LPS from Rhizobiumsin-1 (R.sin-1) can antagonize the production of tumor necrosis factor alpha (TNF-α) by E. coli LPS in human monocytic cells. Therefore these compounds provide interesting leads for the development of therapeutics for the prevention or treatment of septic shock. Detailed structure activity relationship studies have, however, been hampered by the propensity of these compounds to undergo β-elimination to give biological inactive enone derivatives. To address this problem, we have chemically synthesized in a convergent manner a R.sin-1 lipid A derivative in which the β-hydroxy ester at C-3 of the proximal sugar unit has been replaced by an ether linked moiety. As expected, this derivative exhibited a much-improved chemical stability. Furthermore, its ability to antagonize TNF-α production induced by enteric LPS was only slightly smaller than that of the parent ester modified derivative demonstrating that the ether-linked lipids affect biological activities only marginally. Furthermore, it has been shown for the first time that R.sin-1 LPS and the ether modified lipid A are also able to antagonize the production of the cytokine interferon-inducible protein 10, which arises from the TRIF-dependent pathway. The latter pathway was somewhat more potently inhibited than the MyD88-dependent pathway. Furthermore, it was observed that the natural LPS possesses much greater activity than the synthetic and isolated lipid As, which indicates that di-KDO moiety is important for optimal biological activity. It has also been found that isolated R.sin-1 LPS and lipid A agonize a mouse macrophage cell line to induce the production of TNF-α and interferon beta in a Toll-like receptor 4-dependent manner demonstrating species specific properties.
根瘤菌素-1(R.sin-1)中的 LPS 可拮抗大肠杆菌 LPS 在人类单核细胞中产生的肿瘤坏死因子α(TNF-α)。因此,这些化合物为开发预防或治疗脓毒性休克的疗法提供了有趣的线索。然而,由于这些化合物容易发生 β-消除反应,生成无
生物活性的烯酮衍
生物,因此阻碍了详细的结构活性关系研究。为了解决这个问题,我们以聚合的方式
化学合成了一种 R.sin-1 脂质 A 衍
生物,其中近端糖单元 C-3 上的β-羟基酯被一个醚连接分子取代。不出所料,这种衍
生物的
化学稳定性大大提高。此外,它拮抗肠道 LPS 诱导的 TNF-α 生成的能力仅略低于母体酯修饰衍
生物,这表明醚键脂质对
生物活性的影响微乎其微。此外,研究首次表明,R.sin-1 LPS 和经醚修饰的脂质 A 还能拮抗细胞因子干扰素诱导蛋白 10 的产生,而干扰素诱导蛋白 10 是由 TRIF 依赖性途径产生的。与依赖 MyD88 的途径相比,后者的抑制作用更强。此外,还观察到天然 LPS 的活性远高于合成和分离脂质 As,这表明二 KDO 分子对最佳
生物活性非常重要。研究还发现,分离出的 R.sin-1 LPS 和脂质 A 可激动小鼠巨噬
细胞系,以 Toll 样受体 4 依赖性方式诱导 TNF-α 和干扰素 beta 的产生,这表明了物种特异性。