Development of a novel RANKL-based peptide, microglial healing peptide1-AcN (MHP1-AcN), for treatment of ischemic stroke

Although the regulation of post-ischemic inflammation is an important strategy to treat ischemic stroke, all clinical trials have failed to show its efficacy. To solve the problem, we previously developed a novel partial peptide of RANKL, microglial healing peptide 1 (MHP1), which could reduce ischemic injury by inhibiting Toll-like receptor (TLR) induced inflammation. However, optimization of the peptide was necessary to increase the stability and efficacies for clinical use. According to information gathered through HPLC/MS in serum, we have newly designed a series of modified MHP1 peptides and have found that N-terminal acetylation and C-terminal amidation in MHP1 (MHP1-AcN), can strengthen its anti-inflammatory effects and increase its stability with anti-osteoclastogenic effects. Anti-TLR activity was reported to be reduced in MHP1 when incubated at 37 °C for 24 hrs, but MHP1-AcN could keep the activity under the same condition. The therapeutic effect of MHP1-AcN was observed in transient ischemic stroke model at lower dose than MHP1. Importantly, MHP1-AcN did not affect thrombolytic effects of tissue plasminogen activator (tPA) and inhibited tPA-induced hemorrhagic transformation. These findings indicated that MHP1-AcN was stable and effective anti-TLR signal peptide and could be a promising agent for treating stroke patients receiving tPA and endovascular therapy.