Abstract

The diverse cellular effects of lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are transduced by two structurally homologous subfamilies of G protein-coupled receptors, which are encoded by endothelial differentiation genes (Edg Rs). Human umbilical cord vein endothelial cells (HUVECs) express Edg Rs for LPA (Edg2) and S1P (Edg1 and 3), which transduce signals for migration of HUVECs through micropore filters coated with type I collagen. Since activation of integrins is essential for optimal migration of endothelial cells, we now examine the capacity of LPA and S1P to augment integrin mediation of endothelial cell binding to type I collagen. Lysophospholipid enhancement of HUVEC adhesion to type I collagen is detectable within 20 minutes. Enhancement of adhesion by both LPA and S1P is significant at 50 nM and optimal at 5µM. Pertussis toxin (PTx), a specific inhibitor of Gi, and C3 exotoxin, a specific inhibitor of Rho, both suppress LPA and S1P enhancement of HUVEC adhesion. In contrast, PD98059, which blocks MAP kinase kinase (MEK), and wortmannin, which inhibits phosphatidylinositol 3-kinase (PI3K), had no effect on LPA- or S1P-enhancement of HUVEC adhesion. Neutralizing monoclonal antibodies specific for α2 and β1 integrin chains, concomitantly decrease LPA and S1P enhancement of HUVEC adhesion to type I collagen. LPA and S1P thus promote type I collagen-dependent adhesion and migration of HUVECs by recruiting α2 and β1 integrin through both Gi and Rho pathways. Integrin α2/β1 therefore appears to be critical on the effects of LPA and S1P on endothelial cell physiology.

中文摘要

水解磷酸脂LPA 與S1P 之複雜生理功能，是經由與兩類結構相似之接受器結合後 所達成。人類臍帶靜脈內皮細胞表達至少三種水解磷酸脂接受器，活化後會造成細胞於第一類纖維蛋白環境中之移行。由於integrin 蛋白接受器之活化與細胞移行有相當關聯，此研究目的即在於偵測水解磷酸脂是否會影響該蛋白質之活性。研究結果顯示水解磷酸脂的確會於20 分鐘內造成內皮細胞與第一類纖維蛋白之附著且於50 nM 之處理濃度即可見到顯著效果，而於5 µM 之處理濃度達到最高效果。以訊息傳遞之化學抑制物質處理後發現水解磷酸脂之作用是經由Gi 以及Rho 蛋白來達成其作用。而使用integrin蛋白接受器活性抑制抗體處理後之結果發現，α2 與β1 integrin 實際參與了水解磷酸脂增強內皮細胞與第一類纖維蛋白之附著之作用。實驗結論推斷水解磷酸脂應可活化α2與β1 integrin，且於內皮細胞生理現象之調控可能扮演重要角色。

Keyword: LPA, S1P, Adhesion, Endothelial cell, Integrin