Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC70
Regulation of Ion Transport in Cultured Human Bronchial Epithelial Cells by Cordyceps militaris Extract
C. Fung1, W. KO1
1. School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong.
Cordyceps militaris(CM), also known as the caterpillar fungus, is a well-known traditional Chinese medicine. In recent decades, CM extract has been reported to have different biological activities, such as anti-tumor activity (Park et al., 2009) and immuno-modulation (Shin et al., 2010). CM can be used to treat certain respiratory diseases, such as bronchitis and chronic obstructive pulmonary disease (Paterson, 2008). In this study, 16HBE14o-, a human bronchial epithelial cell line, was used as a model to study the regulation of ion transport by CM water extract (Yue et al. 2008). The 16HBE14o- cells were grown on Transwell-COL membranes until confluent (Wong et al., 2009). The monolayers were mounted in Ussing chambers, in which they were bathed in normal Krebs-Henseleit solution with a basolateral-to-apical Cl- gradient. An increase in short-circuit current (ISC) was measured by electrophysiological technique. Apical or basolateral application of CM extract stimulated a dose-dependent increase in ISC. The ISC responses were inhibited by apical pretreatment of 10 μM cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel blocker, CFTRinh-172 (Control (ap): 22.92 ± 2.83 μA/cm2, +CFTRinh-172: 12.00 ± 2.39 μA/cm2, n = 5, P < 0.05; Control (bl): 14.13 ± 1.56 μA/cm2, +CFTRinh-172: 2.92 ± 0.62 μA/cm2, n = 6, P < 0.05). Apical addition of 300 μM DIDS, a calcium-activated Cl- channel (CaCC) blocker, suppressed the increase in CM-induced ISC by 50.3% and 40.6% at the apical and basolateral sides, respectively. The apical ISC response was reduced by 38.1% after the basolateral application of 10 μM TRAM-34, an intermediate conductance Ca2+-activated K+ channel blocker. The basolateral application of chromanol 293B, a cAMP-activated K+ channel blocker, reduced the ISC response by 44.4%. However, both TRAM-34 and chromanol 293B did not significantly reduce ISC response stimulated by CM extract at the basolateral side. Furthermore, the CM extract-induced ISC could be significantly inhibited by adenylate cyclase (AC) inhibitor MDL-12033A, PKA inhibitor H-89, and intracellular Ca2+ chelator BAPTA-AM. In conclusion, CM extract stimulated transepithelial Cl- secretion in 16HBE14o- cells through apical CFTR Cl- channels or CaCC. The basolateral cAMP-or Ca2+-activated K+ channels were activated by CM extract to provide a driving force for apical Cl- secretion. The underlying signal transduction mechanisms involve both AC/cAMP- and Ca2+-dependent pathways.
Where applicable, experiments conform with Society ethical requirements