In vitro toxicity and molecular interacting mechanisms of chloroacetic acid to catalase

A novel two-dimensional metal imidazolate sulphate framework as a versatile platform for enzyme immobilization

The encapsulation of enzymes in ZIF-8 (enzyme@ZIF-8 composites) via co-precipitation has attracted considerable attention. However, enzyme@ZIF-8 composites often exhibit low activity due to the three-dimensional (3D) structural characteristics of ZIF-8 and the protonation of the precursor, 2-methylimidazole (2-MeIm). In this study, a novel 2D catalase@ZIFs(SO4) composite was synthesized as an alternative to the conventional 3D catalase@ZIF-8 composites. The 2D catalase@ZIFs(SO4) composites demonstrated a nine-fold increase in activity and three-fold higher enzyme loading compared to their 3D counterparts. The enhanced catalytic performance is attributed to the 2D structure of the composites and the partial replacement of 2-MeIm with sulfate during enzyme immobilization, which reduces the protonation of 2-MeIm, enhances the hydrophilic microenvironment, and facilitates substrate transfer. Furthermore, compared to free enzymes, the 2D catalase@ZIFs(SO4) composites exhibited an expanded pH tolerance range, superior thermal stability, enhanced resistance to denaturants, and improved storage stability. To validate the concept, glucose oxidase, glutamate oxidase, and phenylalanine ammonia lyase were immobilized using the same approach. All immobilized enzymes demonstrated increased activity relative to the traditional CAT@ZIF-8 composites. This study offers a versatile platform for enzyme encapsulation within ZIF-8 through co-precipitation.

Evolution of pollutant biodegradation

Pollutant-derived risks to human and environmental health are exacerbated by slow natural attenuation rates, often driven by pollutant toxicity to microorganisms that can degrade them or limitations to the ability of microorganisms to metabolise them. This review explores mechanisms employed by bacteria to protect themselves from pollutant toxicity in the context of the evolution of pollutant-degrading abilities. The role of promiscuous enzymes in pollutant transformation is subsequently reviewed, highlighting the emergence of novel metabolic pathways and their transcriptional regulation in response to pollutant exposure, followed by the gene transcription regulation to optimise the cellular component synthesis for adaptation on the novel substrate. Additionally, we discuss epistatic interactions among mutations vital for this process both at macromolecular and at cellular levels. Finally, evolutionary constraints towards enhanced fitness in the context of pollutant degradation are considered, the constraints imposed by the epistasis from mutations on both enzyme level and cellular level, concluding with challenges and emerging opportunities to develop sustainable contaminated site remediation technologies. KEY POINTS: •Pollutants can exert toxicity on cellular membrane, enzyme and gene transcription. •Bacteria can patch promiscuous enzymes into novel pathway to degrade pollutants. •The evolution trajectory is constrained by epistasis from mutations on enzyme and cellular level.

New mechanistic insights into soil ecological risk assessment of arsenite (III) and arsenate (V)：Cellular and molecular toxicity responses in Eisenia fetida

Inorganic arsenic (iAs) is a persistent bioaccumulation carcinogen that is most abundant in soils in the form of arsenite-As (III) and arsenate-As (V). However, there is currently very little explicit evidence about cytotoxicity of As on soil organisms. Moreover, toxicological data for iAs and proteotoxicity is shortage. The purpose of the present work is to elucidate the cytotoxicity mechanism of As (III) and As (V) to earthworms, a soil ecological sentinel species, and the molecular mechanisms by which As (III)/As (V) directly bind to antioxidative enzyme Cu/Zn-superoxide dismutase (Cu/Zn-SOD). Results indicate that iAs triggered cell membrane injury and genotoxicity. As (V) (56.15 %) induced lower cell viability than As (III) (61.88 %). Higher ROS and lipid peroxidation level in As (V) support greater cytotoxicity. Differences in cellular uptake due to valence induced diverse levels of oxidative stress and cytotoxicity. At the molecular level, As (III) (129.33 %) induced higher Cu/Zn-SOD activity than As (V) (110.75 %). Changes in backbone, secondary structure, amino acid microenvironment and particle size of Cu/Zn-SOD further revealed the mechanisms of differential molecular toxicity of As (III) and As (V). Binding reactions with Cu/Zn-SOD explain differences in molecular toxicity. Collective research showed that iAs-induced oxidative stress and binding reactions determine the difference of SOD activity between As (III) and As (V) at the cellular level. This work offers new insights into the health risk assessment of As.

Differential response of catalase to As (III) and As (V): Potential molecular mechanism under valence effect

Arsenic (As) is the most prolific contaminant in food, triggering arseniasis primarily via contaminated rice and drinking contaminated water. However, toxicological data for arsenite (As (III)) and arsenate (As (V)) on antioxidant enzyme catalase (CAT) at molecular level is shortage. The interaction mechanism of As (III) and As (V) with CAT was investigated using enzyme activity detection, multi-spectroscopic techniques, isothermal titration calorimetry and computational simulations. Results indicated As (III) and As (V) induced protein skeleton relaxation, secondary structure transformation, fluorescence sensitization and particle alteration of CAT, particularly As (III). Moreover, As (III)/As (V) bound to CAT through hydrogen bonding and hydrophobic. As (III) and As (V) contacted with core residues His 74, Asn 147 and His A74, Trp A357, respectively, thereby inhibiting CAT activity. Overall, As (III) is more aggressive against the structure and physiological function of CAT than As (V). Our findings enhance the understanding of health risk related to dietary As exposure.

Genotoxicity and endocrine disruption potential of haloacetic acids in human placental and lung cells

Chlorination of water results in the formation of haloacetic acids (HAAs) as major disinfection byproducts (DBPs). Previous studies have reported some HAAs species to act as cytotoxic, genotoxic, and carcinogenic. This work aimed at further exploring the toxicity potential of the most investigated HAAs (chloroacetic (CAA), bromoacetic (BAA), iodoacetic (IAA) acid) and HAAs species with high content of bromine (tribromoacetic acid (TBAA)), and iodine in their structures (chloroiodoacetic (CIAA) and diiodoacetic acid (DIAA)) to human cells. Novel knowledge was generated regarding cytotoxicity, oxidative stress, endocrine disrupting potential, and genotoxicity of these HAAs by using human placental and lung cells as in vitro models, not previously used for DBP assessment. IAA showed the highest cytotoxicity (EC₅₀: 7.5 μM) and ability to generate ROS (up to 3-fold) in placental cells, followed by BAA (EC₅₀: 20-25 μM and 2.1-fold). TBAA, CAA, DIAA, and CIAA showed no significant cytotoxicity (EC₅₀ > 250 μM). All tested HAAs decreased the expression of the steroidogenic gene hsd17b1 up to 40 % in placental cells, and IAA and BAA (0.01-1 μM) slightly inhibited the aromatase activity. HAAs also induced the formation of micronuclei in A549 lung cells after 48 h of exposure. IAA and BAA showed a non-significant increase in micronuclei formation at low concentrations (1 μM), while BAA, CAA, CIAA and TBAA were genotoxic at exposure concentrations above 10 μM (100 μM in the case of DIAA). These results point to genotoxic and endocrine disruption effects associated with HAA exposure at low concentrations (0.01-1 μM), and the usefulness of the selected bioassays to provide fast and sensitive responses to HAA exposure, particularly in terms of genotoxicity and endocrine disruption effects. Further studies are needed to define thresholds that better protect public health.

Establishment of a human induced pluripotent stem cell derived alveolar organoid for toxicity assessment

Alveolar epithelial cells (AECs) are vulnerable to injury, which can result in epithelial hyperplasia, apoptosis, and chronic inflammation. In this study, we developed human induced pluripotent stem cell (hiPS) cell-derived AECs (iAECs) and the iAECs based organoids (AOs) for testing AEC toxicity after chemical exposure. HiPS cells were cultured for 14 days with differentiation medium corresponding to each step, and the iAECs-based AOs were maintained for another 14 days. SFTPC and AQP5 were expressed in the AOs, and mRNA levels of SOX9, NKX2.1, GATA6, HOPX, and ID2 were increased. The AOs were exposed for 24 h to nine chemical substances, and IC₅₀ values of the nine chemicals were determined using MTT assay. When the correlations between iAECs 2D culture and AOs 3D culture were calculated using Pearson's correlation coefficient r value, the nine chemicals that caused a significant decrease of cell viability in 3D culture were found to be highly correlated in 2D culture. The cytotoxicity and nitric oxide release in AO cultured with macrophages were then investigated. When AOs with macrophages were exposed to sodium chromate for 24 h, the IC₅₀ value and nitric oxide production were higher than when the AOs were exposed alone. Taken together, the AO-based 3D culture system provides a useful platform for understanding biological characteristics of AECs and modeling chemical exposures.

Cytotoxicity and Oxidative Stress Effects of Indene on Coelomocytes of Earthworm (Eisenia foetida): Combined Analysis at Cellular and Molecular Levels

Indene (IND) is a kind of important aromatic hydrocarbon that is extracted from coal tar and has important applications in industry and biology. In the process of production and utilization, it is easy to enter the soil and produce toxic effects on the soil or organisms. The earthworm is an important organism in the soil. The toxicity of indene on earthworm coelomocytes is rarely studied, and the oxidative stress effects of IND on earthworm coelomocytes remain unclear. In this study, coelomocytes from earthworms and antioxidant enzymes were selected as the research targets. In addition, IND caused oxidative stress, and its related toxic effects and mechanisms were systematically studied and evaluated at the cellular and molecular levels. The results showed that IND destroyed the redox balance in earthworm coelomocytes, and the large accumulation of reactive oxygen species (ROS) significantly inhibited the activities of the antioxidant system, including superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH), and caused lipid peroxidation and membrane permeability changes, resulting in a decrease in cell viability to 74.5% of the control group. At the molecular level, IND was bound to SOD by the arene-H bond, and the binding constant was 4.95 × 10³. IND changed the secondary structure of the SOD and led to a loosening of the structure of the SOD peptide chain. Meanwhile, IND caused SOD fluorescence sensitization, and molecular simulation showed that IND was mainly bound to the junction of SOD subunits. We hypothesized that the changes in SOD structure led to the increase in SOD activity. This research can provide a scientific basis for IND toxicity evaluation.

Fenpropathrin exposure induces neurotoxicity in zebrafish embryos

Fenpropathrin has been a commonly used insecticide to control agricultural and household insects over a few decades. Up to now, fenpropathrin residue in soil and water has been often determined due to its widespread use, which poses serious threat to environment and aquatic organisms. The potential of fenpropathrin to affect aquatic lives is still poorly understood. In this study, we used zebrafish (Danio rerio) embryo as an experimental model system to evaluate the toxicity of fenpropathrin to the development of zebrafish nervous system. Zebrafish embryos were separately exposed to fenpropathrin at the dose of 0.016 mg/L, 0.032 mg/L, 0.064 mg/L, starting at 6 h post-fertilizationhpf (hpf) up to 96 hpf. The results showed that fenpropathrin exposure gives rise to physiological, behavioral, and neurodevelopmental impairments in zebrafish embryos, including enhanced acetylcholinesterase (AChE) activity, abnormal swimming behavior, karyopyknosis in brain cells, increased intercellular space, and uneven migration of neuron in brain area. In addition, the expressions of genes concerning neurodevelopment and neurotransmitter system were inhibited following fenpropathrin exposure. We also found that fenpropathrin exposure distinctly induced oxidative stress by increasing reactive oxygen species (ROS) generation and inhibiting the production of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). Expectedly, some apoptosis-associated genes were induced and the apoptosis appeared in the brain and heart cells of zebrafish embryos. Moreover, fenpropathrin exposure also inhibited the expressions of genes in Nrf2 signaling pathway, such as heme oxygenase-1 (HO-1) and SOD. In summary, the results of this study indicate that oxidative stress-triggered apoptosis may be an underlying fundamental of fenpropathrin-induced neurotoxicity in zebrafish embryos.

Ferric ions release from iron-binding protein: Interaction between acrylamide and human serum transferrin and the underlying mechanisms of their binding

Acrylamide (ACR) is a surprisingly common chemical due to its widespread use in industry and various other applications. However, its toxicity is a matter of grave concern for public health. Even worse, ACR is frequently detected in numerous fried or baked carbohydrate-rich foods due to the Maillard browning reaction. Herein, this study intends to delineate the underlying molecular mechanisms of Fe ions released from iron-binding protein transferrin (TF) after acrylamide binding by combining multiple methods, including multiple complementary spectroscopic techniques (UV-Vis, fluorescence, and circular dichroism spectroscopy), isothermal titration calorimetry, ICP-MS measurements, and modeling simulations. Results indicated that free Fe was released from TF only under high-dose ACR exposure (>100 μM). Acrylamide binding induced the loosening and unfolding of the backbone and polypeptide chain and destroyed the secondary structure of TF, thereby leading to protein misfolding and denaturation of TF and forming a larger size of TF agglomerates. Of which, H-binding and van der Waals force are the primary driving force during the binding interaction between ACR and TF. Further modeling simulations illustrated that ACR prefers to bind to the hinge region connecting the C-lobe and N-lobe, after that it attaches to the Fe binding sites of this protein, which is the cause of free Fe release from TF. Moreover, ACR interacted with the critical fluorophore residues (Tyr, Trp, and Phe) in the binding pocket, which might explain such a phenomenon of fluorescence sensitization. The two binding sites (Site 2 and Site 3) located around the Fe (III) ions with low-energy conformations are more suitable for ACR binding. Collectively, our study demonstrated that the loss of iron in TF caused by acrylamide-induced structural and conformational changes of transferrin.

Probing the interaction of superparamagnetic iron oxide nanoparticles with lipase and their interacting consequences at the molecular level

Background

Although superparamagnetic iron oxide nanoparticles (SPIONs) are used as carriers for candida rugosa lipase (CRL) in biomedical fields, their interactions and the influences on CRL are still unknown. Consequently, SPIONs were synthesized, characterized, and incubated with CRL to explore their molecular interactions and interacting consequences in this study.

Methods

The toxic effects of SPIONs on CRL and their molecular interactions were explored through transmission electron microscope, isothermal titration calorimetry, zeta potential measurements, multi-spectroscopic techniques, and biological enzyme activity tests.

Results

Results revealed the adsorption of SPIONs to CRL and the reduction of CRL aggregation. The unfolding and loosening of CRL structure as well as the change of secondary structure with the decrease of α-helix were found under SPIONs exposure. Moreover, higher SPIONs concentrations contributed to larger conformational changes and less aggregation of CRL. Meanwhile, it showed that hydrophobic forces were the dominant driving forces in the binding process, with the participation of electrostatic forces. CRL binds to SPIONs with the stoichiometry of 20.7 and the binding constant of 9.9 × 106 M−1. No obvious changes were found in CRL activity due to no interference to Ser-209, Glu-341, and His-449 residues.

Conclusion

This study examined the biological compatibility of SPIONs at the molecular level and provided important information about the structure and function of CRL upon binding to SPIONs. Our work might contribute to comprehend the molecular toxicity of SPIONs and the risks of engineered nanoparticles to human health.

In Vivo Neuropharmacological Potential of Gomphandra tetrandra (Wall.) Sleumer and In-Silico Study against β-Amyloid Precursor Protein

Medicinal plants possess a surplus of novel and biologically active secondary metabolites that are responsible for counteracting diseases. Traditionally, Gomphandra tetrandra (Wall.) Sleumer is used to treat mental disorders. The present research was designed to explore phytochemicals from the ethanol leaf extract of Gomphandra tetrandra (Wall.) Sleumer to identify the potential pharmacophore(s) in the treatment of neurological disorders. The chemical compounds of the experimental plant were identified through GC-MS analysis. In-vitro antioxidant activity was assessed using different methods. Furthermore, in-vivo neurological activity was assessed in Swiss-albino mice. Computer-aided analysis was appraised to determine the best-fit phytoconstituent of a total of fifteen identified compounds in the experimental plant extract against beta-amyloid precursor protein. The experimental extract revealed fifteen compounds in GC-MS analysis and the highest content was 9, 12, 15-octadecatrienoic acid (z,z,z). The extract showed potent antioxidant activity in in-vitro assays. Furthermore, in in-vivo neurological assays, the extract disclosed significant (p < 0.05) neurological activity. The most favorable phytochemicals as neurological agents were selected via ADMET profiling, and molecular docking was studied with beta-amyloid precursor protein. In the computer-aided study, 1, 5-diphenyl-2h-1, 2, 4-triazoline-3-thione (Pub Chem CID: 2802516) was more active than other identified compounds with strong binding affinity to beta-amyloid precursor protein. The present in vivo and in silico studies revealed neuropharmacological features of G. tetrandra leaf extract as a natural agent against neurological disorders, especially Alzheimer’s disease.

Toxic effect and mechanism of ultrafine carbon black on mouse primary splenocytes and two digestive enzymes

This paper investigated the toxic effect and mechanism of ultrafine carbon black (UFCB) on splenocytes and enzymes in the digestive system. It was found that the toxicity of UFCB to splenocytes was dose-dependent. UFCB with a low concentration (<15 μg/mL) had no significant effect on splenocytes while UFCB with high concentration (>15 μg/mL) induced significant oxidative damage with increased content of reactive oxygen species (ROS) (134%) and malonaldehyde (MDA) (222.3%) along with the decreased activity of superoxide dismutase (SOD) (55.63%) and catalase (CAT) (87.73%). Analysis combined cellular and molecular levels indicated that UFCB induced splenocyte toxicity through oxidative stress. The interactions of UFCB with two important digestive enzymes, α-amylase and lipase, were also studied respectively. Results showed that the interaction of UFCB and the two enzymes altered the particle size and fluorescence intensity in both experimental systems. The formation of protein corona also resulted in the contraction of the polypeptide skeleton in both enzymes, which further inhibited their activity. Our work provided basic data on the toxicity of UFCB in the spleen and digestive system and fills the gap in the study of UFPs toxicity. CAPSULE: UFCB induced splenocyte toxicity and enzyme dysfunction through oxidative stress and protein corona formation respectively.

Hypoglycemic effect of biscuits produced from flour blends of three medicinal foods on high-fat diet-streptozotocin-induced diabetic rats

The study evaluated the hypoglycemic effect of biscuits produced from flour blends of three medicinal foods (Unripe plantain fruits, Moringa seed, and pigeon pea) on high-fat diet (HFD)/streptozotocin (STZ)-induced (HFD/STZ) diabetic rats. The formulated biscuits were produced at different proportion of the flour blends and fed to HFD-STZ-induced diabetic rats for 14 days. The result showed that the formulated biscuits caused a significant increase in pancreas, liver, and kidney antioxidant molecules, decreased the production of thiobarbituric reactive acid species (TBARS) in pancreas, liver, and kidney homogenates, and reduced pancreatic α-amylase and intestinal α-glucosidase activities as against untreated diabetic rats. In conclusion, the use of formulated biscuits from the blends of flours from unripe plantain, Moringa seed, and pigeon pea could serve as functional food toward the treatment/management of diabetes and its possible complications such as diabetes-induced liver and kidney damage. PRACTICAL APPLICATIONS: The drug use in the management of diabetes such as acarbose have been reported to have side effects, while diet therapy is gaining much interest in the management of diabetes. Hence, there is a need for diets base therapy that will not only cure diabetes, but also combat its complications. In sight of this, unripe plantain, Moringa seed, and pigeon pea flours were blended and used to produce functional biscuits for diabetic rats. The biscuit could be produced on the large scale under hygienic and regulated condition.