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

Abstract

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.

Keywords: PER1; anxiety; complete darkness; curcumin; dim light at night; metabolism; weight gain.

Figure 1

Effect of exposure to dim light at night (dLAN) and complete darkness (DD) on (a) the percentage of body weight gained and (b) the food intake. Values are represented as mean ± standard deviation (n = 5). Non-parametric one-way ANOVA with Dunnett’s post-hoc test to differentiate the results between the light/dark (LD) control vs. the dLAN control and DD control. All the data were analyzed with GraphPad Prism-8 software. The statistical values * p < 0.05 represent a significant difference among the groups.

Figure 2

Effect of different concentrations (50, 100, and 150 mg/kg) of orally administered curcumin (Cur) on (a) the percentage of body weight gained in dim light at night (dLAN), (b) percentage of body weight gained in complete darkness (DD), (c) food intake in dLAN, and (d) food intake in DD-exposed mice. Values are represented as mean ± standard deviation (n = 5). Non-parametric one-way ANOVA with post-hoc Dunnett’s test was employed to differentiate the results among different treatment groups. All the data were analyzed with GraphPad Prism-8 software.

Figure 3

Effect of exposure to dim light at night (dLAN) and complete darkness (DD) on the anxiety-like behavior of mice. (a) Percentage of freezing time, (b) grooming, and (c) posture. Values are represented as mean ± standard deviation (n = 5). Non-parametric one-way ANOVA with post-hoc Dunnett’s test was employed to match the results between the light/dark (LD) control vs. the dLAN control and DD control. All the data were analyzed with GraphPad Prism-8 software. The statistical values * p < 0.05, ** p < 0.01, and *** p < 0.001 represent a significant difference among the groups.

Figure 4

Effect of different concentrations (50, 100, and 150 mg/kg) of orally administered curcumin on anxiety-like behavior of mice. (a) Percentage of freezing time in dim light at night (dLAN), (b) grooming in dLAN, (c) posture in dLAN, (d) percentage of freezing time in complete darkness (DD), (e) grooming in DD, and (f) posture in DD-exposed mice. Values are represented as mean ± standard deviation (n = 5). Non-parametric one-way ANOVA with post-hoc Dunnett’s test was employed to match the results among different treatment groups. All the data were analyzed with GraphPad Prism-8 software. The statistical values * p < 0.05, ** p < 0.01, and *** p < 0.001 represent a significant difference among the groups.

Figure 5

Effect of different concentrations (50, 100, and 150 mg/kg) of orally administered curcumin on the expression fold change of clock gene PER1 in dim light at night (dLAN) and complete darkness (DD)-exposed mice. (a) Light/Dark (LD) control vs. dLAN and DD, (b) dLAN control vs. dLAN treatment, and (c) DD control vs. DD treatment. Values are represented as mean ± standard deviation (n = 5). One-way ANOVA with post-hoc Dunnett’s test was employed to match the results among the different treatment groups in different lighting conditions. All the data were analyzed with GraphPad Prism software. The statistical value *** p < 0.001 represent a significant difference among the groups.