title: EGCG inhibits Tat-induced LTR transactivation: role of Nrf2, AKT, AMPK signaling pathway.
abstract: OBJECTIVE
  Transcription is a crucial step for human immunodeficiency virus 1 (HIV-1) gene expression in infected host cells. The HIV-1 Tat activates the nuclear factor-kappa B (NF-κB) signaling transduction pathway, which is necessary for viral replication. Epigallocatechin-3-gallate (EGCG) has antioxidant, anti-inflammatory, and anti-viral properties. In this study, we investigated the effects of EGCG on Tat-induced HIV-1 transactivation and potential mechanisms by which EGCG inhibited activation of NF-κB pathway.
  
  
  METHODS
  HeLa-CD4-long terminal repeat (LTR)-β-gal (MAGI) cells were transfected with Tat plasmid. Tat-induced HIV-1 LTR transactivation was determined by MAGI cell assay. The reactive oxygen species (ROS) levels and glutathione (GSH) levels were measured. In addition, the protein expressions were assayed by western blotting.
  
  
  RESULTS
  Tat caused a significant decrease in the intracellular glutathione (GSH) levels, a mild increase in the expression of nuclear levels of NF-E2-related factor-2 (Nrf2), a significant increase in the levels of NF-κB (phosphorylation of p65 and IKK) and a significant increase in ROS production. EGCG supplementation significantly improved the changes associated with Tat-induced oxidative stress by increasing nuclear levels of Nrf2, decreasing levels of NF-κB and ROS production. EGCG reversed Tat-mediated AKT activation and AMPK inhibition in MAGI cells. EGCG inhibited Tat-induced LTR transactivation in a dose-dependent manner.
  
  
  CONCLUSIONS
  The results suggest that Nrf2 signaling pathway may be the primary target for prevention of Tat-induced HIV-1 transactivation by EGCG, and EGCG also reduce NF-κB activation by inhibiting AKT signaling pathway and activating AMPK signaling pathway.
authors.affiliation: College of Life Science & Bioengineering, Beijing University of Technology, Pingleyuan 100#, District of Chaoyang, Beijing, 100124, China. zhanghs@bjut.edu.cn
authors.forename: Hong-Sheng
authors.initials: HS
authors.lastname: Zhang
authors.forename: Tong-Chao
authors.initials: TC
authors.lastname: Wu
authors.forename: Wei-Wei
authors.initials: WW
authors.lastname: Sang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Ruan
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D015153:Blotting, Western; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D020868:Gene Silencing; D005978:Glutathione / Q000378:metabolism; D016325:HIV Long Terminal Repeat / Q000187:drug effects*; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D047468:Immunoprecipitation; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000502:physiology*; D019255:NADPH Oxidases / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000187:drug effects / Q000502:physiology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013662:Tea / Q000737:chemistry; D051996:Transcription Factor RelA / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects*; D014162:Transfection; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000037:antagonists & inhibitors*
chemical_list: D000975:Antioxidants; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D011480:Protease Inhibitors; D017382:Reactive Oxygen Species; D013662:Tea; D051996:Transcription Factor RelA; D054322:tat Gene Products, Human Immunodeficiency Virus; D002392:Catechin; C045651:epigallocatechin gallate; D019255:NADPH Oxidases; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; D020928:Mitogen-Activated Protein Kinases; D005978:Glutathione