Abstract: Chronic inflammation plays a central role in the pathogenesis of lung diseases including asthma, long COVID, chronic obstructive pulmonary disease (COPD), and lung cancer. Lipopolysaccharide (LPS) is a potent inflammatory agent produced by Gram-negative bacteria and also found in cigarette smoke. Our earlier study revealed that intranasal exposure of A/J mice to LPS for 7 days altered gene expression levels in alveolar type II epithelial cells (AECII), which serve as precursors to lung adenocarcinoma and are also preferentially targeted by SARS-CoV-2. In the present work, we employed a comprehensive multi-omics approach to characterize changes in DNA methylation/hydroxymethylation, gene expression, and global protein abundances in AECII of A/J mice following sub-chronic exposure to LPS and after 4-week recovery period. Exposure to LPS led to hypermethylation at regulatory elements within the genome such as enhancer regions and led to expression changes in genes known to play a role in lung cancer tumorigenesis. Changes in protein abundance were consistent with an inflammatory phenotype but also included tumor suppressor proteins. Integration of the multi-omics data resulted in a model where LPS-driven inflammation in AECII triggers epigenetic changes that, along with genetic mutations, contribute to lung cancer development.

Abstract: Studies on populations exposed to inorganic arsenic (iAs) have shown an association with the development of chronic kidney disease (CKD) and renal cell carcinoma (RCC). However, there are few studies addressing how acute exposure of the human kidney to iAs might lead to the long-term alterations that might lead to CKD or RCC. This laboratory’s hypothesis is that renal exposure to iAs might alter the renal cells responsible for the repair and regeneration of nephrons damaged by iAs exposure or other renal toxicants. The kidney possesses a minority epithelial cell population that co-express PROM1 and CD24 that are believed to be involved in renal epithelial cell repair. The purpose of this work is to understand the pathogenesis of CKD in renal cortical epithelial cells. Our model consists with acute and chronic exposure of i-As (III) to “Human Renal Tubular Precursor TERT” (HRTPT). The microarray and gene validation study demonstrated a sudden induction of microfibril associated protein 5 (MFAP5) and carcinoembryonic antigen related cell adhesion molecule 5 & 6 (CEACAM 5& 6) in chronic i-As (III) exposed cells. Chronically exposed cells also exhibited an induction of pAKT/AKT pathway, and SOX9 transcription factor. The targeting of MFAP5 & CEACAM5/6 could therefore provide a potential therapeutic approach to CKD.

Abstract: Honey bees are one of the most significant pollinators and contribute to the pollination of various crops. The honey bee, Apis mellifera (Linnaeus, 1758), has unique characteristics that could be successfully used to improve biomonitoring approaches in assessing environmental interactions. Three apiaries with different rates of honey bee colony losses were included in the study – Dimovtsi, Plovdiv, and Krasnovo, Bulgaria. Male individuals (immature and mature) were collected from five colonies for each of the three apiaries and studied for histopathological changes in the gonads. The results concerning the rate of honey bee colony losses in the studied apiaries from 2022 and 2023 showed honey bee losses in the tested colonies due to queen problems, which were reported for Plovdiv, as well as the death of honey bees or a reduction in their number to a few hundred bees in the colony. The chemical analysis showed the presence of different organic substances such as Coumaphos, DEET (N, N-diethyl-M-toluamide), Fluvalinate, and Piperonyl-butoxide in the alive and dead honey bee samples and those of food stocks (wax, pollen, and honey) within the hives. Among the sample types, those of the dead honey bees contained the greatest variety of pesticide residues, particularly in Plovdiv and Dimovtsi, reinforcing the link between pesticide exposure and honey bee mortality. The histopathological alterations were mainly associated with the thinning of the covering epithelium of the seminiferous tubules and the detachment of the basement membrane of the seminiferous tubule. The more severe histopathological lesion-necrosis was observed in a higher degree of expression in the drones from Plovdiv, indicating а higher pollution level in this region.

Abstract: Graphene and its related nanocomposites have garnered significant interest due to their distinct physiochemical and biological properties. In this study, reduced graphene-oxide-silver hybrid nanostructures were synthesized for applications in biomedical nanotechnology, particularly in targeting cancer stem cells (CSCs). A range of analytical techniques, such as X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and UV-visible absorption spectroscopy (UV-VIS), were employed to characterize graphene oxide (GO), reduced graphene oxide (rGO)-silver nanoparticles (AgNPs) and their composite structures. The GO-rGO-AgNPs exhibited potent anticancer properties as evidenced by cell culture assays, spheroid formation assay, and quantitative RT-PCR analysis. Treatment of breast cancer cells (MCF-7) with GO, rGO, and AgNPs significantly reduced cell proliferation and mammosphere formation. Furthermore, these treatments downregulated the expression of marker genes associated with CSCs in MCF-7 cells. Among the tested materials, rGO-AgNP, sodium citrate- mediated GO-AgNP, and rGO-AgNP nanocomposites demonstrated superior inhibitory effects on cell survival compared to GO alone. These findings suggest that these nanocomposites hold promise as effective and non-toxic therapeutic agents for targeting cancer cells and CSCs, thereby offering a novel approach to cancer treatment.

Abstract: The steroidal sapogenin diosgenin can cause hepatobiliary disease in cattle leading to photosensitization. Diosgenin in Urochloa spp. from the Orinoco Region in Colombia was quantified at 14 and 28 days at different seasons. In general, the lowest diosgenin content was found in U. dictyoneura and U. humidicola, although under particular circumstances (in alluvial valley in June at 28 days) the latter could produce high levels (732 μg/g). Among U. brizantha, U. decumbens and the hybrid called mulato (U. ruziziensis x U. brizantha x U. decumbens), the former presented the lowest levels of diosgenin and the other two the highest, especially in April and June. Rainy weather increased the diosgenin content in U. decumbens and in the hybrid. In the alluvial valley a positive significant correlation between diosgenin content and precipitation, was found for hybrid pastures. Because several saponins are metabolized into diosgenin in ruminants, this metabolite should be considered as the best marker of saponin content in Urochloa spp.

Abstract: For the first time, this study investigates in vivo the potential of Na-modified natural clinoptilolite to mitigate cadmium toxicity in ICR mice, a model relevant to human health. We enhanced natural clinoptilolite to improve its Cd2+ exchange capacity. Mice were exposed to environmentally realistic Cd(NO3)2 doses in their drinking water. The detoxification efficacy of the mineral was evaluated over 45 days in four groups: control (no supplementation), Cd(NO3)2 only, clinoptilolite only, and a combination of Cd(NO3)2 and clinoptilolite. We assessed Cd bioaccumulation in the liver and kidneys, genotoxicity (micronucleus assay), hematological parameters, and oxidative stress markers. Cd exposure resulted in significant bioaccumulation, reduced growth, changes in the erythrogram, DNA damage, and oxidative stress. Mice receiving clinoptilolite alone showed a significant increase in body mass. Modified clinoptilolite led to nearly a 48% reduction in Cd accumulation and a 30% increase in Cd-excretion in the Cd-plus-clinoptilolite group compared to the Cd-only group. Erythrogram and leukogram parameters returned to near-normal levels, with reductions in malondialdehyde (MDA) and increases in glutathione (GSH) observed by the end of the experiment. No elevated levels of micronuclei were found following zeolite supplementation. These results suggest modified clinoptilolite may be a cost-effective detoxifier in Cd-polluted regions.

Abstract: New psychoactive substances (NPS) pose a global public health challenge. Its ongoing evolution intensifies drug abuse cases, complicates regulation, and makes comprehensive studies difficult to conduct. Emerging studies indicate that these substances may severely impact spermatogenesis, reproductive hormones and male fertility. This review aims to consolidate existing knowledge on the impact of NPS on male reproduction, identify gaps in the literature, and suggest directions for future research. This comprehensive review examines original, peer-reviewed studies and clinical reports from PubMed, Semantic Scholar, AJOL, and Google Scholar. Data collection spanned from 2014 to 2024, using keywords such as “amphetamine-type stimulants”, “ATS”, “amphetamine”, “stimulants”, “opioids”, “opioid abuse”, “opioid addiction”, “male reproduction”, “male fertility”, and “reproductive toxicity”. The search encompasses illegal drugs, prescription medications, and over-the-counter (OTC) drugs that induce male reproduction toxicity through chronic use or prolonged exposure. Although current studies have limitations, our findings indicate that both illicit and medicinal ATS and opioids negatively impact male reproduction. These substances can diminish sperm quality, disrupt reproductive hormones, and cause sperm DNA damage. This review highlights further study in formulating public health strategies and supplements that mitigate DNA damage caused by these substances.

Abstract: Nickel (Ni), a heavy metal with extensive industrial applications, poses significant ecological impacts and health risks due to its persistence and bioaccumulation. Although toxicological data in mammals and plants are well-established, its effects on invertebrate models remain insufficiently explored. This study systematically evaluated the multi-dimensional toxicity of nickel on Caenorhabditis elegans, integrating phenotypic assays with transcriptomic profiling to assess impacts on growth, reproduction, neuromuscular function, lifespan, and aging. Chronic nickel exposure [1] induced dose-dependent developmental delays, with 80 μg/L causing a 3.8-fold increase in larval arrest (p < 0.0001). Reproductive capacity declined significantly at ≥8 μg/L, accompanied by impaired pharyngeal pumping rates, indicative of neuromuscular dysfunction. Lifespan analysis revealed non-monotonic mortality patterns, with paradoxical longevity observed at 80 μg/L, potentially linked to hormetic stress responses. Transcriptomic analysis identified 2,235 differentially expressed genes (DEGs) at 8 μg/L, enriched in xenobiotic metabolism, oxidative stress, and dysregulated Wnt/TGF-β signaling. GO and KEGG analyses highlighted collagen metabolism defects, calcium signaling disruption, and lysosomal dysfunction, correlating with cuticle integrity loss, feeding inefficiency, and lipofuscin accumulation. This study provides critical insights into the ecological risks of nickel pollution.

Abstract: Trichloroethylene (TCE) is an organic solvent used in industrial applications worldwide. Despite a recently proposed ban in the US, its usage over the last century produced widespread and long-lasting environmental contamination. TCE has been linked to multiple adverse health outcomes, with evidence growing that is a Parkinson’s disease (PD) risk factor. Exposure to TCE and other solvents in contaminated water at Camp Lejeune, North Carolina is associated with 70% increased PD risk in US veterans who lived on the base. However, little is known about PD risk from TCE in civilian populations, particularly in children who were exposed in early life. Importantly, the developing brain is highly susceptible to toxicant exposure, and previous work shows that exposure to TCE can result in neurodevelopmental deficits that manifest in adolescence and into adulthood. Given the number of individuals who have yet to “age” into idiopathic PD, understanding the mechanisms that underlie neurodegeneration from early life exposure to TCE could help to develop early interventions in at-risk populations. To further examine this, we review the existing literature on environmental exposures to PD-related toxicants during early-life and their long-term consequences. In addition, we discuss the potential for TCE-induced neurotoxic mechanisms to prime the brain for PD risk. Finally, we highlight the need for future studies to evaluate the impact of early-life TCE exposure across the lifespan.

Abstract: Centrilobular hepatocyte hypertrophy is frequently observed in animal studies for chemical safety assessment. Although its toxicological significance and precise mechanism remain unknown, it is considered an adaptive response resulting from the induction of drug-metabolizing enzymes (DMEs). This study aimed to elucidate the association between centrilobular hepatocyte hypertrophy and DME induction using machine learning on toxicogenomic data. Utilizing publicly available gene expression data and pathological findings from rat livers of 134 compounds, we developed six different types of machine learning models to predict the occurrence of centrilobular hepatocyte hypertrophy based on gene expression data as explanatory variables. Among these, a LightGBM-based model demonstrated the best performance with an accuracy of approximately 0.9. With this model, we assessed each gene's contribution to predicting centrilobular hepatocyte hypertrophy using mean absolute SHAP values. The results revealed that Cyp2b1 had an extremely significant contribution, while other DME genes also displayed positive contributions. Additionally, enrichment analysis of the top 100 genes based on mean absolute SHAP values identified "Metabolism of xenobiotics by cytochrome P450" as the most significantly enriched term. In conclusion, the current results suggest that the induction of multiple DMEs, including CYP2B1, is crucial for the development of centrilobular hepatocyte hypertrophy.

Abstract: Lignin, a significant industrial byproduct from paper manufacturing processes, exhibits ultraviolet (UV) radiation absorption properties. Cellulose nanofibers (CNF) demonstrate universal ligand characteristics and represent an innovative approach for converting industrial waste into value-added products. Given their potential applications in cosmetic formulations, efficacy and safety parameters, such as photoprotection mechanisms and phototoxicity, need to be investigated. Therefore, two kraft lignin fractions, LE and R1, along with a kraft bleached-pulp CNF, were evaluated for their phototoxicity and photoprotection mechanisms, both using HaCaT cell line (immortalized human keratinocytes) as in vitro model. Phototoxicity assessment involved exposing cells to UVA radiation (4 J/cm2), with subsequent comparison of cell viability between irradiated and non-irradiated samples. ROS quantification was performed using 2',7'-dichlorofluorescein diacetate (DCF-DA) probe, with fluorescence intensity measurements, and was used to evaluate photoprotection effect. Results demonstrated that both LE and R1 exhibited concentration-dependent increases in phototoxicity, whereas CNF showed no phototoxic effects under the conditions tested. For photoprotection, LE, R1, and CNF reduced UV-induced ROS production, which can be associated with their antioxidant properties in the case of lignin fractions. These findings suggest that both lignin fractions and CNF hold promises for use in renewable and sustainable cosmetic formulations.

Abstract:

There are many RNA polymerase inhibitors, such as rifampicin, which acts as an antituberculosis agent, and relatively new antiviral drugs, such as sofosbuvir. These drugs have a safe profile and strong efficacy in treating tuberculosis and hepatitis C infections. Studies have shown that high doses of these compounds promote cell longevity (prolonging life span) in humans. It is hypothesized that these drugs also affect human RNA polymerases at high doses. We predicted that such inhibition inhibits the RNA transcription machinery, which is considered a pacemaker of the biological clock. It is important to shift research to human RNA polymerase modulators to develop new versions of drugs treating diseases such as neurodegenerative disorders. Although there is no data about the crystal structure of the human RNA polymerase, the mammalian and even the bacterial structures look conserved. It is important to raise concerns about cancer risk from potential new drugs targeting RNA polymerase. However, adding adjuvant therapy, such as vascular endothelial growth factor inhibitors, to RNA polymerase inhibitors can be a wise strategy at the end of the tunnel. The speed of RNA polymerase elongation modulates longevity. Aging affects the transcription machinery, and transcription activity affects longevity, creating a loop.

Abstract: Background: Gaseous elemental mercury (Hg0 or GEM) is an atmospheric form of mercury (Hg) – a toxic heavy metal – that is naturally released in volcanic environments. Research with wild mice demonstrates that chronic exposure to a hydrothermal volcanic environment leads to the bioaccumulation of Hg in the lungs, but also in both the central (CNS) and peripheric (PNS) nervous systems, with marked indications of neurotoxicity. Studies addressing human exposure to volcanogenic Hg0 are scarce, hence its risks are still unknown. This study aims to evaluate the level of exposure to Hg0 in children living in a volcanically active environment. Methodology and main findings: Two groups of school-aged children (6 to 9 years old) were part of this study: one with children inhabiting a hydrothermal area (exposed group), and another with children inhabiting an area without volcanic activity (non-exposed group). Hair samples were collected from each individual for Hg level analysis. It was found that the levels of Hg in the hair of exposed children were 4.2 times higher than in that of non-exposed children (≈ 1797.84 ± 454.92 ppb vs. 430.69 ± 66.43 ppb, respectively). Conclusion: Given the vast health risks Hg poses, the need of monitoring the health of populations inhabiting volcanically active areas is highlighted. Because little is known about the fate, modifications, and effects of Hg0 in the human body, particularly regarding its effects on the nervous system in children, the development of further research within the scope is strongly encouraged.

Abstract:

In this work we demonstrate a novel methodology for personalized diagnosis and spatial characterization of abnormal Magnetic Resonance Imaging R1 (R1 = 1/T1) relaxation rates arising from excessive manganese (Mn) accumulation in welders’ brains. Utilizing voxel-wise population-derived norms based on a frequency age-matched non-exposed group (n = 25), we demonstrate the ability to conduct subject-specific assessments and mapping of Mn exposure using MRI relaxometry. Our results show elevated R1 in multiple brain regions in individual welders, but also extreme between-subject variability in Mn accumulation, debasing the concept that high exposures correlate with uniformly high Mn deposition in the brain. Consequently, the presented personalized methodology serves as a counterpart to group-based comparison, which allows for understanding the level of individual exposure and the toxicokinetics of Mn accumulation. This work lays a foundation for improved occupational health assessments and preventive measures against neurotoxic metal exposure.

Abstract: Tapirira guianensis is a tropical plant from South America widely used by indigenous communities due to its medicinal properties. The seeds are rich in phenolic compounds known for their anti-inflammatory, antioxidant, and antimicrobial properties. This study investigated the chemical composition, antioxidant potential, cytotoxic effects, and antimalarial properties of hydroethanolic, ethanolic, and aqueous seed extracts. The combination of water and ethanol (1:1) in the extraction proved to be efficient in obtaining bioactive compounds, resulting in the highest phenolic compound content and strong antioxidant activity. In addition, it reduced the viability of cancer cells, protected against damage caused by reactive oxygen species (ROS), decreased chromosomal aberrations, and proved to be highly effective against sensitive and resistant to chloroquine Plasmodium falciparum strains. These data indicate a promising profile of T. guianensis seed extracts in cytoprotective, antiproliferative, antioxidant, and antimalarial properties and point to the need for additional in vivo studies to better understand their mechanisms of action and safety.

Abstract:

The city of Macapá in the Brazilian Amazon faces critical aquatic pollution challenges due to inadequate sanitation infrastructure, leading to heavy metal contamination in fish within its urban water bodies. This study evaluates concentrations of metals (Cu, Cd, Cr, Fe, Mn, Ni, Pb, Zn, Hg) in muscle tissues of fish from igarapés, floodplain lakes, and canals. Samples were collected from six sites to investigate the bioaccumulation of these metals and their potential human health risks. Using Atomic Absorption Spectrometry and Inductively Coupled Plasma Optical Emission Spectrometry for Hg, metal levels were analyzed in three carnivorous and seven omnivorous fish species. Cd concentrations in several species exceeded safety thresholds for human consumption, while the estimated daily intake (EDI) of Hg also surpassed reference doses. Risk assessment combining the risk quotient (RQ) for individual metals and the risk index (RI) for metal mixtures indicated considerable health risks associated with consuming fish from these contaminated waters. These findings reveal concerning exposure to contaminants, underscoring the need for environmental management and ongoing monitoring to protect public health in vulnerable urban areas.

Abstract: While two-dimensional (2D) cell cultures, such as Caco-2 and Madin-Darby canine kidney (MDCK) cells are widely used in a variety of biological models, these two-dimensional in vitro systems present inherent limitations in replicating the complexities of in vivo biology. Recent progress in three-dimensional organoid technology has the potential to address these limitations. In this study, the characteristics of conventional 2D cell culture systems were compared to those of canine intestinal organoids (enteroids, ENT and colonoids, COL). Light microscopy and transmission electron microscopy were employed to evaluate the microanatomy of ENT, COL, Caco-2, and MDCK cell monolayers, while transepithelial electrical resistance (TEER) values were measured to assess monolayer integrity. The TEER values of canine ENT monolayers more closely approximated reported TEER values for human small intestines compared to Caco-2 and MDCK monolayers. Additionally, canine ENT demonstrated greater monolayer stability than Caco-2 and MDCK cells. Notably, while all systems displayed tight junctions, canine ENT and COL exclusively produced mucus. These findings highlight the potential of the canine organoid system as a more biologically relevant model for in vitro studies, addressing the limitations of conventional 2D cell culture systems.

Abstract: Ochratoxin A (OTA), a mycotoxin produced by filamentous fungi, is a global food safety due to its nephrotoxic effects, high thermal stability, and persistence in food matrices. Its prolonged lifespan and prevalence in cereals and processed food products under favorable storage conditions increase its potential health risks. The extensive exposure of OTA and environmental factors necessitates the development of effective mitigation strategies to protect public health and food security. This review explores OTA's occurrence, toxicity, and health impacts in food systems, highlighting the limitations of conventional decontamination methods. Moreover, it examines innovative strategies like irradiation, cold plasma (CP), adsorbents, ozone (O3), and bacterial and fungal treatments, emphasizing their potential to reduce OTA contamination effectively. These methods are critically evaluated for their efficacy, impact on food safety, nutritional quality preservation, sensory attributes, and overall consumer acceptance. By integrating insights from recent advancements, the review offers a comprehensive understanding of OTA mitigation, promoting the development of sustainable, scalable, and safe decontamination technologies for improved food safety and public health protection.

Abstract:

Degenerative proteinopathies constitute a set of molecular diseases that are caused by the misfolding of specific proteins, leading them to change their biochemical configuration and become toxic for entire systems of organs. Such protein toxicity induces the lysing of an increasing number of proteins that have a biochemically ‘wild-type’ version, gradually and eventually leading to a complete shift in the ratio between such ‘wild-type’ and ‘altered’ versions of such proteins, which directly precedes the clinical onset of such diseases. Proteinopathies not only involve neurodegenerative illnesses, but also a disease that leads to a progressive rate of blindness. Sadly, all such impairments that are neurodegenerative in nature may only receive palliative treatment, given that they are caused by aggregated proteins that start damaging and destroying entire neuronal systems, which leads to impairments in the neuro-muscular and ultimately to the inability of the patients to perform vital functions, like breathing and deglutition. There is neither a cure, nor a definitive method in which the progression of the illness can be stopped at the present time. Consequently, all neurodegenerative diseases have mortality rates of 100% and clinical approaches aim to reduce the suffering of such patients. Nonetheless, there seems to be a glimmer of hope regarding future prophylactic approaches that could delay the onset of many types of proteinopathies. Namely, an immune application could support efforts of clinical suffering delay and attenuation in an unprecedented manner. At the same time, it is necessary to emphasise upon realistic scenarios, that it remains virtually impossible to delay the onset of proteinopathies to the point of the patient reaching the average number of years in life expectancy without experiencing clinical symptoms yet. Initially, clinicians developed and tested a nasal spray containing a substance known as protollin, which stimulates a restricted extent of adaptive lymphocyte recruitment and transport to the central nervous system areas affected by initial stages of protein aggregation, activating a substantial number of microglial cells and preventing the lysis of numerous astrocytes, which in turn start lysing a number of beta-amyloid protein aggregates together without inducing pathophysiology, given the stage in which the patients have not experienced any clinical manifestation of the neurodegenerative disease yet. In case of an unsuccessful attempt to bring protollin above the threshold levels of clinical safety and efficacy, an immunostimulatory and immunomodulatory substance containing a low concentration of a mixture of recombinant Type I & III Interferons, innate and adaptive lymphocytes, perhaps themselves priorly treated with such IFN glycoproteins, would probably remain a vital candidate for an effective, yet probably still restricted delay of onset of various proteinopathies that could be neurodegenerative and optically degenerative. An existent success rate of the clinical test allows the opening of a window of opportunity regarding an increased efficacy of such adaptive lymphocyte approach, by including recombinant Type I and Type III Interferons into such a nasal spray, which could also enter adaptive lymphocyte and further improve their structural integrity and their multi-lateral functionality. Moreover, a low dose of protollin, Type I Interferons and Type III Interferons could be inserted in combination into adaptive T-Lymphocytes to optimise their defence mechanisms and immune functions, potentially bringing a considerable immunising effect against microbial diseases like HIV-induced, retroviral AIDS. Such an approach could create a stable and wide “highway bridge” of connection between innate and adaptive immunity, aiming for the best version of an immune contribution toward a considerable delay of proteinopathy clinical onset. Overall, there may be a requirement for a bi-lateral update of immunological research covering therapeutics and vaccine development; an immune system based optimisation that builds a stable and wide bridge of connection more directly between pre-cytokine and post-cytokine immune activation, and overall between innate and adaptive immune departments; and a pathogen-based optimisation that either eliminates or partially activates genes suppressive of Type I and Type III Interferon-encoding genes, helping enliven the concept of “United Immune System” as well, though less directly than the immune system-based potential approach.

Abstract: Data are presented on the formation of potentially toxic metabolites of polycyclic aromatic hydrocarbons (PAHs) and the effects of the structure of the compounds on the human metabolic enzymes that catalyze the reactions and the products formed. The tabular data lists the formation of potentially toxic/reactive products. The data obtained from in vitro experiments showed that the oxidative reactions predominate (67% of the potentially toxic reactions). Sulfating reactions participate in 14%, reductions with 12%, and acetylation reactions with 7%. Of the enzymes, cytochrome P450 (P450, CYP) enzymes catalyzed 58% of the reactions, aldo-keto reductases (AKR) 16%, sulfotransferases (SULT) 15%, N-acetyltransferases (NAT) 6%, cytochrome P450 reductase (NPR) 3%, and a group of minor participating enzymes to the extent of 3%. Within the P450 Superfamily, P450 Family 1 (P450 1A1, 1A2, 1B1) participates to the extent of 75%, P450 3A4 with 8%, P450 2W1 with 4%, and the group of minor participating enzymes with 13%. In the C- and N-atom(s)-containing PAHs (N-PAHs), the P450 enzymes dominated with 66%, followed by NAT (14%), SULT (11%), and the group of minor participating enzymes (9%). The P450 Family 1 dominated with 67%. In the C- atom-containing group of PAHs (C-PAHs), the P450 enzymes participated with 51%. AKR with 28%, SULT with 19%, and COX and EH enzymes with 2%. Of the P450 Family 1 enzymes, P450 1A1 dominated with 41% of the reactions. The data show the dominant participation of the P450 enzymes and the effect of the N-atom presence on the toxication reactions of PAHs and the metabolites formed. Selected examples of the PAHs that are activated or proposed to form toxic species are discussed.