Electrical Resistivity Values Research Articles

Influence of the Microstructure of Cutting Ceramics on the Efficiency of the Machining Process

The article deals with the determination of the efficiency of a multi-bladed tool equipped with inserts made of oxide-carbide cutting ceramics, depending on the microstructural parameters of the tool material. The microstructural parameters of the oxide-carbide cutting ceramic, which affect the performance of the tool, are proposed to be determined according to the electrical resistance of the tool material. In order to implement the method for determining the working capacity of the instrument, a basic design of the device for measuring the electrical resistance of the material of the instrument is proposed. The device for measuring the electrical resistance of ceramic plates consists of a body made of a dielectric material, with channels for supplying a conductive material and a groove for installing a case with a test sample. During the test, the channels are filled with a liquid conductive material, which fills the cavity formed by the channel of the case, the groove of the case and the plate itself under test. To ensure uniform filling of the cavity, after the introduction of the liquid conductive material, metal balls are installed into the channels, which are made in such a size as to ensure free sliding along the channel, but not to let the liquid pass into the upper part of the channel. The tested ceramic plate is installed in the walls of the removable case. The walls of the removable case include electrodes, which, when the device is in operation, are inserted into a cavity with a liquid conductive material at one end, and are connected to an ohmmeter at the other. Using a device for measuring the electrical resistance of ceramic plates, it is possible to determine the operability of the tool and guarantee its operation without rejection for a certain period of time, which was confirmed by experimental research in the milling of workpieces of machine parts made of gray cast iron. Experimental studies in multi-edge machining with cutters with different values ​​of electrical resistance of ceramic plates made it possible to plot graphs of the dependence of the quality of machining during milling on the operability of the tool and on the time of the machining process.

Correlation between field electrical resistivity and geotechnical SPT blow counts at tropical soils in Brazil

The joint application of geophysical investigations, non-invasive methods, and geotechnical investigations, invasive methods, in order to interpret the geological features in subsurface has been increasingly accepted, however, the correlation between the values collected by the geophysical methods and the direct investigative techniques have been developed in recent years. The obtained linear relationships are site specific and complementary studies are needed to establish their validation and limitations for each site. In this study, Electrical Resistivity Tomography (ERT) was used with Standard Penetration Test (SPT) for geotechnical investigation at three hillslope sites with different tropical soil properties in Bahia, Brazil. The results from thirteen boreholes were analyzed against data from 2D inverted sections. Linear fitting successfully correlates resistivity and NSPT for one borehole. Correlations of electrical resistivity and NSPT values were also performed using soils with similar compositions and physical characteristics, which showed good results. The coefficient of correlation (R) was 0.94. In addition, results the fitting slope coefficient seems to be dependent of soil genesis (lithology, texture and clay content variation) scription obtained in SPT surveys.

Decrease in Electrical Resistivity below 28 nΩm by Aging in Hyperperitectic Al-Zr Alloys Treated at High Temperatures

High-voltage and alternating current conductors are mainly made up of a steel core and an envelope made of aluminum wires. The alloys commonly used in the shell are of pure aluminum, which provides low electrical resistivity, but also low mechanical resistance. The correlation between resistance and electrical resistivity has become a design limitation, which limits the development of new alloys. Traditional airline conductors limit their service temperature to a maximum of 80 °C. Al-Zr alloys are susceptible to hardening by aging treatment at high temperatures due to the precipitation of the metastable L12-Al3Zr phase, which allows their working temperature to be limited to 300 °C. This work aims to correlate the resistance and electrical resistivity of two alloys with hyperperitectic compositions, subjected to a solution treatment at 640 °C. At the same time, the aging potential at different temperatures is analyzed using aging duration of up to 900 h. Whereas, the ultimate goal is to correlate the results with electrical resistivity, trying to achieve resistivity values lower than 28 nΩm. It is worth mentioning that there is a slow aging process and the inverse correlation between hardness and electrical resistivity. The optimum result is achieved in an alloy with more than 0.4% Zr subjected to aging at 380 °C in a time range between 425 and 900 h. In these cases, electrical resistivity values lower than 26 nΩm were reached. Transmission electron microscopy (TEM) verified the nanometric size of the L12-Al3Zr precipitates and their coherence with the α(Al) matrix. In turn, the size distribution of the precipitates was analyzed, revealing two different families of precipitates with respective averages of 4 and 19 nm. The precipitates associated with the average of 4 nm are the majority when the aging time is 425 h. However, when the aging time increases to 900 h, sizes close to 20 nm are the majority. This confirms the slow growth of the L12-Al3Zr precipitates during aging and the beginning of the over-aging phenomenon after almost 900 h of aging.

Theoretical and Numerical Study on Electrical Resistivity Measurement of Cylindrical Rock Core Samples Using Perimeter Electrodes

The estimation of hydraulic and mechanical properties of bedrock is important for the evaluation of energy-related structures, including high-level nuclear waste repositories, hydraulic fracturing wells, and gas-hydrate production wells. The hydraulic conductivity and stress–strain curves of rocks are conventionally measured through laboratory tests on cylindrical samples. Both ASTM standards for hydraulic conductivity and compressive strength involve the use of the planar bases of a cylindrical sample. Hence, an alternative test method is required for the simultaneous measurement of hydraulic conductivity and stress–strain curves. This study proposes a novel electrical resistivity estimation method using two perimeter electrodes for the estimation of hydraulic properties. The theoretical background for the perimeter electrode setup is derived and the COMSOL MultiPhysics® finite element numerical simulation tool is employed to verify the derived theoretical equation. The accuracy of the numerical simulation tool is first validated by simulating the ASTM standard testing method for electrical resistivity. The electrical resistance values derived from the theoretical equation and numerical simulation are compared for different electrical resistivity and electrode radius. The assumed equidistant, circular equipotential surface results in a theoretical lower bound for the measured electrical resistance in the cylindrical specimen. The introduction of a phenomenological distortion factor to correct for the theoretical equipotential surface results in a good fit with the numerical simulation results. The effects of electrode length and equivalent strap electrodes were investigated to assess the applicability of the suggested method for laboratory testing. Consequently, this study presents an effective alternative theoretical assessment method for the lower bound electrical resistivity of cylindrical rock core samples under confining conditions when the installation of base electrodes is infeasible.

Growth and characterization of ZnO thin films at low temperatures: from room temperature to − 120 °C

ZnO thin films have been grown by e-beam evaporation in the range from room temperature to − 120 °C on two types of substrates, Al2O3 (0001) and Si (100). Although the ZnO/Al2O3 system has been thoroughly characterized, including optical and electrical techniques, the morphological, structural and chemical properties show no significant differences between both substrates. Thus, the general features of the ZnO growth mode at low temperature can be generalized. The relatively low growth temperatures reduce the diffusion of atoms at the surface, which leads to morphological and chemical changes. As the temperature decreases, the growth mode changes from a van der Drift model to a gradual bilayer system composed of an interfacial layer in contact with the substrate and a second columnar-based layer. This second well-ordered film disappears for the lowest temperatures while a Zn-rich interface in contact with the substrate emerges. Precisely from this interface, Zn-rich whiskers develop under the ZnO film and cause the loss of adhesion at temperatures below − 100 °C. These extreme temperatures also affect the crystal size, lattice strain, and total amount of oxygen vacancies. The behavior of the optical and electrical properties in terms of band gap, transparency, electrical resistivity, and Seebeck coefficient is discussed in the light of structural and chemical characterization. Samples grown at 0 °C exhibit an enhanced transmittance compared to those grown at room temperature while preserving similar electrical resistivity values and natural n-type doping. These results open a promising route to enhance ZnO films properties below the typical high temperature window.

Effect of the Geometrical Constraints to the Wenner Four-Point Electrical Resistivity Test of Reinforced Concrete Slabs.

The main objectives of this study are to evaluate the effect of geometrical constraints of plain concrete and reinforced concrete slabs on the Wenner four-point concrete electrical resistivity (ER) test through numerical and experimental investigation and to propose measurement recommendations for laboratory and field specimens. First, a series of numerical simulations was performed using a 3D finite element model to investigate the effects of geometrical constraints (the dimension of concrete slabs, the electrode spacing and configuration, and the distance of the electrode to the edges of concrete slabs) on ER measurements of concrete. Next, a reinforced concrete slab specimen (1500 mm (width) by 1500 mm (length) by 300 mm (thickness)) was used for experimental investigation and validation of the numerical simulation results. Based on the analytical and experimental results, it is concluded that measured ER values of regularly shaped concrete elements are strongly dependent on the distance-to-spacing ratio of ER probes (i.e., distance of the electrode in ER probes to the edges and/or the bottom of the concrete slabs normalized by the electrode spacing). For the plain concrete, it is inferred that the thickness of the concrete member should be at least three times the electrode spacing. In addition, the distance should be more than twice the electrode spacing to make the edge effect almost negligible. It is observed that the findings from the plain concrete are also valid for the reinforced concrete. However, for the reinforced concrete, the ER values are also affected by the presence of reinforcing steel and saturation of concrete, which could cause disruptions in ER measurements.

Acai berry extract as a regulator of intestinal inflammation pathways in a Caco-2 and RAW 264.7 co-culture model.

The aim of this study was to assess the anti-inflammatory effects of acai berries in a Caco-2 and RAW 264.7 macrophage co-culture model. The acai berry extract (ABE) was prepared using 70% ethanol, and total anthocyanin, polyphenol, and flavonoid contents in ABE were analyzed. To the antioxidant activity of ABE, we measured radical scavenging activity as well as ferric reducing antioxidant power values. Prior to inducing inflammation, Caco-2 cells were co-cultured with RAW 264.7. Inflammation was induced using lipopolysaccharides (LPS) in RAW 264.7 cells. The transepithelial electrical resistance value was significantly recovered and the mRNA level of tight junction proteins, including ZO-1, JAM-1, and claudin-4, tended to increase compared with that in the LPS group. LPS-induced interleukin (IL)-6, IL-8, and prostaglandin E2 levels reduced significantly following treatment with the highest ABE concentration. In the highest ABE concentration, the phosphorylation of p65, p38 mitogen-activated protein kinase, and c-Jun N-terminal kinase was downregulated compared with the LPS group. The phosphorylation of extracellular signal-regulated kinase showed a decreased tendency. These results suggest that acai berry may improve gastrointestinal health. PRACTICAL APPLICATIONS: Acai berry is known to have abundant anthocyanin, which has many biological activities, including anti-inflammatory, antioxidant, antihypertensive, and anticytotoxic/cytoprotective activities. This study demonstrated the anti-inflammatory effects of acai berry extracts via TEER value, expression of tight junction protein, and production of inflammatory mediators and cytokines in the Caco-2 and RAW 264.7 co-culture model. Therefore, acai berry has the potential to prevent intestinal inflammatory diseases.

Thermoelectric properties of Spark plasma sintered PbTe synthesized without any surfactant and organic solvent

We report a systematic investigation on structural and thermoelectric properties of Spark plasma sintered Lead telluride synthesized by hydrothermal route and a low temperature aqueous chemical route without using any organic solvent and surfactant. The as-synthesized powder samples obtained from these two different synthesis routes were identically subjected to spark plasma sintering. The size of nanocubes formed by the hydrothermal method, as evident from TEM-HRTEM images, is 50 nm; however, the samples synthesized by aqueous chemical route shows mixed morphology with particle size < 50 nm. The thermoelectric properties of spark plasma sintered bulk nanostructured samples have been measured from RT to 700K. Notably, large Seebeck coefficient and small electrical resistivity values are observed in the sample synthesized by the hydrothermal route, which is ascribed to the charge carrier energy filtering effect. A maximum reduction of ∼38% and ∼58% has been observed in the sample synthesized by the hydrothermal route and aqueous chemical route, respectively, compared to the bulk ingot. The maximum figure of merit attained is 0.18 at 673 K in the lead telluride sample synthesized by the hydrothermal route.

Seawater intrusion characterization based on electrical resistivity and hydrogeochemical methods; surrounding Rosetta branch area, Egypt

Seawater intrusion (SWI) is one of the most common environmental issues in recent years, posing a threat to groundwater quality and sustainability, especially in coastal aquifers. The current climate changes linked to rising sea levels as well as the excessive pumping of groundwater, linked to the lack of natural recharge, have exacerbated this environmental problem. As a result, to characterize and detect seawater intrusion in this region. This paper presents a comprehensive combination of geoelectric methods represented by artificial vertical electrical soundings (VES) and hydrogeochemistry of groundwater. Vertical electrical resistivity values are obtained by Schlumberger's array of twenty-six VESes distributed all over the area using the Eleric-T device. However, the electrical resistivity sounding method succeeded to outline the aquifer depth, extension and thickness. The hydrogeochemical techniques outline the ions, cations, water types and water quality based on the chemical analysis of 26 groundwater samples. Both two types are contributed to emphasis the results. The VES results succeeded to describe the Pleistocene aquifer lithology and subdivides it into fresh, brackish and salt zones (freshwater – saltwater interface). The hydrochemical characteristics of groundwater samples through the physiochemical parameters, Chadha diagram, ionic relations and DWQI confirm the influence of SWI on the chemistry of groundwater in the concerned area. Consequently, these results confirm that the integration between the electrical resistivity and hydrochemical methods are effective tools for the characterization of seawater intrusion in this important region in terms of agricultural activity in Egypt.

Predicting Damage in a Concrete Structure Using Acoustic Emission and Electrical Resistivity for a Low and Intermediate Level Nuclear Waste Repository

In this study, the well-known non-destructive acoustic emission (AE) and electrical resistivity methods were employed to predict quantitative damage in the silo structure of the Wolsong Low and Intermediate Level Radioactive Waste Disposal Center (WLDC), Gyeongju, South Korea. Brazilian tensile test was conducted with a fully saturated specimen with a composition identical to that of the WLDC silo concrete. Bi-axial strain gauges, AE sensors, and electrodes were attached to the surface of the specimen to monitor changes. Both the AE hit and electrical resistance values helped in the anticipation of imminent specimen failure, which was further confirmed using a strain gauge. The quantitative damage (or damage variable) was defined according to the AE hits and electrical resistance and analyzed with stress ratio variations. Approximately 75% of the damage occurred when the stress ratio exceeded 0.5. Quantitative damage from AE hits and electrical resistance showed a good correlation (R = 0.988, RMSE = 0.044). This implies that AE and electrical resistivity can be complementarily used for damage assessment of the structure. In future, damage to dry and heated specimens will be examined using AE hits and electrical resistance, and the results will be compared with those from this study.

Design of a TENS knee pad with integrated textile electrodes

Transcutaneous electrical nerve stimulation (TENS) is defined as the application of electrical current to the skin for paincontrol by the American Physical Therapy Association (APTA). The TENS treatment is extensively preferred since it issafe, not expensive and has no side effects when compared to drug therapy. TENS therapy is applied using clinical orportable type TENS devices and TENS electrodes. However, conventional electrodes are not hygienic because they arenot washable and their sticky structure makes patients uncomfortable. Furthermore, they are not suitable to beintegrated into a smart garment. In this study, a knee pad with integrated electrodes and textile transmission lines havebeen designed and developed to be used for TENS therapy. Electrical resistance values of textile electrodes andtransmission lines which are integrated into the knee pad were measured. The developed knee pad was connected toa commercially available TENS device and electrical current transmission on subjects was tested. Furthermore, washingtests were conducted on the knee pad.

Textile electrodes for bioimpedance measuring

This article deals with the development and comparison of eight different electrodes made out of a cotton fabric substrate, a silver coated yarn and partly conductive finishes, i.e. a PEDOT:PSS Orgacon ICP 1050 dip-coating and a Powersil coating. The purpose is the application especially in the medical field of angiopathy like for bioimpedance measurements during compression therapies. To be able to compare the suitability of the electrodes, various tests have been performed of the coating abrasion resistance, the stability of electrical resistance values, as well as resistance and bioimpedance measurements. Significant differences between the electrodes regarding their resilience and resistance that are visualized in a value-added analysis were found, with one hand-embroidered, one machine-sewn and one commercial electrode showing optimum properties.

The Effects of Corrosion, Fatigue, and Corrosion-fatigue of Multilayer Coated Polyesters for Flexible Electronics Applications

We investigated the electrical and optical properties of ITO/Ag-alloy/ITO films in a corrosive NaCl solution. The effects of bending fatigue combined with aggressive environments pro-vided by the salt solution were also studied. It is shown that exposure to the salt solution can cause the ITO/Ag-alloy/ITO performance to degrade over time. In addition, greater changes in electrical resistance and lower values of optical transmittance were observed at higher concentrations of the salt solution. The combination of stress and corrosion by the aqueous NaCl solution was found to significantly reduce the conductivity of the ITO/Ag-alloy/ITO film. Furthermore, it is shown that the presence of structural defects in the deposited films can provide a driving force to form Ag agglomerations that, in turn, degrade the conductivity of the ITO/Ag-alloy/ITO film. This suggests that defects in the film should be minimized to avoid excessive corrosion.

The Impact of Elongation on Change in Electrical Resistance of Electrically Conductive Yarns Woven into Fabric.

Electrically conductive yarns (ECYs) are gaining increasing applications in woven textile materials, especially in woven sensors suitable for incorporation into clothing. In this paper, the effect of the yarn count of ECYs woven into fabric on values of electrical resistance is analyzed. We also observe how the direction of action of elongation force, considering the position of the woven ECY, effects the change in the electrical resistance of the electrically conductive fabric. The measurements were performed on nine different samples of fabric in a plain weave, into which were woven ECYs with three different yarn counts and three different directions. Relationship curves between values of elongation forces and elongation to break, as well as relationship curves between values of electrical resistance of fabrics with ECYs and elongation, were experimentally obtained. An analytical mathematical model was also established, and analysis was conducted, which determined the models of function of connection between force and elongation, and between electrical resistance and elongation. The connection between the measurement results and the mathematical model was confirmed. The connection between the mathematical model and the experimental results enables the design of ECY properties in woven materials, especially textile force and elongation sensors.

Establishment of an In Vitro Co-Culture Model of the Piglet Gut to Study Inflammatory Response and Barrier Integrity.

In intensive farming, piglets are exposed to various challenges that activate intestinal inflammatory processes, negatively affecting animal health and leading to economic losses. To study the role of the inflammatory response on epithelial barrier integrity, co-culture systems that mimic in vivo complexity are more and more preferred over cell monocultures. In this study, an in vitro gut co-culture model consisting of intestinal porcine epithelial cells and porcine peripheral blood mononuclear cells was established. The model provides an appropriate tool to study the role of the inflammatory response on epithelial barrier integrity and to screen for feed and food components, exerting beneficial effects on gut health. In the established model, inflammation-like reactions and damage of the epithelial barrier, indicated by a decrease of transepithelial electrical resistance, were elicited by activation of peripheral blood mononuclear cells via one of 3 stimuli: lipopolysaccharide, lipoteichoic acid, or concanavalin A. Two phytogenic substances that are commonly used as feed additives, licorice extract and oregano oil, have been shown to counteract the drop in transepithelial electrical resistance values in the gut co-culture model. The established co-culture model provides a powerful in vitro tool to study the role of intestinal inflammation on epithelial barrier integrity. As it consists of porcine epithelial and porcine blood cells it perfectly mimics in vivo conditions and imitates the inter-organ communication of the piglet gut. The developed model is useful to screen for nutritional components or drugs, having the potential to balance intestinal inflammation and strengthen the epithelial barrier integrity in piglets.

IL-6/STAT3 signaling pathway regulates the proliferation and damage of intestinal epithelial cells in patients with ulcerative colitis via H3K27ac.

The aim of the present study was to investigate the effect of the IL-6/STAT3 signaling pathway on intestinal epithelial barrier injury in patients with ulcerative colitis (UC). Fifty-two patients with UC and 21 healthy subjects were recruited. The expression level of IL-6 in plasma was determined by ELISA. Normal human colon mucosal epithelial NCM460 cells were treated with IL-6 or plasma from the patients with UC. Then, the transepithelial electrical resistance value, fluorescein yellow permeability and zonulin release were evaluated. Using reverse transcription-quantitative (q)PCR and western blotting, claudin (CLDN) 1 and CLDN2 expression levels were analyzed. Furthermore, western blotting was used to detect phosphorylation of STAT3. Chromatin immunoprecipitation-qPCR was performed to investigate the enrichment of H3K27ac in the promoter regions of CLDN1 and CLDN2. The present study revealed that IL-6 content was elevated in the plasma from patients with UC and increased with the progression of the disease. IL-6 was also observed to induce intestinal epithelial cell barrier injury and regulate barrier function by influencing the expression of tight junction-related proteins, as well as STAT3. The IL-6/STAT3 signaling pathway regulated transcription of CLDN1 and CLDN2 by affecting the enrichment of histone H3K27ac in their promoter regions. Thus, the significantly increased expression level of IL-6 in the peripheral blood of patients with UC indicates a positive association with the development of UC. Furthermore, the IL-6/STAT3 signaling pathway influences the function of the intestinal barrier by affecting the H3K27ac level in intestinal epithelial cells.

Control of physical vapor deposition and architecture of stoichiometric SnSe heterojunction structures for solar cells

Systematic investigations on microstructural development during the physical vapor deposition of SnSe thin films under high vacuum (10−6 mbar) on glass substrates have been carried out, so as to mold the functional properties for fabrication of novel Au/MoO3/p-SnSe/n-CdS/ITO/SLG heterojunction solar cells. Stoichiometric SnSe crystalline target was prepared using a muffle furnace integrated with an indigenously assembled rotation mechanism and its vapors were condensed by subjecting to facile thermal evaporation process, without any extraneous chemical precursors. Effect of substrate temperature, TS (27–350 °C) on morphology, growth mechanism and lattice periodicity was analyzed with the aid of FESEM, AFM and XRD. Fine tuning of TS (= 250 °C) enabled atomically smooth surfaces with appreciable crystallinity and resulted in orthorhombic structure having preferred orientation of crystallites along (111) direction, devoid of other phases. Chemical homogeneity and phase purity were justified by EDAX, XPS and Raman spectroscopy. The values of band gap, electrical resistivity, mobility and concentration of charge carriers are equal to 1.48 eV, 2.36 Ωcm, 6.36 cm2V−1s−1 and 1.25 × 1018 cm−3 respectively. The attained efficiency (1.39%) of the prepared photovoltaic device promises the versatility of SnSe absorber layers towards the enhancement of solar energy conversion.

Experimental investigation of correlations between electrical resistivity, moisture content and voltage values for leachate contaminated clayey sand

Leachate leakage from landfill sites has become a significant environmental problem in recent years, polluting soil layers and groundwater aquifers. A considerable number of dumpsites near cities are operated traditionally and are not designed as landfills, which increases the risk of leakage. Leachate leakage also changes geotechnical and geo-environmental characteristics of soil, often increases soil permeability. Geo-electrical methods are one of the most common methods in leachate leakage investigation in recent years, which are considered as non-destructive methods. Despite recent studies, there are still challenges in applying geo-electrical methods to study leachate leaking from landfill sites that can be addressed through small-scale laboratory studies. One of the critical parameters in the laboratory study of soil resistivity is the voltage of current injected into the soil sample. In this research, the effect of voltage changes applied to the soil samples contaminated by solutions with different contaminant concentrations was investigated. Also, the relation between soil moisture content and resistivity was studied. It was found that there was a sudden change in the reduction rate of soil resistivity for moisture content larger than 13%, which is equal to soil plastic limit. The results showed that by increasing the voltage injected into the soil sample, fluctuation of resistivity values decreased and the transparency of the results increased.

α-Chaconine Affects the Apoptosis, Mechanical Barrier Function, and Antioxidant Ability of Mouse Small Intestinal Epithelial Cells.

α-Chaconine is the most abundant glycoalkaloid in potato and toxic to the animal digestive system, but the mechanisms underlying the toxicity are unclear. In this study, mouse small intestinal epithelial cells were incubated with α-chaconine at 0, 0.4, and 0.8 μg/mL for 24, 48, and 72 h to examine apoptosis, mechanical barrier function, and antioxidant ability of the cells using a cell metabolic activity assay, flow cytometry, Western blot, immunofluorescence, and fluorescence quantitative PCR. The results showed that α-chaconine significantly decreased cell proliferation rate, increased apoptosis rate, decreased transepithelial electrical resistance (TEER) value, and increased alkaline phosphatase (AKP) and lactate dehydrogenase (LDH) activities, and there were interactions between α-chaconine concentration and incubation time. α-Chaconine significantly reduced the relative and mRNA expressions of genes coding tight junction proteins zonula occludens-1 (ZO-1) and occludin, increased malondialdehyde (MDA) content, decreased total glutathione (T-GSH) content, reduced the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and γ-glutamylcysteine synthetase (γ-GCS) and the mRNA expressions of SOD, CAT, GSH-Px, and γ-GCS genes. In conclusion, α-chaconine disrupts the cell cycle, destroys the mechanical barrier and permeability of mucosal epithelium, inhibits cell proliferation, and accelerates cell apoptosis.

Transcriptome-wide profiling discover: PM2.5 aggravates airway dysfunction through epithelial barrier damage regulated by Stanniocalcin 2 in an OVA-induced model

BackgroundEpidemiologic evidence suggests that PM2.5 exposure aggravates asthma, but the molecular mechanisms are not fully discovered. MethodsOvalbumin (OVA)-induced mice exposed to PM2.5 were constructed. Pathological staining and immunofluorescence were performed in in vivo study. Gene set enrichment analysis (GSEA) was performed to identify the pathway involved in asthma severity by using U-BIOPRED data (human bronchial biopsies) and RNA-seq data (Beas-2B cells treated with PM2.5). Lentiviruses transfection, Real-time qPCR, immunofluorescence staining and trans-epithelial electrical resistance (TEER) measurement were performed for mechanism exploration in vitro. ResultsPM2.5 exposure aggravated airway inflammation and mucus secretion in OVA-induced mice. Based on transcriptome analysis of mild-to-severe asthma from human bronchial biopsies, gene set enrichment analysis (GSEA) showed that up-regulated reactive oxygen species (ROS) pathway gene set and down-regulated apical junction gene set correlated with asthma severity. Consistent with the analysis of mild-to-severe asthma, after PM2.5 exposure, the ROS pathway in Beas-2B cells was up-regulated with the down-regulation of apical junction. The expression levels of genes involved in the specific gene sets were validated by using qPCR. The mRNA levels of junction genes, ZO-1, E-cadherin and Occludin, were significantly decreased in cells exposed to PM2.5. Moreover, it confirmed that inhibition of ROS recovered the expression levels of E-cadherin, Occludin and ZO-1, and ameliorated inflammation and mucus secretion in airway in OVA-induced mice exposed to PM2.5. Meanwhile, ROS level was elevated by PM2.5. By checking trans-epithelial electrical resistance (TEER) value, we also found that epithelial barrier was damaged after PM2.5 exposure. Importantly, Stanniocalcin 2 (STC2) was identified as a key gene in regulation of epithelial barrier. It showed that STC2 expression was up-regulated by PM2.5, which was recovered by NAC as well. Over-expression of STC2 could decrease the expression levels of ZO-1, Occludin and E-cadherin. Contrarily, suppression of STC2 could increase the expression levels of ZO-1, Occludin and E-cadherin reduced by PM2.5. ConclusionsBy using transcriptome analysis, we revealed that STC2 played a key role in PM2.5 aggravated airway dysfunction through regulation of epithelial barrier in OVA-induced mice.