Limits...
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

IFI6 inhibits apoptosis of VECs induced by DENV2.(a and b) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using TUNEL assay after 24, 36, and 48 hrs post DENV2 infection.(c) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using AnnexinV-FITC/PI labeling flow cytometry after 24, 36, and 48 hrs post DENV2 infection.(d) Analysis of AnnexinV positive cell ratio.(e and f) Cell viability was determined by MTT. ***P<0.01.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4526556&req=5

pone.0132743.g003: IFI6 inhibits apoptosis of VECs induced by DENV2.(a and b) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using TUNEL assay after 24, 36, and 48 hrs post DENV2 infection.(c) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using AnnexinV-FITC/PI labeling flow cytometry after 24, 36, and 48 hrs post DENV2 infection.(d) Analysis of AnnexinV positive cell ratio.(e and f) Cell viability was determined by MTT. ***P<0.01.

Mentions: A number of studies had already shown that DENV2 could induce apoptosis in VECs [23–25]. Thus we explored the potentially important role that IFI6 might play in this pathological process of programmed cell death. With the aid of fluorescence confocal microscopy, we observed that the non-structual 1 protein (NS1) of DENV2 appeared in more than 90% of the recombinant VECs after 24 hrs post DENV2 incubation. Evidence of apoptosis was found scattered within the infected cells. However, there seemed to be almost no DNA fragments at the early stages of infection in IFI6+/+ cells, which maintained a lower level of apoptosis as compared with the vector-high cells (Fig 3a). On the contrary, DNA fragments had increased in IFI6-/- cells as compared to vector-low cells at optional time points, especially at 48 hrs after infection (Fig 3b).


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)

IFI6 inhibits apoptosis of VECs induced by DENV2.(a and b) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using TUNEL assay after 24, 36, and 48 hrs post DENV2 infection.(c) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using AnnexinV-FITC/PI labeling flow cytometry after 24, 36, and 48 hrs post DENV2 infection.(d) Analysis of AnnexinV positive cell ratio.(e and f) Cell viability was determined by MTT. ***P<0.01.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0132743.g003: IFI6 inhibits apoptosis of VECs induced by DENV2.(a and b) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using TUNEL assay after 24, 36, and 48 hrs post DENV2 infection.(c) Apoptosis of IFI6+/+ cells, IFI6-/- cells and vector cells were detected using AnnexinV-FITC/PI labeling flow cytometry after 24, 36, and 48 hrs post DENV2 infection.(d) Analysis of AnnexinV positive cell ratio.(e and f) Cell viability was determined by MTT. ***P<0.01.
Mentions: A number of studies had already shown that DENV2 could induce apoptosis in VECs [23–25]. Thus we explored the potentially important role that IFI6 might play in this pathological process of programmed cell death. With the aid of fluorescence confocal microscopy, we observed that the non-structual 1 protein (NS1) of DENV2 appeared in more than 90% of the recombinant VECs after 24 hrs post DENV2 incubation. Evidence of apoptosis was found scattered within the infected cells. However, there seemed to be almost no DNA fragments at the early stages of infection in IFI6+/+ cells, which maintained a lower level of apoptosis as compared with the vector-high cells (Fig 3a). On the contrary, DNA fragments had increased in IFI6-/- cells as compared to vector-low cells at optional time points, especially at 48 hrs after infection (Fig 3b).

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