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Published on: December 26, 2017
[Anti-inflammatory effects of apoprotein AI are mediated via modulating macrophage polarity]
Quanzhong Li1, Zhenli Zhai1, Weihong Ma1
1Department of Cardiology, Affiliated Hospital of Guilin Medical College, Guilin 541001, China.
Objective:
To explore the anti-inflammatory mechanisms of high density lipoprotein (HDL) by observing the effects of apoprotein (apo)AI, a major protein component of HDL, on the inflammatory macrophage cell polarity.
Methods:
Cultured mice marrow-derived macrophages were stimulated with lipopolysaccharide and interferon after 10 µg/ml of apoAI were added to the macrophages for 24 hours. The expression of membrane molecules CD16/32, CD206 were detected by fluorescence activated cell sorting (FACS). ELISA was used to detect the secretion of IL-10 and IL-12. Real-time quantitative PCR was used to detect the mRNA expression of TLR4, MyD88 and IRF5.
Results:
Compared to macrophages stimulated by interferon and lipopolysaccharide but without pretreatment with apoAI, pre-incubation with apoAI significantly downregulated the expression of CD16/32 (91.17% ± 1.99% vs.50.47% ± 1.02%, P < 0.05), IL-12 [(747.27 ± 3.74)pg/ml vs. (73.80 ± 4.56)pg/ml, P < 0.05], upregulated the expression of CD206(0.33% ± 0.12% vs. 3.00% ± 0.36%, P < 0.05), IL -10 expression [(23.56 ± 4.30) pg/ml vs.(32.91 ± 2.47) pg/ml, P < 0.05], and reduced the mRNA expression of TLR4 (1.000 ± 0.025 vs.0.708 ± 0.003, P < 0.05) , MyD88 (1.591 ± 0.005 vs. 1.341 ± 0.005, P < 0.05) , IRF5 (0.954 ± 0.005 vs. 0.463 ± 0.003, P < 0.05) .
Conclusion:
ApoAI enhances the switch of inflammatory macrophages to anti-inflammatory macrophages possibly through inhibiting TLR4-MyD88-IRF5 pathway.
Insights
Apoprotein AI (apoAI) from high-density lipoprotein (HDL) shifts inflammatory macrophages to an anti-inflammatory state. This occurs by inhibiting the Toll-like receptor 4 (TLR4)-MyD88-IRF5 pathway, reducing pro-inflammatory markers.
Area of Science:
- Immunology
- Molecular Biology
- Cardiovascular Research
Background:
- High-density lipoprotein (HDL) plays a crucial role in reverse cholesterol transport and possesses anti-inflammatory properties.
- Apolipoprotein AI (apoAI) is the primary protein component of HDL, mediating many of its biological functions.
- Macrophage polarization is critical in regulating inflammatory responses, with a shift from pro-inflammatory (M1) to anti-inflammatory (M2) phenotypes being therapeutically relevant.
Purpose of the Study:
- To investigate the anti-inflammatory mechanisms of apoAI, a key component of HDL.
- To determine the effect of apoAI on the inflammatory macrophage cell polarity.
- To elucidate the molecular pathways involved in apoAI-mediated macrophage polarization.
Main Methods:
- Murine bone marrow-derived macrophages were cultured and stimulated with lipopolysaccharide (LPS) and interferon (IFN).
- Macrophages were pre-incubated with 10 µg/ml of apoAI for 24 hours prior to stimulation.
- Flow cytometry (FACS) was used to assess surface marker expression (CD16/32, CD206).
- Enzyme-linked immunosorbent assay (ELISA) measured cytokine secretion (IL-10, IL-12).
- Quantitative real-time PCR (qRT-PCR) analyzed mRNA expression of key pathway components (TLR4, MyD88, IRF5).
Main Results:
- ApoAI pre-treatment significantly downregulated the expression of pro-inflammatory markers CD16/32 and IL-12.
- ApoAI significantly upregulated the expression of anti-inflammatory marker CD206 and the anti-inflammatory cytokine IL-10.
- ApoAI significantly reduced the mRNA expression of Toll-like receptor 4 (TLR4), Myeloid differentiation primary response 88 (MyD88), and Interferon regulatory factor 5 (IRF5).
Conclusions:
- ApoAI promotes the polarization of inflammatory macrophages towards an anti-inflammatory phenotype.
- The mechanism involves the inhibition of the TLR4-MyD88-IRF5 signaling pathway.
- These findings highlight apoAI as a potential therapeutic agent for inflammatory diseases.
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