Human cytomegalovirus (CMV) infection has been implicated in cardiac allograft arteriosclerosis, restenosis of coronary arteries following angioplasty, and atherosclerosis. We hypothesized that neointimal proliferation, a common pathologic feature of the above mentioned disorders, might reflect an anti-apoptotic effect of CMV infected vascular cells. We exposed human umbilical endothelial cells (HUVEC) to CMV (VHL strain obtained from WJ Waldman) at a MOI of O.I PFU/cell. Although HUVEC become manifestly infected, they remained >95% viable. To induce apoptosis, we serum starved control HUVEC and cells infected with CMV for 3, 5 and 7 days. Almost half of the uninfected cells lose viability after 48h serum starvation while CMV infected cells were virtually unaffected (<20% death, p<0.01). Uninfected cells showed typical hallmarks of apoptosis. including unique morphological changes and DNA laddering. CMV infected cells, concomitant with their resfstance to serum starvation induced death, displayed none of these characteristics. Active replication of CMV was necessary for the anti-apoptotic effect, since cells treated with UV-inactivaled virus were not protected. To uncover the mechanism, we examined several potential factors, which can influence the cell cycle. By Northern or Western blots we monitored 3 potent anti-apoptotic genes-A20, c-myc, and BCL-2; none was upregulated. However, p53 protein level was elevated in CMV infected cells. p53 is a tumor supressor nuclear transcription factor which results in G\ arrest and apoptosis. Therefore the increased p53 protein level does not fit with our hypothesis, unless CMV infection of HUVEC results in accumulation of inactivated or nuclear-excluded p53. Immunofluorescent staining and Western blot results demonstrate, overwhelming cytoplasmic accumulation and nuclear exclusion of p53 in CMV infected endothelium. In contrast, p53 localized mainly in nuclei of control, uninfected HUVEC. We speculate, that aberrant subceîlular pattern of p53 is responsible for the anti-apoptotic properties of CMV infected endothelium. Thus, we suggest that cytoplasmic sequestration of p53 plays a pathogenic role in CMV mediated vascular diseases, such as post-angioplastic restenosis, cardiac transplant arterio-obliteration and atheroscerosis itself.
|Original language||English (US)|
|Journal||Journal of Investigative Medicine|
|State||Published - Jan 1 1996|