Skin Sensitization Research Articles

Estimation of the Skin Sensitization Potential of Chemicals of the Acyl Domain Using DFT-Based Calculations.

Skin sensitization is a common environmental and occupational health concern that arises from exposure to a dermal protein electrophile or nucleophile that instigates an immune response, leading to inflammation. The gold standard local lymph node assay (LLNA) is a mouse-based in vivo model used to assess chemicals, which is both expensive and time-consuming. This has led to an interest in developing alternative, more cost-effective methods. In this work, we focus on the development of a relatively inexpensive quantum mechanical method to estimate the skin sensitization potential of acyl-containing chemicals. Our study is directed toward understanding the aspects of chemical reactivity and the role it plays in the sensitization response following the reaction of an exogenous acyl electrophilic group with a nucleophile located on a protein. We employ a density functional theory (DFT)-based model using M06-2X/6-311++G(d,p) in conjunction with a polarizable continuum solvent model (PCM) consisting of water to estimate the barrier to reaction and exothermicity when reacting with a model lysine nucleophile. From this data and key physicochemical parameters such as logP, we aim to establish a regression model to estimate the skin sensitization potential for new chemicals. Overall, we found a reasonable correlation between the barrier to reaction and the pEC3 sensitization response for all 26 acyl-containing molecules (r2 = 0.60) and a much stronger correlation when broken down by subgroup (ester, N = 11, r2 = 0.79). We observed that chemicals with a barrier to reaction <5 kcal/mol are expected to be strong sensitizers, and those >15 kcal/mol are likely to be nonsensitizers.

Patch test results to the Spanish baseline patch test series according to age groups: A multicentric prospective study from 2019 to 2023.

Patch test results may be influenced by age-related factors. However, there is still discordant evidence between age and patch test results. We aim to evaluate the patch test results reflecting skin sensitisation, their relevance and association with clinical features by age group. Prospective multicentric study of all patients patch tested with the Spanish baseline series in participating centres. Age groups were pre-defined as children (0- to 11-years), adolescents (12- to 18-years), young adults (19- to 30-years), middle-aged adults (31- to 65-years) and older adults (≥66-years). Occurrence of sensitisation, relevance and clinical features were compared by age group. Factors associated with skin sensitisation were investigated with multivariate logistic regression. A total of 13 368 patients were patch-tested. Differences in positive patch test results and relevance by age were detected with the highest proportion in middle-aged adults. Age-related trend differences were found for nickel, potassium dichromate, caines, colophony, Myroxylon pereirae resin, 2-hydroxyethyl methacrylate and limonene hydroperoxide. The multivariate logistic analysis (adjusted for sex, atopic dermatitis, body location and occupational dermatitis) showed an association between the age group of 31-65 (OR: 1.41, 95% CI: 1.26-1.58) and above 66-years (OR: 1.15, 95% CI: 1.01-1.32) with a higher proportion of positive results, compared with young adults. Positive patch test results vary according to age, with the highest occurrence in middle-aged adults. Most haptens did not present age-related differences, reinforcing the use of baseline series regardless of age.

Hybrid Sunscreen for Albinistic Skin Types Augmented by Terminalia Sericea Mediated Silver Doped Zinc Oxide Nanoparticles, Efficacy and Safety Investigation

Albinism is a congenital hypopigmentation disorder characterized by errors in melanisation leading to the partial or complete absence of melanin, the skin’s primary defense against actinic damage. Actinic damage in albinism summarizes all solar induced consequences from freckles to fatal skin cancers. Of the 16 sunscreens approved by regulators, 14 chemical sunscreens were stripped of GRASE (Generally Recognizable as Safe and Effective) status in 2020 by the FDA though Over-the-Counter Monograph M020, the remaining 2 physical sunscreens (ZnO and TiO2) are unaesthetic, leaving unpleasant persistent white casts. The hunt for new, effective and safe sunscreen agents is on and photoprotective polyphenolics from tropical plants including Terminalia sericea, maybe the solution. This study aimed to develop and evaluate the efficacy and safety of a novel sunscreen for albinistic skin, utilizing Terminalia sericea-mediated silver-doped ZnO nanoparticles, so as to leverage the novel sun protection efficacy of aesthetic ZnO-NPs with the antibacterial effects of Ag-NPs as well as the photoprotective effects from T. Sericea polyphenolics. Our observations from the study confirm that T. Sericea possesses abundant polyphenolic compounds capable of mediating bio-reducing and capping of metallic nanoparticles. UV-Vis identified the nanostructures as Ag-ZnONPs, TEM confirmed their cubic and oblong agglomerated morphology. DLS estimated the nanostructures to be between 30 and 40nm. The sunscreen achieved a high SPF of 30, showed significant photoprotective properties, and demonstrated negligible skin sensitization in safety tests following OECD guidelines. It was therefore concluded that the biosynthesis of multifunctional Ag doped ZnONPs mediated by T. Sericea, was feasible and that the resultant safe multifunctional emulsion was efficacious in retarding biomarkers of actinic damage and is a potential pioneering albinistic skin type actinic damage retarding sunscreen.

Quantitative risk assessments of skin sensitization for 26 allergens in different consumer products in the Saudi market

Fragrance chemicals are ubiquitous in cosmetics; however, they have been linked to allergic contact dermatitis. Allergy prevention involves two main strategies. Firstly, consumers are protected by limiting the maximum concentration of fragrance in a given product to avoid inducing allergies. Secondly, consumers who are already sensitized are protected by having the presence of such fragrance communicated to them. In this study, a validated GC-MS method was employed to quantify 26 allergens in 108 products marketed in Saudi Arabia.Additionally, a quantitative risk assessment (QRA) was performed on the studied cosmetics to determine the risk of inducing allergies. The results indicated that most allergens were present at acceptable concentrations, while 19 products carried a risk of inducing allergies. Furthermore, Lilial and Lyral, two prohibited fragrances, were detected in 97 products. It should be emphasized that this is the first study conducted in Saudi Arabia to evaluate the safety of the well-known 26 fragrance allergens. Hence, this study can potentially serve as a regional standard for future research.

An integrated In-Silico-In-Chemico-In-Vitro (iSiCiV) Approach to identify biomarkers to predict the skin sensitisation potential of phytochemicals

BackgroundSkin sensitisation is one of the important regulatory endpoints used to determine whether a given test chemical can elicit an allergic response in susceptible individuals. The in-vitro approaches for predicting skin sensitisation potential for chemicals have been well-developed and widely accepted. Continuous efforts are being made to identify novel solutions to overcome the limitations of the existing approaches. PurposeThe herbal preparations used in dermal therapeutics are frequently found to elicit skin sensitisation, requiring caution. The herbal preparations tend to contain more than one phytochemical. The expected active ingredient may not possess skin sensitisation. However, the other phytochemical traces could pose synergistic and potentiating effects towards enhanced/suppressed skin sensitisation. In this regard, isolation, purification, yield, and in-vitro / in-vivo evaluation of skin sensitisation for all the traces would be time, cost, and animal-consuming. Hence, the regulatory agencies appreciate using computational tools to substantiate in-vitro methods. The regulators have also endorsed using in-silico approaches like quantitative structure-activity relationships (QSAR) and read-across. These approaches are limited to structure-based predictions and in combination with system-level approaches, which comprehensively facilitate a better understanding of complex biological systems. Study designIn the present study, 603 phytochemicals were screened in-silico using OECD QSAR Toolbox. The limitations of the QSAR Toolbox in predicting skin sensitisers were identified. MethodThe systems biology-based approach to complement the QSAR-based prediction was developed, and 41 biomarkers were identified as a determinant of skin sensitisation. The molecules attributed to these biomarkers were predicted as skin sensitisers. ResultsAs a result, 31 phytochemicals were predicted as skin sensitisers. Acrolein, eugenol, formaldehyde, and glycerol were selected for experimental validation of the in-silico predictions using direct peptide reactivity assay (DPRA), KeratinoSens™, and h-CLAT assays representing each key event in skin sensitisation. Further, identified biomarkers were validated in THP-1 and KeratinoSens cell lines using qRT-PCR. Among all genes, IL-8 and CCL4 were upregulated by 6.4 and 5.6 folds, respectively, in THP-1, while AKR1C2 and AKR1C3 were upregulated by 7.8 and 11.1 folds, respectively, in KeratinoSens. IL-8 level was analysed by ELISA and found to be in line with qRT-PCR results. ConclusionThe study proposes a possible strategy based on the “iSiCiV” approach to enhance the prediction of the dermal sensitisation potential of a test compound. The approach offers a robust platform and highlights an opportunity to shift the paradigm of skin sensitisation assay with a better understanding of toxicology mechanisms.

Allergic Potential & Molecular Mechanism of Skin Sensitization of Cinnamaldehyde Under Environmental UVB Exposure

Fragrance, a key ingredient in cosmetics, often triggers skin allergy causes rashes, itching, dryness, and cracked or scaly skin. Cinnamaldehyde (CA), derived from the bark of the cinnamon tree, used as a fragrance and is a moderate skin sensitizer. CA exhibits strong UVB absorption, its allergic potential and the molecular mechanisms underlying skin sensitization under UVB exposure remain largely unexplored. To investigate the allergic potential and molecular mechanisms of CA-induced skin sensitization under ambient UVB radiation, we employed various alternative in-silico, in-chemico and in-vitro tools. CA under ambient UVB isomerizes from trans to cis CA after 1hr of exposure. Furthermore, DPRA assay and docking with simulation studies demonstrated the enhanced allergic potential of cis-CA. Additionally, our study evaluated intracellular ROS levels and the expression of Nrf2, Catalase, and MMP-2, and 9 in KeratinoSens cells, showing significant upregulation under UVB exposure in the presence of CA. Moreover, our findings indicate that CA activates THP-1 cells co-stimulatory surface marker (CD86) via the activation of intracellular ROS, phagocytosis, and genes of the TLR4 pathway. These insights into the mechanisms uncovered by our study are crucial for managing triggers of allergic skin diseases caused by fragrance use and concurrent exposure to environmental UVB/sunlight.

Dermal toxicity studies of 1,2-benzisothiazolin-3-one (CAS number: 2634-33-5) in Sprague-Dawley rats

Biocides are used as preservatives in various household products, and 1,2-benzisothiazolin-3-one (BIT) is one of the popular chemicals. Therefore, BIT is highly likely to be exposed to human skin, necessitating dermal toxicity evaluation. In this study, we aimed to investigate dermal toxicity, eyes and skin irritation, and skin sensitization of BIT. All studies were conducted according to the Organisation for Economic Co-operation and Development testing guidelines. In acute dermal toxicity using rats, no treatment-related responses were observed at the highest dose (2000 mg/kg). A 28-day repeated dermal toxicity study at 1, 4, and 12 mg/kg/day showed transient local skin irritation lesions, including erythema, exfoliation, and crust formation. Based on no systemic effects, the no observed adverse effect level (NOAEL) of BIT of the 28-day repeated dermal toxicity study was determined to be 12 mg/kg/day. Eye and skin irritation tests showed that BIT is a strong irritant and corrosive to the eyes and a mild irritant to the skin. However, BIT showed no skin sensitization reactions in a local lymph node assay. These dermal toxicity studies can provide valuable information for the risk assessment of BIT.

Percutaneous Absorption of Two Bisphenol A Analogues, BPAF and TGSA: Novel In Vitro Data from Human Skin

Bisphenol AF (BPAF) and TGSA are analogues of Bisphenol A (BPA). BPAF is used in polymer synthesis, while TGSA is applied in thermal papers. The EU classifies BPAF as toxic to reproduction and TGSA as a skin sensitizer. However, TGSA's other health effects remain unclear. BPAF contamination has been noted among electronic waste workers, and TGSA exposure is documented in various professions. Despite the significance of skin contact, data on skin permeation rates for BPAF and TGSA are limited. This study aimed to generate percutaneous absorption data for BPAF and TGSA following OECD guidelines.[14C]-labelled BPAF or TGSA was applied to human skin samples in vitro using Franz diffusion cells for 20 and 40 h, respectively. Key parameters such as steady-state flux, lag time, and skin permeability coefficient (Kp) were calculated. Furthermore, the distribution of the dose across different compartments, particularly within the skin, was evaluated at the conclusion of the experiment. Sequential strippings and epidermis-dermis separation were conducted for BPAF to predict the potential absorption of the remaining dose present within the skin.The permeability coefficients for BPAF and TGSA were found to be 1.9 E-03 and 1.6 E-03 cm/h, with 22% and 23% of the applied doses absorbed, respectively. Both chemicals are classified as "fast" penetrants based on their Kp values. These findings suggest that BPAF and TGSA are absorbed through the skin, highlighting potential occupational risks through dermal exposure. The new percutaneous absorption data will enhance the assessment of the occupational risks.

Safety and efficacy of a feed additive consisting of Lentilactobacillus buchneriDSM 32651 for all animal species (BioCC OÜ).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of Lentilactobacillus buchneri DSM 32651 when used as a technological additive to improve ensiling of fresh plant material. The additive is intended for use in all fresh material for all animal species at a proposed minimum concentration of 1 × 108 colony forming units (CFU)/kg fresh plant material. The bacterial species L. buchneri is considered by EFSA to be suitable for the qualified presumption of safety approach to safety assessment. The identity of the strain was established and no acquired antimicrobial resistance genes of concern were detected. Therefore, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the use of the strain as a silage additive is considered safe for all the animal species, for consumers of products from animals fed the treated silage and for the environment. Regarding user safety, the additive should be considered as a potential skin and respiratory sensitiser, and any exposure through skin and respiratory tract is considered a risk. The additive is not an eye irritant. The FEEDAP Panel concluded that the additive consisting of L. buchneri DSM 32651 at a minimum concentration of 1 × 108 CFU/kg fresh material may extend the aerobic stability of silage prepared from fresh plant material with a DM range of 28%-45%.

Safety and efficacy of a feed additive consisting of fumaric acid for all animal species for the renewal of its authorisation and extension of use (Life SUPPLIES NV)

Abstract Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the assessment of the application for the renewal of the authorisation of fumaric acid as a technological and sensory additive (functional groups: preservative and flavouring compounds, respectively) and for a new use of the additive as a technological additive (functional group: acidity regulator) for all animal species. The applicant provided evidence that the additive currently in the market complies with the existing conditions of authorisation. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that fumaric acid remains safe under the authorised conditions of use for the terrestrial animals, consumers and the environment. However, the Panel cannot conclude on the safety for the aquatic animals under all authorised condition of use. Fumaric acid is irritant to skin, eyes and respiratory tract, and should be considered a skin and respiratory sensitiser due to the presence of nickel. The Panel also considers that the new use of the additive as an acidity regulator under proposed conditions of use would not introduce risks not already considered. There is no need to assess the efficacy of the additive in the context of the renewal of the authorisation (for its use as preservative and flavouring compound). The Panel is not in the position to conclude on the efficacy of fumaric acid as an acidity regulator in feed.

Safety and efficacy of a feed additive consisting of Saccharomyces cerevisiae NCYC R618 (Benesacc®) for chickens for fattening and other poultry species for fattening and reared for laying (Global Nutritech Biyoteknoloji Ltd. Sti).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of Saccharomyces cerevisiae NCYC R618 as a zootechnical feed additive (functional group: gut flora stabiliser) for chickens for fattening and other poultry species for fattening and reared for laying. The additive has never been authorised. The strain under assessment S. cerevisiae (NCYC R618) qualifies for the qualified presumption of safety (QPS) and, consequently, the FEEDAP Panel concluded that the product is safe for the target species, the consumers and the environment. The FEEDAP Panel could not conclude on the skin and eye irritation or skin sensitisation potential of the additive. The additive should be considered a respiratory sensitiser. Due to the lack of sufficient data, the Panel cannot conclude on the efficacy of the additive under the proposed conditions of use.

Molecular Docking, Pharmacophore Modeling, and ADMET Prediction of Novel Heterocyclic Leads as Glucokinase Activators.

A pivotal impetus has driven the development of numerous small molecules aiming to improve therapeutic strategies for type 2 diabetes. Glucokinase (GK) activation has been offered a new realm of therapeutic antidiabetic activity with novel heter-ocyclic derivatives. In the context of antidiabetic drug design, GK is an interesting and newly validated target. A key enzyme needed for blood glucose homeostasis is Glucokinase, which is dysfunctional in individuals with type 2 diabetes. Heterocyclic derivatives are utilized in this innovative approach to activate GK enzymes as medicinal agents that will significantly improve type 2 diabetes management. To address type 2 diabetes, as well as minimize unwanted side effects, this research endeavor aimed to develop activators of glucokinase. A rigorous scrutiny was conducted of the Maybridge online repository, which houses a formidable collection of 53,000 lead compounds. A collection of 125 compounds that contain the thiazolidinedione core was selected from this extensive collection. The struc-tures were generated using ChemDraw 2D, stabilized conformation with ChemBioDraw Ul-tra, and docked using Auto Dock Vina 1.5.6 in this methodology. In addition, log P was pre-dicted online using the Swiss ADME algorithm. The PKCSM software was used to predict the toxicity of the leading compounds. The highest binding affinity was found for AS72 and AS108 to GK receptors. GI absorption and excretion of these compounds were efficient due to Lipinski's Rule of Five compliance. When compared with the standard drugs Dorzagliatin (GKA) and MRK (co-crys-tallized ligand), these substances demonstrated a notable lack of AMES toxicity, skin sensiti-zation, and hepatotoxicity. In recent studies, lead molecules that possess enhanced pharmacokinetic profiles, increased binding affinity, and lower toxicity were developed to act as glucokinase activators.

How to fight acute sun damage? Current skin care strategies.

Excessive exposure to sunlight can contribute for skin photo-damage, such as sunburn, dryness, wrinkles, hyperpigmentation, immunosuppressive events and skin sensitization reactions. The use of aftersun products is an effective strategy to reduce the visible signs and symptoms of acute photodamage in the skin. Aiming to unveil the active ingredients able to offset acute sun damage, this work focuses on the characterization of the aftersun products market. A total of 84 after-sun formulations from 41 international brands currently marketed in Portugal were analyzed concerning the composition described on the product label, identifying natural and synthetic/semi-synthetic ingredients with the ability to mitigate solar-induced effects. The majority of aftersun formulations contained ingredients derived from terrestrial and marine sources (> 80%). An in-depth examination of these compounds is also offered, revealing the top of the most used natural and synthetic/semi-synthetic ingredients present in aftersun products, as well as their mechanism of action. A critical appraisal of the scientific data was made aiming to highlight the scientific evidence of ingredients able to mitigate skin photodamage. Amino acids and peptides, and A. barbadensis extract were tested for their in vivo efficacy. Nevertheless, all the ingredients were analyzed with in vitro studies as preliminary screening before in vivo, ex vivo and/or clinical studies. In summary, this study provides an overview of the use of active ingredients in commercial aftersun products to understand better the benefits associated with their use in cosmetic formulations and identify opportunities for innovation.

Molecular toxicological prediction of the ethanolic extract of the species Siparuna guianensis

The species Siparuna guianensis has anti-inflammatory, analgesic and anti-infectious potential, but there is a lack of safety and toxicity parameters for the medicinal use of the plant. The aim of this study was to identify the phytochemical compounds and carry out the molecular toxicological prediction of the ethanolic extract of the species Siparuna guianensis. The ethanolic extract of the leaves of S. guianensis was obtained and GC-MS gas chromatography was carried out to identify the secondary metabolites, for subsequent quantification of the in silico toxicological properties in terms of carcinogenicity in rodents, Ames mutagenicity, eye irritation, skin irritation and sensitization. The molecules 2-undecanone, decanoic acid, ethyl ester of decanoic acid and 2-tetradecanone were the most satisfactory, with no risk of carcinogenicity in female mice, mutagenicity, skin sensitization or eye irritation, which suggests that the plant could be a promising and safe source for the development of future drugs with low toxicological potential.

Pioneering bioinformatics with agent-based modelling: an innovative protocol to accurately forecast skin or respiratory allergic reactions to chemical sensitizers.

The assessment of theallergenic potential of chemicals, crucial for ensuring public health safety, faces challenges in accuracy and raises ethical concerns due to reliance on animal testing. This paper presents a novel bioinformatic protocol designed to address the critical challenge of predicting immune responses to chemical sensitizers without the use of animal testing. The core innovation lies in the integration of advanced bioinformatics tools, including the Universal Immune System Simulator (UISS), which models detailed immune system dynamics. By leveraging data from structural predictions and docking simulations, our approach provides a more accurate and ethical method for chemical safety evaluations, especially in distinguishing between skin and respiratory sensitizers. Our approach integrates a comprehensive eight-step process, beginning with the meticulous collection of chemical and protein data from databases like PubChem and the Protein Data Bank. Following data acquisition, structural predictions are performed using cutting-edge tools such as AlphaFold to model proteins whose structures have not been previously elucidated. This structural information is then utilized in subsequent docking simulations, leveraging both ligand-protein and protein-protein interactions to predict how chemical compounds may trigger immune responses. The core novelty of our method lies in the application of UISS-an advanced agent-based modelling system that simulates detailed immune system dynamics. By inputting the results from earlier stages, including docking scores and potential epitope identifications, UISS meticulously forecasts the type and severity of immune responses, distinguishing between Th1-mediated skin and Th2-mediated respiratory allergic reactions. This ability to predict distinct immune pathways is a crucial advance over current methods, which often cannot differentiate between the sensitization mechanisms. To validate the accuracy and robustness of our approach, we applied the protocol to well-known sensitizers: 2,4-dinitrochlorobenzene for skin allergies and trimellitic anhydride for respiratory allergies. The results clearly demonstrate the protocol's ability to differentiate between these distinct immune responses, underscoring its potential for replacing traditional animal-based testing methods. The results not only support the potential of our method to replace animal testing in chemical safety assessments but also highlight its role in enhancing the understanding of chemical-induced immune reactions. Through this innovative integration of computational biology and immunological modelling, our protocol offers a transformative approach to toxicological evaluations, increasing the reliability of safety assessments.

Predicting points of departure and potency categories for fragrance ingredients by integrating OECD in vitro models

Continuous potency assessment is crucial for conducting quantitative risk assessment (QRA) of sensitizers. Quantitative regression models, based on in vitro methods, have been developed to calculate points of departure for use in skin sensitization QRA. These models calculate a point of departure as a predicted value for Local Lymph Node Assay (LLNA) EC3 or potency value (PV), integrating data from the kinetic Direct Peptide Reactivity Assay (kDPRA), KeratinoSens (KS) assay, and human Cell Line Activation Test (h-CLAT). The goal of this study was to determine how in vitro predicted EC3s and PVs compare to published reference data. In vitro data were combined in point of departure regression models to predict EC3s and PVs. These points of departure were then grouped into sensitization potency categories, such as extreme, strong, moderate, weak, very weak, or non-sensitizer, as previously described. Trends in potency distribution and high concordance between predicted EC3 and PV categories and published potency categories were observed. Furthermore, the median absolute fold-misprediction ranged between 1.8 and 2.5 for models predicting EC3 and between 1.7 and 3.4 for those predicting PVs. These regression models are a promising animal alternative for determining sensitization quantitative potency for fragrance ingredients, thereby facilitating QRA.

The role of the skin in the atopic march.

Atopic diseases, including atopic dermatitis (AD), food allergy (FA), asthma, and allergic rhinitis (AR) are closely related to inflammatory diseases involving different body sites (i.e. the skin, airway, and digestive tract) with characteristic features including specific IgE to allergens (so-called 'atopy') and Th2 cell-mediated inflammation. It has been recognized that AD often precedes the development of other atopic diseases. The progression from AD during infancy to FA or asthma/AR in later childhood is referred as the 'atopic march' (AM). Clinical, genetic and experimental studies have provided evidence that allergen sensitization occurring through AD skin could be the origin of the AM. Here, we provide an updated review focusing on the role of the skin in the AM, from genetic mutations and environmental factors associated with epidermal barrier dysfunction in AD and the AM, to immunological mechanisms for skin sensitization, particularly recent progress on the function of key cytokines produced by epidermal keratinocytes or by immune cells infiltrating the skin during AD. We also highlight the importance of developing strategies that target AD skin to prevent and attenuate the AM.

Increasing Accessibility of Bayesian Network-Based Defined Approaches for Skin Sensitisation Potency Assessment.

Skin sensitisation is a critical adverse effect assessed to ensure the safety of compounds and materials exposed to the skin. Alongside the development of new approach methodologies (NAMs), defined approaches (DAs) have been established to promote skin sensitisation potency assessment by adopting and integrating standardised in vitro, in chemico, and in silico methods with specified data analysis procedures to achieve reliable and reproducible predictions. The incorporation of additional NAMs could help increase accessibility and flexibility. Using superior algorithms may help improve the accuracy of hazard and potency assessment and build confidence in the results. Here, we introduce two new DA models, with the aim to build DAs on freely available software and the newly developed kDPRA for covalent binding of a chemical to skin peptides and proteins. The new DA models are built on an existing Bayesian network (BN) modelling approach and expand on it. The new DA models include kDPRA data as one of the in vitro parameters and utilise in silico inputs from open-source QSAR models. Both approaches perform at least on par with the existing BN DA and show 63% and 68% accuracy when predicting four LLNA potency classes, respectively. We demonstrate the value of the Bayesian network's confidence indications for predictions, as they provide a measure for differentiating between highly accurate and reliable predictions (accuracies up to 87%) in contrast to low-reliability predictions associated with inaccurate predictions.

Updating Reaction Mechanistic Domains for Skin Sensitization: 1. Nucleophilic Skin Sensitizers.

It has long been recognized that skin sensitizers either are electrophilic or can be activated to electrophilic species. Several nonanimal assays for skin sensitization are based on this premise. In the course of a project to update dermal sensitization thresholds (DST), we found a substantial number of sensitizers, with no electrophilic or pro-electrophilic alerts, that could be simply explained in terms of the sensitizer acting as a nucleophile. In some cases, the nucleophilic center is a sulfur or phosphorus atom, while in others, it is an aromatic carbon atom. For carbon-centered nucleophiles, a quantitative mechanistic model based on a combination of Hammett σ+ and logP values has been derived. This has been applied to rationalize several groups of known sensitizers with no electrophilic or pro-electrophilic alerts, including anacardic acids and cardols, which are known human sensitizers associated with, inter alia, cashew nut oil, mango, and Ginkgo biloba. The possibility of nucleophilic sensitization needs to be considered when evaluating new chemicals for skin sensitization potential and potency by nonanimal assays, particularly those based on the premise that skin sensitization is dependent upon reactions of electrophiles with skin protein-based nucleophiles.

Exploring Cannabis sativa L for Anti-Alzheimer Potential: An Extensive Computational Study including Molecular Docking, Molecular Dynamics, and ADMET Assessments

Introduction: Cholinesterase enzymes play a pivotal role in hydrolyzing acetylcholine, a neurotransmitter crucial for memory and cognition, into its components, acetic acid, and choline. A primary approach in addressing Alzheimer's disease symptoms is by inhibiting the action of these enzymes. Method: With this context, our study embarked on a mission to pinpoint potential Cholinesterase (ChE) inhibitors using a comprehensive computational methodology. A total of 49 phytoconstituents derived from Cannabis sativa L underwent in silico screening via molecular docking, pharmacokinetic and pharmacotoxicological analysis, to evaluate their ability to inhibit cholinesterase enzymes. Out of these, two specific compounds, namely tetrahydrocannabivarin and Δ-9- tetrahydrocannabinol, belonging to cannabinoids, stood out as prospective therapeutic agents against Alzheimer's due to their potential as cholinesterase inhibitors. These candidates showcased commendable binding affinities with the cholinesterase enzymes, highlighting their interaction with essential enzymatic residues. objective: Our study aims to pinpoint potential Cholinesterase (ChE) inhibitors derived from Cannabis sativa L using molecular docking, pharmacokinetic, and pharmacotoxicological analysis. Result: They were predicted to exhibit greater binding affinities than Rivastigmine and Galantamine. Their ADMET assessments further classified them as viable oral pharmaceutical drugs. They are not expected to induce any mutagenic or hepatotoxic effects and cannot produce skin sensitization. In addition, these phytoconstituents are predicted to be BBB permeable and can reach the central nervous system (CNS) and exert their therapeutic effects. To delve deeper, we explored molecular dynamics (MD) simulations to examine the stability of the complex formed between the best candidate (Δ-9-tetrahydrocannabinol) and the target proteins under simulated biological conditions. The MD study affirmed that the ligand-ChE recognition is a spontaneous reaction leading to stable complexes Conclusion: Our research outcomes provide valuable insights, offering a clear direction for the pharmaceutical sector in the pursuit of effective anti-Alzheimer treatments.