Pharmacological blockage of NOP receptors decreases ventral tegmental area dopamine neuronal activity through GABAB receptor-mediated mechanism

The Nociceptin/Orphanin FQ (N/OFQ) peptide and its receptor NOP are highly expressed within several regions of the mesolimbic system, including the ventral tegmental area (VTA). Evidence indicates that the N/OFQ-NOP receptor system is involved in reward processing and historically it has been proposed that activation of NOP receptors attenuates the motivation for substances of abuse. However, recent findings demonstrated that drug self-administration and relapse to drug-seeking are also attenuated after administration of NOP receptor antagonists. Here, to shed light on the mechanisms through which NOP receptor blockers modulate these processes, we utilized ex vivo patch-clamp recordings to investigate the effect of the selective NOP receptor antagonist LY2817412 on VTA dopaminergic (DA) function in male rats. Results showed that, similar to the endogenous NOP receptor agonist N/OFQ, LY2817412 reduced the spontaneous basal firing discharge of VTA DA neurons. Consistently, we found that NOP receptors are expressed both in VTA DA and GABA cells and that LY2817412 slice perfusion increased GABA release onto VTA DA cells. Finally, in the attempt to dissect the role of postsynaptic and presynaptic NOP receptors, we tested the effect of N/OFQ and LY2817412 in the presence of GABA receptors blockers. Results showed that the effect of LY2817412 was abolished following pretreatment with GABABR, but not GABAAR, blockers. Conversely, inhibition of DA neuronal activity by N/OFQ was unaffected by blockade of GABA receptors. Altogether, these results suggest that both NOP receptor agonists and antagonists can decrease VTA DA neuronal activity, but through distinct mechanisms of action. The effect of NOP receptor antagonists occurs through a GABABR-mediated mechanism while NOP receptor agonists seem to act via a direct effect on VTA DA neurons.

Differential Expression of NOTCH-1 and Its Molecular Targets in Response to Metronomic Followed by Conventional Therapy in a Patient with Advanced Triple-Negative Breast Cancer

A group of 27 patients diagnosed with metastatic triple-negative breast cancer (mTNBC) was randomly distributed into two groups and underwent different lines of metronomic treatment (mCHT). The former group (N 14) received first-line mCHT and showed a higher overall survival rate than the second group (N 13), which underwent second-line mCHT. Analysis of one patient still alive from the first group, diagnosed with mTNBC in 2019, showed a complete metabolic response (CMR) after a composite approach implicating first-line mCHT followed by second-line epirubicin and third-line nab-paclitaxel, and was chosen for subsequent molecular characterization. We found altered expression in the cancer stemness-associated gene NOTCH-1 and its corresponding protein. Additionally, we found changes in the expression of oncogenes, such as MYC and AKT, along with their respective proteins. Overall, our data suggest that a first-line treatment with mCHT followed by MTD might be effective by negatively regulating stemness traits usually associated with the emergence of drug resistance.

Ethanol-induced AMPA alterations are mediated by mGLU5 receptors through miRNA upregulation in hippocampal slices

Prenatal alcohol exposure (PAE) affects neuronal networks and brain development causing a range of physical, cognitive and behavioural disorders in newborns that persist into adulthood. The array of consequences associated with PAE can be grouped under the umbrella-term 'fetal alcohol spectrum disorders' (FASD). Unfortunately, there is no cure for FASD as the molecular mechanisms underlying this pathology are still unknown. We have recently demonstrated that chronic EtOH exposure, followed by withdrawal, induces a significant decrease in AMPA receptor (AMPAR) expression and function in developing hippocampus in vitro. Here, we explored the EtOH-dependent pathways leading to hippocampal AMPAR suppression. Organotypic hippocampal slices (2 days in cultures) were exposed to EtOH (150 mM) for 7 days followed by 24 h EtOH withdrawal. Then, the slices were analysed by means of RT-PCR for miRNA content, western blotting for AMPA and NMDA related-synaptic proteins expression in postsynaptic compartment and electrophysiology to record electrical properties from CA1 pyramidal neurons. We observed that EtOH induces a significant downregulation of postsynaptic AMPA and NMDA subunits and relative scaffolding protein expression and, accordingly, a decrease of AMPA-mediated neurotransmission. Simultaneously, we found that chronic EtOH induced-upregulation of miRNA 137 and 501-3p and decreased AMPA-mediated neurotransmission are prevented by application of the selective mGlu5 antagonist MPEP during EtOH withdrawal. Our data indicate mGlu5 via miRNA137 and 501-3p expression as key factors in the regulation of AMPAergic neurotransmission that may contribute, at least in part, to the pathogenesis of FASD.

Co-targeting triple-negative breast cancer cells and endothelial cells by metronomic chemotherapy inhibits cell regrowth and migration via downregulation of the FAK/VEGFR2/VEGF axis and autophagy/apoptosis activation

High-dose standard-of-care chemotherapy is the only option for triple-negative breast cancer (TNBC) patients, which eventually die due to metastatic tumors. Recently, metronomic chemotherapy (mCHT) showed advantages in treating TNBCs leading us to investigate the anti-metastatic and anti-angiogenic potential of metronomic 5-Fluorouracil plus Vinorelbine (5-FU+VNR) on endothelial cells (ECs) and TNBCs in comparison to standard treatment (STD). We found that 10-fold lower doses of 5-FU+VNR given mCHT vs. STD inhibits cell proliferation and survival of ECs and TNBC cells. Both schedules strongly affect ECs migration and invasion, but in TNBC cells mCHT is significantly more effective than STD in impairing cell migration and invasion. The two treatments disrupt FAK/VEGFR/VEGF signaling in both ECs and TNBC cells. mCHT, and to a much lesser extent STD treatment, induces apoptosis in ECs, whereas it switches the route of cell death from apoptosis (as induced by STD) to autophagy in TNBC cells. mCHT-treated TNBCs-derived conditioned medium also strongly affects ECs' migration, modulates different angiogenesis-associated proteins, and hampers angiogenesis in matrix sponge in vivo. In conclusion, mCHT administration of 5-FU+VNR is more effective than STD schedule in controlling cell proliferation/survival and migration/invasion of both ECs and TNBC cells and has a strong anti-angiogenic effect. Our data suggest that the stabilization of tumor growth observed in TNBC patients treated with mCHT therapy schedule is likely due not only to direct cytotoxic effects but also to anti-metastatic and anti-angiogenic effects.

Acute rapamycin rescues the hyperexcitable phenotype of accumbal medium spiny neurons in the valproic acid rat model of autism spectrum disorder

We previously demonstrated that prenatal exposure to valproic acid (VPA), an environmental model of autism spectrum disorder (ASD), leads to a hyperexcitable phenotype associated with downregulation of inward-rectifying potassium currents in nucleus accumbens (NAc) medium spiny neurons (MSNs) of adolescent rats. Aberrant mTOR pathway function has been associated with autistic-like phenotypes in multiple animal models, including gestational exposure to VPA. The purpose of this work was to probe the involvement of the mTOR pathway in VPA-induced alterations of striatal excitability. Adolescent male Wistar rats prenatally exposed to VPA were treated acutely with the mTOR inhibitor rapamycin and used for behavioral tests, ex vivo brain slice electrophysiology, single-neuron morphometric analysis, synaptic protein quantification and gene expression analysis in the NAc. We report that postnatal rapamycin ameliorates the social deficit and reverts the abnormal excitability, but not the inward-rectifying potassium current defect, of accumbal MSNs. Synaptic transmission and neuronal morphology were largely unaffected by prenatal VPA exposure or postnatal rapamycin treatment. Transcriptome analysis revealed extensive deregulation of genes implied in neurodevelopmental disorders and ionic mechanisms exerted by prenatal VPA, which was partially reverted by postnatal rapamycin. The results of this work support the existence of antagonistic interaction between mTOR and VPA-induced pathways on social behavior, neurophysiological phenotype and gene expression profile, thus prompting further investigation of the mTOR pathway in the quest for specific therapeutic targets in ASD.

Moderate ethanol drinking is sufficient to alter Ventral Tegmental Area dopamine neurons activity via functional and structural remodeling of GABAergic transmission

Earlier studies have shown a major involvement of Ventral Tegmental Area (VTA) dopamine (DA) neurons in mediating the rewarding effects of ethanol (EtOH). Much less is known on the role of this system in mediating the transition from moderate to excessive drinking and abuse. Here we sought to explore the hypothesis that early stage drinking in rodents, resembling recreational EtOH use in humans, is sufficient to dysregulate VTA DA transmission thus increasing the propensity to use over time. To this purpose, midbrain slice recordings in mice previously exposed to an escalating (3, 6 and 12%) 18-day voluntary EtOH drinking paradigm was used. By recording from DA and γ-aminobutyric acid (GABA) VTA neurons in midbrain slices, we found that moderate EtOH drinking leads to a significant suppression of the spontaneous activity of VTA DA neurons, while increasing their response to acute EtOH application. We also found that chronic EtOH leads to the enhancement of GABA input frequency onto a subset of DA neurons. Structurally, chronic EtOH induced a significant increase in the number of GABA axonal boutons contacting DA neurons, suggesting deep rewiring of the GABA network. This scenario is consistent with a downmodulation of the reward DA system induced by moderate EtOH drinking, a neurochemical state defined as "hypodopaminergic" and previously associated with advanced stages of drug use in humans. In this context, increased sensitivity of DA neurons towards acute EtOH may represent the neurophysiological correlate of increased unitary rewarding value, possibly driving progression to addiction.

Ethanol neurotoxicity is mediated by changes in expression, surface localization and functional properties of glutamate AMPA receptors

Modifications in the subunit composition of AMPA receptors (AMPARs) have been linked to the transition from physiological to pathological conditions in a number of contexts, including EtOH-induced neurotoxicity. Previous work from our laboratory showed that EtOH withdrawal causes CA1 pyramidal cell death in organotypic hippocampal slices and changes in the expression of AMPARs. Here, we investigated whether changes in expression and function of AMPARs may be causal for EtOH-induced neurotoxicity. To this aim, we examined the subunit composition, localization and function of AMPARs in hippocampal slices exposed to EtOH by using western blotting, surface expression assay, confocal microscopy and electrophysiology. We found that EtOH withdrawal specifically increases GluA1 protein signal in total homogenates, but not in the post-synaptic density-enriched fraction. This is suggestive of overall increase and redistribution of AMPARs to the extrasynaptic compartment. At functional level, AMPA-induced calcium influx was unexpectedly reduced, whereas AMPA-induced current was enhanced in CA1 pyramidal neurons following EtOH withdrawal, suggesting that increased AMPAR expression may lead to cell death because of elevated excitability, and not for a direct contribution on calcium influx. Finally, the neurotoxicity caused by EtOH withdrawal was attenuated by the non-selective AMPAR antagonist 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide disodium salt as well as by the selective antagonist of GluA2-lacking AMPARs 1-naphthyl acetyl spermine. We conclude that EtOH neurotoxicity involves changes in expression, surface localization and functional properties of AMPARs, and propose GluA2-lacking AMPARs as amenable specific targets for the development of neuroprotective drugs in EtOH-withdrawal syndrome.

Neurotoxicity of Unconjugated Bilirubin in Mature and Immature Rat Organotypic Hippocampal Slice Cultures

BACKGROUND

The physiopathology of bilirubin-induced neurological disorders is not completely understood.

OBJECTIVES

The aim of our study was to assess the effect on bilirubin neurotoxicity of the maturity or immaturity of exposed cells, the influence of different unconjugated bilirubin (UCB) and human serum albumin (HSA) concentrations, and time of UCB exposure.

METHODS

Organotypic hippocampal slices were exposed for 48 h to different UCB and HSA concentrations after 14 (mature) or 7 (immature) days of in vitro culture. Immature slices were also exposed to UCB and HSA for 72 h. The different effects of exposure time to UCB on neurons and astrocytes were evaluated.

RESULTS

We found that 48 h of UCB exposure was neurotoxic for mature rat organotypic hippocampal slices while 72 h of exposure was neurotoxic for immature slices. Forty-eight-hour UCB exposure was toxic for astrocytes but not for neurons, while 72-h exposure was toxic for both astrocytes and neurons. HSA prevented UCB toxicity when the UCB:HSA molar ratio was ≤1 in both mature and immature slices.

CONCLUSIONS

We confirmed UCB neurotoxicity in mature and immature rat hippocampal slices, although immature ones were more resistant. HSA was effective in preventing UCB neurotoxicity in both mature and immature rat hippocampal slices.

Two different crystal forms of sorcin, a penta-EF-hand Ca2+-binding protein

Sorcin is a 198 amino-acid Ca(2+)-binding protein that belongs to the penta-EF-hand family. Its Ca(2+)-binding domain (residues 33-198) has been crystallized in the absence of Ca(2+) in two different crystal forms. Two complete data sets have been collected on a synchrotron source under cryocooling conditions from crystals grown using ammonium sulfate as precipitant: monoclinic crystals in space group C2, with unit-cell parameters a = 130.93, b = 103.85, c = 78.55 A, beta = 118.0 degrees, diffracting to 2.1 A, and tetragonal crystals in space group P42(1)2, with unit-cell parameters a = b = 103.33, c = 79.15, diffracting to 2.7 A. Crystals were also grown using PEG 6000 as precipitating agent. They also belong to space group C2, diffract to 2.8 A and their unit-cell parameters are very similar to the first form. Structure determination by molecular replacement has been initiated. Structural information should be useful for elucidating the interaction of sorcin with membrane targets.

Plasticity of secondary structure in the N-terminal region of beta-dystroglycan

The secondary structure content of the N-terminal extracellular domain of beta-dystroglycan (a recombinant fragment extending from positions 654 to 750) has been quantitatively determined by means of CD and FTIR spectroscopies. The elements of secondary structure, namely an 8-10 residue long alpha-helix (10%) and two beta-strands (24%) have been assigned to specific amino acid sequences by means of a GOR constrained prediction method. The remaining 66% of the whole sequence is classified as turns or unordered. The temperature dependence of CD and FTIR spectra has been investigated in detail. A reversible, non-cooperative thermal transition is observed with both CD and FTIR spectroscopies up to 95 degrees C. The profile of the transition is typical of the unfolding of isolated peptides and corresponds to the progressive loss of the secondary structure elements of the protein with no evidence for collapsing phenomena, typical of globular proteins, upon heating.

The unusual dodecameric ferritin from Listeria innocua dissociates below pH 2.0

The stability of the dodecameric Listeria innocua ferritin at low pH values has been investigated by spectroscopic methods and size-exclusion chromatography. The dodecamer is extremely stable in comparison to the classic ferritin tetracosamer and preserves its quaternary assembly at pH 2.0, despite an altered tertiary structure. Below pH 2.0, dissociation into dimers occurs and is paralleled by the complete loss of tertiary structure and a significant decrease in secondary structure elements. Dissociation of dimers into monomers occurs only at pH 1.0. Addition of NaCl to the protein at pH 2.0 induces structural changes similar to those observed upon increasing the proton concentration, although dissociation proceeds only to the dimer stage. Addition of sulfate at pH values >/= 1.5 prevents the dissociation of the dodecamer. The role played by hydrophilic and hydrophobic interactions in determining the resistance to dissociation of L. innocua ferritin at low pH is discussed in the light of its three-dimensional structure.

Iron oxidation and hydrolysis reactions of a novel ferritin from Listeria innocua

Iron deposition in the unusual 12-subunit ferritin from thebacterium Listeria innocua proceeds in three phases: a rapidfirst phase in which Fe(2+) binds to the apoprotein, P(Z) of charge Z, according to the postulatedreaction 2Fe(2+)+P(Z)-->[Fe(2)-P](Z+2)+2H(+), where[Fe(2)-P](Z+2) represents adinuclear iron(II) complex formed at each of the 12 ferroxidase centresof the protein; a second phase corresponding to oxidation of thisputative complex, i.e. [Fe(2)-P](Z+2)+1/2 O(2)-->[Fe(2)O-P](Z)+2H(+);and a third phase of iron(II) oxidation/mineralization, i.e. 4Fe(2+)+O(2)+8H(2)O-->8FeOOH((s))+8H(+) [where FeOOH((s)) represents the hydrous ferric oxidemineral that precipitates from the solution], which occurs when iron isadded in excess of 24Fe(2+)/protein. In contrast with otherferritins, the ferroxidation reaction in L. innocua ferritinproceeds more slowly than the oxidation/mineralization reaction. Wateris the final product of dioxygen reduction in the 12-subunit L.innocua ferritin (the present work) and in the 24-subunit Escherichia coli bacterioferritin, whereas H(2)O(2) is produced in 24-subunit mammalian ferritins. Possible reasonsfor this difference are discussed.

Structure-function relationships in sorcin, a member of the penta EF-hand family. Interaction of sorcin fragments with the ryanodine receptor and an Escherichia coli model system

Sorcin, a 21.6 kDa cytosolic EF-hand protein which undergoes a Ca(2+)-induced translocation from cytoplasm to membranes, has been assigned to the newly defined penta EF-hand family. A molecular model of the C-terminal Ca(2+)-binding domain has been generated using as a template the X-ray coordinates of the corresponding domain in the calpain light subunit, the family prototype [Lin, G., et al. (1997) Nat. Struct. Biol. 4, 539-546]. The model indicates that in sorcin the three-dimensional structure is conserved and in particular that of EF1, the novel EF-hand motif characteristic of the family. On this basis, two stable fragments have been obtained and characterized. Just like the native protein, the sorcin Ca(2+)-binding domain (residues 33-198) is largely dimeric, interacts with the ryanodine receptor at physiological calcium concentrations, and undergoes a reversible, Ca(2+)-dependent translocation from cytosol to target proteins on Escherichia coli membranes. In contrast, the 90-198 fragment (residues 90-198), which lacks EF1 and EF2, does not bind Ca(2+) with high affinity and is unable to translocate. Binding of calcium to the EF1-EF2 pair is therefore required for the activation of sorcin which uses the C-terminal calcium-binding domain for interaction with the ryanodine receptor, a physiological target in muscle cells.

The dodecameric ferritin from Listeria innocua contains a novel intersubunit iron-binding site

Ferritin is characterized by a highly conserved architecture that comprises 24 subunits assembled into a spherical cage with 432 symmetry. The only known exception is the dodecameric ferritin from Listeria innocua. The structure of Listeria ferritin has been determined to a resolution of 2.35 A by molecular replacement, using as a search model the structure of Dps from Escherichia coli. The Listeria 12-mer is endowed with 23 symmetry and displays the functionally relevant structural features of the ferritin 24-mer, namely the negatively charged channels along the three-fold symmetry axes that serve for iron entry into the cavity and a negatively charged internal cavity for iron deposition. The electron density map shows 12 iron ions on the inner surface of the hollow core, at the interface between monomers related by two-fold axes. Analysis of the nature and stereochemistry of the iron-binding ligands reveals strong similarities with known ferroxidase sites. The L. innocua ferritin site, however, is the first described so far that has ligands belonging to two different subunits and is not contained within a four-helix bundle.

Crystallization and preliminary X-ray crystallographic analysis of the unusual ferritin from Listeria innocua

Single crystals of ferritin extracted from Listeria innocua have been obtained by the vapour-diffusion method using PEG 1000 as precipitant. The crystals are orthorhombic, space group P212121, with unit-cell dimensions a = 87.7, b = 137.5, c = 173.1 A. The crystals diffract to 2.9 A resolution on a rotating-anode X-ray source and to 2.35 A resolution on a synchrotron X-ray source. The asymmetric unit contains one molecule formed by 12 subunits, corresponding to a packing density of 2.41 A3 Da-1

Calcium- and pH-linked oligomerization of sorcin causing translocation from cytosol to membranes

Sorcin, a cytosolic calcium-binding protein containing a pair of EF-hand motifs, undergoes a Ca2(+)-dependent translocation to the cell membrane. The underlying conformational change is similar at pH 6.0 and 7.5 and consists in an increase in overall hydrophobicity that involves the aromatic residues and in particular the two tryptophan residues which become less exposed to solvent. The concomitant association from dimers to tetramers indicates that the tryptophan residues, which are located between the EF-hand sites, become buried at the dimer-dimer interface. Ca2(+)-bound sorcin displays a striking difference in solubility as a function of pH that has been ascribed to the formation of calcium-stabilized aggregates.

Effect of the vinyl-globin interactions on the temperature-dependent broadening of the Soret spectra: a study with horse myoglobin and Scapharca dimeric hemoglobin reconstituted with unnatural 2,4-heme derivatives

The temperature dependence of the Soret absorption spectra has been measured over the range 80 to 300 K on deoxygenated and carbonmonoxy horse heart myoglobin and Scapharca inaequivalvis dimeric hemoglobin reconstituted with proto- or with meso- and deutero-heme, in which the vinyl groups have been replaced with ethyl groups or hydrogen atoms, respectively. In the meso- and deutero-derivatives of both proteins the linewidth of the absorption spectra is narrower and less sensitive to thermal broadening effects than in the proto-derivatives. Moreover, the broadening effects are larger in the deoxygenated proteins with respect to the liganded adducts. The quantitative analysis of these effects shows that the change in linewidth is due to a marked decrease in the extent of coupling between the heme vibronic transitions and the protein low-frequency motions. The relevance of the vinyl groups in the dynamics of the heme-globin interaction is highlighted by this experimental approach which shows that the protein is capable of transmitting structural information to the heme by coupling the ensemble of the low-frequency modes to the stereochemistry of the vinyl itself. This mechanism, which entails adjustment of the equilibrium between vinyl torsional conformers, represents an additional pathway for the control of the heme reactivity in addition to the iron-histidine link.

Unusual affinity of cyanide for ferrous and ferric Scapharca inaequivalvis homodimeric hemoglobin. Equilibria and kinetics of the reaction

The homodimeric hemoglobin from the mollusk Scapharca inaequivalvis (HbI) yields very stable ferrous and ferric cyanide adducts. The stability of the ferrous complex is particularly unusual such that it enabled determination of the spectroscopic properties of the complex and the characterization of the cyanide binding reaction to deoxygenated HbI at equilibrium and kinetically. The absorption spectrum of the ferrous cyanide complex is typical of a low-spin derivative; in the near-infrared region, it displays two bands at 695 and 840 nm attributable to charge transfer transitions. At pH 9.2, cyanide binds to deoxy HbI with no cooperativity and an apparent affinity constant of 17 M-1, which is about 10-fold higher than that for deoxy horse heart myoglobin. The rate of cyanide dissociation from both the ferrous and the ferric HbI adducts is slow relative to those of the other hemoproteins investigated to date and provides the major contribution to the unusual affinity for the ligand. The rate of cyanide binding to the ferric protein, in which the pentacoordinate derivative is the dominant species, is about 100-fold faster relative to that of the ferrous protein. In structural terms, the high affinity for cyanide of Scapharca hemoglobin has been ascribed to the decreased overall polarity of the heme pocket which is related to the localization of the heme groups at the subunit interface.

Rigidity of the heme pocket in the cooperative Scapharca hemoglobin homodimer and relation to the direct communication between hemes

The Soret spectra of the dimeric hemoglobin from Scapharca and of horse myoglobin reconstituted with protoporphyrin IX and Zn-protoporphyrin IX have been measured over the range 290-80 K. With increase in temperature the Soret band broadens and shifts to a different extent depending on the protein and the presence of the metal. In the Zn-protoporphyrin IX derivatives the spectral changes are more marked in myoglobin than in the dimeric hemoglobin. In the protoporphyrin IX derivatives, in which the spectral changes are significantly reduced, the opposite is true. The data have been analyzed in terms of coupling of the protein low-frequency vibrational motions to the porphyrin electronic transition (V. Srajer et al., 1986, Phys. Rev. Lett. 57, 1267-1270; A. Di Pace et al., 1992, Biophys. J. 63, 475-484). The analysis indicates that the heme pocket of the dimeric hemoglobin is characterized by an unusual rigidity and that the metal plays a different role in the transmission of the protein motions to the heme moiety in the dimeric hemoglobin and in myoglobin. Static and dynamic fluorescence measurements carried out at room temperature are in line with these conclusions.