Pro‐inflammatory effects of extracellular Hsp70 on NCI‐H292 human bronchial epithelial cell line

Extracellular Hsp70 (eHsp70) exerts its biological actions via Toll‐like receptors 2 and 4, and is increased in sera of chronic obstructive pulmonary disease (COPD) patients. The aim of this study was to explore the pro‐inflammatory effects and cytotoxicity of eHsp70 alone and in combination with bacterial components lipoteichoic acid (LTA) and lipopolysaccharide (LPS) on NCI‐H292 airway epithelial cells. NCI‐H292 cells were treated with recombinant human Hsp70 protein (rhHsp70), LPS, LTA and their combinations for 4, 12, 24 and 48 hours. IL‐6, IL‐8 and TNF‐α levels were measured by an ELISA method. Cell viability was determined by the MTS method, and caspase‐3/7, caspase‐8 and caspase‐9 assays. rhHsp70 induced secretion of IL‐6 and IL‐8 in a concentration‐ and time‐dependent manner, with the highest secretion at 24 hours. rhHsp70 combined with LTA had antagonistic and with LPS synergistic effect on IL‐6 secretion, while the interactions between rhHsp70 and LPS or LTA on IL‐8 were synergistic. TNF‐α was not detected in the applied conditions. rhHsp70, LPS or LTA did not affect cell viability, and rhHsp70 even suppressed caspase‐3/7 activities. We suggest that pro‐inflammatory effects of eHsp70, together with other damaging molecules and/or COPD risk factors, might contribute to the aggravation of chronic inflammation in human bronchial epithelium.