Alterations of keratins, involucrin and filaggrin gene expression in canine atopic dermatitis

Updated insights into the molecular pathogenesis of canine atopic dermatitis

Atopic dermatitis (AD) is a common and chronic inflammatory skin disease with frequent relapses. The genomics revolution has greatly contributed and revolutionised our knowledge of human AD; understanding the molecular skin fingerprint of AD and associated pathogenic immune pathways has led to preclinical assessments of several novel treatments. Initial studies using microarray analysis to analyse transcriptome (gene expression) changes provided relevant insight on the inflammatory and structural changes occurring at the time of acute or chronic AD skin lesions, or after immunomodulating treatments with drugs ciclosporin and dupilumab, a monoclonal antibody anti-IL4 receptor. The studies revealed that human AD is characterised by the activation of multiple cytokine pathways (predominance of T helper cell [Th]2 with some activation of Th1, Th17 and Th22) as well as dysregulated expression of barrier components in the skin. There are several reports on the expression of different single molecular targets (e.g. interleukin [IL]-13, CCL17 and periostin) in spontaneous canine AD (cAD). However, significant studies of the transcriptome have been limited to a single microarray study analysing chronic AD skin lesions in dogs. While revealing a large number of genes differentially expressed in cAD skin, the small sample size (n = 13 dogs) and the lack of changes in key epidermal barrier and inflammatory cytokine genes in the microarrays have inhibited discussion towards specific immunological changes. This review summarises the current literature regarding the molecular mechanisms of spontaneous cAD, including the recent data regarding RNA sequencing, and compares some pathogenic aspects to the previously published data from human AD.

Studies Using Antibodies against Filaggrin and Filaggrin 2 in Canine Normal and Atopic Skin Biopsies

Filaggrin is important for the skin barrier and atopic dermatitis. Another filaggrin-like protein, filaggrin 2, has been described. We evaluated antibodies against both filaggrins in normal and atopic skin biopsies from dogs before and after allergen challenges (D0, D1, D3 and D10). Filaggrins expression was evaluated by immunohistochemistry and Western blot. We used PCR to investigate changes in filaggrin gene expression. Effects of group (p = 0.0134) and time (p = 0.0422) were shown for the intensity of filaggrin staining. Only an effect of group was found for filaggrin 2 (p = 0.0129). Atopic samples had higher intensity of staining than normal dogs [filaggrin on D3 (p = 0.0155) and filaggrin 2 on D3 (p = 0.0038) and D10 (p < 0.0001)]. Atopic samples showed increased epidermal thickness after allergen exposure (D3 vs. D0, p = 0.005), while normal dogs did not. In atopic samples, significant increased gene expression was found for filaggrin overtime but not for filaggrin 2. Western blot showed an increase in filaggrin 2 on D3. A small size band (15 kD) containing a filaggrin sequence was found in Western blots of atopic samples only. We conclude that atopic skin reacts to allergen exposure by proliferating and increasing filaggrin production but that it also has more extensive filaggrin degradation compared to normal skin.

Tissue transcriptome profiling and pathway analyses revealed novel potential biomarkers in the tumor progression of canine oral melanoma

Canine oral melanoma (COM) is an aggressive oral malignancy in dogs, mostly with metastasis. However, the understanding of total gene expression of oral melanoma (OM) at different clinical stages has been limited. The objective of this study was to identify novel mRNA biomarkers of early-stage OM (EOM) and late-stage OM (LOM). Transcriptome sequencing of 3 EOM, 5 LOM and 4 normal gingival tissues (controls) was performed. Selected transcriptome results were validated by quantitative reverse transcription-PCR (qRT-PCR) using 12 LOM and 10 controls. We found 534 differentially expressed in EOM compared with controls, whereas 696 genes in LOM were differentially expressed compared with controls (P < 0.05). Moreover, 27 genes were differentially expressed in LOM compared with EOM (P < 0.05). The genes expressed in COM were involved in the molecular mechanism of cancer and melanocyte development pathways, promoting melanoma progression. qRT-PCR confirmed an increased expression of genes encoding an important protein in chemotherapy resistance (dopachrome tautomerase, DCT) and tumor progression (forkhead box M1, FOXM1), and decreased expression of a tumor suppression gene (N-myc downstream-regulated gene 2, NDRG2) in LOM, concordant with transcriptome results. In conclusion, this study revealed the comprehensive transcriptome from COM tissues, and increased DCT and FOXM1 and decreased NDRG2 gene expression indicated the potential candidate biomarkers in COM progression.

Bioengineered skin constructs based on mesenchymal stromal cells and acellular dermal matrix exposed to inflammatory microenvironment releasing growth factors involved in skin repair

BACKGROUND

Skin tissue engineering is a rapidly evolving field of research that effectively combines stem cells and biological scaffolds to replace damaged tissues. Human Wharton's jelly mesenchymal stromal cells (hWJ-MSCs) are essential to generate tissue constructs, due to their potent immunomodulatory effects and release of paracrine factors for tissue repair. Here, we investigated whether hWJ-MSC grown on human acellular dermal matrix (hADM) scaffolds and exposed to a proinflammatory environment maintain their ability to produce in vitro growth factors involved in skin injury repair and promote in vivo wound healing.

METHODS

We developed a novel method involving physicochemical and enzymatic treatment of cadaveric human skin to obtain hADM scaffold. Subsequently, skin bioengineered constructs were generated by seeding hWJ-MSCs on the hADM scaffold (construct 1) and coating it with human platelet lysate clot (hPL) (construct 2). Either construct 1 or 2 were then incubated with proinflammatory cytokines (IL-1α, IL-1β, IL-6, TNF-α) for 12, 24, 48, 72 and 96 h. Supernatants from treated and untreated constructs and hWJ-MSCs on tissue culture plate (TCP) were collected, and concentration of the following growth factors, bFGF, EGF, HGF, PDGF, VEGF and Angiopoietin-I, was determined by immunoassay. We also asked whether hWJ-MSCs in the construct 1 have potential toward epithelial differentiation after being cultured in an epithelial induction stimulus using an air-liquid system. Immunostaining was used to analyze the synthesis of epithelial markers such as filaggrin, involucrin, plakoglobin and the mesenchymal marker vimentin. Finally, we evaluated the in vivo potential of hADM and construct 1 in a porcine full-thickness excisional wound model.

RESULTS

We obtained and characterized the hADM and confirmed the viability of hWJ-MSCs on the scaffold. In both constructs without proinflammatory treatment, we reported high bFGF production. In contrast, the levels of other growth factors were similar to the control (hWJ-MSC/TCP) with or without proinflammatory treatment. Except for PDGF in the stimulated group. These results indicated that the hADM scaffold maintained or enhanced the production of these bioactive molecules by hWJ-MSCs. On the other hand, increased expression of filaggrin, involucrin, and plakoglobin and decreased expression of vimentin were observed in constructs cultured in an air-liquid system. In vivo experiments demonstrated the potential of both hADM and hADM/hWJ-MSCs constructs to repair skin wounds with the formation of stratified epithelium, basement membrane and dermal papillae, improving the appearance of the repaired tissue.

CONCLUSIONS

hADM is viable to fabricate a tissue construct with hWJ-MSCs able to promote the in vitro synthesis of growth factors and differentiation of these cells toward epithelial lineage, as well as, promote in a full-thickness skin injury the new tissue formation. These results indicate that hADM 3D architecture and its natural composition improved or maintained the cell function supporting the potential therapeutic use of this matrix or the construct for wound repair and providing an effective tissue engineering strategy for skin repair.

Dermatological Problems of Brachycephalic Dogs

Brachycephalic dogs are not only affected by brachycephalic obstructive airway syndrome (BOAS), but are also frequently referred to veterinary dermatologists for skin conditions, with English bulldogs and pugs particularly over-represented. Some skin diseases, such as skin fold dermatitis, are directly associated with the abnormal anatomic conformation of brachycephalic dogs, while for others, such as atopic dermatitis and viral pigmented plaques, there is an underlying genetic basis or a general predisposition. Anatomic alterations associated with brachycephaly, leading to fold formation of the skin and stenosis of the ear canal, together with primary immunodeficiencies described in some breeds, favor the development of pyoderma, Malassezia dermatitis, and otitis externa/media. In addition, the frequently neglected but often lifelong dermatological problems of brachycephalic dogs are an important consideration when discussing genetic and medical conditions affecting the welfare of those dogs. Here we review the current state of knowledge concerning dermatological problems in brachycephalic dogs and combine it with clinical experience in the management of these challenging disorders.

TMT based deep proteome analysis of buffalo mammary epithelial cells and identification of novel protein signatures during lactogenic differentiation

The lactating mammary gland harbours numerous matured alveoli with their lumen surrounded by differentiated mammary epithelial cells (MECs), which are exclusively involved in milk synthesis and secretion. Buffalo (Bubalus bubalis) is the second major milk-producing animal, and its physiology is different from cattle. The complete protein machinery involved in MECs differentiation is still not defined in ruminants, in particular, buffalo. Therefore, we have studied the differential expression of regulated proteins in the in vitro grown buffalo MECs (BuMECs) at different time points (on 3, 6, 12, and 15 days) of their differentiation in the presence of lactogenic hormones. TMT-based MS analysis identified 4,934 proteins; of them, 681 were differentially expressed proteins (DEPs). The principal component analysis suggested a highly heterogeneous expression of DEPs at the four-time points of hormone treatment, with most of them (307) attained the highest expression on 12 days. Bioinformatics analysis revealed the association of DEPs with 24 KEGG pathways. We observed few new proteins, namely ABCA13, IVL, VPS37, CZIB, RFX7, Rab5, TTLL12, SMEK1, GDI2, and TMEM131 in BuMECs. The function of one of the highly upregulated proteins, namely involucrin in the differentiation of BuMECs was confirmed based on biochemical inhibition assay. The results further conclude that the proteins with higher abundance can be considered as the potential biomarkers for differentiation, and they may have a significant association with the lactation process in buffalo too. The proteome dataset obtained can be used to understand the species-specific variations among other lactating animals.

Atopic Dermatitis in Domestic Animals: What Our Current Understanding Is and How This Applies to Clinical Practice

Atopic dermatitis is a clinical syndrome that affects both people and animals. Dogs closely mimic the complexity of the human skin disease, and much progress has been made in recent years in terms of our understanding of the role of skin impairment and the identification of new treatments. Cats and horses also develop atopic syndromes which include both cutaneous and respiratory signs, yet studies in these species are lagging. It is now recognized that atopic dermatitis is not a single disease but a multifaceted clinical syndrome with different pathways in various subgroups of patients. Appreciating this complexity is clinically relevant as we develop more targeted treatments which may work well in some patients but not in others. Different phenotypes of atopic dermatitis have been described in dogs, and it is possible that phenotypes related to breed and age may exist in other animals similar to how they are described in people. The awareness of different mechanisms of disease leads to the desire to correlate different phenotypes with specific biomarkers and responses to treatment. In this review, the current understanding and updated information on atopic syndrome in animals are described, highlighting opportunities for further studies in the future.

Expression of barrier proteins in the skin lesions and inflammatory cytokines in peripheral blood mononuclear cells of atopic dogs

Atopic dermatitis (AD) is one of the most common skin diseases of dogs. Defects in the skin barrier and overproduction of inflammatory cytokines may be the pathogenesis of canine AD. Therefore, the present study was aimed to quantify the gene expression of certain skin barrier proteins and inflammatory cytokines in dogs with AD. Eleven dogs with AD and three healthy dogs were included in the present study. The skin barrier proteins, namely Filaggrin (FLG) and Involucrin (IVL), gene expression was quantified by Real-time PCR in the lesional skin tissues of the atopic dogs and normal skin of the healthy dogs. In addition to the skin proteins, the gene expressions of the interleukin (IL)-13, IL-31, and tumour necrosis factor (TNF)-α were also quantified in the peripheral blood mononuclear cells (PBMCs) of these dogs. Compared to the healthy dogs, significantly higher (P ≤ 0.01) FLG gene expression and significantly (P ≤ 0.05) lower expression of the IVL gene were quantified in the skin of atopic dogs. Further, the dogs with AD revealed significantly higher expression of TNF-α (P ≤ 0.01), IL-31 (P ≤ 0.05), and IL-13 (P ≤ 0.05) as compared to the healthy dogs. The findings of our present study evidently suggest significantly increased and decreased expressions of FLG and IVL genes, respectively, which may be responsible for disruption of the skin barrier in dogs with AD. While, the over-expressions of TNF-α, IL-31, and IL-13 genes might be attributed to the clinical pathology and manifestations of AD in dogs. However, further studies are warranted to substantiate our hypothesis about pathogenesis and clinical manifestation of AD in dogs by including a large number of animals.

Advances in our understanding of canine atopic dermatitis

Canine atopic dermatitis (cAD) is a genetically inherited clinical syndrome that encompasses a diversity of mechanisms and can have a variety of triggers. Development of clinical disease is the result of genetic factors and environmental conditions, which shape the resulting immunological response. Clinical disease becomes evident once a threshold of inflammatory response is achieved. Skin barrier impairment plays a role in promoting cutaneous dysbiosis and increased allergen penetration. Keratinocytes shape the response of dendritic cells and subsequent lymphocytic response. Thymic stromal lymphopoietin is one of the links between the damaged skin barrier and the modulation of a T-helper (Th)2 response. It is still unclear whether mutations in skin barrier genes exist in atopic dogs, as they do in humans, or whether the observed alterations are purely secondary to inflammation. A dysregulated immune response with increased Th2, Th17 and CD4+ CD25+ regulatory T cells has been reported. A variety of cytokines [interleukin(IL)-31, IL-34, Macrophage migration inhibitory factor] are proposed as potential biomarkers and treatment targets because they are increased in the serum of atopic dogs when compared to controls, although a correlation between serum levels of these factors and severity of disease is not always present. The main issue with many published studies is that atopic dogs are always only compared to normal controls. Thus, it is unclear whether the changes that we find are truly a signature of cAD or merely a manifestation of nonspecific broad inflammatory responses. Studies considering comparison with other inflammatory diseases different from cAD are urgently needed to correctly identify what is specific to this complicated syndrome.

Update on canine filaggrin: a review

Human filaggrin (FLG) plays a key role in epidermal barrier function, and loss-of-function mutations of its gene are primarily responsible for the development of human atopic dermatitis (AD). FLG expression is also reduced in the epidermis of atopic patients, due to the transcriptional effect of Th2 type cytokines. Canine atopic dermatitis (CAD) is a prevalent skin disease that shares many clinical and pathogenic features with its human homologue. The aim of this review is discuss current knowledge on canine filaggrin (Flg) in both healthy and atopic dogs, as compared to the human protein. Although the molecular structures of the two proteins, as deduced from the sequences of their gene, are different, their sites of expression and their proteolytic processing in the normal epidermis are similar. Concerning the expression of Flg in CAD, conflicting results have been published at the mRNA level and little accurate information is available at the protein level. It derives from a large precursor, named profilaggrin (proFLG), formed by several FLG units and stored in keratohyalin granules of the stratum granulosum. Canine and human proFLG sequences display little amino acid similarity (33% as shown using the Basic Local Alignment Search Tool (BLAST)) except at the level of the S100 homologous part of the N-terminus (75%). Genetic studies in the dog are at an early stage and are limited by the variety of breeds and the small number of cases included. Many questions remain unanswered about the involvement of Flg in CAD pathogenesis.

Immunohistochemical Expression of Keratins in Normal Ovine Skin and in Chronic Dermatitis due to Sarcoptes scabiei

Hyperproliferation of epidermal keratinocytes is a major histopathological feature of chronic Sarcoptes scabiei dermatitis. We investigated the immunohistochemical expression of several keratins in scabietic dermatitis in sheep and in the skin of healthy sheep, using a panel of commercially available anti-human antibodies for keratins. Keratins AE1/AE3 and 34BE12 were expressed in all epithelial structures in healthy skin. Keratin MNF116 was expressed in the stratum basale and in the three lowest layers of the stratum spinosum, in follicular epithelium and in apocrine glands. Keratin K5/6 expression was seen in the stratum basale, in the two lowest cell layers of the stratum spinosum, in the outer root sheath of hair follicles and in myoepithelial cells of apocrine glands. K14 expression was observed in the stratum basale, in locally extensive regions of the two lowest cell layers of the stratum spinosum, in the outer root sheath of hair follicles and in sebaceous glands. Immunolabelling of K19 antigen was confined to apocrine glands. In scabietic skin, immunolabelling of keratin 34BE12 was seen in all layers of hyperplastic stratum spinosum and stratum granulosum but was restricted to some locally extensive regions in hyperkeratotic and parakeratotic stratum corneum. Keratin MNF116 was widely labelled in all layers of hyperplastic stratum spinosum and stratum granulosum. There was expansive labelling of K5/6 keratin in all layers of hyperplastic stratum spinosum and in locally extensive regions of stratum granulosum, as well as in hyperkeratotic or parakeratotic stratum corneum. Expansive labelling of K14 keratin was detected in all layers of hyperplastic stratum spinosum and in the layers of the hyperplastic stratum granulosum. K5/6 and K14 keratins were also labelled in the inner root sheath of occasional hair follicles.

The Effect of Atopic Dermatitis and Diet on the Skin Transcriptome in Staffordshire Bull Terriers

Canine atopic dermatitis (CAD) has a hereditary basis that is modified by interactions with the environment, including diet. Differentially expressed genes in non-lesional skin, determined by RNA sequencing before and after a dietary intervention, were compared between dogs with naturally occurring CAD (n = 4) and healthy dogs (n = 4). The dogs were fed either a common commercial heat-processed high carbohydrate food (kibble diet) (n = 4), or a non-processed high fat food (raw meat-based diet) (n = 4). At the end of the diet intervention, 149 differentially expressed transcripts were found between the atopic and healthy dogs. The main canonical pathways altered by the dysregulation of these genes were angiopoietin signaling, epidermal growth factor signaling, activation of angiogenesis, and alterations in keratinocyte proliferation and lipid metabolism. On the other hand, 33 differently expressed transcripts were found between the two diet groups, of which 8 encode genes that are annotated in the current version of the dog genome: immunoglobulin heavy constant mu (IGHM), immunoglobulin lambda-like polypeptide 5 (IGLL5), B-cell antigen receptor complex-associated protein beta chain (CD79B), polymeric immunoglobulin receptor (PIGR), cystathionine β-synthase (CBS), argininosuccinate synthase 1 (ASS1), secretory leukocyte peptidase inhibitor (SLPI), and mitochondrial ribosome recycling factor (MRRF). All genes were upregulated in the raw diet group. In conclusion the findings of this study suggest alterations in lipid and keratinocyte metabolism as well as angiogenesis in the skin of atopic dogs. Additionally, a possible enhancement of innate immunity and decrease in oxidative stress was seen in raw food fed dogs, which could have an important role in preventing hypersensitivities and disturbed immunity at young age.

Update on pathogenesis, diagnosis, and treatment of atopic dermatitis in dogs

Improved understanding of the pathogenesis of atopic dermatitis in dogs has led to more effective treatment plans, including skin barrier repair and new targeted treatments for management of allergy-associated itch and inflammation. The intent of this review article is to provide an update on the etiologic rationale behind current recommendations that emphasize a multimodal approach for the management of atopic dermatitis in dogs. Increasing knowledge of this complex disease process will help direct future treatment options.

Elevated circulating Th2 but not group 2 innate lymphoid cell responses characterize canine atopic dermatitis

Atopic dermatitis (AD) is an allergic skin disease that causes significant morbidity and affects multiple species. AD is highly prevalent in companion dogs, and the clinical management of the disease remains challenging. An improved understanding of the immunologic and genetic pathways that lead to disease could inform the development of novel treatments. In allergic humans and mouse models of AD, the disease is associated with Th2 and group 2 innate lymphoid cell (ILC2) activation that drives type 2 inflammation. Type 2 inflammation also appears to be associated with AD in dogs, but gaps remain in our understanding of how key type 2-associated cell types such as canine Th2 cells and ILC2s contribute to the pathogenesis of canine AD. Here, we describe previously uncharacterized canine ILC2-like cells and Th2 cells ex vivo that produced type 2 cytokines and expressed the transcription factor Gata3. Increased circulating Th2 cells were associated with chronic canine AD. Single-cell RNA sequencing revealed a unique gene expression signature in T cells in dogs with AD. These findings underline the importance of pro-allergic Th2 cells in orchestrating AD and provide new methods and pathways that can inform the development of improved therapies.

Interleukin-4 Downregulation of Involucrin Expression in Human Epidermal Keratinocytes Involves Stat6 Sequestration of the Coactivator CREB-Binding Protein

Skin barrier defects play an important role in atopic dermatitis (AD). Involucrin, an important barrier protein suppressed in human AD, is downregulated by interleukin-4 (IL-4). However, the molecular mechanism for IL-4 downregulation of involucrin has not been delineated, and especially how Stat6, a transcriptional activator, represses involucrin expression is unknown. Since Stats usually recruit p300/CBP in the general transcription machinery of their target genes and involucrin expression also involves p300/CBP, we hypothesize that Stat6 activated by IL-4 may sequestrate p300/CBP from the involucrin transcription complex, thus suppressing involucrin expression in keratinocytes. Using IL-4 transgenic mice, an AD mouse model, we find that involucrin expression is similarly downregulated as in human AD. In HaCat cells, the Jak inhibitor and dominant negative studies indicate that the Jaks-Stat6 pathway is involved in IL-4 downregulation of involucrin. Next, we transfected HaCat cells with an involucrin promoter-luciferase construct and then treated them with IL-4. IL-4 greatly suppresses the promoter activity, which is totally abolished by cotransfecting the CREB-binding protein (CBP) expression vector, indicating that IL-4 cannot downregulate involucrin in the presence of excess CBP. Finally, chromatin immunoprecipitation assay demonstrates that IL-4 decreases CBP binding to the involucrin transcription complex. For the first time, we defined a molecular mechanism for IL-4 downregulation of involucrin in keratinocytes, which may play an important role in the pathogenesis of AD.

Decreased expression of caspase-14 in an experimental model of canine atopic dermatitis

Alterations in skin barrier function and filaggrin expression have been reported in atopic dermatitis (AD). Caspase-14, a protease important for filaggrin processing, is decreased in human AD. Atopic Beagle dogs with skin barrier alterations have been validated as model for AD. This study aimed to investigate caspase-14 in normal and atopic Beagle dogs. Skin biopsies from non-lesional and control skin were analyzed for caspase-14 by immunofluorescence. Six images/sections were blindly scored for intensity. Data were tested with unpaired Student's t test. A P value of <0.05 was considered significant. Caspase-14 was decreased in atopic compared to normal skin both quantitatively (P <0.001) and qualitatively (P = 0.006; agreement = 0.93; consistency = 0.94). In conclusion, caspase-14 is decreased in this model similarly to reports in humans, highlighting the relevance of filaggrin metabolic defects in AD.

An update on the treatment of canine atopic dermatitis

Canine atopic dermatitis is a common skin disease seen in veterinary clinical practice. Several factors appear to contribute to the cutaneous inflammation and pruritus. The therapeutic strategy should focus on control of those factors that can be identified and for which interventional measures are feasible; these include ectoparasites, bacterial/fungal infection and dietary hypersensitivity. Ectoparasites, particularly fleas, are not the cause of atopic dermatitis, but they are a confounding factor, which can exacerbate pruritus, and preventative measures are therefore indicated. Bacterial and yeast infections are frequently associated with atopic dermatitis and initial systemic and/or topical therapy should be considered, followed by regular topical treatment for preventing relapse. Concurrent dietary hypersensitivity should be investigated by undertaking an elimination/provocation trial, followed by feeding of a hypoallergenic diet where appropriate. Depending on the severity of the clinical signs of atopic dermatitis and the willingness and expectations of owners, symptomatic treatment and/or specific interventional therapy for environmental allergy (allergen avoidance, allergen-specific immunotherapy) may be implemented. Symptomatic treatment includes use of glucocorticoids (systemically or topically), ciclosporin and oclacitinib. Other treatment modalities of lower or less proven efficacy include antihistamines, dextromethorphan, fatty acids, feline interferon-omega, misoprostol, pentoxifylline, specific serotonin re-uptake inhibitors and tricyclic antidepressant drugs. The therapeutic approach should be reviewed at regular intervals and tailored to the individual's needs. A successful long-term outcome can usually be achieved by combining the various treatment approaches in a way that maximises their benefits and minimises their drawbacks.

The effect of long-term feeding of skin barrier-fortified diets on the owner-assessed incidence of atopic dermatitis symptoms in Labrador retrievers

We investigated the effect of feeding a skin barrier function-augmenting diet early in dogs' lives on the appearance of clinical signs associated with canine atopic dermatitis. Pregnant bitches (starting 5 weeks after mating) and their subsequent litters (up to 1 year of age) were fed either supplemented or unsupplemented diets. Nutrients supplemented were nicotinamide, pantothenate, histidine, inositol and choline. Circulating IgE levels to dust mute allergens Der f and Der p were measured when the puppies were 6 and 12 months old. Two owner questionnaires were used to assess the occurrence of typical signs associated with atopic dermatitis when dogs were between the ages of 22 and 36, and 34 and 48 months. Using linear mixed models we observed higher levels of circulating anti-Der f (P = 0·021) and -Der p IgE (P = 0·01) during the first year in the dogs fed the unsupplemented than in those fed the supplemented diet. The owner-assessed incidence of atopic dermatitis signs amongst the dogs was significantly greater in the unsupplemented group at the time of the second follow-up questionnaire (10/33 dogs v. 2/24 dogs). These outcomes suggest that a nutritionally derived improvement to barrier function early in life may reduce the frequency of signs associated with atopic dermatitis. The effect is possibly the result of making the epidermis, now thought to be a major route of environmental allergen exposure, more resistant to penetration.

Prevalence of and risk factors for increased serum levels of allergen-specific IgE in a population of Norwegian dogs

Background

The importance of different allergens in association with IgE production and canine atopic dermatitis (CAD) has been poorly studied and few studies exist on factors influencing allergen-specific IgE antibodies in serum. The aim of this cross-sectional study was to investigate the prevalence of elevated IgE levels to different environmental allergens in Norwegian dogs with a suspicion of CAD. The secondary aim was to identify risk factors associated with elevated serum levels of allergen-specific IgE.

Results

The study sample consisted of serum from 1313 dogs of 161 different breeds. All samples were submitted for serologic IgE-testing (Fc epsilon R1 alpha-based ELISA) based on suspicion of CAD. Overall, 84.3% of the dogs had elevated IgE levels to one or more of the allergen(s). The predominant allergens amongst the positive results were the indoor allergens (Acarus siro 84.0%, Dermatophagoides farinae 80.2%, Tyrophagus putrescentiae 79.9%). Sheep sorrel was the most commonly encountered outdoor allergen (40.0%). Only 2.6% of the dogs with elevated IgE levels were positive to flea saliva.

The test results varied significantly depending on when the serum samples were taken. Samples taken during summer and autumn more often came out positive than samples taken during winter and spring. Geographical variations were also demonstrated. A greater proportion of females than males had positive test results, and more females than males tested positive to outdoor allergens. The mean age was significantly higher in the dogs testing positive than amongst the dogs testing negative. The allergen-specific IgE levels varied with breed. The boxer was the only breed with a significantly higher proportion of positive test results compared to the other breeds. Boxers also had a higher prevalence of elevated IgE levels to outdoor allergens, whereas the Rottweiler had a higher prevalence of elevated IgE levels to indoor allergens compared to the other breeds.

Conclusions

IgE hypersensitivity was most often associated with indoor allergens. Outdoor allergens were of minor importance and IgE reactivity to flea saliva was rare. Breed differences in allergen-specific IgE levels were identified. Season of sampling, and the dogs’ geographical localisation, sex and age also affected the results of the IgE analysis.

Investigation of the effect of probiotic exposure on filaggrin expression in an experimental model of canine atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) results from complex interactions between an impaired skin barrier and immunological stimulation. Filaggrin is a key protein for the skin barrier, and its expression is decreased in subsets of atopic dogs and can be modified by inflammation; thus, immunomodulatory approaches may alter its expression. Probiotics have been explored for the prevention and treatment of allergies, owing to their immunomodulatory properties; however, it is currently unknown whether they can modulate filaggrin expression.

OBJECTIVE

The purpose of this study was to evaluate whether probiotics can modulate filaggrin expression in an experimental model of canine AD.

ANIMALS AND METHODS

Eighteen atopic (11 probiotic exposed and seven control) and five normal beagles were challenged for three consecutive days with Dermatophagoides farinae. Skin biopsies were taken before (day 0), at the peak (day 3) and after the end of the allergen challenge (day 10). Immunohistochemistry for filaggrin was done using a polyclonal antibody specific for canine filaggrin, and staining was scored both subjectively (for intensity, granularity and continuity) and objectively, by tracing the stratum granulosum and calculating the percentage of filaggrin per unit traced area.

RESULTS

Analysis of variance of the percentage of filaggrin in the stratum granulosum showed a significant effect of group (P = 0.0414, AD < normal), time (P = 0.0066, days 3 and 10 > day 0) and marginal group × time interaction (P = 0.0606). Within the atopic group, exposure to probiotics did not change filaggrin expression. No significant differences were found in the subjective scores among groups.

CONCLUSIONS AND CLINICAL IMPORTANCE

It is concluded that probiotic exposure early in life does not alter filaggrin expression in this AD model.