Microcystin-LR (MC-LR) is the most toxic and frequently detected monocyclic heptapeptide hepatotoxin produced by cyanobacteria, which poses a great threat to the natural ecosystem and public health. It is very important to seek environment-friendly and cost-efficient methods to remove MC-LR in water. In this study, the MC-degrading capacities of a novel indigenous bacterial community designated as YFMCD4 and the influence of environmental factors including various temperatures, MC concentrations and pH on the MC-degrading activities were investigated utilizing high-performance liquid chromatography (HPLC). In addition, the MC-degrading mechanism of YFMCD4 was also studied using HPLC coupled with a mass spectrometry equipped with electrospray ionization interface (HPLC-ESI-MS). The data showed MC-LR was completely removed at the maximum rate of 0.5 µg/(mL·h) under the optimal condition by YFMCD4. Two pure bacterial strains Alcaligenes faecalis and Stenotrophomonas acidaminiohila were isolated from YFMCD4 degraded MC-LR at a slower rate. The MC-degrading rates of YFMCD4 were significantly affected by different temperatures, pH and MC-LR concentrations. Two intermediates of a tetrapeptide and Adda appeared in the degradation process. These results illustrate that the novel YFMCD4 is one of the highest effective MC-degrading bacterial community, which can completely remove MC-LR and possesses a significant potential to treat water bodies contaminated by MC-LR.

Telomerase is constitutively overexpressed in the majority of human cancers and telomerase inhibition provides a promising broad-spectrum anticancer therapeutic strategy. BIBR 1532 is a well-known synthetic telomerase inhibitor that blocks the enzymatic activity of hTERT, the catalytic subunit of telomerase. However, water insolubility of BIBR 1532 leads to low cellular uptake and inadequate delivery and thus, limits its anti-tumor effects. Zeolitic imidazolate framework-8 (ZIF-8) is considered as an attractive drug delivery vehicle for improved transport, release and anti-tumor effects of BIBR 1532. Herein, ZIF-8 and BIBR 1532@ZIF-8 were synthesized, respectively, and the physicochemical characterizations confirmed the successful encapsulation of BIBR 1532 in ZIF-8 coupled with an improved stability of BIBR 1532. ZIF-8 could alter the permeability of lysosomal membrane probably by the imidazole ring-dependent protonation. Moreover, ZIF-8 encapsulation facilitated the cellular uptake and release of BIBR 1532 with more accumulation in the nucleus. BIBR 1532 encapsulation with ZIF-8 triggered a more obvious growth inhibition of cancer cells as compared with free BIBR 1532. A more potent inhibition on hTERT mRNA expression, aggravated G0/G1 arrest accompanied with an increased cellular senescence were detected in BIBR 1532@ZIF-8-treated cancer cells. Our work has provided preliminary information on improving the transport, release and efficacy of water-insoluble small molecule drugs by using ZIF-8 as a delivery vehicle.

6-PPD quinone (6-PPDQ) is widely distributed in environments. In Caenorhabditis elegans, we first examined the effects of 6-PPDQ on glutamate synthesis and receptor function by analyzing glutamate content, related gene expression, and phenotypes after RNAi of these genes. Moreover, we performed glutamate treatment after 6-PPDQ exposure to determine the potential pharmacological effects of glutamate against 6-PPDQ toxicity. After exposure, the glutamate content was reduced by 0.1–10 μg/L 6-PPDQ, which was due to decreased expression of W07E1.1, glna-1/2/3, and alh-6 governing glutamate synthesis from α-ketoglutarate, glutamine, and proline. RNAi of W07E1.1, glna-1/2/3, and alh-6 decreased glutamate content in 6-PPDQ-exposed nematodes, and caused susceptibility to 6-PPDQ toxicity. Among glutamate transporter genes, glt-1 expression was decreased by 0.1–10 μg/L 6-PPDQ. Moreover, 0.1–10 μg/L 6-PPDQ decreased glutamate receptor genes (glr-1, glr-2, and glr-4), and their expression was decreased by RNAi of W07E1.1, glna-1/2/3, alh-6, and glt-1. RNAi of these receptor genes resulted in susceptibility to 6-PPDQ toxicity, and daf-7, jnk-1, and dbl-1 were identified as targets of neuronal glr-1, glr-2, and glr-4. Furthermore, 5 mM glutamate suppressed 6-PPDQ toxicity and increased expression of glr-1, glr-2, and glr-4. Our results demonstrated the risk of 6-PPDQ exposure in disrupting glutamate synthesis and affecting function of glutamate receptors, which was related to 6-PPDQ toxicity induction.

6-PPD quinone (6-PPDQ) is a derivative from 6-PPD, an antioxidant added in tires. Leucine is an important amino acid that needs to be obtained from the diet. In Caenorhabditis elegans, we examined the effect of 6-PPDQ exposure at environmentally relevant concentrations (ERCs) on the content of leucine and underlying mechanisms. In nematodes, 0.1–10 μg/L of 6-PPDQ decreased leucine content. The expression of the aat-1-encoding amino acid transmembrane transporter was decreased by 0.1–10 μg/L of 6-PPDQ, and leucine content was reduced by aat-1 RNAi. Meanwhile, the expression of bcat-1-encoding branched-chain amino acid transferase was increased by 0.1–10 μg/L of 6-PPDQ, and leucine content was increased by bcat-1 RNAi. Additionally, the expressions of dbt-1 and ivd-1 encoding two enzyme genes governing NADH and FADH₂ generations were decreased by 0.1–10 μg/L of 6-PPDQ, and their expressions in 6-PPDQ exposed nematodes were increased by bcat-1 RNAi. After 6-PPDQ exposure, NADH content was reduced by dbt-1 RNAi, and FADH₂ content was reduced by ivd-1 RNAi. Moreover, 6-PPDQ-induced mitochondrial dysfunction and other aspects of toxicity (such as intestinal ROS generation and lipofuscin accumulation, inhibited locomotion, and reduced brood size) were suppressed by bcat-1 RNAi and strengthened by dbt-1 and ivd-1 RNAi. The 6-PPDQ-induced toxicity and the decrease in dbt-1 and ivd-1 expressions could be inhibited by following leucine (5 mM) treatment. Our results demonstrate the important association of leucine adsorption and catabolism with 6-PPDQ toxicity induction.