Abstract
The AMP-activated protein kinase (AMPK) is an important regulator of endothelial metabolic and functional homeostasis. Here, we examined the regulation of AMPK by nitrated oleic acid (OA-NO2) and investigated the implications in endothelial function. Treatment of bovine aortic endothelial cells (BAECs) with OA-NO2 induced a significant increase in both AMPK-Thr172 phosphorylation and AMPK activity as well as upregulation of heme oxygenase (HO)-1 and hypoxia-inducible factor (HIF)-1α. Pharmacologic inhibition or genetic ablation of HO-1 or HIF-1α abolished OA-NO2-induced AMPK phosphorylation. OA-NO2 induced a dramatic increase in extracellular signal-regulated kinase (ERK)1/2 phosphorylation that was abrogated by the HO-1 inhibitor, zinc deuteroporphyrin IX 2,4-bis-ethylene glycol (ZnBG). Inhibition of ERK1/2 using UO126 or PD98059 reduced but did not abolish OA-NO2-induced HIF-1α upregulation, suggesting that OA-NO2/HO-1-initiated HIF-1α induction is partially dependent on ERK1/2 activity. In addition, OA-NO2 enhanced endothelial intracellular Ca2+, an effect that was inhibited by the HIF-1α inhibitor, YC-1, and by HIF-1α siRNA. These results implicate the involvement of HIF-1α. Experiments using the Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) inhibitor STO-609, the selective CaMKII inhibitor KN-93, and an isoform-specific siRNA demonstrated that OA-NO2-induced AMPK phosphorylation was dependent on CaMKKβ. Together, these results demonstrate that OA-NO2 activates AMPK in endothelial cells via an HO-1–dependent mechanism that increases HIF-1α protein expression and Ca2+/CaMKKβ activation.
Highlights
Accumulating evidence indicates that reactive nitrogen species (RNS), which are inflammatory oxidants, mediate diverse physiologic and pathologic processes in cardiovascular, pulmonary, and neurodegenerative diseases [1]
Since oleic acid (OA)-NO2 activated AMPK in both bovine aortic endothelial cells (BAECs) and human umbilical vein endothelial cells (HUVECs) at similar potencies, we performed the majority of our experiments with BAECs
Considerable evidence points to a role for circulating OA-UFAs in vascularprotective effects [9], the mechanisms by which OA-NO2 are incompletely understood
Summary
Accumulating evidence indicates that reactive nitrogen species (RNS), which are inflammatory oxidants, mediate diverse physiologic and pathologic processes in cardiovascular, pulmonary, and neurodegenerative diseases [1]. RNS, such as peroxynitrite (ONOO2), nitrogen-dioxide radical, and nitronium ion, which are formed from nitric oxide (NO), are important factors in complications of obesity and diabetes [2]. RNS react with unsaturated fatty acids to form relatively stable nitrated products (nitroalkene derivatives), including the abundant and clinically important nitrated oleic and linoleic acids [3]. This process occurs via various mechanisms, the common denominator is a proclivity for homolytic addition of nitrogen dioxide (NNO2) to the double bond, yielding an array of regio- and stereoisomers [4]. The beneficial effects of NO2-UFAs include cGMP-dependent vessel relaxation, inhibition of inflammatory cell function, adaptive and anti-inflammatory cell responses, induction of heme oxygenase-1 (HO-1) expression, inhibition of nuclear factor (NF)-kB, and activation of peroxisome proliferator activated receptor (PPAR) and Keap1/Nrf2 [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
