Aqueous humor-borne factor upregulates Bcl-2 expression in corneal endothelial cells.
OBJECTIVE
To determine if factors present in the aqueous humor (AH) protect the corneal endothelium from apoptosis.


METHODS
Mouse and human corneal endothelial cells were cultured in vitro, and apoptosis was induced by nutrient deprivation. AH and supernatant from iris/ciliary body (I/CB) cell cultures were tested for their effect on corneal endothelial cell apoptosis. The effect of I/CB supernatant on Fas, Bax, and Bcl-2 gene transcription was evaluated by Northern blotting. I/CB supernatant was subjected to proteinase analysis to identify the apoptosis inhibitory factor(s).


RESULTS
Rabbit AH and supernatant from mouse I/CB cell cultures inhibited the apoptosis of mouse and human immortalized corneal endothelial cell lines. The inhibition of apoptosis was associated with an upregulation of Bcl-2 gene transcription and Bcl-2 protein expression. Bax gene expression was not significantly affected by I/CB cell supernatant. Induction of apoptosis by stimulation of the Fas receptor was unaffected by I/CB cell supernatant. Protease analyses indicated that the apoptosis inhibitory factor was a protein.


CONCLUSIONS
The inability of corneal endothelial cells to undergo mitosis renders the corneal endothelium vulnerable to loss of physiological function through cellular attrition. However, a protein(s) produced by I/CB cells and present in the AH, upregulates Bcl-2 gene transcription and protects the corneal endothelial cells from apoptosis.
Li
X Y
XY
Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas 75235, USA.
De Marco
B M
BM
Mayhew
E S
ES
Niederkorn
J Y
JY
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001082:Aqueous Humor / Q000502:physiology*; D001685:Biological Factors / Q000502:physiology*; D015152:Blotting, Northern; D002478:Cells, Cultured; D002924:Ciliary Body / Q000166:cytology / Q000502:physiology; D004247:DNA / Q000032:analysis; D017931:DNA Primers / Q000737:chemistry; D015342:DNA Probes; D004728:Endothelium, Corneal / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D019254:Genes, bcl-2 / Q000235:genetics; D006801:Humans; D020287:In Situ Nick-End Labeling; D007498:Iris / Q000166:cytology / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008814:Mice, Inbred NZB; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein; D019014:fas Receptor
C494826:BAX protein, human; C494827:Bax protein, mouse; D001685:Biological Factors; D017931:DNA Primers; D015342:DNA Probes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018124:Receptors, Tumor Necrosis Factor; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D004247:DNA