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Lipopolysaccharide-Induced M2 to M1 Macrophage Transformation for IL-12p70 Production Is Blocked by Candida albicans Mediated Up-Regulation of EBI3 Expression

Zheng, X-F, Hong, Y-X, Zhang, G-F, Rogers, H, Lewis, MAO, Williams, DW, Song, B, Wei, X-Q, Xia, Z-F and Feng, G-J (2013) Lipopolysaccharide-Induced M2 to M1 Macrophage Transformation for IL-12p70 Production Is Blocked by Candida albicans Mediated Up-Regulation of EBI3 Expression PLoS ONE, 8 (5).

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Abstract

Macrophages are heterogeneous cell populations that are present in all tissues. Macrophages can be divided into classically activated inflammatory macrophages (M1) and alternatively activated anti-inflammatory macrophages (M2). It has been generally accepted that M1 macrophages are polarised in an inflammatory environment to produce pro-inflammatory cytokines, whilst M2 macrophages are involved in anti-inflammation and aid tissue repair in wound healing. Bacterial endotoxin (lipopolysaccharide; LPS) is a potent factor in infection, which induces M1 macrophages resulting in higher levels of iNOS, TNFα and IL-12p70 which dictate inflammatory T cell responses. M2 macrophages can be transformed into M1 macrophages following LPS stimulation to promote inflammation. Candida albicans is a commensal fungal microorganism, which has been suggested to induce immune tolerance; however, the mechanism of C. albicans-induced immune tolerance has not been investigated in detail. IL-35 is a recently identified anti-inflammatory cytokine which is a heterodimeric protein consisting of the Epstein-Barr virus-induced gene 3 (EBI3) and IL-12p35. IL-35 shares the protein subunit p35, with IL-12p70. IL-12p70 is the most potent cytokine to induce Th1 responses during inflammation. In this study, we demonstrate that heat-killed C. albicans (HKC) strongly suppressed LPS-induced IL-12p70 production in M2 macrophages. Candida albicans induced a high level of EBI3 expression in M2 macrophages, which served as a mechanism for IL-12p70 suppression by competitive binding of the common protein subunit (p35) of IL-35 and IL-12p70. To demonstrate that EBI3 expression had the ability to block IL-12p70 production intracellularly, a Chinese Hamster Ovary (CHO) cell line with biscistronic expression of IL-12p40 and p35 was constructed, followed by ectopic over-expression of EBI3. The over-expression of EBI3 in the IL-12p70 producing cell line effectively suppressed IL-12p70 production. IL-35 secretion was also detected in the cell line, with suppressed IL-12p70 production by immune-precipitation Western blotting. However, this secretion was not evident in M2 macrophages following stimulation by HKC. This can be explained by the constitutive expression of IL-35 receptors (gp130 and IL-12Rβ2) in M2 macrophages for cytokine consumption. Our results have indicated that C. albicans can suppress host inflammatory responses in mucosal skin by suppressing LPS-induced IL-12p70 production. Lower IL-12p70 production may avoid an unnecessary Th1 response in order to retain immune tolerance, which may be one of the mechanisms by which C. albicans achieves a successful commensal lifestyle without having a detrimental effect on the host's health. © 2013 Zheng et al.

Item Type: Article
Authors :
NameEmailORCID
Zheng, X-FUNSPECIFIEDUNSPECIFIED
Hong, Y-XUNSPECIFIEDUNSPECIFIED
Zhang, G-FUNSPECIFIEDUNSPECIFIED
Rogers, HUNSPECIFIEDUNSPECIFIED
Lewis, MAOUNSPECIFIEDUNSPECIFIED
Williams, DWUNSPECIFIEDUNSPECIFIED
Song, BUNSPECIFIEDUNSPECIFIED
Wei, X-QUNSPECIFIEDUNSPECIFIED
Xia, Z-FUNSPECIFIEDUNSPECIFIED
Feng, G-Jg.feng@surrey.ac.ukUNSPECIFIED
Date : 27 May 2013
Identification Number : https://doi.org/10.1371/journal.pone.0063967
Depositing User : Symplectic Elements
Date Deposited : 17 May 2017 09:56
Last Modified : 17 May 2017 09:56
URI: http://epubs.surrey.ac.uk/id/eprint/825693

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