The pathogenesis of nonalcoholic steatohepatitis (NASH), a severe stage of nonalcoholic fatty liver disease, is complex and implicates multiple cell interactions. However, therapies for NASH that target multiple cell interactions are still lacking. Melatonin (MEL) alleviates NASH with mechanisms not yet fully understood. Thus, we herein investigate the effects of MEL on key cell types involved in NASH, including hepatocytes, macrophages, and stellate cells. In a mouse NASH model with feeding of a methionine and choline-deficient (MCD) diet, MEL administration suppressed lipid accumulation and peroxidation, improved insulin sensitivity, and attenuated inflammation and fibrogenesis in the liver. Specifically, MEL reduced proinflammatory cytokine expression and inflammatory signal activation and attenuated CD11C⁺CD206^– M1-like macrophage polarization in the liver of NASH mice. The reduction of proinflammatory response by MEL was also observed in the lipopolysaccharide-stimulated Raw264.7 cells. Additionally, MEL increased liver fatty acid β-oxidation, leading to reduced lipid accumulation, and restored the oleate-loaded primary hepatocytes. Finally, MEL attenuated hepatic stellate cell (HSC) activation and fibrogenesis in the liver of MCD-fed mice and in LX-2 human HSCs. In conclusion, MEL acts on multiple cell types in the liver to mitigate NASH-associated phenotypes, supporting MEL or its analog as potential treatment for NASH.

非酒精性脂肪性肝炎 (NASH) 是非酒精性脂肪性肝病的严重阶段，其发病机制很复杂，涉及多种细胞相互作用。然而，仍然缺乏针对多细胞相互作用的 NASH 疗法。褪黑激素 (MEL) 以尚未完全了解的机制减轻 NASH。因此，我们在此研究了 MEL 对参与 NASH 的关键细胞类型的影响，包括肝细胞、巨噬细胞和星状细胞。在喂食甲硫氨酸和胆碱缺乏 (MCD) 饮食的小鼠 NASH 模型中，MEL 给药抑制了脂质积累和过氧化，改善了胰岛素敏感性，并减轻了肝脏中的炎症和纤维化。具体来说，MEL 减少了促炎细胞因子的表达和炎症信号的激活，并减弱了 CD11C ⁺CD206 ^– NASH 小鼠肝脏中的 M1 样巨噬细胞极化。在脂多糖刺激的 Raw264.7 细胞中也观察到 MEL 减少了促炎反应。此外，MEL 增加了肝脏脂肪酸 β-氧化，导致脂质积累减少，并恢复了载有油酸盐的原代肝细胞。最后，MEL 减弱了 MCD 喂养小鼠肝脏和 LX-2 人 HSC 中肝星状细胞 (HSC) 的激活和纤维化。总之，MEL 作用于肝脏中的多种细胞类型以减轻 NASH 相关表型，支持 MEL 或其类似物作为 NASH 的潜在治疗方法。