Direct and indirect P-glycoprotein transfers in MCF7 breast cancer cells.

The efflux protein P-glycoprotein (P-gp) is over expressed in many cancer cells and has a known capacity to confer multi-drug resistance to cytotoxic therapies. We provide a mathematical model for the direct cell-to-cell transfer of proteins between cells and the indirect transfer between cells and the surrounding liquid. After a mathematical analysis of the model, we construct an adapted numerical scheme and give some numerical simulations. We observe that we obtain a better fit with the experimental data when we take into account the indirect transfer of the protein released in a dish. This quantity, usually neglected by the experimenters, seems to influence the results.

Neuroendocrine disruption in the shore crab Carcinus maenas: Effects of serotonin and fluoxetine on chh- and mih-gene expression, glycaemia and ecdysteroid levels.

Serotonin, a highly conserved neurotransmitter, controls many biological functions in vertebrates, but also in invertebrates. Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, are commonly used in human medication to ease depression by affecting serotonin levels. Their residues and metabolites can be detected in the aquatic environment and its biota. They may also alter serotonin levels in aquatic invertebrates, thereby perturbing physiological functions. To investigate whether such perturbations can indeed be expected, shore crabs (Carcinus maenas) were injected either with serotonin, fluoxetine or a combination of both. Dose-dependent effects of fluoxetine ranging from 250 to 750nM were investigated. Gene expression of crustacean hyperglycemic hormone (chh) as well as moult inhibiting hormone (mih) was assessed by RT-qPCR at 2h and 12h after injection. Glucose and ecdysteroid levels in the haemolymph were monitored in regular intervals until 12h. Serotonin led to a rapid increase of chh and mih expression. On the contrary, fluoxetine only affected chh and mih expression after several hours, but kept expression levels significantly elevated. Correspondingly, serotonin rapidly increased glycaemia, which returned to normal or below normal levels after 12h. Fluoxetine, however, resulted in a persistent low-level increase of glycaemia, notably during the period when negative feedback regulation reduced glycaemia in the serotonin treated animals. Ecdysteroid levels were significantly decreased by serotonin and fluoxetine, with the latter showing less pronounced and less rapid, but longer lasting effects. Impacts of fluoxetine on glycaemia and ecdysteroids were mostly observed at higher doses (500 and 750nM) and affected principally the response dynamics, but not the amplitude of glycaemia and ecdysteroid-levels. These results suggest that psychoactive drugs are able to disrupt neuroendocrine control in decapod crustaceans, as they interfere with the normal regulation of the serotonergic system.

2-DE Mapping of the Blue Mussel Gill Proteome: The Usual Suspects Revisited.

The Blue Mussel (Mytilus edulis, L. 1758) is an ecologically important and commercially relevant bivalve. Because of its ability to bioconcentrate xenobiotics, it is also a widespread sentinel species for environmental pollution, which has been used in ecotoxicological studies for biomarker assessment. Consequently, numerous proteomics studies have been carried out in various research contexts using mussels of the genus Mytilus, which intended to improve our understanding of complex physiological processes related to reproduction, adaptation to physical stressors or shell formation and for biomarker discovery. Differential-display 2-DE proteomics relies on an extensive knowledge of the proteome with as many proteoforms identified as possible. To this end, extensive characterization of proteins was performed in order to increase our knowledge of the Mytilus gill proteome. On average, 700 spots were detected on 2-DE gels by colloidal blue staining, of which 122 different, non-redundant proteins comprising 203 proteoforms could be identified by tandem mass spectrometry. These proteins could be attributed to four major categories: (i) "metabolism", including antioxidant defence and degradation of xenobiotics; (ii) "genetic information processing", comprising transcription and translation as well as folding, sorting, repair and degradation; (iii) "cellular processes", such as cell motility, transport and catabolism; (iv) "environmental information processing", including signal transduction and signalling molecules and interaction. The role of cytoskeleton proteins, energetic metabolism, chaperones/stress proteins, protein trafficking and the proteasome are discussed in the light of the exigencies of the intertidal environment, leading to an enhanced stress response, as well as the structural and physiological particularities of the bivalve gill tissue.

Exploring modulation of action potential firing by artificial graft of fast GABAergic autaptic afferences in hypophyseal neuroendocrine melanotrope cells.

Excitable cells are connected via electrical and chemical synapses to form a complex plastic network that transmit and modify action potential trains. In vivo and in vitro studies suggest that powerful type A GABAergic self-innervations, known as autapses, play a central role in the shaping of spike discharges. Herein, we have investigated the effects of artificial autaptic activity on action potential firing in cultured hypophyseal neuroendocrine melanotrope cells removed from any synaptic input. Type A autaptic conductances were introduced by using a dedicated dynamic-clamp device, based on a digital signal processor. The results indicate that cells grafted with autaptic dynamic-clamp are subjected to a modulation of both evoked firing and artificial GABA(A)-currents. The autaptic feedback reduced the action potentials amplitude, decreasing both the overshoot and the after-hyperpolarization potential (AHP). In return, the reduced voltage changes diminished the autaptic current amplitudes. The overall effect was a decrease of the cell firing rate. The introduction of a variable autaptic delay strongly altered the cell responses. Under certain conditions, the artificial autaptic current formed an additional component of the AHP which was markedly augmented. This action resulted in a stabilization of the action potential train leading to a more regular firing. In conclusion, it appeared that the autaptic feedback was very dependent on functional parameters such as the autaptic distance. Further investigations are in progress to complete our model, taking the autaptic plasticity into account.