Impaired Junctions and Invaded Macrophages in Oral Epithelia With Oral Pain

Candesartan exhibits low intrinsic permeation capacity and affects buccal tissue viability and integrity: An ex vivo study in porcine buccal mucosa

Candesartan is a nonpeptide angiotensin II receptor blocker that selectively binds to angiotensin II receptor subtype 1. It is administered orally in its ester form (candesartan cilexetil). However, its poor aqueous solubility results in its low bioavailability; therefore, other routes of administration must be explored. The buccal mucosa has been extensively studied as an alternative route for drug delivery as it improves the bioavailability of drugs administered via the peroral route. Porcine buccal mucosa has been widely used as an ex vivo model to study the permeability of various diffusants; however, studies on candesartan are limited. This study aimed to evaluate the ex vivo permeation profile of candesartan and its effects on the viability and integrity of porcine buccal mucosa. Initially, we evaluated the viability, integrity, and barrier function of the buccal tissue before performing permeability tests using freshly excised tissues or tissues after 12 h of resection. Here, three indicators were used: caffeine, β-estradiol, and FD-20 penetration; mucosal metabolic activity, as determined using MTT reduction assay; and haematoxylin and eosin staining. Our results indicated that the porcine buccal mucosa preserved its viability, integrity, and barrier function before the permeation assay, allowing the passage of molecules with a molecular mass of less than 20 kDa, such as caffeine, but not β-estradiol and FD-20. Furthermore, we analyzed the intrinsic capacity of candesartan to diffuse through the fresh porcine buccal mucosa under two pH conditions. The concentration of candesartan in the receptor chamber of Franz diffusion cell was quantified using ultra-high liquid chromatography. In the permeation assay, candesartan exhibited a low intrinsic permeation capacity that impacted the buccal tissue viability and integrity, suggesting that using the buccal mucosa as an alternative route of administration requires developing a pharmaceutical formulation that reduces the adverse effects on mucosa and increasing the buccal permeability of candesartan.

Transient Receptor Potential Channel Vanilloid 1 Contributes to Facial Mechanical Hypersensitivity in a Mouse Model of Atopic Asthma

Sensitive skin, a common pathophysiological feature of allergic diseases, is defined as an unpleasant sensation in response to stimuli that normally should not provoke such sensations. However, the relationship between allergic inflammation and hypersensitive skin in the trigeminal system remains to be elucidated. To explore whether bronchial allergic inflammation affects facial skin and primary sensory neurons, we used an ovalbumin (OVA)-induced asthma mouse model. Significant mechanical hypersensitivity was observed in the facial skin of mice with pulmonary inflammation induced by OVA sensitization compared to mice treated with adjuvant or vehicle as controls. The skin of OVA-treated mice showed an increased number of nerve fibers, especially rich intraepithelial nerves, compared to controls. Transient receptor potential channel vanilloid 1 (TRPV1)-immunoreactive nerves were enriched in the skin of OVA-treated mice. Moreover, epithelial TRPV1 expression was higher in OVA-treated mice than in controls. Trigeminal ganglia of OVA-treated mice displayed larger numbers of activated microglia/macrophages and satellite glia. In addition, more TRPV1 immunoreactive neurons were found in the trigeminal ganglia of OVA-treated mice than in controls. Mechanical hypersensitivity was suppressed in OVA-treated Trpv1-deficient mice, while topical skin application of a TRPV1 antagonist before behavioral testing reduced the reaction induced by mechanical stimulation. Our findings reveal that mice with allergic inflammation of the bronchi had mechanical hypersensitivity in the facial skin that may have resulted from TRPV1-mediated neuronal plasticity and glial activation in the trigeminal ganglion.

Critical roles of adherens junctions in diseases of the oral mucosa

The oral cavity is directly exposed to a variety of environmental stimuli and contains a diverse microbiome that continuously interacts with the oral epithelium. Therefore, establishment and maintenance of the barrier function of the oral mucosa is of paramount importance for its function and for the body's overall health. The adherens junction is a cell-cell adhesion complex that is essential for epithelial barrier function. Although a considerable body of work has associated barrier disruption with oral diseases, the molecular underpinnings of these associations have not been equally investigated. This is critical, since adherens junction components also possess significant signaling roles in the cell, in addition to their architectural ones. Here, we summarize current knowledge involving adherens junction components in oral pathologies, such as cancer and oral pathogen-related diseases, while we also discuss gaps in the knowledge and opportunities for future investigation of the relationship between adherens junctions and oral diseases.

Oral Mucosa as a Potential Site for Diagnosis and Treatment of Allergic and Autoimmune Diseases

Most prevalent food allergies during early childhood are caused by foods with a high allergenic protein content, such as milk, egg, nuts, or fish. In older subjects, some respiratory allergies progressively lead to food-induced allergic reactions, which can be severe, such as urticaria or asthma. Oral mucosa remodeling has been recently proven to be a feature of severe allergic phenotypes and autoimmune diseases. This remodeling process includes epithelial barrier disruption and the release of inflammatory signals. Although little is known about the immune processes taking place in the oral mucosa, there are a few reports describing the oral mucosa-associated immune system. In this review, we will provide an overview of the recent knowledge about the role of the oral mucosa in food-induced allergic reactions, as well as in severe respiratory allergies or food-induced autoimmune diseases, such as celiac disease.

SELL and IFI44 as potential biomarkers of Sjögren's syndrome and their correlation with immune cell infiltration

The onset of Sjögren's syndrome (SS) is hidden, early diagnosis is difficult, and the disorder seriously endangers the physical and mental health of affected people. This study aims to identify potential biomarkers of SS and to investigate the characteristics of immune cell infiltration. We used four SS gene expression profile data series from the Gene Expression Omnibus database, and applied bioinformatics analysis and machine learning algorithms to screen two biomarkers, SELL (L-selectin) and IFI44 (interferon-induced protein 44), from 101 differentially expressed genes. The two-gene model comprising SELL and IFI44 showed good diagnostic ability for SS in the training set (AUC = 0.992) and verification set (AUC = 0.917). Analysis of infiltrating immune cells in SS identified naive B cells, resting CD4 memory T cells, activated CD4 memory T cells, gamma delta T cells, M0 macrophages, M1 macrophages, plasma cells, CD8 T cells, activated NK cells and monocytes as candidate participants in the SS process. Furthermore, SELL was associated with M2 macrophages, activated CD4 memory T cells, gamma delta T cells, resting NK cells and plasma cells, while IFI44 was associated with activated mast cells, resting NK cells, resting mast cells and CD8 T cells. This study demonstrates that SELL and IFI44 can serve as good diagnostic markers for SS and may also be new diagnostic and therapeutic targets for SS.

Enhanced junctional epithelial permeability in TRPV4-deficient mice

Background and Objective

As the interface between the oral cavity and the teeth, the junctional epithelial barrier is critical for gingival defense. The junctional epithelium is subject to mechanical stresses from biting force or external insults such as bacterial attacks, but little is known about the effects of mechanical stimuli on epithelial functions. Transient receptor potential vanilloid 4 (TRPV4) functions as a mechanosensitive nonselective cation channel. In the present study, based on marked expression of TRPV4 in the mouse junctional epithelium, we aimed to clarify the putative links between TRPV4 and junctional complexes in the junctional epithelium.

Methods and Results

Histological observations revealed that the junctional epithelium in TRPV4‐deficient (TRPV4^−/−) mice had wider intercellular spaces than that in wild‐type (TRPV4^+/+) mice. Exogenous tracer penetration in the junctional epithelium was greater in TRPV4^−/− mice than in TRPV4^+/+ mice, and immunoreactivity for adherens junction proteins was suppressed in TRPV4^−/− mice compared with TRPV4^+/+ mice. Analysis of a mouse periodontitis model showed greater bone volume loss in TRPV4^−/− mice compared with TRPV4^+/+ mice, indicating that an epithelial barrier deficiency in TRPV4^−/− mice may be associated with periodontal complications.

Conclusion

The present findings identify a crucial role for TRPV4 in the formation of adherens junctions in the junctional epithelium, which could regulate its permeability. TRPV4 may be a candidate pharmacological target to combat periodontal diseases.