Atopic Dermatitis Skin Lesions Research Articles

417 Inflammatory cytokine mediated induction of serine racemase in atopic dermatitis

Serine racemase (SR) is an enzyme that catalyzes the conversion of L-serine to pyruvate or D-serine, an endogenous agonist for N-methyl-D-aspartate (NMDA) receptors. Our previous study showed the presence of SR protein in the epidermis of wild type (WT) mice but not in SR knockout (KO) mice. Moreover, SR immune-reactivity was only found in the granular and cornified layers of epidermis in WT mice. It was suggested that SR is involved in the differentiation of epidermal keratinocytes and the formation of skin barrier. However, its role in skin barrier dysfunction like atopic dermatitis (AD) remains to be elusive. Therefore, this study was aimed to determine the content of D-serine in stratum corneum in AD patients and healthy controls, using tape stripping method. Skin samples were collected from cheek and upper arm of AD patient’s lesion and healthy persons. Significant difference was found in D-body ratio between AD involved, uninvolved and healthy control in cheek (p<0.005, p<0.001) and upper-arms (p<0.001, p<0.001), respectively. Furthermore, immune-histochemical analysis also revealed increased SR expression in the epidermis of AD patients compared to healthy control. In addition, keratinocytes stimulation with TNF-α or MIF, results in the increased expression of SR. Taken together, these findings suggest that D-serine particularly express in AD lesional skin and SR expression in the keratinocytes is linked to inflammatory cytokines.

EASI p-EASI: Utilizing a combination of serum biomarkers offers an objective measurement tool for disease severity in atopic dermatitis patients

EASI p-EASI: Utilizing a combination of serum biomarkers offers an objective measurement tool for disease severity in atopic dermatitis patients

Current insights into the role of human β-defensins in atopic dermatitis.

Anti-microbial peptides or host defence peptides are small molecules that display both anti-microbial activities and complex immunomodulatory functions to protect against various diseases. Among these peptides, the human β-defensins (hBDs) are localized primarily in epithelial surfaces, including those of the skin, where they contribute to protective barriers. In atopic dermatitis skin lesions, altered skin barrier and immune dysregulation are believed to be responsible for reduced hBD synthesis. Impaired hBD expression in the skin is reportedly the leading cause of increased susceptibility to bacterial and viral infection in patients with atopic dermatitis. Although hBDs have considerable beneficial effects as anti-microbial agents and immunomodulators and may ameliorate atopic dermatitis clinically, recent evidence has also suggested the negative effects of hBDs in atopic dermatitis development. In the current review, we provide an overview of the regulation of hBDs and their role in the pathogenesis of atopic dermatitis. The efforts to utilize these molecules in clinical applications are also described.

Emerging role of interleukin-31 and interleukin-31 receptor in pruritus in atopic dermatitis.

Atopic dermatitis (AD) is a chronic or chronically relapsing, eczematous, severely pruritic skin disorder associated with skin barrier dysfunction. The lesional skin of AD exhibits T helper 2 (TH 2)-deviated immune reactions. Interleukin-31 (IL-31), preferentially produced from TH 2 cells, is a potent pruritogenic cytokine, and its systemic and local administration induces scratching behavior in rodents, dogs and monkeys. Recent clinical trials have revealed that administration of an anti-IL-31 receptor antibody significantly alleviates pruritus in patients with AD. In this review, we summarize recent topics related to IL-31 and its receptor with special references to atopic itch.

House Dust Mite Increases pro-Th2 Cytokines IL-25 and IL-33 via the Activation of TLR1/6 Signaling

House dust mites have been implicated in the etiology and exacerbation of atopic dermatitis. Diverse factors contribute to house dust mite allergenicity through the activation of innate immunity. We investigated whether Dermatophagoides farinae extract (DFE) allergens mediate innate immune activation through specific toll-like receptors (TLRs) in epidermal keratinocytes, a DFE-induced murine atopic dermatitis model, and human atopic dermatitis lesions. DFE activated the expression of TLR1, TLR6, IL-25, and IL-33 in human primary keratinocytes and HaCaT cells. Knockdown of TLR6 inhibited DFE-induced upregulation of IL-25 or IL-33. In addition, the suppression of TLR1 inhibited the release of IL-33. DFE induced the expression of IL-25 and IL-33 by upregulation of IL-1 receptor-associated kinase 1, transforming growth factor-β activated kinase-1, IκB kinase, and NF-κB pathways. Tlr6-/- mice did not show DFE-induced upregulation of IL-25 and IL-33. Furthermore, DFE-induced upregulation of IL-25 was not induced in Tlr1-/- mice. We also identified upregulated mRNA and protein expression of TLR1, TLR6, IL-25, and IL-33 in human atopic dermatitis skin lesions with high house dust mite sensitization. We found that DFE-induced activation of TLR1 and TLR6 may cause polarization toward a T helper type 2 immune response via the release of IL-25 and IL-33.

Prostaglandin E2 stimulates adaptive IL-22 production and promotes allergic contact dermatitis

Atopic dermatitis (AD) and allergic contact dermatitis (ACD) are both forms of eczema and are common inflammatory skin diseases with a central role of T cell-derived IL-22 in their pathogenesis. Although prostaglandin (PG) E2 is known to promote inflammation, little is known about its role in processes related to AD and ACD development, including IL-22 upregulation. We sought to investigate whether PGE2 has a role in IL-22 induction and development of ACD, which has increased prevalence in patients with AD. T-cell cultures and invivo sensitization of mice with haptens were used to assess the role of PGE2 in IL-22 production. The involvement of PGE2 receptors and their downstream signals was also examined. The effects of PGE2 were evaluated by using the oxazolone-induced ACD mouse model. The relationship of PGE2 and IL-22 signaling pathways in skin inflammation were also investigated by using genomic profiling in human lesional AD skin. PGE2 induces IL-22 from T cells through its receptors, E prostanoid receptor (EP) 2 and EP4, and involves cyclic AMP signaling. Selective deletion of EP4 in T cells prevents hapten-induced IL-22 production invivo, and limits atopic-like skin inflammation in the oxazolone-induced ACD model. Moreover, both PGE2 and IL-22 pathway genes were coordinately upregulated in human AD lesional skin but were at less than significant detection levels after corticosteroid or UVB treatments. Our results define a crucial role for PGE2 in promoting ACD by facilitating IL-22 production from T cells.

Altered expression of epidermal lipid bio-synthesis enzymes in atopic dermatitis skin is accompanied by changes in stratum corneum lipid composition

BackgroundThe barrier dysfunction in atopic dermatitis (AD) skin correlates with stratum corneum (SC) lipid abnormalities including reduction of global lipid content, shorter ceramide (CER) as well as free fatty acid (FFA) chain length and altered CER subclass levels. However, the underlying cause of these changes in lipid composition has not been fully investigated. AimWe investigated whether the expression of CER and FFA biosynthesis enzymes are altered in AD skin compared with control skin and determine whether changes in enzyme expression can be related with changes in lipid composition. MethodsIn AD patients and controls the expression of enzymes involved in the biosynthesis of FFAs and CERs was analyzed in relation to the SC lipid composition. These enzymes include stearoyl CoA desaturase (SCD), elongase 1 (ELOVL1) and ELOVL6 involved in FFA synthesis and β-glucocerebrosidase (GBA), acid-sphingomyelinase (aSmase), ceramide synthase 3 (CerS3) involved in CER synthesis. In TH2 treated human skin equivalents (AD HSEs) mimicking lesional AD skin, the mRNA expression of these enzymes was investigated. ResultsThe results reveal an altered expression of SCD and ELOVL1 in AD lesional skin. This was accompanied by functional changes displayed by increased unsaturated FFAs (SCD) and reduced FFA C22-C28 (ELOVL1) in AD lesional skin. The expression of GBA, aSmase and CerS3 were also altered in lesional skin. The CER composition in AD lesional skin showed corresponding changes such as increased CER AS and NS (aSmase) and decreased esterified ω-hydroxy CERs (CerS3). In support of the results from AD skin, the AD HSEs showed reduced mRNA ELOVL1, GBA and a Smase levels. ConclusionThis study shows that alterations in the expression of key enzymes involved in SC lipid synthesis contribute to changes in the lipid composition in AD skin and inflammation may influence expression of these enzymes.

CXCL17 Attenuates Imiquimod-Induced Psoriasis-like Skin Inflammation by Recruiting Myeloid-Derived Suppressor Cells and Regulatory T Cells.

CXCL17 is expressed in a variety of cancers and promotes tumor progression by recruiting myeloid-derived suppressor cells (MDSCs). MDSCs suppress tumor immunity by attracting regulatory T cells (Tregs) into tumor sites through CCL5. In this study, we examined the role of CXCL17 in skin disorders. CXCL17 mRNA levels in psoriasis skin, but not in lesional skin of atopic dermatitis or cutaneous T cell lymphoma, were significantly higher than those in normal skin. CXCL17 was mainly expressed in the epidermis, and IFN-γ dose-dependently increased CXCL17 expression by human keratinocytes in vitro. As CXCL17 mRNA expression was increased by treatment with imiquimod (IMQ), we examined the effects of CXCL17 in IMQ-induced psoriasis-like skin inflammation. Injection of recombinant CXCL17 into the ear before and during IMQ application decreased ear thickness, inflammatory cytokine expression, and the number of infiltrating cells compared with PBS injection. Flow cytometric analysis and immunofluorescent staining revealed that the numbers of MDSCs, which are CD11b+Gr-1+, and that of Tregs, which are CD4+CD25+, were higher in the ear of the CXCL17-injected mice than in PBS-injected mice. MDSCs, but not Tregs, showed chemotaxis to CXCL17 in vitro. When mice were injected with anti-CCL5 Ab or anti-CCL4 Ab simultaneously with recombinant CXCL17, ear thickness and cytokine expression increased to a similar level of mice treated with PBS and control IgG, suggesting that these chemokines were important for anti-inflammatory effects. Taken together, CXCL17 attenuates IMQ-induced psoriasis-like skin inflammation by recruiting MDSCs and Tregs, which may be important for regulating excessive inflammation in psoriasis skin.

Expression of keratin 1, keratin 10, desmoglein 1 and desmocollin 1 in the epidermis: possible downregulation by interleukin-4 and interleukin-13 in atopic dermatitis.

In the pathogenesis of atopic dermatitis (AD), skin barrier dysfunction and T-helper (Th) type 2 immune reactions play important roles. Alterations in the stratum spinosum of AD have not been studied in much detail. In this study, we investigated the changes of structural proteins and adhesion molecules residing in the stratum spinosum of AD lesional skin, and whether Th2 cytokines including interleukin (IL)-4 and IL-13 alter the expression of these proteins. Skin samples were collected from patients with AD and from healthy controls. Normal human epidermal keratinocytes were cultured and differentiated in the presence or absence of either IL-4 or IL-13 in vitro. The expression of keratin 1, keratin 10, desmoglein 1 and desmocollin 1 was examined by immunofluorescence and western blotting. The expression of these proteins was downregulated in AD lesional skin, and IL-4 and IL-13 were shown to suppress their expression. These results suggest that the stratum spinosum is impaired in AD lesional skin, possibly by Th2 cytokines, which may be involved in the pathogenesis of AD.

625 Differential diversity of staphylococcal strains shapes cutaneous response in atopic dermatitis

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disorder associated with staphylococcal skin colonization and often treated with antimicrobials; therefore, it is predicted that these microbes may influence AD progression. To understand this relationship throughout the disease course, AD patients were recruited, and samples from affected skin sites were processed for shotgun metagenomic sequencing. In addition to confirming that staphylococcal species increased during a disease flare as compared to controls, more severely affected children had a predominance of S. aureus, while less severely affected patients had higher S. epidermidis abundances. From analysis of this large sequence dataset, which enabled classifications of microbial communities at the strain level, we determined the specific strains of S. aureus and S. epidermidis that were increased during flare. Isolates were cultured from the same patients and sequenced to confirm matches with metagenomic strain tracking. To evaluate the immunologic effects of these S. aureus and S. epidermidis isolates, these human-derived clinical isolates were applied to the skin of wild-type mice. As often observed in human AD lesional skin, mice topically exposed to AD isolates experienced skin infiltration of CD4+ T cells, neutrophils, and eosinophils. The magnitude of this response varied, depending on the isolate and revealed that functional differences exist between strains of the same species. Overall, using combined sequencing and culturing strategies, we demonstrate how staphylococcal strains may contribute to AD disease progression through activation of the host immune system.

Galectin-7 is extracellularly released from epidermal keratinocytes in atopic dermatitis and serves as immunomodulator of Langerhans cells

A number of galectins are localized in various organs, and galectin-7 is expressed in epidermal keratinocytes (KCs). Our proteome analysis of extracts from human stratum corneum revealed that galectin-7 is highly expressed in atopic dermatitis (AD) patients (Sakabe J et al. JACI 2014). Meanwhile, galectin-7 might bind to hyaluronan, and its intercellular accumulation can yield spongiosis. Thus, it should be elucidated how galectin-7 is induced in the epidermis and whether it can suppress or rather promote skin inflammation. To address these issues, we used 3D cultured KCs to investigate the ability of IL-4/IL-13 to induce galectin-7, and employed murine epidermal Langerhans cells (LCs) for its ability to maturate LCs. Immunohistochemical staining showed that, in healthy skin, galectin-7 was expressed in the cytoplasm of KCs in the prickle layer. In AD lesional skin, however, galectin-7 was positively stained in the intercellular space of KCs. In human 3D skin culture, incubation of KCs with IL-4/IL-13 promoted its expression in the intercellular space, suggesting that these Th2 cytokines stimulate KCs to produce galectin-7 and to extracellularly release it. These findings urged us to further investigate its effect on LCs. Epidermal suspensions were freshly prepared from C57BL/6 mice, and cells were cultured for 24 h with or without 100 ng of mouse recombinant galectin-7. The expression levels of langerin, EpCAM, CD54, CD80, CD86, and MHC class II were examined by flow cytometry. LCs, gated as langerin+ and EpCAM+ cells, expressed increased levels of CD54 and CD86, when epidermal cells were incubated with galectin-7. These results suggest that galectin-7 is extracellularly secreted by epidermal KCs in AD and may play an immunomodulatory effect on LCs.

Diospyros lotus leaf and grapefruit stem extract synergistically ameliorate atopic dermatitis-like skin lesion in mice by suppressing infiltration of mast cells in skin lesions.

Atopic dermatitis, a chronic relapsing and pruritic inflammation of the skin also thought to be involved in, or caused by immune system destruction is an upsetting health problem due to its continuously increasing incidence especially in developed countries. Mast cell infiltration in atopic dermatitis skin lesions and its IgE-mediated activation releases various cytokines and chemokines that have been implicated in the pathogenesis of atopic dermatitis. This study was aimed at investigating synergistic anti-inflammatory, anti-pruritic and anti-atopic dermatitis effects of Diospyros lotus leaf extract (DLE) and Muscat bailey A grapefruit stem extract (GFSE) in atopic dermatitis-like induced skin lesions in mice. Combinations of DLE and GFSE inhibited TNF-α and IL-6 production more than DLE or GFSE in PMA plus calcium ionophore A23187-activated HMC-1 cells. DLE and GFSE synergistically inhibited compound 48/80-induced dermal infiltration of mast cells and reduced scratching behavior than DLE or GFSE. Furthermore, DLE and GFSE synergistically showed a stronger ameliorative effect in skin lesions by reducing clinical scores; dermal infiltration of mast cells; ear and dorsal skin thickness; serum IgE and IL-4 production in atopic dermatitis-like mice. Collectively, these results suggest that DLE and GFSE synergistically exhibit anti-atopic dermatitis effects in atopic dermatitis-like skin lesions in mice.

Persistent kallikrein 5 activation induces atopic dermatitis-like skin architecture independent of PAR2 activity

Upregulation of kallikreins (KLKs) including KLK5 has been reported in atopic dermatitis (AD). KLK5 has biological functions that include degrading desmosomal proteins and inducing proinflammatory cytokine secretion through protease-activated receptor 2 (PAR2). However, due to the complex interactions between various cells in AD inflamed skin, it is difficult to dissect the precise and multiple roles of upregulated KLK5 in AD skin. We investigated the effect of upregulated KLK5 on the expression of epidermal-related proteins and cytokines in keratinocytes and on skin architecture. Lesional and nonlesional AD skin biopsies were collected for analysis of morphology and protein expression. The relationship between KLK5 and barrier-related molecules was investigated using an exvivo dermatitis skin model with transient KLK5 expression and a cell model with persistent KLK5 expression. The influence of upregulated KLK5 on epidermal morphology was investigated using an invivo skin graft model. Upregulation of KLK5 and abnormal expression of desmoglein 1 (DSG1) and filaggrin, but not PAR2 were identified in AD skin. PAR2 was increased in response to transient upregulation of KLK5, whereas persistently upregulated KLK5 did not show this effect. Persistently upregulated KLK5 degraded DSG1 and stimulated secretion of IL-8, IL-10, and thymic stromal lymphopoietin independent of PAR2 activity. With control of higher KLK5 activity by the inhibitor sunflower trypsin inhibitor G, restoration of DSG1 expression and a reduction in AD-related cytokine IL-8, thymic stromal lymphopoietin, and IL-10 secretion were observed. Furthermore, persistently elevated KLK5 could induce AD-like skin architecture in an invivo skin graft model. Persistently upregulated KLK5 resulted in AD-like skin architecture and secretion of AD-related cytokines from keratinocytes in a PAR2 independent manner. Inhibition of KLK5-mediated effects may offer potential as a therapeutic approach in AD.

Intelectin contributes to allergen-induced IL-25, IL-33, and TSLP expression and type 2 response in asthma and atopic dermatitis.

The epithelial and epidermal innate cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) play pivotal roles in the initiation of allergic inflammation in asthma and atopic dermatitis. However, the mechanism by which the expression of these innate cytokines is regulated remains unclear. Intelectin (ITLN) is expressed in airway epithelial cells and promotes allergic airway inflammation. We hypothesized that ITLN is required for allergen-induced IL-25, IL-33 and TSLP expression. In two asthma models, Itln knockdown reduced allergen-induced increases in Il-25, Il-33, and Tslp and development of type 2 response, eosinophilic inflammation, mucus overproduction, and airway hyperresponsiveness. Itln knockdown also inhibited house dust mite (HDM)-induced early upregulation of Il-25, Il-33, and Tslp in a model solely inducing airway sensitization. Using human airway epithelial cells, we demonstrated that HDM-induced increases in ITLN led to phosphorylation of EGFR and ERK which were required for induction of IL-25, IL-33, and TSLP expression. In two atopic dermatitis models, Itln knockdown suppressed expression of Il-33, Tslp and Th2 cytokines and eosinophilic inflammation. In humans, ITLN1 expression was significantly increased in asthmatic airways and in lesional skin of atopic dermatitis. We conclude that intelectin contributes to allergen-induced Il-25, Il-33 and Tslp expression in asthma and atopic dermatitis.

Altered Expression of Genes Encoding Cornulin and Repetin in Atopic Dermatitis

Background: It is assumed that beside alterations in the filaggrin gene (FLG), disturbances within genes encoding other cornified envelope proteins are also involved in atopic dermatitis (AD). To identify new potential markers of AD, we studied the polymorphisms of genes encoding repetin (RPTN), cornulin (CRNN), and their expression in the skin of AD patients. Methods: Polymorphisms in CRNN (rs941934), RPTN (rs284544, rs28441202, rs3001978, and rs12117644), and FLG mutations (R2447X, S3247X) were analyzed by TaqMan genotyping assay and by PCR-RFLP in the blood samples of 159 AD patients and 108 healthy subjects. The expression levels of CRNN and RPTN were determined by qRT-PCR in 34 AD skin samples (17 lesional and 17 nonlesional) and in 27 skin biopsies from healthy volunteers. The AD patients were recruited from the clinic of the university hospital between 2012 and 2014. Results:CRNN rs941934 (A allele) was associated with AD (OR 2.095, p = 0.008), a severe course of disease (p = 0.041), elevated IgE levels (p = 0.047), eosinophilia (p = 0.018), and concomitant asthma (p = 0.004). The mRNA level of CRNN was decreased in the AD skin (p = 0.041). In the AD patients without FLG mutations, the CC genotype of RPTN rs3001978 was associated with AD (OR 0.39, p = 0.037), early age at onset (p = 0.033), pruritus (p = 0.021), severity of AD (p = 0.045), and concomitant asthma (p = 0.041). The elevated mRNA levels of RPTN in lesional (p < 0.001) and nonlesional (p = 0.017) AD skin were observed. Conclusions: The single-nucleotide polymorphisms of CRNN (rs941934) and RPTN (rs3001978, rs28441202) may contribute to AD development, but further studies on a larger group of AD patients are needed to verify this assumption.

Lipid Abnormalities Associated with Skin Lesions in Atopic Dermatitis

Lipid Abnormalities Associated with Skin Lesions in Atopic Dermatitis

Non-invasive evaluation of atopic dermatitis based on redox status using in vivo dynamic nuclear polarization magnetic resonance imaging

Atopic dermatitis (AD) is a chronic inflammatory condition with complex etiology, including genetic, environmental and immunologic factors. Redox imbalance caused by excessive oxidative stress has been shown to mediate disease activity of AD. Currently, an imaging technique that can monitor the redox status of the skin in vivo has not yet been developed. Consequently, we have established such a technique that can detect and visualize the redox status of the skin using in vivo dynamic nuclear polarization magnetic resonance imaging (DNP-MRI). To evaluate this technique, we utilized an AD mouse model that was generated by repeated topical application of mite antigen in NC/Nga mice. We imaged alterations in redox balance of the resulting AD skin lesions of the mice. Using in vivo DNP-MRI and non-toxic nitroxyl radicals to visualize free radicals in vivo, we revealed that AD skin lesions demonstrated more rapid decay rates of image intensity enhancement than normal skin, indicating that our technique can monitor excessive oxidative stress occurring in AD skin lesions. Therefore, this technique has the potential to provide a novel approach for evaluating disease activity of inflammatory skin diseases, including AD, from the view point of altered redox status.

Serum IL-21 levels are elevated in atopic dermatitis patients with acute skin lesions

BackgroundInterleukin (IL)-21 is a member of the type I cytokine family and plays a role in the pathogenesis of T helper type 2 allergic diseases. It has been reported that IL-21 expression is upregulated in acute skin lesions in atopic dermatitis (AD) patients; however, little is known about the serum IL-21 levels of AD patients. The aim of this study was to quantify the serum IL-21 levels of AD patients and to evaluate the relationships between the serum IL-21 level and disease severity, laboratory markers, and eruption type in AD patients. MethodsWe measured the serum IL-21 levels of adult AD patients and healthy control subjects using an enzyme-linked immunosorbent assay. ResultsThe adult AD patients exhibited significantly higher serum IL-21 levels than the healthy control subjects. A comparison of the patients' serum IL-21 levels based on the clinical severity of their AD revealed that the patients with severe AD demonstrated significantly higher serum IL-21 levels than those with mild AD and the healthy control subjects. The serum IL-21 levels were significantly correlated with the skin severity score, and especially with the degree of acute lesions such as erythema and edema/papules. The serum IL-21 level was not associated with laboratory markers, such as the serum IgE level, the serum thymus and activation-related chemokine level, blood eosinophilia, and the serum lactate dehydrogenase level. ConclusionsThese results suggest that IL-21 might be involved in the pathogenesis of AD, especially the development of acute skin lesions.

Acidification of stratum corneum prevents the progression from atopic dermatitis to respiratory allergy.

The presence of congenitally impaired skin barrier followed by atopic dermatitis (AD) is an initial step in the atopic march. The maintenance of acidic pH in the stratum corneum (SC) has been suggested as a therapeutic or preventive strategy for barrier impairment caused by skin inflammation. To determine whether an AD murine model, flaky tail mice, with inherited filaggrin deficiency could develop airway inflammation by repeated topical application followed by nasal inhalation of house dust mite (HDM) antigen (defined as a novel "atopic march animal model"), and whether maintenance of an acidic SC environment by continuous application of acidic cream could interrupt the following atopic march. During the course of HDM treatment, acidic cream (pH2.8) or neutral cream (pH7.4) was applied to flaky tail mice twice daily. Repeated applications and inhalations of HDM to flaky tail mice induced AD skin lesions followed by respiratory allergies. Maintenance of SC acidity inhibited the occurrence of respiratory allergic inflammation as well as AD-like skin lesions. Collectively, a novel atopic march model could be developed by repeated epicutaneous and nasal applications of HDM to flaky tail mice, and that the acidification of SC could prevent the atopic march from AD to respiratory allergy.

Incomplete KLK7 Secretion and Upregulated LEKTI Expression Underlie Hyperkeratotic Stratum Corneum in Atopic Dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disorder. Chronic AD lesions present hyperkeratosis, indicating a disturbed desquamation process. KLK7 is a serine protease involved in the proteolysis of extracellular corneodesmosome components, including desmocollin 1 and corneodesmosin, which leads to desquamation. KLK7 is secreted by lamellar granules and upregulated in AD lesional skin. However, despite increased KLK7 protein levels, immunostaining and electron microscopy indicated numerous corneodesmosomes remaining in the uppermost layer of the stratum corneum from AD lesions. We aimed to clarify the discrepancy between KLK7 overexpression and retention of corneodesmosomes on AD corneocytes. Western blot analysis indicated abnormal corneodesmosin degradation patterns in stratum corneum from AD lesions. The KLK activity of tape-stripped corneocytes from AD lesions was not significantly elevated in in situ zymography, which was our new attempt to detect the protease activity more precisely than conventional assays. This ineffective KLK activation was associated with impaired KLK7 secretion from lamellar granules and increased expression of LEKTI in AD. Such imbalances in protease-protease inhibitor interactions could lead to abnormal proteolysis of corneodesmosomes and compact hyperkeratosis. Upregulated expression of LEKTI might be a compensatory mechanism to prevent further barrier dysfunction in AD.