Thermal taste and anti-aspiration drugs: a novel drug discovery against pneumonia.

Despite the development of strong antibiotics, the pneumonia death is increasing all over the world in these decades. Among the people who died of pneumonia, the majority were 65 years old or over. Although pneumonia is recently categorized into several entities, aspiration pneumonia includes all entities. Therefore, targeting dysphagia and aspiration to treat pneumonia is a promising strategy and anti-aspiration drugs will be a part of pneumonia treatment. The swallowing reflex in elderly people was temperature-sensitive and the improvement of swallowing reflex by temperature stimuli could be mediated by the thermosensing TRP channels at pharynx. The administration of capsaicin as an agonist stimulus of TRPV1, a warm temperature receptor, decreased the delay in swallowing reflex. Red wine polyphenols improved swallowing reflex by enhancing TRPV1 response. Food with menthol, agonist of TRPM8 which is a cold temperature receptor, also decreased the delay in swallowing reflex. Olfactory stimulation such as black pepper was useful to improve the swallowing reflex for people with low ADL levels or with decreased consciousness. Thus, recent advancement of geriatrics found several anti-aspiration drugs such as thermosensing TRP channel agonists, black pepper odor, amantadine, cilostazol, theophylline and angiotensin- converting enzymes inhibitors. Thermosensing TRP channel agonists include capsaicin, capsiate, menthol, and red wine polyphenols. Controls of swallowing are mediated by various stages of neural system from peripheral sensory nerves to the entire cerebral cortex. Each anti-aspiration drug acts on various sites of neural axis of swallowing reflex. The combination of various anti-aspiration drugs may improve dysphagia and prevent aspiration pneumonia.