Characterization of Neuro-Immune Communication in the White Pulp Region of the Spleen

Abstract Norepinephrine (NE) is a ubiquitous neurotransmitter that facilitates cellular communication in the sympathetic nervous system. Recent advancements have shown sympathetic neurons innervate secondary immune organs, such as the spleen, to control immune physiology. Fast-scan cyclic voltammetry (FSCV) is an electrochemical technique that varies an applied potential at a very fast scan rate with micro-electrodes to detect neurotransmitters with high temporal and spatial resolution. FSCV can be used to detect the sub-second release of NE in an ex vivomurine slice model to study the mechanisms related to neuro-immune communication. Our lab is the first to characterize and quantify this spontaneous transient signaling of catecholamines in the white pulp region of the murine spleen with FSCV. The average concentration of catecholamines released is 581 ± 20 nM, with an average inter-event time of 23.4 ± 0.7 s and a duration of 6.6 ± 0.1 s. Norepinephrine transporter (NET) is known to transport NE back into cells after endogenous release. We blocked NET with the inhibitor nomifensine to provide further evidence of NE release and study the mechanisms involved in NE uptake. To study the mechanisms of NE release in the spleen, we blocked α2-adrenoceptor, a known autoreceptor only found on neurons. Yohimbine is an α2-adrenoceptor antagonist, and when applied to slices, it increased catecholamine concentration and duration, demonstrating that we are detecting neuronal release of NE. Furthermore, we used ELISAs to quantify the extent to which the α2-adrenoceptor affects cytokine production, providing further evidence neuronal-regulated immune signaling in the white pulp region of the spleen. Supported by grants from NIH (R01AI151552, R01NS121426)