Carbon monoxide exposure activates ULK1 via AMPK phosphorylation in murine embryonic fibroblasts

Int J Vitam Nutr Res. 2023 Apr;93(2):122-131. doi: 10.1024/0300-9831/a000714. Epub 2021 Jun 2.


Carbon monoxide (CO) is endogenously produced upon degradation of heme by heme oxygenases (HOs) and is suggested to act as a gaseous signaling molecule. The expression of HO-1 is triggered by the Nrf2-Keap1 signaling pathway which responds to exogenous stress signals and dietary constituents such as flavonoids and glucosinolates or reactive metabolic intermediates like 4-hydroxynonenal. Endogenous CO affects energy metabolism, regulates the utilization of glucose and addresses CYP450 enzymes. Using the CO releasing molecule-401 (CORM-401), we studied the effect of endogenous CO on ATP synthesis, AMP-signaling and activation of the AMPK pathway in cell culture. Upon exposure of cells to CORM-401, the mitochondrial ATP production rate was significantly decreased (P=0.007) to about 50%, while glycolytic ATP synthesis was unchanged (P=0.489). Total ATP levels were less affected as determined by mass spectrometry. Instead, levels of ADP and AMP were elevated following CORM-401 exposure by about two- (P=0.022) and four-fold (P=0.012) compared to control, respectively. Increased concentrations of AMP activate AMPK which was demonstrated by a 10 to 15-fold increased phosphorylation of Thr172 of the α-subunit of AMPK (P=0.025). A downstream target of AMPK is the kinase ULK1 which triggers autophagic and mitophagic processes. Activation of ULK1 after CO exposure was proven by a 3 to 5-fold elevated phosphorylation of ULK1 at Ser555 (P=0.004). The present data suggest that production of endogenous CO leads to increasing amounts of AMP which mediates AMPK-dependent downstream effects and likely triggers autophagic processes. Since dietary constituents and their metabolites induce the expression of the CO producing enzyme HO-1, CO signaling may also be involved in the cellular response to nutritional factors.

Keywords: CORMs; mitochondria; mitophagy; nutrition; respiratory chain; signaling.

MeSH terms

  • AMP-Activated Protein Kinases* / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • Carbon Monoxide* / metabolism
  • Fibroblasts / metabolism
  • Heme / metabolism
  • Kelch-Like ECH-Associated Protein 1 / metabolism
  • Mice
  • NF-E2-Related Factor 2 / metabolism
  • Phosphorylation


  • Carbon Monoxide
  • AMP-Activated Protein Kinases
  • Kelch-Like ECH-Associated Protein 1
  • NF-E2-Related Factor 2
  • Heme
  • Adenosine Triphosphate