Hyperinsulinemia down-regulates TLR4 expression in the mammalian heart

Toll-like receptors (TLR) are key regulators of innate immune and inflammatory responses and their activation is linked to impaired glucose metabolism during metabolic disease. Determination of whether TLR4 signaling can be activated in the heart by insulin may shed light on the pathogenesis of diabetic cardiomyopathy, a process that is often complicated by obesity and insulin resistance. The aim of the current study was to determine if supraphysiological insulin concentrations alter the expression of TLR4, markers of TLR4 signaling and glucose transporters (GLUTs) in the heart. Firstly, the effect of insulin on TLR4 protein expression was investigated in vitro in isolated rat cardiac myocytes. Secondly, protein expression of TLR4, the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) suppressor of cytokine signaling 3 (SOCS3) and GLUTs (1, 4, 8, 12) were examined in the equine ventricular myocardium following a prolonged, euglycemic, hyperinsulinemic clamp. Down-regulation of TLR4 protein content in rat cardiac myocytes was observed after incubation with a supraphysiologic concentration of insulin as well as in the equine myocardium after prolonged insulin infusion. Further, cardiac TLR4 expression was negatively correlated with serum insulin concentration. Markers of cardiac TLR4 signaling and GLUT expression were not affected by hyperinsulinemia and concomitant TLR4 down-regulation. Since TLRs are major determinants of the inflammatory response, our findings suggest that insulin infusion exerts an anti-inflammatory effect in the hearts of non-obese individuals. Understanding the regulation of cardiac TLR4 signaling during metabolic dysfunction will facilitate improved management of cardiac sequela to metabolic syndrome and diabetes.

Evidence of associations between cytokine gene polymorphisms and quality of life in patients with cancer and their family caregivers

PURPOSE/OBJECTIVES: To identify latent classes of individuals with distinct quality-of-life (QOL) trajectories, to evaluate for differences in demographic characteristics between the latent classes, and to evaluate for variations in pro- and anti-inflammatory cytokine genes between the latent classes. DESIGN: Descriptive, longitudinal study. SETTING: Two radiation therapy departments located in a comprehensive cancer center and a community-based oncology program in northern California. SAMPLE: 168 outpatients with prostate, breast, brain, or lung cancer and 85 of their family caregivers (FCs). METHODS: Growth mixture modeling (GMM) was employed to identify latent classes of individuals based on QOL scores measured prior to, during, and for four months following completion of radiation therapy. Single nucleotide polymorphisms (SNPs) and haplotypes in 16 candidate cytokine genes were tested between the latent classes. Logistic regression was used to evaluate the relationships among genotypic and phenotypic characteristics and QOL GMM group membership. MAIN RESEARCH VARIABLES: QOL latent class membership and variations in cytokine genes. FINDINGS: Two latent QOL classes were found: higher and lower. Patients and FCs who were younger, identified with an ethnic minority group, had poorer functional status, or had children living at home were more likely to belong to the lower QOL class. After controlling for significant covariates, between-group differences were found in SNPs in interleukin 1 receptor 2 (IL1R2) and nuclear factor kappa beta 2 (NFKB2). For IL1R2, carrying one or two doses of the rare C allele was associated with decreased odds of belonging to the lower QOL class. For NFKB2, carriers with two doses of the rare G allele were more likely to belong to the lower QOL class. CONCLUSIONS: Unique genetic markers in cytokine genes may partially explain interindividual variability in QOL. IMPLICATIONS FOR NURSING: Determination of high-risk characteristics and unique genetic markers would allow for earlier identification of patients with cancer and FCs at higher risk for poorer QOL. Knowledge of these risk factors could assist in the development of more targeted clinical or supportive care interventions for those identified.

Characterisation of cytokine response to Chlamydia pecorum infection in the koala, Phascolarctos cinereus

This thesis aimed at identifying cytokine markers associated with chlamydial infection and disease in koalas which is facing many threats to its survival, Chlamydia pecorum infections being a major one. To identify immunological markers associated with chlamydial infection and disease in koalas, key cytokines such as TNF alpha, IL10, IFN gamma and IL17A were cloned and sequenced and subsequently developed Quantitative Real Time PCR (qrtPCR) assays. The thesis provides preliminary data on the role of these cytokines in koala chlamydial disease and further longitudinal studies are required to confirm the role played by cytokines in pathology and protection against C. pecorum infection in the koala.

Effect of tocopherol on atherosclerosis, vascular function and inflammation in Apolipoprotein E knockout mice with subtotal nephrectomy

Background/Aims: Inflammation and endothelial dysfunction contribute to cardiovascular disease, prevalent in chronic kidney disease (CKD). Antioxidant supplements such as tocopherols may reduce inflammation and atherosclerosis. This study aimed to investigate the effect of tocopherol supplementation on vascular function, aortic plaque formation, and inflammation in apolipoprotein E−/− mice with 5/6 nephrectomy as a model of combined cardiovascular and kidney disease. Methods: Nephrectomized mice were assigned to a normal chow diet group (normal chow), a group receiving 1000 mg/kg diet of α-tocopherol supplementation or a group receiving 1000 mg/kg diet mixed-tocopherol (60% γ-tocopherol). Results: Following 12 weeks, in vitro aortic endothelial-independent relaxation was enhanced with both α-tocopherol and mixed-tocopherol (P < 0.05), while mixed-tocopherol enhanced aortic contraction at noradrenaline concentrations of 3 × 10−7 M to 3 × 10−5 M (P < 0.05), when compared to normal chow. Supplementation with α- and mixed-tocopherol reduced systemic concentrations of IL-6 (P < 0.001 and P < 0.001, respectively) and IL-10 (P < 0.05 and P < 0.001, respectively), while α-tocopherol also reduced MCP-1 (P < 0.05) and tumor necrosis factor (TNF)-α (P < 0.05). Aortic sinus plaque area was significantly reduced with α-tocopherol supplementation when compared to normal chow (P < 0.01). Conclusion: Tocopherol supplementation favorably influenced vascular function and cytokine profile, while it was also effective in reducing atherosclerosis in the apolipoprotein E−/− mouse with CKD.

Activation of membrane-bound proteins and receptor systems: A link between tissue kallikrein and the KLK-related peptidases

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and roles in a range of cellular processes, including proliferation, migration, invasion, differentiation, inflammation and angiogenesis that are required in both normal physiology as well as pathological conditions. These roles require cleavage of a range of substrates, including extracellular matrix proteins, growth factors, cytokines as well as other proteinases. In addition, it has been clear since the earliest days of KLK research that cleavage of cell surface substrates is also essential in a range of KLK-mediated cellular processes where these peptidases are essentially acting as agonists and antagonists. In this review we focus on these KLK-regulated cell surface receptor systems including bradykinin receptors, proteinase-activated receptors, as well as the plasminogen activator, ephrins and their receptors, and hepatocyte growth factor/Met receptor systems and other plasma membrane proteins. From this analysis it is clear that in many physiological and pathological settings KLKs have the potential to regulate multiple receptor systems simultaneously; an important issue when these peptidases and substrates are targeted in disease.

Cytokine secretion in macrophages : SNAREs, Rabs and membrane trafficking

Macrophages have the capacity to rapidly secrete a wide range of inflammatory mediators that influence the development and extent of an inflammatory response. Newly synthesized and/or preformed stored cytokines and other inflammatory mediators are released upon stimulation, the timing, and volume of which is highly regulated. To finely tune this process, secretion is regulated at many levels; at the level of transcription and translation and post-translationally at the endoplasmic reticulum (ER), Golgi, and at or near the cell surface. Here, we discuss recent advances in deciphering these cytokine pathways in macrophages, focusing on recent discoveries regarding the cellular machinery and mechanisms implicated in the synthesis, trafficking, and secretion of cytokines. The specific roles of trafficking machinery including chaperones, GTPases, cytoskeletal proteins, and SNARE membrane fusion proteins will be discussed.

Cytokine expression and secretion by skeletal muscle cells : regulatory mechanisms and exercise effects

Cytokines are important mediators of various aspects of health and disease, including appetite, glucose and lipid metabolism, insulin sensitivity, skeletal muscle hypertrophy and atrophy. Over the past decade or so, considerable attention has focused on the potential for regular exercise to counteract a range of disease states by modulating cytokine production. Exercise stimulates moderate to large increases in the circulating concentrations of interleukin (IL)-6, IL-8, IL-10, IL-1 receptor antagonist, granulocyte-colony stimulating factor, and smaller increases in tumor necrosis factor-α, monocyte chemotactic protein-1, IL-1β, brain-derived neurotrophic factor, IL-12p35/p40 and IL-15. Although many of these cytokines are also expressed in skeletal muscle, not all are released from skeletal muscle into the circulation during exercise. Conversely, some cytokines that are present in the circulation are not expressed in skeletal muscle after exercise. The reasons for these discrepant cytokine responses to exercise are unclear. In this review, we address these uncertainties by summarizing the capacity of skeletal muscle cells to produce cytokines, analyzing other potential cellular sources of circulating cytokines during exercise, and discussing the soluble factors and intracellular signaling pathways that regulate cytokine synthesis (e.g., RNA-binding proteins, microRNAs, suppressor of cytokine signaling proteins, soluble receptors).

Biliverdin modulates the expression of C5aR in response to endotoxin in part via mTOR signaling

Macrophages play a crucial role in the maintenance and resolution of inflammation and express a number of pro- and anti-inflammatory molecules in response to stressors. Among them, the complement receptor 5a (C5aR) plays an integral role in the development of inflammatory disorders. Biliverdin and bilirubin, products of heme catabolism, exert anti-inflammatory effects and inhibit complement activation. Here, we define the effects of biliverdin on C5aR expression in macrophages and the roles of Akt and mammalian target of rapamycin (mTOR) in these responses. Biliverdin administration inhibited lipopolysaccharide (LPS)-induced C5aR expression (without altering basal expression), an effect partially blocked by rapamycin, an inhibitor of mTOR signaling. Biliverdin also reduced LPS-dependent expression of the pro-inflammatory cytokines TNF-alpha and IL-6. Collectively, these data indicate that biliverdin regulates LPS-mediated expression of C5aR via the mTOR pathway, revealing an additional mechanism underlying biliverdin's anti-inflammatory effects.

Recovery after an Ironman triathlon: Sustained inflammatory responses and muscular stress

Ultra-endurance exercise, such as an Ironman triathlon, induces muscle damage and a systemic inflammatory response. As the resolution of recovery in these parameters is poorly documented, we investigated indices of muscle damage and systemic inflammation in response to an Ironman triathlon and monitored these parameters 19 days into recovery. Blood was sampled from 42 well-trained male triathletes 2 days before, immediately after, and 1, 5 and 19 days after an Ironman triathlon. Blood samples were analyzed for hematological profile, and plasma values of myeloperoxidase (MPO), polymorphonuclear (PMN) elastase, cortisol, testosterone, creatine kinase (CK) activity, myoglobin, interleukin (IL)-6, IL-10 and high-sensitive C-reactive protein (hs-CRP). Immediately post-race there were significant (P < 0.001) increases in total leukocyte counts, MPO, PMN elastase, cortisol, CK activity, myoglobin, IL-6, IL-10 and hs-CRP, while testosterone significantly (P < 0.001) decreased compared to prerace. With the exception of cortisol, which decreased below prerace values (P < 0.001), these alterations persisted 1 day post-race (P < 0.001; P < 0.01 for IL-10). Five days post-race CK activity, myoglobin, IL-6 and hs-CRP had decreased, but were still significantly (P < 0.001) elevated. Nineteen days post-race most parameters had returned to prerace values, except for MPO and PMN elastase, which had both significantly (P < 0.001) decreased below prerace concentrations, and myoglobin and hs-CRP, which were slightly, but significantly higher than prerace. Furthermore, significant relationships between leukocyte dynamics, cortisol, markers of muscle damage, cytokines and hs-CRP after the Ironman triathlon were noted. This study indicates that the pronounced initial systemic inflammatory response induced by an Ironman triathlon declines rapidly. However, a low-grade systemic inflammation persisted until at least 5 days post-race, possibly reflecting incomplete muscle recovery.

The effect of osteoimmunomodulation on the osteogenic effects of cobalt incorporated β-tricalcium phosphate

Osteoblast lineage cells are direct effectors of osteogenesis and are, therefore, commonly used to evaluate the in vitro osteogenic capacity of bone substitute materials. This method has served its purposes when testing novel bone biomaterials; however, inconsistent results between in vitro and in vivo studies suggest the mechanisms that govern a material's capacity to mediate osteogenesis are not well understood. The emerging field of osteoimmunology and immunomodulation has informed a paradigm shift in our view of bone biomaterials–from one of an inert to an osteoimmunomodulatory material–highlighting the importance of immune cells in materials-mediated osteogenesis. Neglecting the importance of the immune response during this process is a major shortcoming of the current evaluation protocol. In this study we evaluated a potential angiogenic bone substitute material cobalt incorporated with β-tricalcium phosphate (CCP), comparing the traditional “one cell type” approach with a “multiple cell types” approach to assess osteogenesis, the latter including the use of immune cells. We found that CCP extract by itself was sufficient to enhance osteogenic differentiation of bone marrow stem cells (BMSCs), whereas this effect was cancelled out when macrophages were involved. In response to CCP, the macrophage phenotype switched to the M1 extreme, releasing pro-inflammatory cytokines and bone catabolic factors. When the CCP materials were implanted into a rat femur condyle defect model, there was a significant increase of inflammatory markers and bone destruction, coupled with fibrous encapsulation rather than new bone formation. These findings demonstrated that the inclusion of immune cells (macrophages) in the in vitro assessment matched the in vivo tissue response, and that this method provides a more accurate indication of the essential role of immune cells when assessing materials-stimulated osteogenesis in vitro.

Clinoenstatite coatings have high bonding strength, bioactive ion release, and osteoimmunomodulatory effects that enhance in vivo osseointegration

A number of coating materials have been developed over past two decades seeking to improve the osseointegration of orthopedic metal implants. Despite the many candidate materials trialed, their low rate of translation into clinical applications suggests there is room for improving the current strategies for their development. We therefore propose that the ideal coating material(s) should possess the following three properties: (i) high bonding strength, (ii) release of functional ions, and (iii) favourable osteoimmunomodulatory effects. To test this proposal, we developed clinoenstatite (CLT, MgSiO3), which as a coating material has high bonding strength, cytocompability and immunomodulatory effects that are favourable for in vivo osteogenesis. The bonding strength of CLT coatings was 50.1 ± 3.2 MPa, more than twice that of hydroxyapatite (HA) coatings, at 23.5 ± 3.5 MPa. CLT coatings released Mg and Si ions, and compared to HA coatings, induced an immunomodulation more conducive for osseointegration, demonstrated by downregurelation of pro-inflammatory cytokines, enhancement of osteogenesis, and inhibition of osteoclastogenesis. In vivo studies demonstrated that CLT coatings improved osseointegration with host bone, as shown by the enhanced biomechanical strength and increased de novo bone formation, when compared with HA coatings. These results support the notion that coating materials with the proposed properties can induce an in vivo environment better suited for osseointegration. These properties could, therefore, be fundamental when developing high-performance coating materials.

Enrichment of circulating interleukin-17-secreting interleukin-23 receptor-positive γ/δ T cells in patients with active ankylosing spondylitis

Objective Ankylosing spondylitis (AS) is a common inflammatory arthritis affecting primarily the axial skeleton. IL23R is genetically associated with AS. This study was undertaken to investigate and characterize the role of interleukin-23 (IL-23) signaling in AS pathogenesis. Methods The study population consisted of patients with active AS (n = 17), patients with psoriatic arthritis (n = 8), patients with rheumatoid arthritis, (n = 9), and healthy subjects (n = 20). IL-23 receptor (IL-23R) expression in T cells was determined in each subject group, and expression levels were compared. Results The proportion of IL-23R-expressing T cells in the periphery was 2-fold higher in AS patients than in healthy controls, specifically driven by a 3-fold increase in IL-23R-positive γ/δ T cells in AS patients. The proportions of CD4+ and CD8+ cells that were positive for IL-17 were unchanged. This increased IL-23R expression on γ/δ T cells was also associated with enhanced IL-17 secretion, with no observable IL-17 production from IL-23R-negative γ/δ T cells in AS patients. Furthermore, γ/δ T cells from AS patients were heavily skewed toward IL-17 production in response to stimulation with IL-23 and/or anti-CD3/CD28. Conclusion Recently, mouse models have shown IL-17-secreting γ/δ T cells to be pathogenic in infection and autoimmunity. Our data provide the first description of a potentially pathogenic role of these cells in a human autoimmune disease. Since IL-23 is a maturation and growth factor for IL-17-producing cells, increased IL-23R expression may regulate the function of this putative pathogenic γ/δ T cell population.

Serum levels of soluble receptor for advanced glycation end products and of S100 proteins are associated with inflammatory, autoantibody, and classical risk markers of joint and vascular damage in rheumatoid arthritis

Introduction: The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface receptor molecules. High concentrations of three of its putative proinflammatory ligands, S100A8/A9 complex (calprotectin), S100A8, and S100A12, are found in rheumatoid arthritis (RA) serum and synovial fluid. In contrast, soluble RAGE (sRAGE) may prevent proinflammatory effects by acting as a decoy. This study evaluated the serum levels of S100A9, S100A8, S100A12 and sRAGE in RA patients, to determine their relationship to inflammation and joint and vascular damage. Methods: Serum sRAGE, S100A9, S100A8 and S100A12 levels from 138 patients with established RA and 44 healthy controls were measured by ELISA and compared by unpaired t test. In RA patients, associations with disease activity and severity variables were analyzed by simple and multiple linear regressions. Results: Serum S100A9, S100A8 and S100A12 levels were correlated in RA patients. S100A9 levels were associated with body mass index (BMI), and with serum levels of S100A8 and S100A12. S100A8 levels were associated with serum levels of S100A9, presence of anti-citrullinated peptide antibodies (ACPA), and rheumatoid factor (RF). S100A12 levels were associated with presence of ACPA, history of diabetes, and serum S100A9 levels. sRAGE levels were negatively associated with serum levels of C-reactive protein (CRP) and high-density lipoprotein (HDL), history of vasculitis, and the presence of the RAGE 82Ser polymorphism. Conclusions: sRAGE and S100 proteins were associated not just with RA inflammation and autoantibody production, but also with classical vascular risk factors for end-organ damage. Consistent with its role as a RAGE decoy molecule, sRAGE had the opposite effects to S100 proteins in that S100 proteins were associated with autoantibodies and vascular risk, whereas sRAGE was associated with protection against joint and vascular damage. These data suggest that RAGE activity influences co-development of joint and vascular disease in rheumatoid arthritis patients.

Altered immunoglobulin E diversity and regulation of allergic inflammation in asthma

The clinical efficacy of anti-immunoglobulin E (IgE) therapy indicates a central role for IgE in perpetuation of allergic inflammatory diseases. Omalizumab is now uti- lized in treatment of a wide variety of allergic conditions including severe asthma, allergic rhinitis, atopic dermati- tis, food allergy and urticaria either alone or adjunct with other therapies such as steroid administration or allergen- specific immunotherapy [1, 2]. Current research activity is focused on the cellular and molecular mechanisms by which IgE influences the immunopathogenesis of allergic disease [3]. Increased knowledge of how IgE exerts its effects will underpin effective clinical use of anti-IgE treatment. In this issue Kerzel et al. [4] investigate the effects of altered antibo dy repertoire on the outcomes of an experimental model of allergic asthma.

Antibody treatments of inflammatory arthritis

Inflammatory arthropathies such as rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis are extremely common in the community, with a prevalence of up to 5%, and they cause substantial morbidity. The development of anti-TNF agents for use initially in rheumatoid arthritis, and subsequently more broadly in inflammatory arthritis, represents the biggest advance in management of these conditions since the introduction of corticosteroid agents, and is a major vindication of public funded arthritis research. However, there are limitations of even these highly effective agents. A significant minority of patients with inflammatory arthritis do not respond to these anti-TNF agents, they are associated with substantial risk of toxicity, require parenteral administration, and are extremely expensive. New antibody treatments in development can be divided into anti-cytokine agents, cell-targeted therapies, co-stimulation inhibitors, and treatments aimed at preventing joint erosion consequent on inflammation. This review discusses the state of the art in the development of these agents for management of this common group of diseases.