Enhanced Escherichia coli invasion of human brain microvascular endothelial cells is associated with alterations in cytoskeleton induced by nicotine

Abstract

SummaryAlthough epidemiological studies have shown that exposure to tobacco smoking significantly increases the risk of bacterial meningitis, heretofore the pathogenic effects of smoking on this disease have been poorly understood. In order to dissect this issue, we have investigated the effects of nicotine, the major component of tobacco, on E. coli invasion of human brain microvascular endothelial cells (HBMEC). Our studies showed that E. coli invasion of HBMEC was significantly enhanced by nicotine in a dosedependent manner. The nicotine-mediated enhancement was associated with actin cytoskeleton rearrangement and morphological changes in the eukaryotic host cell that are essential for bacterial entry . The recombinant IbeA protein and α α α α -bungarotoxin (a nicotinic acetylcholine receptor antagonist) were able to efficiently block the nicotine-mediated cellular effects, suggesting the involvement of the IbeA and nicotinic receptors. Blocking of phosphatidylinositol 3-kinase (PI3K) by LY294002 abolished the entry of E. coli in HBMECs treated with nicotine in a dose-dependent manner. Inhibition of PI3K was associated with decreased phosphorylation of Akt and actin cytoskeletal rearrangement. In contrast to PI3K, blockage of Rho kinase (ROCK) by Y27632 upregulated both nicotine-and E. coli -mediated cellular responses. Thus, this study provides experimental evidence for the first time that the major component of tobacco, nicotine, enhances meningitic E. coli invasion of HBMEC through modulation of cytoskeleton.

Cryptococcus neoformans induces alterations in the cytoskeleton of human brain microvascular endothelial cells

“…There is increasing evidence that cytoskeletal rearrangements, such as actin reorganization, play an essential role in pathogenic entry into host cells (Galan & Zhou, 2000;Masuda et al, 2000;Chen et al, 2002;Eugene et al, 2002;Khan et al, 2002). To provide support for our TEM observations at the molecular level, we investigated the phosphorylation status of cofilin during Cryptococcus invasion.…”

“…This in vitro model of the BBB has been used to study the adhesion, invasion and transcytosis of bacterial pathogens across HBMEC, e.g. Escherichia coli (Huang et al, 1995Chen et al, 2002) and Citrobacter (Badger et al, 1999), and another pathogenic yeast, Candida albicans . This in vitro BBB model system is particularly suitable for C. neoformans studies, as the pathogen has a predilection for the brain, resulting in life-threatening meningitis.…”

“…It is commonly observed that the host-cell actin cytoskeleton undergoes extensive remodelling during pathogenic invasion (Galan & Zhou, 2000;Masuda et al, 2000;Chen et al, 2002;Eugene et al, 2002;Khan et al, 2002). The small GTPase Rho regulates such remodelling, but the underlying mechanisms of this regulation vary depending on the pathogen (Kim, 2001).…”

PSF is an IbeA-binding protein contributing to meningitic Escherichia coli K1 invasion of human brain microvascular endothelial cells

“…The presence of these features implies that meningitic strains possess a deWned set of virulence determinants that allow the bacterium to penetrate the BBB and enter the central nervous system. We have shown that the speciWc IbeA-HBMEC surface protein interaction and subsequently induced signal transduction are required for eYcient penetration of E. coli K1 across the BBB [7,13]. However, the identity of the HBMEC surface protein(s) is unknown.…”

Vascular Endothelial Growth Factor Receptor 1 Contributes toEscherichia coliK1 Invasion of Human Brain Microvascular Endothelial Cells through the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway

“…It has been identified that PI3K/Akt signaling results in activation of cofilin, which promotes reorganization of the actin cytoskeleton for E. coli K1 entry into HBMEC (5,29). PI3K is a heterodimer consisting of an 85-kDa regulatory subunit (p85) and a 110-kDa catalytic subunit (p110).…”