The Effect Of PPARγ Ligand Rosiglitazone On Angiogenesis And Vascular Permeability

Pathological angiogenesis is a critical event associated with formation andprogression of tumor, atherosclerosis and diabetic retinopathy. On the one hand,newborn microvessels promote the development of these diseases by supplementingoxgen and nutrients. On the other hand, these microvessels exhibit defective featuresthat are closely associated with the increase of microvascular permeability. Thestructural and functional abnormality, commonly characterized by absence of celljunctions and base membrane as well as peripheral cells, promotes vascularpermeability and results in macromolecules extravasation. Highly permeabible vesselsallow infiltration of tumor cells and inflammatory cells as well as production and localaccumulation of angiogenic factors, ultimately exacerbating vessel-related diseases.Therefore, angiogenesis inhibition is proposed as a promising strategy to limit thesevessel-related diseases. As the effective drug in antagonizing type II diabetes,peroxisome proliferator-activated receptor γ (PPARγ) ligand rosiglitazone is also asignificant modulator of angiogenic processes and may prove to be a potentialtherapeutic strategy in correcting angiogenesis-related diseases. However, studies onPPARγ and the ligand rosiglitazone yielded contradictory findings with regard to its rolein angiogenesis. Additionally, treatment with rosiglitazone often causes side effects likeedema that are related to increased vascular permeability. Thus, the aim of this study isto identify the angiogenic and vascular permeability response to PPARγ activation by itsligand rosiglitazone. Related knowledge could pave way to safe treatment ofangiogenesis-related diseases with rosiglitazone. Resusts are shown below.Chapter one: the regulatory role and mechanism of PPARγ activation by its ligandrosiglitazone in angiogenesis①In vivo zebrafish angiogenesis model, ex vivo rat aortic ring model and in vitrohuman umbilical vein cells (HUVECs) angiogenesis model were used to investigate theeffect of PPARγ ligand rosiglitazone in angiogenesis. Our data showed that activation ofPPARγ by rosiglitazone inhibits in vivo, ex vivo and in vitro angiogenesis. GW9662blocked the inhibitory effect of rosiglitazone on angiogenesis, suggesting thatrosiglitazone functioned in a PPARγ-dependent manner.②Whole-Mount in Situ Hybridization (ISH) and qPCR analysis showed thatrosiglitazone treatment decreased VEGFR2(flk-1) expression in zebrafish, suggesting rosiglitazone may inhibit angiogenesis by downregulating VEGF/VEGFR2signaling.Additionally, immunocytofluorescent analysis found that PPARγ activation byrosiglitazone stimulated p53expression, accordingly, flow cytometry data showed thatPPARγ activation by rosiglitazone promoted HUVECs apoptosis. In addition, p53inhibitor Pifithrin-blocked rosiglitazone-stimulated cell apoptosis, suggesting thatPPARγ activation by rosiglitazone inhibits angiogenic processes through p53apoptoticsignaling.Chapter two: the regulatory role and mechanism of PPARγ activation by its ligandrosiglitazone in vascular permeability①By Miles vascular permeability and HUVECs monolayer permeability analysis,we found that rosiglitazone increased vascular and endothelial permeability②Then, we found that this process was independent on VEGF as analyzed byELISA. Furthermore, we found that PPARγ activation by rosiglitazone stimulatedPI3K/eNOS/NO pathway. Importantly, PPARγ antagonist GW9662, PI3K inhibitorWorthmannin and LY294002, NOS inhibitor L-NAME blocked rosiglitazone-increasedvascular endothelial permeability, suggesting that PI3K/eNOS/NO was involved inrosiglitazone regulation of vascular endothelial permeability.