The transient receptor potential ankyrin (TRPA) channels are Ca
-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is ...widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH
terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca
, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.
Extremely low-frequency electromagnetic stimulation (ELF-EMS) was demonstrated to be significantly beneficial in rodent models of permanent stroke. The mechanism involved enhanced cerebrovascular ...perfusion and endothelial cell nitric oxide production. However, the possible effect on the neuroinflammatory response and its efficacy in reperfusion stroke models remains unclear. To evaluate ELF-EMS effectiveness and possible immunomodulatory response, we studied neurological outcome, behavior, neuronal survival, and glial reactivity in a rodent model of global transient stroke treated with 13.5 mT/60 Hz. Next, we studied microglial cells migration and, in organotypic hippocampal brain slices, we assessed neuronal survival and microglia reactivity. ELF-EMS improved the neurological score and behavior in the ischemia-reperfusion model. It also improved neuronal survival and decreased glia reactivity in the hippocampus, with microglia showing the first signs of treatment effect. In vitro ELF-EMS decreased (Lipopolysaccharide) LPS and ATP-induced microglia migration in both scratch and transwell assay. Additionally, in hippocampal brain slices, reduced microglial reactivity, improved neuronal survival, and modulation of inflammation-related markers was observed. Our study is the first to show that an EMF treatment has a direct impact on microglial migration. Furthermore, ELF-EMS has beneficial effects in an ischemia/reperfusion model, which indicates that this treatment has clinical potential as a new treatment against ischemic stroke.
Vagus nerve stimulation (VNS), most likely via enteric neurons, prevents postoperative ileus (POI) by reducing activation of alpha7 nicotinic receptor (α7nAChR) positive
macrophages (mMφ) and ...dampening surgery-induced intestinal inflammation. Here, we evaluated if 5-HT4 receptor (5-HT4R) agonist prucalopride can mimic this effect in mice and human.
Using Ca
imaging, the effect of electrical field stimulation (EFS) and prucalopride was evaluated in situ on mMφ activation evoked by ATP in jejunal
tissue. Next, preoperative and postoperative administration of prucalopride (1-5 mg/kg) was compared with that of preoperative VNS in a model of POI in wild-type and α7nAChR knockout mice. Finally, in a pilot study, patients undergoing a Whipple procedure were preoperatively treated with prucalopride (n=10), abdominal VNS (n=10) or sham/placebo (n=10) to evaluate the effect on intestinal inflammation and clinical recovery of POI.
EFS reduced the ATP-induced Ca
response of mMφ, an effect that was dampened by neurotoxins tetrodotoxin and ω-conotoxin and mimicked by prucalopride. In vivo, prucalopride administered before, but not after abdominal surgery reduced intestinal inflammation and prevented POI in wild-type, but not in α7nAChR knockout mice. In humans, preoperative administration of prucalopride, but not of VNS, decreased
and
expression in the
and improved clinical recovery.
Enteric neurons dampen mMφ activation, an effect mimicked by prucalopride. Preoperative, but not postoperative treatment with prucalopride prevents intestinal inflammation and shortens POI in both mice and human, indicating that preoperative administration of 5-HT4R agonists should be further evaluated as a treatment of POI.
NCT02425774.
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•LPS activates heterologous TRPV1, TRPM3 and TRPM8, but not TRPV2.•TRPV1 activation by LPS is independent of residues conferring capsaicin sensitivity.•Low temperatures facilitate ...TRPM8 activation by LPS.•Stimulation of mouse sensory neurons by LPS is mainly mediated by TRPA1 and TRPV1.•Sensory TRP channels emerge as newly-described effectors of bacterial endotoxins.
Acute neurogenic inflammation and pain associated to bacterial infection have been traditionally ascribed to sensitization and activation of sensory nerve afferents secondary to immune cell stimulation. However, we recently showed that lipopolysaccharides (LPS) directly activate the Transient Receptor Potential channels TRPA1 in sensory neurons and TRPV4 in airway epithelial cells. Here we investigated whether LPS activates other sensory TRP channels expressed in sensory neurons. Using intracellular Ca2+ imaging and patch-clamp we determined the effects of LPS on recombinant TRPV1, TRPV2, TRPM3 and TRPM8, heterologously expressed in HEK293T cells. We found that LPS activates TRPV1, although with lower potency than for TRPA1. Activation of TRPV1 by LPS was not affected by mutations of residues required for activation by electrophilic agents or by diacylglycerol and capsaicin. On the other hand, LPS weakly activated TRPM3, activated TRPM8 at 25 °C, but not at 35 °C, and was ineffective on TRPV2. Experiments performed in mouse dorsal root ganglion (DRG) neurons revealed that genetic ablation of Trpa1 did not abolish the responses to LPS, but remain detected in 30% of capsaicin-sensitive cells. The population of neurons responding to LPS was dramatically lower in double Trpa1/Trpv1 KO neurons. Our results show that, in addition to TRPA1, other TRP channels in sensory neurons can be targets of LPS, suggesting that they may contribute to trigger and regulate innate defenses against gram-negative bacterial infections.
Lipopolysaccharides (LPS), the major components of the wall of gram-negative bacteria, trigger powerful defensive responses in the airways via mechanisms thought to rely solely on the Toll-like ...receptor 4 (TLR4) immune pathway. Here we show that airway epithelial cells display an increase in intracellular Ca
concentration within seconds of LPS application. This response occurs in a TLR4-independent manner, via activation of the transient receptor potential vanilloid 4 cation channel (TRPV4). We found that TRPV4 mediates immediate LPS-induced increases in ciliary beat frequency and the production of bactericidal nitric oxide. Upon LPS challenge TRPV4-deficient mice display exacerbated ventilatory changes and recruitment of polymorphonuclear leukocytes into the airways. We conclude that LPS-induced activation of TRPV4 triggers signaling mechanisms that operate faster and independently from the canonical TLR4 immune pathway, leading to immediate protective responses such as direct antimicrobial action, increase in airway clearance, and the regulation of the inflammatory innate immune reaction.
Up to 20% of people worldwide develop gastrointestinal symptoms following a meal
, leading to decreased quality of life, substantial morbidity and high medical costs. Although the interest of both ...the scientific and lay communities in this issue has increased markedly in recent years, with the worldwide introduction of gluten-free and other diets, the underlying mechanisms of food-induced abdominal complaints remain largely unknown. Here we show that a bacterial infection and bacterial toxins can trigger an immune response that leads to the production of dietary-antigen-specific IgE antibodies in mice, which are limited to the intestine. Following subsequent oral ingestion of the respective dietary antigen, an IgE- and mast-cell-dependent mechanism induced increased visceral pain. This aberrant pain signalling resulted from histamine receptor H
-mediated sensitization of visceral afferents. Moreover, injection of food antigens (gluten, wheat, soy and milk) into the rectosigmoid mucosa of patients with irritable bowel syndrome induced local oedema and mast cell activation. Our results identify and characterize a peripheral mechanism that underlies food-induced abdominal pain, thereby creating new possibilities for the treatment of irritable bowel syndrome and related abdominal pain disorders.
The cellular and systemic effects induced by bacterial lipopolysaccharides (LPS) have been solely attributed to the activation of the Toll-like receptor 4 (TLR4) signalling cascade. However, recent ...studies have shown that LPS activates several members of the Transient Receptor Potential (TRP) family of cation channels. Indeed, LPS induces activation of the broadly-tuned chemosensor TRPA1 in sensory neurons in a TLR4-independent manner, and genetic ablation of this channel reduced mouse pain and inflammatory responses triggered by LPS and the gustatory-mediated avoidance to LPS in fruit flies. LPS was also shown to activate TRPV4 channels in airway epithelial cells, an effect leading to an immediate production of bactericidal nitric oxide and to an increase in ciliary beat frequency. In this review, we discuss the role of TRP channels as sensors of bacterial endotoxins, and therefore, as crucial players in the timely detection of invading gram-negative bacteria.
Mustard oil (MO) is a plant-derived irritant that has been extensively used in experimental models to induce pain and inflammation 1, 2. The noxious effects of MO are currently ascribed to specific ...activation of the cation channel TRPA1 in nociceptive neurons 3, 4. In contrast to this view, we show here that the capsaicin receptor TRPV1 has a surprisingly large contribution to aversive and pain responses and visceral irritation induced by MO. Furthermore, we found that this can be explained by previously unknown properties of this compound. First, MO has a bimodal effect on TRPA1, producing current inhibition at millimolar concentrations. Second, it directly and stably activates mouse and human recombinant TRPV1, as well as TRPV1 channels in mouse sensory neurons. Finally, physiological temperatures enhance MO-induced TRPV1 stimulation. Our results refute the dogma that TRPA1 is the sole nocisensor for MO and motivate a revision of the putative roles of these channels in models of MO-induced pain and inflammation. We propose that TRPV1 has a generalized role in the detection of irritant botanical defensive traits and in the coevolution of multiple mammalian and plant species.
► Both TRPA1 and TRPV1 mediate the noxious effects of mustard oil in vivo ► Mustard oil directly stimulates recombinant and native TRPV1 channels ► In vivo experimental conditions enhance TRPV1 sensitivity to mustard oil ► TRPV1 is a common locus for the action of a wide variety of plant defensive traits
Microglial cells, as the primary defense line in the central nervous system, play a crucial role in responding to various mechanical signals that can trigger their activation. Despite extensive ...research on the impact of chemical signaling on brain cells, the understanding of mechanical signaling in microglia remains limited. To bridge this gap, we subjected microglial cells to a singular mechanical stretch and compared their responses with those induced by lipopolysaccharide treatment, a well-established chemical activator. Here we show that stretching microglial cells leads to their activation, highlighting their significant mechanosensitivity. Stretched microglial cells exhibited distinct features, including elevated levels of Iba1 protein, a denser actin cytoskeleton, and increased persistence in migration. Unlike LPS-treated microglial cells, the secretory profile of chemokines and cytokines remained largely unchanged in response to stretching, except for TNF-α. Intriguingly, a single stretch injury resulted in more compacted chromatin and DNA damage, suggesting potential long-term genomic instabilities in stretched microglia. Using compartmentalized microfluidic chambers with neuronal networks, we observed that stretched microglial cells exhibited enhanced phagocytic and synaptic stripping activities. These findings collectively suggest that stretching events can unlock the immune potential of microglial cells, contributing to the maintenance of brain tissue homeostasis following mechanical injury.
Summary
Live‐attenuated yellow fever vaccine (YF17D) was developed in the 1930s as the first ever empirically derived human vaccine. Ninety years later, it is still a benchmark for vaccines made ...today. YF17D triggers a particularly broad and polyfunctional response engaging multiple arms of innate, humoral and cellular immunity. This unique immunogenicity translates into an extraordinary vaccine efficacy and outstanding longevity of protection, possibly by single‐dose immunization. More recently, progress in molecular virology and synthetic biology allowed engineering of YF17D as a powerful vector and promising platform for the development of novel recombinant live vaccines, including two licensed vaccines against Japanese encephalitis and dengue, even in paediatric use. Likewise, numerous chimeric and transgenic preclinical candidates have been described. These include prophylactic vaccines against emerging viral infections (e.g. Lassa, Zika and SARS‐CoV‐2) and parasitic diseases (e.g. malaria), as well as therapeutic applications targeting persistent infections (e.g. HIV and chronic hepatitis), and cancer. Efforts to overcome historical safety concerns and manufacturing challenges are ongoing and pave the way for wider use of YF17D‐based vaccines. In this review, we summarize recent insights regarding YF17D as vaccine platform, and how YF17D‐based vaccines may complement as well as differentiate from other emerging modalities in response to unmet medical needs and for pandemic preparedness.
Graphical : Live‐attenuated yellow fever vaccine (YF17D) has emerged as platform to develop prophylactic and therapeutic vaccines against infectious diseases and cancer. In this review, we summarize the unique polyfunctional immunity endowed by original YF17D, and the progress and challenges of recombinant YF17D‐based vaccines for unmet medical needs and pandemic preparedness.
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