Combined cytotoxicity and genotoxicity of a marine toxin and seafood contaminant metal ions (chromium and cadmium)

Bone marrow mesenchymal stem cells repair hexavalent chromium-induced testicular injury by regulating autophagy and ferroptosis mediated by the AKT/mTOR pathway in rats

There is no ideal therapy for testicular damage induced by Cr(VI); however, bone marrow mesenchymal stem cells (BMSCs) transplantation may be a promising therapy. A Cr(VI) solution was administered to rats by intraperitoneal injection for 30 days, then BMSCs from donor rats were transplanted. Two weeks later, decreased activity and appetite, along with other pathological changes, were improved in the BMSCs group. The location of BMSCs in damaged testes was observed via laser confocal microscopy. Chromium content in the Cr(VI) and BMSCs groups significantly increased compared with that in the control group, but there was no significant difference between the two groups, as revealed by atomic absorption spectrometry. The ferrous iron and the total iron content of testes in the BMSCs group were significantly lower than those in the Cr(VI) group, as observed by Lillie staining and a tissue iron assay kit. Western blotting and immunohistochemical analyses revealed that the expression of Beclin 1, LC3B, 4-hydroxynonenal, and transferrin receptor 1 was decreased in the BMSCs group, compared with the Cr(VI) group. The expression of glutathione peroxidase 4 (GPX4), SLC7A11, p-AKT, mammalian target of rapamycin (mTOR), and p-mTOR in the BMSCs group was higher than that in the Cr(VI) group. Taken together, we propose that BMSCs repair Cr(VI)-damaged testes by alleviating ferroptosis and downregulating autophagy-associated proteins through the upregulation of AKT and mTOR phosphorylation.

Heavy metals contaminating the environment of a progressive supranuclear palsy cluster induce tau accumulation and cell death in cultured neurons

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder characterized by the presence of intracellular aggregates of tau protein and neuronal loss leading to cognitive and motor impairment. Occurrence is mostly sporadic, but rare family clusters have been described. Although the etiopathology of PSP is unknown, mutations in the MAPT/tau gene and exposure to environmental toxins can increase the risk of PSP. Here, we used cell models to investigate the potential neurotoxic effects of heavy metals enriched in a highly industrialized region in France with a cluster of sporadic PSP cases. We found that iPSC-derived iNeurons from a MAPT mutation carrier tend to be more sensitive to cell death induced by chromium (Cr) and nickel (Ni) exposure than an isogenic control line. We hypothesize that genetic variations may predispose to neurodegeneration induced by those heavy metals. Furthermore, using an SH-SY5Y neuroblastoma cell line, we showed that both heavy metals induce cell death by an apoptotic mechanism. Interestingly, Cr and Ni treatments increased total and phosphorylated tau levels in both cell types, implicating Cr and Ni exposure in tau pathology. Overall, this study suggests that chromium and nickel could contribute to the pathophysiology of tauopathies such as PSP by promoting tau accumulation and neuronal cell death.

How leachates from wasted cigarette butts influence aquatic life? A case study on freshwater mussel Anodontites trapesiali

There are several reports on the damage smoking causes to human health available in the literature, but little is known about the environmental and biological consequences from inappropriate cigarette butt (CB) disposal in urban and natural environments. The immunotoxic, morphotoxic and mutagenic potential of leachates from cigarette butts (LCB) diluted at environmentally relevant rates (LCB1x: 1.375%; LCB10x: 13.75%) was evaluated in adult representatives of the bivalve species Anodontites trapesialis, which was adopted as model organism. Type II hyalinocytes and granulocytes (phagocytic cells) frequency increased in the hemolymph of subjects exposed to the pollutant for 14 days. Based on this outcome, LCB chemical constituents did not induce immunotoxic effects. The treatments also did not seem to have any impact on the subjects' hemocitary morphometry parameters: diameter, area, perimeter, circularity and nucleus - cytoplasm ratio. However, subjects in groups LCB1x and LCB10x recorded a larger number of hyalinocytes with some nuclear abnormality such as micronucleus, blebbed nucleus, asymmetric constriction nucleus, and nuclear multilobulation and binucleation. The association between these abnormalities and the treatments was confirmed by the Cr, Ni, Pb, Zn, Mn and Na bioaccumulation in tissue samples of the bivalve models exposed to LCB. To the best of our knowledge, this is the first report on LCB mutagenicity in representatives of a freshwater bivalve group. Given the chemical complexity of the addressed pollutants, it is imperative to develop further investigations about the topic.

Chromium-resistant bacteria promote the reduction of hexavalent chromium in soils

Knowledge of the chromium (Cr) redox process in soil is important in addressing Cr bioavailability and risk assessment of contaminated soils. In this study, seven representative agricultural soils with different physicochemical properties were used to investigate the importance of microbially mediated Cr(VI) reduction and the response of soil bacterial community to Cr contamination. Chromium application increased soil bacterial diversity in Periudic Argosols, Calcaric Regosols, Stagnic Anthrosols, Mollisols, Typic Haplustalfs, and Ustic Cambosols, with an exception of Udic Ferrisols. The soil bacterial community responded to Cr contamination through changes in bacterial community structure, with Cr-resistant bacteria becoming the dominant species, and the percentage of Cr-resistant bacteria of total cultivable bacteria was 89.9, 75.2, 92.8, 65.3, 72.8, 77.3, and 65.4%, respectively, for Periudic Argosols, Udic Ferrisols, Calcaric Regosols, Stagnic Anthrosols, Mollisols, Typic Haplustalfs, and Ustic Cambosols. , , , , , , , , , and were identified as the Cr-resistant bacteria. Moreover, our results demonstrated that microbial reduction was an important Cr(VI) reduction pathway, and the relative contribution of microorganisms to Cr(VI) reduction was 14.4, 44.0, 20.6, 34.9, 21.9, 21.7, and 22.0%, respectively for Periudic Argosols, Udic Ferrisols, Calcaric Regosols, Stagnic Anthrosols, Mollisols, Typic Haplustalfs, and Ustic Cambosols. Soil properties, especially Fe(II) and soil particle distribution, affected the microbially mediated Cr(VI) reduction. These results provide useful information for the bioremediation of Cr-contaminated soils under a wide range of environmental conditions.

Effect of okadaic acid on cultured clam heart cells: involvement of MAPkinase pathways

Okadaic acid (OA) is one of the main diarrhetic shellfish poisoning toxins and a potent inhibitor of protein phosphatases 1 and 2A. The downstream signal transduction pathways following the protein phosphatase inhibition are still unknown and the results of most of the previous studies are often conflicting. The aim of the present study was to evaluate the effects of OA on heart clam cells and to analyse its possible mechanisms of action by investigating the signal transduction pathways involved in OA cytotoxicity. We showed that OA at 1 µM after 24 h of treatment induces disorganization of the actin cytoskeleton, rounding and detachment of fibroblastic cells. Moreover, treatment of heart cells revealed a sequential activation of MAPK proteins depending on the OA concentration. We suggest that the duration of p38 and JNK activation is a critical factor in determining cell apoptosis in clam cardiomyocytes. In the opposite, ERK activation could be involved in cell survival. The cell death induced by OA is a MAPK modulated pathway, mediated by caspase 3-dependent mechanism. OA was found to induce no significant effect on spontaneous beating rate or inward L-type calcium current in clam cardiomyocytes, suggesting that PP1 was not inhibited even by the highest dose of OA.

Assessment of Cr(VI)-induced cytotoxicity and genotoxicity using high content analysis

Oral exposure to high concentrations of hexavalent chromium [Cr(VI)] induces intestinal redox changes, villus cytotoxicity, crypt hyperplasia, and intestinal tumors in mice. To assess the effects of Cr(VI) in a cell model relevant to the intestine, undifferentiated (proliferating) and differentiated (confluent) Caco-2 cells were treated with Cr(VI), hydrogen peroxide or rotenone for 2-24 hours. DNA damage was then assessed by nuclear staining intensity of 8-hydroxydeoxyguanosine (8-OHdG) and phosphorylated histone variant H2AX (γ-H2AX) measured by high content analysis methods. In undifferentiated Caco-2, all three chemicals increased 8-OHdG and γ-H2AX staining at cytotoxic concentrations, whereas only 8-OHdG was elevated at non-cytotoxic concentrations at 24 hr. Differentiated Caco-2 were more resistant to cytotoxicity and DNA damage than undifferentiated cells, and there were no changes in apoptotic markers p53 or annexin-V. However, Cr(VI) induced a dose-dependent translocation of the unfolded protein response transcription factor ATF6 into the nucleus. Micronucleus (MN) formation was assessed in CHO-K1 and A549 cell lines. Cr(VI) increased MN frequency in CHO-K1 only at highly cytotoxic concentrations. Relative to the positive control Mitomycin-C, Cr(VI) only slightly increased MN frequency in A549 at mildly cytotoxic concentrations. The results demonstrate that Cr(VI) genotoxicity correlates with cytotoxic concentrations, and that H2AX phosphorylation occurs at higher concentrations than oxidative DNA damage in proliferating Caco-2 cells. The findings suggest that in vitro genotoxicity of Cr(VI) is primarily oxidative in nature at low concentrations. Implications for in vivo intestinal toxicity of Cr(VI) will be discussed.

In vitro evaluation of antibacterial activities and anti-inflammatory effects of Bifidobacterium spp. addressing acne vulgaris

The objective of this study was to evaluate the antibacterial and anti-inflammatory effect of Bifidobacterium spp. In the first part of the study, the antibacterial activities of live and sonicated cells, from a total of 23 Bifidobacterium species, on the growth of 5 different strain of Staphylococcus aureus. Six strains, of sonicated Bifidobacterium, exhibited antibacterial activity against staphylococci samples, and seven Bifidobacterium strains exhibited antibacterial activity on the growth of S. aureus S.P.-N2. In the second part of the study, we tested the antimicrobial activity, of Bifidobacterium against Propionibacterium acne KCTC3320, using the co-culture method. The loss of P. acnes viability, caused by B. adolescentis SPM0308 and B. longum SPM1207, was 84% and 75%, respectively (*p < 0.05). In the third part of the study, the anti-inflammatory activity of B. adolescentis SPM0308 and B. longum SPM1207 were assessed; nitric oxide (NO), and tumor necrosis factor-α (TNF-α), production were tested using the murine macrophage RAW 264.7 cell line. Treatment of RAW 264.7 cells, with Bifidobacterium, decreased production of NO and TNF-α rather than LPS (100 ng/mL) treatment. The results suggest that B. adolescentis SPM0308 could be used as an effective control for P. acnes KCTC3320, and S. aureus, and reduce the risk of acne vulgaris development. We suggest that B. adolescentis SPM0308 may be a useful probiotic microorganism, for prevention of acne vulgaris, without adverse effects.

Okadaic acid induces apoptosis through the PKR, NF-κB and caspase pathway in human osteoblastic osteosarcoma MG63 cells

Okadaic acid (OA) is the major component of diarrheic shellfish poisoning toxins and a potent inhibitor of protein phosphatase 1 and 2A. However, the underlying regulatory mechanisms involved in OA-induced cell death are not well understood. In the present study, we examined the effects of OA on apoptosis of MG63 cells by characterizing apoptotic morphological changes of the cells and DNA fragmentation. The roles of double-stranded RNA-dependent protein kinase (PKR), nuclear factor-κB (NF-κB) and caspase in OA-mediated apoptosis in MG63 cells were also examined. Results showed that OA induced cytotoxicity and apoptosis in MG63 cells at IC50 of 75 nM. A functional PKR pathway is required to induce apoptosis in response to OA treatment. Blockade of NF-κB by ammonium pyrrolidinedithiocarbamate (PDTC) resulted in down-regulation of apoptosis. The caspase-3 and caspase-8 inhibitors blocked apoptosis in MG63 cells. In conclusion, our results imply that OA can induce MG63 cell apoptosis through the PKR, NF-κB and caspase pathway.

Naturally contaminated shellfish samples: quantification of diarrhetic shellfish poisoning toxins in unhydrolysed and hydrolysed extracts and cytotoxicity assessment

Contamination of shellfish from the Portuguese coast with diarrhetic shellfish poisoning (DSP) toxins is a recurrent event, with most of the commercial bivalves contaminated with high percentages of esters of okadaic acid (OA) and dinophysistoxin-2 (DTX2). This report describes the quantification of DSP toxins in unhydrolysed and hydrolysed extracts of several cockle and mussel samples naturally contaminated and the evaluation of their cytotoxicity profiles in V79 cells. The quantification of the acyl esters in the shellfish samples involved the cleavage of the ester bond through alkaline hydrolysis and the release of the parent toxins OA and DTX2. Unhydrolysed and hydrolysed extracts were then analyzed by liquid chromatography (LC) coupled with mass spectrometry (MS) for the detection and quantification of DSP toxins. The cytotoxicity of the analysed extracts was evaluated using the MTT reduction assay and compared with the cytotoxicity presented by different concentrations of OA standard (1-100 nM). OA exhibited marked cytotoxic effects and decreased cell viability in a dose dependent mode, with an IC₅₀ of 27 nM. The cytotoxicity pattern of unhydrolysed extracts was clearly dependent on the concentration of free toxins. Moreover, the cytotoxicity of the esterified toxins present was revealed after their conversion into free toxins by alkaline hydrolysis. For the hydrolysed extracts of cockles and mussels, the cytotoxicity presented was mainly related to the concentration of OA and DTX2.

Evaluation of genotoxicity in gills and hemolymph of clam Ruditapes decussatus fed with the toxic dinoflagellate Prorocentrum lima

Diarrheic shellfish poisoning (DSP) is a gastrointestinal (GIT) disease that appears a few hours after ingesting okadaic acid (OA)-contaminated mollusks; okadaic acid is present in dinoflagellates of the genera Dinophysis and Prorocentrum. Toxic manifestations occur all year round at a higher or lesser intensity, and as a consequence, extractive production factories need to be closed during these periods which affects the economy of aquaculture industries. Although the concentration of harmful algae is usually found at high levels in clam digestive gland, bivalve mortality was not increased. In this study, the genotoxic effects produced by OA in clam Ruditapes decussatus were determined using the comet assay. In vitro (exposing hemocytes to different concentrations of OA) and in vivo (feeding clams with toxic dinoflagellate Prorocentrum lima) experiments were conducted in order to determine the genotoxic effects of OA on bivalve cells. Hemocytes and gill cells were analyzed by in vivo and in vitro approaches. While the in vitro study showed a rapid effect of OA on hemocytes, data obtained in the in vivo experiment reflected contradictory results dependent upon the concentration of OA and cell type evaluated. An increase in DNA damage was observed at the lower concentration and only in gill tissue. The results obtained may contribute to a better understanding of the mechanisms underlying genotoxic effects induced by OA on bivalves.