In vitro oxidative stress, mitochondrial impairment and G1 phase cell cycle arrest induced by alkyl-phosphorus-containing flame retardants.

Phosphorus-containing flame retardants (PFRs) have been frequently detected in various environmental samples at relatively high concentrations and are considered emerging environmental pollutants. However, their biological effects and the underlying mechanism remain unclear, especially alkyl-PFRs. In this study, a battery of in vitro bioassays was conducted to analyze the cytotoxicity, oxidative stress, mitochondrial impairment, DNA damage and the involved molecular mechanisms of several selected alkyl-PFRs. Results showed that alkyl-PFRs induced structural related toxicity, where alkyl-PFRs with higher logKow values induced higher cytotoxicity. Long-chain alkyl-PFRs caused mitochondrial and DNA damage, resulting from intracellular reactive oxygen species (ROS) and mitochondrial superoxide overproduction; while short-chain alkyl-PFRs displayed adverse outcomes by significantly impairing mitochondria without obvious ROS generation. In addition, alkyl-PFRs caused DNA damage-induced cell cycle arrest, as determined by flow cytometry, and transcriptionally upregulated key transcription factors in p53/p21-mediated cell cycle pathways. Moreover, compared to the control condition, triisobutyl phosphate and trimethyl phosphate exposure increased the sub-G1 apoptotic peak and upregulated the p53/bax apoptosis pathway, indicating potential cell apoptosis at the cellular and molecular levels. These results provide insight into PFR toxicity and the involved mode of action and indicate the mitochondria is an important target for some alkyl-PFRs.

A mechanism study on toxicity of graphene oxide to Daphnia magna: Direct link between bioaccumulation and oxidative stress.

Graphene oxide (GO) possesses versatile applicability and high hydrophilicity, thus may have frequent contact with aquatic organisms. However, the ecological risks of GO in aquatic ecosystems remain largely unexplored currently. This study evaluated the comprehensive toxicological effects of GO on Daphnia magna, a key species in fresh water ecosystem. The results revealed nonsevere acute toxicities, including immobility (72 h EC50: 44.3 mg/L) and mortality (72 h LC50: 45.4 mg/L), of GO on D. magna. To understand the underlying mechanism of GO exposure, changes in superoxide dismutase (SOD) and lipid peroxidation (LPO) of D. magna exposed to GO were correlated, which revealed elevated GO-mediated oxidative stress and damages, especially in the long-time and high-dose exposure groups. The observations of in vivo fluorescence labeled with 2', 7'-dichlorofluorescin further demonstrated that reactive oxygen species were concentrated in daphnia guts, which corresponded with the high bioaccumulation level (5 mg/L, 24 h body burden: 107.9 g/kg) of GO in daphnia guts. However, depuration of GO from daphnia was not difficult. Daphnia almost released all GO within 24 h after it was transferred to clean water. These results hence suggest that GO could accumulate and induce significant oxidative stress in the gut of D. magna, while D. daphnia can also relieve the acute toxicity by depurating GO.

Exposure of engineered nanoparticles to Alexandrium tamarense (Dinophyceae): Healthy impacts of nanoparticles via toxin-producing dinoflagellate.

Human activities can enhance the frequency, intensity and occurrence of harmful algal blooms (HABs). Engineered nanoparticles (ENPs), contained in many materials, will inevitably enter coastal waters and thus cause unpredictable impacts on aquatic organisms. However, knowledge of the influence of ENPs on HAB species is still lacking. In this study, we examined the effects of titanium dioxide nanoparticles (nTiO2), zinc oxide nanoparticles (nZnO) and aluminum oxide nanoparticles (nAl2O3) on physiological changes and paralytic shellfish poisoning toxins (PSTs) production of Alexandrium tamarense. We found a dose-dependent decrease in photosynthetic activity of A. tamarense under all three ENPs and a significant growth inhibition induced by nZnO. The largest reactive oxygen species (ROS) production was induced by nTiO2, followed by nZnO and nAl2O3. Moreover, the PSTs production rate increased by 3.9-fold for nTiO2 (p<0.01) and 4.5-fold for nAl2O3 (p<0.01) at a concentration of 200mgL-1. The major component, C2 was transformed to its epimer C1 and the proportion of decarbamoyl toxins increased under 200mgL-1 of nZnO and nAl2O3. In addition, the proportion of carbamate toxins increased upon exposure to 2mgL-1 ENPs, while decreased upon exposure to 200mgL-1 ENPs. The changes in PSTs production and composition might be an adaptive response for A. tamarense to overcome the stress of ENPs exposure. This work brings the first evidence that ENP would affect PSTs production and profiles.

Effects of short-term invasion of Spartina alterniflora and the subsequent restoration of native mangroves on the soil organic carbon, nitrogen and phosphorus stock.

The exotic cordgrass Spartina alterniflora has severely invaded the mangrove wetlands in southern China and ecological restoration using native mangroves was conducted in an attempt to control this invasive species. In this study, the contents and pools of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) were quantified to investigate the invasive effects of S. alterniflora and then to evaluate whether the ecological restoration of native mangrove could reverse those effects. S. alterniflora only showed significantly higher organic carbon content in the surface 0-10 cm of soil than in the uninvaded mudflat. The high δ13C values in the surface soil of the invaded habitat demonstrated that S. alterniflora contributed 42.6-62.2% of the organic carbon. The SOC for invasive S. alterniflora and newly restored mangroves (4 years and 14 years) was not enhanced in comparison to the unvegetated mudflat. S. alterniflora significantly increased the surface soil TN content, but decreased the available phosphorus content and TP density. The TN densities increased gradually with the mangrove restoration, while the TP densities were only slightly influenced. The results suggested that short-term invasion of S. alterniflora and subsequent mangrove restoration did not alter SOC or TN pool sizes, but S. alterniflora was shown to affect the potential carbon storage capacity produced by the mangroves in the Zhangjiang Estuary.

[Comparative study on effects between electroacupuncture and acupuncture for spastic paralysis after stroke].

OBJECTIVE: To observe the differences of therapeutic effect of spastic paralysis after stroke between electroacupuncture and acupuncture and explore the mechanism. METHODS: Sixty-four cases were randomly divided into an electroacupuncture group (n = 33) and an acupuncture group (n = 31). Both groups were treated with Bobath facilitation techniques and medicine treatments. Quchi (LI 11), Hegu (LI 4), Yanglingquan (GB 34), Sanyinjiao (SP 6), et al. on the affected side were selected in each group. The needle was retained for 30 min, and the manipulation was applied for 1 min in the acupuncture group, and electroacupuncture was added in the electroacupuncture group. Stroke Impairment Assessment Set (SIAS) was adopted to assess the whole function status after sroke, and the contents of glutamate (Glu) and gamma-aminobutyric acid (GABA) in serum and clinical efficacy were observed in the two groups. RESULTS: The SIAS score increased after treatment as compared with that before treatment in either group (both P < 0.01), and the electroacupuncture group was superior to the acupuncture group (P < 0.01); the content of Glu in blood serum and ratio of Glu/GABA reduced, while the content of GABA in serum increased after treatment as compared with those before treatment in either group (all P < 0.01), but the improvement of above indices were much more apparently in the electroacupuncture group as compared with those in the acupuncture group (P < 0.01, P < 0.05); the total effective rate of 90.9% (30/33) in the electroacupuncture group was superior to that of 83.9% (26/31) in the acupuncture group (P < 0.05). CONCLUSION: Electroacupuncture can improve therapeutic effect of spastic paralysis after stroke, it's mechanism may be ralated to ajusting the contents of Glu and GABA in serum.

Comparative toxicity of several metal oxide nanoparticle aqueous suspensions to Zebrafish (Danio rerio) early developmental stage.

With the emergence of manufactured nanomaterials, it is urgent to carry out researches on their potential environmental impacts and biological effects. To better understand the potential ecotoxicological impacts of metal oxide nanoparticles released to aquatic environments, the zebrafish 96-h embryo-larval bioassay was used to assess and compare the developmental toxicities of nanoscale zinc oxide (nZnO), titanium dioxide (nTiO(2)) and alumina (nAl(2)O(3)) aqueous suspensions. Toxicological endpoints such as zebrafish embryos or larvae survival, hatching rate and malformation were noted and described within 96 h of exposure. Meanwhile, a comparative experiment with their bulk counterparts (i.e., ZnO/bulk, TiO(2)/bulk and Al(2)O(3)/bulk) was conducted to understand the effect of particle size on their toxicities. The results showed that: (i) both nZnO and ZnO/bulk aqueous suspensions delayed zebrafish embryo and larva development, decreased their survival and hatching rates, and caused tissue damage. The 96-h LC(50) of nZnO and ZnO/bulk aqueous suspensions on the zebrafish survival are 1.793 mg/L and 1.550 mg/L respectively; and the 84-h EC(50) on the zebrafish embryo hatching rate are 2.065 mg/L and 2.066 mg/L respectively. Serious tissue ulceration was found on zebrafish larvae exposed to nZnO and ZnO/bulk aqueous suspensions. (ii) In contrast, neither nTiO(2) and TiO(2)/bulk nor nAl(2)O(3) and Al(2)O(3)/bulk showed any toxicity to zebrafish embryos and larvae under the same experimental condition. It revealed that the metal oxide nanoparticles with different chemical composition have different zebrafish developmental toxicities. (iii) Exposures of nTiO(2), nZnO and nAl(2)O(3) produced toxic effects on zebrafish embryos and larvae, which was not different from the effects caused by exposing to their bulk counterparts. This is the first study about the developmental toxicity of metal oxide nanoparticles, and the results demonstrate that nZnO is very toxic to zebrafish embryos and larvae, which highlights the need to evaluate the potential eco-toxicity of these manufactured nanomaterials (MNMs).