JAM-C调控中性粒细胞转内皮迁移在急性胰腺炎的作用及其机制研究

The main reason for early mortality in patients with severe acute pancreatitis (SAP) is the systemic inflammatory response leading to multiple organ (lung) failure. The role of neutrophils in the AP had been widespread concern, but the exact molecular mechanism is not clear. It has been reported that reverse neutrophil transendothelial cell migration (rTEM) regulated by juctional adhere melocular-C (JAM-C) can contribute to dissemination of systemic inflammation and multiple organ damage. Our preliminary study shows JAM-C gene knockout mice reduced the cerulein-induced pancreatic injury and the degree of leukocyte infiltration, but actually worsened lung injury, which suggests JAM-C may have a complex pathophysiological role in AP. To elucidate the exact molecular mechanisms of rTEM neutrophil promote systemic inflammatory response and lung injury in AP, firstly, by investigating the clinical AP cases, to establish the relationship between TEM and rTEM neutrophils and pancreatic injury and pancreatitis associated systemic inflammatory response and lung injury in AP. Furthermore, by knockout mice and in vitro experiments to elucidate the role and molecular mechanisms of JAM-C on the regulation of neutrophil of TEM and rTEM resulting in the pancreas damage and lung injury in AP. These results will help unravel the molecular pathogenesis of mechanism of SAP and may provide insight into the development of novel therapeutic agent for SAP.

重症急性胰腺炎（SAP）患者早期死亡的主要原因为全身炎症反应导致多脏器（尤其是肺）功能衰竭。中性粒细胞在AP中的作用已受普遍关注，但确切的分子机制尚不明确。研究表明，JAM-C调控的中性粒细胞的反向转内皮细胞迁移（rTEM）能够促进炎症的播散和多器官功能的损伤。我们前期发现，JAM-C基因敲除小鼠减轻了雨蛙肽诱导的胰腺损伤和白细胞浸润程度，但其肺损伤反而加重，初步提示JAM-C在AP中可能具有复杂的病理生理作用。为了阐明rTEM中性粒细胞促进AP相关全身炎症反应和肺损伤的分子机制，本研究将首先通过AP临床病例明确TEM和rTEM中性粒细胞与胰腺局部损伤和胰腺炎相关全身炎症反应和肺损伤的关系，进一步通过基因敲除小鼠和体外实验，阐明JAM-C对中性粒细胞TEM和rTEM的调节以及在胰腺损伤和AP相关肺损伤中的作用和分子机制。本研究的完成将进一步阐清SAP的发病机制，为SAP的治疗提供新的思路。

重症急性胰腺炎（SAP）是一种胰腺损伤相关的炎症性疾病，目前尚无有效治疗手段。SAP患者早期死亡的主要原因为全身炎症反应导致多脏器（尤其是肺）功能衰竭。因此研究SAP相关肺损伤的发病机制对于改善疾病的预后具有重要意义。研究表明，连接粘附分子C（JAM-C）调控的中性粒细胞反向转内皮细胞迁移（rTEM）能够促进炎症的播散和多器官功能的损伤。我们研究发现，AP患者外周血和雨蛙肽诱导的小鼠AP模型外周血中，rTEM中性粒细胞（ICAM-1highCXCR1low）的比例均与肺损伤的严重程度呈正相关，而小鼠胰腺组织中JAM-C的表达却随着肺损伤程度的加重及rTEM中性粒细胞比例的升高呈下调趋势。与野生型AP小鼠相比，JAM-C基因敲除导致了外周血及肺血管灌洗液中的rTEM中性粒细胞比例显著升高；加重了AP相关的肺损伤及全身炎症反应，其肺组织病理学评分、中性粒细胞浸润程度、MPO水平、肺组织中TNFα和IL6的表达水平、外周血白细胞计数、血清TNFα和IL6水平均明显高于野生型AP小鼠；但胰腺损伤在JAM-C基因敲除小鼠中并未出现显著差异。此外，白三烯（LT）B4及其特异性受体BLT1的表达在AP时显著增高。BLT1特异性受体拮抗剂 LY293111显著减轻了 AP严重程度及局部炎症反应，减少了迁移至外周血的中性粒细胞比例，减轻了急胰腺炎相关肺损伤。P物质可以通过增加PKCα和ERK1/2的磷酸化促进胰腺腺泡细胞中 LTB4的合成，CP96345阻断P物质受体NK1R后，减少了LTB4合成的合成并减轻了AP的严重程度。以上结果显示，JAM-C下调促进中性粒细胞反向迁移，参与了急性胰腺炎相关肺损伤；P物质通过调节LTB4的合成促进中性粒细胞反向迁移，也加重了急性胰腺炎相关肺损伤。我们的研究结果揭示了JAM-C和LTB4调控的中性粒细胞转内皮迁移在急性胰腺炎的作用及其相关的分子机制，为急性胰腺炎相关肺损伤的治疗手段提供了理论依据，同时为后续急性胰腺炎的研究开辟了新的领域并提供了新的手段。