Human cytomegalovirus modulates the Ca 2+ response to vasopressin and ATP in fibroblast cultures

Abstract

The free calcium concentrations in the nucleus ([Ca 2+] n) and in cytosol ([Ca 2+] c) of cultured human embryonic lung (HEL) fibroblasts were estimated by confocal laser microscopy using the Ca 2+-indicator Indo-1. In resting HEL cells, the free cellular Ca 2+-concentration significantly increased upon human cytomegalovirus (HCMV) infection. The ratio between [Ca 2+] n and [Ca 2+] c was not affected. Following stimulation by ATP or [Arg 8] vasopressin (AVP), a differential Ca 2+ response of the HCMV-infected HEL cells was observed. While uninfected cells were highly sensitive to AVP and only poorly sensitive to ATP, infected cells showed a high responsiveness to ATP but not to AVP. This switch in sensitivity to the agonists was first observed at 24 h post infection. The Ca 2+-rise following ATP or AVPD stimulation was derived from intracellular Ca 2+ stores. The magnitude of the ATP-induced Ca 2+-rise increased upon infection. In contrast to non-infected cells where [Ca 2+] n > [Ca 2+]c during stimulation with AVP or ATP, no nucleo-cytosolic Ca 2+-gradient was observed in infected cells. Furthermore, the magnitude of the Ca 2+ rise in the two compartments was higher in ATP-stimulated cells. It is concluded that HCMV infection significantly interferes with Ca 2+-homeostasis in HEL cells which could be related to the pathogenesis of the disease.