Nitric oxide down-regulates Epstein-Barr virus reactivation in epithelial cell lines.

Abstract Nitric oxide (NO), a mediator of biological functions, has an antimicrobial activity against a variety of pathogens including viruses. In this study, we found that a constitutive, low level of inducible NO synthase (iNOS) mRNA was expressed in the EBV-infected gastric tissue-derived GT38 and GT39 cell lines, by analysis with the reverse transcription–polymerase chain reaction (RT–PCR) and Southern blotting. Treatment of these cells with a specific NOS inhibitor, N G -monomethyl- l -arginine ( l -NMMA), induced the immediate-early, EBV transactivator gene BZLF1 protein ZEBRA, suggesting a significant increase in EBV reactivation by l -NMMA. Northern blotting demonstrated that BZLF1 and BRLF1 transcripts were also induced by 12- O -tetradecanoylphorbol-13 acetate (TPA). Meanwhile, constitutive expression of iNOS mRNA was inhibited by TPA. l -NMMA also enhanced TPA-induced expression of the BZLF1 gene. On the other hand, a NO donor, S -nitroso- N -acetylpenicillamine (SNAP), which releases NO in an aqueous solution, inhibited the TPA-induced BZLF1 gene expression in a dose-dependent manner at both mRNA and protein levels. These results demonstrated that NO is a regulatory factor in maintaining virus latency via inhibiting EBV reactivation in the infected epithelial cells.