The Impact of Long-Term Exposure to Space Environment on Adult Mammalian Organisms: A Study on Mouse Thyroid and Testis

Hormonal changes in humans during spaceflight have been demonstrated but the underlying mechanisms are still unknown. To clarify this point thyroid and testis/epididymis, both regulated by anterior pituitary gland, have been analyzed on long-term space-exposed male C57BL/10 mice, either wild type or pleiotrophin transgenic, overexpressing osteoblast stimulating factor-1. Glands were submitted to morphological and functional analysis

Phosphatidylcholine/sphingomyelin metabolism crosstalk inside the nucleus

International audienceIt is known that the phospholipids represent a "minor component" of chromatin. Recently it has been highlighted that these lipids are metabolised directly inside the nucleus thanks to the presence of the enzymes related to their metabolism such as neutral sphingomyelinase, sphingomyelin-synthase, reverse sphingomyelin-synthase and phosphatidylcholine-specific phospholipase C. The chromatin enzymatic activities change during cell proliferation, differentiation and/or apoptosis independently of the enzyme activities present in the nuclear membrane, microsomes or cell membranes. The present research was aimed to investigate the crosstalk of the lipid metabolisms in nuclear membrane and chromatin isolated from rat liver in vitro and in vivo. The effect of neutral-sphingomyelinase activity on phosphatidylcholine-specific phospholipase C and sphingomyelin-synthase, which enrich the intranuclear diacylglycerol pool and the effect of phosphatidylcholine-specific phospholipase C activity on neutral sphingomyelinase and reverse sphingomyelin-synthase, which enrich the intranuclear ceramide pool, were investigated. The results show that in chromatin exists a phosphatidylcholine/sphingomyelin metabolism crosstalk which regulates the intranuclear ceramide/diacylglycerol pool. Its specificity was demonstrated by D609 inhibitor effect. The chromatin lipid metabolism is activated in vivo during cell proliferation indicating that it could play a role on cell function. The possible mechanism of the crosstalk was discussed considering the recent literature in the field

Critical Role for the Protons in FRTL-5 Thyroid Cells: Nuclear Sphingomyelinase Induced-Damage

Proliferating thyroid cells are more sensitive to UV-C radiations than quiescent cells. The effect is mediated by nuclear phosphatidylcholine and sphingomyelin metabolism. It was demonstrated that proton beams arrest cell growth and stimulate apoptosis but until now there have been no indications in the literature about their possible mechanism of action. Here we studied the effect of protons on FRTL-5 cells in culture. We showed that proton beams stimulate slightly nuclear neutral sphingomyelinase activity and inhibit nuclear sphingomyelin-synthase activity in quiescent cells whereas stimulate strongly nuclear neutral sphingomyelinase activity and do not change nuclear sphingomyelin-synthase activity in proliferating cells. The study of neutral sphingomyelinase/sphingomyelin-synthase ratio, a marker of functional state of the cells, indicated that proton beams induce FRTL-5 cells in a proapoptotic state if the cells are quiescent and in an initial apoptotic state if the cells are proliferating. The changes of cell life are accompanied by a decrease of nuclear sphingomyelin and increase of bax protein

A firmer understanding of the effect of hypergravity on thyroid tissue: cholesterol and thyrotropin receptor.

Maintaining a good health requires the maintenance of a body homeostasis which largely depends on correct functioning of thyroid gland. The cells of the thyroid tissue are strongly sensitive to hypogravity, as already proven in mice after returning to the earth from long-term space missions. Here we studied whether hypergravity may be used to counteract the physiological deconditioning of long-duration spaceflight. We investigated the influence of hypergravity on key lipids and proteins involved in thyroid tissue function. We quantified cholesterol (CHO) and different species of sphingomyelin (SM) and ceramide, analysed thyrotropin (TSH) related molecules such as thyrotropin-receptor (TSHR), cAMP, Caveolin-1 and molecule signalling such as Signal transducer and activator of transcription-3 (STAT3). The hypergravity treatment resulted in the upregulation of the TSHR and Caveolin-1 and downregulation of STAT3 without changes of cAMP. TSHR lost its specific localization and spread throughout the cell membrane; TSH treatment facilitated the shedding of α subunit of TSHR and its releasing into the extracellular space. No specific variations were observed for each species of SM and ceramide. Importantly, the level of CHO was strongly reduced. In conclusion, hypergravity conditions induce change in CHO and TSHR of thyroid gland. The possibility that lipid rafts are strongly perturbed by hypergravity-induced CHO depletion by influencing TSH-TSHR interaction was discussed

Gentamicin Arrests Cancer Cell Growth: The Intriguing Involvement of Nuclear Sphingomyelin Metabolism

The use of gentamicin for the treatment of bacterial infection has always been an interesting and highly speculated issue for the scientific community. Conversely, its effect on cancer cells has been very little investigated. We studied the effect of high doses of gentamicin on non-Hodgkin’s T-cell human lymphoblastic lymphoma (SUP-T1). We showed that gentamicin delayed cell growth and induced cell death in lymphoma cells with a rather mild effect on lymphocytes. In SUP-T1 cells, GAPDH, B2M, CDKN1A and CDKN1B were down-expressed in comparison with lymphocytes. Gentamicin treatment in SUP-T1 cells restored the expression of GAPDH, B2M and CDKN1A to values similar to those of lymphocytes and caused overexpression of CDKN1B. The drug acted via sphingomyelin metabolism; in whole cells, sphingomyelinase activity was stimulated, whereas in purified nuclei, sphingomyelinase activity was inhibited and that of sphingomyelin-synthase was stimulated, with a consequent high level of nuclear sphingomyelin content. We suggest that the increase of nuclear sphingomyelin might enrich the nucleus of lipid microdomains that act as a platform for active chromatin and, thus, might be responsible for gene expression. It is possible that in lymphoblastic lymphoma, high doses of gentamicin induce a beneficial therapeutic outcome

Physicochemical stability of cabazitaxel and docetaxel solutions

Objectives: It is recommended that the Jevtana (current parenteral cabazitaxel formulation) final infusion solution should be used within 8 h when stored at ambient temperature or within 24 h if refrigerated. We determined the physical and chemical stability of cabazitaxel and docetaxel over prolonged periods after dilution in infusion solutions from their Jevtana and Hospira, respectively, parenteral formulations. Methods: The stability of these antineoplastic drugs was determined after (i) reconstitution of the injection concentrate and (ii) further dilution in 0.9% NaCl solution contained in PVC-free infusion bags. Chemical stability was determined using both high-performance liquid chromatography (HPLC) with ultraviolet detection and high-resolution (HR)-HPLC–mass spectrometry (MS) techniques. Physical stability was determined by visual inspection. Results: The stability tests revealed that reconstituted cabazitaxel solutions (premix solutions) stored at 4°C were physicochemically stable (at a level of ≥95% cabazitaxel) for a minimum of 4 weeks. Diluted infusion solutions in PVC-free infusion bags (docetaxel concentration 0.30 mg/mL; cabazitaxel concentration 0.15 mg/mL) were physicochemically stable (at a level of ≥95% cabazitaxel or docetaxel) for a minimum of 4 weeks, independently of storage temperature (4°C or 25°C). Diluted cabazitaxel infusion solutions appeared stable (at a level of ≥95% cabazitaxel) for a minimum of 4 weeks when stored in the presence of saturated oxygen at 25°C. Conclusions: Cabazitaxel and docetaxel are characterised by high stability in customary infusion fluids for at least 4 weeks