Green tea polyphenol EGCG suppresses cigarette smoke condensate-induced NF-kappaB activation in normal human bronchial epithelial cells

Oncogene. 2007 Feb 1;26(5):673-82. doi: 10.1038/sj.onc.1209829. Epub 2006 Jul 24.

Abstract

Cigarette smoke is a powerful inducer of inflammatory responses resulting in disruption of major cellular pathways with transcriptional and genomic alterations driving the cells towards carcinogenesis. Cell culture and animal model studies indicate that (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol present in green tea, possesses potent anti-inflammatory and antiproliferative activity capable of selectively inhibiting cell growth and inducing apoptosis in cancer cells without adversely affecting normal cells. Here, we demonstrate that EGCG pretreatment (20-80 microM) of normal human bronchial epithelial cells (NHBE) resulted in significant inhibition of cigarette smoke condensate (CSC)-induced cell proliferation. Nuclear factor-kappaB (NF-kappaB) controls the transcription of genes involved in immune and inflammatory responses. In most cells, NF-kappaB prevents apoptosis by mediating cell survival signals. Pretreatment of NHBE cells with EGCG suppressed CSC-induced phosphorylation of IkappaBalpha, and activation and nuclear translocation of NF-kappaB/p65. NHBE cells transfected with a luciferase reporter plasmid containing an NF-kappaB-inducible promoter sequence showed an increased reporter activity after CSC exposure that was specifically inhibited by EGCG pretreatment. Immunoblot analysis showed that pretreatment of NHBE cells with EGCG resulted in a significant downregulation of NF-kappaB-regulated proteins cyclin D1, MMP-9, IL-8 and iNOS. EGCG pretreatment further inhibited CSC-induced phosphorylation of ERK1/2, JNK and p38 MAPKs and resulted in a decreased expression of PI3K, AKT and mTOR signaling molecules. Taken together, our data indicate that EGCG can suppress NF-kappaB activation as well as other pro-survival pathways such as PI3K/AKT/mTOR and MAPKs in NHBE cells, which may contribute to its ability to suppress inflammation, proliferation and angiogenesis induced by cigarette smoke.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Anticarcinogenic Agents / pharmacology*
  • Antioxidants
  • Apoptosis / drug effects
  • Bronchi / cytology
  • Bronchi / drug effects*
  • Bronchi / metabolism
  • Catechin / analogs & derivatives*
  • Catechin / pharmacology
  • Cyclin D1 / metabolism
  • Cyclooxygenase 2 / metabolism
  • DNA / genetics
  • DNA / metabolism
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism
  • Humans
  • Matrix Metalloproteinase 9 / metabolism
  • Membrane Proteins / metabolism
  • Mitogen-Activated Protein Kinases / metabolism
  • NF-kappa B / genetics
  • NF-kappa B / metabolism*
  • Phosphorylation / drug effects
  • Signal Transduction
  • Smoke*
  • Tea*
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • Anticarcinogenic Agents
  • Antioxidants
  • Membrane Proteins
  • NF-kappa B
  • Smoke
  • Tea
  • VEGFA protein, human
  • Vascular Endothelial Growth Factor A
  • Cyclin D1
  • Catechin
  • DNA
  • epigallocatechin gallate
  • Cyclooxygenase 2
  • PTGS2 protein, human
  • Mitogen-Activated Protein Kinases
  • Matrix Metalloproteinase 9