Hematoma Resolution In Vivo Is Directed by Activating Transcription Factor 1

Circ Res. 2020 Sep 11;127(7):928-944. doi: 10.1161/CIRCRESAHA.119.315528. Epub 2020 Jul 1.

Abstract

Rationale: The efficient resolution of tissue hemorrhage is an important homeostatic function. In human macrophages in vitro, heme activates an AMPK (AMP-activated protein kinase)/ATF1 (activating transcription factor-1) pathway that directs Mhem macrophages through coregulation of HO-1 (heme oxygenase-1; HMOX1) and lipid homeostasis genes.

Objective: We asked whether this pathway had an in vivo role in mice.

Methods and results: Perifemoral hematomas were used as a model of hematoma resolution. In mouse bone marrow-derived macrophages, heme induced HO-1, lipid regulatory genes including LXR (lipid X receptor), the growth factor IGF1 (insulin-like growth factor-1), and the splenic red pulp macrophage gene Spic. This response was lost in bone marrow-derived macrophages from mice deficient in AMPK (Prkab1-/-) or ATF1 (Atf1-/-). In vivo, femoral hematomas resolved completely between days 8 and 9 in littermate control mice (n=12), but were still present at day 9 in mice deficient in either AMPK (Prkab1-/-) or ATF1 (Atf1-/-; n=6 each). Residual hematomas were accompanied by increased macrophage infiltration, inflammatory activation and oxidative stress. We also found that fluorescent lipids and a fluorescent iron-analog were trafficked to lipid-laden and iron-laden macrophages respectively. Moreover erythrocyte iron and lipid abnormally colocalized in the same macrophages in Atf1-/- mice. Therefore, iron-lipid separation was Atf1-dependent.

Conclusions: Taken together, these data demonstrate that both AMPK and ATF1 are required for normal hematoma resolution. Graphic Abstract: An online graphic abstract is available for this article.

Keywords: hemorrhage; inflammation; lipids; macrophages; oxidative stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / genetics
  • AMP-Activated Protein Kinases / metabolism*
  • Activating Transcription Factor 1 / genetics
  • Activating Transcription Factor 1 / metabolism*
  • Animals
  • Cells, Cultured
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Disease Models, Animal
  • Erythrocytes / metabolism
  • Female
  • Hematoma / genetics
  • Hematoma / metabolism*
  • Heme Oxygenase-1 / genetics
  • Heme Oxygenase-1 / metabolism
  • Insulin-Like Growth Factor I / genetics
  • Insulin-Like Growth Factor I / metabolism
  • Iron / metabolism
  • Lipid Metabolism
  • Liver X Receptors / genetics
  • Liver X Receptors / metabolism
  • Macrophages / metabolism*
  • Male
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Oxidative Stress
  • Time Factors

Substances

  • Activating Transcription Factor 1
  • Atf1 protein, mouse
  • DNA-Binding Proteins
  • Liver X Receptors
  • Membrane Proteins
  • Spic protein, mouse
  • insulin-like growth factor-1, mouse
  • Insulin-Like Growth Factor I
  • Iron
  • Heme Oxygenase-1
  • Hmox1 protein, mouse
  • Prkab1 protein, mouse
  • AMP-Activated Protein Kinases