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Papers by Valentina Carabelli

Journal of Medicinal Chemistry, Dec 23, 2010

The synthesis and the physico-chemical and biological characterisation of a series of carnosine a... more The synthesis and the physico-chemical and biological characterisation of a series of carnosine amides bearing on the amido group alkyl substituents endowed with different lipophilicity are described. All synthesised products display carnosine-like properties differentiating from the lead for their high serum stability. They are able to complex Cu 2+ ions at physiological pH with the same stoichiometry as carnosine. The newly synthesised compounds display highly significant copper ion sequestering ability and are capable of protecting LDL from oxidation catalysed by Cu 2+ ions, the most active compounds being the most hydrophilic ones. All the synthesised amides show quite potent carnosine-like HNE quenching activity; in particular, 7d, the member of the series selected for this kind of study, is able to cross the blood-brain barrier (BBB) and to protect primary mouse hippocampal neurons against HNE-induced death. These products can be considered metabolically stable analogues of carnosine and are worthy of additional investigation as potential neuroprotective agents.

The Journal of Physiology, Jun 1, 2002

Nitric oxide (NO) regulates the release of catecholamines from the adrenal medulla but the molecu... more Nitric oxide (NO) regulates the release of catecholamines from the adrenal medulla but the molecular targets of its action are not yet well identified. Here we show that the NO donor sodium nitroprusside (SNP, 200 µM) causes a marked depression of the single Ca V 1 L-channel activity in cell-attached patches of bovine chromaffin cells. SNP action was complete within 3-5 min of cell superfusion. In multichannel patches the open probability (NP o) decreased by ~60 % between 0 and +20 mV. Averaged currents over a number of traces were proportionally reduced and showed no drastic changes to their time course. In single-channel patches the open probability (P o) at +10 mV decreased by the same amount as that of multichannel patches (~61 %). Such a reduction was mainly associated with an increased probability of null sweeps and a prolongation of mean shut times, while first latency, mean open time and single-channel conductance were not significantly affected. Addition of the NO scavenger carboxy-PTIO or cell treatment with the guanylate cyclase inhibitor ODQ prevented the SNP-induced inhibition. 8-Bromo-cyclicGMP (8-Br-cGMP; 400 µM) mimicked the action of the NO donor and the protein kinase G blocker KT-5823 prevented this effect. The depressive action of SNP was preserved after blocking the cAMP-dependent upregulatory pathway with the protein kinase A inhibitor H89. Similarly, the inhibitory action of 8-Br-cGMP proceeded regardless of the elevation of cAMP levels, suggesting that cGMP/PKG and cAMP/PKA act independently on L-channel gating. The inhibitory action of 8-Br-cGMP was also independent of the G protein-induced inhibition of L-channels mediated by purinergic and opiodergic autoreceptors. Since Ca 2+ channels contribute critically to both the local production of NO and catecholamine release, the NO/PKG-mediated inhibition of neuroendocrine L-channels described here may represent an important autocrine signalling mechanism for controlling the rate of neurotransmitter release from adrenal glands.

International Journal of Developmental Neuroscience, Dec 1, 2015

The Journal of Physiology, Mar 2, 2017

Mouse chromaffin cells (MCCs) generate spontaneous burst-firing that causes large increases of Ca... more Mouse chromaffin cells (MCCs) generate spontaneous burst-firing that causes large increases of Ca 2+-dependent catecholamine release, and is thus a key mechanism for regulating the functions of MCCs. r With the aim to uncover a physiological role for burst-firing we investigated the effects of acidosis on MCC activity. r Lowering the extracellular pH (pH o) from 7.4 to 6.6 induces cell depolarizations of 10-15 mV that generate bursts of ß330 ms at 1-2 Hz and a 7.4-fold increase of cumulative catecholamine-release. r Burst-firing originates from the inhibition of the pH-sensitive TASK-1-channels and a 60% reduction of BK-channel conductance at pH o 6.6. r Blockers of the two channels (A1899 and paxilline) mimic the effects of pH o 6.6, and this is reverted by the Cav1 channel blocker nifedipine. r MCCs act as pH-sensors. At low pH o , they depolarize, undergo burst-firing and increase catecholamine-secretion, generating an effective physiological response that may compensate for the acute acidosis and hyperkalaemia generated during heavy exercise and muscle fatigue.

Pflügers Archiv: European Journal of Physiology, Oct 13, 2020

To understand the working principles of the nervous system is key to figure out its electrical ac... more To understand the working principles of the nervous system is key to figure out its electrical activity and how this activity spreads along the neuronal network. It is therefore crucial to develop advanced techniques aimed to record in real time the electrical activity, from compartments of single neurons to populations of neurons, to understand how higher functions emerge from coordinated activity. To record from single neurons, a technique will be presented to fabricate patch pipettes able to seal on any membrane with a single glass type and whose shanks can be widened as desired. This dramatically reduces access resistance during whole-cell recording allowing fast intracellular and, if required, extracellular perfusion. To simultaneously record from many neurons, biocompatible probes will be described employing multi-electrodes made with novel technologies, based on diamond substrates. These probes also allow to synchronously record exocytosis and neuronal excitability and to stimulate neurons. Finally, to achieve even higher spatial resolution, it will be shown how voltage imaging, employing fast voltagesensitive dyes and two-photon microscopy, is able to sample voltage oscillations in the brain spatially resolved and voltage changes in dendrites of single neurons at millisecond and micrometre resolution in awake animals.

Frontiers in Cellular Neuroscience, Mar 21, 2023

Biosensors

Platelets are probably the most accessible human cells to study exocytosis by amperometry. These ... more Platelets are probably the most accessible human cells to study exocytosis by amperometry. These cell fragments accumulate biological amines, serotonin in particular, using similar if not the same mechanisms as those employed by sympathetic, serotoninergic, and histaminergic neurons. Thus, platelets have been widely recognized as a model system to study certain neurological and psychiatric diseases. Platelets release serotonin by exocytosis, a process that entails the fusion of a secretory vesicle to the plasma membrane and that can be monitored directly by classic single cell amperometry using carbon fiber electrodes. However, this is a tedious technique because any given platelet releases only 4–8 secretory d-granules. Here, we introduce and validate a diamond-based multielectrode array (MEA) device for the high-throughput study of exocytosis by human platelets. This is probably the first reported study of human tissue using an MEA, demonstrating that they are very interesting lab...

Frontiers in Cell and Developmental Biology

GTPases of the Rho family are components of signaling pathways linking extracellular signals to t... more GTPases of the Rho family are components of signaling pathways linking extracellular signals to the control of cytoskeleton dynamics. Among these, RAC1 plays key roles during brain development, ranging from neuronal migration to neuritogenesis, synaptogenesis, and plasticity. RAC1 activity is positively and negatively controlled by guanine nucleotide exchange factors (GEFs), guanosine nucleotide dissociation inhibitors (GDIs), and GTPase-activating proteins (GAPs), but the specific role of each regulator in vivo is poorly known. ARHGAP15 is a RAC1-specific GAP expressed during development in a fraction of migrating cortical interneurons (CINs) and in the majority of adult CINs. During development, loss of ARHGAP15 causes altered directionality of the leading process of tangentially migrating CINs, along with altered morphology in vitro. Likewise, time-lapse imaging of embryonic CINs revealed a poorly coordinated directional control during radial migration, possibly due to a hyper-ex...

Pflügers Archiv - European Journal of Physiology

The Journal of Physiology

The oligomeric form of the peptide amyloid beta 42 (Abeta42) contributes to the development of sy... more The oligomeric form of the peptide amyloid beta 42 (Abeta42) contributes to the development of synaptic abnormalities and cognitive impairments associated with Alzheimer's disease (AD). To date, there is a gap in knowledge regarding how Abeta42 alters the elementary parameters of GABAergic synaptic function. Here we found that Abeta42 increased the frequency and amplitude of miniature GABAergic currents as well as the amplitude of evoked inhibitory postsynaptic currents. When we focused on paired pulse depression (PPD) to establish whether GABA release probability was affected by Abeta42, we did not observe any significant change. On the other hand, a more detailed investigation of the presynaptic effects induced by Abeta42 by means of multiple probability fluctuation analysis and cumulative amplitude analysis showed an increase in both the size of the readily releasable pool responsible for synchronous release and the number of release sites. We further explored whether ryanodi...

We recorded spontaneous extracellular action potentials (eAPs) from rat chromaffin cells (CCs) at... more We recorded spontaneous extracellular action potentials (eAPs) from rat chromaffin cells (CCs) at 37°C using microelectrode-arrays (MEAs) and compared them with intracellularly recorded APs (iAPs) through conventional patch-clamp recordings at 22°C. We show the existence of two distinct firing modes on MEAs: a ~ 4 Hz irregular continuous firing and a frequent intermittent firing mode where periods of high-intraburst frequency (~ 8 Hz) of ~ 7 s duration are interrupted by silent periods of ~ 12 s. eAPs occurred either as negative- or positive-going signals depending on the contact between cell and microelectrode: either predominantly controlled by junction-membrane ion channels (negative-going) or capacitive/ohmic coupling (positive-going).Negative-going eAPs were found to represent the trajectory of the Na+, Ca2+ and K+ currents passing through the cell area in tight contact with the microelectrode during an AP (point-contact junction). The inward Nav component of eAPs was blocked b...

2022 IEEE International Workshop on Metrology for Industry 4.0 & IoT (MetroInd4.0&IoT)

Frontiers in Neuroscience, 2016

Cell Calcium, 2006

Evidence is accumulating on a key role of T-type channels in neurotransmitter release. Recent wor... more Evidence is accumulating on a key role of T-type channels in neurotransmitter release. Recent works have brought undisputable proofs that T-type channels are capable of controlling hormone and neurotransmitters release in association with exocytosis of large dense-core and synaptic vesicles. T-type channel-secretion coupling is not as ubiquitous as that shown for N-and P/Q-type channels in central neurons. In this case, the high-density of Ca v 2 channel types and co-localization to the release sites ensure high rates of vesicle release and synchronous synaptic responses. Nevertheless, when sufficiently expressed in distal dendrites and neurosecretory cells, T-type channels are able to drive the fast fusion of vesicles ready for release during "low-threshold" Ca 2+-entry. T-type channels appear effectively coupled to fast vesicle depletion and may possibly regulate other Ca 2+-dependent processes like vesicle recycling and vesicle mobilization from a reserve pool that are important mechanisms controlling synaptic activity during sustained stimulation. Here, we will briefly review the main findings that assign a specific task to T-type channels in fast exocytosis discussing their possible involvement in the control of the Ca 2+-dependent processes regulating synaptic activity and vesicular hormone release.