Amlodipine inhibits granulation tissue cell apoptosis through reducing calcineurin activity to attenuate postinfarction cardiac remodeling

Comparison of effects of L/N-type and L-type calcium channel blockers on post-infarct cardiac remodelling in spontaneously hypertensive rats

Hypertension and coronary events are becoming more prevalent in aging societies, and myocardial infarction usually occurs in calcium channel blocker (CCB)-treated hypertensive patients. We herein compared the effects of cilnidipine, an L/N-type CCB and amlodipine, an L-type CCB, on post-infarct left ventricular (LV) remodelling in spontaneously hypertensive rats (SHRs). Male SHRs were subjected to 30 minutes of left coronary artery occlusion followed by reperfusion (MI group). The administration of cilnidipine (10 mg/kg/d; MI + Cil group) or amlodipine (10 mg/kg/d; MI + Aml group) was initiated one week before surgery and continued for five weeks. Both CCBs decreased blood pressure. Four weeks after surgery, cilnidipine, but not amlodipine, attenuated LV dilatation, fractional shortening impairments, end-diastolic pressure elevations, and tau elongation. In the non-infarct region, myocyte hypertrophy and brain natriuretic peptide (BNP) mRNA levels were similarly attenuated by both CCBs. On the other hand, interstitial fibrosis, the mRNA expression of collagen type III and transforming growth factor (TGF) β and immunohistological TGF β protein expression in the non-infarct region were reduced more in the MI + Cil group than in the MI + Aml group. Additionally, elevated angiotensin-converting enzyme activity and interstitial noradrenaline concentrations in the non-infarct region were reduced by cilnidipine. These results suggest that cilnidipine reduced cardiac noradrenaline concentrations and inhibited the renin-angiotensin system, which attenuated post-infarct remodelling more than amlodipine in hypertensive rats.

Hypoxia-induced interaction of filamin with Drp1 causes mitochondrial hyperfission-associated myocardial senescence

Defective mitochondrial dynamics through aberrant interactions between mitochondria and actin cytoskeleton is increasingly recognized as a key determinant of cardiac fragility after myocardial infarction (MI). Dynamin-related protein 1 (Drp1), a mitochondrial fission-accelerating factor, is activated locally at the fission site through interactions with actin. Here, we report that the actin-binding protein filamin A acted as a guanine nucleotide exchange factor for Drp1 and mediated mitochondrial fission-associated myocardial senescence in mice after MI. In peri-infarct regions characterized by mitochondrial hyperfission and associated with myocardial senescence, filamin A colocalized with Drp1 around mitochondria. Hypoxic stress induced the interaction of filamin A with the GTPase domain of Drp1 and increased Drp1 activity in an actin-binding-dependent manner in rat cardiomyocytes. Expression of the A1545T filamin mutant, which potentiates actin aggregation, promoted mitochondrial hyperfission under normoxia. Furthermore, pharmacological perturbation of the Drp1-filamin A interaction by cilnidipine suppressed mitochondrial hyperfission-associated myocardial senescence and heart failure after MI. Together, these data demonstrate that Drp1 association with filamin and the actin cytoskeleton contributes to cardiac fragility after MI and suggests a potential repurposing of cilnidipine, as well as provides a starting point for innovative Drp1 inhibitor development.

Amlodipine Ameliorates Ischemia-Induced Neovascularization in Diabetic Rats through Endothelial Progenitor Cell Mobilization

Objectives. We investigated whether amlodipine could improve angiogenic responses in a diabetic rat model of acute myocardial infarction (AMI) through improving bone marrow endothelial progenitor cell (EPC) mobilization, in the same way as angiotensin converting enzyme inhibitors. Methods. After induction of AMI by coronary artery ligation, diabetic rats were randomly assigned to receive perindopril (2 mgkg⁻¹ day⁻¹), amlodipine (2.5 mgkg⁻¹ day⁻¹), or vehicle by gavage (n = 20 per group). Circulating EPC counts before ligation and on days 1, 3, 5, 7, 14, and 28 after AMI were measured in each group. Microvessel density, cardiac function, and cardiac remodeling were assessed 4 weeks after treatment. The signaling pathway related to EPC mobilization was also measured. Results. Circulating EPC count in amlodipine- and perindopril-treated rats peaked at day 7, to an obvious higher level than the control group peak which was reached earlier (at day 5). Rats treated with amlodipine showed improved postischemia neovascularization and cardiac function, together with reduced cardiac remodeling, decreased interstitial fibrosis, and cardiomyocyte apoptosis. Amlodipine treatment also increased cardiac SDF-1/CXCR4 expression and gave rise to activation of VEGF/Akt/eNOS signaling in bone marrow. Conclusions. Amlodipine promotes neovascularization by improving EPC mobilization from bone marrow in diabetic rats after AMI, and activation of VEGF/Akt/eNOS signaling may in part contribute to this.

OPC-28326, a selective peripheral vasodilator with angiogenic activity, mitigates postinfarction cardiac remodeling

Although OPC-28326, 4-(N-methyl-2-phenylethylamino)-1-(3,5-dimethyl-4-propionyl-aminobenzoyl) piperidine hydrochloride monohydrate, was developed as a selective peripheral vasodilator with α2-adrenergic antagonist properties, it also reportedly exhibits angiogenic activity in an ischemic leg model. The purpose of this study was to examine the effect of OPC-28326 on the architectural dynamics and function of the infarcted left ventricle during the chronic stage of myocardial infarction. Myocardial infarction was induced in male C3H/He mice, after which the mice were randomly assigned into two groups: a control group receiving a normal diet and an OPC group whose diet contained 0.05% OPC-28326. The survival rate among the mice (n = 18 in each group) 4 wk postinfarction was significantly greater in the OPC than control group (83 vs. 44%; P < 0.05), and left ventricular remodeling and dysfunction were significantly mitigated. Histologically, infarct wall thickness was significantly greater in the OPC group, due in part to an abundance of nonmyocyte components, including blood vessels and myofibroblasts. Five days postinfarction, Ki-67-positive proliferating cells were more abundant in the granulation tissue in the OPC group, and there were fewer apoptotic cells. These effects were accompanied by activation of myocardial Akt and endothelial nitric oxide synthase. Hypoxia within the infarct issue, assessed using pimonidazole staining, was markedly attenuated in the OPC group. In summary, OPC-28326 increased the nonmyocyte population in infarct tissue by increasing proliferation and reducing apoptosis, thereby altering the tissue dynamics such that wall stress was reduced, which might have contributed to a mitigation of postinfarction cardiac remodeling and dysfunction.

Phenotype and physiological significance of the endocardial smooth muscle cells in human failing hearts

BACKGROUND

Extravascular smooth muscle cells are often observed in the endocardium of human failing hearts. Here, we characterized the phenotype of those cells and investigated their physiological significance.

METHODS AND RESULTS

We examined left ventricular biopsy specimens obtained from 44 patients with dilated cardiomyopathy and 6 nonfailing hearts. In Masson trichrome-stained histological preparations, bundles of smooth muscle cells were seen localized in the endocardium in 23 of the 44 specimens (none of the 6 controls). These cells were immunopositive for α-smooth muscle actin, type 2 smooth muscle myosin, desmin, and calponin, but were negative for embryonic smooth muscle myosin, vimentin, fibronectin, and periostin. This profile is indicative of a late differentiation (contractile) smooth muscle phenotype. Electron microscopy confirmed that phenotype, revealing the cells to contain abundant myofilaments with dense bodies but little rough endoplasmic reticulum or Golgi apparatus. In the endocardial smooth muscle-positive group, the left ventricular end-systolic volume index (73±34 versus 105±50 mL/m(2); P=0.021), left ventricular peak wall stress (164±47 versus 196±43 dynes 10(3)/cm(2); P=0.023), and left ventricular end-systolic meridional wall stress (97±38 versus 121±37 dynes 10(3)/cm(2); P=0.036) were all significantly smaller, and the ejection fraction was larger (41±8.8 versus 33±9.3%; P=0.005) than in the endocardial smooth muscle-negative group. However, no histological parameters differed between the 2 groups.

CONCLUSIONS

Endocardial smooth muscle cell bundles in hearts with dilated cardiomyopathy exhibit a mature contractile phenotype and may play a compensatory role mitigating heart failure by reducing left ventricular wall stress and systolic dysfunction.

Regenerative healing following foetal myocardial infarction

OBJECTIVES

The adult response to myocardial infarction results in inflammation, scar formation, left ventricular dilatation, and loss of regional and global function. Regenerative scarless healing has been demonstrated in foetal dermis and tendon and is associated with diminished inflammation. We hypothesised that following foetal myocardial infarction, there would be minimal inflammation, regenerative healing, and preservation of function.

METHODS

Anteroapical myocardial infarction encompassing 20% of the left ventricle was created in adult or early gestation foetal sheep. Myocardial function was serially assessed using quantitative echocardiography. Infarct architecture was examined histologically for evidence of scar formation. Cellular inflammation, cellular proliferation, and apoptosis were assessed using immunohistochemistry.

RESULTS

In the adult sheep 4 weeks following myocardial infarction, there was a significant decline in ejection fraction (EF) (41±7.4% to 26±7.4%, p<0.05), and the akinetic myocardial segment increased in size (6.9±0.8 cm to 7.9±1.1 cm, p<0.05). By contrast, there was no decline in the foetal EF (53±8.1% to 55±8.8%) and no akinetic foetal myocardial segment 4 weeks post-infarction. The foetal infarcts lacked an inflammatory cell infiltrate and healed with minimal fibrosis, compared with the adults. Foetal infarcts also demonstrated 5-bromo-2'-deoxyuridine (BrdU)+ proliferating cells, including cardiomyocytes, within the infarct.

CONCLUSIONS

These data demonstrate that the foetal response to myocardial infarction is dramatically different from the adult and is characterised by minimal inflammation, lack of fibrosis, myocardial proliferation and restoration of cardiac function. Diminished inflammation is associated with foetal regenerative cardiac healing following injury. Understanding the mechanisms involved in foetal myocardial regeneration may lead to applications to alter the adult response following myocardial infarction.

Postinfarction gene therapy with adenoviral vector expressing decorin mitigates cardiac remodeling and dysfunction

The small leucine-rich proteoglycan decorin is a natural inhibitor of transforming growth factor-beta (TGF-beta) and exerts antifibrotic effects in heart and to stimulate skeletal muscle regeneration. We investigated decorin's chronic effects on postinfarction cardiac remodeling and dysfunction. Myocardial infarction (MI) was induced in mice by left coronary artery ligation. An adenoviral vector encoding human decorin (Ad. CAG-decorin) was then injected into the hindlimbs on day 3 post-MI (control, Ad.CAG-LacZ). Four weeks post-MI, the decorin-treated mice showed significant mitigation of the left ventricular dilatation and dysfunction seen in control mice. Although infarct size did not differ between the two groups, the infarcted wall thickness was greater and the segmental length of the infarct was smaller in decorin-treated mice. In addition, cellular components, including myofibroblasts and blood vessels, were more abundant within the infarcted area in decorin-treated mice, and fibrosis was significantly reduced in both the infarcted and noninfarcted areas of the left ventricular wall. Ten days post-MI, there was greater cell proliferation and less apoptosis among granulation tissue cells in the infarcted areas of decorin-treated mice. The treatment, however, did not affect proliferation and apoptosis of salvaged cardiomyocytes. Although decorin gene therapy did not affect TGF-beta1 expression in the infarcted heart, it inhibited Smad2/3 activation (downstream mediators of TGF-beta signaling). In summary, postinfarction decorin gene therapy mitigated cardiac remodeling and dysfunction by altering infarct tissue noncardiomyocyte dynamics and preventing cardiac fibrosis, accompanying inhibition of Smad2/3 activation.