Journal of Dental Research, Vol 75, 1002-1007, Copyright © 1996 by International & American Associations for Dental Research Online Journals
Effects of Actinomyces amphiphile on the fluidity of endothelial cells: a spin label study
Y. Hamada
Department of Periodontology, School of Dentistry, Kagoshima University, Japan.
Actinomyces amphiphile (AcA) is an amphipathic molecule produced by
Actinomyces viscosus that exhibits several biological activities. The
effect of AcA on the fluidity and permeability of the plasma membrane in
human umbilical vein endothelial cells was analyzed by a spin label method
with 5- and 16-stearic acid nitroxide labels (SAL). These labels help to
visualize the fluidity at the shallow (5-SAL) and deep (16-SAL) portions of
the lipid bilayer. Cells were incubated with and without AcA (control) at
37 degrees C for 6 hours, and membrane fluidity was periodically measured.
Another spin label, 4-(N, N-dimethyl-N-hexadecyl) ammonium-2, 2, 6,
6-tetramethyl-piperidine-1-oxyliodine (CAT-16), was also used to assess the
physical state of the cell surface. The order parameter of 5-SAL was
significantly lower in the cells incubated with AcA than in control cells
after the six-hour incubation. The motion parameter of 16-SAL was
significantly lower in AcA-treated cells than in controls after 4 and 6
hours of incubation. These findings indicated that the AcA increased the
fluidity. There were no significant differences between the AcA-treated and
control cells incubated for only 2 hours. In addition, there were no
differences in CAT-16 measurements between AcA-treated and control cells.
The release of endoplasmic lactate dehydrogenase (LDH) into the medium
tended to increase in the AcA-treated vs. the control cells. LDH release
increased in both a dose- and time-dependent manner, indicating that AcA
increased the permeability of plasma membranes. These findings suggest that
AcA alters the biophysical properties of the plasma membranes of
endothelial cells, affecting membrane function.
