Vitamin D deficiency causes inward hypertrophic remodeling and alters vascular reactivity of rat cerebral arterioles

BACKGROUND AND PURPOSE: Vitamin D deficiency (VDD) is a global health problem, which can lead to several pathophysiological consequences including cardiovascular diseases. Its impact on the cerebrovascular system is not well understood. The goal of the present work was to examine the effects of VDD on the morphological, biomechanical and functional properties of cerebral arterioles. METHODS: Four-week-old male Wistar rats (n = 11 per group) were either fed with vitamin D deficient diet or received conventional rat chow with per os vitamin D supplementation. Cardiovascular parameters and hormone levels (testosterone, androstenedione, progesterone and 25-hydroxyvitamin D) were measured during the study. After 8 weeks of treatment anterior cerebral artery segments were prepared and their morphological, biomechanical and functional properties were examined using pressure microangiometry. Resorcin-fuchsin and smooth muscle actin staining were used to detect elastic fiber density and smooth muscle cell counts in the vessel wall, respectively. Sections were immunostained for eNOS and COX-2 as well. RESULTS: VDD markedly increased the wall thickness, the wall-to-lumen ratio and the wall cross-sectional area of arterioles as well as the number of smooth muscle cells in the tunica media. As a consequence, tangential wall stress was significantly lower in the VDD group. In addition, VDD increased the myogenic as well as the uridine 5'-triphosphate-induced tone and impaired bradykinin-induced relaxation. Decreased eNOS and increased COX-2 expression were also observed in the endothelium of VDD animals. CONCLUSIONS: VDD causes inward hypertrophic remodeling due to vascular smooth muscle cell proliferation and enhances the vessel tone probably because of increased vasoconstrictor prostanoid levels in young adult rats. In addition, the decreased eNOS expression results in endothelial dysfunction. These morphological and functional alterations can potentially compromise the cerebral circulation and lead to cerebrovascular disorders in VDD

P2 receptors in atherosclerosis and postangioplasty restenosis

Atherosclerosis is an immunoinflammatory process that involves complex interactions between the vessel wall and blood components and is thought to be initiated by endothelial dysfunction [Ross (Nature 362:801–09, 1993); Fuster et al. (N Engl J Med 326:242–50, 1992); Davies and Woolf (Br Heart J 69:S3–S11, 1993)]. Extracellular nucleotides that are released from a variety of arterial and blood cells [Di Virgilio and Solini (Br J Pharmacol 135:831–42, 2002)] can bind to P2 receptors and modulate proliferation and migration of smooth muscle cells (SMC), which are known to be involved in intimal hyperplasia that accompanies atherosclerosis and postangioplasty restenosis [Lafont et al. (Circ Res 76:996–002, 1995)]. In addition, P2 receptors mediate many other functions including platelet aggregation, leukocyte adherence, and arterial vasomotricity. A direct pathological role of P2 receptors is reinforced by recent evidence showing that upregulation and activation of P2Y2 receptors in rabbit arteries mediates intimal hyperplasia [Seye et al. (Circulation 106:2720–726, 2002)]. In addition, upregulation of functional P2Y receptors also has been demonstrated in the basilar artery of the rat double-hemorrhage model [Carpenter et al. (Stroke 32:516–22, 2001)] and in coronary artery of diabetic dyslipidemic pigs [Hill et al. (J Vasc Res 38:432–43, 2001)]. It has been proposed that upregulation of P2Y receptors may be a potential diagnostic indicator for the early stages of atherosclerosis [Elmaleh et al. (Proc Natl Acad Sci U S A 95:691–95, 1998)]. Therefore, particular effort must be made to understand the consequences of nucleotide release from cells in the cardiovascular system and the subsequent effects of P2 nucleotide receptor activation in blood vessels, which may reveal novel therapeutic strategies for atherosclerosis and restenosis after angioplasty

Influence of androgen receptor in vascular cells on reperfusion following hindlimb ischaemia

AIMS:Studies in global androgen receptor knockout (G-ARKO) and orchidectomised mice suggest that androgen accelerates reperfusion of the ischaemic hindlimb by stimulating angiogenesis. This investigation used novel, vascular cell-specific ARKO mice to address the hypothesis that the impaired hindlimb reperfusion in G-ARKO mice was due to loss of AR from cells in the vascular wall. METHODS AND RESULTS:Mice with selective deletion of AR (ARKO) from vascular smooth muscle cells (SM-ARKO), endothelial cells (VE-ARKO), or both (SM/VE-ARKO) were compared with wild type (WT) controls. Hindlimb ischaemia was induced in these mice by ligation and removal of the femoral artery. Post-operative reperfusion was reduced in SM-ARKO and SM/VE-ARKO mice. Immunohistochemistry indicated that this was accompanied by a reduced density of smooth muscle actin-positive vessels but no change in the density of isolectin B4-positive vessels in the gastrocnemius muscle. Deletion of AR from the endothelium (VE-ARKO) did not alter post-operative reperfusion or vessel density. In an ex vivo (aortic ring culture) model of angiogenesis, AR was not detected in vascular outgrowths and angiogenesis was not altered by vascular ARKO or by exposure to dihydrotestosterone (DHT 10(-10)-10(-7)M; 6 days). CONCLUSION:These results suggest that loss of AR from vascular smooth muscle, but not from the endothelium, contributes to impaired reperfusion in the ischaemic hindlimb of G-ARKO. Impaired reperfusion was associated with reduced collateral formation rather than reduced angiogenesis

Le diagnostic transversal : de l'importance des conditions de conception des dispositifs de développement<br />Le projet “Centre de Service et de Compétences Territoriales” de l'Espace Belledonne

Cet article se propose d'examiner l'enjeu de la transversalité de la démarche de diagnostic et les conditions d'une démarche itérative dans l'accompagnement d'un projet de territoire. La démonstration est appuyée sur l'expérience du projet de création d'un Centre de Service et de Compétences de l'Espace Belledonne.Après avoir retracé les étapes à l'origine du diagnostic territorial qui a conduit à envisager la conception du CSCT, l'accent est mis sur la méthode itérative qui a permis de faire émerger les enjeux et les axes stratégiques du projet.De cette expérience, un certain nombre d'enseignements peuvent être dégagés : ils posent en particulier la question d'une transférabilité de cette démarche à d'autres territoires et soulignent la nécessité d'une appropriation collective de la formulation des enjeux et d'un temps suffisant donné à la conduite de la démarche

Osteopontin Stimulates Apoptosis in Adult Cardiac Myocytes via the Involvement of CD44 Receptors, Mitochondrial Death Pathway, and Endoplasmic Reticulum Stress

Increased osteopontin (OPN) expression associates with increased myocyte apoptosis and myocardial dysfunction. The objective of this study was to identify the receptor for OPN and get insight into the mechanism by which OPN induces cardiac myocyte apoptosis. Adult rat ventricular myocytes (ARVMs) and transgenic mice expressing OPN in a myocyte-specific manner were used for in vitro and in vivo studies. Treatment with purified OPN (20 nM) protein or adenoviral-mediated OPN expression induced apoptosis in ARVMs. OPN co-immunoprecipitated with CD44 receptors, not with β1 or β3 integrins. Proximity ligation assay confirmed interaction of OPN with CD44 receptors. Neutralizing anti-CD44 antibodies inhibited OPN-stimulated apoptosis. OPN activated JNKs and increased expression of Bax and levels of cytosolic cytochrome c, suggesting involvement of mitochondrial death pathway. OPN increased endoplasmic reticulum (ER) stress, as evidenced by increased expression of Gadd153 and activation of caspase-12. Inhibition of JNKs using SP600125 or ER stress using salubrinal or caspase-12 inhibitor significantly reduced OPN-stimulated apoptosis. Expression of OPN in adult mouse heart in myocyte-specific manner associated with decreased left ventricular function and increased myocyte apoptosis. In the heart, OPN expression increased JNKs and caspase-12 activities, and expression of Bax and Gadd153. Thus, OPN, acting via CD44 receptors, induces apoptosis in myocytes via the involvement of mitochondrial death pathway and ER stress

C006 Nadph-oxidases and uncoupled endothelial NO-synthase in pulmonary arterial hypertension induced by chronic hypoxia

Nitric oxide (NO) production by endothelial NO-synthase (eNOS) is critically dependent on the cofactor, tetrahydrobiopterin (BH4). Depletion in BH4 consecutive to an increase of reactive oxygen species (ROS) production by NADPH-oxidases and/or eNOS over-expression, favour eNOS uncoupling. This study investigates the potential role of NADPH-oxidases and uncoupled eNOS in pulmonary arterial hypertension induced by chronic hypoxia.Male C57BL/6 and eNOS knockout (eNOS-/-) mice were exposed or not to hypobaric hypoxia (0.5atm) for 21 days. Fulton index (right ventricular / left ventricular + septum weight ratio) was determined. Lungs were used for measurement of BH4 (by HPLC), for expression of eNOS (by western-blotting) and of the NADPH-oxidases subunits Nox1, Nox2 and Nox4 (by RT-PCR). Pulmonary arteries were also mounted in a wire myograph for evaluation of vasomotor responses.Chronic hypoxia induced a marked up-regulation of Nox1, Nox2 and Nox4 mRNAs in lungs, and an increase of ROS levels in pulmonary arteries. BH4 levels, as well as eNOS expression, were enhanced in lungs from hypoxic WT mice (1.25 and 4 fold increase compared to normoxic WT mice, respectively). In pulmonary arteries from hypoxic WT mice, the contractile response to phenylephrine was about 1.8 greater than in those from normoxic WT mice. The use of ROS scavengers (PEG-SOD or catalase) and NOS inhibitor (L-NAME) revealed the involvement of ROS in hypoxia-induced hyper-reactivity to phenylephrine, and a loss of NO-dependent relaxation. Chronic treatment of hypoxic WT mice with the BH4 precursor sepiapterin preserved the vasorelaxant effect of NO. This treatment and the deletion of eNOS gene abolished the inhibitory effect of catalase on phenylephrine-induced contraction, and also attenuated hypoxia-induced right ventricular hypertrophy.These data show that chronic hypoxia induced an up-regulation of Nox isoforms and eNOS in lungs. They suggest that uncoupled eNOS participates to right ventricular hypertrophy and to alterations of vasomotor responses in pulmonary arteries in hypoxia-induced pulmonary hypertension. The weak increase in BH4 and the large over-expression of eNOS suggest the existence of compensatory mechanisms on BH4 synthesis, which may moderate eNOS dysfunction.Grants: Fondation de France, ANR, GRRC (E.D PhD grant