Histone deacetylase 6 (HDAC6) is a potential target for Alzheimer's disease (AD). In this study, a series of novel phenothiazine-, memantine-, and 1,2,3,4-tetrahydro-γ-carboline-based HDAC6 inhibitors with a variety of linker moieties were designed and synthesized. As a hydrochloride salt, the phenothiazine-based hydroxamic acid W5 with a pyridyl-containing linker motif was identified as a high potent and selective HDAC6 inhibitor. It inhibited HDAC6 with an IC₅₀ of 2.54 nM and was more than 290- to 3300-fold selective over other HDAC isoforms. In SH-SY5Y cells, W5 dose-dependently increased the acetylated α-tubulin levels and reduced the hyperphosphorylated tau proteins at Ser396. As an effective metal chelator, W5 inhibited Cu²⁺-induced Aβ_1–42 aggregation and disaggregated Cu²⁺-Aβ₁₋₄₂ oligomers, and showed protective effects on the SH-SY5Y cells against Aβ_1–42- as well as Cu²⁺-Aβ_1–42 induced cell damages, serving as a potential ligand to target AD metal dyshomeostasis. Moreover, W5 promoted the differentiated neuronal neurite outgrowth, increased the mRNA expression of the recognized neurogenesis markers, GAP43, N-myc, and MAP-2. Therefore, W5 might be a good lead for the development of novel HDAC6 inhibitors targeting multi-facets of AD.

组蛋白脱乙酰酶 6 (HDAC6) 是阿尔茨海默病 (AD) 的潜在靶标。在本研究中，设计并合成了一系列新型吩噻嗪、美金刚和 1,2,3,4-四氢-γ-咔啉基 HDAC6 抑制剂，具有多种连接基团。作为盐酸盐，具有含吡啶基的接头基序的吩噻嗪基异羟肟酸W5被鉴定为高效和选择性的 HDAC6 抑制剂。它抑制 HDAC6 的 IC ₅₀为 2.54 nM，其选择性比其他 HDAC 同种型高 290 至 3300 倍。在 SH-SY5Y 细胞中，W5剂量依赖性地增加乙酰化 α-微管蛋白水平并减少 Ser396 位点的过度磷酸化 tau 蛋白。作为一种有效的金属螯合剂，W5可抑制 Cu²⁺ -诱导的 Aβ _1-42聚集和解聚的 Cu ²⁺ -Aβ _1-42寡聚体，并对 SH-SY5Y 细胞对 Aβ _1-42 - 以及 Cu ²⁺ -Aβ _1-42诱导的细胞具有保护作用损伤，作为靶向 AD 金属失调的潜在配体。此外，W5促进了分化的神经元神经突生长，增加了公认的神经发生标志物 GAP43、N-myc 和 MAP-2 的 mRNA 表达。因此，W5可能是开发针对 AD 多方面的新型 HDAC6 抑制剂的良好先导。