Role of platelet-activating factor in pneumolysin-induced acute lung injury. Crit Care Med 2007 Jul;35(7):1756-62
Date
05/25/2007Pubmed ID
17522574DOI
10.1097/01.CCM.0000269212.84709.23Scopus ID
2-s2.0-34250893819 (requires institutional sign-in at Scopus site) 26 CitationsAbstract
OBJECTIVE: Acute respiratory failure is a major complication of severe pneumococcal pneumonia, characterized by impairment of pulmonary microvascular barrier function and pulmonary hypertension. Both features can be evoked by pneumolysin (PLY), an important virulence factor of Streptococcus pneumoniae. We hypothesized that platelet-activating factor (PAF) and associated downstream signaling pathways play a role in the PLY-induced development of acute lung injury.
DESIGN: Controlled, ex vivo laboratory study.
SUBJECTS: Female Balb/C mice, 8-12 wks old.
INTERVENTIONS: Ventilated and blood-free-perfused lungs of wild-type and PAF receptor-deficient mice were challenged with recombinant PLY.
MEASUREMENTS AND MAIN RESULTS: Intravascular PLY, but not the pneumolysoid Pd-B (PLY with a Trp-Phe substitution at position 433), caused an impressive dose-dependent increase in pulmonary vascular resistance and increased PAF in lung homogenates, as detected by reversed-phase high-performance liquid chromatography coupled to tandem mass spectrometry. The pressor response was reduced in lungs of PAF receptor-deficient mice and after PAF receptor blockade by BN 50730. PLY and exogenous PAF increased thromboxane B2 in lung effluate, and thromboxane receptor inhibition by BM 13505 diminished the pressor response to PLY. Differential inhibition of intracellular signaling steps suggested significant contribution of phosphatidylcholine-specific phospholipase C and protein kinase C and of the Rho/Rho-kinase pathway to PLY-induced pulmonary vasoconstriction. Unrelated to the pulmonary arterial pressor response, microvascular leakage of PLY was diminished in lungs of PAF receptor-deficient mice as well.
CONCLUSIONS: PAF significantly contributed to PLY-induced acute injury in murine lungs. The PAF-mediated pressor response to PLY depends on thromboxane and on the downstream effectors phosphatidylcholine-specific phospholipase C, protein kinase C, and Rho-kinase.
Author List
Witzenrath M, Gutbier B, Owen JS, Schmeck B, Mitchell TJ, Mayer K, Thomas MJ, Ishii S, Rosseau S, Suttorp N, Schütte HAuthor
Michael J. Thomas PhD Professor in the Pharmacology and Toxicology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsBacterial Proteins
Disease Models, Animal
Female
Humans
Hypertension, Pulmonary
Intracellular Signaling Peptides and Proteins
Mice
Mice, Inbred BALB C
Platelet Activating Factor
Pneumonia, Pneumococcal
Signal Transduction
Streptolysins
Thromboxane A2
rho-Associated Kinases
