Cell loss in retinal ischemia is associated with increased necroptosis

Abstract

Retinal ischemia plays acentral pathophysiological role in numerous eye diseases, such as glaucoma. In addition to apoptosis, autophagy, necroptosis and ferroptosis are among the cell death mechanisms of ischemia; however, their role is not clearly understood and controversially discussed. The aim of this study is to gain an improved understanding of the role of alternative cell death mechanisms such as autophagy and necroptosis after retinal ischemia. Based on this, future autophagy-based or necroptosis-based therapeutic approaches could be developed. Retinal ischemia reperfusion was induced in one eye of 6 to 8‑week-old rats by temporarily increasing the intraocular pressure to 140 mm Hg (60 min), followed by reperfusion. The untreated contralateral eye served as acontrol. Retinas after ischemia and control retinas were examined 7days after ischemia immunohistochemically with markers for retinal ganglion cells (RGC), astrocytes (GFAP) as well as an autophagy (LAMP1) and anecroptosis marker (RIPK3) (n = 6/group). Ischemia reperfusion resulted in both significant RGC loss (p ≤ 0.001) and asignificant increase of astrocyte area (p = 0.026) after 7days. Interestingly, the number of autophagic LAMP1 positive cells was unchanged 7days after ischemia (p = 0.272), whereas the number of necroptotic RIPK3 positive cells was significantly increased (p ≤ 0.001). Necroptotic processes appear to be activated 7days after ischemia reperfusion, contributing to retinal cell death and activation of astrocytes. Late autophagic processes are not activated 7days after ischemia. Necroptosis-associated parameters could therefore be targeted as an early therapeutic approach after ischemia in the future.