Characterisation of the influences of aspirin-acetylation and glycation on human plasma proteins.

UNLABELLED: The competition effect between aspirin-mediated acetylation and protein glycation has been a matter of concern for decades. However, the exact interactions between these two post-translational modifications are still not well understood. Several efforts have been made to explain how aspirin prevents glycation, but the influence of prior protein glycation on the action of aspirin has never been investigated. This study involved qualitative and quantitative analyses to: 1) identify acetylated and glycated proteins; 2) quantify rates of acetylation and glycation; and 3) elucidate the common modification sites. Human plasma was incubated with 30mM glucose and then 500μM aspirin. A label-free mass spectrometry approach indicated an increase in the acetylation level after this sequential glucose-then-aspirin incubation; these results were also confirmed by Western blot. Interestingly, for several proteins, decreases in glycation levels were evidenced after aspirin incubation. The common modification sites, where both acetylation and glycation took place, were also identified. The influence that glycation and acetylation processes have on each other could reflect conformational changes induced by glucose and aspirin. In future studies, in order to better understand the interactions between these two PTMs, we intend to apply this strategy to other blood compartments and to diabetic patients.

BIOLOGICAL SIGNIFICANCE: Non-enzymatic glycation represents an early stage in the development of the long-lasting complications that are associated with diabetes. Aspirin has been shown to prevent this process in a few reference proteins, but how the two post-translational modifications (PTMs) of aspirin-mediated acetylation and protein glycation interact with each other remains poorly investigated. This study used a label-free quantitative proteomic approach to characterise the extent of aspirin-induced acetylation and protein glycation in human plasma. The results clearly supported a mutual influence between these PTMs, which lead us to propose a potential model based on structural conformational changes.