Abstract
Feline chronic gingivostomatitis (FCGS) is an oral disease. Cats with FCGS experience intense oral pain. Some cats remain refractory to current therapies based on dental extraction and adjuvant medical treatment; it is therefore necessary to investigate alternative therapeutic targets involved in inflammatory mechanisms and pain, namely the endocannabinoid system (ECS). The present study investigated the expression of cannabinoid receptors type 1 (CB1R) and 2 (CB2R), and cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential ankyrin 1 (TRPA1) and serotonin 1a receptor (5-HT1aR), in the oral mucosa of healthy cats to determine whether there was altered expression and distribution in cats with FCGS. Samples of caudal oral mucosa were collected from eight control cats (CTRL cats) and from eight cats with FCGS (FCGS cats). Tissue samples were processed using an immunofluorescence assay with cat-specific antibodies, and the immunolabelling of the receptors studied was semiquantitatively evaluated. The mucosal epithelium of the CTRL cats showed CB1R, TRPA1 and 5-HT1aR immunoreactivity (IR), while CB2R and GPR55 IR were generally not expressed. In the CTRL cats, the subepithelial inflammatory cells expressed CB2R, GPR55 and 5-HT1aR IR. In the FCGS cats, all the receptors studied were markedly upregulated in the epithelium and inflammatory infiltrate. Cannabinoid and cannabinoid-related receptors are widely expressed in the oral mucosa of healthy cats and are upregulated during the course of FCGS. The presence of cannabinoid and cannabinoid-related receptors in healthy tissues suggests the possible role of the ECS in the homeostasis of the feline oral mucosa, while their overexpression in the inflamed tissues of FCGS cats suggests the involvement of the ECS in the pathogenesis of this disease, with a possible role in the related inflammation and pain. Based on the present findings, ECS could be considered a potential therapeutic target for patients with FCGS.
Highlights
The network of sensory neurons, motor neurons, interneurons, and glial cells embedded in the gut walls is called the enteric nervous system (ENS) [1]
In the gastrointestinal tract (GIT), cannabinoid receptors regulate motility, secretion, emesis, food intake, and inflammation [15,17,24,26]. The authors focused their attention on the presence of the endocannabinoid system (ECS) in the ileal myenteric plexus (MP) of pigs, with particular emphasis on both the cannabinoid receptors, namely CB1R and CB2R, and the cannabinoid-related receptors transient potential vanilloid receptor 1 (TRPV1), transient potential ankyrin receptor 1 (TRPA1), and 5-HT1a serotonin receptor (5-HT1aR) by carrying out immunohistochemical analysis
The large percentages of CB1R and TRPV1immunoreactive neurons, which we found in the porcine MP ileum, allowed us to speculate that CB1R and TRPV1 may co-exist on the same subclass of cholinergic neurons as substantiated by functional and immunohistochemical studies [35,63]
Summary
The network of sensory neurons, motor neurons, interneurons, and glial cells embedded in the gut walls is called the enteric nervous system (ENS) [1]. There is a strict interaction between the ENS and the central nervous system (CNS), with a bidirectional information flow between these two systems; the ENS can control digestive functions independently of the CNS [3]. The ENS cooperates with the immune and endocrine systems by adapting nutrient absorption depending on the condition of the gut, thereby preserving mucosal barrier functionality [3]. The endocannabinoid system (ECS) is constituted of three fundamental components: receptors, signaling molecules, and the enzymes responsible for ligand biosynthesis and degradation. It typically comprises the prototypical cannabinoid receptors types 1 and
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