The Effects of Irradiation by Ion Beams on the Morphology and p53–regulated Bcl–2/Bax Expression in the Cultured Ciliary Body

Abstract

Abstract: : Purpose:Active secretion of sodium and potassium was shown to occur in non–pigmented epithelium (NPE) that is responsible for the maintenance of aqueous humor formation in the ciliary body. The ion beams are induced by acceleration of the ionizing atoms of ²⁰Ne, ¹²C, ⁴He, and ¹H, and have characteristics to lose energy and stop at the constant depth of tissue. We studied immunohistochemically about p53–regulated Bcl–2/Bax expression in order to investigate which part of the ciliary body the ion beams influence programmed cell death, and we compared the effects among the species of the ion. As for as we know, this is the first report concerned with the genes related to apoptosis in ciliary body cultured after the ion beam irradiation. Methods: We irradiated the anterior segments dissected from porcine eyes by ion beams. The reaching depth in water is 0.57 mm in ²⁰Ne⁸⁺(350MeV), 1.08 mm in ¹²C⁵⁺(220MeV), 1.64 mm in ⁴He²⁺(50MeV), and 4.02 mm in ¹H⁺(20MeV). The irradiated specimens were fixed in formalin and embedded in paraffin and then incubated with mouse monoclonal anti–human p53, Bcl–2 and Bax antibody. Results: The NPE of the ciliary process was the most injured by ion beams with a short reaching distance such as ²⁰Ne⁸⁺and ¹²C⁵⁺. The Bax expression increased the products and p53 was expressed in the NPE. In the ciliary fold, the ion beam with a long reaching distance by ¹H⁺ damaged the NPE as well as ²⁰Ne⁸⁺. Conclusions: In the ciliary body irradiated by the ion beams, p53 promotes cell death by upregulating bax according to the reaching depth and could selectively irradiate NPE that causes hyper–secretion of aqueous humor.

Keywords: ciliary body • apoptosis/cell death • radiation damage: light/UV