scholarly journals Hypoxia increases transepithelial electrical conductance and reduces occludin at the plasma membrane in alveolar epithelial cells via PKC-ζ and PP2A pathway

2011 ◽  
Vol 300 (4) ◽  
pp. L569-L578 ◽  
Author(s):  
Juan Carlos Caraballo ◽  
Cecilia Yshii ◽  
Maria L. Butti ◽  
Whitney Westphal ◽  
Jennifer A. Borcherding ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Electrical Conductance ◽  
Alveolar Epithelial Cells ◽  
Epithelial Barrier ◽  
Superoxide Dismutase 1 ◽  
Alveolar Epithelial ◽  
Hypoxic Environment ◽  
Phosphatase 2A ◽  
Pkc Ζ

During pulmonary edema, the alveolar space is exposed to a hypoxic environment. The integrity of the alveolar epithelial barrier is required for the reabsorption of alveolar fluid. Tight junctions (TJ) maintain the integrity of this barrier. We set out to determine whether hypoxia creates a dysfunctional alveolar epithelial barrier, evidenced by an increase in transepithelial electrical conductance (Gt), due to a decrease in the abundance of TJ proteins at the plasma membrane. Alveolar epithelial cells (AEC) exposed to mild hypoxia (Po2= 50 mmHg) for 30 and 60 min decreased occludin abundance at the plasma membrane and significantly increased Gt. Other cell adhesion molecules such as E-cadherin and claudins were not affected by hypoxia. AEC exposed to hypoxia increased superoxide, but not hydrogen peroxide (H2O2). Overexpression of superoxide dismutase 1 (SOD1) but not SOD2 prevented the hypoxia-induced Gtincrease and occludin reduction in AEC. Also, overexpression of catalase had a similar effect as SOD1, despite not detecting any increase in H2O2during hypoxia. Blocking PKC-ζ and protein phosphatase 2A (PP2A) prevented the hypoxia-induced occludin reduction at the plasma membrane and increase in Gt. In summary, we show that superoxide, PKC-ζ, and PP2A are involved in the hypoxia-induced increase in Gtand occludin reduction at the plasma membrane in AEC.

scholarly journals Differential effects of claudin-3 and claudin-4 on alveolar epithelial barrier function

2011 ◽  
Vol 301 (1) ◽  
pp. L40-L49 ◽  
Author(s):  
Leslie A. Mitchell ◽  
Christian E. Overgaard ◽  
Christina Ward ◽  
Susan S. Margulies ◽  
Michael Koval
Keyword(s):  
Epithelial Cells ◽  
Tight Junction ◽  
Barrier Function ◽  
Alveolar Epithelium ◽  
Alveolar Epithelial Cells ◽  
Epithelial Barrier ◽  
Tight Junction Proteins ◽  
Epithelial Barrier Function ◽  
Alveolar Epithelial ◽  
Junction Proteins

Alveolar barrier function depends critically on the claudin family tight junction proteins. Of the major claudins expressed by alveolar epithelial cells, claudin (Cldn)-3 and Cldn-4 are the most closely related by amino acid homology, yet they differ dramatically in the pattern of expression. Previously published reports have shown that Cldn-3 is predominantly expressed by type II alveolar epithelial cells; Cldn-4 is expressed throughout the alveolar epithelium and is specifically upregulated in response to acute lung injury. Using primary rat alveolar epithelial cells transduced with yellow fluorescent protein-tagged claudin constructs, we have identified roles for Cldn-3 and Cldn-4 in alveolar epithelial barrier function. Surprisingly, increasing expression of Cldn-3 decreased alveolar epithelial barrier function, as assessed by transepithelial resistance and dye flux measurements. Conversely, increasing Cldn-4 expression improved alveolar epithelial transepithelial resistance compared with control cells. Other alveolar epithelial tight junction proteins were largely unaffected by increased expression of Cldn-3 and Cldn-4. Taken together, these results demonstrate that, in the context of the alveolar epithelium, Cldn-3 and Cldn-4 have different effects on paracellular permeability, despite significant homology in their extracellular loop domains.

Deformation-induced lipid trafficking in alveolar epithelial cells

2001 ◽  
Vol 280 (5) ◽  
pp. L938-L946 ◽  
Author(s):  
Nicholas E. Vlahakis ◽  
Mark A. Schroeder ◽  
Richard E. Pagano ◽  
Rolf D. Hubmayr
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Membrane Trafficking ◽  
Wound Repair ◽  
Alveolar Epithelial Cells ◽  
Fluorescent Properties ◽  
Lipid Trafficking ◽  
Alveolar Epithelial ◽  
Injury And Repair

Mechanical ventilation with a high tidal volume results in lung injury that is characterized by blebbing and breaks both between and through alveolar epithelial cells. We developed an in vitro model to simulate ventilator-induced deformation of the alveolar basement membrane and to investigate, in a direct manner, epithelial cell responses to deforming forces. Taking advantage of the novel fluorescent properties of BODIPY lipids and the fluorescent dye FM1-43, we have shown that mechanical deformation of alveolar epithelial cells results in lipid transport to the plasma membrane. Deformation-induced lipid trafficking (DILT) was a vesicular process, rapid in onset, and was associated with a large increase in cell surface area. DILT could be demonstrated in all cells; however, only a small percentage of cells developed plasma membrane breaks that were reversible and nonlethal. Therefore, DILT was not only involved in site-directed wound repair but might also have served as a cytoprotective mechanism against plasma membrane stress failure. This study suggests that DILT is a regulatory mechanism for membrane trafficking in alveolar epithelia and provides a novel biological framework within which to consider alveolar deformation injury and repair.

Developmental regulation of claudin localization by fetal alveolar epithelial cells

2004 ◽  
Vol 287 (6) ◽  
pp. L1266-L1273 ◽  
Author(s):  
Brandy L. Daugherty ◽  
Madalina Mateescu ◽  
Anand S. Patel ◽  
Kelly Wade ◽  
Shioko Kimura ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Tight Junction ◽  
Barrier Function ◽  
Alveolar Epithelial Cells ◽  
Cell Phenotype ◽  
Tight Junction Proteins ◽  
Alveolar Epithelial ◽  
Cells Cultured ◽  
Junction Proteins

Tight junction proteins in the claudin family regulate epithelial barrier function. We examined claudin expression by human fetal lung (HFL) alveolar epithelial cells cultured in medium containing dexamethasone, 8-bromo-cAMP, and isobutylmethylxanthanine (DCI), which promotes alveolar epithelial cell differentiation to a type II phenotype. At the protein level, HFL cells expressed claudin-1, claudin-3, claudin-4, claudin-5, claudin-7, and claudin-18, where levels of expression varied with culture conditions. DCI-treated differentiated HFL cells cultured on permeable supports formed tight transepithelial barriers, with transepithelial resistance (TER) >1,700 ohm/cm2. In contrast, HFL cells cultured in control medium without DCI did not form tight barriers (TER <250 ohm/cm2). Consistent with this difference in barrier function, claudins expressed by HFL cells cultured in DCI medium were tightly localized to the plasma membrane; however, claudins expressed by HFL cells cultured in control medium accumulated in an intracellular compartment and showed discontinuities in claudin plasma membrane localization. In contrast to claudins, localization of other tight junction proteins, zonula occludens (ZO)-1, ZO-2, and occludin, was not sensitive to HFL cell phenotype. Intracellular claudins expressed by undifferentiated HFL cells were localized to a compartment containing early endosome antigen-1, and treatment of HFL cells with the endocytosis inhibitor monodansylcadaverine increased barrier function. This suggests that during differentiation to a type II cell phenotype, fetal alveolar epithelial cells use differential claudin expression and localization to the plasma membrane to help regulate tight junction permeability.

scholarly journals Shear Stress Induced Reorganization of the Keratin Intermediate Filament Network Requires Phosphorylation by Protein Kinase C ζ

2009 ◽  
Vol 20 (11) ◽  
pp. 2755-2765 ◽  
Author(s):  
Sivaraj Sivaramakrishnan ◽  
Jaime L. Schneider ◽  
Albert Sitikov ◽  
Robert D. Goldman ◽  
Karen M. Ridge
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Epithelial Cells ◽  
Polymer Network ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Dependent Manner ◽  
Structural Remodeling ◽  
Alveolar Epithelial ◽  
Pkc Ζ

Keratin intermediate filaments (KIFs) form a fibrous polymer network that helps epithelial cells withstand external mechanical forces. Recently, we established a correlation between the structure of the KIF network and its local mechanical properties in alveolar epithelial cells. Shear stress applied across the cell surface resulted in the structural remodeling of KIF and a substantial increase in the elastic modulus of the network. This study examines the mechanosignaling that regulates the structural remodeling of the KIF network. We report that the shear stress–mediated remodeling of the KIF network is facilitated by a twofold increase in the dynamic exchange rate of KIF subunits, which is regulated in a PKC ζ and 14-3-3–dependent manner. PKC ζ phosphorylates K18pSer33, and this is required for the structural reorganization because the KIF network in A549 cells transfected with a dominant negative PKC ζ, or expressing the K18Ser33Ala mutation, is unchanged. Blocking the shear stress–mediated reorganization results in reduced cellular viability and increased apoptotic levels. These data suggest that shear stress mediates the phosphorylation of K18pSer33, which is required for the reorganization of the KIF network, resulting in changes in mechanical properties of the cell that help maintain the integrity of alveolar epithelial cells.

Modeling the effect of stretch and plasma membrane tension on Na+-K+-ATPase activity in alveolar epithelial cells

2007 ◽  
Vol 292 (1) ◽  
pp. L40-L53 ◽  
Author(s):  
Jacob L. Fisher ◽  
Susan S. Margulies
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Atpase Activity ◽  
Alveolar Epithelial Cells ◽  
Cyclic Stretch ◽  
Model Parameters ◽  
Membrane Tension ◽  
Membrane Area ◽  
Whole Cell ◽  
Alveolar Epithelial

While a number of whole cell mechanical models have been proposed, few, if any, have focused on the relationship among plasma membrane tension, plasma membrane unfolding, and plasma membrane expansion and relaxation via lipid insertion. The goal of this communication is to develop such a model to better understand how plasma membrane tension, which we propose stimulates Na+-K+-ATPase activity but possibly also causes cell injury, may be generated in alveolar epithelial cells during mechanical ventilation. Assuming basic relationships between plasma membrane unfolding and tension and lipid insertion as the result of tension, we have captured plasma membrane mechanical responses observed in alveolar epithelial cells: fast deformation during fast cyclic stretch, slower, time-dependent deformation via lipid insertion during tonic stretch, and cell recovery after release from stretch. The model estimates plasma membrane tension and predicts Na+-K+-ATPase activation for a specified cell deformation time course. Model parameters were fit to plasma membrane tension, whole cell capacitance, and plasma membrane area data collected from the literature for osmotically swollen and shrunken cells. Predictions of membrane tension and stretch-stimulated Na+-K+-ATPase activity were validated with measurements from previous studies. As a proof of concept, we demonstrate experimentally that tonic stretch and consequent plasma membrane recruitment can be exploited to condition cells against subsequent cyclic stretch and hence mitigate stretch-induced responses, including stretch-induced cell death and stretch-induced modulation of Na+-K+-ATPase activity. Finally, the model was exercised to evaluate plasma membrane tension and potential Na+-K+-ATPase stimulation for an assortment of traditional and novel ventilation techniques.

scholarly journals TRIM72 modulates caveolar endocytosis in repair of lung cells

2016 ◽  
Vol 310 (5) ◽  
pp. L452-L464 ◽  
Author(s):  
Nagaraja Nagre ◽  
Shaohua Wang ◽  
Thomas Kellett ◽  
Ragu Kanagasabai ◽  
Jing Deng ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Cell Injury ◽  
Alveolar Epithelial Cells ◽  
Lung Epithelial Cells ◽  
Functional Domain ◽  
Physical Interaction ◽  
Type I ◽  
Alveolar Epithelial ◽  
Lung Epithelial

Alveolar epithelial and endothelial cell injury is a major feature of the acute respiratory distress syndrome, in particular when in conjunction with ventilation therapies. Previously we showed [Kim SC, Kellett T, Wang S, Nishi M, Nagre N, Zhou B, Flodby P, Shilo K, Ghadiali SN, Takeshima H, Hubmayr RD, Zhao X. Am J Physiol Lung Cell Mol Physiol 307: L449–L459, 2014.] that tripartite motif protein 72 (TRIM72) is essential for amending alveolar epithelial cell injury. Here, we posit that TRIM72 improves cellular integrity through its interaction with caveolin 1 (Cav1). Our data show that, in primary type I alveolar epithelial cells, lack of TRIM72 led to significant reduction of Cav1 at the plasma membrane, accompanied by marked attenuation of caveolar endocytosis. Meanwhile, lentivirus-mediated overexpression of TRIM72 selectively increases caveolar endocytosis in rat lung epithelial cells, suggesting a functional association between these two. Further coimmunoprecipitation assays show that deletion of either functional domain of TRIM72, i.e., RING, B-box, coiled-coil, or PRY-SPRY, abolishes the physical interaction between TRIM72 and Cav1, suggesting that all theoretical domains of TRIM72 are required to forge a strong interaction between these two molecules. Moreover, in vivo studies showed that injurious ventilation-induced lung cell death was significantly increased in knockout (KO) TRIM72KO and Cav1KO lungs compared with wild-type controls and was particularly pronounced in double KO mutants. Apoptosis was accompanied by accentuation of gross lung injury manifestations in the TRIM72KO and Cav1KO mice. Our data show that TRIM72 directly and indirectly modulates caveolar endocytosis, an essential process involved in repair of lung epithelial cells through removal of plasma membrane wounds. Given TRIM72's role in endomembrane trafficking and cell repair, we consider this molecule an attractive therapeutic target for patients with injured lungs.

scholarly journals Determinants of plasma membrane wounding by deforming stress

2010 ◽  
Vol 299 (6) ◽  
pp. L826-L833 ◽  
Author(s):  
Richard A. Oeckler ◽  
Won-Yeon Lee ◽  
Mun-Gi Park ◽  
Othmar Kofler ◽  
Deborah L. Rasmussen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Optical Tweezers ◽  
Cellular Response ◽  
Ex Vivo ◽  
Experimental Models ◽  
Alveolar Epithelial Cells ◽  
Interfacial Stress ◽  
Alveolar Epithelial ◽  
Adhesive Interactions

Once excess liquid gains access to air spaces of an injured lung, the act of breathing creates and destroys foam and thereby contributes to the wounding of epithelial cells by interfacial stress. Since cells are not elastic continua, but rather complex network structures composed of solid as well as liquid elements, we hypothesize that plasma membrane (PM) wounding is preceded by a phase separation, which results in blebbing. We postulate that interventions such as a hypertonic treatment increase adhesive PM-cytoskeletal (CSK) interactions, thereby preventing blebbing as well as PM wounds. We formed PM tethers in alveolar epithelial cells and fibroblasts and measured their retractive force as readout of PM-CSK adhesive interactions using optical tweezers. A 50-mOsm increase in media osmolarity consistently increased the tether retractive force in epithelial cells but lowered it in fibroblasts. The osmo-response was abolished by pretreatment with latrunculin, cytochalasin D, and calcium chelation. Epithelial cells and fibroblasts were exposed to interfacial stress in a microchannel, and the fraction of wounded cells were measured. Interventions that increased PM-CSK adhesive interactions prevented blebbing and were cytoprotective regardless of cell type. Finally, we exposed ex vivo perfused rat lungs to injurious mechanical ventilation and showed that hypertonic conditioning reduced the number of wounded subpleural alveolus resident cells to baseline levels. Our observations support the hypothesis that PM-CSK adhesive interactions are important determinants of the cellular response to deforming stress and pave the way for preclinical efficacy trials of hypertonic treatment in experimental models of acute lung injury.

Sign in / Sign up

Export Citation Format

Share Document