Hyperglycaemia-induced impairment of endothelium-dependent vasorelaxation in rat mesenteric arteries is mediated by intracellular methylglyoxal levels in a pathway dependent on oxidative stress.
OBJECTIVE
Impaired nitric oxide (NO)-dependent vasorelaxation plays a key role in the development of diabetic vascular complications. We investigated the effect of hyperglycaemia on impaired vasoreactivity and a putative role therein of the AGE precursor methylglyoxal.


METHODS
The effects of high glucose and methylglyoxal on NO-dependent vasorelaxation in isolated rat mesenteric arteries from wild-type and transgenic glyoxalase (GLO)-I (also known as GLO1) rats, i.e. the enzyme detoxifying methylglyoxal, were recorded in a wire myograph. AGE formation of the major methylglyoxal-adduct 5-hydro-5-methylimidazolone (MG-H1) was detected with an antibody against MG-H1 and quantified with ultra-performance liquid chromatography (tandem) mass spectrometry. Reactive oxygen species formation was measured with a 5-(and-6)-chloromethyl-2'7'-dichlorodihydrofluorescein diacetate acetyl ester probe and by immunohistochemistry with an antibody against nitrotyrosine.


RESULTS
High glucose and methylglyoxal exposure of mesenteric arteries significantly reduced the efficacy of NO-dependent vasorelaxation (p < 0.05). This impairment was not observed in mesenteric arteries of GLO-I transgenic rats indicating a specific intracellular methylglyoxal effect. The diabetes-induced impaired potency (pD(2)) in mesenteric arteries of wild-type rats was significantly improved by GLO-I overexpression (p < 0.05). Methylglyoxal-modified albumin did not affect NO-dependent vasorelaxation, while under the same conditions the receptor for AGE ligand S100b did (p < 0.05). Methylglyoxal treatment of arteries increased intracellular staining of MG-H1 in endothelial cells and adventitia by fivefold accompanied by an eightfold increase in the oxidative stress marker nitrotyrosine. Antioxidant pre-incubation prevented methylglyoxal-induced impairment of vasoreactivity.


CONCLUSIONS
These data show that hyperglycaemia-induced impairment of endothelium-dependent vasorelaxation is mediated by increased intracellular methylglyoxal levels in a pathway dependent on oxidative stress.
Brouwers
O
O
Department of Internal Medicine, University Hospital Maastricht, P. Debyelaan 25, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands.
Niessen
P M
PM
Haenen
G
G
Miyata
T
T
Brownlee
M
M
Stehouwer
C D
CD
De Mey
J G
JG
Schalkwijk
C G
CG
D000704:Analysis of Variance; D000818:Animals; D002452:Cell Count; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism* / Q000503:physiopathology; D007150:Immunohistochemistry; D007791:Lactoylglutathione Lyase / Q000235:genetics; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D011765:Pyruvaldehyde / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D055647:Rats, Transgenic; D017382:Reactive Oxygen Species / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D011765:Pyruvaldehyde; D007791:Lactoylglutathione Lyase