Department of Microbiology and Immunology, Indiana University School of Medicine, 2101 E. Coliseum Boulevard, Fort Wayne, IN, 46805, USA.
Department of Pharmaceutical Sciences, Manchester University College of Pharmacy, Natural and Health Sciences, Fort Wayne, IN, USA.
J Neuroinflammation. 2021 May 11;18(1):110. doi: 10.1186/s12974-021-02143-w.
Multiple sclerosis (MS) is a progressive autoimmune disease characterized by the accumulation of pathogenic inflammatory immune cells in the central nervous system (CNS) that subsequently causes focal inflammation, demyelination, axonal injury, and neuronal damage. Experimental autoimmune encephalomyelitis (EAE) is a well-established murine model that mimics the key features of MS. Presently, the dietary consumption of foods rich in phenols has been reported to offer numerous health benefits, including anti-inflammatory activity. One such compound, 4-ethylguaiacol (4-EG), found in various foods, is known to attenuate inflammatory immune responses. However, whether 4-EG exerts anti-inflammatory effects on modulating the CNS inflammatory immune responses remains unknown. Thus, in this study, we assessed the therapeutic effect of 4-EG in EAE using both chronic and relapsing-remitting animal models and investigated the immunomodulatory effects of 4-EG on neuroinflammation and Th1/Th17 differentiation in EAE.
Chronic C57BL/6 EAE and relapsing-remitting SJL/J EAE were induced followed by 4-EG treatment. The effects of 4-EG on disease progression, peripheral Th1/Th17 differentiation, CNS Th1/Th17 infiltration, microglia (MG) activation, and blood-brain barrier (BBB) disruption in EAE were evaluated. In addition, the expression of MMP9, MMP3, HO-1, and Nrf2 was assessed in the CNS of C57BL/6 EAE mice.
Our results showed that 4-EG not only ameliorated disease severity in C57BL/6 chronic EAE but also mitigated disease progression in SJL/J relapsing-remitting EAE. Further investigations of the cellular and molecular mechanisms revealed that 4-EG suppressed MG activation, mitigated BBB disruption, repressed MMP3/MMP9 production, and inhibited Th1 and Th17 infiltration in the CNS of EAE. Furthermore, 4-EG suppressed Th1 and Th17 differentiation in the periphery of EAE and in vitro Th1 and Th17 cultures. Finally, we found 4-EG induced HO-1 expression in the CNS of EAE in vivo as well as in MG, BV2 cells, and macrophages in vitro.
Our work demonstrates that 4-EG confers protection against autoimmune disease EAE through modulating neuroinflammation and inhibiting Th1 and Th17 differentiation, suggesting 4-EG, a natural compound, could be potentially developed as a therapeutic agent for the treatment of MS/EAE.
多发性硬化症（MS）是一种进行性自身免疫性疾病，其特征是致病性炎症免疫细胞在中枢神经系统（CNS）中积聚，随后导致局灶性炎症、脱髓鞘、轴突损伤和神经元损伤。实验性自身免疫性脑脊髓炎（EAE）是一种成熟的小鼠模型，可模拟 MS 的关键特征。目前，据报道，富含酚类物质的食物的饮食摄入可带来多种健康益处，包括抗炎活性。4-乙基愈创木酚（4-EG）是一种存在于各种食物中的化合物，可减轻炎症免疫反应。然而，4-EG 是否通过调节 CNS 炎症免疫反应发挥抗炎作用尚不清楚。因此，在这项研究中，我们使用慢性和复发缓解型动物模型评估了 4-EG 在 EAE 中的治疗效果，并研究了 4-EG 对 EAE 中神经炎症和 Th1/Th17 分化的免疫调节作用。
诱导 C57BL/6 慢性 EAE 和 SJL/J 复发缓解型 EAE 后进行 4-EG 治疗。评估 4-EG 对 EAE 疾病进展、外周 Th1/Th17 分化、CNS Th1/Th17 浸润、小胶质细胞（MG）激活和血脑屏障（BBB）破坏的影响。此外，还评估了 C57BL/6 EAE 小鼠中枢神经系统中 MMP9、MMP3、HO-1 和 Nrf2 的表达。
我们的结果表明，4-EG 不仅改善了 C57BL/6 慢性 EAE 的疾病严重程度，而且减轻了 SJL/J 复发缓解型 EAE 的疾病进展。对细胞和分子机制的进一步研究表明，4-EG 抑制了 MG 激活，减轻了 BBB 破坏，抑制了 MMP3/MMP9 的产生，并抑制了 EAE 中枢神经系统中的 Th1 和 Th17 浸润。此外，4-EG 抑制了 EAE 外周和体外 Th1 和 Th17 培养物中的 Th1 和 Th17 分化。最后，我们发现 4-EG 在体内 EAE 以及体外 MG、BV2 细胞和巨噬细胞中诱导了 HO-1 的表达。
我们的工作表明，4-EG 通过调节神经炎症和抑制 Th1 和 Th17 分化来预防自身免疫性疾病 EAE，表明 4-EG 作为一种天然化合物，可能被开发为治疗 MS/EAE 的治疗剂。
