Lucidone suppresses dengue viral replication through the induction of heme oxygenase-1

Dengue virus (DENV) infection causes life-threatening diseases such as dengue hemorrhagic fever and dengue shock syndrome. Currently, there is no effective therapeutic agent or vaccine against DENV infection; hence, there is an urgent need to discover anti-DENV agents. The potential therapeutic efficacy of lucidone was first evaluated <i>in vivo</i> using a DENV-infected Institute of Cancer Research (ICR) suckling mouse model by monitoring body weight, clinical score, survival rate, and viral titer. We found that lucidone effectively protected mice from DENV infection by sustaining survival rate and reducing viral titers in DENV-infected ICR suckling mice. Then, the anti-DENV activity of lucidone was confirmed by western blotting and quantitative-reverse-transcription-polymerase chain reaction analysis, with an EC₅₀ value of 25 ± 3 μM. Lucidone significantly induced heme oxygenase-1 (HO-1) production against DENV replication by inhibiting DENV NS2B/3 protease activity to induce the DENV-suppressed antiviral interferon response. The inhibitory effect of lucidone on DENV replication was attenuated by silencing of HO-1 gene expression or blocking HO-1 activity. In addition, lucidone-stimulated nuclear factor erythroid 2-related factor 2 (Nrf2), which is involved in transactivation of HO-1 expression for its anti-DENV activity. Taken together, the mechanistic investigations revealed that lucidone exhibits significant anti-DENV activity in <i>in vivo</i> and <i>in vitro</i> by inducing Nrf2-mediated HO-1 expression, leading to blockage of viral protease activity to induce the anti-viral interferon (IFN) response. These results suggest that lucidone is a promising candidate for drug development.

登革病毒（Dengue virus, DENV）感染可引发登革出血热、登革休克综合征等致死性疾病。目前尚无针对DENV感染的有效治疗药物或疫苗，因此亟需发掘抗登革病毒制剂。本研究首先采用登革病毒感染的ICR（Institute of Cancer Research）品系乳鼠模型，通过监测小鼠体重、临床评分、存活率及病毒滴度，首次在体内评估了lucidone的潜在治疗功效。研究发现，在登革病毒感染的ICR品系乳鼠中，lucidone可通过维持小鼠存活率、降低病毒滴度，有效保护小鼠免受DENV感染。随后，通过蛋白质印迹法（Western blotting）与定量逆转录聚合酶链式反应分析，证实了lucidone的抗DENV活性，其半数有效浓度（EC₅₀）为25±3 μM。Lucidone可通过抑制DENV NS2B/3蛋白酶活性，逆转被DENV抑制的抗病毒干扰素应答，进而显著诱导血红素氧合酶-1（heme oxygenase-1, HO-1）的表达，发挥抗DENV复制的作用。若敲低HO-1基因表达或阻断HO-1活性，则可削弱lucidone对DENV复制的抑制作用。此外，lucidone可激活核因子红细胞2相关因子2（nuclear factor erythroid 2-related factor 2, Nrf2），而Nrf2参与HO-1表达的反式激活，这是lucidone发挥抗DENV活性的关键机制。综上，机制研究表明，lucidone可通过诱导Nrf2介导的HO-1表达，阻断病毒蛋白酶活性并激活抗病毒干扰素（IFN）应答，从而在体内及体外均展现出显著的抗DENV活性。上述研究结果表明，lucidone是一种极具开发潜力的抗登革病毒药物候选化合物。