Assessment of the neuroprotective effect of coenzyme Q-10 and citicoline treatment in experimental traumatic optic neuropathy in rats: An electrophysiological, histological, and biochemical evaluation

Evaluation of the Neuroprotective Efficacy of Coenzyme Q-10 and Citicoline Treatment in Experimental Traumatic Optic Neuropathy in Rats: An Electrophysiological, Histological, and Biochemical Study OBJECTIVE We aim to establish a perspective on the effectiveness of new neuroprotective therapeutic strategies by developing experimental traumatic optic neuropathy in rats using an optic nerve crush model and evaluating the efficacy of coenzyme Q-10 and citicoline treatments. MATERIALS AND METHODS The study included 40 male Wistar rats (250-300 g) conducted at Ankara Bilkent City Hospital Department of Ophthalmology and Ankara Training and Research Hospital Animal Experiment Laboratory. The rats were randomly divided into 4 groups, each consisting of 10 rats. To induce traumatic optic neuropathy, the optic nerves (OPN) of rats in groups 1, 2, and 3 were clamped for 60 seconds under anesthesia while preserving the artery in the right eyes. In the first group, OPN damage was induced in the right eye without treatment. In the second group, rats received 50 mg/kg/day coenzyme Q-10 via nasogastric tube starting from 24 hours after OPN crush. In the third group, citicoline at a dose of 1 g/kg/day was administered. The fourth group served as a sham (control) group, where only the conjunctiva was opened, and the optic nerve was not damaged or treated. Bilateral flash and pattern visual evoked potential (VEP) tests were performed on all rats to obtain baseline values. Retests were conducted on the right eyes of the rats 48 hours after trauma to assess the impact of the injury. On the 48th hour and the 28th day after trauma, thiol and ischemia-modified albumin (IMA), inflammatory biomarkers in blood, were examined. At the end of the 28th day, high-dose (50 mg/kg) thiopental anesthesia was administered to euthanize the rats. Enucleation was performed for histopathological examinations, and the OPN was extracted. Flash and pattern VEP tests were conducted on the rats before euthanasia. Paraffin blocks were prepared from tissues for histopathological examination, 4-micron-thick sections were stained with hematoxylin-eosin after extraction. After evaluating the stained preparations, anti-glial acidic protein monoclonal antibody (GFAP) was used for immunohistochemical studies on the blocks. All results were statistically compared using IBM SPSS 28 package program, and values below 0.05 were considered significant. RESULTS In Group 4, responses to pVEP and fVEP tests were obtained in all recordings. In Group 1, pVEP waves could not be recorded in 5 out of 10 rats in the 28-day recordings. In Group 2, pVEP waves did not occur in 4 rats in the 2-day recordings after trauma, but by the end of 28 days, all rats in Group 2 showed a pVEP test response. In Group 3, pVEP waves did not occur in 5 rats in the 2-day recordings, but by the end of 28 days, all rats in Group 3 showed a pVEP test response. When examining the VEP test data on the second day, longer latency and lower amplitude values were observed in Groups 1, 2, and 3 compared to Group 4. Significant improvement was detected in the VEP test results of Groups 2 and 3 compared to Group 1 in the 28-day VEP test results. However, there was no statistically significant difference between the data of Groups 2 and 3. According to the results of the second day: native thiol and total thiol values were significantly higher in Group 4 than in other groups; disulfide, disulfide/native thiol, and IMA values were significantly lower. According to the values on the 28th day: total thiol and native thiol values in Group 4 were significantly higher than those in Groups 1 and 2; in Group 3, they were significantly higher than those in Group 2. There was no difference in disulfide values. IMA values were lower in Group 4 compared to Group 1. When comparing the 2-day and 28-day data within groups, significant increases were observed in total thiol and native thiol values in Groups 2 and 3, indicating an increase in peripheral blood antioxidant biomarkers. When comparing the 2-day and 28-day data between groups, Group 4 and Group 3 showed greater increases in native thiol and total thiol values and greater decreases in IMA values compared to Groups 2 and 1. According to the right eye retina GFAP staining data, Group 1 showed more staining than other groups, while Group 4 showed less staining. Differences were observed in the OPN GFAP staining intensities among groups. In Group 1, no eye was stained at grade 1, and in Group 4, no eye was stained at grade 3 intensity. Accordingly, Group 1 had a higher OPN GFAP staining intensity compared to other groups, and Group 4 had a lower OPN GFAP staining intensity compared to other groups. No significant difference was found between Groups 2 and 3. According to the right eye OPN thickness data, Group 1 rats were thicker than those in other groups, and Group 2 rats were thicker than those in Group 3. The OPN thickness, retina GFAP staining, and OPN GFAP staining intensity data of Groups 1, 2, and 3 were higher than the left eye data. CONCLUSION Oral citicoline and coenzyme Q-10 are neuroprotective treatment agents that improve electrophysiological data, increase retinal ganglion cell survival, and increase antioxidant biomarkers in peripheral blood in traumatic optic neuropathy. Keywords: citicoline, coenzyme Q-10, electrophysiology, GFAP, traumatic optic neuropathy