title: In the absence of effector proteins, the Pseudomonas aeruginosa type three secretion system needle tip complex contributes to lung injury and systemic inflammatory responses.
abstract: Herein we describe a pathogenic role for the Pseudomonas aeruginosa type three secretion system (T3SS) needle tip complex protein, PcrV, in causing lung endothelial injury. We first established a model in which P. aeruginosa wild type strain PA103 caused pneumonia-induced sepsis and distal organ dysfunction. Interestingly, a PA103 derivative strain lacking its two known secreted effectors, ExoU and ExoT [denoted PA103 (ΔU/ΔT)], also caused sepsis and modest distal organ injury whereas an isogenic PA103 strain lacking the T3SS needle tip complex assembly protein [denoted PA103 (ΔPcrV)] did not. PA103 (ΔU/ΔT) infection caused neutrophil influx into the lung parenchyma, lung endothelial injury, and distal organ injury (reminiscent of sepsis). In contrast, PA103 (ΔPcrV) infection caused nominal neutrophil infiltration and lung endothelial injury, but no distal organ injury. We further examined pathogenic mechanisms of the T3SS needle tip complex using cultured rat pulmonary microvascular endothelial cells (PMVECs) and revealed a two-phase, temporal nature of infection. At 5-hours post-inoculation (early phase infection), PA103 (ΔU/ΔT) elicited PMVEC barrier disruption via perturbation of the actin cytoskeleton and did so in a cell death-independent manner. Conversely, PA103 (ΔPcrV) infection did not elicit early phase PMVEC barrier disruption. At 24-hours post-inoculation (late phase infection), PA103 (ΔU/ΔT) induced PMVEC damage and death that displayed an apoptotic component. Although PA103 (ΔPcrV) infection induced late phase PMVEC damage and death, it did so to an attenuated extent. The PA103 (ΔU/ΔT) and PA103 (ΔPcrV) mutants grew at similar rates and were able to adhere equally to PMVECs post-inoculation indicating that the observed differences in damage and barrier disruption are likely attributable to T3SS needle tip complex-mediated pathogenic differences post host cell attachment. Together, these infection data suggest that the T3SS needle tip complex and/or another undefined secreted effector(s) are important determinants of P. aeruginosa pneumonia-induced lung endothelial barrier disruption.
authors: Department of Microbiology and Immunology, University of South Alabama, Mobile, Alabama, United States of America ; Center for Lung Biology, University of South Alabama, Mobile, Alabama, United States of America.
authors: Jonathon P
authors: JP
authors: Audia
authors: Ashley S
authors: AS
authors: Lindsey
authors: Nicole A
authors: NA
authors: Housley
authors: Courtney R
authors: CR
authors: Ochoa
authors: Chun
authors: C
authors: Zhou
authors: Michie
authors: M
authors: Toba
authors: Masahiko
authors: M
authors: Oka
authors: Naga S
authors: NS
authors: Annamdevula
authors: Meshann S
authors: MS
authors: Fitzgerald
authors: Dara W
authors: DW
authors: Frank
authors: Diego F
authors: DF
authors: Alvarez
mesh_terms: D000818:Animals; D058947:Bacterial Secretion Systems; D016923:Cell Death; D042783:Endothelial Cells / Q000473:pathology; D008168:Lung / Q000098:blood supply / Q000378:metabolism / Q000382:microbiology*; D008297:Male; D055806:Microvessels / Q000473:pathology; D011552:Pseudomonas Infections / Q000150:complications; D011550:Pseudomonas aeruginosa / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D018746:Systemic Inflammatory Response Syndrome / Q000150:complications / Q000382:microbiology* / Q000473:pathology; D013997:Time Factors
chemical_list: D058947:Bacterial Secretion Systems