Photoperiod integration in C3H rd1 mice

Effect of molecular hydrogen, a novelly-established antioxidant, on the retinal degeneration of hereditary retinitis pigmentosa: an in-vivo study

Objective Our research was performed in order to explore the effects of molecular hydrogen (H2), a novelly-established antioxidant, on the retinal degeneration in rd1 mice, an animal model of inherited retinitis pigmentosa (RP). Methods The rd1 mice were divided randomly into control and H2 intervention groups. Mice from other groups received H2 intervention in three modes, two modes of the hydrogen gas (HG) and one model of hydrogen-rich saline (HRS). At 14 days post born (P14) and P21, various indicators were detected in all mice, including eletroretinogram (ERG), fundus phography, optical coherence tomography (OCT), and retinal immunotaining of microglia cells' marker, Iba1. Results The ERG amplitude in mice from the control and H2 intervention groups showed no statistical differences (p > 0.05). At P14 and P21, no significant difference in the distance from the retinal pigment epithelium to the outer plexiform layer on OCT from mice of the above two groups was found (p > 0.05). The thickness of the outer nuclear layer (ONL) in mice at P14 and P21 showed no statistical differences between the control group and the H2 intervention group (p > 0.05). In the aspect of the number of Iba1-positive cells, we did not found any significant differences between the two groups (p > 0.05). Conclusion Different forms of H2 intervention (hydrogen-rich saline and hydrogen gas) had no obvious effects on the course of retinal degeneration in rd1 mice. The specific mechanism of photoreceptor degeneration in the hereditary RP mouse model may be different, requiring different medical interventions.

Sleep and the sleep electroencephalogram in C57BL/6 and C3H/HeN mice

Different mouse strains used in biomedical research show different phenotypes associated with their genotypes. Two mouse strains commonly used in biomedical sleep research are C57Bl/6 and C3H/He, the strains differ in numerous aspects, including their ability to secrete melatonin as well as the expression of several sleep-related genes. However, sleep regulation has only limitedly been compared between C3H/HeN and C57Bl/6 mice. We therefore compared sleep-wake behaviour and EEG-measured spectral brain activity for C57bl/6 and C3H/HeN mice during a 12:12 h light: dark baseline and during and after a 6 h sleep deprivation. The C3H mice spent more time in NREM sleep around the light-dark transition and more time in REM sleep during the dark phase compared with C57bl/6 mice. The C3H mice also showed more EEG activity in the 4.5-7.5 Hz range during all stages and a stronger 24 h modulation of EEG power density in almost all EEG frequencies during NREM sleep. After the sleep deprivation, C3H mice showed a stronger recovery response, which was expressed in both a larger increase in EEG slow wave activity (SWA) and more time spent in NREM sleep. We show large differences regarding sleep architecture and EEG activity between C3H and C57bl/6 mice. These differences include the amount of waking during the late dark phase, the 24 h amplitude in EEG power density, and the amount of REM sleep during the dark phase. We conclude that differences between mouse strains should be considered when selecting a model strain to improve the generalisability of studies investigating biomedical parameters related to sleep and circadian rhythms.

In light of breathing: environmental light is an important modulator of breathing with clinical implications

In vertebrate animals, the automatic, rhythmic pattern of breathing is a highly regulated process that can be modulated by various behavioral and physiological factors such as metabolism, sleep-wake state, activity level, and endocrine signaling. Environmental light influences many of these modulating factors both indirectly by organizing daily and seasonal rhythms of behavior and directly through acute changes in neural signaling. While several observations from rodent and human studies suggest that environmental light affects breathing, few have systematically evaluated the underlying mechanisms and clinical relevance of environmental light on the regulation of respiratory behavior. Here, we provide new evidence and discuss the potential neurobiological mechanisms by which light modulates breathing. We conclude that environmental light should be considered, from bench to bedside, as a clinically relevant modulator of respiratory health and disease.

Impacts of Circadian Gene Period2 Knockout on Intestinal Metabolism and Hepatic Antioxidant and Inflammation State in Mice

The period circadian regulator 2 (Per2) gene is important for the modulations of rhythmic homeostasis in the gut and liver; disruption will cause metabolic diseases, such as obesity, diabetes, and fatty liver. Herein, we investigated the alterations in intestinal metabolic and hepatic functions in Per2 knockout (Per2^−/−, KO) and wild-type (Per2^+/+, WT) mice. Growth indices, intestinal metabolomics, hepatic circadian rhythms, lipid metabolism, inflammation-related genes, antioxidant capacity, and transcriptome sequencing were performed after euthanasia. Data indicated that KO decreased the intestinal concentrations of amino acids such as γ-aminobutyric acid, aspartic acid, glycine, L-allothreonine, methionine, proline, serine, and valine while it increased the concentrations of carbohydrates such as cellobiose, D-talose, fucose, lyxose, and xylose compared with WT. Moreover, the imbalance of intestinal metabolism further seemed to induce liver dysfunction. Data indicated that Per2 knockout altered the expression of hepatic circadian rhythm genes, such as Clock, Bmal1, Per1, Per3, Cry1, and Cry2. KO also induced hepatic lipid metabolism, because of the increase of liver index and serum concentrations of low-density lipoprotein, and the upregulated expression of Pparα, Cyp7a1, and Cpt1. In addition, KO improved hepatic antioxidant capacity due to the increase activities of SOD and GSH-Px and the decrease in concentrations of MDA. Lastly, KO increased the relative expression levels of hepatic inflammation-related genes, such as Il-1β, Il-6, Tnf-α, Myd88, and Nf-κB p65, which may potentially lead to hepatic inflammation. Overall, Per2 knockout induces gut metabolic dysregulation and may potentially trigger alterations in hepatic antioxidant and inflammation responses.

Normal Light-Dark and Short-Light Cycles Regulate Intestinal Inflammation, Circulating Short-chain Fatty Acids and Gut Microbiota in Period2 Gene Knockout Mice

Regular environmental light–dark (LD) cycle-regulated period circadian clock 2 (Per2) gene expression is essential for circadian oscillation, nutrient metabolism, and intestinal microbiota balance. Herein, we combined environmental LD cycles with Per2 gene knockout to investigate how LD cycles mediate Per2 expression to regulate colonic and cecal inflammatory and barrier functions, microbiome, and short-chain fatty acids (SCFAs) in the circulation. Mice were divided into knockout (KO) and wild type (CON) under normal light–dark cycle (NLD) and short-light (SL) cycle for 2 weeks after 4 weeks of adaptation. The concentrations of SCFAs in the serum and large intestine, the colonic and cecal epithelial circadian rhythm, SCFAs transporter, inflammatory and barrier-related genes, and Illumina 16S rRNA sequencing were measured after euthanasia during 10:00–12:00. KO decreased the feeding frequency at 0:00–2:00 but increased at 12:00–14:00 both under NLD and SL. KO upregulated the expression of Per1 and Rev-erbα in the colon and cecum, while it downregulated Clock and Bmal1. In terms of inflammatory and barrier functions, KO increased the expression of Tnf-α, Tlr2, and Nf-κb p65 in the colon and cecum, while it decreased Claudin and Occludin-1. KO decreased the concentrations of total SCFAs and acetate in the colon and cecum, but it increased butyrate, while it had no impact on SCFAs in the serum. KO increased the SCFAs transporter because of the upregulation of Nhe1, Nhe3, and Mct4. Sequencing data revealed that KO improved bacteria α-diversity and increased Lachnospiraceae and Ruminococcaceae abundance, while it downregulated Erysipelatoclostridium, Prevotellaceae UCG_001, Olsenella, and Christensenellaceae R-7 under NLD in KO mice. Most of the differential bacterial genus were enriched in amino acid and carbohydrate metabolism pathways. Overall, Per2 knockout altered circadian oscillation in the large intestine, KO improved intestinal microbiota diversity, the increase in Clostridiales abundance led to the reduction in SCFAs in the circulation, concentrations of total SCFAs and acetate decreased, while butyrate increased and SCFAs transport was enhanced. These alterations may potentially lead to inflammation of the large intestine. Short-light treatment had minor impact on intestinal microbiome and metabolism.