Oxytocin releases atrial natriuretic peptide by combining with oxytocin receptors in the heart

Navigating Central Oxytocin Transport: Known Realms and Uncharted Territories

Complex mechanisms govern the transport and action of oxytocin (Oxt), a neuropeptide and hormone that mediates diverse physiologic processes. While Oxt exerts site-specific and rapid effects in the brain via axonal and somatodendritic release, volume transmission via CSF and the neurovascular interface can act as an additional mechanism to distribute Oxt signals across distant brain regions on a slower timescale. This review focuses on modes of Oxt transport and action in the CNS, with particular emphasis on the roles of perivascular spaces, the blood-brain barrier (BBB), and circumventricular organs in coordinating the triadic interaction among circulating blood, CSF, and parenchyma. Perivascular spaces, critical conduits for CSF flow, play a pivotal role in Oxt diffusion and distribution within the CNS and reciprocally undergo Oxt-mediated structural and functional reconstruction. While the BBB modulates the movement of Oxt between systemic and cerebral circulation in a majority of brain regions, circumventricular organs without a functional BBB can allow for diffusion, monitoring, and feedback regulation of bloodborne peripheral signals such as Oxt. Recognition of these additional transport mechanisms provides enhanced insight into the systemic propagation and regulation of Oxt activity.

Hepato-cardiac interorgan communication controls cardiac hypertrophy via combined endocrine-autocrine FGF21 signaling

Fibroblast growth factor (FGF) 21 is a hormone produced mainly by the liver but also other organs, including the heart. Although FGF21 analogs are used for treating obesity and metabolic syndrome in humans, preclinical and clinical studies have elicited mixed results about whether prolonged FGF21 signaling is protective or detrimental for cardiac function. Based on our findings, showing elevated serum and cardiac FGF21 levels in humans with increased left ventricular afterload, we explore the involvement of FGF21 in cardiac hypertrophy. Our mouse studies reveal interorgan liver-heart crosstalk, which is controlled by an initial hepatic FGF21 release followed by the induction of cardiomyocyte (CM) FGF21 expression. Tissue-specific genetic ablation or anti-sense oligonucleotide-based inhibition of FGF21 shows that, in response to pressure overload, CM FGF21 upregulation is a critical event that is stimulated by liver-derived FGF21 and drives cardiac hypertrophy likely by interfering with cardioprotective oxytocin signaling. Conclusively, the hepato-cardiac FGF21-based signaling axis governs cardiac hypertrophy.

Role of atrial natriuretic peptide and oxytocin in gastric emptying delay induced by right atrial stretch in rats

Fluid volume and osmolality balance are maintained by complex neuroendocrine and liquid-salt intake behavior, cardiovascular and renal mechanisms, and gastrointestinal adjustments. Mechanical stretching of the right atrium [atrial stretch (AS)] enhances central venous pressure and heart rate while decreasing gastric emptying (GE) of liquid in rats. We evaluated the effect of AS on GE and plasma levels of atrial natriuretic peptide (ANP), oxytocin (OT), and corticosterone (CORT) to determine whether ANP contributes to the OT-mediated GE delay of liquids due to AS in awake rats. Initially, we performed thoracotomy followed by right appendectomy (AX) or sham thoracotomy. One week later, rats were randomly subjected to pretreatment with NaCl 0.15 M (control), atosiban (AT, OT-antagonist), anantin (ANT, ANP-antagonist), or dexamethasone (DEX). Afterward, 50 µL of AS was administered for 5 min or not (sham). Then, the rats were fed a test meal, and GE of liquids or solids was performed. The other animals were pretreated with NaCl 0.15 M, atosiban, anantin, or dexamethasone, followed by OT treatment for GE assessment. Compared with the sham group, 50 µL of AS decreased the GE of the liquid and solid test meals. This phenomenon was prevented by AT, ANT, DEX, and surgical procedures with AX. AS also increased plasma levels of ANP, OT, and CORT. In turn, oxytocin treatment decreased GE and increased plasma ANP, OT, and CORT levels, while AT, ANT, and DEX prevented OT-induced GE delay. Hence, AS delayed GE of liquid in rats, a phenomenon that involves oxytocinergic pathways and ANP activities.NEW & NOTEWORTHY We suggest a cardiogastric reflex with the participation of neuroendocrine mediators, which contributes to regulating liquid balance in the animal's body. Atrial natriuretic peptide and oxytocin are substances recognized for participating in diuresis and regulating the transit of liquids in the gastrointestinal tract in situations of cardiac volume overload, as was simulated with atrial stretching in the present experimental model.

MAGEL2 (patho-)physiology and Schaaf-Yang syndrome

Schaaf-Yang syndrome (SYS) is a complex neurodevelopmental disorder characterized by autism spectrum disorder, joint contractures, and profound hypothalamic dysfunction. SYS is caused by variants in MAGEL2, a gene within the Prader-Willi syndrome (PWS) locus on chromosome 15. In this review, we consolidate decades of research on MAGEL2 to elucidate its physiological functions. Moreover, we synthesize current knowledge on SYS, suggesting that while MAGEL2 loss-of-function seems to underlie several SYS and PWS phenotypes, additional pathomechanisms probably contribute to the distinct and severe phenotype observed in SYS. In addition, we highlight recent therapeutic advances and identify promising avenues for future investigation.

Psycho-Neuro-EndocrinE-Immunology Therapy of Cancer, Autoimmunity, Geriatric Disorders, Covid-19, and Hypertension

Despite the great number of experimental investigations in the area of psycho-neuro-endocrine-immunology showing that endocrine, nervous, and immune systems cannot be in vivo physiologically separated, the diagnosis and therapies of the pathologies of these three functional biological systems continue to be separately performed from a clinical practice point of view. The separation between experimental and clinical medicine became dramatic after the discovery of more than 10 human molecules provided by anti-inflammatory and antitumor activity, completely devoid of any toxicity, which may be subdivided into three fundamental classes, consisting of the pineal indole, beta-carboline, and methoxy-kynuramine hormones. Moreover, human systemic diseases, including cancer, autoimmunity, and cardiovascular pathologies, despite their different pathogenesis and symptomatology, are commonly characterized by a progressive decline in the endogenous production of pineal hormones, endocannabinoids, and Ang 1-7, with a consequent inflammatory status and diminished natural resistance against cancer. Then the evaluation of the functional status of the pineal gland, the endocannabinoid system, and ACE2-Ang 1-7 axis should have to be included within the laboratory analyses for the systemic diseases. Finally, the correction of cancer- and autoimmunity-related neuroimmune and neuroendocrine alterations could influence the clinical course of systemic diseases. In fact, preliminary clinical results would demonstrate that the neuroimmune regimen with pineal hormones, cannabinoids, and Ang 1-7 may allow clinical benefits also in patients affected by systemic pathologies, including cancer, autoimmunity, and cardiovascular diseases, who did not respond to the standard therapies.

A comprehensive review on the effects of sex hormones on chemotherapy-induced cardiotoxicity: are they lucrative or unprofitable?

Chemotherapy is one of the routine treatment for preventing rapid growth of the tumor cells. However, chemotherapeutic agents, especially doxorubicin cause damages to the normal cells especially cardiomyocytes. Cardiotoxicity induced by chemotherapeutic drugs lead to the myocardial cell injury and finally causes left ventricular dysfunction. It seems that there were some differences in the severity of cardiovascular side effects of drugs used in the treatment of cancers. Sex hormones in male and female play crucial roles in cardiovascular development and physiological function of the heart and blood vessels. Gender differences and sex-specific hormones influence various aspects of cardiovascular health, including ventricular function, mitochondrial autophagy, and the development of abdominal aortic aneurysms. The most important gender related hormones are LH, FSH, testosterone, estrogen, progesterone, prolactin and oxytocin. They exert very important cardiovascular effects via different signaling mechanisms. Sex related hormones are also important in the cardiovascular side effects of chemotherapeutic agents, so that chronic cardiotoxicity induced by anthracyclines is more common in women. During different stages of life (before, during, and after sexual life), the levels of these hormones will be changed. This alterations can affect cardiovascular function during physiological conditions and pathological process. Because of the importance of the sex related hormones in the cardiac function, in this review we tried to comprehensively elucidate the role of these physiological hormones in cardiotoxicity induced by chemotherapeutic agents with emphasizing their signaling mechanisms.

Oxytocin Attenuates Sympathetic Innervation with Inhibition of Cardiac Mast Cell Degranulation in Rats after Myocardial Infarction

Sympathetic hyperinnervation is the leading cause of fatal ventricular arrhythmia (VA) after myocardial infarction (MI). Cardiac mast cells cause arrhythmias directly through degranulation. However, the role and mechanism of mast cell degranulation in sympathetic remodeling remain unknown. We investigated the role of oxytocin (OT) in stabilizing cardiac mast cells and improving sympathetic innervation in rats. MI was induced by coronary artery ligation. Western blotting, immunofluorescence, and toluidine staining of mast cells were performed to determine the expression and location of target protein. Mast cells accumulated significantly in peri-infarcted tissues and were present in a degranulated state. They expressed OT receptor (OTR), and OT infusion reduced the number of degranulated cardiac mast cells post-MI. Sympathetic hyperinnervation was attenuated as assessed by immunofluorescence for tyrosine hydroxylase (TH). Seven days post-MI, the arrhythmia score of programmed electrical stimulation was higher in vehicle-treated rats with MI than in rats treated with OT. An in vitro study showed that OT stabilized mast cells via the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. Further in vivo studies on OTR-deficient mice showed worsening mast cell degranulation and worsening sympathetic innervation. OT pretreatment inhibited cardiac mast cell degranulation post-MI and prevented sympathetic hyperinnervation, along with mast cell stabilization via the PI3K/Akt pathway. SIGNIFICANCE STATEMENT: This is the first study to elucidate the role and mechanism of oxytocin (OT) in inflammatory-sympathetic communication mediated sympathetic hyperinnervation after myocardial infarction (MI), providing new approaches to prevent fatal arrhythmias.

Transcriptome Analysis Reveals Enhancement of Cardiogenesis-Related Signaling Pathways by S-Nitroso- N -Pivaloyl- d -Penicillamine: Implications for Improved Diastolic Function and Cardiac Performance

ABSTRACT

We previously reported a novel compound called S-nitroso- N -pivaloyl- d -penicillamine (SNPiP), which was screened from a group of nitric oxide donor compounds with a basic chemical structure of S-nitroso- N -acetylpenicillamine, to activate the nonneuronal acetylcholine system. SNPiP-treated mice exhibited improved cardiac output and enhanced diastolic function, without an increase in heart rate. The nonneuronal acetylcholine-activating effects included increased resilience to ischemia, modulation of energy metabolism preference, and activation of angiogenesis. Here, we performed transcriptome analysis of SNPiP-treated mice ventricles to elucidate how SNPiP exerts beneficial effects on cardiac function. A time-course study (24 and 48 hours after SNPiP administration) revealed that SNPiP initially induced Wnt and cyclic guanosine monophosphate-protein kinase G signaling pathways, along with upregulation of genes involved in cardiac muscle tissue development and oxytocin signaling pathway. We also observed enrichment of glycolysis-related genes in response to SNPiP treatment, resulting in a metabolic shift from oxidative phosphorylation to glycolysis, which was suggested by reduced cardiac glucose contents while maintaining adenosine tri-phosphate levels. In addition, SNPiP significantly upregulated atrial natriuretic peptide and sarcolipin, which play crucial roles in calcium handling and cardiac performance. These findings suggest that SNPiP may have therapeutic potential based on the pleiotropic mechanisms elucidated in this study.

Circulating Plasma Oxytocin Level Is Elevated by High-Intensity Interval Exercise in Men

PURPOSE

We evaluated whether repeated high-intensity interval exercise (HIIE) influences plasma oxytocin (OT) concentration in healthy men, and, given that OT is mainly synthesized in the hypothalamus, we assessed the concentration difference between the arterial (OT ART ) versus the internal jugular venous OT concentration (OT IJV ). Additionally, we hypothesized that an increase in cerebral OT release and the circulating concentration would be augmented by repeated HIIE.

METHODS

Fourteen healthy men (age = 24 ± 2 yr; mean ± SD) performed two identical bouts of HIIE. These HIIE bouts included a warm-up at 50%-60% maximal workload ( Wmax ) for 5 min followed by four bouts of exercise at 80%-90% Wmax for 4 min interspersed by exercise at 50%-60% Wmax for 3 min. The HIIE bouts were separated by 60 min of rest. OT was evaluated in blood through radial artery and internal jugular vein catheterization.

RESULTS

Both HIIE bouts increased both OT ART (median [IQR], from 3.9 [3.4-5.4] to 5.3 [4.4-6.3] ng·mL -1 in the first HIIE, P < 0.01) and OT IJV (from 4.6 [3.4-4.8] to 5.9 [4.3-8.2] ng·mL -1 , P < 0.01), but OT ART-IJV was unaffected (from -0.24 [-1.16 to 1.08] to 0.04 [-0.88 to 0.78] ng·mL -1 , P = 1.00). The increased OT levels were similar in the first and second HIIE bouts (OT ARTP = 0.25, OT IJVP = 0.36).

CONCLUSIONS

Despite no change in the cerebral OT release via the internal jugular vein, circulating OT increases during HIIE regardless of the accumulated exercise volume, indicating that OT may play role as one of the exerkines.

The effect of pituitrin on postoperative outcomes in patients with pulmonary hypertension undergoing cardiac surgery: a study protocol for a randomized controlled trial

Background

The vasoplegic syndrome is one of the major consequences of cardiac surgery. If pulmonary hypertension is additionally involved with vasoplegic syndrome, circulation management becomes much more complicated. According to previous studies, pituitrin (a substitute for vasopressin, which contains vasopressin and oxytocin) not only constricts systemic circulation vessels and increases systemic circulation pressure but also likely decreases pulmonary artery pressure and pulmonary vascular resistance. The aim of this study is to investigate whether pituitrin is beneficial for the postoperative outcomes in patients with pulmonary hypertension undergoing cardiac surgery.

Methods and analysis

The randomized controlled trial will include an intervention group continuously infused with 0.04 U/(kg h) of pituitrin and a control group. Adult patients with pulmonary hypertension undergoing elective cardiac surgery will be included in this study. Patients who meet the conditions and give their consent will be randomly assigned to the intervention group or the control group. The primary outcome is the composite endpoint of all-cause mortality within 30 days after surgery or common complications after cardiac surgery. Secondary outcomes include the incidence of other postoperative complications, length of hospital stay, and so on.

Discussion

Pituitrin constricts systemic circulation vessels, increases systemic circulation pressure, and may reduce pulmonary artery pressure and pulmonary vascular resistance, which makes it a potentially promising vasopressor during the perioperative period in patients with pulmonary hypertension. Therefore, evidence from randomized controlled trials is necessary to elucidate whether pituitrin influences outcomes in patients with pulmonary hypertension following cardiac surgery.

The Role of Central Oxytocin in Autonomic Regulation

Oxytocin (OXT), a neuropeptide originating from the hypothalamus and traditionally associated with peripheral functions in parturition and lactation, has emerged as a pivotal player in the central regulation of the autonomic nervous system (ANS). This comprehensive ANS, comprising sympathetic, parasympathetic, and enteric components, intricately combines sympathetic and parasympathetic influences to provide unified control. The central oversight of sympathetic and parasympathetic outputs involves a network of interconnected regions spanning the neuroaxis, playing a pivotal role in the real-time regulation of visceral function, homeostasis, and adaptation to challenges. This review unveils the significant involvement of the central OXT system in modulating autonomic functions, shedding light on diverse subpopulations of OXT neurons within the paraventricular nucleus of the hypothalamus and their intricate projections. The narrative progresses from the basics of central ANS regulation to a detailed discussion of the central controls of sympathetic and parasympathetic outflows. The subsequent segment focuses specifically on the central OXT system, providing a foundation for exploring the central role of OXT in ANS regulation. This review synthesizes current knowledge, paving the way for future research endeavors to unravel the full scope of autonomic control and understand multifaceted impact of OXT on physiological outcomes.

Design, synthesis, conformational analysis, and biological activity of Cα1-to-Cα6 1,4- and 4,1-disubstituted 1H-[1,2,3]triazol-1-yl-bridged oxytocin analogues

Oxytocin (OT) is a neurohypophyseal peptide hormone containing a disulphide-bridged pseudocyclic conformation. The biomedical use of OT peptides is limited amongst others by disadvantageous pharmacokinetic parameters. To increase the stability of OT by replacing the disulphide bridge with the stable and more rigid [1,2,3]triazol-1-yl moiety, we employed the Cu2+-catalysed side chain-to-side chain azide-alkyne 1,3-cycloaddition. Here we report the design, synthesis, conformational analysis, and in vitro pharmacological activity of a homologous series of Cα1-to-Cα6 side chain-to-side chain [1,2,3]triazol-1-yl-containing OT analogues differing in the length of the bridge, location, and orientation of the linking moiety. Exploiting this macrocyclisation approach, it was possible to generate a systematic series of compounds providing interesting insight into the structure-conformation-function relationship of OT. Most analogues were able to adopt similar conformation to endogenous OT in water, namely, a type I β-turn. This approach may in the future generate stabilised pharmacological peptide tools to advance understanding of OT physiology.

The Regulatory Effect of the Paraventricular Nucleus on Hypertension

Hypertension is among the most harmful factors of cardiovascular and cerebrovascular diseases and poses an urgent problem for the development of human society. In addition to previous studies on its pathogenesis focusing on the peripheral sympathetic nervous system, investigating the central causes of high blood pressure involving the neuroendocrine and neuroinflammatory mechanisms of the hypothalamic paraventricular nucleus (PVN) is paramount. This nucleus is considered to regulate the output of neurohormones and sympathetic nerve activity. In this article, we focussed on the neuroendocrine mechanism, primarily exploring the specific contributions and interactions of various neurons and neuroendocrine hormones, including GABAergic and glutamatergic neurons, nitric oxide, arginine vasopressin, oxytocin, and the renin-angiotensin system. Additionally, the neuroinflammatory mechanism in the PVN was discussed, encompassing microglia, reactive oxygen species, inflammatory factors, and pathways, as well as immune connections between the brain and extracerebral organs. Notably, the two central mechanisms involved in the PVN not only exist independently but also communicate with each other, jointly maintaining the hypertensive state of the body. Furthermore, we introduce well-known molecules and signal transduction pathways within the PVN that can play a regulatory role in the two mechanisms to provide a basis and inspire ideas for further research.

Longitudinal association between N-terminal B-type natriuretic peptide, anxiety and social support in patients with HFpEF: results from the multicentre randomized controlled Aldo-DHF trial

BACKGROUND

Higher plasma levels of natriuretic peptides (NPs) have been associated with reduced anxiety in experimental research and a number of patient samples. As NP levels are elevated in heart failure patients, we investigate whether this elevation is related to anxiety in patients with heart failure with preserved ejection fraction (HFpEF).

METHODS

Post-hoc regression and mediation analyses were conducted, using data of 422 patients with HFpEF from the randomized, placebo-controlled, double-blinded, two-armed, multicentre aldosterone in diastolic heart failure trial, testing associations and their mediators between the N-terminal B-type natriuretic peptide (NT-proBNP) and anxiety at baseline and over 12-month follow-up. Anxiety was measured by the Hospital Anxiety and Depression Scale (HADS), social support by the ENRICHD Social Support Inventory and physical functioning by the Short Form 36 Health Survey.

RESULTS

The mean age of the study population was 66.8 ± 7.6 years, 47.6% were male and 86.0% had NYHA class II. NT-proBNP showed a weak negative correlation with HADS anxiety scores at baseline (r = - 0.087; p = 0.092), which was significant (r = - 0.165; p = 0.028) in men but not in women. NT-proBNP also tended to predict lower anxiety at 12-months in men. On the other hand, higher anxiety at baseline was associated with lower NT-proBNP scores 12 months later (r = - 0.116; p = 0.026). All associations lost significance in multivariate regression for age, perceived social support (ESSI), physical function (SF-36) and study arm. Mediation analyses revealed that social support acts as a full mediator for the link between NT-proBNP levels and anxiety.

CONCLUSION

The mechanisms linking NT-proBNP to anxiety may be more complex than originally assumed. While effects of NT-proBNP on anxiety may be mediated by perceived social support, there may be an additional negative effect of anxiety on NT-proBNP. Future research should consider this possible bi-directionality of the association and assess the potential influence of gender, social support, oxytocin and vagal tone on the interaction of anxiety and natriuretic peptide levels. Trial Registration http://www.controlled-trials.com  (ISRCTN94726526) on 07/11/2006. Eudra-CT-number: 2006-002,605-31.

Effects of Chronically Exogenous Oxytocin on Ovary and Uterus: A Comparison of Intraperitoneal and Intranasal Administration

Oxytocin (OT) has been studied as a therapeutic neuropeptide in various diseases, but its effect on the ovary and uterus is not fully known. This study investigates the effects of intranasal and intraperitoneal OT administration on ovaries and uterus in rats. Four experimental groups were created using 7-week-old Sprague Dawley-type female rats: Control (Ctrl), oxytocin-intraperitoneal (0.1µg/day) (OT-IP), oxytocin-intranasal (0.05µg/day) (OT-IN1), and oxytocin-intranasal (0.1µg/day) (OT-IN2). The blood, the ovarian, and the uterus were collected at the end of the 28th day of OT administration. Afterward, histological and biochemical analyses were performed. We observed that the Graaf follicles were higher in both OT-IN2 and OT-IP groups compared to the Ctrl group. Moreover, the corpus luteum was increased only in the OT-IN2 group. Ki-67, CD31, VEGF, and TGF-ß immunostaining showed no significant change in the ovary. In contrast, Ki-67, VEGF, and OTR expressions demonstrated significant alterations in the uterus. Furthermore, TGF-ß immunohistochemistry and the histopathologic score did not reveal the statistical change in the uterus. Serum hormone levels showed that the anti-Müllerian hormone increased in all OT groups vs. the Ctrl. OT-IP showed an increment of follicle-stimulating hormone and estradiol decrement. There was a decrease in serum E2 levels, although the Graafian follicle number increased in OT-IP groups compared to the Ctrl group. However, luteinizing hormone, gonadotropin-releasing hormone, progesterone, testosterone, OT levels, and oxidative stress index did not reveal any statistical difference. Accordingly, the intranasal route may have beneficial effects compared to the intraperitoneal route regarding exogenous OT administration-related studies. In conclusion, we reported that exogenous OT increases the follicle reserve and may cause histological changes in the reproductive system of female rats.

The Long Way of Oxytocin from the Uterus to the Heart in 70 Years from Its Discovery

The research program on oxytocin started in 1895, when Oliver and Schafer reported that a substance extracted from the pituitary gland elevates blood pressure when injected intravenously into dogs. Dale later reported that a neurohypophysial substance triggers uterine contraction, lactation, and antidiuresis. Purification of this pituitary gland extracts revealed that the vasopressor and antidiuretic activity could be attributed to vasopressin, while uterotonic and lactation activity could be attributed to oxytocin. In 1950, the amino-acid sequences of vasopressin and oxytocin were determined and chemically synthesized. Vasopressin (CYFQNCPRG-NH₂) and oxytocin (CYIQNCPLG-NH₂) differ by two amino acids and have a disulfide bridge between the cysteine residues at position one and six conserved in all vasopressin/oxytocin-type peptides. This characterization of oxytocin led to the Nobel Prize awarded in 1955 to Vincent du Vigneaud. Nevertheless, it was only 50 years later when the evidence that mice depleted of oxytocin or its receptor develop late-onset obesity and metabolic syndrome established that oxytocin regulates energy and metabolism. Oxytocin is anorexigenic and regulates the lean/fat mass composition in skeletal muscle. Oxytocin's effect on muscle is mediated by thermogenesis via a pathway initiated in the myocardium. Oxytocin involvement in thermogenesis and muscle contraction is linked to Prader-Willi syndrome in humans, opening exciting therapeutic avenues.

The Heart as a Target of Vasopressin and Other Cardiovascular Peptides in Health and Cardiovascular Diseases

The automatism of cardiac pacemaker cells, which is tuned, is regulated by the autonomic nervous system (ANS) and multiple endocrine and paracrine factors, including cardiovascular peptides. The cardiovascular peptides (CPs) form a group of essential paracrine factors affecting the function of the heart and vessels. They may also be produced in other organs and penetrate to the heart via systemic circulation. The present review draws attention to the role of vasopressin (AVP) and some other cardiovascular peptides (angiotensins, oxytocin, cytokines) in the regulation of the cardiovascular system in health and cardiovascular diseases, especially in post-infarct heart failure, hypertension and cerebrovascular strokes. Vasopressin is synthesized mostly by the neuroendocrine cells of the hypothalamus. There is also evidence that it may be produced in the heart and lungs. The secretion of AVP and other CPs is markedly influenced by changes in blood volume and pressure, as well as by other disturbances, frequently occurring in cardiovascular diseases (hypoxia, pain, stress, inflammation). Myocardial infarction, hypertension and cardiovascular shock are associated with an increased secretion of AVP and altered responsiveness of the cardiovascular system to its action. The majority of experimental studies show that the administration of vasopressin during ventricular fibrillation and cardiac arrest improves resuscitation, however, the clinical studies do not present consisting results. Vasopressin cooperates with the autonomic nervous system (ANS), angiotensins, oxytocin and cytokines in the regulation of the cardiovascular system and its interaction with these regulators is altered during heart failure and hypertension. It is likely that the differences in interactions of AVP with ANS and other CPs have a significant impact on the responsiveness of the cardiovascular system to vasopressin in specific cardiovascular disorders.

Oxytocin: A Multi-Functional Biomolecule with Potential Actions in Dysfunctional Conditions; From Animal Studies and Beyond

Oxytocin is a hormone secreted from definite neuroendocrine neurons located in specific nuclei in the hypothalamus (mainly from paraventricular and supraoptic nuclei), and its main known function is the contraction of uterine and/or mammary gland cells responsible for parturition and breastfeeding. Among the actions of the peripherally secreted oxytocin is the prevention of different degenerative disorders. These actions have been proven in cell culture and in animal models or have been tested in humans based on hypotheses from previous studies. This review presents the knowledge gained from the previous studies, displays the results from oxytocin intervention and/or treatment and proposes that the well described actions of oxytocin might be connected to other numerous, diverse actions of the biomolecule.

De Novo Whole-Genome Sequencing and Assembly of the Yellow-Throated Bunting (Emberiza elegans) Provides Insights into Its Evolutionary Adaptation

Simple Summary

We report the genomic sequence of Emberiza elegans for understanding the evolutionary mechanisms of environmental adaptation and for studying a more effective genetic monitoring of this species. The E. elegans assembly was approximately 1.14 Gb, with a scaffold N50 of 28.94 Mb. About 15,868 protein-coding genes were predicted, and 16.62% of the genome was identified as having repetitive elements. Our genomic evolution analyses found considerable numbers of adaptive genes that may help the yellow-throated bunting cope with migratory behavior and environmental stressors of diseases. These results provide us with new insights into genomic evolution and adaptation, thus providing a valuable resource for further studies of population genetic diversity and genome evolution in this species.

Abstract

Yellow-throated bunting is a small migratory songbird unique to the Palearctic region. However, the genetic studies of this species remain limited, with no nuclear genomic sequence reported to date. In this study, the genomic DNA from the bird was sequenced in long reads using Nanopore sequencing technology. Combining short-read sequencing, the genome was well-assembled and annotated. The final length of the assembly is approximately 1.14 Gb, with a scaffold N50 of 28.94 Mb. About 15,868 protein-coding genes were predicted, and 16.62% of the genome was identified as having repetitive elements. Comparative genomic analysis showed numerous expanded gene families and positively selected genes significantly enriched in those KEGG pathways that are associated with migratory behavior adaptation and immune response. Here, this newly generated de novo genome of the yellow-throated bunting using long reads provide the research community with a valuable resource for further studies of population genetic diversity and genome evolution in this species.

Oxytocin and cardiometabolic interoception: Knowing oneself affects ingestive and social behaviors

Maintaining homeostasis while navigating one's environment involves accurately assessing and interacting with external stimuli while remaining consciously in tune with internal signals such as hunger and thirst. Both atypical social interactions and unhealthy eating patterns emerge as a result of dysregulation in factors that mediate the prioritization and attention to salient stimuli. Oxytocin is an evolutionarily conserved peptide that regulates attention to exteroceptive and interoceptive stimuli in a social environment by functioning in the brain as a modulatory neuropeptide to control social behavior, but also in the periphery as a hormone acting at oxytocin receptors (Oxtr) expressed in the heart, gut, and peripheral ganglia. Specialized sensory afferent nerve endings of Oxtr-expressing nodose ganglia cells transmit cardiometabolic signals via the Vagus nerve to integrative regions in the brain that also express Oxtr(s). These brain regions are influenced by vagal sensory pathways and coordinate with external events such as those demanding attention to social stimuli, thus the sensations related to cardiometabolic function and social interactions are influenced by oxytocin signaling. This review investigates the literature supporting the idea that oxytocin mediates the interoception of cardiovascular and gastrointestinal systems, and that the modulation of this awareness likewise influences social cognition. These concepts are then considered in relation to Autism Spectrum Disorder, exploring how atypical social behavior is comorbid with cardiometabolic dysfunction.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

The Paraventricular Nucleus of the Hypothalamus in Control of Blood Pressure and Blood Pressure Variability

The paraventricular nucleus (PVN) is a highly organized structure of the hypothalamus that has a key role in regulating cardiovascular and osmotic homeostasis. Functionally, the PVN is divided into autonomic and neuroendocrine (neurosecretory) compartments, both equally important for maintaining blood pressure (BP) and body fluids in the physiological range. Neurosecretory magnocellular neurons (MCNs) of the PVN are the main source of the hormones vasopressin (VP), responsible for water conservation and hydromineral balance, and oxytocin (OT), involved in parturition and milk ejection during lactation. Further, neurosecretory parvocellular neurons (PCNs) take part in modulation of the hypothalamic–pituitary–adrenal axis and stress responses. Additionally, the PVN takes central place in autonomic adjustment of BP to environmental challenges and contributes to its variability (BPV), underpinning the PVN as an autonomic master controller of cardiovascular function. Autonomic PCNs of the PVN modulate sympathetic outflow toward heart, blood vessels and kidneys. These pre-autonomic neurons send projections to the vasomotor nucleus of rostral ventrolateral medulla and to intermediolateral column of the spinal cord, where postganglionic fibers toward target organs arise. Also, PVN PCNs synapse with NTS neurons which are the end-point of baroreceptor primary afferents, thus, enabling the PVN to modify the function of baroreflex. Neuroendocrine and autonomic parts of the PVN are segregated morphologically but they work in concert when the organism is exposed to environmental challenges via somatodendritically released VP and OT by MCNs. The purpose of this overview is to address both neuroendocrine and autonomic PVN roles in BP and BPV regulation.

A Case of Postpartum Pulmonary Edema Induced by Oxytocin

Postpartum dyspnea can be due to many causes, such as pulmonary embolism, amniotic fluid embolism, peripartum cardiomyopathy, but less frequently due to acute pulmonary edema. The incidence of acute pulmonary edema during pregnancy and in the postpartum period has been estimated to be around 0.08%. About half of the cases are attributed to tocolytic therapy. Herein, we present a case of a young woman presenting with acute hypoxia after induction of labor with oxytocin and found to have acute pulmonary edema. This case aims to illustrate and add to a growing body of literature regarding oxytocin-induced acute pulmonary edema and highlights the importance of recognizing the rare complication of oxytocin and necessary interventions to avoid complications. Oxytocin-induced pulmonary edema is a relatively uncommon condition, but physicians should have a high index of suspicion to initiate timely intervention and to avoid fetal complications.

The Gasotransmitter Hydrogen Sulfide and the Neuropeptide Oxytocin as Potential Mediators of Beneficial Cardiovascular Effects through Meditation after Traumatic Events

Trauma and its related psychological and somatic consequences are associated with higher cardiovascular morbidity. The regulation of both the gasotransmitter hydrogen sulfide (H2S) and the neuropeptide oxytocin (OT) have been reported to be affected during physical and psychological trauma. Both mediators are likely molecular correlates of trauma-induced cardiovascular complications, because they share parallel roles and signaling pathways in the cardiovascular system, both locally as well as on the level of central regulation and the vagus nerve. Meditation can alter the structure of specific brain regions and can have beneficial effects on cardiovascular health. This perspective article summarizes the evidence pointing toward the significance of H2S and OT signaling in meditation-mediated cardio-protection.

Oxytocin: A citation network analysis of 10 000 papers

Our understanding of the oxytocin system has been built over the last 70 years by the work of hundreds of scientists, reported in thousands of papers. Here, we construct a map to that literature, using citation network analysis in conjunction with bibliometrics. The map identifies ten major 'clusters' of papers on oxytocin that differ in their particular research focus and that densely cite papers from the same cluster. We identify highly cited papers within each cluster and in each decade, not because citations are a good indicator of quality, but as a guide to recognising what questions were of wide interest at particular times. The clusters differ in their temporal profiles and bibliometric features; here, we attempt to understand the origins of these differences.

Relationship between Oxytocin and Osteoarthritis: Hope or Despair?

Oxytocin (OT) is involved in breastfeeding and childbirth and appears to play a role in regulating the bone matrix. OT is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus and is released in response to numerous stimuli. It also appears to be produced by osteoblasts in the bone marrow, acting as a paracrine–autocrine regulator of bone formation. Osteoarthritis (OA) is a disease of the whole joint. Different tissues involved in OA express OT receptors (OTRs), such as chondrocytes and osteoblasts. This hormone, which levels are reduced in patients with OA, appears to have a stimulatory effect on chondrogenesis. OT involvement in bone biology could occur at both the osteoblast and chondrocyte levels. The relationships between metabolic syndrome, body weight, and OA are well documented, and the possible effects of OT on different parameters of metabolic syndrome, such as diabetes and body weight, are important. In addition, the effects of OT on adipokines and inflammation are also discussed, especially since recent data have shown that low-grade inflammation is also associated with OA. Furthermore, OT also appears to mediate endogenous analgesia in animal and human studies. These observations provide support for the possible interest of OT in OA and its potential therapeutic treatment.

Complementary Role of Oxytocin and Vasopressin in Cardiovascular Regulation

The neurons secreting oxytocin (OXY) and vasopressin (AVP) are located mainly in the supraoptic, paraventricular, and suprachiasmatic nucleus of the brain. Oxytocinergic and vasopressinergic projections reach several regions of the brain and the spinal cord. Both peptides are released from axons, soma, and dendrites and modulate the excitability of other neuroregulatory pathways. The synthesis and action of OXY and AVP in the peripheral organs (eye, heart, gastrointestinal system) is being investigated. The secretion of OXY and AVP is influenced by changes in body fluid osmolality, blood volume, blood pressure, hypoxia, and stress. Vasopressin interacts with three subtypes of receptors: V1aR, V1bR, and V2R whereas oxytocin activates its own OXTR and V1aR receptors. AVP and OXY receptors are present in several regions of the brain (cortex, hypothalamus, pons, medulla, and cerebellum) and in the peripheral organs (heart, lungs, carotid bodies, kidneys, adrenal glands, pancreas, gastrointestinal tract, ovaries, uterus, thymus). Hypertension, myocardial infarction, and coexisting factors, such as pain and stress, have a significant impact on the secretion of oxytocin and vasopressin and on the expression of their receptors. The inappropriate regulation of oxytocin and vasopressin secretion during ischemia, hypoxia/hypercapnia, inflammation, pain, and stress may play a significant role in the pathogenesis of cardiovascular diseases.

Hemodynamic phenotyping of transgenic rats with ubiquitous expression of an angiotensin-(1-7)-producing fusion protein

Activation of the angiotensin (Ang)-converting enzyme (ACE) 2/Ang-(1-7)/MAS receptor pathway of the renin-angiotensin system (RAS) induces protective mechanisms in different diseases. Herein, we describe the cardiovascular phenotype of a new transgenic rat line (TG7371) that expresses an Ang-(1-7)-producing fusion protein. The transgene-specific mRNA and the corresponding protein were shown to be present in all evaluated tissues of TG7371 with the highest expression in aorta and brain. Plasma Ang-(1-7) levels, measured by radioimmunoassay (RIA) were similar to control Sprague-Dawley (SD) rats, however high Ang-(1-7) levels were found in the hypothalamus. TG7371 showed lower baseline mean arterial pressure (MAP), assessed in conscious or anesthetized rats by telemetry or short-term recordings, associated with increased plasma atrial natriuretic peptide (ANP) and higher urinary sodium concentration. Moreover, evaluation of regional blood flow and hemodynamic parameters with fluorescent microspheres showed a significant increase in blood flow in different tissues (kidneys, mesentery, muscle, spleen, brown fat, heart and skin), with a resulting decrease in total peripheral resistance (TPR). TG7371 rats, on the other hand, also presented increased cardiac and global sympathetic tone, increased plasma vasopressin (AVP) levels and decreased free water clearance. Altogether, our data show that expression of an Ang-(1-7)-producing fusion protein induced a hypotensive phenotype due to widespread vasodilation and consequent fall in peripheral resistance. This phenotype was associated with an increase in ANP together with an increase in AVP and sympathetic drive, which did not fully compensate the lower blood pressure (BP). Here we present the hemodynamic impact of long-term increase in tissue expression of an Ang-(1-7)-fusion protein and provide a new tool to investigate this peptide in different pathophysiological conditions.

The Effect of Oxytocin on Intracellular Ca2+ Release in Cardiac Cells

Ca²⁺ signaling is vital for the proper functioning of all cells, including cells of the cardiovascular system. Membrane receptors for many hormones trigger intracellular Ca²⁺ signaling via the activation of phospholipase C and production of inositol-1,4,5-trisphosphate (InsP₃). Several research groups have demonstrated the expression of oxytocin (OXT) and oxytocin receptors (OXTR) in the heart and suggested a cardioprotective role of OXT against several pathological conditions. Here we describe the protocol for measuring the effects of oxytocin on intracellular Ca²⁺ dynamics in newborn rat cardiac myocytes and cardiac fibroblasts maintained in short-term culture.

H2S and Oxytocin Systems in Early Life Stress and Cardiovascular Disease

Today it is well established that early life stress leads to cardiovascular programming that manifests in cardiovascular disease, but the mechanisms by which this occurs, are not fully understood. This perspective review examines the relevant literature that implicates the dysregulation of the gasomediator hydrogen sulfide and the neuroendocrine oxytocin systems in heart disease and their putative mechanistic role in the early life stress developmental origins of cardiovascular disease. Furthermore, interesting hints towards the mutual interaction of the hydrogen sulfide and OT systems are identified, especially with regards to the connection between the central nervous and the cardiovascular system, which support the role of the vagus nerve as a communication link between the brain and the heart in stress-mediated cardiovascular disease.

A functional selective effect of oxytocin secreted under restraint stress in rats

Restraint stress (RS) is an unavoidable stress model that triggers activation of the autonomic nervous system, endocrine activity, and behavioral changes in rodents. Furthermore, RS induces secretion of oxytocin into the bloodstream, indicating a possible physiological role in the stress response in this model. The presence of oxytocin receptors in vessels and heart favors this possible idea. However, the role of oxytocin secreted in RS and effects on the cardiovascular system are still unclear. The aim of this study was to analyze the influence of oxytocin on cardiovascular effects during RS sessions. Rats were subjected to pharmacological (blockade of either oxytocin, vasopressin, or muscarinic receptors) or surgical (hypophysectomy or sinoaortic denervation) approaches to study the functional role of oxytocin and its receptor during RS. Plasma levels of oxytocin and vasopressin were measured after RS. RS increased arterial pressure, heart rate, and plasma oxytocin content, but not vasopressin. Treatment with atosiban (a Gi biased agonist) inhibited restraint-evoked tachycardia without affecting blood pressure. However, this effect was no longer observed after sinoaortic denervation, homatropine (M2 muscarinic antagonist) treatment or hypophysectomy, indicating that parasympathetic activation mediated by oxytocin secreted to the periphery is responsible for blocking the increase in tachycardic responses observed in the atosiban-treated group. Corroborating this, L-368,899 (oxytocin antagonist) treatment showed an opposite effect to atosiban, increasing tachycardic responses to restraint. Thus, this provides evidence that oxytocin secreted to the periphery attenuates tachycardic responses evoked by restraint via increased parasympathetic activity, promoting cardioprotection by reducing the stress-evoked heart rate increase.

Cardiovascular Neuroendocrinology: Emerging Role for Neurohypophyseal Hormones in Pathophysiology

Arginine vasopressin (AVP) and oxytocin (OXY) are released by magnocellular neurosecretory cells that project to the posterior pituitary. While AVP and OXY currently receive more attention for their contributions to affiliative behavior, this mini-review discusses their roles in cardiovascular function broadly defined to include indirect effects that influence cardiovascular function. The traditional view is that neither AVP nor OXY contributes to basal cardiovascular function, although some recent studies suggest that this position might be re-evaluated. More evidence indicates that adaptations and neuroplasticity of AVP and OXY neurons contribute to cardiovascular pathophysiology.

International Survey on the Use of Arginine Vasopressin in the Postoperative Management of Single Ventricle Patients

Management of patients with single ventricle physiology after surgical palliation is challenging. Arginine vasopressin has gained popularity in recent years as a non-catecholamine vasoactive medication due to its unique properties. However, data regarding its use in the pediatric population is limited. Therefore, we designed a survey to explore whether and how clinicians use this medication in intensive care units for the postoperative management of single ventricle patients. This international survey aimed to assess usage, practices, and concepts related to arginine vasopressin in pediatric intensive care units worldwide. Directors of pediatric intensive care units who are members of the following international professional societies: European Society of Pediatric Neonatal Intensive Care, Association for European Pediatric and Congenital Cardiology, and Pediatric Cardiac Intensive Care Society were invited to participate in this survey. Of the 62 intensive care unit directors who responded, nearly half use arginine vasopressin in the postoperative management of neonatal single ventricle patients, and 90% also use the drug in subsequent surgical palliation. The primary indications are vasoplegia, hemodynamic instability, and refractory shock, although it is still considered a second-line medication. Conceptual benefits include improved hemodynamics and end-organ perfusion and decreased incidence of low cardiac output syndrome. Those practitioners who do not use arginine vasopressin cite lack of availability, fear of potential adverse effects, unclear indication for use, and lack of evidence suggesting improved outcomes. Both users and non-users described increased myocardial afterload and extreme vasoconstriction as potential disadvantages of the medication. Despite the lack of conclusive data demonstrating enhanced clinical outcomes, our study found arginine vasopressin is used widely in the care of infants and children with single ventricle physiology after the first stage and subsequent palliative surgeries. While many intensive care units use this medication, few had protocols, offering an area for further growth and development.

Associations between oxytocin and empathy in humans: A systematic literature review

This is a systematic review about the association between empathic behavior and oxytocin (OXT). Searches were conducted in the electronic databases PubMed, Web of Science, PsycINFO, SciELO, and LILACS using the search terms "oxytocin", "empathy", and "empathic". Forty-four studies were reviewed. Scarce findings point to a lack of association between baseline endogenous OXT levels and empathy traits, and for a trend towards a direct relationship between oxytocinergic reactivity and empathic functioning. The results showed that variations in empathy were related to polymorphisms in the OXT receptor gene, especially in rs53576, and that this relationship seems to mediated by individual, ethnic, and cultural characteristics. Most studies on the exogenous administration of OXT tested a single dose (24 IU) with positive effects mainly on the affective domain of empathy. At the neural level, findings were inconsistent. Taken together, the results of the studies reviewed support the existence of a relationship between OXT and empathy that is complex and multifaceted. Robust evidence is still needed to elucidate existing links. Future investigations could benefit from methodological improvements aimed at increasing the reproducibility and applicability of findings, as well as the systematic assessment of the effects of exogenous OXT considering dose and frequency of administration, genotyping, and hormonal availability at the peripheral and central levels. This should lead to significant progress in the understanding of the therapeutic possibilities of OXT in the domain of empathic behavior.

Increased oxytocin release precedes hyponatremia after pituitary surgery

PURPOSE

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a well-known complication of transsphenoidal pituitary surgery, related to inappropriate secretion of arginine vasopressin (AVP). Its diagnosis is based on hyponatremia, with a peak of occurrence around day 7 after surgery and, to date, no early marker has been reported. In particular, copeptin levels are not predictive of hyponatremia in this case. Oxytocin (OXT) is secreted into the peripheral blood by axon terminals adjacent to those of AVP neurons in the posterior pituitary. Besides its role in childbirth and lactation, recent evidences suggested a role for OXT in sodium balance. The contribution of this hormone in the dysnatremias observed after pituitary surgery has however never been investigated.

METHODS

We analyzed the urinary output of OXT in patients subjected to transsphenoidal pituitary surgery.

RESULTS

While OXT excretion remained stable in patients who presented a normonatremic postoperative course, patients who were later diagnosed with SIADH-related hyponatremia presented with a significantly increased urinary secretion of OXT 4 days after surgery.

CONCLUSION

Taken together, these results show for the first time that urinary OXT output remains normally stable after transsphenoidal pituitary surgery. OXT excretion however becomes abnormally high on or around 4 days after surgery in patients later developing hyponatremia, suggesting that this abnormal dynamics of OXT secretion might serve as an early marker for transsphenoidal surgery-related hyponatremia attributed to SIADH.

Pituitary Dysfunction as a Cause of Cardiovascular Disease

The hypothalamic-pituitary axis is responsible for the neuroendocrine control of several organ systems. The anterior pituitary directly affects the functions of the thyroid gland, the adrenal glands, and gonads, and regulates growth and milk production. The posterior hypophysis, through nerve connections with the hypothalamic nuclei, releases vasopressin and oxytocin responsible for water balance and social bonding, sexual reproduction and childbirth, respectively. Pituitary gland hormonal excess or deficiency results in dysregulation of metabolic pathways and mechanisms that are important for the homeostasis of the organism and are associated with increased morbidity and mortality. Cardiovascular (CV) disorders are common in pituitary disease and have a significant impact on survival. Hormonal imbalance is associated with CV complications either through direct effects on the heart structure and function and vasculature or indirectly by altering the metabolic profile. Optimal endocrine control can prevent or reverse CV defects and preserve survival and quality of life. In this review, we discuss the effects of pituitary hormone excess and deficiency on the CV system. Specifically, we assess the impact of Somatotroph, Corticotroph, Gonadotroph, and Lactotroph anterior pituitary axes on the CV system. The effect of posterior pituitary function on the CV system is also explored.

Oxytocin Downregulates the CaV1.2 L-Type Ca2+ Channel via Gi/cAMP/PKA/CREB Signaling Pathway in Cardiomyocytes

Oxytocin (OT) and its receptor (OTR) are expressed in the heart and are involved in the physiological cardiovascular functional system. Although it is known that OT/OTR signaling is cardioprotective by reducing the inflammatory response and improving cardiovascular function, the role of OT in the cardiac electrical excitation modulation has not been clarified. This study investigates the molecular mechanism of the action of OT on cardiomyocyte membrane excitation focusing on the L-type Ca²⁺ channel. Our methodology uses molecular biological methods and a patch-clamp technique on rat cardiomyocytes with OT, combined with several signal inhibitors and/or activators. Our results show that long-term treatment of OT significantly decreases the expression of Cav1.2 mRNA, and reduces the L-type Ca²⁺ channel current (I_Ca.L) in cardiomyocytes. OT downregulates the phosphorylated component of a transcription factor adenosine-3′,5′-cyclic monophosphate (cAMP) response element binding protein (CREB), whose action is blocked by OTR antagonist and pertussis toxin, a specific inhibitor of the inhibitory GTP-binding regulators of adenylate cyclase, Gi. On the other hand, the upregulation of Cav1.2 mRNA expression by isoproterenol is halted by OT. Furthermore, inhibition of phospholipase C (PLC) was without effect on the OT action to downregulate Cav1.2 mRNA—which suggests a signal pathway of Gi/protein kinase A (PKA)/CREB mediated by OT/OTR. These findings indicate novel signaling pathways of OT contributing to a downregulation of the Cav1.2-L-type Ca²⁺ channel in cardiomyocytes.

Confirmation of the cardiac safety of nolasiban in a randomised cohort of healthy female volunteers

Nolasiban is an orally active oxytocin receptor antagonist being developed to increase the efficiency of assisted reproductive technologies. This study evaluated the pharmacokinetics, pharmacodynamics, and cardiac safety of nolasiban in 45 healthy women of child-bearing age. Nolasiban was administered in a fasted state with a standardised lunch served 4.5 h post-dose. Concentration-effect modelling was used to assess the effect of two dosages of nolasiban (900 mg and 1800 mg) on QTc following single-dose administration. We found no significant change in QTc at all tested dosages. Two-sided 90% confidence intervals of geometric mean C_max for estimated QTc effects of nolasiban were below the threshold of regulatory concern. The sensitivity of the assay to detect small changes in QTc was confirmed by a significant shortening of QTc between 2 and 4 h after consumption of a meal, which served to validate the model. Independent of the nolasiban assessment, this study also explored the effects of sex hormones on ECG parameters, especially QT subintervals. We found a significant relationship between JTpc and oestradiol. Heart rate was negatively correlated with progesterone. This study confirms the cardiovascular safety of nolasiban and describes relationships of sex hormones and ECG parameters.

Oxytocin Receptor Signaling in Vascular Function and Stroke

The oxytocin receptor (OXTR) is a G protein-coupled receptor with a diverse repertoire of intracellular signaling pathways, which are activated in response to binding oxytocin (OXT) and a similar nonapeptide, vasopressin. This review summarizes the cell and molecular biology of the OXTR and its downstream signaling cascades, particularly focusing on the vasoactive functions of OXTR signaling in humans and animal models, as well as the clinical applications of OXTR targeting cerebrovascular accidents.

Oxytocin-monomeric red fluorescent protein 1 synthesis in the hypothalamus under osmotic challenge and acute hypovolemia in a transgenic rat line

We generated a transgenic rat line that expresses oxytocin (OXT)-monomeric red fluorescent protein 1 (mRFP1) fusion gene to visualize the dynamics of OXT. In this transgenic rat line, hypothalamic OXT can be assessed under diverse physiological and pathophysiological conditions by semiquantitative fluorometry of mRFP1 fluorescence intensity as a surrogate marker for endogenous OXT. Using this transgenic rat line, we identified the changes in hypothalamic OXT synthesis under various physiological conditions. However, few reports have directly examined hypothalamic OXT synthesis under hyperosmolality or hypovolemia. In this study, hypothalamic OXT synthesis was investigated using the transgenic rat line after acute osmotic challenge and acute hypovolemia induced by intraperitoneal (i.p.) administration of 3% hypertonic saline (HTN) and polyethylene glycol (PEG), respectively. The mRFP1 fluorescence intensity in the paraventricular (PVN) and supraoptic nuclei (SON) was significantly increased after i.p. administration of HTN and PEG, along with robust Fos-like immunoreactivity (co-expression). Fos expression showed neuronal activation in the brain regions that are associated with the hypothalamus and/or are involved in maintaining water and electrolyte homeostasis in HTN- and PEG-treated rats. OXT and mRFP1 gene expressions were dramatically increased after HTN and PEG administration. The plasma OXT level was extremely increased after HTN and PEG administration. Acute osmotic challenge and acute hypovolemia induced upregulation of hypothalamic OXT in the PVN and SON. These results suggest that not only endogenous arginine vasopressin (AVP) but also endogenous OXT has a key role in maintaining body fluid homeostasis to cope with hyperosmolality and hypovolemia.

The Role of Oxytocin in Cardiovascular Protection

The beneficial effects of oxytocin on infarct size and functional recovery of the ischemic reperfused heart are well documented. The mechanisms for this cardioprotection are not well defined. Evidence indicates that oxytocin treatment improves cardiac work, reduces apoptosis and inflammation, and increases scar vascularization. Oxytocin-mediated cytoprotection involves the production of cGMP stimulated by local release of atrial natriuretic peptide and synthesis of nitric oxide. Treatment with oxytocin reduces the expression of proinflammatory cytokines and reduces immune cell infiltration. Oxytocin also stimulates differentiation stem cells to cardiomyocyte lineages as well as generation of endothelial and smooth muscle cells, promoting angiogenesis. The beneficial actions of oxytocin may include the increase in glucose uptake by cardiomyocytes, reduction in cardiomyocyte hypertrophy, decrease in oxidative stress, and mitochondrial protection of several cell types. In cardiac and cellular models of ischemia and reperfusion, acute administration of oxytocin at the onset of reperfusion enhances cardiomyocyte viability and function by activating Pi3K and Akt phosphorylation and downstream cellular signaling. Reperfusion injury salvage kinase and signal transducer and activator of transcription proteins cardioprotective pathways are involved. Oxytocin is cardioprotective by reducing the inflammatory response and improving cardiovascular and metabolic function. Because of its pleiotropic nature, this peptide demonstrates a clear potential for the treatment of cardiovascular pathologies. In this review, we discuss the possible cellular mechanisms of action of oxytocin involved in cardioprotection.

Oxytocin's anti-inflammatory and proimmune functions in COVID-19: a transcriptomic signature-based approach

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a worldwide pandemic, infecting over 16 million people worldwide with a significant mortality rate. However, there is no current Food and Drug Administration-approved drug that treats coronavirus disease 2019 (COVID-19). Damage to T lymphocytes along with the cytokine storm are important factors that lead to exacerbation of clinical cases. Here, we are proposing intravenous oxytocin (OXT) as a candidate for adjunctive therapy for COVID-19. OXT has anti-inflammatory and proimmune adaptive functions. Using the Library of Integrated Network-Based Cellular Signatures (LINCS), we used the transcriptomic signature for carbetocin, an OXT agonist, and compared it to gene knockdown signatures of inflammatory (such as interleukin IL-1β and IL-6) and proimmune markers (including T cell and macrophage cell markers like CD40 and ARG1). We found that carbetocin’s transcriptomic signature has a pattern of concordance with inflammation and immune marker knockdown signatures that are consistent with reduction of inflammation and promotion and sustaining of immune response. This suggests that carbetocin may have potent effects in modulating inflammation, attenuating T cell inhibition, and enhancing T cell activation. Our results also suggest that carbetocin is more effective at inducing immune cell responses than either lopinavir or hydroxychloroquine, both of which have been explored for the treatment of COVID-19.

The Interaction of the Endogenous Hydrogen Sulfide and Oxytocin Systems in Fluid Regulation and the Cardiovascular System

The purpose of this review is to explore the parallel roles and interaction of hydrogen sulfide (H2S) and oxytocin (OT) in cardiovascular regulation and fluid homeostasis. Their interaction has been recently reported to be relevant during physical and psychological trauma. However, literature reports on H2S in physical trauma and OT in psychological trauma are abundant, whereas available information regarding H2S in psychological trauma and OT in physical trauma is much more limited. This review summarizes recent direct and indirect evidence of the interaction of the two systems and their convergence in downstream nitric oxide-dependent signaling pathways during various types of trauma, in an effort to better understand biological correlates of psychosomatic interdependencies.

Oxytocin mediated cardioprotection is independent of coronary endothelial function in rats

The cardioprotective effect of oxytocin (OT) has been well established. However, there are no related studies on the role of endothelia in oxytocin-induced cardioprotection. Endothelial dysfunction (ED) model was established by injection of 0.01 % Triton X-100 in the isolated rat heart. Oxytocin pretreatment was conducted at the end of stabilization for 40 min, followed by 30 min global ischemia and 60 min reperfusion to induce I/R injury. Coronary perfusion pressure, hemodynamics and arrhythmia severity scores were measured respectively. High-sensitivity cardiac troponin T (hs-cTnT) was evaluated by enzyme-linked immunosorbent assay. Infarct size was detected by triphenyltetrazolium chloride staining. The morphological changes in coronary endothelium were observed by scanning electron microscopy. Injection of 0.01 % Triton X-100 caused significant reduction of CPP induced by histamine and endothelium removal from scanning electron microscopy, but SNP had no significant effect. Oxytocin pretreatment showed significant recovery in LVDP, ±dp/dtmax, RPP and SI after reperfusion (P <  0.05). Additionally, I/R injury led to a rise of arrhythmia severity score, hs-cTnT and infarct size. No significant differences between ED-OT-I/R and OT-I/R groups were found in arrhythmia severity score, hs-cTnT, and infarct size (P >  0.05). I/R injury exacerbated the decrease in CPP and worsened the migration, deformation, and fracture of coronary endothelium, while oxytocin reversed these injuries. Despite the presence of endothelial damages, oxytocin partially alleviated I/R- and Triton-induced endothelial damages. The cardioprotective effects of oxytocin are independent of endothelial function in alleviating I/R injury and I/R-induced coronary endothelial dysfunction.

Oxytocin Controls Chondrogenesis and Correlates with Osteoarthritis

This study investigated the relationship of oxytocin (OT) to chondrogenesis and osteoarthritis (OA). Human bone marrow and multipotent adipose-derived stem cells were cultured in vitro in the absence or presence of OT and assayed for mRNA transcript expression along with histological and immunohistochemical analyses. To study the effects of OT in OA in vivo, a rat model and a human cohort of 63 men and 19 women with hand OA and healthy controls, respectively, were used. The baseline circulating OT, interleukin-6, leptin, and oestradiol levels were measured, and hand X-ray examinations were performed for each subject. OT induced increased aggrecan, collagen (Col) X, and cartilage oligomeric matrix protein mRNA transcript levels in vitro, and the immunolabelling experiments revealed a normalization of Sox9 and Col II protein expression levels. No histological differences in lesion severity were observed between rat OA groups. In the clinical study, a multivariate analysis adjusted for age, body mass index, and leptin levels revealed a significant association between OA and lower levels of OT (odds ratio = 0.77; p = 0.012). Serum OT levels are reduced in patients with hand OA, and OT showed a stimulatory effect on chondrogenesis. Thus, OT may contribute to the pathophysiology of OA.

Vasopressin & Oxytocin in Control of the Cardiovascular System: An Updated Review

Since the discovery of vasopressin (VP) and oxytocin (OT) in 1953, considerable knowledge has been gathered about their roles in cardiovascular homeostasis. Unraveling VP vasoconstrictor properties and V1a receptors in blood vessels generated powerful hemostatic drugs and drugs effective in the treatment of certain forms of circulatory collapse (shock). Recognition of the key role of VP in water balance via renal V2 receptors gave birth to aquaretic drugs found to be useful in advanced stages of congestive heart failure. There are still unexplored actions of VP and OT on the cardiovascular system, both at the periphery and in the brain that may open new venues in treatment of cardiovascular diseases. After a brief overview on VP, OT and their peripheral action on the cardiovascular system, this review focuses on newly discovered hypothalamic mechanisms involved in neurogenic control of the circulation in stress and disease.

Oxytocin Reduces Intravesical Pressure in Anesthetized Female Rats: Action on Oxytocin Receptors of the Urinary Bladder

Urinary bladder dysfunction affects several people worldwide and shows higher prevalence in women. Micturition is dependent on the Barrington’s nucleus, pontine urine storage center and periaqueductal gray matter, but other brain stem areas are involved in the bladder regulation. Neurons in the medulla oblongata send projections to hypothalamic nuclei as the supraoptic nucleus, which synthetizes oxytocin and in its turn, this peptide is released in the circulation. We investigated the effects of intravenous injection of oxytocin (OT) on the urinary bladder in sham and ovariectomized rats. We also evaluated the topical (in situ) action of OT on intravesical pressure (IP) as well as the existence of oxytocin receptors in the urinary bladder. In sham female Wistar rats, anesthetized with isoflurane, intravenous infusion of OT (10 ng/kg) significantly decreased the IP (–47.5 ± 1.2%) compared to saline (3.4 ± 0.7%). Similar effect in IP was observed in ovariectomized rats after i.v. OT (–41.9 ± 2.9%) compared to saline (0.5 ± 0.6%). Topical administration (in situ) of 0.1 mL of OT (1.0 ng/mL) significantly reduced the IP (22.3.0 ± 0.6%) compared to saline (0.9 ± 0.7%). We also found by qPCR that the gene expression of oxytocin receptor is present in this tissue. Blockade of oxytocin receptors significantly attenuated the reduction in IP evoked by oxytocin i.v. or in situ. Therefore, the findings suggest that (1) intravenous oxytocin decreases IP due to bladder relaxation and (2) OT has local bladder effect, binding directly in receptors located in the bladder.

Sex Differences in the Regulation of Vasopressin and Oxytocin Secretion in Bile Duct-Ligated Rats

INTRODUCTION

Hyponatremia due to elevated arginine vasopressin (AVP) secretion increases mortality in liver failure patients. No previous studies have addressed sex differences in hyponatremia in liver failure animal models.

OBJECTIVE

This study addressed this gap in our understanding of the potential sex differences in hyponatremia associated with increased AVP secretion.

METHODS

This study tested the role of sex in the development of hyponatremia using adult male, female, and ovariectomized (OVX) female bile duct-ligated (BDL) rats.

RESULTS

All BDL rats had significantly increased liver to body weight ratios compared to sham controls. Male BDL rats had hyponatremia with significant increases in plasma copeptin and FosB expression in supraoptic AVP neurons compared to male shams (all p < 0.05; 5-7). Female BDL rats did not become hyponatremic or demonstrate increased supraoptic AVP neuron activation and copeptin secretion compared to female shams. Plasma oxytocin was significantly higher in female BDL rats compared to female sham (p < 0.05; 6-10). This increase was not observed in male BDL rats. Ovariectomy significantly decreased plasma estradiol in sham rats compared to intact female sham (p < 0.05; 6-10). However, circulating estradiol was significantly elevated in OVX BDL rats compared to the OVX and female shams (p < 0.05; 6-10). Adrenal estradiol, testosterone, and dehydroepiandrosterone (DHEA) were measured to identify a possible source of circulating estradiol in OVX BDL rats. The OVX BDL rats had significantly increased adrenal estradiol along with significantly decreased adrenal testosterone and DHEA compared to OVX shams (all p < 0.05; 6-7). Plasma osmolality, hematocrit, copeptin, and AVP neuron activation were not significantly different between OVX BDL and OVX shams. Plasma oxytocin was significantly higher in OVX BDL rats compared to OVX sham.

CONCLUSIONS

Our results show that unlike male BDL rats, female and OVX BDL rats did not develop hyponatremia, supraoptic AVP neuron activation, or increased copeptin secretion compared to female shams. Adrenal estradiol might have compensated for the lack of ovarian estrogens in OVX BDL rats.

Transient receptor potential vanilloid 4 modulates ion balance through the isotocin pathway in zebrafish (Danio rerio)

Isotocin controls ion regulation through modulating the functions of ionocytes (also called mitochondria-rich cells or chloride cells). However, little is known about the upstream molecule of the isotocin system. Herein, we identify transient receptor potential vanilloid 4 (TRPV4), which regulates the mRNA and protein expressions of isotocin and affects ion regulation through the isotocin pathway. Double immunohistochemical results showed that TRPV4 is expressed in isotocinergic neurons in the hypothalamus of the adult zebrafish brain. To further elucidate the roles of TRPV4, we manipulated TRPV4 protein expression and evaluated its ionoregulatory functions in zebrafish embryos. TRPV4 gene knockdown with morpholino oligonucleotides decreased ionic contents (Na+, Cl−, and Ca2+) of whole larvae and the H+-secreting function of larval skin of zebrafish. mRNA expressions of ionocyte-related transporters, including H+-ATPase, the epithelial Ca2+ channel, and the Na+-Cl− cotransporter, were also suppressed in trpv4 morphants. Numbers of ionocytes (H+-ATPase-rich cells and Na+-K+-ATPase-rich cells) and epidermal stem cells in zebrafish larval skin also decreased after trpv4 knockdown. Our results showed that TRPV4 modulates ion balance through the isotocin pathway.

Oxytocin induces intracellular Ca2+ release in cardiac fibroblasts from neonatal rats

Pituitary neuropeptide oxytocin is increasingly recognised as a cardiovascular hormone, in addition to its many regulatory roles in other organ systems. Studies in atrial and ventricular myocytes from the neonatal and adult rats have identified synthesis of oxytocin and the expression of oxytocin receptors in these cells. In cardiac fibroblasts, the most populous non-myocyte cell type in mammalian heart, the oxytocin receptors have not been described before. In the present study, we have investigated the direct effects of oxytocin on intracellular Ca²⁺ dynamics in ventricular myocytes and fibroblasts from new born rats. In myocytes, oxytocin increased the frequency of spontaneous Ca²⁺ transients and decreased their amplitude. Our data suggest that oxytocin receptors are also present and functional in the majority of cardiac fibroblasts. We used selective oxytocin receptor inhibitor L-371,257 and a number of intracellular Ca ²⁺ release blockers to investigate the mechanism of oxytocin induced Ca²⁺ signalling in cardiac fibroblasts. Our findings suggest that oxytocin induces Ca²⁺ signals in cardiac fibroblasts by triggering endoplasmic reticulum Ca²⁺ release via inositol trisphosphate activated receptors. The functional significance of the oxytocin induced Ca²⁺ signalling in cardiac fibroblasts, especially for their activation into secretory active myofibroblasts, remains to be investigated.