Abstract
Purpose: :
We have shown previously that mice infected systemically with murine cytomegalovirus (MCMV) for 12 weeks (chronic infection) exhibit increased size and severity of experimental choroidal neovascularization (CNV) when compared with animals infected systemically with MCMV for 6 days (acute infection). Additional studies have suggested that enhanced CNV is associated with increased production of VEGF, a mediator of angiogenesis, during chronic MCMV infection. If MCMV-induced VEGF production by macrophages contributes directly to CNV pathogenesis, we hypothesized that ganciclovir (GCV) treatment of chronically infected mice will result in decreased expression of VEGF mRNA by splenic macrophages.
Methods: :
Four groups of C57BL/6 mice were injected intraperitoneally with a non-lethal dose of MCMV or UV-inactivated virus (control). At 6 days or 12 weeks postinoculation, MCMV-infected or mock-infected mice were treated systemically with either GCV (40 mg/kg/day) or PBS for 7 days. Splenic macrophages enriched by MACS separation (~90% purity) were collected from all animals and subjected to real time RT-PCR assay for quantification of VEGF mRNA levels. Measurements of TNFα mRNA levels served as a marker for macrophage activation.
Results: :
As expected, splenic macrophages collected from chronically infected mice showed a 48-fold and 36-fold increase in VEGF and TNFα mRNA levels, respectively, when compared with splenic macrophages collected from acutely infected mice or mock-infected mice whose VEGF and TNFα mRNA levels were equivalent. In contrast, GCV treatment resulted in >90% decrease in VEGF and TNFα mRNA levels in splenic macrophages collected from chronically infected mice.
Conclusions: :
GCV treatment significantly dampened VEGF and TNFα mRNA production by splenic macrophages that were activated during chronic, but not acute, systemic MCMV infection. We conclude that a GCV-sensitive, virus-encoded gene(s) participates in upregulation of VEGF and TNFα mRNAs by activated macrophages during chronic infection. The effect of GCV treatment on CNV severity in chronically infected mice has not yet been determined.
Keywords: cytomegalovirus • choroid: neovascularization • vascular endothelial growth factor