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Stability of CXCL-8 and related AU-rich mRNAs in the context of hepatitis C virus replication in vitro.

BACKGROUND
Previous studies have shown that levels of CXCL-8 are elevated in patients with chronic hepatitis C virus (HCV) infection and are highest in nonresponders to interferon (IFN) therapy and that CXCL-8 inhibits IFN antiviral action. CXCL-8 expression involves AU-rich elements (AREs) in 3' untranslated regions that regulate mRNA stability. CXCL-8 mRNA stability was, therefore, investigated in the context of HCV replication in 4 replicon cell lines, Huh7 and Huh7.5 cells, and primary human fetal hepatocytes.


METHODS
The half-life of CXCL-8 mRNA was measured by use of real-time reverse-transcription polymerase chain reaction following tumor necrosis factor (TNF)- alpha induction in the presence and absence of inhibitors of transcription and translation. Cellular mRNAs containing AREs were assessed by custom microarray analyses.


RESULTS
The half-life of CXCL-8 mRNA increased in 3 of 4 HCV replicon cell lines, particularly after treatment with TNF- alpha , a potent inducer of CXCL-8. CXCL-8 mRNA was superinduced by TNF- alpha in the presence of the protein-synthesis inhibitor cycloheximide. Analysis of >1500 ARE-containing cellular mRNAs, by use of microarrays, revealed that CXCL-8 and other newly identified ARE genes were induced by TNF- alpha in Huh7 cells and were coordinately regulated.


CONCLUSION
The data suggest that increased CXCL-8 gene expression in the context of HCV replication involves posttranscriptional events.