Tissa Hata

Tight junction defects in patients with atopic dermatitis.

BACKGROUND Atopic dermatitis (AD) is characterized by dry skin and a hyperactive immune response to allergens, 2 cardinal features that are caused in part by epidermal barrier defects. Tight junctions (TJs) reside immediately below the stratum corneum and regulate the selective permeability of the paracellular pathway. OBJECTIVE We evaluated the expression/function of the TJ protein claudin-1 in epithelium from AD and nonatopic subjects and screened 2 American populations for single nucleotide polymorphisms in the claudin-1 gene (CLDN1). METHODS Expression profiles of nonlesional epithelium from patients with extrinsic AD, nonatopic subjects, and patients with psoriasis were generated using Illuminas BeadChips. Dysregulated intercellular proteins were validated by means of tissue staining and quantitative PCR. Bioelectric properties of epithelium were measured in Ussing chambers. Functional relevance of claudin-1 was assessed by using a knockdown approach in primary human keratinocytes. Twenty-seven haplotype-tagging SNPs in CLDN1 were screened in 2 independent populations with AD. RESULTS We observed strikingly reduced expression of the TJ proteins claudin-1 and claudin-23 only in patients with AD, which were validated at the mRNA and protein levels. Claudin-1 expression inversely correlated with T(H)2 biomarkers. We observed a remarkable impairment of the bioelectric barrier function in AD epidermis. In vitro we confirmed that silencing claudin-1 expression in human keratinocytes diminishes TJ function while enhancing keratinocyte proliferation. Finally, CLDN1 haplotype-tagging SNPs revealed associations with AD in 2 North American populations. CONCLUSION Collectively, these data suggest that an impairment in tight junctions contributes to the barrier dysfunction and immune dysregulation observed in AD subjects and that this may be mediated in part by reductions in claudin-1.

Filaggrin mutations that confer risk of atopic dermatitis confer greater risk for eczema herpeticum.

BACKGROUND Loss-of-function null mutations R501X and 2282del4 in the skin barrier gene, filaggrin (FLG), represent the most replicated genetic risk factors for atopic dermatitis (AD). Associations have not been reported in African ancestry populations. Atopic dermatitis eczema herpeticum (ADEH) is a rare but serious complication of AD resulting from disseminated cutaneous herpes simplex virus infections. OBJECTIVE We aimed to determine whether FLG polymorphisms contribute to ADEH susceptibility. METHODS Two common loss-of-function mutations plus 9 FLG single nucleotide polymorphisms were genotyped in 278 European American patients with AD, of whom 112 had ADEH, and 157 nonatopic controls. Replication was performed on 339 African American subjects. RESULTS Significant associations were observed for both the R501X and 2282del4 mutations and AD among European American subjects (P = 1.46 x 10(-5), 3.87 x 10(-5), respectively), but the frequency of the R501X mutation was 3 times higher (25% vs 9%) for ADEH than for AD without eczema herpeticum (EH) (odds ratio [OR], 3.4; 1.7-6.8; P = .0002). Associations with ADEH were stronger with the combined null mutations (OR, 10.1; 4.7-22.1; P = 1.99 x 10(-11)). Associations with the R501X mutation were replicated in the African American population; the null mutation was absent among healthy African American subjects, but present among patients with AD (3.2%; P = .035) and common among patients with ADEH (9.4%; P = .0049). However, the 2282del4 mutation was absent among African American patients with ADEH and rare (<1%) among healthy individuals. CONCLUSION The R501X mutation in the gene encoding filaggrin, one of the strongest genetic predictors of AD, confers an even greater risk for ADEH in both European and African ancestry populations, suggesting a role for defective skin barrier in this devastating condition.

Phenotype of Atopic Dermatitis Subjects with a History of Eczema Herpeticum

BACKGROUND A subset of subjects with atopic dermatitis (AD) are susceptible to serious infections with herpes simplex virus, called eczema herpeticum, or vaccina virus, called eczema vaccinatum. OBJECTIVE This National Institute of Allergy and Infectious Diseases-funded multicenter study was performed to establish a database of clinical information and biologic samples on subjects with AD with and without a history of eczema herpeticum (ADEH(+) and ADEH(-) subjects, respectively) and healthy control subjects. Careful phenotyping of AD subsets might suggest mechanisms responsible for disseminated viral infections and help identify at-risk individuals. METHODS We analyzed the data from 901 subjects (ADEH(+) subjects, n = 134; ADEH(-) subjects, n = 419; healthy control subjects, n = 348) enrolled between May 11, 2006, and September 16, 2008, at 7 US medical centers. RESULTS ADEH(+) subjects had more severe disease based on scoring systems (Eczema Area and Severity Index and Rajka-Langeland score), body surface area affected, and biomarkers (circulating eosinophil counts and serum IgE, thymus and activation-regulated chemokine, and cutaneous T cell-attracting chemokine) than ADEH(-) subjects (P < .001). ADEH(+) subjects were also more likely to have a history of food allergy (69% vs 40%, P < .001) or asthma (64% vs 44%, P < .001) and were more commonly sensitized to many common allergens (P < .001). Cutaneous infections with Staphylococcus aureus or molluscum contagiosum virus were more common in ADEH(+) subjects (78% and 8%, respectively) than in ADEH(-) subjects (29% and 2%, respectively; P < .001). CONCLUSION Subjects with AD in whom eczema herpeticum develops have more severe T(H)2-polarized disease with greater allergen sensitization and more commonly have a history of food allergy, asthma, or both. They are also much more likely to experience cutaneous infections with S. aureus or molluscum contagiosum.

Dermal adipocytes protect against invasive Staphylococcus aureus skin infection

Skin infection triggers fat responses Obesity is associated with chronic inflammation, but does fat tissue offer protection during infection? Zhang et al. noticed that the fat layers in the skin of mice thickened after inoculation with the pathogenic bacterium Staphylococcus aureus (see the Perspective by Alcorn and Kolls). Mutant mice incapable of forming new fat cells were more susceptible to infection. The differentiating fat cells secreted a small-molecule peptide called cathelicidin, specifically in response to the infection. By contrast, mature fat cells produce less cathelicidin, and are thus less protective. Science, this issue p. 67; see also p. 26 The subcutaneous fat layer thickens during infection and stimulates adipocytes to secrete a protective peptide. [Also see Perspective by Alcorn and Kolls] Adipocytes have been suggested to be immunologically active, but their role in host defense is unclear. We observed rapid proliferation of preadipocytes and expansion of the dermal fat layer after infection of the skin by Staphylococcus aureus. Impaired adipogenesis resulted in increased infection as seen in Zfp423nur12 mice or in mice given inhibitors of peroxisome proliferator–activated receptor γ. This host defense function was mediated through the production of cathelicidin antimicrobial peptide from adipocytes because cathelicidin expression was decreased by inhibition of adipogenesis, and adipocytes from Camp−/− mice lost the capacity to inhibit bacterial growth. Together, these findings show that the production of an antimicrobial peptide by adipocytes is an important element for protection against S. aureus infection of the skin.

Genetic variants in thymic stromal lymphopoietin are associated with atopic dermatitis and eczema herpeticum

computer instead of at the patient makes care impersonal.’’ Two respondents commented that training programs for clinicians need to be meaningful and efficient, that all clinicians (and not just hospitalists) need to have access to health information technology, and that quantity and diversity made currently available information online daunting to navigate. Do physician researchers have a different perspective on desirable features in an EMR system compared with those who spend their time exclusively in the clinic? This question was explored by comparing the responses of the 2 groups to the questions ‘‘How can informatics be used to make medical care more personalized?’’ and ‘‘How can informatics help translate bench findings to clinical practice?’’ Physician researchers included the following 2 choices in their top 6 more often than those who spent their time mainly in the clinic: (1) the ability to exploit bioinformatic/genetic information to improve care (50% vs 28%; P 5 .03, x) and (2) the need to improve informatics methods (60% vs 42%; but P 5 .09). On-the-field clinical providers are valuable resources to facilitate refinement of health informatics technology to personalize medicine. Actively involving practicing physicians in the design, selection, and deployment of EMR systems is necessary for meaningful adoption and consequent improvement in health care. Deendayal Dinakarpandian, MD, PhD, MS Arthur R. Williams, PhD, MA(Econ), MPA Chitra Dinakar, MD From the School of Computing and Engineering, University of Missouri–Kansas City; the Center for Health Outcomes and Health Services Research, Children’s Mercy Hospitals and Clinics and University of Missouri Medical School, Kansas City; and the Division of Allergy and Immunology, Children’s Mercy Hospitals and Clinics, University of Missouri–Kansas City, Kansas City, Mo. E-mail: cdinakar@cmh.edu. Disclosure of potential conflict of interest: C. Dinakar is Chair of the Health Outcomes, Education, Delivery and Quality (HEDQ) Interest Section of the American Academy of Allergy, Asthma & Immunology and is on the Programming Committee of the American College of Allergy, Asthma and Immunology. The rest of the authors have declared that they have no conflict of interest.

Antimicrobials from human skin commensal bacteria protect against Staphylococcus aureus and are deficient in atopic dermatitis

Commensal skin bacteria produce previously unknown antimicrobial peptides that can inhibit Staphylococcus aureus colonization of atopic dermatitis subjects. Bacterial biological warfare in atopic dermatitis Normal human skin is colonized by a variety of bacteria, which typically do not perturb the host. However, Staphylococcus aureus is known to aggravate symptoms of atopic dermatitis. Nakatsuji et al. report that other strains of Staphylococcus residing on the skin of healthy individuals produce a novel antimicrobial peptide that can inhibit S. aureus growth. Colonization of pigskin or mice with these protective commensals reduced S. aureus replication. Autologous bacterial transplant in a small number of atopic dermatitis patients drastically reduced S. aureus skin burden. This commensal skin transplant is already approved by the U.S. Food and Drug Administration, with a clinical trial underway. The microbiome can promote or disrupt human health by influencing both adaptive and innate immune functions. We tested whether bacteria that normally reside on human skin participate in host defense by killing Staphylococcus aureus, a pathogen commonly found in patients with atopic dermatitis (AD) and an important factor that exacerbates this disease. High-throughput screening for antimicrobial activity against S. aureus was performed on isolates of coagulase-negative Staphylococcus (CoNS) collected from the skin of healthy and AD subjects. CoNS strains with antimicrobial activity were common on the normal population but rare on AD subjects. A low frequency of strains with antimicrobial activity correlated with colonization by S. aureus. The antimicrobial activity was identified as previously unknown antimicrobial peptides (AMPs) produced by CoNS species including Staphylococcus epidermidis and Staphylococcus hominis. These AMPs were strain-specific, highly potent, selectively killed S. aureus, and synergized with the human AMP LL-37. Application of these CoNS strains to mice confirmed their defense function in vivo relative to application of nonactive strains. Strikingly, reintroduction of antimicrobial CoNS strains to human subjects with AD decreased colonization by S. aureus. These findings show how commensal skin bacteria protect against pathogens and demonstrate how dysbiosis of the skin microbiome can lead to disease.

Cathelicidin antimicrobial peptide LL-37 in psoriasis enables keratinocyte reactivity against TLR9 ligands

Here we show that keratinocytes in psoriatic lesional skin express increased Toll-like receptor (TLR) 9 that similarly localizes with elevated expression of the cathelicidin antimicrobial peptide LL-37. In culture, normal human keratinocytes exposed to LL-37 increased TLR9 expression. Furthermore, when keratinocytes were exposed to LL-37 and subsequently treated with TLR9 ligands such as CpG or genomic DNA, keratinocytes greatly increased production of type I interferons. This response mimicked observations in the epidermis of psoriatic lesional skin as keratinocytes in psoriatic lesions produce greater amounts of interferon-β than normal skin lacking LL-37. The mechanism for induction of type I interferons in keratinocytes was dependent on TLR9 expression but not on a DNA-LL-37 complex. These findings suggest that keratinocytes recognize and respond to DNA and can actively participate in contributing to the immunological environment that characterizes psoriasis.

The antimicrobial protein REG3A regulates keratinocyte proliferation and differentiation after skin injury.

Epithelial keratinocyte proliferation is an essential element of wound repair, and abnormal epithelial proliferation is an intrinsic element in the skin disorder psoriasis. The factors that trigger epithelial proliferation in these inflammatory processes are incompletely understood. Here we have shown that regenerating islet-derived protein 3-alpha (REG3A) is highly expressed in keratinocytes during psoriasis and wound repair and in imiquimod-induced psoriatic skin lesions. The expression of REG3A by keratinocytes is induced by interleukin-17 (IL-17) via activation of keratinocyte-encoded IL-17 receptor A (IL-17RA) and feeds back on keratinocytes to inhibit terminal differentiation and increase cell proliferation by binding to exostosin-like 3 (EXTL3) followed by activation of phosphatidylinositol 3 kinase (PI3K) and the kinase AKT. These findings reveal that REG3A, a secreted intestinal antimicrobial protein, can promote skin keratinocyte proliferation and can be induced by IL-17. This observation suggests that REG3A may mediate the epidermal hyperproliferation observed in normal wound repair and in psoriasis.

Human atopic dermatitis complicated by eczema herpeticum is associated with abnormalities in IFN-γ response

BACKGROUND The basis for increased susceptibility of patients with atopic dermatitis (AD) to develop disseminated viral skin infections such as eczema herpeticum (AD with a history of eczema herpeticum, ADEH(+)) is poorly understood. OBJECTIVE We sought to determine whether subjects with AD prone to disseminated viral skin infections have defects in their IFN responses. METHODS GeneChip profiling was used to identify differences in gene expression of PBMCs from patients with ADEH(+) compared with patients with AD without a history of eczema herpeticum (ADEH(-)) and nonatopic controls. Key differences in protein expression were verified by enzyme-linked immunosorbent spot assay and/or ELISA. Clinical relevance was further demonstrated by a mouse model of disseminated viral skin infection and genetic association analysis for genetic variants in IFNG and IFNGR1 and ADEH among 435 cases and controls. RESULTS We demonstrate by global gene expression analysis selective transcriptomic changes within the IFN superfamily of PBMCs from subjects with ADEH(+) reflecting low IFN-γ and IFN-γ receptor gene expression. IFN-γ protein production was also significantly lower in patients with ADEH(+) (n = 24) compared with patients with ADEH(-) (n = 20) and nonatopic controls (n = 20). IFN-γ receptor knockout mice developed disseminated viral skin infection after epicutaneous challenge with vaccinia virus. Genetic variants in IFNG and IFNGR1 single nucleotide polymorphisms (SNPs) were significantly associated with ADEH (112 cases, 166 controls) and IFN-γ production: a 2-SNP (A-G) IFNGR1 haplotype (rs10457655 and rs7749390) showed the strongest association with a reduced risk of ADEH+ (13.2% ADEH(+) vs 25.5% ADEH(-); P = .00057). CONCLUSION Patients with ADEH(+) have reduced IFN-γ production, and IFNG and IFNGR1 SNPs are significantly associated with ADEH(+) and may contribute to an impaired immune response to herpes simplex virus.

Rosacea: part I. Introduction, categorization, histology, pathogenesis, and risk factors.

Rosacea is a chronic inflammatory skin condition that affects approximately 16 million Americans. Four distinct subtypes of rosacea have been recognized, with transient and nontransient facial flushing, telangiectasia, and inflammatory papules and pustules being among the more commonly recognized features. Although the exact pathogenesis of rosacea is unknown, dysregulation of the innate immune system, overgrowth of commensal skin organisms, and aberrant neurovascular signaling may all have a role in promoting the clinical features of rosacea.