Macrophage AXL receptor tyrosine kinase inflames the heart after reperfused myocardial infarction
Matthew DeBerge, Kristofor Glinton, Manikandan Subramanian, Lisa D. Wilsbacher, Carla V. Rothlin, Ira Tabas, Edward B. Thorp
Matthew DeBerge, Kristofor Glinton, Manikandan Subramanian, Lisa D. Wilsbacher, Carla V. Rothlin, Ira Tabas, Edward B. Thorp
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Research Article Cardiology Inflammation

Macrophage AXL receptor tyrosine kinase inflames the heart after reperfused myocardial infarction

Abstract

Tyro3, AXL, and MerTK (TAM) receptors are activated in macrophages in response to tissue injury and as such have been proposed as therapeutic targets to promote inflammation resolution during sterile wound healing, including myocardial infarction. Although the role of MerTK in cardioprotection is well characterized, the unique role of the other structurally similar TAMs, and particularly AXL, in clinically relevant models of myocardial ischemia/reperfusion infarction (IRI) is comparatively unknown. Utilizing complementary approaches, validated by flow cytometric analysis of human and murine macrophage subsets and conditional genetic loss and gain of function, we uncover a maladaptive role for myeloid AXL during IRI in the heart. Cross signaling between AXL and TLR4 in cardiac macrophages directed a switch to glycolytic metabolism and secretion of proinflammatory IL-1β, leading to increased intramyocardial inflammation, adverse ventricular remodeling, and impaired contractile function. AXL functioned independently of cardioprotective MerTK to reduce the efficacy of cardiac repair, but like MerTK, was proteolytically cleaved. Administration of a selective small molecule AXL inhibitor alone improved cardiac healing, which was further enhanced in combination with blockade of MerTK cleavage. These data support further exploration of macrophage TAM receptors as therapeutic targets for myocardial infarction.

Authors

Matthew DeBerge, Kristofor Glinton, Manikandan Subramanian, Lisa D. Wilsbacher, Carla V. Rothlin, Ira Tabas, Edward B. Thorp

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Figure 6

Cross signaling between AXL and TLR4 augments STAT1 activation to fuel proinflammatory responses in macrophages.

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Cross signaling between AXL and TLR4 augments STAT1 activation to fuel p...
(A) Immunoblot or (B) flow cytometry of STAT1 phosphorylation in Axl+/+ or Axl–/– bone marrow–derived macrophages (BMDMs) untreated (Ø) or treated with lipopolysaccharide (LPS). Data are representative of 2–3 independent experiments. n = 3 sets of cells/group. **P < 0.01, ***P < 0.001 by 2-way ANOVA followed by Tukey’s test. See complete unedited blots in the supplemental material. (C) STAT1 phosphorylation in Axl+/+ or Axl–/– cardiac macrophages 3 days after ischemia/reperfusion infarction (IRI). n = 4–5 mice/group pooled from 2 independent experiments. *P < 0.05 by 2-tailed, unpaired t test. (D) HIF-1α protein in Stat1+/+ or Stat1–/– BMDMs treated with LPS for 4 hours as measured by flow cytometry. Data are representative of 2 independent experiments. n = 3 sets of cells/group. *P < 0.05, **P < 0.01, ***P < 0.001 by 2-way ANOVA followed by Tukey’s test. (E) Extracellular acidification rate (ECAR) with quantification of glycolytic function in Stat1+/+ or Stat1–/– BMDMs treated with LPS for 3 hours. Data are representative of 2 independent experiments. n = 6–8 sets of cells/group. *P < 0.05, ***P < 0.001 by 2-way ANOVA followed by Tukey’s test. (F) IL-1β production by Stat1+/+ or Stat1–/– BMDMs primed with LPS for 3 hours followed by activation with ATP for 30 minutes. Data are representative of 2 independent experiments. n = 3 sets of cells/group. *P < 0.05 by 2-tailed, unpaired t test. All data presented as mean ± SEM.