Sino‑French Hoffmann Institute, Guangzhou Medical University, Guangzhou, 511436, Guangdong, People's Republic of China.
Université de Strasbourg, M3I UPR9022 du CNRS, 67000, Strasbourg, France.
Parasit Vectors. 2021 May 25;14(1):279. doi: 10.1186/s13071-021-04790-7.
Hepatic stellate cell (HSC) activation plays a pivotal role in hepatic inflammation and liver fibrosis. TLR4 pathway activation has been reported to be involved in mice liver fibrosis induced by hepatitis virus infection, alcohol abuse, biliary ligation, carbon tetrachloride 4 treatment, and Schistosoma japonicum (Sj) infection. The effect and mechanisms of the cyclooxygenase 2 (COX2)/prostanoid E2 (PGE2) axis on liver fibrosis induced by Sj are still unclear.
Mice liver fibrosis were induced by cutaneous infection of Sj cercariae. COX-2 inhibitor, NS398 were injected from week 5 to week 7, while TLR4 inhibitor TAK242 were injected from week 4 to week 8 post Sj infection. Human HSCs line, LX-2 cells were cultured and exposed to LPS or synthetic PGE2, or pretreated by TAK242, TLR4-siRNA or NS398. Liver tissue and serum or in vitro cultured cell lysaste were collected at indicated time courses for exploring the relationship between TLR4 and COX2-PGE2 axis through qPCR, western blot, immunohistochemical assay, ect. One-way analysis of variance among multiple groups followed by Uncorrected Fisher's LSD-t test or paired comparisons through t test were performed to tell the statistical differences.
This study investigated the link between the COX2/PGE2 axis and TLR4 signaling in the induction of liver fibrogenesis in mice during Sj infection and in vitro culture of HSC strain-LX-2. The COX2/PGE2 axis was positively associated with Sj-induced liver fibrosis. TLR4 pathway activation stimulated the COX2/PGE2 axis in Sj-infected mice and in lipopolysaccharide (LPS)-exposed cultured HSCs. Synthetic PGE2 activated cultured HSCs through upregulation of alpha smooth muscle actin (α-SMA) expression. In LPS-triggered HSCs, NS398, a COX2 inhibitor, led to suppression of PGE2 synthesis and reduced expression of α-SMA and type I collagen (COL I).
These results indicate firstly the positive association of the COX2/PGE2 axis with liver fibrosis induced by Sj infection. TLR4 signaling may at least partially control the COX2/PGE2 axis in Sj-infected mice liver and in vitro cultured HSCs. The COX2/PGE2-EP2/EP4 axis might be a good drug target against liver fibrosis induced by Sj infection.
肝星状细胞（HSC）的激活在肝炎症和肝纤维化中起着关键作用。TLR4 途径的激活已被报道参与乙型肝炎病毒感染、酒精滥用、胆管结扎、四氯化碳 4 处理和日本血吸虫（Sj）感染引起的小鼠肝纤维化。环氧化酶 2（COX2）/前列腺素 E2（PGE2）轴对 Sj 诱导的肝纤维化的作用及其机制尚不清楚。
通过 Sj 尾蚴皮肤感染诱导小鼠肝纤维化。从 Sj 感染后第 5 周到第 7 周注射 COX-2 抑制剂 NS398，从第 4 周到第 8 周注射 TLR4 抑制剂 TAK242。培养人 HSC 系 LX-2 细胞，并用 LPS 或合成 PGE2 或用 TAK242、TLR4-siRNA 或 NS398 预处理，在不同时间点收集肝组织和血清或体外培养细胞裂解物，通过 qPCR、western blot、免疫组化等方法探讨 TLR4 与 COX2-PGE2 轴的关系。采用单因素方差分析，再采用未校正 Fisher LSD-t 检验进行多组间比较，或采用配对 t 检验进行组内比较，以确定统计学差异。
本研究探讨了 Sj 感染诱导的肝纤维化小鼠模型及体外培养的 HSC 株-LX-2 中 COX2/PGE2 轴与 TLR4 信号之间的关系。COX2/PGE2 轴与 Sj 诱导的肝纤维化呈正相关。TLR4 途径激活刺激 Sj 感染小鼠和脂多糖（LPS）暴露培养的 HSCs 中的 COX2/PGE2 轴。合成的 PGE2 通过上调α平滑肌肌动蛋白（α-SMA）表达激活培养的 HSCs。在 LPS 触发的 HSCs 中，COX2 抑制剂 NS398 导致 PGE2 合成减少，α-SMA 和 I 型胶原（COL I）表达减少。
这些结果首先表明 COX2/PGE2 轴与 Sj 感染诱导的肝纤维化呈正相关。TLR4 信号可能至少部分控制 Sj 感染小鼠肝脏和体外培养的 HSCs 中的 COX2/PGE2 轴。COX2/PGE2-EP2/EP4 轴可能是 Sj 感染诱导肝纤维化的一个很好的药物靶点。
