Increased coral biomineralization due to enhanced symbiotic activity upon volcanic ash exposure.

Coral reefs, which are among the most productive ecosystems on earth, are in global decline due to rapid climate change. Volcanic activity also results in extreme environmental changes at local to global scales, and may have significant impacts on coral reefs compared to other natural disturbances. During explosive eruptions, large amounts of volcanic ash are generated, significantly disrupting ecosystems close to a volcano, and depositing ash over distal areas (10s - 1000s of km depending on i.a. eruption size and wind direction). Once volcanic ash interacts with seawater, the dissolution of metals leads to a rapid change in the geochemical properties of the seawater column. Here, we report the first known effects of volcanic ash on the physiology and elemental cycling of a symbiotic scleractinian coral under laboratory conditions. Nubbins of the branching coral Stylophora pistillata were reared in aquaria under controlled conditions (insolation, temperature, and pH), while environmental parameters, effective quantum yield, and skeletal growth rate were monitored. Half the aquaria were exposed to volcanic ash every other day for 6 weeks (250 mg L-1 week-1), which induced significant changes in the fluorescence-derived photochemical parameters (ΦPSII, Fv/Fm, NPQ, rETR), directly enhanced the efficiency of symbiont photosynthesis (Pg, Pn), and lead to increased biomineralization rates. Enhancement of symbiont photosynthesis is induced by the supply of essential metals (Fe and Mn), derived from volcanic ash leaching in ambient seawater or within the organism following ingestion. The beneficial role of volcanic ash as an important micronutrient source is supported by the fact that neither photophysiological stress nor signs of lipid peroxidation were detected. Subaerial volcanism affects micronutrient cycling in the coral ecosystem, but the implication for coral ecophysiology on a reef scale remains to be tested. Nevertheless, exposure to volcanic ash can improve coral health and thus influence resilience to external stressors.

Intracellular Fate of Sub-Toxic Concentration of Functionalized Selenium Nanoparticles in Aggressive Prostate Cancer Cells.

Selenium 0 (Se0) is a powerful anti-proliferative agent in cancer research. We investigated the impact of sub-toxic concentrations of Se0 functionalized nanoparticles (SeNPs) on prostate cancer PC-3 cells and determined their intracellular localization and fate. An in-depth characterization of functionalized selenium nanoparticles composition is proposed to certify that no chemical bias relative to synthesis issues might have impacted the study. Selenium is an extremely diluted element in the biological environment and therefore requires high-performance techniques with a very low detection limit and high spatial resolution for intracellular imaging. This was explored with state-of-the-art techniques, but also with cryopreparation to preserve the chemical and structural integrity of the cells for spatially resolved and speciation techniques. Monodisperse solutions of SeNPs capped with bovine serum albumin (BSA) were shown to slow down the migration capacity of aggressive prostate cancer cells compared to polydisperse solutions of SeNPs capped with chitosan. BSA coating could prevent interactions between the reactive surface of the nanoparticles and the plasma membrane, mitigating the generation of reactive oxygen species. The intracellular localization showed interaction with mitochondria and also a localization in the lysosome-related organelle. The SeNPs-BSA localization in mitochondria constitute a possible explanation for our result showing a very significant dampening of the PC-3 cell proliferation capabilities. The purpose of the use of sublethal compound concentrations was to limit adverse effects resulting from high cell death to best evaluate some cellular changes and the fate of these SeNPs on PC-3. Our findings provide new insight to further study the various mechanisms of cytotoxicity of SeNPs.

Metallome deregulation and health-related impacts due to long-term exposure to recent volcanic ash deposits: New chemical and isotopic insights.

Volcanic ash exposure can lead to significant health risks. Damage to the respiratory and pulmonary systems are the most evident toxic side effects although the causes of these symptoms remain unclear. Conversely, the effects on other organs remain largely under-explored, limiting our understanding of the long-term volcanic ash-related risk at the whole-body scale. The metallome i.e. metal concentrations and isotopic compositions within the body, is suspected to be affected by volcanic ash exposure, having thus the potential for capturing some specificities of ash toxicity. However, the means by and extent to which the metallome is affected at the entire body scale and how the consequent chemical and isotopic deregulations correlate with pathophysiological dysfunctions are currently poorly understood. Here, we adopt a transdisciplinary approach combining high precision chemical analyses (major and trace element concentrations) and CuZn isotope measurements in seven organs and two biological fluids of isogenic mice (C57BL/6) exposed to eruption products from La Soufrière de Guadeloupe (Eastern Carribean), in tandem with biological parameters including physiological and morphological data. Based on principal component analysis, we show that after one month of exposure to volcanic ash deposits, the mice metallome; originally organ-specific and isotopically-typified, is highly disrupted as shown for example by heavy metal accumulation in testis (e.g., Fe, Zn) and Cu, Zn isotopic divergence in liver, intestine and blood. These metallomic variations are correlated with early testicular defects and might reflect the warning signs of premature (entero)hepatic impairments that may seriously affect fertility and favor the emergence of liver diseases after prolonged exposure. Monitoring the temporal evolution of the Cu and Zn isotope compositions seems to be a promising technique to identify the main biological processes and vital functions that are vulnerable to environmental volcanogenic pollutants although this will require further validation on human subjects.

The mouse metallomic landscape of aging and metabolism.

Organic elements make up 99% of an organism but without the remaining inorganic bioessential elements, termed the metallome, no life could be possible. The metallome is involved in all aspects of life, including charge balance and electrolytic activity, structure and conformation, signaling, acid-base buffering, electron and chemical group transfer, redox catalysis energy storage and biomineralization. Here, we report the evolution with age of the metallome and copper and zinc isotope compositions in five mouse organs. The aging metallome shows a conserved and reproducible fingerprint. By analyzing the metallome in tandem with the phenome, metabolome and proteome, we show networks of interactions that are organ-specific, age-dependent, isotopically-typified and that are associated with a wealth of clinical and molecular traits. We report that the copper isotope composition in liver is age-dependent, extending the existence of aging isotopic clocks beyond bulk organic elements. Furthermore, iron concentration and copper isotope composition relate to predictors of metabolic health, such as body fat percentage and maximum running capacity at the physiological level, and adipogenesis and OXPHOS at the biochemical level. Our results shed light on the metallome as an overlooked omic layer and open perspectives for potentially modulating cellular processes using careful and selective metallome manipulation.

Inter-comparison of stable iron, copper and zinc isotopic compositions in six reference materials of biological origin.

There is a lack of certified reference materials with an organic matrix for which metal isotope ratios have been certified. Here, we have determined the iron, copper and zinc stable isotopic compositions for six reference materials of biological origin with diverse matrices, i.e. BCR-380R (whole milk), BCR-383 (beans), ERM-CE464 (tuna fish), SRM-1577c (bovine liver), DORM-4 (fish protein) and TORT-3 (lobster hepatopancreas) in three different labs. The concentrations for six major and sixteen trace elements, spanning almost four orders of magnitude, were also measured and the results obtained show an excellent agreement with certified values, demonstrating that the dissolution step was quantitative for all the standards. By taking literature data into account, 39 possible pair-wise comparisons of mean iron, copper and zinc isotopic values (δ values) could be made. Results of Tukey multiple comparisons of means yielded 11 significantly different pairs. Most of these differences are of the same order of magnitude as the estimated mean expanded uncertainties (U, k = 2) (±0.10‰, ±0.05‰, and ±0.05‰ for the δ56Fe, δ65Cu and δ66Zn values, respectively). The present inter-comparison study finally proposes nineteen new preferred values for the Cu, Zn and Fe isotopic compositions of six reference materials of biological origin.

Isotopic Evidence for Disrupted Copper Metabolism in Amyotrophic Lateral Sclerosis.

Redox-active metals are thought to be implicated in neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). To address this point, we measured the concentrations of 12 elements and, for the first time, the stable isotope compositions of copper (redox-active) and zinc (redox-inactive) in human cerebrospinal fluids of 31 patients with ALS, 11 age-matched controls (CTRL), and 14 patients with Alzheimer disease. We first show that metal concentrations weakly discriminate patients with ALS from the two other groups. We then report that zinc isotopic compositions are similar in the three groups, but that patients with ALS have significantly 65copper-enriched isotopic compositions relative to CTRL and patients with AD. This result unambiguously demonstrates that copper is implicated in ALS. We suggest that this copper isotopic signature may result from abnormal protein aggregation in the brain parenchyma, and propose that isotopic analysis is a potential tool that may help unraveling the molecular mechanisms at work in ALS.

Metallome evolution in ageing C. elegans and a copper stable isotope perspective.

Ageing is accompanied by important chemical deregulations resulting in bodily metal imbalances. The way and extent to which these deregulations are associated with ageing processes are however poorly understood and their use as potential biomarkers of ageing has not been investigated. In this study, we report whole-body elementary concentrations and copper and zinc isotopic compositions of Caenorhabditis elegans in ageing wild type (i.e.'normal'-lived) and mutant (i.e. short and long-lived) strains. We show that the strains are characterized by different levels of mutation-related variations such as in phosphorus and magnesium as well as in zinc isotopic composition. During ageing, strains are affected by elemental age-related variations, such as an increase in calcium and iron concentrations and a decrease in the copper isotopic composition and concentration for long-lived mutants. The deregulated metabolism of copper seems to be connected to ageing probably in association with the production of reactive oxygen species. We emphasize that the copper stable isotope composition could serve as a biomarker of normal or accelerated ageing in the future.

Coral bleaching is linked to the capacity of the animal host to supply essential metals to the symbionts.

Massive coral bleaching events result in extensive coral loss throughout the world. These events are mainly caused by seawater warming, but are exacerbated by the subsequent decrease in nutrient availability in surface waters. It has therefore been shown that nitrogen, phosphorus or iron limitation contribute to the underlying conditions by which thermal stress induces coral bleaching. Generally, information on the trophic ecology of trace elements (micronutrients) in corals, and on how they modulate the coral response to thermal stress is lacking. Here, we demonstrate for the first time that heterotrophic feeding (i.e. the capture of zooplankton prey by the coral host) and thermal stress induce significant changes in micro element concentrations and isotopic signatures of the scleractinian coral Stylophora pistillata. The results obtained first reveal that coral symbionts are the major sink for the heterotrophically acquired micronutrients and accumulate manganese, magnesium and iron from the food. These metals are involved in photosynthesis and antioxidant protection. In addition, we show that fed corals can maintain high micronutrient concentrations in the host tissue during thermal stress and do not bleach, whereas unfed corals experience a significant decrease in copper, zinc, boron, calcium and magnesium in the host tissue and bleach. In addition, the significant increase in δ65 Cu and δ66 Zn signature of symbionts and host tissue at high temperature suggests that these isotopic compositions are good proxy for stress in corals. Overall, present findings highlight a new way in which coral heterotrophy and micronutrient availability contribute to coral resistance to global warming and bleaching.