Hypercapnia alters mitochondrial gene expression and acylcarnitine production in monocytes

David E. Phelan, Catarina Mota, Moritz J. Strowitzki, Masahiko Shigemura, Jacob I. Sznajder, Louise Crowe, Joanne C. Masterson, Sophie E. Hayes, Ben Reddan, Xiaofei Yin, Lorraine Brennan, Daniel Crean, Eoin P. Cummins*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


CO2 is produced during aerobic respiration. Normally, levels of CO2 in the blood are tightly regulated but pCO2 can rise (hypercapnia, pCO2 > 45 mmHg) in patients with lung diseases, for example, chronic obstructive pulmonary disease (COPD). Hypercapnia is a risk factor in COPD but may be of benefit in the context of destructive inflammation. The effects of CO2 per se, on transcription, independent of pH change are poorly understood and warrant further investigation. Here we elucidate the influence of hypercapnia on monocytes and macrophages through integration of state-of-the-art RNA-sequencing, metabolic and metabolomic approaches. THP-1 monocytes and interleukin 4–polarized primary murine macrophages were exposed to 5% CO2 versus 10% CO2 for up to 24 h in pH-buffered conditions. In hypercapnia, we identified around 370 differentially expressed genes (DEGs) under basal and about 1889 DEGs under lipopolysaccharide-stimulated conditions in monocytes. Transcripts relating to both mitochondrial and nuclear-encoded gene expression were enhanced in hypercapnia in basal and lipopolysaccharide-stimulated cells. Mitochondrial DNA content was not enhanced, but acylcarnitine species and genes associated with fatty acid metabolism were increased in hypercapnia. Primary macrophages exposed to hypercapnia also increased activation of genes associated with fatty acid metabolism and reduced activation of genes associated with glycolysis. Thus, hypercapnia elicits metabolic shifts in lipid metabolism in monocytes and macrophages under pH-buffered conditions. These data indicate that CO2 is an important modulator of monocyte transcription that can influence immunometabolic signaling in immune cells in hypercapnia. These immunometabolic insights may be of benefit in the treatment of patients experiencing hypercapnia.

Original languageEnglish (US)
Pages (from-to)556-577
Number of pages22
JournalImmunology and Cell Biology
Issue number6
StatePublished - Jul 2023


  • Acylcarnitine
  • CO
  • RNA-seq
  • carbon dioxide
  • gene expression
  • hypercapnia
  • mitochondria
  • monocyte

ASJC Scopus subject areas

  • Immunology and Allergy
  • Cell Biology
  • Immunology


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