Nucleotide excision repair impairment by nodularin in CHO cell lines due to ERCC1/XPF inactivation

Comprehensive insights into the occurrence and toxicological issues of nodularins

The occurrence of cyanobacterial toxins is being increasingly reported. Nodularins (NODs) are one of the cyanotoxins group mainly produced by Nodularia spumigena throughout the world. NODs may exert adverse effects on animal and human health, and NOD-R variant is the most widely investigated. However, research focused on them is still limited. In order to understand the realistic risk well, the aim of this review is to compile the available information in the scientific literature regarding NODs, including their sources, distribution, structural characteristics, physicochemical properties, biosynthesis and degradation, adverse effects in vitro and vivo, and toxicokinetics. More data is urgently needed to integrate the cumulative or synergistic effects of NODs on different species and various cells to better understand, anticipate and aggressively manage their potential toxicity after both short- and long-term exposure in ecosystem, and to minimize or prevent the adverse effects on human health, environment and the economy.

MicroRNA-200c reverses drug resistance of human gastric cancer cells by targeting regulation of the NER-ERCC3/4 pathway

Gastric cancer (GC) is one of the most common types of malignant tumor. Due to the lack of effective drugs and the emergence of chemotherapy resistance, patients with GC exhibit a poor prognosis and low survival rate. MicroRNAs (miRNAs/miRs) serve an important role in drug resistance of different types of cancer. They may be suitable for use as biomarkers in the diagnosis, treatment and prognosis of tumors. The present study aimed to investigate the molecular mechanism underlying the ability of miR-200c-3p to reverse drug resistance in a SGC7901/DDP GC cell line, particularly its effects on the ERCC excision repair 3, TFIIH core complex helicase subunit (ERCC3) and ERCC excision repair 4, endonuclease catalytic subunit (ERCC4) proteins in the nucleotide excision repair (NER) pathway. Reverse transcription-quantitative polymerase chain reaction demonstrated that miR-200c-3p expression in cisplatin-resistant SGC7901/DDP cells was lower than in parental SGC7901 cells, whereas the protein expression levels of ERCC3 and ERCC4 in these cells were higher by western blot analysis. In SGC7901/DDP-derived miR-200c-3p overexpressing cells, ERCC3 expression, ERCC4 expression and cisplatin resistance were decreased compared with in parental SGC7901/DDP cells and SGC7901/DDP-derived vector control cells. In SGC7901-derived miR-200c-3p knockdown cells, ERCC3 expression, ERCC4 expression and cisplatin resistance were increased compared with in parental SGC7901 cells and SGC7901-derived vector control cells. In conclusion, overexpression of miR-200c-3p may reverse drug resistance in the SGC7901/DDP GC cell line via downregulation of ERCC3 and ERCC4, which suggested this may be part of a mechanism involving the NER pathway.

New record of a bloom forming, genotoxic strain Nodularia strain (KT447209) from Andaman and Nicobar Islands, India

Cyanobacteria blooms in marine waters are limited to only a few taxa; with the genus Nodularia (Nostocales) being one among the most commonly observed and widely studied species. A bloom of Nodularia sp. was observed across a vast area along the coast of the Andaman and Nicobar Islands. The bloom occurred during the summer when salinity was >30‰. This differed to previous reports where blooms have crashed at such high salinities. The molecular phylogeny revealed the Nodularia species to be a novel one. A crude extract from the bloom demonstrated lowed toxicity with an LC₅₀ of 5 mg/ml at 48 h towards Artemia salina and slight genotoxicity when tested against human lymphocytes.

Apoptotic responses of Carassius auratus lymphocytes to nodularin exposure in vitro

Nodularin, a metabolite of Nodularin spumigena, is widely detected in water blooms worldwide and causes serious negative effects on fish. The apoptosis-related cytotoxic effects and mechanisms of nodularin on Carassius auratus lymphocytes were investigated. Transmission electron microscopy results showed that nodularin-treated lymphocytes display a series of morphological changes, including condensed cytoplasm, nuclear chromatin agglutination and marginalization. DNA fragmentation was verified by the DNA-ladder and formation of sub-G1 DNA peaks. These cell characteristics confirmed the occurrence of apoptosis in lymphocytes. Flow cytometric results showed that the percentages of apoptotic cells incubated with 1, 5, 10, and 100 μg/L nodularin for 12 h reached 15.76%, 17.36%, 20.34% and 44.21%, respectively; controls showed low rates of apoptosis (2.4%). The mechanism of apoptosis induced by nodularin was determined, and results showed that nodularin exposure caused a significant increase in intracellular reactive oxygen species (ROS), loss of mitochondrial transmembrane potential in a dose-dependent manner, upregulation of intracellular Ca²⁺, downregulation of Bcl-2 and upregulation of Bax expression at the mRNA and protein levels, and activation of caspase-3 and caspase-9 without caspase-8. In summary, all the results suggest that nodularin induces lymphocyte apoptosis via the mitochondrial apoptotic pathway and destroys the immune response of fish.

Increased expression of DNA repair gene XPF enhances resistance to hydroxycamptothecin in bladder cancer

Background

Xeroderma pigmentosum group F (XPF) is an important participant in the nucleotide excision repair process. This study aimed to investigate the expression of DNA repair gene xeroderma pigmentosum group F (XPF) in bladder cancer and its clinical significance.

Material/Methods

Total RNA and protein were extracted from 45 untreated bladder cancer tissues and 21 hydroxycamptothecin (HCPT)-treated bladder cancer specimens. Real-time PCR and Western blot assay were used to detect the mRNA and protein levels of XPF, respectively. siRNA targeting XPF was used to knock down the XPF expression in T24 cells and 5637 cells, and the sensitivity of XPF-depleted cells to HCPT was measured.

Results

The XPF expressions in the HCPT-treated cancer tissues was significantly higher than those in the untreated cancer tissues at both mRNA and protein levels. Importantly, the enhanced XPF expression decreased the sensitivity of T24 cells and 5637 cells to HCPT. Furthermore, the HCPT treatment significantly increased the apoptosis of T24 cells and 5637 cells. Alternatively, after the XPF gene silencing, the chemotherapeutic resistance of bladder cancer cells was significantly decreased.

Conclusions

Our results show the increased expression of XPF is involved in the chemotherapeutic resistance of bladder cancer, and decreasing XPF expression may become a promising therapeutic strategy for bladder cancer.

Molecular mechanisms of microcystin toxicity in animal cells

Microcystins (MC) are potent hepatotoxins produced by the cyanobacteria of the genera Planktothrix, Microcystis, Aphanizomenon, Nostoc and Anabaena. These cyclic heptapeptides have strong affinity to serine/threonine protein phosphatases (PPs) thereby acting as an inhibitor of this group of enzymes. Through this interaction a cascade of events responsible for the MC cytotoxic and genotoxic effects in animal cells may take place. Moreover MC induces oxidative stress in animal cells and together with the inhibition of PPs, this pathway is considered to be one of the main mechanisms of MC toxicity. In recent years new insights on the key enzymes involved in the signal-transduction and toxicity have been reported demonstrating the complexity of the interaction of these toxins with animal cells. Key proteins involved in MC up-take, biotransformation and excretion have been identified, demonstrating the ability of aquatic animals to metabolize and excrete the toxin. MC have shown to interact with the mitochondria. The consequences are the dysfunction of the organelle, induction of reactive oxygen species (ROS) and cell apoptosis. MC activity leads to the differential expression/activity of transcriptional factors and protein kinases involved in the pathways of cellular differentiation, proliferation and tumor promotion activity. This activity may result from the direct inhibition of the protein phosphatases PP1 and PP2A. This review aims to summarize the increasing data regarding the molecular mechanisms of MC toxicity in animal systems, reporting for direct MC interacting proteins and key enzymes in the process of toxicity biotransformation/excretion of these cyclic peptides.

Cyanobacterial toxins and liver diseaseThis article is one of a selection of papers published in a special issue celebrating the 125th anniversary of the Faculty of Medicine at the University of Manitoba

Blue-green algae, also known as cyanobacteria, produce a variety of toxins, some of which have been implicated in the pathogenesis of severe and potentially life-threatening diseases in humans. As the growth of cyanobacteria within freshwater lakes increases worldwide, it is important to review our present understanding of their toxicity and potential carcinogenicity to gain insight into how these organisms impact human health. This review addresses each of these topics, with special emphasis given to cyanobacterial hepatotoxins within freshwater environments.