The Activation Effect Of Resveratrol On Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel

Resveratrol (3,5,4，-trihydroxystilbene) is a naturally occurring polyphenol compound,which is produced by a wide variety of plants, including red grapes, mulberries, and peanutswhen response to injury, UV-irradiation, and/or pathogen infections. RES has been receivingwide attention because it has been found to have variety of health benefits and favorablebiological activities such as antioxidant, antimutagenic, anti-inflammatory, chemopreventiven,and anticancer activities. RES is also regarded as the possible reason that a low incidence ofcardiovascular diseases may coexist with intake of high fat diet. In2005, Blumenstein andcolleagues demonstrated that RES stimulated cAMP-dependent Cl secretion in T84cancercells and anion secretion in mouse intestinal mucosa. Based on this, they proposed that cAMPstimulated Cl secretion activity is a possible reason for severe diarrhea triggered amongpatients who administered certain plant polyphenols. Recently, Alexander and colleaguesindicated that RES could potentiate transepithelial Cl transport in primary cultured murinenasal septal (MNSE) and human sinonasal epithelial (HSNE) cells. Though, so far, variouscellular effectors have been proposed as potential targets for RES actions, the precisemolecular mechanism whereby RES-induced chloride secretion remained largely elusive.The cystic fibrosis transmembrane conductance regulator (CFTR) is a member ofATP-binding cassette (ABC) transporter family, which is ubiquitously expressed in apicalmembrane of serous epithelial cells in intestines, airways, pancreas, bile ducts, epididymis,and conjunctiva. CFTR plays a crucial role in transepithelial fluid homeostasis because it isthe primary driver of fluid and water secretion. It has been fully confirmed that CFTR is thefinal common pathway for intestinal Cl secretion in response to various agonists. So, wehypothesized that RES may stimulate the activity of CFTR chloride channel.Using cell-based fluorescent assays, transepithelial short-circuit current measurementsand excised inside-out patch-clamp analysis, we found that RES dose-dependently potentiateboth wild-type and two mutant (ΔF508and G551D) CFTR Cl channel activities, which wasreversed by CFTR inhibitors CFTRinh-172and GlyH101. Transepithelial Cl secretion byCFTR-expressing FRT cells was stimulated by RES with half maximal concentration~80μM.Although the activation of CFTR by RES depends on CFTR phosphorylation level, RES cannot elevate intracellular cAMP content in FRT cells. Excised inside-out patch-clamp analysisindicated that RES significantly increased the chloride currents of wild-type, ΔF508andG551D mutant CFTRs. In ex vivo studies, RES stimulated the transmucosal chloride current of rat colon by short-circuit current assays and increased fluid secretion in mouse trachea byoptical measurement of single gland secretion. These data suggested that CFTR is a moleculartarget of RES and that RES may present a novel class of therapeutic lead compounds intreating CFTR-related diseases including cystic fibrosis, habitual constipation anddisseminated bronchiectasis.