The Effects Of Cysteinyl Leukotrienes And Their Receptors On Angiogenesis In Rat Thoracic Aortic Rings

Angiogenesis is a process that forms new blood vessels during development and disorders,such as tumor,inflammation and wound healing.It is reported that inflammation and angiogenesis are always associated with many pathological processes.Vascular endothelial growth factor(VEGF) is a classic angiogenesis-enhancing factor and inflammation-inducing factor,whereas some inflammation mediators induce not only inflammation but also angiogenesis.As a potent inflammatory factor,cysteinyl leukotrienes(CysLTs) and their receptors (including CysLT₁ and CysLT₂ receptors) may participate in angiogenesis.To study their roles in angiogenesis,and to determine whether and how the receptor subtype is involved and interacts with VEGF,we used an angiogenesis model called rat aortic ring assay through embedding rat thoracic aortas in to matrigel.To mimic the high- or low-perfusion situation during inflammatory disorders,we cultured the aortic ring in the presence 25%of serum or absence of serum.Upon administrating the CysLTs receptors agonist(LTD₄),CysLT₁ receptor antagonist montelukast and CysLT₂ receptor antagonist BAY cyslt2,VEGF and the antagonist of VEGF receptor 2 (SU1498) in rat aortic rings with different serum conditions,we observed the changes of the number of microvessel sprouts from the edge of aortic ring.We found that the microvessel growth in 25%serum-containing cultures was significantly inhibited by montelukast(0.1-1μM),but not by BAY cyslt2(0.1-1μM). The microvessel growth in serum-free culture was affected neither by montelukast (0.01-1μM) nor by BAY cyslt2(0.1-1μM).Furthermore,LTD₄ at 100 nM significantly enhanced the microvessel growth in serum-free culture and LTD₄ at 10-100 nM significantly enhanced the microvessel growth in 25%serum-containing culture.The enhancement was abrogated by both montelukast and BAY cyslt2. However,LTD₄-induced angiogenesis was only observed when applied at the beginning of culture but not when applied on the second day of culture.In addition, LTD₄-induced microvessel growth was blocked by SU1498.Furthermore, VEGF-induced microvessel growth was blocked by montelukast,BAY cyslt2 and SU1498.These results indicate that LTD₄ induces angiogenesis through the activation of both CysLT₁ and CysLT₂ receptors,probably via an interaction with VEGF.When there is no exogenous agonist available,CysLT₁ receptor induces angiogenesis in high-perfusion culture.