Aims/hypothesis  

Diabetes mellitus is associated with endothelial dysfunction in human arteries due to the release of superoxide anions (^·O₂ ^–) 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 ^·O₂ ^–.

Methods  

Microscope-based analyses of intracellular free Ca²⁺ 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 Ca²⁺ 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 NFB and AP-1, while SOD prevented tyrosine kinase stimulation but facilitated NFB 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 Ca²⁺ 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/interpretation  

These data suggest that SMC-derived ^·O₂ ^– alter endothelial cytoskeleton organization and Ca²⁺ 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.