Toxicarioside A, isolated from tropical Antiaris toxicaria, blocks endoglin/TGF-β signaling in a bone marrow stromal cell line.
OBJECTIVE
To investigate possible mechanism of toxicarioside A in HS-5 bone stromal cells.


METHODS
HS-5 bone stromal cells were cultured in media supplemented with various concentrations of toxicarioside A or control DMSO (not treatment). Endoglin and TGF-β were detected by Northern and Western blot analysis and quantified in a standard method. Downstream molecules of endoglin and TGF-β (Smad1, Smad2 and their active phosphorylated counterparts, pSmad1 and pSmad2) were also detected and quantified by Western blot analysis. In addition, cell proliferation assay and small interfering RNA (siRNA) against endoglin were used to certificate the function of endolgin in the HS-5 cells.


RESULTS
Compared with the not treated (0 μg/mL) or DMSO treated control HS-5 cells, HS-5 cells treated with toxicarioside A were found significant attenuation of endolgin and TGF-β expression. Significant inhibition of cell proliferation was also found in the HS-5 cells treated with toxicarioside A. ALK1-related Smad1 and ALK5-related Smad2 were decreased in HS-5 cells treated with toxicarioside A. In addition, phosphorylated Smad1 (pSmad1) and Smad2 (pSmad2) were also found attenuation in toxicarioside A-treated HS-5 cells. RNA interference showed that blockage of endoglin by siRNA also decreased Smad1 and Smad2 expression in HS-5 cells.


CONCLUSIONS
Our results indicate that toxicarioside A can influence bone marrow stromal HS-5's function and inhibit HS-5 cell proliferation by alteration of endoglin-related ALK1 (Smad1) and ALK5 (Smad2) signaling.
Agriculture College, and Hainan Provincial Key Laboratory of Tropical Medicine, Hainan University, Haikou, China
Yue-Nan
YN
Li
Feng-Ying
FY
Huang
Wen-Li
WL
Mei
Hao-Fu
HF
Dai
Jun-Li
JL
Guo
Guang-Hong
GH
Tan
Peng
P
Zhou
D031621:Antiaris; D015703:Antigens, CD / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000187:drug effects* / Q000378:metabolism; D002298:Cardenolides / Q000494:pharmacology*; D002460:Cell Line; D049109:Cell Proliferation; D000071063:Endoglin; D006801:Humans; D008297:Male; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051898:Smad1 Protein / Q000187:drug effects / Q000378:metabolism*; D051899:Smad2 Protein / Q000187:drug effects / Q000378:metabolism*; D017154:Stromal Cells / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000378:metabolism
D015703:Antigens, CD; D002298:Cardenolides; C064206:ENG protein, human; D000071063:Endoglin; D011956:Receptors, Cell Surface; D051898:Smad1 Protein; D051899:Smad2 Protein; D016212:Transforming Growth Factor beta