Matera G, Cook J A, Geisel J, Ashton S H, Wise W C, Focá A, Berkowitz B A, Halushka P V
Department of Physiology, Medical University of South Carolina, Charleston 29425.
Antimicrob Agents Chemother. 1993 Mar;37(3):393-7. doi: 10.1128/AAC.37.3.393.
Magainins are novel polycationic peptides with broad-spectrum antimicrobial activity, including activity against gram-negative bacteria. Gram-negative bacteremia can elicit endotoxic shock that is associated with the increased formation of eicosanoids. Inhibition of eicosanoid synthesis has been shown to improve the outcome of experimental endotoxic shock. The aim of the present study was to test the in vitro effects of two magainin peptides, MSI-97 (M1) and MSI-98 (M2), on eicosanoid synthesis by rat peritoneal macrophages (M phi) stimulated by Salmonella enteritidis lipopolysaccharide (LPS; 50 micrograms/ml) and Salmonella minnesota lipid A (5 micrograms/ml) and to compare their effects on LPS reactivity with a metachromatic dye. M1 (100 micrograms/ml) significantly (P < 0.05) reduced LPS-stimulated synthesis of thromboxane B2 (TXB2), without changing 6-keto-prostaglandin F1 alpha in M phi. Similarly, M2 (10 micrograms/ml) significantly attenuated M phi synthesis of TXB2 stimulated by either LPS or lipid A. However, at a higher concentration (100 micrograms/ml), M2 but not M1 significantly augmented LPS-induced increases in TXB2 and 6-keto-prostaglandin F1 alpha. Polymyxin B (40 micrograms/ml) inhibited LPS production and lipid A-stimulated TXB2 production. M1 (100 micrograms/ml) and polymyxin B (10 and 40 micrograms/ml) also inhibited calcium ionophore A23187 (10 microM)-induced synthesis of TXB2. The lipid A moiety of LPS reacts with dimethylmethylene blue dye, providing a metachromatic assay of LPS. This metachromatic reaction with lipid A was significantly reduced by polymyxin B and M2 at all concentrations. M1 was effective only at the highest M1:lipid A concentration ratio (2:1). Thus, M1 and M2 share some similarities with polymyxin B in inhibiting lipid A reactivity with the dye, which suggests that these magainins may also bind to lipid A. However, M1 was devoid of any inhibitory effects on dye reactivity with S. enteritidis LPS and M2 was inhibitory at only one concentration ratio (1:5). In conclusion, the varied effects of the magainin peptides on LPS, lipid A, and M phi eicosanoid synthesis appear to depend on the type of peptide used and on its concentration.
蛙皮素是一类具有广谱抗菌活性的新型多阳离子肽，包括对革兰氏阴性菌的活性。革兰氏阴性菌血症可引发内毒素休克，这与类花生酸形成增加有关。已证明抑制类花生酸合成可改善实验性内毒素休克的结局。本研究的目的是测试两种蛙皮素肽MSI - 97（M1）和MSI - 98（M2）对由肠炎沙门氏菌脂多糖（LPS；50微克/毫升）和明尼苏达沙门氏菌脂质A（5微克/毫升）刺激的大鼠腹腔巨噬细胞（M phi）类花生酸合成的体外影响，并比较它们与一种异染染料对LPS反应性的影响。M1（100微克/毫升）显著（P < 0.05）降低了LPS刺激的血栓素B2（TXB2）合成，而不改变M phi中6 - 酮 - 前列腺素F1α的水平。同样，M2（10微克/毫升）显著减弱了LPS或脂质A刺激的M phi中TXB2的合成。然而，在较高浓度（100微克/毫升）时，M2而非M1显著增强了LPS诱导的TXB2和6 - 酮 - 前列腺素F1α的增加。多粘菌素B（40微克/毫升）抑制LPS产生和脂质A刺激的TXB2产生。M1（100微克/毫升）和多粘菌素B（10和40微克/毫升）也抑制钙离子载体A23187（10微摩尔）诱导的TXB2合成。LPS的脂质A部分与二甲基亚甲基蓝染料反应，提供LPS的异染测定法。多粘菌素B和M2在所有浓度下均显著降低与脂质A的这种异染反应。M1仅在最高的M1：脂质A浓度比（2：1）时有效。因此，M1和M2在抑制脂质A与染料的反应性方面与多粘菌素B有一些相似之处，这表明这些蛙皮素可能也与脂质A结合。然而，M1对与肠炎沙门氏菌LPS的染料反应性没有任何抑制作用，而M2仅在一个浓度比（1：5）时具有抑制作用。总之，蛙皮素肽对LPS、脂质A和M phi类花生酸合成的不同影响似乎取决于所用肽的类型及其浓度。
