Biomedical subjects

Y L Hu

Publications and source records attributed to Y L Hu.

At least 19 recordsLinked to original sources

PubMed2003

PCR amplification and sequencing of ITS1 rDNA of Culicoides arakawae.

The first internal transcribed spacer (ITS1) of nuclear ribosomal DNA from Culicoides arakawae was amplified by PCR, cloned and sequenced. The wDNAsis software was used to analyze the ITS1 sequences of C. arakawae and other nine species of Culicoides, which were obtained from GenBank and EMBL databases. For all species, the lengths of the ITS1 were 316-469 bp, and the G+C contents were 26.79-34.53%. Based on the lengths of the ITS1 sequences, the 10 Culicoides species could be divided into two groups. The first group consisted of C. arakawae, C. albicans, C. cubitalis, C. pulicaris and C. punctatus, and the second group comprised C. impunctatus, C. nubeculosus, C. variipennis, C. grisescens and C. imicola. The lengths for the first group were 316-347 bp and the second group were 457-469 bp. C. arakawae belonged to the first group by its ITS1 sequence length. Sequence analysis revealed that C. arakawae was genetically more similar to the first group than it was to the second group, consistent with results based on sequence length. The alignment of ITS1 (the alignment length was 500 bp including the gaps) sequences showed that there was a highly conserved region, which was between 288 and 388 bp, except for a few insertions and substitutions. These findings have important implications for the molecular identification of C. arakawae, for studying its molecular genetics and epidemiology, and for studying the molecular systematics of Culicoides.

Animals↗

PubMed2001

Lysophosphatidic acid induction of vascular endothelial growth factor expression in human ovarian cancer cells.

BACKGROUND: Lysophosphatidic acid (LPA) stimulates ovarian tumor growth at concentrations present in ascitic fluid. Vascular endothelial growth factor (VEGF) stimulates angiogenesis and plays a pivotal role in the formation of ovarian cancer-associated ascites. We examined whether LPA promotes ovarian tumor growth by increasing angiogenesis via VEGF. METHODS: VEGF expression was examined in a simian virus 40 T-antigen-immortalized ovarian surface epithelial cell line (IOSE-29) and in ovarian cancer cell lines (OVCAR-3, SKOV-3, and CAOV-3) treated with LPA. VEGF promoter activity was measured in OVCAR-3 cells after transfection or cotransfection with c-Fos and c-Jun, components of AP1 transcription factor, potential binding sites for which are present in the VEGF promoter. The expression of the LPA receptors Edg2 and Edg4 was also assessed. All statistical tests were two-sided. RESULTS: LPA treatment increased steady-state VEGF messenger RNA (mRNA) levels in OVCAR-3 cells in a time- and dose-dependent fashion and stimulated VEGF promoter activity without prolonging mRNA half-life in these cells, but LPA had little effect on IOSE-29 cells. Forced overexpression of c-Jun and c-Fos in OVCAR-3 cells stimulated VEGF promoter activity fourfold. LPA also elevated VEGF protein levels by 1.5-fold in SKOV-3 cells (P =.0148), 1.9-fold in CAOV-3 cells (P<.001), and threefold in OVCAR-3 cells (P<.0001). Both Edg2 and Edg4 were detected in ovarian cancer cells; however, only Edg2 was present in normal ovarian surface epithelial cells and IOSE-29 cells. CONCLUSIONS: LPA stimulates ovarian tumor growth, at least in part, via induction of VEGF expression through transcriptional activation. However, this LPA response is not evident in normal ovarian surface epithelial cells. Our data suggest that Edg4, but not Edg2, plays a role in LPA stimulation of ovarian tumor growth.

Antibiotics, Antineoplastic↗

PubMed2001

Age-associated changes in regional aortic pulse wave velocity.

OBJECTIVES: This study was designed to determine noninvasively the age-associated changes in regional mechanical properties in normals using phase-contrast magnetic resonance imaging (PCMRI). BACKGROUND: It has been well documented that there is a progressive increase in aortic pulse wave velocity (PWV) with age. Previously, PWV has been measured at a single aortic location, or has compared arterial waves between carotid and femoral points to determine PWV. METHODS: Applanation tonometry (TONO) and in-plane PCMR was performed in 24 volunteers (12 men) ranging in age from 21 to 72 years old. The PCMRI PWV was measured in three aortic segments. As validation, TONO was performed to determine PWV between the carotid and femoral artery. RESULTS: When PCMRI PWV was averaged over the three locations, it was not different from TONO (7.9 +/- 2.3 vs. 7.6 +/- 2.4 m/s, respectively). When the volunteers were divided into groups of < 55 and > or =55 years old, the younger group showed similar PWV at each aortic location. However, the older group displayed significantly increased PWV in the region spanning the ascending and proximal descending aorta compared with the mid-thoracic or abdominal segments (10.6 +/- 2.5 m/s, 9.2 +/- 2.8 m/s, and 7.1 +/- 1.7 m/s, respectively, p < 0.001, analysis of variance). CONCLUSIONS: In-plane PCMRI permits determination of PWV in multiple aortic locations in a single acquisition. Progressive fragmentation of elastic fibers and alterations in the regulation of vascular tone may result in an age-related, regional increase in PWV primarily affecting the proximal aorta.

Adult↗

PubMed2001

Effects of morphological patterning on endothelial cell migration.

The migration of vascular endothelial cells (ECs) plays an important role in vascular remodeling. Here we studied the effects of cell morphology on the migration of bovine aortic ECs by culturing cells on micropatterned strips of collagen matrix (60-, 30-, and 15-microm wide). The spreading areas of the cells on 15- and 30-microm wide strips were 30% lower than those on 60-microm wide strips and unpatterned collagen. The cells on 15-microm wide strips completely aligned in the direction of the strip, and had significantly lower shape index than those in all other groups. On strips of all widths, ECs tended to migrate in the direction of strips. ECs on 15-microm wide strips had highest speed, particularly in the direction of the strip. Vinculin staining showed that the leading edge of ECs on 15-microm wide strips had focal adhesions that were oriented with their lamellipodial protrusion and the direction of cell migration; this arrangement of the focal adhesions may promote EC migration. The present study provides direct evidence on the role of cell morphology in EC migration, and will help us to understand the mechanisms of EC migration during angiogenesis and wound healing.

Animals↗

PubMed2000

Contractile reserve and contrast uptake pattern by magnetic resonance imaging and functional recovery after reperfused myocardial infarction.

OBJECTIVES: We hypothesized that contrast-enhanced and dobutamine tagged magnetic resonance imaging (MRI) could investigate microvascular integrity and contractile reserve of reperfused myocardial infarction (MI) in one examination. BACKGROUND: In reperfused MI, microvascular integrity and contractile reserve are important determinants of functional recovery. METHODS: Twenty-three patients with a reperfused first MI were studied. On day 3+/-1 after MI, patients underwent tagged MRI at baseline and during infusion of 5 and 10 microg/kg/min of dobutamine followed by contrast-enhanced MRI (first pass and delayed imaging) after a bolus infusion of gadolinium-diethylenetriaminepenta-acetic acid. Tagged MRI was performed 9+/-1 weeks later (follow-up). Eighty-four transmural regions with hyperenhancement on delayed contrast-enhanced images were defined as COMB (first pass hypoenhancement) or HYPER (normal first pass signal enhancement). Percent circumferential segment shortening was measured within the subendocardium and subepicardum of each region of HYPER or COMB at baseline, peak dobutamine and follow-up. RESULTS: Shortening improved in COMB regions from 4+/-1% at baseline to 10+/-1% at peak dobutamine and 10+/-1% at follow-up, respectively (p<0.0003 vs. baseline for both). The HYPER regions likewise improved from 10+/-1% at baseline to 16+/-1% and 17+/-1%, respectively (p<0.0004 vs. baseline for both). Function within COMB regions was less than that of HYPER at baseline, peak dobutamine and follow-up (p<0.0003 for all). CONCLUSIONS: Dobutamine magnetic resonance tagging and contrast enhanced MRI are complementary in assessing functional recovery after reperfused MI. Regions of delayed contrast hyperenhancement demonstrate both contractile reserve and late functional recovery. However, if these regions demonstrate first pass contrast hypoenhancement, they are associated with greater myocardial damage.

Cardiotonic Agents↗

PubMed2000

Effects of active and negative mutants of Ras on rat arterial neointima formation.

BACKGROUND: Ras protein is a key signal transducer in the cause of cell proliferation. We studied the effects of active and negative mutants of the Ras gene on arterial neointimal formation in rats, with the aim of elucidating the molecular mechanisms regulating restenosis following percutaneous transluminal coronary angioplasty. MATERIALS AND METHODS: AdRasV12 and AdRasN17, the recombinant adenoviruses containing a constitutively active mutant and a dominant negative mutant of Ras, respectively, were used to determine whether Ras is necessary and sufficient to modulate the smooth muscle cell proliferation and neointima formation. Following balloon injury, rat common carotid arteries were treated in their distal half with AdRasV12, AdRasN17, or AdLacZ, with the proximal half used as uninfected control. RESULTS: In rat arteries subjected to balloon injury, either uninfected or treated with AdLacZ, there were pronounced SMC proliferation and neointima formation. These changes were markedly augmented by AdRasV12 and reduced by AdRasN17. CONCLUSION: Ras is necessary and sufficient for SMC proliferation and neointima formation and may play a critical role in restenosis following balloon angioplasty.

Adenoviridae↗

PubMed2000

Anti-interleukin-1 and anti-tumor necrosis factor-alpha synergistically inhibit adjuvant arthritis in Lewis rats.

Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) play dominant roles in mediating the progression of many inflammatory joint diseases, including rheumatoid arthritis in humans, collagen-induced arthritis in mice and rats, and adjuvant arthritis in rats. Blockade of either cytokine partially controls these diseases. The present study investigated the value of combination anti-cytokine therapy in arthritis: the efficacy of IL-1 receptor antagonist (IL-1ra) and 30 kDa polyethylene glycol (PEG)-conjugated soluble TNF receptor type I (PEG sTNF-RI) given together was assessed in Lewis rats with adjuvant arthritis. Administration of either IL-1ra or PEG sTNF-RI partially alleviated joint inflammation, loss of bone mineral density, and loss of body weight. In contrast, combination of these anti-cytokine treatments exhibited a synergistic capacity to inhibit these changes, even when combining doses of IL-1ra and PEG sTNF-RI that did not affect lesion severity when used alone. Statistical analysis of these adjuvant arthritis data using the isobologram method proved that IL-1ra and PEG sTNF-RI were clearly synergistic in inhibiting inflammation, loss of bone mineral density, loss of body weight, and histopathologic parameters of inflammation and joint destruction. These results suggest that treating autoimmune arthritic diseases with combinations of anti-IL-1 and anti-TNF molecules will achieve superior efficacy compared to the use of a single class of anti-cytokine agent and may allow for dose reductions that could prove useful in minimizing potential side effects.

Animals↗

PubMed2000

Preparation and cDNA sequence analysis of two novel monoclonal antibodies against magaininII.

By using intrasplenic immunization and the conventional B lymphocyte hybridoma technique, we have established two novel hybridoma cell lines stably secreting specific monoclonal antibodies (MAbs) to magaininII, termed as 2D1 and 3F8, respectively. The two cell lines were then subjected to RNA extraction and the VH and VL segments were obtained by reverse transcription of RNA followed by polymerase chain reaction (RT-PCR) and characterized by nucleotide sequence analysis. The VH segments of 2D1 and 3F8 belong to the VH5 family and the VL segments of 2D1 and 3F8 belong to VK10 and VK1 groups, respectively. The two MAbs utilize different VL segments and have disparities in their HCDR3 regions, which may contribute to the different epitope recognition of the two antibodies.

Amino Acid Sequence↗

PubMed2000

Mechanisms of lysolipid phosphate effects on cellular survival and proliferation.

The specificity of cellular effects of lysolipid phosphate (LLP) growth factors is determined by binding to endothelial differentiation gene-encoded G protein-coupled receptors (EDG Rs), which transduce diverse proliferative and effector signals. The primary determinants of cellular responses to LLPs are the generative and biodegradative events, which establish steady-state concentrations of each LLP at cell surfaces, and the relative frequency of expression of each EDG R. There are major differences among types of cells in the net effective generation of the LLPs, lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), and in their profile of expression of EDG Rs. The less well characterized secondary determinants of cellular specificity of LLPs are high-affinity binding proteins with carrier and cell-presentation functions, cell-selective regulators of expression of EDG Rs, and cellular factors that govern coupling of EDG Rs to G protein transductional pathways. The roles of components of the LLP-EDG R system in normal physiology and disease processes will be definitively elucidated only after development of animal models with biologically meaningful alterations in genes encoding EDG Rs and the discovery of potent and selective pharmacological probes.

Breast Neoplasms↗

PubMed2000

Characterization of signal properties in atherosclerotic plaque components by intravascular MRI.

Magnetic resonance imaging (MRI) is capable of distinguishing between atherosclerotic plaque components solely on the basis of biochemical differences. However, to date, the majority of plaque characterization has been performed by using high-field strength units or special coils, which are not clinically applicable. Thus, the purpose of the present study was to evaluate MRI properties in histologically verified plaque components in excised human carotid endarterectomy specimens with the use of a 5F catheter-based imaging coil, standard acquisition software, and a clinical scanner operating at 0.5 T. Human carotid endarterectomy specimens from 17 patients were imaged at 37 degrees C by use of an opposed solenoid intravascular radiofrequency coil integrated into a 5F double-lumen catheter interfaced to a 0.5-T General Electric interventional scanner. Cross-sectional intravascular MRI (156x250 microm in-plane resolution) that used different imaging parameters permitted the calculation of absolute T1and T2, the magnetization transfer contrast ratio, the magnitude of regional signal loss associated with an inversion recovery sequence (inversion ratio), and regional signal loss in gradient echo (gradient echo-to-spin echo ratio) in plaque components. Histological staining included hematoxylin and eosin, Masson's trichrome, Kossa, oil red O, and Gomori's iron stain. X-ray micrographs were also used to identify regions of calcium. Seven plaque components were evaluated: fibrous cap, smooth muscle cells, organizing thrombus, fresh thrombus, lipid, edema, and calcium. The magnetization transfer contrast ratio was significantly less in the fibrous cap (0.62+/-13) than in all other components (P<0.05) The inversion ratio was greater in lipid (0.91+/-0.09) than all other components (P<0.05). Calcium was best distinguished by using the gradient echo-to-spin echo ratio, which was lower in calcium (0.36+/-0.2) than in all plaque components, except for the organizing thrombus (P<0.04). Absolute T1 (range 300+/-140 ms for lipid to 630+/-321 ms for calcium) and T2 (range 40+/-12 ms for fresh thrombus to 59+/-21 ms for smooth muscle cells) were not significantly different between groups. In vitro intravascular MRI with catheter-based coils and standard software permits sufficient spatial resolution to visualize major plaque components. Pulse sequences that take advantage of differences in biochemical structure of individual plaque components show quantitative differences in signal properties between fibrous cap, lipid, and calcium. Therefore, catheter-based imaging coils may have the potential to identify and characterize those intraplaque components associated with plaque stability by use of existing whole-body scanners.

Carotid Arteries↗

PubMed1999

Distinctive expression and functions of the type 4 endothelial differentiation gene-encoded G protein-coupled receptor for lysophosphatidic acid in ovarian cancer.

Endothelial differentiation gene (edg)-encoded G protein-coupled receptors (Edg Rs)-1, -3, and -5 bind sphingosine 1-phosphate (S1P), and Edg-2 and -4 bind lysophosphatidic acid (LPA). Edg Rs transduce signals from LPA and S1P that stimulate ras- and rho-dependent cellular proliferation, enhance cellular survival, and suppress apoptosis. That high levels of LPA in plasma and ascitic fluid of patients with ovarian cancer correlate with widespread invasion suggested the importance of investigating expression and functions of Edg Rs in ovarian cancer cells (OCCs) as compared with nonmalignant ovarian surface epithelial cells (OSEs). Analyses of Edg Rs by semiquantitative reverse transcription-PCR, a radioactively quantified variant of PCR, and Western blots developed with monoclonal antibodies showed prominent expression of Edg-4 R in primary cultures and established lines of OCCs but none in OSEs. In contrast, levels of Edg-2, -3, and -5 were higher in OSEs than OCCs. LPA stimulated proliferation and signaled a serum response element-luciferase reporter of immediate-early gene activation in OCCs but not OSEs, whereas S1P evoked similar responses in both OSEs and OCCs. Pharmacological inhibitors of Edg R signaling suppressed OCC responses to LPA. A combination of monoclonal anti-Edg-4 R antibody and phorbol myristate acetate, which were inactive separately, evoked proliferative and serum response element-luciferase responses of OCCs but not OSEs. Thus the Edg-4 R may represent a distinctive marker of OCC that transduces growth-promoting signals from the high local concentrations of LPA characteristic of aggressive ovarian cancer.

Female↗

PubMed1999

Early contrast-enhanced MRI predicts late functional recovery after reperfused myocardial infarction.

BACKGROUND: We have observed 3 abnormal patterns on contrast-enhanced MRI early after reperfused myocardial infarction (MI): (1) absence of normal first-pass signal enhancement (HYPO), (2) normal first pass signal followed by hyperenhanced signal on delayed images (HYPER), or (3) both absence of normal first-pass enhancement and delayed hyperenhancement (COMB). This study examines the association between these patterns in the first week after MI and late recovery of myocardial contractile function by use of magnetic resonance myocardial tissue tagging. METHODS AND RESULTS: Seventeen patients (14 men) with a mean age of 53+/-12 years were studied after a reperfused first MI. Contrast-enhanced images were acquired immediately after bolus administration of gadolinium and 7+/-2 minutes later. Tagged images were acquired at weeks 1 and 7. Circumferential segment shortening (%S) was measured in regions displaying HYPER, COMB, or HYPO contrast patterns and in remote regions (REMOTE) at weeks 1 and 7. At week 1, %S was depressed in HYPER, COMB, and HYPO (9+/-8%, 7+/-6%, and 5+/-4%, respectively) and were less than REMOTE (18+/-6%, P<0.003). However, in HYPER, %S improved at week 7 from 9+/-8% to 18+/-5% (P<0.001 versus week 1). In contrast, HYPO did not improve significantly (5+/-4% to 6+/-3%, P=NS) and COMB tended to improve 7+/-6% to 11+/-6% (P=0.06). CONCLUSIONS: HYPER has partially reversible dysfunction and represents predominantly viable myocardium. COMB shows borderline improvement and likely contains an admixture of viable and necrotic myocardium. HYPO shows little functional improvement at 7 weeks, presumably because of irreversible myocardial damage.

Adult↗

PubMed1999

Sustained JNK activation induces endothelial apoptosis: studies with colchicine and shear stress.

The disruption of microtubules by treating bovine aortic endothelial cells with 10(-7)-10(-5) M colchicine caused apoptosis, as evidenced by DNA laddering and TdT-mediated dUTP nick end labeling fluorescence staining. Colchicine treatment also induced a sustained activation of c-Jun NH(2)-terminal kinase (JNK) that lasted for >/=12 h. The blockade of JNK activity by using the negative interfering mutant JNK(K-R) markedly decreased the apoptosis induced by colchicine. Exposure of bovine aortic endothelial cells to laminar shear stress (12 dyn/cm(2)) caused a transient (<2 h) activation of JNK, and there was no induction of apoptosis. The sustained activation of JNK may play a significant role in the apoptosis induced by colchicine.

Animals↗

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↗

PubMed1998

Quantitative assessment of myocardial viability after infarction by dobutamine magnetic resonance tagging.

BACKGROUND: The assessment of return of function within dysfunctional myocardium after acute myocardial infarction (MI) using contractile reserve has been primarily qualitative. Magnetic resonance (MR) myocardial tagging is a novel noninvasive method that measures intramyocardial function. We hypothesized that MR tagging could be used to quantify the intramyocardial response to low-dose dobutamine and relate this response to return of function in patients after first MI. METHODS AND RESULTS: Twenty patients with a first reperfused MI (age, 53+/-12 years; 16 male; 11 inferior MIs) were studied. Patients underwent breath-hold MR-tagged short-axis imaging on day 4+/-2 after MI at baseline and during dobutamine infusion at 5 and 10 microg x kg(-1) x min(-1). At 8+/-1 weeks after MI, patients returned for a follow-up MR tagging study without dobutamine. Quantification of percent intramyocardial circumferential segment shortening (%S) was performed. Low-dose dobutamine MRI was well tolerated. Overall, mean %S was 15+/-11% at baseline (n=227 segments), increased to 16+/-10% at 5 microg x kg(-1) x min(-1) dobutamine (P=NS), 21+/-10% at peak (P<0.0001 versus baseline and 5 microg x kg(-1) x min(-1), and 18+/-10% at 8 weeks (P<0.004 versus baseline and peak). The increase in %S with peak dobutamine was greater in dysfunctional myocardium (103 segments, +9+/-10%) than in normal tissue (124 segments, +4+/-12%, P<0.0001). In dysfunctional regions, %S also increased from 6+/-7% at baseline to 14+/-10% at 8 weeks after MI (P<0.0001). In dysfunctional regions that responded normally to peak dobutamine (> or =5% increase in %S), the increase in %S from baseline to 8 weeks after MI (+9+/-9%) was greater than in those regions that did not respond normally (+5+/-9%, P<0.04). Midmyocardial and subepicardial response to dobutamine were predictive of functional recovery, but the subendocardial response was not. CONCLUSIONS: The response of intramyocardial function to low-dose dobutamine after reperfused MI can be quantified with MR tagging. Dysfunctional tissue after MI demonstrates a larger contractile response to dobutamine than normal myocardium. A normal increase in shortening elicited by dobutamine within dysfunctional midwall and subepicardium predicts greater functional recovery at 8 weeks after MI, but the response within the subendocardium is not predictive.

Adult↗

PubMed1998

Analysis of the promoter of the luteinizing hormone/human chorionic gonadotropin receptor gene in neuroendocrine cells.

We investigated the molecular basis of luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptor gene transcription in immortalized alphaT3 gonadotropes, hypothalamic GT1-7 and hippocampal HN33p neurons. Nuclear run-on transcription, as well as transfection assays with fusion constructs of luciferase and the 5'-flanking region of LH/hCG receptor gene, revealed that GT1-7 neurons transcribe more than the alphaT3 or HN33p cells. Transient transfection of truncated reporter gene constructs and gel mobility shift assays revealed that while all neuroendocrine cells use the same promoter, they contain different levels of promoter binding proteins. Higher levels of these proteins may explain increased transcription of the LH/hCG receptor gene in GT1-7 neurons compared with alphaT3 and HN33p cells.

Animals↗

PubMed1998

Vessel boundary extraction based on a global and local deformable physical model with variable stiffness.

Reliable and efficient vessel cross-sectional boundary extraction is very important for many medical magnetic resonance (MR) image studies. General purpose edge detection algorithms often fail for medical MR images processing due to fuzzy boundaries, inconsistent image contrast, missing edge features, and the complicated background of MR images. In this regard, we present a vessel cross-sectional boundary extraction algorithm based on a global and local deformable model with variable stiffness. With the global model, the algorithm can handle relatively large vessel position shifts and size changes. The local deformation with variable stiffness parameters enable the model to stay right on edge points at the location where edge features are strong and at the same time, fit a smooth contour at the location where edge features are missing. Directional gradient information is used to help the model to pick correct edge segments. The algorithm was used to process MR cine phase-contrast images of the aorta from 20 volunteers (over 500 images) with excellent results.

Algorithms↗

PubMed1997

Fluid shear stress activation of focal adhesion kinase. Linking to mitogen-activated protein kinases.

Shear stress, the tangential component of hemodynamic forces, activates the extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) signal transduction pathways in cultured vascular endothelial cells to induce the transcriptional activation of many immediate early genes. It appears that integrins, protein-tyrosine kinases, and the structural integrity of actin are important factors involved in these shear stress-induced responses. The underlying molecular events were investigated by the application of a shear stress of 12 dyn/cm2 on bovine aortic endothelial cells (BAEC). We found that such a shear stress increased the tyrosine phosphorylation and the kinase activity of focal adhesion kinase (FAK) and its association with growth factor receptor binding protein 2 (Grb2) in a rapid and transient manner, suggesting that FAK may be linked to these mitogen-activated protein kinase signaling pathways through a Grb2. Son of sevenless (Sos) complex. FAK(F397Y), which encodes a dominant negative mutant of FAK, attenuated the shear stress-induced kinase activity of Myc epitope-tagged ERK2 and hemagglutinin epitope-tagged JNK1. DeltamSos1, encoding a dominant negative mutant of Sos in which the guanine nucleotide exchange domain has been deleted, also attenuated shear stress activation of Myc-ERK2 and hemagglutinin-JNK1. Pretreating the confluent BAEC monolayers with a blocking type anti-vitronectin receptor monoclonal antibody had similar inhibitory effects in these shear stress-activated ERKs and JNKs. Confocal microscopic observation further demonstrated that FAK tended to cluster with vitronectin receptor near the abluminal side of the sheared BAEC. These results demonstrate that FAK signaling is critical in the shear stress-induced dual activation of ERK and JNK.

Actins↗