Oxidative stress inhibits IFN-alpha-induced antiviral gene expression by blocking the JAK-STAT pathway.
OBJECTIVE
Unresponsiveness to IFN-alpha is common in chronic hepatitis C. Since conditions associated with an increased oxidative stress (advanced age, steatosis, fibrosis, iron overload, and alcohol consumption) reduce the likelihood of response, we hypothesized that oxidative stress may affect the antiviral actions of IFN-alpha.


METHODS
We examined in a human hepatocellular carcinoma cell line (Huh-7) the effect of hydrogen peroxide (H2O2), as a generator of oxidative stress, on the IFN-alpha signaling pathway.


RESULTS
Pretreatment of Huh-7 cells with 0.5-1 mM H2O2 resulted in the suppression of the IFN-alpha-induced antiviral protein MxA and of IRF-9 mRNA expression. The reduced expression of these genes was associated to H2O2 -mediated suppression of the IFN-alpha-induced assembly of signal transducer and activator of transcription (STAT) factors to specific promoter motifs on IFN-alpha-inducible genes. This was accomplished by preventing the IFN-alpha-induced tyrosine phosphorylation of STAT-1 and STAT-2 through the inactivation of the upstream receptor associated tyrosine kinases, JAK-1 and Tyk-2. The suppression was fast, occurring within 5mins of pretreatment with H2O2, and did not require protein synthesis.


CONCLUSIONS
In conclusion, oxidative stress impairs IFN-alpha signaling and might cause resistance to the antiviral action of IFN-alpha in chronically HCV infected patients with high level of oxidative stress in the liver.
Di Bona
Danilo
D
Cattedra e Unità Operativa di Gastroenterologia, Dipartimento Biomedico e di Medicina Specialistica, University of Palermo, Palermo, Italy. dibona@ibim.cnr.it
Cippitelli
Marco
M
Fionda
Cinzia
C
Cammà
Calogero
C
Licata
Anna
A
Santoni
Angela
A
Craxì
Antonio
A
D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D019204:GTP-Binding Proteins / Q000235:genetics*; D015967:Gene Expression Regulation, Viral / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000077190:Interferon alpha-2; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit / Q000235:genetics*; D016898:Interferon-alpha / Q000494:pharmacology*; D053613:Janus Kinase 1 / Q000378:metabolism*; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D064547:Myxovirus Resistance Proteins; D018384:Oxidative Stress; D012334:RNA, Neoplasm / Q000235:genetics; D011994:Recombinant Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050791:STAT Transcription Factors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
C494227:IRF9 protein, human; D000077190:Interferon alpha-2; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D012334:RNA, Neoplasm; D011994:Recombinant Proteins; D050791:STAT Transcription Factors; D006861:Hydrogen Peroxide; D053613:Janus Kinase 1; D019204:GTP-Binding Proteins