Pseudomonas aeruginosa quorum‐sensing homoserine lactone inhibits O2 consumption and stimulates H+ secretion by airway epithelia (869.2)

Abstract

P. aeruginosa biofilms accumulate in the airways of cystic fibrosis patients and produce the quorum‐sensing molecule N‐(3‐oxododecanoyl)‐homoserine lactone (C12) that depolarizes mitochondria. We tested whether C12 and P. aeruginosa biofilms change O2 consumption and H+ secretion into the extracellular fluid of JME (CF nasal epithelia, ΔF508CFTR) and CFTR‐corrected JME cells studied in Seahorse X24‐well dishes. C12 caused dose‐dependent (min = 1 µM, max = 50 µM) inhibition of O2 consumption (to 0.6x control) and increases in H+ secretion (to 1.3x control), similar to effects of mitochondrial poisons antimycin + rotenone. As measured by pH‐stat, C12 increased H+ secretion into the apical solution of human tracheal epithelial (HTE) cells in primary culture by 0.3 µeq.cm‐2.hr‐1, similar to rates measured using Seahorse. H+ secretion by HTE cells was blocked by Zn2+. PAO1wt biofilms inhibited O2 consumption and increased H+ secretion by JME cells, while PAO1lasI biofilm and planktonic PAO1wt did not. JME and CFTR‐corrected JME cells behaved similarly during all treatments. These data indicated: (i) P. aeruginosa biofilms, most likely operating through C12, inhibit O2 consumption and stimulate H+ secretion by airway epithelia. (ii) H+ secretion occurs through a Zn2+‐sensitive H+ channel in the apical membrane. (iii) Although there is no direct role for CFTR in these processes, a downward spiral in CF is predicted: increased acidity in CF ASL (no HCO3 secretion) → reduced antimicrobial factors → P. aeruginosa accumulation in biofilms → inhibit mitochondrial metabolism and increase anaerobic glycolysis in epithelia → increased epithelial secretion of H+ → increased acidity in ASL → reduced antimicrobial factors → increased P. aeruginosa accumulation.Grant Funding Source: NIH, CFRI