Consolidated and labile odor memory are separately encoded within the Drosophila brain.

Memories are classified as consolidated (stable) or labile according to whether they withstand amnestic treatment, or not. In contrast to the general prevalence of this classification, its neuronal and molecular basis is poorly understood. Here, we focused on consolidated and labile memories induced after a single cycle training in the Drosophila aversive olfactory conditioning paradigm and we used mutants to define the impact of cAMP signals. At the biochemical level we report that cAMP signals misrelated in either rutabaga (rut) or dunce (dnc) mutants separate between consolidated anesthesia-resistant memory (ARM) and labile anesthesia-sensitive memory (ASM). Those functionally distinct cAMP signals act within different neuronal populations: while rut-dependent cAMP signals act within Kenyon cells (KCs) of the mushroom bodies to support ASM, dnc-sensitive cAMP signals support ARM within antennal lobe local neurons (LNs) and KCs. Collectively, different key positions along the olfactory circuitry seem to get modified during storage of ARM or ASM independently. A precise separation between those functionally distinct cAMP signals seems mandatory to allocate how they support appropriate memories.

Intrinsic anticancer drug resistance of malignant melanoma cells is abrogated by IFN-ß and valproic acid.

Malignant melanoma, once metastasized, has a dismal prognosis because of intrinsic resistance to anticancer drugs. First-line therapy includes the methylating agents dacarbazine and temozolomide. Although DNA mismatch repair and O(6)-methylguanine (O(6)MeG)-DNA methyltransferase (MGMT) are key determinants of cellular resistance to these drugs, there is no correlation between these markers and the therapeutic response in melanoma, indicating as yet unknown mechanisms of drug resistance. We show that in malignant melanoma cells with wild-type p53, the temozolomide-induced DNA damage O(6)MeG triggers upregulation of the Fas/CD95/Apo-1 receptor without activating the apoptosis cascade. This is due to silencing of procaspase-8. A single treatment with IFN-ß reactivated procaspase-8 and sensitized melanoma cells to temozolomide. The key role of procaspase-8 in melanoma cell sensitization was verified by experiments in which the death receptor pathway was blocked by expression of dominant-negative FADD, siRNA knockdown of procaspase-8, or stimulation with Fas/CD95/Apo-1 activating antibody. The expression of procaspase-8 could further be enhanced by additional pretreatment with the histone deacetylase inhibitor valproic acid (VPA), which together with IFN-ß caused significant sensitization of melanoma cells in vitro. Sensitization of melanoma cells to temozolomide by IFN-ß and VPA was also shown in a xenograft mouse model. The data provide a plausible explanation why therapy of malignant melanomas with alkylating anticancer drugs failed even in trials where the repair of the critical toxic lesion O(6)MeG was blocked by MGMT inhibitors and suggest approaches to abrogate intrinsic drug resistance by IFN and VPA-mediated reactivation of the death receptor pathway.

Response of pancreatic cancer cells treated with interferon-alpha or beta and co-exposed to ionising radiation.

PURPOSE: Clinical trials on pancreatic cancer demonstrated that interferons (IFN) improve the therapeutic index of combined radio- and chemotherapy. This is believed to be due to radiosensitisation of cells, which, however, needs experimental verification. MATERIALS AND METHODS: Here, we compared the survival response of ten pancreatic tumour cell lines following ionising radiation (IR), interferon-alpha (IFN-alpha), interferon-beta (IFN-beta) and combined treatment. The effect of combination treatment on apoptosis induction was also determined. RESULTS: In most cell lines IFN treatment on its own exerted cytotoxicity, which was independent of the expression level of the IFN receptor on the cell surface. Three cell lines showed a radiosensitisation effect while two showed radioprotection. Although IFN-alpha is commonly used in the clinic, IFN-beta induced a stronger cytotoxic response than IFN-alpha in vitro. The likely mechanism of enhancement of radiosensitivity in the responsive cell lines was shown to be an increase of the radiation-induced apoptotic response by IFN pretreatment. CONCLUSIONS: Given that the in vitro data do not conform to the impressive clinical results observed after combined radio- and chemotherapy with IFN-alpha, it is reasonable to conclude that the sensitising effect of IFN is not mediated through modulating the intrinsic radiosensitivity of pancreatic cancer cells.

Glucocorticoids enhance interleukin-4 production to neo-antigen (hyaluronidase) in children immunocompromised with cytostatic drugs.

Immunoglobulin E (IgE)-mediated immediate-type allergic reactions to hyaluronidase have been observed in children with central nervous system (CNS) tumors. Glucocorticoids, used as therapy for brain edema, are discussed controversially as T helper 2 (Th2) stimulatory factors. In this study we investigated the role of glucocorticoids on a Th2 cytokine-promoting effect in children with CNS tumors. Peripheral blood mononuclear cells (PBMCs) from: 29 children suffering from malignant brain tumors, of whom 23 received short-term glucocorticoid treatment (for 3-4 days) during the course of chemotherapy; 18 children with nephrotic syndrome or renal transplantation receiving long-term glucocorticoid treatment; and 13 healthy children, were incubated with phytohemagglutinin (PHA) and/or anti-CD28 monoclonal antibody (mAb) and, in a second approach, with hyaluronidase. The concentrations of Th cell-mediated cytokines - interleukin (IL)-4, IL-10, and interferon-gamma (IFN-gamma) - were measured in supernatants. The IL-4 production of PBMCs incubated with PHA/anti-CD28 mAb from children with repeated co-administration of glucocorticoids, hyaluronidase, and cytostatic drugs (median: 249.9 pg/ml; range: 234.4-261.7) was significantly higher (p < 0.0001) than IL-4 production of PBMC from children of all the other groups (median: 86.18; range: 16.0-212.5). There was no significant difference in the levels of IL-10 and IFN-gamma within the groups. PBMCs stimulated only with hyaluronidase failed to produce detectable levels of cytokines. The results of this study indicate that repeated co-administration of glucocorticoids and hyaluronidase (a neo-antigen) enhance IL-4 production in vitro and thus may induce the production of specific IgE antibodies in children immunocompromised with cytostatic drugs. Hyaluronidase itself does not stimulate in vitro IL-4 synthesis in PBMCs of children receiving cytostatic drugs.