: Understanding how vitamin D can influence the immune system. Learning Outcome 3: Understanding the limitations with present literature. Abstract: In recent years great attention has been given to the pleiotropic effect of vitamin D, a vitamin well known from its role in bone and calcium homeostasis. Also in the immune system, modulating effects by vitamin D have been described. Receptors for vitamin D are present in cells throughout the immune system and a central role for the antigen presenting dendritic cell and the macrophage in the effect of vitamin D in the immune system is described. The latter cells not only carry receptors, but also contain the machinery to produce themselves the activated form of vitamin D, 1,25dihydroxyvitamin D3. Finally also other immune cells, like T lymphocytes carry receptors for vitamin D. These data suggest a physiological role for vitamin D as an immune modulator. Epidemiology confirms this possible role, indicating correlations between vitamin D deficiency and adverse immune outcomes (more infections, more autoimmune diseases). Animal models confirm this detrimental effect of vitamin D deficiency on immune function and even point towards the possibility of exploiting these effects of vitamin D in a pharmacological way, using analogues of vitamin D as immune modulators or treating immune cells ex vivo. The place for vitamin D in a healthy immune system for clinicians will be discussed. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared.
doi:10.1016/j.bone.2012.02.051
IS30 Vitamin D and cardiovascular disease M.D. Witham⁎ Ageing and Health, University of Dundee, Dundee, UK Learning Outcome 1: The mechanisms by which vitamin D may affect vascular health. Learning Outcome 2: Current observational and interventional evidence regarding vitamin D and vascular health. Learning Outcome 3: The limitations of existing evidence and areas where further research is needed. Abstract: Low circulating 25-hydroxyvitamin D (25OHD) levels are associated with a wide range of vascular disease states, including hypertension, diabetes mellitus, stroke, myocardial infarction and heart failure. These associations have been confirmed by large cross-sectional studies, and evidence from longitudinal cohort studies suggests that low 25OHD levels are an independent predictor of future cardiovascular events and incident hypertension. A range of biological mechanisms exists that might explain these findings, including effects on the renin–angiotensin system, alterations in calcium handling, suppression of pro-inflammatory cytokines involved in atherosclerosis and effects on other vasculotoxic mediators, including parathyroid hormone. Observational data in this area is dogged by confounding and reverse causality however; thus evidence from intervention studies is necessary to elucidate whether low vitamin D levels are a cause of cardiovascular disease. Current evidence suggests weak effects on blood pressure reduction in selected groups, beneficial effects on markers of vascular health in selected groups of patients, but little effect on metabolic control in patients with diabetes. The optimum dose, duration of therapy and target populations for intervention with vitamin D to reduce cardiovascular disease are not known, and large-scale trials of vitamin D designed specifically to reduce cardiovascular events have not been conducted to date. Metaanalyses from osteoporosis trials to date have not found evidence for significant reductions in cardiovascular events, but are dogged by cointervention with calcium.