Rhythmic gamma frequency light flickering ameliorates stress-related behaviors and cognitive deficits by modulating neuroinflammatory response through IL-12-Mediated cytokines production in chronic stress-induced mice.

Chronic stress enhances the risk for psychiatric disorders and induces depression and cognitive impairment. Gamma oscillations are essential for neurocircuit function, emotion, and cognition. However, the influence of gamma entrainment by sensory stimuli on specific aspects of chronic stress-induced responses remains unclear. Mice were subjected to corticosterone (CORT) administration and chronic restraint stress (CRS) for weeks, followed by rhythmic gamma frequency light flickering exposure. Local field potentials (LFPs) were recorded from the V1, CA1, and PFC regions to verify the light flicker on gamma oscillations. Behavioral tests were used to examine stress-related and memory-related behaviors. Golgi staining was performed to observe changes in spine morphology. Synaptosomes were isolated to determine the expression of synapse-related proteins through immunoblotting. RNA sequencing (RNA-seq) was applied to explore specific changes in the transcriptome. Immunofluorescence staining, real-time quantitative polymerase chain reaction (qPCR), and ELISA were used to evaluate microglial activation and cytokine levels. In this study, we demonstrated that rhythmic 40 Hz LF attenuated stress-related behavior and cognitive impairments by ameliorating the microstructural alterations in spine morphology and increasing the expression of GluN2A and GluA1 in chronically stressed mice. Transcriptome analysis revealed that significantly downregulated genes in LF-exposed CRS mice were enriched in neuroimmune-related signaling pathways. Rhythmic 40 Hz LF exposure significantly decreased the number of Iba1-positive microglia in the PFC and hippocampus, and the expression levels of the M1 markers of microglia iNOS and CD68 were reduced significantly in CRS mice. In addition, 40 Hz LF exposure suppressed the secretion of cytokines IL-12, which could regulate the production of IFN-γ and IL-10 in stressed mice. Our results demonstrate that exposure to rhythmic 40 Hz LF induces the neuroimmune response and downregulation of neuroinflammation with attenuated stress-related behaviors and cognitive function in CRS-induced mice. Our findings highlight the importance of sensory-evoked gamma entrainment as a potential therapeutic strategy for stress-related disorders treatment. Abbreviations: CORT, Chronic corticosterone treatment; CRS, Chronic restraint stress; IACUC, Institutional Animal Care and Use Committee; LF, light flickers; FST, Forced swim test; NSFT, Novelty-suppressed feeding test; SPT, Sucrose preference test; NSFT, Novelty-suppressed feeding; qPCR, Quantitative real-time polymerase chain reaction; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; PVDF, polyvinylidene fluoride; PBS, phosphate-buffered saline; PBS-T, phosphate-buffered saline plus 0.1% Tween 20; PVDF, polyvinylidene fluoride; GFAP, Glial fibrillary acidic protein; DAPI, 4',6-Diamid- ino-2-phenylindole; Iba1, Ionized calcium-binding adaptor molecule 1; iNOS, Inducible nitric oxide synthase; IL-10, Interleukin-10; IL6, Interleukin 6; IL-1ß, Interleukin 1ß; IL-12, Interleukin 12; TNF-α, Tumor necrosis factor alpha; IFN-γ, Interferon-gamma; TLR6 and 9, Toll-like Receptor 6 and 9.

IKKα mediates UVB-induced cell apoptosis by regulating p53 pathway activation.

Exposure to ultraviolet B (UVB) has been demonstrated to induce DNA damage as well as angiogenesis-related photo-damages, which are implicated in a variety of medical problems, including sunburn, photo-aging and skin cancers. However, the molecular mechanism related to UVB-induced photo-injuries remained fully elucidated. Here we revealed that one of the catalytic subunits of the IKK complex, IKKα, played a critical role in mediating UVB-induced apoptotic responses in two kinds of UVB sensitive cells, human keratinocyte (HaCat) and mouse embryonic fibroblasts (MEFs). This function of IKKα was unrelated to NF-κB activity, but was delivered by inducing phosphorylation and acetylation of p53 and upregulating the expression of the pro-apoptotic p53 target gene, PERP. Although IKKα kinase activity was required for mediating post-translational modifications and transactivation of 53 and PERP induction, IKKα did not show direct binding ability toward p53. Instead, IKKα could interact with CHK1, the protein kinase leading to p53 phosphorylation, and trigger CHK1 activation and CHK1/p53 complex formation. At the same time, IKKα could also interact with p300 and CBP, the acetyltransferases responsible for p53 acetylation, and trigger p300/CBP activation and p300/p53 or CBP/p53 complex formation under UVB exposure. Taken together, we have identified a novel NF-κB-independent role of IKKα in mediating UVB-induced apoptosis by regulating p53 pathway activation. Targeting IKKα/p53/PERP pathway might be helpful to prevent skin photo-damages induced by sunlight.

Roles of bile acids signaling in neuromodulation under physiological and pathological conditions.

Bile acids (BA) are important physiological molecules not only mediating nutrients absorption and metabolism in peripheral tissues, but exerting neuromodulation effect in the central nerve system (CNS). The catabolism of cholesterol to BA occurs predominantly in the liver by the classical and alternative pathways, or in the brain initiated by the neuronal-specific enzyme CYP46A1 mediated pathway. Circulating BA could cross the blood brain barrier (BBB) and reach the CNS through passive diffusion or BA transporters. Brain BA might trigger direct signal through activating membrane and nucleus receptors or affecting activation of neurotransmitter receptors. Peripheral BA may also provide the indirect signal to the CNS via farnesoid X receptor (FXR) dependent fibroblast growth factor 15/19 (FGF15/19) pathway or takeda G protein coupled receptor 5 (TGR5) dependent glucagon-like peptide-1 (GLP-1) pathway. Under pathological conditions, alterations in BA metabolites have been discovered as potential pathogenic contributors in multiple neurological disorders. Attractively, hydrophilic ursodeoxycholic acid (UDCA), especially tauroursodeoxycholic acid (TUDCA) can exert neuroprotective roles by attenuating neuroinflammation, apoptosis, oxidative or endoplasmic reticulum stress, which provides promising therapeutic effects for treatment of neurological diseases. This review summarizes recent findings highlighting the metabolism, crosstalk between brain and periphery, and neurological functions of BA to elucidate the important role of BA signaling in the brain under both physiological and pathological conditions.

Acute hypoxia induced dysregulation of clock-controlled ovary functions.

High altitudes or exposure to hypoxia leads to female reproductive disorders. Circadian clocks are intrinsic time-tracking systems that enable organisms to adapt to the Earth's 24-h light/dark cycle, which can be entrained by other environmental stimuli to regulate physiological and pathological responses. In this study, we focused on whether ovarian circadian clock proteins were involved in regulating female reproductive dysfunction under hypoxic conditions. Hypobaric hypoxia was found to induce a significantly prolonged estrous cycle in female mice, accompanied by follicular atresia, pituitary/ovarian hormone synthesis disorder, and decreased LHCGR expression in the ovaries. Under the same conditions, the levels of the ovarian circadian clock proteins, CLOCK and BMAL1, were suppressed, whereas E4BP4 levels were upregulated. Results from granulosa cells (GCs) further demonstrated that CLOCK: BMAL1 and E4BP4 function as transcriptional activators and repressors of LHCGR in ovarian GCs, respectively, whose responses were mediated by HIF1ɑ-dependent (E4BP4 upregulation) and ɑ-independent (CLOCK and BMAL1 downregulation) manners. The LHCGR agonist was shown to efficiently recover the impairment of ovulation-related gene (EREG and PGR) expression in GCs induced by hypoxia. We conclude that hypoxia exposure causes dysregulation of ovarian circadian clock protein (CLOCK, BMAL1, and E4BP4) expression, which mediates female reproductive dysfunction by impairing LHCGR-dependent signaling events. Adjusting the timing system or recovering the LHCGR level in the ovaries may be helpful in overcoming female reproductive disorders occurring in the highlands.