The effects of aspirin acetylation of human serum albumin on its interactions with methotrexate

Human serum albumin (HSA) is the most abundant protein in the blood and serves as the primary carrier protein. HSA transports a wide variety of pharmaceuticals and other compounds, influencing the bioavailability of its binding partners. For example, HSA binds to and is acetylated by aspirin. While the acetylation of HSA by aspirin is a well-known reaction, its role in regulating HSA's carrier function has not been thoroughly explored. This study examined the effects of aspirin acetylation on HSA and its interactions with methotrexate in vitro. The acetylation sites on HSA were mapped using mass spectrometry. The results revealed that the pattern of aspirin acetylation of HSA is time-dependent and that aspirin preferentially acetylates lysine residues in both of HSA's principal drug-binding sites. Additionally, aspirin and another pharmaceutical, methotrexate, competed for binding to site 1, as methotrexate inhibited the aspirin-induced acetylation of HSA. Importantly, the results indicated that aspirin acetylation of HSA compromised HSA's ability to bind to methotrexate. Overall this interaction has the potential to modulate the drug binding dynamics of HSA. Further research is needed to determine how the competitive inhibition of aspirin-induced acetylation might influence the pharmacokinetic and pharmacodynamic factors in clinical settings. © 2024 Elsevier B.V.