Antiproliferative and iron chelating efficiency of the new bis-8-hydroxyquinoline benzylamine chelator S1 in hepatocyte cultures

Nitric oxide-donating and reactive oxygen species-responsive prochelators based on 8-hydroxyquinoline as anticancer agents

Metal ion chelators based on 8-hydroxyquinoline (8-HQ) have been widely explored for the treatment of many diseases. When aimed at being developed into potent anticancer agent, a largely unmet issue is how to avoid nonspecific chelation of metal ions by 8-HQ in normal cells or tissues. In the current work, a two-step strategy was employed to both enhance the anticancer activity of 8-HQ and improve its cancer cell specificity. Considering the well-known anticancer activity of nitric oxide (NO), NO donor furoxan was first connected to 8-HQ to construct HQ-NO conjugates. These conjugates were screened for their cytotoxicity, metal-binding ability, and NO-releasing efficiency. Selected conjugates were further modified with a ROS-responsive moiety to afford prochelators. Among all the target compounds, prodrug HQ-NO-11 was found to potently inhibit the proliferation of many cancer cells but not normal cells. The abilities of metal chelation and NO generation by HQ-NO-11 were confirmed by various methods and were demonstrated to be essential for the anticancer activity of HQ-NO-11. In vivo studies revealed that HQ-NO-11 inhibited the growth of SW1990 xenograft to a larger extent than 8-HQ. Our results showcase a general method for designing novel 8-HQ derivatives and shed light on obtaining more controllable metal chelators.

Electronic spectroscopic characterization of the formation of iron(III) metal complexes: The 8-HydroxyQuinoline as ligand case study

Synthetic siderophores derivated from 8-HydroxyQuinoline (HQ) present various biological and pharmacological activities, such as anti-neurodegenerative or anti-oxydative. However, their affinity towards iron(III) seems to depend on the position (i.e., 7 or 2) of the HQ substitution by an electron withdrawing group. Two ester-derivatives of HQ at 2- and 7-position are synthesized and their respective iron-complexation is characterized by a joined experimental and theoretical work. By investigating the stability of all the possible accessible spin states of the iron(III) complexes at density-functional theory (DFT) level, we demonstrate that the high-spin (HS) state is the most stable one, and leads to a UV/vis absorption spectrum in perfect match with experiments. From this DFT protocol, and in agreement with the experimental results, we show that the ester functionalization of HQ in 2-position weakens the formation of the iron(III) complex while its substitution in 7-position allows a salicylate coordination of the metal very close to the ideal octahedral environment.

Investigating the Apoptosis Ability of Ethylenediamine 8-Hydroxyquinolinato Palladium (II) Complex

Purpose: High solubility, low renal toxicity and apoptosis-inducing ability of palladium complexes are the reasons for their synthesis. Methods: In vitro cytotoxic study of previously synthesized [Pd(en)(8HQ)]NO₃ , was carried out on breast cancer MCF-7 cell lines and prostate cancer DU145 cell lines. DNA fragmentation indicative of apoptotic was also evaluated by TUNEL assay on DU145 cell line. Results: FT-IR spectra of final complex confirmed the existence of chelating ligands. The DU145 cells unlike the MCF-7 cells, demonstrated the significant influence of the Pd (II) complex. The IC₅₀ values of [Pd(en)(8HQ)]NO₃ and cisplatin on DU145 cells were 27 and 8.3 μM, respectively. Moreover, nearly 38% apoptosis was evident in DU145 cells after treatment with [Pd(en)(8HQ)]NO₃. Conclusion: [Pd(en)(8HQ)]NO₃ has great potential in DNA binding and induction of apoptosis; thus it can be used in the future against prostate cancer.

Recent advances in cancer treatment by iron chelators

The development of new therapeutic alternatives for cancers is a major public health priority. Among the more promising approaches, the iron depletion strategy based on metal chelation in the tumoral environment has been particularly studied in recent decades. After a short description of the importance of iron for cancer cell proliferation, we will review the different iron chelators developed as potential chemotherapeutics. Finally, the recent efforts to vectorize the chelating agents specifically in the microtumoral environment will be discussed in detail.

Effect of Caseinophosphopeptides from αs- and β-Casein on Iron Bioavailability in HuH7 Cells

Two pools of caseinophosphopeptides (CPPs) obtained from αs- and β-casein fractions (α-CPPs and β-CPPs) were characterized. A total of 16 CPPs were identified in the α-CPPs pool, 9 of them derived from αs1-casein and 7 from αs2-casein. A total of 18 CPPs were identified in the β-CPPs pool. Four of the identified CPPs contained the characteristic phosphoseryl-glutamic acid cluster SpSpSpEE. Calcein assay was used to compare the iron-binding capacity of the α- and β-CPPs pools. At the concentration of 12.5 μM CPPs used in the iron bioavailability assays, β-CPPs pools show greater iron-binding capacity than α-CPPs pools. HuH7 human hepatoma cells show many differentiated functions of liver cells in vivo and can be used to evaluate iron bioavailability (ferritin content and soluble transferrin receptor) from Fe-α-CPPs and Fe-β-CPPs complexes. The α-CPPs and β-CPPs pools did not improve ferritin content or soluble transferrin receptor in HuH7 cells.

8-Hydroxyquinoline: a privileged structure with a broad-ranging pharmacological potential

An overview of the broad-ranging pharmacological applications of 8-HQ derivatives.

Investigation of aromatase inhibitory activity of metal complexes of 8-hydroxyquinoline and uracil derivatives

PURPOSE

Estrogens play important roles in the pathogenesis and progression of breast cancer as well as estrogen-related diseases. Aromatase is a key enzyme in the rate-limiting step of estrogen production, in which its inhibition is one strategy for controlling estrogen levels to improve prognosis of estrogen-related cancers and diseases. Herein, a series of metal (Mn, Cu, and Ni) complexes of 8-hydroxyquinoline (8HQ) and uracil derivatives (4-9) were investigated for their aromatase inhibitory and cytotoxic activities.

METHODS

The aromatase inhibition assay was performed according to a Gentest™ kit using CYP19 enzyme, wherein ketoconazole and letrozole were used as reference drugs. The cytotoxicity was tested on normal embryonic lung cells (MRC-5) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

RESULTS

Only Cu complexes (6 and 9) exhibited aromatase inhibitory effect with IC50 0.30 and 1.7 μM, respectively. Cytotoxicity test against MRC-5 cells showed that Mn and Cu complexes (5 and 6), as well as free ligand 8HQ, exhibited activity with IC50 range 0.74-6.27 μM.

CONCLUSION

Cu complexes (6 and 9) were found to act as a novel class of aromatase inhibitor. Our findings suggest that these 8HQ-Cu-uracil complexes are promising agents that could be potentially developed as a selective anticancer agent for breast cancer and other estrogen-related diseases.

8-Hydroxyquinolines: a review of their metal chelating properties and medicinal applications

Metal ions play an important role in biological processes and in metal homeostasis. Metal imbalance is the leading cause for many neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis. 8-Hydroxyquinoline (8HQ) is a small planar molecule with a lipophilic effect and a metal chelating ability. As a result, 8HQ and its derivatives hold medicinal properties such as antineurodegenerative, anticancer, antioxidant, antimicrobial, anti-inflammatory, and antidiabetic activities. Herein, diverse bioactivities of 8HQ and newly synthesized 8HQ-based compounds are discussed together with their mechanisms of actions and structure–activity relationships.

Novel chelators for cancer treatment: where are we now?

SIGNIFICANCE

Under normal circumstances, cellular iron levels are tightly regulated due to the potential toxic effects of this metal ion. There is evidence that tumors possess altered iron homeostasis, which is mediated by the perturbed expression of iron-related proteins, for example, transferrin receptor 1, ferritin and ferroportin 1. The de-regulation of iron homeostasis in cancer cells reveals a particular vulnerability to iron-depletion using iron chelators. In this review, we examine the absorption of iron from the gut; its transport, metabolism, and homeostasis in mammals; and the molecular pathways involved. Additionally, evidence for alterations in iron processing in cancer are described along with the perturbations in other biologically important transition metal ions, for example, copper(II) and zinc(II). These changes can be therapeutically manipulated by the use of novel chelators that have recently been shown to be highly effective in terms of inhibiting tumor growth.

RECENT ADVANCES

Such chelators include those of the thiosemicarbazone class that were originally thought to target only ribonucleotide reductase, but are now known to have multiple effects, including the generation of cytotoxic radicals.

CRITICAL ISSUES

Several chelators have shown marked anti-tumor activity in vivo against a variety of solid tumors. An important aspect is the toxicology and the efficacy of these agents in clinical trials.

FUTURE DIRECTIONS

As part of the process of the clinical assessment of the new chelators, an extensive toxicological assessment in multiple animal models is essential for designing appropriate dosing protocols in humans.

[Iron chelating therapy in adults: How and when ?]

Iron overload can lead to tissue damage derived from free radical toxicity. Phlebotomy is the treatment of choice for treating iron overload. However, iron chelating therapy can be used if phlebotomies are impossible, mainly because of anemia. In thalassemia major, iron chelating therapy has dramatically improved life expectancy; it is also used in sickle cell disease and myelodysplastic syndromes. Desferioxamine is the gold standard of iron chelation, but parenteral administration and the burden of a daily infusion pump hinder optimal compliance. Deferiprone is orally active but should be administered three times a day. It has the advantage of removing toxic iron from myocardium, but agranulocytosis (1 %) can limit its use. Deferasirox is orally active in a single daily dose, is well tolerated but its cardiac effect is limited. Iron chelating therapy can be considered if serum ferritin is above 1000μg/L and if liver iron concentration assessing by MRI exceeds 80μmol/g. MRI is a very important mean to monitor cardiac iron load. If the relaxing parameter T2* is lower than 20ms, a cardiac effective iron chelator agent or an association with deferoxamine should be used. Benefit/risk ratio should be closely evaluated, mainly in myelodysplastic syndromes.