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En Face Detection of Nitric Oxide and Superoxide in Endothelial Layer of Intact Arteries
Published on: February 25, 2016
Toll-like receptor 4 mutation protects obese mice against endothelial dysfunction by decreasing NADPH oxidase
Chao-Fan Liang1, Jacky Tc Liu, Yu Wang
1Department of Pharmacology, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong.
Objective:
To analyze the role of toll-like receptor 4 in modulating metabolism and endothelial function.
Approach And Results:
Type 2 diabetic mice with mutated toll-like receptor 4 (DWM) were protected from hyperglycemia and hypertension, despite an increased body weight. Isometric tension was measured in arterial rings with endothelium. Relaxations to acetylcholine were blunted in aortae and mesenteric arteries of Lepr(db/db) mice, but not in DWM mice; the endothelial NO synthase dimer/monomer ratio and endothelial NO synthase phosphorylation levels were higher in DWM preparations. These differences were abolished by apocynin. Contractions to acetylcholine (in the presence of L-NAME) were larger in carotid arteries from Lepr(db/db) mice than from DWM mice and were inhibited by indomethacin and SC560, demonstrating involvement of cyclooxygenase-1. The release of 6-ketoprostaglandin F1α was lower in DWM mice arteries, implying lower cyclooxygenase-1 activity. Apocynin, manganese(III) tetrakis(1-methyl-4-pyridyl) porphyrin, catalase, and diethyldithiocarbamate inhibited endothelium-dependent contractions. The mRNA and protein levels of NADPH oxidase isoforms NOX1 and NOX4 were downregulated in DWM mice arteries. The in vivo and in vitro administration of lipopolysaccharide caused endothelial dysfunction in the arteries of wild-type, but not toll-like receptor 4-mutated mice.
Conclusions:
Toll-like receptor 4 plays a key role in obesity and diabetes-associated endothelial dysfunction by increasing oxidative stress.
Insights
Toll-like receptor 4 (TLR4) mutation protects against diabetes-associated endothelial dysfunction by reducing oxidative stress. This finding highlights TLR4
Area of Science:
- Metabolic disease research
- Cardiovascular research
- Immunology
Background:
- Obesity and type 2 diabetes are linked to endothelial dysfunction.
- Toll-like receptor 4 (TLR4) is implicated in metabolic disorders and inflammation.
- The precise role of TLR4 in diabetes-associated endothelial dysfunction requires further elucidation.
Purpose of the Study:
- To investigate the role of toll-like receptor 4 (TLR4) in modulating metabolism and endothelial function in type 2 diabetes.
- To determine if TLR4 mutation impacts hyperglycemia, hypertension, and vascular responses.
Main Methods:
- Utilized type 2 diabetic mice with mutated toll-like receptor 4 (DWM) and control diabetic mice (Lepr(db/db)).
- Measured isometric tension in arterial rings to assess endothelial-dependent relaxations and contractions.
- Analyzed endothelial nitric oxide synthase (eNOS) dimer/monomer ratio, eNOS phosphorylation, and cyclooxygenase-1 (COX-1) activity.
- Quantified mRNA and protein levels of NADPH oxidase isoforms (NOX1, NOX4).
- Administered lipopolysaccharide (LPS) to induce endothelial dysfunction.
Main Results:
- DWM mice were protected from hyperglycemia and hypertension, despite increased body weight.
- Acetylcholine-induced relaxations were preserved in DWM mice aortae and mesenteric arteries.
- Endothelial NO synthase dimer/monomer ratio and phosphorylation were higher in DWM mice, an effect abolished by apocynin.
- Endothelium-dependent contractions involved cyclooxygenase-1 (COX-1) and were modulated by TLR4 mutation.
- NADPH oxidase isoforms NOX1 and NOX4 were downregulated in DWM mice arteries.
- LPS induced endothelial dysfunction in wild-type but not DWM mice.
Conclusions:
- Toll-like receptor 4 (TLR4) is a key mediator of obesity and diabetes-associated endothelial dysfunction.
- TLR4 signaling contributes to endothelial dysfunction primarily through increased oxidative stress.
- Targeting TLR4 may offer a therapeutic strategy for managing metabolic and cardiovascular complications.
