Yanhua Cao

Influenza A Virus Induces Interleukin-27 through Cyclooxygenase-2 and Protein Kinase A Signaling

Background: Interleukin (IL)-27 is significantly elevated in influenza patients. Results: IL-27 inhibits influenza A virus (IAV) replication and its expression is mediated by cyclooxygenase-2, protein kinase A (PKA), and the cAMP-response element-binding protein pathway. Conclusion: IL-27 exerts antiviral function through activation of STAT1/2/3 and PKR phosphorylation. Significance: IL-27 is one host immune factor produced in response to IAV infection. We previously reported that IL-27, which belongs to the IL-12 family of cytokines, is elevated in the serum of patients infected with influenza A virus (IAV). Here, we show that the expression of IL-27 was significantly up-regulated in A549 human lung epithelial cells and human peripheral blood mononuclear cells infected with IAV. Additionally, IAV triggered IL-27 expression through protein kinase A and cAMP-response element-binding protein signaling, which was mediated by cyclooxygenase-2-derived prostaglandin E2. IL-27 inhibited IAV replication by STAT1/2/3 phosphorylation and activated antiviral factor protein kinase R phosphorylation. Clinical analysis showed that IL-27 levels were significantly elevated in a cohort of patients infected with IAV compared with healthy individuals and that circulating IL-27 levels were tightly and positively correlated with prostaglandin E2 levels. These results indicate that IL-27 expression is one host immune factor produced in response to IAV infection and that elevated IL-27 levels inhibit viral replication.

Soluble Interleukin-6 Receptor-Mediated Innate Immune Response to DNA and RNA Viruses

ABSTRACT The interleukin-6 (IL-6) receptor, which exists as membrane-bound and soluble forms, plays critical roles in the immune response. The soluble IL-6 receptor (sIL6R) has been identified as a potential therapeutic target for preventing coronary heart disease. However, little is known about the role of this receptor during viral infection. In this study, we show that sIL6R, but not IL-6, is induced by viral infection via the cyclooxygenase-2 pathway. Interestingly, sIL6R, but not IL-6, exhibited extensive antiviral activity against DNA and RNA viruses, including hepatitis B virus, influenza virus, human enterovirus 71, and vesicular stomatitis virus. No synergistic effects on antiviral action were observed by combining sIL6R and IL-6. Furthermore, sIL6R mediated antiviral action via the p28 pathway and induced alpha interferon (IFN-α) by promoting the nuclear translocation of IFN regulatory factor 3 (IRF3) and NF-κB, which led to the activation of downstream IFN effectors, including 2′,5′-oligoadenylate synthetase (OAS), double-stranded RNA-dependent protein kinase (PKR), and myxovirus resistance protein (Mx). Thus, our results demonstrate that sIL6R, but not IL-6, plays an important role in the host antiviral response.

IL-27, a Cytokine, and IFN-λ1, a Type III IFN, Are Coordinated To Regulate Virus Replication through Type I IFN

IL-27, a member of the IL-12 family, plays a critical role in the control of innate and adaptive immune responses. IFN-λ1, a member of the type III IFN family, shows antiviral abilities. In this study, we investigated the effects of IL-27 and IFN-λ1 on the replication of hepatitis B virus (HBV), a major pathogen associated with a high risk for cirrhosis, liver failure, and hepatocellular carcinoma. We revealed that HBV infection activates IL-27 expression and IFN-λ1 production and demonstrated that viral-activated IL-27 and IFN-λ1 are coordinated to inhibit HBV replication. Initially, HBV infection upregulates IL-27 expression, which, in turn, stimulates IFN-λ1 production through regulating ERK1/2 signaling and by enhancing NF-κB nuclear translocation to bind to the IFN-λ1 promoter. Moreover, IL-27–activated IFN-λ1 upregulates IFN-λ1 receptor (IL-28R1 and IL-10Rβ) activity, resulting in the activation of the STAT1/2 pathway, which, in turn, induces the expression of IFN-stimulated genes, including IFN-inducible dsRNA-activated protein kinase, oligoadenylate synthetase 1, and IFN-induced GTP-binding protein 1 and, finally, inhibits HBV protein expression and viral capsid–associated DNA replication. More interestingly, we also revealed that type I IFN (IFN-α) is also involved in the downregulation of HBV replication mediated by IL-27. Thus, we identified a previously unknown mechanism by which IL-27 and IFN-λ1 are coordinated to regulate virus replication through type I IFN.

The collagen triple helix repeat containing 1 facilitates hepatitis B virus‐associated hepatocellular carcinoma progression by regulating multiple cellular factors and signal cascades

Hepatitis B virus (HBV) infection is one of the major causes of acute and chronic liver diseases, fulminant hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). HCC accounts for more than 85% of primary liver cancers and is the seventh most common cancer and the third leading cause of cancer‐related deaths. However, the mechanism by which HBV induces HCC is largely unknown. Collagen triple helixes repeat containing 1 (CTHRC1) is a secreted protein and has characteristics of a circulating hormone with potentially broad implications for cell metabolism and physiology. CTHRC1 is associated with human cancers, but its effect on HCC is unknown. Here, we revealed that CTHRC1 expression is highly correlated with HCC progression in HBV‐infected patients, and demonstrated that HBV stimulates CTHRC1 expression by activating nuclear factor‐kappa B (NF‐κB) and cAMP response element binding protein (CREB), through extracellular signal‐regulated kinase/c‐Jun N‐terminal kinase (ERK/c‐JNK) pathway. In addition, CTHRC1 activates hypoxia‐inducible factor 1α (HIF‐1α) and vascular endothelial growth factor (VEGF) through regulating phosphoinosmde‐3‐kinase/protein kinase B/mammalian target of rapamycin (PI‐3K/AKT/mTOR) pathway. More interestingly, CTHRC1 enhances colony formation, migration, and invasion of hepatoma cells by regulating p53 and stimulating matrix metalloproteinase‐9 (MMP‐9) expression. In addition, knock‐down of CTHRC1 results in the repression of HBV‐associated carcinogenesis in nude mice. Thus, we revealed a novel mechanism by which HBV facilitates HCC development through activating the oncoprotein CTHRC1, which in turn enhances HBV‐related HCC progression by stimulates colony formation, migration, and invasion of hepatoma cells through regulating multiple cellular factors and signal cascades.

Hepatitis B virus hijacks CTHRC1 to evade host immunity and maintain replication

Hepatitis B virus (HBV) infection causes acute and chronic liver diseases, but is not directly cytopathic. Liver injury results from repeated attempts of the cellular immune response system to control the viral infection. Here, we investigate the roles of cellular factors and signaling pathways involved in the regulation of HBV replication to reveal the mechanism underlying HBV infection and pathogenesis. We show that collagen triple helix repeat containing 1 (CTHRC1) expression is elevated in HBV-infected patients and in HBV-transfected cells through epigenetic modification and transcriptional regulation. CTHRC1 facilitates HBV replication in cultured cells and BALB/c mice by activating the PKCα/ERK/JNK/c-Jun cascade to repress the IFN/JAK/STAT pathway. HBV-activated CTHRC1 downregulates the activity of type I interferon (IFN), the production of IFN-stimulated genes (ISGs), and the phosphorylation of signal transducer and activator of transcription 1/2 (STAT1/2), whereas it upregulates the phosphorylation and ubiquitination of type I IFN receptors (IFNARα/β). Thus, our results show that HBV uses a novel mechanism to hijack cellular factors and signal cascades in order to evade host antiviral immunity and maintain persistent infection. We also demonstrate that CTHRC1 has a novel role in viral infection.

Stimulatory Effect of LPS and Feedback Effect of PGE2 on IL‐27 production

Interleukin (IL)‐27 is a new member of the IL‐6/IL‐12 family, composed of two subunits, the Epstein–Barr virus–induced gene 3 (EBI3) and p28 chains (p28), and produced by activated monocytes and dendritic cells. IL‐27 plays an important role in the regulation of differentiation of naive T helper cells and has diverse effects on innate immune cells. However, the pro‐inflammatory mechanisms of IL‐27 are still not well known. In this study, we investigated the effect of lipopolysaccharide (LPS) on the production of IL‐27. We found that LPS‐stimulated IL‐27 production was in a dose‐dependent and time‐dependent manner in THP‐1 cells. We have also shown that IL‐27 induced PGE2 production and COX‐2 gene expression at the level of mRNA as well as protein. Moreover, we found feed back effect of PGE2 on the production of IL‐27 in THP‐1 cells. The results suggest that PGE2 significantly inhibits LPS‐induced IL‐27 production, without affecting basal IL‐27 expression. Further experiment suggests that PGE2 and LPS regulate IL‐27 through NF‐κB pathway. Our findings may have wide implication for IL‐27 in inflammatory diseases.

ERK/c-Jun Recruits Tet1 to Induce Zta Expression and Epstein-Barr Virus Reactivation through DNA Demethylation

DNA demethylation plays an essential role in the reactivation of Epstein-Barr virus (EBV) from latency infection. However, it is unclear how epigenetic modification is initiated in responding to stimuli. Here, we demonstrate that ERK/c-Jun signaling is involved in DNA demethylation of EBV immediate early (IE) gene Zta in response to 12-O-Tetradecanoylphorbol-13-acetate (TPA) stimulation. Remarkably, Ser73 phosphorylation of c-Jun facilitates Zta promoter demethylation and EBV reactivation, whereas knockdown of c-Jun attenuates Zta demethylation and viral reactivation. More importantly, we reveal for the first time that c-Jun interacts with DNA dioxygenase Tet1 and facilitates Tet1 to bind to Zta promoter. The binding of c-Jun and Tet1 to Zta enhances promoter demethylation, resulting in the activation of Zta, the stimulation of BHRF1 (a lytic early gene) and gp350/220 (a lytic late gene), and ultimately the reactivation of EBV. Knockdown of Tet1 attenuates TPA-induced Zta demethylation and EBV reactivation. Thus, TPA activates ERK/c-Jun signaling, which subsequently facilitates Tet1 to bind to Zta promoter, leading to DNA demethylation, gene expression, and EBV reactivation. This study reveals important roles of ERK/c-Jun signaling and Tet1 dioxygenase in epigenetic modification, and provides new insights into the mechanism underlying the regulation of virus latent and lytic infection.

Hepatitis B Virus e Antigen Activates the Suppressor of Cytokine Signaling 2 to Repress Interferon Action

Hepatitis B virus (HBV) infection causes acute hepatitis B (AHB), chronic hepatitis B (CHB), liver cirrhosis (LC), and eventually hepatocellular carcinoma (HCC). The presence of hepatitis B e antigen (HBeAg) in the serum generally indicates ongoing viral replication and disease progression. However, the mechanism by which HBeAg regulates HBV infection remains unclear. Interferons (IFNs) are pleiotropic cytokines that participate in host innate immunity. After binding to receptors, IFNs activate the JAK/STAT pathway to stimulate expression of IFN-stimulated genes (ISGs), leading to induction of antiviral responses. Here, we revealed that HBeAg represses IFN/JAK/STAT signaling to facilitate HBV replication. Initially, HBeAg stimulates the expression of suppressor of cytokine signaling 2 (SOCS2). Subsequently, SOCS2 impairs IFN/JAK/STAT signaling through reducing the stability of tyrosine kinase 2 (TYK2), downregulating the expression of type I and III IFN receptors, attenuating the phosphorylation and nucleus translocation of STAT1. Finally, SOCS2 inhibits the expression of ISGs, which leads to the repression of IFN action and facilitation of viral replication. These results demonstrate an important role of HBeAg in the regulation of IFN action, and provide a possible molecular mechanism by which HBV resists the IFN therapy and maintains persistent infection.