Anticancer properties of chitosan on human melanoma are cell line dependent

Purpose: Chitosan, a natural macromolecule, is widely used in medical and pharmaceutical fields because of its distinctive properties such as bactericide, fungicide and above all its antitumor effects. Although its antitumor activity against different types of cancer had been previously described, its mechanism of action was not fully understood. Materials and methods: Coating of chitosan has been used in cell cultures with A375, SKMEL28, and RPMI7951 cell lines. Adherence, proliferation and apoptosis were investigated. Results: Our results revealed that whereas chitosan decreased adhesion of primary melanoma A375 cell line and decreased proliferation of primary melanoma SKMEL28 cell line, it had potent pro-apoptotic effects against RPMI7951, a metastatic melanoma cell line. In these latter cells, inhibition of specific caspases confirmed that apoptosis was effected through the mitochondrial pathway and Western blot analyses showed that chitosan induced an up regulation of pro-apoptotic molecules such as Bax and a down regulation of anti-apoptotic proteins like Bcl-2 and Bcl-XL. More interestingly, chitosan exposure induced an exposition of a greater number of CD95 receptor at RPMI7951 surface, making them more susceptible to FasL-induced apoptosis. Conclusion: Our results indicate that chitosan could be a promising agent for further evaluations in antitumor treatments targeting melanoma

Impact of ocean acidification on the sea urchin Echinometra Mathaei and its roles as grazer and bioeroder in coral reefs

Coral reefs are particularly vulnerable to ocean acidification resulting from the increase of anthropogenic carbon dioxide in the atmosphere and its dissolution in seawater. The existence of coral reefs depends on the calcification rate of hermatypic corals that must remain higher than erosion. Sea urchins are, on the one hand, key species for the resilience of coral reefs through their grazing activities of invading macroalgae. On the other hand, they are also major bioeroders of reef substrate. One objective of this study was to evaluate the effect of ocean acidification on the growth and the physiology of sea urchins. The impact of acidification on the balance between coral accretion and bioerosion by sea urchins has also been investigated. The study was conducted in two identical artificial reef mesocosms. Experimental tanks were maintained respectively at mean pHtotal 7.7 and 8.05 (with field-like night and day variations). The major physico-chemical parameters were identical, only pCO2 and pH differed. The growth, the carbonate chemistry of the coelomic fluid and the respiration rate of sea urchins were monitored throughout the experiment, as well as the growth of corals. Biomechanical analyses were performed on sea urchins and coral skeletons. Bioerosion by sea urchins was estimated. Preliminary results indicate that Echinometra mathaei can maintain growth and metabolism, at least at short term and under this moderate acidosis. On the other hand, coral growth was negatively affected. These opposite effects could have an impact on the subtle and dynamic balance between bioerosion by sea urchins and bioaccretion of corals and on the long term survival of coral reefs

Ecophysiological changes of a simplified coral reef community facing ocean acidification: a one year study in artificial reef mesocosms

A simplified reef community has been able to face increased pCO2 during one year: calcification of hermatypic scleractinians were unchanged, or even enhanced for the Pocilloporidae family. The main bioeroders from this reef, Echinometra mathaei, was also able to deal with pCO2 : unchanged growth, respiration or coelomic fluid pH. Nevertheless bio erosion increased: this could shift the balance between a calcifying and an eroding reef

Adult echinoderms from fluctuating environments: Scope for adaptation or acclimatization to ocean acidification?

Numerous echinoderm species are structuring the community in which they live, principally through trophic interactions. Therefore, any impact on these species has a strong risk to affect the whole community. Due to their low metabolism and ion regulation ability, adult echinoderms have been suggested to be particularly sensitive to ocean acidification. However, numerous echinoderms live in habitats characterized by low of fluctuating pH like upwelling zones, intertidal pools or the deep-sea, suggesting that members of this phylum do have adaptation or acclimatization abilities. Therefore, we investigated the response of different echinoderm species living in such fluctuating environments to acidification. The results indicate that different strategies are used in front of acidification. Sea urchins (except cidaroids) have a higher buffer capacity in their inner extracellular fluids than that of seawater and increase this capacity at low pH. Their respiratory metabolism is either increased or unaffected. On the contrary, starfish have a buffer capacity in their inner fluids similar to that of seawater and decrease their metabolism at low pH. In both taxa, this results in reduced differences between the pH of seawater and that of the inner extracellular fluids with decreasing pH. At short term (2 to 4 weeks), neither growth nor protein levels (expressed as RNA/DNA ratios) were affected by reduced pH. These results indicate that adult echinoderms from habitats with fluctuating conditions do have the ability to acclimatize to low pH at least at short term