Assessment of leukocyte activity in mice devoid of the glucocorticoid receptor in the noradrenergic system (GRDBHCre)

Abstract

Disturbances in brain monoamines, overactivity of the hypothalamo-pituitary adrenal (HPA) axis and pro-inflammatory tendency in the immune system are the key features of depressive disorders. Recently, several murine lines with mutations in glucocorticoid receptors (GRs) have been generated and these animals may be utilized for study depressive-like disorders. In the present study, we have investigated whether selective ablation of GRs in noradrenergic neurons affects functional properties of leukocytes and redirects them towards pro-inflammatory activity. Transgenic mice selectively devoid of GRs on noradrenergic cells were constructed using the Cre/loxP approach. Peritoneal leukocytes were collected from mutant and wild type (WT) animals of both sexes and were cultured in vitro for 24h both in basal conditions and after application of selected pro- or anti-inflammatory stimuli. Metabolic activity and adherence were measured in basal conditions. Nitric oxide (NO) synthesis and arginase (ARG) activity were assessed as the markers of functional status of the cells. Because adult mutant mice lack adrenal medulla and thereby peripheral adrenaline, we modulated pro- and anti-inflammatory culture conditions by addition of noradrenaline (10-6M). Finally, effects of in vivo pro-inflammatory challenge (with intraperitoneal administration of lipopolysaccharide) on properties of leukocytes were assessed 24h (in both sexes) and 48h later (in males only). The experiments indicated that selective ablation of GR in noradrenergic neurons did not affect fundamental properties of peritoneal leukocytes and exerted effects only under conditions of selected pro- or anti-inflammatory stimuli in vitro. Stronger response to pro-inflammatory stimulation in terms of NO synthesis and ARG activity may suggest pro-inflammatory tendency in mutant mice. In vivo inflammatory challenge failed to show any effect of GR ablation on selected parameters of leukocyte activity. Both in vitro studies and in vivo challenge revealed mainly sex-related differences in leukocyte activity.

Keywords: Arginase activity; Glucocorticoid receptors; Hypothalamo-pituitary adrenal axis; Nitric oxide; Noradrenergic system; Peritoneal leukocytes; Sex differences.