Regulation of IL-4-induced human macrophage polarization by acetyl-CoA and AMP-activated protein kinase
Biochemistry
Immunology
Cell Biology
Final Report Abstract
Acetyl-coenzyme A (acetyl-CoA) is an intermediate for biosynthesis of fatty acids and cholesterol, and also is a donor of acetyl group for post-translational modification of proteins (acetylation). In particular, acetylation of nuclear histone proteins is an important regulatory mechanism to activate transcription of genes. We investigated the impact of adenosine triphosphate citrate lyase (ACLY), an enzyme responsible for the acetyl-CoA in the cytosol and nucleus of mammalian cells, on the responses of human macrophages to interleukin-4 (IL-4). IL-4 is a cytokine able to trigger anti-inflammatory, tissue regenerative, and pro-fibrotic changes of gene expression in macrophages, a phenotype collectively called alternative activation. Following observations in mouse macrophages, we observed that pharmacological inhibitors of ACLY suppress IL-4- elicited gene expression in primary human macrophages. However, these findings were not recapitulated when ACLY expression was down-regulated using small interfering RNA against ACLY. Furthermore, ACLY inhibition or down-regulation failed to affect acetyl-CoA levels or acetylation of histone proteins. These findings suggested that ACLY pharmacological inhibitors may suppress gene expression through effects unrelated to their action on ACLY. To test this, we employed an alternative approach, abolishing ACLY expression in a monocytic cell line THP-1 using CRISPR-Cas9 technology. ACLY-deficient cells showed reduced proliferation and attenuated histone acetylation, hallmarks of reduced acetyl-CoA production. However, IL-4-elicited gene expression was still sensitive to ACLY inhibitors, confirming their ACLY-independent action. Collectively, our findings indicate that ACLY doesn’t play a major role in acetyl-CoA generation in primary human macrophages and is dispensable for IL-4-induced gene expression. This suggests that there are additional, possibly redundant routes to synthesize acetyl-CoA in the cytosol and nucleus of macrophages, which remain to be elucidated.
Publications
- (2018) AICAR inhibits NFκB DNA binding independently of AMPK to attenuate LPS-triggered inflammatory responses in human macrophages. Sci Rep 8:7801
Kirchner J, Brüne B, Namgaladze D
(See online at https://doi.org/10.1038/s41598-018-26102-3) - (2018) IL-6 augments IL-4-induced polarization of primary human macrophages through synergy of STAT3, STAT6 and BATF transcription factors. Oncoimmunology 7:e1494110
Gupta S, Jain A, Syed SN, Snodgrass RG, Pflüger-Müller B, Leisegang MS, Weigert A, Brandes RP, Ebersberger I, Brüne B, Namgaladze D
(See online at https://doi.org/10.1080/2162402x.2018.1494110) - (2018) Polarization of Human Macrophages by Interleukin-4 Does Not Require ATP-Citrate Lyase. Front Immunol 9:2858
Namgaladze D, Zukunft S, Schnütgen F, Kurrle N, Fleming I, Fuhrmann D, Brüne B
(See online at https://doi.org/10.3389/fimmu.2018.02858) - (2021) Exploring the Role of ATP-Citrate Lyase in the Immune System. Front Immunol 12:632526
Dominguez M, Brüne B, Namgaladze D
(See online at https://doi.org/10.3389/fimmu.2021.632526) - (2021) Pharmacological Activation of p53 during Human Monocyte to Macrophage Differentiation Attenuates Their Pro-Inflammatory Activation by TLR4, TLR7 and TLR8 Agonists. Cancers (Basel) 13:958
Namgaladze D, Brüne B
(See online at https://doi.org/10.3390/cancers13050958)
