Dim Light at Night Exacerbates Pain Associated with Chemotherapy

Rhett C. White*, Jacob R. Bumgarner, Ph.D., William H. Walker ll, Jennifer A. Liu, Hecmarie Melendez-Fernandez, James C. Walton, Randy J. Nelson, Ph.D.
Department of Neuroscience, West Virginia University, Morgantown, WV, 26505

Presentation Category: Health Sciences (Poster presentation)

Student’s Major: Biology

Circadian rhythms are endogenous physiological processes that cycle across the 24-hour day with rhythms of approximately 24 hours. These rhythms are synchronized to precisely 24 hours by environmental cues, the primary of which is light during the day. Disruption of circadian rhythms by exposure to dim light at night (dLAN, ~5 lx) has been linked to a range of negative health effects, including peripheral and central inflammation and altered immune function. Our lab recently demonstrated that dLAN exposure exacerbates pain behavior in mice. Because of these findings, we sought to examine how dLAN may affect pain behavior associated with chemotherapy-induced peripheral neuropathy. We hypothesized that dLAN exacerbates pain behavior associated with chemotherapy induced neuropathy in mice. Female CFW mice received a 5-day injection regimen of either paclitaxel (2mg/kg/day) or vehicle and were placed in dark nights (LD) or dLAN conditions starting on the first night of injections. Pain behavior was assessed using three different assessments prior to and following treatment with chemotherapy. We observed that dLAN exacerbated the allodynia associated with paclitaxel treatment, but not warm and cold thermal challenges. Following behavioral testing, the periaqueductal gray (PAG) and rostral ventromedial medulla (RVM) were dissected for qRT-PCR analysis. This behavior was correlated with an observed upregulation of Il-6 expression in the RVM. These findings represent a crucial step in expanding our understanding of how disruption of circadian rhythms impacts pain. Further, our results suggest that future pain management strategies should consider the effects of disrupted circadian rhythms on patient outcomes.

Funding: NIH

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