G. Fuhrmann

Induction of apoptosis by thymoquinone in lymphoblastic leukemia Jurkat cells is mediated by a p73-dependent pathway which targets the epigenetic integrator UHRF1

The salvage anti-tumoral pathway which implicates the p53-related p73 gene is not yet fully characterized. We therefore attempted to identify the up- and down-stream events involved in the activation of the p73-dependent pro-apoptotic pathway, by focusing on the anti-apoptotic and epigenetic integrator UHRF1 which is essential for cell cycle progression. For this purpose, we analyzed the effects of a known anti-neoplastic drug, thymoquinone (TQ), on the p53-deficient acute lymphoblastic leukemia (ALL) Jurkat cell line. Our results showed that TQ inhibits the proliferation of Jurkat cells and induces G1 cell cycle arrest in a dose-dependent manner. Moreover, TQ treatment triggers programmed cell death, production of reactive oxygen species (ROS) and alteration of the mitochondrial membrane potential (DeltaPsim). TQ-induced apoptosis, confirmed by the presence of hypodiploid G0/G1 cells, is associated with a rapid and sharp re-expression of p73 and dose-dependent changes of the levels of caspase-3 cleaved subunits. These modifications are accompanied by a dramatic down-regulation of UHRF1 and two of its main partners, namely DNMT1 and HDAC1, which are all involved in the epigenetic code regulation. Knockdown of p73 expression restores UHRF1 expression, reactivates cell cycle progression and inhibits TQ-induced apoptosis. Altogether our results showed that TQ mediates its growth inhibitory effects on ALL p53-mutated cells via the activation of a p73-dependent mitochondrial and cell cycle checkpoint signaling pathway which subsequently targets UHRF1.

Somatostatin levels in the central nervous system of the Snell dwarf mouse; is somatostatin excess the primary molecular defect in the dw/dw dwarfism?

The Snell dwarf mouse (dw/dw) shows significantly decreased somatostatin levels in the hypothalamus whereas more or less increased somatostatin concentrations are observed in any central extrahypothalamic sites studied. These opposite results in hypothalamus and extrahypothalamic areas may be linked to the apparently distinct neurohormonal and neuromodulatory functions of somatostatin in the brain. They also provide arguments for the assumption of a primary somatostatin excess which could be related to the dwarf mutation. In hypothalamus, the severe defect in growth hormone of the dwarf mutant may rapidly lead, by failure of a pituitary retro-control, to a reduction in the presumed initially elevated somatostatin levels. In central extrahypothalamic sites, known to escape to GH retro-action, higher somatostatin levels remain.

Dopamine and serotonin metabolism in striatum and in the septohippocampal pathway of the snell dwarf mouse

Dopamine and serotonin neurotransmission has been investigated in striatum and in the septohippocampal pathway of the locomotor activity and memory deficient Snell dwarf mouse. In striatum a sharp decrease in 3-MT levels with a concomitant decrease in DA turnover is indicative of a strong decrement in the functional activity of striatal dopaminergic terminals in the mutant mouse. The observed enhancement in serotoninergic markers (5HT, 5HIAA, 5 HTP), at the opposite, provide evidence for an altered relationship between serotonin and dopamine striatal neurotransmission in the mutant mouse as compared to the normal mouse. Impairment in dopamine and serotonin neurotransmission has also been observed in the septohippocampal pathway where the removal of acidic metabolites of these neurotransmitters from brain appears to be disturbed. The data presented here are discussed with regard to previously noted alterations in cholinergic activity as well as to the behavioral disturbances of the dwarf mutant.

Influence of mouse genotype on responses of central biogenic amines to alcohol intoxication and aging

Dopamine and serotonin responses to various periods of alcohol treatment have been followed in striatum and hippocampus of two inbred strains of mice and related to the effect of aging. A striking strain dependency was noted for chronic alcohol effects and also for senescence. For both neurotransmitters studied the C57Bl strain loses tolerance to prolonged alcohol injury earlier than the Balb/c strain. This loss of tolerance accompanying aging may be indicative of more widespread changes in CNS adaptability in this strain. The unequal capacity to adapt also appears to depend on the nervous structure and the neurotransmitter considered. Alcohol and aging induced changes are not identical. In a given mouse strain, significant effects of either drug or aging induced disturbances are noted. A similar molecular process could operate in both aging and alcohol abuse, but the neurochemical effect might depend on the nervous structure or neurotransmitter involved. Such a phenomenon may be the basis of differences in behavioral changes observed in alcoholics.

Genotypic differences in age and chronic alcohol exposure effects on somatostatin levels in hippocampus and striatum in mice

Somatostatin contents of striatum, hippocampus, and pons medulla have been followed in two inbred strains of mice (C57B1/6J and Balb/cJ) with aging and long term alcohol exposure (over a 25 month period of intoxication). Marked strain dependent differences in basic levels of somatostatin and genotypic variations in reactivity of this neuropeptide to aging processes and chronic alcohol exposure were demonstrated. The Balb/c strain exhibits a significant age dependent decrease in striatal and hippocampal somatostatin levels whereas the C57B1 mice remain unchanged until the 27 month. Moreover, only the Balb/c strain reacts to chronic alcohol exposure, showing a significant increase in somatostatin levels in those structures affected by the aging process. Such genotypic differences may be involved in man in specific pathologies in aged individuals and in alcohol induced behavioral alterations in alcoholics.

Influence of mouse genotype on responses of central cholinergic neurotransmission to long term alcohol intoxication.

Cholinergic neurotransmission has been followed in striatum and hippocampus in two inbred strains of mice (C57Bl/6 and Balb/c) during long term alcohol exposure (over a 25 month period) and with aging. Marked strain dependent differences in reactivity of pre- and postsynaptic cholinergic markers to chronic alcohol exposure and aging were demonstrated in both structures. The Balb/c strain exhibits a remarkable long lasting tolerance to alcohol injury for striatal and hippocampal cholinergic markers (choline acetyltransferase, high affinity choline uptake, muscarinic receptors affinity, acetyl cholinesterase), whereas C57Bl mice appear more sensitive to alcohol intoxication. Likewise aging affects the C57Bl mouse more severely than the Balb/c, a phenomenon which may be involved in the sensitivity of these mice to alcohol intoxication. Moreover long term alcohol exposure, in addition to aging show unequal effects on the diverse cholinergic markers studied. Also divergences of specific brain areas have been noted and should be related to their particular neuroanatomy. Such discrepancies may, in part, explain differences observed in the behavioral effects of chronic alcohol intoxication in alcoholics.

Role of LRP-1 in cancer cell migration in 3-dimensional collagen matrix

ABSTRACT The low-density lipoprotein receptor-related protein-1 (LRP-1) is a member of Low Density Lipoprotein Receptor (LDLR) family, which is ubiquitously expressed and which is described as a multifunctional endocytic receptor which mediates the clearance of various extracellular matrix molecules including serine proteinases, proteinase-inhibitor complexes, and matricellular proteins. Several studies showed that high LRP-1 expression promotes breast cancer cell invasiveness, and LRP-1 invalidation leads to cell motility abrogation in both tumor and non-tumor cells. Furthermore, our group has reported that LRP-1 silencing prevents the invasion of a follicular thyroid carcinoma despite increased pericellular proteolytic activities from MMP2 and uPA using a 2D-cell culture model. As the use of 3D culture systems is becoming more and more popular due to their promise as enhanced models of tissue physiology, the aim of the present work is to characterize for the first time how the 3D collagen type I matrix may impact the ability of LRP-1 to regulate the migratory properties of thyroid carcinoma using as a model FTC-133 cells. Our results show that inhibition of LRP-1 activity or expression leads to morphological changes affecting cell-matrix interactions, reorganizations of the actin-cytoskeleton especially by inhibiting FAK activation and increasing RhoA activity and MLC-2 phosphorylation, thus preventing cell migration. Taken together, our results suggest that LRP-1 silencing leads to a decrease of cell migratory capacity in a 3D configuration.