PIEZO1 variants have been associated with generalized lymphatic dysplasia (GLD) through mechanisms involving reduced PIEZO1 expression. Here, we report variants where the mechanism involves reduced channel mechanical sensitivity. Two of the variants encode amino acid changes in the channel's cap structure (Ile2270Thr and Arg2335Gln), one in the ninth transmembrane helical unit (THU) below the cap (Gly1978Asp) and one in the fifth THU distant from the cap (Glu829Val). Patch-clamp studies of the cap and sub-cap variant channels revealed abolished or reduced channel mechanical sensitivity with the possibility to activate the channels and partly rescue mechanical sensitivity by the small molecule Yoda1. The potency of Yoda1 at the variant channels was less than at the wild-type channel, but chemical synthesis of Yoda1 analogs revealed a molecule with improved potency. The data suggest cases of GLD in which there is decreased channel mechanical sensitivity and the potential to reduce dysfunction pharmacologically.

How cardiovascular activity interacts with lipid homeostasis is incompletely understood. We postulated a role for blood flow acting at endothelium in lipid regulatory organs. Transcriptome analysis was performed on livers from mice engineered for deletion of the flow-sensing PIEZO1 channel in endothelium. This revealed unique up-regulation of Cyp7a1 , which encodes the rate-limiting enzyme for bile synthesis from cholesterol in hepatocytes. Consistent with this effect were increased gallbladder and plasma bile acids and lowered hepatic and plasma cholesterol. Elevated portal fluid flow acting via endothelial PIEZO1 and genetically enhanced PIEZO1 conversely suppressed Cyp7a1 . Activation of hepatic endothelial PIEZO1 channels promoted phosphorylation of nitric oxide synthase 3, and portal flow-mediated suppression of Cyp7a1 depended on nitric oxide synthesis, suggesting endothelium-to-hepatocyte coupling via nitric oxide. PIEZO1 variants in people were associated with hepatobiliary disease and dyslipidemia. The data suggest an endothelial force sensing mechanism that controls lipid regulation in parenchymal cells to modulate whole-body lipid homeostasis.

PIEZO1 channels are mechanically activated cation channels crucial for sensing mechanical forces. Their dysfunction has been associated with pathophysiological states including generalized lymphatic dysplasia, varicose vein disease and hereditary xerocytosis. Thus, investigating PIEZO1 is crucial for the pharmaceutical industry, which requires scalable techniques for drug discovery. Several studies have used high throughput automated patch clamp (APC) combined with Yoda1, a specific gating modifier of PIEZO1 channels, to investigate PIEZO1 in heterologous expression systems and primary cells.

PIEZO1 is a eukaryotic membrane protein that assembles as trimers to form calcium-permeable, non-selective cation channels with exquisite capabilities for mechanical force sensing and transduction of force into effect in diverse cell types that include blood cells, endothelial cells, epithelial cells, fibroblasts and stem cells and diverse systems that include bone, lymphatics and muscle. The channel has wide-ranging roles and is considered as a target for novel therapeutics in ailments spanning cancers and cardiovascular, dental, gastrointestinal, hepatobiliary, infectious, musculoskeletal, nervous system, ocular, pregnancy, renal, respiratory and urological disorders. The identification of PIEZO1 modulators is in its infancy but useful experimental tools emerged for activating, and to a lesser extent inhibiting, the channels. Elementary structure-activity relationships are known for the Yoda series of small molecule agonists, which show the potential for diverse physicochemical and pharmacological properties. Intriguing effects of Yoda1 include the stimulated removal of excess cerebrospinal fluid. Despite PIEZO1's broad expression, opportunities are suggested for selective positive or negative modulation without intolerable adverse effects. Here we provide a focused, non-systematic, narrative review of progress with this pharmacology and discuss potential future directions for research in the area.

BACKGROUND & AIMS:PIEZO1 and TRPV4 are mechanically and osmotically regulated calcium-permeable channels. The aim of this study was to determine the relevance and relationship of these channels in the contractile tone of the hepatic portal vein, which experiences mechanical and osmotic variations as it delivers blood to the liver from the intestines, gallbladder, pancreas and spleen. METHODS:Wall tension was measured in freshly dissected portal veins from adult male mice, which were genetically unmodified or modified for either a non-disruptive tag in native PIEZO1 or endothelial-specific PIEZO1 deletion. Pharmacological agents were used to activate or inhibit PIEZO1, TRPV4 and associated pathways, including Yoda1 and Yoda2 for PIEZO1 and GSK1016790A for TRPV4 agonism, respectively. RESULTS:PIEZO1 activation leads to nitric oxide synthase- and endothelium-dependent relaxation of the portal vein. TRPV4 activation causes contraction, which is also endothelium-dependent but independent of nitric oxide synthase. The TRPV4-mediated contraction is suppressed by inhibitors of phospholipase A2 and cyclooxygenases and mimicked by prostaglandin E2 , suggesting mediation by arachidonic acid metabolism. TRPV4 antagonism inhibits the effect of agonising TRPV4 but not PIEZO1. Increased wall stretch and hypo-osmolality inhibit TRPV4 responses while lacking effects on or amplifying PIEZO1 responses. CONCLUSIONS:The portal vein contains independently functioning PIEZO1 channels and TRPV4 channels in the endothelium, the pharmacological activation of which leads to opposing effects of vessel relaxation (PIEZO1) and contraction (TRPV4). In mechanical and osmotic strain, the PIEZO1 mechanism dominates. Modulators of these channels could present important new opportunities for manipulating liver perfusion and regeneration in disease and surgical procedures.

PIEZO1 trimers form mechanically-activated calcium-permeable non-selective cation channels which are expressed in many types of cells. Mutations in the PIEZO1 gene are associated with generalised lymphatic dysplasia, varicose vein disease, dehydrated hereditary stomatocytosis, malarial resistance and other conditions. Pharmacological modulation of PIEZO1 has been achieved using various compounds, most notably the small-molecule agonist Yoda1 and its inhibitor Dooku1. However, improvements in the potency and pharmacokinetic properties of such compounds are required to increase the usefulness, and small-molecule inhibitors of PIEZO1 are largely lacking. We sought to identify novel small-molecule agonists and inhibitors of mouse and human PIEZO1 channels. Analogues of Yoda1 were generated by medicinal chemistry approaches and a library of 11,200 compounds was screened in a calcium assay using cells overexpressing human PIEZO1. Analogues of hits from the screen were designed and synthesised and then tested for effectiveness in cells overexpressing mouse or human PIEZO1 using an orthogonal calcium assay, conventional (manual) patch-clamp and automated patch-clamp in 384-well format (SyncroPatch 384). We identified Yoda1 analogues with better aqueous solubility and microsomal stability than Yoda1 and improved potency. We identified and validated two novel structurally distinct small-molecule inhibitors of PIEZO1. Automated patch-clamp techniques were refined for activation of PIEZO1 channels by fluid flow in 384-well format. Novel small-molecule modulators of the channels were tested in these automated assays and confirmed as PIEZO1 modulators. We gained preliminary knowledge of the structure-activity relationships and promising compounds for further development. Supported by British Heart Foundation.

ABSTRACT Generalised Lymphatic Dysplasia (GLD) is characterised by widespread lymphoedema, with at least one of the following: fetal hydrops, intestinal or pulmonary lymphangiectasia, pleural effusions, pericardial effusions and ascites. Satisfactory medical therapies are lacking. A genetic association has been identified that prevents expression or surface trafficking of PIEZO1, a subunit of mechanically activated calcium-permeable channels. However, PIEZO1 is a large and highly polymorphic gene and interpretation of variants identified in this gene can be challenging. PIEZO1- related GLD with non-immune fetal hydrops is autosomal recessive, however, heterozygous variants in PIEZO1 (often gain-of-function) causing Dehydrated Hereditary Stomatocytosis (DHS) (a relative mild anaemia), may also present with perinatal non-immune hydrops (not caused by anaemia). Here we sought to develop methods to confirm pathogenicity of missense variants of uncertain significance in PIEZO1 , to gain deeper understanding and pharmacological solutions. Four novel GLD-associated missense variants in PIEZO1 are identified that express and surface localise as full-length protein but with reduced or abolished mechanically activated channel function. Yoda1, a small-molecule agonist, functionally rescues the channels and their physiological regulation by mechanical force and hypo-osmolality. The GLD-associated variants mediate intracellular calcium release as well as calcium entry, suggesting two pools of channels and opportunity for increased rescue through access to the intracellular pool. New Yoda1 analogues are also identified that improve rescue. The functional assays have assisted the interpretation of the variants of uncertain significance as the data suggest loss of PIEZO1 force sensing as a cause of the GLD observed in the patients. The potential to pharmacologically overcome the loss of force sensing was demonstrated and supports the concept of stimulation of PIEZO1 with an agonist to address wide-ranging problems of lymphatic insufficiency. GRAPHICAL ABSTRACT HIGHLIGHTS Previously unrecognised variants in PIEZO1 that associate with GLD are identified and characterised and pathogenicity confirmed The variants encode single amino acid changes that inhibit PIEZO1 channel activation by physiological mechanical forces A small-molecule agonist rescues the channels and their physiological regulation Variants are partly intracellular, suggesting an opportunity for improved rescue through the use of intracellular-acting agonists New agonists are identified that improve rescue, suggesting routes to medical therapies for GLD and potentially other disorders of lymphatic insufficiency

ABSTRACT How cardiovascular activity beneficially regulates lipid homeostasis is unclear. Here we hypothesise a mechanism in which mechanical force sensed by PIEZO1 ion channels in endothelium links blood flow to lipid regulation. We engineered mice for conditional deletion of PIEZO1 in endothelium and determined consequences for lipid regulation. Prominent are upregulated expression of hepatic Cyp7a1 and intestinal Ldlr genes, which are pivotal in cholesterol catabolism and excretion. Consistent with such regulation is endothelial PIEZO1-dependence of hepatic, intestinal and whole body cholesterol and bile homeostasis. There is organ perfusion-dependent gene regulation via endothelial PIEZO1 and downstream nitric oxide synthase. Endothelial PIEZO1-deleted mice are protected against hyperlipidaemia and ectopic fat deposition. Human PIEZO1 gene variants and a recapitulated human PIEZO1 gain-of-function variant in mice associate with dyslipidaemia. The data suggest lipid-promoting effects of endothelial force sensing and new opportunity for understanding and addressing problems of hyperlipidaemia.

PIEZO1 channels are mechanically activated cation channels that play a pivotal role in sensing mechanical forces in various cell types. Their dysfunction has been associated with numerous pathophysiological states, including generalized lymphatic dysplasia, varicose vein disease, and hereditary xerocytosis. Given their physiological relevance, investigating PIEZO1 is crucial for the pharmaceutical industry, which requires scalable techniques to allow for drug discovery. In this regard, several studies have used high-throughput automated patch clamp (APC) combined with Yoda1, a specific gating modifier of PIEZO1 channels, to explore the function and properties of PIEZO1 in heterologous expression systems, as well as in primary cells. However, a combination of solely mechanical stimulation (M-Stim) and high-throughput APC has not yet been available for the study of PIEZO1 channels. Here, we show that optimization of pipetting parameters of the SyncroPatch 384 coupled with multihole NPC-384 chips enables M-Stim of PIEZO1 channels in high-throughput electrophysiology. We used this approach to explore differences between the response of mouse and human PIEZO1 channels to mechanical and/or chemical stimuli. Our results suggest that applying solutions on top of the cells at elevated pipetting flows is crucial for activating PIEZO1 channels by M-Stim on the SyncroPatch 384. The possibility of comparing and combining mechanical and chemical stimulation in a high-throughput patch clamp assay facilitates investigations on PIEZO1 channels and thereby provides an important experimental tool for drug development.

Background and PurposeThe protein PIEZO1 forms mechanically activated, calcium‐permeable, non‐selective cation channels in numerous cell types from several species. Options for pharmacological modulation are limited and so we modified a small‐molecule agonist at PIEZO1 channels (Yoda1) to increase the ability to modulate these channels.Experimental ApproachMedicinal chemistry generated Yoda1 analogues that were tested in intracellular calcium and patch‐clamp assays on cultured cells exogenously expressing human or mouse PIEZO1 or mouse PIEZO2. Physicochemical assays and wire myography assays on veins from mice with genetic disruption of PIEZO1.Key ResultsA Yoda1 analogue (KC159) containing 4‐benzoic acid instead of the pyrazine of Yoda1 and its potassium salt (KC289) have equivalent or improved reliability, efficacy and potency, compared with Yoda1 in functional assays. Tested against overexpressed mouse PIEZO1 in calcium assays, the order of potency (as EC50 values, nM) was KC289, 150 > KC159 280 > Yoda1, 600). These compounds were selective for PIEZO1 over other membrane proteins, and the physicochemical properties were more suited to physiological conditions than those of Yoda1. The vasorelaxant effects were consistent with PIEZO1 agonism. In contrast, substitution with 2‐benzoic acid failed to generate a modulator.Conclusion and Implications4‐Benzoic acid modification of Yoda1 improves PIEZO1 agonist activity at PIEZO1 channels. We suggest naming this new modulator Yoda2. It should be a useful tool compound in physiological assays and facilitate efforts to identify a binding site. Such compounds may have therapeutic potential, for example, in diseases linked genetically to PIEZO1 such as lymphatic dysplasia.

Piezo1 forms mechanically activated nonselective cation channels that contribute to endothelial response to fluid flow. Here we reveal an important role in the control of capillary density. Conditional endothelial cell-specific deletion of Piezo1 in adult mice depressed physical performance. Muscle microvascular endothelial cell apoptosis and capillary rarefaction were evident and sufficient to account for the effect on performance. There was selective upregulation of thrombospondin-2 (TSP2), an inducer of endothelial cell apoptosis, with no effect on TSP1, a related important player in muscle physiology. TSP2 was poorly expressed in muscle endothelial cells but robustly expressed in muscle pericytes, in which nitric oxide (NO) repressed the Tsp2 gene without an effect on Tsp1. In endothelial cells, Piezo1 was required for normal expression of endothelial NO synthase. The data suggest an endothelial cell-pericyte partnership of muscle in which endothelial Piezo1 senses blood flow to sustain capillary density and thereby maintain physical capability.

PIEZO channels are mechanically-activated cation channels that play important roles in biological functions including touch, proprioception, shear stress and stretch sensation as well as blood pressure regulation. Mutations in Homo sapiens PIEZO1 channels are associated with anemia, malarial resistance, lymphatic dysplasia and varicose vein disease, suggesting important red blood cells and vascular roles in humans. The pharmacology of the PIEZO1 channels is in its infancy. Here we sought high throughout methodology for investigating small-molecule modulation in combination with mechanical stimulation. A bottleneck in PIEZO drug development has been the lack of mechanical stimulation in automated patch clamp. Here we show how the optimization of pipetting parameters and the modification of the NPC-384 chip of the SyncroPatch 384 lead to the possibility to mechanically stimulate PIEZO1 channels using high throughput electrophysiology. Data of mouse and human PIEZO1 channels expressed in HEK T-REX 293 cells activated by either mechanical or chemical stimuli will be shown as well as the combination of both methods. Under voltage-clamp we were able to show reliable quantification of PIEZO1 activation by fluid flow, Yoda1 (a small-molecule PIEZO1 agonist) and a Yoda1 analogue. To our knowledge, this is the first time that mechanical stimulation of PIEZO channels in a high throughput planar patch clamp system has been shown. The possibility of comparing and combining mechanical and chemical stimulation in a high throughput electrophysiological assay facilitates the biophysical and pharmacological studies of PIEZO channels. This work was supported by research grants from the Wellcome Trust, British Heart Foundation and has received funding from the European Union's Horizon 2020 research and innovation program.

Modifications at the glycolate moiety of englerin A were made to explore variations at the most sensitive site on the molecule for activity in the NCI 60 screen, wherein englerin A is highly potent and selective for renal cancer cells. Replacement of the glycolate by other functionalities as well as esterification of the glycolate hydroxyl yielded compounds which displayed excellent selectivity and potency compared with the natural product. TRPC4/5 ion channel experiments with five compounds showed delayed or reduced agonism with TRPC5, at much higher concentrations than englerin A. With TRPC4, these compounds all had no effect at 10 μM. The same compounds were not detectable in mouse serum after a single oral dose of 12.5 mg/kg. At 100 mg/kg p.o., no toxicity was observed, and blood levels were barely detectable. Intravenous administration led to toxicity but at substantially lower doses than for englerin A.

PIEZO1 is a subunit of mechanically-activated, nonselective cation channels. Gain-of-function PIEZO1 mutations are associated with dehydrated hereditary stomatocytosis (DHS), a type of anaemia, due to abnormal red blood cell function. Here, we hypothesised additional effects on the heart. Consistent with this hypothesis, mice engineered to contain the M2241R mutation in PIEZO1 to mimic a DHS mutation had increased cardiac mass and interventricular septum thickness at 8–12 weeks of age, without altered cardiac contractility. Myocyte size was greater and there was increased expression of genes associated with cardiac hypertrophy (Anp, Acta1 and β-MHC). There was also cardiac fibrosis, increased expression of Col3a1 (a gene associated with fibrosis) and increased responses of isolated cardiac fibroblasts to PIEZO1 agonism. The data suggest detrimental effects of excess PIEZO1 activity on the heart, mediated in part by amplified PIEZO1 function in cardiac fibroblasts.

Mechanical force is a determinant of Notch signalling but the mechanism of force detection and its coupling to Notch are unclear. We propose a role for Piezo1 channels, which are mechanically-activated non-selective cation channels. In cultured microvascular endothelial cells, Piezo1 channel activation by either shear stress or a chemical agonist Yoda1 activated a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10), a Ca2+-regulated transmembrane sheddase that mediates S2 Notch1 cleavage. Consistent with this observation, we found Piezo1-dependent increase in the abundance of Notch1 intracellular domain (NICD) that depended on ADAM10 and the downstream S3 cleavage enzyme, γ-secretase. Conditional endothelial-specific disruption of Piezo1 in adult mice suppressed the expression of multiple Notch1 target genes in hepatic vasculature, suggesting constitutive functional importance in vivo. The data suggest that Piezo1 is a mechanism conferring force sensitivity on ADAM10 and Notch1 with downstream consequences for sustained activation of Notch1 target genes and potentially other processes.

Mechanical force has emerged as a determinant of Notch signalling but the mechanisms of force sensing and coupling to Notch are unclear. Here we propose a role for Piezo1 channels, the recently identified mechanosensors of mammalian systems. Piezo1 channel opening in response to shear stress or a chemical agonist led to activation of a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10), a Ca-regulated transmembrane sheddase that mediates S2 Notch1 cleavage. Consistent with this observation there was increased Notch1 intracellular domain (NICD) that depended on ADAM10 and the downstream S3 cleavage enzyme, γ-secretase. Endothelial-specific disruption of Piezo1 in mice led to decreased Notch1-regulated gene expression in hepatic vasculature, consistent with prior evidence that Notch1 controls hepatic perfusion. The data suggest Piezo1 as a mechanism for coupling physiological force at the endothelium to ADAM10, Notch1, gene expression and vascular function.