Inhibition of S6K1 accounts partially for the anti-inflammatory effects of the arginase inhibitor L-norvaline.
BACKGROUND
Pharmacological inhibition of endothelial arginase-II has been shown to improve endothelial nitric oxide synthase (eNOS) function and reduce atherogenesis in animal models. We investigated whether the endothelial arginase II is involved in inflammatory responses in endothelial cells.


METHODS
Human endothelial cells were isolated from umbilical veins and stimulated with TNFalpha (10 ng/ml) for 4 hours. Endothelial expression of the inflammatory molecules i.e. vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin were assessed by immunoblotting.


RESULTS
The induction of the expression of endothelial VCAM-1, ICAM-1 and E-selectin by TNFalpha was concentration-dependently reduced by incubation of the endothelial cells with the arginase inhibitor L-norvaline. However, inhibition of arginase by another arginase inhibitor S-(2-boronoethyl)-L-cysteine (BEC) had no effects. To confirm the role of arginase-II (the prominent isoform expressed in HUVECs) in the inflammatory responses, adenoviral mediated siRNA silencing of arginase-II knocked down the arginase II protein level, but did not inhibit the up-regulation of the adhesion molecules. Moreover, the inhibitory effect of L-norvaline was not reversed by the NOS inhibitor L-NAME and L-norvaline did not interfere with TNFalpha-induced activation of NF-kappaB, JNK, p38mapk, while it inhibited p70s6k (S6K1) activity. Silencing S6K1 prevented up-regulation of E-selectin, but not that of VCAM-1 or ICAM-1 induced by TNFalpha.


CONCLUSIONS
The arginase inhibitor L-norvaline exhibits anti-inflammatory effects independently of inhibition of arginase in human endothelial cells. The anti-inflammatory properties of L-norvaline are partially attributable to its ability to inhibit S6K1.
Ming
Xiu-Fen
XF
Vascular Biology, Department of Medicine, Division of Physiology, University of Fribourg, Switzerland. xiu-fen.ming@unifr.ch
Rajapakse
Angana Gupta
AG
Carvas
João Miguel
JM
Ruffieux
Jean
J
Yang
Zhihong
Z
D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001119:Arginase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D001897:Boronic Acids / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D019040:E-Selectin / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D005260:Female; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011247:Pregnancy; D034741:RNA, Small Interfering / Q000235:genetics; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014470:Umbilical Cord / Q000166:cytology; D014633:Valine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism
C425062:(2-boronoethyl)-cysteine; D000893:Anti-Inflammatory Agents; D001897:Boronic Acids; D019040:E-Selectin; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; C005313:norvaline; D052250:Nitric Oxide Synthase Type III; D019893:Ribosomal Protein S6 Kinases; C477631:ARG2 protein, human; D001119:Arginase; D014633:Valine