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Guy Serre - One of the best experts on this subject based on the ideXlab platform.
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The antiperinuclear factor and the so-called antikeratin antibodies are the same rheumatoid arthritis-specific autoantibodies
2016Co-Authors: Mireille Sebbag, E Girbal, Michel Simon, Christian Vincent, Jeanjacques Durieux, Christine Masson-bessiere, Guy SerreAbstract:The so-called antikeratin antibodies (AKA) and the anti-perinuclear factor (APF) are the most specific serological markers of RA. Using indirect immunofluorescence, AKA label the stratum corneum of various cornified epithelia and APF the keratohyalin granules of human buccal mucosa epithelium. We recently demonstrated that AKA recognize human epidermal Filaggrin. Here, we report the identification of the major APF anti-gen as a diffuse protein band of 200-400 kD. This protein is seen to be closely related to human epidermal (pro)f laggrin since it was recognized by four antiFilaggrin mAbs specific for different epitopes, and since the APF titers of RA sera were found to be correlated to their AKA titers and to their immunoblotting reactivities to Filaggrin. Immunoabsorption of RA sera on purified epidermal Filaggrin abolished their reactivities to the granules of buccal epithelial cells and to the 200-400-kD antigen. Moreover, antiFilaggrin autoanti-bodies, i.e., AKA, affinity purified from RA sera, were shown to immunodetect the 200-400-kD antigen and to stain these granules. These results indicate that AKA and APF are largely the same autoantibodies. They recognize human epidermal Filaggrin and (pro)Filaggrin-related proteins of buccal epi-thelial cells. Identification of the epitopes recognized by these autoantibodies, which we propose to name antifilag-grin autoantibodies, will certainly open new paths of re-search into the pathophysiology of RA. (J. Clin. Invest. 1995. 95:2672-2679.) Key words: autoimmunity * autoantigen. keratohyalin granules * proFilaggrin * antiFilaggrin autoanti-bodie
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In a three-dimensional reconstructed human epidermis Filaggrin-2 is essential for proper cornification
Cell Death and Disease, 2015Co-Authors: Valérie Pendaries, Marina Le Lamer, Jeremy Malaisse, Guy Serre, Sanja Kezic, Britta Hansmann, Michel SimonAbstract:Atopic dermatitis is a chronic inflammatory skin disease with defects in the epidermal barrier. In a cohort of African-American children, a FLG2 nonsense mutation has been associated with the disease. In the epidermis of European patients, the expression of Filaggrin-2, the Filaggrin-related protein encoded by FLG2, is decreased. To describe the function of Filaggrin-2 and evaluate the impact of its deficiency, its expression was downregulated using lentivirus-mediated shRNA interference in a three-dimensional reconstructed human epidermis (RHE) model. This resulted in parakeratosis and a compact stratum corneum, presence of abnormal vesicles inside the corneocytes, increased pH and reduced amounts of free amino acids at the RHE surface, leading to increased sensitivity to UVB radiations. The expression of differentiation markers was slightly modified. However, we observed reduced proteolytic processing of corneodesmosin, hornerin and Filaggrin in parallel with reduced amounts of caspase-14 and bleomycin hydrolase. Our data demonstrated that Filaggrin-2 is important for a proper cornification and a functional stratum corneum. Its downregulation in atopic patients may be involved in the disease-associated epidermis impairment.
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Knockdown of Filaggrin in a three-dimensional reconstructed human epidermis impairs keratinocyte differentiation
Journal of Investigative Dermatology, 2014Co-Authors: Valérie Pendaries, Laurence Pellerin, Marina Le Lamer, Jeremy Malaisse, Yves Poumay, Rachida Nachat, Anne-marie Schmitt, Carle Paul, Sanja Kezic, Guy SerreAbstract:Atopic dermatitis is a chronic inflammatory skin disorder characterized by defects in the epidermal barrier and keratinocyte differentiation. The expression of Filaggrin, a protein thought to have a major role in the function of the epidermis, is downregulated. However, the impact of this deficiency on keratinocytes is not really known. This was investigated using lentivirus-mediated small-hairpin RNA interference in a three-dimensional reconstructed human epidermis (RHE) model, in the absence of other cell types than keratinocytes. Similar to what is known for atopic skin, the experimental Filaggrin downregulation resulted in hypogranulosis, a disturbed corneocyte intracellular matrix, reduced amounts of natural moisturizing factor components, increased permeability and UV-B sensitivity of the RHE, and impaired keratinocyte differentiation at the messenger RNA and protein levels. In particular, the amounts of two Filaggrin-related proteins and one protease involved in the degradation of Filaggrin, bleomycin hydrolase, were lower. In addition, caspase-14 activation was reduced. These results demonstrate the importance of Filaggrin for the stratum corneum properties/functions. They indicate that Filaggrin downregulation in the epidermis of atopic patients, either acquired or innate, may be directly responsible for some of the disease-related alterations in the epidermal differentiation program and epidermal barrier function.
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the rheumatoid arthritis associated autoantibodies to Filaggrin label the fibrous matrix of the cornified cells but not the proFilaggrin containing keratohyalin granules in human epidermis
Clinical and Experimental Immunology, 2008Co-Authors: Michel Simon, E Girbal, V Gomesdaudrix, Christian Vincent, Marek Haftek, Mireille Sebbag, Guy SerreAbstract:SUMMARY Since they were first described, serum IgG antibodies to the stratum corneum of rat oesophagus epithelium, highly specific for rheumatoid arthritis (RA), have been consensually called anti-keratin antibodies (AKA). However, we recently demonstrated that they actually recognize three new proteins of rat oesophagus epithelium distinct from cytokeratins, and also human epidermal Filaggrin. In this work we provided further evidence that AKA and RA-associated anti-Filaggrin autoantibodies are the same antibodies. Moreover, analysing by indirect immunofluorescence on human skin a large series of 212 well characterized RA sera and anti-Filaggrin autoantibodies purified from RA sera by affinity chromatography. we demonstrated the specific binding of AKA to the stratum corneum of human epidermis and the absence of any staining of the granular keratinocytes. This binding was confirmed and the AKA antigen precisely localized in human epidermis by immunoelectron microscopy. The antigen was found to be restricted to the Filaggrin-containing intracellular fibrous matrix of the corneocytes, up to the desquamating cells. In contrast, MoAbs directed to human Filaggrin and to proFilaggrin, its precursor, not only stained the intracellular matrix of the tower corneocytes but also the keratohyatin granules of the granular cells, where proFilaggrin is stored. These results reinforced by the absence of immunoblotting reactivity of RA sera to proFilaggrin suggest that the epitopes recognized by AKA are absent from proFilaggrin. Their identification may provide more insight into the pathogenesis of RA.
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identification of citrullinated rheumatoid arthritis specific epitopes in natural Filaggrin relevant for antiFilaggrin autoantibody detection by line immunoassay
Arthritis & Rheumatism, 2002Co-Authors: Ann Union, Guy Serre, L Meheus, Rene Louis Humbel, Karsten Conrad, G Steiner, Henri Moereels, Hans Pottel, Filip De KeyserAbstract:Objective To identify immunodominant epitopes in natural Filaggrin that are reactive with antiFilaggrin autoantibodies (AFA) in the sera of patients with rheumatoid arthritis (RA) and to explore their use in a diagnostic assay format. Methods Based on the results of epitope mapping of human natural Filaggrin as well as molecular modeling and computational chemistry, synthetic peptides together with recombinant citrullinated Filaggrin were evaluated by a line immunoassay (LIA) for AFA detection. Diagnostic performance was assessed using 336 RA and 253 disease control sera and was compared with that of reference methods. Results Several immunoreactive epitopes were identified in natural Filaggrin, all of which contained at least 1 citrulline residue. Three antigenic substrates, including 2 synthetic peptides and recombinant citrullinated Filaggrin showing maximal reactivity on LIA, were finally selected. Using the 3-antigen LIA3, overall sensitivity, specificity, and positive predictive value for RA were 65.2%, 98.0%, and 89.1%, respectively, compared with 61.9%, 98.8%, and 92.8% using the 2-antigen LIA2 (without recombinant protein). Thirty-seven percent of the rheumatoid factor (RF)-negative RA samples (30 of 81) were AFA-positive by LIA2, and 52 of 54 RF-positive control samples had no AFA detected on LIA2. Higher specificity and sensitivity were obtained by LIA2 versus anti-RA33 immunoblot, whereas good agreement was observed with antikeratin antibody testing. LIA performed significantly better than AFA immunoblotting using natural Filaggrin, at a specificity level of 99% (P = 0.0047). Conclusion Citrullinated residues are present in immunoreactive epitopes of natural human Filaggrin. AFA can be readily detected by citrullinated peptides in an LIA-based test, resulting in high specificity and positive predictive value for RA. The LIA could serve as a user-friendly alternative to existing immunofluorescence tests and AFA immunoblot techniques. Given its complementarity to RF, this test can be a valuable tool in the differential diagnosis of arthritis.
J Harper - One of the best experts on this subject based on the ideXlab platform.
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A mechanistic target of rapamycin complex 1/2 (mTORC1)/V-Akt murine thymoma viral oncogene homolog 1 (AKT1)/cathepsin H axis controls Filaggrin expression and processing in skin, a novel mechanism for skin barrier disruption in patients with atopic d
Journal of Allergy and Clinical Immunology, 2017Co-Authors: Aishath S. Naeem, C Tommasi, Christian Cole, Stuart J. Brown, Yanan Zhu, Benjamin Way, Saffron A.g. Willis Owen, Miriam F. Moffatt, William O.c.m. Cookson, J HarperAbstract:Background Filaggrin, which is encoded by the Filaggrin gene (FLG), is an important component of the skin's barrier to the external environment, and genetic defects in FLG strongly associate with atopic dermatitis (AD). However, not all patients with AD have FLG mutations. Objective We hypothesized that these patients might possess other defects in Filaggrin expression and processing contributing to barrier disruption and AD, and therefore we present novel therapeutic targets for this disease. Results We describe the relationship between the mechanistic target of rapamycin complex 1/2 protein subunit regulatory associated protein of the MTOR complex 1 (RAPTOR), the serine/threonine kinase V-Akt murine thymoma viral oncogene homolog 1 (AKT1), and the protease cathepsin H (CTSH), for which we establish a role in Filaggrin expression and processing. Increased RAPTOR levels correlated with decreased Filaggrin expression in patients with AD. In keratinocyte cell cultures RAPTOR upregulation or AKT1 short hairpin RNA knockdown reduced expression of the protease CTSH. Skin of CTSH-deficient mice and CTSH short hairpin RNA knockdown keratinocytes showed reduced Filaggrin processing, and the mouse had both impaired skin barrier function and a mild proinflammatory phenotype. Conclusion Our findings highlight a novel and potentially treatable signaling axis controlling Filaggrin expression and processing that is defective in patients with AD.
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A mechanistic target of rapamycin complex 1/2 (mTORC1)/V-Akt murine thymoma viral oncogene homolog 1 (AKT1)/cathepsin H axis controls Filaggrin expression and processing in skin, a novel mechanism for skin barrier disruption in patients with atopic dermatitis.
'Elsevier BV', 2017Co-Authors: As Naeem, Tommasi C, Cole C, Sj Brown, Zhu Y, Way B, Willis Owen Sag, Moffatt M, Wo Cookson, J HarperAbstract:BACKGROUND: Filaggrin, which is encoded by the Filaggrin gene (FLG), is an important component of the skin's barrier to the external environment, and genetic defects in FLG strongly associate with atopic dermatitis (AD). However, not all patients with AD have FLG mutations. OBJECTIVE: We hypothesized that these patients might possess other defects in Filaggrin expression and processing contributing to barrier disruption and AD, and therefore we present novel therapeutic targets for this disease. RESULTS: We describe the relationship between the mechanistic target of rapamycin complex 1/2 protein subunit regulatory associated protein of the MTOR complex 1 (RAPTOR), the serine/threonine kinase V-Akt murine thymoma viral oncogene homolog 1 (AKT1), and the protease cathepsin H (CTSH), for which we establish a role in Filaggrin expression and processing. Increased RAPTOR levels correlated with decreased Filaggrin expression in patients with AD. In keratinocyte cell cultures RAPTOR upregulation or AKT1 short hairpin RNA knockdown reduced expression of the protease CTSH. Skin of CTSH-deficient mice and CTSH short hairpin RNA knockdown keratinocytes showed reduced Filaggrin processing, and the mouse had both impaired skin barrier function and a mild proinflammatory phenotype. CONCLUSION: Our findings highlight a novel and potentially treatable signaling axis controlling Filaggrin expression and processing that is defective in patients with AD.R.F.L.O. is funded by the Great Ormond Street Hospital Children's Charity. A.S.N. is funded by a British Skin Foundation studentship (2018s). C.C. is funded as part of the Centre for Dermatology and Genetic Medicine, University of Dundee Wellcome Trust Strategic Award (098439/Z/12/Z). S.J.B. is supported by a Wellcome Trust Senior Research Fellowship in Clinical Science (106865/Z/15/Z) and a research grant from the Manknell Charitable Trust
Sanja Kezic - One of the best experts on this subject based on the ideXlab platform.
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concentration of Filaggrin monomers its metabolites and corneocyte surface texture in individuals with a history of atopic dermatitis and controls
Journal of The European Academy of Dermatology and Venereology, 2018Co-Authors: Josefine Bandier, Berit C Carlsen, Niels H H Heegaard, Christoph Riethmuller, K.a. Engebretsen, Sanja Kezic, Allan LinnebergAbstract:Atopic dermatitis (AD) is characterized by skin barrier dysfunction. Notably, a high number of nano-scale protrusions on the surface of corneocytes, which can be expressed by the Dermal Texture Index (DTI), was recently associated with pediatric AD, loss-of-function mutations in Filaggrin gene (FLG), and reduced levels of natural moisturizing factors (NMF). No study has so far examined the association between these parameters and monomeric Filaggrin levels in adults. To determine DTI, monomeric Filaggrin and NMF in healthy controls and a group of patients with controlled dermatitis. A total of 67 adults (20 healthy controls and 47 dermatitis patients) were included. In the patient population, a personal history of AD was diagnosed by the U.K. Working Party's Diagnostic Criteria. All participants were tested for FLG mutations (R501X, 2282del4, R2447X). Transepidermal water loss, monomeric Filaggrin, DTI and NMF were measured. In the patient population, 78.7% (37/47) had a history of AD and 59.5% (28/47) had FLG mutations. Patients had significantly higher levels of DTI and significantly lower levels of monomeric Filaggrin and NMF compared to the 20 healthy controls. Among patients, reduced level of monomeric Filaggrin and NMF correlated with the presence of FLG mutations and clinical phenotypes such as xerosis, palmar hyperlinearity and AD. Among healthy controls, DTI was significantly higher in the oldest age group compared to the two younger age groups. A significant difference in DTI, monomeric Filaggrin and NMF levels was found when comparing dermatitis patients with healthy controls. These findings suggest that even mild dermatitis or non-visible inflammation has a significant and negative effect on the skin barrier as inflammation is known to reduce Filaggrin levels. DTI was significantly increased in aged individuals in the healthy control group, suggesting a gradual change in corneocyte morphology with age. This article is protected by copyright. All rights reserved
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Expression of Filaggrin and its Degradation Products in Human Skin Following Erythemal Doses of Ultraviolet B Irradiation.
Acta Dermato-venereologica, 2017Co-Authors: Stine Simonsen, Steffen Heegaard, Jacob P. Thyssen, Sanja Kezic, Lone SkovAbstract:Epidermal Filaggrin level is affected by ultraviolet B irradiation in animal and experimental models. This study examined the effect of ultraviolet B irradiation on epidermal Filaggrin and natural moisturizing factors in vivo in healthy adults (n = 22). Participants were irradiated with 2 minimal erythema doses of ultraviolet B on the skin. Biopsies and tape strips were collected from skin irradiated 24 and 72 h earlier and from non-irradiated skin (control). Real-time quantitative PCR on skin biopsies showed significantly reduced proFilaggrin mRNA expression 24 h after irradiation (mean relative mRNA expression ± standard deviation: control, 3.86 ± 2.06 vs. 24 h, 1.52 ± 0.640; p = 0.02; n = 8). Immunohistochemistry showed aberrant spatial distribution of Filaggrin protein 72 h after irradiation (n = 3). High-pressure liquid chromatography of tape extracts showed no change in mean total natural moisturizing factor levels after irradiation, but mean trans-urocanic acid was significantly reduced, as expected (n = 8). In conclusion, erythemal doses of ultraviolet B exert acute effects on proFilaggrin mRNA and Filaggrin protein in human skin in vivo
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In a three-dimensional reconstructed human epidermis Filaggrin-2 is essential for proper cornification
Cell Death and Disease, 2015Co-Authors: Valérie Pendaries, Marina Le Lamer, Jeremy Malaisse, Guy Serre, Sanja Kezic, Britta Hansmann, Michel SimonAbstract:Atopic dermatitis is a chronic inflammatory skin disease with defects in the epidermal barrier. In a cohort of African-American children, a FLG2 nonsense mutation has been associated with the disease. In the epidermis of European patients, the expression of Filaggrin-2, the Filaggrin-related protein encoded by FLG2, is decreased. To describe the function of Filaggrin-2 and evaluate the impact of its deficiency, its expression was downregulated using lentivirus-mediated shRNA interference in a three-dimensional reconstructed human epidermis (RHE) model. This resulted in parakeratosis and a compact stratum corneum, presence of abnormal vesicles inside the corneocytes, increased pH and reduced amounts of free amino acids at the RHE surface, leading to increased sensitivity to UVB radiations. The expression of differentiation markers was slightly modified. However, we observed reduced proteolytic processing of corneodesmosin, hornerin and Filaggrin in parallel with reduced amounts of caspase-14 and bleomycin hydrolase. Our data demonstrated that Filaggrin-2 is important for a proper cornification and a functional stratum corneum. Its downregulation in atopic patients may be involved in the disease-associated epidermis impairment.
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causes of epidermal Filaggrin reduction and their role in the pathogenesis of atopic dermatitis
The Journal of Allergy and Clinical Immunology, 2014Co-Authors: Jacob P. Thyssen, Sanja KezicAbstract:The epidermis protects human subjects from exogenous stressors and helps to maintain internal fluid and electrolyte homeostasis. Filaggrin is a crucial epidermal protein that is important for the formation of the corneocyte, as well as the generation of its intracellular metabolites, which contribute to stratum corneum hydration and pH. The levels of Filaggrin and its degradation products are influenced not only by the Filaggrin genotype but also by inflammation and exogenous stressors. Pertinently, Filaggrin deficiency is observed in patients with atopic dermatitis regardless of Filaggrin mutation status, suggesting that the absence of Filaggrin is a key factor in the pathogenesis of this skin condition. In this article we review the various causes of low Filaggrin levels, centralizing the functional and morphologic role of a deficiency in Filaggrin, its metabolites, or both in the etiopathogenesis of atopic dermatitis.
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Knockdown of Filaggrin in a three-dimensional reconstructed human epidermis impairs keratinocyte differentiation
Journal of Investigative Dermatology, 2014Co-Authors: Valérie Pendaries, Laurence Pellerin, Marina Le Lamer, Jeremy Malaisse, Yves Poumay, Rachida Nachat, Anne-marie Schmitt, Carle Paul, Sanja Kezic, Guy SerreAbstract:Atopic dermatitis is a chronic inflammatory skin disorder characterized by defects in the epidermal barrier and keratinocyte differentiation. The expression of Filaggrin, a protein thought to have a major role in the function of the epidermis, is downregulated. However, the impact of this deficiency on keratinocytes is not really known. This was investigated using lentivirus-mediated small-hairpin RNA interference in a three-dimensional reconstructed human epidermis (RHE) model, in the absence of other cell types than keratinocytes. Similar to what is known for atopic skin, the experimental Filaggrin downregulation resulted in hypogranulosis, a disturbed corneocyte intracellular matrix, reduced amounts of natural moisturizing factor components, increased permeability and UV-B sensitivity of the RHE, and impaired keratinocyte differentiation at the messenger RNA and protein levels. In particular, the amounts of two Filaggrin-related proteins and one protease involved in the degradation of Filaggrin, bleomycin hydrolase, were lower. In addition, caspase-14 activation was reduced. These results demonstrate the importance of Filaggrin for the stratum corneum properties/functions. They indicate that Filaggrin downregulation in the epidermis of atopic patients, either acquired or innate, may be directly responsible for some of the disease-related alterations in the epidermal differentiation program and epidermal barrier function.
Aishath S. Naeem - One of the best experts on this subject based on the ideXlab platform.
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A mechanistic target of rapamycin complex 1/2 (mTORC1)/V-Akt murine thymoma viral oncogene homolog 1 (AKT1)/cathepsin H axis controls Filaggrin expression and processing in skin, a novel mechanism for skin barrier disruption in patients with atopic d
Journal of Allergy and Clinical Immunology, 2017Co-Authors: Aishath S. Naeem, C Tommasi, Christian Cole, Stuart J. Brown, Yanan Zhu, Benjamin Way, Saffron A.g. Willis Owen, Miriam F. Moffatt, William O.c.m. Cookson, J HarperAbstract:Background Filaggrin, which is encoded by the Filaggrin gene (FLG), is an important component of the skin's barrier to the external environment, and genetic defects in FLG strongly associate with atopic dermatitis (AD). However, not all patients with AD have FLG mutations. Objective We hypothesized that these patients might possess other defects in Filaggrin expression and processing contributing to barrier disruption and AD, and therefore we present novel therapeutic targets for this disease. Results We describe the relationship between the mechanistic target of rapamycin complex 1/2 protein subunit regulatory associated protein of the MTOR complex 1 (RAPTOR), the serine/threonine kinase V-Akt murine thymoma viral oncogene homolog 1 (AKT1), and the protease cathepsin H (CTSH), for which we establish a role in Filaggrin expression and processing. Increased RAPTOR levels correlated with decreased Filaggrin expression in patients with AD. In keratinocyte cell cultures RAPTOR upregulation or AKT1 short hairpin RNA knockdown reduced expression of the protease CTSH. Skin of CTSH-deficient mice and CTSH short hairpin RNA knockdown keratinocytes showed reduced Filaggrin processing, and the mouse had both impaired skin barrier function and a mild proinflammatory phenotype. Conclusion Our findings highlight a novel and potentially treatable signaling axis controlling Filaggrin expression and processing that is defective in patients with AD.
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an mtorc1 akt1 cathepsin h axis controls Filaggrin expression and processing in skin a novel mechanism for skin barrier disruption in atopic dermatitis
The Journal of Allergy and Clinical Immunology, 2016Co-Authors: Aishath S. Naeem, C Tommasi, Christian Cole, Stuart J. Brown, Yanan Zhu, Benjamin Way, Saffron A.g. Willis Owen, Miriam F. Moffatt, William O.c.m. Cookson, John I. HarperAbstract:BACKGROUND: Filaggrin, encoded by the FLG gene, is an important component of the skin’s barrier to the external environment and genetic defects in FLG strongly associate with Atopic Dermatitis (AD). However, not all AD patients have FLG mutations. OBJECTIVE: We hypothesised that these patients may possess other defects in Filaggrin expression and processing, contributing to barrier disruption and AD, and therefore present novel therapeutic targets for this disease. RESULTS: We describe the relationship between the mTORC1 protein subunit RAPTOR, the serine/threonine kinase AKT1 and the protease cathepsin H, for which we establish a role in Filaggrin expression and processing. Increased RAPTOR levels correlated with decreased Filaggrin expression in AD. In keratinocyte cell culture, RAPTOR up-regulation or AKT1 shRNA knockdown reduced the expression of the protease cathepsin H. Skin of cathepsin H-deficient mice and CTSH shRNA knockdown keratinocytes showed reduced Filaggrin processing and the mouse showed both impaired skin barrier function and a mild proinflammatory phenotype. CONCLUSION: Our findings highlight a novel, potentially treatable, signalling axis controlling Filaggrin expression and processing which is defective in AD.
Leopold Eckhart - One of the best experts on this subject based on the ideXlab platform.
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Filaggrin expression and processing deficiencies impair corneocyte surface texture and stiffness in mice
Journal of Investigative Dermatology, 2020Co-Authors: Jacob P. Thyssen, Ivone Jakasa, Michael P Schon, Jacek Wroblewski, Andrea Braun, Padraic G Fallon, Christoph Riethmuller, Hieronim Jakubowski, Marek Haftek, Leopold EckhartAbstract:Abundant corneocyte surface protrusions, observed in patients with atopic dermatitis with Filaggrin loss-of-function mutations, are inversely associated with levels of natural moisturizing factors (NMFs) in the stratum corneum. To dissect the etiological role of NMFs and Filaggrin deficiency in surface texture alterations, we examined mouse models with genetic deficiencies in the synthesis or degradation of Filaggrin monomers for NMFs, cell stiffness (elastic modulus) and corneocyte surface protrusion density (dermal texture index). Five neonatal and adult mouse models carrying inactivating mutations of SASPase (Sasp−/−), Filaggrin (Flgft/ft and Flg−/−), Filaggrin-hornerin (FlgHrnr−/−), and bleomycin hydrolase (Blmh−/−) were investigated. Sasp−/− and Flg−/− were on the hairless mouse background. Atomic force microscopy was used to determine elastic modulus and dermal texture index. Corneocytes of each neonatal as well as hairless adult knockout mouse exhibited an increased number of protrusions and decreased elastic modulus. In these mice, NMFs were reduced except for Sasp−/−. Dermal texture index was inversely correlated with NMFs and elastic modulus. Our findings demonstrate that any Filaggrin-NMF axis deficiency can affect corneocyte mechanical properties in mice and likely in humans. Differences in NMFs and corneocyte surface texture between neonatal and adult as well as hairless and hairy mice emphasize the need for carefully selecting the most appropriate animal models for studies.
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comparative genomics reveals conservation of Filaggrin and loss of caspase 14 in dolphins
Experimental Dermatology, 2015Co-Authors: Bettina Strasser, Heinz Fischer, Veronika Mlitz, Erwin Tschachler, Leopold EckhartAbstract:The expression of Filaggrin and its stepwise proteolytic degradation are critical events in the terminal differentiation of epidermal keratinocytes and in the formation of the skin barrier to the environment. Here, we investigated whether the evolutionary transition from a terrestrial to a fully aquatic lifestyle of cetaceans, that is dolphins and whales, has been associated with changes in genes encoding Filaggrin and proteins involved in the processing of Filaggrin. We used comparative genomics, PCRs and re-sequencing of gene segments to screen for the presence and integrity of genes coding for Filaggrin and proteases implicated in the maturation of (pro)Filaggrin. Filaggrin has been conserved in dolphins (bottlenose dolphin, orca and baiji) but has been lost in whales (sperm whale and minke whale). All other S100 fused-type genes have been lost in cetaceans. Among Filaggrin-processing proteases, aspartic peptidase retroviral-like 1 (ASPRV1), also known as saspase, has been conserved, whereas caspase-14 has been lost in all cetaceans investigated. In conclusion, our results suggest that Filaggrin is dispensable for the acquisition of fully aquatic lifestyles of whales, whereas it appears to confer an evolutionary advantage to dolphins. The discordant evolution of Filaggrin, saspase and caspase-14 in cetaceans indicates that the biological roles of these proteins are not strictly interdependent.
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cuts by caspase 14 control the proteolysis of Filaggrin
Journal of Investigative Dermatology, 2011Co-Authors: Leopold Eckhart, Erwin TschachlerAbstract:Although mutations in the Filaggrin gene (FLG) have been shown to be associated with ichthyosis vulgaris and atopic dermatitis, the function and regulation of Filaggrin remain incompletely understood. In this issue, Hoste et al. report that Filaggrin is directly cleaved by caspase-14. Acting in concert with other proteases, caspase-14 controls the breakdown of Filaggrin to free amino acids and amino acid derivatives that contribute to the hydration and UVB absorption capacity of the stratum corneum. These findings identify a new layer of complexity in the regulation of epidermal barrier function.
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knockdown of Filaggrin impairs diffusion barrier function and increases uv sensitivity in a human skin model
Journal of Investigative Dermatology, 2010Co-Authors: Michael Mildner, Claudia Ballaun, Maria Buchberger, Veronika Mlitz, Leopold Eckhart, Florian Gruber, Caterina Barresi, Caroline Stremnitzer, Sanja Kezic, Barbara SterniczkyAbstract:Loss-of-function mutations in the Filaggrin gene are associated with ichthyosis vulgaris and atopic dermatitis. To investigate the impact of Filaggrin deficiency on the skin barrier, Filaggrin expression was knocked down by small interfering RNA (siRNA) technology in an organotypic skin model in vitro. Three different siRNAs each efficiently suppressed the expression of proFilaggrin and the formation of mature Filaggrin. Electron microscopy revealed that keratohyalin granules were reduced in number and size and lamellar body formation was disturbed. Expression of keratinocyte differentiation markers and the composition of lipids appeared normal in Filaggrin-deficient models. The absence of Filaggrin did not render keratins 1, 2, and 10 more susceptible to extraction by urea, arguing against a defect in aggregation. Despite grossly normal stratum corneum morphology, Filaggrin-deficient skin models showed a disturbed diffusion barrier function in a dye penetration assay. Moreover, lack of Filaggrin led to a reduction in the concentration of urocanic acid, and sensitized the organotypic skin to UVB-induced apoptosis. This study thus demonstrates that knockdown of Filaggrin expression in an organotypic skin model reproduces epidermal alterations caused by Filaggrin mutations in vivo. In addition, our results challenge the role of Filaggrin in intermediate filament aggregation and establish a link between Filaggrin and endogenous UVB protection.
