title: Influence of dexamethasone on na+/h+ exchanger activity in dendritic cells.
abstract: Glucocorticoids regulate the function of dendritic cells (DCs), antigen-presenting cells linking innate and adaptive immunity. Glucocorticoids influence the function of other cell types by modulating the activity of the Na(+)/H(+)exchanger (NHE), a carrier involved in the regulation of cytosolic pH and cell volume. The present study explored whether dexamethasone influences Na(+)/H(+) exchanger activity in DCs. The DCs were isolated from mouse bone marrow, cell volume was estimated from forward scatter in FACS analysis, cytosolic pH (pH(i)) utilizing BCECF fluorescence and Na(+)/H(+) exchanger activity from the Na(+) dependent realkalinization after an ammonium pulse. Treatment with the glucocorticoid dexamethasone (100 nM; 1, 4, 16 and 24h) significantly decreased pH(i) (≥4 h) and gradually increased Na(+)/H(+) exchanger activity (=16 h). The stimulation of Na(+)/H(+) exchanger activity by dexamethasone was virtually abrogated by glucocorticoid receptor blocker mefiprestone (1 μM) and NHE3 inhibitor dimethyl amiloride (5 μM), but not prevented by NHE1 inhibitor cariporide (10 μM). Dexamethasone treatment significantly increased SGK1 mRNA levels. Stimulation of Na(+)/H(+) exchanger activity by dexamethasone was blunted in DCs lacking SGK1. Dexamethasone treatment did not significantly alter ROS formation but significantly decreased the forward scatter. Exposure of DCs to lipopolysacharide (LPS, 1 μg/ml) led to a transient increase followed by a decline of Na(+)/H(+) exchanger activity and to enhanced forward scatter as well as ROS formation, all effects significantly blunted in the presence of dexamethasone (100 nM). In conclusion, glucocorticoid treatment decreased pH(i) and cell volume, effects paralleled by upregulation of Na(+)/H(+) exchanger activity in DCs. Moreover, glucocorticoids blunted the stimulation of Na(+)/H(+) exchanger activity, cell swelling and ROS formation following LPS treatment.
authors.affiliation: Department of Physiology, University of Tübingen, Tübingen, Germany.
authors.forename: Anand
authors.initials: A
authors.lastname: Rotte
authors.forename: Venkanna
authors.initials: V
authors.lastname: Pasham
authors.forename: Melanie
authors.initials: M
authors.lastname: Eichenmüller
authors.forename: Wenting
authors.initials: W
authors.lastname: Yang
authors.forename: Madhuri
authors.initials: M
authors.lastname: Bhandaru
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D048429:Cell Size / Q000187:drug effects; D003713:Dendritic Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000737:chemistry; D005938:Glucocorticoids / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D051379:Mice; D008810:Mice, Inbred C57BL; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D015854:Up-Regulation; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D003907:Dexamethasone; D005456:Fluorescent Dyes; D005938:Glucocorticoids; D017874:Immediate-Early Proteins; D008070:Lipopolysaccharides; D017346:Protein Serine-Threonine Kinases; D017382:Reactive Oxygen Species; D011965:Receptors, Glucocorticoid; D017923:Sodium-Hydrogen Exchangers; D000099184:Serum-Glucocorticoid Regulated Kinases