Action and interaction of growth factors and regulatory molecules in vascular cells : With special reference to the IGF-I-system

Sammanfattning: Vascular function is greatly influenced by growth factors and regulatory molecules that can interact with each other in a complex pattern in the vascular wall. In this thesis we studied how different substances of special interest in the pathogenesis of vascular disease interact and regulate each other's expressions in endothelial cells and vascular smooth muscle cells (VSMCs).In VSMCs, angiotensin II was shown to delay PDGF-BB induced cell growth. This transient inhibitory effect of angiotensin II was mediated by the AT1-receptor, did not involve autocrine action of transforming growth factor-ß1 (TGF-ß1) and acted at a site downstream of PDGF-ß receptor phosphorylation.The interaction of the insulin-like growth factor-system (IGF-system) with various growth factors, glucose and nitric oxide (NO) was studied in vascular cells. Vascular endothelial growth factor (VEGF) and transforming growth factor-ß1 (TGF-ß1) regulated the expression of insulin-like growth factor-binding proteins (IGFBPs) in large vessel endothelial cells in a way that might cause an increased bioavailability of IGF-I locally in the subendothelial space. Angiotensin II, IGF-I and insulin did not affect IGFBP expression in these cells. The expression of IGFBPs was studied for the first time in human micro vessel endothelial cells. No effect of high glucose treatment on IGFBP expression was seen in either large vessel endothelial cells or microvessel endothelial cells. A possible interaction between NO and the IGF-system was studied in VSMCs. IGF-I did not have any significant effect on NO production in VSMCs and neither exogenous nor endogenous NO had any effect on IGFBP expression.In conclusion, we found that angiotensin II interacts with PDGF-BB in the regulation of VSMC growth. The IGF-system is regulated by VEGF and TGF-ß1 in endothelial cells while no effect of angiotensin II, IGF-I, insulin or high glucose was seen. We found no evidence for interaction of NO and the IGF-system in VSMCs.