Vasodilation of Isolated Vessels and the Isolation of the Extracellular Matrix of Tight-skin Mice.

The interferon regulatory factor 5 (IRF5) is crucial for cells to determine if they respond in a pro-inflammatory or anti-inflammatory fashion. IRF5's ability to switch cells from one pathway to another is highly attractive as a therapeutic target. We designed a decoy peptide IRF5D with a molecular modeling software for designing small molecules and peptides. IRF5D inhibited IRF5, reduced alterations in extracellular matrix, and improved endothelial vasodilation in the tight-skin mouse (Tsk/+). The Kd of IRF5D for recombinant IRF5 is 3.72 ± 0.74 x 10-6 M as determined by binding experiments using biolayer interferometry experiments. Endothelial cells (EC) proliferation and apoptosis were unchanged using increasing concentrations of IRF5D (0 to 100 µg/mL, 24 h). Tsk/+ mice were treated with IRF5D (1 mg/kg/d subcutaneously, 21 d). IRF5 and ICAM expressions were decreased after IRF5D treatment. Endothelial function was improved as assessed by vasodilation of facialis arteries from Tsk/+ mice treated with IRF5D compared to Tsk/+ mice without IRF5D treatment. As a transcription factor, IRF5 traffics from the cytosol to the nucleus. Translocation was assessed by immunohistochemistry on cardiac myocytes cultured on the different cardiac extracellular matrices. IRF5D treatment of the Tsk/+ mouse resulted in a reduced number of IRF5 positive nuclei in comparison to the animals without IRF5D treatment (50 µg/mL, 24 h). These findings demonstrate the important role that IRF5 plays in inflammation and fibrosis in Tsk/+ mice.

An IRF5 Decoy Peptide Reduces Myocardial Inflammation and Fibrosis and Improves Endothelial Cell Function in Tight-Skin Mice.

Interferon regulatory factor 5 (IRF5) has been called a "master switch" for its ability to determine whether cells mount proinflammatory or anti-inflammatory responses. Accordingly, IRF5 should be an attractive target for therapeutic drug development. Here we report on the development of a novel decoy peptide inhibitor of IRF5 that decreases myocardial inflammation and improves vascular endothelial cell (EC) function in tight-skin (Tsk/+) mice. Biolayer interferometry studies showed the Kd of IRF5D for recombinant IRF5 to be 3.72 ± 0.74x10-6M. Increasing concentrations of IRF5D (0-100 µg/mL, 24h) had no significant effect on EC proliferation or apoptosis. Treatment of Tsk/+ mice with IRF5D (1mg/kg/d subcutaneously, 21d) reduced IRF5 and ICAM-1 expression and monocyte/macrophage and neutrophil counts in Tsk/+ hearts compared to expression in hearts from PBS-treated Tsk/+ mice (p<0.05). EC-dependent vasodilatation of facialis arteries isolated from PBS-treated Tsk/+ mice was reduced (~15%). IRF5D treatments (1mg/kg/d, 21d) improved vasodilatation in arteries isolated from Tsk/+ mice nearly 3-fold (~45%, p<0.05), representing nearly 83% of the vasodilatation in arteries isolated from C57Bl/6J mice (~55%). IRF5D (50µg/mL, 24h) reduced nuclear translocation of IRF5 in myocytes cultured on both Tsk/+ cardiac matrix and C57Bl/6J cardiac matrix (p<0.05). These data suggest that IRF5 plays a causal role in inflammation, fibrosis and impaired vascular EC function in Tsk/+ mice and that treatment with IRF5D effectively counters IRF5-dependent mechanisms of inflammation and fibrosis in the myocardium in these mice.