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Neutrophil AKT2 regulates heterotypic cell-cell interactions during vascular inflammation.

ABSTRACT: Interactions between platelets, leukocytes, and activated endothelial cells are important during microvascular occlusion; however, the regulatory mechanisms of these heterotypic cell-cell interactions remain unclear. Here, using intravital microscopy to evaluate mice lacking specific isoforms of the serine/threonine kinase AKT and bone marrow chimeras, we found that hematopoietic cell-associated AKT2 is important for neutrophil adhesion and crawling and neutrophil-platelet interactions on activated endothelial cells during TNF-?-induced venular inflammation. Studies with an AKT2-specific inhibitor and cells isolated from WT and Akt KO mice revealed that platelet- and neutrophil-associated AKT2 regulates heterotypic neutrophil-platelet aggregation under shear conditions. In particular, neutrophil AKT2 was critical for membrane translocation of ?M?2 integrin, ?2-talin1 interaction, and intracellular Ca2+ mobilization. We found that the basal phosphorylation levels of AKT isoforms were markedly increased in neutrophils and platelets isolated from patients with sickle cell disease (SCD), an inherited hematological disorder associated with vascular inflammation and occlusion. AKT2 inhibition reduced heterotypic aggregation of neutrophils and platelets isolated from SCD patients and diminished neutrophil adhesion and neutrophil-platelet aggregation in SCD mice, thereby improving blood flow rates. Our results provide evidence that neutrophil AKT2 regulates ?M?2 integrin function and suggest that AKT2 is important for neutrophil recruitment and neutrophil-platelet interactions under thromboinflammatory conditions such as SCD.

SUBMITTER: Li J

PROVIDER: S-EPMC3973084 | biostudies-other | 2014 Apr

REPOSITORIES: biostudies-other

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Neutrophil AKT2 regulates heterotypic cell-cell interactions during vascular inflammation.

Li Jing J Kim Kyungho K Hahm Eunsil E Molokie Robert R Hay Nissim N Gordeuk Victor R VR Du Xiaoping X Cho Jaehyung J

The Journal of clinical investigation 20140318 4

Interactions between platelets, leukocytes, and activated endothelial cells are important during microvascular occlusion; however, the regulatory mechanisms of these heterotypic cell-cell interactions remain unclear. Here, using intravital microscopy to evaluate mice lacking specific isoforms of the serine/threonine kinase AKT and bone marrow chimeras, we found that hematopoietic cell-associated AKT2 is important for neutrophil adhesion and crawling and neutrophil-platelet interactions on activa ...[more]

PMID: 24642468

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Project description:Adipose-derived stromal/stem cells (ASCs) are a promising cell source for vascular-based approaches to clinical therapeutics, as they have been shown to give rise to both endothelial and perivascular cells. While it is well known that ASCs can present a heterogeneous phenotypic profile, spontaneous interactions among these subpopulations that result in the formation of complex tissue structures have not been rigorously demonstrated. Our study reports the novel finding that ASCs grown in monolayers in the presence of angiogenic cues are capable of self-assembling into complex, three-dimensional vascular structures. This phenomenon is only apparent when the ASCs are seeded at a high density (20,000 cells/cm(2)) and occur through orchestrated interactions among three distinct subpopulations: CD31-positive cells (CD31+), ?-smooth muscle actin-positive cells (?SMA+), and cells that are unstained for both these markers (CD31-/?SMA-). Investigations into the kinetics of the process revealed that endothelial vessel-like structures initially arose from individual CD31+ cells through proliferation and their interactions with CD31-/?SMA- cells. During this period, ?SMA+ cells proliferated and appeared to migrate toward the vessel structures, eventually engaging in cell-cell contact with them after 1 week. By 2 weeks, the lumen-containing CD31+ vessels grew greater than a millimeter in length, were lined with vascular basement membrane proteins, and were encased within a dense, three-dimensional cluster of ?SMA+ and CD31-/?SMA- cells. The recruitment of ?SMA+ cells was largely due to platelet-derived growth factor (PDGF) signaling, as the inhibition of PDGF receptors substantially reduced ?SMA+ cell growth and vessel coverage. Additionally, we found that while hypoxia increased endothelial gene expression and vessel width, it also inhibited the growth of the ?SMA+ population. Together, these findings underscore the potential use of ASCs in forming mature vessels in vitro as well as the need for a further understanding of the heterotypic interactions among ASC subpopulations.

Dataset Information

Neutrophil AKT2 regulates heterotypic cell-cell interactions during vascular inflammation.

Publications

Neutrophil AKT2 regulates heterotypic cell-cell interactions during vascular inflammation.

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