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Differential regulation of soluble interleukin 1 release and membrane expression by pharmacologic agents
1Rheumatic Disease Unit, Montreal General Hospital Research Institute, McGill University, Quebec, Canada.
Abstract:
Membrane IL-1 (mIL-1) expression was compared with release of soluble IL-1 (sIL-1) by C3H/HeNCrl mouse peritoneal macrophages. Selective antagonists of protein kinase C (PKC) (H-7) and calmodulin (W-7) in combination inhibited LPS-induced mIL-1 and sIL-1 production, suggesting a role for these activation pathways in IL-1 induction. Low levels of A23187, when combined with OAG (a direct activator of PKC), stimulated mIL-1 expression in the absence of sIL-1 release. Induction of mIL-1 by LPS was inhibited by PGE2 and dibutyryl cAMP, but higher concentrations were required to inhibit mIL-1 expression compared with sIL-1 release. LTB4 alone did not induce mIL-1 or sIL-1 production. LTB4 did enhance LPS-induced mIL-1 expression but not sIL-1 release. These results indicate that mIL-1 expression and sIL-1 release are differentially regulated. Membrane IL-1 is induced by lower levels of certain stimuli and is less effectively inhibited than is sIL-1 release. This differential regulation is further evidence to support the existance of membrane IL-1.
Insights
This study reveals that membrane interleukin-1 (mIL-1) and soluble interleukin-1 (sIL-1) are regulated differently in mouse macrophages. Membrane IL-1 induction and inhibition show distinct patterns compared to soluble IL-1 release.
Area of Science:
- Immunology
- Cell Biology
Background:
- Interleukin-1 (IL-1) exists in both membrane-bound (mIL-1) and soluble (sIL-1) forms.
- Understanding the differential regulation of these forms is crucial for comprehending immune responses.
Purpose of the Study:
- To compare the regulation of membrane IL-1 (mIL-1) expression with soluble IL-1 (sIL-1) release in mouse peritoneal macrophages.
- To investigate the signaling pathways involved in mIL-1 and sIL-1 production.
Main Methods:
- Macrophages were stimulated with lipopolysaccharide (LPS), calcium ionophore A23187, and phorbol ester OAG.
- Inhibitors of protein kinase C (PKC) and calmodulin were used to probe signaling pathways.
- Effects of prostaglandin E2 (PGE2), dibutyryl cAMP, and leukotriene B4 (LTB4) were assessed.
Main Results:
- Selective antagonists of PKC and calmodulin inhibited both LPS-induced mIL-1 and sIL-1 production.
- Low levels of A23187 with OAG stimulated mIL-1 without sIL-1 release.
- PGE2 and dibutyryl cAMP inhibited mIL-1 induction, but required higher concentrations than for sIL-1 inhibition.
- LTB4 enhanced LPS-induced mIL-1 but not sIL-1 release.
Conclusions:
- Membrane IL-1 expression and soluble IL-1 release are differentially regulated.
- mIL-1 is induced by lower stimulus levels and less effectively inhibited than sIL-1.
- These findings provide further evidence for the distinct biological existence and function of membrane IL-1.