RESUMEN
Exposure to environmental changes often results in the production of reactive oxygen species (ROS), which, if uncontrolled, leads to loss of cellular homeostasis and oxidative distress. However, at physiological levels these same ROS are known to be key players in cellular signaling and the regulation of key biological activities (oxidative eustress). While ROS are known to mediate salinity tolerance in plants, little is known for the animal kingdom. In this study, we use the Mediterranean crab Carcinus aestuarii, highly tolerant to salinity changes in its environment, as a model to test the healthy or pathological role of ROS due to exposure to diluted seawater (dSW). Crabs were injected either with an antioxidant [N-acetylcysteine (NAC), 150 mg·kg-1] or phosphate buffered saline (PBS). One hour after the first injection, animals were either maintained in seawater (SW) or transferred to dSW and injections were carried out at 12-h intervals. After ≈48 h of salinity change, all animals were sacrificed and gills dissected for analysis. NAC injections successfully inhibited ROS formation occurring due to dSW transfer. However, this induced 55% crab mortality, as well as an inhibition of the enhanced catalase defenses and mitochondrial biogenesis that occur with decreased salinity. Crab osmoregulatory capacity under dSW condition was not affected by NAC, although it induced in anterior (non-osmoregulatory) gills a 146-fold increase in Na+/K+/2Cl- expression levels, reaching values typically observed in osmoregulatory tissues. We discuss how ROS influences the physiology of anterior and posterior gills, which have two different physiological functions and strategies during hyper-osmoregulation in dSW.
Asunto(s)
Aclimatación , Braquiuros , Especies Reactivas de Oxígeno , Salinidad , Animales , Especies Reactivas de Oxígeno/metabolismo , Braquiuros/fisiología , Braquiuros/metabolismo , Braquiuros/efectos de los fármacos , Presión Osmótica , Acetilcisteína/farmacología , Agua de Mar , Antioxidantes/metabolismo , Estrés Oxidativo/efectos de los fármacos , Branquias/metabolismo , Branquias/efectos de los fármacos , OsmorregulaciónRESUMEN
Ciliated epithelia perform essential functions in animals across evolution, ranging from locomotion of marine organisms to mucociliary clearance of airways in mammals. These epithelia are composed of multiciliated cells (MCCs) harboring myriads of motile cilia, which rest on modified centrioles called basal bodies (BBs), and beat coordinately to generate directed fluid flows. Thus, BB biogenesis and organization is central to MCC function. In basal eukaryotes, the coiled-coil domain proteins Lrrcc1 and Ccdc61 have previously been shown to be required for proper BB construction and function. Here, we used the Xenopus embryonic ciliated epidermis to characterize Lrrcc1 and Ccdc61 in vertebrate MCCs. We found that they both encode BB components, localized proximally at the junction with striated rootlets. Knocking down either gene caused defects in BB docking, spacing and polarization. Moreover, their depletion impaired the apical cytoskeleton and altered ciliary beating. Consequently, cilia-powered fluid flow was greatly reduced in morphant tadpoles, which displayed enhanced mortality when exposed to pathogenic bacteria. This work illustrates how integration across organizational scales make elementary BB components essential for the emergence of the physiological function of ciliated epithelia.
Asunto(s)
Cuerpos Basales , Cilios , Animales , Cuerpos Basales/metabolismo , Diferenciación Celular/fisiología , Centriolos , Cilios/metabolismo , Xenopus laevisRESUMEN
The contamination of coastal regions with different toxicants, including heavy metal ions such as copper and cadmium jeopardize health and survival of organisms exposed to this habitat. To study the effects of high copper and cadmium concentrations in these marine environments, we used the flatworm Macrostomum lignano as a model. This platyhelminth lives in shallow coastal water and is exposed to high concentrations of all toxicants that accumulate in these sea floors. We could show that both, cadmium and copper show toxicity at higher concentrations, with copper being more toxic than cadmium. At concentrations below acute toxicity, a reduced long-term survival was observed for both metal ions. The effects of sublethal doses comprise reduced physical activities, an increase in ROS levels within the worms, and alterations of the mitochondrial biology. Moreover, cell death events were substantially increased in response to sublethal concentrations of both metal ions and stem cell activity was reduced following exposure to higher cadmium concentrations. Finally, the expression of several genes involved in xenobiotic metabolism was substantially altered by this intervention. Taken together, M. lignano has been identified as a suitable model for marine toxicological studies as it allows to quantify several relevant life-history traits as well as of physiological and behavioral read-outs.
Asunto(s)
Cadmio/toxicidad , Cobre/toxicidad , Estrés Oxidativo/efectos de los fármacos , Platelmintos/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Animales , Relación Dosis-Respuesta a Droga , Platelmintos/genética , Platelmintos/metabolismo , Pruebas de ToxicidadRESUMEN
In the context of global change, there is an urgent need for researchers in conservation physiology to understand the physiological mechanisms leading to the acquisition of stress acclimation phenotypes. Intertidal organisms continuously cope with drastic changes in their environmental conditions, making them outstanding models for the study of physiological acclimation. As the implementation of such processes usually comes at a high bioenergetic cost, a mitochondrial/oxidative stress approach emerges as the most relevant approach when seeking to analyze whole-animal responses. Here we use the intertidal flatworm Macrostomum lignano to analyze the bioenergetics of salinity acclimation and its consequences in terms of reactive oxygen/nitrogen species formation and physiological response to counteract redox imbalance. Measures of water fluxes and body volume suggest that M. lignano is a hyper-/iso-regulator. Higher salinities were revealed to be the most energetically expensive conditions, with an increase in mitochondrial density accompanied by increased respiration rates. Such modifications came at the price of enhanced superoxide anion production, likely associated with a high caspase 3 upregulation. These animals nevertheless managed to live at high levels of environmental salinity through the upregulation of several mitochondrial antioxidant enzymes such as superoxide dismutase. Contrarily, animals at low salinities decreased their respiration rates, reduced their activity and increased nitric oxide formation, suggesting a certain degree of metabolic arrest. A contradictory increase in dichlorofluorescein fluorescence and an upregulation of gluthathione-S-transferase pi 1 (GSTP1) expression were observed in these individuals. If animals at low salinity are indeed facing metabolic depression, the return to seawater may result in an oxidative burst. We hypothesize that this increase in GSTP1 could be a "preparation for oxidative stress", i.e. a mechanism to counteract the production of free radicals upon returning to seawater. The results of the present study shed new light on how tolerant organisms carry out subcellular adaptations to withstand environmental change.