Phospholipases A2 in normal human conjunctiva and from patients with primary open-angle glaucoma and exfoliation glaucoma

Abstract

Chronic situations like long-term use of topical medications induces conjunctival inflammation and is also a significant risk factor for failure of filtering surgery. We evaluated conjunctival expression of group IIA secretory PLA(2) (sPLA(2)-IIA), group V secretory PLA(2) (sPLA(2)-V), calcium-independent PLA(2) (iPLA(2)) and cytosolic PLA(2) (cPLA(2)). Samples were obtained from non-glaucomatous patients (control subjects), and patients with either primary open-angle glaucoma (POAG) or exfoliation glaucoma (ExG). All the glaucoma patients had been treated with antiglaucomatous medication, and underwent deep sclerectomy surgery. Antibodies against sPLA(2)-IIA, sPLA(2)-V, iPLA(2) and cPLA(2) were used for immunohistochemical staining of frozen tissue sections. In the human conjunctiva of non-glaucomatous patients, immunostaining of sPLA(2)-IIA, sPLA(2)-V or cPLA(2) was low and positively stained cells were mainly localized in the surface of the epithelium. In contrast, iPLA(2) was found to predominate in human normal conjunctiva and it demonstrated strong labeling throughout the epithelium. The stromal staining of iPLA(2) was weak. Expression of sPLA(2)-IIA was significantly increased in stromal fibers of patients with POAG or ExG. No changes were found in levels of sPLA(2)-V, iPLA(2) or cPLA(2) between the patient groups and controls. These findings demonstrate that sPLA(2)-IIA, sPLA(2)-V, iPLA(2) and cPLA(2) are expressed in the conjunctiva of non-glaucomatous patients. In the epithelium, sPLA(2)-IIA, sPLA(2)-V, and cPLA(2) may participate in protection against risks caused by mechanical wear and tear stress whereas iPLA(2) may regulate remodeling and maintenance of membrane phospholipids. sPLA(2)-IIA may also have the important role in the degradation of bacteria. In conjunctival stroma of POAG and ExG patients, sPLA(2)-IIA may play a role in the development of scar tissue after glaucoma filtration surgery.