Endogenous Glucocorticoid Deficiency in Psoriasis Promotes Inflammation and Abnormal Differentiation

Transcriptomic Analyses Predict Enhanced Metabolic Activity and Therapeutic Potential of mTOR Inhibitors in Acne-Prone Skin

Current acne therapies center on preventing new lesions in patients with acne. These therapies were historically found to be beneficial yet were chosen without knowledge of the specific changes in the skin that favor lesion development. A major challenge in developing new treatments is the incomplete understanding of nonlesional (NL), acne-prone skin's molecular characteristics. To address this, we compared RNA-sequencing data from NL skin of 49 patients with acne (denoted as NL acne [NLA]) with those from 19 healthy controls with no acne history. We found 77 differentially expressed genes in NLA (log fold change > 1; P < .05), including genes associated with innate immunity and epidermal barrier function. Notably, K RT 6C, K RT 16, S100A8, S100A9, and lactotransferrin were upregulated, and LCE4A, LCE6A, and CTSE were downregulated. Gene set enrichment analysis revealed that metabolic pathways were enriched in NLA skin, whereas keratinization was negatively enriched. To identify compounds that could shift the gene expression signature of NLA skin toward healthy control skin, we performed connectivity mapping with the Library of Integrated Network-Based Signatures. We identified 187 compounds, particularly mTOR inhibitors, that could potentially normalize the gene expression profile of acne-prone skin to that of healthy skin. Our findings indicate that NLA skin has distinct differences in epidermal differentiation, cellular metabolism, and innate immunity that may promote lesion formation and suggest that mTOR inhibitors could restore NLA skin toward a healthier state, potentially reversing the predisposition to lesion development.

Glucocorticoid receptor controls atopic dermatitis inflammation via functional interactions with P63 and autocrine signaling in epidermal keratinocytes

Atopic dermatitis (AD), a prevalent chronic inflammatory disease with multifactorial etiology, features epidermal barrier defects and immune overactivation. Synthetic glucocorticoids (GCs) are widely prescribed for treating AD due to their anti-inflammatory actions; however, mechanisms are incompletely understood. Defective local GC signaling due to decreased production of endogenous ligand and/or GC receptor (GR) levels was reported in prevalent inflammatory skin disorders; whether this is a consequence or contributing factor to AD pathology is unclear. To identify the chromatin-bound cell-type-specific GR protein interactome in keratinocytes, we used rapid immunoprecipitation of endogenous proteins and mass spectrometry identifying 145 interactors that increased upon dexamethasone treatment. GR-interacting proteins were enriched in p53/p63 signaling, including epidermal transcription factors with critical roles in AD pathology. Previous analyses indicating mirrored AD-like phenotypes between P63 overexpression and GR loss in epidermis, and our data show an intricate relationship between these transcription factors in human keratinocytes, identifying TP63 as a direct GR target. Dexamethasone treatment counteracted transcriptional up-regulation of inflammatory markers by IL4/IL13, known to mimic AD, causing opposite shifts in GR and P63 genomic binding. Indeed, IL4/IL13 decreased GR and increased P63 levels in cultured keratinocytes and human epidermal equivalents (HEE), consistent with GR down-regulation and increased P63 expression in AD lesions vs normal skin. Moreover, GR knockdown (GRKD) resulted in constitutive increases in P63, phospho-P38 and S100A9, IL6, and IL33. Also, GRKD culture supernatants showed increased autocrine production of TH2-/TH1-/TH17-TH22-associated factors including IL4, CXCL10, CXCL11, and CXCL8. GRKD HEEs showed AD-like features including hyperplasia and abnormal differentiation, resembling phenotypes observed with GR antagonist or IL4/IL13 treatment. The simultaneous GR/P63 knockdown partially reversed constitutive up-regulation of inflammatory genes in GRKD. In summary, our data support a causative role for GR loss in AD pathogenesis via functional interactions with P63 and autocrine signaling in epidermal keratinocytes.

Effects on peripheral and central nervous system of key inflammatory intercellular signalling peptides and proteins in psoriasis

Psoriasis is a chronic systemic inflammatory cutaneous disease. Where the immune system plays an important role in its pathogenesis, with key inflammatory intercellular signalling peptides and proteins including IL-17 and IL-23. The psychoneurological system also figures prominently in development of psoriasis. There is a high prevalence of comorbidity between psoriasis and mental health disorders such as depression, anxiety and mania. Patients with psoriasis often suffer from pathological pain in the lesions, and their neurological accidents could improve the lesions in innervated areas. The immune system and the psychoneurological system interact closely in the pathogenesis of psoriasis. Patients with psoriasis exhibit abnormal levels of neuropeptides both in circulating and localized lesion, acting as immunomodulators involved in the inflammatory response. Moreover, receptors for inflammatory factors are expressed in both peripheral and central nervous systems (CNSs), suggesting that nervous system can receive and be influenced by signals from immune system. Key inflammatory intercellular signalling peptides and proteins in psoriasis, such as IL-17 and IL-23, can be involved in sensory signalling and may affect synaptic plasticity and the blood-brain barrier of CNS through the circulation. This review provides an overview of the multiple effects on the peripheral and CNS under conditions of systemic inflammation in psoriasis, providing a framework and inspiration for in-depth studies of neuroimmunomodulation in psoriasis.

Metabolomics Reveals Molecular Signatures for Psoriasis Biomarkers and Drug Targets Discovery

Purpose

Psoriasis is a chronic, multi-system skin disease that can be influenced by immunological, environmental, and genetic factors. Plasma metabolomic analysis can provide a great deal of information on potential diagnostic biomarkers, pathogenesis and personalized treatment. However, the role of metabolites in psoriasis is unknown.

Patients and Methods

We performed an untargeted metabolomic analysis of plasma based on high-resolution liquid chromatography mass spectrometry from 10 plaque psoriasis patients and 10 healthy controls.

Results

A total of 301 differential metabolites were detected, of which 10 metabolites were possible potential biomarkers, including vitamins, amino acids, and lipids. At the same time, KEGG pathway enrichment analysis was performed for all detected differential metabolites, and it was found that protein digestion and absorption, amino acid metabolism and lipid metabolism may be jointly involved in regulating the pathogenesis of psoriasis. In addition, the proteins ESR1, OPRM1 and HSD11B1 were identified as possible potential topical therapeutic targets for psoriasis through analysis of the metabolite-protein interaction network.

Conclusion

In this study, we identified 10 differential metabolites as possible potential combinatorial biomarkers for the diagnosis of psoriasis. 12 metabolic pathways were significantly enriched that may be closely related to the occurrence and development of psoriasis. Three proteins, ESR1, OPRM1, and HSD11B1, were identified as possible potential therapeutic targets for psoriasis.

Research progress of metabolomics in psoriasis

ABSTRACT

Psoriasis is a chronic inflammatory skin disease with significant physical and psychological burdens. The interplay between the innate and adaptive immune systems is thought to contribute to the pathogenesis; however, the details of the pathogenesis remain unclear. In addition, reliable biomarkers for diagnosis, assessment of disease activity, and monitoring of therapeutic response are limited. Metabolomics is an emerging science that can be used to identify and analyze low molecular weight molecules in biological systems. During the past decade, metabolomics has been widely used in psoriasis research, and substantial progress has been made. This review summarizes and discusses studies that applied metabolomics to psoriatic disease. These studies have identified dysregulation of amino acids, carnitines, fatty acids, lipids, and carbohydrates in psoriasis. The results from these studies have advanced our understanding of: (1) the molecular mechanisms of psoriasis pathogenesis; (2) diagnosis of psoriasis and assessment of disease activity; (3) the mechanism of treatment and how to monitor treatment response; and (4) the link between psoriasis and comorbid diseases. We discuss common research strategies and progress in the application of metabolomics to psoriasis, as well as emerging trends and future directions.

PARP2 promotes inflammation in psoriasis by modulating estradiol biosynthesis in keratinocytes

Poly(ADP-ribose) polymerase 2 (PARP2) alongside PARP1 are responsible for the bulk of cellular PARP activity, and they were first described as DNA repair factors. However, research in past decades implicated PARPs in biological functions as diverse as the regulation of cellular energetics, lipid homeostasis, cell death, and inflammation. PARP activation was described in Th2-mediated inflammatory processes, but studies focused on the role of PARP1, while we have little information on PARP2 in inflammatory regulation. In this study, we assessed the role of PARP2 in a Th17-mediated inflammatory skin condition, psoriasis. We found that PARP2 mRNA expression is increased in human psoriatic lesions. Therefore, we studied the functional consequence of decreased PARP2 expression in murine and cellular human models of psoriasis. We observed that the deletion of PARP2 attenuated the imiquimod-induced psoriasis-like dermatitis in mice. Silencing of PARP2 in human keratinocytes prevented their hyperproliferation, maintained their terminal differentiation, and reduced their production of inflammatory mediators after treatment with psoriasis-mimicking cytokines IL17A and TNFα. Underlying these observations, we found that aromatase was induced in the epidermis of PARP2 knock-out mice and in PARP2-deficient human keratinocytes, and the resulting higher estradiol production suppressed NF-κB activation, and hence, inflammation in keratinocytes. Steroidogenic alterations have previously been described in psoriasis, and we extend these observations by showing that aromatase expression is reduced in psoriatic lesions. Collectively, our data identify PARP2 as a modulator of estrogen biosynthesis by epidermal keratinocytes that may be relevant in Th17 type inflammation. KEY MESSAGES : PARP2 mRNA expression is increased in lesional skin of psoriasis patients. PARP2 deletion in mice attenuated IMQ-induced psoriasis-like dermatitis. NF-κB activation is suppressed in PARP2-deficient human keratinocytes. Higher estradiol in PARP2-deficient keratinocytes conveys anti-inflammatory effect.

Effects of natural products on skin inflammation caused by abnormal hormones secreted by the adrenal gland

The cortex of adrenal gland produces glucocorticoid, mineralocorticoid, and androgen. The medulla of adrenal gland secrets catecholamines. These hormones play an important role in regulating blood pressure, metabolism, and homeostasis of glucose or electrolytes. Hypersecretion or hyposecretion by the adrenal gland will cause a complex cascade of hormone effects and lead to diseases, including Addison's disease, Cushing's syndrome, and congenital adrenal cortical hyperplasia. Skin is the largest organ of body. It provides protection and acts as a barrier against external damage factors like infectious organisms, chemicals, and allergens. Endocrinologic disorders often induce cutaneous abnormalities. According to the previous evidences, natural products have the potential properties for attenuating skin disorders and improving dermatologic symptoms by inhibiting inflammation through MAPK or PI3K/AKT-dependent NF-κB pathways. The natural products may also promote skin wound healing by inhibiting the production of matrix metalloproteinase-9. We systematically searched the relevant articles from databases, including PubMed, Embase, and Cochrane library databases, to review the effects of natural products on skin disorders. This article summarized the effects of natural products on skin inflammation caused by abnormal hormone secreted by adrenal gland. And the published papers indicated that natural products might be a potential source for treating skin diseases.

Current Knowledge in Skin Metabolomics: Updates from Literature Review

Metabolomic profiling is an emerging field consisting of the measurement of metabolites in a biological system. Since metabolites can vary in relation to different stimuli, specific metabolic patterns can be closely related to a pathological process. In the dermatological setting, skin metabolomics can provide useful biomarkers for the diagnosis, prognosis, and therapy of cutaneous disorders. The main goal of the present review is to present a comprehensive overview of the published studies in skin metabolomics. A search for journal articles focused on skin metabolomics was conducted on the MEDLINE, EMBASE, Cochrane, and Scopus electronic databases. Only research articles with electronically available English full text were taken into consideration. Studies specifically focused on cutaneous microbiomes were also excluded from the present search. A total of 97 papers matched all the research criteria and were therefore considered for the present work. Most of the publications were focused on inflammatory dermatoses and immune-mediated cutaneous disorders. Skin oncology also turned out to be a relevant field in metabolomic research. Only a few papers were focused on infectious diseases and rarer genetic disorders. All the major metabolomic alterations published so far in the dermatological setting are described extensively in this review.

A Poly (Caprolactone)-Cellulose Nanocomposite Hydrogel for Transdermal Delivery of Hydrocortisone in Treating Psoriasis Vulgaris

Psoriasis vulgaris (PV) is a common chronic disease, affecting much of the population. Hydrocortisone (HCT) is currently utilized as a PV treatment; however, it is associated with undesirable side effects. The aim of this research was to create a thermo-responsive nano-hydrogel delivery system. HCT-loaded sorbitan monostearate (SMS)-polycaprolactone (PCL) nanoparticles, encapsulated with thermo-responsive hydrogel carboxymethyl cellulose (CMC), were synthesized by applying the interfacial polymer-deposition method following solvent displacement. The nanoparticles’ properties were evaluated employing Differential Scanning Colorimetry, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Zeta sizer, Ultraviolet/Visual spectroscopy, and cytotoxicity testing. The nanoparticle sizes were 110.5 nm, with polydispersity index of 0.15 and zeta potential of −58.7 mV. A drug-entrapment efficacy of 76% was attained by the HCT-loaded SMS-PCL nanoparticles and in vitro drug-release profiles showed continuous drug release over a period of 24 hrs. Keratinocyte skin cells were treated with HCT-loaded SMS-PCL nanoparticles encapsulated with CMC; the results indicated that the synthesized drug-delivery system was less toxic to the keratinocyte cells compared to HCT. The combined trials and results from the formulation of HCT-loaded SMS-PCL nanoparticles encapsulated with CMC showed evidence that this hydrogel can be utilized as a potentially invaluable formulation for transdermal drug delivery of HCT, with improved efficacy and patient conformity.

Roles Played by Stress-Induced Pathways in Driving Ethnic Heterogeneity for Inflammatory Skin Diseases

Immune-mediated skin conditions (IMSCs) are a diverse group of autoimmune diseases associated with significant disease burden. Atopic dermatitis and psoriasis are among the most common IMSCs in the United States and have disproportionate impact on racial and ethnic minorities. African American patients are more likely to develop atopic dermatitis compared to their European American counterparts; and despite lower prevalence of psoriasis among this group, African American patients can suffer from more extensive disease involvement, significant post-inflammatory changes, and a decreased quality of life. While recent studies have been focused on understanding the heterogeneity underlying disease mechanisms and genetic factors at play, little emphasis has been put on the effect of psychosocial or psychological stress on immune pathways, and how these factors contribute to differences in clinical severity, prevalence, and treatment response across ethnic groups. In this review, we explore the heterogeneity of atopic dermatitis and psoriasis between African American and European American patients by summarizing epidemiological studies, addressing potential molecular and environmental factors, with a focus on the intersection between stress and inflammatory pathways.

Hydrogel-mediated topical delivery of steroids can effectively alleviate psoriasis via attenuating the autoimmune responses

Psoriasis is a systemic, relapsing, and chronic autoimmune inflammatory disease of the skin. Topical use of betamethasone, a glucocorticoid, in the form of creams is a common treatment for psoriasis. However, topical use of these creams is challenging due to the ineffective entrapment of steroids, burst release of the entrapped drugs, poor skin permeability, and high toxicity. Herein, we present the engineering of a betamethasone-loaded topical hydrogel (B-Gel) that can efficiently entrap steroids with high spreadability, and can also maintain the sustained release of drugs. We used an imiquimod (IMQ) induced ear psoriasis model, and demonstrated that topical application of B-Gel can mitigate the autoimmune inflammation reactions, and leads to a reduction in erythema, induration, scaling, and ear thickness. As interleukin 17 (IL-17) secreting T helper 17 (Th17) cells and γδ⁺ T cells are responsible for psoriasis, B-Gel treatment witnessed a reduction in the infiltration of leukocytes, CD4⁺ T cells, Th17 T cells, and dermal γδ⁺ T cells. We further demonstrated that B-Gel mediated reduction of IL-1β, IL-17, and K16 (marker for keratinocyte proliferation) is responsible for alleviation of psoriasis. Therefore, the non-greasy nature of the hydrogel with a cooling effect provides an alternative for topical application of steroids.

A systematic review: metabolomics-based identification of altered metabolites and pathways in the skin caused by internal and external factors

The skin's ability to function optimally is affected by many diverse factors. Metabolomics has a great potential to improve our understanding of the underlying metabolic changes and the affected pathways. Therefore, the objective of this study was to review the current state of the literature and to perform further metabolic pathway analysis on the obtained data. The aim was to gain an overview of the metabolic changes under altered conditions and to identify common and different patterns as a function of the investigated factors. A cross-study comparison of the extracted studies from different databases identified 364 metabolites, whose concentrations were considerably altered by the following factor groups: irradiation, xenobiotics, aging, and skin diseases (mainly psoriasis). Using metabolic databases and pathway analysis tools the individual metabolites were assigned to the corresponding metabolic pathways and the most strongly affected signaling pathways were identified. All factors induced oxidative stress. Thus, antioxidant defense systems, especially coenzyme Q₁₀  (aging) and the glutathione system (irradiation, aging, xenobiotics) were impacted. Lipid metabolism was also impacted by all factors studied. The carnitine shuttle as part of β-oxidation was activated by all factor groups except aging. Glycolysis, Krebs (TCA) cycle and purine metabolism were mainly affected by irradiation and xenobiotics. The pentose phosphate pathway was activated and Krebs cycle was downregulated in response to oxidative stress. In summary, it can be ascertained that mainly energy metabolism, lipid metabolism, antioxidative defense and DNA repair systems were impacted by the factors studied.

The mineralocorticoid receptor in skin disease

The Mineralocorticoid Receptor (MR or NR3C2) is expressed in all cell types of the different skin compartments and can be bound and activated by glucocorticoids (GCs) with higher affinity than its closely related glucocorticoid (GC) receptor (GR or NR3C1). As both corticosteroid receptors co-express in skin, and considering the therapeutic relevance of GCs to combat skin inflammatory diseases, it was proposed that several of the major side-effects of topical GCs such as skin atrophy and delayed wound healing were due to unintended activation of the MR. Indeed, cutaneous MR blockade using genetic and pharmacological approaches in mice and human reduced the GC-associated skin atrophy in conditions of endogenous and pharmacological GC excess. While data support the safety of topical MR antagonists combined with GCs, it is crucial to address the efficacy of treatment in skin inflammatory conditions and its impact on the overall metabolism.

Phospholipase A2 enzymes represent a shared pathogenic pathway in psoriasis and pityriasis rubra pilaris

Altered epidermal differentiation along with increased keratinocyte proliferation is a characteristic feature of psoriasis and pityriasis rubra pilaris (PRP). However, despite this large degree of overlapping clinical and histologic features, the molecular signatures these skin disorders share are unknown. Using global transcriptomic profiling, we demonstrate that plaque psoriasis and PRP skin lesions have high overlap, with all differentially expressed genes in PRP relative to normal skin having complete overlap with those in psoriasis. The major common pathway shared between psoriasis and PRP involves the phospholipases PLA2G2F, PLA2G4D, and PLA2G4E, which were found to be primarily expressed in the epidermis. Gene silencing each of the 3 PLA2s led to reduction in immune responses and epidermal thickness both in vitro and in vivo in a mouse model of psoriasis, establishing their proinflammatory roles. Lipidomic analyses demonstrated that PLA2s affect mobilization of a phospholipid-eicosanoid pool, which is altered in psoriatic lesions and functions to promote immune responses in keratinocytes. Taken together, our results highlight the important role of PLA2s as regulators of epidermal barrier homeostasis and inflammation, identify PLA2s as a shared pathogenic mechanism between PRP and psoriasis, and as potential therapeutic targets for both diseases.

Glucocorticoid Resistance: Interference between the Glucocorticoid Receptor and the MAPK Signalling Pathways

Endogenous glucocorticoids (GCs) are steroid hormones that signal in virtually all cell types to modulate tissue homeostasis throughout life. Also, synthetic GC derivatives (pharmacological GCs) constitute the first-line treatment in many chronic inflammatory conditions with unquestionable therapeutic benefits despite the associated adverse effects. GC actions are principally mediated through the GC receptor (GR), a ligand-dependent transcription factor. Despite the ubiquitous expression of GR, imbalances in GC signalling affect tissues differently, and with variable degrees of severity through mechanisms that are not completely deciphered. Congenital or acquired GC hypersensitivity or resistance syndromes can impact responsiveness to endogenous or pharmacological GCs, causing disease or inadequate therapeutic outcomes, respectively. Acquired GC resistance is defined as loss of efficacy or desensitization over time, and arises as a consequence of chronic inflammation, affecting around 30% of GC-treated patients. It represents an important limitation in the management of chronic inflammatory diseases and cancer, and can be due to impairment of multiple mechanisms along the GC signalling pathway. Among them, activation of the mitogen-activated protein kinases (MAPKs) and/or alterations in expression of their regulators, the dual-specific phosphatases (DUSPs), have been identified as common mechanisms of GC resistance. While many of the anti-inflammatory actions of GCs rely on GR-mediated inhibition of MAPKs and/or induction of DUSPs, the GC anti-inflammatory capacity is decreased or lost in conditions of excessive MAPK activation, contributing to disease susceptibility in tissue- and disease- specific manners. Here, we discuss potential strategies to modulate GC responsiveness, with the dual goal of overcoming GC resistance and minimizing the onset and severity of unwanted adverse effects while maintaining therapeutic potential.

Dysregulated epigenetic modifications in psoriasis

The observed incidence of psoriasis has been gradually increasing over time (J Am Acad Dermatol, 03, 2009, 394), but the underlying pathogenic factors have remained unclear. Recent studies suggest the importance of epigenetic modification in the pathogenesis of psoriasis. Aberrant epigenetic patterns including changes in DNA methylation, histone modifications and non-coding RNA expression are observed in psoriatic skin. Reversing these epigenetic mechanisms has showed improvement in psoriatic phenotypes, making epigenetic therapy a potential avenue for psoriasis treatment. Here, we summarize relevant evidence for epigenetic dysregulation contributing to psoriasis susceptibility and pathogenesis, and the factors responsible for epigenetic modifications, providing directions for potential future clinical avenues.

The Extracellular Matrix in Skin Inflammation and Infection

The extracellular matrix (ECM) is an integral component of all organs and plays a pivotal role in tissue homeostasis and repair. While the ECM was long thought to mostly have passive functions by providing physical stability to tissues, detailed characterization of its physical structure and biochemical properties have uncovered an unprecedented broad spectrum of functions. It is now clear that the ECM not only comprises the essential building block of tissues but also actively supports and maintains the dynamic interplay between tissue compartments as well as embedded resident and recruited inflammatory cells in response to pathologic stimuli. On the other hand, certain pathogens such as bacteria and viruses have evolved strategies that exploit ECM structures for infection of cells and tissues, and mutations in ECM proteins can give rise to a variety of genetic conditions. Here, we review the composition, structure and function of the ECM in cutaneous homeostasis, inflammatory skin diseases such as psoriasis and atopic dermatitis as well as infections as a paradigm for understanding its wider role in human health.

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.

The interaction between autophagy and neuroinflammation in major depressive disorder: From pathophysiology to therapeutic implications

The past decade has revealed neuroinflammation as an important mechanism of major depressive disorder (MDD). Nod-like receptors family pyrin domain containing 3 (NLRP3) inflammasome is the key regulator interleukin-1β (IL-1β) maturation, whose activation has been reported in MDD patients and various animal models. Function as a dominant driver of neuroinflammation, NLRP3 bridges the gap between immune activation with stress exposure, and further leads to subsequent occurrence of neuropsychiatric disorders such as MDD. Of note, autophagy is a tightly regulated cellular degradation pathway that removes damaged organelles and intracellular pathogens, and maintains cellular homeostasis from varying insults. Serving as a critical cellular monitoring system, normal functioned autophagy signaling prevents excessive NLRP3 inflammasome activation and subsequent release of IL-1 family cytokines. This review will describe the current understanding of how autophagy regulates NLRP3 inflammasome activity and discuss the implications of this regulation on the pathogenesis of MDD. The extensive crosstalk between autophagy pathway and NLRP3 inflammasome is further discussed, as it is critical for developing new therapeutic strategies for MDD aimed at modulating the neuroinflammatory responses.

Pruritus in psoriasis and atopic dermatitis: current treatments and new perspectives

Psoriasis and atopic dermatitis (AD) are two common chronic inflammatory skin diseases. Although showing different etiology and clinical manifestations, patients with either disease suffer from low health-related quality of life due to pruritus (dermal itch). Recent studies have revealed that more than 85% of psoriasis patients suffer from pruritus, and it is also the dominating symptom of AD. However, as this is a non-life treating symptom, it was partly neglected for years. In this review, we focus on current findings as well as the impact and potential treatments of pruritus in these two skin diseases. We first distinguish the type of itch based on involved mediators and modulators. This clear delineation between the types of pruritus based on involved receptors and pathways allows for precise treatment. In addition, insights into recent clinical trials aimed to alleviate pruritus by targeting these receptors are presented. We also report about novel advances in combinatorial treatments, dedicated to the type of pruritus linked to a causal disease. Altogether, we suggest that only a focused treatment tailored to the primary disease and the underlying molecular signals will provide fast and sustained relief of pruritus associated with psoriasis or AD.

Inhibition of 11β-HSD1 Expression by Insulin in Skin: Impact for Diabetic Wound Healing

Chronic, non-healing wounds impose a great burden on patients, professionals and health care systems worldwide. Diabetes mellitus (DM) and obesity are globally highly prevalent metabolic disorders and increase the risk for developing chronic wounds. Glucocorticoids (GCs) are endogenous stress hormones that exert profound effects on inflammation and repair systems. 11-beta-hydroxysteroid dehydrogenase 1 (11β-HSD1) is the key enzyme which controls local GC availability in target tissues such as skin. Since treatment with GCs has detrimental side effects on skin integrity, causing atrophy and delayed wound healing, we asked whether the dysregulated expression of 11β-HSD1 and consequently local GC levels in skin contribute to delayed wound healing in obese, diabetic db/db mice. We found increased expression of 11β-HSD1 during disturbed wound healing and in the healthy skin of obese, diabetic db/db mice. Cell analysis revealed increased expression of 11β-HSD1 in fibroblasts, myeloid cells and dermal white adipose tissue from db/db mice, while expression in keratinocytes was unaffected. Among diabetes- and obesity-related factors, insulin and insulin-like growth factor 1 down-regulated 11β-HSD1 expression in fibroblasts and myeloid cells, while glucose, fatty acids, TNF-α and IL-1β did not affect it. Insulin exerted its inhibitory effect on 11β-HSD1 expression by activating PI3-kinase/Akt-signalling. Consequently, the inhibitory effect of insulin is attenuated in fibroblasts from insulin-resistant db/db mice. We conclude that insulin resistance in obesity and diabetes prevents the down-regulation of 11β-HSD1, leading to elevated endogenous GC levels in diabetic skin, which could contribute to impaired wound healing in patients with DM.

Glucocorticoid-dependent transcription in skin requires epidermal expression of the glucocorticoid receptor and is modulated by the mineralocorticoid receptor

Glucocorticoid (GC) actions are mediated through two closely related ligand-dependent transcription factors, the GC receptor (GR) and the mineralocorticoid receptor (MR). Given the wide and effective use of GCs to combat skin inflammatory diseases, it is important to understand the relative contribution of these receptors to the transcriptional response to topical GCs. We evaluated the gene expression profiles in the skin of mice with epidermal-specific loss of GR (GREKO), MR (MREKO), or both (double KO; DKO) in response to dexamethasone (Dex). The overall transcriptional response was abolished in GREKO and DKO skin suggesting dependence of the underlying dermis on the presence of epidermal GR. Indeed, the observed dermal GC resistance correlated with a constitutive decrease in GR activity and up-regulation of p38 activity in this skin compartment. Upon Dex treatment, more than 90% of differentially expressed genes (DEGs) in CO overlapped with MREKO. However, the number of DEGs was fourfold increased and the magnitude of response was higher in MREKO vs CO, affecting both gene induction and repression. Taken together our data reveal that, in the cutaneous transcriptional response to GCs mediated through endogenous receptors, epidermal GR is mandatory while epidermal MR acts as a chief modulator of gene expression.

Flexible liposomal gel dual-loaded with all-trans retinoic acid and betamethasone for enhanced therapeutic efficiency of psoriasis

Background

Psoriasis is a chronic immune-mediated inflammatory skin disease without effective treatment. The utilization of all trans-retinoic acid (TRA) and betamethasone (BT) for the treatment of psoriasis is still facing difficulties, due to their relatively poor stability, limited skin permeation, and systemic side effects. Flexible liposomes are excellent in deeper skin permeation and reducing the side effects of drugs, which is promising for effective treatment of skin disorders. This work aimed to establish dual-loaded flexible liposomal gel for enhanced therapeutic efficiency of psoriasis based on TRA and BT.

Results

Flexible liposomes co-loaded with TRA and BT were successfully prepared in our study. The characterization examination revealed that flexible liposomes featured nano-sized particles (around 70 nm), high drug encapsulation efficiency (> 98%) and sustained drug release behaviors. Flexible liposomes remarkably increased the drug skin permeation and retention as compared with free drugs. Results on HaCaT cells suggested that flexible liposomes were nontoxic, and its cellular uptake has a time-dependent manner. In vivo studies suggested the topical application of TRA and BT dual-loaded liposomal gel had the best ability to reduce the thickness of epidermal and the level of cytokines (TNF-α and IL-6), largely alleviating the symptoms of psoriasis.

Conclusions

Flexible liposomal gel dual-loaded with TRA and BT exerted a synergistic effect, which is a promising topical therapeutic for the treatment of psoriasis.

Pathogenesis of psoriasis in the "omic" era. Part I. Epidemiology, clinical manifestation, immunological and neuroendocrine disturbances

Psoriasis is a common, chronic, inflammatory, immune-mediated skin disease affecting about 2% of the world's population. According to current knowledge, psoriasis is a complex disease that involves various genes and environmental factors, such as stress, injuries, infections and certain medications. The chronic inflammation of psoriasis lesions develops upon epidermal infiltration, activation, and expansion of type 1 and type 17 Th cells. Despite the enormous progress in understanding the mechanisms that cause psoriasis, the target cells and antigens that drive pathogenic T cell responses in psoriatic lesions are still unproven and the autoimmune basis of psoriasis still remains hypothetical. However, since the identification of the Th17 cell subset, the IL-23/Th17 immune axis has been considered a key driver of psoriatic inflammation, which has led to the development of biologic agents that target crucial elements of this pathway. Here we present the current understanding of various aspects in psoriasis pathogenesis.

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.

Adalimumab in Psoriasis: How Much Is Enough?

Biologic therapies targeting tumor necrosis factor have revolutionized treatment of immune-mediated inflammatory diseases such as psoriasis, but optimal dosing and appropriate use of therapeutic drug monitoring are not yet fully understood. Wilkinson et al. explore these questions in a real-world psoriasis cohort on adalimumab monotherapy, defining a therapeutic range and finding value in early measurement for predicting clinical response.

Glucocorticoids and Glucocorticoid-Induced-Leucine-Zipper (GILZ) in Psoriasis

Psoriasis is a prevalent chronic inflammatory human disease initiated by impaired function of immune cells and epidermal keratinocytes, resulting in increased cytokine production and hyperproliferation, leading to skin lesions. Overproduction of Th1- and Th17-cytokines including interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-23, IL-17, and IL-22, is a major driver of the disease. Glucocorticoids (GCs) represent the mainstay protocol for treating psoriasis as they modulate epidermal differentiation and are potent anti-inflammatory compounds. The development of safer GC-based therapies is a high priority due to potentially severe adverse effects associated with prolonged GC use. Specific efforts have focused on downstream anti-inflammatory effectors of GC-signaling such as GC-Induced-Leucine-Zipper (GILZ), which suppresses Th17 responses and antagonizes multiple pro-inflammatory signaling pathways involved in psoriasis, including AP-1, NF-κB, STAT3, and ROR-γt. Here we review evidence regarding defective GC signaling, GC receptor (GR) function, and GILZ in psoriasis. We discuss seemingly contradicting data on the loss- and gain-of-function of GILZ in the imiquimod-induced mouse model of psoriasis. We also present potential therapeutic strategies aimed to restore GC-related pathways.

Transcriptomic Network Interactions in Human Skin Treated with Topical Glucocorticoid Clobetasol Propionate

Glucocorticoids are the most frequently used anti-inflammatory drugs in dermatology. However, the molecular signature of glucocorticoids and their receptor in human skin is largely unknown. Our validated bioinformatics analysis of human skin transcriptome induced by topical glucocorticoid clobetasol propionate (CBP) in healthy volunteers identified numerous unreported glucocorticoid-responsive genes, including over a thousand noncoding RNAs. We observed sexual and racial dimorphism in the CBP response including a shift toward IFN-α/IFN-γ and IL-6/Jak/Signal transducer and activator of transcription (STAT) 3 signaling in female skin; and a larger response to CBP in African-American skin. Weighted gene coexpression network analysis unveiled a dense skin network of 41 transcription factors including circadian Kruppel-like factor 9 (KLF9), and ∼260 of their target genes enriched for functional pathways representative of the entire CBP transcriptome. Using keratinocytes with Kruppel-like factor 9 knockdown, we revealed a feedforward loop in glucocorticoid receptor signaling, previously unreported. Interestingly, many of the CBP-regulated transcription factors were involved in the control of development, metabolism, circadian clock; and 80% of them were associated with skin aging showing similarities between glucocorticoid-treated and aged skin. Overall, these findings indicate that glucocorticoid receptor acts as an important regulator of gene expression in skin-both at the transcriptional and posttranscriptional level-via multiple mechanisms including regulation of noncoding RNAs and multiple core transcription factors.

PI3K inhibitors protect against glucocorticoid-induced skin atrophy

Background

Skin atrophy is a major adverse effect of topical glucocorticoids. We recently reported that REDD1 (regulated in development and DNA damage 1) and FKBP51 (FK506 binding protein 5), negative regulators of mTOR/Akt signaling, are induced by glucocorticoids in mouse and human skin and are central drivers of steroid skin atrophy. Thus, we hypothesized that REDD1/FKBP51 inhibitors could protect skin against catabolic effects of glucocorticoids.

Methods

Using drug repurposing approach, we screened LINCS library (http://lincsproject.org/LINCS/) to identify repressors of REDD1/FKBP51 expression. Candidate compounds were tested for their ability to inhibit glucocorticoid-induced REDD1/FKBP51 expression in human primary/immortalized keratinocytes and in mouse skin. Reporter gene expression, microarray, and chromatin immunoprecipitation were employed to evaluate effect of these inhibitors on the glucocorticoid receptor (GR) signaling.

Findings

Bioinformatics analysis unexpectedly identified phosphoinositide-3-kinase (PI3K)/mTOR/Akt inhibitors as a pharmacological class of REDD1/FKBP51 repressors. Selected PI3K/mTOR/Akt inhibitors-Wortmannin (WM), LY294002, AZD8055, and two others indeed blocked REDD1/FKBP51expression in human keratinocytes. PI3K/mTOR/Akt inhibitors also modified global effect of glucocorticoids on trascriptome, shifting it towards therapeutically important transrepression; negatively impacted GR phosphorylation; nuclear translocation; and GR loading on REDD1/FKBP51 gene promoters. Further, topical application of LY294002 together with glucocorticoid fluocinolone acetonide (FA) protected mice against FA-induced proliferative block and skin atrophy but did not alter the anti-inflammatory activity of FA in ear edema test.

Interpretation

Our results built a strong foundation for development of safer GR-targeted therapies for inflammatory skin diseases using combination of glucocorticoids with PI3K/mTOR/Akt inhibitors.

Fund

Work is supported by NIH grants R01GM112945, R01AI125366, and HESI-THRIVE foundation.

Deletion of the glucocorticoid receptor chaperone FKBP51 prevents glucocorticoid-induced skin atrophy

FKBP51 (FK506-binding protein 51) is a known co-chaperone and regulator of the glucocorticoid receptor (GR), which usually attenuates its activity. FKBP51 is one of the major GR target genes in skin, but its role in clinical effects of glucocorticoids is not known. Here, we used FKBP51 knockout (KO) mice to determine FKBP51's role in the major adverse effect of topical glucocorticoids, skin atrophy. Unexpectedly, we found that all skin compartments (epidermis, dermis, dermal adipose and CD34+ stem cells) in FKBP51 KO animals were much more resistant to glucocorticoid-induced hypoplasia. Furthermore, despite the absence of inhibitory FKBP51, the basal level of expression and glucocorticoid activation of GR target genes were not increased in FKBP51 KO skin or CRISPR/Cas9-edited FKBP51 KO HaCaT human keratinocytes. FKBP51 is known to negatively regulate Akt and mTOR. We found a significant increase in AktSer473 and mTORSer2448 phosphorylation and downstream pro-growth signaling in FKBP51-deficient keratinocytes in vivo and in vitro. As Akt/mTOR-GR crosstalk is usually negative in skin, our results suggest that Akt/mTOR activation could be responsible for the lack of increased GR function and resistance of FKBP51 KO mice to the steroid-induced skin atrophy.

Roles of the Glucocorticoid and Mineralocorticoid Receptors in Skin Pathophysiology

The nuclear hormone receptor (NR) superfamily comprises approximately 50 evolutionarily conserved proteins that play major roles in gene regulation by prototypically acting as ligand-dependent transcription factors. Besides their central role in physiology, NRs have been largely used as therapeutic drug targets in many chronic inflammatory conditions and derivatives of their specific ligands, alone or in combination, are frequently prescribed for the treatment of skin diseases. In particular, glucocorticoids (GCs) are the most commonly used compounds for treating prevalent skin diseases such as psoriasis due to their anti-proliferative and anti-inflammatory actions. However, and despite their therapeutic efficacy, the long-term use of GCs is limited because of the cutaneous adverse effects including atrophy, delayed wound healing, and increased susceptibility to stress and infections. The GC receptor (GR/NR3C1) and the mineralocorticoid receptor (MR/NR3C2) are members of the NR subclass NR3C that are highly related, both structurally and functionally. While the GR is ubiquitously expressed and is almost exclusively activated by GCs; an MR has a more restricted tissue expression pattern and can bind GCs and the mineralocorticoid aldosterone with similar high affinity. As these receptors share 95% identity in their DNA binding domains; both can recognize the same hormone response elements; theoretically resulting in transcriptional regulation of the same target genes. However, a major mechanism for specific activation of GRs and/or MRs is at the pre-receptor level by modulating the local availability of active GCs. Furthermore, the selective interactions of each receptor with spatio-temporally regulated transcription factors and co-regulators are crucial for the final transcriptional outcome. While there are abundant genome wide studies identifying GR transcriptional targets in a variety of tissue and cell types; including keratinocytes; the data for MR is more limited thus far. Our group and others have studied the role of GRs and MRs in skin development and disease by generating and characterizing mouse and cellular models with gain- and loss-of-function for each receptor. Both NRs are required for skin barrier competence during mouse development and also play a role in adult skin homeostasis. Moreover, the combined loss of epidermal GRs and MRs caused a more severe skin phenotype relative to single knock-outs (KOs) in developing skin and in acute inflammation and psoriasis, indicating that these corticosteroid receptors play cooperative roles. Understanding GR- and MR-mediated signaling in skin should contribute to deciphering their tissue-specific relative roles and ultimately help to improve GC-based therapies.

Epidermal glucocorticoid and mineralocorticoid receptors act cooperatively to regulate epidermal development and counteract skin inflammation

Endogenous and synthetic glucocorticoids (GCs) regulate epidermal development and combat skin inflammatory diseases. GC actions can be mediated through the GC receptor (GR) and/or the mineralocorticoid receptor (MR), highly homologous ligand-activated transcription factors. While the role of GR as a potent anti-inflammatory mediator is well known, that of MR is not as clear, nor is whether these receptors cooperate or antagonize each other in the epidermis. To address this, we generated mice with epidermal-specific loss of both receptors (double knockout, DKO), and analyzed the phenotypical and functional consequences relative to single KOs or controls (CO). At birth, DKO epidermis displayed a phenotype of defective differentiation and inflammation, which was more severe than in either single KO, featuring neutrophil-containing infiltrates, and gene dysregulation characteristic of human psoriatic lesions. This phenotype resolved spontaneously. However, in adulthood, single or combined loss of GC receptors increased susceptibility to inflammation and hyperproliferation triggered by phorbol ester which, different to CO, was not effectively counteracted by GC treatment. Also, DKOs were more susceptible to imiquimod-induced psoriasis than CO showing severe defective epidermal differentiation and microabcesses while single KOs showed an intermediate response. Immortalized DKO keratinocytes featured increased proliferation kinetics and reduced cell size, a unique phenotype relative to single KO cells. The lack of GR and MR in keratinocytes, individual or combined, caused constitutive increases in p38 and ERK activities, which were partially reversed upon reinsertion of receptors into DKO cells. DKO keratinocytes also displayed significant increases in AP-1 and NF-κB transcriptional activities, which were partially rescued by ERK and p38 inhibition, respectively. Reinsertion of GR and MR in DKO keratinocytes resulted in physical and cooperative functional interactions that restored the transcriptional response to GCs. In conclusion, our data have revealed that epidermal GR and MR act cooperatively to regulate epidermal development and counteract skin inflammation.

How UV Light Touches the Brain and Endocrine System Through Skin, and Why

The skin, a self-regulating protective barrier organ, is empowered with sensory and computing capabilities to counteract the environmental stressors to maintain and restore disrupted cutaneous homeostasis. These complex functions are coordinated by a cutaneous neuro-endocrine system that also communicates in a bidirectional fashion with the central nervous, endocrine, and immune systems, all acting in concert to control body homeostasis. Although UV energy has played an important role in the origin and evolution of life, UV absorption by the skin not only triggers mechanisms that defend skin integrity and regulate global homeostasis but also induces skin pathology (e.g., cancer, aging, autoimmune responses). These effects are secondary to the transduction of UV electromagnetic energy into chemical, hormonal, and neural signals, defined by the nature of the chromophores and tissue compartments receiving specific UV wavelength. UV radiation can upregulate local neuroendocrine axes, with UVB being markedly more efficient than UVA. The locally induced cytokines, corticotropin-releasing hormone, urocortins, proopiomelanocortin-peptides, enkephalins, or others can be released into circulation to exert systemic effects, including activation of the central hypothalamic-pituitary-adrenal axis, opioidogenic effects, and immunosuppression, independent of vitamin D synthesis. Similar effects are seen after exposure of the eyes and skin to UV, through which UVB activates hypothalamic paraventricular and arcuate nuclei and exerts very rapid stimulatory effects on the brain. Thus, UV touches the brain and central neuroendocrine system to reset body homeostasis. This invites multiple therapeutic applications of UV radiation, for example, in the management of autoimmune and mood disorders, addiction, and obesity.

Past, present and future of in vitro 3D reconstructed inflammatory skin models to study psoriasis

Psoriasis is a common chronic inflammatory skin disease with a significant socio-economic impact that can greatly affect the patients' quality of life. The prevailing dogma in the aetiology and pathophysiology of this complex disease is that skin cells, immune cells and environmental factors contribute to psoriatic skin inflammation. For a better understanding of the disease pathogenesis, models are required that mimic the disease and which can be used to develop therapeutics. Over the last decades, in vitro human reconstructed skin models have been widely used in dermatological research and have also been developed to mimic psoriatic skin. This viewpoint summarizes the most commonly used in vitro models and the latest accomplishments for the combination of the dermal and epidermal compartments with other cell types and factors that are important players in the psoriatic skin environment. We aim to critically list the most complete and best-validated models that include major psoriasis hallmarks with regard to gene and protein expression profile and epidermal morphology, but also discuss the shortcoming of the current models. This viewpoint intends to guide the development of in vitro 3D skin models that faithfully mimic all features of psoriatic skin. Such model will enable fundamental biological studies for a better understanding of the aetiology and pathophysiology of psoriasis and aid in novel therapeutic target identification and drug development studies.

Rapamycin Modulates Glucocorticoid Receptor Function, Blocks Atrophogene REDD1, and Protects Skin from Steroid Atrophy

Glucocorticoids have excellent therapeutic properties; however, they cause significant adverse atrophogenic effects. The mTORC1 inhibitor REDD1 has been recently identified as a key mediator of glucocorticoid-induced atrophy. We performed computational screening of a connectivity map database to identify putative REDD1 inhibitors. The top selected candidates included rapamycin, which was unexpected because it inhibits pro-proliferative mTOR signaling. Indeed, rapamycin inhibited REDD1 induction by glucocorticoids dexamethasone, clobetasol propionate, and fluocinolone acetonide in keratinocytes, lymphoid cells, and mouse skin. We also showed blunting of glucocorticoid-induced REDD1 induction by either catalytic inhibitor of mTORC1/2 (OSI-027) or genetic inhibition of mTORC1, highlighting role of mTOR in glucocorticoid receptor signaling. Moreover, rapamycin inhibited glucocorticoid receptor phosphorylation, nuclear translocation, and loading on glucocorticoid-responsive elements in REDD1 promoter. Using microarrays, we quantified a global effect of rapamycin on gene expression regulation by fluocinolone acetonide in human keratinocytes. Rapamycin inhibited activation of glucocorticoid receptor target genes yet enhanced the repression of pro-proliferative and proinflammatory genes. Remarkably, rapamycin protected skin against glucocorticoid-induced atrophy but had no effect on the glucocorticoid anti-inflammatory activity in different in vivo models, suggesting the clinical potential of combining rapamycin with glucocorticoids for the treatment of inflammatory diseases.

The Genetics of Chronic Itch: Gene Expression in the Skin of Patients with Atopic Dermatitis and Psoriasis with Severe Itch

To identify itch-related mediators and receptors that are differentially expressed in pruritic skin, we used RNA sequencing to analyze the complete transcriptome in skin from paired itchy, lesional and nonitchy, nonlesional skin biopsies from 25 patients with atopic dermatitis and 25 patients with psoriasis and site-matched biopsies from 30 healthy controls. This analysis identified 18,000 differentially expressed genes common between itchy atopic and psoriatic skin compared with healthy skin. Of those, almost 2,000 genes were differentially expressed between itchy and nonitchy skin in atopic and psoriatic subjects. Overexpression of several genes, such as phospholipase A2 IVD, substance P, voltage-gated sodium channel 1.7, and transient receptor potential (TRP) vanilloid 1, in itchy skin was positively correlated with itch intensity ratings in both atopic dermatitis and psoriasis. Cytokines such as IL-17A, IL-23A, and IL-31 had elevated gene transcript levels in both itchy atopic and psoriatic skin. However, expression of genes for TRP vanilloid 2, TRP ankyrin 1, protease-activated receptor 2, protease-activated receptor 4, and IL-10 was found to be increased only in pruritic atopic skin, whereas expression of genes for TRP melastatin 8, TRP vanilloid 3, phospholipase C, and IL-36α/γ was elevated only in pruritic psoriatic skin. This "itchscriptome" analysis will lead to an increased understanding of the molecular mechanisms of chronic pruritus and provide targets for itch treatment irrespective of disease state.