Iron metallodrugs: stability, redox activity and toxicity against Artemia salina

Protective Effect of Ultrasound-Processed Amazonian Sapota-do-Solimões (Quararibea cordata) Juice on Artemia salina Nauplii

Juice processing by non-thermal technology has been extensively studied, aiming at microbial inactivation and quality improvement. However, the knowledge about the possible toxic effects that those technologies can produce in foodstuffs due to the production of reactive oxygen species is still unknown. In this study, sapota-do-Solimões juice processed by ultrasound (2, 6, and 10 min) was evaluated by a toxicity test and protective effect through stress biomarkers (catalase, superoxide dismutase, and lipid peroxidation) using Artemia salina nauplii. The non-thermal processed juice was nontoxic to A. salina. However, the juice fibers imparted some damage to the animal’s body. The ultrasound-processed juice (2 and 6 min) decreased the A. salina mortality to 30% compared to the control assay with H2O2 where mortality was 80% after 48 h of exposure. However, after 72 h of exposure, the A. salina was entirely degraded by H2O2-induced toxicity. Furthermore, the catalase and superoxide dismutase presented the highest activity after A. salina was exposed to the unprocessed juice. Thus, sapota-do-Solimões juice processed by the ultrasound could promote a protective effect on A. salina, revealing this technology’s potential to enhance juice features without toxicity.

Bioresilience to Mercury Chloride of the Brine Shrimp Artemia Salina after Treatment with Homeopathic Mercurius Corrosivus

INTRODUCTION

 Finding solutions to mitigate the impact of pollution on living systems is a matter of great interest. Homeopathic preparations of toxic substances have been described in the literature as attenuation factors for intoxication. Herein, an experimental study using Artemia salina and mercury chloride was developed as a model to identify aspects related to bioresilience.

AIMS

 The aim of the study was to describe the effects of homeopathic Mercurius corrosivus (MC) on Artemia salina cysts hatching and on mercury bioavailability.

METHODS

 Artemia salina cysts were exposed to 5.0 µg/mL of mercury chloride during the hatching phase. MC potencies (6cH, 30cH, and 200cH) were prepared in sterile purified water and poured into artificial sea water. Different controls were used (non-challenged cysts and challenged cysts treated with water, succussed water, and Ethilicum 1cH). Four series of nine experiments were performed to evaluate the percentage of cyst hatching. Soluble total mercury (THg) levels and precipitated mercury content were also evaluated. Solvatochromic dyes were used to check for eventual physicochemical markers of MC biological activity.

RESULTS

 Significant delay (p < 0.0001) in cyst hatching was observed only after treatment with MC 30cH, compared with controls. This result was associated with an increase of THg concentration in water (p = 0.0018) and of chlorine/oxygen ratio (p < 0.0001) in suspended micraggregates, suggesting changes in mercury bioavailability. A specific interaction of MC 30cH with the solvatochromic dye ET33 (p = 0.0017) was found.

CONCLUSION

 Changes in hatching rate and possible changes in Hg bioavailability are postulated as protective effects of MC 30cH on Artemia salina, by improving its natural bioresilience processes.

Short exposure of Artemia salina to group-12 metals: Comparing hatchability, mortality, lipid peroxidation, and swimming speed

The hatchability, mortality rate, lipid peroxide levels, and swimming speed of Artemia salina have been compared based on short exposures of ZnCl₂, CdCl₂, and HgCl₂ in artificial seawater. The hatching tests were carried out for 12, 24, 36, and 48 h at 28 °C. Mortality rate and lipid peroxide (LPO) levels were determined after 24 h of exposure at 28 °C, in the dark, and on living larvae using the FOX method. The swimming speed was determined after 24 h using a microcomputer coupled to a digital camera, with simultaneous treatment of the recorded images every 25 s, at 25 °C, under red-light irradiation. Results showed that Zn caused a gradual inhibition of the hatching for concentrations <900 µmol L^-1; however, Cd and Hg displayed almost complete inhibition for concentrations ≤100 µmol L^-1. Also, the heavy metals caused a dose-dependent increase of mortality (LD50) in the following order: Zn = 3290 µmol L^-1 < Cd = 2206 µmol L^-1 < Hg = 15.6 µmol L^-1. Furthermore, significant LPO levels were found for Cd (1500-2000 µmol L^-1, p < 0.001) and Hg (5-20 µmol L^-1, p < 0.001). Finally, the swimming speed values increased significantly, for Zn ≈ 2.5 mm s^-1 (1500 µmol L^-1, p < 0.001), Cd ≈ 3.5 mm s^-1 (2000 µmol L^-1, p < 0.05), and Hg ≈ 4.0 mm s^-1 (15 µmol L^-1, p < 0.05), after 24 h exposure. There is a clear dose-dependent toxicity, indicating that Zn, Cd and Hg can induce significant changes in hatchability, mortality, and ethological and biochemical parameters.

Fragmentation Study, Dual Anti-Bactericidal and Anti-Viral Effects and Molecular Docking of Cobalt(III) Complexes

Considering our previous findings on the remarkable activity exhibited by cobalt(III) with 2-acetylpyridine-N(4)-R-thiosemicarbazone (Hatc-R) compounds against Mycobacterium tuberculosis, the present study aimed to explored new structure features of the complexes of the type [Co(atc--R)₂]Cl, where R = methyl (Me, 1) or phenyl (Ph, 2) (¹³C NMR, high-resolution mass spectrometry, LC-MS/MS, fragmentation study) together with its antibacterial and antiviral biological activities. The minimal inhibitory and minimal bactericidal concentrations (MIC and MBC) were determined, as well as the antiviral potential of the complexes on chikungunya virus (CHIKV) infection in vitro and cell viability. [Co(atc-Ph)₂]Cl revealed promising MIC and MBC values which ranged from 0.39 to 0.78 µg/mL in two strains tested and presented high potential against CHIKV by reducing viral replication by up to 80%. The results showed that the biological activity is strongly influenced by the peripheral substituent groups at the N(4) position of the atc-R^1- ligands. In addition, molecular docking analysis was performed. The relative binding energy of the docked compound with five bacteria strains was found in the range of -3.45 and -9.55 kcal/mol. Thus, this work highlights the good potential of cobalt(III) complexes and provide support for future studies on this molecule aiming at its antibacterial and antiviral therapeutic application.

Mygalin: An Acylpolyamine With Bactericidal Activity

Inappropriate use of antibiotics favors the selection and spread of resistant bacteria. To reduce the spread of these bacteria, finding new molecules with activity is urgent and necessary. Several polyamine analogs have been constructed and used to control microorganisms and tumor cells. Mygalin is a synthetic acylpolyamine, which are analogs of spermidine, derived from the hemolymph of the spider Acanthoscurria gomesiana. The effective activity of polyamines and their analogs has been associated with their structure. The presence of two acyl groups in the Mygalin structure may give this molecule a specific antibacterial activity. The aim of this study was to identify the mechanisms involved in the interaction of Mygalin with Escherichia coli to clarify its antimicrobial action. The results indicated that Mygalin exhibits intense dose and time-dependent bactericidal activity. Treatment of E. coli with this molecule caused membrane rupture, inhibition of DNA synthesis, DNA damage, and morphological changes. The esterase activity increased along with the intracellular production of reactive oxygen species (ROS) after treatment of the bacteria with Mygalin. In addition, this molecule was able to sequester iron and bind to LPS. We have shown that Mygalin has bactericidal activity with underlying mechanisms involving ROS generation and chelation of iron ions that are necessary for bacterial metabolism, which may contribute to its microbicidal activity. Taken together, our data suggest that Mygalin can be explored as a new alternative drug with antimicrobial potential against Gram-negative bacteria or other infectious agents.

Antimicrobial materials properties based on ion-exchange 4A zeolite derivatives

Zeolites are nanoporous alumina silicates in a framework with cations, exhibiting ion-exchange properties with metal ions making them possible antimicrobial materials. The aim of this study was to evaluate the antimicrobial activity of ion-exchanged zeolites and the toxic potential of these materials. Zeolite-Co2+ and Li+ exhibited the most effective inhibition on Staphylococcus aureus growth than in other microorganisms (Escherichia coli and Pseudomonas aeroginosa) in low concentrations. Zeolite-Cu2+ presented higher zone of inhibition when tested against Candida albicans, while Zeolite-Zn2+ showed similar effectiveness among all the microorganisms. When ion-exchanged zeolites were used in effective concentrations to achieve antimicrobial activity, no alterations against bioindicators organisms as Artemia sp. and L. sativa were found and, in addition, they have non-significant result in terms of DNA cleavage activity. Zeolites have advantage of releasing slowly the metals loaded and this characteristic can to be considered promising as potential antimicrobial materials in concentrations safe for use.

Effect of TiO2-ZnO-MgO Mixed Oxide on Microbial Growth and Toxicity against Artemia salina

Mixed oxide nanoparticles (MONs, TiO₂–ZnO–MgO) obtained by the sol-gel method were characterized by transmission electron microscopy, (TEM, HRTEM, and SAED) and thermogravimetric analysis (TGA/DTGA–DTA). Furthermore, the effect of MONs on microbial growth (growth profiling curve, lethal and sublethal effect) of Escherichia coli, Salmonella paratyphi, Staphylococcus aureus and Listeria monocytogenes, as well as the toxicity against Artemia salina by the lethal concentration test (LC₅₀) were evaluated. MONs exhibited a near-spherical in shape, polycrystalline structure and mean sizes from 17 to 23 nm. The thermal analysis revealed that the anatase phase of MONs is completed around 480–500 °C. The normal growth of all bacteria tested is affected by the MONs presence compared with the control group. MONs also exhibited a reduction on the plate count from 0.58 to 2.10 log CFU/mL with a sublethal cell injury from 17 to 98%. No significant toxicity within 24 h was observed on A. salina. A bacteriostatic effect of MONs on bacteria was evidenced, which was strongly influenced by the type of bacteria, as well as no toxic effects (LC₅₀ >1000 mg/L; TiO₂–ZnO (5%)–MgO (5%)) on A. salina were detected. This study demonstrates the potential of MONs for industrial applications.

Magnetite nanoparticles coated with oleic acid: accumulation in hepatopancreatic cells of the mangrove crab Ucides cordatus

The field of nanotechnology had enormous developments, resulting in new methods for the controlled synthesis of a wide variety of nanoscale materials with unique properties. Efficient methods such as thermal decomposition for efficient size control have been developed in recent years for the synthesis of oleic acid (OA)-coated magnetite (Fe₃O₄) nanoparticles (MNP-OA). These nanostructures can be a source of pollution when emitted in the aquatic environment and could be accumulated by vulnerable marine species such as crustaceans. In this work, we synthesized and characterized MNP-OA of three different diameters (5, 8, and 12 nm) by thermal decomposition. These nanoparticles were remarkably stable after treatment with high affinity iron chelators (calcein, fluorescent desferrioxamine, and fluorescent apotransferrin); however, they displayed pro-oxidant activity after being challenged with ascorbate under two physiological buffers. Free or nanoparticle iron displayed low toxicity to four types of hepatopancreatic cells (E, R, F, and B) of the mangrove crab Ucides cordatus; however, they were promptly bioavailable, posing the risk of ecosystem disruption due to the release of excess nutrients.

Evaluation of iron loading in four types of hepatopancreatic cells of the mangrove crab Ucides cordatus using ferrocene derivatives and iron supplements

The mangrove crab Ucides cordatus is a bioindicator of aquatic contamination. In this work, the iron availability and redox activity of saccharide-coated mineral iron supplements (for both human and veterinary use) and ferrocene derivatives in Saline Ucides Buffer (SUB) medium were assessed. The transport of these metallodrugs by four different hepatopancreatic cell types (embryonic (E), resorptive (R), fibrillar (F), and blister (B)) of U. cordatus were measured. Organic coated iron minerals (iron supplements) were stable against strong chelators (calcein and transferrin). Ascorbic acid efficiently mediated the release of iron only from ferrocene compounds, leading to redox-active species. Ferrous iron and iron supplements were efficient in loading iron to all hepatopancreatic cell types. In contrast, ferrocene derivatives were loaded only in F and B cell types. Acute exposition to the iron compounds resulted in cell viability of 70-95%, and to intracellular iron levels as high as 0.40 μmol L^-1 depending upon the compound and the cell line. The easiness that iron from iron metallodrugs was loaded/transported into U. cordatus hepatopancreatic cells reinforces a cautionary approach to the widespread disposal and use of highly bioavailable iron species as far as the long-term environmental welfare is concerned.

Triphenylphosphonium-desferrioxamine as a candidate mitochondrial iron chelator

Cell-impermeant iron chelator desferrioxamine (DFO) can have access to organelles if appended to suitable vectors. Mitochondria are important targets for the treatment of iron overload-related neurodegenerative diseases. Triphenylphosphonium (TPP) is a delocalized lipophilic cation used to ferry molecules to mitochondria. Here we report the synthesis and characterization of the conjugate TPP-DFO as a mitochondrial iron chelator. TPP-DFO maintained both a high affinity for iron and the antioxidant activity when compared to parent DFO. TPP-DFO was less toxic than TPP alone to A2780 cells (IC₅₀ = 135.60 ± 1.08 and 4.34 ± 1.06 μmol L^-1, respectively) and its native fluorescence was used to assess its mitochondrial localization (Rr = +0.56). These results suggest that TPP-DFO could be an interesting alternative for the treatment of mitochondrial iron overload e.g. in Friedreich's ataxia.

Hepatopancreatic cells of a stone crab Menippe frontalis from Perú: separation, viability study, and evaluation of lipoperoxidation against cadmium contamination

Crustaceans are frequently used as bioindicators, and changes in their metabolism at the hepatopancreas (HP) level are often followed in these studies. The HP is the site of digestion, absorption, nutrient storage, and toxic metal detoxification, enabling crabs to survive in metal contaminated regions. Cellular damage and high lipid peroxidation (LPO) levels have been found in crab populations under high cadmium (Cd) concentrations. The aim of this work was to separate and characterize the HP cells of the stone crab Menippe frontalis from the Pacific Ocean, Perú (5° 5' 21″ S-81° 6' 51″ W) and to measure the cellular viability and LPO after exposure to the non-essential metal Cd. The HP cells were dissociated by magnetic stirring, with posterior separation by sucrose gradient at concentrations of 10, 20, 30, and 40%. We found the same cell types that were described for other species (e.g., Ucides cordatus, Atlantic Ocean, Brazil). High cellular viability against 1 mmol L^-1 of Cd was observed for resorptive (R) cells in 20% sucrose layer (88 ± 8%, *P < 0.05, ANOVA), and blister (B) cells in the 40% sucrose layers (92 ± 7%, *P < 0.05, ANOVA). Cd (1 mmol L^-1) caused an increase in LPO levels, suggesting that crabs from polluted areas can be affected by toxic metals, generating a physiological stress. The gradient sucrose methodology can be used for different species and results in a similar separation, viability, and cellular identification. The results are a starting point for toxic metal studies for species distributed across different geographic coordinates.

Desferrioxamine and desferrioxamine-caffeine as carriers of aluminum and gallium to microbes via the Trojan Horse Effect

Iron acquisition by bacteria and fungi involves in several cases the promiscuous usage of siderophores. Thus, antibiotic resistance from these microorganisms can be circumvented through a strategy of loading toxic metals into siderophores (Trojan Horse Effect). Desferrioxamine (dfo) and its cell-permeant derivative desferrioxamine-caffeine (dfcaf) were complexed with aluminum or gallium for this purpose. The complexes Me(dfo) and Me(dfcaf) (Me=Al³⁺ and Ga³⁺) were synthesized and characterized by mass spectroscopy and cyclic voltammetry. Their relative stabilities were studied through competitive equilibria with fluorescent probes calcein, fluorescein-desferrioxamine and 8-hydroxyquinoline. Me(dfo) and Me(dfcaf) were consistently more toxic than free Me³⁺ against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans, demonstrating the Trojan Horse Effect. Wide spectrum antimicrobial action can be obtained by loading non-essential or toxic metal ions to microbes via a convenient siderophore carrier.

Toxicity assessment of zero valent iron nanoparticles on Artemia salina

The present study deals with the toxicity assessment of two differently synthesized zero valent iron nanoparticles (nZVI, chemical and biological) as well as Fe²⁺ ions on Artemia salina at three different initial concentrations of 1, 10, and 100 mg/L of these particles. The assessment was done till 96 h at time intervals of 24 h. EC₅₀ value was calculated to evaluate the 50% mortality of Artemia salina at all exposure time durations. Between chemically and biologically synthesized nZVI nanoparticles, insignificant differences in the level of mortality were demonstrated. At even 24 h, Fe²⁺ ion imparted complete lethality at the highest exposure concentration (100 mg/L). To understand intracellular oxidative stress because of zero valent iron nanoparticles, ROS estimation, SOD activity, GSH activity, and catalase activity was performed which demonstrated that ionic form of iron is quite lethal at high concentrations as compared with the same concentration of nZVI exposure. Lower concentrations of nZVI were more toxic as compared with the ionic form and was in order of CS-nZVI > BS-nZVI > Fe²⁺ . Cell membrane damage and bio-uptake of nanoparticles were also evaluated for all three concentrations of BS-nZVI, CS-nZVI, and Fe²⁺ using adult Artemia salina in marine water; both of which supported the observations made in toxicity assessment. This study can be further explored to exploit Artemia salina as a model organism and a biomarker in an nZVI prone aquatic system to detect toxic levels of these nanoparticles. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1617-1627, 2017.

Physiological differences in the crab Ucides cordatus from two populations inhabiting mangroves with different levels of cadmium contamination

Crustaceans found in metal-contaminated regions are able to survive, and the authors investigated the physiological mechanisms involved by comparing populations from contaminated and noncontaminated areas. The objective of the present study was to measure the cellular transport of a nonessential metal (cadmium [Cd]) in gills and hepatopancreas of Ucides cordatus, together with cell membrane fluidity, metallothionein levels, and lipid peroxidation. The 2 populations compared were from a polluted and a nonpolluted mangrove area of São Paulo State, Brazil. The authors found, for the first time, larger Cd transport in gills and hepatopancreatic cells from crabs living in polluted mangrove areas. The cells also had lower plasma membrane fluidity, increased lipid peroxidation and less metallothionein compared to those from nonpolluted regions. The authors also found larger amounts of Cd in intracellular organelles of gills, but not in the hepatopancreas, from crabs in polluted regions. Therefore, in polluted areas, these animals showed higher Cd transport and lower plasma membrane fluidity and storage of Cd intracellularly in gill cells, whereas hepatopancreatic cells used metallothionein as their main line of defense. The findings suggest that crabs from polluted areas can accumulate Cd more easily than crabs from nonpolluted areas, probably because of an impairment of the regulatory mechanisms of cell membrane transport. Environ Toxicol Chem 2017;36:361-371. © 2016 SETAC.

Paulo T, de França Lopes LG, Sousa EHS. A biphosphinic ruthenium complex with potent anti-bacterial and anti-cancer activity

Photorelease of CO and moderate binding to DNA did not seem to be essential features for potent biological activities.