Immunopharmacology and inflammationFumigaclavine C exhibits anti-inflammatory effects by suppressing high mobility group box protein 1 relocation and release
Graphical abstract
Introduction
High mobility group box protein 1 (HMGB-1) is described as an intranuclear protein. It functions as a danger signal molecule in somatic cells (Harris and Andersson, 2004). Activated HMGB-1 involves relocation and migration from the nucleus to cytoplasm (Youn and Shin, 2006). Secreted HMGB-1 can induce inflammation via binding to the multiple receptors, such as the receptor for advanced glycation end products (RAGE), toll-like receptor 2/4/9 (TLR-2/4/9), and syndecan, and activate intracellular signaling components including NF-kappaB (NF-κB), protein kinase B (Akt), and mitogen-activated protein kinases (MAPKs) (Chen et al., 2014a, Chen et al., 2014b, Chen et al., 2014c, Li et al., 2007). When HMGB-1 releases, it acts as a stimulator that induces various cellular pro-inflammatory cytokines or booster that exacerbates inflammatory processes (Kim et al., 2012, Shin et al., 2014). Indeed, substantial evidences have revealed that HMGB-1 as an allimportant late-phase alarmin activated immune cells, such as monocytes, macrophages, and hepatocytes (Li et al., 2011, Shen et al., 2014, Zhou et al., 2014). Recent papers have supported that HMGB-1 might be related to hepatic ischemia-reperfusion injury, acute liver injury, and hepatic inflammation (Tong et al., 2013, Zhou et al., 2012a, Zhou et al., 2012b).
In the liver, HMGB-1 takes part in whole hepatic inflammatory processes (Chen et al., 2014a, Chen et al., 2014b, Chen et al., 2014c, Kim et al., 2013a, Kim et al., 2013b). Moreover, HMGB-1 is notably stimulated in activated kupffer cells, monocytes, and microvascular structures (Xiao et al., 2014, Zhou et al., 2012a, Zhou et al., 2012b). Emerging papers have suggested that blockade of HMGB-1 could ameliorate various liver diseases (Cheng et al., 2014, Oh et al., 2011). HMGB-1 contains A box, B box, and an acidic C-terminus. Emerging studies have supported that HMGB-1 was released and relocated due to the acetylation of B box on certain lysine-rich residues (Hidaka et al., 2011, Wu et al., 2012). Hence, directly binding to some certain lysine residues of HMGB-1 B box is considered to be a promising therapeutic target.
As shown in Fig. 1A, fumigaclavine C (FC), the major active ergot alkaloid, was obtained from Aspergillus fumigatus CY018 by the leaf of Cynodon dactylon (Poaceae) (Yao et al., 2014, Zhu et al., 2014). It possesses multiple beneficial effects, such as anti-atherosclerosis (Ma et al., 2006), anti-tumor (Li et al., 2013), anti-inflammation (Wu et al., 2005, Yu et al., 2011, Yu et al., 2014, Yu et al., 2015), immunosuppressive activity (Du et al., 2011). We have previously indicated that FC had a potential immunosuppressive activity against concanavalin A-induced hepatitis in mice through attenuating lymphocyte adhesion and TNF-α production (Zhao et al., 2004). However, the precise mechanisms of the anti-inflammatory and hepatoprotective effects of FC are incompletely delineated. In this study, we further investigated the protective effects of FC on lipopolysaccharide (LPS)-induced murine RAW264.7 cells and the underlying molecular mechanism in liver kupffer cells.
Section snippets
Materials
FC (≥ 99.5%) was obtained from Aspergillus fumigatus CY018 by the leaf of Cynodon dactylon (Poaceae) (Yao et al., 2014, Zhu et al., 2014). TNF-α, IFN-γ, IL-1β, IL-6, and HMGB-1 ELISA Kits were obtained from R&D Systems (Minneapolis, MN, USA). Primary antibodies for HMGB-1, PI3K, PDK1, total of protein kinase C (PKCs), phospho-PI3K (p-PI3K), p-PDK1, p-PKC, p-PKCα, p-PKCβI, p-PKCβII, p-PKCγ, phosphoserine, β-actin, Histone H3.1, and secondary antibodies were purchased Cell Signaling Technology
FC inhibits nitrite production
To eliminate cells’ necrotic secretion of HMGB-1, cytotoxic effects were measured with MTT assays. As shown in Fig. 1B, the tested concentrations of FC had low cytotoxicity in macrophages. These data suggested that HMGB-1 secretion was mainly from the active pathway. To evaluate whether FC possessed potential anti-inflammatory activity, we determined the inhibitory effect of FC on levels of nitrite. As shown in Fig. 1C, LPS treatment significantly elevated the nitrite concentrations (P <
Discussion
We have previously indicated that FC had a potential immunosuppressive activity against concanavalin A-induced hepatitis in mice through attenuating lymphocyte adhesion and TNF-α production (Zhao et al., 2004). However, the precise mechanisms of the anti-inflammatory and hepatoprotective effects of FC were incompletely delineated. Hence, we tried to elucidate the correlation between FC and HMGB-1.
Acute liver injury is a typical feature of hepatitis. It is caused via multiple pro-inflammatory
Conclusions
In conclusion, this study elucidated that FC exhibited anti-inflammatory and hepatoprotective effects via suppressing HMGB-1 relocation and release. The molecular mechanisms might be involved in: ① FC differentially attenuating pro-inflammatory cytokines and the mRNA expression, ② FC suppressing LPS-induced HMGB-1 nucleo-cytoplasmic shuttling relocation and release, ③ FC modulating the PI3K-PDK1-PKCβII/γ signaling pathway, and ④ FC directly binding to the HMGB-1 B box interfering with Lys90 and
Conflict of interest statement
The authors have no competing financial conflict of interest.
Acknowledgments
This work was supported by the National High Technology Research and Development Program of China (2013AA092901), the National Special Fund for State Key Laboratory of Bioreactor Engineering (2060204), and Guangxi Natural Science Foundation (2016GXNSFBA380075).
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