Functional characterization of the muscarinic receptors involved in endothelium-dependent relaxation in isolated canine uterine artery

Endothelium-Derived Dopamine and 6-Nitrodopamine in the Cardiovascular System

The review deals with the release of endothelium-derived dopamine and 6-nitrodopamine (6-ND) and its effects on isolated vascular tissues and isolated hearts. Basal release of both dopamine and 6-ND is present in human isolated umbilical cord vessels, human popliteal vessels, nonhuman primate vessels, and reptilia aortas. The 6-ND basal release was significantly reduced when the tissues were treated with Nω-nitro-l-arginine methyl ester and virtually abolished when the endothelium was mechanically removed. 6-Nitrodopamine is a potent vasodilator, and the mechanism of action responsible for this effect is the antagonism of dopamine D2-like receptors. As a vasodilator, 6-ND constitutes a novel mechanism by which nitric oxide modulates vascular tone. The basal release of 6-ND was substantially decreased in endothelial nitric oxide synthase knockout (eNOS-/-) mice and not altered in neuronal nitric oxide synthase knockout (nNOS-/-) mice, indicating a nonneurogenic source for 6-ND in the heart. Indeed, in rat isolated right atrium, the release of 6-ND was not affected when the atria were treated with tetrodotoxin. In the rat isolated right atrium, 6-ND is the most potent endogenous positive chronotropic agent, and in Langendorff's heart preparation, it is the most potent endogenous positive inotropic agent. The positive chronotropic and inotropic effects of 6-ND are antagonized by β1-adrenoceptor antagonists at concentrations that do not affect the effects induced by noradrenaline, adrenaline, and dopamine, indicating that blockade of the 6-ND receptor is the major modulator of heart chronotropism and inotropism. The review proposes that endothelium-derived catecholamines may constitute a major mechanism for control of vascular tone and heart functions, in contrast to the overrated role attributed to the autonomic nervous system.

Doppler ultrasonographic evaluation of medically treated female dogs with cystic endometrial hyperplasia-pyometra complex

Monitoring the treatment outcome of canine cystic endometrial hyperplasia-pyometra complex (CEH-P) is essential to identify nonresponding patients who might require a rapid intervention to avoid life-threatening conditions. Uterine artery Doppler characterization may contribute to monitoring medically treated CEH-P, but published studies are currently lacking. Therefore, the aim of this longitudinal prospective observational study was to evaluate uterine artery resistance changes in the medical treatment of female dogs with CEH-P. Twelve diestrous female dogs suffering from CEH-P were treated with a combined protocol of cabergoline, cloprostenol, and antibiotics. The animals were clinically and ultrasonographically evaluated before the beginning of treatment (day 0) and on days 3, 7, 14, 21, and 28. The widest transverse diameter and luminal diameter of uterine horns were measured, as well as the peak systolic velocity (PSV) and end diastolic velocity (EDV) of uterine arteries. The resistance index (RI), pulsatility index (PI), and notch deep index (NDI) were calculated. On day 3, nine of 12 animals showed clinical improvement. In all these female dogs, the widest transverse sectional diameter (P < 0.01), luminal diameter (P < 0.01), PSV (P < 0.01), and EDV (P < 0.01) progressively decreased, while RI (P < 0.01), PI (P < 0.01), and NDI (P < 0.01) increased up to day 21. In nonresponding dogs (3/12), Doppler parameters remained unchanged. Although comparisons of PSV, EDV, and NDI were significantly different, these results should be cautiously interpreted due to the low statistical power. female dogs that responded to this treatment showed an increase in uterine artery resistance, along with clinical and ultrasonographic improvement.

Effects of oleuropein on rat's atria and thoracic aorta: a study of antihypertensive mechanisms

Oleuropein (OLE) is the main bioactive ingredient in the leaves of the olive plant Olea europaea L. (Oleaceae), which has proven beneficial due to the antiinflammatory, antiatherogenic, anticancer, antimicrobial, and antiviral effects. This study aimed to investigate the antihypertensive and vasodilator potential of OLE by analyzing its acute effects on spontaneous atrial contractions and vasomotor responses of the isolated thoracic aorta in rats. We showed that the application of OLE induces negative chronotropic and inotropic effects on the heart. OLE also causes mild aortic vasodilation given that the maximal reduction in tension of intact aortic rings precontracted with phenylephrine was approximately 30%. This vasodilation is likely dependent on the nitric oxide released from the endothelium based on the effect obtained on denuded and phenylephrine precontracted aortic rings and responses reordered following vasoconstriction induced by high concentrations of K⁺ and heparin. Our findings provide a basis for further testing of OLE cardiovascular effects, which may lead to subsequent clinical research for its application in the treatment of hypertension and heart disease.

Escherichia Coli -induced Inflammation Changes the Expression of Acetylcholine Receptors (M2R, M3R, and α-7 nAChR) in the Pig Uterus

Introduction

The influence of inflammation on the patterns of muscarinic 2 and 3 receptor subtypes (M2R and M3R), and α-7 nicotinic acetylcholine receptor (α-7 nAChR) expression in the porcine uterus was investigated.

Material and Methods

On day three of the oestrous cycle of gilts aged 7-8 months with body weight 90-120 kg, either an E. coli suspension (E. coli group, n = 5) or saline (Sal group, n = 5) was administered into the uterine horns via laparotomy or only laparotomy was performed on control swine (Ctrl group, n = 5). After eight days, and the onset of severe acute endometritis in the E. coli group, the uterine mRNA and protein receptor expression levels were determined using real-time RT-PCR and Western blotting, respectively, with receptor localisation by immunofluorescence.

Results

The studied receptors were in the luminal epithelium, glands, blood vessels, and myometrial muscle cells of all gilts. The M2R mRNA level was lower in the inflamed endometrium compared to the Ctrl and Sal groups. Also in this tissue, the expression of M3R mRNA and protein was lower than in the Ctrl and Sal groups. The M3R protein level in the bacterially challenged myometrium was found to be increased compared to unadministered groups. In the endometrium of the E. coli group, the α-7 nAChR protein level was lower than in the Sal group, and in the myometrium it was reduced in relation to both the other groups. P values were ≤ 0.05 in all cases.

Conclusion

Inflammation causes alterations in the M2R, M3R, and α-7 nAChR expression in the pig uterus, suggesting their significance in the course and repercussions of uterine inflammation.

The role of α2-adrenergic receptors in hypertensive preeclampsia: A hypothesis

Preeclampsia, a major disorder of human pregnancy, manifests as persistent hypertension and proteinuria presenting after 20 weeks of pregnancy. Multiple systemic symptoms might be associated with preeclampsia including thrombocytopenia, liver impairment, pulmonary edema, and cerebral disturbances. However, vascular dysfunction remains the core pathological driver of preeclampsia. Defective placental implantation followed by dysfunctional placental spiral artery development promotes a hypoxic environment. Massive endothelial dysfunction characterized by reduced vasodilation, augmented vasoconstriction, and increased vascular permeability and inflammation ensues. Interestingly, the same signaling and inflammatory pathways implicated in preeclampsia appear to be shared with other vascular disorders involving alteration of α₂ -AR function. The role of α₂ -ARs in the regulation of microcirculatory function has long been recognized, thus raising the question of whether they are involved in the pathogenesis of vascular dysfunction in preeclampsia. Here, we review possible interplay between signaling and inflammatory pathways common to preeclampsia and α₂ -AR function/regulation. We speculate on the potential contribution of these receptors to the observed phenotype and the potential role for their pharmacological modulators as therapeutic interventions with preeclampsia.

New conception for the development of hypertension in preeclampsia

Placental vascular dysfunction was suggested to be critical for placental ischemia-initiated hypertension in preeclampsia, although the contributions of endothelium involved are unclear. The present study found, unlike non-placental vessels, acetylcholine showed no vasodilatation effect on placental vessels, indicating that endothelial-derived nitric oxide (NO) was extremely weak in placental vessels. Placental vascular responses to exogenous NO from sodium nitroprusside (SNP) were significantly different from non-placental vessels. These results were further confirmed in sheep, and rat vessels. In preeclamptic placental vessels, acetylcholine also showed no vasodilatation effects, while vascular responses to SNP were suppressed, associated with impaired cGMP/sGC pathway in vascular smooth muscle cells (VSMCs). The current theory on placental ischemia-initiated hypertension in preeclampsia focused on changes in placental vascular functions, including endothelial dysfunction. This study found the placental endothelium contributed very poorly to vasodilatation, and altered vascular functions in preeclampsia mainly occurred in VSMCs instead of endothelial cells. The findings contribute importantly to understanding the special feature of placental vascular functions and its pathophysiological changes in the development of hypertension in preeclampsia.

What is precise pathophysiology in development of hypertension in pregnancy? Precision medicine requires precise physiology and pathophysiology

It is widely accepted that placental ischemia is central in the evolution of hypertension in pregnancy. Many studies and reviews have targeted placental ischemia to explain mechanisms for initiating pregnancy hypertension. The placenta is rich in blood vessels, which are the basis for developing placental ischemia. However, is the physiology of placental vessels the same as that of nonplacental vessels? What is the pathophysiology of placental vessels in development of pregnancy hypertension? This review aims to provide a comprehensive summary of special features of placental vascular regulations and the pathophysiological changes linked to preeclamptic conditions. Interestingly, some popular theories or accepted concepts could be based on our limited knowledge and evidence regarding placental vascular physiology, pharmacology and pathophysiology. New views raised could offer interesting ideas for future investigation of mechanisms as well as targets for pregnancy hypertension.

Role of muscarinic receptors in the contraction of jejunal smooth muscle in the horse: An in vitro study

Nonselective antimuscarinic drugs are clinically useful in several pathologic conditions of horses, but, blocking all muscarinic receptor (MR) subtypes, may cause several side effects. The availability of selective antimuscarinic drugs could improve therapeutic efficacy and safety. We aimed to enlighten the role of different MR subtypes by evaluating the effects of nonselective, and selective M₁, M₂ and M₃ MR antagonists on the contractions of horse jejunum. Segments of circular muscle of equine jejunum, were put into organ baths, connected to isotonic transducers, and the effects on ACh concentration-response curves, and on electrical field stimulation (EFS)-evoked contractions of intestinal preparations, induced by nonselective or selective MR antagonists, compared to pre-drug level, were studied. Atropine (nonselective MR antagonist), pirenzepine (selective M₁ antagonist), and p-FHHSiD (selective M₃ antagonist) competitively antagonized ACh (pA₂=9.78±0.21; 7.14±0.25 and 7.56±0.17, respectively). Methoctramine (selective M₂ antagonist) antagonized ACh in a concentration-unrelated fashion; however, it competitively antagonized carbachol, a nonselective muscarinic agonist (pA₂=6.42±0.23). Atropine dose-dependently reduced EFS-evoked contractions, reaching a maximal effect of -45.64±6.54%; the simultaneous block of neurokinin receptors, almost completely abolished the atropine-insensitive contractions. p-FHHSiD dose-dependently reduced EFS-induced contractions, while pirenzepine caused a minor decrease. Methoctramine, ineffective up to 10^-7M, enhanced the contractions at 10^-6M; the block of neurokinin receptors abolished the increase of contraction. Cholinergic contractions of horse jejunum are mainly mediated by M₃ receptors; M₂ selective antagonists seem to scarcely affect cholinergic, and to enhance neurokininergic contractions of equine jejunum, thus their use entails a lower risk of causing intestinal hypomotility, compared to nonselective drugs.

Muscarinic-mediated vasoconstriction in human, rat and sheep umbilical cords and related vasoconstriction mechanisms

OBJECTIVE

The umbilical cord provides nutrition and oxygen to the fetus. The aim of this study was to determine the effects of acetylcholine (ACh) on umbilical cords from humans and other mammals, and the mechanisms of ACh-mediated vasoconstriction in the human umbilical cord.

DESIGN

Human and animal umbilical cords used in vascular and cellular experiments.

SETTING

Institute for Fetology, First Hospital of Soochow University, Suzhou, China.

POPULATION

A total of 85 pregnant women, 16 Sprague Dawley rats and seven pregnant sheep.

METHODS

Umbilical cord veins and arteries from humans, rats and sheep, aortas and mesenteric arteries from rats, and mesenteric, carotid and femoral arteries from ovine fetuses were used to compare vascular functions in response to ACh and to determine the mechanisms of ACh-mediated umbilical vasoconstriction. Vascular tension and ion channel currents were measured on isolated vessels and smooth muscle cells from human umbilical cords.

MAIN OUTCOME MEASURES

Provision of new evidence to conclude that ACh-stimulated vasoconstriction is common to all umbilical cords, and cellular mechanisms are linked to potassium channels.

RESULTS

ACh caused reliable vasoconstriction in umbilical veins/arteries in humans, rats and sheep, but not in any other vessels, including fetal vessels. Atropine inhibited the effects of ACh. The mRNA of ACh-muscarinic receptor subtypes M1 -M5 was expressed in human umbilical vessels. The protein kinase C antagonist GF109203X and the calcium inhibitor nifedipine decreased ACh-induced vasoconstriction in human umbilical vessels. ACh also caused a reduction in whole-cell potassium channel currents and the single-channel current of large-conductance calcium-activated potassium (BKca) channels.

CONCLUSION

Umbilical vessels are significantly different from other vessels in their response to ACh. BKca channels in smooth muscle cells may play important roles in ACh-mediated vasoconstriction in human umbilical cords. This information may be important for fetal medicine and practice with regard to the effect on fetal development of umbilical vascular functions.

Neuronal nitric oxide synthase-derived nitric oxide is involved in gastric mucosal hyperemic response to capsaicin in rats

BACKGROUND AND AIMS

Activation of transient receptor potential vanilloid type 1 (TRPV1) by capsaicin leads to gastric hyperemic response through capsaicin-sensitive sensory nerves and nitric oxide (NO). The aim of the present study is to examine which isoform of nitric oxide synthase (NOS)/NO is involved in the hyperemic response to capsaicin in the rat stomach.

METHODS

Gastric mucosal blood flow (GMBF) was measured by laser Doppler flowmetry in rats. The localizations of TRPV1 and neuronal NOS (nNOS) in the rat gastric mucosa were detected by immunohistochemical staining.

RESULTS

The nNOS inhibitor N(5)-[imino(propylamino)methyl]-L-ornithine substantially reduced GMBF during capsaicin application, whereas the endothelial NOS (eNOS) inhibitor N(5)-(1-iminomethyl)-L-ornithine did not affect the effect of capsaicin during the application. The nonselective NOS inhibitor N(G)-nitro-L-arginine methyl ester apparently inhibited the capsaicin-induced GMBF, while the inducible NOS inhibitor 1400W did not affect GMBF response to capsaicin. The immunohistochemical studies revealed nerve fibers coexpressing TRPV1 and nNOS around blood vessels in the gastric submucosa.

CONCLUSION

We demonstrated for the first time that nNOS/NO is involved in gastric hyperemic responses to capsaicin.

Vascular dysfunction in young, mid-aged and aged mice with latent cytomegalovirus infections

Human cytomegalovirus (HCMV) is associated with vascular diseases in both immunosuppressed and immunocompetent individuals. CMV infections cycle between active and latent phases throughout life. We and others have shown vascular dysfunction during active mouse CMV (mCMV) infections. Few studies have examined changes in physiology during latent CMV infections, particularly vascular responses or whether the negative effects of aging on vascular function and fertility will be exacerbated under these conditions. We measured vascular responses in intact mesenteric and uterine arteries dissected from young, mid-aged, and aged latently mCMV-infected (mCMV genomes are present but infectious virus is undetectable) and age-matched uninfected mice using a pressure myograph. We tested responses to the α(1)-adrenergic agonist phenylephrine, the nitric oxide donor sodium nitroprusside, and the endothelium-dependent vasodilator methacholine. In young latently mCMV-infected mice, vasoconstriction was increased and vasodilation was decreased in mesenteric arteries, whereas both vasoconstriction and vasodilation were increased in uterine arteries compared with those in age-matched uninfected mice. In reproductively active mid-aged latently infected mice, mesenteric arteries showed little change, whereas uterine arteries showed greatly increased vasoconstriction. These vascular effects may have contributed to the decreased reproductive success observed in mid-aged latently mCMV-infected compared with age-matched uninfected mice (16.7 vs. 46.7%, respectively). In aged latently infected mice, vasodilation is increased in mesenteric and uterine arteries likely to compensate for increased vasoconstriction to mediators other than phenylephrine. The novel results of this study show that even when active mCMV infections become undetectable, vascular dysfunction continues and differs with age and artery origin.