Piezo1 is a mechanically activated ion channel and mediates pressure induced pancreatitis

Mechanosensing by Piezo1 and its implications in the kidney

Piezo1 is an essential mechanosensitive transduction ion channel in mammals. Its unique structure makes it capable of converting mechanical cues into electrical and biological signals, modulating biological and (patho)physiological processes in a wide variety of cells. There is increasing evidence demonstrating that the piezo1 channel plays a vital role in renal physiology and disease conditions. This review summarizes the current evidence on the structure and properties of Piezo1, gating modulation, and pharmacological characteristics, with special focus on the distribution and (patho)physiological significance of Piezo1 in the kidney, which may provide insights into potential treatment targets for renal diseases involving this ion channel.

Extracorporeal Shock-Wave Lithotripsy and Endoscopy for the Treatment of Pain in Chronic Pancreatitis : A Sham-Controlled, Randomized Trial

BACKGROUND

No randomized controlled trials have substantiated endoscopic decompression of the pancreatic duct in patients with painful chronic pancreatitis.

OBJECTIVE

To investigate the pain-relieving effect of pancreatic duct decompression in patients with chronic pancreatitis and intraductal stones.

DESIGN

24-week, parallel-group, randomized controlled trial (ClinicalTrials.gov: NCT03966781).

SETTING

Asian Institute of Gastroenterology in India from February 2021 to July 2022.

PARTICIPANTS

106 patients with chronic pancreatitis.

INTERVENTION

Combined extracorporeal shock-wave lithotripsy (ESWL) and endoscopic retrograde pancreatography (ERP) compared with sham procedures.

MEASUREMENTS

The primary end point was pain relief on a 0- to 10-point visual analog scale (VAS) at 12 weeks. Secondary outcomes were assessed after 12 and 24 weeks and included 30% pain relief, opioid use, pain-free days, questionaries, and complications to interventions.

RESULTS

52 patients in the ESWL/ERP group and 54 in the sham group were included. At 12 weeks, the ESWL/ERP group showed better pain relief compared with the sham group (mean difference in change, -0.7 [95% CI, -1.3 to 0] on the VAS; P = 0.039). The difference between groups was not sustained at the 24-week follow-up, and no differences were seen for 30% pain relief at 12- or 24-week follow-up. The number of pain-free days was increased (median difference, 16.2 days [CI, 3.9 to 28.5 days]), and the number of days using opioids was reduced (median difference, -5.4 days [CI, -9.9 to -0.9 days]) in the ESWL/ERP group compared with the sham group at 12-week follow-up. Safety outcomes were similar between groups.

LIMITATION

Single-center study and limited duration of follow-up.

CONCLUSION

In patients with chronic pancreatitis and intraductal stones, ESWL with ERP provided modest short-term pain relief.

PRIMARY FUNDING SOURCE

Asian Institute of Gastroenterology and Aalborg University Hospital.

Urolithin A's Role in Alleviating Severe Acute Pancreatitis via Endoplasmic Reticulum-Mitochondrial Calcium Channel Modulation

Severe acute pancreatitis (SAP), characterized by pancreatic acinar cell death, currently lacks effective targeted therapies. Ellagic acid (EA), rich in pomegranate, shows promising anti-inflammatory and antioxidant effects in SAP treatment. However, the roles of other forms of EA, such as plant extracellular vesicles (EVs) extracted from pomegranate, and Urolithin A (UA), converted from EA through gut microbiota metabolism in vivo, have not been definitively elucidated. Our research aimed to compare the effects of pomegranate-derived EVs (P-EVs) and UA in the treatment of SAP to screen an effective formulation and to explore its mechanisms in protecting acinar cells in SAP. By comparing the protective effects of P-EVs and UA on injured acinar cells, UA showed superior therapeutic effects than P-EVs. Subsequently, we further discussed the mechanism of UA in alleviating SAP inflammation. In vivo animal experiments found that UA could not only improve the inflammatory environment of pancreatic tissue and peripheral blood circulation in SAP mice but also revealed that the mechanism of UA in improving SAP might be related to mitochondria and endoplasmic reticulum (ER) through the results including pancreatic tissue transcriptomics and transmission electron microscopy. Further research found that UA could regulate ER-mitochondrial calcium channels and reduce pancreatic tissue necroptosis. In vitro experiments of mouse pancreatic organoids and acinar cells also confirmed that UA could improve pancreatic inflammation by regulating the ER-mitochondrial calcium channel and necroptosis pathway proteins. This study not only explored the therapeutic effect of plant EVs on SAP but also revealed that UA could alleviate SAP by regulating ER-mitochondrial calcium channel and reducing acinar cell necroptosis, providing insights into the pathogenesis and potential treatment of SAP.

Pleiotropic physiological functions of Piezo1 in human body and its effect on malignant behavior of tumors

Mechanosensitive ion channel protein 1 (Piezo1) is a large homotrimeric membrane protein. Piezo1 has various effects and plays an important and irreplaceable role in the maintenance of human life activities and homeostasis of the internal environment. In addition, recent studies have shown that Piezo1 plays a vital role in tumorigenesis, progression, malignancy and clinical prognosis. Piezo1 is involved in regulating the malignant behaviors of a variety of tumors, including cellular metabolic reprogramming, unlimited proliferation, inhibition of apoptosis, maintenance of stemness, angiogenesis, invasion and metastasis. Moreover, Piezo1 regulates tumor progression by affecting the recruitment, activation, and differentiation of multiple immune cells. Therefore, Piezo1 has excellent potential as an anti-tumor target. The article reviews the diverse physiological functions of Piezo1 in the human body and its major cellular pathways during disease development, and describes in detail the specific mechanisms by which Piezo1 affects the malignant behavior of tumors and its recent progress as a new target for tumor therapy, providing new perspectives for exploring more potential effects on physiological functions and its application in tumor therapy.

Piezo1-induced durotaxis of pancreatic stellate cells depends on TRPC1 and TRPV4 channels

Pancreatic stellate cells (PSCs) are primarily responsible for producing the stiff tumor tissue in pancreatic ductal adenocarcinoma (PDAC). Thereby, PSCs generate a stiffness gradient between the healthy pancreas and the tumor. This gradient induces durotaxis, a form of directional cell migration driven by differential stiffness. The molecular sensors behind durotaxis are still unclear. To investigate the role of mechanosensitive ion channels in PSC durotaxis, we established a two-dimensional stiffness gradient mimicking PDAC. Using pharmacological and genetic methods, we investigated the role of the ion channels Piezo1, TRPC1, and TRPV4 in PSC durotaxis. We found that PSC migration towards a stiffer substrate is diminished by altering Piezo1 activity. Moreover, disrupting TRPC1 along with TRPV4 abolishes PSC durotaxis even when Piezo1 is functional. Hence, PSC durotaxis is optimal with an intermediary level of mechanosensitive channel activity, which we simulated using a numerically discretized mathematical model. Our findings suggest that mechanosensitive ion channels, particularly Piezo1, detect the mechanical microenvironment to guide PSC migration.

Piezo1, the new actor in cell volume regulation

All animal cells control their volume through a complex set of mechanisms, both to counteract osmotic perturbations of the environment and to enable numerous vital biological processes, such as proliferation, apoptosis, and migration. The ability of cells to adjust their volume depends on the activity of ion channels and transporters which, by moving K+, Na+, and Cl- ions across the plasma membrane, generate the osmotic gradient that drives water in and out of the cell. In 2010, Patapoutian's group identified a small family of evolutionarily conserved, Ca2+-permeable mechanosensitive channels, Piezo1 and Piezo2, as essential components of the mechanically activated current that mediates mechanotransduction in vertebrates. Piezo1 is expressed in several tissues and its opening is promoted by a wide range of mechanical stimuli, including membrane stretch/deformation and osmotic stress. Piezo1-mediated Ca2+ influx is used by the cell to convert mechanical forces into cytosolic Ca2+ signals that control diverse cellular functions such as migration and cell death, both dependent on changes in cell volume and shape. The crucial role of Piezo1 in the regulation of cell volume was first demonstrated in erythrocytes, which need to reduce their volume to pass through narrow capillaries. In HEK293 cells, increased expression of Piezo1 was found to enhance the regulatory volume decrease (RVD), the process whereby the cell re-establishes its original volume after osmotic shock-induced swelling, and it does so through Ca2+-dependent modulation of the volume-regulated anion channels. More recently we reported that Piezo1 controls the RVD in glioblastoma cells via the modulation of Ca2+-activated K+ channels. To date, however, the mechanisms through which this mechanosensitive channel controls cell volume and maintains its homeostasis have been poorly investigated and are still far from being understood. The present review aims to provide a broad overview of the literature discussing the recent advances on this topic.

OCaR1 endows exocytic vesicles with autoregulatory competence by preventing uncontrolled Ca2+ release, exocytosis, and pancreatic tissue damage

Regulated exocytosis is initiated by increased Ca2+ concentrations in close spatial proximity to secretory granules, which is effectively prevented when the cell is at rest. Here we showed that exocytosis of zymogen granules in acinar cells was driven by Ca2+ directly released from acidic Ca2+ stores including secretory granules through NAADP-activated two-pore channels (TPCs). We identified OCaR1 (encoded by Tmem63a) as an organellar Ca2+ regulator protein integral to the membrane of secretory granules that controlled Ca2+ release via inhibition of TPC1 and TPC2 currents. Deletion of OCaR1 led to extensive Ca2+ release from NAADP-responsive granules under basal conditions as well as upon stimulation of GPCR receptors. Moreover, OCaR1 deletion exacerbated the disease phenotype in murine models of severe and chronic pancreatitis. Our findings showed OCaR1 as a gatekeeper of Ca2+ release that endows NAADP-sensitive secretory granules with an autoregulatory mechanism preventing uncontrolled exocytosis and pancreatic tissue damage.

Acute pancreatitis: pathogenesis and emerging therapies

Acute pancreatitis is a severe inflammatory disorder with limited treatment options. Improved understanding of disease mechanisms has led to new and potential therapies. Here we summarize what we view as some of the most promising new therapies for treating acute pancreatitis, emphasizing the rationale of specific treatments based on disease mechanisms. Targeted pharmacologic interventions are highlighted. We explore potential treatment benefits and risks concerning reducing acute injury, minimizing complications, and improving long-term outcomes. Mechanisms associated with acute pancreatitis initiation, perpetuation, and reconstitution are highlighted, along with potential therapeutic targets and how these relate to new treatments.

Recent advances in the understanding and management of chronic pancreatitis pain

Abdominal pain is the most common symptom of chronic pancreatitis (CP) and is often debilitating for patients and very difficult to treat. To date, there exists no cure for the disease. Treatment strategies focus on symptom management and on mitigation of disease progression by reducing toxin exposure and avoiding recurrent inflammatory events. Traditional treatment protocols start with medical management followed by consideration of procedural or surgical intervention on selected patients with severe and persistent pain. The incorporation of adjuvant therapies to treat comorbidities including psychiatric disorders, exocrine pancreatic insufficiency, mineral bone disease, frailty, and malnutrition, are in its early stages. Recent clinical studies and animal models have been designed to improve investigation into the pathophysiology of CP pain, as well as to improve pain management. Despite the array of tools available, many therapeutic options for the management of CP pain provide incomplete relief. There still remains much to discover about the neural regulation of pancreas-related pain. In this review, we will discuss research from the last 5 years that has provided new insights into novel methods of pain phenotyping and the pathophysiology of CP pain. These discoveries have led to improvements in patient selection for optimization of outcomes for both medical and procedural management, and identification of potential future therapies.

Piezo channels in the intestinal tract

The intestine is the largest mechanosensitive organ in the human body whose epithelial cells, smooth muscle cells, neurons and enteroendocrine cells must sense and respond to various mechanical stimuli such as motility, distension, stretch and shear to regulate physiological processes including digestion, absorption, secretion, motility and immunity. Piezo channels are a newly discovered class of mechanosensitive ion channels consisting of two subtypes, Piezo1 and Piezo2. Piezo channels are widely expressed in the intestine and are involved in physiological and pathological processes. The present review summarizes the current research progress on the expression, function and regulation of Piezo channels in the intestine, with the aim of providing a reference for the future development of therapeutic strategies targeting Piezo channels.

Cysteine-modified PEGylated nanoparticles for targeted delivery of methylprednisolone to pancreatitis

The timely suppression of inflammatory mediator production and mitigation of their effects on pancreatic acinar cells are crucial for the successful management of acute pancreatitis. To achieve effective treatment, we present a novel approach utilizing cysteine modified PEG nanoparticles for both precise accumulation at the site of pancreatitis and specific targeting of acinar cells. Methylprednisolone, a nonsteroidal anti-inflammatory drug, was tailored to enhance its circulation time in the bloodstream, preferentially accumulate in the pancreas and enhance cell uptake efficiency by acinar cells through specifically targeting L-Type amino acid transporter 1. The nanosystem significantly downregulated pro-inflammatory cytokines in plasma, resulting in the effective suppression of inflammation in acinar cells within an acute pancreatitis rat model. The utilization of the dual targeted therapy strategy holds considerable potential for the clinical management of pancreatitis.

Bioelectricity in dental medicine: a narrative review

BACKGROUND

Bioelectric signals, whether exogenous or endogenous, play crucial roles in the life processes of organisms. Recently, the significance of bioelectricity in the field of dentistry is steadily gaining greater attention.

OBJECTIVE

This narrative review aims to comprehensively outline the theory, physiological effects, and practical applications of bioelectricity in dental medicine and to offer insights into its potential future direction. It attempts to provide dental clinicians and researchers with an electrophysiological perspective to enhance their clinical practice or fundamental research endeavors.

METHODS

An online computer search for relevant literature was performed in PubMed, Web of Science and Cochrane Library, with the keywords "bioelectricity, endogenous electric signal, electric stimulation, dental medicine."

RESULTS

Eventually, 288 documents were included for review. The variance in ion concentration between the interior and exterior of the cell membrane, referred to as transmembrane potential, forms the fundamental basis of bioelectricity. Transmembrane potential has been established as an essential regulator of intercellular communication, mechanotransduction, migration, proliferation, and immune responses. Thus, exogenous electric stimulation can significantly alter cellular action by affecting transmembrane potential. In the field of dental medicine, electric stimulation has proven useful for assessing pulp condition, locating root apices, improving the properties of dental biomaterials, expediting orthodontic tooth movement, facilitating implant osteointegration, addressing maxillofacial malignancies, and managing neuromuscular dysfunction. Furthermore, the reprogramming of bioelectric signals holds promise as a means to guide organism development and intervene in disease processes. Besides, the development of high-throughput electrophysiological tools will be imperative for identifying ion channel targets and precisely modulating bioelectricity in the future.

CONCLUSIONS

Bioelectricity has found application in various concepts of dental medicine but large-scale, standardized, randomized controlled clinical trials are still necessary in the future. In addition, the precise, repeatable and predictable measurement and modulation methods of bioelectric signal patterns are essential research direction.

Structural and thermodynamic framework for PIEZO1 modulation by small molecules

Mechanosensitive PIEZO channels constitute potential pharmacological targets for multiple clinical conditions, spurring the search for potent chemical PIEZO modulators. Among them is Yoda1, a widely used synthetic small molecule PIEZO1 activator discovered through cell-based high-throughput screening. Yoda1 is thought to bind to PIEZO1's mechanosensory arm domain, sandwiched between two transmembrane regions near the channel pore. However, how the binding of Yoda1 to this region promotes channel activation remains elusive. Here, we first demonstrate that cross-linking PIEZO1 repeats A and B with disulfide bridges reduces the effects of Yoda1 in a redox-dependent manner, suggesting that Yoda1 acts by perturbing the contact between these repeats. Using molecular dynamics-based absolute binding free energy simulations, we next show that Yoda1 preferentially occupies a deeper, amphipathic binding site with higher affinity in PIEZO1 open state. Using Yoda1's binding poses in open and closed states, relative binding free energy simulations were conducted in the membrane environment, recapitulating structure-activity relationships of known Yoda1 analogs. Through virtual screening of an 8 million-compound library using computed fragment maps of the Yoda1 binding site, we subsequently identified two chemical scaffolds with agonist activity toward PIEZO1. This study supports a pharmacological model in which Yoda1 activates PIEZO1 by wedging repeats A and B, providing a structural and thermodynamic framework for the rational design of PIEZO1 modulators. Beyond PIEZO channels, the three orthogonal computational approaches employed here represent a promising path toward drug discovery in highly heterogeneous membrane protein systems.

Piezo1：the potential new therapeutic target for fibrotic diseases

Fibrosis is a pathological process that occurs in various organs, characterized by excessive deposition of extracellular matrix (ECM), leading to structural damage and, in severe cases, organ failure. Within the fibrotic microenvironment, mechanical forces play a crucial role in shaping cell behavior and function, yet the precise molecular mechanisms underlying how cells sense and transmit these mechanical cues, as well as the physical aspects of fibrosis progression, remain less understood. Piezo1, a mechanosensitive ion channel protein, serves as a pivotal mediator, converting mechanical stimuli into electrical or chemical signals. Accumulating evidence suggests that Piezo1 plays a central role in ECM formation and hemodynamics in the mechanical transduction of fibrosis expansion. This review provides an overview of the current understanding of the role of Piezo1 in fibrosis progression, encompassing conditions such as myocardial fibrosis, pulmonary fibrosis, renal fibrosis, and other fibrotic diseases. The main goal is to pave the way for potential clinical applications in the field of fibrotic diseases.

Neutrophil-specific ORAI1 Calcium Channel Inhibition Reduces Pancreatitis-associated Acute Lung Injury

Acute pancreatitis is initiated within pancreatic exocrine cells and sustained by dysregulated systemic inflammatory responses mediated by neutrophils. Store-operated Ca2+ entry (SOCE) through ORAI1 channels in pancreatic acinar cells triggers acute pancreatitis, and ORAI1 inhibitors ameliorate experimental acute pancreatitis, but the role of ORAI1 in pancreatitis-associated acute lung injury has not been determined. Here, we showed mice with pancreas-specific deletion of Orai1 (Orai1ΔPdx1, ∼70% reduction in the expression of Orai1) are protected against pancreatic tissue damage and immune cell infiltration, but not pancreatitis-associated acute lung injury, suggesting the involvement of unknown cells that may cause such injury through SOCE via ORAI1. Genetic (Orai1ΔMRP8) or pharmacological inhibition of ORAI1 in murine and human neutrophils decreased Ca2+ influx and impaired chemotaxis, reactive oxygen species production, and neutrophil extracellular trap formation. Unlike pancreas-specific Orai1 deletion, mice with neutrophil-specific deletion of Orai1 (Orai1ΔMRP8) were protected against pancreatitis- and sepsis-associated lung cytokine release and injury, but not pancreatic injury in experimental acute pancreatitis. These results define critical differences between contributions from different cell types to either pancreatic or systemic organ injury in acute pancreatitis. Our findings suggest that any therapy for acute pancreatitis that targets multiple rather than single cell types is more likely to be effective.

Spinal afferent innervation in flat-mounts of the rat stomach: anterograde tracing

The dorsal root ganglia (DRG) project spinal afferent axons to the stomach. However, the distribution and morphology of spinal afferent axons in the stomach have not been well characterized. In this study, we used a combination of state-of-the-art techniques, including anterograde tracer injection into the left DRG T7-T11, avidin-biotin and Cuprolinic Blue labeling, Zeiss M2 Imager, and Neurolucida to characterize spinal afferent axons in flat-mounts of the whole rat stomach muscular wall. We found that spinal afferent axons innervated all regions with a variety of distinct terminal structures innervating different gastric targets: (1) The ganglionic type: some axons formed varicose contacts with individual neurons within myenteric ganglia. (2) The muscle type: most axons ran in parallel with the longitudinal and circular muscles and expressed spherical varicosities. Complex terminal structures were observed within the circular muscle layer. (3) The ganglia-muscle mixed type: some individual varicose axons innervated both myenteric neurons and the circular muscle, exhibiting polymorphic terminal structures. (4) The vascular type: individual varicose axons ran along the blood vessels and occasionally traversed the vessel wall. This work provides a foundation for future topographical anatomical and functional mapping of spinal afferent axon innervation of the stomach under normal and pathophysiological conditions.

Mechanotransductive receptor Piezo1 as a promising target in the treatment of fibrosis diseases

Fibrosis could happen in every organ, leading to organic malfunction and even organ failure, which poses a serious threat to global health. Early treatment of fibrosis has been reported to be the turning point, therefore, exploring potential correlates in the pathogenesis of fibrosis and how to reverse fibrosis has become a pressing issue. As a mechanism-sensitive cationic calcium channel, Piezo1 turns on in response to changes in the lipid bilayer of the plasma membrane. Piezo1 exerts multiple biological roles, including inhibition of inflammation, cytoskeletal stabilization, epithelial-mesenchymal transition, stromal stiffness, and immune cell mechanotransduction, interestingly enough. These processes are closely associated with the development of fibrotic diseases. Recent studies have shown that deletion or knockdown of Piezo1 attenuates the onset of fibrosis. Therefore, in this paper we comprehensively describe the biology of this gene, focusing on its potential relevance in pulmonary fibrosis, renal fibrosis, pancreatic fibrosis, and cardiac fibrosis diseases, except for the role of drugs (agonists), increased intracellular calcium and mechanical stress using this gene in alleviating fibrosis.

Immune response mechanisms in acute and chronic pancreatitis: strategies for therapeutic intervention

Acute pancreatitis (AP) is one of the most common inflammatory diseases of the gastrointestinal tract and a steady rising diagnosis for inpatient hospitalization. About one in four patients, who experience an episode of AP, will develop chronic pancreatitis (CP) over time. While the initiating causes of pancreatitis can be complex, they consistently elicit an immune response that significantly determines the severity and course of the disease. Overall, AP is associated with a significant mortality rate of 1-5%, which is caused by either an excessive pro-inflammation, or a strong compensatory inhibition of bacterial defense mechanisms which lead to a severe necrotizing form of pancreatitis. At the time-point of hospitalization the already initiated immune response is the only promising common therapeutic target to treat or prevent a severe disease course. However, the complexity of the immune response requires fine-balanced therapeutic intervention which in addition is limited by the fact that a significant proportion of patients is in danger of development or progress to recurrent and chronic disease. Based on the recent literature we survey the disease-relevant immune mechanisms and evaluate appropriate and promising therapeutic targets for the treatment of acute and chronic pancreatitis.

Mechanosensing Piezo channels in gastrointestinal disorders

All cells in the body are exposed to physical force in the form of tension, compression, gravity, shear stress, or pressure. Cells convert these mechanical cues into intracellular biochemical signals; this process is an inherent property of all cells and is essential for numerous cellular functions. A cell's ability to respond to force largely depends on the array of mechanical ion channels expressed on the cell surface. Altered mechanosensing impairs conscious senses, such as touch and hearing, and unconscious senses, like blood pressure regulation and gastrointestinal (GI) activity. The GI tract's ability to sense pressure changes and mechanical force is essential for regulating motility, but it also underlies pain originating in the GI tract. Recent identification of the mechanically activated ion channels Piezo1 and Piezo2 in the gut and the effects of abnormal ion channel regulation on cellular function indicate that these channels may play a pathogenic role in disease. Here, we discuss our current understanding of mechanically activated Piezo channels in the pathogenesis of pancreatic and GI diseases, including pancreatitis, diabetes mellitus, irritable bowel syndrome, GI tumors, and inflammatory bowel disease. We also describe how Piezo channels could be important targets for treating GI diseases.

Endotherapy for Pancreas Divisum

Pancreas divisum (PD) is a common anatomic variant of the pancreatic duct. Causal association between PD and pancreatitis has been debated for many years. Minor papilla sphincterotomy (miES) is offered in clinical practice to patients with idiopathic acute recurrent pancreatitis (iRAP) and PD. However, available data originate mainly from observational studies with many limitations. An ongoing international, multicenter, sham-controlled trial is evaluating the efficacy of miES in iRAP and PD. Endoscopic therapy for pain relief has limited to no benefit in patients with chronic abdominal pain or chronic pancreatitis who have PD and is not recommended.

Pressure stress delays cyclooxygenase-2 expression induced by interleukin-1β in cultured human pulmonary artery smooth muscle cells

Introduction

Pulmonary artery smooth muscle cells (PASMCs) play an important role in the sequence of events leading to the formation of pulmonary hypertension (PH). However, little is known about the direct effects of high pressure on the function and intercellular signaling pathways of PASMCs. The aim of this study was to evaluate the effect of pressure stress that simulates PH on interleukin (IL)-1β- or angiotensin II-induced cyclooxygenase-2 (COX-2) expression in cultured human PASMCs.

Methods

Either 20 or 60 mmHg atmospheric pressure was applied to PASMCs by a pressure-loading apparatus. Protein expression and phosphorylation were analyzed by western blotting. mRNA expression was analyzed by quantitative real-time reverse transcription-polymerase chain reaction.

Results

IL-1β-induced COX-2 protein expression peaked at 6 h in non-pressurized cells, whereas COX-2 expression was delayed, peaking at 12 h, in 20 and 60 mmHg pressurized cells. Both pressures also delayed the time to peak COX-2 mRNA expression induced by IL-1β. In addition, pressure stress delayed the time to peak mitogen-activated protein kinase (MAPK) phosphorylation induced by IL-1β. In contrast, angiotensin II-induced transient COX-2 mRNA expression and MAPK phosphorylation were not affected by pressure stress.

Conclusion

These results suggest that pressure stress delays IL-1β-induced COX-2 expression via the delayed activation of MAPKs in PASMCs, and the effects of pressure stress differ according to the bioactive substance being stimulated. Our results demonstrate that the application of pressure stress to PASMCs directly alters cell function, which may provide a basic insight into our understanding of the pathogenesis of PH.

Barasertib impedes chondrocyte senescence and alleviates osteoarthritis by mitigating the destabilization of heterochromatin induced by AURKB

Osteoarthritis (OA) is a common joint disease characterized by progressive cartilage loss that causes disability worldwide. The accumulation of senescent chondrocytes in aging human cartilage contributes to the high incidence of OA. Heterochromatin instability, the hallmark and driving factor of senescence, regulates the expression of the senescence-associated secretory phenotype that induces inflammation and cartilage destruction. However, the role of heterochromatin instability in OA progression remains unclear. In this work, we identified AURKB as a key senescence-associated chromatin regulator using bioinformatics methods. We found that AURKB was upregulated in OA cartilage and chondrocytes exposed to abnormal mechanical strain. Overexpression of AURKB could cause senescence and heterochromatin instability. Furthermore, the AURKB inhibitor Barasertib reversed senescence and heterochromatin instability in chondrocytes and alleviated OA in a rat model. Mechanistically, abnormal mechanical strain increased AURKB levels through the Piezo1/Ca2+ signaling axis. Blocking Piezo1/Ca2+ signaling by short interfering RNA against Piezo1 and Ca2+ chelator BAPTA could reduce the expression of AURKB and alleviate senescence in chondrocytes exposed to abnormal mechanical strain. In conclusion, our data confirmed that abnormal mechanical strain increases the expression of AURKB by activating the Piezo1/Ca2+ signaling axis, leading to destabilized heterochromatin and senescence in chondrocytes, whereas Barasertib consolidates heterochromatin, counteracts senescence and alleviates OA.

Senso-immunology: the past, present, and future

Pain and mechanical stimulation are thought to be alarm systems that alert the brain to physical abnormalities. When we experience unpleasant feelings in infected or traumatized tissues, our awareness is directed to the afflicted region, prompting activities such as resting or licking the tissue. Despite extensive research into the molecular biology of nociceptors, it was unclear whether their role was limited to the generation and transmission of unpleasant feelings or whether they actively modulate the pathogenesis of infected or traumatized tissues. Recently, it has become clear how the sensory and immune systems interact with one another and share similar receptors and ligands to modify the pathogenesis of various diseases. In this paper, we summarize the mechanisms of crosstalk between the sensory and immune systems and the impact of this new interdisciplinary field, which should be dubbed 'senso-immunology,' on medical science.

Slowed Intestinal Transit Induced by Less Mucus in Intestinal Goblet Cell Piezo1-Deficient Mice through Impaired Epithelial Homeostasis

Mucus secreted by goblet cells (GCs) may play an important role in intestinal transit function. Our previous study found that Piezo1 protein is essential for GC function; however, the effect of GC Piezo1 on intestinal transit function is unclear. Our study aimed to investigate the effect of Piezo1 in GCs on intestinal transit and the potential mechanism. We compared intestinal mucus, fecal form, intestinal transit time, intestinal epithelial cell composition, and stem cell function in WT and GC-specific Piezo1-deficient (Piezo1ΔGC) mice. Our results revealed a correlation between mucus and intestinal transit: the less mucus there was, the slower the intestinal transit. Piezo1 deficiency in GCs led to decreased mucus synthesis and also disrupted the ecological niche of colon stem cells (CSCs). Through organoid culture, we found that the capacity of proliferation and differentiation in Piezo1ΔGC mouse CSCs was significantly decreased, which also led to a reduced source of GCs. Further studies found that the reduced Wnt and Notch signals in colon crypts might be the potential mechanism. These results indicated the importance of GC Piezo1 in intestinal transit function, which acts by maintaining the homeostasis of intestinal epithelial cells and mucus.

Inhibition of Piezo1 Ameliorates Intestinal Inflammation and Limits the Activation of Group 3 Innate Lymphoid Cells in Experimental Colitis

Piezo1, the mechanosensory ion channel, has attracted increasing attention for its essential roles in various inflammatory responses and immune-related diseases. Although most of the key immune cells in inflammatory bowel disease (IBD) have been reported to be regulated by Piezo1, the specific role of Piezo1 in colitis has yet to be intensively studied. The present study investigated the impact of pharmacological inhibition of Piezo1 on dextran sulfate sodium (DSS)-induced colitis and explored the role of Piezo1 in intestinal immune cells in the context of colitis. We observed upregulated expression of Piezo1 in the colon tissue of mice with DSS-induced colitis. Pharmacological inhibition of Piezo1 by GsMTx4 diminished the severity of colitis. Piezo1 inhibition downregulated the expression of pro-inflammatory mediators Il1b, Il6, and Ptgs2 in colonic tissue and suppressed the production of IL-6 from macrophages and dendritic cells without altering the balance of T helper (Th) cells. In particular, Piezo1 did not affect cell viability but regulated cell proliferation and production of IL-17A in group 3 innate lymphoid cells (ILC3s), which is dependent on the PI3K-Akt-mTOR signaling pathway. Our findings uncover Piezo1 as an effective regulator of gut inflammation. Targeting Piezo1 could be a promising strategy to modulate intestinal immunity in IBD.

Mechanosensitive Piezo1 channel in physiology and pathophysiology of the central nervous system

Since the discovery of the mechanosensitive Piezo1 channel in 2010, there has been a significant amount of research conducted to explore its regulatory role in the physiology and pathology of various organ systems. Recently, a growing body of compelling evidence has emerged linking the activity of the mechanosensitive Piezo1 channel to health and disease of the central nervous system. However, the exact mechanisms underlying these associations remain inadequately comprehended. This review systematically summarizes the current research on the mechanosensitive Piezo1 channel and its implications for central nervous system mechanobiology, retrospects the results demonstrating the regulatory role of the mechanosensitive Piezo1 channel on various cell types within the central nervous system, including neural stem cells, neurons, oligodendrocytes, microglia, astrocytes, and brain endothelial cells. Furthermore, the review discusses the current understanding of the involvement of the Piezo1 channel in central nervous system disorders, such as Alzheimer's disease, multiple sclerosis, glaucoma, stroke, and glioma.

Piezo1 in Digestive System Function and Dysfunction

Piezo1, a non-selective cation channel directly activated by mechanical forces, is widely expressed in the digestive system and participates in biological functions physiologically and pathologically. In this review, we summarized the latest insights on Piezo1's cellular effect across the entire digestive system, and discussed the role of Piezo1 in various aspects including ingestion and digestion, material metabolism, enteric nervous system, intestinal barrier, and inflammatory response within digestive system. The goal of this comprehensive review is to provide a solid foundation for future research about Piezo1 in digestive system physiologically and pathologically.

Piezo1 channel activation stimulates ATP production through enhancing mitochondrial respiration and glycolysis in vascular endothelial cells

BACKGROUND AND PURPOSE

Piezo1 channels are mechanosensitive cationic channels that are activated by mechanical stretch or shear stress. Endothelial Piezo1 activation by shear stress caused by blood flow induces ATP release from endothelial cells; however, the link between shear stress and endothelial ATP production is unclear.

EXPERIMENTAL APPROACH

The mitochondrial respiratory function of cells was measured by using high-resolution respirometry system Oxygraph-2k. The intracellular Ca2+ concentration was evaluated by using Fluo-4/AM and mitochondrial Ca2+ concentration by Rhod-2/AM.

KEY RESULTS

The specific Piezo1 channel activator Yoda1 or its analogue Dooku1 increased [Ca2+ ]i in human umbilical vein endothelial cells (HUVECs), and both Yoda1 and Dooku1 increased mitochondrial oxygen consumption rates (OCRs) and mitochondrial ATP production in HUVECs and primary cultured rat aortic endothelial cells (RAECs). Knockdown of Piezo1 inhibited Yoda1- and Dooku1-induced increases of mitochondrial OCRs and mitochondrial ATP production in HUVECs. The shear stress mimetics, Yoda1 and Dooku1, and the Piezo1 knock-down technique also demonstrated that Piezo1 activation increased glycolysis in HUVECs. Chelating extracellular Ca2+ with EGTA or chelating cytosolic Ca2+ with BAPTA-AM did not affect Yoda1- and Dooku1-induced increases of mitochondrial OCRs and ATP production, but chelating cytosolic Ca2+ inhibited Yoda1- and Dooku1-induced increase of glycolysis. Confocal microscopy showed that Piezo1 channels are present in mitochondria of endothelial cells, and Yoda1 and Dooku1 increased mitochondrial Ca2+ in endothelial cells.

CONCLUSION AND IMPLICATIONS

Piezo1 channel activation stimulates ATP production through enhancing mitochondrial respiration and glycolysis in vascular endothelial cells, suggesting a novel role of Piezo1 channel in endothelial ATP production.

The role of Ca2+ signalling in the pathology of exocrine pancreas

Exocrine pancreas has been the field of many successful studies in pancreatic physiology and pathology. However, related disease - acute pancreatitis (AP) is still takes it toll with more than 100,000 related deaths worldwide per year. In spite of significant scientific progress and several human trials currently running for AP, there is still no specific treatment in the clinic. Studies of the mechanism of initiation of AP have identified two crucial conditions: sustained elevations of cytoplasmic calcium concentration (Ca2+ plateau) and significantly reduced intracellular energy (ATP depletion). These hallmarks are interdependent, i.e., Ca2+ plateau increase energy demand for its clearance while energy production is greatly affected by the pathology. Result of long standing Ca2+ plateau is destabilisation of the secretory granules and premature activation of the digestive enzymes leading to necrotic cell death. Main attempts so far to break the vicious circle of cell death have been concentrated on reduction of Ca2+ overload or reduction of ATP depletion. This review will summarise these approaches, including recent developments of potential therapies for AP.

Transcranial Magneto-Acoustic Stimulation Attenuates Synaptic Plasticity Impairment through the Activation of Piezo1 in Alzheimer's Disease Mouse Model

The neuropathological features of Alzheimer's disease include amyloid plaques. Rapidly emerging evidence suggests that Piezo1, a mechanosensitive cation channel, plays a critical role in transforming ultrasound-related mechanical stimuli through its trimeric propeller-like structure, but the importance of Piezo1-mediated mechanotransduction in brain functions is less appreciated. However, apart from mechanical stimulation, Piezo1 channels are strongly modulated by voltage. We assume that Piezo1 may play a role in converting mechanical and electrical signals, which could induce the phagocytosis and degradation of Aβ, and the combined effect of mechanical and electrical stimulation is superior to single mechanical stimulation. Hence, we design a transcranial magneto-acoustic stimulation (TMAS) system, based on transcranial ultrasound stimulation (TUS) within a magnetic field that combines a magneto-acoustic coupling effect electric field and the mechanical force of ultrasound, and applied it to test the above hypothesis in 5xFAD mice. Behavioral tests, in vivo electrophysiological recordings, Golgi-Cox staining, enzyme-linked immunosorbent assay, immunofluorescence, immunohistochemistry, real-time quantitative PCR, Western blotting, RNA sequencing, and cerebral blood flow monitoring were used to assess whether TMAS can alleviate the symptoms of AD mouse model by activating Piezo1. TMAS treatment enhanced autophagy to promote the phagocytosis and degradation of β-amyloid through the activation of microglial Piezo1 and alleviated neuroinflammation, synaptic plasticity impairment, and neural oscillation abnormalities in 5xFAD mice, showing a stronger effect than ultrasound. However, inhibition of Piezo1 with an antagonist, GsMTx-4, prevented these beneficial effects of TMAS. This research indicates that Piezo1 can transform TMAS-related mechanical and electrical stimuli into biochemical signals and identifies that the favorable effects of TMAS on synaptic plasticity in 5xFAD mice are mediated by Piezo1.

Novel identification and modulation of the mechanosensitive Piezo1 channel in human myometrium

Approximately 10% of US births deliver preterm before 37 weeks of completed gestation. Premature infants are at risk for life-long debilitating morbidities and death, and spontaneous preterm labour explains 50% of preterm births. In all cases existing treatments are ineffective, and none are FDA approved. The mechanisms that initiate preterm labour are not well understood but may result from dysfunctional regulation of quiescence mechanisms. Human pregnancy is accompanied by large increases in blood flow, and the uterus must enlarge by orders of magnitude to accommodate the growing fetus. This mechanical strain suggests that stretch-activated channels may constitute a mechanism to explain gestational quiescence. Here we identify for the first time that Piezo1, a mechanosensitive cation channel, is present in the uterine smooth muscle and microvascular endothelium of pregnant myometrium. Piezo is downregulated during preterm labour, and stimulation of myometrial Piezo1 in an organ bath with the agonist Yoda1 relaxes the tissue in a dose-dependent fashion. Further, stimulation of Piezo1 while inhibiting protein kinase A, AKT, or endothelial nitric oxide synthase mutes the negative inotropic effects of Piezo1 activation, intimating that actions on the myocyte and endothelial nitric oxide signalling contribute to Piezo1-mediated contractile dynamics. Taken together, these data highlight the importance of stretch-activated channels in pregnancy maintenance and parturition, and identify Piezo1 as a tocolytic target of interest. KEY POINTS: Spontaneous preterm labour is a serious obstetric dilemma without a known cause or effective treatments. Piezo1 is a stretch-activated channel important to muscle contractile dynamics. Piezo1 is present in the myometrium and is dysregulated in women who experience preterm labour. Activation of Piezo1 by the agonist Yoda1 relaxes the myometrium in a dose-dependent fashion, indicating that Piezo1 modulation may have therapeutic benefits to treat preterm labour.

Aging-associated Decline in Vascular Smooth Muscle Cell Mechanosensation is Mediated by Piezo1 Channel

Aging of the vasculature is associated with detrimental changes in vascular smooth muscle cell (VSMC) mechanosensitivity to extrinsic forces in their surrounding microenvironment. However, how chronological aging alters VSMCs' ability to sense and adapt to mechanical perturbations remains unexplored. Here, we show defective VSMC mechanosensation in aging measured with ultrasound tweezers-based micromechanical system, force instantaneous frequency spectrum and transcriptome analyses. The mechanobiological study reveals that aged VSMCs adapt a relatively inert solid-like state with altered actin cytoskeletal integrity, resulting in an impairment in their mechanosensitivity and dynamic mechanoresponse to mechanical perturbations. The aging-associated decline in mechanosensation behaviors is mediated by hyperactivity of Piezo1-dependent calcium signaling. Inhibition of Piezo1 alleviates vascular aging and partially restores the loss in dynamic contractile properties in aged cells. Altogether, our study reveals the novel signaling pathway underlying aging-associated aberrant mechanosensation in VSMC and identifies Piezo1 as a potential therapeutic mechanobiological target to alleviate vascular aging.

Mechanical homeostasis imbalance in hepatic stellate cells activation and hepatic fibrosis

Chronic liver disease or repeated damage to hepatocytes can give rise to hepatic fibrosis. Hepatic fibrosis (HF) is a pathological process of excessive sedimentation of extracellular matrix (ECM) proteins such as collagens, glycoproteins, and proteoglycans (PGs) in the hepatic parenchyma. Changes in the composition of the ECM lead to the stiffness of the matrix that destroys its inherent mechanical homeostasis, and a mechanical homeostasis imbalance activates hepatic stellate cells (HSCs) into myofibroblasts, which can overproliferate and secrete large amounts of ECM proteins. Excessive ECM proteins are gradually deposited in the Disse gap, and matrix regeneration fails, which further leads to changes in ECM components and an increase in stiffness, forming a vicious cycle. These processes promote the occurrence and development of hepatic fibrosis. In this review, the dynamic process of ECM remodeling of HF and the activation of HSCs into mechanotransduction signaling pathways for myofibroblasts to participate in HF are discussed. These mechanotransduction signaling pathways may have potential therapeutic targets for repairing or reversing fibrosis.

Piezo inhibition prevents and rescues scarring by targeting the adipocyte to fibroblast transition

While past studies have suggested that plasticity exists between dermal fibroblasts and adipocytes, it remains unknown whether fat actively contributes to fibrosis in scarring. We show that adipocytes convert to scar-forming fibroblasts in response to Piezo -mediated mechanosensing to drive wound fibrosis. We establish that mechanics alone are sufficient to drive adipocyte-to- fibroblast conversion. By leveraging clonal-lineage-tracing in combination with scRNA-seq, Visium, and CODEX, we define a "mechanically naïve" fibroblast-subpopulation that represents a transcriptionally intermediate state between adipocytes and scar-fibroblasts. Finally, we show that Piezo1 or Piezo2 -inhibition yields regenerative healing by preventing adipocytes' activation to fibroblasts, in both mouse-wounds and a novel human-xenograft-wound model. Importantly, Piezo1 -inhibition induced wound regeneration even in pre-existing established scars, a finding that suggests a role for adipocyte-to-fibroblast transition in wound remodeling, the least-understood phase of wound healing. Adipocyte-to-fibroblast transition may thus represent a therapeutic target for minimizing fibrosis via Piezo -inhibition in organs where fat contributes to fibrosis.

Piezo1-mediated mechanotransduction promotes entheseal pathological new bone formation in ankylosing spondylitis

OBJECTIVE

The aim of this study was to identify the role of Piezo1-mediated mechanotransduction in entheseal pathological new bone formation and to explore the underlying molecular mechanism.

METHODS

Spinal ligament tissues were collected from 14 patients with ankylosing spondylitis (AS) and 14 non-AS controls and bulk RNA sequencing was conducted. Collagen antibody-induced arthritis models were established to observe pathological new bone formation. Pharmacological inhibition and genetic ablation of Piezo1 was performed in animal models to identify the essential role of Piezo1. Entheseal osteo-chondral lineage cells were collected and in vitro cell culture system was established to study the role and underlying mechanism of Piezo1 in regulation of chondrogenesis, osteogenesis and its own expression.

RESULTS

Piezo1 was aberrantly upregulated in ligaments and entheseal tissues from patients with AS and animal models. Pharmaceutical and genetic inhibition of Piezo1 attenuated while activation of Piezo1 promoted pathological new bone formation. Mechanistically, activation of CaMKII (Calcium/calmodulin dependent protein kinase II) signalling was found essential for Piezo1-mediated mechanotransduction. In addition, Piezo1 was upregulated by AS-associated inflammatory cytokines.

CONCLUSION

Piezo1-mediated mechanotransduction promotes entheseal pathological new bone formation through CaMKII signalling in AS.

Preclinical safety evaluation of calcineurin inhibitors delivered through an intraductal route to prevent post-ERCP pancreatitis demonstrates endocrine and systemic safety

OBJECTIVE

There is an urgent need for safe and targeted interventions to mitigate post-ERCP pancreatitis (PEP). Calcineurin inhibitors (CnIs) offer therapeutic promise as calcineurin signaling within acinar cells is a key initiating event in PEP. In previous proof-of-concept studies using experimental models, we showed that concurrent intra-pancreatic ductal administration of the CnIs, tacrolimus (Tac) or cyclosporine A (CsA) with the ERCP radiocontrast agent (RC) prevented PEP. To translate this finding clinically, we investigated potential toxic effects of intraductal delivery of a single-dose RC-CnI formulation on endocrine pancreas function and systemic toxicities in a preclinical PEP model.

METHODS

C57BL/6J mice underwent ductal cannulation and received a single, intra-pancreatic ductal infusion of RC or RC with Tac or CsA (treatment groups) or underwent ductal cannulation without infusion ('sham' group). To assess endocrine function, intraperitoneal glucose tolerance test (IPGTT) was performed at two days before infusion and on day 2 and 14 post-surgery. To evaluate off-target tissue toxicities, renal and hepatic function-related parameters including blood urea nitrogen, plasma creatinine, potassium, aspartate aminotransferase, alanine aminotransferase, and total bilirubin were measured at the same time-points as IPGTT. Histological and biochemical indicators of pancreas injury and inflammation were also evaluated.

RESULTS

No abnormalities in glucose metabolism, hepatic or renal function were observed on day 2 or 14 in mice administered with intraductal RC or RC with Tac or CsA.

CONCLUSION

Intraductal delivery of RC-CnI formulation was safe and well-tolerated with no significant acute or subacute endocrine or systemic toxicities, underscoring its clinical utility to prevent PEP.

The Role of the Piezo1 Mechanosensitive Channel in the Musculoskeletal System

Since the recent discovery of the mechanosensitive Piezo1 channels, many studies have addressed the role of the channel in various physiological or even pathological processes of different organs. Although the number of studies on their effects on the musculoskeletal system is constantly increasing, we are still far from a precise understanding. In this review, the knowledge available so far regarding the musculoskeletal system is summarized, reviewing the results achieved in the field of skeletal muscles, bones, joints and cartilage, tendons and ligaments, as well as intervertebral discs.

The role of PIEZO ion channels in the musculoskeletal system

PIEZO1 and PIEZO2 are mechanosensitive cation channels that are highly expressed in numerous tissues throughout the body and exhibit diverse, cell-specific functions in multiple organ systems. Within the musculoskeletal system, PIEZO1 functions to maintain muscle and bone mass, sense tendon stretch, and regulate senescence and apoptosis in response to mechanical stimuli within cartilage and the intervertebral disc. PIEZO2 is essential for transducing pain and touch sensations as well as proprioception in the nervous system, which can affect musculoskeletal health. PIEZO1 and PIEZO2 have been shown to act both independently as well as synergistically in different cell types. Conditions that alter PIEZO channel mechanosensitivity, such as inflammation or genetic mutations, can have drastic effects on these functions. For this reason, therapeutic approaches for PIEZO-related disease focus on altering PIEZO1 and/or PIEZO2 activity in a controlled manner, either through inhibition with small molecules, or through dietary control and supplementation to maintain a healthy cell membrane composition. Although many opportunities to better understand PIEZO1 and PIEZO2 remain, the studies summarized in this review highlight how crucial PIEZO channels are to musculoskeletal health and point to promising possible avenues for their modulation as a therapeutic target.

Mechanosensitive ion channels in apoptosis and ferroptosis: focusing on the role of Piezo1

Mechanosensitive ion channels sense mechanical stimuli applied directly to the cellular membranes or indirectly through their tethered components, provoking cellular mechanoresponses. Among others, Piezo1 mechanosensitive ion channel is a relatively novel Ca2+-permeable channel that is primarily present in non-sensory tissues. Recent studies have demonstrated that Piezo1 plays an important role in Ca2+-dependent cell death, including apoptosis and ferroptosis, in the presence of mechanical stimuli. It has also been proven that cancer cells are sensitive to mechanical stresses due to higher expression levels of Piezo1 compared to normal cells. In this review, we discuss Piezo1-mediated cell death mechanisms and therapeutic strategies to inhibit or induce cell death by modulating the activity of Piezo1 with pharmacological drugs or mechanical perturbations induced by stretch and ultrasound. [BMB Reports 2023; 56(3): 145-152].

PIEZO1-Related Physiological and Pathological Processes in CNS: Focus on the Gliomas

PIEZO1 is ubiquitously expressed in cells in different kinds of tissues throughout the body, which can sense physical or mechanical stimuli and translate them into intracellular electrochemical signals to regulate organism functions. In particular, PIEZO1 appears in complex interactive regulatory networks as a central node, governing normal and pathological functions in the body. However, the effect and mechanism of the activation or expression of PIEZO1 in diseases of the central nervous system (CNS) remain unclear. On one hand, in CNS diseases, pathophysiological processes in neurons and glial are often accompanied by variations in the mechanical properties of the cellular and extracellular matrix stiffness. The expression of PIEZO1 can therefore be upregulated, in responding to mechanical stimulation, to drive the biological process in cells, which in turns indirectly affects the cellular microenvironment, resulting in alterations of the cellular status. On the other hand, it may have contradictory effects with the change of active patterns and/or subcellular location. This review highlights the biological processes involved with PIEZO1 in CNS cells, with special emphasis on its multiple roles in glioma-associated phenotypes. In conclusion, PIEZO1 can be used as an indicator to assess the malignancy and prognosis of patients with gliomas, as well as a therapeutic target for clinical application following fully exploring the potential mechanism of PIEZO1 in CNS diseases.

The mechanosensitive ion channel Piezo1 modulates the migration and immune response of microglia

Microglia are the brain's resident immune cells, performing surveillance to promote homeostasis and healthy functioning. While microglial chemical signaling is well-studied, mechanical cues regulating their function are less well-understood. Here, we investigate the role of the mechanosensitive ion channel Piezo1 in microglia migration, pro-inflammatory cytokine production, and stiffness sensing. In Piezo1 knockout transgenic mice, we demonstrated the functional expression of Piezo1 in microglia and identified genes whose expression was consequently affected. Functional assays revealed that Piezo1 deficiency in microglia enhanced migration toward amyloid β-protein, and decreased levels of pro-inflammatory cytokines produced upon stimulation by lipopolysaccharide, both in vitro and in vivo. The phenomenon could be mimicked or reversed chemically using a Piezo1-specific agonist or antagonist. Finally, we also showed that Piezo1 mediated the effect of substrate stiffness-induced migration and cytokine expression. Altogether, we show that Piezo1 is an important molecular mediator for microglia, its activation modulating microglial migration and immune responses.

The Mechanosensitive Ion Channel PIEZO1 in Intestinal Epithelial Cells Mediates Inflammation through the NOD-Like Receptor 3 Pathway in Crohn's Disease

BACKGROUND

Crohn's disease (CD) is an incurable chronic intestinal inflammatory disease with no recognized cause. It has been reported that the mechanosensitive ion channel PIEZO1 initiates proinflammatory responses. However, little is known about the role of PIEZO1 in CD.

METHODS

Ileum biopsies were obtained from 30 patients with CD and 15 healthy volunteers. Clinical data were collected to determine the relationship between CD and PIEZO1. First, HT29 cells were incubated with Yoda1 and GsMTx4 (Grammostola spatulata mechanotoxin 4) to activate and inhibit PIEZO1, respectively. Second, PIEZO1 knockdown was performed using small interfering RNA. Third, calcium imaging, flow cytometry, and immunofluorescence were used to detect intracellular calcium and mitochondrial function. Last, real-time quantitative polymerase chain reaction, immunoblotting, and enzyme-linked immunosorbent assay were used to quantify PIEZO1, proinflammatory cytokines, and NLRP3 (NOD-like receptor 3)-related compounds.

RESULTS

PIEZO1 was highly expressed in the ileum of patients with CD and correlated positively with the Crohn's Disease Activity Index, platelet count, and hematocrit and fecal calprotectin levels. In HT29 cells, Yoda1 triggered calcium influx, which was inhibited by GsMTx4 treatment and small interfering RNA-mediated PIEZO1 knockdown. Increased calcium concentrations resulted in increased reactive oxygen species accumulation and decreased mitochondrial membrane potential, whereas decreased calcium concentrations caused by GsMTx4 and PIEZO1 knockdown had the opposite effect. Mechanistically, molecules in the NLRP3 pathway were activated in patients with CD and HT29 cells were stimulated by lipopolysaccharide; these effects were reversed by the knockdown of PIEZO1. Finally, PIEZO1 and NLRP3 knockdown decreased proinflammatory cytokine levels in HT29 cells.

CONCLUSIONS

PIEZO1 in intestinal epithelial cells caused calcium influx, which resulted in mitochondrial dysfunction and activated the NLRP3 inflammasome, mediating intestinal inflammation.

Microglial Piezo1 senses Aβ fibril stiffness to restrict Alzheimer's disease

The pathology of Alzheimer's disease (AD) is featured with extracellular amyloid-β (Aβ) plaques, whose impact on the mechanical properties of the surrounding brain tissues is unclear. Microglia sense and integrate biochemical cues of the microenvironment. However, whether the microglial mechanosensing pathways influence AD pathogenesis is unknown. Here, we surveyed the elevated stiffness of Aβ-plaque-associated tissues and observed the selective upregulation of the mechanosensitive ion channel Piezo1 in Aβ-plaque-associated microglia. Piezo1 sensed the stiffness stimuli of Aβ fibrils and subsequently induced Ca²⁺ influx for microglial clustering, phagocytosis, and compacting of Aβ plaques. Microglia lacking Piezo1 led to the exacerbation of Aβ pathology and cognitive decline, whereas pharmacological activation of microglial Piezo1 ameliorated brain Aβ burden and cognitive impairment in 5 × FAD mice. Together, our results reveal that Piezo1, a mechanosensor of Aβ fibril stiffness in microglia, represents a potential therapeutic target for AD.

Watching Living Cells in Action in the Exocrine Pancreas: The Palade Prize Lecture

George Palade's pioneering electron microscopical studies of the pancreatic acinar cell revealed the intracellular secretory pathway from the rough endoplasmic reticulum at the base of the cell to the zymogen granules in the apical region. Palade also described for the first time the final stage of exocytotic enzyme secretion into the acinar lumen. The contemporary studies of the mechanism by which secretion is acutely controlled, and how the pancreas is destroyed in the disease acute pancreatitis, rely on monitoring molecular events in the various identified pancreatic cell types in the living pancreas. These studies have been carried out with the help of high-resolution fluorescence recordings, often in conjunction with patch clamp current measurements. In such studies we have gained much detailed information about the regulatory events in the exocrine pancreas in health as well as disease, and new therapeutic opportunities have been revealed.

Nicotinic stimulation of splenic T cells is protective in endoscopic retrograde cholangiopancreatography-induced acute pancreatitis in mice

It has previously been shown that current smoking is protective against endoscopic retrograde cholangiopancreatography (ERCP)-induced acute pancreatitis, but the mechanism of this effect was not identified. We tested the hypothesis that nicotine is the active factor in this protection in a mouse model of ERCP. Pretreatment with nicotine dose dependently inhibited acute pancreatitis caused by infusion of ERCP contrast solution into the main pancreatic duct in mice. 3-2,4-Dimethoxybenzylidene anabaseine (GTS-21), a specific partial agonist of the α7 nicotinic cholinergic receptor (α7nAChR), also protected the pancreas against ERCP-induced acute pancreatitis. The effects of GTS-21 were abolished by pretreatment with the nicotinic receptor antagonist mecamylamine. Surgical splenectomy performed 7 days before ERCP-induced pancreatitis blocked the protective effects of GTS-21. Intravenous injection of a crude preparation of total splenocytes prepared from mice pretreated with GTS-21 inhibited ERCP-induced pancreatitis; splenocytes from mice treated with vehicle had no effect. When T cells were removed from the crude GTS-21-treated splenocyte preparation by immunomagnetic separation, the remaining non-T-cell splenocytes did not protect against ERCP-induced acute pancreatitis. We conclude that nicotine protects against ERCP-induced acute pancreatitis and that splenic T cells are required for this effect. Stimulation of α7 nicotinic cholinergic receptors may protect against ERCP-induced acute pancreatitis and may also be a novel approach to therapeutic reversal of ongoing acute pancreatitis.NEW & NOTEWORTHY Epidemiological evidence indicated that acute smoking reduced the risk of endoscopic retrograde cholangiopancreatography (ERCP)-induced pancreatitis, but the mechanism has remained elusive. The current findings indicate the nicotine reduces the severity of ERCP-induced pancreatitis by stimulating a population of splenic T cells that exert a protective effect on the pancreas. These findings raise the possibility that nicotinic agonists might be useful in treating pancreatitis.

Calcium, mitochondria and the initiation of acute pancreatitis

Acute pancreatitis is characterized by necrosis of its parenchymal cells and influx and activation of inflammatory cells that further promote injury and necrosis. This review is intended to discuss the central role of disorders of calcium metabolism and mitochondrial dysfunction in the mechanism of pancreatitis development. The disorders are placed in context of calcium and mitochondria in physiologic function of the pancreas. Moreover, we discuss potential therapeutics for preventing pathologic calcium signals that injure mitochondria and interventions that promote the removal of injured mitochondria and regenerate new and heathy populations of mitochondria.

Intraductal pressure in experimental models of acute and chronic pancreatitis in mice

BACKGROUND/OBJECTIVES

Pancreatic intraductal pressure is related to the development of pancreatitis, including post-ERCP (endoscopic retrograde cholangiopancreatography) pancreatitis. In this study, we investigate pancreatic intraductal pressure in various mouse models of acute and chronic pancreatitis.

METHODS

Post-ERCP pancreatitis was induced by retrograde infusion of normal saline or radiocontrast at the constant rate of 10 or 20 μL/min. Obstructive pancreatitis was induced by ligation of the pancreatic duct followed by a single injection of caerulein and the changes of intraductal pressure were recorded in day 3 for obstructive acute pancreatitis and day 14 for obstructive chronic pancreatitis. Non-obstructive pancreatitis was induced by repetitive intraperitoneal injections of caerulein. The changes of intraductal pressure were recorded right after the last caerulein injection for non-obstructive acute pancreatitis and after the completion of 4-week caerulein injections for non-obstructive chronic pancreatitis.

RESULTS

Elevated pancreatic intraductal pressure was observed in both normal saline and radiocontrast infusion groups and was furtherly indicated that was positively correlated with the viscosity of solution but not genders. In the models of obstructive pancreatitis, a rise in intraductal pressure was observed in both acute and chronic pancreatitis; whereas in the models of non-obstructive pancreatitis, a rise in intraductal pressure was only observed in chronic, but not acute pancreatitis.

CONCLUSIONS

During ERCP, the elevations in pancreatic intraductal pressure are induced by increasing rate or viscous solution of infusion. During different forms of experimental acute and chronic pancreatitis, obstructive or non-obstructive etiologies of pancreatitis also induces the elevations in pancreatic intraductal pressure.

Infection-induced membrane ruffling initiates danger and immune signaling via the mechanosensor PIEZO1

Microorganisms are generally sensed by receptors recognizing microbial molecules, which evoke changes in cellular activities and gene expression. Bacterial pathogens induce secretion of the danger signal ATP as an early alert response of intestinal epithelial cells, initiating overt inflammation. However, what triggers ATP secretion during infection is unclear. Here we show that the inherently mechanosensitive plasma membrane channel PIEZO1 acts as a sensor for bacterial entry. PIEZO1 is mechanically activated by invasion-induced membrane ruffles upstream of Ca²⁺ influx and ATP secretion. Mimicking mechanical stimuli of pathogen uptake with sterile beads equally elicits ATP secretion. Chemical or genetic PIEZO1 inactivation inhibits mechanically induced ATP secretion. Moreover, chemical or mechanical PIEZO1 activation evokes gene expression in immune and barrier pathways. Thus, mechanosensation of invasion-induced plasma membrane distortion initiates immune signaling upon infection, independently of detection of microbial molecules. Hence, PIEZO1-dependent detection of infection is driven by physical signals instead of chemical ligands.

Cellular Mechanosensitivity: Validation of an Adaptable 3D-Printed Device for Microindentation

Mechanotransduction refers to the cellular ability to sense mechanical stimuli from the surrounding environment and convert them into biochemical signals that regulate cellular physiology and homeostasis. Mechanosensitive ion channels (MSCs), especially ones of Piezo family (Piezo1 and Piezo2), play a crucial role in mechanotransduction. These transmembrane proteins directly react to mechanical cues by triggering the onset of an ionic current. The relevance of this mechanism in driving physiology and pathology is emerging, and there is a growing need for the identification of an affordable and reliable assay to measure it. Setting up a mechanosensitivity assay requires exerting a mechanical stimulus on single cells while observing the downstream effects of channels opening. We propose an open-hardware approach to stimulate single adherent cells through controlled microindentation, using a 3D-printed actuation platform. We validated the device by measuring the mechanosensitivity of a neural mice cell line where the expression level and activity of Piezo1 were genetically and pharmacologically manipulated. Moreover, this extremely versatile device could be integrated with different read-out technologies, offering a new tool to improve the understanding of mechanotransduction in living cells.

USP25 Deficiency Exacerbates Acute Pancreatitis via Up-Regulating TBK1-NF-κB Signaling in Macrophages

BACKGROUND & AIMS

Severe acute pancreatitis can easily lead to systemic inflammatory response syndrome and death. Macrophages are known to be involved in the pathophysiology of acute pancreatitis (AP), and macrophage activation correlates with disease severity. In this study, we examined the role of ubiquitin-specific protease 25, a deubiquitinating enzyme and known regulator of macrophages, in the pathogenesis of AP.

METHODS

We used L-arginine, cerulein, and choline-deficient ethionine-supplemented diet-induced models of AP in Usp25^-/- mice and wild-type mice. We also generated bone marrow Usp25^-/- chimeric mice and initiated L-arginine-mediated AP. Primary acinar cells and bone marrow-derived macrophages were isolated from wild-type and Usp25^-/- mice to dissect molecular mechanisms.

RESULTS

Our results show that Usp25 deficiency exacerbates pancreatic and lung injury, neutrophil and macrophage infiltration, and systemic inflammatory responses in L-arginine, cerulein, and choline-deficient ethionine-supplemented diet-induced models of AP. Bone marrow Usp25^-/- chimeric mice challenged with L-arginine show that Usp25 deficiency in macrophages exaggerates AP by up-regulating the TANK-binding kinase 1 (TBK1)-nuclear factor-κB (NF-κB) signaling pathway. Similarly, in vitro data confirm that Usp25 deficiency enhances the TBK1-NF-κB pathway, leading to increased expression of inflammatory cytokines in bone marrow-derived macrophages.

CONCLUSIONS

Usp25 deficiency in macrophages enhances TBK1-NF-κB signaling, and the induction of inflammatory chemokines and type I interferon-related genes exacerbates pancreatic and lung injury in AP.