G-CSF improves murine G6PC3-deficient neutrophil function by modulating apoptosis and energy homeostasis

• Published in: Blood 2011-04, Vol.117 (14), p.3881-3892
• Main Authors: Jun, Hyun Sik, Lee, Young Mok, Song, Ki Duk, Mansfield, Brian C., Chou, Janice Y.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - genetics; Biological and medical sciences; Cells, Cultured; Drug Evaluation, Preclinical; eIF-2 Kinase - metabolism; eIF-2 Kinase - physiology; Energy Metabolism - drug effects; Energy Metabolism - genetics; Glucose-6-Phosphatase - genetics; Glucose-6-Phosphatase - physiology; Granulocyte Colony-Stimulating Factor - pharmacology; Hematologic and hematopoietic diseases; Homeostasis - drug effects; Homeostasis - genetics; Medical sciences; Mice; Mice, Inbred C57BL; Mice, Knockout; Neutrophils - drug effects; Neutrophils - metabolism; Neutrophils - physiology; Phagocytes, Granulocytes, and Myelopoiesis; Phosphatidylinositol Phosphates - metabolism; Protein Subunits; Proto-Oncogene Proteins c-akt - metabolism; Proto-Oncogene Proteins c-akt - physiology; Signal Transduction - drug effects; Signal Transduction - genetics
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2010-08-302059

G6PC3 (or glucose-6-phosphatase-β) deficiency underlies a congenital neutropenia syndrome in which neutrophils exhibit enhanced endoplasmic reticulum (ER) stress, increased apoptosis, impaired energy homeostasis, and impaired functionality. Here we show that murine G6pc3−/− neutrophils undergoing ER stress activate protein kinase-like ER kinase and phosphatidylinositol 3,4,5-trisphosphate/Akt signaling pathways, and that neutrophil apoptosis is mediated in part by the intrinsic mitochondrial pathway. In G6PC3-deficient patients, granulocyte colony-stimulating factor (G-CSF) improves neutropenia, but its impact on neutrophil apoptosis and dysfunction is unknown. We now show that G-CSF delays neutrophil apoptosis in vitro by modulating apoptotic mediators. However, G6pc3−/− neutrophils in culture exhibit accelerated apoptosis compared with wild-type neutrophils both in the presence or absence of G-CSF. Limiting glucose (0.6mM) accelerates apoptosis but is more pronounced for wild-type neutrophils, leading to similar survival profiles for both neutrophil populations. In vivo G-CSF therapy completely corrects neutropenia and normalizes levels of p-Akt, phosphatidylinositol 3,4,5-trisphosphate, and active caspase-3. Neutrophils from in vivo G-CSF–treated G6pc3−/− mice exhibit increased glucose uptake and elevated intracellular levels of G6P, lactate, and adenosine-5′-triphosphate, leading to improved functionality. Together, the results strongly suggest that G-CSF improves G6pc3−/− neutrophil survival by modulating apoptotic mediators and rectifies function by enhancing energy homeostasis.