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

The intertwining of oxytocin's effects on social affiliation and inflammation

•Oxytocin is an ancient adaptive hormone that promotes social affiliation to maximize fitness and longevity.•Oxytocin is a multifaceted hormone that regulates stress responses at all levels of cellular organization within individuals.•Oxytocin's dual actions on sociability and inflammation highlight its powerful capacity as a modulator of human health.

Severe PTSD is marked by reduced oxytocin and elevated vasopressin

Neuroendocrine analyses of posttraumatic stress disorder (PTSD) have generally focused on hypothalamic-pituitary-adrenal (HPA) axis alterations. In the present analyses, we examine two additional neuroendocrine factors that have been previously implicated in biological stress responses: oxytocin (OT) and arginine vasopressin (AVP). Here we examined basal neuropeptide status in military veterans clinically diagnosed with PTSD (n = 29) and in two non-traumatized comparison groups with previous stress exposure (n = 11 SWAT trainees and n = 21 ultramarathon runners). PTSD patients showed low levels of plasma OT and high levels of AVP. The ratio of AVP/OT robustly related to PTSD status, and emerged as a statistically plausible mediator of relationships between the number of personal traumatic experiences and subsequent PTSD symptom burden. Over the course of behavioral therapy for PTSD, measures of OT showed a significant but modest normalization. Plasma cortisol levels were not statistically different among the three groups. This study suggests that AVP/OT ratios may represent a neuroendocrine predictor of severe PTSD, as well as a potential treatment response biomarker.

Exploring the interplay between stress mediators and skin microbiota in shaping age-related hallmarks: A review

Psychological stress is a major contributing factor to several health problems (e.g., depression, cardiovascular disease). Around 35 % of the world's population suffers from it, including younger generations. Physiologically, stress manifests through neuroendocrine pathways (Hypothalamic-Pituitary-Adrenal (HPA) axis and Sympathetic-Adrenal-Medullary (SAM) system) which culminate in the production of stress mediators like cortisol, epinephrine and norepinephrine. Stress and its mediators have been associated to body aging, through molecular mechanisms such as telomere attrition, mitochondrial dysfunction, cellular senescence, chronic inflammation, and dysbiosis, among others. Regarding its impact in the skin, stress impacts its structural integrity and physiological function. Despite this review focusing on several hallmarks of aging, emphasis was placed on skin microbiota dysbiosis. In this line, several studies, comprising different age groups, demographic contexts and body sites, have reported skin microbiota alterations associated with aging, and some effects of stress mediators on skin microbiota have also been reviewed in this paper. From a different perspective, since it is not a "traditional" stress mediator, oxytocin, a cortisol antagonist, has been related to glucorticoids inhibition and to display positive effects on cellular aging. This hormone dysregulation has been associated to psychological issues such as depression, whereas its upregulation has been linked to positive social interaction.

History of Diversification and Adaptation from North to South Revealed by Genomic Data: Guanacos from the Desert to Sub-Antarctica

The increased availability of quality genomic data has greatly improved the scope and resolution of our understanding of the recent evolutionary history of wild species adapted to extreme environments and their susceptibility to anthropogenic impacts. The guanaco (Lama guanicoe), the largest wild ungulate in South America, is a good example. The guanaco is well adapted to a wide range of habitats, including the Sechura Desert, the high Andes Mountains to the north, and the extreme temperatures and conditions of Navarino Island to the south. Guanacos also have a long history of overexploitation by humans. To assess the evolutionary impact of these challenging habitats on the genomic diversity, we analyzed 38 genomes (∼10 to 16×) throughout their extensive latitudinal distribution from the Sechura and Atacama Desert to southward into Tierra del Fuego Island. These included analyses of patterns of unique differentiation in the north and geographic region further south with admixture among L. g. cacsilensis and L. g. guanicoe. Our findings provide new insights on the divergence of the subspecies ∼800,000 yr BP and document two divergent demographic trajectories and to the initial expansion of guanaco into the more southern portions of the Atacama Desert. Patagonian guanacos have experienced contemporary reductions in effective population sizes, likely the consequence of anthropogenic impacts. The lowest levels of genetic diversity corresponded to their northern and western limits of distribution and some varying degrees of genetic differentiation. Adaptive genomic diversity was strongly linked with environmental variables and was linked with colonization toward the south followed by adaptation.

The beneficial effects of social support and prosocial behavior on immunity and health: A psychoneuroimmunology perspective

The COVID-19 pandemic emphasized the pivotal role of the social environment, prompting a surge in research on its impact on well-being and health. This article aims to examine the link between the social environment, the immune system, and health outcomes, with a particular focus on positive aspects like social support and prosocial behaviors that are under-explored. Different aspects of the social environment are examined: the negative effects of loneliness and adverse social conditions, contrasted with the benefits of social support and prosocial behaviors. While the mechanisms behind negative effects are partially studied, those driving the positive effects remain elusive. Understanding the mechanisms of lack of social connection and their effects will allow us to explore the benefits of social connections and whether they can reverse the adverse outcomes. Potential psychoneuroimmunology mechanisms are proposed, highlighting the promotion of a 'safe' state by the vagus nerve, oxytocin circuits, and the additional contribution of the reward pathways. This article reviews the need to bridge knowledge gaps, urging further research to study the causal effects of positive social interactions on immune response and health outcomes to raise clinical awareness and interventions. Such interventions may include integrating lonely individuals with prosocial activities, thereby improving their physical and mental health. There is growing potential to harness the power of social connections for the betterment of individual health and society as a whole.

Effects of prenatal psychosocial stress and COVID-19 infection on infant attention and socioemotional development

BACKGROUND

The COVID-19 pandemic dramatically altered the psychosocial environment of pregnant women and new mothers. In addition, prenatal infection is a known risk factor for altered fetal development. Here we examine joint effects of maternal psychosocial stress and COVID-19 infection during pregnancy on infant attention at 6 months postpartum.

METHOD

One-hundred and sixty-seven pregnant mothers and infants (40% non-White; n = 71 females) were recruited in New York City (n = 50 COVID+, n = 117 COVID-). Infants' attentional processing was assessed at 6 months, and socioemotional function and neurodevelopmental risk were evaluated at 12 months.

RESULTS

Maternal psychosocial stress and COVID-19 infection during pregnancy jointly predicted infant attention at 6 months. In mothers reporting positive COVID-19 infection, higher prenatal psychosocial stress was associated with lower infant attention at 6 months. Exploratory analyses indicated that infant attention in turn predicted socioemotional function and neurodevelopmental risk at 12 months.

CONCLUSIONS

These data suggest that maternal psychosocial stress and COVID-19 infection during pregnancy may have joint effects on infant attention at 6 months. This work adds to a growing literature on the effects of the COVID-19 pandemic on infant development, and may point to maternal psychosocial stress as an important target for intervention.

IMPACT

This study found that elevated maternal psychosocial stress and COVID-19 infection during pregnancy jointly predicted lower infant attention scores at 6 months, which is a known marker of risk for neurodevelopmental disorder. In turn, infant attention predicted socioemotional function and risk for neurodevelopmental disorder at 12 months. These data suggest that maternal psychosocial stress may modulate the effects of gestational infection on neurodevelopment and highlight malleable targets for intervention.

The effect of a prosocial environment on health and well-being during the first COVID-19 lockdown and a year later

The outset of the COVID-19 pandemic was characterized by prolonged periods of chronic stress and social isolation. While studies have investigated the changes to well-being (WB) during this period, the impact of the social environment on long-term physical and mental health requires further study. This study aimed to assess the factors influencing WB and health outcomes, with the hypothesis that a positive social environment would play a significant immediate and long-term role in improving WB and preventing the effects of anxiety associated with the pandemic. At time point 1 (April 2020), an Israeli sample of 206 participants (84% female, mean age 31.5) responded to traditional questionnaires assessing mental health and social support. Factors affecting WB were assessed within subjects during the first COVID-19 lockdown for 6 weeks using a daily survey (Beiwe phone application). A year later, in May 2021, at time point 2, the initial questionnaires were readministered to a subset of the same participants (N = 94). We found that anxiety during the first lockdown adversely affected WB and predicted health and WB deterioration a year later. In contrast, a high quality of social relationships was associated with better short- and long-term WB, and mitigated the adverse effects of anxiety. Daily activities, including physical activity, meditation, and romantic relations, were also positively associated with WB during the first lockdown but did not have long-term effects. In summary, our study underscores the enduring health advantages of a positive social environment, particularly during stressful periods. These results have implications for health policymakers: programs which support individuals with high anxiety and low support, by integrating them into community-based interventions, promise to enhance well-being (WB) and health, as well as to fortify the community as a whole.

Oxytocin and the microbiome

The mammalian host microbiome affects many targets throughout the body, at least in part through an integrated gut-brain-immune axis and neuropeptide hormone oxytocin. It was discovered in animal models that microbial symbionts, such as Lactobacillus reuteri, leverage perinatal niches to promote multigenerational good health and reproductive fitness. While roles for oxytocin were once limited to women, such as giving birth and nurturing offspring, oxytocin is now also proposed to have important roles linking microbial symbionts with overall host fitness and survival throughout the evolutionary journey.

A long and winding road: My personal journey to oxytocin with no return

The present paper is the personal narration of the author reviewing her scientific pathways that led her toward the study of oxytocin. My work began with a pioneering study showing a decreased number of the serotonin transporter proteins in romantic lovers. This unexpected finding promoted my interest in the neurobiology of human emotions and feelings, and significantly shifted my research focus from diseases to physiological states that underlie "love." During this time increasing experimental data broadened the spectrum of activities of oxytocin from female functions, such as parturition and lactation, to modulation of the stress and immune system. The literature also began to reveal an important role for oxytocin in a sense of safety and wellbeing, processes that are critical to both love and survival. I suggest here that future studies should disentangle different emerging questions regarding the exact role of oxytocin within human nature, as well as its possible therapeutic applications in different physiological conditions and pathological states. Understanding these, in turn, holds the potential to improve the lives of both individuals and societies.

Brain trust

This narrative describes a personal journey that led to the discovery of a profound connection between microbial symbionts and oxytocin. Pivotal oxytocin discoveries began to emerge in 2011 while this researcher's multidisciplinary team explored gut microbial priming of the immune system and perinatal health. Inspired by oxytocin's role in early life events of milk release, neural connections, and social bonding, the team hypothesized a symbiotic relationship between microbes and oxytocin. Scientific experiments demonstrated that specific milk-borne microbes boosted oxytocin levels through a vagus nerve-mediated gut-brain pathway, affecting immune functions and wound healing capacity in the host animal. The exploration then expanded to microbial impacts on reproductive fitness, body weight, and even mental health. Overarching hypotheses envisioned a nurturing symbiosis promoting survival and societal advancement. Ultimately, this oxytocin-mediated partnership between microbes and mammals is portrayed as a harmonious legacy of neurological stability, empathy, and universal wisdom, transcending generations. The author's personal journey underscores the beauty and inspiration found in her scientific exploration.

Oxytocin: A developmental journey

The neuropeptide hormone oxytocin is involved in many processes in our bodies, linking our social lives to our internal states. I started out my career studying primate families, an interest that expanded into the role of oxytocin in family-oriented behaviors such as pair bonding and parenting in prairie voles, humans, and other primates. Starting as a post-doc with Dr. C. Sue Carter, I also became interested in the role of oxytocin during development and the way that we manipulate oxytocin clinically. During that post-doc and then as a faculty member at the University of California, Davis, I have worked on a number of these questions.

Close encounters with oxytocin

The purpose of this narrative review is to use a personal perspective to describe unanticipated and pivotal findings that drew the author into the study oxytocin. Oxytocin was originally described as a "female reproductive hormone." However, supporting reproduction is only one of a myriad of functions now attributed to oxytocin. Oxytocin promotes survival and resilience in both sexes and across the lifespan, especially in the context of stress or trauma and helps to explain the health benefits of relationships. Oxytocin works in the context of individual histories and in conjunction with other molecules, as well as the autonomic nervous system and immune factors. The chemical properties of oxytocin make it biologically active, but difficult to measure. As a deeper understanding of the biology of oxytocin is emerging, we may use knowledge of the properties of oxytocin to uncover adaptive strategies that protect and heal in the face of stress and adversity in both males and females.

Sex, love and oxytocin: Two metaphors and a molecule

Dozens of studies, most conducted in the last four decades, have implicated oxytocin, as well as vasopressin and their receptors, in processes that mediate selective sociality and the consequences of early experience. Oxytocin is critical for the capacity to experience emotional safety and healthy sexuality. Oxytocin also plays a central role in almost every aspect of physical and mental health, including the coordination of sociality and loving relationships with physiological reactions to challenges across the lifespan. Species, including prairie voles, that share with humans the capacity for selective social bonds have been a particularly rich source of insights into the behavioral importance of peptides. The purpose of this historical review is to describe the discovery of a central role for oxytocin in behavioral interactions associated with love, and in the capacity to use sociality to anticipate and cope with challenges across the lifespan - a process that here is called "sociostasis."