17β-Estradiol's salutary effects on splenic dendritic cell functions following trauma-hemorrhage are mediated via estrogen receptor-α

Although 17β-estradiol administration following trauma-hemorrhage attenuates Kupffer cell, splenic and peritoneal macrophage functions, it remains unknown whether 17β-estradiol has any salutary effects on splenic dendritic cell (DC) functions and if so, whether such effects are mediated via the estrogen receptors (ER). We hypothesized that 17β-estradiol administration following trauma-hemorrhage has salutary effects on splenic DC functions. Male C3H/HeN (6-8 weeks) mice were randomly assigned to sham operation or trauma-hemorrhage. Trauma-hemorrhage was induced by midline laparotomy and ∼90 min of hemorrhagic shock (blood pressure [BP] 35 mmHg), followed by fluid resuscitation (4× the shed blood volume in the form of Ringer's lactate). Estrogen receptor (ER)-α agonist propyl pyrazole triol (PPT; 5 μg/kg), ER-β agonist diarylpropionitrile (DPN; 5 μg/kg), 17β-estradiol (50 μg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Two hours later, the mice were sacrificed, splenic DCs were isolated and the changes in their apoptosis, co-stimulating factors and MHC class II expression, ability to produce cytokines, and antigen presentation capacity were measured. Apoptosis of splenic DC increased following trauma-hemorrhage; however, 17β-estradiol administration after trauma-hemorrhage normalized the rate of apoptosis. Moreover, splenic DC cytokines production, co-stimulating factors and MHC class II expression, and antigen presentation capacity were significantly decreased following trauma-hemorrhage; however, 17β-estradiol as well as PPT also prevented these depressions. In contrast, DPN did not attenuate splenic DC functions following trauma-hemorrhage. Since PPT administration following trauma-hemorrhage was more effective in normalizing splenic DC functions than DPN, the salutary effects of 17β-estradiol on splenic DC functions are mediated predominantly via ER-α.