Proteinase-activated receptor 2 (PAR2) deficiency protects against cartilage degradation in experimental osteoarthritis (OA). The wider impact of this pathway upon OA-associated pathologies such as ...osteophyte formation and pain is unknown. Herein, we investigated early temporal bone and cartilage changes in experimental OA in order to further elucidate the role of PAR2 in OA pathogenesis.
OA was induced in wild-type (WT) and PAR2-deficient (PAR2
) mice by destabilisation of the medial meniscus (DMM). Inflammation, cartilage degradation and bone changes were monitored using histology and microCT. In gene rescue experiments, PAR2
mice were intra-articularly injected with human PAR2 (hPAR2)-expressing adenovirus. Dynamic weight bearing was used as a surrogate of OA-related pain.
Osteophytes formed within 7 days post-DMM in WT mice but osteosclerosis was only evident from 14 days post induction. Importantly, PAR2 was expressed in the proliferative/hypertrophic chondrocytes present within osteophytes. In PAR2
mice, osteophytes developed significantly less frequently but, when present, were smaller and of greater density; no osteosclerosis was observed in these mice up to day 28. The pattern of weight bearing was altered in PAR2
mice, suggesting reduced pain perception. The expression of hPAR2 in PAR2
mice recapitulated osteophyte formation and cartilage damage similar to that observed in WT mice. However, osteosclerosis was absent, consistent with lack of hPAR2 expression in subchondral bone.
This study clearly demonstrates PAR2 plays a critical role, via chondrocytes, in osteophyte development and subchondral bone changes, which occur prior to PAR2-mediated cartilage damage. The latter likely occurs independently of OA-related bone changes.
Angiotensin II-type 1 receptor stimulation is recognised to promote inflammation, a state central to the development and maintenance of rheumatoid arthritis. Herein we examined the use of losartan, ...an angiotensin II-type 1 receptor antagonist, on vascular reactivity, knee joint diameter and behavioural assessment of pain in a Freund's complete adjuvant (FCA) mouse model of joint inflammation.
Monoarthritis was induced via FCA in the presence or absence of losartan with naive mice serving as controls. Knee joint swelling, joint pain (assessed by dynamic weight bearing of limb use), knee joint artery reactivity (assessed ex vivo) and blood perfusion of the knee joint (assessed in vivo) were determined.
FCA mediated a significant increase in knee joint diameter and reduced weight-bearing (a surrogate for pain sensation) of the affected limb. Notably, these phenomena were substantially reduced when mice were prophylactically treated with losartan. Assessment of arterial relaxation and blood perfusion with acetylcholine stimulation revealed that FCA resulted in significant vascular dysfunction, which was resolved to naïve levels with losartan treatment.
Through the actions of losartan, these findings indicate that the angiotensin II-type 1 receptor is a likely therapeutic target of importance in the development of the physical changes, pain sensation and vascular dysfunction found in inflammatory arthritis.
Biological therapies such as tumor necrosis factor-alpha inhibitors have advanced the treatment of rheumatoid arthritis, but one-third of patients do not respond to such therapy. Furthermore, these ...inhibitors are now usually administered in combination with conventional disease-modifying antirheumatic drugs, suggesting they have not achieved their early promise. This study investigates a novel therapeutic target, proteinase-activated receptor (PAR)-2, in joint inflammation. Intra-articular carrageenan/kaolin (C/K) injection in mice resulted in joint swelling that was associated with synovial PAR2 up-regulation. Inhibiting receptor up-regulation using small interfering RNA technology, as confirmed by immunoblotting, substantially reduced the inflammatory response in the joint. Serine proteinase-induced joint swelling was mediated primarily via PAR2 activation, since the response to exogenous application of trypsin and tryptase was absent in PAR2 knockout mice. Furthermore, serine proteinase inhibitors were effective anti-inflammatory agents in this model. Disrupting proteolytic activation of PAR2 using antiserum (B5) directed to the receptor cleavage/activation site also attenuated C/K-induced inflammation, as did the similarly targeted PAR2 monoclonal antibody SAM-11. Finally, we report the activity of a novel small molecule PAR2 antagonist, N1-3-methylbutyryl-N4-6-aminohexanoyl-piperazine (ENMD-1068), that dose dependently attenuated joint inflammation. Our findings represent a major advance in collectively identifying PAR2 as a novel target for the future treatment of arthritis.
Fibrolamellar carcinoma has a distinctive morphology and immunophenotype, including cytokeratin 7 and CD68 co-expression. Despite the distinct findings, accurate diagnosis of fibrolamellar carcinoma ...continues to be a challenge. Recently, fibrolamellar carcinomas were found to harbor a characteristic somatic gene fusion, DNAJB1-PRKACA. A break-apart fluorescence in situ hybridization (FISH) assay was designed to detect this fusion event and to examine its diagnostic performance in a large, multicenter, multinational study. Cases initially classified as fibrolamellar carcinoma based on histological features were reviewed from 124 patients. Upon central review, 104 of the 124 cases were classified histologically as typical of fibrolamellar carcinoma, 12 cases as 'possible fibrolamellar carcinoma' and 8 cases as 'unlikely to be fibrolamellar carcinoma'. PRKACA FISH was positive for rearrangement in 102 of 103 (99%) typical fibrolamellar carcinomas, 9 of 12 'possible fibrolamellar carcinomas' and 0 of 8 cases 'unlikely to be fibrolamellar carcinomas'. Within the morphologically typical group of fibrolamellar carcinomas, two tumors with unusual FISH patterns were also identified. Both cases had the fusion gene DNAJB1-PRKACA, but one also had amplification of the fusion gene and one had heterozygous deletion of the normal PRKACA locus. In addition, 88 conventional hepatocellular carcinomas were evaluated with PRKACA FISH and all were negative. These findings demonstrate that FISH for the PRKACA rearrangement is a clinically useful tool to confirm the diagnosis of fibrolamellar carcinoma, with high sensitivity and specificity. A diagnosis of fibrolamellar carcinoma is more accurate when based on morphology plus confirmatory testing than when based on morphology alone.
Background: Obesity in pregnancy is increasing and is a risk factor for metabolic pathology such as preeclampsia. In the nonpregnant, obesity is associated with dyslipidemia, vascular dysfunction, ...and low-grade chronic inflammation.
Aim: Our aim was to measure microvascular endothelial function in lean and obese pregnant women at intervals throughout their pregnancies and at 4 months after delivery. Plasma markers of endothelial function, inflammation, and placental function and their association with microvascular function were also assessed.
Methods: Women in the 1st trimester of pregnancy were recruited, 30 with a body mass index (BMI) less than 30 kg/m2 and 30 with a BMI more than or equal to 30 kg/m2 matched for age, parity, and smoking status. In vivo endothelial-dependent and -independent microvascular function was measured using laser Doppler imaging in the 1st, 2nd, and 3rd trimesters of pregnancy and at 4 months postnatal. Plasma markers of endothelial activation soluble intercellular cell adhesion molecule-1 (sVCAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWF), and plasminogen activator inhibitor (PAI)-1, inflammation (IL-6, TNFα, C-reactive protein, and IL-10), and placental function (PAI-1/PAI-2 ratio) were also assessed at each time point.
Results: The pattern of improving endothelial function during pregnancy was the same for lean and obese, but endothelial-dependent vasodilation was significantly lower (P < 0.05) in the obese women at each trimester (51, 41, and 39%, respectively). In the postpartum period, the improvement in endothelial-dependent vasodilation persisted in the lean women but declined to near 1st trimester levels in the obese (lean/obese difference, 115%; P < 0.01). There was a small but significant difference in endothelial-independent vasodilation between the two groups, lean response being greater than obese (P = 0.021), and response declined in both groups in the postpartum period. In multivariate analysis, time of sampling had the most impact on endothelial-independent function 18.5% (adjusted sum of squares expressed as a percentage of total means squared), P < 0.001 for sodium nitroprusside response; 9.8%, P < 0.001 for acetylcholine response, and obesity had the most impact on endothelial-dependent microvascular function (1.7%, P = 0.046 for sodium nitroprusside response; 19.3%, P < 0.001 for acetylcholine response). Time of sampling (11.2%, P < 0.001), IL-6 (4.0%, P = 0.002), and IL-10 (2.4%, P = 0.018) were significant independent contributors to variation in endothelial-dependent microvascular function. When obesity was entered into the model, the association with IL-6 and IL-10 was no longer significant, and obesity explained 6.8% (P < 0.001) of the variability in endothelial-dependent microvascular function. In the 1st trimester, obese women had a significantly higher PAI-1/PAI-2 ratio obese median (interquartile range), 0.87 (0.54–1.21) vs. lean 0.30 (0.21–0.47), P < 0.001), reflecting the lower PAI-2 levels in obese pregnant women. In a multivariate analysis, 1st trimester BMI (7.6%, P = 0.012), IL-10 (8.2%, P < 0.001), and sVCAM-1 (0.73%, P = 0.007) contributed to the 1st trimester PAI-1/PAI-2 ratio.
Conclusion: Obese mothers have a lower endothelium-dependent and -independent vasodilation when compared with lean counterparts. There was a higher PAI-1/ PAI-2 ratio in the 1st trimester in obese women, which improved later in pregnancy. Obese pregnancy is associated with chronic preexisting endothelial activation and impairment of endothelial function secondary to increased production of inflammatory T-helper cells-2 cytokines.
Obesity is increasing in prevalence worldwide and in all age groups. In nonpregnant individuals, obesity is associated with dyslipidemia; hyperinsulinemia; vascular dysfunction; and, more recently, ...low-grade chronic inflammation. However, whether such effects are sustained during pregnancy has been sparsely investigated but is important to establish, given the association of maternal obesity with numerous adverse metabolic and vascular consequences.
We consecutively recruited 47 healthy women in the third trimester of pregnancy and divided the participants into 2 groups, lean n = 24; median body mass index (BMI), 22.1 kg/m2 and obese (n = 23; median BMI, 31.0 kg/m2) around the median first trimester BMI. The age, parity, and smoking history were comparable in both groups. A detailed panel of metabolic and inflammatory parameters was measured and an in vivo assessment of endothelial-dependent and -independent microvascular function made using laser doppler imaging. Although low-density lipoprotein cholesterol and glycosylated hemoglobin were similar, fasting triglyceride concentrations were higher 2.70 (interquartile range, 2.3–3.21) vs. 2.20 (IQ range, 2.0–2.6) mmol/liter, P = 0.02 and high-density lipoprotein concentrations were lower 1.55 (IQ range, 1.1–1.7) vs. 1.72 (IQ range, 1.4–2.0) mmol/liter, P = 0.02 in the obese group. Leptin 55.6 (range, 45–64.4) ng/ml vs. 23.8 (range, 13.2–35.2) ng/ml, P < 0.0001 and fasting insulin 14.5 (range, 11.4–27.3) vs. 6.5 (range, 4.6–9.7) mU/liter, P < 0.0001 levels were more than double. Similarly, levels of inflammatory parameters, IL-6 3.15 (range, 2.4–3.5) vs. 2.1 (range, 1.73–2.85) pg/ml, P = 0.003, and sensitive C-reactive protein 4.45 (range, 2.9–6.6) vs. 2.25 (range, 0.92–3.65) mg/ml, P = 0.0015 were also substantially elevated. Both endothelial-dependent and -independent vasodilatory responses were significantly reduced in the obese group (P = 0.0003 and P = 0.02, respectively, ANOVA) and systolic blood pressure was higher (P = 0.01). Metabolic factors, C-reactive protein (r = 0.289, P = 0.049), and insulin (r = 0.339, P = 0.02) were related inversely to endothelial-dependent function.
These comprehensive data demonstrate that, as in nonpregnant obese individuals, obesity in pregnancy is associated not only with marked hyperinsulinemia (without necessarily glucose dysregulation) and dyslipidemia but also impaired endothelial function, higher blood pressure, and inflammatory up-regulation. Such a spectrum of risk factors may contribute to maternal complications in obese women and, as a result, influence fetal programming of adult vascular disease. Clearly, these data provide further rationale to examine the potential benefits of preconceptual weight loss and antenatal exercise.
We investigated whether a session of prior exercise could ameliorate postprandial endothelial dysfunction.
Endothelial function is impaired after fat ingestion, and this may be related to rises in ...triglyceride concentrations. Exercise reduces postprandial triglyceride concentrations.
Ten lean (waist <90 cm) and 10 centrally obese (waist >100 cm) middle-aged men each underwent two oral fat tolerance tests (blood taken fasting and for 8 h after a high-fat meal containing 80 g fat and 70 g carbohydrate). On the afternoon before one test, subjects performed a 90-min treadmill walk (exercise); no exercise was performed before the control test. Endothelium-dependent and -independent microvascular function was assessed using laser Doppler imaging in the fasted state and at two hourly intervals during the 8-h postprandial period.
Exercise reduced both fasting and postprandial triglyceride concentrations by 25% in both the lean and centrally obese groups (p < 0.0005). For all subjects taken together, exercise improved fasting endothelium-dependent function by 25% (p < 0.05), and, although there was a significant postprandial decrease in both endothelium-dependent and -independent function in both the control and exercise trials (p < 0.01), postprandial endothelium-dependent and -independent function were 15% and 20% higher, respectively, in the exercise trial than the control trial (both p < 0.05).
A session of prior exercise improves fasting and postprandial vascular function in middle-aged men. This may be one mechanism by which exercise influences cardiovascular risk.
A role for endothelium-derived constricting factors (EDCF), and the angiotensin II type 1 receptor (AT1R) pathway, in the vascular impairment found in the rat Freund's complete adjuvant (FCA)-model ...of rheumatoid arthritis (RA) was examined. FCA arthritis was induced in rats±losartan. Vehicle-treated rats served as controls. Knee-joint swelling and red blood cell (RBC) aggregation were measured as indicators of inflammation and endothelium reactivity assessed by response to acetylcholine (ACh) on aortic rings. Results show that knee-joint swelling and RBC aggregation were elevated in the FCA+vehicle group and restored to control levels in the FCA+losartan-treated animals. ACh-induced relaxation of aortic rings taken from FCA+vehicle animals was significantly impaired compared to vehicle-controls and this vasoreactivity was restored to control levels in the FCA+losartan-treated group. Further examination of aorta from the FCA+vehicle animals revealed an EDCF that was reliant on cyclooxygenase-2 (but not cyclooxygenase-1), generation of superoxide anion generation (but not hydrogen peroxide) and activation of thromboxane-prostanoid receptor. Losartan administration in vivo or ex vivo (to aortic rings) prevented the generation of the EDCF. In summary, this is the first evidence of an EDCF in a model of RA and identifies this mechanism as potentially significant in the cardiovascular disorder associated with the disease.
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Protease-activated receptor-2 (PAR2) is one member of a small family of transmembrane, G-protein-coupled receptors. These receptors are activated
cleavage of their N terminus by serine proteases ...(e.g., tryptase), unveiling an N terminus tethered ligand which binds to the second extracellular loop of the receptor. Increasing evidence has emerged identifying key pathophysiological roles for PAR2 in both rheumatoid arthritis (RA) and osteoarthritis (OA). Importantly, this includes both pro-inflammatory and destructive roles. For example, in murine models of RA, the associated synovitis, cartilage degradation, and subsequent bone erosion are all significantly reduced in the absence of PAR2. Similarly, in experimental models of OA, PAR2 disruption confers protection against cartilage degradation, subchondral bone osteosclerosis, and osteophyte formation. This review focuses on the role of PAR2 in rheumatic disease and its potential as an important therapeutic target for treating pain and joint degradation.
Using physiological, pharmacological, and gene disruption approaches, we demonstrate that proteinase-activated receptor-2 (PAR-2) plays a pivotal role in mediating chronic inflammation. Using an ...adjuvant monoarthritis model of chronic inflammation, joint swelling was substantially inhibited in PAR-2-deficient mice, being reduced by more than fourfold compared with wild-type mice, with virtually no histological evidence of joint damage. Mice heterozygous for PAR-2 gene disruption showed an intermediate phenotype. PAR-2 expression, normally limited to endothelial cells in small arterioles, was substantially upregulated 2 weeks after induction of inflammation, both in synovium and in other periarticular tissues. PAR-2 agonists showed potent proinflammatory effects as intra-articular injection of ASKH95, a novel synthetic PAR-2 agonist, induced prolonged joint swelling and synovial hyperemia. Given the absence of the chronic inflammatory response in the PAR-2-deficient mice, our findings demonstrate a key role for PAR-2 in mediating chronic inflammation, thereby identifying a novel and important therapeutic target for the management of chronic inflammatory diseases such as rheumatoid arthritis.
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