Psychological stress downregulates epidermal antimicrobial peptide expression and increases severity of cutaneous infections in mice

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

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

New Insights into the Role of PPARγ in Skin Physiopathology

Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor expressed in many tissues, including skin, where it is essential for maintaining skin barrier permeability, regulating cell proliferation/differentiation, and modulating antioxidant and inflammatory responses upon ligand binding. Therefore, PPARγ activation has important implications for skin homeostasis. Over the past 20 years, with increasing interest in the role of PPARs in skin physiopathology, considerable effort has been devoted to the development of PPARγ ligands as a therapeutic option for skin inflammatory disorders. In addition, PPARγ also regulates sebocyte differentiation and lipid production, making it a potential target for inflammatory sebaceous disorders such as acne. A large number of studies suggest that PPARγ also acts as a skin tumor suppressor in both melanoma and non-melanoma skin cancers, but its role in tumorigenesis remains controversial. In this review, we have summarized the current state of research into the role of PPARγ in skin health and disease and how this may provide a starting point for the development of more potent and selective PPARγ ligands with a low toxicity profile, thereby reducing unwanted side effects.

Correlation of non-invasive psycho-physiological and skin-physiological measures

INTRODUCTION

Psychological stress alters epidermal barrier function. While intensive studies on the underlying mechanism have been performed in mice, human studies are limited. Non-invasive skin-physiology measures have not yet been directly linked to non-invasive psycho-physiological assessments.

METHODS

Standard measures of (I) transepidermal water loss prior to and after experimental barrier perturbation via tape stripping, (II) skin surface pH, (III) electrodermal activity, and (IV) heart rate function were taken over a 24 h time period. To document perceived stress, a standardized stress self-assessment questionnaire, namely the Trierer Inventar zum chronischen Stress (TICS), was utilized.

RESULTS

Twenty healthy, Caucasian (Fitzpatrick skin phototype I-II), female volunteers (21-32 years, mean age 27, SD = 3.67 years) were included in this study (random sample). Significant correlations were shown for 24 h delta transepidermal water loss changes, that is, barrier repair kinetics (sympathetic activity) and heart rate variability (parasympathetic activity). Further correlations were noted for electrodermal activity and skin surface pH. Perceived stress, as documented by the TICS questionnaire, did not correlate with psycho- and skin physiological parameters, respectively.

CONCLUSION

The presented approaches may provide a basis for non-invasive objective research on the correlation between psychological stressors and epidermal barrier function.

Transcriptomic profiling of Rana [Lithobates] catesbeiana back skin during natural and thyroid hormone-induced metamorphosis under different temperature regimes with particular emphasis on innate immune system components

As amphibians undergo thyroid hormone (TH)-dependent metamorphosis from an aquatic tadpole to the terrestrial frog, their innate immune system must adapt to the new environment. Skin is a primary line of defense, yet this organ undergoes extensive remodelling during metamorphosis and how it responds to TH is poorly understood. Temperature modulation, which regulates metamorphic timing, is a unique way to uncover early TH-induced transcriptomic events. Metamorphosis of premetamorphic tadpoles is induced by exogenous TH administration at 24 °C but is paused at 5 °C. However, at 5 °C a "molecular memory" of TH exposure is retained that results in an accelerated metamorphosis upon shifting to 24 °C. We used RNA-sequencing to identify changes in Rana (Lithobates) catesbeiana back skin gene expression during natural and TH-induced metamorphosis. During natural metamorphosis, significant differential expression (DE) was observed in >6500 transcripts including classic TH-responsive transcripts (thrb and thibz), heat shock proteins, and innate immune system components: keratins, mucins, and antimicrobial peptides (AMPs). Premetamorphic tadpoles maintained at 5 °C showed 83 DE transcripts within 48 h after TH administration, including thibz which has previously been identified as a molecular memory component in other tissues. Over 3600 DE transcripts were detected in TH-treated tadpoles at 24 °C or when tadpoles held at 5 °C were shifted to 24 °C. Gene ontology (GO) terms related to transcription, RNA metabolic processes, and translation were enriched in both datasets and immune related GO terms were observed in the temperature-modulated experiment. Our findings have implications on survival as climate change affects amphibia worldwide.

Alterations in gene expression and microbiome composition upon calcium-sensing receptor deletion in the mouse esophagus

The calcium-sensing receptor (CaSR), a G protein-coupled receptor, regulates Ca2+ concentration in plasma by regulating parathyroid hormone secretion. In other tissues, it is reported to play roles in cellular differentiation and migration and in secretion and absorption. We reported previously that CaSR can be conditionally deleted in the mouse esophagus. This conditional knockout (KO) (EsoCaSR-/-) model showed a significant reduction in the levels of adherens and tight junction proteins and had a marked buildup of bacteria on the luminal esophageal surface. To further examine the role of CaSR, we used RNA sequencing to determine gene expression profiles in esophageal epithelia of control and EsoCaSR-/-mice RNA Seq data indicated upregulation of gene sets involved in DNA replication and cell cycle in EsoCaSR-/-. This is accompanied by the downregulation of gene sets involved in the innate immune response and protein homeostasis including peptide elongation and protein trafficking. Ingenuity pathway analysis (IPA) demonstrated that these genes are mapped to important biological networks including calcium and Ras homologus A (RhoA) signaling pathways. To further explore the bacterial buildup in EsoCaSR-/- esophageal tissue, 16S sequencing of the mucosal-associated bacterial microbiome was performed. Three bacterial species, g_Rodentibacter, s_Rodentibacter_unclassified, and s_Lactobacillus_hilgardi were significantly increased in EsoCaSR-/-. Furthermore, metagenomic analysis of 16S sequences indicated that pathways related to oxidative phosphorylation and metabolism were downregulated in EsoCaSR-/- tissues. These data demonstrate that CaSR impacts major pathways of cell proliferation, differentiation, cell cycle, and innate immune response in esophageal epithelium. The disruption of these pathways causes inflammation and significant modifications of the microbiome.NEW & NOTEWORTHY Calcium-sensing receptor (CaSR) plays a significant role in maintaining the barrier function of esophageal epithelium. Using RNA sequencing, we show that conditional deletion of CaSR from mouse esophagus causes upregulation of genes involved in DNA replication and cell cycle and downregulation of genes involved in the innate immune response, protein translation, and cellular protein synthesis. Pathway analysis shows disruption of signaling pathways of calcium and actin cytoskeleton. These changes caused inflammation and esophageal dysbiosis.

Competition between skin antimicrobial peptides and commensal bacteria in type 2 inflammation enables survival of S. aureus

During inflammation, the skin deploys antimicrobial peptides (AMPs) yet during allergic inflammation it becomes more susceptible to Staphylococcus aureus. To understand this contradiction, single-cell sequencing of Il4ra^-/- mice combined with skin microbiome analysis reveals that lower production of AMPs from interleukin-4 receptor α (IL-4Rα) activation selectively inhibits survival of antibiotic-producing strains of coagulase-negative Staphylococcus (CoNS). Diminished AMPs under conditions of T helper type 2 (Th2) inflammation enable expansion of CoNS strains without antibiotic activity and increase Staphylococcus aureus (S. aureus), recapitulating the microbiome on humans with atopic dermatitis. This response is rescued in Camp^-/- mice or after topical steroids, since further inhibition of AMPs enables survival of antibiotic-producing CoNS strains. In conditions of Th17 inflammation, a higher expression of host AMPs is sufficient to directly inhibit S. aureus survival. These results show that antimicrobials produced by the host and commensal bacteria each act to control S. aureus on the skin.

Alterations in epidermal function in type 2 diabetes: Implications for the management of this disease

Epidermal function is regulated by numerous exogenous and endogenous factors, including age, psychological stress, certain skin disorders, ultraviolet irradiation and pollution, and epidermal function itself can regulate cutaneous and extracutaneous functions. The biophysical properties of the stratum corneum reflect the status of both epidermal function and systemic conditions. Type 2 diabetes in both murine models and humans displays alterations in epidermal functions, including reduced levels of stratum corneum hydration and increased epidermal permeability as well as delayed permeability barrier recovery, which can all provoke and exacerbate cutaneous inflammation. Because inflammation plays a pathogenic role in type 2 diabetes, a therapy that improves epidermal functions could be an alternative approach to mitigating type 2 diabetes and its associated cutaneous disorders.

Regulatory Roles of Antimicrobial Peptides in the Nervous System: Implications for Neuronal Aging

Antimicrobial peptides (AMPs) are classically known as important effector molecules in innate immunity across all multicellular organisms. However, emerging evidence begins to suggest multifunctional properties of AMPs beyond their antimicrobial activity, surprisingly including their roles in regulating neuronal function, such as sleep and memory formation. Aging, which is fundamental to neurodegeneration in both physiological and disease conditions, interestingly affects the expression pattern of many AMPs in an infection-independent manner. While it remains unclear whether these are coincidental events, or a mechanistic relationship exists, previous studies have suggested a close link between AMPs and a few key proteins involved in neurodegenerative diseases. This review discusses recent literature and advances in understanding the crosstalk between AMPs and the nervous system at both molecular and functional levels, with the aim to explore how AMPs may relate to neuronal vulnerability in aging.

Oral 11β-HSD1 inhibitor AZD4017 improves wound healing and skin integrity in adults with type 2 diabetes mellitus: a pilot randomized controlled trial

BACKGROUND

Chronic wounds (e.g. diabetic foot ulcers) reduce the quality of life, yet treatments remain limited. Glucocorticoids (activated by the enzyme 11β-hydroxysteroid dehydrogenase type 1, 11β-HSD1) impair wound healing.

OBJECTIVES

Efficacy, safety, and feasibility of 11β-HSD1 inhibition for skin function and wound healing.

DESIGN

Investigator-initiated, double-blind, randomized, placebo-controlled, parallel-group phase 2b pilot trial.

METHODS

Single-center secondary care setting. Adults with type 2 diabetes mellitus without foot ulcers were administered 400 mg oral 11β-HSD1 inhibitor AZD4017 (n = 14) or placebo (n = 14) bi-daily for 35 days. Participants underwent 3-mm full-thickness punch skin biopsies at baseline and on day 28; wound healing was monitored after 2 and 7 days. Computer-generated 1:1 randomization was pharmacy-administered. Analysis was descriptive and focused on CI estimation. Of the 36 participants screened, 28 were randomized.

RESULTS

Exploratory proof-of-concept efficacy analysis suggested AZD4017 did not inhibit 24-h ex vivoskin 11β-HSD1 activity (primary outcome; difference in percentage conversion per 24 h 1.1% (90% CI: -3.4 to 5.5) but reduced systemic 11β-HSD1 activity by 87% (69-104%). Wound diameter was 34% (7-63%) smaller with AZD4017 at day 2, and 48% (12-85%) smaller after repeat wounding at day 30. AZD4017 improved epidermal integrity but modestly impaired barrier function. Minimal adverse events were comparable to placebo. Recruitment rate, retention, and data completeness were 2.9/month, 27/28, and 95.3%, respectively.

CONCLUSION

A phase 2 trial is feasible, and preliminary proof-of-concept data suggests AZD4017 warrants further investigation in conditions of delayed healing, for example in diabetic foot ulcers.

SIGNIFICANCE STATEMENT

Stress hormone activation by the enzyme 11β-HSD type 1 impairs skin function (e.g. integrity) and delays wound healing in animal models of diabetes, but effects in human skin were previously unknown. Skin function was evaluated in response to treatment with a 11β-HSD type 1 inhibitor (AZD4017), or placebo, in people with type 2 diabetes. Importantly, AZD4017 was safe and well tolerated. This first-in-human randomized, controlled, clinical trial found novel evidence that 11β-HSD type 1 regulates skin function in humans, including improved wound healing, epidermal integrity, and increased water loss. Results warrant further studies in conditions of impaired wound healing, for example, diabetic foot ulcers to evaluate 11β-HSD type 1 as a novel therapeutic target forchronic wounds.

Identification and validation a costimulatory molecule gene signature to predict the prognosis and immunotherapy response for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Costimulatory molecules have been proven to be the foundation of immunotherapy. However, the potential roles of costimulatory molecule genes (CMGs) in HCC remain unclear. Our study is aimed to develop a costimulatory molecule-related gene signature that could evaluate the prognosis of HCC patients.

METHODS

Based on The Cancer Gene Atlas (TCGA) database, univariate Cox regression analysis was applied in CMGs to identify prognosis-related CMGs. Consensus clustering analysis was performed to stratify HCC patients into different subtypes and compared them in OS. Subsequently, the LASSO Cox regression analysis was performed to construct the CMGs-related prognostic signature and Kaplan-Meier survival curves as well as ROC curve were used to validate the predictive capability. Then we explored the correlations of the risk signature with tumor-infiltrating immune cells, tumor mutation burden (TMB) and response to immunotherapy. The expression levels of prognosis-related CMGs were validated based on qRT-PCR and Human Protein Atlas (HPA) databases.

RESULTS

All HCC patients were classified into two clusters based on 11 CMGs with prognosis values and cluster 2 correlated with a poorer prognosis. Next, a prognostic signature of six CMGs was constructed, which was an independent risk factor for HCC patients. Patients with low-risk score were associated with better prognosis. The correlation analysis showed that the risk signature could predict the infiltration of immune cells and immune status of the immune microenvironment in HCC. The qRT-PCR and immunohistochemical results indicated six CMGs with differential expression in HCC tissues and normal tissues.

CONCLUSION

In conclusion, our CMGs-related risk signature could be used as a prediction tool in survival assessment and immunotherapy for HCC patients.

Skin senescence: mechanisms and impact on whole-body aging

The skin is the largest organ and has a key protective role. Similar to any other tissue, the skin is influenced not only by intrinsic/chronological aging, but also by extrinsic aging, triggered by environmental factors that contribute to accelerating the skin aging process. Aged skin shows structural, cellular, and molecular changes and accumulation of senescent cells. These senescent cells can induce or accelerate the age-related dysfunction of other nearby cells from the skin, or from different origins. However, the extent and underlying mechanisms remain unknown. In this opinion, we discuss the possible relevant role of skin senescence in the induction of aging phenotypes to other organs/tissues, contributing to whole-body aging. Moreover, we suggest that topical administration of senolytics/senotherapeutics could counteract the overall whole-body aging phenotype.

Host Defence Peptides in Diabetes Mellitus Type 2 Patients with Periodontal Disease. A Systematic Review

The aim of the study was to critically assess and review the latest evidence relating the associations between host defence peptides (HDPs), periodontal diseases (PD) and diabetes mellitus type 2 (DM2). To explore studies on HDPs, periodontal disease, and DM2, researchers utilised specific key phrases to search the electronic databases PubMed (National Library of Medicine), Embase (Ovid), Medline (EBSCO), and Dentistry and Oral Sciences (EBSCO). Quality assessment was conducted by means of the Newcastle Ottawa scale and the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool. Following a thorough screening process, a total of 12 papers (4 case-control, 6 cross-sectional, 1 animal, and 1 in vitro) fulfilled the selection criteria and were included. The majority of research found that HDPs were upregulated in DM2 patients with PD. Three investigations, however, found that HDPs were downregulated in DM2 patients with PD. HDPs play a part in the pathophysiology of PD and DM2. Nonetheless, more human, animal and laboratory investigations are needed to fully understand validation of the link, as the evidence is limited. Understanding HDPs as common moderators is critical, aimed at unlocking their potential as therapeutic and diagnostic agents.

The psychobiological links between chronic stress-related diseases, periodontal/peri-implant diseases, and wound healing

Chronic stress is a relevant disease to periodontal practice, encompassing 25%-28% of the US population (American Psychological Association 2015). While it is well established that chronic psychologic stress can have significant deleterious systemic effects, only in recent decades have we begun to explore the biochemical, microbial, and physiologic impacts of chronic stress diseases on oral tissues. Currently, chronic stress is classified as a "risk indicator" for periodontal disease. However, as the evidence in this field matures with additional clinically controlled trials, more homogeneous data collection methods, and a better grasp of the biologic underpinnings of stress-mediated dysbiosis, emerging evidence suggests that chronic stress and related diseases (depression, anxiety) may be significant contributing factors in periodontal/peri-implant disease progression and inconsistent wound healing following periodontal-related therapeutics. Ideal solutions for these patients include classification of the disease process and de-escalation of chronic stress conditions through coping strategies. This paper also summarizes periodontal/implant-related therapeutic approaches to ensure predictable results for this specific patient subpopulation.

Mechanisms for control of skin immune function by the microbiome

The skin represents the largest area for direct contact between microbes and host immunocytes and is a site for constant communication between the host and this diverse and essential microbial community. Coagulase-negative staphylococci are an abundant bacterial genus on the human skin and are regulated through various mechanisms that include the epidermal barrier environment and innate and adaptive immune systems within the epidermis and dermis. In turn, some species and strains of these bacteria produce beneficial products that augment host immunity by exerting specifically targeted antimicrobial, anti-inflammatory, or anti-neoplastic activity while also promoting broad innate and adaptive immune responses. The use of selected skin commensals as a therapeutic has shown promise in recent human clinical trials. This emerging concept of bacteriotherapy is defining mechanisms of action and validating the dependence on the microbiome for maintenance of immune homeostasis.

A Lipid Mixture Enriched by Ceramide NP with Fatty Acids of Diverse Chain Lengths Contributes to Restore the Skin Barrier Function Impaired by Topical Corticosteroid

INTRODUCTION

The stratum corneum (SC) is a skin barrier that consists of corneocytes, intercellular lipids, and corneodesmosomes. Ceramides are composed of sphingoid bases linked with various types of fatty acids (FAs), and they are an essential constituent of SC intercellular lipids. Among their subtypes, ceramide NP with a phytosphingosine base is especially important. Most of the previous studies on barrier recovery have focused on a specific ceramide with a single chain FA, not with diverse chain lengths. Skin barrier function is impaired by various factors, including topical corticosteroid.

OBJECTIVE

We evaluated whether a lipid mixture enriched by ceramide NP with FAs of diverse chain lengths (CER [NP]*) can restore the skin barrier function impaired by topical corticosteroid.

METHODS

Twenty-seven healthy adult male volunteers were recruited. Topical corticosteroid was applied on both volar forearms of volunteers. Then, the test cream containing a lipid mixture with CER (NP)* was applied on the left forearm, and a vehicle cream without a lipid mixture was applied on the right forearm of each subject. The functional parameters of the skin barrier were compared before and after the treatment. Epidermal differentiation markers, hyaluronic acid synthase 3 (HAS3), cytokine levels, and the lipid profiles in the SC were analyzed.

RESULTS

The functional parameters of the skin barrier, such as barrier recovery rate, SC integrity, and SC hydration were significantly improved in the test cream-applied site compared to the vehicle cream-applied sites. Filaggrin and HAS3 levels were significantly higher in the sites applied with the test cream. Interleukin (IL)-1α levels were also significantly increased in these sites. IL-2, IL-6, IL-10, and IL-13 levels were significantly decreased in the test cream-applied sites. Lipid analyses showed that C18, C20, and total ceramide NP levels significantly increased in the sites where the test cream was applied. Also, C16, C18, C20, C24, and total ceramide NP levels were significantly elevated in the test cream-applied sites after acute barrier disruption.

CONCLUSION

Our results demonstrate that a lipid mixture enriched by CER (NP)* could recover the barrier function impaired by topical corticosteroid.

The significance of CYP11A1 expression in skin physiology and pathology

CYP11A1, a member of the cytochrome P450 family, plays several key roles in the human body. It catalyzes the first and rate-limiting step in steroidogenesis, converting cholesterol to pregnenolone. Aside from the classical steroidogenic tissues such as the adrenals, gonads and placenta, CYP11A1 has also been found in the brain, gastrointestinal tract, immune systems, and finally the skin. CYP11A1 activity in the skin is regulated predominately by StAR protein and hence cholesterol levels in the mitochondria. However, UVB, UVC, CRH, ACTH, cAMP, and cytokines IL-1, IL-6 and TNFα can also regulate its expression and activity. Indeed, CYP11A1 plays several critical roles in the skin through its initiation of local steroidogenesis and specific metabolism of vitamin D, lumisterol, and 7-dehydrocholesterol. Products of these pathways regulate the protective barrier and skin immune functions in a context-dependent fashion through interactions with a number of receptors. Disturbances in CYP11A1 activity can lead to skin pathology.

Scabies itch: an update on neuroimmune interactions and novel targets

Frequently described as 'the worst itch' one can ever experience scabies itch is the hallmark of Sarcoptes scabiei mite infestation. Notably, the itchiness often persists for weeks despite scabicides therapy. The mechanism of scabies itch is not yet fully understood, and effective treatment modalities are still missing which can severely affect the quality of life. The aim of this review is to provide an overview of the scope of itch in scabies and highlight candidate mechanisms underlying this itch. We herein discuss scabies itch, with a focus on the nature, candidate underlying mechanisms and treatment options. We also synthesize this information with current understanding of the mechanisms contributing to non-histaminergic itch in other conditions. Itch is a major problem in scabies and can lead to grave consequences. We provide the latest insights on host-mite interaction, secondary microbial infection and neural sensitization with special emphasis on keratinocytes and mast cells to better understand the mechanism of itch in scabies. Also, the most relevant current modalities remaining under investigation that possess promising perspectives for scabies itch (i.e. protease-activated receptor-2 (PAR-2) inhibitor, Mas-related G protein-coupled receptor X2 (MRGPRX2) antagonist) are discussed. Greater understanding of these diverse mechanisms may provide a rational basis for the development of improved and targeted approaches to control itch in individuals with scabies.

Evolutionary Significance of the Neuroendocrine Stress Axis on Vertebrate Immunity and the Influence of the Microbiome on Early-Life Stress Regulation and Health Outcomes

Stress is broadly defined as the non-specific biological response to changes in homeostatic demands and is mediated by the evolutionarily conserved neuroendocrine networks of the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic nervous system. Activation of these networks results in transient release of glucocorticoids (cortisol) and catecholamines (epinephrine) into circulation, as well as activation of sympathetic fibers innervating end organs. These interventions thus regulate numerous physiological processes, including energy metabolism, cardiovascular physiology, and immunity, thereby adapting to cope with the perceived stressors. The developmental trajectory of the stress-axis is influenced by a number of factors, including the gut microbiome, which is the community of microbes that colonizes the gastrointestinal tract immediately following birth. The gut microbiome communicates with the brain through the production of metabolites and microbially derived signals, which are essential to human stress response network development. Ecological perturbations to the gut microbiome during early life may result in the alteration of signals implicated in developmental programming during this critical window, predisposing individuals to numerous diseases later in life. The vulnerability of stress response networks to maladaptive development has been exemplified through animal models determining a causal role for gut microbial ecosystems in HPA axis activity, stress reactivity, and brain development. In this review, we explore the evolutionary significance of the stress-axis system for health maintenance and review recent findings that connect early-life microbiome disturbances to alterations in the development of stress response networks.

Cutaneous antimicrobial peptides: New "actors" in pollution related inflammatory conditions

Ozone (O₃) exposure has been reported to contribute to various cutaneous inflammatory conditions, such as eczema, psoriasis, rush etc. via a redox-inflammatory pathway. O₃ is too reactive to penetrate cutaneous tissue; it interacts with lipids present in the outermost layer of skin, resulting in formation of oxidized molecules and hydrogen peroxide (H₂O₂). Interestingly, several inflammatory skin pathologies demonstrate altered levels of antimicrobial peptides (AMPs). These small, cationic peptides are found in various cells, including keratinocytes, eccrine gland cells, and seboctyes. Classically, AMPs function as antimicrobial agents. Recent studies indicate that AMPs also play roles in inflammation, angiogenesis, and wound healing. Since altered levels of AMPs have been detected in pollution-associated skin pathologies, we hypothesized that exposure to O₃ could affect the levels of AMPs in the skin. We examined levels of AMPs using qRT-PCR, Western blotting, and immunofluorescence in vitro (human keratinocytes), ex vivo (human skin explants), and in vivo (human volunteer subjects exposed to O₃) and observed increased levels of all the measured AMPs upon O₃ exposure. In addition, in vitro studies have confirmed the redox regulation of AMPs in keratinocytes. This novel finding suggests that targeting AMPs could be a possible defensive strategy to combat pollution-associated skin conditions.

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AMPs (hBDs1-3, CAMP) increase in O₃ exposed human skin by a redox mechanism.

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Transcriptional upregulation of AMPs in response to O₃ exposure is due to an altered redox status.

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Pollution increase AMPs could be the connection between pollution exposure and the development/exacerbation of inflammatory skin conditions.

A randomised controlled pilot trial of oral 11β-HSD1 inhibitor AZD4017 for wound healing in adults with type 2 diabetes mellitus.. [DOI: 10.1101/2021.03.23.21254200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Chronic wounds (e.g. diabetic foot ulcers) have a major impact on quality of life, yet treatments remain limited. Glucocorticoids impair wound healing; preclinical research suggests that blocking glucocorticoid activation by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) improves wound repair. This investigator-initiated double-blind, randomised, placebo-controlled parallel-group phase 2b pilot trial investigated efficacy, safety and feasibility of 11β-HSD1 inhibition for 35 days by oral AZD4017 (AZD) treatment in adults with type 2 diabetes (n=14) compared to placebo (PCB, n=14) in a single-centre secondary care setting. Computer-generated 1:1 randomisation was pharmacy-administered. From 300 screening invitations, 36 attended, 28 were randomised. There was no proof-of-concept that AZD inhibited 24 hour skin 11β-HSD1 activity at day 28 (primary outcome: adjusted difference AZD-PCB 90% CI (diffCI)=-3.4,5.5) but systemic 11β-HSD1 activity (median urinary [THF+alloTHF]/THE ratio) was 87% lower with AZD at day 35 (PCB 1.00, AZD 0.13, diffCI=-1.04,-0.69). Mean wound gap diameter (mm) following baseline 2mm punch biopsy was 34% smaller at day 2 (PCB 1.51, AZD 0.98, diffCI=-0.95,-0.10) and 48% smaller after repeat wounding at day 30 (PCB 1.35, AZD 0.70, diffCI=-1.15,-0.16); results also suggested greater epidermal integrity but modestly impaired barrier function with AZD. AZD was well-tolerated with minimal side effects and comparable adverse events between treatments. Staff availability restricted recruitment (2.9/month); retention (27/28) and data completeness (95.3%) were excellent. These preliminary findings suggest that AZD may improve wound healing in patients with type 2 diabetes and warrant a fully-powered trial in patients with active ulcers. [Trial Registry: www.isrctn.com/ISRCTN74621291.

Funding

MRC Confidence in Concept and NIHR Senior Investigator Award.]

Single Sentence Summary

AZD4017 was safe; data suggested improved skin healing / integrity, and modestly reduced epidermal barrier function in patients with type 2 diabetes.

Disclosure Summary

I certify that neither I nor my co-authors have a conflict of interest as described above that is relevant to the subject matter or materials included in this Work.

Topical Applications of a Heparinoid-Containing Product Attenuate Glucocorticoid-Induced Alterations in Epidermal Permeability Barrier in Mice

INTRODUCTION

Either systemic or topical glucocorticoids (GCs) can cause significant adverse effects on cutaneous structure and function. Although some products and ingredients can improve GC-induced abnormalities in epidermal permeability barrier, the efficacy is moderate. Prior studies in normal mice showed that topical applications of a heparinoid-containing product, Hirudoid® cream, improve epidermal barrier function by upregulation of epidermal proliferation, expression of mRNA for epidermal differentiation, and lipid production.

OBJECTIVE

The objective of this study was to assess whether topical applications of this product could prevent GC-induced changes in epidermal function in murine skin.

MATERIALS AND METHODS

One group of C57BL/6J mice was treated topically with 0.05% clobetasol propionate twice daily for 6 days, while another group was treated topically with Hirudoid® cream 30 min after each application of clobetasol propionate. Untreated mice served as normal controls. Transepidermal water loss (TEWL) rates, stratum corneum hydration, and skin surface pH were measured using respective probes connected to an MPA5 physiology monitor. qPCR was used to measure the expression levels of mRNA for keratinocyte differentiation-related proteins and lipid synthetic enzymes.

RESULTS

Co-applications of Hirudoid® cream with GC minimally, but significantly, increased skin thickness in comparison to GC treatment alone (p < 0.05), in parallel with increased expression levels of mRNA for PCNA in both the dermis and the epidermis. Moreover, Hirudoid® cream largely prevented GC-induced elevation in basal TEWL (p < 0.001) and delay in barrier recovery (p < 0.05), accompanied by upregulation in the expression levels of mRNA for epidermal involucrin, HMGCoA, and SPT1. However, both stratum corneum hydration and skin surface pH were comparable in the skin treated with GC alone versus GC + Hirudoid® cream.

CONCLUSION

Topical heparinoid-containing product can partially prevent GC-induced alterations in some epidermal functions.

Inherited ichthyosis and fungal infection: an update on pathogenesis and treatment strategies

Inherited ichthyoses are a group of genodermatoses classified as either nonsyndromic or syndromic. Nonsyndromic ichthyoses and keratitis, ichthyosis and deafness (KID) syndrome predispose to fungal infection. The diagnosis and treatment of fungal infections underlying ichthyoses are challenging. In this review, we summarize reported cases of ichthyosis with fungal infection over the past 50 years. Atypical manifestations such as alopecia, papules and brittle nails occurred in patients with ichthyosis combined with fungal infection. Various pathogenic mechanisms have been implicated, including mutations of ichthyosis-related genes leading to disruption of the skin barrier via multiple pathways. Host immune disorders, including atopy and abnormal innate immunity also contribute to susceptibility. Specific fungi may escape the immune response. Extensive and recurrent fungal infections are not uncommon in patients with ichthyosis, making a cure more difficult and increasing the need for systemic antifungal therapy. Traditional and new ichthyosis treatments aiming to improve skin barrier function could help prevent fungal infection. In conclusion, the close relationship between ichthyosis and fungal infection is of vital importance in clinical practice and requires more attention from physicians. More studies are required to investigate the mechanisms and explore useful treatment strategies.

Could cellular and signaling abnormalities converge to provoke atopic dermatitis?

Diverse inherited and acquired abnormalities in epidermal structural and enzymatic proteins compromise permeability, barrier function and antimicrobial defense in atopic dermatitis (AD). Though several mutations in filaggrin (FLG) predominate, alterations in other S-100, cornified envelope precursor proteins (hornerin [HRNR], filaggrin 2 [FLG2], SPRR3, mattrin) which regulate lamellar body formation; SPINK5, which encodes the serine protease inhibitor, LEKTI1, and a fatty acid transporter, FATP4, are all separately associated with an AD phenotype. Exogenous and endogenous stressors, such as prolonged psychological stress, a low environmental humidity, or exposure to basic soaps and surfactants can further compromise barrier function and are often required to trigger disease. In the immunologists' view, the barrier abnormality is relevant only because it allows antigen and pathogen access, while stimulating Th2 cytokine production. These proteins in turn downregulate lipid synthetic enzyme and antimicrobial peptide levels, as well as multiple epidermal structural proteins, including filaggrin. Each inherited and acquired abnormality can independently compromise lamellar body secretion production, resulting in defective lamellar membrane organization and antimicrobial defense. Furthermore, elevated pH of the SC is critical for AD pathogenesis, compromising post-secretory lipid processing, while also enhancing inflammation. There are various therapeutic options that interdict different stages in this pathogenic paradigm.

Role of Antimicrobial Peptides in Skin Barrier Repair in Individuals with Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that exhibits a complex interplay of skin barrier disruption and immune dysregulation. Patients with AD are susceptible to cutaneous infections that may progress to complications, including staphylococcal septicemia. Although most studies have focused on filaggrin mutations, the physical barrier and antimicrobial barrier also play critical roles in the pathogenesis of AD. Within the physical barrier, the stratum corneum and tight junctions play the most important roles. The tight junction barrier is involved in the pathogenesis of AD, as structural and functional defects in tight junctions not only disrupt the physical barrier but also contribute to immunological impairments. Furthermore, antimicrobial peptides, such as LL-37, human b-defensins, and S100A7, improve tight junction barrier function. Recent studies elucidating the pathogenesis of AD have led to the development of barrier repair therapy for skin barrier defects in patients with this disease. This review analyzes the association between skin barrier disruption in patients with AD and antimicrobial peptides to determine the effect of these peptides on skin barrier repair and to consider employing antimicrobial peptides in barrier repair strategies as an additional approach for AD management.

Particulate Matter Induces Tissue OxInflammation: From Mechanism to Damage

Significance: Oxidative stress and oxidative damage are central hypothetical mechanisms for the adverse effects of airborne particulate matter (PM). Activation of inflammatory cells capable of generating reactive oxygen and nitrogen species is another proposed damage pathway. Understanding the interplay between these responses can help us understand the adverse health effects attributed to breathing polluted air. Recent Advances: The consequences of PM exposure on different organs are oxidative damage, decreased function, and inflammation, which can lead to the development/exacerbation of proinflammatory disorders. Mitochondrial damage is also an important event in PM-induced cytotoxicity. Critical Issues: Reactive oxygen species (ROS) are generated during phagocytosis of the particles, leading to enhancement of oxidative stress and triggering the inflammatory response. The activation of inflammatory signaling pathways results in the release of cytokines and other mediators, which can further induce ROS production by activating endogenous enzymes, leading to a positive feedback loop, which can aggravate the effects triggered by PM exposure. Future Directions: Further research is required to elucidate the exact mechanisms by which PM exposure results in adverse health effects, in terms of the relationship between the redox responses triggered by the presence of the particles and the inflammation observed in the different organs, so the development/exacerbation of PM-associated health problems can be prevented.

The Lipoxin Receptor/FPR2 Agonist BML-111 Protects Mouse Skin Against Ultraviolet B Radiation

Excessive exposure to UV, especially UVB, is the most important risk factor for skin cancer and premature skin aging. The identification of the specialized pro-resolving lipid mediators (SPMs) challenged the preexisting paradigm of how inflammation ends. Rather than a passive process, the resolution of inflammation relies on the active production of SPMs, such as Lipoxins (Lx), Maresins, protectins, and Resolvins. LXA4 is an SPM that exerts its action through ALX/FPR2 receptor. Stable ALX/FPR2 agonists are required because SPMs can be quickly metabolized within tissues near the site of formation. BML-111 is a commercially available synthetic ALX/FPR2 receptor agonist with analgesic, antioxidant, and anti-inflammatory properties. Based on that, we aimed to determine the effect of BML-111 in a model of UVB-induced skin inflammation in hairless mice. We demonstrated that BML-111 ameliorates the signs of UVB-induced skin inflammation by reducing neutrophil recruitment and mast cell activation. Reduction of these cells by BML-111 led to lower number of sunburn cells formation, decrease in epidermal thickness, collagen degradation, cytokine production (TNF-α, IL-1β, IL-6, TGF, and IL-10), and oxidative stress (observed by an increase in total antioxidant capacity and Nrf2 signaling pathway), indicating that BML-111 might be a promising drug to treat skin disorders.

THE SKIN MICROBIOTA AND ITCH: Is There a Link?

Itch is an unpleasant sensation that emanates primarily from the skin. The chemical mediators that drive neuronal activity originate from a complex interaction between keratinocytes, inflammatory cells, nerve endings, and the skin microbiota, relaying itch signals to the brain. Stress also exacerbates itch via the skin-brain axis. Recently, the microbiota has surfaced as a major player to regulate this axis, notably during stress settings aroused by actual or perceived homeostatic challenge. The routes of communication between the microbiota and brain are slowly being unraveled and involve neurochemicals (i.e., acetylcholine, histamine, catecholamines, and corticotropin) that originate from the microbiota itself. By focusing on itch biology and by referring to the more established field of pain research, this review examines the possible means by which the skin microbiota contributes to itch.

The Potential Impact of Social Genomics on Wound Healing

Significance: Human skin wounds carry an immense epidemiologic and financial burden, and their impact will continue to grow with an aging population and rising incidence of comorbid conditions known to affect wound healing. To comprehensively address this growing clinical issue, physicians should also be aware of how conditions of the human social environment may affect wound healing. Here we provide a review of the emerging field of social genomics and its potential impact on the wound healing. Recent Advances: Multiple studies using human and animal models have correlated social influences and their contributing effects to acute and chronic stress with delays in wound healing. Furthermore, observations between nongenetic factors such as nutrition, socioeconomic, and educational status have also shown to have a direct or indirect impact on clinical outcomes of wound healing. Critical Issues: Nutrition, financial burden, socioeconomic and education status, and acute and chronic stress are variables that have either direct (epigenetic) or indirect impact on wound healing and patients' quality of life. Wound care is costly and remains a challenge placing economic burden on patients. Furthermore, poor clinical outcomes and complications including loss of mobility and disability may lead to job loss, further contributing to socioeconomic related stress. Thus, the economic burden and inadequate wound healing are intertwined, making each other worse. Future Directions: Although some evidence regarding the specific changes in genetic pathways imparted by conditions of the social environment exists, further studies are warranted to identify potential mechanisms, interventions, and prevention approaches.

The Skin Microbiota and Itch: Is There a Link?

Itch is an unpleasant sensation that emanates primarily from the skin. The chemical mediators that drive neuronal activity originate from a complex interaction between keratinocytes, inflammatory cells, nerve endings and the skin microbiota, relaying itch signals to the brain. Stress also exacerbates itch via the skin–brain axis. Recently, the microbiota has surfaced as a major player to regulate this axis, notably during stress settings aroused by actual or perceived homeostatic challenge. The routes of communication between the microbiota and brain are slowly being unraveled and involve neurochemicals (i.e., acetylcholine, histamine, catecholamines, corticotropin) that originate from the microbiota itself. By focusing on itch biology and by referring to the more established field of pain research, this review examines the possible means by which the skin microbiota contributes to itch.

Extra-adrenal glucocorticoid biosynthesis: implications for autoimmune and inflammatory disorders

Glucocorticoid synthesis is a complex, multistep process that starts with cholesterol being delivered to the inner membrane of mitochondria by StAR and StAR-related proteins. Here its side chain is cleaved by CYP11A1 producing pregnenolone. Pregnenolone is converted to cortisol by the enzymes 3-βHSD, CYP17A1, CYP21A2 and CYP11B1. Glucocorticoids play a critical role in the regulation of the immune system and exert their action through the glucocorticoid receptor (GR). Although corticosteroids are primarily produced in the adrenal gland, they can also be produced in a number of extra-adrenal tissue including the immune system, skin, brain, and intestine. Glucocorticoid production is regulated by ACTH, CRH, and cytokines such as IL-1, IL-6 and TNFα. The bioavailability of cortisol is also dependent on its interconversion to cortisone which is inactive, by 11βHSD1/2. Local and systemic glucocorticoid biosynthesis can be stimulated by ultraviolet B, explaining its immunosuppressive activity. In this review, we want to emphasize that dysregulation of extra-adrenal glucocorticoid production can play a key role in a variety of autoimmune diseases including multiple sclerosis (MS), lupus erythematosus (LE), rheumatoid arthritis (RA), and skin inflammatory disorders such as psoriasis and atopic dermatitis (AD). Further research on local glucocorticoid production and its bioavailability may open doors into new therapies for autoimmune diseases.

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).

Expression and Function of Host Defense Peptides at Inflammation Sites

There is a growing interest in the complex role of host defense peptides (HDPs) in the pathophysiology of several immune-mediated inflammatory diseases. The physicochemical properties and selective interaction of HDPs with various receptors define their immunomodulatory effects. However, it is quite challenging to understand their function because some HDPs play opposing pro-inflammatory and anti-inflammatory roles, depending on their expression level within the site of inflammation. While it is known that HDPs maintain constitutive host protection against invading microorganisms, the inducible nature of HDPs in various cells and tissues is an important aspect of the molecular events of inflammation. This review outlines the biological functions and emerging roles of HDPs in different inflammatory conditions. We further discuss the current data on the clinical relevance of impaired HDPs expression in inflammation and selected diseases.

The impact of perceived stress on skin ageing

Skin ageing can be divided according to phenotypical features into intrinsic (by the passage of time) and extrinsic (with the addition of the effects of environmental factors). Photoageing is by far the most researched factor of extrinsic ageing but the additional impact of other factors such as cigarette smoking and exposure to air pollution ought to be taken into account. One of the least researched topics in relation to extrinsic skin ageing is the impact of psychological stress. A contemporary review of response of human skin to stress describes the molecular mechanisms of extrinsic skin ageing, but has fallen short of explaining resilience to stress exhibited by people. Mechanisms to regulate gene expression, define cellular identity and promote functionality are responsible for the adaptive response to stressful events. Conversely, maladaptive response of human tissues to chronic stress appears to have an impact on gene regulation. Epigenetics is the study of heritable changes in organisms due to modifications in gene activity and expression, as opposed to the genetic code (DNA genome). Chronic stress appears to be an important factor in determining an individual's vulnerability to ageing and age-related comorbidities via epigenetic modifications. Forerunners in epigenetic research recognized the necessity of a reliable biomarker in order to develop a better understanding of the role of epigenomics in ageing. Genomic DNA methylation patterns (DNAm) appear to be valuable in age prediction but variability in specificity exists across species of mammals, human races and tissues. Neuroscience research appears to be leading the way in epigenomics whilst the lack of a valid and reliable DNAm-associated age predictor compatible with human skin tissue hinders research endeavours for the epigenetics of skin ageing.

Architecture of antimicrobial skin defense

The skin is the largest and the most exposed organ in the body and its defense is regulated at several anatomical levels. Here, we explore how skin layers, including the epidermis, dermis, adipose tissue, and skin appendages, as well as cutaneous microbiota, contribute to the function of skin antimicrobial defense. We highlight recent studies that reveal the differential and complementary responses of skin layers to bacterial, viral, and fungal infection. In particular, we focus on key soluble mediators in the layered skin defense, such as antimicrobial peptides, as well as on lipid antimicrobials, cytokines, chemokines, and barrier-maintaining molecules. We include our own evaluative analyses of transcriptomic datasets of human skin to map the involvement of antimicrobial peptides in skin protection under both steady state and infectious conditions. Furthermore, we explore the versatility of the mechanisms underlying skin defense by highlighting the role of the immune and nervous systems in their interaction with cutaneous microbes, and by illustrating the multifunctionality of selected antimicrobial peptides in skin protection.

Aging of the skin barrier

The skin barrier is mainly present in the stratum corneum (SC), composed of corneocytes surrounded by intercellular lipid lamellae, and attached by corneodesmosome. The tight junction attached to the lateral walls of keratinocytes in the upper part of the stratum granulosum is also included in the skin barrier. During aging, the following structures and functions of the skin barrier are changed or disturbed: (1) skin barrier structure, (2) permeability barrier function, (3) epidermal calcium gradient, (4) epidermal lipid synthesis and SC lipid processing, (5) cytokine production and response after insults, (6) SC acidity, (7) SC hydration, and (8) antimicrobial barrier. Patients with diabetes also show changes in the skin barrier similar to those in aged skin, and the characteristics of the skin barrier are very similar. Understanding the pathogenic mechanisms of the skin barrier in aging will permit us to develop therapeutic strategies for aged or diabetic skin.

The impact of stress on epidermal barrier function: an evidence-based review

BACKGROUND

The epidermal barrier functions to limit skin infection and inflammation by inhibiting irritant and immunogen invasion. Abundant evidence suggests that psychological stress stemming from crowding, isolation, nicotine smoking, insomnia, mental arithmetic tasks, physical pain, real-life stressors (examinations and marital strain) and lack of positive personality traits may impart both acute and chronic epidermal dysfunction.

OBJECTIVES

To review the relationship between stress and epidermal barrier dysfunction.

METHODS

A review of the PubMed and Embase databases was conducted to identify all English-language case-control, cross-sectional and randomized control trials that have reported the effect of stress on epidermal barrier function. The authors' conclusions are based on the available evidence from 21 studies that met the inclusion and exclusion criteria.

RESULTS

Psychological stressors upregulate the hypothalamic-pituitary-adrenal axis to stimulate local and systemic stress hormone production. This ultimately leads to aberrant barrier dysfunction, characterized by decreased epidermal lipid and structural protein production, decreased stratum corneum hydration and increased transepidermal water loss.

CONCLUSIONS

This evidence-based review explores the adverse effects of psychological stressors on epidermal barrier function. Future investigations using more real-life stressors are needed to elucidate further their impact on skin physiology and identify practical stress-relieving therapies that minimize and restore epidermal barrier dysfunction, particularly in at-risk populations. What's already known about this topic? The literature reports the negative effect of stress on prolonged wound healing. Less is known about the relationship between stress and epidermal barrier dysfunction, a chronic, superficial wound involving the upper epidermal layers. What does this study add? Psychological stressors impact epidermal barrier function by activating the hypothalamic-pituitary-adrenal axis to stimulate local and systemic stress hormone production. Stress hormones negatively affect the epidermal barrier by decreasing epidermal lipids and structural proteins, decreasing stratum corneum hydration and increasing transepidermal water loss. Identification of such stressors can promote stress-avoidance and stress-reduction behaviours that protect epidermal barrier function and prevent certain dermatological conditions.

Treatment with maresin 1, a docosahexaenoic acid-derived pro-resolution lipid, protects skin from inflammation and oxidative stress caused by UVB irradiation

Acute exposure to UVB irradiation causes skin inflammation and oxidative stress, and long-term exposure to UVB irradiation may lead to carcinogenesis. Our organism has endogenous mechanisms to actively limit inflammation. Maresin 1 (MaR1; 7R,14S-dihydroxy-docosa-4Z,8E,10E,12Z,16Z,19Z-hexaenoic acid) is a pro-resolution lipid mediator derived from the docosahexaenoic acid, which presents anti-inflammatory and pro-resolution effects. However, it remains to be determined if treatment with MaR1 can inhibit inflammatory and oxidative alterations in the skin triggered by UVB. The treatment with MaR1 (0.1-10 ng/mice at -10 min relative to the UVB irradiation protocol) reduced UVB-induced skin edema, neutrophil recruitment (MPO; myeloperoxidase activity, and migration of LysM-eGFP⁺ cells), cytokine production, matrix metalloproteinase-9 activity, keratinocyte apoptosis, epidermal thickening, mast cells counts and degradation of skin collagen in hairless mice. UVB irradiation caused a decrease of GSH (reduced glutathione) levels, activity of the enzyme catalase, ferric reducing ability (FRAP), and ABTS radical scavenging capacity as well as induced lipid hydroperoxide, superoxide anion production, and gp91^phox mRNA expression. These parameters that indicate oxidative stress were inhibited by MaR1 treatment. Therefore, these data suggest MaR1 as a promising pharmacological tool in controlling the deleterious effects related to UVB irradiation.

Chronic psychological stress impairs germinal center response by repressing miR-155

Germinal centers (GC) are vital to adaptive immunity. BCL6 and miR-155 are implicated in control of GC reaction and lymphomagenesis. FBXO11 causes BCL6 degradation through ubiquitination in B-cell lymphomas. Chronic psychological stress is known to drive immunosuppression. Corticosterone (CORT) is an adrenal hormone expressed in response to stress and can similarly impair immune functions. However, whether GC formation is disrupted by chronic psychological stress and its molecular mechanism remain to be elucidated. To address this issue, we established a GC formation model in vivo, and a GC B cell differentiation model in vitro. Comparing Naive B cells to GC B cells in vivo and in vitro, the differences of BCL6 and FBXO11 mRNA do not match the changes at the protein level and miR-155 levels that were observed. Next we demonstrated that CORT increase, induced by chronic psychological stress, reduced GC response, IgG1 antibody production and miR-155 level in vivo. The effect of chronic psychological stress can be blocked by a glucocorticoid receptor (GR) antagonist. Similarly, impaired GC B cell generation and isotope class switching were observed. Furthermore, we found that miR-155 and BCL6 expression were downregulated, but FBXO11 expression was upregulated in GC B cells treated with CORT in vitro. In addition, we demonstrated that miR-155 directly down-regulated FBXO11 expression by binding to its 3́-untranslated region. The subsequent overexpression of miR-155 significantly blocked the stress-induced impairment of GC response, due to changes in FBXO11 and BCL6 expression, as well as increased apoptosis in B cells both in vivo and in vitro. Our findings suggest perturbation of GC reaction may play a role in chronic psychological stress-induced immunosuppression through a glucocorticoid pathway, and miR-155-mediated post-transcriptional regulation of FBXO11 and BCL6 expression may contribute to the impaired GC response.

Topical nicotinic receptor activation improves wound bacterial infection outcomes and TLR2-mediated inflammation in diabetic mouse wounds

The cholinergic anti-inflammatory pathway can directly affect skin antibacterial responses via nicotinic acetylcholine receptors (nAChRs). In particular, α7 nAChR (CHRNA7) present in the epidermis modulates the host response to wounding and/or wound bacterial infection. While physiologic inflammation is required to initiate normal wound repair and can be triggered by Toll-like receptor (TLR) activation, chronic inflammation is frequently observed in diabetic wounds and can occur, in part, via excessive TLR2 activation or production. Consequently, this can delay physiologic wound healing responses and increase diabetic host susceptibility to bacterial infection. In this study, we demonstrate that topical nAChR activation diminishes bacterial survival and systemic dissemination in a mouse model of diabetic wound infection, while reducing wound TLR2 production, relative to control mice. We further determined that the antimicrobial peptide activity of diabetic mouse wounds is increased compared to control mice, but this effect is lost following topical nAChR activation. Finally, we observed that human diabetic wounds exhibit impaired α7 nAChR (CHRNA7) abundance and localization relative to human control (nondiabetic) skin. These findings suggest that topical administration of nAChR agonists may improve wound healing and infection outcomes in diabetic wounds by dampening TLR2-mediated inflammation and antimicrobial peptide response, and that the diabetic microenvironment may promote aberrant CHRNA7 production/activation that likely contributes to diabetic wound pathogenesis.

Stress-related salivary proteins affect the production of volatile sulfur compounds by oral bacteria

OBJECTIVE

To determine whether stress-related substances and sex hormones influence the growth and in vitro production of volatile sulfur compounds (VSCs) by Solobacterium moorei and Fusobacterium nucleatum.

MATERIALS AND METHODS

Bacteria growth and VSCs production were evaluated in the presence of alpha-amylase, beta-defensin-2, mucin, estradiol, and progesterone. Growth was evaluated by colony counting, and the production of the VSCs hydrogen sulfide (H₂ S) and methyl mercaptan (CH₃ SH) was measured using the Oral Chroma™ instrument.

RESULTS

Mucin induced the production of H₂ S by both bacteria, but had a slight inhibitory effect on CH₃ SH production by F. nucleatum. It also increased the viability of F. nucleatum. Alpha-amylase increased H₂ S production by S. moorei and CH₃ SH production by F. nucleatum, but had no effect on H₂ S production by F. nucleatum. No substance altered the viability of S. moorei. No effects of beta-defensin-2, estradiol, or progesterone were observed.

CONCLUSION

The salivary stress-related proteins mucin and alpha-amylase altered VSCs production by F. nucleatum and S. moorei, favoring H₂ S production. These findings are a step toward understanding the relation between stress and increased amounts of H₂ S.

Psychological Stress Deteriorates Skin Barrier Function by Activating 11β-Hydroxysteroid Dehydrogenase 1 and the HPA Axis

Psychological stress (PS) increases endogenous glucocorticoids (GC) by activating the hypothalamic-pituitary-adrenal axis. The negative effects of GC on skin barrier function under PS have been well-established. However, endogenous GC can also be active when cortisone (inactive form) is converted to cortisol (active form) by 11β-hydroxysteroid dehydrogenase type I (11ß-HSD1) in the peripheral tissue. Here, we evaluated the changes in 11ß-HSD1 and barrier function under PS. Elevated 11ß-HSD1 in oral mucosa correlated with increased cortisol in the stratum corneum and deteriorated barrier function. Expression of 11ß-HSD1 in the oral mucosa correlated with that in the epidermal keratinocytes. We further investigated whether barrier function improved when PS was relieved using a selective serotonin reuptake inhibitor (SSRI) in patients with anxiety. Decreased 11ß-HSD1 and improved barrier function were observed after SSRI treatment. The collective findings suggest that elevated 11ß-HSD1 under PS increases the level of cutaneous GC and eventually impairs barrier function. PS-alleviating drugs, such as SSRI, may help to treat PS-aggravated skin diseases.

Chronic social stress Ameliorates psoriasiform dermatitis through upregulation of the Hypothalamic-Pituitary-Adrenal axis

Acute stress is a physiological response of an organism to adverse conditions, contributing to survival; however, persistence through time may lead to disease. Indeed, exacerbation of inflammatory conditions such as psoriasis has been reported to follow stressors in susceptible patients. Because chronic stress cannot ethically be elicited in patients under controlled laboratory conditions, we studied genetically modified mice that naturally develop psoriasiform dermatitis, and subjected them to an ethological chronic social contact stress paradigm. Although we found elevated pro-inflammatory neuropeptide production of substance P (SP), calcitonin-gene-related peptide (CGRP) and nerve-growth factor (NGF) mRNA in the dorsal root ganglia (DRG) as well as pro-inflammatory cytokines in response to the social stressor, stress paradoxically prevented the development of the skin lesions. This effect of stress could be reversed by the treatment with glucocorticoid (GC) receptor blockers, suggesting that it was mediated through the upregulation of corticosterone secretion. Extrapolating to humans, the worsening of disease in susceptible patients with psoriasis could be attributed to a defect in the Hypothalamic-Pituitary-Adrenal (HPA) axis with an impaired production of GC during situations of adversity, thus rendering them unable to counteract the pro-inflammatory effects of chronic stressors.

The Pathophysiological Mechanisms and the Quest for Biomarkers in Psoriasis, a Stress-Related Skin Disease

Psoriasis is a physically, emotionally, and socially invalidating multifactorial disorder, with a significant impact on the patients' quality of life. Stress is one of the leading triggers for psoriasis and has been associated with disease onset and subsequent flare-ups, while the flare-ups by themselves often lead to psychological discomfort. The treatment of psoriasis is individualized, depending on the patients' measurable severity of illness, as well as the impact the skin condition has on patients' quality of life, as assessed by standardized questionnaires. The clinical scales used nowadays for measuring the severity of psoriasis are characterized by low reproducibility and high variability between examiners. Hence, there is a real need to identify objectively measurable biomarkers to standardize the assessment of the severity of psoriasis. We aim to review the pathophysiological mechanisms involved in psoriasis, focusing on the most critical advances in psoriasis biomarker discovery, pointing out those biomarkers which have also been studied in other stress-related conditions, thus emphasizing the relationship between psoriasis and stress.

Co-Activation of Glucocorticoid Receptor and Peroxisome Proliferator-Activated Receptor-γ in Murine Skin Prevents Worsening of Atopic March

Children with atopic dermatitis show an increased risk to develop asthma later in life, a phenomenon referred to as "atopic march," which emphasizes the need for secondary prevention therapies. This study aimed to investigate whether relief of skin inflammation by glucocorticoids and peroxisome proliferator-activated receptor agonists might influence the subsequent development of asthma in a murine model for the atopic march in which mice were repeatedly exposed to house dust mite via the skin, followed by exposure to house dust mite in lungs. To abrogate atopic dermatitis, mice received topical treatment with glucocorticoid receptor/peroxisome proliferator-activated receptor-γ agonists. Nuclear receptor ligand effects were assessed on primary keratinocytes and dendritic cells, as central players in skin inflammation. Prior house dust mite-induced skin inflammation aggravates allergic airway inflammation and induces a mixed T helper type 2/T helper type 17 response in the lungs. Cutaneous combined activation of glucocorticoid receptor/peroxisome proliferator-activated receptor-γ reduced skin inflammation to a higher extent compared to single activation. Additive anti-inflammatory effects were more prominent in dendritic cells, as compared to keratinocytes. Alleviation of allergic skin inflammation by activation of glucocorticoid receptor/peroxisome proliferator-activated receptor-γ appeared insufficient to avoid the allergic immune response in the lungs, but efficiently reduced asthma severity by counteracting the Th17 response. Glucocorticoid receptor/peroxisome proliferator-activated receptor-γ co-activation represents a potent remedy against allergic skin inflammation and worsening of atopic march.

Association between Stress and the HPA Axis in the Atopic Dermatitis

The hypothalamic–pituitary–adrenal (HPA) axis is one of the body’s neuroendocrine networks that responds to psychological stress (PS). In the skin, there exists a peripheral HPA axis similar to the central axis. Glucocorticoids (GCs) are key effector molecules of the HPA axis and are essential for cutaneous homeostasis. Atopic dermatitis (AD) is a condition typically characterized by a chronic relapsing course that often results in PS. HPA dysfunction is present in AD patients by the decreased response of GCs elevation to stress as compared to those unaffected by AD. Nevertheless, in skin, acute PS activates several metabolic responses that are of immediate benefit to the host. During the acute phase of PS, increased endogenous GCs have been shown to provide benefit rather than by aggravating cutaneous inflammatory dermatoses. However, a chronic T helper cell type 2 (Th2) predominant cytokine profile acts as a negative feedback loop to blunt the HPA axis response in AD. In this article, we reviewed the role of CRF, pro-opiomelanocortin (POMC)-derived peptides, GCs of the HPA, and 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) in AD, with a discussion of the pathogenetic mechanisms of inflammation and skin barrier functions, including antimicrobial defense, and their association with PS.

Cutaneous Glucocorticoidogenesis and Cortisol Signaling Are Defective in Psoriasis

Hannen et al. report that cutaneous glucocorticoidogenesis and expression of glucocorticoid receptors are inhibited in psoriatic skin. These findings substantiate the previous concept that deficient feedback of local proopiomelanocortin and glucocorticoids on cutaneous immunity contributes to inflammatory and autoimmune dermatoses. Restoration of efficient endogenous glucocorticoid signaling represents a realistic goal in treating psoriasis.

Glucocorticoids Inhibit Wound Healing: Novel Mechanism of Action

Jozic et al. describe mechanisms of glucocorticoid (GC) downregulation of wound healing by interaction with the membrane bound GC receptor, followed by stimulation of β-catenin and c-myc pathways. Targeting the membrane bound GC receptor or the recently discovered interaction of GC with mineralocorticoid receptors may counteract negative effects of GC on the skin barrier and potentially could serve as a remedy for age-related skin atrophy.