Evaluation of mutagenic activity of platinum complexes in somatic cells of Drosophila melanogaster

Mutagenicity of the agriculture pesticide chlorothalonil assessed by somatic mutation and recombination test in Drosophila melanogaster

Chlorothalonil (CTL) is a pesticide widely used in Brazil, yet its mutagenic potential is not fully determined. Thus, we assessed the mutagenicity of CTL and its bioactivation metabolites using the somatic mutation and recombination test (SMART) in Drosophila melanogaster, by exposing individuals, with basal and high bioactivation capacities (standard and high bioactivation cross offspring, respectively), from third instar larval to early adult fly stages, to CTL-contaminated substrate (0.25, 1, 10 or 20 μM). This substrate served as food and as physical medium. Increased frequency of large single spots in standard cross flies' wings exposed to 0.25 μM indicates that, if CTL is genotoxic, it may affect Drosophila at early life stages. Since the total spot frequency did not change, CTL cannot be considered mutagenic in SMART. The same long-term exposure design was performed to test whether CTL induces oxidative imbalance in flies with basal (wild-type, WT) or high bioactivation (ORR strain) levels. CTL did not alter reactive oxygen species and antioxidant capacity against peroxyl radicals levels in adult flies. However, lipid peroxidation (LPO) levels were increased in WT male flies exposed to 1 μM CTL. SMART and LPO alterations were observed only in flies with basal bioactivation levels, pointing to direct CTL toxicity to DNA and lipids. Survival, emergence and locomotor behavior were not affected, indicating no bias due to lethality, developmental and behavioral impairment. We suggest that, if related to CTL exposure, DNA and lipid damages may be residual damage of earlier life stages of D. melanogaster.

The Excretion of Cisplatin after Hyperthermic Intrathoracic Chemotherapy

Hyperthermic intrathoracic chemotherapy (HITOC) is an additional intraoperative treatment option within the multimodality therapy of pleural malignancies. A chemotherapy perfusion with high-dose cisplatin is performed over a period of 60 min after surgical cytoreduction to improve local tumour control through the eradication of residual tumour cells. Although HITOC is increasingly used, there is only little scientific evidence about the necessary safety measures after HITOC. Therefore, the objective of this study was an analysis of cisplatin excretion via various body fluids after HITOC, with the aim of providing recommendations on occupational health and safety. Five patients undergoing HITOC were included. Before and after the HITOC, as well as during the following days, serum, urine, and bronchial secretion, as well as pleural effusion, were sampled. The platinum levels in the samples were measured using ICP-MS (inductively coupled plasma-mass spectrometry). Immediately after the HITOC, the mean levels of cisplatin increased dramatically in the serum (from 0.79 to 1349 µg/L), urine (from 3.48 to 10,528 µg/g creatinine), and bronchial secretion (from 0.11 to 156 µg/L). Thereafter, the cisplatin levels dropped to 133 µg/L in the serum and 994 µg/g creatinine in the urine within nine days after the HITOC. The AUC ratio shows 59% of the cisplatin being excreted via the urine after 48 h. The sampling of pleural effusion started 24 h after the HITOC, and the cisplatin levels decreased from 618 to 93 µg/L within nine days. Although the cisplatin levels in the body fluids of HITOC patients are much lower compared to patients receiving intravenous chemotherapy, a significant amount of cisplatin is excreted via these body fluids. Consequently, safety precautions must be implemented in the post-HITOC care of patients to avoid occupational exposure to cisplatin.

Evaluation of toxicity and mutagenicity of oxaliplatin on germ cells in an alternative in vivo model Caenorhabditis elegans

The platinum compound oxaliplatin is a widely used chemotherapeutic drug that shows a broad spectrum of activity in various human tumors. While the treatment-related side effects of oxaliplatin on directly treated individuals have been well-documented, little is known about the influence of oxaliplatin on germ cells and non-exposed progenies. Here we investigated the reproductive toxicity of oxaliplatin in a 3R-compliant in vivo model Caenorhabditis elegans, and evaluated the germ cell mutagenicity of oxaliplatin by using whole genome sequencing. Our results indicated that oxaliplatin treatment significantly disrupts development of spermatids and oocytes. By treating parental worms with oxaliplatin for three successive generations, sequencing data unveiled the clear mutagenic effects of oxaliplatin on germ cells. Analysis of genome-wide mutation spectra showed the preferentially induction of indels by oxaliplatin. In addition, we uncovered the involvement of translesion synthesis polymerase ζ in modulating mutagenic effects of oxaliplatin. These findings suggest that germ cell mutagenicity is worthy of consideration for the health risk assessment of chemotherapeutic drugs, while the combined use of alternative in vivo models and next generation sequencing technology appears to be a promising way for the preliminary safety assessment of various drugs.

A comparative analysis of the mutagenicity of platinum-containing chemotherapeutic agents reveals direct and indirect mutagenic mechanisms

Platinum-based drugs are a mainstay of cancer chemotherapy. However, their mutagenic effect can increase tumour heterogeneity, contribute to the evolution of treatment resistance and also induce secondary malignancies. We coupled whole genome sequencing with phenotypic investigations on two cell line models to compare the magnitude and examine the mechanism of mutagenicity of cisplatin, carboplatin and oxaliplatin. Cisplatin induced significantly more base substitution mutations than carboplatin or oxaliplatin when used at equitoxic concentrations on human TK6 or chicken DT40 cells, and also induced the highest number of short insertions and deletions. The analysis of base substitution spectra revealed that all three tested platinum drugs elicit both a direct mutagenic effect at purine dinucleotides, and an indirect effect of accelerating endogenous mutagenic processes, whereas the direct mutagenic effect appeared to correlate with the level of DNA damage caused as assessed through histone H2AX phosphorylation and single-cell agarose gel electrophoresis, the indirect mutagenic effects were equal. The different mutagenicity and DNA-damaging effect of equitoxic platinum drug treatments suggest that DNA damage independent mechanisms significantly contribute to their cytotoxicity. Thus, the comparatively high mutagenicity of cisplatin should be taken into account in the design of chemotherapeutic regimens.

Metallodrugs are unique: opportunities and challenges of discovery and development

Metals play vital roles in nutrients and medicines and provide chemical functionalities that are not accessible to purely organic compounds. At least 10 metals are essential for human life and about 46 other non-essential metals (including radionuclides) are also used in drug therapies and diagnostic agents. These include platinum drugs (in 50% of cancer chemotherapies), lithium (bipolar disorders), silver (antimicrobials), and bismuth (broad-spectrum antibiotics). While the quest for novel and better drugs is now as urgent as ever, drug discovery and development pipelines established for organic drugs and based on target identification and high-throughput screening of compound libraries are less effective when applied to metallodrugs. Metallodrugs are often prodrugs which undergo activation by ligand substitution or redox reactions, and are multi-targeting, all of which need to be considered when establishing structure-activity relationships. We focus on early-stage in vitro drug discovery, highlighting the challenges of evaluating anticancer, antimicrobial and antiviral metallo-pharmacophores in cultured cells, and identifying their targets. We highlight advances in the application of metal-specific techniques that can assist the preclinical development, including synchrotron X-ray spectro(micro)scopy, luminescence, and mass spectrometry-based methods, combined with proteomic and genomic (metallomic) approaches. A deeper understanding of the behavior of metals and metallodrugs in biological systems is not only key to the design of novel agents with unique mechanisms of action, but also to new understanding of clinically-established drugs.

Cisplatin affects locomotor activity and physiological endpoints of Daphnia magna

Cisplatin (CPL) is a common antineoplastic drug used in human medicine for treatment of various cancer types. Since the knowledge about its effects on crustacean behavioral and physiological parameters is very scarce, the aim of our study was to determine the influence of CPL at concentrations of 125 μg/L, 200 μg/L, 500 μg/L and 1000 μg/L on swimming behavior (swimming speed, distance travelled, hopping frequency, propelling efficiency index - a novel parameter) and physiological parameters (heart rate, thoracic limb activity) of Daphnia magna with the use of video digital analysis. The results showed that distance travelled, swimming speed, hopping frequency and propelling efficiency were inhibited as early as after 24 h in concentration- and time-dependent manner. On the other hand, heart rate was stimulated in the animals treated with 125 μg/L of CPL after 48 h, 72 h and 120 h of the exposure, however it was decreased at the higher concentrations. Although thoracic limb activity was considerably increased in daphnids exposed to 125 μg/L and 200 μg/L after 72 h, it was inhibited at the higher concentrations of the drug. The study suggests that since CPL affected daphnid parameters at the environmental concentration, it should be considered as hazardous to zooplankton.