新趋化因子PSMP介导的炎症反应对GVHD发生的影响

GVHD (graft-versus-host disease) is a common complication occurring after the human allogeneic stem cell transplantation, which is believed to be the main obstacle of the recovery from HSCT. PSMP (PC3 secreted micro-protein) is found as a novel chemokine, whose amino acid sequence contains the classical chemokine motif: CC and CXC. PSMP has been reported to be a high affinity ligand of CCR2 by our chemotaxis assay, and PSMP protein could chemo-attract human peripheral blood monocyte (PBM) and peripheral blood lymphocyte (PBL). According to the result of IHC, PSMP was found high expressed in multiple human inflammatory and tumor tissues, including ulcerative colitis, acute liver injury. Monocyte and macrophage have been reported by many research teams that they would be attracted and accumulated at the intestinal mucous, liver and skin during the GVHD occurring and aggravate GVHD. Until now, we have found PSMP dramatically highly expressed at the intestinal and colonic mucous, liver tissue of GVHD mice mode; PSMP overexpressed abdominal cavity in situ and colonic epithelium in situ could specifically chemo-attract the monocyte to abdominal cavity and colonic tissue with a CCR2 dependent manner; moreover, after colitis mice mode were treated with PSMP’s neutralizing antibody, the colitis symptom would be dramatically alleviated, and the inflammatory monocyte and macrophage would be reduced, inflammatory cytokines would be lower, which indicated PSMP may participate in the GVHD occurring.

GVHD（graft-versus-host disease）是异基因造血干细胞移植术后的主要并发症，其中GVHD肠道炎症是导致患者死亡的重要原因。因此，研究GVHD肠道炎症的发生机制，发现预防或治疗GVHD的关键靶点显得尤为重要。PSMP（PC3 secreted micro-protein）是我们新发现的趋化因子，能特异趋化CCR2高表达的单核细胞和淋巴细胞。我们的前期研究结果显示：PSMP在GVHD动物模型的肠粘膜、肝脏组织呈现特异性高表达；肠粘膜原位上调表达PSMP可以特异性地富集单核细胞和巨噬细胞；PSMP的中和抗体可以明显缓解肠炎模型小鼠的肠炎症状。以上结果都提示PSMP介导的炎症与GVHD肠炎存在密切的关系。因此本课题拟在研究PSMP在GVHD肠炎高表达时通过趋化哪些炎症细胞参与肠炎，另外抗体中和PSMP能否明显的抑制GVHD肠炎的发生，PSMP能否成为治疗GVHD的靶点。

PSMP作为启动结肠炎症的关键趋化因子，其作用机制已经阐明：结肠上皮细胞受到微生物攻击时会迅速上调PSMP的表达，并通过PSMP-CCR2-monocyte/macrophage轴启动结肠炎症反应，PSMP KO小鼠、CCR2 KO小鼠以及PSMP中和抗体都可以显著的减弱肠炎的症状。我们进一步使用PSMP中和抗体对急性GVHD和慢性GVHD小鼠模型进行治疗，发现PSMP中和抗体并不能抑制骨髓移植后活化T细胞的数量，对急性GVHD的发病严重程度也没有缓解；然而，PSMP中和抗体对慢性GVHD有显著的治疗效果，能明显的改善小鼠皮炎症状、肝损伤、肾损伤和自身抗体的水平。在慢性GVHD相关机制的研究中，我们发现PSMP中和抗体和PSMP KO小鼠在诱导慢性GVHD时肝脏巨噬细胞比例明显降低，而对肝脏kupffer细胞没有影响。另外，我们还发现PSMP蛋白能明显影响单核细胞膜表面黏附分子的表达和巨噬细胞的极化过程。慢性GVHD是一个慢性免疫失衡的过程，靶器官纤维化和间质化是主要的组织形态学改变，而巨噬细胞往往广泛参与其中，因此，我们推断PSMP可能由干细胞移植后慢性排斥过程中由肝脏、肠道、皮肤的上皮细胞表达，趋化单核细胞并诱导巨噬细胞分化，进而导致皮肤角质化、肝脏纤维化、肺间质化等症状。另外，我们还发现PSMP中和抗体能有效的抑制非酒精性肝硬化小鼠模型的疾病进程和严重程度，通过关键的几个动物实验，我们证明了PSMP参与非酒精性肝硬化机制是肝脏细胞受到有害物质损伤后，上调PSMP的表达，进而通过PSMP-CCR2-单核细胞轴趋化单核细胞至肝脏，并引发炎症；PSMP主要影响肝脏巨噬细胞的比例和数量，不影响kupffer细胞，这与慢性GVHD肝损伤的机制非常相似。此外，我们还发现PSMP中和抗体能有效的抑制前列腺癌细胞系皮下成瘤模型中肿瘤的生长；能有效地降低前列腺转移瘤模型的死亡率。经过对相应的机制研究，我们发现PSMP参与前列腺癌的进展和转移可能与PSMP直接刺激肿瘤细胞生长、上皮间质样改变有关，也与重塑肿瘤的微环境有关。以上研究成果具有较好的临床转化应用前景，都有研究论文发表，也申请了中国和美国发明专利。