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At least 19 recordsLinked to original sources
PubMed2006

DNA microarray study on gene expression profiles in co-cultured endothelial and smooth muscle cells in response to 4- and 24-h shear stress.

Shear stress, a major hemodynamic force acting on the vessel wall, plays an important role in physiological processes such as cell growth, differentiation, remodelling, metabolism, morphology, and gene expression. We investigated the effect of shear stress on gene expression profiles in co-cultured vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Human aortic ECs were cultured as a confluent monolayer on top of confluent human aortic SMCs, and the EC side of the co-culture was exposed to a laminar shear stress of 12 dyn/cm(2) for 4 or 24 h. After shearing, the ECs and SMCs were separated and RNA was extracted from the cells. The RNA samples were labelled and hybridized with cDNA array slides that contained 8694 genes. Statistical analysis showed that shear stress caused the differential expression (p < or = 0.05) of a total of 1151 genes in ECs and SMCs. In the co-cultured ECs, shear stress caused the up-regulation of 403 genes and down-regulation of 470. In the co-cultured SMCs, shear stress caused the up-regulation of 152 genes and down-regulation of 126 genes. These results provide new information on the gene expression profile and its potential functional consequences in co-cultured ECs and SMCs exposed to a physiological level of laminar shear stress. Although the effects of shear stress on gene expression in monocultured and co-cultured EC are generally similar, the response of some genes to shear stress is opposite between these two types of culture (e.g., ICAM-1 is up-regulated in monoculture and down-regulated in co-culture), which strongly indicates that EC-SMC interactions affect EC responses to shear stress.

Cells, Cultured↗
PubMed1995

Regulation of endothelial cell nitric oxide synthase mRNA expression by shear stress.

Shear stress enhances expression of Ca(2+)-calmodulin-sensitive endothelial cell nitric oxide synthase (ecNOS) mRNA and protein in bovine aortic endothelial cells (BAEC). The present studies were performed to investigate mechanisms responsible for regulation of ecNOS mRNA expression by shear stress and to determine if this induction of ecNOS mRNA is accompanied by an enhanced nitric oxide (NO) production. Shear stresses of 15 dyn/cm2 for 3-24 h resulted in a two- to threefold increase of ecNOS mRNA content quantified by Northern analysis in BAEC. Shear stresses (1.2-15 dyn/cm2) for 3 h resulted in an induction of ecNOS mRNA in a dose-dependent manner. In human aortic endothelial cells, shear stresses of 15 dyn/cm2 for 3 h also resulted in ecNOS mRNA induction. In BAEC, this induction in ecNOS mRNA was prevented by coincubation with actinomycin D (10 micrograms/ml). The K+ channel antagonist tetraethylammonium chloride (3 mM) prevented increase in ecNOS mRNA in response to shear stress. The ecNOS promotor contains putative binding domains for AP-1 complexes, potentially responsive to activation of protein kinase C (PKC). However, selective PKC inhibitor calphostin C (100 nM) did not inhibit ecNOS induction by shear stress. Finally, production of nitrogen oxides under both basal conditions and in response to the calcium ionophore A-23187 (1 microM) by BAEC exposed to shear stress was increased approximately twofold compared with cells not exposed to shear stress. These data suggest that ecNOS mRNA expression is regulated by K+ channel opening, but not by activation of PKC, and that shear not only enhances ecNOS mRNA expression but increases capacity of endothelial cells to release NO.

Animals↗
PubMed1975

Fragility of abnormal erythrocytes evaluated by response to shear stress.

Shear stress is a potential cause of erythrocyte fragmentation and hemolysis in flowing blood. In this study, the response of abnormal human erythrocytes to shear stress in virto was evaluated using a concentric cylinder viscometer. Compared to normal red cells, deoxygenated erythrocytes from persons with sicle cell anemia were particularly susceptible to fragmentation and hemolysis by shear stress. Oxygenation of sicke cell blood improved the resistance of those red cells to shear stress; they remain, however, more susceptible to shear stress than normal erythrocytes. Erythrocytes from patients with iron deficiency, thalassemia minor, and erythrocyte pyruvate kinase deficiency showed fragmentation and hemolysis at threshold shear stresses intermediate between those ovserved for blood from patients with sickle cell anemia and normal persons. Blood samples from patients with hereditary spherocytosis were more resistant to shear stress than normal blood. These results indicate that there are important differences in the response of various red cells to shear stress.

Anemia, Hypochromic↗
PubMed1997

Suppression of angiotensin-converting enzyme expression and activity by shear stress.

Shear stress caused by the frictional forces of a fluid moving over a cell monolayer is an important regulator of gene expression. In this study, we investigated the effect of shear stress on angiotensin-converting enzyme (ACE) expression and promoter activity in vitro and on local vascular ACE activity in vivo. ACE activity measured in bovine pulmonary artery endothelial (BPAE) cells was reduced by 49.5% after exposure to a shear stress of 20 dyne/cm2 for 18 hours. Short-term shearing (2 hours) elevated ACE activity in BPAE cells, whereas long-term shearing produced a time-dependent reduction in ACE activity by 23.3%, 33.5%, and 48.9% at 8, 12, and 18 hours, respectively. Northern blot analysis revealed that shear stress (20 dyne/cm2 for 18 hours) significantly reduced ACE mRNA expression by 82%. To determine the mechanism of ACE activity and message reduction, the effect of shear on transcriptionally related events was determined in a rabbit aortic endothelial cell line (W3LUC) stably transfected with 1.3 kb of a rat ACE promoter/luciferase construct. Different shear stress magnitudes (5 to 20 dyne/cm2) caused suppression of luciferase activity by an average of 40.7%. ACE promoter activity was suppressed by 2 hours of shear stress (24.7%) and was further inhibited at time periods > 8 hours. In vivo elevations in shear stress were created by placing a stainless steel clip over a 12-mm region of the rat abdominal aorta. Restriction of vessel diameter increased blood flow velocity and caused reduction in vascular ACE activity by 40%. These studies suggest that elevations in the level of shear stress alter endothelial cell function by suppressing ACE gene and protein expression in vitro and in vivo.

Acetylcholine↗
PubMed2003

Shear stress attenuates endothelin and endothelin-converting enzyme expression through oxidative stress.

Shear stress is known to dilate blood vessels and exert an antiproliferative effect on vascular walls. These effects have partly been ascribed to shear stress-induced regulation of the secretion of endothelium-derived vasoactive substances. In this study, to elucidate the role of shear stress in endothelin production by endothelial cells, we examined the effect of physiological shear stress on the mRNA expression of endothelin-converting enzyme-1 (ECE-1) as well as endothelin-1 (ET-1) in cultured bovine carotid artery endothelial cells (BAECs) and human umbilical vein endothelial cells (HUVECs), using a parallel plate-type flow chamber. ECE-1 mRNA expression was significantly down-regulated by shear stress in an intensity- and time-dependent manner within the physiological range (1.5 to 15 dyn/cm(2)). ET-1 mRNA expression decreased together with ECE-1 mRNA expression. Shear stress at 15 dyn/cm(2) for 30 min induced a significant increase in the intracellular peroxide concentration, and the down-regulation of ECE-1 and ET-1 mRNA expression by shear stress was attenuated almost completely on treatment with N-acetyl cysteine (NAC), an antioxidant (20 mM). Furthermore, when H(2)O(2) (0.5 to 2 mM) was added to BAECs in static culture, the ECE-1 as well as ET-1 mRNA expression was attenuated in proportion to the concentration of H(2)O(2). It is suggested that endothelial cells sense shear stress as oxidative stress and transduce signal for the regulation of the gene expression of ECE as well as ET to attenuate vascular tone and inhibit the proliferation of vascular smooth muscle cells.

Acetylcysteine↗
PubMed1999

Distinct roles for the small GTPases Cdc42 and Rho in endothelial responses to shear stress.

Shear stress, the tangential component of hemodynamic forces, plays an important role in endothelial remodeling. In this study, we investigated the role of Rho family GTPases Cdc42 and Rho in shear stress-induced signal transduction and cytoskeleton reorganization. Our results showed that shear stress induced the translocation of Cdc42 and Rho from cytosol to membrane. Although both Cdc42 and Rho were involved in the shear stress-induced transcription factor AP-1 acting on the 12-O-tetradecanoyl-13-phorbol-acetate-responsive element (TRE), only Cdc42 was sufficient to activate AP-1/TRE. Dominant-negative mutants of Cdc42 and Rho, as well as recombinant C3 exoenzyme, attenuated the shear stress activation of c-Jun NH2-terminal kinases (JNKs), suggesting that Cdc42 and Rho regulate the shear stress induction of AP-1/TRE activity through JNKs. Shear stress-induced cell alignment and stress fiber formation were inhibited by the dominant-negative mutants of Rho and p160ROCK, but not by the dominant-negative mutant of Cdc42, indicating that the Rho-p160ROCK pathway regulates the cytoskeletal reorganization in response to shear stress.

Animals↗
PubMed2005

Shear stress and shear rate differentially affect the multi-step process of leukocyte-facilitated melanoma adhesion.

Previous studies have shown that neutrophils (PMNs) facilitate melanoma cell extravasation [M.J. Slattery, C. Dong, Neutrophils influence melanoma adhesion and migration under flow conditions, Intl. J. Cancer 106 (2003) 713-722] Little is known, however, about the specific interactions between PMNs, melanoma and the endothelium (EC) or the molecular mechanism involved under flow conditions. The aim of this study is to investigate a "two-step adhesion" hypothesis that involves initial PMN tethering on the EC and subsequent melanoma cells being captured by tethered PMNs. Different effects of hydrodynamic shear stress and shear rate were analyzed using a parallel-plate flow chamber. Results indicate a novel finding that PMN-facilitated melanoma cell arrest on the EC is modulated by shear rate, which is inversely-proportional to cell-cell contact time, rather than by the shear stress, which is proportional to the force exerted on formed bonds. Beta2 integrins/ICAM-1 adhesion mechanisms were examined and the results indicate LFA-1 and Mac-1 cooperate to mediate the PMN-EC-melanoma interactions under shear conditions. In addition, endogenously produced IL-8 contributes to PMN-facilitated melanoma arrest on the EC through the CXC chemokine receptors 1 and 2 (CXCR1 and CXCR2) on PMN. These results provide new evidence for the complex role of hemodynamic forces, secreted chemokines and PMN-melanoma adhesion in the recruitment of metastatic cancer cells to the EC.

Cell Adhesion↗
PubMed2005

A mechanosensory complex that mediates the endothelial cell response to fluid shear stress.

Shear stress is a fundamental determinant of vascular homeostasis, regulating vascular remodelling, cardiac development and atherogenesis, but the mechanisms of transduction are poorly understood. Previous work showed that the conversion of integrins to a high-affinity state mediates a subset of shear responses, including cell alignment and gene expression. Here we investigate the pathway upstream of integrin activation. PECAM-1 (which directly transmits mechanical force), vascular endothelial cell cadherin (which functions as an adaptor) and VEGFR2 (which activates phosphatidylinositol-3-OH kinase) comprise a mechanosensory complex. Together, these receptors are sufficient to confer responsiveness to flow in heterologous cells. In support of the relevance of this pathway in vivo, PECAM-1-knockout mice do not activate NF-kappaB and downstream inflammatory genes in regions of disturbed flow. Therefore, this mechanosensing pathway is required for the earliest-known events in atherogenesis.

Animals↗
PubMed2003

[Morphological parameters for endothelial cells under shear stress].

Shear stresses acting on vascular endothelial cells due to blood fluid flow play an vital role in regulating their morphology, structure, growth rate and functions. The change in morphology is an instinctive response to biomechanical environment and is an indicator for the functional changes in the cells. In this paper, the morphological research literatures of endothelial cells in the recent years are reviewed and the common morphological parameters are described in detail. At the end, the difficulties of quantitative study of endothelial cell morphology and the future direction of morphological parameters research are also discussed.

Animals↗
PubMedDate not supplied

Obtaining the shear stress versus shear rate relationship and yield stress of blood from capillary viscometry data by Tikhonov regularization.

This paper describes a procedure, based on Tikhonov regularization, for extracting the shear stress versus shear rate relationship and yield stress of blood from capillary viscometry data. The relevant equations and the mathematical nature of the problem are briefly described. The procedure is then applied to three sets of capillary viscometry data of blood taken from the literature. From each data set the procedure computes the complete shear stress versus shear rate relationship and the yield stress. Since the procedure does not rely on any assumed constitutive equation, the computed rheological properties are therefore model-independent. These properties are compared against one another and against independent measurements. They are found to be in good agreement for shear stress greater than 0.1 Pa but show significant deviations for shear stress below this level. A possible way of improving this situation is discussed.

Blood Viscosity↗
PubMed1993

Wall shear stress rather than shear rate regulates cytoplasmic Ca++ responses to flow in vascular endothelial cells.

Recent evidence suggests that the vascular endothelial cell (EC) can sense the flow-rate over its surface and according to the information, regulates not only its own morphology and functions but also those of the surrounding smooth muscle and other tissues. There is now a discussion over which of the following mechanisms actually initiates the signal-transacting response of EC against flow: the mechanical shear deformation of the cell due to flow-oriented wall shear stress (tau), or the diffusional accumulation of vasoactive agonists on the cell surface modulated by wall shear rate (gamma) or both. To identify the relative importance of each mechanism, we examined quantitative changes in the cytoplasmic free Ca++ concentration ([Ca++]i) in cultured EC in the presence of the Ca++ mobilizing agonist ATP, i.e., a second messenger response of the internal signalling system, following the perfusion of two buffers with different viscosities (mu), which relates these factors as tau = mu gamma. The results of in vitro fluorescence photometry in EC with Fura-2 showed that the [Ca++]i level was enhanced with increase in the shear rate but to a greater extent with higher viscosity, and that the [Ca++]i levels at the same calculated level of shear stress were virtually identical, regardless of difference in shear rate and viscosity. This quantitative one-to-one relationship between the shear stress and the second messenger response suggests that wall shear stress rather than wall shear rate is the principal physical factor eliciting EC responses to flow.

Animals↗
PubMed2003

High glucose induced NF-kappaB DNA-binding activity in HAEC is maintained under low shear stress but inhibited under high shear stress: role of nitric oxide.

In the present study, we investigated whether low shear (LS, 2 dyn/cm2) favors high glucose (HG, 30 mM) induced nuclear factor kappa B (NF-kappaB) activity by regulating NO release in human aortic endothelial cells (HAEC). The results show that (i) under LS, the NF-kappaB activity of HAEC exposed to HG was significantly higher than HAEC in normal glucose (NG, 5.5mM) (P < 0.05). In contrast, under HS, the activation of NF-kappaB in HAEC exposed to HG showed no significant difference compared to that of NG. (ii) The NF-kappaB activity induced by HG is suppressed by high shear (HS) in the absence of a NO synthase inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME) but restored in its presence, while LS + HG induced NF-kappaB activity remains the same in the presence or absence of L-NAME. (iii) Endothelial nitric oxide synthase (eNOS) protein expression and quantitative detection of NO indicated that high shear stress significantly induced higher eNOS expression and NO production compared to low shear stress condition. Collectively, these data suggest that HS exerts a protective effect on HG induced NF-kappaB activity through NO mediated signaling. LS, on the other hand, may down-regulate eNOS expression resulting in reduced NO release, and thereby maintain high glucose induced NF-kappaB DNA-binding activity. These observations explain, in part, the mechanism by means of which hyperglycemia accelerates the focal development of atherosclerotic lesions in low shear (lesion prone) areas of the arterial tree.

Analysis of Variance↗
PubMed2002

[Time-dependent effects of interleukin-8 gene expression in endothelial cells exposed on fluid shear stress].

Fluid shear stress plays an important role in vascular biology. In vivo, endothelial cells are continuously exposed to mechanical shear stress generated by the flowing blood. Previous studies have identified the exposure of vascular endothelial cells to fluid mechanical forces can modulate the expression of many genes involved in vascular physiology and pathophysiology. To investigate the role of fluid shear stress on IL-8 expression in human umbilical vein endothelial cells (HUVECs), we employed quantitative reversal transcription-polymerase chain reaction (qRT-PCR) to assay the expression of IL-8 mRNA. Here we show that IL-8 mRNA did not express in HUVECs untreated with fluid shear stress. IL-8 mRNA expression increased when HUVECs exposed to fluid shear stress for 1 h, and it reached the summit when HUVECs exposed to fluid shear stress for 2 h. Then IL-8 expression gradually decreased at 3 h of stimulation by shear stress and remained at a constant level throughout the time course of the study. The increase of IL-8 expression by shear stress was time-dependent. The biphasic response of IL-8 gene expression was found in experiments in which the applied shear stress was 2.23 dyne/cm2, 4.20 dyne/cm2, or 6.08 dyne/cm2. IL-8 gene expression in response to shear stress was very similar to NF-kappa B in response to shear stress. The induction of IL-8 gene expression by fluid shear stress is probably due to the activation of NF-kappa B. This in vitro study demonstrates the expression of IL-8 gene can be regulated by shear stress. Fluid shear stress induces a biphasic response of human IL-8 gene expression in HUVECs. These considerations suggest that IL-8 expression induced by fluid shear stress in HUVECs may play an important role in the genesis and development of both inflammation and arterioatherosclerosis.

Cells, Cultured↗
PubMed2004

[Time-dependent increase of interleukin-8 production in endothelial cells exposed to fluid shear stress].

Fluid shear stress plays an important role in many physiological and pathological processes of the cardiovascular system. Being constantly exposed to mechanical shear stress, vascular endothelial cells can sense the changes of blood flow forces and regulate vascular structure and function. Previous studies demonstrated that IL-8 mRNA expression in endothelial cells was modulated by fluid shear stress. To identify the effect of fluid shear stress on IL-8 protein production of human umbilical vein endothelial cells (HUVECs), we employed quantitative sandwich enzyme-linked immunosorbent assay (ELISA) to measure the IL-8 protein. It was found that the HUVECs not treated with fluid shear stress secreted very little IL-8 in culture media. However, after 1 hour of exposure to shear stress, the secretion of IL-8 increased; at 5 hours of exposure, the seceretion reached the summit; at 8 hours of exposure, the secretion of IL-8 decreased and then remained at a constant level till the end (12 hours) of the experiment. The increase of IL-8 secretion induced by shear stress was time-dependent. The biphasic response of IL-8 protein production was found in experiments in which the shear stress applied was 2.09 dyne/cm2, 4.61 dyne/cm2, and 6.19 dyne/cm2. The IL-8 protein production in response to shear stress was very similar to the IL-8 gene expression in response to shear stress, and had the obvious delay. The induction of IL-8 protein production by fluid shear stress is probably due to the gene expression. This in vitro study demonstrates that the production of IL-8 can be regulated by fluid shear stress. Fluid shear stress induces a biphasic response of human HUVECs' production of IL-8 protein. These observations suggest that the process of the fluid shear stress induced HUVECs' production of IL-8 may play an important role in the genesis and development of both inflammation and atherosclerosis.

Cells, Cultured↗
PubMedDate not supplied

Role of viscoelastic properties of differentiated SH-SY5Y human neuroblastoma cells in cyclic shear stress injury.

Shear stress and strain lead to neurodegeneration in vivo during head injury, glaucoma, and certain repetitive motion disorders. In vitro, shear stress and strain have been shown to lead to cell injury in a number of models using neurons and neuron-like cells. In the present study we examined the relationship between shear stress, strain, and the extent of cell injury in a cyclic shear stress induced model of cell injury using differentiated SH-SY5Y (human neuroblastoma) cells. Shear stress led to cell strain that increased with increasing stress and diminished upon cessation of shear. Strain rate during cyclic application of shear stress increased by over an order of magnitude from the first to all subsequent cycles, suggesting that the cell and/or its polymer network became more elastic upon cyclic shear stress application. To support this conclusion we measured the degree of cytoskeletal polymerization before and after exposure of cells to cyclic shear stress and found that the fraction of polymerized tubulin in the cell relative to total tubulin decreased by a factor of 2 after six cycles of shear stress. The extent of injury, as indicated by the fraction of cells with fragmented DNA, was three times higher for cyclic shear stress than for steady shear stress and may be related to the change in strain rate and/or cytoskeletal reorganization associated with cyclic stress. These findings may aid in understanding the mechanism by which neurons and neuron-like cells respond to cyclic shear stress and strain and lead to new treatments for disease or injury arising from the exposure of neurons to abnormal cyclic or repetitive stress and strain.

Cell Differentiation↗
PubMed2004

[Force-dependent effects of interleukin-8 production in endothelial cells exposed to fluid shear stress].

Fluid shear stress plays a key role in many physiological activities and pathological processes of the cardiovascular diseases. In vivo, endothelial cells (ECs) are constantly exposed to hemodynamic force which can modulate structure and function of ECs. Previous studies have demonstrated that IL-8 protein production in endothelial cells was modulated by fluid shear stress, and IL-8 protein production induced by fluid shear stress was time-dependent. In order to identify the role of intensity of fluid shear stress on IL-8 protein production of human umbilical vein endothelial cells (HUVECs), we had HUVECs exposed to shear stress 2.09, 4.61, 6.19, 8.51, 10.50, 12.59, 14.41, 17.22, 18.32 dyne/cm2 respectively and employed quantitative sandwich enzyme-linked immunosorbent assay (ELISA) to measure the IL-8 protein. Here we show that HUVECs untreated with fluid shear stress secreted very little IL-8 in culture media. The IL-8 protein production induced by shear stress was force intensity-dependent. After HUVECs being subjected to low fluid shear stress (2.09 dyne/cm2) for 5 h or 6 h, IL-8 protein production increased and was nearly 6 times or 7 times over that of HUVECs subjected to high fluid shear stress (18.32 dyne/cm2). The linear regression equations between IL-8 protein production (y) and shear stress (dyne/cm2, x) are y=760.12-36.06x, gamma=-0.978 (for 5 h); y=781.87-36.66x, gamma=-0.980 (for 6 h). This in vitro study demonstrates that the production of IL-8 can be regulated by fluid shear stress, and the production of IL-8 induced by shear stress is not only time-dependent but also force intensity-dependent. These observations suggest that the low fluid shear stress induces much more IL-8 secretion, which may play an important role in the pathogenesis and development of both inflammation and atherosclerosis.

Cells, Cultured↗
PubMed2002

[Force-dependent effects of interleukin-8 gene expression in endothelial cells exposed on fluid shear stress].

Fluid shear stress plays an important role in many physiological and pathophysiological processes of the cardiovascular system. Previous studies have identified the exposure of vascular endothelial cells to fluid mechanical forces can modulate the expression of many genes, including IL-8 gene expression, and IL-8 expression induced by fluid shear stress was time-dependent. To investigate the role of intensity of fluid shear stress on IL-8 expression in human umbilical vein endothelial cells (HUVECs), we had HUVECs exposed to shear stress 2.23, 4.20, 6.08, 8.19, 9.67, 12.15, 14.40, 16.87, and 19.29 dyne/cm2 respectively and employed quantitative reversal transcription-polymerase chain reaction (qRT-PCR) to assay the expression of IL-8 mRNA. The results show that IL-8 mRNA did not express in HUVECs untreated with fluid shear stress. The IL-8 mRNA expression by shear stress was force intensity-dependent. After HUVECs exposed to low fluid shear stress (2.23 dyne/cm2) for 1 h or 2 h, IL-8 mRNA expression increased near 68 or 52 times as that of HUVECs exposed to high fluid shear stress (19.29 dyne/cm2). The linear regression equations between IL-8 mRNA expression (log (copies), y) and shear stress (dyne/cm2, x) are: y = 7.57 - 0.11x, r = 0.97 (for 1 h); y = 7.92 - 0.10x, r = 0.96 (for 2 h). This in vitro study demonstrates the expression of IL-8 gene can be regulated by fluid shear stress. The low shear stress could induces much more expression of IL-8 mRNA, which plays probably an important role in the pathogenesis of inflammation and arteroatherosclerosis.

Cells, Cultured↗
PubMed2003

Role of xanthine oxidoreductase and NAD(P)H oxidase in endothelial superoxide production in response to oscillatory shear stress.

Oscillatory shear stress occurs at sites of the circulation that are vulnerable to atherosclerosis. Because oxidative stress contributes to atherosclerosis, we sought to determine whether oscillatory shear stress increases endothelial production of reactive oxygen species and to define the enzymes responsible for this phenomenon. Bovine aortic endothelial cells were exposed to static, laminar (15 dyn/cm2), and oscillatory shear stress (+/-15 dyn/cm2). Oscillatory shear increased superoxide (O2.-) production by more than threefold over static and laminar conditions as detected using electron spin resonance (ESR). This increase in O2*- was inhibited by oxypurinol and culture of endothelial cells with tungsten but not by inhibitors of other enzymatic sources. Oxypurinol also prevented H2O2 production in response to oscillatory shear stress as measured by dichlorofluorescin diacetate and Amplex Red fluorescence. Xanthine-dependent O2*- production was increased in homogenates of endothelial cells exposed to oscillatory shear stress. This was associated with decreased xanthine dehydrogenase (XDH) protein levels and enzymatic activity resulting in an elevated ratio of xanthine oxidase (XO) to XDH. We also studied endothelial cells lacking the p47phox subunit of the NAD(P)H oxidase. These cells exhibited dramatically depressed O2*- production and had minimal XO protein and activity. Transfection of these cells with p47phox restored XO protein levels. Finally, in bovine aortic endothelial cells, prolonged inhibition of the NAD(P)H oxidase with apocynin decreased XO protein levels and prevented endothelial cell stimulation of O2*- production in response to oscillatory shear stress. These data suggest that the NAD(P)H oxidase maintains endothelial cell XO levels and that XO is responsible for increased reactive oxygen species production in response to oscillatory shear stress.

Animals↗