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Serum amyloid P-component-induced colony-stimulating factors production by macrophages
1Department of Biotechnology, National Institute of Pharmaceutical Education and Research, S. A. S. Nagar, India.
Abstract:
Purified mouse serum amyloid P-component (SAP; 0.5-50 microg/kg), injected intravenously into Swiss mice, induced the production of serum colony-stimulating factors (CSFs); the maximum induction was observed at 10.0 microg/kg. Further, in vitro purified mouse SAP (0.1-50 microg/ml) stimulated the mouse elicited peritoneal macrophages to elaborate CSFs in the conditioned medium (CM); 5.0 microg/ml SAP appeared to be the optimum. Both in vivo and in vitro the maximum production of CSFs occurred 6 h after initiation of stimulation, and returned to the background levels by 48 h. Mannose 6-P, mannose 1-P and mannose, and not other sugars inhibited the SAP-induced production of CSFs by macrophages which suggests that SAP interaction with macrophages was mediated by specific glycoprotein-receptors. A neutralizing (100%) concentration of rabbit antimouse interleukin (IL)-1 polyclonal antibody had no effect on the SAP-induced CSF production, indicating that it would be IL-1-independent. SAP-induced CSFs, both in serum and CM, were functionally similar as they supported the formation of granulocyte (G), macrophage (M) and GM colonies in similar proportions. The production of CSFs appeared to be lipopolysaccharide (LPS)-independent as it was not inhibited by polymyxin B sulfate (25.0 microg/ml), and heat-inactivated (80 degrees C, 1 h, pH 7.0) SAP did not induce the production of CSFs. The CSFs were produced de novo because cycloheximide (50.0 microg/ml) completely inhibited their production. These results demonstrate that purified mouse SAP, in a dose-dependent manner, can induce the production of serum CSFs in mice, and can induce LPS-independent de novo production of CSFs by elicited macrophages in vitro.
Insights
Serum amyloid P-component (SAP) induces colony-stimulating factors (CSFs) in mice and macrophages. This process is dose-dependent, occurs within hours, and involves specific receptors, independent of IL-1 and LPS.
Area of Science:
- Immunology
- Hematology
- Biochemistry
Background:
- Serum amyloid P-component (SAP) is a conserved pentraxin protein found in vertebrate sera.
- Colony-stimulating factors (CSFs) are crucial cytokines regulating hematopoiesis, particularly granulocyte and macrophage production.
- The regulatory mechanisms of CSF production, especially in response to non-infectious stimuli like SAP, require further elucidation.
Purpose of the Study:
- To investigate the ability of purified mouse serum amyloid P-component (SAP) to induce the production of colony-stimulating factors (CSFs).
- To determine the dose-dependency, kinetics, and cellular mechanisms underlying SAP-induced CSF production both in vivo and in vitro.
- To explore the potential involvement of specific receptors and signaling pathways, such as IL-1 and LPS, in this process.
Main Methods:
- Intravenous injection of purified mouse SAP into Swiss mice to assess in vivo CSF induction.
- In vitro stimulation of mouse elicited peritoneal macrophages with purified SAP to evaluate CSF elaboration in conditioned medium.
- Inhibition studies using specific sugars (mannose derivatives), anti-IL-1 antibody, and polymyxin B sulfate; assessment of de novo synthesis using cycloheximide.
Main Results:
- Intravenous SAP administration induced a dose-dependent increase in serum CSFs, with optimal induction at 10.0 microg/kg.
- In vitro, SAP stimulated macrophages to produce CSFs, with optimal concentration at 5.0 microg/ml; maximum production observed at 6 hours.
- SAP-induced CSF production was inhibited by mannose derivatives, suggesting specific glycoprotein-receptor interactions, and was independent of IL-1 and LPS.
Conclusions:
- Purified mouse SAP induces the production of functional CSFs in vivo and in vitro in a dose-dependent and time-specific manner.
- The mechanism involves specific SAP-macrophage interactions mediated by mannose-binding receptors and is independent of IL-1 and LPS.
- SAP represents a novel inducer of de novo CSF synthesis, highlighting its potential role in modulating hematopoiesis.
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