Identification of differentially expressed proteins in heart of mouse death from smother based on label-free proteomics

Identification of mechanical asphyxia deaths without obvious injuries is a difficult problem for forensic medicine. This study aimed to identify molecular biological markers to predict death from mechanical asphyxia (smother). We established a smother model of mice by over the head with plastic bag tightly until the mice died and applied label-free proteomic technology to identify differentially expressed proteins (DEPs) in heart. A total of 3307 proteins were quantified, and a Fold Change (FC) > 1.2 (or <1/1.2) and Q value < 0.05 were considered as DEPs. Through comparative analysis, we identified 606 DEPs compared to the control group, comprising 219 upregulated and 387 downregulated proteins. Bioinformatics analysis (MCODE analysis) showed that the candidate proteins were mainly involved in regulation of ribosome function, myocardial contraction and calcium regulation, regulation of coagulation and regulation of mitochondrial oxidative respiration. Seven of these proteins were validated using parallel reaction monitoring (PRM), including fibrinogen alpha chain (FIBA), fibrinogen gamma chain (FIBG), Calsequestrin-2 (CASQ2), NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 11 (NDUAB), NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 3 (NDUA3), NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 13 (NDUAD) and Rab7 (RAB7A). CASQ2 and FIBG were further validated by immunohistochemistry. In conclusion, our results may provide some auxiliary indices for identifying the death from mechanical asphyxia.