Biomedical subjects

K L Davenpeck

Publications and source records attributed to K L Davenpeck.

14 recordsLinked to original sources

PubMed2001

Oxidative stress and lipid retention in vascular grafts: comparison between venous and arterial conduits.

BACKGROUND: Because saphenous vein grafts (SVGs) exhibit greater cellular heterogeneity and worse clinical outcomes than arterial grafts (AGs), we examined oxidative stress and lipid retention in different vascular conduits. METHODS AND RESULTS: In a porcine model of graft interposition into carotid artery, superoxide anion (.O(2)(-)) was measured at 2 weeks after surgery. SVGs demonstrated increased.O(2)(-) production compared with AGs (SOD-inhibitable nitro blue tetrazolium reduction, P<0.01). The NAD(P)H oxidase inhibitor diphenyleneiodonium (P<0.01) abolished SVG-derived.O(2)(-), whereas the inhibitors of other pro-oxidant enzymes were ineffective. The change in oxidative stress was also reflected by lower activity of the endogenous antioxidant superoxide dismutase in SVGs than in AGs (P<0.001). SVG remodeling was associated with increased synthesis of sulfated glycosaminoglycans and augmented expression of a core protein, versican. These changes were accompanied by SVGs retaining significantly more (125)I-labeled LDL than AGs ex vivo (P<0.001). In hyperlipemic animals, lipid accumulation and oxidized epitopes were preferentially noted in the intima of SVGs at 1 month after surgery. CONCLUSIONS: This study demonstrated significant differences in the biology of SVGs and AGS: SVGs exhibited higher oxidative stress, LDL accumulation, and the presence of oxidized epitopes. These findings suggest that proatherogenic changes in SVGs may commence early after surgical revascularization.

Animals↗

PubMed2001

Regional differences in integrin expression: role of alpha(5)beta(1) in regulating smooth muscle cell functions.

There is increasing evidence to suggest that coronary smooth muscle cells (SMCs) differ from noncoronary SMCs. As integrin adhesion molecules regulate many SMC functions, we hypothesized that differences in integrin expression on coronary and noncoronary SMCs may account for cellular differences. Analysis of integrin expression on freshly isolated porcine coronary and noncoronary SMCs revealed that coronary SMCs express significantly less alpha(5)beta(1) than noncoronary SMCs, whereas the expression of total beta(1) and that of alpha(v)beta(3) are similar. Consistent with these findings, coronary SMCs demonstrated significantly less adhesion to fibronectin, compared with carotid artery SMCs. As alpha(5)beta(1)-mediated signaling has been associated with cellular proliferation, the effects of differential alpha(5)beta(1) expression on cell proliferation were examined by comparing primary coronary and carotid artery SMC proliferation. Coronary SMC growth was significantly lower than that of carotid artery SMCs when plated on fibronectin or type I collagen. Blocking alpha(5)beta(1) function on carotid artery SMCs produced a significant decrease in cellular proliferation, resulting in growth similar to that of coronary SMCs. Furthermore, blocking alpha(5)beta(1), but not alpha(v)beta(3), inhibited loss of alpha-smooth muscle actin in proliferating SMCs. Proliferating coronary SMCs were found to upregulate alpha(5)beta(1) expression, further indicating a role for alpha(5)beta(1) in SMC growth. These results suggest that dissimilar alpha(5)beta(1) integrin expression may mediate regional differences in phenotype of vascular SMCs.

Animals↗

PubMed2001

Increased NAD(P)H oxidase and reactive oxygen species in coronary arteries after balloon injury.

Reactive oxygen species (ROS), produced by cellular constituents of the arterial wall, provide a signaling mechanism involved in vascular remodeling. Because adventitial fibroblasts are actively involved in coronary remodeling, we examined whether the changes in the redox state affect their phenotypic characteristics. To this end, superoxide anion production and NAD(P)H oxidase activity were measured in porcine coronary arteries in vivo, and the effect of ROS generation on adventitial fibroblast proliferation was examined in vitro. Superoxide production (SOD- and Tiron-inhibitable nitro blue tetrazolium [NBT] reduction) increased significantly within 24 hours after balloon-induced injury, with the product of NBT reduction present predominantly in adventitial fibroblasts. These changes were NAD(P)H oxidase-dependent, because diphenyleneiodonium (DPI) abolished superoxide generation (P<0.001). Furthermore, the injury-induced superoxide production was associated with augmented NAD(P)H oxidase activity and upregulation of p47(phox) and p67(phox) in adventitial fibroblasts (immunohistochemistry). Serum stimulation of isolated adventitial fibroblasts produced time-dependent increases in ROS production (peak 3 to 6 hours). The inhibition of ROS generation with NAD(P)H oxidase inhibitor (DPI) or the removal of ROS with antioxidants (Tiron, catalase) abrogated proliferation of adventitial fibroblasts. These results indicate that vascular NAD(P)H oxidase plays a central role in the upregulation of oxidative stress after coronary injury, providing pivotal growth signals for coronary fibroblasts.

Animals↗

PubMed2000

Activation of human leukocytes reduces surface P-selectin glycoprotein ligand-1 (PSGL-1, CD162) and adhesion to P-selectin in vitro.

P-selectin glycoprotein ligand-1 (PSGL-1), the primary ligand for P-selectin, is constitutively expressed on the surface of circulating leukocytes. The objective of this study was to examine the effect of leukocyte activation on PSGL-1 expression and PSGL-1-mediated leukocyte adhesion to P-selectin. PSGL-1 expression was examined via indirect immunofluorescence and flow cytometry before and after leukocyte stimulation with platelet activating factor (PAF) and PMA. Human neutrophils, monocytes, and eosinophils were all demonstrated to have significant surface expression of PSGL-1 at baseline, which decreased within minutes of exposure to PAF or PMA. PSGL-1 was detected in the supernatants of PAF-activated neutrophils by immunoprecipitation. Along with the expression data, this suggests removal of PSGL-1 from the cell surface. Soluble PSGL-1 was also detected in human bronchoalveolar lavage fluids. Down-regulation of PSGL-1 was inhibited by EDTA. However, inhibitors of L-selectin shedding and other sheddase inhibitors did not affect PSGL-1 release, suggesting that PSGL-1 may be shed by an as yet unidentified sheddase or removed by some other mechanism. Functionally, PSGL-1 down-regulation was associated with decreased neutrophil adhesion to immobilized P-selectin under both static and flow conditions, with the most profound effects seen under flow conditions. Together, these data indicate that PSGL-1 can be removed from the surface of activated leukocytes, and that this decrease in PSGL-1 expression has profound effects on leukocyte binding to P-selectin, especially under conditions of flow.

Allergens↗

PubMed2000

Inhibition of adhesion of human neutrophils and eosinophils to P-selectin by the sialyl Lewis antagonist TBC1269: preferential activity against neutrophil adhesion in vitro.

BACKGROUND: Leukocyte rolling on vascular endothelium is mediated by selectins and their carbohydrate-containing counterligands. The tetrasaccharide sialyl Lewis(x) (sLe(x)) binds to all 3 selectins, so compounds that mimic sLe(x) are potential antagonists. OBJECTIVE: Our purpose was to examine the ability of the sLe(x) mimetic TBC1269 to inhibit binding of human neutrophils and eosinophils to P-selectin. METHODS: Expression of the primary P-selectin ligand, P-selectin glycoprotein ligand-1 (PSGL-1), was examined on neutrophils and eosinophils, and their adhesion to immobilized P-selectin was examined under both static and dynamic conditions in the presence and absence of TBC1269. RESULTS: Neutrophils and eosinophils expressed PSGL-1, with eosinophils expressing about twice as much as neutrophils. In the absence of TBC1269, both cell types adhered avidly to P-selectin under static and dynamic conditions. For neutrophils, preincubation of P-selectin-coated plates with TBC1269 (1 to 1000 microgram/mL) resulted in concentration-dependent decreases in neutrophil adhesion, with significant inhibition seen at concentrations >/=100 microgram/mL. Eosinophil adhesion to P-selectin was more refractory to inhibition by TBC1269 and was only partially inhibited at the highest concentration tested (1000 microgram/mL). Two structurally related control compounds, TBC1900 and TBC746, had no effect when tested at similar concentrations. CONCLUSION: These data indicate that an sLe(x) mimetic can exhibit cell type-specific differences in potencies with respect to antagonism of P-selectin adhesion. Although this may in part be the result of differences in PSGL-1 expression, the discrepancy in potencies may also be due to other differences, including carbohydrate composition and binding affinity of PSGL-1.

Anti-Asthmatic Agents↗

PubMed1998

Lipopolysaccharide-induced leukocyte rolling and adhesion in the rat mesenteric microcirculation: regulation by glucocorticoids and role of cytokines.

A common side effect of high dose glucocorticoid therapy is increased susceptibility to bacterial infection, an effect that is in part mediated through inhibition of leukocyte recruitment to infected areas. However, the sites at which glucocorticoids act to prevent the multistep process of leukocyte recruitment have not been fully established. In this study, the effects of the glucocorticoid dexamethasone (DEX) on leukocyte-endothelial interactions, in response to bacterial LPS, were examined utilizing a model of rat mesenteric intravital microscopy. Pretreatment of rats with DEX (0.5 mg/kg) for 18 h or 30 min before stimulation with LPS significantly inhibited LPS-induced leukocyte rolling and adhesion in mesenteric postcapillary venules. Pretreatment with DEX also inhibited LPS-induced changes in expression of L-selectin and a shared epitope of CD11b/c on circulating neutrophils. These effects of DEX may be due to DEX inhibition of IL-1, TNF, and cytokine-induced neutrophil chemoattractant-1 (CINC-1) generation, since antagonists to these mediators were able to mimic DEX effects on leukocyte-endothelial interactions and circulating leukocyte phenotype. These data indicate that inhibition of cytokine- and chemokine-induced leukocyte-endothelial interactions may be a primary mechanism by which glucocorticoids inhibit leukocyte recruitment to bacterial agents and thus increase susceptibility to infection.

Animals↗

PubMed1998

Rat neutrophils express alpha4 and beta1 integrins and bind to vascular cell adhesion molecule-1 (VCAM-1) and mucosal addressin cell adhesion molecule-1 (MAdCAM-1).

The alpha4 integrins, which are constitutively expressed on all human leukocyte subtypes except neutrophils, interact with vascular cell adhesion molecule-1 (VCAM-1) and mucosal addressin cell adhesion molecule (MAdCAM-1) on endothelium to mediate selective recruitment of leukocyte subpopulations, other than neutrophils, to sites of inflammation. However, here we report that a different paradigm of leukocyte recruitment may exist in the rat. Flow cytometric analysis of rat neutrophils using a panel of monoclonal antibodies which recognize rat alpha4 and beta1 integrins showed consistent, low levels of expression. Although alpha4 was expressed at lower levels on neutrophils than all other rat leukocytes, this level of expression was sufficient to mediate significant levels of alpha4- and beta1-dependent neutrophil adhesion to rat and human VCAM-1, and alpha4-dependent, but beta1-independent, adhesion to human MAdCAM-1. These data suggest that rat neutrophils, unlike other species, may use alpha4 integrins to traffic to sites of inflammation in vivo.

Animals↗

PubMed1997

P- and L-selectin mediate distinct but overlapping functions in endotoxin-induced leukocyte-endothelial interactions in the rat mesenteric microcirculation.

Endotoxin is a potent stimulus of leukocyte infiltration, but the adhesion-related mechanisms responsible for LPS-induced cell recruitment events in vivo remain poorly characterized. Utilizing intravital microscopy, we examined the role of P- and L-selectin in LPS-induced inflammation. We demonstrated that superfusion of rat mesentery with LPS resulted in significant increases in both leukocyte rolling and adherence, which were maintained for at least 2 h. Pretreatment with a P-selectin neutralizing mAb only partially inhibited LPS-induced leukocyte rolling, but completely inhibited LPS-induced leukocyte adherence throughout the 2-h observation period. Pretreatment with an L-selectin neutralizing mAb dramatically inhibited LPS-induced increases in leukocyte rolling, but unlike the P-selectin mAb did not inhibit leukocyte adhesion. Fucoidin, which blocks both P- and L-selectin function, completely inhibited LPS-induced leukocyte rolling and adhesion. Consistent with previous studies, leukocyte rolling velocities on P-selectin were observed to be far less than velocities observed for leukocytes rolling on L-selectin in vivo. These data suggest that P-selectin plays a role in LPS-induced rolling and is essential for LPS-induced leukocyte adherence, while L-selectin functions in LPS-induced rolling, but not in adhesion.

Animals↗

PubMed1995

Carboxyfluorescein diacetate labeling does not affect adhesion molecule expression or function in human neutrophils or eosinophils.

Fluorescently labeled leukocytes are commonly used in in vitro and in vivo experimental systems. However, the effects of fluorescent labeling on the expression and function of leukocyte adhesion molecules has not been examined in part because the extreme intensity of fluorescence tends to obscure signals from other fluorochromes used for dual color analysis. We have utilized a novel technique involving a 7-amino-4-methylcoumarin-3-acetic acid (AMCA) fluorophore-conjugated F(ab')2 fragment excitable in the ultraviolet wavelength range (350-450 nm) and dual-laser flow cytometry to determine if labeling of human neutrophils and eosinophils with the fluorescent dye 5-(6)-carboxyfluorescein diacetate (CFDA) alters surface expression of the primary leukocyte adhesion molecules involved in leukocyte-endothelial interactions. Simultaneously, adhesion molecule function was assessed by comparing the ability of CFDA-labeled vs. control cells to adhere to cultured human umbilical vein endothelial cells (HUVEC) and purified immobilized adhesion molecules. Isolated human eosinophils and neutrophils were fluorescently labeled by incubation with CFDA. Flow cytometric comparisons of labeled and unlabeled cells demonstrated that fluorescence labeling of neutrophils and eosinophils with CFDA did not alter basal surface expression of the beta 2 integrins (i.e., CD11a CD11b or, CD18). Stimulation of neutrophils with fMLP and eosinophils with PMA resulted in increased surface expression of CD11b and CD18 which was not altered by CFDA labeling. Likewise, CFDA labeling of neutrophils and eosinophils did not significantly alter their integrin-dependent adhesion to activated HUVEC under static or rotational conditions. Similarly, adhesion to immobilized recombinant E- and P-selectin was unaltered. These data demonstrate that fluorescent labeling of human neutrophils and eosinophils with CFDA does not alter surface expression or function of several adhesion molecules necessary for leukocyte-endothelial interactions. The use of CFDA-labeled cells in experiments employing intravital microscopy should therefore provide valid information on adhesion molecule function in vivo.

Cell Adhesion↗

PubMed1995

Desmopressin induces endothelial P-selectin expression and leukocyte rolling in postcapillary venules.

Desmopressin, (DDAVP; 1-desamino-8-D-arginine vasopressin) increases the release and activity of von Willebrand factor (vWF); however, its effects on the other major constituent of endothelial Weibel-Palade bodies, P-selectin, has not been investigated. DDAVP-induced P-selectin expression may explain DDAVP's efficacy in bleeding disorders in which vWF levels are normal. Therefore, the objective of this study is to assess the effect of DDAVP on P-selectin expression on endothelial cells of postcapillary venules in vivo and on human umbilical vein endothelium in vitro, and to determine whether DDAVP has direct effects on leukocyte behavior in postcapillary venules. DDAVP (0.1 and 1.0 microgram/mL) induced a significant but transient increase in P-selectin expression on human umbilical vein endothelial cells as well as on rat and human platelets. Immunohistochemical analysis of rat postcapillary venules showed that in contrast to saline, DDAVP injection (1 microgram/kg, intravenous) induced significant endothelial P-selectin expression. DDAVP administration also induced a rapid and significant increase in leukocyte rolling in rat mesenteric venules in vivo. This response was entirely dependent on P-selectin, as an anti-P-selectin antibody rapidly reversed the DDAVP-induced increase in leukocyte rolling. DDAVP induced leukocyte rolling in medium (20 to 40 microns) and large (> 40 microns), but not small (< 20 microns), postcapillary venules. In animals that were treated with DDAVP, there was a steady and significant increase in leukocyte adhesion. This study shows that DDAVP can directly induce P-selectin expression on endothelium in vitro and in vivo and that the latter response is capable of supporting prolonged leukocyte rolling in rat postcapillary venules.

Animals↗

PubMed1994

Inhibition of endothelial-derived nitric oxide promotes P-selectin expression and actions in the rat microcirculation.

BACKGROUND/AIMS: Inhibition of nitric oxide synthesis increases leukocyte and endothelial interaction in mesenteric venules. In this study, the relationship between inhibition of NO and expression of the adhesion molecule P-selectin was examined. METHODS: The rat mesentery was superfused with the NO inhibitor NG-nitro-L-arginine methyl ester (L-NAME) either alone or in combination with intravenous infusions of L-arginine, D-arginine, a P-selectin-neutralizing monoclonal antibody (PB1.3 [1 mg/kg]), recombinant human superoxide dismutase (hSOD), or 8 bromoguanosine 3',5'-cyclic monophosphate (8-br-cGMP). Leukocyte rolling and adherence were monitored in mesenteric venules via intravital microscopy. Ileal tissue superfused with L-NAME was examined immunohistochemically for P-selectin expression. RESULTS: Superfusion of the rat mesentery with L-NAME resulted in a significant increase in leukocyte rolling and adherence in the mesenteric venule, which was attenuated by administration of L-arginine but not D-arginine. Monoclonal antibody PB1.3 as well as hSOD and 8-br-cGMP administered before initiation of L-NAME superfusion significantly attenuated the increase in leukocyte rolling and adherence. Immunohistochemistry showed a significant increase in P-selectin expression after 60 minutes of superfusion with L-NAME, which was attenuated by L-arginine, hSOD, and 8-br-cGMP. CONCLUSIONS: These data indicate an important functional relationship between endothelial-derived NO production and expression of the endothelial adhesion molecule P-selectin.

Animals↗

PubMed1994

Nitric oxide attenuates leukocyte-endothelial interaction via P-selectin in splanchnic ischemia-reperfusion.

We studied the effects of exogenous nitric oxide (NO) on leukocyte-endothelial interaction after 60 min of splanchnic artery ischemia and 120 min of reperfusion (SAO/R) in pentobarbital sodium-anesthetized rats via intravital microscopy. Treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP, 20 micrograms/kg bolus followed by infusion at 20 micrograms.kg-1.h-1), beginning 10 min before reperfusion, resulted in significantly decreased leukocyte-endothelial interaction. This was manifested by a significant decrease in leukocyte rolling and adherence in the postcapillary venules. Tissue protection was demonstrated by a significantly lower plasma free amino-nitrogen concentration in the SNAP-treated SAO/R rats compared with those receiving NO-depleted SNAP (P < 0.05). Immunohistochemical localization of P-selectin showed significantly decreased P-selectin expression on the venular endothelium after SAO/R in rats given SNAP 10 min before reperfusion (23.0 +/- 3.2% vs. 54.9 +/- 12.1% positive staining, respectively, P < 0.01). From these data, we conclude that the effects of exogenous NO on leukocyte-endothelial interaction after ischemia-reperfusion appear to be at least partially mediated through the endothelial adhesion molecule P-selectin.

Animals↗

PubMed1994

Role of P-selectin in microvascular leukocyte-endothelial interaction in splanchnic ischemia-reperfusion.

The role of P-selectin in leukocyte-endothelial interaction after splanchnic arterial occlusion and reperfusion (SAO/R) in pentobarbital-anesthetized rats was investigated employing a P-selectin-neutralizing monoclonal antibody (i.e., MAb PB1.3). MAb PB1.3 (1 mg/kg) given intravenously to SAO/R rats just before reperfusion significantly attenuated leukocyte rolling and adherence in mesenteric postcapillary venules as observed via intravital microscopy. Likewise, ileal myeloperoxidase (MPO) activity was decreased from 4.6 +/- 0.6 in nontreated ischemic rats to 2.0 +/- 0.2 U/100 mg (P < 0.01), indicating a lesser degree of polymorphonuclear leukocyte (PMN) accumulation. A significantly lower plasma free amino-nitrogen concentration was observed in MAb PB1.3-treated rats vs. untreated (P < 0.01), suggesting decreased tissue injury after reperfusion. Immunohistochemical localization demonstrated significant expression of P-selectin in endothelial cells lining ileal postcapillary venules 30 min after reperfusion of the ischemic splanchnic circulation. Thus P-selectin appears to plays an important role in leukocyte accumulation after splanchnic ischemia-reperfusion, and the MAb PB1.3 attenuates the accumulation of PMNs in the ischemic-reperfused small bowel, resulting in reduced tissue injury.

Animals↗

PubMedDate not supplied

Pulmonary artery endothelial dysfunction following ischemia and reperfusion of the rabbit lung.

We studied endothelial dysfunction of the rabbit pulmonary artery following in vivo ischemia and reperfusion of the lung, and also investigated the mechanisms of endothelium-dependent relaxation in these arteries. Intrapulmonary arteries were isolated from rabbits subjected to ischemia and reperfusion of one lung. Percent relaxation values of sham-operated (i.e. nonischemic) pulmonary arteries to endothelium-dependent vasodilators acetylcholine (ACh) and A23187 were 72 +/- 4 and 65 +/- 4%, respectively, while relaxation to the endothelium-independent dilator NaNO2 was 97 +/- 1%. The relaxation of control artery rings to ACh and A23187 were significantly decreased to 2 +/- 1 and 5 +/- 4%, respectively, following addition of N omega-nitro-L-arginine methyl ester, while relaxation following treatment with indomethacin or glybenclamide remained normal. Relaxation to NaNO2 was not altered by pretreatment with any of the above compounds. Thus, pulmonary artery relaxation to the endothelium-dependent dilators ACh and A23187 appears to be mediated by the release of EDRF. Endothelium-dependent relaxation of pulmonary arteries from lungs exposed to 90 min of ischemia and 30 min of reperfusion remained essentially normal, while 90 min of ischemia followed by 60 min of reperfusion resulted in a significant decrease in endothelium-dependent relaxation to A23187 to 37 +/- 7% (p < 0.05), whereas the response to ACh was reduced only to 57 +/- 3% (not significant). 90 min of ischemia followed by 90 min of reperfusion resulted in significant attenuation of endothelium-dependent relaxation to both ACh (36 +/- 4%) and A23187 (33 +/- 7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗