Apoptotic mechanisms within the retina in Staphylococcus epidermidis experimental endophthalmitis.
OBJECTIVE
To investigate the potential involvement of apoptosis and its regulators Bcl-2, Bax, and Fas within the retina in Staphylococcus epidermidis experimental endophthalmitis.


METHODS
Endophthalmitis was induced in 48 male Lewis rats by unilateral 25-mircrol intravitreal injection of 7,000 viable organisms of slime-producing S. epidermidis strain ATCC 35983 (experimental group). Forty-eight other Lewis rats received a similar sterile normal saline injection (control group). The injected eyes were graded for clinical inflammation and were removed in groups at 6, 12, 24, 48, 72, and 168 hours post-injection. After surgical separation, retinal tissue specimens were fixed, and paraffin sections underwent hematoxylin-eosin staining, immunohistochemistry against Bcl-2, Bax, and Fas, and TUNEL assay for detection of apoptotic cells. Following morphometric analysis, the apoptotic body index (ABI) was calculated.


RESULTS
While Bcl-2 expression was absent, Bax and Fas expression and apoptosis in ganglion cells, bipolar cells, and photoreceptors, were significantly higher in the experimental group compared to the control group (P < 0.05). In the experimental group, inflammation peaked at 24 hours, Bax and Fas expression at 48 hours and the ABI at 72 hours post-injection.


CONCLUSIONS
Apoptosis is increased within the retina in S. epidermidis experimental endophthalmitis through upregulation of Bax and Fas, peaking soon after peak inflammation.
Pharmakakis
Nikolaos M
NM
Department of Ophthalmology, School of Medicine, University of Patras, Patras, Greece. npharmak@med.upatras.gr
Petropoulos
Ioannis K
IK
Georgakopoulos
Constantine D
CD
Vantzou
Chrysoula V
CV
Anastassiou
Evangelos D
ED
Mavropoulos
Anestis
A
Zolota
Vassiliki
V
D000818:Animals; D017209:Apoptosis; D004195:Disease Models, Animal; D009877:Endophthalmitis / Q000378:metabolism / Q000382:microbiology / Q000473:pathology*; D015818:Eye Infections, Bacterial / Q000378:metabolism / Q000382:microbiology / Q000473:pathology*; D007124:Immunoenzyme Techniques; D020287:In Situ Nick-End Labeling; D008297:Male; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D012160:Retina / Q000378:metabolism / Q000473:pathology*; D051245:Retinal Bipolar Cells / Q000378:metabolism / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology; D013203:Staphylococcal Infections / Q000378:metabolism / Q000382:microbiology / Q000473:pathology*; D013212:Staphylococcus epidermidis / Q000502:physiology*; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
C494828:Bax protein, rat; C491898:Fas protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D019014:fas Receptor