Acute myocardial infarction is a common condition responsible for heart failure and sudden death. Here, we show that following acute myocardial infarction in mice, CD8+ T lymphocytes are recruited and activated in the ischemic heart tissue and release Granzyme B, leading to cardiomyocyte apoptosis, adverse ventricular remodeling and deterioration of myocardial function. Depletion of CD8+ T lymphocytes decreases apoptosis within the ischemic myocardium, hampers inflammatory response, limits myocardial injury and improves heart function. These effects are recapitulated in mice with Granzyme B-deficient CD8+ T cells. The protective effect of CD8 depletion on heart function is confirmed by using a model of ischemia/reperfusion in pigs. Finally, we reveal that elevated circulating levels of GRANZYME B in patients with acute myocardial infarction predict increased risk of death at 1-year follow-up. Our work unravels a deleterious role of CD8+ T lymphocytes following acute ischemia, and suggests potential therapeutic strategies targeting pathogenic CD8+ T lymphocytes in the setting of acute myocardial infarction.

Background-Constitutive bradykinin B 1 receptors have been identified in dogs; however, their physiological implications involving the coronary circulation remain to be determined. This study examined, in conscious dogs, the coronary response to des-Arg 9 -bradykinin (a B 1 receptor agonist) and the mechanisms involved. Methods and Results-Eleven dogs were instrumented with a left ventricular micromanometer, a circumflex coronary catheter, a cuff occluder, a Doppler flow probe, and ultrasonic crystals to measure coronary blood flow velocity (CBFv) and coronary diameter (CD). Intracoronary des-Arg 9 -bradykinin (3 to 100 ng/kg) and bradykinin (0.1 to 10 ng/kg) did not modify systemic hemodynamics but dose-dependently increased CBFv and CD. Des-Arg 9 -bradykinin was less potent than bradykinin. Hoe 140 (a B 2 antagonist, 10 g/kg) abolished the effects of bradykinin but did not influence the effects of des-Arg 9 -bradykinin. When CBFv increase was prevented by the cuff occluder, CD responses to bradykinin and des-Arg 9 -bradykinin were maintained. Intracoronary lisinopril (0.75 mg) increased the CD response to bradykinin, with only minimal effect on CBFv, and extended the duration of the effect. Lisinopril did not alter des-Arg 9 -bradykinin responses. Intracoronary N -nitro-L-arginine (2 mg/kg) decreased the CD effect of bradykinin and prevented the CBFv and CD effects of des-Arg 9 -bradykinin. The relaxing effect of des-Arg 9 -bradykinin on isolated coronary rings was prevented by des-Arg 9 ,[Leu 8 ]-bradykinin. Conclusions-In the conscious dog, B 1 receptors are present in coronary vessels, and their stimulation produces vasodilation in conductance and resistance vessels, which is mediated essentially by NO but not modulated by angiotensin-converting enzyme. However, the coronary vasodilation induced by B 1 receptor stimulation is not as great as that produced by B 2 receptor stimulation.

ObjectivesThe aim of this study was to investigate the potential of coronary ultrafast Doppler angiography (CUDA), a novel vascular imaging technique based on ultrafast ultrasound, to image noninvasively with high sensitivity the intramyocardial coronary vasculature and quantify the coronary blood flow dynamics.BackgroundNoninvasive coronary imaging techniques are currently limited to the observation of the epicardial coronary arteries. However, many studies have highlighted the importance of the coronary microcirculation and microvascular disease.MethodsCUDA was performed in vivo in open-chest procedures in 9 swine. Ultrafast plane-wave imaging at 2,000 frames/s was combined to an adaptive spatiotemporal filtering to achieve ultrahigh-sensitive imaging of the coronary blood flows. Quantification of the flow change was performed during hyperemia after a 30-s left anterior descending (LAD) artery occlusion followed by reperfusion and was compared to gold standard measurements provided by a flowmeter probe placed at a proximal location on the LAD (n = 5). Coronary flow reserve was assessed during intravenous perfusion of adenosine. Vascular damages were evaluated during a second set of experiments in which the LAD was occluded for 90 min, followed by 150 min of reperfusion to induce myocardial infarction (n = 3). Finally, the transthoracic feasibility of CUDA was assessed on 2 adult and 2 pediatric volunteers.ResultsUltrahigh-sensitive cine loops of venous and arterial intramyocardial blood flows were obtained within 1 cardiac cycle. Quantification of the coronary flow changes during hyperemia was in good agreement with gold standard measurements (r2 = 0.89), as well as the assessment of coronary flow reserve (2.35 ± 0.65 vs. 2.28 ± 0.84; p = NS). On the infarcted animals, CUDA images revealed the presence of strong hyperemia and the appearance of abnormal coronary vessel structures in the reperfused LAD territory. Finally, the feasibility of transthoracic coronary vasculature imaging was shown on 4 human volunteers.ConclusionsUltrafast Doppler imaging can map the coronary vasculature with high sensitivity and quantify intramural coronary blood flow changes.

AimsThis study aimed to determine the role of the renin-angiotensin system (RAS) in high-salt (HS) diet-induced left ventricular hypertrophy (LVH). Methods and resultsSwiss mice were subjected to regular salt (RS) diet (0.6% NaCl), HS diet (4% NaCl), and HS plus irbesartan (50 mg/ kg/day) or ramipril (1 mg/kg/day). After 8 weeks, arterial pressure was similar in all groups and similar to baseline, whereas left ventricle/body weight ratio was higher in HS mice than in RS mice (P , 0.005). There were also significant increases in collagen density, angiotensin-converting enzyme activity, angiotensin II type 1 receptor (AT1 receptor) density, and extracellular signal-regulated kinase (ERK1/2) phosphorylation in the left ventricle. Interestingly, increases in wall thickness and ERK1 phosphorylation were more marked in the septum than in the rest of the left ventricle. Irbesartan or ramipril treatment prevented LVH and the increase in ERK phosphorylation and reduced collagen content and AT1 up-regulation but up-regulated AT2 receptors. ConclusionIn normal mice, HS diet induces septum-predominant LVH and fibrosis through activation of the cardiac RAS-ERK pathway, which can be blocked by irbesartan or ramipril, indicating a key role of the cardiac RAS in HS diet-induced LVH.-High-salt diet † Left ventricular hypertrophy † Blood pressure † Renin -angiotensin system † Mitogen-activated protein kinases † Mice

Cardiomyopathy in GRMD dogs is characterized by profound LV subendocardial dysfunction, abnormal sarcomeric protein phosphorylation, and impaired e/nNOS, which can be normalized by bradykinin treatment. These data provide new insights into the pathophysiological mechanisms accounting for DMD cardiomyopathy and open new therapeutic perspectives.

Little is known about the vascular function and expression of endothelial and neuronal nitric oxide synthases (eNOS and nNOS) in Duchenne muscular dystrophy (DMD). Bradykinin is involved in the regulation of eNOS expression induced by angiotensin-converting enzyme inhibitors. We characterized the vascular function and eNOS and nNOS expression in a canine model of DMD and evaluated the effects of chronic bradykinin treatment. Vascular function was examined in conscious golden retriever muscular dystrophy (GRMD) dogs with left ventricular dysfunction (measured by echocardiography) and in isolated coronary arteries. eNOS and nNOS proteins in carotid arteries were measured by western blot and cyclic guanosine monophosphate (cGMP) content was analyzed by radioimmunoassay. Compared with controls, GRMD dogs had an impaired vasodilator response to acetylcholine. In isolated coronary artery, acetylcholine-elicited relaxation was nearly absent in placebo-treated GRMD dogs. This was explained by reduced nNOS and eNOS proteins and cGMP content in arterial tissues. Chronic bradykinin infusion (1 μg/min, 4 weeks) restored in vivo and in vitro vascular response to acetylcholine to the level of control dogs. This effect was NO-mediated through upregulation of eNOS and nNOS expression. In conclusion, this study is the first to demonstrate that DMD is associated with NO-mediated vascular endothelial dysfunction linked to an altered expression of eNOS and nNOS, which can be overcome by bradykinin.

1 This study examined whether NO is involved in the in-vivo coronary vasodilator e ects of amlodipine (a calcium channel blocker) and whether heart failure (HF) alters the coronary responses to amlodipine. 2 Nine conscious dogs were chronically instrumented to measure circum¯ex coronary blood¯ow (CBF) and coronary diameter (CD). Drugs were administered directly into the circum¯ex artery through an indwelling catheter to avoid systemic changes. HF was induced by right ventricular pacing (240 b.p.m., 3 weeks).3 Compared with control (C), in HF, coronary responses to acetylcholine (1 ± 10 ng kg 71 ) were reduced while responses to nitroglycerin (0.1 ± 0.5 mg kg 71 ) were unchanged. In C, amlodipine (30 ± 150 mg kg 71 ), increased dose-dependently CBF and CD. After LNA (a NO synthase inhibitor, 2 mg kg 71 ), amlodipine produced less increases in CBF and CD (+121+26 ml min 71 and +76+35 mm versus +196+40 ml min 71 and +153+39 mm respectively for 150 mg kg 71 amlodipine alone, both P50.05). In HF, the coronary responses to amlodipine were reduced (150 mg kg 71 of amlodipine increased CBF and CD +121+23 ml min 71 and +77+21 mm respectively, both P50.05). After LNA, the CBF responses to amlodipine tended to be reduced (+94+19 ml min 71 at 150 mg kg 71 ) but CD responses were signi®cantly reduced (+41+16 mm, P50.05). The supplementation with L-arginine did not enhance the coronary responses to amlodipine. 4 These results indicate that, in conscious dogs, NO participates in the coronary responses to amlodipine and in HF, the coronary responses to amlodipine are reduced, which is related to a reduced NO production.

Systolic function is often evaluated by measuring ejection fraction and its preservation is often assimilated with the lack of impairment of systolic left ventricular (LV) function. Considering the left ventricle as a muscular pump, we explored LV function during chronic hypertension independently of increased afterload conditions. Fourteen conscious and chronically instrumented pigs received continuous infusion of either angiotensin II (n = 8) or saline (n = 6) during 28 days. Hemodynamic recordings were regularly performed in the presence and 1 h after stopping angiotensin II infusion to evaluate intrinsic LV function. Throughout the protocol, the mean arterial pressure steadily increased by 55 ± 4 mmHg in angiotensin II-treated animals. There were no significant changes in stroke volume, LV fractional shortening or LV wall thickening, indicating the lack of alterations in LV ejection. In contrast, we observed maladaptive changes with (1) the lack of reduction in isovolumic contraction and relaxation durations with heart rate increases, (2) abnormally blunted isovolumic contraction and relaxation responses to dobutamine and (3) a linear correlation between isovolumic contraction and relaxation durations. None of these changes were observed in saline-infused animals. In conclusion, we provide evidence of impaired LV function with concomitant isovolumic contraction and relaxation abnormalities during chronic hypertension while ejection remains preserved and no sign of heart failure is present. The evaluation under unloaded conditions shows intrinsic LV abnormalities.