Role of the Sympathetic Nervous System and Spleen in Experimental Stroke-Induced Immunodepression

BACKGROUND The mechanism of stroke-induced immunodepression syndrome (SIDS) remains uncertain. Some studies suggest that hyperactivation of the sympathetic nervous system (SNS) may be the key factor underlying SIDS. Catecholamines impair early lymphocyte response, which can increase the risk of stroke-associated infection (SAI). MATERIAL/METHODS Our study focused on dynamic changes of metanephrine (MN), normetanephrine (NMN), cytokines, and spleen volume in the rat middle cerebral artery occlusion (MCAO) model. RESULTS After MCAO, there is hyperactivation of SNS and pro-/anti-inflammatory imbalance, indicating systemic immunodepression. In addition, rat spleen size was reduced. Correlation analysis indicated that MCAO-induced spleen size reduction correlated with the changes in MN, NMN, and cytokines. Blocking SNS with propranolol can partly reverse the immunodepression and the reduction in spleen volume. CONCLUSIONS Taken together, these findings suggest that acute ischemic stroke induces over-activation of the SNS, which lowers the threshold of infection and increases the risk of infection.