Guangzhong Liu

Ketamine-induced ventricular structural, sympathetic and electrophysiological remodelling: pathological consequences and protective effects of metoprolol

BACKGROUND AND PURPOSE Growing evidence suggests that long‐term abuse of ketamine does harm the heart and increases the risk of sudden death. The present study was performed to explore the cardiotoxicity of ketamine and the protective effects of metoprolol.

Hydrogen sulfide reduces serum triglyceride by activating liver autophagy via the AMPK-mTOR pathway

Autophagy plays an important role in liver triglyceride (TG) metabolism. Inhibition of autophagy could reduce the clearance of TG in the liver. Hydrogen sulfide (H2S) is a potent stimulator of autophagic flux. Recent studies showed H2S is protective against hypertriglyceridemia (HTG) and noalcoholic fatty liver disease (NAFLD), while the mechanism remains to be explored. Here, we tested the hypothesis that H2S reduces serum TG level and ameliorates NAFLD by stimulating liver autophagic flux by the AMPK-mTOR pathway. The level of serum H2S in patients with HTG was lower than that of control subjects. Sodium hydrosulfide (NaHS, H2S donor) markedly reduced serum TG levels of male C57BL/6 mice fed a high-fat diet (HFD), which was abolished by coadministration of chloroquine (CQ), an inhibitor of autophagic flux. In HFD mice, administration of NaSH increased the LC3BII-to-LC3BI ratio and decreased the p62 protein level. Meanwhile, NaSH increased the phosphorylation of AMPK and thus reduced the phosphorylation of mTOR in a Western blot study. In cultured LO2 cells, high-fat treatment reduced the ratio of LC3BII to LC3BI and the phosphorylation of AMPK, which were reversed by the coadministration of NaSH. Knockdown of AMPK by siRNA in LO2 cells blocked the autophagic enhancing effects of NaSH. The same qualitative effect was observed in AMPKα2(-/-) mice. These results for the first time demonstrated that H2S could reduce serum TG level and ameliorate NAFLD by activating liver autophagy via the AMPK-mTOR pathway.

Fenofibrate inhibits atrial metabolic remodelling in atrial fibrillation through PPAR-α/sirtuin 1/PGC-1α pathway

Atrial metabolic remodelling is critical for the process of atrial fibrillation (AF). The PPAR‐α/sirtuin 1 /PPAR co‐activator α (PGC‐1α) pathway plays an important role in maintaining energy metabolism. However, the effect of the PPAR‐α agonist fenofibrate on AF is unclear. Therefore, the aim of this study was to determine the effect of fenofibrate on atrial metabolic remodelling in AF and explore its possible mechanisms of action.

Upregulation of β3-adrenergic receptors contributes to atrial structural remodeling in rapid pacing induced atrial fibrillation canines.

Accumulating evidence suggests that the adrenergic receptors (ARs) play an important role in cardiac diseases. The expression of β3-AR has been recently demonstrated in atria, however, its role in atrial structural remodeling of atrial fibrillation (AF) is unclear. Therefore, the present study was designed to investigate the role of β3-AR in atrial structural remodeling in AF and to clarify its possible mechanisms. Twenty-eight dogs were randomly divided into sham, pacing, β3-AR agonist (BRL37344) and β3-AR antagonist (L748337) groups. AF was induced by rapid atrial pacing at 600 beats per minute for 3 weeks and evaluated by determining the ultrastructure and function of atria. The expression of β3-AR and p38 mitogen-activated protein kinase (MAPK) was examined by western blot, immunohistochemistry and real-time RT-PCR. Additionally, the extent of oxidative stress was tested. We found the atrial enlargement and dysfunction in pacing group. Moreover, atrial interstitial fibrosis, apoptosis and oxidative stress were increased and the levels of β3-AR and phosphorylated p38 MAPK were increased after pacing. Activation of β3-AR exacerbated the pathologic changes and oxidative stress, which were effectively inhibited by L748337. We concluded that β3-AR was upregulated in paced atria, which contributed to oxidative stress and exacerbated atrial structural remodeling by regulating p38 MAPK. Our study provides novel insights into the pharmacological role of β3-AR in AF.

(–)-Epicatechin Suppresses Angiotensin II-induced Cardiac Hypertrophy via the Activation of the SP1/SIRT1 Signaling Pathway

Background/Aims: Flavonol (–)-epicatechin (EPI) is present in high amounts in cocoa and tea products, and has been shown to exert beneficial effects on the cardiovascular system. However, the precise mechanism of EPI on cardiomyocyte hypertrophy has not yet been determined. In this study, we examined whether EPI could inhibit cardiac hypertrophy. Methods: We utilised cultured neonatal mouse cardiomyocytes and mice for immunofluorescence, immunochemistry, qRT-PCR, and western blot analyses. Results: 1µM EPI significantly inhibited 1µM angiotensin II (Ang II)-induced increase of cardiomyocyte size, as well as the mRNA and protein levels of ANP, BNP and β-MHC in vitro. The effects of EPI were accompanied with an up-regulation of SP1 and SIRT1, and were abolished by SP1 inhibition. Up-regulation of SP1 could block Ang II-induced increase in cardiomyocyte size, as well as the mRNA and protein levels of ANP, BNP and β-MHC, and increase the protein levels of SIRT1 in vitro. Moreover, 1 mg/kg body weight/day EPI significantly inhibited mouse cardiac hypertrophy induced by Ang II, which could be eliminated by SP1 inhibition in vivo. Conclusion: Our data indicated that EPI inhibited AngII-induced cardiac hypertrophy by activating the SP1/SIRT1 signaling pathway.

β3-Adrenoceptor Impairs Mitochondrial Biogenesis and Energy Metabolism During Rapid Atrial Pacing-Induced Atrial Fibrillation

Background: The β3-adrenoceptor (β3-AR) is implicated in cardiac remodeling. Since metabolic dysfunction due to loss of mitochondria plays an important role in heart diseases, we examined the effects of β3-AR on mitochondrial biogenesis and energy metabolism in atrial fibrillation (AF). Methods: Atrial fibrillation was created by rapid atrial pacing in adult rabbits. Rabbits were randomly divided into 4 groups: control, pacing (P7), β3-AR antagonist (L748337), and β3-AR agonist (BRL37344) groups. Atrial effective refractory period (AERP) and AF induction rate were measured. Atrial concentrations of adenine nucleotides and phosphocreatine were quantified through high-performance liquid chromatography. Mitochondrial DNA content was determined. Real-time polymerase chain reaction and Western blot were used to examine the expression levels of signaling intermediates related to mitochondrial biogenesis. Results: After pacing for 7 days, β3-AR was significantly upregulated, AERP was reduced, and the AF induction rate was increased. The total adenine nucleotides pool was significantly reduced due to the decrease in adenosine triphosphate (ATP). The P7 group showed decreased activity of F0F1-ATPase. Mitochondrial DNA content was decreased and mitochondrial respiratory chain subunits were downregulated after pacing. Furthermore, expression of transcription factors involved in mitochondrial biogenesis, including peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), nuclear respiratory factor 1 (NRF-1), and mitochondrial transcription factor A (Tfam), was lower in the P7 group in response to β3-AR activation. Further stimulation of β3-AR with BRL37344 exacerbated these effects, together with a significant decrease in the levels of phosphocreatine. In contrast, inhibition of β3-AR with L748337 partially restored mitochondrial biogenesis and energy metabolism of atria in the paced rabbits. Conclusion: The activation of β3-AR contributes to atrial metabolic remodeling via transcriptional downregulation of PGC-1α/NRF-1/Tfam pathway that are involved in mitochondrial biogenesis, which ultimately perturbs mitochondrial function in rapid pacing-induced AF. The β3-AR is therefore a potential novel therapeutic target for the treatment or prevention of AF.

Chronic obstructive sleep apnea promotes aortic remodeling in canines through miR-145/Smad3 signaling pathway

Obstructive sleep apnea (OSA) is a causal pathogenetic factor of many cardiovascular diseases, however, its role in aortic diseases remains unknown. Therefore, this study was performed to explore the potential effects and pathophysiological mechanisms of chronic OSA on aortic remodeling in a canine model. After chronic OSA, the morphological changes of ascending aorta were characterized by thinner cells with pycnotic nuclei and swollen mitochondria, and obvious hyperplasia of collagenous fiber in the matrix. Both the apoptotic ratio and collagen volume fraction were significantly increased in ascending aorta of chronic OSA canines. Besides, aortic sympathetic nerve sprouting increased significantly in chronic OSA group. Meanwhile, protein expression of TGF-β1, Smad3, collagenI, apoptosis-inducing factor (AIF), tyrosine hydroxylase (TH) and growth associated protein-43 (GAP43) was upregulated after chronic OSA. Additionally, chronic OSA also strikingly increased pro-inflammatory factors like tumor necrosis factor α (TNF-α), NOD-like receptor 3 (NLRP3), NF-κB-p65 and oxidative stress factors like xanthine oxidase (XOD), malondialdehyde (MDA) while declined superoxide dismutase (SOD) activity. Furthermore, suppressed miR-145 and subsequently increased Smad3 expression were found obviously in vascular smooth muscle cells (VSMCs) treated by hypoxia. Luciferase reporter assays confirmed that Smad3 was one of the targets of miR-145. In conclusion, OSA could exacerbate aortic remodeling by aortic fibrosis, apoptosis and sympathetic nerve sprouting. miR-145/Smad3 signaling pathway might promote aortic remodeling during OSA. These findings provide novel information of chronic OSA-induced vascular dysfunction.

The β3 Adrenergic Receptor Agonist BRL37344 Exacerbates Atrial Structural Remodeling Through iNOS Uncoupling in Canine Models of Atrial Fibrillation

Background/Aims: The role of the β3-adrenergic receptor (β3-AR) agonist BRL37344 in atrial fibrillation (AF) structural remodeling and the underlying mechanisms as a therapeutic target were investigated. Methods: Four groups of dogs were evaluated: sham, pacing, β3-AR agonist BRL37344 (β3-AGO), and β3-AR antagonist L748337 (β3-ANT) groups. Dogs in the pacing, β3-AGO and β3-ANT groups were subjected to rapid atrial pacing for four weeks. Atrial structure and function, AF inducibility and duration, atrial myocyte apoptosis and interstitial fibrosis were assessed. Atrial superoxide anions were evaluated by fluorescence microscopy and colorimetric assays. Cardiac nitrate+nitrite levels were used to assess nitric oxide (NO) production. Protein and mRNA expression of β3-AR, neuronal NO synthase (nNOS), inducible NO synthase (iNOS), endothelial NO synthase (eNOS) and guanosine triphosphate cyclohydrolase-1 (GCH-1) as well as tetrahydrobiopterin (BH4) levels were measured. Results: β3-AR was up-regulated in AF. Stimulation of β3-AR significantly increased atrial myocyte apoptosis, fibrosis and atrial dilatation, resulting in increased AF induction and prolonged duration. These effects were attenuated by β3-ANT. Moreover, β3-AGO reduced BH4 and NO production and increased superoxide production, which was inhibited by the specific iNOS inhibitor, 1400w β3-AGO also increased iNOS but decreased eNOS and had no effect on nNOS expression in AF. Conclusions: β3-AR stimulation resulted in atrial structural remodeling by increasing iNOS uncoupling and related oxidative stress. β3-AR up-regulation and iNOS uncoupling might be underlying AF therapeutic targets.

Effects of different doses of ticagrelor on platelet aggregation and endothelial function in diabetic patients with stable coronary artery disease

Abstract We performed this study to observe the effects of different doses of ticagrelor and standard-dose clopidogrel on platelet reactivity and endothelial function in diabetic patients with stable coronary artery disease (CAD). Sixty type 2 diabetic patients were assigned to one-quarter standard-dose ticagrelor, half standard-dose ticagrelor, standard-dose ticagrelor and standard-dose clopidogrel groups. Light transmission aggregometry (LTA) and VerifyNow assay were used to measure platelet function. Endothelial function was assessed by measurement of flow-mediated vasodilation (FMD) and plasma von Willebrand factor (VWF) levels were detected. Enzyme-linked immunosorbent assay (ELISA) examined the Interleukin-8(IL-8) and IL-10. The results suggested that the one-quarter dose (34.0%± 14.7%), half-dose (26.9%± 11.6%) and standard-dose (17.3%± 10.3%) ticagrelor showed lower platelet aggregation rate than clopidogrel (52.8%± 18.3%; P ＜0.0001). PRU values in three ticagrelor groups were lower than that in clopidogrel group (102 (76–184)；75 (33–88)；38 (11–52) versus 194 (138–271) and；P ＜0.0001). FMD levels were higher in ticagrelor groups compared with baseline levels while lower in clopidogrel group after treatment. However, no significant differences were found in the percentage increase in the FMD between ticagrelor groups and clopidogrel group. The levels of VWF after treatment were lower than the baseline levels, but there was no statistically significant difference between ticagrelor group and clopidogrel group after treatment. The concentration of IL-8 and IL-10 were decreased in patients with half and standard-dose ticagrelor group. In conclusion, one-quarter standard-dose ticagrelor produced similar inhibitory effects on platelet aggregation as standard-dose clopidogrel in diabetic patients with stable CAD. The half standard-dose ticagrelor had a similar inhibitory effect on platelet inhibition as standard-dose ticagrelor, which was stronger than that of clopidogrel. Moreover, the half-dose ticagrelor had equal protection of endothelial function and inhibition of inflammatory factor as standard-dose ticagrelor.

A calpain inhibitor elevated expressions of NF-κB in atrial fibrillation canine atria

This aim of this study is to observe the alterations of calpain proteolytic system and effect of a calpain I inhibitor on NF-κB expressions in rapid pacing canine atrial fibrillation (AF) models. Twenty-one dogs were divided equally into three groups: a sham operation group, a control AF group and a calpain inhibitor group. Rapid right atrium pacing at 600 beats per min was applied in the control AF group and the calpain inhibitor group. N-Acetyl-Leu-Leu-Met (1.0 mg/kg/day) was administered in the calpain inhibitor group for three weeks. The protein expressions of NF-κB, calpain I, calpain II and calpastatin were assessed by immunohistochemistry and gene amplification of NF-κB and calpain I were detected by quantitative real time polymerase chain reaction. The highest density of calpain I was shown in the control AF group (p < 0.01, vs. calpain inhibitor group and sham operation group). Protein expression of calpain II and calpastatin had no significant difference among the three groups. Gene amplification results of calpain I unveiled the most active transcription was in the calpain inhibitor group (p < 0.01, vs. control AF group and sham operation group). The mRNA expression of NFκB were elevated in the calpain inhibitor group, the cycle of threshold means were (20.1±5.1), while were (33.4±6.1) and (30.4±5.8) in the sham operation group and control AF group, respectively. NF-κB protein expressions in calpain inhibitor group were positive, while were negative in the other two groups. In canine heart muscle cells, atrial fibrillation elevated calpain I gene transcription, promoted protein expression and enhanced protease activity. The calpain I inhibitor N-Acetyl-Leu-Leu-Met promoted NF-κB gene transcription and protein expressions in AF canine models.