In vitro vascular toxicity of tariquidar, a potential tool for in vivo PET studies

New uracil analog as inhibitor/modulator of ABC transporters or/and NF-κB in taxol-resistant MCF-7/Tx cell line

PURPOSE

The global increase in breast cancer cases necessitates ongoing exploration of advanced therapies. Taxol (Tx), an initial breast cancer treatment, induces mitotic arrest but faces limitations due to side effects and the development of resistance. Addressing Tx resistance involves understanding the complex molecular mechanisms, including alterations in tubulin dynamics, NF-κB signaling, and overexpression of ABC transporters (ABCB1 and ABCG2), leading to multidrug resistance (MDR).

METHODS

Real-time PCR and ELISA kits were used to analyze ABCB1, ABCG2 and NF-κB gene and protein expression levels, respectively. An MDR test assessed the resistance cell phenotype.

RESULTS

MCF-7/Tx cells exhibited a 24-fold higher resistance to Tx. Real-time PCR and ELISA analysis revealed the upregulation of ABCB1, ABCG2, and NF-κB. U-359 significantly downregulated both ABCB1 and ABCG2 gene and protein levels. Co-incubation with Tx and U-359 further decreased the mRNA and protein expression of these transporters. The MDR test indicated that U-359 increased MDR dye retention, suggesting its potential as an MDR inhibitor. U-359 and Tx, either individually or combined, modulated NF-κBp65 protein levels.

CONCLUSION

The development of a Taxol-resistant MCF-7 cell line provided valuable insights. U-359 demonstrated effectiveness in reducing the expression of ABC transporters and NF-κB, suggesting a potential solution for overcoming multidrug resistance in breast cancer cells. The study recommends a strategy to enhance the sensitivity of cancer cells to chemotherapy by integrating U-359 with traditional drugs.

Biological Evaluation and In Vitro Characterization of ADME Profile of In-House Pyrazolo[3,4-d]pyrimidines as Dual Tyrosine Kinase Inhibitors Active against Glioblastoma Multiforme

The therapeutic use of tyrosine kinase inhibitors (TKIs) represents one of the successful strategies for the treatment of glioblastoma (GBM). Pyrazolo[3,4-d]pyrimidines have already been reported as promising small molecules active as c-Src/Abl dual inhibitors. Herein, we present a series of pyrazolo[3,4-d]pyrimidine derivatives, selected from our in-house library, to identify a promising candidate active against GBM. The inhibitory activity against c-Src and Abl was investigated, and the antiproliferative profile against four GBM cell lines was studied. For the most active compounds endowed with antiproliferative efficacy in the low-micromolar range, the effects toward nontumoral, healthy cell lines (fibroblasts FIBRO 2-93 and keratinocytes HaCaT) was investigated. Lastly, the in silico and in vitro ADME properties of all compounds were also assessed. Among the tested compounds, the promising inhibitory activity against c-Src and Abl (K_i 3.14 µM and 0.44 µM, respectively), the irreversible, apoptotic-mediated death toward U-87, LN18, LN229, and DBTRG GBM cell lines (IC₅₀ 6.8 µM, 10.8 µM, 6.9 µM, and 8.5 µM, respectively), the significant reduction in GBM cell migration, the safe profile toward FIBRO 2-93 and HaCaT healthy cell lines (CC₅₀ 91.7 µM and 126.5 µM, respectively), the high metabolic stability, and the excellent passive permeability across gastrointestinal and blood-brain barriers led us to select compound 5 for further in vivo assays.

Overcoming multidrug resistance through targeting ABC transporters: lessons for drug discovery

INTRODUCTION

The argument around cancer therapy is an old one. Using chemotherapeutic drugs, as one of the most effective strategies in treatment of malignancies, is restricted by various issues that progress during therapy and avoid achieving clinical endpoints. Multidrug resistance (MDR), frequently mediated by ATP-binding cassette (ABC) transporters, is one of the most recognized obstacles in the success of pharmacological anticancer approaches. These transporters efflux diverse drugs to extracellular environment, causing MDR and responsiveness of tumor cells to chemotherapy diminishes.

AREAS COVERED

Several strategies have been used to overcome MDR phenomenon. Succession in this field requires complete knowledge about features and mechanism of ABC transporters. In this review, conventional synthetic and natural inhibitors are discussed first and then novel approaches including RNA, monoclonal antibodies, nanobiotechnology, and structural modification techniques are represented.

EXPERT OPINION

With increasing frequency of MDR in cancer cells, it is essential to develop new drugs to inhibit MDR. Using knowledge acquired about ABC transporter's structure, rational design of inhibitors is possible. Also, some herbal products have shown to be potential lead compounds in drug discovery for reversal of MDR.

Sdox, a H2S releasing anthracycline, with a safer profile than doxorubicin toward vasculature

Sdox is a synthetic H₂S-releasing doxorubicin (Dox) less cardiotoxic and more effective than Dox in pre-clinical, Dox-resistant tumour models. The well-known anthracycline vascular toxicity, however, might limit Sdox clinical use. This study aimed at evaluating Sdox vascular toxicity in vitro, using Dox as reference compound. Both vascular smooth muscle A7r5 and endothelial EA.hy926 cells were more sensitive to Dox than Sdox, although both drugs equally increased intracellular free radical levels. Sdox released H₂S in both cell lines. The H₂S scavenger hydroxocobalamin partially reverted Sdox-induced cytotoxicity in A7r5, but not in EA.hy926 cells, suggesting a role for H₂S in smooth muscle cell death. Markers of Sdox-induced apoptosis were significantly lower than, in A7r5 cells, and comparable to those of Dox in EA.hy926 cells. In A7r5 cells, Dox increased the activity of caspase 3, 8, and 9, Sdox affecting only that of caspase 3. Moreover, both drugs induced comparable DNA damage in A7r5 cells, while Sdox was less toxic than Dox in Ea.hy926 cells. In fresh aorta rings, only Dox weakly increased phenylephrine-induced contraction when endothelium was present. In rings cultured with both drugs for 7 days, Sdox blunted phenylephrine- and high K⁺-induced contractions though at a concentration 10-fold higher than that of Dox. In conclusion, Sdox may represent the prototype of an innovative anthracycline, effective against Dox-resistant tumours, displaying a more favourable vascular toxicity profile compared to the parent compound.

Acacia catechu Willd. Extract Protects Neuronal Cells from Oxidative Stress-Induced Damage

Oxidative stress (OS) and the resulting reactive oxygen species (ROS) generation and inflammation play a pivotal role in the neuronal loss occurring during the onset of neurodegenerative diseases. Therefore, promising future drugs that would prevent or slow down the progression of neurodegeneration should possess potent radical-scavenging activity. Acacia catechu Willd. heartwood extract (AC), already characterized for its high catechin content, is endowed with antioxidant properties. The aim of the present study was to assess AC neuroprotection in both human neuroblastoma SH-SY5Y cells and rat brain slices treated with hydrogen peroxide. In SH-SY5Y cells, AC prevented a decrease in viability, as well as an increase in sub-diploid-, DAPI positive cells, reduced ROS formation, and recovered the mitochondrial potential and caspase-3 activation. AC related neuroprotective effects also occurred in rat brain slices as a reversal prevention in the expression of the main proteins involved in apoptosis and signalling pathways related to calcium homeostasis following OS-mediated injury. Additionally, unbiased quantitative mass spectrometry allowed for assessing that AC partially prevented the hydrogen peroxide-induced altered proteome, including proteins belonging to the synaptic vesicle fusion apparatus. In conclusion, the present results suggest the possibility of AC as a nutraceutical useful in preventing neurodegenerative diseases.

Hibiscus Flower and Olive Leaf Extracts Activate Apoptosis in SH-SY5Y Cells

Compounds of natural origin may constitute an interesting tool for the treatment of neuroblastoma, the most prevalent extracranial solid tumor in children. PRES is a commercially available food supplement, composed of a 13:2 (w/w) extracts mix of Olea europaea L. leaves (OE) and Hibiscus sabdariffa L. flowers (HS). Its potential towards neuroblastoma is still unexplored and was thus investigated in human neuroblastoma SH-SY5Y cells. PRES decreased the viability of cells in a concentration-dependent fashion (24 h IC₅₀ 247.2 ± 31.8 µg/mL). Cytotoxicity was accompanied by an increase in early and late apoptotic cells (AV-PI assay) and sub G0/G1 cells (cell cycle analysis), ROS formation, reduction in mitochondrial membrane potential, and caspases activities. The ROS scavenger N-acetyl-L-cysteine reverted the cytotoxic effects of PRES, suggesting a key role played by ROS in PRES-mediated SH-SY5Y cell death. Finally, the effects of OE and HS extracts were singularly tested and compared to those of the corresponding mixture. OE- or HS-mediated cytotoxicity was always significantly lower than that caused by PRES, suggesting a synergic effect. In conclusion, the present findings highlight the potential of PRES for the treatment of neuroblastoma and offers the basis for a further characterization of the mechanisms underlying its effects.

Clinically-Relevant ABC Transporter for Anti-Cancer Drug Resistance

Multiple drug resistance (MDR), referring to the resistance of cancer cells to a broad spectrum of structurally and mechanistically unrelated drugs across membranes, severely impairs the response to chemotherapy and leads to chemotherapy failure. Overexpression of ATP binding cassette (ABC) transporters is a major contributing factor resulting in MDR, which can recognize and mediate the efflux of diverse drugs from cancer cells, thereby decreasing intracellular drug concentration. Therefore, modulators of ABC transporter could be used in combination with standard chemotherapeutic anticancer drugs to augment the therapeutic efficacy. This review summarizes the recent advances of important cancer-related ABC transporters, focusing on their physiological functions, structures, and the development of new compounds as ABC transporter inhibitors.

In vitro vascular toxicity assessment of NitDOX, a novel NO-releasing doxorubicin

The conjugation of doxorubicin (DOX) with nitric oxide (NO)-releasing groups gave rise to novel anthracyclines, such as nitrooxy-DOX (NitDOX), capable to overcome multidrug resistance. The widely described anthracycline cardiovascular toxicity, however, might limit their clinical use. This study aimed to investigate NitDOX-induced effects, as potential hazard, on vascular smooth muscle A7r5 and endothelial EA.hy926 cell viability, on the mechanical activity of freshly and cultured rat aorta rings, as well as on Ca_v1.2 channels of A7r5 cells. DOX was used as a reference compound. Although an increase in intracellular radicals and a reduction in mitochondrial potential occurred upon treatment with both drugs, A7r5 and EA.hy926 cells proved to be more sensitive to DOX than to NitDOX. Both compounds promoted comparable effects in A7r5 cells, whereas NitDOX was less active than DOX in inducing DNA damage and in eliciting apoptotic-mediated cell death revealed as an increase in sub-diploid-, DAPI- and annexin V-positive- EA.hy926 cell percentage. Moreover, in EA.hy926 cells, NitDOX doubled basal NO content, while preincubation with the NO-scavenger PTIO increased NitDOX-induced cytotoxicity. DOX exhibited a negligible contracturing effect in endothelium-intact rings, while NitDOX induced a significant ODQ-sensible, vasodilation in endothelium-denuded rings. In arteries cultured with both drugs for 7 days, NitDOX prevented either phenylephrine- or KCl-induced contraction at a concentration 10-fold higher than that of DOX. These results demonstrate that NitDOX displays a more favourable vascular toxicity profile than DOX. Taking into account its greater efficacy against drug-resistant cells, NitDOX is worth of further investigations in preclinical and clinical settings.

β-Naphthoflavone and Ethanol Reverse Mitochondrial Dysfunction in A Parkinsonian Model of Neurodegeneration

The 1-methyl-4-phenylpyridinium (MPP⁺) is a parkinsonian-inducing toxin that promotes neurodegeneration of dopaminergic cells by directly targeting complex I of mitochondria. Recently, it was reported that some Cytochrome P450 (CYP) isoforms, such as CYP 2D6 or 2E1, may be involved in the development of this neurodegenerative disease. In order to study a possible role for CYP induction in neurorepair, we designed an in vitro model where undifferentiated neuroblastoma SH-SY5Y cells were treated with the CYP inducers β-naphthoflavone (βNF) and ethanol (EtOH) before and during exposure to the parkinsonian neurotoxin, MPP⁺. The toxic effect of MPP⁺ in cell viability was rescued with both βNF and EtOH treatments. We also report that this was due to a decrease in reactive oxygen species (ROS) production, restoration of mitochondrial fusion kinetics, and mitochondrial membrane potential. These treatments also protected complex I activity against the inhibitory effects caused by MPP⁺, suggesting a possible neuroprotective role for CYP inducers. These results bring new insights into the possible role of CYP isoenzymes in xenobiotic clearance and central nervous system homeostasis.

Apoptotic-Induced Effects of Acacia Catechu Willd. Extract in Human Colon Cancer Cells

The research for innovative treatments against colon adenocarcinomas is still a great challenge. Acacia catechu Willd. heartwood extract (AC) has health-promoting qualities, especially at the gastrointestinal level. This study characterized AC for its catechins content and investigated the apoptosis-enhancing effect in human colorectal adenocarcinoma HT-29 cells, along with its ability to spare healthy tissue. MTT assay was used to describe the time course, concentration dependence and reversibility of AC-mediated cytotoxicity. Cell cycle analysis and AV-PI and DAPI-staining were performed to evaluate apoptosis, together with ROS formation, mitochondrial membrane potential (MMP) changes and caspase activities. Rat ileum and colon rings were tested for their viability and functionality to explore AC effects on healthy tissue. Quantitative analysis highlighted that AC was rich in (±)-catechin (31.5 ± 0.82 mg/g) and (−)-epicatechin (12.5 ± 0.42 mg/g). AC irreversibly decreased cell viability in a concentration-dependent, but not time-dependent fashion. Cytotoxicity was accompanied by increases in apoptotic cells and ROS, a reduction in MMP and increases in caspase-9 and 3 activities. AC did not affect rat ileum and colon rings’ viability and functionality, suggesting a safe profile toward healthy tissue. The present findings outline the potential of AC for colon cancer treatment.

Apoptotic-induced Effects of Castanea sativa Bark Extract in Human SH-SY5Y Neuroblastoma Cells

Castanea sativa Mill. wood extract (ENC) has health-promoting qualities such as antibacterial, antiviral, antispasmodic, cardio- and neuroprotective-activities. Its potential towards cancer cells of the central nervous system, however, is still unexplored. This study investigates the apoptotic-enhancing effect of ENC in human neuroblastoma SH-SY5Y cell line. This extract irreversibly decreased cell viability with IC50 of 142.8±20.2, 109.3±16.6 and 82.5±8.6 μg/mL for 24h, 48 and 72h of treatment, respectively. This was accompanied by cell shrinkage and tendency to round-up. A concentration-dependent increase in sub G0/G1 cells as well as a rise in cells with nuclear fragmentation and chromatin condensation, both typical of apoptosis, was also observed. In conclusion, the present findings provide initial data on the potential of ENC for neuroblastoma treatment and offer the rationale for further studies aimed at elucidating the full mechanism(s) underlying its effects.