Treatment of adult systemic mastocytosis with a PAF-acether antagonist BN52063

Treatment strategies in mastocytosis

Treatment recommendations for mastocytosis are based mostly on expert opinion rather than evidence obtained from controlled clinical trials. In this article, treatment options for mastocytosis are presented, with a focus on the control of mediator-related symptoms in patients with indolent disease.

Mastocytosis and the skin

The most frequent site of organ involvement in individuals with any form of mastocytosis is the skin. Cutaneous lesions include urticaria pigmentosa, mastocytoma, diffuse and erythematous cutaneous mastocytosis, and telangiectasia macularis eruptiva perstans. The major histologic feature is an increase in the number of mast cells in the dermis. Treatment depends on the type of skin lesions.

In situ expression of platelet-activating factor (PAF)-receptor gene in rat skin and effects of PAF on proliferation and differentiation of cultured human keratinocytes

Platelet-activating factor (PAF) is a potent lipid mediator that exhibits versatile biologic activities in many diverse systems by binding to a specific cell-surface receptor (PAFR). Although the production of PAF in cultured keratinocytes and fibroblasts has been reported, physiologic roles of this mediator in skin remain unclear. In this study, we examined in situ expression of PAFR gene in rat skin and the effects of PAF on the proliferation and differentiation of cultured human keratinocytes. In rat epidermis, PAFR mRNA expression was found from the basal cells to the granular cells, and strong signals were seen in the stratum spinosum. In cultured human keratinocytes, a 3.8 kb PAFR mRNA expression was demonstrated by northern blotting, and two distinct type transcripts driven by different promoters were detected by reverse transcriptase polymerase chain reaction analysis. Addition of PAF (30-100 nM) to cultured keratinocytes during a growth phase inhibited the proliferation. This effect was receptor dependent, because the inhibition was completely blocked by a PAFR antagonist, WEB 2086 (100 nM). On the other hand, whereas PAF (30-100 nM) alone did not affect the cornified envelope formation during the process of keratinocyte differentiation, WEB 2086 (30-300 nM) accelerated it in a concentration-dependent manner. Addition of PAF (100 nM) reversed the effect of WEB 2086, suggesting that WEB 2086 induced cornification by inhibiting PAF endogeneously produced by keratinocytes in an autocrine manner. Thus, we propose that PAF is an intrinsic regulator of keratinocyte during proliferation and differentiation.

The hemolytic uremic syndrome

HUS is the most common cause of acute renal failure in infants and young children and follows a diarrheal prodrome about 90% of the time. Persuasive evidence shows that virtually all of postdiarrheal cases are caused by EHEC infections, and that the great majority of cases in the United States are caused by the EHEC serotype O157:H7. Mortality is approximately 5%, and approximately 10% of survivors are left with severe sequelae. A much larger number (30%-50%) experience mild chronic renal damage. Public health strategies, including zero tolerance for fecal contamination in slaughter houses and additional public education on proper food handling and cooking, does much to decrease the prevalence of the syndrome. Efforts to further dissect the postdiarrheal pathogenic cascade should continue, and an animal model needs to be developed. Only then will researchers be positioned to develop effective intervention strategies. Preventing life-threatening extrarenal complications, especially of the CNS, is a major challenge. Idiopathic nondiarrheal HUS accounts for approximately 10% of cases and comprises a poorly understood composite of HUS subsets. Research directed toward a better understanding of these mysterious variants also is a priority for the years ahead.

Southwestern Internal Medicine Conference: mastocytosis: developments during the past decade

Mastocytosis is a spectrum of disorders characterized by an aberrant proliferation of tissue mast cells. Although this disease process often affects the skin, it may involve multiple organs. The clinical disorder varies according to patient age, the clinical manifestations demonstrated, and the extent of the mast cell proliferative process. A myriad of clinical symptoms occur, and these may be localized to the organ system involved or may be systemic, depending on whether there is local or generalized mast cell mediator release. Diagnosis includes the demonstration of increased tissue mast cells in involved organs as well as increased levels of biochemical mediators. Patients with cutaneous involvement only have the best prognosis. Treatment is directed toward stabilizing mast cell mediator release and blocking the effects of those mediators generated.

The effect of topical application of the platelet-activating factor-antagonist, Ro 24-0238, in psoriasis vulgaris--a clinical and immunohistochemical study

Platelet-activating factor (PAF) is considered to be one of the most potent lipid mediators in allergic and inflammatory reactions. Suggestions that PAF is produced by cutaneous cells, and cells infiltrating the skin from the blood, have been reported. PAF has been identified in allergic cutaneous reactions and also in psoriatic lesions. The biological activity of PAF is thought to be mediated by cell membrane receptors. Studies revealed that PAF-antagonists can be active in animal models of cutaneous inflammation. In humans PAF-antagonists showed minimal therapeutic improvement in studies of antigen-induced cutaneous responses in atopic subjects. No data are available on the effects of PAF-antagonists in psoriasis. The objective of this study was to investigate the effect of a potent PAF-antagonist (Ro 24-0238, 10% solution in diethylene glycol monoethyl ether) in 10 patients with chronic plaque psoriasis, a placebo-controlled double-blind study. Clinical response was evaluated and markers of inflammation, differentiation and proliferation were studied immunohistochemically on punch biopsies taken from actively treated and placebo-treated lesions, before and after treatment. This study demonstrated that a 10% solution of the PAF-antagonist Ro 24-0238 was not effective at the clinical or cell biological level after a 4-week treatment period. The most likely explanation for these negative observations is that PAF is not a significant factor in the pathogenesis of psoriasis.

The role of platelet-activating factor (PAF) in experimental glomerular injury

Platelet-activating factor (PAF) is a potent autacoid that participates in inflammation and other pathophysiological processes. In this review we deal with recent evidence suggesting that PAF is a mediator that is released early during glomerular injury. PAF can be synthesized in the glomerulus by infiltrating intrinsic glomerular cells. Normal glomeruli produce PAF upon stimulation, and glomerular PAF synthesis is increased in a variety of experimental glomerulopathies. The local infusion of PAF into the renal artery of isolated blood-free kidneys induces proteinuria. PAF attracts and activates inflammatory cells. Glomerular mesangial, endothelial and epithelial cells are also targets for PAF. Therapy with specific PAF receptor antagonists has prevented or reduced proteinuria and improved glomerular inflammation in several experimental models of proliferative glomerulonephritis and minimal change nephrosis. However, the beneficial effect of administration of PAF antagonists once proteinuria is fully developed has been minimal. PAF may also play a role in the recruitment of inflammatory interstitial cells.

In vitro platelet aggregability studies: lack of evidence for platelet hyperactivity in systemic sclerosis

Systemic sclerosis is characterised by vascular endothelial damage. Platelets adhering to the exposed subendothelium may contribute to the inflammatory changes found in the vessel wall. Increased in vitro platelet aggregability in systemic sclerosis has been reported. In vitro platelet aggregation of platelet rich plasma obtained from patients with systemic sclerosis (CREST (calcinosis, Raynaud's phenomenon oesophageal dysmotility, sclerodactyly, telangiectasia) variant) and from controls matched for age and sex was compared. Collagen, ADP, and platelet activating factor were used as aggregating agents. The actions of a platelet activating factor antagonist, BN52063, were also examined. Each agonist caused dose dependent platelet aggregation; there was no difference in either rate of primary aggregation or maximum percentage aggregation between platelets derived from patients with systemic sclerosis and from the control group (analysis of variance). BN52063 was shown to be a dose dependent, competitive antagonist of platelet aggregation induced by platelet activating factor; there was no difference in its action on platelets derived from patients with systemic sclerosis or controls. These results do not support the hypothesis that platelets from patients with systemic sclerosis are hyperactive and may explain the disappointing results obtained with antiplatelet drugs in systemic sclerosis.

The Skin in Mastocytosis

The most frequent site of organ involvement in patients with any form of mastocytosis is the skin. Cutaneous expressions include urticaria pigmentosa, mastocytoma, diffuse and erythrodermic cutaneous mastocytosis, and telangiectasia macularis eruptiva perstans. The cutaneous lesions tend to appear early in life. Although urticaria pigmentosa has been reported in 12 pairs of twins and one set of triplets, the majority of affected individuals have no familial association. Most patients with systemic mastocytosis have skin lesions; however, an occasional patient will have systemic disease with no other skin features than flushing. In lesional cutaneous sites and in non-lesional skin, there is an increase in the number of mast cells. Electron microscopy shows quantitative differences between lesional skin mast cells from patients with and without systemic disease. The mast cells from adult patients with systemic disease have a larger mean cytoplasmic area, nuclear size, and granule diameter. The granules contain predominantly grating/lattice structures. The cutaneous mast cells contain tryptase and chymase. They retain their functional reactivities to relevant secretory stimuli, such as C3a, morphine sulfate, and calcium ionophore A23187. Lesional skin contains histamine, leukotriene B4, prostaglandin D2, 5-hydroxyeicosatetraenoic acid, platelet-activating factor, and heparin. Treatment of the cutaneous manifestations includes the use of H1 and H2 antihistamines, oral disodium cromoglycate, psoralens plus ultraviolet A photochemotherapy, and potent topical corticosteroid preparations.

Systemic Mastocytosis: Retrospective Review of a Decade's Clinical Experience at the Brigham and Women's Hospital

The clinical experience with a group of 21 patients with systemic mastocytosis followed at our institution is summarized. Cutaneous and gastrointestinal symptoms and findings were the most prominent chronic manifestations; episodic vascular collapse was the most dramatic acute event. All patients had indolent mastocytosis. There was no mortality.

Cromolyn sodium in the management of systemic mastocytosis

A multicenter, double-blind, placebo-controlled trial of the efficacy of oral cromolyn sodium (200 mg orally four times per day) was conducted in 11 patients with systemic mastocytosis who had been maintained with the drug on an individualized compassionate-need basis. Efficacy was measured by physician assessment of overall disease severity based on history and physical examination at specified intervals and by the average daily patient symptom diary scores for each of three mastocytosis-related symptoms that had previously appeared to be alleviated by the use of this drug. Efficacy variables were compared for a 4-week baseline period, during which patients received open-labeled cromolyn sodium, and at 4-week intervals during a 16-week period of random assignment to cromolyn sodium or placebo. Overall disease severity and symptoms recorded in patient diaries were graded on a scale of 0 (absent) to 5 (incapacitating). The average physician assessment of disease severity and symptom scores of the patients in the placebo-treated group increased significantly during the randomization phase relative to patients in the cromolyn sodium-treated group, reflecting an exacerbation of symptoms with drug withdrawal (p less than 0.05 and less than 0.028, respectively). When the symptom scores were analyzed separately for gastrointestinal manifestations of disease (diarrhea, abdominal pain, nausea, and vomiting), cromolyn sodium treatment was significantly beneficial relative to placebo (p less than 0.02), whereas the benefit for nongastrointestinal manifestations did not reach statistical significance.