包括吗啡和甲基苯丙胺在内的精神活性物质已被证明能够以非对映选择性方式与经典先天免疫受体 Toll 样受体 4 (TLR4) 及其伴侣蛋白骨髓分化蛋白 2 (MD2) 相互作用。 (-)-尼古丁是烟草中的主要生物碱，也是高度成瘾性香烟的关键成分，它以 TLR4/MD2 为目标，影响 TLR4 信号通路。作为两种对映体存在，TLR4/MD2 在先天免疫反应中对尼古丁的立体选择性识别仍不清楚。在这项研究中，我们合成了 ()-尼古丁，并研究了它与 (-)-尼古丁一起对脂多糖 (LPS) 诱导的 TLR4 信号传导的影响。 (-)-尼古丁剂量依赖性地抑制促炎因子，例如肿瘤坏死因子 α (TNF-α)、白细胞介素 6 (IL-6) 和环氧合酶-2 (COX-2)。相比之下，( )-尼古丁则没有表现出这种抑制作用。分子动力学模拟表明，(-)-尼古丁与 TLR4 辅助受体 MD2 的亲和力比 (-)-尼古丁更强。此外，计算机模拟显示，两种尼古丁对映体最初附着在 MD2 腔的入口处，在完全进入腔之前形成亚稳态。在亚稳态下，与( )-尼古丁相比，(-)-尼古丁在MD2腔入口处与周围残基建立了更稳定的相互作用。这凸显了 MD2 腔入口在尼古丁手性识别中的关键作用。这些发现为了解尼古丁对映体与 TLR4 辅助受体 MD2 之间的独特相互作用提供了有价值的见解，强调了尼古丁对调节 TLR4 信号传导的对映选择性作用。

Psychoactive substances, including morphine and methamphetamine, have been shown to interact with the classic innate immune receptor Toll-like receptor 4 (TLR4) and its partner protein myeloid differentiation protein 2 (MD2) in a nonenantioselective manner. (-)-Nicotine, the primary alkaloid in tobacco and a key component of highly addictive cigarettes, targets the TLR4/MD2, influencing TLR4 signaling pathways. Existing as two enantiomers, the stereoselective recognition of nicotine by TLR4/MD2 in the context of the innate immune response remains unclear. In this study, we synthesized (+)-nicotine and investigated its effects alongside (-)-nicotine on lipopolysaccharide (LPS)-induced TLR4 signaling. (-)-Nicotine dose-dependently inhibited proinflammatory factors such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and cyclooxygenase-2 (COX-2). In contrast, (+)-nicotine showed no such inhibitory effects. Molecular dynamics simulations revealed that (-)-nicotine exhibited a stronger affinity with the TLR4 coreceptor MD2 than (+)-nicotine. Additionally, in silico simulations revealed that both nicotine enantiomers initially attach to the entrance of the MD2 cavity, creating a metastable state before they fully enter the cavity. In the metastable state, (-)-nicotine established more stable interactions with the surrounding residues at the entrance of the MD2 cavity compared to those of (+)-nicotine. This highlights the crucial role of the MD2 cavity entrance in the chiral recognition of nicotine. These findings provide valuable insights into the distinct interactions between nicotine enantiomers and the TLR4 coreceptor MD2, underscoring the enantioselective effect of nicotine on modulating TLR4 signaling.