Mechanosensitive Cation Channel Piezo1 Is Involved in Renal Fibrosis Induction.

Renal fibrosis, the result of different pathological processes, impairs kidney function and architecture, and usually leads to renal failure development. Piezo1 is a mechanosensitive cation channel highly expressed in kidneys. Activation of Piezo1 by mechanical stimuli increases cations influx into the cell with slight preference of calcium ions. Two different models of Piezo1 activation are considered: force through lipid and force through filament. Expression of Piezo1 on mRNA and protein levels was confirmed within the kidney. Their capacity is increased in the fibrotic kidney. The pharmacological tools for Piezo1 research comprise selective activators of the channels (Yoda1 and Jedi1/2) as well as non-selective inhibitors (spider peptide toxin) GsMTx4. Piezo1 is hypothesized to be the upstream element responsible for the activation of integrin. This pathway (calcium/calpain2/integrin beta1) is suggested to participate in profibrotic response induced by mechanical stimuli. Administration of the Piezo1 unspecific inhibitor or activators to unilateral ureter obstruction (UUO) mice or animals with folic acid-induced fibrosis modulates extracellular matrix deposition and influences kidney function. All in all, according to the recent data Piezo1 plays an important role in kidney fibrosis development. This channel has been selected as the target for pharmacotherapy of renal fibrosis.

Piezo1 involves in intracellular osteogenic transformation signal to promote the ossification of ligamentum flavum.

Ectopic osteogenesis refers to the occurrence of osteoblasts in soft tissues other than bone tissue and the formation of bone tissue. The ligamentum flavum is an essential connecting structure between adjacent vertebral lamina, which participates in the formation of the vertebral canal's posterior wall and maintains the vertebral body's stability. Ossification of the ligamentum flavum (OLF) is one of the manifestations of systemic ossification of the spinal ligaments and one of the degenerative diseases related to the spine. However, there is a lack of research on the expression and biological function of Piezo1 in ligamentum flavum. Whether Piezo1 participates in the development of OLF is still unclear. The FX-5000C cell or tissue pressure culture and real-time observation and analysis system was applied to stretch ligamentum flavum cells to detect the expression of mechanical stress channel and osteogenic markers after the effect of different stretching durations. The results showed elevated expression of mechanical stress channel Piezo1 and osteogenic markers with the effect of tensile time duration. In conclusion, Piezo1 involves in intracellular osteogenic transformation signal to promote the ossification of ligamentum flavum. An approved explanatory model and further research will be required in the future.

Piezo1 in endothelial cells is involved in vitamin D-induced vascular calcification.

The relationship between the Piezo1 channel of vascular endothelial cells and vascular calcification is unknown. In this study, after subcutaneous injection of vitamin D for 10 consecutive days, the mice showed an increase in serum calcium, aortic calcium content, vascular tension and pulse wave velocity. Piezo1channel antagonist, GsMTx4 alleviated arteriosclerosis and decreased the aortic calcium content, while Piezo1 agonist Yoda1 produced opposite effect. In addition, activation of Piezo1 by Yoda1 impaired the function of human umbilical vein endothelial cells (HUVECs), as evidenced by further decreased production of NO, reduction in expression levels of eNOS, MMP-2, PCNA and VEGFA. When co-culture of HUVECs and vascular smooth muscle cells (VSMCs), activation of Piezo1 in HUVECs enhanced expression levels of calcification-related SOX9 and Runx2 genes, increased ALP activity and calcium deposition in VSMCs. We concluded that Piezo1 in endothelial cells is involved in the pathogenesis of vascular calcification. This study provides a new experimental basis for the prevention and treatment of vascular calcification.

Prolonged Piezo1 Activation Induces Cardiac Arrhythmia.

The rhythmical nature of the cardiovascular system constantly generates dynamic mechanical forces. At the centre of this system is the heart, which must detect these changes and adjust its performance accordingly. Mechanoelectric feedback provides a rapid mechanism for detecting even subtle changes in the mechanical environment and transducing these signals into electrical responses, which can adjust a variety of cardiac parameters such as heart rate and contractility. However, pathological conditions can disrupt this intricate mechanosensory system and manifest as potentially life-threatening cardiac arrhythmias. Mechanosensitive ion channels are thought to be the main proponents of mechanoelectric feedback as they provide a rapid response to mechanical stimulation and can directly affect cardiac electrical activity. Here, we demonstrate that the mechanosensitive ion channel PIEZO1 is expressed in zebrafish cardiomyocytes. Furthermore, chemically prolonging PIEZO1 activation in zebrafish results in cardiac arrhythmias. indicating that this ion channel plays an important role in mechanoelectric feedback. This also raises the possibility that PIEZO1 gain of function mutations could be linked to heritable cardiac arrhythmias in humans.

Functional Expression of Mechanosensitive Piezo1/TRPV4 Channels in Mouse Osteoblasts.

Mechanical stress is an important regulatory factor in bone homeostasis. Mechanical stimulation of osteoblasts has been shown to elicit an increase in the concentration of intracellular free Ca2+ ([Ca2+]i). The pattern of functional expression of mechanosensitive ion channels remains unclear, however. Therefore, the purpose of this study was to investigate the pharmacological characteristics of [Ca2+]i in response to direct mechanical stimulation in osteoblasts. The morphological expression of mechanosensitive ion channels was also examined. Mouse osteoblast-like cells (MC3T3-E1 cells) were loaded with fura-2-acetoxymethyl ester, after which [Ca2+]i was measured. Increased levels of [Ca2+]i were observed in MC3T3-E1 cells in response to direct mechanical stimulation by means of a glass micropipette, but no desensitization. Application of a hypotonic solution also induced an increase in [Ca2+]i but was accompanied by a desensitizing effect. Extracellular Gd3+, GsMTx4, or RN-1734 reversibly inhibited this mechanical stimulation-induced increase in [Ca2+]i, whereas no inhibitory effect was observed with HC030031 or clemizole. When osteoblasts were stimulated with Yoda1, an increase was observed in [Ca2+]i together with a significant desensitizing effect. Immunoreactivity against Piezo1 and TRPV4 channel antibodies was detected in MC3T3-E1 cells. These results suggest that osteoblasts express Piezo1 and TRPV4 channels, which are involved in mechanosensitive processes during mechanical stress.

Chemical activation of the Piezo1 channel drives mesenchymal stem cell migration via inducing ATP release and activation of P2 receptor purinergic signaling.

In this study, we examined the Ca2+ -permeable Piezo1 channel, a newly identified mechanosensing ion channel, in human dental pulp-derived mesenchymal stem cells (MSCs) and hypothesized that activation of the Piezo1 channel regulates MSC migration via inducing ATP release and activation of the P2 receptor purinergic signaling. The Piezo1 mRNA and protein were readily detected in hDP-MSCs from multiple donors and, consistently, brief exposure to Yoda1, the Piezo1 channel-specific activator, elevated intracellular Ca2+ concentration. Yoda1-induced Ca2+ response was inhibited by ruthenium red or GsMTx4, two Piezo1 channel inhibitors, and also by Piezo1-specific siRNA. Brief exposure to Yoda1 also induced ATP release. Persistent exposure to Yoda1 stimulated MSC migration, which was suppressed by Piezo1-specific siRNA, and also prevented by apyrase, an ATP scavenger, or PPADS, a P2 generic antagonist. Furthermore, stimulation of MSC migration induced by Yoda1 as well as ATP was suppressed by PF431396, a PYK2 kinase inhibitor, or U0126, an inhibitor of the mitogen-activated protein kinase MEK/ERK signaling pathway. Collectively, these results suggest that activation of the Piezo1 channel stimulates MSC migration via inducing ATP release and subsequent activation of the P2 receptor purinergic signaling and downstream PYK2 and MEK/ERK signaling pathways, thus revealing novel insights into the molecular and signaling mechanisms regulating MSC migration. Such findings provide useful information for evolving a full understanding of MSC migration and homing and developing strategies to improve MSC-based translational applications.

Mechanosensitive ion channel Piezo1 is expressed in antral G cells of murine stomach.

G cells in the antrum region of the murine stomach produce gastrin, the central hormone for controlling gastric activities. Secretion of gastrin is induced mainly by protein breakdown products but also by distensions of the stomach wall. Although G cells respond to protein fragments via distinct chemosensory receptor types, the mechanism underlying G cell activation upon distention is entirely ambiguous. Mechanosensitive ion channels are considered as potential candidates for such a task. Therefore, we explore the possibility of whether Piezo1, a polymodal sensor for diverse mechanical forces, is expressed in antral G cells. The experimental analyses revealed that the vast majority of G cells indeed expressed Piezo1. Within flask-like G cells at the base of the antral invaginations, the Piezo1 protein was primarily located at the basolateral portion, which is thought to be the release site for the exocytic secretion of gastrin. In the spindle-like G cells, which are oriented parallel to the invaginations, Piezo1 protein was restricted to the cell body where the hormone was also located, whereas the long processes appeared to be devoid of Piezo1 protein. Our results suggest that mechanosensitive channels such as Piezo1, located in close proximity to hormone-release sites, enable G cells to respond directly to antrum distensions with gastrin secretion.

Activation of Piezo1 channels enhances spontaneous contractions of isolated human bladder strips via acetylcholine release from the mucosa.

Enhanced spontaneous bladder contractions (SBCs) have been thought one of the important underlying mechanisms for detrusor overactivity (DO). Piezo1 channel has been demonstrated involved in bladder function and dysfunction in rodents. We aimed to investigate the modulating role of Piezo1 in SBCs activity of human bladder. Human bladder tissues were obtained from 24 organ donors. SBCs of isolated bladder strips were recorded in organ bath. Piezo1 expression was examined with reverse transcription-quantitative polymerase chain reaction and immunofluorescence staining. ATP and acetylcholine release in cultured human urothelial cells was measured. Piezo1 is abundantly expressed in the bladder mucosa. Activation of Piezo1 with its specific agonist Yoda1 (100 nM-100 µM) enhanced the SBCs activity in isolated human bladder strips in a concentration-dependent manner. The effect of Yoda1 mimicked the effect of a low concentration (30 nM) of carbachol, which can be attenuated by removing the mucosa, blocking muscarinic receptors with atropine (1 µM), and blocking purinergic receptors with pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS, 30 µM), but not by tetrodotoxin (1 µM). Activation of urothelial Piezo1 with Yoda1 (30 µM) or hypotonic solution induced the release of ATP and acetylcholine in cultured human urothelial cells. In patients with benign prostatic hyperplasia, greater Piezo1 expression was observed in bladder mucosa from patients with DO than patients without DO. We conclude that upregulation and activation of Piezo1 may contribute to DO generation in patients with bladder outlet obstruction by promoting the urothelial release of ATP and acetylcholine. Inhibition of Piezo1 may be a novel therapeutic approach in the treatment of overactive bladder.

Regulatory role of Piezo1 channel in endothelium-dependent hyperpolarization-mediated vasorelaxation of small resistance vessels and its anti-inflammatory action.

AIMS: Although endothelial Piezo1 channel is known to induce NO-mediated vasorelaxation of conduit vessels, it remains largely unknown if it can induce endothelial-dependent hyperpolarization (EDH)-mediated vasorelaxation of resistance vessels. Therefore, the present study aims to investigate Piezo1/EDH-mediated vasorelaxation in health and its involvement in ulcerative colitis (UC) and sepsis, two intractable and deadly inflammatory diseases. MAIN METHODS: The tension of the second-order branch of mouse mesenteric artery was measured via the Danish DMT600M microvascular measurement system. The changes in cytoplasmic calcium ([Ca2+]cyt) signaling in vascular endothelial cells were detected by fluorescent calcium assay, and the membrane potential changes were monitored by patch clamp. Experimental murine models of UC and sepsis were induced by dextran sulfate sodium (DSS) and lipopolysaccharides (LPS), respectively. KEY FINDINGS: A selective activator of Piezo1 channel, Yoda1, dose-dependently induced vasorelaxation of the second-order branch of mouse mesenteric artery in an endothelium-dependent manner. The endothelial Piezo1 channel mediated the vasorelaxation through EDH mechanism by a functional coupling of Piezo1 and TRPV4 channels. Their function and coupling were verified by [Ca2+]cyt imaging and patch clamp study in single endothelial cells. Moreover, while ACh-induced vasorelaxation played a major role in health, it was significantly impaired in the pathogenesis of UC and sepsis; however, Piezo1/EDH-mediated vasorelaxation remained intact. Finally, Piezo1/EDH-mediated vasorelaxation recovered ACh-induced vasorelaxation impaired in UC and sepsis. SIGNIFICANCE: Piezo1/TRPV4/EDH-mediated vasorelaxation rescues the impaired ACh-induced vasorelaxation to likely recover hemoperfusion to organs, leading to organ protection against UC and sepsis. Our study not only suggests that endothelial Piezo1, TRPV4 and KCa channels are the potential therapeutic targets, but also implies that Piezo1 activators may benefit to prevent/treat UC and sepsis.

Activation of Piezo1 or TRPV2 channels inhibits human ureteral contractions via NO release from the mucosa.

We aimed to investigate the expression and motor modulatory roles of several mechano-sensitive channels (MSCs) in human ureter. Human proximal ureters were obtained from eighty patients subjected to nephrectomy. Expression of MSCs at mRNA, protein and functional levels were examined. Contractions of longitudinal ureter strips were recorded in organ bath. A fluorescent probe Diaminofluoresceins was used to measure nitric oxide (NO). RT-PCR analyses revealed predominant expression of Piezo1 and TRPV2 mRNA in intact ureter and mucosa. Immunofluorescence assays indicate proteins of MSCs (Piezo1/Piezo2, TRPV2 and TRPV4) were mainly distributed in the urothelium. Ca2+ imaging confirmed functional expression of TRPV2, TRPV4 and Piezo1 in cultured urothelial cells. Specific agonists of Piezo1 (Yoda1, 3-300 µM) and TRPV2 (cannabidiol, 3-300 µM) attenuated the frequency of ureteral contractions in a dose-dependent manner while the TRPV4 agonist GSK1016790A (100 nM-1 µM) exerted no effect. The inhibitory effects of Piezo1 and TRPV2 agonists were significantly blocked by the selective antagonists (Dooku 1 for Piezo1, Tranilast for TRPV2), removal of the mucosa, and pretreatment with NO synthase inhibitor L-NAME (10 µM). Yoda1 (30 µM) and cannabidiol (50 µM) increased production of NO in cultured urothelial cells. Our results suggest that activation of Piezo1 or TRPV2 evokes NO production and release from mucosa that may mediate mechanical stimulus-induced reduction of ureter contractions. Our findings support the idea that targeting Piezo1 and TRPV2 channels may be a promising pharmacological strategy for ureter stone passage or colic pain relief.

Piezo1 channels mediate vasorelaxation of uterine arteries from pseudopregnant rats.

Introduction: There is a great increase in uterine arterial blood flow during normal pregnancy, which is a result of the cardiovascular changes that occur in pregnancy to adapt the maternal vascular system to meet the increased metabolic needs of both the mother and the fetus. The cardiovascular changes include an increase in cardiac output and more importantly, dilation of the maternal uterine arteries. However, the exact mechanism for the vasodilation is not fully known. Piezo1 mechanosensitive channels are highly expressed in endothelial and vascular smooth muscle cells of small-diameter arteries and play a role in structural remodeling. In this study, we hypothesize that the mechanosensitive Piezo1 channel plays a role in the dilation of the uterine artery (UA) during pregnancy. Methods: For this, 14-week-old pseudopregnant and virgin Sprague Dawley rats were used. In isolated segments of UA and mesenteric resistance arteries (MRA) mounted in a wire myograph, we investigated the effects of chemical activation of Piezo1, using Yoda 1. The mechanism of Yoda 1 induced relaxation was assessed by incubating the vessels with either vehicle or some inhibitors or in the presence of a potassium-free physiological salt solution (K+-free PSS). Results: Our results show that concentration-dependent relaxation responses to Yoda 1 are greater in the UA of the pseudo-pregnant rats than in those from the virgin rats while no differences between groups were observed in the MRAs. In both vascular beds, either in virgin or in pseudopregnant, relaxation to Yoda 1 was at least in part nitric oxide dependent. Discussion: Piezo1 channel mediates nitric oxide dependent relaxation, and this channel seems to contribute to the greater dilation that occurs in the uterine arteries of pseudo-pregnant rats.

Mechanosensitive Piezo1 protein as a novel regulator in macrophages and macrophage-mediated inflammatory diseases.

Macrophages are the most important innate immune cells in humans. They are almost ubiquitous in peripheral tissues with a large variety of different mechanical milieus. Therefore, it is not inconceivable that mechanical stimuli have effects on macrophages. Emerging as key molecular detectors of mechanical stress, the function of Piezo channels in macrophages is becoming attractive. In this review, we addressed the architecture, activation mechanisms, biological functions, and pharmacological regulation of the Piezo1 channel and review the research advancements in functions of Piezo1 channels in macrophages and macrophage-mediated inflammatory diseases as well as the potential mechanisms involved.

Accelerated Bone Reconstruction by the Yoda1 Bilayer Membrane via Promotion of Osteointegration and Angiogenesis.

Guided bone regeneration membranes are widely used to prevent fibroblast penetration and facilitate bone defect repair by osteoblasts. However, the current clinically available collagen membranes lack bone induction and angiogenic capacities, exhibiting limited bone regeneration. The mechanically sensitive channel, Piezo1, which is activated by Yoda1, has been reported to play crucial roles in osteogenesis and angiogenesis. Nevertheless, the application of Yoda1 alone is unsustainable to maintain this activity. Therefore, this study fabricates a Yoda1-loading bilayer membrane using electrospinning technology. Its inner layer in contact with the bone defect is composed of vertically aligned fibers, which regulate the proliferation and differentiation of cells, release Yoda1, and promote bone regeneration. Its outer layer in contact with the soft tissue is dense with oriented fibers by UV cross-linking, mainly preventing fibroblast infiltration and inhibiting the immune response. Furthermore, the loaded Yoda1 affects osteogenesis and angiogenesis via the Piezo1/RhoA/Rho-associated coiled-coil-containing protein kinase 1/Yes1-associated transcriptional regulator signaling pathway. The results reveal that the Yoda1 bilayer membrane is efficient and versatile in accelerating bone regeneration, suggesting its potential as a novel therapeutic agent for various clinical issues.

Piezo1 activation induces relaxation of the pudendal artery and corpus cavernosum.

Piezo1 channel is a sensor for shear-stress in the vasculature. Piezo1 activation induces vasodilation, and its deficiency contributes to vascular disorders, such as hypertension. In this study, we aimed to determine whether Piezo1 channel has a functional role in the dilation of pudendal arteries and corpus cavernosum (CC). For this, male Wistar rats were used, and the relaxation of the pudendal artery and CC was obtained using the Piezo1 activator, Yoda1, in the presence and absence of Dooku (Yoda1 antagonist), GsMTx4 (non-selective mechanosensory channel inhibitor) and L-NAME (nitric oxide synthase inhibitor). In the CC, Yoda1 was also tested in the presence of indomethacin (non-selective COX inhibitor) and tetraethylammonium (TEA, non-selective potassium channel inhibitor). The expression of Piezo1 was confirmed by Western blotting. Our data show that Piezo1 activation leads to the relaxation of the pudendal artery and CC as the chemical activator of Piezo1, Yoda1, relaxed the pudendal artery (47%) and CC (41%). This response was impaired by L-NAME and abolished by Dooku and GsMTx4 in the pudendal artery only. Indomethacin and TEA did not affect the relaxation induced by Yoda1 in the CC. Limited tools to explore this channel prevent further investigation of its underlying mechanisms of action. In conclusion, our data demonstrate that Piezo1 is expressed and induced the relaxation of the pudendal artery and CC. Further studies are necessary to determine its role in penile erection and if erectile dysfunction is associated with Piezo1 deficiency.

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.

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.

Inflammation condition sensitizes Piezo1 mechanosensitive channel in mouse cerebellum astrocyte.

Piezo1 mechanosensitive ion channel (MSC) plays a significant role in human physiology. Despite several research on the function and expression of Piezo1 in the nervous system, its electrophysiological properties in neuroinflammatory astrocytes remain unknown. We tested whether astrocytic neuroinflammatory state regulates Piezo1 using electrical recordings, calcium imaging, and wound healing assays on cultured astrocytes. In this study, we determined whether neuroinflammatory condition regulates astrocytic Piezo1 currents in astrocytes. First, we performed electrophysiological recordings on the mouse cerebellum astrocytes (C8-S) under lipopolysaccharide (LPS)-induced neuroinflammatory condition. We found that LPS treatment significantly increased MSC currents in C8-S. The half-maximal pressure of LPS treated MSC currents was left-shifted but the slope sensitivity was not altered by LPS treatment. LPS-induced increase of MSC currents were further augmented by Piezo1 agonist, Yoda1 but were normalized by Piezo1 inhibitor, GsMTx4. Furthermore, silencing Piezo1 in LPS treated C8-S normalized not only MSC currents but also calcium influx and cell migration velocity. Together, our results show that LPS sensitized Piezo1 channel in C8-S astrocytes. These findings will suggest that astrocytic Piezo1 is a determinant of neuroinflammation pathogenesis and may in turn become the foundation of further research into curing several neuronal illnesses and injury related inflammation of neuronal cells.

PIEZO1 is downregulated in glenohumeral chondrocytes in early cuff tear arthropathy following a massive rotator cuff tear in a mouse model.

Introduction: A massive rotator cuff tear (RCT) leads to glenohumeral joint destabilization and characteristic degenerative changes, termed cuff tear arthropathy (CTA). Understanding the response of articular cartilage to a massive RCT will elucidate opportunities to promote homeostasis following restoration of joint biomechanics with rotator cuff repair. Mechanically activated calcium-permeating channels, in part, modulate the response of distal femoral chondrocytes in the knee against injurious loading and inflammation. The objective of this study was to investigate PIEZO1-mediated mechanotransduction of glenohumeral articular chondrocytes in the altered biomechanical environment following RCT to ultimately identify potential therapeutic targets to attenuate cartilage degeneration after rotator cuff repair. Methods: First, we quantified mechanical susceptibility of chondrocytes in mouse humeral head cartilage ex vivo with treatments of specific chemical agonists targeting PIEZO1 and TRPV4 channels. Second, using a massive RCT mouse model, chondrocytes were assessed for mechano-vulnerability, PIEZO1 expression, and calcium signaling activity 14-week post-injury, an early stage of CTA. Results: In native humeral head chondrocytes, chemical activation of PIEZO1 (Yoda1) significantly increased chondrocyte mechanical susceptibility against impact loads, while TRPV4 activation (GSK101) significantly decreased impact-induced chondrocyte death. A massive RCT caused morphologic and histologic changes to the glenohumeral joint with decreased sphericity and characteristic bone bruising of the posterior superior quadrant of the humeral head. At early CTA, chondrocytes in RCT limbs exhibit a significantly decreased functional expression of PIEZO1 compared with uninjured or sham controls. Discussion: In contrast to the hypothesis, PIEZO1 expression and activity is not increased, but rather downregulated, after massive RCT at the early stage of cuff tear arthropathy. These results may be secondary to the decreased axial loading after glenohumeral joint decoupling in RCT limbs.

A review of the pathophysiology and the role of ion channels on bronchial asthma.

Asthma is one of the main non-communicable chronic diseases and affects a huge portion of the population. It is a multifactorial disease, classified into several phenotypes, being the allergic the most frequent. The pathophysiological mechanism of asthma involves a Th2-type immune response, with high concentrations of allergen-specific immunoglobulin E, eosinophilia, hyperreactivity and airway remodeling. These mechanisms are orchestrated by intracellular signaling from effector cells, such as lymphocytes and eosinophils. Ion channels play a fundamental role in maintaining the inflammatory response on asthma. In particular, transient receptor potential (TRP), stock-operated Ca2+ channels (SOCs), Ca2+-activated K+ channels (IKCa and BKCa), calcium-activated chloride channel (TMEM16A), cystic fibrosis transmembrane conductance regulator (CFTR), piezo-type mechanosensitive ion channel component 1 (PIEZO1) and purinergic P2X receptor (P2X). The recognition of the participation of these channels in the pathological process of asthma is important, as they become pharmacological targets for the discovery of new drugs and/or pharmacological tools that effectively help the pharmacotherapeutic follow-up of this disease, as well as the more specific mechanisms involved in worsening asthma.

Mechanosensitive Piezo1 channel in rat epididymal epithelial cells promotes transepithelial K+ secretion.

The Piezo1 channel, a mechanosensitive channel that exhibit a preference for Ca2+, play multifarious physiological and pathological roles in the endothelium and epithelium of various tissues. However, the functional expression of Piezo1 channel in the epithelium of the male reproductive tract remains unknown. In the present study, the expression of Piezo1 channel in the rat epididymis was determined by real-time quantitative PCR, western blot and immunohistochemical analysis. Our data revealed that Piezo1 channel was located in the epithelial layer of the rat epididymis, with higher expression levels in the corpus and cauda regions. The pro-secretion function of Piezo1 channel was then investigated using short circuit current (ISC) and intracellular Ca2+ imaging techniques. Application of Yoda1, a selective Piezo1 channel activator, stimulated a remarkable decrease in the ISC of the epididymal epithelium. Pharmacological experiments revealed that the ISC response induced by Piezo1 channel activation was abolished by pretreating epithelial cells with the Yoda1 analogue, Dooku1, the selective mechanosensitive cation channel blocker, GsMTx4, or removal of basolateral K+. Meanwhile, we demonstrated that activation of Piezo1 channel triggered a robust Ca2+ influx in epididymal epithelial cells. The possible involvement of Ca2+- activated K+channels (KCa) in transepithelial K+ secretion was then evaluated. And that big conductance KCa (BK), but not small conductance or intermediate conductance KCa, mediated Piezo1-elicited transepithelial K+ secretion. Moreover, we demonstrated that NKCC and NKA were responsible for supplying substrate K+ during transepithelial K+ secretion. These data demonstrate that the activation of Piezo1 channel promotes BK-mediated transepithelial K+ secretion, and thus may plays an important role in the formation of a high K+ concentration in epididymal intraluminal fluid.