CB1 Cannabinoid Receptor is a Target for Neuroprotection in Light Induced Retinal Degeneration

Abstract

In the last few years, an increasing interest in the neuroprotective effect of cannabinoidshas taken place. The aim of the present work was to study the effects of modulatingcannabinoid receptor 1 (CB1) in the context of light induced retinal degeneration (LIRD),using an animal model that resembles many characteristics of human age-related maculardegeneration (AMD) and other degenerative diseases of the outer retina. Sprague Dawleyrats (n = 28) were intravitreally injected in the right eye with either a CB1 agonist (ACEA), oran antagonist (AM251). Contralateral eyes were injected with respective vehicles ascontrols. Then, rats were subjected to continuous illumination (12,000 lux) for 24 h.Retinas from 28 animals were processed by GFAP-immunohistochemistry (IHC),TUNEL technique, Western blotting (WB), or qRT-PCR. ACEA-treated retinas showeda significantly lower number of apoptotic nuclei in the outer nuclear layer (ONL), lower levelsof activated Caspase-3 by WB, and lower levels of glial reactivity by both GFAP-IHC andWB. qRT-PCR revealed that ACEA significantly decreased the expression of Bcl-2 andCYP1A1. Conversely, AM251-treated retinas showed a higher number of apoptotic nucleiin the ONL, higher levels of activated Caspase-3 by WB, and higher levels of glial reactivityas determined by GFAP-IHC and WB. AM251 increased the expression of Bcl-2, Bad,Bax, Aryl hydrocarbon Receptor (AhR), GFAP, and TNFα. In summary, the stimulation ofthe CB1 receptor, previous to the start of the pathogenic process, improved the survival ofphotoreceptors exposed to LIRD. The modulation of CB1 activity may be used as aneuroprotective strategy in retinal degeneration and deserves further studies