Presence of the house dust mite allergen in the gastrointestinal tract of dogs with chronic enteropathy: A potential inducer of interleukin-1β

Toll-like receptor 2 activation induces C-C motif chemokine ligand 5 production in canine keratinocytes

BACKGROUND

Toll-like receptor 2 (TLR2) in keratinocytes can be activated by Staphylococcus spp. that are frequently detected on the skin of dogs with atopic dermatitis (AD). C-C motif chemokine ligand 5 (CCL5) produced by keratinocytes has been considered to be involved in the pathogenesis of canine AD (cAD). However, whether TLR2 activation induces CCL5 production in canine keratinocytes remains unclear.

HYPOTHESIS/OBJECTIVES

To elucidate the effect of TLR2 agonists on CCL5 production in canine keratinocytes, possible synergy with interferon (IFN)-γ, interleukin (IL)-13 or IL-4 and underlying mechanisms.

MATERIALS AND METHODS

Canine progenitor epidermal keratinocyte (CPEK) cells were stimulated with TLR2 agonists with or without inhibitors of the TLR2 signalling pathway or IFN-γ, a T-helper (Th)1-type cytokine and/or IL-13 or IL-4, a Th2-type cytokine. CCL5 protein concentrations in the culture supernatant were measured by enzyme-linked immunosorbent assay. Additionally, TLR2 mRNA expression was measured by real-time PCR in CPEK cells stimulated with IFN-γ.

RESULTS

TLR2 agonists increased CCL5 production in CPEK cells. Inhibitors of the TLR2 signalling pathway suppressed CCL5 production. IFN-γ, but not IL-13 or IL-4, synergistically enhanced TLR2 agonist-induced CCL5 production. IFN-γ partially increased TLR2 mRNA expression in CPEK cells.

CONCLUSIONS AND CLINICAL RELEVANCE

TLR2 activation by Staphylococcus spp. may produce CCL5 in canine keratinocytes, thereby recruiting immune cells into the skin of dogs with AD. During the Th1-activated chronic phase of cAD, where TLR2 expression may be partially upregulated, Staphylococcus spp. may exacerbate skin inflammation. Further studies are warranted to determine the clinical significance and mechanisms of skin bacteria-mediated CCL5 production in keratinocytes.

Chronic Enteropathy and Vitamins in Dogs

Chronic enteropathy (CE) or chronic inflammatory enteropathy is a group of diseases with multiple and different etiologies characterized by chronic gastrointestinal signs such as vomiting, diarrhea, anorexia, weight loss for more than 3 weeks, and inflammatory cell infiltration, such as lymphoplasmacytic cells in the intestinal mucosal lamina propria. The diagnosis was histologically confirmed after excluding other diseases such as parasitic infections, tumors, pancreatitis, exocrine pancreatic insufficiency, metabolic diseases, and endocrine diseases, such as hypoadrenocorticism. Nutritional management depends on several important functions, such as digestion and absorption processes, digestive enzymes and nutritional transporters, and barrier functions. Intestinal dysbiosis may have been found to be involved in various functions. Recently, cobalamin (vitamin B12) and vitamin D have been considered negative prognostic factors in dogs with CE. Cobalamin supplementation ameliorates clinical disease severity in dogs with CE, and vitamin D supplementation ameliorates hypocalcemia in dogs with CE and hypoalbuminemia. Therefore, the aim of this review is to provide an overview of CE and present treatment and nutritional management strategies for CE and prognostic vitamins.

A newborn's perspective on immune responses to food

In this review, we will highlight infants' immune responses to food, emphasizing the unique aspects of early-life immunity and the critical role of breast milk as a food dedicated to infants. Infants are susceptible to inflammatory responses rather than immune tolerance at the mucosal and skin barriers, necessitating strategies to promote oral tolerance that consider this susceptibility. Breast milk provides nutrients for growth and cell metabolism, including immune cells. The content of breast milk, influenced by maternal genetics and environmental exposures, prepares the infant's immune system for the outside world, including solid foods. To do this, breast milk promotes immune system development through antigen-specific and non-antigen-specific immune education by exposing the newborn to food and respiratory allergens and acting on three key targets for food allergy prevention: the gut microbiota, epithelial cells, and immune cells. Building knowledge of how the maternal exposome and human milk composition influence offspring's healthy immune development will lead to recommendations that meet the specific needs of the developing immune system and increase the chances of promoting an appropriate immune response to food in the long term.

Beyond allergic progression: From molecules to microbes as barrier modulators in the gut-lung axis functionality

The "epithelial barrier hypothesis" states that a barrier dysfunction can result in allergy development due to tolerance breakdown. This barrier alteration may come from the direct contact of epithelial and immune cells with the allergens, and indirectly, through deleterious effects caused by environmental changes triggered by industrialization, pollution, and changes in the lifestyle. Apart from their protective role, epithelial cells can respond to external factors secreting IL-25 IL-33, and TSLP, provoking the activation of ILC2 cells and a Th2-biased response. Several environmental agents that influence epithelial barrier function, such as allergenic proteases, food additives or certain xenobiotics are reviewed in this paper. In addition, dietary factors that influence the allergenic response in a positive or negative way will be also described here. Finally, we discuss how the gut microbiota, its composition, and microbe-derived metabolites, such as short-chain fatty acids, alter not only the gut but also the integrity of distant epithelial barriers, focusing this review on the gut-lung axis.

House dust mite-derived serine protease upregulates gene expression of interleukin-33 in canine keratinocytes via protease-activated receptor-2

BACKGROUND

The involvement of interleukin (IL)-33 produced by keratinocytes has been suggested in the pathogenesis of canine atopic dermatitis (cAD). House dust mite (HDM)-derived proteases induce the production of various cytokines and chemokines in keratinocytes via protease-activated receptor-2 (PAR-2); however, their effects on IL-33 mRNA expression in canine keratinocytes have not been determined.

HYPOTHESIS/OBJECTIVE

To clarify whether HDM-derived proteases induce IL-33 mRNA expression in canine keratinocytes via PAR-2.

METHODS AND MATERIALS

Expression of IL-33 mRNA was quantified by real-time PCR in a cell line of canine progenitor epidermal keratinocytes (CPEK) stimulated with Dermatophagoides farinae (Der f) whole body extract, Der f pre-treated with cysteine protease and serine protease inhibitors, and trypsin. Trypsin and Der f-mediated IL-33 mRNA expression also was measured in CPEK cells treated with a PAR-2 antagonist.

RESULTS

Der f enhanced IL-33 mRNA expression in CPEK cells in incubation time- and dose-dependent manners. Der f pre-treated with a serine protease inhibitor, and not a cysteine protease inhibitor, abrogated an increase in IL-33 mRNA expression in CPEK cells. Trypsin also enhanced IL-33 mRNA expression in CPEK cells. Trypsin-mediated IL-33 mRNA expression was completely abolished by a PAR-2 antagonist, while Der f-mediated IL-33 mRNA expression was partially and significantly diminished by it.

CONCLUSIONS AND CLINICAL RELEVANCE

Der f-derived serine protease upregulated IL-33 mRNA expression in CPEK cells at least in part via PAR-2. These findings suggest that HDM may be involved in the development of _C AD by increasing IL-33 mRNA expression in keratinocytes.