Intracellular thiol redox status affects rat cytomegalovirus infection of vascular cells

There is increasing evidence for cytomegalovirus (CMV) induced vascular pathology during acute infection in the immunocompromised host. Inflammation is involved in such processes, which is frequently associated with increased levels of oxidative mediators and reduced anti-oxidant protection. A relation between viral infection and oxidative stress has been recognized for human immunodeficiency virus and herpes simplex virus-1 infections, but little is known in this respect for CMV infections. We investigated if there is a relation between CMV infection of vascular cells and the intracellular redox status using an in vitro rat model. We measured intracellular glutathione levels and rat CMV (RCMV) permissiveness of rat heart endothelial cell lines (RHEC), rat smooth muscle cells (RSMC), and compared these with fully CMV-permissive rat fibroblasts (REF and Rat 2). In addition, the effects of the anti-oxidant N-acetylcysteine (NAC) and the glutathione synthesis inhibitor buthionine sulfoximide (BSO) on CMV permissiveness and replication were investigated in these cell lines. Finally, we investigated infection of vascular cells under inflammatory conditions in an in vivo rat model for acute CMV infection. The results show a very high endogenous glutathione level in RHEC compared to REF, Rat 2 cells and RSMC. This is associated with a low CMV permissiveness in RHEC as opposed to full permissiveness in REF, Rat 2 cells and RSMC in vitro. In addition, modulation of the intracellular thiol redox status affected CMV infection and replication only in RHEC, but not in RSMC and Rat 2 cells. During acute infection in vivo under immunosuppressed conditions rat endothelial cells first become activated and subsequently infected leading to vascular damage and pathology. This study suggests that a high endogenous thiol redox status may contribute to the apparent barrier function of endothelial cells with respect to CMV infection and that oxidative stress may facilitate CMV infection of the vascular wall.