Cigarette smoke induced pathophysiological changes in the extracellular matrix but not inflammation as early events in fresh human lung tissue

Abstract

Cigarette smoke (Cs) inhalation is a main reason to develop chronic obstructive pulmonary disease (COPD), characterised by degradation of alveoli, mucus hypersecretion, emphysema development and inflammation [1]. The pathophysiology of COPD is not well understood so the mechanisms that underlie various components of COPD need to be modelled in vitro, specifically using Cs. We assessed the pathophysiological effects of Cs and Cs condensate (Csc) on fresh human lung tissue. Human Precision Cut Lung Slices (PCLS) were exposed to Csc submerged or whole Cs in an Air-Liquid Interface using the in vitro exposure device P.R.I.T.® ExpoCube®. Cytotoxicity, release of cytokines and extracellular matrix (ECM) proteins were measured and gene expression analysis upon RNA isolation from PCLS was performed. PCLS exposed to Csc or Cs showed concentration-dependent loss of tissue viability. Gene expression analysis upon RNA isolated from lung tissue exposed to nontoxic doses of Csc of literature-based COPD-relevant genes indicate damage of epithelium by upregulation of genes involved in tissue injury (e.g. mmp) and specific metabolic activity (e.g. cyp1a1). Samples exposed to control substance LPS did not show increased expression in emphysema associated genes but in genes indicating inflammation (e.g. il-6). These data can be supported by increased production of proteins related to the extracellular matrix (e.g. MMP9, RAGE) and inhibited expression in pro-inflammatory cytokines after Cs exposure in an air-liquid culture. Supportive results were presented in BAL samples from COPD subjects showing markers of apoptosis [2]. These results indicate that early stages of Cs induced lung tissue changes are primarily not provoked by immunological processes but by apoptosis, increased specific metabolic activity and damage of the epithelium. [1] Hodge, S. et al. (2005). ERJ 25 (3), S. 447-454. [2] Shaykhiev, R.; Crystal, R. (2014). AnnalsATS 11 Suppl 5, S252-8