Polyclonal anti-histamine H2 receptor antibodies detect differential expression of H2 receptor protein in primary vascular cell types

Exposure to DEP Modifies the Human Umbilical Artery Vascular Resistance Contributing to Hypertension in Pregnancy

Hypertensive disorders in pregnancy (HDP) are the most prevalent diseases during pregnancy. In addition to the already identified risk factors, exposure to environmental contaminants has been also considered a new one. Phthalates, which are classified as priority environmental pollutants due to their ubiquitousness and endocrine disrupting properties, have been implicated in HDP in some epidemiological studies. Nevertheless, phthalates' vascular impacts still need to be clarified. Thus, we aimed to understand the connection between phthalates exposure and the occurrence of gestational hypertension, as well as the pathway involved in the pathological vascular effects. We investigated diethyl phthalate's (DEP) effect on the vascular reactivity of the human umbilical arteries (HUAs) from normotensive and hypertensive pregnant women. Both DEP's nongenomic (within minutes effect) and genomic (24 h exposure to DEP) actions were evaluated, as well as the contribution of cyclic guanosine monophosphate and Ca2+ channel pathways. The results show that short-term exposure to DEP interferes with serotonin and histamine receptors, while after prolonged exposure, DEP seems to share the same vasorelaxant mechanism as estrogens, through the NO/sGC/cGMP/PKG signaling pathway, and to interfere with the L-type Ca2+ channels. Thus, the vascular effect induced by DEP is similar to that observed in HUA from hypertensive pregnancies, demonstrating that the development of HDP may be a consequence of DEP exposure.

Disrupting effects of the emerging contaminant octylmethoxycinnamate (OMC) on human umbilical artery relaxation

Cardiovascular diseases (CVD) represent the number one cause of death worldwide. The vascular endothelium may play a role in the pathophysiology of CVD diseases. Octylmethoxycinnamate (OMC) is a UV-B filter (CAS number: 5466-77-3) widely used worldwide in numerous personal care products, including sunscreens, daily creams, and makeup. This UV-B filter is considered an endocrine disruptor. Therefore, this investigation aimed to evaluate the direct effects of OMC in human umbilical arteries (HUAs) with endothelium and the possible mechanisms involved in the response. The results demonstrated that OMC exerts a rapid (non-genomic) and endothelium-dependent arterial relaxant effect on HUAs previously contracted with serotonin (5-HT) and Histamine (His). On the other hand, when HUAs were contracted with potassium chloride (KCl), the relaxing effect was only observed in HUAs without endothelium, and it appeared to be inhibited in HUAs with endothelium. Thus, the vasorelaxant effect of OMC depends on the endothelium and depends on the contractile agent used, suggesting that OMC may act through different signaling pathways. Furthermore, computational modulation studies, corroborated the binding of OMC to all the proteins under investigation (eNOS, COX-2, ET-1, and TxA2), with higher affinity for COX-2. In summary, the vascular effect of OMC may involve activating different pathways, i.e., acting through the NO pathway, COX pathway, or activating the endothelin-1 pathway.

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).

Histamine-dependent prolongation by aldosterone of vasoconstriction in isolated small mesenteric arteries of the mouse

In arterioles, aldosterone counteracts the rapid dilatation (recovery) following depolarization-induced contraction. The hypothesis was tested that this effect of aldosterone depends on cyclooxygenase (COX)-derived products and/or nitric oxide (NO) synthase (NOS) inhibition. Recovery of the response to high K+ was observed in mesenteric arteries of wild-type and COX-2−/− mice but it was significantly diminished in preparations from endothelial NOS (eNOS)−/− mice. Aldosterone pretreatment inhibited recovery from wild-type and COX-2−/− mice. The NO donor sodium nitroprusside (SNP) restored recovery in arteries from eNOS−/− mice, and this was inhibited by aldosterone. Actinomycin-D abolished the effect of aldosterone, indicating a genomic effect. The effect was blocked by indomethacin and by the COX-1 inhibitor valeryl salicylate but not by NS-398 (10−6 mol/l) or the TP-receptor antagonist S18886 (10−7 mol/l). The effect of aldosterone on recovery in arteries from wild-type mice and the SNP-mediated dilatation in arteries from eNOS−/− mice was inhibited by the histamine H2 receptor antagonist cimetidine. RT-PCR showed expression of mast cell markers in mouse mesenteric arteries. The adventitia displayed granular cells positive for toluidine blue vital stain. Confocal microscopy of live mast cells showed loss of quinacrine fluorescence and swelling after aldosterone treatment, indicating degranulation. RT-PCR showed expression of mineralocorticoid receptors in mesenteric arteries and in isolated mast cells. These findings suggest that aldosterone inhibits recovery by stimulation of histamine release from mast cells along mesenteric arteries. The resulting activation of H2 receptors decreases the sensitivity to NO of vascular smooth muscle cells. Aldosterone may chronically affect vascular function through paracrine release of histamine.

Histamine induces activation of protein kinase D that mediates tissue factor expression and activity in human aortic smooth muscle cells

Histamine, an inflammatory mediator, has been shown to influence the pathogenesis of vascular wall cells. However, the molecular basis of its influence is not well understood. Our data reveal that histamine markedly induces protein kinase D (PKD) activation in human aortic smooth muscle cells. PKD belongs to a family of serine/threonine protein kinases, and its function in vascular disease is largely unknown. Our data show that histamine-induced PKD phosphorylation is dependent on the activation of histamine receptor 1 and protein kinase C (PKC). To determine the role of PKD in the histamine pathway, we employed a small-interfering RNA approach to downregulate PKD expression and found that PKD1 and PKD2 are key mediators for expression of tissue factor (TF), which is the key initiator of blood coagulation and is important for thrombosis. Our results show that PKD2 predominantly mediates histamine-induced TF expression via the p38 mitogen-activated protein kinase (MAPK) pathway, whereas PKD1 mediates histamine-induced TF expression through a p38 MAPK-independent pathway. We demonstrate that histamine induces TF expression via the PKC-dependent PKD activation. Our data provide the first evidence that PKD is a new component in histamine signaling in live cells and that PKD has a novel function in the histamine signaling pathway leading to gene expression, as evidenced by TF expression. Importantly, our data reveal a regulatory link from histamine to PKD and TF, providing new insights into the mechanisms of coagulation and the development of atherothrombosis.

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.