Extracellular HMGB1 regulates multi-walled carbon nanotube-induced inflammation in vivo

Abstract

Endotoxin is often used to activate NF-κB in vitro when assessing NLRP3 inflammasome activation by various exogenous particles including nanoparticles. However, the endogenous source of this signal 1 is unknown. High-mobility group box 1 (HMGB1) is known to play a critical role in acute lung injury, however the potential contribution of the alarmin HMGB1 to NLRP3 Inflammasome activation has not been determined in response to nanoparticles in vivo. In this study, the ability of multi-walled carbon nanotubes (MWCNT) to cause release of HMGB1 in vitro and in vivo, as well as the potential of HMGB1 to function as signal 1 in vitro and in vivo, was determined. HMGB1 activity in vivo was assessed by administration of HMGB1 neutralization antibodies following MWCNT exposure. Caspase-1^−/− mice were utilized to elucidate the dependence of HMGB1 secretion on NLRP3 inflammasome activity. MWCNT exposure increased extracellular HMGB1 levels in primary alveolar macrophages from C57Bl/6 mice and C10 mouse epithelial cell culture supernatants, and in C57Bl/6 mouse lung lavage fluid. MWCNT-induced HMGB1 secretion was dependent upon caspase-1. HMGB1 increased MWCNT-induced IL-1β release from macrophages in vitro, and neutralization of extracellular HMGB1 reduced MWCNT-induced IL-1β secretion in vivo. HMGB1 neutralization was accompanied with overall decreased inflammation. In summary, this study suggests extracellular HMGB1 participates in NLRP3 inflammasome activity and regulates IL-1β associated sterile inflammation induced by MWCNT.

• Caspase-1
• DAMP
• IL-1β
• MWCNT
• sterile inflammation

Acknowledgements

The authors thank Center for Environmental Health Sciences core scientists, Mary Buford (Inhalation and Pulmonary Physiology Core), Brittan Postma (Animal Core), Lou Herritt (Molecular Histology and Fluorescence Imaging Core) and Dr Chris Migliaccio (Inhalation and Pulmonary Physiology Core Director) and Ray Hamilton for contributions of expertise and advice needed to conduct the experiments discussed in this manuscript. The content is solely the responsibility of the authors, and does not necessarily represent the official views of the NIH or PhRMA Foundation.

Declaration of interest

The authors declare no conflicts of interest. The authors alone are responsible for the content and writing of this manuscript. Research reported in this publication was supported grants from the National Institute of General Medical Sciences of the National Institutes of Health (NIH) under award number P30GM103338, National Institute of Environmental Health Sciences under award number RC2-ES018742 and a Pre-doctoral fellowship from PhRMA Foundation (Forrest Jessop).

Supplementary material available online

Supplementary materials S1–S3