A Natural Plant-Derived Dihydroisosteviol Prevents Cholera Toxin-Induced Intestinal Fluid Secretion

Abstract

Stevioside and its major metabolite, steviol, have been reported to affect ion transport in many types of tissues, such as the kidney, pancreas, and intestine. The effect of stevioside, steviol, and its analogs on intestinal Cl Ϫ secretion was investigated in a human T84 epithelial cell line. Short-circuit current measurements showed that steviol and analogs isosteviol, dihydroisosteviol, and isosteviol 16-oxime inhibited in a dosedependent manner forskolin-induced Cl Ϫ secretion with IC 50 values of 101, 100, 9.6, and 50 M, respectively, whereas the parent compound stevioside had no effect. Apical Cl Ϫ current measurement indicated that dihydroisosteviol targeted the cystic fibrosis transmembrane regulator (CFTR). The inhibitory action of dihydroisosteviol was reversible and was not associated with changes in the intracellular cAMP level. In addition, dihydroisosteviol did not affect calcium-activated chloride secretion and T84 cell viability. In vivo studies using a mouse closed-loop model of cholera toxin-induced intestinal fluid secretion showed that intraluminal injection of 50 M dihydroisosteviol reduced intestinal fluid secretion by 88.2% without altering fluid absorption. These results indicate that dihydroisosteviol and similar compounds could be a new class of CFTR inhibitors that may be useful for further development as antidiarrheal agents.

Activation of AMP-Activated Protein Kinase by a Plant-Derived Dihydroisosteviol in Human Intestinal Epithelial Cell

“…DHIS was prepared from stevioside as previously described. 14) Purity of DHIS was >99% using thin layer chromatography and nuclear magnetic resonance spectroscopy analyses. CFTR inh -172 was purchased from Calbiochem (San Diego, Ca, U.S.a.).…”

“…1) as the most potent steviol derivative that inhibited cAMP-activated Cl − secretion across T84 cell monolayers (IC 50 9.6 µm) by mechanisms involving inhibition of CFTR Cl − channel activity. 14) Importantly, intraluminal administration of DHIS reduced cholera toxin-induced intestinal fluid secretion by approximate 90%. 14) However, the exact mechanism by which DHIS inhibits CFTR remains unexplored.…”

“…14) Importantly, intraluminal administration of DHIS reduced cholera toxin-induced intestinal fluid secretion by approximate 90%. 14) However, the exact mechanism by which DHIS inhibits CFTR remains unexplored. The present study, therefore, aimed to investigate the mechanism of CFTR inhibition by DHIS using both heterologous expression systems (Fisher rat thyroid cells stably transfected with wild-type human CFTR/FRT-CFTR cells) and T84 cells.…”

“…14) Structural modifications of stevioside have identified dihydroisosteviol (DHIS) (Fig. 1) as the most potent steviol derivative that inhibited cAMP-activated Cl − secretion across T84 cell monolayers (IC 50 9.6 µm) by mechanisms involving inhibition of CFTR Cl − channel activity.…”

“…14) As Fisher rat thyroid (FRT) cells exhibit low baseline Cl − transport and no cAMP-activated Cl − current, FRT cells stably transfected with wild-type human CFTR (FRT-CFTR cells) represent an appropriate cell model for studying effects of DHIS on CFTR function. 15) To determine the effects of DHIS on CFTR function, we performed apical Cl − current analysis of FRT-CFTR cell monolayers.…”