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Effects of hypoxia-induced intrauterine growth restriction on cardiac siderosis and oxidative stress. J Dev Orig Health Dis 2012; 3:350-7. [DOI: 10.1017/s2040174412000219] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We have previously shown that adult rat offspring born intrauterine growth restricted (IUGR) as a result of a prenatal hypoxic insult exhibit several cardiovascular characteristics that are compatible with common manifestations of chronic iron toxicity. As hypoxia is one of the major regulators of iron absorption and metabolism, we hypothesized that hypoxia-induced IUGR offspring will have long-term changes in their ability to regulate iron metabolism leading to myocardial iron deposition and induction of myocardial oxidative stress. Pregnant Sprague Dawley rats were randomized to control (n = 8) or maternal hypoxia (11.5% oxygen; n = 8) during the last 6 days of pregnancy. At birth, litters were reduced to eight pups (four male and four female). At 4 or 12 months of age, offspring were euthanatized and samples (blood and myocardium) were collected. In only the male offspring, IUGR and aging were associated with an increase in myocardial markers of oxidative stress such as oxidized/reduced glutathione ratio and malondialdehyde. Aged male IUGR offspring also exhibited interstitial myocardial remodeling characterized by myocyte loss and disrupted extracellular matrix.Contrary to our hypothesis, however, neither IUGR nor aging were associated with changes in any systemic or local markers of iron metabolism. Our results suggest that hypoxic insults leading to IUGR produce long-term effects on the levels of oxidative stress and connective tissue distribution in the myocardium of male but not female offspring.
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102
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The Effects of Prenatal Protein Restriction on β-Adrenergic Signalling of the Adult Rat Heart during Ischaemia Reperfusion. J Nutr Metab 2012; 2012:397389. [PMID: 22536490 PMCID: PMC3321448 DOI: 10.1155/2012/397389] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 01/18/2012] [Accepted: 01/20/2012] [Indexed: 01/04/2023] Open
Abstract
A maternal low-protein diet (MLP) fed during pregnancy leads to hypertension in adult rat offspring. Hypertension is a major risk factor for ischaemic heart disease. This study examined the capacity of hearts from MLP-exposed offspring to recover from myocardial ischaemia-reperfusion (IR) and related this to cardiac expression of β-adrenergic receptors (β-AR) and their associated G proteins. Pregnant rats were fed control (CON) or MLP diets (n = 12 each group) throughout pregnancy. When aged 6 months, hearts from offspring underwent Langendorff cannulation to assess contractile function during baseline perfusion, 30 min ischemia and 60 min reperfusion. CON male hearts demonstrated impaired recovery in left ventricular pressure (LVP) and dP/dtmax (P < 0.01) during reperfusion when compared to MLP male hearts. Maternal diet had no effect on female hearts to recover from IR. MLP males exhibited greater membrane expression of β2-AR following reperfusion and urinary excretion of noradrenaline and dopamine was lower in MLP and CON female rats versus CON males. In conclusion, the improved cardiac recovery in MLP male offspring following IR was attributed to greater membrane expression of β2-AR and reduced noradrenaline and dopamine levels. In contrast, females exhibiting both decreased membrane expression of β2-AR and catecholamine levels were protected from IR injury.
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103
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Richter HG, Camm EJ, Modi BN, Naeem F, Cross CM, Cindrova-Davies T, Spasic-Boskovic O, Dunster C, Mudway IS, Kelly FJ, Burton GJ, Poston L, Giussani DA. Ascorbate prevents placental oxidative stress and enhances birth weight in hypoxic pregnancy in rats. J Physiol 2012; 590:1377-87. [PMID: 22289909 PMCID: PMC3382329 DOI: 10.1113/jphysiol.2011.226340] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 01/24/2012] [Indexed: 01/23/2023] Open
Abstract
This study isolated the effects of maternal hypoxia independent of changes in maternal nutrition on maternal circulatory and placental molecular indices of oxidative stress and determined whether maternal antioxidant treatment conferred protection. Pregnant rats were subjected to normoxic pregnancy or 13% O2 chronic hypoxia for most of gestation with and without maternal treatment with vitamin C in the drinking water. Maternal hypoxia with and without vitamin C did not affect maternal food or water intake and led to a significant increase in maternal and fetal haematocrit. At gestational day 20, maternal plasma urate and L-cysteine concentrations, and placental levels of 4-hydroxynonenal and heat shock protein 70 were increased while placental heat shock protein 90 levels were decreased in hypoxic pregnancy. The induction of maternal circulatory and placental molecular indices of oxidative stress in hypoxic pregnancies was prevented by maternal treatment with vitamin C. Maternal hypoxia during pregnancy with or without vitamin C increased placental weight, but not total or compartmental volumes. Maternal treatment with vitamin C increased birth weight in both hypoxic and normoxic pregnancies. The data show that maternal hypoxia independent of maternal undernutrition promotes maternal and placental indices of oxidative stress, effects that can be prevented by maternal treatment with vitamin C in hypoxic pregnancy. While vitamin C may not be the ideal candidate of choice for therapy in pregnant women, and taking into consideration differences in ascorbic acid metabolism between rats and humans, the data do underlie that antioxidant treatment may provide a useful intervention to improve placental function and protect fetal growth in pregnancy complicated by fetal hypoxia.
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Affiliation(s)
- H G Richter
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
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Abstract
OBJECTIVES We used magnetic resonance imaging (MRI) to perform volumetry of foetuses with and without growth restriction, and identify deviations in organ growth. STUDY DESIGN 20 growth restricted and 19 normal foetuses were scanned once during pregnancy at gestational age 20.53-36.57 weeks. MRI scans were performed on a 1.5T system using ssFSE sequences. Manual segmentation of whole body, brain, heart, lung, liver, thymus and kidney volume was performed. Data on the severity of foetal growth restriction and pregnancy outcome was collected. RESULTS There was a significant reduction in foetal whole body volume and volume of all internal organs except the brain in growth restricted foetuses. A brain:liver ratio above 3.0 was associated with a 3.3 fold increase in risk of perinatal mortality (95% CI=1.68-6.47). CONCLUSION MRI provides an accurate assessment of foetal organ growth. It may have a role to play in monitoring disease severity and the effect of future interventions.
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105
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Chronic hypoxia increases peroxynitrite, MMP9 expression, and collagen accumulation in fetal guinea pig hearts. Pediatr Res 2012; 71:25-31. [PMID: 22289847 DOI: 10.1038/pr.2011.10] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
INTRODUCTION Chronic hypoxia increases the expression of inducible nitric oxide synthase (iNOS) mRNA and protein levels in fetal guinea pig heart ventricles. Excessive generation of nitric oxide (NO) can induce nitrosative stress leading to the formation of peroxynitrite, which can upregulate the expression of matrix metalloproteinases (MMPs). This study tested the hypothesis that maternal hypoxia increases fetal cardiac MMP9 and collagen through peroxynitrite generation in fetal hearts. RESULTS In heart ventricles, levels of malondialdehyde, 3-nitrotyrosine (3-NT), MMP9, and collagen were increased in hypoxic (HPX) vs. normoxic (NMX) fetal guinea pigs. DISCUSSION Thus, maternal hypoxia induces oxidative-nitrosative stress and alters protein expression of the extracellular matrix (ECM) through upregulation of the iNOS pathway in fetal heart ventricles. This identifies iNOS-derived NO as an important stimulus for initiating the adverse effects of peroxynitrite in HPX fetal hearts. METHODS Pregnant guinea pigs were exposed to normoxia (room air) or hypoxia (10.5% O(2), 14 d) before term (term ≈ 65 d) and administered water, L-N6-(1-iminoethyl)-lysine (LNIL), an iNOS inhibitor, or N-acetylcysteine (NAC), an antioxidant.
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106
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Herrera EA, Camm EJ, Cross CM, Mullender JL, Wooding FBP, Giussani DA. Morphological and functional alterations in the aorta of the chronically hypoxic fetal rat. J Vasc Res 2011; 49:50-8. [PMID: 21985843 DOI: 10.1159/000330666] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Accepted: 06/15/2011] [Indexed: 11/19/2022] Open
Abstract
In human pregnancy, reduced placental perfusion has been associated with fetal aortic thickening. However, the relative contributions of fetal undernutrition versus fetal underoxygenation to triggering alterations in fetal cardiovascular development remain uncertain. Here, we isolate the effects of chronic fetal hypoxia on fetal cardiovascular development in a specific rodent model of chronic fetal hypoxia independent of changes in nutrition during pregnancy. Pregnant rats were housed under normoxic (21% O(2)) or hypoxic (13% O(2)) conditions from day 6 to day 20 of gestation. At day 20, pups and placentas were weighed. Fetal thoraces were fixed for quantitative histological analysis of the aorta. In a separate group, fetal aortic reactivity was assessed via in vitro wire myography. The experiments controlled for sex and within-litter variation. Placental weight was increased and fetal weight maintained in hypoxic pregnancy. Hypoxic pregnancy led to a 176% increment in wall thickness and a 170% increment in the wall-to-lumen area ratio of the fetal aorta. Fetal aortic vascular reactivity was markedly impaired, showing reduced constrictor and relaxant responsiveness in hypoxic pregnancy. Chronic developmental hypoxia independent of changes in nutrition has profound effects on the morphology and function of the fetal aorta in a mammalian species.
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Affiliation(s)
- Emilio A Herrera
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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107
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Tong W, Zhang L. Fetal hypoxia and programming of matrix metalloproteinases. Drug Discov Today 2011; 17:124-34. [PMID: 21946060 DOI: 10.1016/j.drudis.2011.09.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 06/15/2011] [Accepted: 09/14/2011] [Indexed: 12/17/2022]
Abstract
Fetal hypoxia adversely affects the brain and heart development, yet the mechanisms responsible remain elusive. Recent studies indicate an important role of the extracellular matrix in fetal development and tissue remodeling. The matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs) have been implicated in a variety of physiological and pathological processes in the cardiovascular and central nervous systems. This review summarizes current knowledge of the mechanisms by which fetal hypoxia induces the imbalance of MMPs, TIMPs and collagen expression patterns, resulting in growth restriction and aberrant tissue remodeling in the developing heart and brain. Collectively, this information could lead to the development of preventive diagnoses and therapeutic strategies in the fetal programming of cardiovascular and neurological disorders.
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Affiliation(s)
- Wenni Tong
- Center for Perinatal Biology, Division of Pharmacology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA
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108
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Epigenetic mechanisms in developmental programming of adult disease. Drug Discov Today 2011; 16:1007-18. [PMID: 21945859 DOI: 10.1016/j.drudis.2011.09.008] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 07/05/2011] [Accepted: 09/09/2011] [Indexed: 12/13/2022]
Abstract
Adverse insults during intrauterine life can result in permanent changes in the physiology and metabolism of the offspring, which in turn leads to an increased risk of disease in adulthood. This is an adaptational response by the fetus to changes in the environmental signals that it receives during early life to ensure its survival and prepare itself for postnatal life. Increasing evidence suggests that the epigenetic regulation of gene expression patterns has a crucial role in the developmental programming of adult disease. This review summarizes recent studies of epigenetic mechanisms and focuses particularly on studies that explore identifiable epigenetic biomarkers in the promoters of specific disease-associated genes. Such biomarkers would enable early recognition of children who might be at risk of developing adult disease with fetal origins.
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109
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Tong W, Xue Q, Li Y, Zhang L. Maternal hypoxia alters matrix metalloproteinase expression patterns and causes cardiac remodeling in fetal and neonatal rats. Am J Physiol Heart Circ Physiol 2011; 301:H2113-21. [PMID: 21856922 DOI: 10.1152/ajpheart.00356.2011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Fetal hypoxia leads to progressive cardiac remodeling in rat offspring. The present study tested the hypothesis that maternal hypoxia results in reprogramming of matrix metalloproteinase (MMP) expression patterns and fibrillar collagen matrix in the developing heart. Pregnant rats were treated with normoxia or hypoxia (10.5% O(2)) from day 15 to 21 of gestation. Hearts were isolated from 21-day fetuses (E21) and postnatal day 7 pups (PD7). Maternal hypoxia caused a decrease in the body weight of both E21 and PD7. The heart-to-body weight ratio was increased in E21 but not in PD7. Left ventricular myocardium wall thickness and cardiomyocyte proliferation were significantly decreased in both fetal and neonatal hearts. Hypoxia had no effect on fibrillar collagen content in the fetal heart, but significantly increased the collagen content in the neonatal heart. Western blotting revealed that maternal hypoxia significantly increased collagen I, but not collagen III, levels in the neonatal heart. Maternal hypoxia decreased MMP-1 but increased MMP-13 and membrane type (MT)1-MMP in the fetal heart. In the neonatal heart, MMP-1 and MMP-13 were significantly increased. Active MMP-2 and MMP-9 levels and activities were not altered in either fetal or neonatal hearts. Hypoxia significantly increased tissue inhibitors of metalloproteinase (TIMP)-3 and TIMP-4 in both fetal and neonatal hearts. In contrast, TIMP-1 and TIMP-2 were not affected. The results demonstrate that in utero hypoxia reprograms the expression patterns of MMPs and TIMPs and causes cardiac tissue remodeling with the increased collagen deposition in the developing heart.
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Affiliation(s)
- Wenni Tong
- Center for Perinatal Biology, Division of Pharmacology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA
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Menendez-Castro C, Fahlbusch F, Cordasic N, Amann K, Münzel K, Plank C, Wachtveitl R, Rascher W, Hilgers KF, Hartner A. Early and late postnatal myocardial and vascular changes in a protein restriction rat model of intrauterine growth restriction. PLoS One 2011; 6:e20369. [PMID: 21655297 PMCID: PMC3105022 DOI: 10.1371/journal.pone.0020369] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 05/01/2011] [Indexed: 01/21/2023] Open
Abstract
Intrauterine growth restriction (IUGR) is a risk factor for cardiovascular disease in later life. Early structural and functional changes in the cardiovascular system after IUGR may contribute to its pathogenesis. We tested the hypothesis that IUGR leads to primary myocardial and vascular alterations before the onset of hypertension. A rat IUGR model of maternal protein restriction during gestation was used. Dams were fed low protein (LP; casein 8.4%) or isocaloric normal protein diet (NP; casein 17.2%). The offspring was reduced to six males per litter. Immunohistochemical and real-time PCR analyses were performed in myocardial and vascular tissue of neonates and animals at day 70 of life. In the aortas of newborn IUGR rats expression of connective tissue growth factor (CTGF) was induced 3.2-fold. At day 70 of life, the expression of collagen I was increased 5.6-fold in aortas of IUGR rats. In the hearts of neonate IUGR rats, cell proliferation was more prominent compared to controls. At day 70 the expression of osteopontin was induced 7.2-fold. A 3- to 7-fold increase in the expression of the profibrotic cytokines TGF-β and CTGF as well as of microfibrillar matrix molecules was observed. The myocardial expression and deposition of collagens was more prominent in IUGR animals compared to controls at day 70. In the low-protein diet model, IUGR leads to changes in the expression patterns of profibrotic genes and discrete structural abnormalities of vessels and hearts in adolescence, but, with the exception of CTGF, not as early as at the time of birth. Invasive and non-invasive blood pressure measurements confirmed that IUGR rats were normotensive at the time point investigated and that the changes observed occurred independently of an increased blood pressure. Hence, altered matrix composition of the vascular wall and the myocardium may predispose IUGR animals to cardiovascular disease later in life.
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Affiliation(s)
- Carlos Menendez-Castro
- Department of Pediatrics and Adolescent Medicine, University of Erlangen-Nürnberg, Erlangen, Germany.
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Rueda-Clausen CF, Dolinsky VW, Morton JS, Proctor SD, Dyck JR, Davidge ST. Hypoxia-induced intrauterine growth restriction increases the susceptibility of rats to high-fat diet-induced metabolic syndrome. Diabetes 2011; 60:507-16. [PMID: 21270262 PMCID: PMC3028350 DOI: 10.2337/db10-1239] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE It is recognized that there is a remarkable variability in the systemic response to high-fat (HF) diets that cannot be completely explained by genetic factors. In addition, pregnancy complications leading to intrauterine growth restriction (IUGR) have been associated with an increased risk of developing metabolic syndrome (MetS) later in life. Thus, we hypothesized that offspring born with IUGR exhibit permanent metabolic changes that make them more susceptible to HF diet-induced MetS. RESEARCH DESIGN AND METHODS SD rats born normal (control) or with hypoxia-induced IUGR were randomized to low-fat (10% fat) or HF (45% fat) diets. After 9 weeks of feeding, physiological and molecular pathways involved in the MetS were evaluated. RESULTS IUGR offspring exhibited decreased energy intake and physical activity relative to controls. In offspring fed a HF diet, IUGR was associated with decreased total body fat content, a relative increase in intra-abdominal fat deposition and adipocyte size, an increase in fasting plasma concentrations of leptin, triglyceride and free fatty acids, and an increased concentration of triglycerides and ceramides in both liver and skeletal muscle. These changes in lipid homeostasis were accompanied by in vivo insulin resistance and impaired glucose tolerance and associated with increased phosphorylation of protein kinase C , inhibition of insulin receptor substrate 1, and a decreased activation of protein kinase B (PKB; also known as Akt) in liver and skeletal muscle in response to insulin. CONCLUSIONS IUGR enhances specific deleterious metabolic responses to a HF diet. Our results suggest that offspring born with IUGR may require special attention and follow-up to prevent the early onset of MetS.
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Affiliation(s)
- Christian F. Rueda-Clausen
- Department of Physiology, University of Alberta, Edmonton, Canada
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
| | - Vernon W. Dolinsky
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Department of Pediatrics, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
| | - Jude S. Morton
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Department of Obstetrics and Gynecology, University of Alberta, Edmonton, Canada
| | - Spencer D. Proctor
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
- Alberta Institute for Human Nutrition, University of Alberta, Edmonton, Canada
| | - Jason R.B. Dyck
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Department of Pediatrics, University of Alberta, Edmonton, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Canada
| | - Sandra T. Davidge
- Department of Physiology, University of Alberta, Edmonton, Canada
- Women and Children’s Health Research Institute, University of Alberta, Edmonton, Canada
- Cardiovascular Research Centre, University of Alberta, Edmonton, Canada
- Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada
- Department of Obstetrics and Gynecology, University of Alberta, Edmonton, Canada
- Corresponding authors: Sandra T. Davidge, , and Jason R.B. Dyck,
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112
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Patterson AJ, Zhang L. Hypoxia and fetal heart development. Curr Mol Med 2011; 10:653-66. [PMID: 20712587 DOI: 10.2174/156652410792630643] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 06/30/2010] [Indexed: 12/18/2022]
Abstract
Fetal hearts show a remarkable ability to develop under hypoxic conditions. The metabolic flexibility of fetal hearts allows sustained development under low oxygen conditions. In fact, hypoxia is critical for proper myocardial formation. Particularly, hypoxia inducible factor 1 (HIF-1) and vascular endothelial growth factor play central roles in hypoxia-dependent signaling in fetal heart formation, impacting embryonic outflow track remodeling and coronary vessel growth. Although HIF is not the only gene involved in adaptation to hypoxia, its role places it as a central figure in orchestrating events needed for adaptation to hypoxic stress. Although "normal" hypoxia (lower oxygen tension in the fetus as compared with the adult) is essential in heart formation, further abnormal hypoxia in utero adversely affects cardiogenesis. Prenatal hypoxia alters myocardial structure and causes a decline in cardiac performance. Not only are the effects of hypoxia apparent during the perinatal period, but prolonged hypoxia in utero also causes fetal programming of abnormality in the heart's development. The altered expression pattern of cardioprotective genes such as protein kinase c epsilon, heat shock protein 70, and endothelial nitric oxide synthase, likely predispose the developing heart to increased vulnerability to ischemia and reperfusion injury later in life. The events underlying the long-term changes in gene expression are not clear, but likely involve variation in epigenetic regulation.
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Affiliation(s)
- A J Patterson
- Center for Perinatal Biology, Department of Physiology and Pharmacology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA.
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113
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Rueda-Clausen CF, Morton JS, Lopaschuk GD, Davidge ST. Long-term effects of intrauterine growth restriction on cardiac metabolism and susceptibility to ischaemia/reperfusion. Cardiovasc Res 2010; 90:285-94. [PMID: 21097804 DOI: 10.1093/cvr/cvq363] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
AIMS Adult offspring who are born intrauterine growth restricted (IUGR) are at risk of developing cardiovascular diseases during adulthood. Additionally, several cardiac diseases are associated with changes in myocardial energy metabolism. However, the potential long-term effects of being born IUGR on cardiac energetics are unknown. The aim of this study was to assess the long-term effect of IUGR on cardiac performance and energy metabolism under aerobic conditions and after ischaemia/reperfusion (IR) injury. METHODS AND RESULTS To induce IUGR, pregnant Sprague-Dawley rats were randomly assigned to hypoxic (11.5% O(2)) or control (21% O(2)) environments from day 15 to 21 of pregnancy. Cardiac susceptibility to IR was evaluated in male and female offspring at 4 (young-adult) or 12 (ageing) months of age using isolated working hearts. Cardiac production of energy was evaluated using radiolabelled substrates. Both male and female IUGR offspring exhibited an increased susceptibility to IR injury compared with controls (P< 0.05) as well as an increased post-ischaemic production of protons (P< 0.001) secondary to a mismatch between myocardial glycolysis and glucose oxidation rates. Moreover, offspring born IUGR exhibited an increased myocardial production of acetyl-CoA during reperfusion. The mismatch between energy production and cardiac performance indicates that in IUGR offspring, cardiac efficiency during reperfusion was decreased relative to controls. CONCLUSION Our results suggest that hypoxia-induced IUGR has long-term effects on cardiac susceptibility to IR injury that are independent of sex and age. Moreover, we identified a mismatch in glucose metabolism, leading to proton accumulation in the post-ischaemic myocardium of offspring born IUGR as a potential mechanism involved.
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114
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Early life exposure to hypoxia: a developmental insult critical to the programming of cardiovascular risk. Am J Hypertens 2010; 23:1158. [PMID: 20956963 DOI: 10.1038/ajh.2010.197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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115
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Xue Q, Dasgupta C, Chen M, Zhang L. Foetal hypoxia increases cardiac AT(2)R expression and subsequent vulnerability to adult ischaemic injury. Cardiovasc Res 2010; 89:300-8. [PMID: 20870653 DOI: 10.1093/cvr/cvq303] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
AIMS Hypoxia is a common stress to the foetus and results in increased cardiac vulnerability to adult ischaemic injury. This study tested the hypothesis that foetal hypoxia causes programming of increased AT(2) receptor (AT(2)R) expression in the heart, resulting in the heightened cardiac susceptibility to adult ischaemic injury. METHODS AND RESULTS Time-dated pregnant rats were divided between normoxic and hypoxic (10.5% O(2) from days 15 to 21 of gestation) groups. Hypoxia resulted in significantly increased AT(2)R in the heart of adult offspring. Multiple glucocorticoid response elements (GREs) were identified at the AT(2)R promoter, deletion of which increased the promoter activity. Consistently, ex vivo treatment of isolated foetal hearts with dexamethasone for 48 h decreased AT(2)R expression, which was inhibited by RU 486. Hypoxia decreased glucocorticoid receptors (GRs) in the hearts of foetal, 3-week-old and 3-month-old offspring, resulting in decreased GR binding to the GREs at the AT(2)R promoter. The inhibition of AT(2)R improved postischaemic recovery of left ventricular function and rescued the foetal hypoxia-induced cardiac ischaemic vulnerability in male adult animals. In contrast, the inhibition of AT(1) receptors decreased the postischaemic recovery. CONCLUSION The results demonstrate that in utero hypoxia causes programming of increased AT(2)R gene expression in the heart by downregulating GR, which contributes to the increased cardiac vulnerability to adult ischaemic injury caused by prenatal hypoxic exposure.
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Affiliation(s)
- Qin Xue
- Institute for Fetal Origin Diseases, First Hospital of Soochow University, Suzhou 215000, China
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116
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Patterson AJ, Chen M, Xue Q, Xiao D, Zhang L. Chronic prenatal hypoxia induces epigenetic programming of PKC{epsilon} gene repression in rat hearts. Circ Res 2010; 107:365-73. [PMID: 20538683 DOI: 10.1161/circresaha.110.221259] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
RATIONALE Epidemiological studies demonstrate a clear association of adverse intrauterine environment with an increased risk of ischemic heart disease in adulthood. Hypoxia is a common stress to the fetus and results in decreased protein kinase C epsilon (PKCepsilon) expression in the heart and increased cardiac vulnerability to ischemia and reperfusion injury in adult offspring in rats. OBJECTIVES The present study tested the hypothesis that fetal hypoxia-induced methylation of cytosine-phosphate-guanine dinucleotides at the PKCepsilon promoter is repressive and contributes to PKCepsilon gene repression in the heart of adult offspring. METHODS AND RESULTS Hypoxic treatment of pregnant rats from days 15 to 21 of gestation resulted in significant decreases in PKCepsilon protein and mRNA in fetal hearts. Similar results were obtained in ex vivo hypoxic treatment of isolated fetal hearts and rat embryonic ventricular myocyte cell line H9c2. Increased methylation of PKCepsilon promoter at SP1 binding sites, -346 and -268, were demonstrated in both fetal hearts of maternal hypoxia and H9c2 cells treated with 1% O(2) for 24 hours. Whereas hypoxia had no significant effect on the binding affinity of SP1 to the unmethylated sites in H9c2 cells, hearts of fetuses and adult offspring, methylation of both SP1 sites reduced SP1 binding. The addition of 5-aza-2'-deoxycytidine blocked the hypoxia-induced increase in methylation of both SP1 binding sites and restored PKCepsilon mRNA and protein to the control levels. In hearts of both fetuses and adult offspring, hypoxia-induced methylation of SP1 sites was significantly greater in males than in females, and decreased PKCepsilon mRNA was seen only in males. In fetal hearts, there was significantly higher abundance of estrogen receptor alpha and beta isoforms in females than in males. Both estrogen receptor alpha and beta interacted with the SP1 binding sites in the fetal heart, which may explain the sex differences in SP1 methylation in the fetal heart. Additionally, selective activation of PKCepsilon restored the hypoxia-induced cardiac vulnerability to ischemic injury in offspring. CONCLUSIONS The findings demonstrate a direct effect of hypoxia on epigenetic modification of DNA methylation and programming of cardiac PKCepsilon gene repression in a sex-dependent manner, linking fetal hypoxia and pathophysiological consequences in the hearts of adult offspring.
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Affiliation(s)
- Andrew J Patterson
- Center for Perinatal Biology, Department of Physiology and Pharmacology, Loma Linda University School of Medicine, CA 92350, USA
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117
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Abstract
The developing mammalian heart responds to a variety of conditions, including changes in nutrient availability, blood oxygenation, hemodynamics, or tissue homeostasis, with impressive growth plasticity. This ensures the formation of a functional and normal sized organ by birth. During embryonic and fetal development the heart is exposed to various physiological and potentially pathological changes in the intrauterine environment which dramatically impact on normal cardiac function, tissue composition, and morphology. This paper summarizes the mechanisms employed by the embryonic and fetal heart to adapt to various intrauterine challenges to prevent or minimize postnatal consequences of impaired cardiac development. Future investigations of this growth plasticity might lead to new therapeutic strategies for the prevention of cardiac disease in postnatal life.
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Tong W, Chen W, Ostrowski RP, Ma Q, Souvenir R, Zhang L, Zhang JH, Tang J. Maternal hypoxia increases the activity of MMPs and decreases the expression of TIMPs in the brain of neonatal rats. Dev Neurobiol 2010; 70:182-94. [PMID: 20017119 DOI: 10.1002/dneu.20770] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A recent study has shown that increased activity of matrix metalloproteinases-2 and metalloproteinases-9 (MMP-2 and MMP-9) has detrimental effect on the brain after neonatal hypoxia. The present study determined the effect of maternal hypoxia on neuronal survivability and the activity of MMP-2 and MMP-9, as well as the expression of tissue inhibitors of metalloproteinase 1 and 2 (TIMP-1 and TIMP-2) in the brain of neonatal rats. Pregnant rats were exposed to 10.5% oxygen for 6 days from the gestation day 15 to day 21. Pups were sacrificed at day 0, 4, 7, 14, and 21 after birth. Body weight and brain weight of the pups were measured at each time point. The activity of MMP-2 and MMP-9 and the protein abundance of TIMP-1 and TIMP-2 were determined by zymography and Western blotting, respectively. The tissue distribution of MMPs was examined by immunofluorescence staining. The neuronal death was detected by Nissl staining. Maternal hypoxia caused significant decreases in body and brain size, increased activity of MMP-2 at day 0, and increased MMP-9 at day 0 and 4. The increased activity of the MMPs was accompanied by an overall tendency towards a reduced expression of TIMPs at all ages with the significance observed for TIMPs at day 0, 4, and 7. Immunofluorescence analysis showed an increased expression of MMP-2, MMP-9 in the hippocampus at day 0 and 4. Nissl staining revealed significant cell death in the hippocampus at day 0, 4, and 7. Functional tests showed worse neurobehavioral outcomes in the hypoxic animals.
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Affiliation(s)
- Wenni Tong
- Department of Physiology and Pharmacology, Loma Linda University School of Medicine, Loma Linda, California 92350, USA
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119
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Ojeda NB, Grigore D, Alexander BT. Role of fetal programming in the development of hypertension. Future Cardiol 2009; 4:163-74. [PMID: 19672482 DOI: 10.2217/14796678.4.2.163] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Epidemiological studies have suggested that size at birth contributes to increased cardiovascular disease (CVD) risk in later life. Findings from experimental studies are providing insight into the mechanisms linking impaired fetal growth and the increased risk of CVD and hypertension in adulthood. This article summarizes potential mechanisms involved in the fetal programming of hypertension and CVD, including alterations in the organs and regulatory systems critical to long-term control of sodium and volume homeostasis.
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Affiliation(s)
- Norma B Ojeda
- University of Mississippi Medical Center, Department of Physiology & Biophysics, The Center for Excellence in Cardiovascular-Renal Research, 2500 North State Street, Jackson, MS 39216-4505, USA.
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120
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121
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Xue Q, Zhang L. Prenatal hypoxia causes a sex-dependent increase in heart susceptibility to ischemia and reperfusion injury in adult male offspring: role of protein kinase C epsilon. J Pharmacol Exp Ther 2009; 330:624-32. [PMID: 19470841 PMCID: PMC2713094 DOI: 10.1124/jpet.109.153239] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 05/22/2009] [Indexed: 01/21/2023] Open
Abstract
The present study tested the hypothesis that protein kinase C (PKC) epsilon plays a key role in the sex dichotomy of heart susceptibility to ischemia and reperfusion injury in adult offspring resulting from prenatal hypoxic exposure. Time-dated pregnant rats were divided between normoxic and hypoxic (10.5% O(2) on days 15-21 of gestation) groups. Hearts of 3-month-old progeny were subjected to ischemia and reperfusion (I/R) injury in a Langendorff preparation. Preischemic values of left ventricle (LV) function were the same between control and hypoxic animals. Prenatal hypoxia significantly decreased postischemic recovery of LV function and increased cardiac enzyme release and infarct size in adult male, but not female, rats. This was associated with significant decreases in PKC(epsilon) and phospho-PKC(epsilon) levels in the LV of the male, but not female, rats. The PKC(epsilon) translocation inhibitor peptide (PKC(epsilon)-TIP) significantly decreased phospho-PKC(epsilon) in control male rats to the levels found in the hypoxic animals and abolished the difference in I/R injury observed between the control and hypoxic rats. In females, PKC(epsilon)-TIP inhibited PKC(epsilon) phosphorylation and decreased postischemic recovery of LV function equally well in both control and hypoxic animals. PKC(epsilon)-TIP had no effect on PKCdelta activation in either male or female hearts. The results demonstrated that prenatal hypoxia caused an increase in heart susceptibility to ischemia and reperfusion injury in offspring in a sex-dependent manner, which was due to fetal programming of PKC(epsilon) gene repression resulting in a down-regulation of PKC(epsilon) function in the heart of adult male offspring.
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Affiliation(s)
- Qin Xue
- Department of Physiology and Pharmacology, Loma Linda University School of Medicine, Center for Perinatal Biology, Loma Linda, California 92350, USA
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122
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Le Clair C, Abbi T, Sandhu H, Tappia PS. Impact of maternal undernutrition on diabetes and cardiovascular disease risk in adult offspring. Can J Physiol Pharmacol 2009; 87:161-79. [PMID: 19295658 DOI: 10.1139/y09-006] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Epidemiological, clinical, and experimental observations have led to the hypothesis that the risk of developing chronic diseases in adulthood is influenced not only by genetic and adult lifestyle factors, but also by environmental factors during early life. Low birth weight, a marker of intrauterine stress, has been linked to predisposition to cardiovascular disease (CVD) and diabetes. The compelling animal evidence and significant human data to support this conclusion are reviewed. Specifically, the review discusses the role of maternal nutrition before and during pregnancy, placental insufficiencies and epigenetic changes in the increased predisposition to diabetes and CVD in adult life. The impact of low birth weight and catch-up growth as they pertain to risk of disease in adult life is also discussed. In addition, adult disease risk in the overnourished fetus is also mentioned. Reference is made to some of the mechanisms of the induction of diabetes and CVD phenotype. It is proposed that fetal nutrition, growth and development through efficient maternal nutrition before and during pregnancy could constitute the basis for nutritional strategies for the primary prevention of diabetes and CVD.
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Affiliation(s)
- Caroline Le Clair
- I.H. Asper Clinical Research Institute, St. Boniface Hospital Research Centre, and Department of Human Nutritional Sciences, Faculty of Human Ecology, University of Manitoba, Winnipeg, MB R2H2A6, Canada
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123
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Calvert JW, Lefer DJ, Gundewar S, Poston L, Coetzee WA. Developmental programming resulting from maternal obesity in mice: effects on myocardial ischaemia-reperfusion injury. Exp Physiol 2009; 94:805-14. [PMID: 19395658 DOI: 10.1113/expphysiol.2009.047183] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A comprehensive number of epidemiological and animal studies suggest that prenatal and early life events are important determinants for disorders later in life. Among them, prenatal stress (i.e. stress experienced by the pregnant mother with impact on the fetal ontogeny) has clear programming effects on the cardiovascular system. A fetus developing in adverse conditions becomes an adult who is susceptible to disease, which may include hypertension, insulin resistance, altered blood lipid levels and cardiovascular disease. Recent evidence demonstrates that maternal programming can occur in the absence of other adverse environmental factors. Obesity, which is becoming a problem of large proportions in Western countries, is a possible cause of programming. With over 30% of the population of the USA currently obese, many mothers suffer from obesity during their child-bearing years (in fact, these conditions are often aggravated during pregnancy). One of the targets of programming is the cardiovascular system, and reported consequences include hypertension, endothelial dysfunction and vascular abnormalities. The overall goal of our study was to investigate the susceptibility of the heart to ischaemia-reperfusion in an animal model of maternal obesity. Our data demonstrate that normal (non-mutant) offspring from obese agouti mouse dams had an increased susceptibility to ischaemia-reperfusion injury. These data may provide insights into the long-term cardiovascular consequences of programming.
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Affiliation(s)
- John W Calvert
- Department of Surgery, Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, GA, USA
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124
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Wang Z, Huang Z, Lu G, Lin L, Ferrari M. Hypoxia during pregnancy in rats leads to early morphological changes of atherosclerosis in adult offspring. Am J Physiol Heart Circ Physiol 2009; 296:H1321-8. [PMID: 19304947 DOI: 10.1152/ajpheart.00440.2008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exposure to an adverse intrauterine environment increases the risk of cardiovascular disease later in adult life. However, the time course relationship between prenatal hypoxia and the onset of atherosclerosis in offspring remains unknown. The purpose of this study is to evaluate the role of reduced fetal oxygen supply on early development of atherogenesis in the adult offspring and further assess its susceptibility to sex-, hyperlipidemia-, and postnatal hypoxemia-related differences. Based on a 4 x 2 full factorial design consisting of four factors of maternal hypoxia, sex, hyperlipidemia, and postnatal hypoxemia, characteristics of growth were determined, and histopathological observation and morphometric analysis of the thoracic aortas were performed in Sprague-Dawley rat offspring. Intrauterine growth restriction, altered body shape at birth, and accelerated postnatal weight gain occurred in the maternal hypoxia group but did not occur in the control group. In 16-mo-old maternal hypoxia offspring, the thoracic aortas exhibited lesions similar to early events in atherosclerosis that involved impaired endothelial cells, thickening and fibration of intimas, infiltration of inflammatory cells to the subendothelial space, and migration and proliferation of vascular smooth muscle cells to the intima. In contrast, no detectable pathological changes were observed in the offspring without maternal hypoxia exposure. Morphometric analysis further demonstrated that prenatal hypoxia caused a significant thickening of intima (P < 0.001) with a main effect of 5.5 mum, an approximately twofold increase compared with controls. In addition, there was a positive additive relationship between prenatal hypoxia and hyperlipidemia on the intimal thickness (P < 0.05). There were no other main effects or interaction among these four factors. In summary, our results indicate that maternal hypoxia during pregnancy leads to early pathological appearances of atherogenesis in adult offspring. This effect was enhanced with hyperlipemia but was unaffected by postnatal hypoxia or sex.
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Affiliation(s)
- Zhenhua Wang
- Dept. of Cardiology, Second Affiliated Hospital of Fujian Medical Univ., Zhongshan North Road 34, 362000 Quanzhou, Fujian, P. R. China
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125
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Meyer KD, Zhang H, Zhang L. Prenatal cocaine exposure abolished ischemic preconditioning-induced protection in adult male rat hearts: role of PKCepsilon. Am J Physiol Heart Circ Physiol 2009; 296:H1566-76. [PMID: 19286950 DOI: 10.1152/ajpheart.00898.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Prenatal cocaine exposure in rats resulted in decreased PKCepsilon protein expression in the heart of adult male but not female offspring. The present study determined its functional consequence of inhibiting cardioprotection mediated by ischemic preconditioning. Pregnant Sprague-Dawley rats were administered intraperitoneally saline or cocaine (30 mg.kg(-1).day(-1)) from day 15 to day 21 of gestational age. Hearts were isolated from 3-mo-old offspring and were subjected to ischemia and reperfusion injury in a Langendorff preparation, with or without prior ischemic preconditioning. Preischemic values of left ventricular function were the same between the saline control and cocaine-treated animals. Ischemic preconditioning of two episodes of 5-min ischemia significantly decreased infarct size and enhanced postischemic functional recovery of the left ventricle in the saline control animals. This ischemic preconditioning was associated with increased phospho-PKCepsilon, but not phospho-PKCdelta, levels and was blocked by a PKCepsilon translocation inhibitor peptide. Prenatal cocaine treatment abolished the ischemic preconditioning-mediated increase in phospho-PKCepsilon and cardioprotection in the heart of male offspring. In contrast, the cardioprotective effect was fully maintained in female offspring that were exposed to cocaine before birth. The results suggest that prenatal cocaine exposure causes a sex-specific loss of cardioprotection by ischemic preconditioning in adult offspring, which is most likely due to fetal programming of PKCepsilon gene repression, resulting in a downregulation of PKCepsilon function in the heart of adult male offspring.
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Affiliation(s)
- Kurt D Meyer
- Center for Perinatal Biology, Dept. of Physiology & Pharmacology, Loma Linda Univ. School of Medicine, Loma Linda, CA 92350, USA
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126
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Long-term effects of prenatal stress: Changes in adult cardiovascular regulation and sensitivity to stress. Neurosci Biobehav Rev 2009; 33:191-203. [DOI: 10.1016/j.neubiorev.2008.08.001] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Revised: 07/21/2008] [Accepted: 08/01/2008] [Indexed: 02/06/2023]
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127
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Hauton D, Ousley V. Prenatal hypoxia induces increased cardiac contractility on a background of decreased capillary density. BMC Cardiovasc Disord 2009; 9:1. [PMID: 19126206 PMCID: PMC2627821 DOI: 10.1186/1471-2261-9-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Accepted: 01/06/2009] [Indexed: 11/15/2022] Open
Abstract
Background Chronic hypoxia in utero (CHU) is one of the most common insults to fetal development and may be associated with poor cardiac recovery from ischaemia-reperfusion injury, yet the effects on normal cardiac mechanical performance are poorly understood. Methods Pregnant female wistar rats were exposed to hypoxia (12% oxygen, balance nitrogen) for days 10–20 of pregnancy. Pups were born into normal room air and weaned normally. At 10 weeks of age, hearts were excised under anaesthesia and underwent retrograde 'Langendorff' perfusion. Mechanical performance was measured at constant filling pressure (100 cm H2O) with intraventricular balloon. Left ventricular free wall was dissected away and capillary density estimated following alkaline phosphatase staining. Expression of SERCA2a and Nitric Oxide Synthases (NOS) proteins were estimated by immunoblotting. Results CHU significantly increased body mass (P < 0.001) compared with age-matched control rats but was without effect on relative cardiac mass. For incremental increases in left ventricular balloon volume, diastolic pressure was preserved. However, systolic pressure was significantly greater following CHU for balloon volume = 50 μl (P < 0.01) and up to 200 μl (P < 0.05). For higher balloon volumes systolic pressure was not significantly different from control. Developed pressures were correspondingly increased relative to controls for balloon volumes up to 250 μl (P < 0.05). Left ventricular free wall capillary density was significantly decreased in both epicardium (18%; P < 0.05) and endocardium (11%; P < 0.05) despite preserved coronary flow. Western blot analysis revealed no change to the expression of SERCA2a or nNOS but immuno-detectable eNOS protein was significantly decreased (P < 0.001) in cardiac tissue following chronic hypoxia in utero. Conclusion These data offer potential mechanisms for poor recovery following ischaemia, including decreased coronary flow reserve and impaired angiogenesis with subsequent detrimental effects of post-natal cardiac performance.
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Affiliation(s)
- David Hauton
- Department of Physiology, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK.
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128
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Rueda-Clausen CF, Morton JS, Davidge ST. Effects of hypoxia-induced intrauterine growth restriction on cardiopulmonary structure and function during adulthood. Cardiovasc Res 2008; 81:713-22. [DOI: 10.1093/cvr/cvn341] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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129
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Tian G, Singh U, Yu Y, Ellsworth BS, Hemberger M, Geyer R, Stewart MD, Behringer RR, Fundele R. Expression and function of the LIM homeobox containing genes Lhx3 and Lhx4 in the mouse placenta. Dev Dyn 2008; 237:1517-25. [PMID: 18425848 DOI: 10.1002/dvdy.21546] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The LIM homeobox containing genes of the LIM-3 group, Lhx3 and Lhx4, are critical for normal development. Both genes are involved in the formation of the pituitary and the motoneuron system and loss of either gene causes perinatal lethality. Previous studies had shown that Lhx3 is overexpressed in hyperplastic placentas of mouse interspecies hybrids. To determine the role of LHX3 in the mouse placenta, we performed expression and function analyses. Our results show that Lhx3 exhibits specific spatial and temporal expression in the mouse placenta. However, deletion of Lhx3 does not produce a placental phenotype. To test whether this is due to functional substitution by Lhx4, we performed a phenotype analysis of Lhx3-/-; Lhx4-/- double-mutant placentas. A subset of Lhx3-/-; Lhx4-/- placentas exhibited abnormal structure of the labyrinth. However, absence of both LIM-3 genes did not interfere with placental transport nor consistently with expression of target genes such as Gnrhr. Thus, LHX3 and LHX4 appear to be dispensable for placental development and function.
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Affiliation(s)
- Geng Tian
- Department of Animal Genetics and Development, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
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130
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Porrello ER, Widdop RE, Delbridge LMD. Early origins of cardiac hypertrophy: does cardiomyocyte attrition programme for pathological 'catch-up' growth of the heart? Clin Exp Pharmacol Physiol 2008; 35:1358-64. [PMID: 18759854 DOI: 10.1111/j.1440-1681.2008.05036.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
1. Epidemiological and experimental evidence suggests that adult development of cardiovascular disease is influenced by events of prenatal and early postnatal life. Cardiac hypertrophy is recognized as an important predictor of cardiovascular morbidity and mortality, but the developmental origins of this condition are not well understood. 2. In the heart, a switch from hyperplastic to hypertrophic cellular growth occurs during late prenatal or early postnatal life. Postnatal growth of the heart is almost entirely reliant on hypertrophy of individual cardiomyocytes, and damage to heart muscle in adulthood is typically not reparable by cell replacement. Therefore, a reduced number of cardiomyocytes may render the heart more vulnerable in situations where an increased workload is required. 3. A number of different animal models have been used to study fetal programming of adult diseases, including nutritional, hypoxic, maternal/neonatal endocrine stress and genetic models. Although studies investigating the cellular basis of myocardial disease in growth-restricted models are limited, a reduction in cardiomyocyte number through either reduced cellular proliferation or increased apoptosis appears to be a central feature. 4. The mechanisms responsible for the programming of adult cardiovascular disease are poorly understood. We hypothesize that cardiac hypertrophy can have a developmental origin in excess cardiomyocyte attrition during a critical perinatal growth window. Findings that have directly assessed the impact of fetal growth restriction on the myocardium are considered and cellular and molecular mechanisms involved in the potential pathological 'catch-up' growth of the heart during later maturation are identified.
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Affiliation(s)
- Enzo R Porrello
- Department of Physiology, The University of Melbourne, Melbourne, Victoria, Australia
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131
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Cheng Y, Hauton D. Cold acclimation induces physiological cardiac hypertrophy and increases assimilation of triacylglycerol metabolism through lipoprotein lipase. Biochim Biophys Acta Mol Cell Biol Lipids 2008; 1781:618-26. [PMID: 18722549 PMCID: PMC2568868 DOI: 10.1016/j.bbalip.2008.07.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/15/2008] [Accepted: 07/15/2008] [Indexed: 12/24/2022]
Abstract
The contribution of triacylglycerol to energy provision in the hypertrophied heart, mediated through lipoprotein lipase (LPL) is largely unknown and the contribution of very-low-density lipoprotein (VLDL) receptor to control of LPL presentation at the endothelium is unclear. For isolated perfused rat hearts, cold acclimation (CA) induced volume-overload hypertrophy, with decreased developed pressure (P < 0.01), increased end-diastolic volume of the left ventricle (P < 0.001) and a loss of contractile reserve in response to dobutamine challenge (P < 0.01). Oleate utilisation by perfused hearts was unchanged by CA, however uptake of intralipid emulsion increased 3-fold (P < 0.01). CA increased the proportion of lipid deposited in tissue lipids from 10% in euthermic controls to 40% (P < 0.01) although the overall contribution of individual lipid classes was unaffected. Cold acclimation significantly increased heparin-releasable LPL (P < 0.05) and tissue residual LPL (P < 0.01). Western blot analysis indicated preserved expression of proteins coding for SERCA2, muscle-CPT1 and VLDL-receptor following CA, while AMPKα2 and phospho-AMPKα2 were unaffected. These observations indicate that for physiological hypertrophy AMPK phosphorylation does not mediate the enhanced translocation of LPL to cardiac endothelium.
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Affiliation(s)
- Y Cheng
- Department of Physiology, Division of Medical Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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132
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Soukhova-O'Hare GK, Ortines RV, Gu Y, Nozdrachev AD, Prabhu SD, Gozal D. Postnatal Intermittent Hypoxia and Developmental Programming of Hypertension in Spontaneously Hypertensive Rats. Hypertension 2008; 52:156-62. [DOI: 10.1161/hypertensionaha.108.110296] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Obstructive and central apneas during sleep are associated with chronic intermittent hypoxia (CIH) and increased cardiovascular morbidity. Spontaneously hypertensive rats exposed to CIH during postnatal days 4 to 30 develop exaggerated hypertension as adults. We hypothesized that reactive oxygen species and altered L-Ca
2+
channel activity may underlie the postnatal programming of exaggerated blood pressure and cardiac remodeling. Newborn male spontaneously hypertensive rats were exposed to CIH (10% and 21% O
2
alternating every 90 seconds, 12 h/d, for postnatal days 4 to 30) or normoxia (room air). In each condition, spontaneously hypertensive rats received daily (SC) 1 of 3 treatments:
l
-calcium channel blocker nifedipine (5 mg/kg), superoxide dismutase mimetic MnTMPyP pentachloride (10 mg/kg), or vehicle (polyethylene glycol). Blood pressure was evaluated monthly for 6 months after birth, and echocardiographic assessments were conducted at 6 months of age. CIH vehicle-treated rats presented higher systolic blood pressure (187±5 mm Hg) as compared with normoxic vehicle treated controls (163±2 mm Hg;
P
<0.001). Postnatal CIH elicited marked increases in left ventricular wall thickness in a pattern of concentric hypertrophy with augmented systolic contractility. The treatment with nifedipine in the CIH group attenuated blood pressure (159±2 mm Hg;
P
<0.001) and normalized left ventricular wall thickness and systolic function, whereas the treatment with SOD mimetic decreased blood pressure (165±2 mm Hg;
P
<0.001) and reduced left ventricular wall thickness without changes in the systolic function. We conclude that Ca
2+
and reactive oxygen species–mediated signaling during intermittent hypoxia are critical mechanisms underlying postnatal programming of an increased severity of hypertension and hypertrophic cardiac remodeling in a genetically susceptible rodent model.
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Affiliation(s)
- Galia K. Soukhova-O'Hare
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Roger V. Ortines
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Yan Gu
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Alexander D. Nozdrachev
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Sumanth D. Prabhu
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - David Gozal
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
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133
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Abstract
Intrauterine growth restriction (IUGR), which complicates approximately 3% to 10% of all pregnancies leads to preferential hemodynamic changes in affected fetuses. Advanced ultrasound modalities allow reliable and reproducible assessment of the intrauterine fetal cardiac function. Among other methods, combined cardiac output, individual ventricular ejection forces, E/A ratio, and Tei index can be utilized to quantify fetal heart function. While systolic ejection forces significantly increase with advancing gestational age in normal fetuses, there is a significant decline in the systolic function in IUGR fetuses. From the diastolic cardiac function point, IUGR fetuses have significantly lower left and right ventricular diastolic filling without significant changes in diastolic function. Overall, IUGR fetuses demonstrate progressive hemodynamic changes. It appears that there is an earlier and more pronounced right than left and diastolic than systolic fetal cardiac function deterioration in growth-restricted fetuses.
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Affiliation(s)
- Mert Ozan Bahtiyar
- Section of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology, and ReproductiveSciences, Yale University School of Medicine, 333 Cedar Street, POBox 208063, New Haven, CT 06520-8063, USA.
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134
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Ream M, Ray AM, Chandra R, Chikaraishi DM. Early fetal hypoxia leads to growth restriction and myocardial thinning. Am J Physiol Regul Integr Comp Physiol 2008; 295:R583-95. [PMID: 18509101 DOI: 10.1152/ajpregu.00771.2007] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hypoxia is necessary for fetal development; however, excess hypoxia is detrimental. Hypoxia has been extensively studied in the near-term fetus, but less is known about earlier fetal effects. The purpose of this study was to determine the window of vulnerability to severe hypoxia, what organ system(s) is most sensitive, and why hypoxic fetuses die. We induced hypoxia by reducing maternal-inspired O2 from 21% to 8%, which decreased fetal tissue oxygenation assessed by pimonidazole binding. The mouse fetus was most vulnerable in midgestation: 24 h of hypoxia killed 89% of embryonic day 13.5 (E13.5) fetuses, but only 5% of E11.5 and 51% of E17.5 fetuses. Sublethal hypoxia at E12.5 caused growth restriction, reducing fetal weight by 26% and protein by 45%. Hypoxia induced HIF-1 target genes, including vascular endothelial growth factor (Vegf), erythropoietin, glucose transporter-1 and insulin-like growth factor binding protein-1 (Igfbp-1), which has been implicated in human intrauterine growth restriction (IUGR). Hypoxia severely compromised the cardiovascular system. Signs of heart failure, including loss of yolk sac circulation, hemorrhage, and edema, were caused by 18-24 h of hypoxia. Hypoxia induced ventricular dilation and myocardial hypoplasia, decreasing ventricular tissue by 50% and proliferation by 21% in vivo and by 40% in isolated cultured hearts. Epicardial detachment was the first sign of hypoxic damage in the heart, although expression of epicardially derived mitogens, such as FGF2, FGF9, and Wnt9b was not reduced. We propose that hypoxia compromises the fetus through myocardial hypoplasia and reduced heart rate.
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Affiliation(s)
- Margie Ream
- Department of Neurobiology, Box 3209, Duke University Medical Center, Durham, NC 27710, USA
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135
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Choi H, Rauh V, Garfinkel R, Tu Y, Perera FP. Prenatal exposure to airborne polycyclic aromatic hydrocarbons and risk of intrauterine growth restriction. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:658-65. [PMID: 18470316 PMCID: PMC2367680 DOI: 10.1289/ehp.10958] [Citation(s) in RCA: 151] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Accepted: 01/28/2008] [Indexed: 05/19/2023]
Abstract
BACKGROUND Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous air pollutants generated by combustion of organic material, including fossil fuel. OBJECTIVES It has been an open question whether prenatal exposure to air pollution in general and PAHs in particular significantly increases the risk of intrauterine growth restriction, including small size for gestational age (SGA), and preterm delivery. Here, we have examined this hypothesis in a cohort of mothers and newborns in New York City. METHODS Subjects were young, nonsmoking, healthy African-American (n = 224) and Dominican (n = 392) mother-newborn pairs residing in New York City whose prenatal PAH exposures were estimated by personal air monitoring. Questionnaire and medical record data were obtained. RESULTS A 1 natural-log (ln)-unit increase in prenatal PAH exposure was associated with a 2-fold increase in risk of symmetric intrauterine growth restriction (i.e., SGA and fetal growth ratio < 85%) among full-term African Americans (p < 0.05). Preterm delivery risk was 5-fold greater among African Americans per ln-unit increase in prenatal PAH exposure. The same unit increase in exposure significantly increased the ratio of head circumference to birth weight by 0.04% in African Americans. These effects were not observed in Dominicans. CONCLUSION Prenatal PAH exposure is likely to contribute to the occurrence of SGA as well as preterm births among African Americans. The lack of an association in Dominicans might reflect modification of the risk by healthful cultural practices among recent Dominican immigrants. Given that PAHs are globally generated and distributed pollutants, our observations have potential implications for environmental health and energy policies.
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Affiliation(s)
- Hyunok Choi
- Columbia Center for Children’s Environmental Health, Mailman School of Public Health, Columbia University, New York, New York, USA
| | - Virginia Rauh
- Columbia Center for Children’s Environmental Health, Mailman School of Public Health, Columbia University, New York, New York, USA
| | - Robin Garfinkel
- Columbia Center for Children’s Environmental Health, Mailman School of Public Health, Columbia University, New York, New York, USA
| | - Yihsuan Tu
- Department of Statistics, National Cheng Kung University, Tainan, Taiwan
| | - Frederica P. Perera
- Columbia Center for Children’s Environmental Health, Mailman School of Public Health, Columbia University, New York, New York, USA
- Address correspondence to F.P. Perera, Columbia University, 100 Haven Ave., #25F, Tower 3, New York, NY 10032 USA. Telephone: (212) 304-7280. Fax: (212) 544-1943. E-mail:
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Elmes MJ, McMullen S, Gardner DS, Langley-Evans SC. Prenatal diet determines susceptibility to cardiac ischaemia–reperfusion injury following treatment with diethylmaleic acid and N-acetylcysteine. Life Sci 2008; 82:149-55. [DOI: 10.1016/j.lfs.2007.10.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 10/25/2007] [Accepted: 10/25/2007] [Indexed: 11/30/2022]
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137
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Lawrence J, Xiao D, Xue Q, Rejali M, Yang S, Zhang L. Prenatal nicotine exposure increases heart susceptibility to ischemia/reperfusion injury in adult offspring. J Pharmacol Exp Ther 2007; 324:331-41. [PMID: 17947495 DOI: 10.1124/jpet.107.132175] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
In the present study we tested the hypothesis that prenatal nicotine exposure increases heart susceptibility to ischemia/reperfusion (I/R) injury in adult offspring. Nicotine was administered to pregnant rats via subcutaneous osmotic minipumps throughout gestation. Nicotine treatment resulted in a rapid and transient decrease in food-intake and a moderate decrease in maternal body weight gain. Hearts were isolated from adult male and female offspring and subjected to I/R in a Langendorff preparation. Nicotine significantly attenuated left ventricle (LV) developed pressure, heart rate, and coronary flow rate in female but not male hearts at baseline. Additionally, nicotine significantly increased LV infarct size and attenuated postischemic recovery of LV function in both male and female offspring with more pronounced effects in females. In female but not male hearts, nicotine significantly decreased the postischemic coronary flow rate. However, coronary nitric oxide release was decreased in male but not female hearts. Caspase-3, -8, and -9 levels were not significantly changed in either female or male hearts. However, nicotine caused a significant decrease in protein levels of protein kinase (PK) Cepsilon in both male and female hearts and a decrease in PKCdelta levels in female hearts only. Control studies of maternal food restriction showed that a moderate decrease in maternal body weight gain had no effect on female hearts but significantly improved postischemic recovery of LV function in male hearts. The results suggest that prenatal nicotine exposure causes in utero programming of the PKC isozyme gene expression pattern in the developing heart and increases heart susceptibility to I/R injury in adult offspring.
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Affiliation(s)
- Jennifer Lawrence
- Center for Perinatal Biology, Department of Pharmacology and Physiology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA
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138
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Elmes MJ, Gardner DS, Langley-Evans SC. Fetal exposure to a maternal low-protein diet is associated with altered left ventricular pressure response to ischaemia-reperfusion injury. Br J Nutr 2007; 98:93-100. [PMID: 17445339 DOI: 10.1017/s000711450769182x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Rats exposed to protein restriction as fetuses develop hypertension as adults. Hypertension increases the risk of myocardial ischaemia and infarction. We investigated whether rats exposed to low-protein diets in utero are more susceptible to myocardial ischaemia-reperfusion (IR) injury. Pregnant Wistar rats were fed control or low-protein (MLP) diets throughout pregnancy. At 4 and 8 weeks postnatal age systolic blood pressure was determined in the offspring using tail-cuff plethysmography. At 6 months of age, rats were treated with saline or N-acetylcysteine (NAC) for 48 h. Rapidly excised hearts were retro-perfused (Langendorff) to assess isolated cardiac function before (baseline), during 30 min ischaemia (no coronary perfusion) and for 60 min after reinstating coronary perfusion (reperfusion). Hearts were then harvested and treated appropriately for analysis of infarct size. Exposure to the MLP diet in utero significantly increased systolic blood pressure at 4 and 8 weeks of age (6-13 mmHg increase; P < 0.001) and significantly impaired recovery of left ventricular developed pressure after ischaemia at 6 months of age in male offspring only (P < 0.003). Pre-treatment with NAC prevented this impairment of recovery in MLP male offspring and improved recovery in all females. Myocardial infarct size was not different between dietary groups after IR, but NAC pre-treatment significantly reduced the degree of infarction (P < 0.001). In conclusion, an MLP diet throughout gestation significantly impairs recovery of the 6-month-old adult rat heart to IR-induced injury in a sex-specific manner. Undernutrition during development may increase susceptibility to CHD by impairing recovery from coronary events.
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Affiliation(s)
- Matthew J Elmes
- Division of Nutritional Sciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, UK.
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Ostadal B, Kolar F. Cardiac adaptation to chronic high-altitude hypoxia: beneficial and adverse effects. Respir Physiol Neurobiol 2007; 158:224-36. [PMID: 17442631 DOI: 10.1016/j.resp.2007.03.005] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Revised: 03/06/2007] [Accepted: 03/06/2007] [Indexed: 01/28/2023]
Abstract
This review deals with the capability of the heart to adapt to chronic hypoxia in animals exposed to either natural or simulated high altitude. From the broad spectrum of related issues, we focused on the development and reversibility of both beneficial and adverse adaptive myocardial changes. Particular attention was paid to cardioprotective effects of adaptation to chronic high-altitude hypoxia and their molecular mechanisms. Moreover, interspecies and age differences in the cardiac sensitivity to hypoxia-induced effects in various experimental models were emphasized.
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Affiliation(s)
- B Ostadal
- Centre for Cardiovascular Research, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
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