Mechanisms Of Ebola Virus Infection Inhibition And Steatohepatitis Induced By Tamoxifen

Since the outbreak of Ebola haemorrhagic fever (EHF) in West Africa at the end of 2013, the epidemic has already caused more than ten thousand deaths. Currently, no Food and Drug Administration (FDA)-approved therapeutics exist to prevent/treat Ebola infections. For clinical application as soon as possible, many researchers screened drugs with anti-Ebola activity from ex-FDA approved drugs.80 drugs with anti-Ebola activity have been identified, including tamoxifen. However, the inhibitory mechanisms of these drugs against Ebola infection are elusive. Based on these, the present study attempts to clarify the specific mechanism of Ebola infection inhibition by tamoxifen, and provide a theoretical basis and reference for clinical application of these drugs to EHF patients.In this study, the results demonstrated that tamoxifen can selectively inhibit the release of Ebola pseudovirion from the two pore segment channel 2 positive (TPC2+) lysosome (Lys) into the cytoplasm, and this inhibition was independent of the estrogen receptor signaling pathway. Subsequently, we ruled out the possibility that tamoxifen inhibit the Ebola infection through interaction with NPC intracellular cholesterol transporter 1 (NPC1) domain A or C to disturb the interaction of NPC1 domain C with Ebola GP. Structurely,45 of 80 screened drugs with anti-Ebola activity are cationic amphiphilic drug (CAD), and many of them have been reported of the same adverse effects. So we speculated that the adverse effects and inhibition of Ebola infection were due to the structural properties of CAD. Subsequently, the results demonstrated that tamoxifen significantly reduced the cellular sphingosine, and induced the accumulation of calcium in late-endosome/lysosome (LE/Lys). Meanwhile, chelating LE/Lys calcium also selectively inhibited the Ebola release from the TPC2+ Lys. These results indicate that tamoxifen (even CAD) is most likely to reduce the cellular sphingosine, subsequently disrupting the LE/Lys calcium, thereby inhibiting the Ebola release from the LE/Lys, and inhibiting the Ebola infection.Tamoxifen inhibits the Ebola infection, meanwhile it has many reports of steatohepatitis during clinical application. But the mechanism of tamoxifen-induced steatohepatitis is still blurry. In this study, the results demonstrated that, besides to the accumulation of lipid, tamoxifen also increased the mRNA levels of inflammatory factors(IFN-β, IL-6, IL-8 and TNF-a) in human liver hepatocellular carcinoma cell line (HepG2), and induced the Toll-like receptor 4 (TLR4) accumulation in cytoplasm. Therefore, we speculated that, in addition to the direct effects of tamoxifen on lipid metabolism-related genes, tamoxifen may also disrupt the LE/Lys system, leading the accumulation of TLR4 in LE/Lys and activation of TLR4 signaling pathway to secrete inflammatory cytokines. Conversely, the sustained inflammation could aggravate the disorder of lipid metabolism, resulting in the steatohepatitis.Taken together, the mechanisms of Ebola infection inhibition and steatohepatitis induced by tamoxifen are that, the structural properties lead to the accumulation of tamoxifen in LE/Lys, disrupting the LE/Lys system, eventually leading to Ebola infection inhibition and steatohepatitis. These findings provide a theoretical basis and drug reference for the clinical application of tamoxifen to EHF patients, and provide a new direction for the further study of tamoxifen-induced steatohepatitis.