Intercellular signalling within vascular cells under high D-glucose involves free radical-triggered tyrosine kinase activation.
OBJECTIVE
Diabetes mellitus is associated with endothelial dysfunction in human arteries due to the release of superoxide anions (*O(2)(-)) that was found to occur predominantly in smooth muscle cells (SMC). This study was designed to elucidate the impact of high glucose concentration mediated radical production in SMC on EC. Pre-treatment of vascular SMC with increased D-glucose enhanced release of *O(2)(-).


METHODS
Microscope-based analyses of intracellular free Ca(2+) concentration (fura-2), immunohistochemistry (f-actin) and tyrosine kinase activity were performed. Furthermore, RT-PCR and Western blots were carried out.


RESULTS
Interaction of EC with SMC pre-exposed to high glucose concentration yielded changes in endothelial Ca(2+) signalling and polymerization of f-actin in a concentration-dependent and superoxide dismutase (SOD) sensitive manner. This interaction activated endothelial tyrosine kinase(s) but not NFkappaB and AP-1, while SOD prevented tyrosine kinase stimulation but facilitated NFkappaB and AP-1 activation. Erbstatin, herbimycin A and the src family specific kinase inhibitor PP-1 but not the protein kinase C inhibitor GF109203X prevented changes in endothelial Ca(2+) signalling and cytoskeleton organization induced by pre-exposure of SMC to high glucose concentration. Adenovirus-mediated expression of kinase-inactive c-src blunted the effect of pre-exposure of SMC to high glucose concentration on EC.


CONCLUSIONS
These data suggest that SMC-derived *O(2)(-) alter endothelial cytoskeleton organization and Ca(2+) signalling via activation of c-src. The activation of c-src by SMC-derived radicals is a new concept of the mechanisms underlying vascular dysfunction in diabetes.
Schaeffer
G
G
Department of Medical Biochemistry and Medical Molecular Biology, University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Levak-Frank
S
S
Spitaler
M M
MM
Fleischhacker
E
E
Esenabhalu
V E
VE
Wagner
A H
AH
Hecker
M
M
Graier
W F
WF
D000818:Animals; D001011:Aorta; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D006943:Hyperglycemia; D066298:In Vitro Techniques; D008353:Mannitol / Q000494:pharmacology; D016328:NF-kappa B / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013481:Superoxides / Q000378:metabolism*; D013552:Swine; D018808:Transcription Factor AP-1 / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D016328:NF-kappa B; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D013481:Superoxides; D008353:Mannitol; D011505:Protein-Tyrosine Kinases