Resistance toPseudomonas aeruginosaChronic Lung Infection Requires Cystic Fibrosis Transmembrane Conductance Regulator-Modulated Interleukin-1 (IL-1) Release and Signaling through the IL-1 Receptor

Abstract

Innate immunity is critical for clearing Pseudomonas aeruginosa from the lungs. In response to P. aeruginosa infection, a central transcriptional regulator of innate immunity-NF-B-is translocated within 15 min to the nuclei of respiratory epithelial cells expressing wild-type (WT) cystic fibrosis (CF) transmembrane conductance regulator (CFTR). P. aeruginosa clearance from lungs is impaired in CF, and rapid NF-B nuclear translocation is defective in cells with mutant or missing CFTR. We used WT and mutant P. aeruginosa and strains of transgenic mice lacking molecules involved in innate immunity to identify additional mediators required for P. aeruginosa-induced rapid NF-B nuclear translocation in lung epithelia. We found neither Toll-like receptor 2 (TLR2) nor TLR4 nor TLR5 were required for this response. However, both MyD88-deficient mice and interleukin-1 receptor (IL-1R)-deficient mice failed to rapidly translocate NF-B to the nuclei of respiratory epithelial cells in response to P. aeruginosa. Cultured human bronchial epithelial cells rapidly released IL-1␤ in response to P. aeruginosa; this process was maximized by expression of WT-CFTR and dramatically muted in cells with ⌬F508-CFTR. The IL-1R antagonist blocked P. aeruginosa-induced NF-B nuclear translocation. Oral inoculation via drinking water of IL-1R knockout mice resulted in higher rates of lung colonization and elevated P. aeruginosaspecific antibody titers in a manner analogous to that of CFTR-deficient mice. Overall, rapid IL-1 release and signaling through IL-1R represent key steps in the innate immune response to P. aeruginosa infection, and this process is deficient in cells lacking functional CFTR.

Airway epithelial control of Pseudomonas aeruginosa infection in cystic fibrosis

“…Subsequently, the microbial cells survive and grow within a hypoxic environment [7,34], wherein increased production of alginate occurs [7,35], further serving to protect the microbe from host defenses. In transgenic CFTR-knockout mice, NF-κB nuclear translocation occurs much later in the airway epithelial cells [28], probably contributing more to the harmful inflammation that ensues in this environment instead of the protective inflammation that occurs when functional CFTR is present. Overall, this scenario wherein WT-CFTR binding of P. aeruginosa leads to protection and failure of this interaction in CF leads to infection is supported by data obtained in numerous in vitro and, importantly, in υivo, studies demonstrating CFTR-dependent responses to P. aeruginosa in a variety of lung epithelial cell lines and in transgenic animals [8][9][10][11][12][27][28][29]31,36].…”

“…In transgenic CFTR-knockout mice, NF-κB nuclear translocation occurs much later in the airway epithelial cells [28], probably contributing more to the harmful inflammation that ensues in this environment instead of the protective inflammation that occurs when functional CFTR is present. Overall, this scenario wherein WT-CFTR binding of P. aeruginosa leads to protection and failure of this interaction in CF leads to infection is supported by data obtained in numerous in vitro and, importantly, in υivo, studies demonstrating CFTR-dependent responses to P. aeruginosa in a variety of lung epithelial cell lines and in transgenic animals [8][9][10][11][12][27][28][29]31,36]. Thus, it seems that CFTR facilitates bacterial clearance and modulates innate immunity towards P. aeruginosa in lung epithelial cells by being the linchpin needed for coordinating multiple host responses involved in resisting infection and maintaining tissue homeostasis in the long run.…”

“…Signaling through the IL-1 receptor leads to NF-κB nuclear translocation within 10-20 min of infection [28]. Consistent with these findings, the lungs of IL-1 receptor-deficient mice can be chronically infected with P. aeruginosa after oral exposure via drinking water [28], in the same way that chronic infections can be established in transgenic CF mice [42]. Overall, the key host responses to P. aeruginosa mediating highlevel resistance to infection involves CFTR-dependent recognition and response to this pathogen, a modulated host inflammatory response that includes limited neutrophil recruitment to the lungs dependent on signaling involving MyD88, contributions from TLRs that are not dependent on a single TLR due to redundancy in this host response system and resolution of this sub-clinical, beneficial inflammatory response by proper apoptosis of involved cells.…”

“…P. aeruginosa recognition by WT-CFTR is due to the specific binding of amino acids 108-117 to the conserved bacterial outer core LPS [11,12,27]. CFTR binding to P. aeruginosa results in release of interleukin-1b from preformed stores in lung epithelial cells within 2-15 min [28], followed by rapid formation (5-15 min) of CFTR-containing lipid rafts in the plasma membrane, with P. aeruginosa cells attached to the CFTR. Subsequently, nuclear translocation of nuclear factor-κB (NF-κB) occurs over the next 10-30 min [12] due both to signals transduced by the interleukin-1 (IL-1) receptor and additional, unknown signals dependent on the formation of the lipid rafts.…”

“…Subsequently, nuclear translocation of nuclear factor-κB (NF-κB) occurs over the next 10-30 min [12] due both to signals transduced by the interleukin-1 (IL-1) receptor and additional, unknown signals dependent on the formation of the lipid rafts. NF-κB nuclear translocation is dependent on the signaling adaptor protein myeloid differentiation factor 88 (MyD88) [28]. An additional component of the WT-CFTRdependent response to P. aeruginosa is endocytosis by the epithelial cells and subsequent clearance of infected epithelial cells by desquamation over the next few hours [11,27].…”