Podolnikova Nataly P, Lishko Valeryi K, Roberson Robert, Koh Zhiqian, Derkach Dmitry, Richardson David, Sheller Michael, Ugarova Tatiana P
School of Life Sciences, Arizona State University, Tempe, AZ, United States.
bioSyntagma Inc., Tempe, AZ, United States.
Front Cell Infect Microbiol. 2023 Oct 4;13:1217103. doi: 10.3389/fcimb.2023.1217103. eCollection 2023.
The complement receptor CR3, also known as integrin Mac-1 (CD11b/CD18), is one of the major phagocytic receptors on the surface of neutrophils and macrophages. We previously demonstrated that in its protein ligands, Mac-1 binds sequences enriched in basic and hydrophobic residues and strongly disfavors negatively charged sequences. The avoidance by Mac-1 of negatively charged surfaces suggests that the bacterial wall and bacterial capsule possessing net negative electrostatic charge may repel Mac-1 and that the cationic Mac-1 ligands can overcome this evasion by acting as opsonins. Indeed, we previously showed that opsonization of Gram-negative with several cationic peptides, including PF4 (Platelet Factor 4), strongly augmented phagocytosis by macrophages. Here, we investigated the effect of recombinant PF4 (rPF4) on phagocytosis of Gram-positive and examined its impact in a mouse model of peritonitis. Characterization of the interaction of rPF4 with nonencapsulated and encapsulated showed that rPF4 localizes on the bacterial surface, thus making it available for Mac-1. Furthermore, rPF4 did not have direct bactericidal and bacteriostatic activity and was not toxic to host cells. rPF4 enhanced phagocytosis of bioparticles by various primary and cultured Mac-1-expressing leukocytes by several folds. It also increased phagocytosis of live nonencapsulated and encapsulated bacteria. Notably, the augmentation of phagocytosis by rPF4 did not compromise the intracellular killing of by macrophages. Using a murine peritonitis model, we showed that treatment of infected mice with rPF4 caused a significant increase in the clearance of antibiotic-susceptible and its methicillin-resistant (MRSA) variant and markedly improved survival. These findings indicate that rPF4 binding to the bacterial surface circumvents its antiphagocytic properties, improving host defense against antibiotic-susceptible and antibiotic-resistant bacteria.
补体受体CR3，也称为整合素Mac-1（CD11b/CD18），是中性粒细胞和巨噬细胞表面主要的吞噬受体之一。我们之前证明，在其蛋白质配体中，Mac-1结合富含碱性和疏水残基的序列，并且强烈排斥带负电荷的序列。Mac-1对带负电荷表面的回避表明，具有净负静电电荷的细菌壁和细菌荚膜可能排斥Mac-1，而阳离子Mac-1配体可以作为调理素克服这种逃避。事实上，我们之前表明，用包括PF4（血小板因子4）在内的几种阳离子肽对革兰氏阴性菌进行调理，可显著增强巨噬细胞的吞噬作用。在此，我们研究了重组PF4（rPF4）对革兰氏阳性菌吞噬作用的影响，并在腹膜炎小鼠模型中考察了其作用。rPF4与非包膜和包膜细菌相互作用的表征表明，rPF4定位于细菌表面，从而使其可被Mac-1利用。此外，rPF4没有直接的杀菌和抑菌活性，对宿主细胞也无毒。rPF4使各种原代和培养的表达Mac-1的白细胞对细菌生物颗粒的吞噬作用增强了几倍。它还增加了对活的非包膜和包膜细菌的吞噬作用。值得注意的是，rPF4增强吞噬作用并没有损害巨噬细胞对细菌的细胞内杀伤。使用小鼠腹膜炎模型，我们表明用rPF4治疗感染小鼠可显著增加对抗生素敏感菌及其耐甲氧西林（MRSA）变体的清除率，并显著提高生存率。这些发现表明，rPF4与细菌表面结合可规避其抗吞噬特性，改善宿主对抗生素敏感菌和耐药菌的防御。
