Ligand-specific c-Fos expression emerges from the spatiotemporal control of ErbB network dynamics.

Activation of ErbB receptors by epidermal growth factor (EGF) or heregulin (HRG) determines distinct cell-fate decisions, although signals propagate through shared pathways. Using mathematical modeling and experimental approaches, we unravel how HRG and EGF generate distinct, all-or-none responses of the phosphorylated transcription factor c-Fos. In the cytosol, EGF induces transient and HRG induces sustained ERK activation. In the nucleus, however, ERK activity and c-fos mRNA expression are transient for both ligands. Knockdown of dual-specificity phosphatases extends HRG-stimulated nuclear ERK activation, but not c-fos mRNA expression, implying the existence of a HRG-induced repressor of c-fos transcription. Further experiments confirmed that this repressor is mainly induced by HRG, but not EGF, and requires new protein synthesis. We show how a spatially distributed, signaling-transcription cascade robustly discriminates between transient and sustained ERK activities at the c-Fos system level. The proposed control mechanisms are general and operate in different cell types, stimulated by various ligands.

A preliminary investigation of the impact of artificially carbonated water bathing on canine skin physiological and barrier function.

BACKGROUND: The effect of carbon dioxide (CO2 )-rich water bathing on the skin has been studied extensively in humans. However, there have been few studies evaluating the impact of CO2 -rich water bathing on canine skin physiology and barrier functions. OBJECTIVES: To evaluate the impact of artificially carbonated water (ACW) bathing on skin parameters in healthy beagles. ANIMALS: Six healthy beagles with no history of skin disease. MATERIALS AND METHODS: Body temperature, skin temperature, transepidermal water loss (TEWL), skin hydration and skin blood flow were evaluated before and after single ACW bathing (37°C, 20 min) with a CO2 concentration of >1000 ppm. RESULTS: After ACW bathing, skin blood flow significantly increased (p < 0.0001), yet there were no significant changes in body temperature (p = 0.3124), skin temperature (p = 0.4911), TEWL (p = 0.5167) or skin hydration (p = 0.3084). There were no adverse events during the trials. CONCLUSIONS AND CLINICAL IMPORTANCE: Artificially carbonated water water bathing could potentially increase skin blood flow without affecting skin temperature, body temperature and skin barrier function in dogs, similar to its effects in humans.

Validation of laser doppler flowmetry to measure dermal blood flow of the pinnae in dogs with pinnal alopecia.

BACKGROUND: Laser Doppler flowmetry (LDF) is a noninvasive method of measuring regional blood flow in humans. However, this method has not been widely applied to measure blood flow in dogs. HYPOTHESIS/OBJECTIVES: We hypothesised that LDF can measure changes in blood flow in canine pinnae accurately. The objectives were to determine whether LDF could accurately detect dermal blood flow changes in canine pinnae caused by haemodynamic drugs and characterize the dermal blood flow in dogs with pinnal alopecia. ANIMALS: Sixteen laboratory-owned healthy dogs, 25 client-owned healthy control dogs and six dogs with pinnal alopecia suspected to be secondary to ischaemic dermatoses. MATERIALS AND METHODS: Clinical doses of the haemodynamic drugs atropine, medetomidine and dibutyryl cyclic adenosine monophosphate (dBcAMP), as well as topical dBcAMP, were administered to healthy beagles. Subsequently, an LDF apparatus was attached to the pinnae to analyse changes in dermal blood flow. Finally, LDF was used to measure auricular dermal blood flow in dogs with pinnal alopecia compared to healthy dogs. RESULTS: Dermal blood flow increased after atropine injection, during dBcAMP infusion and after topical dBcAMP ointment application, and decreased after medetomidine injection. Auricular dermal blood flow (in mL/min/100 g tissue) was significantly (p < 0.05) lower in dogs with pinnal alopecia than in healthy dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Laser Doppler flowmetry is useful for measuring dermal blood flow in canine pinnae; it can be a noninvasive method to monitor ischaemic conditions of dog skin.

Clinical efficacy of artificially carbonated water bathing on superficial bacterial folliculitis in dogs.

BACKGROUND: Bathing with artificially carbonated water is reported to be a valuable therapeutic option for various human skin disorders. OBJECTIVE: To evaluate the clinical efficacy of artificially carbonated water bathing on superficial bacterial folliculitis (SBF) caused by Staphylococcus pseudintermedius (SP) in dogs. ANIMALS: Nineteen dogs with SBF from whom SP was isolated from skin lesions were enrolled. METHODS AND MATERIALS: Dogs with SBF were allocated randomly to either the artificially carbonated water bathing group or the control group bathed with tap water. The dogs were bathed with the designated water type on day (D)0, D7 and D14. Clinical scores and skin surface pH were evaluated on D0 and D21. Colony forming unit (cfu) assays were performed in vitro to investigate whether the artificially carbonated water affected growth of clinical SP isolates. RESULTS: The mean rate of improvement in the clinical scores was significantly higher in the carbonated water group than in the control group. Dogs bathed with carbonated water exhibited significant decreases in their skin surface pH after bathing; dogs bathed with tap water did not. No dogs experienced significant adverse events. The cfus of SP incubated in vitro with artificially carbonated water did not significantly differ from those incubated with tap water. CONCLUSION: Bathing with artificially carbonated water might be an effective and safe adjunctive therapy for canine SP-induced SBF.

Narrow-band ultraviolet B therapy attenuates cutaneous T-cell responses in hapten-induced, experimental contact dermatitis in beagles.

BACKGROUND: In human medicine, narrow-band ultraviolet B (NB-UVB) phototherapy has been used to treat various T-cell-mediated skin diseases. However, the effect of NB-UVB on inflamed canine skin remains uncertain. OBJECTIVES: To investigate the effect of NB-UVB phototherapy on the skin of dogs with hapten-induced contact dermatitis. ANIMALS: Seven healthy beagles without skin problems. METHODS AND MATERIALS: Dogs were irradiated with varying doses of NB-UVB to determine the minimal erythema dose (MED). After determining the MEDs of six dogs (excluding one of the seven whose skin did not show a visible reaction), we investigated the effect of NB-UVB on their inflamed skin by topically applying 2,4-dinitrochlorobenzene (DNCB), which causes type 1 helper T cell (Th1)- and cytotoxic T-cell (Tc)1-induced skin inflammation. We then irradiated the skin with NB-UVB. We analysed the treated skin samples via histopathological and immunohistochemical methods, and TdT-mediated dUTP nick-end labelling (TUNEL) to demonstrate apoptotic cells. We also analysed the cytokine gene transcription via real-time quantitative reverse transcription PCR. RESULTS: The NB-UVB MEDs caused mild inflammatory changes yet no severe epidermal exfoliations in the irradiated skin. In DNCB-treated skin irradiated by the NB-UVB MEDs, TUNEL-positive dermal apoptotic cells were increased significantly compared with those of DNCB-treated, nonirradiated skin. INF-γ and TNF-α transcription levels in DNCB-treated, irradiated skin were significantly lower than those in the DNCB-treated, nonirradiated skin. CONCLUSION AND CLINICAL RELEVANCE: Phototherapy using NB-UVB MEDs attenuated cutaneous Th1 and Tc1 cytokine responses with minimal skin damage in a canine model of hapten-induced contact dermatitis.

Progenitor cells expressing nestin, a neural crest stem cell marker, differentiate into outer root sheath keratinocytes.

BACKGROUND: Nestin, which was originally described as a neural crest stem cell marker, is known to be expressed in bulge follicle cells of human, canine and murine anagen hairs. However, the capacity of nestin-expressing cells to differentiate into the components of the hair follicle or the epidermis has been insufficiently investigated. HYPOTHESIS/OBJECTIVES: To determine whether nestin-expressing cells are capable of differentiating into keratinocytes. ANIMALS/MATERIALS: A double-transgenic mouse line Nes-Cre/CAG-CAT-EGFP, in which enhanced green fluorescent protein (EGFP) is expressed upon Cre-based recombination driven by the nestin promoter. METHODS AND MATERIALS: The tissue distribution of EGFP+ and nestin+ cells in the skin of the mouse line was analysed by immunofluorescence and immunohistochemical analyses. RESULTS: EGFP+ cells were recognized in the outer epithelial cell layers of anagen and telogen hair follicles, but rarely seen in the interfollicular epidermis. The EGFP+ cells in the outer layers of the hair follicles coexpressed keratin 14, a marker of the outer root sheath (ORS) keratinocytes, but not trichohyalin granules, an inner root sheath keratinocyte cell marker. Immunostaining for nestin failed to detect its expression in the majority of hair follicle epithelial cells, suggesting that the EGFP+ cells in the ORS were derived from nestin-expressing progenitor cells that had become further committed along the epithelial cell lineage, where nestin is no longer expressed. CONCLUSIONS AND CLINICAL IMPORTANCE: These results suggest that progenitor cells that differentiate into ORS keratinocytes are distinct from those for other hair follicle or epidermal components and provide implications for regenerative medicine and the molecular classification of hair follicle tumours.

Staphylococcus aureus penetrate the interkeratinocyte spaces created by skin-infiltrating neutrophils in a mouse model of impetigo.

BACKGROUND: Impetigo is a bacterial skin disease characterized by intraepidermal neutrophilic pustules. Previous studies have demonstrated that exfoliative toxin producing staphylococci are isolated in the cutaneous lesions of human and canine impetigo. However, the mechanisms of intraepidermal splitting in impetigo remain poorly understood. OBJECTIVE: To determine how staphylococci penetrate the living epidermis and create intraepidermal pustules in vivo using a mouse model of impetigo. METHODS: Three Staphylococcus aureus strains harbouring the etb gene and three et gene negative strains were epicutaneously inoculated onto tape-stripped mouse skin. The skin samples were subjected to time course histopathological and immunofluorescence analyses to detect intraepidermal neutrophils and infiltrating staphylococci. To determine the role of neutrophils on intraepidermal bacterial invasion, cyclophosphamide (CPA) was injected intraperitoneally into the mice to cause leucopenia before the inoculation of etb gene positive strains. RESULTS: In mice inoculated with etb gene positive S. aureus, intraepidermal pustules resembling impetigo were detected as early as 4 h post-inoculation (hpi). Neutrophils in the epidermis were detected from 4 hpi, whereas intraepidermal staphylococci was detected from 6 hpi. The dimensions of the intraepidermal clefts created in mice inoculated with etb gene positive strains at 6 hpi were significantly larger than those in mice inoculated with et gene negative strains. In CPA treated mice, staphylococci or neutrophils were not detected in the deep epidermis until 6 hpi. CONCLUSION: Our findings indicate that intraepidermal neutrophils play an important role in S. aureus invasion into the living epidermis in a mouse model of impetigo.

Genome-wide comprehensive analysis of transcriptional regulation by ArgR in Thermus thermophilus.

ArgR is known to serve as a repressor/activator of the metabolism of arginine. To elucidate the role of ArgR in the metabolism of Thermus thermophilus cells, comparative genome-wide comprehensive analysis was conducted for wild-type T. thermophilus and its mutant lacking the argR gene. Transcriptome analysis and chromatin affinity precipitation coupled with high-density tiling chip (ChAP-chip) analysis identified 34 genetic loci that are directly regulated by ArgR and indicated that ArgR decreases the expression of arginine biosynthesis and also regulates several other genes involved in amino acid metabolism, including lysine biosynthetic genes, as suggested by our previous study. Among genes whose expression was regulated by ArgR, the largest effect of argR knockout was observed in a putative operon, including genes TTHA0284, TTHA0283, and TTHA0282 involved in arginine biosynthesis. The promoter of this operon, argG, was repressed approximately 21-fold by ArgR. DNase I footprint analysis coupled with electrophoretic mobility shift assay suggested that high arginine-dependent repression was attributed to the fact that the promoter contains three operators for ArgR binding and ArgR is bound to the binding sites cooperatively, possibly forming a DNA loop, in the hexameric form stabilized by arginine binding.

Suspected renal interstitial cell tumor causing polycythemia in two dogs.

Here we report a case series of two dogs diagnosed as renal interstitial cell tumor (RICT) accompanied by elevated serum erythropoietin level and marked polycythemia. RICT is a rare tumor in dogs, originating from renal interstitial cells. While several renal tumors such as renal lymphoma, adenocarcinoma, carcinoma, sarcoma, fibrosarcoma and nephroblastoma may cause polycythemia, polycythemia caused by RICT has never been reported in dogs. The tumors in both dogs were solitary and lied within cortex or cortico-medullary junction. Histopathology revealed spindle-shaped cells suggesting mesenchymal origin, with no mitotic figures suggesting that the tumors in both dogs were benign. Following surgical removal of the affected kidney, serum erythropoietin level and polycythemia normalized in both dogs.

Skin lipid profiling in normal and seborrhoeic shih tzu dogs.

BACKGROUND: Seborrhoea is a clinical condition resulting in excessive lipid and/or scale on the skin and is a common and important skin disease of dogs. However, there is little information on the skin surface lipid composition of dogs with seborrhoea. HYPOTHESIS/OBJECTIVES: To compare skin surface lipid profiles in normal and seborrhoeic shih tzu dogs. METHODS: Fourteen client-owned dogs (seven seborrhoeic and seven normal) were investigated. Lipids in sebaceous glands (SGs) were extracted from homogenized tissues of SG hyperplasia. Surface lipid was collected by tape stripping [stratum corneum (SC)-enriched fraction] and acetone-wetted cotton swab (acetone-extracted fraction). Lipids in SGs, SC-enriched fractions and acetone-extracted fractions were evaluated by high-performance thin-layer chromatography. RESULTS: Lipids in SGs mainly consisted of cholesterol esters, wax esters and triglycerides, whereas lipids in the SC-enriched fraction mainly consisted of ceramides. The acetone-extracted fraction contained a mixture of lipid classes recognized in SG- and SC-enriched fractions. In seborrhoeic dogs, concentrations of wax esters and triglycerides in the acetone-extracted fraction were significantly higher than in control dogs (P = 0.0285). Amounts of total ceramides (in micrograms) per milligram of SC were not significantly different between the two groups (P = 0.5204). Interestingly, two unknown ceramide fractions, which accounted for 20% of the total ceramides, were recognized exclusively in seborrhoeic dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: These results provide evidence that the skin surface lipid profiles are altered in shih tzu dogs with seborrhoea.

Usefulness of cefovecin disk-diffusion test for predicting mecA gene-containing strains of Staphylococcus pseudintermedius and clinical efficacy of cefovecin in dogs with superficial pyoderma.

BACKGROUND: Cefovecin has been widely used to treat skin infections in dogs. The relationship of the cefovecin disk-diffusion test results to the presence of the mecA gene and the clinical efficacy of cefovecin have not been fully evaluated. HYPOTHESIS/OBJECTIVES: To determine the usefulness of an in vitro cefovecin disk-diffusion test in predicting the presence of the mecA gene in Staphylococcus pseudintermedius, as well as the in vivo efficacy of cefovecin therapy in dogs with superficial pyoderma. METHODS: Twenty-six S. pseudintermedius strains isolated from 22 dogs with pyoderma were used. In vitro disk-diffusion test results of cefovecin were compared with agar-dilution test results, the presence of the mecA gene, and the improvement in clinical scores of dogs with superficial pyoderma at 14 days post treatment. RESULTS: There was a significant linear correlation (r = -0.83) between the diameter of the obvious zone of inhibition by disk diffusion and the minimal inhibitory concentration for cefovecin (P < 0.0001). Receiver operating characteristic analysis revealed that zone diameters between 25 and 27 mm exhibited better sensitivity (92.9%) and specificity (100.0%) for detection of strains carrying the mecA gene. The mean improvement in clinical scores in dogs carrying cefovecin-resistant strains was significantly lower than in dogs carrying cefovecin-susceptible strains (P < 0.01). CONCLUSIONS AND CLINICAL IMPORTANCE: The cefovecin disk-diffusion test with a cut-off value estimated in this study was valuable for predicting mecA gene carriage in S. pseudintermedius, as well as the in vivo efficacy of cefovecin therapy in dogs with superficial pyoderma caused by S. pseudintermedius.

Transcription profile of chemokine receptors, cytokines and cytotoxic markers in peripheral blood of dogs with epitheliotropic cutaneous lymphoma.

BACKGROUND: Mycosis fungoides (MF) is the most common form of canine epitheliotropic cutaneous lymphoma, which is characterized by the accumulation of neoplastic CD8(+) T cells. Given that multifocal skin lesions are commonly seen in MF, neoplastic lymphocytes may actively migrate into the blood circulation. HYPOTHESIS/OBJECTIVES: Cytotoxic T cells with a skin-homing phenotype could be increased in the blood circulation of dogs with MF. ANIMALS: Ten dogs with MF and 10 age-matched healthy dogs were included. METHODS: The transcription levels of chemokine receptors, cytokines and cytotoxic markers in peripheral blood of dogs with MF were quantified by real-time RT-PCR. RESULTS: The dogs with MF had lower transcription levels of chemokine receptors associated with skin homing (CCR4), epitheliotropism (CXCR3), lymph node homing (CCR7), a type-1 cytokine (LT-α) and cytotoxic markers (perforin and granzyme B) in the circulation than healthy control dogs (P < 0.05). CONCLUSIONS AND CLINICAL IMPORTANCE: The present results suggest that the number of peripheral cytotoxic T cells with a skin-homing phenotype could be decreased in the peripheral blood of dogs with MF, which might be due to the sequestration of cytotoxic T cells in the lesional skin.

Epidermal structure created by canine hair follicle keratinocytes enriched with bulge cells in a three-dimensional skin equivalent model in vitro: implications for regenerative therapy of canine epidermis.

BACKGROUND: Keratinocytes in the hair follicle bulge region have a high proliferative capacity, with characteristics of epithelial stem cells. This cell population might thus be an ideal source for generating the interfollicular epidermis in a canine skin equivalent. HYPOTHESIS/OBJECTIVES: This study was designed to determine the ability of canine hair follicle bulge cell-enriched keratinocytes to construct canine living skin equivalents with interfollicular epidermis in vitro. ANIMALS: Four healthy beagle dogs from a research colony. METHODS: Bulge cell-enriched keratinocytes showing keratin 15 immunoreactivity were isolated from canine hair follicles and cultured on dermal equivalent containing canine fibroblasts. Skin equivalents were subjected to histological, immunohistochemical, western blot and RT-PCR analyses after 10-14 days of culture at the air-liquid interface. RESULTS: The keratinocyte sheets showed an interfollicular epidermal structure comprising four to five living cell layers covered with a horny layer. Immunoreactivities for keratin 14 and desmoglein 3 were detected in the basal and immediate suprabasilar layers of the epidermis, while keratin 10 and desmoglein 1 occurred in more superficial layers. Claudin 1 immunoreactivity was seen in the suprabasalar layer of the constructed epidermis, and filaggrin monomers and loricrin were detected in the uppermost layer. Basal keratinocytes in the skin equivalent demonstrated immunoreactivity to antibodies against basement membrane zone molecules. CONCLUSIONS AND CLINICAL IMPORTANCE: A bulge stem cell-enriched population from canine hair follicles formed interfollicular epidermis within 2 weeks in vitro, and thus represents a promising model for regenerative therapy of canine skin.

Antimicrobial resistance and genotyping of Pseudomonas aeruginosa isolated from the ear canals of dogs in Japan.

The strong bond between dogs and their owners creates a close association that could result in the transfer of antibiotic-resistant bacteria from canines to humans, potentially leading to the spread of antimicrobial resistance genes. Pseudomonas aeruginosa, a common causative agent of persistent ear infections in dogs, is often resistant to multiple antibiotics. Assessing the antimicrobial resistance profile and genotype of P. aeruginosa is crucial for the appropriate use of veterinary pharmaceuticals. However, in recent years, few studies have been conducted on this bacterium in Japan. We determined the antimicrobial resistance profile and genotype of P. aeruginosa isolated from the ear canal of dogs in Japan in 2020. Analysis of antimicrobial resistance using disk diffusion tests indicated a high frequency of resistance to most antimicrobial agents. Particularly, 29 isolates from the ear canals of the 29 affected dogs (100%) were resistant to cefovecin, cefpodoxime, and florfenicol; however, they were susceptible to cefepime and piperacillin/tazobactam. Only 3.4, 10.3, and 10.3% of the isolates were resistant to ceftazidime, tobramycin, and gentamicin, respectively. Furthermore, upon analyzing the population structure using multilocus sequence typing, a considerably large clonal complex was not observed in the tested isolates. Three isolates, namely ST3881, ST1646, and ST532, were clonally related to the clinically isolated sequence types in Japan (such as ST1831, ST1413, ST1812, and ST1849), which is indicative of dog-to-human transmission. Considering the variation in antibiotic resistance compared to that reported by previous studies and the potential risk of dog-to-human transmission, we believe that the survey for antimicrobial resistance profile and population structure should be continued regularly. However, the prevalence of multidrug-resistant P. aeruginosa in dogs in Japan is not a crisis.

Nestin is a marker of unipotent embryonic and adult progenitors differentiating into an epithelial cell lineage of the hair follicles.

Nestin is an intermediate filament protein transiently expressed in neural stem/progenitor cells. We previously demonstrated that outer root sheath (ORS) keratinocytes of adult hair follicles (HFs) in mice descend from nestin-expressing cells, despite being an epithelial cell lineage. This study determined the exact stage when nestin-expressing ORS stem/precursor cells or their descendants appear during HF morphogenesis, and whether they are present in adult HFs. Using Nes-Cre/CAG-CAT-EGFP mice, in which enhanced green fluorescent protein (EGFP) is expressed following Cre-based recombination driven by the nestin promoter, we found that EGFP+ cells appeared in the epithelial layer of embryonic HFs as early as the peg stage. EGFP+ cells in hair pegs were positive for keratin 14 (K14) and K5, but not vimentin, SOX2, SOX10, or S100 alpha 6. Tracing of tamoxifen-induced EGFP+ cells in postnatal Nes-CreERT2/CAG-CAT-EGFP mice revealed labeling of some isthmus HF epithelial cells in the first anagen stage. EGFP+ cells in adult HFs were not immunolabeled for K15, an HF multipotent stem cell marker. However, when hairs were depilated in Nes-CreERT2/CAG-CAT-EGFP mice to induce the anagen stage after tamoxifen injection, the majority of ORS keratinocytes in depilation-induced anagen HFs were labeled for EGFP. Our findings indicate that nestin-expressing unipotent progenitor cells capable of differentiating into ORS keratinocytes are present in HF primordia and adult HFs.

Effects of age, sex, and breed on the composition of free extractable ceramides in the stratum corneum of healthy dogs.

Ceramide (CER), an important component of the extracellular lamellar lipids in the stratum corneum (SC), plays a critical role in maintaining the cutaneous barrier function. This study aimed to determine whether the quantity of free extractable SC CERs in dogs was affected by the age, sex, or breed. Fifty-eight dogs from the breeds Shiba Inu, beagle, miniature dachshund, shih tzu, and golden retriever, without any history of skin problems, were enrolled in this study. Lipid extracts from the SC were subjected to high-performance thin-layer chromatography to quantify the free extractable CERs. There were weak negative correlations between the age and the amount of free extractable CERs, CER [NP] (non-hydroxy fatty acids linked to phytosphingosines), CER [AS/NH] (α-hydroxy fatty acids linked to sphingosines/non-hydroxy fatty acids linked to 6-hydroxysphingosines), and CER [AP] (α-hydroxy fatty acids and phytosphingosines). There were no significant sex- or breed-related differences in the amounts of free extractable SC CERs in the dogs. These findings imply that aging causes a decline in the amount of free extractable SC CERs in dogs, similar to that observed in humans. The sex or breed of the dogs investigated in this study did not influence the amount of free extractable SC CERs.

Alteration of stratum corneum ceramide profiles in spontaneous canine model of atopic dermatitis.

Ceramides (CERs) in the stratum corneum (SC) are thought to play a key role in cutaneous barrier function. It has been reported that human SC contains 11 free CER classes and that their profiles are altered in humans with atopic dermatitis (AD). Although decreased proportions of free CERs or quantities of protein-bound CERs in the SC have been reported in dogs with AD, the overall profile of CERs in the canine SC has not been fully elucidated. The aim of this study was thus to investigate the profile of free CERs in the canine SC and to identify alterations in the CER profiles in dogs with AD. Normal-phase liquid chromatography-electrospray ionization-mass spectrometry indicated 11 clusters of peaks for free CER classes, similar to those recognized in the human SC. The fractions of free SC CER in dogs with AD and in breed- and age-matched healthy dogs were quantitatively compared using high-performance thin-layer chromatography. CER[EOS], CER[EOP] and CER[NP], which are known to be decreased in the skin of humans with AD, were also decreased in the skin of dogs with AD. These findings highlight canine AD as a spontaneous animal model for investigating the disruption of CER-associated cutaneous barrier functions in the corresponding human disease.

Staphylococcus pseudintermedius exfoliative toxin EXI selectively digests canine desmoglein 1 and causes subcorneal clefts in canine epidermis.

Staphylococcal exfoliative toxins are known to digest desmoglein (Dsg) 1, a desmosomal cell-cell adhesion molecule, thus causing intraepidermal splitting in human bullous impetigo, staphylococcal scalded skin syndrome and swine exudative epidermitis. Recently, a novel exfoliative toxin gene (exi), whose sequence shares significant homology with previously identified exfoliative toxins, was isolated from Staphylococcus pseudintermedius. Little is known about the pathogenic involvement of this toxin in canine pustular diseases such as impetigo. The aim of this study was to determine whether EXI, the product of the exi gene, digests canine Dsg1 and causes intraepidermal splitting in canine skin. An exi gene was isolated from chromosomal DNA of an S. pseudintermedius strain obtained from a pustule of a dog with impetigo, and was used to produce a recombinant EXI by Escherichia coli expression. When purified recombinant EXI was injected intradermally into normal dogs, it caused the development of vesicles or erosions with superficial epidermal splitting. In addition, the EXI abolished immunofluorescence for Dsg1, but not for Dsg3, at the injection sites. Moreover, the EXI directly degraded baculovirus-secreted recombinant extracellular domains of canine Dsg1, but not that of canine Dsg3, in vitro. The EXI also degraded mouse Dsg1α and swine Dsg1, but not human Dsg1, mouse Dsg1ß and Dsg1γ. Conversely, recombinant SIET, previously designated as S. intermedius exfoliative toxin, did not cause intraepidermal splitting or degradation of any Dsgs. These findings indicate that EXI has a proteolytic activity that digests canine Dsg1, and this characteristic might be involved in the pathogenesis of intraepidermal splitting in canine impetigo.

Expression analysis of desmosomal components of the novel canine epidermal keratinocyte cell line (MSCEK).

A novel canine epidermal keratinocyte cell line, MSCEK, was developed from skin of a healthy dog. The aim of this study was to determine its expression of desmosomal components and to evaluate its use as a detection tool for circulating autoantibodies in canine pemphigus. Immunofluorescence and western blotting analyses revealed that MSCEK expresses desmoglein (Dsg) 1, Dsg2, Dsg3, desmoplakin, plakoglobin and cytokeratins. Moreover, positive fluorescent reactions on the surface of MSCEK cells were observed when the cells were incubated with sera obtained from four dogs diagnosed with pemphigus complex. These findings indicate that MSCEK should be a useful tool for future research to characterize circulating autoantibodies that recognize desmosomal components in dogs with pemphigus.