Cécile Guillaume

Obesity affects the chondrocyte responsiveness to leptin in patients with osteoarthritis.

IntroductionIncreasing evidence support the regulatory role of leptin in osteoarthritis (OA). As high circulating concentrations of leptin disrupt the physiological function of the adipokine in obese individuals, the current study has been undertaken to determine whether the elevated levels of leptin found in the joint from obese OA patients also induce changes in the chondrocyte response to leptin.MethodsChondrocytes isolated from OA patients with various body mass index (BMI) were treated with 20, 100 or 500 ng/ml of leptin. The expression of cartilage-specific components (aggrecan, type 2 collagen), as well as regulatory (IGF-1, TGFβ, MMP-13, TIMP 2) or inflammatory (COX-2, iNOS, IL-1) factors was investigated by real-time PCR to evaluate chondrocyte responsiveness to leptin. Furthermore, the effect of body mass index (BMI) on leptin signalling pathways was analyzed with an enzyme-linked immunosorbent assay for STATs activation.ResultsLeptin at 20 ng/ml was unable to modulate gene expression in chondrocytes, except for MMP-13 in obese OA patients. Higher leptin levels induced the expression of IGF-1, type 2 collagen, TIMP-2 and MMP-13. However, the activity of the adipokine was shown to be critically dependent on both the concentration and the BMI of the patients with a negative association between the activation of regulated genes and BMI for 100 ng/ml of adipokine, but a positive association between chondrocyte responsiveness and BMI for the highest leptin dose. In addition, the gene encoding MMP-13 was identified as a target of leptin for chondrocytes originated from obese patients while mRNA level of TIMP-2 was increased in leptin-treated chondrocytes collected from normal or overweight patients. The adipokine at 500 ng/ml triggered signal transduction through a STAT-dependent pathway while 100 ng/ml of leptin failed to activate STAT 3 but induced STAT 1α phosphorylation in chondrocytes obtained from obese patients.ConclusionsThe current study clearly showed that characteristics of OA patients and more expecially obesity may affect the responsiveness of cultured chondrocytes to leptin. In addition, the BMI-dependent effect of leptin for the expression of TIMP-2 and MMP-13 may explain why obesity is associated with an increased risk for OA.

Articular diffusion of Meloxicam after a single oral dose : Relationship to cyclo-oxygenase inhibition in synovial cells

ObjectiveTo investigate the distribution of meloxicam in the human knee joint and to compare it with the inhibition of cyclo-oxygenase (COX) activity in synovial cells.DesignProspective pharmacokinetic study and in vitro laboratory investigation.Patients and participants42 male and female patients aged 26 to 85 years hospitalised for rheumatic disease and requiring a diagnostic and/or therapeutic knee puncture.MethodsAfter a single oral dose of meloxicam 15mg, synovial fluid and blood samples were collected once per patient at various intervals after administration. Meloxicam concentrations were determined by a validated high performance liquid chromatography assay, protein binding by equilibrium dialysis, and pharmacokinetic parameters were calculated by noncompartmental analysis from the mean drug concentration-time profiles. The inhibitory effect of meloxicam on COX activity was investigated separately in unstimulated or interleukin-1 β-stimulated human synovial cells from osteoarthritic patients.ResultsMeloxicam was found in synovial fluid at the earliest sampling time (1 hour). Peak concentrations were reached approximately 6 hours postdose in both plasma (842 µg/L) and synovial fluid (320 µg/L). A plateau was observed after the distribution phase (6 hours), corresponding to a constant ratio of drug concentration between synovial fluid and plasma of about 0.47. This ratio was higher in patients with acute inflammation (0.58) than in those with no inflammation (0.38). Meloxicam was extensively bound to protein, mainly to serum albumin. The area under the drug concentration-time curve (AUC) in plasma was more than 2.5 times that in synovial fluid. The AUC for free meloxicam was similar in plasma and synovial fluid. The 50% inhibitory concentrations (IC50) for basal and stimulated COX activity in human synovial cells were 33.7 nmol/L+ (11.8 µg/L) and 2.0 nmol/L (0.70 µg/L), respectively. The free concentration of meloxicam in synovial fluid was higher than the IC50 for stimulated COX activity from 6 to 36 hours postdose.ConclusionOn the basis of free synovial concentrations and the IC50 for stimulated COX activity, meloxicam is expected to have a long duration of action. Inhibition of COX activity is expected to be more marked in inflamed synovium compared with non-inflamed synovium.

Synovial fluid levels of adipokines in osteoarthritis: Association with local factors of inflammation and cartilage maintenance

The role of body weight in the pathogenesis of osteoarthritis (OA) - previously considered the sole factor in the association between obesity and OA - is being re-evaluated as the contribution of adiposity to the cartilage degenerative process becomes clearer. The current study has been undertaken to better understand the role of adipose-derived proteins, namely adipokines, in OA. For this purpose, we investigated in patients with OA the relationships between the joint levels of leptin, adiponectin and resistin and those of factors involved in inflammation and cartilage maintenance. The sandwich enzyme-linked immunosorbent assays were used to determine in the synovial fluid (SF) from 35 OA patients, the concentrations of adipokines, interleukin-6 (IL-6) and transforming growth factor-β (TGF-β). The soluble form of leptin receptor (sOb-R) was also examined to evaluate the biological active free form of leptin. Correlation analysis indicate that IL-6 levels are positively related to the levels of resistin and adiponectin. Surprisingly, the free form of leptin, but not the total leptin, is negatively associated with IL-6. Beside, adiponectin is the single adipokine that is correlated with TGF-β. Interestingly, a sexual dimorphism is observed in the study as correlations between adipokines and IL-6 or TGF-β are found only with female OA patients. Taken together, these findings suggest that only adiponectin may contribute to the metabolic changes associated with OA. The three adipokines may also be involved in inflammation, but with opposite effects. Both resistin and adiponectin may exhibit pro-inflammatory activity while the free form of leptin may down-regulate the inflammation.

Association between the chondrocyte phenotype and the expression of adipokines and their receptors: Evidence for a role of leptin but not adiponectin in the expression of cartilage-specific markers

Although extensive evidence support the key role of adipokines in cartilage homeostasis, contradictory data have been found for their expression and their effects in chondrocytes. This study was then undertaken to determine whether a phenotypic modulation may affect the expression of adipokines and their receptors in human chondrocytes. The expression of leptin, adiponectin and their receptors, as well as cartilage‐specific genes was examined in chondrocytes obtained from patients with osteoarthritis either directly after cells harvest or after culture in monolayer or in alginate beads. The results showed major changes in the gene expression pattern after culture in monolayer with a shift from the adipokines to their receptors. Interestingly, this downregulation of adipokines was associated with a loss of chondrocyte phenotype, and chondrocytes recovered a cartilage‐like expression profile of leptin and adiponectin when cultured in a tridimensional chondrocyte phenotype‐inducing system, but ceased expressing their receptors. Further experiments clearly showed that leptin but not adiponectin promoted the expression of cartilage‐specific markers through mitogen‐activated protein kinase, Janus kinase and phosphatidylinositol‐3 kinase signaling pathways. In conclusion, our data indicate that any phenotypic modulation could affect chondrocyte responsiveness to leptin or adiponectin, and provide evidence for an important role for leptin in regulating the expression of cartilage‐specific markers. J. Cell. Physiol. 226: 2790–2797, 2011.

THE ORGANISATIONAL NATURE OF UNION CAREERS

ABSTRACT The equality agenda has gained a much higher visibility in the UK and in France. Most unions have adopted specific measures to improve womens representation in their structures. However, even in highly feminised unions, women remain under-represented in union leadership positions. To understand the gap between the presence of women in the lay membership/activist population and their slow disappearance at the higher levels of the union hierarchy, this study is focused on the role of organizational contexts. We argue that to understand the feminisation of union leadership, we need to consider the characteristics of ‘internal union labour markets’: ports of entry, typical/atypical career routes, norms of job evaluation, internal job segregation and hierarchy, human resources management and gender-equality policies. To fully grasp the influence of contexts on the process of feminisation, specific attention to the evolution of the repertoires of action by unions is also useful.

Interaction of the Electrophilic Ketoprofenyl-Glucuronide and Ketoprofenyl-Coenzyme A Conjugates with Cytosolic Glutathione S-Transferases

Carboxylic acid-containing drugs are metabolized mainly through the formation of glucuronide and coenzyme A esters. These conjugates have been suspected to be responsible for the toxicity of several nonsteroidal anti-inflammatory drugs because of the reactivity of the electrophilic ester bond. In the present study we investigated the reactivity of ketoprofenyl-acylglucuronide (KPF-OG) and ketoprofenyl-acyl-coenzyme A (KPF-SCoA) toward cytosolic rat liver glutathione S-transferases (GST). We observed that KPF-SCoA, but not KPF-OG inhibited the conjugation of 1-chloro-2,4-dinitrobenzene and 4-nitroquinoline N-oxide catalyzed by both purified cytosolic rat liver GST and GST from FAO and H5-6 rat hepatoma cell lines. Photoaffinity labeling with KPF-SCoA suggested that the binding of this metabolite may overlap the binding site of 4-methylumbelliferone sulfate. Furthermore, high-performance liquid chromatography and mass spectrometry analysis showed that both hydrolysis and transacylation reactions were observed in the presence of GST and glutathione. The formation of ketoprofenyl-S-acyl-glutathione could be kinetically characterized (apparent Km = 196.0 ± 70.6 μM). It is concluded that KPF-SCoA is both a GST inhibitor and a substrate of a GST-dependent transacylation reaction. The reactivity and inhibitory potency of thioester CoA derivatives toward GST may have potential implications on the reported in vivo toxicity of some carboxylic acid-containing drugs.

Challenges and pitfalls for workplace unionism in a restructured public service

In the context of restructuring that has swept across Europe in recent years, this article discusses the conditions of workplace unionism resilience in a small, predominantly female UK public service occupation – probation. Using both quantitative and qualitative data, the article offers comprehensive insights into members’ expectations towards their union branches and provides evidence of even more accountable and responsive relationships between local reps and their members following restructuring. Factors that contributed to the resilience of the union included the influence of a shared occupational identity, the legacy of large and confident branches and the (gender) democratic tradition of the union. However, the research also highlights some limitations for the permanence of effective workplace unionism in a context of socio-demographic changes as well as organizational difficulties linked to the restructuring and outsourcing process.

Response to: ‘Spontaneous hypertensive rat exhibits bone and meniscus phenotypes of osteoarthritis: is it an appropriate control for MetS-associated OA?’ by Chan and Wen

We thank Dr Chan and Dr Wen for their interest in our report1 and their resulting eLetter.2 We fully agree that, among the different components of metabolic syndrome (MetS), hypertension has very recently been brought out as a critical feature in the development of osteoarthritis (OA) in humans.3 4 In these reports using either data from the Framingham OA study3 or the Osteoarthritis Initiative study,4 it has been emphasised that high blood pressure (diastolic or systolic, respectively) was associated with increased incidence of radiographic knee OA. In order to further experimentally investigate the actual role of hypertension in OA onset and development, Chan and colleagues describe in a yet unpublished study the development of OA features in the spontaneous hypertensive rat (SHR) model, a widely characterised model of systemic hypertension.2 5 Although the spontaneous hypertensive heart failure (SHHF) rat strain we employed is deriving from the SHR strain6 and suffers high …