Abstract
Methylglyoxal (MG), a reactive metabolite of glucose, has high affinity for arginine and is a precursor of advanced glycation endproducts (AGEs). We tested the hypothesis that l-arginine, and its inactive isomer d-arginine, can efficiently scavenge MG, administered exogenously or produced endogenously from high glucose, and attenuate its harmful effects including endothelial dysfunction and oxidative stress by an endothelial nitric-oxide synthase (eNOS)-independent mechanism. We used isolated aortic rings from 12-week-old male Sprague-Dawley rats and cultured human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (VSMCs). Both d-arginine and l-arginine prevented the attenuation of acetylcholine-induced endothelium-dependent vasorelaxation by MG and high glucose. However, the inhibitory effect of the NOS inhibitor Nω-nitro-l-arginine methyl ester on vasorelaxation was prevented by l-arginine, but not d-arginine. MG and high glucose increased protein expression of arginase, a novel finding, NADPH oxidase 4, and nuclear factor κB and increased production of reactive oxygen species in HUVECs and VSMCs, which were attenuated by d-arginine and l-arginine. However, d-arginine and l-arginine did not attenuate MG- and high glucose-induced increased arginase activity in VSMCs and the aorta. d-Arginine and l-arginine also attenuated the increased formation of the MG-specific AGE Nε-carboxyethyl lysine, caused by MG and high glucose in VSMCs. In conclusion, arginine attenuates the increased arginase expression, oxidative stress, endothelial dysfunction, and AGE formation induced by MG and high glucose by an eNOS-independent mechanism. The therapeutic potential of arginine against MG- and high glucose-induced pathology merits further investigation.
Footnotes
This work was supported by a grant-in-aid from the Heart and Stroke Foundation of Saskatchewan (to K.D. and L.W.) and a New Investigator Establishment Grant from the Saskatchewan Health Research Foundation (to K.D.).
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
ABBREVIATIONS:
- NOS
- nitric-oxide synthase
- eNOS
- endothelial NOS
- ACh
- acetylcholine
- AGE
- advanced glycation endproduct
- CEL
- Nε-carboxyethyl lysine
- Con
- control
- DCF
- dichlorofluorescein
- l-Arg
- l-arginine
- d-Arg
- d-arginine
- FBS
- fetal bovine serum
- Glu
- glucose
- HPLC
- high-performance liquid chromatography
- HUVEC
- human umbilical vein endothelial cell
- MG
- methylglyoxal
- l-NAME
- Nω-nitro-l-arginine methyl ester
- NAC
- N-acetyl cysteine
- NF-κB
- nuclear factor κB
- NOX4
- NADPH oxidase 4
- PBS
- phosphate-buffered saline
- PE
- phenylephrine
- VSMC
- vascular smooth muscle cell.
- Received January 21, 2012.
- Accepted April 18, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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