Novel therapeutic strategy in the treatment of infectious diseases by anti-microbial, endotoxin-neutralizing proteins.

我们从兔和人中性粒细胞中发现了具有lps中和活性的18kDa阳离子抗微生物蛋白（CAP18）。人类CAP18蛋白的c端27mer片段（27mer; CAP18_<109-135>）被鉴定为抗微生物和脂多糖中和结构域。我们研究了修饰和/或取代CAP18肽的氨基酸残基对其活性的影响。27mer的n端乙酰化和c端酰胺化可以增强其lps中和和抗菌活性。将E_<119>和K_<128>的27mer替换为L （27LL）或F (27FF)，可提高LPS结合活性（约30-40倍），并阻断LPS诱导的小鼠死亡。将E_<119>替换为L_<119>可提高lps结合活性（约8倍），但该肽（27L）对内毒素休克没有保护作用。从27mer （18mer: CAP18_<118-135>）的n端截断9个氨基酸导致lps结合活性显著降低，尽管这两个末端都经过了化学修饰。增加18mer （18LL）中疏水氨基酸残基（Leucin=L）可提高lps结合活性（约30倍）和对革兰氏阳性细菌如MRSA（耐甲氧西林金黄色葡萄球菌；bbbb3倍）的抑菌活性，但18LL对小鼠内毒素休克无保护作用。赖氨酸(K)进一步取代18LL的三个位置，显著提高了lps结合活性（约120倍），对革兰氏阴性菌（如大肠杆菌O157: H7和鼠伤寒杆菌）的抗菌活性，并保护小鼠免受内毒素休克。这些结果提示了α -螺旋结构的稳定性以及CAP18肽中疏/亲水性（碱性）氨基酸残基的平衡的重要性。

We have found 18kDa cationic anti-microbial proteins (CAP18) with LPS-neutralizing activity from rabbit and human neutrophils. The 27mer C-terminal fragment of human CAP 18 (27mer ; CAP18_<109-135>) has been identified as the anti-microbial and LPS-neutralizing domain. We investigated the effects of modification and/or substitution of amino acid residues of CAP18 peptides on their activities. Acetylation of N-terminal and amidation of C-terminal residues of the 27mer in-creased LPS-neutralizing and antimicrobial activities. Substitution of E_<119> and K_<128> of 27mer to L (27LL) or F (27FF) increased LPS binding activity (〜30-40 fold) and also blocked LPS-induced lethality in mice. Substitution of E_<119> to L_<119> increased LPS-binding activity (〜8 -fold), however, this peptide (27L) could not protect vs. endotoxin shock. Truncation of 9 amino acids from the N-terminus of 27mer (18mer : CAP18_<118-135>) resulted in a significant decrease in LPS-binding activity even though both terminuses are chemically modified. Increasing the hydrophobic amino acid residues (Leucin=L) in 18mer (18LL) increased LPS-binding activity (〜30-fold) and anti-microbial activity versus gram-positive bacteria such as MRSA (methicillin resistant staphylococcus aureus ; >3 -folds), however, 18LL could not protect vs. endotoxin shock in mice. Further replacement of three positions of 18LL by lysine (K) significantly increased LPS-binding activity (〜120-fold), antimicrobial activity vs. gram negative bacteria such as E.coli O157 : H7 and S.typhimurium, and protect mice from endotoxin shock.From these results, the importance of the stability of alpha-helical structure, and the balance of hydrophobic/ hydrophilic (basic) amino acid residues in CAP18 peptide was suggested.