Linoleic acid improves PIEZO2 dysfunction in a mouse model of Angelman Syndrome.

Angelman syndrome (AS) is a neurogenetic disorder characterized by intellectual disability and atypical behaviors. AS results from loss of expression of the E3 ubiquitin-protein ligase UBE3A from the maternal allele in neurons. Individuals with AS display impaired coordination, poor balance, and gait ataxia. PIEZO2 is a mechanosensitive ion channel essential for coordination and balance. Here, we report that PIEZO2 activity is reduced in Ube3a deficient male and female mouse sensory neurons, a human Merkel cell carcinoma cell line and female human iPSC-derived sensory neurons with UBE3A knock-down, and de-identified stem cell-derived neurons from individuals with AS. We find that loss of UBE3A decreases actin filaments and reduces PIEZO2 expression and function. A linoleic acid (LA)-enriched diet increases PIEZO2 activity, mechano-excitability, and improves gait in male AS mice. Finally, LA supplementation increases PIEZO2 function in stem cell-derived neurons from individuals with AS. We propose a mechanism whereby loss of UBE3A expression reduces PIEZO2 function and identified a fatty acid that enhances channel activity and ameliorates AS-associated mechano-sensory deficits.

Genetic- and diet-induced ω-3 fatty acid enrichment enhances TRPV4-mediated vasodilation in mice.

TRPV4 channel activation in endothelial cells leads to vasodilation, while impairment of TRPV4 activity is implicated in vascular dysfunction. Strategies that increase TRPV4 activity could enhance vasodilation and ameliorate vascular disorders. Here, we show that supplementation with eicosapentaenoic acid (EPA), an ω-3 polyunsaturated fatty acid known to have beneficial cardiovascular effects, increases TRPV4 activity in human endothelial cells of various vascular beds. Mice carrying the C. elegans FAT-1 enzyme, which converts ω-6 to ω-3 polyunsaturated fatty acids, display higher EPA content and increased TRPV4-mediated vasodilation in mesenteric arteries. Likewise, mice fed an EPA-enriched diet exhibit enhanced and prolonged TRPV4-dependent vasodilation in an endothelial cell-specific manner. We also show that EPA supplementation reduces TRPV4 desensitization, which contributes to the prolonged vasodilation. Neutralization of positive charges in the TRPV4 N terminus impairs the effect of EPA on channel desensitization. These findings highlight the beneficial effects of manipulating fatty acid content to enhance TRPV4-mediated vasodilation.

TRPV6 channel mediates alcohol-induced gut barrier dysfunction and systemic response.

Intestinal epithelial tight junction disruption is a primary contributing factor in alcohol-associated endotoxemia, systemic inflammation, and multiple organ damage. Ethanol and acetaldehyde disrupt tight junctions by elevating intracellular Ca2+. Here we identify TRPV6, a Ca2+-permeable channel, as responsible for alcohol-induced elevation of intracellular Ca2+, intestinal barrier dysfunction, and systemic inflammation. Ethanol and acetaldehyde elicit TRPV6 ionic currents in Caco-2 cells. Studies in Caco-2 cell monolayers and mouse intestinal organoids show that TRPV6 deficiency or inhibition attenuates ethanol- and acetaldehyde-induced Ca2+ influx, tight junction disruption, and barrier dysfunction. Moreover, Trpv6-/- mice are resistant to alcohol-induced intestinal barrier dysfunction. Photoaffinity labeling of 3-azibutanol identifies a histidine as a potential alcohol-binding site in TRPV6. The substitution of this histidine, and a nearby arginine, reduces ethanol-activated currents. Our findings reveal that TRPV6 is required for alcohol-induced gut barrier dysfunction and inflammation. Molecules that decrease TRPV6 function have the potential to attenuate alcohol-associated tissue injury.

Deficiency of Inositol Monophosphatase Activity Decreases Phosphoinositide Lipids and Enhances TRPV1 Function In Vivo.

Membrane remodeling by inflammatory mediators influences the function of sensory ion channels. The capsaicin- and heat-activated transient receptor potential vanilloid 1 (TRPV1) channel contributes to neurogenic inflammation and pain hypersensitivity, in part because of its potentiation downstream of phospholipase C-coupled receptors that regulate phosphoinositide lipid content. Here, we determined the effect of phosphoinositide lipids on TRPV1 function by combining genetic dissection, diet supplementation, and behavioral, biochemical, and functional analyses in Caenorhabditis elegans As capsaicin elicits heat and pain sensations in mammals, transgenic TRPV1 worms exhibit an aversive response to capsaicin. TRPV1 worms with low levels of phosphoinositide lipids display an enhanced response to capsaicin, whereas phosphoinositide lipid supplementation reduces TRPV1-mediated responses. A worm carrying a TRPV1 construct lacking the distal C-terminal domain features an enhanced response to capsaicin, independent of the phosphoinositide lipid content. Our results demonstrate that TRPV1 activity is enhanced when the phosphoinositide lipid content is reduced, and the C-terminal domain is key to determining agonist response in vivo.

Publisher Correction: A dietary fatty acid counteracts neuronal mechanical sensitization.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A dietary fatty acid counteracts neuronal mechanical sensitization.

PIEZO2 is the essential transduction channel for touch discrimination, vibration, and proprioception. Mice and humans lacking Piezo2 experience severe mechanosensory and proprioceptive deficits and fail to develop tactile allodynia. Bradykinin, a proalgesic agent released during inflammation, potentiates PIEZO2 activity. Molecules that decrease PIEZO2 function could reduce heightened touch responses during inflammation. Here, we find that the dietary fatty acid margaric acid (MA) decreases PIEZO2 function in a dose-dependent manner. Chimera analyses demonstrate that the PIEZO2 beam is a key region tuning MA-mediated channel inhibition. MA reduces neuronal action potential firing elicited by mechanical stimuli in mice and rat neurons and counteracts PIEZO2 sensitization by bradykinin. Finally, we demonstrate that this saturated fatty acid decreases PIEZO2 currents in touch neurons derived from human induced pluripotent stem cells. Our findings report on a natural product that inhibits PIEZO2 function and counteracts neuronal mechanical sensitization and reveal a key region for channel inhibition.

Omega-3 Fatty Acids Modulate TRPV4 Function through Plasma Membrane Remodeling.

Dietary consumption of ω-3 polyunsaturated fatty acids (PUFAs), present in fish oils, is known to improve the vascular response, but their molecular targets remain largely unknown. Activation of the TRPV4 channel has been implicated in endothelium-dependent vasorelaxation. Here, we studied the contribution of ω-3 PUFAs to TRPV4 function by precisely manipulating the fatty acid content in Caenorhabditis elegans. By genetically depriving the worms of PUFAs, we determined that the metabolism of ω-3 fatty acids is required for TRPV4 activity. Functional, lipid metabolome, and biophysical analyses demonstrated that ω-3 PUFAs enhance TRPV4 function in human endothelial cells and support the hypothesis that lipid metabolism and membrane remodeling regulate cell reactivity. We propose a model whereby the eicosanoid's epoxide group location increases membrane fluidity and influences the endothelial cell response by increasing TRPV4 channel activity. ω-3 PUFA-like molecules might be viable antihypertensive agents for targeting TRPV4 to reduce systemic blood pressure.

Hyaluronan modulates TRPV1 channel opening, reducing peripheral nociceptor activity and pain.

Hyaluronan (HA) is present in the extracellular matrix of all body tissues, including synovial fluid in joints, in which it behaves as a filter that buffers transmission of mechanical forces to nociceptor nerve endings thereby reducing pain. Using recombinant systems, mouse-cultured dorsal root ganglia (DRG) neurons and in vivo experiments, we found that HA also modulates polymodal transient receptor potential vanilloid subtype 1 (TRPV1) channels. HA diminishes heat, pH and capsaicin (CAP) responses, thus reducing the opening probability of the channel by stabilizing its closed state. Accordingly, in DRG neurons, HA decreases TRPV1-mediated impulse firing and channel sensitization by bradykinin. Moreover, subcutaneous HA injection in mice reduces heat and capsaicin nocifensive responses, whereas the intra-articular injection of HA in rats decreases capsaicin joint nociceptor fibres discharge. Collectively, these results indicate that extracellular HA reduces the excitability of the ubiquitous TRPV1 channel, thereby lowering impulse activity in the peripheral nociceptor endings underlying pain.

The influence of cold temperature on cellular excitability of hippocampal networks.

The hippocampus plays an important role in short term memory, learning and spatial navigation. A characteristic feature of the hippocampal region is its expression of different electrical population rhythms and activities during different brain states. Physiological fluctuations in brain temperature affect the activity patterns in hippocampus, but the underlying cellular mechanisms are poorly understood. In this work, we investigated the thermal modulation of hippocampal activity at the cellular network level. Primary cell cultures of mouse E17 hippocampus displayed robust network activation upon light cooling of the extracellular solution from baseline physiological temperatures. The activity generated was dependent on action potential firing and excitatory glutamatergic synaptic transmission. Involvement of thermosensitive channels from the transient receptor potential (TRP) family in network activation by temperature changes was ruled out, whereas pharmacological and immunochemical experiments strongly pointed towards the involvement of temperature-sensitive two-pore-domain potassium channels (K(2P)), TREK/TRAAK family. In hippocampal slices we could show an increase in evoked and spontaneous synaptic activity produced by mild cooling in the physiological range that was prevented by chloroform, a K(2P) channel opener. We propose that cold-induced closure of background TREK/TRAAK family channels increases the excitability of some hippocampal neurons, acting as a temperature-sensitive gate of network activation. Our findings in the hippocampus open the possibility that small temperature variations in the brain in vivo, associated with metabolism or blood flow oscillations, act as a switch mechanism of neuronal activity and determination of firing patterns through regulation of thermosensitive background potassium channel activity.