Changes in the level of tyrosinase expression in the retinal pigment epithelium during the development of experimental optic nerve degeneration

BACKGROUND: With optic nerve degeneration of various origins, retinal neurons are the most vulnerable, and their state under these conditions has been studied in sufficient detail. At the same time, the retinal pigment epithelium plays a very important role, realizing the synthesis of melanin and performing antioxidant, phagocytic, transport, protective, and homeostatic functions. Tyrosinase serves as a key enzyme in melanogenesis by cells of this epithelium. The development of methods for early diagnosis of optic nerve atrophy is extremely important due to the fact that functional visual impairments appear later than structural ones, at more advanced stages of the disease. The retinal pigment epithelium cannot be insensitive to the processes that occur during optic nerve degeneration. That is why its study in experimental degeneration of the optic nerve is necessary for a more complete understanding of the processes occurring in the visual analyzer under these conditions.

AIM: To study changes in the level of tyrosinase expression in the retinal pigment epithelium at different development stages of experimental optic nerve degeneration based on morphological data.

MATERIAL AND METHODS: The subjects of the study were 40 rat eyes after creating a model of optic nerve atrophy using methanol. The animals were divided into five groups: the first group — control; the second to fifth groups included animals whose eyes were enucleated 1, 3, 6 and 9 weeks after the creation of the aminophylline-methanol model of optic nerve atrophy, respectively. The retinal pigment epithelium was studied using fluorescent antibodies to tyrosinase Tyrosinase Mouse Monoclonal. Immunofluorescence staining was performed on fixed transverse sections of the eyeball. Statistical analysis and visualization of the obtained data were carried out using the environment for statistical computing R 4.2.2.

RESULTS: A comparative analysis of the results obtained revealed that the level of tyrosinase expression in the fifth group was on average 4.21 times [95% confidence interval (CI) 2.49–7.13, p=0.00076], 9.31 times (95% CI 5.47–15.85, p=0.00033), 2.63 times (95% CI 1.51–4.58, p=0.0009) and 3.44 times (95% CI 1.96–6.03, p=0.00055) higher compared to the first, second, third and fourth groups, respectively. The level of tyrosinase in experimental samples in the first, third and fourth groups was statistically higher compared to the level of tyrosinase in the second group by an average of 2.21 times (95% CI 1.33–3.66, p=0.0003), 3.53 times (95% CI 2.08–6.02, p=0.00069) and 2.71 times (95% CI 1.58–4.65, p=0.00022), respectively.

CONCLUSION: As degenerative processes develop in the optic nerve fibers under these conditions, the integrity of the retinal pigment epithelium is disrupted, which is characterized by an increase in antibodies to tyrosinase in the retinal pigment epithelium of experimental animals.