Effects of Prunus mume Siebold & Zucc. in the pacemaking activity of interstitial cells of Cajal in murine small intestine

Abstract

Abstract. Interstitial cells of Cajal (ICCs) function as pacemaker cells in the gastrointestinal (GI) tract and therefore, serve an important role in regulating GI motility. The effects of a species of plum (Prunus mume Siebold & Zucc.) on cultured ICC cluster-induced pacemaker potentials in the mouse small intestine were investigated, and the effects of a methanolic extract of Prunus mume (m-PM) on ICC pacemaker activities were examined using the whole-cell patch-clamp technique. ICC pacemaker membrane potentials were depolarized by m-PM in a concentration dependent manner in current clamp mode. 4-Diphenylacetoxy-N-methyl-piperidine methiodide, which is a muscarinic 3 (M 3 ) receptor antagonist, was able to block m-PM-induced pacemaker potential increases, whereas methoctramine, which is a muscarinic 2 (M 2 ) receptor antagonist, was not. When 1 mM guanosine diphosphate β-5 was present in the pipette solution, m-PM induced slight pacemaker depolarization. Following pretreatment in bath solution of Ca 2+ -free solution or a Ca 2+ -ATPase inhibitor in endoplasmic reticulum, the pacemaker currents were inhibited. Furthermore, pretreatment with PD98059, SB203580 or SP600125, which is a c-jun NH2-terminal kinase inhibitor, blocked m-PM-induced ICC potential depolarization. Furthermore, m-PM inhibited transient receptor potential melastatin (TRPM) 7 channels, but did not affect Ca 2+ -activated Cl -channels. These results suggest that m-PM is able to modulate pacemaker potentials through the muscarinic M 3 receptor, via G-protein and external and internal Ca 2+ , in a mitogen-activated protein kinase and TRPM7-dependent manner. Therefore, m-PM may provide a basis for the development of a novel gastroprokinetic agent. IntroductionThe fruit of the plum tree Prunus mume Siebold & Zucc. (PM) is used across East Asia, particularly in Korea and Japan (1), as a traditional herbal medicine for the relief of digestive problems, fatigue and fever. PM contains a number of phenolic compounds, including phenolic acids and flavonoids (1,2), which have antioxidant and free radical scavenging activities in vivo (3-6). Furthermore, PM extracts exhibit many pharmacological activities, including antimicrobial (7-10), immune enhancing (11), anti-cancer (1,12,13), and anti-fatigue (14) effects, and have been demonstrated to enhance osteoclast differentiation (15) and improve blood flow (16). Additionally, previous studies have reported that using PM extracts with probiotics inhibits the development of atopic dermatitis (17) and enhances immunity (18).Interstitial cells of Cajal (ICCs) are the pacemakers of the gastro-intestinal tract and generate rhythmic responses in cell membrane electrical potentials (19,20), thus serving important roles in the regulation of GI motility (21). Additionally, endogenous agents are able to regulate GI motility function via ICCs (22-25). Furthermore, transient receptor potential melastatin (TRPM) 7 (26) or Cl -channels, such as anoctamin1 (ANO1) (27)(28)(29), are associated with pacemaker potentials in the...