Preferential energy- and potential-dependent accumulation of cisplatin-gutathione complexes in human cancer cell lines (GLC4 and K562): A likely role of mitochondria

Integrins as the pivotal regulators of cisplatin response in tumor cells

Cisplatin (CDDP) is a widely used first-line chemotherapeutic drug in various cancers. However, CDDP resistance is frequently observed in cancer patients. Therefore, it is required to evaluate the molecular mechanisms associated with CDDP resistance to improve prognosis among cancer patients. Integrins are critical factors involved in tumor metastasis that regulate cell-matrix and cell-cell interactions. They modulate several cellular mechanisms including proliferation, invasion, angiogenesis, polarity, and chemo resistance. Modification of integrin expression levels can be associated with both tumor progression and inhibition. Integrins are also involved in drug resistance of various solid tumors through modulation of the tumor cell interactions with interstitial matrix and extracellular matrix (ECM). Therefore, in the present review we discussed the role of integrin protein family in regulation of CDDP response in tumor cells. It has been reported that integrins mainly promoted the CDDP resistance through interaction with PI3K/AKT, MAPK, and WNT signaling pathways. They also regulated the CDDP mediated apoptosis in tumor cells. This review paves the way to suggest the integrins as the reliable therapeutic targets to improve CDDP response in tumor cells.

Pyruvate dehydrogenase is a potential mitochondrial off-target for gentamicin based on in silico predictions and in vitro inhibition studies

During the drug development process, organ toxicity leads to an estimated failure of one-third of novel chemical entities. Drug-induced toxicity is increasingly associated with mitochondrial dysfunction, but identifying the underlying molecular mechanisms remains a challenge. Computational modeling techniques have proven to be a good tool in searching for drug off-targets. Here, we aimed to identify mitochondrial off-targets of the nephrotoxic drugs tenofovir and gentamicin using different in silico approaches (KRIPO, ProBis and PDID). Dihydroorotate dehydrogenase (DHODH) and pyruvate dehydrogenase (PDH) were predicted as potential novel off-target sites for tenofovir and gentamicin, respectively. The predicted targets were evaluated in vitro, using (colorimetric) enzymatic activity measurements. Tenofovir did not inhibit DHODH activity, while gentamicin potently reduced PDH activity. In conclusion, the use of in silico methods appeared a valuable approach in predicting PDH as a mitochondrial off-target of gentamicin. Further research is required to investigate the contribution of PDH inhibition to overall renal toxicity of gentamicin.

The multifaceted roles of mitochondria at the crossroads of cell life and death in cancer

Mitochondria are the cytoplasmic organelles mostly known as the "electric engine" of the cells; however, they also play pivotal roles in different biological processes, such as cell growth/apoptosis, Ca²⁺ and redox homeostasis, and cell stemness. In cancer cells, mitochondria undergo peculiar functional and structural dynamics involved in the survival/death fate of the cell. Cancer cells use glycolysis to support macromolecular biosynthesis and energy production ("Warburg effect"); however, mitochondrial OXPHOS has been shown to be still active during carcinogenesis and even exacerbated in drug-resistant and stem cancer cells. This metabolic rewiring is associated with mutations in genes encoding mitochondrial metabolic enzymes ("oncometabolites"), alterations of ROS production and redox biology, and a fine-tuned balance between anti-/proapoptotic proteins. In cancer cells, mitochondria also experience dynamic alterations from the structural point of view undergoing coordinated cycles of biogenesis, fusion/fission and mitophagy, and physically communicating with the endoplasmic reticulum (ER), through the Ca²⁺ flux, at the MAM (mitochondria-associated membranes) levels. This review addresses the peculiar mitochondrial metabolic and structural dynamics occurring in cancer cells and their role in coordinating the balance between cell survival and death. The role of mitochondrial dynamics as effective biomarkers of tumor progression and promising targets for anticancer strategies is also discussed.

Polymerized human hemoglobin increases the effectiveness of cisplatin-based chemotherapy in non-small cell lung cancer

Cisplatin is a promising therapeutic for the treatment of non-small cell lung cancer (NSCLC). Unfortunately, a significant portion of NSCLC patients relapse due to cisplatin chemoresistance. This chemoresistance is thought to be primarily associated with hypoxia in the tumor microenvironment. Administration of hemoglobin (Hb)-based oxygen (O2) carriers (HBOCs) is a promising strategy to alleviate hypoxia in the tumor, which may make cisplatin more effective. In this study, we administered a high O2 affinity, relaxed state (R-state) polymerized hemoglobin (PolyHb) to three different NSCLC cell lines cultured in vitro and implanted in vivo into healthy mice. The R-state PolyHb administered in this study is unable to deliver O2 unless under severe hypoxia which significantly limits its oxygenation potential. In vitro sensitivity studies indicate that the administration of PolyHb increases the effectiveness of cisplatin under hypoxic conditions. Additional animal studies revealed that co-administration of PolyHb with cisplatin attenuated tumor growth without alleviating hypoxia. Analysis of reactive O2 species production in the presence of hypoxic culture indicates that exogenous ROS production by oxidized PolyHb may the mechanism of chemosensitization. This ROS mechanism, coupled with oxygenation, may be a potential chemosensitizing strategy for use in NSCLC treatment.

The Role of Mitochondria in Drug-Induced Kidney Injury

The kidneys utilize roughly 10% of the body’s oxygen supply to produce the energy required for accomplishing their primary function: the regulation of body fluid composition through secreting, filtering, and reabsorbing metabolites and nutrients. To ensure an adequate ATP supply, the kidneys are particularly enriched in mitochondria, having the second highest mitochondrial content and thus oxygen consumption of our body. The bulk of the ATP generated in the kidneys is consumed to move solutes toward (reabsorption) or from (secretion) the peritubular capillaries through the concerted action of an array of ATP-binding cassette (ABC) pumps and transporters. ABC pumps function upon direct ATP hydrolysis. Transporters are driven by the ion electrochemical gradients and the membrane potential generated by the asymmetric transport of ions across the plasma membrane mediated by the ATPase pumps. Some of these transporters, namely the polyspecific organic anion transporters (OATs), the organic anion transporting polypeptides (OATPs), and the organic cation transporters (OCTs) are highly expressed on the proximal tubular cell membranes and happen to also transport drugs whose levels in the proximal tubular cells can rapidly rise, thereby damaging the mitochondria and resulting in cell death and kidney injury. Drug-induced kidney injury (DIKI) is a growing public health concern and a major cause of drug attrition in drug development and post-marketing approval. As part of the article collection “Mitochondria in Renal Health and Disease,” here, we provide a critical overview of the main molecular mechanisms underlying the mitochondrial damage caused by drugs inducing nephrotoxicity.

Sulforaphane Potentiates Anticancer Effects of Doxorubicin and Cisplatin and Mitigates Their Toxic Effects

The success of cancer therapy is often compromised by the narrow therapeutic index of many anticancer drugs and the occurrence of drug resistance. The association of anticancer therapies with natural compounds is an emerging strategy to improve the pharmaco-toxicological profile of cancer chemotherapy. Sulforaphane, a phytochemical found in cruciferous vegetables, targets multiple pathways involved in cancer development, as recorded in different cancers such as breast, brain, blood, colon, lung, prostate, and so forth. As examples to make the potentialities of the association chemotherapy raise, here we highlight and critically analyze the information available for two associations, each composed by a paradigmatic anticancer drug (cisplatin or doxorubicin) and sulforaphane.

Subcellular drug distribution: mechanisms and roles in drug efficacy, toxicity, resistance, and targeted delivery

After administration, drug molecules usually enter target cells to access their intracellular targets. In eukaryotic cells, these targets are often located in organelles, including the nucleus, endoplasmic reticulum, mitochondria, lysosomes, Golgi apparatus, and peroxisomes. Each organelle type possesses unique biological features. For example, mitochondria possess a negative transmembrane potential, while lysosomes have an intraluminal delta pH. Other properties are common to several organelle types, such as the presence of ATP-binding cassette (ABC) or solute carrier-type (SLC) transporters that sequester or pump out xenobiotic drugs. Studies on subcellular drug distribution are critical to understand the efficacy and toxicity of drugs along with the body's resistance to them and to potentially offer hints for targeted subcellular drug delivery. This review summarizes the results of studies from 1990 to 2017 that examined the subcellular distribution of small molecular drugs. We hope this review will aid in the understanding of drug distribution within cells.

Protective roles of fenofibrate against cisplatin-induced ototoxicity by the rescue of peroxisomal and mitochondrial dysfunction

Cisplatin is an alkylating agent that interferes with DNA replication and kills proliferating carcinogenic cells. Several studies have been conducted to attenuate the side effects of cisplatin; one such side effect in cancer patients undergoing cisplatin chemotherapy is ototoxicity. However, owing to a lack of understanding of the precise mechanism underlying cisplatin-induced side effects, management of cisplatin-induced ototoxicity remains unsolved. We investigated the protective effects of fenofibrate, a PPAR-α activator, on cisplatin-induced ototoxicity. Fenofibrate prevented cisplatin-induced loss of hair cells and improved cell viability; moreover, fenofibrate significantly attenuated the threshold of auditory brainstem responses (ABR) in cisplatin-injected mice. Fenofibrate significantly increased PPAR-α, PPAR-γ, and PGC-1α expression, which consequently resulted in increased number and functional enzyme levels of peroxisomes and mitochondria, and markedly decreased phospho-p53 (S15), activated caspase-3, cleaved-PARP, and NF-κB p65 nuclear translocation, which reduced NADPH oxidase isoform (NOX3 and NOX4) expression, thereby decreasing reactive oxygen species (ROS) production in cisplatin-treated tissues ex vivo. Taken together, these results indicate that fenofibrate rescues cisplatin-induced ototoxicity by maintaining peroxisome and mitochondria number and function, reducing inflammation, and decreasing ROS levels. Our findings suggest that fenofibrate administration might serve as an effective therapeutic agent against cisplatin-induced ototoxicity.

Tunable Biodegradable Nanocomposite Hydrogel for Improved Cisplatin Efficacy on HCT-116 Colorectal Cancer Cells and Decreased Toxicity in Rats

This work describes the development of a modified nanocomposite thermosensitive hydrogel for controlled cisplatin release and improved cytotoxicity with decreased side effects. The system was characterized in terms of physical properties, morphological architecture and in vitro cisplatin release. Cytotoxicity was tested against human colorectal carcinoma HCT-116. In vivo studies were conducted to evaluate the acute toxicity in terms of rats' survival rate and body weight loss. Nephro and hepatotoxicities were evaluated followed by histopathological alterations of various tissue organs. Nanocomposite thermosensitive hydrogel containing nanosized carrier conferred density and stiffness allowing a zero order drug release for 14 days. Enhanced cytotoxicity with 2-fold decrease in cisplatin IC50 was accomplished. A linear in vivo-in vitro correlation was proved for the system degradation. Higher animal survival rate and lower tissue toxicities proved the decreased toxicity of cisplatin nanocomposite compared to its solution.

Mechanism of Cisplatin-Induced Cytotoxicity Is Correlated to Impaired Metabolism Due to Mitochondrial ROS Generation

The chemotherapeutic use of cisplatin is limited by its severe side effects. In this study, by conducting different omics data analyses, we demonstrated that cisplatin induces cell death in a proximal tubular cell line by suppressing glycolysis- and tricarboxylic acid (TCA)/mitochondria-related genes. Furthermore, analysis of the urine from cisplatin-treated rats revealed the lower expression levels of enzymes involved in glycolysis, TCA cycle, and genes related to mitochondrial stability and confirmed the cisplatin-related metabolic abnormalities. Additionally, an increase in the level of p53, which directly inhibits glycolysis, has been observed. Inhibition of p53 restored glycolysis and significantly reduced the rate of cell death at 24 h and 48 h due to p53 inhibition. The foremost reason of cisplatin-related cytotoxicity has been correlated to the generation of mitochondrial reactive oxygen species (ROS) that influence multiple pathways. Abnormalities in these pathways resulted in the collapse of mitochondrial energy production, which in turn sensitized the cells to death. The quenching of ROS led to the amelioration of the affected pathways. Considering these observations, it can be concluded that there is a significant correlation between cisplatin and metabolic dysfunctions involving mROS as the major player.

Defining cisplatin incorporation properties in thermosensitive injectable biodegradable hydrogel for sustained delivery and enhanced cytotoxicity

Injectable thermoreversible chitosan (CS)/β-glycerophosphate (β-GP) hydrogels were developed for prolonged localized delivery of cisplatin (Cis). The effects of formulation variables on the thermoreversible hydrogels preparation as well as the impact of drug incorporation method on Cis release were studied. Antitumor activity of Cis CS/β-GP thermoreversible hydrogels were evaluated against HCT-116 human colorectal cancer cells and MCF-7 human breast cancer cells. Incorporation of Cis to CS solution adjusted at pH 6.2 prior to hydrogel preparation deemed necessary to achieve a sustained release up to 4 days. Cis loaded CS/β-GP thermoreversible hydrogels showed enhanced antitumor activity with about 1.2 fold and 2.05 fold that of Cis solution against HCT-116 cancer cells and MCF-7 cancer cells respectively. The obtained enhanced antitumor activity elected this delivery system for further in vivo and toxicological investigations.

Effect of reactivity on cellular accumulation and cytotoxicity of oxaliplatin analogues

The purpose of this study was to systematically investigate the relationships between reactivity, cellular accumulation, and cytotoxicity of a panel of oxaliplatin analogues with different leaving groups in human carcinoma cells. The reactivity of the complexes towards the nucleotides 2'-deoxyguanosine 5'-monophosphate and 2'-deoxyadenosine 5'-monophosphate was studied using capillary electrophoresis. Cellular accumulation and cytotoxicity were measured in an oxaliplatin-sensitive and oxaliplatin-resistant ileocecal colorectal adenocarcinoma cell line pair (HCT-8/HCT-8ox). Platinum concentrations were determined by flameless atomic absorption spectrometry. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess cytotoxicity. Early cellular platinum accumulation was predominantly affected by lipophilicity. A relationship between reactivity and cellular accumulation was observed for three of four platinum complexes investigated, whereas the most lipophilic oxaliplatin analogue was an exception. Increased reactivity and reduced lipophilicity were associated with high cytotoxic activity. Resistance was influenced by lipophilicity but not by reactivity. The observed relationships may help in the design of analogues with high antitumoral activity in oxaliplatin-sensitive as well as oxaliplatin-resistant cells.

Characterization of the anti-Leishmania effect induced by cisplatin, an anticancer drug

The cis-diamminedichloroplatinum(II), known as cis-DDP or cisplatin is a widely used drug in cancer chemotherapy. Although a recent study has shown the anti-Leishmania activity of some cis-DDP derivatives, the cytotoxic properties were measured only on promastigotes, the insect vector form of the parasite. In this study the effect of cis-DDP on promastigotes and amastigotes, the vertebrate stage of the parasite is reported. The IC50, determined by flow cytometry, after 72 h of drug incubation was four times higher, 7.73+/-1.03 microM in the case of promastigotes compared to axenic amastigotes, 1.88+/-0.10 microM. In intracellular amastigotes the IC50, determined by counting the parasite index was 1.85+/-0.22 microM. By using flow cytometry, two patterns of cell cycle changes was observed: cis-DDP treated promastigotes and amastigotes accumulated in S phase and G2 phase, respectively. The cis-DDP response was also found to involve an "apoptosis-like" death of both promastigotes and amastigotes. However, DNA fragmentation was only detected in promastigote forms. In contrast mitochondrial transmembrane potential loss was observed for both stages of the parasite. Upon incubation of parasites with the drug an increase on GSH and GSSG levels and reactive oxygen species could be detected in the case of promastigote. Moreover, a slight increase of GSH level was detected on amastigote form. Taken together, these observations indicate that amastigotes are more sensitive to cis-DDP when compared to promastigotes. However, the signaling pathways leading to cell death could be different.

Preparation and cytotoxicity of cisplatin-containing liposomes

We encapsulated cisplatin into stealth pH-sensitive liposomes and studied their stability, cytotoxicity and accumulation in a human small-cell lung carcinoma cell line (GLC4) and its resistant subline (GLC4/CDDP). Since reduced cellular drug accumulation has been shown to be the main mechanism responsible for resistance in the GLC4/CDDP subline, we evaluated the ability of this new delivery system to improve cellular uptake. The liposomes were composed of dioleoylphosphatidylethanolamine (DOPE), cholesteryl hemisuccinate (CHEMS), and distearoylphosphatidylethanolamine-polyethyleneglycol 2000 (DSPE-PEG2000) and were characterized by determining the encapsulation percentage as a function of lipid concentration. Among the different formulations, DOPE/CHEMS/DSPE-PEG liposomes (lipid concentration equal to 40 mM) encapsulated cisplatin more efficiently than other concentrations of liposomes (about 20.0%, mean diameter of 174 nm). These liposomes presented good stability in mouse plasma which was obtained using a 0.24-M EDTA solution (70% cisplatin was retained inside the liposomes after 30 min of incubation). Concerning cytotoxic effects, they are more effective (1.34-fold) than free cisplatin for growth inhibition of the human lung cancer cell line A549. The study of cytotoxicity to GLC4 and GLC4/CDDP cell lines showed similar IC50 values (approximately 1.4 microM), i.e., cisplatin-resistant cells were sensitive to this cisplatin formulation. Platinum accumulation in both sensitive and resistant cell lines followed the same pattern, i.e., approximately the same intracellular platinum concentration (4.0 x 10-17 mol/cell) yielded the same cytotoxic effect. These results indicate that long-circulating pH-sensitive liposomes, also termed as stealth pH-sensitive liposomes, may present a promising delivery system for cisplatin-based cancer treatment. This liposome system proved to be able to circumvent the cisplatin resistance, whereas it was not observed when using non-long-circulating liposomes composed of phosphatidylcholine, phosphatidylserine, and cholesterol.

The role of the mitochondria in mediating cytotoxicity of anti-cancer therapies

Optimal cytotoxic anticancer therapy, at the cellular level, requires effective and selective induction of cell death to achieve a net reduction of biomass of malignant tissues. Standard cytotoxic chemotherapeutics have been developed based on the observations that mitotically active cancer cells are more susceptible than quiescent normal cells to chromosomal, microtubular or metabolic poisons. More recent development of molecularly targeted drugs for cancer focuses on exploiting biological differentials between normal and transformed cells for selective eradication of cancers. The common thread of "standard" and "novel" cytotoxic drugs is their ability to activate the apoptosis-inducing machinery mediated by mitochondria, also known as the intrinsic death signaling cascade. The aim of this article is to provide an overview of the role of the mitochondria, an energy-generating organelle essential for life, in mediating death when properly activated by cytotoxic stresses.