Proteomic analysis of spinal cord tissue in a rat model of cancer-induced bone pain

Abstract

BackgroundCancer-induced bone pain (CIBP) is a moderate to severe pain and seriously affects patients’ quality of life. Spinal cord plays critical roles in pain generation and maintenance. Identifying differentially expressed proteins (DEPs) in spinal cord is essential to elucidate the mechanisms of cancer pain.MethodsCIBP rat model was established by the intratibial inoculation of MRMT-1 cells. Positron emission tomography (PET) scan and transmission electron microscopy (TEM) were used to measure the stats of spinal cord in rats. Label free Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) were used to analyze the whole proteins from the lumbar spinal cord. Differentially expressed proteins (DEPs) were performed using Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, and verified using Western blot and immunofluorescence assay.ResultsIn the current study, CIBP rats exhibited bone damage, spontaneous pain, mechanical hyperalgesia, and impaired motor ability. In spinal cord, an hypermetabolism and functional abnormality were revealed on CIBP rats. An increase of synaptic vesicles density in active zone and a disruption of mitochondrial structure in spinal cord of CIBP rats were observed. Meanwhile, 422 DEPs, consisting of 167 up-regulated and 255 down-regulated proteins, were identified among total 1539 proteins. GO enrichment analysis indicated that the DEPs were mainly involved in catabolic process, synaptic function, and enzymic activity. KEGG pathway enrichment analysis indicated a series of pathways, including nervous system disease, hormonal signaling pathways and amino acid metabolism, were involved. Expression change of synaptic and mitochondrial related protein, such as complexin 1 (CPLX1), synaptosomal-associated protein 25 (SNAP25), synaptotagmin 1 (SYT1), aldehyde dehydrogenase isoform 1B1 (ALDH1B1), Glycine amidinotransferase (GATM) and NADH:ubiquinone oxidoreductase subunit A11 (NDUFA11), were further validated using immunofluorescence and Western blot analysis.ConclusionThis study provides valuable information for understanding the mechanisms of CIBP, and supplies potential therapeutic targets for cancer pain.

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“…Mitochondrion are dynamic organelles whose distribution quantity and morphology changes depending on energy requirements 56 . During chronic pain processing, mitochondrial fragment and dysfunction are induced in the spinal cord, which consequently lead to mitochondrial ROS release 17 . GSK‐3β plays a key role in maintaining mitochondrial function.…”

“…Mitochondria are the powerhouses of eukaryotic cells via oxidative phosphorylation, perform crucial functions in bioenergetics, metabolism and signalling, and associate with numerous diseases, such as Alzheimer's disease and Parkinson's disease 14–16 . Our previous study on cancer‐induced bone pain animal showed morphologic and proteomic changes in mitochondria 17 . Mitochondrial dysfunction is strongly correlated with inflammatory response.…”

“…[14][15][16] Our previous study on cancer-induced bone pain animal showed morphologic and proteomic changes in mitochondria. 17 Mitochondrial dysfunction is strongly correlated with inflammatory response. The highly oxidative environment causes mitochondrial membrane potential loss and consequently NLRP3 inflammasome activation and inflammatory cytokine secretion.…”