Untargeted metabolomics analysis of serum and urine unveils the protective effect of cilastatin on altered metabolic pathways during cisplatin-induced acute kidney injury.

Acute kidney injury (AKI) is one of the most serious complications of cisplatin anticancer therapies. Cilastatin is a highly promising nephroprotective agent to eventually enter clinical use, but its biochemical mechanism is still not fully understood. We have employed an untargeted metabolomics approach based on capillary electrophoresis mass spectrometry (CE-MS) analysis of serum and urine from an in vivo rat model, to explore the metabolic pathways involved in cisplatin-induced AKI and cilastatin nephroprotection. A total of 155 and 76 identified metabolites were found to be significantly altered during cisplatin treatment in urine and serum, respectively. Most of these altered metabolites were either partially or totally recovered by cilastatin and cisplatin co-treatment. The main metabolic pathways disturbed by cisplatin during AKI involved diverse amino acids metabolism and biosynthesis, tricarboxylic acids (TCA) cycle, nicotinate and nicotinamide metabolism, among others. Cilastatin was proved to protect diverse cisplatin-altered pathways involving metabolites related to immunomodulation, inflammation, oxidative stress and amino acid metabolism in proximal tubules. However, cisplatin-altered mitochondrial metabolism (especially, the energy-producing TCA cycle) remained largely unprotected by cilastatin, suggesting an unresolved mitochondrial direct damage. Multivariate analysis allowed effective discrimination of cisplatin-induced AKI and cilastatin renoprotection based on metabolic features. A number of potential serum and urine biomarkers could also be foreseen for cisplatin-induced AKI detection and cilastatin nephroprotection.

Human intake assessment of triclosan associated with the daily use of polypropylene-made antimicrobial food packaging.

In this work, we aimed to evaluate human intake of triclosan (TCS) associated with real-life use of different brands of Microban™ microwave-safe food packaging. Calculations were based on: TCS migration data (under the worst-case foreseeable conditions), MPs abundance and TCS bioaccessibility from microplastics (MPs), leached from containers under microwave heating. Bioaccessibility studies were performed with in vitro digestion of MPs, followed by liquid-liquid extraction of TCS from digestive fluids and LC-QqQ-MS analysis yielding values of 46 ± 9%. The estimated weekly intake (EWI) of TCS ranged between 11 and 42 µg/kg body weight/week, with migration being the largest contribution (0.6-2.3 mg/week), compared to leaching of MPs (75-300 µg/week). These values represent a significant source of human exposure to TCS, emphasizing the need to harmonize the ban of TCS in food contact materials worldwide and improve compliance testing of food contact articles, particularly those marketed through online sales platforms.

Risk assessment of silver and microplastics release from antibacterial food containers under conventional use and microwave heating.

The evaluation of the migration of ionic silver and nanoparticulated silver (AgNPs) from antimicrobial plastic packaging to food is crucial to ensure its safety. Migration assays were performed on reusable silver-containing polypropylene (PP) food containers and a silicone baby bottle, using food simulants, under conventional or microwave heating and repeated use. The PP containers released significant amounts of silver, increasing with temperature, contact time, acidity and lower crystallinity. Silver migration in the silicone bottle was much lower. Risk assessment of released silver was done considering European authorities safety recommendations, with some containers far exceeding these levels. No significant AgNPs release was detected in the simulants by single particle-ICPMS. Silver-containing microplastics and silicone microparticles were detected by SEM in the food simulants after the migration assays. Consumers may be continuously exposed to the harmful effects of ionic silver and microplastics, which can potentially lead to health issues.

Lipidomics Reveals Cisplatin-Induced Renal Lipid Alterations during Acute Kidney Injury and Their Attenuation by Cilastatin.

Nephrotoxicity is a major complication of cisplatin-based chemotherapy, leading to acute kidney injury in ca. 30% of patients, with no preventive intervention or treatment available for clinical use. Cilastatin has proved to exert a nephroprotective effect for cisplatin therapies in in vitro and in vivo models, having recently entered clinical trials. A deeper understanding at the molecular level of cisplatin-induced renal damage and the effect of potential protective agents could be key to develop successful nephroprotective therapies and to establish new biomarkers of renal damage and nephroprotection. A targeted lipidomics approach, using LC-MS/MS, was employed for the quantification of 108 lipid species (comprising phospholipids, sphingolipids, and free and esterified cholesterol) in kidney cortex and medulla extracts from rats treated with cisplatin and/or cilastatin. Up to 56 and 63 lipid species were found to be altered in the cortex and medulla, respectively, after cisplatin treatment. Co-treatment with cilastatin attenuated many of these lipid changes, either totally or partially with respect to control levels. Multivariate analysis revealed that lipid species can be used to discriminate renal damage and nephroprotection, with cholesterol esters being the most discriminating species, along with sulfatides and phospholipids. Potential diagnostic biomarkers of cisplatin-induced renal damage and cilastatin nephroprotection were also found.

Diet-induced dyslipidemia induces metabolic and migratory adaptations in regulatory T cells.

AIMS: A hallmark of advanced atherosclerosis is inadequate immunosuppression by regulatory T (Treg) cells inside atherosclerotic lesions. Dyslipidemia has been suggested to alter Treg cell migration by affecting the expression of specific membrane proteins, thereby decreasing Treg cell migration towards atherosclerotic lesions. Besides membrane proteins, cellular metabolism has been shown to be a crucial factor in Treg cell migration. We aimed to determine whether dyslipidemia contributes to altered migration of Treg cells, in part, by affecting cellular metabolism. METHODS AND RESULTS: Dyslipidemia was induced by feeding Ldlr-/- mice a western-type diet for 16-20 weeks and intrinsic changes in Treg cells affecting their migration and metabolism were examined. Dyslipidemia was associated with altered mTORC2 signalling in Treg cells, decreased expression of membrane proteins involved in migration, including CD62L, CCR7, and S1Pr1, and decreased Treg cell migration towards lymph nodes. Furthermore, we discovered that diet-induced dyslipidemia inhibited mTORC1 signalling, induced PPARδ activation and increased fatty acid (FA) oxidation in Treg cells. Moreover, mass-spectrometry analysis of serum from Ldlr-/- mice with normolipidemia or dyslipidemia showed increases in multiple PPARδ ligands during dyslipidemia. Treatment with a synthetic PPARδ agonist increased the migratory capacity of Treg cells in vitro and in vivo in an FA oxidation-dependent manner. Furthermore, diet-induced dyslipidemia actually enhanced Treg cell migration into the inflamed peritoneum and into atherosclerotic lesions in vitro. CONCLUSION: Altogether, our findings implicate that dyslipidemia does not contribute to atherosclerosis by impairing Treg cell migration as dyslipidemia associated with an effector-like migratory phenotype in Treg cells.

Lipid imaging for visualizing cilastatin amelioration of cisplatin-induced nephrotoxicity.

Nephrotoxicity is a major limitation to cisplatin antitumor therapies. Cilastatin, an inhibitor of renal dehydropeptidase-I, was recently proposed as a promising nephroprotector against cisplatin toxicity, preventing apoptotic cell death. In this work, cilastatin nephroprotection was further investigated in a rat model, with a focus on its effect on 76 renal lipids altered by cisplatin, including 13 new cisplatin-altered mitochondrial cardiolipin species. Lipid imaging was performed with MALDI mass spectrometry imaging (MALDI-MSI) in kidney sections from treated rats. Cilastatin was proved to significantly diminish the lipid distribution alterations caused by cisplatin, lipid levels being almost completely recovered to those of control samples. The extent of recovery of cisplatin-altered lipids by cilastatin turned out to be relevant for discriminating direct or secondary lipid alterations driven by cisplatin. Lipid peroxidation induced by cisplatin was also shown to be reduced when cilastatin was administered. Importantly, significant groups separation was achieved during multivariate analysis of cortex and outer-medullary lipids, indicating that damaged kidney can be discerned from the nephroprotected and healthy groups and classified according to lipid distribution. Therefore, we propose MALDI-MSI as a powerful potential tool offering multimolecule detection possibilities to visualize and evaluate nephrotoxicity and nephroprotection based on lipid analysis.

Dual Internal Standards with Metals and Molecules for MALDI Imaging of Kidney Lipids.

The quest for internal standards useful in MALDI imaging studies goes on to get not only lateral distribution but also reliable relative quantitative information. We developed a method based on application of matrix and dual internal standards to allow intra- and intersample normalization of lipids intensities in kidney sections of control and cisplatin-treated Wistar rats. An inkjet printer was used to deposit a custom-prepared ink with DHB as MALDI matrix, a primary lipids-based internal standard, and a spiked lanthanide as a secondary internal standard. We applied different laser energy and varied the amounts of matrix-internal standards mixture to evaluate the normalization potential of the internal standards. Successful correction of intensity artifacts caused by instrumental drifts was possible, but not those resulting from uneven matrix application. ICP-MS absolute quantification of the lanthanide in the printed layer ensured the reproducibility of the matrix and internal standards application with RSD of 10-15%. Internal standard-normalized data allowed intrasample modification of the MALDI image to make it compatible with the optical image. Normalization to internal standards corrected a 2-fold difference in lipids intensity, which allowed a meaningful comparison of tissue lipids in control and cisplatin-treated kidneys. More importantly, normalization of lipid relative abundances based on the same adduct type (H+, Na+, and K+) for analyte and internal standard corrected for different ionization efficiencies showing a realistic signal level and enabling reliable comparison of different samples on relative quantitative basis.

MALDI-LTQ-Orbitrap mass spectrometry imaging for lipidomic analysis in kidney under cisplatin chemotherapy.

Imaging techniques for mapping molecular distributions in tissue sections can reveal valuable information on biomolecules involved in relevant biochemical processes. A method has been developed for comprehensive, reproducible and sensitive lipid imaging by matrix-assisted laser/desorption ionization-LTQ-Orbitrap mass spectrometry in kidney sections, showing the benefits of exact mass determination. Matrix deposition parameters for positive and negative lipid ion imaging using different matrices such as 2,5-dihydroxybenzoic acid (DHB), 9-aminoacridine (9-AA) or α-cyano-4-hydroxycinnamic acid (CHCA) have been optimized for the broadest detection and identification of renal lipids. The combination of 9-AA and DHB was found as the most suitable for negative and positive ion mode lipid imaging, respectively. Lipid mapping and related identification strategies and limitations have also been discussed. Production of 100-µm resolution images was proved to be enough for discerning lipid distribution in kidney substructures. Imaging reproducibility was assessed on parallel kidney slices with time. This method has been applied to the lipidomics analysis on kidney sections from rats treated with the antitumor drug cisplatin and compared to healthy control rats. Up to 66 different renal lipids out of 450 extracted ion images (mainly phospholipid species, in addition to sulfatides and cholesterol sulfate) have been found and identified showing a modified distribution pattern due to cisplatin-induced nephrotoxicity. These lipid species reflect either topographic, signaling or structural processes in damaged kidney and could potentially be used for nephrotoxicity assessment or as therapeutic targets. This is, to our knowledge, the first imaging lipidomics study for nephrotoxicity assessment of cisplatin chemotherapy.

A novel method for serum lipoprotein profiling using high performance capillary isotachophoresis.

A new capillary isotachophoresis (cITP) method for lipoprotein profiling with superior lipoprotein coverage compared to previous methods has been developed, resolving twice as many lipoprotein species (18 peaks/fractions) in serum or plasma in less than 9.5 min. For this, a novel mixture of 24 spacers, including amino acids, dipeptides and sulfonic acids, was developed and fine-tuned, using predictive software (PeakMaster) and testing of spiked serum samples. Lipoprotein peaks were identified by serum-spiking with reference lipoproteins. Compatibility with common lipophilic stains for selective lipoprotein detection with either UV/Vis or laser-induced fluorescence was demonstrated. A special new capillary with a neutral coating (combining water-compatible OV1701-OH deactivation and methylation) was used for the first time for electrodriven separations, allowing very stable separations in a pH 8.8-9.4 gradient system, being functional for more than 100 injections. Excellent reproducibility was achieved, with coefficients of variation lower than 2.6% for absolute migration times. Comparison was performed with human plasma samples analyzed by NMR, leading to similar results with cITP after multivariate statistics, regarding group-clustering and lipoprotein species correlation. The new cITP method was applied to the analysis of serum samples from a LDL receptor knock-out mice model fed either a normal diet or a western-type diet. Differences in the lipoprotein levels and in the sublipoprotein types were detected, showing a shift to more atherogenic particles due to the high cholesterol diet. In summary, this novel method will allow more detailed and informative profiling of lipoprotein particle subtypes for cardiovascular disease research.

Bacterial surface layer proteins as a novel capillary coating material for capillary electrophoretic separations.

A novel concept for stable coating in capillary electrophoresis, based on recrystallization of surface layer proteins on hydrophobized fused silica capillaries, was demonstrated. Surface layer protein A (SlpA) from Lactobacillus acidophilus bacteria was extracted, purified and used for coating pre-silanized glass substrates presenting different surface wettabilities (either hydrophobic or hydrophilic). Contact angle determination on SlpA-coated hydrophobic silica slides showed that the surfaces turned to hydrophilic after coating (53 ± 5°), due to a protein monolayer formation by protein-surface hydrophobic interactions. Visualization by atomic force microscopy demonstrated the presence of a SlpA layer on methylated silica slides displaying a surface roughness of 0.44 ± 0.02 nm. Additionally, a protein layer was visualized by fluorescence microscopy in methylated silica capillaries coated with SlpA and fluorescein isothiocyanate-labeled. The SlpA-coating showed an outstanding stability, even after treatment with 20 mM NaOH (pH 12.3). The electroosmotic flow in coated capillaries showed a partial suppression at pH 7.50 (3.8 ± 0.5 10(-9) m(2) V(-1) s(-1)) when compared with unmodified fused silica (5.9 ± 0.1 10(-8) m(2) V(-1) s(-1)). To demonstrate the potential of this novel coating, the SlpA-coated capillaries were applied for the first time for electrophoretic separation, and proved to be very suitable for the isotachophoretic separation of lipoproteins in human serum. The separations showed a high degree of repeatability (absolute migration times with 1.1-1.8% coefficient-of-variation (CV) within a day) and 2-3% CV inter-capillary reproducibility. The capillaries were stable for more than 100 runs at pH 9.40, and showed to be an exceptional alternative for challenging electrophoretic separations at long-term use.

A shotgun approach for the identification of platinum-protein complexes.

A shotgun approach including peptide-based OFFGEL-isoelectric focusing (IEF) fractionation has been developed with the aim of improving the identification of platinum-binding proteins in biological samples. The method is based on a filter-aided sample preparation (FASP) tryptic digestion under denaturing and reducing conditions of cisplatin-, oxaliplatin-, and carboplatin-protein complexes, followed by OFFGEL-IEF separation of the peptides. Any risk of platinum loss is minimized throughout the procedure due to the removal of the reagents used after each stage of the FASP method and the absence of thiol-based reagents in the focusing buffer employed in the IEF separation. The platinum-peptide complexes stability after the FASP digestion and the IEF separation was confirmed by size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS). The suitability of peptide-based OFFGEL-IEF fractionation for reducing the sample complexity for further nano-liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS/MS) analysis has been demonstrated, allowing the detection of platinum-containing peptides, with significantly lower abundance and ionization efficiency than unmodified peptides. nLC-MS/MS analysis of selected OFFGEL-IEF fractions from tryptic digests with different complexity degrees: standard human serum albumin (HSA), a mixture of five proteins (albumin, transferrin, carbonic anhydrase, myoglobin, and cytochrome-c) and human blood serum allowed the identification of several platinum-peptides from cisplatin-HSA. Cisplatin-binding sites in HSA were elucidated from the MS/MS spectra and assessed considering the protein three-dimensional structure. Most of the potential superficial binding sites available on HSA were identified for all the samples, including a biologically relevant cisplatin-cross-link of two protein domains, demonstrating the capabilities of the methodology.

Cilastatin protects against cisplatin-induced nephrotoxicity without compromising its anticancer efficiency in rats.

Cisplatin is an anticancer agent marred by nephrotoxicity; however, limiting this adverse effect may allow the use of higher doses to improve its efficacy. Cilastatin, a small molecule inhibitor of renal dehydropeptidase I, prevents proximal tubular cells from undergoing cisplatin-induced apoptosis in vitro. Here, we explored the in vivo relevance of these findings and the specificity of protection for kidney cells in cisplatin-treated rats. Cisplatin increased serum blood urea nitrogen and creatinine levels, and the fractional excretion of sodium. Cisplatin decreased the glomerular filtration rate, promoted histological renal injury and the expression of many pro-apoptotic proteins in the renal cortex, increased the Bax/Bcl2 ratio, and oxidative stress in kidney tissue and urine. All these features were decreased by cilastatin, which preserved renal function but did not modify the pharmacokinetics of cisplatin area under the curve. The cisplatin-induced death of cervical, colon, breast, and bladder-derived cancer cell lines was not prevented by cilastatin. Thus, cilastatin has the potential to prevent cisplatin nephrotoxicity without compromising its anticancer efficacy.

Characterization of Pt-protein complexes by nHPLC-ESI-LTQ MS/MS using a gel-based bottom-up approach.

The suitability of in-gel digestion for the characterization of Pt-binding proteins by gel-based bottom-up MS approaches has been evaluated regarding the preservation of Pt-protein bonds during the process. Standard proteins (albumin, transferrin, carbonic anhydrase, myoglobin and cytochome c) incubated with cisplatin were separated by nrSDS-PAGE and in-gel trypsin-digested. The whole in-gel digestion protocol included treatment with reagents such as: ammonium bicarbonate, acetonitrile, formic acid, trypsin as enzyme and alternatively, dithiotreitol and iodoacetamide as reducing and alkylating agents. Digests were analyzed by nHPLC-ESI-LTQ-MS/MS and Pt-peptides were recognized in all the proteins studied on the basis of their isotopic pattern. Only when the reducing and alkylating reagents were used, the amount of detectable Pt-peptides decreased due to the high reactivity of thiol containing reagents towards Pt. Furthermore, the repeated use of acetonitrile could lead to the replacement of ligands originally attached to Pt by CN(-), but does not affect the Pt-protein binding. Platinum-binding sites on the proteins were elucidated from the CID-MS/MS fragmentation spectra and assessed by evaluation of protein structures. Several histidines, cysteines and methionines were identified as platinum binding sites in the different standard proteins. Results were in accordance to those obtained with in-solution digestions.

Identification of olive (Olea europaea) pulp proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nano-liquid chromatography tandem mass spectrometry.

Proteins in the pulp of olive ( Olea europaea ) constitute a minor fraction. They have been sparsely studied despite their suggested role in oil stability and olive allergenicity. The analysis of a pulp protein extract by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed a major band at 24 kDa that was subjected to tryptic in-gel digestion. Peptide extracts were analyzed by MALDI-TOF MS and nanoLC-MS/MS. The use of different search engines enabled the assignment of a number of fragmentation spectra to peptide sequences, identifying a major band as a thaumatin-like protein and other low-abundant proteins such a drought-induced protein SDi-6-like, an acyl carrier protein, Cu/Zn and Mn superoxide dismutases, a small heat shock protein, and an ATP-dependent protease subunit. Many of the produced spectra did not give good matches in the database searches, due to the scarce presence of O. europaea entries in protein databases. Nevertheless, a huge number of spectra corresponded to peptides, which showed a high degree of homology with others from sequenced organisms. These results proved that database searching with MS/MS spectra constitutes a promising approach for the characterization of olive pulp proteins.

Elemental bioimaging in kidney by LA-ICP-MS as a tool to study nephrotoxicity and renal protective strategies in cisplatin therapies.

A laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)-based methodology is presented for Pt, Cu, and Zn bioimaging on whole kidney 3 µm sagittal sections from rats treated with pharmacological doses of cisplatin, which were sacrificed once renal damage had taken place. Pt turned out to accumulate in the kidney cortex and corticomedullary junction, corresponding to areas where the proximal tubule S3 segments (the most sensitive cells to cisplatin nephrotoxicity) are located. This demonstrates the connection between platinum accumulation and renal damage proved by histological examination of HE-stained sections and evaluation of serum and urine biochemical parameters. Cu and Zn distribution maps revealed a significant displacement in cells by Pt, as compared to control tissues. A dramatic decrease in the Pt accumulation in the cortex was observed when cilastatin was coadministered with cisplatin, which can be related to its nephroprotective effect. Excellent imaging reproducibility, sensitivity (LOD 50 fg), and resolution (down to 8 µm) were achieved, demonstrating that LA-ICP-MS can be applied as a microscopic metal detector at cellular level in certain tissues. A simple and quick approach for the estimation of Pt tissue levels was proposed, based on tissue spiking.

OFFGEL isoelectric focusing and polyacrylamide gel electrophoresis separation of platinum-binding proteins.

In this work a 2D electrophoretic separation procedure able to maintain the integrity of platinum-protein bonds has been developed. The method is based on the use of sequential OFFGEL isoelectric focussing (IEF) and PAGE. A systematic study of the reagents used for PAGE, for OFFGEL-IEF separation, and post-separation treatment of gels (such as enzymatic digestion and sample preparation for MS analysis) was tackled regarding their suitability for the identification of platinum binding proteins using standard proteins incubated with cisplatin. The distribution of platinum in high and low molecular weight fractions (separated by cut-off filters) was determined by ICP-MS, which allows evaluating platinum-protein bond stability under the conditions studied. SDS-PAGE in the absence of ß-mercaptoethanol or dithiotreitol preserved the platinum-protein bonds. In addition, neither the influence of the electric field during the electrophoretic separation, nor the processes of fixing, staining and destaining of proteins in the gel did result in the loss of platinum from platinum binding proteins. SDS-PAGE under non-reducing conditions provides separation of platinum-binding proteins in very narrow bands with quantitative recoveries. Different amounts of platinum-bound proteins covering the range 0.3-2.0 µg were separated and mineralised for platinum determination, showing good platinum linearity. Limits of detection for a mixture of five standard proteins incubated with cisplatin were between the range of 2.4 and 13.9 pg of platinum, which were satisfactory for their application to biological samples. Regarding OFFGEL-IEF, a denaturing solution without thiourea and without dithiotreitol is recommended. The suitability of the OFFGEL-IEF for the separation of platinum binding proteins of a kidney cytosol was demonstrated.

Analytical methodologies for metallomics studies of antitumor Pt-containing drugs.

Pt-containing drugs are nowadays essential components in cancer chemotherapy. However, drug resistance and side effects limit the efficiency of the treatments. In order to improve the response to Pt-based drugs, different administration strategies or new Pt-compounds have been developed with little success. The reason for this failure could be that the mechanism of action of these drugs is not completely understood. In this way, metallomics studies may contribute to clarify the interactions of Pt-containing drugs within the organism. This review is mainly focused on the role of Analytical Chemistry on the study of the interactions between Pt-based drugs and biomolecules. A summary of the analytical techniques and the most common sample treatment procedures currently used in metallomics studies of these drugs is presented. Both are of paramount importance to study these complex samples preserving the drug-biomolecule interaction. Separation and detection techniques must be carefully selected in order to achieve the intended goals. The use of multidimensional hyphenated techniques is usually necessary for a better understanding of the Pt-based drugs interactions in the organism. An overview of Pt-drugs biological interactions is presented, considering the different sample matrices and the drugs course through the organism. Samples analysed in the included studies are blood, urine, cell cytosol, DNA as well as the drugs themselves and their derivatives. However, most of these works are based on in vitro experiments or incubations of standards, leading in some cases to contradictory results depending on the experimental conditions used. Though in vivo experiments represent a great challenge due to the high complexity and the low concentrations of the Pt-adducts in real samples, these studies must be undertaken to get a deeper understanding of the real interactions concerning Pt-containing drugs.

Cilastatin attenuates cisplatin-induced proximal tubular cell damage.

A major area in cancer therapy is the search for protective strategies against cisplatin-induced nephrotoxicity. We investigated the protective effect of cilastatin on cisplatin-induced injury to renal proximal tubular cells. Cilastatin is a specific inhibitor of renal dehydrodipeptidase I (DHP-I), which prevents hydrolysis of imipenem and its accumulation in the proximal tubule. Primary cultures of proximal cells were treated with cisplatin (1-30 microM) in the presence or absence of cilastatin (200 microg/ml). Apoptosis and mitochondrial injury were assessed by different techniques. Cisplatin uptake and DNA binding were measured by inductively coupled plasma spectrometry. HeLa cells were used to control the effect of cilastatin on the tumoricidal activity of cisplatin. Cisplatin increased cell death, apoptotic-like morphology, caspase activation, and mitochondrial injury in proximal tubular cells in a dose- and time-dependent way. Concomitant treatment with cilastatin reduced cisplatin-induced changes. Cilastatin also reduced the DNA-bound platinum but did not modify cisplatin-dependent up-regulation of death receptors (Fas) or ligands (tumor necrosis factor alpha, Fas ligand). In contrast, cilastatin did not show any effects on cisplatin-treated HeLa cells. Renal DHP-I was virtually absent in HeLa cells. Cilastatin attenuates cisplatin-induced cell death in proximal tubular cells without reducing the cytotoxic activity of cisplatin in tumor cells. Our findings suggest that the affinity of cilastatin for renal dipeptidase makes this effect specific for proximal tubular cells and may be related to a reduction in intracellular drug accumulation. Therefore, cilastatin administration might represent a novel strategy in the prevention of cisplatin-induced acute renal injury.

Novel insights into the bottom-up mass spectrometry proteomics approach for the characterization of Pt-binding proteins: The insulin-cisplatin case study.

The characterization of the interaction of platinum drugs with proteins has been previously performed using bottom-up proteomics approaches (enzymatic digestion followed by MS analysis). Nevertheless, the study of the stability of the Pt-protein bonds along the whole process has been obviated for the moment. Herein the suitability of the treatments implied during enzymatic digestion of Pt-protein adducts has been evaluated, focusing on the stability of the Pt bonds. Insulin-cisplatin adducts were generated in vitro and separated from unreacted cisplatin by HPLC, the separation being checked by HPLC-ICP-MS. The chromatographically isolated Pt-insulin adducts have been proved to resist overnight digestion including treatment with Urea, DTT, IAA and trypsin in a Tris buffer. Direct analysis of the peptides generated by nESI-LIT MS allowed the determination of Pt-binding sites in insulin as: B Chain N-terminus, His5, His10, Cys7, Cys19 and A Chain Cys6, Cys7, Cys20. Results have been compared to a previous top-down approach, indicating that more complete information can be obtained with the bottom-up approach. Reactivity of free cysteines has been proved to prevail to N-donor groups, but when cysteines participate in disulfide bonds, their reactivity is comparable to N-donor sites (N-terminus, His). Preliminary results indicate that the use of High Intensity Focused Ultrasound for accelerating the enzymatic digestions is compatible with preserving Pt-protein bonds, allowing a reduction in the total digestion time to 5 min. Pt-containing peptides were fragmented and sequenced by CID, and results were compared with those obtained by the use of ETD, being CID spectra far more informative.

Top-down mass spectrometric approach for the full characterization of insulin-cisplatin adducts.

The interaction of the antitumor drug cisplatin with insulin was studied using a top-down mass spectrometric approach. In vitro incubations were prepared under acidic and physiological conditions at different insulin/cisplatin molar ratios for different incubation times. Size exclusion chromatography-inductively coupled plasma mass spectrometry (SEC-ICPMS) analysis enabled the specific detection of platinum containing species attributed to the binding of the drug to the protein. Further analysis through matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and nanoelectrospray ionization mass spectrometry using a linear ion trap (nESI-LIT-MS) allowed the identification of platinated mono-, di-, and even triadducts in the incubations. Platinum binding sites were identified by CID-MS(n) as B chain N-terminus, His5, and probably His10 residues, which turned out to be the same, regardless of the incubation conditions. Evidence on the binding of Pt to B chain Cys7 was also observed. Working with the LIT zoom scan mode provides enough resolution to discern the isotopic pattern for both precursor and fragment ions, allowing the differentiation of platinum-containing ions. The elucidation of platinum binding sites in a native protein through a top-down approach has been performed for the first time with this type of instrument.