Hemolytic Phospholipase C Inhibition Protects Lung Function during Pseudomonas aeruginosa Infection (original) (raw)
2011, American Journal of Respiratory and Critical Care Medicine
While studies have examined the role of many Pseudomonas aeruginosa virulence factors during infection none have demonstrated direct effects on pulmonary physiology, which manifests as no therapies designed to explicitly protect lung function during bacterial infection. Here we show that a single extracellular bacterial protein with phospholipase C/sphingomyelinase (PC-PLC/SMase) activity alters respiratory physiology during infection and we have identified a small molecule that inhibits this PC-PLC/SMase activity and demonstrated that it can protect lung function during infection in the mouse. Conservation of this specific PC-PLC/SMase family in other respiratory pathogens, including Mycobacterium tuberculosis, suggests that this inhibitor could have broad efficacy. Abstract Rationale: The opportunistic pathogen Pseudomonas aeruginosa causes both acute and chronic lung infections and is particularly problematic in patients with cystic fibrosis and those undergoing mechanical ventilation. Decreased lung function contributes significantly to morbidity and mortality during P. aeruginosa infection, and damage inflicted by P. aeruginosa virulence factors contribute to lung function decline. Objectives: We sought to describe direct contribution of a bacterial phospholipase C/sphingomyelinase, PlcHR, to alteration of host lung physiology and characterize a potential therapeutic for protection of lung function. Methods: We infected C57Bl/6 mice with P. aeruginosa WT or isogenic plcHR deletion strains and measured lung function using computer-controlled ventilators. For in vivo testing, miltefosine was delivered intraperitoneally one hour post-infection. Infection and respiratory endpoints were at 24 hours post-infection. Measurements and Main Results: P. aeruginosa wild-type infection caused significant lung function impairment, while the effects of a ∆plcHR strain infection were much less severe. Surfactometry analysis of bronchoalveolar lavage fluid indicated that PlcHR decreased pulmonary surfactant function. Miltefosine has structural similarity to the PC and sphingomyelin substrates of PlcHR, and we found that it inhibits the cleavage of these choline-containing lipids in vitro. Miltefosine administration after P. aeruginosa infection limited the negative effects of PlcHR activity on lung function. Page 3 of 50 4 Conclusions: We have directly linked production of a single virulence factor in P. aeruginosa with effects on lung function, and demonstrated that the inhibitor miltefosine protects lung function from PlcHR-dependent surfactant dysfunction. Abstract word count = 235 7 with a similar deletion mutant, the ∆plcHR deletion produced no choline-induced NPPC hydrolysis activity (16).
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