Therapy Insight: managing cardiovascular risk in patients with rheumatoid arthritis

Chronic low-grade inflammation was recognized during the past decade as an important risk factor for the development of atherosclerosis and, more recently, for the development of heart failure. Patients with rheumatoid arthritis (RA) are at increased risk of morbidity and mortality from ischemic cardiovascular events and heart failure. Epidemiologic and clinical studies indicate that RA is an independent risk factor for cardiovascular disease, which suggests that chronic exposure to high levels of inflammatory mediators contributes to this enhanced risk. The relative contribution of conventional risk factors to the acceleration of cardiovascular disease does not seem to be increased in patients with RA compared with control populations. Nonetheless, some preclinical laboratory measures of risk factors (e.g. insulin sensitivity) are adversely modulated in the context of the highly inflammatory rheumatoid microenvironment. Discerning the net effect of RA therapies on cardiovascular disease is also challenging because, theoretically, their biologic effects could either promote or attenuate atherosclerosis and ventricular dysfunction; however, available data suggest a beneficial effect on cardiovascular morbidity and mortality in patients with RA. This review provides an overview of the potential influence of RA and its treatment on the development and progression of cardiovascular disease, and outlines some preliminary recommendations for prevention and management of this complication in patients with RA.

Infliximab treatment maintains employability in patients with early rheumatoid arthritis

OBJECTIVE

To evaluate the impact of infliximab therapy on the employment status of patients with early rheumatoid arthritis (RA).

METHODS

Methotrexate (MTX)-naive patients with active early RA were randomly allocated to receive MTX plus placebo or MTX plus infliximab (3 mg/kg or 6 mg/kg) at weeks 0, 2, and 6 and then every 8 weeks through week 46. Data for patients younger than age 65 years were included in the analyses. A patient was categorized as employable if he or she was employed or felt well enough to work if a job were available.

RESULTS

The change in actual employment was not significantly different between patients receiving MTX plus infliximab and those receiving MTX plus placebo (0.5% versus 1.3%; P > 0.5). However, the proportion of patients whose status changed from employable at baseline to unemployable at week 54 was smaller in the group receiving MTX plus infliximab compared with that in the group receiving MTX alone (8% versus 14%; P = 0.05). Patients who were treated with infliximab plus MTX had a significantly greater likelihood of improvement rather than deterioration in employability (odds ratio 2.4; P < 0.001); this likelihood was not significantly greater in patients receiving MTX alone. The proportion of employed patients who lost workdays during the trial was smaller in the MTX plus infliximab group than in the MTX-alone group (P = 0.010).

CONCLUSION

The actual employment rates among patients in the 2 treatment groups were not different. However, patients with early RA who were treated with MTX plus infliximab had a higher probability of maintaining their employability compared with those who were treated with MTX alone.

Safety and efficacy of etanercept treatment in elderly subjects with rheumatoid arthritis

OBJECTIVE

To evaluate safety and efficacy of etanercept treatment in elderly (age > or = 65 yrs) and younger adult subjects (age < 65 yrs) with rheumatoid arthritis (RA).

METHODS

Subset analyses were used to describe the safety and efficacy of etanercept in elderly and younger subjects treated for early and disease modifying antirheumatic drug-resistant or late-stage RA (ERA and LRA) in one of 4 randomized controlled clinical studies (N = 1353) or 2 longterm extensions (N = 1049).

RESULTS

Rates of serious adverse events tended to be higher in elderly than younger subjects; however, rates of safety events observed in elderly etanercept-treated subjects did not exceed rates in elderly placebo or methotrexate (MTX)-treated subjects. With regard to efficacy measures [American College of Rheumatology 20% response (ACR20), ACR50, and ACR70], elderly subjects tended to have somewhat less robust responses to treatment than younger subjects. However, for both age groups, treatment with etanercept resulted in improved efficacy and function compared with control treatment, and combination therapy with etanercept plus MTX resulted in greater efficacy than either etanercept or MTX used alone. Efficacy responses of elderly subjects were sustained for up to 6 years. Radiographic progression (measured using modified Sharp Score) after one year of treatment was lower in subjects treated with both etanercept and MTX compared with subjects treated with either agent used alone, and this pattern was similar in both age groups.

CONCLUSION

Consistent with responses in younger subjects, elderly subjects with RA treated with etanercept experienced significant improvement in disease activity and function without incurring additional safety concerns.

Predictors of joint damage in patients with early rheumatoid arthritis treated with high-dose methotrexate with or without concomitant infliximab: Results from the ASPIRE trial

OBJECTIVE

To identify disease characteristics leading to progression of joint damage in patients with early rheumatoid arthritis (RA) treated with methotrexate (MTX) versus those treated with infliximab plus MTX.

METHODS

Patients who had not previously been treated with MTX with active RA were randomly assigned to receive escalating doses of MTX up to 20 mg/week plus placebo or infliximab at weeks 0, 2, and 6, and every 8 weeks thereafter through week 46. Radiographic joint damage was assessed using the modified Sharp/van der Heijde score (SHS). The relationship between disease activity measures at baseline and week 14, as well as those averaged over time, were examined in relation to the change in SHS from baseline through week 54.

RESULTS

C-reactive protein (CRP) levels, erythrocyte sedimentation rate (ESR), and swollen joint count were associated with greater joint damage progression in the MTX-only group, while none of these parameters was associated with progression in the infliximab plus MTX group. Mean changes in SHS among patients in the highest CRP (> or = 3 mg/dl) and ESR (> or = 52 mm/hour) tertiles in the MTX-only group were 5.62 and 5.89, respectively, compared with 0.73 and 1.12 in the infliximab plus MTX group (P < 0.001). Patients with greater joint damage at baseline (SHS > or = 10.5) showed less progression with infliximab plus MTX compared with MTX alone (-0.39 versus 4.11; P < 0.001). Patients receiving MTX alone who had persistently active disease at week 14 showed greater radiographic progression of joint damage than those taking MTX plus infliximab.

CONCLUSION

High CRP level, high ESR, or persistent disease activity was associated with greater radiographic progression in the group taking MTX alone, while little radiographic progression was seen in patients receiving both MTX and infliximab, regardless of the abnormal levels of these traditional predictors.

Myocardial dysfunction in rheumatoid arthritis: epidemiology and pathogenesis

Data from population- and clinic-based epidemiologic studies of rheumatoid arthritis patients suggest that individuals with rheumatoid arthritis are at risk for developing clinically evident congestive heart failure. Many established risk factors for congestive heart failure are over-represented in rheumatoid arthritis and likely account for some of the increased risk observed. In particular, data from animal models of cytokine-induced congestive heart failure have implicated the same inflammatory cytokines produced in abundance by rheumatoid synovium as the driving force behind maladaptive processes in the myocardium leading to congestive heart failure. At present, however, the direct effects of inflammatory cytokines (and rheumatoid arthritis therapies) on the myocardia of rheumatoid arthritis patients are incompletely understood.

Longterm safety, efficacy, and radiographic outcome with etanercept treatment in patients with early rheumatoid arthritis

OBJECTIVE

To evaluate safety, efficacy, and radiographic progression in patients with early rheumatoid arthritis (RA) undergoing longterm treatment with etanercept.

METHODS

Patients with early RA (disease duration of 3 years or less) who had completed a 2-year efficacy study comparing etanercept and methotrexate (MTX) were followed in an extension where they received 25 mg etanercept twice weekly. Safety was summarized descriptively and compared with data from the efficacy study. Efficacy and radiographic progression were assessed using American College of Rheumatology response criteria, disease activity scores, and Total Sharp Score (TSS).

RESULTS

Rates of serious adverse events and serious infections did not increase with longterm exposure to etanercept, and were similar to rates reported for the blinded portion of the efficacy study. Efficacy was sustained in patients who completed 5 years of etanercept treatment at the time of this report (N = 201), even in those who decreased or discontinued use of MTX or corticosteroids. No radiographic progression (change in TSS < or = 0) was seen in 55% of patients with 5-year radiographs; negative change (TSS < 0) was seen in 11%.

CONCLUSION

Etanercept treatment in patients with early RA was generally well tolerated for up to 5 years. The results indicate sustained efficacy and decreased rate of radiographic progression. The rate of radiographic progression was low compared with other studies, emphasizing the benefit gained in patients with early aggressive RA who undergo longterm treatment with etanercept.

The role of biologicals in early rheumatoid arthritis

Recent emphasis on early diagnosis and treatment of rheumatoid arthritis (RA) to improve long-term disease outcome has raised important questions about optimal therapy for early RA. With an expanding armamentarium of disease-modifying antirheumatic drugs including biological agents, there are now several therapeutic choices available to clinicians. However, at early stages of arthritis, difficulty in accurately predicting individual prognosis and response to therapy continues to pose a significant challenge. Future research in biomarkers of progressive, erosive disease and controlled trials to establish the most effective therapies in early RA will greatly enhance our ability to minimize the impact of this potentially disabling disease.

Etanercept: a clinical review of current and emerging indications

The recent development of inhibitors of TNF-alpha has provided the opportunity for a more targeted and highly effective approach to the treatment of chronic inflammatory illnesses such as rheumatoid arthritis. Since the initial approval of etanercept as a treatment for rheumatoid arthritis, additional indications, including psoriatic arthritis, juvenile rheumatoid arthritis and ankylosing spondylitis, have also received FDA approval. More than 220,000 patients have been treated with etanercept so far. This review summarises the body of knowledge accumulated so far on etanercept (Enbrel) since it entered the market 5 years ago.

Serious infections associated with anticytokine therapies in the rheumatic diseases

The ability to target and neutralize macrophage-derived inflammatory cytokines, particularly tumor necrosis factor-alpha (TNF-alpha), has emerged in recent years as one of the most important advances in the treatment of rheumatoid arthritis, Crohn's disease, and several other systemic inflammatory diseases. In rheumatoid arthritis, for example, these biological agents rapidly reduce signs and symptoms of joint inflammation and profoundly slow the progression of joint damage. However, data that have emerged following Food and Drug Administration approval of these agents have alerted clinicians to an increased likelihood of opportunistic infections in patients treated with these agents, particularly tuberculosis. The effect of TNF inhibition on the frequency of infection with more common bacterial pathogens is less clear. Animal models of tuberculosis and other opportunistic infections have demonstrated the importance of TNF-alpha in controlling and containing intracellular pathogens. The spectrum of infections reported to date in the setting of anti-TNF-alpha treatment is reviewed here. In addition, relevant animal data illustrating potential mechanistic roles for TNF-alpha in host responses to infection are also reviewed.

Combination of infliximab and methotrexate therapy for early rheumatoid arthritis: a randomized, controlled trial

OBJECTIVE

To compare the benefits of initiating treatment with methotrexate (MTX) and infliximab (anti-tumor necrosis factor alpha [anti-TNFalpha] monoclonal antibody) with those of MTX treatment alone in patients with rheumatoid arthritis (RA) of < or =3 years' duration.

METHODS

RA patients were eligible if they had active disease and no prior treatment with MTX or a TNFalpha inhibitor. One thousand forty-nine patients were randomly assigned in a 4:5:5 ratio to 3 treatment groups: MTX-placebo, MTX-3 mg/kg infliximab, and MTX-6 mg/kg infliximab. MTX dosages were rapidly escalated to 20 mg/week, and infliximab or placebo infusions were given at weeks 0, 2, and 6, and every 8 weeks thereafter through week 46.

RESULTS

At week 54, the median percentage of American College of Rheumatology improvement (ACR-N) was higher for the MTX-3 mg/kg infliximab and MTX-6 mg/kg infliximab groups than for the MTX-placebo group (38.9% and 46.7% versus 26.4%, respectively; P < 0.001 for both comparisons). Patients in the MTX-3 mg/kg infliximab and MTX-6 mg/kg infliximab groups also showed less radiographic progression than those receiving MTX alone (mean +/- SD changes in van der Heijde modification of the total Sharp score at week 54: 0.4 +/- 5.8 and 0.5 +/- 5.6 versus 3.7 +/- 9.6, respectively; P < 0.001 for each comparison). In addition, physical function improved significantly more in the MTX-3 mg/kg infliximab and MTX-6 mg/kg infliximab groups than in the MTX-placebo group. Infliximab therapy was associated with a significantly higher incidence of serious infections, especially pneumonia.

CONCLUSION

For patients with active RA in its early stages, combination therapy with MTX and infliximab provides greater clinical, radiographic, and functional benefits than treatment with MTX alone.

Spirituality, well-being, and quality of life in people with rheumatoid arthritis

OBJECTIVE

To evaluate spirituality, well-being, and quality of life (QOL) among people with rheumatoid arthritis (RA).

METHODS

Questionnaires assessing positive and negative affect, depression, QOL and spirituality were completed. Disease activity was assessed by rheumatologic examination.

RESULTS

Women (n = 62) had a mean (+/- SD) age of 53.0 (+/- 13.0) years with 12 (+/- 13) swollen and tender joints (STJ). Men (n = 15) were 61.9 (+/- 13.0) years with 7 (+/- 11) STJ. Disease activity was associated (P < 0.05) positively with depression (r = 0.23), pain (r = 0.26), poorer self-ratings of health (r = 0.29) and physical role limitations (r = 0.26). Spirituality was associated directly with positive affect (r = 0.26) and higher health perceptions (r = 0.29). In multiple regression, spirituality was an independent predictor of happiness and positive health perceptions, even after controlling disease activity and physical functioning, for age and mood.

CONCLUSION

Spirituality may facilitate emotional adjustment and resilience in people with RA by experiencing more positive feelings and attending to positive elements of their lives.

The Early Rheumatoid Arthritis (ERA) trial comparing the efficacy and safety of etanercept and methotrexate

The Early Rheumatoid Arthritis (ERA) trial compared monotherapy with etanercept or methotrexate in patients with early erosive rheumatoid arthritis. Over the initial period of 12, and subsequently 24, months both treatments were associated with a profound reduction in radiographic progression of joint damage, as well as a reduction in signs and symptoms of disease. Etanercept showed slight superiority to methotrexate in reducing subsequent radiographic erosions and in the rapidity of the clinical response. Both therapies proved to be safe and well tolerated and, importantly, the relative safety and tolerance of a rapidly escalated dosing regimen for methotrexate was demonstrated. In summary, early aggressive treatment of RA is associated with clinical and radiographic benefit that can be demonstrated after a relatively short period of treatment.

Knee osteoarthritis compromises early mobility function: The Women's Health and Aging Study II

OBJECTIVE

To examine associations between osteoarthritis (OA) of the knee and early functional limitations in a cohort of high-functioning older women, and evaluate the contributions of muscle strength, body weight, and pain severity to these limitations. Methods. Cross sectional analyses were conducted on baseline data of the Women's Health and Aging Study II (WHAS II), an observational study of disability transitions in a cohort of women aged 70-79 upon entry and who were representative of the one-third highest-functioning community-resident women. Standardized questionnaires and examinations were used to assess knee OA features, medication use, pain severity, knee extensor muscle strength, and body weight. Functional limitation was assessed using validated performance measures and self-report measures of task modification and task difficulty.

RESULTS

Sixty-nine women classified as "symptomatic" for knee OA, 48 with "asymptomatic/intermittently symptomatic," knee OA, and 285 with "no knee OA" were included in the final analysis. Despite selection for their high level of self-reported function, performance was slower and task modification was more frequently reported among women with knee OA than women without knee OA. Lower knee extensor strength, higher body weight, and greater pain severity were associated with knee OA, and also with functional limitations. Conclusion. Knee OA appeared to be associated with early functional limitations in this cohort of high-functioning, older, community-resident women. Lower knee extensor strength, higher body weight, and pain severity were closely associated with these limitations. The extent to which modification of these factors attenuates knee OA associated functional decline should be investigated.

Concomitant leflunomide therapy in patients with active rheumatoid arthritis despite stable doses of methotrexate. A randomized, double-blind, placebo-controlled trial

BACKGROUND

Disease-modifying antirheumatic drugs may confer greater benefits when combined with the antimetabolite methotrexate.

OBJECTIVE

To evaluate the efficacy and safety of leflunomide versus placebo when added to ongoing, stable-dose methotrexate therapy in patients with persistently active rheumatoid arthritis.

DESIGN

24-week, multicenter, randomized, double-blind, placebo-controlled trial.

SETTING

20 centers in the United States and Canada.

PATIENTS

Patients with persistent rheumatoid arthritis, as defined by American College of Rheumatology (ACR) criteria, despite receiving methotrexate for at least 6 months.

INTERVENTION

Leflunomide or matching placebo added to existing methotrexate therapy.

MEASUREMENTS

The primary efficacy variable was the rate of achievement of 20% improvement in ACR criteria (ACR20) at the end of the study. The Health Assessment Questionnaire Disability Index was assessed at each visit, and the Medical Outcomes Study 36-Item Short Form was completed as an end point analysis.

RESULTS

In the leflunomide and placebo groups, 46.2% and 19.5% of patients, respectively, met ACR20 criteria at 24 weeks (P < 0.001). Clinical improvement was demonstrated by statistically significant mean changes in individual components of the ACR20 response criteria. Discontinuation rates were similar in both treatment groups (23.1% in the leflunomide group and 24.8% in the placebo group), as were the overall incidences of adverse events (89.2% vs. 89.5%, respectively). Adverse events were predominantly mild or moderate.

CONCLUSIONS

Combination therapy with leflunomide and methotrexate provides statistically significant clinical benefit in patients with active rheumatoid arthritis who are receiving methotrexate therapy. Leflunomide plus methotrexate is generally well tolerated and can be used safely with appropriate liver enzyme and hematologic monitoring.

Etanercept versus methotrexate in patients with early rheumatoid arthritis: two-year radiographic and clinical outcomes

OBJECTIVE

To compare the clinical and radiographic outcomes in patients with rheumatoid arthritis (RA) who received monotherapy with either etanercept or methotrexate (MTX) for 2 years and to assess the safety of this therapy.

METHODS

In the Enbrel ERA (early rheumatoid arthritis) trial, 632 patients with early, active RA were randomized to receive either twice-weekly subcutaneous etanercept (10 mg or 25 mg) or weekly oral MTX (mean dosage 19 mg per week) for at least 1 year in a double-blind manner. Following the blinded phase of the trial, 512 patients continued to receive the therapy to which they had been randomized for up to 1 additional year, in an open-label manner. Radiograph readers remained blinded to treatment group assignment and the chronologic order of images.

RESULTS

At 24 months, more 25-mg etanercept patients than MTX patients met American College of Rheumatology 20% improvement criteria (72% and 59%, respectively; P = 0.005), and more had no increase in total score and erosion scores on the Sharp scale (P = 0.017 and P = 0.012, respectively). The mean changes in total Sharp score and erosion score in the 25-mg etanercept group (1.3 and 0.66 units, respectively) were significantly lower than those in the MTX group (3.2 and 1.86 units, respectively; P = 0.001). Significantly more patients in the 25-mg etanercept group (55%) than in the MTX group (37%) had at least 0.5 units of improvement in the Health Assessment Questionnaire disability index (P < 0.001). Fewer patients in the etanercept group than in the MTX group experienced adverse events or discontinued treatment because of adverse events.

CONCLUSION

Etanercept as monotherapy was safe and was superior to MTX in reducing disease activity, arresting structural damage, and decreasing disability over 2 years in patients with early, aggressive RA.

How common is hip pain among older adults? Results from the Third National Health and Nutrition Examination Survey

OBJECTIVE

To determine the incidence of self-reported significant hip pain using a nationally representative sample of older adults in the United States.

STUDY DESIGN

Subjects were interviewed to determine their leisure time physical activity levels and whether they experienced severe hip pain. Sampling weights were calculated to account for unequal selection probabilities. The impact of race, age, and physical activity status was examined as influential factors affecting hip pain.

POPULATION

We interviewed 6596 adults aged 60 years and older as part of the third National Health and Nutrition Examination Survey (NHANES III).

OUTCOME MEASURED

We measured the prevalence of hip pain.

RESULTS

A total of 14.3% of participants aged 60 years and older reported significant hip pain on most days over the past 6 weeks. Men reported hip pain less frequently than women. Age did not influence self-reported hip pain in men. The lowest prevalence of hip pain was found in women aged 60 to 70 years. Sixteen percent of non-Hispanic white women reported hip pain, compared with 14.8% of black women and 19.3% of Mexican American women. Among non-Hispanic white men, 12.4% reported hip pain, a proportion no different from that of their black and Mexican American male counterparts. Among older US adults, 18.4% of those who had not participated in leisure time physical activity during the previous month reported severe hip pain; 12.6% of those who did engage in physical activity reported hip pain.

CONCLUSIONS

Self-reported hip pain has increased since NHANES I (1971-1975). Further studies are needed to identify individuals at highest risk for severe hip pain and to identify optimal treatment of hip pain.

A comparison of etanercept and methotrexate in patients with early rheumatoid arthritis

BACKGROUND

Etanercept, which blocks the action of tumor necrosis factor, reduces disease activity in patients with long-standing rheumatoid arthritis. Its efficacy in reducing disease activity and preventing joint damage in patients with active early rheumatoid arthritis is unknown.

METHODS

We treated 632 patients with early rheumatoid arthritis with either twice-weekly subcutaneous etanercept (10 or 25 mg) or weekly oral methotrexate (mean, 19 mg per week) for 12 months. Clinical response was defined as the percent improvement in disease activity according to the criteria of the American College of Rheumatology. Bone erosion and joint-space narrowing were measured radiographically and scored with use of the Sharp scale. On this scale, an increase of 1 point represents one new erosion or minimal narrowing.

RESULTS

As compared with patients who received methotrexate, patients who received the 25-mg dose of etanercept had a more rapid rate of improvement, with significantly more patients having 20 percent, 50 percent, and 70 percent improvement in disease activity during the first six months (P<0.05). The mean increase in the erosion score during the first 6 months was 0.30 in the group assigned to receive 25 mg of etanercept and 0.68 in the methotrexate group (P= 0.001), and the respective increases during the first 12 months were 0.47 and 1.03 (P=0.002). Among patients who received the 25-mg dose of etanercept, 72 percent had no increase in the erosion score, as compared with 60 percent of patients in the methotrexate group (P=0.007). This group of patients also had fewer adverse events (P=0.02) and fewer infections (P= 0.006) than the group that was treated with methotrexate.

CONCLUSIONS

As compared with oral methotrexate, subcutaneous [corrected] etanercept acted more rapidly to decrease symptoms and slow joint damage in patients with early active rheumatoid arthritis.

Prevalence of significant knee pain among older Americans: results from the Third National Health and Nutrition Examination Survey

OBJECTIVE

To assess the prevalence of persistent knee pain among older adults in the US.

DESIGN

A nationally representative cross-sectional survey with an in-person interview and medical examination

SETTING AND PARTICIPANTS

Between 1988 and 1994, 6596 adults aged 60 to 90+ years were examined as part of the National Health and Nutrition Examination Survey III. Mexican Americans and non-Hispanic blacks were over-sampled to produce reliable estimates for these groups.

MAIN OUTCOME MEASUREMENTS

Participants were asked to report whether they had experienced knee pain on most days for the 6 weeks preceding their medical exam.

RESULTS

Overall, 18.1% of US men and 23.5% of US women aged 60 years and older reported knee pain. Sixty- to ninety-year-old men reported knee pain less frequently than their age-matched female counterparts. There was a trend for reports of knee pain to increase steadily as these adults aged from 60 to 85 years. The highest prevalence of knee pain was reported among 85- to 90-year-old men (23.7%) and women (30.0%). Among non-Hispanic white adults older than age 60, 18.4% of men and 22.0% of women reported knee pain. Reports of knee pain among non-Hispanic black men and Mexican American men were similar to those of their non-Hispanic white counterparts. In contrast, 26.4% of Mexican American women and 32.8% of non-Hispanic black women reported knee pain. We also found that difficulty in performing physical functioning activities was associated with a higher prevalence of knee pain.

CONCLUSIONS

Many US adults older than age 60 years report knee pain, and the prevalence is higher in older adults. Reports of knee pain are highest among non-Hispanic black women and the oldest Americans. Intervention strategies are needed to prevent and better manage knee pain among older US adults to stem the adverse health consequences and diminished quality of life associated with this common problem.

Comparison of the responses of B1 and B2 kinin receptors to agonist stimulation

The human B2 kinin receptor (B2KR), stably expressed in Chinese hamster ovary cells, responded to bradykinin stimulation with rapid (within minutes) ligand internalization and loss of cell surface receptors (sequestration). By contrast, B1 kinin receptors (B1KR) showed almost no ligand internalization or receptor sequestration upon stimulation with des-Arg10-Kallidin (DAK). The ability of the B2KR to internalize and sequester is conferred by information in the cytoplasmic tail of the receptor. It is normally impossible to determine receptor affinity at 37 degrees C because of internalization and sequestration processes. We created a mutant B2KR, truncated at K315 of the cytoplasmic tail, that was no longer able to internalize or sequester, and compared the affinity of this mutant, and of the B1KR, at 0 degrees C and 37 degrees C. The B1KR receptor showed the same affinity (Kd = 0.4 nM) at both 0 degrees C and 37 degrees C. By contrast, the K315 mutant of the B2KR showed a lower affinity (Kd = 2.9 nM) at 37 degrees C than at 0 degrees C (Kd = 1.4 nM), indicating more rapid ligand dissociation at 37 degrees C. After ligand exposure, clones expressing B1KR exhibited a very slow dissociation of DAK, even at 37 degrees C. Although both kinin receptor subtypes induce the generation of inositol phosphates, functional responses showed clear differences. The response to stimulation of the B2KR comprises a rapid loss of functional responses, receptor sequestration, and ligand dissociation, and, upon long term stimulation, downregulation. By contrast, ligand stimulation of the B1KR, once this receptor is expressed de novo under pathological conditions, results in persistent signaling due to lack of ligand dissociation, desensitization and receptor sequestration. Moreover, long term stimulation of this receptor actually leads to increased expression.

Coupling of the PTH/PTHrP receptor to multiple G-proteins. Direct demonstration of receptor activation of Gs, Gq/11, and Gi(1) by [alpha-32P]GTP-gamma-azidoanilide photoaffinity labeling

Parathyroid hormone (PTH) elicits many of its physiological effects by activating distinct, G-protein-coupled signaling cascades that lead to synthesis of cyclic AMP and hydrolysis of phosphatidylinositol 4,5-bisphosphate. Using the nonhydrolyzable photo-reactive GTP analog [alpha-32P]GTP-gamma-azidoanilide (GTP-AA) and peptide antisera raised against G-protein alpha-subunits, we studied coupling of the PTH receptor to G-proteins in rat osteoblast-like cells (ROS 17/2.8), and in human embryonal kidney cells expressing the cloned human PTH/parathyroid hormone-related peptide (PTHrP) receptor at 40,000 receptors/cell (C20) or 400,000 receptors/cell (C21). Incubation of C21 membranes (but not C20 membranes) with [Nle8,18, Tyr34]-bovine PTH(1-34) amide (bPTH[1-34]) led to concentration-dependent incorporation of GTP-AA into the two isoforms of G alpha s, into G alpha q/11, and to a much lesser extent into G alpha i(1). In ROS 17/2.8 cells, bPTH(1-34) increased the incorporation of GTP-AA into G alpha s, but not into G alpha q/11 or G alpha i. The ability of bPTH(1-34) to increase labeling of G alpha s and G alpha q/11 was correlated with the receptor-dependent sensitivity of the adenylyl cyclase and phospholipase C signaling pathways to the hormone.

Osteoarthritis in older adults

OBJECTIVE

This review highlights the clinical and pathophysiologic features of osteoarthritis (OA) of the peripheral joints and discusses the current and future management options for this common but potentially disabling disease. This article also addresses the contribution of osteoarthritis to falls and functional impairment in older people.

DESIGN

A critical assessment of current data regarding the pathogenesis of osteoarthritis, current and future therapies, and the potential role of OA in falls and functional impairment in older people.

CONCLUSIONS

Osteoarthritis is the most prevalent articular disease in older adults. Disease markers that will detect early disease and allow early intervention with pharmacologic agents that modify, if not halt, disease progression are much needed, but they are presently unavailable. Current management should include safe and adequate pain relief using systemic and local therapies and should also include medical and rehabilitative interventions to prevent, or at least compensate for, functional deficits. Although OA can result in impaired mobility and lower extremity function, its contribution as a cause of recurrent falls or impaired self-care, relative to other comorbid conditions, remains ill-defined. Further analysis of the determinants of disability, loss of mobility and falls in older patients with OA is needed.

Soluble recombinant neutral endopeptidase (CD10) as a potential antiinflammatory agent

Several endogenous peptides, including bradykinin and substance P, have potent inflammatory effects in the joint. Levels of these peptides are regulated by plasma and cell-associated peptide degrading enzymes. One of these peptidases, neutral endopeptidase-24.11 (NEP-24.11), is expressed constitutively and in high density on human synovial cells and is presumed to play a critical role in local regulation of peptide levels in the joint. We examined the role of endogenous NEP-24.11 in regulating bradykinin-mediated effects in an articular model, and investigated the ability of soluble, recombinant human NEP-24.11 to augment the effects of the endogenous enzyme. Our studies demonstrate that endogenous synovial NEP-24.11 does not significantly modulate inflammatory peptide effects on cells when competing with colocalizing peptide receptors expressed in high density. Administration of excess, soluble recombinant NEP-24.11 can overcome this problem, however. Furthermore, the activity of the recombinant enzyme was not compromised in the presence of oxidants or inflammatory joint fluids. Recombinant NEP-24.11 holds promise as a novel therapeutic strategy for the treatment of inflammatory arthritis.

Influence of the cytosolic carboxyl termini of human B1 and B2 kinin receptors on receptor sequestration, ligand internalization, and signal transduction

To determine the role of the cytoplasmic carboxyl termini of human B1 and B2 kinin receptors (B1KR and B2KR, respectively) in the internalization of their respective ligands, des-Arg10-kallidin and bradykinin (BK), both wild type receptors, as well as truncated B2KRs, a mutated B2KR, and chimeric receptors were stably expressed in Chinese hamster ovary cells. Incubation of [3H]BK at 37 degrees C with cells expressing wild type B2KR resulted in pronounced and rapid ligand internalization ( approximately 80% after 10 min). By contrast, incubation of 3H-labeled des-Arg10-kallidin with cells expressing B1KR resulted in a modest, slow internalization of the ligand (<20% after 10 min). Replacement, from Cys324, of the cytoplasmic carboxyl terminus of the B2KR with that of the B1KR from Cys330 (both Cys residues are putative palmitoylation sites) greatly reduced ligand internalization ( approximately 40% after 10 min) without significantly altering Kd or ligand-induced signal activation. By marked contrast, the corresponding replacement, of the sequence from Cys330 of the cytoplasmic carboxyl terminus of the B1KR with the segment of the B2KR, led to a striking increase of ligand internalization ( approximately 75% within 10 min) without altering Kd or ligand-induced signal activation. Truncation of the B2KR to within three amino acids of Cys324 (truncation at Gly327) led to strongly reduced ligand internalization ( approximately 40% after 10 min). Truncation of the B2KR up to Lys315 almost completely abolished internalization of [3H]BK (10% after 10 min). This additional reduction is apparently not caused by the loss of the potential palmitoylation site at Cys324, since a B2KR with a point mutation of Cys324 to Ala internalized [3H]BK as rapidly as the wild type B2KR. From these results we conclude that the cytoplasmic carboxyl terminus of the human B2KR contains sequences that are necessary and sufficient to permit rapid ligand-induced sequestration of human kinin receptors and internalization of their agonists.

Stable expression of the human kinin B1 receptor in Chinese hamster ovary cells. Characterization of ligand binding and effector pathways

To delineate ligand binding and functional characteristics of the human B1 kinin receptor, a stable clone of Chinese hamster ovary cells expressing a single class of binding sites for [3H]des-Arg10-lysylbradykinin with a Kd of 0.3 nM and a Bmax of 38 fmol/mg protein ( approximately 40,000 receptors/cell) was isolated. Studies with peptide analogs showed that a lysine residue at position 1 (based on the lysylbradykinin sequence) of ligands was essential for high affinity binding to the human B1 receptor. In marked contrast to cloned Chinese hamster ovary cells expressing the human kinin B2 receptor, which internalized approximately 80% of the ligand within 5 min upon exposure to 2 nM [3H]bradykinin, exposure of cells expressing the B1 receptor to 1 nM [3H]des-Arg10-lysylbradykinin resulted in minimal ligand internalization. Stimulation of the B1 receptor led to inositol phosphate generation and transient increases in intracellular calcium, confirming coupling to phospholipase C, while immunoprecipitation of photoaffinity-labeled G-proteins from membranes indicated specific coupling of the receptor to Galphaq/11 and Galphai1,2. The B1, unlike the B2, receptor does not desensitize (as demonstrated by continuous phosphoinositide hydrolysis), enhancing the potential role of this receptor during inflammatory events.