Abstract
The histamine H-1 G protein-coupled receptor (GPCR) plays an important role in allergy and inflammation. Existing drugs that address the H-1 receptor differ in their chemical structure, pharmacology, and side effects. Light-controllable spatial and temporal activity regulation of photochromic H-1 ligands may contribute to a better mechanistic understanding and the development of improved ...
Abstract
The histamine H-1 G protein-coupled receptor (GPCR) plays an important role in allergy and inflammation. Existing drugs that address the H-1 receptor differ in their chemical structure, pharmacology, and side effects. Light-controllable spatial and temporal activity regulation of photochromic H-1 ligands may contribute to a better mechanistic understanding and the development of improved correlations between ligand structure and pharmacologic effects. We report photochromic H-1 receptor ligands, which were investigated in an organ-pharmacological assay. Initially, five photochromic azobenzene derivatives of reported dual H-1-H-4 receptor antagonists were designed, synthesized, photochemically characterized, and organ-pharmacologically tested on the isolated guinea pig ileum. Among them, one compound [trans-19: (Z)-1-(4-chlorophenyl)-1-(4-methylpiperazin-1-yl)-N-(4-((E)-phenyldiazenyl)phenyl)methanimine] retained the antagonistic activity of its non-photochromic lead, and trans-cis isomerization by irradiation induced a fourfold difference in the pharmacological response. Further structural optimization resulted in two bathochromically shifted derivatives of 19 [NO2-substituted 35 {(Z)-1-(4-chlorophenyl)-1-(4-methylpiperazin-1-yl)-N-(4-((E)-(4-nitrophenyl)diazenyl)phenyl)methanimine} and SO3--substituted 41 {4-((E)-(4-(((Z)-(4-chlorophenyl)(4-methylpiperazin-1-yl)methylene)amino)phenyl)diazenyl)benzenesulfonate}], which do not require the use of UV light for photoisomerization and which also have improved solubility and show reduced tissue impairment. The trans isomers of both compounds showed a remarkable increase in antagonistic activity relative to their lead trans-19; furthermore, a 46-fold difference in activity on the isolated guinea pig ileum was observed between trans- and cis-35.
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