Pathogenetic determinants in Kawasaki disease: the haematological point of view.

Kawasaki disease is a multisystemic vasculitis that can result in coronary artery lesions. It predominantly affects young children and is characterized by prolonged fever, diffuse mucosal inflammation, indurative oedema of the hands and feet, a polymorphous skin rash and non-suppurative lymphadenopathy. Coronary artery involvement is the most important complication of Kawasaki disease and may cause significant coronary stenosis resulting in ischemic heart disease. The introduction of intravenous immunoglobulin decreases the incidence of coronary artery lesions to less than 5%. The etiopathogenesis of this disease remains unclear. Several lines of evidence suggest that an interplay between a microbial infection and a genetic predisposition could take place in the development of the disease. In this review, we summarize the state of the art of pathogenetic mechanisms of Kawasaki disease underscoring the relevance of haematological features as a novel field of investigation.

Thrombosis in adult patients with acute leukemia.

PURPOSE OF REVIEW: Recent studies indicate that the risk of thrombosis in hematologic patients may be similar or even higher than that found in patients with solid tumors. However, available information about pathogenesis and incidence of thrombosis in acute leukemia is limited. This review focuses on mechanisms underlying thrombosis in acute leukemia and discusses recent literature data. RECENT FINDINGS: In the last few years, proofs have been provided that leukemic cells release free prothrombotic products, such as micro-vesicles, tissue factors, circulating free DNA and RNA. Furthermore, leukemic blasts can activate the procoagulant population of platelets, which initiate and amplify coagulation, causing thrombosis. In addition to factors produced by acute leukemia itself, others concur to trigger thrombosis. Some drugs, infections and insertion of central venous catheter have been described to increase risk of thrombosis in patients with acute leukemia. SUMMARY: Thrombosis represents a serious complication in patients affected by myeloid and lymphoid acute leukemia. A proper knowledge of its pathophysiology and of the predisposing risk factors may allow to implement strategies of prevention. Improving prevention of thrombosis appears a major goal in patients whose frequent conditions of thrombocytopenia impede an adequate delivery of anticoagulant therapy.

Downstream effects of endocannabinoid on blood cells: implications for health and disease.

Endocannabinoids (eCBs), among which N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) are the most biologically active members, are polyunsaturated lipids able to bind cannabinoid, vanilloid and peroxisome proliferator-activated receptors. Depending on the target engaged, these bioactive mediators can regulate different signalling pathways, at both central and peripheral levels. The biological action of eCBs is tightly controlled by a plethora of metabolic enzymes which, together with the molecular targets of these substances, form the so-called "endocannabinoid system". The ability of eCBs to control manifold peripheral functions has received a great deal of attention, especially in the light of their widespread distribution in the body. In particular, eCBs are important regulators in blood, where they modulate haematopoiesis, platelet aggregation and apoptosis, as well as chemokine release and migration of immunocompetent cells. Here, we shall review the current knowledge on the pathophysiological roles of eCBs in blood. We shall also discuss the involvement of eCBs in those disorders affecting the haematological system, including cancer and inflammation. Knowledge gained to date underlines a fundamental role of the eCB system in blood, thus suggesting that it may represent a therapeutic promise for a broad range of diseases involving impaired hematopoietic cell functions.

Fibroblast autophagy in fibrotic disorders.

Fibrotic disorders are multistage progressive processes that often arise from different causes and are commonly associated with chronic inflammation. Excessive deposition of extracellular matrix is the hallmark of many fibrotic diseases. This may be due to an excess of fibroblast recruitment and activation, as well as to their differentiation in myofibroblasts. These events may be triggered by cytokines, chemokines and growth factors released by lymphocytes or macrophages. The excessive production of extracellular matrix is apparently due to alterations of metabolic pathways in activated fibroblasts. It has been suggested that a defective autophagy, an important subcellular pathway with multiple homeostatic roles, also recognized as a key component of both innate and acquired immunity, could play a role. In this review we illustrate recent insights in the field, suggesting the possible implication of the immune system in orchestrating the fibrotic response via the modulation of autophagic pathways.

Redox modulation of Ecto-NOX1 in human platelets.

By modulating the cellular redox state, the plasma membrane electron transport (PMET) is important in platelet biology; indeed, the oxidant/antioxidant balance plays a central role during activation of the coagulation pathway. None the less, in human platelets, the PMET system has not yet been fully characterized and the molecular identities of most components are unknown. Here, for the first time, the presence of the plasma membrane hydroquinone (NADH) oxidase Ecto-NOX1 in human platelets has been described. We found that Ecto-NOX1 expression is modulated by capsaicin: Indeed, it is positively regulated through a mechanism requiring binding of capsaicin to its receptor, namely the transient receptor potential vanilloid subtype 1 (TRPV1). Ligand-receptor interaction triggers a signalling cascade leading to ROS production, which in turn enhances expression and activity of Ecto-NOX1. Redox regulation of Ecto-NOX1 may be important to platelet recruitment and activation during inflammatory diseases.

Oxidative stress and defective platelet apoptosis in naïve patients with Kawasaki disease.

Kawasaki disease (KD) is a rare and often undiagnosed disease, at least in the western countries. It is characterized by an inflammatory acute febrile vasculitis of medium sized arteries with a propensity to damage the coronary arteries. It normally occurs in the early childhood and the diagnosis is based on clinical symptoms. During the progression of the disease thrombocytosis is usually detected. This can exert a pathogenetic role in the cardiovascular complications occurring in KD. In the present work peripheral blood plasma and platelets from twelve naïve patients with KD were analyzed in order to detect possible pathogenetic determinants or progression markers. Morphological, biochemical and flow cytometrical methods have been used. With respect to age-matched healthy donors, we found an increase of platelet activation markers, i.e. degranulation, phosphatidylserine (PS) externalization and leukocyte-red cell-platelet aggregates. Some significant alterations that could represent suitable diagnostic determinants have also been detected in patient plasma: (i) decreased antioxidant power, (ii) decreased levels of asymmetric dymethylarginine (ADMA), a naturally occurring chemical interfering with the production of nitric oxide, and (iii) increased levels of soluble P-Selectin and soluble annexin V. Since PS externalizing platelets are known to exert a pro-coagulant activity, our data suggest the hypothesis that increased risk of vascular complications in KD could depend on platelet stimulation and defective apoptosis probably related to nitrosative stress.

The plasma membrane redox system in human platelet functions and platelet-leukocyte interactions.

The plasma membrane electron transport is crucial for blood coagulation and thrombosis, since reactive oxygen species and thiol changes, generated by plasma membrane redox reactions, modulate activation of platelets, as well as their interaction with leukocytes. Several antioxidants are linked to this system; thus, platelets are also able to counterbalance radical production and to regulate thrombus growth. Aim of this review is to give an update on the plasma membrane redox system in platelets, as well as on its role in platelet functions and leukocyte-platelet cross-talk.

Management of acute childhood idiopathic thrombocytopenic purpura according to AIEOP consensus guidelines: assessment of Italian experience.

BACKGROUND: Consensus guidelines for diagnosis and treatment of acute childhood idiopathic thrombocytopenic purpura (ITP) were published in 2000 by the Italian Association of Pediatric Haematology and Oncology (AIEOP). The assessment of guideline implementation was the primary objective of the present study. PATIENTS AND METHODS: Information on each newly diagnosed case of ITP referring to centres conforming with the guidelines was obtained by a questionnaire. RESULTS: Data concerning 609 new cases of acute childhood ITP were collected including 346 (56.8%) asymptomatic-paucisymptomatic forms (type A), 262 (43%) intermediate clinical forms (type B), and 1 (0.2%) severe form (type C). At diagnosis, 82% of cases were hospitalized. Age, platelet count and duration of hospitalization were significantly different in type A and type B cases. Of the total number of cases, 25% were kept under observation, 38.6% received intravenous immunoglobulins, 23.9% oral or parenteral steroids, and 12.7% other treatments. The initial treatment turned out to be appropriate for 428 cases (72.2%), of uncertain appropriateness in 71 (11.9%), and inappropriate in 95 cases (15.9%). The total level of implementation was 84.1%. CONCLUSIONS: A high rate of guideline implementation was observed during the study period. The guidelines should be reviewed taking into account more recent evidence.

Kawasaki disease: guidelines of Italian Society of Pediatrics, part II - treatment of resistant forms and cardiovascular complications, follow-up, lifestyle and prevention of cardiovascular risks.

This second part of practical Guidelines related to Kawasaki disease (KD) has the goal of contributing to prompt diagnosis and most appropriate treatment of KD resistant forms and cardiovascular complications, including non-pharmacologic treatments, follow-up, lifestyle and prevention of cardiovascular risks in the long-term through a set of 17 recommendations.Guidelines, however, should not be considered a norm that limits the treatment options of pediatricians and practitioners, as treatment modalities other than those recommended may be required as a result of peculiar medical circumstances, patient's condition, and disease severity or individual complications.

Kawasaki disease: guidelines of the Italian Society of Pediatrics, part I - definition, epidemiology, etiopathogenesis, clinical expression and management of the acute phase.

The primary purpose of these practical guidelines related to Kawasaki disease (KD) is to contribute to prompt diagnosis and appropriate treatment on the basis of different specialists' contributions in the field. A set of 40 recommendations is provided, divided in two parts: the first describes the definition of KD, its epidemiology, etiopathogenetic hints, presentation, clinical course and general management, including treatment of the acute phase, through specific 23 recommendations.Their application is aimed at improving the rate of treatment with intravenous immunoglobulin and the overall potential development of coronary artery abnormalities in KD. Guidelines, however, should not be considered a norm that limits treatment options of pediatricians and practitioners, as treatment modalities other than those recommended may be required as a result of peculiar medical circumstances, patient's condition, and disease severity or complications.

Translational control of the ascorbic acid transporter SVCT2 in human platelets.

Reactive oxygen species (ROS) and redox state have emerged as physiological mediators, controlling blood coagulation and thrombosis. The redox balance is obviously linked to the presence of antioxidants; in particular, vitamin C appears to be a key modulator of platelet oxidative state, since these cells physiologically accumulate ascorbic acid and, moreover, platelet ascorbate plays a role during aggregation. Here, we showed that platelets could compensate for fluctuations in ascorbate levels by modulating the expression of the Na+-dependent transporter SVCT2. Furthermore, the use of anucleated cells demonstrated, for the first time, that SVCT2 expression could be regulated at the translational level. The control of ascorbic acid uptake, through regulation of its carrier, was not only related to substrate availability, but it also occurred during platelet activation, which was accompanied by vitamin C deprivation and alteration in the redox state. Finally, we showed that changes in intracellular ascorbic acid content had physiological relevance, since they modulate the surface sulfhydryl content and the thrombus viscoelastic properties. Beside its role during aggregation, vitamin C may also have important effects during postaggregatory events.

The relevance of estrogen/estrogen receptor system on the gender difference in cardiovascular risk.

It has been reported that the incidence of thrombotic events can display a gender disparity. In particular, a lower thrombotic risk has been described in female gender. The mechanisms underlying this disparity are still poorly understood. Of great interest is the hypothesis that hormones, estrogen in particular, could play a key role. In fact, the possibility that some hormonal factors could protect women from thrombotic events appears well documented in literature. For instance, several studies aimed at the analysis of the impact of estrogen and estrogen receptors in thrombogenesis claim for the implication of these hormones either in megakaryocyte differentiation or, more intriguingly, directly affecting platelet integrity and function. In consideration of the absence of the nucleus, platelet susceptibility appears quite striking and probably due to the non-nuclear estrogen receptor function. In this review we briefly summarize our knowledge as concerns the role of estrogen and estrogen receptors in determining megakaryocyte/platelet functions and thrombogenicity.

Activation of human platelets by 2-arachidonoylglycerol is enhanced by serotonin.

The endocannabinoid 2-arachidonoylglycerol (2-AG) has been shown to activate human platelets in platelet-rich plasma, by binding to a "platelet-type" cannabinoid receptor (CB(PT)). Here, washed human platelets were used to characterize the binding of [(3)H]2-AG to CB(PT), showing a dissociation constant (Kd) of 140 +/- 31 nM and a maximum binding (Bmax) of 122 +/- 10 pmol.mg protein(-1). Selective antagonists of both CB1 and CB2 cannabinoid receptors inhibited this binding, which was enhanced up to approximately 230% over the controls by 1 micro M serotonin (5-hydroxytryptamine, 5-HT). Human platelets were also able to bind [(3)H]5-HT (Kd = 79 +/- 17 nM, Bmax = 14.6 +/- 1.3 pmol.mg protein(-1)), and 1 micro M 2-AG enhanced this binding up to approximately 150%. Moreover, they were able to take up [(3)H]5-HT through a high affinity transporter (Michaelis-Menten constant = 22 +/- 2 nM, maximum velocity = 344 +/- 15 pmol.min(-1).mg protein(-1)), which was not affected by 2-AG. Interestingly, 5-HT did not affect the activity of the 2-AG transporter of human platelets. Treatment of washed platelets with 1 micro M 2-AG led to increased intracellular inositol-1,4,5-trisphosphate (up to approximately 300%) and decreased cyclic AMP (down to approximately 50%). Furthermore, treatment of pre-loaded platelets with 1 micro M 2-AG induced a approximately 300% increase in [(3)H]2-AG release, according to a CBPT-dependent mechanism. Also, 1 micro M 5-HT enhanced the effect of 2-AG on inositol-1,4,5-trisphosphate ( approximately 500% of the controls), cyclic AMP ( approximately 20%) and [(3)H]2-AG release ( approximately 570%), and the latter process was shown to be partly ( approximately 50%) involved in the 5-HT-dependent platelet activation. Taken together, reported findings represent the first demonstration that 2-AG and 5-HT can mutually reinforce their receptor binding on platelet surface, which might have therapeutic implications.

Redox control of platelet functions in physiology and pathophysiology.

SIGNIFICANCE: An imbalance between the production and the detoxification of reactive oxygen species and reactive nitrogen species (ROS/RNS) can be implicated in many pathological processes. Platelets are best known as primary mediators of hemostasis and can be either targets of ROS/RNS or generate radicals during cell activation. These conditions can dramatically affect platelet physiology, leading even, as an ultimate event, to the cell number modification. In this case, pathological conditions such as thrombocytosis (promoted by increased cell number) or thrombocytopenia and myelodysplasia (promoted by cell decrease mediated by accelerated apoptosis) can occur. RECENT ADVANCES: Usually, in peripheral blood, ROS/RNS production is balanced by the rate of oxidant elimination. Under this condition, platelets are in a nonadherent "resting" state. During endothelial dysfunction or under pathological conditions, ROS/RNS production increases and the platelets respond with specific biochemical and morphologic changes. Mitochondria are at the center of these processes, being able to both generate ROS/RNS, that drive redox-sensitive events, and respond to ROS/RNS-mediated changes of the cellular redox state. Irregular function of platelets and enhanced interaction with leukocytes and endothelial cells can contribute to pathogenesis of atherosclerotic and thrombotic events. CRITICAL ISSUES: The relationship between oxidative stress, platelet death, and the activation-dependent pathways that drive platelet pro-coagulant activity is unclear and deserves to be explored. FUTURE DIRECTIONS: Expanding knowledge about how platelets can mediate hemostasis and modulate inflammation may lead to novel and effective therapeutic strategies for the long and growing list of pathological conditions that involve both thrombosis and inflammation.

Does oxidative stress play a critical role in cardiovascular complications of Kawasaki disease?

The aim of the present work was to evaluate the contribution of the different reactive oxidizing species to systemic oxidative stress in the whole blood of patients with Kawasaki disease (KD). This is a rare generalized systemic vasculitis typical of the early childhood characterized by inflammation and endothelial dysfunction with a high risk for cardiovascular fatal events. We found that, compared to age-matched healthy donors, blood from KD patients showed increased production of oxygen- and nitrogen-derived species as detected by electron paramagnetic resonance (EPR) spin probing with the cyclic hydroxylamine 1-hydroxy-3-carboxy-pyrrolidine. The (•)NO pathway involvement was also confirmed by the decreased concentrations of the endogenous (•)NO synthase inhibitor asymmetric dimethyl-arginine and the increased amounts of 3-nitrotyrosine in plasma. Further, increased plasma yields of the proinflammatory enzyme myeloperoxidase were also observed. The appearance of circulating red blood cell alterations typically associated with oxidative imbalance and premature aging (e.g., decrease of total thiol content, glycophorin A, and CD47 expression, as well as increase of phosphatidylserine externalization) has also been detected. Collectively, our observations lead to hypothesize that the simultaneous oxidative and nitrative stress occurrence in the blood of KD patients may play a pathogenetic role in the cardiovascular complications often associated with this rare disease.

Trans-plasma membrane electron transport in mammals: functional significance in health and disease.

Trans-plasma membrane electron transport (t-PMET) has been established since the 1960s, but it has only been subject to more intensive research in the last decade. The discovery and characterization at the molecular level of its novel components has increased our understanding of how t-PMET regulates distinct cellular functions. This review will give an update on t-PMET, with particular emphasis on how its malfunction relates to some diseases, such as cancer, abnormal cell death, cardiovascular diseases, aging, obesity, neurodegenerative diseases, pulmonary fibrosis, asthma, and genetically linked pathologies. Understanding these relationships may provide novel therapeutic approaches for pathologies associated with unbalanced redox state.

Defective autophagy in fibroblasts may contribute to fibrogenesis in autoimmune processes.

Fibrosis may represent the final step induced by autoimmune mechanism(s). This may be due to the excess in fibroblast recruitment, activation and differentiation in myofibroblasts. These events may be triggered by cytokines, chemokines and growth factors released by lymphocytes or macrophages. Autophagy is an essential conserved homeostatic process that has long been appreciated for cell adaptation to nutrient deprivation. Autophagy is also recognized as an important component of both innate and acquired immunity to pathogens. Recently, dysregulation of autophagy in haematopoietic cells has been suggested to amplify the autoimmune responses. On the other hand, it is possible that defective autophagy in non-haematopoietic cells contributes to the progression to fibrosis. In fibroblasts some alterations in the metabolic pathways and pharmacological data suggest that a defective autophagy could contribute to excess in the production of extracellular matrix by altering the turnover of protein such as collagen. Our goal in this review is to describe the current knowledge on the role of autophagy in the development of fibrotic autoimmune diseases. Further studies could confirm whether agents modulating autophagy may be used in the treatment of these autoimmune diseases.