Isotope Dilution NanoLC-MS/MS Quantitation of Methylglyoxal DNA-Protein Cross-Links: Formation and Repair in Human
Reinner O Omondi1, Elijah M Barnes1, Krishna C Gurajala1
1Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 44045, United States.
Abstract:
DNA-protein cross-links (DPCs) represent a prevalent form of DNA damage that forms when cellular proteins become covalently trapped to DNA strands upon exposure to various endogenous and exogenous agents. Methylglyoxal is an endogenous metabolite that reacts with guanine and adenine bases in DNA and RNA, as well as cysteine, arginine, and lysine residues in proteins, generating advanced glycation end-products (AGEs), including DPCs. These modifications have been linked to human disease, including cancer, liver disease, diabetes, and neurodegenerative disorders. Herein, we present a mass spectrometry method for quantifying MGO-induced DNA-protein cross-links (DPCs) in human cells. We prepared an isotope 15N213C6-dG-MGO-Lys internal standard and developed a quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detecting and quantifying the formation and repair of dG-MGO-Lys DPCs in cells. Genomic DNA was extracted, subjected to sequential protease and nuclease digestion, purified by offline high-performance liquid chromatography (HPLC), and analyzed by LC-MS/MS. The method's standard curve showed a strong linear relationship across a concentration range of 10-1000 fmol (R2 = 0.9994). The method achieved limits of detection (LOD) and quantification (LOQ) of 10 and 20 fmol, respectively. Inhibition of proteasome and SPRTN activity revealed that SPRTN functions as a predominant proteolytic enzyme in MGO DPC repair. Overall, this analytical approach can offer valuable insights into the relevance of DPCs in diseases linked to elevated MGO levels.
