IgG-induced experimental immune synovitis: hormonal modulation of in vitro splenic immune responses to homologous antigens.

The effect of oestrogen or anti-oestrogen administration on gross pathology and in vitro cell-mediated immune responses to homologous IgG, native and denatured interstitial collagens and PPD was studied in an IgG-induced rabbit model of immune synovitis. During induction of synovitis, rabbits were administered oestradiol valerate (0.075 mg/kg/day) or tamoxifen, an anti-oestrogen (2.0 mg/kg/day, high dose or 0.5 mg/kg/day, low dose) or placebo injections. Low dose tamoxifen administration was associated with significant improvement P less than 0.05 in immune synovitis with regard to gross pathology, when compared to placebo and the oestradiol treatment group. High dose tamoxifen treatment was not associated with significant improvement in observed synovitis. With regard to cell-mediated immune responses, spleen cells derived from immune synovitis rabbits were observed to increase 3H-thymidine uptake on incubation with native or denatured homologous collagens. Modulation of these immune responses to antigens was observed in anti-oestrogen treated rabbits with immune synovitis. In vitro cell-mediated immune responses to denatured type I, II and III collagens, PPD, as well as native type II and III collagens were not observed in the low dose tamoxifen treatment group. However, in vitro immune responses to these antigens were observed in spleen cell cultures from immune synovitis rabbits treated with either high dose tamoxifen or oestradiol valerate. The data suggest that in vivo anti-oestrogen administration can modulate the in vitro cell-mediated immune response to connective tissue constituents observed in immune synovitis. Concomitant with reduced immune responses is a significant reduction in the observed lesions of the inflammatory response.

Estradiol and tamoxifen stimulation of lapine articular chondrocyte prostaglandin synthesis.

The effect of estradiol and tamoxifen on prostaglandin (PG) synthesis by rabbit articular chondrocytes in secondary monolayer cultures was investigated. Radioimmunoassay for PGE2, PGF2 alpha, 6-oxo-PGF1 alpha and thromboxane B2 was performed on media from cultures containing estradiol and tamoxifen (10-12M-10-7M). Radiometric thin-layer chromatography was also carried out. The time course of estradiol/tamoxifen effect on chondrocyte PG synthesis was evaluated and its relationship to cell density in culture examined. Estradiol stimulated the synthesis of PGs by chondrocytes. Stimulation was noted at picomolar concentrations of estradiol without further stimulation at markedly higher concentrations. In time studies, after a lag, the effect of estradiol was present fully by 5 hrs, remained steady for 24 hrs and then declined by 48 hrs. Estradiol stimulation of PG synthesis was dependent upon chondrocyte culture plating density. Tamoxifen stimulated chondrocyte PG synthesis to relatively lower levels than estradiol. The characteristics of estradiol/tamoxifen stimulation of chondrocyte PG synthesis suggest a mechanism involving estradiol cytoplasmic receptors.

Intraarticular hyaluronic acid injection and synovial prostaglandins in experimental immune synovitis.

In vitro studies suggest that synovial fluid hyaluronic acid may have a role in reducing joint inflammation. The effect of intraarticular injection of sodium hyaluronate in a model of experimental immune synovitis was assessed. In addition, tissue prostaglandin content of synovia with and without immune synovitis was compared. Intraarticular hyaluronic acid administered at 2 doses was not effective in reducing the induced inflammation. With immune synovitis there was an increase in the total synovial prostaglandins. When related to total prostaglandins, prostacyclin was decreased, prostaglandin F2 alpha and thromboxane were increased and prostaglandin E2 was the same in synovitis as compared to controls.