Uridine-5'-triphosphate and Adenosine Triphosphate γS Induce Mucin Secretion Via Ca²⁺-dependent Pathways in Human Nasal Epithelial Cells

Abstract

Objectives—Nucleotides such as adenosine triphosphate (ATP) and uridine-5'-triphosphate (UTP) play fundamental roles in the early stage of secretion in nasal epithelial cells via the P2Y receptor. In this study, we examined the expression pattern of P2Y subtypes and their functions on Ca²⁺ influx ([Ca²⁺]_i) in normal human nasal epithelial (NHNE) cells. We also examined the effect of UTP (an agonist for P2Y₂) and ATPγS (an agonist for P2Y₁₁) on mucin secretion and mucin gene expression.

Material and Methods—The expression pattern of P2Y receptors and the mRNA levels of MUC5AC, MUC5B and MUC8 were examined after treatment with UTP and ATPyS by means of reverse transcriptase polymerase chain reaction. Mucin was quantified by an immunoblotting assay. We measured [Ca²⁺]_i) in NHNE cells using a double perfusion chamber.

Results—Two uracil-sensitive receptors (P2Y₂, P2Y₄) and two adenine-selective receptors (P2Y₁, P2Y₁₁) were expressed in NHNE cells. UTP and ATPyS increased [Ca²⁺]_i via caffeine-sensitive pathways, and these two agonists stimulated mucin secretion to a similar magnitude without their gene enhancement. In addition, the mucin stimulatory effects subsided when the intracellular Ca²⁺ was removed by 2-bis-(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester.

Conclusion—This study showed that P2Y₂ and P2Y₁₁ receptors were expressed in NHNE cells and that their agonists, UTP and ATPyS, act as secretogogues on mucin secretion via Ca²⁺-dependent pathways.

Key words:

• caffeine
• nasal mucosa
• nucleotide
• purinergic receptor