Acute hyperglycemia causes intracellular formation of CML and activation of ras, p42/44 MAPK, and nuclear factor kappaB in PBMCs.
Twenty-three nondiabetic volunteers were divided into three groups. In group A (n = 9), the glucose infusion was adjusted to maintain blood glucose at 5 mmol/l (euglycemic clamp). In group B (n = 9), the glucose infusion was adjusted to maintain blood glucose at 10 mmol/l (hyperglycemic clamp) over 2 h. Group C consisted of five volunteers who were studied as the control group. Peripheral blood mononuclear cells (PBMCs) were isolated before and at the end of a 2-h clamp. In group C, PBMCs were isolated before and after 2 h without performing a clamp. The euglycemic clamp as well as "no clamp" had no effects on all parameters studied. In contrast, a significant increase in carboxymethyllysine (CML) content and p21(ras) and p42/44 mitogen-activated protein kinase (MAPK) phosphorylation was observed at the end of a 2-h hyperglycemic clamp. The nuclear factor (NF)-kappaB (but not Oct-1) binding activity increased significantly in the hyperglycemic clamp. Western blots confirmed NF-kappaB-p65-antigen translocation into the nucleus. IkappaBalpha did not change significantly in both groups. Hyperglycemia-mediated NF-kappaB activation and increase of CML content, p21(ras), and p42/44 MAPK phosphorylation was also seen in ex vivo-isolated PBMCs stimulated with 5 or 10 mmol/l glucose. Addition of insulin did not influence the results. Inhibition of activation of ras, MAPK, or protein kinase C blocked hyperglycemia-mediated NF-kappaB activation in ex vivo-isolated PBMCs stimulated with 10 mmol/l glucose. Similar data were obtained using an NF-kappaB-luciferase reporter plasmid. Therefore, we can conclude that an acute hyperglycemia-mediated mononuclear cell activation is dependent on activation of ras, p42/p44 MAPK phosphorylation, and subsequent NF-kappaB activation and results in transcriptional activity in PBMCs.
Schiekofer
Stephan
S
Department of Medicine I, University of Heidelberg, Bergheimerstrasse 58, 69115 Heidelberg, Germany. stephan.schiekofer@gmx.de
Andrassy
Martin
M
Chen
Jiang
J
Rudofsky
Gottfried
G
Schneider
Jochen
J
Wendt
Thoralf
T
Stefan
Norbert
N
Humpert
Per
P
Fritsche
Andreas
A
Stumvoll
Michael
M
Schleicher
Erwin
E
Häring
Hans-Ulrich
HU
Nawroth
Peter P
PP
Bierhaus
Angelika
A
D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000378:metabolism; D015309:Glucose Clamp Technique; D006801:Humans; D006943:Hyperglycemia / Q000097:blood*; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D008239:Lysine / Q000031:analogs & derivatives* / Q000097:blood*; D019950:Mitogen-Activated Protein Kinase 1 / Q000097:blood; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000097:blood*; D016328:NF-kappa B / Q000097:blood*; D009687:Nuclear Proteins / Q000097:blood; D010766:Phosphorylation; D016283:Proto-Oncogene Proteins p21(ras) / Q000097:blood*; D015398:Signal Transduction; D014162:Transfection
D016328:NF-kappa B; D009687:Nuclear Proteins; C048496:N(6)-carboxymethyllysine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D008239:Lysine