Philanthotoxin-343 attenuates retinal and optic nerve injury, and protects visual function in rats with N-methyl-D-aspartate-induced excitotoxicity

Fazel, Muhammad Fattah; Abu, Izuddin Fahmy; Mohamad, Mohamad Haiqal Nizar; Agarwal, Renu; Iezhitsa, Igor; Bakar, Nor Salmah; Juliana, Norsham; Mellor, Ian R.; Franzyk, Henrik

Abstract

Retinal ganglion cell (RGC) loss and optic neuropathy, both hallmarks of glaucoma, have been shown to involve N-methyl-D-aspartate receptor (NMDAR)-mediated excitotoxicity. This study investigated the neuroprotective effects of Philanthotoxin (PhTX)-343 in NMDA-induced retinal injury to alleviate ensuing visual impairments. Sprague-Dawley rats were divided into three; Group I was intravitreally injected with phosphate buffer saline as the control, Group II was injected with NMDA (160 nM) to induce retinal excitotoxic injury, while Group III was injected with PhTX-343 (160 nM) 24 h prior to excitotoxicity induction with NMDA. Rats were subjected to visual behaviour tests seven days post-treatment and subsequently euthanized. Rat retinas and optic nerves were subjected to H&E and toluidine blue staining, respectively. Histological assessments showed that NMDA exposure resulted in significant loss of retinal cell nuclei and thinning of ganglion cell layer (GCL). PhTX-343 pre-treatment prevented NMDA-induced changes where the RGC layer morphology is similar to the control. The numbers of nuclei in the NMDA group were markedly lower compared to the control (p[less than] 0.05). PhTX-343 group had significantly higher numbers of nuclei within 100 ?m length and 100 ?m2 area of GCL (2.9- and 1.7-fold, respectively) compared to NMDA group (p [less than] 0.05). PhTX-343 group also displayed lesser optic nerve fibres degeneration compared to NMDA group which showed vacuolation in all sections. In the visual behaviour test, the NMDA group recorded higher total distance travelled, and lower total immobile time and episodes compared to the control and PhTX-343 groups (p [less than] 0.05). Object recognition tests showed that the rats in PhTX-343 group could recognize objects better, whereas the same objects were identified as novel by NMDA rats despite multiple exposures (p [less than] 0.05). Visual performances in the PhTX-343 group were all comparable with the control (p[less than] 0.05). These findings suggested that PhTX-343 inhibit retinal cell loss, optic nerve damage, and visual impairments in NMDA-induced rats.

• Journal Article Type: Article
• Acceptance Date: Jul 6, 2020
• Online Publication Date: Jul 24, 2020
• Publication Date: Jul 24, 2020
• Deposit Date: Nov 10, 2020
• Publicly Available Date: Nov 12, 2020
• Journal: PLOS ONE
• Electronic ISSN: 1932-6203
• Publisher: Public Library of Science
• Peer Reviewed: Peer Reviewed
• Volume: 15
• Issue: 7
• Article Number: e0236450
• DOI: https://doi.org/10.1371/journal.pone.0236450
• Keywords: Multidisciplinary
• Public URL: https://nottingham-repository.worktribe.com/output/4817169
• Publisher URL: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236450