Influence of β-adrenoceptor antagonists on hemorrhage-induced cellular immune suppression

Hemorrhagic shock is associated with increasing catecholamine plasma concentrations. Plasma catecholamines are known to affect cellular immune functions. We therefore, investigated the effect of endogenously released catecholamines on lymphocyte distribution (CD4⁺ lymphocytes, CD8⁺ lymphocytes, and natural killer (NK) cells), splenocyte apoptosis (Annexin V binding), tumor necrosis factor-α (TNF-α), and interleukin 10 (IL-10) release during a volume-controlled hemorrhagic shock in mice. Mice received either saline (HEM), the non-selective β-adrenoceptor antagonist propranolol (PROP; 2 mg/kg i.p.), or the β₁-adrenoceptor antagonist metoprolol (MET; 2 mg/kg i.p.) before induction of hemorrhage. Mice were sacrificed to obtain the spleen and whole blood 1 h after hemorrhage, 1 h after fluid resuscitation, and 24 h after hemorrhage. Flow cytometric analysis revealed an increase in circulating NK cells in the HEM group. This effect was completely abolished by pretreatment with propranolol or metoprolol. Furthermore, administration of either β-adrenoceptor antagonist led to a decrease of circulating CD8⁺ lymphocyte numbers. Monitoring of splenocyte apoptosis by determination of Annexin V binding revealed an increase in splenocyte apoptosis 24 h after hemorrhage in the HEM group but not in the animals pretreated with propranolol or metoprolol. Induction of hemorrhage did not affect TNF-α or IL-10 plasma concentrations in either experimental group. We conclude that plasma catecholamines affect cellular immunity in the early phase of trauma via a β-adrenergic pathway.