Impact of acute stress on itch sensation and scratching behaviour in patients with atopic dermatitis and healthy controls

The mind-skin connection: A narrative review exploring the link between inflammatory skin diseases and psychological stress

Inflammatory skin diseases are known to negatively impact patient psychology, with individuals experiencing higher rates of stress and subsequent diminished quality of life, as well as mental health issues including anxiety and depression. Moreover, increased psychological stress has been found to exacerbate existing inflammatory skin diseases. The association between inflammatory skin diseases and psychological stress is a timely topic, and a framework to better understand the relationship between the two that integrates available literature is needed. In this narrative review article, we discuss potential neurobiological mechanisms behind psychological stress due to inflammatory skin diseases, focusing mainly on proinflammatory cytokines in the circulating system (the brain-gut-skin communications) and the default mode network in the brain. We also discuss potential descending pathways from the brain that lead to aggravation of inflammatory skin diseases due to psychological stress, including the central and peripheral hypothalamic-pituitary-adrenal axes, peripheral nerves and the skin barrier function.

The skin-brain connection and pleasant touch as supportive care for psychocutaneous disorders

Psychodermatology is a subdiscipline of dermatology at the intersection of dermatology, psychiatry, and psychology. In dermatology clinical practice, patients may present with skin disease that affects their mental health, or skin disorders induced or worsened by psychological/psychiatric problems so there is a need for specialised education of dermatologists, as well as multidisciplinary teams, to achieve better management of these patients. Understanding the interaction between the central nervous system and the skin underlying psychocutaneous disorders could help identify alternative therapies that may improve patient well-being. The concept of pleasurable touch has received increasing attention following the discovery of C-tactile (CT) fibres. While afferent C-fibre stimulation is usually associated with pain, temperature, or itch, CT-fibres are stimulated optimally by a stimulus not in the nociceptor range but by a gentle, low-force stroking. As this affective touch may counteract unpleasurable sensations, such as pain and itch, and elicit positive feelings, the potential benefits of gentle touch and massage are interesting for dermatological, especially psychocutaneous, disorders. Here we provide an overview of the skin-brain connection to help understand the benefits of touch and massage, as illustrated with studies on atopic dermatitis and burns, as an adjunct to dermatological treatment for improving patient well-being and optimising treatment outcomes.

Integrating Osteopathic Principles for Enhanced Dermatological Outcomes: A Literature Review

This paper explores the impact of osteopathic medicine's principles and philosophy on dermatology conditions, focusing specifically on atopic dermatitis (AD), bullous pemphigoid (BP), and acne scars. The aim is to investigate how integrating osteopathic principles into dermatology can improve patient outcomes by addressing visible and internal health factors. The review was conducted through a literature search utilizing PubMed and Journal Storage. By focusing on the interconnectedness of mind, body, and spirit, osteopathic medicine could contribute to the effective treatment of AD. Stress management techniques have been found to significantly aid in the treatment of AD, as stress levels and social stress have a significant impact on the exacerbation of AD symptoms. Micro-needling is a promising treatment for atrophic acne scars, reducing scar severity scores by up to 68.3%. Combining micro-needling with trichloroacetic acid or non-ablative fractional laser technology further enhances treatment efficacy. The development of BP has been linked to alterations in the epidermis. Granzyme B has been identified as a contributing factor in dermal-epidermal junction separation and autoantibody formation, leading to BP. However, the specific link between osteopathic manipulation and Granzyme B levels in BP is not yet firmly established. Although osteopathic manipulation may impact the immune system and inflammation, further investigation is required to determine its precise effects on granzyme B and BP. Nonetheless, integrating osteopathic principles and philosophy into dermatology can improve patient outcomes by addressing visible and internal health factors. The benefits of such integration include improved patient-provider relationships, innovative treatments, better stress management, and individualized care plans. Practitioners should be educated on the significance of complete skin examinations for all patients, and future research should focus on exploring the benefits of osteopathic manipulation for dermatologic conditions. Further investigations into new dermatological treatment methods rooted in osteopathic principles are encouraged. The foundation of dermatology and osteopathic medicine share the importance of physical touch for diagnosis and treatment. An osteopathic approach to dermatology considers the link between cutaneous diseases and systemic health. This approach aligns with the four fundamental osteopathic beliefs: the body functions as a whole unit; a person is an integration of body, mind, and spirit that cannot be separated. The body can regulate itself, heal itself, and maintain its health. The body's structure and function are interdependent and work together. Rational treatment is based upon an understanding of the basic principles of body unity, self-regulation, and the interrelationship of structure and function.

Prevalence of autoimmune and inflammatory diseases and mental health conditions among an alopecia areata cohort from a US administrative claims database

Alopecia areata (AA) is associated with an increased burden of autoimmune and inflammatory disease and mental health conditions that may have a negative impact on quality of life. However, the exact burden of comorbidities on US patients with AA and the clinical subtypes alopecia totalis (AT) and alopecia universalis (AU) compared with those without AA is not well understood. This retrospective cohort study aimed to assess the incidence rates and prevalence of AA and its clinical subtypes and examine the autoimmune and inflammatory disease and mental health condition diagnosis burden in US patients with AA and a matched cohort without AA. The Optum Clinformatics Data Mart database was used to select patients aged ≥12 years enrolled between October 1, 2016, and September 30, 2020, who had two or more AA diagnosis codes for the AA cohort. Three patients without AA were age-, sex-, and race-matched to each patient with AA. Autoimmune and inflammatory diseases and mental health conditions were evaluated at baseline and up to 2 years after the index date. In total, 8784 patients with AA (599 with AT/AU) and 26 352 matched patients without AA were included. The incidence rate of AA was 17.5 per 100 000 person-years (PY; AT/AU: 1.1 per 100 000 PY; non-AT/AU: 16.3 per 100 000 PY), and the prevalence was 54.9 per 100 000 persons (AT/AU: 3.8; non-AT/AU: 51.2). Patients with AA had a higher prevalence of autoimmune and inflammatory diseases than the matched non-AA cohort, including allergic rhinitis (24.0% vs 14.5%), asthma (12.8% vs 8.8%), atopic dermatitis (8.3% vs 1.8%), and psoriasis (5.0% vs. 1.6%). The proportions of anxiety (30.7% vs 21.6%) and major depressive disorder (17.5% vs 14.0%) were higher in patients with AA than those without AA. Patients with AT/AU generally had a greater prevalence of autoimmune and inflammatory disease and mental health conditions than patients with non-AT/AU AA.

Psychopathology Associated with Chronic Pruritus: A Systematic Review

There are no previous studies of the psychopathology associated with different aetiologies of chronic pruritus. A systematic review was performed of cohort and case-control studies comparing healthy controls with patients with chronic pruritus related to primary dermatoses, systemic diseases, psychogenic pruritus, idiopathic pruritus, prurigo nodularis and/or lichen simplex chronicus. The review was registered in PROSPERO and performed according to the PRISMA statement, which allowed the inclusion of 26 studies. The quality of eligible studies was assessed using the modified Newcastle-Ottawa Scale. Most of the studies concern primary dermatoses and systemic diseases. Sleep disorders are a common comorbidity interrelated with pruritus, anxiety and depressive symptoms, in primary dermatoses. Sleep disorders are linked with pruritus and depressive symptoms in end-stage renal disease and hepatobiliary disease. Depressive and anxiety symptoms are associated with psychogenic pruritus. Psychogenic pruritus, lichen simplex chronicus and some primary dermatoses are linked with personality characteristics. Further studies are required to explore in depth the psychopathology linked with psychogenic pruritus and prurigo nodularis, as well as psychopathology linked with other primary dermatoses and systemic disorders associated with chronic pruritus, and to better differentiate psychogenic pruritus from psychopathological characteristics linked with other aetiologies of chronic pruritus, in order to improve the management of patients with chronic pruritus.

Effect of Sopoongsan on Skin Inflammation and Hyperlocomotion in Socially Isolated Mice with Atopic Dermatitis

Psychological stress is a major exacerbating factor of atopic dermatitis (AD), a chronic inflammatory skin disease. Sopoongsan (SPS), a traditional herbal formula, has been indicated for the treatment of various skin disorders, including AD. This study investigated the effects of SPS on a 2,4-dinitrochlorobenzene- (DNCB-) induced AD mice model exposed to social isolation (SI) stress. The severity of the AD symptoms and behavioral abnormalities was evaluated. SPS reduced the clinical skin score as evaluated with the SCORing Atopic Dermatitis (SCORAD) index and suppressed the cutaneous infiltration of T-lymphocyte cells, mast cells, and eosinophils in SI-AD mice. The SPS treatment decreased the total distance and mean speed and increased resting time in the open field test (OFT) for these mice. In addition, the time spent in the social zone in the social interaction test also improved when SPS treatment was given. The levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in the prefrontal cortex (PFC) in the SI-AD mice were reduced by the oral administration of SPS. HaCaT and BV2 cells were used for the in vitro experiments. The pretreatment with SPS reduced the protein levels of the thymus and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC) in the HaCaT cells stimulated with TNF-α and interferon-gamma (IFN-γ) (TI). SPS also suppressed TNF-α and IL-6 secretion in lipopolysaccharide- (LPS-) stimulated BV2 cells. These results imply that SPS could be a promising candidate for the treatment of AD in patients under stress conditions and at risk of exacerbation.

European guideline (EuroGuiDerm) on atopic eczema - part II: non-systemic treatments and treatment recommendations for special AE patient populations

The evidence- and consensus-based guideline on atopic eczema was developed in accordance with the EuroGuiDerm Guideline and Consensus Statement Development Manual. Four consensus conferences were held between December 2020 and July 2021. Twenty-nine experts (including clinicians and patient representatives) from 12 European countries participated. This second part of the guideline includes recommendations and detailed information on basic therapy with emollients and moisturizers, topical anti-inflammatory treatment, antimicrobial and antipruritic treatment and UV phototherapy. Furthermore, this part of the guideline covers techniques for avoiding provocation factors, as well as dietary interventions, immunotherapy, complementary medicine and educational interventions for patients with atopic eczema and deals with occupational and psychodermatological aspects of the disease. It also contains guidance on treatment for paediatric and adolescent patients and pregnant or breastfeeding women, as well as considerations for patients who want to have a child. A chapter on the patient perspective is also provided. The first part of the guideline, published separately, contains recommendations and guidance on systemic treatment with conventional immunosuppressive drugs, biologics and janus kinase (JAK) inhibitors, as well as information on the scope and purpose of the guideline, and a section on guideline methodology.

Biological and psychosocial factors associated with the persistence of pruritus symptoms: protocol for a prospective, exploratory observational study in Germany (individual project of the Interdisciplinary SOMACROSS Research Unit [RU 5211])

INTRODUCTION

Chronic pruritus (CP) is a symptom of dermatologic, neurologic, systemic and psychosomatic diseases. CP has a prevalence of ~20% in the general population and is therefore a significant burden on society, but the transition from acute pruritus to CP is not well understood. It probably involves interactions between biological and psychosocial factors and pruritus-specific risk factors as well as mechanisms shared with other persistent somatic symptoms addressed in other projects of the SOMACROSS Research Unit (RU). Here we aim to identify psychosocial and biological factors and their interactions which might be associated with the persistence of CP with and without immunologic/inflammatory origin, that is, atopic dermatitis and pruritus on non-inflamed skin. We expect that psychosocial factors relevant to the persistence of symptoms such as fatigue and pain may also show associations to CP.

METHODS AND ANALYSIS

In this prospective, exploratory observational study situated in Germany, three cohorts of 40 patients each with acute exacerbation of atopic dermatitis and chronic atopic dermatitis and 40 CP patients with unaffected skin will be recruited for a comprehensive translational investigation including pruritus-specific and the shared psychosocial assessments of the RU SOMACROSS. Pruritus-specific measures will include questionnaires, quantitative sensory testing, cutaneous nerve fibre morphology, skin barrier morphology, epidermal metabolism and pruritogen blood levels. Within 1 year, patients and 80 age-matched and sex-matched healthy controls will be examined at three time points, allowing cross-sectional comparison and a longitudinal investigation of predictive outcome factors in patients under treatment according to existing guidelines.

ETHICS AND DISSEMINATION

The study has been approved by the ethics committees of Hamburg (2020-10200-BO-ff) and Münster (2020-676 f-S), Germany. All participants are required to provide written informed consent. Findings will be disseminated through peer-reviewed publications, scientific conferences and involvement of relevant stakeholders, patients and the lay public.

TRIAL REGISTRATION NUMBER

DRKS00026646.

The Trinity of Skin: Skin Homeostasis as a Neuro–Endocrine–Immune Organ

For a long time, skin was thought to be no more than the barrier of our body. However, in the last few decades, studies into the idea of skin as an independent functional organ have gradually deepened our understanding of skin and its functions. In this review, we gathered evidence that presented skin as a “trinity” of neuro–endocrine–immune function. From a neuro perspective, skin communicates through nerves and receptors, releasing neurotrophins and neuropeptides; from an endocrine perspective, skin is able to receive and secrete most hormones and has the cutaneous equivalent of the hypothalamic-pituitary-adrenal (HPA) axis; from an immune perspective, skin is protected not only by its physical barrier, but also immune cells and molecules, which can also cause inflammation. Together as an organ, skin works bidirectionally by operating peripheral neuro–endocrine–immune function and being regulated by the central nervous system, endocrine system and immune system at the same time, maintaining homeostasis. Additionally, to further explain the “trinity” of cutaneous neuro–endocrine–immune function and how it works in disease pathophysiology, a disease model of rosacea is presented.

Moderate-to-severe atopic dermatitis and lifestyle factors in the Dutch general population

Background

Studies on the association between severity of atopic dermatitis (AD) and lifestyle factors in adults have not been conducted in the Netherlands to date.

Aim

To explore the association between moderate to severe AD and lifestyle factors in adults in the Dutch general population.

Methods

We conducted this cross‐sectional study within the Lifelines Cohort Study by sending a digital AD questionnaire to 135 950 adults in 2020. We extracted data on lifestyle factors from baseline, collected between 2006 and 2013. We analysed the association between lifestyle factors and presence of AD of any severity and of moderate to severe AD, using binary logistic regression and linear regression models.

Results

We enrolled 56 896 participants (mean age 55.8 years, 39.7% males). The lifetime prevalence of self‐reported physician‐diagnosed AD was 9.1%, and the point prevalence of any AD and of moderate to severe AD was 3.3% and 2.3%, respectively. We found that moderate to severe AD was associated with smoking habit of > 15 pack‐years, alcohol consumption of > 2 drinks per day, chronic stress, Class I obesity, and both shorter and longer sleep duration. Moreover, we found dose–response associations with increases in smoking pack‐years and level of chronic stress. We observed no associations with abdominal obesity, physical activity, diet quality or a vegetarian/vegan diet.

Conclusion

We found associations between moderate to severe AD and some modifiable lifestyle factors. Our findings indicate that more screening and counselling for lifestyle factors, particularly smoking, alcohol use, stress, obesity and sleep disturbances, appears warranted in patients with moderate to severe AD. Further longitudinal studies are required to better characterize the direction of these associations and to develop strategies for prevention.

An Open Trial on the Feasibility and Efficacy of a Mindfulness-Based Intervention with Psychoeducational Elements on Atopic Eczema and Chronic Itch

(1) Background: Mindfulness-based interventions (MBI) are psychological group interventions conducted over several weeks. Their effects on reducing stress and improving physical and psychological health have been proven in various clinical populations. Growing evidence suggests that MBIs might be beneficial for dermatology patients. This article reports on a novel Mindfulness-based Training for chronic Skin Conditions (MBTSC) with psychoeducational elements that was developed with the goal of improving self-regulation including stress management and emotion regulation in patients and to help in coping with disease symptoms such as itch and scratching. The intervention was tested in a pilot efficacy trial in order to examine feasibility and to collect preliminary data on the effectiveness of the intervention on disease severity including itch perception and on psychological distress in an atopic dermatitis (AD) sample. (2) Methods: Following an uncontrolled pre-test-post-test design based on standardized self-report measures, nine adult AD patients were recruited from a dermatology clinic. Data were collected at baseline, post-treatment and 3 month follow-up. Patients completed questionnaires assessing disease severity, itch perception, stress, anxiety and depression, mindfulness and intervention acceptability. The 7 week intervention included seven weekly sessions and a daily home-practice requirement, supported by guided audio-meditations and reading material. (3) Results: Quantitative data showed improvements in disease severity, itch perception and stress levels with small to medium effect sizes. Psychological distress increased at post-treatment—significantly in the case of depression. Qualitative data highlighted the mixed effects of MBTSC on symptoms. Treatment acceptability was high and 100% of the participants completed the intervention; (4) Conclusions: These data indicate that MBTSC is feasible and that it might be a useful tool as adjunct therapy for AD. Further studies with larger samples and control groups are needed.

Flare management in atopic dermatitis: from definition to treatment

Atopic dermatitis (AD) is a skin immune-mediated inflammatory disease with a chronic-recurrent course. Acute exacerbations or flares are an integral part of the AD course and are generally defined as disease worsening, requiring escalation/intensification of treatment. Management of flares is crucial since their prevention is a key aim of long-term disease control. Nevertheless, difficulties related to this aspect are several, starting from the definition of flare itself, which is not always satisfactory or unambiguous, and needs clarification. Indeed, this hurdle may reduce clarity on treatment choice and generate difficulties when comparing data between studies. Deepening our knowledge on flares could be highly relevant to both clinicians and patients to provide adequate control of the disease through patient education and appropriate treatment. This review aims to summarize current knowledge on the management of AD flares from definition to treatment, highlighting aspects that are still unclear, and identifying any necessary unmet needs to better manage AD.

Attentional Bias Modification Training for Itch: A Proof-of-Principle Study in Healthy Individuals

Itch draws our attention to allow imposing action against bodily harm (e.g., remove insects). At the same time, itch is found to interfere with ongoing tasks and daily life goals. Despite the key role of attention in itch processing, interventions that train individuals to automatically disengage attention from itch cues are lacking. The present proof-of-principle attention bias modification (ABM) training study was aimed at investigating whether attention to itch as well as sensitivity to mild itch can be changed. Healthy volunteers were randomized over three ABM-training conditions. Training was done via a modified pictorial dot-probe task. In particular, participants were trained to look away from itch stimuli (n = 38), toward itch stimuli (n = 40) or not trained toward or away from itch at all (sham training, n = 38). The effects of the ABM-training were tested primarily on attention to itch pictures. Secondarily, it was investigated whether training effects generalized to alterations in attention to itch words and mechanical itch sensitivity. The ABM-training did not alter attention toward the itch pictures, and there was no moderation by baseline levels of attention bias for itch. Also, attention bias to the itch words and itch sensitivity were not affected by the ABM-training. This study was a first step toward trainings to change attention toward itch. Further research is warranted to optimize ABM-training methodology, for example increasing motivation of participants. Eventually, an optimized training could be used in patient populations who suffer most from distraction by their symptoms of itch.

Clinical Trial Registration: Identifier: NL6134 (NTR6273). The website URL is: https://www.trialregister.nl/

Stress and Nasal Allergy: Corticotropin-Releasing Hormone Stimulates Mast Cell Degranulation and Proliferation in Human Nasal Mucosa

Psychological stress exacerbates mast cell (MC)-dependent inflammation, including nasal allergy, but the underlying mechanisms are not thoroughly understood. Because the key stress-mediating neurohormone, corticotropin-releasing hormone (CRH), induces human skin MC degranulation, we hypothesized that CRH may be a key player in stress-aggravated nasal allergy. In the current study, we probed this hypothesis in human nasal mucosa MCs (hM-MCs) in situ using nasal polyp organ culture and tested whether CRH is required for murine M-MC activation by perceived stress in vivo. CRH stimulation significantly increased the number of hM-MCs, stimulated both their degranulation and proliferation ex vivo, and increased stem cell factor (SCF) expression in human nasal mucosa epithelium. CRH also sensitized hM-MCs to further CRH stimulation and promoted a pro-inflammatory hM-MC phenotype. The CRH-induced increase in hM-MCs was mitigated by co-administration of CRH receptor type 1 (CRH-R1)-specific antagonist antalarmin, CRH-R1 small interfering RNA (siRNA), or SCF-neutralizing antibody. In vivo, restraint stress significantly increased the number and degranulation of murine M-MCs compared with sham-stressed mice. This effect was mitigated by intranasal antalarmin. Our data suggest that CRH is a major activator of hM-MC in nasal mucosa, in part via promoting SCF production, and that CRH-R1 antagonists such as antalarmin are promising candidate therapeutics for nasal mucosa neuroinflammation induced by perceived stress.

Electrically Evoked Itch in Human Subjects

Administration of chemicals (pruritogens) into the skin evokes itch based on signal transduction mechanisms that generate action potentials mainly in mechanically sensitive and insensitive primary afferent C-fibers (pruriceptors). These signals from peripheral neurons are processed in spinal and supra-spinal centers of the central nervous system and finally generate the sensation of itch. Compared to chemical stimulation, electrical activation of pruriceptors would allow for better temporal control and thereby a more direct functional assessment of their activation. Here, we review the electrical stimulation paradigms which were used to evoke itch in humans in the past. We further evaluate recent attempts to explore electrically induced itch in atopic dermatitis patients. Possible mechanisms underlying successful pruritus generation in chronic itch patients by transdermal slowly depolarizing electrical stimulation are discussed.

Direct evidence that the brain reward system is involved in the control of scratching behaviors induced by acute and chronic itch

In the present study, we demonstrated that there is a direct relationship between scratching behaviors induced by itch and functional changes in the brain reward system. Using a conditional place preference test, the rewarding effect was clearly evoked by scratching under both acute and chronic itch stimuli. The induction of ΔFosB, a member of the Fos family of transcription factors, was observed in dopamine transporter (DAT)-positive dopamine neurons in the ventral tegmental area (VTA) of mice suffering from a chronic itch sensation. Based on a cellular analysis of scratching-activated neurons, these neurons highly expressed tyrosine hydroxylase (TH) and DAT genes in the VTA. Furthermore, in an in vivo microdialysis study, the levels of extracellular dopamine in the nucleus accumbens (NAcc) were significantly increased by transient scratching behaviors. To specifically suppress the mesolimbic dopaminergic pathway using pharmacogenetics, we used the TH-cre/hM4Di mice. Pharmacogenetic suppression of mesolimbic dopaminergic neurons significantly decreased scratching behaviors. Under the itch condition with scratching behaviors restricted by an Elizabethan collar, the induction of ΔFosB was found mostly in corticotropin-releasing hormone (CRH)-containing neurons of the hypothalamic paraventricular nucleus (PVN). These findings suggest that repetitive abnormal scratching behaviors under acute and chronic itch stimuli may activate mesolimbic dopamine neurons along with pleasant emotions, while the restriction of such scratching behaviors may initially induce the activation of PVN-CRH neurons associated with stress.

Social and psychosocial effects on atopic eczema symptom severity - a scoping review of observational studies published from 1989 to 2019

Social and psychosocial factors are thought to have an effect on the course of atopic eczema. The aim of this scoping review was to search for and summarize observational studies that investigated the effects of (psycho-)social factors on symptoms in atopic eczema and to identify research gaps. We searched PubMed and PsycINFO for literature published between 1 January 1989 and 31 December 2019 using a systematic search strategy. We included observational studies that analysed the effect of (psycho-)social factors on symptom severity in atopic eczema patients. Reviews and non-observational studies, articles with research on animals, and articles with languages other than English or German were excluded. We identified 17 observational studies that met the inclusion criteria. Several studies found significant results for an exacerbating effect of stress on atopic eczema severity. Although coping and social support does not seem to moderate the effect of stress, coping strategies might mediate the impact that stress has on symptoms. Depression is associated with atopic eczema severity. The effect of depression as a consequence of atopic eczema severity is stronger than the effect as an exacerbating factor. Illness identity, anger, frustration and psychosomatic states have been found to affect atopic eczema symptoms. For attachment security, anxiety and social status, contradictory results were found. Statistically non-significant results were reported for personality, being in a partnership, satisfaction with the partnership, childhood experiences and body consciousness. Only the association between psychosocial stress and atopic eczema symptom severity seems robust. To date, other (psycho-)social factors, especially protective and health-promoting factors, were analysed only in a few studies, mostly with low sample sizes and cross-sectional design. Biopsychosocial interactions between stress, protective factors and the course of atopic eczema as well as the psycho-neuroimmunological mechanisms underlying those interactions are considered fields for future research contributions.

Social defeat stress exacerbates atopic dermatitis through downregulation of DNA methyltransferase 1 and upregulation of C-C motif chemokine receptor 7 in skin dendritic cells

DNA methylation is an epigenetic modification that regulates gene transcription. DNA methyltransferase 1 (DNMT1) plays an important role in DNA methylation. However, the involvement of DNMT1 and DNA methylation in the pathogenesis of atopic dermatitis (AD) remains unclear. In this study, microarray analysis revealed that peripheral blood mononuclear cells of AD patients with low DNMT1 expression (DNMT1-low) highly expressed dendritic cell (DC) activation-related genes. Also, DNMT1-low AD patients exhibited a higher itch score compared to AD patients with high DNMT1 expression (DNMT1-high). By using an AD-like mouse model induced by the application of Dermatophagoides farinae body ointment, we found that Dnmt1 expression was decreased, while the expression of C-C chemokine receptor type 7 (Ccr7) was upregulated in mouse skin DCs. Furthermore, mice exposed to social defeat stress exhibited Dnmt1 downregulation and Ccr7 upregulation in skin DCs. Additionally, dermatitis and itch-related scratching behavior were exacerbated in AD mice exposed to stress. The relationship between low DNMT1 and itch induction was found in both human AD patients and AD mice. In mouse bone marrow-derived DCs, Ccr7 expression was inhibited by 5-aza-2-deoxycytidine, a methylation inhibitor. Furthermore, in mouse skin DCs, methylation of CpG sites in Ccr7 was modified by either AD induction or social defeat stress. Collectively, these findings suggest that social defeat stress exacerbates AD pathology through Dnmt1 downregulation and Ccr7 upregulation in mouse skin DCs. The data also suggest a role of DNMT1 downregulation in the exacerbation of AD pathology.

Effects of Stress on Itch

PURPOSE

Psychological stress and ensuing modulation of the immune and nervous systems can have a significant impact on itch. Stress can exacerbate itch and vice versa, resulting in a vicious cycle that can greatly impair a patient's quality of life. This review summarizes the association between stress and itch, elucidates the mechanism by which these two phenomena influence one another, and explores treatment modalities that aim to reduce stress-induced itch.

METHODS

A complete search of the PubMed and Google Scholar databases was completed and literature pertinent to this review was compiled.

FINDINGS

Both acute and chronic stress can significantly affect itch in healthy individuals and in those diagnosed with itchy skin diseases as well as systemic diseases, thus resulting in a vicious cycle in which stress exacerbates itch and vice versa. The mechanisms by which stress induces or aggravates itch include both central and peripheral activation of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system. Activation of these systems, in turn, affects the mast cells, keratinocytes, and nerves that secrete neuropeptides, such as substance P, nerve growth factor, acetylcholine, histamine, and itchy cytokines. A dysfunctional parasympathetic response is thought to be involved in the chronic stress/itch response. Brain structures associated with emotion, such as the limbic system and periaqueductal gray, which work on the descending facilitation of itch, play a significant role in stress-induced itch.

IMPLICATIONS

As specific brain structures are associated with stress, drug treatments targeting these areas (ie, γ-aminobutyric acid-ergic drugs, serotonin and norepinephrine reuptake inhibitors) may help to modulate itch. Stress can also be combatted using nonpharmacologic treatments such as cognitive-behavioral therapies and stress-relieving holistic approaches (eg, yoga, acupuncture).

What is new in the psychology of chronic itch?

Itch is often regarded as unpleasant or bothersome and is accompanied by symptoms of distress and impairments in daily life. The biopsychosocial model of chronic itch describes how psychological factors can contribute to the improvement or exacerbation of chronic itch and related scratching behaviour. Recent research underlines the important role of cognitive-affective information processing, such as attention, affect and expectancies. This may not only play a role for acute itch states, but may particularly apply to the process of itch chronification, for example, due to the vicious cycle in which these factors shape the experience of itch. The present paper focuses on new insights into the relation between itch and the cognitive-affective factors of attention, affect and expectancies. These factors are thought to play a possible aggravating role in itch in the long term and have received increasing attention in the recent empirical literature on maintaining and exacerbating factors for chronic physical symptoms. Possible psychophysiological and neurobiological pathways regarding these factors are discussed, as well as possible intervention methods.

Gene-environment interactions in primary atopic disorders

Environmental factors modify disease presentation and severity in allergic disorders. Primary atopic disorders (PADs) are a heterogenous group of single gene disorders that lead to significant atopic and allergic disease manifestations. However, a number of these monogenic diseases have variable penetrance suggesting that gene-gene and/or gene-environment interactions could modulate the clinical phenotype. Environmental factors such as diet, the microbiome at the epithelial-environment interface, the presence and/or extent of infection, and psychologic stress can alter disease phenotypic expression of allergic diseases, and PADs provide discrete contexts in which to understand these influences. We outline how gene-environment interactions likely contribute to a variable penetrance and expressivity in PADs. Dietary modifications of both macronutrients and/or micronutrients alter T-cell metabolism and may influence effector T-cell function. The mucosal microbiome may affect local inflammation and may remotely influence regulatory elements, while psychologic stress can affect mast cell and other allergic effector cell function. Understanding gene-environment interactions in PADs can hopefully provide a foundation for interrogating gene-environment interactions to common allergic disorders, and also present opportunities for personalized interventions based on the altered pathways and environmental influences in affected individuals.

Why does stress aggravate itch? A possible role of the amygdala

Stress is the exacerbating factor of itch across patients with chronic itch due to different origins. However, the precise mechanisms behind stress-induced exacerbation of itch remain unknown. Chronic stress induces hyperexcitability of the amygdala, the centre of emotional processing. Recent findings on the itch neuronal pathways support a pivotal role of the amygdala for itch processing. We hypothesized that itch is enhanced by stress through hyperexcitation of the amygdala. Modulation of amygdala activity, therefore, may have therapeutic potential in the treatment of chronic itch.