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N.M. Pharmakakis, C.V. Vantzou, I.K. Petropoulos, E. Anastasiou, J.X. Koliopoulos, V. Zolota; Apoptotic Mechanisms in Staphylococcus epidermidis Experimental Endophthalmitis . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1441.
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Purpose: To investigate the role of apoptosis in the pathogenesis of Staphylococcus epidermidis experimental endophthalmitis. Methods: Experimental endophthalmitis was induced in one eye of 48 inbred male Lewis rats by a 25-µL intravitreal pars plan injection of 7000 viable organisms of Staphylococcus epidermidis slime producing strain ATCC 35983 (experimental group). One eye of 48 control Lewis rats received a similar sterile normal saline injection (control group). The injected eyes were graded daily for signs of clinical inflammation using slit-lamp biomicroscopy, and they were removed in groups at 6, 12, 24, 48, 72 hours, and 7 days after injection, following the animals’ sacrifice. Retina was surgically separated, and retinal specimens were examined using an immunoenzymic method (streptabidin – viotin – peroxidase) for the detection of Bcl-2, Bax, and Fas expression, as well as using the TUNEL method for the detection of apoptotic cells. Results: Clinical scores of intraocular inflammation reached maximum (3+ to 4+) by the end of the first post-injection day, and they were almost abolished by day 7 (0.5+). The Bcl-2 gene was not expressed in retinal layers of either the experimental or the control group. The Bax and Fas genes were expressed in a higher percentage of the photoreceptors of eyes with endophthalmitis, with maximum expression at 48 hours post-injection. TUNEL-positive nuclei of photoreceptors were detected in the eyes of both the experimental and control group, however their percentage was higher in the experimental group and reached maximum levels at 48 hours post-injection. Conclusions: The mechanism of apoptosis seems to be involved in the pathogenesis of Staphylococcus epidermidis experimental endophthalmitis. The apoptotic rate of the photoreceptors reaches maximum levels soon after maximum expression of the inflammatory process. In infectious endophthalmitis, the apoptotic mechanisms are correlated with the expression of the genes of Bcl-2 and Fas families. Apoptosis through Fas expression is not only involved in cytotoxicity, but also in the regulation of immune responses of immune-privileged tissues like the eye.
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