Chaetocin reactivates the lytic replication of Epstein-Barr virus from latency via reactive oxygen species

Epstein-Barr virus as a potentiator of autoimmune diseases

The Epstein-Barr virus (EBV) is epidemiologically associated with development of autoimmune diseases, including systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis and multiple sclerosis. Although there is well-established evidence for this association, the underlying mechanistic basis remains incompletely defined. In this Review, we discuss the role of EBV infection as a potentiator of autoimmune rheumatic diseases. We review the EBV life cycle, viral transcription programmes, serological profiles and lytic reactivation. We discuss the epidemiological and mechanistic associations of EBV with systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis and multiple sclerosis. We describe the potential mechanisms by which EBV might promote autoimmunity, including EBV nuclear antigen 1-mediated molecular mimicry of human autoantigens; EBV-mediated B cell reprogramming, including EBV nuclear antigen 2-mediated dysregulation of autoimmune susceptibility genes; EBV and host genetic factors, including the potential for autoimmunity-promoting strains of EBV; EBV immune evasion and insufficient host responses to control infection; lytic reactivation; and other mechanisms. Finally, we discuss the therapeutic implications and potential therapeutic approaches to targeting EBV for the treatment of autoimmune disease.

Chaetocin exhibits anticancer effects in esophageal squamous cell carcinoma via activation of Hippo pathway

Dysfunction of the Hippo pathway is common in esophageal squamous carcinoma (ESCC). Chaetocin, a small molecular compound isolated from the marine fungus, exhibits potent anticancer effects. However, the anticancer effects of chaetocin on ESCC and its potential relationship to Hippo pathway remain unclear. Here, we demonstrated that chaetocin dramatically inhibited the proliferation in ESCC cells by causing cycle arrest in the M phase and activating the caspase-dependent apoptosis signaling pathway in vitro, and we also found that chaetocin induced the accumulation cellular reactive oxygen species (ROS). The RNA-seq analysis indicated that the Hippo pathway is one of the most enriched pathways after chaetocin treatment. We further revealed that chaetocin triggered the activation of Hippo pathway in ESCC cells, which is characterized by elevated phosphorylation levels of almost all core proteins in Hippo pathway, such as MST1 (Thr183), MST2 (Thr180), MOB1 (Thr35), LAST1 (Thr1079 and Ser909) and YAP (Ser127), ultimately leading to decreased nuclear translocation of YAP. Moreover, the MST1/2 inhibitor XMU-MP-1 not only partially rescued the inhibitory effect chaetocin-induced proliferation, but also rescued the chaetocin-induced apoptosis in ESCC cells. Furthermore, in vivo results confirmed the antitumor effect of chaetocin and its relationship with Hippo pathway. Taken together, our study demonstrates that chaetocin exhibits anticancer effects in ESCC via activation of Hippo pathway. These results provide an important basis for further research of chaetocin as a potential candidate for ESCC treatment.

T cell-mediated immunity during Epstein-Barr virus infections in children

Epstein-Barr virus (EBV) infection is extremely common worldwide, with approximately 90% of adults testing positive for EBV antibodies. Human are susceptible to EBV infection, and primary EBV infection typically occurs early in life. EBV infection can cause infectious mononucleosis (IM) as well as some severe non-neoplastic diseases, such as chronic active EBV infection (CAEBV) and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which can have a heavy disease burden. After primary EBV infection, individuals develop robust EBV-specific T cell immune responses, with EBV-specific CD8⁺ and part of CD4⁺ T cells functioning as cytotoxic T cells, defending against virus. Different proteins expressed during EBV's lytic replication and latent proliferation can cause varying degrees of cellular immune responses. Strong T cell immunity plays a key role in controlling infection by decreasing viral load and eliminating infected cells. However, the virus persists as latent infection in EBV healthy carriers even with robust T cell immune response. When reactivated, it undergoes lytic replication and then transmits virions to a new host. Currently, the relationship between the pathogenesis of lymphoproliferative diseases and the adaptive immune system is still not fully clarified and needs to be explored in the future. Investigating the T cell immune responses evoked by EBV and utilizing this knowledge to design promising prophylactic vaccines are urgent issues for future research due to the importance of T cell immunity.

The Human Cytomegalovirus β2.7 Long Non-Coding RNA Prevents Induction of Reactive Oxygen Species to Maintain Viral Gene Silencing during Latency

Human cytomegalovirus (HCMV) is a significant source of disease for the immunosuppressed and immunonaive. The treatment of HCMV is made more problematic by viral latency, a lifecycle stage in which the virus reduces its own gene expression and produces no infectious virus. The most highly expressed viral gene during HCMV latency is the viral β2.7 long non-coding RNA. Although we have recently shown that the β2.7 lncRNA lowers levels of reactive oxygen species (ROS) during infection in monocytes, how this impacts latency is unclear. We now show that β2.7 is important for establishing and maintaining HCMV latency by aiding the suppression of viral lytic gene expression and that this is directly related to its ability to quench reactive oxygen species (ROS). Consistent with this, we also find that exogenous inducers of ROS cause reactivation of latent HCMV. These effects can be compensated by treatment with an antioxidant to lower ROS levels. Finally, we show that ROS-mediated reactivation is independent of myeloid differentiation, but instead relies on NF-κB activation. Altogether, these results reveal a novel factor that is central to the complex process that underpins HCMV latency. These findings may be of particular relevance in the transplant setting, in which transplanted tissue/organs are subject to very high ROS levels, and HCMV reactivation poses a significant threat.

ROS/JNK/C-Jun Pathway is Involved in Chaetocin Induced Colorectal Cancer Cells Apoptosis and Macrophage Phagocytosis Enhancement

There is an urgent need for novel agents for colorectal cancer (CRC) due to the increasing number of cases and drug-resistance related to current treatments. In this study, we aim to uncover the potential of chaetocin, a natural product, as a chemotherapeutic for CRC treatment. We showed that, regardless of 5-FU-resistance, chaetocin induced proliferation inhibition by causing G2/M phase arrest and caspase-dependent apoptosis in CRC cells. Mechanically, our results indicated that chaetocin could induce reactive oxygen species (ROS) accumulation and activate c-Jun N-terminal kinase (JNK)/c-Jun pathway in CRC cells. This was confirmed by which the JNK inhibitor SP600125 partially rescued CRC cells from chaetocin induced apoptosis and the ROS scavenger N-acetyl-L-cysteine (NAC) reversed both the chaetocin induced apoptosis and the JNK/c-Jun pathway activation. Additionally, this study indicated that chaetocin could down-regulate the expression of CD47 at both mRNA and protein levels, and enhance macrophages phagocytosis of CRC cells. Chaetocin also inhibited tumor growth in CRC xenograft models. In all, our study reveals that chaetocin induces CRC cell apoptosis, irrelevant to 5-FU sensitivity, by causing ROS accumulation and activating JNK/c-Jun, and enhances macrophages phagocytosis, which suggests chaetocin as a candidate for CRC chemotherapy.

Stress-Induced Epstein-Barr Virus Reactivation

Epstein-Barr virus (EBV) is typically found in a latent, asymptomatic state in immunocompetent individuals. Perturbations of the host immune system can stimulate viral reactivation. Furthermore, there are a myriad of EBV-associated illnesses including various cancers, post-transplant lymphoproliferative disease, and autoimmune conditions. A thorough understanding of this virus, and the interplay between stress and the immune system, is essential to establish effective treatment. This review will provide a summary of the interaction between both psychological and cellular stressors resulting in EBV reactivation. It will examine mechanisms by which EBV establishes and maintains latency and will conclude with a brief overview of treatments targeting EBV.

Suppression effect of plant-derived berberine on cyprinid herpesvirus 2 proliferation and its pharmacokinetics in Crucian carp (Carassius auratus gibelio)

Cyprinid herpesvirus 2 (CyHV-2), which infects silver crucian carp including goldfish (Carassius auratus auratus) and Crucian carp (Carassius auratus gibelio) with high mortality, is an emerging viral pathogen worldwide. Previous studies showed that berberine (BBR), a bioactive plant-derived alkaloid, demonstrated potential antiviral actions against many different viruses. Here, we assessed the effect of berberine hydrochloride (BBH) on the replication of CyHV-2 in vitro and in vivo. Cytotoxicity assay indicated that 5-25 μg/mL BBH was non-toxic to the RyuF-2 cells. In viral inhibition assays, real time PCR was employed to titrate the genomic copy number of progeny virus, real time RT-PCR was applied to monitor the transcriptional levels of viral genes, and Western blot analysis was performed to detect the synthetic levels of viral proteins. The results demonstrated that BBH systematically impedes the viral gene transcription and suppressed the replication of CyHV-2 in RyuF-2 cells. In animal challenge test, BBH was confirmed to protect Crucian carps from CyHV-2 infection in a dose-dependent manner, which was supported by suppressed viral replication levels, reduced viral pathogenesis and higher survival rates. Furthermore, pharmacokinetics data of BBH in Crucian carp revealed its rapid absorption (T_max of 1.5 h), suitable plasma half-life (t_1/2z/h of 7-12 h depending on oral dosage), and dose-dependent drug exposure properties following oral administration (revealed by AUC_0-t values). These findings shed light on repurposing BBH to treat CyHV-2 infections in silver crucian carp.

Targeting Epstein-Barr virus oncoprotein LMP1-mediated high oxidative stress suppresses EBV lytic reactivation and sensitizes tumors to radiation therapy

Generating oxidative stress is a critical mechanism by which host cells defend against infection by pathogenic microorganisms. Radiation resistance is a critical problem in radiotherapy against cancer. Epstein-Barr virus (EBV) is a cancer-causing virus and its reactivation plays an important role in the development of EBV-related tumors. This study aimed to explore the inner relationship and regulatory mechanism among oxidative stress, EBV reactivation, and radioresistance and to identify new molecular subtyping models and treatment strategies to improve the therapeutic effects of radiotherapy.

Methods: ROS, NADP⁺/NADPH, and GSSG/GSH were detected to evaluate the oxidative stress of cells. 8-OHdG is a reliable oxidative stress marker to evaluate the oxidative stress in patients. Its concentration in serum was detected using an ELISA method and in biopsies was detected using IHC. qPCR array was performed to evaluate the expression of essential oxidative stress genes. qPCR, Western blot, and IHC were used to measure the level of EBV reactivation in vitro and in vivo. A Rta-IgG ELISA kit and EBV DNA detection kit were used to analyze the reactivation of EBV in serum from NPC patients. NPC tumor tissue microarrays was used to investigate the prognostic role of oxidative stress and EBV reactivation. Radiation resistance was evaluated by a colony formation assay. Xenografts were treated with NAC, radiation, or a combination of NAC and radiation. EBV DNA load of tumor tissue was evaluated using an EBV DNA detection kit. Oxidative stress, EBV reactivation, and the apoptosis rate in tumor tissues were detected by using 8-OHdG, EAD, and TUNEL assays, respectively.

Results: We found that EBV can induce high oxidative stress, which promotes its reactivation and thus leads to radioresistance. Basically, EBV caused NPC cells to undergo a process of 'Redox Resetting' to acquire a new redox status with higher levels of ROS accumulation and stronger antioxidant systems by increasing the expression of the ROS-producing enzyme, NOX2, and the cellular master antioxidant regulator, Nrf2. Also, EBV encoded driving protein LMP1 promotes EBV reactivation through production of ROS. Furthermore, high oxidative stress and EBV reactivation were positively associated with poor overall survival of patients following radiation therapy and were significant related to NPC patients' recurrence and clinical stage. By decreasing oxidative stress using an FDA approved antioxidant drug, NAC, sensitivity of tumors to radiation was increased. Additionally, 8-OHdG and EBV DNA could be dual prognostic markers for NPC patients.

Conclusions: Oxidative stress mediates EBV reactivation and leads to radioresistance. Targeting oxidative stress can provide therapeutic benefits to cancer patients with radiation resistance. Clinically, we, for the first time, generated a molecular subtyping model for NPC relying on 8-OHdG and EBV DNA level. These dual markers could identify patients who are at a high risk of poor outcomes but who might benefit from the sequential therapy of reactive oxygen blockade followed by radiation therapy, which provides novel perspectives for the precise treatment of NPC.

Rapamycin enhances lytic replication of Epstein-Barr virus in gastric carcinoma cells by increasing the transcriptional activities of immediate-early lytic promoters

Epstein-Barr virus (EBV), a human herpesvirus, is linked to both epithelial and lymphoid malignancies. Induction of EBV reactivation is a potential therapeutic strategy for EBV-associated tumors. In this study, we assessed the effects of rapamycin on EBV reactivation in gastric carcinoma cells. We found that rapamycin upregulated expression of EBV lytic proteins and increased the viral proliferation triggered by the EBV lytic inducer sodium butyrate. Reverse transcription-qPCR, luciferase activity assays, chromatin immunoprecipitation and western blotting were employed to explore the mechanism by which rapamycin promotes EBV reactivation. Our results showed that rapamycin treatment resulted in increased mRNA levels of EBV immediate-early genes. Rapamycin also enhanced the transcriptional activities of the EBV immediate-early lytic promoters Zp and Rp by strengthening Sp1 binding. Repression of the cellular ataxia telangiectasia-mutated/p53 pathway by siRNA-mediated knockdown of the ataxia telangiectasia-mutated gene significantly abrogated virus reactivation by rapamycin/sodium butyrate treatment, indicating that the ataxia telangiectasia-mutated/p53 pathway is involved in rapamycin-promoted EBV reactivation. Taken together, these findings demonstrate that rapamycin might have the potential to enhance the effectiveness of oncolytic viral therapies developed for EBV-associated malignancies.