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1.
Exp Physiol ; 104(8): 1164-1178, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31140668

RESUMO

NEW FINDINGS: What is the central question of this study? The impact of pulmonary arterial hypertension on open-loop baroreflex function, which determines how powerfully and rapidly the baroreflex operates to regulate arterial pressure, remains poorly understood. What is the main finding and its importance? The gain of the baroreflex total arc, indicating the baroreflex pressure-stabilizing function, is markedly attenuated in rats with monocrotaline-induced pulmonary arterial hypertension. This is caused by a rightward shift of the baroreflex neural arc and a downward shift of the peripheral arc. These findings contribute greatly to our understanding of arterial pressure regulation by the sympathetic nervous system in pulmonary arterial hypertension. ABSTRACT: Sympathoexcitation has been documented in patients with established pulmonary arterial hypertension (PAH). Although the arterial baroreflex is the main negative feedback regulator of sympathetic nerve activity (SNA), the way in which PAH impacts baroreflex function remains poorly understood. In this study, we conducted baroreflex open-loop analysis in a rat model of PAH. Sprague-Dawley rats were injected with monocrotaline (MCT) s.c. to induce PAH (60 mg kg-1 ; n = 11) or saline as a control group (CTL; n = 8). At 3.5 weeks after MCT injection, bilateral carotid sinuses were isolated, and intrasinus pressure (CSP) was controlled while SNA at the coeliac ganglia and arterial pressure (AP) were recorded. To examine the static baroreflex function, CSP was increased stepwise while steady-state AP (total arc) and SNA (neural arc) responses to CSP and the AP response to SNA (peripheral arc) were measured. Monocrotaline significantly decreased the static gain of the baroreflex total arc at the operating AP compared with CTL (-0.80 ± 0.31 versus -0.22 ± 0.22, P < 0.05). Given that MCT markedly increased plasma noradrenaline, an index of SNA, by approximately 3.6-fold compared with CTL, calibrating SNA by plasma noradrenaline revealed that MCT shifted the neural arc to a higher SNA level and shifted the peripheral arc downwards. Monocrotaline also decreased the dynamic gain of the baroreflex total arc (-0.79 ± 0.16 versus -0.35 ± 0.17, P < 0.05), while the corner frequencies that reflect the speed of the baroreflex remained unchanged (0.06 ± 0.02 versus 0.08 ± 0.02 Hz, n.s.). In rats with MCT-induced PAH, the suppressed baroreflex peripheral arc overwhelms the augmented neural arc and, in turn, attenuates the gain of the total arc, which determines the pressure-stabilizing capacity of the baroreflex.

2.
Physiol Rep ; 7(7): e14025, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30927327

RESUMO

Hypoxemia is seen in patients with pulmonary hypertension and hypoxic pulmonary vasoconstriction worsens their clinical condition. However, vasoconstriction is not the only aspect through which hypoxia induces the progression to pulmonary hypertension. Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor responding to hypoxic conditions by regulating hundreds of genes involved in angiogenesis, erythropoiesis, inflammation, and proliferation. We sought to determine the contribution of HIF-1α in myeloid lineage cells to the pulmonary vascular response to chronic exposure to hypoxia. We generated myeloid-specific HIF-1α knockout (MyeHIF1KO) mice by using Cre-lox P system, and exposed them to hypoxic conditions for 3 weeks to induce pulmonary hypertension. Macrophages from MyeHIF1KO and control mice were used for western blotting, RT-qPCR, chemotaxis assay, and ATP assay. MyeHIF1KO mice exposed to hypoxia for 3 weeks exhibited a significant reduction in the right ventricular systolic pressure accompanied by a decrease in the ratio of the right ventricular weight to left ventricular weight, muscularization of the small pulmonary arteries, and infiltration of macrophages into the lung and right ventricle compared with control mice. HIF-1α-deficient peritoneal macrophages showed less migration toward monocyte chemoattractant protein-1 and a decrease in intracellular ATP levels. These results indicate that HIF-1α in macrophages contributes to the progression of pulmonary vascular remodeling and pulmonary hypertension induced by chronic exposure to hypoxic conditions. The inhibition of myeloid-specific HIF-1α may be a novel therapeutic strategy for the treatment of pulmonary hypertension.

4.
Am J Physiol Heart Circ Physiol ; 316(4): H828-H839, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30608176

RESUMO

Baroreflex dysfunction contributes to the pathogenesis of cardiovascular diseases. The baroreflex comprises a negative feedback loop to stabilize arterial pressure (AP); its pressure-stabilizing capacity is defined as the gain ( G) of the transfer function ( H) of the baroreflex total loop. However, no method exists to evaluate G in a clinical setting. A feedback system with H attenuates pressure disturbance (PD) to PD/(1 + H). We hypothesized that the baroreflex attenuates the power spectrum density (PSD) of AP in the baroreflex functioning frequency range. We created graded baroreflex dysfunction in rats using a modified sinoaortic denervation (SAD) method [SAD; control (no SAD): n = 9; partial SAD (SAD in the right carotid sinus): n = 6, and total SAD (SAD in the bilateral carotid sinuses): n = 6] and evaluated the PSD of 12-h telemetric AP recordings in the light phase. Using the ratio of PSD at 0.01-0.1 Hz (PSD slope), we normalized them with the PSD in rats with complete baroreflex failure and derived the baroreflex index (BRI), which directly reflects G. We compared BRI and G obtained from a baroreflex open-loop experiment (reference G). The PSD slope became steeper with progression of baroreflex dysfunction. BRI (control: 2.00 ± 0.31, partial SAD: 1.28 ± 0.30, and total SAD: 0.06 ± 0.10, P < 0.05) was linearly correlated with reference G ( R2 = 0.91, P < 0.01). BRI accurately estimated G of the baroreflex and may serve as a novel tool for estimating the pressure-stabilizing capacity of the baroreflex in clinical settings. NEW & NOTEWORTHY This study proposed a novel method to estimate the gain of the baroreflex total loop, the so-called "baroreflex index" (BRI). BRI focuses on action potential variability in the frequency domain, considering baroreflex low-pass filter characteristics within 0.01-0.1 Hz. We demonstrated that BRI was linearly correlated with the reference gain of baroreflex in rats. Thus, BRI may contribute greatly to the development of a clinical tool for estimating baroreflex pressure-stabilizing capacity.

5.
JACC Basic Transl Sci ; 3(5): 657-671, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30456337

RESUMO

This study aimed to elucidate the therapeutic effects of electrical vagal nerve stimulation (VNS) on severe pulmonary arterial hypertension in a rat model. In a pathophysiological study, VNS significantly restored autonomic balance, decreased mean pulmonary arterial pressure, attenuated pulmonary vascular remodeling, and preserved right ventricular function. In a survival study, VNS significantly improved the survival rate in both the prevention (VNS from 0 to 5 weeks after a SU5416 injection) and treatment (VNS from 5 to 10 weeks) protocols. Thus, VNS may serve as a novel therapeutic strategy for pulmonary arterial hypertension.

6.
Conf Proc IEEE Eng Med Biol Soc ; 2018: 1-4, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30440289

RESUMO

Although daily variations of blood pressure (BP) predict cardiovascular event risk, their assessment requires ambulatory BP monitoring which hinders the clinical application of this approach. Since the baroreflex is a major determinant of BP variations, especially in the frequency range of 0.01-0.1 Hz (baro-frequency), we hypothesized that the power spectral density (PSD) of short-term BP recordings in the baro-frequency range may predict daily variations of BP. In nine-week-old Wister-Kyoto male rats (N =5) with or without baroreflex dysfunction, we telemetrically recorded continuous BP for 24 hours and estimated PSD using Welch's periodogram for the recordings during the 12-hour light period. We compared the reference PSD of 12-hour recording with the PSDs obtained from shorter data lengths ranging from 5 to 240 minutes. The 30-minute BP recordings reproduced PSD of 12-hour recordingswell, and PSD in the baro-frequency range paralleled the standard deviation of 12-hour BP. Thus, the PSD of 30-minute BP reflects the daily BP variability in rats. In human subjects, we estimated PSD from 30-minute noninvasive continuous BP recordings. The rat and human PSDs shared remarkably similar characteristics. Furthermore, comparison of PSD between elderly and young subjects suggested that the baro-frequency range in humans overlapped with that in rats. In conclusion, PSD derived from 30-minute BP recordings is capable of predicting daily BP variations. Our proposed method may serve as a simple, noninvasive and practical tool for predicting cardiovascular events in the clinical setting.

7.
Cardiovasc Res ; 2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30423156

RESUMO

Aims: Pulmonary hypertension is characterized by progressive increases in pulmonary vascular resistance. Thrombotic lesions are common pathological findings. The pulmonary artery has a unique property regarding the vasoconstrictive response to thrombin, which is mediated by proteinase-activated receptor 1 (PAR1). We aim to elucidate the role of PAR1 in the development and progression of pulmonary hypertension. Methods and Results: A rat model of monocrotaline-induced pulmonary hypertension and a mouse model of hypoxia-induced pulmonary hypertension were used to investigate the effects of atopaxar (a PAR1 antagonist) and PAR1 knockout on hemodynamic parameters, right ventricular hypertrophy, vascular remodeling and survival. In perfused lung preparations, the pressor response to PAR1 agonist was significantly augmented in monocrotaline-induced pulmonary hypertension. Both the preventive and therapeutic administration of atopaxar significantly inhibited the increase in pulmonary vascular resistance and the development of right ventricular hypertrophy and prolonged survival. A real-time PCR revealed that the level of PAR1 mRNA in the pulmonary artery was significantly higher than that in any of the systemic arteries examined in control rats, and the level was significantly upregulated in monocrotaline-induced pulmonary hypertension. PAR1 gene knockout significantly attenuated the hemodynamic and histological findings in the mouse model of hypoxia-induced pulmonary hypertension. Conclusions: The specific expression of PAR1 in the pulmonary artery and its upregulation were suggested to play a critical role in the development and progression of experimental pulmonary hypertension in murine models. PAR1 is a potential therapeutic target for the treatment of pulmonary hypertension.

8.
Physiol Rep ; 6(19): e13887, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30307125

RESUMO

Although low pressure baroreflex (LPB) has been shown to elicit various cardiovascular responses, its impact on sympathetic nerve activity (SNA) and arterial baroreflex (ABR) function has not been fully elucidated. The aim of this study was to clarify how volume loading-induced acute LPB activation impacts on SNA and ABR function in normal rats. In 20 anesthetized Sprague-Dawley rats, we isolated bilateral carotid sinuses, controlled carotid sinus pressure (CSP), and measured central venous pressure (CVP), splanchnic SNA, and arterial pressure (AP). We infused blood stepwise (3 mL/kg/step) to activate volume loading-induced LPB. Under the ABR open-loop condition, stepwise volume loading markedly increased SNA by 76.8 ± 21.6% at CVP of 3.6 ± 0.2 mmHg. In contrast, further volume loading suppressed SNA toward the baseline condition. Bilateral vagotomy totally abolished the changes in SNA by volume loading. To assess the impact of LPB on ABR function, we changed CSP stepwise. Low volume loading (CVP = 3.6 ± 0.4 mmHg) significantly shifted the sigmoidal CSP-SNA relationship (central arc) upward from baseline, whereas high volume loading (CVP = 5.4 ± 0.4 mmHg) returned it to the baseline level. Volume loading shifted the linear SNA-AP relationship (peripheral arc) upward without significant changes in slope. In conclusions, volume loading-induced acute LPB activation evoked two-phase changes, an initial increase followed by decline from baseline value, in SNA via resetting of the ABR central arc. LPB may contribute greatly to stabilize AP in response to volume status.

9.
Artigo em Inglês | MEDLINE | ID: mdl-30339460

RESUMO

Patients with diabetes mellitus (DM) often show arterial pressure (AP) lability associated with cardiovascular autonomic neuropathy. Since the arterial baroreflex tightly regulates AP via sympathetic nerve activity (SNA), we investigated the systematic baroreflex function considering the control theory in DM by an open-loop analysis. We used Zucker Diabetic Fatty (ZDF)-Fatty rats as a type 2 DM model. Under general anesthesia, we isolated the carotid sinuses from systemic circulation, changed intra-carotid sinus pressure (CSP), and recorded SNA and AP responses. We compared the CSP-AP (total loop), CSP-SNA (afferent arc), and SNA-AP (efferent arc) relationships between ZDF-Lean (n=8) and ZDF-Fatty rats (n=6). Although the total loop gain of baroreflex (ΔAP/ΔCSP) at the operating point did not differ between the two groups, the averaged gain in the lower CSP range was markedly reduced in ZDF-Fatty rats (0.03±0.01 vs. 0.87±0.10mmHg/mmHg, p <0.001).The afferent arc showed the same trend as the total loop with a response threshold of 139.8±1.0 mmHg in ZDF-Fatty rats.There were no significant differences in the gain of efferent arc between the two groups. Simulation study indicated markedly higher AP fall and lower total loop gain of baroreflex in ZDF-Fatty than in ZDF-Lean rats against hypotensive stress, because the efferent arc intersected with the afferent arc in the SNAunresponsive range. Thus, we concluded that impaired baroreflex sympathetic regulation in the lower AP range attenuates the pressure response against hypotensive stress and may partially contribute to AP lability in DM.

10.
Life Sci ; 212: 225-232, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30300657

RESUMO

AIMS: Although pulmonary arterial remolding in pulmonary hypertension (PH) changes the mechanical properties of the pulmonary artery, most clinical studies have focused on static mechanical properties (resistance), and dynamic mechanical properties (compliance) have not attracted much attention. As arterial compliance plays a significant role in determining afterload of the right ventricle, we evaluated how PH changes the dynamic mechanical properties of the pulmonary artery using high-resolution, wideband input impedance (ZPA). We then examined how changes in ZPA account for arterial remodeling. Clarification of the relationship between arterial remodeling and ZPA could help evaluate arterial remodeling according to hemodynamics. MAIN METHODS: PH was induced in Sprague-Dawley rats with an injection of Sugen5416 (20 mg/kg) and 3-week exposure to hypoxia (10% oxygen) (SuHx). ZPA was evaluated from pulmonary artery pressure and flow under irregular pacing. Pulmonary histology was examined at baseline and 1, 3, and 8 weeks (n = 7, each) after Sugen5416 injection. KEY FINDINGS: SuHx progressively increased pulmonary arterial pressure. ZPA findings indicated that SuHx progressively increased resistance (baseline: 9.3 ±â€¯3.6, SuHx1W: 20.7 ±â€¯7.9, SuHx3W: 48.8 ±â€¯6.9, SuHx8W: 62.9 ±â€¯17.8 mm Hg/mL/s, p < 0.01) and decreased compliance (baseline: 11.9 ±â€¯2.1, SuHx1W: 5.3 ±â€¯1.7, SuHx3W: 2.1 ±â€¯0.7, SuHx8W: 1.9 ±â€¯0.6 × 10-3 mL/mm Hg, p < 0.01). The time constant did not significantly change. The progressive reduction in compliance was closely associated with wall thickening of small pulmonary arteries. SIGNIFICANCE: The finding that changes in resistance were reciprocally associated with those in compliance indicates that resistant and compliant vessels are anatomically inseparable. The analysis of ZPA might help evaluate arterial remodeling in PH according to hemodynamics.

11.
Cardiovasc Res ; 2018 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-30239623

RESUMO

Aims: Recent accumulating evidence suggests that sterile inflammation plays a crucial role in the progression of various cardiovascular diseases. However, its contribution to right ventricular (RV) dysfunction remains unknown. The aim of the present study was to elucidate whether toll-like receptor 9 (TLR9)-NF-κB‒mediated sterile inflammation plays a critical role in the pathogenesis of RV dysfunction. Methods and results: We performed main pulmonary artery banding (PAB) in rats to induce RV pressure overload and dysfunction. On day 14 after PAB, the pressure overload impaired RV function as indicated by increased RV end-diastolic pressure concomitant with macrophage infiltration and fibrosis, as well as maximal activation of NF-κB and TLR9. Short-term administration (days 14 to 16 after PAB) of a specific TLR9 inhibitor, E6446, or an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC) significantly attenuated NF-κB activation. Furthermore, long-term administration of E6446 (treatment: days 14 to 28) or PDTC (prevention: days -1 to 28; treatment: days 14 to 28) improved RV dysfunction associated with mitigated macrophage infiltration and fibrosis in RV and decreased serum BNP levels. Conclusions: Inhibition of TLR9-NF-κB pathway‒mediated sterile inflammation improved PAB‒induced RV dysfunction in rats. This pathway plays a major role in the progression of pressure overload‒induced RV dysfunction, and is potentially a novel therapeutic target for the disorder.

12.
Hypertens Res ; 41(11): 947-956, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30072732

RESUMO

It is not established whether central blood pressure (BP) evaluated by a radial pulse wave analysis is useful to predict cardiovascular prognoses. We tested the hypothesis that central BP predicts future cardiovascular events in treated hypertensive subjects. We conducted a multicenter, observational cohort study of 3566 hypertensives being treated with antihypertensive medications at 27 institutions in Japan. We performed the radial pulse wave analyses using applanation tonometry in all subjects. The primary outcome was the incidence of any of the following: stroke, myocardial infarction (MI), sudden cardiac death, and acute aortic dissection. The mean age of the subjects was 66.0 ± 10.9 years, and 50.6% were male. The mean brachial SBP and central SBP were 138 ± 18 mm Hg and 128 ± 19 mm Hg, respectively. When the central SBP was divided into quintiles, the number of events was least in the 2nd quintile, and we set it as the reference. In the Cox regression analysis adjusting for age, sex, body mass index, creatinine, diabetes, use of ß-blocker, and history of MI/stroke, the patients in the 3rd (hazard ratio (HR) 3.55, 95% confidence interval 1.29-9.78, p = 0.014), 4th (HR 4.12, 95% CI 1.53-11.10, p = 0.005), and 5th quintiles (HR 2.87, 95% CI 1.01-8.18, p = 0.048) had a significantly higher incidence of cardiovascular events compared to the 2nd quintile. The results were essentially unchanged when brachial DBP was additionally adjusted. In conclusion, in treated hypertensives, high central SBP was associated with worse cardiovascular outcomes.

13.
Circ Heart Fail ; 11(5): e004397, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29739745

RESUMO

BACKGROUND: Acute myocardial infarction remains a leading cause of chronic heart failure. Excessive myocardial oxygen demand relative to supply is the fundamental mechanism of myocardial infarction. We thus hypothesized that left ventricular (LV) mechanical unloading by the total support of transvascular LV assist device Impella could minimize oxygen demand, thereby reducing infarct size and preventing subsequent heart failure. METHODS AND RESULTS: In 20 dogs, we ligated the left anterior descending coronary artery for 180 minutes and then reperfused. We introduced Impella from 60 minutes after the onset of ischemia to 60 minutes after reperfusion. In the partial support group, Impella supported 50% of total cardiac output. In the total support group, systemic flow totally depends on Impella flow. Four weeks after ischemia/reperfusion (I/R), we compared LV function and infarct size among 4 groups: sham (no I/R), I/R (no Impella support), partial support, and total support. Compared with I/R, total support lowered LV end-diastolic pressure (15.0±3.5 versus 4.7±1.7 mm Hg; P<0.001), increased LV end-systolic elastance (4.3±0.8 versus 13.9±5.1 mm Hg/mL; P<0.001), and decreased NT-proBNP (N-terminal pro-B-type natriuretic peptide) level (4081±1123 versus 1773±390 pg/mL; P<0.05). Furthermore, total support markedly reduced infarct size relative to I/R, whereas partial support decreased infarct size to a lesser extent (I/R, 16.3±2.6; partial support, 8.5±4.3; and total support, 2.1±1.6%; P<0.001). CONCLUSIONS: LV mechanical unloading by the total support of Impella during the acute phase of myocardial infarction reduced infarct size and prevented subsequent heart failure in dogs.

14.
Artigo em Inglês | MEDLINE | ID: mdl-29736746

RESUMO

The oxygen supply-demand imbalance is the fundamental pathophysiology of myocardial infarction (MI). Reducing myocardial oxygen consumption (MVO2) in acute MI (AMI) reduces infarct size. Since left ventricular (LV) mechanical work and heart rate are major determinants of MVO2, we hypothesized that the combination of LV mechanical unloading and chronotropic unloading during AMI can reduce infarct size via synergistic suppression of MVO2. In a dog model of ischemia-reperfusion, as we predicted, the combination of mechanical unloading by Impella and bradycardic agent, ivabradine (IVA), synergistically reduced MVO2. This was translated into the striking reduction of infarct size with Impella + IVA administered 60 min after the onset of ischemia compared to no treatment (control) and Impella groups (control 56.3 ± 6.5, Impella 39.9 ± 7.4 and Impella + IVA 23.7 ± 10.6%, p < 0.001). In conclusion, Impella + IVA during AMI reduced infarct size via marked suppression of MVO2. The mechano-chronotropic unloading may serve as a powerful therapeutic option for AMI.

15.
PLoS One ; 13(1): e0190830, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29329321

RESUMO

BACKGROUND: Lipopolysaccharide (LPS) induces acute inflammation, activates sympathetic nerve activity (SNA) and alters hemodynamics. Since the arterial baroreflex is a negative feedback system to stabilize arterial pressure (AP), examining the arterial baroreflex function is a prerequisite to understanding complex hemodynamics under LPS challenge. We investigated the impact of LPS-induced acute inflammation on SNA and AP regulation by performing baroreflex open-loop analysis. METHODS: Ten anesthetized Sprague-Dawley rats were used. Acute inflammation was induced by an intravenous injection of LPS (60 µg/kg). We isolated the carotid sinuses from the systemic circulation and controlled carotid sinus pressure (CSP) by a servo-controlled piston pump. We matched CSP to AP to establish the baroreflex closed-loop condition, whereas we decoupled CSP from AP to establish the baroreflex open-loop condition and changed CSP stepwise to evaluate the baroreflex open-loop function. We recorded splanchnic SNA and hemodynamic parameters under baroreflex open- and closed-loop conditions at baseline and at 60 and 120 min after LPS injection. RESULTS: In the baroreflex closed-loop condition, SNA continued to increase after LPS injection, reaching three-fold the baseline value at 120 min (baseline: 94.7 ± 3.6 vs. 120 min: 283.9 ± 31.9 a.u.). In contrast, AP increased initially (until 75 min), then declined to the baseline level. In the baroreflex open-loop condition, LPS reset the neural arc (CSP-SNA relationship) upward to higher SNA, while shifted the peripheral arc (SNA-AP relationship) downward at 120 min after the injection. As a result, the operating point determined by the intersection between function curves of neural arc and peripheral arc showed marked sympatho-excitation without substantial changes in AP. CONCLUSIONS: LPS-induced acute inflammation markedly increased SNA via resetting of the baroreflex neural arc, and suppressed the peripheral arc. The balance between the augmented neural arc and suppressed peripheral arc determines SNA and hemodynamics in LPS-induced acute inflammation.


Assuntos
Barorreflexo , Pressão Sanguínea/fisiologia , Inflamação/induzido quimicamente , Lipopolissacarídeos/toxicidade , Animais , Masculino , Ratos , Ratos Sprague-Dawley
16.
J Physiol Sci ; 68(2): 203, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29164388

RESUMO

The article Physiological insights of recent clinical diagnostic and therapeutic technologies for cardiovascular diseases, written by Kenji Shigemi, Soichiro Fuke, Dai Une, Keita Saku, Shuji Shimizu, Toru Kawada, Toshiaki Shishido, Kenji Sunagawa and Masaru Sugimachi, was originally published Online First without open access.

17.
Physiol Rep ; 5(23)2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29208691

RESUMO

It is widely accepted that impaired bioavailability of endothelial nitric oxide (NO) plays a critical role in the pathophysiology of pulmonary arterial hypertension (PAH). However, there are published data that show that relatively many PAH patients respond favorably to acetylcholine-induced pulmonary vasodilation during their follow-up period, when diverse stages of the disorder are included. We hypothesized that NO bioavailability varies depending on the progression of PAH Adult rats were exposed to the VEGF receptor blocker Sugen5416 and 3 weeks of hypoxia followed by return to normoxia for various additional weeks. All rats developed increased right ventricular systolic pressure (RVSP) and occlusive lesion formation at 1, 3, 5, and 8 weeks after the Sugen5416 injection. Acute NO synthase blockade did not change the elevated RVSP at the 1-week time point, while it further increased RVSP markedly at the 3-, 5-, and 8-week time points, leading to death in all rats tested at 8 weeks. Acetylcholine caused significant reduction in RVSP at the 8-week but not the 1-week time point, whereas sodium nitroprusside decreased the pressure similarly at both time points. Increased NO-mediated cGMP production was found in lungs from the 8-week but not the 1-week time point. In conclusion, despite its initial impairment, NO bioavailability is restored and endogenous NO plays a critical protective role by counteracting severe pulmonary vasoconstriction in established stages of PAH in the Sugen5416/hypoxia/normoxia-exposed rats. Our results provide solid pharmacological evidence for a major contribution of a NO-suppressed vasoconstrictor component in the pathophysiology of established PAH.


Assuntos
Hipertensão Pulmonar/metabolismo , Óxido Nítrico Sintase/metabolismo , Vasoconstrição , Acetilcolina/farmacologia , Animais , Pressão Sanguínea , GMP Cíclico/metabolismo , Hipertensão Pulmonar/fisiopatologia , Indóis/farmacologia , Pulmão/metabolismo , Masculino , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Artéria Pulmonar/efeitos dos fármacos , Artéria Pulmonar/metabolismo , Artéria Pulmonar/fisiopatologia , Pirróis/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Fatores de Crescimento do Endotélio Vascular/antagonistas & inibidores
18.
Conf Proc IEEE Eng Med Biol Soc ; 2017: 4321-4324, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-29060853

RESUMO

Numerous studies have shown in animal models that vagal nerve stimulation (VNS) strikingly reduces infarct size of acute myocardial infarction (AMI) and prevents heart failure. However, the lack of techniques to noninvasively stimulate the vagal nerve hinders VNS from clinical applications. Transcranial magnetic stimulation is noninvasive and capable of stimulating central neurons in patients. In this study, we examined whether the magnetic stimulation could noninvasively activate the cervical vagal nerve in healthy human. Sixteen healthy males and 4 females were enrolled in this study. We used Magstim Rapid2 with a 70-mm double coil in the right neck. We randomly assigned the subjects to 5 Hz or 20 Hz stimulation. We defined the maximum intensity of stimulation (MAX) which is the intensity just below the threshold of adverse effects. We defined HALF as a half of MAX. Protocols comprised 2 sets of MAX and 2 sets of HALF. Each stimulation continued for 3 minutes. We monitored heart rate (HR) and assessed the bradycardic response as an index of successful VNS. Nineteen subjects completed all protocols. They had no problematic adverse events during and/or after magnetic VNS. The magnetic VNS induced transient bradycardic responses in some subjects, whereas failed to induce sustained bradycardia in pooled data in any settings. Arterial pressure did not change either. Successful magnetic stimulation requires technical improvements including narrowing the magnetic focus and optimization of stimulation site. These improvements may enable us to apply magnetic VNS in the management of AMI.


Assuntos
Estimulação do Nervo Vago , Feminino , Insuficiência Cardíaca , Frequência Cardíaca , Humanos , Masculino , Infarto do Miocárdio , Nervo Vago
19.
Physiol Rep ; 5(17)2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28899913

RESUMO

Central chemoreflex activation induces sympatho-excitation. However, how central chemoreflex interacts with baroreflex function remains unknown. This study aimed to examine the impact of central chemoreflex on the dynamic as well as static baroreflex functions under open-loop conditions. In 15 anesthetized, vagotomized Sprague-Dawley rats, we isolated bilateral carotid sinuses and controlled intra-sinus pressure (CSP). We then recorded sympathetic nerve activity (SNA) at the celiac ganglia, and activated central chemoreflex by a gas mixture containing various concentrations of CO2 Under the baroreflex open-loop condition (CSP = 100 mmHg), central chemoreflex activation linearly increased SNA and arterial pressure (AP). To examine the static baroreflex function, we increased CSP stepwise from 60 to 170 mmHg and measured steady-state SNA responses to CSP (mechanoneural arc), and AP responses to SNA (neuromechanical arc). Central chemoreflex activation by inhaling 3% CO2 significantly increased SNA irrespective of CSP, indicating resetting of the mechanoneural arc, but did not change the neuromechanical arc. As a result, central chemoreflex activation did not change baroreflex maximum total loop gain significantly (-1.29 ± 0.27 vs. -1.68 ± 0.74, N.S.). To examine the dynamic baroreflex function, we randomly perturbed CSP and estimated transfer functions from 0.01 to 1.0 Hz. The transfer function of the mechanoneural arc approximated a high-pass filter, while those of the neuromechanical arc and total (CSP-AP relationship) arcs approximated a low-pass filter. In conclusion, central chemoreflex activation did not alter the transfer function of the mechanoneural, neuromechanical, or total arcs. Central chemoreflex modifies hemodynamics via sympatho-excitation without compromising dynamic or static baroreflex AP buffering function.


Assuntos
Barorreflexo , Dióxido de Carbono/sangue , Seio Carotídeo/fisiologia , Sistema Nervoso Simpático/fisiologia , Animais , Pressão Sanguínea , Seio Carotídeo/inervação , Células Quimiorreceptoras/fisiologia , Masculino , Ratos , Ratos Sprague-Dawley
20.
Circ J ; 82(1): 148-158, 2017 12 25.
Artigo em Inglês | MEDLINE | ID: mdl-28824029

RESUMO

BACKGROUND: The mineralocorticoid receptor antagonist eplerenone improved clinical outcomes among patients with heart failure with reduced ejection faction (HFrEF) in the EMPHASIS-HF (Eplerenone in Mild Patients Hospitalization And SurvIval Study in Heart Failure) study. However, similar efficacy and safety have not been established in Japanese patients. We evaluated the efficacy and safety of eplerenone in patients with HFrEF in a multicenter, randomized, double-blind placebo-controlled outcome study (ClinicalTrials.gov Identifier: NCT01115855). The aim of the study was to evaluate efficacy predefined as consistency of the primary endpoint with that of EMPHASIS-HF at a point estimate of <1 for the hazard ratio.Methods and Results:HFrEF patients with NYHA functional class II-IV and an EF ≤35% received eplerenone (n=111) or placebo (n=110) on top of standard therapy for at least 12 months. The primary endpoint was a composite of death from cardiovascular causes or hospitalization for HF. The primary endpoint occurred in 29.7% of patients in the eplerenone group vs. 32.7% in the placebo group [hazard ratio=0.85 (95% CI: 0.53-1.36)]. Hospitalization for any cause and changes in plasma BNP and LVEF were favorable with eplerenone. A total of 17 patients (15.3%) in the eplerenone group and 10 patients (9.1%) in the placebo group died. Adverse events, including hyperkalemia, were similar between the groups. CONCLUSIONS: Eplerenone was well-tolerated in Japanese patients with HFrEF and showed results consistent with those reported in the EMPHASIS-HF study.

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