Changes In Cellular Permeability Research Articles

Altered Moesin and Actin Cytoskeleton Protein Rearrangements Affect Transendothelial Permeability in Human Endothelial Cells upon Dengue Virus Infection and TNF-α Treatment.

It has been hypothesized that the host, viral factors, and secreted cytokines (especially TNF-α) play roles in the pathogenesis of secondary dengue infections. Mass spectrometry-based proteomic screening of cytoskeleton fractions isolated from human endothelial (EA.hy926) cells upon dengue virus (DENV) infection and TNF-α treatment identified 450 differentially altered proteins. Among them, decreased levels of moesin, actin stress fiber rearrangements, and dot-like formations of vinculin were observed with western blot analyses and/or immunofluorescence staining (IFA). In vitro vascular permeability assays using EA.hy926 cells, seeded on collagen-coated transwell inserts, showed low levels of transendothelial electrical resistance in treated cells. The synergistic effects of DENV infection and TNF-α treatment caused cellular permeability changes in EA.hy926 cells, which coincided with decreasing moesin levels and the production of abnormal organizations of actin stress fibers and vinculin. Functional studies demonstrated moesin overexpression restored transendothelial permeability in DENV/TNF-α-treated EA.hy926 cells. The present study improves the understanding of the disruption mechanisms of cytoskeleton proteins in enhancing vascular permeability during DENV infection and TNF-α treatment. The study also suggests that these disruption mechanisms are major factors contributing to vascular leakage in severe dengue patients.

Heparan sulfate is an important mediator of Ebola virus infection in polarized epithelial cells

BackgroundCurrently, no FDA-approved vaccines or treatments are available for Ebola virus disease (EVD), and therapy remains largely supportive. Ebola virus (EBOV) has broad tissue tropism and can infect a variety of cells including epithelial cells. Epithelial cells differ from most other cell types by their polarized phenotype and barrier function. In polarized cells, the apical and basolateral membrane domains are demarcated by tight junctions, and specialized sorting machinery, which results in a difference in composition between the two membrane domains. These specialized sorting functions can have important consequences for viral infections. Differential localization of a viral receptor can restrict virus entry to a particular membrane while polarized sorting can lead to a vectorial virus release. The present study investigated the impact of cell polarity on EBOV infection.MethodsCharacteristics of EBOV infection in polarized cells were evaluated in the polarized Caco-2 model grown on semipermeable transwells. Transepithelial resistance (TEER), which is a function of tight junctions, was used to assess epithelial cell polarization. EBOV infection was assessed with immunofluorescence microscopy and qPCR. Statistical significance was calculated using one-way ANOVA and significance was set at p < 0.05.ResultsOur data indicate that EBOV preferentially infects cells from the basolateral route, and this preference may be influenced by the resistance across the Caco-2 monolayer. Infection occurs without changes in cellular permeability. Further, our data show that basolateral infection bias may be dependent on polarized distribution of heparan sulfate, a known viral attachment factor. Treatment with iota-carrageenan, or heparin lyase, which interrupts viral interaction with cellular heparan sulfate, significantly reduced cell susceptibility to basolateral infection, likely by inhibiting virus attachment.ConclusionsOur results show cell polarity has an impact on EBOV infection. EBOV preferentially infects polarized cells through the basolateral route. Access to heparan sulfate is an important factor during basolateral infection and blocking interaction of cellular heparan sulfate with virus leads to significant inhibition of basolateral infection in the polarized Caco-2 cell model.

Essentiality of mmpL3 and impact of its silencing on Mycobacterium tuberculosis gene expression

MmpL3 is an inner membrane transporter of Mycobacterium tuberculosis responsible for the export of trehalose momomycolate, a precursor of the mycobacterial outer membrane component trehalose dimycolate (TDM), as well as mycolic acids bound to arabinogalactan. MmpL3 represents an emerging target for tuberculosis therapy. In this paper, we describe the construction and characterization of an mmpL3 knockdown strain of M. tuberculosis. Downregulation of mmpL3 led to a stop in bacterial division and rapid cell death, preceded by the accumulation of TDM precursors. MmpL3 was also shown to be essential for growth in monocyte-derived human macrophages. Using RNA-seq we also found that MmpL3 depletion caused up-regulation of 47 genes and down-regulation of 23 genes (at least 3-fold change and false discovery rate ≤1%). Several genes related to osmoprotection and metal homeostasis were induced, while several genes related to energy production and mycolic acids biosynthesis were repressed suggesting that inability to synthesize a correct outer membrane leads to changes in cellular permeability and a metabolic downshift.

Extracellular Calcium Reduction Strongly Increases the Lytic Capacity of Pneumolysin From Streptococcus Pneumoniae in Brain Tissue

Background. Streptococcus pneumoniae causes serious diseases such as pneumonia and meningitis. Its major pathogenic factor is the cholesterol-dependent cytolysin pneumolysin, which produces lytic pores at high concentrations. At low concentrations, it has other effects, including induction of apoptosis. Many cellular effects of pneumolysin appear to be calcium dependent.Methods. Live imaging of primary mouse astroglia exposed to sublytic amounts of pneumolysin at various concentrations of extracellular calcium was used to measure changes in cellular permeability (as judged by lactate dehydrogenase release and propidium iodide chromatin staining). Individual pore properties were analyzed by conductance across artificial lipid bilayer. Tissue toxicity was studied in continuously oxygenated acute brain slices.Results. The reduction of extracellular calcium increased the lytic capacity of the toxin due to increased membrane binding. Reduction of calcium did not influence the conductance properties of individual toxin pores. In acute cortical brain slices, the reduction of extracellular calcium from 2 to 1 mM conferred lytic activity to pathophysiologically relevant nonlytic concentrations of pneumolysin.Conclusions. Reduction of extracellular calcium strongly enhanced the lytic capacity of pneumolysin due to increased membrane binding. Thus, extracellular calcium concentration should be considered as a factor of primary importance for the course of pneumococcal meningitis.

Original article. The role of p38MAPK in asymmetric dimethylarginineinduced cytoskeleton and cellular permeability changes in cultured endothelial cells

Abstract Background: Asymmetric dimethylarginine (ADMA) induces endothelial cell barrier dysfunction via cytoskeleton activation and contraction. It is supposed that activated p38 mitogen-activated protein kinase (MAPK) would trigger the formation of stress fibers and increase cellular permeability. Objective: Explore p38 MAPK as a potentially important enzyme in ADMA-mediated endothelial cell contractile response and permeability change. Methods: Human umbilical endothelial cells (HUVECs) were cultured, where ADMA and/or SB203580 (the specific inhibitor of p38MAPK) were used to stimulate HUVECs. Immunofluorescent staining was carried out to examine the expression and distribution of F-actin, flow cytometry was used to quantify F-actin, and Transwell was applied to test cellular permeability with FITC-labelled human serum albumin (HSA). Scanning electronic microscopy (SEM) was utilized to observe the changes of intercellar contact. Results: ADMA induced significant p38MAPK activation in a dose-dependent manner, which correlated with increased stress fibers. SB-203580 attenuated the formation of actin stress fiber and the increase of cellular permeability induced ADMA in the HUVECs (p&lt;0.01, LSCM; p&lt;0.01, cytometry; p&lt;0.05, Transwell). Widened intercellular space induced by ADMA was detected and could be inhibited by SB-203580 (SEM). SB-203580 alone had no effect on cytoskeleton and cellular permeability. Conclusion: p38MAPK activation participated in cytoskeleton and cellular permeability changes induced by ADMA in HUVECs.

Modified Annexin V/Propidium Iodide Apoptosis Assay For Accurate Assessment of Cell Death

Studies of cellular apoptosis have been significantly impacted since the introduction of flow cytometry-based methods. Propidium iodide (PI) is widely used in conjunction with Annexin V to determine if cells are viable, apoptotic, or necrotic through differences in plasma membrane integrity and permeability1,2. The Annexin V/ PI protocol is a commonly used approach for studying apoptotic cells3. PI is used more often than other nuclear stains because it is economical, stable and a good indicator of cell viability, based on its capacity to exclude dye in living cells 4,5. The ability of PI to enter a cell is dependent upon the permeability of the membrane; PI does not stain live or early apoptotic cells due to the presence of an intact plasma membrane 1,2,6. In late apoptotic and necrotic cells, the integrity of the plasma and nuclear membranes decreases7,8, allowing PI to pass through the membranes, intercalate into nucleic acids, and display red fluorescence 1,2,9. Unfortunately, we find that conventional Annexin V/ PI protocols lead to a significant number of false positive events (up to 40%), which are associated with PI staining of RNA within the cytoplasmic compartment10. Primary cells and cell lines in a broad range of animal models are affected, with large cells (nuclear: cytoplasmic ratios <0.5) showing the highest occurrence10. Herein, we demonstrate a modified Annexin V/ PI method that provides a significant improvement for assessment of cell death compared to conventional methods. This protocol takes advantage of changes in cellular permeability during cell fixing to promote entry of RNase A into cells following staining. Both the timing and concentration of RNase A have been optimized for removal of cytoplasmic RNA. The result is a significant improvement over conventional Annexin V/ PI protocols (< 5% events with cytoplasmic PI staining).

Inhibition of vascular endothelial growth factor (VEGF) is sufficient to completely restore barrier malfunction induced by growth factors in microvascular retinal endothelial cells

BackgroundDeregulated expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) or insulin-like growth factor-1 (IGF-1) is associated with the pathogenesis of diabetic retinopathy. The VEGF165-induced increase in...

Effects of high frequency electromagnetic fields on sperm membrane permeability

OBJECTIVE: Previous research from this laboratory has suggested that electromagnetic fields (EMF) interfere with normal sperm function over time. While the effect appears to be field strength dependent, extremely high levels of EMF (> 200uG) where shown to cause decreased semen parameters as early as 2-3 hours. As changes in cell function would be preceded by changes in cell chemistry, the objective of the current study was to determine how early damage could be detected using changes in cellular permeability.

Species and response dependent differences in the effects of MAPK inhibitors on P2X7 receptor function

Recent studies have implicated the mitogen activated protein kinase (MAPK) in cellular permeability changes following P2X(7) receptor activation in native tissues. In this study we have further studied the effect of MAPK inhibitors on recombinant and native P2X(7) receptors. The MAPK inhibitors SB-203580, SB-202190 and SB-242235 were examined in HEK293 cells expressing recombinant P2X(7) receptors and in THP-1 cells expressing native human P2X(7) receptors using a range of experimental approaches. At human recombinant P2X(7) receptors, SB-203580 and SB-202190 were weak, non-competitive inhibitors (pIC(50)= 4.8 - 6.4) of ethidium accumulation stimulated by 2'- & 3'-O-(4benzoylbenzoyl)-ATP (BzATP) but SB-242235 (0.1-10 microM) had no effect. SB-203580 and SB-202190 had no effect on rat or mouse recombinant P2X(7) receptors and studies with chimeric P2X(7) receptors suggested that SB-203580 was only effective in chimeras containing the N-terminal 255aa of the human P2X(7) receptor. SB-203580 did not consistently affect BzATP-mediated increases in cell calcium levels and, in electrophysiological studies, it slightly decreased responses to 30 microM BzATP but potentiated responses to 100 microM BzATP. In THP1 cells, SB-203580 modestly inhibited BzATP-stimulated ethidium accumulation (pIC(50) 5.7 - < 5) but SB-202190 had no effect. Finally, SB-203580 did not block BzATP-stimulated interleukin-1beta release in THP-1 cells. This study confirms that high concentrations of SB-203580 and SB-202190 can block human P2X(7) receptor-mediated increases in cellular ethidium accumulation but suggest this is not related to MAPK inhibition. Overall, the data cast doubt on a general role of MAPK in mediating P2X(7) receptor mediated changes in cellular permeability.

Effects of Shock Waves on Microcirculation, Perfusion, and Pain Management in Critical Limb Ischemia

Shock waves (SW) are used to control pain in different clinical conditions (eg, painful knee, elbow, and shoulder, etc). The effects of SWs may be due to cellular ;;stunning'' (particularly nervous components). It may also be the consequence of unknown metabolic actions on tissues, which may include changes in cellular permeability, the liberation of proteins and mediators locally acting on pain and nerve endings. The aim of this study was to evaluate the reduction in pain and the improvement in microcirculation induced by SW treatment in a 2-week study in patients with chronic limb ischemia (CLI). Of the 32 patients with CLI, 30 (20 with rest pain only, 10 with necrosis) completed the study. The treatment was well tolerated. Foot radiographs performed before and after treatment indicate no bone damage after treatment. Foot (tibial arteries) blood pressure was unchanged after 2 weeks. The increase in laser Doppler flux was significant (p <0.05) after treatment. The ORACLE score at 2 weeks was decreased (p <0.05). The same trend was observed with the analogue scale line for pain (p <0.05). Partial pressure of oxygen (PO2) increased (p <0.05) and partial pressure of carbon dioxide (PCO2) decreased (p <0.05). In all patients an increase in pain-free walking distance was observed (the distance increased on average 2.4 times). Flux improvement was still present after 1 month. The outcome at 3 months in these patients indicates that the improvement (concerning the survival of the limbs) was persistent. In conclusion SWs treatment in CLI produced changes both on the microcirculation and pain. These results are very interesting, confirming previous observations, and opening new treatment options in CLI. The skin flow improvement did not relate to an increase in pressure.

Increase of activity of tioconazole against resistant microorganisms by the addition of butylated hydroxyanisole

Tioconazole (TCZ) killed resistant Candida albicans in less than 3 min, after the addition of butylated hydroxyanisole (BHA), a phenolic antioxidant, at subinhibitory concentrations. The bactericidal activity was also rapid against resistant Escherichia coli. BHA increased the TCZ activity in RPMI 1640 medium 18 times against ten strains of resistant C. albicans as judged by MIC and increased the activity 43 times against ten resistant E. coli strains. BHA at subinhibitory concentrations promoted the reduction of C. albicans virulence by reducing 180 times the hyphal cells of TCZ and decreasing hydrophobicity. The synergy could be due to changes in cellular permeability because of increased leakage of cellular enzymes.

Possible implications of biocide accumulation in the environment on the prevalence of bacterial antibiotic resistance.

The lethality of biocides depends upon their interaction with a number of distinct biochemical targets. This often reflects reactive chemistry for any given agent, such as thiol oxidation. Susceptibility may vary markedly between different target organisms, and changes within the more sensitive targets can alter the inhibitory effect. The multiplicity of potential targets, however, usually dictates against the development of overt resistance to concentrations used for hygienic applications. Similarly, although changes in cellular permeability toward such agents, mediated either by envelope modification or the induction of efflux-pumps may reduce susceptibility, they rarely influence the outcome of treatments at use-concentration. It has recently been proposed that chronic exposure of the environment to biocides used in a variety of commercial products might expose some microbial communities to subeffective concentrations causing emergence of resistant clones. Such resistance might relate to mutational changes in the most susceptible target or to regulatory mutants that cause the constitutive expression of certain efflux pumps. Although selection of organisms with such modifications is unlikely to influence the effectiveness of the biocides, changes in their susceptibility to third-party antibiotics can be postulated. This is particularly the case where a cellular target is shared between a biocide and an antibiotic, or where induction of efflux is sufficient to confer antibiotic resistance in the clinic. Although such linkage has been demonstrated in the laboratory in pure culture, it has not been documented in environments commonly exposed to biocides. In nature, the effects of chronic stressing with biocides are complicated by competition between microbial community members that may result in clonal expansion of naturally insusceptible clones.

Possible implications of biocide accumulation in the environment on the prevalence of bacterial antibiotic resistance

The lethality of biocides depends upon their interaction with a number of distinct biochemical targets. This often reflects reactive chemistry for any given agent, such as thiol oxidation. Susceptibility may vary markedly between different target organisms, and changes within the more sensitive targets can alter the inhibitory effect. The multiplicity of potential targets, however, usually dictates against the development of overt resistance to concentrations used for hygienic applications. Similarly, although changes in cellular permeability toward such agents, mediated either by envelope modification or the induction of efflux-pumps may reduce susceptibility, they rarely influence the outcome of treatments at use-concentration. It has recently been proposed that chronic exposure of the environment to biocides used in a variety of commercial products might expose some microbial communities to subeffective concentrations causing emergence of resistant clones. Such resistance might relate to mutational changes in the most susceptible target or to regulatory mutants that cause the constitutive expression of certain efflux pumps. Although selection of organisms with such modifications is unlikely to influence the effectiveness of the biocides, changes in their susceptibility to third-party antibiotics can be postulated. This is particularly the case where a cellular target is shared between a biocide and an antibiotic, or where induction of efflux is sufficient to confer antibiotic resistance in the clinic. Although such linkage has been demonstrated in the laboratory in pure culture, it has not been documented in environments commonly exposed to biocides. In nature, the effects of chronic stressing with biocides are complicated by competition between microbial community members that may result in clonal expansion of naturally insusceptible clones.

Change in colony morphology influences the virulence as well as the biochemical properties of theMycobacterium aviumcomplex

Factors that influence colony morphology are of crucial importance for drug development as well as for understanding the virulence ofMycobacterium aviumcomplex (MAC) strains. The MAC 101 strain used in the present study grows as smooth transparent (SmT) colonies that tend to become opaque and pigmented when incubated for long periods of time. However, when MAC was passaged in animals, two types of colonies were recovered. The new rough transparent (RgT) colony morphology appeared more flat and transparent, having a central spot, irregular edges at times, and a dry, granular appearance like that of the rough mutants. In animal studies, the RgT bacilli multiplied at a much faster rate than that of the SmT bacilli, causing 60–80% mortality compared with the 10% mortality observed in mice infected with SmT.In vitrostudies indicated that the SmT MAC did not grow and multiply as well in resident peritoneal macrophages as the RgT MAC did. The two morphotypes did not differ in their growth ratesin vitrobut the RgT MAC failed to reduce dimethylthiazol-diphenyltetrazolium bromide (MTT), alamar blue and neutral red, suggesting that there might be significant changes in the cell wall or elsewhere causing changes in cellular permeability. These two morphotypes could serve as models for studying the biochemical markers or the identification of factors responsible for the virulence of the MAC.

Effects of excitotoxins on free radical indices in mouse brain

Excitotoxins and free radicals individually have been implicated in several neurological disorders including those associated with aging. We observed that systemically administered domoic acid enhanced mouse brain Superoxide dismutase activity with either an associated decrease or no change in mouse brain lipid peroxidation. These findings reflect a state of adequately compensated oxidative stress induced by excitotoxins. In homogenates containing disrupted cells from various regions of mouse brain, however, kainic acid produced a 2 to 5-fold increase in lipid peroxidation. This suggests that excitotoxins cause lipid peroxidation possibly by acting at intracellular loci which become more accessible following disruption of cells in vitro and by extrapolation, possibly in vivo due to cellular permeability changes during the edematous stage of ischemic and other related neuropathological conditions.

Inhibition of sodium-dependent taurine transport in red blood cells from the marine polychaete, Glycera dibranchiata, after exposure to mercury.

An earlier study (Chen and Preston, 1987) demonstrated that HgCI 2 at low concentrations (20 ~M) inhibited the transport of the amino acid, taurine, by the hemoglobin containing coelomocytes (red blood cells, RBCs) of the marine polychaete, Glycera dibranchiata. These red cells maintain an internal concentration of 190 mM taurine compared with an external concentration in the coelomic fluid of approximately 0.2 mM. This high gradient appears to be generated via a Na and CI dependent active transport system which is specific for taurine and closely related analogues (Preston and Chen, 1986; Chen and Preston, 1986). This taurine transport system resembles other taurine transport systems observed in heart and kidney tissue (Awapara and Berg, 1985; Wolff et al, 1985). It appears that Glycera RBCs provide an excellent model system to study the mechanism of heavy metal inhibition of transport function. We proposed that one possible mechanism for the action of HgCI 2 is that this molecule binds to sulfhydryl groups in the Na binding site of the transport protein. In order to test this hypothesis we conducted a series of kinetic studies to analyze in more detail the interaction oi Na and Hg with the transport system. In addition, we conducted experiments to determine whether the effects of HgCI 2 treatment could also be due to generalized changes in cellular permeability.

Amino acid and protein metabolism in dorsal root ganglia of rabbits with experimental allergic neuritis.

Amino acid and protein metabolism has been studied in the dorsal root ganglia of rabbits with experimental allergic neuritis (EAN). The concentrations of a number of nonessential amino acids (glutamine, serine, aspartate, and glutamate) were reduced in the spinal ganglia of EAN animals without any comparable change in the blood plasma. The short-term influx of glycine and GABA was decreased in EAN animals, whereas that of histidine and valine was not altered. The prolonged accumulation of all the four amino acids was unchanged. These results suggest alterations in the cell metabolism of the dorsal root ganglia, rather than unspecific changes in cellular permeability. Furthermore, incorporation of tritiated valine, histidine, and glycine into proteins of EAN-ganglia in vitro was significantly increased. Autoradiography of the protein-bound [3H]-valine indicated alterations in the protein synthesis of the ganglion neurons: A decreased grain density was found in ganglion neurons of EAN animals. The increased grain densities in the affected ganglia were observed in macrophages, and possible in activated Schwann cells, over the demyelinated spots. The results suggest intraneuronal changes in the dorsal root ganglia of amino acid and protein metabolism, possibly in response to peripheral axonal injury and/or to nonspecific cytotoxic effect of active lymphocytes and macrophages.

Reversible inhibition of protein synthesis in lung by halothane.

Alterations in the synthesis and degradation of proteins were investigated in intact lungs exposed to the volatile anaesthetic halothane. In rat lungs perfused in situ with Krebs-Henseleit bicarbonate buffer containing 4.5% (w/v) bovine serum albumin, 5.6 mM-glucose, plasma concentrations of 19 amino acids and 690 microM-[U-14C]-phenylalanine and equilibrated with O2/N2/CO2 (4:15:1), protein synthesis, calculated based on the specific radioactivity of aminoacyl-tRNA, was inhibited by halothane. The anaesthetic did not affect degradation of lung proteins. The inhibition of protein synthesis was rapid in onset, dose-dependent, and quickly reversible. It did not appear to be associated with overall energy depletion, with non-specific changes in cellular permeability, or with decreased availability of amino acids as substrates for protein synthesis.

The effect of ionophore A23187 and 2,4-dinitrophenol on the structure and function of cultured liver cells

Adult rat hepatocytes maintained in primary culture have been used as a model system to study cellular injury dependent upon extracellular calcium. Incubation of hepatocytes with ionophore A23187 (1 to 5 μ m) resulted in leakage of cytoplasmic enzymes, an increase in the number of cells stained with trypan blue, blebing of the plasma membrane, and changes in mitochondrial structure characterized by mitochondrial swelling. Moreover, a 60% decrease in cellular ATP was observed to precede changes in cellular permeability. These cytotoxic alterations induced by ionophore were dependent upon the presence of extracellular calcium. In contrast, 2,4-dinitrophenol depleted ATP much more extensively and induced extensive swelling of mitochondria at concentrations which failed to induce significant leakage of cytoplasmic enzymes. Cytotoxic changes induced by ionophore were potentiated by 2,4-dinitrophenol but not ethionine which has been shown to cause a reduction in cellular ATP levels. However, ethionine potentiated the cytotoxicity induced by 2,4-dinitrophenol.

Virally mediated changes in cellular permeability.

Conferences on membranes are now held as frequently as those on intermediary metabolism or proteins were some years ago; few discussions of membranes, however, deal with disease. And of those that do, the word “virus” hardly ever appears in the index (e.g., Trump and Arstila 1975; Bolis et al. 1976; Miller and Shamoo 1977; Andreoli et al. 1978). Yet it is obvious that viral diseases involve the surface membrane of cells: the initial interaction between viruses and susceptible cells is at the cell surface, membrane damage is a characteristic feature of infected cells (e.g., Thigpen 1971; Fenner et al. 1974), the interplay between infected cells and the immune system takes place at the cell surface, and the action of interferon in protecting against viral attack begins at the cell surface. The features of the cell surface that have been particularly studied to date (e.g., Poste and Nicholson 1977) are the nature of virus receptors (proteins and glycoproteins), the mechanism by which viruses enter cells (endocystosis or, in the case of certain enveloped viruses, virus-cell fusion), the appearance of viral antigens (proteins and glycoproteins) on the surface of infected cells, the mechanism of viral release, and the participation of surface-bound antigens in eliciting an immune (cell-mediated) response. What has been relatively less explored is the way in which the cytopathic effects of viruses come about. The aim of this chapter is to suggest that a change in cellular permeability is at the root of some of these effects and that such a change may underlie the pathological consequences, that is, the diseases, that result from viral infection in certain cases.