HMGB1 mediates Aspergillus fumigatus-induced inflammatory response in alveolar macrophages of COPD mice via activating MyD88/NF-κB and syk/PI3K signalings.

The incidence and mortality of Aspergillus fumigatus (A. fumigatus) infected chronic obstructive pulmonary disease (COPD) patients are increasing. HMGB1, which mediates inflammatory response, is increased in COPD patients. However, the role and mechanism of HMGB1 in A. fumigatus-infected alveolar macrophages of COPD mice remain unknown. Alveolar macrophages isolated from COPD mice were infected with A. fumigatus conidia and then HMGB1 expression was assayed. The levels of pro-inflammatory cytokines, which was confirmed by TLR2/4 or Dectin-1 siRNA, RAGE, Dectin-1, and TLR2/4 levels were assayed after HMGB1 knockdown. The effects of HMGB1 on MyD88/NF-κB and syk/PI3K signaling pathways were explored with PDTC (NF-κB inhibitor) and R406 (syk inhibitor). The potential role of HMGB1 was also confirmed in A. fumigatus-infected COPD mice. HMGB1 expression was increased in A. fumigatus-infected COPD alveolar macrophages. The levels of pro-inflammatory cytokines induced in A. fumigatus-infected COPD but not control alveolar macrophages were reduced by HMGB1, TLR2/4 or Dectin-1 siRNA. The expression of Dectin-1 and TLR2/4, but not RAGE was decreased by HMGB1 siRNA. The expression of MyD88, p-p65, p-syk, and PI3K was decreased and IκB increased by HMGB1 knockdown. PDTC and R406 showed the similar effects as HMGB1 siRNA on levels of pro-inflammatory cytokines. The expression of HMGB1, TNF-α, IL-1β, TLR2/4 and Dectin-1, and the activation of MyD88/NF-κB and syk/PI3K signalings in mice were consistent with the in vitro study. In conclusion, HMGB1 is responsible for A. fumigatus-induced inflammatory response in COPD alveolar macrophage via Dectin-1 and TLR2/4 receptor through activating MyD88/NF-κB and syk/PI3K signalings.