HIV-1 Tat increases endothelial solute permeability through tyrosine kinase and mitogen-activated protein kinase-dependent pathways
Oshima, Tadayuki; Flores, Sonia C.a; Vaitaitis, Giselaa; Coe, Laura L.; Joh, Takashib; Park, Jae H.; Zhu, Yanan; Alexander, Brett; Alexander, J. Steven
From the Department of Molecular and Cellular Physiology, Louisiana State University Health Science Center, Shreveport, aWebb-Waring Institute for Biomedical Research, Denver, Colorado, USA, bFirst Department of Internal Medicine, Nagoya City University Medical School, Japan.
Sponsorship: Supported by NIH grants DK43785, HL47615, and HL59785.
Requests for reprints to: J.S. Alexander. Department of Molecular and Cellular Physiology, Louisiana State University Medical Center, 1501 Kings Highway, Shreveport, Louisiana, 71130-3932, USA.
Received: 24 August 1999;
revised: 25 November 1999; accepted: 8 December 1999.
Objective: HIV-1 infection is associated with alterations of several vascular endothelial functions including adhesion molecule expression, growth, and vascular permeability. The bases of these errors are not known, but might involve secretion of the HIV-1 derived transcription factor `Tat-1'. This study investigated Tat-1 mediated endothelial barrier changes and second message regulation of this phenomenon.
Methods: We exposed human umbilical vein endothelial cell monolayers to Tat-1 (0–150 ng/ml) for up to 48 h and measured resulting changes in monolayer permeability. We also investigated the role of tyrosine and mitogen activated protein (MAP) kinases, and protein kinase G using the pharmacological blockers genistein, PD98059 and KT5823 respectively.
Results: Tat-1 significantly reduced monolayer barrier and increased albumin permeability within 24 h. Tat-1 also stimulated tyrosine phosphorylation of multiple endothelial proteins, disorganized junctional phosphotyrosine staining and increased the number of these immunostaining structures. The increased permeability produced by Tat-1 was blocked by genistein and PD98059, but not by KT5823. Genistein and PD98059 pretreatment also prevented the changes in phosphotyrosine immunostaining produced by Tat-1 and blocked phosphorylation of several proteins including MAP kinase.
Conclusion: These results suggest that HIV may dysregulate endothelial barrier through the effects of Tat-1. These blocker experiments suggest that the effects of Tat are transcription/translation-dependent. These data demonstrate that Tat increases endothelial albumin permeability in vitro through tyrosine kinase and MAP kinase, but not protein kinase G pathways.
Several endothelial functions are altered during HIV infection including endothelial cell adhesion molecule expression, leukocyte adhesion, and microvascular integrity. The mechanisms by which HIV enters and disseminates throughout the body are now fairly well understood; manifestations of HIV infection often do not correlate directly with viral titers, but rather reflect the effects of several factors released following HIV infection. It is known that HIV appears in the circulation early after infection, commonly in CD4 T-cells and cells of the monocyte lineage [1,2]. Later, HIV infected macrophages are detected throughout many organ systems . Initially, studies suggested HIV infection of endothelial cells was a possible mode of HIV tissue transmission [4,5]; however, HIV rarely, if ever, infects endothelial cells [6,7]. Thus, HIV infection of tissues is probably mediated by transmission of HIV or HIV infected cells across the endothelial barrier.
Many effects of HIV infection are not mediated by lytic propagation of viral particles in cells, but by the activity of secreted viral factors. For example, Tat-1, a virus encoded transactivating protein plays a critical role in replication of HIV-1 [8–13]. In addition to its transactivation function in viral replication, Tat exerts several effects on non-infected cells, e.g., as an extracellular ligand which modulates endothelial proliferation. The observations that Tat is secreted by acutely infected cells , and that anti-Tat antibodies are frequently detected in the serum of AIDS patients are consistent with a role for extracellular Tat in infected individuals , independent of HIV. Tat may modulate endothelial proliferation by promoting secretion of growth regulatory cytokines such as interleukin-6  or by activating the FLK-1 receptor . Both FLK-1 receptor binding and interleukin-6 might also influence vascular integrity and increase endothelial monolayer permeability [18,19].
The molecular mechanism(s) responsible for the multiple effects of Tat remain unknown. Since HIV infection is associated with diminished vascular integrity, Tat-1 might also modulate the endothelial barrier. This might involve Tat binding to the FLK-1 receptor and altered tyrosine kinase activity  or altered gene transcription transcription and translation. Tat helps to activate the HIV promoter , and also represses transcription of several genes through effects on Sp-1 like elements [10,11]. Tat also influences elongation factor activity  and also modulates expression of endothelial cell adhesion molecules . Therefore Tat receptor binding, uptake in cells  or modulation of transcription/translation could contribute to this loss of endothelial integrity.
In this study, we show that recombinant Tat protein increases endothelial monolayer permeability in a time and concentration-dependent manner. We determined the signal pathways involved in Tat-mediated permeability, and examined how Tat redistributes tyrosine-phosphorylated junction proteins. Lastly, we investigated the molecular weights of Tat-phosphorylated proteins as a function of time. Our data indicate that at least some detrimental effects of HIV, e.g., vascular permeability, may be mediated by Tat through mitogen activated protein (MAP)/tyrosine kinase pathways. These findings suggest that some pathological effects of HIV on the vasculature might be treated using inhibitors of these signal pathways.
Materials and methods
The procedures used to obtain human endothelial cells were approved by the Institutional Review Board for Human Research at the Louisiana State University Health Science Center. Each subject provided written consent and was paid for participating in the study.
Purification of HIV Tat protein
Purification of recombinant Tat from a glutathione S transferase (GST)–Tat fusion vector was essentially as described previously . In brief, the pure Tat protein (40 ng/μl) was cleaved from a GST–Tat fusion vector by thrombin digestion and flash frozen in liquid nitrogen in a buffer containing 7.6 mM dithiothreitol, 33 mM Tris–HCl, pH 7.4 and 20% glycerol. A similar extract from cells expressing the non-fusion GST protein was used as a control. Tat activity was measured by light emission in a HeLa line into which an HIV-LTR driven luciferase reporter had previously been electroporated. Purified Tat was added to HeLa cells, and light emission measured and used as an index of Tat activity. Only Tat preparations that consistently gave multiple-fold increase in luciferase activity in the reporter assay were used in our studies.
Endothelial cell culture
Human umbilical vein endothelial cells (HUVEC) were harvested from umbilical cords by collagenase treatment as described previously . The cells were cultured in endothelial cell growth medium (Clonetics, San Diego, California, USA) supplemented with 10% calf serum (Hyclone, Logan, Maryland, USA), heparin sodium (10 IU/ml; Sigma Chemical Co. St. Louis, Missouri, USA), antibiotics (100 IU/ml penicillin, 100 mg/ml streptomycin, and 0.125 mg amphotericin B), and endothelial cell growth factor (80 ng/ml; Biomedical Technologies, Stoughton, Massachusetts, USA). All other tissue culture reagents were obtained from Gibco (Grand Island, New York). The cell cultures were incubated at 37°C in a 100% humidified atmosphere with 5% CO2 and expanded by brief trypsinization (0.25% trypsin in phosphate buffered saline) containing 0.02 % EDTA. Primary passage HUVEC were seeded onto fibronectin coated (25 μg/ml) tissue culture plates and used when confluent. Culture medium was replaced every second day. Only first-passage cultures were used in these studies. Cells were identified as endothelial cells by their cobblestone appearance at confluence, and by positive labeling with (i) acetylated low density lipoprotein labeled with Dil-Ac-LDL (Biomedical Technologies) and (ii) mouse anti-human factor VIII (Calbiochem, San Diego, California, USA).
Endothelial electrical resistance
HUVEC were plated on 8-μm pore size tissue culture inserts (Becton Dickinson, Franklin Lakes, New Jersey, USA) coated with fibronectin (25 μg/ml) at approximately 75% confluency. The resistance across the monolayer was measured using WPI (New Haven, Connecticut, USA) EVOM volt–ohm meter with `chopstick' electrodes. The value obtained from a blank insert coated with fibronectin was subtracted to give the net resistance, which was multiplied by the membrane area to give the resistance in area-corrected units. Values were expressed as Ω/cm2, taking into account the surface area of the filter (0.38 cm2).
At 100% confluence, trans-monolayer electrical resistance was measured. When resistance was stable (at > 12 Ω/cm2), the culture medium from the upper (apical) compartment of the monolayer was removed, and replaced with medium containing Tat (1, 10, 100, 150 or 500 ng/ml) or control medium containing 19 nM dithiothreitol, 0.05% glycerol and 6.25 pg/ml (the buffer that Tat is usually dissolved in).
We measured endothelial permeability in response to Tat exposure, using fluorescein isothiocyanate labeled bovine serum albumin (FITC–BSA) as a permeable tracer that will pass across endothelial monolayers, by the method described by Maruo et al. with minor modifications. Endothelial monolayers were grown on the surface of 8-μm pore membrane filters (Becton Dickinson). These cell monolayers were washed twice with Hank's balanced salt solution (HBSS), and then placed on 24-well plates (Becton Dickinson) with 1 ml HBSS in the lower chamber. Five-hundred μl HBSS containing 10 μg/ml FITC–BSA were put into the luminal chamber, and then the apparatus was placed in a CO2 incubator at 37°C. After incubation for 30 min, a 100 μl sample was taken from the lower chamber and the absorbance of FITC–BSA was determined at 492 nm with a spectrophotometer (Titertek MCC 340). The data were expressed as follows:EQUATION
Our preliminary data indicate that as the trans- endothelial electrical resistance decreases, the endothelial permeability index increases (data not shown). Permeability measurements were made under control conditions, following exposure to Tat and following pretreatment with the protein kinase inhibitors which were used at their IC50 concentration (the concentration giving 50% inhibition of enzyme activity), genistein (20 μM), PD98059 (20 μM), KT5823 (0.5 μM) (Calbiochem). After cells were pretreated with these inhibitors for 1 h, Tat was added to the culture, and permeability was measured at the time points described.
Western analysis of cell lysates
Equal quantities of protein (75 μg) from each sample were separated by electrophoresis on 7.5% acrylamide gels containing sodium dodecyl sulphate. Proteins were transferred to nitrocellulose membranes (Sigma) and blocked with 5% milk powder in phosphate buffered saline at 4°C overnight. The membranes were washed twice for 10 min in wash buffer (0.1% milk powder in phosphate buffered saline). Primary mouse anti-phosphotyrosine monoclonal (Santa Cruz Biotechnology Inc. Santa Cruz, California, USA) or rabbit anti-active MAP kinase polyclonal antibody (Promega Corporation, Madison, Michigan, USA) was added at a concentration of 0.05 μg/ml and incubated at room temperature for 1 h. The membrane was washed twice with wash buffer. Secondary goat anti-mouse horseradish peroxidase conjugated secondary antibody (Sigma) or goat anti-rabbit alkaline phosphatase conjugate antibody (Sigma) was added at a 1 : 5000 dilution for 1 h. Finally, membranes were washed three times and developed using the enhanced chemiluminescence detection system (Amersham, La Jolla, California, USA) or nitro blue tetrazolium/bromo chloro indolyl phospate (Sigma).
Immunofluorescence staining of junctional proteins
HUVEC were grown to confluency on coverslips and exposed to Tat, with and without genistein, PD98059, or appropriate Tat buffer controls. Samples were fixed with ethanol and acetone  and stained for phosphotyrosine. Mouse anti-phosphotyrosine monoclonal antibody was used at a concentration of 4 μg/ml. Cy3 goat anti-mouse secondary antibody (Jackson Immunoresearch Laboratories Inc. Westgrove, Pasadena, USA) was used at a 1 : 250 dilution. Photomicrographs were taken at 1000 × magnification using 12 s exposure times with T-Max 400 film.
All values are expressed as mean ± SE. Data were analyzed using one-way ANOVA with Bonferroni's correction for multiple comparisons. Significance was accepted at P < 0.05.
Effect of Tat on HUVEC monolayer resistance
The electrical resistance of confluent HUVEC monolayers was 16.29 ± 0.72 Ω/cm2. Incubation of HUVEC monolayers with Tat (50, 150 ng/ml) for 24 and 48 h elicited dose-dependent decreases in the electrical resistance with a maximum by 24 h (fig. 1). Tat (150 ng/ml) significantly decreased electrical resistance to 72.00 ± 3.45%, by 24 h, whereas Tat (50 ng/ml) did not have a significant effect. The effects of 150 ng/ml Tat were not significant before 24 h. Tat (100 and 500 ng/ml) also decreased electrical resistance as 150 ng/ml Tat (data not shown). Subsequent removal of Tat resulted in recovery of monolayer resistance within 48 h (data not shown).
Effect of Tat on HUVEC monolayer permeability
We next determined whether solute-flux measurements of FITC–BSA would give similar results to the change of the electrical resistance. Incubation of HUVEC monolayer with Tat (10, 100, 500 ng/ml) for 24 h elicited a dose-dependent increase in FITC–BSA permeability (P < 0.05) (fig. 2a). For further experiments a dose of 100 ng/ml Tat that showed a measurable disruption of monolayer barrier integrity was chosen for subsequent studies. Incubation of HUVEC monolayer with Tat (100 ng/ml) for 12, 24, and 48 h elicited a time-dependent increase in FITC–BSA permeability with a maximum increase by 24 h and a continued decrease up to 48 h (fig. 2b).
Effects of protein kinase inhibitors on Tat-induced endothelial permeability
To examine the effect of kinase inhibitors, HUVEC were pretreated with genistein, PD98059, or KT5823. Pre-incubation of monolayers with 20 μM genistein prevented Tat-dependent increases in permeability (fig. 2c). The effects of Tat on permeability were also blocked by 20 μM PD98059, a specific inhibitor of MAP kinase kinase-1, but not by 0.5 μM KT5823, protein kinase G inhibitor (fig. 2c). Inhibitors alone had no effect on permeability (data not shown).
Effect of Tat on tyrosine phosphorylation
The effect of extracellular Tat on tyrosine phosphorylation was next investigated. When analyzed using phosphotyrosine immnoblotting, Tat altered the tyrosine phosphorylation pattern in a time-dependent manner (fig. 3). The tyrosine phosphorylation of several proteins (68, 75, 85, 98, 125, 142, 170, 180, 190, and 205 kDa molecular weight) was increased by Tat.
Immunofluorescent staining of phosphotyrosine in vitro
Phosphotyrosine expression on HUVEC was assessed by indirect immunofluorescence. The cells treated with control medium exhibited weak junctional and filamentous staining (fig. 4a). Tat (100 ng/ml) disorganized the junction associated staining, and induced a marked increase in the immunofluorescent staining of slash-like filaments, with an increase in the number of these immunostaining structures (fig. 4b). Pretreatment with the tyrosine kinase inhibitor, genistein, or the MAP kinase inhibitor, PD98059 attenuated the increase in the immunofluorescent staining of these structures induced by Tat (100 ng/ml) (Figs 4c and 4d).
Effects of protein kinase inhibitors on Tat-induced tyrosine phosphorylation
To examine the effects of protein kinase inhibitors, HUVEC were pretreated with genistein, or PD98059. Pre-incubation of monolayers with 20 μM genistein prevented Tat-dependent increases in protein phosphorylation (fig. 5a). The effects of Tat on protein phosphorylation were also blocked by 20 μM PD98059.
The effect of both classes of kinase inhibitors (genistein, PD98059) on Tat-induced MAP kinase phosphorylation was next investigated. Pre-incubation of monolayers with 20 μM genistein prevented Tat-induced MAP kinase phosphorylation. The effect of Tat on MAP kinase phosphorylation was also blocked by 20 μM PD98059 (fig. 5b).
In the present report, we examined the effect of Tat protein on endothelial permeability. We found that endothelial permeability was increased by Tat in a time- and dose-dependent manner (Figs 1 and 2). We chose HUVEC as a model system because endothelial cells appear to be significantly activated by Tat protein . One important index of activation, increased expression of adhesion molecules on endothelial cells, can be induced by Tat protein exposure [16,20]. These observations suggest that Tat alone can activate human vascular endothelium, indicating that this increased vascular permeability may facilitate permeation of HIV into the tissue surrounding infected cells and may explain some of the vascular leakage phenomena related to HIV infection. In fact, it has been proposed that Tat vaccines could be beneficial in that they might bind Tat, prevent permeability, and slow the exchange of HIV and HIV infected cells , as after HIV gains entry into extravascular tissue spaces, infection may be transferred to endogenous tissue macrophages either by direct infection or by cell fusion.
Tat might activate cells at either the plasma membrane, or within the cytoplasm or nucleus. Thus, Tat could be taken up by the target cells and affect genes, or might act like a hormone, binding to cell surface receptors, to generate intracellular signals. Extracellularly applied exogenous Tat rapidly enters into cells and accumulates in the nucleus [21,26]. However, it has also been reported recently that Tat can activate endothelial cells by binding to the Flk-1/KDR receptor for vascular endothelial growth factor (VEGF), promoting tyrosine autophosphorylation of the receptor and its associated downstream effects which might include increased permeability [17,18]. Our results also show that HIV Tat protein, when applied extracellularly, induces the activation of protein kinases in endothelial cells (Figs 3 and 4). Tat produced a striking increase in tyrosine phosphorylation of several endothelial proteins. The Tat-induced tyrosine phosphorylation is both rapid and concentration-dependent (data not shown).
There are several reports that show Tat activates paxillin, p125FAK, p130CAS and MAP kinase [27–30]. Our results also show that Tat activates MAP kinase in endothelial cells (fig. 5b) and suggests that Tat contributes to the tyrosine phosphorylation of these proteins in endothelial cells. Although protein phosphorylation is observed within 1 h of exposure to Tat, permeability responses were not observed until at least 24 h later (Figs 1 and 2). The Tat-dependent increases in permeability were blocked by tyrosine and MAP kinase blockers (fig. 2c). Therefore, despite the difference in time, these early tyrosine phosphorylation changes appear to be critical in the 24 h permeability response. Co-incubation of monolayers with Tat plus genistein or PD98059, attenuated Tat-dependent immunofluorescent staining changes (fig. 4), Tat-dependent protein phosphorylation and MAP kinase phosphorylation (fig. 5). By 24 h, we no longer observed a significant difference in the phosphotyrosine pattern within HUVEC (data not shown).
We have previously shown that VEGF-mediated permeability occurs through disorganization of endothelial junctions, e.g., occludin, and that this effect is blocked by PD98059 . In another report, VEGF was shown to stimulate focal adhesion kinase and paxillin tyrosine phosphorylation . Although we failed to demonstrate a change in junctional proteins (e.g., occludin, VE-cadherin), the change of phosphotyrosine immunofluorescent staining to a focal adhesion `slashes' may represent the phosphorylation of focal adhesion molecules such as paxillin, FAK and p130CAS. To define precisely the events which modulate adhesive plaque reorganization following Tat exposure clearly requires further investigation.
We previously demonstrated that VEGF-dependent endothelial permeability was attenuated significantly by tyrosine and MAP kinase inhibitors . Therefore the data presented here appear superficially to be consistent with permeability changes occurring as a result of FLK-1 receptor binding. However, in our previous study, we reported that FLK-1 receptor binding altered endothelial permeability in a very rapid (< 1 h) manner, which reversed on a similar time scale. Our results in this current report show that unlike FLK-1 receptor binding, Tat-mediated permeability changes do not occur until at least 24 h after Tat exposure, and this effect did not reverse until 48 h after Tat washout. Therefore, while Tat-mediated permeability shares the tyrosine and MAP kinase signal dependence seen with FLK-1, the timing of these events are inconsistent with permeability responses as a result of FLK-1 receptor binding.
The targets responsible for Tat-mediated permeability have still not been identified. Besides its ability to bind to FLK-1 receptors and enter the cytoplasm, Tat also binds to several proteins including a 90 kDa binding protein and RGD-motif containing matrix proteins including fibronectin, laminin and fibrinogen . Tat is also thought to play a significant role in tissue remodeling through its ability to promote matrix metalloproteinase (MMP) formation leading to vessel injury. Interactions of monocytes with human endothelial cells stimulate monocyte MMP production and monocytes appear to be the dominant source of MMP in this type of injury [33–35]. However, it has been reported that cytokines such as tumor necrosis factor-α may contribute to endothelial permeability through the synthesis and activation of endothelial MMP ; therefore we cannot exclude the possibility that Tat may increase endothelial solute permeability by the enhanced endothelial expression of MMP in this model.
In summary, we have provided evidence that the HIV transcriptional regulator, Tat, increases endothelial monolayer solute permeability, and that Tat-induced permeability increase is apparently mediated through the tyrosine kinase and MAP kinase signal transduction cascades. The release of Tat protein in to the vascular microenvironment by infected cells may contribute to the dissemination of HIV-infected cells into tissue and therefore, may enhance disease progression. Therefore, it is possible that MAP kinase and tyrosine kinase antagonists might be beneficial in limiting some of the effects of Tat following HIV infection.
1. Lane HC, Fauci AS. Immunologic abnormalities in the acquired immunodeficiency syndrome.
Annu Rev Immunol 1985, 3: 477 –500.
2. Folks TM, Justement J, Kinter A, Dinarello CA, Fauci AS. Cytokine-induced expression of HIV-1 in a chronically infected promonocyte cell line.
Science 1987, 238: 800 –802.
3. Gartner S, Markovits P, Markovitz DM, Kaplan MH, Gallo RC, Popovic M. The role of mononuclear phagocytes in HTLV-III/LAV infection.
Science 1986, 233: 215 –219.
4. Pomerantz RJ, Kuritzkes DR, de la Monte SM. et al
. Infection of the retina by human immunodeficiency virus type I.
New Engl J Med 1987, 317: 1643 –1647.
5. Pumarola-Sune T, Navia BA, Cordon-Cardo C, Cho ES, Price RW. HIV antigen in the brains of patients with the AIDS dementia complex.
Ann Neurol 1987, 21: 490 –496.
6. Nelson JA, Reynolds-Kohler C, Oldstone MB, Wiley CA. HIV and HCMV coinfect brain cells in patients with AIDS.
Virology 1988, 165: 286 –290.
7. Faber DW, Wiley CA, Lynn GB, Gross JG, Freeman WR. Role of HIV and CMV in the pathogenesis of retinitis and retinal vasculopathy in AIDS patients.
Invest Ophthalmol Vis Sci 1992, 33: 2345 –2353.
8. Jones KA. Tat and the HIV-1 promoter.
Curr Opin Cell Biol 1993, 5: 461 –468.
9. Vaishnav YN, Wong-Staal F. The biochemistry of AIDS.
Annu Rev Biochem 1991, 60: 577 –630.
10. Howcroft TK, Palmer LA, Brown J. et al
. HIV Tat represses transcription through Sp1-like elements in the basal promoter.
Immunity 1995, 3: 127 –138.
11. Rice AP, Mathews MB. Transcriptional but not translational regulation of HIV-1 by the tat gene product.
Nature 1988, 332: 551 –553.
12. Rosen CA, Pavlakis GN. Tat and Rev: positive regulators of HIV gene expression.
AIDS 1990, 4: 499 –509.
13. Kato H, Sumimoto H, Pognonec P, Chen CH, Rosen CA, Roeder RG. HIV-1 Tat acts as a processivity factorin vitroin conjunction with cellular elongation factors.
Genes Dev 1992, 6: 655 –666.
14. Ensoli B, Barillari G, Salahuddin SZ, Gallo RC, Wong-Staal F. Tat protein of HIV-1 stimulates growth of cells derived from Kaposi's sarcoma lesions of AIDS patients.
Nature 1990, 345: 84 –86.
15. Aldovini A, Debouck C, Feinberg MB, Rosenberg M, Arya SK, Wong-Staal F. Synthesis of the complete trans-activation gene product of human T-lymphotropic virus type III inEscherichia coli: demonstration of immunogenicityin vivoand expressionin vitro.
Proc Natl Acad Sci USA 1986, 83: 6672 –6676.
16. Hofman FM, Wright AD, Dohadwala MM, Wong-Staal F, Walker SM. Exogenous tat protein activates human endothelial cells.
Blood 1993, 82: 2774 –2780.
17. Albini A, Soldi R, Giunciuglio D. et al
. The angiogenesis induced by HIV-1 tat protein is mediated by the Flk-1/KDR receptor on vascular endothelial cells.
Nature Med 1996, 2: 1371 –1375.
18. Kevil CG, Payne DK, Mire E, Alexander JS. Vascular permeability factor/vascular endothelial cell growth factor-mediated permeability occurs through disorganization of endothelial junctional proteins.
J Biol Chem 1998, 273: 15099 –15103.
19. Maruo N, Morita I, Shirao M, Murota S. IL-6 increases endothelial permeability in vitro.
Endocrinology 1992, 131: 710 –714.
20. Dhawan S, Puri RK, Kumar A, Duplan H, Masson JM, Aggarwal BB. Human immunodeficiency virus-1-tat protein induces the cell surface expression of endothelial leukocyte adhesion molecule-1, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 in human endothelial cells.
Blood 1997, 90: 1535 –1544.
21. Frankel AD, Pabo CO. Cellular uptake of the tat protein from human immunodeficiency virus.
Cell 1988, 55: 1189 –1193.
22. Herrmann CH, Rice AP. Specific interaction of the human immunodeficiency virus Tat proteins with a cellular protein kinase.
Virology 1993, 197: 601 –608.
23. Yoshida N, Granger DN, Anderson DC, Rothlein R, Lane C, Kvietys PR. Anoxia/reoxygenation-induced neutrophil adherence to cultured endothelial cells.
Am J Physiol 1992, 262: H1891 –H1898.
24. Kevil CG, Okayama N, Trocha SD. et al
. Expression of zonula occludens and adherens junctional proteins in human venous and arterial endothelial cells: role of occludin in endothelial solute barriers.
Microcirculation 1998, 5: 197 –210.
25. Goldstein G. HIV-1 Tat protein as a potential AIDS vaccine.
Nature Med 1996, 2: 960 –964.
26. Mann DA, Frankel AD. Endocytosis and targeting of exogenous HIV-1 Tat protein.
EMBO J 1991, 10: 1733 –1739.
27. Ganju RK, Munshi N, Nair BC, Liu ZY, Gill P, Groopman JE. Human immunodeficiency virus tat modulates the Flk-1/KDR receptor, mitogen-activated protein kinases, and components of focal adhesion in Kaposi's sarcoma cells.
J Virol 1998, 72: 6131 –6137.
28. Milani D, Mazzoni M, Zauli G. et al
. HIV-1 Tat induces tyrosine phosphorylation of p125FAK and its association with phosphoinositide 3-kinase in PC12 cells.
AIDS 1998, 12: 1275 –1284.
29. Li CJ, Ueda Y, Shi B. et al
. Tat protein induces self-perpetuating permissivity for productive HIV-1 infection.
Proc Natl Acad Sci USA 1997, 94: 8116 –8120.
30. Menegon A, Leoni C, Benfenati F, Valtorta F. Tat protein from HIV-1 activates MAP kinase in granular neurons and glial cells from rat cerebellum.
Biochem Biophys Res Commun 1997, 238: 800 –805.
31. Abedi H, Zachary I. Vascular endothelial growth factor stimulates tyrosine phosphorylation and recruitment to new focal adhesions of focal adhesion kinase and paxillin in endothelial cells.
J Biol Chem 1997, 272: 15442 –15451.
32. Weeks BS, Desai K, Loewenstein PM. et al
. Identification of a novel cell attachment domain in the HIV-1 Tat protein and its 90-kDa cell surface binding protein.
J Biol Chem 1993, 268: 5279 –5284.
33. Lafrenie RM, Wahl LM, Epstein JS, Hewlett IK, Yamada KM, Dhawan S. HIV-1-Tat modulates the function of monocytes and alters their interactions with microvessel endothelial cells.
:A mechanism of HIV pathogenesis.
J Immunol 1996, 156: 1638 –1645.
34. Dhawan S, Toro LA, Jones BE, Meltzer MS. Interactions between HIV-infected monocytes and the extracellular matrix: HIV-infected monocytes secrete neutral metalloproteases that degrade basement membrane protein matrices.
J Leukoc Biol 1992, 52: 244 –248.
35. Amorino GP, Hoover RL. Interactions of monocytic cells with human endothelial cells stimulate monocytic metalloproteinase production.
Am J Pathol 1998, 152: 199 –207.
36. Partridge CA, Jeffrey JJ, Malik AB. A 96-kDa gelatinase induced by TNF-alpha contributes to increased microvascular endothelial permeability.
Am J Physiol 1993, 265: L438 –L447.
This article has been cited 28 time(s).
American Journal of Translational Research
HIV-1 Tat-induced microglial activation and neuronal damage is inhibited via CD45 modulation: A potential new treatment target for HAND
American Journal of Translational Research, 4(3):
Asian Pacific Journal of Tropical MedicinePredictors of mortality among HIV-infected patients initiating anti retroviral therapy at a tertiary care hospital in Eastern IndiaAsian Pacific Journal of Tropical Medicine
ToxicologyAttenuated expression of the tight junction proteins is involved in clopidogrel-induced gastric injury through p38 MAPK activationToxicology
HIV-1 penetrates coronary artery endothelial cells by transcytosis
Molecular Medicine, 7(3):
International Journal of CardiologyHIV-associated vascular diseases: Structural and functional changes, clinical implicationsInternational Journal of Cardiology
Critical Reviews in Therapeutic Drug Carrier Systems
Cracking the junction: Update on the progress of gastrointestinal absorption enhancement in the delivery of poorly absorbed drugs
Critical Reviews in Therapeutic Drug Carrier Systems, 25(2):
American Journal of Physiology-Cell PhysiologyAspirin induces gastric epithelial barrier dysfunction by activating p38 MAPK via claudin-7American Journal of Physiology-Cell Physiology
Journal of Cerebral Blood Flow and MetabolismSignaling mechanisms of HIV-1 Tat-induced alterations of claudin-5 expression in brain endothelial cellsJournal of Cerebral Blood Flow and Metabolism
Plos OneHIV-1 Tat Co-Operates with IFN-gamma and TNF-alpha to Increase CXCL10 in Human AstrocytesPlos One
Journal of NeurovirologyHuman immunodeficiency virus type 1 gp120-mediated disruption of tight junction proteins by induction of proteasome-mediated degradation of zonula occludens-1 and-2 in human brain microvascular endothelial cellsJournal of Neurovirology
Extracellular signal-regulated protein kinase activation during reoxygenation is required to restore ischaemia-induced endothelial barrier failure
Biochemical Journal, 367():
Journal of Investigative Medicine
Mitogen-activated protein kinases in endothelial pathophysiology
Journal of Investigative Medicine, 51(6):
World Journal of SurgeryCurrent update on HIV-associated vascular disease and endothelial dysfunctionWorld Journal of Surgery
Journal of Cellular BiochemistryExpression analysis and modulation by HIV-Tat of the tyrosine phosphatase HD-PTPJournal of Cellular Biochemistry
Biochemical and Biophysical Research CommunicationsOxidative stress induces gastric epithelial permeability through claudin-3Biochemical and Biophysical Research Communications
Journal of Neurochemistry
Pro-inflammatory and pro-oxidant properties of the HIV protein Tat in a microglial cell line: attenuation by 17 beta-estradiol
Journal of Neurochemistry, 78(6):
Journal of Immunology
HIV-1 Tat-mediated apoptosis in human brain microvascular endothelial cells
Journal of Immunology, 170(5):
Journal of Immunology
HIV-1 Tat protein stimulates in vivo vascular permeability and lymphomononuclear cell recruitment
Journal of Immunology, 166(2):
American Journal of Physiology-Heart and Circulatory PhysiologyGlutamate causes a loss in human cerebral endothelial barrier integrity through activation of NMDA receptorAmerican Journal of Physiology-Heart and Circulatory Physiology
Journal of NeurochemistryPPAR alpha and PPAR gamma effectively protect against HIV-induced inflammatory responses in brain endothelial cellsJournal of Neurochemistry
Cellular and Molecular NeurobiologyMechanisms of the blood-brain barrier disruption in HIV-1 infectionCellular and Molecular Neurobiology
Journal of Neuroscience ResearchHIV-1 Tat protein alters tight junction protein expression and distribution in cultured brain endothelial cellsJournal of Neuroscience Research
Journal of VirologyHuman immunodeficiency virus type 1 tat regulates endothelial cell actin cytoskeletal dynamics through PAK1 activation and oxidant productionJournal of Virology
Frontiers in Bioscience
The tyrosine phosphatase HD-PTP is regulated by FGF-2 through proteasome degradation
Frontiers in Bioscience, 11():
Cellular and Molecular Life SciencesWip1 protects hydrogen peroxide-induced colonic epithelial barrier dysfunctionCellular and Molecular Life Sciences
International Journal of Biochemistry & Cell Biology
Interactions between endothelial cells and HIV-1
International Journal of Biochemistry & Cell Biology, 33(4):
Journal of Cerebral Blood Flow and MetabolismHIV-TAT protein upregulates expression of multidrug resistance protein 1 in the blood-brain barrierJournal of Cerebral Blood Flow and Metabolism
JAIDS Journal of Acquired Immune Deficiency SyndromesSerum Albumin Is a Powerful Predictor of Survival Among HIV-1-Infected WomenJAIDS Journal of Acquired Immune Deficiency Syndromes
HIV-1; Tat; vascular permeability; signal transduction
© 2000 Lippincott Williams & Wilkins, Inc.
What does "Remember me" mean?
By checking this box, you'll stay logged in until you logout. You'll get easier access to your articles, collections,
media, and all your other content, even if you close your browser or shut down your
To protect your most sensitive data and activities (like changing your password),
we'll ask you to re-enter your password when you access these services.
What if I'm on a computer that I share with others?
If you're using a public computer or you share this computer with others, we recommend
that you uncheck the "Remember me" box.
Highlight selected keywords in the article text.
Data is temporarily unavailable. Please try again soon.