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D O Haskard

Publications and source records attributed to D O Haskard.

At least 37 records · Page 2Linked to original sources
PubMed2001

Pathogenesis of crystal-induced inflammation.

Crystals are an important cause of inflammatory rheumatic diseases and provide relatively simple paradigms for modelling inflammatory responses in general. Thus, in the case of gout, we know that hyperuricemia leads to precipitation of monosodium urate (MSU) crystals in joints, which are taken up by leukocytes, and then an acute attack of arthritis is triggered. However, fundamental questions remain unanswered. Why are only certain hyperuricemic individuals, and then only certain joints, affected? What factors maintain joints in a quiescent state, what prompts the resolution of an inflammatory attack, and are these related? This article draws on developments during the past year to support the idea that the mononuclear phagocyte may play a key role within the synovial compartment, tipping the balance from the asymptomatic state to acute inflammation, or vice versa, depending on their state of monocyte to macrophage differentiation.

Arthritis↗
PubMed2001

The antithrombotic and antiinflammatory mechanisms of action of aprotinin.

Aprotinin (Trasylol) is generally regarded to be an effective hemostatic agent that prevents blood loss and preserves platelet function during cardiac surgery procedures requiring cardiopulmonary bypass (CBP). However, its clinical use has been limited by the concern that such a potent hemostatic agent might be prothrombotic, particularly in relation to coronary vein graft occlusion. In this review we present a mechanism of action that challenges such a viewpoint and explains how aprotinin can be simultaneously hemostatic and antithrombotic. Aprotinin achieves these two apparently disparate properties by selectively blocking the proteolytically activated thrombin receptor on platelets, the protease-activated receptor 1 (PAR1), while leaving other mechanisms of platelet aggregation unaffected. We also review recent research leading to the discovery of novel antiinflammatory targets for aprotinin. A better understanding of its mechanisms of action has led to the conclusion that aprotinin is a remarkable drug with the capacity to correct many of the imbalances that develop in the coagulation system and the inflammatory system after CPB. Nonetheless, it has been clinically underused for fear of causing thrombotic complications, a fear that in light of recent evidence may be unfounded.

Animals↗
PubMed2001

New antiinflammatory and platelet-preserving effects of aprotinin.

The clinical benefit of aprotinin with respect to improved hemostasis, platelet function, and inflammatory response to cardiopulmonary bypass (CPB) surgery has been well documented, but these benefits have been overshadowed by the concern that such a potently hemostatic agent might also be prothrombotic. In this article, we discuss recent advances in the understanding of the basic mechanism of aprotinin that have led to the identification of new antiinflammatory targets and the discovery that aprotinin is, in fact, antithrombotic with respect to platelets. Its antithrombotic action is mediated by the selective blocking of the major thrombin receptor, the protease-activated receptor 1 (PAR1), but not other receptors of platelet activation (ie, collagen, adenosine diphosphate [ADP], or epinephrine receptors). The selective targeting of PAR1 enables aprotinin to protect platelets from unwanted activation by thrombin generated during CPB surgery (consistent with a role in platelet-preservation), while permitting the participation of platelets in the formation of hemostatic plugs at wound and suture sites, where collagen, ADP, and epinephrine are most likely to be expressed. Aprotinin therefore exerts a subtle hemostatic yet antithrombotic mechanism of action, which, when allied with its multitiered antiinflammatory effect, makes this drug a valuable companion to cardiac surgery.

Anti-Inflammatory Agents↗
PubMed2001

Vascular endothelial function and oxidative stress mechanisms in patients with Behçet's syndrome.

OBJECTIVES: We sought to test the hypothesis that vascular endothelial function is impaired in Behçet's syndrome and reflects increased levels of oxidative stress. BACKGROUND: Behçet's syndrome is a multisystem inflammatory disorder commonly complicated by vascular thrombosis and arterial aneurysm formation. The precise mechanisms underlying vascular disease in Behçet's syndrome are not known. METHODS: We studied 19 patients with Behçet's syndrome (18 to 50 years old, 9 men) and 21 healthy volunteers (18 to 50 years old, 10 men). Brachial artery flow-mediated dilation (endothelium-dependent), and nitroglycerin (NTG)-induced dilation (endothelium-independent) were measured. To investigate oxidative stress mechanisms, vascular studies were repeated 1 h after administration of vitamin C (1 g, intravenous) in 12 patients and 12 control subjects. RESULTS: Flow-mediated dilation was reduced in patients with Behcet's syndrome as compared with control subjects (0.7 +/- 0.9% vs. 5.7 +/- 0.9%, p = 0.001). In contrast, there were no significant differences in the brachial artery diameter (4.2 +/- 0.2 vs. 4.0 +/- 0.2 mm, p = 0.47) or NTG-induced dilation (19.7 +/- 1.9% vs. 19.7 +/- 1.2%, p = 0.98). In regression analysis, Behçet's syndrome was associated with impaired flow-mediated dilation independent of age, gender, brachial artery diameter, blood pressure, cholesterol and glucose. Vitamin C increased flow-mediated dilation in Behçet's syndrome (0.2 +/- 0.7% to 3.5 +/- 1.0%, p = 0.002), but not in control subjects (4.3 +/- 0.6% to 4.7 +/- 0.4%, p = 0.51). In both groups, NTG-induced dilation and brachial artery diameter were unchanged after vitamin C treatment. CONCLUSIONS: Vascular endothelial function is impaired in Behcet's syndrome and can be rapidly improved by vitamin C treatment. Our results support a role for oxidative stress in the pathophysiology of Behçet's syndrome and provide a rationale for therapeutic studies aimed at reducing vascular complications in this disorder.

Adolescent↗
PubMed2001

Effect of aprotinin on endothelial cell activation.

BACKGROUND: Cardiopulmonary bypass surgery is often accompanied by a systemic inflammatory response, which can lead to postoperative complications in high-risk patients. This is mediated in part through a systemic rise in inflammatory cytokine levels and the sequestration of leukocytes within organs. Aprotinin has previously been shown to exert an anti-inflammatory effect by preventing the capacity of leukocytes to transmigrate through vascular endothelium. Here we have focused on whether aprotinin has an effect on endothelial cell activation and adhesion molecule expression in response to tumor necrosis factor-alpha, particularly with reference to whether aprotinin inhibits tumor necrosis factor-stimulated neutrophil transendothelial migration. METHODS AND RESULTS: Intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin expression was studied in tumor necrosis factor-alpha-activated human umbilical vein endothelial cells in the presence of aprotinin at 200, 800, and 1600 kIU/mL. Aprotinin inhibited tumor necrosis factor-alpha-stimulated expression of intercellular adhesion molecule-1 (P =.019 at 1600 kIU/mL) and vascular cell adhesion molecule-1 (P =.003 at 1600 kIU/mL) but not E-selectin. Similar results were obtained in the dermal microvascular endothelial cell line, HMEC-1, which exhibited diminished intercellular adhesion molecule-1 expression in the presence of aprotinin (P =.040 at 800 kIU/mL and P <.001 at 1600 kIU/mL). Aprotinin also significantly inhibited neutrophil transmigration across tumor necrosis factor-alpha-activated human umbilical vein endothelial cells (P =.046 at 1600 kIU/mL). CONCLUSIONS: We have demonstrated that aprotinin inhibits intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, but not E-selectin, expression on tumor necrosis factor-alpha-activated endothelial cells and that transendothelial migration by neutrophils is also specifically suppressed under these conditions. Our results indicate that endothelial cells can be specifically targeted by aprotinin, therefore adding to our understanding of the anti-inflammatory mechanism of action of aprotinin during cardiopulmonary bypass.

Aprotinin↗
PubMed2001

Limited endothelial E- and P-selectin expression in MRL/lpr lupus-prone mice.

OBJECTIVE: Inflammation in MRL/lpr mice may involve dysfunctional leucocyte-endothelial cell (EC) interactions. Previously, we have shown that intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) increase with age in a tumour necrosis factor alpha (TNF alpha)- and interleukin-1 (IL-1)-dependent manner. The object of this study was to determine the expression of E- and P-selectin. METHODS: Selectin expression was quantified in MRL/lpr mice and BALB/c controls by intravenous injection of differentially radio-labelled antibodies. RESULTS: E-selectin, but not P-selectin, was up-regulated in the kidneys of older mice. Neither was up-regulated elsewhere. There was no defect in selectin inducibility, as a further inflammatory stimulus (intraperitoneal lipopolysaccharide) resulted in up-regulation. Serum from older MRL/lpr did not induce selectin expression by EC in vitro. CONCLUSION: The increase in E-selectin in the kidney may contribute to the development of glomerulonephritis. However, the lack of systemic E- and P-selectin expression may represent a protective mechanism which limits the interaction between leucocytes and the endothelium in the chronic inflammatory context.

Animals↗
PubMed2001

Labyrinthine involvement in Behçet's syndrome.

We report the neuro-otological findings in 26 consecutive patients with definite and probable Behçet's syndrome unselected for audiovestibular complaints. Auditory and/or vestibular abnormalities were found in 19 (73 per cent) patients, with auditory involvement in 14 (54 per cent) and vestibular in 10 (38.5 per cent) of patients. Peripheral involvement was more common than central involvement for both auditory and vestibular lesions. Bilateral cochlear hearing impairment was the most common audiological finding, whereas unilateral peripheral dysfunction was the prevailing vestibular abnormality. No correlation has been found between audiovestibular lesions and other organ lesions, disease duration or age or sex of the patients. Moreover, there was a lack of interdependence between cochlear and vestibular labyrinthine lesions. We conclude that a full neuro-otological assessment in patients under investigation for Behçet's syndrome may reveal labyrinth involvement in a substantial proportion of patients. In view of the absence of a specific diagnostic test for Behçet's syndrome, audiovestibular lesions may provide further diagnostic support for this disorder.

Adult↗
PubMed2001

Potential new therapeutic options in Behçet's syndrome.

Behçet's syndrome is a multisystem disorder that causes orogenital ulceration, skin lesions and intraocular inflammation with uveitis and retinal vasculitis. A proportion of affected individuals also develop vascular and central nervous system manifestations, with significant morbidity and mortality. Although the aetiopathogenesis of Behçet's syndrome is poorly understood, the condition is considered to be driven, at least in part, by autoimmune mechanisms. Conventional therapy relies on available anti-inflammatory and immunomodulatory agents, and, in view of the paucity of controlled clinical trials, it is to a large extent empirical. Oral ulcers can often be treated by topical application of corticosteroids. In addition to corticosteroids, agents used to treat ocular inflammation and significant systemic manifestations include colchicine, thalidomide, azathioprine, mycophenolate mofetil, cyclosporin, tacrolimus, cyclophosphamide and chlorambucil. The response to these agents is variable and there is a distinct need for more effective rational treatment. Over the last decade, a number of open studies have produced promising results using recombinant interferon-alpha preparations. Evaluating, in a methodical manner, the other new biological agents that are becoming available for the treatment of inflammatory diseases offers great promise, not only for effective management but also for providing insights into aetiopathogenesis.

Anti-Inflammatory Agents↗
PubMed2001

Effect of aprotinin (trasylol) on the inflammatory and thrombotic complications of conventional cardiopulmonary bypass surgery.

Before the discovery of its hemostatic properties, aprotinin was thought of as a potential anti-inflammatory agent. Its clinical introduction in 1987 to prevent blood loss during cardiac surgery [Royston 1987, van Oeveren 1987] led to its anti-inflammatory benefits being largely overlooked in favor of a vigorous debate centering on whether aprotinin may be pro-thrombotic when given to patients. In this article, we summarize evidence for the anti-inflammatory activity of aprotinin and discuss our recent contributions in this area. We also summarize the state of the thrombosis debate and discuss our recent evidence from purified platelets which shows that aprotinin is simultaneously hemostatic yet anti-thrombotic.

Animals↗
PubMed2000

VCAM-1 has a tissue-specific role in mediating interleukin-4-induced eosinophil accumulation in rat models: evidence for a dissociation between endothelial-cell VCAM-1 expression and a functional role in eosinophil migration.

Eosinophil accumulation has been associated with the pathogenesis of numerous allergic inflammatory disorders. Despite the great interest in this response, many aspects of eosinophil accumulation remain unknown. This is particularly true with respect to tissue-specific mechanisms that may regulate the accumulation of eosinophils in different organs. This study addressed this issue by investigating and comparing the roles of alpha(4)-integrins and vascular cell adhesion molecule 1 (VCAM-1) adhesion pathways in interleukin 4 (IL-4)-induced eosinophil accumulation in 2 different rat models of inflammation, namely pleural and cutaneous inflammation. Similar to our previous findings in studies in rat skin, locally administered IL-4 induced a time- and dose-dependent accumulation of eosinophils in rat pleural cavities, a response that was associated with generation of the chemokine eotaxin. The IL-4-induced eosinophil accumulation in skin and pleural cavities was totally inhibited by an antirat alpha(4)-integrins monoclonal antibody (mAb) (TA-2). In contrast, whereas an antirat VCAM-1 mAb (5F10) totally blocked the response in skin, IL-4-induced eosinophil accumulation in rat pleural cavities was not affected by VCAM-1 blockade. A radiolabeled mAb technique demonstrated that endothelial-cell VCAM-1 expression was induced in response to IL-4 in both skin and pleural membrane. The results indicate that although endothelial-cell VCAM-1 is present in skin and pleura, a functional role for it in IL-4-induced eosinophil accumulation was evident only in skin. These findings suggest the existence of tissue-specific adhesive mechanisms in regulating leukocyte migration in vivo and demonstrate a dissociation between VCAM-1 expression and eosinophil accumulation.

Animals↗
PubMed2000

Induction of decay-accelerating factor by thrombin through a protease-activated receptor 1 and protein kinase C-dependent pathway protects vascular endothelial cells from complement-mediated injury.

There is increasing evidence for functional crosstalk between inflammatory and thrombotic pathways in inflammatory vascular diseases such as atherosclerosis and vasculitis. Thus, complement activation on the endothelial cell (EC) surface during inflammation may generate thrombin via the synthesis of tissue factor. We explored the hypothesis that thrombin induces EC expression of the complement-regulatory proteins decay-accelerating factor (DAF), membrane cofactor protein (MCP), and CD59 and that this maintains vascular integrity during coagulation associated with complement activation. Thrombin increased DAF expression on the surface of ECs by 4-fold in a dose- and time-dependent manner as measured by flow cytometry. DAF up-regulation was first detectable at 6 hours and maximal 24 hours poststimulation, whereas no up-regulation of CD59 or MCP was seen. Thrombin-induced expression required increased DAF messenger RNA and de novo protein synthesis. The response depended on activation of protease-activated receptor 1 (PAR1) and was inhibited by pharmacologic antagonists of protein kinase C (PKC), p38 and p42/44 mitogen-activated protein kinase, and nuclear factor-kappa B. The increased DAF expression was functionally relevant because it significantly reduced C3 deposition and complement-mediated EC lysis. Thus, thrombin-generated at inflammatory sites in response to complement activation-is a physiologic agonist for the PKC-dependent pathway of DAF regulation, thereby providing a negative feedback loop protecting against thrombosis in inflammation. (Blood. 2000;96:2784-2792)

CD55 Antigens↗
PubMed2000

Cloning of porcine intercellular adhesion molecule-1 and characterization of its induction on endothelial cells by cytokines.

BACKGROUND: The transplantation of pig organs into humans requires a detailed knowledge of similarities and differences between the two species in the molecular physiology of host defense mechanisms. We therefore set out to identify porcine intercellular adhesion molecule (ICAM)-1 and to characterize its expression by endothelial cells. METHODS: Porcine ICAM-1 cDNA was isolated from an endothelial cell cDNA library. An anti-pig ICAM-1 monoclonal antibody was generated and used to investigate the regulation by cytokines of ICAM-1 expression by porcine aortic endothelial cells (PAEC), using flow cytometry. RESULTS: We found that porcine ICAM-1 was similar in primary structure to human ICAM-1, with five Ig-like domains. COS-7 cells transfected with porcine ICAM-1 supported beta2 but not alpha4 integrin-dependent adhesion of human T lymphoblasts. There was a low-level surface expression of ICAM-1 on unstimulated PAEC and increased expression after stimulation with tumor necrosis factor (TNF)-alpha. However expression of ICAM-1 seemed to be significantly lower than that of vascular cell adhesion molecule-1, both on unstimulated and TNF-alpha-activated PAEC. Recombinant porcine interferon-gamma weakly stimulated ICAM-1 expression when incubated alone with PAEC but had an inhibitory effect on the increase in ICAM-1 due to TNF-alpha, both at 8 and 24 hr. CONCLUSIONS: Our observations confirm the existence of ICAM-1 in the pig and provide novel insights into how porcine and human endothelial cells differ in terms of adhesion molecule expression and cytokine responsiveness. Such differences are potentially important in interpreting models of inflammation in the pig and also in understanding the process of rejection of porcine xenografts.

Amino Acid Sequence↗
PubMed2000

TNF-alpha, IL-4, and IFN-gamma regulate differential expression of P- and E-selectin expression by porcine aortic endothelial cells.

P- and E-selectin are surface glycoproteins that mediate leukocyte rolling on the surface of endothelium in inflammation. We have cloned porcine P-selectin cDNA and generated a mAb, 12C5, with which to examine P-selectin expression by porcine aortic endothelial cells (PAEC) in comparison with that of E-selectin. Basal expression by PAEC of P-selectin was greater than that of E-selectin, whereas E-selectin expression was more prominently enhanced than that of P-selectin by stimulation with TNF-alpha or IL-1alpha. Both human or porcine IL-4 led to an increase in P-selectin expression, with kinetics that were delayed compared with those seen following stimulation with TNF-alpha or IL-1alpha, but IL-4 did not stimulate expression of E-selectin. When cells were stimulated with TNF-alpha in the presence of IL-4, we observed enhanced P-selectin expression with a parallel reduction in E-selectin expression. Finally, the increase in P-selectin expression due to human IL-4 was reduced in the presence of porcine but not human IFN-gamma. These observations show that E-selectin and P-selectin expression are differentially regulated in PAEC, and that IL-4 leads to a shift in the relative surface density of the two molecules toward P-selectin. The ability of porcine IFN-gamma to inhibit IL-4-induced P-selectin expression suggests that the balance between Th1 and Th2 cytokine production may determine the relative densities of the two selectins in chronic immune-mediated inflammation. Because the increased expression of P-selectin induced by human IL-4 was not inhibited by human IFN-gamma, this balance may be shifted toward P-selectin expression in porcine xenografts infiltrated by human lymphocytes.

Amino Acid Sequence↗
PubMed2000

Noninflammatory phagocytosis of monosodium urate monohydrate crystals by mouse macrophages. Implications for the control of joint inflammation in gout.

OBJECTIVE: We have hypothesized that the process of monocyte to macrophage differentiation may alter the inflammatory response of mononuclear phagocytes to the uptake of monosodium urate monohydrate (MSU) crystals. METHODS: Eight mouse monocyte/macrophage cell lines were arranged in increasing order of differentiation, as judged by expression of the macrophage markers F4/80 and BM 8 and by phagocytic capacity. Secretion of tumor necrosis factor alpha (TNFalpha) in response to MSU was measured by enzyme-linked immunosorbent assay. RESULTS: The panel of monocyte/macrophage cell lines revealed a close linkage between the state of differentiation and the capacity of the cells to ingest MSU crystals. TNFalpha production, however, was not linked to phagocytic ability. Peak TNFalpha levels were synthesized by cells at an intermediate state of differentiation (3.2-14.1 ng/ml), whereas mature macrophages, which efficiently phagocytosed crystals, did not secrete TNFalpha. Mature cell lines produced TNFalpha when stimulated with zymosan (5.9-6.2 ng/ml), but this was abolished by coincubation with MSU crystals. Suppression of the zymosan response was not due to apoptosis or steric hindrance by MSU crystals. Culture supernatants from mature macrophages did not stimulate endothelial cell activation, in contrast to MSU-treated cells at an earlier stage of differentiation, which stimulated intercellular adhesion molecule 1 expression on sEND endothelioma cells through the release of TNFalpha (inhibited 80.6% by anti-TNFa). CONCLUSION: We demonstrated that phagocytosis and TNFalpha production are distinct events in the response of mononuclear phagocytes to urate crystals, and these events can be distinguished at the level of macrophage differentiation. The noninflammatory removal of urate crystals by mature macrophages defines a new pathway that may be important in controlling the development of acute gout in patients with hyperuricemia.

Animals↗
PubMed2000

Leukocyte integrin expression in patients undergoing cardiopulmonary bypass.

BACKGROUND: The recruitment of leukocytes to vascular endothelium is controlled by adhesion events mediated through the beta2 integrins, whereas the response of extravasated leukocytes within the tissues is controlled through the beta1 integrins. Although cardiopulmonary bypass (CPB) has been shown to be associated with a systemic inflammatory response and elevated levels of beta2 integrins on leukocytes, its effect on the beta1 integrins is not known. This study investigated the effect of the protease inhibitor aprotinin on the expression of the beta1 and beta2 integrins on circulating leukocytes in patients undergoing CPB. METHODS: Patients undergoing primary elective coronary artery bypass grafting were randomized into full-dose aprotinin or placebo groups. Blood samples were obtained at nine time points preoperatively, intraoperatively, and up to 6 days postoperatively. The surface expression of the beta1 integrins VLA-1, -3, -4, -5, and -6 and of the beta2 integrins CD11a/CD18, CD11b/CD18, and CD11c/CD18 was measured by flow cytometry on gated neutrophil and monocyte subpopulations in whole blood. RESULTS: Expression of the beta1 integrins was not significantly altered during the study period and, therefore, aprotinin had no effect on the expression of these molecules. Of the beta2 integrins, CD11b/CD18 expression was significantly increased on neutrophils at 15 minutes after onset of CPB in the placebo group (p < 0.01) but not in the aprotinin group. CONCLUSIONS: This study showed that expression of the beta1 integrins on neutrophils and monocytes did not alter during the first 6 days after CPB. Expression of the beta2 integrin CD11b/CD18 increased significantly on neutrophils during CPB in control patients but not in patients treated with full-dose aprotinin.

Aprotinin↗
PubMed2000

Tumour necrosis factor-alpha (TNF-alpha) enhances lymphocyte migration into rheumatoid synovial tissue transplanted into severe combined immunodeficient (SCID) mice.

Adhesion mechanisms play a major role in the recruitment of peripheral blood lymphocytes (PBL) which characteristically infiltrate rheumatoid arthritis (RA) synovium and other chronically inflamed tissues. Through a sequential series of complex integrated adhesion and signalling events, 'multistep model of migration', specific subsets of PBL are recruited into inflamed tissues. In this process both leucocyte receptors and microvascular endothelial (MVE) counter-receptors play a critical role. The MVE in particular, during an inflammatory state, is the target of various inflammatory mediators that cause the up-regulation of several cell adhesion molecules (CAM). One of the most important factors known to be a powerful inducer of MVE CAM is TNF-alpha. Conversely, blocking TNF-alpha causes a down-modulation of CAM expression. To test directly the capacity of TNF-alpha to induce cell migration into RA synovium we adapted a model in which synovial grafts were implanted into SCID mice subcutaneously. Using this model we demonstrate that: (i) transplants remain viable and become vascularized and fed by mouse subdermal vessels; (ii) the mouse vasculature connects to the transplant vasculature which maintains the ability to express human CAM; (iii) intragraft injections of TNF-alpha up-regulate the expression of human CAM, following the down-regulation which occurred 4 weeks post-transplantation; and (iv) the up-regulation of graft CAM is associated with increased human PBL migration into the transplants. This study provides direct evidence in vivo of the capacity of TNF-alpha to induce cell migration. In addition, it provides the experimental background for the optimal use of this model.

Animals↗