Carvone protects against paclitaxel-induced retinal and optic nerve cytotoxicity: a histopathological study

Purpose: Carvone (CVN) is a natural monoterpene found in essential oils of many aromatic plant species. In this study, we investigated the protective effect of CVN against paclitaxel (PTX)-induced retinal and optic nerve cytotoxicity in rats. Methods: Twenty-four male adult Wistar albino rats (250-400 g) were randomized into four equal groups comprising six animals in each. Group 1 (control group) received intraperitoneal (i.p.) saline solution (0.5 mL/200 g) weekly for 4 weeks. Group 2 received i.p. CVN [(S)-(+)- CVN, (5S)-5-Isopropenyl-2-methyl-2-cyclohexen-1-one, C₁₀H₁₄, 25 mg/kg], while Group 3 received i.p. PTX (5 mg/kg) weekly for 4 weeks. Group 4 received i.p. CVN (25 mg/kg) 30 min after i.p. PTX (5 mg/kg) weekly for 4 weeks. At the end of the experimental period, retinal and optic nerve tissues were evaluated histopathologically. Results: All retinal specimens in control and CVN groups were histopathologically normal. In PTX group all eyes (6/6) demonstrated increased retinal vascularity and rosette-like structures in the outer nuclear layer, while in PTX-CVN group all eyes (6/6) demonstrated normal retinal vascularity and absence of rosette-like structures. All optic nerve specimens in control and CVN groups were histopathologically normal. In PTX group all eyes (6/6) demonstrated severe vacuolization and decrease in the number of astrocytes and oligodendrocytes, while 3 eyes (3/6) demonstrated marked single cell necrosis. In PTX-CVN group, 4 eyes (4/6) demonstrated moderate vacuolization while, 2 eyes (2/6) had none. Compared with PTX group, 1 eye (1/6) in PTX-CVN group demonstrated a decrease in numbers of astrocytes and oligodendrocytes while 5 eyes (5/6) were normal. No remarkable single cell necrosis was observed in PTX-CVN group. Conclusions: Our histopathological findings demonstrated the potential protective role of CVN against PTX-induced retinal and optic nerve cytotoxicity. CVN might be a promising molecule in counteracting oxidative stress-based cytotoxicity in the field of retinal and optic nerve disorders.