Down-regulation of miR-383-5p suppresses apoptosis in oxidative stress rat hepatocytes by targeting Bcl2.

miRNAs are a class of small non-coding RNAs that are involved in various biological processes. In the preliminary work of the laboratory, found that miR-383-5p was down-regulated in the liver tissue of acute cold stress rats and has been shown to be an important regulatory factor in tumour proliferation, but there are very few studies involving the mediation of cold stress in rat liver tissues. Therefore, the purpose of this study was to determine the effect of miR-383-5p on the livers of cold stress rats by simulating the cold stress state of rat liver tissues in vitro using H2 O2 to induce rat hepatocyte oxidative stress. The results showed that MDA content, Caspase 3 and Cyto C protein levels increased significantly; GPx activity and SOD1 protein levels decreased significantly and miR-383-5p expression was significantly down-regulated in rat liver tissues after cold stress. Different concentrations of H2 O2 was added to rat hepatocytes, and the results showed that the expression of miR-383-5p, the ROS level, and the apoptosis rate in rat hepatocytes was increased significantly in a concentration-dependent fashion. Transfection of miR-383-5p inhibitor revealed that the apoptosis rate of rat hepatocytes, and the protein level of apoptosis-related protein Caspase 3 were reduced; the results of the dual-luciferase reporter gene assay showed that miR-383-5p targeted regulation of Bcl2. The results suggested that the expression of miR-383-5p was up-regulated in oxidative stress rat hepatocytes and may aggravate the apoptosis of rat hepatocytes induced by targeting inhibition of Bcl2 translation.

Neuroinflammation induced by secretion of acetylated HMGB1 from activated microglia in hippocampi of mice following chronic cold exposure.

Stress is a nonspecific response to adverse circumstances and chronic stress can destroy homeostasis, leading to various primary diseases. Although chronic cold stress is becoming increasingly important for individuals living or working in extreme environments, the risk of associated disorders of the central nervous system remains unstudied. Here, male C57BL/6 mice were exposed to a temperature of 4 °C, for three hours each day for one, two or three weeks. Glial cell activation, neuronal structure, and neuroinflammation were then evaluated by western blotting, immunofluorescence, Nissl staining and co-immunoprecipitation. Microglial activation, accompanied by activation of the NF-κB signaling pathway, release of pro-inflammatory cytokines and loss of Nissl bodies, was observed in mouse hippocampal tissue following cold exposure. We speculate that these phenomena are mediated by the HMGB1/TLR4/NF-κB pathway and closely associated with acetylation of HMGB1 in the hippocampus. These findings provide new insights into the mechanisms of the cold stress response, which should inform the development of new strategies to combat the effects of hypothermia.

Oxidation Stress-Mediated MAPK Signaling Pathway Activation Induces Neuronal Loss in the CA1 and CA3 Regions of the Hippocampus of Mice Following Chronic Cold Exposure.

Chronic stress can damage homeostasis and induce various primary diseases. Although chronic cold stress is becoming an increasing problem for people who must work or live in extreme environments, risk-induced diseases in the central nervous system remain unstudied. Male C57BL/6 mice were exposed to an environment of 4 °C, 3 h per day for 1, 2, and 3 weeks and homeostasis in the hippocampus and neuronal apoptosis were evaluated by Western blotting, immunohistochemistry, TdT-mediated dUTP Nick-End Labeling (TUNEL) staining, and immunofluorescence. The phenomena of oxidation stress, MAPK signaling pathway activation, anti-oxidation protein release, neuronal apoptosis increases, and neuronal proliferation inhibition were demonstrated in the CA1 and CA3 regions of mouse hippocampal tissues following cold exposure. We speculated that these phenomena were mediated by the MAPK pathway and were closely linked with oxidative stress in the hippocampus. This study provides novel concepts regarding neurodegenerative diseases, suggesting that chronic cold stress may be a critical factor to induce neurodegenerative diseases.

Microglia Activated by Excess Cortisol Induce HMGB1 Acetylation and Neuroinflammation in the Hippocampal DG Region of Mice Following Cold Exposure.

Cold stress can induce neuroinflammation in the hippocampal dentate gyrus (DG), but the mechanism underlying neuronal apoptosis induced by cold stress is not well-understood. To address this issue, male and female C57BL/6 mice were exposed to a temperature of 4 °C for 3 h per day for 1 week, and glial cell activation, neuronal apoptosis, and neuroinflammation were evaluated by western blotting, immunofluorescence, terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate (dUTP) nick end labeling, Nissl staining, and immunohistochemistry. Additionally, BV2 cells were treated with different concentrations of cortisol (CORT) for 3 h to mimic stress and molecular changes were assessed by western blotting, immunofluorescence, and co-immunoprecipitation. We found that excess CORT activated glial cells and increased neuroinflammation in the DG of mice exposed to cold temperatures, which was associated with increased acetylation and nuclear factor-κB signaling. These effects were mediated by the acetylation of lysine 9 of histone 3 and lysine 310 of p65, which resulted in increased mitogen-activated protein kinase phosphorylation, nuclear translocation of p65, microglia activation, and acetylation of high-mobility group box 1. Neuroinflammation was more severe in male compared to female mice. These findings provide new insight into the mechanisms of the cold stress response, which can inform the development of new strategies to combat the effects of hypothermia.

Cortisol Excess-Mediated Mitochondrial Damage Induced Hippocampal Neuronal Apoptosis in Mice Following Cold Exposure.

Cold stress can induce neuronal apoptosis in the hippocampus, but the internal mechanism involving neuronal loss induced by cold stress is not clear. In vivo, male and female C57BL/6 mice were exposed to 4 °C, 3 h per day for 1 week. In vitro, HT22 cells were treated with different concentrations of cortisol (CORT) for 3 h. In vivo, CORT levels in the hippocampus were measured using ELISA, western blotting, and immunohistochemistry to assess the neuronal population and oxidation of the hippocampus. In vitro, western blotting, immunofluorescence, flow cytometry, transmission electron microscopy, and other methods were used to characterize the mechanism of mitochondrial damage induced by CORT. The phenomena of excessive CORT-mediated oxidation stress and neuronal apoptosis were shown in mouse hippocampus tissue following cold exposure, involving mitochondrial oxidative stress and endogenous apoptotic pathway activation. These processes were mediated by acetylation of lysine 9 of histone 3, resulting in upregulation involving Adenosine 5'-monophosphate (AMP)-activated protein kinase (APMK) phosphorylation and translocation of Nrf2 to the nucleus. In addition, oxidation in male mice was more severe. These findings provide a new understanding of the underlying mechanisms of the cold stress response and explain the apoptosis process induced by CORT, which may influence the selection of animal models in future stress-related studies.