Peter Hwang MD's Laboratory
Electrophysiologic Features of Sinonasal Airway Epithelia
Electrophysiologic features of sinonasal airway epithelia
Air-liquid interface (ALI) cultures of airway epithelial cells reproduce key aspects of airway epithelial structure and function and have proved to be invaluable for understanding airway diseases such as cystic fibrosis. However, the applicability of in vitro findings to humans has important limitations. In vivo or ex vivo models are necessary to resolve whether observed findings in the cultured cells are intrinsic, acquired, or somehow related to the in vitro culture system. These uncertainties highlight the limitations of the in vitro approach and point to the need to ultimately verify the findings in a human model.
1. Development of ex vivo assayFreshly excised human sinonasal epithelia are easily accessible in the clinic or during sinus surgery, yielding satisfactory surface area for analysis. We have developed a platform for analyzing the electrophysiologic properties of freshly excised sinonasal epithelium using Ussing chambers. This ex vivo assay may serve as a novel, low cost screening tool for evaluating functional properties of CFTR chloride channel activity and other ion channels in various disease states, or in response to drug or antioxidant therapy.
2. L-ascorbate (Vitamin C) enhances chloride secretion in freshly excised human sinus and nasal mucosaL-ascorbate is an essential nutrient most notable for its role as a powerful antioxidant. Unlike most animals, humans must take it through diet because we do not synthesize it from D-glucose via the glucuronic pathway. We have found that topical administration of L-ascorbate increases Cl currents across freshly excised human sinonasal epithelial tissue from both normal subjects and sinusitis patients. L-ascorbate-stimulated Cl currents are significantly lower in sinonasal epithelia from sinusitis patients than epithelia from normal controls. We are continuing to explore potential therapeutic applications of L-ascorbate in sinonasal diseases.
3. Inflammatory processes in the airway activates proton (H+) secretion and acidify the air-surface liquid (ASL)The airway surface epithelium is lined with a thin layer of fluid called the airway surface liquid (ASL). A hyper-acidic pH may be associated with airway inflammation and is detrimental for airway functions such as mucociliary transport. We systematically studied the upper airway proton secretion in freshly excised human tissues. The Hydrogen Voltage-gated Channel 1 (HVCN1) is a novel proton channel that is expressed in airway epithelial cells. Channels like HVCN1 provide the proton conductance to release excess intracellular H+ ions across the apical membrane (Figure), which accumulate during the activity of dual NADPH oxidases (Duox1/2). We are studying proton secretory activity in airway epithelium, both normal and diseased, including the potential role of the HVCN1 proton channels.
