Targeted therapy of cognitive deficits in fragile X syndrome.

Breaking an impasse in finding mechanism-based therapies of neuropsychiatric disorders requires a strategic shift towards alleviating individual symptoms. Here we present a symptom and circuit-specific approach to rescue deficits of reward learning in Fmr1 knockout mice, a model of Fragile X syndrome (FXS), the most common monogenetic cause of inherited mental disability and autism. We use high-throughput, ecologically-relevant automated tests of cognition and social behavior to assess effectiveness of the circuit-targeted injections of designer nanoparticles, loaded with TIMP metalloproteinase inhibitor 1 protein (TIMP-1). Further, to investigate the impact of our therapeutic strategy on neuronal plasticity we perform long-term potentiation recordings and high-resolution electron microscopy. We show that central amygdala-targeted delivery of TIMP-1 designer nanoparticles reverses impaired cognition in Fmr1 knockouts, while having no impact on deficits of social behavior, hence corroborating symptom-specificity of the proposed approach. Moreover, we elucidate the neural correlates of the highly specific behavioral rescue by showing that the applied therapeutic intervention restores functional synaptic plasticity and ultrastructure of neurons in the central amygdala. Thus, we present a targeted, symptom-specific and mechanism-based strategy to remedy cognitive deficits in Fragile X syndrome.

A role for CXCR4 signaling in survival and migration of neural and oligodendrocyte precursors.

Oligodendrocyte development is controlled by a number of survival and migratory factors. The present study shows that signaling of CXCR4 receptor by the chemokine CXCL12 regulates survival and migration of neural precursors (NP) as well as oligodendrocyte progenitors (OP). CXCR4 is expressed by E14 striatal NP and OP generated by neurospheres. In CXCR4-defective mice, the number of NP in neurosphere outgrowth was twofold less than in wild-type (WT) mice; NP radial cell migration was also decreased. In contrast, the addition of CXCL12 to WT NP increased radial migration from the sphere in a dose-dependent manner with a maximal response at 200 nM. When oligodendrocytes differentiated in neurosphere outgrowth, CXCR4 was downregulated. OP isolated from newborn brain coexpressed CXCR4 with platelet-derived growth factor receptor-alpha (PDGFR alpha) or chondroitin sulfate proteoglycan; receptor expression also decreased during differentiation in vitro. Neonatal OP showed a peak migratory response to 20 nM of CXCL12 in chemotactic chambers, a migration inhibited by a CXCR4 antagonist and anti-CXCL12 antibody. In the embryonic spinal cord, the number of OP-expressing PDGFR alpha was reduced more than twofold in CXCR4-defective mice compared with WT and the ratio of ventral to dorsal OP was significantly increased. This indicates a defect in OP survival and their dorsal migration from the ventral cord region, probably because CXCR4(-/-) OP are unable to respond to CXCL12 made by vascular endothelia and the pia mater. We propose that CXCR4 signaling regulate survival and outward chemotactic migration of OP during embryonic and postnatal CNS development.

Effect of nuclear factor kappaB inhibition on tumor cell sensitivity to natural killer-mediated cytolytic function.

Inhibition of the transcription factor NF-kappaB has been reported to increase cell sensitivity to TNF and some cytotoxic drugs. We investigated the effect of NK-kappaB inhibition on the susceptibility of tumor cells to freshly isolated, nonactivated, human NK cells and to a TCRgamma/delta T cell clone displaying an MHC-unrestricted "NK-like" lysis. Using electrophoretic mobility shift assay, we first demonstrated that NF-kappaB/DNA binding activity was induced in target cells following coculture with NK cells or TCRgamma/delta T cell clone. To investigate the effect of target cell NF-kappaB inhibition on NK-mediated lysis, we blocked NF-kappaB translocation by introducing a human cDNA coding for a mutated IkappaB-alpha. Interestingly, our results indicated that inhibition of NF-kappaB did not induce any increase in either granzyme-dependent non-MHC-restricted cytotoxicity mediated by fresh non-stimulated NK cells and by TCR gamma/delta T cell clone or in CD95-mediated lysis. These results emphasize that NF-kappaB expressed in target cells does not play a role in the molecular process related to the control of target cell susceptibility to NK-mediated lysis and suggest that the NF-kappaB pathway is not a general mechanism for controlling the cytotoxic response.