ABSTRACT
Behaviour is the response of living things to their environment and external stimulation, and is one of the parameters to be observed when assessing animal welfare. Any alteration from the conditions found in nature can lead to the occurrence of some specific behaviours, called stereotypies which are characterised as repetitive, consistent patterns of behaviour usually defined as having no apparent ultimate or proximal functions. It has been reported that once stabled or subjected to stressful activities, horses have more susceptibility of developing behavioural disturbances; therefore, behavioural disorders in horses are a strong indicator of poor welfare. Cannabis spp.-derived molecules have been studied under different medical conditions; the therapeutic potentials of phytocannabinoids are related to the effects of delta-9-tetrahydrocannabinol, cannabidiol (CBD), and other compounds. Cannabidiol has many activities within the central nervous system, such as anxiolytic, antidepressant, antipsychotic, anticonvulsant, and anti-inflammatory activities. Some studies have recently shown the potential and successful therapeutic use of phytocannabinoids in veterinary medicine. This clinical case report described a 22-year-old mare suffering from chronic crib-biting and wind-sucking, and the successful outcome of four weeks-therapy with CBD. This is the first report of the successful therapeutic use of phytocannabinoids in equine behavioural disorders.
ABSTRACT
Background: Atopic dermatitis (AD) is one of the most common cutaneous inflammatory and pruritic diseases in dogs. Considering its multifactorial nature, AD can be a challenging disease to manage, and the therapeutic strategy must often be multimodal. In recent years, research has been moving toward the use of natural products which have beneficial effects on inflammation and itching, and no side effects. Cannabinoid receptors have been demonstrated to be expressed in healthy and diseased skin; therefore, one of the potential alternative therapeutic targets for investigating AD is the endocannabinoid system (ECS). Objective: To immunohistochemically investigate the expression of the cannabinoid receptor type 2 (CB2R), and the cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) in mast cells (MCs), macrophages, dendritic cells (DCs), T cells, and neutrophils of the skin of dogs with AD. Animals: Samples of skin tissues were collected from eight dogs with AD (AD-dogs). Materials and methods: The immunofluorescent stained cryosections of the skins of 8 dogs with AD having antibodies against CB2R, GPR55, TRPV1, TRPA1 were semiquantitatively evaluated. The inflammatory cells were identified using antibodies against tryptase (mast cells), ionized calcium binding adaptor molecule 1 (IBA1) (macrophages/DCs), CD3 (T cells), and calprotectin (neutrophils). The proportions of MCs, macrophages/DCs, T cells, and neutrophils expressing CB2R, GPR55, TRPV1 and TRPA1 were evaluated. Results: The cells of the inflammatory infiltrate showed immunoreactivity (IR) for all or for some of the cannabinoid and cannabinoid-related receptors studied. In particular, MCs and macrophages/DCs showed CB2R-, GPR55-, TRPA1-, and TRPV1-IR; T cells showed CB2R-, GPR55- and TRPA1-IR, and neutrophils expressed GPR55-IR. Co-localization studies indicated that CB2R-IR was co-expressed with TRPV1-, TRPA1-, and GPR55-IR in different cellular elements of the dermis of the AD-dogs. Conclusions and clinical importance: Cannabinoid receptor 2, and cannabinoid-related receptors GPR55, TRPV1 and TRPA1 were widely expressed in the inflammatory infiltrate of the AD-dogs. Based on the present findings, the ECS could be considered to be a potential therapeutic target for dogs with AD, and may mitigate itch and inflammation.
ABSTRACT
It is commonly accepted that some form of skin barrier dysfunction is present in canine atopic dermatitis (AD), one of the most common cutaneous pruritic inflammatory diseases of dogs. The impaired skin barrier function facilitates the penetration of allergens and subsequently stronger sensitization responses. The role of the endocannabinoid system (ECS) in the physiology and pathology of the skin is becoming increasingly established. It has been demonstrated that cannabinoid receptors are expressed in healthy and diseased skin and, based on current knowledge, it could be stated that cannabinoids are important mediators in the skin. The present study has been designed to immunohistochemically investigate the expression of the cannabinoid receptors type 1 (CB1R) and 2 (CB2R) and the cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), peroxisome proliferator-activated receptors alpha (PPARα), and serotoninergic receptor 1a (5-HT1aR) in keratinocytes of healthy dogs and of dogs with AD. Samples of skin tissues were collected from 7 healthy controls (CTRL-dogs) and from 8 dogs with AD (AD-dogs). The tissue samples were processed using an immunofluorescence assay with commercially available antibodies, and the immunolabelling of the receptors studied was quantitatively evaluated. The keratinocytes of the CTRL- and the AD-dogs showed immunoreactivity for all the receptors investigated with a significant upregulation of CB2R, TRPA1, and 5-HT1aR in the epidermis of the AD-dogs. The presence of cannabinoid and cannabinoid-related receptors in healthy keratinocytes suggested the possible role of the ECS in canine epidermal homeostasis while their overexpression in the inflamed tissues of the AD-dogs suggested the involvement of the ECS in the pathogenesis of this disease, having a possible role in the related skin inflammation and itching. Based on the present findings, the ECS could be considered a potential therapeutic target for dogs with AD.
