Anti-inflammatory effects of new human histamine H3 receptor ligands with flavonoid structure on BV-2 neuroinflammation

Abstract

Objective: Microglia play an important role in the neuroinflammation developed in response to various pathologies. In this study, we examined the anti-inflammatory effect of the new human histamine H3 receptor (H3R) ligands with flavonoid structure in murine microglial BV-2 cells. Material and methods: The affinity of flavonoids (E243 -flavone and IIIa–IIIc—chalcones) for human H3R was evaluated in the radioligand binding assay. The cytotoxicity on BV-2 cell viability was investigated with the MTS assay. Preliminary evaluation of anti-inflammatory properties was screened by the Griess assay in an in vitro neuroinflammation model of LPS-treated BV-2 cells. The expression and secretion of pro-inflammatory cytokines were evaluated by real-time qPCR and ELISA, respectively. The expression of microglial cell markers were determined by immunocytochemistry. Results: Chalcone derivatives showed high affinity at human H3R with Ki values < 25 nM. At the highest nontoxic concentration (6.25 μM) compound IIIc was the most active in reducing the level of nitrite in Griess assay. Additionally, IIIc treatment attenuated inflammatory process in murine microglia cells by down-regulating pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) at both the level of mRNA and protein level. Our immunocytochemistry studies revealed expression of microglial markers (Iba1, CD68, CD206) in BV-2 cell line. Conclusions: These results emphasize the importance of further research to accurately identify the anti-inflammatory mechanism of action of chalcones.