Wen-Hao Liu

Atrial myocardial nox2 containing NADPH oxidase activity contribution to oxidative stress in mitral regurgitation: potential mechanism for atrial remodeling

BACKGROUND Oxidative stress is linked with several cardiovascular diseases. However, the NADPH oxidase activity in severe mitral regurgitation patients with and without atrial fibrillation has not yet been explored. METHODS This study involved 16 adult patients (eight patients with persistent atrial fibrillation and eight with sinus rhythm) with severe mitral and moderate-to-severe tricuspid regurgitation and five control patients without mitral and tricuspid disease. Atrial tissues of the right and left atrial appendages were obtained during surgery. Superoxide anion production was measured by lucigenin-enhanced chemiluminescence, and the expression of nox2 containing NADPH oxidase mRNA was measured by quantitative real-time RT-PCR. Additionally, immunohistochemical study was performed. RESULTS NADPH-stimulated superoxide release was significantly higher than basal superoxide production from right [5671.9±3498.7 vs. 232.7±70.0 relative light units per second per milligram of protein (RLU s(-1) mg protein(-1)), P=.008) and left atrial homogenates (6475.1±1890.8 vs. 229.0±79.6 RLU s(-1) mg protein(-1), P=.008) in atrial fibrillation patients. The NADPH-stimulated superoxide release from right atrial homogenates was also significantly higher than basal superoxide production in sinus patients (6809.1±1327.1 vs. 244.2±65.5 RLU s(-1) mg protein(-1), P=.008). Additionally, there was a borderline significant correlation between NADPH-stimulated superoxide production from left atrial homogenates and left atrial sizes (r=0.683, P=.062) in atrial fibrillation patients. Membrane-bound nox2 containing NADPH oxidase mRNA expression was increased and was similar in both the atrial fibrillation patients and sinus patients. The NADPH-stimulated superoxide production in right atrial homogenates in control atrial samples was 1863.7±137.2 RLU s(-1) mg protein(-1). Immunohistochemical study demonstrated increased expression of nox2 in myocytes with moderate-to-severe myolysis and hypertrophy. CONCLUSIONS Results of this study demonstrate that membrane-bound nox2 containing NADPH oxidase activity and expression in the atrial myocardium is increased in patients with severe mitral regurgitation, possibly contributing to atrial remodeling in this clinical setting.

Autophagy as a mechanism for myolysis of cardiomyocytes in mitral regurgitation

Eur J Clin Invest 2011; 41 (3): 299–307

Dedifferentiation of atrial cardiomyocytes in cardiac valve disease: unrelated to atrial fibrillation.

BACKGROUND Valvular heart disease has become an important public health concern. The increased wall stress and underlying disease entity associated with mitral valve disease provide unfavorable circumstances for atrial cardiomyocytes. The expression of the alpha-smooth muscle actin isoform is considered characteristic of cardiomyocyte dedifferentiation (embryonic cardiomyocyte), and cardiomyocyte dedifferentiation may indicate an adaptive state, enabling cardiomyocytes to survive despite unfavorable circumstances. METHODS This study comprised 20 adult patients with symptomatic severe mitral valve disease and moderate to severe tricuspid valve disease and without coronary artery disease undergoing valve operations for congestive heart failure. Ten patients had persistent atrial fibrillation and 10 patients had never been in atrial fibrillation by history and electrocardiograms before surgery. Atrial tissues of the right atrial appendage were obtained during surgery. RESULTS Immunohistochemical study demonstrated that alpha-smooth muscle actin protein expression was not altered by atrial fibrillation, and alpha-smooth muscle actin protein expression in atrial tissues was higher in patients with sinus rhythm than in those with atrial fibrillation (the percentage of cells that were alpha-smooth muscle actin-positive was 51.5+/-34.9% for right atria from patients in sinus rhythm vs. 16.2+/-15.0% for right atria from patients with atrial fibrillation) (P<.03). Semiquantitation of alpha-smooth muscle actin by immunoblotting of extracts from atrial tissues showed similar findings as in the immunohistochemical observations: that is, atrial fibrillation did not influence the expression of alpha-smooth muscle actin protein. Interstitial fibrosis represented 43.2+/-13.9% of the right atrial tissue in the sinus group, whereas interstitial fibrosis comprised 49.8+/-8.2% of the right atrial tissue in the atrial fibrillation group (P=.320). CONCLUSIONS Dedifferentiation of atrial cardiomyocytes occurs in patients with cardiac valve disease, even without atrial fibrillation.

DNA repair in TUNEL-positive atrial cardiomyocytes of mitral and tricuspid valve diseases: Potential mechanism for preserving cardiomyocytes

BACKGROUND The reported presence of DNA breaks, based on a positive reaction to the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end-labelling (TUNEL) assay, in fibrillating human right atria of cardiac valve disease may suggest apoptotic myocyte death. However, TUNEL positivity may reflect conditions other than cell death. METHODS This study comprised 27 adult patients (14 patients with persistent atrial fibrillation and 13 in sinus rhythm) with significant mitral and tricuspid valve diseases. Atrial tissues were obtained during surgery. RESULTS Immunohistochemical study demonstrated that 31.1±12.2% of the myocytes had TUNEL-positive nuclei in the fibrillating right atria whereas 37.4±23.2% of the myocytes had TUNEL-positive nuclei in the right atrial myocardium in sinus rhythm (p=0.505). However, most nuclei of TUNEL-positive myocytes in the right atria also expressed proliferating cell nuclear antigen (PCNA), an indicator of DNA replication and repair but never Ki-67, a replication-associated antigen (TUNEL(+)/PCNA(+) vs. TUNEL(+)/PCNA(-), 30.5±10.8% vs. 1.2±1.5%, p=0.005, in the atrial fibrillation group and 32.8±18.6% vs. 4.6±8.1%, p=0.003, in the sinus group), suggesting that most TUNEL-positive myocytes were undergoing DNA repair. In addition, the incidence of TUNEL-positive myocytes significantly and positively correlated with the incidence of PCNA-positive myocytes (r=0.5, p<0.03 in the right atria; r=0.661, p<0.04 in the left atria). CONCLUSIONS Cell death by apoptosis occurs in a small percentage of atrial cardiomyocytes in mitral and tricuspid valve diseases and DNA repair is more important and preserves the cardiomyocytes.

Relationship of the percentage of circulating endothelial progenitor cell to the severity of coronary artery disease

Previous study demonstrated that the percentage of circulating endothelial progenitor cells was reduced in patients with coronary artery disease. However, the relationship of the percentage of circulating endothelial progenitor cells to the severity of coronary artery disease has not been investigated. The percentages of circulating endothelial progenitor cells were measured in 78 consecutive patients with unstable angina, as well as in 32 healthy volunteers. Dual-stained cells expressing CD34 and vascular endothelial growth factor receptor-2 were judged to be endothelial progenitor cells and were analyzed using flow cytometry. On stepwise multiple linear regression analysis, the percentages of circulating endothelial progenitor cells were independently decreased in patients with unstable coronary artery disease compared with those in the healthy volunteers (P < 0.05). Among patients with unstable coronary artery disease, the percentage of patients with at least one occluded vessel was significantly higher in patients with multi-vessel disease than in patients with single-vessel disease (P < 0.04). On stepwise multiple linear regression analysis, the percentages of circulating endothelial progenitor cells were independently decreased in patients with multi-vessel coronary artery disease compared with those in patients with single-vessel coronary artery disease (P < 0.03). Among patients with unstable coronary artery disease, the percentage of circulating endothelial progenitor cells was significantly related to the severity of coronary artery disease.

Increased serum oxidative stress in patients with severe mitral regurgitation: A new finding and potential mechanism for atrial enlargement

OBJECTIVE The aim of this study was to examine the serum oxidative stress in patients with severe mitral regurgitation. DESIGN AND METHODS This study analyzed serum oxidative stress index in patients with severe mitral regurgitation [persistent atrial fibrillation (AF) or sinus rhythm], paroxysmal lone AF patients and healthy subjects. RESULTS The serum oxidative stress index was significantly higher in the mitral regurgitation AF group and sinus group than in the lone AF group and healthy subjects (p<0.0001). Left atrial size was significantly larger in the mitral regurgitation AF group and sinus group than in the lone AF group and healthy subjects (p<0.0001). The oxidative stress index significantly and positively correlated with left atrial size in the overall study population (r=0.439, p=0.0008). CONCLUSIONS This study provides new evidence of increased oxidative stress in human severe mitral regurgitation, probably contributing to atrial enlargement.

Right Ventricular Outflow Tract Pacing Causes Intraventricular Dyssynchrony in Patients With Sick Sinus Syndrome: A Real-Time Three-Dimensional Echocardiographic Study

BACKGROUND The optimal right ventricular pacing site remains controversial. The aim of this study was to assess how acute right ventricular outflow tract (RVOT) pacing affects global left ventricular function and intraventricular dyssynchrony of the left ventricle. METHODS Thirty-six patients with sick sinus syndrome and intact intrinsic atrioventricular conduction were enrolled. All patients underwent dual-chamber permanent pacemaker implantation, with the atrial lead placed in the right atrial appendage and the right ventricle lead positioned at the septal site of the RVOT. Chamber size, dyssynchrony index, myocardial performance index, and global left ventricular ejection fraction were determined using transthoracic two-dimensional echocardiography, tissue Doppler echocardiography, and real-time three-dimensional echocardiography. RESULTS RVOT pacing increased the myocardial performance index (0.42 +/- 0.21 with RVOT pacing vs 0.35 +/- 0.21 without RVOT pacing, P = .002) and decreased the global left ventricular ejection fraction on real-time 3-dimensional echocardiography (51.4 +/- 6.2% with RVOT pacing vs 55.9 +/- 7.1% without RVOT pacing, P = .001). Intraventricular dyssynchrony of the left ventricle induced by RVOT pacing was determined by increased septal-to-posterior wall motion delay (69.7 +/- 54.0 ms with RVOT pacing vs 22.8 +/- 22.3 ms without RVOT pacing, P < .0001), increased systolic and diastolic dyssynchrony by tissue Doppler echocardiography, and increased systolic dyssynchrony index when assessed using real-time three-dimensional echocardiography (5.56 +/- 1.74% with RVOT pacing vs 4.05 +/- 1.61% without RVOT pacing, P < .0001). CONCLUSION Acute RVOT pacing adversely affects left ventricular function and increases intraventricular dyssynchrony in patients with sick sinus syndrome.

Influence and predicting variables of obstructive sleep apnea on cardiac function and remodeling in patients without congestive heart failure.

STUDY OBJECTIVE Obstructive sleep apnea syndrome (OSAS) has been considered to be an important predisposing factor for cardiovascular disease. This study aims to investigate the impact of OSAS on cardiac function and remodeling in patients without congestive heart failure. METHODS A total of 79 patients with sleep disordered breathing, preserved systolic function, and normal pro-brain natriuretic peptide level were enrolled. Sixty-five patients were classified to have moderate to severe OSAS (apnea-hypopnea index [AHI] ≥ 15/h), while the other 14 patients with mild or no OSAS (AHI < 15/h) served as control subjects. Baseline clinical and polysomnographic variables as well as tissue Doppler imaging and three-dimensional echocardiographic parameters were obtained. RESULTS The body mass index, neck circumference, Epworth Sleepiness Scale, desaturation index, arousal index, and snoring index were significantly higher in patients with moderate to severe OSAS than those without (p < 0.05). The left atrial size, mitral A-wave velocity, and left ventricular end-diastolic volume were significantly larger, while E/A ratio was lower in patients with moderate to severe OSAS than those without (p < 0.05). Notably, AHI in REM sleep was significantly correlated with the aortic root size, E/A ratio, left ventricular volume, and stroke volume. In addition, the area under the receiver operator characteristic curve for AHI in REM sleep ≥ 32.3/h was 0.647 (95% CI [0.525, 0.769]) in predicting the development of left ventricular diastolic dysfunction. AHI in REM sleep ≥ 32.3/h was the only independent variant in predicting diastolic dysfunction after adjusting the variables including age, gender, hypertension, and body mass index. CONCLUSIONS Patients with moderate to severe OSAS tend to have cardiac dysfunction revealed by echocardiography. High AHI in REM sleep is significantly associated with cardiovascular remodeling and ventricular diastolic dysfunction, and may be a potential variable to predict cardiac dysfunction.

Atrial enlargement in symptomatic heart block patients with preserved left ventricular function: Possibly related to atrioventricular dyssynchrony

BACKGROUND Right ventricular apical pacing may possibly induce atrial dilatation as a consequence of atrioventricular dyssynchrony. However, atrial enlargement associated with atrioventricular dyssynchrony due to atrioventricular block has never been studied. METHODS This case-control survey involved 90 patients with symptomatic atrioventricular block [29 patients with Mobitz type 2 atrioventricular block, 22 patients with high degree of atrioventricular block and 39 patients with complete atrioventricular block]. The control group comprised 54 age- and sex-matched patients with sick sinus syndrome and intact intrinsic atrioventricular conduction. The M-mode measurements were obtained before implant and the left and right atrial areas were measured by planimetry. RESULTS The peri-implant right atrial area (17.4±3.7 vs. 15.3±3.4 cm2, p=0.002), left atrial area (24.9±4.2 vs. 21.0±3.7 cm2, p<0.001) and left atrial diameter (36.4±5.5 vs. 33.3±4.8 mm, p=0.001) were significantly greater in atrioventricular block patients than in sick sinus syndrome patients. The two groups had similar left ventricular ejection fraction. The right atrial area (p=0.01) and left atrial area (p=0.006) remained significantly greater in atrioventricular block patients than in sick sinus syndrome patients after adjustments for age, gender, body surface area, left ventricular dimension and left ventricular ejection fraction in multiple logistic regression analysis. CONCLUSIONS Atrial enlargement occurs in patients with symptomatic atrioventricular block. This phenomenon is possibly related to atrioventricular dyssynchrony.

Expression of spliceosome assembly factor SC-35 in TUNEL-positive atrial cardiomyocytes in mitral and tricuspid regurgitation: viability of atrial cardiomyocytes.

BACKGROUND Most of the atrial cardiomyocytes with positive terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end-labelling (TUNEL) reaction are not apoptotic in patients with mitral and tricuspid valve diseases. The TUNEL-positive myocytes with expression of spliceosome assembly factor SC-35, an indicator of increased RNA synthesis, should be living cardiomyocytes. METHODS This study analyzed twenty-three patients with significant mitral and tricuspid regurgitation. Fifteen patients had persistent atrial fibrillation, and eight had sinus rhythm. Atrial appendageal tissues were obtained during surgery. Immunohistochemical study was performed. RESULTS Immunohistochemical study of fibrillating right atrial myocardium demonstrated that 44.8 ± 24.6% of myocytes had TUNEL-positive nuclei whereas 39.4 ± 21.4% of myocytes had TUNEL-positive nuclei in sinus right atrial myocardium (p=0.682). However, most (81.6%) nuclei of TUNEL-positive myocytes in the fibrillating right atria also expressed proliferating cell nuclear antigen (PCNA), an indicator of DNA replication and repair, and most nuclei (91.8%) of TUNEL-positive myocytes also expressed SC-35. In fibrillating left atria, most (88.1%) nuclei of TUNEL-positive myocytes also expressed SC-35. Similarly, in sinus right atrial myocardium, most (78.0%) nuclei of TUNEL-positive myocytes expressed PCNA, and most (91.4%) nuclei of TUNEL-positive myocytes also expressed SC-35, but none expressed Ki-67, a replication-associated antigen. Additionally, the percentage of TUNEL-positive myocytes in the right atria significantly and positively correlated with the percentage of PCNA-positive myocytes (r=0.826, p<0.001) and SC-35 positive myocytes (r=0.713, p<0.001). CONCLUSIONS Most TUNEL-positive atrial cardiomyocytes in patients with mitral and tricuspid regurgitation are living cardiomyocytes.