Testosterone and cholesterol vasodilation of rat aorta involves L-type calcium channel inhibition

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.

Vascular mechanisms of testosterone: The non-genomic point of view

Testosterone (T) is the predominant endogenous androgen in the bloodstream. At the vascular level, T presents genomic and non-genomic effects, and both effects may overlap. The genomic actions assume that androgens can freely cross the plasma membrane of target cells and bind to nuclear androgen receptors, inducing gene transcription and protein synthesis. The non-genomic effects have a more rapid onset and may be related to the interaction with protein/receptor/ion channels of the plasma membrane. The key T effect at the vascular level is vasorelaxation, which is primarily due to its rapid effect. Thus, the main purpose of this review is to discuss the T non-genomic effects at the vascular level and the molecular pathways involved in its vasodilator effect observed in in vivo and in vitro studies. In this sense, the nuclear receptor activation, the influence of vascular endothelium and the activation or inhibition of ion channels (potassium and calcium channels, respectively) will be reviewed regarding all the data that corroborated or not. Moreover, this review also provides a brief update on the association of T with the risk factors for cardiovascular diseases, namely metabolic syndrome, type 2 diabetes mellitus, obesity, atherosclerosis, dyslipidaemia, and hypertension. In summary, in this paper we consider the non-genomic vascular mode of action of androgen in physiological conditions and the main risk factors for cardiovascular diseases.

A high throughput zebrafish chemical screen reveals ALK5 and non-canonical androgen signalling as modulators of the pkd2-/- phenotype

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic cause of end-stage renal failure in humans and results from germline mutations in PKD1 or PKD2. Despite the recent approval of tolvaptan, safer and more effective alternative drugs are clearly needed to slow disease progression. As a first step in drug discovery, we conducted an unbiased chemical screen on zebrafish pkd2 mutant embryos using two publicly available compound libraries (Spectrum, PKIS) totalling 2,367 compounds to identify novel treatments for ADPKD. Using dorsal tail curvature as the assay readout, three major chemical classes (steroids, coumarins, flavonoids) were identified from the Spectrum library as the most promising candidates to be tested on human PKD1 cystic cells. Amongst these were an androgen, 5α−androstane 3,17-dione, detected as the strongest enhancer of the pkd2 phenotype but whose effect was found to be independent of the canonical androgen receptor pathway. From the PKIS library, we identified several ALK5 kinase inhibitors as strong suppressors of the pkd2 tail phenotype and in vitro cyst expansion. In summary, our results identify ALK5 and non-canonical androgen receptors as potential therapeutic targets for further evaluation in drug development for ADPKD.

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).

Cardiovascular Response of Rat Aorta to Di-(2-ethylhexyl) Phthalate (DEHP) Exposure

Phthalates are one of the main constituents of plastic, reaching up to 40% of the total plastic weight, and their main function is to impart flexibility/elasticity to polymers that would otherwise be rigid. Phthalates are known as endocrine disruptors, since they can interfere with hormone homeostasis. Regarding the cardiovascular system, it was already shown the effects of di-(2-ethylhexyl) phthalate (DEHP) exposure with significant changes in several calcium-handling proteins and an increase in the blood pressure of mice offspring, suggesting that DEHP leads to vasocontraction. However, the mechanisms involved were not elucidated yet. The aim of this study is to analyse the involvement of calcium channels in the effects induced by DEHP on vascular smooth muscle cells. Endothelium-denuded aorta artery rings were prepared from male Wistar rats and incubated in an organ bath, and the whole-cell configuration of Patch Clamp technique was used to measure the activity of L-type Ca²⁺ channels (LTCC) in A7r5 cells. Overall, DEHP caused relaxation on KCl-induced contraction at higher concentrations and inhibited the basal and BAY K8644-stimulated calcium current, indicating that this drug blocks LTCC. These results suggest that DEHP induces relaxation on vascular smooth muscle cells due to the inhibition of calcium channels.

Inhibition of L-type calcium channels by Bisphenol A in rat aorta smooth muscle

Bisphenol A (BPA) is an endocrine disrupting chemical used on a wide range in industry. This compound has been used in the production of polycarbonate plastics and epoxy resins. For this reason and their global use, BPA is one of the most common environmental chemicals to which humans are exposed. This exposure can cause several adverse health outcomes, including at the cardiovascular level. The regulation of ion channels in vascular smooth muscle is pivotal and important for vasoreactivity, and changes in their flux can be involved in the pathophysiology of some cardiovascular diseases. This study aims to analyse in rat aorta whether the vasorelaxant effect of BPA is mediated by L-type Ca²⁺ channels inhibition. Using male Wistar rat aorta artery rings in the organ bath we analysed the contractility, and to study the activity of calcium current in A7r5 cells we used the whole cell configuration of Patch Clamp technique. Regarding the contractility experiences we observed that in both NA and KCl contraction, BPA caused a rapid and concentration-dependent relaxation. The electrophysiology experiments showed that BPA inhibited the basal and BAY K8644-stimulated whole-cell L-type Ca²⁺ channel (W-CLTCC) currents, indicating that this drug blocks the L-type Ca²⁺ channels. Our results suggest that BPA inhibits the W-CLTCC, leading to the relaxation of vascular smooth muscle.

Caveolar disruption causes contraction of rat femoral arteries via reduced basal NO release and subsequent closure of BKCa channels

Background and Purpose. Caveolae act as signalling hubs in endothelial and smooth muscle cells. Caveolar disruption by the membrane cholesterol depleting agent methyl-β-cyclodextrin (M-β-CD) has various functional effects on arteries including (i) impairment of endothelium-dependent relaxation, and (ii) alteration of smooth muscle cell (SMC) contraction independently of the endothelium. The aim of this study was to explore the effects of M-β-CD on rat femoral arteries. Methods. Isometric force was measured in rat femoral arteries stimulated to contract with a solution containing 20 mM K(+) and 200 nM Bay K 8644 (20 K/Bay K) or with one containing 80 mM K(+)(80 K). Results. Incubation of arteries with M-β-CD (5 mM, 60 min) increased force in response to 20 K/Bay K but not that induced by 80 K. Application of cholesterol saturated M-β-CD (Ch-MCD, 5 mM, 50 min) reversed the effects of M-β-CD. After mechanical removal of endothelial cells M-β-CD caused only a small enhancement of contractions to 20 K/Bay K. This result suggests M-β-CD acts via altering release of an endothelial-derived vasodilator or vasoconstrictor. When nitric oxide synthase was blocked by pre-incubation of arteries with L-NAME (250 µM) the contraction of arteries to 20 K/Bay K was enhanced, and this effect was abolished by pre-treatment with M-β-CD. This suggests M-β-CD is inhibiting endothelial NO release. Inhibition of large conductance voltage- and Ca(2+)-activated (BKCa) channels with 2 mM TEA(+) or 100 nM Iberiotoxin (IbTX) enhanced 20 K/Bay K contractions. L-NAME attenuated the contractile effect of IbTX, as did endothelial removal. Conclusions. Our results suggest caveolar disruption results in decreased release of endothelial-derived nitric oxide in rat femoral artery, resulting in a reduced contribution of BKCa channels to the smooth muscle cell membrane potential, causing depolarisation and contraction.

Testosterone and atrial natriuretic peptide share the same pathway to induce vasorelaxation of human umbilical artery

We recently observed in human umbilical artery smooth muscle cells that testosterone activates protein kinase G and stimulates large-conductance Ca²⁺ activated (BKCa) and voltage sensitive (KV) potassium channels. In the same work, we also show that atrial natriuretic peptide (ANP), an activator of particulate guanylate cyclase (pGC), stimulates the activity of BKCa and KV channels because of protein kinase G activation. The aim of this work was to prove that the relaxant effects of testosterone are also because of the increase of cGMP because of activation of the pGC. Subsarcolemmal cGMP signals were monitored in single cells by recording the cGMP-gated current (ICNG) in human umbilical artery smooth muscle cells expressing the wild-type rat olfactory cyclic nucleotide-gated (CNG) channel. Sodium nitroprusside (10 and 100 μM), ANP (0.1 and 1 μM), or testosterone (0.1, 1, and 10 μM) induced activation of ICNG. This activation induced by testosterone and ANP is bigger than that elicited by sodium nitroprusside. In summary, our study reveals that testosterone and ANP activate the pGC and induce vasorelaxation of human umbilical artery.

Modulation of neointimal lesion formation by endogenous androgens is independent of vascular androgen receptor

Aims

Low androgen levels have been linked with an increased risk of cardiovascular disease in men. Previous studies have suggested that androgens directly inhibit atherosclerotic lesion formation although the underlying mechanisms for this remain unclear. This study addressed the hypothesis that endogenous androgens inhibit arterial remodelling by a direct action on the androgen receptor (AR) in the vascular wall.

Methods and results

We studied a series of novel mouse lines with cell-specific deletion of the AR in either the endothelium or in smooth muscle cells or both cell types. Findings were compared with a model of global androgen deficiency in wild-type mice (castrated). We characterized the cardiovascular phenotype, vascular pharmacology and histology, and assessed neointimal lesion formation following vascular injury to the femoral artery. Cell-specific AR deletion did not alter body weight, circulating testosterone levels or seminal vesicle weight, but caused limited alterations in arterial contractility and blood pressure. Neointimal lesion formation was unaltered by selective deletion of AR from the vascular endothelium, smooth muscle, or both cell types. Castration in wild-type mice increased neointimal lesion volume (Sham vs. Castration: 2.4 × 10⁷ ± 4.5 × 10⁶ vs. 3.9 × 10⁷ ± 4.9 × 10⁶ µm³, P = 0.04, n = 9–10).

Conclusion

Vascular cell-specific AR deletion had no effect on neointimal lesion formation, while low systemic androgen levels adversely affect neointimal lesion size. These findings suggest that the cardio-protective effects of androgens are mediated either by AR outside the vasculature or by AR-independent mechanisms.

Long- and short-term effects of androgens in human umbilical artery smooth muscle

The aim of the present study was to determine the effects of androgens in the regulation of human umbilical artery (HUA) contractility. The short-term effects of testosterone on the tone of the HUA were investigated, as were the long-term effects of dihydrotestosterone (DHT) on the expression of some proteins involved in the contractile process. Endothelium-denuded HUA were treated for 24 h with DHT (2 μmol/L) or the vehicle control (ethanol) to analyse the genomic effects of androgens. Twenty-four hour treatment of HUA with DHT increased the mRNA expression of the β(1)-subunit of the large-conductance Ca(2+)-activated (BK(Ca)) channel and decreased expression of the α-subunit of L-type calcium channels. In organ bath studies, testosterone (1-100 μmol/L) produced similar relaxant responses in DHT- and vehicle-treated HUA rings precontracted with 5-HT, histamine and KCl. However, the relaxation response obtained by the combined application of testosterone (100 μmol/L) and nifedipine (10 μmol/L) was significantly greater in DHT- compared with vehicle-treated HUA. The results indicate that the rapid vasorelaxant effects of testosterone that are dependent on both BK(Ca) and voltage-sensitive potassium (K(V)) channel activity in control arteries become dependent solely on K(V) channel activity in DHT-treated HUA. Thus, the present study reveals the importance of the investigation of both the short- and long-term effects of androgens in human arteries.

Non-genomic vasorelaxant effects of 17β-estradiol and progesterone in rat aorta are mediated by L-type Ca2+ current inhibition

AIM

The sex hormones 17β-estradiol (βES) and progesterone (PRG) induce rapid non-genomic vasodilator effects which could be protective for the cardiovascular system. The purpose of this study was to analyze the mechanisms underlying their vasodilator effect in rat aortic smooth muscle preparations.

METHODS

Endothelium-denuded aorta artery rings were prepared from male Wistar rats and incubated in an organ bath. The contractions of the preparation were recorded through isometric transducers. The effects of the hormones on K(+) current and L-type Ca(2+) current (LTCC) were analyzed by using the whole cell voltage-clamp technique in A7r5 cells.

RESULTS

Both βES and PRG (1-100 μmol/L) concentration-dependently relaxed the endothelium-denuded aortic rings contracted by (-)-Bay K8644 (0.1 μmol/L) or by KCl (60 mmol/L). The IC(50) values of the two hormones were not statistically different. The K(V) channel blocker 4-aminopyridine (2 mmol/L), BK(Ca) channel blocker tetraethylammonium (1 mmol/L) and K(ATP) channel blocker glibenclamide (10 μmol/L) did not significantly modify the relaxant effect of the hormones. On the other hand, the blockage of the intracellular βES and PRG receptors with estradiol receptor antagonists ICI 182,780 (1 μmol/L) and PRG receptor antagonist mifepristone (30 μmol/L), respectively, did not significantly modify the relaxant action of the hormones. In A7r5 cells, both the hormones (1-100 μmol/L) rapidly and reversibly inhibited the basal and BAY-stimulated LTCC. However, these hormones had no effect on the basal K(+) current.

CONCLUSION

The vasorelaxant effects of βES and PRG are due to the inhibition of LTCC. The K(+) channels are not involved in the effects.

PKG is involved in testosterone-induced vasorelaxation of human umbilical artery

The cyclic nucleotides involvement in the vasorelaxation induced by testosterone in human umbilical artery was investigated. The effect of this hormone on denuded human umbilical arteries contracted by serotonin (5-HT), histamine or KCl was analysed. Testosterone effect on potassium current (IK) was also studied in human umbilical artery vascular smooth muscle cells (HUASMC). In general, the relaxant effects of testosterone, sodium nitroprusside (SNP) and atrial natriuretic peptide (ANP) are similar. The testosterone relaxant effect is not different to the induced by the conjoint application of ANP and testosterone. However, the effects of SNP and testosterone seem additive. The inhibition of protein kinase A (PKA) did not modify the testosterone relaxant effect, but protein kinase G (PKG) inhibition significantly reduced the testosterone effect independently of the contractile stimuli. In HUASMC, the IK is mainly constituted by potassium exit through voltage sensitive (KV) and large-conductance Ca2+ activated (BKCa) potassium channels. Testosterone significantly activates the basal IK. SNP does not induce a significant modification in basal or testosterone stimulated IK. In contrast, ANP stimulates the basal IK, but does not increase the testosterone stimulation on IK. The IK increases induced by testosterone or by ANP are not significantly affected by the PKA inhibition, but are completely inhibited by the PKG inhibition. Our results show that testosterone and ANP stimulate the activity of BKCa and KV channels due to PKG activation and suggest that this hormone relaxes by activating particulate guanylate cyclase which increases the cGMP intracellular level.