This journal is c The Royal Society of Chemistry 2013 Metallomics, 2013, 5, 197--207 197 Cite this: Metallomics, 2013, 5, 197 N-Acetyl-L-cysteine modulates the metabolism of cis-platin in human plasma in vitro† Melani Sooriyaarachchi, a Aru Narendran b and Ju ¨rgen Gailer* a 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 Z 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. Introduction Cis-Platin (CP) is currently used to treat humans who suffer from bladder, gastric, lung, head and neck, cervical, testicular and ovarian cancers. 1,2 Despite some disadvantages that are associated with CP, this metal-based drug remains an effective and indispensable anticancer drug for certain cancers. 3 The two major drawbacks of CP are drug resistance 4 and severe toxic side-effects, such as nephrotoxicity, ototoxicity and neu- rotoxicity. 5 Thus, there is an urgent need to develop more effective Pt-based anticancer drugs which are associated with less or ideally no toxic side-effects. 6,7 To this end, more than 3000 Pt-based anticancer drugs have so far been synthesized, but only six have been approved for clinical use. 8–11 An alter- native strategy to transform CP into a better medicinal drug would be to selectively mitigate its toxic side-effects while leaving its efficacy largely uncompromised. Several studies have demonstrated that so-called chemoprotective agents can signifi- cantly reduce the toxic side-effects of Pt-based anti-cancer drugs, 12,13 while leaving their antitumor activity intact. 14 Direct experimental evidence in favor of a reduction in CP mediated toxic side-effects by sodium thiosulfate (STS), 15,16 N-acetyl-L- cysteine (NAC), 17,18 D-methionine, 19 amifostine, 20 sodium diethyl- dithiocarbamate 21,22 and L-glutathione 23 has been reported using a variety of model organisms. These rather phenomenological observations, however, are not well understood at the molecular level which must be attributed to the lack of appropriate tools to visualize the underlying biochemical processes. Considering that both CP and chemoprotective agents are intravenously administered, the bloodstream represents the initial milieu where relevant biochemical transformations may ensue. We have developed a bioanalytical method which allows one to rapidly determine changes of the distribution of multiple metal species in blood plasma over time. 24,25 This methodology is based on the separation of plasma proteins on a size-exclusion chromatography (SEC) column and the on-line detection of the separated metal entities in the effluent by means of an induc- tively coupled plasma atomic emission spectrometer (ICP-AES). 26 To date, this methodology has already been used to visualize the hydrolysis and the plasma protein binding of CP and carboplatin a Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada. E-mail: jgailer@ucalgary.ca; Fax: +1-403-289-9488; Tel: +1-403-210-8899 b Division of Pediatric Oncology, Alberta Children’s Hospital, Calgary, AB, Canada † Electronic supplementary information (ESI) available. See DOI: 10.1039/ c3mt00012e Received 10th January 2013, Accepted 13th February 2013 DOI: 10.1039/c3mt00012e www.rsc.org/metallomics Metallomics PAPER Downloaded from https://academic.oup.com/metallomics/article/5/3/197/6007582 by guest on 22 January 2024