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Platelets from mice lacking the aryl hydrocarbon receptor exhibit defective collagen‐dependent signaling
Author(s) -
Lindsey S.,
Jiang J.,
Woulfe D.,
Papoutsakis E. T.
Publication year - 2014
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.12490
Subject(s) - aryl hydrocarbon receptor , platelet , thrombopoietin , thrombopoiesis , chemistry , medicine , microbiology and biotechnology , endocrinology , megakaryocyte , thrombin , biology , immunology , progenitor cell , biochemistry , haematopoiesis , stem cell , transcription factor , gene
Summary Background We previously identified aryl hydrocarbon receptor ( AHR ) as a novel regulator of megakaryocytic differentiation and polyploidization and reported that AHR ‐null mice have approximately 15% fewer platelets than do wild‐type mice, yet they exhibit a dramatic, unexplained bleeding phenotype. Objectives The current work tests our hypothesis that AHR ‐null platelets are functionally deficient, contributing to the previously reported (yet unexplained) bleeding phenotype present in AHR ‐null mice. Methods AHR‐null bone marrow was ex vivo differentiated with thrombopoietin with or without AHR ligands or AHR inhibitors and analyzed for degree of megakaryopoiesis and polyploidization. Platelet function of AHR ‐null mice was assessed with aggregation and spreading assays. Platelet signaling was examined using W estern analysis and R ac activity assays. Results AHR ligands differentiate murine bone marrow–derived progenitors into polyploid megakaryocytes in the absence of thrombopoietin, and AHR inhibitors block thrombopoietin‐induced megakaryocytic differentiation. Despite their responsiveness toward thrombin, AHR ‐null platelets demonstrate decreased aggregation and spreading in response to collagen compared with wild‐type platelets. AHR ‐null platelets bind fibrinogen after stimulation with thrombin or AYPGKF and aggregate in response to AYP GKF and adenosine diphosphate. Mechanistically, AHR absence led to down‐regulation of V av1 and V av3, altered phospholipase Cγ2 phosphorylation, decreased R ac1 activation, and reduced platelet activation in response to collagen. Conclusions These results are consistent with a role for AHR in platelet function, especially as it relates to platelet aggregation and spreading in response to collagen. Our work suggests AHR is a critical component of the physiologic response that platelets undergo in response to collagen and may provide novel treatment options for patients with bleeding disorders.