Dysphagia is a big issue for a large number of patients with cerebrovascular and other neurodegenerative diseases. Animal models are essential for understanding the pathophysiology of these conditions and developing effective treatments. In this study, we developed an animal model with attenuated pharyngeal constriction during swallowing using denervation of the pharyngeal branch of the vagus nerve. Our findings suggest that the pharyngeal area and pharyngeal transit duration during the pharyngeal stage of swallowing were increased compared to those in sham-operated and control animals. We investigated the potential of the anti-oxidant Twendee X in preventing oxidative stress caused by denervation-induced muscle damage, which could suppress muscle atrophy. Hence, we tested the effect of oral application of the Twendee X on swallowing function in the dysphagia model animals.

Our results indicate that Twendee X administration resulted in less increase in the pharyngeal area and pharyngeal transit duration compared to those in the dysphagia animal model. The thyropharyngeal muscles were also thicker than those in the nerve-sectioned animals. Overall, our findings suggest that Twendee X may have a possible role in preventing oxidative stress by the denervation of the pharyngeal constrictor muscle, leading to the suppression of denervation-induced muscle atrophy. Further studies are necessary to ascertain the clinical effects of Twendee X on bulbar paralysis in stroke patients. This study provides important insights into the potential use of Twendee X as a treatment for dysphagia patients.

Vocalization is a complex laryngeal function that involves intricate neuronal networks in the brain. This function depends on vocal fold vibration, which requires adequate subglottic pressure, vocal fold adduction, and tension. However, excessive use of vocal folds can damage the tissue structure of the vocal folds, as well as the laryngeal and respiratory muscles, possibly due to oxidative stress. Therefore, we conducted a study investigating whether vocal loading could lead to functional deterioration of the vocal-related muscles. 

Thus, we achieved an animal model, in which excessive vocal fold use induces hoarseness, produced by repetitive forced vocalization triggered by electrical stimulation of the midbrain periaqueductal grey in guinea pigs.

To examine oxidative stress of the laryngeal and respiratory muscles of vocal-loaded animals, we then compared the formation of malondialdehyde protein adducts of the laryngeal and respiratory muscles for a representative vocal-loaded animal with a control animal. The intralaryngeal and expiratory respiratory muscles showed higher levels of malondialdehyde in a vocal-loaded animal.

While additional experiments are required to substantiate this hypothesis, these results may give a new perspective on evaluating vocal fatigue in individuals who use their voices excessively. They may also help identify potential interventions or treatments for vocal disorders.

Airway reflexes such as coughing, sneezing, and the expiration reflex are essential in preventing foreign body from staying in the airway. These defensive reflexes should be appropriately activated against foreign bodies entering both the upper and lower airways. However, excessive responses to airway stimulation can lead to further airway distress and result in complications such as an overactive cough reflex and sneezing.

Allergic airway diseases, such as asthma and allergic rhinitis (AR), are typically chronic and are occasionally characterized by excessive and prolonged Th2 responses to inhaled allergens. They are assumed to be linked to oxidative stress. Asthma is associated with decreased antioxidant defenses, such as superoxide dismutase, catalase, and glutathione. Patients with AR have systemically elevated oxidative stress and systemically elevated serum total antioxidant status levels. Concomitant use of nasal steroids and antihistamines significantly decreases total oxidative stress in AR patients. Significant improvement in clinical outcome was observed in subjects who received antioxidants along with intranasal steroid fluticasone furoate. Other treatments that have been reported to improve symptoms of respiratory allergic diseases by enhancing antioxidant status include hydrogen-rich saline, crocin, curcumin, and silymarin. 

Interleukin (IL)-4 and IL-13 are critical cytokines in the induction of the pathogenic Th2 responses. They induce periostin in the airway tract that is highly expressed in chronic inflammatory diseases―asthma, atopic dermatitis, eosinophilc chronic sinusitis/chronic rhinosinusitis with nasal polyp, and allergic conjunctivitis. 

In this presentation, we will briefly review previous studies regarding airway disorders linked to oxidative stress. We will also introduce our recent project regarding airway hyperresponsiveness and the involvement of periostin in respiratory allergic diseases using periostin-knockout mice and respiratory allergic models. Further studies are necessary to evaluate the possibility of anti-oxidative treatment for the hypersensitivity caused by allergic airway inflammation.