title: Activation of hexosamine pathway impairs nitric oxide (NO)-dependent arteriolar dilations by increased protein O-GlcNAcylation.
abstract: We hypothesized that under high glucose conditions, activation of the hexosamine pathway leads to impaired nitric oxide (NO)-dependent arteriolar dilation. Skeletal muscle arterioles (diameter: ~160μm) isolated from male Wistar rats were exposed to normal glucose (NG, 5.5mmol/L) or high glucose concentrations (HG, 30mmol/L, for 2h) and agonist-induced diameter changes were measured with videomicroscopy. Western blots were performed to identify the vascular levels of protein O-linked-N-acetyl-glucosamine (O-GlcNAc) and phosphorylated endothelial NO synthase (eNOS). In arterioles exposed to HG, dilations to histamine were abolished compared to those exposed to NG (max: -6±6% and 69±9%, respectively), while acetylcholine-induced responses were not affected. Inhibition of NO synthesis with N(G)-nitro-l-arginine methyl ester (L-NAME) reduced histamine-induced dilations in NG arterioles, but it had no effect on microvessels exposed to HG. Dilations to the NO donor, sodium nitroprusside and constrictions to norepinephrine and serotonin were similar in the two groups. In the presence of the inhibitor of hexosamine pathway, azaserine, histamine-induced dilations were significantly augmented in arterioles exposed to HG (max: 67±2%). Moreover, exposure of vessels to glucosamine (5mmol/L, for 2h) resulted in reduced histamine-induced arteriolar dilations (max: 26±3%). The level of protein O-GlcNAcylation was increased, whereas the P-eNOS (Ser-1177) was decreased in HG exposed vessels. These findings indicate that a high concentration of glucose may lead to glucosamine formation, which impairs histamine-induced, NO-mediated arteriolar dilations. We propose that interfering with the hexosamine pathway may prevent microvascular complications in diabetes.
authors.affiliation: Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
authors.forename: Timea
authors.initials: T
authors.lastname: Beleznai
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Bagi
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D049148:Aminoacylation / Q000187:drug effects; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D003925:Diabetic Angiopathies / Q000517:prevention & control; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing) / Q000037:antagonists & inhibitors / Q000378:metabolism; D006595:Hexosamines / Q000378:metabolism*; D006943:Hyperglycemia / Q000378:metabolism* / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D006595:Hexosamines; D014665:Vasodilator Agents; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing); D000117:Acetylglucosamine