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Cardiovascular Research 2003 60(2):413-420; doi:10.1016/S0008-6363(03)00535-2
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Copyright © 2003, European Society of Cardiology

Impact of chymase inhibitor on cardiac function and survival after myocardial infarction

Denan Jina,*, Shinji Takaia, Mayumi Yamadaa, Masato Sakaguchia, Keiichi Kamoshitab, Koichi Ishidab, Yoshikazu Sukenagab and Mizuo Miyazakia

aDepartment of Pharmacology, Osaka Medical College, 2–7 Daigaku-machi, Takatsuki City, Osaka 569-8686, Japan
bResearch and Development Division, Nippon Kayaku Co., Ltd., Kita-ku, Tokyo 115-8588, Japan

*Corresponding author. Tel.: +81-72-684-6418; fax: +81-72-684-6518. Email address: pha012{at}art.osaka-med.ac.jp

Received 17 January 2003; accepted 23 July 2003


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
Objectives: Recent studies have demonstrated that hamsters, like humans, possess both angiotensin converting enzyme (ACE)- and chymase-dependent angiotensin (Ang) II-forming pathways in cardiovascular tissues. We recently found that, after myocardial infarction (MI) in hamsters, cardiac chymase was significantly activated. In order to determine whether suppression of cardiac chymase activity could provide prognostic benefit after MI, we examined the effects of NK3201, a novel, orally active and specific chymase inhibitor, on cardiac function and survival during the acute phase of MI in hamsters. Methods: Two hundred and ten male Syrian hamsters were used in the present study. The left coronary artery of each hamster was ligated to induce MI. NK3201 at a dose of 30 mg/kg per day was administered orally by gastric gavage, starting either 3 days before or 1 day after MI. Results: ACE and chymase activities were significantly increased in the infarcted left ventricle 3 days after MI. NK3201 treatment starting 3 days before MI significantly inhibited the increase in cardiac chymase activity, while it did not affect ACE activity either in plasma or in heart 3 days after MI. A significant improvement in cardiac function was observed 3 and 14 days after MI in the group receiving NK3201. Compared with vehicle treatment, NK3201 treatment initiated either 3 days before or 1 day after MI significantly reduced the mortality rate during the 14 days of observation following MI. Conclusions: These findings indicate that cardiac chymase plays an important role after MI and this finding may provide a novel therapeutic target in post-MI treatment.

KEYWORDS Angiotensin; Heart failure; Infarction; Ischemia; Ventricular function


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 References
 
It is well known that the cardiac expression and activity of angiotensin converting enzyme (ACE), the angiotensin (Ang) II concentration, and Ang II type 1 (AT1) receptors are increased in infarcted hearts [1–3]. A growing body of evidence has also confirmed that blockade of Ang II action improves post-myocardial infarction (MI) prognosis in both patients and animals [4–6], suggesting that an increase in Ang II generation may have a deleterious effect after MI. Since ACE inhibitor therapy was introduced for the treatment of heart failure (HF) due to MI, it has certainly saved many thousands of lives. The mechanism for ACE inhibition is mainly considered to result from the reduction of Ang II generation from Ang I [7,8]. However, despite adequate ACE inhibitor therapy, the deleterious effects of Ang II may not always be eradicated completely. For example, the plasma Ang II concentration under long-term ACE inhibitor treatment returns to normal levels after a significant drop during the initial phase of treatment when this inhibitor is administered to patients with MI [9]. It has also been reported that the prognosis for a significant subset of patients treated with ACE inhibitors after MI did not significantly improve [10,11]. Interestingly, compared to the ACE inhibitor captopril, treatment with losartan, an AT1 receptor antagonist, showed an unexpected survival benefit in patients with symptomatic heart failure in the ELITE study [5]. These findings suggest that Ang II production through ACE-independent Ang II-forming pathways may still occur under such conditions even after ACE has been fully inhibited.

From recently accumulated evidence, the chymase-dependent Ang II-forming pathway is thought to be the most probable candidate for this ACE-independent Ang II-forming pathway [12–17]. In isolated human gastroepiploic arteries, for example, 30% of the Ang I-dependent vasocontractile responses are reportedly suppressed by ACE inhibition, and the remainder was blocked by chymase inhibition [18]. It has also been reported that cardiac chymase in human hearts accounts for >90% of Ang II formation [12]. However, this chymase-dependent Ang II-forming pathway seems to vary among various animal species [13,14]. In monkey, dog and hamster cardiovascular tissues, chymase has been reported to act as an efficient Ang II converting enzyme as in humans, whereas in rat and rabbit, chymase was reported to act as an Ang I degrading enzyme [13,14,19]. For this reason, different effects seem to occur for different species in response to ACE inhibitor treatment. Previous studies have demonstrated that the beneficial effects of ACE inhibitors on cardiac function and survival in a rat MI model were similar to those of AT1 receptor antagonists [20]. However, we recently found that the activation of cardiac chymase in a hamster MI model was more striking than that of ACE, and that AT1 receptor antagonist treatment rather than ACE inhibitor treatment alone provided more significant beneficial effects on cardiac function and survival [21]. These findings suggested that the increase in Ang II production via activated cardiac chymase plays an important role after MI. It also led us to suspect that the different effects of ACE inhibitors in rat and hamster following MI might depend on whether or not the cardiac tissues contain Ang II-generating chymase.

As is well known, this issue cannot be clarified without chymase specific inhibitors. Recently, an orally active and specific chymase inhibitor, NK3201 (2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[{3,4-dioxo-1-phenyl-7-(2-pyridyloxy)}-2-heptyl]acetamide), was newly developed [22–24]. In this study, in order to clarify the pathophysiological role of activated cardiac chymase after MI, the effects of NK3201 on cardiac function and survival were determined in a hamster model of MI.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 References
 
The chymase inhibitor NK3201 was kindly donated by Nippon Kayaku Co., Ltd. (Tokyo, Japan). Two hundred and ten male Syrian hamsters (SLC, Shizuoka, Japan) aged 6 weeks and weighing 90–110 g were used. The experimental procedures for animals were conducted in accordance with the guidelines of Osaka Medical College for medical experiments approved by the ethics committee. The hamsters were fed regular hamster chow, had free access to tap water, and were housed in a temperature-, humidity-, and light-controlled room.

2.1. Myocardial infarction
MI was induced in hamsters using techniques described previously [21]. In brief, the animals were anesthetized with sodium pentobarbital (50 mg/kg, i.p.) and a left-sided thoracotomy was performed under positive ventilation. After opening the chest, the left coronary artery (LCA) was ligated near its origin, and then the thoracotomy site was closed in layers. After surgery, the hamsters received food and water ad libitum. It has been reported that the mortality rate in rats within the first 48 h after MI is about 40% [2,25], but in hamsters, it was less than 5% in this study. Seventy hamsters underwent LCA ligation for vehicle treatment, and two of them were dead within 24 h. In the group receiving NK3201 treatment initiated 3 days before induction of MI, 69 hamsters underwent LCA ligation, and two of them were dead within 24 h. In the group receiving NK3201 treatment initiated 1 day after induction of MI, 40 hamsters underwent LCA ligation, and one of them was dead within 24 h.

2.2. Preparation of tissue samples
On days 3 and 14 after MI, hamsters were sacrificed with an overdose of sodium pentobarbital within 1 to 3 h after the final administration of NK3201. After collection of trunk blood, the hearts were harvested and some of them were divided into infarcted and non-infarcted (sham-operated hamster) left ventricle (LV), septum, and right ventricle (RV), and were frozen at –80°C for biochemical assays. For the determination of infarct size, four transverse slices approximately 3 mm thick were cut from apex to base in the other hearts and these slices were fixed in methanol–Carnoy's fixative and embedded in paraffin.

2.3. Assessment of infarct size
Four 5-µm sections were cut from each slice. To measure infarct size, every section was stained with azan Mallory stain and the infarct size was determined by using a computerized morphometry system, MacSCOPE Ver 2.2 (Mitani Co., Hukui, Japan). Infarct size was expressed as a percentage of the LV circumference. Mean infarct sizes of less than 15% were excluded from the analysis. One vehicle-treated hamster, two hamsters in the group receiving NK3201 treatment starting 3 days before induction of MI, and two hamsters in the group receiving NK3201 treatment starting 1 day after induction of MI were excluded from the analysis due to small infarction size.

2.4. Biochemical assays
ACE and chymase activities were measured according to methods described previously [21,26,27]. In brief, tissues were minced and homogenized in five volumes (w/v) of 20 mM Tris–HCl buffer, pH 8.3, containing 5 mM Mg(CH3COO)2, 30 mM KCl, 250 mM sucrose and 0.5% Nonidet P-40. An aliquot of the homogenate was used for the measurement of ACE and chymase activities. ACE activity in plasma or in tissue extracts was measured using a synthetic substrate, hippuryl-His-Leu (HHL), that was specifically designed for ACE (Peptide Institute, Inc., Osaka, Japan). Chymase activity in the tissue extract was measured with Ang I as a substrate in the presence of inhibitors of ACE and angiotensinases (5 mM ethylenediaminetetraacetic acid, 8 mM dipyridyl and 0.77 mM diisopropyl phosphorofluoridate). Total Ang II-forming activity in cardiac slices tissue was measured according to methods described previously [28]. Plasma renin activity (PRA) was measured by radioimmunoassay of [125I]-Ang I using an SRL kit (TFB, Tokyo, Japan). Protein concentration was measured using the bicinchoninic acid protein assay reagent (Pierce Chemical, Rockford, IL, USA) using bovine serum albumin as a standard.

2.5. Administration of NK3201
We reported that oral administration of NK3201 at a dose of 30 mg/kg per day significantly inhibited the increased chymase activity observed in injured uterus and successfully prevented peritoneal adhesion formation in hamsters [24]. Therefore, this dose was chosen in the present study. NK3201 was suspended in 5% gum arabic solution and was administered orally by gastric gavage, starting either 3 days before or 1 day after MI. Untreated animals were administered vehicle (0.2 ml of 5% gum arabic solution) in the same manner.

2.6. Hemodynamic measurement
Hamsters were re-anesthetized with pentobarbital sodium and the trachea was intubated at 3 and 14 days after the operation. A polyethylene catheter was introduced into the right carotid artery. The catheter was then connected to a pressure transducer (TP-200T; Nihon Kohden, Tokyo, Japan) and the mean arterial blood pressure (MABP) and heart rate (HR) were measured. After this procedure, the thorax was opened under positive-pressure respiration and a catheter was inserted into the LV chamber via its apex, where left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), as well as maximal positive and negative rates of pressure development (+dP/dt and –dP/dt) were measured. Finally, trunk blood and hearts were harvested for later biochemical assay and infarct size assessments.

2.7. Echocardiographic study
Three days after surgery, echocardiographic studies were performed for the three groups [(i) sham-operated hamsters, (ii) vehicle-treated hamsters and (iii) NK3201-treated hamsters; NK3201 treatment was initiated 3 days before induction of MI] using an echocardiographic system (Nemio 30, Toshiba, Japan) according to methods described previously [29]. In brief, after intraperitoneal injection of ketamine HCl (25 to 50 mg/kg) and xylazine (5 to 10 mg/kg), M-mode tracings and pulse-wave Doppler spectra (E and A waves) of mitral inflow were recorded for each group.

2.8. Survival studies
The effects of NK3201 (30 mg/kg, per day) on survival were assessed in the three groups (the vehicle-treated group and the two NK3201-treated groups in which treatment was initiated either 3 days before or 1 day after MI) and were followed for 14 days after MI. During the treatment period, cages were inspected daily for animals that had died. To determine infarct size in the surviving hamsters, hearts were harvested at the end of 14 days.

2.9. Statistical analysis
All numerical data shown in the text are expressed as the mean±standard error of the mean (S.E.M.). Significant differences between the mean values of two groups were evaluated by Student's t-test for unpaired data. Significant differences among the mean values of multiple groups were evaluated by one-way ANOVA followed by a post-hoc analysis (Fisher's test). Survival data are presented as Kaplan–Meier curves. The survival curves of individual groups were compared by the log-rank test. P<0.05 was used as the threshold for signifying a statistically significant difference.


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 References
 
Table 1 shows changes in body weight (BW), the ratio of whole heart weight (HW) to BW, and infarct size, 3 and 14 days after surgery. NK3201 treatment was initiated 3 days before induction of MI. There were no significant differences in BW among the sham-operated hamsters and the MI hamsters treated with vehicle or NK3201 3 days after the operation. However, BW was significantly lower in both vehicle-treated and NK3201-treated MI hamsters 14 days after the operation. On the other hand, there was no significant difference in BW between the MI hamsters treated with vehicle and NK3201 14 days after MI. Compared with sham-operated hamsters, the ratio of whole HW to BW was increased significantly in the vehicle-treated MI hamsters 3 and 14 days after operation, suggesting that cardiac hypertrophy might appear early after MI in this model. NK3201 treatment starting 3 days before MI significantly suppressed the cardiac hypertrophy resulting from MI. After a permanent LCA ligation in hamsters, our histological examination showed that all infarctions were transmural and involved only the free wall of the LV in the present study (data not shown). The mean infarct size of the vehicle-treated MI hamsters did not differ significantly from that of the NK3201-treated MI hamsters 3 and 14 days after operation.


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  		Table 1 Body weight, heart weight and infarct size of the sham-operated hamsters and the infarcted hamsters treated with vehicle or NK 3201

 
Table 2 shows the changes in enzyme activities in sham-operated hamsters, as well as in vehicle-treated and NK3201-treated MI hamsters 3 days after operation. NK3201 treatment was also initiated 3 days before induction of MI. PRA, as well as ACE and chymase activities in the infarcted LV, were significantly increased 3 days after LCA ligation when compared with these activities after sham operation. On the other hand, both the ACE and chymase activities of the vehicle-treated MI hamsters did not differ significantly from the sham-operated hamsters in either the noninfarcted LV (septum) or in the RV 3 days after operation. The plasma ACE activity of the vehicle-treated MI hamsters did not differ significantly from that of the sham-operated hamsters. Compared with vehicle treatment, NK3201 treatment significantly inhibited chymase activity in the infarcted LV and RV and tended to suppress chymase activity in the noninfarcted septum 3 days after MI. NK3201 treatment did not affect ACE activity in either cardiac tissue or in plasma 3 days after MI. Compared with vehicle-treated MI hamsters, PRA was further elevated in NK3201-treated hamsters, although this difference did not achieve statistical significance. Compared with the sham-operated group, the total Ang II-forming activity in heart slices was increased markedly 3 days after MI (Fig. 1). This increase was suppressed significantly by treatment with NK3201.


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  		Table 2 Chymase, angiotensin converting enzyme and renin activities in cardiac tissues and plasma from the sham-operated hamsters and the infarcted hamsters treated with vehicle or NK 3201 3 days after operation

 

Figure 1
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  		Fig. 1 Bar graph showing the formation of Ang II in sham-operated hamsters and in myocardial-infarcted hamsters treated with vehicle or NK3201 3 days after operation. The heart slices were incubated with 50 µm Ang I for 30 min. Each bar represents the mean±S.E.M. of data for seven hamsters. **P<0.01, ***P<0.001, vs. sham; {dagger}{dagger}P<0.01, vs. vehicle.

 
Table 3 shows changes in hemodynamic parameters in the three groups 3 and 14 days after surgery. Compared with sham-operated hamsters, significant decreases in HR, MABP, LVSP, and positive and negative dP/dt were observed in the vehicle-treated MI hamsters 3 and 14 days after surgery. LVEDP tended to increase in vehicle-treated MI hamsters compared with the sham-operated hamsters 3 and 14 days after the operation. Compared with the condition of MI hamsters treated with vehicle, NK3201 treatment starting 3 days before induction of MI reversed these hemodynamic changes to some extent 3 and 14 days after MI. In the present study, the hemodynamic parameters were also analyzed in two subgroups divided by infarct sizes (moderate MI vs. large MI). As can be seen in Table 3, there was a greater number of hamsters who survived in the NK3201-treated large MI group (infarct size >45%) and the total hemodynamic benefit was mainly due to improvement in cardiac function in the moderate MI group (infarct size range >15 to 45%).


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  		Table 3 Hemodynamic parameters from total hamsters or the hamsters classified according to infarct size as having moderate (>15 to 45%) and large (>45%) myocardial infarcts

 
Fig. 2 shows representative echocardiograms of sham-operated hamsters and of MI hamsters treated with either vehicle or NK3201 3 days after the operation. As can be seen in Table 4, MI resulted in a substantial reduction in ejection fraction (EF) and fractional shortening (FS) and tended to increase the ratio of E-wave to A-wave velocity (E/A). NK3201 treatment starting 3 days before induction of MI significantly increased EF and FS and tended to decrease E/A compared with vehicle-treated hamsters, indicating improvement of cardiac function by NK3201 due mainly to improvement in systolic function. These functional improvements were similar to the findings observed from direct measurements of hemodynamics, in which positive dP/dt and LVSP significantly improved and LVEDP also tended to decrease 3 days after MI in the NK3201-treated hamsters (Table 3).


Figure 2
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  		Fig. 2 Representative M-mode echocardiograms (A) and doppler spectra of mitral inflow (B) from sham-operated hamsters (Sham) and myocardial-infarcted hamsters treated with vehicle (Vehicle) or NK3201 (NK3201) 3 days after operation. NK3201 treatment was initiated 3 days before MI. LVDd, left ventricular dimension end diastole; LVDs, left ventricular dimension end systole; E, E-wave velocity; A, A-wave velocity.

 

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  		Table 4 Body weight, infarct size and echocardiographic parameters of the sham-operated hamsters and the infarcted hamsters treated with vehicle or NK3201 3 days after operation

 
Fig. 3 illustrates survival curves for vehicle-treated and NK3201-treated MI hamsters during the 14-day observation period after MI. Vehicle-treated MI hamsters exhibited a 14-day mortality rate of 52.7%. NK3201 treatment starting 3 days before MI reduced the 14-day mortality rate significantly in comparison with vehicle-treated MI hamsters (16.7%, P = 0.0015).


Figure 3
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  		Fig. 3 Cumulative survival rates of MI hamsters treated with vehicle or NK3201.

 
The purpose of the present study was to confirm whether suppression of the activated cardiac chymase provides functional and survival benefits after MI. For this reason, NK3201 treatment was initiated 3 days before induction of MI to obtain an assured inhibitory effect. However, medication is generally initiated after an MI in a clinic, so it was very important to determine if post-MI treatment can also provide similar benefits to medication started 3 days before MI. As can be seen in Fig. 3, if the intervention (NK3201, 30 mg/kg per day) was initiated 1 day after MI, deaths appeared earlier than if the NK3201 treatment had been started 3 days before induction of MI. However, the 14-day mortality rate was still significantly suppressed in this group compared with vehicle-treated hamsters (18.4%, P = 0.0027). Similar to the hamsters treated with NK3201 3 days before MI, the post-MI treatment also significantly improved cardiac function (LVSP, positive and negative dP/dt; data not shown). Infarct size in the post-MI treated group was also similar to that in the hamsters treated with NK3201 starting 3 days before induction of MI (39±2%, P>0.05).


   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
References
 
In the present study, inhibition of the coronary ligation-induced increase in cardiac chymase activity by NK3201, a chymase specific inhibitor, was associated with improvement in cardiac function and in survival rate after MI, indicating that the activation of cardiac chymase following MI plays an important role in post-MI pathology.

We previously found that the activation of cardiac chymase and ACE reached a peak and cardiac function decreased significantly in the infarcted hamsters 3 days after MI [21]. Hence, this point was chosen as the time to examine the relationship between the inhibition of activated cardiac chymase and cardiac function. Consistent with our previous report, cardiac chymase and ACE activities at the infarcted LV wall increased significantly 3 days after MI. It should be noted, however, that measuring chymase activity in tissue homogenates may yield an overestimate of the amount of chymase activity as compared to values for whole organs, since chymase is usually stored in mast cell granules and cannot exert its enzymatic action without degranulation. In the present study, the total Ang II-forming activity measured in tissues slices was also increased significantly 3 days after MI. Cardiac hypertrophy appeared from 3 days after MI and was sustained up to 14 days after MI. Cardiac function decreased significantly in the vehicle-treated MI hamsters, as indicated by the significant reduction in the LVSP, as well as the reductions in the positive and negative dP/dt and the slight increase in LVEDP 3 and 14 days after MI. Similar results were also obtained from the echocardiographic study. Deaths of vehicle-treated MI hamsters were seen starting from 3 days after MI and the mortality rate during the 14-day observation period reached about 52.7%. NK3201 treatment initiated 3 days before LCA ligation significantly inhibited cardiac chymase activity and total Ang II-forming activity, and these reductions were associated with a significant improvement in cardiac function, structural remodeling (cardiac hypertrophy) and survival rate. Because the occurrence of cardiac events is usually hard to predict, medication in a clinic is generally initiated after the cardiac event. Therefore, it is very important to determine for a new agent whether post-MI treatment can also provide prognostic benefit. Compared with vehicle-treated MI hamsters, NK3201 treatment initiated 1 day after MI also significantly improved survival rate, although the agent was somewhat less effective than if the treatment had been initiated 3 days before induction of MI. These results demonstrate that an increase in cardiac chymase activity may have harmful effects after permanent LCA ligation.

A marked beneficial effect of cardiac chymase inhibition by NK3201 on cardiac function and survival rate is not likely due to differences in infarct size in the three groups because NK3201 treatment did not significantly affect the mean infarct size at any observation point. Hamster chymase has been known to be an effective Ang II-generating enzyme [13,17], so these beneficial effects of NK3201 treatment after MI may be closely related to the reduction of Ang II generation, although changes in Ang II concentration in the present study could not be determined for technical reasons. This hypothesis is supported by the inhibitory effects of NK3201 on cardiac hypertrophy and the elevation of PRA after NK3201 treatment in this model. Furthermore, results from the experiment measuring total Ang II-forming activity indicated that the increased capacity of Ang II-generation in infarcted hearts was significantly inhibited by NK3201 treatment 3 days after MI. In reports using dog models of cardiovascular pathology, it was noted that the tissue Ang II concentration in either vein grafts [30] or failing hearts [31] was decreased by treatment with a chymase specific inhibitor. All traditional components of the renin–angiotensin system (RAS) are known to be activated following MI [1–3]. This activation, per se, appears to primarily maintain systemic homeostasis. However, the compensatory effects of the activated RAS may also produce other injurious actions [32,33]. Ang II, the final physiologically active product of the RAS pathway, accelerates cardiac hypertrophy and fibrosis in the non-infarcted myocardium, which is considered to be the major reason for the development of chronic heart failure after MI [32,33]. On the other hand, Ang II also facilitates the release of norepinephrine (NE) from cardiac sympathetic nerve endings, a phenomenon which may be closely related to sudden cardiac death during the post-MI acute phase [5,33–35]. In this study, death of vehicle-treated MI hamsters was seen as early as 3 days after MI, so these deaths may result from acute heart failure due to certain lethal arrhythmias. During this time, PRA, cardiac ACE and cardiac chymase activities reached their peak levels in this model [21]. A previous study also showed that the blockade of Ang II at the receptor level provided significant beneficial effects on cardiac function and survival rate [21], indicating that the increase of tissue Ang II concentration may be a major factor in the prognosis after MI in this model. On the other hand, in view of the fact that specific cardiac chymase inhibition also provided functional and survival benefits in the present study, these findings are similar to those observed with an AT1 receptor antagonist, suggesting that chymase-dependent Ang II formation is closely related to cardiac disorders after MI in hamsters.

In theory, if there is excessive Ang II production via both ACE and chymase under some pathological conditions, a more complete prevention of their injurious actions can be achieved by intercepting their target receptors rather than by inhibiting one of their generating enzymes. Recently, the ELITE study showed that losartan treatment provided more beneficial effects on survival and sudden cardiac death than captopril treatment in heart failure in the elderly [5], suggesting that the non-ACE-dependent Ang II-forming pathway may participate in such effects. However, this evidence was not supported by a later large-scale trial [36]. Furthermore, Val-HeFT also showed that the combined use of an AT1 receptor antagonist with an ACE inhibitor did not provide a survival advantage compared with an ACE inhibitor alone in patients with heart failure [37]. Thus, whether or not non-ACE-dependent Ang II formation is involved in such diseases is still controversial. One AT1 receptor antagonist trial is now underway to discover whether blockading Ang II action at the receptor level will provide more beneficial effects in comparison with ACE inhibition alone after MI in patients [38]. Therefore, further evidence of the pathophysiological role of the non-ACE-dependent Ang II-forming pathway after MI in humans should be awaited until this trial is completed.

In conclusion, inhibition of the increase in cardiac chymase activity that follows MI is associated with significant improvements in cardiac function, structural remodeling and survival rate, demonstrating that cardiac chymase participates in the pathophysiological state after MI.


   Acknowledgements
 
This study was supported, in part, by Grant-in-Aid 13670102 for Scientific Research (C) from the Ministry of Education, Science, Sports and Culture, Japan.


   Notes
 
Time for primary review 44 days


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 

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