Extracellular Hsp70 modulates inflammatory response in PBEC cells from COPD patients

Abstract

Cigarette smoke is one of the major risk factors for development of chronic obstructive pulmonary disease (COPD), characterized by chronic inflammation. Bacterial infections can increase inflammatory responses and cause exacerbations in COPD. Extracellular Hsp70 (eHsp70) can act pro-inflammatory via Toll-like receptors (TLR) 2 or 4, and was found elevated in sera of COPD patients. We hypothesized that eHsp70 modulates the inflammatory response provoked by bacterial compounds and cigarette smoke. Therefore, we aimed to investigate the effect of eHsp70 present together with lipopolysaccharide (LPS), lipoteichoic acid (LTA) or cigarette smoke extract (CSE) on interleukin-8 (IL-8) secretion. We treated primary tracheo-bronchial epithelial cells (PBEC) isolated from healthy controls and COPD patients either with recombinant human (rh) Hsp70 (0.1, 1 and 3 µg/ml), 0.1 µg/ml LPS, 1 µg/ml LTA and CSE (2.5 and 15%) alone or with their combinations. IL-8 levels in cell-free supernatants were determined by ELISA. RhHsp70, LTA and CSE alone increased IL-8 secretion in PBEC both from healthy volunteers and COPD patients, while LPS had no significant effect. Instead of an additive effect, combined treatment with rhHsp70 reduced IL-8 levels compared to the presence of LPS, LTA or CSE alone in COPD-derived PBEC, but not those from healthy controls. In conclusion, rhHsp70 reduces the pro-inflammatory effects of bacterial components and CSE in PBEC cells from COPD patients. Their combined presence could lead to attenuation of pro-inflammatory epithelial responses in COPD patients, and Hsp70 could have a protective instead of detrimental effect in COPD.