Proteomic profiling of heterotopic heart-transplanted rats using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry: Potential biomarkers and drug targets

Objective Methotrexate and rapamycin demonstrate an additive effect in prolonging cardiac allograft survival in a major histocompatibility complex mismatched rat model. The present study aimed to identify functional proteins involved in the allograft-protective effects of these two agents and reveal potential diagnostic markers for treating rejection. Methods Serum samples from heterotopic heart-transplanted LEW(RT-1(1)) rats (either without immunosuppressive treatment or treated with methotrexate alone, rapamycin alone, or methotrexate and rapamycin combined) were analysed by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. Protein profiles obtained using a weak cation exchange ProteinChip (R) CM-10 array were then analysed using ProteinChip (R) Software. Results Of 28 rejection-related proteins identified, isoelectric point and mass information from two potential candidate proteins matched information from the UniProtKB/Swiss-prot database, suggesting them to be complement component C3f fragment and complement component 4A (C4A, anaphylatoxin). Conclusions Proteomic analysis revealed 28 proteins as potential diagnostic markers of tissue rejection. Of these, 11 proteins may represent targets relating to the additive effects of methotrexate and rapamycin. Two protein peaks, with mass-to-charge ratios of 1950 Da and 8577 Da, may have potential for use in post-transplant diagnosis of rejection.