Study on the combined toxicity of DEHP and lead on the blood system of rats.

Di(2-ethylhexyl) phthalate (DEHP) is a commonly used phthalate ester compound, while lead is a persistent and bioaccumulative heavy metal. Both can be exposed to the body through a variety of ways, which may have an impact on the blood system. In this study, we examined the impact of co-exposure to DEHP (0, 10, 100 mg/kg) and Pb (0, 5, 50 mg/kg) on the blood system of male SD rats. The study revealed that continuous exposure to DEHP and Pb for 20 days resulted in a decrease in leukocytes and lymphocytes, while an increase in neutrophils and monocytes. Co-exposure led to a significant decrease in the spleen coefficients. Furthermore, the combined exposure could increase the ratio of bone marrow cells in G1 phase, and decrease the ratio of cells in S phase and G2 phase. Cytokine testing showed that combined exposure affects the secretion of hematopoietic factors and may cause bone marrow cell apoptosis. Single or combined exposure to DEHP and Pb can cause oxidative stress in serum and bone marrow. Overall, these results indicate that the co-exposure of DEHP and Pb adversely affected the blood system of rats, mainly due to the induction of oxidative stress and ultimately affects the secretion of cytokines. The combined effect of the two substances is primarily antagonistic. These results have important implications for the risk assessment of combined pollution and provide valuable theoretical guidance.

Dimethyl phthalate induces blood immunotoxicity through oxidative damage and caspase-dependent apoptosis.

Dimethyl phthalate (DMP), a low-molecular-weight phthalate ester, exists in ectoparasiticides, plastics, and insect repellants, and has been linked to neurotoxic, reproductive, and endocrine disruptive responses. However, its blood immunotoxic effects and mechanism are still poorly understood. In this study, rats were exposed to gradient concentrations of DMP through intragastric administration to assess the blood immunotoxic effects in the combined assay of biomarker, cytometry, and transcriptomics. DMP treatment altered the redox status of rats, thus causing oxidative damage. Significantly decreased blood cell counts and disordered antibody and cytokine secretion were observed in treated rats, suggesting the suppressed immune defense and destructed inflammatory regulation. Flow cytometry showed that in lymphocytes, especially CD3+CD4+ T cells, the occurrence of apoptosis/necrosis was positively related to DMP exposure level. Transcriptomics revealed an oxidative stress-related mechanism. The overexpression of the Bcl-2 family genes and the activation of the Fas/FasL pathway triggered downstream caspase cascade and caused reactive oxygen species signaling-mediated apoptosis/necrosis. To the best of our knowledge, it was the first report that the exposure to low-molecular-weight phthalate esters potentially triggered blood immunotoxicity. The result and underlying mechanisms can provide an essential basis for understanding phthalate ester toxicity and usage regulation.

Investigation on the interaction between Ag+ and bovine hemoglobin using spectroscopic methods.

Silver ions (Ag+) can be released by silver nanoparticles (AgNPs) which are widely used in diverse fields. Ag+ can exist inside cells to produce cytotoxicity. This report uses spectroscopic methods to reveal the interactions between Ag+ and bovine hemoglobin (BHb). The results of the quenching rate constant (Kq) and the fluorescence lifetime detection showed that the quenching mechanism of BHb by Ag+ was static. Thermodynamic investigations indicated that Ag+ can interact with BHb with one binding site to form complex mainly through van der Waals interactions and hydrogen bonds. The UV-vis absorption and synchronous fluorescence spectra showed that Ag+ changed the conformation of BHb, which may affect protein functions. This research is favorable for understanding the molecular toxic mechanism of Ag+ in vivo.

Biodegradation performance and biofouling control of a halophilic biocarriers-MBR in saline pharmaceutical (ampicillin-containing) wastewater treatment.

This work develops a halophilic biocarriers-MBR for saline pharmaceutical wastewater treatment. The system has effectively treated the ampicillin-containing saline wastewater for 32 days, when the ampicillin concentration is lower than 20 mg/L. The system can tolerate the saline organic wastewater with a reasonable biodegradability (removals of COD over 75%) when the ampicillin concentration is 50 mg/L. The system has a bad performance in biodegradation (COD removals around 60-70%) and fouled within 16 days at a high ampicillin concentration of 100 mg/L. At high transmembrane pressures over 30 KPa, some ampicillin molecules may permeate through the membrane causing decreases in the ampicillin removal. The concentrations of protein and carbohydrate in EPS and SMP have increased over time and with increasing the ampicillin concentration. The method of biofouling control in MBR for the ampicillin situations has been proposed based on monitoring the concentrations of EPS and SMP. The drying-assisted monitoring of membrane biofoulants has showed a better efficiency than the monitoring of transmembrane pressure for membrane anti-biofouling in the treatment of pharmaceutical saline wastewaters where a spectroscopic detection can be hardly applied. This work may benefit relative research works for the control of biodegradation performance and membrane biofouling to better treat saline pharmaceutical wastewaters.

Revealing the toxicity of dimethyl phthalate (DMP) to the oxygen-carrying function of red blood cells (RBCs): The iron release mechanism.

Phthalic acid esters (PAEs), as typical hormone pollutants, do harms to human health after enrichment over a long term exposure, causing the loss of oxygen-carrying function of red blood cells (RBCs). This study has investigated the mechanism for the toxicity of dimethyl phthalate (DMP) on the oxygen-carrying function of RBCs by measuring the iron release content of hemoglobin (Hb) in vivo and in vitro. The hematologic examination showed that the high dose of DMP at 1000 mg/kg significantly reduced the Hb content and increased the granulocyte content, whereas such toxicity was not relatively observed at a low (50 mg/kg) or a medium (250 mg/kg) dose of DMP. The in vitro experiments showed that DMP, incubated with RBCs, increased the iron release content as a function of DMP concentration. Interestingly, such a phenomenon was not observed when DMP was incubated with Hb alone, indicating that the release of hemoglobin iron could not directly caused by the combination of DMP and hemoglobin. The in vivo experiments indicated that DMP induced iron release and oxidative stress for rat RBCs. Moreover, vitamin C and E was found to reduce the level of iron release by recovering erythrocytes from the oxidative stress induced by DMP. This work has revealed that the oxidative stress induced by DMP, causing the release of Hb iron from RBCs, is the reason for the toxicity of DMP to the oxygen-carrying function.

A novel mitochondrial-targeted two-photon fluorescent probe for ultrafast monitoring of SO2 derivatives and its applications.

SO2 derivatives maintain a certain balance and play an important role in many metabolic processes. However, excessive ingestion of them can lead to serious complications of various diseases. Therefore, a rapid and precision detection of SO2 derivatives with high selectivity and sensitivity would be an advance for their bio-analytic studies. Accordingly, a novel deep red and two-photon fluorescent SO2 derivatives probe (DRQ) was developed here for the first time. The probe showed fast ratio response rate (within 5 s), excellent sensitivity (the detection limit is 103 nM for red channel and 17 nM for green channel), and outstanding selectivity toward SO2 derivatives in 10 mM PBS buffer. Moreover, the ratiometric probe DRQ displays a 99 nm blue-shift in emission upon addition of SO2 derivatives. Intriguingly, the probe can be made into test papers for real-time monitoring of SO2 derivatives. Moreover, it can be also applied for visual ratio imaging of SO2 derivatives in cellular mitochondria and zebrafish under two-photon absorption (green channel) and one-photon absorption (red channel).

Impact Assessment of heavy metal cations to the characteristics of photosynthetic phycocyanin.

This work has assessed the impact of typical heavy metal cations on C-phycocyanin in vitro and in silico. At low concentrations (<2×10-6 mol/L), the influence of Pb2+ is the highest on the light absorption of C-phycocyanin trimer. At higher concentrations, however, a new order of influence on the light absorption has been observed with Cd2+ < Cu2+ < Pb2+ < Zn2+. The fluorescence polarization has changed from the order of Cd2+ < Pb2+≈Cu2+ < Zn2+ to Cd2+ < Cu2+ < Pb2+ < Zn2+, when the metal concentrations reaches 2×10-6 mol/L. The mechanisms for these findings have been studied using FTIR, hydrophobic probe, isothermal titration calorimetry and molecular docking for the analysis of structure disorder of C-phycocyanin. It has been suggested that the secondary structure of C-phycocyanin affects more to the light absorbance while the fluorescence characteristics relies more on the tertiary structure. The interaction between Pb2+ and C-phycocyanin is both enthalpically and entropically favoured, whereas the interactions for Cd2+, Cu2+ and Zn2+ are entropically driven. The ion-molecular docking suggests that the structure disorder of C-phycocyanin relies on the molecular interactions with metal ions. The in silico study also showed that the binding cites of Zn2+ are closer to chromophores.

In vitro toxicity of dimethyl phthalate to human erythrocytes: From the aspects of antioxidant and immune functions.

In the study, the effects of dimethyl phthalate (DMP) on the antioxidant defense capacity and immune functions of human erythrocytes were experimentally explored. DMP affected the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) and the contents of glutathione (GSH) and malondialdehyde (MDA) in erythrocytes, thus impairing the function of antioxidant defense system of erythrocytes. When DMP concentration increased from 0 to 28 µmol L-1, the SOD and GPX activities were increased firstly and then gradually decreased. When DMP concentration was below 20 µmol L-1, the relative activity of SOD was enhanced by DMP and the effect was known as hormesis. The relative activity of GPX was also increased when the concentration of DMP was below 12 µmol L-1. The CAT activity was more significantly inhibited by DMP than the activities of SOD and GPX, whereas the relative GSH content was increased by DMP. MDA levels were significantly changed after the exposure to DMP (0-24 µmol L-1). The experimental results of the activity of SOD and CAT, and the content of MDA also suggested that DMP could inhibit the immune functions of red blood cells (RBCs), which were further proved by the decrease of two indicators (RBC-C3b and RBC-IC) due to the destruction of C3b receptor with immune adherence function on erythrocyte membrane. The study provides a deep understanding of the toxicity of DMP on erythrocytes.

Comparative study on the toxic mechanisms of medical nanosilver and silver ions on the antioxidant system of erythrocytes: from the aspects of antioxidant enzyme activities and molecular interaction mechanisms.

BACKGROUND: The wide application of silver nanoparticles (AgNPs) in medicals and daily utensils increases the risk of human exposure. The study on cell and protein changes induced by medical AgNPs (20 nm) and Ag+ gave insights into the toxicity mechanisms of them. RESULTS: AgNPs and Ag+ affected the enzymatic and non-enzymatic antioxidant systems of red blood cells (RBCs). When RBCs were exposed to AgNPs or Ag+ (0-0.24 µg/mL), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) were more sensitive to Ag+, whereas the RBCs had slightly higher glutathione (GSH) contents treated by AgNPs. Both AgNPs and Ag+ increased the malondialdehyde (MDA) content of RBCs, but the difference was not significant. The difference in the change of the enzyme activity indicated that AgNPs and Ag+ have different influencing mechanisms on CAT and GPX. And SOD has stronger resistance to both of AgNPs and Ag+. When AgNPs or Ag+ (0-10 µg/mL) was directly applied on enzymatic proteins, although AgNPs or Ag+ at a high concentration was toxic, at the concentration below 0.4 µg/mL could promote the activities of CAT/SOD/GPX. The spectroscopic results (fluorescence, synchronous fluorescence, resonance light scattering and ultraviolet absorption), including the changes in amino acid microenvironment, peptide chain conformation, and aggregation state, indicated that the interaction mechanism and conformational changes were also the important factors for the changes in the activities of SOD/CAT when SOD/CAT were directly exposed to AgNPs or Ag+. CONCLUSIONS: Low concentration (< 0.4 µg/mL) of AgNPs is relatively safe and the direct effects of AgNPs and Ag+ on enzymes are important reasons for the change in antioxidant capacity of RBCs.

In vitro assessment of the toxicity of small silver nanoparticles and silver ions to the red blood cells.

This work reports the toxicity of small silver nanoparticles (nanoAg, 20 nm) and silver ions (Ag+) to the red blood cells with the silver concentration level of 10-6 g/mL. Results show that red blood cells (RBCs) start hemolysis when treated by nanoAg of 1.5 × 10-5 g/mL or Ag+ of 2.9 × 10-7 g/mL. A low ATPase activity of 30% has been observed after RBCs being treated with Ag+ of 2.6 × 10-7 g/mL, while the nanoAg does not obviously affect the ATPase activity. In molecular level, Ag+ is more toxic to the amino acid residues than nanoAg according to the change of fluorescence characteristics of hemoglobin (Hb). However, the nanoAg has been found to be more toxic than Ag+ to the secondary structure of Hb in terms of the loss of α-helix content.

The toxicity of cadmium ion (Cd2+) to phycocyanin: an in vitro spectroscopic study.

The pollution of heavy metals is a severer problem for the ecosystems in waters. The toxicity of Cd2+ on phycocyanin (PC) is studied in molecular level in this work. The fluorescence quenching of PC is observed by the adding Cd2+ from 0 to 500 × 10-7 mol L-1. From the theoretical calculation and the time-resolved fluorescence decay profiles, the fluorescence quenching of PC by Cd2+ is found to be static. The synchronous fluorescence spectra are used to study the change in amino acid residues of PC molecules, indicating that the effect of Cd2+ on the Trp of PC is more significant than the Tyr. The UV-Vis absorbance of tetrapyrrole decreases from 0.26 to 0.23 cps with increasing Cd2+ concentration, suggesting that Cd2+ affects the light adsorption and the photosynthesis function of PC. The circular dichroism spectra reveal that adding Cd2+ also changes the secondary structure (α-helix) of PC.

In vitro assessment of the toxicity of lead (Pb2+) to phycocyanin.

This work reports the influence of lead (Pb2+) on fluorescence characteristics and protein structure of phycocyanin molecules experimentally in vitro. The fluorescence intensity decreases with the increasing concentration of Pb2+ from 0 to 5 × 10-5 mol L-1, showing the fluorescence quenching of phycocyanin by Pb2+. The quenching process is suggested to be static regarding the calculation results and the experimental results of time-resolved fluorescence decay profiles. The synchronous fluorescence spectra show that the effect of Pb2+ on the Tyr residues of phycocyanin is more significant than the Trp residues. The forming of aggregation by the interaction of Pb2+ with phycocyanin molecules is suggested from the results of resonance light scattering spectra. The UV-Vis spectra of the protein skeleton of phycocyanin have a red-shift of about 10 nm with increasing the Pb2+ concentration from 0 to 5 × 10-5 mol L-1, indicating a change in the protein skeleton and its secondary structure. With the increasing Pb2+ concentration, the two negative peaks (209 nm and 218 nm) on circular dichroism spectra become smaller, showing a decrease of the α-helix structure. These results may give people a deeper understanding of that how the heavy metal (Pb2+) can affect the chemo-physical properties of phycocyanin.

Interaction studies of polybrominated diphenyl ethers (PBDEs) with human serum albumin (HSA): Molecular docking investigations.

This work has evaluated the interactions of HSA and typical PBDEs (BDE47, BDE99, BDE100, BDE153 and BDE209) at molecular level by modelling. Apart from the BDE209, PBDEs with higher molecular weight show higher binding energy with the residues of HSA. The BDE209 without H atoms has the lowest binding energy (-ΔGbinding: 4.30calmol-1) than other PBDEs (-ΔGbinding: 7.93-8.42calmol-1). The BDE99 shows a higher binding energy than its isomer (BDE100). On the other hand, the lgKow-depth plotting figure shows that a higher Kow value (hydrophobicity) of PBDEs is accompanied by a deeper binding site within the central channel of HSA. This work may provide a theoretical method to assess the transport and distribution of PBDEs in human body.

In vitro assessment of phthalate acid esters-trypsin complex formation.

In this work, interactions of three phthalate acid esters (PAEs), including dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP), with trypsin have been studied in vitro, under simulated physiological conditions using multi-spectroscopic techniques and molecular modeling. The results show that these PAEs can bind to the trypsin, forming trypsin-PAEs complexes, mainly via hydrophobic interactions, with the affinity order of DMP > DEP > DBP. Binding to the PAEs is found to result in molecular deformation of trypsin. The modeling results suggest that only DBP can bind with the amino acid residues of the catalytic triad and S1 binding pocket of trypsin, leading to potential competitive enzyme inhibition.

Study on the interaction between typical phthalic acid esters (PAEs) and human haemoglobin (hHb) by molecular docking.

This work has evaluated the binding force between hHb and typcial PAEs (DMP, DEP, DPRP, DBP, DIBP, DHP and DPHP) using molecule docking technique. The DPHP with 3 aromatic rings has the strongest binding (-ΔGbinding: 6.0kcalmol-1) than other PAEs (-ΔGbinding: 2.91∼4.48kcalmol-1). The DMP with the lowest molecular weight has a high binding force (-ΔGbinding: 4.48kcalmol-1), while the DHP with the highest molecular weight has the lowest binding force (-ΔGbinding: 2.91kcalmol-1). When the length of side chain increases, the binding force trend to decrease, regarding the VDW forces and H-bonding. The lgKow-ΔGbinding plotting figure shows that a higher Kow value is accompanied by a lower binding force. The aromatic ring existed in PAEs largely increases the binding force between the hHb and the PAEs. On the other hand, the PAEs with higher number of carbon, meaning a higher hydrophobicity, can enter into the hydrophobic space of hHb centre deeper and bond to different position. The aromatic ring decreases the depth of binding position in the hydrophobic space. This work provides basic data and a theoretical method to assess the transport and accumulation of PAEs in human body, and the cytotoxicity of PAEs to hBRCs.

In vitro cytotoxicity of decabrominated diphenyl ether (PBDE-209) to human red blood cells (hRBCs).

This work presents the effect of decabrominated diphenyl ether (PBDE-209) on the anti-oxidative defense capacity, and ATPase activity (structure and function) of human red blood cells (hRBCs). The results show that the PBDE-209 influences the activity and content of typical biomolecules (SOD, CAT, GSH-Px, GSH and MDA) in hRBCs, causing a decline in the function of the antioxidant defense system. The PBDE-209 with a concentration of 10 µmol/L resulted in the cytoplasmic projections and structure deformation of the hRBCs. When its concentration exceeds 25 µmol/L, the relative ATPase activity was decreased to 20% of the initial activity. Since the discovered effects of PBDE-209 on hRBCs are in cell level, this study may offer some information to advise the related in vivo cytotoxicity works.

Study on the Mechanism of Interaction between Phthalate Acid Esters and Bovine Hemoglobin.

Phthalate acid esters (PAEs) are widely used in plastic products as a series of chemical softeners. However, PAEs, which now exist in many environmental media such as the atmosphere, water, and soil, have been shown to be environmental endocrine disruptors. Hemoglobin is a functional protein that carries oxygen in the red blood cells of animals. This study aims at revealing the interactions between bovine hemoglobin (BHb) and PAEs using spectroscopic and molecular modeling methods. The results indicate that the selected representative PAEs-dimethyl phthalate (DMP), diethyl phthalate (DEP), and dibutyl phthalate (DBP)-can interact with BHb to form BHb-PAE complexes with one binding site, mainly relying on hydrophobic forces, with the affinity order DMP > DEP > DBP, opposite to the order of side-chain length. The binding of PAEs can cause conformational and micro-environmental changes in BHb, which may affect the physiological functions of Hb. Furthermore, molecular docking was applied to define the specific binding sites, the results of which show that all the three PAEs can bind into the central cavity of BHb. The study contributes to expound the toxic mechanism of PAEs in vivo from the point of hematological toxicology.

Study on the mechanism of action between dimethyl phthalate and herring sperm DNA at molecular level.

Dimethyl phthalate (DMP), a typical phthalic acid ester, is widespread in the environment and causes extensive concern due to its adverse effects on human health. To understand the genotoxicity of DMP at molecular level, the toxic interaction of DMP with herring sperm (hs) deoxyribonucleic acid (DNA; hs-DNA) was investigated in vitro under simulated physiological conditions using multi-spectroscopic techniques and a molecular modeling method. The results of Ultraviolet-Visible absorption spectroscopy, fluorescence emission spectroscopy, and circular dichroism spectra indicated that DMP interacts with hs-DNA in a groove-binding mode that changes the double helical structure of DNA. The binding constant and the number of binding sites calculated from the fluorescence quenching data were 565.718 L mol(-1) and 0.7872, respectively. A molecular modeling study revealed that DMP tends to bind with DNA in the A-T-rich regions of minor groove and that hydrogen bonding and van der Waals forces play main roles in the interaction. This research can help to elucidate the mechanism of DMP toxicity in vivo.

Binding of the veterinary drug tetracycline to bovine hemoglobin and toxicological implications.

Tetracycline (TC) is a widely used veterinary drug in animal breeding and fishery. Because of its low bioavailability, the TC residue extensively exists in the environment (e.g. soils, lakes and rivers), which can enter the human body, being potentially harmful. Hemoglobin (Hb) is a protein responsible for oxygen carrying in the vascular system of animals. The aim of this study was to investigate the interaction of bovine hemoglobin (BHb) with TC through spectroscopic and molecular modeling methods. The experimental results revealed that TC can interact with BHb with one binding site to form a TC-BHb complex, mainly through van der Waals interactions and hydrogen bonds. The UV-visible absorption, synchronous fluorescence, and circular dichroism (CD) results revealed that the binding of TC can cause conformational and some microenvironmental changes of BHb, which may affect BHb physiological functions. The synchronous fluorescence experiment disclosed that TC binds into BHb central cavity, which was verified by molecular modeling study. The work contributes to clarify the molecular mechanism of TC toxicity in vivo.

Probing the in vitro cytotoxicity of the veterinary drug oxytetracycline.

The study investigated the effect of oxytetracycline (OTC) on the anti-oxidative defense system, the structure (hemolysis rate and morphology) and function (ATP enzyme activity) of human red blood cells (hRBCs) to investigate the possible toxic mechanism of OTC to hRBCs. The experimental results indicate that OTC can cause a decline in the function of the antioxidant defense system of hRBCs, resulting in oxidative stress. OTC can bring about morphological changes to hRBCs, and further leads to hemolysis, when the concentration of OTC is over 8×10(-5) M (about 164 µg/ml). At a low OTC concentration, below 4×10(-5) M (82 µg/ml), OTC can enhance the activity of ATP enzyme of hRBCs, known as hormesis. However, at a high concentration, above 4×10(-5) M (about 82 µg/ml), the ATP enzymatic activity was inhibited, affecting the function of hRBCs. The estalished mechanism of toxicity of OTC to hRBCs can facilitate a deeper understanding of the toxicity of OTC in vivo.