Low molecular weight hyaluronan, via AP-1 and NF-κB signalling, induces IL-8 in transformed bronchial epithelial cells.

QUESTIONS UNDER STUDY New evidence demonstrated that high tidal volume mechanical ventilation results in substantial bronchial airway mechanical strain. In addition, high tidal volume mechanical ventilation has been shown to increase IL-8 production in a mechanism mediated, at least in part, by low molecular weight hyaluronan (LWM-HA). In the present study, it was investigated whether LMW-HA synthesised in the lung, in response to cyclic stretch, increased IL-8 production in the bronchial epithelium. METHODS This question was approached by stimulating a transformed human bronchial epithelial cell line with LMW-HA isolated from stretched human lung fibroblasts and probed for the activation of extracellular signal-regulated kinase pathways. RESULTS LMW-HA increased IL-8 secretion in transformed bronchial epithelial cells. Additionally, LMW-HA augmented the levels of phospho c-Jun NH2-terminal kinase (JNK) and phospho extracellular signal-regulated kinase 1/2 (ERK1/2), and also mobilised nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) from the cytoplasm to the nucleus. The inhibition of JNK, ERK1/2 and NF-κB blocked IL-8 secretion in response to LMW-HA. CONCLUSION The data suggest that LMW-HA produced by lung fibroblasts in response to cyclic stretch increases the secretion of IL-8 in transformed bronchial epithelial cells via AP-1 and NF-κB signalling pathways. These findings support the hypothesis that LMW-HA plays an active role in acute lung inflammation triggered by mechanical strain.