Eicosanoid production in rheumatoid synovitis

Interactions of hydroxyapatite and fluorapatite particles on human osteoarthritis type B synoviocytes: effects on interleukin-1 alpha levels and lipoxygenase pathways

We investigated the effects of the biomaterials hydroxyapatite (HAP) and fluorapatite (FAP) on cultured human osteoarthritis type B synoviocytes by analyzing interleukin-1 alpha (IL-1 alpha) production and arachidonic acid metabolism via lipoxygenase pathways. A portion of opsonized particles was endocytosed and was found in numerous phagolysosomes in human synoviocyte cytoplasms. The present study demonstrates that HAP and FAP calcined at 700 degrees C induced a decrease in IL-1 alpha production but markedly decreased the synthesis of lipoxygenase products after 1-month incubation with the particles. This model will allow us to study the possible inflammatory response (arachidonic acid metabolism, proinflammatory cytokines) that can be induced by any biomaterials used in orthopedics.

Peripheral blood neutrophil leukotriene B4 release and migration in rheumatoid arthritis

The present study was designed to compare peripheral blood neutrophil migration and leukotriene (LT) release between patients with rheumatoid arthritis (RA) and healthy controls and to correlate the neutrophil functions with clinical disease activity. Nineteen patients with moderately active RA and 19 age and sex matched healthy volunteers participated in this study. Isolated peripheral blood neutrophils from RA patients released equal amounts of LTB4 but their random migration was enhanced as compared with neutrophils from healthy controls. LTB4 release in whole blood was significantly lower in samples from RA patients than in those from the healthy volunteers (13.5 +/- 1.4 and 19.1 +/- 1.4 ng/10(6) neutrophils respectively; P < 0.001). LTB4 release from isolated RA neutrophils correlated with the levels of C-reactive protein, duration of morning stiffness and Ritchie articular swelling index. Concentrations of hyaluronate, cyclic AMP and 13, 14-dihydro-15-keto prostaglandin were not different between patients with RA and healthy volunteers. Neither was there any difference in TXB2 production by platelets during blood clotting. In conclusion, peripheral blood neutrophils of RA patients seem to be primed and/or activated as their random migration is enhanced as compared with those of healthy volunteers. In RA, LTB4 release from peripheral blood neutrophils seems to reflect the clinical activity of the disease. However, RA neutrophils released smaller (in whole blood) or equal (isolated cells) amount of LTB4 as compared with the respective controls. These contradictory findings suggest that LTB4 release from peripheral blood neutrophils has no major role in the regulation of disease activity in rheumatoid arthritis.

Lipoxygenase products and expression of 5-lipoxygenase and 5-lipoxygenase-activating protein in human cultured synovial cells

5-Lipoxygenase products are pro-inflammatory mediators. Their roles and cellular origin in chronic inflammatory rheumatisms such as rheumatoid arthritis (RA) are poorly understood. The expression of arachidonate 5-lipoxygenase (5-LOX, arachidonate: oxygen 5-oxydoreductase; EC 1.13.11.34) and the 5-lipoxygenase activating protein (FLAP) genes in osteoarthritis and RA synoviocytes was studied at the transcriptional level by reverse transcription-polymerase chain reaction (RT-PCR) methodology. Arachidonic acid metabolism was analyzed by reverse-phase high pressure liquid chromatography. 5-LOX and FLAP mRNA were detectable using RT-PCR in all sources of synoviocytes tested. The expression of 5-LOX and FLAP mRNA led to the synthesis of 5-LOX metabolites. 12- and 15-LOX activities were also present. These LOX products can participate in inflammatory processes leading to joint destruction in RA.