The Effect of Carvacrol on 5-Fluorouracil-Induced Optic Neuropathy in Rats. Histopathological and Biochemical Analysis

5-Fluorouracil (5-FU) is also known to cause ocular toxicity. The purpose of this study was to investigate the effects of Carvacrol upon possible 5-FU-induced optic nerve damage in rats biochemically and histopathologically. In this study totally, eighteen albino Wistar male rats were used. The rats were grouped under three categories as the healthy (HG) (n=6), 100 mg/kg 5-FU treated alone (FUG) (n=6) and 50 mg/ kg Carvacrol+100 mg/kg 5-FU (CFU) groups (n=6). Carvacrol at 50 mg/kg was injected intraperitoneally (ip) to the CFU group. The same volume of 0.9% NaCl was administered as the solvent ip to HG and FUG groups. One hour after administrating Carvacrol and solvent, 100 mg/kg 5-FU was ip injected to CFU and FUG groups. Carvacrol was administered once daily for 10 days. Three-dose 5-FU was administered on the 1st, 3rd, and 5th days as one dose each. On the 10th day, the animals were euthanised with high-dose anesthesia and optic nerve tissues were removed. Malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and Interleukin (IL-6) levels were measured in optic nerve tissues. The tissues were also examined histopathologically. The results obtained from HG and CFU groups were compared with the FUG group. Significantly higher MDA and IL-6 levels (p < 0.001) and significantly lower (p < 0.001) tGSH, SOD, and CAT levels were determined in optic nerve samples of the FUG group rather than HG and CFU groups. In histopathological analyses, determined that astrocyte and oligodendrocyte nuclei were mostly darkly stained, the majority of astrocytes were hypertrophied and degenerated, and some oligodendrocytes were degenerated in the FUG group unlike HG and CFU groups. Moreover, the optic nerve tissue was determined to be vacuolized and intensely edematous, and blood capillaries were intensely dilated and congested. In conclusion, 5-FU caused optic neuropathy due to oxidative and inflammatory damage, and Carvacrol reduced this oxidative and inflammatory damage and histopathological changes in tissues. This revealed that Carvacrol was possibly to be efficient upon 5-FU-induced optic nerve toxicity. © 2023, Colegio de Farmaceuticos de la Provincia de Buenos Aires. All rights reserved.