Rational design of peptide derivatives for inhibition of MyD88‐mediated toll‐like receptor signaling in human peripheral blood mononuclear cells and epithelial cells exposed to Francisella tularensis

• Published in: Chemical biology & drug design 2017-12, Vol.90 (6), p.1190-1205
• Main Authors: Ryan, Daniel A., Degardin, Melissa, Alam, Shahabuddin, Kissner, Teri L., Hale, Martha, Cameron, Michael D., Rebek, Mitra, Ajami, Dariush, Saikh, Kamal U., Rebek, Julius
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Cells, Cultured; Cytokines - metabolism; Drug Design; Epithelial Cells - cytology; Epithelial Cells - metabolism; Epithelial Cells - microbiology; Francisella tularensis; Francisella tularensis - metabolism; Francisella tularensis - physiology; Genes, Reporter; Half-Life; HEK293 Cells; Humans; Leukocytes, Mononuclear - cytology; Leukocytes, Mononuclear - metabolism; Leukocytes, Mononuclear - microbiology; Lipopolysaccharides - toxicity; Microsomes, Liver - metabolism; MyD88; Myeloid Differentiation Factor 88 - chemistry; Myeloid Differentiation Factor 88 - metabolism; NF-kappa B - genetics; NF-kappa B - metabolism; Peptides - chemistry; Peptides - metabolism; Peptides - pharmacology; proinflammatory cytokines; sepsis; Signal Transduction - drug effects; TIR domain inhibitors; TLR signaling inhibitors; Toll-Like Receptors - antagonists & inhibitors; Toll-Like Receptors - metabolism; Transcriptional Activation - drug effects
• ISSN: 1747-0277; 1747-0285
• DOI: 10.1111/cbdd.13039

Small molecules were developed to attenuate proinflammatory cytokines resulting from activation of MyD88‐mediated toll‐like receptor (TLR) signaling by Francisella tularensis. Fifty‐three tripeptide derivatives were synthesized to mimic a key BB‐loop region involved in toll‐like/interleukin‐1 receptor recognition (TIR) domain interactions. Compounds were tested for inhibition of TNF‐α, IFN‐γ, IL‐6, and IL‐1β in human peripheral blood mononuclear cells (PBMCs) and primary human bronchial epithelial cells exposed to LPS extracts from F. tularensis. From 53 compounds synthesized and tested, ten compounds were identified as effective inhibitors of F. tularensisLPS‐induced cytokines. Compound stability testing in the presence of human liver microsomes and human serum resulted in the identification of tripeptide derivative 7 that was a potent, stable, and drug‐like small molecule. Target corroboration using a cell‐based reporter assay and competition experiments with MyD88 TIR domain protein supported that the effect of 7 was through MyD88 TIR domain interactions. Compound 7 also attenuated proinflammatory cytokines in human peripheral blood mononuclear cells and bronchial epithelial cells challenged with a live vaccine strain of F. tularensis at a multiplicity of infection of 1:5. Small molecules that target TIR domain interactions in MyD88‐dependent TLR signaling represent a promising strategy toward host‐directed adjunctive therapeutics for inflammation associated with biothreat agent‐induced sepsis. Small molecules were developed to attenuate proinflammatory cytokines resulting from activation of MyD88‐mediated TLR signaling by F. tularensis, a causative agent of tularemic sepsis. Lead compound 7 attenuated proinflammatory cytokines in human peripheral blood mononuclear cells and bronchial epithelial cells challenged with a live vaccine strain of F. tularensis. Small molecules that target TIR domain interactions in MyD88‐dependent TLR signaling represent a promising strategy toward host‐directed adjunctive therapeutics for inflammation associated with biothreat agent‐induced sepsis.