Urinary TIINE concentrations in a randomized controlled trial of doxycycline in knee osteoarthritis: Implications of the lack of association between TIINE levels and joint space narrowing

Erythromycin acts through the ghrelin receptor to attenuate inflammatory responses in chondrocytes and maintain joint integrity

Osteoarthritis (OA) is a prevalent disease characterized by chronic joint degeneration and low-grade localized inflammation. There is no available treatment to delay OA progression. We report that in human primary articular chondrocytes, erythromycin, a well-known macrolide antibiotic, had the ability to inhibit pro-inflammatory cytokine Interleukin 1β (IL-1β)-induced catabolic gene expression and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. Furthermore, erythromycin inhibited monosodium iodoacetate (MIA)-induced joint inflammation and cartilage matrix destruction in mice, an arthritis model that reflects the inflammatory and cartilage matrix loss aspects of OA. EM900, an erythromycin-derivative lacking antibiotic function, had the same activity as erythromycin in vitro and in vivo, indicating distinct anti-inflammatory and antibiotic properties. Using an antibody against erythromycin, we found erythromycin was present on chondrocytes in a dose-dependent manner. The association of erythromycin with chondrocytes was diminished in ghrelin receptor null chondrocytes, and administration of the ghrelin ligand prevented the association of erythromycin with chondrocytes. Importantly, the anti-inflammatory activity of erythromycin was diminished in ghrelin receptor null chondrocytes. Moreover, erythromycin could not exert its chondroprotective effect in ghrelin receptor null mice, and the loss of ghrelin receptor further augmented joint damage upon MIA-injection. Therefore, our study identified a novel pharmacological mechanism for how erythromycin exerts its chondroprotective effect. This mechanism entails ghrelin receptor signaling, which is necessary for alleviating inflammation and joint destruction.

The Chondroprotective Role of Erythromycin in a Murine Joint Destruction Model

OBJECTIVE

Inflammation is a major player in the joint destruction process. Macrolide antibiotics have recently been found to have a novel anti-inflammatory function, but their effects on the joint are unknown. Our objective was to investigate the effect of macrolide antibiotic erythromycin on cartilage gene expression under inflammatory conditions as well as on joint pathology in an in vivo inflammatory joint destruction model.

DESIGN

In our in vivo studies, mouse knee joints were injected with monosodium iodoacetate (MIA), a chemical that inhibits glycolysis and causes joint inflammation and matrix loss. Erythromycin was administered by daily intraperitoneal injection. Changes in joint cartilage and synovium were evaluated by histological analysis. In our in vitro studies, primary bovine articular chondrocytes were treated with erythromycin in the presence of pro-inflammatory cytokine IL-1β or lipopolysaccharide (LPS), and cartilage gene expression analysis was performed.

RESULTS

Regional differences in cartilage matrix destruction along the medial-lateral axis were observed in joints of MIA-injected mice. Erythromycin treatment inhibited cartilage matrix loss and synovitis in these joints. In addition, erythromycin inhibited IL-1β and LPS-induced expression of MMPs and iNOS, as well as the positive regulatory loop between IL-1β and Toll-like receptor 4 (TLR4) in articular chondrocytes. Furthermore, erythromycin prevented LPS-induced NF-κB activation, a key mediator of TLR4-mediated cartilage destruction process.

CONCLUSIONS

Erythromycin has the ability to inhibit catabolic gene expression mediated by IL-1β and TLR4 in chondrocytes in vitro and maintains cartilage matrix levels in experimental inflammatory joint destruction in vivo, suggesting that it possesses a chondroprotective activity.

The road forward: the scientific basis for tetracycline treatment of arthritic disorders

The potential role of a collagenase inhibitor for treatment of arthritis was recognized almost immediately after the discovery of vertebrate collagenase. Yet despite vast efforts from the pharmaceutical industry, no such drug has been approved for such use by a regulatory agency. Although two semisynthetic antimicrobial tetracyclines, viz. minocycline and doxycycline, have been shown to have modest clinical benefits in over a dozen trials in rheumatoid arthritis, neither drug is in widespread use. The almost universal use of methotrexate and the rapid development of potent biologic agents have eclipsed the potential usage of TETs for RA. Ironically, it is in osteoarthritis, where there has only been one clinical trial which essentially failed, that the best potential exists for use of an MMP-inhibiting TET.

Osteoarthritis: an update with relevance for clinical practice

Osteoarthritis is thought to be the most prevalent chronic joint disease. The incidence of osteoarthritis is rising because of the ageing population and the epidemic of obesity. Pain and loss of function are the main clinical features that lead to treatment, including non-pharmacological, pharmacological, and surgical approaches. Clinicians recognise that the diagnosis of osteoarthritis is established late in the disease process, maybe too late to expect much help from disease-modifying drugs. Despite efforts over the past decades to develop markers of disease, still-imaging procedures and biochemical marker analyses need to be improved and possibly extended with more specific and sensitive methods to reliably describe disease processes, to diagnose the disease at an early stage, to classify patients according to their prognosis, and to follow the course of disease and treatment effectiveness. In the coming years, a better definition of osteoarthritis is expected by delineating different phenotypes of the disease. Treatment targeted more specifically at these phenotypes might lead to improved outcomes.

Application of biomarkers in the development of drugs intended for the treatment of osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is a chronic and slowly progressive disease for which biomarkers may be able to provide a more rapid indication of therapeutic responses to therapy than is currently available; this could accelerate and facilitate OA drug discovery and development programs. The goal of this document is to provide a summary and guide to the application of in vitro (biochemical and other soluble) biomarkers in the development of drugs for OA and to outline and stimulate a research agenda that will further this goal.

METHODS

The Biomarkers Working Group representing experts in the field of OA biomarker research from both academia and industry developed this consensus document between 2007 and 2009 at the behest of the Osteoarthritis Research Society International Federal Drug Administration initiative (OARSI FDA initiative).

RESULTS

This document summarizes definitions and classification systems for biomarkers, the current outcome measures used in OA clinical trials, applications and potential utility of biomarkers for development of OA therapeutics, the current state of qualification of OA-related biomarkers, pathways for biomarker qualification, critical needs to advance the use of biomarkers for drug development, recommendations regarding practices and clinical trials, and a research agenda to advance the science of OA-related biomarkers.

CONCLUSIONS

Although many OA-related biomarkers are currently available they exist in various states of qualification and validation. The biomarkers that are likely to have the earliest beneficial impact on clinical trials fall into two general categories, those that will allow targeting of subjects most likely to either respond and/or progress (prognostic value) within a reasonable and manageable time frame for a clinical study (for instance within 1-2 years for an OA trial), and those that provide early feedback for preclinical decision-making and for trial organizers that a drug is having the desired biochemical effect. As in vitro biomarkers are increasingly investigated in the context of specific drug treatments, advances in the field can be expected that will lead to rapid expansion of the list of available biomarkers with increasing understanding of the molecular processes that they represent.

Relationship between radiographic changes and symptoms or physical examination findings in subjects with symptomatic medial knee osteoarthritis: a three-year prospective study

BACKGROUND

Although osteoarthritis (OA) of the knee joints is the most common and debilitating joint disease in developed countries, the factors that determine the severity of symptoms are not yet understood well. Subjects with symptomatic medial knee OA were followed up prospectively to explore the relationship between radiographic changes and symptoms or physical examination findings.

METHODS

One-hundred six OA knees in 68 subjects (mean age 71.1 years; 85% women) were followed up at 6-month intervals over 36 months. At each visit, knee radiographs were obtained, symptoms were assessed by a validated questionnaire, and the result of physical examination was recorded systematically using a specific chart. Correlations between the change of radiographs and clinical data were investigated in a longitudinal manner.

RESULTS

During the study period, the narrowing of joint space width (JSW) was observed in 34 joints (32%). Although those knees were clinically or radiographically indistinguishable at baseline from those without JSW narrowing, differences became apparent at later visits during the follow-up. The subjects with knees that underwent JSW narrowing had severer symptoms, and the symptoms tended to be worse for those with higher rates of narrowing. A significant correlation was not found between the severity of symptoms and the growth of osteophytes. For the knees that did not undergo radiographic progression, the range of motion improved during the follow-up period, possibly due to the reduction of knee pain. Such improvement was not observed with the knees that underwent JSW narrowing or osteophyte growth.

CONCLUSION

The result of this study indicates that the symptoms of knee OA patients tend to be worse when JSW narrowing is underway. This finding may explain, at least partly, a known dissociation between the radiographic stage of OA and the severity of symptoms.

Cartilage degradation biomarkers predict efficacy of a novel, highly selective matrix metalloproteinase 13 inhibitor in a dog model of osteoarthritis: confirmation by multivariate analysis that modulation of type II collagen and aggrecan degradation peptides parallels pathologic changes

OBJECTIVE

To demonstrate that the novel highly selective matrix metalloproteinase 13 (MMP-13) inhibitor PF152 reduces joint lesions in adult dogs with osteoarthritis (OA) and decreases biomarkers of cartilage degradation.

METHODS

The potency and selectivity of PF152 were evaluated in vitro using 16 MMPs, TACE, and ADAMTS-4 and ADAMTS-5, as well as ex vivo in human cartilage explants. In vivo effects were evaluated at 3 concentrations in mature beagles with partial medial meniscectomy. Gross and histologic changes in the femorotibial joints were evaluated using various measures of cartilage degeneration. Biomarkers of cartilage turnover were examined in serum, urine, or synovial fluid. Results were analyzed individually and in combination using multivariate analysis.

RESULTS

The potent and selective MMP-13 inhibitor PF152 decreased human cartilage degradation ex vivo in a dose-dependent manner. PF152 treatment of dogs with OA reduced cartilage lesions and decreased biomarkers of type II collagen (type II collagen neoepitope) and aggrecan (peptides ending in ARGN or AGEG) degradation. The dose required for significant inhibition varied with the measure used, but multivariate analysis of 6 gross and histologic measures indicated that all doses differed significantly from vehicle but not from each other. Combined analysis of cartilage degradation markers showed similar results.

CONCLUSION

This highly selective MMP-13 inhibitor exhibits chondroprotective effects in mature animals. Biomarkers of cartilage degradation, when evaluated in combination, parallel the joint structural changes induced by the MMP-13 inhibitor. These data support the potential therapeutic value of selective MMP-13 inhibitors and the use of a set of appropriate biomarkers to predict efficacy in OA clinical trials.

In vitro inhibition of aggrecanase activity by tetracyclines and proteoglycan loss from osteoarthritic human articular cartilage

Tetracyclines were reported to slow down the progression of cartilage damage both in an animal model of osteoarthritis (OA) and in humans. In search for the underlying mechanisms we examined whether tetracyclines possess an inhibitory potential on the activity of aggrecanases and inflammatory mediators and can thus prevent proteoglycan (PG) loss from human articular cartilage. In vitro activity of aggrecanase-1 and -2 was recorded in the presence of 1-100 microM tetracycline, minocycline, or doxycyline. Human knee articular cartilage explants were sorted according to the degree of OA and treated for 10 days with tetracycline derivatives in the presence of interleukin-1 (IL-1beta). Synthesis and loss of PGs, nitric oxide (NO), and prostaglandin E(2) (PGE(2)), as well as the viability were determined. Tetracyclines derivatives dose-dependently inhibited the activities of both aggrecanases in vitro, whereas no inhibitory effect of tetracyclines on any proteoglycanolytic activities within IL-1beta-treated human cartilage explants were found. Tetracyclines can significantly modulate NO and PGE(2) levels, but have no effect on PG synthesis and loss within the same human cartilage explant cultures. Altogether, our data show that tetracyclines have no inhibitory potential on any proteoglycanolytic activities within mild or moderately affected human OA cartilage at therapeutic achievable plasma levels.

Serum and urinary biochemical markers for knee and hip-osteoarthritis: a systematic review applying the consensus BIPED criteria

CONTEXT

Molecules that are released into biological fluids during matrix metabolism of articular cartilage, subchondral bone, and synovial tissue could serve as biochemical markers of the process of osteoarthritis (OA). Unfortunately, actual breakthroughs in the biochemical OA marker field are limited so far.

OBJECTIVE

By reviewing the status of commercially available biochemical OA markers according to the "Burden of disease, Investigative, Prognostic, Efficacy of intervention, and Diagnostic" ("BIPED") classification, future use of this "BIPED" classification is encouraged and more efficient biochemical OA marker research stimulated.

DATA SOURCES

Three electronic databases [PubMed, Scopus, EMBASE (1997-May 2009)] were searched for publications on blood and urinary biochemical markers in human primary knee and hip-OA.

STUDY SELECTION

Stepwise selection of original English publications describing human studies on blood or urinary biochemical markers in primary knee or hip-OA was performed. Selected articles were fully read to determine whether biochemical markers were investigated on performance within any of the "BIPED" categories. Eighty-four relevant publications were identified.

DATA EXTRACTION

Data from relevant publications were tabulated according to the "BIPED" classification. Individual analyses within a publication were summarized in general "BIPED" scores.

DATA SYNTHESIS

An uneven distribution of scores on biochemical marker performance and heterogeneity among the publications complicated direct comparison of individual biochemical markers. Comparison of categories of biochemical markers was therefore performed instead. In general, biochemical markers of cartilage degradation were investigated most extensively and performed well in comparison with other categories of biochemical markers. Biochemical markers of bone metabolism performed less adequately. Biochemical markers of synovial tissue metabolism were not investigated extensively, but performed quite well.

CONCLUSIONS

Specific biochemical markers and categories of biochemical markers as well as their nature, origin and metabolism, need further investigation. International standardization of future investigations should be pursued to obtain more high-quality, homogenous data on the full spectrum of biochemical OA markers.

Selective MMP13 inhibitors

Pharmacology of MMP13 and MMP13 selective inhibitors is reviewed.

Biomarkers in the development of novel disease-modifying therapies for osteoarthritis

Identification and utilization of biomarkers is vitally important for the successful development of disease-modifying osteoarthritis drugs. Biochemical and imaging platforms hold great promise to deliver such biomarkers. Studies indicate a marked increase in biochemical products arising from the breakdown and biosynthesis of collagen, extracellular matrix and bone in osteoarthritis. These molecules have been associated with disease severity and may also have prognostic value as indicators of disease progression. However, issues including biological variability and lack of tissue specificity currently hinder the utility of these molecular markers in drug development. Imaging technologies hold great potential for sensitive and accurate measurement of disease-related structural damage. Drawbacks, including expense, need for validation and limited accessibility also limit the utility of these technologies. In this article, the potential value and challenges in developing and utilizing biomarkers in disease-modifying osteoarthritis drug development will be discussed.