(A) Schematic protocol of MI/R study. (B) Representative images of heart sections from mice treated with M3mP6- or scrambled peptide HLPN (Evans blue/TTC stain). (C) Quantification of the infarct area (white) as percentage of the area at risk (white and red) as shown in A (n=4 for each group, t-test, *P<0.05). (D) Quantification of risk area as percentage of the entire heart section. (n=4 for each group, t-test, ns, not significant (P>0.05) (E) Representative M-mode long-axis echo images for (i) sham control; (ii) MI/R treated with scrambled peptide HLPN; and (iii) MI/R treated with M3mP6 HLPN. (F) Mouse left ventricle ejection fraction (n=11 for sham and M3mP6 groups, n=10 for scrambled peptide group, mean ± SEM, one-way ANOVA). (G) Immunohistochemistry staining of platelets in mouse heart sections 24 h after MI/R using rat anti-integrin αIIb antibody. The representative sections are from (i) sham control; (ii) MI/R treated with scrambled peptide HLPN; and (iii) MI/R treated with M3mP6 HLPN. (iv) αIIb positive staining was quantified using image J and presented as percentage of total tissue area (n=9 for sham, n=10 for both M3mP6 and scrambled peptide groups, mean±SEM, Mann-Whitney test). (H) Immunohistochemistry staining of neutrophils in mouse heart sections 24 h after MI/R using rat anti-Ly6G antibody. The representative sections are from (i) sham control; (ii) MI/R treated with scrambled peptide HLPN; and (iii) MI/R treated with M3mP6 HLPN. (iv) Ly6G-positive cells/mm2 were counted using imageJ software (n=6 for sham, n=22 for scrambled peptide, n=12 for M3mP6, mean±SEM, Mann-Whitney test, **P<0.01) (I) Mouse plasma MPO concentrations 24 hours after MI/R. (sham: n=6, scrambled HLPN treatment: n=11, M3mP6 HLPN treatment: n=9, mean±SEM, t-test, *P<0.05) (J) Kaplan-Meier survival curve of mice 7 days after MI/R surgery treated with M3mP6 HLPN or scrambled peptide HLPN (n=12 for M3mP6 treatment, n=14 for scrambled peptide treatment). Sham surgery caused no death in 6 tested mice.