Proximal tubule apical endocytosis is modulated by fluid shear stress via an mTOR-dependent pathway

Cells lining the proximal tubule (PT) have unique membrane specializations that are required to maintain the high-capacity ion transport and endocytic functions of this nephron segment. PT cells in vivo acutely regulate ion transport in response to changes in glomerular filtration rate (GFR) to maintain glomerulotubular balance. PT cells in culture up-regulate endocytic capacity in response to acute changes in fluid shear stress (FSS); however, it is not known whether GFR modulates PT endocytosis to enable maximally efficient uptake of filtered proteins in vivo. Here, we show that cells cultured under continuous FSS develop an expanded apical endocytic pathway and increased endocytic capacity and lysosomal biogenesis. Furthermore, endocytic capacity in fully differentiated cells is rapidly modulated by changes in FSS. PT cells exposed to continuous FSS also acquired an extensive brush border and basolateral membrane invaginations resembling those observed in vivo. Culture under suboptimal levels of FSS led to intermediate phenotypes, suggesting a threshold effect. Cells exposed to FSS expressed higher levels of key proteins necessary for PT function, including ion transporters, receptors, and membrane-trafficking machinery, and increased adenine nucleotide levels. Inhibition of the mechanistic target of rapamycin (mTOR) using rapamycin prevented the increase in cellular energy levels, lysosomal biogenesis, and endocytic uptake, suggesting that these represent a coordinated differentiation program. In contrast, rapamycin did not prevent the FSS-induced increase in Na+/K+-ATPase levels. Our data suggest that rapid tuning of the endocytic response by changes in FSS may contribute to glomerulotubular balance in vivo. Moreover, FSS provides an essential stimulus in the differentiation of PT cells via separate pathways that up-regulate endocytosis and ion transport capacity. Variations in FSS may also contribute to the maturation of PT cells during kidney development and during repair after kidney injury.

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ShearFAST: a user-friendly in vitro toolset for high throughput, inexpensive fluid shear stress experiments.

10.1101/2020.01.31.929513 ◽

2020 ◽

Author(s):

Thomas Brendan Smith ◽

Alessandro Marco De Nunzio ◽

Kamlesh Patel ◽

Haydn Munford ◽

Tabeer Alam ◽

...

Keyword(s):

Shear Stress ◽

High Throughput ◽

Fluid Shear Stress ◽

Tracking System ◽

Frequency Measurement ◽

Camera Motion ◽

Fluid Shear ◽

Mean Frequency

Fluid shear stress is a key modulator of cellular physiology in vitro and in vivo, but its effects are under-investigated due to requirements for complicated induction methods. Herein we report the validation of ShearFAST; a smartphone application that measures the rocking profile on a standard laboratory cell rocker and calculates the resulting shear stress arising in tissue culture plates. The accuracy with which this novel approach measured rocking profiles was validated against a graphical analysis, and also against measures reported by an 8-camera motion tracking system. ShearFASTs angle assessments correlated well with both analyses (r ≥0.99, p ≤0.001) with no significant differences in pitch detected across the range of rocking angles tested. Rocking frequency assessment by ShearFAST also correlated well when compared to the two independent validatory techniques (r ≥0.99, p ≤0.0001), with excellent reproducibility between ShearFAST and video analysis (mean frequency measurement difference of 0.006 ± 0.005Hz) and motion capture analysis (mean frequency measurement difference of 0.008 ± 0.012Hz). These data make the ShearFAST assisted cell rocker model make it an attractive approach for economical, high throughput fluid shear stress experiments. Proof of concept data presented reveals a protective effect of low-level shear stress on renal proximal tubule cells submitted to simulations of pretransplant storage.

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Nanoparticle localization in blood vessels: dependence on fluid shear stress, flow disturbances, and flow-induced changes in endothelial physiology

Nanoscale ◽

10.1039/c8nr03440k ◽

2018 ◽

Vol 10 (32) ◽

pp. 15249-15261 ◽

Cited By ~ 21

Author(s):

M. Juliana Gomez-Garcia ◽

Amber L. Doiron ◽

Robyn R. M. Steele ◽

Hagar I. Labouta ◽

Bahareh Vafadar ◽

...

Keyword(s):

Shear Stress ◽

Fluid Shear Stress ◽

Fluid Shear ◽

Nanoparticle Distribution ◽

Flow Models ◽

Flow Disturbances ◽

Induced Changes ◽

Stress Flow

Hemodynamic factors drive nanoparticle distribution in vivo and in vitro in cell-based flow models.

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CD44 regulates blood-brain barrier integrity in response to fluid shear stress

10.1101/2020.01.28.924043 ◽

2020 ◽

Author(s):

Brandon J. DeOre ◽

Paul P. Partyka ◽

Fan Fan ◽

Peter A. Galie

Keyword(s):

Blood Flow ◽

Shear Stress ◽

Blood Brain Barrier ◽

Fluid Shear Stress ◽

Small Gtpase ◽

Brain Barrier ◽

Fluid Shear ◽

Blood Brain

AbstractFluid shear stress is an important mediator of vascular permeability, yet the molecular mechanisms underlying the response of the blood-brain barrier to shear have yet to be studied in cerebral vasculature despite its importance for brain homeostasis. The goal of this study is to probe components of shear mechanotransduction within the blood-brain barrier to gain a better understanding of pathologies associated with changes in cerebral blood flow including ischemic stroke. Interrogating the effects of shear stress in vivo is complicated by the complexity of factors in the brain parenchyma and the difficulty associated with modulating blood flow regimes. Recent advances in the ability to mimic the in vivo microenvironment using three-dimensional in vitro models provide a controlled setting to study the response of the blood-brain barrier to shear stress. The in vitro model used in this study is compatible with real-time measurement of barrier function using transendothelial electrical resistance as well as immunocytochemistry and dextran permeability assays. These experiments reveal that there is a threshold level of shear stress required for barrier formation and that the composition of the extracellular matrix, specifically the presence of hyaluronan, dictates the flow response. Gene editing to modulate the expression of CD44, a receptor for hyaluronan that previous studies have identified to be mechanosensitive, demonstrates that the receptor is required for the endothelial response to shear stress. Manipulation of small GTPase activity reveals CD44 activates Rac1 while inhibiting RhoA activation. Additionally, adducin-γ localizes to tight junctions in response to shear stress and RhoA inhibition and is required to maintain the barrier. This study identifies specific components of the mechanosensing complex associated with the blood-brain barrier response to fluid shear stress, and therefore illuminates potential targets for barrier manipulation in vivo.

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PGC1α Regulates the Endothelial Response to Fluid Shear Stress via Telomerase Reverse Transcriptase Control of Heme Oxygenase-1

10.1101/2021.05.26.445830 ◽

2021 ◽

Author(s):

Shashi Kant ◽

Khanh-Van Tran ◽

Miroslava Kvandova ◽

Amada D. Caliz ◽

Hyung-Jin Yoo ◽

...

Keyword(s):

Shear Stress ◽

Reverse Transcriptase ◽

Heme Oxygenase ◽

Fluid Shear Stress ◽

Heme Oxygenase 1 ◽

Telomerase Reverse Transcriptase ◽

Fluid Shear ◽

Flow Alignment

Fluid shear stress (FSS) is known to mediate multiple phenotypic changes in the endothelium. Laminar FSS (undisturbed flow) is known to promote endothelial alignment to flow that is key to stabilizing the endothelium and rendering it resistant to atherosclerosis and thrombosis. The molecular pathways responsible for endothelial responses to FSS are only partially understood. Here we have identified peroxisome proliferator gamma coactivator-1α (PGC-1α) as a flow-responsive gene required for endothelial flow alignment in vitro and in vivo. Compared to oscillatory FSS (disturbed flow) or static conditions, laminar FSS (undisturbed flow) increased PGC-1α expression and its transcriptional co-activation. PGC-1α was required for laminar FSS-induced expression of telomerase reverse transcriptase (TERT) in vitro and in vivo via its association with ERRα and KLF4 on the TERT promoter. We found that TERT inhibition attenuated endothelial flow alignment, elongation, and nuclear polarization in response to laminar FSS in vitro and in vivo. Among the flow-responsive genes sensitive to TERT status was heme oxygenase-1 (HMOX1), a gene required for endothelial alignment to laminar FSS. Thus, these data suggest an important role for a PGC-1α-TERT-HMOX1 axis in the endothelial stabilization response to laminar FSS.

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Exposure of proximal tubule cells to fluid shear stress alters transcription of metabolic pathway enzymes

The FASEB Journal ◽

10.1096/fasebj.2018.32.1_supplement.868.4 ◽

2018 ◽

Vol 32 (S1) ◽

Author(s):

Qidong Ren ◽

Megan L. Eshbach ◽

Natalie L. Rittenhouse ◽

Kimberly R. Long ◽

Youssef Rbaibi ◽

...

Keyword(s):

Shear Stress ◽

Proximal Tubule ◽

Metabolic Pathway ◽

Fluid Shear Stress ◽

Fluid Shear ◽

Proximal Tubule Cells ◽

Tubule Cells

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Faculty Opinions recommendation of Proximal tubule apical endocytosis is modulated by fluid shear stress via an mTOR-dependent pathway.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.727819314.793536661 ◽

2017 ◽

Author(s):

Heike Fölsch

Keyword(s):

Shear Stress ◽

Proximal Tubule ◽

Fluid Shear Stress ◽

Fluid Shear ◽

Dependent Pathway

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Differential Responses of Endothelial Cells to Positive and Negative Wall Shear Stress Gradients

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19535 ◽

2010 ◽

Author(s):

Jennifer Dolan ◽

Sukhjinder Singh ◽

Hui Meng ◽

John Kolega

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Vessel Wall ◽

Fluid Shear Stress ◽

Cerebral Aneurysms ◽

In Vivo Studies ◽

Outer Side ◽

Fluid Shear ◽

Wall Shear

Cerebral aneurysms tend to develop at bifurcation apices or the outer side of curved vessels where the blood vessel wall experiences complex hemodynamics. In vivo studies have recently revealed that the initiation of cerebral aneurysms is confined to a well-defined hemodynamic microenvironment. Specifically aneurysms form where the vessel wall experiences high fluid shear stress (wall shear stress, WSS) and flow is accelerating, so that the wall is exposed to a positive spatial gradient in the fluid shear stress (wall shear stress gradient, WSSG)[1,2]. Closer examination of such in vivo studies reveals that exposure of the vessel wall to equally high WSS in the presence of decelerating flow, that is, negative WSSG, does not result in aneurysm-like remodeling.

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