Vascular Biology and Stroke Research Laboratory, Department of Neurosurgery, Louisiana State University Health Science Center in Shreveport, Shreveport, Louisiana, United States of America.
PLoS One. 2013 Jun 6;8(6):e64631. doi: 10.1371/journal.pone.0064631. Print 2013.
Recent work has revealed an essential involvement of soluble CD40L (sCD40L) in inflammation and vascular disease. Activated platelets are the major source of sCD40L, which has been implicated in platelet and leukocyte activation, although its exact functional impact on leukocyte-platelet interactions and the underlying mechanisms remain undefined. We aimed to determine the impact and the mechanisms of sCD40L on neutrophils. We studied neutrophil interactions with activated, surface-adherent platelets as a model for leukocyte recruitment to the sites of injury. Our data show that CD40L contributes to neutrophil firm adhesion to and transmigration across activated surface-adherent platelets, possibly through two potential mechanisms. One involves the direct interaction of ligand-receptor (CD40L-CD40), i.e., platelet surface CD40L interaction with neutrophil CD40; another involves an indirect mechanism, i.e. soluble CD40L stimulates activation of the leukocyte-specific β2 integrin Mac-1 in neutrophils and thereby further promotes neutrophil adhesion and migration. Activation of the integrin Mac-1 is known to be critical for mediating neutrophil adhesion and migration. sCD40L activated Mac-1 in neutrophils and enhanced neutrophil-platelet interactions in wild-type neutrophils, but failed to elicit such responses in CD40-deficient neutrophils. Furthermore, our data show that the protein kinase C zeta (PKCζ) is critically required for sCD40L-induced Mac-1 activation and neutrophil adhesive function. sCD40L strongly stimulated the focal clustering of Mac-1 (CD11b) and the colocalization of Mac-1 with PKCζ in wild-type neutrophils, but had minimal effect in CD40-deficient neutrophils. Blocking PKCζ completely inhibited sCD40L-induced neutrophil firm adhesion. Moreover, sCD40L strongly stimulates neutrophil oxidative burst via CD40-dependent activation of PI3K/NF-KB, but independent of Mac-1 and PKCζ. These findings may contribute to a better understanding of the underlying mechanisms by which sCD40L/CD40 pathway contributes to inflammation and vascular diseases.
最近的研究揭示了可溶性 CD40L（sCD40L）在炎症和血管疾病中的重要作用。活化的血小板是 sCD40L 的主要来源，它被认为参与了血小板和白细胞的激活，尽管其对白细胞-血小板相互作用的确切功能影响和潜在机制仍未确定。我们旨在确定 sCD40L 对中性粒细胞的影响及其机制。我们研究了中性粒细胞与活化的表面黏附血小板的相互作用，作为白细胞募集到损伤部位的模型。我们的数据表明，CD40L 有助于中性粒细胞牢固地黏附并穿过活化的表面黏附血小板，这可能涉及两种潜在的机制。一种涉及配体-受体（CD40L-CD40）的直接相互作用，即血小板表面的 CD40L 与中性粒细胞的 CD40 相互作用；另一种涉及间接机制，即可溶性 CD40L 刺激白细胞特异性β2 整合素 Mac-1 在中性粒细胞中的激活，从而进一步促进中性粒细胞的黏附和迁移。整合素 Mac-1 的激活被认为是介导中性粒细胞黏附和迁移的关键。sCD40L 在中性粒细胞中激活了 Mac-1，并增强了野生型中性粒细胞中的中性粒细胞-血小板相互作用，但在缺乏 CD40 的中性粒细胞中未能引起这种反应。此外，我们的数据表明，蛋白激酶 C ζ（PKCζ）对于 sCD40L 诱导的 Mac-1 激活和中性粒细胞黏附功能至关重要。sCD40L 强烈刺激了 Mac-1（CD11b）的局灶性聚集以及 Mac-1 与 PKCζ 在野生型中性粒细胞中的共定位，但在缺乏 CD40 的中性粒细胞中几乎没有影响。阻断 PKCζ 完全抑制了 sCD40L 诱导的中性粒细胞牢固黏附。此外，sCD40L 通过 CD40 依赖性激活 PI3K/NF-κB 强烈刺激中性粒细胞的氧化爆发，但不依赖于 Mac-1 和 PKCζ。这些发现可能有助于更好地理解 sCD40L/CD40 途径促进炎症和血管疾病的潜在机制。
