Dim Light at Night Induced Neurodegeneration and Ameliorative Effect of Curcumin

Abstract

It is a well-known fact that following a proper routine light/dark or diurnal rhythm controls almost all biological processes. With the introduction of modern lighting and artificial illumination systems, continuous exposure to light at night may lead to the disruption of diurnal rhythm. However, the effect of light during the night on brain anatomy, physiology, and human body functions is less explored and poorly understood. In this study, we have evaluated the effect of exposure to dim light (5 lux) at night (dLAN) on Swiss Albino mice over a duration of three consecutive weeks. Results have revealed that exposure to dLAN led to an impairment of cognitive and non-cognitive behaviour, oxidative stress–mediated elevation of lipid peroxidation, and reduction of superoxide dismutase and catalase activity. It also led to the downregulation of hippocampal proteins (BDNF, Synapsin II and DCX) at both protein and mRNA level. Additionally, there was downregulation of CREB and SIRT1 mRNAs and neurodegeneration-associated miRNA21a-5p and miRNA34a-5p. The pyramidal and cortical neurons started showing pyknotic and chromatolysis characteristics. However, a dose of curcumin administered to the mice positively modulated these parameters in our experimental animals. We proposed the modulatory role of curcumin in addressing the deleterious effects of dLAN.

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

“…However, the administration of curcumin (150mg/kg) had effectively restored some of the anxiety-like behaviors including the percentage freezing time and frequency of grooming in mice. Corroborating this finding, in our previous study, we observed that the administration of curcumin in the Cd-induced neurotoxic mice model and normal light/dark-exposed mice revealed increased locomotor activity, reduced stress and anxiety-like behavior, and improved spatial learning and retention memory through the promotion of hippocampal neurogenesis [ 21 , 41 , 42 ].…”

“…Animals’ physiological processes are tuned to the external light/dark cycle of their surroundings. The effects of night-time light and constant darkness on the brain and behavior of laboratory animals are recent findings [ 21 ]. Recent studies show that chronic exposure to artificial light during the night elevates the chances of developing behavioral impairment in laboratory animals, such as sleep disturbance [ 34 , 35 ], mood fluctuation [ 36 ], and metabolic disorders [ 37 ].…”

“…The cDNA was synthesized by using the High-Capacity cDNA kit (Thermo Fisher, Waltham, MA, USA). In brief, the RNA was reverse transcribed following the manufacturer's instructions wherein 1000 ng of total RNA and 10X RT primers were used (21). The synthesized cDNA was stored at −20 • C in a freezer for subsequent analyses.…”

“…Earlier, we reported that exposure to dLAN and complete darkness (DD) for three weeks in Swiss Albino mice impaired both cognitive and non-cognitive behaviors through the modulation of hippocampal protein expression and that of core genes ( BDNF, CREB, DCX, SYN , and SIRT1 ) associated with neurodegeneration [ 21 ]. Therefore, in this study, we undertook three weeks of exposure of mice to dLAN and DD to assess anxiety and altered homeostasis, together with the expressional change of the sleep gene PER1 .…”

Early Life Irradiation-Induced Hypoplasia and Impairment of Neurogenesis in the Dentate Gyrus and Adult Depression Are Mediated by MicroRNA- 34a-5p/T-Cell Intracytoplasmic Antigen-1 Pathway

“…miR-34a targets E2F3, Numbl, platelet-derived growth factor receptor A (PDGFRA), synaptotagmin 1 (Syt1), autophagy-related 9a (Atg9a), CD44, cyclic AMP response-element binding protein (CREB), brain-derived neurotrophic factor (BDNF) to inhibit cell proliferation, migration, invasion and adhesion [ 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. It regulates extracellular signal-regulated kinase 1/2 (ERK) and p38, and increases nuclear factor kappa light chain enhancer of activated B cells (NF-κB), Sirtuin 1 (SIRT1) and Bcl2, to promote or reduce apoptosis [ 66 , 67 , 68 ].…”