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

Anxiety caused by chronic exposure to methylisothiazolinone in zebrafish: Behavioral analysis, brain histology and gene responses

Methylisothiazolinones (MIT) are a class of preservatives and biocides extensively utilized in everyday products, industrial processes, and medical and healthcare applications. However, reports have indicated that MIT may cause skin irritation and neurotoxicity. Given its pervasive use, the neurotoxic potential of MIT has garnered increasing attention. Recent in vitro cellular experiments have demonstrated that MIT inhibits synaptic growth, although the neurotoxic effects and underlying mechanisms at the organismal level remain largely unexplored. In this study, it was found for the first time that long-term exposure to MIT resulted in anxiety, brain tissue inflammation, and a reduction in the number of Nissl bodies in the brain. Additionally, transcriptomic analysis indicated that exposure to 300 μg/L MIT induced a greater number of differentially expressed genes compared to 30 μg/L MIT, relative to the control group. Enrichment analysis, trend analysis, and GSEA analysis collectively identified the involvement of Steroid hormone metabolism, oxidative metabolism, and the Hedgehog pathway in MIT-induced neurotoxicity. Furthermore, a subsequent reduction in green fluorescence was observed in the MLS-EGFP zebrafish strain larvae of the HD group, suggesting that high dosage of MIT exerts an inhibitory effect on mitochondrial activity. This study confirmed the neurotoxic effects of MIT and investigated the potential genetic networks behind anxiety behavior. These findings contributed to the identification of key brain genes involved in the detection and monitoring of MIT, offering new insights into the neuroendocrine toxicity of other imidazolidinone compounds.

A systematic review and BMD modeling approach to develop an AOP for humidifier disinfectant-induced pulmonary fibrosis and cell death

Dosimetry modeling and point of departure (POD) estimation using in vitro data are essential for mechanism-based hazard identification and risk assessment. This study aimed to develop a putative adverse outcome pathway (AOP) for humidifier disinfectant (HD) substances used in South Korea through a systematic review and benchmark dose (BMD) modeling. We collected in vitro toxicological studies on HD substances, including polyhexamethylene guanidine hydrochloride (PHMG-HCl), PHMG phosphate (PHMG-p), a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (CMIT/MIT), CMIT, and MIT from scientific databases. A total of 193 sets of dose-response data were extracted from 34 articles reporting in vitro experimental results of HD toxicity. The risk of bias (RoB) in each study was assessed following the office of health assessment and translation (OHAT) guideline. The BMD of each HD substance at different toxicity endpoints was estimated using the US Environmental Protection Agency (EPA) BMD software (BMDS). Interspecies- or interorgan differences or most critical effects in the toxicity of the HD substances were analyzed using a 95% lower confidence limit of the BMD (BMDL). We found a critical molecular event and cells susceptible to each HD substance and constructed an AOP of PHMG-p- or CMIT/MIT-induced damage. Notably, PHMG-p induced ATP depletion at the lowest in vitro concentration, endoplasmic reticulum (ER) stress, epithelial-to-mesenchymal transition (EMT), inflammation, leading to fibrosis. CMIT/MIT enhanced mitochondrial reactive oxygen species (ROS) production, oxidative stress, mitochondrial dysfunction, resulting in cell death. Our approach will increase the current understanding of the effects of HD substances on human health and contribute to evidence-based risk assessment of these compounds.

Alveoli-Like Multifunctional Scaffolds for Optical and Electrochemical In Situ Monitoring of Cellular Responses from Type II Pneumocytes

While breathing, alveoli are exposed to external irritants, which contribute to the pathogenesis of lung disease. Therefore, in situ monitoring of alveolar responses to stimuli of toxicants under in vivo environments is important to understand lung disease. For this purpose, 3D cell cultures are recently employed for examining cellular responses of pulmonary systems exposed to irritants; however, most of them have used ex situ assays requiring cell lysis and fluorescent labeling. Here, an alveoli-like multifunctional scaffold is demonstrated for optical and electrochemical monitoring of cellular responses of pneumocytes. Porous foam with dimensions like the alveoli structure is used as a backbone for the scaffold, wherein electroactive metal-organic framework crystals, optically active gold nanoparticles, and biocompatible hyaluronic acid are integrated. The fabricated multifunctional scaffold allows for label-free detection and real-time monitoring of oxidative stress released in pneumocytes under toxic-conditions via redox-active amperometry and nanospectroscopy. Moreover, cellular behavior can be statistically classified based on fingerprint Raman signals collected from the cells on the scaffold. The developed scaffold is expected to serve as a promising platform to investigate cellular responses and disease pathogenesis, owing to its versatility in monitoring electrical and optical signals from cells in situ in the 3D microenvironments.

Adverse effects of SYP-3343 on zebrafish development via ROS-mediated mitochondrial dysfunction

As a newly-invented and highly-efficiency strobilurin fungicide, pyraoxystrobin (SYP-3343) has been recognized as a highly poisonous toxin for a variety of aquatic organisms. Nevertheless, the developmental toxicity and potential mechanism of SYP-3343 have not been well-documented. The results showed that SYP-3343 was relatively stable and maintained within the range of 20 % in 24 h, and the LC₅₀ value to embryos at 72 hpf was 17.13 μg/L. The zebrafish embryotoxicity induced by 1, 2, 4, and 8 μg/L SYP-3343 is demonstrated by repressive embryo incubation, enhancive mortality rate, abnormal heart rate, malformed morphological characteristic, and impaired spontaneous coiling, indicating SYP-3343 mostly exerted its toxicity in a dose- and time-dependent manner. Besides SYP-3343 was critically involved in regulating cell cycle, mitochondrial membrane potential, and reactive oxygen species production as well as zebrafish primary cells apoptosis, which can be mitigated using antioxidant N-acetyl-L-cysteine. A significant change occurred in total protein content, the biochemical indices, and antioxidant capacities owing to SYP-3343 exposure. Additionally, SYP-3343 altered the mRNA levels of heart development-, mitochondrial function-, and apoptosis-related genes in zebrafish embryos. These results indicated that SYP-3343 induced apoptosis accompanying reactive oxygen species-initiated mitochondrial dysfunction in zebrafish embryos.

Functional and dynamic mitochondrial damage by chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) mixture in brain endothelial cell lines and rat cerebrovascular endothelium

The mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT, chloromethylisothiazolinone) and 2-methyl-4-isothiazolin-3-one (MIT, methylisothiazolinone) is a commonly used biocide in consumer products. Despite the health issues related to its usage in cosmetics and humidifier disinfectants (HD), understanding its adverse outcome is still limited. Using in vitro cell lines and ex vivo rat models, we examined the effects of CMIT/MIT on the cellular redox homeostasis and energy metabolism in the brain microvascular endothelium, a highly restrictive interface between the bloodstream and brain. In murine bEND.3 and human hCMEC/D3, CMIT/MIT significantly amplified the mitochondrial-derived oxidative stress causing disruption of the mitochondrial membrane potential and oxidative phosphorylation at a sub-lethal concentration (1 μg/mL) or treatment duration (1 h). In addition, CMIT/MIT significantly increased a dynamic imbalance between mitochondrial fission and fusion, and endogenous pathological stressors significantly potentiated the CMIT/MIT-induced endothelial dysfunction. Notably, in the brain endothelium isolated from intravenously CMIT/MIT-administered rats, we observed significant mitochondrial damage and decreased tight junction protein. Taken together, we report that CMIT/MIT significantly impaired mitochondrial function and dynamics resulting in endothelial barrier dysfunction, giving an insight into the role of mitochondrial damage in CMIT/MIT-associated systemic health effects.

Toxicity of innovative antifouling additives on an early life stage of the oyster Crassostrea gigas: short- and long-term exposure effects

Recent advances in nanotechnology have allowed the encapsulation of hazardous antifouling (AF) biocides in silica mesoporous nanocapsules (SiNC) reducing their short-term toxicity. However, the chronic effects of such novel nanoadditives remain understudied. The present study aimed to assess short- and long-term sub-lethal effects of soluble forms (DCOIT and Ag) and nanostructured forms (SiNC-DCOIT and SiNC-DCOIT-Ag) of two AF biocides and the "empty" nanocapsule (SiNC) on juveniles of Crassostrea gigas after 96 h and 14 days of exposure. Juvenile oysters exposed for a short period to free DCOIT and AgNO₃ presented worse physiological status comparing with those exposed to the nanostructured forms. The long-term exposure to DCOIT and Ag⁺ caused an extensive biochemical impairment comparing with the tested nanomaterials, which included oxidative damage, activation of the antioxidant defense system, and neurotransmission impairment. Despite the negative effects mostly observed on the health condition index and AChE, the encapsulation of the abovementioned AF biocides into SiNC seems to be a technological advantage towards the development of AF nanoadditives with lower long-term toxicity comparing with the soluble forms of such biocides.

Isothiazolinones as Novel Candidate Insecticides for the Control of Hemipteran Insects

Hemipteran insects, such as whiteflies, aphids and planthoppers, resemble one of the most important pest groups threating food security. While many insecticides have been used to control these pests, many issues such as insecticide resistance have been found, highlighting the urgent need to develop novel insecticides. Here, we first observed that a commercial tetramycin solution was highly effective in killing whitefly. The major bioactive constituents were identified to be isothiazolinones, a group of biocides. We then tested the toxicity of several isothiazolinones to five hemipteran insects. The results show that Kathon, a widely used biocide against microorganisms, and its two constituents, chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT), can cause considerable levels of mortality to whiteflies and aphids when applied at concentrations close to, or lower than, the upper limit of these chemicals permitted in cosmetic products. The results also indicate that two other isothiazolinones, benzisothiazolinone (BIT) and octylisothiazolinone (OIT) can cause considerable levels of mortality to whitefly and aphids but are less toxic than Kathon. Further, we show that Kathon marginally affects whitefly endosymbionts, suggesting its insecticidal activity is independent of its biocidal activity. These results suggest that some isothiazolinones are promising candidates for the development of a new class of insecticides for the control of hemipteran pests.

Critical window of exposure of CMIT/MIT with respect to developmental effects on zebrafish embryos: Multi-level endpoint and proteomics analysis

Systemic toxicity, particularly, developmental defects of humidifier disinfectant chemicals that have caused lung injuries in Korean children, remains to be elucidated. This study evaluated the mechanisms of the adverse effects of 5-chloro-2-methyl-4-isothiazoline-3-one/2methyl-4-isothiazolin-3-one (CMIT/MIT), one of the main biocides of the Korean tragedy, and identify the most susceptible developmental stage when exposed in early life. To this end, the study was designed to analyze several endpoints (morphology, heart rate, behavior, global DNA methylation, gene expressions of DNA methyl-transferases (dnmts) and protein profiling) in exposed zebrafish (Danio rerio) embryos at various developmental stages. The results showed that CMIT/MIT exposure causes bent tail, pericardial edema, altered heart rates, global DNA hypermethylation and significant alterations in the locomotion behavior. Consistent with the morphological and physiological endpoints, proteomics profiling with bioinformatics analysis suggested that the suppression of cardiac muscle contractions and energy metabolism (oxidative phosphorylation) were possible pivotal underlying mechanisms of the CMIT/MIT mediated adverse effects. Briefly, multi-level endpoint analysis indicated the most susceptible window of exposure to be ≤ 6 hpf followed by ≤ 48 hpf for CMIT/MIT. These results could potentially be translated to a risk assessment of the developmental exposure effects to the humidifier disinfectants.

Early life exposure of a biocide, CMIT/MIT causes metabolic toxicity via the O-GlcNAc transferase pathway in the nematode C. elegans

Unusual cases of fatal lung injury, later determined to be a result of exposure to chemicals used as humidifier disinfectants, were reported among Korean children from 2006 to 2011. This resulted in considerable study of the pulmonary toxicity of humidifier disinfectant chemicals to establish the causal relationship between exposure and lung disease. However, the systemic toxicity of the former and health effects other than lung disease are not fully understood. Here, we investigated the effect of 5-chloro-2-methyl-4-isothiazoline-3-one and 2-methyl-4-isothiazolin-3-one (CMIT/MIT), among the humidifier disinfectants used in the accidents, on the development of metabolic toxicity in the model organism, Caenorhabditis elegans using an exposure scenario comparison. We screened the potential of CMIT/MIT to induce metabolic toxicity using C. elegans oga-1(ok1207) and ogt-1(ok1474) mutants. We also performed a pathway analysis based on C. elegans transcription factor RNAi library screening to identify the underlying toxicity mechanisms. Finally, to understand the critical window of exposure for metabolic toxicity, responses to exposure during different periods in the life cycles of the worms were compared. We determined that CMIT/MIT could induce metabolic toxicity through O-linked N-acetylglucosamine transferase and early life seems to be the critical window for exposure for metabolic toxicity for this substance. The O-linked N-acetylglucosamine transferase pathway is conserved from worms to humans; our results thus insinuate that early-life exposure to CMIT/MIT could cause metabolic health problems during adult life in humans. We therefore suggest that a systemic toxicity approach should be considered to comprehensively understand the adverse health effects of humidifier disinfectant misuse.

Effects of sublethal concentrations of the antifouling biocide Sea-Nine on biochemical parameters of the marine polychaete Perinereis aibuhitensis

Sea-Nine™ 211 is an emerging biocide that has an adverse impact on aquatic environments. In this study, the marine polychaete Perinereis aibuhitensis was exposed to Sea-Nine (0.1, 1, and 10 μg L^-1), and acute toxicity and biochemical responses such as changes in the intracellular contents of malondialdehyde (MDA) and glutathione (GSH) and enzymatic activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and acetylcholinesterase (AChE) were evaluated over a period of 14 d. Determined median lethal doses, LC50 were 268 μg L^-1, 142 μg L^-1, and 55 μg L^-1 at 24 h, 96 h, and 14 d, respectively. The MDA content increased significantly in a dose- and time-dependent manner, indicative of lipid peroxidation-related oxidative damage. Significantly higher intracellular GSH levels and antioxidant defense-related enzyme (CAT, SOD, GPx, GR, and GST) activities were observed after exposure to 10 μg L^-1 Sea-Nine. In contrast, Sea-Nine treatment significantly reduced AChE activity at the highest concentration of Sea-Nine used (10 μg L^-1). Taken together, these results indicate that sublethal concentrations of Sea-Nine are toxic to marine polychaetes through potential lipid peroxidation, induction of oxidative stress, and modulation of the cholinergic system. Our results can contribute to biomonitoring of aquatic environments and ecotoxicological research through the measurements of polychaete cellular defenses against waterborne biocides.

Effects of the biocide methylisothiazolinone on Xenopus laevis wound healing and tail regeneration

The South African clawed frog, Xenopus laevis, has a strong history as a suitable model for environmental studies. Its embryos and transparent tadpoles are highly sensitive to the environment and their developmental processes are well described. It is also amenable for molecular studies. These characteristics enable its use for rapid identification and understanding of exposure-induced defects. To investigate the consequences of chemical exposure on aquatic animals, Xenopus laevis embryos and tadpoles were exposed to the biocide, methylisothiazolinone (MIT). Frog tadpoles exposed to MIT following tail amputation lost their natural regenerative ability. This inhibition of regeneration led to a failure to regrow tissues including the spinal cord, muscle, and notochord. This MIT-dependent regenerative defect is due to a failure to close the amputation wound. A wound healing assay revealed that while untreated embryos close their wounds within one day after injury, MIT-treated animals maintained open wounds that did not reduce in size and caused lethality. Concomitant exposure of MIT with chemicals containing thiol groups such as glutathione and N-acetyl cysteine restored normal wound healing and regeneration responses in tadpoles. Together these results indicate that exposure to MIT impairs developmental wound repair and tissue regeneration in Xenopus laevis. Thus, this study reveals new aspects of MIT activity and demonstrates that Xenopus laevis is a well-suited model for facilitating future research into chemical exposure effects on injury responses.

Abnormal visual processing and increased seizure susceptibility result from developmental exposure to the biocide methylisothiazolinone

Methylisothiazolinone (MIT) is a commonly used biocide known to be neurotoxic in vitro. Brief exposure of cortical neurons in culture to MIT results in increased neurodegeneration, whereas chronic exposure of developing neurons in culture to low concentrations of MIT has been shown to interfere with normal neurite outgrowth. However, the effects of chronic MIT exposure on the developing nervous system have not been tested in vivo. Here we expose Xenopus laevis tadpoles to sub-lethal concentrations of MIT during a critical period in neural development. We find that MIT exposure results in deficits in visually mediated avoidance behavior and increased susceptibility to seizures, as well electrophysiological abnormalities in optic tectal function, without any effects on overall morphology, gross anatomy of the visual projections, overall visual function, and swimming ability. These effects indicate that chronic exposure to low levels of MIT results in neural circuit-level deficits that result in abnormal neurological function without causing increased mortality or even gross anatomical defects. Our findings, combined with the fact that the long-term neurological impacts of environmental exposure to MIT have not been determined, suggest a need for a closer evaluation of the safety of MIT in commercial and industrial products.

Protective effect of components isolated from Lindera erythrocarpa against oxidative stress-induced apoptosis of H9c2 cardiomyocytes

Eight compounds were isolated from the methanol fraction of Lindera erythrocarpa and assessed for their ability to protect H9c2 cardiomyocytes against oxidative stress-induced cell death. Three of the compounds significantly reduced the release of lactate dehydrogenase from H9c2 cardiomyocytes treated with buthionine-[S,R]-sulfoximine and reduced the uptake of propidium iodide by these cells. These effects were concentration-dependent. The three inhibitory compounds were identified as (-)-epicatechin, avicularin and quercitrin by spectroscopic techniques including one- and two-dimensional NMR and mass spectroscopy.

New insights in toxic epidermal necrolysis (Lyell's syndrome): clinical considerations, pathobiology and targeted treatments revisited

Drug-induced toxic epidermal necrolysis (TEN), also known as Lyell's syndrome, is a life-threatening drug reaction characterized by extensive destruction of the epidermis and mucosal epithelia. The eyes are typically involved in TEN. At present, the disease has a high mortality rate. Conceptually, TEN and the Stevens-Johnson syndrome are closely related, although their severity and outcome are different. Distinguishing TEN from severe forms of erythema multiforme relies on consideration of aetiological, clinical and histological characteristics. The current understanding of the pathomechanism of TEN suggests that keratinocytes are key initiator cells. It is probable that the combined deleterious effects on keratinocytes of both the cytokine tumour necrosis factor (TNF)-alpha and oxidative stress induce a combination of apoptotic and necrotic events. As yet, there is no evidence indicating the superiority of monotherapy with corticosteroids, ciclosporin (cyclosporine) or intravenous immunoglobulins over supportive care only for patients with TEN. However, the current theory of TEN pathogenesis supports the administration of a combination of antiapoptotic/antinecrotic drugs (e.g. anti-TNF-alpha antibodies plus N-acetylcysteine) targeting different levels of the keratinocyte failure machinery.

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.

Structure-activity relationships for the impact of selected isothiazol-3-one biocides on glutathione metabolism and glutathione reductase of the human liver cell line Hep G2

To investigate the toxic mode of action of isothiazol-3-one biocides the four compounds N-methylisothiazol-3-one (MIT), 5-chloro-N-methylisothiazol-3-one (CIT), N-octylisothiazol-3-one (OIT) and 4,5-dichloro-N-octylisothiazol-3-one (DCOIT) were purified and tested as single chemical entities for their effects on the human hepatoblastoma cell line Hep G2 and on isolated and cellular glutathione reductase GR). The two chlorinated substances CIT and DCOIT significantly decreased the amount of total cellular glutathione (GSx) in a dose and time dependent manner. Concomitantly, an increase in the level of oxidised glutathione (GSSG) was observed. The resulting shift in the GSH/GSSG ratio entailing the breakdown of the cellular thiol reduction potential was accompanied by necrotic morphological changes like swelling of the plasma membrane and subsequent lysis of the cells. Additionally, CIT and DCOIT were found to inhibit cellular GR in the cells in a concentration dependent manner. The T-SAR-based (thinking in terms of structure-activity relationships) comparison of the chlorine-substituted structures CIT and DCOIT with their non-chlorinated and less active analogues MIT and OIT identified the chlorine substituents and the resulting reaction mechanisms to be the key structural mediators of the observed toxic effects. Furthermore, differences in the activity of both chlorinated substances could be explained using the T-SAR approach to link the lipophilicity and the intrinsic glutathione-reactivity of the compounds to the expected target site concentrations inside the cells.

Induction of keratinocyte apoptosis by photosensitizing chemicals plus UVA

BACKGROUND

The capacity of photosensitizing chemicals with ultraviolet A light (UVA) to induce apoptosis is one of the methods to assess their phototoxic and potentially photoallergic properties, since apoptotic cells may be easily presented by antigen-presenting cells.

OBJECTIVES

We examined the photoaggravated ability to induce keratinocyte apoptosis of various chemicals that are known as causative agents of photocontact dermatitis and drug photosensitivity involving photoallergic and/or phototoxic mechanisms.

METHODS

HaCaT keratinocytes were incubated with 3,3',4',5-tetrachlorosalicylanilide (TCSA), bithionol, diphenylhydramine, chlorpromazine, 6-methylcoumarin, sparfloxacin, and enoxacin at 10(-7) to 10(-4)M and irradiated with UVA at 4J/cm(2). As positive control, 8-methoxypsoralen (8-MOP) was also tested. Apoptosis and necrosis were evaluated by flow cytometric enumeration of annexin V(+) 7-AAD(-) and annexin V(+) 7-AAD(+) cells, respectively. The expression of apoptosis-related molecules, caspase-3 and poly (ADP-ribose) polymerase (PARP), was tested by flow cytometric and Western blotting analyses.

RESULTS

In a comparison with non-irradiated cells, significant apoptosis was found in TCSA, bithionol, chlorpromazine, sparfloxacin and enoxacin at 10(-4) or 10(-5)M as well as 8-MOP as assessed by both annexin V and active caspase-3 stainings, while necrosis occurred in most of these chemicals at 10(-4)M. Neither apoptosis nor necrosis was seen in diphenylhydramine or 6-methylcoumarin. PARP were activated in HaCaT cells phototreated with TCSA, bithionol and chlorpromazine.

CONCLUSIONS

We suggest that our method is useful for in vitro assessment of phototoxicity and potential photoallergenicity of chemicals.

Psychosine-induced apoptosis and cytokine activation in immune peripheral cells of Krabbe patients

Globoid cell leukodystrophy or Krabbe disease (KD), is a hereditary disorder caused by galactosylceramidase deficiency. Progressive accumulation of psychosine is considered to be the critical pathogenetic mechanism of cell death in the Krabbe brain. Psychosine mechanism of action has not been fully elucidated. It seems to induce apoptosis in oligodendrocytes through a mitochondrial pathway and to up-regulate inflammatory cytokines production resulting in oligodendrocyte loss. Our aim was to evaluate the role of psychosine in apoptotic cell death and inflammatory response in a group of patients affected by KD using peripheral blood lymphocytes (PBLs) and peripheral blood mononuclear cells (PBMCs) as a cellular model. PBLs from KP and healthy controls were exposed to 20 microM psychosine and analysed by flow cytometry, agarose gel electrophoresis and fluorescence microscopy. Our results showed that psychosine induces apoptosis in PBLs through a mitochondrial pathway, but the apoptotic response was quite low especially KP. The role of psychosine in the up-regulation of cytokines (TNFalpha, IL8 and MCP1) has been evaluated by ELISA in PBMCs from KP and controls after stimulation with LPS and phytohemagglutinin. Both in basal condition and after LPS stimulation, cells from KP showed a significant increase in TNF-alpha production, reduced MCP1 levels and no modification in IL8. These results indicate that lymphomonocytes from KP had a basal proinflammatory pattern that was amplified by psychosine. In conclusion, the reduced apoptotic response and the atypical cytokine production observed in our experiments, suggest an involvement of inflammatory pattern in immune peripheral cells of KP.

Date seed oil limit oxidative injuries induced by hydrogen peroxide in human skin organ culture

The skin is chronically exposed to pro-oxidant agents, leading to the generation of reactive oxygen species (ROS). To protect the skin against an over-load of oxidant species, we studied the chemoprotective effect of one new natural product: "date seed oil: DSO". This oil may serve as a potential source of natural antioxidants such as phenols and tocopherols. Here, the antioxidative potential of DSO was compared that of to extra virgin olive oil. Adult human skin was maintained in organ culture in the presence of the DSO and extra virgin olive oil before the addition of hydrogen peroxide (H2O2), in order to prevent the tissue from its oxidizing effects. Skin specimens were collected for histology and for melanin studies. In the investigated model system, DSO protects skin against oxidative injuries. It has a significant chemoprotective effect, by inhibition of damage caused by H_{2}O_{2} compared with specimens without such addition endowing with a radical scavenging ability. The various components from DSO were much more potent antioxidant and more free radical scavengers of the H2O2 than those of olive oil. Our study shows that topical DSO treatment of the skin stimulates events in the epidermis leading to repair skin damage possibly due to antioxidant synergisms.

Methylisothiazolinone, a neurotoxic biocide, disrupts the association of SRC family tyrosine kinases with focal adhesion kinase in developing cortical neurons

Methylisothiazolinone (MIT) is a biocide widely used in industrial and cosmetic products with potential as a neurotoxicant. We previously reported that short acute exposures to relatively high concentrations of MIT (100 microM) lead to widespread and selective neuronal death in vitro. To evaluate the biological properties of chronic exposures to MIT, freshly dissociated rat cortical neurons were continuously exposed to low concentrations (0.1-3 microM) of the biocide in serum-containing media. Although we observed minimal effects on cell viability, MIT induced a dramatic inhibition of neurite outgrowth. Immunoblotting and immunoprecipitation experiments revealed that focal adhesion kinase (FAK) phosphorylation was primarily affected by the MIT treatment. The phosphorylation level at tyrosines 576 and 861 of FAK was significantly decreased and likely contributed to the overall reduction of tyrosine phosphorylation of this protein. MIT inhibited Src family kinases (SFKs) in cell-free assays and led to the physical dissociation of FAK from the signaling complexes that it normally forms with c-Src and Fyn in developing neurons. High-density neuronal cultures were then employed to increase cell-to-cell contact. This approach resulted in an overall enhancement of SFKs and FAK phosphorylation and could overcome the deficits induced by MIT. This study suggests that a disruption of FAK-SFK complexes due to SFK inhibition leads to FAK dysfunction, with detrimental effects to immature neurons. Prolonged exposure to low levels of MIT and related compounds may have damaging consequences to the developing nervous system.

Programmed cell death of stressed keratinocytes and its inhibition by vitamin D: The role of death and survival signaling pathways

The epidermis is confronted with multiple environmental and pathophysiological stresses. This study shows that TNFalpha, oxidative stress, hyperosmotic and heat shock induced both caspase-dependent and independent cell death in human HaCaT keratinocytes. The hormonal form of vitamin D, 1,25(OH)2D3, which is an autocrine hormone in the epidermis, protected the cells from all the examined stresses and pathways leading to cell death. We aimed to define the signaling pathways that determine the life-death balance of stressed keratinocytes and participate in their protection by 1,25(OH)2D3. As assessed by employing specific inhibitors, the survival pathways mediated by the EGF receptor, ERK, PI-3K or Src kinase, or basal transcriptional activity are important for unstressed cell survival. However, only the EGF receptor, PI-3K and the Src kinase pathways mediate the survival of stressed cells in a stimulus-specific manner. Inhibition of the p38 and/or the JNK death pathways reduced caspase activation induced by oxidative stress, hyperosmotic shock and TNFalpha. The protective effect of 1,25(OH)2D3 was not mediated by the examined survival pathways. 1,25(OH)2D3 inhibited the stress-induced activation of p38 and JNK. Since mimicking this effect by pharmacological inhibition resulted in the attenuation of caspase activation, we infer that these pathways are involved in keratinocyte protection by 1,25(OH)2D3.

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.

Human fibroblasts undergo oxidative stress-induced apoptosis without internucleosomal DNA fragmentation

In order to evaluate the reliability of fibroblasts as a cell model for studying apoptosis, we tested the response of normal human fibroblasts to the oxidative stress inducers H(2)O(2) and 2-deoxy-D-ribose (dRib). Our results showed that fibroblasts treated with dRib and H(2)O(2) are induced to undergo apoptosis as demonstrated by reduction in total cell number, chromatin condensation, phosphatidylserine (PS) exposure, activation of caspase-3 and 7, changes in mitochondrial membrane potential and increase in the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive nuclei. However we only found a slight increase in the percentage of cells in the sub-G1 region evaluated by flow cytometry, and we did not observe DNA fragmentation by agarose gel electrophoresis. Early in apoptosis, DNA cleavage generates high molecular weight (HMW) fragments which can be detected by TUNEL assay; successively followed by a pronounced DNA brake down into low molecular weight (LMW) fragments, detected as a "DNA ladder" by conventional agarose gel electrophoresis and as an hypodiploid peak by propidium iodide (PI) flow cytometry assay. Our results thus suggest that only HMW fragmentation occurs in fibroblasts exposed to dRib or H(2)O(2) and the lack of internucleosomal DNA fragmentation may depend on the peculiar characteristics of human fibroblasts themselves, irrespective of the apoptotic stimulus used. The existence of distinct events leading to cell death in different cell types makes it necessary to use a combination of strategies and techniques to evaluate the occurrence of apoptosis.

Protective effect of KR-31378 on oxidative stress in cardiac myocytes

In this study, we investigated whether a novel anti-ischemic KATP opener KR-31378 [(2S,3S,4R)-N"-cyano-N-(6-amino-3,4-dihydro-3-hydroxy-2-methly-2-dimethoxymethly-2H-benzopyran-4-yl)-N'-benzylguanidine] has protective effect against oxidative stress-induced death in heart-derived H9c2 cells. Cell death was induced by BSO, butionine sulfoximine, which inhibits GSH synthesis and subsequently increases reactive oxygen species (ROS) level. Cell death was quantitatively determined by measuring lactate dehydrogenase (LDH) activity and stained by Hoechst 33258. BSO-induced ROS production and mitochondrial membrane potential (MMP) were measured using 2',7'-dichlorofluorescein diacetate oxidation and rhodamine 123, respectively. Both the LDH release and the ROS elevation induced by treatment of H9c2 cells with 10 mM BSO, were significantly decreased by KR-31378. These protective effect and antioxidant effect of KR-31378 appeared to be independent on KATP channel opening. Cells exposed to BSO showed an early reduction in MMP, and this reduction in MMP was significantly reversed by treatment with KR-31378. Caspase-3 activity in BSO treated H9c2 cells was remarkably increased, and this increased caspase-3 activity was significantly reversed by KR-31378. In conclusion, our results suggest that KR-31378 can produce cardioprotective effect against oxidative stress-induced cell death through antioxidant mechanism.

Psi-Screen, an In Vitro Toxicity Test System: Applications in the Bioassay of Perfumes and Fragrance Chemicals

The effects of 65 perfume formulations (perfume oils, perfumes, eau de parfum, eau de toilette) on mitochondrial membrane potential (ΔΨm) and mitochondrial respiration have been investigated using a mitochondria-based assay for ΔΨm, termed Psi-Screen. All the perfume formulations tested are highly active in the Psi-Screen assay, and the major site of inhibition in all cases is NADH-ubiquinone reductase (Complex I). This is confirmed in studies on the inhibition of NADH oxidase and NADH-ubiquinone reductase. Some formulations also inhibit succinate oxidation at either Complex II or Complex III. Evidence for the inhibition of mitochondrial ATPase is presented, as well as for the induction of reactive oxygen species production by perfume inhibition of Complex I. Thus, perfume formulations are multiple inhibitor mixtures which inhibit multiple bioenergetic functions at high dilutions (103 to 7 × 104). The implications of these findings are discussed with respect to cell toxicity via necrosis and/or apoptosis. Twenty candidate fragrance chemicals were investigated and all inhibited Complex I (5 at < 35μM). Mass screening strategies and high-throughput screening assays are discussed.

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.

Novel Treatments for Drug-Induced Toxic Epidermal Necrolysis (Lyell’s Syndrome)

Drug-induced toxic epidermal necrolysis (TEN) is a life-threatening disease characterized by extensive destruction of the epidermis. It apparently results from the formation of specific toxic drug metabolites by the keratinocytes. The mortality rate which averages 25-30% is mainly due to secondary septicemia, and to ionic and metabolic disturbances following loss of epidermal integrity. Apoptosis is the likely mechanism leading to massive keratinocyte death in TEN. Dysregulations in the tumor necrosis factor-alpha (TNF-alpha) pathway, CD95 system (Fas ligand, CD95L; Fas receptor, CD95R) and calcium homeostasis in the epidermis are involved in this apoptotic process. An active role has also been ascribed to T lymphocytes, macrophages and factor XIIIa-positive dermal dendrocytes. Despite progress, treatment of TEN remains controversial. In the past, systemic glucocorticoids were used in order to target the inflammatory reaction in TEN. However, there was no evidence for improvement of the healing process, while corticosteroids worsened the prognosis by increasing the risk of septicemia. Only a few cases have been treated with other drugs including cyclophosphamide, pentoxyfilline, thalidomide, anti-TNF-alpha antibodies and cyclosporin A. In the recent past, some TEN patients were treated with intravenous human immunoglobulins (IVIG). The rationale for such a treatment was to block the CD95 system on keratinocytes. The early promising clinical results of IVIG treatment in TEN were subsequently challenged. This review compares the effectiveness and drawbacks of the major drugs presently used in TEN treatment. Some future prospects in TEN management are also discussed.

Hydrogen peroxide-induced cell death in normal human keratinocytes is differentiation dependent

More than other tissues, skin is exposed to numerous external stresses generating ROS that, in addition to endogenous oxygen radicals, cause keratinocyte alterations and contribute in part to photocarcinogenesis and aging. Recent evidence suggests a differentiation-dependent susceptibility of keratinocytes to apoptosis. We explored hydrogen peroxide-induced cell death in normal human keratinocytes according to their differentiation. On H(2)O(2)-exposed skin explants, caspase-3 was strongly activated in basal keratinocytes double stained with beta(1) integrin, whereas DNA fragmentation occurred in suprabasal cells only without caspase-3 activation. In addition, isolated basal keratinocytes, selected by adhesion to type IV collagen, were more sensitive than nonadherent cells to H(2)O(2)-induced apoptosis with regard to mitochondrial transmembrane potential (Deltapsi(mt)) collapse and membrane integrity. Similarly, necrotic/late apoptotic cells were present at low levels only in the adherent epidermal population. Furthermore, in primary cultures of undifferentiated keratinocytes H(2)O(2)-induced cell death appeared via a mitochondrial failure. Deltapsi(mt) collapse was associated with a strong early activation of the initiatory caspase-8, then the executive caspase-3, and, to a lesser extent, the inflammatory caspase-1. Finally, undifferentiated basal cells possess a higher sensitivity than differentiated suprabasal cells to H(2)O(2)-induced cell death, and apoptosis in human keratinocytes occurs via different pathways depending on the cell's differentiation state.

Selectivity of protein carbonylation in the apoptotic response to oxidative stress associated with photodynamic therapy: a cell biochemical and proteomic investigation

We previously reported that photodynamic therapy (PDT) using Purpurin-18 (Pu-18) induces apoptosis in HL60 cells. Using flow cytometry, two-dimensional electrophoresis coupled with immunodetection of carbonylated proteins and mass spectrometry, we now show that PDT-induced apoptosis is associated with increased reactive oxygen species generation, glutathione depletion, changes in mitochondrial transmembrane potential, simultaneous downregulation of mitofilin and carbonylation of specific proteins: glucose-regulated protein-78, heat-shock protein 60, heat-shock protein cognate 71, phosphate disulphide isomerase, calreticulin, beta-actin, tubulin-alpha-1-chain and enolase-alpha. Interestingly, all carbonylated proteins except calreticulin and enolase-alpha showed a pI shift in the proteome maps. Our results suggest that PDT with Pu-18 perturbs the normal redox balance and shifts HL60 cells into a state of oxidative stress, which systematically induces the carbonylation of specific chaperones. As these proteins normally produce a prosurvival signal during oxidative stress, we hypothesize that their carbonylation represents a signalling mechanism for apoptosis induced by PDT.

Bacteriocin of Enterococcus from lactoserum able to cause oxidative stress in Staphylococcus aureus

The effect of a bacteriocin of Enterococcus on the oxidative metabolism of sensitive bacteria was investigated through the detection of oxidative stress by chemiluminescence (CL). The bacteriocin named EntB was purified to study the action on Staphylococcus aureus isolated from cosmetic. Chromatographic separation of EntB indicated different states of oligomerization with molecular weights multiple of 12,000Da monomeric form. The monomer purified by ion exchange was studied in its capacity to affect the oxidative metabolism of S. aureus, which showed increase of anion superoxide (O(2)(-)) when incubated with EntB. This effect was compared to the action of EntB on leukocytes as an assay of toxicity. EntB did not generate significant oxidative stress in leukocytes. Pyoverdin, a leukotoxic pigment of Pseudomonas fluorescens, was taken as reference, and it was found that this pigment caused similar oxidative stress to EntB in S. aureus; however, pyoverdin generated high production of anion superoxide (O(2)(-)) in leukocytes, while EntB did not increase the level of O(2)(-).