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Interleukin-4 regulates macrophage interleukin-12 protein synthesis through a c-fos mediated mechanism
S Roy1, R Charboneau, D Melnyk
1Departments of Surgery, Pharmacology, and Anesthesiology, University of Minnesota, Minneapolis Veterans Affairs Medical Center, 55417, USA.
Background:
Interleukin-4 (IL-4) treatment after lipopolysaccharide (LPS) induction inhibits macrophage (Mphi) IL-12 synthesis; however, IL-4 pretreatment (PreTx) primes the Mphi for increased LPS-induced IL-12 production. In this study we study the role of c-fos in the IL-4 priming of Mphi IL-12 synthesis.
Methods:
With a murine in vitro peritoneal M phi model, we studied the effect of either c-fos deficiency (wild type, WT; homozygous c-fos knockout, Homo KO) or c-fos overexpression to study the role of c-fos in IL-4 priming of LPS-induced M phi IL-12 synthesis.
Results:
(1) We first show that IL-4 PreTx results in a 72% decrease in Mphi c-fos mRNA compared with vehicle PreTx. (2) With respect to IL-12 p70 protein, IL-4 PreTx in the WT group increased LPS-induced Mphi IL-12 p70 2.2-fold compared with vehicle PreTx. Compared with vehicle PreTx in the WT group, vehicle PreTx in the Homo KO group followed by LPS stimulation resulted in a 2.8-fold increase in IL-12 p70 in the Homo KO group. IL-4 PreTx did not significantly increase IL-12 p70 over vehicle PreTx in the Homo KO group. (3) We studied the effect of c-fos overexpression on LPS-induced Mphi IL-12 production when primed with IL-4. Overexpression of c-fos completely inhibited IL-4 primed LPS-induced IL-12 p70 protein synthesis.
Conclusions:
These data demonstrated that down-regulation of c-fos is an integral part of the IL-4 priming process for Mphi IL-12 production.
Insights
Interleukin-4 (IL-4) pretreatment primes macrophages for increased IL-12 production by down-regulating c-fos. This study reveals c-fos
Area of Science:
- Immunology
- Molecular Biology
Background:
- Interleukin-4 (IL-4) differentially regulates macrophage (Mphi) IL-12 synthesis post-lipopolysaccharide (LPS) induction.
- IL-4 pretreatment (PreTx) primes Mphi for enhanced LPS-induced IL-12 production, a mechanism not fully understood.
Purpose of the Study:
- To investigate the role of the transcription factor c-fos in IL-4-mediated priming of Mphi IL-12 synthesis.
Main Methods:
- Utilized a murine in vitro peritoneal Mphi model.
- Examined the effects of c-fos deficiency (homozygous c-fos knockout, Homo KO) and c-fos overexpression on IL-4 priming and LPS-induced IL-12 production.
Main Results:
- IL-4 PreTx significantly decreased Mphi c-fos mRNA levels by 72%.
- In wild-type (WT) Mphi, IL-4 PreTx increased LPS-induced IL-12 p70 protein by 2.2-fold.
- In Homo KO Mphi, IL-4 PreTx did not enhance IL-12 p70 production, and c-fos overexpression completely inhibited IL-4 primed IL-12 p70 synthesis.
Conclusions:
- Down-regulation of c-fos is a critical component of the IL-4 priming mechanism in Mphi.
- These findings elucidate a novel regulatory pathway for IL-12 production in macrophages.