Prostaglandin e production by cultured inflamed rat synovium; stimulation by colchicine and inhibition by chloroquine

Acute arthritis was induced by injection of cell-free extract of group A type 4 Streptococci, into the knee joints of three month old male rats. Slices of the inflamed synovium obtained from these rats were incubated for 60–240 minutes, and the rate of prostaglandin E accumulation in the medium was measured by radioimmunoassay.Prostaglandins of the E type accumulated in the medium at a near linear rate during the incubation of the inflamed synovium for 4 hours. Incubation of inflamed synovium in the presence of colchicine (10 μg/ml) brought about a two-fold increase in the prostaglandin E accumulation in the medium after a latency of one hour. Tissue content of prostaglandin E after 4 hours of incubation of inflamed synovium with colchicine doubled as well. In contrast, incubation of inflamed synovium with chloroquine (10 μg/ml), corticosterone or dexamethasone (100 μg/ml each) reduced prostaglandin E accumulation in the medium by 50% at 1–4 hours. Likewise, chloroquine, corticosterone or dexamethasone reduced the tissue content of prostaglandin E in the inflamed synovium after 4 hours of incubation. The suppressive action of chloroquine was prevented by addition to the medium of arachidonic acid (2 μg/ml).It is concluded that the anti-inflammatory properties of colchicine are probably not related to prostaglandin biosynthesis. On the other hand chloroquine exerts its anti-inflammatory properties by curtailing substrate availability (arachidonic acid) for prostaglandin production, similarly to the anti-inflammatory mechanism of steroid hormones.