Objective: The aim of this study was to investigate the protein expression of chronic unpredictable mild stress (CUMS)-induced senile depression in SAMP-8 mice's frontal lobe cortex and the regulating effect of the kidney tonifying and liver dispersing (KTLD) formula.
Materials and methods: A total of 15 male SAMP-8 mice were randomly divided into control, CUMS, and KTLD groups. CUMS and KTLD mice were subjected to CUMS for 21 days. Control group mice were kept to normal feeding. At the same time as molding, the herbal gavage (KTLD formula, 19.5 g/kg/d) was given from the beginning of the stress stimulation, while the control group and the CUMS group mice were given the same volume of saline for 21 days. Open-field testing (OFT) was used to assess the mice's depression levels. Isobaric tags for relative and absolute quantification (iTRAQ) were used to identify differentially expressed proteins (DEPs) in mice's frontal lobe cortex. Bioinformatics analysis including Gene Ontology (GO); Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and protein-protein interaction (PPI) networks were utilized to study the DEPs connections.
Results: Results revealed that mice with senile depression experienced more anxiety and depression than control mice, whereas KTLD mice had the opposite experience. Biological processes including transport, regulation of transcription, and DNA-templated were identified in both KTLD and CUMS. The KEGG enrichment study of the DEPs in KTLD revealed their involvement in the MAPK signaling pathway, glutamatergic synapse, dopaminergic synapse, axon guidance, and ribosome. KEGG pathway enrichment showed that the mechanism of senile depression and the pathway of KTLD are closely related to axonal conductance and ribosomes. According to the PPI analysis, disease-related proteins regulated by KTLD revealed that some proteins, such as GLOI1 and TRRAP, have potential interactions. This provides fresh insight into how KTLD works to cue senile depression.
Conclusions: KTLD treats senile depression via multiple targets and pathways, which may include regulations of 467 DEPs. Proteomics showed significant changes in protein levels in geriatric depression and after KTLD intervention. Senile depression involves the cross-linking and modulation of signal pathways, presenting a pattern of multiple pathways and multiple targets. According to a protein pathway enrichment and protein interaction model of KTLD in senile depression, KTLD is capable of treating senile depression via multiple pathways and targets.