Human cytomegalovirus infection impairs endothelial cell chemotaxis by disturbing VEGF signalling and actin polymerization.

AIMS: Human cytomegalovirus (HCMV) infection has been linked to the pathogenesis of vasculopathies; however, its pathogenic relevance remains to be established. A prerequisite for vascular repair is endothelial cell migration. We evaluated the influence of HCMV on chemokinesis and chemotactic response of human coronary artery endothelial cells (HCAEC) towards vascular endothelial growth factor (VEGF). METHODS AND RESULTS: A virus dose-dependent reduction in chemokinesis and VEGF-dependent chemotaxis was observed (P < 0.05). UV-inactivated virus did not inhibit chemotaxis or chemokinesis, indicating that viral gene expression is mandatory. We identified two HCMV-induced mechanisms explaining the reduction of chemotaxis: first, a non-ambiguous reduction of VEGFR-2 protein was observed, due to decreased transcription. This protein down-modulation could not be inhibited by Ganciclovir. The remaining VEGFR-2 expressed on infected HCAEC was able to stimulate cell activation. Second, HCMV infection influences actin polymerization in HCAEC as shown by FACS analysis: actin polymerization was significantly reduced to 53 and 51% (P < 0.05) compared with non-infected HCAEC at 24 and 72 h p.i., respectively. Genetically and pharmacologically eliminated VEGFR-2 function resulted in a significant (P < 0.05) reduction of VEGF-induced activation of actin polymerization. CONCLUSION: We demonstrated a significant reduction of the chemotactic mobility of HCMV-infected HCAEC mediated by down-modulation of the VEGFR-2 and by inhibition of actin polymerization. This VEGF resistance of HCMV-infected endothelial cells is likely to promote atherogenesis.

HCMV-infection in a human arterial organ culture model: effects on cell proliferation and neointimal hyperplasia.

BACKGROUND: The impact of infections with the human cytomegalovirus (HCMV) for the development of atherosclerosis and restenosis is still unclear. Both a clear correlation and no correlation at all have been reported in clinical, mostly serological studies. In our study we employed a human non-injury ex vivo organ culture model to investigate the effect of an in vitro permissive HCMV-infection on cell proliferation and neointimal hyperplasia for a period of 56 days. RESULTS: During routine-nephrectomies parts of renal arteries from 71 patients were obtained and prepared as human organ cultures. Cell free HCMV infection was performed with the fibroblast adapted HCMV strain AD169, the endotheliotropic strain TB40E, and a clinical isolate (AN 365). After 3, 7, 14, 21, 28, 35, and 56 days in culture staining of HCMV-antigens was carried out and reactive cell proliferation and neointimal thickening were analysed. Successful HCMV-infection was accomplished with all three virus strains studied. During the first 21 days in organ culture no cell proliferation or neointimal hyperplasia was detected. At day 35 and day 56 moderate cell proliferation and neointimal hyperplasia was found both in HCMV-infected segments and mock infected controls. Neointimal hyperplasia in productively HCMV-infected segments was lower than in non infected at day 35 and day 56, but relatively higher after infection with the endotheliotropic TB40E in comparison with the two other strains. CONCLUSION: The data do not support the hypothesis that HCMV-infection triggers restenosis via a stimulatory effect on cell proliferation and neointimal hyperplasia in comparison to non infected controls. Interestingly however, even after lytic infection, a virus strain specific difference was observed.

Human cytomegalovirus-induced reduction of extracellular matrix proteins in vascular smooth muscle cell cultures: a pathomechanism in vasculopathies?

Human cytomegalovirus (HCMV) infection appears to be linked to the pathogenesis of atherosclerosis. An association between HCMV infection and an enhanced restenosis rate as well as the induction of vasculopathies after solid organ transplantation has been documented. Knowledge of the cellular and molecular basis of these findings is limited, however. By Northern blot and RT-PCR analysis of human foreskin fibroblasts (HFF) and human coronary artery smooth muscle cells (SMC), we identified extracellular matrix (ECM) genes that were downregulated after HCMV infection, including collagen type I and fibronectin. Quantitative immunoassays showed a significant reduction of soluble collagen type I and fibronectin proteins in supernatants of both cell types. This was shown to be a direct effect of HCMV infection and not due to a response to interferons released from infected cells, since neutralization of alpha and beta interferon activity could not block virus-induced downregulation of matrix proteins. As the amount of ECM depends on both synthesis and degradation, we also assessed the influence of HCMV on the activity of matrix metalloproteinases (MMP). Interestingly, a significant difference in virus-induced matrix degradation could be shown between the two cell types. HCMV upregulated MMP-2 protein and activity in SMC but not in HFF. Thus, HCMV infection of SMC reduces ECM dramatically by inducing two independent mechanisms that influence synthesis as well as degradation of ECM. These may represent molecular mechanisms for HCMV-induced pathogenesis of inflammatory vasculopathies and may facilitate dissemination of HCMV by promoting the detachment of infected cells in vivo.

HCMV infection of human vascular smooth muscle cells leads to enhanced expression of functionally intact PDGF beta-receptor.

BACKGROUND: Cytomegaloviruses have been shown to promote atherogenesis in animal models. In humans, several epidemiological and clinical studies suggest involvement of the human cytomegalovirus (HCMV) in the development of atherosclerosis. HCMV is suspected to be associated with an enhanced restenosis rate and the occurrence of vasculopathies after solid organ transplantation. However, knowledge about the cellular and molecular bases of these findings is very limited. METHODS AND RESULTS: Human coronary artery smooth muscle cells (HCASMC) were successfully infected with HCMV in vitro. Infection of HCASMC with all HCMV strains analyzed resulted in a substantial upregulation of the beta-receptor of platelet-derived growth factor (PDGFR-beta) expression as demonstrated by immunohistochemistry, immunofluorescence, FACS, and Western blot analysis. The amount of PDGFR-beta protein present in HCASMC rapidly increased after 12 h of infection and this difference persisted for 72 h post-infection. We showed by quantitative FACS analysis that the extent of PDGFR-beta upregulation differed significantly between the HCMV strains TB40E, Toledo, and AD169. The expression of insulin-like growth factor receptors as well as hepatocyte growth factor receptors, however, was down-modulated in HCMV-infected HCASMC. Most importantly, the HCMV-associated upregulation of PDGFR-beta protein resulted in functionally intact receptors. A significantly higher increase of proliferative activity following stimulation with PDGF-BB was observed in HCMV-infected HCASMC compared to the uninfected control. CONCLUSIONS: Our data suggest that HCMV directly activates the PDGF system, which could promote atherogenesis and restenosis by activation of smooth muscle cell proliferation and neointima formation.

Upregulation of functionally active vascular endothelial growth factor by human cytomegalovirus.

Human cytomegalovirus (HCMV) infection is known to modulate host gene expression and has been linked to the pathogenesis of vasculopathies; however, relevant pathomechanisms are still unclear. It was shown that HCMV infection leads to upregulation of vascular endothelial growth factor (VEGF) expression in human foreskin fibroblasts and coronary artery smooth muscle cells (SMC). Activation of VEGF transcription by HCMV infection was confirmed by transient-expression experiments, which revealed that a short promoter fragment, pLuc135 (-85 to +50), is sufficient for activation. Site-directed mutagenesis of Sp1-recognition sites within this fragment abolished the upregulation of transcription. Functional VEGF protein is released into the culture supernatant of infected SMC. Incubation of endothelial cells with supernatants from HCMV-infected SMC cultures induced upregulation of VEGF receptor-2 expression on endothelial cells, as well as a significant upregulation of DNA synthesis, implicating cell proliferation. The mean incline of DNA synthesis at 48 and 72 h post-infection was 148 and 197 %, respectively. Addition of neutralizing antibodies against VEGF completely abolished this effect. Supernatants from SMC cultures incubated with UV-inactivated virus induced a comparable effect. This virus-induced paracrine effect may represent a molecular mechanism for HCMV-induced pathogenesis, such as inflammatory vasculopathies, by inducing a proatherogenic phenotype in SMC.

Human cytomegalovirus infection in human renal arteries in vitro.

Studies with animal cytomegaloviruses, epidemiological data from humans as well as in vitro studies suggest the involvement of the human cytomegalovirus (HCMV) in the development of atherosclerosis. Cell culture systems are insufficient for examination of the entire pathogenetic process and a satisfactory animal model for HCMV is not available. An organ culture model was established for HCMV infection of human renal arteries in vitro. After infection with three representative HCMV strains, infectious virus was recovered from supernatants until 144 days post-infection with a peak around day 30 due to a long-lasting productive HCMV infection in still vital cells. Differences in cell tropism and kinetics of infection were identified between the HCMV strains. Specifically, differences in infecting endothelial cells and virus penetration into the lamina media were observed. In infected artery segments, but also in some non-infected arteries from seropositive donors, HCMV DNA could be localized by in situ PCR. Nevertheless, HCMV early antigen was detected by immunohistochemistry exclusively in artery segments infected in vitro. The new organ culture model will permit the study of functional and molecular consequences of HCMV infection in a more physiological micro-environment.

Comparison of two different doses of iodide in the prevention of gestational goiter in marginal iodine deficiency: a longitudinal study.

OBJECTIVE: A prospective randomized trial was performed to assess the usefulness of iodine supplementation in the prevention of goiter in pregnant women living in marginally iodine-deficient areas. DESIGN: Eighty-six pregnant women were recruited and randomized in two groups and treated daily for up to six months after delivery with 200 microg iodide (group A) or 50 microg iodide (group B). Sixty-seven women (32 in group A and 35 in group B) completed the study. METHODS: Thyroid volume (TV), thyroid functional parameters and urinary iodine concentration were determined in all subjects at booking, at the 18th-26th, and the 29th-33rd week of gestation, and at the 3rd and 6th month after delivery. RESULTS: A slight but not significant increase in TV during gestation was observed only in group B. After delivery a progressive decrease in TV was documented in both groups, the final TV being significantly reduced with respect to the initial volume in group A. No significant changes in serum free thyroid hormones and TSH concentrations were found during gestation in either group. Postpartum thyroiditis was observed in 5 women (2 in group A, 3 in group B). No side effects were seen. CONCLUSION: The present data indicate that in marginally iodine-deficient areas, the administration of iodide is recommended in pregnancy and lactation. In the conditions of the present trial a dose of 50 microg iodide/day is a safe and effective measure in preventing an increase in TV during pregnancy but a dose of 200 microg iodide/day appeared to be more effective without inducing side effects and without enhancing the frequency of post-partum thyroiditis.

Opinion article: cytomegalovirus is a risk factor in atherogenesis.

Whether or not infectious agents are involved in the pathogenesis of atherosclerosis has been a matter of discussion for the past 2 decades. Although there is no definite proof of a causal role of human cytomegalovirus in atherogenesis, a body of knowledge supports the concept that this virus is involved in the development of atherosclerotic lesions. This review assesses the most important data published in support of this hypothesis.