Cytotoxicity inhibition of catechol's type molecules by grafting on TiO2 and Fe2O3 nanoparticles surface.

The potential toxicity deriving from the interaction between chemicals and manufactured nanoparticles (NPs) represents an emerging threat to the environment and human health. Several studies have focused on the risks and (eco)toxicity of manufactured NPs as a consequence of their extensive use in recent years, however, there is still a limited understanding of the combined effects caused by manufactured NPs in the presence of other environmental contaminants. This is particularly relevant to aquatic environments, where many types of pollutants are inevitably released and can be involved in many kinds of reactions. In this context, the interaction between catecholate type ligands and two different nanomaterials, namely TiO2 and Fe2O3 NPs, was investigated by performing cytotoxicity assays with the topminnow fish hepatoma cell line (PLHC-1) using: i) the original organic molecules, ii) pristine NPs alone, and iii) modified NPs obtained by grafting the ligands on the NPs surface. Cytotoxic effects were explored at three different levels, specifically on cellular metabolism, membrane integrity and lysosomal activity. The outcomes from these assays showed cytotoxicity only for the free catechol type ligands, while in general no significant decrease in cell viability was observed for pristine NPs, as well as for the modified NPs, regardless the initial cytotoxicity level of the organic ligands These results suggest that the binding of catechols on the NPs' surface inhibited their cytotoxicity, indicating that TiO2 and Fe2O3 NPs may act as sorbents of these contaminants, thus reducing their possible detrimental effects.

Assessing the Morphological and Behavioral Toxicity of Catechol Using Larval Zebrafish.

Catechol is a ubiquitous chemical used in the manufacturing of fragrances, pharmaceuticals and flavorants. Environmental exposure occurs in a variety of ways through industrial processes, during pyrolysis and in effluent, yet despite its prevalence, there is limited information regarding its toxicity. While the genotoxicity and gastric carcinogenicity of catechol have been described in depth, toxicological studies have potentially overlooked a number of other effects relevant to humans. Here, we have made use of a general and behavioral larval zebrafish toxicity assay to describe previously unknown catechol-based toxicological phenomena. Behavioral testing revealed catechol-induced hypoactivity at concentrations an order of magnitude lower than observable endpoints. Catechol exposure also resulted in punctate melanocytes with concomitant decreases in the expression of pigment production and regulation markers mitfa, mc1r and tyr. Because catechol is converted into a number of toxic metabolites by tyrosinase, an enzyme found almost exclusively in melanocytes, an evaluation of the effects of catechol on these cells is critical to evaluating the safety of this chemical. This work provides insights into the toxic nature of catechol and highlights the benefits of the zebrafish larval testing platform in being able to dissect multiple aspects of toxicity with one model.

Astrocyte Reaction to Catechol-Induced Cytotoxicity Relies on the Contact with Microglia Before Isolation.

Astrocytes preserve the brain microenvironment homeostasis in order to protect other brain cells, mainly neurons, against damages. Glial cells have specific functions that are important in the context of neuronal survival in different models of central nervous system (CNS) diseases. Microglia are among these cells, secreting several molecules that can modulate astrocyte functions. Although 1,2-dihydroxybenzene (catechol) is a neurotoxic monoaromatic compound of exogenous origin, several endogenous molecules also present the catechol group. This study compared two methods to obtain astrocyte-enriched cultures from newborn Wistar rats of both sexes. In the first technique (P1), microglial cells began to be removed early 48 h after primary mixed glial cultures were plated. In the second one (P2), microglial cells were late removed 7 to 10 days after plating. Both cultures were exposed to catechol for 72 h. Catechol was more cytotoxic to P1 cultures than to P2, decreasing cellularity and changing the cell morphology. Microglial-conditioned medium (MCM) protected P1 cultures and inhibited the catechol autoxidation. P2 cultures, as well as P1 in the presence of 20% MCM, presented long, dense, and fibrillary processes positive for glial fibrillary acidic protein, which retracted the cytoplasm when exposed to catechol. The Ngf and Il1beta transcription increased in P1, meanwhile astrocytes expressed more Il10 in P2. Catechol decreased Bdnf and Il10 in P2 cultures, and it decreased the expression of Il1beta in both conditions. A prolonged contact with microglia before isolation of astrocyte-enriched cultures modifies astrocyte functions and morphology, protecting these cells against catechol-induced cytotoxicity.

Study on the differences in sludge toxicity and microbial community structure caused by catechol, resorcinol and hydroquinone with metagenomic analysis.

The aerobic biodegradation rate, organic toxicity and microbial community structure of activated sludge acclimated by catechol, resorcinol and hydroquinone were investigated, to study the relationship between microbial structure and sludge organic toxicity caused by phenolic compounds. At the stable operation stage, the degradation rates of the dihydroxy benzenes in a single sequencing batch reactor (SBR) cycle were followed the order: resorcinol (89.71%) > hydroquinone (85.64%) > catechol (59.62%). Sludge toxicity bioassay indicated that the toxicity of sludge was catechol (45.63%) > hydroquinone (40.28%) > resorcinol (38.15%). The accumulation of secondary metabolites such as 5-10 kDa tryptophan and tyrosine protein substances caused the differential sludge toxicity. Microbial metagenomic analysis showed that the toxicity of sludge was significantly related to the microbial community structure. Thauera, Azoarcus, Pseudomonas and other Proteobacteria formed in the sludge during acclimation. Catechol group had the least dominant bacteria and loop ring opening enzyme genes (catA, dmpB, dxnF, hapD) numbers. Therefore, the degradation of catechol was the most difficult than resorcinol and hydroquinone, resulting the highest sludge toxicity.

Preparation of External Stimulus-Free Gelatin-Catechol Hydrogels with Injectability and Tunable Temperature Responsiveness.

Gelatin is one of the most versatile biopolymers in various biomedical applications. A gelatin derivative gelatin-catechol (Gel-C) was developed in this study to further optimize its chemical and physical properties such as thermal reversibility and injectability. We found that Gel-C remains in a solution state at room temperature, and the temperature-dependent gelation capability of gelatin is well preserved in Gel-C. Its gel-forming temperature decreased to about 10 °C (about 30 °C for gelatin), and a series of gelatin derivatives with different gel-forming temperatures (10-30 °C) were formed by mixing gelatin and Gel-C in different ratios. Additionally, irreversible Gel-C hydrogels could be made without the addition of external stimuli by combining the physical cross-linking of gelatin and the chemical cross-linking of catechol. At the same time, properties of Gel-C hydrogels such as thermal reversibility and injectability could be manipulated by controlling the temperature and pH of the precursor solution. By simulating the formation of an irreversible Gel-C hydrogel in vivo, an in situ gelling system was fabricated by lowering the local temperature of the hydrogel with cold shock, thus realizing targeted and localized molecular delivery with prolonged retention time. This simple system integrated with the temperature responsiveness of gelatin and chemical cross-linking of catechol groups thus provides a promising platform to fabricate an in situ gelling system for drug delivery.

Complexation of Fe(III)/Catechols in atmospheric aqueous phase and the consequent cytotoxicity assessment in human bronchial epithelial cells (BEAS-2B).

Recent research has shown that the complexation of metals-organics plays an important role in atmospheric particulate matter, whose health effects should be taken into account. This work investigates the interactions between catechols (CAs), i.e., 4-nitrocatechol (4NC) and 4-methylcatechol (4MC), and transition metals (i.e., Fe) in the aqueous phase dark reaction. The formation of Fe/CAs complexes and secondary organics products are analyzed by UV-Vis spectroscopy, stopped-flow spectroscopy, high-resolution mass spectrometry and Raman spectroscopy, while the insoluble particulate matter formed from the CAs/Fe mixtures are characterized by the FTIR, X-ray photoelectron spectroscopy (XPS) and thermogravimetric-quadrupole-mass spectrometry (TG-Q-MS). On the basis of the density functional theory (DFT) calculation and experimental results, the possible formation pathways for the complexes of Fe(III) with 4NC (a proxy for organics) are proposed. The Fe/CAs complexes and organics products perhaps have significant sources of light absorption which play an important role in influencing the intensity of atmospheric radiation and particulate phase photochemistry. Besides, the cytotoxicity is tested as a function of concentrations for CAs/Fe mixtures in BEAS-2B cells. Our results show that CAs/Fe mixtures have strong association with cytotoxicity, indicating the mixtures have potential influence to human health.

Ionization Neutralizes the Allergy-Inducing Property of 3-Pentadecylcatechol: A Urushiol Derivative.

Urushiols are amphipathic compounds found in Rhus verniciflua Stokes that exhibit various biological activities. However, their practical use is very restricted due to their contact dermatitis-inducing property. Therefore, we applied the ionization method to remove the allergenic properties of the urushiols and to increase their usability. One of the natural urushiols, 3-pentadecylcatechol (PDC), was heated for 30 min with a solution of H2O and sodium carbonate (Na2CO3). The reaction product was analyzed by electrospray ionization mass spectrometry (ESI-MS). Ionized PDC with an m/z value of 316.9 and complexed PDCs with Na+ of 1 - 3 atoms with m/z values of 340.8, 365.2, and 380.8 were detected. PDC and ionized PDC (3 µmol/3 mg of Vaseline) treatments were applied on the rear of left ear of Sprague-Dawley rats once daily for 10 days. Erythema and swelling were observed on the ear skin treated with PDC, but not in case of ionized PDC. Compared with control, contact hypersensitivity-related biomarkers (neutrophils, eosinophils, immunoglobulin E, and histamine) in the blood were significantly higher only in the PDC-treated group. In addition, Il-1b, Il-6, Tnfα, and Cox-2 mRNA expression levels were dramatically increased in the ear tissue of PDC-treated rats, but in the ionized PDC-treated group, they were similar to those in the control group. Overall, it was confirmed that the allergenic property of the urushiol PDC was removed by ionization. This method is expected to be useful for preventing allergy induction in cooking and food processing using R. verniciflua Stokes.

In vivo antitumoral effect of 4-nerolidylcatechol (4-NC) in NRAS-mutant human melanoma.

NRAS-mutations arise in 15-20% of all melanomas and are associated with aggressive disease and poor prognosis. Besides, the treatment for NRAS-mutant melanoma are not very efficient and is currently limited to immune checkpoints inhibitors or aggressive chemotherapy. 4-nerolidylcathecol (4-NC), a natural product extracted from Pothomorphe umbellata, induces apoptosis in melanoma cells by ROS production, DNA damage and increased p53 expression, in addition to inhibiting invasion in reconstructed skin. Moreover, 4-NC showed cytotoxicity in BRAF/MEKi-resistant and naive melanoma cells by Endoplasmic Reticulum (ER) stress induction in vitro. We evaluated the in vivo efficacy and the systemic toxicity of 4-NC in a NRAS-mutant melanoma model. 4-NC was able to significantly suppress tumor growth 4-fold compared to controls. Cleaved PARP and p53 expression were increased indicating cell death. As a proof of concept, MMP-2 and MMP-14 gene expression were decreased, demonstrating a possible role of 4-NC in melanoma invasion inhibition. Toxicological analysis indicated minor changes in the liver and bone marrow, but this toxicity was very mild when compared to other proteasome inhibitors and ER stress inductors already described. Our data indicate that 4-NC can counteract melanoma growth in vivo with minor adverse effects, suggesting further investigation as a potential NRAS-mutant melanoma treatment.

Impaired dopamine metabolism in Parkinson's disease pathogenesis.

A full understanding of Parkinson's Disease etiopathogenesis and of the causes of the preferential vulnerability of nigrostriatal dopaminergic neurons is still an unsolved puzzle. A multiple-hit hypothesis has been proposed, which may explain the convergence of familial, environmental and idiopathic forms of the disease. Among the various determinants of the degeneration of the neurons in Substantia Nigra pars compacta, in this review we will focus on the endotoxicity associated to dopamine dyshomeostasis. In particular, we will discuss the relevance of the reactive dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) in the catechol-induced neurotoxicity. Indeed, the synergy between the catechol and the aldehyde moieties of DOPAL exacerbates its reactivity, resulting in modification of functional protein residues, protein aggregation, oxidative stress and cell death. Interestingly, αSynuclein, whose altered proteostasis is a recurrent element in Parkinson's Disease pathology, is considered a preferential target of DOPAL modification. DOPAL triggers αSynuclein oligomerization leading to synapse physiology impairment. Several factors can be responsible for DOPAL accumulation at the pre-synaptic terminals, i.e. dopamine leakage from synaptic vesicles, increased rate of dopamine conversion to DOPAL by upregulated monoamine oxidase and decreased DOPAL degradation by aldehyde dehydrogenases. Various studies report the decreased expression and activity of aldehyde dehydrogenases in parkinsonian brains, as well as genetic variants associated to increased risk in developing the pathology. Thus, we discuss how the deregulation of these enzymes might be considered a contributing element in the pathogenesis of Parkinson's Disease or a down-stream effect. Finally, we propose that a better understanding of the impaired dopamine metabolism in Parkinson's Disease would allow a more refined patients stratification and the design of more targeted and successful therapeutic strategies.

Microbial metabolites of proanthocyanidins reduce chemical carcinogen-induced DNA damage in human lung epithelial and fetal hepatic cells in vitro.

Seven selected microbial metabolites of proanthocyanidins (MMP), 3-phenylpropionic, 4-hydroxyphenyl acetic, 3-(4-hydroxyphenyl) propionic, p-coumaric, benzoic acid, pyrogallol (PG), and pyrocatechol (PC) were evaluated for their ability to reduce chemical carcinogen-induced toxicity in human lung epithelial cells (BEAS-2B) and human fetal hepatic cells (WRL-68). Cells pre-treated with MMP were exposed to a known chemical carcinogen, 4-[(acetoxymethyl) nitrosamino]-1-(3-pyridyl)-1-butanone (NNKOAc) to assess MMP-mediated cytoprotection and reduction of DNA damage. PG in BEAS-2B and PC in WRL-68 cells mitigated the NNKOAc-induced cytotoxicity. Pre-incubation of PG depicted significant protection against NNKOAc-induced DNA damage in BEAS-2B cells. PC in WRL-68 cells showed similar activity. To understand the mechanisms of PG- and PC-mediated DNA damage reduction, the effect on DNA damage response (DDR) proteins, cellular reactive oxygen species (ROS), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and caspase activity were studied. PG and PC alter the DDR and may promote ATR-Chk1 and ATM-Chk2 pathways, respectively. Cellular oxidative stress induced by NNKOAc was mitigated by PG and PC through enhanced GPx expression and TAC. PG and PC suppressed the activation of the extrinsic apoptotic pathway (caspase 3 and 8) provoked by NNKOAc. MMP are beneficial in chemoprevention by reducing cellular DNA damage.

Robust and Biocompatible Functionalization of ZnS Nanoparticles by Catechol-Bearing Poly(2-methyl-2-oxazoline)s.

Zinc sulfide (ZnS) nanoparticles (NPs) are particularly interesting materials for their electronic and luminescent properties. Unfortunately, their robust and stable functionalization and stabilization, especially in aqueous media, has represented a challenging and not yet completely accomplished task. In this work, we report the synthesis of colloidally stable, photoluminescent and biocompatible core-polymer shell ZnS and ZnS:Tb NPs by employing a water-in-oil miniemulsion (ME) process combined with surface functionalization via catechol-bearing poly-2-methyl-2-oxazoline (PMOXA) of various molar masses. The strong binding of catechol anchors to the metal cations of the ZnS surface, coupled with the high stability of PMOXA against chemical degradation, enable the formation of suspensions presenting excellent colloidal stability. This feature, combined with the assessed photoluminescence and biocompatibility, make these hybrid NPs suitable for optical bioimaging.

Para-tertiary butyl catechol induces eryptosis in vitro via oxidative stress and hemoglobin leakage in human erythrocytes.

Exposure of human population to industrial chemicals is believed as a significant contributing factor to the outgrowth of occupational diseases especially in developing countries due to improper safety measures and sanitary conditions. Para-tertiary butylcatechol (PTBC) widely employed in petrochemical, thermofax and phototypesetting industries, induces melanocytotoxicity and contact dermatitis leading to occupational leukoderma/vitiligo. Few vitiligo patients were reported for oxidative stress-induced hemolytic anemia and thrombocytopenia, however its impact on blood components is still not clear. Erythrocytes are the major cell population in circulation and play a prominent role in various diseases. In this work, the effect of PTBC on human erythrocytes is evaluated in vitro. PTBC induces oxidative stress-mediated eryptosis (erythrocyte death) causing detrimental changes such as depleted antioxidant levels, altered surface morphology, hemoglobin denaturation and heinz body formation. These findings validate that PTBC could induce toxic effects on human erythrocytes. Exposure of humans to toxic chemicals constitutes an important issue in various industries; one such issue is the exposure of PTBC at work place resulting in a spectrum of dermal complications. Therefore, it is imperative to appraise the long-term toxicities in order to further delineate the mechanisms of resultant disorders associated with PTBC and to establish the therapeutic interventions.

Effect of the Catechol-O-Methyltransferase Inhibitors Tolcapone and Entacapone on Fatty Acid Metabolism in HepaRG Cells.

Tolcapone and entacapone are catechol-O-methyltransferase inhibitors used in patients with Parkinson's disease. For tolcapone, patients with liver failure have been reported with microvesicular steatosis observed in the liver biopsy of 1 patient. We therefore investigated the impact of tolcapone and entacapone on fatty acid metabolism in HepaRG cells exposed for 24 h and on acutely exposed mouse liver mitochondria. In HepaRG cells, tolcapone induced lipid accumulation starting at 100 µM, whereas entacapone was ineffective up to 200 µM. In HepaRG cells, tolcapone-inhibited palmitate metabolism and activation starting at 100 µM, whereas entacapone did not affect palmitate metabolism. In isolated mouse liver mitochondria, tolcapone inhibited palmitate metabolism starting at 5 µM and entacapone at 50 µM. Inhibition of palmitate activation could be confirmed by the acylcarnitine pattern in the supernatant of HepaRG cell cultures. Tolcapone-reduced mRNA and protein expression of long-chain acyl-CoA synthetase 1 (ACSL1) and protein expression of ACSL5, whereas entacapone did not affect ACSL expression. Tolcapone increased mRNA expression of the fatty acid transporter CD36/FAT, impaired the secretion of ApoB100 by HepaRG cells and reduced the mRNA expression of ApoB100, but did not relevantly affect markers of fatty acid binding, lipid droplet formation and microsomal lipid transfer. In conclusion, tolcapone impaired hepatocellular fatty acid metabolism at lower concentrations than entacapone. Tolcapone increased mRNA expression of fatty acid transporters, inhibited activation of long-chain fatty acids and impaired very low-density lipoprotein secretion, causing hepatocellular triglyceride accumulation. The findings may be relevant in patients with a high tolcapone exposure and preexisting mitochondrial dysfunction.

Editor's Highlight: An Impaired Immune Tolerance Animal Model Distinguishes the Potential of Troglitazone/Pioglitazone and Tolcapone/Entacapone to Cause IDILI.

We have developed an animal model of amodiaquine-induced liver injury that has characteristics very similar to idiosyncratic drug-induced liver injury (IDILI) in humans by impairing immune tolerance using a PD1-/- mouse and cotreatment with anti-CTLA-4. In order to test the usefulness of this model as a general model for human IDILI risk, pairs of drugs with similar structures were tested, one of which is associated with a relatively high risk of IDILI and the other not. One such pair is troglitazone and pioglitazone; troglitazone has caused fatal cases of IDILI while pioglitazone is quite safe. Another pair is tolcapone and entacapone; tolcapone can cause serious IDILI; in contrast, although entacapone has been reported to cause liver injury, it is relatively safe. PD1-/- mice treated with anti-CTLA-4 and troglitazone or tolcapone displayed liver injury as determined by ALT levels and histology, while pioglitazone and entacapone showed less signs of liver injury. One possible mechanism by which drugs could induce an immune response leading to IDILI is by causing the release of danger-associated molecular pattern molecules that activate inflammasomes. We found that the supernatants from incubations of troglitazone, tolcapone, or entacapone with hepatocytes were also able to activate inflammasomes in macrophages, while the supernatant from pioglitazone incubations did not. These results are consistent with an immune mechanism for troglitazone- and tolcapone-induced IDILI and add to the evidence that this may be a general model for IDILI.

Simultaneous removal of dihydroxybenzenes and toxicity reduction by Penicillium chrysogenum var. halophenolicum under saline conditions.

The dihydroxybenzenes are widely found in wastewater and usually more than one of these aromatic compounds co-exist as pollutants of water resources. The current study investigated and compared the removal efficiency of hydroquinone, catechol and resorcinol in binary substrate systems under saline conditions by Penicillium chrysogenum var. halophenolicum, to clarify the potential of this fungal strain to degrade these aromatic compounds. Since P. chrysogenum is a known penicillin producer, biosynthetic penicillin genes were examined and antibiotic was quantified in mono and binary dihydroxybenzene systems to elucidate the carbon flux of dihydroxybenzenes metabolism in the P. chrysogenum var. halophenolicum to the secondary metabolism. In binary substrate systems, the three assayed dihydroxybenzene compounds were found to be co-metabolized by fungal strain. The fungal strain preferentially degraded hydroquinone and catechol. Resorcinol was degraded slower and supports higher antibiotic titers than either catechol or hydroquinone. Dihydroxybenzenes were faster removed in mixtures compared to mono substrate systems, except for the case of hydroquinone. In this context, the expression of penicillin biosynthetic gene cluster was not related to the removal of dihydroxybenzenes. Penicillin production was triggered simultaneously or after dihydroxybenzene degradation, but penicillin yields, under these conditions, did not compromise dihydroxybenzene biological treatment. To investigate the decrease in dihydroxybenzenes toxicity due to the fungal activity, viability tests with human colon cancer cells (HCT116) and DNA damage by alkaline comet assays were performed. For all the conditions assays, a decrease in saline medium toxicity was observed, indicating its potential as detoxification agent.

Changes in DNA methylation of erythroid-specific genes in K562 cells exposed to catechol in long term.

Catechol is one of phenolic metabolites of benzene that is a general occupational hazard and a ubiquitous environmental air pollutant. Catechol also occurs naturally in fruits, vegetables and cigarettes. Previous studies have revealed that 72h exposure to catechol improved hemin-induced erythroid differentiation of K562 cells accompanied with elevated methylation in erythroid specific genes. In present study, K562 cells were treated with 0, 10 or 20µM catechol for 1-4weeks, hemin-induced hemoglobin synthesis increased in a concentration- and time-dependent manner and the enhanced hemoglobin synthesis was relatively stable. The mRNA expression of α-, ß- and γ-globin genes, erythroid heme synthesis enzymes PBGD and ALAS2, transcription factor GATA-1 and NF-E2 showed a significant increase in K562 cells exposed to 20µM catechol for 3w, and catechol enhanced hemin-induced mRNA expression of these genes. Quantitative MassARRAY methylation analysis also confirmed that the exposure to catechol changed DNA methylation levels at several CpG sites in several erythroid-specific genes and their far upstream of regulatory elements. These results demonstrated that long-term exposure to low concentration of catechol enhanced the hemin-induced erythroid differentiation of K562 cells, in which DNA methylation played a role by up-regulating erythroid specific genes.

The catechol-O-methyltransferase inhibitors tolcapone and entacapone uncouple and inhibit the mitochondrial respiratory chain in HepaRG cells.

The catechol-O-methyltransferase inhibitor tolcapone causes hepatotoxicity and mitochondrial damage in animal models. We studied the interaction of tolcapone with mitochondrial respiration in comparison to entacapone in different experimental models. In HepaRG cells (human cell-line), tolcapone decreased the ATP content (estimated IC50 100±15µM) and was cytotoxic (estimated IC50 333±45µM), whereas entacapone caused no cytotoxicity and no ATP depletion up to 200µM. Cytochrome P450 induction did not increase the toxicity of the compounds. In HepaRG cells, tolcapone (not entacapone) inhibited maximal complex I- and complex II-linked oxygen consumption. In intact mouse liver mitochondria, tolcapone stimulated state 2 complex II-linked respiration and both compounds inhibited state 3 respiration of complex IV. Mitochondrial uncoupling was confirmed for both compounds by stimulation of complex I-linked respiration in the presence of oligomycin. Inhibition of complex I, II and IV for tolcapone and of complex I and IV for entacapone was directly demonstrated in disrupted mouse liver mitochondria. In HepaRG cells, tolcapone-induced inhibition of mitochondrial respiration was associated with increased lactate and ROS production and hepatocyte necrosis. In conclusion, both compounds uncouple oxidative phosphorylation and inhibit mitochondrial enzyme complexes. Tolcapone is a more potent mitochondrial toxicant than entacapone. Mitochondrial toxicity is a possible mechanism for tolcapone-associated hepatotoxicity.

Targeting the Nrf2/Amyloid-Beta Liaison in Alzheimer's Disease: A Rational Approach.

Amyloid is a prominent feature of Alzheimer's disease (AD). Yet, a linear linkage between amyloid-ß peptide (Aß) and the disease onset and progression has recently been questioned. In this context, the crucial partnership between Aß and Nrf2 pathways is acquiring paramount importance, offering prospects for deciphering the Aß-centered disease network. Here, we report on a new class of antiaggregating agents rationally designed to simultaneously activate transcription-based antioxidant responses, whose lead 1 showed interesting properties in a preliminary investigation. Relying on the requirements of Aß recognition, we identified the catechol derivative 12. In SH-SY5Y neuroblastoma cells, 12 combined remarkable free radical scavenger properties to the ability to trigger the Nrf2 pathway and induce the Nrf2-dependent defensive gene NQO1 by means of electrophilic activation of the transcriptional response. Moreover, 12 prevented the formation of cytotoxic stable oligomeric intermediates, being significantly more effective, and per se less toxic, than prototype 1. More importantly, as different chemical features were exploited to regulate Nrf2 and Aß activities, the two pathways could be tuned independently. These findings point to compound 12 and its derivatives as promising tools for investigating the therapeutic potential of the Nrf2/Aß cellular network, laying foundation for generating new drug leads to confront AD.

Strategic Drug Design to Avoid the Metabolic Activation of Hepatotoxic Drugs.

Adverse reactions are one of the most important issues in drug development, as well as in the therapeutic usage of drugs during the post-approval stage. Specifically, idiosyncratic adverse drug reactions (IDR) occur in only a small group of patients who are treated with certain drugs, and are unpredictable. It is widely accepted that drug-induced IDR is often associated with CYP-mediated bioactivation. Benzbromarone (BBR) is effective in the treatment of hyperuricemia, and has been used as an effective drug in Japan for a long time. However, BBR has been associated with hepatotoxicity, including fatal liver injury. We identified 2,6-dibromohydroquinone (DBH) and mono-debrominated catechol (CAT) as novel metabolites of BBR in human and rat liver microsomal systems, by comparison with chemically synthesized authentic compounds via ipso-substitution, which we previously discovered to be a unique metabolic reaction of substituted phenols by CYP. Furthermore, CAT, DBH and the oxidized form of DBH (DBBQ) were highly cytotoxic in human hepatocellular carcinoma cells, compared with BBR. We consider that the formation of these metabolites from BBR is linked to the mechanism involved in BBR-induced hepatotoxicity because catechols, hydroquinones, and their oxidized forms are known to be toxic.

Plantamajoside from Plantago asiatica modulates human umbilical vein endothelial cell dysfunction by glyceraldehyde-induced AGEs via MAPK/NF-κB.

BACKGROUND: Plantago asiatica has been traditionally used for traditional medicine around East Asia. Plantamajoside (PM), which is isolated from this plant, is known for biological properties including anti-inflammation and antioxidant activity. To demonstrate the biological activity of PM against endothelial dysfunction induced by advanced glycation end-products (AGEs), a cellular inflammatory mechanism system was evaluated in human umbilical vein endothelial cells (HUVECs). METHODS: We obtained PM through previous research in our laboratory. We formed the AGEs from bovine serum albumin with glyceraldehyde in the dark for seven days. To confirm the modulation of the inflammatory mechanism in endothelial dysfunction, we quantified the various pro-inflammatory cytokines and endothelial dysfunction-related proteins in the HUVECs with Western blotting and with real-time and quantitative real-time polymerase chain reactions. RESULTS: Co-treatment with PM and AGEs significantly suppressed inflammatory cytokines and adhesion molecule expression. Moreover, the PM treatment for down-regulated inflammatory signals and blocked monocyte adhesion on the HUVECs. CONCLUSIONS: Theses results demonstrated that PM, as a potential natural compound, protects AGE-induced endothelial cells against inflammatory cellular dysfunction.