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Effects of aldosterone on cardiac local rennin- angiotensin -aldosterone system: an important role of cardiac fibroblasts
The 8th Annual Scientific Meeting
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JHFS
S175
O-081
O-083
Effects of Aldosterone on Cardiac Local Rennin- Angiotensin -Aldosterone System: An Important Role of Cardiac Fibroblasts
Hypertrophic Stimuli Activate Cardiac Aldosterone System and Induce the Association Between Mineralocorticoid Receptor and p300 in Cardiac Myocytes KAWAMURA TERUHISA1, ONO KOH1, MORIMOTO TATSUYA2, YOSHIDA YOSHINORI2, ABE YUKIKO1, SOWA NAOYA1, KITA TORU2, HASEGAWA KOJI1 1 Division of Translational Research, Kyoto Medical Center, National Hospital Organization, Kyoto, Japan, 2Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University
UEHARA YOSHIKI, NAKABAYASHI YUMI, AZUMA YOSHIYUKI, SHIMIZU MITSUYUKI, MOCHIZUKI SEIBU Division of Cardiology, Department of Internal Medicine, Jikei University School of Medicine, Chiba, Japan Recent studies showed cardiac local renin-angiotensin-aldosterone system (RAAS) play a pivotal role in pathophysiology in heart, and spironolactone, which is aldosterone blockade has beneficial effects on prognosis of patients with heart failure. We sought to determine how aldosterone, which is distal component of RAAS, acts on cardiac local RAAS using cultured cardiac myocytes and fibroblasts, and whether spironolactone inhibits these effects. Cultured cardiocytes were prepared from 1- or 2-day-old neonatal SpragueDawley rats by digestion with collagenase and pancratin. Cardiac myocytes and fibroblasts were separated by Percoll method and cultivated. After starvation period, aldosterone was added to culture medium and later, total RNA was extracted from the cells. mRNAs of renin, angiotensiongen, and ACE were semiquantified by RT-PCR. Basal mRNA expressions of renin, angiotensinogen, and ACE were observed in both cadiac myocytes and fibroblasts. After 48 hours of aldosterone stimulation, ACE mRNA was significantly upregulated in cardiac fibroblasts, however, gene expressions of renin and angiotensinogen were unchanged in cardiac fibroblasts and none of these RAAS component was upregulated in cardiac myocytes. Moreover, spironolactone completely inhibited aldosterone-induced augmentation of ACE gene expression in cardiac fibroblasts.In conclusion, our data support an idea that cardiac local RAAS has positive feedback system, which mainly depends on cardiac fibroblasts, and clinical beneficial effects of spironolactone may be partly due to blockage of positive feedback circuit.
Aldosterone (ALD) has now revealed to be produced in the heart as well as the adreanals and to play a pivotal role in the development of left ventricular hypertrophy and heart failure in vivo. However, the precise role of cardiac ALD system in the pathogenesis of heart failure remains unknown. To solve this problem, we investigated direct effects of ALD on cardiac myocytes and their intracellular signalling pathways. In primary neonatal rat cardiac myocytes, stimulation with either ALD or phenylephrine (PE) was sufficient to increase the cell size and to activate hypertrophyassociated gene transcription. Co-stimulation of PE with ALD further augmented these hypertrophic responses. In addition, PE induced expression of an asldosterone synthase CYP11B2 and translocation of mineralocorticoid receptor (MR), a target molecule of ALD into cardiac nuclei. Conversely, spironolactone blocked this translocation and specifically inhibited PE-induced hypertrophic responses. Furthermore, we provide the first evidence that MR associates with p300 which functions as a transcriptional coactivator of hypertrophy-responsive transcription factors such as GATA4. Stimulation of cardiac myocyes with PE markedly increased MR/p300 association. Furthermore, co-transfection of MR and p300 revealed synergistic activation of GATA-4-dependent atrial natriuretic factor promoter activities. These findings demonstrate that hypertrophic stimuli induce translocation of MR into nuclei and association of MR with p300 in cardiac myocytes, resulting in the augmentation of p300/GATA-4-dependent transcriptional pathways of hypertrophy.
O-082
O-084
The Effect of Low Salt Diet and Aldosterone Blockade After Myocardial Infarction in Rats URABE AKIHIRO, ABE YUICHI, IZUMI TAKEHIKO, NAGAI MAKOTO, TANIGUCHI IKUO, MOCHIZUKI SEIBU The Jikei University School of Medicine, Division of Cardiology, Department of Internal Medicine
Clinical Significance of B-type Natriuretic Peptide in the Management of Heart Failure with Atrial Fibrillation KOITABASHI TOSHIMI, INOMATA TAKAYUKI, NAKANO HIRONARI, TAKEUCHI ICHIRO, SHINAGAWA HISAHITO, NISHII MOTOTSUGU, TAKEHANA HITOSHI, KUROKAWA SHINGO, IZUMI TOHRU Department of Internal Medicine and Cardiology, Kitasato University School of Medicine, Kanagawa, Japan
Purpose: We examined the effect of low salt intake and/or aldosterone blockade on the treatment of heart failure after MI. Methods: Rats weighing 250-300g were divided into 4 groups. 1) Sham operation (S), 2) MI with normal salt diet group (C), 3) MI with low salt diet group (CL) 4) MI with low salt diet and low dose of Ep treated group (EL). Rats were anesthetized with isoflurane. Chests were opened, and left anterior descending was ligated. After operation, rats were treated as described previously. An echocardiogram was performed to evaluate cardiac function and myocardial remodeling. To investigate cardiac fibrosis, rats were sacrificed, hearts were excised, and histological examination was performed. Results: One month after MI, mortality rate in CL group was decreased significantly compared with C group. However, Mortality rate in EL group was no significant change compared with CL group. Cardiac function was improved and cardiac fibrosis was decreased in CL group compared with C group. However, these parameters were no significant change between CL group and EL group. Conclusion These results suggest that useful effects of aldosterone receptor blockade after MI might be mainly due to sodium dependent pathway. Therefore, not only aldosterone receptor blockade but low salt diet is very important to prevent congestive heart failure after MI.
Background: B-type natriuretic peptide (BNP)-guided management has been widely used for the treatment of heart failure (HF). We previously reported that BNP-guided pharmacological intensification to achieve plasma BNP levels below 200 pg/ml improved the prognosis of HF in patients (pts) with atrial fibrillation (AF) more than in those with sinus rhythm (SR). It has never been investigated,however,whether the targeted levels of plasma BNP should be altered for adequate HF management in cases with AF. Purpose: We compared the plasma BNP levels with prognosis for HF between pts with SR and with AF. Methods: Pts who were admitted to our hospital for HF exacerbation in 1996-2001 were classified into an AF group (n ⫽ 44) and SR group (n ⫽ 75) according to basic cardiac rhythms. Cardiac events including worsening HF during 40 months after hospital discharge were respectively analyzed in relation to plasma BNP levels at discharge with receiver operating characteristic analysis. Results: The optimal threshold of plasma BNP to identify re-hospitalization was 155 pg/ml with sensitivity of 82% and specificity of 67% in patients with AF,while it was 75 pg/ml with sensitivity of 74% and specificity of 52% in patients with SR. Conclusion: The optimal plasma BNP level for adequate HF management should be modified in cases with AF.
•
JHFS
S175
O-081
O-083
Effects of Aldosterone on Cardiac Local Rennin- Angiotensin -Aldosterone System: An Important Role of Cardiac Fibroblasts
Hypertrophic Stimuli Activate Cardiac Aldosterone System and Induce the Association Between Mineralocorticoid Receptor and p300 in Cardiac Myocytes KAWAMURA TERUHISA1, ONO KOH1, MORIMOTO TATSUYA2, YOSHIDA YOSHINORI2, ABE YUKIKO1, SOWA NAOYA1, KITA TORU2, HASEGAWA KOJI1 1 Division of Translational Research, Kyoto Medical Center, National Hospital Organization, Kyoto, Japan, 2Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University
UEHARA YOSHIKI, NAKABAYASHI YUMI, AZUMA YOSHIYUKI, SHIMIZU MITSUYUKI, MOCHIZUKI SEIBU Division of Cardiology, Department of Internal Medicine, Jikei University School of Medicine, Chiba, Japan Recent studies showed cardiac local renin-angiotensin-aldosterone system (RAAS) play a pivotal role in pathophysiology in heart, and spironolactone, which is aldosterone blockade has beneficial effects on prognosis of patients with heart failure. We sought to determine how aldosterone, which is distal component of RAAS, acts on cardiac local RAAS using cultured cardiac myocytes and fibroblasts, and whether spironolactone inhibits these effects. Cultured cardiocytes were prepared from 1- or 2-day-old neonatal SpragueDawley rats by digestion with collagenase and pancratin. Cardiac myocytes and fibroblasts were separated by Percoll method and cultivated. After starvation period, aldosterone was added to culture medium and later, total RNA was extracted from the cells. mRNAs of renin, angiotensiongen, and ACE were semiquantified by RT-PCR. Basal mRNA expressions of renin, angiotensinogen, and ACE were observed in both cadiac myocytes and fibroblasts. After 48 hours of aldosterone stimulation, ACE mRNA was significantly upregulated in cardiac fibroblasts, however, gene expressions of renin and angiotensinogen were unchanged in cardiac fibroblasts and none of these RAAS component was upregulated in cardiac myocytes. Moreover, spironolactone completely inhibited aldosterone-induced augmentation of ACE gene expression in cardiac fibroblasts.In conclusion, our data support an idea that cardiac local RAAS has positive feedback system, which mainly depends on cardiac fibroblasts, and clinical beneficial effects of spironolactone may be partly due to blockage of positive feedback circuit.
Aldosterone (ALD) has now revealed to be produced in the heart as well as the adreanals and to play a pivotal role in the development of left ventricular hypertrophy and heart failure in vivo. However, the precise role of cardiac ALD system in the pathogenesis of heart failure remains unknown. To solve this problem, we investigated direct effects of ALD on cardiac myocytes and their intracellular signalling pathways. In primary neonatal rat cardiac myocytes, stimulation with either ALD or phenylephrine (PE) was sufficient to increase the cell size and to activate hypertrophyassociated gene transcription. Co-stimulation of PE with ALD further augmented these hypertrophic responses. In addition, PE induced expression of an asldosterone synthase CYP11B2 and translocation of mineralocorticoid receptor (MR), a target molecule of ALD into cardiac nuclei. Conversely, spironolactone blocked this translocation and specifically inhibited PE-induced hypertrophic responses. Furthermore, we provide the first evidence that MR associates with p300 which functions as a transcriptional coactivator of hypertrophy-responsive transcription factors such as GATA4. Stimulation of cardiac myocyes with PE markedly increased MR/p300 association. Furthermore, co-transfection of MR and p300 revealed synergistic activation of GATA-4-dependent atrial natriuretic factor promoter activities. These findings demonstrate that hypertrophic stimuli induce translocation of MR into nuclei and association of MR with p300 in cardiac myocytes, resulting in the augmentation of p300/GATA-4-dependent transcriptional pathways of hypertrophy.
O-082
O-084
The Effect of Low Salt Diet and Aldosterone Blockade After Myocardial Infarction in Rats URABE AKIHIRO, ABE YUICHI, IZUMI TAKEHIKO, NAGAI MAKOTO, TANIGUCHI IKUO, MOCHIZUKI SEIBU The Jikei University School of Medicine, Division of Cardiology, Department of Internal Medicine
Clinical Significance of B-type Natriuretic Peptide in the Management of Heart Failure with Atrial Fibrillation KOITABASHI TOSHIMI, INOMATA TAKAYUKI, NAKANO HIRONARI, TAKEUCHI ICHIRO, SHINAGAWA HISAHITO, NISHII MOTOTSUGU, TAKEHANA HITOSHI, KUROKAWA SHINGO, IZUMI TOHRU Department of Internal Medicine and Cardiology, Kitasato University School of Medicine, Kanagawa, Japan
Purpose: We examined the effect of low salt intake and/or aldosterone blockade on the treatment of heart failure after MI. Methods: Rats weighing 250-300g were divided into 4 groups. 1) Sham operation (S), 2) MI with normal salt diet group (C), 3) MI with low salt diet group (CL) 4) MI with low salt diet and low dose of Ep treated group (EL). Rats were anesthetized with isoflurane. Chests were opened, and left anterior descending was ligated. After operation, rats were treated as described previously. An echocardiogram was performed to evaluate cardiac function and myocardial remodeling. To investigate cardiac fibrosis, rats were sacrificed, hearts were excised, and histological examination was performed. Results: One month after MI, mortality rate in CL group was decreased significantly compared with C group. However, Mortality rate in EL group was no significant change compared with CL group. Cardiac function was improved and cardiac fibrosis was decreased in CL group compared with C group. However, these parameters were no significant change between CL group and EL group. Conclusion These results suggest that useful effects of aldosterone receptor blockade after MI might be mainly due to sodium dependent pathway. Therefore, not only aldosterone receptor blockade but low salt diet is very important to prevent congestive heart failure after MI.
Background: B-type natriuretic peptide (BNP)-guided management has been widely used for the treatment of heart failure (HF). We previously reported that BNP-guided pharmacological intensification to achieve plasma BNP levels below 200 pg/ml improved the prognosis of HF in patients (pts) with atrial fibrillation (AF) more than in those with sinus rhythm (SR). It has never been investigated,however,whether the targeted levels of plasma BNP should be altered for adequate HF management in cases with AF. Purpose: We compared the plasma BNP levels with prognosis for HF between pts with SR and with AF. Methods: Pts who were admitted to our hospital for HF exacerbation in 1996-2001 were classified into an AF group (n ⫽ 44) and SR group (n ⫽ 75) according to basic cardiac rhythms. Cardiac events including worsening HF during 40 months after hospital discharge were respectively analyzed in relation to plasma BNP levels at discharge with receiver operating characteristic analysis. Results: The optimal threshold of plasma BNP to identify re-hospitalization was 155 pg/ml with sensitivity of 82% and specificity of 67% in patients with AF,while it was 75 pg/ml with sensitivity of 74% and specificity of 52% in patients with SR. Conclusion: The optimal plasma BNP level for adequate HF management should be modified in cases with AF.