Amphiphilic small peptides for delivery of plasmid DNAs and siRNAs.

Although various delivery systems for nucleic acids have been reported, development of an efficient and non-toxic delivery carrier is still a key subject for gene therapy. To find new efficient delivery carriers for nucleic acids, we synthesized amphiphilic peptides composed of a guanidino group, an oleyl group, and a cysteine. We prepared both linear and branched types of peptides and found that the linear peptides were superior to the branched peptides as nucleic acid carriers. Our study also suggested that the intermolecular cysteine disulfides might allow the linear peptides to form the optimal particle sizes with nucleic acids for cellular uptake. The incorporation of a benzoyl group to the linear peptide gave rise to smaller, less suitable particle size with plasmid DNA, which greatly reduced the efficiency of plasmid DNA delivery. On the other hand, the benzoyl modification maintained the optimal particle size with siRNA, and interestingly it significantly enhanced the siRNA delivery. The higher efficiency is because the hydrophobicity from the benzoyl group might assist in interacting with the hydrophobic cell membrane. This demonstrates that a small structural change can modulate the preference of the carriers. Our study may provide an insight designing efficient delivery carriers.

Identification of the First Selective Activin Receptor-Like Kinase 1 Inhibitor, a Reversible Version of L-783277.

We synthesized 1 (San78-130), a reversible version of L-783277, as a selective and potent ALK1 inhibitor. Our study showed that 1 possesses great kinase selectivity against a panel of 342 kinases and more potent activity against ALK1 than L-783277. Among the six ALK isotypes (ALK1-6), ALK1 is most significantly inhibited by compound 1. Compound 1 suppresses the BMP9-induced Smad1/5 pathway by mainly inhibiting ALK1 in C2C12 cells. Our molecular dynamics simulations suggest that H-bonding interaction between the C-4' hydroxyl group of 1 and Arg334 of ALK1 substantially contributes to the ALK1 inhibition. To the best of our knowledge, 1 is the first selective ALK1 inhibitor. Furthermore, compound 1 promoted angiogenesis in both endothelial tube formation and microfluidic chip based 3D angiogenesis assays, suggesting that 1 could be a lead compound for therapeutic angiogenesis agents. Our study may provide an insight into designing selective and potent inhibitors against ALK1.