Sphaerococcus coronopifolius bromoterpenes as potential cancer stem cell-targeting agents

Cancer is one of the major threats to human health and, due to distinct factors, it is expected that its incidence will increase in the next decades leading to an urgent need of new anticancer drugs development. Ongoing experimental and clinical observations propose that cancer cells with stem-like properties (CSCs) are involved on the development of lung cancer chemoresistance. As tumour growth and metastasis can be controlled by tumour-associated stromal cells, the main goal of this study was to access the antitumor potential of five bromoterpenes isolated from Sphaerococcus coronopifolius red alga to target CSCs originated in a co-culture system of fibroblast and lung malignant cells. Cytotoxicity of compounds (10-500 μM; 72 h) was evaluated on monocultures of several malignant and non-malignant cells lines (HBF, BEAS-2B, RenG2, SC-DRenG2) and the effects estimated by MTT assay. Co-cultures of non-malignant human bronchial fibroblasts (HBF) and malignant human bronchial epithelial cells (RenG2) were implemented and the compounds ability to selectively kill CSCs was evaluated by sphere forming assay. The interleucine-6 (IL-6) levels were also determined as cytokine is crucial for CSCs. Regarding the monocultures results bromosphaerol selectively eliminated the malignant cells. Both 12S-hydroxy-bromosphaerol and 12R-hydroxy-bromosphaerol steroisomers were cytotoxic towards non-malignant bronchial BEAS-2B cell line, IC₅₀ of 4.29 and 4.30 μM respectively. However, none of the steroisomers induced damage in the HBFs. As to the co-cultures, 12R-hydroxy-bromosphaerol revealed the highest cytotoxicity and ability to abrogate the malignant stem cells; however its effects were IL-6 independent. The results presented here are the first evidence of the potential of these bromoterpenes to abrogate CSCs opening new research opportunities. The 12R-hydroxy-bromosphaerol revealed to be the most promising compound to be test in more complex living models.

From Marine Origin to Therapeutics: The Antitumor Potential of Marine Algae-Derived Compounds

Marine environment has demonstrated to be an interesting source of compounds with uncommon and unique chemical features on which the molecular modeling and chemical synthesis of new drugs can be based with greater efficacy and specificity for the therapeutics. Cancer is a growing public health threat, and despite the advances in biomedical research and technology, there is an urgent need for the development of new anticancer drugs. In this field, it is estimated that more than 60% of commercially available anticancer drugs are natural biomimetic inspired. Among the marine organisms, algae have revealed to be one of the major sources of new compounds of marine origin, including those exhibiting antitumor and cytotoxic potential. These compounds demonstrated ability to mediate specific inhibitory activities on a number of key cellular processes, including apoptosis pathways, angiogenesis, migration and invasion, in both in vitro and in vivo models, revealing their potential to be used as anticancer drugs. This review will focus on the bioactive molecules from algae with antitumor potential, from their origin to their potential uses, with special emphasis to the alga Sphaerococcus coronopifolius as a producer of cytotoxic compounds.

Human bronchial epithelial cells malignantly transformed by hexavalent chromium exhibit an aneuploid phenotype but no microsatellite instability

Hexavalent chromium [Cr(VI)] is a well-recognized human lung carcinogen. In order to gain further insight into Cr(VI)-induced carcinogenesis, we have established an adequate in vitro cellular model for the study of this process. To this end, BEAS-2B cells were used. Chronic exposure of cells to 1 microM Cr(VI) induced changes in the cells' ploidy and a decrease in cloning efficiency, although cultures continued to progress to confluence. After prolonged exposure (12 passages), the culture became heterogeneous, exhibiting areas where apparently normal epithelial cells and morphologically altered cells coexisted. Subsequent culture at a very low density strongly accentuated the Cr(VI)-induced changes in morphology and pattern of growth. Three individual colonies were then ring-cloned and expanded into three subclonal aneuploid cell lines. These subclonal cell lines showed changes in growth pattern and morphology, as well as a karyotype drift concomitant with the overexpression of genes commonly involved in malignant transformation (c-MYC, EGFR, HIF-1alpha and LDH-A). Moreover, when one of these cell lines (RenG2) was injected into nude mice, it showed the ability to induce tumors. This cell line revealed no microsatellite instability (MSI), which points to the expression of a functional MLH1 protein and an active mismatch repair (MMR) system. Therefore, the progression to malignancy of the BEAS-2B cells involved Cr(VI)-induced transformants that retained the ability to repair DNA damage, suggesting that genotoxicity underlies the ongoing carcinogenic process.

A role for transforming growth factor-beta apoptotic signaling pathway in liver injury induced by ingestion of water contaminated with high levels of Cr(VI)

Hexavalent chromium [Cr(VI)] exposure is commonly associated with lung cancer. Although other adverse health effects have been reported, some authors, on assuming that orally ingested Cr(VI) is efficiently detoxified upon reduction by body fluids, believe that Cr(VI) do not target cells other than respiratory tract cells. In rodents, ingested Cr(VI)-contaminated water was reported to induce, in the liver, increases in TGF-beta transcripts. As TGF-beta dependent signaling pathways are closely associated with hepatic injury, the present study was undertaken addressing two specific issues: the effects of ingestion of water contaminated with high levels of Cr(VI) in rat liver structure and function; and the role of the TGF-beta pathway in Cr(VI)-induced liver injury. Examination of Wistar rats exposed to 20 ppm Cr(VI)-contaminated water for 10 weeks showed increased serum glucose and alanine aminotransferase (ALT) levels. Liver histological examination revealed hepatocellular apoptosis, further confirmed by immunohystochemical study of Caspase 3 expression. Liver gene expression analysis revealed increased expression of Smad2/Smad4 and Dapk, suggesting the involvement of the TGF-beta pathway in the apoptotic process. Since no changes in Smad3 expression were observed it appears apoptosis is using a Smad3-independent pathway. Increased expression of both Caspase 8 and Daxx genes suggests also the involvement of the Fas pathway. Gene expression analysis also revealed that a p160(ROCK)-Rho-independent pathway operates, leading to cell contraction and membrane blebbing, characteristic apoptotic features. These findings suggest that either the amount of Cr(VI) ingested overwhelmed the body fluids reductive capacity or some Cr(VI) escapes the reductive protection barrier, thus targeting the liver and inducing apoptosis.

Chromium(VI) interaction with plant and animal mitochondrial bioenergetics: a comparative study

The mechanism of Cr(VI)-induced toxicity in plants and animals has been assessed for mitochondrial bioenergetics and membrane damage in turnip root and rat liver mitochondria. By using succinate as the respiratory substrate, ADP/O and respiratory control ratio (RCR) were depressed as a function of Cr(VI) concentration. State 3 and uncoupled respiration were also depressed by Cr(VI). Rat mitochondria revealed a higher sensitivity to Cr(VI), as compared to turnip mitochondria. Rat mitochondrial state 4 respiration rate triplicated in contrast to negligible stimulation of turnip state 4 respiration. Chromium(VI) inhibited the activity of the NADH-ubiquinone oxidoreductase (complex I) from rat liver mitochondria and succinate-dehydrogenases (complex II) from plant and animal mitochondria. In rat liver mitochondria, complex I was more sensitive to Cr(VI) than complex II. The activity of cytochrome c oxidase (complex IV) was not sensitive to Cr(VI). Unique for plant mitochondria, exogenous NADH uncoupled respiration was unaffected by Cr(VI), indicating that the NADH dehydrogenase of the outer leaflet of the plant inner membrane, in addition to complexes III and IV, were insensitive to Cr(VI). The ATPase activity (complex V) was stimulated in rat liver mitochondria, but inhibited in turnip root mitochondria. In both, turnip and rat mitochondria, Cr(VI) depressed mitochondrial succinate-dependent transmembrane potential (Deltapsi) and phosphorylation efficiency, but it neither affected mitochondrial membrane permeabilization to protons (H+) nor induced membrane lipid peroxidation. However, Cr(VI) induced mitochondrial membrane permeabilization to K+, an effect that was more pronounced in turnip root than in rat liver mitochondria. In conclusion, Cr(VI)-induced perturbations of mitochondrial bioenergetics compromises energy-dependent biochemical processes and, therefore, may contribute to the basal mechanism underlying its toxic effects in plant and animal cells.

Diversity of chromium-resistant and -reducing bacteria in a chromium-contaminated activated sludge

AIMS

This study attempts to establish a relationship between the Cr(VI) resistance of the culturable microbial community and the Cr(VI) resistance and Cr(VI)-reducing ability of representative strains of each population, in order to assess whether these are exclusive characteristics of one microbial group or abilities shared among many groups.

METHODS AND RESULTS

A group of 48 Cr(VI)-resistant isolates, with different colony types, was isolated from chromium-contaminated activated sludge. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis protein patterns and fatty acid methyl ester analysis identified six populations, representing 54% of the isolated bacteria, as belonging to the genera Acinetobacter and Ochrobactrum. The remaining populations included strains identified as species of the beta-Proteobacteria and high G + C Gram-positive bacteria. The Cr(VI) resistance and reduction ability of the strains were tested. All but two isolates grew in the presence of 1 mmol l(-1) Cr(VI). During enrichment, all isolates were able to survive to 2 mmol l(-1) Cr(VI) and complete Cr(VI) reduction was achieved. Representative strains of each population were able to partially reduce (5.4-39.1%) the Cr(VI) present in the growth medium.

CONCLUSIONS

Most of the identified isolates have never been reported to be Cr(VI)-resistant and/or Cr(VI)-reducing strains. The mechanisms of Cr(VI) resistance and reduction may differ from group to group; therefore, it is evident that both Cr(VI) resistance and reduction are shared abilities and not an exclusive characteristic of a single group, possibly reflecting horizontal genetic transfer resulting from selective pressure in this contaminated environment.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, this is the first study of a microbial community under chronic chromate stress and, as the success of microbial-based metal remediation technologies requires a better understanding of the microbial community and the population response to metal stress, it may contribute to the implementation of a strategy of bioremediation of chromate-contaminated environments.

Effects of NADH and H(2)O(2) on chromate-induced human erythrocytes hemoglobin oxidation and peroxidation

The effects of NADH and H(2)O(2) on chromate-induced human erythrocyte hemoglobin oxidation and peroxidation were studied. It was observed that NADH decreases the levels of chromate-induced human erythrocyte hemoglobin oxidation and peroxidation. H(2)O(2) decreases the levels of chromate-induced hemoglobin oxidation, but increases the levels of chromate-induced peroxidation. The ability of H(2)O(2) to decrease the levels of chromate-induced hemoglobin oxidation is higher than that observed for NADH. Furthermore, H(2)O(2) increases the inhibitory effect of NADH on chromate-induced hemoglobin oxidation, but decreases the NADH effect on chromate-induced peroxidation. The meaning of these results is discussed in terms of involvement of reactive chromium(V) species and reactive oxygen species in the mechanism by which chromate induces its effects in human erythrocytes.

Chromate-induced human erythrocytes haemoglobin oxidation and peroxidation: influence of vitamin E, vitamin C, salicylate, deferoxamine, and N-ethylmaleimide

In order to attenuate or to prevent chromate-induced human erythrocytes injury, the influence of vitamin E, vitamin C, salicylate, deferoxamine, and N-ethylmaleimide on chromate-induced human erythrocytes haemoglobin oxidation and peroxidation were investigated. It was observed that pretreatment of human erythrocytes with vitamin E (20 microM), vitamin C (1 mM), salicylate (3 mM), and deferoxamine (4 mM) significantly increased (P=0.0001) chromate-induced human erythrocytes haemoglobin oxidation in a time dependent manner, while it was significantly decreased (P=0.0001) by pretreatment with N-ethylmaleimide (1 mM). In contrast, pretreatment of human erythrocytes with deferoxamine (4 mM) immediately inhibited (P=0.0001) chromate-induced human erythrocytes peroxidation, while it was significantly increased (P=0.0001) by pretreatment with N-ethylmaleimide (1 mM) during the first 4 h of cells exposition to chromate. For time periods superior to 6 h pretreatment with N-ethylmaleimide (1 mM) significantly decreased (P=0.0001) chromate-induced human erythrocytes peroxidation. It was concluded that care must be taken as these drugs are used to prevent against toxicity induced by chromium(VI) compounds.

Human erythrocytes are protected against chromate-induced peroxidation

In previous studies performed in this laboratory it was realized that in a broad concentration range (0.5-8 mM) dichromate does not induced red blood cell (RBC) peroxidation. To investigate the reasons behind RBC protection against chromate-induced peroxidation, the effects of 8 mM dichromate on white ghost and RBC peroxidation, RBC antioxidant system and hemoglobin status, as well as RBC osmotic fragility and morphology, were studied in more detail. It was observed that the peroxidation level induced by dichromate on RBCs is practically negligible when compared with the peroxidation induced in white ghosts. Furthermore, the osmotic fragility of RBCs exposed to dichromate is not altered, but the cells undergo echinocytic transformation, probably due to chromate-induced structural RBC membrane modifications. The activities of catalase, gluthatione peroxidase, and superoxide dismutase of RBCs exposed to dichromate were similar to those observed in controls, but the gluthatione reductase and GSH levels were significantly reduced (P<0. 05). Concomitantly, GSSG and methemoglobin levels increased and NADH-methemoglobin reductase activity decreased. These results indicate that chromate does not induce RBC peroxidation, but does promote echinocytic shape transformation, oxidation of hemoglobin and GSH, and inhibition of gluthatione reductase and methemoglobin reductase. The enzymatic antioxidant defense system and hemoglobin oxidation are probably involved in the mechanism of RBC proctection against chromate-induced peroxidation, as is discussed.

Preparation, physico-chemical characterization, and relaxometry studies of various gadolinium(III)-DTPA-bis(amide) derivatives as potential magnetic resonance contrast agents

Macroscopic protonation constants were measured for a series of DTPA mono- and bis-amide ligands using potentiometric titrations. Proton NMR pH titrations yielded protonation populations of the various nitrogen and oxygen basic sites of the ligands for the different protonation stages. Amide formation decreased the basicity of the backbone nitrogens of the ligands and the thermodynamic stability of the corresponding Gd3+ chelates. Nuclear magnetic relaxation dispersion (NMRD) profiles and ESR linewidths were measured for the Gd3+ chelates. Some of these exhibited an elevated high field relaxivity relative to Gd(DTPA)2-, in response to their high molecular weight. As opposed to Gd(DTPA)2-, at 5 degrees C the chemical exchange process of the single inner-sphere water molecule of the bis-amide complexes becomes so slow that it governs the paramagnetic relaxation process, causing the observed NMRD profiles to be close to those expected for the outer-sphere contribution. The chelates containing long alkyl side chains, such as Gd(DTPA-HPA2), showed increased relaxivity values in the presence of human serum albumin (HSA), indicative of noncovalent interaction with the protein. These chelates could be useful as nonionic hepatobiliary contrast agents.