lncRNA GAS5 regulates myocardial infarction by targeting the miR-525-5p/CALM2 axis.

Long noncoding RNAs (lncRNAs) play critical roles in the pathogenesis of cardiovascular diseases, especially in myocardial infarction (MI). However, the underlying molecular mechanism of how lncRNA involves and affect MI still remains unclear. This study aimed to investigate the expression of lncRNA growth arrest-specific transcript 5 (GAS5) and its effects on myocardial cells' proliferation, cell cycle, and apoptosis. The possible mechanisms involved in GAS5, calmodulin 2 (CALM2), and microRNA (miR)-525-5p were also explored. The messenger RNA (mRNA) level of CALM2, GAS5, and miR-525-5p in postmyocardial infarction (MI) and normal cells were examined by quantitative real-time polymerase chain reaction (RT-qPCR). Western blot analysis assay was conducted to detect the protein levels of CALM2. The changes of cell cycle/apoptosis and cell viability of post-MI myocardial cells (PMMC) were determined by flow cytometry analysis and MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay after knockdown of GAS5 or CALM2, respectively. Dual luciferase reporter assay and RNA-binding protein immunoprecipitation (RIP) assay were performed to verify the targeting relationship between miR-525-5p and GAS5, CALM2 in myocardial. Hypoxic preconditioning was performed in normal cells, which constructed a simulated MI environment, and the effect of GAS5 on cardiomyocyte apoptosis was detected. Our data showed that the expression of GAS5 and CALM2 in PMMC was significantly upregulated, while the expression of miR-525-5p was downregulated. Overexpression of GAS5 and CALM2 profoundly promoted the apoptosis of myocardial cell. However, the proliferation of myocardial cell was inhibited by the upregulation of GAS5 and CALM2. Moreover, GAS5 was proved to be the target of miR-525-5p and GAS5 downregulated the expression of miR-525-5p and CALM2. In addition, lncRNA GAS5 promotes MI, while CALM2 induced MI can be reversed by miR-525-5p. These data suggested that lncRNA GAS5 promoted the development and progression of MI via targeting of the miR-525-5p/CALM2 axis and it has the potential to be explored as a therapeutic target for the treatment of MI in the future.

Fluctuation correlation spectroscopy and its applications in homogeneous analysis.

Fluctuation correlation spectroscopy (FCS) is a single-molecule/particle detection technique based on measuring signal fluctuations in a highly focused detection volume. Multiple-parameter information can be obtained from the FCS measurement including the amplitude, characteristic diffusion time of correlation curve, and brightness of the adopted probes. The multiple-parameter change is related with physical or chemical change occurring in the probes. Meanwhile, the detection method has advantages such as short sample time in seconds, sample volume with low limit in femtoliters, and mixing to detection without any separations. These advantages make the FCS technique suitable for homogeneous analysis. In this review, we summarized recent novel applications of FCS and its variants in homogeneous analysis including nucleic acid analysis, protein analysis, enzyme activity assay, direct characterization of nanoparticles in solution, and others. Graphical abstract.

Autonomic Remodeling: How Atrial Fibrillation Begets Atrial Fibrillation in the First 24 Hours.

BACKGROUND: The mechanism(s) of how atrial fibrillation (AF) sustains itself in the first 24 hours is not well understood. OBJECTIVE: We sought to investigate the role of autonomic remodeling in the first 24 hours of AF simulated by rapid atrial pacing (RAP). METHODS: Forty-eight rabbits were divided into 6 groups. One group (n = 8) was euthanized after baseline recordings. Another group (n = 8) did not receive RAP during the 24-hour period to serve as controls. In the other 4 groups, rabbits were euthanized after RAP for 4, 8, 12, or 24 hours (n = 8 for each). Before and after designated hours of RAP, atrial effective refractory period, heart rate variability, and left vagal and sympathetic nerve activity (VNA and SNA, respectively) were determined. The right and left atrial tissues were obtained for immunocytochemical analysis for growth-associated protein 43 (GAP43), tyrosine hydroxylase (TH), and choline acetyltransferase (ChAT). RESULTS: RAP resulted in progressively shortened atrial effective refractory period and slower heart rate. In the first 12 hours of RAP, both SNA and VNA progressively increased. Then, VNA remained stably elevated but SNA began to attenuate. The high-frequency component and low-frequency/high-frequency ratio of heart rate variability followed the trend of VNA and SNA, respectively. The density of GAP43-positive, ChAT-positive, and TH-positive neural elements in the right and left atria was progressively higher with RAP. CONCLUSIONS: AF resulted in progressive autonomic remodeling, manifesting as nerve sprouting, sympathetic and vagal hyperinnervation. Autonomic remodeling may play an important role in sustaining AF in the first 24 hours.

Effect of interconnection between cervical vagus trunk, epicardial fat pad on sinus node function, and atrial fibrillation.

BACKGROUND: The epicardial fat pad (FP) integrates the autonomic innervation between the extrinsic and intrinsic cardiac autonomic nervous system and affects atrial electrophysiology and pathophysiology. METHODS: Eighteen dogs were divided into two groups: sequential ablation of sinoatrial node FP (SAN-FP) and atrioventricular node FP (AVN-FP). Sinus rate (SR), atrial fibrillation (AF) inducibility, and effective refractory period (ERP) changes during electrical stimulation of the vagus trunk were detected before and after ablation. RESULTS: In the SAN-FP group, the SR slowing, increasing AF inducibility, and ERP shortening that induced by vagus trunk stimulation were significantly attenuated by isolated SAN-FP ablation, compared with the same group prior to ablation (all P < 0.05). Subsequent AVN-FP ablation following SAN-FP ablation almost cannot produce further attenuation during vagus trunk stimulation, compared with isolated SAN-FP ablation (P > 0.05). In the AVN-FP group, SR slowing, increasing AF inducibility, and ERP shortening that induced by vagus trunk stimulation were completely eliminated by isolated AVN-FP ablation, compared with the same group prior to ablation (all P < 0.05). Subsequent SAN-FP ablation following AVN-FP ablation produced no further attenuation, compared with isolated AVN-FP ablation (P > 0.05). CONCLUSIONS: A neural pathway from the cervical vagus trunk to the sinus node and atrium runs through the SAN-FP, but eventually converges at the AVN-FP and also suggested that the AVN-FP serves as an "integration center" for the SAN-FP to modulate sinus node function. The AVN-FP may play a more critical role in the initiation and maintenance of AF.

The effects of subclinical hypothyroidism on serum lipid level and TLR4 expression of monocyte in peripheral blood of rats.

OBJECTIVE: To observe effect of subclinical hypothyroidism (SCH) on serum lipid level and expression of toll-like receptor 4 (TLR4) in rats' peripheral blood mononuclear cells (PBMC). METHODS: Fifty Wistar female rats were divided into three groups: normal control (NC group; n=10), sham group (n=10), and L-T-4 (L-thyroxine) group (n=30, with thyroidectomy, fed with rich-calcium water after operation. 5 weeks later, abdominal subcutaneous injection of L-T-4: 0.95 µg/100g/d). 8 weeks later, the rats were killed then the peripheral blood was collected to determine the levels of serum thyroid-stimulating hormone (TSH), total thyroid hormone (TT4), total cholesterol (TC) and low density lipoprotein cholesterin (LDL-C). Rats in L-T-4 group were divided into normal lipid (NL) group) and high lipid (HL) group) according to lipid value of NC group. Monocytes were separated from blood to determine TLR4 expression by flow cytometry. RESULTS: In NL and HL groups TSH were higher than in NC and Sham groups (p<0.05). TT4 have no significant differences (p>0.05). TLR4, TLR4 mRNA, NF-κB (p65) were increased (p<0.05). TNF-α, IL-6 and IL-1ß were higher than in NC and sham groups (p<0.01). There were no significant differences of TLR4, TLR4 mRNA, NF-κB (p65), TNF-α, IL-6 and IL-1ß expression between NL and HL groups (p>0.05). CONCLUSION: TLR4, TLR4 mRNA, NF-κB (p65) of PBMC and TNF-α, IL-6, IL-1ß expression in serum were all increased in SCH rats, which was not related to serum dyslipidemia.

Fosinoprilat alleviates lipopolysaccharide (LPS)-induced inflammation by inhibiting TLR4/NF-κB signaling in monocytes.

OBJECTIVE: To evaluate the effect of the fosinoprilat on lipopolysacharides (LPS) induced inflammation in monocytes in vitro. METHODS: Human mononuclear THP1 cells were cultured in complete medium, treated with or without LPS and different concentrations (0,0.25,0.5,1,5,and 10µmol/L) of fosinoprilat. Toll-like receptor (TLR4) mRNA expression was detected by real-time RT-PCR and TLR4 protein level on the surface of monocyte was determined by flow cytometry. Nuclear factor-kappa B (NF-κB) protein level was detected by Western blotting. Cultured supernatant of the THP1 cells in different groups were analyzed by ELISA to detect the levels of interleukin (IL)-1ß, IL-6 and tumor necrosis factor (TNF-α). RESULTS: Both the mRNA and surface protein level of the TLR4 in the THP1 cells were enhanced by the LPS treatment and down-regulated by pretreatment of the fosinoprilat. Accordingly, LPS-induced NF-κB protein was decreased by the fosinoprilat treatment. The increasing secretion of IL-1ß, IL-6 and TNF-α induced by LPS could also be attenuated by the fosinoprilat treatment. CONCLUSION: The inhibitory effect of the fosinoprilat on the TRL4/NF-κB signaling pathway reveals a potential anti-inflammatory and anti-atherosclerosis target.

Effect of the stellate ganglion on atrial fibrillation and atrial electrophysiological properties and its left-right asymmetry in a canine model.

OBJECTIVE: To investigate the effect of the stellate ganglion (SG) and its left-right asymmetry on atrial fibrillation (AF) inducibility, AF duration and atrial electrophysiological properties. METHODS: Sixteen adult mongrel dogs were randomly assigned to three groups. The control group (n=4) underwent 6 h rapid atrial pacing (RAP) only; the right SG (RSG) group (n=6) underwent 6 h RSG stimulation plus RAP; and the left SG (LSG) group (n=6) underwent 6 h LSG stimulation plus RAP. AF induction rate, AF duration, effective refractory period (ERP) and dispersion of ERP (dERP) were measured. RESULTS: In the RSG group, the induction rate of AF was significantly increased in sites in the right atrium (RA) compared with baseline (P<0.05). In the LSG group, the induction rate of AF was significantly increased (P<0.05) compared with baseline in the left atrium (LA), left superior pulmonary vein and left inferior pulmonary vein, respectively. Compared with RSG stimulation, right stellate ganglionectomy markedly decreased the AF induction rate of the RA (P<0.05). Compared with LSG stimulation, left stellate ganglionectomy markedly decreased the AF induction rate of the LA, the left superior pulmonary vein and the left inferior pulmonary vein (P<0.05). In the RSG group, the ERP was significantly shortened (P<0.05) and the dERP was significantly increased (P<0.05) in RA sites (P<0.05). The ERP was significantly shortened in the LSG group (P<0.05). The dERP was significantly increased (P<0.05) in LA and pulmonary vein sites (P<0.05). CONCLUSIONS: Unilateral electrical stimulation of the SG in combination with RAP can successfully establish a canine model of acute AF mediated by excessive sympathetic activity. SG stimulation facilitates AF induction and aggravates electrical remodelling in sites in the atrium and pulmonary vein. Inhibiting sympathetic nerve activation through unilateral stellate ganglionectomy can reduce AF initiation.

Ambient temperature and ambulatory blood pressure: An hourly-level, longitudinal panel study.

BACKGROUND: Variations of blood pressure (BP) related to air temperature have been reported previously; however, no evidence is available regarding the association of hourly ambient temperature with ambulatory blood pressure. METHODS: We conducted a longitudinal panel study among 1895 patients from an outpatient department who received repeated ambulatory blood pressure monitoring in Urumqi, China between July 2020 and December 2021. We obtained hourly ambient temperature from the nearest monitoring station to the residential address, and measured 4 ambulatory blood pressure indicators. Linear mixed-effect model combined with distributed lag models were applied to investigate the cumulative associations of hourly temperature with BP. RESULTS: A total of 97,466 valid blood pressure measurements were evaluated. We observed almost linear and monotonically decreasing relationships between temperature and blood pressure. The effects occurred in the same hour, attenuated thereafter and became insignificant approximately 36 h. A 10 °C decrease in temperature was significantly associated with increments of 0.84 mmHg in systolic blood pressure, 0.56 mmHg in diastolic blood pressure, 1.38 mmHg in mean arterial pressure, and 0.66 mmHg in pulse pressure over lag 0 to 36 h. Stronger associations were found among patients of female sex, age between 18 and 65 years, overweight or obesity, minority, less education or in the cold season, as well as those without hypertension or with coronary heart disease, or did not take anti-hypertension medication. CONCLUSION: Our study provides robust evidence that hourly ambient temperature is inversely associated with ambulatory blood pressure. It also highlights a linear relationship between decreased ambient temperature and elevated BP, which may have implications for the prevention and management of hypertension in susceptible populations.

[The changes of cardioelectrical activity of rat with myocardial infarction receiving sarcoplasmic reticulum Ca(2+)-ATPase gene modified bone marrow stem cell transplantation by microelectrode array technology].

OBJECTIVE: Therapy effects and cardiac electrical activity comparison of bone marrow stem cells (BMSCs) transplantation and sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) gene modified BMSCs transplantation after acute myocardial infarction (AMI) in rats. METHODS: Rats with AMI were divided into 4 groups (n = 30) randomly: normal group (n = 6), saline group (control group, n = 8), BMSCs transplantation group (BMSCs group, n = 8) and SERCA2a gene modified BMSCs transplantation group (BMSCs + rAd.SERCA2a group, n = 8). After 14 days, cardiac function was evaluated by echocardiography and heart electrical activity was evaluated by electrocardiogram and microelectrode array (MEA) technology. RESULTS: (1) The transduction ratio of rAd.SERCA2a to BMSCs were 80% to 90%. (2) Left ventricular ejection fraction on 14 days after therapy was significantly higher in BMSCs group and BMSCs + rAd.SERCA2a group than in control group (all P < 0.05). (3) QT duration was significantly shorter [(80.30 ± 6.53) ms vs. (105.31 ± 21.89) ms, P < 0.05] and ventricular premature beats less frequent in BMSCs + rAd. SERCA2a group than in the control group. (4) MEA results suggested that isolated heart beat was significantly slowed down and frequent ventricular arrhythmias and atrioventricular block were recorded in control group. The maximum field potential and field potential duration on infarcted myocardium area in BMSCs group and BMSCs + rAd.SERCA2a group were significantly longer than those in control group[the maximum field potential: (0.51 ± 0.15), (0.55 ± 0.16), (0.23 ± 0.10) mV; field potential duration: (104.5 ± 25.43), (107.67 ± 24.01), (63.00 ± 20.34) ms; all P < 0.05]. (5) The conduction time was the shortest and the cardiac electrical conduction consistency in myocardial infarction tissue was significantly improved in BMSCs + rAd.SERCA2a group. CONCLUSIONS: BMSCs and SERCA2a gene modified BMSCs transplantation could significantly improve cardiac function and BMSCs + rAd.SERCA2a could also effectively improve electrical conduction of infarcted myocardium and attenuate the incidence of arrhythmia after myocardial infarction in rats.

A meta-analysis of the comparative efficacy of ablation for atrial fibrillation with and without ablation of the ganglionated plexi.

BACKGROUND: Ganglionated plexi (GP) is claimed to be potentially responsible for atrial fibrillation (AF). The efficacy and safety of GP ablation remains controversial. This meta-analysis aimed to assess the efficacy of procedure with or without ablation of GP. METHODS AND RESULTS: We included controlled clinical trials or randomized controlled trials comparing procedures of GP ablation plus pulmonary vein isolation (PVI), GP ablation plus Maze, or GP ablation alone (experimental arm), with PVI or Maze without GP ablation (control arm). The early episodes of atrial arrhythmia recurrence (early recurrence) and freedom from AF (primary efficacy endpoint) were estimated. Six trials with a total of 342 patients (172 per experimental arm, 170 per control arm) were included in the meta-analysis. Subgroup analysis demonstrated that there was no significant difference in early recurrence between additional GP ablation to PVI or Maze, and PVI or Maze without ablation of GP (P = 0.06). However, early recurrence was significantly higher after GP ablation alone, compared with PVI alone (P = 0.02). Freedom from AF recurrence was significantly improved by additional GP ablation to PVI and Maze, compared with PVI and Maze without ablation of GP (P < 0.01). However, it was significantly aggravated by GP ablation alone, compared with PVI alone (P = 0.006). CONCLUSION: The short and relatively long-term success rate of additional GP ablation to PVI or Maze is superior to PVI or Maze without ablation of GP. GP ablation alone is less effective than PVI alone for the treatment of AF. Future studies are necessary to establish and standardize the targeting sites, endpoints, and methods of GP ablation.

[Efficacy of sequential ablation of sinus atrial node fat pad and atrial ventricular node fat pad on inducibility of atrial fibrillation evoked by vagus trunk stimulation].

OBJECTIVE: To explore the efficacy of sequential ablation of epicardial fat pad on inducibility of atrial fibrillation (AF) evoked by stimulating vagus trunk. METHODS: Eighteen adult mongrel dogs were randomly divided into 2 groups (n = 9 each): Group A underwent pre-ablation of sinus-atrial node fad pad (SANFP) and subsequent ablation of atria-ventricular node fad pad (AVNFP). Group B underwent pre-ablation of AVNFP and subsequent ablation of SANFP. AF was induced by high-frequency electrical stimulation of bilateral vagus trunks. The AF inducibility and effective refractory period (ERP) changes during vagus trunk stimulation were examined before and after ablation in atria and pulmonary veins. RESULTS: (1) AF could be induced by vagus trunk stimulation and the incidence was higher during right vagus trunk (RVG) stimulation than left vagus trunk (LVG) stimulation [(60.0 ± 0.0)% vs (18.4 ± 22.1)%]. (2) SANFP ablation significantly attenuated AF inducibility with LVG stimulation and RVG stimulation at 2 V (decreased 67.0% and 72.0%, respectively). Subsequent AVNFP ablation after SANFP ablation further reduced AF inducibility with LVG and RVG stimulation at 2 V (decreased 100.0% and 95.5%, respectively). (3) AVNFP ablation (decreased 95.7% and 96.3%, respectively) and subsequent SANFP ablation after AVNFP ablation (decreased 98.0% and 100.0%, respectively) significantly attenuated AF inducibility with LVG stimulation and RVG stimulation at 2V. (4) Vagal stimulation induced ERP shortening was significantly attenuated by isolated SANFP ablation or AVNFP. Subsequent AVNFP ablation after SANFP induced significant ERP shortening in right atrial site compared with isolated SANFP ablation. However, changes of ERP shortening were similar between AVNFP ablation and subsequent SANFP ablation after AVNFP ablation. CONCLUSIONS: Epicardial fat pad ablation reduced the AF inducibility and prolonged ERP of atria and pulmonary veins during vagus trunk stimulation. AVNFP, as the "integration centers" modulating the vagal innervation to the atria, may be the more effective target of ablation for treating AF.

[Metal stress-induced arrhythmia and thoracic spinal cord 1-5 nerve remodeling and myocardial electrophysiological remodeling in rats].

OBJECTIVE: The study aimed to investigate the relationship between arrhythmia occurrence and nerve remodeling of thoracic spinal cord 1-5 nerves as well as myocardial electrophysiological remodeling in a metal stress rat model. METHODS: Thirty SD rats (weight 180-250 g) were randomly divided into control group (n = 10), stress group (n = 10) and fluoxetine group (n = 10, 10 mg/kg i.p. for 3 weeks). Stress model (given by unpredicted chronic mild stress) was established according to Cronli's protocol. Following parameters were observed:(1) ECG waveform change and arrhythmias;(2) tissue field action potential duration (FAPD) of thoracic spinal cord 1-5 and cardiac tissue mapped by microelectrode arrays (MEA) technique;(3) myocardial growth-associated protein (GAP-43), tyrosine hydroxylase (TH), choline acetyltransferase (CHAT) distribution observed by immunofluorescence and confocal laser scanning microscope (LSCM). RESULTS: Three weeks later: (1) The body weight, food intake, consumption of sugar water, the horizontal and vertical movement score, cleaning action of rats were significantly decreased, and fecal grains significantly increased, P-wave, P-R interval, QRS-wave and Q-T interval were significantly prolonged and heart rate was significantly reduced in stress group compared with control group (all P < 0.05). Incidence of ventricular premature beat was 80% in stress group and 0% in control group (P < 0.05). The FAPD of thoracic spinal cord 1-5 nerves [(144.25 ± 12.63)ms vs (79.56 ± 8.01)ms] and of cardiac tissue [LA(122.43 ± 19.34)ms vs (92.59 ± 7.61)ms, RA(149.89 ± 14.68)ms vs (105.18 ± 15.94)ms, LV(162.62 ± 7.04)ms vs (110.45 ± 6.92)ms, RV(152.21 ± 30.49)ms vs (131.06 ± 12.04)ms] were significantly prolonged, FAPD dispersion (FAPDd) significantly increased [thoracic spinal cord 1-5(13.3 ± 9.11)ms vs (9.36 ± 7.01)ms] in stress group compared with the control group. Disarrangement of myocardial cells, proliferation of collagen fiber, infiltration of neutrophil and lymphocytes in the cardiac tissue were also observed and distribution of GAP-43, TH and CHAT was significantly increased in stress group. (2) All these changes could be partly reversed by the treatment with fluoxetine. CONCLUSION: Metal stress induced cardiac autonomic nerve and myocardial electrophysiological remodeling and ventricular arrhythmia in rats which could be significantly attenuated by fluoxetine in this model.

[Value of aVR lead four steps algorithm on differential diagnosis of wide QRS complex tachycardia].

OBJECTIVE: The aVR lead four steps is a new algorithm for differential diagnosis of wide QRS complex tachycardia (WCT). The study explores the clinical value of this new algorithm on differential diagnosis of WCT. METHODS: Application of aVR lead four steps to analysis the electrocardiogram of patients with WCT proved by electrophysiological study. Every step's accuracy rate, sensitivity and specificity to differential diagnosis of ventricular tachycardia (VT) were calculated. The first step diagnosed VT according to presence of an initial R wave in the aVR lead. The second step diagnosed VT according to width of an initial r or q wave > 40 ms in the aVR lead. The third step diagnosed VT according to notching on the initial downstroke of a predominantly negative QRS complex in the aVR lead. The fourth step diagnosis VT according to ventricular activation-velocity ratio (Vi/Vt) in the aVR lead, Vi/Vt ≤ 1 suggested VT. Results derived from aVR lead four steps algorithm were compared with results derived from Brugada and Vereckei four steps algorithm. RESULTS: A total of 113 patients with WCT were analyzed (31 supraventricular tachycardia, SVT and 82 ventricular tachycardia, VT). The accuracy rate of differential diagnosis VT is 91.2%, sensitivity is 90.2% and specificity is 77.4%. The accuracy and sensitivity of the aVR lead four steps algorithm for differential diagnosis of WCT were superior to the Brugada Vereckei four steps algorithm (P < 0.05). The specificity of the Vereckei four steps algorithm was superior to aVR lead and Brugada four steps algorithm (P < 0.05), while the specificity of the aVR lead four steps algorithm was similar as Brugada four steps algorithm (P > 0.05). CONCLUSIONS: The aVR lead four steps algorithm is associated with excellent accuracy rate, sensitivity for differential diagnosis of WCT. This algorithm is simple and could be easily learned and applied by physician.

[Impact of magnetic field exposure on cardiac autonomic tone and inducibility of atrial fibrillation in dogs].

OBJECTIVE: To observe the maximal heart rate changes, atrioventricular (A-V) conduction block and atrial fibrillation (AF) inducibility in dogs with vagosympathetic trunk exposed to electromagnetic fields (EMFs). METHODS: The vagosympathetic trunk of adult dogs was separated and exposed to EMFs 0.043 kHz (2.87 microG, n = 5) and to EMFs 2 kHz (0.34 microG, n = 6) for two to three hours. Simultaneously, the vagosympathetic trunk was stimulated with 20 Hz frequency and 1 - 8 V intensity for 0.1 ms. Heart rate, presence of A-V conduction block and AF inducibility were determined. RESULTS: After 5-minutes exposure to EMFs 0.043 kHz (2.87 microG), the maximal heart rate decreased 29%, the voltage applied to vagosympathetic trunk required to induce A-V conduction block decreased by 60% in experimental group versus 5% increase in control group. This effect lasted 2 to 3 hours. While vagosympathetic trunk exposure to EMFs 2 kHz (0.34 microG) was associated with significant increase in the incidence of atrial premature beats, atrial tachycardia and AF, these effects could be blocked by propranolol and atropine. CONCLUSIONS: Our results showed that 0.043 kHz (2.87 microG) EMFs exposure might reduce while 2 kHz (0.34 microG) EMFs exposure might increase AF inducibility. Our study thus suggested autonomic nervous system of dogs could be affected by EMFs exposure and 0.043 kHz (2.87 microG) EMFs exposure might be a novel option for AF prevention.

Investigation of the alterations in cellular electrophysiology underlying ventricular arrhythmia in dogs with the multiple organ dysfunction syndrome.

BACKGROUND: Multiple organ dysfunction syndrome (MODS)-specific cellular electrophysiological changes have so far not been reported and it seemed unlikely that they were related to arrhythmogenesis. METHODS AND RESULTS: Twelve dogs, weight 12 +/- 2 kg, were divided into a control group (n = 6) and an MODS group (n = 6). MODS lasting for 72 h was induced by the 'two-hit' method in 6 dogs. Ventricular myocytes were enzymatically isolated. Early afterdepolarizations (EADs), action potential duration (APD) and L-type calcium currents (ICa,L) were assessed. Sinus arrhythmias in all MODS dogs (100%; 6 of 6) and premature ventricular beats in 4 MODS dogs (66%; 4 of 6) were recorded, while no arrhythmias were found in the control animals. The prolongation of the APD was associated with a decreased ICa,L, and frequently provoked EADs were the typical electrophysiological alterations in the myocytes of MODS dogs. The action potential prolongation was shortened, the ICa,L blocked and EAD suppressed by using verapamil (100 micromol/l) in the myocytes of MODS dogs (66%; 4 of 6). CONCLUSION: The changes in cellular electrophysiology within 72 h in the heart of MODS dogs are APD prolongation, markedly decreased ICa,L as well as frequently provoked EAD, the most common types of arrhythmia being sinus arrhythmia and premature ventricular beats. This study suggests that verapamil appears to be an effective agent in reversing alterations in cellular electrophysiology at the early stage of MODS.

[Nerve remodeling in a canine model of atrial fibrillation induced by 48 hours right atrial pacing].

OBJECTIVE: To evaluate the nerve remodeling induced by 48 hours right atrial pacing in a canine model. METHODS: Rapid right atrial pacing (600 beats/min) was performed in 6 mongrel dogs of either sex for 48 hours to induce sustained atrial fibrillation (AF). Six dogs without pacing served as controls. Cardiac nerves were immunocytochemically stained using anti-growth-associated protein 43 (GAP43) and anti-choline acetyltransferase (CHAT) antibodies to compare nerve sprouting and pneumogastric nerve remodeling between the 2 groups. RESULTS: In dogs with AF, the GAP43-positive and CHAT-positive nerve densities in the left atrium, left auricular appendage, right atrium and right auricular appendage were significantly higher than in control animals (all P < 0.05). Moreover, nerve density was significantly higher in the right atrium than in the left atrium in dogs with AF. Microscopic examinations revealed an inhomogeneous distribution of cardiac nerves. CONCLUSION: Significant nerve sprouting and pneumogastric nerve remodeling were evidenced in the right and left atrium in a canine model of sustained AF induced by 48 hours right atrial pacing.

[Microelectrode arrays mapped tissue field action potential duration changes of thoracic spinal cord 1 - 5 nerves and heart in chronic stress rat model].

OBJECTIVE: To investigate chronic stress induced tissue action potential and pathological changes of thoracic spinal cord 1 - 5 nerves and heart in SD rats. METHODS: SD rats (weighing 180 - 250 g) were randomly divided into depressive group and control group (n = 10 each). Depressive model (unpredicted chronic mild stress) was established according to Gronli's protocol. The heart rhythm, tissue field action potential duration (FAPD) of thoracic spinal cord 1 - 5 nerves, atrium and ventricle were mapped by microelectrode arrays (MEA) technique. Heart was sectioned and stained with Massion and HE for pathological analysis. RESULTS: After 3 weeks chronic stress, P wave [(35.09 +/- 7.92) ms vs. (25.43 +/- 3.38) ms, P<0.05] and Q-T interval [(114.64 +/- 35.08) ms vs. (81.93 +/- 16.35) ms, P<0.01] were significantly increased, FAPD of thoracic spinal cord 1 - 5 nerves and heart was significantly prolonged, atrial field action potential duration dispersion (FAPDd) was significantly increased, atrial premature beats (n = 2) and ventricular premature beats ( n = 3) were also recorded in rats from depressive group. Moreover, increased collagen deposition was evidenced in Massion stained myocardium and increased inflammatory cell infiltration in the heart was found by both HE stain and electron microscope from depressive rats. CONCLUSION: Chronic mild stress could activate sympathetic nerves system, promote inflammatory cell myocardial infiltration and myocardial fibrosis, induce arrhythmias by prolonging FAPD and increasing FADPd in thoracic spinal cord 1 - 5 nerves and/or heart tissue.

[Cardiac field potentials and activation sequence in Langendorff perfused heart, cardiac tissue slices and cultured ventricular myocytes recorded by microelectrode arrays system.].

OBJECTIVE: To observe field potentials (FPs) and activation sequence at Langendorff perfused guinea pigs heart, SD rat cardiac tissue strips perfused by Tyrode's solution and cultured ventricular cardiomyocytes of suckling mice by microeletrode arrays (MEA) technique. METHOD: FPs and activation sequence were recorded from perfused heart, cardiac tissue strips (5 mm x 5 mm) and cultured ventricular cardiomyocytes by MEA. RESULTS: (1) FPs could be recorded in hearts perfused for 30 to 90 min with a heart rate 90 - 120 beats/min. FP durations of both ventricular and atrial tissue were (210 +/- 78) ms and (164 +/- 58) ms, respectively and atrial ventricular conduction time was (320 +/- 150) ms. (2) The excitability of Tyrode's solution perfused tissue strips was visible for more than 2 h, and FP durations of ventricular and atrial tissue strips were (115.80 +/- 11.61) ms and (83.71 +/- 6.48) ms, respectively. (3) Spontaneous beating frequency (150 +/- 100) beats/min and FPs could be readily recorded in cardiomyocytes cultured between 2 to 72 hours. CONCLUSION: MEAs is a sensitive, low noise and stable technique for observing local tissue action potential and activation sequence of whole heart, cardiac tissue strips and cultured cardiomyocytes.

Time-dependent cervical vagus nerve stimulation and frequency-dependent right atrial pacing mediates induction of atrial fibrillation.

OBJECTIVE: This study aimed to investigate the effects of right cervical vagus trunk simulation (RVTS) and/or right atrial pacing (RAP) on the induction of atrial fibrillation (AF). METHODS: Twenty-four healthy adult dogs were randomly divided into four groups: RAP groups comprising RAP500 (RAP with 500 beats/min) and RAP1000 (RAP with 1000 beats/min) and RVTS groups comprising RVTS and RAP500+RVTS. All dogs underwent 12-h intermittent RAP and/or RVTS once every 2 h. The AF induction rate, AF duration, atrial effective refractory period (ERP), and dispersion of ERP (dERP) were compared after every 2 h of RAP or/and RVTS. RESULTS: All groups had successful AF induction. The RAP1000 group had the highest AF induction rate and the longest AF duration. The RAP1000 group also had a shortened ERP in comparison to the other groups as well as the maximum dERP. Compared to the RAP500 group, RAP500+RVTS had an increased capacity to induce AF as measured by the AF induction rates, AF duration, ERP, and dERP. CONCLUSION: Increased tension in the vagus nerve and the intrinsic cardiac autonomic nervous system plays an important role in AF induction through different potential mechanisms. Interventions involving the vagus nerve and/or intrinsic cardiac autonomic nervous system can be a future potential therapy for AF.

Valproic acid regulates Ang II-induced pericyte-myofibroblast trans-differentiation via MAPK/ERK pathway.

Myocardial fibrosis (MF) plays an important part in cardiovascular diseases. The main cytological characteristics of MF is the increased number of myofibroblasts, which have multiple sources such as EMT, EndMT, myeloid progenitors, monocytes, and fibrocytes. Recent data showed that pericytes may represent a major source of myofibroblasts in kidney fibrosis. Valproic acid (VPA) is a kind of short-chain fatty acid. It was reported in recent studies that VPA regulates gene expression and influences various signal pathways. HDACs inhibitors can hinder the growth of tumor cells and differentiation of stem cells. And little is known about the effects of HDACs inhibitors on myofibroblasts transdiffererntiaton. This study focused on the role of HDACs in pericyte-myofibroblast trans-differentiation and how HDACs inhibitor VPA influenced proliferation, migration, viability and myofibroblast trans-differentiation of pericytes for the first time. Rat cardiac fibrosis model was induced by Ang II. Immunohistochemistry was employed to examine cardiac fibrosis and flow cytometry was used to analyze whether inflammatory cells involve VPA-induced trans-differentiation. Pericytes proliferation, migration and differentiation to myofibroblasts were performed to examine the role of VPA on pericyte trans-differentiation. Immunoblot and qPCR were applied to identify the signal transduction involving in VPA-induced trans-differentiation. In vivo study showed that HDAC inhibitor VPA blocks cardiac fibrosis, and inflammation inhibition was not involved in this process. VPA treatment inhibited Ang II pericyte proliferation, migration and transdifferentiation to myofibroblast. Furthermore, the inhibition of α-SMA expression by VPA was related to reduce phosphorylation of ERK, and a pharmacological inhibitor of MEK suppressed Ang II-induced α-SMA expression. HDAC4 knockdown resulted in inhibiting Ang II-mediated α-SMA expression as well as the phosphorylation of ERK. Moreover, the inhibitors of protein phosphatase 2A and 1 (PP2A and PP1) restored the Ang II-stimulated α-SMA expression from the inhibitory effect of VPA. Together, the current data indicate that the differentiation of pericytes to myofibroblasts is HDAC4 dependent and requires phosphorylation of ERK.