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Human cytomegalovirus infection stimulates Cl-/HCO-3 exchanger activity in human fibroblasts
L M Maglova1, W E Crowe, A A Altamirano
1Department of Physiology, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania 19129, USA.
Abstract:
The effects of human cytomegalovirus (HCMV) infection on Cl-/HCO-3 exchanger activity in human lung fibroblasts (MRC-5 cells) were studied using fluorescent, ion-sensitive dyes. The intracellular pH (pHi) of mock- and HCMV-infected cells bathed in a solution containing 5% CO2-25 mM HCO-3 were nearly the same. However, replacement of external Cl- with gluconate caused an H2DIDS-inhibitable (100 microM) increase in the pHi of HCMV-infected cells but not in mock-infected cells. Continuous exposure to hyperosmotic external media containing CO2/HCO-3 caused the pHi of both cell types to increase. The pHi remained elevated in mock-infected cells. However, in HCMV-infected cells, the pHi peaked and then recovered toward control values. This pHi recovery phase was completely blocked by 100 microM H2DIDS. In the presence of CO2/HCO-3, there was an H2DIDS-sensitive component of net Cl- efflux (external Cl- was substituted with gluconate) that was less in mock- than in HCMV-infected cells. When nitrate was substituted for external Cl- (in the nominal absence of CO2/HCO-3), the H2DIDS-sensitive net Cl- efflux was much greater from HCMV- than from mock-infected cells. In mock-infected cells, H2DIDS-sensitive, net Cl- efflux decreased as pHi increased, whereas for HCMV-infected cells, efflux increased as pHi increased. All these results are consistent with an HCMV-induced enhancement of Cl-/HCO-3 exchanger activity.
Insights
Human cytomegalovirus (HCMV) infection enhances Cl-/HCO-3 exchanger activity in lung fibroblasts. This leads to increased chloride efflux and altered intracellular pH regulation in infected cells.
Area of Science:
- Cell Biology
- Virology
- Physiology
Background:
- Human cytomegalovirus (HCMV) is a common pathogen.
- Intracellular pH regulation is crucial for cell function.
- Chloride/bicarbonate (Cl-/HCO-3) exchangers play a role in maintaining pH balance.
Purpose of the Study:
- To investigate the effect of HCMV infection on Cl-/HCO-3 exchanger activity in human lung fibroblasts (MRC-5 cells).
- To determine if HCMV alters intracellular pH dynamics.
- To elucidate the mechanism of pH regulation changes during HCMV infection.
Main Methods:
- Utilized fluorescent, ion-sensitive dyes to monitor intracellular pH (pHi).
- Employed mock- and HCMV-infected MRC-5 cells.
- Manipulated external ion concentrations (Cl-, gluconate, nitrate) and osmolarity.
- Assessed the effect of H2DIDS, a Cl-/HCO-3 exchanger inhibitor.
Main Results:
- HCMV infection led to an H2DIDS-inhibitable increase in pHi upon Cl- removal.
- HCMV-infected cells showed a pHi recovery phase during hyperosmotic stress, blocked by H2DIDS.
- Net Cl- efflux was enhanced in HCMV-infected cells, particularly when nitrate replaced Cl-.
- The relationship between pHi and Cl- efflux differed between mock- and HCMV-infected cells.
Conclusions:
- HCMV infection significantly enhances Cl-/HCO-3 exchanger activity in human lung fibroblasts.
- This enhanced activity contributes to altered intracellular pH regulation during HCMV infection.
- The findings suggest a novel mechanism by which HCMV may modulate host cell physiology.