Curcumin Inhibits Heat-Induced Apoptosis by Suppressing NADPH Oxidase 2 and Activating the Akt/mTOR Signaling Pathway in Bronchial Epithelial Cells

Cell Physiol Biochem. 2017;41(5):2091-2103. doi: 10.1159/000475444. Epub 2017 Apr 17.

Abstract

Background: Heat causes bronchial epithelial cell apoptosis, which is a known factor contributing to airway damage during inhalation injury. Accumulating evidence has shown the effect of curcumin on inhibiting apoptosis. In this study, we investigated whether curcumin suppresses heat-induced apoptosis in bronchial epithelial cells and the underlying mechanism.

Methods: Bronchial epithelial cell line 16HBE140 cells were incubated at either 42 °C, 47 °C, 52 °C, or 57 °C for 5 min in a cell incubator and then returned back to normal culture conditions (37 °C). An in vivo thermal inhalation injury rat model was established with a heat gun blowing hot air into the airway of rats. 16HBE140 cells and lung tissue were obtained for further study with or without curcumin treatment. Cell viability was determined by measuring the absorbance of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). 2',7'-dichlorofluorescein diacetate fluorescence was used as a measure of reactive oxygen species (ROS) production. Levels of Bcl2, Bax, α-ATP, cleaved Poly (ADP-ribose) polymerase (PARP), cleaved caspase-3, gp91phox, p47phox, p67phox, p22phox, p40phox, and Rac were determined by Western blotting. TUNEL staining was used to determine apoptosis.

Results: Heat treatment triggered the apoptosis of 16HBE140 cells as shown by the increase in apoptosis molecular markers, including Bcl-2, Bax, cleaved PARP, and cleaved caspase-3. Administration of curcumin significantly inhibited apoptosis of 16HBE140 cells and suppressed the membrane translocation of NADPH oxidase 2 cytosolic components, as well as ROS production. Downregulation of Akt and mTOR phosphorylation induced by heat was also reversed by curcumin. Furthermore, we demonstrated that NADPH oxidase 2 is upstream of Akt/mTOR in heat-induced apoptosis. The protective role of curcumin on bronchial epithelia apoptosis was also confirmed in vivo by a rat inhalation injury model.

Conclusion: This study demonstrates that one of the critical mechanisms underlying curcumin inhibiting heat-induced apoptosis is through suppressing NADPH Oxidase 2 and activating the Akt/mTOR signaling pathway in bronchial epithelial cells.

Keywords: Akt/mTOR; Apoptosis; Curcumin; Heat; NADPH Oxidase 2; Thermal Inhalation Injury.

Publication types

  • Retracted Publication

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Bronchi / enzymology*
  • Bronchi / pathology
  • Cell Line
  • Curcumin / pharmacology*
  • Epithelial Cells / enzymology*
  • Epithelial Cells / pathology
  • Hot Temperature*
  • Humans
  • Membrane Glycoproteins / metabolism*
  • NADPH Oxidase 2
  • NADPH Oxidases / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Rats
  • Respiratory Mucosa / enzymology*
  • Respiratory Mucosa / pathology
  • Signal Transduction / drug effects*
  • TOR Serine-Threonine Kinases / metabolism*

Substances

  • Membrane Glycoproteins
  • CYBB protein, human
  • Cybb protein, rat
  • NADPH Oxidase 2
  • NADPH Oxidases
  • MTOR protein, human
  • mTOR protein, rat
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases
  • Curcumin