Abstract 16279: Serine Protease Inhibitor (serpin) Reactive Site Loop Peptides Prevent Transplant Vasculopathy and Inflammatory Vasculitis

Abstract

Aim: Ser ine p rotease in hibitors ( Serpins ) regulate key clotting and inflammatory pathways. Two anti-inflammatory Serpins , neuroserpin (NSP) and Serp-1 markedly reduce arterial inflammation and plaque growth in a rodent aortic transplant vasculitis model after single dose infusion. NSP is a mammalian serpin that inhibits thrombolytic proteases and Serp-1 is a virus-derived serpin that inhibits both thrombotic and thrombolytic proteases. We postulated that proteolytic cleavage of the reactive site loop (RSL) produces active peptide derivatives with expanded functions. 8 peptide sequences encompassing predicted cleavage sites for Serp-1 and NSP were synthesized and tested in mouse aortic allograft transplant and herpesvirus (MHV68) vasculitis models. The main aim was to assess therapeutic potential for RSL peptides derived from NSP and Serp-1 in vascular inflammation. Methods: We assessed the capacity of 8 predicted serpin RSL peptides, 4 from Serp-1 and 4 from NSP to reduce vascular inflammation. 40 C57BL/6 mice had aortic allograft transplant with a single IV injection of each single peptide. 29 IFN-γR KO mice had MHV-68 infection and were treated for 10 days with S-2 (ISRMAV), S-7 (GTTASSDTAITLIPR), Inverse S-7 (RPILTIATDSSATTG), S-8 (MAVLYPQVIVDHPFFFLIRNR) peptides, or Saline control. Results: RSL peptides with R or RN sequences, but not RM, and with 0-+1 charge significantly reduced vascular inflammatory cell invasion and plaque growth after aortic transplant from C57Bl/6 donor to BALB/c recipient transplant mice (5-6 transplants/peptide) (P < 0.01). S-1, S-3, S-7 & S-8 peptides reduced inflammation and plaque in aortic transplant. Hydrophobicity and negative charge in S-6 peptide increased thrombosis. S-7 peptide also significantly improved survival in a lethal MHV68 infection vasculitic model (150 days survival; P < 0.043), while inactive S-2 peptide, Inverse S-7 and S-8 had no effect (P = NS; 40 days) (P< 0.043). Conclusions: In conclusion, a series of serpin RSL peptides were synthesized based upon natural protease cleavage sites. RSL peptides have demonstrated significant efficacy in reducing inflammatory vasculitis after transplant or after lethal mouse herpesviral (MHV) infections, extending serpin regulatory activity.