Distribution of receptors mediating phosphoinositide hydrolysis in cultured human umbilical artery smooth muscle and endothelial cells

UV-B Filter Octylmethoxycinnamate Alters the Vascular Contractility Patterns in Pregnant Women with Hypothyroidism

Increasing evidence relating the exposure and/or bioaccumulation of endocrine-disrupting compounds (EDCs) with cardiovascular system are arising. Octylmethoxycinnamate (OMC) is the most widely used UV-B filter and as EDC interacts with TH receptors. However, their effects on thyroid diseases during pregnancy remain unknown. The purpose of this work was to assess the short- and long-term effects of OMC on arterial tonus of pregnant women with hypothyroidism. To elucidate this, human umbilical artery (HUA) rings without endothelium were used to explore the vascular effects of OMC by arterial and cellular experiments. The binding energy and the modes of interaction of the OMC into the active center of the TSHR and THRα were analyzed by molecular docking studies. Our results indicated that OMC altered the contractility patterns of HUA contracted with serotonin, histamine and KCl, possibly due to an interference with serotonin and histamine receptors or an involvement of the Ca²⁺ channels. The molecular docking analysis show that OMC compete with T₃ for the binding center of THRα. Taken together, these findings pointed out to alterations in HUA reactivity as result of OMC-exposure, which may be involved in the development and increased risk of cardiovascular diseases.

Effects of di(2-etilhexil) phthalate on human umbilical artery

Di(2-etilhexil) phthalate (DEHP) is a compound used in plastic materials, which has endocrine disrupting properties. The human DEHP exposure depend on the use of plastics in toys, medical devices and food and beverage containers. The DEHP effects were studied in some physiological systems; nevertheless, the actions in human arteries were never described. We analysed the DEHP effect on endothelium denuded human umbilical artery (HUA), an important artery to ensure gases and nutrients exchange with fetus. We assessed DEHP short-term effects on contractility, occurring few minutes after DEHP is in contact with HUA in the organ bath receptacles. The long-term effects on HUA, observed after 24 h in presence of DEHP, were assessed in the organ bath system, and also through the analysis of receptors expression (5-HT_2A and H₁) and of cellular viability, by using HUA smooth muscle cells. DEHP (1 nM-100 μM) induced a short-term relaxing effect on HUA contracted by 5-HT, histamine or KCl. DEHP long-term exposure of arteries (1 nM, 10 μM and 100 μM) reduced its own relaxant effect on HUA contracted by 5-HT and histamine and, precisely, 24 h exposure to DEHP 1 nM reverted the relaxant effect on 5-HT contractility. Long-term exposure at more than 10 nM of DEHP decreased 5HT_2A receptors expression. In conclusion, DEHP short-term exposition elicit vasodilation of HUA contracted by different agents. DEHP long-term exposition reduced the expression of 5HT_2A receptors. The DEHP long-term exposition decrease the short-term relaxant effect and, at low concentrations can increase the contractile effect of 5-HT.

UV-B Filter Octylmethoxycinnamate Induces Vasorelaxation by Ca2+ Channel Inhibition and Guanylyl Cyclase Activation in Human Umbilical Arteries

Ultraviolet (UV) filters are chemicals widely used in personal care products (PCPs). Due to their effect as endocrine disruptor compounds (EDCs), the toxicity of UV filters is a current concern for human health. EDC exposure may be correlated to cardiovascular diseases (CVD), but to our knowledge, no studies assessed the UV filters effects as human EDCs at the vascular level. Octylmethoxycinnamate (OMC) is the world's most widely used UV-B filter, present in more than 90% of PCPs. Due to its demonstrated multiple hormonal activities in animal models, this substance is also suspected to be a human EDC. The purpose of this study was to assess the rapid/short-term effects of OMC on arterial tonus and analyse its mode of action (MOA). Using human umbilical arteries, the endocrine effects of OMC were evaluated in in vitro (cellular and organ) experiments by planar cell surface area (PCSA) and organ bath, respectively. Our data show that OMC induces a rapid/short-term smooth muscle relaxation acting through an endothelium-independent MOA, which seems to be shared with oestrogens, involving an activation of soluble guanylyl cyclase (sGC) that increases the cyclic guanosine monophosphate (cGMP) intracellular levels and an inhibition of L-type voltage-operated Ca²⁺ channels (L-Type VOCC).

How is the human umbilical artery regulated?

The purpose of this review is to present an update of the main mechanisms involved in the physiological regulation of contraction and relaxation of the human umbilical artery (HUA) smooth muscle cells. A literature review was performed based on the analysis of papers available on PubMed. The most important and relevant studies regarding the regulation of the HUA are presented in this article. The vascular smooth muscle is a highly specialized structure, whose main function is to regulate the vascular tonus. This is controlled by a balance between the cellular signaling pathways that mediate contraction and relaxation. The cells responsible for the contractile property of this muscle are the smooth muscle cells (SMC), and an excellent source of these cells is the HUA, involved in fetoplacental circulation. Since the umbilical blood vessels are not innervated, the HUA tonus is modulated by vasoactive substances that regulate the contractile process. The main vasoactive substances that induce contraction are serotonin, histamine, thromboxane, bradykinin, endothelin 1 and prostaglandin F2α, that are linked to the activation of proteins G_q and G_i/0 . On the other hand, the main vasorelaxation mechanisms are the activation of adenyl and guanil cyclases, potassium channels and the inhibition of calcium channels. The SMC from the HUA allow the study of different cellular mechanisms and their functions. Therefore, these cells are an important tool to study the mechanisms regulating the contractility of this artery, allowing to detect potential therapeutic targets to treat HUA disorders (gestational hypertension and pre-eclampsia).

Tributyltin role on the serotonin and histamine receptors in human umbilical artery

Some studies in animals suggest that TBT may constitute a risk factor for cardiovascular diseases. Hence, the main purpose of this study was to investigate in human umbilical artery (HUA) the effect of TBT on vascular reactivity, manly in serotonin (5-HT) and histamine receptors. Using standard organ bath techniques, rings of HUA without endothelium were contracted by 5-HT and histamine. We also investigated the effect of TBT on the expression of the receptors using Real-time PCR. The results show that TBT short term effects include concentration-dependent relaxation. Moreover, at long term exposures, the arteries treated with 100 μM of TBT do not have contraction capacity when 5-HT is added, and the gene expression of 5-HT2A receptor decrease. Regarding histamine, it was demonstrated that TBT induces a concentration-dependent relaxation and the H1 gene expression levels decrease. In conclusion TBT modifies the activity and expression of 5-HT and histamine receptors.

The Effects of Bumetanide on Human Umbilical Artery Contractions

The authors investigate the effect of bumetan ide, an inhibitor of NKCC1 and a loop diuretic, on the tone of human umbilical artery (HUA). Rings of HUA (n = 35) from vaginal deliveries were suspended for isometric tension recordings in organ baths. Cumulative concentration-response curves to serotonin, histamine, and KCl were performed in the absence (control) or in the presence of bumetanide. The relaxant effect of bumetanide was also evaluated in serotonin- and histamine-induced contractions. Bumetanide inhibited HUA tone in serotonin- and histamine-induced contractions with significant changes in the potency (pD(2)) and maximum contractile response (E(max)) values. However, only pD( 2) values for KCl-induced contraction significantly changed in the presence of bumetanide. Bumetanide caused concentration-dependent and sustained relaxations in serotonin-induced contraction; however, there was refractoriness in histamine-induced contraction. These findings raise the possibility that NKCC1 may play a role in the regulation of the umbilical artery tone.

Regulation of human umbilical artery contractility by different serotonin and histamine receptors

We studied the role of several serotonin (5-HT) and histamine receptors in the regulation of human umbilical artery (HUA) contractility. Among the 5-HT agonists used, only the 5-HT( 2A) and 5HT(1B/D) agonists contracts HUA. The 5-HT-induced contractions were fully inhibited by ketanserin (5-HT(2A) antagonist). The 5-HT( 7)-activation also relaxes and increases intracellular cyclic adenosine monophosphate (cAMP). Among the histamine receptor agonists, only betahistine (H(1) agonist) induced significant contractile effect. Histamine-induced contraction was partially relaxed by pyrilamine (H(1) antagonist). Betahistine-induced contraction was partially blocked by dimaprit (H( 2) agonist) and by the H(3) agonist when a low concentration of forskolin is present. Both, H(2) and H(3) agonists increased the cAMP intracellular levels in HUA smooth muscle. These findings show that in HUA, 5-HT(2A)- and 5-HT(1B/1D)-activation lead to vasoconstriction and 5-HT(7)-activation induces vasorelaxation. Concerning histamine receptors, H(1)-activation induces contraction and H(2)- and H(3)-activation lead to vasorelaxation.

PDE4 and PDE5 regulate cyclic nucleotides relaxing effects in human umbilical arteries

Cyclic nucleotides (cAMP and cGMP) are the main second messengers linked to vasodilatation. They are synthesized by cyclases and degraded by different types of phosphodiesterases (PDE). The effect of PDE inhibition and cyclases stimulation on 5-hydroxytryptamine (5-HT; 1 microM) and histamine (10 microM) contracted arteries was analysed. Stimulation of guanylate cyclase or adenylate cyclase relaxed the histamine- and 5-HT-induced contractions indicating that intracellular increase of cyclic nucleotides leads to vasodilatation of the human umbilical artery. We investigated the role of different PDE families in the regulation of this effect. The presence of the different PDE types in human umbilical artery smooth muscle was analysed by RT-PCR and the expression of PDE1B, PDE3A, PDE3B, PDE4C, PDE4D and PDE5A was detected. The unspecific PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX; 50 microM) relaxed histamine-contracted human umbilical artery on 47.4+/-7.2%. This effect seems to be due to PDE4 and PDE5 inhibition because among the selective PDE inhibitors used only the PDE4 inhibitor (rolipram; 1 microM) and the PDE5 inhibitors (dipyridamole and T0156; 3 microM and 1 microM respectively) induced significant relaxation (39.0+/-8.7, 30.4+/-6.0 and 36.3+/-2.8 respectively). IBMX, dipyridamole and T0156 produced similar relaxation on 5-HT-induced contraction. After forskolin, the addition of IBMX or rolipram increased the effect of the adenylate cyclase stimulator and almost completely relaxed the human umbilical artery contracted by histamine (92.5+/-4.9 and 90.9+/-4.7 respectively), suggesting a main role of PDE4. The data obtained with 5-HT contracted arteries confirmed this, because only rolipram and IBMX significantly increased the forskolin vasodilator effect. The administration of dipyridamole and T0156 after sodium nitroprusside (SNP) induced a significant increase of the SNP relaxant effect on histamine-contracted arteries, but PDE1 and PDE3 inhibition did not increase the effect of the guanylate cyclase stimulator. Similar effects were obtained in 5-HT contracted arteries, the SNP induced relaxation was increased by the PDE5 inhibition, but not by PDE1 or PDE3 inhibition. In summary, our results demonstrate that: 1) the increase of cAMP and/or cGMP levels induces relaxation of the human umbilical vascular smooth muscle; 2) four families of PDE are expressed in this smooth muscle: PDE1, PDE3, PDE4 and PDE5; 3) between these families, PDE4 and PDE5 are the key enzymes involved in the regulation of the relaxation associated to cAMP and cGMP, respectively.

Functional acetylcholine muscarinic receptor subtypes in human brain microcirculation: identification and cellular localization

Acetylcholine is an important regulator of local cerebral blood flow. There is, however, limited information available on the possible sites of action of this neurotransmitter on brain intraparenchymal microvessels. In this study, a combination of molecular and functional approaches was used to identify which of the five muscarinic acetylcholine receptors (mAChR) are present in human brain microvessels and their intimately associated astroglial cells. Microvessel and capillary fractions isolated from human cerebral cortex were found by reverse transcriptase-polymerase chain reaction to express m2, m3, and, occasionally, m1 and m5 receptor subtypes. To localize these receptors to a specific cellular compartment of the vessel wall, cultures of human brain microvascular endothelial and smooth muscle cells were used, together with cultured human brain astrocytes. Endothelial cells invariably expressed m2 and m5 receptors, and occasionally the m1 receptor; smooth muscle cells exhibited messages for all except the m4 mAChR subtypes, whereas messages for all five muscarinic receptors were identified in astrocytes. In all three cell types studied, acetylcholine induced a pirenzepine-sensitive increase (62% to 176%, P<0.05 to 0.01) in inositol trisphosphate, suggesting functional coupling of m1, m3, or m5 mAChR to a phospholipase C signaling cascade. Similarly, coupling of m2 or m4 mAChR to adenylate cyclase inhibition in endothelial cells and astrocytes, but not in smooth muscle cells, was demonstrated by the ability of carbachol to significantly reduce (44% to 50%, P<0.05 to 0.01) the forskolin-stimulated increase in cAMP levels. This effect was reversed by the mAChR antagonist AFDX 384. The results indicate that microvessels are able to respond to neurally released acetylcholine and that mAChR, distributed in different vascular and astroglial compartments, could regulate cortical perfusion and, possibly, blood-brain barrier permeability, functions that could become jeopardized in neurodegenerative disorders such as Alzheimer's disease.

Pharmacological and histochemical evidence for P2X receptors in human umbilical vessels

The presence of P2X purinoceptors in human umbilical vessels were studied with organ bath recording, radioligand binding assays, autoradiography, and immunohistochemistry. In isolated umbilical arteries and veins from normal term pregnancy, both ATP and alpha,beta-methylene ATP caused concentration-dependent contractions. ATP-induced responses were blocked by desensitisation with alpha,betamethylene ATP. However, both the ATP- and alpha,beta-methylene ATP-induced responses were not antagonised by suramin. No significant difference in responses was observed in the vessels with or without endothelial cells. Radioligand binding assays using [3H]alpha,beta-methylene ATP showed the presence of a population of high-affinity binding sites in both the arteries and veins. The Kd values of the binding sites were 2.77 + 1.10 nM for the arteries, and 3.23+/-1.22 nM for the veins. The maximum binding site densities were 634+/-237 and 947+/-308 fmol/mg protein for the arteries and the veins, respectively. Autoradiographic localisation with [3H]alpha,beta-methylene ATP demonstrated that the specific binding sites were only distributed over the smooth muscle cells of the vessels. Immunohistochemical studies with specific polyclonal antibodies against P2X1-6 receptors showed that positive immunostaining was also restricted to smooth muscle cells. Antibodies against P2X1 receptors produced the strongest signals, while antibodies against the other five P2X subtypes produced much weaker signals. The results in the present study indicate the existence of P2X purinoceptors in the smooth muscle of human umbilical vessels. Their physiological functions remain to be studied.

Receptor-stimulated phospholipase C activity in human umbilical artery cultured endothelial cells grown in a low oxygen environment

Endothelial cells of the human umbilical blood vessels are widely cultured in an oxygen tension (21%) far above that in which they exist in vivo (3%). This study investigates the effect of the long term culture (ca. 1 month) of human umbilical artery endothelial cells in a reduced oxygen environment (3%: HUAEC3) in comparison to cells grown in a 'normoxic' environment (21%: HUAEC21). Despite reports of altered metabolic pathways and reduced membrane integrity in other cell types, the characteristics of HUAEC3 were found to be similar to those of HUAEC21 with respect to morphology, immunocytochemical profile and in vitro growth rates. Cellular glutathione was maintained in these cells although ATP levels in HUAEC3 were found to be significantly lower than those observed in HUAEC21. The phosphoinositide responses of the HUAEC3 to a variety of agonists were also found to be of similar magnitude to those observed in HUAEC21. In addition, the pharmacological characteristics of the phospholipase C-linked histamine H1 and P2y2 (P2U) receptors were not changed by culture of cells in a low oxygen environment.

5-Hydroxytryptamine stimulates phosphoinositide hydrolysis and contraction in the ovine umbilical artery

5-Hydroxytryptamine-stimulated contraction and generation of inositol phosphates (InsPs) were investigated in isolated ovine umbilical artery from near term pregnant sheep. 5-Hydroxytryptamine produced a concentration-dependent contraction in the presence or absence of external Ca2+, however, the contractile response in Ca(2+)-free medium was depressed by 67% (P < 0.05). The initial increase of either inositol monophosphate (InsP1) or inositol bisphosphate (InsP2) was not apparent, although a significant rise in both InsP1 and InsP2 was observed at 30 min (107 and 100% over basal level, P < 0.05). The generation of inositol trisphosphate (InsP3) was rapid and reached its peak at 60-90 s (35% over basal level, P < 0.05), followed by a second rise at 30 min (96% over basal level, P < 0.05). The generation of InsPs stimulated by 5-hydroxytryptamine was also concentration-dependent. In agreement with previous contraction studies, the generation of InsPs stimulated by 5-hydroxytryptamine was blocked by 10 nM ketanserin, a specific 5-HT2A receptor antagonist. A temporal study revealed that the generation of InsP3 coincided with the phasic component of the contractile response induced by 5-hydroxytryptamine. Our results suggest that through activation of 5-HT2A receptors, the generation of InsP3 plays a critical role in the contraction induced by 5-hydroxytryptamine in the ovine umbilical artery.