Role of Visual and Non-Visual Opsins in Blue Light–Induced Neurodegeneration in Drosophila melanogaster

Marina Piacenti-Silva^1*Samuel de Mattos Alves²Hulder Henrique Zaparoli^3*Marcela De Oliveira¹Juliano Morimoto^4,5Carolina L Zilli Vieira⁶

• ¹Universidade Estadual Paulista Julio de Mesquita Filho - Campus de Bauru, Bauru, Brazil
• ²Universidade Estadual Paulista Julio de Mesquita Filho - Campus de Botucatu, Botucatu, Brazil
• ³Center for Applied Psychology, Faculty of Sciences, São Paulo State University, Bauru, Brazil
• ⁴Universidade Federal do Parana, Curitiba, Brazil
• ⁵University of Aberdeen School of Natural and Computing Sciences, Aberdeen, United Kingdom
• ⁶Harvard T H Chan School of Public Health Department of Environmental Health, Boston, United States

Light regulates circadian rhythms and downstream physiological and behavioural functions. Excessive exposure to artificial light, particularly blue light (450-500 nm), results in adverse health effects such as sleep disturbance, neurodegeneration and metabolic disorders. Visual opsins represent a keystone factor in the interaction between light and physiological processes, and their absence compromises photosensitive dependent functions. However, organisms also express nonvisual opsins which could interact with light to regulate physiology and behaviour independent of vision, but the role of visual and non-visual opsins in mediating blue light-induced stress remains unknown. Here, we used two knock-out Drosophila melanogaster lines for visual rhodopsin 1 (Rh11) and non-visual rhodopsin 7 (Rh71) opsins and quantified DNA damage (γ-H2Av staining) and vacuole formation in the central nervous system upon prolonged exposure to blue light exposure (continuous 24 h/day at 488 nm; 1320 lux; 1120 μW·cm⁻²) from egg deposition to 20 days old flies. We found that Rh11 flies exhibit the highest levels of DNA damage and vacuolization compared with wild-type (w1118) and Rh71, particularly in brain regions associated with sensory processing and neurotransmission. Thus, our findings indicate that Rh1 plays a more significant role than Rh7 in the production of DNA damage and neurodegeneration-associated vacuolization in the nervous system in response to blue light. More broadly, they suggest that visual opsins, rather than non-visual ones, can mediate neurodegeneration in the central nervous system.