Progressive Reduction in Myocyte Autophagy After Myocardial Infarction in Rabbits: Association with Oxidative Stress and Left Ventricular Remodeling.

BACKGROUND/AIMS: The alterations in myocyte autophagy after myocardial infarction (MI) and the underlying mechanisms have not been fully understood. In this study, we investigated the temporal changes of myocyte autophagy in the remote non-infarcted myocardium in rabbits after MI and the relationships between alterations of myocyte autophagy and left ventricular (LV) remodeling and myocardial oxidative stress. METHODS: Rabbits were assigned to MI or sham operation. Rabbits with MI or sham were randomly assigned to receive chloroquine, an autophagy inhibitor, antioxidant vitamins C and E or placebo for 4 weeks. H9C2 cardiomyocytes were subjected to hypoxia or hydrogen peroxide (H2O2) treatment. RESULTS: MI rabbits exhibited progressive increases of LV end-diastolic dimension (EDD), and decreases of LV fractional shortening (FS) and dP/dt over 8 weeks. Myocyte autophagy assessed by the scores of LC3 and Beclin1 expression was progressively decreased at 1, 4 and 8 weeks after MI. The ratio of LC3 II/I and Beclin1 and Atg5 proteins were also decreased at 4 weeks after MI. There was a negative correlation between autophagy and LV EDD and a positive correlation between autophagy and LV FS and dP/dt. The autophagy inhibitor chloroquine worsened LV remodeling after MI. Decreased myocyte autophagy was associated with increased myocardial 4-hydroxynonenal. Antioxidant vitamins C and E prevented the decrease in myocyte autophagy after MI. In cultured H9C2 cardiomyocytes, the LC3 II/I ratio was decreased at 4 and 8 h after exposure to hypoxia, and the change was associated with increased 8-hydroxy-2-deoxyguanosine. A low concentration of H2O2 decreased the LC3 II/I ratio. CONCLUSION: Progressive reduction in myocyte autophagy in the remote non-infarcted myocardium was associated with myocardial oxidative stress and LV remodeling after MI. Antioxidants prevented the reduction in myocyte autophagy after MI, suggesting that oxidative stress mediates reduction in myocyte autophagy that contributes to post-MI remodeling.

Activation of NADPH oxidase mediates increased endoplasmic reticulum stress and left ventricular remodeling after myocardial infarction in rabbits.

Nicotinamide adenine dinucleotide 3-phosphate (NADPH) oxidase activity and endoplasmic reticulum (ER) stress are increased after myocardial infarction (MI). In this study, we proposed to test whether activation of the NADPH oxidase in the remote non-infarcted myocardium mediates ER stress and left ventricular (LV) remodeling after MI. Rabbits with MI or sham operation were randomly assigned to orally receive an NADPH oxidase inhibitor apocynin or placebo for 30 days. The agents were administered beginning at 1 week after surgery. MI rabbits exhibited decreases in LV fractional shortening, LV ejection fraction and the first derivative of the LV pressure rise, which were abolished by apocynin treatment. NADPH oxidase Nox2 protein and mRNA expressions were increased in the remote non-infarcted myocardium after MI. Immunolabeling further revealed that Nox2 was increased in cardiac myocytes in the remote myocardium. The apocynin treatment prevented increases in the Nox2 expression, NADPH oxidase activity, oxidative stress, myocyte apoptosis and GRP78, CHOP and cleaved caspase 12 protein expression in the remote myocardium. The apocynin treatment also attenuated increases in myocyte diameter and cardiac fibrosis. In cultured H9C2 cardiomyocytes exposed to angiotensin II, an important stimulus for post-MI remodeling, Nox2 knockdown with siRNA significantly inhibited angiotensin II-induced NADPH oxidase activation, reactive oxygen species and GRP78 and CHOP protein expression. We conclude that NADPH oxidase inhibition attenuates increased ER stress in the remote non-infarcted myocardium and LV remodeling late after MI in rabbits. These findings suggest that the activation of NADPH oxidase in the remote non-infarcted myocardium mediates increased ER stress, contributing to myocyte apoptosis and LV remodeling after MI.

[Levels of autoantibodies against AT1-receptor in hypertensive patients with acute coronary syndromes and its role in coronary artery vasoconstriction].

OBJECTIVE: To explore the levels of autoantibodies against AT1-receptor (AT1-AA) in hypertensive patients with acute coronary syndrome (ACS) and observe the in vitro effects of AT1-AA on resting tension of isolated anterior descending artery of vascular ring in male Wistar rats. METHODS: All patients were recruited from June 2007 to August 2008. There were hypertensive patients with ACS (n = 120), those with simple hypertension (n = 253) and those with simple ACS (n = 115). And the outpatients for health examination during the same period were selected as healthy control group (n = 188). The second extracellular loop amino acid sequences of peptides of ATI receptor was synthesized and used as antigen (AT1-Ag) and sialic acid-enzyme-linked immunosorbent assay (SA-ELISA) for detect the serum levels of AT1-AA. Microvascular ring tension technology was used to test the vascular loop resting tension of anterior descending coronary artery from rats induced by a high-fat diet. RESULTS: The positive rates of AT1-AA in patients with simple hypertension (35.2%) and those with simple ACS (30.4%) were significantly higher than those in healthy control group (7.2%, P < 0.01). And the positive rate of AT1-AA in hypertensive patients with ACS (43.3%) was significantly higher than that in those with simple hypertension (35.2%, P < 0.05) and that in healthy control group (7.2%, P < 0.05).Furthermore, AT1-AA increased the vascular loop resting tension of anterior descending coronary artery rings in rats induced by a high-fat diet in a dose-dependant manner. And the vasoconstrictive action of AT1-AA was equal to 46.4% of AngII's action. And such an action was blocked by losartan and antigens. CONCLUSION: The level of AT1-AA increases markedly in hypertensive patients with ACS. And AT1-AA induces vasoconstrictive effects on anterior descending artery rings in rats induced by a high-fat diet.

[Cardiac protective effect of the autoantibody against ß3-adrenoceptor in rats with experimental heart failure].

OBJECTIVE: To explore the effect of the autoantibody against the ß3-adrenoceptor on rats with experimental heart failure. METHOD: The peptide corresponding to the sequence of ß3 adrenoceptor was synthesized to actively immunize the rats, ELISA was used to detect the serum level of autoantibody against the ß3-adrenoceptor (ß3AA). Total IgGs were extracted from the serum containing ß3AA in immunized rats. Aortic banding surgery was used to establish the heart failure model in male Wistar rats and rats were divided into the sham group (n = 8), heart failure group(n = 8),ß3AA-immunized heart failure group (HF+ß3AA, n = 8) and corresponding negative IgG-immunized heart failure group (HF+ IgG, n = 8).In 6 weeks and 8 weeks after aortic banding surgery, the serum levels of NT-pro brain natriuretic peptide (NT-proBNP) were assayed with ELISA assay and cardiac function was assessed by echocardiography. RESULTS: ß3AA was used to immunize rat with heart failure, the serum level of ß3AA was stable at 50 days post immunization. At 8 weeks after aortic banding surgery, heart failure group showed significantly increased LVEDD [(6.92 ± 0.22) mm vs.(5.62 ± 0.19) mm, P < 0.001], LVESD [(4.63 ± 0.23) mm vs.(3.50 ± 0.20) mm, P < 0.01] and IVS [(2.44 ± 0.06) mm vs.(2.28 ± 0.05) mm, P < 0.05], and decreased LVEF[(62.07 ± 3.99)% vs.(79.63 ± 3.02)%, P < 0.01] and LVFS [(31.46 ± 3.22)% vs.(43.65 ± 2.68) %, P < 0.05] compared with the sham group.HF+ß3AA IgG group showed decreased LVEDD [(6.07 ± 0.30) mm vs.(6.92 ± 0.24) mm, P < 0.05] and LVESD [(3.92 ± 0.22) mm vs.(4.68 ± 0.23) mm, P < 0.05], and higher LVEF [(70.29 ± 1.78)% vs.(61.95 ± 3.03)%, P < 0.05] and LVFS [(38.08 ± 2.32)% vs.(30.50 ± 1.82)%, P < 0.05] compared to the HF+ IgG group.In addition, compared with the HF+ IgG group, HF+ß3AA IgG group showed decreased serum levels of NT-proBNP [(196.43 ± 6.56) pg/ml vs.(242.13 ± 7.86) pg/ml, P < 0.01]. CONCLUSION: Our results demonstrate that ß3AA can improve cardiac function and reduce the serum levels of NT-proBNP in rat with heart failure.

A novel LMNA indel mutation identified in a family with atrioventricular block and atrial fibrillation.

ABSTRACT: It is well known that many genetic factors are involved in the occurrence and progression of atrioventricular block (AV block) and atrial fibrillation (AF). However, the genetic variants discovered so far have only explained parts of these processes. More genes and variants remain to be identified. In the present study, a three-generation family with an autosomal dominant form of AV block and AF was enrolled. Whole exome sequencing was conducted in three affected and one unaffected family member. A total of 64 nonsynonymous variants was shared by three affected individuals and not present in the unaffected individual. By selection of variants absent in the known databases and were predicted to be deleterious, 4 novel variants were identified. Only one novel frameshift insertion in the LMNA gene (c.825_826insCAGG) was identified in another affected family member and not detected in other non-affected family members and the 100 controls. Our finding expanded the spectrum of variants associated with AV block and AF, and was valuable in the genetic diagnosis of AV block and AF.

Lysophosphatidic Acid Is Associated With Cardiac Dysfunction and Hypertrophy by Suppressing Autophagy via the LPA3/AKT/mTOR Pathway.

Background: Lysophosphatidic acid (LPA), as a phospholipid signal molecule, participates in the regulation of various biological functions. Our previous study demonstrated that LPA induces cardiomyocyte hypertrophy in vitro; however, the functional role of LPA in the post-infarct heart remains unknown. Growing evidence has demonstrated that autophagy is involved in regulation of cardiac hypertrophy. The aim of the current work was to investigate the effects of LPA on cardiac function and hypertrophy during myocardial infarction (MI) and determine the regulatory role of autophagy in LPA-induced cardiomyocyte hypertrophy. Methods: In vivo experiments were conducted in Sprague-Dawley rats subjected to MI surgery or a sham operation, and rats with MI were assigned to receive an intraperitoneal injection of LPA (1 mg/kg) or vehicle for 5 weeks. The in vitro experiments were conducted in H9C2 cardiomyoblasts. Results: LPA treatment aggravated cardiac dysfunction, increased cardiac hypertrophy, and reduced autophagy after MI in vivo. LPA suppressed autophagy activation, as indicated by a decreased LC3II-to-LC3I ratio, increased p62 expression, and reduced autophagosome formation in vitro. Rapamycin, an autophagy enhancer, attenuated LPA-induced autophagy inhibition and H9C2 cardiomyoblast hypertrophy, while autophagy inhibition with Beclin1 siRNA did not further enhance the hypertrophic response in LPA-treated cardiomyocytes. Moreover, we demonstrated that LPA suppressed autophagy through the AKT/mTOR signaling pathway because mTOR and PI3K inhibitors significantly prevented LPA-induced mTOR phosphorylation and autophagy inhibition. In addition, we found that knockdown of LPA3 alleviated LPA-mediated autophagy suppression in H9C2 cardiomyoblasts, suggesting that LPA suppresses autophagy through activation of the LPA3 and AKT/mTOR pathways. Conclusion: These findings suggest that LPA plays an important role in mediating cardiac dysfunction and hypertrophy after a MI, and that LPA suppresses autophagy through activation of the LPA3 and AKT/mTOR pathways to induce cardiomyocyte hypertrophy.

Caffeoylxanthiazonoside exerts cardioprotective effects during chronic heart failure via inhibition of inflammatory responses in cardiac cells.

Caffeoylxanthiazonoside (CYT) is an active constituent isolated from the fruit of the Xanthium strumarium L plant. The aim of the present study was to investigate the cardioprotective effects of oral administration of CYT on chronic heart failure (CHF) and its underlying mechanisms. A rat model of CHF was first established, and cardiac function indices, including the heart/body weight index, left heart/body weight index, fractional shortening (FS), ejection fraction (EF), cardiac output (CO) and heart rate (HR), were subsequently determined by cardiac ultrasound. Serum levels of lactate dehydrogenase (LDH) and creatine kinase (CK), and the levels of pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1ß in heart tissues and cardiac microvascular endothelial cells (CMECs) were determined using ELISA. In addition, the protein expression levels of nuclear factor-κB (NF-κB) signaling pathway members were determined by western blotting in CMECs. The results demonstrated that oral administration of 10, 20, 40 mg/kg CYT significantly reduced cardiac hypertrophy and reversed FS, EF, CO and HR when compared with CHF model rats. In addition, CYT administration significantly decreased the levels of TNF-α, IL-6 and IL-1ß in heart tissues, as well as serum LDH and CK levels. Furthermore, exposure of CMECs to 20, 40 and 80 µg/ml CYT significantly decreased the production of TNF-α, IL-1ß and IL-6. The protein expression levels of cytoplasmic NF-κB p65 and IκB were upregulated, while nuclear NF-κB p65 was downregulated following treatment of CMECs with 20, 40 and 80 µg/ml CYT when compared with untreated CHF model controls. In conclusion, the results of the current study suggest that CYT demonstrates cardioprotective effects in CHF model rats by suppressing the expression of pro-inflammatory cytokines and the NF-κB signaling pathway.

Association between N-terminal proB-type Natriuretic Peptide and Depressive Symptoms in Patients with Acute Myocardial Infarction.

BACKGROUND: While depression and certain cardiac biomarkers are associated with acute myocardial infarction (AMI), the relationship between them remains largely unexplored. We examined the association between depressive symptoms and biomarkers in patients with AMI. METHODS: We performed a cross-sectional study using data from 103 patients with AMI between March 2013 and September 2014. The levels of depression, N-terminal proB-type natriuretic peptide (NT-proBNP), and troponin I (TnI) were measured at baseline. The patients were divided into two groups: those with depressive symptoms and those without depressive symptoms according to Zung Self-rating Depression Scale (SDS) score. Baseline comparisons between two groups were made using Student's t-test for continuous variables, Chi-square or Fisher's exact test for categorical variables, and Wilcoxon test for variables in skewed distribution. Binomial logistic regression and multivariate linear regression were performed to assess the association between depressive symptoms and biomarkers while adjusting for demographic and clinical variables. RESULTS: Patients with depressive symptoms had significantly higher NT-proBNP levels as compared to patients without depressive symptoms (1135.0 [131.5, 2474.0] vs. 384.0 [133.0, 990.0], Z = -2.470, P = 0.013). Depressive symptoms were associated with higher NT-proBNP levels (odds ratio [OR] = 2.348, 95% CI: 1.344 to 4.103, P = 0.003) and higher body mass index (OR = 1.169, 95% confidence interval [CI]: 1.016 to 1.345, P = 0.029). The total SDS score was associated with the NT-proBNP level (ß= 0.327, 95% CI: 1.674 to 6.119, P = 0.001) after multivariable adjustment. In particular, NT-proBNP was associated with three of the depressive dimensions, including core depression (ß = 0.299, 95% CI: 0.551 to 2.428, P = 0.002), cognitive depression (ß = 0.320, 95% CI: 0.476 to 1.811, P = 0.001), and somatic depression (ß = 0.333, 95% CI: 0.240 to 0.847, P = 0.001). Neither the overall depressive symptomatology nor the individual depressive dimensions were associated with TnI levels. CONCLUSIONS: Depressive symptoms, especially core depression, cognitive depression, and somatic depression, were related to high NT-proBNP levels in patients with AMI.

Analysis of urgent reconstruction of electrical injuries.

OBJECTIVE: To summarize the reconstruction exp erience of the electrical injuries in emergency. METHODS: All 309 wounds in 105 patients who suffered from elect rical injuries were reviewed during a 10 year period from Jan. 1st 1986 to Dec. 31st, 1996. Treatment method, patient data and results wer e compared and analyzed. A comprehensive urgent reconstruction alternative used in all cases included the followings, 1) debriding the wound in emergency, 2) preserving the vital tissues as much as possible, even devitalized tissues or loca l necrosis, 3) transplanting these vital tissues during the first surgery if the functional reconstruction required, 4) nourishing the wound bed by tissue flaps covering with rich blood supply, 5) improving flap survival by continuous irrig ation for 24-720 hours beneath the flaps with a compound medicine after surgery. RESULTS: Satisfactory results were obtained with the extremity loss ratio of less than 7% in this group compared with 42.5% which was 10 ye ars before 1984 in the same hospital. CONCLUSIONS: This urgent comprehensive reconstruction alternati ve is an effective and workable method for reducing extremity loss of electrical injuries.