Biomedical subjects

K Zahedi

Publications and source records attributed to K Zahedi.

22 records · Page 2Linked to original sources

PubMed1990

IL-1 and IL-6 mediate increased production and synthesis by hepatocytes of acute-phase reactant mouse serum amyloid P-component (SAP).

Primary mouse hepatocytes exposed to the inflammatory cytokines IL-1 and IL-6 in vitro displayed an increase in the production of the major acute-phase reactant, serum amyloid P-component (SAP). Antiserum to recombinant human IL-6 selectively neutralized the SAP-inducing activity secreted by human diploid fibroblasts. Purified mouse interferon-beta (IFN-beta), but not IFN-alpha, also induced SAP production. Addition of 0.05 ng/ml of recombinant mouse IL-1 alpha induced a 10-fold increase in SAP production, whereas recombinant human and recombinant mouse IL-6 displayed optimal SAP-inducing activity of four-fold and seven-fold at 10 ng/ml and 1 unit/ml/2 x 10(5) mouse hepatocytes, respectively. The SAP-inducing activity was neutralized by antibodies to each of the recombinant cytokines. The kinetics of the SAP response in vitro was similar for all of the cytokines. Addition of a mixture of IL-1 and IL-6 to the hepatocytes resulted in SAP production that was not synergistic, but additive, over a range of concentrations for each cytokine. The increase in SAP production mediated by the cytokines was in part the result of an increase in the level of SAP mRNA. Metabolic incorporation of [35S]methionine into mouse SAP occurred in response to both IL-1 and IL-6. Therefore, mouse SAP should be classified among the subset of acute-phase proteins that can be induced by the direct action of either IL-1 or IL-6 on hepatocytes.

Animals↗

PubMed1989

Acute phase induction of mouse serum amyloid P component. Correlation with other parameters of inflammation.

Hepatic mRNA levels of the mouse major acute phase proteins serum amyloid P component (SAP) and serum amyloid A component (SAA) were monitored at timed intervals after i.p. injection of thioglycollate or s.c. injection of azocasein. Both mRNA increased dramatically in response to either inflammatory stimulus. The increase in SAA mRNA levels accompanied an abrupt change in mRNA size from 650 to 750 bases. Peak SAA mRNA concentrations were observed 18 h after either stimulus; by 72 h concentrations had returned to preinflammatory levels. Peak SAP mRNA concentrations were observed 8 h after thioglycollate and 12 to 18 h after azocasein injection; by 36 h concentrations were close to preinflammatory levels. All mRNA species studied (SAP, SAA and the complement components C3, C5 and factor B) were induced more rapidly by the thioglycollate stimulus and reached higher peak concentrations. SAP mRNA levels were correlated with other parameters of inflammation: infiltration of peritoneal exudate cells (PEC) into the peritoneum after thioglycollate injection, and serum concentrations of SAP after azocasein injection. Serum SAP concentrations rose 20-fold in response to the latter stimulus by 36 h, i.e., 18 to 24 h after the peak SAP mRNA levels. The highest numbers of PEC were present 24 h after the thioglycollate stimulus, i.e. 16 h after the maximum SAP mRNA concentration, indicating the continuation of an active local inflammation many hours after one aspect of the systemic response has ceased.

Animals↗

PubMed1989

Binding of human C-reactive protein to mouse macrophages is mediated by distinct receptors.

Human C-reactive protein (CRP) is known to activate mouse macrophages (M phi) to a tumoricidal state and to serve as an opsonin for M phi. Therefore, cell surface receptors for CRP on mouse M phi were characterized and their relationship to the IgG FcR determined. The specific binding of 125I-CRP to resident or elicited mouse M phi was saturable, reversible, and involved both a high and a low affinity receptor population. Binding of CRP to the mouse M phi cell lines PU5 1.8 and J774 was nearly identical to that observed with peritoneal M phi. The high affinity receptor population had a calculated K of 10 nM and a receptor density of approximately 10(5) sites per cell. Mouse Ig of the IgG2a, IgG2b, or IgG1 isotypes inhibited binding of 125I-CRP to PU5 1.8 cells at concentrations five-fold greater than that of the homologous ligand. In the converse experiment, unlabeled CRP failed to inhibit specific binding of 125I-labeled IgG2a, IgG2b or IgG1. Isolation of CRP binding proteins from surface iodinated PU5 1.8 cells by ligand-affinity chromatography or chemical cross-linking yielded a major protein band of 57 to 60 kDa which appeared to be distinct from the IgG1/IgG2b FcR (FcR-II) membrane proteins. Removal of radiolabeled IgG2b/IgG1 binding membrane proteins by affinity chromatography did not remove CRP-binding proteins. The rat mAb 2.4G2 which inhibits binding of radiolabeled mouse IgG2b, did not inhibit the binding of CRP. A rat polyclonal antiserum to CRP-binding membrane proteins of PU5 1.8 cells inhibited 125I-CRP binding, but not 125IgG2b binding. The rat polyclonal antibody reacted with two 57 to 60 kDa membrane proteins from PU5 1.8 cells that appear to be of a similar size on Western blots. The 125I-CRP was internalized via endosomes and intact CRP subunits could be detected intracellularly. The findings suggest that binding of CRP occurs through a receptor that is distinct from the IgG FcRs, but that CRP-R activity may be influenced by an association with an IgG FcR.

Animals↗

PubMed1986

Macrophage tumoricidal activity induced by human C-reactive protein.

Purified C-reactive protein (CRP), the prototypical acute phase reactant of humans, activated inflammatory mouse macrophages to a tumoricidal state. The activation by CRP was not due to small amounts of contaminating lipopolysaccharide. CRP at 10 micrograms/ml induced significant tumoricidal capacity in resident macrophages; the mouse macrophage cell lines PU5 1.8, RAW 264.7, and J774; as well as elicited macrophages from two lipopolysaccharide nonresponder strains, C3H/HeJ and C57BL/10Sc. Macrophages obtained from bone marrow-derived monocytes grown in vitro and exudate macrophages depleted of T-cells were also readily activated by microgram/ml amounts of CRP. Removal of CRP from culture medium using anti-CRP antibodies or phosphorylcholine-agarose beads abrogated the induction of tumoricidal activity. CRP acted independently of both lymphokines and lipopolysaccharide. Therefore, CRP may serve as a physiologically relevant macrophage activator, contributing to the heightened nonspecific host resistance associated with the early stages of a systemic inflammatory response.

Animals↗