Introduction

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Targeting the nitric oxide signalling pathway to modulate platelet function

Nitric oxide (NO) negatively regulates platelets and impaired NO signalling can lead to arterial thrombosis. The source of platelet-derived NO is unclear with recent proposals of NO synthase (NOS) independent NO sources, such as S-nitrosothiols (RSNOs) and inorganic nitrate/nitrite. Sildenafil citrate, a phosphodiesterase 5 (PDE5) inhibitor, enhances NO/cGMP signals in cells expressing PDE5 such as platelets. The aims of this study were to investigate the antiplatelet properties of sildenafil, its mechanism of action and to determine the upstream sources of NO affecting platelet function. The functional effect of sildenafil was determined using a range of in vitro and in vivo platelet assays. The mechanism of action of sildenafil and upstream sources of NO/cGMP signals were assessed pharmacologically using established methods of in vitro and in vivo platelet aggregation. Bioconversion of nitrate to nitrite was determined using gas-phase chemiluminescence. The functional significance of NO/cGMP signalling events in platelets were investigated in vivo in W.T and eNOS-/- (a model of vascular dysfunction) mice. Sildenafil exerted an antiplatelet effect by enhancing transient NO/cGMP signals generated by platelets independent of NOS activity in vitro. Inhibition of proposed mechanisms of NO release from RSNOs did not modify the inhibitory effect of sildenafil suggesting that RSNOs did not mediate platelet NO/cGMP signals. Nitrite was able to drive inhibitory cGMP signalling events in platelets in vitro. Furthermore, nitrate inhibited platelet function in eNOS-/- mice in vivo following enhanced bioconversion to nitrite, potentially as a compensatory mechanism due to impaired NO signalling. In conclusion, inorganic nitrate/nitrite may critically regulate platelets following bioconversion to NO and dietary sources of nitrate/nitrite may generate compensatory NO during vascular disease. Furthermore, sildenafil may be beneficial in reducing the risk of platelet-driven cardiovascular disease by enhancing NO/cGMP signalling derived from both enzymic and inorganic sources and restoring impaired NO signalling during endothelial dysfunction.Open Acces

PPAR Medicines and Human Disease: The ABCs of It All

ATP-dependent binding cassette (ABC) transporters are a family of transmembrane proteins that pump a variety of hydrophobic compounds across cellular and subcellular barriers and are implicated in human diseases such as cancer and atherosclerosis. Inhibition of ABC transporter activity showed promise in early preclinical studies; however, the outcomes in clinical trials with these agents have not been as encouraging. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that regulate genes involved in fat and glucose metabolism, and inflammation. Activation of PPAR signaling is also reported to regulate ABC gene expression. This suggests the potential of PPAR medicines as a novel means of controlling ABC transporter activity at the transcriptional level. This paper summarizes the advances made in understanding how PPAR medicines affect ABC transporters, and the potential implications for impacting on human diseases, in particular with respect to cancer and atherosclerosis

Il miraggio dell'esistenza libera e dignitosa

Il saggio riflette sulla natura dell’attività lavorativa come mezzo e strumento che, attraverso la retribuzione, deve garantire un’esistenza libera e dignitosa. Si esaminano anche la difficoltà nell’applicare l’art. 36 Cost., oltre che sul significato che tale norma costituzionale ha assunto nel tempo grazie all’interpretazione offerta dai giudici di merito, di legittimità e costituzionale. Questo porta a una discussione sulla previsione, attualmente molto dibattuta, relativa al salario minimo. Poiché i Costituenti avevano previsto che questa garanzia sarebbe stata fornita attraverso i contratti collettivi nazionali di lavoro, come stabilito dall’art. 39, quarto comma, Cost., e siccome tale norma non è stata attuata, si verificano sempre più frequentemente casi di sfruttamento dei lavoratori che non sono in alcun modo compatibili con la Costituzione. La Direttiva UE 2022/2041 sembra rappresentare un passo in avanti nell’assicurare una retribuzione dignitosa che consenta di condurre una vita degna. Questo non mira a sostituire la contrattazione collettiva, ma a rafforzarla al fine di rispettare l’imperativo costituzionale. Tuttavia, nel contesto di questa normativa, sono messi in luce anche alcuni punti problematici che richiedono attenzione

Una nuova stagione di riforme costituzionali?

L'editoriale si interroga sulle numerose proposte di riforma costituzionale a sei mesi dall'avvio della XIX Legislatur

La necessità di ripensare il rapporto con gli "organi di garanzia" in un sistema parlamentare monocamerale

l saggio prende l’abbrivio da un’ipotesi di lavoro: il definitivo superamento dell’attuale sistema bicamerale italiano, con la creazione di un Parlamento monocamerale. Questa evenienza potrebbe costituire una soluzione alle pesanti problematiche che affliggono il parlamentarismo italiano ormai da tempo. Da questa possibilità, il contributo ragiona attorno alle funzioni degli organi di garanzia (Corte costituzionale e Presidente della Repubblica) in questo quadro rinnovato, interrogandosi su come la semplificazione del bicameralismo incida nell’asseto globale dei rapporti interorganici. Dal punto di vista degli organi di garanzia, tale innovazione produce un necessario ripensamento di alcuni poteri o di usi consuetudinari che di questi si fanno

Lo spazio-tempo del d.d.l. Calderoli: accelerazioni e rinvii oltre l'attuazione procedurale

Il paper si occupa di analizzare il d.d.l. Calderoli relativo all'attuazione della c.d. autonomia differenziata con particolare riguardo all'iter procedural

Role of inorganic nitrate and nitrite in driving nitric oxide-cGMP-mediated inhibition of platelet aggregation in vitro and in vivo

This is the peer reviewed version of the article, which has been published in final form at [doi: 10.1111/jth.12711. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.Nitric oxide (NO) is a critical negative regulator of platelets that is implicated in the pathology of thrombotic diseases. Platelets generate NO, but the presence and functional significance of NO synthase (NOS) in platelets is unclear. Inorganic nitrate/nitrite is increasingly being recognized as a source of bioactive NO, although its role in modulating platelets during health and vascular dysfunction is incompletely understood. METHODS: We investigated the functional significance and upstream sources of NO-cGMP signaling events in platelets by using established methods for assessing in vitro and in vivo platelet aggregation, and assessed the bioconversion of inorganic nitrate to nitrite during deficiency of endothelial NOS (eNOS). RESULTS: The phosphodiesterase 5 (PDE5) inhibitor sildenafil inhibited human platelet aggregation in vitro. This inhibitory effect was abolished by a guanylyl cyclase inhibitor and NO scavengers, but unaffected by NOS inhibition. Inorganic nitrite drove cGMP-mediated inhibition of human platelet aggregation in vitro and nitrate inhibited platelet function in eNOS(-/-) mice in vivo in a model of thromboembolic radiolabeled platelet aggregation associated with an enhanced plasma nitrite concentration as compared with wild-type mice. CONCLUSIONS: Platelets generate transient, endogenous cGMP signals downstream of NO that are primarily independent of NOS and may be enhanced by inhibition of PDE5. Furthermore, nitrite can generate transient NO-cGMP signals in platelets. The absence of eNOS leads to enhanced plasma nitrite levels following nitrate administration in vivo, which negatively impacts on platelet function. Our data suggest that inorganic nitrate exerts an antiplatelet effect during eNOS deficiency, and, potentially, that dietary nitrate may reduce platelet hyperactivity during endothelial dysfunction.British Pharmacological Society Integrative Pharmacology Fund Pump Priming Grant

Dynamical modelling of the human larynx in phonation

Producing an accurate model of the human voice has been the goal of researchers for a very long time, but is extremely challenging due to the complexity surrounding the way in which the voice functions. One of the more complicated aspects of modelling the voice is the fluid dynamics of the airflow, by which the process of self-oscillation of the vocal folds is sustained. This airflow also provides the only means by which the ventricular bands (two vocal fold-like structures located a short distance above the vocal folds) are driven into self-oscillation. These have been found to play a significant role in various singing styles and in voice pathologies. This study considers the airflow and flow-structure interaction in an artificial up-scaled model of the human larynx, including self-oscillating vocal folds and fixed ventricular bands. As the majority of any significant fluid-structure interaction takes place between structures found within the larynx, this thesis is limited only to examining this component of the voice organ. Particle Image Velocimetry (PIV) has been used to produce full field measurements of the flow velocity for the jet emerging from the oscillating vocal folds. An important advance in this study is the ability to observe the glottal jet from the point at which it emerges from the vocal folds, thus permitting a more complete view of the overall jet geometry within the laryngeal ventricle than in previous work. Ensemble-averaged PIV results are presented for the experimental model at different phase steps, both with and without ventricular bands, to examine their impact on the dynamics of the human larynx and the glottal jet. Finally, the three-dimensional nature of the glottal jet is considered in order to further understand and test currently held assumptions about this aspect of the jet dynamics. This was achieved by undertaking PIV in a plane perpendicular to that already considered. It is shown that the ventricular bands have an impact on the flow separation point of the glottal jet and on the deflection of the jet centreline. Furthermore, the dynamics of the vocal folds alters when ventricular bands are present, but the glottal jet is found to exhibit similar three-dimensional behaviour whether or not ventricular bands are present