Sirt6 enhances macrophage lipophagy and improves lipid metabolism disorder by regulating the Wnt1/ß-catenin pathway in atherosclerosis.

Lipid metabolism disorders are considerably involved in the pathology of atherosclerosis; nevertheless, the fundamental mechanism is still largely unclear. This research sought to examine the function of lipophagy in lipid metabolism disorder-induced atherosclerosis and its fundamental mechanisms. Previously, Sirt6 has been reported to stimulate plaque stability by promoting macrophage autophagy. However, its role in macrophage lipophagy and its relationship with Wnt1 remains to be established. In this study, ApoE-/-: Sirt6-/- and ApoE-/-: Sirt6Tg mice were used and lipid droplets were analysed via transmission electron microscopy and Bodipy 493/503 staining in vitro. Atherosclerotic plaques in ApoE-/-: Sirt6-/- mice showed greater necrotic cores and lower stability score. Reconstitution of Sirt6 in atherosclerotic mice improved lipid metabolism disorder and prevented the progression of atherosclerosis. Furthermore, macrophages with Ac-LDL intervention showed more lipid droplets and increased expression of adipophilin and PLIN2. Reconstitution of Sirt6 recruited using SNF2H suppressed Wnt1 expression and improved lipid metabolism disorder by promoting lipophagy. In addition, downregulation of Sirt6 expression in Ac-LDL-treated macrophages inhibited lipid droplet degradation and stimulated foam cell formation. Innovative discoveries in the research revealed that atherosclerosis is caused by lipid metabolism disorders due to downregulated Sirt6 expression. Thus, modulating Sirt6's function in lipid metabolism might be a useful therapeutic approach for treating atherosclerosis.

The Protective Effects of Preconditioning With Dioscin on Myocardial Ischemia/Reperfusion-Induced Ventricular Arrhythmias by Increasing Connexin 43 Expression in Rats.

Myocardial ischemia-reperfusion (IR) injury is associated with high disability and mortality worldwide. This study was to explore the roles of dioscin in the myocardial IR rats and discover the related molecular mechanisms. Rats were divided into 5 groups: sham, IR, IR + 15 mg/kg dioscin, IR + 30 mg/kg dioscin, and IR + 60 mg/kg dioscin. Heart rate (HR), mean arterial blood pressure (MAP), and rate pressure product (RPP) were evaluated at 10 minutes before ischemia, immediately after ischemia, and at the beginning, middle, and end of reperfusion. Arrhythmia score and myocardial infarct size were examined in rats of all groups. The serum creatine kinase-muscle/brain (CKMB) and cardiac troponin I (cTnI) levels were analyzed via enzyme-linked immunosorbent assay. Protein amount of total connexin 43 (T-Cx43) and phosphorylated connexin 43 (P-Cx43) was evaluated by Western blot. Ischemia reperfusion significantly decreased HR, MAP, and RPP of rats compared to the sham group. However, dioscin significantly attenuated the above phenomena in a dose-dependent manner. Dioscin markedly inhibited IR-induced increase in arrhythmias score, infarct size, and serum CKMB and cTnI levels. In addition, dioscin strikingly induced IR-repressed expression of T-Cx43 and P-Cx43. Our results suggested that dioscin pretreatment exhibited protective effects against myocardial IR injury. Moreover, we found that dioscin attenuated myocardial IR-induced ventricular arrhythmias via upregulating Cx43 expression and activation.

Astaxanthin ameliorates cardiomyocyte apoptosis after coronary microembolization by inhibiting oxidative stress via Nrf2/HO-1 pathway in rats.

Coronary microembolization (CME) caused by physical obstruction in coronary microcirculation induces myocardial apoptosis and cardiac dysfunction, and it was reported that the inactivation of the Nrf2/HO-1 signaling was involved in this process. Astaxanthin (AST) is a reddish pigment that belongs to keto-carotenoids. It is also a potent antioxidant and has been reported to activate Nrf2/HO-1 signaling in vein endothelial cells. However, it is still unknown whether AST is able to activate Nrf2/HO-1 signaling pathway to protect cardiac functions from CME in vivo. To address this question, rats were orally administrated with AST or AST plus Zinc protoporphyrin IX (ZnPP, a HO-1 inhibitor), followed by CME modeling operation. Then, cardiac function was evaluated by echocardiographic measurement. Myocardial infarction was measured by HBFP staining, and apoptosis was assessed by TUNEL staining. The protein levels and mRNA expressions of Bax and Bcl-2 were measured by Western blot and qRT-PCR, respectively. ELISA was performed to measure the activity of enzymes related to oxidative stress. AST pretreatment dramatically attenuated CME-induced cardiac dysfunction, myocardial infarction, and cardiomyocyte apoptosis. Mechanistically, AST suppressed CME-induced oxidative stress by re-activating Nrf2/HO-1 signaling. HO-1 inhibitor ZnPP completely eliminated the benefits of AST in CEM, supporting the critical role of Nrf2/HO-1 signaling in mediating the cardioprotective function of AST in CME. Conclusion: AST suppresses oxidative stress via activating Nrf2/HO-1 pathway and thus prevents CME-induced cardiomyocyte apoptosis and ameliorates cardiac dysfunction in rats.

Helix B surface peptide attenuates diabetic cardiomyopathy via AMPK-dependent autophagy.

BACKGROUND: Erythropoietin (EPO) has been reported to exert protective effects on a host of damaged tissues. However, the erythropoietic effect of this hormone can result in high risks of thrombosis, stroke, and hypertension, remarkably limiting the clinical use of EPO. Helix B surface peptide (HBSP) is a small peptide derived from the helix-B domain of EPO. Surprisingly, HBSP retains the tissue protective properties of EPO without altering the hematocrit. Thus, we evaluated the possible role of HBSP on diabetic cardiomyopathy. METHODS: Diabetes was induced in mice by intraperitoneal injections of streptozocin (STZ). Mice were randomly treated with normal saline or HBSP. Cardiac function, fibrosis, apoptosis, and myocardial mitochondrial morphology were examined. For in vitro experiments, H9C2 myoblast cells were randomly grouped as normal glucose (NG, 5 mM), NG+HBSP (100 nM), high glucose (HG, 33 mM), HG+HBSP (100 nM), HG+HBSP+3-methyladenine (3-MA, 10 mM), HG+rapamycin (Rapa, 100 nM), and HG+HBSP+Compound C (CC, 10 mM). Autophagosomes, LC3 dots, apoptosis and mitochondria membrane potential (MMP) of H9C2 cells were examined.The expressions of LC3, p62, p-AMPK (Thr172) and p-mTOR (Ser2448) were examined by Western blot. RESULTS: HBSP markedly improved cardiac function, attenuated cardiac interstitial fibrosis, inhibited myocardial apoptosis, and ameliorated mitochondrial ultrastructure in mice with diabetic cardiomyopathy. HG reduced autophagy in H9C2 cells. HBSP enhanced autophagy in HG-treated H9C2 cells. HBSP reduced the apoptosis index of HG-treated H9C2 cells. HBSP increased the MMP of HG-treated H9C2 cells. HBSP increased the levels of p-AMPK (Thr172), and reduced p-mTOR (Ser2448) in HG-treated H9C2 cells, and the increase of p-AMPK (Thr172) was accompanied by the stimulation of autophagy. Autophagy inhibitor 3-MA and AMPK inhibitor CC mitigated HBSP-induced beneficial effect, whereas autophagy inducer Rapa alleviated the HG-induced cell apoptosis. CONCLUSIONS: HBSP attenuates diabetic cardiomyopathy via autophagy mediated by AMPK-dependent pathway. HBSP may be a potential therapeutic intervention for diabetic cardiomyopathy.

Notch3 Ameliorates Cardiac Fibrosis After Myocardial Infarction by Inhibiting the TGF-ß1/Smad3 Pathway.

Notch3 and TGF-ß1 signaling play a key role in the pathogenesis and progression of chronic cardiovascular disease. However, whether Notch3 protects against myocardial infarction (MI) and the underlying mechanisms remains unknown. C57BL/6 mice were randomized to be treated with Notch3 siRNA (siNotch3) or lentivirus carrying Notch3 cDNA (Notch3) before coronary artery ligation. Four weeks after constructing MI model, cardiac function and fibrosis were compared between groups. The cardiac fibroblast cells (CFs) were isolated from newborn C57BL/6 mice (1-3 days old) and transfected with lentivirus carrying Notch3 cDNA. TGF-ß1 (5 ng/ml), a well-known pro-fibrotic factor, was administered 72 h after Notch3 cDNA administration in CFs. The related proteins of fibrosis such as a-smooth muscle actin (a-SMA), Type I collagen, metalloprotease (MMP)-9 and the tissue inhibitor of metalloproteinases (TIMP)-2 were examined by western blot analysis. Notch3 cDNA treatment attenuated cardiac damage and inhibited fibrosis in mice with MI. Meanwhile, Notch3 siRNA administration aggravated cardiac function damage and markedly enhanced cardiac fibrosis in mice with MI. Overexpression of Notch3 inhibited TGF-ß1-induced fibroblast-myofibroblast transition of mouse cardiac fibroblast cells, as evidenced by down-regulating a-SMA and Type I collagen expression. Notch3 cDNA treatment also increased MMP-9 expression and decreased TIMP-2 expression in the TGF-ß1-stimulated cells. This study indicates that Notch3 is an important protective factor for cardiac fibrosis in a MI model, and the protective effect of Notch3 is attributable to its action on TGF-ß1/Smad3 signaling.