How Clearing Dead Cells Helps Repair Arteries, and Why DNMT3A Mutations May Block It
A JCI commentary explains how DNMT3A drives DNA repair in macrophages after efferocytosis and why clonal hematopoiesis mutations may impair plaque healing.
Resumen
This commentary reviews a study by Avrampou and colleagues on how macrophages that eat dying cells (efferocytosis) repair their own DNA and promote healing in atherosclerotic plaques. The study found that efferocytosis activates DNMT3A, an enzyme often mutated in clonal hematopoiesis (CH), to drive base excision repair that removes oxidized DNA damage (8-OHdG). This supports macrophage proliferation and tissue repair. In mouse models of DNMT3A-driven CH, LDL lowering failed to thicken the plaque's fibrous cap or boost pro-resolving macrophage markers as it did in normal mice. The work suggests that people with DNMT3A-CH may respond differently to lipid-lowering therapy. It also points to pro-resolving pathways as therapeutic targets. The findings are preclinical, and human studies are still needed.
Resumen detallado
Atherosclerosis is the leading cause of death worldwide. Most therapies target inflammation, using statins, colchicine, or IL-6 blockade. Researchers increasingly argue that actively promoting the resolution of inflammation and tissue repair may matter just as much. A key resolution process is efferocytosis, in which macrophages clear apoptotic cells. Pro-resolving mediators such as resolvins, protectins, and maresins enhance this process, and they are depleted in vulnerable plaques.
This commentary in the Journal of Clinical Investigation discusses new work by Avrampou and colleagues. Earlier research showed that macrophages take up methionine from apoptotic cells. The methionine is converted to S-adenosylmethionine, which activates DNMT3A-mediated DNA methylation and ERK1/2–TGF-β1 signaling, promoting resolution. DNMT3A is also the most commonly mutated gene in clonal hematopoiesis (CH), a condition in which blood cells carrying acquired somatic mutations expand. DNMT3A-CH is linked to higher coronary heart disease risk in humans and accelerated atherosclerosis in mice. Human genetic data suggest the mechanism does not depend on IL-6.
In mouse and human macrophages, Avrampou et al. found that efferocytosis activates base excision repair to remove 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidized DNA, and that this depends on DNMT3A. Efferocytosis increased PARP1 binding to chromatin, which helps assemble the repair complex. It also increased nuclear MTH1, which hydrolyzes 8-OHdG. Both effects required DNMT3A, and the repair process promoted efferocytosis-induced macrophage proliferation. In a dexamethasone-induced thymocyte apoptosis model, the DNMT3A-dependent pathway was needed for thymic repair.
The authors then built an Ldlr–/– mouse model of DNMT3A-CH to test relevance to atherosclerosis regression. LDL lowering in wild-type mice thickened the fibrous cap, a sign of plaque stabilization, and raised pro-resolving macrophage markers. DNMT3A-CH mice showed markedly less cap thickening and little to no marker increase. This implicates DNA repair as a link between apoptotic cell–derived methionine, DNMT3A methylation, and pro-resolving macrophage proliferation.
The commentary notes that the studied mutation, R882H, causes loss of function in the methyltransferase domain. It may therefore be more relevant to cardiovascular disease than other DNMT3A variants. The findings suggest that statin-induced regression might be blunted in DNMT3A-CH carriers, and clinical studies of lipid-lowering in this group are warranted. Single-cell profiling could define the macrophage subsets involved. The overlap with inflammatory pathways in heart failure and cardiac fibrosis also deserves study. These data are preclinical, and the commentary does not report human outcomes.
Hallazgos clave
- Efferocytosis activates DNMT3A-dependent base excision repair that removes oxidized DNA damage (8-OHdG) in mouse and human macrophages.
- Efferocytosis increases PARP1 chromatin binding and nuclear MTH1, both of which require DNMT3A, to support repair and macrophage proliferation.
- DNMT3A-dependent efferocytosis was needed for thymic repair after dexamethasone-induced thymocyte apoptosis in mice.
- In Ldlr–/– DNMT3A-CH mice, LDL lowering produced much less fibrous cap thickening and pro-resolving marker expression than in wild-type mice.
- The R882H loss-of-function variant may be especially relevant to cardiovascular risk and to responses to lipid-lowering therapy.
Metodología
This is a commentary on a primary preclinical study (Avrampou et al.) that used mouse and human macrophages, a thymocyte apoptosis model, and an Ldlr–/– mouse model of DNMT3A-CH with LDL-lowering to assess plaque regression. The commentary itself presents no new data and summarizes the study and its context.
Limitaciones del estudio
The evidence is preclinical, drawn largely from mouse models, and the commentary does not report human outcome data. Findings may be specific to the R882H variant and may not extend to other DNMT3A mutations. Details of effect sizes, sample sizes, and statistics are not given, and the specific macrophage populations involved remain undefined.
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