Veterans Affairs Puget Sound Medical Center, Seattle, WA 98108, USA.
J Immunol. 2010 Mar 1;184(5):2677-85. doi: 10.4049/jimmunol.0903274. Epub 2010 Feb 1.
Chemokine-glycosaminoglycan (GAG) interactions are thought to result in the formation of tissue-bound chemokine gradients. We hypothesized that the binding of chemokines to GAGs would increase neutrophil migration toward CXC chemokines instilled into lungs of mice. To test this hypothesis we compared neutrophil migration toward recombinant human CXCL8 (rhCXCL8) and two mutant forms of CXCL8, which do not bind to heparin immobilized on a sensor chip. Unexpectedly, when instilled into the lungs of mice the CXCL8 mutants recruited more neutrophils than rhCXCL8. The CXCL8 mutants appeared in plasma at significantly higher concentrations and diffused more rapidly across an extracellular matrix in vitro. A comparison of the murine CXC chemokines, KC and MIP-2, revealed that KC was more effective in recruiting neutrophils into the lungs than MIP-2. KC appeared in plasma at significantly higher concentrations and diffused more rapidly across an extracellular matrix in vitro than MIP-2. In kinetic binding studies, KC, MIP-2, and rhCXCL8 bound heparin differently, with KC associating and dissociating more rapidly from immobilized heparin than the other chemokines. These data suggest that the kinetics of chemokine-GAG interactions contributes to chemokine function in tissues. In the lungs, it appears that chemokines, such as CXCL8 or MIP-2, which associate and disassociate slowly from GAGs, form gradients relatively slowly compared with chemokines that either bind GAGs poorly or interact with rapid kinetics. Thus, different types of chemokine gradients may form during an inflammatory response. This suggests a new model, whereby GAGs control the spatiotemporal formation of chemokine gradients and neutrophil migration in tissue.
趋化因子-糖胺聚糖 (GAG) 相互作用被认为会导致组织结合趋化因子梯度的形成。我们假设趋化因子与 GAG 的结合会增加向小鼠肺部注入的 CXC 趋化因子诱导的中性粒细胞迁移。为了验证这一假设，我们比较了向重组人 CXCL8（rhCXCL8）和两种不与固定在传感器芯片上的肝素结合的 CXCL8 突变体注入的中性粒细胞的迁移。出乎意料的是，当注入小鼠肺部时，CXCL8 突变体招募的中性粒细胞比 rhCXCL8 多。CXCL8 突变体在血浆中的浓度明显更高，并且在体外更快地扩散穿过细胞外基质。对小鼠 CXC 趋化因子 KC 和 MIP-2 的比较表明，KC 比 MIP-2 更有效地将中性粒细胞募集到肺部。KC 在血浆中的浓度明显更高，并且在体外比 MIP-2 更快地扩散穿过细胞外基质。在动力学结合研究中，KC、MIP-2 和 rhCXCL8 与肝素的结合方式不同，KC 与固定化肝素的结合和解离速度比其他趋化因子更快。这些数据表明趋化因子-GAG 相互作用的动力学有助于趋化因子在组织中的功能。在肺部，似乎像 CXCL8 或 MIP-2 这样与 GAG 结合和解离较慢的趋化因子，与那些与 GAG 结合不良或与快速动力学相互作用的趋化因子相比，形成梯度的速度相对较慢。因此，在炎症反应过程中可能会形成不同类型的趋化因子梯度。这表明了一种新的模型，即 GAG 控制趋化因子梯度和组织中中性粒细胞迁移的时空形成。
