Human secretory phospholipase A(2), group IB in normal eyes and in eye diseases

Secretory phospholipases A(2) (sPLA(2)) are enzymes involved in lipid turnover. We recently identified sPLA(2) group IB (GIB) in the rat retina as well as in cerebral neurons and found upregulation to occur in response to light damage and seizures, respectively. The purpose of the present study was to identify human GIB (hGIB) in the normal human eye and investigate the pattern of expression in patients with eye diseases involving hGIB-rich cells.

Human GIB mRNA was identified in the human retina by means of in situ hybridization and polymerase chain reaction. Antibodies against hGIB were obtained and immunohistochemical staining was performed on paraffin-embedded sections of normal and pathological eyes. Donor eyes from patients with descemetization of the cornea, Fuchs' corneal endothelial dystrophy, age-related macular degeneration, malignant choroidal melanoma, retinitis pigmentosa and glaucoma were evaluated.

Expression of hGIB was found in various cells of the eye. The most abundant expression was found in retinal pigment epithelium (RPE) cells, the inner photoreceptor segments, ganglion cells and the corneal endothelium. We explored diseases involving hGIB-rich cells and found downregulation of hGIB in proliferating RPE cells as well as in diseased corneal endothelial cells.

Human GIB is highly expressed in cells with neurodermal origin. The pattern of expression of hGIB in diseases involving hGIB-rich cells demonstrated a downregulation of hGIB in migrating RPE cells and in diseased corneal endothelium.