The Cytolethal Distending Toxin of Haemophilus ducreyi Inhibits Endothelial Cell Proliferation

Abstract

Haemophilus ducreyi, the etiologic agent of the sexually transmitted disease chancroid, produces a cytolethal distending toxin (HdCDT) that inhibits mammalian cell proliferation. We investigated the effects of HdCDT on normal human endothelial cells and on tubule formation in an in vitro model of angiogenesis. Endothelial cells were arrested in the G2 phase of the cell cycle, and tubule formation was inhibited in a dose-dependent manner. The antiproliferative activities of HdCDT on endothelial cells might contribute to the characteristic slow healing and persistence of chancroid ulcers

Cytolethal Distending Toxin from Shiga Toxin-Producing Escherichia coli O157 Causes Irreversible G 2 /M Arrest, Inhibition of Proliferation, and Death of Human Endothelial Cells

“…This suggestion is based on the fact that the accumulation of phosphorylated cdc2 kinase, a mediator of G 2 arrest, preceded the development of the G 2 /M block in both of these cell lines. Moreover, the mechanism which underlies the CDT-mediated G 2 /M block in these cell lines is similar to that described previously for primary endothelial cells, including HUVEC and HVMEC-d (54). Thus, our present data do not allow us to determine a basis for the observed cell type-specific effects of CDT-V on the cell cycle of the endothelial cells investigated.…”

“…However, the responses to CDT-V differed among the cell cultures investigated. This phenomenon has not been reported for primary endothelial cells (54). Although both HUVEC and EA.hy 926 cells displayed slowly developing G 2 /M arrest, they substantially differed in the proportions of cells arrested in G 2 /M.…”

“…The observation in HUVEC of the same pattern in the response to nocodazole, which synchronizes cells in mitosis (10,13), suggests that this incomplete G 2 arrest probably reflects a finite life span of these cells, which divide relatively slowly (54), rather than an additional block in G 1 ; the latter scenario was previously reported for human foreskin and embryonic lung fibroblasts (13). The incomplete G 2 /M block in HUVEC and HMVEC-d was also observed after treatment with HdCDT (54) and might be a consequence of a relatively low sensitivity of heterogeneous primary cell populations to CDT (54). Accordingly, the CD 50 of CDT-V in our study is approximately 10-fold higher for HUVEC than for each of the cell lines.…”

“…This ability was previously shown only for HdCDT (54) and not for other members of the CDT family, although the latter CDTs have the capacity to interact with many other cell types, including epithelial cells, keratinocytes, and fibroblasts (1,10,12,13,26,34,44,45,51,58). Moreover, our finding that CDT-V affects, in addition to primary cells, endothelial cell lines, including HUVEC-derived EA.hy 926 cells and HBMEC, extends a previous report (54) that HdCDT affects primary endothelial cells (HUVEC and microvascular endothelial cells from human dermal tissue [HMVEC-d]). Specifically, CDT-V induced, in a dose-dependent manner, irreversible G 2 /M arrest, which led to cell distension, inhibition of proliferation, and ultimately lethality in HUVEC and in each of the cell lines.…”

“…Recently, Svensson and colleagues (54) reported that HdCDT, another member of the CDT family, has antiproliferative effects on microvascular endothelial cells from human skin and hypothesized that these effects may play a role in the pathogenesis of the disease caused by H. ducreyi (54). The earlier finding of CDT-V in STEC of serotypes frequently associated with HUS, combined with the results of that report (54), prompted us to investigate the effects of CDT-V on human endothelial cells in vitro.…”