ABSTRACT
BACKGROUND AND PURPOSE: We have shown that endogenous glucocorticoids control neutrophil mobilization in the absence of inflammation. In this study the role of the glucocorticoid receptor (GR) in the physiological control of neutrophil mobilization was investigated, focusing on the specific mechanisms for mature neutrophils in bone marrow, circulating neutrophils and endothelial cells. EXPERIMENTAL APPROACH: Male Wistar rats were treated with RU 38486 or adrenalectomized. Cell numbers in bone marrow and circulation were morphologically quantified and expressions of L-selectin determined by flow cytometry. Expressions of P-selectin, E-selectin, PECAM-1, VCAM-1 and ICAM-1 were measured by immunohistochemistry on vessels of cremaster muscle and their mRNA levels quantified in primary cultured endothelial cells. NF-kappaB activity in neutrophils and endothelium was quantified by EMSA. KEY RESULTS: RU 38486 treatment altered the maturation phases of neutrophilic lineage and reduced expression of L-selectin in mature neutrophils from bone marrow; increased the number of neutrophils in the circulation and elevated the expression of L-selectin in these cells. P-selectin and E-selectin expression in endothelial cells was unchanged by adrenalectomy or RU 38486 treatment. Membrane expressions, mRNA levels of ICAM-1, VCAM-1 and PECAM-1 and NF-kappaB translocation into the nucleus were higher in the endothelium of adrenalectomized and RU 38486 treated rats. CONCLUSIONS AND IMPLICATIONS: Endogenous glucocorticoids, through activation of GR on neutrophils, physiologically control the rolling behaviour of these cells and, by modulating endothelial functions, affect their adhesiveness. The molecular mechanism induced by activated GR is different in each cell, as NF-kappaB translocation was only altered in endothelial cells.
Subject(s)
Glucocorticoids/metabolism , Neutrophils/metabolism , Receptors, Glucocorticoid/metabolism , Adrenalectomy , Animals , Bone Marrow/metabolism , Endothelial Cells/metabolism , Flow Cytometry , Gene Expression Regulation , Immunohistochemistry , Intercellular Adhesion Molecule-1/metabolism , L-Selectin/metabolism , Male , Mifepristone , NF-kappa B/metabolism , Platelet Endothelial Cell Adhesion Molecule-1/metabolism , RNA, Messenger/metabolism , Rats , Rats, Wistar , Vascular Cell Adhesion Molecule-1/metabolismABSTRACT
The hormone melatonin produced by the pineal gland during the daily dark phase regulates a variety of biological processes in mammals. The aim of this study was to determine the effect of melatonin and its precursor N-acetylserotonin on the microcirculation during acute inflammation. Arteriolar diameter, blood flow rate, leukocyte rolling and adhesion were measured in the rat microcirculation in situ by intravital microscopy. Melatonin alone or together with noradrenaline did not affect the arteriolar diameter or blood flow rate. Melatonin inhibited both leukocyte rolling and leukotriene B(4) induced adhesion while its precursor N-acetylserotonin inhibits only leukocyte adhesion. The rank order of potency of agonists and antagonist receptor selective ligands suggested that the activation of MT(2) and MT(3) melatonin binding sites receptors modulate leukocyte rolling and adhesion, respectively. The effect of melatonin and N-acetylserotonin herein described were observed with concentrations in the range of the nocturnal surge, providing the first evidence for a possible physiological role of these hormones in acute inflammation.
