Chronic Dim Light at Night Disrupts Immune Function and Increases Mortality in Aged Females

Jordan Payton*, Jennifer A. Liu, Jacob R. Bumgarner, William H. Walker, O. Hecmarie Meléndez-Fernández, Ning Zhang, James C. Walton, A. Courtney DeVries, and Randy J. Nelson.

Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown WV 26506

Presentation Category: Health Sciences (Poster Presentation #126)

Student’s Major: Psychology and Biology

Organisms have evolved endogenous rhythms that mimic the natural solar day; these internal circadian rhythms have a period of ~24 hours and synchronize physiology and behavior to precisely 24 hours in response to exogenous environmental cues such as light. Aging is considered a nonmodifiable risk factor for chronic disease and aged individuals are especially susceptible to disease and infection. Disruptions to circadian rhythms can alter aspects of the immune system including the regulation of proinflammatory cytokines, resulting in dysregulated immune activation and increased risk for disease/shortened life expectancy. Previous studies from our lab have reported that exposure to dim light at night (dLAN) disrupts immune function; thus, we tested the hypothesis that chronic dLAN exacerbates the effects of aging on immune function and mortality. Twenty month old male and female mice were monitored for 24 weeks in normal light-dark conditions or dLAN (5 lux), and immune function was tested through a cell-mediated delayed type hypersensitivity test (DTH). There was a significant decrease in life expectancy of females housed in dLAN compared to LD and males in either lighting condition. Additionally, there was an interaction effect of light and swelling response during DTH, where dLAN females had significantly impaired inflammatory response from day 3-6 of the analysis. Further, females had increased adrenal weights compared to males, and dLAN females compared to LD. Together, these data suggest that a sex difference in survival after chronic exposure to dLAN exists; females are especially susceptible to the detrimental consequences of disrupted circadian rhythms.

Funding: National Institute of Health (NIH)

Program/mechanism supporting research/creative efforts: WVU's Research Apprenticeship Program (RAP) & accompanying HONR 297-level course