New/emerging psychoactive substances and associated psychopathological consequences

Submitted 24 November 2018, Revised 18 June 2019, Accepted 26 June 2019, Published online 22 July 2019BackgroundThe present paper provides an updated review of both the large number of new/novel/emerging psychoactive substances (NPS) and their associated psychopathological consequences. Focus was here given on identification of those NPS being commented in specialised online sources and the related short-/long-term psychopathological and medical ill-health effects.MethodsNPS have been identified through an innovative crawling/navigating software, called the 'NPS.Finder®', created in order to facilitate the process of early recognition of NPS online. A range of information regarding NPS, including chemical and street names; chemical formula; three-dimensional image and anecdotally reported clinical/psychoactive effects, were here made available.ResultsUsing the 'NPS.Finder®' approach, a few thousand NPS were here preliminarily identified, a number which is about 4-fold higher than those figures suggested by European and international drug agencies. NPS most commonly associated with the onset of psychopathological consequences included here synthetic cannabinoids/cannabimimetics; new synthetic opioids; ketamine-like dissociatives; novel stimulants; novel psychedelics and several prescription and over-the-counter medicines.ConclusionsThe ever-increasing changes in terms of recreational psychotropics' availability represent a relatively new challenge for psychiatry, as the pharmacodynamics and pharmacokinetics of many NPS have not been thoroughly understood. Health/mental health professionals should be informed about the range of NPS; their intake modalities; their psychoactive sought-after effects; the idiosyncratic psychotropics' combinations and finally, their medical and psychopathological risks.Peer reviewe

Defective ENaC processing and function in tissue kallikrein-deficient mice

An inverse relationship exists between urinary tissue kallikrein (TK) excretion and blood pressure in humans and rodents. In the kidney TK is synthesized in large amounts in the connecting tubule and is mainly released into the urinary fluid where its function remains unknown. In the present study mice with no functional gene coding for TK (TK-/-) were used to test whether the enzyme regulates apically expressed sodium transporters. Semiquantitative immunoblotting of the renal cortex revealed an absence of the 70-kDa form of gamma-ENaC in TK-/- mice. Urinary Na+ excretion after amiloride injection was blunted in TK-/- mice, consistent with reduced renal ENaC activity. Amiloride-sensitive transepithelial potential difference in the colon, where TK is also expressed, was decreased in TK-/- mice, whereas amiloride-sensitive alveolar fluid clearance in the lung, where TK is not expressed, was unchanged. In mice lacking the B2 receptor for kinins, the abundance of the 70-kDa form of gamma-ENaC was increased, indicating that its absence in TK-/- mice is not kinin-mediated. Incubation of membrane proteins from renal cortex of TK-/- mice with TK resulted in the appearance of the 70-kDa band of the gamma-ENaC, indicating that TK was able to promote gamma-ENaC cleavage in vitro. Finally, in mouse cortical collecting ducts isolated and microperfused in vitro, the addition of TK in the luminal fluid increased significantly intracellular Na+ concentration, consistent with an activation of the luminal entry of the cation. The results demonstrate that TK, like several other proteases, can activate ENaC in the kidney and the colon

The guinea-pig tracheal potential difference as an in vivo model for the study of epithelial sodium channel function in the airways

Background and purpose: The epithelial sodium channel (ENaC) is a key regulator of airway mucosal hydration and mucus clearance. Negative regulation of airway ENaC function is predicted to be of clinical benefit in the cystic fibrosis lung. The aim of this study was to develop a small animal model to enable the direct assessment of airway ENaC function in vivo. Experimental approach: Tracheal potential difference (TPD) was utilized as a measure of airway epithelial ion transport in the guinea-pig. ENaC activity in the trachea was established with a dose-response assessment to a panel of well-characterized direct and indirect pharmacological modulators of ENaC function, delivered by intra-tracheal (i.t.) instillation. Key results: The TPD in anaesthetized guinea-pigs was attenuated by the direct ENaC blockers: amiloride, benzamil and CF552 with ED 50 values of 16, 14 and 0.2 μg kg -1 (i.t.), respectively. 5-(N-Ethyl-N-isopropyl) amiloride, a structurally related compound but devoid of activity on ENaC, was without effect on the TPD. Intra-tracheal dosing of the Kunitz-type serine protease inhibitors aprotinin and placental bikunin, which have previously been demonstrated to inhibit proteolytic activation of ENaC, likewise potently attenuated TPD in guinea-pigs, whereas α 1-antitrypsin and soya bean trypsin inhibitor were without effect. Conclusions and implications: The pharmacological sensitivity of the TPD to amiloride analogues and also to serine protease inhibitors are both consistent with that of ENaC activity in the guinea-pig trachea. The guinea-pig TPD therefore represents a suitable in vivo model of human airway epithelial ion transport. © 2008 Macmillan Publishers Limited All rights reserved

Energetic and Structural Basis for Activation of the Epithelial Sodium Channel by Matriptase

Limited proteolysis, accomplished by endopeptidases, is a ubiquitous phenomenon underlying the regulation and activation of many enzymes, receptors and other proteins synthesized as inactive precursors. Serine proteases are one of the largest and conserved families of endopeptidases involved in diverse cellular activities including wound healing, blood coagulation and immune responses. Heteromeric α,β,γ-epithelial sodium channels (ENaC) associated with diseases like cystic fibrosis and Liddle’s syndrome, are irreversibly stimulated by membrane-anchored proteases (MAPs) and furin-like convertases. Matriptase/Channel activating protease-3 (CAP3) is one of the several MAPs that potently activate ENaC. Despite identification of protease cleavage sites, the basis for enhanced susceptibility of α- and γ-ENaC to proteases remains elusive. Here, we elucidate the energetic and structural bases for activation of ENaC by CAP3. We find a region near the γ-ENaC furin site that is previously unidentified as a critical cleavage site for CAP3-mediated stimulation. We also report that CAP3 mediates cleavage of ENaC at basic residues downstream of the furin site. Our results indicate that surface proteases alone are sufficient to fully activate uncleaved ENaC, and explain how ENaC in epithelia expressing surface-active proteases can appear refractory to soluble proteases. Our results support a model in which proteases prime ENaC for activation by cleaving at the furin site, and cleavage at downstream sites is accomplished by membrane surface proteases or extracellular soluble proteases. Based on our results, we propose a dynamics-driven “anglerfish” mechanism that explains less stringent sequence requirements for substrate recognition and cleavage by matriptase compared to furin