Mass-spectrometry-based quantitative proteomic analysis reveals that methylglyoxal and carnosine influence oxidative stress and RNA-processing associated proteins in renal proximal tubule epithelial cells.

Abstract

Background: Tubular injury triggered by hyperglycemia is an important pathological characteristic in diabetic nephropathy (DN). Accumulated advanced glycation end products and their precursor methylglyoxal (MGO), contribute to the development of DN. Carnosine has been shown to prevent the development of DN but the underlying mechanism still needs to be studied in depth. In this study, we explored the potential proteins influenced by MGO and carnosine in tubule epithelial cells.

Methods and results: HK-2 cells were treated with MGO, carnosine, or a combination. Differentially expressed proteins (DEPs) between different groups were identified by isobaric tag for relative and absolute quantitation-based mass spectrometry. In the comparison between MGO and control, 29 DEPs were found to be associated with antioxidation and RNA methylation. In the comparison between carnosine and control, 10 DEPs were associated with ubiquitin protein ligase activity and RNA metabolism. In the comparison between MGO + carnosine and MGO, carnosine-induced DEPs in the presence of MGO were mainly related to RNA splicing and mRNA processing. MGO effects on OSTC expression was inversely correlated with that of carnosine. Some DEPs (OSTC, PRDX5, NEDD4L, NOP2, TRMT6, and GEMIN2) were validated by Western blotting. Additional experiments showed the 28 kD particle of Smith antigen was also influenced by MGO and carnosine.

Conclusions: Carnosine can influence RNA processing and spliceosome-related proteins, and change MGO's effect on HK-2 cells. This study helps to understand the mechanism by which MGO contributes to the development of DN and promotes further identification of carnosine downstream proteins as therapeutic targets for DN.