A hypothermia mimetic molecule (zr17-2) reduces ganglion cell death and prevents electroretinogram distortion following intraorbital optic nerve crush (IONC) in the rat

Abstract

Purpose : Ocular and periocular traumatisms may result in loss of vision. Our previous work showed that hypothermia prevents retinal damage caused by traumatic neuropathy. We generated and characterized small molecules that elicit the beneficial effects of hypothermia at normal body temperature. Here we investigate whether one of these mimetic molecules, zr17-2, is able to preserve the function of retinas exposed to trauma.

Methods : Intraorbital optic nerve crush (IONC) or sham manipulation was applied to Sprague-Dawley rats. One hour after surgery, 5 ul of 330 nmols/L zr17-2 or PBS, as vehicle, were injected in the vitreum of treated animals. Electroretinograms were performed 30 days after surgery and a-, b-wave amplitude and oscillatory potentials (OP), were calculated. Animals for TUNEL analysis were sacrificed 6 days after surgery . Western blotting was performed for cold inducible RNA-binding protein (CIRP), the target of zr17-2.

Results : Previous studies showed that zr17-2 does not cross the blood-ocular barrier, thus preventing systemic treatment. Here we show that intravitreal injection of zr17-2 results in a very significant increase in CIRP protein expression in the eye, providing mechanistic support for its pharmacological use in ocular conditions. The amplitude of a- and b-waves, as well as the OP, was significantly reduced in IONC-affected retinas (p<0.05). These parameters were significantly corrected by injection of zr17-2 (p<0.05) (Fig. 1). IONC resulted in a very significant increase of TUNEL-positive cells in the ganglion cell layer (p<0.001) whereas injection of zr17-2 significantly reduced the number of apoptotic cells (p<0.001) (Fig. 2).

Conclusions : We have shown that intravitreal injection of the hypothermia mimetic, zr17-2, increases CIRP protein expression and, as a result, significantly reduces the morphological and electrophysiological consequences of ocular traumatism and may represent a new treatment for this cause of visual loss.
*DSC, *MR-F, *RP,contributed equally
#CFL, #AM and #IML contributed equally

This is a 2021 ARVO Annual Meeting abstract.

 

Figure 1. Amplitude of the b wave of the electroretinogram in the 4 experimental groups(n=10). *: p<0.05 vs sham; #:p<0.05 vs IONC vehicle.

 

Figure 2. Quantification of TUNEL-positive cells in the ganglion cell layer of the 4 experimental groups (n=10). ***: p<0.001 vs sham; ###:p<0.001 vs IONC vehicle.