Increased expression of pSTAT3 and CNTF in the retina of a rat glaucoma model

Abstract

Purpose: To investigate the expression of pSTAT3 (phosphorylated signal transducer and activator of transcription) and CNTF (ciliary neurotrophic factor) in the retina after experimental increase of intraocular pressure (IOP). Methods: Elevated IOP of the right eye of adult SD rats was induced by argon laser photocoagulation of the episcleral and limbal veins. Some animals received a second laser treatment after 7 days. Animals were killed at various times (6 hours to 14 days) after the first laser treatment. The retinas were processed for immunoblottings or immunhistochemistry using pSTATA3 or CNTF antibodies. Results: No detectable level of pSTAT3 was observed in normal retina using immunoblotting. Following laser treatment, the expression of pSTAT3 was up-regulated by 6 hours and decreased markedly by 4 days. CNTF was expressed at low level in normal retina. After laser treatment, the expression was increased by 6 hours and reached a high level at 14 days as detected by immunoblotting. No pSTAT3 staining was observed with immunohistochemistry in normal retina but pSTAT3-positive cells were found in the ganglion cell layer (GCL) and inner nuclear layer by 6 hours after first laser treatment. No positive cells were observed on day 4. CNTF-positive cells were observed in the GCL of normal retina. After laser treatment, in addition to cells in the GCL, Muller cells became CNTF-positive by 2 days and the staining intensity increased until 14 days. Conclusions: Following elevation of IOP, the up-regulation of pSTAT3 and CNTF may represent an endogenous neuroprotective response of the retina. Supported by An award from The University of Hong Kong