Effects of centrally acting antihypertensive drugs on the microcirculation of spontaneously hypertensive rats

Submitted by Sandra Infurna ([email protected]) on 2018-12-08T12:43:04Z No. of bitstreams: 1 vanessa_estato_etal_IOC_2010.pdf: 483607 bytes, checksum: 0b1e979a20cd14b3d85ada4e43e9f990 (MD5)Approved for entry into archive by Sandra Infurna ([email protected]) on 2018-12-08T12:53:06Z (GMT) No. of bitstreams: 1 vanessa_estato_etal_IOC_2010.pdf: 483607 bytes, checksum: 0b1e979a20cd14b3d85ada4e43e9f990 (MD5)Made available in DSpace on 2018-12-08T12:53:06Z (GMT). No. of bitstreams: 1 vanessa_estato_etal_IOC_2010.pdf: 483607 bytes, checksum: 0b1e979a20cd14b3d85ada4e43e9f990 (MD5) Previous issue date: 2010Fundação Oswaldo cruz. Instituto Oswaldo Cruz. Departamento de Fisiologia e Farmacodinâmica. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo cruz. Instituto Oswaldo Cruz. Departamento de Fisiologia e Farmacodinâmica. Rio de Janeiro, RJ, Brasil.Université Louis Pasteur. Faculté de Médecine. Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire. Strasbourg, France.Fundação Oswaldo cruz. Instituto Oswaldo Cruz. Departamento de Fisiologia e Farmacodinâmica. Rio de Janeiro, RJ, Brasil.We investigated the acute effects of centrally acting antihypertensive drugs on the microcirculation of pentobarbital-anesthetized spontaneously hypertensive rats (SHR). The effects of the sympatho-inhibitory agents clonidine and rilmenidine, known to activate both α2-adrenoceptors and nonadrenergic I1-imidazoline binding sites (I1BS) in the central nervous system, were compared to those of dicyclopropylmethyl-(4,5-dimethyl-4,5-dihydro-3H-pyrrol-2-yl)-amine hydrochloride (LNP 509), which selectively binds to the I1BS. Terminal mesenteric arterioles were observed by intravital microscopy. Activation of the central sympathetic system with L-glutamate (125 µg, ic) induced marked vasoconstriction of the mesenteric microcirculation (27 ± 3%; N = 6, P < 0.05). In contrast, the marked hypotensive and bradycardic effects elicited by intracisternal injection of clonidine (1 µg), rilmenidine (7 µg) and LNP 509 (60 µg) were accompanied by significant increases in arteriolar diameter (12 ± 1, 25 ± 10 and 21 ± 4%, respectively; N = 6, P < 0.05). The vasodilating effects of rilmenidine and LNP 509 were two-fold higher than those of clonidine, although they induced an identical hypotensive effect. Central sympathetic inhibition elicited by baclofen (1 µg, ic), a GABAB receptor agonist, also resulted in vasodilation of the SHR microvessels. The acute administration of clonidine, rilmenidine and LNP 509 also induced a significant decrease of cardiac output, whereas a decrease in systemic vascular resistance was observed only after rilmenidine and LNP 509. We conclude that the normalization of blood pressure in SHR induced by centrally acting antihypertensive agents is paralleled by important vasodilation of the mesenteric microcirculation. This effect is more pronounced with substances acting preferentially (rilmenidine) or exclusively (LNP 509) upon I1BS than with those presenting important α2-adrenergic activity (clonidine)

Effects of centrally acting antihypertensive drugs on the microcirculation of spontaneously hypertensive rats

We investigated the acute effects of centrally acting antihypertensive drugs on the microcirculation of pentobarbital-anesthetized spontaneously hypertensive rats (SHR). The effects of the sympatho-inhibitory agents clonidine and rilmenidine, known to activate both alpha2-adrenoceptors and nonadrenergic I1-imidazoline binding sites (I1BS) in the central nervous system, were compared to those of dicyclopropylmethyl-(4,5-dimethyl-4,5-dihydro-3H -pyrrol-2-yl)-amine hydrochloride (LNP 509), which selectively binds to the I1BS. Terminal mesenteric arterioles were observed by intravital microscopy. Activation of the central sympathetic system with L-glutamate (125 µg, ic) induced marked vasoconstriction of the mesenteric microcirculation (27 ± 3%; N = 6, P < 0.05). In contrast, the marked hypotensive and bradycardic effects elicited by intracisternal injection of clonidine (1 µg), rilmenidine (7 µg) and LNP 509 (60 µg) were accompanied by significant increases in arteriolar diameter (12 ± 1, 25 ± 10 and 21 ± 4%, respectively; N = 6, P < 0.05). The vasodilating effects of rilmenidine and LNP 509 were two-fold higher than those of clonidine, although they induced an identical hypotensive effect. Central sympathetic inhibition elicited by baclofen (1 µg, ic), a GABA B receptor agonist, also resulted in vasodilation of the SHR microvessels. The acute administration of clonidine, rilmenidine and LNP 509 also induced a significant decrease of cardiac output, whereas a decrease in systemic vascular resistance was observed only after rilmenidine and LNP 509. We conclude that the normalization of blood pressure in SHR induced by centrally acting antihypertensive agents is paralleled by important vasodilation of the mesenteric microcirculation. This effect is more pronounced with substances acting preferentially (rilmenidine) or exclusively (LNP 509) upon I1BS than with those presenting important alpha2-adrenergic activity (clonidine)

Investigation of the haemodynamic effects of phoneutria nigriventer venom in anaesthetised rabbits

The haemodynamic alterations induced by the central and peripheral administration of the armed spider (Phoneutria nigriventer) venom (PNV) were investigated in anaesthetised rabbits. The intracerebroventricular injection of increasing doses of PNV (30 and 100 mu g/ kg) elicited a biphasic cardiovascular response characterised by a brief hypotension (1-3 min) followed by a marked and sustained (more than 30 min) increase in mean arterial pressure (61 +/- 5 and 61 +/- 10%, respectively) and in systemic vascular resistance (135 +/- 21 and 161 + 37%) accompanied by mild increases in cardiac contractility. Systemic alterations such as salivation and muscular fasciculation were also observed. At the opposite, the dose of 100 mu g/kg of PNV injected intravenously produced only a hypotensive effect (29 +/- 4% decrease in mean arterial pressure) and a decrease in vascular resistance (38 +/- 5%). Nevertheless, a much higher dose of PNV (1 mg/kg) injected intravenously produced a hypertensive response analogous to the one observed upon central administration. The central hypertensive response induced by PNV was not affected by pretreating the animals with selective antagonists of receptors of different neurotransmitters or endogenous mediators such as: acethylcoline muscarinic, bradykinin B-2, angiotensin II AT(1) receptors and also antagonists of the excitatory aminoacid receptors of the central nervous system. Nevertheless, the intravenous pretreatment with the selective al-adrenergic receptor antagonist prazosin significantly blunted the excitatory cardiovascular response evoked by the central injection of PNV. It is concluded that PNV call induce central as well as peripheral haemodynamic effects. The central component seems to be mediated by the activation of cardiovascular centres which in turn lead to an increase in the sympathetic outflow to the periphery, whereas the peripheral component can be accounted for either by direct activation of the vascular;alpha(1)-adrenergic receptors or by catecholamine release from the sympathetic nerve endings38684185

Statins Decrease Neuroinflammation and Prevent Cognitive Impairment after Cerebral Malaria

<div><p>Cerebral malaria (CM) is the most severe manifestation of <em>Plasmodium falciparum</em> infection in children and non-immune adults. Previous work has documented a persistent cognitive impairment in children who survive an episode of CM that is mimicked in animal models of the disease. Potential therapeutic interventions for this complication have not been investigated, and are urgently needed. HMG-CoA reductase inhibitors (statins) are widely prescribed for cardiovascular diseases. In addition to their effects on the inhibition of cholesterol synthesis, statins have pleiotropic immunomodulatory activities. Here we tested if statins would prevent cognitive impairment in a murine model of cerebral malaria. Six days after infection with <em>Plasmodium berghei</em> ANKA (PbA) mice displayed clear signs of CM and were treated with chloroquine, or chloroquine and lovastatin. Intravital examination of pial vessels of infected animals demonstrated a decrease in functional capillary density and an increase in rolling and adhesion of leukocytes to inflamed endothelium that were reversed by treatment with lovastatin. In addition, oedema, ICAM-1, and CD11b mRNA levels were reduced in lovastatin-treated PbA-infected mice brains. Moreover, HMOX-1 mRNA levels are enhanced in lovastatin-treated healthy and infected brains. Oxidative stress and key inflammatory chemokines and cytokines were reduced to non-infected control levels in animals treated with lovastatin. Fifteen days post-infection cognitive dysfunction was detected by a battery of cognition tests in animals rescued from CM by chloroquine treatment. In contrast, it was absent in animals treated with lovastatin and chloroquine. The outcome was similar in experimental bacterial sepsis, suggesting that statins have neuroprotective effects in severe infectious syndromes in addition to CM. Statin treatment prevents neuroinflammation and blood brain barrier dysfunction in experimental CM and related conditions that are associated with cognitive sequelae, and may be a valuable adjuvant therapeutic agent for prevention of cognitive impairment in patients surviving an episode of CM.</p> </div

Lovastatin improves microvascular function and decreases leukocyte rolling and adhesion during PbA infection.

<p>A–J: representative images of fluorescence intravital microscopy of pial vessels of uninfected mice (A and B; Magnification 100×) or infected mice (C and D) treated with vehicle or lovastatin, respectively (Magnification 40×). Venules with adherent and rolling rhodamine-labeled leukocytes in uninfected mice (E and F) or infected mice (G and H) treated with vehicle or lovastatin, respectively (Magnification 200×). Rhodamine-labeled leukocytes were associated with the venular endothelium in animals treated with vehicle (G) whereas they were largely free in the blood stream in lovastatin-treated mice (H). Fluorescent <i>Plasmodium berghei</i> (GFP)-infected RBC in venules of mice treated with vehicle (I) or lovastatin (J) (Magnification 200×). Mean ± SEM of functional capillary density (K), of rolling-rhodamine labeled leukocytes (L), and of number of adherent leukocytes (M) in pial venules (n = 6/group); *p<0.05 in relation to control (RBC) and vehicle-treated groups (Bonferroni's Multiple Comparison Test) and between PbA and PbA-lovastatin group (Bonferroni's Multiple Comparison Test; Scale bar, 100 µm).</p

Lovastatin treatment prevents impairment of short and long-term aversive memory after sepsis.

<p>C57BL/6 mice (n = 5–10/group) were inoculated with fecal supernatant (2.5 mg/g b.w.). For control, one group was inoculated with saline (0.9%). Control and mice challenged with fecal supernatant were divided and one group was treated with lovastatin (20 mg/kg b.w.) 1 hour prior to feces or saline injection respectively, and every 24 h for 3 days. All the animals received imipenem (10 mg/kg b.w.) 6 hours after inoculation and every 24 h for 3 days. On day 15 all animals were subjected to a training session of inhibitory avoidance task, where the latency time on the platform is recorded and an electrical shock is given immediately after the mice step down onto the bars. (A) 1.5 (Short-term memory) and (B) 24 h (long-term memory) aversive memory was then tested by recording the latency time on the platform (with a cut-off of 180 sec). Data are expressed as individual values and horizontal lines represent the mean of latency, in seconds; significant difference compared between saline versus feces injected mice (comparisons among groups were performed by Mann-Whitney U test, *p<0.05).</p

Lovastatin treatment decreases ICAM-1 and CD11b expression and vascular permeability and induce HMOX-1 expression in the brains of mice with CM.

<p>Panels illustrate histological examinations of cerebral cortex on day 6 post-infection, immunostained for ICAM-1 (brown and arrow) and counterstained with hematoxylin-eosin. Brain histology was examined using tissue from the following groups of animals: uninfected (A), uninfected treated with lovastatin (B), PbA-infected (C), and PbA-infected treated with lovastatin (D). Vascular congestion and edema (*) were observed in all PbA-infected mice, but were not seen in controls or treated animals. Scale bar: 50 µm. E: Dose-response relationships for effects of lovastatin on edema formation measured by Evans Blue Dye accumulation in the brain tissue on day 7 post-infection. F–H: ICAM-1, CD11b, and HMOX-1 expression in brain samples evaluated by semi-quantitative PCR on day 6 post-infection; *p<0.05 by Tukey's Multiple Comparison Test (n = 3–5/group). I-representative macroscopic image of Evans blue dye extravasation in the brain, demonstrating a marked reduction in PbA mice treated with lovastatin (20 mg/kg) on day 7-post infection.</p

Effect of lovastatin on parasitemia and survival rate after infection with PbA (n = 12–20/group).

<p>Data on parasitemia (A) are shown as mean ± SEM. On day 6 post-infection mice were separated in two groups and one received lovastatin (10–40 mg/kg b.w.) daily for 7 days. Comparisons of C57BL6-PbA versus C57BL6-PbA treated animals (*) were significant by Mann-Withney Comparison test. There was no difference in parasitaemia when PbA and PbA-lovastatin treatment were compared (Mann-Withney Comparison test). (<b>B</b>) No differences in survival were observed among the groups (Log-rank (Mantel-Cox) and Gehan-Breslow-Wilcoxon tests).</p

Lovastatin treatment ameliorates oxidative stress in the brains of mice with CM.

<p>Oxidative stress was assayed by measuring MDA formation (A) and free thiols levels (B) in brains 6 days post-infection of mice with PbA (10⁶ PRBC, n = 10–15/group). Control groups received the same number of uninfected RBC (10⁶). Results are expressed as mean ± S.E.M. and * represents p<0.05 compared to RBC group and # in relation to PbA-infected group, according to Tukey's Multiple Comparison Test.</p

Lovastatin treatment prevents contextual and aversive memory impairment after CM.

<p>C57BL/6 mice (n = 12–20/group) were infected with PbA (10⁶ PRBC). As a control, one group was inoculated with the same number of uninfected RBC (n = 6–12/group). Starting on day 6-post infection, uninfected and PbA-infected mice were divided into 2 groups and treated orally with chloroquine (25 mg/kg b.w.), or with the combination of chloroquine/lovastatin for 7 days. On days 15 and 16 post-infection all the animals were submitted to open field training and test sessions (A–B), and to inhibitory avoidance sessions tasks (C–D). Data are expressed as mean ± SEM of crossings (A) and rearings (B) in training (<i>gray bars</i>) and test (<i>black bars</i>) sessions. *Significant difference between groups in training and test sessions (p<0.05, Student's t test). C–D: animals were subjected to a training session in which the latency time on the platform is recorded when an electrical shock is given immediately after the mice step down onto the bars. (C) 1.5 (Short-term memory) and (D) 24 h (long-term memory) aversive memory was tested by recording the latency time on the platform (with a cut-off of 180 sec). Data are expressed as individual values and horizontal lines represent the mean of latency, in seconds; *Significant difference compared with uninfected controls and between infected groups (comparisons among groups were performed by Mann-Whitney U test, <i>p<0.05</i>).</p