Cholesterol 25-hydroxylase inhibits encephalomyocarditis virus replication through enzyme activity-dependent and independent mechanisms

Expression Pattern of Cholesterol 25-Hydroxylase and Serum Level of 25-Hydroxycholesterol and Relevant Inflammatory Cytokines in Patients with Varying Disease Severity of COVID-19

Cholesterol 25-hydroxylase (CH25H) and its product 25-hydroxycholesterol (25HC) showed antiviral effects against various viruses in vitro. CH25H expression is regulated in mice by pro-inflammatory cytokine interferons (IFNs) in mice but data on its possible correlation with IFNs in humans are still unclear. We examined gene expression of CH25H, IFN-α, and IFN-β and serum levels of 25HC in Iranian patients with mild and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Fifty intensive care unit (ICU) patients and outpatients with SARS-CoV-2 and 25 healthy controls were studied. Gene expression of CH25H and relevant inflammatory cytokines was quantified in peripheral blood mononuclear cells by real-time polymerase chain reaction. The expression of CH25H and serum levels of 25HC were significantly higher in ICU patients with SARS-CoV-2. Notably, IFN-α levels increased in healthy controls. However, compared to healthy controls, IFN-β was considerably higher in outpatients. Finally, statistical analysis shows that no correlation was found between CH25H and IFN-α expression; nevertheless, a lower correlation was found with IFN-β. The data revealed that CH25H and 25HC levels increase after SARS-CoV-2 infection. In other words, decreased levels of those factors in severe patients compared with mild patients may indicate the importance of their function in controlling the progression of the disease.

Cholesterol 25-hydroxylase suppresses avian reovirus replication by its enzymatic product 25-hydroxycholesterol

Avian reovirus (ARV) causing viral arthritis/tenosynovitis and viral enteritis in domestic fowl has significantly threatened on the poultry industry worldwide. ARV is a non-enveloped fusogenic virus that belongs to the Reoviridae family. Previous research revealed that cellular cholesterol in lipid rafts is essential for ARV replication. It has been reported that cholesterol 25-hydroxylase (CH25H) and its product 25-hydroxycholesterol (25HC) have antiviral activities against enveloped viruses. However, few studies characterized the association of non-enveloped viruses with CH25H and the role of CH25H in the regulation of ARV replication. In this study, the expression of chicken CH25H (chCH25H) was found to be upregulated in ARV-infected cells at the early stage of infection. The results of overexpression and knockdown assays revealed that chCH25H has a significant antiviral effect against ARV infection. Furthermore, a 25HC treatment significantly inhibited ARV replication in a dose-dependent manner at both the entry and post-entry stages, and a chCH25H mutant lacking hydroxylase activity failed to inhibit ARV infection. These results indicate that CH25H, depending on its enzyme activity, exerts the antiviral effect against ARV via the synthesis of 25HC. In addition, we revealed that 25HC produced by CH25H inhibits viral entry by delaying the kinetics of ARV uncoating, and CH25H blocks cell-cell membrane fusion induced by the p10 protein of ARV. Altogether, our findings showed that CH25H, as a natural host restriction factor, possessed antiviral activity against ARV targeting viral entry and syncytium formation, through an enzyme activity-dependent way. This study may provide new insights into the development of broad-spectrum antiviral therapies.

BmCH25H, a vertebrate interferon-stimulated gene(ISG) homolog, inhibits BmNPV infection dependent on its hydroxylase activity in Bombyx mori

Cholesterol-25-hydroxylase (CH25H) has been identified as an interferon-stimulated gene (ISG) in mammals that exerts its antiviral effects by catalyzing the conversion of cholesterol to 25-hydroxycholesterol (25HC). However, invertebrates lack an antiviral system homologous to vertebrate interferons (IFNs) because the genomes of invertebrates do not encode IFN-like cytokines. Nevertheless, CH25H is present in insect genomes and it therefore deserves further study of whether and by which mechanism it could exert an antiviral effect in invertebrates. In this study, the Bombyx mori CH25H (BmCH25H) gene, of which the encoded protein has high homology with other lepidopteran species, was identified and located on chromosome 9. Interestingly, we found that the expression of BmCH25H was significantly upregulated in B. mori nucleopolyhedrovirus (BmNPV) -infected BmN cells and silkworm (B. mori) larvae at the early infection stage. The inhibitory effect of BmCH25H on BmNPV replication was further demonstrated to depend on its catalytic residues to convert cholesterol to 25HC. More importantly, we demonstrated that during BmNPV infection, BmCH25H expression was increased through the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway, similar to the induction of ISGs following virus infection in vertebrates. This is the first report that CH25H has antiviral effects in insects; the study also elucidates the regulation of its expression and its mechanism of action.

Curcumol inhibits EMCV replication by activating CH25H and inhibiting the formation of ROs

BACKGROUND

Zedoary turmeric oil extracted from the roots of curcuma (Curcuma aeruginosa Roxb.) is used for the treatment of myocarditis in China. EMCV infection causes abortion in pregnant sows and myocarditis in piglets. Our previous studies demonstrated that curcumol significantly increased the expression of IFN-β in EMCV infected HEK-293T cells. The present results showed that curcumol inhibits EMCV replication by interfering the host cell cholesterol homeostasis and reducing ROs production through activation of the JAK/STAT signaling pathway.

METHOD

This study was designed to explore whether curcumol can inhibit the replication of encephalomyocarditis viruses (EMCV) in cell culture. The expression level of JAK1, IRF9, STAT2, P-STAT2, CH25H, PI4KA and OSBP in EMCV-infected HEK-293T cells treated with curcumol, ribavirin or hydroxypropyl-β-CD (HPCD) were determined by Western blotting (WB). The cholesterol level in EMCV infected HEK-293T cells treated with curcumol and HPCD were detected using Amplex™ Red Cholesterol Assay Kit. The antiviral effects of curcumol and HPCD on EMCV were also quantitatively detected by real-time fluorescence quantitative PCR (q-PCR). The amount and morphology of ROs were observed by transmission electron microscopy (TEM).

RESULTS

The results demonstrated that curcumol significantly (P < 0.05) increased the expression of JAK1, IRF9, P-STAT2 and CH25H proteins, while that of STAT2, PI4KA and OSBP were remained unchanged. Compared with virus group (0.134 μg.μg^-1 proteins), the total cholesterol level was significantly (P < 0.05) reduced by curcumol (0.108 μg.μg^-1 proteins) and HPCD (0.089 μg.μg^-1 proteins). Compared with virus group (88237 copies), curcumol (41802 copies) and HPCD (53 copies) significantly (P < 0.05) reduced EMCV load. Curcumol significantly reduced the production of ROs in EMCV-infected HEK-293T cells and activated CH25H through the JAK/STAT signaling pathway.

CONCLUSION

Curcumol inhibited EMCV replication by affecting the cholesterol homeostasis and the production of ROs in HEK-293T cell.

The game between host antiviral innate immunity and immune evasion strategies of senecavirus A - A cell biological perspective

Innate immunity is the first line of the cellular host to defend against viral infection. Upon infection, viruses can be sensed by the cellular host's pattern recognition receptors (PRRs), leading to the activation of the signaling cascade and the robust production of interferons (IFNs) to restrict the infection and replication of the viruses. However, numerous cunning viruses have evolved strategies to evade host innate immunity. The senecavirus A (SVA) is a newly identified member of the Picornaviridae family, causing severe vesicular or ulcerative lesions on the oral mucosa, snout, coronary bands, and hooves of pigs of different ages. During SVA infection, the cellular host will launch the innate immune response and various physiological processes to restrict SVA. In contrast, SVA has evolved several strategies to evade the porcine innate immune responses. This review focus on the underlying mechanisms employed by SVA to evade pattern recognition receptor signaling pathways, type I interferon (IFN-α/β) receptor (IFNAR) signaling pathway, interferon-stimulated genes (ISGs) and autophagy, and stress granules. Deciphering the antiviral immune evasion mechanisms by SVA will enhance our understanding of SVA's pathogenesis and provide insights into developing antiviral strategies and improving vaccines.

Studies in the antiviral molecular mechanisms of 25-hydroxycholesterol: Disturbing cholesterol homeostasis and post-translational modification of proteins

Efficient antiviral drug discovery has been a pressing issue of global public health concern since the outbreak of coronavirus disease 2019. In recent years, numerous in vitro and in vivo studies have shown that 25-hydroxycholesterol (25HC), a reactive oxysterol catalyzed by cholesterol-25-hydroxylase, exerts broad-spectrum antiviral activity with high efficiency and low toxicity. 25HC restricts viral internalization and disturbs the maturity of viral proteins using multiple mechanisms. First, 25HC reduces lipid rafts and cholesterol in the cytomembrane by inhibiting sterol-regulatory element binding proteins-2, stimulating liver X receptor, and activating Acyl-coenzyme A: cholesterol acyl-transferase. Second, 25HC impairs endosomal pathways by restricting the function of oxysterol-binding protein or Niemann-pick protein C1, causing the virus to fail to release nucleic acid. Third, 25HC disturbs the prenylation of viral proteins by suppressing the sterol-regulatory element binding protein pathway and glycosylation by increasing the sensitivity of glycans to endoglycosidase. This paper reviews previous studies on the antiviral activity of 25HC in order to fully understand its role in innate immunity and how it may contribute to the development of urgently needed broad-spectrum antiviral drugs.

Coronavirus Infection and Cholesterol Metabolism

Host cholesterol metabolism remodeling is significantly associated with the spread of human pathogenic coronaviruses, suggesting virus-host relationships could be affected by cholesterol-modifying drugs. Cholesterol has an important role in coronavirus entry, membrane fusion, and pathological syncytia formation, therefore cholesterol metabolic mechanisms may be promising drug targets for coronavirus infections. Moreover, cholesterol and its metabolizing enzymes or corresponding natural products exert antiviral effects which are closely associated with individual viral steps during coronavirus replication. Furthermore, the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 infections are associated with clinically significant low cholesterol levels, suggesting cholesterol could function as a potential marker for monitoring viral infection status. Therefore, weaponizing cholesterol dysregulation against viral infection could be an effective antiviral strategy. In this review, we comprehensively review the literature to clarify how coronaviruses exploit host cholesterol metabolism to accommodate viral replication requirements and interfere with host immune responses. We also focus on targeting cholesterol homeostasis to interfere with critical steps during coronavirus infection.

Oxysterols: From redox bench to industry

More and more attention is nowadays given to the possible translational application of a great number of biochemical and biological findings with the involved molecules. This is also the case of cholesterol oxidation products, redox molecules over the last years deeply investigated for their implication in human pathophysiology. Oxysterols of non-enzymatic origin, the excessive increase of which in biological fluids and tissues is of toxicological relevance for their marked pro-oxidant and pro-inflammatory properties, are increasingly applied in clinical biochemistry as molecular markers in the diagnosis and monitoring of several human and veterinary diseases. Conversely, oxysterols of enzymatic origin, the production of which is commonly under physiological regulation, could be considered and tested as promising pharmaceutical agents because of their antiviral, pro-osteogenic and antiadipogenic properties of some of them. Very recently, the quantification of oxysterols of non-enzymatic origin has been adopted in a systematic way to evaluate, monitor and improve the quality of cholesterol-based food ingredients, that are prone to auto-oxidation, as well as their industrial processing and the packaging and the shelf life of the finished food products. The growing translational value of oxysterols is here reviewed in its present and upcoming applications in various industrial fields.

LINC01915 Facilitates the Conversion of Normal Fibroblasts into Cancer-Associated Fibroblasts Induced by Colorectal Cancer-Derived Extracellular Vesicles through the miR-92a-3p/KLF4/CH25H Axis

Increasing long non-coding RNAs are reported to regulate the cell growth, apoptosis, and metastasis of cancer-associated fibroblasts (CAFs).This study aimed to explore how LINC01915 influences the conversion of normal fibroblasts (NFs) into CAFs in colorectal cancer (CRC). LINC01915 expression was initially measured in clinical tissue samples and in NFs and CAFs. Identification of the interaction between LINC01915, miR-92a-3p, KLF4, and CH25H was done. The effects of LINC01915, miR-92a-3p, and KLF4 on the angiogenesis, extracellular vesicle (EV) uptake by NFs, and activation of stromal cells were assessed using gain- or loss-of-function approaches. Xenograft mouse models were established to validate these in vitro findings in vivo. EVs were shown to stimulate NF proliferation, migration, and angiogenesis, as well as facilitate NF conversion into CAFs. CRC tissues and CAFs showed downregulated expression of LINC01915, which was associated with poor prognosis of patients. Moreover, employed LINC01915 inhibited tumor angiogenesis, CAF activation, and the uptake of tumor-derived EVs by NFs. Mechanistically, LINC01915 could competitively bind to miR-92a-3p and caused upregulation of the miR-92a-3p target KLF4 which, in turn, promoted the transcription of CH25H, leading to the suppressed uptake of EVs by NFs. The in vivo and in vitro experimental results showed that LINC01915 inhibited the uptake of CRC-derived EVs by NFs through the miR-92a-3p/KLF4/CH25H axis, thus arresting the angiogenesis and the conversion of NFs into CAFs and in turn prevent tumor growth. These data together supported the inhibiting role of LINC01915 in the conversion of NFs into CAFs triggered by the CRC-derived EVs and the ensuing tumor growth, which may be related to its regulation on the miR-92a-3p/KLF4/CH25H axis.

Evasion of Antiviral Innate Immunity by Porcine Reproductive and Respiratory Syndrome Virus

Innate immunity is the front line for antiviral immune responses and bridges adaptive immunity against viral infections. However, various viruses have evolved many strategies to evade host innate immunity. A typical virus is the porcine reproductive and respiratory syndrome virus (PRRSV), one of the most globally devastating viruses threatening the swine industry worldwide. PRRSV engages several strategies to evade the porcine innate immune responses. This review focus on the underlying mechanisms employed by PRRSV to evade pattern recognition receptors signaling pathways, type I interferon (IFN-α/β) receptor (IFNAR)-JAK-STAT signaling pathway, and interferon-stimulated genes. Deciphering the antiviral immune evasion mechanisms by PRRSV will enhance our understanding of PRRSV’s pathogenesis and help us to develop more effective methods to control and eliminate PRRSV.

Correlation between bioactive lipids and novel coronavirus: constructive role of biolipids in curbing infectivity by enveloped viruses, centralizing on EPA and DHA

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) belongs to the family coronaviridae. It is spherical and possesses proteins called spikes, which can clamp onto the human cells. Once in close interaction with the human cells, these viruses undergo structural change and can fuse with the cell membrane. The virus enters the host and starts the process of translation and transcription in the cells and uncoated genome, respectively. Due to the rapid transmittable nature of the virus, extant actions should be taken. The fatty acids administrated orally, or intravenously, could help us gear things up in providing resistance and preventing infection. Hence, the multiplication of the virus could be hindered by arachidonic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). In that context, the current review highlights the role of these unsaturated fatty acids and their derivatives such as lipoxins and resolvins in the inactivation of the enveloped coronavirus disease 2019 (COVID-19).

Multiple Roles of 25-Hydroxycholesterol in Lipid Metabolism, Antivirus Process, Inflammatory Response, and Cell Survival

As an essential lipid, cholesterol is of great value in keeping cell homeostasis, being the precursor of bile acid and steroid hormones, and stabilizing membrane lipid rafts. As a kind of cholesterol metabolite produced by enzymatic or radical process, oxysterols have drawn much attention in the last decades. Among which, the role of 25-hydroxycholesterol (25-HC) in cholesterol and bile acid metabolism, antivirus process, and inflammatory response has been largely disclosed. This review is aimed at revealing these functions and underlying mechanisms of 25-HC.