Conceptual development of the immune system as a sixth sense

Neuroimmune interactions and their roles in neurodegenerative diseases

The nervous system possesses bidirectional, sophisticated and delicate communications with the immune system. These neuroimmune interactions play a vitally important role in the initiation and development of many disorders, especially neurodegenerative diseases. Although scientific advancements have made tremendous progress in this field during the last few years, neuroimmune communications are still far from being elucidated. By organizing recent research, in this review, we discuss the local and intersystem neuroimmune interactions and their roles in Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Unveiling these will help us gain a better understanding of the process of interplay inside the body and how the organism maintains homeostasis. It will also facilitate a view of the diseases from a holistic, pluralistic and interconnected perspective, thus providing a basis of developing novel and effective methods to diagnose, intervene and treat diseases.

Steroid Hormones as Modulators of Emotional Regulation in Male Urogenital Cancers

BACKGROUND

Tumors develop within an organism operating in a specific social and physical environment. Cortisol and dehydroepiandrosterone (DHEA), two of the most abundant steroid hormones in humans, are involved in both emotional regulation and the tumor progression. Several studies reported preclinical findings that DHEA can have preventive and therapeutic efficacy in treating major age-associated diseases, including cancer, although the mechanisms of action are not yet defined. The main aim of current study was to investigate the relationship between psychological and physiological emotional regulation and cancer development.

METHOD

This study assessed the quality of life of urogenital cancer male patients using several validated tools, including the Functional Assessment of Cancer Therapy-General and the Profile of Mood States. Saliva samples were collected to monitor peripheral activity of both cortisol and DHEA. It was hypothesized that patients with a better quality of life would have higher levels of the DHEA/cortisol ratios.

RESULTS

We found that the quality of life was positively related to DHEA, but not cortisol levels. Negative mood increases were related to lower levels of DHEA. Logistic regression of the predictors of metastases indicated three main independent factors involved: DHEA, age, and cortisol. In other words, the higher the DHEA levels in comparison to cortisol levels, controlling for age, the lower the probability of metastases.

CONCLUSION

Our results appear to support the hypothesis that emotional dysregulation mediated by DHEA/cortisol activity is a key factor in the probability of metastasis in urogenital cancers.

Unveiling the Link: Exploring Mitochondrial Dysfunction as a Probable Mechanism of Hepatic Damage in Post-Traumatic Stress Syndrome

PTSD is associated with disturbed hepatic morphology and metabolism. Neuronal mitochondrial dysfunction is considered a subcellular determinant of PTSD, but a link between hepatic mitochondrial dysfunction and hepatic damage in PTSD has not been demonstrated. Thus, the effects of experimental PTSD on the livers of high anxiety (HA) and low anxiety (LA) rats were compared, and mitochondrial determinants underlying the difference in their hepatic damage were investigated. Rats were exposed to predator stress for 10 days. Then, 14 days post-stress, the rats were evaluated with an elevated plus maze and assigned to HA and LA groups according to their anxiety index. Experimental PTSD caused dystrophic changes in hepatocytes of HA rats and hepatocellular damage evident by increased plasma ALT and AST activities. Mitochondrial dysfunction was evident as a predominance of small-size mitochondria in HA rats, which was positively correlated with anxiety index, activities of plasma transaminases, hepatic lipids, and negatively correlated with hepatic glycogen. In contrast, LA rats had a predominance of medium-sized mitochondria. Thus, we show links between mitochondrial dysfunction, hepatic damage, and heightened anxiety in PTSD rats. These results will provide a foundation for future research on the role of hepatic dysfunction in PTSD pathogenesis.

The brain is not mental! coupling neuronal and immune cellular processing in human organisms

Significant efforts have been made in the past decades to understand how mental and cognitive processes are underpinned by neural mechanisms in the brain. This paper argues that a promising way forward in understanding the nature of human cognition is to zoom out from the prevailing picture focusing on its neural basis. It considers instead how neurons work in tandem with other type of cells (e.g., immune) to subserve biological self-organization and adaptive behavior of the human organism as a whole. We focus specifically on the immune cellular processing as key actor in complementing neuronal processing in achieving successful self-organization and adaptation of the human body in an ever-changing environment. We overview theoretical work and empirical evidence on "basal cognition" challenging the idea that only the neuronal cells in the brain have the exclusive ability to "learn" or "cognize." The focus on cellular rather than neural, brain processing underscores the idea that flexible responses to fluctuations in the environment require a carefully crafted orchestration of multiple cellular and bodily systems at multiple organizational levels of the biological organism. Hence cognition can be seen as a multiscale web of dynamic information processing distributed across a vast array of complex cellular (e.g., neuronal, immune, and others) and network systems, operating across the entire body, and not just in the brain. Ultimately, this paper builds up toward the radical claim that cognition should not be confined to one system alone, namely, the neural system in the brain, no matter how sophisticated the latter notoriously is.

Injury, illness, and emotion: A review of the motivational continuum from trauma through recovery from an ecological perspective

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The converging paradigms of holism and complexity: An exploration of naturopathic clinical case management using complexity science principles

RATIONALE

Traditional whole systems of medicine, such as naturopathy, are founded upon holism; a philosophical paradigm consistent with contemporary complexity science. Naturopathic case management is predicated upon the understanding of an intimately interconnected internal physiological and external context of the human organism-potentially indicating a worldview aligned with a complexity perspective. In this study we investigate naturopathic clinical reasoning using a complexity lens with the aim of ascertaining the extent of correspondence between the two.

METHOD

Mind maps depicting case presentations were sought from Australian degree qualified naturopaths. A network mapping was undertaken, which was then analysed in accordance with a complexity science framework using exploratory data analysis and network analysis processes and tools.

RESULTS

Naturopathic case schematics, in the form of mind maps (n = 70), were collected, network mapped, and analysed. A total of 739 unique elements and 2724 links were identified across the network. Integral elements across the network were: stress, fatigue, general anxiety, systemic inflammation, gut dysbiosis, and diet. A modularity algorithm detected 11 communities, the primary ones of these representing the nervous system and mood; the gastrointestinal tract, liver, and nutrition; immune function and the immune system; and diet and nutrients.

CONCLUSIONS

Naturopathic case management is holistic and based on a perspective of an integrated physiology and external context of the human organism. The traditional concept of holism, when subjected to a complexity lens, leads to the emergence of a contemporary holistic paradigm cognisant of the human organism being a complex system. The application of complexity science to investigate naturopathic case management as employed in this study, demonstrates that it is possible to investigate traditional philosophies and principles in a scientific and critical manner. A complexity science research approach may offer a suitable scientific paradigm to develop our understanding of traditional whole systems of medicine.

Chronic Cancer Pain: Opioids within Tumor Microenvironment Affect Neuroinflammation, Tumor and Pain Evolution

Pain can be a devastating experience for cancer patients, resulting in decreased quality of life. In the last two decades, immunological and pain research have demonstrated that pain persistence is primarily caused by neuroinflammation leading to central sensitization with brain neuroplastic alterations and changes in pain responsiveness (hyperalgesia, and pain behavior). Cancer pain is markedly affected by the tumor microenvironment (TME), a complex ecosystem consisting of different cell types (cancer cells, endothelial and stromal cells, leukocytes, fibroblasts and neurons) that release soluble mediators triggering neuroinflammation. The TME cellular components express opioid receptors (i.e., MOR) that upon engagement by endogenous or exogenous opioids such as morphine, initiate signaling events leading to neuroinflammation. MOR engagement does not only affect pain features and quality, but also influences directly and/or indirectly tumor growth and metastasis. The opioid effects on chronic cancer pain are also clinically characterized by altered opioid responsiveness (tolerance and hyperalgesia), a hallmark of the problematic long-term treatment of non-cancer pain. The significant progress made in understanding the immune-mediated development of chronic pain suggests its exploitation for novel alternative immunotherapeutic approaches.

Embracing the Complexity of Primary Health Care: System-Based Tools and Strategies for Researching the Case Management Process

The provision of health care is frequently a complex process, and favourable clinical outcomes are dependent on the effective management of this complexity. Contemporary medicine and health care practices that are biomedically aligned have been informed by a reductionist paradigm, potentially creating a misalignment between health care and the human organism as a complex adaptive system. Complexity science is increasingly gaining momentum within the academic literature and is being employed across a wide range of scientific disciplines, although this is less evident in medicine. Limited evidence was found within the literature of a complexity science framework being used to explore and inform individual health care practices; in this paper, this gap will be explored through consideration of the use of strategies and tools (specifically mind maps, computer-generated network mappings, exploratory data analysis, and computer-derived network analysis) which are congruent with a complexity science framework. This information may be useful to researchers investigating health care provision and to clinicians wishing to incorporate a complexity sensibility within their practice.

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Integrated neuroimmune processing of threat, injury, and illness: An ecological framework mapping social alienation onto lifetime health vulnerability

Social alienation is a pre-eminent ecological threat for humans. In clinical and social care settings its impact is acknowledged in conditions as diverse as severe mood disturbance, chronic pain, and metabolic non-communicable diseases. An integrated psychoneuroimmune perspective shows how threat, injury, healing, and recovery follow through as a continuous process, but accepted cultural and clinical paradigms separating mental from physical illness provide little common ground on which to analyse and apply this continuum in practice. By reviewing the ecological relationships between emotional threat, tissue dyshomeostasis and injury, infection, pain, and mood this article explores not only how primeval somatic responses underpin the evolutionary foundations of depression and somatisation, but also links them to escalating physical non-communicable disease through archived socioeconomic adversity (allostatic load). Social alienation (in the absence of trauma) may prime and activate this ancient repertoire in which sensitised responses lay the foundation for persistent maladaptive states of aversive sensory misinterpretation, behavioural avoidance, anhedonia, and neuroinflammation presenting as widespread non-nociceptive pain, non-pain somatisation, and severe depression. The ecological perspective illuminates perverse clinical presentations, shows how some approaches to care may facilitate self-reinforcement in maladaptive syndromes, and offers pointers for inclusive rehabilitative clinical and social care.

A "Drug-Dependent" Immune System Can Compromise Protection against Infection: The Relationships between Psychostimulants and HIV

Psychostimulant use is a major comorbidity in people living with HIV, which was initially explained by them adopting risky behaviors that facilitate HIV transmission. However, the effects of drug use on the immune system might also influence this phenomenon. Psychostimulants act on peripheral immune cells even before they reach the central nervous system (CNS) and their effects on immunity are likely to influence HIV infection. Beyond their canonical activities, classic neurotransmitters and neuromodulators are expressed by peripheral immune cells (e.g., dopamine and enkephalins), which display immunomodulatory properties and could be influenced by psychostimulants. Immune receptors, like Toll-like receptors (TLRs) on microglia, are modulated by cocaine and amphetamine exposure. Since peripheral immunocytes also express TLRs, they may be similarly affected by psychostimulants. In this review, we will summarize how psychostimulants are currently thought to influence peripheral immunity, mainly focusing on catecholamines, enkephalins and TLR4, and shed light on how these drugs might affect HIV infection. We will try to shift from the classic CNS perspective and adopt a more holistic view, addressing the potential impact of psychostimulants on the peripheral immune system and how their systemic effects could influence HIV infection.

Chronic cancer and non-cancer pain and opioid-induced hyperalgesia share common mechanisms: neuroinflammation and central sensitization

Neuroinflammation, a peculiar form of inflammation that occurs in response to noxious stimuli in peripheral and central nervous system (CNS), consists in altered vascular permeability followed by leukocyte recruitment and activation in the inflamed tissue, release of inflammatory mediators including cytokines and chemokines, and finally in the activation of microglia and astrocytes in the spinal cord and CNS. This phenomenon mediates and even worsen the inflammatory pain in many painful states and is responsible for central sensitization leading to pain chronicity. We describe the major neuroinflammatory mechanisms shared by cancer and non-cancer pain. Particular attention is given to two different chronic inflammatory painful diseases such as the complex regional pain syndrome and the rheumatoid arthritis as prototypes of neuroinflammatory diseases (gliopathies). In addition, we describe the complexity of tumor microenvironment, their main cellular components (tumor cells, tumor infiltrating leukocytes and sensory neurons) and their reciprocal interactions that characterize different forms and intensity of cancer pain. We also hypothesize that one type of cancer pain, the breakthrough pain, can be attributable to receptor-mediated interaction of opioids with tumor cells and intratumoral leukocytes. Surprisingly, long-term opioid treatment shares the same neuroinflammatory potential responsible for the chronicity of both cancer and non-cancer pain; thus, resulting in paradoxical worsening rather than relieving pain. This paradox has upset the world of pain therapy, with neuroinflammation now being a main target of emerging therapies.

Environmental enrichment modulates inflammation during development in long-evans rats (Rattus norvegicus)

It is unknown whether increased production of pro-inflammatory mediators during the life span is caused by aging per se or via the combination of a cumulative allostatic load due to life challenges. This study aimed to investigate the long-term effects of stress and environmental enrichment on the inflammatory status associated with aging in rats. Animals were assigned to the following five treatment groups: chronic stress with and without environmental enrichment; acute stress with and without environmental enrichment; control animals. Enrichment was provided as an open field containing novel objects (30 min three times per week). Animals assigned to chronic stress groups were exposed to predator sound stressors (e.g., hawk sound) for 30 min daily, while animals assigned to acute stress groups were exposed once a week for 30 min. The interaction between the hypothalamic-pituitary-adrenal axis and the immune system was investigated by measuring metabolized dehydroepiandrosterone (DHEA) levels and peripheral levels of the cytokines IL-6 and IL-10. Results suggested that inflamm-aging was more pronounced in animals with low DHEA levels, which in turn were affected by exposure to environmental enrichment and acute stress. This study showed that environmental enrichment and acute stress can significantly attenuate disruptions in DHEA production, consequently contributing to improved neuroimmune function of aging animals.

The bitterness of genitourinary infections: Properties, ligands of genitourinary bitter taste receptors and mechanisms linking taste sensing to inflammatory processes in the genitourinary tract

BACKGROUND

Though, first identified in the gastrointestinal tract, bitter taste receptors are now believed to be ubiquitously expressed in several regions of the body, including the respiratory tract, where they play a critical role in sensing and clearance of excess metabolic substrates, toxins, debris, and pathogens. More recently, bitter taste receptor expression has been reported in cells, tissues and organs of the genitourinary (GU) system, suggesting that these receptors may play an integral role in mediating inflammatory responses to microbial aggression in the GU tract. However, the mechanisms, linking bitter taste receptor sensing with inflammatory responses are not exactly clear. Here, I review recent data on the properties and ligands of bitter taste receptors and suggest mechanisms of bitter taste receptor signaling in the GU tract, and the molecular pathways that link taste sensing to inflammatory responses in GU tract.

METHOD

Computer-aided search was conducted in Scopus, PubMed, Web of Science and Google Scholar for relevant peer-reviewed articles published between 1990 and 2018, investigating the functional implication of bitter taste receptors in GU infections, using the following keywords: extra-oral bitter taste receptors, bitter taste receptors, GU bitter taste receptors, kidney OR renal OR ureteral OR urethral OR bladder OR detrusor smooth muscle OR testes OR spermatozoa OR prostate OR vaginal OR cervix OR ovarian OR endometrial OR myometrial OR placenta OR cutaneous bitter taste receptors. To identify research gaps on etiopathogenesis of GU infections/inflammation, additional search was conducted using the following keywords: GU inflammatory signaling, GU microbes, GU bacteria, GU virus, GU protozoa, GU microbial metabolites, and GU infection. The retrieved articles were filtered and further screened for relevance according to the aim of the study. A narrative review was performed for selected literatures.

RESULTS

Bitter taste receptors of the GU tract may constitute essential components of the pathogenetic mechanisms of GU infections/inflammation that are activated by microbial components, known as quorum sensing signal molecules. Based on accumulating evidences, indicating that taste receptors may signal downstream to activate inflammatory cascades, in addition to the nitric oxide-induced microbicidal effects produced upon taste receptor activation, it is suggested that the anti-inflammatory activities of bitter taste receptor stimulation are mediated via pathways involving the nuclear factor κB by downstream signaling of the metabolic and stress sensors, adenosine monophosphate-activated protein kinase and nicotinamide adenine dinucleotide-dependent silent mating type information regulation 2 homolog 1 (sirtuin 1), resulting to the synthesis of anti-inflammatory cytokines/chemokines, and antimicrobial factors, which ultimately, under normal conditions, leads to the elimination of microbial aggression.

CONCLUSIONS

GU bitter taste receptors may represent critical players in GU tract infections/inflammation. Bitter taste receptors may serve as important therapeutic target for treatment of a number of infectious diseases that affect the GU tract.

Pavlovian Conditioning of Immunological and Neuroendocrine Functions

The phenomenon of behaviorally conditioned immunological and neuroendocrine functions has been investigated for the past 100 yr. The observation that associative learning processes can modify peripheral immune functions was first reported and investigated by Ivan Petrovic Pavlov and his co-workers. Their work later fell into oblivion, also because so little was known about the immune system’s function and even less about the underlying mechanisms of how learning, a central nervous system activity, could affect peripheral immune responses. With the employment of a taste-avoidance paradigm in rats, this phenomenon was rediscovered 45 yr ago as one of the most fascinating examples of the reciprocal functional interaction between behavior, the brain, and peripheral immune functions, and it established psychoneuroimmunology as a new research field. Relying on growing knowledge about efferent and afferent communication pathways between the brain, neuroendocrine system, primary and secondary immune organs, and immunocompetent cells, experimental animal studies demonstrate that cellular and humoral immune and neuroendocrine functions can be modulated via associative learning protocols. These (from the classical perspective) learned immune responses are clinically relevant, since they affect the development and progression of immune-related diseases and, more importantly, are also inducible in humans. The increased knowledge about the neuropsychological machinery steering learning and memory processes together with recent insight into the mechanisms mediating placebo responses provide fascinating perspectives to exploit these learned immune and neuroendocrine responses as supportive therapies, the aim being to reduce the amount of medication required, diminishing unwanted drug side effects while maximizing the therapeutic effect for the patient’s benefit.

Chronic Systemic Symptoms in Head and Neck Cancer Patients

The systemic effects and manifestations of disease and treatment have been of interest for millennium. Until recently, basic and clinical research is just now reaching a watershed. Systemic symptoms usually do not occur in isolation but rather in clusters; however, much of the cutting-edge research pertaining to the etiology, mechanism, manifestations, and moderators of systemic symptoms in humans has been directed at individual symptoms, thus creating silos of knowledge. Breaching these silos and bridging the knowledge from disparate arenas of investigation to build a comprehensive depiction of acute and chronic systemic symptoms has been a challenge. In addition, much of the recent work in systemic symptoms has been conducted in the setting of nonmalignant disease. The degree to which the findings from other chronic disease processes can be translated into the oncologic realm is unknown. This article will explore inflammation as a major contributing factor to systemic symptoms and sickness behavior, discuss the most common manifestations in cancer survivors, and, where available, discuss specific data pertaining to head and neck cancer survivors.

The Sleep-Immune Crosstalk in Health and Disease

Sleep and immunity are bidirectionally linked. Immune system activation alters sleep, and sleep in turn affects the innate and adaptive arm of our body's defense system. Stimulation of the immune system by microbial challenges triggers an inflammatory response, which, depending on its magnitude and time course, can induce an increase in sleep duration and intensity, but also a disruption of sleep. Enhancement of sleep during an infection is assumed to feedback to the immune system to promote host defense. Indeed, sleep affects various immune parameters, is associated with a reduced infection risk, and can improve infection outcome and vaccination responses. The induction of a hormonal constellation that supports immune functions is one likely mechanism underlying the immune-supporting effects of sleep. In the absence of an infectious challenge, sleep appears to promote inflammatory homeostasis through effects on several inflammatory mediators, such as cytokines. This notion is supported by findings that prolonged sleep deficiency (e.g., short sleep duration, sleep disturbance) can lead to chronic, systemic low-grade inflammation and is associated with various diseases that have an inflammatory component, like diabetes, atherosclerosis, and neurodegeneration. Here, we review available data on this regulatory sleep-immune crosstalk, point out methodological challenges, and suggest questions open for future research.

Taste receptors, innate immunity and longevity: the case of TAS2R16 gene

Background

Innate immunity utilizes components of sensory signal transduction such as bitter and sweet taste receptors. In fact, empirical evidence has shown bitter and sweet taste receptors to be an integral component of antimicrobial immune response in upper respiratory tract infections. Since an efficient immune response plays a key role in the attainment of longevity, it is not surprising that the rs978739 polymorphism of the bitter taste receptor TAS2R16 gene has been shown to be associated with longevity in a population of 941 individuals ranging in age from 20 to 106 years from Calabria (Italy). There are many possible candidate genes for human longevity, however of the many genes tested, only APOE and FOXO3 survived to association in replication studies. So, it is necessary to validate in other studies genes proposed to be associated with longevity. Thus, we analysed the association of the quoted polymorphism in a population of long lived individuals (LLIs) and controls from another Italian population from Cilento.

Methods

The analysis has been performed on data previously obtained with genome-wide association study on a population of LLIs (age range 90–109 years) and young controls (age range 18–45 years) from Cilento (Italy).

Results

Statistical power calculations showed that the analysed cohort represented by 410 LLIs and 553 young controls was sufficiently powered to replicate the association between rs978739 and the longevity phenotype according to the effect size and frequencies described in the previous paper, under a dominant and additive genetic model. However, no evidence of association between rs978739 and the longevity phenotype was observed according to the additive or dominant model.

Conclusion

There are several reasons for the failure of the confirmation of a previous study. However, the differences between the two studies in terms of environment of the population adopted and of the criteria of inclusion have made difficult the replication of the findings.

Immunomodulatory Effects of Stress and Environmental Enrichment in Long-Evans Rats (Rattus norvegicus)

Stress can influence the secretion of neuroendocrine mediators, thereby exposing immune cells to altered signaling and interactions. Here we investigated the synergetic effect of stress and environmental enrichment on the immune response of Long-Evans rats. Subjects (n = 46) were assigned to 5 treatment groups: acute compared with chronic stress with or without environmental enrichment, plus an unmanipulated control group. Animals also were classified as active, passive, and flexible copers according to back-test assessment. Rats were exposed to enrichment in an open-field containing objects in different areas for 30 min 3 times each week, thus modeling the effects of a temporary increase in environmental stimuli. Animals assigned to chronic stress groups were exposed to predator sound stressors for 30 min daily, whereas animals assigned to acute stress groups were exposed once each week. After 7 wk, a dermal punch biopsy was administered to activate the immune response, after which rats were challenged through a forced swim test. Biologic samples were collected to measure corticosterone, dehydroepiandrosterone (DHEA), oxytocin, testosterone, and the cytokines IL6 and IL10. Rats exposed to chronic stress had lower DHEA:corticosterone ratios, suggesting increased allostatic load. Enrichment exposure modulated these effects, lowering overall corticosterone and testosterone levels and increasing DHEA and oxytocin levels in animals exposed to the predator sound. The immune response was decreased in rats exposed to chronic stress, but the effect of environmental enrichment helped to mitigate the negative influence on cells producing IL6. Combining acute stress and exposure to an enriched environment returned a healthier profile in terms of both immune activation and stress regulation. By using a multidimensional scaling model, we found that a combination of 'good' stress and exposure to brief sessions of enriching stimuli can reliably predict health in Long-Evans rats.

Melatonin enhances responsiveness to Dichelobacter nodosus vaccine in sheep and increases peripheral blood CD4 T lymphocytes and IgG-expressing B lymphocytes

The immunomodulatory functions mediated by melatonin support its use as vaccine adjuvant. Previously, we have demonstrated that melatonin enhances antibody responses in sheep vaccinated against Dichelobacter nodosus. Here, we analyze the effect of melatonin on T and B lymphocyte subsets in peripheral blood of sheep vaccinated against D. nodosus. We also compare the use of melatonin in implants and in injections. Melatonin administration either as implants or by injection produced higher antibody titers against A1 and C serotypes compared to those animals that received only the vaccine. These results support the use of melatonin as an adjuvant in vaccination against D. nodosus. Firstly, melatonin induces higher antibody titer than the vaccine alone, secondly, melatonin increase IgG+ B lymphocytes and CD4+ T lymphocytes in vaccinated sheep. These results suggest that melatonin enhances T CD4 cell activation and subsequently secondary humoral immune responses. Further studies are required to determine the mechanism underlining the immunomodulatory role of melatonin in the context of vaccination.

Anesthetic Immunomodulation of the Neuroinflammation in Postoperative Cognitive Dysfunction

Postoperative delirium and cognitive dysfunction are phenomena that are associated with increases in morbidity, mortality, and resource utilization after surgery. This review scrutinized a number of studies in order to better characterize the biochemical basis for associated cognitive dysfunction and delirium, with particular focus paid to the interactions of the cholinergic system with innate immunity and how the modulation of the immune system contributes to associated neuroinflammation. Despite the clinical impact of postoperative cognitive dysfunction, evidence-based protocols for the prevention and treatment of these disorders are still lacking. Several previous trials have attempted to prevent or treat clinical manifestation by modulation of the cholinergic system with acetylcholinesterase inhibitors, the results of which have been largely ambiguous at best. As the biochemical basis of postoperative cognitive dysfunction becomes more clearly defined, future research into therapeutics based on immune modulation and treatment of neuroinflammation may prove to be very promising.

Activation of airway epithelial bitter taste receptors by Pseudomonas aeruginosa quinolones modulates calcium, cyclic-AMP, and nitric oxide signaling

Bitter taste receptors (taste family 2 bitter receptor proteins; T2Rs), discovered in many tissues outside the tongue, have recently become potential therapeutic targets. We have shown previously that airway epithelial cells express several T2Rs that activate innate immune responses that may be important for treatment of airway diseases such as chronic rhinosinusitis. It is imperative to more clearly understand what compounds activate airway T2Rs as well as their full range of functions. T2R isoforms in airway motile cilia (T2R4, -14, -16, and -38) produce bactericidal levels of nitric oxide (NO) that also increase ciliary beating, promoting clearance of mucus and trapped pathogens. Bacterial quorum-sensing acyl-homoserine lactones activate T2Rs and stimulate these responses in primary airway cells. Quinolones are another type of quorum-sensing molecule used by Pseudomonas aeruginosa To elucidate whether bacterial quinolones activate airway T2Rs, we analyzed calcium, cAMP, and NO dynamics using a combination of fluorescent indicator dyes and FRET-based protein biosensors. T2R-transfected HEK293T cells, several lung epithelial cell lines, and primary sinonasal cells grown and differentiated at the air-liquid interface were tested with 2-heptyl-3-hydroxy-4-quinolone (known as Pseudomonas quinolone signal; PQS), 2,4-dihydroxyquinolone, and 4-hydroxy-2-heptylquinolone (HHQ). In HEK293T cells, PQS activated T2R4, -16, and -38, whereas HHQ activated T2R14. 2,4-Dihydroxyquinolone had no effect. PQS and HHQ increased calcium and decreased both baseline and stimulated cAMP levels in cultured and primary airway cells. In primary cells, PQS and HHQ activated levels of NO synthesis previously shown to be bactericidal. This study suggests that airway T2R-mediated immune responses are activated by bacterial quinolones as well as acyl-homoserine lactones.

Immunity - a significant pathogenic factor as well as an integral part of the psychoneuroendocrine-immune regulations

Immunity plays an important role in the reactivity of the organism and, in this context, is an essential factor in the pathogenesis of many diseases. Basically, there is no system or organ in the body, whose dysfunction is not related to immunity consequences. In addition, there are also multisystem diseases simultaneously involving multiple body systems. They are not always caused by weak immunity, but also often by modified immune reactions known as overshooting. The essence of all these diseases is a change in the reactivity of the organism where immunity plays an important role. The immunity as such is then part of the systems of neuroendocrine-immune regulation, which have common mediators and receptors. The establishment of psychoneuroimmunology, a relatively new discipline in neuroscience, contributed to a detailed understanding of these mechanisms between central and peripheral nervous system, the endocrine system and the immune system. This research enabled the uncovering of the nature of stress-diseases and impact of other regulatory disturbances on the function of various body organs and systems of the organism as a whole. The aim of this short review is to show complex interconnections of these relationships to better understand the human health and disease.

Effects of prenatal alcohol exposure (PAE): insights into FASD using mouse models of PAE

The potential impact of prenatal alcohol exposure (PAE) varies considerably among exposed individuals, with some displaying serious alcohol-related effects and many others showing few or no overt signs of fetal alcohol spectrum disorder (FASD). In animal models, variables such as nutrition, genetic background, health, other drugs, and stress, as well as dosage, duration, and gestational timing of exposure to alcohol can all be controlled in a way that is not possible in a clinical situation. In this review we examine mouse models of PAE and focus on those with demonstrated craniofacial malformations, abnormal brain development, or behavioral phenotypes that may be considered FASD-like outcomes. Analysis of these data should provide a valuable tool for researchers wishing to choose the PAE model best suited to their research questions or to investigate established PAE models for FASD comorbidities. It should also allow recognition of patterns linking gestational timing, dosage, and duration of PAE, such as recognizing that binge alcohol exposure(s) during early gestation can lead to severe FASD outcomes. Identified patterns could be particularly insightful and lead to a better understanding of the molecular mechanisms underlying FASD.

Resident murine macrophage migration and phagocytosis are modulated by growth hormone

Growth hormone (GH) plays a physiological role in the immune system. In macrophages, GH enhances the production of hydrogen peroxide, superoxide anions, nitric oxide, cytokines, and chemokines, including interferon-γ and macrophage inflammatory protein-1α. However, some of the effects of GH stimulation on the biological functions of macrophages remain to be elucidated. Herein, we showed that in vivo GH treatment resulted in decreased expression of VLA-5 and VLA-6 integrins on the macrophage surface, accompanied by a reduction in macrophage adhesion to extracellular matrix (ECM) ligands, fibronectin, and laminin. Additionally, a decrease in macrophage adhesion to laminin was observed when the cells were treated in vitro with GH. In transwell migration assays, GH-treated macrophages showed increased migration after 6 h. Although in vitro GH treatment did not influence the phagocytic activity of macrophages, when the treatment was performed in vivo, peritoneal macrophages from GH-treated mice showed a higher percentage of phagocytosis and higher phagocytic capacity than cells from control animals. These results led us to analyse the role of insulin-like growth factor-1 (IGF-1), a GH stimulated factor, on macrophage phagocytosis. We observed an increase in phagocytic activity when J774 murine macrophages were treated with IGF-1 for 24 h. Our results revealed an important role for GH in resident macrophage migration and phagocytic activity. Specifically, we demonstrate that IGF-1 may be the GH stimulated factor that induces macrophage phagocytosis in vivo.

Space allowance influences individually housed Holstein bull calf innate immune measures and standing behaviors after castration at 3 weeks of age

Dairy calves in the Southwest regions of the United States are typically raised individually in wooden hutches with 1.23 m² of space. The objective of the study was to determine if increased space allowance in wooden hutches influences measures of innate immunity and behaviors of Holstein bull calves pre- and postcastration. Calves were randomly assigned at 4 d of age to conventional (CONV; 1.23 m² of space; n = 18), moderate (MOD; 1.85 m² space; n = 17), or maximized space allowance (MAX; 3.71 m² space; n = 19) in hutches. Calves were surgically castrated at 24 d of age. Peripheral whole blood samples were collected at -1, +1, +5, and +12 d of castration. Accelerometer loggers (n = 16 calves per treatment) were used from -3 to +5 d of castration to assess standing behaviors. All calves decreased total standing duration the day of castration versus precastration. Overall, MAX spent the most time in the stand position postcastration versus CONV and MOD. Within treatments, MOD and MAX had increased plasma cortisol 1 d postcastration versus precastration. A treatment × time tendency was observed for cortisol at 12 d postcastration; MAX had the least circulating cortisol. A treatment × time tendency for circulating haptoglobin (Hp) was observed and Hp was greatest among CONV 1 d pre- and 12 d postcastration. Compared with precastration, CONV had increased Hp at 1, 5, and 12 d, whereas MOD had increased Hp at 5 d, and Hp remained similar within MAX. A treatment × time tendency for tumor necrosis factor-α (TNF-α) from lipopolysaccharide-stimulated whole blood was observed; at 1 d postcastration, MOD had the most TNF-α, whereas MAX had the least. Within MAX, calves had increased TNF-α from precastration to 5 d postcastration. A treatment × time interaction was observed for whole blood bactericidal activity against Escherichia coli (WB anti-E). The CONV tended to have the greatest WB anti-E at d -1, but at d 1 and 5 postcastration, CONV had the least WB anti-E. Overall, MAX had less intensity of neutrophil oxidative burst versus CONV and MOD. The lower response of neutrophil oxidative burst and slower Hp secretion after castration is indicative that the wound site likely had less microbial exposure. The findings of this study suggest that calves housed with more space are potentially at less risk of too much inflammation after castration, which may likely be due to the effects of increased space on hide cleanliness and increased standing time.

Neuroendocrine-immune interaction: Evolutionarily conserved mechanisms that maintain allostasis in an ever-changing environment

It has now become accepted that the immune system and neuroendocrine system form an integrated part of our physiology. Immunological defense mechanisms act in concert with physiological processes like growth and reproduction, energy intake and metabolism, as well as neuronal development. Not only are psychological and environmental stressors communicated to the immune system, but also, vice versa, the immune response and adaptation to a current pathogen challenge are communicated to the entire body, including the brain, to evoke adaptive responses (e.g., fever, sickness behavior) that ensure allocation of energy to fight the pathogen. This phenomenon is evolutionarily conserved. Hence it is both interesting and important to consider the evolutionary history of this bi-directional neuroendocrine-immune communication to reveal phylogenetically ancient or relatively recently acquired mechanisms. Indeed, such considerations have already disclosed an extensive "common vocabulary" of information pathways as well as molecules and their receptors used by both the neuroendocrine and immune systems. This review focuses on the principal mechanisms of bi-directional communication and the evidence for evolutionary conservation of the important physiological pathways involved.

Skin Exposure to Ultraviolet B Rapidly Activates Systemic Neuroendocrine and Immunosuppressive Responses

The back skin of C57BL/6 mice was exposed to a single 400 mJ cm^-2 dose of ultraviolet B (UVB), and parameters of hypothalamic-pituitary-adrenal (HPA) axis in relation to immune activity were tested after 30-90 min following irradiation. Levels of brain and/or plasma corticotropin-releasing hormone (CRH), β-endorphin, ACTH and corticosterone (CORT) were enhanced by UVB. Hypophysectomy had no effect on UVB-induced increases of CORT. Mitogen-induced IFNγ production by splenocytes from UVB-treated mice was inhibited at 30, 90 min and after 24 h. UVB also led to inhibition of IL-10 production indicating an immunosuppressive effect on both Th1 and Th2 cytokines. Conditioned media from splenocytes isolated from UVB-treated animals had no effect on IFNγ production in cultured normal splenocytes; however, IFNγ increased with conditioned media from sham-irradiated animals. Sera from UVB-treated mice suppressed T-cell mitogen-induced IFNγ production as compared to sera from sham-treated mice. IFNγ production was inhibited in splenocytes isolated from UVB-treated animals with intact pituitary, while stimulated in splenocytes from UVB-treated hypophysectomized mice. Thus, cutaneous exposure to UVB rapidly stimulates systemic CRH, ACTH, β-endorphin and CORT production accompanied by rapid immunosuppressive effects in splenocytes that appear to be independent of the HPA axis.

New insights into upper airway innate immunity

BACKGROUND

Protecting the upper airway from microbial infection is an important function of the immune system. Proper detection of these pathogens is paramount for sinonasal epithelial cells to be able to prepare a defensive response. Toll-like receptors and, more recently, bitter taste receptors and sweet taste receptors have been implicated as sensors able to detect the presence of these pathogens and certain compounds that they secrete. Activation of these receptors also triggers innate immune responses to prevent or counteract infection, including mucociliary clearance and the production and secretion of antimicrobial compounds (e.g., defensins).

OBJECTIVE

To provide an overview of the current knowledge of the role of innate immunity in the upper airway, the mechanisms by which it is carried out, and its clinical relevance.

METHODS

A literature review of the existing knowledge of the role of innate immunity in the human sinonasal cavity was performed.

RESULTS

Clinical and basic science studies have shown that the physical epithelial cell barrier, mucociliary clearance, and antimicrobial compound secretion play pivotal innate immune roles in defending the sinonasal cavity from infection. Clinical findings have also linked dysfunction of these defense mechanisms with diseases, such as chronic rhinosinusitis and cystic fibrosis. Recent discoveries have elucidated the significance of bitter and sweet taste receptors in modulating immune responses in the upper airway.

CONCLUSION

Numerous innate immune mechanisms seem to work in a concerted fashion to keep the sinonasal cavity free of infection. Understanding sinonasal innate immune function and dysfunction in health and disease has important implications for patients with respiratory ailments, such as chronic rhinosinusitis and cystic fibrosis.

Expectancy Effect in Three Mind-Body Clinical Trials

Expectancy, arguably the prime component of the placebo effect, has been shown to significantly modify the effects of many treatments. Furthermore, various forms of mind-body interventions have demonstrated effective improvements in outcomes. The aim of this study was to examine the relationship between pretreatment expectations and symptom reduction in a secondary analysis of 3 mind-body intervention programs. An adjusted correlation and regression analysis compared data from a 6-question expectancy questionnaire to a self-reported clinical impression of change score. Only 1 of the 6 expectancy questions in 1 of the 3 studies reached significance (B = 0.087; P = .025). The combined data from all 3 studies did not reveal significant expectancy effects. The positive effects of mindfulness meditation appear to be independent of an expectancy effect.

Stress, immunity, and the management of calves

Despite many advances in management and housing of dairy calves, 1 in 10 US dairy heifers die before weaning. A better understanding of the internal and external stimuli that contribute to the physiological and behavioral responses of calves to stressors is needed to reduce the risk of morbidity and mortality. Feeding calves their first meal is crucial, as successful passive transfer reduces the risk of mortality and morbidity. Sexually dimorphic immune and stress responses appear to be present in young cattle, but more research is needed to determine if this is caused by human bias for female calves. After that first feeding, 1 in 10 heifers and most bull calves in the United States are transported to specialized calf-raising facilities, yet information is lacking on the newborn calf stress response during transit. Whether calves are raised on site or at a calf ranch, individual housing systems are commonly used in the United States to reduce the risk of pathogen exposure and provide individual feeding and healthcare. However, health, growth, and social implications may be present for calves in alternative systems with greater space allowance than conventional systems or group housing. Disbudding and castration are typically performed at an early age for dairy calves during the pre-wean stage. These stressors often take place when the calf has decreased passive transfer of Ig and immunity is developing. Availability of pain mitigation through anesthetics and analgesics is limited, but evidence indicates that analgesics attenuate suppressed leukocyte function during these procedures. Solid-feed intake is a primary measure for determining weaning readiness, but some milk replacer formulas may influence the calf's oral behaviors before weaning; therefore, alternate weaning methods may need to coincide with alternate milk replacer formulas. The calf's behavioral and stress response at weaning may influence its immunity during the transition from individual to group housing (commingling). Alternate commingling strategies and nutritional supplements may help with this transition, but more research is needed to explore feasible alternatives. Optimizing the calf's health and well-being at these early stages may improve its long-term health and welfare.

Has bioscience reconciled mind and body?

AIMS AND OBJECTIVES

The aim of this discursive paper is to explore the question 'has biological science reconciled mind and body?'.

BACKGROUND

This paper has been inspired by the recognition that bioscience has a historical reputation for privileging the body over the mind. The disregard for the mind (emotions and behaviour) cast bioscience within a 'mind-body problem' paradigm. It has also led to inherent limitations in its capacity to contribute to understanding the complex nature of health.

DESIGN

This is a discursive paper.

METHODS

Literature from the history and sociology of science and psychoneuroimmunology (1975-2015) inform the arguments in this paper. The historical and sociological literature provides the basis for a socio-cultural debate on mind-body considerations in science since the 1970s. The psychoneuroimmunology literature draws on mind-body bioscientific theory as a way to demonstrate how science is reconciling mind and body and advancing its understanding of the interconnections between emotions, behaviour and health.

RESULTS

Using sociological and biological evidence, this paper demonstrates how bioscience is embracing and advancing its understanding of mind-body interconnectedness. It does this by demonstrating the emotional and behavioural alterations that are caused by two common phenomena; prolonged, chronic peripheral inflammation and prolonged psychological stress. The evidence and arguments provided has global currency that advances understanding of the inter-relationship between emotions, behaviour and health.

CONCLUSIONS

This paper shows how bioscience has reconciled mind and body. In doing so, it has advanced an understanding of science's contribution to the inter-relationship between emotions, behaviour and health.

RELEVANCE TO CLINICAL PRACTICE

The biological evidence supporting mind-body science has relevance to clinical practice for nurses and other healthcare professions. This paper discusses how this evidence can inform and enhance clinical practice directly and through research, education and policy.

An Act of Balance Between Adaptive and Maladaptive Immunity in Depression: a Role for T Lymphocytes

Historically the monoaminergic neurotransmitter system, in particular the serotonergic system, was seen as being responsible for the pathophysiology of major depressive disorder (MDD). With the advent of psychoneuroimmunology an important role of the immune system in the interface between the central nervous systems (CNS) and peripheral organ systems has emerged. In addition to the well-characterised neurobiological activities of cytokines, T cell function in the context of depression has been neglected so far. In this review we will investigate the biological roles of T cells in depression. Originally it was thought that the adaptive immune arm including T lymphocytes was excluded from the CNS. It is now clear that peripheral naïve T cells not only carry out continuous surveillance within the brain but also maintain neural plasticity. Furthermore animal studies demonstrate that regulatory T lymphocytes can provide protection against maladaptive behavioural responses associated with depression. Psychogenic stress as a major inducer of depression can lead to transient trafficking of T lymphocytes into the brain stimulating the secretion of certain neurotrophic factors and cytokines. The separate and combined mechanism of CD4 and CD8 T cell activation is likely to determine the response pattern of CNS specific neurokines and neurotrophins. Under chronic stress-induced neuroinflammatory conditions associated with depression, T cell responses may become maladaptive and can be involved in neurodegeneration. Additionally, intracellular adhesion and MHC molecule expression as well as glucocorticoid receptor expression within the brain may play a role in determining T lymphocyte functionality in depression. Taken together, T lymphocyte mechanisms, which confer susceptibility or resilience to MDD, are not yet fully understood. Further insight into the cellular and molecular mechanisms which balance the adaptive and maladaptive roles of T lymphocytes may provide a better understanding of both the neuro- degenerative and -regenerative repair functions as present within the neuroimmune network during depression. Furthermore T cells may be important players in restoration of normal behaviour and immune cell homeostasis in depression.

Sinonasal solitary chemosensory cells "taste" the upper respiratory environment to regulate innate immunity

BACKGROUND

It is not fully understood how sinonasal epithelial cells detect the presence of pathogens and activate innate defense responses necessary for protecting the upper airway from infection. One mechanism is through bitter taste receptors (T2Rs), which are expressed in the sinonasal cavity. One T2R isoform, T2R38, is expressed in ciliated cells and detects quorum-sensing molecules from gram-negative bacteria, activating antimicrobial nitric oxide production. More recent studies have examined the role of T2Rs expressed in a sinonasal cell type that has only recently been identified in humans, the solitary chemosensory cell (SCC). We sought to provide an overview of SCCs and taste receptor function in human sinonasal defense as well as implications for chronic rhinosinusitis (CRS).

METHODS

A literature review of the current knowledge of SCCs and taste receptors in sinonasal physiology and CRS was conducted.

RESULTS

Human sinonasal SCCs express both bitter T2R and sweet T1R2/3 receptors. Activation of SCC T2Rs activates a calcium signal that propagates to the surrounding epithelial cells and causes secretion of antimicrobial peptides. T1R2/3 sweet receptor activation by physiological airway surface liquid (ASL) glucose concentrations attenuates the T2R response, likely as a mechanism to prevent full activation of the T2R pathway except during times of infection, when pathogens may consume ASL glucose and reduce its concentration.

CONCLUSION

SCCs appear to be important mediators of upper airway innate immunity, as the SCC T2Rs regulate antimicrobial peptide secretion, but further study is needed to determine the specific T2R isoforms involved as well as whether polymorphisms in these isoforms affect susceptibility to infection or patient outcomes in CRS. The inhibitory role of T1R2/3 sweet receptor suggests that T1R2/3 blockers may have therapeutic potential in some CRS patients, particularly those with diabetes mellitus. However, further clinical study of the relationship between infection and T1R2/3 genotype is required.

Taste receptors in innate immunity

Taste receptors were first identified on the tongue, where they initiate a signaling pathway that communicates information to the brain about the nutrient content or potential toxicity of ingested foods. However, recent research has shown that taste receptors are also expressed in a myriad of other tissues, from the airway and gastrointestinal epithelia to the pancreas and brain. The functions of many of these extraoral taste receptors remain unknown, but emerging evidence suggests that bitter and sweet taste receptors in the airway are important sentinels of innate immunity. This review discusses taste receptor signaling, focusing on the G-protein-coupled receptors that detect bitter, sweet, and savory tastes, followed by an overview of extraoral taste receptors and in-depth discussion of studies demonstrating the roles of taste receptors in airway innate immunity. Future research on extraoral taste receptors has significant potential for identification of novel immune mechanisms and insights into host-pathogen interactions.

Ocular Mucosal Immunity

Mucosal immunity defends the ocular surface against antigenic challenge and microbial invasion. The principal effector site is the lacrimal gland, where immunoglobulin A (IgA) antibodies are produced. Nasal-associated lymphoid tissue and posterior cervical lymph nodes function as major inductive sites for tear IgA responses. Neural connections and systemic hormones maintain the integrity and function of the ocular surface. Neuroenzyme activities in the lacrimal gland are influenced by ocular infections, leading to reduced expression of acetylcholine and modulation of receptors on acinar cells and on plasma cells, thereby decreasing fluid and immunoglobulin secretion. T lymphocyte-dependent responses result in production of interleukin-4 in lacrimal glands, thereby influencing cholinergic enzyme activity affecting immune processes and lacrimal physiology. Furthermore, neuropeptides released into lymphoid structures or inflamed tissues are chemotactic for antigen-presenting cells and affect their interactions with T cells. Thus, in developing therapeutic approaches for treating dry-eye conditions and vaccination strategies to elicit protective ocular mucosal immune responses, the entire lacrimal functional unit should be considered.

Maternal immune-mediated conditions, autism spectrum disorders, and developmental delay

The maternal immune system may play a role in offspring neurodevelopment. We examined whether maternal autoimmune disease, asthma, and allergy were associated with child autism spectrum disorder (ASD) and developmental delay without autism (DD) using 560 ASD cases, 391 typically developing controls, and 168 DD cases from the CHildhood Autism Risk from Genetics and the Environment (CHARGE) study. Results from conditional logistic regression demonstrated few significant associations overall. Maternal autoimmune disease was significantly associated with a modest increase in odds of developmental disorders (combined ASD + DD; OR = 1.46, 95% CI 1.01, 2.09) but not of ASD alone. Associations with certain allergens and onset periods were also suggested. These findings suggest maternal autoimmune disease may modestly influence childhood developmental disorders (ASD + DD).

Bitter and sweet taste receptors in the respiratory epithelium in health and disease

Taste receptors on the tongue communicate information to the brain about the nutrient content or potential toxicity of ingested foods. However, recent research has now shown that taste receptors are also expressed far beyond the tongue, from the airway and gastrointestinal epithelia to the pancreas and brain. The functions of many of these so-called extraoral taste receptors remain unknown, but emerging basic science and clinical evidence suggests that bitter and sweet taste receptors in the airway are important in sensing bacteria and regulating innate immunity. This review focuses on the role of bitter and sweet taste receptors in human airway innate immunity and the potential clinical relevance to airway infections. The T2R38 bitter taste receptor in sinonasal cilia detects bitter bacterial quorum-sensing molecules and activates nitric oxide-dependent innate immune responses. Polymorphisms that underlie T2R38 functionality also appear to be involved in susceptibility to upper respiratory infection and chronic rhinosinusitis (CRS). Bitter and sweet receptors in specialized sinonasal solitary chemosensory cells control antimicrobial peptide secretion, which may have important implications for airway infections in CRS patients as well as patients with diabetes mellitus. Future research on taste receptors in the airway has tremendous potential to identify immune mechanisms involved in host-pathogen interactions and thus reveal novel therapeutic targets.

Two faces of inflammation: an immunopharmacological view

Inflammation is a protective response intended to eliminate pathogens and other offending agents which have potential to cause cell injury, as well as malignant and necrotic cells. However, if the inflammatory response is dysregulated or inappropriately focused, it has considerable potential to cause harm and can lead to development of inflammatory diseases such as allergic and autoimmune diseases. Despite the recent success in cytokine-targeted therapies, for example by the use of specific biological drugs, there are still considerable unmet needs in the treatment of inflammatory diseases. Further, recent discoveries in many diseases in addition to the classical inflammatory diseases have revealed inflammation to be a major factor participating in the underlying pathophysiological processes, either through activation of inflammatory cells or through triggering of inflammatory signalling mechanisms in the tissue cells. Examples of such diseases and conditions are many cardiovascular, metabolic and degenerative diseases, as well as cancer, obesity and pain. This brings the immunopharmacological approach into a new perspective in the drug development in very wide therapeutic areas. Immunopharmacology investigates mechanisms of inflammation and potential molecules and targets to treat inflammatory diseases. The current issue of Basic and Clinical Pharmacology and Toxicology focuses on some of the novel inflammatory mechanisms with potential in anti-inflammatory drug development, including kinase pathways, TRP ion channels, eicosanoid system, obesity-related adipokines, autoantibodies against citrullinated proteins, eosinophils, platelets and pathways connecting nervous and immune systems. The MiniReviews are based on lectures given at the symposium "Novel Drugs and Drug Targets to Treat Inflammation" in Ylläs, Finland, in March 2013.

Learned Placebo Effects in the Immune System

Associative learning processes are one of the major neuropsychological mechanisms steering the placebo response in different physiological systems and end organ functions. Learned placebo effects on immune functions are based on the bidirectional communication between the central nervous system (CNS) and the peripheral immune system. Based on this “hardware,” experimental evidence in animals and humans showed that humoral and cellular immune functions can be affected by behavioral conditioning processes. We will first highlight and summarize data documenting the variety of experimental approaches conditioning protocols employed, affecting different immunological functions by associative learning. Taking a well-established paradigm employing a conditioned taste aversion model in rats with the immunosuppressive drug cyclosporine A (CsA) as an unconditioned stimulus (US) as an example, we will then summarize the efferent and afferent communication pathways as well as central processes activated during a learned immunosuppression. In addition, the potential clinical relevance of learned placebo effects on the outcome of immune-related diseases has been demonstrated in a number of different clinical conditions in rodents. More importantly, the learned immunosuppression is not restricted to experimental animals but can be also induced in humans. These data so far show that (i) behavioral conditioned immunosuppression is not limited to a single event but can be reproduced over time, (ii) immunosuppression cannot be induced by mere expectation, (iii) psychological and biological variables can be identified as predictors for this learned immunosuppression. Together with experimental approaches employing a placebo-controlled dose reduction these data provide a basis for new therapeutic approaches to the treatment of diseases where a suppression of immune functions is required via modulation of nervous system-immune system communication by learned placebo effects.

Learned placebo responses in neuroendocrine and immune functions

The phenomenon of learned placebo responses in neuroendocrine and immune functions is a fascinating example of communication between the brain and both the endocrine and peripheral immune systems. In this chapter, we will give a short overview of afferent and efferent communication pathways, as well as the central mechanisms, which steer the behavioral conditioned immune response. Subsequently, we will focus on data that provides evidence for learned immune responses in experimental animals and learned neuroendocrine and immune placebo responses in humans. Finally, we will take a critical look at these learning protocols, to determine whether or not they can be considered a viable additional treatment option to pharmacological regimens in clinical routine. This is fundamental, since there are still a number of issues, which need to be solved, such as the potential reproducibility, predictability, and extinction of the learned neuroendocrine and immune responses. Together, these findings not only provide an excellent basis to increase our understanding of human biology but may also have far reaching clinical implications. They pave the way for the ultimate aim of employing associative learning protocols as supportive treatment strategies in pharmacological regimens. As a result, medication levels may be reduced, as well as their unwanted side effects, providing a maximized therapeutic outcome to the benefit of the patient.

Key role of CRF in the skin stress response system

The discovery of corticotropin-releasing factor (CRF) or CRH defining the upper regulatory arm of the hypothalamic-pituitary-adrenal (HPA) axis, along with the identification of the corresponding receptors (CRFRs 1 and 2), represents a milestone in our understanding of central mechanisms regulating body and local homeostasis. We focused on the CRF-led signaling systems in the skin and offer a model for regulation of peripheral homeostasis based on the interaction of CRF and the structurally related urocortins with corresponding receptors and the resulting direct or indirect phenotypic effects that include regulation of epidermal barrier function, skin immune, pigmentary, adnexal, and dermal functions necessary to maintain local and systemic homeostasis. The regulatory modes of action include the classical CRF-led cutaneous equivalent of the central HPA axis, the expression and function of CRF and related peptides, and the stimulation of pro-opiomelanocortin peptides or cytokines. The key regulatory role is assigned to the CRFR-1α receptor, with other isoforms having modulatory effects. CRF can be released from sensory nerves and immune cells in response to emotional and environmental stressors. The expression sequence of peptides includes urocortin/CRF→pro-opiomelanocortin→ACTH, MSH, and β-endorphin. Expression of these peptides and of CRFR-1α is environmentally regulated, and their dysfunction can lead to skin and systemic diseases. Environmentally stressed skin can activate both the central and local HPA axis through either sensory nerves or humoral factors to turn on homeostatic responses counteracting cutaneous and systemic environmental damage. CRF and CRFR-1 may constitute novel targets through the use of specific agonists or antagonists, especially for therapy of skin diseases that worsen with stress, such as atopic dermatitis and psoriasis.

The neuro-immune axis: prospect for novel treatments for mental disorders

Disturbed bidirectional pathways between the (central) nervous system and immune system have been implicated in various mental disorders, including depressive and neurodevelopmental disorders. In this minireview, the role of the neuro-immune axis and its targetability in relation to major depression and autism spectrum disorder will be discussed. All together, the management of these and possibly other multi-factorial mental disorders needs a new and integrated therapeutic approach. Pharmacologically bioactive molecules as well as medical nutrition targeting the (gut)-immune-brain axis could be such an approach.