Dermal exposure to toluene diisocyanate and respiratory cancer risk

Ferroptosis contributes to airway epithelial E-cadherin disruption in a mixed granulocytic asthma mouse model

Aberrant expression of airway epithelial E-cadherin is a key feature of asthma, yet the underlying mechanisms are largely unknown. Ferroptosis is a novel form of regulated cell death involved in asthma pathogenesis. This study was aimed to evaluate the role of ferroptosis and to investigate whether ferroptosis mediates E-cadherin disruption in mixed granulocyte asthma (MGA). Two murine models of MGA were established using toluene diisocyanate (TDI) or ovalbumin with Complete Freund's Adjuvant (OVA/CFA). Specific antagonists of ferroptosis, including Liproxstatin-1 (Lip-1) and Ferrostatin-1 (Fer-1) were given to the mice. The allergen-exposed mice displayed markedly shrunk mitochondria in the airway epithelia, with decreased volume and denser staining accompanied by down-regulated GPX4 as well as up-regulated FTH1 and malondialdehyde, which are markers of ferroptosis. Decreased pulmonary expression of E-cadherin was also observed, with profound loss of membrane E-cadherin in the airway epithelia, as well as increased secretion of sE-cadherin. Treatment with Lip-1 not only showed potent protective effects against the allergen-induced airway hyperresponsiveness and inflammatory responses, but also rescued airway epithelial E-cadherin expression and inhibited the release of sE-cadherin. Taken together, our data demonstrated that ferroptosis mediates airway epithelial E-cadherin dysfunction in MGA.

2D MXenes and their composites; design, synthesis, and environmental sensing applications

Novel 2D layered MXene materials were first reported in 2011 at Drexel University. MXenes are widely used in multidisciplinary applications due to their anomalous electrical conductivity, high surface area, and chemical, mechanical, and physical properties. This review summarises MXene synthesis and applications in environmental sensing. The first section describes different methods for MXene synthesis, including fluorinated and non-fluorinated methods. MXene's layered structure, surface terminal groups, and the space between layers significantly impact its properties. Different methods to separate different MXene layers are also discussed using various intercalation reagents and commercially synthesized MXene without compromising the environment. This review also explains the effect of MXene's surface functionalization on its characteristics. The second section of the review describes gas and pesticide sensing applications of Mxenes and its composites. Its good conductivity, surface functionalization with negatively charged groups, intrinsic chemical nature, and good mechanical stability make it a prominent material for room temperature sensing of environmental samples, such as polar and nonpolar gases, volatile organic compounds, and pesticides. This review will enhance the young scientists' knowledge of MXene-based materials and stimulate their diversity and hybrid conformation in environmental sensing applications.

Volatile organic compounds: A threat to the environment and health hazards to living organisms - A review

Volatile organic compounds (VOCs) are the organic compounds having a minimum vapor pressure of 0.13 kPa at standard temperature and pressure (293 K, 101 kPa). Being used as a solvent for organic and inorganic compounds, they have a wide range of applications. Most of the VOCs are non-biodegradable and very easily become component of the environment and deplete its purity. It also deteriorates the water quality index of the water bodies, impairs the physiology of living beings, enters the food chain by bio-magnification and degrades, decomposes and manipulates the physiology of living organisms. To unveil the adverse impacts of volatile organic compounds (VOCs) and their rapid eruption and interference in the living world, a review has been designed. This review presents an insight into the currently available VOCs, their sources, applications, sampling methods, analytic procedures, imposition on the health of aquatic and terrestrial communities and their contamination of the environment. Elaboration has been done on representation of toxicological effects of VOCs on vertebrates, invertebrates, and birds. Subsequently, the role of environmental agencies in the protection of environment has also been illustrated.

HMGB1 inhibition reduces TDI-induced occupational asthma through ROS/AMPK/autophagy pathway

Exposure to toluene diisocyanate (TDI) can cause pulmonary diseases such as asthma. Inhibition of high mobility group box 1 protein (HMGB1) has been found to be protective against the toxic effects of TDI on human bronchial epithelial (HBE) cells. Here, we evaluated the in vivo positive roles of HMGB1 in the TDI-caused asthma mice and explored its underlying mechanisms in HBE cells. We found that suppression of HMGB1 obviously alleviated airway inflammation, airway hyperresponsiveness, and airway remodeling in the lung tissue of the asthma mice. The in vitro results showed that inhibition of HMGB1 ameliorated TDI-induced reactive oxygen species (ROS) release, inflammatory response, and activation of autophagy in HBE cells. At the molecular level, inhibition of HMGB1 decreased the expressions of HMGB1, Toll-like receptor 4, Vimentin and matrix metalloproteinase-9 proteins, activated NF-κB and NOD-like receptor protein 3 (NLRP3) inflammasome, and increased E-cadherin expression. Importantly, activation of autophagy could lead to the overactivation of NLRP3 inflammasome in TDI-induced asthma. These results suggest that inhibition of HMGB1 can alleviate TDI-induced asthma through ROS/AMPK/autophagy pathways, which may provide valuable evidence for the pathogenesis and therapeutic targets of TDI-induced asthma.

Development of a new SPE UPLC-MS/MS method for extraction and quantitation of toluene diamine on gloves following toluene diisocyanate exposure

RATIONALE

Toluene diisocyanate (TDI) is a highly reactive isocyanate commonly used as a mixture of 2,4- and 2,6- isomers in the production of flexible foams. Exposure to TDI occurs primarily through vapour inhalation in workplaces where TDI is produced or used, but dermal exposure is also possible during some tasks. To ensure workplace safety, accurate monitoring of TDI and toluene diamine (TDA) levels is required. Methods of quantifying field effectiveness of gloves in preventing dermal exposure have not been established. Therefore, there is a need to develop a new practical method for assessing glove effectiveness for TDI/TDA.

METHOD

A new offline SPE UPLC-MS/MS method for the quantitation of TDA isomers from TDI-exposed gloves was developed. Gloves were dipped in a solution of 1% acetic acid leading to a full conversion to TDA. TDA-free amine compounds were derivatized with acetic anhydride to increase chromatographic retention and signal intensity.

RESULTS

2,4-Diaminotoluene-α, α, α-d3 (2,4-d₃ -TDA) was selected as a surrogate standard to minimise the variability in sample preparation and instrumental sensitivity. The choice of UPLC-MS/MS operated in multiple reaction monitoring (MRM) mode allowed to reach much lower limits of detection (LOD). The LOD of the method was 6.86 and 2.83 ng/mL (0.03 and 0.01 μg) for 2,6-TDA and 2,4-TDA, respectively. The limit of quantitation (LOQ) was 22.85 and 9.42 ng/mL (0.11 and 0.05 μg) for 2,6-TDA and 2,4-TDA, respectively.

CONCLUSION

A new UPLC-MS/MS analytical method has been developed to determine field effectiveness of gloves for preventing dermal exposure to TDI/TDA. The new technique overcomes some limitations for measuring putative dermal exposure to isocyanates and may be useful in exposure monitoring and future research on isocyanate health risks.

Hyperelastic, shape‐memorable, and ultra‐cell‐adhesive degradable polycaprolactone‐polyurethane copolymer for tissue regeneration

Novel polycaprolactone‐based polyurethane (PCL‐PU) copolymers with hyperelasticity, shape‐memory, and ultra‐cell‐adhesion properties are reported as clinically applicable tissue‐regenerative biomaterials. New isosorbide derivatives (propoxylated or ethoxylated ones) were developed to improve mechanical properties by enhanced reactivity in copolymer synthesis compared to the original isosorbide. Optimized PCL‐PU with propoxylated isosorbide exhibited notable mechanical performance (50 MPa tensile strength and 1150% elongation with hyperelasticity under cyclic load). The shape‐memory effect was also revealed in different forms (film, thread, and 3D scaffold) with 40%–80% recovery in tension or compression mode after plastic deformation. The ultra‐cell‐adhesive property was proven in various cell types which were reasoned to involve the heat shock protein‐mediated integrin (α5 and αV) activation, as analyzed by RNA sequencing and inhibition tests. After the tissue regenerative potential (muscle and bone) was confirmed by the myogenic and osteogenic responses in vitro, biodegradability, compatible in vivo tissue response, and healing capacity were investigated with in vivo shape‐memorable behavior. The currently exploited PCL‐PU, with its multifunctional (hyperelastic, shape‐memorable, ultra‐cell‐adhesive, and degradable) nature and biocompatibility, is considered a potential tissue‐regenerative biomaterial, especially for minimally invasive surgery that requires small incisions to approach large defects with excellent regeneration capacity.

Crinum jagus (J. Thomps. Dandy): Antioxidant and protective properties as a medicinal plant on toluene-induced oxidative stress damages in liver and kidney of rats

Crinum jagus (C. jagus; J. Thomps.) Dandy (Liliaceae) is a pantropical plant known for its medicinal values and pharmacological properties. The study assessed the protective effects and changes in oxidative stress indices due to C. jagus leaf extracts on the toluene-induced liver and kidney injuries in rats. The study was conducted on 8-week-old male Wistar rats (n = 80), weighing 243.3 ± 1.42 g. Group I, 1 ml/kg distilled water for 7 days; Group II, 4.5 ml/kg toluene once, 1 ml/kg distilled water for 7 days; Group III, 4.5 ml/kg toluene once, 500 mg/kg methanolic extract for 7 days; Group IV, 4.5 ml/kg toluene once, 500 mg/kg aqueous extract for 7 days; Group V, 500 mg/kg methanolic extract for 7 days; Group VI, 500 mg/kg aqueous extract for 7 days; Group VII, 500 mg/kg of vitamin C for 7 days; Group, VIII, 4.5 ml/kg toluene once, 500 mg/kg vitamin C for 7 days, all administrations were given by oral gavage. The phytochemical contents, absolute and relative organ weights of liver and kidneys, liver and kidney function tests, antioxidant status, as well as histological tests were analyzed using standard protocols. The tannins, flavonoids, and polyphenols were in highest concentration in both extracts, content in methanol extract (57.04 ± 1.51 mgg-1, 35.43 ± 1.03 mgg-1, 28.2 ± 0.34 mgg-1 respectively) > aqueous extract (18.74 ± 1.01 mgg-1, 13.43 ± 0.47 mgg-1, 19.65 ± 0.21 mgg-1 respectively). In the negative control group (II), bodyweights significantly (P < 0.05) reduced by 22%, liver weight and kidney weight significantly (P < 0.05) increased by 42% and 83% respectively, liver-to-bodyweight and kidney-to-bodyweight ratios increased significantly (P < 0.05); serum liver function tests (LFTs) i.e., bilirubin, alkaline phosphatase (ALP), Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), Gamma-glutamyl transferase (GGT), and serum kidney function tests (creatinine and urea) were significantly (P < 0.05) elevated; oxidant status (tissue malondialdehyde; MDA) was significantly (P < 0.05) elevated, antioxidant status i.e., tissue superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels was significantly (P < 0.05) reduced; with markedly visible renal and hepatic histopathological findings, compared to the normal control group. In C. jagus extract test groups (III and IV), the parameters were significantly (P < 0.05) alleviated and reversed to normal/near normal compared to the negative control. The LFTs, kidney function tests, and antioxidant status were significantly (P < 0.05) more improved with the methanol extract test and standard control groups compared to the aqueous extract test group; Also, the methanol extract test group showed better histological features than the aqueous extract test and standard control groups. The methanolic extract shows better antioxidant potential due to the availability of more nonenzymatic antioxidants (tannins, flavonoids, and polyphenols). The findings showed that toluene is a very aggressive xenobiotic due to the promotion of oxidative stress and peroxidation of cellular lipids, but C. jagus leaves provide significant protection through the reducing power of nonenzymatic antioxidants and their ability to induce endogenous antioxidant enzymes (SOD, CAT, and glutathione reductase or GR) causing reduced cellular lipid peroxidation and tissue damages, quickened tissue repair, and improved cell biology of liver and kidneys during toluene toxicity. The methanol leaf extract provides better protection and should be advanced for more experimental and clinical studies to confirm its efficacy in alleviating oxidative stress tissue injuries, specifically due to toluene.

Exposure to Toluene Di-isocyanate and Respiratory Effects in Flexible Polyurethane Foam Industries in Western India

Background:

Flexible foam industry largely uses 2,4 and 2,6 Toluene di-isocyanate as main raw materials and chronic exposure to its result in occupational asthma. The exposure to di-isocyanates might be higher due to the usage of obsolete technology, hand-mixing methods and working in confined spaces with insufficient local exhaust ventilation systems in developing countries. Exposure studies in flexible foam industries have not been done in developing countries.

Objective:

The present cross-sectional study was conducted to evaluate toluene di-isocyanate (TDI) exposures and respiratory health of the workers working in the seven flexible polyurethane foam industries located in Western India during 2010-2013.

Method:

A total of 128 personal air samples collected and evaluated for total TDI concentration using improved Occupational Safety and Head Administration method number 42. Then 194 workers were covered for complete clinical examination and spirometry for assessing respiratory health.

Results:

In all, 17.83% of air samples exceeded the ACGIH TWA-TLV of 0.005 ppm for TDI. Though only 11 (5.6%) workers had respiratory complaints, the spirometry revealed that 19 (9.8%) and four (2.1%) had restrictive and obstructive type of pulmonary function impairment, respectively.

Conclusion:

The TWA concentration of TDI exceeded at raw material storage, mixing, foaming, block cutting and curing areas in four out of seven industries even in the presence of local exhaust systems. The respiratory health effect is less when compared to exposure to TDI, suitable preventive and control measures were suggested based on the study findings to the stakeholders to prevent the increase of respiratory health effects.

Polythiourethanes Crosslinked with Dynamic Disulfide Bonds: Synthesis via Nonisocyanate Approach, Thermomechanical and Reprocessing Properties

Polythiourethanes (PTUs) crosslinked with dynamic disulfide bonds are synthesized via a nonisocyanate approach. First, a difunctional five-membered cyclic trithiocarbonate (1) is synthesized via the reaction of diglycidyl ether of bisphenol A (DGEBA) with carbon disulfide (CS₂ ). Thereafter, the step-growth polymerizations of 1 with α,ω-diamino poly(propylene oxide)s with various molar masses are carried out to obtain a series of linear poly(mercapto thiourethane)s. These linear poly(mercapto thiourethane)s are readily crosslinked upon formation of disulfide bonds, which are generated via radical coupling reaction with the side mercapto groups. These crosslinked PTUs can be tailored into the materials from thermosetting plastics to crosslinked elastomers, depending on the molar masses of α,ω-diamino poly(propylene oxide)s. More importantly, these crosslinked PTUs display excellent reprocessing properties at elevated temperatures, which is attributable to the metathesis reaction of dynamic disulfide bonds.

Selective Toluene Detection with Mo2CTx MXene at Room Temperature

MXenes are a promising class of two-dimensional materials with several potential applications, including energy storage, catalysis, electromagnetic interference shielding, transparent electronics, and sensors. Here, we report a novel Mo₂CT_x MXene sensor for the successful detection of volatile organic compounds (VOCs). The proposed sensor is a chemiresistive device fabricated on a Si/SiO₂ substrate using photolithography. The impact of various MXene process conditions on the performance of the sensor is evaluated. The VOCs, such as toluene, benzene, ethanol, methanol, and acetone, are studied at room temperature with varying concentrations. Under optimized conditions, the sensor demonstrates a detection limit of 220 ppb and a sensitivity of 0.0366 Ω/ppm at a toluene concentration of 140 ppm. It exhibits an excellent selectivity toward toluene against the other VOCs. Ab initio simulations demonstrate selectivity toward toluene in line with the experimental results.

Evaluating the toxicity of polyurethane during marine clay stabilisation

In civil engineering, many geotechnical and forensic projects employ polyurethane (PU) for ground improvement, and the results have shown to be effective in terms of time and cost savings. However, similar to many other chemical stabilisers, the use of PU for soil stabilisation may have environmental repercussions. Therefore, this paper utilised a toxicity characteristic leaching procedure (TCLP) to investigate the potential for ground contamination resulting from the application of PU for the stabilisation of marine clay. Furthermore, the hazardousness of PU during the stabilisation of marine clay was investigated by testing its reactivity, ignitability, corrosivity and physical properties. The results reveal that the quantity of heavy metals present in PU is far below the regulatory limits. The results further confirm that PU is odourless and non-corrosive and that it is non-cyanide and non-sulphide-bearing. However, PU is capable of igniting. Overall, the potential application of PU for ground improvement is promising due to its environmental friendliness.

Mechanistic formation of hazardous molecular heterocyclic amines from high temperature pyrolysis of model biomass materials: cellulose and tyrosine

Background

Research inventories on the co-pyrolysis of major biomass components such as cellulose with amino acid materials is scarce in literature despite the fact that such studies are critical in understanding toxic product relations from high temperature cooking, combustion of bio-fuels, cigarette smoking and forest fires. This paper explores, quantitatively, the yields of heterocyclic nitrogenated molecular reaction products of grave mutagenetic concern from the co-pyrolysis of model biomass materials; tyrosine and cellulose. Research has established that heterocyclic amines such as isocyanates are mutagens as well precursors for asthma, and other respiratory disorders.

Methods

An equimassic mixture of tyrosine and cellulose (50 ± 2 mg) by weight were pyrolyzed in a tubular quartz reactor in flowing nitrogen at 1 atm. Besides, varying combinations of tyrosine and cellulose in the ratios 3:1 and 1:3 were also explored for comparison. The reaction time was set at 2 s so as to simulate combustions events in nature. The pyrolysate was collected over 5 mL dichloromethane and characterized using a gas chromatograph coupled to a mass spectrometer detector.

Results

Evidently, it was noted that 1-methylindazole was released in high yields at 300 °C, constituting ~ 300 µg in the entire pyrolysis temperature range (200–700 °C). Nonetheless, isoindazole gave the highest yield ~ 730 µg while 1-naphthyl isocyanate gave a total yield of ~ 336 µg in the same temperature range. Remarkably, the change in char yield between 300 and 450 °C for the pyrolysis of 25% tyrosine in 75% cellulose was found to be ~ 48% whereas the change in char yield for the pyrolysis of 75% tyrosine in 25% cellulose was 49%.

Conclusion

The char and tar yields considered important residues of biomass burning have been reported in this study and found to be consistent with other research output in literature. The striking similarities of % yield of char across all temperatures for various combinations was the most significant observation in this investigation—char yield was independent of the mixing ratio during pyrolysis. From a mechanistic standpoint, it was noted that tyrosine inhibited cellulose based nitrogenated products. Thus N-products dominated the O-products.

Isocyanic acid (HNCO) and its fate in the atmosphere: a review

Isocyanic acid (HNCO) has recently been identified in ambient air at potentially concerning concentrations for human health. Since its first atmospheric detection, significant progress has been made in understanding its sources and sinks. The chemistry of HNCO is governed by its partitioning between the gas and liquid phases, its weak acidity, its high solubility at pH above 5, and its electrophilic chemical behaviour. The online measurement of HNCO in ambient air is possible due to recent advances in mass spectrometry techniques, including chemical ionization mass spectrometry for the detection of weak acids. To date, HNCO has been measured in North America, Europe and South Asia as well as outdoors and indoors, with mixing ratios up to 10s of ppbv. The sources of HNCO include: (1) fossil fuel combustion such as coal, gasoline and diesel, (2) biomass burning such as wildfires and crop residue burning, (3) secondary photochemical production from amines and amides, (4) cigarette smoke, and (5) combustion of materials in the built environment. Then, three losses processes can occur: (1) gas phase photochemistry, (2) heterogenous uptake and hydrolysis, and (3) dry deposition. HNCO lifetimes with respect to photolysis and OH radical oxidation are on the order of months to decades. Consequently, the removal of HNCO from the atmosphere is thought to occur predominantly by dry deposition and by heterogeneous uptake followed by hydrolysis to NH3 and CO2. A back of the envelope calculation reveals that HNCO is an insignificant global source of NH3, contributing only around 1%, but could be important for local environments. Furthermore, HNCO can react due to its electrophilic behaviour with various nucleophilic functionalities, including those present in the human body through a reaction called protein carbamoylation. This protein modification can lead to toxicity, and thus exposure to high concentrations of HNCO can lead to cardiovascular and respiratory diseases, as well as cataracts. In this critical review, we outline our current understanding of the atmospheric fate of HNCO and its potential impacts on outdoor and indoor air quality. We also call attention to the need for toxicology studies linking HNCO exposure to health effects.

Andrographolide prevented toluene diisocyanate-induced occupational asthma and aberrant airway E-cadherin distribution via p38 MAPK-dependent Nrf2 induction

Toluene diisocyanate (TDI) is a major cause of chemical-induced occupational asthma, which contributes about 15% of global asthma burden. Resistance and compounded side effects associated with the use of corticosteroid in asthma necessitate the search for alternative drugs. Andrographolide (AGP), a naturally occurring diterpene lactone is known to exhibit various bioactivities. Its ability to ameliorate cardinal features of allergic asthma was previously suggested in an eosinophilic asthma endotype. However, its potential antiasthma activity and mechanism of action in a neutrophilic occupational asthma model, as well as its effect on epithelial dysfunction remain unknown. BALB/c mice were dermally sensitised with 0.3% TDI or acetone olive oil (AOO) vehicle on day 1 and 8, followed by 0.1% TDI intranasal challenge on days 15, 18 and 21. Endpoints were evaluated via bronchoalveolar lavage fluid (BALF) cell analysis, 2',7'-dichlorofluorescein diacetate (DCFDA) assays, immunoblotting, immunohistochemistry and methacholine challenge test. Decreases in total and differential leukocyte counts of BALF were recorded in AGP-treated animals. The compound dose-dependently reduced intracellular de-esterification of DCFDA, thus suggesting AGP's potential to inhibit intracellular reactive oxygen species (ROS). Mechanistically, the treatment prevented TDI-induced aberrant E-cadherin distribution and restored airway epithelial β-catenin at cell to cell contact site. Furthermore, AGP ameliorated TDI induced pulmonary collagen deposition. In addition, the treatment significantly upregulated pulmonary HO-1, Nrf2 and phospho-p38 levels. Airway hyperresponsiveness was markedly suppressed among AGP-treated animals. Collectively, these findings suggest AGP's protective function against TDI-induced airway epithelial barrier dysfunction and oxidative lung damage possibly through the upregulation of adherence junction proteins and the activation of p38/Nrf2 signalling. This study elucidates the therapeutic potential of AGP in the control and management of chemical-induced allergic asthma. To the best of our knowledge, the potential anti-asthma activity of AGP in TDI-induced occupational asthma has not been reported previously.