In vitro Inhibition of Lamivudine-Resistant Hepatitis B Virus Replication by Phyllanthus urinaria koreanis Extract
Jung, Jaesung; Kim, Kyongmin
Department of Microbiology
Long-term treatment of chronic hepatitis B with nucleos(t)ide analogues can lead to the emergence of hepatitis B virus (HBV) drug-resistant mutants within the polymerase (P) gene. The Phyllanthus plant has anti-HBV activity; however, the antiviral activity of HBV drug-resistant mutants has never been examined. In this study, HBV P gene variants of the YMDD (203tyrosine-methionine-aspartate-aspartate206) reverse transcriptase (RT) active site, including rtM204I, rtM204V, and rtM204S mutants which are major mutations in lamivudine (LMV)-resistant mutants, were tested for their sensitivity to Phyllanthus urinaria koreanis extract. HBV DNA synthesis and HBV surface antigen (HBsAg) and HBV core antigen (HBcAg) secretions were examined in variant-transfected and extract-treated cells since core protein expression, core particle formation, and pregenomic RNA encapsidation were not decreased in HBV wild type (wt)-transfected and extract-treated HepG2 cells. Analysis of intracellular HBV DNA demonstrated that all variants were almost equally sensitive to the Phyllanthus extract as wt HBV. HBsAg and HBcAg secretion was also reduced in a dose-dependent manner. The extract induced interferon-beta (IFN-b), cyclooxygenase-2 (COX-2), and interleukin-6 (IL-6) mRNA expression in HBV wt-transfecte d Phyllanthus extract-treated HepG2 cells, possibly through an intracellular signaling cascade. HBV transfection without extract treatment or extract treatment alone did not induce this signaling cascade. Taken together, we suggest that Phyllanthus urinaria koreanis extract may inhibit HBV DNA synthesis and HBsAg and HBcAg secretion by inducing IFN-b, COX-2, and IL-6 expression in HBV wt and LMV-resistant variants replicating cells.
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