Department of Clinical Nutrition, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, Nanjing 210008, P.R. China.
Department of Gastroenterology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, Nanjing 210008, P.R. China.
Inflamm Bowel Dis. 2023 Dec 5;29(12):1929-1940. doi: 10.1093/ibd/izad099.
Honokiol (HKL), a natural extract of the bark of the magnolia tree and an activator of the mitochondrial protein sirtuin-3 (SIRT3), has been proposed to possess anti-inflammatory effects. This study investigated the inhibitory effects of HKL on T helper (Th) 17 cell differentiation in colitis.
Serum and biopsies from 20 participants with ulcerative colitis (UC) and 18 healthy volunteers were collected for the test of serum cytokines, flow cytometry analysis (FACS), and relative messenger RNA (mRNA) levels of T cell subsets, as well as the expression of SIRT3 and phosphorylated signal transducer and activator of transcription/retinoic acid-related orphan nuclear receptor γt (p-STAT3/RORγt) signal pathway in colon tissues. In vitro, naïve clusters of differentiation (CD) 4 + T cells isolated from the mouse spleen differentiated to subsets including Th1, Th2, Th17, and regulatory T (Treg) cells. Peripheral blood monocytes (PBMCs) from healthy volunteers were induced to the polarization of Th17 cells. After HKL treatment, changes in T cell subsets, related cytokines, and transcription factors were measured. The dextran sulfate sodium (DSS)-induced colitis and interleukin (IL)-10-deficient mice were intraperitoneally injected with HKL. These experiments were conducted to study the effect of HKL on the development, cytokines, and expression of signaling pathway proteins in colitis.
Patients with UC had higher serum IL-17 and a higher proportion of Th17 differentiation in blood compared with healthy participants; while IL-10 level and the proportion of Treg cells were lower. Higher relative mRNA levels of RORγt and a lower SIRT3 expression in colon tissues were observed. In vitro, HKL had little effect on the differentiation of naïve CD4+ T cells to Th1, Th2, or Treg cells, but it downregulated IL-17 levels and the Th17 cell ratio in CD4+ T cells from the mouse spleen and human PBMCs under Th17 polarization. Even with a STAT3 activator, HKL still significantly inhibited IL-17 levels. In DSS-induced colitis mice and IL-10 deficient mice treated with HKL, the length of the colon, weight loss, disease activity index, and histopathological scores were improved, IL-17 and IL-21 levels, and the proportion of Th17 cells were decreased. Sirtuin-3 expression was increased, whereas STAT3 phosphorylation and RORγt expression were inhibited in the colon tissue of mice after HKL treatment.
Our study demonstrated that HKL could partially protect against colitis by regulating Th17 differentiation through activating SIRT3, leading to inhibition of the STAT3/RORγt signaling pathway. These results provide new insights into the protective effects of HKL against colitis and may facilitate the research of new drugs for inflammatory bowel disease.
厚朴酚（HKL）是从木兰树皮中提取的天然产物，也是线粒体蛋白 SIRT3 的激活剂，被认为具有抗炎作用。本研究旨在探讨 HKL 对结肠炎中辅助性 T 细胞 17（Th17）分化的抑制作用。
收集 20 例溃疡性结肠炎（UC）患者和 18 名健康志愿者的血清和活检组织，用于检测血清细胞因子、流式细胞术分析（FACS）以及 T 细胞亚群的相对信使 RNA（mRNA）水平，同时检测结肠组织中 SIRT3 和磷酸化信号转导子和转录激活子/维甲酸相关孤儿核受体γt（p-STAT3/RORγt）信号通路的表达。体外，从小鼠脾脏分离的幼稚 CD4+T 细胞分化为 Th1、Th2、Th17 和调节性 T（Treg）细胞等亚群。来自健康志愿者的外周血单核细胞（PBMCs）被诱导极化形成 Th17 细胞。经 HKL 处理后，检测 T 细胞亚群、相关细胞因子和转录因子的变化。采用葡聚糖硫酸钠（DSS）诱导结肠炎和白细胞介素（IL）-10 缺陷型小鼠腹腔内注射 HKL，以研究 HKL 对结肠炎发展、细胞因子和信号通路蛋白表达的影响。
UC 患者的血清 IL-17 水平和血液中 Th17 分化比例高于健康参与者，而 IL-10 水平和 Treg 细胞比例较低。结肠组织中 RORγt 的相对 mRNA 水平较高，SIRT3 的表达水平较低。体外，HKL 对幼稚 CD4+T 细胞向 Th1、Th2 或 Treg 细胞的分化影响较小，但可下调 Th17 极化时 CD4+T 细胞中 IL-17 水平和 Th17 细胞比例。即使使用 STAT3 激活剂，HKL 仍能显著抑制 IL-17 水平。在 DSS 诱导的结肠炎小鼠和 IL-10 缺陷型小鼠中，HKL 治疗可改善结肠长度、体重减轻、疾病活动指数和组织病理学评分，降低 IL-17 和 IL-21 水平及 Th17 细胞比例。HKL 治疗后，小鼠结肠组织中 Sirtuin-3 表达增加，STAT3 磷酸化和 RORγt 表达受到抑制。
本研究表明，HKL 通过激活 SIRT3 部分调节 Th17 分化，从而抑制 STAT3/RORγt 信号通路，对结肠炎具有一定的保护作用。这些结果为 HKL 对结肠炎的保护作用提供了新的见解，并可能为炎症性肠病的新药研究提供帮助。
