Importantly, the compensatory upregulation of single HRs in H1H2RKO and H3H4RKO mice may explain the opposing results obtained using pharmacological approaches, where agonists of H1R and H2R inhibited proliferation and cytokine production by antigen-specific T PLX4032 chemical structure cells and the H2R agonist dimaprit reduced the severity of EAE [[29, 47]]. In contrast,

we can exclude an effect of a T-cell HDC-HA compensatory loop on the HRKO EAE phenotypes since HR expression does not affect HDC expression or HA production by activated CD4+ T cells from B6, H1H2RKO, and H3H4RKO mice. HA has a long history as a DMT in MS and is purported to improve electrical conductance through demyelinated axons, actively/passively enhance myelin repair and remyelination, and increase the oxygenation of affected CNS tissues by influencing cerebrovascular blood flow and perfusion [[48, 49]]. HA signaling through its receptors is highly complex and diverse because of the number of receptors, the relative proportion of the receptor subtypes on a given cell type, differences in receptor affinity,

and due to the concentration of HA in the local microenvironment. In this study, we used a dual-gene KO approach to understand the role of HRs coupled to second messenger signaling pathways via stimulatory and inhibitory G proteins as potential targets for effective DMT in MS. Previous epidemiological and clinical studies indicate that the use of H1R-specific blockers is associated with decreased MS risk or stabilization of the disease in MS patients [[22, 23]]. HA, acting through H2R, can regulate MHC class II Crizotinib expression on immunoreactive cells and the receptor antagonist ranitidine has been used as a long-term therapy in controlling autoimmune psoriasis [[50]]. Our results presented here indicate that administering antagonists

of both H1R and H2R simultaneously may be protective in CNS disease due to the upregulation of the antipathogenic H3R and H4R. Results of Pregnenolone the present study indicate that the absence of H3R or H4R signaling has a negative effect on EAE susceptibility and encephalitogenic T-cell activity, suggesting that agonists for this class of receptors may have a beneficial effect in the treatment of CNS autoimmune diseases by overriding HA signaling through the propathogenic H1R and H2R. Therefore, the combined pharmacological targeting of each HR may prove to be an appropriate ancillary DMT in the treatment of MS. There is an increasing need for new DMT in the treatment of MS and other immunopathologic diseases. Although the lack of specific and highly selective agonists or antagonists for H3R and H4R have precluded their targeting in the clinical treatment of disease, research in recent years has progressed to the point where their use in the clinic is highly likely. Our results, using HR KO mice that couple to two distinct classes of G proteins (stimulatory vs.