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•The ions release of the metal oxide NPs was evaluated.•The toxicity of the NPs supernatants and suspensions were determined.•ZnO NP toxicity was due solely to the released Zn ...ions.•CuO NP toxicity originated from both the released Cu ions and the CuO particles.•Toxicity of Fe2O3, Co3O4, Cr2O3, and NiO were caused by the NPs themselves.
The toxicity of metal oxide nanoparticles (NPs) has aroused great concern over the past few years. However, there still remains the question whether the toxicity of the metal oxide NPs originates from the released ions or the NPs themselves. In this study, the metal ion release of CuO, Fe2O3, ZnO, Co3O4, Cr2O3, and NiO NPs in aqueous media was investigated, and their contributions to the metal oxide NPs’ inhibition on the bioluminescence of Photobacterium phosphoreum were studied. It was found that the ions release of the metal oxide NPs in aqueous media was complex, depending on both the dissolution and adsorption processes of the metal oxide NPs. The relationships between the metal oxide NPs’ antibacterial effects and their released metal ions could be divided into three categories: (1) the ZnO NPs’ antibacterial effect was due solely to the released Zn2+; (2) the CuO NPs’ antibacterial effect originated from both the released Cu2+,and the CuO particles; and (3) the antibacterial effects of Fe2O3, Co3O4, Cr2O3, and NiO NPs were caused by the NPs themselves. Our findings suggest that the ions release and their contributions to the NPs’ toxicity should be considered in the toxicity evaluations of the metal oxide NPs.
Metal(loid)s pollution of groundwater in northern China is of great concern due to the increasing shortage of fresh water resources. In the present study, total 159 of groundwater samples were ...collected from the Miyun-Huairou-Shunyi (MHS) districts in Beijing city and the Hutuo River Plain (HRP) in Shijiazhuang city. Nineteen trace elements dissolved in groundwater were measured. Results showed that Al (12.3 %), Mn (5.3%), Zn (1.8%), As (1.8%), and Pb (1.8%) in the MHS samples, and Mn (2.2%) in the HRP samples exceeded their standard threshold of WHO and China. Exceedance of trace elements was attributed to both geochemical background and local human activities. Human health risk assessment showed that local consumers were exposed at a low level of health risk, except in specific area with a high level of arsenic. Elements of arsenic and chromium were important risk contributors in the two regions. The risk of oral exposure was greater than that of skin uptake. Children were more susceptible to non-carcinogenic risk and less to carcinogenic risk than adults. A Nemerow index and CRITIC-weighted WQI were applied to classify groundwater quality. The results from the two methods were comparable to a large extend. More population living in plain rather than mountain resulted in a gradual deterioration trend of groundwater quality from mountain to plain. The samples with poor water quality were almost collected in the area with heavy industrial and agricultural activities. The CRITIC-weighted WQI was recommended for groundwater quality assessment. A simple classification criterion was reformulated based on the MHS hazard index analysis. The groundwaters in the two research fields were not seriously polluted, but potential risks should not be ignored.
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Traditional Chinese medicine (TCM) has been long practiced and is becoming ever more widely recognized as providing curative and/or healing treatments for a number of diseases and physiological ...conditions. This paper posits that herbal medicines used in TCM treatments may act through hormetic dose-response mechanisms. It is proposed that the stimulatory (i.e., low dose) and inhibitory (i.e., high dose) components of the hormetic dose response correspond to respective “regulating” and “curing” aspects of TCM herbal treatments. Specifically, the “regulating” functions promote adaptive or preventive responses, while “curing” treatments alleviate the clinical symptoms. Patterns of hormetic responses are described, and the applicability of these processes to herbal medicines of TCM are explicated. It is noted that a research agenda aimed at elucidating these mechanisms and patterns would be expansive and complex. However, we argue its value, in that hormesis may afford something akin to a Rosetta Stone with which to interpret, translate, and explain TCM herbology in ways that are aligned with biomedical perspectives that could enable a more integrative approach to medicine.
► The antagonistic effect between SAs and TMP in acute test. ► The synergistic effect between SAs and TMP in chronic test. ► The different protein receptors of SAs in acute and chronic toxicity. ► ...The different concentrations of SA-binding-receptor in acute and chronic toxicity.
Organisms are typically exposed to mixtures of chemicals over long periods of time; thus, chronic mixture toxicity analysis is the best way to perform risk assessment in regards to organisms. However, most studies focus on the acute mixture toxicity. To investigate the difference between chronic mixture toxicity and acute mixture toxicity, Photobacterium phosphoreum were exposed to chronic (24h exposure) and acute (15min exposure) toxicity of single sulfonamide (SA) and their potentiator (trimethoprim, TMP), both individually and mixtures (SA with TMP). A comparison of chronic vs. acute mixture toxicity revealed the presence of an interesting phenomenon, that is, that the joint effects vary with the duration of exposure; the acute mixture toxicity was antagonistic, whereas the chronic mixture toxicity was synergistic. Based on the approach of Quantitative Structure Activity Relationships (QSARs) and molecular docking, this phenomenon was proved to be caused by the presence of two points of dissimilarity between the acute and chronic mixture toxicity mechanism: (1) the receptor protein of SAs in acute toxicity was Luc, while in chronic toxicity it was Dhps, and (2) there is a difference between actual concentration of binding-Luc in acute toxicity and individual binding-Dhps in chronic toxicity. This deep insight into the difference between chronic and acute mixture toxicity will benefit environmental science, medical science, and other disciplines. The existence of these differences poses a challenge for the assessment of routine combinations in medicine, risk assessment, and mixture pollutant control, in which, previously, only a synergistic effect has been observed between SA and their potentiator.
Hormesis has aroused much attention during the past two decades and may have great implications on many fields, including toxicology and risk assessment. However, the observation of hormesis remains ...challenged under laboratory conditions. To determine favorable conditions under which to observe hormesis, we investigated the hormetic responses of Escherichia coli (E. coli) upon exposure of different concentrations of sulfonamides and erythromycin at different time points and in different culture media: Luria-Bertani (LB) broth and Mueller Hinton (MH) broth. Our results reveal that the antibiotics, both individually and combined, produce hormetic effects on E. coli growth in MH broth at the stationary phase, with the maximum stimulatory response increasing with time. However, in LB broth, the hormetic response was not observed, which can be explained by an analogous "wood barrel theory". Our study suggests that the culture medium and time should be taken into consideration in hormetic studies, and compound mixtures should also receive more attention for their potential to induce hormesis.
Direct evidence was first demonstrated for the oxidative degradation of decabromodiphenyl ether (BDE209) in aqueous TiO2 dispersions under UV irradiation (λ > 340 nm). BDE209 was hardly debrominated ...over TiO2 in UV-irradiated acetonitrile dispersions, but the addition of water into the dispersions greatly enhanced its photocatalytic oxidative debromination. The debromination efficiency of BDE209 as high as 95.6% was achieved in aqueous TiO2 dispersions after 12 h of UV irradiation. The photocatalytic oxidation of BDE209 resulted in generation of aromatic ring-opening intermediates such as brominated dienoic acids, which were further degraded by prolonging UV irradiation time. The photocatalytic oxidative debromination of BDE209 was further confirmed by the observation that the BDE209 degradation in water–acetonitrile mixtures with different water contents was positively correlated with the formation of •OH radicals, but not photogenerated electrons. The use of water not only avoided the scavenging of reactive radicals by organic solvent but also enhanced the adsorption of BDE209 on the surface of TiO2, both of which favor the contact of BDE209 with photogenerated holes and •OH species. The confirmation of efficient oxidative degradation and debromination of BDE209 is very important for finding new ways to remove polybrominated diphenyl ethers from the environment.
► Different hormetic effects were determined in antibiotics and their mixtures. ► CA or IA models cannot predict the hormetic effects of interactive mixtures. ► Six-point approach can successfully ...predicted the hormetic effects of mixtures.
The determination of the hormetic effects of a mixture is quite difficult because of the moderate simulation and the complexity of measurement in low doses. In the present study, two typical models for mixture toxicity prediction, concentration additive (CA) and independent action (IA), were used to predict the hormetic effects of mixtures. The predictive power of those models was validated by the hormetic effects (24-h exposure) of antibiotic’s binary mixtures to Vibrio fischeri. The results showed that CA and IA were unable to predict the hormetic dose-response of mixture, especially those of the interactive mixtures. As an alternative, a novel model, which was named as “six-point” and developed based on the quantitative features in the determined dose-response curve and on the Quantitative Structure Activity Relationships (QSARs) approach, was proposed for predicting the hormetic effects of mixtures in low dose. The results indicated that the “six-point” model can accurately predict the mixture hormetic effects in low dose, not only for non-interactive mixtures but also for interactive mixtures. Therefore, the “six-point” model is a powerful tool to predict the mixture hormetic effects at low dose, and may offer an important approach in the environment risk assessment of mixtures.
During the past two decades, the phenomenon of hormesis has gained increasing recognition in environmental and toxicological communities. However, the mechanistic understanding of hormesis, to date, ...is extremely limited. Herein is proposed a novel parametric model with a mechanistic basis and two model-based parameters for hormesis that was successfully applied to the hormetic dose–response observed in the chronic toxicity of sulfonamides on Photobacterium phosphoreum. On the basis of the methods of molecular docking and quantitative structure–activity relationships (QSARs), we proposed a mechanistic hypothesis for hormesis that introduces for the first time the concept of quorum sensing in toxicological studies and explains the mechanism at the level of the receptors. The mechanistic hypothesis stated that (1) specific target binding like interaction with LuxR may contribute to transcriptional activation leading to enhanced luciferase activity at low dose exposure of sulfonamides, and (2) as the dose of sulfonamides increases, more sulfonamides competitively bind to dihydropteroate synthase, which inhibit the biosynthesis of folic acid and thus provoke toxicity. This mechanistic hypothesis, which explains both the dose-dependent and time-dependent features of hormesis, could give new insight into the mechanistic study of hormesis.
Sulfonamides (SAs), a kind of commonly used antibiotics, have been frequently detected in the environment. Due to their potential threat to the ecological environment, the toxicity of SAs to bacteria ...have been determined in depth, and the toxic mechanism is found to target dihydropteroate synthase (DHPS). However, other toxic mechanism may also exist for SAs, which is still unclear to us. In this paper, the toxic mechanism of sulfachloropyridazine (SCP, as a representative of SAs) was investigated thoroughly on Aliivibrio fischeri (A. fischeri) from the perspective of quorum sensing (QS). The results reveal that SCP may act on three signaling pathways, i.e., Pathway I, II and III, which triggers, maintains and destroys the homeostasis of A. fischeri respectively. In Pathway I, SCP changes the active form of LitR that regulates the expression of lux-related genes, inducing inhibition on bacterial growth while stimulation on luminescence; in Pathway II, SCP facilitates the production of C6HSL signaling molecules, maintaining the homeostasis in LitR and DHPS proteins; whereas in Pathway III, SCP typically combines with DHPS to inhibit the folate metabolism. This study can provide a deeper and more comprehensive understanding on the toxicity of SAs and help the environmental risk assessment of SAs.
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•SCP may act on three signaling pathways (Pathway I, II, and III) in A. fischeri.•SCP changes the active form of LitR to trigger the homeostasis in Pathway I.•SCP facilitates the C6HSL signals to maintain the homeostasis in Pathway II.•SCP combines with DHPS to destroy the homeostasis in Pathway III.
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