RESUMO
Diabetes is associated with increased formation of advanced glycation end products (AGEs), which have been implicated in micro and macrovascular complications of diabetes. Our earlier reports showed proangiogenic effect of AGE-bovine serum albumin (BSA). In order to understand the mechanism of AGE-mediated angiogenesis, the possibility of involvement of peroxisome prolifeator activated receptor (PPAR) , a ligand activated transcription factor was examined. The angiogenic effect was studied in chick chorio allantoic membrane (CAM) and by analyzing angiogenic markers in human umbilical vein endothelial cells (HUVECs) in culture. The involvement of PPAR was investigated using synthetic PPAR agonist GW 1929 and antagonist GW 9662 and by RT-PCR. In CAM assay, PPAR antagonist GW 9662 reversed the AGE-induced effect on vascularity. In HUVECs in culture, GW 9662 reversed the effect of AGE-BSA and decreased the expression of CD 31, E-Selectin and VEGF. RT-PCR analysis showed that treatment with AGE-BSA caused upregulation of PPAR mRNA levels. The reversal of the effect of AGE on angiogenesis by treatment with PPAR antagonists and up-regulation of PPAR gene in HUVECs treated with AGE-BSA suggested the possible involvement of PPAR -dependent downstream pathway in mediating the angiogenic effect of AGE.
Assuntos
Indutores da Angiogênese/metabolismo , Anilidas/farmacologia , Animais , Molécula-1 de Adesão Celular Endotelial a Plaquetas/efeitos dos fármacos , Molécula-1 de Adesão Celular Endotelial a Plaquetas/metabolismo , Benzofenonas/farmacologia , Células Cultivadas , Embrião de Galinha , Membrana Corioalantoide/efeitos dos fármacos , Membrana Corioalantoide/metabolismo , Diabetes Mellitus/metabolismo , Selectina E/metabolismo , /farmacologia , Células Endoteliais da Veia Umbilical Humana/metabolismo , PPAR gama/antagonistas & inibidores , PPAR gama/antagonistas & inibidores , PPAR gama/efeitos dos fármacos , PPAR gama/metabolismo , RNA/efeitos dos fármacos , RNA/metabolismo , Tirosina/análogos & derivados , Tirosina/farmacologia , Fator A de Crescimento do Endotélio Vascular/efeitos dos fármacos , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Temperature up to 16°C reduced endocytosis of [35S]-proteoglycans by human skin fibroblasts to less than 15% of that at 37°C. At temperatures between 20-26°C endocytosis was more than 50%. At temperatures below 26°C, the relative rate of degradation of endocytosed [35S]-proteoglycans was several fold less than the rate of endocytosis. Codistribution of endocytosed [35S]-proteoglycans and the lysosomal marker enzyme b- hexosaminidase upon subcellular fractionation indicated that endocytotic vesicles containing [35S]-proteoglycans had fused with lysosomes at 37°C and at 16°C. The prolonged halflives of endocytosed [35S]-proteoglycans at 16-26°C could not be explained merely by a temperature dependent reduction of catalytic activity of lysosomal enzymes participating in the degradation of sulphated proteoglycans.