Research progress of celastrol on the prevention and treatment of metabolic associated fatty liver disease / 生理学报

Metabolic associated fatty liver disease (MAFLD) is a liver disease with hepatocyte steatosis caused by metabolic disorders, which is closely related to obesity, diabetes, metabolic dysfunction, and other factors. Its pathological process changes from simple steatosis, liver inflammation to non-alcoholic steatohepatitis (NASH), and then leads to liver fibrosis, cirrhosis, and liver cancer. At present, no specific therapeutics are available for treatment of MAFLD targeting its etiology. Celastrol is the main active component of the traditional Chinese medicine Celastrus orbiculatus Thunb. In recent years, it has been found that celastrol shows important medicinal value in regulating lipid metabolism, reducing fat and weight, and protecting liver, and then ameliorates MAFLD. This article reviews the related research progress of celastrol in the prevention and treatment of MAFLD, so as to provide a reference for the comprehensive development and utilization of celastrol.

Neuroprotective Effects of Molecular Hydrogen: A Critical Review / 神经科学通报·英文版

Molecular hydrogen (H

Oxidized phospholipids and atherosclerosis / 生理学报

Phospholipids are important components of biomembrane and lipoproteins. Phospholipids can be oxidized by free radicals/nonradicals and enzymes to form oxidized phospholipids (OxPLs), which can lead to further generation of oxidation products with different biological activities. Clinical evidence shows that OxPLs are constantly generated and transformed during the pathogenesis of atherosclerosis and accumulated at the lesion sites. OxPLs are highly heterogeneous mixtures that can influence the progress of atherosclerosis through a variety of related receptors or signaling pathways. This review summarizes the process of phospholipid oxidation, the related products, the interaction of OxPLs with endothelial cells, monocytes/macrophages, smooth muscle cells, platelets and lipoproteins involved in the pathological process of atherosclerosis, and the progress of the researches using OxPLs as a target to inhibit atherosclerosis in recent years.

Different types of molecular hydrogen donors and their pharmacokinetics in vivo / 生理学报

Molecular hydrogen (H) has been shown to have diverse biomedical effects. As a small molecular gas, hydrogen can be diffused to the target without hindrance. A variety of related hydrogen products used in medical research and public health have been developed. There are various methods of administration of H, mainly including inhaling hydrogen gas, drinking hydrogen water, injecting hydrogen-saline, orally taking solid-state H sustained-release agents, and stimulating intestinal microbiomes to produce hydrogen. Pharmacokinetics of H in vivo vary with methods of administration and thus influence its biomedical effects. This review summarizes the types of H donors and their pharmacokinetics in vivo.

Research advances on preventive and therapeutic effects of hydrogen on cardiovascular and cerebrovascular diseases and underlying mechanisms / 生理学报

For a long time, hydrogen (H) has been considered as a physiological inert gas. However, recent studies have demonstrated that molecular H exerts significant therapeutic effects on various disease models due to its antioxidative, anti-inflammatory and anti-apoptotic capabilities, which have also been well confirmed in many clinical trials. Cardiovascular and cerebrovascular diseases (CCVDs) are the leading cause of death in the world, constituting a serious threat to human life and public health. In this paper, we reviewed the latest research progress of the biomedical effects of H in CCVDs and its possible molecular mechanisms, in the hope of providing new clues for the treatment of some CCVDs.

Changes in biological functions of high-density lipoprotein after abnormal modification / 生理学报

High-density lipoprotein (HDL) is composed of apolipoproteins, lipids and functional proteins. HDL protects against atherosclerosis (AS) by reverse cholesterol transport (RCT). HDL inhibits the lipid oxidation, inflammation and restores endothelial function. During systemic inflammation or metabolic disorders, HDL can be modified abnormally and converted to a dysfunctional type, which results in the loss of anti-inflammatory factors including apolipoprotein A-I (apoA-I), paraoxonase (PON) and platelet activating factor acetylhydrolase (PAF-AH), and gains of pro-inflammatory factors such as serum amyloid A (SAA), triglyceride (TG) and oxidative lipid. Therefore, understanding the changes in compositions and biological functions of dysfunctional HDL might help to comprehend its pathogenic mechanism.

The relationship of autophagy with endoplasmic reticulum stress and its role in pathogenesis, prevention and therapy of atherosclerosis / 生理学报

Autophagy is a cellular catabolic process responsible for removing the injured proteins and organelles via lysosome-dependent pathway, and it plays an important role in maintaining cellular homeostasis. Recent studies have shown that autophagy is activated and implicated in the pathogenesis of atherosclerosis. Autophagy can be triggered by oxidative lipids, cytokines and advanced glycation end products, and exerts protective or detrimental functions in the progression of atherosclerosis. However, the precise role and mechanisms of autophagy in different stages of atherosclerosis are still not fully clarified. This review highlights recent findings regarding autophagy response in vascular cells and its potential contribution to atherogenesis. Additionally, the relationship of autophagy with endoplasmic reticulum stress and whether autophagy could be a new therapeutic target for atherosclerosis are also discussed.

Activating transcription factor 6-C/EBP homologous protein pathway mediates advanced glycated albumin-induced macrophage apoptosis / 生理学报

The purpose of this study was to investigate whether activating transcription factor 6 (ATF6), a sensor to endoplasmic reticulum stress (ERS), would mediate advanced glycated albumin (AGE-alb)-induced macrophage apoptosis and to elucidate the possible molecular mechanisms. RAW264.7 macrophages were cultured in vitro and treated with AGE-alb (2, 4 and 6 g/L), normal control albumin or tunicamycin (TM, 4 mg/L) for 24 h. ATF6 small interfering RNA (siRNA) was transfected to RAW264.7 cells by Lipofectamine 2000. Cell viability and apoptosis were determined by MTT method and Annexin V-FITC/propidium iodide apoptosis detection kit, respectively. The activities of lactate dehydrogenase (LDH) in medium and caspase-3 in cells were measured by corresponding detection kits. ATF6 nuclear translocation was detected by Western blot and immunofluorescence cytochemistry. Protein and mRNA levels of C/EBP homologous protein (CHOP, a key-signaling component of ERS-induced apoptosis) were detected by Western blot and real-time fluorescence quantitative PCR, respectively. The results showed that similar to TM, AGE-alb increased the expression of CHOP at both the protein and mRNA levels in a concentration dependent manner. ATF6, as a factor that positively regulates CHOP expression, was activated by AGE-alb in a concentration dependent manner. siRNA-mediated knockdown of ATF6 significantly inhibited AGE-alb-induced macrophage injury, as indicated by the increased cell viability and the decreased LDH release, apoptosis and caspase-3 activation. Additionally, ATF6 siRNA attenuated AGE-alb-induced CHOP upregulation at both the protein and mRNA levels. These results suggest that ATF6 and its downstream molecule CHOP are involved in AGE-alb-induced macrophage apoptosis.

Ox-LDL down-regulates expression of pigment epithelium-derived factor in human umbilical vein endothelial cells / 生理学报

Pigment epithelium-derived factor (PEDF) is a multifunctional protein with anti-inflammatory, antioxidant and antithrombotic properties and plays a protective role against atherosclerosis (AS). The purpose of the present study is to explore the effects of oxidized low density lipoprotein (ox-LDL) on the expression of PEDF in cultured human umbilical vein endothelial cells (HUVECs). HUVECs were cultured and incubated with ox-LDL at different concentrations (6.25, 12.5, 25, 50, 100 and 150 mg/L) for 24 h. Apoptosis of endothelial cells were assayed by morphological staining and flow cytometry. The intracellular reactive oxygen species (ROS) levels were measured by flow cytometry. Cell viability was assayed by MTT assay. PEDF protein and mRNA expressions in HUVECs were analyzed by Western blot and quantitative real-time PCR, respectively. The results showed that ox-LDL significantly induced apoptosis, reduced cell viability, increased intracellular ROS levels and decreased the PEDF expression in HUVECs in a concentration-dependent manner. Ox-LDL at 50 mg/L obviously decreased the PEDF protein expression compared with control group (P < 0.05), whereas 25 mg/L ox-LDL already markedly reduced the PEDF mRNA expression (P < 0.05). In conclusion, the results suggest that ox-LDL down-regulates the PEDF expression through an increased ox-LDL-induced intracellular production of ROS.

Endoplasmic reticulum stress mediates oxidized low density lipoprotein-induced scavenger receptor A1 upregulation in macrophages / 生理学报

The present study was to investigate whether endoplasmic reticulum stress (ERS) was involved in oxidized low density lipoprotein (ox-LDL)-induced scavenger receptor A1 (SR-A1) upregulation in macrophages. RAW264.7 cells were pretreated with 20 mmol/L of 4-phenylbutyric acid (PBA) for 30 min and then treated with ox-LDL (50 mg/L) for 12 h or stimulated with 2 mg/L tunicamycin (TM) or 2 μmol/L thapsigagin (TG) for 4 h. In addition, RAW264.7 cells were incubated with 0.5, 1 and 2 mg/L TM for 4 h or treated with 2 mg/L TM for 1, 2 and 4 h, respectively. The intracellular total cholesterol (TC) content was measured using a tissue/cell total cholesterol assay kit. The protein and mRNA expressions of SR-A1 and glucose-regulated protein 78 (GRP78) were analyzed by Western blot and real-time PCR, respectively. Dil-ox-LDL uptake was detected using a microplate reader. The results showed that ox-LDL-induced cholesterol accumulation in macrophages was attenuated by PBA, an ERS inhibitor. Ox-LDL caused significant SR-A1 upregulation with concomitant activation of ERS as assessed by upregulation of GRP78, whereas PBA significantly inhibited the ox-LDL-induced SR-A1 upregulation (P < 0.05) and slightly decreased GRP78 expression by 39.3% (P = 0.057). TM, an ERS inducer, upregulated SR-A1 protein expression and ox-LDL uptake in dose- and time-dependent manner, but had no significant effect on SR-A1 mRNA level. However, the TM- or TG-induced SR-A1 upregulation and ox-LDL uptake were significantly mitigated by PBA. These data indicate that ERS plays a critical role in ox-LDL-induced SR-A1 upregulation, which in turn enhances the foam cell formation by uptaking more ox-LDL.

Inhibitory effect of quercetin preconditioning on tunicamycin-induced apoptosis in macrophages and its mechanism / 生理学报

The purposes of the present study were to investigate the inhibitory effect of quercetin (QUE) preconditioning on endoplasmic reticulum stress (ERS) inducer tunicamycin (TM)-induced apoptosis in RAW264.7 macrophages and the underlying molecular mechanisms. RAW264.7 cells were pretreated with different concentrations (20, 40, and 80 μmol/L) of QUE for 30 min and then treated with TM (5 mg/L) for 12 h. Cell viability and apoptosis were determined using MTT assay and Annexin V-FITC apoptosis detection kit, respectively. The nuclear translocation of activating transcription factor 6 (ATF6) in cells was detected by immunofluorescence analysis and Western blot. Protein and mRNA expressions of C/EBP homologous protein (CHOP) and Bcl-2 were examined by Western blot and real-time PCR, respectively. The results showed that TM reduced cell viability and induced apoptosis in RAW264.7 macrophages. The cytotoxic effects of TM were significantly inhibited by QUE pretreatment at the concentrations of 40 and 80 μmol/L. Interestingly, we found that QUE also significantly suppressed the TM-induced translocation of ATF6, an ERS sensor, from the cytoplasm to the nucleus. In addition, exposure of RAW264.7 macrophages to TM resulted in a significant increase of the expression of CHOP, a transcription factor regulated by ATF6 under conditions of ERS, as well as a decrease of Bcl-2 at transcript and protein levels. QUE blocked these effects in a dose-dependent manner. These data indicate that QUE can protect RAW264.7 cells from TM-induced apoptosis and that the mechanism at least partially involves its ability to inhibit the ATF6-CHOP signaling pathway.

Differential time attachment: optimization of the adherent time to obtain mouse bone marrow-derived endothelial progenitor cells / 生理学报

The different biological functions were studied in mouse bone marrow-derived endothelial progenitor cells isolated by differential time attachment to obtain the optimal adherent time in this study. Density gradient centrifugation-isolated bone marrow mononuclear cells were seeded on the fibronectin-coated dish. The 1-day cultured unattached cells were seeded on the second dish for 2 more days. Then unattached cells in the second dish were seeded on the third dish. The cells on 3 dishes were defined as 1-day adherent cells, 3-day adherent cells and 3-day unattached cells, respectively. After 20-day culture, the biological functions, such as the percentage of biomarkers, the ability of adhesion, and the ability of forming tubes in vitro were analyzed. The results showed that the percentages of positive CD34, FLK-1, and CD34/FLK-1 expressions in 1-day attached cells were significantly increased compared to those in the 3-day adherent or unattached cells (P < 0.01), which showed the strongest adhesion ability. The expression of eNOS in 1- or 3-day adherent cells was significantly higher than that in 3-day unattached cells (P < 0.01). The expression of VEGF in 3-day adherent cells was significantly higher than that in 1-day adherent cells or 3-day unattached cells (P < 0.01). These results suggest the biological functions of 1-day adherent cells are significantly stronger than that of 3-day adherent or unattached cells. VEGF expression in 3-day adherent cells is higher than that in 1-day adherent cells or 3-day unattached cells. The expression of eNOS in 1-day adherent cells or 3-day adherent cells is higher than that in 3-day unattached cells. The optimal adherent time to obtain mouse bone marrow-derived endothelial progenitor cells is 1-3 d.

Oxidized low density lipoprotein induces macrophage endoplasmic reticulum stress via CD36 / 生理学报

The purpose of the present study is to explore the effect of oxidized low density lipoprotein (ox-LDL) on the induction of endoplasmic reticulum stress (ERS) and the underlying mechanisms in ox-LDL-induced macrophage foam-forming process. RAW264.7 macrophages were cultured in DMEM medium containing 10% fetal bovine serum, and then treated with ox-LDL (25, 50 and 100 mg/L), anti-CD36 monoclonal antibody+ox-LDL and tunicamycin (TM), respectively. After incubation for 24 h, the cells were collected. The cellular lipid accumulation was showed by oil red O staining and the content of cellular total cholesterol was quantified by enzymatic colorimetry. The expression of glucose-regulated protein 94 (GRP94), a molecular marker of ERS, was determined by immunocytochemistry assay. The levels of GRP94 protein, phosphorylated inositol-requiring enzyme 1 (p-IRE1) and X box binding protein 1 (XBP1) in RAW264.7 cells were detected by Western blotting. The results indicated that after incubation with ox-LDL (25, 50 and 100 mg/L) for 24 h, a large amount of lipid droplets were found in the cytoplasm, and the contents of cellular total cholesterol were increased by 2.1, 2.8 and 3.1 folds compared with the control, respectively. Anti-CD36 antibody decreased markedly the cellular lipid accumulation induced by ox-LDL at 100 mg/L. Both ox-LDL and TM, a specific ERS inducer, could up-regulate the protein expression of GRP94 in a dose-dependent manner. Furthermore, p-IRE1 and XBP1, two key components of the unfolded protein response, were also significantly induced by the treatment with ox-LDL. The up-regulations of the three proteins induced by ox-LDL were inhibited significantly when the macrophages were pre-incubated with anti-CD36 antibody. These results suggest that ox-LDL may induce ERS in a dose-dependent way and subsequently activate the unfolded protein response signaling pathway in RAW264.7 macrophages, which is potentially mediated by scavenger receptor CD36.