Recent progress in understanding Bartonella-induced vascular proliferation.

The ability to induce endothelial cell proliferation is a common feature of human pathogenic Bartonella species. Recent data have indicated that bartonellae can provoke angioproliferation by at least two independent mechanisms: directly, by triggering proliferation and inhibiting apoptosis of endothelial cells; and indirectly, by stimulating a paracrine angiogenic loop of vascular endothelial growth factor production by infected macrophages. A NF-kappaB-mediated acute inflammatory reaction of the Bartonella-infected endothelium appears to be critical for the recruitment of monocytes/macrophages and the initiation and maintenance of a paracrine angiogenic loop. Given that bartonellae effectively adhere to and invade endothelial cells, their ability to trigger angioproliferation might represent a dedicated pathogenic strategy for expanding the bacterial host cell habitat.