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Antimicrobial Peptides from Human Platelets

机译：来自人类血小板的抗菌肽

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Platelets share structural and functional similarities with granulocytes known to participate in antimicrobial host defense. To evaluate the potential antimicrobial activities of platelet proteins, normal human platelets were stimulated with human thrombin in vitro. Components of the stimulated-platelet supernatants were purified to homogeneity by reversed-phase high-performance liquid chromatography. Purified peptides with inhibitory activity against Escherichia coli ML35 in an agar diffusion antimicrobial assay were characterized by mass spectrometry, amino acid analysis, and sequence determination. These analyses enabled the identification of seven thrombin-releasable antimicrobial peptides from human platelets: platelet factor 4 (PF-4), RANTES, connective tissue activating peptide 3 (CTAP-3), platelet basic protein, thymosin β-4 (Tβ-4), fibrinopeptide B (FP-B), and fibrinopeptide A (FP-A). With the exception of FP-A and FP-B, all peptides were also purified from acid extracts of nonstimulated platelets. The in vitro antimicrobial activities of the seven released peptides were further tested against bacteria (E. coli and Staphylococcus aureus) and fungi (Candida albicans and Cryptococcus neoformans). Each peptide exerted activity against at least two organisms. Generally, the peptides were more potent against bacteria than fungi, activity was greater at acidic pHs, and antimicrobial activities were dose dependent. Exceptions to these observations were observed with PF-4, which displayed a bimodal dose-response relationship in microbicidal assays, and Tβ-4, which had greater activity at alkaline pHs. At concentrations at which they were individually sublethal, PF-4 and CTAP-3 exerted synergistic microbicidal activity against E. coli. Collectively, these findings suggest a direct antimicrobial role for platelets as they are activated to release peptides in response to trauma or mediators of inflammation.
机译：血小板与已知参与抗微生物宿主防御的粒细胞具有相似的结构和功能。为了评估血小板蛋白的潜在抗菌活性，在体外用人凝血酶刺激正常的人血小板。通过反相高效液相色谱将刺激的血小板上清液的成分纯化至均质。通过质谱，氨基酸分析和序列测定，对在琼脂扩散抗微生物试验中具有对大肠杆菌 ML35抑制活性的纯化肽进行了表征。这些分析能够从人血小板中鉴定出七个可释放凝血酶的抗菌肽：血小板因子4（PF-4），RANTES，结缔组织活化肽3（CTAP-3），血小板碱性蛋白，胸腺素β-4（Tβ-4） ），纤维蛋白肽B（FP-B）和纤维蛋白肽A（FP-A）。除了FP-A和FP-B以外，还从非刺激性血小板的酸性提取物中纯化了所有肽。进一步测试了这7种释放肽的体外抗菌活性，分别针对细菌（ Eco。和 Staphylococcus aureus ）和真菌（ Candida albicans 和新隐球菌）。每种肽对至少两种生物均具有活性。通常，该肽对细菌的作用比真菌更强，在酸性pH值下活性更高，且抗菌活性与剂量有关。 PF-4和Tβ-4在碱性pH值下具有更大的活性，而PF-4在杀微生物测定中显示出双峰剂量反应关系，而Tβ-4在碱性pH值下具有更大的活性，但这些观察结果却例外。在它们分别致死的浓度下，PF-4和CTAP-3发挥了针对 E的协同杀微生物活性。大肠杆菌。总的来说，这些发现表明血小板对血小板具有直接的抗菌作用，因为它们响应创伤或炎症介质而被激活释放肽。

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