Ruth Jeffrey H, Haas Christian S, Park Christy C, Amin M Asif, Martinez Rita J, Haines G Kenneth, Shahrara Shiva, Campbell Phillip L, Koch Alisa E
University of Michigan Medical School, Ann Arbor 48109-0680, USA.
Arthritis Rheum. 2006 Mar;54(3):765-78. doi: 10.1002/art.21662.
Rheumatoid arthritis (RA) is characterized by profound mononuclear cell (MNC) recruitment into synovial tissue (ST), thought to be due in part to tumor necrosis factor alpha (TNFalpha), a therapeutic target for RA. Although chemokines may also be involved, the mechanisms remain unclear. We undertook this study to examine the participation of CXCL16, a novel chemokine, in recruitment of MNCs to RA ST in vivo and to determine the signal transduction pathways mediating this process.
Using a human RA ST-SCID mouse chimera, immunohistochemistry, enzyme-linked immunosorbent assay, real-time reverse transcription-polymerase chain reaction, flow cytometry, and in vitro chemotaxis assays, we defined the expression and function of CXCL16 and its receptor, CXCR6, as well as the signal transduction pathways utilized by them for MNC homing in vitro and in vivo.
CXCL16 was markedly elevated in RA synovial fluid (SF) samples, being as high as 145 ng/ml. Intense macrophage and lining cell staining for CXCL16 in RA ST correlated with increased CXCL16 messenger RNA levels in RA ST compared with those in osteoarthritis and normal ST. By fluorescence-activated cell sorting analysis, one-half of RA SF monocytes and one-third of memory lymphocytes expressed CXCR6. In vivo recruitment of human MNCs to RA ST implanted in SCID mice occurred in response to intragraft injection of human CXCL16, a response similar to that induced by TNFalpha. Lipofection of MNCs with antisense oligodeoxynucleotides for ERK-1/2 resulted in a 50% decline in recruitment to engrafted RA ST and a 5-fold decline in recruitment to regional lymph nodes. Interestingly, RA ST fibroblasts did not produce CXCL16 in response to TNFalpha in vitro, suggesting that CXCL16 protein may function in large part independently of TNFalpha.
Taken together, these results point to a unique role for CXCL16 as a premier MNC recruiter in RA and suggest additional therapeutic possibilities, targeting CXCL16, its receptor, or its signaling pathways.
类风湿关节炎（RA）的特征是大量单核细胞（MNC）募集到滑膜组织（ST）中，这被认为部分归因于肿瘤坏死因子α（TNFα），它是RA的一个治疗靶点。尽管趋化因子可能也参与其中，但其机制仍不清楚。我们开展这项研究以检测新型趋化因子CXCL16在体内MNC募集至RA ST过程中的作用，并确定介导此过程的信号转导途径。
使用人RA ST - SCID小鼠嵌合体、免疫组织化学、酶联免疫吸附测定、实时逆转录 - 聚合酶链反应、流式细胞术和体外趋化性测定，我们确定了CXCL16及其受体CXCR6的表达和功能，以及它们在体内外用于MNC归巢的信号转导途径。
CXCL16在RA滑膜液（SF）样本中显著升高，高达145 ng/ml。与骨关节炎和正常ST相比，RA ST中CXCL16在巨噬细胞和衬里细胞中的强烈染色与RA ST中CXCL16信使RNA水平升高相关。通过荧光激活细胞分选分析，RA SF单核细胞的一半和记忆淋巴细胞的三分之一表达CXCR6。将人MNC体内募集至植入SCID小鼠的RA ST是对移植内注射人CXCL16的反应，该反应类似于TNFα诱导的反应。用针对ERK - 1/2的反义寡脱氧核苷酸对MNC进行脂质转染导致募集至植入的RA ST减少50%，募集至区域淋巴结减少5倍。有趣的是，RA ST成纤维细胞在体外对TNFα无反应而不产生CXCL16，这表明CXCL16蛋白可能在很大程度上独立于TNFα发挥作用。
综上所述，这些结果表明CXCL16作为RA中主要的MNC募集因子具有独特作用，并提示针对CXCL16、其受体或其信号转导途径的额外治疗可能性。
