Abstract
Aquaporins (AQPs) are water-specific membrane channel proteins that regulate cellular and organismal water homeostasis. The nose, an organ with important respiratory and olfactory functions, is the first organ exposed to external stimuli. Nose-related topics such as allergic rhinitis (AR) and chronic rhinosinusitis (CRS) have been the subject of extensive research. These studies have reported that mechanisms that drive the development of multiple inflammatory diseases that occur in the nose and contribute to the process of olfactory recognition of compounds entering the nasal cavity involve the action of water channels such as AQPs. In this review, we provide a comprehensive overview of the relationship between AQPs and rhinologic conditions, focusing on the current state of knowledge and mechanisms that link AQPs and rhinologic conditions. Key conclusions include the following: (1) Various AQPs are expressed in both nasal mucosa and olfactory mucosa; (2) the expression of AQPs in these tissues is different in inflammatory diseases such as AR or CRS, as compared with that in normal tissues; (3) the expression of AQPs in CRS differs depending on the presence or absence of nasal polyps; and (4) the expression of AQPs in tissues associated with olfaction is different from that in the respiratory epithelium.
Highlights
Aquaporins (AQPs), called water channels, are ubiquitous, integral membrane proteins belonging to a larger major family of intrinsic proteins that form pores in the membranes of biological cells and facilitate the intercellular transport of water [1]
There were no significant differences in expression of AQP1, AQP3, or AQP5 mRNAs among control, allergic rhinitis (AR), and CRS with nasal polyps (CRSwNP) patients
Histamine induced a concentration-dependent inhibition of phosphorylated CREB (p-CREB) (Ser133) in human nasal epithelial cells (HNEpCs), in association with a concentration-dependent downregulation of AQP5 mRNA and protein. These findings suggested that histamine downregulates AQP5 production in HNEpCs by inhibiting p-CREB (Ser133), which can cause hypersecretion in the AR by impairing clearance of airway epithelial secretions
Summary
Aquaporins (AQPs), called water channels, are ubiquitous, integral membrane proteins belonging to a larger major family of intrinsic proteins that form pores in the membranes of biological cells and facilitate the intercellular transport of water [1]. 13 types of AQPs have been identified, named AQP0 to AQP12 These proteins have been divided into three groups based on their structural and functional characteristics: (1) orthodox AQPs (AQP0, -1, -2, -4, -5, -6, and -8), which are selectively permeable to water; (2) aquaglyceroporins (AQP3, -7, -9, and -10), which are permeable to glycerol, urea, and other small solutes, in addition to water; and (3) S-aquaporins (super- or subcellular AQP, AQP11, and -12), which have peculiar intracellular localizations and functions that are currently under investigation [4,5,6,7]. Non-transport functions, such as cell–cell adhesion, membrane polarization, and regulation of interacting proteins, such as ion channels, have been suggested for some AQPs [2,3,8].
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