Masakuni Kido

Induction of pulmonary hypertension by an angiopoietin 1/TIE2/serotonin pathway

Smooth muscle cell proliferation around small pulmonary vessels is essential to the pathogenesis of pulmonary hypertension. Here we describe a molecular mechanism and animal model for this vascular pathology. Rodents engineered to express angiopoietin 1 (Ang-1) constitutively in the lung develop severe pulmonary hypertension. These animals manifest diffuse medial thickening in small pulmonary vessels, resulting from smooth muscle cell hyperplasia. This pathology is common to all forms of human pulmonary hypertension. We demonstrate that Ang-1 stimulates pulmonary arteriolar endothelial cells through a TIE2 (receptor with tyrosine kinase activity containing IgG-like loops and epidermal growth factor homology domains) pathway to produce and secrete serotonin (5-hydroxytryptamine), a potent smooth muscle mitogen, and find that high levels of serotonin are present both in human and rodent pulmonary hypertensive lung tissue. These results suggest that pulmonary hypertensive vasculopathy occurs through an Ang-1/TIE2/serotonin paracrine pathway and imply that these signaling molecules may be targets for strategies to treat this disease.

The suppressor of cytokine signaling-1 (SOCS1) is a novel therapeutic target for enterovirus-induced cardiac injury.

Enteroviral infections of the heart are among the most commonly identified causes of acute myocarditis in children and adults and have been implicated in dilated cardiomyopathy. Although there is considerable information regarding the cellular immune response in myocarditis, little is known about innate signaling mechanisms within the infected cardiac myocyte that contribute to the host defense against viral infection. Here we show the essential role of Janus kinase (JAK) signaling in cardiac myocyte antiviral defense and a negative role of an intrinsic JAK inhibitor, the suppressor of cytokine signaling (SOCS), in the early disease process. Cardiac myocyte-specific transgenic expression of SOCS1 inhibited enterovirus-induced signaling of JAK and the signal transducers and activators of transcription (STAT), with accompanying increases in viral replication, cardiomyopathy, and mortality in coxsackievirus-infected mice. Furthermore, the inhibition of SOCS in the cardiac myocyte through adeno-associated virus-mediated (AAV-mediated) expression of a dominant-negative SOCS1 increased the myocyte resistance to the acute cardiac injury caused by enteroviral infection. These results indicate that strategies directed at inhibition of SOCS in the heart and perhaps other organs can augment the host-cell antiviral system, thus preventing viral-mediated end-organ damage during the early stages of infection.

A new animal model for pulmonary hypertension based on the overexpression of a single gene, angiopoietin-1.

BACKGROUND Angiopoietin-1 gene expression in human pulmonary hypertensive lungs is directly proportional to increasing pulmonary vascular resistance. We hypothesized that targeted overexpresssion of angiopoietin-1 in the lung would cause persistent pulmonary hypertension in an animal model. METHODS We injected 2 x 10(10) genomic particles of adeno-associated virus-angiopoietin-1 (AAV-Ang-1) into the right ventricular outflow tract of 30 Fischer rats while using adeno-associated virus-lacZ (AAV-lacZ) injected rats and carrier-injected rats as our control groups. All animals underwent survival surgery and were sacrificed at serial timepoints postgene delivery. At each timepoint, pulmonary artery pressures were measured and pulmonary angiography using the Microfil polymer perfusion technique was performed. The lungs were harvested for pathologic analysis, mRNA analysis, Western blot assays, and in situ RNA hybridization to localize gene expression. RESULTS Pulmonary artery pressures of AAV-Ang-1 injected rats were significantly increased compared with the control groups (p < 0.01) at all timepoints. Pathologic analysis of AAV-Ang-1 lung specimens demonstrated increased smooth muscle cell proliferation within the medial layer of arterioles with obliteration of small vessels similar to that seen in human pulmonary hypertension. Angiograms of AAV-Ang-1 injected lungs showed blunting of small peripheral arterioles consistent with advanced pulmonary hypertension. In situ RNA hybridization localized angiopoietin-1 expression to the vascular wall of small-caliber pulmonary vessels. Protein and mRNA assays confirmed persistent angiopoietin-1 expression in the lung for up to 60 days postgene delivery. CONCLUSIONS Overexpression of angiopoietin-1 using an adeno-associated virus vector causes pulmonary hypertension in rats. These data provide a novel physiologic animal model for pulmonary hypertension.

Role of mitochondrial KATP channels and protein kinase C in ischaemic preconditioning.

1. Activation of mitochondrial KATP (mitoKATP) channels and protein kinase C (PKC) has been implicated in cardioprotective mechanisms of ischaemic preconditioning (IPC). However, the exact role of these events in early IPC remains unclear.

Integrated pharmacological preconditioning in combination with adenosine, a mitochondrial KATP channel opener and a nitric oxide donor.

BACKGROUND Mitochondrial K(ATP) channel activation is an essential component of ischemic preconditioning. These channels are selectively opened by diazoxide and may be up-regulated by adenosine and nitric oxide. Therefore, pharmacological preconditioning with diazoxide in combination with adenosine and a nitric oxide donor (triple-combination pharmacological preconditioning) may enhance cardioprotection. METHODS AND RESULTS Isolated and perfused rat hearts underwent ischemic preconditioning with 3 cycles of 5 minutes of ischemia and 5 minutes of reperfusion before 5 minutes of oxygenated potassium cardioplegia and 35 minutes of ischemia. Pharmacological preconditioning was performed by adding adenosine, diazoxide, and a nitric oxide donor S-nitroso-N-acetyl-penicillamine each alone or in combinations for 25 minutes followed by 10 minutes washout before cardioplegic arrest. Only triple-combination pharmacological preconditioning conferred significant cardioprotection as documented by highly improved left ventricular function and limited creatine kinase release during reperfusion that was comparable to that afforded by ischemic preconditioning. Mitochondrial K(ATP) channel activity assessed by flavoprotein oxidation was increased by diazoxide, but no further increase in flavoprotein oxidation was obtained by ischemic preconditioning and triple-combination pharmacological preconditioning. Significant activation of protein kinase C-epsilon was observed in only ischemic preconditioning and triple-combination pharmacological preconditioning. Pretreatment with the mitochondrial K(ATP) channel inhibitor 5-hydroxydecanoate or the protein kinase C inhibitor chelerythrine abrogated activation of protein kinase C-epsilon and cardioprotection afforded by ischemic preconditioning and triple-combination pharmacological preconditioning. CONCLUSIONS Integrated pharmacological preconditioning is not simply mediated by enhanced mitochondrial K(ATP) channel activation, but is presumably mediated through amplified protein kinase C signaling promoted by coordinated interaction of adenosine, mitochondrial K(ATP) channel activation, and nitric oxide.

Pulmonary sequestration with myocardial ischemia caused by vasospasm and steal

We describe patient with a rare pulmonary sequestration with myocardial ischemia in the left coronary artery caused by vasospastic angina and stealing from coronary circulation. The anterior atrial branch from the left circumflex artery gave rise to a large and anomalous vessel in the right posterior lung field. Both the surgical and medical treatment of this pulmonary sequestration improved the control of angina attacks.

Effects Of The Na+/H+ Exchange Inhibitor Cariporide (HOE 642) On Cardiac Function And Cardiomyocyte Cell Death In Rat Ischaemic–Reperfused Heart

1. Na+/H+ exchange has been implicated in the mechanism of reperfusion injury. We examined the effects of the cardiac‐specific Na+/H+ exchange inhibitor cariporide (HOE 642) on postischaemic recovery of cardiac function and cardiomyocyte cell death (i.e. necrosis and apoptosis).

Combined pharmacological preconditioning with a G‐protein‐coupled receptor agonist, a mitochondrial KATP channel opener and a nitric oxide donor mimics ischaemic preconditioning

1. Although pharmacological preconditioning (PPC) has emerged as an alternative to ischaemic preconditioning (IPC) in cardioprotection, the efficacy of PPC compared with IPC has not been investigated. Because IPC is mediated by complex signalling cascades arising from multiple triggers, we have hypothesized that combined PPC is necessary to mimic IPC.

Potential role of vacuolar H+–adenosine triphosphatase in neointimal formation in cultured human saphenous vein☆

OBJECTIVE Vacuolar H(+)-adenosine triphosphatase plays a pivotal role in pH regulation and molecular transport across the vacuolar membranes and is involved in cell proliferation and transformation. In the present study, possible involvement of vacuolar H(+)-adenosine triphosphatase in neointimal formation was investigated in an organ culture model of human saphenous vein. METHODS AND RESULTS Cultured saphenous vein segments developed neointimal formation and marked thickening of the media within 14 days. Neointimal formation and medial thickening were completely inhibited by 10 nmol/L bafilomycin A(1), a selective inhibitor of vacuolar H(+)-adenosine triphosphatase, although structurally related macrolide antibiotics FK-506 and erythromycin were without an effect. The neointimal cells were positive for alpha-smooth muscle actin and vimentin but negative for desmin, indicative of myofibroblasts. The emergence of myofibroblasts was inhibited, and endothelial cells were preserved in the saphenous vein segments treated with bafilomycin A(1). Uptake of bromodeoxyuridine, a proliferation marker, by myofibroblasts was abrogated in the saphenous vein segments treated with 10 nmol/L bafilomycin A(1). Detection of apoptotic cells by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling concomitant with identification of desmin-expressing smooth muscle cells demonstrated that neointimal myofibroblasts, but not medial smooth muscle cells, that expressed desmin underwent apoptosis by treatment with bafilomycin A(1). CONCLUSIONS These results suggest that vacuolar H(+)-adenosine triphosphatase may be involved in myofibroblast growth that contributes to neointimal formation and medial thickening in cultured human saphenous vein. Increased sensitivity of myofibroblasts, but not endothelial cells, and differentiated smooth muscle cells to bafilomycin A(1) may have potential therapeutic implications in the treatment for vein graft disease.

One stage operation for aneurysm of the diverticulum of the ductus arteriosus and coronary artery bypass grafting

Aneurysm of the diverticulum of the ductus arteriosus in the adult is rare. One stage operation for aneurysm of the diverticulum of the ductus arteriosis and coronary artery bypass grafting (CABG) is reported. A 61-year-old man was admitted for diagnosis of thoracic aneurysm on chest X-ray and CT. Chest CT scan showed an aneurysm above the left main pulmonary artery. An aortography showed the left vertebral artery originated directly from the aortic arch and a saccular aneurysm arising from the aortic isthmus and lesser curvature of the aortic arch. Coronary arteriography showed 75% stenosis at the right coronary artery (seg. #1) and 75% stenosis at the left anterior descending artery. Operation was performed through a median sternotomy. The aneurysm of 6 to 3 cm was located between the aortic isthmus and left pulmonary artery. Ascending aorta and right atrium were used to institute cardiopulmonary bypass (CPB). CABG (LITA to #7, SVG to #4 PD) was performed. Arterial cannulation was then switched to the left femoral artery. The proximal aorta was cross-clamped between the left vertebral artery and the left subclavian artery under the partial CPB, and the distal aorta was occluded with a occulusive balloon catheter via the right femoral artery. The selective left axillar artery cannulation was performed to perfuse LITA. The aneurysm was resected and closed with a patch. His post-operative course was uneventful.