藥物再利用 (Drug repurposing) 是一種藥物開發的策略，提供已知化學品新的使用途徑，可以增加化學品的應用性並降低研究成本。目前在抗登革病毒藥物的發展中也應用此概念，測試各種已知作用目標的小分子抑制劑，對抗登革病毒感染的可能性。針對組蛋白甲基轉移酶的抑制劑，已被證明可以抑制同為黃質病毒屬的茲卡病毒。在本篇研究中，我們發現一個原先利用在干擾人類泡疹病毒再活化的去甲基酶抑制劑 ML324，可以有效降低登革病毒 RNA 、蛋白的表現以及感染效價，並且無需透過細胞內的作用目標 JMJD2 蛋白，而以新的途徑抑制登革病毒感染。藉由登革病毒持續感染的細胞 N18/D2p 與攜帶登革病毒複製子的細胞株 DV2-SGR 中，我們發現 ML324 不影響病毒 RNA 的複製。透過病毒黏附的試驗，我們發現預先給予細胞 ML324 的處理，在短時間內就能夠有效抑制登革病毒黏附到細胞的能力；對於表面蛋白已由胰蛋白酶處理過的細胞， ML324 抗病毒的效果則明顯下降。因此我們認為 ML324 可能是以細胞表面受器為標的，直接抑制登革病毒感染的抑制劑。儘管目前對於 ML324 的瞭解是調控細胞甲基化修飾的分子，未來或許可以針對 ML324 結構為模板，進一步的修改，提供發展抗登革病毒藥物的新方向。
關鍵字: 登革病毒、組蛋白去甲基酶抑制劑

Drug repurposing is a concept investigating existing chemicals for new therapeutic purposes. Epigenetic modifiers might turn genes on or off that have been repurposed as candidates suppressing DNA and RNA viruses, but little about dengue virus (DENV). Here we treated the DENV-infected human A549 cells with chemicals modulating histone methylation to explore the role of histone methylation in DENV infection. Among the four chemicals we tested, the histone demethylase inhibitor ML324, a suppressor of herpes simplex virus reactivation, could reduce all the levels of DENV RNA, proteins, and titers in a dose-dependent manner. The anti-DENV effect was also observed in cells silencing the expression of ML324 targeting histone demethylase JMJD2, implying that ML324 may inhibit DENV directly. By using N18 cells persistently infected with DENV and cells harboring a DENV replicon DV2-SGR, we found ML324 failed to impair DENV RNA replication. Unexpectedly, we found the pretreatment of ML324 in short time effectively inhibited the DENV binding to the cell surface at 4 °C. The anti-DENV effect of ML324 was diminished in the trypsin-treated cells with most surface protein digested, suggesting that ML324 might inhibit DENV infection by directly targeting cell surface receptors. In conclusion, an unexpected anti-DENV effect of ML324 might suppress DENV infection by interfering with multiple steps of its lifecycle, including binding. Despite ML324 mainly regulating histone methylation in current understanding, the structure of ML324 might provide a reference backbone for anti-DENV agent development.
Keywords: dengue virus, histone demethylase inhibitor, ML324

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