Pseudomonas aeruginosa–Induced Apoptosis in Airway Epithelial Cells Is Mediated by Gap Junctional Communication in a JNK-Dependent Manner

Abstract

Chronic infection and inflammation of the airways is a hallmark of cystic fibrosis (CF), a disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. The response of the CF airway epithelium to the opportunistic pathogen Pseudomonas aeruginosa is characterized by altered inflammation and apoptosis. In this study, we examined innate immune recognition and epithelial responses at the level of the gap junction protein connexin43 (Cx43) in polarized human airway epithelial cells upon infection by PAO1. We report that PAO1 activates cell surface receptors to elicit an intracellular signaling cascade leading to enhancement of gap junctional communication. Expression of Cx43 involved an opposite regulation exerted by JNK and p38 MAPKs. PAO1-induced apoptosis was increased in the presence of a JNK inhibitor, but latter effect was prevented by lentiviral expression of a Cx43-specific short hairpin RNA. Moreover, we found that JNK activity was upregulated by pharmacological inhibition of CFTR in Calu-3 cells, whereas correction of a CF airway cell line (CF15 cells) by adenoviral expression of CFTR reduced the activation of this MAPK. Interestingly, CFTR inhibition in Calu-3 cells was associated with decreased Cx43 expression and reduced apoptosis. These results indicate that Cx43 expression is a component of the response of airway epithelial cells to innate immune activation by regulating the survival/apoptosis balance. Defective CFTR could alter this equilibrium with deleterious consequences on the CF epithelial response to P. aeruginosa

Elimination of Pseudomonas aeruginosa through Efferocytosis upon Binding to Apoptotic Cells

“…Although to reach late stages of apoptosis upon their induction by P . aeruginosa infection epithelial cells need times longer than those used in our settings [26, 27], we checked whether P . aeruginosa infection increased the number of apoptotic cells.…”

Pseudomonas aeruginosa infection stimulates mitogen‐activated protein kinases signaling pathway in human megakaryocytes

“…Both heat‐killed PAO1 and its lysate induced cytotoxicity in short time exposed Mo7e cells, whereas with longer exposure we observed cytotoxicity only with lysate. Earlier studies have reported that P. aeruginosa infection induces apoptosis in NK cells, macrophages and airway epithelial cells in a caspase 9 dependent manner and through interactions between cytotoxins (exoenzymes S, T and U) and host cells. Similarly, pyocyanin and exotoxin A of P. aeruginosa have also been reported to induce cytoxicity in neutrophils and mouse fibroblasts .…”

CXCL4 contributes to host defense against acute Pseudomonas aeruginosa lung infection

“…CXCL4 binds to bacteria[ 22 , 23 ] and activates neutrophils through multiple intracellular signals and pathways[ 24 ]. Previous studies have shown essential roles for PI3K[ 25 ], Syk[ 26 ], JNK[ 27 ], p38[ 28 ] and JAK/STAT[ 29 , 30 ] signaling during host defense against P . aeruginosa , suggesting a potential role of CXCL4 in P .…”