Department of Experimental Medicine, Pharmacology Division, University of Campania "L. Vanvitelli", 80138 Naples, Italy.
Institute of Biomolecular Chemistry (ICB) of National Research Council (CNR), 80078 Pozzuoli, Italy.
Int J Mol Sci. 2021 Feb 2;22(3):1491. doi: 10.3390/ijms22031491.
Toll-like receptors (TLRs) are key receptors through which infectious and non-infectious challenges act with consequent activation of the inflammatory cascade that plays a critical function in various acute and chronic diseases, behaving as amplification and chronicization factors of the inflammatory response. Previous studies have shown that synthetic analogues of lipid A based on glucosamine with few chains of unsaturated and saturated fatty acids, bind MD-2 and inhibit TLR4 receptors. These synthetic compounds showed antagonistic activity against TLR4 activation in vitro by LPS, but little or no activity in vivo. This study aimed to show the potential use of -palmitoyl-D-glucosamine (PGA), a bacterial molecule with structural similarity to the lipid A component of LPS, which could be useful for preventing LPS-induced tissue damage or even peripheral neuropathies. Molecular docking and molecular dynamics simulations showed that PGA stably binds MD-2 with a MD-2/(PGA)3 stoichiometry. Treatment with PGA resulted in the following effects: (i) it prevented the NF-kB activation in LPS stimulated RAW264.7 cells; (ii) it decreased LPS-induced keratitis and corneal pro-inflammatory cytokines, whilst increasing anti-inflammatory cytokines; (iii) it normalized LPS-induced miR-20a-5p and miR-106a-5p upregulation and increased miR-27a-3p levels in the inflamed corneas; (iv) it decreased allodynia in peripheral neuropathy induced by oxaliplatin or formalin, but not following spared nerve injury of the sciatic nerve (SNI); (v) it prevented the formalin- or oxaliplatin-induced myelino-axonal degeneration of sciatic nerve. SIGNIFICANCE STATEMENT We report that PGA acts as a TLR4 antagonist and this may be the basis of its potent anti-inflammatory activity. Being unique because of its potency and stability, as compared to other similar congeners, PGA can represent a tool for the optimization of new TLR4 modulating drugs directed against the cytokine storm and the chronization of inflammation.
Toll 样受体（TLRs）是关键的受体，通过它们，传染性和非传染性的挑战会随之而来，从而激活炎症级联反应，在各种急性和慢性疾病中发挥关键作用，作为炎症反应的放大和慢性化因素。先前的研究表明，基于几链不饱和和饱和脂肪酸的氨基葡萄糖的脂质 A 合成类似物与 MD-2 结合并抑制 TLR4 受体。这些合成化合物在体外通过 LPS 显示出对 TLR4 激活的拮抗活性，但在体内几乎没有或没有活性。本研究旨在展示 -棕榈酰-D-氨基葡萄糖（PGA）的潜在用途，PGA 是一种与 LPS 脂质 A 成分具有结构相似性的细菌分子，它可能有助于预防 LPS 诱导的组织损伤甚至周围神经病变。分子对接和分子动力学模拟表明，PGA 与 MD-2 稳定结合，MD-2/（PGA）3 比例。PGA 处理产生以下效果：（i）它防止 LPS 刺激的 RAW264.7 细胞中 NF-kB 的激活；（ii）它减少 LPS 诱导的角膜炎和角膜促炎细胞因子，同时增加抗炎细胞因子；（iii）它使 LPS 诱导的 miR-20a-5p 和 miR-106a-5p 上调正常化，并增加炎症角膜中的 miR-27a-3p 水平；（iv）它减少了奥沙利铂或甲醛诱导的周围神经病变中的痛觉过敏，但对坐骨神经（SNI）的 spared 神经损伤没有影响；（v）它防止了甲醛或奥沙利铂诱导的坐骨神经髓鞘轴突变性。意义陈述我们报告 PGA 作为 TLR4 拮抗剂发挥作用，这可能是其强大抗炎活性的基础。与其他类似同系物相比，PGA 因其效力和稳定性而具有独特性，PGA 可以作为一种工具，用于优化针对细胞因子风暴和炎症慢性化的新型 TLR4 调节药物。
