Differential roles of phosphatidylinositol 3-kinase/akt pathway in retinal ganglion cell survival in rats with or without acute ocular hypertension

by Selleckchem | Apr 03 2023

Intraocular pressure (IOP) elevation has often been used as an experimental model to study mechanisms underlying retinal ganglion cell (RGC) death associated with ocular ischemic injury and glaucoma. The aim of the present study, using both in vitro and in vivo approaches, was to investigate the role of phosphatidylinositol 3-kinase (PI3K)/akt pathway in RGC viability in normal rats and rats following transient IOP elevation. For in vivo studies, pathway inhibitors were administered intravitreally on days 3, 9, and 15 post-2-h IOP elevation at 110 mm Hg. Toward the end of the 3-week examination period, the fluorescent dye Fluorogold was used to retrogradely label surviving RGCs. In order to examine the role of macrophages that were recruited into the eye following the pathway inhibition, clodronate liposomes were used to deplete phagocytic cells in the eye. PI3K/akt pathway activity and location in the retina were examined using Western blot and immunohistochemistry, respectively. Here we showed that PI3K/akt inhibitors 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002) and KY12420 at low concentrations (2 microM or 20 microM) did not influence RGC survival but caused RGC loss at high concentration (200 muM) in retinal explants derived from intact rats. In contrast, both LY294002 and KY12420 at 20 microM led to RGC loss in retinal explants derived from IOP-elevated eyes. A detrimental action of phagocytic cells on RGC survival was also seen in these retinas. In vivo results confirmed the detrimental actions of PI3K/akt inhibition and macrophages on RGC survival in IOP-elevated, but not intact eyes even with high concentration of LY294002. Low level of PI3K/akt activity was detected in the ganglion cell layer (GCL) in intact retina. Acute IOP elevation activated PI3K/akt pathway in the inner nuclear layer and GCL including RGCs. This study thus demonstrates that PI3K/akt pathway mediates RGC survival after IOP elevation but not under normal condition.

Comments：

The present study aimed to investigate the role of the phosphatidylinositol 3-kinase (PI3K)/akt pathway in the viability of retinal ganglion cells (RGCs) in normal rats and rats following transient intraocular pressure (IOP) elevation. The study utilized both in vitro and in vivo approaches to examine the pathway's activity and location in the retina and RGC survival.

The results of the study showed that PI3K/akt inhibitors LY294002 and KY12420 at low concentrations did not affect RGC survival in intact rats but caused RGC loss at high concentration in retinal explants derived from intact rats. However, both inhibitors at 20 microM led to RGC loss in retinal explants derived from IOP-elevated eyes. These findings suggest that the PI3K/akt pathway is involved in RGC survival after IOP elevation but not under normal conditions.

The study also found that acute IOP elevation activated the PI3K/akt pathway in the inner nuclear layer and GCL, including RGCs. Low levels of PI3K/akt activity were detected in the GCL in intact retina.

In vivo results confirmed the detrimental actions of PI3K/akt inhibition and macrophages on RGC survival in IOP-elevated eyes but not in intact eyes, even with a high concentration of LY294002. The study also showed that phagocytic cells recruited into the eye following pathway inhibition had a detrimental effect on RGC survival.

In conclusion, the present study provides evidence that the PI3K/akt pathway mediates RGC survival after IOP elevation but not under normal conditions. The findings suggest that targeting this pathway may be a potential therapeutic approach for treating glaucoma and other ocular ischemic injuries associated with RGC death.