STAT3 Protects Ganglion Cells in Ischemic Mouse Retina

Abstract

Abstract: : Purpose: CNTF has been shown to have neuroprotective functions. To determine the role of STAT3, a downstream target of CNTF, in responses to ischemia–reperfusion insult, we evaluated neuronal protection by STAT3 in vitro and in vivo. Methods: All mouse protocols were in accordance with ARVO guidelines and were approved by the IACUC of Yale School of Medicine. For in vivo experiments, a 110 cm–high–PBS reservoir connected with the anterior chamber produced ischemia in right eye. The contralateral eye served as control. Reperfusion occurred after 1–hr of ischemia, and eyes were enucleated 1, 6, 18, or 24 hours later. STAT3 antisera were used to localize these proteins in the retina sections. Retina sheets were used for TUNEL staining. For in vitro experiments, purified mouse and rat ganglion cells were incubated with or without glutamate. Recombinant wild–type STAT3, constitutively active and dominant negative forms of STAT3 adenoviruses were used to transfect ganglion cells in vitro. GFP adenovirus and constitutively active forms of STAT3 adenovirus were also used in vivo. Results: In normal mouse retina, STAT3 co–localized with Müller cell processes in the retinal ganglion cell layer (RGCL), inner plexiform layer (IPL) and inner nuclear layer (INL). STAT3 was also expressed by other INL cells as well as ganglion cells. 1 hr after ischemia–reperfusion, STAT3 expression decreased in RGCL. By 6 hr, an over expression of STAT3 was noted. TUNEL positive nuclei peaked in the RGCL at 18 hr after reperfusion. Injection of constitutively active STAT3 adenoviruses one day before ischemia–reperfusion rescued retina ganglion cells compared with GFP control virus. In vitro, activated STAT3 also can protect isolated ganglion cells following glutamate exposure. Conclusions: Our results indicate that STAT3 responds to the ischemia–reperfusion insult by changing its level of expression. Maintained levels of STAT3 expression protect RGCs against ischemic damage suggesting that modulation of STAT3 pathways might be a useful therapeutic approach in human glaucoma.

Keywords: signal transduction • ganglion cells • neuroprotection