Artificial Light at Night Reduces Anxiety-like Behavior in Female Mice with Exacerbated Mammary Tumor Growth

Abstract

Artificial light at night (ALAN) is a pervasive phenomenon. Although initially assumed to be innocuous, recent research has demonstrated its deleterious effects on physiology and behavior. Exposure to ALAN is associated with disruptions to sleep/wake cycles, development of mood disorders, metabolic disorders, and cancer. However, the influence of ALAN on affective behavior in tumor-bearing mice has not been investigated. We hypothesize that exposure to ALAN accelerates mammary tumor growth and predict that ALAN exacerbates negative affective behaviors in tumor-bearing mice. Adult (> 8 weeks) female C3H mice received a unilateral orthotropic injection of FM3A mouse mammary carcinoma cells (1.0 × 105 in 100 μL) into the fourth inguinal mammary gland. Nineteen days after tumor inoculation, mice were tested for sucrose preference (anhedonia-like behavior). The following day, mice were subjected to an open field test (anxiety-like behavior), followed by forced swim testing (depressive-like behavior). Regardless of tumor status, mice housed in ALAN increased body mass through the first ten days. Tumor-bearing ALAN-housed mice demonstrated reduced latency to tumor onset (day 5) and increased terminal tumor volume (day 21). Exposure to ALAN reduced sucrose preference independent of tumor status. Additionally, tumor-bearing mice housed in dark nights demonstrated significantly increased anxiety-like behavior that was normalized via housing in ALAN. Together, these data reaffirm the negative effects of ALAN on tumorigenesis and demonstrate the potential anxiolytic effect of ALAN in the presence of mammary tumors.

Chronic phase advances reduces recognition memory and increases vascular cognitive dementia-like impairments in aged mice

“…These cognitive deficits were associated with increased vascular tortuosity in the isocortex, which is associated in humans with increased risk of vascular diseases and changes to cerebral blood flow. In conclusion, these results demonstrate that exposure to chronic phase advances results in sex-dependent differences, by increasing cognitive aging and impairments through altering spatial recognition memory, and auditory-cued fear associative learning in aged mice 12 , 16 .…”

“…Locomotor exploratory and anxiety-like behaviors were assessed in a 36 cm × 36 cm polypropylene open field arena housed in a sound- and light-attenuating chamber, equipped with infrared sensors to detect horizontal and vertical movement (Open Field Photobeam Activity System, San Diego Instruments Inc., San Diego, CA USA) as previously described 12 . Mice were habituated to the testing room 30 min prior to behavioral testing.…”

Circadian Disruption and Consequences on Innate Immunity and Inflammatory Response

“…For example, mice exposed to either ALAN (5 lx) or an HFD for 4 weeks showed up-regulated expression of inflammatory markers Tnfα and macrophage-1 antigen ( Mac-1 ) in white adipose tissue, while ALAN further potentiated HFD-induced inflammation [ 139 ]. In cancer research, dim ALAN has been shown to favor tumor growth, especially in models of mammary cancer [ 143 , 144 ]. C3H mice exposed to ALAN (5 lx) for 3 weeks and then injected with FM3A mammary carcinoma cells displayed earlier tumor onset and increased terminal tumor volume compared to tumor-bearing mice housed in the LD regime [ 143 ].…”

“…In cancer research, dim ALAN has been shown to favor tumor growth, especially in models of mammary cancer [ 143 , 144 ]. C3H mice exposed to ALAN (5 lx) for 3 weeks and then injected with FM3A mammary carcinoma cells displayed earlier tumor onset and increased terminal tumor volume compared to tumor-bearing mice housed in the LD regime [ 143 ]. In another study in nude rats, chronic ALAN even with a very low light intensity of 0.2 lx accelerated mammary tumor growth [ 144 ].…”

Prognostic Value of Negative Emotions on the Incidence of Breast Cancer: A Systematic Review and Meta-Analysis of 129,621 Patients with Breast Cancer

“…Earlier studies suggested that several factors connect to depressive symptoms in BC patients, including demographics, disease-related factors, and distinct psychosocial characteristics such as coping styles and personality traits [21][22][23][24]. Emotional suppression is one of the coping style strategies, whereby, the individual can intentionally regulate the expression of NEs including, anxiety, anger, and sadness.…”