title: G-CSF, but not corticosterone, mediates circulating neutrophilia induced by febrile-range hyperthermia.
abstract: We previously showed that sustained exposure to febrile-range hyperthermia (FRH) for 24 h caused an increase in circulating granulocyte colony-stimulating factor (G-CSF) levels and a peripheral neutrophilia in mice (Hasday J, Garrison A, Singh I, Standiford T, Ellis G, Rao S, He JR, Rice P, Frank M, Goldblum S, and Viscardi R. Am J Pathol 162: 2005-2017, 2003). In this study, we utilized a conscious temperature-clamped mouse model to analyze the kinetics of G-CSF expression and peripheral neutrophil expansion and the contributions of FRH-induced G-CSF expression, glucocorticoid generation, and catecholamine-induced neutrophil demargination. In conscious mice housed at an ambient temperature of 34.5 degrees C, core temperature rapidly equilibrated at 39.5-40 degrees C. Peripheral neutrophil counts increased 2-fold after 24-h exposure to hyperthermia, peaked at 3.6-fold baseline levels after 36-h exposure to FRH, and returned to baseline levels after 42 h of sustained hyperthermia. Plasma G-CSF levels were increased by 6.8-fold after 24 h and peaked at 40-fold baseline levels after 36 h in the hyperthermic mice. Plasma corticosterone levels peaked at 3.3-fold baseline levels after 30-h sustained hyperthermia and returned to baseline by 42 h. Immunoneutralization of G-CSF blocked FRH-induced peripheral neutrophilia, but blockade of the glucocorticoid receptor with mifepristone failed to modify FRH-induced neutrophilia. Epinephrine induced similar increases in peripheral blood absolute neutrophil counts in euthermic mice (2.2-fold increase) and mice exposed to FRH for 36 h (1.8-fold increase). Collectively, these data suggest that FRH-induced expression of G-CSF drives the sustained peripheral neutrophilia that occurs during sustained (36 h) hyperthermia, whereas glucocorticoid generation and catecholamine-induced demargination play little role in this response.
authors.affiliation: Divisions of Pulmonary and Critical Care Medicine, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Garrettson S
authors.initials: GS
authors.lastname: Ellis
authors.forename: Drew E
authors.initials: DE
authors.lastname: Carlson
authors.forename: Lisa
authors.initials: L
authors.lastname: Hester
authors.forename: Ju-Ren
authors.initials: JR
authors.lastname: He
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Bagby
authors.forename: Ishwar S
authors.initials: IS
authors.lastname: Singh
authors.forename: Jeffery D
authors.initials: JD
authors.lastname: Hasday
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000097:blood*; D005334:Fever / Q000097:blood*; D016179:Granulocyte Colony-Stimulating Factor / Q000097:blood* / Q000502:physiology; D008297:Male; D051379:Mice; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*
chemical_list: D016179:Granulocyte Colony-Stimulating Factor; D003345:Corticosterone