Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Radiofrequency radiations constitute a new form of environmental pollution. Among them, millimeter waves (MMW) will be widely used in the near future for high speed communication systems. This study aimed therefore to evaluate the biocompatibility of MMW at 60 GHz. For this purpose, we used a whole gene expression approach to assess the effect of acute 60 GHz exposure on primary cultures of human keratinocytes. Controls were performed to dissociate the electromagnetic from the thermal effect of MMW. Microarray data were validated by RT-PCR, in order to ensure the reproducibility of the results. MMW exposure at 20 mW/cm2, corresponding to the maximum incident power density authorized for public use (local exposure averaged over 1 cm2), led to an increase of temperature and to a strong modification of keratinocyte gene expression (665 genes differentially expressed). Nevertheless, when temperature is artificially maintained constant, no modification in gene expression was observed after MMW exposure. However, a heat shock control did not mimic exactly the MMW effect, suggesting a slight but specific electromagnetic effect under hyperthermia conditions (34 genes differentially expressed). By RT-PCR, we analyzed the time course of the transcriptomic response and 7 genes have been validated as differentially expressed: ADAMTS6, NOG, IL7R, FADD, JUNB, SNAI2 and HIST1H1A. Our data evidenced a specific electromagnetic effect of MMW, which is associated to the cellular response to hyperthermia. This study raises the question of co-exposures associating radiofrequencies and other environmental sources of cellular stress.
ISSN: 1932-6203

hal-01118066
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118066
PUBMED : 25302706
DOI : 10.1371/journal.pone.0109435
PUBMEDCENTRAL : PMC4193780

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Cnidarian-dinoflagellate symbiosis mainly relies on nutrient recycling, thus providing both partners with a competitive advantage in nutrient-poor waters. Essential processes related to lipid metabolism can be influenced by various factors, including hyperthermal stress. This can affect the lipid content and distribution in both partners, while contributing to symbiosis disruption and bleaching. In order to gain further insight into the role and distribution of lipids in the cnidarian metabolism, we investigated the lipid composition of the sea anemone Anemonia viridis and its photosynthetic dinoflagellate endosymbionts (Symbiodinium). We compared the lipid content and fatty acid profiles of the host cellular layers, non-symbiotic epidermal and symbiont-containing gastrodermal cells, and those of Symbiodinium, in a mass spectrometry-based assessment. Lipids were more concentrated in Symbiodinium cells, and the lipid class distribution was dominated by polar lipids in all tissues. The fatty acid distribution between host cell layers and Symbiodinium cells suggested potential lipid transfers between the partners. The lipid composition and distribution was modified during short-term hyperthermal stress, mainly in Symbiodinium cells and gastrodermis. Exposure to elevated temperature rapidly caused a decrease in polar lipid C18 unsaturated fatty acids and a strong and rapid decrease in the abundance of polar lipid fatty acids relative to sterols. These lipid indicators could therefore be used as sensitive biomarkers to assess the physiology of symbiotic cnidarians, especially the effect of thermal stress at the onset of cnidarian bleaching. Overall, the findings of this study provide some insight on key lipids that may regulate maintenance of the symbiotic interaction.
ISSN: 1095-6433

hal-01546160
https://hal.archives-ouvertes.fr/hal-01546160
DOI : 10.1016/j.cbpa.2015.10.017

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Cnidarian-dinoflagellate symbiosis disruption and subsequent bleaching are major concerns, especially regarding their ecological consequences on coral reefs and temperate coralligenous communities. Cnidarian bleaching is caused by a variety of environmental stressors, such as elevated seawater temperature associated with global climate change, and by pollutants, such as herbicides and metals. Several cellular events have been described to explain symbiosis dysfunction and bleaching. Excess or damaged Symbiodinium symbionts are removed through a variety of mechanisms, including exocytosis, apoptosis, necrosis and autophagy. However, few studies have compared in the same species the relative involvement of these mechanisms, according to the stress inducing the bleaching. In this study, we used two different treatments —temperature and menthol— to induce bleaching in the sea anemone Anemonia viridis. By monitoring the ultrastructural tissue modifications, in control specimens we observed a basal rate of in situ symbiont digestion —or symbiophagy— induced by starvation. Symbiophagy was strongly induced in menthol-treated specimens and was the main cellular process of bleaching, whereas apoptosis and necrosis predominated in hyperthermal-induced bleaching. These results suggested a host effect through autophagy in menthol-treated specimens. These observations also suggested that symbiont removal may result from reengagement of the phagosomal maturation process in the host. These overall data demonstrate that several Symbiodinium cell removal mechanisms coexist and that stressors can activate one or more of these pathways, depending on the stress type, intensity or duration.
ISSN: 0334-5114

hal-01546908
http://hal.upmc.fr/hal-01546908
DOI : 10.1007/s13199-016-0406-y