Time-dependent inactivation of glucose-6-phosphate dehydrogenase from yeast by aluminum

Are we neglecting earth while conquering space? Effects of aluminized solid rocket fuel combustion on the physiology of a tropical freshwater invertebrate

Space launchers often use aluminized-solid fuel ("propergol") as propellant and its combustion releases tons of Al₂O₃ and HCl that sink in terrestrial and aquatic environments, polluting and decreasing water pH. We studied the impact of these events on the biochemical/physiological performance of the freshwater shrimp Macrobrachium jelskii, with wild specimens collected from a non-impacted site in French Guiana. In the laboratory, shrimps were exposed for one week to: i) undisturbed conditions; ii) Al₂O₃ exposure (0.5 mg L^-1) at normal pH (6.6); iii) decreased pH (4.5) (mimicking HCl release in the environment) with no Al₂O₃; or iv) Al₂O₃ 0.5 mg L^-1 and pH 4.5, representing the average conditions found in the water bodies around the Ariane 5 launch pad. Results showed that shrimps bioaccumulated aluminium (Al) regardless of water pH. The combined effect of Al₂O₃ and low pH caused the most impact: acetylcholinesterase and carboxylesterase activities decreased, indicating neurotoxicity and reduced detoxification capacity, respectively. Animal respiration was enhanced with Al₂O₃ and pH variations alone, but the synergic interaction of both stressors caused respiration to decrease, suggesting metabolic depression. Oxidative damage followed a similar pattern to respiration rates across conditions, suggesting free radical-mediation in Al toxicity. Antioxidant activities varied among enzymes, with glutathione reductase being the most impacted by Al₂O₃ exposure. This study shows the importance of addressing space ports' impact on the environment, setting the bases for selecting the most appropriate biomarkers for future monitoring programs using a widespread and sensitive crustacean in the context of an increasing space-oriented activity across the world.

Ions released from a S-PRG filler induces oxidative stress in Candida albicans inhibiting its growth and pathogenicity

Candida albicans causes opportunistic fungal infections usually hidden among more dominant bacteria and does not exhibit high pathogenicity in vivo. Among the elderly, due to reduced host resistance to pathogens attributable to immunoscenesence, oral candidiasis is more likely to develop often leading to systemic candidiasis. Surface pre-reacted glass ionomer filler (S-PRG filler) is an ion-releasing functional bioactive glass that can release and recharge six ions which in turn strengthens tooth structure, inhibits demineralization arising from dental caries, and suppresses dental plaque accumulation. However, its effects on C. albicans have never been elucidated. Here, we evaluated the effects of ion released from S-PRG filler on C. albicans. Results show that extraction liquids containing released ions (ELIS) decreased the amount of hydrogen peroxide and catalase activity in C. albicans. Moreover, ELIS presence was found to affect C. albicans: (1) suppression of fungal growth and biofilm formation, (2) prevent adherence to denture base resin, (3) inhibit dimorphism conversion, and (4) hinder the capability to produce secreted aspartyl proteinase. Taken together, our findings suggest that ELIS induces oxidative stress in C. albicans and suppresses its growth and pathogenicity. In this regard, we propose that ELIS has the potential to be clinically used to help prevent the onset and inhibition of oral candidiasis among the elderly population.

Microbial interactions with aluminium

Although aluminium is the most abundant metal in the Earth's crust, it lacks biological functions and shows a low bioavailability. Acid rain, however, solubilizes aluminium to toxic levels. Most research on the biological effects of aluminium has been centred on the analysis of aluminium-tolerant plants as well as its possible relationship with neurological disorders in humans. Also, several studies have been reported concerning aluminium effects on microorganisms, with more interest directed to cyanobacteria, soil bacteria and mycorrhizal fungi. Competition with iron and magnesium, and binding to DNA, membranes or cell walls are considered the main toxic effects of aluminium in microbes.

Protection of a rat tracheal epithelial cell line from paraquat toxicity by inhibition of glucose-6-phosphate dehydrogenase

Transformed rat tracheal epithelial cells (U2) were found to be 3.6-fold more sensitive than lung fibroblasts (RLF) to paraquat. Although the toxic effects of paraquat are associated with the generation of very active superoxides, U2 cells contained higher levels of superoxide dismutase and catalase than RLF cells. On the other hand, the specific activities of both NADPH-cytochrome c reductase and glucose-6-phosphate dehydrogenase (G6DP) were 3- to 4-fold higher in U2 cells than in RLF cells. Treatment with dehydroepiandrosterone (DHEA) and epiandrosterone (EPI), G6PD inhibitors, significantly decreased the intracellular NADPH and protected U2 cells from paraquat toxicity. Since DHEA and EPI treatment did not affect the uptake of paraquat, our results suggest that paraquat sensitivity may depend on the redox cycling-associated activities of paraquat.