Signaling pathways involved in phase II gene induction by alpha, beta-unsaturated aldehydes

Toxicol Ind Health. 2009 May-Jun;25(4-5):269-78. doi: 10.1177/0748233709102209.

Abstract

Phase II enzymes are induced primarily through the common electrophile response element (EpRE) signaling. Studies performed in different cell types and with different inducer appear to indicate variation in the upstream signaling pathways involved in the induction of these phase II genes. Nonetheless, whether variation in signaling among phase II genes in the same cell with the same inducer is unclear. This study is designed to answer this question using human bronchial epithelial cells (HBE1 cells) as a model and screening with a variety of protein kinase inhibitors with varying degrees of specificity. Two electrophiles, 4-hydroxynonenal (HNE) and acrolein, induced the expression of phase II genes (GCLC, GCLM, NQO1, NQO2, HO-1, and GSTM-1). Nrf2 silencing significantly decreased the induction of all of these genes, confirming the involvement of Nrf2-EpRE signaling. ERK and p38MAPK inhibitors had no effect, while a JNK inhibitor abrogated the GCLC and GCLM induction by HNE, but not that by acrolein. Among the PKC inhibitors used, one eliminated gene induction by HNE and acrolein, while two others showed no effects. One PI3K inhibitor decreased the induction of GCLM, NQO1, NQO2 and HO-1, but not GCLC and GST-M1; on the other hand, the inhibitory effects of another PI3K inhibitor on gene induction seems to be gene- and inducer- specific. In conclusion, our data suggest that although phase II genes are coordinately induced through Nrf2-EpRE signaling by electrophiles, the upstream signaling pathways involved are gene- and inducer- specific. It is also suggested that commercial kinase inhibitors may produce non-specific effects on phase II gene expression via mechanisms unrelated to their purported specificity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acrolein / pharmacology*
  • Aldehydes / pharmacology*
  • Bronchi / cytology
  • COUP Transcription Factor II / genetics
  • Cell Line
  • Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
  • Gene Silencing
  • Glutamate-Cysteine Ligase / biosynthesis*
  • Glutamate-Cysteine Ligase / genetics
  • Glutathione Transferase / biosynthesis*
  • Glutathione Transferase / genetics
  • Heme Oxygenase-1 / biosynthesis*
  • Heme Oxygenase-1 / genetics
  • Humans
  • JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Phosphoinositide-3 Kinase Inhibitors
  • Quinone Reductases / biosynthesis*
  • Quinone Reductases / genetics
  • RNA, Messenger / biosynthesis
  • Respiratory Mucosa / cytology
  • Response Elements
  • Signal Transduction
  • p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors

Substances

  • Aldehydes
  • COUP Transcription Factor II
  • NR2F2 protein, human
  • Phosphoinositide-3 Kinase Inhibitors
  • RNA, Messenger
  • tert-4-hydroxy-2-nonenal
  • Acrolein
  • HMOX1 protein, human
  • Heme Oxygenase-1
  • Quinone Reductases
  • Glutathione Transferase
  • Extracellular Signal-Regulated MAP Kinases
  • JNK Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Glutamate-Cysteine Ligase