Influence of different LED wavelengths on retinal melatonin levels - A rodent study

Stelyna Joylin; Srinivas Mutalik; Manokaran Kalaivani; Revathi P Shenoy; Mousumi Ghosh; Nishitha; Elizebeth Olive Akansha Manoj Kumar; Nagarajan Theruveethi

doi:10.1016/j.scitotenv.2023.166665

Influence of different LED wavelengths on retinal melatonin levels - A rodent study

Sci Total Environ. 2023 Dec 15:904:166665. doi: 10.1016/j.scitotenv.2023.166665. Epub 2023 Aug 30.

Authors

Stelyna Joylin¹, Srinivas Mutalik², Manokaran Kalaivani³, Revathi P Shenoy⁴, Mousumi Ghosh¹, Nishitha¹, Elizebeth Olive Akansha Manoj Kumar⁵, Nagarajan Theruveethi⁶

Affiliations

¹ Department of Optometry, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, India.
² Department of Pharmaceutics, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, India.
³ Department of Biochemistry, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India.
⁴ Department of Medical Laboratory Technology, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, India.
⁵ Department of Optometry, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, India; College of Optometry, University of Houston, Houston, TX, USA.
⁶ Department of Optometry, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, India. Electronic address: nagarajan.t@manipal.edu.

PMID: 37652369
DOI: 10.1016/j.scitotenv.2023.166665

Abstract

Background: Retinal melatonin is crucial for neuroprotection. Exposure to light-emitting diodes (LEDs) affects retinal neurons, possibly influencing retinal melatonin levels. Hence, we aimed to quantify the retinal melatonin level with different LED wavelengths.

Method: A total of 24 Sprague Dawley (SD) male rats were divided into four groups (n = 6 in each group) as normal controls (NC), blue light (BL), white light (WL), and yellow light (YL). The rats in the experimental groups were exposed to different wavelengths of LEDs for 28 days (12:12 h light-dark cycle) with uniform illumination of 450-500 lx. Following exposure, the rats were subjected to behavioral tests such as passive avoidance and elevated plus maze tests. Following the behavior tests, the rats were sacrificed, eyes were enucleated, and retinal tissue was stored at -80 °C. The homogenized retina was used for reactive oxygen species (ROS) and melatonin quantification using an enzyme-linked immunosorbent assay (ELISA) kit.

Results: Passive avoidance test revealed a significant difference across the groups (p < 0.0004). The BL exposure group demonstrated increased latency to enter the dark compartment (DC) and impaired motor memory. The elevated plus maze test revealed a significant difference across all the groups (p < 0.012), where the time spent in the closed arm was greater in the BL exposure group. Comparison of ROS levels revealed a significant difference across the groups (p < 0.0001), with increased nitric oxide concentrations in the experimental groups. Melatonin levels were significantly decreased in the light exposure groups (p < 0.0001) compared to the NC group.

Conclusion: Cumulative exposure to different LED wavelengths resulted in increased anxiety with impaired motor activity. This was also complemented by the addition of oxidative stress leading to decreased melatonin levels in the retina, which might trigger retinal neuronal damage.

Keywords: Blue light; Circadian cycle; Light exposure; Melatonin; Rats; White light; Yellow light.

MeSH terms

Animals
Circadian Rhythm
Light
Male
Melatonin*
Rats
Rats, Sprague-Dawley
Reactive Oxygen Species
Retina / physiology
Rodentia

Substances

Melatonin
Reactive Oxygen Species