Functions of 5-HT2A receptor and its antagonists in the cardiovascular system

Antidepressant and anxiolytic effects of activating 5HT2A receptors in the anterior cingulate cortex and the theoretical mechanisms underlying them - A scoping review of available literature

Psychedelic drugs that activate the 5HT2A receptor have long been the target of extensive clinical research, particularly in models of psychiatric illness. The aim of this literature review was to investigate the therapeutic effects of 5HT2A receptor activation in the anterior cingulate cortex (ACC) and the respective mechanisms that underlie them. Based on the available research, I suggest that 5HT2A receptors in the ACC exert profound changes in excitatory neurotransmission and brain network connectivity in a way that reduces anxious preoccupation and obsessional thoughts, as well as promoting cognitive flexibility and long-lasting mood improvements in anhedonia. This is possibly due to a complex interplay with glutamate and gamma-butyric acid neurotransmission, particularly 5HT2A activation enhances α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor signalling, thus altering the ratio of AMPA to N-methyl-D-Aspartate (NMDA) activity in the ACC, which can dismantle previously established neuronal connections and aid the formation of new ones, an effect that may be beneficial for fear extinction and reversal learning. Psychedelics potentially change intra- and internetwork connectivity, strengthening connectivity from the dorsal ACC / Salience Network to the Default Mode Network (DMN) and Central Executive Network (CEN), which correlates with improvements in attentional shifting and anti-anhedonic effects. Additionally, they may decrease inhibitory influence of the DMN over the CEN which may reduce overevaluation of internal states and ameliorate cognitive deficits. Activation of ACC 5HT2A receptors also has important downstream effects on subcortical areas, including reducing amygdala reactivity to threatening stimuli and enhancing mesolimbic dopamine, respectively improving anxiety and the experience of natural rewards.

Role of Vasoactive Hormone-Induced Signal Transduction in Cardiac Hypertrophy and Heart Failure

Heart failure is the common concluding pathway for a majority of cardiovascular diseases and is associated with cardiac dysfunction. Since heart failure is invariably preceded by adaptive or maladaptive cardiac hypertrophy, several biochemical mechanisms have been proposed to explain the development of cardiac hypertrophy and progression to heart failure. One of these includes the activation of different neuroendocrine systems for elevating the circulating levels of different vasoactive hormones such as catecholamines, angiotensin II, vasopressin, serotonin and endothelins. All these hormones are released in the circulation and stimulate different signal transduction systems by acting on their respective receptors on the cell membrane to promote protein synthesis in cardiomyocytes and induce cardiac hypertrophy. The elevated levels of these vasoactive hormones induce hemodynamic overload, increase ventricular wall tension, increase protein synthesis and the occurrence of cardiac remodeling. In addition, there occurs an increase in proinflammatory cytokines and collagen synthesis for the induction of myocardial fibrosis and the transition of adaptive to maladaptive hypertrophy. The prolonged exposure of the hypertrophied heart to these vasoactive hormones has been reported to result in the oxidation of catecholamines and serotonin via monoamine oxidase as well as the activation of NADPH oxidase via angiotensin II and endothelins to promote oxidative stress. The development of oxidative stress produces subcellular defects, Ca2+-handling abnormalities, mitochondrial Ca2+-overload and cardiac dysfunction by activating different proteases and depressing cardiac gene expression, in addition to destabilizing the extracellular matrix upon activating some metalloproteinases. These observations support the view that elevated levels of various vasoactive hormones, by producing hemodynamic overload and activating their respective receptor-mediated signal transduction mechanisms, induce cardiac hypertrophy. Furthermore, the occurrence of oxidative stress due to the prolonged exposure of the hypertrophied heart to these hormones plays a critical role in the progression of heart failure.

The Benzoylpiperidine Fragment as a Privileged Structure in Medicinal Chemistry: A Comprehensive Review

The phenyl(piperidin-4-yl)methanone fragment (here referred to as the benzoylpiperidine fragment) is a privileged structure in the development of new drugs considering its presence in many bioactive small molecules with both therapeutic (such as anti-cancer, anti-psychotic, anti-thrombotic, anti-arrhythmic, anti-tubercular, anti-parasitic, anti-diabetic, and neuroprotective agents) and diagnostic properties. The benzoylpiperidine fragment is metabolically stable, and it is also considered a potential bioisostere of the piperazine ring, thus making it a feasible and reliable chemical frame to be exploited in drug design. Herein, we discuss the main therapeutic and diagnostic agents presenting the benzoylpiperidine motif in their structure, covering articles reported in the literature since 2000. A specific section is focused on the synthetic strategies adopted to obtain this versatile chemical portion.

Hydrophobicity modulation via the substituents at positions 2 and 4 of 1,3,5-triazine to enhance therapeutic ability against Alzheimer's disease for potent serotonin 5-HT6R agents

Alzheimer's disease (AD), a neurodegenerative disorder with a complex aetiology, is the most common memory dysfunction particularly affecting the elderly. Various protein targets have been classified to be involved in the AD treatment, including 5-HT6 receptor (5-HT6R). So far, the 5-HT6R ligands obtained by our research group have become a good basis for hydrophobicity modulation to give a chance for more effective action toward AD by additional influence on target enzymes, e.g. cyclin-dependent kinase 5 (CDK5). In the search for 5-HT6R agents with additional inhibitory action on the enzyme, a series of 25 new 1,3,5-triazines (7-31) as modifications of lead, 4-[1-(2,5-dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazine-2-amine (6), was rationally designed. Molecular modelling, synthesis, crystallographic studies, in vitro biological assays and behavioral studies in vivo were performed. The new triazines showed high affinity (Ki < 100 nM) and selectivity for 5-HT6R. The most effective one, 4-[1-(2,5-difluorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazine-2-amine (8), exhibited the strong antagonistic action towards 5-HT6R (Ki = 5 nM, pKb = 8.16), had an impact on the memory processes in the Novel Object Recognition test and displayed anxiolytic-like activity in the Elevated Plus Maze test in rats. Moreover, it had the antiplatelet effect as well as very good permeability (PAMPA model), high metabolic stability (RLMs) and satisfactory safety in vitro. Although the CDK5 inhibitory effects in vitro for the tested compounds (8, 10, 14, 18, 26-31) missed the potency expected from in silico simulations, the novel antagonist (8) with a very satisfying pharmacological and ADMET profile can serve as a new lead structure in further searches for innovative therapy against AD with accompanying symptoms.

Insights into the advances in therapeutic drugs for neuroinflammation-related diseases

Studies have shown that neurodegenerative diseases such as AD and PD are related to neuroinflammation. Neuroinflammation is a common inflammatory condition that can lead to a variety of dysfunction in the body. At present, it is no medications specifically approved to prevent or cure neuroinflammation, so even though many drugs can temporarily control the neurological symptoms of neuroinflammation, but no one can reverse the progress of neuroinflammation, let al.one completely cure neuroinflammation. Therefore, it is urgent to develop new drug development for neuroinflammation treatment. In this review, we highlight the therapeutic advancement in the field of neurodegenerative disorders, by focusing on the impact of neuroinflammation treatment has on these conditions, and the effective drugs for the treatment of neuroinflammation and neurodegenerative diseases and their latest research progress are reviewed according to the related signaling pathway, as well as the prospect of their clinical application is also discussed. The purpose of this review is to enable specialists to better understand the mechanisms underlying neuroinflammation and anti-inflammatory drugs, promote the development of therapeutic drugs for neuroinflammation and neurodegenerative diseases, and further provide therapeutic references for clinical neurologists.

Psilocybin history, action and reaction: A narrative clinical review

Hallucinogenic mushrooms have been used in religious and cultural ceremonies for centuries. Of late, psilocybin, the psychoactive compound in hallucinogenic mushrooms, has received increased public interest as a novel drug for treating mood and substance use disorders (SUDs). In addition, in recent years, some states in the United States have legalized psilocybin for medical and recreational use. Given this, clinicians need to understand the potential benefits and risks related to using psilocybin for therapeutic purposes so that they can accurately advise patients. This expert narrative review summarizes the scientific basis and clinical evidence on the safety and efficacy of psilocybin-assisted therapy for treating psychiatric disorders and SUDs. The results of this review are structured as a more extensive discussion about psilocybin's history, putative mechanisms of action, and recent legislative changes to its legal status. There is modest evidence of psilocybin-assisted therapy for treating depression and anxiety disorders. In addition, early data suggest that psilocybin-assisted therapy may effectively reduce harmful drinking in patients with alcohol use disorders. The evidence further suggests psilocybin, when administered under supervision (psilocybin-assisted therapy), the side effects experienced are mild and transient. The occurrence of severe adverse events following psilocybin administration is uncommon. Still, a recent clinical trial found that individuals in the psilocybin arm had increased suicidal ideations and non-suicidal self-injurious behaviors. Given this, further investigation into the safety and efficacy of psilocybin-assisted therapy is warranted to determine which patient subgroups are most likely to benefit and which are most likely to experience adverse outcomes related to its use.

Cardioprotective Effect of Flibanserin against Isoproterenol-Induced Myocardial Infarction in Female Rats: Role of Cardiac 5-HT2A Receptor Gene/5-HT/Ca2+ Pathway

Myocardial infarction (MI) is a life-threatening ischemic disease and is one of the leading causes of morbidity and mortality worldwide. Serotonin (5-HT) release during myocardial ischemia plays an important role in the progression of myocardial cellular injury. This study was conducted to investigate the possible cardioprotective effect of flibanserin (FLP) against isoproterenol (ISO)-induced MI in rats. Rats were randomly divided into five groups and were treated orally (p.o.) with FLP (15, 30, and 45 mg/kg) for 28 days. ISO was administered subcutaneously (S.C.) (85 mg/kg) on the 27th and 28th days to induce MI. ISO-induced myocardial infarcted rats exhibited a significant increase in cardiac markers, oxidative stress markers, cardiac and serum 5-HT levels, and total cardiac calcium (Ca2+) concentration. ISO-induced myocardial infarcted rats also revealed a remarkable alteration of electrocardiogram (ECG) pattern and significantly upregulated expression of the 5-Hydroxytryptamine 2A (5-HT2A) receptors gene. Moreover, ISO-induced myocardial infarcted rats showed significant histopathological findings of MI and hypertrophic signs. However, pretreatment with FLP significantly attenuated the ISO-induced MI in a dose-dependent manner, as the effect of FLP (45 mg/kg) was more pronounced than that of the other two doses, FLP (15 and 30 mg/kg). The present study provides evidence for the cardioprotective efficacy of FLP against ISO-induced MI in rats.

Systematic Review of the Serotonergic System in the Pathophysiology of Severe Dengue: The Theory of Thrombocytopenia and Vascular Extravasation

BACKGROUND

Severe dengue is characterized by thrombocytopenia, hemorrhaging, and/or capillary extravasation and may be linked to a reduced plasma concentration of serotonin (5-hydroxytriptamine, or 5-HT).

OBJECTIVE

The aim of the current contribution was to conduct a systematic bibliographic review of reports on the role of the peripheral serotonergic system in the pathophysiology of severe dengue.

METHODS

A bibliographic review was carried out of in vivo/in vitro models, clinical trials, and case series studies from 2010-2019. The selective criteria were the use of treatments with serotonin reuptake inhibitors and/or agonists/antagonists of 5-HT receptors and their impact on inflammation, coagulation, and endothelium. Moreover, cross-sectional and cohort studies on the relationship between intraplatelet and plasma 5-HT levels in patients with dengue were also included. The risk of bias in the selected reports was examined with domain-based assessment utilizing Cochrane-type criteria. The main results are summarized in Tables and Figures.

RESULTS

Based on descriptions of the effect of serotonergic drugs on 5-HT levels and the findings of clinical trials of dengue treatment, most receptors of the peripheral serotonergic system, and especially 5-HT2A, seem to participate in regulating serum 5-HT during severe dengue. Therefore, the peripheral serotonergic system probably contributes to thrombocytopenia and capillary extravasation.

CONCLUSION

Regarding dengue, 5-HT may be a key parameter for predicting severity, and an understanding of 5-HT-related mechanisms could possibly facilitate the development of new therapies. These proposals require further research due to the limited number of publications on the role of serotonergic receptors at the peripheral level.

Adolescent and adult time trends in US hallucinogen use, 2002-19: any use, and use of ecstasy, LSD and PCP

BACKGROUND AND AIMS

Hallucinogen use is potentially harmful. Information on whether such use has increased in recent decades is lacking. This study assessed overall and age-specific time trends in the prevalence of 12-month hallucinogen use in the US general population.

DESIGN

Cross-sectional.

SETTING

Data from the US National Survey on Drug Use and Health, 2002-19.

PARTICIPANTS

Respondents aged ≥ 12 years (n = 1 006 051).

MEASUREMENTS

Predictors were continuous years. Outcome variables included any hallucinogen use and use of lysergic acid diethylamide (LSD), ecstasy and phencyclidine (PCP) in the past year. Socio-demographic variables (gender, age, race/ethnicity, educational level and family income) were covariates.

FINDINGS

Overall, hallucinogen use increased between 2015 and 2019 [prevalence difference (PD) = +0.44, P < 0.05]. Since 2002, hallucinogen use has increased in adults aged ≥ 26 years (PD, 2002-14 = +0.24, P < 0.05; PD, 2015-19 = +0.45, P < 0.001) and decreased in adolescents aged 12-17 years (PD, 2002-14 = -1.60, P < 0.0001; PD, 2015-19 = -0.73, P < 0.001). Ecstasy use has decreased in adolescents (PD, 2002-14 = -0.56, P < 0.001), adults aged 18-25 years (PD, 2015-19 = -0.96, P < 0.01) and ≥ 26 years (PD, 2015-19 = -0.13, P < 0.05). LSD use between 2002 and 2019 increased overall (PD = +0.71, P < 0.0001) and in all age groups (12-17: PD = +0.67, P < 0.001; 18-25: PD = +3.12, P < 0.0001; ≥ 26: PD = +0.36, P < 0.0001). Conversely, PCP use between 2002 and 2019 decreased overall (PD = -0.06, P < 0.001), in adolescents (PD = -0.24, P < 0.001) and young adults (PD = -0.32, P < 0.0001).

CONCLUSIONS

Since 2002, hallucinogen use in the United States has decreased among adolescents but increased in adults and is now estimated to affect more than 3 million adults aged 26+ years and more than 5.5 million adults aged 18+ years.

Effect of sarpogrelate treatment on 5-HT modulation of vascular sympathetic innervation and platelet activity in diabetic rats

This study aimed to investigate whether the 5-HT₂ receptor blockade alters the 5-HT effect on vascular sympathetic neurotransmission and platelet activation in type 1 diabetes. 28-day diabetes was obtained by alloxan (150 mg/kg; s.c.) in male Wistar rats, administering sarpogrelate (5-HT₂ blocker; 30 mg/kg/day; p.o.) for 14 days. Blood glucose and body weight were monitored for 28 days. After 4 weeks of diabetes induction, food and drink intake, urine, plasma-platelet 5-HT, and platelet activation were determined in normoglycemic, non-treated diabetic and sarpogrelate-treated diabetic rats. Another set of diabetic rats were pithed to run the vascular sympathetic stimulation or exogenous noradrenaline administration, examining the induced vasoconstrictor responses. Sarpogrelate treatment significantly reduced drink intake and urine, whereas BW gain, hyperglycemia, and food intake were not modified in diabetic rats. The platelet activation and plasma 5-HT concentration were decreased (increasing the stored 5-HT platelet) by 5-HT₂ blockade in diabetic animals. The sympathetic-induced vasoconstrictions were higher in non-treated than in sarpogrelate-treated diabetic rats. 5-HT inhibited these vasopressor responses, reproduced exclusively by the 5-HT_1/5/7 receptor agonist, 5-CT. The 5-CT-produced inhibition was partly reversed by 5-HT_1D or 5-HT₇ antagonists (LY310762 or SB-258719, respectively), and totally annulled by the mixture of LY310762+SB-258719. Noradrenaline-caused vasoconstrictions were also decreased by 5-CT. In conclusion, our results reveal that 14-day sarpogrelate treatment improves polydipsia and polyuria, reduces platelet hyperactivation, plasma 5-HT and the vascular sympathetic tone, and changes 5-HT receptors inhibiting noradrenergic drive in diabetic rats: pre and/or postjunctional 5-HT_1D/7 are involved in the sympatho-inhibition.

Hypertensive Anaphylaxis After Moderna COVID-19 Vaccination: A Case Report

Hypotension after exposure to an allergen is a well-known indicator of an anaphylactic reaction. However, hypertensive anaphylaxis often goes unrecognized. Increased blood pressure can present as an anaphylactic reaction, which is called hypertensive anaphylaxis. A 48-year-old woman complained of a tickle sensation in the throat and dyspnea 30 minutes after being administered the first dose of the Moderna coronavirus disease 2019 (COVID-19) vaccine. The patient had no history of hypertension, anxiety, or panic disorder. Forty-five minutes after the vaccination, stridor was noted, and the patient developed severe hypertension with a blood pressure of 197/153 mmHg. The patient also had tachycardia, cervical angioedema, and nausea, which occurred in a short period of time, indicating type I hypersensitivity reaction, that is, an anaphylactic reaction. The patient was diagnosed with Brighton classification Level 1 anaphylaxis caused by COVID-19 vaccination. For managing the patient, two intramuscular adrenaline injections, famotidine, chlorpheniramine, metoclopramide, and methylprednisolone were administered via intravenous infusion. After the administration of medications, all symptoms resolved, and the blood pressure was reduced. Other differential diagnoses for increased blood pressure after vaccination were excluded; therefore, we concluded that this phenomenon of increased blood pressure was hypertensive anaphylaxis. Not only hypotension but also the acute onset of increased blood pressure after vaccination may occur as a premonitory symptom of anaphylaxis. In hypertensive anaphylaxis, both anaphylaxis and increased blood pressure can be treated with intramuscular adrenaline injection. Clinicians should be aware of the occurrence of hypertensive anaphylaxis.

Psychedelics and Anti-inflammatory Activity in Animal Models

The serotonin (5-hydroxytryptamine, 5-HT) 2A receptor is most well known as the common target for classic psychedelic compounds. Interestingly, the 5-HT_2A receptor is the most widely expressed mammalian serotonin receptor and is found in nearly every examined tissue type including neural, endocrine, endothelial, immune, and muscle, suggesting it could be a novel and pharmacological target for several types of disorders. Despite this, the bulk of research on the 5-HT_2A receptor is focused on its role in the central nervous system (CNS). Recently, activation of 5-HT_2A receptors has emerged as a new anti-inflammatory strategy. This review will describe recent findings regarding psychedelics as anti-inflammatory compounds, as well as parse out differences in functional selectivity and immune regulation that exist between a number of well-known hallucinogenic compounds.

Exploring the antiplatelet activity of serotonin 5-HT2A receptor antagonists bearing 6-fluorobenzo[d]isoxazol-3-yl)propyl) motif- as potential therapeutic agents in the prevention of cardiovascular diseases

Small drug-like molecules that can block the function of serotonin 5-HT_2A receptors have garnered considerable attention due to their ability to inhibit platelet aggregation and the possible prevention of atherosclerotic lesions. Although clinical data provided compelling evidence for the efficacy of this approach in the prevention of various cardiovascular conditions, the chemical space of 5-HT_2A receptor antagonists is limited to ketanserin and sarpogrelate. To expand the portfolio of novel chemical motifs with potential antiplatelet activity, we evaluated the antiplatelet activity of a series of 6-fluorobenzo[d]isoxazole derivatives that possess a high affinity for 5-HT_2A receptor. Here we describe in vitro studies showing that 6-fluorobenzo[d]isoxazole derivatives exert promising antiplatelet activity in three various in vitro models of platelet aggregation, as well as limit serotonin-induced vasoconstriction. Compound AZ928 showed in vitro activity greater than the clinically approved drug sarpogrelate. In addition to promising antiplatelet activity, the novel series was characterized by a favorable safety profile. Our findings show that the novel series exerts promising antiplatelet efficacy while being deprived of potential side effects, such as hemolytic activity, which render these compounds as potential substances for further investigation in the field of cardiovascular research.

Serotonin 5-HT2A receptor activity mediates adipocyte differentiation through control of adipogenic gene expression

Serotonin 5-HT2 receptors are expressed in many tissues and play important roles in biological processes. Although the 5-HT2A receptor is primarily known for its role in central nervous system, it is also expressed in peripheral tissues. We have found that 5-HT2A receptor antagonists inhibit human subcutaneous primary adipocyte differentiation. We also show that siRNA knockdown of the 5-HT2A receptor blocks differentiation. Using gene expression analysis in combination with receptor antagonists we found that activity of 5-HT2A receptors is necessary very early in the differentiation process to mediate expression of adipogenic genes, including peroxisome proliferator-activated receptor gamma (ppar-γ), adipocyte protein 2 (aP2), adiponectin, and serine/threonine-protein kinase 1 (sgk1). We show here for the first time that 5-HT2A receptor activity is necessary for differentiation of human primary subcutaneous preadipocytes to adipocytes, and that 5-HT2A receptor activity mediates key genes related to adipogenesis during this process. Importantly, this work contributes to a greater understanding of the adipocyte differentiation process, as well as to the role of 5-HT2A receptors in peripheral tissues, and may be relevant to the development of novel therapeutic strategies targeting this receptor for the treatment of obesity related diseases.

Novel serotonin 5-HT2A receptor antagonists derived from 4-phenylcyclohexane-5-spiro-and 5-methyl-5-phenyl-hydantoin, for use as potential antiplatelet agents

BACKGROUND

Antiplatelet drugs have been used in the treatment of acute coronary syndromes and for the prevention of recurrent events. Unfortunately, many patients remain resistant to the available antiplatelet treatment. Therefore, there is a clinical need to synthesize novel antiplatelet agents, which would be associated with different pathways of platelet aggregation, to develop an alternative or additional treatment for resistant patients. Recent studies have revealed that 5-HT_2A receptor antagonists could constitute alternative antiplatelet therapy.

METHODS

Based on the structures of the conventional 5-HT_2A receptor ligands, two series of compounds with 4-phenylcyclohexane-5-spiro- or 5-methyl-5-phenyl-hydantoin core linked to various arylpiperazine moieties were synthesized and their affinity for 5-HT_2A receptor was assessed. Further, we evaluated their antagonistic potency at 5-HT_2A receptors using isolated rat aorta and cells expressing human 5-HT_2A receptors. Finally, we studied their anti-aggregation effect and compared it with ketanserin and sarpogrelate, the reference 5-HT_2A receptor antagonists. Moreover, the structure-activity relationships were studied following molecular docking to the 5-HT_2A receptor model.

RESULTS

Functional bioassays revealed some of the synthesized compounds to be moderate antagonists of 5-HT_2A receptors. Among them, 13, 8-phenyl-3-(3-(4-phenylpiperazin-1-yl)propyl)-1,3-diazaspiro[4.5]decane-2,4-dione, inhibited collagen stimulated aggregation (IC₅₀ = 27.3 μM) being more active than sarpogrelate (IC₅₀ = 66.8 μM) and comparable with ketanserin (IC₅₀ = 32.1 μM). Moreover, compounds 2-5, 9-11, 13, 14 inhibited 5-HT amplified, ADP- or collagen-induced aggregation.

CONCLUSIONS

Our study confirmed that the 5-HT_2A antagonists effectively suppress platelet aggregation and remain an interesting option for the development of novel antiplatelet agents with an alternative mechanism of action.

The effect of ergot alkaloid exposure during gestation on the microscopic morphology and vasculature of the ovine placenta

Ergot alkaloids, a class of mycotoxins associated with ergotism, act as agonists on serotonin (5HT) receptors, specifically 5HT2a, which mediate smooth muscle contraction and vasoconstriction. The objective of this study was to examine the impact of ergot alkaloid exposure during mid and late gestation on microscopic placental structure and vascular development. Ewes were fed endophyte-infected tall fescue seed containing ergot alkaloids (E+/E+, 1.77 mg ewe^-1 d^-1) or endophyte-free tall fescue seed (E-/E-, 0 mg ergot alkaloids) during both mid (d 35 to d 85) and late gestation (d 86 to d 133). On d 133 of gestation, a terminal surgery was performed and two placentomes of the type B morphology were collected for microscopic analyses. Amorphous connective tissue regions were larger (p < 0.0001) and more numerous (p = 0.025) in the placentome of ergot alkaloid exposed ewes. Staining showed no difference (p = 0.83) in the number of vessels present, but luminal area of maternal vasculature was 117% greater (p < 0.0001) in ergot alkaloid exposed ewes. Results showed that exposure to ergot alkaloids during gestation slowed maturation of the fetal villi as indicated by greater amorphous connective tissue regions, and altered size and shape of blood vessels to counteract reductions in blood flow caused by vasoconstriction.

Antiallergic drug desloratadine as a selective antagonist of 5HT2A receptor ameliorates pathology of Alzheimer's disease model mice by improving microglial dysfunction

Alzheimer's disease (AD) is a progressively neurodegenerative disease characterized by cognitive deficits and alteration of personality and behavior. As yet, there is no efficient treatment for AD. 5HT_2A receptor (5HT_2A R) is a subtype of 5HT₂ receptor belonging to the serotonin receptor family, and its antagonists have been clinically used as antipsychotics to relieve psychopathy. Here, we discovered that clinically first-line antiallergic drug desloratadine (DLT) functioned as a selective antagonist of 5HT_2A R and efficiently ameliorated pathology of APP/PS1 mice. The underlying mechanism has been intensively investigated by assay against APP/PS1 mice with selective 5HT_2A R knockdown in the brain treated by adeno-associated virus (AAV)-ePHP-si-5HT_2A R. DLT reduced amyloid plaque deposition by promoting microglial Aβ phagocytosis and degradation, and ameliorated innate immune response by polarizing microglia to an anti-inflammatory phenotype. It stimulated autophagy process and repressed neuroinflammation through 5HT_2A R/cAMP/PKA/CREB/Sirt1 pathway, and activated glucocorticoid receptor (GR) nuclear translocation to upregulate the transcriptions of phagocytic receptors TLR2 and TLR4 in response to microglial phagocytosis stimulation. Together, our work has highly supported that 5HT_2A R antagonism might be a promising therapeutic strategy for AD and highlighted the potential of DLT in the treatment of this disease.

Effects of M-1, a Major Metabolite of Sarpogrelate, on 5-HT-Induced Constriction of Isolated Human Internal Thoracic Artery

Sarpogrelate, a selective 5-hydroxytryptamine (5-HT)_2A receptor antagonist, inhibits 5-HT-induced platelet aggregation and vasoconstriction. It improves ischemic symptoms in patients with arteriosclerosis obliterans. M-1 is a major metabolite of sarpogrelate, and has been reported to show a higher affinity for the 5-HT_2A receptor on platelets than sarpogrelate. However, the effects of M-1 on 5-HT-induced constrictive response in human blood vessels have not been investigated. The internal thoracic artery (ITA) is the key conduit for coronary artery bypass grafting (CABG). 5-HT has been implicated as playing an important role in the pathogenesis of vasospasm. Thus, in the present study, the effects of M-1 on 5-HT-induced vasoconstriction were examined in isolated human endothelium denuded ITA. M-1 inhibited 5-HT-induced vasoconstriction in a concentration-dependent manner. At the highest concentration, M-1 almost completely inhibited the 5-HT-induced vasoconstriction. Expression of 5-HT_2A and 5-HT_1B receptor proteins in the membrane fraction of ITA smooth muscle cells was confirmed by Western blot analysis. Individually, supramaximal concentrations of sarpogrelate and SB224289, a selective 5-HT_1B receptor antagonist, only partially inhibited the 5-HT-induced vasoconstriction. However, simultaneous pretreatment with both these antagonists almost completely inhibited the 5-HT-induced vasoconstriction. The inhibitory effect of M-1 pretreatment mimicked the inhibitory effect of simultaneous pretreatment with sarpogrelate and SB224289. These results suggest that M-1 has antagonistic effects not only on the 5-HT_2A receptor but also on the 5-HT_1B receptor in human ITA smooth muscle cells. M-1 may be useful as a lead compound for the development of drugs for the treatment of 5-HT-induced vasospasms in CABG.

The therapeutic potential of microdosing psychedelics in depression

Microdosing psychedelics is the repeated use of small doses of, for example, lysergic acid diethylamide (LSD) and psilocybin, typically for a few weeks. Despite the popular and scientific attention in recent years, and claims by users that it has therapeutic value in affective disorders like depression, little scientific knowledge is available to back this. The purpose of this review was to investigate whether there are scientific grounds to state that this practice could be helpful in the treatment of affective disorders, and safe to use repeatedly. To that end, the literature (PubMed, MedLine) was searched, looking for (controlled) experimental studies with low doses of LSD and/or psilocybin, in healthy volunteers and patient samples. After a selection process and the addition of relevant articles, 14 experimental studies entered this review. Findings show that both LSD (10-20 mcg) and psilocybin (<1-3 mg) have subtle (positive) effects on cognitive processes (time perception, convergent and divergent thinking) and brain regions involved in affective processes. Besides the pleasant experience, increased anxiety and a cycling pattern of depressive and euphoric mood were also found. With regard to safety, it was demonstrated that low doses are well tolerated (in healthy volunteers) and have no-to-minimal effects on physiological measures. While it is yet unclear whether psychedelic microdosing is of therapeutic value for depression, the aforementioned effects on selective processes suggest that low doses of psychedelics could play a role in depression by inducing some kind of cognitive flexibility, which might lead to decreased rumination. While previous studies were conducted mostly in small samples of healthy volunteers, future placebo-controlled clinical trials in depressed patients are required to understand the therapeutic value of microdosing psychedelics, how this differs from therapy using full psychedelic doses, and whether different psychedelics have different effect patterns. The proposed research will give new insights into the potential of future alternative psychiatric treatment forms that are fiercely needed.

The serotonin 2A receptor agonist 25CN-NBOH increases murine heart rate and neck-arterial blood flow in a temperature-dependent manner

BACKGROUND

Serotonin 2A receptors, the molecular target of psychedelics, are expressed by neuronal and vascular cells, both of which might contribute to brain haemodynamic characteristics for the psychedelic state.

AIM

Aiming for a systemic understanding of psychedelic vasoactivity, here we investigated the effect of N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine - a new-generation agonist with superior serotonin 2A receptor selectivity - on brain-supplying neck-arterial blood flow.

METHODS

We recorded core body temperature and employed non-invasive, collar-sensor based pulse oximetry in anesthetised mice to extract parameters of local blood perfusion, oxygen saturation, heart and respiration rate. Hypothesising an overlap between serotonergic pulse- and thermoregulation, recordings were done under physiological and elevated pad temperatures.

RESULTS

N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine (1.5 mg/kg, subcutaneous) significantly increased the frequency of heart beats accompanied by a slight elevation of neck-arterial blood flow. Increasing the animal-supporting heat-pad temperature from 37°C to 41°C enhanced the drug's effect on blood flow while counteracting tachycardia. Additionally, N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine promoted bradypnea, which, like tachycardia, quickly reversed at the elevated pad temperature. The interrelatedness of N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine's respiro-cardiovascular effects and thermoregulation was further corroborated by the drug selectively increasing the core body temperature at the elevated pad temperature. Arterial oxygen saturation was not affected by N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine at either temperature.

CONCLUSIONS

Our findings imply that selective serotonin 2A receptor activation modulates systemic cardiovascular functioning in orchestration with thermoregulation and with immediate relevance to brain-imminent neck (most likely carotid) arteries. As carotid branching is a critical last hub to channel cardiovascular output to or away from the brain, our results might have implications for the brain haemodynamics associated with psychedelia.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of low dose lysergic acid diethylamide (LSD) in healthy older volunteers

Research has shown that psychedelics, such as lysergic acid diethylamide (LSD), have profound anti-inflammatory properties mediated by 5-HT2A receptor signaling, supporting their evaluation as a therapeutic for neuroinflammation associated with neurodegenerative disease.

OBJECTIVE

This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of orally repeated administration of 5 μg, 10 μg, and 20 μg LSD in older healthy individuals. In the current paper, we present safety, tolerability, pharmacokinetics, and pharmacodynamic measures that relate to safety, tolerability, and dose response.

METHODS

This was a phase 1 double-blind, placebo-controlled, randomized study. Volunteers were randomly assigned to 1 of 4 dose groups (5 μg, 10 μg, 20 μg LSD, and placebo), and received their assigned dose on six occasions (i.e., every 4 days).

RESULTS

Forty-eight older healthy volunteers (mean age = 62.9 years) received placebo (n = 12), 5 μg (n = 12), 10 μg (n = 12), or 20 μg (n = 12) LSD. LSD plasma levels were undetectable for the 5 μg group and peak blood plasma levels for the 10 μg and 20 μg groups occurred at 30 min. LSD was well tolerated, and the frequency of adverse events was no higher than for placebo. Assessments of cognition, balance, and proprioception revealed no impairment.

CONCLUSIONS

Our results suggest safety and tolerability of orally administered 5 μg, 10 μg, and 20 μg LSD every fourth day over a 21-day period and support further clinical development of LSD for the treatment and prevention of Alzheimer's disease (AD).

Association between serotonin 2A receptor (HTR2A) genetic variations and risk of hypertension in a community-based cohort study

Background

Hypertension is one of the risk factors for obesity-related cardiovascular diseases. We investigated whether genetic variations in serotonin 2A receptor (HTR2A) were associated with hypertension.

Methods

We carried out a cross-sectional study in cohorts A (Ansan-Ansung cohort, N = 6039) and B (Wonju-Pyengchang cohort, N = 7524). Several genetic variants in HTR2A including rs7330636, rs9590999, rs2183057, and rs4942595 were selected and genotyped.

Results

In hypertensive participants in cohort A, the baseline systolic blood pressure and body mass index were 141.80 ± 17.20 mg/dL and 24.48 ± 4.75 kg/m², respectively, which were higher than in those without hypertension (p < 0.001). rs4942595TC genotype was associated with hypertension in cohort A (OR = 0.739), after adjusting for variables. Subjects with rs4942578AA genotype had a decreased risk of hypertension after adjusting for clinical factor (OR = 0.735) in cohort B, and an elevated risk of hypertension in cohort A (OR = 1.562). The logistic regression analysis showed that participants with rs4941573TC genotype were 1.327 times more likely to have a higher blood pressure than those with TT genotype (95% CI 1.101–1.599) in cohort B. Whereas, the OR for developing hypertension in subjects with rs17069883CC genotype compared to those with AA genotype was 1.447 (95% CI 1.018–2.056; p for trend = 0.040) in cohort A.

Conclusions

HTR2A genetic variations were associated with hypertension risk in our study.

[Platelets, hemostasis and mental disorders]

Platelets are an easily accessible model for the study of biochemical mechanisms of mental diseases, including schizophrenia and depression. This literature review addresses a role of platelet activation in the pathogenesis of mental diseases. Platelet activation observed in patients with schizophrenia, depression and other mental illnesses is associated with the development of cardiovascular disease and an increased risk of thrombotic complications, which can be the main cause of morbidity and mortality in patients with mental disorders. A deeper understanding of the biochemical mechanisms of mental disorders will help in the study of clinical consequences of these disorders and in choosing the right therapeutic strategy for patients.

The Prevention of Contrast Induced Nephropathy by Sarpogrelate: a Prospective Randomized Controlled Clinical Trial

BACKGROUND

Although some strategies are used for prophylaxis of contrast induced nephropathy, their efficacy is not fully established. Sarpogrelate can relieve vasospasm and have anti-inflammatory action. This study examined whether sarpogrelate reduces the incidence of contrast induced nephropathy (CIN) or subsequent renal impairment during four weeks after coronary angiography compared with a control group.

METHODS

Seventy-four participants with chronic renal failure were randomly assigned to the sarpogrelate or control group. Patients assigned to the sarpogrelate group received oral saporogelate from 24 hours before contrast exposure up to one month after contrast exposure. The primary outcome of this study was the incidence of CIN within 48 hours after exposure to the contrast agent.

RESULTS

Thirty-one subjects in the control group and 35 subjects in the sarpogrelate group were used for the analysis. Cumulative CIN occurred numerically more at 48 hours in the sarpogrelate group and less at one month without statistical significance (11.4% vs. 6.5% at 48 hours and 11.4% vs. 16.1% at one month, respectively). Baseline renal function was similar in both groups, but the estimated glomerular filtration rate (eGFR) was lower in the sarpogrelate group at 12 and 48 hours compared with the control group (45.6 vs. 54.7 mL/min/1.73m²; P = 0.023 and 39.9 vs. 50.6 mL/min/1.73m²; P = 0.020, respectively). At one month, the eGFR became comparable between the two groups because the eGFR was aggravated in the control group and maintained in the sarpogrelate group.

CONCLUSION

This study failed to demonstrate that sarpogrelate has a renoprotective effect against contrast induced acute kidney injury.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01165567.

Activation of 5-HT2 Receptors Reduces Inflammation in Vascular Tissue and Cholesterol Levels in High-Fat Diet-Fed Apolipoprotein E Knockout Mice

Coronary artery disease (CAD) is a progressive cardiovascular syndrome characterized by cholesterol-induced focal arterial lesions that impair oxygen delivery to the heart. As both innate and adaptive immune cells play critical roles in the formation and progression of arterial plaques and endothelial cell dysfunction, CAD is commonly viewed as a chronic inflammatory disorder. Our lab has previously discovered that 5-HT_2A receptor activation with the 5-HT₂ receptor selective agonist (R)-2,5-dimethoxy-4-iodoamphetamine [(R)-DOI] has potent anti-inflammatory activity in both cell culture and whole animal models. Here we have examined the putative therapeutic effects of (R)-DOI in the ApoE^−/− high fat model of cardiovascular disease. Subcutaneously implanted osmotic minipumps were used to infuse sustained low rates (0.15 μg / hr) of (R)-DOI∙HCl to mice fed a high-fat “Western” diet. (R)-DOI treated mice had significant reductions in expression levels of mRNA for inflammatory markers like Il6 in vascular tissue, normalized glucose homeostasis, and reduced circulating cholesterol levels. As cardiovascular disease is a leading cause of death both globally and in the Western world, activation of 5-HT_2A receptors at sub-behavioral levels may represent a new strategy to treat inflammation-based cardiovascular disease.

Psychedelics as anti-inflammatory agents

Serotonin (5-hydroxytryptamine, 5-HT)_2A receptor agonists have recently emerged as promising new treatment options for a variety of disorders. The recent success of these agonists, also known as psychedelics, like psilocybin for the treatment of anxiety, depression, obsessive-compulsive disorder (OCD), and addiction, has ushered in a renaissance in the way these compounds are perceived in the medical community and populace at large. One emerging therapeutic area that holds significant promise is their use as anti-inflammatory agents. Activation of 5-HT_2A receptors produces potent anti-inflammatory effects in animal models of human inflammatory disorders at sub-behavioural levels. This review discusses the role of the 5-HT_2A receptor in the inflammatory response, as well as highlight studies using the 5-HT_2A agonist (R)-2,5-dimethoxy-4-iodoamphetamine [(R)-DOI] to treat inflammation in cellular and animal models. It also examines potential mechanisms by which 5-HT_2A agonists produce their therapeutic effects. Overall, psychedelics regulate inflammatory pathways via novel mechanisms, and may represent a new and exciting treatment strategy for several inflammatory disorders.

Genetic architecture and candidate genes detected for chicken internal organ weight with a 600 K single nucleotide polymorphism array

Objective

Internal organs indirectly affect economic performance and well-being of animals. Study of internal organs during later layer period will allow full utilization of layer hens. Hence, we conducted a genome-wide association study (GWAS) to identify potential quantitative trait loci or genes that potentially contribute to internal organ weight.

Methods

A total of 1,512 chickens originating from White Leghorn and Dongxiang Blue-Shelled chickens were genotyped using high-density Affymetrix 600 K single nucleotide polymorphism (SNP) array. We conducted a GWAS, linkage disequilibrium analysis, and heritability estimated based on SNP information by using GEMMA, Haploview and GCTA software.

Results

Our results displayed that internal organ weights show moderate to high (0.283 to 0.640) heritability. Variance partitioned across chromosomes and chromosome lengths had a linear relationship for liver weight and gizzard weight (R² = 0.493, 0.753). A total of 23 highly significant SNPs that associated with all internal organ weights were mainly located on Gallus gallus autosome (GGA) 1 and GGA4. Six SNPs on GGA2 affected heart weight. After the final analysis, five top SNPs were in or near genes 5-Hydroxytryptamine receptor 2A, general transcription factor IIF polypeptide 2, WD repeat and FYVE domain containing 2, non-SMC condensin I complex subunit G, and sonic hedgehog, which were considered as candidate genes having a pervasive role in internal organ weights.

Conclusion

Our findings provide an understanding of the underlying genetic architecture of internal organs and are beneficial in the selection of chickens.

Citalopram inhibits platelet function independently of SERT-mediated 5-HT transport

Citalopram prevents serotonin (5-HT) uptake into platelets by blocking the serotonin reuptake transporter (SERT). Although some clinical data suggest that selective serotonin reuptake inhibitors (SSRIs) may affect haemostasis and thrombosis, these poorly-characterised effects are not well understood mechanistically and useful in vitro data is limited. We sought to determine whether the inhibitory effects of citalopram on platelets are mediated via its pharmacological inhibition of 5-HT transport. We quantified the inhibitory potency of (RS)-, (R)- and (S)-citalopram on platelet function. If SERT blockade is the primary mechanism for citalopram-mediated platelet inhibition, these potencies should show quantitative congruence with inhibition of 5-HT uptake. Our data show that citalopram inhibits platelet aggregation, adhesion and thromboxane production with no difference in potency between (R)- and (S)-isomers. By contrast, citalopram had a eudysmic ratio of approximately 17 (S > R) for SERT blockade. Furthermore, nanomolar concentrations of citalopram inhibited 5-HT uptake into platelets but had no effect on other platelet functions, which were inhibited by micromolar concentrations. Our data indicate that citalopram-induced inhibition of platelets in vitro is not mediated by blockade of 5-HT transport. This raises a new question for future investigation: by what mechanism(s) does citalopram inhibit platelets?

Platelet haemostatic function in psychiatric disorders: Effects of antidepressants and antipsychotic drugs

Objectives Platelets, the smallest anucleated blood cells, play an essential role in the first step of complex haemostatic process. This review presents the haemostatic function of blood platelets related to their activation in psychiatric disorders (schizophrenia, depression), the role of antipsychotic and antidepressant medication, and introduces the mechanisms by which activated platelets may be involved in the pathophysiology of these disorders. Methods Platelets are interesting and easily accessible blood cells to study biochemical pathways related to schizophrenia and other psychiatric disorders, and their complex activation process might be useful as a diagnostic peripheral marker for studying psychiatric disorders and haemostatic complications. Results The excessive activation of platelets observed in patients with depression and schizophrenia is involved in cardiovascular diseases, stroke and increased risk of thrombotic complications that may be major causes of morbidity and mortality of patients. The use of antidepressants or antipsychotic drugs in depression and schizophrenia treatment is often associated with haematological side effects such as bleeding, venous thromboembolism and impaired platelet function. Conclusions Understanding the role of platelet activation in psychiatric disorders such as schizophrenia or depression and medication may improve therapies in the future.

Integrated Proteomic and Metabolomic prediction of Term Preeclampsia

Term preeclampsia (tPE), ≥37 weeks, is the most common form of PE and the most difficult to predict. Little is known about its pathogenesis. This study aims to elucidate the pathogenesis and assess early prediction of tPE using serial integrated metabolomic and proteomic systems biology approaches. Serial first- (11-14 weeks) and third-trimester (30-34 weeks) serum samples were analyzed using targeted metabolomic (¹H NMR and DI-LC-MS/MS) and proteomic (MALDI-TOF/TOF-MS) platforms. We analyzed 35 tPE cases and 63 controls. Serial first- (sphingomyelin C18:1 and urea) and third-trimester (hexose and citrate) metabolite screening predicted tPE with an area under the receiver operating characteristic curve (AUC) (95% CI) = 0.817 (0.732-0.902) and a sensitivity of 81.6% and specificity of 71.0%. Serial first [TATA box binding protein-associated factor (TBP)] and third-trimester [Testis-expressed sequence 15 protein (TEX15)] protein biomarkers highly accurately predicted tPE with an AUC (95% CI) of 0.987 (0.961-1.000), sensitivity 100% and specificity 98.4%. Integrated pathway over-representation analysis combining metabolomic and proteomic data revealed significant alterations in signal transduction, G protein coupled receptors, serotonin and glycosaminoglycan metabolisms among others. This is the first report of serial integrated and combined metabolomic and proteomic analysis of tPE. High predictive accuracy and potentially important pathogenic information were achieved.

Use of antidepressants and risk of hospitalization for acute myocardial infarction: A nationwide case-crossover study

BACKGROUND

We aimed to investigate the association between antidepressant use and the risk of hospitalization for acute myocardial infarction (AMI).

METHODS

A case-crossover study was conducted using a nationwide population-based sample from Taiwan's National Health Insurance Research Database. A total of 18,631 patients with incident AMI were included in this study. The effects of antidepressant use as well as that of various classes (including tricyclic or tetracyclic antidepressants; selective serotonin reuptake inhibitors; or serotonin norepinephrine reuptake inhibitors), doses, and receptor-binding profiles of the antidepressants on AMI were assessed. Conditional logistic regression models with adjustment for potential confounding factors were applied to determine the effects of antidepressant use on the risk of AMI during case and control time periods of 15, 30, and 60 days, respectively. The modifiable effects of age, gender, and comorbidity were evaluated by stratified analysis.

RESULTS

Antidepressant use was not associated with the risk of AMI (adjusted odds ratio [AOR] = 1.04; 95% confidence interval (CI): 0.88-1.24). Likewise, neither the class, dose, nor the binding affinity of serotonin transporter or norepinephrine transporter was associated with AMI risks, and there was no modifying effect of age, gender, or comorbid medical condition on the association between antidepressant use and AMI.

CONCLUSIONS

Use of antidepressant drugs was not associated with the risk of AMI.

Association between T102C 5-HT2A receptor gene polymorphism and 5-year mortality risk among Brazilian Amazon riparian elderly population

OBJECTIVE

Serotonin (5-HT) is a pleiotropic molecule that exerts several functions on brain and peripheral tissues via different receptors. The gene for the 5-HT2A receptor shows some variations, including a T102C polymorphism, that have been associated with increased risk of neuropsychiatric and vascular disorders. However, the potential impact of 5-HT2A imbalance caused by genetic variations on the human lifespan has not yet been established.

METHODS

We performed a prospective study involving an Amazon riparian elderly free-living population in Maués City, Brazil, with a 5-year follow-up. Out of a cohort of 637 subjects selected in July, 2009, we genotyped 471 individuals, including 209 males (44.4%) and 262 females (55.6%), all averaging 72.3 ± 7.8 years of age (ranging from 60 to 100 years).

RESULTS

The T102C-SNP genotypic frequencies were 14.0% TT, 28.0% CC, and 58.0% CT. From 80 elderly individuals who died during the period investigated, we observed significantly (P = .005) higher numbers of TT carriers (27.3%) and CC carriers (21.2%), compared to heterozygous CT carriers (12.5%). Cox-regression analysis showed that association between the T102C-SNP and elderly survival was independent of age, sex, and other health variables.

CONCLUSIONS

Our findings strongly suggest that imbalance in 5-HT2A may cause significant disturbances that lead to an increased susceptibility to death for individuals who are over 60 years of age.

Psilocybin-Assisted Therapy: A Review of a Novel Treatment for Psychiatric Disorders

Recent research suggests that functional connectivity changes may be involved in the pathophysiology of psychiatric disorders. Hyperconnectivity in the default mode network has been associated with psychopathology, but psychedelic serotonin agonists like psilocybin may profoundly disrupt these dysfunctional neural network circuits and provide a novel treatment for psychiatric disorders. We have reviewed the current literature to investigate the efficacy and safety of psilocybin-assisted therapy for the treatment of psychiatric disorders. There were seven clinical trials that investigated psilocybin-assisted therapy as a treatment for psychiatric disorders related to anxiety, depression, and substance use. All trials demonstrated reductions in psychiatric rating scale scores or increased response and remission rates. There were large effect sizes related to improved depression and anxiety symptoms. Psilocybin may also potentially reduce alcohol or tobacco use and increase abstinence rates in addiction, but the benefits of these two trials were less clear due to open-label study designs without statistical analysis. Psilocybin-assisted therapy efficacy and safety appear promising, but more robust clinical trials will be required to support FDA approval and identify the potential role in clinical psychiatry.

Licochalcones extracted from Glycyrrhiza inflata inhibit platelet aggregation accompanied by inhibition of COX-1 activity

Licochalcones extracted from Glycyrrhiza inflata are known to have a variety of biological properties such as anti-inflammatory, anti-bacterial, and anti-tumor activities, but their action on platelet aggregation has not yet been reported. Therefore, in this study we investigated the effects of licochalcones on platelet aggregation. Collagen and U46619, a thromboxane A₂ receptor agonist, caused rabbit platelet aggregation, which was reversed by pretreatment with licochalcones A, C and D in concentration-dependent manners. Among these compounds, licochalcone A caused the most potent inhibitory effect on collagen-induced platelet aggregation. However, the licochalcones showed marginal inhibitory effects on thrombin or ADP-induced platelet aggregation. In addition to rabbit platelets, licochalcone A attenuated collagen-induced aggregation in human platelets. Because licochalcone A also inhibited arachidonic acid-induced platelet aggregation and production of thromboxane A₂ induced by collagen in intact platelets, we further examined the direct interaction of licochalcone A with cyclooxygenase (COX)-1. As expected, licochalcone A caused an inhibitory effect on both COX-1 and COX-2 in vitro. Regarding the effect of licochalcone A on COX-1 enzyme reaction kinetics, although licochalcone A showed a stronger inhibition of prostaglandin E₂ synthesis induced by lower concentrations of arachidonic acid, Vmax values in the presence or absence of licochalcone A were comparable, suggesting that it competes with arachidonic acid at the same binding site on COX-1. These results suggest that licochalcones inhibit collagen-induced platelet aggregation accompanied by inhibition of COX-1 activity.

The fibrinolytic system: A new target for treatment of depression with psychedelics

Current understanding of the neurobiology of depression has grown over the past few years beyond the traditional monoamine theory of depression to include chronic stress, inflammation and disrupted synaptic plasticity. Tissue plasminogen activator (tPA) is a key factor that not only promotes fibrinolysis via the activation of plasminogen, but also contributes to regulation of synaptic plasticity and neurogenesis through plasmin-mediated activation of a probrain derived neurotrophic factor (BDNF) to mature BDNF. ProBDNF activation could potentially be supressed by competition with fibrin for plasmin and tPA. High affinity binding of plasmin and tPA to fibrin could result in a decrease of proBDNF activation during brain inflammation leading to fibrosis further perpetuating depressed mood. There is a paucity of data explaining the possible role of the fibrinolytic system or aberrant extravascular fibrin deposition in depression. We propose that within the brain, an imbalance between tPA and urokinase plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) and neuroserpin favors the inhibitors, resulting in changes in neurogenesis, synaptic plasticity, and neuroinflammation that result in depressive behavior. Our hypothesis is that peripheral inflammation mediates neuroinflammation, and that cytokines such as tumor necrosis factor alpha (TNF-α) can inhibit the fibrinolytic system by up- regulating PAI-1 and potentially neuroserpin. We propose that the decrement of the activity of tPA and uPA occurs with downregulation of uPA in part involving the binding and clearance from the surface of neural cells of uPA/PAI-1 complexes by the urokinase receptor uPAR. We infer that current antidepressants and ketamine mitigate depressive symptoms by restoring the balance of the fibrinolytic system with increased activity of tPA and uPA with down-regulated intracerebral expression of their inhibitors. We lastly hypothesize that psychedelic 5-ht2a receptor agonists, such as psilocybin, can improve mood through anti- inflammatory and pro-fibrinolytic effects that include blockade of TNF-α activity leading to decreased PAI-1 activity and increased clearance. The process involves disinhibition of tPA and uPA with subsequent increased cleavage of proBDNF which promotes neurogenesis, decreased neuroinflammation, decreased fibrin deposition, normalized glial-neuronal cross-talk, and optimally functioning neuro-circuits involved in mood. We propose that psilocybin can alleviate deleterious changes in the brain caused by chronic stress leading to restoration of homeostatic brain fibrinolytic capacity leading to euthymia.

Elevated K+ channel activity opposes vasoconstrictor response to serotonin in cerebral arteries of the Fawn Hooded Hypertensive rat

Previous studies suggest that middle cerebral arteries (MCAs) of Fawn Hooded Hypertensive (FHH) rats exhibit impaired myogenic response and introgression of a small region of Brown Norway chromosome 1 containing 15 genes restored the response in FHH.1^BN congenic rat. The impaired myogenic response in FHH rats is associated with an increase in the activity of the large conductance potassium (BK) channel in vascular smooth muscle cells (VSMCs). The present study examined whether the increased BK channel function in FHH rat alters vasoconstrictor response to serotonin (5-HT). Basal myogenic tone and spontaneous myogenic response of the MCA was attenuated by about twofold and about fivefold, respectively in FHH compared with FHH.1^BN rats. 5-HT (0.1 μM)-mediated vasoconstriction was about twofold lower, and inhibition of the BK channel increased the vasoconstrictor response by about threefold in FHH compared with FHH.1^BN rats. 5-HT (3 μM) decreased BK channel and spontaneous transient outward currents in VSMCs isolated from FHH.1^BN but had no effect in FHH rats. 5-HT significantly depolarized the membrane potential in MCAs of FHH.1^BN than FHH rats. Blockade of the BK channel normalized 5-HT-induced depolarization in MCAs of FHH rats. The 5-HT-mediated increase in cytosolic calcium concentration was significantly reduced in plateau phase in the VSMCs of FHH relative to FHH.1^BN rats. These findings suggest that sequence variants in the genes located in the small region of FHH rat chromosome 1 impairs 5-HT-mediated vasoconstriction by decreasing its ability to inhibit BK channel activity, depolarize the membrane and blunt the rise in cytosolic calcium concentration.

Blocking 5-HT2 receptor restores cardiovascular disorders in type 1 experimental diabetes

This study aimed to determine whether the serotonergic modulation, through selective 5-HT₂ receptor blockade, restores cardiovascular disturbances in type 1 diabetic rats. Diabetes was induced by alloxan (150 mg/kg, s.c.) and maintained for 4 weeks. 5-HT₂ receptor was blocked by sarpogrelate (30 mg/kg.day; 14 days; p.o.). Systolic blood pressure (SBP), heart rate (HR), glycaemia and body weight (BW) were monitored periodically. Animals were sacrificed at the end of the study and the heart, right kidney and thoracic aorta were removed; plasma samples were also obtained. Left ventricular hypertrophy index (LVH) and renal hypertrophy index (RH) were determined. Vascular function was studied in aorta rings; additionally, superoxide anion (O₂•⁻) production (by lucigenin-enhanced chemiluminescence) and lipid peroxidation (by thiobarbituric acid reactive substances assay) were measured. Neither alloxan nor sarpogrelate treatments altered HR, LVH or endothelium-independent relaxation. SBP, glycaemia, BW, RH, O₂•⁻ production and lipid peroxidation were significantly altered in diabetic animals compared with controls. Sarpogrelate treatment considerably decreased SBP, RH, O₂•⁻ production and lipid peroxidation. Endothelium-dependent relaxation was severely reduced in diabetic animal aortas compared to controls; sarpogrelate treatment markedly improved it. Our outcomes show that selectively blocking 5-HT₂ receptors has beneficial effects on impaired cardiovascular parameters in diabetes.

Comprehensive Proteome Profiling of Platelet Identified a Protein Profile Predictive of Responses to An Antiplatelet Agent Sarpogrelate

Sarpogrelate is an antiplatelet agent widely used to treat arterial occlusive diseases. Evaluation of platelet aggregation is essential to monitor therapeutic effects of sarpogrelate. Currently, no molecular signatures are available to evaluate platelet aggregation. Here, we performed comprehensive proteome profiling of platelets collected from 18 subjects before and after sarpogrelate administration using LC-MS/MS analysis coupled with extensive fractionation. Of 5423 proteins detected, we identified 499 proteins affected by sarpogrelate and found that they strongly represented cellular processes related to platelet activation and aggregation, including cell activation, coagulation, and vesicle-mediated transports. Based on the network model of the proteins involved in these processes, we selected three proteins (cut-like homeobox 1; coagulation factor XIII, B polypeptide; and peptidylprolyl isomerase D) that reflect the platelet aggregation-related processes after confirming their alterations by sarpogrelate in independent samples using Western blotting. Our proteomic approach provided a protein profile predictive of therapeutic effects of sarpogrelate.

Sarpogrelate, a 5-HT2A receptor antagonist in intermittent claudication. A Phase II European study

This was a multinational, multicentre, double-blind Phase II study in Europe to evaluate the efficacy and safety of two dose regimens (200 mg bid and 200 mg tid) of sarpogrelate (MCI-9042, 5-HT2A receptor antagonist) compared to placebo in patients with stable, moderately severe intermittent claudication. Following a single-blind placebo run-in period of 6 weeks, 364 (309 male and 55 female) patients (59.2 ± 8.4 years, mean SD) were randomized to receive sarpogrelate 200 mg bid, 200 mg tid or placebo for 24 weeks with a follow-up of 8 weeks. The primary objective was the increase of absolute claudication distance (ACD) at the end of treatment (week 24) compared to placebo. Analysis of covariance (ANCOVA) was performed on the log-transformed percentage of baseline ACD: loge (ACD/baseline). A responder analysis (defined as a 50% improvement in ACD) was also performed. There was a marked training/placebo effect on the ACD which persisted up to 16 weeks. At 24 weeks the primary objective did not reach statistical significance (200 mg bid vs placebo, p = 0.225; 200 mg tid vs placebo, p = 0.580). In the responder analysis, 200 mg bid showed a statistically significant difference vs placebo ( p = 0.035). In the exploratory analysis with completers (patients completing all treadmill tests), there was a statistical difference in ACD/baseline change for 200 mg bid ( p = 0.035) and in the responder analysis for 200 mg tid ( p = 0.044) at 24 weeks compared to placebo. Both treatments showed a carry-over effect for ACD during the 8-week follow-up (weeks 28-32). The treatment was well tolerated and no clinically significant safety concerns were reported. In conclusion, the study results confirm that sarpogrelate is well tolerated and although the primary endpoint failed to reach statistical significance, the responder analysis showed an increased absolute walking distance, which makes a further trial warranted, including a larger population, and possibly also a longer treatment period.