Effects of different ages on ventricular remodeling after ischemic heart failure in mice

AIM: To observe ventricular remodeling induced by ischemic heart failure in the mice at different ages.METHODS: Three-month-old (young group, n=50) and 18-month-old (old group, n=50) male C57BL/6J mice were selected in the study. Forty mice underwent ligation of left coronary artery with certain infarct size, and 10 were sham-operated for control. Echocardiography was performed after 8 weeks of infarction. All mice were killed and the hearts were collected for examinations. Masson trichrome staining was used to detect myocardial fibrosis. The expression of type I and type Ⅲ collagens was measured by the method of immunohistochemistry.RESULTS: The incidences of cardiac rupture (18% vs 10%, P<0.05) and heart failure (22% vs 10%, P<0.05) were significantly higher in aged mice than those in young mice. The degrees of left ventricular dilation, contractile dysfunction and heart rate were significantly higher in aged mice than those in young mice (P<0.05). The left ventricular mass index, collagen volume fraction, the expression of type I collagen and ratio of type Ⅰ/Ⅲ collagens were significantly increased in aged mice as compared with young mice (P<0.05).CONCLUSION: After heart failure, aged mice show abnormal collagen distribution, and suffer from worse cardiac functions and more serious ventricular remodeling.     

Inhibitory effect of aerobic exercise on left ventricular remodeling and sympathetic neural remodeling in rats with heart failure after myocardial infarction

AIM: To investigate the effects of long-term aerobic exercise on the heart and sympathetic neural remodeling (structure and function remodeling) in heart failure rats induced by myocardial infarction. METHODS: Heart failure model after myocardial infarction was performed by ligating anterior descending coronary artery in the Wistar rats. Four weeks after operation, the rats were randomly divided into sham operation sedentary (S) group, heart failure sedentary (H) group and heart failure exercise (HE) group. The animals in HE group underwent 10-week treadmill running, while those in S group and H group were sustained in a resting state. The cardiac structure and function including left ventricular internal diameter at diastole (LVIDd), left ventricular internal diameter at systole (LVIDs), left ventricular anterior wall diameter at diastole (LVAWDd), left ventricular anterior wall diameter at systole (LVAWDs), left ventricular posterior wall diameter at diastole (LVPWDd) and left ventricular posterior wall diameter at systole (LVPWDs), and cardiac function parameters including fractional shortening (FS) and left ventricular ejection fraction (LVEF) were measured by echocardiography. The myocardium was collected for histopathological observation with Masson staining, and the collagen volume fraction (CVF) was determined. The concentrations of norepinephrine (NE) in the myocardium and plasma were measured by high-pressure liquid chromatography. The frequency domain analysis was applied for determining the heart rate variability (HRV) via subcutaneous recording electrode involving total power (TP), normalized low power (LFn), normalized high power (HFn) and LF/HF ratio. The mRNA expression of collagen type I (Col-I), collagen type III (Col-III), atrial natriuretic factor (ANF), α-myosin heavy chain (α-MHC), β-myosin heavy chain (β-MHC), sarcoplasmic endoplasmic reticulum Ca²⁺-ATPase (SERCA2a) was detected by real-time PCR. The protein levels of nerve growth factor (NGF) and its receptor (TrkA), and tyrosine hydroxylase (TH) were measured by Western blotting. RESULTS: (1) Compared with S group, body weight (BW), LVIDd, FS, LVEF, TP, HFn, the mRNA expression of α-MHC and SERCA2a, and the protein levels of NGF, TrkA and TH decreased (P<0.05). Left ventricular weight (LVW), left ventricular mass index (LVMI), LVAWDd, LVAWDs, LVPWDd, LVPWDs, CVF, plasma and myocardial NE content, LFn, LF/HF, and the mRNA expression of ANF, β-MHC, Col-I and Col-III increased (P<0.05) in H group. (2) Compared with H group, LVW, LVMI, LVIDd, FS, LVEF, TP, HFn, the mRNA expression of α-MHC and SERCA2a, and the protein levels of NGF, TrkA and TH were raised (P<0.05), while CVF, plasma and myocardial NE content, LFn, LF/HF, and the mRNA expression of ANF, β-MHC, Col-I and Col-III decreased (P<0.05) in HE group. CONCLUSION: Long-term aerobic exercise training leads to inhibition of heart and sympathetic neural remodeling and improvement of cardiac function and autonomic modulation in the rats after myocardial infarction.     

Role of cytokines in the pathogenesis of heart failure

Previous reports have shown that cytokines and cytokine receptors are independent predictors of mortality in patients with advanced heart failure. Recent studies demonstrate that cytokines, such as tumor necrosis factor, interleukin 1 and interleukin 6, play an important role in the pathogenesis of heart dysfunction in patients with heart failure. In this review, we summarized the importance, expression and mechanism of cytokines in the development and progression of heart failure.     

Expression of calcium handling protein in diastolic heart failure

AIM:To elucidate molecular mechanisms underlying calcium handling protein in diastolic heart failure (DHF) from mRNA level and protein expression, including calcium adenosine triphosphatase (Ca²⁺-ATPase), phospholamban, ryanodine receptor, calsequestrin and L-type calcium channel.METHODS:The mRNA of these calcium handling genes were detected by RT-PCR, and the protein levels were analyzed by Western blot analysis.RESULTS:Compared with sham-operated rabbits, the steady-state levels of mRNA encoding the SR Ca²⁺-ATPase and cardiac L-type calcium channel were decreased significantly in rabbits with DHF, and protein level of SR Ca²⁺-ATPase was greatly reduced, whereas the mRNA and protein levels of other calcium handling protein were unchanged.CONCLUSION:L-type calcium channel and the sarcoplasmic reticular Ca²⁺-ATPase were down regulated in DHF. These changes may be a contributory factor for DHF.     

Mechanisms of heart failure induced by adriamycin

AIM: To investigate the changes of cardiac function, oxidative stress and apoptosis in myocardium of rat model of heart failure induced by adriamycin (ADR). METHODS: At the end of the study, we observed content of malondialdehyde (MDA), activity of superoxide dismutase (SOD) and apoptosis. Expression of P53 protein and p53 mRNA were measured with immunohistochemical method and RT-PCR, respectively. RESULTS: Our data showed that content of MDA increased, activity of SOD decreased and apoptosis in myocardium happened while cardiac function decreased after ADR treatment. p53 gene expression and P53 protein obviously increased in heart failure group. CONCLUSION: There were oxidative stress and apoptosis occurred significantly in a model of heart failureinduced by ADR. p53 gene might play an important role in the apoptosis. Correlation analyses suggested that apoptosis in myocardium was related to oxidative stress in ADR-induced heart failure model.     

Over-expression of SK2 channel in PVN reduces renal sympathetic nerve activity in chronic heart failure rats

AIM：To investigate the effect of over-expression of small-conductance calcium-activated potassium channel subtype 2 (SK2) in the paraventricular nucleus (PVN) of hypothalamus on heart rate(HR), mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) of the rats with chronic heart failure (CHF). METHODS：Adenovirus vector encoding SK2 (pDC316-mCMV-EGFP-rKCNN2) was constructed.The CHF model of the male Sprague Dawley (SD) rats was established by the ligation of anterior descending coronary artery. Echocardiogram was used at the 6th week after the operation to identify the CHF model. Adenovirus vector encoding SK2 (pDC316-mCMV-EGFP-rKCNN2) or control adenovirus vector (pDC316-mCMV-EGFP) were transfected into the PVN in vivo. The cardiac function was monitored by echocardiogram. The expression of SK2 at mRNA and protein levels was determined by RT-PCR, Western blotting and immunofluorescence. The HR, MAP and RSNA were measured by PowerLab 8/30 in anesthetized rats with bilateral PVN microinjection of SK channel blocker apamin. RESULTS：Treatment with pDC316-mCMV-EGFP-rKCNN2 significantly decreased the renal sympathetic nerve activity in the rat with CHF. Injection of pDC316-mCMV-EGFP did not change the renal sympathetic nerve activity in the rats in sham group. CONCLUSION：The expression and function of SK channels in PVN in the heart failure rats were decreased, suggesting a reduced negative regulation of sympathetic activity in central neural system. Increased expression of SK2 in the PVN leads to a reduction in sympathetic outflow under the condition of CHF, which may provide a new target for the treatment of heart failure.     

Astragalus polysaccharides improve chronic heart failure by promoting myocardial FFA metabolism via AMPK pathway

AIM: To investigate the effect of Astragalus polysaccharides (APS) on chronic heart failure and its mechanism. METHODS: Male SD rats (n=32) were randomly divided into control group, sham group, model group and APS group (8 rats in each group). The left coronary artery ligation in the rats was conducted to establish myocardial infarction heart failure model. After modeling, the rats in APS group were given APS (3 g·kg^-1·d^-1) by intragastric administration for 6 weeks. Left ventricular diastolic diameter (LVD), left ventricular systolic diameter (LVS), left ventricular ejection fraction (LVEF) and fractional shortening (FS) were detected by echocardiography. HE staining was used to observe the pathological changes. The concentrations of free fatty acid (FFA) in the serum and myocardium were observed by the method of acetyl coenzyme A synthetase and acetyl coenzyme A oxidase (ACS-ACOD). The protein levels of total AMP-activated protein kinase (AMPK), phosphorylated AMP-activated protein kinase (p-AMPK), fatty acid translocase (FAT/CD36) and carnitine palmitoyltransferase I (CPT-1) were measured by Western blotting. RESULTS: No significant difference in each index between sham group and control group was observed. Compared with control group, LVEF and FS in model group was significantly decreased, while LVD and LVS was significantly increased (P<0.05). The LVEF and FS in APS group were significantly improved compared with model group (P<0.05), and there was no significant difference between APS group and control group. LVD and LVS in APS group were obviously improved compared with mo-del group (P<0.05), and the difference was significant compared with control group (P<0.05). Compared with control group, focal myocardial necrosis increased, and residual myocardial cells reduced in model group, while those was much better in APS group as compared with model group (P<0.05). The FFA concentrations in the serum and myocardium in model group increased significantly compared with control group (P<0.05), while those decreased significantly in APS group as compared with model group (P<0.05). The protein levels of p-AMPK, CPT-1, and cell membrane FAT/CD36 in model group decreased significantly compared with control group (P<0.05), and those in APS group increased obviously compared with control group (P<0.05). CONCLUSION: APS improves chronic heart failure by activating the AMPK pathway and promoting myocardial ingestion and utiliation of FFA.     

Effects of catestatin on ventricular arrhythmia in isolated rat hearts with chronic heart failure

AIM:To determine the effects of catestatin (CST) on ventricular arrhythmia (VA) in isolated rat hearts with chronic heart failure (CHF). METHODS:Fifty-one male rats were randomly divided into 2 groups: control (CTL) group (n=17) and CHF group (n=34), which were injected with 0.9% normal saline (1 mL·kg-1·d-1, ip) and isoproterenol (ISO, 5 mg·kg-1·d-1, ip) for 7 d,respectively. The echocardiography was used to assess the cardiac functions 2 weeks after the end of modeling in both groups. The CHF rats were divided into non-treatment group (n=17) and CST treatment group (CST group, n=17). The rats in CST group was given CST (2 nmol·kg-1·d-1, ip) for 3 weeks, while 0.9% normal saline (1 mL·kg-1·d-1, ip) was applied to the rats in non-treatment group. To all the whole Langendorff-perfused hearts, the monophasic action potential (MAP) and the ventricular effective refractory period (VERP) were recorded and measured in left anterior free wall (LAF). The programmed electrical stimulation and burst pacing were used to induce action potential duration (APD) alternans (ALT) and VA in the LAF, respectively. The car-diac myocytes of LAF were enzymatically isolated and the technique of whole-cell patch clamp was used to record L-type Ca2+ current (ICa-L). RESULTS:Compared with CTL group, the peak ICa-L density, 90% of MAP duration (MAPD90), VERP, median of maximum pacing cycle length (PCLmax) inducing APD-ALT and incidence of VA (83.33% vs 1667%) were significantly increased in non-treatment group (all P<0.01). Compared with non-treatment group, the peak ICa-L density, MAPD90, VERP, median of PCLmax inducing APD-ALT and incidence of VA were significantly decreased in CST group (all P<0.05). CONCLUSION: Treatment with CST reduces the incidence of VA in CHF rats, which might be associated with the inhibition of ICa-L.     

Cardiac L-type calcium channel and its alterations in cardiac hypertrophy and heart failure

There are two type of cardiac calcium channel current, both are inward current: (1) L-type Ca²⁺channel current (I_ca-L), plays a major role in determining myocyte action potential plateau characteristics as well as initiating the myocyte excitation-contraction coupling; (2) T-type Ca²⁺ channel current (I_ca-T), probably plays an important role in pacemaker activity. The alterations of L-type calcium channel abundance and function in cardiac hypertrophy and heart failure are determined by the the species difference, especially by the stage of the disease process and the degree of the disease. Both abundance and function of L-type calcium channel decrease in severe hypertrophy and heart failure.     

The changes of intrarenal endothelin system in the course of congestive heart failure induced by rapid right ventricular pacing in dogs

AIM: To investigate the changes of intrarenal endothelin system in the course of congestive heart failure. METHODS: A canine congestive heart failure model induced by rapid right ventricular pacing was used in the present study. Twenty-one mongrel dogs divided randomly into 3 groups: control, congestive heart failure 2 weeks (CHF2) and congestive heart failure 4 weeks (CHF4). The severity of heart failure was evaluated by means of hemodynamic measurement. The concentration of plasma endothelin was detected via RIA, and the expression of endothelin was detected by RT-PCR. RESULTS: The concentration of plasma endothelin in both of CHF2 and CHF4 elevated significantly. In CHF2, the expression of endothelin receptor B(ETB) in renal medulla increased significantly. And in CHF4, the expression of preproendothelin, endothelin receptor A (ETA) and ETB increased both in renal cortex and medulla. Furthermore, in cortex, the expression of ETA increased more significantly than ETB, while in medulla, ETB expressed much more than ETA. CONCLUSION: The changes of renal endothelin system expression plays a role in the regulation of water and electrolyte balance during the progress of congestive heart failure.     

Effects of cardiac contractility modulation on ventricular electrical remodeling in rabbits with chronic heart failure

AIM: To investigate the effects of cardiac contractility modulation (CCM) on ventricular electrical remodeling in a rabbit model of chronic heart failure. METHODS: The rabbits were divided into sham group, heart failure(HF) group and HF+ CCM group. The rabbit model of chronic heart failure was established by ligating the ascending aortic root. Then electrical stimulations during the absolute refractory period were delivered lasting 6 h everyday for 4 weeks in rabbits of HF+ CCM group. The QTc and ventricular effective refrective period (VERP) were recorded. The protein and mRNA levels of Kv1.4, Kv4.3 and connexin 43 (Cx43) were determined by Western blot and RT-qPCR. RESULTS: Compared with sham group, QTc were significantly prolonged in HF rabbits at week 12 (P<0.05). CCM therapy shortened QTc of rabbits with heart failure at week 16 (P<0.05). Compared with sham group, VERP significantly increased in HF group and HF+ CCM group, while CCM therapy shortened VERP of rabbits with heart failure at week 16 (P<0.05). Compared with sham group, the mRNA and protein levels of Kv1.4, Kv4.3 and Cx43 were decreased in HF group and HF+ CCM group (P<0.05). However, CCM therapy restored the mRNA and protein levels of Kv1.4, Kv4.3 and Cx43 of rabbits with heart failure (P<0.05). CONCLUSION: CCM suppresses ventricular electrical remodeling in heart failure and the underlying mechanism may be associated with increasing Kv1.4, Kv4.3 and Cx43 expression.     

Effects of cardiac contractility modulation applied to different locations of heart on cardiac functions in rabbits with heart failure

AIM: To investigate the effects of cardiac contractility modulation (CCM) applied to different locations of the heart on cardiac functions and cardiac dys-synchrony in the rabbits with chronic heart failure, and to explore the best pattern of CCM.METHODS: Forty rabbits were divided into 4 groups according to the location of receiving CCM: heart failure (HF) group, left ventricular anterior wall (LVAW-CCM) group, left ventricular posterior lateral wall (LVPLW-CCM) group and right ventricular apex (RVA-CCM) group. The model of chronic heart failure was made by ligating ascending aortic root of the rabbits. After 12 weeks, the electrical stimulations during the absolute refractory period were delivered in different locations of the heart, lasting 6 h everyday for 7 days. The changes of cardiac functions and cardiac dys-synchrony were observed by cardiac ultrasonic cardiogram before and after CCM stimulation. The plasma level of brain natriuretic peptide (BNP) was detected by ABC-ELISA method. Pulsed-wave Doppler was used to acquire aortic pre-ejection interval (APEI) and pulmonary pre-ejection internal (PPEI), and inter-ventricular mechanical delay (IVMD) was calculated to evaluate the cardiac dys-synchrony.RESULTS: Compared with HF group, left ventricular end-systolic dimension (LVESD) and left ventricular end-diastolic dimension (LVEDD) in LVAW-CCM group, LVPLW-CCM group and RVA-CCM group were significantly decreased (P<0.05), while left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) were significantly increased (P<0.05), especially in LVAW-CCM group. Interventricular septal thickness (IVS) and left ventricular posterior wall thickness (LVPW) were similar among groups. No significant difference of plasma BNP level before CCM delivery among the 4 groups was observed. However, the plasma BNP level in control group was the highest, followed by LVPLW-CCM group and RVA-CCM group, and LVAW-CCM group was the lowest after CCM delivery. No change of IVMD was observed among groups before and after CCM delivery.CONCLUSION: The effect of CCM applied to different locations of the heart on cardiac functions is different.The optimal site of CCM delivery is left ventricular anterior wall. No influence of interventricular dys-synchrony was observed during application of CCM.     

Effects of FKBP12.6 gene on canine heart failure transfected by ultrasound mediated destruction of microbubbles

AIM: To investigate the effect of gene transfection of FKBP12.6 (FK12.6 binding protein) on the canine failing heart induced by rapid ventricular pacing. METHODS: Three weeks after onset of rapid ventricular pacing (250 bpm), 28 canines were divided into 4 groups. Either pcDNA3.1-FKBP12.6 plasmid encoding human FKBP12.6 gene (transfection groupⅠ,Ⅱ; observed at the 4th or 14th days respectively after transfection) or empty vector (controlⅠ,Ⅱ) was transferred into myocardium under ultrasonic microbubble destruction. After transfection, maintenance pacing at a reduced rate (190 beats/min) was continued until end-point of experiment. Echocadiographic, hemodynamic and plasmic ANP (atrial natriuretic peptide), BNP (brain natriuretic peptide) data were collected three times (before pacing, before transfection and endpoint). Semiquantative RT-PCR was used to identify FKBP12.6 expression in myocardium. RESULTS: Gene transfection of FKBP12.6 elevated expression of FKBP12.6 mRNA 3.5 folds at day 4, and 1.7 folds at day 14 respectively, compared with control group. Significant improvements of cardiac function, hemodynamics and plasmic concentrations of ANP, BNP were observed in transfection groupⅠ and these effects were stable for at least 2 weeks. Cardiac output (CO), ejection fraction (EF) and fractional shortening (FS) were still lower than pre-pacing although they increased in transfection groups. Left ventricular end-diastolic diameter (LVEDD) and left ventricular end-diastolic volume (LVEDV) decreased at day 14 but LVEDD remained unchanged at day 4 compared with pre-transfection. CONCLUSION: Gene transfection of FKBP12.6 improves cardiac functions in the failing heart and reverses myocyte remodeling. This might be a novel therapeutic application for treating human heart failure.     

Effects of Xinkang recipe on myocardial miR-25-3p expression and SERCA2a activity in heart failure rats

AIM: To investigate the effects of Xinkang recipe on myocardial miR-25-3p expression and sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) activity in heart failure rats. METHODS: Male SD rats were randomly divided into normal group, sham group, model group, Xinkang recipe group (Xinkang group), and captopril group. The heart failure rat model was induced by intraperitoneal injection of doxorubicin. Distilled water, Xinkang recipe and captopril were administrated by gastric gavage for 35 d, respectively. The indexes of cardiac function and plasma level of brain natriuretic peptide (BNP) were measured. The SERCA2a activity was determined by the inorganic phosphorus method. The myocardial protein expression of SERCA2a and phospholamban (PLB) was detected by Western blot. The myocardial expression of miR-25-3p was detected by stem-loop RT-qPCR. RESULTS: Cardiac output (CO), left ventricular fractional shortening (LVFS) and left ventricular ejection fraction (LVEF) in Xinkang group and captopril group were significantly higher while the plasma levels of BNP were significantly lower than those in model group (P<0.01). The myocardial expression levels of miR-25-3p in Xinkang group and captopril group were significantly lower while the myocardial protein le-vels of SERCA2a and PLB were significantly higher than those in model group (P<0.01). The SERCA2a/PLB ratio and SERCA2a activity in Xinkang group were significantly higher than those in model group (P<0.05), and no significant change was observed between captopril group and model group. CONCLUSION: Xinkang recipe therapy may improve cardiac function in heart failure rats, which may be related to inhibiting the expression of miR-25-3p, increasing the SERCA2a/PLB ratio and enhancing SERCA2a activity in the myocardium.     

Transfection of rAAV1-SERCA2a improves cardiac function of beagles with heart failure

AIM:To study the effects of recombinant adeno-associated virus type 1 (rAAV1)-sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a) transfection on the cardiac function of beagles with heart failure (HF). METHODS:The beagles were used to make an animal model with heart failure after rapid right ventricular pacing (230 beats/min) for 30 d. A reduced rate (180 beats/min) was continuously applied for another 30 d. The beagles were divided into 4 groups (n=4): control group, HF group, HF+EGFP group and HF+SERCA2a group. rAAV1-EGFP and rAAV1-SERCA2a (both 1×1012 viral genomes) were intramyocardially injected into the animals in the latter 2 groups, respectively. RESULTS:After transfection for 30 d, the left ventricular systolic function in HF+SERCA2a group was similar to that in control group, and significantly higher than that in HF group (P<0.05). The ratio of SERCA2a mRNA/GAPDH mRNA was significantly higher in HF+SERCA2a group than that in HF group (P<0.05). The expression level of SERCA2a in the myocardial tissues was higher in HF+SERCA2a group than that in HF group (P<0.05). The apoptotic index of the cardiomyocytes and the protein expression of MMP-9 were much lower in HF+ SERCA2a group than those in HF group (P<0.05). No significant difference of all parameters was observed between HF group and HF+EGFP group. The mRNA level of phospholamban was unchanged. CONCLUSION:Transfection of SERCA2a improves the expression of SERCA2a, restores the cardiac function and inhibits left ventricular remodeling by reducing the cardiac cell apoptosis and the MMP-9 expression in the heart failure beagles.