Laminar Shear Research Articles

Nuclear Mechanosensation and Mechanotransduction in Vascular Cells.

Vascular cells are constantly subjected to physical forces associated with the rhythmic activities of the heart, which combined with the individual geometry of vessels further imposes oscillatory, turbulent, or laminar shear stresses on vascular cells. These hemodynamic forces play an important role in regulating the transcriptional program and phenotype of endothelial and smooth muscle cells in different regions of the vascular tree. Within the aorta, the lesser curvature of the arch is characterized by disturbed, oscillatory flow. There, endothelial cells become activated, adopting pro-inflammatory and athero-prone phenotypes. This contrasts the descending aorta where flow is laminar and endothelial cells maintain a quiescent and atheroprotective phenotype. While still unclear, the specific mechanisms involved in mechanosensing flow patterns and their molecular mechanotransduction directly impact the nucleus with consequences to transcriptional and epigenetic states. The linker of nucleoskeleton and cytoskeleton (LINC) protein complex transmits both internal and external forces, including shear stress, through the cytoskeleton to the nucleus. These forces can ultimately lead to changes in nuclear integrity, chromatin organization, and gene expression that significantly impact emergence of pathology such as the high incidence of atherosclerosis in progeria. Therefore, there is strong motivation to understand how endothelial nuclei can sense and respond to physical signals and how abnormal responses to mechanical cues can lead to disease. Here, we review the evidence for a critical role of the nucleus as a mechanosensor and the importance of maintaining nuclear integrity in response to continuous biophysical forces, specifically shear stress, for proper vascular function and stability.

Design of a Biaxial Laminar Shear Box for 1g Shaking Table Tests

In this paper, the design of a new laminar shear box at the Laboratory of Earthquake Engineering and Dynamic Analysis (L.E.D.A.) of the University of Enna “Kore” (Sicily, Italy), is presented. The laminar box has been developed to investigate the liquefaction phenomenon and to validate advanced numerical models and/or the numerical approaches assessed to simulate and prevent related effects. The first part of the paper describes in detail the types of soil containers that have been used in the last three decades around the world. Particular attention is paid to laminar shear box and liquefaction studies. Moreover, the most important factors that affect the performance of a laminar shear box are reported. The last part of the paper describes components, properties, and design advantages of the new laminar shear box for 1g shaking table tests at L.E.D.A. The new laminar box has a rectangular cross section and consists of 16 layers. Each layer is composed of two frames: an inner frame and an outer frame. The inner frame has an internal dimension of 2570 mm by 2310 mm, while the outer frame has an internal dimension of 2700 mm by 2770 mm. Between the layers, there is a 20 mm gap, making the total height 1600 mm.

Flow over a confined mounted fence at low and moderate Reynolds number: A numerical study

Direct numerical simulations of a flow over a wall mounted fence confined by two parallel walls were conducted at low and transitional Reynolds number (50⩽ReD⩽2000) for blockage ratios ranging from 0.25 (low blockage) to 0.9 (high blockage). A primary recirculation bubble forms downstream of the fence and the length of this recirculation region increased with Reynolds numbers. A secondary recirculation bubble appeared on the opposite wall to the mounted fence for the laminar cases with higher blockage ratios at sufficiently large Reynolds number. The separation and reattachment locations were documented and compared with numerical and experimental data. The length of the primary recirculation bubble in current simulations are consistent with the literature while the comparison of the secondary recirculation bubble with experimental data had limited agreement. This secondary recirculation bubble disappeared for the cases at transitional Reynolds number. Instead, the strong primary recirculation bubble induced a corner eddy at the rear of the fence. ‘Packets’ of cross stream velocity fluctuations were observed as the initially 2D, steady, laminar shear layer breakdowns to a 3D turbulent flow. The space–time diagram also showed ripple-like fluctuations of the shear layer further downstream of the fence with a single distinct peak observed in the streamwise and cross flow velocity fluctuations spectra. This peak in the spectra can be predicted by linear stability analysis of a mixing layer (Yasuo et al., 1986). In the near wake, scale-like features were observed while patches of fluctuations of a longer timescale were noted in the recirculation region.

A mitochondrial contribution to anti-inflammatory shear stress signaling in vascular endothelial cells.

Atherosclerosis, the major cause of myocardial infarction and stroke, results from converging inflammatory, metabolic, and biomechanical factors. Arterial lesions form at sites of low and disturbed blood flow but are suppressed by high laminar shear stress (LSS) mainly via transcriptional induction of the anti-inflammatory transcription factor, Kruppel-like factor 2 (Klf2). We therefore performed a whole genome CRISPR-Cas9 screen to identify genes required for LSS induction of Klf2. Subsequent mechanistic investigation revealed that LSS induces Klf2 via activation of both a MEKK2/3-MEK5-ERK5 kinase module and mitochondrial metabolism. Mitochondrial calcium and ROS signaling regulate assembly of a mitophagy- and p62-dependent scaffolding complex that amplifies MEKK-MEK5-ERK5 signaling. Blocking the mitochondrial pathway in vivo reduces expression of KLF2-dependent genes such as eNOS and inhibits vascular remodeling. Failure to activate the mitochondrial pathway limits Klf2 expression in regions of disturbed flow. This work thus defines a connection between metabolism and vascular inflammation that provides a new framework for understanding and developing treatments for vascular disease.

Oscillatory shear stress augments endothelial pannexin1 by inhibiting macro-autophagy

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Atherosclerotic lesions preferentially develop in arterial regions exposed to disturbed blood flow, which are characterized by a dysfunctional proinflammatory endothelial cell (EC) phenotype. ECs release ATP in response to changes in wall shear stress (WSS), which subsequently regulates the inflammatory response. ATP can be released from cells in a controlled manner through Pannexin1 (Panx1) channels. Objective To study the expression of Panx1 in response to WSS and its role in the endothelium. Methods Human ECs (HUVECs or EA.hy926) were exposed to physiological high laminar shear stress (HLSS) and atheroprone oscillatory shear stress (OSS) for 48h using an orbital shaker. Panx1 transcript and protein levels were determined by qPCR and Western blot, respectively. mRNA was extracted for RNAseq. WSS-modifying casts were placed for 1 week around the carotid artery of mice and Panx1 expression was analyzed en face. Carotid WSS-modifying casts were also placed in Tie2CreTgPanx1fl/flApoE-/- and Panx1fl/flApoE-/- mice followed by 9 weeks high fat diet. CD68+ cells were quantified in OSS-induced atherosclerotic lesions. Results We found that Panx1 expression was increased in carotid regions exposed to OSS as compared to HLSS regions. These results were confirmed in vitro in HUVECs. In silico analysis of the promotor of Panx1 revealed binding sites for the WSS-sensitive transcription factors NF-kB and CREB. NF-kB and CREB mRNA levels were similar under OSS and HLSS, however NF-kB activation (phospho-NF-kB) was detected in ECs under OSS. Surprisingly, Panx1 mRNA level was not affected under these conditions, suggesting that the increased Panx1 protein observed under OSS may be due to decreased Panx1 degradation rather than to increased synthesis of the protein. Unbiased analysis of differential gene expression in ECs exposed to HLSS or OSS revealed 320 up-regulated and 353 down-regulated genes under OSS. Down-regulated genes included proteins involved in macro-autophagy. Inhibition of macro-autophagy in ECs by exposure to chloroquine for 6h increased the expression of glycosylated Panx1, suggestive for more Panx1 channels at the plasma membrane under these conditions. Finally, we observed that atherosclerotic lesions in OSS regions of Tie2CreTgPanx1fl/flApoE-/- mice contained more CD68+ cells than Panx1fl/flApoE-/- controls. Conclusion Endothelial Panx1 expression is upregulated in response to OSS. Absence of OSS effects on NF-kB, CREB and Panx1 mRNA revealed that the upregulation of Panx1 protein is not due to transcriptional effects of OSS. Expression of genes involved in the macro-autophagic process were down-regulated under OSS, and chemical inhibition of macro-autophagy augmented the plasma membranous form of Panx1. OSS-induced decrease in autophagic flux may enhance ATP release through Panx1 channels, thereby counterbalancing leukocyte recruitment in atherosclerosis.

Mechanical property of jute fibre reinforced polymer composite filled with clam shell filler: a marine waste

ABSTRACT The present work utilises clam shell, a marine waste as filler material in a natural fibre composite.Different contents of clam shell filler of 0, 5 and 10 wt.% are considered for preparing the composite by the hand lay-up technique. The addition clamshell filler in the composite improves the tensile strength and tensile modulus by 51.40 and 63.47 % from 0 to 5 wt.% of clam shell filler, respectively. Similarly, flexural strength, flexural modulus and inter laminar shear strength of the composites show the maximum value at 5 wt.% filler addition. Beyond this value, the mechanical strength is reduced. Hardness values of the composites are increased with the increase in inclusion of the clam shell filler. In contrast, the addition of filler reduces the impact strength of the composites. Again, to determine the viscoelastic behaviour of the jute epoxy composite with the clam shell filler, dynamic mechanical analysis is performed. Storage modulus and loss modulus are found to be increasing with the increase in wt.% of filler. For all composites, the damping factor improves with the increase in temperature and obtained the highest height in the transition region. It is low below the glass transition temperature.

Activation of AMPK/miR-181b Axis Alleviates Endothelial Dysfunction and Vascular Inflammation in Diabetic Mice.

Hyperglycemia in diabetes mellitus impairs endothelial function and disrupts microRNA (miRNA) profiles in vasculature, increasing the risk of diabetes-associated complications, including coronary artery disease, diabetic retinopathy, and diabetic nephropathy. miR-181b was previously reported to be an anti-inflammatory mediator in vasculature against atherosclerosis. The current study aimed to investigate whether miR-181b ameliorates diabetes-associated endothelial dysfunction, and to identify potential molecular mechanisms and upstream inducer of miR-181b. We found that miR-181b level was decreased in renal arteries of diabetic patients and in advanced glycation end products (AGEs)-treated renal arteries of non-diabetic patients. Transfection of miR-181b mimics improved endothelium-dependent vasodilation in aortas of high fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice, accompanied by suppression of superoxide overproduction and vascular inflammation markers. AMPK activator-induced AMPK activation upregulated miR-181b level in human umbilical vein endothelial cells (HUVECs). Chronic exercise, potentially through increased blood flow, activated AMPK/miR-181b axis in aortas of diabetic mice. Exposure to laminar shear stress upregulated miR-181b expression in HUVECs. Overall, our findings highlight a critical role of AMPK/miR-181b axis and extend the benefits of chronic exercise in counteracting diabetes-associated endothelial dysfunction.

Stress- and process model for dispersing of nanoparticulate suspensions in laminar shear flow

This work presents a stress model and a process model for dispersing processes in laminar shear flow, which are performed in devices such as kneaders, extruders and three roller mills. Based on deep investigations of two kneaders (lab- and pilot-scale) a methodology is presented, which allows modelling the dispersing process by applying a stress model along with a population balance model to the given task. Stress models describe how often particles are stressed during the process and which energy is transferred to the particles. For dispersing in laminar shear flow, it is crucial to distinguish between dispersing-effective and ineffective stress events based on whether the stress intensity is high enough to overcome the particle strength. Results suggest, that the effective specific energy input determines the dispersing progress independent of the process scale. A process model in form of a population balance was required to obtain otherwise unknown parameters for the stress model. The applied population balance model accounts for the acting working principles during dispersing. For such a mechanistic depiction of the dispersing progress, the trilateral dependency between particle size, resulting viscosity, particle stressing and fragmentation must be modelled. It was found that based on the models, the process behaviour on both scales can be depicted, which offers the perspective of a knowledge-based scale-up of machines and processes, process control and process design based on these results.

Exposure of human cerebral microvascular endothelial cells hCMEC/D3 to laminar shear stress induces vascular protective responses

Endothelial cells (ECs) are constantly submitted in vivo to hemodynamical forces derived from the blood circulation, including shear stress (SS). ECs are able to detect SS and consequently adapt their phenotype, thus affecting many endothelial functions. If a plethora of shear stress-regulated molecular networks have been described in peripheral ECs, less is known about the molecular responses of microvascular brain ECs which constitute the blood–brain barrier (BBB). In this work, we investigated the response of human cerebral microvascular ECs to laminar physiological shear stress using the well characterized hCMEC/D3 cell line. Interestingly, we showed that hCMEC/D3 cells responded to shear stress by aligning perpendicularly to the flow direction, contrary to peripheral endothelial cells which aligned in the flow direction. Whole proteomic profiles were compared between hCMEC/D3 cells cultured either in static condition or under 5 or 10 dyn.cm−2 SS for 3 days. 3592 proteins were identified and expression levels were significantly affected for 3% of them upon both SS conditions. Pathway analyses were performed which revealed that most proteins overexpressed by SS refer to the antioxidant defense, probably mediated by activation of the NRF2 transcriptional factor. Regarding down-regulated proteins, most of them participate to the pro-inflammatory response, cell motility and proliferation. These findings confirm the induction of EC quiescence by laminar physiological SS and reveal a strong protective effect of SS on hCMEC/D3 cells, suggesting a similar effect on the BBB. Our results also showed that SS did not significantly increase expression levels nor did it affect the localization of junctional proteins and did not afect either the functional activity of several ABC transporters (P-glycoprotein and MRPs). This work provides new insights on the response of microvascular brain ECs to SS and on the importance of SS for optimizing in vitro BBB models.

Role of an auxilliary subunit of voltage-gated Na+ channels in endothelial functions: Is Navβ3, a novel actor of vascular mechanosignaling?

The endothelial cell (EC) is a central actor to maintain vascular tone and homeostasis. Endothelial dysfunction is responsible for the development of many cardiovascular diseases including atherosclerosis. The endothelial function is mainly stimulated by the shear stress generated by blood flow. The physical forces produced by flow are detected by many mechanosensors in EC, which trigger intracellular signaling pathways influencing endothelial physiology. Among these mechanosensors, several ion channels have been identified. Voltage-gated Na+ (Nav) channels have been shown to be mechanosensitive in cardiac and intestinal cells. These ion channels are also expressed in EC and then we aim to investigate their role in EC responses to shear stress. Confluent Human Umbilical Vein EC (HUVEC) and Human Aorta EC (teloHAEC) were exposed to laminar (LSS, 20 dynes/cm 2 ) or oscillatory shear stress (OSS, 20 dynes/cm 2 , 0.5 Hz frequency) using the Ibidi® pump system. Cell orientation was quantified by local gradient orientation method with Fiji software. RTqPCR and western blot were used to characterize Nav channel subunits at both transcriptional and protein levels. Exposition of HUVEC and TeloHAEC to a LSS for 24 hours and 4 days induced cell orientation in the direction of flow and activated the atheroprotective signaling pathway (KLF2/KLF4, eNOS). Interestingly, shear stress deep changes in several Nav channels subunits expression level. Notably, SCN3B expression, encoding the Ig-CAM Navβ3 protein, was increased with a 2.1 fold increase at 24 hours, 3.9 at 4 days and 12.6 at 7 days in HUVEC and 2.9 at 4 days in teloHAEC. Moreover, trans-resveratrol-induced KLF2 expression led to increase SCN3B expression, suggesting that this atheroprotective transcription factor might be involved in SCN3B regulation. Indeed, OSS, corresponding to an atherogenic flow, did not induce HUVEC alignment in the direction of flow neither activation of atheroprotective signaling pathway nor a significant increase of SCN3B expression. Taken together, our results suggest that Navβ3 could be a putative novel actor in the mechanotransduction of flow and thus in vasculoprotection.

Influence of large seed particle on acoustic particle interaction dynamics: A numerical study

Acoustic agglomeration as a promising preconditioning process for fine particle removal has been proven to be inefficient for submicron particles. In order to enhance the performance of acoustic agglomeration, large seed particles have been introduced into the flue gas. To understand the influence of seed particles on acoustic agglomeration, a nondimensional model of particle interaction was developed by taking into account all important particle interaction mechanisms. The simulated particle trajectories were validated against experimental data. The interaction dynamics of a seed particle and its neighboring fine particles was examined, and the dimensionless first collision time under different conditions was obtained. The results suggest that the enhancement of acoustic agglomeration with seed particle is mainly due to the acoustic wake effect. The overall collision kernel for the acoustic agglomeration was referred from the collision time. The results reveal that the dimensionless collision kernel almost increases linearly with the Stokes number of the seed particle, whereas its dependence on the Schmidt number of the fine particle varies significantly. The collision kernel for acoustic agglomeration was further compared with traditional collision kernels based on differential sedimentation, Brownian diffusion, laminar shear and turbulent shear. The results demonstrate that acoustic field indeed remarkably enhances the collision rate.

Human dermal microvascular endothelial cell morphological response to fluid shear stress

As the cells that line the vasculature, endothelial cells are continually exposed to fluid shear stress by blood flow. Recent studies suggest that the morphological response of endothelial cells to fluid shear stress depends on the endothelial cell type. Thus, the present study characterizes the morphological response of human dermal microvascular endothelial cells (HMEC-1) and nuclei to steady, laminar, and unidirectional fluid shear stress. Cultured HMEC-1 monolayers were exposed to shear stress of 0.3 dyn/cm2, 16 dyn/cm2, or 32 dyn/cm2 for 72 h with hourly live-cell imaging capturing both the nuclear and cellular morphology. Despite changes in elongation and alignment occurring with increasing fluid shear stress, there was a lack of elongation and alignment over time under each fluid shear stress condition. Conversely, changes in cellular and nuclear area exhibited dependence on both time and fluid shear stress magnitude. The trends in cellular morphology differed at shear stress levels above and below 16 dyn/cm2, whereas the nuclear orientation was independent of fluid shear stress magnitude. These findings show the complex morphological response of HMEC-1 to fluid shear stress.

Laminar shear stress inhibits inflammation by activating autophagy in human aortic endothelial cells through HMGB1 nuclear translocation.

Prevention and treatment of atherosclerosis (AS) by targeting the inflammatory response in vascular endothelial cells has attracted much attention in recent years. Laminar shear stress (LSS) has well-recognized anti-AS properties, however, the exact molecular mechanism remains unclear. In this study, we found that LSS could inhibit the increased expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), cyclooxygenase-2 (COX-2), and matrix metallopeptidase-9 (MMP-9) caused by TNF-α in an autophagy-dependent pathway in human aortic endothelial cells (HAECs) and human umbilical vein endothelial cells (HUVECs). Whole-transcriptome sequencing analysis revealed that erythropoietin-producing hepatocyte receptor B2 (EPHB2) was a key gene in response to LSS. Moreover, co-immunoprecipitation assay indicated that LSS could enhance the EPHB2-mediated nuclear translocation of high mobility group box-1 (HMGB1), which interacts with Beclin-1 (BECN1) and finally leads to autophagy. Simultaneously, we identified an LSS-sensitive long non-coding RNA (lncRNA), LOC10798635, and constructed an LSS-related LOC107986345/miR-128-3p/EPHB2 regulatory axis. Further research revealed the anti-inflammatory effect of LSS depends on autophagy activation resulting from the nuclear translocation of HMGB1 via the LOC107986345/miR-128-3p/EPHB2 axis. Our study demonstrates that LSS could regulate the expression of EPHB2 in HAECs, and the LOC107986345/miR-128-3p/EPHB2 axis plays a vital role in AS development.

Mechanosensory channel Piezo1 contributes to T lymphocyte migration through direct interaction with integrins

Abstract Response to mechanical signals is an important mechanism by which T lymphocytes drive inflammation. A potential contributor in this process is Piezo1, a mechanosensitive cation channel which is abundantly expressed in T lymphocytes. Previously, our lab has shown that Piezo1 colocalizes with high affinity LFA-1 on activated human T lymphocytes during chemokine-activated crawling, suggesting a role for Piezo1 in the adhesion cascade. However, the mechanism by which Piezo1 contributes to the regulation of the adhesion cascade is unknown. We hypothesize that Piezo1 mediates T lymphocyte migration through direct contact with integrin to regulate its function. We investigate the role of Piezo1 in the expression, binding affinity, and turnover of LFA-1 and VLA-4. Co-immunoprecipitation revealed a preferential association of Piezo1 with the alpha subunit of integrins, specifically LFA-1, MAC-1, and VLA-4 in the active forms. Moreover, microfluidic devices were used to study the contribution of Piezo1 on T lymphocytes under laminar flow-induced shear stress. We found that activated T lymphocytes with CRISPR/Cas9-mediated Piezo1 ablation resulted in a reduced chemokine-induced crawling speed that correlates to the efficiency of Piezo1 gene ablation. Finally, in studies of lymph node homing where fluorescently labeled T lymphocytes were tracked in vivo, Piezo1 deficient cells exhibit increased ingress and decreased egress through the lymph node, suggesting an intricate role of Piezo1 on T lymphocyte migration. Taken together, our data support the hypothesis that Piezo1 modulates inflammatory processes through complex integrin interactions and mediates T lymphocyte migration from the lymph node to the site of inflammation. Case Postbaccalaureate Research Education Program grant NIH/NIGMS 5R25GM075207-15; St. Baldrick’s Foundation; Hyundai Hope-on-Wheels Program; The I’m Not Done Yet Foundation; and Pediatric Cancer Research Foundation

Activating P2Y1receptors improves function in arteries with repressed autophagy

Objective and hypothesisThe importance of endothelial cell (EC) autophagy to vascular homeostasis in the context of health and disease is evolving. Earlier we reported that intact EC autophagy is requisite to maintain shear‐stress‐induced nitric oxide (NO) generation via glycolysis‐dependent purinergic signaling to eNOS. Here we illustrate the translational and functional significance of these findings.Methods and ResultsFirst, we assessed translational relevance using older male humans and mice that exhibit blunted EC autophagy and impaired arterial function vs. adult controls. Active hyperemia evoked by rhythmic handgrip exercise elevated radial artery shear rate similarly from baseline in adult (23±1 y) and older (68±2 y) subjects for 60‐min. Compared to baseline, indexes of autophagy initiation, p‐eNOSS1177 activation, and NO generation, occurred in radial artery ECs obtained from adult but not older volunteers. Regarding mice, indexes of autophagy and p‐eNOSS1177 activation were robust in ECs from adult (7 ± 1 months) but not older (23 ± 1 months) animals that completed 60‐min treadmill‐running. Further, results concerning the extracellular acidification rate (ECAR; Seahorse Bioanalyzer) indicate glycolysis and glycolytic capacity were elevated in response to 20 dyn/cm2 laminar shear stress x 45‐min in primary arterial ECs obtained from adult but not older mice. We next questioned whether the inability to initiate EC autophagy, glycolysis, and p‐eNOSS1177 precipitates dysfunction in arteries from older vs. adult mice. Compromised intraluminal flow‐mediated vasodilation displayed by arteries from older vs. adult mice was recapitulated in vessels from adult mice by : (i) NO synthase inhibition; (ii) acute autophagy impairment using 3‐methyladenine (3‐MA); (iii) EC Atg3 depletion (Atg3EC‐/‐ mice); (iv) purinergic 2Y1‐receptor (P2Y1‐R) blockade; and (v) germline depletion of P2Y1‐Rs. Importantly, P2Y1‐R activation using 2‐methylthio‐ADP (2‐Me‐ADP) improved vasodilatory capacity in arteries from : (i) adult mice treated with 3‐MA; (ii) adult Atg3EC‐/‐ mice; and (iii) older animals with repressed EC autophagy.ConclusionsArterial dysfunction concurrent with pharmacological, genetic, and age‐associated EC autophagy disruption is improved by activating P2Y1‐Rs.

Laminar Shear Stress Enhances Cytosolic PINK1 Expression: Increased Mitophagic Sensitivity Toward Mitochondrial Dysfunction

PURPOSEPhosphatase and tensin homolog (PTEN)‐induced putative kinase 1 (PINK1) is an essential molecule in mitophagy process and known to act as a cytoprotective protein in mammalian cells. Mutation or deficiency of PINK1 has been closely related to several disease conditions. The purpose of this study was to determine PINK1 expression levels and subcellular localization under exercise‐mimic laminar shear stress (LSS) condition in human aortic endothelial cells (HAECs) or in exercising mice, and its implication on endothelial homeostasis and cardiovascular disease (CVD) prevention.METHODS & RESULTSFirst, we measured full‐length PINK1 (FL‐PINK1) mRNA and protein expression levels in HAECs under unidirectional laminar shear stress (LSS) at 15 dyne/cm2 for 48h. LSS significantly elevated both FL‐PINK1 mRNA and protein expressions in HAECs compared to static control. Mitochondrial fractionation assays showed a decrease in FL‐PINK1 accumulation in the mitochondria with a compensatory increase in the cytosolic FL‐PINK1 level under LSS. Confocal microscopic analysis confirmed these subcellular localization patterns suggesting downregulation of mitophagy induction. Also, mitophagy flux was decreased under LSS, determined by a mtKeima probe. Mitochondrial morphometric analysis and mitochondrial membrane potential (JC‐1) showed mitochondrial elongation and increased mitochondrial membrane potential, respectively, suggesting that an elevation of cytosolic PINK1 is not related to an immediate induction of mitophagy. Based on this observation, we further hypothesized that the elevation of the cytosolic pool of FL‐PINK1 would increase the sensitivity to mitophagic signals in pathological conditions. Preconditioned HAECs with LSS showed lower mtDNA lesions under angiotensin II stimulation (100 nM, 6h). Moreover, LSS‐preconditioned ECs showed rapid Parkin recruitment and mitophagy induction in response to mitochondrial toxin (i.e. CCCP) treatment compared to the control. We measured PINK1 expression at ECs of the thoracic aorta in exercised mice, a physiological LSS‐enhanced model, which was significantly elevated compared to sedentary animals. In addition, exercise‐preconditioned mice were more protective to angiotensin II‐induced mtDNA lesion formation in the mouse abdominal aorta than sedentary mice, suggesting a potential protective mechanism of exercise in a PINK1‐dependent manner.CONCLUSIONLSS increases a cytosolic pool of FL‐PINK1, which may elevate the mitophagic sensitivity toward dysfunctional mitochondria or activate other cytoprotective mechanisms in endothelial cells. Our data suggest that exercise may support mitochondrial homeostasis in vascular endothelial cells by enhancing PINK1‐dependent cell protection mechanisms.

Oil droplet breakup during pressure swirl atomization of emulsions: Influence of emulsion viscosity and viscosity ratio

The atomization of oil-in-water emulsions for spray drying is a common task in food engineering. During atomization with pressure swirl atomizers, the emulsions are subjected to high stresses that can lead to deformation and breakup not only of the liquid itself but also of the disperse oil droplets therein. In this study, the effect of the viscosity ratio λ of the emulsion (0.2–33) and of the emulsion viscosity (5–50 mPa⋅s) on oil droplet breakup during atomization was investigated at atomization pressures between 50 and 250 bar. A systematic influence of λ on the oil droplet size was observed with maximum oil droplet breakup for λ between 0.2 and 1.2. At a constant viscosity ratio of ∼ 1, the resulting oil droplet size was almost independent of the emulsion viscosity, even when volume flow rates and spray droplet sizes during atomization showed a clear dependence on this parameter. A model based on existing knowledge on droplet breakup in laminar shear flow is developed, by which oil droplet sizes after atomization can be predicted. This model may serve as a tool to control oil droplet size after atomization by defining appropriate atomization conditions and emulsion formulation. This is especially relevant for spray drying applications in which the oil droplet size in the powder is an important quality parameter. • Viscosity ratio λ influences oil droplet breakup during pressure swirl atomization. • At λ ∼ 1 the emulsion viscosity per se has little influence on oil droplet breakup. • Oil droplet breakup follows the theory of droplet breakup in laminar shear flow. • A model is proposed that serves as a tool to predict oil droplet breakup.

Effect of fiber orientation on the mechanical properties of unidirectional basalt fiber reinforced polymer matrix composites

Polymer matrix composite materials have attracted the researchers over a period due to its superior specific strength, compared to conventional materials. Bio-based fibers have started to emerge rapidly for industrial components, encompassing the technological/scientific aspects and the economic, environmental and social issues. Amongst the variety of bio-based fibers, basalt fiber occupies a prominent position, due to its overall production and unique chemistry-related features. It is chemically inert and non-reactive. In the present investigation, unidirectional basalt fiber of 240GSM at different orientations is added as reinforcement with a fixed weight percentage of 55% to LY556-HY951 epoxy-hardener combination as matrix. Fabrication is carried out by conventional hand lay-up technique. Mechanical characterization such as, tensile, flexural, hardness and inter laminar shear strength tests are conducted for the fabricated material. Morphological studies are conducted using scanning electron microscope (SEM) to visualize the fiber pull out, presence of voids and matrix-fiber adhesion characteristics. From the results obtained, it can be concluded that the highest strengths are obtained for laminates with zero-degree fiber orientation, which makes it suitable to be used for engineering, structural and biomedical applications

Influence of stacking sequence on flax/kevlar hybrid epoxy composites: Mechanical and morphological studies

AbstractIn this research work, the natural fiber reinforced hybrid epoxy composites were fabricated using the hand lay‐up method. The flax and kevlar are used as a reinforcement and epoxy as a binding material. This study aims to analyze the influence of stacking sequence and hybridization on the mechanical, water absorption, and morphological properties of polymer composites. The results reveal that the neat kevlar reinforced composite achieved a maximum tensile strength, modulus, and impact strength of 189.94 MPa, 2345.35 MPa and 37.16 kJ/m2 respectively with less water absorption behavior. Whereas, the hybrid composite with kevlar as an outer layers and flax as core layers was exhibited a maximum flexural strength, modulus, and inter laminar shear strength of 360.76, 37124.2, and 213.51 MPa, respectively. The water absorption percentage was more in neat natural flax reinforced epoxy composite due to its more hydrophilic nature. The scanning electron microscope analysis reveals the proper bonding and adhesion of both kevlar and flax fabrics with the epoxy matrix.

Activating P2Y1 receptors improves function in arteries with repressed autophagy.

The importance of endothelial cell (EC) autophagy to vascular homeostasis in the context of health and disease is evolving. Earlier, we reported that intact EC autophagy is requisite to maintain shear-stress-induced nitric oxide (NO) generation via glycolysis-dependent purinergic signalling to endothelial NO synthase (eNOS). Here, we illustrate the translational and functional significance of these findings. First, we assessed translational relevance using older male humans and mice that exhibit blunted EC autophagy and impaired arterial function vs. adult controls. Active hyperaemia evoked by rhythmic handgrip exercise-elevated radial artery shear-rate similarly from baseline in adult and older subjects for 60 min. Compared with baseline, indexes of autophagy initiation, p-eNOSS1177 activation, and NO generation, occurred in radial artery ECs obtained from adult but not older volunteers. Regarding mice, indexes of autophagy and p-eNOSS1177 activation were robust in ECs from adult but not older animals that completed 60-min treadmill-running. Furthermore, 20 dyne • cm2 laminar shear stress × 45-min increased autophagic flux, glycolysis, ATP production, and p-eNOSS1177 in primary arterial ECs obtained from adult but not older mice. Concerning functional relevance, we next questioned whether the inability to initiate EC autophagy, glycolysis, and p-eNOSS1177in vitro precipitates arterial dysfunction ex vivo. Compromised intraluminal flow-mediated vasodilation displayed by arteries from older vs. adult mice was recapitulated in vessels from adult mice by (i) NO synthase inhibition; (ii) acute autophagy impairment using 3-methyladenine (3-MA); (iii) EC Atg3 depletion (iecAtg3KO mice); (iv) purinergic 2Y1-receptor (P2Y1-R) blockade; and (v) germline depletion of P2Y1-Rs. Importantly, P2Y1-R activation using 2-methylthio-ADP (2-Me-ADP) improved vasodilatory capacity in arteries from (i) adult mice treated with 3-MA; (ii) adult iecAtg3KO mice; and (iii) older animals with repressed EC autophagy. Arterial dysfunction concurrent with pharmacological, genetic, and age-associated EC autophagy compromise is improved by activating P2Y1-Rs.