title: Betulinic Acid Increases eNOS Phosphorylation and NO Synthesis via the Calcium-Signaling Pathway.
abstract: Betulinic acid (BA) is a naturally occurring pentacyclic triterpene that attenuates vascular diseases and atherosclerosis, but the mechanism by which it stimulates endothelial nitric oxide synthase (eNOS) is unclear. eNOS is the key regulatory enzyme in the vascular endothelium. This study examined the intracellular pathways underlying the effects of BA on eNOS activity and endothelial nitric oxide (NO) production in endothelial cells. BA treatment induced both eNOS phosphorylation at Ser1177 and NO production. It also increased the level of intracellular Ca(2+) and phosphorylation of Ca(2+)/calmodulin-dependent kinase IIα (CaMKIIα) and Ca(2+)/calmodulin-dependent protein kinase kinase β (CaMKKβ). Inhibition of the L-type Ca(2+) channel (LTCC) and the ryanodine receptor (RyR) abolished BA-induced intracellular levels of Ca(2+) and eNOS phosphorylation. Treatment with W7 (a CaM antagonist), KN-93 (a selective inhibitor of CaMKII), and STO 609 (a selective inhibitor of CaMKK) suppressed eNOS phosphorylation and NO production. Moreover, AMP-activated protein kinase (AMPK) was induced by BA, and BA-induced eNOS phosphorylation was inhibited by compound C, an AMPK inhibitor. Taken together, these results indicate that BA activates eNOS phosphorylation and NO synthesis via the Ca(2+)/CaMKII and Ca(2+)/CaMKK/AMPK pathways. These findings provide further insight into the eNOS signaling pathways involved in the antiatherosclerosis effects of BA.
authors.affiliation: College of Pharmacy, Chungnam National University , Daejeon 305-764, Republic of Korea.
authors.forename: Sun Woo
authors.initials: SW
authors.lastname: Jin
authors.affiliation: Jeollanamdo Institute of Natural Resources Research , Jeollanamdo 529-851, Republic of Korea.
authors.forename: Chul Yung
authors.initials: CY
authors.lastname: Choi
authors.forename: Yong Pil
authors.initials: YP
authors.lastname: Hwang
authors.affiliation: College of Pharmacy, Chungnam National University , Daejeon 305-764, Republic of Korea.
authors.forename: Hyung Gyun
authors.initials: HG
authors.lastname: Kim
authors.affiliation: College of Pharmacy, Chungnam National University , Daejeon 305-764, Republic of Korea.
authors.forename: Se Jong
authors.initials: SJ
authors.lastname: Kim
authors.forename: Young Chul
authors.initials: YC
authors.lastname: Chung
authors.affiliation: Department of Convergence Medicine, Asan Institute for Life Sciences, University of Ulsan College of Medicine , Asan Medical Center, Seoul 138-736, Republic of Korea.
authors.forename: Kyung Jin
authors.initials: KJ
authors.lastname: Lee
authors.affiliation: College of Pharmacy, Yeungnam University , Gyeongsan 712-749, Republic of Korea.
authors.forename: Tae Cheon
authors.initials: TC
authors.lastname: Jeong
authors.affiliation: College of Pharmacy, Chungnam National University , Daejeon 305-764, Republic of Korea.
authors.forename: Hye Gwang
authors.initials: HG
authors.lastname: Jeong
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D009569:Nitric Oxide / Q000096:biosynthesis*; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism*; D053978:Pentacyclic Triterpenes; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014315:Triterpenes / Q000494:pharmacology*; D000094062:Betulinic Acid
chemical_list: D053978:Pentacyclic Triterpenes; D014315:Triterpenes; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D055372:AMP-Activated Protein Kinases; D002118:Calcium; D000094062:Betulinic Acid
keywords: AMPK; CaMKII; CaMKK; betulinic acid; eNOS