Synergistic Effect Between Ouabain and Glucocorticoids for the Induction of Thymic Atrophy

Abstract

The present report shows that thymocyte death, induced by glucocorticoids, may be modulated in vivo by ouabain. Young, ten days old, mice injected with 140 mg/kg sodium succcinate of hydrocortisone (HC) intraperitonially (i.p.) displayed, 24 h after the injection, a decrease in thymus size and cellular content, an effect that was magnified when ouabain (OUA) 0.56 mg/kg, i.p. was given 1 h prior to the HC injection. Ouabain per se was not capable of producing these changes. Both HC and the combination OUA plus HC induced the death of immature double positive lymphocytes (CD4+CD8+) whereas CD69+ cells survived both treatments. An increase in annexin positive cells and a decrease in mitochondrial membrane potential, assessed by cytofluorimetry, using the fluorescent dye DiOC6, was observed in thymocytes from HC treated animals indicating apoptosis of these cells. Furthermore, a synergistic effect between OUA and HC was also observed using this parameter. The synergy observed in the thymus of animals treated with glucocorticoids and OUA might occur under stress, when both hormones are released, or in situations when ouabain is administered exogenously in a moment of the circadian cycle when glucocorticoid levels are elevated. However the impact of this effect on the immune response is still unknown.

Endogenous Cardiotonic Steroids: Physiology, Pharmacology, and Novel Therapeutic Targets

“…The interactions between signaling through the Na + /K + -ATPase and cell death seem to be both complex and variable, depending on cell type and on treatment conditions (Winnicka et al, 2007; Newman et al, 2008). It should also be noted that beyond death signals, the Na + /K + -ATPase signal cascade seems to be involved in a variety of cell biological functions including adhesion and differentiation (Zhang et al, 1991; Numazawa et al, 1994; Kawazoe et al, 1999; Ghoumari et al, 2006; Larre et al, 2006; Rodrigues-Mascarenhas et al, 2006). …”

Modulation of mature B cells in mice following treatment with ouabain

“…The inhibitory effect observed on CFU-S cells when bone marrow was treated in vitro with ouabain and subsequently transferred in vivo, was produced when concentrations of 10 −11 , 10 −9 or 10 −6 M were used (Spivak et al 1980). The dose of ouabain used in vivo in this study was previously determined by Rodrigues-Mascarenhas et al (2006) and coincides with pharmacological concentration (10 −7 M). In stress situations the concentration can rise above 10 −7 M which corresponds to the dose used in vivo in this study (Bauer et al 2005), however, physiological concentrations of ouabain are between 10 −11 and 10 −9 M in plasma (Hansen 2003).…”

“…Both groups were treated for 3 consecutive days. The concentrations used throughout this study were determined before (Rodrigues-Mascarenhas et al 2006). To use as a positive control, in some experiments a third group was added and treated with 140 mg/kg hydrocortisone i.p.…”

“…Our group demonstrated that ouabain was capable of inhibiting cell cycle progression of activated mature lymphocytes, inducing apoptosis in these cells, producing a rapid elevation of intracellular calcium in thymocytes and increasing the expression of the early activation molecule CD69 on the thymocyte surface Olej et al 1998;Pires et al 1997;Rodrigues-Mascarenhas et al 2003). It has also been demonstrated that the combination ouabain plus corticoids produce a synergistic effect in vivo inducing thymic atrophy (Rodrigues-Mascarenhas et al 2006).…”

Dynamics of murine B lymphocytes is modulated by in vivo treatment with steroid ouabain

“…In vivo administration of ouabain alone does not induce cell death in double-positive thymocytes in mice but synergizes with glucocorticoids inducing apoptosis of these cells (Rodrigues-Mascarenhas et al, 2006).…”