Loss of 2 Akt (Protein Kinase B) Isoforms in Hematopoietic Cells Diminished Monocyte and Macrophage Survival and Reduces Atherosclerosis in Ldl Receptor-Null Mice.

Babaev VR, Ding L, Zhang Y, May JM, Ramsey SA, Vickers KC, Linton MF
Arterioscler Thromb Vasc Biol. 2019 39 (2): 156-169

PMID: 30567482 · PMCID: PMC6344270 · DOI:10.1161/ATVBAHA.118.312206

Objective- Macrophages express 3 Akt (protein kinase B) isoforms, Akt1, Akt2, and Akt3, which display isoform-specific functions but may be redundant in terms of Akt survival signaling. We hypothesize that loss of 2 Akt isoforms in macrophages will suppress their ability to survive and modulate the development of atherosclerosis. Approach and Results- To test this hypothesis, we reconstituted male Ldlr mice with double Akt2/Akt3 knockout hematopoietic cells expressing only the Akt1 isoform (Akt1). There were no differences in body weight and plasma lipid levels between the groups after 8 weeks of the Western diet; however, Akt1→ Ldlr mice developed smaller (57.6% reduction) atherosclerotic lesions with more apoptotic macrophages than control mice transplanted with WT (wild type) cells. Next, male and female Ldlr mice were reconstituted with double Akt1/Akt2 knockout hematopoietic cells expressing the Akt3 isoform (Akt3). Female and male Akt3→ Ldlr recipients had significantly smaller (61% and 41%, respectively) lesions than the control WT→ Ldlr mice. Loss of 2 Akt isoforms in hematopoietic cells resulted in markedly diminished levels of white blood cells, B cells, and monocytes and compromised viability of monocytes and peritoneal macrophages compared with WT cells. In response to lipopolysaccharides, macrophages with a single Akt isoform expressed low levels of inflammatory cytokines; however, Akt1 macrophages were distinct in expressing high levels of antiapoptotic Il10 compared with WT and Akt3 cells. Conclusions- Loss of 2 Akt isoforms in hematopoietic cells, preserving only a single Akt1 or Akt3 isoform, markedly compromises monocyte and macrophage viability and diminishes early atherosclerosis in Ldlr mice.

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