Prolonged P-wave duration has been observed in diabetes. However, the underlying mechanisms remain unclear. The aim of this study was to elucidate the possible mechanisms. A rat model of type 2 diabetes mellitus (T2DM) was used. P-wave durations were obtained using surface electrocardiography and sizes of the left atrium were determined using echocardiography. Cardiac inward rectifier K+ currents (I(k1)), Na+ currents (I(Na)), and action potentials were recorded from isolated left atrial myocytes using patch clamp techniques. Left atrial tissue specimens were analyzed for total connexin-40 (Cx40) and connexin-43 (Cx43) expression levels on western-blots. Specimens were also analyzed for Cx40 and Cx43 distribution and interstitial fibrosis by immunofluorescent and Masson trichrome staining, respectively. The mean P-wave duration was longer in T2DM rats than in controls; however, the mean left atrial sizes of each group of rats were similar. The densities of I(k1) and I(Na) were unchanged in T2DM rats compared to controls. The action potential duration was longer in T2DM rats, but there was no significant difference in resting membrane potential or action potential amplitude compared to controls. The expression level of Cx40 protein was significantly lower, but Cx43 was unaltered in T2DM rats. However, immunofluorescent labeling of Cx43 showed a significantly enhanced lateralization. Staining showed interstitial fibrosis was greater in T2DM atrial tissue. Prolonged P-wave duration is not dependent on the left atrial size in rats with T2DM. Dysregulation of Cx40 and Cx43 protein expression, as well as fibrosis, might partly account for the prolongation of P-wave duration in T2DM.
Action Potentials ; Animals ; Blotting, Western ; Connexin 43/metabolism ; Connexins/metabolism ; Diabetes Mellitus, Type 2/*physiopathology ; Disease Models, Animal ; Echocardiography ; Electrocardiography ; Fibrosis/pathology ; Heart Atria/*diagnostic imaging/physiopathology ; In Vitro Techniques ; Male ; Membrane Potentials ; Microscopy, Fluorescence ; Patch-Clamp Techniques ; Potassium Channels/metabolism ; Rats ; Rats, Wistar

Swelling-activated chloride currents (ICl.swell) are thought to play a role in several physiologic and pathophysiologic processes and thus represent a target for therapeutic approaches. However, the mechanism of ICl.swell regulation remains unclear. In this study, we used the whole-cell patch-clamp technique to examine the role of protein kinase C (PKC) in the regulation of ICl.swell in human atrial myocytes. Atrial myocytes were isolated from the right atrial appendages of patients undergoing coronary artery bypass and enzymatically dissociated. ICl.swell was evoked in hypotonic solution and recorded using the whole-cell patch-clamp technique. The PKC agonist phorbol dibutyrate (PDBu) enhanced ICl.swell in a concentration-dependent manner, which was reversed in isotonic solution and by a chloride current inhibitor, 9-anthracenecarboxylicacid. Furthermore, the PKC inhibitor bis-indolylmaleimide attenuated the effect and 4α-PDBu, an inactive PDBu analog, had no effect on ICl.swell. These results, obtained using the whole-cell patch-clamp technique, demonstrate the ability of PKC to activate ICl,swell in human atrial myocytes. This observation was consistent with a previous study using a single-channel patch-clamp technique, but differed from some findings in other species.
Anthracenes ; pharmacology ; Chloride Channels ; metabolism ; Chlorides ; agonists ; antagonists & inhibitors ; metabolism ; Culture Media ; metabolism ; pharmacology ; Dose-Response Relationship, Drug ; Evoked Potentials ; drug effects ; physiology ; Heart Atria ; cytology ; drug effects ; metabolism ; Humans ; Hypotonic Solutions ; metabolism ; pharmacology ; Indoles ; pharmacology ; Ion Transport ; drug effects ; Maleimides ; pharmacology ; Myocytes, Cardiac ; cytology ; drug effects ; metabolism ; Patch-Clamp Techniques ; Phorbol 12,13-Dibutyrate ; pharmacology ; Primary Cell Culture ; Protein Kinase C ; metabolism

OBJECTIVESK channels are existed in hearts of mouse, rat, and human. Biochemical evidence indicates that SK2 channels are expressed more in atrial than in ventricular tissue. SK channels are highly sensitive to the calcium concentration of the pipette solution. In the present study, performed whole-cell patch clamp was used to detect the calcium sensitivity of small conductance Ca(2+)-activated K+ channels (SK) currents between sinus ryhthm (SR) and auricular fibrillation (AF).

METHODSThe patients who accepted cardiopulmonary bypass were divided into two groups: 21 patients with SR and 8 patients with AF. The enzymatic dissociation method was improved according to the previous research by our lab. The performed whole cell patch-clamp technique was used to record SK2 currents in both SR and AF groups at room temperature.

RESULTSThe SK2 current density was (-2.92 +/- 0.35) pA/pF in SR group (n = 6) vs (-6.83 +/- 0.19) pA/pF in AF group at -130 mV (n = 3, P < 0.05). In SR group, the SK2 current densities in calcium concentration of the pipette solution are (-1.43 +/- 0.33) pA/pF (n = 7), (-2.92 +/- 0.35) pA/pF (n = 6), (-10.11 +/- 2.15) pA/pF (n = 8, P < 0.05); In AF group, the SK2 current densities are (-2.17 +/- 0.40) pA/pF (n = 4), (-6.83 +/- 0.19) pA/pF (n = 3), (-14.47 +/- 2.89 pA/pF) (n = 4, P < 0.05).

CONCLUSIONThe SK2 currents recorded in this experiment are voltage-independent, inwardly rectifying and apamin-sensitive. When the calcium concentration of the pipette solution is 5 x 10(-7) mol/L, SK2 current density in AF group are significantly larger than those in SR group. It suggests that SK currents involve the cardiomyocytes electric remodeling in AF. In AF group, the SK2 currents are more sensitive to free calcium ion. It shows that the increased sensitivity of SK2 currents to the calcium contribute to the occurrence and maintenance of AF.

Atrial Fibrillation ; metabolism ; physiopathology ; Calcium ; metabolism ; Cells, Cultured ; Heart Atria ; metabolism ; Humans ; Membrane Potentials ; physiology ; Myocytes, Cardiac ; metabolism ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; physiology

OBJECTIVETo observe the effect of sodium tanshinone II (A) sulfonate (STS) on Ang II -induced atrial fibroblast collagen synthesis and TGF-beta1 activation.

METHODAtrial fibroblasts of neonatal rats were cultured to determine the content of collagen protein. The original synthesis rate determined by the [3H]-proline incorporation method was taken as the index for myocardial fibrosis. The content of active TGF-beta1 and total TGF-beta1 in cell culture supernatants were tested and cultured by ELISA. The expression of thrombospondin-1 (TSP-1) was assessed by using Western blot.

RESULTAng II could significantly increase the content of atrial fibroblast collagen and the collagen synthesis rate, the TSP-1 expression and the concentration of active TGF-beta1, without any obvious change in total TGF-beta1. After the STS treatment, all of the indexes, apart from total TGF-beta1, were obviously down-regulated.

CONCLUSIONSTS could decrease the secretion of Ang II -induced atrial fibroblast collagen and the synthesis rate. Its mechanism is related to the inhibition of TSP-1/TGF-beta1 pathway.

Angiotensin II ; pharmacology ; Animals ; Collagen ; biosynthesis ; Fibroblasts ; cytology ; drug effects ; metabolism ; Gene Expression Regulation ; drug effects ; Heart Atria ; cytology ; Phenanthrenes ; pharmacology ; Rats ; Rats, Wistar ; Signal Transduction ; drug effects ; Thrombospondin 1 ; metabolism ; Transforming Growth Factor beta1 ; metabolism

BACKGROUNDIt has been reported that endogenous or exogenous hydrogen sulfide (H(2)S) exerts physiological effects in the vertebrate cardiovascular system. We have also demonstrated that H(2)S acts as an important regulator of electrophysiological properties in guinea pig papillary muscles and on pacemaker cells in sinoatrial nodes of rabbits. This study was to observe the electrophysiological effects of H(2)S on human atrial fibers.

METHODSHuman atrial samples were collected during cardiac surgery. Parameters of action potential in human atrial specialized fibers were recorded using a standard intracellular microelectrode technique.

RESULTSNaHS (H(2)S donor) (50, 100 and 200 µmol/L) decreased the amplitude of action potential (APA), maximal rate of depolarization (V(max)), velocity of diastolic (phase 4) depolarization (VDD) and rate of pacemaker firing (RPF), and shortened the duration of 90% repolarization (APD(90)) in a concentration-dependent manner. ATP-sensitive K(+) (K(ATP)) channel blocker glibenclamide (Gli, 20 µmol/L) partially blocked the effects of NaHS (100 µmol/L) on human atrial fiber cells. The L-type Ca(2+) channel agonist Bay K8644 (0.5 µmol/L) also partially blocked the effects of NaHS (100 µmol/L). An inhibitor of cystathionine γ-lyase (CSE), DL-propargylglycine (PPG, 200 µmol/L), increased APA, V(max), VDD and RPF, and prolonged APD(90).

CONCLUSIONSH(2)S exerts a negative chronotropic action and accelerates the repolarization of human atrial specialized fibers, possibly as a result of increases in potassium efflux through the opening of K(ATP) channels and a concomitant decrease in calcium influx. Endogenous H(2)S may be generated by CSE and act as an important regulator of electrophysiological properties in human atrial fibers.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; pharmacology ; Action Potentials ; drug effects ; Calcium Channel Agonists ; pharmacology ; Calcium Channels, L-Type ; metabolism ; Cystathionine gamma-Lyase ; metabolism ; Electrophysiology ; methods ; Glyburide ; pharmacology ; Heart Atria ; drug effects ; metabolism ; Humans ; Hydrogen Sulfide ; metabolism ; In Vitro Techniques ; KATP Channels ; antagonists & inhibitors ; metabolism ; Sulfides ; pharmacology

OBJECTIVETo assess the changes of serum C-reactive protein (CRP) level, left atrial size and atrial premature contraction (PAC) in patients with obstructive sleep apnea syndrome (OSAS).

METHODSThis study involved 277 patients with OSAS diagnosed after an overnight polysomnography, who underwent a 24-h Holter electrocardiography and ambulatory blood pressure monitoring for detection of PAC. According to the apnea-hypopnea index (AHI), 137 patients with PAC identified from these patients were classified into 3 groups, namely the mild (5≥AHI<15), moderate (15≥AHI<30) and severe (AHI≥30) groups. Serum CRP level was assessed by a high-sensitivity radio-immunoassay. The left atrial diameter and echocardiographic parameters were recorded by transthoracic Doppler echocardiography (TTE).

RESULTSWe found a high prevalence of PAC in these OSAS patients (137/277, 49.4%). Serum CRP was significantly higher in severe OSAS group (5.01∓4.68 mg/L) than in the moderate (3.03∓1.94 mg/L) and mild OSAS (2.98∓1.82 mg/L) groups (P=0.040 and 0.033, respectively). The left atrial diameter was significantly increased in severe OSAS group (40.1∓7.9 mm) as compared to that in moderate (37.9∓5.5 mm) and mild (33.7 ∓ 3.8 mm) groups (P=0.025 and 0.002, respectively). The severity of OSAS was positively correlated to both CRP (r=0.304, P=0.034) and left atrial diameter (r=0.411, P=0.003). After adjusting for gender, age and body mass index (BMI), a strong correlation was found between the left atrial diameter and CRP (r=0.594, P=0.0005).

CONCLUSIONThere is a high prevalence of PAC in OSAS patients. The progression of OSAS is associated with increased serum CRP level and left atrial size in patients with premature atrial complexes. Our study suggests that inflammation associated with OSAS might contribute to atrial structural and electrical remodeling in OSAS patients with PAC.

Adult ; Aged ; Atrial Premature Complexes ; complications ; pathology ; C-Reactive Protein ; metabolism ; Electrocardiography ; Female ; Heart Atria ; pathology ; Humans ; Male ; Middle Aged ; Polysomnography ; Prevalence ; Sleep Apnea Syndromes ; blood ; complications

BACKGROUNDTumor necrosis factor-alpha (TNF-α) is a pleiotropic proinflammatory cytokine and contributes to many kinds of cardiovascular diseases via its receptors (TNFR1/TNFR2). We hypothesize that TNF-α plays a role in the pathogenesis of chronic atrial fibrillation (AF).

METHODSSixty-seven consecutive patients who were scheduled to have cardiac surgery were enrolled into the study. Thirty-one patients with rheumatic heart disease (RHD) and AF were enrolled as study group (AF group). The sinus rhythm (SR) control groups consisted of 20 patients with RHD and 16 patients with coronary artery disease (CAD). Peripheral blood sample was collected before the operation. About 5 mm(3) left atrial tissue was disserted during the operation and was separated into three parts for Western blotting, real time polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) analysis.

RESULTSCompared with the controls (RHD SR and CAD SR), the levels of TNF-α ((14.40 ± 5.45) pg/ml vs. (4.20 ± 3.19) pg/ml vs. (2.68 ± 2.20) pg/ml, P = 0.000) and its soluble receptor 1 (sTNFR1) ((1623.9 ± 558.6) pg/ml vs. (1222.3 ± 175.6) pg/ml vs. (1387.5 ± 362.2) pg/ml, P = 0.001) in plasma were higher in patients with AF. TNF-α level had positive correlation with the left atrial diameter (LAD) (r = 0.642, P = 0.000). Western blotting analysis showed that the protein levels of TNF-α (0.618 ± 0.236 vs. 0.234 ± 0.178 vs. 0.180 ± 0.103, P = 0.000) were higher in patients with AF. The RT-PCR analysis results demonstrated that the mRNA expression of TNF-α (0.103 ± 0.047 vs. 0.031 ± 0.027 vs. 0.023 ± 0.018, P = 0.000) increased in patients with AF. IHC analysis displayed that, comparing to the SR, the expression of TNF-α (0.125 ± 0.025 vs. 0.080 ± 0.027 vs. 0.070 ± 0.023, P = 0.000) increased in the AF group. The protein level and mRNA expression of TNF-α also had positive correlation with left atrium diameter (LAD) (r = 0.415, P = 0.000 and r = 0.499, P = 0.000).

CONCLUSIONSThe results revealed that TNF-α elevated in the plasma and left atrial tissue and had positive correlation with LAD in patients of chronic AF. TNF-α might involve in the pathogenesis of chronic AF.

Aged ; Atrial Fibrillation ; blood ; metabolism ; Blotting, Western ; Female ; Heart Atria ; metabolism ; Humans ; Immunohistochemistry ; Male ; Middle Aged ; Real-Time Polymerase Chain Reaction ; Tumor Necrosis Factor-alpha ; blood ; genetics ; metabolism

OBJECTIVESTo investigate the relationship of the transforming growth factor beta1 (TGF-β1) mRNA expression in atrial myocardium and the effectiveness of radiofrequency Maze procedure in patients with rheumatic valvular disease (RHD) and permanent atrial fibrillation (AF).

METHODSBetween January 2008 and September 2008, 40 patients with RHD and AF underwent a radiofrequency Maze procedure with concomitant valvular surgery. The patients were assigned to normal sinus rhythm (SR) group (group A) and persistence AF group (group B) according to the results of the 6-month follow-up. Another 10 patients with SR and RHD undergone valvular surgery alone were assigned to control group (group C). Left atrial appendage were obtained in all patients. Expressions of TGF-β1 mRNA were detected by semiquantitative RT-PCR technique. CVF-I and CVF-III were observed by sirius red staining.

RESULTSAt 6-month follow-up, there were 28 patients in group A and 12 in group B. Patients in group A and group B had higher mRNA expressions of TGF-β1, CVF-I and CVF-I/CVF-III compared with group C (P < 0.05). Also, the group B had higher mRNA expressions of TGF-β1, CVF-I and CVF-I/CVF-III than group A (P < 0.05). The patients who had return of functional atrial contraction in group A had lower mRNA expression than the non-return patients (39 ± 12 vs. 60 ± 12, P < 0.05). The TGF-β1 mRNA expression had a correlation with both the contents of CVF-I and left atrial diameter (r = 0.786, P < 0.05; r = 0.858, P < 0.05). Multiple logistic regression analysis revealed that the risk factors which independently associated with the postoperative persistence of atrial fibrillation at 6-month follow-up includes mRNA expression levels of TGF-β1 (OR = 1.13, 95%CI 1.05 - 1.18, P = 0.031), CVF-I (OR = 1.07, 95%CI 1.00 - 1.13, P = 0.037) and lett atrial diameter (OR = 2.23, 95%CI 1.08 - 4.59, P = 0.042).

CONCLUSIONSThe atrial TGF-β1 mRNA expression level could predict the persistence of AF and the return of the functional atrial contraction at 6-month follow-up in patients who underwent rheumatic valvular surgery and concomitant radiofrequency Maze procedure.

Atrial Fibrillation ; etiology ; metabolism ; surgery ; Catheter Ablation ; Follow-Up Studies ; Heart Atria ; metabolism ; Humans ; Rheumatic Heart Disease ; complications ; Transforming Growth Factor beta1 ; metabolism ; Treatment Outcome

BACKGROUNDWe hypothesize that increased atrial oxidative stress and inflammation may play an important role in atrial nerve sprouting and heterogeneous sympathetic hyperinnervation during atrial fibrillation (AF). To test the hypothesis, we examined whether the antioxidant and anti-inflammatory treatment with probucol attenuates atrial autonomic remodeling in a canine model of AF produced by prolonged rapid right atrial pacing.

METHODSTwenty-one dogs were divided into a sham-operated group, a control group and a probucol group. Dogs in the control group and probucol group underwent right atrial pacing at 400 beats per minute for 6 weeks, and those in the probucol group received probucol 1 week before rapid atrial pacing until pacing stopped. After 6-week rapid atrial pacing, general properties including left atrial structure and function, atrial hemodynamics and the inducibility and duration of AF were measured in all the groups. Atrial oxidative stress markers and serum C-reactive protein (CRP) concentration were estimated. The degree of nerve sprouting and sympathetic innervation at the right atrial anterior wall (RAAW) and the left atrial anterior wall (LAAW) were quantified by immunohistochemistry, atrial norepinephrine contents were also detected. Atrial beta-nerve growth factor (beta-NGF) mRNA and protein expression at the RAAW and LAAW were assessed by real-time quantitative RT-PCR and Western blotting respectively.

RESULTSAtrial tachypacing induced significant nerve sprouting and heterogeneous sympathetic hyperinnervation, and the magnitude of nerve sprouting and hyperinnervation was higher in the RAAW than in the LAAW. Atrial beta-NGF mRNA and protein levels were significantly increased at the RAAW and LAAW, and the upregulation of beta-NGF expression was greater at the RAAW than at the LAAW in the control group. The beta-NGF protein level was positively correlated with the density of sympathetic nerves in all groups. Probucol decreased the increase of CRP concentration and attenuated atrial oxidative stress caused by atrial tachypacing. In addition, probucol could effectively inhibit atrial beta-NGF upregulation, significantly attenuate atrial nerve sprouting and heterogeneous sympathetic hyperinnervation, and dramatically reduce the inducibility and duration of AF.

CONCLUSIONSThe atrial over-expression of beta-NGF possibly caused by increased oxidative stress and inflammation may be the main mechanism underlying atrial autonomic remodeling during AF. Probucol attenuates atrial autonomic remodeling possibly by its antioxidant and anti-inflammatory actions.

Animals ; Antioxidants ; therapeutic use ; Atrial Fibrillation ; drug therapy ; Blotting, Western ; C-Reactive Protein ; metabolism ; Cardiac Pacing, Artificial ; adverse effects ; Disease Models, Animal ; Dogs ; Electrocardiography ; Female ; Heart Atria ; Immunohistochemistry ; Male ; Nerve Growth Factor ; genetics ; metabolism ; Norepinephrine ; metabolism ; Probucol ; therapeutic use ; Reverse Transcriptase Polymerase Chain Reaction

Animals ; Atrial Fibrillation ; drug therapy ; Dogs ; Female ; Heart Atria ; drug effects ; ultrastructure ; Male ; Malondialdehyde ; metabolism ; Microscopy, Electron, Transmission ; Platelet Activation ; drug effects ; Trimetazidine ; pharmacology ; therapeutic use ; Vasodilator Agents ; pharmacology ; therapeutic use