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Human IL-I -stimulated chondrocytes derived from rabbit, bovine, and human articular cartilage produce proteoglycan-and collagen-degrading enzymes. These studies demonstrate that the biological activity of IL-1 is not species specific. Several thiol, carboxyalkyl, and hydroxamic acid peptide inhibitors showed differential effects. The thiols were equipotent inhibitors of both the collagen-and proteoglycan-degrading enzymes whereas the carboxyalkyls appear to inhibit solely the proteoglycan-degrading enzyme(s). The hydroxamic acid peptides, the most potent inhibitors, appear to be more active against the proteoglycan-degrading enzymes. These synthetic inhibitors of proteoglycan-and/or collagendegrading enzymes may represent a new class of diseasemodifying antiarthritic agents.

Properties of progestin binding sites in adult male rabbit lung cytosol were analyzed using [³H] promegestone ([³H]R5020). At concentrations of 0.05–10 nM, [³H]R5020 bound to two saturable sites with differing affinities: a high affinity site (K_d = 0.34 nM, Bmax = 57 fmol/mg protein) and a moderate affinity site (K_d = 60 nM, B_max = 540 fmol/mg protein). [³H]R5020 binding, under conditions selected to favor binding to the high affinity site, was reversible, protease-sensitive and inhibited in a concentration-dependent manner by steroids with the following order of potency: R5020 > norgestrel > norethindrone > progesterone > norethindrone acetate > norethynodrel > deoxycorticosterone > lynestrenol > quingestanol > testosterone > 17β-estradiol > cortisol. Upon sucrose density gradient ultracentrifugation analysis, a peak of [³H]R5020 binding activity was observed in the 6-7S region in the absence of KCl and in the 3-4S region in the presence of KCl. The progestin-binding activity of adult male rabbit lung cytosol thus possesses those characteristics conventionally accorded to a hormone receptor and suggests that lung tissue may be progesterone-responsive.

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Supernatants from the P388D1 macrophage cell line as well as human interleukin-1 (IL-1) stimulated primary rabbit articular chondrocytes to produce collagen- (C-ase) and proteoglycan- (PG-ase) degrading proteases. The P388D1 derived factor had a molecular weight of 16,000-20,000 and a pI of 4.5-5.0. Both protease activities were metal dependent and inhibited by EDTA, phenanthroline, and alpha 2-macroglobulin but not by PMSF, TLCK, pepstatin, or alpha 1-antitrypsin. Size exclusion chromatography indicated the molecular weights for latent PG-ase and C-ase were 44,000-56,000 and 34,000-44,000, respectively. Chemical synthesis efforts produced two classes of C-ase inhibitors--thiols and hydroxamic acids. The former had IC50 values of 10(-5)-10(-6) M while the latter approached 10(-7) M.