Histamine H-3 Receptor Integrates Peripheral Inflammatory Signals in the Neurogenic Control of Immune Responses and Autoimmune Disease Susceptibility

Histamine H-3 receptor (Hrh3/H3R) is primarily expressed by neurons in the central nervous system (CNS) where it functions as a presynaptic inhibitory autoreceptor and heteroreceptor. Previously, we identified an H3R-mediated central component in susceptibility to experimental allergic encephalomyelitis (EAE), the principal autoimmune model of multiple sclerosis (MS), related to neurogenic control of blood brain barrier permeability and peripheral T cell effector responses. Furthermore, we identified Hrh3 as a positional candidate for the EAE susceptibility locus Eae8. Here, we characterize Hrh3 polymorphisms between EAE-susceptible and resistant SJL and B10.S mice, respectively, and show that Hrh3 isoform expression in the CNS is differentially regulated by acute peripheral inflammatory stimuli in an allele-specific fashion. Next, we show that Hrh3 is not expressed in any subpopulations of the immune compartment, and that secondary lymphoid tissue is anatomically poised to be regulated by central H3R signaling. Accordingly, using transcriptome analysis, we show that, inflammatory stimuli elicit unique transcriptional profiles in the lymph nodes of H3RKO mice compared to WT mice, which is indicative of negative regulation of peripheral immune responses by central H3R signaling. These results further support a functional link between the neurogenic control of T cell responses and susceptibility to CNS autoimmune disease coincident with acute and/or chronic peripheral inflammation. Pharmacological targeting of H3R may therefore be useful in preventing the development and formation of new lesions in MS, thereby limiting disease progression.