5-hydroxtryptamine receptors in systemic hypertension: an arterial focus

Patients with uncontrolled hypertension subjected to cardiopulmonary bypass have altered coronary vasomotor responses to serotonin

BACKGROUND

We previously found that cardioplegic arrest and cardiopulmonary bypass are associated with altered coronary arteriolar response to serotonin in patients undergoing cardiac surgery. In this study, we investigated the effects of hypertension on coronary microvascular vasomotor tone in response to serotonin and alterations in serotonin receptor protein expression in the setting of cardioplegic arrest and cardiopulmonary bypass.

METHODS

Coronary arterioles were dissected from harvested pre- and post-cardioplegic arrest and cardiopulmonary bypass right atrial tissue samples of patients undergoing cardiac surgery with normotension, well-controlled hypertension, and uncontrolled hypertension. Vasomotor tone was assessed by video-myography, and protein expression was measured with immunoblotting.

RESULTS

Pre-cardioplegic arrest and cardiopulmonary bypass, serotonin induced moderate relaxation responses of coronary arterioles in normotension and well-controlled hypertension patients, whereas serotonin caused moderate contractile responses in uncontrolled hypertension patients. Post-cardioplegic arrest and cardiopulmonary bypass, serotonin caused contractile responses of coronary arterioles in all 3 groups. The post-cardioplegic arrest and cardiopulmonary bypass contractile response to serotonin was significantly higher in the uncontrolled hypertension group compared with the normotension or well-controlled hypertension groups (P < .05). Pre-cardioplegic arrest and cardiopulmonary bypass, expression of the serotonin 1A receptor was significantly lower in the uncontrolled hypertension group compared with the well-controlled hypertension and normotension groups (P = .01 and P < .001). Serotonin 1B receptor expression was higher in the uncontrolled hypertension group compared with the normotension or well-controlled hypertension groups post-cardioplegic arrest and cardiopulmonary bypass (P = .03 and P = .046).

CONCLUSION

Uncontrolled hypertension is associated with an increased coronary contractile response of coronary microvessels to serotonin and altered serotonin receptor protein expression after cardioplegic arrest and cardiopulmonary bypass. These findings may contribute to a worse postoperative coronary spasm and worsened recovery of coronary perfusion in patients with uncontrolled hypertension after cardioplegic arrest and cardiopulmonary bypass and cardiac surgery.

Involvement of neuronal factors in tumor angiogenesis and the shaping of the cancer microenvironment

Emerging evidence suggests that nerves within the tumor microenvironment play a crucial role in regulating angiogenesis. Neurotransmitters and neuropeptides released by nerves can interact with nearby blood vessels and tumor cells, influencing their behavior and modulating the angiogenic response. Moreover, nerve-derived signals may activate signaling pathways that enhance the production of pro-angiogenic factors within the tumor microenvironment, further supporting blood vessel growth around tumors. The intricate network of communication between neural constituents and the vascular system accentuates the potential of therapeutically targeting neural-mediated pathways as an innovative strategy to modulate tumor angiogenesis and, consequently, neoplastic proliferation. Hereby, we review studies that evaluate the precise molecular interplay and the potential clinical ramifications of manipulating neural elements for the purpose of anti-angiogenic therapeutics within the scope of cancer treatment.

Untapped potential of gut microbiome for hypertension management

The gut microbiota has been shown to be associated with a range of illnesses and disorders, including hypertension, which is recognized as the primary factor contributing to the development of serious cardiovascular diseases. In this review, we conducted a comprehensive analysis of the progression of the research domain pertaining to gut microbiota and hypertension. Our primary emphasis was on the interplay between gut microbiota and blood pressure that are mediated by host and gut microbiota-derived metabolites. Additionally, we elaborate the reciprocal communication between gut microbiota and antihypertensive drugs, and its influence on the blood pressure of the host. The field of computer science has seen rapid progress with its great potential in the application in biomedical sciences, we prompt an exploration of the use of microbiome databases and artificial intelligence in the realm of high blood pressure prediction and prevention. We propose the use of gut microbiota as potential biomarkers in the context of hypertension prevention and therapy.

Cardiovascular health in kratom users; a narrative review

BACKGROUND

Kratom, also known as Mitragyna speciosa, is a plant that originates in Southeast Asia and possesses unique pharmacological characteristics. It is commonly consumed in the form of tea made by boiling the leaves or using the leaves to create the powder. According to its pain-relieving effects, the prevalence of kratom use around the world has increased, which has various implications for healthcare providers. Mitragynine is a well-known active compound in kratom.

OBJECTIVE

This review aims to provide a comprehensive perspective on the cardiovascular effects of mitragynine and its potential cardiotoxicity through the literature.

METHOD

Authors searched PubMed, Scopus, and Google Scholar databases using appropriate search strategies for each database. After the screening, all relevant studies were included.

RESULTS

Although kratom may have the potential for therapeutic benefits, it has been associated with multi-organ damage and cardiac toxicity in some cases. According to the available data, tachycardia and hypertension are the most common adverse effects. Other possible cardiovascular effects include atherosclerosis, ventricular arrhythmia, cardiomyopathy, dose-dependent prolonged QTc interval, myocarditis, cardiomegaly, and cardiopulmonary arrest.

CONCLUSION

While prior research has indicated the possible negative effects of mitragynine overdose on the cardiovascular system, there are no definitive conclusions, and additional investigations are needed.

Activation of renal vascular smooth muscle TRPV4 channels by 5-hydroxytryptamine impairs kidney function in neonatal pigs

Control of microvascular reactivity by 5-hydroxytryptamine (5-HT; serotonin) is complex and may depend on vascular bed type and 5-HT receptors. 5-HT receptors consist of seven families (5-HT1-5-HT7), with 5-HT2 predominantly mediating renal vasoconstriction. Cyclooxygenase (COX) and smooth muscle intracellular Ca2+ levels ([Ca2+]i) have been implicated in 5-HT-induced vascular reactivity. Although 5-HT receptor expression and circulating 5-HT levels are known to be dependent on postnatal age, control of neonatal renal microvascular function by 5-HT is unclear. In the present study, we demonstrate that 5-HT stimulated human TRPV4 transiently expressed in Chinese hamster ovary cells. 5-HT2A is the predominant 5-HT2 receptor subtype in freshly isolated neonatal pig renal microvascular smooth muscle cells (SMCs). HC-067047 (HC), a selective TRPV4 blocker, attenuated cation currents induced by 5-HT in the SMCs. HC also inhibited the 5-HT-induced increase in renal microvascular [Ca2+]i and constriction. Intrarenal artery infusion of 5-HT had minimal effects on systemic hemodynamics but reduced renal blood flow (RBF) and increased renal vascular resistance (RVR) in the pigs. Transdermal measurement of glomerular filtration rate (GFR) indicated that kidney infusion of 5-HT reduced GFR. HC and 5-HT2 receptor antagonist ritanserin attenuated 5-HT effects on RBF, RVR, and GFR. Moreover, the serum and urinary COX-1 and COX-2 levels in 5-HT-treated piglets were unchanged compared with the control. These data suggest that activation of renal microvascular SMC TRPV4 channels by 5-HT impairs kidney function in neonatal pigs independently of COX production.

Serotonergic Modulation of Neurovascular Transmission: A Focus on Prejunctional 5-HT Receptors/Mechanisms

5-Hydroxytryptamine (5-HT), or serotonin, plays a crucial role as a neuromodulator and/or neurotransmitter of several nervous system functions. Its actions are complex, and depend on multiple factors, including the type of effector or receptor activated. Briefly, 5-HT can activate: (i) metabotropic (G-protein-coupled) receptors to promote inhibition (5-HT₁, 5-HT₅) or activation (5-HT₄, 5-HT₆, 5-HT₇) of adenylate cyclase, as well as activation (5-HT₂) of phospholipase C; and (ii) ionotropic receptor (5-HT₃), a ligand-gated Na⁺/K⁺ channel. Regarding blood pressure regulation (and beyond the intricacy of central 5-HT effects), this monoamine also exerts direct postjunctional (on vascular smooth muscle and endothelium) or indirect prejunctional (on autonomic and sensory perivascular nerves) effects. At the prejunctional level, 5-HT can facilitate or preclude the release of autonomic (e.g., noradrenaline and acetylcholine) or sensory (e.g., calcitonin gene-related peptide) neurotransmitters facilitating hypertensive or hypotensive effects. Hence, we cannot formulate a specific impact of 5-HT on blood pressure level, since an increase or decrease in neurotransmitter release would be favoured, depending on the type of prejunctional receptor involved. This review summarizes and discusses the current knowledge on the prejunctional mechanisms involved in blood pressure regulation by 5-HT and its impact on some vascular-related diseases.

Quality marker discovery of Danggui Jianzhong decoction for treating primary dysmenorrhoea based on chinmedomics strategy

BACKGROUND

Danggui Jianzhong Decoction (DGJZD) has been proven as an effective classical prescription for clinically treating primary dysmenorrhoea (PD). However, the industrialisation development and drug innovation of DGJZD remain limited due to its undefined effective constituents and quality markers (Q-markers).

PURPOSE

Elucidating the Q-markers of DGJZD, which is related to clinical efficacy.

METHODS

In accordance with chinmedomics strategy, we evaluated the therapeutic efficacy of DGJZD on the basis of the metabolomic profile and biomarker of a PD rat model to further identify the constituents of DGJZD in vivo that originated from the formula under the acting condition of DGJZD. The potential effective constituents and Q-markers were identified by mining the dynamic relation between the constituents in vivo and the biomarkers.

RESULTS

Subsequently, 29 serum metabolites were characterized as biomarkers for PD, and DGJZD adjusted the levels of the primary biomarkers involved in arachidonic acid metabolism, glycerophospholipid metabolism, tryptophan metabolism as well as the synthesis of steroid hormones. Under the active condition of DGJZD, 20 prototype ingredients and 4 metabolites of DGJZD were found in vivo, five of which were mostly related with the efficacy of PD, namely, ferulic acid, zizyphusin, cinnamic acid, protocatechuic acid-3-glucoside, and azelaic acid. They were the potential pharmacodynamic constituents for treating PD, and they could be regarded as the Q-markers of DGJZD.

CONCLUSION

Taken together, the Q-markers of DGJZD identified in this research are credible and assist in solving problems related to quality control and drug innovation, accelerating industrialisation development. Besides, the efficacy, mechanism and active ingredients of DGJZD for the treatment of PD were innovatively elucidated for the first time on the basis of the chinmedomics strategy for uncovering the Q-markers of drugs from the system perspective.

Telotristat ethyl reverses myxomatous changes in mice mitral valves

Rationale

Myxomatous mitral valve degeneration is a common pathological manifestation of mitral valve regurgitation, with or without valvular prolapse. In addition to similarities between naturally occurring and serotonergic valve degeneration, an increasing body of evidence has recently suggested that serotonin signaling is a regulator of degenerative valvulopathies. Studies have found that serotonin can be synthesized locally by valvular cells and serotonin receptors in turn may be activated to promote signaling. Recently, telotristat ethyl (TE) has been introduced as a treatment for carcinoid disease, by selectively inhibiting tryptophan hydroxylase 1, the rate-limiting enzyme in peripheral serotonin synthesis. TE provides a unique tool to test inhibition of serotonin synthesis in vivo, without impacting brain serotonin, to further confirm the role of local serotonin synthesis on heart valves.

Objective

To confirm the link between serotonin and myxomatous valvular disease in vivo.

Methods and results

A hypertension-induced myxomatous mitral valve disease mouse model was employed to test the effect of TE on valvular degeneration. Circulating serotonin and local serotonin in valve tissues were tested by enzyme immunoassay and immunohistochemistry, respectively. TE was administrated in two modes: (1) parallel with angiotensin II (A2); (2) post A2 treatment. Myxomatous changes were successfully recapitulated in hypertensive mice, as determined by ECM remodeling, myofibroblast transformation, and serotonin signaling activation. These changes were at least partially reversed upon TE administration.

Conclusion

This study provides the first evidence of TE as a potential therapeutic for myxomatous mitral disease, either used to prevent or reverse myxomatous degeneration.

Effect of 5-HT2C receptor gene polymorphism (HTR2C-759C/T) on metabolic adverse effects in Thai psychiatric patients treated with risperidone

BACKGROUND

The use of Atypical antipsychotics (AAPs) is related to metabolic disturbances, which put psychiatric patients at risk for cardiovascular morbidity and mortality. Evidence is emerging of genetic risk factors. The HTR2C gene is an essential candidate in pharmacogenetic studies of antipsychotic-induced metabolic effects. Nevertheless, there were inconsistent results among studies.

OBJECTIVE

To investigate the relationship between -759C/T, functional polymorphism of the HTR2C gene and metabolic adverse effects in Thai psychiatric patients treated with risperidone monotherapy.

METHOD

In this cross-sectional study, 108 psychiatric patients treated with risperidone monotherapy for ≥3 months were recruited. Anthropometric measurements and laboratory tests were obtained upon enrollment and history of treatment was reviewed from medical records. Weight gain was defined as an increase ≥7% of baseline weight. Metabolic syndrome was evaluated according to the 2005 International Diabetes Federation (IDF) Asia criteria. The -759C/T, polymorphism was genotyped. The associations between -759C/T polymorphism and metabolic side effects were analyzed. Multiple logistic regression was used for determining potential confounders.

RESULTS

Neither weight gain nor metabolic syndrome was significantly associated with -759C/T allelic and genotype variants of HTR2C. However, T allele of -759C/T polymorphism significantly associated with the hypertension. This association was not affected by possible confounding factors such as gender, risperidone dose, duration of treatment and family history of hypertension.

CONCLUSION

Our findings suggest that psychiatric patients with T allele of -759C/T polymorphism may be at higher risk for hypertension. Further study with prospective design with larger patient groups are needed.

Deletion of murine slc29a4 modifies vascular responses to adenosine and 5-hydroxytryptamine in a sexually dimorphic manner

Equilibrative nucleoside transporter 4 (ENT4), encoded by SLC29A4, mediates the flux of both 5‐hydroxytryptamine (5‐HT) and adenosine across cell membranes. We hypothesized that loss of ENT4 function in mice would modify the effects of these established regulators of vascular function. Male and female wild‐type (WT) and slc29a4‐null (ENT4‐KO) mice were compared with respect to their hemodynamics and mesenteric vascular function. Male ENT4‐KO mice had a complete loss of myogenic tone in their mesenteric resistance arteries. This was accompanied by a decrease in blood flow in the superior mesenteric artery in the male ENT4‐KO mice, and a reduced responsiveness to 5‐HT. In contrast, endothelium‐dependent relaxations of mesenteric arteries from female ENT4‐KO mice were more sensitive to Ca²⁺‐activated K⁺ (K_Ca) channel blockade than WT mice. Female ENT4‐KO mice also demonstrated an enhanced vasodilatory response to adenosine in vivo that was not seen in males. Ketanserin (5‐HT_2A inhibitor) and GR55562 (5‐HT_1B/1D inhibitor) decreased 5‐HT‐induced tone, but only ketanserin inhibited the relaxant effect of 5‐HT in mesenteric arteries. 5‐HT‐evoked increases in tone were elevated in arteries from ENT4‐KO mice upon block of endothelial relaxant pathways, with arteries from female ENT4‐KO mice showing the greatest increase. Adenosine A_2b receptor expression was decreased, while other adenosine transporter subtypes, as well as adenosine deaminase and adenosine kinase were increased in mesenteric arteries from male, but not female, ENT4‐KO mice. These findings indicate that deletion of slc29a4 leads to sex‐specific changes in vascular function with significant consequences for regulation of blood flow and pressure by adenosine and 5‐HT.

Serotonin Pathway in Cancer

Serotonin (5-hydroxytryptamine, 5-HT) is a biogenic monoamine produced from the essential amino acid tryptophan. Serotonin's role as a neurotransmitter in the central nervous system and a motility mediator in the gastrointestinal tract has been well defined, and its function in tumorigenesis in various cancers (gliomas, carcinoids, and carcinomas) is being studied. Many studies have shown a potential stimulatory effect of serotonin on cancer cell proliferation, invasion, dissemination, and tumor angiogenesis. Although the underlying mechanism is complex, it is proposed that serotonin levels in the tumor and its interaction with specific receptor subtypes are associated with disease progression. This review article describes serotonin's role in cancer pathogenesis and the utility of the serotonin pathway as a potential therapeutic target in cancer treatment. Octreotide, an inhibitor of serotonin release, is used in well-differentiated neuroendocrine cancers, and the tryptophan hydroxylase (TPH) inhibitor, telotristat, is currently being investigated in clinical trials to treat patients with metastatic neuroendocrine tumors and advanced cholangiocarcinoma. Several in vitro studies have shown the anticancer effect of 5-HT receptor antagonists in various cancers such as prostate cancer, breast cancer, urinary bladder, colorectal cancer, carcinoid, and small-cell lung cancer. More in vivo studies are needed to assess serotonin's role in cancer and its potential use as an anticancer therapeutic target. Serotonin is also being evaluated for its immunoregulatory properties, and studies have shown its potential anti-inflammatory effect. Therefore, it would be of interest to explore the combination of serotonin antagonists with immunotherapy in the future.

Association of 5-HTTLPR/rs25531 with depressive symptoms in patients with coronary heart disease: A prospective study

BACKGROUND

5-HTTLPR/rs25531 is suspected to be involved in the pathogenesis of both coronary heart disease (CHD)¹ and depression. We aimed to investigate the role of 5-HTTLPR/rs25531 in the development of depressive symptoms among CHD patients in a longitudinal design.

METHODS

N = 265 participants with CHD diagnosis were included while hospitalized in a department of cardiology and genotyped for the 5-HTTLPR/rs25531. Depressive symptoms were measured using the Patient Health Questionnaire (PHQ-9)⁷ at baseline and after 6 and 12 months. Binary logistic regression models were used to analyze the association of 5-HTTLPR/rs25531 with the prevalence of depressive symptoms at each time point as well as with the incidence and persistence of depressive symptoms at follow-up.

RESULTS

"L_AL_A" genotype was associated with a higher prevalence of depressive symptoms 12 months after study inclusion. "L_AL_A" genotype was associated with a higher incidence of depressive symptoms 6 and 12 months after study inclusion. There was no association of 5-HTTLPR/rs25531 with the persistence of depressive symptoms.

LIMITATIONS

Inclusion criteria did not demand a particular cardiac event at baseline, which aggravated the interpretation of the time-specific results. The majority of the participants was of male gender which could cause bias. The present study only vaguely differentiated between ethnical groups which might cause bias regarding nationality-dependent allele distributions.

CONCLUSION

The present study suggests a time-dependent association of the "L_AL_A" genotype with depressive symptoms in CHD patients. 5-HTTLPR/rs25531 might be an important marker to detect risk groups for later onset depressive symptoms among CHD patients.

Metabolism of vascular smooth muscle cells in vascular diseases

Vascular smooth muscle cells (VSMCs) are the fundamental component of the medial layer of arteries and are essential for arterial physiology and pathology. It is becoming increasingly clear that VSMCs can alter their metabolism to fulfill the bioenergetic and biosynthetic requirements. During vascular injury, VSMCs switch from a quiescent "contractile" phenotype to a highly migratory and proliferative "synthetic" phenotype. Recent studies have found that the phenotype switching of VSMCs is driven by a metabolic switch. Metabolic pathways, including aerobic glycolysis, fatty acid oxidation, and amino acid metabolism, have distinct, indispensable roles in normal and dysfunctional vasculature. VSMCs metabolism is also related to the metabolism of endothelial cells. In the present review, we present a brief overview of VSMCs metabolism and how it regulates the progression of several vascular diseases, including atherosclerosis, systemic hypertension, diabetes, pulmonary hypertension, vascular calcification, and aneurysms, and the effect of the risk factors for vascular disease (aging, cigarette smoking, and excessive alcohol drinking) on VSMC metabolism to clarify the role of VSMCs metabolism in the key pathological process.

Effects of new generation triptans - frovatriptan and almotriptan - on hemodynamic parameters in intact male and female rats

The introduction of the second generation triptans in clinical and experimental practice was a major progress in the pharmacotherapy of migraine. Frovatriptan is a second generation triptan with strong 5-HT1B/1D serotonergic agonism and low 5-HT1A/7 receptor affinity, while almotriptan possesses not only the typical 5-HT1B/1D receptor agonist activity, but shows an affinity to the 5-HT1F receptor. The aim of our study was to assess the impact of frovatriptan and almotriptan on hemodynamics in male and female rats. We used a non-invasive "tail-cuff" method to measure the arterial blood pressure. Female and male Wistar rats were treated separately with high and low dosages of frovatriptan and almotriptan. Male and female rats showed reduction in all hemodynamic parameters, but only male rats showed an increase in the heart rate. In general, we could say that both almotriptan and frovatriptan potentiate cardiovascular safety.

Effect of Intravenous Ondansetron on Spinal Anesthesia-Induced Hypotension and Bradycardia: A Randomized Controlled Double-Blinded Study

Background:

Spinal anesthesia is a safe anesthetic technique commonly practiced. However, it is associated with hypotension (33%), bradycardia (13%), and shivering which are induced by hypovolemia, sympathetic blockade, and Bezold–Jarisch reflex through intracardiac serotonin (5HT3) receptors and vagus nerve.

Aim:

To study the effect of intravenous (i.v.) ondansetron on hypotension and bradycardia induced by spinal anesthesia.

Setting and Design:

This was a randomized controlled double-blinded study done in a tertiary care teaching hospital.

Methods:

Of 140 patients, 70 in Group A received 2 mL of i.v. ondansetron 4 mg and 70 in the Group B received 2 mL of i.v. normal saline. 3 mL of 0.5% hyperbaric bupivacaine was injected intrathecally. Measurements of blood pressure and heart rate (HR) were taken every 3 min for 30 min after spinal anesthesia was performed. Mean arterial pressure (MAP) drop more than 20% was considered as incidence of hypotension and ephedrine 6 mg i.v. was given. HR drop >20% was regarded as bradycardia and atropine 0.5 mg i.v. was given.

Statistical Tests:

Quantitative data were analyzed using ANOVA test and qualitative data were analyzed using Chi-square test.

Results:

Both groups are comparable in demographic data. Four (5.7%) patients in Group B and no patients in Group A had incidence of bradycardia and atropine requirement (P = 0.120). There was no statistically significant difference in systolic blood pressure, diastolic blood pressure, and MAP. 19 (27%) patients in Group A and 33 (47.1%) in Group B required ephedrine with P = 0.029. 12 (17.1%) in Group B and no patients in Group A had shivering with P = 0.0001.

Conclusion:

Our study indicates that prophylactic use of ondansetron before spinal anesthesia significantly reduces the requirement of ephedrine and shivering.

Postnatal outcomes in lambs exposed antenatally and acutely postnatally to fluoxetine

BACKGROUND

Approximately 1/3 of newborns exposed antenatally to selective serotonin reuptake inhibitors (SSRIs) exhibit poor neonatal adaptation. Although several potential mechanisms have been proposed, the actual mechanism has not been elucidated.

METHODS

We investigated outcomes in neonatal lambs exposed prenatally or postnatally to fluoxetine (FX). Daily FX injections (50 mg) were given intravenously (i.v.) to five pregnant ewes via implanted catheters beginning at 131-132 days gestation (term = 147 days) for 2 weeks. In another group, lambs with implanted vascular catheters had sterile water (n = 9) or FX (1 mg/kg, n = 12) injected i.v. on ~postnatal day (PND) 4.

RESULTS

Prenatal FX-exposed lambs (n = 7) were hyperactive during PND 4 to 14 and their heart rate variability (HRV) was significantly lower than in control lambs (n = 7) on PND 2. In contrast, arterial pressure, heart rate, electrocardiogram, arterial blood gases, pH, glucose, lactate, cortisol, and sleep-activity cycles were not altered following postnatal FX injection.

CONCLUSION

This abnormal postnatal hyperactivity with antenatal FX exposure may reflect increased maturity in terms of locomotory activity. The results suggest that altered brain development may be involved in the poor neonatal adaptation in human infants exposed to FX in utero.

Management of severe arterial hypertension associated with serotonin syndrome: a case report analysis based on systematic review techniques

Serotonin syndrome is thought to arise from serotonin excess. In many cases, symptoms are mild and self-limiting. But serotonin syndrome can become life threatening, when neuromuscular hyperexcitability spins out of control. Uncontainable neuromuscular hyperexcitability may lead to cardiovascular complications, linked to extreme changes in blood pressure. Currently, there is little guidance on how to control blood pressure in hyperserotonergic states. We report a case with treatment-resistant arterial hypertension, followed by a clinical review (using systematic review principles and techniques) of the available evidence from case reports published between 2004 and 2016 to identify measures to control arterial hypertension associated with serotonin syndrome. We conclude that classic antihypertensives may not be effective for the treatment of severe hypertension associated with serotonin syndrome. Benzodiazepines may lower blood pressure. Patients with severe hypertension not responding to benzodiazepines may benefit from cyproheptadine, propofol or both. In severe cases, higher cyproheptadine doses than currently recommended may be necessary.

Fenfluramine-induced PVAT-dependent contraction depends on norepinephrine and not serotonin

Perivascular adipose tissue (PVAT) modulates vascular tone and altered PVAT function is observed in vascular diseases such as hypertension and atherosclerosis. We discovered that the PVAT surrounding rat thoracic aorta (RA) and the superior mesenteric artery (SMA) contain significant amounts of 5-hydroxytryptamine (5-HT). We hypothesized that the 5-HT contained within the PVAT is functional and vasoactive. Isolated tissue baths were used for isometric contractility studies and high performance liquid chromatography was used to quantitatively measure amines in the PVAT and release studies. The 5-HT releaser fenfluramine (10 nM-100 μM) was tested for its ability to contract arteries with and without PVAT. Contraction was reported as a percentage of the initial contraction to 10 μM phenylephrine. The RA with PVAT contracted to fenfluramine to a greater maximum (98 ± 10%) than RA without PVAT (24 ± 4%), while no difference in contraction of SMA to maximum fenfluramine with (78 ± 2%) and without (75 ± 6%) PVAT was observed. Contradicting our hypothesis, the maximum contraction of RA with PVAT to fenfluramine was diminished by the alpha-1 adrenoreceptor antagonist prazosin (100 nM; vehicle: 71 ± 4%, prazosin: 24 ± 2%) and the norepinephrine transporter (NET) inhibitor nisoxetine (1 μM; vehicle: 71 ± 4%, nisoxetine: 25 ± 4%) but not the 5-HT_2A/2C receptor antagonist ketanserin (10 nM) or serotonin specific reuptake inhibitor fluoxetine (10 μM). To test if fenfluramine caused release of 5-HT or NE from PVAT, PVAT from RA was incubated with vehicle or fenfluramine (10 μM-10 mM), and amines released into the incubating buffer were quantified. A pronounced concentration-dependent NE-release (more than 5-HT) was observed. Collectively, this research illustrates the pharmacology of fenfluramine to primarily stimulate NE release (better than 5-HT) in a NET-dependent manner, leading to vasoconstriction. This adds additional support to PVAT as being an important reservoir of amines.

Inhibition of 5-Hydroxytryptamine Receptor 2B Reduced Vascular Restenosis and Mitigated the β-Arrestin2-Mammalian Target of Rapamycin/p70S6K Pathway

BACKGROUND

As a monoamine neurotransmitter, 5-hydroxytryptamine (5-HT) or serotonin modulates mood, appetite, and sleep. Besides, 5-HT also has important peripheral functions. 5-HT receptor 2B (5-HT2BR) plays a key role in cardiovascular diseases, such as pulmonary arterial hypertension and cardiac valve disease. Percutaneous intervention has been used to restore blood flow in occlusive vascular disease. However, restenosis remains a significant problem. Herein, we investigated the role of 5-HT2BR in neointimal hyperplasia, a key pathological process in restenosis.

METHODS AND RESULTS

The expression of 5-HT2BR was upregulated in wire-injured mouse femoral arteries. In addition, BW723C86, a selective 5-HT2BR agonist, promoted the injury response during restenosis. 5-HT and BW723C86 stimulated migration and proliferation of rat aortic smooth muscle cells. Conversely, LY272015, a selective antagonist, attenuated the 5-HT-induced smooth muscle cell migration and proliferation. In vitro study showed that the promigratory effects of 5-HT2BR were mediated through the activation of mammalian target of rapamycin (mTOR)/p70S6K signaling in a β-arrestin2-dependent manner. Inhibition of mammalian target of rapamycin or p70S6K mitigated 5-HT2BR-mediated smooth muscle cell migration. Mice with deficiency of 5-HT2BR showed significantly reduced neointimal formation in wire-injured arteries.

CONCLUSIONS

These results demonstrated that activation of 5-HT2BR and β-arrestin2-biased downstream signaling are key pathological processes in neointimal formation, and 5-HT2BR may be a potential target for the therapeutic intervention of vascular restenosis.

Multiple activation mechanisms of serotonin-mediated contraction in the carotid arteries obtained from spontaneously hypertensive rats

Serotonin (5-hydroxytryptamine, 5-HT) is an important endogenous substance that regulates the vascular tone, and the abnormal signaling of 5-HT has been observed in the arteries under several pathophysiological conditions such as diabetes and hypertension. However, signaling pathways of 5-HT-mediated vasocontraction in hypertension remain unclear. Therefore, we tested the hypothesis that 5-HT-mediated contraction and contributions of various kinases such as mitogen-activated protein kinases (MAPKs), phosphoinositide 3-kinase (PI3K), Rho kinase (ROCK), and 3-phosphoinositide-dependent kinase 1 (PDK1) to the contraction would be altered in the carotid arteries obtained from spontaneously hypertensive rats (SHR) compared to control Wistar Kyoto (WKY) rats. In the carotid arteries from SHR (vs. those from WKY), (1) the 5-HT-mediated contraction was increased, whereas the norepinephrine-mediated contraction was not; (2) 5-HT-mediated contractions were partly inhibited by each kinase (extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, c-Jun N-terminal kinase (JNK), PI3K, ROCK, and PDK1) inhibitor; and (3) 5-HT-stimulated phosphorylation of ERK1/2, p38 MAPK, JNK, myosin phosphatase target subunit 1 (MYPT1), and PDK1 was increased. The expression of ROCK2 but not ROCK1 was increased in the carotid arteries from SHR compared to WKY. The expression of 5-HT2A receptor, a major receptor of 5-HT-mediated contraction in rat carotid artery, was similar in carotid arteries between the two groups. These results suggest that 5-HT-mediated contraction was utilized multiple signaling pathways such as ERK1/2, p38 MAPK, JNK, PI3K, ROCK, and PDK1. Although 5-HT-mediated contraction was increased in the carotid arteries obtained from SHR, further studies are necessary to clarify how each kinase may integrate in the vascular smooth muscles under hypertension.

Contractile effects of 3,4-methylenedioxymethamphetamine on the human internal mammary artery

Since the late 1980s numerous reports have detailed adverse reactions to the use of 3,4-methylenedioxymethamphetamine (MDMA) associated with cardiovascular collapse and sudden death, following ventricular tachycardia and hypertension. For a better understanding of the effects of MDMA on the cardiovascular system, it is critical to determine their effects at the vasculature level, including the transporter or neurotransmitter systems that are most affected at the whole range of drug doses. With this purpose in mind, the aim of our study was to evaluate the contractile effect of MDMA in the human internal mammary artery, the contribution of SERT for this effect and the responsiveness of this artery to 5-HT in the presence of MDMA. We have also studied the possible involvement of 5-HT2 receptors on the MDMA contractile effect in this human blood vessel using ketanserin. Our results showed that MDMA contracted the studied human's internal mammary artery in a SERT-independent form, through activation of 5-HT2A receptors. Considering the high plasma concentrations achieved in heavy users or in situations of acute exposure to drugs, this effect is probably involved in the cardiovascular risk profile of this psychostimulant, especially in subjects with pre-existing cardiovascular disease.

Duloxetine and escitalopram for hot flushes: efficacy and compliance in breast cancer survivors

Selective serotonin reuptake inhibitors (SSRI) and serotonin-norepinephrine reuptake inhibitors (SNRI) might be an effective treatment for hot flushes (HFs) in breast cancer survivors (BCSs). This study aims to compare the efficacy and tolerability of duloxetine (SNRI) versus escitalopram (SSRI) in reducing frequency and severity of HFs in BCSs and to assess the effect on depression. Thirty-four symptomatic BCSs with emotional impairment received randomly duloxetine 60 mg daily or escitalopram 20 mg daily for 12 weeks. Patients were asked to record in a diary HF frequency and severity at baseline and after 4 and 12 weeks of treatment. Depression was evaluated through validated questionnaires (Beck Depression Inventory and Montgomery Asberg Depression Rating Scale) at baseline and after 4 and 12 weeks of treatment. Both drugs showed a significant reduction of HF frequency and severity after 12 weeks of treatment with no significant difference between the two groups. A significant improvement in depression symptoms was observed at the end of the study period within both the groups, without difference between the two drugs. In conclusion, escitalopram and duloxetine are both effective treatment for the relief of HFs in BCSs, with similar beneficial effect. A significant improvement of depression was obtained with no major side effects.

Insulin augments serotonin-induced contraction via activation of the IR/PI3K/PDK1 pathway in the rat carotid artery

Hyperinsulinemia associated with type 2 diabetes may contribute to the development of vascular diseases. Although we recently reported that enhanced contractile responses to serotonin (5-hydroxytryptamine, 5-HT) are observed in the arteries of type 2 diabetes models, the causative factors and detailed signaling pathways involved remain unclear. The purpose of this study was to investigate whether high insulin would be an amplifier of 5-HT-induced contraction in rat carotid arteries and whether the contraction involves phosphoinositide 3-kinase (PI3K)/3-phosphoinositide-dependent protein kinase 1 (PDK1) signaling, an insulin-mediated signaling pathway. In rat carotid arteries organ-cultured with insulin (for 24 h), (1) the contractile responses to 5-HT were significantly greater (vs. vehicle), (2) the insulin-induced enhancement of 5-HT-induced contractions was largely suppressed by inhibitors of the insulin receptor (IR) (GSK1838705A), PI3K (LY294002), and PDK1 (GSK2334470), and (3) the levels of phosphorylated forms of both PDK1 and myosin phosphatase target subunit 1 (MYPT1) were greater upon 5-HT stimulation. In addition, in rat carotid arteries organ-cultured with an activator of PDK1 (PS48), the 5-HT-induced contraction was greater, and this was suppressed by PDK1 inhibition but not PI3K inhibition. In addition, MYPT1 and PDK1 phosphorylation upon 5-HT stimulation was enhanced (vs. vehicle). These results suggest that high insulin levels amplify 5-HT-induced contraction. Moreover, the present results indicated the direct linkage between IR/PI3K/PDK1 activation and 5-HT-induced contraction in rat carotid arteries for the first time.

Alteration of Gene Expression Profile in Kidney of Spontaneously Hypertensive Rats Treated with Protein Hydrolysate of Blue Mussel (Mytilus edulis) by DNA Microarray Analysis

Marine organisms are rich sources of bioactive components, which are often reported to have antihypertensive effects. However, the underlying mechanisms have yet to be fully identified. The aim of this study was to investigate the antihypertensive effect of enzymatic hydrolysis of blue mussel protein (HBMP) in rats. Peptides with in vitro ACE inhibitory activity were purified from HBMP by ultrafiltration, gel filtration chromatography and reversed-phase high performance liquid chromatography. And the amino acid sequences of isolated peptides were estimated to be Val-Trp, Leu-Gly-Trp, and Met-Val-Trp-Thr. To study its in vivo action, spontaneously hypertensive rats (SHRs) were orally administration with high- or low-dose of HBMP for 28 days. Major components of the renin-angiotensin (RAS) system in serum of SHRs from different groups were analyzed, and gene expression profiling were performed in the kidney of SHRs, using the Whole Rat Genome Oligonucleotide Microarray. Results indicated although genes involved in RAS system were not significantly altered, those related to blood coagulation system, cytokine and growth factor, and fatty acids metabolism were remarkablely changed. Several genes which were seldom reported to be implicated in pathogenesis of hypertension also showed significant expression alterations after oral administration of HBMP. These data provided valuable information for our understanding of the molecular mechanisms that underlie the potential antihypertensive activities of HBMP, and will contribute towards increased value-added utilization of blue mussel protein.

A molecular signature in the pannexin1 intracellular loop confers channel activation by the α1 adrenoreceptor in smooth muscle cells

Both purinergic signaling through nucleotides such as ATP (adenosine 5'-triphosphate) and noradrenergic signaling through molecules such as norepinephrine regulate vascular tone and blood pressure. Pannexin1 (Panx1), which forms large-pore, ATP-releasing channels, is present in vascular smooth muscle cells in peripheral blood vessels and participates in noradrenergic responses. Using pharmacological approaches and mice conditionally lacking Panx1 in smooth muscle cells, we found that Panx1 contributed to vasoconstriction mediated by the α1 adrenoreceptor (α1AR), whereas vasoconstriction in response to serotonin or endothelin-1 was independent of Panx1. Analysis of the Panx1-deficient mice showed that Panx1 contributed to blood pressure regulation especially during the night cycle when sympathetic nervous activity is highest. Using mimetic peptides and site-directed mutagenesis, we identified a specific amino acid sequence in the Panx1 intracellular loop that is essential for activation by α1AR signaling. Collectively, these data describe a specific link between noradrenergic and purinergic signaling in blood pressure homeostasis.

Vascular targets for cannabinoids: animal and human studies

Application of cannabinoids and endocannabinoids to perfused vascular beds or individual isolated arteries results in changes in vascular resistance. In most cases, the result is vasorelaxation, although vasoconstrictor responses are also observed. Cannabinoids also modulate the actions of vasoactive compounds including acetylcholine, methoxamine, angiotensin II and U46619 (thromboxane mimetic). Numerous mechanisms of action have been proposed including receptor activation, potassium channel activation, calcium channel inhibition and the production of vasoactive mediators such as calcitonin gene-related peptide, prostanoids, NO, endothelial-derived hyperpolarizing factor and hydrogen peroxide. The purpose of this review is to examine the evidence for the range of receptors now known to be activated by cannabinoids. Direct activation by cannabinoids of CB1 , CBe , TRPV1 (and potentially other TRP channels) and PPARs in the vasculature has been observed. A potential role for CB2, GPR55 and 5-HT1 A has also been identified in some studies. Indirectly, activation of prostanoid receptors (TP, IP, EP1 and EP4 ) and the CGRP receptor is involved in the vascular responses to cannabinoids. The majority of this evidence has been obtained through animal research, but recent work has confirmed some of these targets in human arteries. Vascular responses to cannabinoids are enhanced in hypertension and cirrhosis, but are reduced in obesity and diabetes, both due to changes in the target sites of action. Much further work is required to establish the extent of vascular actions of cannabinoids and the application of this research in physiological and pathophysiological situations.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6.

Upregulation of 5-hydroxytryptamine receptor signaling in coronary arteries after organ culture

Background

5-Hydroxytryptamine (5-HT) is a powerful constrictor of coronary arteries and is considered to be involved in the pathophysiological mechanisms of coronary-artery spasm. However, the mechanism of enhancement of coronary-artery constriction to 5-HT during the development of coronary artery disease remains to be elucidated. Organ culture of intact blood-vessel segments has been suggested as a model for the phenotypic changes of smooth muscle cells in cardiovascular disease.

Methodology/Principal Findings

We wished to characterize 5-HT receptor-induced vasoconstriction and quantify expression of 5-HT receptor signaling in cultured rat coronary arteries. Cumulative application of 5-HT produced a concentration-dependent vasoconstriction in fresh and 24 h-cultured rat coronary arteries without endothelia. 5-HT induced greater constriction in cultured coronary arteries than in fresh coronary arteries. U46619- and CaCl₂-induced constriction in the two groups was comparable. 5-HT stimulates the 5-HT_2A receptor and cascade of phospholipase C to induce coronary vasoconstriction. Calcium influx through L-type calcium channels and non-L-type calcium channels contributed to the coronary-artery constrictions induced by 5-HT. The contractions mediated by non-L-type calcium channels were significantly enhanced in cultured coronary arteries compared with fresh coronary arteries. The vasoconstriction induced by thapsigargin was also augmented in cultured coronary arteries. The decrease in Orai1 expression significantly inhibited 5-HT-evoked entry of Ca²⁺ in coronary artery cells. Expression of the 5-HT_2A receptor, Orai1 and STIM1 were augmented in cultured coronary arteries compared with fresh coronary arteries.

Conclusions

An increased contraction in response to 5-HT was mediated by the upregulation of 5-HT_2A receptors and downstream signaling in cultured coronary arteries.

7-3-Chlorophenypiperazinylalkyl derivatives of 8-alkoxy-purine-2,6-dione as a serotonin receptor ligands with potential antidepressant activity

BACKGROUND

The previous study showed that arylpiperazine can condition affinity to α-adrenoceptors, 5-HT1A/5-HT2A receptors and compounds with arylpiperazine had antidepressant-like effect. The aim of this study was to determine the antidepressant-like activity of new arylpiperazines containing novel 8-alkoxy-purine-2,6-dione fragments.

METHODS

New 3-chloroarylpiperazinylalkyl analogs of 8-alkoxy-purine-2,6-dione and their purine-2,6,8-trione analogs (2-5) were tested for their α1, α2, 5-HT1A,5-HT2A, and 5-HT7 receptor affinities in radioreceptor binding study. Moreover, in search for potential antidepressant properties of these compounds, the forced swim test in mice was conducted.

RESULTS

Compounds 2 and 3 were potent 5-HT1A receptor ligands with Ki within the range on 12-15 nM. All investigated compounds were found to be highly active 5-HT2A receptor (Ki 15-28 nM) and α1 adrenoceptor (Ki 21-89 nM) ligands. In the forced swim test all the compounds showed a significantly activity in spite of their reducing ability of locomotor activity. The most potent effect was produced by compound 4 and 5, which reduced the immobility time in this test in all used doses.

CONCLUSION

In our study the most potent antidepressant-like activity was produced by compounds 4 and 5, which are selective for the 5-HT2A and α1 receptors.

Cyclopiazonic acid alters serotonin-induced responses in rat thoracic aorta

We previously showed that endothelin A (ETA) receptor antagonist BQ-123 partially inhibited cyclopiazonic acid (CPA)-enhanced endothelin-1 (ET-1)-induced contractions suggesting enhancement of ETA receptor internalization in caveolar structures by sarco/endoplasmic reticulum Ca+2 ATPase (SERCA) blockade. Since serotonin (5-Hydroxytryptamine, 5-HT) receptors are reported to be localized on caveolar membranes, we investigated whether SERCA inhibition affects 5-HT-induced responses and 5-HT receptor antagonism. For this purpose, vascular responses were measured in thoracic aorta segments from male Wistar albino rats using isolated tissue experiments. Data showed that CPA inhibits 5-HT- and PE-induced contractions in intact vessels while potentiating those in endothelium-denuded. Furthermore, non-selective 5-HT receptor blocker methysergide partially inhibited CPA-induced 5-HT contractions. However, α1-adrenergic receptor antagonist prazosin totally inhibited CPA-potentiated PE contractions. We suggest that SERCA inhibition results in 5-HT receptor internalization similar to ETA receptors possibly through protein kinase C activation by increased subsarcolemmal Ca2+ levels, eventually preventing 5-HT receptor antagonism.

Serotonin 5-HT2A receptor activation blocks TNF-α mediated inflammation in vivo

Tumor necrosis factor alpha (TNF-α) plays a key role in inflammation, and its production and signaling contribute to many inflammatory related diseases. Recently, we discovered that selective activation of serotonin 5-HT2A receptors with the agonist (R)-DOI produces a super-potent blockade of proinflammatory markers in primary rat aortic smooth muscle cells. Here, we demonstrate that systemic administration of (R)-DOI can block the systemic effects of TNF-α in whole animal, with potent anti-inflammatory effects in the aortic arch and small intestine. This includes blockade of TNF-α-induced expression of pro-inflammatory cell adhesion (Icam-1, Vcam-1), cytokine (Il-6, IL-1b), and chemokine (Mcp-1, Cx3cl1) genes, and expression of VCAM-1 protein in the intestine. Further, systemic (R)-DOI also prevents the TNF-α-induced increase of circulating IL-6. Importantly, utilizing receptor selective antagonists, we have demonstrated that the mechanism underlying the systemic anti-inflammatory effects of (R)-DOI is activation of serotonin 5-HT2A receptors. Our results highlight a powerful new role for the serotonin 5-HT2A receptor in inflammatory processes, and indicate that agonism of serotonin receptors may represent an effective and novel approach to develop powerful small molecule therapeutics for inflammatory diseases and conditions such as atherosclerosis and inflammatory bowel disease.

Peroxisome proliferator-activated receptor-γ ameliorates pulmonary arterial hypertension by inhibiting 5-hydroxytryptamine 2B receptor

An elevated plasma level of 5-hydroxytryptamine (5-HT) or upregulation of 5-HT receptor signaling or both is implicated in vascular contraction and remodeling in pulmonary arterial hypertension (PAH). Recently, peroxisome proliferator-activated receptor-γ (PPARγ) agonists have been shown to ameliorate PAH. However, their effects on the 5-HT-induced contraction of pulmonary arteries remain unknown. Here, we examined the role of PPARγ in inhibiting 5-HT2B receptor (5-HT2BR) to ameliorate PAH. Pulmonary arteries from PAH rats induced by monocrotaline or chronic hypoxia showed an enhanced vasoconstriction in response to BW723C86, a specific agonist for 5-HT2BR. Expression of 5-HT2BR was also increased in pulmonary arteries from the PAH rats, accompanied by vascular remodeling and right ventricular hypertrophy. Treatment with the PPARγ agonist rosiglitazone in vivo reversed the expression and the vasocontractive effect of 5-HT2BR as well as the thickening of pulmonary arteries. In pulmonary artery smooth muscle cells, 5-HT induced the gene expression of 5-HT2BR, which was inhibited by rosiglitazone, pioglitazone, or adenovirus-mediated overexpression of constitutively activated PPARγ. The pharmacological effect of PPARγ was through the suppression of the 5-HT-induced activator protein-1 activity. These results demonstrated the beneficial effect of PPARγ on 5-HT2BR-mediated vasocontraction, providing a new mechanism for the potential use of PPARγ agonists in PAH.

Serotonin passes through myoendothelial gap junctions to promote pulmonary arterial smooth muscle cell differentiation

Myoendothelial gap junctional signaling mediates pulmonary arterial endothelial cell (PAEC)-induced activation of latent TGF-β and differentiation of cocultured pulmonary arterial smooth muscle cells (PASMCs), but the nature of the signal passing from PAECs to PASMCs through the gap junctions is unknown. Because PAECs but not PASMCs synthesize serotonin, and serotonin can pass through gap junctions, we hypothesized that the monoamine is the intercellular signal. We aimed to determine whether PAEC-derived serotonin mediates PAEC-induced myoendothelial gap junction-dependent activation of TGF-β signaling and differentiation of PASMCs. Rat PAECs and PASMCs were monocultured or cocultured with (touch) or without (no-touch) direct cell-cell contact. In all cases, tryptophan hydroxylase 1 (Tph1) transcripts were expressed predominantly in PAECs. Serotonin was detected by immunostaining in both PAECs and PASMCs in PAEC/PASMC touch coculture but was not found in PASMCs in either PAEC/PASMC no-touch coculture or in PASMC/PASMC touch coculture. Furthermore, inhibition of gap junctions but not of the serotonin transporter in PAEC/PASMC touch coculture prevented serotonin transfer from PAECs to PASMCs. Inhibition of serotonin synthesis pharmacologically or by small interfering RNAs to Tph1 in PAECs inhibited the PAEC-induced activation of TGF-β signaling and differentiation of PASMCs. We concluded that serotonin synthesized by PAECs is transferred through myoendothelial gap junctions into PASMCs, where it activates TGF-β signaling and induces a more differentiated phenotype. This finding suggests a novel role of gap junction-mediated intercellular serotonin signaling in regulation of PASMC phenotype.

Inhibition of allergic inflammation by supplementation with 5-hydroxytryptophan

Clinical reports indicate that patients with allergy/asthma commonly have associated symptoms of anxiety/depression. Anxiety/depression can be reduced by 5-hydroxytryptophan (5-HTP) supplementation. However, it is not known whether 5-HTP reduces allergic inflammation. Therefore, we determined whether 5-HTP supplementation reduces allergic inflammation. We also determined whether 5-HTP decreases passage of leukocytes through the endothelial barrier by regulating endothelial cell function. For these studies, C57BL/6 mice were supplemented with 5-HTP, treated with ovalbumin fraction V (OVA), house dust mite (HDM) extract, or IL-4, and examined for allergic lung inflammation and OVA-induced airway responsiveness. To determine whether 5-HTP reduces leukocyte or eosinophil transendothelial migration, endothelial cells were pretreated with 5-HTP, washed and then used in an in vitro transendothelial migration assay under laminar flow. Interestingly, 5-HTP reduced allergic lung inflammation by 70-90% and reduced antigen-induced airway responsiveness without affecting body weight, blood eosinophils, cytokines, or chemokines. 5-HTP reduced allergen-induced transglutaminase 2 (TG2) expression and serotonylation (serotonin conjugation to proteins) in lung endothelial cells. Consistent with the regulation of endothelial serotonylation in vivo, in vitro pretreatment of endothelial cells with 5-HTP reduced TNF-α-induced endothelial cell serotonylation and reduced leukocyte transendothelial migration. Furthermore, eosinophil and leukocyte transendothelial migration was reduced by inhibitors of transglutaminase and by inhibition of endothelial cell serotonin synthesis, suggesting that endothelial cell serotonylation is key for leukocyte transendothelial migration. In summary, 5-HTP supplementation inhibits endothelial serotonylation, leukocyte recruitment, and allergic inflammation. These data identify novel potential targets for intervention in allergy/asthma.

Alteration of serotonin system by polychlorinated biphenyls exposure

Although commercial production of polychlorinated biphenyls (PCBs) was banned in 1979, PCBs continue to be an environmental and health concern due to their high bioaccumulation and slow degradation rates. In fact, PCBs are still present in our food supply (fish, meat, and dairy products). In laboratory animals, exposure to single PCB congener or to mixtures of different congeners induces a variety of physiological alterations. PCBs cross the placenta and even exposure at low level is harmful for the foetus by leading to neurodevelopment alterations. Serotonin system which regulates many physiological functions from platelet activation to high cerebral processes and neurodevelopment is one of the targets of PCBs toxicity. The effects of PCBs exposure on serotonin system have been investigated although to a lesser extent compared to its effect in other neurotransmitter systems. This review provides a summary of the results concerning the impact of PCBs exposure (in vitro and in vivo) on serotonin system. Further research is needed to correlate specific deficits with PCB-induced changes in the serotonin system.

5-hydroxytryptamine (5-HT) reduces total peripheral resistance during chronic infusion: direct arterial mesenteric relaxation is not involved

Serotonin (5-hydroxytryptamine; 5-HT) delivered over 1 week results in a sustained fall in blood pressure in the sham and deoxycorticosterone acetate (DOCA)-salt rat. We hypothesized 5-HT lowers blood pressure through direct receptor-mediated vascular relaxation. In vivo, 5-HT reduced mean arterial pressure (MAP), increased heart rate, stroke volume, cardiac index, and reduced total peripheral resistance during a 1 week infusion of 5-HT (25 µg/kg/min) in the normotensive Sprague Dawley rat. The mesenteric vasculature was chosen as an ideal candidate for the site of 5-HT receptor mediated vascular relaxation given the high percentage of cardiac output the site receives. Real-time RT-PCR demonstrated that mRNA transcripts for the 5-HT_2B, 5-HT_1B, and 5-HT₇ receptors are present in sham and DOCA-salt superior mesenteric arteries. Immunohistochemistry and Western blot validated the presence of the 5-HT_2B, 5- HT_1B and 5-HT₇ receptor protein in sham and DOCA-salt superior mesenteric artery. Isometric contractile force was measured in endothelium-intact superior mesenteric artery and mesenteric resistance arteries in which the contractile 5- HT_2A receptor was antagonized. Maximum concentrations of BW-723C86 (5- HT_2B agonist), CP 93129 (5-HT_1B agonist) or LP-44 (5-HT₇ agonist) did not relax the superior mesenteric artery from DOCA-salt rats vs. vehicle. Additionally, 5-HT (10^–9 M to 10^–5 M) did not cause relaxation in either contracted mesenteric resistance arteries or superior mesenteric arteries from normotensive Sprague- Dawley rats. Thus, although 5-HT receptors known to mediate vascular relaxation are present in the superior mesenteric artery, they are not functional, and are therefore not likely involved in a 5-HT-induced fall in total peripheral resistance and MAP.

Blood pressure and mesenteric vascular reactivity in spontaneously hypertensive rats 7 months after gonadectomy

OBJECTIVE

Sexual dimorphism in the degree of high blood pressure (BP) has been observed in both animal and human hypertension. However, the mechanisms are still poorly understood. We tested the hypothesis that long-term loss of sex steroids promotes changes in mesenteric vascular reactivity that impact the maintenance of hypertension in the spontaneously hypertensive rats (SHR).

METHODS

Male SHR were sham operated (M-SHAM) or castrated (M-CX), and female SHR were sham-operated (F-SHAM) or ovariectomized (F-OVX) at 3 weeks of age. Seven months later, BP was measured in anesthetized rats, and vascular responsiveness was evaluated in the isolated perfused mesentery.

RESULTS

Mean arterial BP (mm Hg) was significantly greater in M-SHAM (186 ± 6) compared with F-SHAM (159 ± 5). Gonadectomy reduced BP in male SHR (M-CX: 160 ± 4) but had no significant effect in female SHR (F-OVX: 153 ± 7). Norepinephrine-induced constriction was similar in all groups. Gonadectomy attenuated serotonin-induced vasoconstriction in the mesentery. Acetylcholine (ACh)- and isoproterenol (ISO)-induced vasodilation was greater in female than male SHR. Ovariectomy of female SHR blunted ACh and ISO dilatory responses. ISO dose-response curves were shifted to the left in castrated male SHR.

CONCLUSIONS

Gonadectomy exerts long-term effects on mesenteric vascular reactivity and hypertension in the SHR.