Showing papers by "Andrea J. Tenner published in 1984"

Lipoproteins containing apoprotein B are a major regulator of neutrophil responses to monosodium urate crystals.

Abstract: The inflammatory response to intraarticular urate crystals is known to be variable in gouty arthritis. One source of variability may be the modulation of cellular responses by crystal-bound proteins. We have identified three apolipoproteins among the polypeptides bound to urate crystals exposed to plasma. Identification was first based on their coelectrophoresis with polypeptides from isolated lipoproteins and diminution in the protein coat of crystals exposed to lipoprotein-depleted plasma. The apoproteins were immunochemically identified by the Western blotting technique as apoprotein A-I, apoprotein B (apo B), and apoprotein E. Because neutrophils play a central role in acute gout, we investigated the potential effects of lipoproteins on neutrophil-urate crystal interactions. Plasma profoundly inhibited urate crystal-induced neutrophil luminol-dependent chemiluminescence (CL). Lipoprotein depletion by KBr density gradient centrifugation completely abrogated the inhibitory effect of plasma on urate-induced CL. The inhibitory activity of lipoprotein-depleted plasma was restored by adding back the d less than or equal to 1.25 g/cm3 lipoprotein fraction. Plasma also inhibited urate crystal-induced neutrophil superoxide generation and cytolysis (lactic dehydrogenase loss). This inhibition was significantly diminished by lipoprotein depletion, indicating that the lipoprotein effect was not limited to CL. Lipoprotein-depleted plasma reconstituted with very low, intermediate, and low density lipoproteins (LDL) inhibited crystal-induced CL. High density lipoprotein reconstitution was without effect. Immunodepletion from plasma of all apo B lipoproteins by agarose-bound apo B-specific antibody also removed all inhibitory activity for urate-induced CL. Thus, apo B lipoproteins were shown to be the inhibitory species in plasma. Binding of apo B lipoproteins to urate crystals and inhibition of CL was also seen in the absence of other plasma proteins. In addition, the binding of whole lipoprotein particles to the crystals was verified by detection of crystal-associated cholesterol in addition to the apoprotein. The effects of LDL on urate crystal-induced CL were stimulus specific. Coincubation of urate crystals and neutrophils in the presence of 10 micrograms/ml LDL resulted in 83% inhibition. In contrast, CL responses to a chemotactic hexapeptide, opsonized zymosan, and Staphylococcus aureus were not inhibited by LDL. The effects of depletion of apo B lipoproteins on plasma suppression of urate crystal-induced CL appeared to be unique. Plasma or sera depleted of other urate crystal-binding proteins including fibrinogen, fibronectin, C1q, and IgG retained virtually all their CL inhibitory activity. Lipoproteins containing apo B are thus a major regulator of neutrophil responses to urate crystals. These lipoproteins are present in variable concentration in synovial fluid and may exert an important influence on the course of gout.

Antibody-independent C1 activation by E. coli.

Abstract: Antibody-independent interactions of C1 with several E. coli strains were examined. Purified C1 was directly activated by the semi-rough mutant E. coli J-5, its parental wild-type strain, E. coli 0111:B4, and two clinical isolates, E. coli (P) and E. coli (A), in the absence of C1 inhibitor. E. coli J-5 activated C1 about 10-fold more rapidly and bound approximately threefold more C1 than the other strains. E. coli J-5, but not the other strains, also bound C1s2, provided that the subcomponent was offered to the bacteria in the presence of C1q and calcium; such binding was thus independent of the presence or absence of C1r2. After C1 activation in the absence of C1 inhibitor, activated C1s spontaneously dissociated from E. coli 0111:B4, (P), and (A), but remained associated with E. coli J-5. The regulatory protein C1 inhibitor prevented C1 activation by the weaker activators, E. coli strains 0111:B4, (P), and (A), but had no effect on C1 activation by E. coli J-5. Although C1 inhibitor thus failed to modulate C1 activation by E. coli J-5, it did block the enzymatic activity of activated C1 bound to this strain. Analyses of the molecular processes involved revealed differences with other systems. In the presence of C1 inhibitor, the C1s subunit of C1 activated by E. coli J-5 underwent further cleavage with the release into the supernatant of C1s fragments and complexes of C1 inhibitor with light chain fragments. Such fragments were not disulfide-linked to the remainder of the C1s molecule. The bulk of the heavy chain remained adherent to the surface of E. coli J-5. This finding documents the presence of a binding site for activated C1s on the surface of E. coli J-5 and localizes this site to the heavy chain. These studies thus indicate that several E. coli strains are direct C1 activators. Furthermore, E. coli J-5 provides another example of a direct C1 activator having binding sites not only for C1q but also for dimeric C1s. The studies also show that there are multiple properties of particles which determine the ability to activate C1, the rate of activation, the possibility of regulation of the activation process by C1 inhibitor, and the fate of activated C1.