Arctigenin alleviates ER stress via activating AMPK.
OBJECTIVE
To investigate the protective effects of arctigenin (ATG), a phenylpropanoid dibenzylbutyrolactone lignan from Arctium lappa L (Compositae), against ER stress in vitro and the underlying mechanisms.


METHODS
A cell-based screening assay for ER stress regulators was established. Cell viability was measured using MTT assay. PCR and Western blotting were used to analyze gene and protein expression. Silencing of the CaMKKβ, LKB1, and AMPKα1 genes was achieved by RNA interference (RNAi). An ATP bioluminescent assay kit was employed to measure the intracellular ATP levels.


RESULTS
ATG (2.5, 5 and 10 μmol/L) inhibited cell death and unfolded protein response (UPR) in a concentration-dependent manner in cells treated with the ER stress inducer brefeldin A (100 nmol/L). ATG (1, 5 and 10 μmol/L) significantly attenuated protein synthesis in cells through inhibiting mTOR-p70S6K signaling and eEF2 activity, which were partially reversed by silencing AMPKα1 with RNAi. ATG (1-50 μmol/L) reduced intracellular ATP level and activated AMPK through inhibiting complex I-mediated respiration. Pretreatment of cells with the AMPK inhibitor compound C (25 μmol/L) rescued the inhibitory effects of ATG on ER stress. Furthermore, ATG (2.5 and 5 μmol/L) efficiently activated AMPK and reduced the ER stress and cell death induced by palmitate (2 mmol/L) in INS-1 β cells.


CONCLUSIONS
ATG is an effective ER stress alleviator, which protects cells against ER stress through activating AMPK, thus attenuating protein translation and reducing ER load.
Department of Tumor Pharmacology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China.
Yuan
Y
Gu
Xiao-xiao
XX
Sun
Ji-ming
JM
Ye
Li
L
He
Shou-sheng
SS
Yan
Hao-hao
HH
Zhang
Li-hong
LH
Hu
Jun-ying
JY
Yuan
Qiang
Q
Yu
D000091162:AMP-Activated Protein Kinase Kinases; D000818:Animals; D031170:Arctium / Q000737:chemistry*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects*; D005663:Furans / Q000302:isolation & purification / Q000494:pharmacology*; D056945:Hep G2 Cells; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects; D017705:Lignans / Q000302:isolation & purification / Q000494:pharmacology*; D008297:Male; D010168:Palmitates / Q000494:pharmacology; D014176:Protein Biosynthesis / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D056811:Unfolded Protein Response / Q000187:drug effects
D005663:Furans; D017705:Lignans; D010168:Palmitates; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; C071942:arctigenin