Functional vanilloid receptor-1 in human submandibular glands

Area of Science:

• Physiology
• Molecular Biology
• Glandular Biology

Background:

• Vanilloid receptor-1 (VR1), initially identified in the nervous system, is now recognized for its expression in diverse cell types.
• Evidence suggests VR1's potential role beyond neuronal functions, prompting investigation into non-neuronal tissues.

Purpose of the Study:

• To investigate the presence and function of Vanilloid receptor-1 (VR1) in the human submandibular gland (SMG).
• To determine VR1's involvement in the regulation of salivary secretion.

Main Methods:

• Detection of VR1 mRNA and protein expression in human SMGs and salivary cell lines.
• Immunohistochemical localization of VR1 within SMG cell types.
• Assessment of capsaicin-induced intracellular calcium changes, ERK phosphorylation, and aquaporin 5 (AQP5) trafficking.
• Evaluation of capsaicin's effect on salivary secretion in vivo.
• Inhibition studies using the VR1 antagonist capsazepine.

Main Results:

• VR1 mRNA and protein were confirmed in human SMGs and salivary intercalated duct cells.
• VR1 was predominantly localized in serous acinar and ductal cells, absent in mucous acinar cells.
• Capsaicin stimulation led to increased intracellular calcium, ERK phosphorylation, and AQP5 trafficking to the plasma membrane, effects blocked by capsazepine.
• Topical application of capsaicin stimulated salivary secretion.

Conclusions:

• A functional Vanilloid receptor-1 (VR1) is expressed in the human submandibular gland.
• VR1 plays a role in regulating salivary secretion, partly by mediating AQP5 trafficking.
• These findings highlight VR1 as a potential target for modulating salivary gland function.