Anti-Inflammatory Effects of Heliangin from Jerusalem Artichoke (Helianthus tuberosus) Leaves Might Prevent Atherosclerosis

Atherosclerosis is considered the major cause of cardiovascular and cerebrovascular diseases, which are the leading causes of death worldwide. Excessive nitric oxide production and inflammation result in dysfunctional vascular endothelial cells, which are critically involved in the initiation and progression of atherosclerosis. The present study aimed to identify a bioactive compound from Jerusalem artichoke leaves with anti-inflammatory activity that might prevent atherosclerosis. We isolated bioactive heliangin that inhibited NO production in LPS-induced macrophage-like RAW 264.7 cells. Heliangin suppressed ICAM-1, VCAM-1, E-selectin, and MCP-1 expression, as well as NF-κB and IκBα phosphorylation, in vascular endothelial cells stimulated with TNF-α. These results suggested that heliangin suppresses inflammation by inhibiting excessive NO production in macrophages and the expression of the factors leading to the development of atherosclerosis via the NF-κB signaling pathway in vascular endothelial cells. Therefore, heliangin in Jerusalem artichoke leaves could function in the prevention of atherosclerosis that is associated with heart attacks and strokes.

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Abstract 153: Bile Acid Receptor TGR5 Agonism Represents Anti-inflammatory Effects via Stimulating Nitric Oxide Production in Vascular Endothelial Cells

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.32.suppl_1.a153 ◽

2012 ◽

Vol 32 (suppl_1) ◽

Author(s):

Taiki Kida ◽

Yoshiki Tsubosaka ◽

Masatoshi Hori ◽

Hiroshi Ozaki ◽

Takahisa Murata

Keyword(s):

Nitric Oxide ◽

Endothelial Cells ◽

Bile Acids ◽

Inflammatory Responses ◽

Vascular Endothelial Cells ◽

Lithocholic Acid ◽

Signal Pathways ◽

No Production ◽

Vascular Endothelial ◽

Anti Inflammatory

Objective TGR5, a membrane-bound, G-protein-coupled receptor for bile acids, is known to be involved in regulation of energy homeostasis and inflammation. However, little is known about the function of TGR5 in vascular endothelial cells. In the present study, we examined whether TGR5 agonism represents anti-inflammatory effects in vascular endothelial cells focusing on nitric oxide (NO) production. Methods and Results In human umbilical vein endothelial cells (HUVECs), treatment with taurolithocholic acid (TLCA), which has the highest affinity to TGR5 among various bile acids, significantly reduced tumor necrosis factor (TNF)-α-induced vascular cell adhesion molecule (VCAM)-1 protein expression and adhesion of human monocytes, U937. These effects were abrogated by a NO synthase (NOS) inhibitor, N G -Monomethyl-L-arginine (L-NMMA). In bovine aortic endothelial cells (BAECs), treatment with TLCA as well as lithocholic acid, which also has high affinity to TGR5, significantly increased the NO production. In contrast, deoxycholic acid and chenodeoxycholic acid, which possess low affinity to TGR5, did not affect the NO production. Gene depletion of TGR5 by siRNA transfection abolished TLCA-induced NO production in BAECs. TLCA-induced NO production was also observed in HUVECs measured as intracellular cGMP accumulation. We next investigated the signal pathways responsible for the TLCA-induced NO production in endothelial cells. Treatment with TLCA increased endothelial NOS (eNOS) ser1177 phosphorylation in HUVECs. This response was accompanied by increased Akt ser473 phosphorylation and intracellular Ca 2+ ([Ca 2+ ] i ). Treatment with phosphoinositide 3-kinase (PI3K) inhibitor, LY294002, or blockade of calcium channel with La 3+ , significantly decreased TLCA-induced eNOS ser1177 phosphorylation and subsequent NO production. Conclusion These results indicate that TGR5 agonism can mediate anti-inflammatory responses by suppressing VCAM-1 expression and monocytes adhesion to endothelial cells. This function is dependent on NO production via Akt activation and [Ca 2+ ] i increase.

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