1School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor, Malaysia.
School of Biological Sciences, Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia.
Trop Biomed. 2019 Sep 1;36(3):776-791.
Malarial pathogenesis involves among others, uncontrolled or excessive cytokine production arising from dysregulated immune responses mounted by the host to eliminate the plasmodial parasite. The ubiquitous serine/threonine kinase, glycogen synthase kinase3β (GSK3β) is a crucial regulator of the balance between pro- and anti-inflammatory cytokine productions in the inflammatory response to pathogenic infections. Andrographolide, a bioactive compound in Andrographis paniculata, displays GSK3- inhibitory effects. A previous study elsewhere has shown that this compound has antimalarial activity but the molecular basis of its action is yet to be elucidated. Here we aimed to study the anti-malarial activity of andrographolide in a murine model of malarial infection to investigate whether its mechanism of action involves cytokine modulation and inhibition of GSK3β. Andrographolide showed strong and selective anti-plasmodial activity (IC = 13.70±0.71 µM; SI = 30.43) when tested against cultures of P. falciparum 3D7. Intraperitoneal administration of andrographolide (5 mg/kg body weight (bw)) into P. berghei NK65-infected ICR mice resulted in chemo-suppression of 60.17±2.12%, and significantly (P<0.05) improved median survival time of infected mice compared to nontreated control. In addition, andrographolide treatment significantly (P<0.05) decreased the level of serum pro-inflammatory cytokine, IFN-γ (1.4-fold) whilst the anti-inflammatory cytokines, IL-10 and IL-4 were increased 2.3- and 2.6-fold respectively. Western blot analyses revealed that andrographolide treatment of P. berghei NK65-infected mice resulted in an increased level of phosphorylated GSK3β (Ser9) in liver of infected mice. Andrographolide administration also decreased the levels of phosphorylated NF-κB p65 (Ser536) and phosphorylated Akt (Ser473) in liver of malaria- infected animals. Taken together, our findings demonstrate that the cytokine-modulating effect of andrographolide in experimental malarial infection involves at least in part inhibition of NF-κB activation as a consequence of GSK3β inhibition. Based on its cytokine-modulating effects, andrographolide is thus a plausible candidate for adjunctive therapy in malaria subject to clinical evaluations.
疟原虫病的发病机制包括宿主对疟原虫寄生虫的免疫反应失调导致的不受控制或过度的细胞因子产生。广泛存在的丝氨酸/苏氨酸激酶糖原合酶激酶 3β（GSK3β）是炎症反应中促炎和抗炎细胞因子产生平衡的关键调节剂。穿心莲内酯是穿心莲中的一种生物活性化合物，具有抑制 GSK3-β的作用。之前的一项研究表明，这种化合物具有抗疟原虫活性，但作用机制尚不清楚。在这里，我们旨在研究穿心莲内酯在疟原虫感染的小鼠模型中的抗疟原虫活性，以研究其作用机制是否涉及细胞因子调节和 GSK3β抑制。当测试对 3D7 培养的疟原虫时，穿心莲内酯表现出强烈和选择性的抗疟原虫活性（IC = 13.70±0.71 µM；SI = 30.43）。腹腔内给予 5mg/kg 体重（bw）的穿心莲内酯到 P. berghei NK65 感染的 ICR 小鼠中，导致化学抑制率为 60.17±2.12%，与未治疗的对照组相比，感染小鼠的中位生存时间显著（P<0.05）提高。此外，穿心莲内酯治疗显著（P<0.05）降低了血清促炎细胞因子 IFN-γ的水平（1.4 倍），而抗炎细胞因子 IL-10 和 IL-4 分别增加了 2.3 倍和 2.6 倍。Western blot 分析显示，穿心莲内酯处理 P. berghei NK65 感染的小鼠导致感染小鼠肝脏中磷酸化 GSK3β（Ser9）水平升高。穿心莲内酯给药还降低了疟疾感染动物肝脏中磷酸化 NF-κB p65（Ser536）和磷酸化 Akt（Ser473）的水平。总之，我们的研究结果表明，穿心莲内酯在实验性疟原虫感染中的细胞因子调节作用至少部分涉及 NF-κB 激活的抑制，这是 GSK3β 抑制的结果。基于其细胞因子调节作用，穿心莲内酯是疟疾辅助治疗的潜在候选药物，有待临床评估。
