Ucn Through The Regulation Of Icam-1 Expression To Promote Rats Thromboangiitis Obliterans Inflammation Process

Thromboangiitis obliterans (TAO; Buerger's disease) is a non-atherosclerotic, segmental, vasculitic disease that most commonly affects the small and medium-sized arteries and veins of the extremities. It is characterized by thrombogenesis and recanalization of the affected vessels. Thus far, the etiology is now well illustrated, yet. But abundant clinical reports and epidemic studies have demonstrated that the disease is well correlated with smoking. TAO is now internationally defined as an auto-immune disease. In the clinical studies of TAO, reports indicated that autoantibodies such as anti-endothelial cell antibody (AECA) are significantly increased, the affected endarterium is damaged, the adhesion molecules such as ICAM-1 and inflammatory cytokines such as interlectin (IL)-6 are significantly elevated. But till now, there is no effective medical or therapeutic strategy towards this disease, yet.Urocortin (Ucn), a 40 aa corticotropin-releasing hormone (CRH) family peptide, was first found in rat midbrain in the year 1995. It is widely distributed in the central and peripheral tissues, including central nervous system, cardiovascular system, immunologic system, et al., but its expression differed among different organs and tissues. Ucn may bind with CRH receptor -1 (CRH-1) and -2 to function, which may be mediated by CRH binding protein (CRH-BP) at the same time; besides CRH-R, our lab has demonstrated that it may also function via Ca2+ ion channel. Besides its cardiovascular protective property, Ucn is now considered to be a potent immunomodulatory factor which participates in a sort of immune responses. Reports have demonstrated that it can induce the expression of inflammatory cytokines, such as IL-6 and IL-1, and participates in the development of inflammatory process. Our lab observed that Ucn may promote mast cell Ca²⁺ inflow and activation via CRH-R, and deteriorate rat allergic asthma. There is report indicating that CRH can promote hCAM and ICAM-1 expression in human keratinocytes via CRH-R1. Previously, we have observed that CRH dramatically increased VCAM-1 mRNA and protein expression in LDLr-/- mice and promoted the development of atherosclerosis. Converging lines indicate that Ucn, an important CRH family peptide, may also participate in the development of TAO; what's more, blockade or decrease ICAM-1 expression may be of great significance to TAO treatment.The in vitro and in vivo observations are included in the present study. In the in vitro part, primary culture of rat aortic endothelial cells (RAECs) was applied and LPS-induced ICAM-1 expression in RAECs was determined by immunocytochemistry, ELISA, RT-PCR and Western Blot techniques after different treatment of the cells. In the in vivo part, sodium laurate-induced TAO model rat was applied; ELISA, HE-staining, transmission electron microscopy, RT-PCR and Western Blot techniques were utilized to illustrate the influence of Ucn and CRH-R antagonists on TAO rat.In the present study, it is found that Ucn can significantly promote LPS-induced ICAM-1/sICAM-1 expression in RAECs in a time- and concentration-dependent manner; CRH-R2 antagonist, antisauvagine-30, can block this effect of Ucn. The platelet count was found to be dramatically elevated in TAO model rat, the blood was in a hypercoagulable state, plasma sICAM-1 was significantly increased. Compared with control group, Ucn, CRH-R1, CRH-R1α, and ICAM-1 mRNA/protein expressions were dramatically increased in femoral artery of the model rats; pretreatment the model rats with Ucn resulted in the further increment of TXA₂ and ICAM-1 expression, different from findings in RAECs, these effects of Ucn can be blocked and reversed by selective CRH-R1 antagonist, NBI-27914, or non-selective CRH-R antagonist, astressin.In summary, the present study first demonstrated and reported that Ucn could promote ICAM-1 expression in RAECs and TAO model rats, and deteriorate blood hypercoagulable state in TAO model rats. The present study accumulated experimental and theoretical evidences for illuminating the etiology and pathogenesis of TAO, especially the importance of ICAM-1 in the development of the disease.The major contributions of the present study lie in:1. The present work was the first study observing the influence of Urocortin and CRH-R antagonists on rat thromboangiitis obliterans model. It is found that Urocortin could promote development of the vasculitis and deteriorate rat blood hypercoagulable state via CRH-R1; blockade of CRH-R1 could significantly improve the signs and symptoms of rat thromboangiitis obliterans.2. The present work was the first report that Urocortin could increase LPS-induced ICAM-1 mRNA/protein expression in rat aortic endothelial cells via CRH-R2.3. It was first exploring blockade of CRH-R in decreasing ICAM-1 expression and first proposing that blockade/decreasing of ICAM-1 expression may have dramatic impact on vasculitic treatment.