The Chemokine CXCL12 Cleaved Form SDF-1(5-67) is Involved in the Trabecular Cell Apoptosis via CXCR3

Abstract

Purpose: : To study the role of CXCL12 (SDF-1) and its cleaved form SDF-1(5-67) in the trabecular cell viability.

Methods: : Expression of CXC12 and both CXCR3 and CXCR4 receptors was studied under various experimental conditions in human glaucomatous trabecular meshwork (TM) samples and a trabecular cell (TC) line using RT-PCR, immunofluorescence, flow cytometry (FCM), and ELISA. A specific anti-SDF-1(5-67) antibody was used to detect the TC production of this truncated form of CXCL12 by Western Blot. CXCL12 and SDF-1(5-67) effects on the TC viability were studied by microplate cytofluorometry and FCM in a TC model of induced apoptosis. Non-peptide specific antagonists of chemokine receptors CXCR3 and CXCR4 were tested in order to determine the receptor involved.

Results: : CXCL12, CXCR3 and CXCR4 were detected in both human glaucomatous TM tissue and TC line. In vitro the expression of the chemokine and of both receptors was differently enhanced by TNF-a and TGF-b2. The basal TC production of SDF-1(5-67) was also enhanced by both cytokines and reduced by MMP inhibitors (P<0.05). CXCL12 significantly promoted TC survival via its binding to CXCR4, whereas SDF-1(5-67) induced apoptosis in a dose-dependent manner via CXCR3 and caspase 3 activation.

Conclusions: : We demonstrate that CXCL12 and its truncated form SDF-1(5-67) regulate the TC survival through two different chemokine receptors. Such a balance is regulated by cytokines and MMPs previously detected in the glaucomatous TM. SDF-1(5-67) and CXCR3 could be involved in pathological changes observed in the TM in glaucoma.

Keywords: apoptosis/cell death • inflammation