Comparative effects of losartan, captopril, and enalapril on murine acute myocarditis due to encephalomyocarditis virus

Therapies to limit myocardial injury in animal models of myocarditis: a systematic review and meta-analysis

Current myocarditis guidelines do not advocate treatment to prevent myocardial injury and scar deposition in patients with myocarditis and normal left ventricular ejection fraction. We aimed to ascertain the utility of beta blockers, calcium channel blockers and antagonists of the renin–angiotensin system in ameliorating myocardial injury, scar formation and calcification in animal in vivo models of myocarditis. The project was prospectively registered with the PROSPERO database of systematic reviews (CRD42018089336). Primary outcomes (necrosis, fibrosis and calcification) were meta-analysed with random-effects modelling. 52 studies were systematically reviewed. Meta-analysis was performed compared with untreated controls. In each study, we identified all independent comparisons of treatment versus control groups. The pooled weighted mean difference (WMD) indicated treatment reduced necrosis by 16.9% (71 controlled analyses, 95% CI 13.2–20.7%; P < 0.001), however there was less evidence of an effect after accounting for publication bias. Treatment led to a 12.8% reduction in fibrosis (73 controlled analyses, 95% CI 7.6–18.0%; P < 0.001). After accounting for publication bias this was attenuated to 7.8% but remained significant. Treatment reduced calcification by 4.1% (28 controlled analyses, 95% CI 0.2–8.0%; P < 0.0395). We observed significant heterogeneity in effect size in all primary endpoints, which was predominantly driven by differences between drug categories. Beta blockers and angiotensin-converting enzyme (ACE) inhibitors were the only agents that were effective for both necrosis and fibrosis, while only ACE inhibitors had a significant effect on calcification. This study provides evidence for a role for ACE inhibitors and beta blockers to prevent myocardial injury and scar deposition in in vivo models of myocarditis. There is a need for further well-designed studies to assess the translational application of these treatments.

Established and novel treatment options in acute myocarditis, with or without heart failure

INTRODUCTION

Acute myocarditis is a disorder characterized by an unpredictable clinical course which ranges from asymptomatic, incidentally discovered forms, to cases with fulminant course and adverse outcome. The most challenging issues in the context of acute myocarditis are the appearance of difficult to treat heart failure in the acute phase and the potential progression in the long-term to dilated cardiomyopathy. Areas covered: With respect to available treatment options in acute myocarditis, in the absence of specific guidelines, management is supportive and overall empirical, especially for the oligo- or asymptomatic patients with preserved ejection fraction. Haemodynamically instable patients should be treated in referral centers with capability of advanced cardiopulmonary support. Patients with heart failure but without haemodynamic impairment should be treated according to the heart failure guidelines. Endomyocardial biopsy may be performed in an individualized basis both for diagnostic purposes and to guide treatment, based on the detection or not of viral genome. Expert commentary: Apart from the already established treatments, novel therapies against several targets are currently investigated and are expected to contribute to a more efficacious management options in the future. Increased awareness among medical professionals is essential for the early diagnosis and best care of acute myocarditis patients.

Protective effects of losartan in mice with chronic viral myocarditis induced by coxsackievirus B3

AIM

To investigate whether losartan has protective effects in mice with chronic viral myocarditis induced by coxsackievirus B3 (CVB3).

MAIN METHODS

Thirty two male Balb/c mice were intraperitoneally injected with CVB3 (10×TCID50) to induce chronic viral myocarditis (CVM). Losartan at 12.5mg/kg (n=16) or normal saline (n=16) were orally administered daily for 28 days to these mice. Uninfected mice (n=6) were used as controls. On day 29, all mice underwent anesthesia and echocardiography prior to sacrifice. Serum IL-17, IL-4, IFN-γ and TNF-α levels were measured by enzyme-linked immunosorbent assay, and cardiac tissues were histologically examined after hematoxylin & eosin staining. In addition, the effect of losartan on the virus titers in primary cultured neonatal rat cardiomyocytes infected with CVB3 was measured on Hep-2 cells at 72 h post infection.

KEY FINDINGS

Mice infected with CBV3 had significantly increased mortality, heart/body weight ratios, necrosis and inflammatory scores and decreased cardiac ejection fractions, compared with the controls (all P<0.05). Losartan significantly decreased mortality from 40.0% to 12.5%, heart/body weight ratios from 7.08 ± 2.17 to 4.15 ± 0.99, and necrosis and inflammatory scores from 3.33 ± 0.50 to 2.50 ± 0.65 (all P<0.05), and increased ejection fractions from 55.80 ± 9.25 to 72.31 ± 12.15 (P<0.05). Losartan significantly enhanced IL-4, and decreased IFN-γ, TNF-α and IL-17 (all P<0.05). In the in vitro experiment, losartan had no influence on virus titers.

SIGNIFICANCE

Losartan protects mice against CVB3-induced CVM, most likely through upregulating Th2 responses, and down-regulating Th1 and Th17 responses.

Oral administration of candesartan improves the survival of mice with viral myocarditis through modification of cardiac adiponectin expression

PURPOSE

We examined the effects of the angiotensin II receptor type 1 blocker candesartan on myocarditis injury in a murine model of acute myocarditis. We hypothesized that candesartan improves cardiac damage by inducing cardiac expression of adiponectin.

METHODS AND RESULTS

We examined changes in heart failure caused by myocarditis in mice by candesartan based on induction of cardiac adiponectin expression. We intraperitoneally injected encephalomyocarditis virus in C3H mice, then orally administered candesartan (10 mg/kg/day) or vehicle (control). The 7 day survival rate was 18% in the control group, but 60% in the candesartan group. The heart weight/body weight ratio in the candesartan group was significantly lower than in the control group. Circulating adiponectin concentrations on day 7 were significantly higher in the candesartan group compared with the control group (7.91 +/- 0.61 vs. 6.04 +/- 2.26 microg/ml, P < 0.05). Comparative expression of cardiac adiponectin mRNA in the candesartan group was significantly higher than in the control group on day 7 (55.4 +/- 41.3 vs. 5.3 +/- 7.7, P < 0.05). Immunohistochemical staining and in situ hybridization showed that cardiac expression of adiponectin protein and mRNA was present in the candesartan group on day 7.

CONCLUSION

Oral administration of candesartan improves survival and decreases myocardial damage in mice with viral myocarditis and induces expression of cardiac adiponectin. The induction of adiponectin might provide cardioprotective effects against acute heart failure due to viral myocarditis.

Comparison of angiotensin converting enzyme inhibition and angiotensin II receptor blockade for the prevention of experimental autoimmune myocarditis

The angiotensin converting enzyme inhibitor captopril prevents myosin-induced experimental autoimmune myocarditis. Captopril inhibits production of angiotensin II and increases bradykinin signaling, among other actions. To test whether captopril inhibits disease through blockade of angiotensin signaling, we tested the ability of losartan, an angiotensin II receptor blocker, to prevent myosin-induced myocarditis. A/J mice immunized with the heavy chain of cardiac myosin in complete Freund's adjuvant develop acute myocarditis by day 21 post-immunization, consisting of severe focal inflammation, necrosis and fibrosis. Administration of losartan (250 mg/L in the drinking water) or captopril (75 mg/L in the drinking water) significantly reduced inflammation, necrosis and fibrosis in myosin-immunized mice. The heart weights and the heart weight-to-body weight ratios were also significantly reduced in both treatment groups. However, whereas captopril reduced myosin-specific delayed-type hypersensitivity, losartan did not. Both captopril-treated mice and losartan-treated mice showed a decrease in myosin-specific autoantibody production. Because losartan treatment significantly reduced myocarditis, fibrosis and autoantibody production in EAM, it is likely that prevention of angiotensin II receptor stimulation is a major mechanism underlying the inhibition of myosin-induced myocarditis by captopril.

Systemic inhibition of the angiotensin-converting enzyme limits lipopolysaccharide-induced lung neutrophil recruitment through both bradykinin and angiotensin II-regulated pathways

Recruitment of neutrophils to the lung is a sentinel event in acute lung inflammation. Identifying mechanisms that regulate neutrophil recruitment to the lung may result in strategies to limit lung damage and improve clinical outcomes. Recently, the renin angiotensin system (RAS) has been shown to regulate neutrophil influx in acute inflammatory models of cardiac, neurologic, and gastrointestinal disease. As a role for the RAS in LPS-induced acute lung inflammation has not been described, we undertook this study to examine the possibility that the RAS regulates neutrophil recruitment to the lung after LPS exposure. Pretreatment of mice with the angiotensin-converting enzyme (ACE) inhibitor enalapril, but not the anti-hypertensive hydralazine, decreased pulmonary neutrophil recruitment after exposure to LPS. We hypothesize that inhibition of LPS-induced neutrophil accumulation to the lung with enalapril occurred through both an increase in bradykinin, and a decrease in angiotensin II (ATII), mediated signaling. Bradykinin receptor blockade reversed the inhibitory effect of enalapril on neutrophil recruitment. Similarly, pretreatment with bradykinin receptor agonists inhibited IL-8-induced neutrophil chemotaxis and LPS-induced neutrophil recruitment to the lung. Inhibition of ATII-mediated signaling, with the ATII receptor 1a inhibitor losartan, decreased LPS-induced pulmonary neutrophil recruitment, and this was suggested to occur through decreased PAI-1 levels. LPS-induced PAI-1 levels were diminished in animals pretreated with losartan and in those deficient for the ATII receptor 1a. Taken together, these results suggest that ACE regulates LPS-induced pulmonary neutrophil recruitment via modulation of both bradykinin- and ATII-mediated pathways, each regulating neutrophil recruitment by separate, but distinct, mechanisms.

Collagen production in cardiac fibroblasts during inhibition of angiotensin-converting enzyme and aminopeptidases

OBJECTIVE

To determine whether lisinopril, an angiotensin-converting enzyme (ACE) inhibitor, and bestatin, an aminopeptidase inhibitor with broad specificity, could affect collagen production in control and transforming growth factor (TGF)-beta1-treated cardiac fibroblasts.

DESIGN AND METHODS

Cardiac fibroblasts from passage 2 from normal male adult rats were cultured to confluency, incubated with or without 600 pmol/l TGF-beta1 for 2 days in serum-free Dulbecco's modified Eagle's medium and then incubated with the test products (lisinopril or bestatin) for 1 day in this medium with added ascorbic acid, beta-aminoproprionitrile and tritiated proline. Soluble collagen was measured in the conditioned medium and non-soluble collagen in the cell layer. ACE activity was measured fluorimetrically with hippuryl-histidyl-leucine as substrate, and DNA with the bisbenzimide dye, Hoechst 33,258. Aminopeptidase activity was estimated by spectrophotometric determination of the liberation of p-nitroaniline from alanine-p-nitroanilide.

RESULTS

Lisinopril dose-dependently reduced ACE activity in control and TGF-beta1-treated cardiac fibroblasts. Bestatin inhibited the basal and TGF-beta1-stimulated aminopeptidase activity in a concentration-dependent manner. Lisinopril (10 micromol/l) decreased (P < 0.05) the production of soluble and non-soluble collagen in control cardiac fibroblasts. TGF-beta1 (600 pmol/l) increased (P < 0.05) the production of soluble and non-soluble collagen, and this effect was decreased (P < 0.05) by lisinopril. Bestatin (100 micromol/l) reduced (P < 0.01) the production of soluble collagen in control and TGF-beta1-treated cardiac fibroblasts, but did not affect the production of non-soluble collagen in these cells.

CONCLUSIONS

Our data suggest that ACE and aminopeptidases are involved in the basal and TGF-beta1-stimulated production of collagen in adult rat cardiac fibroblasts in culture.

Effects of losartan on pressure overload-induced cardiac gene expression profiling in rats

1. In the present study, the effects of losartan on myocardial gene expression changes following cardiac hypertrophy were investigated. 2. Male Wistar rats were randomized to receive 5 or 30 mg/kg per day losartan (i.p.) 1 day after suprarenal abdominal aortic constriction. Two weeks later, cardiac morphology and function were recorded with echocardiography and mean arterial central pressure was measured using carotid catheters. Myocardial gene expression was assessed with cDNA microarrays. 3. The ratios of left ventricular weights to bodyweights, the posterior thickness of the left ventricle and mean arterial central pressure were significantly increased by aortic constriction and attenuated by losartan in a dose-related manner. Genes in different functional categories were regulated in pressure overload-induced cardiac hypertrophy and the majority of changes in gene expression were inhibited by losartan in a dose-dependent manner. 4. However, there were still some genes that were unaffected by losartan, even at a higher dose. In contrast, losartan, especially at a lower dose, was able to induce changes in the expression of several additional genes that were unregulated in simple aortic constriction. 5. In conclusion, losartan is able to inhibit pressure overload-induced cardiac hypertrophy, as well as the majority of pressure overload-related changes in gene expression. The genes that remained unaffected or those that were additionally induced by losartan are likely to be new targets for investigation or therapy.

Captopril prevents experimental autoimmune myocarditis

Captopril, an angiotensin-converting enzyme inhibitor, is widely used in the treatment of a variety of cardiomyopathies, but its effect on autoimmune myocarditis has not been addressed experimentally. We investigated the effect of captopril on myosin-induced experimental autoimmune myocarditis. A/J mice, immunized with syngeneic cardiac myosin, were given 75 mg/L of captopril in their drinking water. Captopril dramatically reduced the incidence and severity of myocarditis, which was accompanied by a reduction in heart weight to body weight ratio and heart weight. Captopril specifically interfered with cell-mediated immunity as myosin delayed-type hypersensitivity (DTH) was reduced, while anti-myosin Ab production was not affected. Captopril-treated, OVA-immunized mice also exhibited a decrease in OVA DTH. In myosin-immunized, untreated mice, injection of captopril directly into the test site also suppressed myosin DTH. Interestingly, captopril did not directly affect Ag-specific T cell responsiveness because neither in vivo nor in vitro captopril treatment affected the proliferation, IFN-gamma secretion, or IL-2 secretion by Ag-stimulated cultured splenocytes. These results indicate that captopril ameliorates experimental autoimmune myocarditis and may act, at least in part, by interfering with the recruitment of cells to sites of inflammation and the local inflammatory environment.

Temocapril treatment ameliorates autoimmune myocarditis associated with enhanced cardiomyocyte thioredoxin expression

Thioredoxin (TRX) is a redox regulatory protein that protects cells from various stresses. Angiotensin-converting enzyme (ACE) inhibitor was reported to enhance endogenous antioxidant enzyme activities. This study was carried out to investigate whether temocapril, a novel non-sulfhydryl containing ACE inhibitor, reduces the severity of myocarditis via redox regulation mechanisms involving TRX. Western blot showed that temocapril enhanced cytosolic redox regulatory protein TRX expression, but neither mitochondrial TRX2 nor antioxidant enzymes, such as copper-zinc superoxide dismutase (Cu/Zn-SOD) or manganese superoxide dismutase (Mn-SOD) expression, was increased by the preconditioning treatment. In rats with experimental autoimmune myocarditis (EAM), the protein carbonyl content, a marker of cellular protein oxidation, was increased accompanied with enhanced TRX expression. An immunohistochemical study showed that TRX stain was enhanced in infiltrating inflammatory cells and in damaged myocytes. The severity of the myocarditis and the protein carbonyl contents were less increased in temocapril treatment (10 mg/kg/day, orally) from day 1 to day 21 in which TRX was up regulated when the inflammation started, but not in temocapril treatment from day 15-21 in which TRX was not up-regulated when the inflammation started. The results suggest that TRX and the redox state modified by TRX may play a crucial role in the pathophysiology of EAM. Temocapril ameliorates myocarditis associated with inducing TRX increase in a preconditioning manner, although the mechanism of TRX induction by temocapril remains to be elucidated.

Captopril ameliorates myocarditis in acute experimental Chagas disease

BACKGROUND

Captopril, an angiotensin-converting enzyme inhibitor, is commonly prescribed to patients with Chagas heart disease (CHD). There are few human studies and no animal studies on the effects of captopril in CHD. We investigated the effects of captopril on myocarditis and the host immune response to Trypanosoma cruzi in an experimental model of acute CHD.

METHODS AND RESULTS

A/J mice infected with Brazil strain of T cruzi developed acute myocarditis by day 21 after infection, consisting of severe focal inflammation, necrosis, fibrosis, and T cruzi pseudocysts. Administration of captopril (5 mg/L in the water) significantly reduced necrosis and fibrosis in infected mice. Increasing the captopril dose also led to a decrease in inflammation. Captopril did not affect overall mortality but did delay death while having no effect on parasitemia or cardiac parasite load. Treatment did not affect humoral immunity against T cruzi or cardiac myosin (autoimmunity) but did decrease delayed-type hypersensitivity responses against both antigens. Interestingly, increasing the dose of captopril induced mortality in infected mice in a dose-dependent manner. Mortality was apparently not due to T cruzi because neither parasitemia nor cardiac parasitosis was affected. The combination of captopril and infection may have impaired renal function because these mice had increased water consumption, decreased body mass, and increased serum BUN/creatinine ratio.

CONCLUSIONS

Captopril ameliorates the myocarditis associated with acute T cruzi infection.

Diagnosis and management of pediatric myocarditis

Myocarditis is an insidious inflammatory disorder of the myocardium. As a clinical entity, it has been recognized for two centuries, but it defies traditional diagnostic tests. A greater understanding of the immune response underlying the pathobiology of the disorder can lead to a more rational therapeutic approach. The presentation, course and therapeutic options appear to be different in the pediatric compared with the adult population. An understanding of the difference between fulminant and acute progressive myocarditis has led to successful treatment strategies. A variety of new therapies are available, including antiviral agents, immunosuppression, and modulation of the biological response to inflammation. The specific question for patients with myocarditis is whether regimens designed to reduce or eliminate inflammation can provide clinical benefits compared with conventional heart failure therapy. This review highlights pathological mechanisms, modalities of diagnosis, and novel therapies which may improve outcomes.

Effect of N-acetyl-seryl-aspartyl-lysyl-proline on DNA and collagen synthesis in rat cardiac fibroblasts

N:-Acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural inhibitor of pluripotent hematopoietic stem cell entry into the S phase of the cell cycle and is normally present in human plasma. Ac-SDKP is exclusively hydrolyzed by ACE, and its plasma concentration is increased 5-fold after ACE inhibition in humans. We examined the effect of 0.05 to 100 nmol/L Ac-SDKP on 24-hour (3)H-thymidine incorporation (DNA synthesis) by cardiac fibroblasts both in the absence and presence of 5% FCS. Captopril (1 micromol/L) was added in all cases to prevent the degradation of Ac-SDKP. Treatment of cardiac fibroblasts with 5% FCS increased thymidine incorporation from a control value of 12 469+/-594 to 24 598+/-1051 cpm (P:<0.001). Cotreatment with 1 nmol/L Ac-SDKP reduced stimulation to control levels (10 373+/-200 cpm, P:<0.001). We measured hydroxyproline content and incorporation of (3)H-proline into collagenous fibroblast proteins and found that Ac-SDKP blocked endothelin-1 (10(-8) mol/L)-induced collagen synthesis in a biphasic and dose-dependent manner, causing inhibition at low doses, whereas high doses had little or no effect. It also blunted the activity of p44/p42 mitogen-activated protein kinase in a biphasic and dose-dependent manner in serum-stimulated fibroblasts, suggesting that the inhibitory effect of DNA and collagen synthesis may depend in part on blocking mitogen-activated protein kinase activity. Participation of p44/p42 in collagen synthesis was confirmed, because a specific inhibitor for p44/p42 activation (PD 98059, 25 micromol/L) was able to block endothelin-1-induced collagen synthesis, similar to the effect of Ac-SDKP. The fact that Ac-SDKP inhibits DNA and collagen synthesis in cardiac fibroblasts suggests that it may be an important endogenous regulator of fibroblast proliferation and collagen synthesis in the heart. Ac-SDKP may participate in the cardioprotective effect of ACE inhibitors by limiting fibroblast proliferation (and hence collagen production), and therefore it would reduce fibrosis in patients with hypertension.