Role of central PGE2 on sympathetic excitation in chronic heart failure

AIM: To observe the effect of central prostaglandin E₂ (PGE₂) on sympathetic activation in chronic heart failure (CHF) and to explore the underlying mechanism. METHODS: Male SD rats were subjected to coronary artery ligation to induce heart failure (HF), and the intracerebroventricular infusion was performed by osmotic pump continuously. The rats in sham group and HF group were given artificial cerebrospinal fluid (0.25 μL/h). The rats in HF plus treatment group was given celecoxib (CLB; 20 mg/h). After 4 weeks, the levels of PGE₂ in cerebrospinal fluid (CSF), the sympathetic nerve excitability and cardiac function were measured, and the changes of corticotropin-hormone releasing hormone (CRH)-containing neurons activation and neurotransmitter contents in the hypothalamic paraventricular nucleus (PVN) were also determined. RESULTS: Compared with the sham-operated rats, the HF rats had raised level of PGE₂ in CSF, up-regulated renal sympathetic nerve activity and plasma norepinephrine, increased left ventricular end diastolic pressure, lung-to-body weight and right ventricular-to-body weight ratios, and decreased maximal increase and decreased rate of left ventricular pressure (P<0.05). In addition, the number of CRH positive neurons in PVN and the level of plasma adrenocorticotropic hormone were higher in HF rats than those in sham-operated rats (P<0.05). After administration of CLB into the lateral ventricle of HF rats, the contents of PGE₂ in CSF were significantly reduced, the number of activation CRH neurons in PVN was decreased, the excitability of sympathetic nerves was down-regulated and cardiac function was improved (P<0.05). Compared with the sham-operated rats, the content of glutamic acid in PVN of HF rats was increased, the content of γ-aminobutyric acid and the number of glutamate decarboxylase 67-positive neurons were decreased (P<0.05). After the CLB was given, the above indexes were reversed (P<0.05). CONCLUSION: These findings indicate that in CHF, the increased central PGE₂ may activate CRH-containing PVN neurons and contribute to the augmented sympathetic drive possibly by modulating the neurotransmitters within the PVN.     

Microinjection of AT1 and AT2 receptor antagonists into PVN affects renal sympathetic nerve activity in chronic heart failure rats

AIM: To examine the renal sympathoexcitation affected by microinjection of angiotensin Ⅱ type 1 (AT₁) receptor antagonist L-158809 and angiotensin Ⅱ type 2 (AT₂) receptor antagonist PD123319 into paraventricular nucleus (PVN) in heart failure rats.METHODS: Left anterior descending coronary artery ligation was used to induce rat heart failure (HF) . Four weeks after operation, the left ventricular end-diastolic pressure (LVEDP), the ratios of heart weight/body weight and lung weight/body weight, and the ratio of infarct area of the left ventricle were observed. Under anesthesia, SD rats were fixed into the brain stereo controller to locate PVN for microinjection and the artificial cerebrospinal fluid (ACSF) was used for control. The left kidney was exposed by retroperitoneal approach and the renal sympathetic nerve was separated under surgical microscope. The heart rate, blood pressure and the activity of renal sympathetic nerve discharge (RSNA) were recorded by POWERLAB 8/30 system. RESULTS: Microinjection of AT₁ receptor antagonist into PVN induced a decrease in RSNA in both HF rats and sham rats. The RSNA responses to L-158809 in the HF rats were significantly greater (P<0.05) than those in the sham rats. However, microinjection of AT₂ receptor antagonist and ACSF into PVN induced no change of RSNA in both HF and sham rats. CONCLUSION: There are some differences of sympathetic nerve outputs between using AT₁ receptor antagonist and AT₂ receptor antagonist on PVN, indicating the up-regulation of AT₁ receptors in PVN during HF. The central renin-angiotensin-aldosterone system(RAAS) may be affected by AT₁ receptor, not by AT₂ receptor.     

Role of bradykinin in the therapeutic effect of enalapril on left ventricular hypertrophy and cardiac function after myocardial infarction in rats

AIM:To investigate the influences of bradykinin(BK)on left ventricular hypertrophy and cardiac function in angiotensin-converting enzyme inhibitor(ACEI) therapy in rats after myocardial infarction.METHODS:The effects of enalapril (500 μg·kg^-1·d^-1), enalapril (500 μg·kg^-1·d^-1)with BKB₂ receptor antagonist (Hoe-140 500 μg·kg^-1·d^-1), losartan(3 mg·kg^-1·d^-1) on left ventricular end-diastolic pressure (LVEDP), maximum positive left ventricular pressure change (+dp/dt_max) and LVW/BW as well as V(m)n of noinfarcted area were examined after 4 weeks treatment in rats after myocardial infarction.RESULTS:The values of LVEDP, LVW/BW and V(m)n of three treatment groups were higher than that of untreated MI group (P＜0.05),but the +dp/dt_max of three treatment groups were not significantly different compared with the untreated MI group. In addition, no significant difference in MAP was observed among the three treatment groups, but the LVW/BW and V(m)n of enalapril+Hoe-140-treated group were higher than that of enalapril-treated group (P＜0.05) .CONCLUSION:Enalapril can prevent left ventricular hypertrophy and improve cardiac function independent of blood pressure after myocardial infarction, which is partly due to the inhibition of BK degradation.     

Downregulated transient outward potassium channel protein Kv4.2 and Kv4.3 expression in PVN contributes to sympathoexcitation in rats with chronic heart failure

AIM: To investigate the transient outward potassium channel protein expression in paraventricular nucleus(PVN) and its contribution to renal sympathetic nerve activity(RSNA) in rats with chronic heart failure(CHF).METHODS: A rat model of CHF was prepared by acute myocardial infarction that was induced by ligation of the left anterior descending coronary artery. Four weeks after heart failure, echocardiogram was applied to identify the CHF model and plasma norepinephrine(NE), serum NH₂-terminal pro-brain natriuretic peptide(NT-proBNP) were detected by ELISA. The expression of ransient outward potassium channel proteins Kv4.2 and Kv4.3 at mRNA and protein levels was determined by real-time PCR and Western blot. The mean arterial pressure(MAP), heart rate(HR) and RSNA were measured in anesthetized rats with PVN microinjection of potassium channel blockers 4-AP. RESULTS: In CHF group, the rat cardiac function and Kv4.2 and Kv4.3 expression in PVN were obviously lower while plasma NE and serum NT-proBNP were obviously higher than those in sham group. Microinjection of 4-AP into PVN induced an increase in MAP, HR and RSNA in both sham and CHF rats, while the CHF rats exhibited smaller responses to 4-AP than sham-operated rats.CONCLUSION: Downregulation of Kv4.2 and Kv4.3 expression in the PVN may be a potential mechanism for sympathoexciation in the rats with chronic heart failure.     

Relationship between the intracellular calcium concentration changes and left ventricular hypertrophy and function in the spontaneously hypertensive rats

AIM:To elucidate the relationship between the intracellular calcium concentration changes and left ventricular hypertrophy and function in the spontaneously hypertensive rats (SHR).METHODS:Intracellular free calcium concentrations were measured by Fura 2 methodology and left ventricular function quantitated by cardiac catheterization in 20 SHR aged 10, 22, and 34 weeks and 20 age-matched Wistar-kyoto (WKY) rats.RESULTS:(1) The systolic blood pressure(SBP), intracellular calcium concentrations and left ventricular mass / body weight index (LVM/BW) were significantly higher in all three age groups of SHR than the corresponding groups of WKY; (2) Compared with age-matched WKY groups, the peak left ventricular pressure descending rate(-dp／dt_max) decreased while left ventricular relaxation time constant (τ)increased significantly in SHR aged 22 and 34 weeks. The peak left ventricular pressure ascending rate(dp／dt_max) and the left ventricular contractility index were significantly increased only in the 34 weeks SHR; (3) Intracellular calcium concentrations showed a positive correlation with LVM/BW,SBP,-dp／dt_max and τ(r=0.47-0.83,P<0.01)and a negative correlation with dp／dt_max and the left ventricular contractility index (r=-0.46,P<0.05 and r=-0.81, P<0.01).CONCLUSION:Intracellular calcium overload is one of the potential mechanisms in the induction of left ventricular hypertrophy as well as of systolic and diastolic dysfunction.     

Long-term effects of TCV116 on left ventricular remodeling and heart function after myocardial infarction in rats

AIM: To investigate the effects of long-term TCV116 on left ventricular remodeling and heart function after myocardial infarction. METHODS: Myocardial infarction (MI) was caused by ligation of the left anterior descending coronary artery in rats. One week after the surgical performance, the surviving rats were randomly assigned to the following treatment protocols: (1) MI rats with no therapy; (2) MI rats treated with TCV116 2 mg/kg per day; (3) Sham-operated control; (4) Sham-operated rats, treated with TCV116 2 mg/kg per day. At 22 weeks, cardiac hemodynamic parameters such as MAP, LVSP, dp/dt_max and LVEDP, and histomorphometric parameters such as LVW/BW and LVCA/BW were measured, mRNA of cardiac genes such as βMHC, BNP, TGF-β₁, collagen I and III were quantified, and survival rates were calculated. RESULTS: Compared with sham-operated rats, MI rats without therapy showed significant increases in histomorphometric parameters as well as in mRAN expressions of cardiac genes (P<0.01); While their hemodynamic parameters were significantly impaired (P<0.01), and survival duration shortened (P<0.05). Compared with MI rats without therapy, MI rats treated with TCV116 showed significant attenuation of mRAN expression of cardiac genes (P<0.01); While their hemodynamic parameters were significantly improved (P<0.05 or P＜0.01), and survival duration extended (P<0.05). CONCLUSION: Treatment with long-term angiotensin II type 1 receptor antagonist may improve left ventricular remodeling and cardiac function after MI in rats.     

Effect of arachidonylethanolamide in paraventricular nucleus on cardiac function and sympathetic nerve activity in rats with heart failure

AIM:To determine the roles of the arachidonylethanolamide (AEA) in the paraventricular nucleus (PVN) in cardiac function and sympathetic activity in the rats with chronic heart failure (CHF). METHODS:Chronic heart failure was induced by left coronary ligation in Wistar rats and was confirmed using echocardiography. The rats with CHF and the sham-operated controls (sham group) were treated for 4 weeks with a continuous PVN infusion of AEA, cal-cium-calmodulin-dependent protein kinase Ⅱ (CaMKⅡ) selective inhibitor KN-93, transient receptor potential vanilloid type 1 (TRPV1) channel blocker capsazepine (CPZ), intracellular calcium chelator BAPTA-AM, small-conductance calcium-activated potassium channel (SK channel) blocker apamin and artificial cerebrospinal fluid (vehicle). Sympathetic drive indexes and cardiac function were detected. NG108 cells were incubated with AEA, and then the intracellular cal-cium concentration was measured by fluorometry. The protein expression levels of CaMKⅡ, SK₂ and phosphorylated TRPV1 were determined by Western blot. RESULTS:Compared with sham group, the left ventricular end-diastolic pressure (LVEDP) increased significantly, while peak rate of rise/decline of left ventricular pressure (±dp/dt_max) and ejection fraction (EF) decreased significantly in the CHF group. The concentrations of AEA and intracellular calcium, and the protein levels of CaMKⅡ, SK₂ and phosphorylated TRPV1 in PVN were significantly lower in CHF rats. Compared with the vehicle group, the mortality and sympathetic drive were decreased significantly and cardiac function was improved after treatment with AEA in CHF group. However, PVN perfusion of KN-93, CPZ, BAPTA-AM or apamin contributed to the sympathetic drive and deteriorated the cardiac function. AEA dose-dependently increased intracellular calcium ion concentration, and the protein levels of CaMKⅡ, SK₂ and phosphorylated TRPV1 in NG108 cells. CONCLUSION:AEA in the PVN may be involved in the improvement of cardiac function and sympathetic overdrive via CaMKⅡ/TRPV1/Ca²⁺/SK₂ pathway in rats with CHF.     

Effects of non-excitatory electric stimulation on cardiac function in normal and infarcted heart rabbits and it's regional effect on myocardium

AIM: To investigate the influences of electric stimulation applied during the absolute refractory period (ARP) on the cardiac function of normal rabbits and rabbits after myocardial infarction (MI) and to observe the regional effects of this electric stimulation. METHODS: 64 rabbits were randomly assigned to normal and MI groups and each group was then divided into the anterior and posterior groups. A thoracotomy was performed 4 weeks after MI in rabbits. One set of electrodes was inserted into the anterior and posterior wall of left ventricle of the anterior and posterior groups, respectively. Current pulses were delivered during the ARP (called CCM) during sinus rhythm in rabbits. The left ventricular systolic pressure (LVSP) and the left ventricular end diastolic pressure(LVEDP) as well as maximum positive and negative left ventricular pressure change (±dp/dt_max) were observed. RESULTS: In the normal and MI groups, LVSP, +dp/dt_max significantly increased, and LVEDP, -dp/dt_max were reduced during CCM stimulation compared with the baseline (P<0.05). In the normal rabbits, electric stimulation in the anterior group improved the cardiac function more significantly than that in the posterior group (P<0.05). In the MI rabbits, there was no difference between the anterior and the posterior groups (P>0.05). CONCLUSION: Electric stimulation delivered during the ARP significantly enhances the contractility and the relaxation of myocardium in normal rabbits and rabbits after MI, and the effects of CCM stimulation on heart are regional.     

Protective role of carnosine on cardiac dysfunction in type 1 diabetes mellitus rat model

AIM:To explore the effects of carnosine (CAR) on cardiac dysfunction in type 1 diabetic mellitus rats and the underlying mechanism. METHODS:The SD rats were randomly divided into 4 groups:control (C) group, control+carnosine (C+CAR) group, diabetes mellitus (DM) group and diabetes mellitus+carnosine (DM+CAR) group (n=10). The rats were sacrificed after 12 weeks. The cardiac function was assessed by ventricular cannulation. The activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA) were assessed by ELISA. The mRNA levels of tumor necrosis factor α(TNF-α), interleukin-1β(IL-1β) and IL-6 were measured by real-time PCR. The distribution of connexin 43 (Cx43) was examined by immunofluorescence. The protein levels of Cx43 and protein kinase C (PKC) were determined by Western blot. RESULTS:Compared with the C group, the left ventricular end diastolic pressure (LVEDP) was increased whereas the left ventricular pressure maximum rise/fall velocity (±dp/dt_max) was decreased in the DM group (P<0.01). The activity of SOD decreased while the MDA increased in the left ventricular tissues (P<0.01). The mRNA levels of TNF-α, IL-1β and IL-6 were increased (P<0.01). The Cx43 distribution was irregular. The protein levels of phosphorylated Cx43 and PKCε were elevated (P<0.01). Compared with the DM group, the cardiac function of LVEDP and ±dp/dt_max in DM+CAR group was ameliorated (P<0.01), with increased SOD activity and decreased MDA content (P<0.05). The mRNA levels of TNF-α, IL-1β and IL-6 were reduced (P<0.01). The Cx43 distribution was improved and the protein levels of phosphorylated Cx43 and PKCε were decreased (P<0.01). CONCLUSION:CAR treatment can improve the cardiac function by its anti-oxidative and anti-inflammation effects and suppression of Cx43 abnormalities through PKCε in DM rats.     

Combinational effects of trimetazidin and parecoxib on acute myocardial infarction in rats

AIM: To investigate the protective effects and mechanisms of combinational use of trimetazidine(TMZ) and parecoxib sodium on acute myocardial infarction (AMI) in rats. METHODS: Sixty-six Sprague-Dawley rats were randomly divided into 5 groups: sham group; AMI group; AMI+TMZ group; AMI+parecoxib group; AMI+TMZ+parecoxib group. All rats were sacrificed and cardiac functions (HR, LVSP, LVEDP, +dp/dt_max,-dp/dt_max) were measured with a Pclab-3804 biological signal processing system on the 8th day. The infarct size in each group was checked up by TTC staining method. RT-PCR was employed to detect the bax mRNA and bcl-2 mRNA. The protein levels of COX-2, Bax, Bcl-2 and cleaved caspase-3 in myocardium were determined by Western blotting. The activity of caspase-3 in each group was measured by colorimetric assay kit, and the apoptotic rates were detected with DNA ladder kit.RESULTS: Compared with sham group, increased expression of COX-2 protein (P<0.01) was observed in AMI group. The expression of COX-2 protein in parecoxib group was lower than that in AMI group (P<0.01). Compared with AMI group, the combinational use of trimetazidin and parecoxib improved contractile functions (LVSP and +dp/dt_max), reduced the infarct size and lowered the apoptotic rates remarkably. Specifically, the combinational use of trimetazidin and parecoxib showed better effects than use of trimetazidin or parecoxib alone. Reduced expression of Bax/Bcl-2 mRNA and protein, the reduced caspase-3 activity and cleaved caspase-3 expression were also found in combinational group as compared with other groups (P<0.05).CONCLUSION: The combinational use of trimetazidin and parecoxib effectively improves cardiac functions and reduces infarct size. The mechanism of the protective effect is probably associated with inhibiting apoptosis of cardiac myocytes.     

Effects of different β-adrenergic receptors on cardiac systolic and diastolic functions in hypoxic stress rats

AIM:To explore the effects of different β-adrenergic receptors (β-AR) on the left and right ventricular systolic and diastolic functions in rats under acute hypoxic stress. METHODS:The healthy male SD rats were randomly divided into 4 groups (n=7):control group, non-selected β-AR blocker propranolol group, selected β₁-AR blocker atenolol group and selected β₂-AR blocker ICI 118,551 group, and then the rats were exposed to normoxia (20.9% O₂, 79.1% N₂) and hypoxia (15.0% O₂, 85.0% N₂) condition respectively at the altitude of 2 260 m (Xining, China). The heart rate (HR), the left ventricular systolic pressure (LVSP), the right ventricular systolic pressure (RVSP), and the maximum raise/decline rate of left and right ventricular pressure (±dp/dt_max) were monitored, and the arterial blood gas in normoxia and hypoxia condition were compared to explore the effect of β-AR on the left and right ventricular systolic and diastolic functions in acute hypoxic stress rats. RESULTS:Under normoxia condition, the LVSP, ±dp/dt_max of left ventricular were decreased in propranolol group, atenolol group and ICI 118,551 group, the RVSP and ±dp/dt_max of right ventricle were decreased in propranolol group and atenolol group (P<0.05). Under hypoxia condition, the PaO₂, LVSP, ±dp/dt_max of left ventricle were decreased in all groups compared with the normoxia group, and the ±dp/dt_max of right ventricle was increased in all groups (P<0.05), also the degree of index change in control group was more obvious than that in propranolol group and atenolol group. CONCLUSION:The activation of β₁-AR is an important compensatory regulation for heart function during hypoxic stress. However, the compensatory enhancement of right heart function under acute hypoxia condition which through tonogenic dilation is more significant for maintaining the normal circulating blood flow.     

Short-term cardioprotective effects of trimetazidine on acute myocardial infarction in rats

AIM: To observe the myocardial protective effects of trimetazidine on myocardial infarction (MI) in Sprague-Dawley (SD) rats. METHODS: Ninety SD rats were randomly assigned to 3 groups (n=30 each): myocardial infarction group (MI group), MI+trimetazidine group (MT group) and sham group (S group). By permanently ligating the left anterior descending artery, the MI model was set up in the rats in MI group and MT group. Before and after setting up the MI model, normal saline was given to the rats in MI and S group by gavage. On the other hand, trimetazidine (3 mg/kg,twice per day) was given to the rats in MT group by gavage. At 8 h, 24 h and 48 h after applying trimetazidine, the serum level of cardiac troponin I (cTnI) was measured. At the 1st week, 2nd week and 4th week after treated with trimetazidine, the size of myocardial infarction, the maximum rising rate of the left ventricular systolic pressure (+dp/dt_max) and the maximum descending rate of the left ventricular diastolic pressure (-dp/dt_max) were measured. Also at the 1st week after applying trimetazidine, the cardiomyocyte apoptotic index was detected. RESULTS: Compared with MI group 2 weeks after applying trimetazidine, +dp/dt_max significantly increased in MT group , and -dp/dt_max also significantly increased in MT group . Four weeks after applying trimetazidine, +dp/dt_max significantly increased in MT group , and -dp/dt_max also significantly increased in MT group . At 8 h and 48 h after applying trimetazidine, no statistically significant difference (P＞0.05) of serum cTnI between MI group and MT group was observed. However, at 24 h after applying trimetazidine, the serum level of cTnI decreased in MT group as compared with MI group . Aditionally, trimetazidine significantly decreased the infarction size of myocardium in MT group (0.248±0.052) as compared with MI group (0.362±0.082, P<0.01). CONCLUSION: Trimetazidine has short-term cardioprotective effects on the rats with acute MI by improving myocardial systolic and diastolic functions, reducing infarct size and inhibiting apoptosis.     

Endogenous basic fibroblst growth factor is a protective factor against myocardial ischemia/reperfusion injury of rats

AIM: To observe the role of exogenous and endogenous basic fibroblst growth factor (bFGF) on myocardial ischemia/reperfusion(I/R) injury of rats.METHODS:bFGF and bFGF antiserum were applied to rat isolated I/R heart. Myocardial function, coronary effluent volume,protein and myoglobin content as well as LDH activity in coronary effluent fluid, myocardial calcium, MDA and ATP concentration as well as PKC, MAPK activity were measured. RESULTS:Compared with control, myocardial function in I/R group significantly decreased. Protein, myoglobin content and LDH activity in coronary effluent liquid as well as myocardial MDA and calcium content increased, while myocardial ATP concentration decreased(all P＜0.01). Compared with I/R group, ±LV dp/dt_max in bFGF group increased by 43% and 26%, respectively. LVEDP decreased by 40%. HRr/HRi and B/A augmented by 42% and 20%, respectively. Protein and myoglobin content as well as LDH activity lowered by 29%,30％ (all P＜0.01) and 33％ (P＜0.05) respectively. Myocardial MDA and calcium content decreased by 44% and 35%, respectively, while myocardial ATP level as well as PKC and MAPK activity increased by 34%,41％ and 10% (all P＜0.01), respectively. In bFGF antiserum group, ±LV dp/dt_max were 35% and 38% lower than those in I/R group. LVEDP increased by 93%. HRr/HRi and B/A decreased by 36% and 45%, respectively. Protein and myoglobin content as well as LDH activity augmented by 54%,96％ (all P＜0.01) and 34％ (P＜0.05) respectively. Myocardial MDA and calcium content increased by 24% and 50%, respectively, while myocardial ATP level as well as PKC and MAPK activity lowered by 28%,21％ and 8% (all P＜0.01), respectively. CONCLUSION:Endogenous bFGF is a protective factor against myocardial ischemia/reperfusion injury of rats.     

Effect of ACTH on pain behavior and the level of brain-derived neurotrophic factor and corticotropin-releasing hormone in the hippocampus of rats with chronic pain

AIM: To observe the effect of adrenocorticotropic hormone(ACTH) on the levels of brain-derived neurotrophic factor(BDNF), trkB and corticotropin-releasing hormone(CRH) in the hippocampus of arthritic rats.METHODS: The BDNF immunoreactivity(IR) and CRH-positive neurons were stained with immunohistochemistry and in situ hybridization methods, respectively.RESULTS: The BDNF-IR, CRH mRNA-positive neurons in the contralateral hippocampus of the arthritic rats were increased significantly, which was decreased markedly by intraperitoneal injection of ACTH. However, the effect of ACTH was attenuated after adrenalectomy(ADX).CONCLUSION: These results suggest that BDNF and CRH in the hippocampus of arthritic rats were involved in the modulation of chronic pain, ACTH produced its analgesic effect by inhibiting the increase in BDNF and CRF level. Adrenal is critical to the analgesic action of ACTH.     

Role of GRP78 in alteration of myocardium induced by intestinal endotoxemia in cirrhotic rats

AIM: To explore the role of glucose-regulated protein 78 (GRP78) in the alteration of myocardium induced by intestinal endotoxemia in cirrhotic rats. METHODS: Fifty-one male Wistar rats were randomly divided into liver cirrhosis groups of 4-week, 6-week and 8-week, and normal control groups at corresponding time points. The cardiac functions of the 8-week rats were measured. Tumor necrosis factor α(TNF-α) and malondialdehyde(MDA) in myocardial tissues were detected. The number of myocardial cells and the collagen volume fraction (CVF) were determined with toluidine blue and van Giesan staining, respectively. The expression of GRP78 and hypoxia-inducible facotr 1α(HIF-1α) was analyzed by the method of immnunohistochemistry. RESULTS: Compared with normal control group at corresponding time point, left ventricular end-diastolic pressure(LVEDP) and ±LV dp/dt_max in 8-week group were significantly decreased (P<0.05). The levels of TNF-α, MDA and CVF, the protein expression of GRP78 and HIF-1α in the myocardial tissues were significantly increased in every model group (P<0.05), and the number of myocardial cells was gradually decreased (P<0.05). Elevated levels of endotoxin in plasma were positively correlated with the levels of alanine aminotransferase (ALT),homocysteine (Hcy) and TNF-α in plasma, the levels of TNF-α, MDA and CVF, and protein levels of GRP78 and HIF-1α in the myocardial tissues (P<0.05). Elevated protein expression of GRP78 in the myocardial tissues was positively correlated with the levels of ALT, Hcy in plasma and MDA, CVF, HIF-1α protein in the myocardial tissues (P<0.05). CONCLUSION: Intestinal endotoxemia induced by liver cirrhosis may directly or indirectly lead to endoplasmic reticulum stress and overexpression of GRP78. GRP78 may be a key molecule in the pathogenesis of myocardial remodeling and functional alteration induced by liver cirrhosis.     

Upregulated FAAH expression in PVN contributes to sympathoexcitation in rat with chronic heart failure

AIM: To investigate the expression of fatty-acid amide hydrolase (FAAH) in paraventricular nucleus (PVN) and its contribution to renal sympathetic nerve activity in rats with chronic heart failure (CHF). METHODS: A rat model of CHF was established by ligation of the left coronary artery to induce acute myocardial infarction. Eight weeks after ischemia, the rat model of CHF was identified by echocardiogram and histopathological observation. The plasma level of norepinephrine (NE) was detected by ELISA. The protein expression levels of FAAH in the PVN were determined by Western blot. The N-arachidonoylethanolamide (AEA) generation in PVN was analyzed by high-performance liquid chromatography. After microinjection of AEA, PF3845 (an FAAH inhibitor) or rAAV2-FAAH shRNA virus in PVN, the sympathetic drive indexes were recorded in different experiment groups. RESULTS: Compared with the rats in sham group, the cardiac function and AEA concentration in PVN were significantly reduced, while the plasma NE level and FAAH expression in PVN were obviously increased in the CHF rats (P<0.05). After microinjecion of PF3845, AEA or rAAV2-FAAH shRNA virus in PVN, the sympathetic drive indexes were decreased significantly and the cardiac function were improved in the CHF rats. CONCLUSION: Upregulated FAAH expression in PVN may result in sympathoexcitation in the rat with CHF.     

Influence of vestibular training on plasma levels of stress-related hormones in rats with motion sickness

AIM: To investigate the relationship between motion sickness and the plasma levels of stress-related hormones in the rats before and after vestibular training.METHODS: Conditioned taste aversion (CTA) was induced in 72 female SD rats after rotatory stimulation. The magnitude of CTA was measured to reflect the susceptibility of rats to motion sickness. The plasma levels of corticosterone, adrenocorticotrophic hormone (ACTH), corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) were analyzed by radioimmunoassay. Hormone levels were determined before and after rotatory stimulation, and after 1 month of vestibular training when the rats obtained habituation to this rotation.RESULTS: CTA to 0.15% saccharin solution in rats after the rotatory stimulation was completely inhibited after vestibular training, suggesting that a habituation of the rats to motion sickness was obtained. The rotatory stimulation induced an elevation in the plasma levels of corticosterone, ACTH and AVP, and this response of corticosterone to rotation was greatly reduced after vestibular training. The plasma levels of all 4 hormones in the rats insusceptible to motion sickness were higher than those in susceptible group, especially the plasma levels of corticosterone and ACTH after rotation, and the basal level of CRH. In addition, after vestibular training, the basal plasma levels of corticosterone, ACTH and CRH in both groups were higher than those before training, and a slight elevation was also observed in the basal level of AVP.CONCLUSION: Vestibular training may induce a habituation to rotatory stimulation in rats, thus inhibiting the development of motion sickness. The difference of the susceptibility of rats to motion sickness may negatively relate to the basal plasma levels of stress-related hormones.     

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.     

Effects of exogenous ADM on HPA axis in early stage of acute mechanical renal trauma

AIM: To explore the effects of exogenous adrenomedullin(ADM) on hypothalamus-pituitary-adrenal cortex (HPA)axis in the early stage of acute mechanical renal trauma.METHODS: Healthy adult Wistar rats were randomly divided into 4 groups: 8 in control group, 32 in trauma group, 32 in the group injected with ADM before trauma and 32 in the group injected with ADM after trauma. To induce renal trauma, the rats in the latter 3 groups were subjected to mechanical impact directly on the skin of renal region by a free-fall iron hammer. The rats in 2 treatment groups were injected with ADM (0.1 nmol/kg) intraperitoneally 10 min just before and after trauma,respectively. The rats in the 3 groups with kidney injury were executed in batches by drawing all the blood quickly in the hearts at the time points of 1 h, 6 h, 12 h and 24 h after trauma. The hypothalamus tissues were also collected. The expression of corticotropin-releasing hormone(CRH) in hypothalamus and the concentrations of adrenocorticotropic hormone(ACTH) and cortisol(CORT) in plasma were detected by immunohistochemical method and radioimmunoassay. RESULTS: The expression of CRH in hypothalamus and the concentrations of ACTH and CORT in plasma in trauma group,but were slightly higher than those in control group,but without statistical significance. The expression of CRH in hypothalamus at 1 h and 24 h, the concentration of ACTH in plasma at 12 h and CORT at 6 h,12 h and 24 h in the group injected with ADM before trauma significantly higher than those in trauma group and control group (P<0.05). The expression of CRH in hypothalamus at 1 h, 6 h and 12 h and the concentration of CORT in plasma at 12 h and 24 h in the group injected with ADM after trauma were obviously higher than those in trauma group and control group (P<0.05). CONCLUSION: Exogenous ADM stimulates HPA axis and activates the function of HPA axis markedly. However, the different layers of HPA axis have different responses to exogenous ADM. Injection of ADM before or after trauma has different effects on HPA axis.