Hexavalent chromium induced oxidative stress and apoptosis in Pycnoporus sanguineus

ATF4-mediated different mode of interaction between autophagy and mTOR determines cell fate dependent on the level of ER stress induced by Cr(VI)

Hexavalent chromium [Cr(VI)] exists widely in occupational environments. The mechanistic target of rapamycin (mTOR) has been well-documented to regulate autophagy negatively. However, we found that low concentration of Cr(VI) (0.2 μM) elevated both mTOR and autophagy and promote cell survival. Conversely, high concentration of Cr(VI) (6 μM) caused cell death by inhibiting mTOR and subsequently inducing autophagy. Tunicamycin (Tm), as an Endoplasmic reticulum (ER) stress activator was used to induce mild ER stress at 0.1 μg/ml and it activated both autophagy and mTOR, which also caused cell migration in a similar manner to that observed with low concentration of Cr(VI). Severe ER stress caused by Tm (2 μg/ml) decreased mTOR, increased autophagy and then inhibited cell migration, which was the same as 6 μM Cr(VI) treatment, although Cr(VI) in high concentration inhibited ER stress. Activating transcription factor 4 (ATF4), a downstream target of ER stress, only increased under mild ER stress but decreased under severe ER stress and 6 μM Cr(VI) treatment. Chromatin immunoprecipitation (ChIP) experiment indicated that ATF4 could bind to the promoter of ATG4B and AKT1. To sum up, our data revealed that mild ER stress induced by low concentration of Cr(VI) could enhance transcriptional regulation of ATG4B and AKT1 by ATF4, which induced both autophagy and mTOR to promote cell viability.

Metabolic perturbation and oxidative damage induced by tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and tris(2-ethylhexyl) phosphate (TEHP) on Escherichia coli through integrative analyses of metabolome

Organophosphate esters (OPEs) are one of the emerging environmental threats, causing the hazard to ecosystem safety and human health. Yet, the toxic effects and metabolic response mechanism after Escherichia coli (E.coli) exposed to TDCIPP and TEHP is inconclusive. Herein, the levels of SOD and CAT were elevated in a concentration-dependent manner, accompanied with the increase of MDA contents, signifying the activation of antioxidant response and occurrence of lipid peroxidation. Oxidative damage mediated by excessive accumulation of ROS decreased membrane potential and inhibited membrane protein synthesis, causing membrane protein dysfunction. Integrative analyses of GC-MS and LC-MS based metabolomics evinced that significant perturbation to the carbohydrate metabolism, nucleotide metabolism, lipids metabolism, amino acid metabolism, organic acids metabolism were induced following exposure to TDCIPP and TEHP in E.coli, resulting in metabolic reprogramming. Additionally, metabolites including PE(16:1(5Z)/15:0), PA(17:0/15:1(9Z)), PC(20:2(11Z,14Z)/12:0), LysoPC(18:3(6Z,9Z,12Z)/0:0) were significantly upregulated, manifesting that cell membrane protective molecule was afforded by these differential metabolites to improve permeability and fluidity. Overall, current findings generate new insights into the molecular toxicity mechanism by which E.coli respond to TDCIPP and TEHP stress and supply valuable information for potential ecological risks of OPEs on aquatic ecosystems.

Couples' preconception urinary essential trace elements concentration and spontaneous abortion risk: A nested case-control study in a community population

BACKGROUND

Previous studies have indicated a correlation between maternal imbalances in essential trace elements during pregnancy and the occurrence of spontaneous abortion (SA). Nonetheless, the impact of these elements from both partners and during the preconception period remains unexplored.

OBJECTIVE

This study sought to evaluate the relationship between preconception essential trace elements and spontaneous abortion (SA) based on husband-wife dyads.

METHODS

This study selected 390 couples with spontaneous abortion (SA) and 390 matched couples with live births from a preconception cohort of 33,687 couples. Urine samples collected prior to pregnancy were analyzed for ten essential trace elements (Se, Cr, Mo, Cu, Zn, Fe, Mn, V, Co, and Ni) using inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Multivariate conditional logistic regression analysis identified that elevated concentrations of Zn (OR = 0.73) and Ni (OR = 0.69) in couples were associated with a reduced risk of SA, whereas elevated levels of Cr (OR = 1.30) and Mn (OR = 1.39) were linked to an increased risk. Restricted cubic spline models suggested a U-shaped association between couples' Cu and Co concentrations and SA. Bayesian Kernel Machine Regression further supported a U-shaped relationship between the mixture of ten elements and SA, showing significant protection at the 50th and 55th percentiles compared to the 10th percentile. Additionally, the effects of Cr, Zn, Mn, and Ni on SA varied when the concentrations of the other nine elements were held constant at their 25th, 50th, and 75th percentiles. Stratified analysis revealed that maternal Cu (OR = 0.43) and Fe (OR = 0.63) reduced the risk of SA when paternal Cu and Fe were in the lower quartile. Conversely, maternal Cu (OR = 2.03) and Fe (OR = 1.77) increased the risk of SA when paternal concentrations were in the higher quartile. Similar patterns were observed for Cr, Mn, Co, and Zn.

CONCLUSION

Elevated urinary concentrations of Zn and Ni in couples were associated with a reduced risk of SA, while higher levels of Cr and Mn were linked to an increased risk. Cu, Co, and a mixture of ten essential trace elements exhibited a U-shaped relationship with SA. The impact of certain essential trace elements (Cu, Fe, Cr, Mn, Co, and Zn) on SA in one partner was influenced by their concentrations in the other partner.

Enhanced kidney damage induced by increasing nonylphenol doses: impact on autophagy-related proteins and proinflammatory cytokines in rats

Nonylphenol (NP) is an organic pollutant and endocrine disruptor chemical that has harmful effects on the environment and living organisms. This study looked at whether kidney tissues subjected to increasing doses of nonylphenol generated alterations in histopathologic, pro-inflammatory, and autophagic markers. Fifty rats were divided into five groups of ten each: group I: healthy group, II: control (corn oil), group III: 25 μl/kg NP, group IV: 50 μl/kg NP, group V: 75 μl/kg NP. The kidney tissue samples were obtained for histopathological, immunohistochemical, and biochemical analyses. The histological deteriorations observed in all NP groups included tubular epithelial cell degeneration, inflammation areas, and hemorrhage. The immunohistochemical investigations showed that NP significantly elevated the autophagy markers (Beclin-1, LC3A/B, p62), pro-inflammatory cytokines (TNF-α, IL-6), HIF-1α, and eNOS in group III, IV and V compared with group I and II. The biochemical analysis also revealed that pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) increased in correlation with the NP doses, but only IL-1β reached statistical significance in NP treated rats kidney tissue. The biochemical findings have been confirmed by the histological studies. The damage to renal tissue caused by NP exposure may worsen it by increasing inflammatory and autophagic markers.

Elucidating the mechanisms and mitigation strategies for six-phthalate-induced toxicity in male germ cells

Phthalate esters (PAEs) are primary plasticizers and endocrine-disrupting chemicals (EDCs) that are extensively used in numerous everyday consumer products. Although the adverse effects of single PAEs have been studied, our understanding of the effect of multiple phthalate exposure on male germ cell vitality remains limited. Therefore, this study aimed to investigate the collective effects of a mixture of PAEs (MP) comprising diethyl-, bis (2-ethylhexyl)-, dibutyl-, diisononyl-, diisobutyl-, and benzyl butyl-phthalates in the proportions of 35, 21, 15, 15, 8, and 5%, respectively, on differentiated male germ cells using GC-1 spermatogonia (spg) cells. As a mixture, MP substantially hindered GC-1 spg cell proliferation at 3.13 μg/mL, with a half-maximal inhibitory concentration of 16.9 μg/mL. Treatment with 25 μg/mL MP significantly induced reactive oxygen species generation and promoted apoptosis. Furthermore, MP activated autophagy and suppressed phosphorylation of phosphoinositide 3-kinase, protein kinase B, and mammalian target of rapamycin (mTOR). The triple inhibitor combination treatment comprising parthenolide, N-acetylcysteine, and 3-methyladenine effectively reversed MP-induced GC-1 spg cell proliferation inhibition, mitigated apoptosis and autophagy, and restored mTOR phosphorylation. This study is the first to elucidate the mechanism underlying MP-induced male germ cell toxicity and the restoration of male germ cell proliferation mediated by chemical inhibitors. Therefore, it provides valuable insights into the existing literature by proposing a combinatorial toxicity mitigation strategy to counteract male germ cell toxicity induced by various EDCs exposure.

Autophagy: A potential target for natural products in the treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease primarily affecting the mucosa of the colon and rectum. UC is characterized by recurrent episodes, often necessitating lifelong medication use, imposing a significant burden on patients. Current conventional and advanced treatments for UC have the disadvantages of insufficient efficiency, susceptibility to drug resistance, and notable adverse effects. Therefore, developing effective and safe drugs has become an urgent need. Autophagy is an intracellular degradation process that plays an important role in intestinal homeostasis. Emerging evidence suggests that aberrant autophagy is involved in the development of UC, and modulating autophagy can effectively alleviate experimental colitis. A growing number of studies have established that autophagy can interplay with endoplasmic reticulum stress, gut microbiota, apoptosis, and the NLRP3 inflammasome, all of which contribute to the pathogenesis of UC. In addition, a variety of intestinal epithelial cells, including absorptive cells, goblet cells, and Paneth cells, as well as other cell types like neutrophils, antigen-presenting cells, and stem cells in the gut, mediate the development of UC through autophagy. To date, many studies have found that natural products hold the potential to exert therapeutic effects on UC by regulating autophagy. This review focuses on the possible effects and pharmacological mechanisms of natural products to alleviate UC with autophagy as a potential target in recent years, aiming to provide a basis for new drug development.

Global responses to tris(1-chloro-2-propyl) phosphate and tris(2-butoxyethyl) phosphate in Escherichia coli: Evidences from biomarkers, and metabolic disturbance using GC-MS and LC-MS metabolomics analyses

Tris(1-chloro-2-propyl) phosphate (TCPP) and tris(2-butoxyethyl) phosphate (TBEP) as pollutants of emerging concern have aroused the rising attention due to their potential risks on aquatic ecosystem and public health. Nevertheless, there is a lack of toxicological mechanisms exploration of TCPP and TBEP at molecular levels. Herein, the toxicity effects and molecular mechanism of them were fully researched and summarized on Escherichia coli (E.coli). Acute exposure to them significantly activated antioxidant defense system and caused lipid peroxidation, as proved by the changes of antioxidant enzymes and MDA. The ROS overload resulted in the drop of membrane potential as well as the downregulated synthesis of ATPase, endorsing that E. coli cytotoxicity was ascribed to oxidative stress damage induced by TCPP and TBEP. The combination of GC-MS and LC-MS based metabolomics validated that TCPP and TBEP induced metabolic reprogramming in E.coli. More specifically, the responsive metabolites in carbohydrate metabolism, lipids metabolism, nucleotide metabolism, amino acid metabolism, and organic acids metabolism were significantly disturbed by TCPP and TBEP, confirming the negative effects on metabolic functions and key bioprocesses. Additionally, several biomarkers including PE(16:1(5Z)/15:0), PA(17:1(9Z)/18:2(9Z,12Z)), PE(19:1(9Z)/0:0), and LysoPE(0:0/18:1(11Z)) were remarkably upregulated, verifying that the protection of cellular membrane was conducted by regulating the expression of lipids-associated metabolites. Collectively, this work sheds new light on the potential molecular toxicity mechanism of TCPP and TBEP on aquatic organisms, and these findings using GC-MS and LC-MS metabolomics generate a fresh insight into assessing the effects of OPFRs on target and non-target aquatic organisms.

Fungal biomineralization of toxic metals accelerates organic pollutant removal

Fungal biomineralization plays an important role in the biogeochemical cycling of metals in the environment and has been extensively explored for bioremediation and element biorecovery. However, the cellular and metabolic responses of fungi in the presence of toxic metals during biomineralization and their impact on organic matter transformations are unclear. This is an important question because co-contamination by toxic metals and organic pollutants is a common phenomenon in the natural environment. In this research, the biomineralization process and oxidative stress response of the geoactive soil fungus Aspergillus niger were investigated in the presence of toxic metals (Co, Cu, Mn, and Fe) and the azo dye orange II (AO II). We have found that the co-existence of toxic metals and AO II not only enhanced the fungal biomineralization of toxic metals but also accelerated the removal of AO II. We hypothesize that the fungus and in situ mycogenic biominerals (toxic metal oxalates) constituted a quasi-bioreactor, where the biominerals removed organic pollutants by catalyzing reactive oxygen species (ROS) generation resulting from oxidative stress. We have therefore demonstrated that a fungal/biomineral system can successfully achieve the goal of toxic metal immobilization and organic pollutant decomposition. Such findings inform the potential development of fungal-biomineral hybrid systems for mixed pollutant bioremediation as well as provide further understanding of fungal organic-inorganic pollutant transformations in the environment and their importance in biogeochemical cycles.

Diisobutyl phthalate (DiBP)-induced male germ cell toxicity and its alleviation approach

Diisobutyl phthalate (DiBP) is a commonly used plasticizer in manufacturing consumer and industrial products to improve flexibility and durability. Despite of the numerous studies, however, the direct mechanism underlying the male reproductive damage of DiBP is poorly understood. In this study, we investigated the male germ cell toxicity of DiBP using GC-1 spermatogonia (spg) cells. Our results indicated that DiBP exposure causes oxidative stress and apoptosis in GC-1 spg cells. In addition, DiBP-derived autophagy activation and down-regulation of phosphoinositide 3-kinase (PI3K)-AKT and extracellular signal-regulated kinase (ERK) pathways further inhibited GC-1 spg cell proliferation, indicating that DiBP can instigate male germ cell toxicity by targeting several pathways. Importantly, a combined treatment of parthenolide, N-acetylcysteine, and 3-methyladenine significantly reduced DiBP-induced male germ cell toxicity and restored proliferation. Taken together, the results of this study can provide valuable information to the existing literature by enhancing the understanding of single phthalate DiBP-derived male germ cell toxicity and the therapeutic interventions that can mitigate DiBP damage.

Multiomics Reveals Mechanisms of Alternaria oxytropis Inhibiting Pathogenic Fungi in Oxytropis ochrocephala

Endophytic fungi can benefit the host plant and increase the plant resistance. Now, there is no in-depth study of how Alternaria oxytropis (A. oxytropis) is enhancing the ability of inhibiting pathogenic fungi in Oxytropis ochrocephala (O. ochrocephala). In this study, the fungal community and metabolites associated with endophyte-infected (EI) and endophyte-free (EF) O. ochrocephala were compared by multiomics. The fungal community indicated that there was more A. oxytropis, less phylum Ascomycota, and less genera Leptosphaeria, Colletotrichum, and Comoclathris in the EI group. As metabolic biomarkers, the levels of swainsonine and apigenin-7-O-glucoside-4-O-rutinoside were significantly increased in the EI group. Through in vitro validation experiments, swainsonine and apigenin-7-O-glucoside-4-O-rutinoside can dramatically suppress the growth of pathogenic fungi Leptosphaeria sclerotioides and Colletotrichum americae-borealis by increasing the level of oxidative stress. This work suggested that O. ochrocephala containing A. oxytropis could increase the resistance to fungal diseases by markedly enhancing the content of metabolites inhibiting pathogenic fungi.

Effects of hexavalent chromium on mitochondria and their implications in carcinogenesis

Hexavalent chromium (Cr(VI)) is a well-known occupational and environmental human carcinogen. The cellular effect of Cr(VI) is complex and often nonspecific due to its ability to modulate multiple cellular targets. The toxicity of Cr(VI) is strongly linked to the generation of reactive oxygen species (ROS) during its reduction process. ROS can cause oxidation of cellular macromolecules, such as proteins, lipids, and DNA, thereby altering their functions. A major genotoxic effect of Cr(VI) that contributes to carcinogenesis is the formation of DNA adducts, which can lead to DNA damage. Modulations of cellular signaling pathways and epigenetics may also contribute to the carcinogenic effects of Cr(VI). Cr(VI) has a major impact on many aspects of mitochondrial biology, including oxidative phosphorylation, mitophagy, and mitochondrial biogenesis. These effects have the potential to alter the trajectory of Cr(VI)-induced carcinogenic process. This perspective article summarizes current understandings of the effect of Cr(VI) on mitochondria and discusses the future directions of research in this area, particularly with regard to carcinogenesis.

Hexavalent chromium caused DNA damage repair and apoptosis via the PI3K/AKT/FOXO1 pathway triggered by oxidative stress in the lung of rat

Hexavalent chromium [Cr(VI)] is an occupational carcinogen that accumulates in the lungs and causes lung injury and even lung cancer. 36 SD male rats received inhalable intratracheal instillation of Cr(VI) (0.05, 0.25 mg Cr/kg) or the same volume (3 ml/kg) of normal saline weekly for 28 days (total 5 times). After 28 days of exposure, half of the rats in each group were sacrificed for investigation, and the rest stopped exposure and began to be self-repaired for two weeks. Histopathology analyses revealed that Cr(VI) induced slight dilatation and hemorrhage of perialveolar capillaries, pulmonary bronchodilation, and congestion with peripheral flaky-like necrosis accompanied by inflammatory cell infiltration, especially the 0.25 mg Cr/kg group. Cr(VI) exposure caused the increase of blood Cr, urinary Cr, MDA, urinary 8-hydroxy-2' -deoxyguanosine (8-OHdG), and the decrease of GSH and MDA, while two-week repair only reduced urinary Cr. Exposure to Cr(VI) significantly upregulated FOXO1 and downregulated p-AKT and p-FOXO1 for two weeks. PI3K in the 0.25 mg Cr/kg group was inhibited after two weeks of repair. Cr(VI) exposure mainly promoted GADD45a and CHK2 in the exposure group, promoted Bim, Bax/Bcl-2, and suppressed Bcl-2 and Bcl-xL in the repair group. These results demonstrate that Cr(VI) may induce DNA damage repair and apoptosis in the lung by activating the PI3K/AKT/FOXO1 pathway. Two-week repair may alleviate oxidative stress and DNA damage induced by Cr(VI) exposure but couldn't eliminate its effects. This study provides a new perspective for exploring the Cr(VI) induced lung cancer mechanism.

Therapeutic effect of thymoquinone on brain damage caused by nonylphenol exposure in rats

Nonylphenol (NP), causes various harmful effects such as cognitive impairment and neurotoxicity. Thymoquinone (TQ), has antioxidant, anti-inflammatory, and neuroprotective properties. In this study, our aim is to investigate the effects of TQ on the brain damage caused by NP. Corn oil was applied to the control group. NP (100 mg/kg/day) was administered to the NP and NP + TQ groups for 21 days. TQ (5 mg/kg/day) was administered to the NP + TQ and TQ groups for 7 after 21 days. At the end of the experiment, the new object recognition test was applied to the rats and the rats were killed and their brain tissues were removed. Sections taken from brain tissues were stained with hematoxylin-eosin for histopathological evaluation. In addition, neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP), Cas-3, and nerve growth factor (NGF) immunoreactivities were evaluated in brain tissue sections. In addition, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were determined. Comet assay was applied to determine DNA damage in cells. The results of our study showed that NP, caused behavioral disorders and damage to the cerebral cortex in rats. This damage in the form of neuron degeneration seen in the cortex was associated with apoptosis involving Cas-3 activation, increased DNA damage, and free oxygen radicals. NP, SOD, and CAT caused a decrease in enzyme activities. In addition, the cellular protein NeuN was decreased, astrocytosis-associated GFAP was increased, and growth factor NGF was decreased. When all our evaluations are taken together, treatment with TQ showed an ameliorative effect on the behavioral impairment and brain damage caused by NP exposure.

Alleviative effects of quercetin of Botrytis cinerea-induced toxicity in zebrafish (Danio rerio) larvae

Quercetin is a kind of flavonoid substance extensively existing in the plant, which has antioxidant, anti-inflammatory, and anti-apoptosis effects. It was reported that the higher concentration of spores present in the environment could cause abnormal development in zebrafish larvae. Therefore, this study set out to investigate whether quercetin could reduce the zebrafish larvae damage caused by Botrytis cinerea exposure as well as to examine the molecular basis for this action. The findings demonstrated that 50 μM quercetin improved the developmental dysplasia of zebrafish larvae induced by 102 CFU/mL Botrytis cinerea spore suspension, reduced abnormal apoptosis, enhanced antioxidant system, relieved inflammation, reshaped intestinal morphology and recovered intestinal motility. At the molecular level, quercetin decreased the transcriptional abundance of pro-apoptotic factors (bax, p53, caspase3, and caspase9) and up-regulated the anti-apoptotic gene (bcl-2) expression to reduce apoptosis. Moreover, quercetin enhanced the activities of downstream antioxidant enzymes (SOD and CAT) to clear excess ROS and MDA due to Botrytis cinerea exposure by up-regulating the expression of antioxidant genes (nrf2, ho-1, sod, and cat) in the Keap1-Nrf2 pathway. Additionally, quercetin inhibited the elevation of TNF-α by regulating the gene expression of key targets (jak3, pi3k, pdk1, akt, and ikk2) and the content of major proteins NF-κB (P65) and IκB in the NF-κB pathway. In conclusion, this work enriched the contents of the biological research of Botrytis cinerea and provided a new direction for the drug development and targeted therapy of quercetin.

A review of chromium (Cr) epigenetic toxicity and health hazards

Carcinogenic metals affect a variety of cellular processes, causing oxidative stress and cancer. The widespread distribution of these metals caused by industrial, residential, agricultural, medical, and technical activities raises concern for adverse environmental and human health effects. Of these metals, chromium (Cr) and its derivatives, including Cr(VI)-induced, are of a public health concern as they cause DNA epigenetic alterations resulting in heritable changes in gene expression. Here, we review and discuss the role of Cr(VI) in epigenetic changes, including DNA methylation, histone modifications, micro-RNA changes, biomarkers of exposure and toxicity, and highlight prevention and intervention strategies to protect susceptible populations from exposure and adverse occupational health effects. Cr(VI) is a ubiquitous toxin linked to cardiovascular, developmental, neurological, and endocrine diseases as well as immunologic disorders and a high number of cancer types in humans following inhalation and skin contact. Cr alters DNA methylation levels as well as global and gene-specific histone posttranslational modifications, emphasizing the importance of considering epigenetics as a possible mechanism underlying Cr(VI) toxicity and cell-transforming ability. Our review shows that determining the levels of Cr(VI) in occupational workers is a crucial first step in shielding health problems, including cancer and other disorders. More clinical and preventative measures are therefore needed to better understand the toxicity and safeguard employees against cancer.

Characterization of a cadmium-resistant functional bacteria (Burkholderia sp. SRB-1) and mechanism analysis at physiochemical and genetic level

In this study, the capacity of cadmium (Cd)-resistant plant growth-promoting bacteria (PGPB) Burkholderia sp. SRB-1 (SRB-1) and its mechanisms were explored through morphological characterizations, biochemical response, plant growth-promoting traits, and functional gene expression patterns. The results showed that SRB-1 was an excellent Cd-resistant bacteria (MIC was 420 mg L^-1), and its maximum Cd removal rate reached 72.25%. Biosorption was the main removal method of Cd for SRB-1, preventing intracellular Cd accumulation and maintaining cellular metabolism. Various functional groups on the cell wall were involved in Cd binding, which deposited as CdS and CdCO₃ on the cell surface according to XPS analysis and might be critical for reducing Cd physiochemical toxicity. Furthermore, metals exporting (zntA, czcA, czcB, czcC), detoxification (dsbA, cysM), and antioxidation (katE, katG, SOD1) related genes were annotated in the SRB-1 genome. The results of Cd distribution and antioxidative enzyme activity in SRB-1 also illustrated that Cd²⁺ efflux and antioxidative response were the main intracellular Cd-resistant mechanisms. These conclusions were further verified by qRT-PCR analysis. Overall, the strategies of extracellular biosorption, cation efflux, and intracellular detoxification jointly build the Cd-resistant system, which invested Burkholderia sp. SRB-1 with potential for bioremediation in heavily Cd-contaminated environmental sites.

Stereoselective accumulation and biotransformation of chiral fungicide epoxiconazole and oxidative stress, detoxification, and endogenous metabolic disturbance in earthworm (Eisenia foetida)

>80 % of applied pesticides in agriculture will enter the soil and be exposed to soil animals. Little is known about the stereoselective metabolic effects of epoxiconazole (EPO) on soil animals. In this study, EPO-mediated stereoselective enrichment, biotransformation, oxidative stress, detoxification, and global metabolic profiles in earthworms were investigated by exposure to EPO and its enantiomers at 1 mg/kg and 10 mg/kg doses. Preferential enrichment of (-)-EPO was observed, and the five transformation products (TPs) exhibited the chemically specific stereoselective accumulation with inconsistent configurations. Biochemical markers related to reactive oxygen species (ROS) and detoxification (·OH^- content, SOD, CAT, GST, and CYP450 enzymes) showed a significant stereoselective activation overall at the low-level exposure (p-value <0.05). Based on untargeted metabolomic analysis, the steroid biosynthesis and ROS-related biotransformation, glutathione metabolism, TCA cycle, amino acid metabolism, purine and pyrimidine metabolism of earthworms were significantly interfered with by EPO and its enantiomer exposure. More pronounced stereoselectivity was observed at the level of the global metabolic profile, while comparable levels of metabolic perturbations were identified at the individual metabolite level. This study provides novel insights into the stereoselective effects of the chiral fungicide EPO, and valuable evidence for soil environmental risk assessments.

Integration of transcriptomic and proteomic reveals the toxicological molecular mechanisms of decabromodiphenyl ethane (DBDPE) on Pleurotus ostreatus

Decabromodiphenyl ethane (DBDPE), as one of the most widely used new brominated flame retardants (NBFRs), can pose a potential threat to human health and the environment. An integrated transcriptome and proteome was performed for investigating the toxicological molecular mechanisms of Pleurotus ostreatus (P. ostreatus) during the biodegradation of DBDPE at the concentrations of 5 and 20 mg/L. A total of 1193/1018 and 92/126 differentially expressed genes/proteins (DEGs/DEPs) were found, respectively, with DBDPE exposure at 5 and 20 mg/L. These DEGs and DEPs were mainly involved in the cellular process as well as metabolic process. DEPs for oxidation-reduction process and hydrolase activity were up-regulated, and those for membrane, lipid metabolic process and transmembrane transport were down-regulated. The DEGs and DEPs related to some key enzymes were down-regulated, such as NADH dehydrogenase/oxidoreductase, succinate dehydrogenase, cytochrome C1 protein, cytochrome-c oxidase/reductase and ATP synthase, which indicated that DBDPE affected the oxidative phosphorylation as well as tricarboxylic acid (TCA) cycle. Cytochrome P450 enzymes (CYPs) might be involved in DBDPE degradation through hydroxylation and oxidation. Some stress proteins were induced to resist DBDPE toxicity, including major facilitator superfamily (MFS) transporter, superoxide dismutase (SOD), molecular chaperones, heat shock proteins (HSP20, HSP26, HSP42), 60S ribosomal protein and histone H4. The findings help revealing the toxicological molecular mechanisms of DBDPE on P. ostreatus, aiming to improve the removal of DBDPE.

Selenium Alleviates Chromium(VI)-Induced Ileum Damage and Cecal Microbial Disturbances in Mice

Hexavalent chromium [Cr(VI)] is one of the most common environmental contaminants caused by its broad industrial applications. Importantly, exposure to Cr(VI) induces oxidative damage and apoptosis in animal cells. Studies have shown that selenium (Se) can alleviate the toxic effects of Cr(VI) by functioning as an antioxidant and/or by chelating Cr(VI) into biologically inert complexes, but the underlying mechanism remains unknown. Here, we evaluated whether Se can ameliorate ileum damage and cecal microbial disturbances induced by Cr(VI) in vivo. Mice administered Cr(VI) for 30 days presented histopathological damage, reduced responses to oxidative stress, and increased expression of apoptosis-related genes in the ileum compared with those in the control (non-exposed) group. Se alleviated the histopathological damage and decreased the oxidative stress and apoptosis induced by Cr(VI) in the ileum. In addition, Cr(VI) disturbed cecal microflora, and it was partially reversed by Se treatment. These findings demonstrate that the damaging and potentially pathological effects of Cr(VI) on the ileum and cecal microflora can be effectively alleviated with Se treatment.

Selenium regulates the mitogen-activated protein kinase pathway to protect broilers from hexavalent chromium-induced kidney dysfunction and apoptosis

Hexavalent chromium [Cr (VI)] is a common environmental pollutant. Although selenium (Se) can antagonize the toxicity of Cr (VI), the specific underlying mechanism has not been identified. To investigate this mechanism, we used potassium dichromate (K₂Cr₂O₇) and selenium-rich yeast (SeY) to construct single Cr (VI)- and combined Se/Cr (VI)-exposed broiler models during a 42-day period. Broilers were randomly assigned to the control (C), SeY (Se), SeY + Cr (VI) (Se/Cr), and Cr (VI) (Cr) groups. The antagonistic mechanisms of Se and Cr (VI) were evaluated using histopathological evaluation, serum and tissue biochemical tests, real-time fluorescence quantitative polymerase chain reaction, and western blotting. The results suggested that Se alleviated the morphological and structural damage to renal tubules and glomeruli, while reducing the organ index, creatinine levels, and blood urea nitrogen levels in the kidneys of Cr (VI)-exposed broilers. Furthermore, Cr (VI) reduced the levels of superoxide dismutase and glutathione, and increased the levels of malondialdehyde, in broiler kidney tissues. However, Se alleviated Cr (VI)-induced oxidative stress by increasing the levels of superoxide dismutase and glutathione, and decreasing the levels of malondialdehyde, within a certain range. Compared to the C group, the levels of p38, JNK, p-p38, p-JNK, p-p38/p38, and p-JNK/JNK significantly increased, whereas those of ERK, p-ERK, and p-ERK/ERK decreased, in the Cr group. Compared to the Cr group, the levels of p38, JNK, p-p38, p-JNK, p-p38/p38, and p-JNK/JNK significantly decreased, whereas those of ERK, p-ERK, and p-ERK/ERK increased, in the Se/Cr group. Furthermore, the levels of p53, c-Myc, Bax, Cyt-c, caspase-9, and caspase-3 significantly increased, and those of Bcl-2 and Bcl-2/Bax significantly decreased, following Cr (VI) exposure, while Se restored the expression of these genes. In conclusion, our findings suggest that SeY can protect against Cr (VI)-induced dysfunction and apoptosis by regulating the mitogen-activated protein kinase pathway activated by oxidative stress in broiler kidney tissues.

Toxicity evaluation of decabromodiphenyl ethane (DBDPE) to Pleurotus ostreatus: Oxidative stress, morphology and transcriptomics

Decabromodiphenyl ethane (DBDPE), one widely used new brominated flame retardant, was of great concern due to its biotoxicity. The toxic evaluation of DBDPE (1-50 mg/L) to white-rot fungus (Pleurotus ostreatus), including oxidative stress, morphology and transcriptomics was conducted aiming at improving its biodegradation. Fungal growth and ATPase activity were obviously inhibited by DBDPE at ≥ 10 mg/L with the exposure from 48 h to 96 h. DBDPE could induce oxidative stress to P. ostreatus. The activity of SOD (superoxide dismutase), CAT (catalase) and GSH (glutathione) were all promoted by DBDPE at ≤ 5 mg/L and inhibited at > 5 mg/L with 96-h exposure. MDA (malondialdehyde) content rose obviously with DBDPE exposure (10-50 mg/L). The mycelium was wizened under 20 mg/L DBDPE exposure according to SEM observation. Transcriptomics analysis suggested that DBDPE could change many functional genes expression of P. ostreatus. GO analysis indicated DBDPE could affect biological process and cellular component by inhibiting electron transport, mitochondrial ATP synthesis, oxidoreductase activity as well as transporter activity. KEGG enrichment pathways analysis indicated DBDPE could inhibit oxidative phosphorylation, tricarboxylic acid (TCA) cycle and carbon metabolism by down-regulating the genes related to NADH reductase/dehydrogenase, succinate dehydrogenase, cytochrome-c reductase/oxidase, cytochrome C1 protein and ATP synthase.

Lung cell toxicity of co-exposure to airborne particulate matter and extremely low-frequency magnetic field

Although the toxic effects of urban airborne particulate matter (PM) have been known on lung cells, there is less attention to co-exposure to PM and extremely low frequency magnetic (ELF-MF) in occupational settings. The present study investigated the influences of PM and ELF-MF co-exposure on toxicity in human lung cells (A549).In this case, total PM (TPM) was evaluated according to NIOSH-0500. The TPM SiO₂ and metal contents were determined based on NIOSH-7602 and 7302, respectively. Besides, 900 mG ELF-MF exposure was simulated based on field measurements. The toxicity mechanisms were assessed by examining malondialdehyde, glutathione ratio, gene expression, and DNA strand breaks. Also, the toxicity indicators of the TPM samples were MDA generation, glutathione depletion, and DNA damage, and their impacts were analysed at doses below the LD₅₀ (4 µg).In addition, gene expression of OGG1 and MTH1 was upregulated after TPM exposure at the lowest dose (2 µg). But ITPA was upregulated in the presence of ELF-MF. The co-exposure to TPM and ELF-MF decreased oxidative stress and DNA damage levels compared to a single exposure to TPM.Although the ELF-MF reduced toxicity in response to TPM, this reduction was not lower than the unexposed cells.

Physiological mechanism of the response to Cr(VI) in the aerobic denitrifying ectomycorrhizal fungus Pisolithus sp.1

Pisolithus sp. 1 (P sp. 1) is an ectomycorrhizal fungus (EMF) with a strong Cr(VI) tolerance and reduction ability. The noninvasive microttest technique (NMT), real-time quantitative PCR (qRT-PCR), and the three-dimensional excitation-emission matrix (3D-EEM) were used to deeply explore the physiological mechanism of the P sp. 1 response to Cr(VI) and investigate the relationship between Cr(VI) reduction and denitrification in P sp. Cr(VI) induced the strongest elevations in nitrate reductase (NR) activity and NO production in the mycelia after treatment with Cr(VI) for 48 h under aerobic conditions. The NR inhibitor tungstate significantly inhibited Cr(VI) reduction, proton efflux and the expression of the NR gene (niaD) and NiR gene (niiA). In addition, NO was generated via NR-regulated denitrification. Combined treatments with Cr(VI) and the NO scavenger carboxy-PTIO (cPTIO) significantly increased O₂^-, H₂O₂ and MDA contents and reduced SDH, CAT, GSH, GR and GSNOR activity. Therefore, the NR-driven aerobic denitrifying process requires protons, and the generated NO reduces the oxidative stress effect of Cr(VI) on mycelia by reducing ROS accumulation and lipid peroxidation, enhancing mycelial and CAT activity, and promoting GSH recycling and regeneration. Psp.1 can also secrete humic acid-like and protein-like substances to combine with Cr(III) in a culture system.

Metabolomic analysis and oxidative stress response reveals the toxicity in Escherichia coli induced by organophosphate flame retardants tris(2-chloroethyl) phosphate and triphenyl phosphate

Organophosphate flame retardants (OPFRs) are emerging environmental pollutants that are increasingly being used in consumer commodities. The adverse effects on biota induced by tris(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPHP) have become a growing concern. Unfortunately, toxic mechanisms at the molecular level for OPFRs in organisms are still lacking. Herein, Escherichia coli (E.coli) was exposed to TCEP and TPHP for 24 and 48 h to reveal oxidative stress response and molecular toxicity mechanisms. The results indicated that promotion of ROS overload occurred at higher dosages groups. The levels of SOD and CAT were significantly elevated along with the increase of MDA attributed to lipid peroxidation. Additionally, apoptosis rates increased, accompanied by a decline in membrane potential and Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase contents, signifying that E. coli cytotoxicity induced by TCEP and TPHP was mediated by oxidative stress. Based on metabolomic analysis, different metabolic pathways were disrupted, including glycolysis/gluconeogenesis, pentose phosphate metabolism, purine metabolism, glutathione metabolism, amino acid biosynthesis, butanoate metabolism, alanine and aspartate metabolism. Most differentially expressed metabolites were downregulated, indicating an inhibitory effect on metabolic functions and key metabolic pathways. These findings generated new insights into the potential environmental risks of OPFRs in aquatic organisms.

Biodegradation of decabromodiphenyl ethane (DBDPE) by white-rot fungus Pleurotus ostreatus: Characteristics, mechanisms, and toxicological response

Decabromodiphenyl ethane (DBDPE) can pose a potential toxic threat to human beings and the environment. P. ostreatus, as one of the typical white-rot fungi, can effectively degrade various refractory pollutants. The biodegradable characteristics of DBDPE by P. ostreatus, as well as the mechanisms, and toxicological response were investigated in this study. The removal rate reached 47.73% and 43.20%, respectively, for 5 and 20 mg/L DBDPE after 120-h degradation by P. ostreatus. As a coexisting substance, Pb could inhibit the biodegradation. It is found that both the intracellular enzyme (P450) and extracellular enzymes (manganese peroxidase (MnP), lignin peroxidase (LiP), and laccase (Lac)) played a very important role in the biodegradation of DBDPE, of which Lac dominated the degradation. The toxic response was monitored during the degradation. The activities of SOD and CAT were enhanced to eliminate excess ROS in P. ostreatus triggered by DBDPE. In addition, debromination, hydroxylation, and oxidation were inferred as the main degradation pathways preliminarily. The findings provide a theoretical basis for the application of microbial degradation of DBDPE contamination.

Mechanism of Cr (VI) reduction by Pichia guilliermondii ZJH-1

Background

Chromium is one of the most used toxic heavy metals. A large amount of chromium waste is discharged into the environment every year, causing serious environmental pollution, especially the pollution of soil and water by hexavalent chromium. Eliminating hexavalent chromium is the primary challenge to achieve a pollution-free environment.

Objectives

This study aims to understand the mechanism of Pichia guilliermondii's reduction of hexavalent chromium through enzymatic characteristic, oxidative stress response, and reduction product.

Material and Methods

The strain Pichia guilliermondii ZJH-1 was isolated and stored in our laboratory. The hexavalent chromium uses 1,5-diphenyl carbazide method (DPC) to measure. The UV spectrophotometer was used to measure the intracellular antioxidant enzyme activity, and the kit was used to measure the activity of catalase and glutathione reductase. The reduction products were analyzed by ultraviolet full-wavelength scanning and FTIR.

Results

The reduction of hexavalent chromium by ZJH-1 is accompanied by an increase in active oxygen and antioxidant levels. Chromate reductase mainly exists in the extracellular fluid, and the carboxyl, amide, hydroxide and other groups of the cell wall are involved in the bioremediation of Cr(VI) by complexing with Cr(VI) and Cr(III). After ZJH-1 was treated with different concentrations of Cr(VI), the expression of proteins with molecular weights of 15 kDa, 18 kDa, 35 kDa, 62 kDa, and 115 kDa increased significantly. This strain is the most suitable for chromate reductase (CChR). The optimum temperature is 40℃ and the optimum pH is 7.0. Cu2+ can enhance the activity of chromate reductase. At the optimum temperature and pH, the chromate reductase Km of this strain is 0.40 μmol and Vmax is 14.47 μmoL.L^-1·min^-1.

Conclusions

The bioremediation of Cr(VI) by Pichia guilliermondii ZJH-1 is attributable to the reduction product (Cr(III)) that can be removed in the precipitate and can be fixed on the cell surface and accumulated in the cell.

Causation of Oxidative Stress and Defense Response of a Yeast Cell Model after Treatment with Orthodontic Alloys Consisting of Metal Ions

Misaligned teeth have a tremendous impact on oral and dental health, and the most efficient method of correcting the problem is orthodontic treatment with orthodontic appliances. The study was conducted to investigate the metal composition of selected orthodontic alloys, the release of metal ions, and the oxidative consequences that the metal ions may cause in the cell. Different sets of archwires, stainless steel brackets, and molar bands were incubated in artificial saliva for 90 days. The composition of each orthodontic material and quantification of the concentration of metal ions released were evaluated. Metal ion mixtures were prepared to determine the occurrence of oxidative stress, antioxidant enzyme defense system, and oxidative damage to proteins. The beta titanium alloy released the fewest metal ions and did not cause oxidative stress or protein damage. The metal ions from stainless steel and the cobalt-chromium alloy can cause oxidative stress and protein damage only at high concentrations. All metal ions from orthodontic alloys alter the activity of antioxidant enzymes in some way. The determined amounts of metal ions released from orthodontic appliances in a simulated oral environment are still below the maximum tolerated dose, and the concentrations of released metal ions are not capable of inducing oxidative stress, although some changes in antioxidant enzyme activity were observed at these concentrations.

Exploring the Cr(VI) removal mechanism of Sporosarcina saromensis M52 from a genomic perspective

Serious hexavalent chromium [Cr(VI)] pollution has continuously threatened ecological security and public health. Microorganism-assisted remediation technology has strong potential in the treatment of environmental Cr(VI) pollution due to its advantages of high efficiency, low cost, and low secondary pollution. Sporosarcina saromensis M52, a strain with strong Cr(VI) removal ability, isolated from coastal intertidal zone was used in this study. Scanning electron microscopy coupled with energy dispersive X-ray analysis indicated M52 was relatively stable under Cr(VI) stress and trace amount of Cr deposited on the cell surface. X-ray photoelectron spectroscopy and X-ray diffraction analyses exhibited M52 could reduce Cr(VI) into Cr(III). Fourier transform infrared spectroscopy showed the bacterial surface was mainly consisted of polysaccharides, phosphate groups, carboxyl groups, amide II (NH/CN) groups, alkyl groups, and hydroxyl groups, while functional groups involving in Cr(VI) bio-reduction were not detected. According to these characterization analyses, the removal of Cr(VI) was primarily depended on bio-reduction, instead of bio-adsorption by M52. Genome analyses further indicated the probable mechanisms of bio-reduction, including the active efflux of Cr(VI) by chromate transporter ChrA, enzymatic redox reactions mediated by reductases, DNA-repaired proteases ability to minimize the ROS damage, and the formation of specific cell components to minimize the biofilm injuries caused by Cr(VI). These studies provided a theoretical basis which was useful for Cr(VI) remediation, especially in terms of increasing its effectiveness. THE MAIN FINDING OF THE WORK: M52 realized the bioremediation of Cr(VI) majorly through bio-reduction, including Cr(VI) efflux, chromate reduction, DNA repair, and the formation of specific cell components, instead of bio-adsorption.

Genome wide profiling of miRNAs relevant to the DNA damage response induced by hexavalent chromium exposure (DDR-related miRNAs in response to Cr (VI) exposure)

AIM

We aimed to explore the expression of miRNAs and their potential roles in the DNA damage response (DDR) induced by Cr (VI) exposure in human B lymphoblast cells (HMy2.CIR cells) and in a population of Cr (VI)-exposed humans.

METHODS

Differentially expressed miRNAs were found by a combination of miRNA sequencing and RT-qPCR validation in HMy2.CIR cells treated with K₂Cr₂O₇. Differentially expressed miRNAs related to DDR were selected for functional study. The expression levels of differential miRNAs were also investigated in chromate workers.

RESULTS

A total of 214 differentially expressed miRNAs were identified by sequencing, and the expression of 5 miRNAs among 25 associated with DDR was found to be consistent between sequencing and validation studies.Functional studies showed that miR-148a-3p, miR-21-5p, and miR-424-3p might be related to Cr (VI)-induced cell apoptosis, and miR-221-3p might participate in Cr (VI)-induced DDR. We also found that the expression of miR-21-5p and miR-424-3p was upregulated in chromate workers.

CONCLUSIONS

Cr (VI) exposure could significantly impact miRNAs expression in vitro and in chromate workers. Functional studies showed that miR-148a-3p, miR-21-5p and miR-221-3p might take a crucial role in the cellular DDR induced by Cr (VI) exposure.

Dietary chromium modulates glucose homeostasis and induces oxidative stress in Pacific white shrimp (Litopenaeus vannamei)

While chromium (Cr) has been recognized as an essential nutrient for all animals, and dietary supplementation can be beneficial, it can also be toxic. The present study aimed to investigate the contrasting effects of dietary chromium in Pacific white shrimp Litopenaeus vannamei. Five experimental diets were formulated to contain Cr at levels of 0.82 (Cr0.82, unsupplemented diet), 1.01 (Cr1.01), 1.22 (Cu1.22), 1.43 (Cr1.43) and 1.63 (Cr1.63) mg/kg and were fed to shrimp for 8 weeks. Highest weight gain was recorded in shrimp fed the diet containing 1.22 mg/kg Cr. Shrimp fed the diet containing the highest level of Cr (1.63 mg/kg) showed the lowest weight gain and clear signs of oxidative stress and apoptosis as evidenced by higher levels of H₂O₂, malondialdehyde and 8-hydroxydeoxyguanosine, and expression of caspase 2, 3, 5, and lower contents of total and oxidized glutathione, and expression of Cu/Zn sod, cat, gpx, mt, bcl2. Chromium supplementation promoted glycolysis and inhibited gluconeogenesis as shown by increased activities of hexokinase, phosphofructokinase and pyruvate kinase, and reduced activity of phosphoenolpyruvate carboxykinase in shrimp fed the diet containing 1.43 mg/kg Cr. Shrimp fed the diet with 1.63 mg/kg Cr had lowest contents of crustacean hyperglycemic hormone and insulin like peptide in hemolymph. Expression of genes involved in insulin signaling pathway and glycose metabolism including insr, irs1, pik3ca, pdpk1, akt, acc1, gys, glut1, pk, hk were up-regulated, and foxO1, gsk-3β, g6pc, pepck were down-regulated in shrimp fed the diets supplemented with Cr. This study demonstrated that optimum dietary supplementation of Cr had beneficial effects on glucose homeostasis and growth, whereas excess caused oxidative damage and impaired growth. The results contribute to our understanding of the biological functions of chromium in shrimp.

Selenium restores mitochondrial dysfunction to reduce Cr-induced cell apoptosis in Chinese cabbage (Brassica campestris L. ssp. Pekinensis) root tips

Chromium (Cr) disrupts the growth and physiology of plants. Selenium (Se) is considered as a promising option to help plants ameliorate Cr toxicity. To investigate the effects of exogenous Se on reactive oxygen species (ROS) burst and programmed cell death (PCD) in root tip cells under Cr stress, hydroponic experiments were carried out with Chinese cabbage seedlings grown in Hoagland solution containing 1 mg L^-1 Cr and 0.1 mg L^-1 Se. Results showed that Se scavenged the overproduction of H₂O₂ and O₂^－·, and alleviated the level of lipid peroxidation in root tips stressed by Cr. Moreover, Se effectively prevented DNA degradation and reduced the number of apoptotic cells in root tips. Compared with Cr treatment, Se supplementation reduced the content of ROS and malondialdehyde in mitochondria by 38.23% and 17.52%, respectively. Se application decreased the opening degree of mitochondrial permeability transition pores by 32.30%, increased mitochondrial membrane potential by 40.91%, alleviated the release of cyt c from mitochondria into cytosol by 18.42% and caused 57.40% decrease of caspase 3-like protease activity, and thus restored mitochondrial dysfunction caused by Cr stress. In addition, the alteration of Se on mitochondrial physiological properties maintained calcium homeostasis between mitochondria and cytosol, which further contributed to reducing the appearance of Cr-induced PCD. Findings suggested that Se restored mitochondrial dysfunction, which further rescued root tip cells from PCD, consequently activating defense strategies to protect plants from Cr toxicity and maintaining plant growth.

Iron oxide minerals promote simultaneous bio-reduction of Cr(VI) and nitrate: Implications for understanding natural attenuation

Nitrate and Cr(VI) coexist in aquifers, posing a potential threat to ecological environment and public health. Iron oxide minerals (hematite and magnetite) exist ubiquitously in groundwater, which are hot spots for biogeochemical transformation. However, there is still a knowledge gap anout the effect of iron oxide minerals on bioreduction of nitrate and Cr(VI). Here we observed that iron oxide minerals can significantly improve the ability of microorganisms to simultaneously reduce nitrate and Cr(VI), the reduction rates of nitrate and Cr(VI) increased by 7.3 and 8.5 times, respectively. The addition of minerals reinforced biofilm formation and shaped microbial communities with a new dominant strain of Azoarcus. The expression levels of functional genes were also upregulated, including napA, narG, nfsA, yieF, POD, and CAT. Furthermore, nitrate and chromate reductases' activities increased by 11 and 5 folds, respectively. These results demonstrated that iron oxide minerals participated in the bio-transformation of nitrate and Cr(VI) co-contamination, alleviating oxidative stress, shaping the microbial community, and ultimately accelerating bio-transformation. These findings offer a window into the biological transformation of co-contamination in the presence of iron oxide minerals, and insights to reveal strategies for microbial detoxification and to develop promising approaches for dealing with complex pollution conditions.

Cr(VI) promotes tight joint and oxidative damage by activating the Nrf2/ROS/Notch1 axis

This study aimed to investigate whether Cr(VI) induced tight joint and oxidative damage in the small intestine, as mediated by the nuclear factor erythroid 2-related factor 2 (Nrf2)/reactive oxygen species (ROS)/Notch1 axis crosstalk. Thirty-two ICR mice were obtained and subjected to Cr(VI) via intragastric administration daily for 5 days. Western blot (WB) analysis, enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC) staining, and immunofluorescence (IF) staining were applied to detect small intestinal damage, Nrf2, Notch1, and respective downstream targets in this research. Results showed that Cr(VI) led to the tight joint and oxidative damage in the small intestine of mice. Nrf2 was stimulated, and Notch1 (Notch intracellular domain, NICD1) was activated to translocate into the nucleus and activate an antioxidant action. These findings were validated by WB analysis and IF staining. ROS levels increased as the Cr(VI) concentration increased. The colocalization analysis of Nrf2 and NICD1 implied that a crosstalk between Nrf2 and Notch1 existed. Therefore, this study indicated that the Nrf2/ROS/Notch1 axis crosstalk could aggravate the tight joint and oxidative damage in the small intestine after Cr(VI) treatment.

Antigenotoxic effects of (-)-epigallocatechin-3-gallate (EGCG) and its relationship with the endogenous antioxidant system, 8-hydroxydeoxyguanosine adduct repair (8-OHdG), and apoptosis in mice exposed to chromium(VI)

This study aimed to investigate the relationship between endogenous antioxidant system, 8-hydroxydeoxyguanosine adduct (8-OHdG) repair, and apoptosis in mice treated with chromium(VI) alone and in the presence of the antigenotoxic compound (-)-epigallocatechin-3-gallate (EGCG). Groups of 5 Hsd:ICR male mice were divided and treated as follows: (1) control, vehicle only; (2) EGCG, 8.5 mg/kg by gavage alone; (3) CrO₃, 20 mg/kg intraperitoneally alone; and (4) EGCG combined with CrO₃, EGCG was administered 4 hr prior to CrO₃. Peripheral blood parameters were analyzed before treatment administration (time 0), and 48 hr after exposure. The administration of EGCG increased 8-OHdG levels and superoxide dismutase (SOD) activity. Treatment with CrO₃ increased number of micronucleus (MN) presence, elevated apoptotic/necrotic cells frequencies, decreased 8-OHdG levels, diminished total antioxidant capacity (TAC), increased glutathione (GSH) total levels, and lowered SOD activity. Administration of EGCG prior to treatment with CrO₃ resulted in lower concentrations of MN, reduced apoptotic and necrotic cell number, and restored TAC and SOD activity to control levels. It is conceivable that the dose of EGCG plays an important role in the genotoxic damage protection pathways. Thus, this study confirms the action of EGCG as an antigenotoxic agent against chromium(VI)-induced oxidative insults and demonstrates potential protective pathways for EGCG actions to counteract genotoxic damage induced by this metal.

Improvement in the growth status and carbohydrate utilization of Labeo rohita (Hamilton, 1822) fingerlings with dietary supplementation of chromium picolinate

A 60-day feeding experiment was conducted to evaluate the effects of dietary chromium (Cr) on carbohydrate utilization and growth performance of Labeo rohita fingerlings. Fishes were fed with four high carbohydrate (53%), isonitrogenous (crude protein 35%), and isocaloric (415 Kcal, 100 gm^-1) experimental diets containing different levels of dietary chromium picolinate (Cr-Pic) viz.0, 400, 800, and 1200 μg kg^-1 diet. Weight gain (WG%), specific growth rate (SGR), feed efficiency ratio (FER), and protein efficiency ratio (PER) were significantly increased at 800 μg kg^-1 diet chromium supplementation (P < 0.05). Cr-Pic supplementation (800 μg kg^-1) also significantly (P < 0.05) enhanced the protein: DNA ratio in muscle, while DNA: RNA and DNA: tissue ratios were significantly (P < 0.05) decreased indicating higher growth. Significantly higher amylase, protease, and lipase activities were recorded in 800 μg Cr-Pic kg^-1 diet fed fishes (P < 0.05), while any of the experimental groups showing no significant (P > 0.05) change in hexokinase activity, indicating normal glycolysis in all. Furthermore, significant (P < 0.05) decrease of glucose-6-phospatase activity in 800 μg Cr-Pic kg^-1 diet fed group, showcasing an evidence for protein-sparing action with Cr-Pic supplementation. Significantly (P < 0.05) higher serum insulin and liver glycogen in 800 μg Cr-Pic kg^-1 diet fed fishes denote an improvement in carbohydrate metabolism. However, significantly (P < 0.05) higher ATPase and SOD activities were also observed when chromium supplementation was more than 800 μg kg^-1 diet, indicating stress at higher level. The present study indicates that growth and carbohydrate utilization can significantly (P < 0.05) be improved by feeding the L. rohita fingerlings with Cr-Pic (800 μg kg^-1 diet) supplemented diet in laboratory condition.

Study on the oxidative stress and transcriptional level in Cr(VI) and Hg(II) reducing strain Acinetobacter indicus yy-1 isolated from chromium-contaminated soil

The bioreduction of Cr(VI) and Hg(II) has become a hot topic in the field of heavy metals bioremediation. However, the mechanism of antioxidant stress in Cr(VI) and Hg(II) reducing bacteria is still not clear. In this work, a novel Cr(VI) and Hg(II) reducing strain Acinetobacter indicus yy-1, was isolated from chromium landfill at a chromate factory, which was used to investigate the mechanism of antioxidant stress during the Cr(VI) and Hg(II) reduction process. The results demonstrated that the removal of Cr(VI) and Hg(II) by A. indicus yy-1 from solution was through reduction rather than biosorption. The reduction rates of Cr(VI) and Hg(II) by resting cells reached 59.71% and 31.73% at 24 h with initial concentration of 10 mg L^-1, respectively. X-ray photoelectron spectroscopy (XPS) analysis further showed that Cr(III) and Hg(0) were mainly the Cr(VI)- and Hg(II)-reduced productions, respectively. Results of physiological assays showed Hg(II) was more toxic to A. indicus yy-1 than Cr(VI), and the activities of antioxidant enzymes (SOD and CAT) were significantly increased in A. indicus yy-1 for relieving the oxidative stress. The transcriptional level of genes related to Cr(VI) and Hg(II) reductases and antioxidant enzymes were up-regulated, indicating that the reductases have participated in the reduction of Cr(VI) and Hg(II), and SOD and CAT served as the vital antioxidant enzymes for defending the oxidative stress. This work provides a deep insight into the mechanism of antioxidant stress in Cr(VI) and Hg(II) reducing bacteria, which helps seek the highly resistant heavy metal reducing bacteria.

Uptake of hexavalent chromium by Lactuca sativa and Triticum aestivum plants and mediated effects on their performance, linked with associated public health risks

Plants exposed to toxic Cr(VI) concentrations show reduced biomass production and yield. The present study examined (1) the impacts of increasing Cr(VI) exposure (0.05, 0.5, 1, 5 and 10 mg L-1 K2Cr2O7 in irrigation water) on the growth and development, yield, and stress physiology of two important crop species, such as wheat (Triticum aestivum L.) and lettuce (Lactuca sativa L.), and (2) the associated human health risks due to the consumption of these commodities. Plants in all Cr(VI) treatments preserved similar growth rates and phenotypes with control, untreated plants, with no remarkable modulations in biomass yield (fresh/dry weight, plant height, straw/grain weight). Grains harvested from plants exposed to all Cr(VI) treatments had increased size and 1000 grain weight, partially suggesting hormetic effect. Elevated K2Cr2O7 concentrations (5 and 10 mg L-1) resulted in increased photosynthetic pigments' levels in lettuce leaves. Lipid peroxidation and H2O2 content also revealed the absence of oxidative stress in lettuce plants. Non-carcinogenic (target hazard quotient) and carcinogenic risks from the consumption of these commodities grown under the conditions described in this study were found de minimis. However, more studies are needed in order to obtain more solid information on the safety of Cr(VI)-contaminated water irrigation.

Enantioselective residues and toxicity effects of the chiral triazole fungicide hexaconazole in earthworms (Eisenia fetida)

The enantioselective toxic effect and environmental behavior of chiral pesticides have attracted increasing research attention. In this study, the enantioselective toxicity and residues of hexaconazole (HEX) in earthworms (Eisenia fetida) were investigated. In the present study, significant enantioselective degradation characteristics were observed in artificial soil with the R-enantiomer preferentially degrading (p < 0.05); however, no significant enantioselective bioaccumulation was observed in the earthworms (p > 0.05). The acute toxicity of S-(+)-HEX was higher than that of R-(-)-HEX in earthworms, with 48-h LC₅₀ values of 8.62 and 22.35 μg/cm², respectively. At 25 mg/kg, enantiospecific induction of oxidative stress was observed in earthworms; moreover, S-(+)-HEX had a greater influence on the contents of malonaldehyde, cytochrome P450, and 8-hydroxy-2-deoxyguanosine than R-(-)-HEX. These results were consistent with those of the enrichment analysis of differentially expressed genes. The transcriptome sequencing results showed that S-(+)-HEX had a more significant influence on steroid biosynthesis, arachidonic acid metabolism, and cell cycle processes than R-(-)-HEX, leading to abnormal biological function activities. These results indicate that S-(+)-HEX may pose a higher risk to soil organisms than R-(-)-HEX. This study suggests that the environmental risk of chiral pesticides to nontarget organisms should be assessed at the enantiomeric level.

Subcellular mechanism of microbial inactivation during water disinfection by cold atmospheric-pressure plasma

Although the identification of effective reactive oxygen species (ROS) generated by plasma has been extensively studied, yet the subcellular mechanism of microbial inactivation has never been clearly elucidated in plasma disinfection processes. In this study, subcellular mechanism of yeast cell inactivation during plasma-liquid interaction was revealed in terms of comprehensive factors including cell morphology, membrane permeability, lipid peroxidation, membrane potential, intracellular redox homeostasis (intracellular ROS and H₂O₂, and antioxidant system (SOD, CAT and GSH)), intracellular ionic equilibrium (intracellular H⁺ and K⁺) and energy metabolism (mitochondrial membrane potential, intracellular Ca²⁺ and ATP level). The ROS analysis show that ·OH, ¹O₂, ·O₂^-and H₂O₂ were generated in this plasma-liquid interaction system and ·O₂^-served as the precursor of ¹O₂. Additionally, the solution pH was reduced. Plasma can effectively inactivate yeast cells mainly via apoptosis by damaging cell membrane, intracellular redox and ion homeostasis and energy metabolism as well as causing DNA fragmentation. ROS scavengers (l-His, d-Man and SOD) and pH buffer (phosphate buffer solution, PBS) were employed to investigate the role of five antimicrobial factors (·OH, ¹O₂, ·O₂^-, H₂O₂ and low pH) in plasma sterilization. Results show that they have different influences on the aforementioned cell physiological activities. The ·OH and ¹O₂ contributed most to the yeast inactivation. The ·OH mainly attacked cell membrane and increased cell membrane permeability. The disturb of cell energy metabolism was mainly attributed to ¹O₂. The damage of cell membrane as well as extracellular low pH could break the intracellular ionic equilibrium and further reduce cell membrane potential. The remarkable increase of intracellular H₂O₂ was mainly due to the influx of extracellular H₂O₂ via destroyed cell membrane, which played a little role in yeast inactivation during 10-min plasma treatment. These findings provide comprehensive insights into the antimicrobial mechanism of plasma, which can promote the development of plasma as an alternative water disinfection strategy.

Physiological responses of Arthrobacter sp. JQ-1 cell interfaces to co-existed di-(2-ethylhexyl) phthalate (DEHP) and copper

Arthrobacter sp. JQ-1 can completely degrade 500 mg/L of DEHP within 3 days. The minimum inhibitory concentrations (MICs) of Cu²⁺ could reach 1.56 mM, however, 5.0 mg/L Cu²⁺ apparently inhibited DEHP degradation and bacterial growth. Consequently, JQ-1 was exposed to the DEHP-copper environment to verify the toxicity mechanism based on the physiological responses of cellular multiple interfaces (cellular surface, membrane and intracellular characteristics). The results showed the combination of 500 mg/L DEHP and 5.0 mg/L Cu²⁺ significantly decreased cell surface hydrophobicity (CSH) and the absolute value of zeta potential, which implied the bioavailability of DEHP was decreased. The cellular surface changes were mainly due to the interaction between Cu²⁺ and some functional groups (CH₂, CH₃, aromatic rings, and amide). The weakened proton-motive force (PMF) across the plasma membrane may interfere the formation and utilization of energy, which is not conducive to the repair process of cellular damages. In this study, Non-invasive micro-test technology (NMT) was applied to the research of combined toxicity of DEHP and heavy metal ions for the first time. DEHP-copper intensified K⁺ efflux and Ca²⁺ influx across the plasma membrane, which disturbed ion homeostasis of K⁺ and Ca²⁺ and might induce apoptosis and further inhibit DEHP degradation. The decline of intracellular esterase activity indicated that the metabolic capacity is apparently restrained. This study enhances our understanding of cellular different interface processes responding to combined pollutants.

Response of Trametes hirsuta to hexavalent chromium promotes laccase-mediated decolorization of reactive black 5

The recalcitrant azo dyes combined with heavy metals constitute a major challenge for the bioremediation of industrial effluents. This study aimed to investigate the effect and mechanism of action of a white-rot fungus Trametes hirsuta TH315 on the simultaneous removal of hexavalent chromium [Cr(VI)] and azo dye (Reactive Black 5, RB5). Here, this study discovered that toxic Cr(VI) (1 mM) greatly promoted RB5 decolorization (from 57.15% to 83.65%) by white-rot fungus Trametes hirsuta with high Cr(VI)-reducing ability (>96%), resulting in the simultaneous removal of co-contaminants. On the basis of transcriptomic and biochemical analysis, our study revealed that the oxidative stress in co-contaminants mainly caused by Cr(VI), and a number of dehydrogenases and oxidases showed up-regulation in response to Cr(VI) stress. It was noteworthy that the oxidative stress caused by Cr(VI) in co-contaminants can both significantly induce glutathione S-transferase and laccase expression. Glutathione S-transferase potentially involved in antioxidation against Cr(VI) stress. Laccase was found to play a key role in RB5 decolorization by T. hirsuta. These results suggested that the simultaneous removal of co-contaminants by T. hirsuta could be achieved with Cr(VI) exposure. Overall, the elucidation of the molecular basis in details will help to advance the general knowledge about the fungus by facing harsh environments, and put forward a further possible application of fungi on environmental remediation.

Effects of nonylphenol induced oxidative stress on apoptosis and autophagy in rat ovarian granulosa cells

Nonylphenol (NP) is a kind of environmental endocrine disruptors which is generally recognized to cause female reproductive toxicity, but its basic mechanism has not been fully elucidated. In this study, granulosa cells (GCs) were treated with 0-70 μM NP for 24 h, the cell viability of GCs was reduced significantly, as well as increased cell apoptosis with G2/M arrest. Furthermore, NP significantly induced autophagy and the production of reactive oxygen species (ROS). However, these phenomenons were inhibited by blocking the production of ROS with N-Acetyl-l-cysteine (NAC) administration. Intriguingly, the inhibition of autophagy with 3-Methyladenine (3-MA) could enhance the apoptosis induced by NP. Moreover, the down regulating of p-Akt/Akt, p-mTOR/mTOR and subsequent up-regulation of p-AMPK/AMPK induced by NP can be rescued by pretreatment of NAC. Our findings suggested that NP promotes rat ovarian GCs apoptosis and autophagy simultaneously, which may involve the activation of ROS-dependent Akt/AMPK/mTOR pathway. Whatever, the activation of autophagy is likely to develop a protective mechanism to improve the apoptosis of rat ovarian GCs induced by NP.

Cellular response of Brevibacterium casei #NIOSBA88 to arsenic and chromium-a proteomic approach

Cellular response against different heavy metal stress differs with the metal. Arsenic and chromium are heavy metals and toxic to living systems. The concentration of these metals in seawater is very low. However, due to their solubility in nature, they actively enter cells via various transport mechanisms and cause damage to the cells. Brevibacterium casei #NIOSBA88, a marine-derived, gram-positive isolate was multi-metal tolerant. Proteomic analysis of this isolate in response to arsenic and chromium resulted in the identification of total 2549 proteins, out of which 880 proteins were found to be commonly expressed at 750 mgL^-1 arsenic and 100 mgL^-1 chromium and in absence of both the metals. In contrast, 533, 212, and 270 proteins were found to be unique in the absence of any metal, 750 mgL^-1 of arsenic and 100 mgL^-1 of chromium respectively. Proteins such as antibiotic biosynthesis monooxygenase, ArsR family transcriptional regulator, cytochrome C oxidase subunit II, and thioredoxin reductase were exclusively expressed only in response to arsenic and chromium. Other proteins like superoxide dismutase, lipid hydroperoxide reductase, and thioredoxin-disulfide reductase were found to be upregulated in response to both the metals. Most of the proteins involved in the normal cell functioning were found to be downregulated. Major metabolic functions affected include amino acid metabolism, carbohydrate metabolism, translation, and energy metabolism. Peptide mass fingerprinting of Brevibacterium casei #NIOSBA88 exposed to arsenic and chromium respectively revealed the deleterious effect of these metals on the bacterium and its strategy to overcome the stress.

Genotoxicity induced by hexavalent chromium leading to eryptosis in Ctenopharyngodon idellus

The initiation of eryptosis as a result of genotoxic action of Cr(VI), seen through micronucleus and comet assay in the peripheral erythrocytes of Ctenopharyngodon idellus was evaluated through RT-qPCR. For this, fish was exposed to sublethal concentration of hexavalent chromium (5.30 and 10.63 mg/L), and the blood was sampled on different endpoints (15, 30 and 45 days). Accumulation of chromium in the erythrocytes was also studied, which depicted a significant increase in toxicant concentration and time dependent manner. Both concentrations of hexavalent chromium induced DNA damage, visible in the form of comet tails. The presence of micronuclei in the erythrocytes was accompanied with occurrence of nuclear bud (NBu), lobed nucleus (Lb), notched nucleus (Nt), vacuolated nucleus (Vn), binucleated cell (Bn) as nuclear abnormalities; and acanthocytes (Ac), echinocytes (Ec), notched cells (Nc), microcytes (Mc) and vacuolated cytoplasm (Vc) as cytoplasmic abnormalities. The expression of genes related to intrinsic apoptotic pathway induced by Cr(VI) presented significant (p < 0.05) upregulation in the expression of p53, Bax, Apaf-1, caspase9 and caspase3, and downregulation of Bcl2; inferring the initiation of apoptotic pathway. The ration of Bax and Bcl2 also appended the apoptotic state of the erythrocytes. From the present investigation, it can be concluded that genotoxicity induced by hexavalent chromium lead to eryptosis in C. idellus.

Proteomic mechanism of decabromodiphenyl ether (BDE-209) biodegradation by Microbacterium Y2 and its potential in remediation of BDE-209 contaminated water-sediment system

The investigation of BDE-209 degradation by Microbacterium Y2 under different condition was conducted. Cell membrane permeability, cell surface hydrophobicity (CSH), membrane potential (MP) and reactive oxygen species (ROS) production were altered under BDE-209 stress. Eleven debrominated congeners were identified, suggesting that BDE-209 biodegradation by Microbacterium Y2 was dominantly a successive debromination process. Proteome analysis showed that the overexpression of haloacid dehalogenases, glutathione S-transferases (GSTs) and ATP-binding cassette (ABC) transporters might occupy important roles in BDE-209 biotransformation. Meanwhile, heat shock proteins (HSPs), ribonuclease E, oligoribonuclease (Orn) and ribosomal protein were activated to counter the BDE-209 toxicity. The up-regulated pyruvate dehydrogenase E1 component beta subunit and dihydrolipoamide dehydrogenase suggested that the pyruvate metabolism pathway was activated. Bioaugmentation of BDE-209 polluted water-sediments system with Microbacterium Y2 could efficiently improve BDE-209 removal. The detection of total 16S rRNA genes in treatment system suggested that Microbacterium (25.6 %), Luteimonas (14.3 %), Methylovorus (12.6 %), Hyphomicrobium (9.2 %) were the dominant genera and PICRUSt results further revealed that the diminution of BDE-209 was owed to cooperation between the introduced bacteria and aboriginal ones.

Phytostabilization of Pb-Zn Mine Tailings with Amorpha fruticosa Aided by Organic Amendments and Triple Superphosphate

A greenhouse pot trial was conducted to investigate the effect of organic amendments combined with triple superphosphate on the bioavailability of heavy metals (HMs), Amorpha fruticosa growth and metal uptake from Pb-Zn mine tailings. Cattle manure compost (CMC), spent mushroom compost (SMC) and agricultural field soil (AFS) were applied to tailings at 5%, 10%, 20% and 30% w/w ratio, whereas sewage sludge (SS) and wood biochar (WB) were mixed at 2.5%, 5%, 10% and 20% w/w ratio. Triple superphosphate (TSP) was added to all the treatments at 4:1 (molar ratio). Amendments efficiently decreased DTPA-extracted Pb, Zn, Cd and Cu in treatments. Chlorophyll contents and shoot and root dry biomass significantly (p < 0.05) increased in the treatments of CMC (except T4 for chlorophyll b) and SMC, whereas treatments of SS (except T1 for chlorophyll a and b), WB and AFS (except T4 for chlorophyll a and b) did not show positive effects as compared to CK1. Bioconcentration factor (BCF) and translocation factor (TF) values in plant tissues were below 1 for most treatments. In amended treatments, soluble protein content increased, phenylalanine ammonialyase (PAL) and polyphenol oxidase (PPO) decreased, and catalase (CAT) activity showed varied results as compared to CK1 and CK2. Results suggested that A. fruticosa can be a potential metal phytostabilizer and use of CMC or SMC in combination with TSP are more effective than other combinations for the in situ stabilization of Pb-Zn mine tailings.

Di-2-ethylhexyl phthalate (DEHP) induces apoptosis and autophagy of mouse GC-1 spg cells

As a widely used plasticizer in industry, di-2-ethylhexylphthalate (DEHP) can cause testicular toxicity, yet little is known about the potential mechanism. In this study, DEHP exposure dramatically inhibited cellviability and induced apoptosis of mouse GC-1 spg cells. Furthermore, DEHP significantly increased the levels of autophagy proteins LC3-II, Beclin1 and Atg5, as well as the ratio ofLC3-II/LC3-I. Transmission electron microscopy (TEM) further confirmed that DEHP induced autophagy of mouse GC-1 spg cells. DEHP was also shown to induceoxidative stress; while inhibition of oxidative stress with NAC could increase cell viability and inhibit DEHP-induced apoptosis and autophagy. These results suggested that DEHP induced apoptosis and autophagy of mouse GC-1 spg cells via oxidative stress. 3-MA, an inhibitor of autophagy, could rescue DEHP-induced apoptosis. In summary, DEHP induced apoptosis and autophagy of mouse GC-1 spg cells via oxidative stress, and autophagy might exert a cytotoxic effect on DEHP-induced apoptosis.

Effect of hexavalent chromium on the biodegradation of tetrabromobisphenol A (TBBPA) by Pycnoporus sanguineus

The influence of Cr(VI) on the degradation of tetrabromobisphenol A (TBBPA) by a typical species of white rot fungi, Pycnoporus sanguineus, was investigated in this study. The results showed that P. sanguineus together with its intracellular and extracellular enzyme could effectively degrade TBBPA. The degradation efficiency of TBBPA by both P. sanguineus and its enzymes decreased significantly when Cr(VI) concentration increased from 0 to 40 mg/L. The subsequent analysis about cellular distribution of TBBPA showed that the extracellular amount of TBBPA increased with the increment of Cr(VI) concentration, but the content of TBBPA inside fungal cells exhibited an opposite variation tendency. The inhibition of TBBPA degradation by P. sanguineus was partly attributed to the increase of cell membrane permeability and the decrease of cell membrane fluidity caused by Cr(VI). In addition, the decline of H⁺-ATPase and Mg²⁺-ATPase activities was also an important factor contributing to the suppression of TBBPA degradation in the system containing concomitant Cr(VI). Moreover, the activities of two typical extracellular lignin-degrading enzymes of P. sanguineus, MnP and Lac, were found to descend with ascended Cr(VI) level. Cr(VI) could also obviously suppress the gene expression of four intracellular enzymes implicated in TBBPA degradation, including two cytochrome P450s, glutathione S-transferases and pentachlorophenol 4-monooxygenase, which resulted in a decline of TBBPA degradation efficiency by fungal cells and intracellular enzyme in the presence of Cr(VI). Overall, this study provides new insights into the characteristics and mechanisms involved in TBBPA biodegradation by white rot fungi in an environment where heavy metals co-exist.

Biodegradation of tricresyl phosphate isomers by Brevibacillus brevis: Degradation pathway and metabolic mechanism

Tricresyl phosphates (TCPs), a typical sort of organophosphate flame retardants, has received extensive concerns due to its potential adverse effects. However, limited information is available on the efficient and safe removal methods of TCPs. In this regard, TCPs were tentatively biodegraded with Brevibacillus brevis. A probable degradation pathway was further proposed with the cellular reactions discussed in detail. Experiments showed that B. brevis at 2 g L^-1 could degrade 1 mg L^-1 tri-m-cresyl phosphate, tri-p-cresyl phosphate, and tri-o-cresyl phosphate by 82.91%, 93.91%, and 53.92%, respectively, within five days. In the process of biodegradation, B. brevis metabolism caused the release of Na⁺ and Cl^- as well as the absorption of some nutrient ions including K⁺, PO₄^3-, Mg²⁺, and SO₄^2-; the presence of oxalic acid, citric acid, acetic acid, and malonic acid was also detected. Similar metabolic pathways were found among different TCPs isomers, but tri-o-cresyl phosphate induced more reactive oxygen species than the other two did. This work develops novel insights into the potential mechanisms of TCPs biodegradation by microorganisms.