Polysaccharides of Dendrobium officinale induce aquaporin 5 translocation by activating M3 muscarinic receptors.

Dendrobium officinale is an herbal medicine that has been clinically used to promote body fluid production. Previous works demonstrated that D. officinale polysaccharides could ameliorate symptoms of salivary secretion of patients with Sjögren's syndrome and in a respective mice model. In the present study, we investigated the underlying mechanism by which D. officinale polysaccharides activate M3 muscarinic receptors and induce extracellular calcium influx, leading to the translocation of aquaporin 5, a water channel protein, to the apical membrane of human submandibular gland epithelial cells. Enzymatic treatment of D. officinale polysaccharides suggested that they are hydrolyzed but do not permeate cell membranes. This finding supports the pharmacological activity of D. officinale polysaccharides to promote salivary secretion.