Association between the cumulative triglyceride-glucose index and the recurrence of atrial fibrillation after radiofrequency catheter ablation.

BACKGROUND: Triglyceride-glucose (TyG) index values are a new surrogate marker for insulin resistance. This study aimed to explore the relationship between cumulative TyG index values and atrial fibrillation (AF) recurrence after radiofrequency catheter ablation (RFCA). METHODS: A total of 576 patients with AF who underwent RFCA at the Second Affiliated Hospital of Xi'an Jiaotong University were included in this study. The participants were grouped based on cumulative TyG index values tertiles within 3 months after ablation. Cox regression and restricted cubic spline analyses were used to determine the relationship between cumulative TyG index values and AF recurrence. The predictive value of all risk factors was assessed by receiver operating curve analysis. RESULTS: There were 375 patients completed the study (age: 63.23 ± 10.73 years, 64.27% male). The risk of AF recurrence increased with increasing cumulative TyG index values tertiles. After adjusting for potential confounders, patients in the medium cumulative TyG index group [hazard ratio (HR) = 4.949, 95% CI: 1.778-13.778, P = 0.002] and the high cumulative TyG index group (HR = 8.716, 95% CI: 3.371-22.536, P < 0.001) had a higher risk of AF recurrence than those in the low cumulative TyG index group. The restricted cubic spline regression model also showed an increased risk of AF recurrence with increasing cumulative TyG index values. When considering cumulative TyG index values, left atrial diameter, and lactate dehydrogenase levels as a comprehensive factor, the model could effectively predict AF recurrence after RFCA [area under the curve (AUC) = 0.847, 95% CI: 0.797-0.897, P < 0.001]. CONCLUSIONS: Cumulative TyG index values were a risk factor for AF recurrence after RFCA. Monitoring longitudinal TyG index values may assist with optimized for risk stratification and outcome prediction for AF recurrence.

Sema3A alleviates viral myocarditis by modulating SIRT1 to regulate cardiomyocyte mitophagy.

Viral myocarditis (VMC) is a common myocardial inflammatory disease characterized by inflammatory cell infiltration and cardiomyocyte necrosis. Sema3A was reported to reduce cardiac inflammation and improve cardiac function after myocardial infarction, but its role in VMC remains to be explored. Here, a VMC mouse model was established by infection with CVB3, and Sema3A was overexpressed in vivo by intraventricular injection of an adenovirus-mediated Sema3A expression vector (Ad-Sema3A). We found that Sema3A overexpression attenuated CVB3-induced cardiac dysfunction and tissue inflammation. And Sema3A also reduced macrophage accumulation and NLRP3 inflammasome activation in the myocardium of VMC mice. In vitro, LPS was used to stimulate primary splenic macrophages to mimic the macrophage activation state in vivo. Activated macrophages were co-cultured with primary mouse cardiomyocytes to evaluate macrophage infiltration-induced cardiomyocyte damage. Ectopic expression of Sema3A in cardiomyocytes effectively protected cardiomyocytes from activated macrophage-induced inflammation, apoptosis, and ROS accumulation. Mechanistically, cardiomyocyte-expressed Sema3A mitigated macrophage infiltration-caused cardiomyocyte dysfunction by promoting cardiomyocyte mitophagy and hindering NLRP3 inflammasome activation. Furthermore, NAM (a SIRT1 inhibitor) reversed the protective effect of Sema3A against activated macrophage-induced cardiomyocyte dysfunction by suppressing cardiomyocyte mitophagy. In conclusion, Sema3A promoted cardiomyocyte mitophagy and suppressed inflammasome activation by regulating SIRT1, thereby attenuating macrophage infiltration-induced cardiomyocyte injury in VMC.

Higher serum sST2 is associated with increased left atrial low-voltage areas and atrial fibrillation recurrence in patients undergoing radiofrequency ablation.

OBJECTIVE: To conduct a comprehensive analysis of prospectively measuring the concentration of soluble suppression of tumorigenicity 2 (sST2) to predict left atrial (LA) low-voltage areas (LVAs) and atrial fibrillation (AF) recurrence after radiofrequency catheter ablation (RFA). METHODS: This was a prospective cohort study. A total of 84 patients, including 54 paroxysmal AF cases and 30 persistent AF cases who underwent RFA, were recruited. Electroanatomical voltage mapping determined the extent of LVAs. The serum level of sST2 was measured by enzyme-linked immunosorbent assay. All patients were followed for 12 months after the RFA procedure to verify AF recurrence. RESULTS: The concentration of sST2 measured in the sample was 17.90-198.77 pg/mL, and the range of LA LVAs was 0-85.6%. The sST2 level positively correlated with LVAs (r = 0.40; P = 0.005). When comparing the top and bottom quartile, sST2 is significantly associated with LA LVAs (OR = 1.833, 95% CI: 1.582-2.011, P = 0.004). When compared with the 1st quartile group, the multivariable adjusted hazard ratios for AF recurrence after RFA were 1.57 (95% CI: 1.182-1.795) for the 4th quartile group, 1.44 (95% CI: 1.085-1.598) for the 3rd quartile group, and 1.27 (95% CI: 0.954-1.318) for the 2nd quartile group. The AF-free survival rates of patients with 1st quartile and 4th quartile sST2 levels after ablation were 95% and 59.6%, respectively (Log Rank test, P = 0.027). CONCLUSION: Elevated sST2 levels of AF patients were associated with higher LA LVAs and a significantly increased risk of recurrence. The circulating sST2 concentration might be a pre-diagnostic marker of AF recurrence after RFA.

ABCG1 Attenuates Oxidative Stress Induced by H2O2 through the Inhibition of NADPH Oxidase and the Upregulation of Nrf2-Mediated Antioxidant Defense in Endothelial Cells.

Summary. Oxidative stress is an important factor that is related to endothelial dysfunction. ATP-binding cassette transporter G1 (ABCG1), a regulator of intracellular cholesterol efflux, has been found to prevent endothelial activation in vessel walls. To explore the role of ABCG1 in oxidative stress production in endothelial cells, HUAECs were exposed to H2O2 and transfected with the specific ABCG1 siRNA or ABCG1 overexpression plasmid. The results showed that overexpression of ABCG1 by ABCG1 plasmid or liver X receptor (LXR) agonist T0901317 treatment inhibited ROS production and MDA content induced by H2O2 in HUAECs. Furthermore, ABCG1 upregulation blunted the activity of prooxidant NADPH oxidase and the expression of Nox4, one of the NADPH oxidase subunits. Moreover, the increased migration of Nrf2 from the cytoplasm to the nucleus and antioxidant HO-1 expression were detected in HUAECs with upregulation of ABCG1. Conversely, ABCG1 downregulation by ABCG1 siRNA increased NADPH oxidase activity and Nox4 expression and abrogated the increase at Nrf2 nuclear protein levels. In addition, intracellular cholesterol load interfered with the balance between NADPH oxidase activity and HO-1 expression. It was suggested that ABCG1 attenuated oxidative stress induced by H2O2 in endothelial cells, which might be involved in the balance between decreased NADPH oxidase activity and increased Nrf2/OH-1 antioxidant defense signaling via its regulation for intracellular cholesterol accumulation.

Thiopental sodium loaded solid lipid nano-particles attenuates obesity-induced cardiac dysfunction and cardiac hypertrophy via inactivation of inflammatory pathway.

This work evaluates solid lipid nanoparticles of thiopental sodium against obesity-induced cardiac dysfunction and hypertrophy and explores the possible mechanism of action. TS loaded SLNs were formulated by hot-homogenization and solvent diffusion method. TS-SLNs were scrutinized for entrapment efficiency, drug loading capacity, gastric stability, particle size, in vitro drug release. Mice were feed with the normal chow or high-fat diet for 08 weeks to induce obesity and primary cardiomyocytes. The therapeutic effects of thiopental sodium in the high fat diet (HFD) induced cardiac hypertrophy. Systolic blood pressure (SBP) was estimated at a regular time interval. At the end of the experimental study, systolic pressure left ventricular, LV end-diastolic pressure and rate of increase of LV pressure and antioxidant, apoptosis, cytokines and inflammatory scrutinized. HFD induced group mice exhibited a reduction in the body weight and enhancement of cardiac hypertrophy marker and dose-dependent treatment of thiopental sodium up-regulation the body weight and down-regulated the cardiac hypertrophy. Thiopental sodium significantly (p < .001) dose-dependently altered the antioxidant, biochemical, cardiac parameters and remodeling. Thiopental sodium significantly (p < .001) dose-dependently reduced the SBP. Thiopental sodium altered the apoptosis marker, pro-inflammatory cytokines, inflammatory parameters along with reduced the p38-MAPK level. The cardiac protective effect of thiopental sodium shed light on future therapeutic interventions in obesity and related cardiovascular complications via inflammatory pathway.

NLRP3 inflammasome promotes diabetes-induced endothelial inflammation and atherosclerosis.

BACKGROUND: NLRP3 inflammasome can be activated by high glucose and links inflammation and metabolic disease. This study aimed to investigate the role of NLRP3 inflammasome in hyperglycemia-induced endothelial inflammation and diabetic atherosclerosis. METHODS: NLRP3 levels in peripheral blood mononuclear cell (PBMC) and plasma IL-1ß level were measured in diabetes patients. The activation of NLPR3 was detected in diabetic ApoE-/- mice and human umbilical vein endothelial cells (HUVECs). RESULTS: Compared with healthy controls, NLRP3 expression levels in PBMC and plasma IL-1ß level were significantly higher in diabetes patients but considerably decreased after lifestyle interventions and medicine. Moreover, carotid atherosclerosis was significantly related to plasma IL-1ß level in diabetes patients. In diabetic atherosclerosis mouse model, NLRP3 knockdown suppressed NLRP3 inflammasome activation, inhibited the expression of adhesion molecules ICAM-1 and VCAM-1 in intima, reduced atherosclerosis and stabilized atherosclerotic plaque. In vitro, the expression of NLRP3 inflammasome components and the secretion of IL-1ß were augmented by high glucose in HUVECs. Moreover, either high glucose or IL-1ß promoted the expression of adhesion molecules, which were suppressed by NLRP3 knockdown or IL-1ß receptor antagonist. CONCLUSION: These findings provide novel insights into pathological mechanisms of diabetic atherosclerosis and have potential therapeutic implications for cardiovascular complications in diabetes.

Phloroglucinol averts isoprenaline hydrochloride induced myocardial infarction in rats.

Myocardial infarction (MI) is indicated by the symptoms like sharp chest pain, sweating, palpitations, and nervousness finally leading to heart attack. MI occurs mainly due to the risk factors like smoking, elevated blood pressure, diabetes, hypercholesterolemia, obesity, decreased HDL level, elevated LDL level, hyperlipoproteinemia and aging consequently leads to demandable coronary blood supply, oxidative stress, and acute necrosis of the myocardium. Cardioprotective potential of the phloroglucinol (PG) was assessed by treating isoprenaline hydrochloride (ISO; 85 mg/kg b.w., s.c.) induced MI model in rats. Pretreatment with PG in a dose of 30 mg/kg was done for 28 days and followed by ISO (for MI induction) on 29th and 30th days, exhibited decline in the abnormalities in the ECG patterns, cardiac marker enzymes, enzymic and nonenzymic antioxidants, lipid peroxidation, lipid profiles, and histopathological investigations compared to isoprenaline alone treated group. On the whole, the present investigations elucidate the significance of PG in alleviating the pathological process and appreciably prevent the induction of MI in experimental rats.

Resveratrol ameliorates sepsis-induced acute kidney injury in a pediatric rat model via Nrf2 signaling pathway.

Acute kidney injury (AKI) is a hyper-inflammation-induced abrupt loss of kidney function and has become a major public health problem. The cecal ligation and puncture (CLP) model of peritonitis in rat pups mimics the development of sepsis-induced pediatric AKI is pre-renal without morphological changes of the kidneys and high lethality. Resveratrol, a natural polyphenolic compound with low toxicity, has obvious anti-oxidant and anti-inflammatory properties. The present study aimed to determine whether resveratrol alleviates pediatric AKI and investigated the potential mechanism. Thus, a CLP model of 17-18 day-old rat pups was used to mimic the development of sepsis-induced AKI in children. In the group treated with resveratrol, renal injury induced by CLP was alleviated with downregulation of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß and kidney injury molecule (KIM)-1 expression. Nuclear factor-erythroid-2-related factor 2 (Nrf2) signaling is known to effectively inhibit inflammation, the present study found that resveratrol reduced the lipopolysaccharide-induced inflammatory response in kidney cells in vitro and induced the activation of Nrf2 signaling, including accumulation of nuclear Nrf2 and increase of the expression of Nrf2 target genes heme oxygenase (HO)-1 and NAD(P)H dehydrogenase (quinone) 1 (NQO1); this was confirmed by the induction of the expression of HO-1 and NQO1 by treatment of resveratrol in vitro and in vivo. Of note, knockdown of Nrf2 effectively abrogated the downregulation of TNF-α, IL-1ß and KIM-1 expression induced by resveratrol in vitro. These results suggested that resveratrol ameliorates sepsis-induced acute kidney injury in a pediatric model of AKI via the Nrf2 signaling pathway.

Relationship of microRNA 616 gene polymorphism with prognosis of patients with premature coronary artery disease.

OBJECTIVE: To investigate the relationship of microRNA 616 (has-miR-616) single nucleotide polymorphisms (SNPs) and its target gene paraoxonase 1 (PON 1) with the prognosis of patients with premature coronary artery disease (pCAD). METHODS: 266 pCAD cases in the case group and 300 cases in the control group were collected. Using the polymorphism method of polymerase chain reaction and restriction fragment length, the has-miR-616 rs3735590 genotypes of target gene PON 1 were detected. RESULTS: In the changes of rs3735590 C/T SNPs, compared with CC genotypes, the risk of coronary heart disease of the individuals carrying CT and TT genotypes were reduced by 42% and 31%, respectively (p < 0.05). The risk of developing coronary heart disease in individuals carrying CT and TT genotypes were reduced significantly in the population with levels of total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol. CONCLUSION: Target gene PON 1 of hsa-miRNA-616 rs3735590C-T SNPs is associated with the reduced incidence risk of pCAD, and carrying C alleles is an independent risk factor for pCAD.

ACE2-Ang (1-7) axis is induced in pressure overloaded rat model.

ACE2-Ang (1-7) axis is a key regulator in cardiac hypertrophy, myocardial remodeling and development of heart failure. To investigate how ACE2-Ang (1-7) axis function in pressure-overload-induced heart failure, male SD rats (weighing about 250 g) were used to establish the model of pressure-overload-induced heart failure using aortic stenosis surgery. The level of plasma ACE2, ACE and Ang (1-7) from heart failure group were significantly up-regulated compared with the sham group by ELISA test. The mRNA and protein expression of ACE2 in myocardial tissue from heart failure group also showed remarkably increased. Importantly, we found that the expression of ACE2 and Ang (1-7) were reversed in heart failure group after treatment with AT1 receptor antagonist telmisartan. Compared with heart failure group, the level of plasma ACE2, ACE and Ang (1-7) were significantly decreased in telmisartan treated group. The mRNA and protein expression of ACE2 in cardiac tissue from telmisartan group was also significantly decreased, while Mas mRNA and protein level was increased. Taken together, these studies demonstrated that the expression of ACE2-Ang (1-7) axis was induced in pressure-overload-induced heart failure model, suggesting that ACE2-Ang (1-7) axis may have a protective role in the development of heart failure and may provide a new target for drug development of heart failure.

Effects of monocyte-endothelium interactions on the expression of type IV collagenases in monocytes.

The adhesion of monocytes to endothelial cells is one of the early stages in the development of atherosclerosis. The expression of type IV collagenases, which include matrix metalloproteinase (MMP)-2 and MMP-9, in monocytes is hypothesized to play an important role in monocyte infiltration and transformation into foam cells. The aim of the present study was to examine the effects of monocyte-endothelium interactions on the expression levels of type IV collagenases and their specific inhibitors in monocytes, and to investigate the roles of tumor necrosis factor (TNF)-α and interleukin (IL)-1ß in this process. Monocytes were single-cultured or co-cultured with endothelial cells. The expression of the type IV collagenases, MMP-2 and MMP-9, and their specific inhibitors, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2, in monocytes was determined by immunohistochemistry followed by image analysis. The expression levels of MMP-2 and MMP-9 were found to be low in the single-culture monocytes, but increased significantly when the monocytes and endothelial cells were co-cultured. However, treatment with monoclonal TNF-α or IL-1ß antibodies partially inhibited the upregulated expression of MMP-2 and MMP-9 in the co-cultured monocytes. Expression of TIMP-1 and TIMP-2 was observed in the single monocyte culture, and a small increase in the expression levels was observed when the monocytes were co-cultured with endothelial cells. Therefore, monocyte-endothlium interactions were shown to increase the expression of type IV collagenases in monocytes, resulting in the loss of balance between MMP-2 and -9 with TIMP-1 and -2. In addition, TNF-α and IL-1ß were demonstrated to play important roles in this process.

Novel distribution of calreticulin to cardiomyocyte mitochondria and its increase in a rat model of dilated cardiomyopathy.

BACKGROUND: Calreticulin (CRT), a Ca(2+)-binding chaperone of the endoplasmic reticulum, can also be found in several other locations including the cytosol, nucleus, secretory granules, the outer side of the plasma membrane, and the extracellular matrix. Whether CRT is localized at mitochondria of cardiomyocytes and whether such localization is affected under DCM are still unclear. METHODS AND RESULTS: The DCM model was generated in rats by the daily oral administration of furazolidone for thirty weeks. Echocardiographic and hemodynamic studies demonstrated enlarged left ventricular dimensions and reduced systolic and diastolic function in DCM rats. Immuno-electron microscopy and Western blot showed that CRT was present in cardiomyocyte mitochondria and the mitochondrial content of CRT was increased in DCM hearts (P<0.05). Morphometric analysis showed notable myocardial apoptosis and mitochondrial swelling with fractured or dissolved cristae in the DCM hearts. Compared with the control group, the mitochondrial membrane potential level of the freshly isolated cardiac mitochondria and the enzyme activities of cytochrome c oxidase and succinate dehydrogenase in the model group were significantly decreased (P<0.05), and the myocardial apoptosis index and the caspase activities of caspase-9 and caspase-3 were significantly increased (P<0.05). Pearson linear correlation analysis showed that the mitochondrial content of CRT had negative correlations with the mitochondrial function, and a positive correlation with myocardial apoptosis index (P<0.001). The protein expression level of cytochrome c and the phosphorylation activity of STAT3 in the mitochondrial fraction were significantly decreased in the model group compared with the control group (P<0.05). CONCLUSIONS: These data demonstrate that CRT is localized at cardiomyocyte mitochondria and its mitochondrial content is increased in DCM hearts.

Combination of mean platelet volume and the GRACE risk score better predicts future cardiovascular events in patients with acute coronary syndrome.

Both the Global Registry of Acute Coronary Events (GRACE) risk score and mean platelet volume (MPV) can independently predict adverse cardiovascular disease (CVD) events in patients with acute coronary syndrome (ACS). This study was aimed at investigating whether MPV was related to the GRACE risk score and whether the combination of them could have a better performance in predicting CVD in Patients with ACS. Totally 297 ACS patients were included. MPV was measured on admission. The GRACE risk score was calculated and its predictive value alone and together with MPV was assessed, respectively. During a median period of 52 months (range, 6 to 65), 11 of the 297 subjects (3.7%) were lost to follow-up, and 132 (46.2%) had adverse CVD including 32 deaths. Both MPV and the GRACE score were higher in patients with CVD events than those without events, and the GRACE score increased with the increase of MPV. Multivariate Cox analysis demonstrated that both MPV and the GRACE score were significant and independent predictors for CVD events (HR: 1.13; 95% CI: 1.10 to 1.15; p = 0.006; HR: 1.30; 95% CI: 1.24 to 1.37; p < 0.001; respectively). The area under the ROC curve was 0.70 (95% CI: 0.64 to 0.76, p < 0.001) when the GRACE score was calculated alone, whereas it increased to 0.85 (95% CI: 0.81 to 0.90, p < 0.001) with the addition of MPV, indicating that the combination of MPV with the scoring system improved the predictive value. This study demonstrates for the first time that MPV is positively associated with the GRACE risk score and it may complement the scoring system in predicting CVD events in patients with ACS.

PI3K/AKT signaling pathway plays a role in enhancement of eNOS activity by recombinant human angiotensin converting enzyme 2 in human umbilical vein endothelial cells.

The aim of this study was to investigate the effect of PI3K/AKT signaling pathway in the activity of recombinant human angiotensin converting enzyme 2 (rhACE2) promoted the activity of endothelial nitric oxide synthase (eNOS). The human umbilical vein endothelial cells (HUVEC) were cultured in vitro. Then treated with Ang II (1×10(-6) mol/L) for 24 h. The rhACE2 (100 µmol/L) was added and incubated for 5, 10, 15, 30, 60 min respectively which was based on Ang II intervention. The effect of rhACE2 on phosphorylation eNOS level was also observed in the presence of LY294002 (10 µmol/L) (PI3K/AKT inhibitors). Griess reagent method was applied to measure NO contents in cell culture supernatant, RT-PCR to detect the expression of eNOSmRNA in HUVEC, and Western blot to detect the expression of eNOS and phosphorylated eNOS. In Ang II intervention group, NO contents were significantly lower than control group (P < 0.05). Through rhACE2 treatment, the NO contents in cell culture medium and the expression level of phosphorylated eNOS were significantly higher than in Ang II intervention group (P < 0.05), but eNOSmRNA and non-phosphorylated eNOS protein expression level showed no significant difference (P > 0.05). After HUVEC was intervened by PI3K/AKT pathway inhibitor LY294002, the expression level of phosphorylated eNOS was significantly lower than that in the rhACE2 30 min treatment group (P < 0.05). rhACE2 may reduce the activity of Ang II inhibited endothelial cell eNOS, which can be blocked by PI3K/AKT pathway inhibitor LY294002, suggesting PI3K/AKT signaling pathway plays an important role in rhACE2's promotion of the activity of endothelial cell eNOS.

Protein kinase RNA-like endoplasmic reticulum kinase (PERK) signaling pathway plays a major role in reactive oxygen species (ROS)-mediated endoplasmic reticulum stress-induced apoptosis in diabetic cardiomyopathy.

BACKGROUND: Endoplasmic reticulum (ER) stress is considered one of the mechanisms contributing to reactive oxygen species (ROS)-mediated cell apoptosis. In diabetic cardiomyopathy (DCM), cell apoptosis is generally accepted as the etiological factor and closely related to cardiac ROS generation. ER stress is proposed the link between ROS and cell apoptosis; however, the signaling pathways and their roles in participating ER stress-induced apoptosis in DCM are still unclear. METHODS: In this study, we investigated the signaling transductions in ROS-dependent ER stress-induced cardiomocyte apoptosis in animal model of DCM. Moreover, in order to clarify the roles of IRE1 (inositol-requiring enzyme-1), PERK (protein kinase RNA (PKR)-like ER kinase) and ATF6 (activating transcription factor-6) in conducting apoptotic signal in ROS- dependent ER stress-induced cardiomocyte apoptosis, we further investigated apoptosis in high-glucose incubated cardiomyocytes with IRE1, ATF6 and PERK-knocked down respectively. RESULTS: we demonstrated that the ER stress sensors, referred as PERK, IRE1 and ATF6, were activated in ROS-mediated ER stress-induced cell apoptosis in rat model of DCM which was characterized by cardiac pump and electrical dysfunctions. The deletion of PERK in myocytes exhibited stronger protective effect against apoptosis induced by high-glucose incubation than deletion of ATF6 or IRE in the same myocytes. By subcellular fractionation, rather than ATF6 and IRE1, in primary cardiomyocytes, PERK was found a component of MAMs (mitochondria-associated endoplasmic reticulum membranes) which was the functional and physical contact site between ER and mitochondria. CONCLUSIONS: ROS-stimulated activation of PERK signaling pathway takes the major responsibility rather than IRE1 or ATF6 signaling pathways in ROS-medicated ER stress-induced myocyte apoptosis in DCM.

Calreticulin-STAT3 signaling pathway modulates mitochondrial function in a rat model of furazolidone-induced dilated cardiomyopathy.

BACKGROUND: Calreticulin is a Ca(2+)-binding chaperone of the endoplasmic reticulum which regulates the signal transducer and activator of transcription 3 (STAT3). The effects of the calreticulin-STAT3 signaling pathway on cardiac mitochondria and on the progress of dilated cardiomyopathy (DCM) are still unclear. METHODS AND RESULTS: The DCM model was generated in rats by the daily oral administration of furazolidone. Echocardiographic and hemodynamic studies demonstrated enlarged LV dimensions and reduced systolic and diastolic functions at thirty weeks after the first furazolidone administration. Morphometric analysis showed significant myocardial degeneration, interstitial fibrosis, and mitochondrial swelling with fractured or dissolved cristae in the model group. Compared with the control group, the mitochondrial membrane potential (MMP) level of the freshly isolated cardiac mitochondria and the enzyme activities of cytochrome c oxidase and succinate dehydrogenase in the model group were significantly decreased (P<0.05). Real-time PCR and western-blot revealed the increased expression of calreticulin associated with decreased activity of STAT3 in the model group. When cultured neonatal rat cardiomyocytes were exposed to furazolidone, a dose-dependent decrease in cell viability and MMP, and the increase of apoptosis rate were observed. The mRNA and protein expression of CRT gradually increased with the increase of furazolidone concentration, associated with a gradual decrease of the STAT3 phosphorylation level both in the whole cell and mitochondrial fraction. When calreticulin was knocked down with siRNA in cardiomyocytes, these changes of cardiomyocytes and mitochondria induced by furazolidone were significantly attenuated. CONCLUSIONS: A rat model of DCM induced by furazolidone is successfully established. The calreticulin-STAT3 signaling pathway is involved in cardiac mitochondrial injury and the progress of furazolidone induced DCM.

[Change of cardiac mitochondrial STAT3 activity in rats with selenium deficiency and its relation with myocardial injury].

OBJECTIVE: To study the phosphorylation activity of mitochondrial signal transducer and activator of transcription 3 (STAT3) in the myocardium of rats with selenium deficiency and its association with myocardial injury. METHODS: Thirty-six rats were randomized into normal control group (n=18) and selenium deficiency model group (n=18) for feeding with normal and low-selenium chow, respectively, for 20, 30 and 40 weeks. The cardiac function of the rats was evaluated by carotid artery intubation, and the damage of cardiac mitochondria was observed under electron microscopy. The cardiac mitochondria were extracted for assessing succinate dehydrogenase and cytochrome C oxidase activities, and the protein expressions of phosphorylated and total STAT3 were detected. RESULTS: Compared with the corresponding control groups, the rats in the model group showed significantly decreased cardiac function with obvious structural and functional damage of the cardiac mitochondria (P<0.05), which aggravated as the low-selenium feeding time extended (P<0.05). The rats in the model group also showed significantly decreased mitochondrial STAT3 activity (p-STAT3/STAT3) in the myocardium as the low-selenium feeding time prolonged (P<0.05). Pearson linear correlation analysis showed that the activity of cardiac mitochondrial STAT3 had positive correlations with the left ventricular systolic pressure, maximal increased rate of the left ventricular pressure, and the activities of succinate dehydrogenase and cytochrome C oxidase (P<0.01). CONCLUSION: Selenium deficiency down-regulates the activity of mitochondrial STAT3 in rat heart to contribute to cardiac mitochondrial injury and the progression of heart failure.

ABCG1 deficiency promotes endothelial apoptosis by endoplasmic reticulum stress-dependent pathway.

The present study was focused on whether ABCG1 deficiency was involved in endothelial apoptosis and its possible mechanism. Human umbilical artery endothelial cells were transfected with ABCG1 siRNA and/or ABCG1 expression plasmid. We observed that silencing of endothelial ABCG1 reduced cholesterol efflux to HDL and increased intracellular lipid content. Moreover, reduction of ABCG1 promoted endothelial apoptosis and expression of endoplasmic reticulum (ER) stress-related molecules GRP78 and CHOP. In contrast, transfection of ABCG1 overexpression plasmid reversed endothelial apoptosis and intracellular lipid accumulation as well as decreased expression of GRP78 and CHOP in ABCG1-deficient endothelial cells. Furthermore, endothelial apoptosis and ER stress-related molecules were induced by repletion of endothelial cells with cholesterol-loaded cyclodextrin, otherwise endothelial apoptotic response and expression of GRP78 and CHOP were suppressed by depletion of cellular cholesterol in ABCG1-deficient endothelial cells. The present results suggest that reduction of ABCG1 induces endothelial apoptosis, which seems associated with intracellular free cholesterol accumulation and subsequent ER stress.

ATP-binding cassette transporter G1 protects against endothelial dysfunction induced by high glucose.

AIMS: ATP binding cassette transporter G1 (ABCG1), a regulator of cholesterol efflux to HDL, has been shown to decrease in macrophages and smooth muscle cells under high glucose conditions. Endothelial cells have a high capacity to efflux sterols and express ABCG1. In the present study we explored the role of ABCG1 in high glucose-induced endothelial dysfunction. METHODS: Human aortic endothelial cells (HAECs) were cultured under high glucose conditions. ABCG1 mRNA and protein expression in HAECs were measured by real time PCR and Western blot. Cholesterol efflux and NO synthesis (NOS) activity were determined by means of scintillation counting. Total intracellular cholesterol was determined by gas-liquid chromatography. The secretion of IL-6 and ICAM-1 was measured using ELISA. The generation of intracellular reactive oxygen species (ROS) was measured using a fluorescence microscope. RESULTS: We observed that high glucose suppressed ABCG1 expression and intracellular cholesterol efflux to HDL. Furthermore, high glucose increased the secretion of IL-6 and ICAM, as well as decreased phospho-eNOS protein expression and NOS activity. These processes were reversed by the up-regulation of ABCG1 using the liver X receptor (LXR) agonist T0901307 and an ABCG1 expression vector. In addition, high glucose-induced oxidative stress was reduced by the upregulation of ABCG1. In contrast, knock-down of ABCG1 in HAECs significantly increased the secretion of IL-6 and ICAM, as well as decreased phospho-eNOS protein expression and NOS activity. CONCLUSIONS: The present results suggest that ABCG1 plays an important role in protecting against endothelial dysfunction induced by high glucose.

[Endothelial dysfunction induced by high glucose is associated with decreased ATP-binding cassette transporter G1 expression].

OBJECTIVE: To investigate the role of ATP-binding cassette transporter G1 (ABCG1) in endothelial dysfunction induced by high glucose. METHODS: Human aortic endothelial cells (HAECs) were incubated in the presence of 5.6 or 30 mmol/L glucose for 24-72 h with or without a 2-h pretreatment with the LXR agonist 22(R)-hydroxycholesterol. Real-time PCR and Western blotting were used to measure the mRNA and protein expressions of ABCG1; the intracellular cholesterol efflux and endothelial nitric oxide synthase (eNOS) activity were measured by scintillation counting. RESULTS: High glucose time-dependently suppressed ABCG1 expression and cholesterol efflux to HDL in HAECs. High glucose also decreased eNOS activity. ABCG1 down-regulation induced by high glucose, along with decreased cholesterol efflux and eNOS activity, was abolished by treatment of the cells with the LXR agonist. CONCLUSION: Endothelial dysfunction induced by high glucose is associated with decreased ABCG1 expression.