Blood flow-associated shear stress causes physiological and pathophysiological biochemical processes in endothelial cells that may be initiated by alterations in plasma membrane lipid domains characterized as liquidordered (lo), such as rafts or caveolae, or liquid-disordered (ld). To test for domain-dependent shear sensitivity, we used time-correlated single photon counting instrumentation to assess the photophysics and dynamics of the domain-selective lipid analogues DiI-C 12 and DiI-C18 in endothelial cells subjected to physiological fluid shear stress. Under static conditions, DiI-C12 fluorescence lifetime was less than DiI-C18 lifetime and the diffusion coefficient of DiI-C12 was greater than the DiI-C 18 diffusion coefficient, confirming that DiI-C12 probes ld, a more fluid membrane environment, and DiI-C18 probes the lo phase. Domains probed by DiI-C12 exhibited an early (10 s) and transient decrease of fluorescence lifetime after the onset of shear while domains probed by DiI-C18 exhibited a delayed decrease of fluorescence lifetime that was sustained for the 2 min the cells were subjected to flow. The diffusion coefficient of DiI-C18 increased after shear imposition, while that of DiI-C12 remained constant. Determination of the number of molecules (N) in the control volume suggested that DiI-C 12-labeled domains increased in N immediately after step-shear, while N for DiI-C18-stained membrane transiently decreased. These results demonstrate that membrane microdomains are differentially sensitive to fluid shear stress.
All Science Journal Classification (ASJC) codes
- Modeling and Simulation
- Biochemistry, Genetics and Molecular Biology(all)