Yongtai Gong

The effects of cilazapril and valsartan on the mRNA and protein expressions of atrial calpains and atrial structural remodeling in atrial fibrillation dogs.

AbstractOwing to relative inefficacy and side effects of currently available antiarrhythmic drugs, current interest has shifted to treatments that target atrial fibrillation (AF) substrate. It has been suggested that calpain-induced atrial structural remodelling is under the control of renin-angiotensin system during AF. The purpose of this study is to investigate the effects of cilazapril and valsartan on the mRNA and protein expression of atrial calpains and atrial structural remodelling in AF dogs induced by chronic rapid atrial pacing. Twenty-seven dogs were randomly divided into sham-operated group (n = 6), control group (n = 7), cilazapril group (n = 7) and valsartan group (n = 7). One thin silicon plaque containing 4 pairs of electrodes was sutured to each atrium. A pacemaker was implanted in a subcutaneous pocket and attached to a screw-in epicardial lead in the right atrial appendage. The dogs in control group, cilazapril group and valsartan group were paced at 400 beats per minutes for 6 weeks. The dogs in cilazapril and valsartan groups received cilazapril (1mg · kg−· d−) or valsartan (30mg · kg−· d−) 1 week before rapid atrial pacing until pacing stop respectively. Transthoracic and transoesophageal echocardiographic examinations were performed in order to detect the changes of left atrium volume and contractile function. The inducibility and duration of AF were measured in all the groups. The expressions of atrial calpain I and calpain II mRNA were semi-quantified by reverse transcription-polymerase chain reaction. The protein levels of calpain I and calpain II in atrial myocardium were measured by Western-blot method. Pathohistological and ultrastructural changes in atrial tissue were tested by light and electron microscopy. Compared with the sham-operated control group, dramatic smaller left atrium and left atrial appendage volumes and significant higher atrial contractile function were observed in the cilazapril and valsartan groups. After 6-week atrial tachy-pacing, the mRNA and protein expressions of calpain I increased dramatically in the control group than that in the sham group, tissue calpain protein expression in all groups significantly correlated with the myolysis (r = 0.89, P < 0.01). Cilazapril and valsartan could significantly inhibit the gene and protein expressions of calpain I. No differences were found in the expression of calpain II mRNA and protein between the groups. Compared with atrial myocytes obtained from sham dogs, atrial myocytes from the control group dogs showed a reduced number of sarcomeres, a significant higher myolytic area of atria (24.3% vs. 3.1%, P < 0.01), increased vacuolization and dissolution. Cilazapril and valsartan could effectively prevent the pathohistological and ultrastructural changes induced by chronic rapid atrial pacing, dramatically decrease the area of myolysis (P < 0.05) and significantly reduce the inducibility and duration of AF. The expression of calpain I mRNA and protein increased remarkably in AF dogs. Cilazapril and valsartan can inhibit calpain I up-regulation, suppress atrial structural remodeling, and prevent the induction and promotion of AF in chronic rapid atrial pacing dogs.

Probucol attenuates atrial structural remodeling in prolonged pacing-induced atrial fibrillation in dogs

AIMS Oxidative stress has recently been implicated in atrial fibrillation (AF); however, the mechanisms remain unclear. Herein, we hypothesize that probucol can attenuate atrial structure remodeling. METHODS Twenty dogs were randomly divided into sham-operated, control, and probucol-treated groups. We identified apoptosis and histopathological changes in the atria. Oxidative stress was measured by lipid peroxidation and echocardiographic examinations were performed. RESULTS Atrial apoptosis indexes were dramatically decreased in the probucol-treated group compared to the control group. Relative to the control group, the percentage of myolysis was dramatically decreased in the probucol-treated group (p < 0.01). There was less lipid peroxidation in the probucol-treated group than the control group. Atrial function was dramatically elevated in the probucol-treated group. CONCLUSIONS The results of this study indicate that the antioxidant probucol suppresses atrial structural remodeling and may act as a new therapy for AF.

Plasma MicroRNAs as Potential Noninvasive Biomarkers for In-Stent Restenosis

Objective To investigate whether microRNAs (miRs) can serve as novel biomarkers for in-stent restenosis (ISR). Methods This retrospective, observational single-centre study was conducted at the cardiovascular department of a tertiary hospital centre in the north of China. Follow-up coronary angiography at 6 to 12 months was performed in 181 consecutive patients implanted with drug-eluting stents. Fifty-two healthy volunteers served as the control group. The plasma miRs levels were analyzed by quantitative real-time PCR. Receiver-operating characteristic curve (ROC) analysis was performed to investigate the characters of these miRs as potential biomarkers of ISR. Results MiR-21 levels in ISR patients were significantly higher than those in non-ISR patients and healthy controls (P<0.05), while miR-100 (P<0.05), miR-143 (P<0.001) and miR-145 (P<0.0001) levels were significantly decreased in ISR patients. Further analysis showed that miR-21 levels were remarkably increased (P = 0.045), while miR-100 (P = 0.041), miR-143 (P = 0.029) and miR-145 (P<0.01) levels were dramatically decreased in patients with diffuse ISR compared to those with focal ISR. ROC analysis demonstrated that the area under curve of miR-145, miR-143, miR-100 and miR-21 were 0.880 (95% confidence interval; CI = 0.791–0.987, P<0.001), 0.818 (95% confidence interval; CI = 0.755–0.963, P<0.001), 0.608 (95% confidence interval; CI = 0.372–0.757, P<0.05) and 0.568 (95% confidence interval; CI = 0.372–0.757, P<0.05), with specificity of 83.1%, 80.1%, 68.9% and 68.6%, and sensitivity of 88.7%, 82.1%, 60.2% and 50.1%, respectively. Conclusions Circulating miR-143 and miR-145 levels are associated with the occurrence of ISR and can serve as novel noninvasive biomarkers for ISR.

Blockade of PDE4B limits lung vascular permeability and lung inflammation in LPS-induced acute lung injury.

Acute lung injury (ALI), acute respiratory distress syndrome (ARDS), is actually involved in an ongoing and uncontrolled inflammatory response in lung tissues. Although extensive studies suggested that phospodiesterase type 4B (PDE4B) may be related to inflammation, the underlying cell biological mechanism of ALI remains unclear. To further investigate the mechanism how PDE4B take part in inflammatory response and the maintenance of vascular integrity, we established the experimental model of ALI in vitro and in vivo. In vitro, we found that Cilomilast, Diazepam and PDE4B knockout could potently inhibit the LPS-induced NF-κB activation and inflammatory response in multiple cell types, including lung epithelial cells (A549), pulmonary microvascular endothelial cells (PMVECs) and vascular smooth muscle cells (VSMCs). Besides, PDE4B deletion attenuated the LPS-induced ROS generation. In vivo, PDE4B deletion could attenuate the lung water content, histological signs of pulmonary injury and elevate the ratio of partial pressure of arterial O2 to fraction of inspired O2 (PaO2/FIO2 ratio). Additionally, PDE4B deletion reduced LPS-induced vascular permeability. Collectively, our results strongly indicates that PDE4B is a valid target for anti-ALI.

Obstructive sleep apnea increases systolic and diastolic blood pressure variability in hypertensive patients

Objective Obstructive sleep apnea (OSA) has been identified as the most common secondary contributing factor for the development and worsening of hypertension. However, the underlying relationships between blood pressure variability (BPV) and OSA are still not very clear. Therefore, we investigated the influences of OSA on BPV in hypertensive patients and explored the potential pathophysiologic mechanisms. Participants and methods Ambulatory blood pressure (BP) monitoring was carried out and polysomnography was performed to detect sleep apnea. A total of 86 hypertensive individuals were divided into patients without OSA (n=43) and patients with severe OSA (n=43). Systolic and diastolic BPV were obtained by calculating the SD, coefficient of variation, and average real variability during day-time, night-time, and over 24 h. The relationship between OSA and BPV was assessed after adjustment for potential confounding variables (age, sex, BMI, neck circumference, heart rate, and snoring history). Results Compared with participants without OSA, nocturnal systolic BPV and 24-h systolic BP average real variability from OSA participants were obviously increased (P<0.05), but there were no statistically significant differences in day-time and 24-h systolic BP SD and coefficient of variation (P>0.05). Compared with participants without OSA, 24-h diastolic BPV and day-time diastolic BP SD from OSA participants were markedly increased (P<0.05), but nocturnal indices showed no significant differences between the two groups. Conclusion OSA mainly increases night-time systolic and 24-h diastolic BPV in hypertensive patients. This may provide a plausible explanation for OSA remaining a major risk determinant for cardiovascular diseases.

Myocardial bridge: Is the risk of perforation increased?

It has been demonstrated that stent implantation in a myocardial bridge is associated with a high restenosis rate; however, coronary perforation caused by stent implantation has been reported. The present report describes two myocardial bridge cases with severe coronary rupture soon after stent implantation. Previous studies have reported that the diameter of the bridge vessels was less than that of the proximal and distal vessels; thus, coronary perforation may be due to stent oversizing. To determine the risks and benefits associated with this therapeutic option, interventional therapy should be critically evaluated, and careful selection of balloon and drug-eluting stent size using intravascular ultrasound is recommended.

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.

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.

ROLE OF ADAM-12/SYNDECAN-4 SIGNALLING PATHWAY IN VENTRICULAR REMODELLING IN RATS WITH ALCOHOLIC CARDIOMYOPATHY

Objectives Chronic excessive consumption of alcohol causes cardiac remodelling and eventually leads to alcoholic cardiomyopahty (ACM). A disintegrin and metalloproteinase-12 (ADAM-12) is involved in degradation of extracellular matrix using syndecan-4 as a primary cell surface receptor. This study aimed to investigate the role of ADAM-12/syndecan-4 signalling pathway in ventricular remodelling of ACM. Methods Fifty healthy Wistar rats were randomly divided into a control group (n=20) and an ACM group (n=30). Animals in the ACM group were given 10% alcohol ad libitum as the drinking water and 60% alcohol (5 ml kg−1 once per day) by intragastric administration in the first week; 10% alcohol ad libitum as the drinking water and 60% alcohol (10 ml kg−1 twice per day) by intragastric administration in the second week; 20% alcohol ad libitum as the drinking water and 60% alcohol (15 ml kg−1 twice per day) by intragastric administration from week 3 to week 16; and 30% alcohol ad libitum as the drinking water and 60% alcohol (15 ml kg−1 twice per day) by intragastric administration from week 17 to month 6. Animals in the control group received purified drinking water in the same regimen with alcohol treatment. Before and 6 months after initiating the study, left ventricular end diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), and fractional shortening (FS) were assessed by echocardiography. Histopathology and ultrastructure of myocardium were examined with light and electron microscopy; mRNA expressions of ADAM-12 and syndecan-4 were evaluated by real-time PCR; and protein expressions of ADAM-12 and syndecan-4 were analysed using immunohistochemistry and western blot, respectively. The expression of TIMP-3, an endogenous inhibitor of ADAM-12, was also tested. Results Following 6 months of alcohol feeding, LVEF and FS were reduced p<0.05 for both), while LVEDD was augmented in the ACM group p<0.05), as compared with the control group. In addition, severe changes in cardiac structure were seen in the ACM group. The mRNA and protein expressions of ADAM-12 and syndecan-4 were up-regulated in the ACM group in comparison with the control group p<0.05 for all), while those of TIMP-3 were down-regulated. In both groups, the protein expression of ADAM-12 positively correlated with that of syndecan-4 and LVEDD p<0.05 for both), whereas it negatively correlated with LVEF p<0.05). Conclusions Along with decreased expression of TIMP-3, ADAM-12 and syndecan-4 are over-expressed and are associated with ventricular remodelling in ACM. Therefore, the ADAM-12/syndecan-4 signalling pathway may represent a new therapeutic target in the prevention and treatment of ventricular remodelling in ACM.