ExoU-induced procoagulant activity in Pseudomonas aeruginosa-infected airway cells

¹ Departamento de Microbiologia, Imunologia e Parasitologia, Faculdade de Ciências Médicas, Universidade do Estado do Rio de Janeiro, Brazil

^* To whom correspondence should be addressed. E-mail: crisplot{at}yahoo.com.br.

	Abstract

This report addressed the question whether ExoU, a P. aeruginosa toxin with PLA₂ activity, may induce airway epithelial cells to overexpress tissue factor (TF) and exhibit a procoagulant phenotype.

Cells from the BEAS-2B line were infected with an ExoU-producing P. aeruginosa strain, pretreated or not with the cPLA₂ inhibitor MAFP, or with two ExoU deficient mutants. Control noninfected and infected cells were assessed for the expression of i) TF mRNA by RT-PCR; ii) cell-associated TF by enzyme immunoassay and flow cytometry; iii) procoagulant activity by a colorimetric assay and iv) microparticle-associated TF by flow cytometry. Enzyme immunoassay was also used to assess cell-associated TF in lung extracts from mice infected intratracheally with ExoU-producing and deficient bacteria.

Cells infected with the wild type bacteria had higher levels of TF mRNA, cell-associated TF expression, procoagulant activity and released microparticle-associated TF than cells infected with the mutants. Bacterial treatment with MAFP reduced significantly the expression of TF by infected cells. Lung samples from mice infected with the wild type bacteria exhibited higher levels of cell-associated TF and procoagulant activity.

Our results demonstrate that ExoU may contribute to pathogenesis of lung injury by inducing a TF-dependent procoagulant activity in airway epithelial cells.