Deciphering exogenous chemical carcinogenicity through interpretable deep learning: A novel approach for evaluating atmospheric pollutant hazards

Cancer remains a significant global health concern, with millions of deaths attributed to it annually. Environmental pollutants play a pivotal role in cancer etiology and contribute to the growing prevalence of this disease. The carcinogenic assessment of these pollutants is crucial for chemical health evaluation and environmental risk assessments. Traditional experimental methods are expensive and time-consuming, prompting the development of alternative approaches such as in silico methods. In this regard, deep learning (DL) has shown potential but lacks optimal performance and interpretability. This study introduces an interpretable DL model called CarcGC for chemical carcinogenicity prediction, utilizing a graph convolutional neural network (GCN) that employs molecular structural graphs as inputs. Compared to existing models, CarcGC demonstrated enhanced performance, with the area under the receiver operating characteristic curve (AUCROC) reaching 0.808 on the test set. Due to air pollution is closely related to the incidence of lung cancers, we applied the CarcGC to predict the potential carcinogenicity of chemicals listed in the United States Environmental Protection Agency's Hazardous Air Pollutants (HAPs) inventory, offering a foundation for environmental carcinogenicity screening. This study highlights the potential of artificially intelligent methods in carcinogenicity prediction and underscores the value of CarcGC interpretability in revealing the structural basis and molecular mechanisms underlying chemical carcinogenicity.

Identification and determination of phenyl methyl carbamate released from adducted hemoglobin for methyl isocyanate exposure verification

Methyl isocyanate (MIC), an intermediate in the synthesis of carbamate pesticides, is a toxic industrial chemical that causes irritation and damage to the eyes, respiratory tract, and skin. Due to the high reactivity of MIC, it binds to proteins to form protein adducts. While these adducts can be used as biomarkers to verify exposure to MIC, methods to detect MIC adducts are cumbersome, typically involving enzymatic (pronase) or strong acid (Edman degradation) hydrolysis of hemoglobin. Hence, in this study, a simple method was developed which utilizes base hydrolysis of MIC-tyrosine adducts from isolated hemoglobin to form phenyl methyl carbamate (PMC), followed by rapid liquid-liquid extraction, and liquid chromatography tandem mass spectrometry analysis. The hydrolysis chemistry is the first report of base hydrolysis of a tyrosine-β-C-hydroxo phenol bond in aqueous solution. The method produced excellent sensitivity (detection limit of 0.02 mg/kg), linearity (R² = 0.998, percent residual accuracies > 96), and dynamic range (0.06‒15 mg/kg). The accuracy and precision (100 ± 9% and < 10% relative standard deviation, respectively) of the method were outstanding compared to existing techniques. The validated method was able to detect significantly elevated levels of PMC from hemoglobin isolated from MIC-exposed rats.

Synthesis of unsymmetrical urea derivatives via Cu-catalysed reaction of acylazide and secondary amine

The synthesis of unsymmetrical urea generally requires toxic reagent, solvent and harsh reaction condition. Herein, we introduce Cu-catalyzed greener and safer unsymmetrical urea derivatives synthesis in ethyl acetate. This method minimized utilization of toxic reagent. A variety of indole, amines, and azides with bis-indole successfully employed leading to high yields and gram scale synthesis of isolated urea.

Susceptibility of the Bhopal-methyl isocyanate (MIC)-gas-tragedy survivors and their offspring to COVID-19: What we know, what we don't and what we should?

There is credible evidence that the 1984-Bhopal-methyl isocyanate (MIC)-gas-exposed long-term survivors and their offspring born post-exposure are susceptible to infectious/communicable and non-communicable diseases. Bhopal's COVID-19 fatality rate suggests that the MIC-gas tragedy survivors are at higher risk, owing to a weakened immune system and co-morbidities. This situation emboldened us to ponder over what we know, what we don't, and what we should know about their susceptibility to COVID-19. This article aims at answering these three questions that emerge in the minds of public health officials concerning prevention strategies against COVID-19 and health promotion in the Bhopal MIC-affected population (BMAP). Our views and opinions presented in this article will draw attention to prevent and reduce the consequences of COVID-19 in BMAP. From the perspective of COVID-19 prophylaxis, the high-risk individuals from BMAP with co-morbidities need to be identified through a door-to-door visit to the severely gas-affected regions and advised to maintain good respiratory hygiene, regular intake of immune-boosting diet, and follow healthy lifestyle practices.

Determination of methyl isopropyl hydantoin from rat erythrocytes by gas-chromatography mass-spectrometry to determine methyl isocyanate dose following inhalation exposure

Methyl isocyanate (MIC) is an important precursor for industrial synthesis, but it is highly toxic. MIC causes irritation and damage to the eyes, respiratory tract, and skin. While current treatment is limited to supportive care and counteracting symptoms, promising countermeasures are being evaluated. Our work focuses on understanding the inhalation toxicity of MIC to develop effective therapeutic interventions. However, in-vivo inhalation exposure studies are limited by challenges in estimating the actual respiratory dose, due to animal-to-animal variability in breathing rate, depth, etc. Therefore, a method was developed to estimate the inhaled MIC dose based on analysis of an N-terminal valine hemoglobin adduct. The method features a simple sample preparation scheme, including rapid isolation of hemoglobin, hydrolysis of the hemoglobin adduct with immediate conversion to methyl isopropyl hydantoin (MIH), rapid liquid-liquid extraction, and gas-chromatography mass-spectrometry analysis. The method produced a limit of detection of 0.05 mg MIH/kg RBC precipitate with a dynamic range from 0.05-25 mg MIH/kg. The precision, as measured by percent relative standard deviation, was <8.5%, and the accuracy was within 8% of the nominal concentration. The method was used to evaluate a potential correlation between MIH and MIC internal dose and proved promising. If successful, this method may be used to quantify the true internal dose of MIC from inhalation studies to help determine the effectiveness of MIC therapeutics.

In silico docking of methyl isocyanate (MIC) and its hydrolytic product (1, 3-dimethylurea) shows significant interaction with DNA Methyltransferase 1 suggests cancer risk in Bhopal-Gas- Tragedy survivors

DNA methyltransferase 1 (DNMT1) is a relatively large protein family responsible for maintenance of normal methylation, cell growth and survival in mammals. Toxic industrial chemical exposure associated methylation misregulation has been shown to have epigenetic influence. Such misregulation could effectively contribute to cancer development and progression. Methyl isocyanate (MIC) is a noxious industrial chemical used extensively in the production of carbamate pesticides. We here applied an in silico molecular docking approach to study the interaction of MIC with diverse domains of DNMT1, to predict cancer risk in the Bhopal population exposed to MIC during 1984. For the first time, we investigated the interaction of MIC and its hydrolytic product (1,3-dimethylurea) with DNMT1 interacting (such as DMAP1, RFTS, and CXXC) and catalytic (SAM, SAH, and Sinefungin) domains using computer simulations. The results of the present study showed a potential interaction of MIC and 1,3-dimethylurea with these domains. Obviously, strong binding of MIC with DNMT1 interrupting normal methylation will lead to epigenetic alterations in the exposed humans. We suggest therefore that the MIC- exposed individuals surviving after 1984 disaster have excess risk of cancer, which can be attributed to alterations in their epigenome. Our findings will help in better understanding the underlying epigenetic mechanisms in humans exposed to MIC.

On the long-term effects of methyl isocyanate on cell-mediated immunity in Bhopal gas-exposed long-term survivors and their offspring

Methyl isocyanate (MIC) is a toxic industrial chemical that is documented as a potent respiratory toxicant. We investigated cell-mediated immunity (CMI) in the MIC-exposed long-term survivors and their offspring born after the Bhopal gas-leak tragedy in 1984. Several earlier reports show inconsistency in the assessment of immunological effects of MIC on the human population. In these studies, important factors including lifestyle attributes were overlooked. We incorporated these factors also in our study of the basic cell-mediated immune function in the Bhopal MIC-affected population. Twenty-seven years after exposure, we assessed the circulating T-lymphocyte frequency using E-Rosette assay. A total of 46 MIC-exposed healthy long-term survivors and their offspring were studied vis-a-vis parallel gender–age group-matched unexposed controls from Bhopal and various other regions of India. The influence of several lifestyle variabilities (smoking, alcohol intake, and tobacco chewing) on T-lymphocyte frequency was also taken into consideration. Our observations suggest that Erythrocyte-Rosette-forming cell (E-RFC) distribution frequency is largely insignificant in the MIC-affected population as compared to controls ( p > 0.05). In the MIC-affected tobacco chewers, there was a trend of suppression in CMI (relative decrease = 10.3%) as compared to nonchewers. Overall, our results show negligible long-term effect of MIC on CMI measured in terms of E-RFC frequency. These observations are not in agreement with earlier findings that immunosuppressive effects of MIC exposure persist in the T-cells of the affected population. However, atypical lymphocytes were frequently observed as E-RFC in the exposed females when compared to all other subgroups. Hematopoietic disorders (atypical lymphocytosis) in the MIC-affected population along with previous reports on the cytogenetic and humoral immune system linking cancer risk and chronic obstructive pulmonary disease (COPD) are important.