Proteinase activated receptor-2 and autophagy regulation: implications for premature lung ageing?

Chronic Obstructive Pulmonary Disease (COPD) lungs display hallmarks of premature ageing. Autophagy is the catabolic process that eukaryotic cells utilise to degrade and recycle cellular components, increasing longevity and delaying the ageing process. COPD patients exhibit reduced lung autophagy, contributing to cellular senescence, although the underlying mechanisms are unclear. Proteinase activated receptor-2 (PAR2) is an important drug target for inflammatory conditions, which has documented roles in lung pathology. However, a role for PAR2 in lung ageing is hitherto unexplored.
Methods: Human epithelial cells (A549 and BEAS-2B lines, primary) were cultured prior to stimulation using PAR2 agonists (SLIGKV, trypsin) and autophagy quantified using a fluorescent marker of autophagosomes (CYTO-ID detection kit). Western blotting to analyse expression of ATGs (autophagy related genes) was used to confirm findings. PAR2 cellular expression was assessed by immunofluorescence.
PAR2 expression was demonstrated in human airway epithelial cells. Autophagic vesicles were successfully detected, and fluorescence levels detected modulated by appropriate autophagy controls. Stimulation of PAR2 activity, assessed alone and in combination with inflammatory stimuli, also caused modulation of the level of autophagic activity within airway epithelial cultures.
Our data indicate PAR2 as a potential regulator of autophagy in lung airway epithelia, suggesting a possible novel role in conditions such as COPD that feature premature lung ageing.