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

Filaggrin Mutation Status and Prevention of Atopic Dermatitis with Maternal Probiotic Supplementation

The World Allergy Organization recommends probiotics in the prevention of atopic dermatitis in high-risk populations. Mutations in the filaggrin gene (FLG) result in an increased risk of atopic dermatitis through disruption of the skin keratin layer. This exploratory study investigated whether the preventive effect of maternal probiotics was evident in children with and without FLG mutations. DNA was collected from children (n =   228) from the Probiotic in the Prevention of Allergy among Children in Trondheim (ProPACT) study. Samples were analysed for 3 common FLG mutations (R501X, R2447X, and 2282del4). Overall, 7% of children had heterozygous FLG mutations; each child had only one of the 3 mutations. Mutation status had no association with atopic dermatitis (RR = 1.1; 95% CI 0.5 to 2.3). The risk ratio (RR) for having atopic dermatitis following maternal probiotics was 0.6 (95% CI 0.4 to 0.9) and RR was similar if the child expressed an FLG mutation (RR = 0.6; 95% CI 0.1 to 4.1) or wildtype FLG (RR = 0.6; 95% CI 0.4 to 0.9). The preventive  effect of probiotics for atopic dermatitis was also evident in children without FLG mutation. Larger confirmatory studies are needed.

Update on the skin barrier, cutaneous microbiome and host defence peptides in canine atopic dermatitis

BACKGROUND

Canine atopic dermatitis (AD) is a complex inflammatory skin disease associated with cutaneous microbiome, immunological and skin barrier alterations. This review summarises the current evidence on skin barrier defects and on cutaneous microbiome dysfunction in canine AD.

OBJECTIVE

To this aim, online citation databases, abstracts and proceedings from international meetings on skin barrier and cutaneous microbiome published between 2015 and 2023 were reviewed.

RESULTS

Since the last update on the pathogenesis of canine AD, published by the International Committee on Allergic Diseases of Animals in 2015, 49 articles have been published on skin barrier function, cutaneous/aural innate immunity and the cutaneous/aural microbiome in atopic dogs. Skin barrier dysfunction and cutaneous microbial dysbiosis are essential players in the pathogenesis of canine AD. It is still unclear if such alterations are primary or secondary to cutaneous inflammation, although some evidence supports their primary involvement in the pathogenesis of canine AD.

CONCLUSION AND CLINICAL RELEVANCE

Although many studies have been published since 2015, the understanding of the cutaneous host-microbe interaction is still unclear, as is the role that cutaneous dysbiosis plays in the development and/or worsening of canine AD. More studies are needed aiming to design new therapeutic approaches to restore the skin barrier, to increase and optimise the cutaneous natural defences, and to rebalance the cutaneous microbiome.

Enhanced In Vitro Expression of Filaggrin and Antimicrobial Peptides Following Application of Glycosaminoglycans and a Sphingomyelin-Rich Lipid Extract

Filaggrin is an epidermal protein involved in skin barrier formation and hydration, whose expression is altered in canine atopic dermatitis (CAD). CAD patients also present an abnormal immune response with an altered expression of antimicrobial peptides (AMPs), such as β-defensins and cathelicidins. Sphingolipids and glycosaminoglycans (GAGs) have been reported to improve the skin barrier in several animal species, including dogs. Our objective was to evaluate the in vitro effects of a sphingomyelin-rich lipid extract (LE), a hyaluronic acid-rich GAG matrix, and their combination, on the expression of filaggrin and human β-defensin 2 (hBD-2). Filaggrin expression was quantified in a reconstructed human epidermis (RHE), and hBD-2 in normal human epidermal keratinocyte (NHEK) cultures. LE and GAGs were tested at 0.02 mg/mL, with or without adding a cytokine mix. A significant increase in mean hBD-2, compared to the control (99 pg/mL) was achieved with LE (138 pg/mL) and LE+GAGs (165 pg/mL). Filaggrin increased with GAGs (202% ± 83) and LE (193% ± 44) vs. the stimulated control, but this difference was statistically significant (p < 0.05) only with LE+GAGs (210% ± 39). In conclusion, the tested GAGs and LE enhance filaggrin and AMP expression in vitro, which might benefit CAD patients if applied in vivo.

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.

Polyphenols and Cannabidiol Modulate Transcriptional Regulation of Th1/Th2 Inflammatory Genes Related to Canine Atopic Dermatitis

Canine atopic dermatitis (AD) is a multifactorial allergic disease associated with immune and abnormal skin barrier dysfunction and it is one of the primary causes of pruritus. Using a novel in vitro model of AD, here we tried to revert the alteration of transcriptional regulation of AD canine key genes testing a nutraceutical mixture containing flavonoids, stilbene, and cannabinoids, which are already well-known for their applications within dermatology diseases. The nutraceutical mixture induced in inflamed cells a significant downregulation (p < 0.05) of the gene expression of ccl2, ccl17, and tslp in keratinocytes and of ccl2, ccl17, and il31ra in monocytes. Consistent with the observed alterations of tslp, ccl2, ccl17, and il31ra messenger RNA (mRNA) levels, a significant increase (p < 0.05) of DNA methylation at specific CpG sites on the gene regulatory regions was found. These results lay the foundation for the use of these natural bioactives in veterinary medicine and provide a model for deeper understanding of their mechanisms of action, with potential translation to human research.

Atopic dermatitis in cats and dogs: a difficult disease for animals and owners

The purpose of this review article is to give an overview of atopic dermatitis in companion animals and of recent developments including knowledge on immunological background, novel treatment options and difficulties in disease management. The prevalence of hypersensitivities seems to be increasing. The pathogenetic mechanisms are not fully understood, yet multiple gene abnormalities and altered immunological processes are involved. In dogs and cats, the diagnosis of atopic dermatitis is based on history, clinical examination and exclusion of other differential diagnoses. Intradermal testing or testing for serum allergen-specific Immunoglobulin E is only used to identify allergens for inclusion in the extract for allergen immunotherapy. Symptomatic therapy includes glucocorticoids, ciclosporin, essential fatty acids and antihistamines. A selective janus kinase 1 inhibitor and a caninized monoclonal interleukin-31 antibody are the newest options for symptomatic treatment, although longterm effects still need to be assessed. The chronic and often severe nature of the disease, the costly diagnostic workup, frequent clinical flares and lifelong treatment are challenging for owners, pets and veterinarians. Patience and excellent communication skills are needed to achieve a good owner compliance and satisfactory clinical outcome for the animal.

Therapies in Canine Atopic Dermatitis: An Update

Canine atopic dermatitis (AD) is one of the most common inflammatory skin diseases in dogs. The pathogenesis is complex and not completely understood. Many therapeutic options are available; however, because of cost, side effects, or a long lag phase, new compounds are constantly produced. This article provides a comprehensive review of the latest compounds for the treatment of canine AD. In addition, a brief review of new studies on conventional medications is provided. For a successful long-term therapeutic approach, it is important to considerate the status of the disease, as well as the patients' and their owners' needs.

Probiotics against airway allergy: host factors to consider

The worldwide prevalence of allergic diseases has drastically increased in the past decades. Recent studies underline the importance of microbial exposure for the development of a balanced immune system. Consequently, probiotic bacteria are emerging as a safe and natural strategy for allergy prevention and treatment. However, clinical probiotic intervention studies have so far yielded conflicting results. There is increasing awareness about the importance of host-associated factors that determine whether an individual will respond to a specific probiotic treatment, and it is therefore crucial to promote a knowledge-based instead of an empirical selection of promising probiotic strains and their administration regimen.In this Review, we summarize the insights from animal model studies of allergic disease, which reveal how host-related factors - such as genetic makeup, sex, age and microbiological status - can impact the outcomes of preventive or curative probiotic treatment. We explore why and how these factors can influence the results of probiotic studies and negatively impact the reproducibility in animal experiments. These same factors might profoundly influence the outcomes of human clinical trials, and can potentially explain the conflicting results from probiotic intervention studies. Therefore, we also link these host-related factors to human probiotic study outcomes in the context of airway allergies.

The Parathyroid Hormone Second Receptor PTH2R and its Ligand Tuberoinfundibular Peptide of 39 Residues TIP39 Regulate Intracellular Calcium and Influence Keratinocyte Differentiation

Genes related to the parathyroid hormone (PTH) influence cutaneous immune defense and development, but the full functions of the PTH family in cutaneous biology remain incompletely understood. In this study, we examined the expression and potential functions of the PTH second receptor (PTH2R) and its ligand, the tuberoinfundibular peptide of 39 residues (TIP39), in the skin. TIP39 and PTH2R mRNA and protein were detectable in both human and mouse skin, and in cultured keratinocytes and adipocytes. TIP39 was observed in the basal layer of human skin, whereas PTH2R was detected in the spinous to granular layer. The subcellular localization of TIP39 in keratinocytes changed during calcium-induced differentiation and shifted to colocalize with PTH2R at the membrane. The addition of recombinant TIP39 to normal human keratinocytes in culture induced an increase in intercellular calcium and triggered aspects of terminal differentiation including decreased keratin-14 and increased involucrin expression. Consistent with these observations, PTH2R(-/-) mice were observed to have increased epidermal thickness. In summary, identification of TIP39 and its receptor in the epidermis reveals an additional PTH family member that is expressed in the skin and may influence keratinocyte function.

Treatment of canine atopic dermatitis: 2015 updated guidelines from the International Committee on Allergic Diseases of Animals (ICADA)

Background

In 2010, the International Task Force on Canine Atopic Dermatitis (now International Committee on Allergic Diseases of Animals, ICADA) published the first consensus guidelines for the treatment of atopic dermatitis (AD) in dogs. This is the first 5-year minor update of this document.

Results

The treatment of acute flares of AD should involve the search for, and then elimination of, the cause of the flares, bathing with mild shampoos, and controlling pruritus and skin lesions with interventions that include topical and/or oral glucocorticoids or oclacitinib. For chronic canine AD, the first steps in management are the identification and avoidance of flare factors, as well as ensuring that there is adequate skin and coat hygiene and care; this might include more frequent bathing and possibly increasing essential fatty acid intake. The medications currently most effective in reducing chronic pruritus and skin lesions are topical and oral glucocorticoids, oral ciclosporin, oral oclacitinib, and, where available, injectable recombinant interferons. Allergen-specific immunotherapy and proactive intermittent topical glucocorticoid applications are the only interventions likely to prevent or delay the recurrence of flares of AD.

Conclusions

This first 5-year minor update of the international consensus guidelines for treatment of AD in dogs further establishes that the treatment of this disease is multifaceted, and that interventions should be combined for a proven (or likely) optimal benefit. Importantly, treatment plans are likely to vary between dogs and, for the same dog, between times when the disease is at different stages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0514-6) contains supplementary material, which is available to authorized users.

Probiotics and prebiotics in dermatology

The rapid increase in the medical use of probiotics and prebiotics in recent years has confirmed their excellent safety profile. As immune modulators, they have been used in inflammatory skin conditions, such as atopic dermatitis. We review the literature regarding the use of probiotics and prebiotics in dermatology. Probiotics and prebiotics appear to be effective in reducing the incidence of atopic dermatitis in infants, but their role in atopic dermatitis treatment is controversial. Their role in acne, wound healing, and photoprotection is promising, but larger trials are needed before a final recommendation can be made.