Temperature-Dependent Olive Pomace Extraction for Obtaining Bioactive Compounds Preventing the Death of Murine Cortical Neurons.

High-pressure and temperature extraction (HPTE) can effectively recover bioactive compounds from olive pomace (OP). HPTE extract obtained by extracting OP with ethanol and water (50:50 v/v) at 180 °C for 90 min demonstrated a pronounced ability to preserve intracellular calcium homeostasis, shielding neurons from the harmful effects induced by N-methyl-d-aspartate (NMDA) receptor (NMDAR) overactivation, such as aberrant calpain activation. In this study, the extraction temperature was changed from 37 to 180 °C, and the extracts were evaluated for their antioxidant potency and ability to preserve crucial intracellular Ca2+-homeostasis necessary for neuronal survival. Additionally, to verify the temperature-induced activity of the extract, further extractions on the exhausted olive pomace were conducted, aiming to identify variations in the quality and quantity of extracted phenolic molecules through HPLC analysis. The results revealed a significant increase in bioactive compounds as a function of temperature variation, reaching 6.31 ± 0.09 mgCAE/mL extract for the extraction performed at 180 °C. Subsequent extraction of the exhausted residues yielded extracts that remained active in preventing calcium-induced cell death. Moreover, despite increased antiradical power, extracts re-treated at 180 °C did not display cell protection activity. Our results indicate that the molecules able to maintain physiological Ca2+-homeostasis in murine cortical neurons in conditions of cytotoxic stimulation of NMDAR are wholly recovered from olive pomace only following extraction performed at 180 °C.

Modulation of Plasmatic Matrix Metalloprotease 9: A Promising New Tool for Understanding the Variable Clinical Responses of Patients with Cystic Fibrosis to Cystic Fibrosis Transmembrane Conductance Regulator Modulators.

BACKGROUND: The most recent modulator combination, elexacaftor/tezacaftor/ivacaftor (Trikafta®), has been shown to improve clinical outcomes in most patients with cystic fibrosis (PwCF). Unfortunately, the clinical benefits are sometimes variable; thus, improving our knowledge of the possible causes of this variability can help reduce it. METHODS: Circulating mononuclear cells (CMCs) and plasma were collected from 16 PwCF (including those on Trikafta® therapy) and 4 non-CF subjects. Cystic fibrosis transmembrane conductance regulator (CFTR) activity and matrix metalloprotease 9 (MMP9) expression were monitored before and after therapy, together with some clinical parameters. The relationship between MMP9 expression and the modulation of the extracellular-regulated 1/2 (ERK1/2) and nuclear factor-kB (NF-kB) pathways was also analyzed. RESULTS: MMP9, markedly expressed in the CMCs and plasma of all the patients included in the study, was downregulated in the clinically responsive PwCF. In the non-responder, the MMP9 levels remained high. The modulation of MMP9 following treatment with Trikafta® may be controlled by the NF-kB pathway. CONCLUSIONS: These data strongly suggest that MMP9 downregulation is a potential biomarker of therapy efficacy and that it could be useful in understanding the molecular events underlying the variable clinical responses of patients to Trikafta®. This knowledge could be helpful for future studies of personalized medicine and thereby ensure improvements in individual responses to therapies.

Heteromerization of Dopamine D2 and Oxytocin Receptor in Adult Striatal Astrocytes.

The ability of oxytocin (OT) to interact with the dopaminergic system through facilitatory D2-OT receptor (OTR) receptor-receptor interaction in the limbic system is increasingly considered to play roles in social or emotional behavior, and suggested to serve as a potential therapeutic target. Although roles of astrocytes in the modulatory effects of OT and dopamine in the central nervous system are well recognized, the possibility of D2-OTR receptor-receptor interaction in astrocytes has been neglected. In purified astrocyte processes from adult rat striatum, we assessed OTR and dopamine D2 receptor expression by confocal analysis. The effects of activation of these receptors were evaluated in the processes through a neurochemical study of glutamate release evoked by 4-aminopyridine; D2-OTR heteromerization was assessed by co-immunoprecipitation and proximity ligation assay (PLA). The structure of the possible D2-OTR heterodimer was estimated by a bioinformatic approach. We found that both D2 and OTR were expressed on the same astrocyte processes and controlled the release of glutamate, showing a facilitatory receptor-receptor interaction in the D2-OTR heteromers. Biochemical and biophysical evidence confirmed D2-OTR heterodimers on striatal astrocytes. The residues in the transmembrane domains four and five of both receptors are predicted to be mainly involved in the heteromerization. In conclusion, roles for astrocytic D2-OTR in the control of glutamatergic synapse functioning through modulation of astrocytic glutamate release should be taken into consideration when considering interactions between oxytocinergic and dopaminergic systems in striatum.

The Involvement of Polyamines Catabolism in the Crosstalk between Neurons and Astrocytes in Neurodegeneration.

In mammalian cells, the content of polyamines is tightly regulated. Polyamines, including spermine, spermidine and putrescine, are involved in many cellular processes. Spermine oxidase specifically oxidizes spermine, and its deregulated activity has been reported to be linked to brain pathologies involving neuron damage. Spermine is a neuromodulator of a number of ionotropic glutamate receptors and types of ion channels. In this respect, the Dach-SMOX mouse model overexpressing spermine oxidase in the neocortex neurons was revealed to be a model of chronic oxidative stress, excitotoxicity and neuronal damage. Reactive astrocytosis, chronic oxidative and excitotoxic stress, neuron loss and the susceptibility to seizure in the Dach-SMOX are discussed here. This genetic model would help researchers understand the linkage between polyamine dysregulation and neurodegeneration and unveil the roles of polyamines in the crosstalk between astrocytes and neurons in neuroprotection or neurodegeneration.

Heterodimer of A2A and Oxytocin Receptors Regulating Glutamate Release in Adult Striatal Astrocytes.

BACKGROUND: Roles of astrocytes in the modulatory effects of oxytocin (OT) in central nervous system are increasingly considered. Nevertheless, OT effects on gliotransmitter release have been neglected. METHODS: In purified astrocyte processes from adult rat striatum, we assessed OT receptor (OTR) and adenosine A2A receptor expression by confocal analysis. The effects of receptors activation on glutamate release from the processes were evaluated; A2A-OTR heteromerization was assessed by co-immunoprecipitation and PLA. Structure of the possible heterodimer of A2A and OT receptors was estimated by a bioinformatic approach. RESULTS: Both A2A and OT receptors were expressed on the same astrocyte processes. Evidence for A2A-OTR receptor-receptor interaction was obtained by measuring the release of glutamate: OT inhibited the evoked glutamate release, while activation of A2A receptors, per se ineffective, abolished the OT effect. Biochemical and biophysical evidence for A2A-OTR heterodimers on striatal astrocytes was also obtained. The residues in the transmembrane domains 4 and 5 of both receptors are predicted to be mainly involved in the heteromerization. CONCLUSIONS: When considering effects of OT in striatum, modulation of glutamate release from the astrocyte processes and of glutamatergic synapse functioning, and the interaction with A2A receptors on the astrocyte processes should be taken into consideration.

Revisiting the Role of Leukocytes in Cystic Fibrosis.

Cystic fibrosis in characterized by pulmonary bacterial colonization and hyperinflammation. Lymphocytes, monocytes/macrophages, neutrophils, and dendritic cells of patients with CF express functional CFTR and are directly affected by altered CFTR expression/function, impairing their ability to resolve infections and inflammation. However, the mechanism behind and the contribution of leukocytes in the pathogenesis of CF are still poorly characterized. The recent clinical introduction of specific CFTR modulators added an important tool not only for the clinical management of the disease but also to the investigation of the pathophysiological mechanisms related to CFTR dysfunction and dysregulated immunity. These drugs treat the basic defect in cystic fibrosis (CF) by increasing CFTR function with improvement of lung function and quality of life, and may improve clinical outcomes also by correcting the dysregulated immune function that characterizes CF. Measure of CFTR function, protein expression profiling and several omics methods were used to identify molecular changes in freshly isolated leukocytes of CF patients, highlighting two roles of leukocytes in CF: one more generally related to the mechanism(s) causing immune dysregulation in CF and unresolved inflammation, and another more applicative role, which identifies in myeloid cells, an important tool predictive of the therapeutic response of CF patients. In this review we will summarize available data on CFTR expression and function in leukocyte populations and will discuss potential clinical applications based on available data.

Reactive Astrocytosis in a Mouse Model of Chronic Polyamine Catabolism Activation.

BACKGROUND: In the brain, polyamines are mainly synthesized in neurons, but preferentially accumulated in astrocytes, and are proposed to be involved in neurodegenerative/neuroinflammatory disorders and neuron injury. A transgenic mouse overexpressing spermine oxidase (SMOX, which specifically oxidizes spermine) in the neocortex neurons (Dach-SMOX mouse) was proved to be a model of increased susceptibility to excitotoxic injury. METHODS: To investigate possible alterations in synapse functioning in Dach-SMOX mouse, both cerebrocortical nerve terminals (synaptosomes) and astrocytic processes (gliosomes) were analysed by assessing polyamine levels, ezrin and vimentin content, glutamate AMPA receptor activation, calcium influx, and catalase activity. RESULTS: The main findings are as follows: (i) the presence of functional calcium-permeable AMPA receptors in synaptosomes from both control and Dach-SMOX mice, and in gliosomes from Dach-SMOX mice only; (ii) reduced content of spermine in gliosomes from Dach-SMOX mice; and (iii) down-regulation and up-regulation of catalase activity in synaptosomes and gliosomes, respectively, from Dach-SMOX mice. CONCLUSIONS: Chronic activation of SMOX in neurons leads to major changes in the astrocyte processes including reduced spermine levels, increased calcium influx through calcium-permeable AMPA receptors, and stimulation of catalase activity. Astrocytosis and the astrocyte process alterations, depending on chronic activation of polyamine catabolism, result in synapse dysregulation and neuronal suffering.

Identification of Potential Leukocyte Biomarkers Related to Drug Recovery of CFTR: Clinical Applications in Cystic Fibrosis.

The aim of this study was the identification of specific proteomic profiles, related to a restored cystic fibrosis transmembrane conductance regulator (CFTR) activity in cystic fibrosis (CF) leukocytes before and after ex vivo treatment with the potentiator VX770. We used leukocytes, isolated from CF patients carrying residual function mutations and eligible for Ivacaftor therapy, and performed CFTR activity together with proteomic analyses through micro-LC-MS. Bioinformatic analyses of the results obtained revealed the downregulation of proteins belonging to the leukocyte transendothelial migration and regulation of actin cytoskeleton pathways when CFTR activity was rescued by VX770 treatment. In particular, we focused our attention on matrix metalloproteinase 9 (MMP9), because the high expression of this protease potentially contributes to parenchyma lung destruction and dysfunction in CF. Thus, the downregulation of MMP9 could represent one of the possible positive effects of VX770 in decreasing the disease progression, and a potential biomarker for the prediction of the efficacy of therapies targeting the defect of Cl- transport in CF.

A Bioactive Olive Pomace Extract Prevents the Death of Murine Cortical Neurons Triggered by NMDAR Over-Activation.

We have recently demonstrated that bioactive molecules, extracted by high pressure and temperature from olive pomace, counteract calcium-induced cell damage to different cell lines. Here, our aim was to study the effect of the same extract on murine cortical neurons, since the preservation of the intracellular Ca2+-homeostasis is essential for neuronal function and survival. Accordingly, we treated neurons with different stimuli in order to evoke cytotoxic glutamatergic activation. In these conditions, the high-pressure and temperature extract from olive pomace (HPTOPE) only abolished the effects of N-methyl-d-aspartate (NMDA). Particularly, we observed that HPTOPE was able to promote the neuron rescue from NMDA-induced cell death. Moreover, we demonstrated that HPTOPE is endowed with the ability to maintain the intracellular Ca2+-homeostasis following NMDA receptor overactivation, protecting neurons from Ca2+-induced adverse effects, including aberrant calpain proteolytic activity. Moreover, we highlight the importance of the extraction conditions used that, without producing toxic molecules, allow us to obtain protecting molecules belonging to proanthocyanidin derivatives like procyanidin B2. In conclusion, we can hypothesize that HPTOPE, due to its functional and nontoxic properties on neuronal primary culture, can be utilized for future therapeutic interventions for neurodegeneration.

A2A-D2 Heteromers on Striatal Astrocytes: Biochemical and Biophysical Evidence.

Our previous findings indicate that A2A and D2 receptors are co-expressed on adult rat striatal astrocytes and on the astrocyte processes, and that A2A-D2 receptor⁻receptor interaction can control the release of glutamate from the processes. Functional evidence suggests that the receptor⁻receptor interaction was based on heteromerization of native A2A and D2 receptors at the plasma membrane of striatal astrocyte processes. We here provide biochemical and biophysical evidence confirming that receptor⁻receptor interaction between A2A and D2 receptors at the astrocyte plasma membrane is based on A2A-D2 heteromerization. To our knowledge, this is the first direct demonstration of the ability of native A2A and D2 receptors to heteromerize on glial cells. As striatal astrocytes are recognized to be involved in Parkinson's pathophysiology, the findings that adenosine A2A and dopamine D2 receptors can form A2A-D2 heteromers on the astrocytes in the striatum (and that these heteromers can play roles in the control of the striatal glutamatergic transmission) may shed light on the molecular mechanisms involved in the pathogenesis of the disease.

A new human calpastatin skipped of the inhibitory region protects calpain-1 from inactivation and degradation.

Several human acute and chronic diseases involve calpain over-activation. However, the mechanistic linkages between the etiology and the progression of cell damages are not yet completely understood. Here we show that different human cells and tissues, including brain tumor specimens, cell lines of nerve origin, breast tumor samples and peripheral blood mononuclear cells from healthy donors, express a calpastatin form that lacks all the exons coding for the domains responsible of calpain inhibition. The open reading frame of this new form of calpastatin, named hcast 3-25, starts inside the L-domain (exons 2 and 3) and continues with the exons from 25 to 29 that code for the conserved C-terminal tail shared by all the full-length calpastatins. We have here observed that unlike the other calpastatins forms, that are predominantly Δ3 splice variants, hcast 3-25 is endowed with exon 3. At a functional level, recombinant hcast 3-25 operates as a positive modulator of calpain-1 in vitro by preventing 1) calpain-1-mediated proteolytic degradation of the activated enzyme and 2) binding to calpain-1 of inhibitory calpastatins that contain the L-domain. Thus hcast 3-25 can be considered as a novel member and possible modulator of the calpain/calpastatin system acting by a mechanism alternative to inhibition.

Production and Purification of Recombinant Calpastatin.

The production of recombinant calpastatin in E. coli has become an efficient tool to obtain discrete amounts of a specific calpastatin species that can be present concomitantly with other calpastatin fragments/forms in the same tissue or cell type in a given condition. Indeed, at present, it is still difficult to distinguish the various calpastatin species for several reasons among which: calpastatins differ only at the N-terminus, can undergo calpain-dependent cleavage generating discrete fragments, and show anomalous electrophoretic mobility. Another benefit of using recombinant calpastatin is that, as the wild-type forms, it is heat resistant and thus can be efficiently isolated taking advantage of a simple quick purification step. Finally, the lack of posttranslational modifications makes recombinant calpastatin species particularly suitable for studying in vitro the biochemical features of specific parts of the inhibitor that following controlled posttranslational modifications change their functional interaction with calpain. In this chapter, we describe, starting from the mRNA sequence, how to produce rat calpastatin Type I in E. coli. We use routinely the same method, with minor modifications, for the production of other calpastatin species deriving from different tissues or organisms and calpastatin constructs having only specific domains. The possibility to obtain large amounts of a single calpain inhibitor form is a great advantage for studying the calpain/calpastatin system in vitro.

Isolation of Endogenous Calpastatin.

We here describe the purification of calpastatin from human erythrocytes. When calpastatin is purified from tissues, it is necessary to measure its inhibitory activity against calpain in the presence of Ca2+ to specifically identify the protein. Thus, the purification steps necessary to obtain the inhibitor protein were originally designed to obtain calpain from the same tissue. For this reason, in addition to calpastatin purification, we also include a method for purifying human erythrocyte calpain and globin. We routinely use these two components for assaying calpastatin inhibition.

Immunoblotting for Calpastatin Expression.

Immunoblotting is a procedure routinely used to analyze calpastatin expression. However, immunoblotting alone may not be adequate for this task, since calpastatin isoforms can vary by tissue, can be modified by partial digestion, and can undergo posttranslational modifications. Here we describe a method for more precise evaluation of calpastatin expression by combining immunoblot analysis with an assay for the inhibitory activity of a single calpastatin species isolated by SDS-PAGE and protein elution from the gel.

Cell protection from Ca2+-overloading by bioactive molecules extracted from olive pomace.

We are reporting in the present study that molecules extracted from olive pomace prevent cell death induced by Ca2+-overloading in different cell types. Exposure of cells to these molecules counteracts the Ca2+-induced cell damages by reducing the activation of the Ca2+-dependent protease calpain, acting possibly through the modification of the permeability to Ca2+ of the plasma membrane. The purification step by RP-HPLC suggests that effective compound(s), differing from the main biophenols known to be present in the olive pomace extract, could be responsible for this effect. Our observations suggest that bioactive molecules present in the olive pomace could be potential candidates for therapeutic applications in pathologies characterised by alterations of intracellular Ca2+ homeostasis.

Unexpected role of the L-domain of calpastatin during the autoproteolytic activation of human erythrocyte calpain.

Autoproteolysis of human erythrocyte calpain-1 proceeds in vitro at high [Ca2+], through the conversion of the 80-kDa catalytic subunit into a 75-kDa activated enzyme that requires lower [Ca2+] for catalysis. Importantly, here we detect a similar 75 kDa calpain-1 form also in vivo, in human meningiomas. Although calpastatin is so far considered the specific inhibitor of calpains, we have previously identified in rat brain a calpastatin transcript truncated at the end of the L-domain (cast110, L-DOM), coding for a protein lacking the inhibitory units. Aim of the present study was to characterize the possible biochemical role of the L-DOM during calpain-1 autoproteolysis in vitro, at high (100 µM) and low (5 µM) [Ca2+]. Here we demonstrate that the L-DOM binds the 80 kDa proenzyme in the absence of Ca2+ Consequently, we have explored the ability of the 75 kDa activated protease to catalyze at 5 µM Ca2+ the intermolecular activation of native calpain-1 associated with the L-DOM. Notably, this [Ca2+] is too low to promote the autoproteolytic activation of calpain-1 but enough to support the catalysis of the 75 kDa calpain. We show for the first time that the L-DOM preserves native calpain-1 from the degradation mediated by the 75 kDa form. Taken together, our data suggest that the free L-domain of calpastatin is a novel member of the calpain/calpastatin system endowed with a function alternative to calpain inhibition. For this reason, it will be crucial to define the intracellular relevance of the L-domain in controlling calpain activation/activity in physiopathological conditions having altered Ca2+ homeostasis.

Calpain-1 resident in lipid raft/caveolin-1 membrane microdomains plays a protective role in endothelial cells.

We are here reporting that calpain-1 is a constitutive component of a distinct lipid raft/caveolin-1 microdomain isolated from bEnd5 cells in association with endothelial nitric oxide synthase (eNOS) and heat shock protein 90 (HSP90). Perturbations in intracellular calcium concentration by Ca2+-ionophore A23187 or prolonged cell exposure to high glucose induce a significant decrease in the level of eNOS accompanied by a recruitment of additional HSP90 molecules at this site. In these conditions the cells are more resistant to cell death by Ca2+ overload. The decrease of eNOS has been due not only to its Ca2+-mediated release from the caveolin-1 aggregates but also to its digestion by calpain-1. The specific involvement of calpain-1 in digestion of eNOS is supported by the preventive effect of a synthetic calpain inhibitor (CI-2) and by the absence of calpain-2 and calpastatin in the caveolin-1 microdomain. These results suggest that the protein adjustments observed in lipid raft/caveolin-1 microdomains could be visualized as a process required to protect the cells against NO overproduction and aberrant calpain activation. Alterations in eNOS, calpain-1 and HSP90 levels have been observed in aorta of Zucker Diabetic Rats (ZDR). The loss of HSP90 occurring in these animals indicates an aberrant activation of calpain and thereby the transition from a physiological to a pathological cell condition.

Abnormal activation of calpain and protein kinase Cα promotes a constitutive release of matrix metalloproteinase 9 in peripheral blood mononuclear cells from cystic fibrosis patients.

Matrix metalloproteinase 9 (MMP9) is physiologically involved in remodeling the extracellular matrix components but its abnormal release has been observed in several human pathologies. We here report that peripheral blood mononuclear cells (PBMCs), isolated from cystic fibrosis (CF) patients homozygous for F508del-cystic fibrosis transmembrane conductance regulator (CFTR), express constitutively and release at high rate MMP9 due to the alteration in their intracellular Ca(2+) homeostasis. This spontaneous and sustained MMP9 secretion may contribute to the accumulation of this protease in fluids of CF patients. Conversely, in PBMCs isolated from healthy donors, expression and secretion of MMP9 are undetectable but can be evoked, after 12 h of culture, by paracrine stimulation which also promotes an increase in [Ca(2+)]i. We also demonstrate that in both CF and control PBMCs the Ca(2+)-dependent MMP9 secretion is mediated by the concomitant activation of calpain and protein kinase Cα (PKCα), and that MMP9 expression involves extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) phosphorylation. Our results are supported by the fact that either the inhibition of Ca(2+) entry or chelation of [Ca(2+)]i as well as the inhibition of single components of the signaling pathway or the restoration of CFTR activity all promote the reduction of MMP9 secretion.

Natural Killer (NK)/melanoma cell interaction induces NK-mediated release of chemotactic High Mobility Group Box-1 (HMGB1) capable of amplifying NK cell recruitment.

In this study we characterize a new mechanism by which Natural Killer (NK) cells may amplify their recruitment to tumors. We show that NK cells, upon interaction with melanoma cells, can release a chemotactic form of High Mobility Group Box-1 (HMGB1) protein capable of attracting additional activated NK cells. We first demonstrate that the engagement of different activating NK cell receptors, including those mainly involved in tumor cell recognition can induce the active release of HMGB1. Then we show that during NK-mediated tumor cell killing two HMGB1 forms are released, each displaying a specific electrophoretic mobility possibly corresponding to a different redox status. By the comparison of normal and perforin-defective NK cells (which are unable to kill target cells) we demonstrate that, in NK/melanoma cell co-cultures, NK cells specifically release an HMGB1 form that acts as chemoattractant, while dying tumor cells passively release a non-chemotactic HMGB1. Finally, we show that Receptor for Advanced Glycation End products is expressed by NK cells and mediates HMGB1-induced NK cell chemotaxis. Proteomic analysis of NK cells exposed to recombinant HMGB1 revealed that this molecule, besides inducing immediate chemotaxis, also promotes changes in the expression of proteins involved in the regulation of the cytoskeletal network. Importantly, these modifications could be associated with an increased motility of NK cells. Thus, our findings allow the definition of a previously unidentified mechanism used by NK cells to amplify their response to tumors, and provide additional clues for the emerging role of HMGB1 in immunomodulation and tumor immunity.

Physiological Roles of Calpain 1 Associated to Multiprotein NMDA Receptor Complex.

We have recently demonstrated that in resting conditions calpain 1, but not calpain 2, is specifically associated to the N-Methyl-D-Aspartate receptor (NMDAR) multiprotein complex. We are here reporting that in SKNBE neuroblastoma cells or in freshly isolated nerve terminals from adult rat hippocampus, the proteolytic activity of calpain 1 resident at the NMDAR is very low under basal conditions and greatly increases following NMDAR stimulation. Since the protease resides at the NMDAR in saturating amounts, variations in Ca2+ influx promote an increase in calpain 1 activity without affecting the amount of the protease originally associated to NMDAR. In all the conditions examined, resident calpain 1 specifically cleaves NR2B at the C-terminal region, leading to its internalization together with NR1 subunit. While in basal conditions intracellular membranes include small amounts of NMDAR containing the calpain-digested NR2B, upon NMDAR stimulation nearly all the receptor molecules are internalized. We here propose that resident calpain 1 is involved in NMDAR turnover, and following an increase in Ca2+ influx, the activated protease, by promoting the removal of NMDAR from the plasma membranes, can decrease Ca2+ entrance through this channel. Due to the absence of calpastatin in such cluster, the activity of resident calpain 1 may be under the control of HSP90, whose levels are directly related to the activation of this protease. Observations of different HSP90/calpain 1 ratios in different ultrasynaptic compartments support this conclusion.