Aberrant Lighting Causes Anxiety-like Behavior in Mice but Curcumin Ameliorates the Symptoms.

Dhondup Namgyal,Kumari Chandan,Sher Ali,Maha J Hashim,Ajaz Ahmad,Maryam Sarwat

doi:10.3390/ani11092590

Abstract

Simple SummaryIn the present study, we exposed mice to aberrant lighting system and noticed anxiety-like behavior. These symptoms were ameliorated by oral administration of curcumin. The study was carried out on the animals for three weeks in dim light at night (dLAN) and complete darkness (DD), monitoring the body weight, daily food intake, anxiety-like behavior, and expression of the period (PER1) gene. The exposure to dim light at night was found to significantly enhance the anxiety-like behavior and increased the body weight possibly through altered metabolism in mice. In contrast, exposure to DD caused increased anxiety but no significant difference in the body weight. Moreover, the expression of the PER1 gene involved in sleep was also found to be decreased in the aberrant light conditions (dLAN and DD). Although the treatment of curcumin had no effect on the body weight, it had ameliorated the anxiety-like behavior possibly by modulating the expression of the PER1 gene. Thus, the alteration in the light/dark cycle has negative influences on body weight, affecting even the emotional quotient. This study identifies the risk factors associated with aberrant lighting conditions in laboratory animal and ameliorative effects of curcumin. In the modern research field, laboratory animals are constantly kept under artificial lighting conditions. However, recent studies have shown the effect of artificial light on animal behavior and metabolism. In the present study on mice, following three weeks of housing in dim light at night (dLAN; 5lux) and complete darkness (DD; 0lux), we monitored the effect on body weight, daily food intake, anxiety-like behavior by employing the open field test, and expression of the period (PER1) gene. We also studied the effect of oral administration of different concentrations of curcumin (50, 100, and 150 mg/kg) for three weeks in the same mice and monitored these parameters. The exposure to dLAN had significantly increased the anxiety-like behavior and body weight possibly through the altered metabolism in mice, whereas exposure to DD caused increased anxiety but no significant difference in weight gain. Moreover, the expression of the PER1 gene involved in sleep was also found to be decreased in the aberrant light conditions (dLAN and DD). Although the treatment of curcumin had no effect on body weight, it ameliorated the anxiety-like behavior possibly by modulating the expression of the PER1 gene. Thus, alteration in the light/dark cycle had a negative effect on laboratory animals on the body weight and emotions of animals. The present study identifies the risk factors associated with artificial lighting systems on the behavior of laboratory animals and the ameliorative effects of curcumin, with a focus on anxiety-like behavior.

Highlights

The environmental lighting modulates several physiological and behavioral processes such as the sleep-wake cycle [1], blood pressure [2], hormone secretion [3], body temperature [4], and organ activities [5]
Mice exposed to dim light at night (dLAN) for three weeks gained significant body weight (F2,12 = 8.391, p < 0.05) compared to the normal LD control group (Figure 1a)
This finding is supported by the result of dLAN and complete darkness (DD)-exposed mice as there is no significant difference in the percentage of weight gain between the mice exposed to DD (p > 0.05) and the LD control group (Figure 1a)

Summary

Introduction

The environmental lighting modulates several physiological and behavioral processes such as the sleep-wake cycle [1], blood pressure [2], hormone secretion [3], body temperature [4], and organ activities [5]. Mankind has illuminated the nocturnal environment and adopted the artificial lighting system [6]. This has created overwhelming pollution, making natural celestial light almost unavailable to laboratory animals [7,8]. Exposure to dim light at night (dLAN) has shown to raise various health issues such as disrupted metabolism, changes in immunological attributes, oxidative stress, sleep problems, and an alteration in circadian timing [19]. The absence of light can be detrimental, especially in nocturnal animals It can increase the active phase directly affecting the feeding and locomotor behavior of animals [20]. A better understanding of the effect of aberrant lighting on emotional regulations will enhance our understanding on the circadian rhythm and its associated attributes in laboratory animals

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Results

Conclusion