Dingyu Wang

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.

Metoprolol Inhibits Cardiac Apoptosis and Fibrosis in a Canine Model of Chronic Obstructive Sleep Apnea

Aims: Emerging evidence suggested that obstructive sleep apnea (OSA) was independently associated with the development of heart failure. In this study, we explored the influence of chronic OSA on left ventricular structural remodeling in canines, and the potential therapeutical role of metoprolol. Methods: Chronic OSA model was established by stopping the ventilator and closing the airway for 4 h/day apnea-ventilation cycles every other day for 12 weeks while metoprolol (5 mg· kg-1· day-1) were administered continuously. Norepinephrine concentration was measured by Enzyme Linked Immunosorbent Assay. Transmission electron microscopy, Hematoxylin and eosin, TUNEL and Masson trichrome staining were employed to detect the morphology, apoptosis and fibrosis of cardiomyocytes. Protein expression of apoptosis and fibrosis-related factors including apoptosis-inducing factor (AIF), caspase 3, Bcl-2, Bax, α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), and p38 mitogen-activated protein kinase (MAPK) were examined by Western blotting. Results: Norepinephrine concentration was markedly increased in chronic OSA dogs and reduced by metoprolol. Both the apoptotic ratio and collagen volume fraction were significantly increased in left ventricular myocytes of chronic OSA dogs, and was reversed by metoprolol. Moreover, chronic OSA-induced upregulation of AIF, cleaved caspase 3, Bax, α-SMA, and TGF-β1 as well as downregulation of Bcl-2 was markedly recovered by metoprolol, which was mediated by p38 MAPK. Conclusion: Metoprolol protects against chronic OSA-induced cardiac apoptosis and fibrosis in left ventricular myocytes of canines, which may provide new potential strategy for drug therapy of OSA.

Valsartan Reduced Atrial Fibrillation Susceptibility by Inhibiting Atrial Parasympathetic Remodeling through MAPKs/Neurturin Pathway.

Background/Aims: Angiotensin II receptor blockers (ARBs) have been proved to be effective in preventing atrial structural and electrical remodelinq in atrial fibrillation (AF). Previous studies have shown that parasympathetic remodeling plays an important role in AF. However, the effects of ARBs on atrial parasympathetic remodeling in AF and the underlying mechanisms are still unknown. Methods: Canines were divided into sham-operated, pacing and valsartan + pacing groups. Rats and HL-1 cardiomyocytes were divided into control, angiotensin II (Ang II) and Ang II + valsartan groups, respectively. Atrial parasympathetic remodeling was quantified by immunocytochemical staining with anti-choline acetyltransferase (ChAT) antibody. Western blot was used to analysis the protein expression of neurturin. Results: Both inducibility and duration were increased in chronic atrial rapid-pacing canine model, which was significantly inhibited by the treatment with valsartan. The density of ChAT-positive nerves and the protein level of neurturin in the atria of pacing canines were both increased than those in sham-operated canines. Ang II treatment not only induced atrial parasympathetic remodeling in rats, but also up-regulated the protein expression of neurturin. Valsartan significantly prevented atrial parasympathetic remodeling, and suppressed the protein expression of neurturin. Meanwhile, valsartan inhibited Ang II -induced up-regulation of neurturin and MAPKs in cultured cardiac myocytes. Inhibition of MAPKs dramatically attenuated neurturin up-regulation induced by Ang II. Conclusion: Parasympathetic remodeling was present in animals subjected to rapid pacing or Ang II infusion, which was mediated by MAPKs/neurturin pathway. Valsartan is able to prevent atrial parasympathetic remodeling and the occurrence of AF via inhibiting MAPKs/neurturin pathway.

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.

Chronic obstructive sleep apnea accelerates pulmonary remodeling via TGF-β/miR-185/CoLA1 signaling in a canine model

Chronic obstructive sleep apnea syndrome (OSAS) is considered to be associated with pulmonary diseases. However, the roles and mechanisms of OSA in pulmonary remodeling remain ambiguous. Thus, this study was aimed to elucidate the morphological and mechanical action of OSA in lung remodeling. In the present study, we employed a novel OSA model to mimic the OSA patient and investigate the role of OSA in pulmonary remodeling. We showed that pulmonary artery pressure of OSA group has no significant increased compared with the sham group. Nevertheless, we found that fibrotic tissue was predominantly located around the bronchi and vascular in the lung. Additionally, inflammatory cell infiltration was also detected in the peribonchial and perivascular space. The morphological change in OSA canines was ascertained by ultrastructure variation characterized by mitochondrial swelling, lamellar bodies degeneration and vascular smooth muscle incrassation. Moreover, sympathetic nerve sprouting was markedly increased in OSA group. Mechanistically, we showed that several pivotal proteins including collagen type I(CoLA1), GAP-43, TH and NGF were highly expressed in OSA groups. Furthermore, we found OSA could activated the expression of TGF-β, which subsequently suppressed miR-185 and promoted CoL A1 expression. This signaling cascade leads to pulmonary remodeling. In conclusion, Our data demonstrates that OSA can accelerate the progression of pulmonary remodeling through TGF-β/miR-185/CoLA1 signaling, which would potentially provide therapeutic strategies for chronic OSAS.

Autophagy exacerbates electrical remodeling in atrial fibrillation by ubiquitin-dependent degradation of L-type calcium channel

Autophagy, a bidirectional degradative process extensively occurring in eukaryotes, has been revealed as a potential therapeutic target for several cardiovascular diseases. However, its role in atrial fibrillation (AF) remains largely unknown. This study aimed to determine the role of autophagy in atrial electrical remodeling under AF condition. Here, we reported that autophagic flux was markedly activated in atria of persistent AF patients and rabbit model of atrial rapid pacing (RAP). We also observed that the key autophagy-related gene7 (ATG7) significantly upregulated in AF patients as well as tachypacing rabbits. Moreover, lentivirus-mediated ATG7 knockdown and overexpression in rabbits were employed to clarify the effects of autophagy on atrial electrophysiology via intracardiac operation and patch-clamp experiments. Lentivirus-mediated ATG7 knockdown or autophagy inhibitor chloroquine (CQ) restored the shortened atrial effective refractory period (AERP) and alleviated the AF vulnerability caused by tachypacing in rabbits. Conversely, ATG7 overexpression significantly promoted the incidence and persistence of AF and decreased L-type calcium channel (Cav1.2 α-subunits), along with abbreviated action potential duration (APD) and diminished L-type calcium current (ICa,L). Furthermore, the co-localization and interaction of Cav1.2 with LC3B-positive autophagosomes enhanced when autophagy was activated in atrial myocytes. Tachypacing-induced autophagic degradation of Cav1.2 required ubiquitin signal through the recruitment of ubiquitin-binding proteins RFP2 and p62, which guided Cav1.2 to autophagosomes. These findings suggest that autophagy induces atrial electrical remodeling via ubiquitin-dependent selective degradation of Cav1.2 and provide a novel and promising strategy for preventing AF development.

Presence of Severe Stenosis in Most Culprit Lesions of Patients with ST-segment Elevation Myocardial Infarction

Background: Previous studies revealed that culprit vessels of ST-segment elevation myocardial infarction (STEMI) were often related to mild or moderate stenosis. However, recent studies suggested that severe stenosis was primarily found in culprit lesions. The objective of this study was to analyze the stenosis severity of culprit lesions in STEMI patients and to clarify the paradoxical results. Methods: A total of 489 consecutive STEMI patients who underwent primary percutaneous coronary intervention were retrospectively studied from January 2012 to December 2014. The patients were divided into three groups based on stenosis severity using quantitative coronary analysis: Group A, 314 cases, stenosis ≥70%; Group B, 127 cases, stenosis 50–70%; and Group C, 48 cases, stenosis ⩽50%. The clinical, demographic, and angiographic data of all groups were analyzed. Results: Patients in Group A exhibited a significantly higher prevalence of history of angina pectoris (95.9% vs. 62.5%, P < 0.001), multivessel disease (73.2% vs. 54.2%, P = 0.007), and lower cardiac ejection fraction (53.3 ± 8.6 vs. 56.8 ± 8.4, P = 0.009) than those in Group C. Multivariable analysis revealed that history of angina pectoris (odds ratio [OR]: 13.89, 95% confidence interval [CI]: 6.21–31.11) and multivessel disease (OR: 2.32, 95% CI: 1.25–4.31) were correlated with severe stenosis of the culprit lesion in Group A. Conclusions: Most culprit lesions in STEMI patients were severe stenosis. These patients exhibited a higher prevalence of angina history and multivessel diseases.