The thermolysin-like metalloproteinase and virulence factor LasB from pathogenic Pseudomonas aeruginosa induces anoikis of human vascular cells

Abstract

SummaryDisruption of cell/ECM interactions resulting from uncontrolled pericellular proteolysis leads to detachment-induced cell apoptosis (anoikis), contributing to the morbid evolution of inflammatory vascular diseases. During cardiovascular infections, bacterial proteinases might induce vascular cells to enter a similar pathway. We focused on LasB, the predominant metalloproteinase secreted by the haematotropic pathogen Pseudomonas aeruginosa. While the exosecretome of the LasBdeficient pseudomonal strain PAO1lasBD had limited impact on human vascular cell adherence and viability, secretomes from the LasBexpressing reference strain, PAO1, or clinical isolates from patients with cardiac infection all induced anoikis, as did purified LasB. Immunofluorescence and/or immunoblotting analysis of heart valve myofibroblast cultures or whole tissue revealed an extensive, LasB-dependent degradation of ECM-associated fibronectin and vitronectin, that preceded cell de-adherence, whereas type I collagen showed limited degradation. Moreover, LasB produced a rapid endoproteolysis of the cell-associated urokinase receptor/uPAR, leaving a truncated receptor that is unable to support cell adherence and survival via interactions with vitronectin and integrins. Conversely, major myofibroblast integrins showed no or only minor alterations. Thus, among P. aeruginosa-secreted metalloproteinases, LasB can induce vascular cell anoikis through simultaneous proteolysis of ECM components and cell receptors, suggesting the uPAR-vitronectin axis as a major target in this process.

Disturbed integrin expression in the vascular media in CADASIL

“…Anoikis, a Greek word meaning loss of home or homelessness, is due to loss or inappropriate cell adhesion to ECM. Anoikis is observed both physiologically (in normal skin, in colonic epithelium, in the involuting mammillary glands), as well as in many pathologic conditions such as metastatic spreading and cardiovascular degenerative processes including VSMCs disappearance in aneurysms and varicose veins, extensive loss of vascular cells during cardiovascular infections, cardiac myocyte detachment in heart failure, and plaque rupture in atherosclerosis [4,12,27].…”

Anoikis: an emerging hallmark in health and diseases

“…Enhancement of anoikis, not compensated by cell healing or overcompensated by a dysfunctional healing process, as observed during fibrosclerosis, is probably responsible for cardiovascular degenerative pathologies, such as cardiac myocyte detachment in heart failure, plaque rupture in atherosclerosis, smooth muscle cell disappearance in aneurysms and varicose veins and extensive loss of vascular cells during cardiovascular infections [146][147][148]. Proteases able to degrade ECM proteins induce anoikis of endothelial cells or other components of the cardiovascular system, such as smooth muscle cells, fibroblasts and cardiac myocytes.…”

“…Beaufort and collegues have recently reported that the haematotropic pathogen Pseudomonas aeroginosa induce an intense anoikis of cardiomyocytes and valvular myofibroblasts, thus contributing to host tissue destruction [146]. In particular, the uncontrolled pericellular proteolysis responsible for extensive cell detachment mainly depends on the metalloproteinase LasB, one of the well-known proteolytic enzymes secreted by P. aeruginosa.…”

“…LasB causes a massive degradation of ECM-associated fibronectin and vitronectin, which precedes cell de-adherence. Moreover, LasB produces a rapid endoproteolysis of the cell-associated urokinase receptor uPAR, leaving a truncated receptor that is unable to support cell adhesion and survival via interactions with vitronectin and integrins [146]. The LasB-dependent proteolysis of ECM components and loss of functional cell receptors affect most vascular tissues, both in the acute infectious context and likely during chronic vascular disease, including atherosclerosis and aneurysm.…”

Predominant Role of Host Proteases in Myocardial Damage Associated with Infectious Endocarditis Induced by Enterococcus faecalis in a Rat Model

“…We recently reported in a different context that the persistence of an infected thrombus in contact with the underlying tissue represents a source of blood-conveyed proteases, including both bacterial and host leukocyte proteases released upon activation (4,8). For example, neutrophil elastase has been shown to induce cell death subsequent to pericellular proteolysis and to be deleterious for vascular tissues (9,10).…”