Endothelin-converting enzyme 2 differentially regulates opioid receptor activity.

BACKGROUND AND PURPOSE: Opioid receptor function is modulated by post-activation events such as receptor endocytosis, recycling and/or degradation. While it is generally understood that the peptide ligand gets co-endocytosed with the receptor, relatively few studies have investigated the role of the endocytosed peptide and peptide processing enzymes in regulating receptor function. In this study, we focused on endothelin-converting enzyme 2 (ECE2), a member of the neprilysin family of metallopeptidases that exhibits an acidic pH optimum, localizes to an intracellular compartment and selectively processes neuropeptides including opioid peptides in vitro, and examined its role in modulating µ receptor recycling and resensitization. EXPERIMENTAL APPROACH: The effect of ECE2 inhibition on hydrolysis of the endocytosed peptide was examined using thin-layer chromatography and on µ opioid receptor trafficking using either elisa or microscopy. The effect of ECE2 inhibition on receptor signalling was measured using a cAMP assay and, in vivo, on antinociception induced by intrathecally administered opioids by the tail-flick assay. KEY RESULTS: The highly selective ECE2 inhibitor, S136492, significantly impaired µ receptor recycling and signalling by only those ligands that are ECE2 substrates and this was seen both in heterologous cells and in cells endogenously co-expressing µ receptors with ECE2. We also found that ECE2 inhibition attenuated antinociception mediated only by opioid peptides that are ECE2 substrates. CONCLUSIONS AND IMPLICATIONS: These results suggest that ECE2, by selectively processing endogenous opioid peptides in the endocytic compartment, plays a role in modulating opioid receptor activity. LINKED ARTICLES: This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

Quasi-one-dimensional molecular magnets based on derivatives of (fluorobenzyl)pyridinium with the [M(mnt)2] monoanion (M = Ni, Pd or Pt; mnt2- = maleonitriledithiolate): syntheses, crystal structures and magnetic properties.

The syntheses, structural characterizations and magnetic behaviors of three new complexes, 1-(3',4',5'-trifluorobenzyl)pyridinium [M(mnt)2]- [M = Ni (1), Pd (2) or Pt (3)], are reported. These complexes are isomorphous and their prominent structural character is that the [M(mnt)2]- anions form columnar stacks, in which the dimerization was observed. Complexes 2 and 3 are diamagnetic, while 1 possesses an energy gap of 2474 K. For crystal 4, 1-(4'-fluorobenzyl)pyridinium [Ni(mnt)2] (its structure and magnetic susceptibility were briefly reported earlier), the magnetic behavior can be divided into two regimes, namely, weakly ferromagnetic coupling above 93 K and strongly antiferromagnetic coupling below 93 K. A transition occurs at 93 K which switches the magnetic exchange nature from ferromagnetic to antiferromagnetic. A sharp thermal abnormality with lambda-shape, associated with the transition, appears from its heat capacity measurement to indicate that the transition is first order. The temperature dependences of the superlattice diffractions revealed the existence of the pretransitional phenomena up to at least 140 K. The unusual magnetic behavior of 4, such as the origin of the ferromagnetic interaction in the high temperature phase and what causes the spin transition, are discussed further.

Structural phase transition driven by spin-lattice interaction in a quasi-one-dimensional spin system of [1-(4'-iodobenzyl)pyridinium][Ni(mnt)2].

Crystal structures and magnetic properties were determined for two novel compounds, [1-(4'-iodobenzyl)pyridinium][M(mnt)2] (mnt2- = maleonitriledithiolate; M = Ni (1) or Cu (2)). At room temperature, single crystals of 1 and 2 were isostructural, featuring the formation of segregated columnar structures with regular stacks of cations and anions. For crystal 1, a magnetic transition was observed at approximately 120 K; furthermore, its magnetic behavior was consistent with that of a regular Heisenberg antiferromagnetic (AFM) chain of S = 1/2 in the high-temperature phase (HT phase) and that of a spin-gap system in the low-temperature phase (LT phase). Such a phenomenon is similar to the spin-Peierls transition. However, the crystal structure of 1 in the LT phase at 100 K revealed that its structural transition is associated with the magnetic transition. Because crystal 2 (S = 0) did not exhibit a structural transition, the structural transition of 1 is driven by spin-lattice interaction.

Photoinduced phase transition in an organic radical crystal with room-temperature optical and magnetic bistability.

A phase control by photoirradiation is successfully achieved in a spin-Peierls system of the organic radical crystal, 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA), which exhibits optical and magnetic bistability around room temperature with a large hysteresis loop. A nanosecond laser pulse is found to induce a transition from a diamagnetic low-temperature phase to a paramagnetic high-temperature phase both inside (296 K) and outside (11 K) the hysteresis loop. Comparison of the excitation energy dependence between transition efficiency and photoconductivity suggests that the photoinduced transition is driven by suppression of the spin-Peierls instability by the accumulation of photocarriers.

Room-Temperature Magnetic Bistability in Organic Radical Crystals.

A large first-order magnetic phase transition in an organic radical, 1,3,5-trithia-2,4,6-triazapentalenyl, is described. The transition occurs with a wide thermal hysteresis loop over the temperature range 230 to 305 kelvin. The high-temperature phase is paramagnetic, and its structure consists of a uniform one-dimensional stacking of the radical. The low-temperature phase is diamagnetic because of strong dimerization along the stacking direction. The results may have applications in thermal sensors, switching units, and information storage media based on organic radical crystals.

[Acute appendicitis: a study on 118 patients].

One hundred eighteen patients with acute appendicitis operated on at Kawasaki Medical School Hospital during the 8-year period from Aug. 1, 1976 to Feb. 29, 1984 were reviewed. There were 78 children and 40 adults. The clinico-pathological types of acute appendicitis were: simple acute in 35 cases (29.7%); phlegmonous in 30 cases (25.4%); gangrenous in 24 cases (20.3%) and perforated in 29 cases (24.6%). Of the 78 children, 27 (34.6%) had perforated appendixes, whereas of the 40 adults only 2 (5.0%) showed perforated appendicitis. The initial symptoms were abdominal pain in 96.6%; nausea, vomiting or both in 33.1%, and fever in 11.9%. The physical findings on admission were abdominal tenderness in 99.2%, rebound tenderness in 52.5% and palpable mass in 17.8%. The mean body temperature on admission was 37.2 degrees C, and mean WBC count was 12,900/mm3. The roentgenography of the abdomen revealed the "sentinel loop sign" in 66.3%. In the patients under 15 years of age, the frequency of perforation seen in those underwent operation within 24 hours after onset and in those after 24 hours was 12.7% and 56.4%, respectively. From this result, it is advised that all the young patients suspected of having acute appendicitis should be admitted to the hospital promptly, and the diagnosis should be made within 24 hours.

Multiple fibrofolliculomas with trichodiscomas and acrochordons.

The syndrome of multiple fibrofolliculomas with trichodiscomas and acrochordons clinically is characterized by asymptomatic dome-shaped papules primarily involving the head, neck, chest, back, and arms. These tumors represent benign proliferations of the mesodermal and ectodermal components of the pilar apparatus. Substantial overlap between each of these lesions exists. Individual patients also exhibit a disease spectrum in which various tumors preponderate. The stimulus for this proliferation may be genetically determined, but the cause remains unknown. Merkel's cells were not identified in an electron microscopic study of a single trichodiscoma, but banded structures similar to those described in the closely related lesions of perifollicular fibroma and fibrous papule were seen.