Salvianolic acid B protects human endothelial cells from oxidative stress damage: a possible protective role of glucose-regulated protein 78 induction.
OBJECTIVE
The purposes of the present study were to both evaluate the protective effects of Salvianolic acid B (Sal B) and to determine the possible molecular mechanisms by which Sal B protects endothelial cells from damage caused by oxidative stress.


RESULTS
Pretreatment with Sal B markedly attenuated H(2)O(2)-induced viability loss, lactate dehydrogenase leakage and apoptosis in human umbilical vein endothelial cells (HUVECs). The mechanism of Sal B protection was studied using two-dimensional gel electrophoresis coupled with hybrid quadrupole time-of-flight mass spectrometry. Database searching implicated that glucose-regulated protein 78 (GRP78), a central regulator for endoplasmic reticulum (ER) stress, was up-regulated in Sal B-exposed HUVECs. GRP78 expression regulation was confirmed by western blot and RT-PCR (reverse transcription-polymerase chain reaction) analyses. Additionally, GRP94, which shares significant sequence homology with GRP78, was also up-regulated in Sal B-treated cells. Sal B caused pancreatic ER kinase (PKR)-like ER kinase (PERK) activation followed by the phosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2 alpha) and the expression of activating transcription factor 4 (ATF4). Knockdown of endogenous ATF4 expression partially repressed Sal B-induced GRP78 induction. Further investigation showed that ATF6 was also activated by Sal B. Knockdown of GRP78 by siRNA significantly reduced the protective effects of Sal B.


CONCLUSIONS
The results suggest that Sal B induces the expression of GRP78 by activating ATF6 and the PERK-eIF2 alpha-ATF4 pathway. Furthermore, up-regulation of GRP78 by Sal B may play an important role in protecting human endothelial cells from oxidative stress-induced cellular damage.
Wu
Hong-Li
HL
Department of Pharmacology, School of Basic Medical Sciences, Health Science Center, Peking University, Xueyuan Road, Haidian District, Beijing 100083, PR China.
Li
Yu-Hua
YH
Lin
Yan-Hua
YH
Wang
Rui
R
Li
Ying-Bo
YB
Tie
Lu
L
Song
Qian-Liu
QL
Guo
De-An
DA
Yu
He-Ming
HM
Li
Xue-Jun
XJ
D051701:Activating Transcription Factor 4 / Q000378:metabolism; D051702:Activating Transcription Factor 6 / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology; D001572:Benzofurans / Q000494:pharmacology*; D002478:Cells, Cultured; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D019892:eIF-2 Kinase / Q000378:metabolism; D053630:Depsides
D051701:Activating Transcription Factor 4; D051702:Activating Transcription Factor 6; D001572:Benzofurans; D004365:Drugs, Chinese Herbal; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D006861:Hydrogen Peroxide; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; D034741:RNA, Small Interfering; D014157:Transcription Factors; D019892:eIF-2 Kinase; C497109:ATF4 protein, human; C497111:ATF6 protein, human; C000717247:HSPA5 protein, human; C053387:endoplasmin; C101003:ELF2 protein, human; C076944:salvianolic acid B; D053630:Depsides