Tamura Tetsuro, Cazander Gwendolyn, Rooijakkers Suzan H M, Trouw Leendert A, Nibbering Peter H
Department of Infectious Diseases, Leiden University Medical Center, Leiden, the Netherlands.
Department of Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Wound Repair Regen. 2017 Jan;25(1):41-50. doi: 10.1111/wrr.12504. Epub 2017 Mar 6.
Larvae of the blowfly Lucilia sericata facilitate wound healing by removing dead tissue and biofilms from non-healing and necrotic wounds. Another beneficial action of larvae and their excretions/secretions (ES) is down-regulation of excessive inflammation. As prolonged complement activation is key to excessive inflammation, the aim of this study was to elucidate the mechanisms underlying the anti-complement activities of ES. Results revealed that heat sensitive serine proteases in ES degrade multiple complement proteins in all steps of the three complement activation pathways. Importantly, C3a and C5a-major activators of inflammation-were also degraded by ES and pretreatment of these factors with ES completely blocked their ability to induce activation of human neutrophils. Pre-exposure of the neutrophils to ES did not affect their responsiveness to C3a/C5a and fMLP, indicating that the receptors for these activators on neutrophils were not affected by ES. Surprisingly, heat and serine protease inhibitor pretreatment did not affect the ability of ES to inhibit C5b-9 complex formation despite degrading complement proteins, indicating a second complement-inhibiting molecule in ES. Heated ES was as effective as intact ES in inhibiting C3 deposition upon activation of the alternative pathway, but was significantly less effective in wells with a classical or lectin pathway-specific coating. Unfortunately, the molecules affecting the complement system could not be identified due to an insufficient database for L. sericata. Together, larval ES inhibit complement activation by two different mechanisms and down-regulate the C3a/C5a-mediated neutrophil activation. This attenuates the inflammatory process, which may facilitate wound healing.
丝光绿蝇幼虫通过清除难愈合和坏死伤口中的死组织及生物膜来促进伤口愈合。幼虫及其排泄物/分泌物（ES）的另一项有益作用是下调过度炎症反应。由于补体的持续激活是过度炎症反应的关键，本研究旨在阐明ES抗补体活性的潜在机制。结果显示，ES中的热敏感丝氨酸蛋白酶在三条补体激活途径的所有步骤中均能降解多种补体蛋白。重要的是，炎症主要激活因子C3a和C5a也会被ES降解，用ES预处理这些因子可完全阻断它们诱导人中性粒细胞激活的能力。中性粒细胞预先暴露于ES并不影响其对C3a/C5a和fMLP的反应性，这表明中性粒细胞上这些激活因子的受体不受ES影响。令人惊讶的是，尽管ES能降解补体蛋白，但热和丝氨酸蛋白酶抑制剂预处理并不影响其抑制C5b - 9复合物形成的能力，这表明ES中存在第二种补体抑制分子。加热后的ES在替代途径激活时抑制C3沉积的效果与完整ES相同，但在具有经典或凝集素途径特异性包被的孔中效果明显较差。遗憾的是，由于丝光绿蝇的数据库不足，影响补体系统的分子无法确定。总之，幼虫ES通过两种不同机制抑制补体激活，并下调C3a/C5a介导的中性粒细胞激活。这减轻了炎症过程，可能有助于伤口愈合。
