The chemokine CXCL16 modulates neurotransmitter release in hippocampal CA1 area.

Chemokines have several physio-pathological roles in the brain. Among them, the modulation of synaptic contacts and neurotransmission recently emerged as crucial activities during brain development, in adulthood, upon neuroinflammation and neurodegenerative diseases. CXCL16 is a chemokine normally expressed in the brain, where it exerts neuroprotective activity against glutamate-induced damages through cross communication with astrocytes and the involvement of the adenosine receptor type 3 (A3R) and the chemokine CCL2. Here we demonstrated for the first time that CXCL16 exerts a modulatory activity on inhibitory and excitatory synaptic transmission in CA1 area. We found that CXCL16 increases the frequency of the miniature inhibitory synaptic currents (mIPSCs) and the paired-pulse ratio (PPR) of evoked IPSCs(eIPSCs), suggesting a presynaptic modulation of the probability of GABA release. In addition, CXCL16 increases the frequency of the miniature excitatory synaptic currents (mEPSCs) and reduces the PPR of evoked excitatory transmission, indicating that the chemokine also modulates and enhances the release of glutamate. These effects were not present in the A3RKO mice and in WT slices treated with minocycline, confirming the involvement of A3 receptors and introducing microglial cells as key mediators of the modulatory activity of CXCL16 on neurons

Identification and characterization of privet leaf blotch-associated virus, a novel idaeovirus

A novel virus has been identified by next-generation sequencing (NGS) in privet (Ligustrum japonicum L.) affected by a graft-transmissible disease characterized by leaf blotch symptoms resembling infectious variegation, a virus-like privet disease with an unclear aetiology. This virus, which has been tentatively named ‘privet leaf blotch-associated virus’ (PrLBaV), was absent in non-symptomatic privet plants, as revealed by NGS and reverse transcription-polymerase chain reaction (RT-PCR). Molecular characterization of PrLBaV showed that it has a segmented genome composed of two positive single-stranded RNAs, one of which (RNA1) is monocistronic and codes for the viral replicase, whereas the other (RNA2) contains two open reading frames (ORFs), ORF2a and ORF2b, coding for the putative movement (p38) and coat (p30) proteins, respectively. ORF2b is very probably expressed through a subgenomic RNA starting with six nucleotides (AUAUCU) that closely resemble those found in the 5′-terminal end of genomic RNA1 and RNA2 (AUAUUU and AUAUAU, respectively). The molecular signatures identified in the PrLBaV RNAs and proteins resemble those of Raspberry bushy dwarf virus (RBDV), currently the only member of the genus Idaeovirus. These data, together with phylogenetic analyses, are consistent with the proposal of considering PrLBaV as a representative of the second species in the genus Idaeovirus. Transient expression of a recombinant PrLBaV p38 fused to green fluorescent protein in leaves of Nicotiana benthamiana, coupled with confocal laser scanning microscopy assays, showed that it localizes at cell plasmodesmata, strongly supporting its involvement in viral movement/trafficking and providing the first functional characterization of an idaeovirus encoded protein

Interactions between nematodes and fungi: a concise review

A short review of the complex interactions is reported between nematodes and fungi, which are not always clear because of the rhizosphere complexity and inadequate techniques of investigation

Basal adenosine modulates the functional properties of AMPA receptors in mouse hippocampal neurons through the activation of A1R A2AR and A3R

Adenosine is a widespread neuromodulator within the CNS and its extracellular level is increased during hypoxia or intense synaptic activity, modulating pre- and postsynaptic sites. We studied the neuromodulatory action of adenosine on glutamatergic currents in the hippocampus, showing that activation of multiple adenosine receptors (ARs) by basal adenosine impacts postsynaptic site. Specifically, the stimulation of both A1R and A3R reduces AMPA currents, while A2AR has an opposite potentiating effect. The effect of ARs stimulation on glutamatergic currents in hippocampal cultures was investigated using pharmacological and genetic approaches. A3R inhibition by MRS1523 increased GluR1-Ser845 phosphorylation and potentiated AMPA current amplitude, increasing the apparent affinity for the agonist. A similar effect was observed blocking A1R with DPCPX or by genetic deletion of either A3R or A1R. Conversely, impairment of A2AR reduced AMPA currents, and decreased agonist sensitivity. Consistently, in hippocampal slices, ARs activation by AR agonist NECA modulated glutamatergic current amplitude evoked by AMPA application or afferent fiber stimulation. Opposite effects of AR subtypes stimulation are likely associated to changes in GluR1 phosphorylation and represent a novel mechanism of physiological modulation of glutamatergic transmission by adenosine, likely acting in normal conditions in the brain, depending on the level of extracellular adenosine and the distribution of AR subtypes

Electrophysiological Properties of CA1 Pyramidal Neurons along the Longitudinal Axis of the Mouse Hippocampus

Evidence for different physiological properties along the hippocampal longitudinal axis is emerging. Here, we examined the electrophysiological features of neurons at different dorso-ventral sites of the mouse CA1 hippocampal region. Cell position was defined with respect to longitudinal coordinates of each slice. We measured variations in neuronal excitability, subthreshold membrane properties and neurotransmitter responses along the longitudinal axis. We found that (i) pyramidal cells of the dorsal hippocampus (DH) were less excitable than those of the ventral hippocampus (VH). Resting Membrane Potential (RMP) was more hyperpolarized and somatic Input Resistance (Ri) was lower in DH compared to VH. (ii) The Paired-pulse ratio (PPR) of focally induced synaptic responses was systematically reduced from the DH to the VH; (iii) Long-term-potentiation was most pronounced in the DH and fell gradually in the intermediate hippocampus and in the VH; (iv) the frequency of miniature GABAergic events was higher in the VH than in the DH; (v) the PPR of evoked inhibitory post-synaptic current (IPSC) was higher in the DH than in the VH. These findings indicate an increased probability of both GABA and glutamate release and a reduced plasticity in the ventral compared to more dorsal regions of the hippocampus

Chemokine fractalkine/CX3CL1 negatively modulates active glutamatergic synapses in rat hippocampal neurons

We examined the effects of the chemokine fractalkine (CX3CL1) on EPSCs evoked by electrical stimulation of Schaffer collaterals in patch-clamped CA1 pyramidal neurons from rat hippocampal slices. Acute application of CX3CL1 caused a sustained reduction of EPSC amplitude, with partial recovery after washout. CX3CL1-induced EPSC depression is postsynaptic in nature, because paired-pulse ratio was maintained, amplitude distribution of spontaneous excitatory postsynaptic currents shifted to lower values, and whole-cell current responses to AMPA were reversibly inhibited. EPSC depression by CX3CL1 is mediated by CX3CL1 receptor (CX3CR1), because CX3CL1 was unable to influence EPSC amplitude in CA1 pyramidal neurons from CX3CR1 knock-out mice. CX3CL1-induced depression of both EPSC and AMPA current was not observed in the absence of afferent fiber stimulation or AMPA receptor activation, respectively, indicating the requirement of sustained receptor activity for its development. Findings obtained from hippocampal slices, cultured hippocampal neurons, and transfected human embryonic kidney cells indicate that a Ca2+-, cAMP-, and phosphatase-dependent process is likely to modulate CX3CL1 effects because of the following: (1) CX3CL1-induced depression was antagonized by intracellular BAPTA, 8Br-cAMP, phosphatase inhibitors, and pertussis toxin (PTX); (2) CX3CL1 inhibited forskolin-induced cAMP formation sensitive to PTX; and (3) CX3CL1 inhibited forskolin-induced Ser845 GluR1 phosphorylation, which was sensitive to PTX and dependent on Ca2+ and phosphatase activity. Together, these findings indicate that CX3CL1 negatively modulates AMPA receptor function at active glutamatergic synapses through cell-signaling pathways by influencing the balance between kinase and phosphatase activity

TRPV1 channels are critical brain inflammation detectors and neuropathic pain biomarkers in mice

The capsaicin receptor TRPV1 has been widely characterized in the sensory system as a key component of pain and inflammation. A large amount of evidence shows that TRPV1 is also functional in the brain although its role is still debated. Here we report that TRPV1 is highly expressed in microglial cells rather than neurons of the anterior cingulate cortex and other brain areas. We found that stimulation of microglial TRPV1 controls cortical microglia activation per se and indirectly enhances glutamatergic transmission in neurons by promoting extracellular microglial microvesicles shedding. Conversely, in the cortex of mice suffering from neuropathic pain, TRPV1 is also present in neurons affecting their intrinsic electrical properties and synaptic strength. Altogether, these findings identify brain TRPV1 as potential detector of harmful stimuli and a key player of microglia to neuron communication

KCa3.1 channel inhibition sensitizes malignant gliomas to temozolomide treatment

Malignant gliomas are among the most frequent and aggressive cerebral tumors, characterized by high proliferative and invasive indexes. Standard therapy for patients, after surgery and radiotherapy, consists of temozolomide (TMZ), a methylating agent that blocks tumor cell proliferation. Currently, there are no therapies aimed at reducing tumor cell invasion. Ion channels are candidate molecular targets involved in glioma cell migration and infiltration into the brain parenchyma. In this paper we demonstrate that: i) blockade of the calcium-activated potassium channel KCa3.1 with TRAM-34 has co-adjuvant effects with TMZ, reducing GL261 glioma cell migration, invasion and colony forming activity, increasing apoptosis, and forcing cells to pass the G2/M cell cycle phase, likely through cdc2 de-phosphorylation; ii) KCa3.1 silencing potentiates the inhibitory effect of TMZ on glioma cell viability; iii) the combination of TMZ/TRAM-34 attenuates the toxic effects of glioma conditioned medium on neuronal cultures, through a microglia dependent mechanism since the effect is abolished by clodronate-induced microglia killing; iv) TMZ/TRAM-34 co-treatment increases the number of apoptotic tumor cells, and the mean survival time in a syngeneic mouse glioma model (C57BL6 mice implanted with GL261 cells); v) TMZ/TRAM-34 co-treatment reduces cell viability of GBM cells and cancer stem cells (CSC) freshly isolated from patients.Taken together, these data suggest a new therapeutic approach for malignant glioma, targeting both glioma cell proliferating and migration, and demonstrate that TMZ/TRAM-34 co-treatment affects both glioma cells and infiltrating microglia, resulting in an overall reduction of tumor cell progression

Cestrum yellow leaf curling virus (CmYLCV) promoter: a new strong constitutive promoter for heterologous gene expression in a wide variety of crops

Appropriately regulated gene expression requires a suitable promoter. A number of promoters have been isolated and shown to be functional in plants, but only a few of them activate transcription of transgenes at high levels constitutively. We report here the cloning and characterization of a novel, constitutively expressed promoter isolated from Cestrum yellow leaf curling virus (CmYLCV), a double-stranded DNA plant pararetrovirus belonging to the Caulimoviridae family. The CmYLCV promoter is highly active in callus, meristems and vegetative and reproductive tissues in Arabidopsis thaliana, Nicotiana tabacum, Lycopersicon esculentum,Zea mays and Oryza sativa. Furthermore, the level of expression is comparable to, or higher than, that from the CaMV 35S, the 'ssuper-promoter' or the maize ubiquitin 1 promoters, three frequently used promoters in agricultural biotechnology. The heritable, strong and constitutive activity in both monocotyledonous and dicotyledonous plants, combined with the extremely narrow CmYLCV host range, makes the CmYLCV promoter an attractive tool for regulating transgene expression in a wide variety of plant specie