Water-filtered infrared-A radiation (wIRA) is not implicated in cellular degeneration of human skin

Rapport de synthèse : Introduction : le vieillissement cutané est un processus biologique complexe auquel participe une exposition excessive au rayonnement ultraviolet du soleil. En particulier, les longueurs d'onde des rayons ultraviolets A et B (UV-A et UV-B) peuvent induire une augmentation de la synthèse de protéases, comme la métalloprotéinase matricielle 1 (MMP-1), qui est impliquée dans le processus de vieillissement. La thermothérapie par infrarouges, dont les longueurs d'onde sont plus longues que celles des UV, est largement utilisée à des fins thérapeutiques ou cosmétiques. Or, il a été démontré que les infrarouges en filtration aqueuse (IRFA) pouvaient induire une augmentation de la production de MMP-1 et par conséquent être nocifs. Il serait donc intéressant d'évaluer les effets des IRFA au niveau cellulaire et moléculaire. But Expérimental : étudier les effets des lampes à infrarouges en filtration aqueuse utilisées en clinique sur des fibroblastes cutanés humains en culture, afin d'analyser l'expression du gène codant pour la protéine MMP-1. Méthode : des fibroblastes cutanés humain ont été irradiés d'une part avec approximativement 88% d'IRFA (780-1400 nm) et 12% de lumière rouge (LR, 665-780 nm) avec 380 mW/cm2 IRFA(+LR) (333 mW/cm2 IRFA) et d'autre part avec des UV-A comme contrôle. Des courbes de survie cellulaire ont été établies après une exposition allant de 15 minutes à 8 heures au IRFA(+LR) (340-10880 J/cm2 wIRA(+RL), 300-9600 J/cm2 wIRA) ou de 15 à 45 minutes aux UV-A(+BL) (25-75 J/cm2 UV-A(+BL). L'induction de l'ARNm du gène de la MMP-1 a été analysé dans les fibroblastes cutanés humain à deux températures physiologiques (30°C et 37°C) lors d'expositions uniques de 15 à 60 minutes aux IRFA(+LR) (340-1360 J/cm2 IRFA(+LR), 300-1200 J/cm2 IRFA) ou de 30 minutes aux UV-A(+BL) (50 J/cm2 UVA(+BL)). De plus, nous avons effectué des irradiations répétées, une a chaque passage cellulaire jusqu'au passage. 10 de 15 minutes d'IRFA(+LR) 340 J/cm2 IRFA(+LR), 300 J/cm2 IRFA) . Résultats : une exposition unique aux UV-A (+BL) entraîne chez des fibroblastes cutanés humains une augmentation de la mort cellulaire, ainsi qu'une forte augmentation de l'expression du gène codant pour la MMP-1. L'augmentation mise en évidence pour cet ARNm varie en fonction de la technique utilisée : elle est de 11 ± 1 fois par RT-PCR classique, de 76 ± 2 fois par RT-PCR quantitative à 30°C, et de 75 ± 1 fois par RT-PCR quantitative à 37°C. Par contre, une exposition unique ou répétée aux IRFA (+LR) n'induit aucune augmentation de la mort cellulaire, ni de l'expression de l'ARNm de la MMP-1 chez ces fibroblastes. Conclusions : les résultats de cette étude montrent que, contrairement aux rayons ultraviolets, les IRFA (+LR) ne semblent impliqués ni dans le vieillissement, ni dans la mort cellulaire, même utilisés à des doses très élevées. Ces résultats sont en accord avec certaines investigations in vivo montrant une induction de MMP-1 par des UV et non des infrarouges. Ces dernières études suggèrent d'ailleurs plutôt un rôle protecteur des IRFA (+LR).

Water-filtered infrared-A radiation (wIRA) is not implicated in cellular degeneration of human skin.

BACKGROUND: Excessive exposure to solar ultraviolet radiation is involved in the complex biologic process of cutaneous aging. Wavelengths in the ultraviolet-A and -B range (UV-A and UV-B) have been shown to be responsible for the induction of proteases, e. g. the collagenase matrix metalloproteinase 1 (MMP-1), which are related to cell aging. As devices emitting longer wavelengths are widely used in therapeutic and cosmetic interventions and as the induction of MMP-1 by water-filtered infrared-A (wIRA) had been discussed, it was of interest to assess effects of wIRA on the cellular and molecular level known to be possibly involved in cutaneous degeneration. OBJECTIVES: Investigation of the biological implications of widely used water-filtered infrared-A (wIRA) radiators for clinical use on human skin fibroblasts assessed by MMP-1 gene expression (MMP-1 messenger ribonucleic acid (mRNA) expression).Methods: Human skin fibroblasts were irradiated with approximately 88% wIRA (780-1400 nm) and 12% red light (RL, 665-780 nm) with 380 mW/cm(2) wIRA(+RL) (333 mW/cm(2) wIRA) on the one hand and for comparison with UV-A (330-400 nm, mainly UV-A1) and a small amount of blue light (BL, 400-450 nm) with 28 mW/cm(2) UV-A(+BL) on the other hand. Survival curves were established by colony forming ability after single exposures between 15 minutes and 8 hours to wIRA(+RL) (340-10880 J/cm(2) wIRA(+RL), 300-9600 J/cm(2) wIRA) or 15-45 minutes to UV-A(+BL) (25-75 J/cm(2) UV-A(+BL)). Both conventional Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and quantitative real-time RT-PCR techniques were used to determine the induction of MMP-1 mRNA at two physiologic temperatures for skin fibroblasts (30 degrees C and 37 degrees C) in single exposure regimens (15-60 minutes wIRA(+RL), 340-1360 J/cm(2) wIRA(+RL), 300-1200 J/cm(2) wIRA; 30 minutes UV-A(+BL), 50 J/cm(2) UV-A(+BL)) and in addition at 30 degrees C in a repeated exposure protocol (up to 10 times 15 minutes wIRA(+RL) with 340 J/cm(2) wIRA(+RL), 300 J/cm(2) wIRA at each time). RESULTS: Single exposure of cultured human dermal fibroblasts to UV-A(+BL) radiation yielded a very high increase in MMP-1 mRNA expression (11 +/-1 fold expression for RT-PCR and 76 +/-2 fold expression for real-time RT-PCR both at 30 degrees C, 75 +/-1 fold expression for real-time RT-PCR at 37 degrees C) and a dose-dependent decrease in cell survival. In contrast, wIRA(+RL) did not produce cell death and did not induce a systematic increase in MMP-1 mRNA expression (less than twofold expression, within the laboratory range of fluctuation) detectable with the sensitive methods applied. Additionally, repeated exposure of human skin fibroblasts to wIRA(+RL) did not induce MMP-1 mRNA expression systematically (less than twofold expression by up to 10 consecutive wIRA(+RL) exposures and analysis with real-time RT-PCR). CONCLUSIONS: wIRA(+RL) even at the investigated disproportionally high irradiances does not induce cell death or a systematic increase of MMP-1 mRNA expression, both of which can be easily induced by UV-A radiation. Furthermore, these results support previous findings of in vivo investigations on collagenase induction by UV-A but not wIRA and show that infrared-A with appropriate irradiances does not seem to be involved in MMP-1 mediated photoaging of the skin. As suggested by previously published studies wIRA could even be implicated in a protective manner.

Desensitization of thermal hyperemia in the skin is reproducible.

OBJECTIVE: Local heating increases skin blood flow SkBF (thermal hyperemia). In a previous study, we reported that a first local thermal stimulus could attenuate the hyperemic response to a second one applied later on the same skin spot, a phenomenon that we termed desensitization. However, other studies found no evidence for desensitization in similar conditions. The aim of the present work was to test whether it was related to differences in instrumentation. METHODS: Twenty-eight healthy young males were studied. Two pairs of heating chambers, one custom-made (our study) and one commercial (other groups), were affixed to forearm skin. SkBF was measured with single-point laser-Doppler flowmetry (LDF) (780nm) in one pair, and laser-Doppler imaging (LDI) (633nm) in the other. A temperature step from 34 to 41°C, was applied for 30minutes and repeated after two hours. RESULTS: During the second thermal challenge, the plateau SkBF was lower than during the first thermal and was observed with each of the four combinations of SkBF measurement techniques and heating equipment (p<0.05 for all conditions, range -9% to -16% of the initial value). CONCLUSION: Desensitization of thermal hyperemia is not specific to peculiar operating conditions.

Nuclear factor I-C links platelet-derived growth factor and transforming growth factor beta1 signaling to skin wound healing progression.

Transforming growth factor beta (TGF-beta) and platelet-derived growth factor A (PDGFAlpha) play a central role in tissue morphogenesis and repair, but their interplay remain poorly understood. The nuclear factor I C (NFI-C) transcription factor has been implicated in TGF-beta signaling, extracellular matrix deposition, and skin appendage pathologies, but a potential role in skin morphogenesis or healing had not been assessed. To evaluate this possibility, we performed a global gene expression analysis in NFI-C(-/-) and wild-type embryonic primary murine fibroblasts. This indicated that NFI-C acts mostly to repress gene expression in response to TGF-beta1. Misregulated genes were prominently overrepresented by regulators of connective tissue inflammation and repair. In vivo skin healing revealed a faster inflammatory stage and wound closure in NFI-C(-/-) mice. Expression of PDGFA and PDGF-receptor alpha were increased in wounds of NFI-C(-/-) mice, explaining the early recruitment of macrophages and fibroblasts. Differentiation of fibroblasts to contractile myofibroblasts was also elevated, providing a rationale for faster wound closure. Taken together with the role of TGF-beta in myofibroblast differentiation, our results imply a central role of NFI-C in the interplay of the two signaling pathways and in regulation of the progression of tissue regeneration.

Swiss clinical practice guidelines for skin cancer in organ transplant recipients.

Patients with a solid organ transplant have increased in numbers and in individual survival in Switzerland over the last decades. As a consequence of long-term immunosuppression, skin cancer in solid organ recipients (SOTRs) has been recognized as an important problem. Screening and education of potential SOTRs about prevention of sun damage and early recognition of skin cancer are important before transplantation. Once transplanted, SOTRs should be seen by a dermatologist yearly for repeat education as well as early diagnosis, prevention and treatment of skin cancer. Squamous cell carcinoma of the skin (SCC) is the most frequent cancer in the setting of long-term immunosuppression. Sun protection by behaviour, clothing and daily sun screen application is the most effective prevention. Cumulative sun damage results in field cancerisation with numerous in-situ SCC such as actinic keratosis and Bowen's disease which should be treated proactively. Invasive SCC is cured by complete surgical excision. Early removal is the best precaution against potential metastases of SCC. Reduction of immunosuppression and switch to mTOR inhibitors and potentially, mycophenolate, may reduce the incidence of further SCC. Chemoprevention with the retinoid acitretin reduces the recurrence rate of SCC. The dermatological follow-up of SOTRs should be integrated into the comprehensive post-transplant care.

Retinal pigment epithelium tears after intravitreal injection of ranibizumab for predominantly classic neovascular membranes secondary to age-related macular degeneration.

PURPOSE: Retinal pigment epithelium (RPE) tear is an extremely rare complication in patients with classic neovascular membranes without RPE detachment. We evaluate their incidence and functional outcome following treatment with intravitreal ranibizumab. METHODS: Observational study of 72 consecutive patients (74 eyes) treated at Jules Gonin University Eye Hospital, Lausanne, with intravitreal ranibizumab 0.5 mg for classic choroidal neovascularization (CNV) between March 2006 and February 2008. Best-corrected visual acuity (BCVA), fundus examination and optical coherence tomography were recorded monthly; fluorescein angiography was performed at baseline and repeated at least every 3 months. RESULTS: RPE tears occurred in four (5.4%) eyes temporal to the fovea, after a mean of four injections (range 3-6). Mean baseline BCVA was 0.25 decimal equivalent (logMAR 0.67) and improved despite the RPE tear to 0.6 decimal equivalent (logMAR 0.22). CONCLUSION: RPE tears following intravitreal ranibizumab injections for classic CNV can occur in about 5% of patients, even in the absence of baseline RPE detachment. Nevertheless, vision may improve provided the fovea is not involved.

NR2E3 mutations in enhanced S-cone sensitivity syndrome (ESCS), Goldmann-Favre syndrome (GFS), clumped pigmentary retinal degeneration (CPRD), and retinitis pigmentosa (RP).

NR2E3, also called photoreceptor-specific nuclear receptor (PNR), is a transcription factor of the nuclear hormone receptor superfamily whose expression is uniquely restricted to photoreceptors. There, its physiological activity is essential for proper rod and cone photoreceptor development and maintenance. Thirty-two different mutations in NR2E3 have been identified in either homozygous or compound heterozygous state in the recessively inherited enhanced S-cone sensitivity syndrome (ESCS), Goldmann-Favre syndrome (GFS), and clumped pigmentary retinal degeneration (CPRD). The clinical phenotype common to all these patients is night blindness, rudimental or absent rod function, and hyperfunction of the "blue" S-cones. A single p.G56R mutation is inherited in a dominant manner and causes retinitis pigmentosa (RP). We have established a new locus-specific database for NR2E3 (www.LOVD.nl/eye), containing all reported mutations, polymorphisms, and unclassified sequence variants, including novel ones. A high proportion of mutations are located in the evolutionarily-conserved DNA-binding domains (DBDs) and ligand-binding domains (LBDs) of NR2E3. Based on homology modeling of these NR2E3 domains, we propose a structural localization of mutated residues. The high variability of clinical phenotypes observed in patients affected by NR2E3-linked retinal degenerations may be caused by different disease mechanisms, including absence of DNA-binding, altered interactions with transcriptional coregulators, and differential activity of modifier genes.

NLRP3 promotes inflammation-induced skin cancer but is dispensable for asbestos-induced mesothelioma.

Asbestos exposure can result in serious and frequently lethal diseases, including malignant mesothelioma. The host sensor for asbestos-induced inflammation is the NLRP3 inflammasome and it is widely assumed that this complex is essential for asbestos-induced cancers. Here, we report that acute interleukin-1β production and recruitment of immune cells into peritoneal cavity were significantly decreased in the NLRP3-deficient mice after the administration of asbestos. However, NLRP3-deficient mice displayed a similar incidence of malignant mesothelioma and survival times as wild-type mice. Thus, early inflammatory reactions triggered by asbestos are NLRP3-dependent, but NLRP3 is not critical in the chronic development of asbestos-induced mesothelioma. Notably, in a two-stage carcinogenesis-induced papilloma model, NLRP3-deficient mice showed a resistance phenotype in two different strain backgrounds, suggesting a tumour-promoting role of NLRP3 in certain chemically-induced cancer types.

Molecular mechanisms for the regulation of skin homeostasis

L'ubiquitination est une modification des protéines conservée, consistant en l'addition de résidus « ubiquitine » et régulant le destin cellulaire des protéines. La protéine « TRAF-interacting protein » TRAIP (ou TRIP) est une ligase E3 qui catalyse l'étape finale de l'ubiquitination. TRAIP est conservé dans l'évolution et est nécessaire au développement des organismes puisque l'ablation de TRAIP conduit à la mort embryonnaire aussi bien de la drosophile que de la souris. De plus, la réduction de l'expression de TRAIP dans des kératinocytes épidermiques humains réprime la prolifération cellulaire et induit un arrêt du cycle cellulaire en phase Gl, soulignant le lien étroit entre TRAIP et la prolifération cellulaire. Comme les mécanismes de régulation de la prolifération jouent un rôle majeur dans l'homéostasie de la peau, il est important de caractériser la fonction de TRAIP dans ces mécanismes. En utilisant des approches in vitro, nous avons déterminé que la protéine TRAIP est instable, modifiée par l'addition d'ubiquitine et ayant une demi-vie d'environ 4 heures. Nos analyses ont également révélé que l'expression de TRAIP est dépendante du cycle cellulaire, atteignant un pic d'expression en phase G2/M et que l'induction de son expression s'effectue principalement au cours de la transition Gl/S. Nous avons identifié le facteur de transcription E2F1 comme en étant le responsable, en régulant directement le promoteur de TRAIP. Aussi, TRAIP endogène ou surexprimée est surtout localisée au niveau du nucléole, une organelle nucléaire qui est désassemblée pendant la division cellulaire. Pour examiner la localisation subcellulaire de TRAIP pendant la mitose, nous avons imagé la protéine TRAIP fusionnée à une protéine fluorescente, à l'intérieur de cellules vivantes nommées HeLa, à l'aide d'un microscope confocal. Dans ces conditions, TRAIP est majoritairement localisée autour des chromosomes en début de mitose, puis est arrangée au niveau de l'ADN chromosomique en fin de mitose. La détection de TRAIP endogène à l'aide d'un anticorps spécifique a confirmé cette localisation. Enfin, l'inactivation de TRAIP dans les cellules HeLa par interférence ARN a inhibé leur capacité à s'arrêter en milieu de mitose. Nos résultats suggèrent que le mécanisme sous-jacent peut être lié au point de contrôle de l'assemblage du fuseau mitotique. - Ubiquitination of proteins is a post-translational modification which decides the cellular fate of the protein. The TRAF-interacting protein (TRAIP, TRIP) functions as an E3 ubiquitin ligase mediating addition of ubiquitin moieties to proteins. TRAIP interacts with the deubiquitinase CYLD, a tumor suppressor whose functional inactivation leads to skin appendage tumors. TRAIP is required for early embryonic development since removal of TRAIP either in Drosophila or mice by mutations or knock¬out is lethal due to aberrant regulation of cell proliferation and apoptosis. Furthermore, shRNA- mediated knock-down of TRAIP in human epidermal keratinocytes (HEK) repressed cell proliferation and induced a Gl/S phase block in the cell cycle. Additionally, TRAIP expression is strongly down- regulated during keratinocyte differentiation supporting the notion of a tight link between TRAIP and cell proliferation. We thus examined the biological functions of TRAIP in epithelial cell proliferation. Using an in vitro approach, we could determine that the TRAIP protein is unstable, modified by addition of ubiquitin moieties after translation and exhibits a half-life of 3.7+/-1-6 hours. Our analysis revealed that the TRAIP expression is modulated in a cell-cycle dependent manner, reaching a maximum expression level in G2/M phases. In addition, the expression of TRAIP was particularly activated during Gl/S phase transition and we could identify the transcription factor E2F1 as an activator of the TRAIP gene promoter. Both endogenous and over-expressed TRAIP mainly localized to the nucleolus, a nuclear organelle which is disassembled during cell division. To examine the subcellular localization of TRAIP during M phase, we performed confocal live-cell imaging of a functional fluorescent protein TRAIP-GFP in HeLa cells. TRAIP was distributed in the cytoplasm and accumulated around mitotic chromosomes in pro- and meta-phasic cells. TRAIP was then confined to chromosomal DNA location in anaphase and later phases of mitosis. Immune-detection of endogenous TRAIP protein confirmed its particular localization in mitosis. Finally, inactivating TRAIP expression in HeLa cells using RNA interference abrogated the cells ability to stop or delay mitosis progression. Our results suggested that TRAIP may involve the spindle assembly checkpoint.

AFT3 as a new therapeutic target for skin field cancerization in antagonism with compromised Notch/CSL signaling

Les interactions épithélio-mésenchymateuses jouent un rôle important dans le contrôle du développement normal de la peau, son homéostasie et sa tumorigenèse. Les fibroblastes dermiques (DFs) représentent la catégorie cellulaire la plus abondante dans le stroma et leur rôle est de plus en plus considéré. En ce qui concerne particulièrement la tumorigenèse, des facteurs diffusibles produits par les fibroblastes entourant les tumeurs épithéliales, appelés 'fibroblastes associés au cancer (CAF)', interagissent au niveau de l'inflammation impliquée directement ou indirectement dans la signalisation paracrine, entre le stroma et les cellules épiéliales cancéreuses. Le risque de cancer de la peau augmente de façon exponentielle avec l'âge. Comme un lien probable entre les deux, la sénescence des fibroblastes résulte de la production du sécrétome favorisant la sénescence (SMS), un groupe de facteurs diffusibles induisant une stimulation paracrine de la croissance, l'inflammation et le remodelage de la matrice. De façon fort intéressante, l'induction de ces gènes est aussi une caractéristique des CAFs. Cependant, le lien entre les deux événements cellulaires sénescence et activation des CAFs reste en grande partie inexploré. L'ATF3 (Activating Transcription Factor 3) est un facteur de transcription induit en réponse au stress, dont les fonctions sont hautement spécifiques du type cellulaire. Bien qu'il ait été découvert dans notre laboratoire en tant que promoteur de tumeurs dans les kératinocytes, ses fonctions biologique et biochimique dans le derme n'ont pas encore été étudiées. Récemment, nous avons constaté que, chez la souris, l'abrogation de la voie de signalisation de Notch/CSL dans les DFs, induisait la formation de tumeurs kératinocytaires multifocales. Ces dernières proviennent de la cancérisation en domaine, un phénomène associé à une atrophie du stroma, des altérations de la matrice et de l'inflammation. D'autres études ont montré que CSL agissait comme un régulateur négatif de gènes impliqués dans sénescence des DFs et dans l'activation des CAFs. Ici, nous montrons que la suppression ou l'atténuation de l'expression de ATF3 dans les DFs induit la sénescence et l'expression des gènes liés aux CAFs, de façon similaire à celle déclenchée par la perte de CSL, tandis que la surexpression de ATF3 supprime ces changements. Nous émettons l'hypothèse que ATF3 joue un rôle suppresseur dans l'activation des CAFs et dans la progression des tumeurs kératinocytaires, en surmontant les conséquences de l'abrogation de la voie de signalisation Notch/CSL. En concordance avec cette hypothèse, nous avons constaté que la perte de ATF3 dans les DFs favorisait la tumorigénicité des kératinocytes via le contrôle négatif de cytokines, des enzymes de la matrice de remodelage et de protéines associées au cancer, peut-être par liaison directe des effecteurs de la voie Notch/CSL : IL6 et les gènes Hes. Enfin, dans les échantillons cliniques humains, le stroma sous-jacent aux lésions précancéreuses de kératoses actiniques montre une diminution significative de l'expression de ATF3 par rapport au stroma jouxtant la peau normale. La restauration de l'expression de ATF3 pourrait être utilisée comme un outil thérapeutique en recherche translationnelle pour prévenir ou réprimer le processus de cancérisation en domaine. - Epithelial-mesenchymal interactions play an important role in control of normal skin development, homeostasis and tumorigenesis. The role of dermal fibroblasts (DFs) as the most abundant cell type in stroma is increasingly appreciated. Especially during tumorigenesis, fibroblasts surrounding epithelial tumors, called Cancer Associated Fibroblasts (CAFs), produce diffusible factors (growth factors, inflammatory cytokines, chemokines and enzymes, and matrix metalloproteinases) that mediate inflammation either directly or indirectly through paracrine signaling between stroma and epithelial cancer cells. The risk of skin cancer increases exponentially with age. As a likely link between the two, senescence of fibroblasts results in production of the senescence-messaging-secretome (SMS), a panel of diffusible factors inducing paracrine growth stimulation, inflammation, and matrix remodeling. Interestingly, induction of these genes is also a characteristic of Cancer Associated Fibroblasts (CAFs). However, the link between the two cellular events, senescence and CAF activation is largely unexplored. ATF3 is a key stress response transcription factor with highly cell type specific functions, which has been discovered as a tumor promoter in keratinocytes in our lab. However, the biological and biochemical function of ATF3 in the dermal compartment of the skin has not been studied yet. Recently, we found that compromised Notch/CSL signaling in dermal fibroblasts (DFs) in mice is a primary cause of multifocal keratinocyte tumors called field cancerization associated with stromal atrophy, matrix alterations and inflammation. Further studies showed that CSL functions as a negative regulator of genes involved in DFs senescence and CAF activation. Here, we show that deletion or silencing of the ATF3 gene in DFs activates senescence and CAF-related gene expression similar to that triggered by loss of CSL, while increased ATF3 suppresses these changes. We hypothesize that ATF3 plays a suppressing role in CAF activation and keratinocyte tumor progression, overcoming the consequences of compromised Notch/CSL signaling. In support of this hypothesis, we found that loss of ATF3 in DFs promotes tumorigenic behavior of keratinocytes via negative control of cytokines, matrix-remodeling enzymes and cancer-associated proteins, possibly through direct binding to Notch/CSL targets, IL6 and Hes genes. On the other hand, in human clinical samples, stromal fields underlying premalignant actinic keratosis lesions showed significantly decreased ATF3 expression relative to stroma of flanking normal skin. Restoration of ATF3, which is lost in cancer development, may be used as a therapeutic tool for translational research to prevent or suppress the field cancerization process.

Mutations of the Serine Protease CAP1/Prss8 Lead to Reduced Embryonic Viability, Skin Defects, and Decreased ENaC Activity.

CAP1/Prss8 is a membrane-bound serine protease involved in the regulation of several different effectors, such as the epithelial sodium channel ENaC, the protease-activated receptor PAR2, the tight junction proteins, and the profilaggrin polypeptide. Recently, the V170D and the G54-P57 deletion mutations within the CAP1/Prss8 gene, identified in mouse frizzy (fr) and rat hairless (fr(CR)) animals, respectively, have been proposed to be responsible for their skin phenotypes. In the present study, we analyzed those mutations, revealing a change in the protein structure, a modification of the glycosylation state, and an overall reduction in the activation of ENaC of the two mutant proteins. In vivo analyses demonstrated that both fr and fr(CR) mutant animals present analogous reduction of embryonic viability, similar histologic aberrations at the level of the skin, and a significant decrease in the activity of ENaC in the distal colon compared with their control littermates. Hairless rats additionally had dehydration defects in skin and intestine and significant reduction in the body weight. In conclusion, we provided molecular and functional evidence that CAP1/Prss8 mutations are accountable for the defects in fr and fr(CR) animals, and we furthermore demonstrate a decreased function of the CAP1/Prss8 mutant proteins. Therefore, fr and fr(CR) animals are suitable models to investigate the consequences of CAP1/Prss8 action on its target proteins in the whole organism.