The Pseudomonas aeruginosa Secretory Product Pyocyanin Inactivates α ₁ Protease Inhibitor: Implications for the Pathogenesis of Cystic Fibrosis Lung Disease

Abstract

α1 Protease inhibitor (α1PI) modulates serine protease activity in the lung. Reactive oxygen species inactivate α1PI, and this process has been implicated in the pathogenesis of a variety of forms of lung injury. An imbalance of protease-antiprotease activity is also detected in the airways of patients with cystic fibrosis-associated lung disease who are infected withPseudomonas aeruginosa. P. aeruginosa secretes pyocyanin, which, through its ability to redox cycle, induces cells to generate reactive oxygen species. We tested the hypothesis that redox cycling of pyocyanin could lead to inactivation of α1PI. When α1PI was exposed to NADH and pyocyanin, a combination that results in superoxide production, α1PI lost its ability to form an inhibitory complex with both porcine pancreatic elastase (PPE) and trypsin. Similarly, addition of pyocyanin to cultures of human airway epithelial cells to which α1PI was also added resulted in a loss of the ability of α1PI to form a complex with PPE or trypsin. Neither superoxide dismutase, catalase, nor dimethylthiourea nor depletion of the media of O2 to prevent formation of reactive oxygen species blocked pyocyanin-mediated inactivation of α1PI. These data raise the possibility that a direct interaction between reduced pyocyanin and α1PI is involved in the process. Consistent with this possibility, pretreatment of α1PI with the reducing agent β-mercaptoethanol also inhibited binding of trypsin to α1PI. These data suggest that pyocyanin could contribute to lung injury in the P. aeruginosa-infected airway of cystic fibrosis patients by decreasing the ability of α1PI to control the local activity of serine proteases.

ThePseudomonassecretory product pyocyanin inhibits catalase activity in human lung epithelial cells

“…In the present work, we report that exposure of A549 airway epithelial cells to the P. aeruginosa-derived secretory product pyocyanin, a compound known to increase the production of ROS in these and other cells (24), failed to cause the expected increase in a variety of antioxidant responses. We found no evidence that 24 h of pyocyanin exposure, at concentrations we have previously shown lead to production of superoxide in this cell line (12) and that are present in the respiratory secretions of P. aeruginosa-infected patients (7,11,71), leads to alterations in the cellular levels of MnSOD, CuZnSOD, or HSP70.…”

Pharmacodynamics of ciprofloxacin againstPseudomonas aeruginosaplanktonic and biofilm‐derived cells

“…Metabolising cells will continue to produce reactive oxygen species (Britigan et al . ) and extracellular proteins such as toxin A, proteases and elastases (Bjorn et al . ) leading to tissue damage, cleavage of transferrin and triggering further immune responses.…”

Pseudomonas aeruginosa pyocyanin inactivates lung epithelial vaculoar ATPase-dependent cystic fibrosis transmembrane conductance regulator expression and localization

“…Furthermore, PCN inhibits the release of IL‐2, thus limiting growth of T‐lymphocytes and secretion of immunoglobulin by B‐lymphocytes (Muhlradt et al ., 1986). PCN also induces apoptosis in neutrophils (Usher et al ., 2002), disrupts glutathione cycling (Muller, 2002; O’Malley et al ., 2004) and inactivates the α1‐protease inhibitor, which contributes to the imbalance of protease–antiprotease activity (Britigan et al ., 1999). Finally, PCN inactivates catalase activity of lung epithelia (O’Malley et al ., 2003).…”