Regulatory Mechanisms of Uterine Artery Contractility : Effect of Pregnancy

Regulation of uterine blood flow during pregnancy is important not only for the growth and survival of the fetus but also for cardiovascular well-being of the mother. Pregnancy is associated with a significant decrease in uterine artery vascular tone and a dramatic increase in uterine blood flow. Previous studies have been focused on adaptation of the endothelium to pregnancy and indicated that increased NO sythesis/release plays an important role in vasodilation of the uterine artery in pregnancy. However, little is known about the adaptation of contractile mechanisms of the uterine artery to pregnancy. The central hypothesis of the proposed studies is that extracellular signal-regulated kinase (ERK) and protein kinase C (PKC) pathways interact in the regulation of uterine artery contractility and play an important role in the adaptation of uterine artery contractile mechanisms to pregnancy. To test this hypothesis, we propose a series of experiments in the uterine arteries obtained from nonpregnant and near-term (~140 Days) pregnant sheep. We found that ERK plays an important role in the regulation of uterine artery contractility, and its effect is agonist-dependent. More importantly, pregnancy selectively enhances the role of ERK in α1-adrenoceptor-mediated contractions and its effect in suppressing protein kinase C-mediated contraction in the uterine artery. Our data indicate that ERK potentiates the thick filament regulatory pathway by enhancing LC20 phosphorylation via increases in [Ca2+] and Ca2+ sensitivity of LC20 phosphorylation. In contrast, ERK attenuates the thin filament regulatory pathway, and suppresses contractions independent of changes in LC20 phosphorylation in the uterine artery. We also found that pregnancy upregulates α1-adrenoceptor-mediated Ca2+ mobilization and LC20 phosphorylation. In contrast, pregnancy downregulates the Ca2+ sensitivity of myofilaments, which is medicated by both thick and then filament pathways. ERK inhibitor, PD098059 significantly inhibited ERK44/42, MYPT1/Thr850 phosphorylation but not MYPT1/Thr696 and CPI-17/Thr38. It suggests that ERK mediated Ca2+ sensitivity is due to, at least, partly though inhibition of MLCP activity. On the other hand, activation of PKC by PDBu results increase in CPI-17/Thr38 phosphorylation and contraction without changes in LC20 phosphorylation. These results imply that PKC-CPI-17-mediated Ca2+ sensitivity of contraction might be through thin filament pathway in the uterine artery

Cardiovascular Adaptation to High-Altitude Hypoxia

High-altitude exposure has been well recognized as a hypoxia exposure that significantly affects cardiovascular function. However, the pathophysiologic adaptation of cardiovascular system to high-altitude hypoxia (HAH) varies remarkably. It may depend on the exposed time and oxygen partial pressure in the altitude place. In short-term HAH, cardiovascular adaptation is mainly characterized by functional alteration, including cardiac functional adjustments, pulmonary vascular constriction, transient pulmonary hypertension, and changes in cerebral blood flow (CBF). These changes may be explained mainly by ventilatory acclimatization and variation of autonomic nervous activity. In long-term HAH, cardiovascular adaptation is mainly characterized by both functional and structural alterations. These changes include right ventricle (RV) hypertrophy, persistent pulmonary hypertension, lower CBF and reduced uteroplacental and fetal volumetric blood flows

Therapeutic Implication of miRNA in Human Disease

MicroRNAs (miRNAs) are a class of short non-coding RNA molecules that are involved in development and diseases. Early studies are focusing on the miRNA profile as a biomarker in disease. As discovery of human miRNAs increased in the setting of disease, the research focus was gradually shifted towards miRNA therapeutic strategy for diagnostic and treatment of disease. Increasing evidences suggest that miRNAs are the next important class of antisense therapeutic molecules, which have significant advantage over antisense such as siRNAs because miRNAs are naturally occurring endogenous molecules. Aberrant alteration of the endogenous miRNAs has been linked to the development of certain diseases. Correcting these altered miRNAs by their mimics or inhibitors has been developed as potential therapeutic approaches. Some of the miRNA-based therapeutics are processed in preclinical and clinical trial for treatment hepatitis C, liver cancer, and other diseases. Currently, the major focus in the development of miRNA-based therapeutics is how to increase the miRNA stability and optimize delivery systems for specific disease with minimal off-target effect. This chapter will first overview the miRNA biogenesis, patho- and physiologic function, and regulation of miRNA molecules. Then, we discuss the miRNA-based potential therapeutic approaches and implication in disease

Effect of cGMP on Pharmacomechanical Coupling in the Uterine Artery of Near-Term Pregnant Sheep

ABSTRACT The present study examined the role of cGMP in the regulation of ␣ 1 -adrenoceptor-mediated pharmacomechanical coupling in the uterine artery of near-term pregnant sheep. The cellpermeable cGMP analog 8-bromo-cGMP produced a dosedependent relaxation of the uterine artery and shifted norepinephrine (NE) dose-response curve to the right with a decreased maximal contraction. Accordingly, 8-bromo-cGMP significantly decreased the potency and the maximal response of NEinduced inositol 1,4,5-trisphosphate (IP 3 ) synthesis in the uterine artery. In addition, 8-bromo-cGMP significantly reduced the binding affinity of IP 3 to the IP 3 receptor. The uterine circulation during pregnancy functions as a low-resistance shunt to accommodate the large increase of uteroplacental blood flow required for normal fetal development. The mechanisms in maintaining the low uterine vascular tone in pregnancy are complex and not fully understood. A number of studies in humans and animals have demonstrated that endothelial nitric oxide plays an important role in maintaining low vascular resistance of the uterine circulation in pregnancy Whereas it is clear that cGMP is the mediator of NOdependent vasorelaxation, it is unknown whether and to what extent cGMP regulates vasoconstrictor-mediated contractions of the uterine artery in pregnancy. In vivo studies in pregnant sheep have demonstrated attenuated vasoconstriction of the uterine artery to norepinephrine and angiotensin I

Epigenetic Down-Regulation of Sirt 1 via DNA Methylation and Oxidative Stress Signaling Contributes to the Gestational Diabetes Mellitus-Induced Fetal Programming of Heart Ischemia-Sensitive Phenotype in Late Life.

Rationale: The incidence of gestational diabetes mellitus (GDM) is increasing worldwide. However, whether and how GDM exposure induces fetal programming of adult cardiac dysfunctional phenotype, especially the underlying epigenetic molecular mechanisms and theranostics remain unclear. To address this problem, we developed a late GDM rat model. Methods: Pregnant rats were made diabetic on day 12 of gestation by streptozotocin (STZ). Experiments were conducted in 6 weeks old offspring. Results: There were significant increases in ischemia-induced cardiac infarction and gender-dependent left ventricular (LV) dysfunction in male offspring in GDM group as compared to controls. Exposure to GDM enhanced ROS level and caused a global DNA methylation in offspring cardiomyocytes. GDM attenuated cardiac Sirt 1 protein and p-Akt/Akt levels, but enhanced autophagy-related proteins expression (Atg 5 and LC3 II/LC3 I) as compared to controls. Ex-vivo treatment of DNA methylation inhibitor, 5-Aza directly inhibited Dnmt3A and enhanced Sirt 1 protein expression in fetal hearts. Furthermore, treatment with antioxidant, N-acetyl-cysteine (NAC) in offspring reversed GDM-mediated DNA hypermethylation, Sirt1 repression and autophagy-related gene protein overexpression in the hearts, and rescued GDM-induced deterioration in heart ischemic injury and LV dysfunction. Conclusion: Our data indicated that exposure to GDM induced offspring cardiac oxidative stress and DNA hypermethylation, resulting in an epigenetic down-regulation of Sirt1 gene and aberrant development of heart ischemia-sensitive phenotype, which suggests that Sirt 1-mediated signaling is the potential therapeutic target for the heart ischemic disease in offspring

Inhibition of Autophagy Signaling via 3-methyladenine Rescued Nicotine-Mediated Cardiac Pathological Effects and Heart Dysfunctions.

Rationale: Cigarette smoking is a well-established risk factor for myocardial infarction and sudden cardiac death. The deleterious effects are mainly due to nicotine, but the mechanisms involved and theranostics remain unclear. Thus, we tested the hypothesis that nicotine exposure increases the heart sensitivity to ischemia/reperfusion injury and dysfunction, which can be rescued by autophagy inhibitor. Methods: Nicotine or saline was administered to adult rats via subcutaneous osmotic minipumps in the absence or presence of an autophagy inhibitor, 3-methyladenine (3-MA). After 30 days of nicotine treatment, the rats underwent the cardiac ischemia/reperfusion (I/R) procedure and echocardiography analysis, and the heart tissues were isolated for molecular biological studies. Results: Nicotine exposure increased I/R-induced cardiac injury and cardiac dysfunction as compared to the control. The levels of autophagy-related proteins including LC3 II, P62, Beclin1, and Atg5 were upregulated in the reperfused hearts isolated from nicotine-treated group. In addition, nicotine enhanced cardiac and plasma ROS production, and increased the phosphorylation of GSK3β (ser9) in the left ventricle tissues. Treatment with 3-MA abolished nicotine-mediated increase in the levels of autophagy-related proteins and phosphorylation of GSK3β, but had no effect on ROS production. Of importance, 3-MA ameliorated the augmented I/R-induced cardiac injury and dysfunction in the nicotine-treated group as compared to the control. Conclusion: Our results demonstrate that nicotine exposure enhances autophagy signaling pathway, resulting in development of ischemic-sensitive phenotype of heart. It suggests a potentially novel therapeutic strategy of autophagy inhibition for the treatment of ischemic heart disease

Repression of the Glucocorticoid Receptor Aggravates Acute Ischemic Brain Injuries in Adult Mice.

Strokes are one of the leading causes of mortality and chronic morbidity in the world, yet with only limited successful interventions available at present. Our previous studies revealed the potential role of the glucocorticoid receptor (GR) in the pathogenesis of neonatal hypoxic-ischemic encephalopathy (HIE). In the present study, we investigate the effect of GR knockdown on acute ischemic brain injuries in a model of focal cerebral ischemia induced by middle cerebral artery occlusion (MCAO) in adult male CD1 mice. GR siRNAs and the negative control were administered via intracerebroventricular (i.c.v.) injection 48 h prior to MCAO. The cerebral infarction volume and neurobehavioral deficits were determined 48 h after MCAO. RT-qPCR was employed to assess the inflammation-related gene expression profiles in the brain before and after MCAO. Western Blotting was used to evaluate the expression levels of GR, the mineralocorticoid receptor (MR) and the brain-derived neurotrophic factor/tropomyosin receptor kinase B (BDNF/TrkB) signaling. The siRNAs treatment decreased GR, but not MR, protein expression, and significantly enhanced expression levels of pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α) in the brain. Of interest, GR knockdown suppressed BDNF/TrkB signaling in adult mice brains. Importantly, GR siRNA pretreatment significantly increased the infarction size and exacerbated the neurobehavioral deficits induced by MCAO in comparison to the control group. Thus, the present study demonstrates the important role of GR in the regulation of the inflammatory responses and neurotrophic BDNF/TrkB signaling pathway in acute ischemic brain injuries in adult mice, revealing a new insight into the pathogenesis and therapeutic potential in acute ischemic strokes

Upregulation of Bax and Bcl-2 following prenatal cocaine exposure induces apoptosis in fetal rat brain

<p>Cocaine abuse during pregnancy has been associated with numerous adverse perinatal outcomes. <b>Aims: </b>The present study was to determine whether prenatal cocaine exposure induced apoptosis and the possible role of Bcl-2 family genes in the programming cell death in fetal rat brain. <b>Main methods:</b> Pregnant rats were treated with cocaine subcutaneously (30 &#38; 60 mg/kg/day) from day 15 to 21 of gestation. Then the fetal and maternal brains were isolated. <b>Key findings:</b> Cocaine produced a dose-dependent decrease in fetal brain weight and brain/body weight ratio (P&#60;0.05). Apoptotic nuclei in fetal brain were increased from 2.6 &#177; 0.1 (control) to 8.1&#177; 0.6 (low dose) and 10.4 &#177; 0.2% (high dose) (P&#60;0.05). In accordance, cocaine dose dependently increased activities of caspase-3, caspase-8, and caspase-9 (% of control) in the fetal brain by 177%, 155%, 174%, respectively, at 30 mg/kg/day, and by 191%, 176%, 274%, respectively, at 60 mg/kg/day. In contrast, cocaine showed no effect on caspase activities in the maternal brain. Cocaine produced a dose-dependent increase in both Bcl-2 and Bax protein expression in the fetal brain, and increased the ratio of Bax/Bcl-2 at dose of 30 mg/kg/day (P&#60;0.05). <b>Significance: </b>Our study has demonstrated that prenatal cocaine exposure induces apoptosis in the fetal brain, and suggested that up-regulating Bax/Bcl-2 gene expression may be involved in cocaine-induced apoptosis. The increased apoptosis of neuronal cells in the fetal brain is likely to play a key role in cocaine-induced neuronal defects during fetal development.</p

Estrogen Regulates Angiotensin II Receptor Expression Patterns and Protects the Heart from Ischemic Injury in Female Rats.

Previous studies have shown that female offspring are resistant to fetal stress-induced programming of ischemic-sensitive phenotype in the heart; however, the mechanisms responsible remain unclear. The present study tested the hypothesis that estrogen plays a role in protecting females in fetal programming of increased heart vulnerability. Pregnant rats were divided into normoxic and hypoxic (10.5% O2 from Day 15 to 21 of gestation) groups. Ovariectomy (OVX) and estrogen (E2) replacement were performed in 8-wk-old female offspring. Hearts of 4-mo-old females were subjected to ischemia and reperfusion injury in a Langendorff preparation. OVX significantly decreased postischemic recovery of left ventricular function and increased myocardial infarction, and no difference was observed between normoxic and hypoxic groups. The effect of OVX was rescued by E2 replacement. OVX decreased the binding of glucocorticoid receptor (GR) to glucocorticoid response elements at angiotensin II type 1 (Agtr1) and type 2 (Agtr2) receptor promoters, resulting in a decrease in Agtr1 and an increase in Agtr2 in the heart. Additionally, OVX decreased estrogen receptor (ER) expression in the heart and inhibited ER/GR interaction in binding to glucocorticoid response elements at the promoters. Consistent with the changes in Agtrs, OVX significantly decreased Prkce abundance in the heart. These OVX-induced changes were abrogated by E2 replacement. The results indicate that estrogen is not directly responsible for the sex dimorphism in fetal programming of heart ischemic vulnerability but suggest a novel mechanism of estrogen in regulating cardiac Agtr1/Agtr2 expression patterns and protecting female hearts against ischemia and reperfusion injury