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IFI6 Inhibits Apoptosis via Mitochondrial-Dependent Pathway in Dengue Virus 2 Infected Vascular Endothelial Cells.

Qi Y, Li Y, Zhang Y, Zhang L, Wang Z, Zhang X, Gui L, Huang J - PLoS ONE (2015)

Bottom Line: Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects.We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells.By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Diseases Control, Ministry of Education, Guangzhou, PR China.

ABSTRACT
Dengue hemorrhagic fever (DHF)/Dengue shock syndrome (DSS) is a fatal infectious disease that demands an effective treatment. Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects. Among ISGs, IFN-α inducible gene 6 (IFI6) was increased in DENV infected human umbilical vascular endothelial cells (HUVECs) by microarray analysis in our previous study. However, its function is incompletely understood. In this study, we confirmed that IFI6 was markedly induced in DENV infection of both primary HUVECs and EA.hy926 cell lines. Recombinant EA.hy926 cell lines in which IFI6 was either over-expressed (IFI6+/+) or knocked-down (IFI6-/-) were generated. The activation of caspase-3 and intrinsic apoptosis-related protein caspase-9 were down-regulated in IFI6+/+ but up-regulated in IFI6-/- cells at 24-48 hrs post-infection. After incubation with DENV for 48 hrs, the mitochondrial membrane potential (Δψ(m)) was more stable in IFI6+/+ cells but reduced in IFI6-/- cells, as assayed by fluorescence staining with JC-1. We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells. By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells. It is presumed that the anti-apoptotic function of IFI6 is expressed by regulating the rheostatic balance between bcl-2/bax expression and inhibition of Δψ(m) depolarization during DENV infection of vascular endothelial cells(VECs). In addition, the pro-apoptotic protein X-linked Inhibitor of Apoptosis (XIAP)-Associated Factor 1(XAF1) expression had been reported to be up-regulated and led to the induction of apoptosis in DENV2-infected VECs,but the relationship between XAF1 and IFI6 dengue virus-induced apoptosis in VECs warrants further study.

No MeSH data available.


Related in: MedlinePlus

Changes in mitochondrial membrane potential (Δψm) in infected recombinant VECs.Δψm was measured by fluorescence microscopy in vector-hi/IFI6+/+ cells (a) and vector-low/IFI6-/- cells (b) stained by JC-1 after 24, 36 and 48 hrs post DENV2 infection. Scale bar = 50 μm.
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pone.0132743.g005: Changes in mitochondrial membrane potential (Δψm) in infected recombinant VECs.Δψm was measured by fluorescence microscopy in vector-hi/IFI6+/+ cells (a) and vector-low/IFI6-/- cells (b) stained by JC-1 after 24, 36 and 48 hrs post DENV2 infection. Scale bar = 50 μm.

Mentions: It has been established that caspase-9 plays an important role in the intrinsic apoptosis pathway [26], which is mediated by activation of mitochondria. We assayed alterations in the mitochondrial membrane potential (Δψm) in situ by a cationic and voltage-sensitive vital fluorochrome, called JC-1. The lipid dye emits differential fluorescence that is depended on different polymerization forms. In healthy mitochondria with normal Δψm, JC-1 always transfers into the mitochondria and aggregates to a polymer, and emits red fluorescent signals. On damage to the mitochondria, there is depolarization of Δψm, and JC-1 is released to the cytoplasm, where the fluorescence changes to a green signal. As shown in Fig 5, the continued decline of Δψm in both vector cell lines was conspicuous from 24 hrs to 48 hrs after DENV2 infection. The infected IFI6+/+ cells displayed a stable Δψm as shown by a sustained aggregation of the red JC-1 fluorescence over periods of time (Fig 5a). By contrast, IFI6-/- cells appeared to be more sensitive to DENV2, which was indicated by complete vanishing of the red fluorescent signal at early-stages post-infection, and the ongoing enhanced green fluorescence of the JC-1 aggregates (Fig 5b).


IFI6 Inhibits Apoptosis via Mitochondrial-Dependent Pathway in Dengue Virus 2 Infected Vascular Endothelial Cells.

Qi Y, Li Y, Zhang Y, Zhang L, Wang Z, Zhang X, Gui L, Huang J - PLoS ONE (2015)

Changes in mitochondrial membrane potential (Δψm) in infected recombinant VECs.Δψm was measured by fluorescence microscopy in vector-hi/IFI6+/+ cells (a) and vector-low/IFI6-/- cells (b) stained by JC-1 after 24, 36 and 48 hrs post DENV2 infection. Scale bar = 50 μm.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4526556&req=5

pone.0132743.g005: Changes in mitochondrial membrane potential (Δψm) in infected recombinant VECs.Δψm was measured by fluorescence microscopy in vector-hi/IFI6+/+ cells (a) and vector-low/IFI6-/- cells (b) stained by JC-1 after 24, 36 and 48 hrs post DENV2 infection. Scale bar = 50 μm.
Mentions: It has been established that caspase-9 plays an important role in the intrinsic apoptosis pathway [26], which is mediated by activation of mitochondria. We assayed alterations in the mitochondrial membrane potential (Δψm) in situ by a cationic and voltage-sensitive vital fluorochrome, called JC-1. The lipid dye emits differential fluorescence that is depended on different polymerization forms. In healthy mitochondria with normal Δψm, JC-1 always transfers into the mitochondria and aggregates to a polymer, and emits red fluorescent signals. On damage to the mitochondria, there is depolarization of Δψm, and JC-1 is released to the cytoplasm, where the fluorescence changes to a green signal. As shown in Fig 5, the continued decline of Δψm in both vector cell lines was conspicuous from 24 hrs to 48 hrs after DENV2 infection. The infected IFI6+/+ cells displayed a stable Δψm as shown by a sustained aggregation of the red JC-1 fluorescence over periods of time (Fig 5a). By contrast, IFI6-/- cells appeared to be more sensitive to DENV2, which was indicated by complete vanishing of the red fluorescent signal at early-stages post-infection, and the ongoing enhanced green fluorescence of the JC-1 aggregates (Fig 5b).

Bottom Line: Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects.We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells.By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Diseases Control, Ministry of Education, Guangzhou, PR China.

ABSTRACT
Dengue hemorrhagic fever (DHF)/Dengue shock syndrome (DSS) is a fatal infectious disease that demands an effective treatment. Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects. Among ISGs, IFN-α inducible gene 6 (IFI6) was increased in DENV infected human umbilical vascular endothelial cells (HUVECs) by microarray analysis in our previous study. However, its function is incompletely understood. In this study, we confirmed that IFI6 was markedly induced in DENV infection of both primary HUVECs and EA.hy926 cell lines. Recombinant EA.hy926 cell lines in which IFI6 was either over-expressed (IFI6+/+) or knocked-down (IFI6-/-) were generated. The activation of caspase-3 and intrinsic apoptosis-related protein caspase-9 were down-regulated in IFI6+/+ but up-regulated in IFI6-/- cells at 24-48 hrs post-infection. After incubation with DENV for 48 hrs, the mitochondrial membrane potential (Δψ(m)) was more stable in IFI6+/+ cells but reduced in IFI6-/- cells, as assayed by fluorescence staining with JC-1. We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells. By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells. It is presumed that the anti-apoptotic function of IFI6 is expressed by regulating the rheostatic balance between bcl-2/bax expression and inhibition of Δψ(m) depolarization during DENV infection of vascular endothelial cells(VECs). In addition, the pro-apoptotic protein X-linked Inhibitor of Apoptosis (XIAP)-Associated Factor 1(XAF1) expression had been reported to be up-regulated and led to the induction of apoptosis in DENV2-infected VECs,but the relationship between XAF1 and IFI6 dengue virus-induced apoptosis in VECs warrants further study.

No MeSH data available.


Related in: MedlinePlus