Protein biosynthetic activity of polymorphonuclear leukocytes in inflammatory arthropathies. Increased synthesis and release of fibronectin

We have investigated protein synthesis and release by polymorphonuclear leukocytes (PMN) to compare the protein biosynthetic activity of peripheral blood PMN and inflammatory synovial fluid (SF) PMN from patients with inflammatory arthropathies. We analyzed and compared the protein profiles produced by these cells, using patient matched peripheral blood and SF PMN as well as peripheral blood PMN from normals. Twenty-five patients with either rheumatoid arthritis, psoriatic arthritis or gout were studied. Fluorographs of SDS-polyacrylamide slab gels, performed using cell supernatants from metabolically labelled cells, revealed an increased release of de novo synthesized proteins by inflammatory SF PMN compared to peripheral blood PMN. Under reducing conditions, 4 clearly distinguishable high molecular mass products were observed (Mr 230,000, 185,000, 170,000 and 95,000). Two of the protein bands were found to be gelatin binding (Mr 230,000 and Mr 95,000). By Western blot, the Mr 230,000 protein was found to be fibronectin and the Mr 95,000 protein was shown to be identical to a recently described gelatinase. Thus, the activation of PMN in inflammation is accompanied by an increased release of a number of de novo synthesized proteins, including fibronectin. Our studies directly pertain to the in vivo inflammatory process since the PMN were not activated artificially in vitro.