Hewins Peter, Williams Julie M, Wakelam Michael J O, Savage Caroline O S
Renal Immunobiology, MRC Centre for Immune Regulation, The Medical School, University of Birmingham, Birmingham, United Kingdom.
J Am Soc Nephrol. 2004 Mar;15(3):796-808. doi: 10.1097/01.asn.0000113241.98702.77.
Antineutrophil cytoplasm antibodies (ANCA) activate TNF-alpha-primed neutrophils to undergo a respiratory burst. The intracellular signals that mediate activation have not been studied extensively but could increase the understanding of the pathogenesis small vessel vasculitis. It was demonstrated that ANCA-IgG induced phosphorylation of the tyrosine kinase Syk in TNF-alpha-primed neutrophils from healthy donors. Syk was not phosphorylated in response to ANCA F(ab')(2). Furthermore, Syk phosphorylation was attenuated by blockade of both low-affinity Fcgamma receptors and CD18. Similarly, low-affinity Fcgamma receptor blockade reduced ANCA-induced superoxide production. In patient-derived neutrophils, the high-affinity Fcgamma receptor FcgammaRI was also demonstrated to be involved in ANCA-induced superoxide production. However, Syk phosphorylation was not attenuated by blockade of the FcgammaRI, present on neutrophils from vasculitis patients. The tyrosine kinase inhibitor 4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine inhibited the ANCA-induced respiratory burst and Syk phosphorylation, suggesting that Src kinases lie upstream of Syk activation but downstream of ANCA engagement of Fcgamma receptors. Piceatannol, another tyrosine kinase inhibitor, also inhibited ANCA-induced Syk phosphorylation and the ANCA-stimulated respiratory burst, supporting the proposed functional role for Syk in ANCA signaling. ANCA-induced phosphorylation of Cbl and intracellular calcium transients, potential downstream mediators of Syk activation, were also blocked by tyrosine kinase inhibitors. While it has previously been shown that pertussis toxin diminishes the ANCA-induced respiratory burst, indicating heterotrimeric G protein involvement, Syk phosphorylation and calcium transients were unaffected by pertussis toxin. Collectively, these data show that Syk phosphorylation is induced during ANCA-triggered neutrophil activation.
抗中性粒细胞胞浆抗体（ANCA）可激活经肿瘤坏死因子-α（TNF-α）预刺激的中性粒细胞，使其发生呼吸爆发。介导激活的细胞内信号尚未得到广泛研究，但可能有助于增进对小血管血管炎发病机制的理解。研究表明，ANCA-IgG可诱导健康供体经TNF-α预刺激的中性粒细胞中酪氨酸激酶Syk发生磷酸化。ANCA F(ab')(2)刺激后，Syk未发生磷酸化。此外，低亲和力Fcγ受体和CD18的阻断可减弱Syk磷酸化。同样，低亲和力Fcγ受体阻断可降低ANCA诱导的超氧化物生成。在患者来源的中性粒细胞中，高亲和力Fcγ受体FcγRI也被证明参与ANCA诱导的超氧化物生成。然而，血管炎患者中性粒细胞上FcγRI的阻断并未减弱Syk磷酸化。酪氨酸激酶抑制剂4-氨基-5-（4-氯苯基）-7-（叔丁基）吡唑并[3,4-d]嘧啶可抑制ANCA诱导的呼吸爆发和Syk磷酸化，提示Src激酶位于Syk激活的上游，但在ANCA与Fcγ受体结合的下游。另一种酪氨酸激酶抑制剂白皮杉醇也可抑制ANCA诱导的Syk磷酸化和ANCA刺激的呼吸爆发，支持了Syk在ANCA信号传导中的拟议功能作用。酪氨酸激酶抑制剂还可阻断ANCA诱导的Cbl磷酸化和细胞内钙瞬变，这两者是Syk激活的潜在下游介质。虽然此前已表明百日咳毒素可减弱ANCA诱导的呼吸爆发，提示异源三聚体G蛋白参与其中，但Syk磷酸化和钙瞬变不受百日咳毒素影响。总体而言，这些数据表明，在ANCA触发的中性粒细胞激活过程中可诱导Syk磷酸化。
