In vitro induction of apoptosis vs. necrosis by widely used preservatives: 2-phenoxyethanol, a mixture of isothiazolinones, imidazolidinyl urea and 1,2-pentanediol

Physiological impact of personal care product constituents on non-target aquatic organisms

Personal care products (PCPs) are products used in cleaning, beautification, grooming, and personal hygiene. The rise in diversity, usage, and availability of PCPs has resulted in their higher accumulation in the environment. Thus, these constitute an emerging category of environmental contaminants due to the potential of its constituents (chemical and non-chemical) to induce various physiological effects even at lower concentrations (ng/L). For analyzing the impact of the PCPs constituents on the non-target organism about 300 article including research articles, review articles and guidelines were studied from 2000 to 2023. This review aims to firstly discuss the fate and accumulation of PCPs in the aquatic environment and organisms; secondly provides overview of environmental risks that are linked to PCPs; thirdly review the trends, current status of regulations and risks associated with PCPs and finally discuss the knowledge gaps and future perspectives for future research. The article discusses important constituents of PCPs such as antimicrobials, cleansing agents and disinfectants, fragrances, insect repellent, moisturizers, plasticizers, preservatives, surfactants, UV filters, and UV stabilizers. Each of them has been found to display certain toxic impact on the aquatic organisms especially the plasticizers and UV filters. These continuously and persistently release biologically active and inactive components which interferes with the physiological system of the non-target organism such as fish, corals, shrimps, bivalves, algae, etc. With a rise in the number of toxicity reports, concerns are being raised over the potential impacts of these contaminant on aquatic organism and humans. The rate of adoption of nanotechnology in PCPs is greater than the evaluation of the safety risk associated with the nano-additives. Hence, this review article presents the current state of knowledge on PCPs in aquatic ecosystems.

Tamarix articulata extract offers protection against toxicity induced by beauty products in Hs27 human skin fibroblasts

The current study evaluates the cytotoxicity, mode of cell death and chemical analysis of selected beauty products and evaluation of the protective effect of Tamarix articulata (TA) extract against toxicity induced by beauty products in skin fibroblasts (Hs27). MTT and Crystal violet (CV) assays were used to determine the dose-dependent cytotoxic effects of beauty products against Hs27 fibroblasts. DNA fragmentation assay and annexin-V staining were conducted to determine the mode of cell killing induced by evaluated beauty products. Quantification of reactive oxygen species (ROS) and antioxidant enzyme levels were used to evaluate the oxidative stress. Chemical analysis and heavy metals were evaluated to determine beauty products. Pre-treatment with TA extract for different time points followed by time-dependent exposure with beauty products to assess the protective effect of TA extract in Hs27 cells was analyzed by MTT and CV assays. Owing to the presence of various harmful heavy metals such as arsenic (As), chromium (Cr), cadmium (Cd), nickel (Ni), and lead (Pb) in beauty products, our results revealed that all beauty products induce significant cytotoxicity over time (1, 4 h) in a dose-dependent (125, 250, 500 μg/mL) manner. DNA fragmentation assay, quantification of apoptosis by annexin-V staining, determination of ROS and antioxidant enzymes (CAT, GSH-Px and SOD) revealed that the induced cytotoxicity was caused by oxidative stress-mediated apoptosis. However, pre-incubation with a safe dose (50 μg/mL) of TA for different times (24, 48 h) followed by exposure to various doses (62.5, 125, 250, 500 μg/mL) of beauty products for different times (1, 4 h) revealed significant (*p≤0.05, **p≤0.01) protection against beauty product-mediated cytotoxicity. The effect was more pronounced for 1 h exposure to beauty products compared to 4 h. Our study demonstrates that the due to the presence of heavy metals in synthetic beauty products exhibit marked toxicity to skin fibroblasts due to oxidative stress-mediated apoptosis. However, the presence of abundant bioactive polyphenols with promising antiscavenging activity in TA extracts significantly nullifies cytotoxicity promoted by examined beauty products in skin fibroblasts (Hs27).

Aluminium alkyl complexes supported by imino-phosphanamide ligand as precursors for catalytic guanylation reactions of carbodiimides

Herein, we report the synthesis, characterisation, and application of three aluminium alkyl complexes, [κ²-{NHI^RP(Ph)NDipp}AlMe₂] (R = Dipp (2a), Mes (2b); tBu (2c), Dipp = 2,6-diisopropylphenyl, Mes = mesityl, and tBu = tert-butyl), supported by unsymmetrical imino-phosphanamide [NHI^RP(Ph)NDipp]⁻ [R = Dipp (1a), Mes (1b), tBu (1c)] ligands as molecular precursors for the catalytic synthesis of guanidines using carbodiimides and primary amines. All the imino-phosphanamide ligands 1a, 1b and 1c were prepared in good yield from the corresponding N-heterocyclic imine (NHI) with phenylchloro-2,6-diisopropylphenylphosphanamine, PhP(Cl)NHDipp. The aluminium alkyl complexes 2a, 2b and 2c were obtained in good yield upon completion of the reaction between trimethyl aluminium and the protic ligands 1a, 1b and 1c in a 1 : 1 molar ratio in toluene via the elimination of methane, respectively. The molecular structures of the protic ligands 1b and 1c and the aluminium complexes 2a, 2b and 2c were established via single-crystal X-ray diffraction analysis. Complexes 2a, 2b and 2c were tested as pre-catalysts for the hydroamination/guanylation reaction of carbodiimides with aryl amines to afford guanidines at ambient temperature. All the aluminium complexes exhibited a high conversion with 1.5 mol% catalyst loading and broad substrate scope with a wide functional group tolerance during the guanylation reaction. We also proposed the most plausible mechanism, involving the formation of catalytically active three-coordinate Al species as the active pre-catalyst.

Three aluminium alkyl complexes, [κ²-{Im^RNP(Ph)NDipp}AlMe₂] (2a–2c), supported by unsymmetrical imino-phosphanamide were synthesised and utilised as competent precatalysts for the hydroamination of carbodiimides under ambient conditions.

Tuning the Reaction Selectivity over MgAl Spinel-Supported Pt Catalyst in Furfuryl Alcohol Conversion to Pentanediols

Catalytic conversion of biomass-derived feedstock to high-value chemicals is of remarkable significance for alleviating dependence on fossil energy resources. MgAl spinel-supported Pt catalysts were prepared and used in furfuryl alcohol conversion. The approaches to tune the reaction selectivity toward pentanediols (PeDs) were investigated and the catalytic performance was correlated to the catalysts’ physicochemical properties based on comprehensive characterizations. It was found that 1–8 wt% Pt was highly dispersed on the MgAl2O4 support as nanoparticles with small sizes of 1–3 nm. The reaction selectivity did not show dependence on the size of Pt nanoparticles. Introducing LiOH onto the support effectively steered the reaction products toward the PeDs at the expense of tetrahydrofurfuryl alcohol (THFA) selectivity. Meanwhile, the major product in PeDs was shifted from 1,5-PeD to 1,2-PeD. The reasons for the PeDs selectivity enhancement were attributed to the generation of a large number of medium-strong base sites on the Li-modified Pt catalyst. The reaction temperature is another effective factor to tune the reaction selectivity. At 230 °C, PeDs selectivity was enhanced to 77.4% with a 1,2-PeD to 1,5-PeD ratio of 3.7 over 4Pt/10Li/MgAl2O4. The Pt/Li/MgAl2O4 catalyst was robust to be reused five times without deactivation.

The Beast of Beauty: Environmental and Health Concerns of Toxic Components in Cosmetics

Cosmetic products are used in large quantities across the world. An increasing number of chemical compounds are being added to the formulation of cosmetic products as additives, fragrances, preservatives, stabilizers, surfactants, dye and shine to potentiate their quality, property and shelf life. Owing to their widespread use, active residues of cosmetic products are continuously introduced into the environment in several ways. Many of these chemicals are bioactive and are characterized by potential bioaccumulation ability and environmental persistence, thus exerting a major risk to humans and the health of ecosystems. Hence, the indiscriminate consumption of cosmetics may present a looming issue with significant adverse impacts on public health. This review intends to spotlight a current overview of toxic ingredients used in formulating cosmetics such as parabens, triclosan, benzalkonium chloride, 1,4-dioxane, plastic microbeads, formaldehyde, diazolidinyl urea, imidazolidinyl urea, sunscreen elements (organic and inorganic UV filters) and trace metals. Specific focus is given to illustrate the biological risks of these substances on human health and aquatic system in terms of genotoxicity, cytotoxicity, neurotoxicity mutagenicity, and estrogenicity. In addition to conclusive remarks, future directions are also suggested.

An insight into toxicity and human-health-related adverse consequences of cosmeceuticals - A review

In recent years, the use of cosmeceutical-based personal care and beauty products has ever increased, around the world. Currently, an increasing number of compounds are being assimilated in the formulation of cosmetic products as preservatives, fragrances, surfactants, etc. to intensify the performance, quality, value, and lifespan of cosmetics. Nevertheless, many of these chemical additives pose toxic effects to the human body, exhibiting health risks from a mild hypersensitivity to life-threatening anaphylaxis or lethal intoxication. Therefore, the indiscriminate application of cosmeceuticals has recently become a mounting issue confronting public health. The present review focuses on exposure to a large variety of toxic substances used in cosmetic formulations such as 1,4-dioxane formaldehyde, paraformaldehyde, benzalkonium chloride, imidazolidinyl urea, diazolidinyl urea, trace heavy metals, parabens derivatives, phthalates, isothiazolinone derivatives (methylchloroiso-thiazolinone, and methylisothiazolinone), methyldibromo glutaronitrile, and phenoxy-ethanol. The biological risks related to these substances that they can pose to human health in terms of cytotoxicity, genotoxicity, mutagenicity, neurotoxicity oestrogenicity or others are also discussed. Researchers from academia, consultancy firms, governmental organizations, and cosmetic companies should carry out further progress to keep updating the consumers regarding the dark-sides, and health-related harmful apprehensions of cosmetics. In addition, the industry-motivated initiatives to abate environmental impact through green, sustainable and eco-friendly product development grasp significant perspective.

Methylisothiazolinone may induce cell death and inflammatory response through DNA damage in human liver epithelium cells

Methylisothiazolinone (MIT) is a powerful biocide and preservative, which is widely used alone or in a 1:3 ratio with methylchloroisothiazolinone (MCIT) under the trade name of Kathons in the manufacture of numerous personal and household products. Considering that Kathons injected intravenously is distributed in the blood and then in the liver, we explored the toxic mechanism of MIT on human liver epithelium cells. At 24 h after exposure, MIT bound to the plasma membrane and the inner wall of vacuoles in the cells, and rupture of the cell membrane and nuclear envelop, autophagosome-like vacuoles formation and mitochondrial damage were observed. Cell viability dose-dependently decreased accompanying an increase of apoptotic cells, and the level of LDH, NO, IFN-gamma, IL-10 and IL-8, but not IL-1β, significantly increased in the culture media of cells exposed to MIT. Additionally, expression of autophagy-, membrane damage- and apoptosis-related proteins was notably enhanced, and the produced ATP level dose-dependently decreased with the reduced mitochondrial activity. Furthermore, the increased DNA damage and the decreased transcription activity were observed in MIT-treated cells. Meanwhile, the intracellular ROS level did not show dose-dependent change at the same time-point. Then we explored the role of autophagy in MIT-induced cytotoxicity by inhibiting or inducing the autophagic signal. Intriguingly, no additional cell death induced by autophagic modulation occurred when MIT was treated. Taken together, we suggest that MIT may induce multiple pathways of cell death and inflammatory response through DNA damage caused by rupture of the nuclear envelope.

An investigation of the effects of dithranol-induced apoptosis in a human keratinocyte cell line

Objectives

Dithranol, one of the most successful topical agents for the treatment of psoriasis, has been shown to exert its therapeutic effect by inducing keratinocyte apoptosis. To gain further insights into dithranol-induced apoptotic events in vitro, a detailed investigation of its time- and dose-dependent effects has been performed through the evaluation of selected apoptotic markers, using a human keratinocyte cell line (HaCaT) as a model.

Methods

The time- and dose-dependent effects of dithranol on a human keratinocyte cell line (HaCaT) were investigated through the evaluation of a series of apoptotic markers; morphological changes (electron microscopy), phosphatidylserine externalisation (flow cytometry), and caspase-3/7 activation.

Key findings

The dithranol-induced apoptotic cascade was found to follow a well-defined dose and time-course, with the concentration and the period of exposure to the drug acting as the two major factors influencing the events and nature of cell death. The earliest apoptotic event detected was caspase activation (after 6 h), followed by the occurrence of phosphatidylserine externalisation (after 9 h) and subsequently the morphological characteristics associated with early and late stage apoptosis/necrosis (after 12 h).

Conclusions

This study has elucidated the dose- and time-response effects of dithranol-induced apoptosis in human keratinocytes in vitro.

Safety Assessment of 1,2-Glycols as Used in Cosmetics

Caprylyl glycol and related 1,2-glycols are used mostly as skin and hair conditioning agents and viscosity agents in cosmetic products, and caprylyl glycol and pentylene glycol also function as cosmetic preservatives. The Cosmetic Ingredient Review (CIR) Expert Panel noted that, while these ingredients are dermally absorbed, modeling data predicted decreased skin penetration of longer chain 1,2-glycols. Because the negative oral toxicity data on shorter chain 1,2-glycols and genotoxicity data support the safety of the 1,2-glycols reviewed in this safety assessment, the Panel concluded that these ingredients are safe in the present practices of use and concentration described in this safety assessment.

Heparin can liberate high molecular weight DNA from secondary necrotic cells

The borderline between necrosis and apoptosis is indistinct, but that between types of cell death is important because necrosis may lead to local inflammation, whereas apoptosis usually does not. In certain autoimmune disorders, inhibition of cell death is crucial, since macromolecules released from the dead cells may accelerate the autoimmune processes. We have used various cell death inhibitors to block cell death induced by 4HPR [N-(4-hydroxyphenil)-retinamide] the BL41 and U937 cell lines. VD-FMK, a general caspase inhibitor, inhibited DNA fragmentation induced by 4HPR, but not PI (propidium iodide) uptake and necrosis. Interestingly heparin, a serine-protease inhibitor, lowered the PI fluorescence of the dead cell population and increased the sub-G1 population as measured by flow cytometry. Regarding these changes, we found that heparin failed to increase DNA fragmentation, but merely liberated high molecular mass DNA fragments from dead cells. The exact mechanism is unclear, but heparin during secondary necrosis might enter the cells, bind RNPs (ribonucleoproteins), and pull them out with the attached DNA, where they would be sensitive to enzymatic degradation. Thus, the results suggest that heparin treatment helps in the clearance of cell debris and decreases the immunogenity of secondary necrotic cells.

In vitro anti-breast cancer activity of ethanolic extract of Wrightia tomentosa: role of pro-apoptotic effects of oleanolic acid and urosolic acid

ETHNOPHARMACOLOGICAL RELEVANCE

Wrightia tomentosa Roem. & Schult. (Apocynaceae) is known in the traditional medicine for anti-cancer activity along with other broad indications like snake and scorpion bites, renal complications, menstrual disorders etc. However, the anti-cancer activity of this plant or its constituents has never been studied systematically in any cancer types so far.

AIM OF THE STUDY

To evaluate the anti-cancer activities of the ethanolic extract of W. tomentosa and identified constituent active molecule(s) against breast cancer.

MATERIAL AND METHODS

Powdered leaves of W. tomentosa were extracted with ethanol. The ethanolic extract, subsequent hexane fractions and fraction F-4 of W. tomentosa were tested for its anti-proliferative and pro-apoptotic effects in breast cancer cells MCF-7 and MDA-MB-231.

RESULTS

The ethanolic extract, subsequent hexane fractions and fraction F-4 of W. tomentosa inhibited the proliferation of human breast cancer cell lines, MCF-7 and MDA-MB-231. The fraction F-4 obtained from hexane fraction inhibited proliferation of MCF-7 and MDA-MB-231 cells in concentration and time dependent manner with IC₅₀ of 50 μg/ml and 30 μg/ml for 24 h, 28 μg/ml and 22 μg/ml for 48 h and 25 μg/ml and 20 μg/ml for 72 h respectively. The fraction F-4 induced G1 cell cycle arrest, reactive oxygen species (ROS) generation, loss of mitochondrial membrane potential and subsequent apoptosis. Apoptosis is indicated in terms of increased Bax/Bcl-2 ratio, enhanced Annexin-V positivity, caspase 8 activation and DNA fragmentation. The active molecule isolated from fraction F-4, oleanolic acid and urosolic acid inhibited cell proliferation of MCF-7 and MDA-MB-231 cells at IC₅₀ value of 7.5 μM and 7.0 μM respectively, whereas there is devoid of significant cell inhibiting activity in non-cancer originated cells, HEK-293. In both MCF-7 and MDA-MB-231, oleanolic acid and urosolic acid induced cell cycle arrest and apoptosis as indicated by significant increase in Annexin-V positive apoptotic cell counts.

CONCLUSION

Our results suggest that W. tomentosa extracts has significant anti-cancer activity against breast cancer cells due to induction of apoptosis pathway. Olenolic and urosolic acid are important constituent molecules in the extract responsible for anti-cancer activity of W. tomentosa.

Delayed caspase-8 activation and enhanced integrin β1-activated FAK underpins anoikis in oesophageal carcinoma cells harbouring mt p53-R175H

FAK (focal adhesion kinase)-mediated signalling reportedly suppresses caspase-8 activation and, as a consequence, rescues epithelial cells from Fas-mediated anoikis. Critical was the use of a HOSCC (human oesophageal squamous carcinoma) cell line harbouring mt (mutant) p53-R175H and displaying resistance to detachment and Tyr397 dephosphorylation of FAK. Here we show, although caspase-8 activation is delayed in the mt p53-R175H cell line, comparable apoptotic events evidenced in the wt (wild type) p53 HOSCC cell lines could be induced in the mt p53-R175H cell line by strengthening the apoptotic stimulus. Significant to anoikis-related regulation, the delay in caspase-8 activation was accompanied by the maintenance of FAK Tyr397 phosphorylation, integrin β1-associated FAK and a FAK/caspase-8 complex. Thus, mt p53-R175H may desensitize tumours to Fas-mediated anchorage-independent death via a FAK-dependent mechanism.

Vibrational spectra and assignments of 2-phenylethanol and 2-phenoxyethanol

The structural stability of 2-phenyl- and 2-phenoxyethanols were investigated at the DFT-B3LYP/6-311G**, MP2 and MP4(SDQ) levels of theory. From the calculations at the three levels of theory 2-phenylethanol and 2-phenoxyethanol were predicted to exist predominantly in non-planar gauche conformations. For 2-phenylethanol the lowest energy Gg1 structure was predicted to be stabilized by an interaction between the hydroxyl H atom and the phenyl ring. For 2-phenoxyethanol the Ggg1 structure was predicted to be strongly stabilized by dipolar interactions between the hydroxyl H atom and the phenoxy O atom of the alcohol. For both alcohols the planar trans structure with minimum steric interactions between the CH(2) groups was predicted to be significantly higher in energy than the ground state gauche structure of the alcohols. The dipolar interactions are reported to play more important role than steric ones in stabilizing the molecules. The vibrational frequencies of each of the two alcohols in its lowest energy gauche structure were computed at the B3LYP level and tentative vibrational assignments were made for their normal modes on the basis of the calculated and experimental data.

Development and Validation of a RPLC Method for the Determination of 2-Phenoxyethanol in Senselle Lubricant Formulation

A new and simple reversed-phase liquid chromatographic method has been developed and validated for the determination of 2-phenoxyethanol preservative (0.3%, w/w) in senselle lubricant formulation. The separation was achieved with acetonitrile-tetrahydrofuran-water (21:13:66, v/v/v) as mobile phase, a C(8) column, and UV detection at 258 nm. The calibration curve is linear (r(2)= 0.9999) from 20-140% of the analytical concentration of 0.75 mg/ml. The mean percent relative standard deviation values for intra- and inter-day precision studies are <1%. The recovery of 2-phenoxyethanol ranged between 99.76 and 100.03% from lubricant formulation. The limits of detection and quantitation are determined to be 0.094 and 0.15 mg/ml, respectively. The method was found to be robust and can be successfully and reliably used to determine the 2-phenoxyethanol preservative content of marketed formulations.

Preliminary evaluation of the genotoxic potential of a hydrophilic polymer with three preservation systems

This study compared the genotoxic potential of a polymeric associative thickener used in topically applied emulsions preserved with three different preservative systems. The method used for the assessment of genotoxicity is the in vitro micronucleus test [Organization for Economic Cooperation and Development (OECD) guideline number 487]. When changing an additive such as a preservation system in a raw material, it is crucial to re-evaluate its toxicity potential because this change may significantly alter its properties. This study shows that at the levels tested neither of the systems evaluated demonstrated any cytotoxic or genotoxic effects. Skin exposure must take into consideration factors such as duration, skin condition and metabolism, but most importantly concentration. Although preservatives can be toxic at high concentrations, they are usually safe at the concentrations used in cosmetic raw materials and formulations. If used to preserve raw materials, they undergo further dilution when added to the formulation.

Dual role of nanoparticles as drug carrier and drug

The conventional chemotherapeutic agents used in the treatment of human malignancies are directed nonspecifically against both malignant and nonmalignant cells, often limiting their efficacy with having serious side effects. Recent development of drug delivery vehicles has opened up the possibility of targeted drug delivery systems with the potential of achieving maximum efficacy with minimal toxicity. The possibility of using a nanomaterial as a combinational drug component is intuitively evident as it would compensate the toxicity level by enhancing drug delivery efficiency. Additionally, cell-specific cytotoxicity (reported earlier by our group) of the nanovehicle itself may potentiate a more effective targeted cell killing. In this paper, we explore the possibility of using gold nanoparticles playing the dual role of an anticancer agent and a carrier of a chemotherapeutic drug. This is demonstrated using vincristine sulfate (VS), salt of an alkaloid often used in the treatment of multiple myeloma (MM), and U266 as a test MM cell line. The drug VS shows the expected G2-M-phase arrest of cells. Notably, bare gold nanoparticle shows arrest of the S phase cells that may be particularly important in case of slow-growing malignancies like MM where most of the cells remain in G1 phase of the cell cycle. The VS conjugated gold retains the activity of both gold nanoparticle and VS leading to a synergistic rise of the apoptotic cell population.

Role of p53/FAK association and p53Ser46 phosphorylation in staurosporine-mediated apoptosis: wild type versus mutant p53-R175H

A novel survival role of focal adhesion kinase (FAK) that involves its nuclear translocation and direct association with p53 has been demonstrated. Here we examined the relationship between the p53/FAK interaction and Ser46 phosphorylation of p53 (p-p53(Ser46)) in the apoptotic regulation of human esophageal squamous cell carcinoma (HOSCC) cell lines, expressing either wild type (wt) p53 or mutant (mt) p53-R175H. In contrast to the wt p53 cell lines, the mt p53-R175H cell line was resistant to staurosporine (STS)-mediated detachment and caspase-3 activation. Furthermore, despite the resistance of mt p53-R175H to Ser46 phosphorylation, both wt and mt HOSCC cells translocate FAK into the nucleus and maintain the p53/FAK interaction post STS treatment. These findings provide unique insight into how tumor cells harboring the R175H mutant may resist chemotherapeutic intervention.

Role of intracellular calcium and S-glutathionylation in cell death induced by a mixture of isothiazolinones in HL60 cells

Previously we reported that brief exposure of HL60 cells to a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI) shifts the cells into a state of oxidative stress that induces apoptosis and necrosis. In this study, flow cytometric analysis showed that CMI/MI induces early perturbation of calcium homeostasis, increasing cytosolic and mitochondrial calcium and depleting the intracellular endoplasmic reticulum (ER) stores. The calcium chelator BAPTA-AM reduced necrosis and secondary necrosis, the loss of DeltaPsim and S-glutathionylation induced by necrotic doses of CMI/MI, but did not protect against CMI/MI-induced apoptosis, mitochondrial calcium uptake and mitochondrial hyperpolarization. This indicates that increased cytoplasmic calcium does not have a causal role in the induction of apoptosis, while cross-talk between the ER and mitochondria could be responsible for the induction of apoptosis. GSH-OEt pretreatment, which enhances cellular GSH content, reduced S-glutathionylation and cytosolic and mitochondrial calcium levels, thus protecting against both apoptosis and necrosis shifting to apoptosis. Therefore, the degree of GSH depletion, paralleled by the levels of protein S-glutathionylation, may have a causal role in increasing calcium levels. The mitochondrial calcium increase could be responsible for apoptosis, while necrosis is associated with cytoplasmic calcium overload. These findings suggest that S-glutathionylation of specific proteins acts as a molecular linker between calcium and redox signalling.

Synthesis of mono- and symmetrical di-N-hydroxy- and N-aminoguanidines

Novel mono- and symmetrical di-N-hydroxy- and N-aminoguanidines were readily prepared from the reaction of diverse hydroxylamines or hydrazines with reagent classes di(benzotriazol-1-yl)methanimine 6, (bis-benzotriazol-1-yl-methylene)amines 8a,b, benzotriazole-1-carboxamidines 10a-i, benzotriazole-1-carboximidamides 11a,b, and N'-hydroxy-1H-1,2,3-benzotriazole-1-carboximidamide 18. The preparation is described for a variety of N-hydroxy- and N-aminoguanidines with different substitution patterns in good yields.

Development of a mechanistically-based genetically engineered PC12 cell system to detect p53-mediated cytotoxicity

The human wild type p53 gene, key for apoptosis, was introduced into the pheochromocytoma (PC12) cell line, to create a mechanistically-based in vitro test model for the detection of p53-mediated toxicity. Expression of the wt p53 gene was regulated by a system, which allowed or blocked expression p53 by absence or presence of tetracycline in the culture media. Western blot analyses confirmed an inducible and tetracycline-dependent expression of the wt p53 protein. Functionality of the p53 protein was verified by camptothecin treatment, known to induce p53-dependent apoptosis. Results showed that p53-expressing cells were significantly more sensitive to camptothecin induced cytotoxicity compared to non-expressing cells, and presented a significantly higher incidence of apoptosis. A screening study on 31 metal compounds, showed that the classified human carcinogens (NaAsO2, CdSO4 .8H2O, Na2CrO4 .4H2O, MnCl2, (NH4)2PtCl6) significantly increased cytotoxicity in p53-expressing cells compared to non-expressing cells, suggesting that their cytotoxicity was p53-mediated. Finally, acute and subchronic treatment with methyl mercury showed no significant differences in cytotoxicity and the percentage of apoptosis or necrosis between p53-expressing and non-expressing differentiated cells, suggesting that methyl mercury cytotoxicity was p53-independent.

GSH depletion, protein S-glutathionylation and mitochondrial transmembrane potential hyperpolarization are early events in initiation of cell death induced by a mixture of isothiazolinones in HL60 cells

We recently described that brief exposure of HL60 cells to a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI) induces apoptosis at low concentrations (0.001-0.01%) and necrosis at higher concentrations (0.05-0.1%). In this study, we show that glutathione (GSH) depletion, reactive oxygen species generation, hyperpolarization of mitochondrial transmembrane potential (DeltaPsim) and formation of protein-GSH mixed disulphides (S-glutathionylation) are early molecular events that precede the induction of cell death by CMI/MI. When the cells exhibit common signs of apoptosis, they show activation of caspase-9, reduction of DeltaPsim and, more importantly, decreased protein S-glutathionylation. In contrast, necrosis is associated with severe mitochondrial damage and maximal protein S-glutathionylation. CMI/MI-induced cytotoxicity is also accompanied by decreased activity of GSH-related enzymes. Pre-incubation with L-buthionine-(S,R)-sulfoximine (BSO) clearly switches the mode of cell death from apoptosis to necrosis at 0.01% CMI/MI. Collectively, these results demonstrate that CMI/MI alters the redox status of HL60 cells, and the extent and kinetics of GSH depletion and S-glutathionylation appear to determine whether cells undergo apoptosis or necrosis. We hypothesize that S-glutathionylation of certain thiol groups accompanied by GSH depletion plays a critical role in the molecular mechanism of CMI/MI cytotoxicity.

The relative cytotoxicity of personal care preservative systems in Balb/C 3T3 clone A31 embryonic mouse cells and the effect of selected preservative systems upon the toxicity of a standard rinse-off formulation

Biocide chemicals are commonly used as preservatives for cosmetic and personal care products and the conditions for their use are stipulated in Annex VI of the Cosmetics Directive. In these studies the cytotoxicity (EC50 and EC90) of a range of preservatives including the isothiazolinone family, formaldehyde donors, parabens mixtures and organic acids have been established in the Balb/C 3T3 clone A31 fibroblast cell-line following a 1h exposure. Cell viability was established using the neutral red uptake assay 24h after exposure. The potency of the preservatives spanned several orders of magnitude from the isothiazolinones (EC50<10ppm) to the organic acids (EC50>10,000ppm). Although these values are directly proportional to the anti-microbial efficacy of the actives, they do not reflect the addition levels commonly used to preserve formulations, which are intended to provide prolonged protection against a wide spectrum of spoilage organisms. In a further study, the cytotoxic profile of an unpreserved standard rinse-off body wash formulation was assessed. Two concentrations of the formulation were selected: 0.1% v/v (EC98) and 0.15% v/v (EC82) to study the effects of selected preservative chemicals at recommended addition levels upon the cytotoxicity of the formulation. At 0.1%, only preservation with benzoate/sorbate at the highest addition level increased the toxicity, whereas at 0.15%, preservation with 2-bromo-2-nitro-propane-1,3-diol increased the cytotoxicity of the formulation. No other preservatives, including isothiazolinones and formaldehyde donors affected the basal cytotoxicity of the formulation. Theses studies have provided a standardised assessment of the cytotoxicity of cosmetic preservatives and demonstrated that preservation of a rinse-off formulation at recommended addition levels is unlikely to affect the cytotoxic profile.

Estrogenic activity of 37 components of commercial sunscreen lotions evaluated by in vitro assays

Thirty-seven chemical components of commercial sunscreen lotions were evaluated for estrogen agonistic and/or antagonistic activity using two in vitro assays, (1) an ELISA-based estrogen receptor competitive binding assay (ER-ELISA) and (2) a modified yeast two-hybrid estrogen assay, with and without addition of a rat liver preparation, S9 mix. Eleven compounds, most of which were benzophenone derivatives and parabens, showed binding affinity to ER by ER-ELISA without S9 mix. Although the activities of almost all of the compounds were attenuated by addition of S9 mix, 4-octylphenylsalicylate and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone acquired estrogenic activity, suggesting metabolic activation of these compounds. Two benzophenones showed agonistic activity in the yeast two-hybrid assay without S9 mix. The activity of one of these was reduced by S9 treatment and a further two benzophenones was activated. Eight parabens were active in this assay without S9 exposure, but their activities were eliminated by S9 treatment. Benzophenones with para-phenolic hydroxyl groups and parabens with branched and/or longer linear chains were generally more potent in both bioassays. In addition, weak antagonistic activity of 4-t-butylphenyl-salicylate, 2-ethylhexyl 4-dimethylaminobenzoate and (+/-)-alpha-tocopherolacetate was observed with S9 treatment. In vivo testing of the compounds reported here to have estrogen agonistic and antagonistic activities is required to confirm their effects at an organismal level.

Biochemical and biological aspects of protein thiolation in cells and plasma

Protein thiolation is elicited by oxidation by different mechanisms and is involved in a variety of biological processes. Thiols, protein SH (PSH) and non-protein SH groups (NPSH, namely GSH), are in competition in all biological environments in the regulation of oxidant homeostasis because oxidants thiolate proteins, whereas GSH dethiolates them (e.g., GSSG + PSH --> GSSP + GSH). Although poorly investigated, the elimination of disulfides from thiolated proteins to regenerate critical PSH is important. These aspects are poorly known in cells, where glutaredoxin and peroxiredoxin operate as enzymes or potential chaperones to accelerate dethiolation. On the contrary, studies with plasma or albumin have highlighted the importance of protein conformation in dethiolation processes and have clarified the reason why homocysteine (thiol with potential toxicity) is preferentially bound to albumin as protein-thiol mixed disulfide with respect to other NPSH. Here we provide an overview of protein thiolation/dethiolation processes, with an emphasis on recent developments and future perspectives in this field.

Metronidazole induces programmed cell death in the protozoan parasite Blastocystis hominis

Previous studies by the authors have shown that the protozoan parasite Blastocystis hominis succumbed to a cytotoxic monoclonal antibody with a number of cellular and biochemical features characteristic of apoptosis in higher eukaryotes. The present study reports that apoptosis-like features are also observed in growing cultures of axenic B. hominis upon exposure to metronidazole, a drug commonly used for the treatment of blastocystosis. Upon treatment with the drug, B. hominis cells displayed key morphological and biochemical features of programmed cell death (PCD), viz. nuclear condensation and nicked DNA in nucleus, reduced cytoplasmic volume, externalization of phosphatidylserine and maintenance of plasma membrane integrity with increasing permeability. This present study also supports the authors' previously postulated novel function for the B. hominis central vacuole in PCD; it acts as a repository where apoptotic bodies are stored before being released into the extracellular space. The implications and possible roles of PCD in B. hominis are discussed.

Involvement of oxidative stress in apoptosis induced by a mixture of isothiazolinones in normal human keratinocytes

A 3:1 combination of 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI) is widely used to preserve cosmetic products. We show here that CMI/MI induced apoptosis in normal human keratinocytes (NHK) as at low concentrations (0.001-0.05% documented by subdiploid DNA content and phosphatidylserine exposure, while at the highest concentration (0.1% as supplied, 15 p.p.m.) the response was necrosis. Various molecular events accompanied the cytotoxic effects of CMI/MI. Generation of ROS and hyperpolarization of mitochondrial transmembrane potential (DeltaPsim) were early events, followed by increased Fas expression and activation of caspase-8, and then activation of caspase-3 and -9. The drop in DeltaPsim occurred only later in the cell death pathway, when NHK showed signs of apoptosis. Pretreatment of cells for 2 h with the redox-active agent N-acetyl-L-cysteine conferred complete protection against the CMI/MI-induced cytotoxic effects, DeltaPsim loss, and apoptosis. The pan-caspase inhibitor Z-Val-Ala-Asp(OMe)-CH2F blocked the CMI/MI-induced apoptosis without preventing ROS generation and the drop in DeltaPsim. These results indicate that the generation of ROS plays an important part in mediating apoptosis and necrosis associated with CMI/MI treatment. This new aspect of the in vitro toxicity of CMI/MI may provide important information about the relationship between the preservative's in vitro apoptotic activity and its in vivo toxicity.

Antioxidants in dermocosmetology: from the laboratory to clinical application

Oxygen situated in cutaneous cells can be activated by light. This makes the integumentary apparatus particularly vulnerable to oxidative damage and is responsible for the immediate cutaneous damage that is the basis of late phenomena, such as photo-induced ageing and tumours. Thus, the cosmetic industry has undertaken research and development into antioxidant-based products able to protect the skin from the effect of pro-oxidizing noxae. This review re-examines both antioxidants suitable for dermatological application and skin care products with antioxidant capacity, as well as the laboratory methods used to evaluate the effects and in vivo efficacy of antioxidants.

In vitro neurotoxicity of methylisothiazolinone, a commonly used industrial and household biocide, proceeds via a zinc and extracellular signal-regulated kinase mitogen-activated protein kinase-dependent pathway

Neurodegenerative disorders in humans may be triggered or exacerbated by exposure to occupational or environmental agents. Here, we show that a brief exposure to methylisothiazolinone, a widely used industrial and household biocide, is highly toxic to cultured neurons but not to glia. We also show that the toxic actions of this biocide are zinc dependent and require the activation of p44/42 extracellular signal-regulated kinase (ERK) via a 12-lipoxygenase-mediated pathway. The cell death process also involves activation of NADPH oxidase, generation of reactive oxygen species, DNA damage, and overactivation of poly(ADP-ribose) polymerase, all occurring downstream from ERK phosphorylation. The toxic effects of methylisothiazolinone and related biocides on neurons have not been reported previously. Because of their widespread use, the neurotoxic consequences of both acute and chronic human exposure to these toxins need to be evaluated.