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Upton JEM, Grunebaum E, Sussman G, Vadas P. Platelet Activating Factor (PAF): A Mediator of Inflammation. Biofactors 2022; 48:1189-1202. [PMID: 36029481 DOI: 10.1002/biof.1883] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 07/21/2022] [Indexed: 12/24/2022]
Abstract
Platelet-activating factor (PAF) is a phospholipid-derived mediator with an established role in multiple inflammatory states. PAF is synthesized and secreted by multiple cell types and is then rapidly hydrolyzed and degraded to an inactive metabolite, lyso-PAF, by the enzyme PAF acetylhydrolase. In addition to its role in platelet aggregation and activation, PAF contributes to allergic and nonallergic inflammatory diseases such as anaphylaxis, sepsis, cardiovascular disease, neurological disease, and malignancy as demonstrated in multiple animal models and, increasingly, in human disease states. Recent research has demonstrated the importance of the PAF pathway in multiple conditions including the prediction of severe pediatric anaphylaxis, effects on blood-brain barrier permeability, effects on reproduction, ocular diseases, and further understanding of its role in cardiovascular risk. Investigation of PAF as both a biomarker and a therapeutic target continues because of the need for directed management of inflammation. Collectively, studies have shown that therapies focused on the PAF pathway have the potential to provide targeted and effective treatments for multiple inflammatory conditions.
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Affiliation(s)
- Julia E M Upton
- Division of Immunology and Allergy, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Eyal Grunebaum
- Division of Immunology and Allergy, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
- Developmental and Stem Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Gordon Sussman
- Division of Clinical Immunology and Allergy, Department of Medicine, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Peter Vadas
- Division of Clinical Immunology and Allergy, Department of Medicine, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
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Forty Years Since the Structural Elucidation of Platelet-Activating Factor (PAF): Historical, Current, and Future Research Perspectives. Molecules 2019; 24:molecules24234414. [PMID: 31816871 PMCID: PMC6930554 DOI: 10.3390/molecules24234414] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Revised: 11/29/2019] [Accepted: 12/02/2019] [Indexed: 12/11/2022] Open
Abstract
In the late 1960s, Barbaro and Zvaifler described a substance that caused antigen induced histamine release from rabbit platelets producing antibodies in passive cutaneous anaphylaxis. Henson described a ‘soluble factor’ released from leukocytes that induced vasoactive amine release in platelets. Later observations by Siraganuan and Osler observed the existence of a diluted substance that had the capacity to cause platelet activation. In 1972, the term platelet-activating factor (PAF) was coined by Benveniste, Henson, and Cochrane. The structure of PAF was later elucidated by Demopoulos, Pinckard, and Hanahan in 1979. These studies introduced the research world to PAF, which is now recognised as a potent phospholipid mediator. Since its introduction to the literature, research on PAF has grown due to interest in its vital cell signalling functions and more sinisterly its role as a pro-inflammatory molecule in several chronic diseases including cardiovascular disease and cancer. As it is forty years since the structural elucidation of PAF, the aim of this review is to provide a historical account of the discovery of PAF and to provide a general overview of current and future perspectives on PAF research in physiology and pathophysiology.
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A Review on Platelet Activating Factor Inhibitors: Could a New Class of Potent Metal-Based Anti-Inflammatory Drugs Induce Anticancer Properties? Bioinorg Chem Appl 2017; 2017:6947034. [PMID: 28458618 PMCID: PMC5387815 DOI: 10.1155/2017/6947034] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Accepted: 02/27/2017] [Indexed: 12/12/2022] Open
Abstract
In this minireview, we refer to recent results as far as the Platelet Activating Factor (PAF) inhibitors are concerned. At first, results of organic compounds (natural and synthetic ones and specific and nonspecific) as inhibitors of PAF are reported. Emphasis is given on recent results about a new class of the so-called metal-based inhibitors of PAF. A small library of 30 metal complexes has been thus created; their anti-inflammatory activity has been further evaluated owing to their inhibitory effect against PAF in washed rabbit platelets (WRPs). In addition, emphasis has also been placed on the identification of preliminary structure-activity relationships for the different classes of metal-based inhibitors.
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Salleron J, Danese S, D'Agay L, Peyrin-Biroulet L. Effectiveness Research in Inflammatory Bowel Disease: A Necessity and a Methodological Challenge. J Crohns Colitis 2016; 10:1096-102. [PMID: 26944416 DOI: 10.1093/ecco-jcc/jjw068] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 02/29/2016] [Indexed: 12/17/2022]
Abstract
Efficacy, safety and economic issues are the main factors influencing the use of inflammatory bowel disease [IBD]-related medications. The best level of evidence comes from randomised clinical trials. The benefit of the intervention observed in a clinical trial could be reduced once it is implemented in clinical practice: its real-life efficacy, known as effectiveness, could be questioned. That is why effectiveness research based on observational studies is required to obtain-long term data on natural history, including surgery or hospitalisation, and safety. Before starting these real-life studies, it is crucial to be aware of the inherent risks of bias and confounding, to develop a good study plan, and to select the optimal design. Even if the choice of the design is optimal and if the risks of bias and confounding are minimised, the implementation of robust statistical methodology is necessary to increase the validity of the results and allow their dissemination into clinical practice. The objective of this paper is to highlight some inherent methodological problems in effectiveness research and to review some statistical tools with a focus on IBD studies and trials.
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Affiliation(s)
- Julia Salleron
- Department of Biostatistics and Data Management, Institut de Cancérologie de Lorraine, Vandoeuvre-Lès-Nancy, France
| | | | | | - Laurent Peyrin-Biroulet
- University Hospital of Nancy-Brabois, Department of Hepatogastroenterology, Université Henri Poincaré 1, France
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Safety and activity of dersalazine sodium in patients with mild-to-moderate active colitis: double-blind randomized proof of concept study. Inflamm Bowel Dis 2014; 20:2004-12. [PMID: 25192498 DOI: 10.1097/mib.0000000000000166] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Dersalazine sodium is an inhibitor of platelet activator factor with potential efficacy in patients with ulcerative colitis through an alternative mechanism of action. The study was a first proof of clinical safety and activity of dersalazine sodium in patients with ulcerative colitis. METHODS A double-blind study of randomized patients with ulcerative colitis (Mayo score ≥ 5 and ≤ 10, including a sigmoidoscopy subscore ≥ 2) to dersalazine sodium 1200 mg/12 h, mesalazine 1200 mg/12 h, or placebo for 4 weeks. Mayo scores were calculated on week 2 (partial Mayo) and week 4 (full Mayo). All patients received open-label mesalazine for 4 additional weeks, and a final visit was done at week 8. RESULTS The study included 34 patients (13 dersalazine sodium, 10 mesalazine, and 11 placebo). Clinical remission was observed in 46.2% patients treated with dersalazine sodium versus 12.5% in mesalazine and 10% in placebo after 4 weeks of treatment. Colon biopsies showed significantly decreased expression of inflammatory genes in dersalazine sodium patients. Adverse events at least possibly related to treatment were observed in 23%, 12.5%, and 7.6% of patients receiving dersalazine sodium, mesalazine, and placebo, respectively; no serious adverse reactions were reported. Increased liver enzymes were reported in 2/13 patients receiving dersalazine sodium, with normal bilirubin levels; both returned to normal values on treatment interruption. CONCLUSIONS Studies in wider populations are needed to confirm the clinical activity of dersalazine sodium. Weekly measurements of liver function tests may be necessary for early detection of adverse events.
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Garud S, Brown A, Cheifetz A, Levitan EB, Kelly CP. Meta-analysis of the placebo response in ulcerative colitis. Dig Dis Sci 2008; 53:875-91. [PMID: 17934839 DOI: 10.1007/s10620-007-9954-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Accepted: 07/24/2007] [Indexed: 12/14/2022]
Abstract
PURPOSE The placebo response rate in randomized controlled trials (RCTs) in ulcerative colitis (UC) varies from 0 to 76%. The aims of this study were to quantify the pooled placebo response rate and identify the factors affecting it. METHODS We performed a meta-analysis of 110 RCTs carried out between 1955 and 2005 and published in English. Regression analysis was used to identify factors significantly modifying placebo response. RESULTS The pooled placebo remission rate was 23% (95%CI: 18.4-28%) and the pooled placebo improvement rate was 32.1% (95%CI: 28.1-36.3%). Multivariate analysis showed that the country where the study was performed (P = 0.025 for placebo remission and P = 0.0083 for placebo response rates) significantly influenced the placebo remission and response rates. CONCLUSION Placebo remission and response rates in RCTs of UC are highly variable and are significantly influenced by the country in which the RCT is performed.
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Affiliation(s)
- Sagar Garud
- Department of Medicine, Beth Israel Deaconess Medical Center, 300 Deaconess Building, 1 Deaconess Road, Boston, MA 02215, USA.
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Bélanger C, Elimam H, Lefebvre J, Borgeat P, Marleau S. Involvement of endogenous leukotriene B4 and platelet-activating factor in polymorphonuclear leucocyte recruitment to dermal inflammatory sites in rats. Immunology 2008; 124:295-303. [PMID: 18217950 DOI: 10.1111/j.1365-2567.2007.02767.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
A critical role for leukotriene B(4) (LTB(4)) and/or platelet-activating factor (PAF) in regulating polymorphonuclear cell (PMN) trafficking to inflammatory sites has been reported in a number of experimental inflammatory models. In vitro, newly synthesized LTB(4) and PAF were shown to act in an autocrine/paracrine or intracrine fashion to enhance intracellular arachidonic acid availability and leukotriene biosynthesis. This suggested potentially cooperative effects of these lipid mediators in regulating PMN extravasation. The present study aimed to elucidate whether endogenous LTB(4) and PAF may both act to regulate plasma extravasation and PMN trafficking to inflammatory sites in experimental inflammation. With this aim, we have used selective and potent PAF and LTB(4) receptor antagonist pretreatments in dermal and pulmonary inflammation models in rats. Our results show additive inhibitory effects of dual LTB(4) and PAF receptor blockade in either PAF- or LTB(4)-elicited cutaneous PMN accumulation compared to single-drug administration. Furthermore, the combined administration of the drugs inhibited the PMN accumulation induced by the chemically unrelated soluble agonists tumour necrosis factor-alpha and C5a. Finally, in a model of pulmonary inflammation induced by the intravenous injection of Sephadex beads, lung neutrophilia was reduced by 63% following the administration of LTB(4) and PAF antagonists, in contrast with the lack of effect of single drug administration. Our results strongly support a role of both endogenous LTB(4) and PAF in regulating PMN trafficking to inflammatory sites in various experimental conditions.
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Raithel M, Winterkamp S, Weidenhiller M, Müller S, Hahn EG. Combination therapy using fexofenadine, disodium cromoglycate, and a hypoallergenic amino acid-based formula induced remission in a patient with steroid-dependent, chronically active ulcerative colitis. Int J Colorectal Dis 2007; 22:833-9. [PMID: 16944185 DOI: 10.1007/s00384-006-0120-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/07/2006] [Indexed: 02/04/2023]
Abstract
Corticosteroids and 5-aminosalicylic acid are the primary standard therapy for inflammatory bowel disease. Recent immunologic data implicate an involvement of mast cell activation followed by increased histamine secretion and elevated tissue concentrations of histamine in the pathogenesis of ulcerative colitis. In the present case, the clinical course of a 35-year-old man with steroid-dependent chronic active ulcerative colitis, who did not respond to high-dose steroids, antibiotics, or azathioprine during 3 years, is reported. Clinical disease activity and established serological markers were recorded during 6 weeks of unsuccessful therapy and during the next 6 weeks, as a new nonsedative antihistaminergic drug, a mast cell stabilizer, and an hypoallergenic diet were implemented in addition to conventional therapy. Induction of remission was achieved within 2 weeks after treatment with fexofenadine, disodium cromoglycate, and an amino acid-based formula. Clinical disease activity, stool frequency, leukocytes, c-reactive protein, and orosomucoid levels in serum decreased rapidly. Daily steroid administration could be gradually reduced along with 6 weeks of this treatment. This report suggests that histamine and mast cell activity may be important pathophysiological factors responsible for persistent clinical and mucosal inflammatory activity in ulcerative colitis despite the use of steroids. In ulcerative colitis, patients unresponsive to conventional treatment, therapeutic considerations should also include an antiallergic approach when further signs of atopy or intestinal hypersensitivity are present.
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Affiliation(s)
- M Raithel
- Functional Tissue Diagnostics, Department of Medicine I, University Erlangen-Nuremberg, Ulmenweg 18, 91054, Erlangen, Germany.
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de Bièvre MA, Vrij AA, Schoon EJ, Dijkstra G, de Jong AE, Oberndorff-Klein Woolthuis AH, Hemker HC, Stockbrügger RW. Randomized, placebo-controlled trial of low molecular weight heparin in active ulcerative colitis. Inflamm Bowel Dis 2007; 13:753-8. [PMID: 17260365 DOI: 10.1002/ibd.20085] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND In several open and 1 controlled trial, unfractionated heparin was effective in the treatment of active ulcerative colitis (UC). Low molecular weight heparin (LMWH) had a similar effect in several open studies. METHODS We studied the efficacy, safety, and tolerability of LMWH in mild to moderately active UC in a randomized, double-blind, placebo-controlled trial. In all, 29 patients with a mild or moderate recurrence of UC during salicylate treatment were randomized to receive either reviparin 3,436 IU (n = 15) subcutaneously twice daily or placebo (n = 14). The study period was 8 weeks. Treatment was discontinued if there was no improvement at 4 weeks or at any disease progression. Primary outcome measure was clinical improvement at 8 weeks measured by the Colitis Activity Index (CAI) and the Clinical Symptoms Grading (CSG, based on the CAI). Endoscopic and histologic grading and quality of life as measured by the Inflammatory Bowel Disease Questionnaire (IBDQ) were secondary outcome measures. Patients were closely monitored for adverse events. RESULTS Twenty of 29 patients finished the 8-week treatment period (reviparin versus placebo: 11 versus 9; P = 0.70). There was no difference in CSG, CAI, endoscopic and histologic grading, or IBDQ. Treatment was well tolerated and no serious adverse events occurred. CONCLUSION In this study, treatment with LMWH showed no significant clinical advantage compared to placebo in mild to moderately active UC.
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Abstract
Interaction between thrombosis and inflammation is increasingly recognized. With this, interest has arisen in the role of thrombosis in inflammatory conditions, including the inflammatory bowel diseases. Although the association between active inflammatory bowel disease and thromboembolic complications has long been known, there has been a resurgence in research into the role of thrombosis and the hemostatic system in the pathogenesis of both ulcerative colitis and Crohn's disease. Here we review the increased frequency of thromboembolic complications occurring in patients with inflammatory bowel disease; whether thrombosis might play a part in the initiation and maintenance of inflammation in inflammatory bowel disease; abnormalities of the coagulation system found in patients with inflammatory bowel disease; platelet dysfunction in inflammatory bowel disease; the mechanisms by which hemostatic processes might be proinflammatory in inflammatory bowel disease; and how these interactions might impact not only on the prevention of complications, but also on the treatment of the underlying inflammation in inflammatory bowel disease.
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Affiliation(s)
- Peter M Irving
- Centre for Gastroenterology, Institute of Cell and Molecular Science, Barts and The London NHS Trust, United Kingdom
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Abstract
Historically, mast cells were known as a key cell type involved in type I hypersensitivity. Until last two decades, this cell type was recognized to be widely involved in a number of non-allergic diseases including inflammatory bowel disease (IBD). Markedly increased numbers of mast cells were observed in the mucosa of the ileum and colon of patients with IBD, which was accompanied by great changes of the content in mast cells such as dramatically increased expression of TNF-α, IL-16 and substance P. The evidence of mast cell degranulation was found in the wall of intestine from patients with IBD with immunohistochemistry technique. The highly elevated histamine and tryptase levels were detected in mucosa of patients with IBD, strongly suggesting that mast cell degranulation is involved in the pathogenesis of IBD. However, little is known of the actions of histamine, tryptase, chymase and carboxypeptidase in IBD. Over the last decade, heparin has been used to treat IBD in clinical practice. The low molecular weight heparin (LMWH) was effective as adjuvant therapy, and the patients showed good clinical and laboratory response with no serious adverse effects. The roles of PGD2, LTC4, PAF and mast cell cytokines in IBD were also discussed. Recently, a series of experiments with dispersed colon mast cells suggested there should be at least two pathways in man for mast cells to amplify their own activation-degranulation signals in an autocrine or paracrine manner. The hypothesis is that mast cell secretogogues induce mast cell degranulation, release histamine, then stimulate the adjacent mast cells or positively feedback to further stimulate its host mast cells through H1 receptor. Whereas released tryptase acts similarly to histamine, but activates mast cells through its receptor PAR-2. The connections between current anti-IBD therapies or potential therapies for IBD with mast cells were discussed, implicating further that mast cell is a key cell type that is involved in the pathogenesis of IBD. In conclusion, while pathogenesis of IBD remains unclear, the key role of mast cells in this group of diseases demonstrated in the current review implicates strongly that IBD is a mast cell associated disease. Therefore, close attentions should be paid to the role of mast cells in IBD.
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Affiliation(s)
- Shao-Heng He
- Allergy and Inflammation Research Institute, Medical College, Shantou University, Shantou 515031, Guangdong Province, China.
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Abstract
The pathophysiology of inflammatory bowel disease (IBD) is gradually being unravelled and new therapies are being developed to target the disturbed biological processes. This article outlines the clinical features of IBD, its current therapy and pathogenesis. The difficulties for clinical pharmacologists and gastroenterologists associated with designing, executing and interpreting clinical trials in IBD are then discussed. The final section reviews methods that can used to demonstrate the pharmacological actions of new treatments in patients with IBD. It is emphasized that proof of the therapeutic efficacy of a novel agent with a specific mechanism of action yields not only clinical benefit to patients with IBD, but also indicates the importance of the targeted biochemical pathway in the pathogenesis of the disease.
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Affiliation(s)
- E Carty
- Academic Department of Adult and Paediatric Gastroenterology, Barts and The London School of Medicine, Start 1 Building, 2, Newark Street, London E1 2AD, UK
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Abstract
Ulcerative colitis is a chronic inflammatory disease of the rectum and colon. Results from many studies in people and animals of intestinal inflammation suggest that ulcerative colitis results from environmental factors triggering a loss of tolerance for normal intestinal flora in genetically susceptible individuals. Although progress has been made in the overall management of the disease, no innovative treatment has been developed. By contrast with Crohn's disease, there are few clinical data on biological agents. Probiotics seem the most promising of several experimental and traditional agents that have been investigated in controlled clinical trials.
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Affiliation(s)
- Richard J Farrell
- Division of Gastroenterology, Center for Inflammatory Bowel Disease, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
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Abstract
The last decade has seen tremendous advances in our knowledge, which has led to genuine improvements in our understanding of the pathogenesis and management of inflammatory bowel disease (IBD). The combined power of cellular and molecular biology has begun to unveil the enigmas of IBD, and, consequently, substantial gains have been made in the treatment of IBD. Refinements in drug formulation have provided the ability to target distinct sites of delivery, while enhancing the safety and efficacy of older agents. Simultaneous progress in biotechnology has fostered the development of new agents that strategically target pivotal processes in disease pathogenesis. This article addresses our current understanding of the pathogenesis of IBD, including the latest developments in animal models and covers agents currently used in the treatment of IBD as well as emerging therapies.
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Affiliation(s)
- R J Farrell
- Division of Gastroenterology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA
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Vrij AA, Rijken J, Van Wersch JW, Stockbrügger RW. Platelet factor 4 and beta-thromboglobulin in inflammatory bowel disease and giant cell arteritis. Eur J Clin Invest 2000; 30:188-94. [PMID: 10691994 DOI: 10.1046/j.1365-2362.2000.00616.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND As platelet factors are important in the inflammatory response, we examined the course of platelet factor 4 and beta-thromboglobulin in relation to disease activity in inflammatory bowel disease and in giant cell arteritis. PATIENTS AND METHODS In a prospective study, the platelet count, platelet factor 4 and beta-thromboglobulin were measured in 20 patients with Crohn's disease, 18 with ulcerative colitis and 19 with giant cell arteritis, during active and inactive disease, as well as in 51 controls without inflammation. RESULTS Platelet counts were significantly higher in active vs. inactive Crohn's disease, ulcerative colitis and giant cell arteritis. Levels of platelet factor 4 and beta-thromboglobulin were significantly higher in active inflammatory bowel disease and giant cell arteritis, as well as in inactive inflammatory bowel disease and giant cell arteritis, than in the non-inflammatory controls. A positive correlation was found between the Crohn's disease activity index and the platelet count, platelet factor 4 and beta-thromboglobulin. Also, a positive correlation was found between the ulcerative colitis activity index and beta-thromboglobulin. However, even after 12 months of follow-up, in Crohn's disease and ulcerative colitis the mean levels of platelet factor 4 and beta-thromboglobulin were significantly higher than the levels of the controls. CONCLUSION Platelet factors were correlated with inflammatory bowel disease activity. Levels of platelet factor 4 and beta-thromboglobulin, however, were markedly raised for a long time in clinically inactive inflammatory bowel disease, which might point to a pre-thrombotic state of disease.
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Affiliation(s)
- A A Vrij
- Department of Gastroenterology, University Hospital, Maastricht; the Netherlands.
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Ishii S, Shimizu T. Platelet-activating factor (PAF) receptor and genetically engineered PAF receptor mutant mice. Prog Lipid Res 2000; 39:41-82. [PMID: 10729607 DOI: 10.1016/s0163-7827(99)00016-8] [Citation(s) in RCA: 279] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a biologically active phospholipid mediator. Although PAF was initially recognized for its potential to induce platelet aggregation and secretion, intense investigations have elucidated potent biological actions of PAF in a broad range of cell types and tissues, many of which also produce the molecule. PAF acts by binding to a unique G-protein-coupled seven transmembrane receptor. PAF receptor is linked to intracellular signal transduction pathways, including turnover of phosphatidylinositol, elevation in intracellular calcium concentration, and activation of kinases, resulting in versatile bioactions. On the basis of numerous pharmacological reports, PAF is thought to have many pathophysiological and physiological functions. Recently advanced molecular technics enable us not only to clone PAF receptor cDNAs and genes, but also generate PAF receptor mutant animals, i.e., PAF receptor-overexpressing mouse and PAF receptor-deficient mouse. These mutant mice gave us a novel and specific approach for identifying the pathophysiological and physiological functions of PAF. This review also describes the phenotypes of these mutant mice and discusses them by referring to previously reported pharmacological and genetical data.
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Affiliation(s)
- S Ishii
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
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Abstract
Advances in the treatment of ulcerative colitis have continued to focus on improved local delivery of existing agents, such as 5-aminosalicylate and corticosteroids, and on novel immunosuppressive agents. Although newer preparations of 5-aminosalicylate continue to provide incremental benefits in safety, tolerance, and efficacy, there is a growing understanding of the limits of benefit from increasing doses. Knowledge of the safety of these agents, particularly in regard to their use in pregnancy, continues to expand. Novel corticosteroids are used in much of the world for the treatment of ulcerative colitis, with the exception of the United States, with anticipated benefits in safety but little additional therapeutic benefit. Innovative use of oral emulsion preparations of cyclosporine has been reported in the treatment of ulcerative colitis and adds to the growing body of literature on the efficacy of cyclosporine in severe disease. Relatively limited experience with other immunosuppressive agents, such as tacrolimus, has been reported. The role of antibiotics in the treatment of ulcerative colitis has continued to present controversy.
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Affiliation(s)
- C J Ooi
- Center for the Study of Inflammatory Bowel Diseases, Gastrointestinal Unit, Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts 02114, USA
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Abstract
Looking back at successes and failures in newer approaches to treating IBD, it is tempting--although still difficult--to draw conclusions about pathogenesis. When a therapy proves effective, do clinicians truly know how it works? Even with a therapy as specific as anti-TNF antibody, it is not clear if the benefit is attributable to simple binding and clearance of TNF-alpha or to binding on the cell surface and subsequent deletion of the activated macrophage. When a drug appears to be less effective than preclinical models suggest, can failures in effectiveness from delivery or dosing be differentiated? The disappointing results of clinical trials with IL-10--so at odds with the prediction of benefit from animal models--bring into question the validity of those models as well as the soundness of design of the clinical trials on which efficacy of IL-10 is judged. The variability of response even to the most narrowly targeted agents suggests that these diseases are far more heterogeneous in humans than in their murine counterparts. Clinicians are only just beginning to recognize subclinical markers of response, and it may soon be possible to predict response on the basis of genetic composition. For the moment, however, the field of pharmacogenetics is embryonic. Challenges in developing new therapeutic strategies include not only identifying novel agents, but also improving the definitions of clinical endpoints and defining efficacy at the biologic level. Only through considered evaluation of clinical evidence may clinicians determine which therapies should remain novelties and which should become an accepted part of the armamentarium.
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Affiliation(s)
- B E Sands
- Harvard Medical School, Massachusetts General Hospital, Boston, USA
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