N-acetylcysteine and acute retinal laser lesions in the colubrid snake eye

Abstract

This study examined the role of oxidative stress and the effect of a single dose treatment with N-Acetylcysteine (NAC) on the temporal development of acute laser-induced retinal injury. We used the snake eye/Scanning Laser Ophthalmoscope (SLO) model, an in vivo, non-invasive ocular imaging technique, which has the ability to image cellular retinal detail and allows for studying morphological changes of retinal injury over time. For this study 12 cornsnakes (Elaphe g. guttata) received 5 laser exposures per eye, followed by either a single dose of the antioxidant NAC (150mg/kg, IP in sterile saline) or placebo. Laser exposures were made with a Nd: VO 4 DPSS, 532nm laser, coaxially aligned to the SLO. Shuttered pulses were 20msec x 50 mW; 1mJ each. Retinal images were taken using a Rodenstock cSLO and were digitally recorded at 1, 6, 24-hrs, and at 3-wks post-exposure. Lesions were assessed by two raters blind to the conditions of the study yielding measures of damaged area and counts of missing or damaged photoreceptors. Treated eyes showed a significant beneficial effect overall, and these results suggest that oxidative stress plays a role in laser-induced retinal injury. The use of NAC or a similar antioxidant shows promise as a therapeutic tool.

Functional and cellular responses to laser injury in the rat snake retina

“…49 Nevertheless, previous work with the snake eye model revealed that laser exposures of the magnitude used in the current research also induce oxidative stresss. 20 Moreover, visible laser exposure produces photo-oxidative stress through the interaction of light with susceptible chromophores, such as melanin in the RPE cells, resulting in the formation of reactive free radicals. 3 4 This process does not involve additional energy sources, or other enzymatic pathways (such as oxidases), although various enzyme-catalyzed reactions may also be involved.…”

“…In the snake retina, previous studies have documented the role of photo-oxidative stress in inducing photoreceptor damage. 20 The present research was designed to characterize the laser-induced response of intracellular signaling pathways, in particular, the transcription factor, NF-KB, that are known to be responsive to oxidative stress. Many external stressors activate NF-KB, including toxins, pathogens (including bacteria and viruses), physiological stress (e.g.…”