The crosstalk between the immune and neuroendocrine systems is critical for intestinal homeostasis and gut-brain communications. However, it remains unclear how immune cells participate in gut ...sensation of hormones and neurotransmitters release in response to environmental cues, such as self-lipids and microbial lipids. We show here that lipid-mediated engagement of invariant natural killer T (iNKT) cells with enterochromaffin (EC) cells, a subset of intestinal epithelial cells, promoted peripheral serotonin (5-HT) release via a CD1d-dependent manner, regulating gut motility and hemostasis. We also demonstrated that inhibitory sphingolipids from symbiotic microbe Bacteroides fragilis represses 5-HT release. Mechanistically, CD1d ligation on EC cells transduced a signal and restrained potassium conductance through activation of protein tyrosine kinase Pyk2, leading to calcium influx and 5-HT secretion. Together, our data reveal that by engaging with iNKT cells, gut chemosensory cells selectively perceive lipid antigens via CD1d to control 5-HT release, modulating intestinal and systemic homeostasis.
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•Lipid-induced gut motility is mediated by 5-HT•Enterochromaffin (EC) cell-derived CD1d is critical for 5-HT release•Pyk2-Kv1.2 axis is required for gut CD1d-mediated 5-HT release•Bacteroides fragilis sphingolipids repress intestinal 5-HT secretion
Enterochromaffin (EC) cells are known as the major source of gut-derived serotonin (5-HT). Luo et al. demonstrate that lipid-mediated engagement of invariant natural killer T (iNKT) cells with EC cells regulates peripheral 5-HT release via a CD1d-dependent manner, indicating an immune-mediated selective neuroendocrine response to lipid antigens.
Intestinal mucus forms the first line of defense against bacterial invasion while providing nutrition to support microbial symbiosis. How the host controls mucus barrier integrity and commensalism is ...unclear. We show that terminal sialylation of glycans on intestinal mucus by ST6GALNAC1 (ST6), the dominant sialyltransferase specifically expressed in goblet cells and induced by microbial pathogen-associated molecular patterns, is essential for mucus integrity and protecting against excessive bacterial proteolytic degradation. Glycoproteomic profiling and biochemical analysis of ST6 mutations identified in patients show that decreased sialylation causes defective mucus proteins and congenital inflammatory bowel disease (IBD). Mice harboring a patient ST6 mutation have compromised mucus barriers, dysbiosis, and susceptibility to intestinal inflammation. Based on our understanding of the ST6 regulatory network, we show that treatment with sialylated mucin or a Foxo3 inhibitor can ameliorate IBD.
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•A local sialyltransferase dominantly controls intestinal protein sialylation•Sialylation protects intestinal mucus integrity from bacterial degradation•Mucus sialylation is critical for commensalism and bacterial metabolite homeostasis•Treatment with sialylated mucins ameliorates gut inflammation
Sialylation plays an essential role in protecting mucus barrier integrity from bacterial degradation and is governed by ST6GALNAC1 (ST6), a local sialyltransferase in the gut. ST6-mediated mucus homeostasis controls commensalism to establish intestinal host-microbe symbiosis. ST6 deficiency disrupts this mutualism, increasing susceptibility to intestinal inflammation.
Neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, are devastating diseases in the elderly world, which are closely associated with progressive neuronal loss induced by ...a variety of genetic and/or environmental factors. Unfortunately, currently available treatments for neurodegenerative disorders can only relieve the symptoms but not modify the pathological processes. Over the past decades, our group by collaborating with Profs. Yuan‐Ping Pang and Paul R. Carlier has developed three series of homo/hetero dimeric acetylcholinesterase inhibitors derived from tacrine and/or huperzine A. The representative dimers bis(3)‐Cognitin (B3C), bis(12)‐hupyridone, and tacrine(10)‐hupyridone might possess disease‐modifying effects through the modulation of N‐methyl‐d‐aspartic acid receptors, the activation of myocyte enhancer factor 2D gene transcription, and the promotion of neurotrophic factor secretion. In this review, we summarize that the representative dimers, such as B3C, provide neuroprotection against a variety of neurotoxins via multiple targets, including the inhibitions of N‐methyl‐d‐aspartic acid receptor with pathological‐activated potential, neuronal nitric oxide synthase, and β‐amyloid cascades synergistically. More importantly, B3C might offer disease‐modifying potentials by activating myocyte enhancer factor 2D transcription, inducing neuritogenesis, and promoting the expressions of neurotrophic factors in vitro and in vivo. Taken together, the novel dimers might offer synergistic disease‐modifying effects, proving that dimerization might serve as one of the strategies to develop new generation of therapeutics for neurodegenerative disorders.
Over the past decades, several series of homo/hetero dimeric acetylcholinesterase (AChE) inhibitors derived from tacrine and/or huperzine A have been developed. In this review, we summarize that the representative dimers, such as bis(7)‐cognitin (B7C) and bis(3)‐cognitin (B3C), provide neuroprotection against a variety of neurotoxins via multiple targets, including the inhibitions of neuronal nitric oxide synthase (nNOS), N‐methyl‐D‐aspartic acid (NMDA) receptor with pathological‐activated potential and β‐amyloid cascades synergistically. More importantly, B3C might offer disease‐modifying potentials by activating Myocyte enhancer factor 2D (MEF2D) transcription, inducing neuritogenesis, and promoting the expressions of neurotrophic factors in vitro and in vivo, proving that dimerization might serve as one of the strategies to develop new generation of therapeutics for neurodegenerative disorders.
In the present study, ATP-activated currents (I
ATPs) recorded from rat trigeminal ganglion (TG) neurons using whole-cell patch clamp technique are classified into three types (F, I and S) based on ...the characteristics of their activation and desensitization. The time of rising phase (R
10–90) of types F, I and S of I
ATP is measured to be 33.6
±
4.5, 62.2
±
9.9 and 302.1
±
62.0 ms respectively, and positively correlated to cell size. The time of decaying phases (D
10–90) of types F and S is 399.4
±
58.2 and >
1500 ms, respectively. The dose–response curves for the three types of I
ATP show that their EC
50 values are close (3.44
×
10
−
5
, 4.89
×
10
−
5
and 4.14
×
10
−
5
M for types F, I and S respectively,
P
>
0.05). Their reversal potentials are basically the same, varying from +
4 to +
10 mV. In addition, using whole-cell patch clamp technique in combination with single cell immunohistochemical staining for P2X receptor subunits, our results suggest that the type distinction of ATP-activated current was associated with cell size and P2X receptor subunits: small-sized cells with type F of I
ATP express only P2X1 and/or P2X3 subunits, while cells with types S and I of I
ATP express P2X2 or P2X4 in addition to P2X1 and P2X3.
Crystal structures activate innate immune cells, especially macrophages and initiate inflammatory responses. We aimed to understand the role of the mechanosensitive TRPV4 channel in crystal-induced ...inflammation. Real-time RT-PCR, RNAscope in situ hybridisation, and
mice were used to examine TRPV4 expression and whole-cell patch-clamp recording and live-cell Ca
imaging were used to study TRPV4 function in mouse synovial macrophages and human peripheral blood mononuclear cells (PBMCs). Both genetic deletion and pharmacological inhibition approaches were used to investigate the role of TRPV4 in NLRP3 inflammasome activation induced by diverse crystals in vitro and in mouse models of crystal-induced pain and inflammation in vivo. TRPV4 was functionally expressed by synovial macrophages and human PBMCs and TRPV4 expression was upregulated by stimulation with monosodium urate (MSU) crystals and in human PBMCs from patients with acute gout flares. MSU crystal-induced gouty arthritis were significantly reduced by either genetic ablation or pharmacological inhibition of TRPV4 function. Mechanistically, TRPV4 mediated the activation of NLRP3 inflammasome by diverse crystalline materials but not non-crystalline NLRP3 inflammasome activators, driving the production of inflammatory cytokine interleukin-1β which elicited TRPV4-dependent inflammatory responses in vivo. Moreover, chemical ablation of the TRPV1-expressing nociceptors significantly attenuated the MSU crystal-induced gouty arthritis. In conclusion, TRPV4 is a common mediator of inflammatory responses induced by diverse crystals through NLRP3 inflammasome activation in macrophages. TRPV4-expressing resident macrophages are critically involved in MSU crystal-induced gouty arthritis. A neuroimmune interaction between the TRPV1-expressing nociceptors and the TRPV4-expressing synovial macrophages contributes to the generation of acute gout flares.
Background and Purpose
Hair follicle telogen to anagen transition results in a break in cellular quiescence of the hair follicle stem cells, which subsequently promotes hair follicle regeneration. ...Many critical molecules and signalling pathways are involved in hair follicle cycle progression. Transient receptor potential vanilloid 4 (TRPV4) is a polymodal sensory transducer that regulates various cutaneous functions under both normal and disease conditions. However, the role of TRPV4 in hair follicle regeneration in vivo remains incompletely understood.
Experimental Approach
Using adult C57BL/6J mice, keratinocyte (K14Cre; Trpv4f/f) and macrophage (Cx3cr1Cre; Trpv4f/f) Trpv4 conditional knockout (cKO) mice, Trpv4−/− mice, we investigated the effect of a single intradermal injection of GSK1016790A, a potent and selective small molecule TRPV4 activator, on hair follicle regeneration. Chemical cues and signal molecules involved in hair follicle cycle progression were measured by immunofluorescence staining, quantitative RT‐PCR and western blotting.
Key Results
Here, we show that a single intradermal injection of GSK1016790A is sufficient to induce telogen to anagen transition and hair follicle regeneration in mice by increasing the expression of the anagen‐promoting growth factors and down‐regulating the expression of growth factors that inhibit anagen. The action of GSK1016790A relies largely on the function of TRPV4 in skin and involves activation of downstream ERK signalling.
Conclusion and Implications
Our results suggest that transient chemical activation of TRPV4 in the skin induces hair follicle regeneration in mice, which might provide an effective therapeutic strategy for the treatment of hair loss and alopecia.
Abstract
The gastrointestinal tract is known as the largest endocrine organ that encounters and integrates various immune stimulations and neuronal responses due to constant environmental challenges. ...Enterochromaffin (EC) cells, which function as chemosensors on the gut epithelium, are known to translate environmental cues into serotonin (5-HT) production, contributing to intestinal physiology. However, how immune signals participate in gut sensation and neuroendocrine response remains unclear. Interleukin-33 (IL-33) acts as an alarmin cytokine by alerting the system of potential environmental stresses. We here demonstrate that IL-33 induced instantaneous peristaltic movement and facilitated Trichuris muris expulsion. We found that IL-33 could be sensed by EC cells, inducing release of 5-HT. IL-33-mediated 5-HT release activated enteric neurons, subsequently promoting gut motility. Mechanistically, IL-33 triggered calcium influx via a non-canonical signaling pathway specifically in EC cells to induce 5-HT secretion. Our data establish an immune-neuroendocrine axis in calibrating rapid 5-HT release for intestinal homeostasis.
Background and Purpose
TMEM16A, also known as anoctamin 1 channel, is a member of the Ca2+‐activated chloride channels family and serves as a heat sensor in the primary nociceptors. Eact is a ...recently discovered small molecule activator of the TMEM16A channel. Here, we asked if Eact produces pain‐ and itch‐related responses in vivo and investigated the cellular and molecular basis of Eact‐elicited responses in dorsal root ganglia (DRG) neurons.
Experimental Approach
We employed behavioural testing combined with pharmacological inhibition and genetic ablation approaches to identify transient receptor potential vanilloid 1 (TRPV1) as the prominent mediator for Eact‐evoked itch‐ or pain‐related responses. We investigated the effects of Eact on TRPV1 and TMEM16A channels expressed in HEK293T cells and in DRG neurons isolated from wild type and Trpv1−/− mice using Ca2+ imaging and patch‐clamp recordings. We also used site‐directed mutagenesis to determine the molecular basis of Eact activation of TRPV1.
Key Results
Administration of Eact elicited both itch‐ and pain‐related behaviours. Unexpectedly, the Eact‐elicited behavioural responses were dependent on the function of TRPV1, as shown by pharmacological inhibition and genetic ablation studies. Eact activated membrane currents and increased intracellular free Ca2+ in both TRPV1‐expressing HEK293T cells and isolated DRG neurons in a TRPV1‐dependent manner. Eact activation of the TRPV1 channel was severely attenuated by mutations disrupting the capsaicin‐binding sites.
Conclusions and Implications
Our results suggest that Eact activates primary sensory nociceptors and produces both pain and itch responses mainly through direct activation of TRPV1 channels.
The environmental irritant chloroform, a naturally occurring small volatile organohalogen, briefly became the world's most popular volatile general anesthetic (VGA) before being abandoned because of ...its low therapeutic index. When chloroform comes in contact with skin or is ingested, it causes a painful burning sensation. The molecular basis for the pain associated with chloroform remains unknown. In this study, we assessed the role of transient receptor potential (TRP) channel family members in mediating chloroform activation and the molecular determinants of VGA activation of TRPV1. We identified the subpopulation of dorsal root ganglion (DRG) neurons that are activated by chloroform. Additionally, we transiently expressed wild-type or specifically mutated TRP channels in human embryonic kidney cells and used calcium imaging or whole-cell patch-clamp electrophysiology to assess the effects of chloroform or the VGA isoflurane on TRP channel activation. The results revealed that chloroform activates DRG neurons via TRPV1 activation. Furthermore, chloroform activates TRPV1, and it also activates TRPM8 and functions as a potent inhibitor of the noxious chemical receptor TRPA1. The results also indicate that residues in the outer pore region of TRPV1 previously thought to be required for either proton or heat activation of the channel are also required for activation by chloroform and isoflurane. In addition to identifying the molecular basis of DRG neuron activation by chloroform and the opposing effects chloroform has on different TRP channel family members, the findings of this study provide novel insights into the structural basis for the activation of TRPV1 by VGAs.
Gastrointestinal tract motility may be demoted significantly after surgery operations at least in part due to anaesthetic agents, but there is no comprehensive explanation of the molecular ...mechanism(s) of such adverse effects. Anesthetics are known to interact with various receptors and ion channels including several subtypes of transient receptor potential (TRP) channels. Two members of the canonical subfamily of TRP channels (TRPC), TRPC4 and TRPC6 are Ca2+-permeable cation channels involved in visceral smooth muscle contractility induced by acetylcholine, the primary excitatory neurotransmitter in the gut. In the present study, we aimed to study the effect of anesthetics on muscarinic receptor-mediated excitation and contraction of intestinal smooth muscle. Here we show that muscarinic cation current (mICAT) mediated by TRPC4 and TRPC6 channels in mouse ileal myocytes was strongly inhibited by isoflurane (0.5mM), one of the most commonly used inhalation anesthetics. Carbachol-activated mICAT was reduced by 63 ± 11% (n = 5), while GTPγS-induced (to bypass muscarinic receptors) current was inhibited by 44 ± 9% (n = 6). Furthermore, carbachol-induced ileum and colon contractions were inhibited by isoflurane by about 30%. We discuss the main sites of isoflurane action, which appear to be G-proteins and muscarinic receptors, rather than TRPC4/6 channels. These results contribute to our better understanding of the signalling pathways affected by inhalation anesthetics, which may cause ileus, and thus may be important for the development of novel treatment strategies during postoperative recovery.
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