N-acetyl-L-cysteine modulates the metabolism of cis-platin in human plasma in vitro.

Cis-Platin (CP) is a remarkably effective Pt-based anticancer drug, but it also exhibits severe toxic side-effects, including nephrotoxicity and ototoxicity. Previous studies conducted with mammalian model organisms have clearly demonstrated that the intravenous administration of N-acetyl-L-cysteine (NAC) or sodium thiosulfate (STS) along with CP can significantly reduce these toxic side effects. A molecular understanding of the biochemical events that unfold in the bloodstream when these 'ameliorating agents' and CP are co-administered, therefore, constitutes an important first step in devising novel strategies to ultimately improve the quality of life of patients undergoing treatment with CP. We have employed size exclusion chromatography (SEC) coupled on-line to an inductively coupled plasma atomic emission spectrometer (ICP-AES) to visualize how NAC affects the metabolism of CP in human plasma (obtained from healthy male volunteers) in vitro. Clinically relevant doses of CP and NAC were added to plasma at various NAC : CP molar ratios and the Pt-distribution was determined after 10 and 50 min. The results revealed that a putative Pt-NAC complex was formed in plasma with NAC : CP molar ratios ≥ 50 : 1 and that plasma protein binding of CP-derived Pt-species was marginally affected by NAC. In addition, the anti-tumor active CP remained in plasma for more than 50 min. Furthermore, NAC (but not CP) adversely affected the integrity of Fe and Zn plasma metalloproteins in a dose and a time dependent manner. Based on these in vitro data, NAC appears to be a less ideal ameliorating agent to mitigate CP toxicity compared to STS.