TLR4 activation alters labile heme levels to regulate BACH1 and heme oxygenase-1 expression in macrophages - Inserm - Institut national de la santé et de la recherche médicale Accéder directement au contenu
Article Dans Une Revue Free Radical Biology and Medicine Année : 2019

TLR4 activation alters labile heme levels to regulate BACH1 and heme oxygenase-1 expression in macrophages

Résumé

Heme oxygenase (HO)-1, a stress-inducible enzyme that converts heme into carbon monoxide (CO), iron and biliverdin, exerts important anti-inflammatory effects in activated macrophages. HO-1 expression is mainly governed by a mutual interplay between the transcriptional factor NRF2 and the nuclear repressor BTB and CNC homology 1 (BACH1), a heme sensor protein. In the current study we hypothesized that alterations in the levels of intracellular labile heme in macrophages stimulated by lipopolysaccharide (LPS), a prototypical pro-inflammatory Toll-like receptor (TLR)4 agonist, are responsible for BACH1-dependent HO-1 expression. To this end, labile heme was determined in both mouse bone marrow-derived macrophages (mBMDMs) and human monocyte-derived macrophages (hMDMs) using an apo-horseradish peroxidase-based assay. We found that LPS raised the levels of labile heme, depressed BACH1 protein and up-regulated HO-1 in mBMDMs. In contrast, in hMDMs LPS decreased labile heme levels while increasing BACH1 expression and down-regulating HO-1. These effects were abolished by the TLR4 antagonist TAK-242, suggesting that TLR4 activation triggers the signaling cascade leading to changes in the labile heme pool. Studies using mBMDMs from BACH1-/- and NRF2-/- mice revealed that regulation of HO-1 and levels of labile heme after LPS stimulation are strictly dependent on BACH1, but not NRF2. A strong interplay between BACH1-mediated HO-1 expression and intracellular levels of labile heme was also confirmed in hMDMs with siRNA knockdown studies and following inhibition of de novo heme synthesis with succinylacetone. Finally, CORM-401, a compound that liberates CO, counteracted LPS-dependent down-regulation of HO-1 and restored levels of labile heme in hMDMs. In conclusion, alterations of labile heme levels in macrophages following TLR4 stimulation play a crucial role in BACH1-mediated regulation of HO-1 expression.
Fichier principal
Vignette du fichier
1-s2.0-S0891584919302692-main.pdf (2.39 Mo) Télécharger le fichier
Origine : Publication financée par une institution

Dates et versions

inserm-03215564 , version 1 (03-05-2021)

Identifiants

Citer

Kritika Sudan, Vijith Vijayan, Kukuh Madyaningrana, Faikah Gueler, Kazuhiko Igarashi, et al.. TLR4 activation alters labile heme levels to regulate BACH1 and heme oxygenase-1 expression in macrophages. Free Radical Biology and Medicine, 2019, 137, pp.131-142. ⟨10.1016/j.freeradbiomed.2019.04.024⟩. ⟨inserm-03215564⟩

Collections

INSERM IMRB UPEC
32 Consultations
107 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More