Astringent Effects of Red Wine Associated with Responses of Aquaporins Found in Human Tongue and Salivary Tissues

Aquaporin (AQP) water channels facilitate fluid transport
across
cell membranes, are implicated in rodent oral water sensing, and were
examined in the human tongue for their modulation by mouthfeel compounds
and ensuing effects on perception and saliva tribology. Immunohistochemistry
demonstrated abundant AQP1 and AQP2 and moderate AQP5 in human tongue
and high AQP5 in salivary gland. Trained human tasting panels evaluated
astringency intensities; results correlated with wine tannin measures
and inhibition of AQP1 water flux (R2 ≥
0.9). Wine tannin extract additions of 1 g/L reduced cell swelling
−125 ± 20% (SE) (P < 0.0001), increased
saliva-tannin friction coefficient 16.0 ± 1.9% (P < 0.0001) and astringency scores 17.3 ± 5.5% (P < 0.006). Osmotic swelling assays identified wines, red wine
polyphenols, alum sulfate, and tannic acidall archetypal astringentsas
inhibitors of AQP1 and to a lesser extent AQP5. Astringent block of
AQPs present in tongue and salivary gland suggests a mechanistic role
of water flux in drying sensations, beyond the established changes
in saliva resulting from tannin and proline-rich-protein interactions.
Insights into AQPs as molecular components of mouthfeel could inform
fundamental debates on how astringent phenomena arise and increase
understanding of nutrient sensing and uptake as found within the digestive
tract and throughout the body.

水通道蛋白（Aquaporin, AQP）可介导流体跨细胞膜转运，参与啮齿动物的口腔水分感知过程；本研究针对口腔感觉物质对其的调控作用，以及由此对感知与唾液摩擦学产生的后续影响，在人类舌组织中对该蛋白展开了检测。
免疫组织化学检测结果显示，人类舌组织中存在大量AQP1与AQP2、中等量AQP5，而唾液腺中则高表达AQP5。
经过训练的人类感官评价小组对涩感强度进行了评估；所得结果与葡萄酒单宁含量测定值以及AQP1水通量抑制率呈显著相关（决定系数R²≥0.9）。
当葡萄酒单宁提取物添加量为1 g/L时，细胞肿胀度被抑制125 ± 20%（标准误SE，P < 0.0001），唾液-单宁摩擦系数升高16.0 ± 1.9%（P < 0.0001），涩感评分升高17.3 ± 5.5%（P < 0.006）。
渗透肿胀实验证实，葡萄酒、红酒多酚、硫酸铝与单宁酸——均为典型的涩感物质——均可抑制AQP1的活性，对AQP5的抑制作用相对较弱。
舌组织与唾液腺中存在的AQP被涩感物质阻断这一现象，表明水通量在口腔干燥感的产生中具有机械作用机制，这一机制超越了此前公认的、由单宁与富脯氨酸蛋白相互作用所引发的唾液成分变化。
将AQP作为口腔感觉的分子组分的相关研究进展，可为涩感现象产生机制的基础争论提供新思路，并有助于加深我们对消化道乃至全身营养物质感知与摄取过程的理解。