Summary Uterine vascular tone significantly decreases while uterine blood flow dramatically increases during pregnancy. However, the complete molecular mechanisms remain elusive. We hypothesized that increased BKCa channel activity contributes to the decreased myogenic tone of uterine arteries in pregnancy. Resistance-sized uterine arteries were isolated from nonpregnant and near-term pregnant sheep. Electrophysiological studies revealed a greater whole-cell K+ current density in pregnant than nonpregnant uterine arteries. Tetraethylammonium and iberoitoxin inhibited K+ currents to the same extent in uterine arterial myocytes. The BKCa channel current density was significantly increased in pregnant uterine arteries. In accordance, tetraethylammonium significantly increased pressure-induced myogenic tone in pregnant uterine arteries and abolished the difference in myogenic responses between pregnant and nonpregnant uterine arteries. Activation of protein kinase C produced a similar effect to tetraethylammonium by inhibiting BKCa channel activity and increasing myogenic tone in pregnant uterine arteries. Chronic treatment of nonpregnant uterine arteries with physiologically relevant concentrations of 17β-estradiol and progesterone caused a significant increase in the BKCa channel current density. Western blot analyses demonstrated a significant increase of the β1, but not α, subunit of BKCa channels in pregnant uterine arteries. In accordance, steroid treatment of nonpregnant uterine arteries resulted in an upregulation of the β1, but not α, subunit expression. The results indicate that the steroid hormone-mediated upregulation of the β1 subunit and BKCa channel activity may play a key role in attenuating myogenic tone of the uterine artery in pregnancy.

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 (PKC) 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-phosphateguanine dinucleotides at the PKC promoter is repressive and contributes to PKC 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 PKC 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 PKC 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 PKC 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 PKC mRNA was seen only in males. In fetal hearts, there was significantly higher abundance of estrogen receptor ␣ and ␤ isoforms in females than in males. Both estrogen receptor ␣ and ␤ 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 PKC restored the hypoxia-induced cardiac vulnerability to ischemic injury in offspring. Key Words: fetal heart Ⅲ PKC Ⅲ hypoxia Ⅲ epigenetics Ⅲ DNA methylation H eart disease is the leading cause of death in the United States. In addition to other risk factors, recent epidemiological and animal studies have shown a clear association of adverse intrauterine environment with an increased risk of hypertension and ischemic heart disease in adulthood. [1][2][3][4] Hypoxia is a common form of intrauterine stress, and the fetus may experience prolonged hypoxic stress under a variety of conditions, including pregnancy at high altitude, pregnancy with anemia, placental insufficiency, cord compression, preeclampsia, heart, lung and kidney disease, or with hemoglobinopathy. Animal studies suggest a possible link between fetal hypoxia and increased risk of cardiovascular disease in offspring. [5][6][7][8][9][10][11][12][13] Studies in rats have demonstrated that maternal hypoxia results in an increase in cardiac vulnerability to ischemia and reperfusion injury in m...

Abstract-Epidemiological studies suggest that maternal cigarette smoking is associated with an increased risk of elevated blood pressure (BP) in postnatal life. The present study tested the hypothesis that prenatal nicotine exposure causes an increase in BP response to angiotensin II (Ang II) in adult offspring. Nicotine was administered to pregnant rats via subcutaneous osmotic minipumps throughout the gestation. BP and vascular responses to Ang II were measured in 5-month-old adult offspring. Prenatal nicotine had no effect on baseline BP but significantly increased Ang II-stimulated BP in male but not female offspring. The baroreflex sensitivity was significantly decreased in both male and female offspring. Prenatal nicotine significantly increased arterial media thickness in male but not female offspring.In male offspring, nicotine exposure significantly increased Ang II-induced contractions of aortas and mesenteric arteries. These responses were not affected by inhibition of endothelial NO synthase activity. Losartan blocked Ang II-induced contractions in both control and nicotine-treated animals. In contrast, PD123319 had no effect on Ang II-induced contractions in control but inhibited them in nicotine-treated animals. Nicotine significantly increased Ang II type 1 receptor but decreased Ang II type 2 receptor protein levels, resulting in a significant increase in the ratio of Ang II type 1 receptor/Ang II type 2 receptor in the aorta. Furthermore, the increased contractions of mesenteric arteries were mediated by increases in intracellular Ca 2ϩ concentrations and Ca 2ϩ sensitivity. These results suggest that prenatal nicotine exposure alters vascular function via changes in Ang II receptor-mediated signaling pathways in adult offspring in a gender-specific manner, which may lead to an increased risk of hypertension in male offspring. Key Words: nicotine Ⅲ fetal programming Ⅲ gender Ⅲ angiotensin II Ⅲ vascular contractility M aternal cigarette smoking probably is the single most widespread prenatal insult in the world. Recent epidemiological studies have demonstrated that in utero exposure to maternal smoking is associated with elevated blood pressure (BP) and/or cardiovascular disease in offspring later in life. 1,2 As one of the major components in cigarette smoking, nicotine is likely to contribute to the developmental programming of cardiovascular disorders. Nicotine readily crosses the placenta, and maternal cigarette smoking produces higher nicotine concentrations in fetal circulation than that experienced by the mother. 3,4 In the developing fetus, chronic nicotine exposure resulted in permanent changes in nicotinic receptors and alterations in the activity of the central and peripheral nervous systems. 5 Our recent studies in the rat have demonstrated that fetal nicotine exposure causes reprogramming of vascular reactivity and produces genderdependent alterations in both ␣ 1 -adrenoceptor-mediated contractions and endothelial NO synthase (eNOS) activity of arteries in adult offspring. 6 In additi...

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) C in both male and female hearts and a decrease in PKC␦ 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.Epidemiological studies have demonstrated that in utero exposure to maternal cigarette smoking is a significant risk factor for sudden infant death syndrome and is associated with elevated blood pressure and cardiovascular disease in offspring later in life (Beratis et al., 1996;Blake et al., 2000). As one of the major components in cigarette smoking, nicotine is likely to contribute to the development of cardiovascular disorders. Nicotine readily crosses the placenta and maternal cigarette smoking produces higher nicotine concentrations in fetal circulation than that experienced by the mother (Lambers and Clark, 1996). Because nicotine is an agonist of nicotinic acetylcholine receptors, exposure to nicotine early in life may cause permanent changes in nicotinic receptors and consequent cell function (Slotkin, 1998). We have recently demonstrated that fetal and neonatal nicotine exposure alters vascular function in adult offspring in a gender-specific manner, which may lead to an increased risk of cardiovascular dysfunction in adult life (Xiao et al., 2007).The effects of prenatal nicotine exposure on fetal heart development and their long-term pathophysiological consequences in the adult heart have not been determined. Human epidemiological studies suggested a link between adverse intrauterine environme...

Our previous study demonstrated that increased Ca2+-activated K+ (BKCa) channel activity played a key role in the normal adaptation of reduced myogenic tone of uterine arteries in pregnancy. The present study tested the hypothesis that chronic hypoxia during gestation inhibits pregnancy-induced upregulation of BKCa channel function in uterine arteries. Resistance-sized uterine arteries were isolated from nonpregnant and near-term pregnant sheep maintained at sea level (≈300 m) or exposed to high-altitude (3801 m) hypoxia for 110 days. Hypoxia during gestation significantly inhibited pregnancy-induced upregulation of BKCa channel activity and suppressed BKCa channel current density in pregnant uterine arteries. This was mediated by a selective downregulation of BKCa channel β1 subunit in the uterine arteries. In accordance, hypoxia abrogated the role of the BKCa channel in regulating pressure-induced myogenic tone of uterine arteries that was significantly elevated in pregnant animals acclimatized to chronic hypoxia. In addition, hypoxia abolished the steroid hormone-mediated increase in the β1 subunit and BKCa channel current density observed in nonpregnant uterine arteries. Although the activation of protein kinase C inhibited BKCa channel current density in pregnant uterine arteries of normoxic sheep, this effect was ablated in the hypoxic animals. The results demonstrate that selectively targeting BKCa channel β1 subunit plays a critical role in the maladaption of uteroplacental circulation caused by chronic hypoxia, which contributes to the increased incidence of preeclampsia and fetal intrauterine growth restriction associated with gestational hypoxia.

The results demonstrate that hypoxia induces epigenetic repression of the PKCε gene through a NADPH oxidase-independent ROS-mediated pathway in the foetal heart, leading to heightened heart vulnerability to ischaemic injury in offspring.

this study demonstrates that prolonged nicotine exposure increases the sympathetic neurotransmitter release in the foetal heart and causes programming of PKCε gene repression through promoter methylation, linking maternal smoking to pathophysiological consequences in the offspring heart.

Abstract-Previous studies in ovine uterine arteries have demonstrated that sex steroid hormones upregulate extracellular signal-regulated kinase 1/2 expression and downregulate the protein kinase C signaling pathway, resulting in the attenuated myogenic tone in pregnancy. The present study tested the hypothesis that chronic hypoxia during gestation inhibits the sex steroid-mediated adaptation of extracellular signal-regulated kinase 1/2 and protein kinase C signaling pathways and increases the myogenic tone of uterine arteries. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep that had been maintained at sea level (Ϸ300 m) or exposed to high-altitude (3801 m) hypoxia for 110 days. In contrast to the previous findings in normoxic animals, 17␤-estradiol and progesterone failed to suppress protein kinase C-induced contractions and the pressure-induced myogenic tone in uterine arteries from hypoxic animals. Western analyses showed that the sex steroids lost their effects on extracellular signal-regulated kinase 1/2 expression and phospho-extracellular signal-regulated kinase 1/2 levels, as well as the activation of protein kinase C isozymes in uterine arteries of hypoxic ewes. In normoxic animals, pregnancy and the sex steroid treatments significantly increased uterine artery estrogen receptor-␣ and progesterone receptor B expression. Chronic hypoxia selectively downregulated estrogen receptor-␣ expression in uterine arteries of pregnant animals and eliminated the upregulation of estrogen receptor-␣ in pregnancy or by the steroid treatments observed in normoxic animals. The results demonstrate that, in the ovine uterine artery, chronic hypoxia in pregnancy inhibits the sex steroid hormone-mediated adaptation of decreased myogenic tone by downregulating estrogen receptor-␣ expression, providing a mechanism linking hypoxia and maladaptation of uteroplacental circulation and an increased risk of preeclampsia in pregnancy. (Hypertension. 2010;56:750-757.)Key Words: hypoxia Ⅲ pregnancy Ⅲ steroids Ⅲ uterine artery Ⅲ myogenic tone P regnancy is associated with a significant decrease in uterine vascular tone and an increase in uterine blood flow to meet the increasing metabolic demands of the mother and developing fetus. Pressure-dependent myogenic contraction is an important physiological mechanism in regulating basal vascular tone and organ blood flow, and decreased pressure-induced myogenic responses of the uterine arteries contribute significantly to the adaptation of uterine vascular hemodynamics in pregnancy. [1][2][3][4][5] Recently, we have demonstrated a direct genomic effect of the sex steroid hormones, estrogen and progesterone, in upregulating the extracellular signal-regulated kinase (ERK) 1/2 expression and downregulating protein kinase C (PKC) signaling pathway, resulting in the attenuated myogenic tone of uterine arteries in pregnancy. 6 Several studies in animal models suggest that a chronic reduction of uteroplacental perfusion leads to the characteristics of preeclampsia found...