Inhibition of antigen-induced arthritis in guinea pigs by a selective LTB4 receptor antagonist LY293111Na

Development of predictive quantitative structure–activity relationship model and its application in the discovery of human leukotriene A4 hydrolase inhibitors

Background: Human LTA4H catalyzes the conversion of LTA4 to LTB4 and plays a key role in innate immune responses. Inhibition of this enzyme can be a valid method in the treatment of inflammatory response exhibited through LTB4. Results & discussion: The quantitative structure–activity relationship (QSAR) models were developed using genetic function approximation and validated. A training set of 26 diverse compounds and their molecular descriptors were used to develop highly correlating QSAR models. A six-descriptor model explaining the biological activity of the training and test sets with correlation values of 0.846 and 0.502, respectively, was selected as the best model and used in a database screening of drug-like Maybridge database followed by molecular docking. Conclusion: Based on the predicted potent inhibitory activities, expected binding mode and molecular interactions at the active site of hLTA4H final leads were selected as to be utilized in designing future hLTA4H inhibitors.

Relationship between arthroscopic joint evaluation and the levels of Coll2-1, Coll2-1NO(2), and myeloperoxidase in the blood and synovial fluid of horses affected with osteochondrosis of the tarsocrural joint

OBJECTIVE

To evaluate the levels of plasmatic and synovial Coll2-1, Coll2-1NO(2) and myeloperoxidase (MPO) in horses with osteochondral lesions of the tarsocrural joint and to investigate how these levels relate to arthroscopic findings of inflammation and degeneration.

MATERIALS AND METHODS

Venous blood and synovial fluid samples were collected from 63 horses presented for arthroscopic removal of osteochondral fragments in the tarsocrural joint. Prior to removal of the osteochondral fragment, an exploration of the joint was performed and an inflammatory and degenerative score was determined. The blood and synovial levels of Coll2-1, Coll2-1NO(2) and MPO were also measured. The effects of the arthroscopic evaluation (inflammatory and degenerative classes) on the blood and synovial markers were evaluated using a linear model (GLM procedure), and correlations between biochemical markers in the blood and synovial fluid and the arthroscopic evaluation (inflammatory and degenerative classes) were established (Pearson's correlations).

RESULTS

Significantly higher levels of Coll2-1 were detected in synovial fluid of higher degenerative classes. There was a significant correlation between the degenerative score and the synovial levels of Coll2-1 (r=0.27). According to the logistic regression model, there was a significant effect of the degenerative class on synovial levels of Coll2-1.

CONCLUSIONS

Coll2-1 correlates well with the degenerative state of tarsocrural joints as evaluated by arthroscopy. This marker can therefore be classified as a burden-of-disease marker in the assessment of joint disease in horses.

Coll2-1, Coll2-1NO2 and myeloperoxidase concentrations in the synovial fluid of equine tarsocrural joints affected with osteochondrosis

The measurement of biomarkers that reflect cartilage breakdown is a powerful tool for investigating joint damage caused by disease or injury. Particularly in cases of osteochondrosis, synovial concentrations of these biomarkers may reveal the presence of osteoarthritic changes. Coll2-1, Coll2-1 NO2 and myeloperoxidase have recently been introduced in equine osteoarticular research but comparison between the concentrations of these markers in OCD affected and healthy joints has not been made. Therefore, this study aimed at reporting the synovial concentrations of these biomarkers in joints affected with osteochondral fragments in the tarsocrural joint compared to unaffected joints. Myeloperoxidase and Coll2-1NO2 revealed to have similar levels between affected joints and controls. However, in contrast to previous studies using C2C the present study demonstrated that synovial levels of Coll2-1 were significantly elevated in tarsocrural joints affected with osteochondrosis. Thus, Coll2-1 may be an earlier marker of cartilage degeneration than other cartilage degradation markers that have been previously used in equine medicine.

Identification of key residues determining species differences in inhibitor binding of microsomal prostaglandin E synthase-1

Microsomal prostaglandin E synthase-1 (MPGES1) is induced during an inflammatory reaction from low basal levels by pro-inflammatory cytokines and subsequently involved in the production of the important mediator of inflammation, prostaglandin E(2). Nonsteroidal anti-inflammatory drugs prevent prostaglandin E(2) production by inhibiting the upstream enzymes cyclooxygenases 1 and 2. In contrast to these conventional drugs, a new generation of NSAIDs targets the terminal enzyme MPGES1. Some of these compounds potently inhibit human MPGES1 but do not have an effect on the rat orthologue. We investigated this interspecies difference in a rat/human chimeric form of the enzyme as well as in several mutants and identified key residues Thr-131, Leu-135, and Ala-138 in human MPGES1, which play a crucial role as gate keepers for the active site of MPGES1. These residues are situated in transmembrane helix 4, lining the entrance to the cleft between two subunits in the protein trimer, and regulate access of the inhibitor in the rat enzyme. Exchange toward the human residues in rat MPGES1 was accompanied with a gain of inhibitor activity, whereas exchange in human MPGES1 toward the residues found in rat abrogated inhibitor activity. Our data give evidence for the location of the active site at the interface between subunits in the homotrimeric enzyme and suggest a model of how the natural substrate PGH(2), or competitive inhibitors of MPGES1, enter the active site via the phospholipid bilayer of the membrane.

Relationship between biochemical markers and radiographic scores in the evaluation of the osteoarticular status of Warmblood stallions

Establishing the osteoarticular status of the horse is often performed by means of radiological screening of the animals. Widespread blood sampling could reveal to be an interesting alternative to this procedure which is time consuming and sometimes technically difficult. The aim of this study was to investigate the relationship between the radiological status of the horses and the levels of biochemical markers of cartilage degradation and synovial inflammation. A specific radiological scoring and classification system was therefore developed and applied on 63 stallions presented for studbook admission. Additionally, groups of horses were established according to the occurrence of osteochondrosis, degenerative joint disease and distal interphalangeal joint effusion. Insulin growth factor-I, myeloperoxidases, Coll2-1 and Coll2-1NO(2) were used as blood markers. The combination of the blood parameters did not seem to correlate with the used scoring system. Coll2-1NO(2) levels however tended to increase with poorer radiological class and this could therefore potentially be a useful predictor of the osteoarticular status in the horse. Coll2-1 levels were significantly higher in the degenerative joint disease group. A high percentage of horses with distal interphalangeal joint effusion was present in this study and was associated with decreased IGF-I and increased Coll2-1 levels.

A type II-collagen derived peptide and its nitrated form as new markers of inflammation and cartilage degradation in equine osteochondral lesions

Markers of cartilage breakdown enable studying the degradation of cartilage matrix in equine joint pathologies. This study was designed to determine the levels of Coll2-1, a peptide of the triple helix of type II collagen, and Coll2-1NO(2), its nitrated form in the plasma of healthy horses (controls; n=37) and horses suffering from osteochondrosis (n=34). Clinical and arthroscopic scores were attributed reflecting the severity of lesions and were related to the plasma levels of Coll2-1 and Coll2-1NO(2). The median of Coll2-1 was significantly higher in the control group, whereas the mean of Coll2-1NO(2) showed significant elevation in the pathological group. However, the measurement means of scoring classes did not vary significantly. The markers were able to differentiate the group of horses suffering from osteochondrosis from the group of healthy horses. The elevation of Coll2-1NO(2) in the pathological group indicates an inflammation, mediated through reactive oxygen species and/or increased myeloperoxidase activity.

Plasma Concentrations of a Type II Collagen-derived Peptide and Its Nitrated Form in Growing Ardenner Sound Horses and in Horses Suffering from Juvenile Digital Degenerative Osteoarthropathy

Several breeds of draft horses suffer from degenerative digital osteoarthropathy, resulting in a reduced active lifespan. A group of 30 Ardenner horses was followed, in standardized conditions, from 15 to 28 months of age to detect the early manifestations of the disease. The severity of the disease was assessed according to a personal grading system including clinical and radiographic items. Coll 2-1, a peptide of the helical region of type II collagen, and its nitrated form (Coll 2-1 NO(2)) were assayed in blood plasma collected at 452 +/- 18 days, 504 +/- 20 days, 558 +/- 18 days, 613 +/- 19 days, 675 +/- 19 days, 752 +/- 21 days and 852 +/- 19 days of age. At the end of the follow-up period, 53.3% of Ardenner horses were affected by a degenerative digital osteoarthropathy. A significant effect (p<0.05) of time, sex and pathology was observed for Coll 2-1 NO(2). Variations of Coll 2-1 were not significant except for the time effect. The elevation of Coll 2-1 NO(2) in the pathological group could indicate an inflammatory process during the growth of the affected horses, as nitration of tyrosine is mediated through reactive oxygen/nitrogen species and/or myeloperoxidase activity. Coll 2-1 NO(2) appears to be an interesting early marker of cartilage degradation and oxidation in degenerative osteoarthropathy.

Cartilage-derived biomarkers and lipid mediators of inflammation in horses with osteochondritis dissecans of the distal intermediate ridge of the tibia

OBJECTIVE

To assess whether reported alterations in metabolism of cartilage matrix in young (0 to 24 months old) horses with osteochondritis dissecans (OCD) may also be found in older (24 to 48 months old) horses with clinical signs of OCD and to investigate the role of eicosanoids in initiating these clinical signs.

SAMPLE POPULATION

Synovial fluid was collected from 38 tarsocrural joints of 24 warmblood horses with (22 joints of 16 horses) or without (16 joints of 8 horses) clinical signs and a radiographic diagnosis of OCD of the distal intermediate ridge of the tibia.

PROCEDURES

Turnover of type II collagen was investigated by use of specific immunoassays for synthesis (carboxypropeptide of type II collagen [CPII]) and degradation (collagenase-cleaved fragments of type II collagen [C2C]) products. Furthermore, glycosaminoglycan (GAG), leukotriene (LT) B(4), cysteinyl LTs, and prostaglandin (PG) E(2) concentrations were determined, and concentrations in joints with OCD were compared with those in joints without OCD.

RESULTS

Concentrations of CPII, C2C, and GAG did not differ significantly between affected and nonaffected joints. Fluid from joints with OCD had significantly higher LTB(4) and PGE(2) concentrations than did fluids from nonaffected joints.

CONCLUSIONS AND CLINICAL RELEVANCE

Altered collagen or proteoglycan turnover was not detected in 24- to 48-month-old horses at the time they developed clinical signs of OCD of the distal intermediate ridge of the tibia. However, increased concentrations of LTB(4) and PGE(2) in fluid of joints with OCD implicate these mediators in the initiation of clinical signs of OCD.

Blockade of leukotriene B4 prevents articular incapacitation in rat zymosan-induced arthritis

We investigated whether leukotrienes mediate cell influx and articular incapacitation in zymosan-induced arthritis. Rats received 1 mg zymosan intra-articularly (i.a.). The hyperalgesia was measured using the rat articular incapacitation test. Cell influx, leukotriene B(4) and prostaglandin E(2) levels were assessed in the joint exudate, at 6 h. Groups received either the leukotriene B(4) synthesis inhibitor MK 886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl)]-2,2-dimethylpropanoic acid 30 min before or 2 h after the zymosan; 0.3-3 mg kg(-1) i.p.), the leukotrienes synthesis inhibitor BWA(4)C (N-(3-phenoxycinnamyl)-acetohydroxamic acid--2 h after the zymosan; 10 microg i.a.) or the peptido-leukotrienes antagonist sodium montelukast (30 min before and 2 h after the zymosan; 10 mg kg(-1) per os). MK 886 inhibited the articular incapacitation and cell influx, while reducing leukotriene B(4), but not prostaglandin E(2) levels. BWA(4)C inhibited the articular incapacitation. Sodium montelukast did not affect either of the parameters. The data suggest that leukotriene B(4) is involved in cell influx and articular incapacitation in zymosan arthritis.