R 217Effects of metabolic stress on retinal cells and vasculature
R. H. W. Funk
Purpose: Chronic vascular spasms as well as loss of capillaries (e.g. by arteriosclerosis) lead to metabolic stress of the cells in retina and papilla and is followed by apoptosis. An additional factor can be the formation of advanced glycation end products (AGEs).
In order to test the effect of metabolic stress in retinal cells and ist effect on the capillary tone we induced the rapid formation of AGEs by glyoxal. The proapoptotic effects were tested by different markers and the effects on the retinal capillaries by in vivo microscopy.
Material and methods: Retinal organ cultures (rat) were established for 24h in AMES medium containing 0 (control), 5, 150 and 300 µM glyoxal. The exp ression of bax, bcl-2, caspase 3 and the accumulation of CML were studied by using immunohistochemistry after paraffin embedding. Retinal capillaries were observed using high resolution DIC-microscopy and on-line and subsequent video analysis of the capillary wall.
Results: Our data indicate that small amounts of CML and the apoptosis-promoting factors bax and caspase 3 are present in non-diabetic retinae as a common constituent and were increased after incubation with glyoxal in all cells of retinal organ culture.
The apoptosis-inhibitor bcl-2 was found to be expressed in low levels in Müller cells only.
Müller cells show stronger and selective expression of bcl-2 the higher the concentration of glyoxal they are incubated in. In the first two hours of glyoxal incubation a compensatory dilation of the capillaries could be measured.
Discussion: Accumulation of advanced glycation end products (AGEs) in retinal cells is known to be associated with the risk of diabetic retinopathy. The increasing amounts of the oxidatively formed CML show the ability of our model to simulate AGE-related effects in the retina in vitro. The dose-dependent expression of apoptosis-promotor molecules demonstrates that the apoptosis-inducing machinery starts in optical ganglion cells within 24h. Retinal Müller cells are the only retinal cells which have a protective system by bcl-2 induction. Influences of the metabolic situation on the capillary tone could be demonstrated.
Institut für Anatomie, Medizinische Fakultät der Technischen Universität Dresden, Fetscherstr. 74, 01307 Dresden