PT  - JOURNAL ARTICLE
AU  - Leonarda Di Candia
AU  - Ruth Saunders
AU  - John Challiss
AU  - Christopher Brightling
TI  - HMGB1 is upregulated in ASM in asthma and induces ASM contraction via TLR4
AID  - 10.1183/13993003.congress-2015.PA5099
DP  - 2015 Sep 01
TA  - European Respiratory Journal
PG  - PA5099
VI  - 46
IP  - suppl 59
4099  - http://erj.ersjournals.com/content/46/suppl_59/PA5099.short
4100  - http://erj.ersjournals.com/content/46/suppl_59/PA5099.full
SO  - Eur Respir J2015 Sep 01; 46
AB  - Introduction: High mobility group box-1 (HMGB1) is released during tissue damage and inflammation, and is involved in inflammatory diseases including asthma. We hypothesised that HMGB1 expression in airway smooth muscle (ASM) of asthmatics is increased and amplifies agonist-induced ASM contraction via receptor for advanced glycosylation end products (RAGE) and/or Toll-like receptor 4 (TLR4).Methods: HMGB1 expression was assessed in bronchial biopsies of asthmatics (n=16) and healthy controls (n=10). HMGB1, RAGE and TLR4 expression in primary ASM cells was measured by flow cytometry. The effect of HMGB1 on bradykinin-induced ASM contraction was assessed in collagen gel-embedded ASM cells in the presence or absence of soluble RAGE, an antagonist of RAGE activation, and the TLR4 antagonist LPS-RS.Results: HMGB1 expression was increased in ASM of asthmatics vs non-asthmatics (546±127 vs 211±36 HMGB1+ve cells/mm2 ASM; p=0.021). HMGB1 expression was upregulated in primary ASM cells stimulated with pro-inflammatory cytokines (IL-1β, TNFα, and IFNγ, n=14; p<0.001), and with the TLR3 agonist poly(I:C) (n=11; p=0.007). Cell-surface RAGE and TLR4 were detected in ASM cells (n=8). HMGB1 stimulation caused a 27% increase in bradykinin-induced ASM cell contraction and this was inhibited by LPS-RS, but not by soluble RAGE (n=5; p=0.013).Conclusions: HMGB1 upregulation ex vivo in ASM of asthmatics and in vitro following activation suggests that ASM can release HMGB1 in a pro-inflammatory environment or following viral exposure. HMGB1 amplifies ASM agonist-induced contraction via a TLR4-dependent mechanism suggesting HMGB1 may act upon ASM in an autocrine/paracrine manner to enhance airway hyperresponsiveness in asthma.