Chronic exposure to dim light at night disrupts cell-mediated immune response and decreases longevity in aged female mice

ABSTRACT

Circadian rhythms are endogenous biological cycles that regulate physiology and behavior for optimal adaptive function and survival; they are synchronized to precisely 24 hours by daily light exposure. Disruption of the daily light–dark (LD) cycle by exposure to artificial light at night (ALAN) dysregulates core clock genes and biological function. Exposure to ALAN has been associated with increased health risks in humans, and elderly individuals are at elevated risk for poor outcome from disease and often experience elevated exposure to ALAN due to increased care requirements. The role of disrupted circadian rhythms in healthy, aged animals remains unspecified; thus, we hypothesized that disrupted circadian rhythms via chronic exposure to dim ALAN (dLAN) impair immune response and survival in aged mice. Twenty-month-old C57BL/6 male and female mice were exposed to 24 weeks of LD conditions or dLAN (5 lux); then, cell-mediated immune response was assessed using a delayed-type hypersensitivity test. Aged female mice exposed to dLAN displayed dysregulated hypersensitivity and inflammation as a measure of cell-mediated immune response and decreased lifespan compared to females housed in dark nights. Nighttime lighting did not affect cell-mediated immune response or lifespan in males but dysregulated body mass and increased adrenal mass after immune challenge after chronic exposure to dLAN. Together, these data indicate that chronic exposure to dLAN affects lifespan in aged females and suggest that females are more susceptible to the detrimental consequences of disrupted circadian rhythms.

KEYWORDS:

• Circadian rhythms
• light at night
• aging
• mortality
• light pollution
• immune response

Acknowledgements

All experiments were approved by West Virginia University Institutional Animal Care and Use Committee and animals were maintained in accordance with NIH Animal Welfare guidelines. J.A.L., J. R. B., W. H. W. II and O. H. M. assisted with data collection. J.A.L., J.C.W., A.C.D. and R.J.N. designed, wrote and edited the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

The data generated and analyzed during this study are available from Mendeley Data. Liu, Jennifer (2022), “Chronobiology International - Data Set,” Mendeley Data, V1, doi: 10.17632/85dyc9v5xk.1

Additional information

Funding

This work was supported by the National Institute of Neurological Disorders and Stroke [5R01NS092388-05, 5R01NS092388S1]; National Institute of General Medical Sciences [NIGMS 5U54GM104942-04].