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Host Responses and Regulation by NFκB Signaling in the Liver and Liver Epithelial Cells Infected with A Novel Tick-borne Bunyavirus.

Sun Q, Jin C, Zhu L, Liang M, Li C, Cardona CJ, Li D, Xing Z - Sci Rep (2015)

Bottom Line: Viral nonstructural protein NSs was inhibitory to the induction of IFN-β, but interestingly, NFκB activation was enhanced in the presence of NSs.Therefore, NSs plays dual roles in the suppression of antiviral IFN-β induction as well as the promotion of proinflammatory responses.Our findings provide the first evidence for elucidating host responses and regulation in liver epithelial cells infected by an emerging bunyavirus.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory of Pharmaceutical Biotechnology and Medical School, Nanjing University, Nanjing, China.

ABSTRACT
Infection in humans by severe fever with thrombocytopenia syndrome virus (SFTSV), a novel bunyavirus transmitted by ticks, is often associated with pronounced liver damage, especially in fatal cases. Little has been known, however, about how liver cells respond to SFTSV and how the response is regulated. In this study we report that proinflammatory cytokines were induced in liver tissues of C57/BL6 mice infected with SFTSV, which may cause tissue necrosis in mice. Human liver epithelial cells were susceptible to SFTSV and antiviral interferon (IFN) and IFN-inducible proteins were induced upon infection. We observed that infection of liver epithelial cells led to significant increases in proinflammatory cytokines and chemokines, including IL-6, RANTES, IP-10, and MIP-3a, which were regulated by NFκB signaling, and the activation of NFκB signaling during infection promoted viral replication in liver epithelial cells. Viral nonstructural protein NSs was inhibitory to the induction of IFN-β, but interestingly, NFκB activation was enhanced in the presence of NSs. Therefore, NSs plays dual roles in the suppression of antiviral IFN-β induction as well as the promotion of proinflammatory responses. Our findings provide the first evidence for elucidating host responses and regulation in liver epithelial cells infected by an emerging bunyavirus.

No MeSH data available.


Related in: MedlinePlus

Regulation of proinflammatory cytokine gene transcripts by NFκB.HepG2 cells were pretreated with an NFκB specific inhibitor at 100 nM 1.5 hrs prior to SFTSV infection. Total RNA were prepared at 24, 48, and 72 hrs p.i for reverse transcription. cDNA was used for realtime PCR with specific primers to measure fold changes of cytokine transcripts at different time points. Each assay was repeated at least three times. (A-F) Fold change of IL-6, CCL5, IP-10, MIP-3a, IL-8, and IL-1β transcripts. (G) Inhibition of viral RNA replication by the inhibitor of NFκB. Realtime RT-PCR with specific primers to the viral S gene was performed to measure the S gene copy numbers in infected cells treated or non-treated with the NFκB inhibitor. Mean fold changes plus standard deviation of the viral S copy numbers were presented from two or three independent assays (*p < 0.05).
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f8: Regulation of proinflammatory cytokine gene transcripts by NFκB.HepG2 cells were pretreated with an NFκB specific inhibitor at 100 nM 1.5 hrs prior to SFTSV infection. Total RNA were prepared at 24, 48, and 72 hrs p.i for reverse transcription. cDNA was used for realtime PCR with specific primers to measure fold changes of cytokine transcripts at different time points. Each assay was repeated at least three times. (A-F) Fold change of IL-6, CCL5, IP-10, MIP-3a, IL-8, and IL-1β transcripts. (G) Inhibition of viral RNA replication by the inhibitor of NFκB. Realtime RT-PCR with specific primers to the viral S gene was performed to measure the S gene copy numbers in infected cells treated or non-treated with the NFκB inhibitor. Mean fold changes plus standard deviation of the viral S copy numbers were presented from two or three independent assays (*p < 0.05).

Mentions: To understand how proinflammatory and antiviral cytokines were regulated in SFTSV-infected liver epithelial cells, we examined NFκB signaling and its role in the regulation of the corresponding cytokines. Bay11-7082, an inhibitor of NFκB signaling through preventing phosphorylation and activation of IKKβ and suppressing IKK activity, was used to pre-treat HepG2 cells before viral infection. While no obvious toxicity was observed in the cells treated with Bay11-7082 at the indicated concentrations (data not show), we found significant differences in the induction of the cytokines between untreated and treated cells. The induction of proinflammatory IL-6, RANTES, IP-10, and MIP-3α was significantly suppressed in the presence of the inhibitor (Fig. 8A–D), suggesting that NFκB is responsible for the induction of these cytokines and may play a critical role in immunopathogenicity. On the other hand, the expression of IL-8 was not affected by the treatment of the NFκB inhibitor (Fig. 8E), and the induction of IL-1β was even further increased in the presence of the inhibitor (Fig. 8F), suggesting that the induction of IL-1β occurred in response to SFTSV infection but was somehow suppressed by NFκB signaling in human liver epithelial cells. Meanwhile, our data showed that the S gene copy numbers were significantly decreased in the cells treated with Bay11-7082 (Fig. 8G), compared to those without treatment, suggesting that NF-κB signaling may enhance viral replication in SFTSV-infected cells.


Host Responses and Regulation by NFκB Signaling in the Liver and Liver Epithelial Cells Infected with A Novel Tick-borne Bunyavirus.

Sun Q, Jin C, Zhu L, Liang M, Li C, Cardona CJ, Li D, Xing Z - Sci Rep (2015)

Regulation of proinflammatory cytokine gene transcripts by NFκB.HepG2 cells were pretreated with an NFκB specific inhibitor at 100 nM 1.5 hrs prior to SFTSV infection. Total RNA were prepared at 24, 48, and 72 hrs p.i for reverse transcription. cDNA was used for realtime PCR with specific primers to measure fold changes of cytokine transcripts at different time points. Each assay was repeated at least three times. (A-F) Fold change of IL-6, CCL5, IP-10, MIP-3a, IL-8, and IL-1β transcripts. (G) Inhibition of viral RNA replication by the inhibitor of NFκB. Realtime RT-PCR with specific primers to the viral S gene was performed to measure the S gene copy numbers in infected cells treated or non-treated with the NFκB inhibitor. Mean fold changes plus standard deviation of the viral S copy numbers were presented from two or three independent assays (*p < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488873&req=5

f8: Regulation of proinflammatory cytokine gene transcripts by NFκB.HepG2 cells were pretreated with an NFκB specific inhibitor at 100 nM 1.5 hrs prior to SFTSV infection. Total RNA were prepared at 24, 48, and 72 hrs p.i for reverse transcription. cDNA was used for realtime PCR with specific primers to measure fold changes of cytokine transcripts at different time points. Each assay was repeated at least three times. (A-F) Fold change of IL-6, CCL5, IP-10, MIP-3a, IL-8, and IL-1β transcripts. (G) Inhibition of viral RNA replication by the inhibitor of NFκB. Realtime RT-PCR with specific primers to the viral S gene was performed to measure the S gene copy numbers in infected cells treated or non-treated with the NFκB inhibitor. Mean fold changes plus standard deviation of the viral S copy numbers were presented from two or three independent assays (*p < 0.05).
Mentions: To understand how proinflammatory and antiviral cytokines were regulated in SFTSV-infected liver epithelial cells, we examined NFκB signaling and its role in the regulation of the corresponding cytokines. Bay11-7082, an inhibitor of NFκB signaling through preventing phosphorylation and activation of IKKβ and suppressing IKK activity, was used to pre-treat HepG2 cells before viral infection. While no obvious toxicity was observed in the cells treated with Bay11-7082 at the indicated concentrations (data not show), we found significant differences in the induction of the cytokines between untreated and treated cells. The induction of proinflammatory IL-6, RANTES, IP-10, and MIP-3α was significantly suppressed in the presence of the inhibitor (Fig. 8A–D), suggesting that NFκB is responsible for the induction of these cytokines and may play a critical role in immunopathogenicity. On the other hand, the expression of IL-8 was not affected by the treatment of the NFκB inhibitor (Fig. 8E), and the induction of IL-1β was even further increased in the presence of the inhibitor (Fig. 8F), suggesting that the induction of IL-1β occurred in response to SFTSV infection but was somehow suppressed by NFκB signaling in human liver epithelial cells. Meanwhile, our data showed that the S gene copy numbers were significantly decreased in the cells treated with Bay11-7082 (Fig. 8G), compared to those without treatment, suggesting that NF-κB signaling may enhance viral replication in SFTSV-infected cells.

Bottom Line: Viral nonstructural protein NSs was inhibitory to the induction of IFN-β, but interestingly, NFκB activation was enhanced in the presence of NSs.Therefore, NSs plays dual roles in the suppression of antiviral IFN-β induction as well as the promotion of proinflammatory responses.Our findings provide the first evidence for elucidating host responses and regulation in liver epithelial cells infected by an emerging bunyavirus.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory of Pharmaceutical Biotechnology and Medical School, Nanjing University, Nanjing, China.

ABSTRACT
Infection in humans by severe fever with thrombocytopenia syndrome virus (SFTSV), a novel bunyavirus transmitted by ticks, is often associated with pronounced liver damage, especially in fatal cases. Little has been known, however, about how liver cells respond to SFTSV and how the response is regulated. In this study we report that proinflammatory cytokines were induced in liver tissues of C57/BL6 mice infected with SFTSV, which may cause tissue necrosis in mice. Human liver epithelial cells were susceptible to SFTSV and antiviral interferon (IFN) and IFN-inducible proteins were induced upon infection. We observed that infection of liver epithelial cells led to significant increases in proinflammatory cytokines and chemokines, including IL-6, RANTES, IP-10, and MIP-3a, which were regulated by NFκB signaling, and the activation of NFκB signaling during infection promoted viral replication in liver epithelial cells. Viral nonstructural protein NSs was inhibitory to the induction of IFN-β, but interestingly, NFκB activation was enhanced in the presence of NSs. Therefore, NSs plays dual roles in the suppression of antiviral IFN-β induction as well as the promotion of proinflammatory responses. Our findings provide the first evidence for elucidating host responses and regulation in liver epithelial cells infected by an emerging bunyavirus.

No MeSH data available.


Related in: MedlinePlus