Human C-peptide antagonises high glucose-induced endothelial dysfunction through the nuclear factor-kappaB pathway.
OBJECTIVE
Endothelial dysfunction in diabetes is predominantly caused by hyperglycaemia leading to vascular complications through overproduction of oxidative stress and activation of the transcription factor nuclear factor-kappaB (NF-kappaB). Many studies have suggested that decreased circulating levels of C-peptide may play a role in diabetic vascular dysfunction. To date, the possible effects of C-peptide on endothelial cells and intracellular signalling pathways are largely unknown. We therefore investigated the effect of C-peptide on several biochemical markers of endothelial dysfunction in vitro. To gain insights into potential intracellular signalling pathways affected by C-peptide, we tested NF-kappaB activation, since it is known that inflammation, secondary to oxidative stress, is a key component of vascular complications and NF-kappaB is a redox-dependent transcription factor.


METHODS
Human aortic endothelial cells (HAEC) were exposed to 25 mmol/l glucose in the presence of C-peptide (0.5 nmol/l) for 24 h and tested for expression of the gene encoding vascular cell adhesion molecule-1 (VCAM-1) by RT-PCR and flow cytometry. Secretion of IL-8 and monocyte chemoattractant protein-1 (MCP-1) was measured by ELISA. NF-kappaB activation was analysed by immunoblotting and ELISA.


RESULTS
Physiological concentrations of C-peptide affect high glucose-induced endothelial dysfunction by: (1) decreasing VCAM-1 expression and U-937 cell adherence to HAEC; (2) reducing secretion of IL-8 and MCP-1; and (3) suppressing NF-kappaB activation.


CONCLUSIONS
During hyperglycaemia, C-peptide directly affects VCAM-1 expression and both MCP-1 and IL-8 HAEC secretion by reducing NF-kappaB activation. These effects suggest a physiological anti-inflammatory (and potentially anti-atherogenic) activity of C-peptide on endothelial cells.
Luppi
P
P
Division of Immunogenetics, Department of Pediatrics, Rangos Research Center, Children's Hospital of Pittsburgh, 3460 Fifth Avenue, Pittsburgh, PA 15213, USA. luppip@pitt.edu
Cifarelli
V
V
Tse
H
H
Piganelli
J
J
Trucco
M
M
D001011:Aorta; D002096:C-Peptide / Q000494:pharmacology*; D018929:Cell Culture Techniques; D018932:Chemokine CCL2 / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D005947:Glucose / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology*; D018384:Oxidative Stress / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019010:Vascular Cell Adhesion Molecule-1 / Q000187:drug effects / Q000235:genetics
D002096:C-Peptide; C111835:CCL2 protein, human; D018932:Chemokine CCL2; D016209:Interleukin-8; D016328:NF-kappa B; D019010:Vascular Cell Adhesion Molecule-1; D005947:Glucose