The effects of caffeine on bone mineral density and fracture risk.

Caffeine is a regular part of the diet of many adults (coffee, tea, soft drinks, and energy drinks). Multiple molecular effects of caffeine suggest that it may promote bone loss. Given the extensive consumption of caffeine worldwide, any impact of caffeine consumption on bone strength and/or density would have large population health implications. The most well-established pharmacological effect of caffeine is non-specific antagonism of adenosine receptors. Adenosine regulates bone metabolism in a complex manner, with in vitro studies suggesting that direct stimulation of adenosine A2A and A2B receptors induces bone formation by activating osteoblasts and suppressing osteoclast differentiation and function. Thus, competitive inhibition of adenosine A2 receptors by caffeine may inhibit bone formation and promote bone resorption. However, antagonism of adenosine A1 receptors may have opposing effects. Caffeine has also been suggested to affect bone through derangement of calcium metabolism, alteration of vitamin D responses, and other mechanisms. In clinical and population-based studies, the impact of caffeine consumption on bone metabolism offers a mixed picture, with some but not all studies suggesting a potential link between caffeine intake and reduced bone mineral density or increased fracture risk. Differences in methodology, selected populations, and duration/timing of the studies may account for study outcome discrepancies. The in vitro effects of caffeine on cells involved in bone metabolism suggest that caffeine intake may promote osteoporosis, and some but not all clinical studies support a modest adverse caffeine impact. Herein, we describe the basic biology of caffeine as it pertains to bone, review the clinical literature to date, and consider the implications of the current data on clinical practice and future studies.

Critical appraisal of intra-articular glucocorticoid injections for symptomatic osteoarthritis of the knee.

OBJECTIVE: Intra-articular (IA) injections of glucocorticoids (GCs) have been shown to decrease pain, increase mobility, and improve quality of life in patients with osteoarthritis (OA) of the knee. Concerns about cartilage loss with IA GCs have prompted reconsideration of their use in knee OA. This review has three objectives: 1) critically review the clinical, molecular, and structural effects of IA GCs in knee OA; 2) provide a design for a clinical trial aimed at improving our understanding of the long-term consequences of IA GCs; and 3) provide practical guidance on the use of IA GCs in patients with knee OA based on current information. DESIGN: A narrative review of current literature on the use of IA GCs for OA of the knee. RESULTS: Important questions remain to be fully answered with respect to IA GCs, including long-term effects on all aspects of the structural and molecular environment of the knee, and identification of factors that can reliably predict a positive or negative response to IA GCs. CONCLUSIONS: While awaiting results from an appropriately designed study, several provisional statements regarding IA GCs can be put forward: 1) IA GCs appear to be a relatively safe option that is effective in specific patients with symptomatic knee OA; 2) there is no definitive evidence that IA GCs accelerate joint deterioration to an important extent or hastens the requirement for knee replacement; and 3) there are few contraindications to IA GCs and injection-associated complications are rare when IA GCs are delivered with proper technique.

The association between asymptomatic hyperuricemia and knee osteoarthritis: data from the third National Health and Nutrition Examination Survey.

OBJECTIVE: In vitro and clinical studies suggest that urate may contribute to osteoarthritis (OA) risk. We tested the associations between hyperuricemia and knee OA, and examined the role of obesity, using a cross-sectional, nationally representative dataset. METHOD: National Health and Nutrition Examination Survey (NHANES) III used a multistage, stratified probability cluster design to select USA civilians from 1988 to 1994. Using NHANES III we studied adults >60 years, with or without hyperuricemia (serum urate > 6.8 mg/dL), excluding individuals with gout (i.e., limiting to asymptomatic hyperuricemia (AH)). Radiographic knee OA (RKOA) was defined as Kellgren-Lawrence grade ≥ 2 in any knee, and symptomatic radiographic knee osteoarthritis (RKOA) (sRKOA) was defined as RKOA plus knee pain (most days for 6 weeks) in the same knee. RESULTS: AH prevalence was 17.9% (confidence interval (CI) 15.3-20.5). RKOA prevalence was 37.7% overall (CI 35.0-40.3), and was 44.0% for AH vs 36.3% for normouricemic adults (p = 0.056). symptomatic radiographic knee osteoarthritis (sRKOA) was more prevalent in AH vs normouricemic adults (17.4% vs 10.9%, p = 0.046). In multivariate models adjusting for obesity, model-based associations between AH and knee OA were attenuated (for RKOA, prevalence ratio (PR) = 1.14, 95% CI 0.95, 1.36; for sRKOA, PR = 1.40, 95% CI 0.98, 2.01). In stratified multivariate analyses, AH was associated with sRKOA in adults without obesity (PR = 1.66, 95% CI 1.02, 2.71) but not adults with obesity (PR = 1.21, 95% CI 0.66, 2.23). CONCLUSIONS: Among adults aged 60 or older, AH is associated with knee OA risk that is more apparent in adults without obesity.

Molecular characteristics of antibodies bearing an anti-DNA-associated idiotype.

Anti-double-stranded DNA antibodies are the hallmark of the disease systemic lupus erythematosus and are believed to contribute to pathogenesis. While a large number of anti-DNA antibodies from mice with lupus-like syndromes have been characterized and their variable region genes sequenced, few human anti-DNA antibodies have been reported. We describe here the variable region gene sequences of eight antibodies produced by Epstein-Barr virus (EBV)-transformed B cells that bear the 3I idiotype, an idiotype expressed on anti-DNA antibodies and present in high titer in patients with systemic lupus. The comparison of these antibodies to the light chains of 3I+ myeloma proteins and serum antibodies reveals that EBV transformation yields B cells producing antibodies representative of the expressed antibody repertoire. The analysis of nucleotide and amino acid sequences of these antibodies suggests the first complementarity determining region of the light chain may be important in DNA binding and that paradigms previously generated to account for DNA binding require modification. The understanding of the molecular genetics of the anti-DNA response requires a more complete description of the immunoglobulin germ line repertoire, but data reported here suggest that somatic diversification is a characteristic of the anti-DNA response.

Carboxyl methylation of Ras-related proteins during signal transduction in neutrophils.

In human neutrophils, as in other cell types, Ras-related guanosine triphosphate-binding proteins are directed toward their regulatory targets in membranes by a series of posttranslational modifications that include methyl esterification of a carboxyl-terminal prenylcysteine residue. In intact cells and in a reconstituted in vitro system, the amount of carboxyl methylation of Ras-related proteins increased in response to the chemoattractant N-formyl-methionyl-leucyl-phenylalanine (FMLP). Activation of Ras-related proteins by guanosine-5'-O-(3-thiotriphosphate) had a similar effect and induced translocation of p22rac2 from cytosol to plasma membrane. Inhibitors of prenylcysteine carboxyl methylation effectively blocked neutrophil responses to FMLP. These findings suggest a direct link between receptor-mediated signal transduction and the carboxyl methylation of Ras-related proteins.

Design and Rationale for the Veterans Affairs "Cooperative Study Program 594 Comparative Effectiveness in Gout: Allopurinol vs. Febuxostat" Trial.

BACKGROUND: Gout patients do not routinely achieve optimal outcomes related in part to suboptimal administration of urate lowering therapy (ULT) including first-line xanthine oxidase inhibitors allopurinol or febuxostat. Studies leading to the approval of febuxostat compared this agent to allopurinol in inappropriately low, fixed doses. We will compare allopurinol with febuxostat in gout using appropriately titrated doses of both agents and a "treat-to-target" strategy congruent with specialty guidelines. METHODS: We have planned and initiated the Veterans Affairs (VA) Cooperative Study Program (CSP) 594, Comparative Effectiveness in Gout: Allopurinol vs Febuxostat study. This large double-blind, non-inferiority trial will enroll 950 gout patients randomized to receive allopurinol or febuxostat. Patients will be followed for a total of 72 weeks encompassing 3 distinct 24-week study phases. During Phase I (0-24 weeks), participants will undergo gradual dose titration of ULT until achievement of serum uric acid (sUA) <6.0 mg/dL or <5.0 mg/dL if tophi are present. Dose escalation will not be allowed during final three study visits of Phase 2 (24-48 weeks) and during Phase 3 (48-72 weeks). The primary study outcome is the proportion of participants experiencing at least one gout flare during Phase 3. Subsequent to the 72-week study, participants will be followed passively for up to 10 years after the study to assess long-term health outcomes. CONCLUSION: With its completion, the VA Comparative Effectiveness in Gout: Allopurinol vs Febuxostat study will demonstrate the central role of gradual ULT dose escalation and a treat-to-target strategy in gout management.

Integrin-dependent homotypic adhesion of neutrophils. Arachidonic acid activates Raf-1/Mek/Erk via a 5-lipoxygenase- dependent pathway.

AA stimulates integrin-dependent neutrophil adhesion, a critical early step in acute inflammation. However, neither the signaling pathway(s) of AA-stimulated adhesion, nor whether AA acts directly or through the generation of active metabolites, has been elucidated. Previously, we have observed a tight association between neutrophil Erk activation and homotypic adhesion in response to chemoattractants acting through G protein-linked receptors. We now report a similar association between homotypic adhesion and Erk activation in response to AA. Erk activation was cyclooxygenase independent and required AA metabolism to 5(S)- hydroperoxyeicosatetraenoic acid (5-HpETE) via 5-lipoxygenase, but not the further lipoxygenase-dependent metabolism of 5-HpETE to leukotrienes. AA stimulation of Erk was accompanied by Raf-1 activation and was sensitive to inhibitors of Raf-1 and Mek. Whereas activation of Erk by AA was pertussis toxin sensitive, [3H]-AA binding to neutrophils was not saturable, suggesting that an AA metabolite activates a G protein. Consistent with this hypothesis, Erk activation by 5(S)-hydroxyeicosatetraenoic acid (5-HETE; lipoxygenase-independent metabolite of 5-HpETE) was also pertussis toxin sensitive. These data suggest that a 5-lipoxygenase metabolite of AA, e.g., 5-HETE, is released from AA-treated cells to engage a plasma membrane-associated, pertussis toxin-sensitive, G protein-linked receptor, leading to activation of Erk and adhesion via the Raf-1/Mek signal transduction pathway.

Dimethylfumarate inhibits tumor-necrosis-factor-induced CD62E expression in an NF-kappa B-dependent manner.

Fumaric acid esters are thought to improve psoriasis by altering leukocyte, keratinocyte, and/or endothelial functions. To determine specificity, kinetics, and molecular mechanisms of different fumaric acid esters in their ability to inhibit endothelial cell activation, we analyzed CD62E and CD54 expression in endothelial cells in vivo and in vitro. In lesional skin of psoriatic patients, oral fumaric acid ester treatment resulted in a marked reduction of CD62E but not CD54 expression on dermal microvessels. Using human umbilical vein endothelial cells, dimethylfumarate almost completely inhibited tumor-necrosis-factor-induced CD62E, but not CD54 expression at concentrations < or = 70 microM, mimicking the situation in vivo. A 60 min dimethylfumarate preincubation was sufficient to block tumor-necrosis-factor-induced CD62E expression for up to 24 h. In contrast, equimolar concentrations of methylhydrogenfumarate, the hydrolysis product of dimethylfumarate, did not suppress tumor-necrosis-factor-induced CD62E expression. Likewise, all fumaric acid esters other than dimethylfumarate were ineffective. Using CD62E, NF-kappa B, or AP-1-responsive promoter constructs, dimethylfumarate inhibited tumor-necrosis-factor-induced activation of the CD62E and the NF-kappa B but not the AP-1 promoter construct. In summary, at a dose range < or = 70 microM, dimethylfumarate appeared to be a specific inhibitor of CD62E expression in an NF-kappa B-dependent manner.

Platelet endothelial cell adhesion molecule-1 and vascular endothelial cadherin cooperatively regulate fibroblast growth factor-induced modulations of adherens junction functions.

Cellular adherens junctions are formed by cadherins linked to proteins of the catenin family. In endothelial cells, not only vascular endothelial cadherin but also platelet endothelial cell adhesion molecule-1 localizes into junctions and associates with beta-catenin. To explore a putative cooperation of platelet endothelial cell adhesion molecule-1 and vascular endothelial cadherin, we analyzed transfectants expressing either platelet endothelial cell adhesion (CD31 cells) or vascular endothelial cadherin (CD144 cells) or both molecules (CD31/CD144 cells), and, for comparison, human umbilical vein endothelial cells. Basic fibroblast growth factor completely dissociated vascular endothelial cadherin/beta-catenin complexes and robustly moved beta-catenin into the nucleus in CD144 cells, whereas in CD31/CD144 cells as well as in human umbilical vein endothelial cells, fibroblast growth factor only partially dissociated the junctional complex followed by a significantly reduced nuclear translocation of beta-catenin. In contrast, in CD31 cells, the subcellular distribution of beta-catenin remained unaffected by fibroblast growth factor. As a functional consequence, fibroblast growth factor induced a complete collapse of the F-actin network in CD144 cells, a limited rearrangement of F-actin fibers in CD31/CD144 cells and no F-actin rearrangement in CD31 cells. We also analyzed the effect of fibroblast growth factor-induced rearrangement of junctions on junction permeability for leukocytes: in line with our observation that vascular endothelial cadherin was required for cells to respond to fibroblast growth factor, only in CD31/CD144 cells, but not in CD31 cells, leukocyte transmigration was significantly enhanced by fibroblast growth factor. In conclusion platelet endothelial cell adhesion molecule-1 cooperates with vascular endothelial cadherin in a mutual fashion; platelet endothelial cell adhesion molecule-1 reduces and temporarily limits fibroblast growth factor-induced dissociation of vascular endothelial cadherin/beta-catenin complexes, but requires vascular endothelial cadherin to control leukocyte transmigration in dependence of fibroblast growth factor.

Prenylcysteine analogs to study function of carboxylmethylation in signal transduction.

Carboxylmethylation of ras-related proteins is stimulated immediately on exposure of myeloid cells to inflammatory agonists. When the methylation reaction is inhibited with prenylcysteine analogs, G-protein-mediated signal transduction responses are disrupted, but responses to phorbol ester, calcium ionophore, and phospholipase C (PLC) remain intact. Furthermore, prenylcysteine analogs block GTP gamma S-induced aggregation of permeabilized platelets. Together, these results suggest that protein prenylcysteine methylation can play a role in signal transduction. A number of studies with AdoMet antagonists have suggested a role for methylation in cell-cycle regulation and stimulus-response coupling. Because the compounds generally inhibit all cellular methylation events, however, their effects have been difficult to interpret. On the other hand, prenylcysteine analogs have proved to be specific inhibitors of protein prenylcysteine methylation, as opposed to other types of methylation reactions. This enables the segregation of the role of methylation at C-terminal prenylcysteine residues from methylation at other sites, such as the carboxyl terminus of the catalytic subunit of PP2A. It should be emphasized, however, that prenylcysteine tails of proteins may interact with other target sites in addition to the methyltransferase enzyme(s), and prenylcysteine analogs may compete for these sites as well. One cannot assume that the inhibition of a response by the drugs necessarily implicates the involvement of a prenylcysteine methylation reaction. Studies with the analogs must be interpreted in conjunction with other results to ascertain the locus of their effects.

Pathogenic anti-DNA antibodies in SLE: idiotypic families and genetic origins.

We have adopted an idiotypic approach to study the double stranded DNA (dsDNA) binding antibodies of systemic lupus erythematosus (SLE). Three anti-idiotypic reagents, 8.12, 3I, and F4, identify cross reactive idiotypes that are each expressed on anti-dsDNA antibodies in the sera of many patients with SLE. These idiotypic antibodies are implicated in the pathogenesis of SLE as they are present in immune complex deposits in the kidneys of patients with SLE glomerulonephritis. The autoantibody associated idiotypes are also expressed on antibodies that do not bind DNA. We are investigating the origin of the pathogenic anti-dsDNA antibodies of SLE by comparing the autoantibodies, the antibodies to foreign antigens, and the myeloma proteins that express each SLE associated idiotype. In conjunction with serological analysis of these idiotypic systems, molecular genetic studies indicate that both the 8.12 and the 3I autoantibody associated idiotypes may be germline encoded, while the F4 idiotype is generated by somatic mutation. The data further suggest that the antigenic specificity of the pathogenic anti-DNA antibodies of SLE is acquired through somatic mutation of germline immunoglobulin genes. By studying the regulation of genes capable of encoding pathogenic autoantibodies, in both SLE patients and non-autoimmune individuals, we may be able to elucidate the pathogenesis of autoimmune disease and begin to design more effective therapeutic interventions.

Wegener's granulomatosis in a patient receiving propylthiouracil for Graves' disease.

CONTEXT: The use of propylthiouracil (PTU) in patients with Graves' disease has been associated with multiple complications including rash, leukocytoclastic vasculitis, pulmonary hemorrhage, glomerulonephritis, and the presence of perinuclear antineutrophilic cytoplasmic antibodies (pANCA). OBJECTIVES: To report the association of Wegener's granulomatosis (WG) with the use of PTU in a patient with Graves' disease and to review the spectrum of systemic vasculitis seen in patients with Graves' disease taking PTU. DESIGN: Retrospective review of data collected in a patient with WG. In addition, a Medline search (1980 to present) for PTU-associated vasculitis was conducted. RESULTS: We report WG in a patient treated with PTU who fulfilled the criteria of the American College of Rheumatology for this disease. Furthermore, his serum was positive for cytosolic antineutrophil cytoplasmic antibodies (cANCA) and anti-proteinase-3 (PR3) antibodies by indirect immunofluorescence and enzyme linked immunosorbent assay (ELISA), respectively. WG is associated with high morbidity and mortality and usually requires extensive therapy with prednisone and cyclophosphamide. Our patient, however, did not need specific therapy except discontinuation of PTU to make a full recovery. In previous reports, PTU has been associated with different forms of vasculitis, but this is a the first description of classic WG in a patient treated with PTU. CONCLUSIONS: PTU is capable of causing WG in susceptible patients with Graves' disease. Our patient did not require specific therapy for vasculitis and improved after discontinuation of PTU.

Reiter's syndrome among Asian shipboard immigrants: the case of The Golden Venture.

OBJECTIVE: To assess the incidence of Reiter's syndrome aboard The Golden Venture, a ship carrying illegal immigrants from China to the United States. METHODS: After identification of an index case, we conducted telephone interviews with medical staff at immigrant detention centers in Pennsylvania, New York, and Virginia. When a potential case was identified at one facility, we performed a site inspection, reviewing the medical records of all detainees and performing histories and physicals on all those with joint and/or ocular complaints. RESULTS: We identified two patients, both HLA B27 positive, with Reiter's syndrome. The observed incidence (0.87%) approximated the predicted incidence but may have underestimated the actual incidence. We review the history of shipboard Reiter's syndrome, and discuss the pathogenic roles of HLA B27 and particular infectious agents. CONCLUSION: Continued transportation of illegal immigrants from China and other parts of the world is likely to result in occasional clusters of Reiter's syndrome. Physicians treating immigrant populations should remain aware of the possibility of reactive arthritis.

The neutrophil in rheumatoid arthritis.

The destructive capacity of the neutrophil has long been appreciated, and the presence of extraordinary numbers of neutrophils in the synovial fluid of patients with RA supports a role for these cells in the pathogenesis of joint destruction. In this article, we reviewed the current state of knowledge of neutrophil function in the inflammatory response, and emphasized the subjects of neutrophil/endothelial adhesion and the role of chemoattractants and cytokines in neutrophil mobilization. We also discussed the mechanisms of action of neutrophil destruction of cartilage and the interplay of signals between the neutrophil and the chondrocyte. The capacity of many of the drugs used to treat RA to interfere with one or several of these processes underscores the importance of the neutrophil in RA and suggests that future therapeutic strategies could target neutrophil activation within the synovial space.