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Lin C, Mazzuca MQ, Khalil RA. Increased uterine arterial tone, stiffness and remodeling with augmented matrix metalloproteinase-1 and -7 in uteroplacental ischemia-induced hypertensive pregnancy. Biochem Pharmacol 2024:116227. [PMID: 38643908 DOI: 10.1016/j.bcp.2024.116227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 03/29/2024] [Accepted: 04/18/2024] [Indexed: 04/23/2024]
Abstract
Preeclampsia is a pregnancy-related disorder manifested as hypertensive pregnancy (HTN-Preg) and often fetal growth restriction (FGR), but the mechanisms involved are unclear. We have reported enhanced reactivity of systemic vessels in HTN-Preg rats, but the critical changes in the uterine circulation are less clear. We tested whether HTN-Preg involves localized aberrations in uterine arterial tone, stiffness and remodeling by matrix metalloproteinases (MMPs). Blood pressure (BP) and litter size were recorded in normal pregnant (Preg) rats and Preg rats with reduced uteroplacental perfusion pressure (RUPP). Isolated uterine arteries were placed in a pressure myograph for measuring intrinsic and extrinsic tone and arterial stiffness. Arteries were bathed in normal Krebs solution (2.5 mM Ca2+), Ca2+-free (2 mM EGTA) Krebs, treated with sodium nitroprusside (SNP), or endothelium denuded, then pressurized at 10 mmHg steps from 10 to 110 mmHg, and the % change in diameter was analyzed to measure total (active + passive), active Ca2+-dependent myogenic, passive, and endothelium-dependent tone, respectively. BP was higher and the litter size and pup weight were reduced in RUPP vs Preg rats. In normal Krebs, increasing intraluminal pressure caused smaller increments in diameter in arteries of RUPP vs Preg rats, suggesting greater total vascular tone. Arterial incubation in Ca2+-free Krebs, treatment with SNP or endothelium-removal abolished the differences in vascular tone, and subtraction of each of these components from total vascular tone revealed significant active Ca2+-dependent myogenic, passive, and endothelium-dependent tone, respectively, in RUPP vs Preg rats. The total and passive strain-stress curves were shifted leftward in arteries of RUPP vs Preg rats, indicating increased uterine arterial stiffness. Arterial sections showed decreased lumen/total and increased wall/total area, and immunohistochemistry revealed greater MMP-1 and MMP-7 staining particularly in the media, suggesting uterine arterial remodeling by MMPs in RUPP vs Preg rats. The increased uterine arterial active myogenic, passive, and endothelium-dependent tone, arterial stiffness and remodeling by MMPs would further reduce uterine blood flow and exacerbate uteroplacental ischemia, FGR and HTN-Preg.
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Affiliation(s)
- Chen Lin
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA, United States
| | - Marc Q Mazzuca
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA, United States
| | - Raouf A Khalil
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA, United States.
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Mazzuca MQ, Buyukcelebi K, Lin C, Khalil RA. Increased Ca 2+-dependent intrinsic tone and arterial stiffness in mesenteric microvessels of hypertensive pregnant rats. Biochem Pharmacol 2023; 208:115353. [PMID: 36435203 PMCID: PMC9877182 DOI: 10.1016/j.bcp.2022.115353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/17/2022] [Accepted: 11/18/2022] [Indexed: 11/26/2022]
Abstract
Preeclampsia is a pregnancy-related hypertensive disorder (HTN-Preg) with unclear mechanisms. We have shown increased vascular reactivity to extrinsic vasoconstrictors in HTN-Preg rats. Here, we test whether microvascular intrinsic tone and arterial stiffness could contribute to HTN-Preg, and examined the underlying cellular mechanisms. On gestational day 19, BP was recorded in normal pregnant (Preg) rats and Preg rats with reduced uterine perfusion pressure (RUPP), and mesenteric microvessels were mounted on a pressure myograph for measurement of intrinsic tone, simultaneous changes in [Ca2+]i (fura-2 340/380 ratio), and arterial stiffness. Arteries were incubated in Ca2+-containing and 0 Ca2+ (2 mM EGTA) Krebs, pressurized at 10 to 110 mmHg in 10 mmHg increments, and the % change in vessel diameter from initial diameter at 10 mmHg was analyzed for measurement of total (active + passive) intrinsic tone and passive intrinsic response, respectively. The passive response was then subtracted from the total intrinsic tone to determine the active myogenic tone. The strain-stress relationship was also constructed as a measure of arterial stiffness. BP was higher in RUPP vs Preg rats. In Ca2+-containing Krebs, increases in intraluminal pressure caused smaller increases in diameter and greater increases in [Ca2+]i in microvessels of RUPP vs Preg rats, suggesting increased Ca2+-dependent myogenic tone. In 0 Ca2+ Krebs, increases in pressure also caused less increases in diameter in microvessels of RUPP vs Preg rats, but with no changes in [Ca2+]i, suggesting changes in the structure and mechanics of the arterial wall. The total and passive strain-stress relationship was shifted to the left in microvessels of RUPP vs Preg rats, suggesting increased arterial wall stiffness. Histology and immunohistochemistry showed greater vascular wall thickness and collagen-I staining in RUPP vs Preg rats, supporting changes in the wall architecture and structural proteins. The increased active myogenic tone and underlying increases in Ca2+ signaling as well as the increased passive intrinsic response, arterial stiffness and collagen-I in the mesenteric microvessels could play a role in the regulation of blood flow to the splanchnic region and the increased vascular resistance and BP in HTN-Preg.
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Affiliation(s)
- Marc Q Mazzuca
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA, United States
| | - Kadir Buyukcelebi
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA, United States
| | - Chen Lin
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA, United States
| | - Raouf A Khalil
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA, United States.
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Denton KM. "The more I learn, the more I realize how much I don't know." - The role of the renal nerves in hypertension. Hypertension 2019; 74:743-744. [PMID: 31401876 DOI: 10.1161/hypertensionaha.119.13561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Kate M Denton
- From the Cardiovascular Disease Program, Monash Biomedicine Discovery Institute, Monash University, Wellington Road, Clayton, Victoria, Australia
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Walton SL, Tjongue M, Tare M, Kwok E, Probyn M, Parkington HC, Bertram JF, Moritz KM, Denton KM. Chronic low alcohol intake during pregnancy programs sex-specific cardiovascular deficits in rats. Biol Sex Differ 2019; 10:21. [PMID: 31010438 PMCID: PMC6477739 DOI: 10.1186/s13293-019-0235-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Accepted: 04/02/2019] [Indexed: 02/08/2023] Open
Abstract
Background Exposure to an adverse environment in early life can have lifelong consequences for risk of cardiovascular disease. Maternal alcohol (ethanol) intake is common and associated with a variety of harmful effects to the fetus. However, examining the effects on the cardiovascular system in adult offspring has largely been neglected. The objectives of this study were to investigate the influence of chronic, low ethanol consumption throughout pregnancy on blood pressure, vascular reactivity and wall stiffness, all key determinants of cardiovascular health, in both male and female rat offspring. Methods Female Sprague-Dawley rats were fed an ad libitum liquid diet ± 6% vol/vol ethanol throughout pregnancy. Male and female offspring were studied at 12 months of age. Arterial pressure, heart rate and locomotor activity were measured over 7 days via radiotelemetry. Renal lobar arteries were isolated and studied using wire and pressure myography. Results Basal mean arterial pressure in female ethanol-exposed rats was reduced by ~ 5–6 mmHg compared to control female offspring, whereas arterial pressure was unaffected in male offspring. Ethanol-exposed offspring had an attenuated pressor response to an acute restraint stress, with this effect most evident in females. Renal artery function was not affected by prenatal ethanol exposure. Conclusions We show for the first time that low level chronic maternal alcohol intake during pregnancy influences arterial pressure in adult offspring in the absence of fetal growth restriction. Electronic supplementary material The online version of this article (10.1186/s13293-019-0235-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sarah L Walton
- Cardiovascular Disease Program, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia.,Department of Physiology, Monash University, Clayton, VIC, Australia
| | - Melissa Tjongue
- Cardiovascular Disease Program, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia.,Department of Physiology, Monash University, Clayton, VIC, Australia
| | - Marianne Tare
- Department of Physiology, Monash University, Clayton, VIC, Australia.,Monash Rural Health, Churchill, VIC, Australia
| | - Edmund Kwok
- Cardiovascular Disease Program, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia.,Department of Physiology, Monash University, Clayton, VIC, Australia
| | - Megan Probyn
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
| | | | - John F Bertram
- Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.,Kidney Developmental Programming and Disease Laboratory, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia
| | - Karen M Moritz
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia.,Child Health Research Centre, The University of Queensland, St Lucia, QLD, Australia
| | - Kate M Denton
- Cardiovascular Disease Program, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia. .,Department of Physiology, Monash University, Clayton, VIC, Australia.
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Khammy MM, Angus JA, Wright CE. Vascular reactivity of rabbit isolated renal and femoral resistance arteries in renal wrap hypertension. Eur J Pharmacol 2016; 773:32-41. [PMID: 26806799 DOI: 10.1016/j.ejphar.2016.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 12/22/2015] [Accepted: 01/21/2016] [Indexed: 11/24/2022]
Abstract
In rabbits with cellophane renal wrap hypertension, hindquarter and total vascular resistance changes to pressor and depressor agents are amplified compared to those of normotensive rabbits. The aim of the present study was to evaluate the in vitro pharmacodynamics of hypertensive and normotensive rabbit small artery segments isolated from the renal and hindquarter vascular beds. Using wire myography, the full range (Emax) and sensitivity (EC50) to a range of agonists of segments of renal interlobar (≈ 600 µm i.d.), renal arcuate (≈ 250 µm i.d.) and deep femoral branch (≈ 250 µm i.d.) arteries were assessed under normalised conditions of passive tension. Interlobar arteries from hypertensive rabbits were more sensitive (EC50) than those from normotensive rabbits to noradrenaline (6-fold), methoxamine (3-fold) and angiotensin II (3-fold). Arcuate artery reactivity was largely unaffected by hypertension. Deep femoral arteries from hypertensive rabbits had enhanced sensitivity only to noradrenaline (2-fold) and methoxamine (4-fold). Sensitivity to relaxation by acetylcholine was unaffected by hypertension in all arteries. Deep femoral arteries from hypertensive rabbits were more sensitive to sodium nitroprusside than normotensive counterparts. Adenosine caused little relaxation in renal arteries, but full relaxation in deep femoral arteries, unaltered by hypertension. This study found substantial heterogeneity in the pharmacodynamic profile of vessels isolated from different vascular beds and between arterial segments within the kidney. These profiles were differentially affected by hypertension suggesting that hypertension per se is not a resultant of general vascular dysfunction.
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Affiliation(s)
- Makhala M Khammy
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Victoria 3010, Australia.
| | - James A Angus
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Victoria 3010, Australia.
| | - Christine E Wright
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Victoria 3010, Australia.
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6
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Burke SL, Lukoshkova EV, Head GA. Characteristics of renal sympathetic nerve single units in rabbits with angiotensin-induced hypertension. Exp Physiol 2015; 101:50-66. [PMID: 26467849 DOI: 10.1113/ep085472] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 10/06/2015] [Indexed: 11/08/2022]
Abstract
We examined the effect of chronic angiotensin (Ang II)-induced hypertension on activity of postganglionic renal sympathetic units to determine whether altered whole renal nerve activity is due to recruitment or changes in firing frequency. Rabbits were treated with a low (20 ng kg(-1) min(-1), 8 weeks) or high dose (50 ng kg(-1) min(-1), 4 weeks) of Ang II before the experiment under chloralose-urethane anaesthesia. Spontaneously active units were detected from multiunit recordings using an algorithm that separated units by action potential shape using templates that matched spikes within a prescribed standard deviation. Multiunit sympathetic nerve activity was 40% higher in rabbits treated with low-dose Ang II than in sham (P = 0.012) but not different in high-dose Ang II. Resting firing frequency was similar in sham rabbits (1.00 ± 0.09 spikes s(-1), n = 144) and in those treated with high-dose Ang II (1.10 ± 0.08 spikes s(-1), n = 112) but was lower with low-dose Ang II (0.65 ± 0.08 spikes s(-1), n = 149, P < 0.05). Unit firing rhythmicity was linked to the cardiac cycle and was similar in sham and low-dose Ang II groups but 29-32% lower in rabbits treated with high-dose Ang II (P < 0.001). Cardiac linkage followed a similar pattern during hypoxia. All units showed baroreceptor dependency. Baroreflex gain and range were reduced and curves shifted to the right in Ang II groups. Firing frequency during hypoxia increased by +39% in low-dose Ang II and +82% in shams, but the greatest increase was in the high-dose Ang II group (+103%, P(dose) = 0.001). Responses to hypercapnia were similar in all groups. Increases in sympathetic outflow in hypertension caused by low-dose chronic Ang II administration are due to recruitment of neurons, but high-dose Ang II increases firing frequency in response to chemoreceptor stimuli independently of the arterial baroreceptors.
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Affiliation(s)
- Sandra L Burke
- Neuropharmacology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Elena V Lukoshkova
- Department of Cardiovascular Regulation, Russian Cardiology Research Centre, Moscow, Russia
| | - Geoffrey A Head
- Neuropharmacology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia.,Department of Pharmacology, Monash University, Clayton, Victoria, Australia
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Zhao D, Liu Q, Ji Y, Wang G, He X, Tian W, Xu H, Lei T, Wang Y. Effect of 18β-glycyrrhetinic acid on cerebral vasospasm caused by asymmetric dimethylarginine after experimental subarachnoid hemorrhage in rats. Neurol Res 2014; 37:476-83. [DOI: 10.1179/1743132814y.0000000462] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Lankadeva YR, Singh RR, Moritz KM, Parkington HC, Denton KM, Tare M. Renal dysfunction is associated with a reduced contribution of nitric oxide and enhanced vasoconstriction after a congenital renal mass reduction in sheep. Circulation 2014; 131:280-8. [PMID: 25369804 DOI: 10.1161/circulationaha.114.013930] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
BACKGROUND Children born with reduced congenital renal mass have an increased risk of hypertension and chronic kidney disease in adulthood, although the mechanisms are poorly understood. Similar sequelae occur after fetal uninephrectomy (uni-x) in sheep, leading to a 30% nephron deficit. We hypothesized that renal dysfunction is underpinned by a reduced contribution of nitric oxide (NO) and vascular dysfunction in uni-x sheep. METHODS AND RESULTS In 5-year-old female uni-x and sham sheep, mean arterial pressure, glomerular filtration rate, and renal blood flow were measured before and during NO inhibition (N(ω)-nitro-l-arginine methyl ester [L-NAME]). Reactivity was assessed in resistance arteries, including renal lobar and arcuate arteries. Basal mean arterial pressure was 15 mm Hg higher and glomerular filtration rate and renal blood flow were ≈30% lower (P<0.001) in uni-x animals. L-NAME increased mean arterial pressure by ≈17 mm Hg in both groups, whereas glomerular filtration rate and renal blood flow were decreased less in uni-x sheep (PInteraction<0.01). Endothelial NO synthase and Ser-1177-phosphorylated endothelial NO synthase protein levels were upregulated in renal cortex of uni-x sheep (P<0.05). Lobar arteries of uni-x sheep had enhanced responsiveness to phenylephrine and nitrotyrosine staining and reduced sensitivity to endothelial stimulation. Vasodilator prostanoid contribution to endothelium-dependent relaxation was reduced in lobar arteries of uni-x sheep, accompanied by reduced cyclooxygenase-1 and -2 gene expression (P<0.05). Neurovascular constriction was enhanced ≈1.5-fold in renal arteries of uni-x sheep (P<0.05). CONCLUSIONS Renal dysfunction after congenital renal mass reduction is associated with impaired regulation of renal hemodynamics by NO. Reductions in renal blood flow and glomerular filtration rate are underpinned by impaired basal NO contribution, endothelial dysfunction, and enhanced vascular responsiveness to sympathetic nerve stimulation.
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Affiliation(s)
- Yugeesh R Lankadeva
- From the Department of Physiology (Y.R.L., R.R.S., H.C.P., K.M.D., M.T.) and Department of Anatomy and Developmental Biology (R.R.S.), Monash University, Victoria, Australia; and School of Biomedical Sciences, University of Queensland, St. Lucia, Australia (R.R.S., K.M.M.)
| | - Reetu R Singh
- From the Department of Physiology (Y.R.L., R.R.S., H.C.P., K.M.D., M.T.) and Department of Anatomy and Developmental Biology (R.R.S.), Monash University, Victoria, Australia; and School of Biomedical Sciences, University of Queensland, St. Lucia, Australia (R.R.S., K.M.M.)
| | - Karen M Moritz
- From the Department of Physiology (Y.R.L., R.R.S., H.C.P., K.M.D., M.T.) and Department of Anatomy and Developmental Biology (R.R.S.), Monash University, Victoria, Australia; and School of Biomedical Sciences, University of Queensland, St. Lucia, Australia (R.R.S., K.M.M.)
| | - Helena C Parkington
- From the Department of Physiology (Y.R.L., R.R.S., H.C.P., K.M.D., M.T.) and Department of Anatomy and Developmental Biology (R.R.S.), Monash University, Victoria, Australia; and School of Biomedical Sciences, University of Queensland, St. Lucia, Australia (R.R.S., K.M.M.)
| | - Kate M Denton
- From the Department of Physiology (Y.R.L., R.R.S., H.C.P., K.M.D., M.T.) and Department of Anatomy and Developmental Biology (R.R.S.), Monash University, Victoria, Australia; and School of Biomedical Sciences, University of Queensland, St. Lucia, Australia (R.R.S., K.M.M.)
| | - Marianne Tare
- From the Department of Physiology (Y.R.L., R.R.S., H.C.P., K.M.D., M.T.) and Department of Anatomy and Developmental Biology (R.R.S.), Monash University, Victoria, Australia; and School of Biomedical Sciences, University of Queensland, St. Lucia, Australia (R.R.S., K.M.M.).
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Bohlender J, Nussberger J, Imboden H. Angiotensinergic innervation of the kidney: present knowledge and its significance. Curr Hypertens Rep 2012. [PMID: 23197298 DOI: 10.1007/s11906-012-0322-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intrarenal neurotransmission implies the co-release of neuropeptides at the neuro-effector junction with direct influence on parameters of kidney function. The presence of an angiotensin (Ang) II-containing phenotype in catecholaminergic postganglionic and sensory fibers of the kidney, based on immunocytological investigations, has only recently been reported. These angiotensinergic fibers display a distinct morphology and intrarenal distribution, suggesting anatomical and functional subspecialization linked to neuronal Ang II-expression. This review discusses the present knowledge concerning these fibers, and their significance for renal physiology and the pathogenesis of hypertension in light of established mechanisms. The data suggest a new role of Ang II as a co-transmitter stimulating renal target cells or modulating nerve traffic from or to the kidney. Neuronal Ang II is likely to be an independent source of intrarenal Ang II. Further physiological experimentation will have to explore the role of the angiotensinergic renal innervation and integrate it into existing concepts.
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Affiliation(s)
- Jürgen Bohlender
- Hôpital fribourgeois/CHUV and Institute of Cell Biology, University of Bern, Case postale, Fribourg, Switzerland.
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Tare M, Emmett SJ, Coleman HA, Skordilis C, Eyles DW, Morley R, Parkington HC. Vitamin D insufficiency is associated with impaired vascular endothelial and smooth muscle function and hypertension in young rats. J Physiol 2011; 589:4777-86. [PMID: 21807617 DOI: 10.1113/jphysiol.2011.214726] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Increasing evidence links vitamin D deficiency and cardiovascular dysfunction in human adults. There is a worldwide increase in the prevalence of vitamin D deficiency in women of reproductive age, particularly dark-skinned and/or veiled women and their infants. We used a rat model to determine the functional impact of vitamin D deficiency during intra uterine and early life on resistance artery reactivity and blood pressure in the offspring as young adults. Rat dams were maintained on vitamin D deficient or replete chow before and during pregnancy and lactation. The offspring were maintained on the same chow until studied at 7-8 weeks of age. Conscious blood pressure was measured. Endothelial and smooth muscle function were tested in mesenteric arteries on a pressure myograph. Vitamin D deficient male and female offspring had a 10-fold lower serum 25-hydroxyvitamin D (P < 0.0001) and markedly elevated blood pressures (11-20 mmHg, P < 0.001) and heart rates (21-40 beats min(-1), P < 0.02) than control fed offspring. Serum calcium was unchanged. Mesenteric artery myogenic tone was doubled in vitamin D deficiency. Endothelium-derived nitric oxide-evoked dilation was halved in arteries from vitamin D deficient males and dioestrous females. Dilation attributed to endothelium-derived hyperpolarizing factor was all but abolished in vitamin D deficient oestrous females. Nitroprusside-evoked dilation was unaltered in arteries from males, but was markedly reduced in vessels of vitamin D deplete females. In conclusion, early life vitamin D deficiency is associated with endothelial vasodilator dysfunction, and this is likely to contribute to the accompanying elevation in blood pressure and an increased cardiovascular disease risk.
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Affiliation(s)
- Marianne Tare
- Department of Physiology, Monash University, Victoria 3800, Australia
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11
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Haddock RE, Hill CE. Sympathetic overdrive in obesity involves purinergic hyperactivity in the resistance vasculature. J Physiol 2011; 589:3289-307. [PMID: 21576274 DOI: 10.1113/jphysiol.2011.207944] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
While a close correlation exists in obese humans between sympathetic, adrenergic hyperactivity and structural and functional organ damage, a role for the co-transmitter, ATP, in vascular function remains unexplored. We therefore studied sympathetic nerve-mediated responses of pressurised small mesenteric arteries from control and obese rats. Diet-induced obesity significantly increased the amplitude of vasoconstriction to transmural nerve stimulation (1-10 Hz; P <0.05). At 1 and 5 Hz, both adrenergic and purinergic responses were significantly augmented, while only the purinergic component was increased at 10 Hz (P <0.05). Nerve stimulation at 1 Hz evoked contractions and underlying excitatory junction potentials (EJPs), which were both significantly increased in amplitude during obesity (P <0.05) and abolished by αβ-methylene ATP (1 μM; desensitises purinergic receptors). The rise time and rate of decay of these EJPs were significant decreased (P <0.05), without change in resting membrane potential. Amplitude and frequency of spontaneous EJPs and the density of perivascular sympathetic nerves were also significantly increased (P <0.05). Inhibition of sensory neurotransmitter release (capsaicin; 10 μM) significantly increased the amplitude of nerve-mediated contraction (P <0.05), with a greater effect in control than obese animals, although the density of sensory nerves was unaffected by obesity. We demonstrate that sympathetic nerve-mediated vasoconstriction is enhanced by diet-induced obesity due to upregulation of purinergic, in addition to adrenergic, neurotransmission. Changes result from increased perivascular sympathetic innervation and release of ATP. We conclude that augmented sympathetic control of vasoconstriction induced by obesity could contribute directly to hypertension and global organ damage. A decrease in sensitivity to sensory vasodilatory neurotransmitters may also affect these processes.
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Affiliation(s)
- Rebecca E Haddock
- Department of Neuroscience, John Curtin School of Medical Research, Australian National University, GPO Box 334, Canberra, ACT, 0200, Australia.
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12
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Yu H, Guo Y, Mi L, Wang X, Li L, Gao W. Mitofusin 2 inhibits angiotensin II-induced myocardial hypertrophy. J Cardiovasc Pharmacol Ther 2010; 16:205-11. [PMID: 21106870 DOI: 10.1177/1074248410385683] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND OBJECTIVES Myocardial hypertrophy is a common clinical finding leading to heart failure and sudden death. Mitofusin 2 (Mfn2), a hyperplasia suppressor protein, is downregulated in hypertrophic heart. This study examined the role of Mfn2 in myocardial hypertrophy and its potential signal pathway. METHODS AND RESULTS In in vitro studies, neonatal cardiac myocytes were isolated and cultured. Incubation of cultured cardiomycytes with angiotensin II (Ang II) inhibited gene expression of Mfn2; induced cell hypertrophy and protein synthesis; and activated protein kinase Akt. Pretreatment of cells with AdMfn2-a replication-deficient adenoviral vector encoding rat Mfn2 gene-upregulated Mfn2 expression and subsequently attenuated Ang II-induced cell hypertrophy; protein synthesis; and Akt activation. In in vivo studies, direct gene delivery of AdMfn2 into myocardium decreased the infusion of Ang II-induced atrial natriuretic factor (ANF, a hypertrophic marker) expression and cardiomyocyte cross-sectional area. Consistently, upregulation of Mfn2 in myocardium decreased the thicknesses of anterior and posterior walls of left ventricle (LV) and the ratio of LV mass/body weight in Ang II-treated rats. Of note, AdGFP (control for AdMfn2) did not affect the effects of Ang II in vitro or in vivo. CONCLUSIONS Upregulation of Mfn2 inhibits Ang II-induced myocardial hypertrophy. In this process, inhibition of Akt activation seems to play a significant role. These findings indicate Mfn2 is a critical protein in modulating myocyte hypertrophy.
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Affiliation(s)
- Haiyi Yu
- Department of Cardiology, Peking University Third Hospital and Key Laboratory of Molecular Cardiovascular Sciences Ministry of Education, Beijing, PR China
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Evans RG, Burke SL, Lambert GW, Head GA. Renal responses to acute reflex activation of renal sympathetic nerve activity and renal denervation in secondary hypertension. Am J Physiol Regul Integr Comp Physiol 2007; 293:R1247-56. [PMID: 17626124 DOI: 10.1152/ajpregu.00217.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested whether the responsiveness of the kidney to basal renal sympathetic nerve activity (RSNA) or hypoxia-induced reflex increases in RSNA, is enhanced in angiotensin-dependent hypertension in rabbits. Mean arterial pressure, measured in conscious rabbits, was similarly increased (+16 ± 3 mmHg) 4 wk after clipping the left ( n = 6) or right ( n = 5) renal artery or commencing a subcutaneous ANG II infusion ( n = 9) but was not increased after sham surgery ( n = 10). Under pentobarbital sodium anesthesia, reflex increases in RSNA (51 ± 7%) and whole body norepinephrine spillover (90 ± 17%), and the reductions in glomerular filtration rate (−27 ± 5%), urine flow (−43 ± 7%), sodium excretion (−40 ± 7%), and renal cortical perfusion (−7 ± 3%) produced by hypoxia were similar in normotensive and hypertensive groups. Hypoxia-induced increases in renal norepinephrine spillover tended to be less in hypertensive (1.1 ± 0.5 ng/min) than normotensive (3.7 ± 1.2 ng/min) rabbits, but basal overflow of endogenous and exogenous dihydroxyphenolglycol was greater. Renal plasma renin activity (PRA) overflow increased less in hypertensive (22 ± 29 ng/min) than normotensive rabbits (253 ± 88 ng/min) during hypoxia. Acute renal denervation did not alter renal hemodynamics or excretory function but reduced renal PRA overflow. Renal vascular and excretory responses to reflex increases in RSNA induced by hypoxia are relatively normal in angiotensin-dependent hypertension, possibly due to the combined effects of reduced neural norepinephrine release and increased postjunctional reactivity. In contrast, neurally mediated renin release is attenuated. These findings do not support the hypothesis that enhanced neural control of renal function contributes to maintenance of hypertension associated with activation of the renin-angiotensin system.
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Affiliation(s)
- Roger G Evans
- Department of Physiology, Monash University, Victoria 3800, Australia.
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Rummery NM, Brock JA, Pakdeechote P, Ralevic V, Dunn WR. ATP is the predominant sympathetic neurotransmitter in rat mesenteric arteries at high pressure. J Physiol 2007; 582:745-54. [PMID: 17510179 PMCID: PMC2075333 DOI: 10.1113/jphysiol.2007.134825] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Most studies of neurovascular transmission in isolated small mesenteric arteries have used either isometric recording techniques or measured vasoconstriction in vessels with no distending pressure. Here we have used pressure myography to assess the contribution of noradrenaline and ATP to sympathetic neurotransmission in rat second-order mesenteric arteries. In arteries pressurized to 30 or 90 mmHg, activation of sympathetic axons with trains of electrical stimuli (50 pulses, 0.5-10 Hz) evoked frequency-dependent vasoconstrictions that increased in amplitude at higher pressure. In the presence of the P2-receptor antagonist suramin (0.1 mM), the amplitude of vasoconstrictions to trains at 2 and 10 Hz did not differ at 30 and 90 mmHg. In contrast, in the presence of the alpha(1)-adrenoceptor antagonist prazosin (0.1 microm) vasoconstrictions at 90 mmHg were larger than those at 30 mmHg. At both pressures, the combination of prazosin and suramin virtually abolished constrictions. The purinergic component of vasoconstriction (prazosin-resistant) was almost abolished by the L-type Ca(2+) channel antagonist nifedipine (1 microm). Increasing pressure from 30 to 90 mmHg decreased the resting membrane potential and increased the amplitude of purinergic excitatory junction potentials. These findings indicate that the contribution of ATP to neurovascular transmission increases when the pressure is raised from 30 to 90 mmHg, which is similar to the pressure second-order mesenteric arteries experience in vivo, and that Ca(2+) influx through L-type Ca(2+) channels is largely responsible for purinergic activation of the vascular smooth muscle.
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Affiliation(s)
- Nicole M Rummery
- School of Biomedical Sciences, University of Nottingham, Nottingham NG7 2UH, UK
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Burke SL, Head GA, Lambert GW, Evans RG. Renal Sympathetic Neuroeffector Function in Renovascular and Angiotensin II–Dependent Hypertension in Rabbits. Hypertension 2007; 49:932-8. [PMID: 17309940 DOI: 10.1161/01.hyp.0000260251.11364.1f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We tested the hypotheses that the gains of specific renal sympathetic neuroeffector mechanisms are altered in secondary hypertension and that the nature of these alterations depends on the precise experimental setting of the kidney. Rabbits were sham operated, or made comparably hypertensive (mean arterial pressure increased 17% to 24%) by clipping the left or right renal artery or by chronic infusion of angiotensin II (20 to 50 ng kg
−1
min
−1
SC). Four to 6 weeks later, under pentobarbital anesthesia, the left renal nerves were sectioned and electrically stimulated at low (0 to 2 Hz) and high (4 to 8 Hz) frequencies. Neurally evoked reductions in total renal blood flow, cortical perfusion, urine flow, and sodium excretion and increases in renal norepinephrine spillover were not significantly greater in kidneys of hypertensive rabbits than normotensive controls. Neurally evoked increases in renal renin release and the slope of the relationship between renin release and norepinephrine spillover were less in kidneys of hypertensive rabbits than normotensive controls. Low-frequency renal nerve stimulation reduced medullary perfusion, which was negatively correlated with renal norepinephrine spillover in kidneys from all 3 groups of hypertensive rabbits but not normotensive controls. Two-hertz stimulation reduced medullary perfusion by 19% in hypertensive rabbits but not in normotensive rabbits. Thus, of all of the renal sympathetic neuroeffector mechanisms studied, only neural control of medullary perfusion was enhanced in these models of secondary hypertension. This effect appears to be mediated postjunctionally, not through enhanced neural norepinephrine release, and may contribute to the development and/or maintenance of hypertension in these models.
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Shweta A, Denton KM, Kett MM, Bertram JF, Lambert GW, Anderson WP. Paradoxical structural effects in the unilaterally denervated spontaneously hypertensive rat kidney. J Hypertens 2005; 23:851-9. [PMID: 15775791 DOI: 10.1097/01.hjh.0000163155.29740.d2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To determine the effects of chronic denervation on renal vascular structure and function in young adult spontaneously hypertensive rats (SHRs). DESIGN Unilateral renal denervation (SHRUDx) or sham-operation (SHRS) was performed in SHRs at 6 weeks of age. At 10 weeks, rats were allocated to one of three procedures designed to examine renal vascular structure and function. A further group underwent bilateral renal denervation. METHODS In SHRUDx or SHRS groups, either the kidneys were perfusion-fixed for stereological estimates of artery wall and lumen dimensions or for vascular casting to determine arteriole lumen diameters, or the rats were anaesthetized for estimation of glomerular capillary pressure. RESULTS Chronic unilateral renal denervation had no significant effect on the development of hypertension between 6 and 10 weeks of age, as previously reported, but resulted in luminal narrowing of the interlobular artery (denervated group 52 +/- 2 mum, sham-operated group 64 +/- 1 mum; P < 0.01 for interaction between strain and treatment), without alterations in interlobular or arcuate artery wall dimensions. There were no significant effects on either afferent or efferent arteriole lumen diameters. Estimated glomerular capillary pressure was significantly lower in the denervated kidneys of SHRUDx (47 +/- 1 mmHg) compared with kidneys of the SHRS (50 +/- 1 mmHg; P < 0.04). Mean arterial pressure was approximately 12 mmHg lower in the bilaterally denervated SHRs than in the sham-operated SHRs. CONCLUSIONS Although bilateral denervation attenuated the development of hypertension in SHRs, unilateral denervation did not, indicating that one neurally intact kidney was sufficient to drive the normal development of SHR hypertension, but only with apparent prohypertensive compensatory changes in the denervated kidney.
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Affiliation(s)
- Amany Shweta
- Department of Physiology, Monash University, Victoria, Australia
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Dibona GF, Sawin LL. Effect of endogenous angiotensin II on the frequency response of the renal vasculature. Am J Physiol Renal Physiol 2004; 287:F1171-8. [PMID: 15292048 DOI: 10.1152/ajprenal.00201.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The renal vasculature functions as an efficient low-pass filter of the multiple frequencies contained within renal sympathetic nerve activity. This study examined the effect of angiotensin II on the frequency response of the renal vasculature. Physiological changes in the activity of the endogenous renin-angiotensin system were produced by alterations in dietary sodium intake. The frequency response of the renal vasculature was evaluated using pseudorandom binary sequence renal nerve stimulation, and the role of angiotensin II was evaluated by the administration of the angiotensin II AT1-receptor antagonist losartan. In low-sodium-diet rats with increased renin-angiotensin system activity, losartan steepened the renal vascular frequency response (i.e., greater attenuation); this was not seen in normal- or high-sodium-diet rats with normal or decreased renin-angiotensin system activity. Analysis of the transfer function from arterial pressure to renal blood flow, i.e., dynamic autoregulation, showed that the tubuloglomerular feedback but not the myogenic component was enhanced in low- and normal- but not in high-sodium-diet rats and that this was reversed by losartan administration. Thus physiological increases in endogenous renin-angiotensin activity inhibit the renal vascular frequency response to renal nerve stimulation while selectively enhancing the tubuloglomerular feedback component of dynamic autoregulation of renal blood flow.
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Affiliation(s)
- Gerald F Dibona
- Department of Internal Medicine, University of Iowa College of Medicine, 200 Hawkins Dr., Iowa City, IA 52242, USA.
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