Oxytocin ameliorates skin damage and oxidant gastric injury in rats with thermal trauma

Oxytocin impairs wound-healing during social isolation but not social living

Social isolation hampers immune system function, and the biological mechanisms driving this effect remain understudied. We hypothesized that oxytocin (OT), a key neuropeptide involved in social cognition, is a critical mediator of social context on immune function. In the California mouse (Peromyscus californicus), we examined how female and male immune function is influenced by (1) social isolation from same-sex peers, (2) social peer affiliation, and (3) exogenous OT. We evaluated immune function through wound size progression following a skin biopsy and proinflammatory cytokines in the wound fluid. Unexpectedly, social isolation alone did not influence wound healing, but isolation + OT increased wound size in a dose dependent manner. Wound size progression interacted with sex and OT in socially-housed mice, suggesting that OT increases inflammation in females, while decreasing inflammation in males in a social context-dependent manner. Inflammatory biomarker interleukin-6 (IL-6) mRNA expression correlated with wound size overall, supporting wound healing as an index of inflammatory response. However, isolation + OT mice did not have higher levels of IL-6, suggesting that the mechanism through which isolation + OT influences wound size is not through IL-6 activity. Behaviorally, higher levels of affiliation were negatively associated with wound size, and this effect was diminished by OT treatment. Our results highlight that the anti-inflammatory effects of OT are likely highly dependent on social context.

Oxytocin/Oxytocin Receptor Signalling in the Gastrointestinal System: Mechanisms and Therapeutic Potential

The neuropeptide hormone oxytocin (OT) is involved in various physiological and pathological processes via the oxytocin receptor (OTR). While OT is most widely known as a reproductive system hormone and a nervous system neurotransmitter, the OT/OTR system has gradually gained much attention for its role in the gastrointestinal (GI) system, such as the GI motility, secretion, and bowel inflammatory reactions. Its importance in GI cancers has also been reported in the past few decades. The promising clinical observations have revealed OT's anti-nociceptive effect, protective effect over gut injury, and the potential of using microbiota to naturally increase endogenous OT levels, which shed a light on the management of GI disorders with lower side effects. However, no current comprehensive review is available on the actions of OT/OTR in the GI tract. This review aims to present the lesser-known role of the OT/OTR system in the GI tract, and the most recent findings are discussed regarding the distribution and functional role of OTR signalling in regulating (patho)physiological functions of the GI tract. Special emphasis is placed on its therapeutic potential for clinical management of GI disorders, such as GI pain, inflammatory bowel disease (IBD), and irritable bowel syndrome (IBS). The recent characterisation of the OTR's crystal structure has advanced research for designing and identifying new OTR-specific molecules. Future in-depth basic and clinical research is needed to further elucidate the involvement and detailed mechanism of OT/OTR in GI disorders, and the development of OTR-specific ligands.

Kinetics of Inflammatory Mediators in the Immune Response to Burn Injury: Systematic Review and Meta-Analysis of Animal Studies

Burns are often accompanied by a dysfunctional immune response, which can lead to systemic inflammation, shock, and excessive scarring. The objective of this study was to provide insight into inflammatory pathways associated with burn-related complications. Because detailed information on the various inflammatory mediators is scattered over individual studies, we systematically reviewed animal experimental data for all reported inflammatory mediators. Meta-analyses of 352 studies revealed a strong increase in cytokines, chemokines, and growth factors, particularly 19 mediators in blood and 12 in burn tissue. Temporal kinetics showed long-lasting surges of proinflammatory cytokines in blood and burn tissue. Significant time-dependent effects were seen for IL-1β, IL-6, TGF-β1, and CCL2. The response of anti-inflammatory mediators was limited. Burn technique had a profound impact on systemic response levels. Large burn size and scalds further increased systemic, but not local inflammation. Animal characteristics greatly affected inflammation, for example, IL-1β, IL-6, and TNF-α levels were highest in young, male rats. Time-dependent effects and dissimilarities in response demonstrate the importance of appropriate study design. Collectively, this review presents a general overview of the burn-induced immune response exposing inflammatory pathways that could be targeted through immunotherapy for burn patients and provides guidance for experimental set-ups to advance burn research.

Microbial stimulation of oxytocin release from the intestinal epithelium via secretin signaling

Intestinal microbes impact the health of the intestine and organs distal to the gut. Limosilactobacillus reuteri is a human intestinal microbe that promotes normal gut transit, the anti-inflammatory immune system, wound healing, normal social behavior in mice, and prevents bone reabsorption. Oxytocin impacts these functions and oxytocin signaling is required for L. reuteri-mediated wound healing and social behavior; however, the events in the gut leading to oxytocin stimulation and beneficial effects are unknown. Here we report evolutionarily conserved oxytocin production in the intestinal epithelium through analysis of single-cell RNA-Seq datasets and imaging of human and mouse intestinal tissues. Moreover, human intestinal organoids produce oxytocin, demonstrating that the intestinal epithelium is sufficient to produce oxytocin. We find that L. reuteri facilitates oxytocin secretion from human intestinal tissue and human intestinal organoids. Finally, we demonstrate that stimulation of oxytocin secretion by L. reuteri is dependent on the gut hormone secretin, which is produced in enteroendocrine cells, while oxytocin itself is produced in enterocytes. Altogether, this work demonstrates that oxytocin is produced and secreted from enterocytes in the intestinal epithelium in response to secretin stimulated by L. reuteri. This work thereby identifies oxytocin as an intestinal hormone and provides mechanistic insight into avenues by which gut microbes promote host health.

Human sweat contains oxytocin

BACKGROUND

Oxytocin (OT) has been detected in various body fluids, including blood, urine, saliva, breastmilk, and spinal fluid. Consistent with models that regard skin as a social organ and in line with studies demonstrating that skin cells express both OT and its receptor, our study sought to examine the presence of OT in human sweat.

METHODS

Overall, 553 individuals participated in a pilot study and three experiments. Firstly, 50 participants provided sweat after engaging in various sports for different durations. Secondly, 26 participants provided sweat from forehead, upper-chest, forearm, and underarm, including 11 in natural setting and 15 following OT administration and a 30-minute exercise. Thirdly, of 435 volunteers, 97 provided sufficient axillary sweat for assaying. Of these, 84 participated in a naturalistic experiment that involved saliva and sweat collection in response to physical activity in either solitary or social settings. OT and testosterone (TS) were assayed in sweat and saliva.

RESULTS

Intense activity for at least 25 min was required to produce sufficient sweat for OT analysis. Highest OT levels were found in axillary sweat compared to sweat from the forehead, upper-chest, and forearm. Salivary OT and TS increased after both solitary and social physical activity; however, higher sweat OT was found after solitary sports. Post-hoc preliminary findings indicate that highly extroverted individuals exercising in solitary environments showed the highest sweat OT levels.

CONCLUSIONS

Findings demonstrate, for the first time, the presence of OT in human sweat and show the feasibility of its measurement. Much further research is required to illuminate how sweat OT is impacted by personality and social context and to uncover the role of the skin in OT production.

Microbial stimulation of oxytocin release from the intestinal epithelium via secretin signaling

Intestinal microbes impact the health of the intestine and organs distal to the gut. Limosilactobacillus reuteri is a human intestinal microbe that promotes normal gut transit 1 , the anti-inflammatory immune system 2-4 , wound healing 5-7 , normal social behavior in mice 8-10 , and prevents bone reabsorption 11-17 . Each of these functions is impacted by oxytocin 18-22 , and oxytocin signaling is required for L. reuteri- mediated wound healing 5 and social behavior 9 ; however, the initiating events in the gut that lead to oxytocin stimulation and related beneficial functions remain unknown. Here we found evolutionarily conserved oxytocin production in the intestinal epithelium through analysis of single-cell RNA-Seq datasets and imaging of human and mouse intestinal tissues. Moreover, human intestinal organoids produce oxytocin, demonstrating that the intestinal epithelium is sufficient to produce oxytocin. We subsequently found that L. reuteri facilitates oxytocin secretion directly from human intestinal tissue and human intestinal organoids. Finally, we demonstrate that stimulation of oxytocin secretion by L. reuteri is dependent on the gut hormone secretin, which is produced in enteroendocrine cells 23 , while oxytocin itself is produced in enterocytes. Altogether, this work demonstrates that oxytocin is produced and secreted from enterocytes in the intestinal epithelium in response to secretin stimulated by L. reuteri . This work thereby identifies oxytocin as an intestinal hormone and provides mechanistic insight into avenues by which gut microbes promote host health.

Evaluation of the oxytocin effect in a rat model with experimental periodontitis

The aim of the present study was to evaluate the inhibitory effects of oxytocin on the development of periodontitis based on its properties against bone loss and resorption. Thirty-two Wistar albino rats were divided into four equal groups: control, periodontitis + saline, periodontitis + 0.5 mg/kg/day oxytocin, and periodontitis + 1 mg/kg/day oxytocin. Periodontitis groups received 4.0 silk ligatures around their cervixes of the right and left mandibular incisors in an "8" shape, kept for 14 days. Animals in oxytocin groups were injected once every day during 14 days with oxytocin. The mandibles were fixed and scanned using microcomputed tomography to quantify bone resorption and volumetric measurements. Blood samples were collected to analyze the concentrations of macrophage colony-stimulating factor (M-CSF), receptor activator of nuclear factor-κΒ ligand (RANKL), osteoprotegerin (OPG), matrix metalloproteinase-8 (MMP-8), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, glutathione peroxidase (GPx), superoxide dismutase (SOD), and malondialdehyde (MDA). Histopathological evaluations were conducted to examine the gingiva and alveolar bone. Oxytocin prevented the development of periodontitis by decreasing ligament deteriorations and leukocytes in the gingival connective tissue and promoting reintegration with the alveolar bone. Bone resorption in all regions was less in the periodontitis + 1 mg/kg/day oxytocin group than in the periodontitis + saline group. Although TNF-α, IL-6, and RANKL values were lower in the periodontitis + 1 mg/kg/day oxytocin group, OPG was higher than that in the periodontitis + saline group. M-CSF, MMP-8, and MDA were lower in the oxytocin groups than in the periodontitis + saline group. Oxytocin may be an effective agent for periodontal diseases because it decreased bone resorption, oxidative stress, and inflammation in an experimental periodontitis.

Exosomes Derived from Bone Marrow Mesenchymal Stem Cells Alleviate Ischemia-Reperfusion Injury and Promote Survival of Skin Flaps in Rats

Free tissue flap transplantation is a classic and important method for the clinical repair of tissue defects. However, ischemia-reperfusion (IR) injury can affect the success rate of skin flap transplantation. We used a free abdomen flap rat model to explore the protective effects of exosomes derived from bone marrow mesenchymal stem cells (BMSCs-exosomes) against the IR injury of the skin flap. Exosomes were injected through the tail vein and the flaps were observed and obtained on day 7. We observed that BMSCs-exosomes significantly reduced the necrotic lesions of the skin flap. Furthermore, BMSCs-exosomes relieved oxidative stress and reduced the levels of inflammatory factors. Apoptosis was evaluated via the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and Western blot analysis of Bax, Bcl-2. Simultaneously, BMSCs-exosomes promoted the formation of new blood vessels in the IR flap, as confirmed by the increased expression level of VEGFA and the fluorescence co-staining of CD31 and PCNA. Additionally, BMSCs-exosomes considerably increased proliferation and migration of human umbilical vein endothelial cells and promoted angiogenesis in vitro. BMSCs-exosomes could be a promising cell-free therapeutic candidate to reduce IR injury and promote the survival of skin flaps.

Oxytocin and oxygen: the evolution of a solution to the ‘stress of life’

Oxytocin (OT) and the OT receptor occupy essential roles in our current understanding of mammalian evolution, survival, sociality and reproduction. This narrative review examines the hypothesis that many functions attributed to OT can be traced back to conditions on early Earth, including challenges associated with managing life in the presence of oxygen and other basic elements, including sulfur. OT regulates oxidative stress and inflammation especially through effects on the mitochondria. A related nonapeptide, vasopressin, as well as molecules in the hypothalamic–pituitary–adrenal axis, including the corticotropin-releasing hormone family of molecules, have a broad set of functions that interact with OT. Interactions among these molecules have roles in the causes and consequence of social behaviour and the management of threat, fear and stress. Here, we discuss emerging evidence suggesting that unique properties of the OT system allowed vertebrates, and especially mammals, to manage over-reactivity to the ‘side effects’ of oxygen, including inflammation, oxidation and free radicals, while also supporting high levels of sociality and a perception of safety.

This article is part of the theme issue ‘Interplays between oxytocin and other neuromodulators in shaping complex social behaviours’.

Potential of Endogenous Oxytocin in Endocrine Treatment and Prevention of COVID-19

Coronavirus disease 2019 or COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a significant threat to the health of human beings. While wearing mask, maintaining social distance and performing self-quarantine can reduce virus spreading passively, vaccination actively enhances immune defense against COVID-19. However, mutations of SARS-CoV-2 and presence of asymptomatic carriers frustrate the effort of completely conquering COVID-19. A strategy that can reduce the susceptibility and thus prevent COVID-19 while blocking viral invasion and pathogenesis independent of viral antigen stability is highly desirable. In the pathogenesis of COVID-19, endocrine disorders have been implicated. Correspondingly, many hormones have been identified to possess therapeutic potential of treating COVID-19, such as estrogen, melatonin, corticosteroids, thyroid hormone and oxytocin. Among them, oxytocin has the potential of both treatment and prevention of COVID-19. This is based on oxytocin promotion of immune-metabolic homeostasis, suppression of inflammation and pre-existing comorbidities, acceleration of damage repair, and reduction of individuals' susceptibility to pathogen infection. Oxytocin may specifically inactivate SARS-COV-2 spike protein and block viral entry into cells via angiotensin-converting enzyme 2 by suppressing serine protease and increasing interferon levels and number of T-lymphocytes. In addition, oxytocin can promote parasympathetic outflow and the secretion of body fluids that could dilute and even inactivate SARS-CoV-2 on the surface of cornea, oral cavity and gastrointestinal tract. What we need to do now is clinical trials. Such trials should fully balance the advantages and disadvantages of oxytocin application, consider the time- and dose-dependency of oxytocin effects, optimize the dosage form and administration approach, combine oxytocin with inhibitors of SARS-CoV-2 replication, apply specific passive immunization, and timely utilize efficient vaccines. Meanwhile, blocking COVID-19 transmission chain and developing other efficient anti-SARS-CoV-2 drugs are also important. In addition, relative to the complex issues with drug applications over a long term, oxytocin can be mobilized through many physiological stimuli, and thus used as a general prevention measure. In this review, we explore the potential of oxytocin for treatment and prevention of COVID-19 and perhaps other similar pathogens.

Consequences of pandemic-associated social restrictions: Role of social support and the oxytocin system

During pandemics, governments take drastic actions to prevent the spreading of the disease, as seen during the present COVID-19 crisis. Sanctions of lockdown, social distancing and quarantine urge people to exclusively work and teach at home and to restrict social contacts to a minimum; lonely people get into further isolation, while families` nerves are strained to the extreme. Overall, this results in a dramatic and chronic increase in the level of psychosocial stress over several months mainly caused by i) social isolation and ii) psychosocial stress associated with overcrowding, social tension in families, and domestic violence. Moreover, pandemic-associated social restrictions are accompanied by loss of an essential stress buffer and important parameter for general mental and physical health: social support. Chronic psychosocial stress and, in particular, social isolation and lack of social support affect not only mental health, but also the brain oxytocin system and the immune system. Hence, pandemic-associated social restrictions are expected to increase the risk of developing psychopathologies, such as depression, anxiety-related and posttraumatic stress disorders, on the one hand, but also to induce a general inflammatory state and to impair the course of infectious disorders on the other. Due to its pro-social and stress-buffering effects, resulting in an anti-inflammatory state in case of disease, the role of the neuropeptide oxytocin will be discussed and critically considered as an emerging treatment option in cases of pandemic-induced psychosocial stress, viral infection and during recovery. In this review, we aim to critically focus on possible short- and long-term consequences of social restrictions on mental health and the immune system, while discussion oxytocin as a possible treatment option.

Oxytocin induces anti-catabolic and anabolic effects on protein metabolism in the female rat oxidative skeletal muscle

AIMS

Although it is well established that skeletal muscle contains oxytocin (OT) receptors and OT-knockout mice show premature development of sarcopenia, the role of OT in controlling skeletal muscle mass is still unknown. Therefore, the present work aimed to determine OT's effects on skeletal muscle protein metabolism.

MAIN METHODS

Total proteolysis, proteolytic system activities and protein synthesis were assessed in isolated soleus muscle from prepubertal female rats. Through in vivo experiments, rats received 3-day OT treatment (3UI.kg^-1.day^-1, i.p.) or saline, and muscles were harvested for mass-gain assessment.

KEY FINDINGS

In vitro OT receptor stimulation reduced total proteolysis, specifically through attenuation of the lysosomal and proteasomal proteolytic systems, and in parallel activated the Akt/FoxO1 signaling and suppressed atrogenes (e.g., MuRF-1 and atrogin-1) expression induced by motor denervation. On the other hand, the protein synthesis was not altered by in vitro treatment with the OT receptor-selective agonist. Although short-term OT treatment did not change the atrogene mRNA levels, the protein synthesis was stimulated, resulting in soleus mass gain, probably through an indirect effect.

SIGNIFICANCE

Taken together, these data show for the first time that OT directly inhibits the proteolytic activities of the lysosomal and proteasomal systems in rat oxidative skeletal muscle by suppressing atrogene expression via stimulation of Akt/FoxO signaling. Moreover, the data obtained from in vivo experiments suggest OT's ability to control rat oxidative skeletal muscle mass.

Can intravenous oxytocin infusion counteract hyperinflammation in COVID-19 infected patients?

OBJECTIVES

Based on its well-documented anti-inflammatory and restorative properties we propose trials with the natural hormone oxytocin for treatment of hospitalised Covid-19 patients.

METHODS

We searched for, retrieved, and commented on specific literature regarding multiple functions of oxytocin with a special focus on its modulation of inflammatory, immune, and restorative functions.

RESULTS

Available data gathered in animals and humans support the anti-inflammatory properties of oxytocin. The multiple anti-inflammatory effects of oxytocin have been demonstrated in vitro and in vivo in various animal models and also in humans in response to intravenous infusion of oxytocin. Furthermore, oxytocin has been documented to activate several types of protective and restorative mechanisms and to exert positive effects on the immune system.

CONCLUSIONS

In addition, to being anti-inflammatory, it may be hypothesised, that oxytocin may be less suppressive on adaptive immune systems, as compared with glucocorticoids. Finally, by its restorative effects coupled with its anti-stress and healing properties, oxytocin may shorten the recovery period of the Covid-19 patients.

Is Oxytocin "Nature's Medicine"?

Oxytocin is a pleiotropic, peptide hormone with broad implications for general health, adaptation, development, reproduction, and social behavior. Endogenous oxytocin and stimulation of the oxytocin receptor support patterns of growth, resilience, and healing. Oxytocin can function as a stress-coping molecule, an anti-inflammatory, and an antioxidant, with protective effects especially in the face of adversity or trauma. Oxytocin influences the autonomic nervous system and the immune system. These properties of oxytocin may help explain the benefits of positive social experiences and have drawn attention to this molecule as a possible therapeutic in a host of disorders. However, as detailed here, the unique chemical properties of oxytocin, including active disulfide bonds, and its capacity to shift chemical forms and bind to other molecules make this molecule difficult to work with and to measure. The effects of oxytocin also are context-dependent, sexually dimorphic, and altered by experience. In part, this is because many of the actions of oxytocin rely on its capacity to interact with the more ancient peptide molecule, vasopressin, and the vasopressin receptors. In addition, oxytocin receptor(s) are epigenetically tuned by experience, especially in early life. Stimulation of G-protein-coupled receptors triggers subcellular cascades allowing these neuropeptides to have multiple functions. The adaptive properties of oxytocin make this ancient molecule of special importance to human evolution as well as modern medicine and health; these same characteristics also present challenges to the use of oxytocin-like molecules as drugs that are only now being recognized. SIGNIFICANCE STATEMENT: Oxytocin is an ancient molecule with a major role in mammalian behavior and health. Although oxytocin has the capacity to act as a "natural medicine" protecting against stress and illness, the unique characteristics of the oxytocin molecule and its receptors and its relationship to a related hormone, vasopressin, have created challenges for its use as a therapeutic drug.

What's Love Got to do with it: Role of oxytocin in trauma, attachment and resilience

Oxytocin (OT) is a neurohypophysial hormone and neuropeptide produced by the hypothalamus and released by the pituitary gland. It has multiple physiological roles including stimulation of parturition and lactation, and promotion of pro-adaptive social behaviors necessary for mammalian survival. OT interacts with one receptor subtype: the OT receptor (OTR) which, upon stimulation, triggers different intracellular signal transduction cascades to mediate its physiological actions. Preclinical studies show that OT regulates social behaviors such as pair bonding, recognition and social interaction. It also coordinates the activation of the hypothalamic-pituitary-adrenal (HPA) axis and the release of corticotrophin-releasing hormone. Further evidence suggests that OT plays an important role in regulating caloric intake and metabolism, and in maintaining electrolyte and cardiovascular homeostasis. OT is also involved in attenuating the neurophysiological and neurochemical effects of trauma on the brain and body by facilitating both physical attachment such as wound healing, and psychological/social attachment, thereby increasing resilience to subsequent traumatic events. Clinical trials have reported that intranasal administration of OT provides therapeutic benefits for patients diagnosed with traumatic stress-related diseases such as major depressive disorders and post-traumatic stress disorder. OT's therapeutic benefits may result from context-dependent interactions with key neural pathways (social, cognitive, and reward), neurotransmitters (dopamine, norepinephrine, serotonin, and endogenous opioids), and biomarkers (adrenocorticotropic hormone, cortisol, and dehydroepiandrosterone sulfate), that lead to a decrease in stress -associated behaviors, and facilitate post-traumatic growth, ultimately leading to increased resilience, through improved social cohesion and attachment. OT induced-augmentation of physical and cognitive resilience may play a significant role in both the prevention of, and improved clinical outcomes for, traumatic stress-related disorders following either acute or enduring traumatic experiences.

Regular moderate exercise alleviates gastric oxidative damage in rats via the contribution of oxytocin receptors

KEY POINTS

A moderate level of exercise has beneficial effects for the prevention of gastric ulcers. Although regular aerobic exercise was shown to elevate serum oxytocin levels and exogenously administered oxytocin exerts an anti-ulcer activity, the role of endogenous oxytocin in the gastroprotective effects of exercise has not yet been elucidated. We showed that increased anxiety and oxidative gastric damage induced by gastric ulcers were reversed in pre-exercised rats, while reduced hypothalamic oxytocin expression and decreased myenteric oxytocin receptor expression due to gastric ulcers were abolished by exercise. We also reported that the blockade of oxytocin receptors exaggerated gastric damage in exercised rats with ulcers. Our data establish that endogenous oxytocin is the key mediator in the beneficial effects of regular physical activity in alleviating gastric injury.

ABSTRACT

Exercise increases serum oxytocin levels and exogenous oxytocin exerts an anti-ulcer activity; but the role of oxytocin in the protective effects of exercise against gastric ulcers has not yet been evaluated. This study was designed to investigate the impact of regular swimming exercise on oxidative gastric injury, and the role of oxytocin receptor activity in the anxiolytic and anti-inflammatory actions of exercise. Adult Wistar albino rats of both sexes performed swimming exercise (30 min/day, 5 days) or stayed sedentary. At the end of the 6-week exercise/sedentary protocol, rats were injected intraperitoneally with atosiban (0.1 mg/kg/day) or saline for 4 days. On the 5th day, under anaesthesia, acetic acid (ulcer) or saline (sham) was applied onto the gastric serosa and the treatments were continued. On the 9th day, anxiety levels were determined; gastric blood flow was measured, and blood, gastric and brain tissues were obtained. Induction of ulcers in sedentary rats increased anxiety and serum corticosterone levels; but reduced gastric blood flow and resulted in apoptosis and oxidative gastric damage with increased cytokine expressions. However, when ulcers were induced in pre-exercised rats, behavioural and biochemical alterations due to gastric damage were reversed. The inhibition of oxytocin receptors by atosiban exaggerated pro-inflammatory cytokine expressions and gastric lipid peroxidation in the stomachs of exercised rats with ulcers. When rats had regularly exercised prior to ulcer induction, reductions in the immunolabelling of hypothalamic oxytocin and myenteric oxytocin receptors were abolished, suggesting that exercise-induced alleviation of gastric injury may involve the reversal of down-regulated oxytocinergic activity.

Oxytocin may have a therapeutical potential against cardiovascular disease. Possible pharmaceutical and behavioral approaches

Based on the ancient role of oxytocin and its homologues as amplifiers of reproduction we argue for an evolutionary coupling of oxytocin to signaling pathway which support restorative mechanisms of cells and tissue. In particular, the survival and function of different categories of stem cells and primordial cells are enhanced by mitogen-activated protein kinase (MAPK) pathways. Furthermore, oxytocin stimulates the AMP-activated protein kinase pathway (AMPK) in numerous of cell types which promotes the maintenance of different cell structures. This involves autophagic processes and, in particular, may support the renewal of mitochondria. Mitochondrial fitness may protect against oxidative and inflammatory stress - a well-documented effect of oxytocin. The combined specific trophic and protective effects oxytocin may delay several degenerative phenomena including sarcopenia, type-2 diabetes and atherosclerosis. These effects may be exerted both on a central level supporting the function and integrity of the hypothalamus and peripherally acting directly on blood vessels, pancreas, heart, skeletal muscles and adipose tissue etc. Furthermore, in the capacity of being both a hormone and neuromodulator, oxytocin interacts with numerous of regulatory mechanisms particularly the autonomic nervous system and HPA-axis which may reduce blood pressure and affect the immune function. The potential of the oxytocin system as a behavioral and molecular target for the prevention and treatment of cardiovascular disease is discussed. Focus is put on the affiliative and sexual significance and the different options and limitations associated with a pharmaceutical approach. MeSH: Aging, Atherosclerosis, Heart, Hypothalamus, Inflammation, Love, Orgasm, Oxytocin.

Dietary Nitrate Protects Against Skin Flap Ischemia-Reperfusion Injury in Rats via Modulation of Antioxidative Action and Reduction of Inflammatory Responses

Dietary nitrate, found abundant in green vegetables, can be absorbed into the blood and be converted to nitric oxide (NO) in the body. Dietary nitrate has been proved to have many positive physiological functions in the body. Here, we evaluated the therapeutic effects of dietary nitrate on skin flap recovery following ischemia reperfusion (IR). Wistar rats were pretreated with nitrate from one week prior to ischemia to the end of reperfusion. It was found that oral administration of nitrate increased serum nitrate and nitrite levels, protected cells from apoptosis, and attenuated flap tissue edema. In the meantime, the oxidative stress marker malondialdehyde was reduced, while the activities of antioxidant enzymes were restored after nitrate treatment. Moreover, the macrophage and neutrophil infiltration in the flap was significantly attenuated by nitrate supplementation, as were the pro-inflammatory cytokines. In sum, we found that oral administration of nitrate can attenuate skin flap IR injury through the regulation of oxidative stress and inflammatory response.

The inflammatory event of birth: How oxytocin signaling may guide the development of the brain and gastrointestinal system

The role of oxytocin (OT) as a neuropeptide that modulates social behavior has been extensively studied and reviewed, but beyond these functions, OT's adaptive functions at birth are quite numerous, as OT coordinates many physiological processes in the mother and fetus to ensure a successful delivery. In this review we explore in detail the potential adaptive roles of oxytocin as an anti-inflammatory, protective molecule at birth for the developing fetal brain and gastrointestinal system based on evidence that birth is a potent inflammatory/immune event. We discuss data with relevance for a number of neurodevelopmental disorders, as well as the emerging role of the gut-brain axis for health and disease. Finally, we discuss the potential relevance of sex differences in OT signaling present at birth in the increased male vulnerability to neurodevelopmental disabilities.

Oxytocin system alleviates intestinal inflammation by regulating macrophages polarization in experimental colitis

Inflammatory bowel disease (IBD) is a chronic intestinal inflammation, but the accurate etiology remains to be elucidated. Increasing evidence has shown that macrophages polarize to different phenotypes depending on the intestinal microenvironment and are associated with the progression of IBD. In the present study, we investigated the effect of oxytocin, a neuroendocrinal, and pro-health peptide, on the modulation of macrophages polarization and the progression of experimental colitis. Our data demonstrated that oxytocin decreased the sensitivity of macrophages to lipopolysaccharide stimulation with lower expression of inflammatory cytokines, like IL-1β, IL-6, and TNF-α, but increased the sensitivity to IL-4 stimulation with enhanced expression of M2-type genes, arginase I (Arg1), CD206, and chitinase-like 3 (Chil3). This bidirectional modulation was partly due to the up-regulation of β-arrestin2 and resulted in the inhibition of NF-κB signaling and reinforcement of Signal transducer and activator of transcription (STAT) 6 phosphorylation. Moreover, oxytocin receptor (OXTR) myeloid deficiency mice were more susceptible to dextran sulfate sodium (DSS) intervention compared with the wild mice. For the first time, we reveal that oxytocin-oxytocin receptor system participates in modulating the polarization of macrophages to an anti-inflammatory phenotype and alleviates experimental colitis. These findings provide new potential insights into the pathogenesis and therapy of IBD.

Oxytocin alleviates cellular senescence through oxytocin receptor-mediated extracellular signal-regulated kinase/Nrf2 signalling

BACKGROUND

Oxytocin (OT) is a neuropeptide hormone that has many beneficial biological effects, including protection against age-related disorders. However, less is known about its role in intrinsic skin ageing, which is accelerated by an increase in senescent cell fraction in skin tissue.

OBJECTIVES

To investigate the novel function and the underlying mechanism of OT in preventing cellular senescence in normal human dermal fibroblasts (NHDFs) isolated from the skin of female donors of different ages.

METHODS

NHDFs from young and old donors were exposed to conditioned medium from senescent or control NHDFs in the presence or absence of 10 nmol L^-1 OT for 3 days, and were continuously subcultured for 12 days. Subsequently, various age-associated signs of senescence including decreased proliferation rate, elevated p16 and p21 levels, and positivity for senescence-associated β-galactosidase expression were examined.

RESULTS

We found that OT suppressed senescence-associated secretory phenotype-induced senescence in NHDFs, and its effect depended on the age of the donor's NHDFs. The inhibitory effects of OT required signalling by OT receptor-mediated extracellular signal-regulated kinase/Nrf2 (nuclear factor erythroid 2-related factor 2). The age-dependent antisenescence effects of OT are closely related to hypermethylation of the OT receptor gene (OXTR).

CONCLUSIONS

Our findings bring to light the role of OT in the prevention of skin ageing, which might allow development of new clinical strategies. What's already known about this topic? Senescent keratinocytes and fibroblasts accumulate with age in the skin and contribute to the loss of skin function and integrity during ageing. Senescent cells secrete senescence-associated secretory phenotype (SASP), which includes the release of proinflammatory cytokines such as interleukin (IL)-6 and IL-1, chemokines, extracellular matrix-remodelling proteases and growth factors. The neuropeptide oxytocin (OT) and its receptor (OXTR) have protective effects against various age-related disorders. What does this study add? OT suppressed SASP-induced cellular senescence in normal human dermal fibroblasts (NHDFs), depending on the age of the NHDFs' donor. The inhibitory effects of OT on cellular senescence required OXTR-mediated phosphorylation of extracellular signal-regulated kinase, which enhanced nuclear localization of Nrf2, a vital factor in the antioxidant defence system. The age-specific antisenescent effects of OT were closely related to hypermethylation of OXTR. What is the translational message? Our results suggest that OT and OXTR agonists could be clinically promising agents for the improvement of age-associated skin ageing, especially in women.

Effects of burns on gut motor and mucosa functions

This review analyzed the published studies on the effects of thermal injury on gastrointestinal motility and mucosal damage. Our strategy was to integrate all available evidence to provide a complete review on the prokinetic properties of variable reagents and the potential clinical treatment of mucosal damage and gastrointestinal dysmotility after thermal injury. We classified the studies into two major groups: studies on gastrointestinal dysmotility and studies on mucosal damage. We also subclassified the studies into 3 parts: stomach, small intestine, and colon. This review shows evidence that ghrelin can recover burn-induced delay in gastric emptying and small intestinal transit, and can protect the gastric mucosa from burn-induced injury. Oxytocin and β-glucan reduced the serum inflammatory mediators, and histological change and mucosal damage indicators, but did not show evidence of having the ability to recover gastrointestinal motility. Using a combination of different reagents to protect the gastrointestinal mucosa against damage and to recover gastrointestinal motility is an alternative treatment for thermal injury.

Chronic intermittent hypoxia induces hormonal and male sexual behavioral changes: Hypoxia as an advancer of aging

Sleep apnea is a common sleep disorder characterized by intermittent periods of low blood oxygen levels. The risk for sleep apnea increases with age and is more prevalent in men than women. A common comorbidity of sleep apnea includes male sexual dysfunction, but it is not clear if a causal relationship exists between sleep apnea and sexual dysfunction. Possible mechanisms that link these two disorders include oxidative stress and testosterone. Oxidative stress is elevated in clinical patients with sleep apnea and in rodents exposed to chronic intermittent hypoxia (CIH), an animal model for apnea-induced hypopnea. Further, oxidative stress levels increase with age. Therefore, age may play a role in sleep apnea-induced sexual dysfunction and oxidative stress generation. To investigate this relationship, we exposed gonadally intact 3 (young) and 12 (middle-aged) month old male F344/BN F1 hybrid male rats to 8 days of CIH, and then examined male sexual function. Plasma was used to assess circulating oxidative stress and hormone levels. Middle-aged male rats had lower testosterone levels with increased sexual dysfunction and oxidative stress, independent of CIH. However, CIH decreased testosterone levels and increased sexual dysfunction and oxidative stress only in young gonadally intact male rats, but not in gonadectomized young rats with physiological testosterone replacement. In sum, CIH had a greater impact on younger gonadally intact animals, with respect to sexual behaviors, testosterone, and oxidative stress. Our data indicate CIH mimics the effects of aging on male sexual behavior in young gonadally intact male rats.

Oxytocin effects on experimental skin wound healing

OBJECTIVE

Oxytocin (OXY) has significant effects on mammalian behavior. Next to its role in lactation and social interactions, it is described to support better wound healing as well. However, direct OXY effects on wound healing and the regeneration of the microvascular network are still not clarified. We therefore examined the effects of OXY and an OXY receptor antagonist [atosiban (ATO)] on skin wound healing, focusing on epithelialization and neovascularization.

METHODS

Skin wound healing has been assessed using intravital fluorescence microscopy in a model of full dermal thickness wounds in the dorsal skin fold chamber of hairless mice. Animals received repetitive low or high doses of OXY or ATO. Morphological and cellular characterization of skin tissue repair was performed by histology and in vitro cell assays.

RESULTS

The assessment of skin tissue repair using this therapy regimen showed that OXY and ATO had no major influence on epithelialization, neovascularization, wound cellularity, or inflammation. Moreover, OXY and ATO did neither stimulate nor deteriorate keratinocyte or fibroblast migration and proliferation.

CONCLUSION

In summary, this study is the first to demonstrate that OXY application does not impair skin wound healing or cell behavior. However, until now, the used transmitter system seems not to be clarified in detail, and it might be proposed that it is associated with the stress response of the organism to various stimuli.

Effects of Ankaferd BloodStopper on dermal healing in diabetic rats

BACKGROUND/AIM

Diabetes mellitus inhibits wound-induced angiogenesis, impairs the wound healing process, and leads to the development of chronic wounds. Ankaferd BloodStopper (ABS) is a new and promising local haemostatic agent. Although the mechanism of ABS-mediated haemostasis is well established, little is known about the associated histological and biochemical tissue reactions. The aim of this study was to evaluate the effects of this new-generation local haemostatic agent on short-term soft-tissue healing in streptozotocin (STZ)-treated rats.

MATERIALS AND METHODS

The 24 Wistar albino rats used in this study were divided into STZ-treated (STZ, n = 12) and nontreated groups (control, n = 12). Four days prior to surgery, rats in the STZ group were subcutaneously administered 60 mg/kg STZ intraperitoneally, while rats in the control group were administered 1 mL saline/kg. An incision was made in the dorsal dermal tissue of all rats, and either ABS or no haemostatic agent (NHAA) was applied to the wound before suturing. All of the rats were euthanised on postoperative day 4. Blood and skin samples were evaluated biochemically and histologically.

RESULTS

The results showed that STZ treatment impaired soft-tissue healing, assessed by measuring glutathione and lipid peroxidation levels. Moreover, while good histological results were obtained in the control group treated with ABS, there were fewer benefits in the STZ-treated group.

CONCLUSION

ABS's benefits in the control group seemed to lose their effectiveness under STZ medication.

Approaches Mediating Oxytocin Regulation of the Immune System

The hypothalamic neuroendocrine system is mainly composed of the neural structures regulating hormone secretion from the pituitary gland and has been considered as the higher regulatory center of the immune system. Recently, the hypothalamo-neurohypophysial system (HNS) emerged as an important component of neuroendocrine–immune network, wherein the oxytocin (OT)-secreting system (OSS) plays an essential role. The OSS, consisting of OT neurons in the supraoptic nucleus, paraventricular nucleus, their several accessory nuclei and associated structures, can integrate neural, endocrine, metabolic, and immune information and plays a pivotal role in the development and functions of the immune system. The OSS can promote the development of thymus and bone marrow, perform immune surveillance, strengthen immune defense, and maintain immune homeostasis. Correspondingly, OT can inhibit inflammation, exert antibiotic-like effect, promote wound healing and regeneration, and suppress stress-associated immune disorders. In this process, the OSS can release OT to act on immune system directly by activating OT receptors or through modulating activities of other hypothalamic–pituitary–immune axes and autonomic nervous system indirectly. However, our understandings of the role of the OSS in neuroendocrine regulation of immune system are largely incomplete, particularly its relationship with other hypothalamic–pituitary–immune axes and the vasopressin-secreting system that coexists with the OSS in the HNS. In addition, it remains unclear about the relationship between the OSS and peripherally produced OT in immune regulation, particularly intrathymic OT that is known to elicit central immunological self-tolerance of T-cells to hypophysial hormones. In this work, we provide a brief review of current knowledge of the features of OSS regulation of the immune system and of potential approaches that mediate OSS coordination of the activities of entire neuroendocrine–immune network.

Microbes and Oxytocin: Benefits for Host Physiology and Behavior

It is now understood that gut bacteria exert effects beyond the local boundaries of the gastrointestinal tract to include distant tissues and overall health. Prototype probiotic bacterium Lactobacillus reuteri has been found to upregulate hormone oxytocin and systemic immune responses to achieve a wide array of health benefits involving wound healing, mental health, metabolism, and myoskeletal maintenance. Together these display that the gut microbiome and host animal interact via immune-endocrine-brain signaling networks. Such findings provide novel therapeutic strategies to stimulate powerful homeostatic pathways and genetic programs, stemming from the coevolution of mammals and their microbiome.

Hydrogen peroxide-induced oxidative damage in peripheral blood lymphocytes from rats chronically treated with corticosterone: The protective effect of oxytocin treatment

Contemporary lifestyle is commonly associated with chronic stress, an environmental factor contributing to development of various psychological and somatic disorders. Increased levels of glucocorticoids, observed in the chronic stress, induce the production of reactive oxygen species leading to genotoxicity. The aim of this study was to investigate whether chronic administration of oxytocin (OXY) 10 IU/400 μL/day, s.c., for 14 days, a hormone presumed to exert antioxidant effect, may prevent DNA damage in the comet assay of peripheral blood lymphocytes of Wistar rats treated chronically with corticosterone (CORT) 100 mg/L ad libitum, per os, for 21 days, as well as, to influence some plasma oxidative stress parameters, i.e. levels of total lipid hydroperoxide (LOOH), and malondialdehyde (MDA), and the activity of antioxidative enzyme superoxide dismutase (SOD). Even though there was no reduction in overall number of damaged cells after oxytocin treatment only, the marked increase in total comet score (TCS) after incubation with H2O2 in CORT group compared to controls, was absent in the CORT + OXY experimental group. Furthermore, significant decrease of highly damaged cells compared to corticosterone group was noted. Chronic oxytocin administration thus protected lymphocytes from high intensity damage that leads to cellular death. In addition, treatment with OXY along with CORT, significantly decreased concentration of LOOH in plasma, and increased SOD compared to CORT treatment only. This finding corresponds well with current reports on beneficial effects of OXY in conditions of HPA axis hyperactivity, and supports the hypothesis of OXY-mediated antioxidant action.

Oxytocin-secreting system: A major part of the neuroendocrine center regulating immunologic activity

Interactions between the nervous system and immune system have been studied extensively. However, the mechanisms underlying the neural regulation of immune activity, particularly the neuroendocrine regulation of immunologic functions, remain elusive. In this review, we provide a comprehensive examination of current evidence on interactions between the immune system and hypothalamic oxytocin-secreting system. We highlight the fact that oxytocin may have significant effects in the body, beyond its classical functions in lactation and parturition. Similar to the hypothalamo-pituitary-adrenal axis, the oxytocin-secreting system closely interacts with classical immune system, integrating both neurochemical and immunologic signals in the central nervous system and in turn affects immunologic defense, homeostasis, and surveillance. Lastly, this review explores therapeutic potentials of oxytocin in treating immunologic disorders.

Oxytocin: recent developments

Oxytocin is a neurohypophyseal hormone that is produced centrally by neurons in the paraventricular nucleus and supraoptic nucleus of the hypothalamus. It is released directly into higher brain centres and into the peripheral circulation where it produces a multitude of effects. Classically, oxytocin is known for inducing uterine contractions at parturition and milk ejection during suckling. Oxytocin also acts in a species and gender specific manner as an important neuromodulator. It can affect behaviours associated with stress and anxiety, as well social behaviours including sexual and relationship behaviours, and maternal care. Additionally, oxytocin has been shown to have a variety of physiological roles in peripheral tissues, many of which appear to be modulated largely by locally produced oxytocin, dispelling the notion that oxytocin is a purely neurohypophyseal hormone. Oxytocin levels are altered in several diseases and the use of oxytocin or its antagonists have been identified as a possible clinical intervention in the treatment of mood disorders and pain conditions, some cancers, benign prostatic disease and osteoporosis. Indeed, oxytocin has already been successful in clinical trials to treat autism and schizophrenia. This review will report briefly on the known functions of oxytocin, it will discuss in depth the data from recent clinical trials and highlight future targets for oxytocinergic modulation.

Beneficial effects of hydrogen-rich saline on early burn-wound progression in rats

Introduction

Deep burn wounds undergo a dynamic process known as wound progression that results in a deepening and extension of the initial burn area. The zone of stasis is more likely to develop more severe during wound progression in the presence of hypoperfusion. Hydrogen has been reported to alleviate injury triggered by ischaemia/reperfusion and burns in various organs by selectively quenching oxygen free radicals. The aim of this study was to investigate the possible protective effects of hydrogen against early burn-wound progression.

Methods

Deep-burn models were established through contact with a boiled, rectangular, brass comb for 20 s. Fifty-six Sprague-Dawley rats were randomly divided into sham, burn plus saline, and burn plus hydrogen-rich saline (HS) groups with sacrifice and analysis at various time windows (6 h, 24 h, 48 h) post burn. Indexes of oxidative stress, apoptosis and autophagy were measured in each group. The zone of stasis was evaluated using immunofluorescence staining, ELISA, and Western blot to explore the underlying effects and mechanisms post burn.

Results

The burn-induced increase in malondialdehyde was markedly reduced with HS, while the activities of endogenous antioxidant enzymes were significantly increased. Moreover, HS treatment attenuated increases in apoptosis and autophagy postburn in wounds, according to the TUNEL staining results and the expression analysis of Bax, Bcl-2, caspase-3, Beclin-1 and Atg-5 proteins. Additionally, HS lowered the level of myeloperoxidase and expression of TNF-α, IL-1β, and IL-6 in the zone of stasis while augmenting IL-10. The elevated levels of Akt phosphorylation and NF-κB p65 expression post burn were also downregulated by HS management.

Conclusion

Hydrogen can attenuate early wound progression following deep burn injury. The beneficial effect of hydrogen was mediated by attenuating oxidative stress, which inhibited apoptosis and inflammation, and the Akt/NF-κB signalling pathway may be involved in regulating the release of inflammatory cytokines.

Oxytocin regulates gastrointestinal motility, inflammation, macromolecular permeability, and mucosal maintenance in mice

Enteric neurons express oxytocin (OT); moreover, enteric neurons and enterocytes express developmentally regulated OT receptors (OTRs). Although OT (with secretin) opposes intestinal inflammation, physiological roles played by enteric OT/OTR signaling have not previously been determined. We tested hypotheses that OT/OTR signaling contributes to enteric nervous system (ENS)-related gastrointestinal (GI) physiology. GI functions and OT effects were compared in OTR-knockout (OTRKO) and wild-type (WT) mice. Stool mass and water content were greater in OTRKO mice than in WT. GI transit time in OTRKO animals was faster than in WT; OT inhibited in vitro generation of ENS-dependent colonic migrating motor complexes in WT but not in OTRKO mice. Myenteric neurons were hyperplastic in OTRKO animals, and mucosal exposure to cholera toxin (CTX) in vitro activated Fos in more myenteric neurons in OTRKO than WT than in WT mice; OT inhibited the CTX response in WT but not in OTRKO mice. Villi and crypts were shorter in OTRKO than in WT mice, and transit-amplifying cell proliferation in OTRKO crypts was deficient. Macromolecular intestinal permeability in OTRKO was greater than WT mice, and experimental colitis was more severe in OTRKO mice; moreover, OT protected WT animals from colitis. Observations suggest that OT/OTR signaling acts as a brake on intestinal motility, decreases mucosal activation of enteric neurons, and promotes enteric neuronal development and/or survival. It also regulates proliferation of crypt cells and mucosal permeability; moreover OT/OTR signaling is protective against inflammation. Oxytocinergic signaling thus appears to play an important role in multiple GI functions that are subject to neuronal regulation.

Neonatal manipulation of oxytocin prevents lipopolysaccharide-induced decrease in gene expression of growth factors in two developmental stages of the female rat

Oxytocin production and secretion is important for early development of the brain. Long-term consequences of manipulation of oxytocin system might include changes in markers of brain plasticity - cytoskeletal proteins and neurotrophins. The aim of the present study was (1) to determine whether neonatal oxytocin administration affects gene expression of nestin, microtubule-associated protein-2 (MAP-2), brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the brain of two developmental stages of rat and (2) to evaluate whether neonatal oxytocin administration protects against lipopolysaccharide (LPS) induced inflammation. Neonatal oxytocin did not prevent a decrease of body weight in the LPS treated animals. Oxytocin significantly increased gene expression of BDNF in the right hippocampus in 21-day and 2-month old rats of both sexes. Gene expression of NGF and MAP-2 significantly increased in males treated with oxytocin. Both, growth factors and intermediate filament-nestin mRNA levels, were reduced in females exposed to LPS. Oxytocin treatment prevented a decrease in the gene expression of only growth factors. In conclusion, neonatal manipulation of oxytocin has developmental and sex-dependent effect on markers of brain plasticity. These results also indicate, that oxytocin may be protective against inflammation particularly in females.

Oxytocin ameliorates remote liver injury induced by renal ischemia-reperfusion in rats

Renal ischemia-reperfusion (IR) causes remote liver damage. Oxytocin has anti-inflammatory and antioxidant effects. The main purpose of this study was to evaluate the protective function of oxytocin (OT) in remote liver damage triggered by renal IR in rats. Twenty four rats were randomly divided into four different groups, each containing 8 rats. The groups were as follows: (1) Sham operated group; (2) Sham operated+OT group (3) Renal IR group; (4) Renal IR+OT group. OT (500µg/kg) was administered subcutaneously 12 and 24 hours before and immediately after ischemia. At the end of experimental procedure, the rats were sacrificed, and liver specimens were taken for histological assessment or determination of malondialdehyde (MDA), total oxidant status (TOS), total antioxidant status (TAS), paraoxonase (PON-1) activity and nitric oxide (NO). The results showed that renal IR injury constituted a notable elevation in MDA, TOS, Oxidative stress index (OSI) and significantly decreased TAS, PON-1 actvity and NO in liver tissue (p<0.05). Additionally renal IR provoked significant augmentation in hepatic microscopic damage scores. However, alterations in these biochemical and histopathological indices due to IR injury were attenuated by OT treatment (p<0.05). These findings show that OT ameliorates remote liver damage triggered by renal ischemia-reperfusion and this preservation involves suppression of inflammation and regulation of oxidant-antioxidant status.

Oxytocin does not attenuate the ex vivo production of inflammatory cytokines by lipopolysaccharide-activated monocytes and macrophages from healthy male and female donors

BACKGROUND

Oxytocin (OT) is a neuropeptide shown to attenuate inflammatory responses in both humans and animals, but the specific mechanism underlying these actions has not yet been identified. Preliminary research in humans suggests that monocytes (MOs) and macrophages (MPs) could be the target of anti-inflammatory actions of OT. Here, we present a series of ex vivo experiments in human MOs and MPs, testing whether OT attenuates the cytokine responses of these cells to a common bacterial product, lipopolysaccharide (LPS).

METHODS

MO experiments were conducted using blood samples taken from healthy volunteers after obtaining informed consent. MPs were purchased frozen from a cell supplier. All samples were cultured under standard conditions: for 6 h at 37°C in a 5% CO2 atmosphere. A number of variables were considered: volunteer sex, method of MO isolation, LPS concentration, OT concentration, preincubation with OT, cytokines measured, and method of cytokine measurement.

RESULTS

Regardless of the specific conditions, no attenuation of LPS-stimulated cytokine production by OT was observed in either MOs or MPs.

CONCLUSION

OT does not attenuate MO or MP inflammatory cytokine production following LPS stimulation. The previously observed anti-inflammatory properties of OT may be attributable to effects on other classes of immune cells or actions in other lymphoid compartments. Alternatively, the effects of OT on inflammation could be secondary to other neurohormonal changes it elicits.

Effect of oxytocin on neuroblastoma cell viability and growth

Oxytocin, released in response to different physiological stimuli, could play a key role in reducing stress reaction. It was suggested that it has protective effect against inflammation and consequences of oxidative stress. Mechanisms how oxytocin effects mediated in the brain tissue are unclear. In this study, oxytocin effect on cell growth and neuronal viability was examined. Human neuroblastoma (SH-SY5Y and SK-N-SH) and glioblastoma (U87MG) cells were exposed to different concentrations of oxytocin for 12-96 h. Potential protective effect of oxytocin treatment was investigated after exposing cells to oxidative stress using hydrogen peroxide (50 mM, 2 h) or 6-hydroxydopamine (25 μM, 24 h). Cell proliferation was measured by cell counting and cell viability was examined by MTT assay. Protein expression of selected neurotrophic factors was measured as an additional parameter. Oxytocin (1 μM) significantly increased cell number in all three cell types. Viability of SH-SY5Y cells was increased in the presence of oxytocin without significant effect of dose (0.01-1 μM). Cell death induced by hydrogen peroxide was not prevented by incubation with oxytocin. Oxytocin pretreatment blunted neurotoxin 6-OHDA reduction of cell viability in SH-SY5Y cells. Oxytocin (1 μM, 12 h) elevated amount of total proteins without increasing levels of brain-derived neurotrophic factor and neurotrophic growth factor. In conclusion, oxytocin increases growth and viability of neuroblastoma and glioblastoma cells without activation of neurotrophic factors. Oxytocin does not have protective effect in oxidative stress; however, it might be important for neuroprotection to dopaminergic neurons. Its proliferative effect might be important in native cell life, euplastic processes, and tumor progression.

Oxytocin is expressed in epidermal keratinocytes and released upon stimulation with adenosine 5'-[γ-thio]triphosphate in vitro

Oxytocin is a neuropeptide produced primarily in the hypothalamus and is best known for its roles in parturition and lactation. It also influences behaviour, memory and mental state. Recent studies have suggested a variety of roles for oxytocin in peripheral tissues, including skin. Here we show that oxytocin is expressed in human skin. Immunohistochemical studies showed that oxytocin and its carrier protein, neurophysin I, are predominantly localized in epidermis. RT-PCR confirmed the expression of oxytocin in both skin and cultured epidermal keratinocytes. We also show that oxytocin is released from keratinocytes after application of adenosine 5'-[γ-thio]triphosphate (ATPγS, a stable analogue of ATP) in a dose-dependent manner. The ATPγS-induced oxytocin release was inhibited by removal of extracellular calcium, or by the P2X receptor antagonist 2',3'-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate (TNP-ATP). These results suggest that oxytocin is produced in human epidermal keratinocytes and is released in response to calcium influx via P2X receptors.

Is preconditioning by oxytocin administration mediated by iNOS and/or mitochondrial K(ATP) channel activation in the in vivo anesthetized rabbit heart?

AIMS

Oxytocin (OXT) pretreatment protects the heart during ischemia-reperfusion injury by activating ATP-dependent potassium (K(ATP)) channels. The aim of the current study was to elucidate the roles of nitric oxide synthaseNOS and myocardial biochemistry in the cardioprotective effects of OXT and ischemic preconditioning (IPC).

MAIN METHODS

Male New Zealand White anesthetized rabbits (13 groups) were subjected to 30 min of occlusion of the left coronary artery and 120 min of reperfusion with or without IPC.

KEY FINDINGS

IPC (1 cycle), OXT (0.03 μg/kg, i.p.) or IPC + OXT yield significant infarct size reductions (21.8±1.5%, 20.5±1.2% and 19.4±1.4%, respectively, versus 38.9±3.5% in the S-CONT group; P<0.01) and antiarrhythmic effects, including VF (0%, 0% and 0%, versus 50% in S-CONT group; P<0.05) sustained VT (13%, 13% and 13%, versus 100% in S-CONT group; P<0.005) and other arrhythmias (25%, 13% and 25%, versus 100% in S-CONT group; P<0.005, P<0.01 and P<0.005, respectively). Atosiban (ATO, a selective OXT receptor antagonist), 5-HD and L-NAME (a nonspecific NOS inhibitor) abolished the beneficial effects of IPC and OXT, suggesting that the benefits are achieved via selective activation of OXT receptors, mitochondrial K(ATP) channels and NO. An iNOS inhibitor (1400 W) blocked the beneficial effects of IPC but not OXT. The IPC, OXT, IPC + OXT and 1400 W + OXT interventions significantly preserved ATP levels in the heart.

SIGNIFICANCE

This study demonstrates similarities between acute OXT pretreatment and IPC in terms of infarct size reduction, antiarrhythmic activity, and metabolic status.

Salubrious effects of oxytocin on social stress-induced deficits

Social relationships are a fundamental aspect of life, affecting social, psychological, physiological, and behavioral functions. While positive social interactions can attenuate stress and promote health, the social environment can also be a major source of stress when it includes social disruption, confrontation, isolation, or neglect. Social stress can impair the basal function and stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis, impairing function of multiple biological systems and posing a risk to mental and physical health. In contrast, social support can ameliorate stress-induced physiological and immunological deficits, reducing the risk of subsequent psychological distress and improving an individual's overall well-being. For better clinical treatment of these physiological and mental pathologies, it is necessary to understand the regulatory mechanisms of stress-induced pathologies as well as determine the underlying biological mechanisms that regulate social buffering of the stress system. A number of ethologically relevant animal models of social stress and species that form strong adult social bonds have been utilized to study the etiology, treatment, and prevention of stress-related disorders. While undoubtedly a number of biological pathways contribute to the social buffering of the stress response, the convergence of evidence denotes the regulatory effects of oxytocin in facilitating social bond-promoting behaviors and their effect on the stress response. Thus, oxytocin may be perceived as a common regulatory element of the social environment, stress response, and stress-induced risks on mental and physical health. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Lycopene inhibits caspase-3 activity and reduces oxidative organ damage in a rat model of thermal injury

Oxidative stress has been implicated in various pathological processes including burn induced multiple organ damage. This study investigated the effects of lycopene treatment against oxidative injury in rats with thermal trauma. Under ether anesthesia, shaved dorsum of the rats was exposed to 90°C bath for 10s to induce burn and treated either vehicle (olive oil) or lycopene (50mg/kg orally). Rats were decapitated 48 h after injury and the tissue samples from lung and kidney were taken for histological analysis and the determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO), superoxide dismutase (SOD), catalase (CAT) and caspase-3 activities. Proinflammatory cytokines, TNF-α and IL-1β, were assayed in blood samples. Severe skin scald injury caused a significant decrease in GSH levels, SOD and CAT activities, and significant increases in MDA levels, MPO and caspase-3 activities of tissues. Similarly, plasma TNF-α and IL-1β were elevated in the burn group as compared to the control group. Lycopene treatment reversed all these biochemical indices. According to the findings of the present study, lycopene possesses antiinflammatory, antiapoptotic and antioxidant effects that prevents burn-induced oxidative damage in remote organs.

Modeling social influences on human health

Social interactions have long-term physiological, psychological, and behavioral consequences. Social isolation is a well-recognized but little understood risk factor and prognostic marker of disease; it can have profoundly detrimental effects on both mental and physical well-being, particularly during states of compromised health. In contrast, the health benefits associated with social support (both reduced risk and improved recovery) are evident in a variety of illnesses and injury states; however, the mechanisms by which social interactions influence disease pathogenesis remain largely unidentified. The substantial health impact of the psychosocial environment can occur independently of traditional disease risk factors and is not accounted for solely by peer-encouraged development of health behaviors. Instead, social interactions are capable of altering shared pathophysiological mechanisms of multiple disease states in distinct measurable ways. Converging evidence from animal models of injury and disease recapitulates the physiological benefits of affiliative social interactions and establishes several endogenous mechanisms (inflammatory signals, glucocorticoids, and oxytocin) by which social interactions influence health outcomes. Taken together, both clinical and animal research are undoubtedly necessary to develop a complete mechanistic understanding of social influences on health.

Delayed gastric emptying and disruption of the interstitial cells of Cajal network after gastric ischaemia and reperfusion

BACKGROUND

Gastrointestinal tract is one of the most susceptible organ systems to ischaemia. Not only mucosal injury but also alterations of the intestinal motility and loss of interstitial cells of Cajal (ICC) have been reported in response to ischaemia and reperfusion (I/R). However, there are few reports on the changes in the gastric motility after gastric I/R. The present study was designed to investigate the alterations in gastric emptying, the ICC and enteric nerves that regulate smooth muscle function in response to gastric I/R.

METHODS

Seven-week-old male Wistar rats were exposed to gastric I/R, and the gastric emptying rates at 12 and 48 h after I/R were evaluated by the phenol red method. Expressions of gene product of c-kit receptor tyrosine kinase (c-Kit), a marker of ICC, and of neuronal proteins were also examined.

KEY RESULTS

Gastric emptying was transiently delayed at 12 h after I/R, but returned to normal by 48 h. Expression of c-Kit protein as assessed by Western blotting and immunofluorescent staining of the smooth muscle layer, as well as expression of the mRNA of stem cell factor, the ligand for c-Kit, were reduced at both 12 and 48 h after I/R. The expression of neuronal nitric oxide synthase (nNOS) protein as assessed by Western blotting and immunofluorescent staining was also decreased at 12 h after I/R, but was restored to normal by 48 h.

CONCLUSIONS & INFERENCES

Gastric I/R evokes transient gastroparesis with delayed gastric emptying, associated with disruption of the ICC network and nNOS-positive neurons.

Role of hydrogen sulfide in severe burn injury-induced inflammation in mice

Endogenous hydrogen sulfide (H(2)S) is naturally synthesized in many types of mammalian cells from L-cysteine in the reactions catalyzed by cystathionine-β-synthase and cystathionine-γ-lyase (CSE). H(2)S has been demonstrated to play a proinflammatory role in various animal models of hindpaw edema, acute pancreatitis, lipopolysaccharide-induced endotoxemia and cecal ligation, and puncture-induced sepsis. Full-thickness burns that exceed 25% of the total body surface area (TBSA) produce a profound systemic inflammatory reaction characterized by leukocyte activation and plasma leakage in the microvasculature of tissues and organs remote from the wound. The aim of this study was to investigate the effect of local burn injury on induced distant organ endogenous H(2)S release and expression of CSE. Male BALB/c mice were subjected to 30% TBSA full-thickness burn and treated with saline (administered intraperitoneally [i.p.]); DL-propargylglycine (PAG, 50 mg/kg i.p.), which is a CSE inhibitor; or sodium hydrosulfide (NaHS, 10 mg/kg i.p.), which is an H(2)S donor. PAG was administered either 1 h before or 1 h after the burn injury, whereas NaHS was given at the same time as the burn injury. Measurements of liver myeloperoxidase (MPO) activities, liver H(2)S-synthesizing activity, plasma H(2)S level and liver and lung CSE mRNA expression and histological examination of tissues were performed after burn injury. Burn injury significantly increased the plasma H(2)S level and liver H(2)S synthesis 8 h after burn compared with the sham group. Burn injury also resulted in a significant upregulation of CSE mRNA in liver and lung. Prophylactic as well as therapeutic administration of PAG significantly reduced burn-associated systemic inflammation, as evidenced by MPO activity and histological changes in liver and lung. Injection of NaHS significantly aggravated burn-associated systemic inflammation. Therefore, our findings show for the first time the role of H(2)S in contributing to inflammatory damage after burn injury.