trans-Endothelial neutrophil migration activates bactericidal function via Piezo1 mechanosensing

Roles of Piezo1 in chronic inflammatory diseases and prospects for drug treatment (Review)

The human body is chronically stimulated by various mechanical forces and the body cells can sense harmful stimuli through mechanotransduction to induce chronic inflammation. Piezo type mechanosensitive ion channel component 1 (Piezo1), a novel transmembrane mechanosensitive cation channel, is widely expressed in inflammatory cells, such as neutrophils, macrophages and endothelial cells, as well as in non‑inflammatory cells, such as osteoblasts, osteoclasts and periodontal cells. A growing number of studies have demonstrated that Piezo1 senses changes in environmental mechanical forces, regulates cellular functions and influences the development and regression of chronic inflammation. The present study summarized the roles of Piezo1 and its possible mechanisms in some common chronic inflammatory diseases and evaluated the potential application of drugs that modulate its activity, so as to prove that Piezo1 is likely to become a new target for the treatment of inflammatory diseases.15.

Weakened Airway Epithelial Junctions and Enhanced Neutrophil Elastase Release Contribute to Age-Dependent Bacteremia Risk Following Pneumococcal Pneumonia

Streptococcus pneumoniae (Sp; pneumococcus), the most common agent of community-acquired pneumonia, can spread systemically, particularly in the elderly, highlighting the need for adjunctive therapies. The airway epithelial barrier defends against bacteremia and is dependent upon apical junctional complex (AJC) proteins such as E-cadherin. After mouse lung challenge, pneumolysin (PLY), a key Sp virulence factor, stimulates epithelial secretion of an inflammatory eicosanoid, triggering the infiltration of polymorphonuclear leukocytes (PMNs) that secrete high levels of neutrophil elastase (NE), thus promoting epithelial damage and systemic infection. Here, pulmonary E-cadherin staining of intratracheally (i.t.) inoculated mice revealed PLY-mediated disruption of AJC independently of PMNs. Apical infection of air-liquid interface (ALI) respiratory epithelial monolayers similarly showed that PLY disrupts AJCs. This epithelial damage promoted PMN transmigration and bacterial apical-to-basolateral translocation, and pharmacologically fortifying epithelial barrier function diminished both barrier breach in vitro and bacteremia in vivo. E-cadherin staining after Sp i.t. inoculation of > 20-month-old mice, or apical infection of ALI monolayers derived from these mice, revealed an age-associated vulnerability to PLY-mediated AJC disruption, which in turn enhanced PMN migration and bacteremia. In addition, we found that PMNs from aged mice secrete increased levels of tissue-damaging NE. Simultaneous pharmacological inhibition of tissue-destructive NE and fortification of pulmonary epithelial barrier function was required to reduce the level of Sp bacteremia in aged mice to that of young mice. This work underscores the importance of fully characterizing the multifactorial sources of age-associated susceptibility in devising adjunctive therapies to mitigate invasive pneumococcal disease in the elderly.

The Integrated Pulmonary Immune Response to Pneumonia

Pneumonia is an acute respiratory infection of the lower respiratory tract. The effectiveness of the host immune response determines the severity of infection, or whether pneumonia occurs at all. The lungs house both innate and adaptive immune systems, which integrate their activities to provide host defense that eliminates microbes and prevents lower respiratory infection from becoming severe. Professional immune cells in the lung, like macrophages and lymphocytes, work with lung constituents, like epithelial cells and fibroblasts, to optimize antimicrobial defense. The dynamics of the immune response during infection and the immune components contributing to defense are influenced by prior experiences with respiratory pathogens, remodeling lung immunity in ways that improve responses against subsequent infections. This review covers how innate and adaptive immune activities coordinate inside the lung to provide integrated and effective immune resistance against respiratory pathogens.

Endothelium Piezo1 deletion alleviates experimental varicose veins by attenuating perivenous inflammation

Previous large-scale genetic studies have prioritized the causal genes piezo type mechanosensitive ion channel component 1 (PIEZO1) and castor zinc finger 1 (CASZ1) associated with varicose veins (VVs). This study aims to evaluate their roles in both clinical and experimental VVs. In this study, we investigated abundance of PIEZO1 and CASZ1 in both varicose and normal veins from the same patients. Yoda1 (a selective PIEZO1 agonist, 2.6 mg/kg/day) or vehicle was administered intraperitoneally for 3 weeks to evaluate the effect of PIEZO1 activation on experimental VVs. Subsequently, endothelial Piezo1 deletion mice (Piezo1iΔEC mice) were generated to explored the role of endothelial PIEZO1 on VVs. Laser speckle imaging, flow cytometry, cell tracing with Evans blue or rhodamine-6G, and histopathological staining were utilized to evaluate the pathophysiology of VVs. Our results showed that mRNA expression of PIEZO1, but not CASZ1, was abundant and increased in clinical VVs. The Piezo1tP1-td mice revealed endothelium-specific expression of PIEZO1 in mice veins. By establishing iliac vein ligation-induced VVs in mice, Yoda1 exacerbated experimental VVs with increased inflammatory cell infiltration. Subsequently, endothelial Piezo1 deletion (Piezo1iΔEC mice) alleviated experimental VVs and vascular remodeling by directly reducing vascular permeability and leukocyte-endothelium interactions compared to the control (Piezo1fl/fl mice). PIEZO1 is highly expressed in clinical VVs, meanwhile, activation or inhibition of PIEZO1 exerts a remarkable effect on experimental VVs. Furthermore, Piezo1 may constitute a potential therapeutic approach for the medical treatment of VVs.

Confinement by Liquid-Liquid Interface Replicates In Vivo Neutrophil Deformations and Elicits Bleb-Based Migration

Leukocytes forge paths through interstitial spaces by exerting forces to overcome confining mechanical pressures provided by surrounding cells. While such mechanical cues regulate leukocyte motility, engineering an in vitro system that models the deformable cellular environment encountered in vivo has been challenging. Here, microchannels are constructed with a liquid-liquid interface that exerts confining pressures similar to cells in tissues, and thus, is deformable by cell-generated forces. Consequently, the balance between migratory cell-generated and interfacial pressures determines the degree of confinement. Pioneer cells that first contact the interfacial barrier require greater deformation forces to forge a path for migration, and as a result migrate slower than trailing cells. Critically, resistive pressures are tunable by controlling the curvature of the liquid interface, which regulates motility. By granting cells autonomy in determining their confinement, and tuning environmental resistance, interfacial deformations match those of surrounding cells in vivo during interstitial neutrophil migration in a larval zebrafish model. It is discovered that neutrophils employ a bleb-based mechanism of force generation to deform a soft barrier exerting cell-scale confining pressures. In all, this work introduces a tunable in vitro material interface that replicates confining pressures applied by soft tissue environments.

Piezo1 Regulates Odontogenesis via a FAM83G-Mediated Mechanism in Dental Papilla Cells In Vitro and In Vivo

This study explored the role of Piezo1 in the odontogenic differentiation of dental papilla cells (DPCs) and tissue, focusing on a mechanism involving family with sequence similarity 83, member G (FAM83G). Here, we found Piezo1, a mechanosensitive cation channel, was upregulated during odontogenesis in DPCs and dental papilla tissues. Knockdown of Piezo1 impaired odontogenic differentiation, while its activation by Yoda1 enhanced the process. Using a 3D culture model and an ectopic transplantation model, we confirmed Piezo1's role in vivo. RNA sequencing (RNA-seq) analysis revealed that FAM83G was upregulated in Piezo1-knockdown cells, and FAM83G silencing enhanced odontogenesis in DPCs. These findings indicate that Piezo1 positively regulates odontogenesis by inhibiting FAM83G in DPCs both in vitro and in vivo, with Piezo1 representing a potential target for dental tissue regeneration.

Inflammatory stimuli impact on cellular uptake and biodistribution of perfluorocarbon nanoemulsions

Intravenously administered perfluorocarbon nanoemulsions (PFCs) are taken up by phagocytic immune cells, which enables the noninvasive visualization of inflammatory hot spots by combined 1H/19F magnetic resonance imaging. However, little is known about the influence of inflammatory stimuli on cellular uptake and biodistribution of PFCs. Here, we systematically investigated the impact of inflammation induced by subcutaneous implantation of Matrigel/lipopolysaccharide or myocardial infarction (50 min ischemia reperfusion) on PFC uptake and biodistribution in C57BL/6J mice. We detected strong 19F signals in Matrigel/lipopolysaccharide plugs and infarcted hearts, which were completely absent in controls. Cellular uptake of PFCs was increased in neutrophils isolated from the blood and Matrigel/lipopolysaccharide plugs, whereas uptake by monocytes was only slightly elevated. In contrast, myocardial infarction caused only a moderate early increase of PFC uptake in monocytes and neutrophils. Interestingly, the inflammatory model did also affect the biodistribution of the PFCs. The blood half-life of PFCs was slightly increased after Matrigel/lipopolysaccharide implantation, whereas it was reduced after myocardial infarction. Compared to controls, the 19F signal of the liver was significantly stronger in Matrigel/lipopolysaccharide but not in myocardial infarction animals. Interestingly, stimulation of primary immune cells and RAW264.7 macrophages with lipopolysaccharide had no effect on PFC uptake, whereas C-reactive protein incubation elevated internalization of PFCs at least in RAW264.7 cells. In conclusion, we show that the cellular PFC uptake can differ between individual inflammatory conditions. This is an important aspect that has to be considered for the proper interpretation of 1H/19F magnetic resonance imaging data obtained from inflammatory hot spots.

Piezo1 Enhances Macrophage Phagocytosis and Pyrin Activation to Ameliorate Fungal Keratitis

Purpose

Fungal keratitis (FK) remains a treatment challenge, necessitating new therapeutic targets. Piezo1, a mechanosensitive ion channel, regulates calcium signaling and immune cell function. This study investigates its role in macrophage-mediated antifungal responses in FK.

Methods

Piezo1 and Pyrin expression in corneas and bone marrow-derived macrophages (BMDMs) were assessed by RNAseq, quantitative real-time PCR (qRT-PCR), Western blot, and immunofluorescence. Intracellular calcium ion concentration was detected by Fluo-4 AM fluorescent probe staining. Heterozygous Piezo1 deficiency (Piezo1+/-) mice and Yoda1 were performed to regulate the expression of Piezo1.

Results

Our investigation demonstrates elevated expression of Piezo1 in the corneas of patients with FK and infected mice. This upregulation of Piezo1 corresponded with the swift recruitment of macrophages via the limbus. Additionally, Piezo1+/- mice exacerbate the progression of FK in the infection model. Furthermore, Piezo1 knockdown in macrophages exhibit a notable reduction phagocytic capacity, accompanied by an increase in viable colony-forming units in an in vitro model of fungal infection. Moreover, using a pharmacologic activator of Piezo1 (Yoda1), a calcium ion (Ca2+) chelator of BAPTA or Piezo1+/- mice, we demonstrate that Piezo1 activation triggers the Pyrin inflammasome via augmented calcium ion influx, which is required for protection against FK in murine hosts.

Conclusions

Piezo1 is crucial for innate immunity in FK, enhancing macrophage recruitment, activation, and Pyrin inflammasome-mediated antifungal activity via calcium signaling. Using Piezo1+/- mice and Yoda1, we confirm Piezo1's role in fungal clearance. Targeting Piezo1 offers a novel strategy to improve FK outcomes by boosting macrophage function and immune response.

Neutrophils exhibit distinct migration phenotypes that are regulated by transendothelial migration

The extravasation of polymorphonuclear neutrophils (PMNs) is a critical component of the innate immune response that involves transendothelial migration (TEM) and interstitial migration. TEM-mediated interactions between PMNs and vascular endothelial cells (VECs) trigger a cascade of biochemical and mechanobiological signals whose effects on interstitial migration are currently unclear. To address this question, we cultured human VECs on a fibronectin-treated transwell insert to model the endothelium and basement membrane, loaded PMN-like differentiated HL60 (dHL-60) cells in the upper chamber of the insert, and collected the PMNs that crossed the membrane-supported monolayer from the lower chamber. The 3D chemotactic migration of the TEM-conditioned PMNs through collagen matrices was then quantified. Data collected from over 50,000 trajectories showed two distinct migratory phenotypes, i.e., a high-persistence phenotype and a low-persistence phenotype. These phenotypes were conserved across treatment conditions, and their existence was confirmed in human primary PMNs. The high-persistence phenotype was characterized by more straight trajectories and faster migration speeds, whereas the low-persistence one exhibited more frequent sharp turns and loitering periods. A key finding of our study is that TEM induced a phenotypic shift in PMNs from high-persistence migration to low-persistence migration. Changes in the relative proportion of high-persistence and low-persistence populations correlated with GRK2 expression levels. Inhibiting GRK2 hindered the TEM-induced shift in migratory phenotype and impaired the phagocytic function of PMNs. Overall, our study suggests that TEM-mediated GRK2 signaling primes PMNs for a migration phenotype better suited for spatial exploration and inflammation resolution. These observations provide novel insight into the biophysical impacts of TEM that priming PMNs is essential to conduct sentinel functions.

Mechanism and therapeutic targets of circulating immune cells in diabetic retinopathy

Diabetic retinopathy (DR) continues to be the leading cause of preventable vision loss among working-aged adults, marked by immune dysregulation within the retinal microenvironment. Typically, the retina is considered as an immune-privileged organ, where circulating immune cells are restricted from entry under normal conditions. However, during the progression of DR, this immune privilege is compromised as circulating immune cells breach the barrier and infiltrate the retina. Increasing evidence suggests that vascular and neuronal degeneration in DR is largely driven by the infiltration of immune cells, particularly neutrophils, monocyte-derived macrophages, and lymphocytes. This review delves into the mechanisms and therapeutic targets associated with these immune cell populations in DR, offering a promising and innovative approach to managing the disease.

The diverse roles of neutrophils from protection to pathogenesis

Neutrophil granulocytes are the most abundant leukocytes in the blood and constitute a critical arm of innate immunity. They are generated in the bone marrow, and under homeostatic conditions enter the bloodstream to patrol tissues and scout for potential pathogens that they quickly destroy through phagocytosis, intracellular degradation, release of granules and formation of extracellular traps. Thus, neutrophils are important effector cells involved in antibacterial defense. However, neutrophils can also be pathogenic. Emerging data suggest they have critical functions related to tissue repair and fibrosis. Moreover, similarly to other innate immune cells, neutrophil cell states are affected by their microenvironment. Notably, this includes tumors that co-opt neutrophils. Neutrophils can undergo transcriptional and epigenetic reprogramming, thus causing or modulating inflammation and injury. It is also possible that distinct neutrophil subsets are generated with designated functions in the bone marrow. Understanding neutrophil plasticity and alternative cell states will help resolve their contradictive roles. This Review summarizes the most recent key findings surrounding protective versus pathogenic functions of neutrophils; elaborating on phenotype-specific subsets of neutrophils and their involvement in homeostasis and disease.

Mechanisms of mechanotransduction and physiological roles of PIEZO channels

Mechanical force is an essential physical element that contributes to the formation and function of life. The discovery of the evolutionarily conserved PIEZO family, including PIEZO1 and PIEZO2 in mammals, as bona fide mechanically activated cation channels has transformed our understanding of how mechanical forces are sensed and transduced into biological activities. In this Review, I discuss recent structure-function studies that have illustrated how PIEZO1 and PIEZO2 adopt their unique structural design and curvature-based gating dynamics, enabling their function as dedicated mechanotransduction channels with high mechanosensitivity and selective cation conductivity. I also discuss our current understanding of the physiological and pathophysiological roles mediated by PIEZO channels, including PIEZO1-dependent regulation of development and functional homeostasis and PIEZO2-dominated mechanosensation of touch, tactile pain, proprioception and interoception of mechanical states of internal organs. Despite the remarkable progress in PIEZO research, this Review also highlights outstanding questions in the field.

β2-integrins control HIF1α activation in human neutrophils

During inflammation, human neutrophils engage β2-integrins to migrate from the blood circulation to inflammatory sites with high cytokine but low oxygen concentrations. We tested the hypothesis that the inhibition of prolyl hydroxylase domain-containing enzymes (PHDs), cytokines, and β2-integrins cooperates in HIF pathway activation in neutrophils. Using either the PHD inhibitor roxadustat (ROX) (pseudohypoxia) or normobaric hypoxia to stabilize HIF, we observed HIF1α protein accumulation in adherent neutrophils. Several inflammatory mediators did not induce HIF1α protein but provided additive or even synergistic signals (e.g., GM-CSF) under pseudohypoxic and hypoxic conditions. Importantly, and in contrast to adherent neutrophils, HIF1α protein expression was not detected in strictly suspended neutrophils despite PHD enzyme inhibition and the presence of inflammatory mediators. Blocking β2-integrins in adherent and activating β2-integrins in suspension neutrophils established the indispensability of β2-integrins for increasing HIF1α protein. Using GM-CSF as an example, increased HIF1α mRNA transcription via JAK2-STAT3 was necessary but not sufficient for HIF1α protein upregulation. Importantly, we found that β2-integrins led to HIF1α mRNA translation through the phosphorylation of the essential translation initiation factors eIF4E and 4EBP1. Finally, pseudohypoxic and hypoxic conditions inducing HIF1α consistently delayed apoptosis in adherent neutrophils on fibronectin under low serum concentrations. Pharmacological HIF1α inhibition reversed delayed apoptosis, supporting the importance of this pathway for neutrophil survival under conditions mimicking extravascular sites. We describe a novel β2-integrin-controlled mechanism of HIF1α stabilization in human neutrophils. Conceivably, this mechanism restricts HIF1α activation in response to hypoxia and pharmacological PHD enzyme inhibitors to neutrophils migrating toward inflammatory sites.

Neutrophils under the microscope: neutrophil dynamics in infection, inflammation, and cancer revealed using intravital imaging

Neutrophils rapidly respond to inflammation resulting from infection, injury, and cancer. Intravital microscopy (IVM) has significantly advanced our understanding of neutrophil behavior, enabling real-time visualization of their migration, interactions with pathogens, and coordination of immune responses. This review delves into the insights provided by IVM studies on neutrophil dynamics in various inflammatory contexts. We also examine the dual role of neutrophils in tumor microenvironments, where they can either facilitate or hinder cancer progression. Finally, we highlight how computational modeling techniques, especially agent-based modeling, complement experimental data by elucidating neutrophil kinetics at the level of individual cells as well as their collective behavior. Understanding the role of neutrophils in health and disease is essential for developing new strategies for combating infection, inflammation and cancer.

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.

Investigating the efficacy of vacuum sealing drainage versus traditional negative pressure drainage in treating deep incision infections following posterior cervical internal fixation-a retrospective cohort study

BACKGROUND

Assessing the efficacy and safety of Vacuum Sealing Drainage (VSD) in treating deep incision infections (DII) following posterior cervical internal fixation.

METHODS

We retrospectively studied the clinical effects of VSD and Traditional Negative Pressure Drainage (TND) on 12 patients with deep incision infection after posterior cervical fixation surgery who were treated in our department from 2012 to 2020. A comparison of patient-related factors (age, gender, BMI, comorbidities, initial internal fixation surgery segment, preoperative laboratory inflammation indicators) and surgical-related factors (postoperative duration of fever, positive rate of drainage fluid bacterial culture, Visual Analogue Scale (VAS) score at 3 days after surgery, laboratory indicators at 3 days after surgery, debridement frequency and drainage time, hospital stay, internal fixation retention rate, and infection recurrence rate) between the VSD group and the TND group was conducted using independent sample t tests to draw experimental conclusions.

RESULTS

This study included 12 patients, with six cases of VSD (5 males and 1 female) and six cases of TND (4 males and 2 females). The VSD group had significantly lower postoperative fever time (1.50 ± 0.46 days vs. 4.28 ± 0.97 days, P < 0.05), a higher positive rate of bacterial cultures in drainage fluid (5/6 vs. 2/6, P < 0.05), lower 3 day VAS scores (3.13 ± 0.83 vs. 3.44 ± 0.88, P < 0.05), lower 3 day CRP levels (66.89 ± 23.65 mg/L vs. 57.11 ± 18.18 mg/L, P < 0.05), a shorter total drainage time (14.50 ± 2.98 days vs. 22.56 ± 3.01 days, P < 0.05), and a higher total drainage flow rate (395.63 ± 60.97 ml vs. 155.56 ± 32.54 ml, P < 0.05) than the TND group (the total drainage volume throughout the entire treatment process). In addition, the frequency of debridement (2.67 ± 0.52 times vs. 3.17 ± 0.41 times, P < 0.05) and average hospital stay (23.13 ± 3.27 days vs. 34.33 ± 6.86 days, P < 0.05) were significantly lower in the VSD group, although both groups retained internal fixation.

CONCLUSIONS

VSD is a secure and effective treatment for deep incision infections that results from cervical posterior internal fixation surgery.

NADPH Oxidase 3: Beyond the Inner Ear

Reactive oxygen species (ROS) were formerly known as mere byproducts of metabolism with damaging effects on cellular structures. The discovery and description of NADPH oxidases (Nox) as a whole enzyme family that only produce this harmful group of molecules was surprising. After intensive research, seven Nox isoforms were discovered, described and extensively studied. Among them, the NADPH oxidase 3 is the perhaps most underrated Nox isoform, since it was firstly discovered in the inner ear. This stigma of Nox3 as "being only expressed in the inner ear" was also used by me several times. Therefore, the question arose whether this sentence is still valid or even usable. To this end, this review solely focuses on Nox3 and summarizes its discovery, the structural components, the activating and regulating factors, the expression in cells, tissues and organs, as well as the beneficial and detrimental effects of Nox3-mediated ROS production on body functions. Furthermore, the involvement of Nox3-derived ROS in diseases progression and, accordingly, as a potential target for disease treatment, will be discussed.

In Vitro Neutrophil-Bacteria Assay in Whole Blood Microenvironments with Single-Cell Confinement

Blood is a common medium through which invasive bacterial infections disseminate in the human body. In vitro neutrophil-bacteria assays allow flexible mechanistic studies and screening of interventional strategies. In standard neutrophil-bacteria assays, both the immune cells and microorganisms are typically interrogated in an exogenous, homogeneous, bulk fluid environment (e.g., culture media or bacterial broth in microtiter plates), lacking the relevant physicochemical factors in the heterogenous blood-tissue microenvironment (e.g., capillary bed) with single-cell confinement. Here we present an in vitro neutrophil-bacteria assay by leveraging an open microfluidic model known as "μ-Blood" that supports sub-microliter liquid microchannels with single-cell confinement. In this study we compare the exogenous and endogenous fluids including neutrophils in RPMI (standard suspension cell culture media) and whole blood in response to Staphylococcus aureus ( S. aureus , a gram-positive, non-motile bacterium) in phosphate buffered saline (PBS), Mueller Hinton Broth (MHB), and human serum. Our results reveal a significant disparity between the exogenous and endogenous fluid microenvironments in the growth kinetics of bacteria, the spontaneous generation of capillary (i.e., Marangoni) flow, and the outcome of neutrophil intervention on the spreading bacteria.