As a central feature of neuroinflammation, microglial dysfunction has been increasingly considered a causative factor of neurodegeneration implicating an intertwined pathology with amyloidogenic ...proteins. Herein, we report the smallest synthetic molecule (N,N′-diacetyl-p-phenylenediamine DAPPD), simply composed of a benzene ring with 2 acetamide groups at the para position, known to date as a chemical reagent that is able to promote the phagocytic aptitude ofmicroglia and subsequently ameliorate cognitive defects. Based on our mechanistic investigations in vitro and in vivo, 1) the capability of DAPPD to restore microglial phagocytosis is responsible for diminishing the accumulation of amyloid-β (Aβ) species and significantly improving cognitive function in the brains of 2 types of Alzheimer’s disease (AD) transgenic mice, and 2) the rectification of microglial function by DAPPD is a result of its ability to suppress the expression of NLRP3 inflammasome-associated proteins through its impact on the NF-κB pathway. Overall, our in vitro and in vivo investigations on efficacies andmolecular-level mechanisms demonstrate the ability of DAPPD to regulate microglial function, suppress neuroinflammation, foster cerebral Aβ clearance, and attenuate cognitive deficits in AD transgenic mouse models. Discovery of such antineuroinflammatory compounds signifies the potential in discovering effective therapeutic molecules against AD-associated neurodegeneration.
Tire wear particle (TWP)-derived compounds may be of high concern to consumers when released in the root zone of edible plants. We exposed lettuce plants to the TWP-derived compounds ...diphenylguanidine (DPG), hexamethoxymethylmelamine (HMMM), benzothiazole (BTZ), N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), and its quinone transformation product (6PPD-q) at concentrations of 1 mg L–1 in hydroponic solutions over 14 days to analyze if they are taken up and metabolized by the plants. Assuming that TWP may be a long-term source of TWP-derived compounds to plants, we further investigated the effect of leaching from TWP on the concentration of leachate compounds in lettuce leaves by adding constantly leaching TWP to the hydroponic solutions. Concentrations in leaves, roots, and nutrient solution were quantified by triple quadrupole mass spectrometry, and metabolites in the leaves were identified by Orbitrap high resolution mass spectrometry. This study demonstrates that TWP-derived compounds are readily taken up by lettuce with measured maximum leaf concentrations between ∼0.75 (6PPD) and 20 μg g–1 (HMMM). Although these compounds were metabolized in the plant, we identified several transformation products, most of which proved to be more stable in the lettuce leaves than the parent compounds. Furthermore, continuous leaching from TWP led to a resupply and replenishment of the metabolized compounds in the lettuce leaves. The stability of metabolized TWP-derived compounds with largely unknown toxicities is particularly concerning and is an important new aspect for the impact assessment of TWP in the environment.
The voltage-gated potassium channel KCNQ2 is responsible for M-current in neurons and is an important drug target to treat epilepsy, pain and several other diseases related to neuronal ...hyper-excitability. A list of synthetic compounds have been developed to directly activate KCNQ2, yet our knowledge of their activation mechanism is limited, due to lack of high-resolution structures. Here, we report cryo-electron microscopy (cryo-EM) structures of the human KCNQ2 determined in apo state and in complex with two activators, ztz240 or retigabine, which activate KCNQ2 through different mechanisms. The activator-bound structures, along with electrophysiology analysis, reveal that ztz240 binds at the voltage-sensing domain and directly stabilizes it at the activated state, whereas retigabine binds at the pore domain and activates the channel by an allosteric modulation. By accurately defining ligand-binding sites, these KCNQ2 structures not only reveal different ligand recognition and activation mechanisms, but also provide a structural basis for drug optimization and design.
Nonspecific histone deacetylase (HDAC) inhibition has been shown to facilitate the extinction of drug-seeking behavior in a manner resistant to reinstatement. A key open question is which specific ...HDAC is involved in the extinction of drug-seeking behavior. Using the selective HDAC3 inhibitor RGFP966, we investigated the role of HDAC3 in extinction and found that systemic treatment with RGFP966 facilitates extinction in mice in a manner resistant to reinstatement. We also investigated whether the facilitated extinction is related to the enhancement of extinction consolidation during extinction learning or to negative effects on performance or reconsolidation. These are key distinctions with regard to any compound being used to modulate extinction, because a more rapid decrease in a defined behavior is interpreted as facilitated extinction. Using an innovative combination of behavioral paradigms, we found that a single treatment of RGFP966 enhances extinction of a previously established cocaine-conditioned place preference, while simultaneously enhancing long-term object-location memory within subjects. During extinction consolidation, HDAC3 inhibition promotes a distinct pattern of histone acetylation linked to gene expression within the infralimbic cortex, hippocampus, and nucleus accumbens. Thus, the facilitated extinction of drug-seeking cannot be explained by adverse effects on performance. These results demonstrate that HDAC3 inhibition enhances the memory processes involved in extinction of drug-seeking behavior.
Amino antioxidants (AAOs), a suite of emerging organic contaminants, have been widely used in numerous industrial and commercial products to inhibit oxidation and corrosion. Recently, their ...environmental ubiquity, health risks, bioaccumulative and toxic potential have led to mounting public concern. This review summarizes the current state of knowledge on the production and usage, environmental occurrence, bioavailability, human exposure, and aquatic toxicity of representative AAOs, and provides suggestions for future research directions. Previous studies have revealed widespread distribution of many AAOs in various environmental matrixes, including air, water, sediment, dust, and biota. In addition to parent compounds, their degradation products, such as 2-anilino-5-(1,3-dimethylbutylamino)-1,4-benzoquinone (6PPD-Q) and 4-nitrodiphenylamine (4-NO2-DPA), have also been detected at high levels in multiple compartments. Dust ingestion and air inhalation are the two most well-investigated routes for human exposure to AAOs and their transformation products, while studies on other pathways (e.g., skin contact and dietary intake) still remain extremely limited. Moreover, AAO burdens in human tissue have been poorly documented. Toxicological data have shown that a few AAOs may cause teratogenic, developmental, reproductive, endocrinic, neuronic, and genetic toxicity to aquatic organisms, and the toxic capacities of degradation products differ from their precursors. Future studies should focus on elucidating AAO exposure for humans and associated health risks. Additionally, more attention should be given to AAO transformation products (particularly those quinoid derivatives possessing substantial affinity with DNA) and to the effects of complex mixtures of these chemicals.
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•Environmental profiles of amino antioxidants (AAOs) are comprehensively compiled.•Both wildlife and humans are experiencing appreciable exposure to AAOs.•Research concerning aquatic toxicity of AAOs remains relatively lagged.•Studies should be extended to transformation products and less-studied AAOs.
Background
p‐Phenylenediamine (PPD) is the primary patch test screening agent for hair dye contact allergy, and approximately 100 different hair dye chemicals are allowed.
Objectives
To examine ...whether PPD is an optimal screening agent for diagnosing hair dye allergy or whether other clinically important sensitizers exist.
Methods
Two thousand nine hundred and thirty‐nine consecutive patients in 12 dermatology clinics were patch tested with five hair dyes available from patch test suppliers. Furthermore, 22 frequently used hair dye ingredients not available from patch test suppliers were tested in subgroups of ∼ 500 patients each.
Results
A positive reaction to PPD was found in 4.5% of patients, and 2.8% reacted to toluene‐2,5‐diamine (PTD), 1.8% to p‐aminophenol, 1% to m‐aminophenol, and 0.1% to resorcinol; all together, 5.3% (n = 156). Dying hair was the most frequently reported cause of the allergy (55.4%); so‐called ‘temporary henna’ tattoos were the cause in 8.5% of the cases. p‐Methylaminophenol gave a reaction in 20 patients (2.2%), 3 of them with clinical relevance, and no co‐reaction with the above five well‐known hair dyes.
Conclusions
Hair dyes are the prime cause of PPD allergy. PPD identifies the majority of positive reactions to PTD, p‐aminophenol and m‐aminophenol, but not all, which justifies additional testing with hair dye ingredients from the used product.
N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPDQ), one of the oxidation products of rubber antioxidant 6PPD, has been identified as a novel toxicant to many organisms. However, an ...understanding of its underlying toxicity mechanisms remained elusive. In this study, we reported that 6PPDQ could react with deoxyguanosine to form one isomer of 3-hydroxy-1, N2-6PPD-etheno-2′-deoxyguanosine (6PPDQ-dG). Next, by employing an ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method, we found that 6PPDQ-dG could be detected in genomic DNA from 6PPDQ-treated mammalian cells and Chlamydomonas reinhardtii. We observed positive correlations between concentrations of exogenous 6PPDQ and the amounts of 6PPDQ-dG, and a recovery period after removal of 6PPDQ also led to decreased levels of the adduct in both organisms, which suggested potential repair pathways for this adduct in mammalian cells and unicellular algae. Additionally, we extracted the genomic DNA from tissues of frozen capelin and observed substantial amounts of the adduct in roe and gills, as well as livers at a relatively lower level. These results provided insights into the target organs and tissues that 6PPDQ might accumulate or harm fish. Overall, our study provides a new understanding of the mechanisms of toxicity of 6PPDQ in mammalian cells and aqueous organisms.
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•6PPDQ can react with deoxyguanosine to form isomer-specific 3-hydroxy-1,N2-6PPD-etheno-2′-deoxyguanosine (6PPDQ-dG) in flasks.•6PPDQ-dG can be observed in mammalian cells and Chlamydomonas reinhardtii exposed to 6PPDQ.•6PPDQ-dG can be detected in the liver, gill, and roe from frozen capelin.
Ferroptosis is a form of cell death primed by iron and lipid hydroperoxides and prevented by GPx4. Ferrostatin-1 (fer-1) inhibits ferroptosis much more efficiently than phenolic antioxidants. ...Previous studies on the antioxidant efficiency of fer-1 adopted kinetic tests where a diazo compound generates the hydroperoxyl radical scavenged by the antioxidant. However, this reaction, accounting for a chain breaking effect, is only minimally useful for the description of the inhibition of ferrous iron and lipid hydroperoxide dependent peroxidation. Scavenging lipid hydroperoxyl radicals, indeed, generates lipid hydroperoxides from which ferrous iron initiates a new peroxidative chain reaction. We show that when fer-1 inhibits peroxidation, initiated by iron and traces of lipid hydroperoxides in liposomes, the pattern of oxidized species produced from traces of pre-existing hydroperoxides is practically identical to that observed following exhaustive peroxidation in the absence of the antioxidant. This supported the notion that the anti-ferroptotic activity of fer-1 is actually due to the scavenging of initiating alkoxyl radicals produced, together with other rearrangement products, by ferrous iron from lipid hydroperoxides. Notably, fer-1 is not consumed while inhibiting iron dependent lipid peroxidation. The emerging concept is that it is ferrous iron itself that reduces fer-1 radical. This was supported by electroanalytical evidence that fer-1 forms a complex with iron and further confirmed in cells by fluorescence of calcein, indicating a decrease of labile iron in the presence of fer-1. The notion of such as pseudo-catalytic cycle of the ferrostatin-iron complex was also investigated by means of quantum mechanics calculations, which confirmed the reduction of an alkoxyl radical model by fer-1 and the reduction of fer-1 radical by ferrous iron. In summary, GPx4 and fer-1 in the presence of ferrous iron, produces, by distinct mechanism, the most relevant anti-ferroptotic effect, i.e the disappearance of initiating lipid hydroperoxides.
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•Ferroptosis is a non-apoptotic form of cell death primed by lipid peroxidation.•Ferrostatin-1, a synthetic antioxidant, contributed to the definition of Ferroptosis.•Ferrostatin-1 inhibits lipid peroxidation much more efficiently than phenolic antioxidants.•Ferrostatin-1 scavenges the alkoxyl radicals without being consumed during the process.•Ferrostatin-1 is regenerated by ferrous iron, reducing back fer-1 radical.
The rubber antioxidant 6PPD has gained significant attention due to its highly toxic transformation product, 6PPD-quinone (6PPDQ). Despite their detection in urines of pregnant women, the placental ...transfer and developmental toxicity of 6PPD and 6PPDQ are unknown. Here, we treated C57Bl/6 mice with 4 mg/kg 6PPD or 6PPDQ to investigate their urine excretion and placental transfer. Female and male mice exhibited sex difference in excretion profiles of 6PPD and 6PPDQ. Urine concentrations of 6PPDQ were one order of magnitude lower than those of 6PPD, suggesting lower excretion and higher bioaccumulation of 6PPDQ. In pregnant mice treated with 6PPD or 6PPDQ from embryonic day 11.5 to 15.5, 6PPDQ showed ∼1.5–8 times higher concentrations than 6PPD in placenta, embryo body, and embryo brain, suggesting higher placental transfer of 6PPDQ. Using in vitro dual-luciferase reporter assays, we revealed that 6PPDQ activated the human retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) at concentrations as low as 0.3 μM, which was ∼10-fold higher than the concentrations detected in human urines. 6PPD activated the RXRα at concentrations as low as 1.2 μM. These results demonstrate the exposure risks of 6PPD and 6PPDQ during pregnancy and emphasize the need for further toxicological and epidemiological investigations.
A novel electrochemical sensor based on a molecularly imprinted polymer, poly(o-phenylenediamine) (PoPD), has been developed for selective and sensitive detection of furosemide. The sensor was ...prepared by incorporating of furosemide as template molecules during the electropolymerization of o-phenylenediamine on a gold electrode. To develop the molecularly imprinted polymer (MIP), the template molecules were removed from the modified electrode's surface by washing it with 0.25molL−1 NaOH solution. The imprinted layer was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The sensor′s preparation conditions including furosemide concentration, the number of CV cycles in the electropolymerization process, extraction solution of the template from the imprinted film, the incubation time and the pH level were optimized. The incubation of the MIP-modified electrode, with respect to furosemide concentration, resulted in a suppression of the K4Fe(CN)6 oxidation process. Under the optimal experimental conditions, the response of the imprinted sensor was linear in the range of 1.0×10−7–7.0×10−6molL−1 of furosemide. The detection limit was obtained as 7.0×10−8molL−1 for furosemide by using this sensor. The sensor was successfully used to determine the furosemide amount in the tablet and in human urine samples with satisfactory results.
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•A sensor based on molecularly imprinted polymer was constructed for determination of furosemide.•Furosemide was incorporated during the electropolymerization of o-phenylenediamine.•This sensor was applied for determination of furosemide in tablet and human urine samples.
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