Aberrant Expression of Bacterial Pattern Recognition Receptor NOD2 of Basophils and Microbicidal Peptides in Atopic Dermatitis

Risk of Inflammatory Bowel Disease in Patients With Atopic Dermatitis

Importance

Data on the association between atopic dermatitis (AD) and inflammatory bowel disease (IBD) are inconsistent. Few studies have examined the association of AD or AD severity with risk of ulcerative colitis (UC) and Crohn disease (CD) separately.

Objectives

To examine the risk of new-onset IBD, UC, and CD in children and adults with AD.

Design, Setting, and Participants

This population-based cohort study assessed patients with AD matched with up to 5 controls on age, practice, and index date. Treatment exposure was used as a proxy for AD severity. Data were retrieved from The Health Improvement Network, a UK electronic medical record database, for January 1, 1994, to February 28, 2015. Data analysis was performed from January 8, 2020, to June 30, 2023.

Main Outcomes and Measures

Outcomes of interest were incident IBD, UC, and CD. Logistic regression was used to examine the risk for each outcome in children and adults with AD compared with controls.

Results

A total of 1 809 029 pediatric controls were matched to 409 431 children with AD (93.2% mild, 5.5% moderate, and 1.3% severe). The pediatric cohort ranged in median age from 4 to 5 years (overall range, 1-10 years), was predominantly male (936 750 [51.8%] controls, 196 996 [51.6%] with mild AD, 11 379 [50.7%] with moderate AD, and 2985 [56.1%] with severe AD), and with similar socioeconomic status. A total of 2 678 888 adult controls were matched to 625 083 adults with AD (65.7% mild, 31.4% moderate, and 2.9% severe). The adult cohort ranged in median age from 45 to 50 years (overall range, 30-68 years) and was predominantly female (1 445 589 [54.0%] controls, 256 071 [62.3%] with mild AD, 109 404 [55.8%] with moderate AD, and 10 736 [59.3%] with severe AD). In fully adjusted models, children with AD had a 44% increased risk of IBD (hazard ratio [HR], 1.44; 95% CI, 1.31-1.58) and a 74% increased risk of CD (HR, 1.74; 95% CI, 1.54-1.97), which increased with worsening AD; however, they did not have increased risk of UC (HR, 1.09; 95% CI, 0.94-1.27) except for those with severe AD (HR, 1.65; 95% CI, 1.02-2.67). Adults with AD had a 34% (HR, 1.34; 95% CI, 1.27-1.40) increased risk of IBD, a 36% (HR, 1.36; 95% CI, 1.26-1.47) increased risk of CB, and a 32% (HR, 1.32; 95% CI, 1.24-1.41) increased risk of UC, with risk increasing with worsening AD.

Conclusion and Relevance

In this cohort study, children and adults with AD had an increased risk of IBD, with risk varying by age, AD severity, and IBD subtype. These findings provide new insights into the association between AD and IBD. Clinicians should be aware of these risks, particularly when selecting systemic treatments for AD in patients who may have coincident gastrointestinal symptoms.

Pathogenesis of allergic diseases and implications for therapeutic interventions

Allergic diseases such as allergic rhinitis (AR), allergic asthma (AAS), atopic dermatitis (AD), food allergy (FA), and eczema are systemic diseases caused by an impaired immune system. Accompanied by high recurrence rates, the steadily rising incidence rates of these diseases are attracting increasing attention. The pathogenesis of allergic diseases is complex and involves many factors, including maternal-fetal environment, living environment, genetics, epigenetics, and the body's immune status. The pathogenesis of allergic diseases exhibits a marked heterogeneity, with phenotype and endotype defining visible features and associated molecular mechanisms, respectively. With the rapid development of immunology, molecular biology, and biotechnology, many new biological drugs have been designed for the treatment of allergic diseases, including anti-immunoglobulin E (IgE), anti-interleukin (IL)-5, and anti-thymic stromal lymphopoietin (TSLP)/IL-4, to control symptoms. For doctors and scientists, it is becoming more and more important to understand the influencing factors, pathogenesis, and treatment progress of allergic diseases. This review aimed to assess the epidemiology, pathogenesis, and therapeutic interventions of allergic diseases, including AR, AAS, AD, and FA. We hope to help doctors and scientists understand allergic diseases systematically.

Potential biomarkers of atopic dermatitis

Atopic dermatitis (AD) is a chronic, recurrent inflammatory skin disease with a wide range of heterogeneity. Accurate biomarkers or predictors are the keys to instructing personalized tailored precise treatment. The development of technology such as transcriptomics, genomics, and proteomics provides novel insights into the possibility to find potential biomarkers. Meanwhile, emerging minimally invasive methods such as tape stripping were used to reveal different profiles of patients' skin without biopsy. Several potential biomarkers or predictors have been found. In this review, we summarized the current development of potential biomarkers of AD. Nitric oxide synthase 2/inducible nitric oxide synthase (NOS2/iNOS), human beta-defensin-2 (hBD-2), and matrix metalloproteinases 8/9 (MMP8/9) may be the candidate biomarkers for AD diagnosis. Filaggrin (FLG) gene mutation increased the occurrence risk of AD. Fatty-acid-binding protein 5 (FABP5) may serve as an effective biomarker for the atopic march (AM). Squamous cell carcinoma antigen 2 (SCCA2), serum thymus and activation-regulated chemokine (TARC), cutaneous T-cell-attracting chemokine (CTACK), eosinophil-derived neurotoxin (EDN), macrophage-derived chemokine (MDC), lactate dehydrogenase (LDH), and interleukin (IL)-18 can be the candidate biomarkers for disease severity monitoring. IL-17, IL-23, IL-33, and indoleamine 2,3-dioxygenase (IDO1) can be used as predictive biomarkers for AD comorbidities. LDH, TARC, pulmonary and activation-regulated chemokine (PARC), periostin, IL-22, eotaxin-1/3, and IL-8 may be the candidate biomarkers for monitoring treatment effects. There are still unmet needs and a long way to go for more convenient, non-invasive, and effective predictors and biomarkers to better guide personalized precise treatment.

IL-6 effector function of group 2 innate lymphoid cells (ILC2) is NOD2 dependent

Cutaneous group 2 innate lymphoid cells (ILC2) are spatially and epigenetically poised to respond to barrier compromise and associated immunological threats. ILC2, lacking rearranged antigen-specific receptors, are primarily activated by damage-associated cytokines and respond with type 2 cytokine production. To investigate ILC2 potential for direct sensing of skin pathogens and allergens, we performed RNA sequencing of ILC2 derived from in vivo challenged human skin or blood. We detected expression of NOD2 and TLR2 by skin and blood ILC2. Stimulation of ILC2 with TLR2 agonist alone not only induced interleukin-5 (IL-5) and IL-13 expression but also elicited IL-6 expression in combination with Staphylococcus aureus muramyl dipeptide (MDP). Heat-killed skin-resident bacteria provoked an IL-6 profile in ILC2 in vitro that was notably impaired in ILC2 derived from patients with nucleotide-binding oligomerization domain-containing protein 2 (NOD2) mutations. In addition, we show that NOD2 signaling can stimulate autophagy in ILC2, which was also impaired in patients with NOD2 mutations. Here, we have identified a role for ILC2 NOD2 signaling in the differential regulation of ILC2-derived IL-6 and have reported a previously unrecognized pathway of direct ILC2 bacterial sensing.

Molecular Mechanisms of Atopic Dermatitis Pathogenesis

Atopic dermatitis is a chronic, non-infectious inflammatory dermatosis. Acharacteristic feature is persistent itching of the skin. The chronic, relapsing course of the disease, economic burden, and the whole family’s involvement in the treatment process immensely reduce the quality of life of patients and their families. The disease emerges as a social problem by increasing indirect costs, such as visiting a doctor, absenteeism from work and school, and avoiding social interactions. Thepathophysiology of atopic dermatitis is complex and multifactorial. It includes genetic disorders, a defect in the epidermal barrier, an altered immune response, anddisruption of the skin’s microbial balance. The numerous complex changes at thegenetic level and innate and adaptive immunity provide the basis for characterizing the various phenotypes and endotypes of atopic dermatitis. Emerging therapies rely on the action of specific molecules involved in the disease’s pathogenesis. It may be the starting point for the individualization of atopic dermatitis treatment. This paper will try to present some molecular mechanisms of atopic dermatitis and their clinical implications.

Immunological Roles of NLR in Allergic Diseases and Its Underlying Mechanisms

Our understanding on the immunological roles of pathogen recognition in innate immunity has vastly increased over the past 20 years. Nucleotide-binding oligomerization domain (NOD)-like receptors (NLR) are cytosolic pattern recognition receptors (PRR) that are responsible for sensing microbial motifs and endogenous damage signals in mammalian cytosol for immune surveillance and host defense. The accumulating discoveries on these NLR sensors in allergic diseases suggest that the pathogenesis of allergic diseases may not be confined to the adaptive immune response. Therapy targeting NLR in murine models also shields light on its potential in the treatment of allergies in man. In this review, we herein summarize the recent understanding of the role of NLR sensors and their molecular mechanisms involved in allergic inflammation, including atopic dermatitis and allergic asthma.

Copy Number Variation of Multiple Genes in SAPHO Syndrome

OBJECTIVE

SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome is a type of rare chronic aseptic inflammation of unknown etiology. To date, no research to our knowledge has reported copy number variation (CNV) of genes that could affect predisposition to SAPHO syndrome. We investigated the association between CNV profile and SAPHO syndrome.

METHODS

We used array comparative genomic hybridization (CGH) to screen for CNV in a nuclear family including 2 patients and a healthy control. We then validated the copy numbers of candidate genes found in the array CGH assay and other candidate genes by TaqMan real-time PCR in 360 case and control samples.

RESULTS

Ten regions from 8 chromosomes were found to have abnormal gene copies in the nuclear family, so the CNV of candidate genes (ADAM5, CSF2RA, IL3RA, and 9 other genes) were tested by TaqMan PCR. Significant copy number loss of CSF2RA (p = 0.000) and NOD2 (p = 0.005), and significant copy number gain of MEGF6 (p = 0.002) and ADAM5 (p = 0.000) were seen in patients with SAPHO compared with controls at the a = 0.05 level. There were no differences in the other 8 candidate genes between patient and control samples (p > 0.05).

CONCLUSION

Our study established the first association between CNV in CSF2RA, NOD2, MEGF6, and ADAM5 and SAPHO syndrome. These findings may offer insight into the pathogenesis of SAPHO and provide the basis for improved diagnosis and treatment.

Synergistic induction of CCL5, CXCL9 and CXCL10 by IFN-γ and NLRs ligands on human fibroblast-like synoviocytes-A potential immunopathological mechanism for joint inflammation in rheumatoid arthritis

Interferon-γ (IFN-γ) is traditionally regarded as a proinflammatory cytokine by virtue of its strong macrophage activating potential and its association with Th1 driven immune responses. NOD1 and NOD2 are cytoplasmic receptors that can initiate the initial immune response by sensing bacterial components or danger signals. In this study, we investigated the immunopathological roles of IFN-γ and NOD1, 2 ligands iE-DAP/MDP on the activation of fibroblast-like synoviocytes (FLS) in RA. FLS constitutively express functional NOD1 and NOD2, and the gene and protein expression of NOD1 and NOD2 could be enhanced by the treatment with IFN-γ. The synergistic effect was observed in the combined treatment of IFN-γ and NOD1 ligand iE-DAP or NOD2 ligand MDP on the release of CCL5, CXCL9 and CXCL10 from FLS, and its effect was in a dose-dependent manner. The co-stimulation which IFN-γ combined with iE-DAP/MDP could abolish the inhibition of CXCL8 level by IFN-γ alone. Further investigations showed that synergistic effects on the production of CCL5, CXCL9 and CXCL10 in FLS stimulated by IFN-γ and iE-DAP/MDP were differentially regulated by intracellular activation of NF-κB, p38MAPK and ERK pathways. In conclusion, our data confirmed the inflammatory effect of IFN-γ and iE-DAP/MDP on human FLS for the first time and therefore provided a new insight into the IFN-γ combined with NOD1 or NOD2 activated immunopathological mechanisms mediated by distinct intracellular signal transduction in joint inflammation of RA.

NOD2 and inflammation: current insights

The nucleotide-binding oligomerization domain (NOD) protein, NOD2, belonging to the intracellular NOD-like receptor family, detects conserved motifs in bacterial peptidoglycan and promotes their clearance through activation of a proinflammatory transcriptional program and other innate immune pathways, including autophagy and endoplasmic reticulum stress. An inactive form due to mutations or a constitutive high expression of NOD2 is associated with several inflammatory diseases, suggesting that balanced NOD2 signaling is critical for the maintenance of immune homeostasis. In this review, we discuss recent developments about the pathway and mechanisms of regulation of NOD2 and illustrate the principal functions of the gene, with particular emphasis on its central role in maintaining the equilibrium between intestinal microbiota and host immune responses to control inflammation. Furthermore, we survey recent studies illustrating the role of NOD2 in several inflammatory diseases, in particular, inflammatory bowel disease, of which it is the main susceptibility gene.

Clinical Signs, Staphylococcus and Atopic Eczema-Related Seromarkers

Childhood eczema or atopic dermatitis (AD) is a distressing disease associated with pruritus, sleep disturbance, impaired quality of life and Staphylococcus aureus isolation. The pathophysiology of AD is complex and various seromarkers of immunity are involved. We investigated if anti-staphylococcal enterotoxin IgE (anti-SE), selected seromarkers of T regulatory (Treg), T helper (Th) and antigen-presenting cells (APC) are associated with clinical signs of disease severity and quality of life. Disease severity was assessed with the Scoring Atopic Dermatitis (SCORAD) index, and quality of life with the Children's Dermatology Life Quality Index (CDLQI) in AD patients ≤18 years old. Concentrations of anti-staphylococcus enterotoxin A and B immunoglobulin E (anti-SEA and anti-SEB), selected Treg/Th/APC chemokines, skin hydration and transepidermal water loss (TEWL) were measured in these patients. Forty patients with AD [median (interquartile range) age of 13.1 (7.9) years) were recruited. Backward stepwise linear regression (controlling for age, personal allergic rhinitis and asthma, and other blood markers) showed the serum anti-SEB level was positively associated with S. aureus and S. epidermidis isolations, objective SCORAD, clinical signs and CDLQI. TNF-α (a Th1 cytokine) was positively associated with objective SCORAD (B = 4.935, p = 0.010), TGF-β (a Treg cytokine) negatively with disease extent (B = -0.015, p = 0.001), IL-18 (an APC cytokine) positively with disease extent (B = 0.438, p = 0.001) and with TEWL (B = 0.040, p = 0.010), and IL-23 (an APC cytokine) negatively with disease extent (B = -2.812, p = 0.006) and positively with pruritus (B = 0.387, p = 0.007).

CONCLUSIONS

Blood levels of anti-SEB, Th1, Treg and APC cytokines are correlated with various clinical signs of AD. AD is a systemic immunologic disease involving Staphylococcus aureus, cellular, humoral, cytokine and chemokine pathophysiology.

The Evolution of Human Basophil Biology from Neglect towards Understanding of Their Immune Functions

Being discovered long ago basophils have been neglected for more than a century. During the past decade evidence emerged that basophils share features of innate and adaptive immunity. Nowadays, basophils are best known for their striking effector role in the allergic reaction. They hence have been used for establishing new diagnostic tests and therapeutic approaches and for characterizing natural and recombinant allergens as well as hypoallergens, which display lower or diminished IgE-binding activity. However, it was a long way from discovery in 1879 until identification of their function in hypersensitivity reactions, including adverse drug reactions. Starting with a historical background, this review highlights the modern view on basophil biology.

Molecular Mechanisms of Cutaneous Inflammatory Disorder: Atopic Dermatitis

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease resulting from interactions between genetic susceptibility and environmental factors. The pathogenesis of AD is poorly understood, and the treatment of recalcitrant AD is still challenging. There is accumulating evidence for new gene polymorphisms related to the epidermal barrier function and innate and adaptive immunity in patients with AD. Newly-found T cells and dendritic cell subsets, cytokines, chemokines and signaling pathways have extended our understanding of the molecular pathomechanism underlying AD. Genetic changes caused by environmental factors have been shown to contribute to the pathogenesis of AD. We herein present a review of the genetics, epigenetics, barrier dysfunction and immunological abnormalities in AD with a focus on updated molecular biology.