Abstract
High-mobility group box-1 (HMGB1) protein, as one of the well-known damage-associated molecular pattern molecules (DAMPs), is enriched in chronic hepatitis B virus (HBV) infection and has a context-dependent role in autophagy, a highly conserved self-digestive process in response to environmental stress. Recent mouse studies indicate that autophagy is highly active in regulatory T (Treg)-cells. In the present study, we evaluated spontaneous and induced autophagy of peripheral Treg cells from 98 patients with chronic hepatitis B (CHB), by measuring levels of lipidated form of microtubule-associated light chain 3 (LC3-II, marker for closed autophagosomes) and observing autophagic vacuoles (AV) with transmission electron microscope. No significant difference was found in spontaneous autophagy of either Treg or CD4+ naive cells when comparing CHB patients with healthy subjects, apart from CHB-Treg showed significantly higher autophagic activity after activation by anti-CD3–CD28 beads. Besides, incubation of CHB-Treg cells with CHB-serum greatly maintained their autophagic behaviour, which could be significantly diminished by blocking HMGB1 with the neutralizing antibody. Further, we characterized time- and dose-dependent effects by recombinant HMGB1 protein on autophagy of CHB-Treg cells. We also documented a significant up-regulation of HMGB1 and its receptors [toll-like receptor (TLR4), receptor for advanced glycation end-product (RAGE)] in both peripheral and intra-hepatic microenvironments of CHB patients. Moreover, the RAGE–extracellular regulated protein kinases (ERK) axis and rapamycin-sensitive components of mammalian target of rapamycin (mTOR) pathways were demonstrated in vitro to be involved in HMGB1-induced autophagy of Treg cells. Additionally, HMGB1-induced autophagy could maintain cell survival and functional stability of CHB-Treg cells. Our findings could open new perspectives in developing therapeutic strategies to activate specific anti-HBV immunity by diminishing Treg autophagy.
- autophagy
- chronic hepatitis B
- high-mobility group box-1
- regulatory T-cells
Abbreviations
- ALT,
- alanine aminotransferase;
- 7-AAD,
- 7-Aminoactinomycin D;
- AMPK,
- AMP-activated protein kinase;
- APC,
- allophycocyanin;
- Atg,
- autophagy-related genes;
- AST,
- aspartate aminotransferase;
- AV,
- annexin V;
- AVs,
- autophagic vacuoles;
- CCK-8,
- cell counting kit 8;
- CHB,
- chronic hepatitis B;
- CQ,
- chloroquine;
- CTLA-4,
- cytotoxic T-lymphocyte antigen-4;
- DAMP,
- damage-associated molecular pattern molecule;
- ERK,
- extracellular regulated protein kinases;
- Foxp3,
- forkhead box P3;
- HBc,
- HBV core;
- HBeAg,
- HBV e antigen;
- HBsAg,
- HBV surface antigen;
- HBV,
- hepatitis B virus;
- HBX,
- HBV X protein;
- HC,
- healthy controls;
- HMGB1,
- high-mobility group box-1;
- HRP,
- horseradish peroxidase;
- IFN,
- interferon;
- IL,
- interleukin;
- JNK,
- c-Jun N-terminal kinase;
- LAL,
- limulus amebocyte lysate;
- LC3,
- microtubule-associated light chain 3;
- mAb,
- monoclonal antibody;
- MAPK,
- mitogen-activated protein kinases;
- MFI,
- mean fluorescence intensity;
- mTOR,
- mammalian target of rapamycin;
- mTORC,
- mTOR complex;
- PAMPs,
- pathogen-associated molecular patterns;
- PBMCs,
- peripheral blood mononuclear cells;
- PE,
- phosphatidylethanolamine;
- PRR,
- pattern recognition receptor;
- RAGE,
- receptor for advanced glycation end-products;
- rHMGB1,
- recombinant HMGB1;
- rIL-2,
- recombinant human IL-2;
- RT,
- reverse transcription;
- SAPK,
- stress-activated protein kinase;
- TGF,
- transforming growth factor;
- TLR,
- toll-like receptor;
- Treg,
- regulatory T;
- ULK1,
- unc-51-like kinase;
- ULN,
- upper limit of normal
- © 2017 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society
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March 2017
Volume: 131 Issue: 5
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