Interaction of Bartonella henselae with endothelial cells results in rapid bacterial rRNA synthesis and replication

Abstract

Bartonella henselae is a slow‐growing microorganism and the causative pathogen of bacillary angiomatosis in man. Here, we analysed how interaction of B. henselae with endothelial cells might affect bacterial growth. For this purpose, bacterial rRNA production and ribosome content was determined by fluorescence in situ hybridization (FISH) using rRNA‐targeted fluorescence‐labelled oligonucleotide probes. B. henselae grown on agar plates showed no detectable rRNA content by means of FISH, whereas B. henselae co‐cultured with endothelial cells showed a rapid increase of rRNA production within the first 18 h after inoculation. The increased rRNA synthesis was paralleled by a ∼1000‐fold intracellular bacterial replication, whereas bacteria grown on agar base showed only a ∼10‐fold replication within the first 48 h of culture. Pretreatment of host cells with paraformaldehyde prevented adhesion, invasion, intracellular replication and bacterial rRNA synthesis of B. henselae. In contrast, inhibition of host cell protein synthesis by cycloheximide did not affect bacterial adhesion and invasion, but prevented intracellular replication although bacterial rRNA content was increased. Inhibition of actin polymerization by cytochalasin D did not affect adhesion, invasion, increased rRNA content or intracellular replication of B. henselae. These results demonstrate that rRNA synthesis and replication of B. henselae is promoted by viable host cells with intact de novo protein synthesis.

Evidence of a leading role for VEGF inBartonella henselae-induced endothelial cell proliferations

“…Bartonella henselae attachment to, and entry into, human epithelial and endothelial cells has been reported previously (Batterman et al, 1995;Dehio et al, 1997;Kempf et al, 2000). Invasion of cultured epithelial cells by B. henselae may be preceded by cell adherence mediated by the expression of type 4-like pili (Batterman et al, 1995).…”

“…By triggering VEGF production in BA/BP, B. henselae might create its own habitat, as B. henselae growth is promoted by proliferating endothelial cells in which B. henselae replicates intracellularly (Kempf et al, 2000). A similar mechanism has been described for the plant pathogen Agrobacterium tumefaciens, which is phylogenetically closely related to B. henselae (Matthysse, 1987;Christie and Vogel, 2000).…”

“…Bartonella henselae replicates in endothelial cells (Kempf et al, 2000). Therefore, bacteria-triggered proliferation of endothelial cells might, in turn, promote the growth of Bartonella.…”

“…HUVEC culture was performed in endothelial growth medium (Promocell) as described previously (Dehio et al, 1997;Kempf et al, 2000) with few modifications. For infection, cells were seeded in 24-well dishes (1.0 Â 10 5 cells per well) on the day before the experiment.…”

“…The pathogenic process of this bacteria-triggered tumour induction is poorly understood. Recently, it has been described that B. henselae replicates within endothelial cells (Kempf et al, 2000). Moreover, a proliferative effect of B. henselae on endothelial cells has been shown in vitro (Conley et al, 1994;Maeno et al, 1999).…”