The fruit juice of Morinda citrifolia (noni) downregulates HIF-1α protein expression through inhibition of PKB, ERK-1/2, JNK-1 and S6 in manganese-stimulated A549 human lung cancer cells

Int J Mol Med. 2012 Mar;29(3):499-504. doi: 10.3892/ijmm.2011.860. Epub 2011 Dec 14.

Abstract

High exposure of manganese is suggested to be a risk factor for many lung diseases. Evidence suggests anticancerous and antiangiogenic effects by products derived from Morinda citrifolia (noni) fruit. In this study, we investigated the effect of noni fruit juice (NFJ) on the expression of HIF-1α, a tumor angiogenic transcription factor in manganese-chloride (manganese)-stimulated A549 human lung carcinoma cells. Treatment with manganese largely induced expression of HIF-1α protein but did not affect HIF-1α mRNA expression in A549 cells, suggesting the metal-mediated co- and/or post-translational HIF-1α upregulation. Manganese treatment also led to increased phosphorylation of extracellular-regulated protein kinase-1/2 (ERK-1/2), c-Jun N-terminal kinase-1 (JNK-1), protein kinase B (PKB), S6 and eukaryotic translation initiation factor-2α (eIF-2α) in A549 cells. Of note, the exposure of NFJ inhibited the manganese-induced HIF-1α protein upregulation in a concentration-dependent manner. Importantly, as assessed by results of pharmacological inhibition and siRNA transfection studies, the effect of NFJ on HIF-1α protein downregulation seemed to be largely associated with the ability of NFJ to interfere with the metal's signaling to activate PKB, ERK-1/2, JNK-1 and S6 in A549 cells. It was further shown that NFJ could repress the induction of HIF-1α protein by desferoxamine or interleukin-1β (IL-1β), another HIF-1α inducer in A549 cells. Thus, the present study provides the first evidence that NFJ has the ability to strongly downregulate manganese-induced HIF-1α protein expression in A549 human lung cancer cells, which may suggest the NFJ-mediated beneficial effects on lung pathologies in which manganese and HIF-1α overexpression play pathogenic roles.

MeSH terms

  • Cell Line, Tumor
  • Down-Regulation / drug effects
  • Eukaryotic Initiation Factor-2 / metabolism
  • Fruit / chemistry*
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Lung Neoplasms / enzymology
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism*
  • Manganese / pharmacology*
  • Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Mitogen-Activated Protein Kinase 8 / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase 8 / metabolism
  • Morinda / chemistry*
  • Phosphorylation / drug effects
  • Plant Extracts / pharmacology*
  • Protein Stability / drug effects
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors*
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / metabolism
  • Ribosomal Protein S6 Kinases / antagonists & inhibitors
  • Ribosomal Protein S6 Kinases / metabolism
  • Signal Transduction / drug effects

Substances

  • Eukaryotic Initiation Factor-2
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Plant Extracts
  • Manganese
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinase 8