Activation of pruritogenic TGR5, MRGPRA3, and MRGPRC11 on colon-innervating afferents induces visceral hypersensitivity

Itch induces scratching that removes irritants from the skin, whereas pain initiates withdrawal or avoidance of tissue damage. While pain arises from both the skin and viscera, we investigated whether pruritogenic irritant mechanisms also function within visceral pathways. We show that subsets of colon-innervating sensory neurons in mice express, either individually or in combination, the pruritogenic receptors Tgr5 and the Mas-gene-related GPCRs Mrgpra3 and Mrgprc11. Agonists of these receptors activated subsets of colonic sensory neurons and evoked colonic afferent mechanical hypersensitivity via a TRPA1-dependent mechanism. In vivo intracolonic administration of individual TGR5, MRGPRA3, or MRGPRC11 agonists induced pronounced visceral hypersensitivity to colorectal distension. Coadministration of these agonists as an "itch cocktail" augmented hypersensitivity to colorectal distension and changed mouse behavior. These irritant mechanisms were maintained and enhanced in a model of chronic visceral hypersensitivity relevant to irritable bowel syndrome. Neurons from human dorsal root ganglia also expressed TGR5, as well as the human ortholog MRGPRX1, and showed increased responsiveness to pruritogenic agonists in pathological states. These data support the existence of an irritant-sensing system in the colon that is a visceral representation of the itch pathways found in skin, thereby contributing to sensory disturbances accompanying common intestinal disorders. - 2019 American Society for Clinical Investigation. All rights reserved.Work was supported by a National Health and Medical Research Council of Australia (NHMRC) Project Grant (1083480 to SMB and DPP), an NHMRC R.D. Wright Biomedical Research Fellow (APP1126378 to SMB), and an Australian Research Council (ARC) Discovery Early Career Research Award (DE130100223 to AMH). NWB was supported by grants from the NIH (NS102722; DE026806; DK118971) and the US Department of Defence (W81XWH1810431).Scopu

Filamentary structure formation in the Interstellar Radiation Field (ISRF)

A new mechanism is proposed for the formation of filament/core structure by ISRF and clumpy molecular cloud interaction. The derived characterizes of the filament/core network is consistent with that produced by the compressive forcing turbulence model

Estimating cost efficiency and sources of inefficiency in paddy farming: A study in Vietnam’s Mekong Delta

The misuse of chemical fertilizers, pesticides and herbicides in rice cultivation is leading to low-quality outputs, high production costs, health issues and environmental problems (e.g., degraded soil quality, water pollution and increasing greenhouse gases). The efficient use of production inputs would be a feasible way to mitigate these issues. This paper employed a true random-effects model to measure cost efficiency and investigate the factors affecting cost inefficiency among Vietnamese rice producers. This study used the surveyed data of 350 rice households collected in the Mekong Delta, Vietnam. The findings of this research show that the mean cost efficiency score is 0.92 with a wide variation (0.26 – 0.99). This study indicates that there is still potential for inefficient rice producers to save production costs by improving their cost inefficiency. The study also reveals a positive relationship between cost inefficiency and farm size, natural disasters and rice diseases. This suggests that as farms grow, natural disasters and rice diseases become more prevalent and rice producers become increasingly incapable of managing input costs. This study suggests that supportive policies should focus on improving rice farmers’ skills to manage production inputs and deal with rice diseases and natural disasters to minimize rice production costs

Protease-activated receptor-2 in endosomes signals persistent pain of irritable bowel syndrome

Published online July 16, 2018Once activated at the surface of cells, G protein-coupled receptors (GPCRs) redistribute to endosomes, where they can continue to signal. Whether GPCRs in endosomes generate signals that contribute to human disease is unknown. We evaluated endosomal signaling of protease-activated receptor-2 (PAR₂), which has been proposed to mediate pain in patients with irritable bowel syndrome (IBS). Trypsin, elastase, and cathepsin S, which are activated in the colonic mucosa of patients with IBS and in experimental animals with colitis, caused persistent PAR₂-dependent hyperexcitability of nociceptors, sensitization of colonic afferent neurons to mechanical stimuli, and somatic mechanical allodynia. Inhibitors of clathrin- and dynamin-dependent endocytosis and of mitogen-activated protein kinase kinase-1 prevented trypsin-induced hyperexcitability, sensitization, and allodynia. However, they did not affect elastase- or cathepsin S-induced hyperexcitability, sensitization, or allodynia. Trypsin stimulated endocytosis of PAR₂, which signaled from endosomes to activate extracellular signal-regulated kinase. Elastase and cathepsin S did not stimulate endocytosis of PAR₂, which signaled from the plasma membrane to activate adenylyl cyclase. Biopsies of colonic mucosa from IBS patients released proteases that induced persistent PAR₂-dependent hyperexcitability of nociceptors, and PAR₂ association with β-arrestins, which mediate endocytosis. Conjugation to cholestanol promoted delivery and retention of antagonists in endosomes containing PAR₂. A cholestanol-conjugated PAR₂ antagonist prevented persistent trypsin- and IBS protease-induced hyperexcitability of nociceptors. The results reveal that PAR₂ signaling from endosomes underlies the persistent hyperexcitability of nociceptors that mediates chronic pain of IBS. Endosomally targeted PAR₂ antagonists are potential therapies for IBS pain. GPCRs in endosomes transmit signals that contribute to human diseases.Nestor N. Jimenez-Vargas, Luke A. Pattison, Peishen Zhao, TinaMarie Lieu, Rocco Latorre, Dane D. Jensen, Joel Castro, Luigi Aurelio, Giang T. Le, Bernard Flynn, Carmen Klein Herenbrink, Holly R. Yeatman, Laura Edgington-Mitchell, Christopher J. H. Porter, Michelle L. Halls, Meritxell Canals, Nicholas A. Veldhuis, Daniel P. Poole, Peter McLean, Gareth A. Hicks, Nicole Scheff, Elyssa Chen, Aditi Bhattacharya, Brian L. Schmidt, Stuart M. Brierley, Stephen J. Vanner, and Nigel W. Bunnet

Neurokinin 1 receptor signaling in endosomes mediates sustained nociception and is a viable therapeutic target for prolonged pain relief

International audienceTypically considered to be cell surface sensors of extracellular signals, heterotrimeric GTP-binding protein (G protein)-coupled receptors (GPCRs) control many pathophysiological processes and are the target of 30% of therapeutic drugs. Activated receptors redistribute to endosomes, but researchers have yet to explore whether endosomal receptors generate signals that control complex processes in vivo and are viable therapeutic targets. We report that the substance P (SP) neurokinin 1 receptor (NK1R) signals from endosomes to induce sustained excitation of spinal neurons and pain transmission and that specific antagonism of the NK1R in endosomes with membrane-anchored drug conjugates providesmore effective and sustained pain relief than conventional plasmamembrane-targeted antagonists. Pharmacological and genetic disruption of clathrin, dynamin, and b-arrestin blocked SP-induced NK1R endocytosis and prevented SP-stimulated activation of cytosolic protein kinase C and nuclear extracellular signal-regulated kinase, as well as transcription. Endocytosis inhibitors prevented sustained SP-induced excitation of neurons in spinal cord slices in vitro and attenuated nociception in vivo. When conjugated to cholestanol to promote endosomal targeting, NK1R antagonists selectively inhibited endosomal signaling and sustained neuronal excitation. Cholestanol conjugation amplified and prolonged the antinociceptive actions of NK1R antagonists. These results reveal a critical role for endosomal signaling of the NK1R in the complex pathophysiology of pain and demonstrate the use of endosomally targeted GPCR antagonists