iTRAQ-based quantitative proteomic analysis of low molybdenum inducing thymus atrophy and participating in immune deficiency-related diseases.

Molybdenum is a trace element with extremely uneven distribution in the environment. It constitutes the active sites of molybdenum enzymes that can catalyze redox reactions in almost all organisms. In this study, a mouse model with a low molybdenum diet was established to investigate the differential protein expressions in the thymus and the mechanism of molybdenum regulating thymocyte development. Results showed that the thymus evidently atrophied, and the weight and organ index of the thymus substantially decreased under the condition of low molybdenum (P < 0.01). A total of 274 differentially expressed proteins (DEPs) were screened through isobaric tag for relative and absolute quantification; amongst them, ribosomal proteins (38) were the most abundant. Bioinformatics analysis revealed that DEPs were mainly involved in protein metabolism (18%), nucleus (15%) and nucleic acid binding activity (17%), corresponding to biological process, cellular component and molecular function, respectively. Moreover, DEPs induced by low molybdenum were enriched in 94 pathways, of which typical maps including ribosome, oxidative phosphorylation and systemic lupus erythematosus. Flow cytometry analysis indicated the prominent imbalances of CD4+ and CD8+ cell ratios (P < 0.05, P < 0.01), suggesting the disordered development of T cell subsets. Overall, low molybdenum resulted in thymus atrophy by interfering with ribosomal protein expression and protein metabolism. This study provides a data platform for revealing the linkage between molybdenum and thymus-dependent immunity.