Development of antiviral drugs from marine natural products and investigation of drug target against virus

• Main Authors: Chun-kuang Lin, 林俊光
• Other Authors: Chih-Chuang Liaw
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9s549w

博士 === 國立中山大學 === 海洋生物科技博士學位學程 === 106 === Hepatitis C virus (HCV) infection causes chronic inflammation of liver, leading to the development of cirrhosis and hepatocellular carcinoma (HCC). Infection of dengue virus (DENV) caused diseases ranging from acute self-limiting febrile illness to life-threatening dengue hemorrhagic fever and dengue shock syndrome. The purposes of present dissertation are to discover the anti-viral agents from marine natural products and to investigate the impact of cellular factors on DENV replication. For finding the potential antivirals, we found that betulinic acid (BA) and acteoside (AM-4) extracted from Avicennia marina could reduce HCV replication. The mechanism study demonstrated that BA reduced HCV replication through decreasing the NF-κB- and ERK1/2-mediated cyclooxygenase-2 (COX-2) expression. The AM-4 suppressed HCV infection by blocking viral entry into cells and cell-to-cell spread of HCV. In addition, we identified that lobohedleolide extracted from soft coral exhibited anti-HCV activity by suppression of HCV-induced COX-2 expression. Using various COX-2 promoter deletion constructs linked to luciferase reporter gene, we first identified CCAAT/enhancer-binding protein (C/EBP) as a key transcription factor for the down-regulation of COX-2 by lobohedleolide, and then demonstrated that the HCV-induced C/EBP expression could be suppressed by lobohedleolide through inhibiting the phosphorylation of JNK and c-Jun. Notably, combination treatment of BA, AM-4 and lobohedleolide with several clinically used HCV drugs synergistically inhibited HCV RNA replication, indicating that these three natural products exhibited a high biomedical potential to be used as a supplementary agent for control of HCV infection. Besides, BA and lobohedleolide also exhibited anti-DENV activity. For finding the therapeutic targets from cellular gene against DENV, we observed an increased level of COX-2 in patients with dengue fever compared with healthy individuals. Then, an elevated level of COX-2 expression was also observed in DENV-infected ICR suckling mice. COX-2 gene silencing and catalytic inhibition sufficiently suppressed DENV-2 replication. Using ICR suckling mouse model, we identified that the COX-2 inhibitor NS398 protected mice from succumbing to life-threatening DENV-2 infection, revealing targeting COX-2 is a promising strategy to control DENV infection. In addition, we found that the expression of prostasin, a serine protease, is lower in patients with dengue fever than in healthy individuals. Exogenous expression of prostasin could protect ICR suckling mice from life-threatening DENV-2 infection and reduce DENV-2 propagation in Huh-7 cells. We further revealed that prostasin reduced DENV replication through proteolytic cleavage of epithelial growth factor receptor (EGFR). The activity of proteolytic cleavage of prostasin is dependent on the expression of matriptase and hepatocyte growth factor activator inhibitor type 2 (HAI-2). Collectively, COX-2 and prostasin exhibited highly potential to serve as therapeutic targets against DENV replication.