| Summary: | 博士 === 國立東華大學 === 生命科學系 === 103 === In recent year, marine natural products have been emerging as a new era in drug development. The cembrane-type diterpenoids from soft corals belonging to the genus Sinularia, Chandonanthus and Sarcophyton have been reported as the new potent marine drugs. Cembrane-type diterpenoids can exhibit biological activities including antitumor, anti-inflammatory, neuroprotective, antibacterial, antivirual and cytotoxic activity. Chemical investigations on soft coral Lobophytum crassum have led to the isolation and identification of varieties of oxygenated cembrane-type diterpenoids. Here, we examined the immunomodulatory effects of marine cembrane-type compounds, (9E,13E)-5-acetoxy-6-hydroxy-9,13-dimethyl-3-methylene-3,3a,4,5,6,7,8,11,12,14a-decahydro-2H-cyclotrideca[b]furan-2-one (1), (9E,13E)-5-acetoxy-6-acetyl-9,13-dimethyl-3-methylene-3,3a,4,5,6,7,8,11,12,14a-decahydro-2H-cyclotrideca[b]furan-2-one (2), lobocrassin B (3), (−)14-deoxycrassin (4), cembranolide B (5) and 13-acetoxysarcocrassolide (6) isolated from a soft coral, Lobophytum crassum, on mouse bone marrow-derived dendritic cells (BMDCs). Dendritic cells (DCs) are antigen presenting cells, which can present antigens to T-cells and play an important role in linking innate and adaptive immunity. DC maturation can be induced by many stimuli, including pro-inflammatory cytokines and bacterial products, such as TNF-α and LPS. Our results revealed that cembrane-type diterpenoids, especially lobocrassin B, effectively inhibited LPS-induced BMDC activation by inhibiting the production of TNF-α. Pre-treatment of BMDCs with Lobocrassin B for 1 h is essential to prohibit the following activation induced by various toll-like receptor (TLR) agonists, such as LPS, zymosan, lipoteichoic acid (LTA) and Pam2CSK4. Inhibition of NF-κB nuclear translocation by lobocrassin B, which is a key transcription factor for cytokine production in TLR signaling, was evident as assayed by high-content image analysis. Lobocrassin B attenuated DC maturation and endocytosis as the expression levels of MHC class II and the co-stimulatory molecules were downregulated, which may affect the function of DCs to initiate the T-cell responses. Thus, the marine cembrane-type compounds with anti-inflammatory activities had also shown the immunomodulation effects on dendritic cells, which largely expanded the application profile of such amazing compounds in anti-inflammation and immune dysregulated diseases.
Another dimension of biological activities exerted by marine cembrane-type compounds was conducted to anti-viral research. Now, over forty antiviral compounds extracted from marine life forms are present in the pharmacological market. Some of these compounds are undergoing clinical and preclinical stages. Chemical and biological studies of the soft corals (Sinula riagyrosa, Sarcophyton ehrenbergi and Lobophytum crissum) had exhibited antiviral activities against Human cytomegalovirus (HCMV), but none was reported to exhibit anti- Japanese encephalitis virus (JEV) activities. JEV, an arbovirus transmitted by mosquito, can cause the neurological damage of the central nervous system in human. Although vaccines have been developed for the prevention of JEV infection, people once infected were hospitalized with flaviviral encephalitis and had no drug available for the treatment. The cembrane-type diterpenoids WS 9-5 and WS 9-7 were extracted from cultured soft corals Sinularia flexibilis, and were shown to have the potency to inhibit JEV infection. By JEV-infected cell based assay, WS 9-5 inhibited JEV NS1 expression with the EC50 of 28.24 μM (SI=3.64) in BHK cells and 22.74 (SI=3.08) in N18 cells while its potency (EC50) in reducing JEV double-stranded RNA (dsRNA) expression is about 26.74 μM (SI=3.85) and 16.98 μM (SI=4.12), respectively. The capability in the reduction of JEV infectious virus particle release was more profound in the treatment of WS 9-5 than that of WS 9-7, and both the therapeutic and preventive capabilities of WS 9-5 were demonstrated in JEV-infected cells either pretreated or posttreated with compounds in a time-dependent manner. Unexpectedly, pre-incubation of WS 9-5 or WS 9-7 with JEV not only substantially neutralizes virus binding to host cells but also effectively suppresses the JEV infection. Molecular docking was conducted to predict the interaction between JEV envelope protein and WS 9-5 or WS 9-7. Furthermore, the combination of both compounds has shown a significant inhibition of JEV NS1 expression as compared to WS 9-5 or WS 9-7 alone. Molecules participating in innate antiviral immunity were evaluated, the type I interferon beta (IFN-) seems not involved in WS 9-5 or WS 9-7-mediated JEV inhibition.
Collectively, these results suggest that cembrane-type diterpenoids extracted from soft coals may exert many biological activities, such as anti-inflammation, immunomodulation of DCs and antiviral activities, and may have the potential to be developed as the drugs for clinical applications in the future.
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