Studies of platelet 5-hydroxytryptamine (serotonin) in storage pool disease and albinism

Role of Amine Neurotransmitters and Their Receptors in Skin Pigmentation: Therapeutic Implication

Skin pigmentation can occur due to increased melanin, including melanocyte proliferation, melanin biosynthesis, or melanocyte migration. There are many factors that influence the melanin production process, but the role of neurotransmitters in this process is still unclear. We found that histamine and serotonin influence the different stages of melanogenesis and melanogenesis, which increase melanogenesis. Since then, several related papers have been published, and from these papers, it has been recognised that the role of neurotransmitters in skin-pigment-related diseases needs to be summarised. By introducing the role of neurotransmitters in the regulation of various pigment disorders, including vitiligo and melasma, through this review, many researchers can be expected to try to apply neurotransmitter-related agonists and antagonists as treatments for skin pigment disorders.

Defective acid hydrolase secretion in RUNX1 haplodeficiency: Evidence for a global platelet secretory defect

BACKGROUND

RUNX1 haplodeficiency is associated with thrombocytopenia, platelet dysfunction and a predisposition to acute leukaemia. Platelets possess three distinct types of granules and secretory processes involving dense granules (DG), α-granules and vesicles or lysosomes containing acid hydrolases (AH). Dense granules and granule deficiencies have been reported in patients with RUNX1 mutations. Little is known regarding the secretion from AH-containing vesicles.

METHODS AND RESULTS

We studied two related patients with a RUNX1 mutation, easy bruising, and mild thrombocytopenia. Platelet aggregation and 14 C serotonin in platelet-rich plasma (PRP) were impaired in response to ADP, epinephrine, collagen and arachidonic acid. Contents of DG (ATP, ADP), α-granules (β-thromboglobulin) and AH-containing vesicles (β-glucuronidase, β-hexosaminidase, α-mannosidase) were normal or minimally decreased. Dense granules secretion on stimulation of gel-filtered platelets with thrombin and divalent ionophore A23187 (4-12 μmol L-1 ) were diminished. β-thromboglobulin and AH secretion was impaired in response to thrombin or A23187. We studied thromboxane-related pathways. The incorporation of 14 C -arachidonic acid into phospholipids and subsequent arachidonic acid release on thrombin activation was normal. Platelet thromboxane A2 production in whole blood serum and on thrombin stimulation of PRP was normal, suggesting that the defective secretion was not due to impaired thromboxane production.

CONCLUSIONS

These studies provide the first evidence in patients with a RUNX1 mutation for a defect in AH (lysosomal) secretion, and for a global defect in secretion involving all three types of platelet granules that is unrelated to a granule content deficiency. They highlight the pleiotropic effects and multiple platelet defects associated with RUNX1 mutations.

Postural orthostatic tachycardia syndrome is associated with platelet storage pool deficiency

Mechanisms have been postulated to explain postural orthostatic tachycardia syndrome (POTS), however, the etiology of this often debilitating disorder remains unknown. We conducted a retrospective case-control study of 181 POTS patients who exhibited/reported bleeding symptoms for a specific platelet (PL) dysfunction disorder, delta granule storage pool deficiency (δ-SPD).Patients were included only if results of blood tests for δ-SPD were available. Electron microscopy was utilized to diagnose δ-SPD. An ELISA assay was used to determine serotonin (5HT) concentration in PLs and medical record review was employed to collect patients' clinical symptoms.The most common bleeding symptom was easy bruising (71%) but frequent nose bleeds, heavy menstrual bleeding, and a family history of bleeding were also commonly reported. Of the patients studied, 81% were diagnosed with δ-SPD. Our investigation of 5HT concentration extracted from PLs revealed significantly lower levels of 5HT in POTS patients when compared to that of control subjects. Our data suggest that patients with POTS have significant comorbidities including bleeding symptoms and/or family bleeding histories, and have diminished PL 5HT levels supporting the hypothesis that POTS is a low 5HT level disorder. While we describe a significant relationship with POTS and δ-SPD, this finding does not constitute an etiology for POTS.Our results establish an additional comorbidity frequently seen in POTS that could explain a number of disparate symptoms often affecting the severity of POTS.

Effect of Cordycepin-Enriched WIB801C from Cordyceps militaris Suppressing Fibrinogen Binding to Glycoprotein IIb/IIIa

In this study, we investigated the effects of cordycepin-enriched (CE)-WIB801C, a n-butanol extract of Cordyceps militaris-hypha on collagen-stimulated platelet aggregation. CE-WIB801C dose dependently inhibited collagen-induced platelet aggregation, and had a synergistic effect together with cordycepin (W-cordycepin) from CE-WIB801C on the inhibition of collagen-induced platelet aggregation. CE-WIB801C and cordycepin stimulated the phosphorylation of VASP (Ser(157)) and the dephosphorylation of PI3K and Akt, and inhibited the binding of fibrinogen to glycoprotein IIb/IIIa (αIIb/β3) and the release of ATP and serotonin in collagen-induced platelet aggregation. A-kinase inhibitor Rp-8-Br-cAMPS reduced CE-WIB801C-, and cordycepin-increased VASP (Ser(157)) phosphorylation, and increased CE-WIB801C-, and cordycepin-inhibited the fibrinogen binding to αIIb/β3. Therefore, we demonstrate that CE-WIB801C-, and cordycepin-inhibited fibrinogen binding to αIIb/β3 are due to stimulation of cAMP-dependent phosphorylation of VASP (Ser(157)), and inhibition of PI3K/Akt phosphorylation. These results strongly indicate that CE-WIB801C and cordycepin may have preventive or therapeutic potential for platelet aggregation-mediated diseases, such as thrombosis, myocardial infarction, atherosclerosis, and ischemic cerebrovascular disease.

Inhibition of human platelet function by sulfatides

Sulfatides are glycolipid constituents of human platelet cell membranes and have been shown to interact with platelet-binding proteins involved in hemostasis. Because little is known about the physiological role of sulfatides in platelet function, the effect of sulfatide on platelet adhesion, aggregation, release, and ristocetin-induced platelet agglutination (RIPA) was studied. These processes are inhibited when exogenous sulfatide is present in vitro. Inhibition of aggregation induced by collagen, thrombin, and ristocetin by sulfatide was dose dependent. Adenosine diphosphate-mediated adhesion and aggregation were not significantly affected by sulfatide, nor was serotonin- and epinephrine-mediated aggregation. Collagen mediate release of serotonin was reduced sulfatide. RIPA demonstrated dose-dependent inhibition in response to sulfatide. These results suggest that sulfatide may play a role in modulating platelet activation.

Perturbed epidermal pterin metabolism in Hermansky-Pudlak syndrome

In Hermansky-Pudlak Syndrome (HPS) a mutation in a 79.3 kDa transmembrane protein has been shown. The function of this protein has escaped definition so far. This study unveils a defective (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (6BH4) de novo synthesis/recycling for this cofactor in HPS, where activities of the key enzyme GTP-cyclohydrolase I are in the normal range, but total biopterin levels are significantly decreased in homozygotes (n = 5) compared with unaffected controls (n = 4) (p = 0.00001). Phenylalanine hydroxylase and 4a-hydroxy-6BH4-dehydratase activities are significantly lower. mRNA of all enzymes involved in 6BH4 biosynthesis/recycling and GTP-cyclohydrolase I feedback regulatory protein were expressed in keratinocytes from homozygotes, heterozygotes, and healthy controls. Thioredoxin/thioredoxin reductase can directly control the redox status of 6BH4. These activities are allosterically controlled by calcium. Therefore calcium would directly affect this redox status. In HPS these enzyme activities are low concomitant with a defective calcium uptake, suggesting an extracellular accumulation of this second messenger. In this context phenylalanine hydroxylase is subject to phosphorylation/activation by calcium/calmodulin activated kinases. Therefore it was anticipated that calcium could directly affect the cellular L-phenylalanine turnover to L-tyrosine. A significantly more rapid L-phenylalanine uptake and its turnover to L-tyrosine was identified in normal human melanocytes (n = 5) and keratinocytes (n = 2), and was more enhanced in melanocytes in the presence of 2 x 10(-3) M calcium. The turnover to L-tyrosine was significantly slower. Based on all evidence to date, we speculate that the mutated protein in HPS could be primarily involved in maintaining calcium homeostasis in this patient group.

The empty sack syndrome: a platelet storage pool deficiency associated with empty dense granules

Two sisters with lifelong bleeding tendencies were examined to determine whether their condition was associated with a platelet defect. Their platelet aggregation in response to epinephrine and collagen was abnormal, and the secretion of serotonin and ATP was markedly reduced. The platelet contents of serotonin, ADP, and ATP were all diminished and the ATP:ADP ratio was increased. Direct enumeration by whole-mount and quinacrine-fluorescence techniques demonstrated that the platelets from both sisters had significantly fewer dense granules than controls. These characteristics are similar to an individual with Hermansky-Pudlak syndrome and are consistent with a platelet dense granule deficiency. In contrast, immunofluorescence studies using an antibody against the dense granule membrane protein granulophysin suggested that both sisters had numbers of granules within the normal range. Evaluation by immunoblotting and ELISA indicated the presence of normal levels of granulophysin in the platelets from both sisters; FACS analysis demonstrated the surface expression of granulophysin under conditions of selective dense granule release. These results are consistent with these sisters having a form of dense granule storage pool deficiency where the granular membranes are present but the granules have reduced contents. This observation represents a novel form of storage pool disease which we have termed the empty sack syndrome.

Inherited bleeding disorders

Congenital bleeding disorders comprise a heterogeneous group of diseases that reflect abnormalities of blood vessels, coagulation proteins and platelets. Studies of these diseases, many of which are rare and several of which result in a mild bleeding diathesis only, have significantly increased our understanding of normal haemostasis. Two lessons have been learned. First, quantitative abnormalities of coagulation proteins and platelets are an important, but not the only, cause of significant haemorrhage; some cases of inherited bleeding disorders reflect synthesis of a dysfunctional coagulation protein or production of abnormal platelets. Diagnostic tests that reflect qualitative abnormalities are therefore important in the evaluation of selected patients with inherited bleeding disorders. Second, in occasional patients the inherited disorder is complex and reflects combined abnormalities of coagulation proteins alone or in association with platelet disorders. In clinical practice it is useful to distinguish disorders that cause significant clinical bleeding from those that cause few or no symptoms. Examples of the former include severe deficiencies of factors VIII and IX, and the homozygous forms of factor II, V, VII, X, XI, XIII, fibrinogen and von Willebrand factor. Comparable platelet disorders include the inherited thrombocytopenias with platelet counts less than 20 x 10(9) litre-1 and the homozygous forms of Bernard-Soulier syndrome and Glanzmann's thrombasthenia. The most frequently encountered mild haemostatic abnormalities include type I von Willebrand's disease, the platelet storage pool deficiency syndromes and the mild and moderate forms of haemophilia A and B; occasionally heterozygous or homozygous forms of the rarer coagulation disorders, e.g. factor XI deficiency, may present with a mild bleeding diathesis. Finally, some disorders are entirely asymptomatic, e.g. factor XII deficiency and deficiencies of other contact coagulation factors. Management of patients with inherited bleeding disorders should reflect knowledge of the specific disorder to be treated plus careful consideration of the clinical circumstance for which therapy is proposed. In all cases, once a decision to treat has been made, the safest efficacious therapy should be given (for example DDAVP in the treatment of patients with mild haemophilia A or type I von Willebrand's disease). Although blood products are now much safer and the risk of blood transmitted viral infections is low, there still remains a risk that transfusion of any blood product may be associated with serious side-effects. As a result, therapy should be given only after careful consideration of the risk: benefit ratio and not merely to treat an abnormal laboratory result.(ABSTRACT TRUNCATED AT 400 WORDS)

The Hermansky-Pudlak syndrome. Variable reaction to 1-desamino-8D-arginine vasopressin for correction of the bleeding time

The effect of the synthetic vasopressin derivative 1-desamino-8D-arginine vasopressin (DDAVP = Minrin) on bleeding time was studied in nine patients with Hermansky-Pudlak syndrome; four of them were Dutch, five were Belgian. Shortening of bleeding time was observed in four of the patients with this type of storage pool disease; in one patient the response was equivocal, in two patients the response was not dramatic and in two there was no response at all. DDAVP may be useful in managing the bleeding disorder in some patients with Hermansky-Pudlak syndrome. Therefore, every patient with this syndrome should be tested with DDAVP as a preventive measure.

Structural defects in inherited and giant platelet disorders

As diverse as the group of inherited structural defects and giant platelet disorders presented in this chapter may seem, there is a common thread that ties them together. All appear to represent some form of membrane aberration. Sometimes only a small inclusion identifies the membrane defect, sometimes a massive increase in size. In others, whole populations of organelles are missing or surface membranes lack specific glycoproteins essential for their function. All of them are born in the deep recesses of a hidden cell, the bone marrow megakaryocyte. Getting the megakaryocyte out into the light of day, or at least into a culture medium, should certainly lead to the solution of many, if not all, of the disorders of platelet membranes and membrane disorders. We have not been completely successful in our efforts to study the megakaryocyte in vitro. As a result, we do not yet understand the normal megakaryocyte, much less normal platelet. The megakaryocyte presents one of the greatest of challenges to our understanding of membrane biology. As our knowledge of how its cytoplasm fills with interiorly and exteriorly derived membranes, and the mechanisms underlying their organization into platelet surfaces, channels of the OCS and DTS, membrane complexes, and five kinds of organelles become clear, our ability to define the basic nature and inheritance of defects will improve rapidly. Within the next decade most aspects of platelet molecular genetics and cell biology will be solved.

Hermansky-Pudlak syndrome: correction of bleeding time by 1-desamino-8D-arginine vasopressin

The effect of the synthetic vasopressin derivative 1-desamino-8D-arginine vasopressin (DDAVP = desmopressin) on bleeding time was studied in three patients with Hermansky Pudlak syndrome. A good response was observed in this type of storage pool disease. DDAVP might be useful in managing the bleeding disorder found in patients with the Hermansky-Pudlak syndrome.

Circulating monoamine oxidase B and phenolsulfotransferase activities in essential hypertensive patients

Circulating monoamine oxidase (MAO) and phenolsulfotransferase M and P (PST M, PST P) activities were determined in 24 untreated essential hypertensive patients and in 35 age-matched normotensive healthy controls. These enzymes are involved in the inactivation of monoamines and their metabolites. After lysis of blood, enzymatic activities were determined by radioenzymatic techniques using as substrates [14C]-beta-phenylethylamine for MAO, 3-methoxy-4-hydroxyphenylglycol for PST M and phenol for PST P. MAO activity measured by this method is fully accounted for by platelet MAO B activity. Women presented higher MAO activity than men. Significantly lower MAO-B activities were observed in hypertensive patients, both in men and in women, when compared to normotensive controls. Circulating PST activities, of which more than 80% is platelet-derived, were similar in hypertensive and normotensive subjects. These data suggest that the intracellular serotonin inactivation processes, through MAO and PST, cannot account for the reduction of platelet 5-HT content observed in essential hypertension.

Hereditary and acquired thrombopathias

Normal platelet function is essential for hemostasis. The pathophysiologic processes that result in acquired quantitative platelet abnormalities are detailed. Platelet pathophysiology associated with acquired qualitative disorders, either drug-induced or secondary to disease, is discussed. Numerous hereditary platelet defects also exist. Their functional and biochemical features are presented.

Interaction between lymphocytes and platelets in the synthesis of prostacyclin

To test the hypothesis that prostacyclin (PGI2) is formed via a biochemical interaction between platelets and lymphocytes, we measured eicosanoids by high performance liquid chromatography (HPLC) and radioimmunoassay (RIA). A distinct 6-keto-prostaglandin F1 alpha (6KPGF1 alpha) peak was noted when [14C]arachidonic acid ([14C]AA) was added to the mixed cell preparations which was increased by pretreating platelets with 1-benzylimidazole (1-BI). Lymphocytes prelabeled with [14C]AA failed to form 6KPGF1 alpha when stimulated with phytohemagglutinin (PHA) or ionophore A23187. When the prelabeled platelets were suspended together with aspirin-treated lymphocytes and stimulated with ionophore, thrombin, or collagen, a 6KPGF1 alpha peak was detected and enhanced by 1-BI. These results were supported by quantifying the 6KPGF1 alpha content in the HPLC-purified fraction by RIA. Adding prostaglandin H2 (PGH2) directly to lymphocytes led to 6KPGF1 alpha production. Platelet aggregation and release were inhibited by lymphocytes in a dose-related manner. We conclude that lymphocytes possess PGI2 synthase activity which is capable of converting platelet-derived PGH2 into PGI2. PGI2 formed is sufficient to inhibit platelet function.

Hermansky-Pudlak platelets: further studies on release reaction and protein phosphorylations

Platelets from a patient with the Hermansky-Pudlak syndrome were studied. These platelets had decreased amounts of serotonin and adenine nucleotides, and a decreased number of mepacrine-labeled dense bodies. beta-Thromboglobulin and acid hydrolases contained in alpha-granules and lysosomes respectively were present in normal amount. Platelets in platelet-rich plasma did not respond to collagen, but arachidonic acid and ionophore A 23187 induced normal aggregation and normal thromboxane (TX) synthesis. Alpha-granule release was found impaired and remained subnormal even with high doses of inducers. In response to thrombin aggregation, release and TX synthesis of isolated metrizamide gradient platelets were found at lower than normal levels. Phosphorylation of P20 and P43 proteins was normal. Only a combination of ADP plus thrombin could restore a normal aggregation, with normal alpha-granule and lysosome release and normal TX synthesis. These results indicated that in the absence of dense bodies: the release of other granules is impaired; the TX synthesis is delayed except when induced by arachidonic acid and A 23187 ionophore; the absence of dense bodies could be compensated for by the addition of ADP which restores the impaired release reaction and TX formation; and P20 and P43 polypeptides were phosphorylated as rapidly as those in normal platelets.

Inherited abnormalities of the platelet membrane and secretory granules

Platelet stimulus-activation-contraction-secretion coupling is linked to fundamental modifications in the biochemistry and ultrastructure of the platelet surface and the membranes enclosing storage organelles. It is not surprising, therefore, that membrane defects are common in platelets from patients with inherited hemorrhagic disorders caused by platelet dysfunction. In fact, it might be stated that all inherited disorders of platelet function are related directly or indirectly to abnormalities of membranes. The current review discusses the state of knowledge on inherited platelet membrane defects of the cell surface and storage organelles.

Hemostatic defects in response to aspirin challenge in hypothyroidism

A patient with hypothyroidism had ingested aspirin and bled profusely following dental extraction. The only abnormalities noted on coagulation survey were a prolonged aspirin bleeding time and reduced retention of platelets on glass beads. Based on this index case, an additional 12 hypothyroid patients, on no medications, were evaluated for a mild bleeding disorder, including studies with aspirin challenge. The results indicate that thrombin-induced platelet serotonin release, following aspirin ingestion, was subnormal in most hypothyroid patients. However, only hypothyroid individuals with TSH levels of greater than 60 microU/ml have an increased hemostatic sensitivity to aspirin, as measured by the bleeding time test. These findings did not appear to result from decreased synthesis of the factor VIII-von Willebrand factor complex. As this drug is commonly ingested, the effects of aspirin on bleeding may explain the easy bruising and menorrhagia that occur in hypothyroid individuals.

Effects of phorbol diesters and teleocidin on normal human platelets

Teleocidins are newly described indole alkaloid tumor promoters that are structurally distinct from phorbol diesters (PDE). We compared the effects of teleocidin and selected PDE on platelet aggregation, secretion and aspects of arachidonate metabolism. Three tumor-promoting PDE (phorbol myristate acetate (PMA), phorbol dibutyrate (PDBu) and 4-beta-phorbol didecanoate (4-beta-PDD] and a non-tumor promoting PDE (4-alpha-phorbol didecanoate (4-alpha-PDD] were used. Teleocidin and tumor promoting PDE caused platelet aggregation after a delay that was inversely related to tumor promoter concentration and also triggered secretion of alpha- and dense granules and selective release of lysosomal enzymes. Aggregation and its associated 125I-fibrinogen binding to platelets were both inhibited by Na2EDTA. 4-alpha-PDD was ineffective. Analysis of platelet aggregation responses and activation kinetics revealed that PDBu was 11.7 times less potent than teleocidin PMA, or 4-beta-PDD. Neither PDE nor teleocidin stimulated 14C-arachidonate release from normal human platelets, and both aggregated aspirin-treated platelets. These results show that representatives of two structurally distinct classes of tumor promoters, phorbol diesters and indole alkaloids, are potent activators of platelet aggregation, fibrinogen binding, and granule/lysosomal secretion, by a mechanism that bypasses arachidonate release and formation of cyclooxygenase-dependent arachidonate metabolites.

Platelet granule disorders

The present review has cataloged the inherited and acquired disorders of platelet granules. Unfortunately, a mere listing of different conditions in which dense bodies, alpha granules, or both are decreased, absent, or fused does little to define their importance in human platelet physiology or as a causative factor in hemorrhagic disease. The inherited disorders serve as the best index of granule involvement in platelet hemostatic function. Our experience with storage pool deficiency in patients with Hermansky-Pudlak syndrome has suggested that in many individuals virtual absence of dense bodies and their contents does not present a serious threat to hemostasis. Placing HPS patients on aspirin did not cause spontaneous hemorrhage, suggesting that secretion of dense body contents and synthesis of endoperoxides and thromboxane A2 are not absolutely essential for platelet function. However, the literature strongly suggests that many patients with HPS and SPD face a serious risk from bleeding, and hemorrhage may cause death. We can only conclude that some patients with HPS have platelet defects or other hemostatic problems that render SPD a far more serious threat than in other patients who appear to have the same disease. Dense bodies of and by themselves do not appear absolutely required for platelet function. Isolated deficiency of alpha granules presents the same enigma. Only a few patients with this rare inherited disease have been reported. They are generally considered to have mild to severe hemorrhagic problems. However, the past medical history of our two patients with GPS has recently been reviewed and platelet function studies repeated. Despite the mild thrombocytopenia, they are free of any significant bleeding episodes and their platelet function appears virtually normal. Our findings do not support the concept that alpha granules are essential for platelet function. The only condition that seems to support a critical role for storage organelles in hemostasis is the combined alpha-granule, dense body deficiency in one patient reported by Weiss. This patient does have bleeding problems. However, it is difficult to draw conclusions based on a single patient, and the discovery of other patients will help to clarify the hemostatic problem of patients with dual storage organelle deficiencies. In the meantime, we have prepared platelets from normal individuals free of storage granules by sedimentation through gradients containing cytochalasin B. The function of the normal agranular platelets is compromised, but they do respond to some aggregating agents.(ABSTRACT TRUNCATED AT 400 WORDS)

ATP-ADP compartmentation in storage pool deficient platelets: correlation between granule-bound ADP and the bleeding time

Platelets contain two major compartments of ATP and ADP, the cytosol and the dense granules. We separated the two compartments by controlled digitonin-induced cell lysis and measured both fractions directly in the platelets of 16 patients with storage pool deficiency. The total contents of ATP and ADP in the platelets of these patients was significantly lower than in normal controls. This was primarily caused by decreased amounts of ATP and ADP in the granule compartment, but also cytosolic ADP was low in these patients. In contrast, cytosolic ATP was not significantly decreased. The lower the amount of granule-bound ATP and ADP, the longer was the bleeding time in these patients. The best correlation was found with granule ADP. These data may indicate that ADP stored in platelet dense granules plays a role in the arrest of bleeding.

Evidence that abnormal platelet functions in human Chédiak-Higashi syndrome are the result of a lack of dense bodies

The structure and functions of platelets from three patients with the Chédiak-Higashi syndrome were examined. Electron-microscopic observations revealed a large reduction in the number of serotonin-storage granules or dense bodies but otherwise normal ultrastructure and normal amounts of alpha-granules and catalase-positive granules. The number of mepacrine-labeled granules was also reduced. Platelets contained normal amounts of beta-thromboglobulin and Platelet Factor 4. The platelet release reaction studied with thrombin as the inducer was impaired. The serotonin uptake by the patients' platelets was low and not inhibited by reserpine, and its metabolism was increased. These findings clearly show that platelets from human Chédiak-Higashi syndrome are deficient in the storage pool of dense granule substances and suggest that this granule defect has an influence on the release mechanism of other granule constituents.

Mechanisms of abnormal platelet aggregation in systemic lupus erythematosus

Platelet aggregation was measured in 14 patients with systemic lupus erythematosus (SLE) and 13 normal controls. Ten SLE patients (group I) showed decreased responsiveness to collagen, while aggregation was normal in 4 (group II). Group I patients also responded poorly to epinephrine. Platelets from SLE patients did not differ from controls in the production of malondialdehyde in response to N-ethylmaleimide, suggesting intact prostaglandin synthetic pathways. However, a significant decrease (P less than 0.005) in platelet levels of the dense granule constituent, serotonin, was noted in group I SLE patients. Treatment of SLE platelet-rich plasma with deoxyribonuclease (DNase) resulted in enhancement of collagen-induced aggregation in 4 group I SLE patients, but not in 1 group II or 8 normal individuals. These results suggest that defective aggregation in SLE platelets may be partially related to a storage pool deficiency state. However, the ability to restore aggregation to collagen by digestion of platelet-rich plasma with DNase indicates that the defect is reversible and that it is perhaps mediated by plasma or platelet-associated DNA.

Effects of colchicine and vinblastine on platelet contractility and release

Pre-incubation of normal platelet-rich plasma for 30 minutes at 37 degrees C with concentrations of colchicine (2.5 x 10(-4)M) or vinblastine (1.1 x 10(-4)M) which disrupt platelet microtubles did not inhibit aggregation induced by ADP or collagen. Even following pre-incubation of platelets with a 10-fold higher concentration of colchicine (2.5 x 10(-3)M), platelets released 14C-serotonin and aggregated in response to collagen. In the presence of a 10-fold higher vinblastine concentration (1.1 x 10(-3)M), platelets lysed and released 51Cr. Dynamic viscoelastic measurements on recalcified platelet-rich plasma in a Weissenberg rheogoniometer demonstrated that neither colchicine (2.5 x 10(-4)M to 5 x 10(-3)M) nor vinblastine (1.1 x 10(-4)M) interferes with the initiation, rate of generation, or extent of contractile force produced in platelet-fibrin clots. These results indicate that polymerized tubulin is not essential for collagen-induced release of platelet dense granule contents. In addition, intact tubulin polymers are not required to support the platelet surface configuration necessary for platelet-fibrin adherence and the platelet contractile events which result in platelet-fibrin clot retraction.

Ophthalmic manifestations of the Hermansky-Pudlak syndrome (oculocutaneous albinism and hemorrhagic diathesis)

We report the association of oculocutaneous albinism and defective platelet function, the Hermansky-Pudlak syndrome, in two young Puerto Rican patients, a 17-year-old boy and a 9-year-old girl. Wide variation in pigmentation may obscure the diagnosis of albinism. Puerto Rican albinos are at increased risk of inheriting this autosomal recessive syndrome. Although usually mild, bleeding in affected patients can be life-threatening, especially after aspirin administration. Albino patients should be questioned about a history of bleeding and referred for hematologic consultation.

Decreased platelet serotonin levels in systemic lupus erythematosus

Platelet serotonin levels were measured in 41 patients with systemic lupus erythematosus (SLE) and 36 normal controls. SLE patients had significantly lower mean serotonin levels (243 +/- 131 versus 414 +/- 175 ng/10(9) platelets, P less than 0.001); the lowest levels occurred in those patients with active disease. No differences in mean platelet serotonin levels were found when we compared patients with or without a history of renal disease, thrombocytopenia, or neuropsychiatric involvement. Decreased release of platelet granule constituents, as measured by plasma levels of the alpha-granule protein, beta-thromboglobulin.

Standardization of platelet function tests

Methods for the standardization of several currently used platelet function tests (bleeding time, capillary fragility, platelet retention, platelet aggregation, platelet factor 3, and platelet volume profiles) are presented, Different variables than may interfere with the reproducibility of the results of each assay were identified and standardized. Using the standardized techniques, the range of normal values for each test was determined in a large population of normal volunteers and used to identify disease states by comparing patient results with those of the normal population. A format for presenting the entire profile of platelet function parameters is proposed.

Hermansky-Pudlak syndrome: albinism with lipofuscin storage

The Hermansky-Pudlak Syndrome, a "tyrosinase positive' form of oculocutaneous albinism, is a triad comprising albinism, a hemorrhagic diathesis and ceroid-lipofuscin storage. A pedigree is presented showing consanguinity with a pattern of pseudodominance. Electroretinography in two isolated Hermansky-Pudlak subjects was distinctly abnormal, showing decreased rod and cone responses (as well as abnormal flicker fusion responses) in one patient, and reduced photopic and scotopic responses in another. The decreased ERG responses are discussed with reference to the known retinal abnormalities in both generalized oculocutaneous albinism and Batten's disease, another ceroid-lipofuscin storage disorder.

Radioenzymatic assay of platelet serotonin, dopamine and norepinephrine in subjects with normal and increased serotonin production

Platelet serotonin, dopamine and norepinephrine concentrations were determined with sensitive and specific radioenzymatic methods in normal volunteers and in sick subjects with both normal and increased serotonin production. In the assays, a 3H-labeled methyl group is transferred from [3H]S-adenosyl methionine to the monoamine under investigation by a semi-purified enzyme. The platelet serotonin concentration (expressed as pmol serotonin/mg platelet protein) was significantly higher in the patients with increased serotonin production from carcinoid tumors (5400 +/-0 500) than in the normal volunteers (900 +/- 100) or the sick subjects with normal serotonin production (900 +/- 100). Although eight of the subjects with increased serotonin production had symptoms of the carcinoid syndrome such as flushing and diarrhea, two of the subjects with increased serotonin production did not have these symptoms. The radioenzymatic method of platelet serotonin measurement was as effective as a conventional fluorometric technique for serum serotonin in detecting patients with serotonin overproduction from carcinoid tumors, and had the advantages of being more sensitive and specific. The great sensitivity and specificity of the radioenzymatic techniques suggest that it might be useful in evaluating disease states in which platelet serotonin is decreased. Using these techniques we found that dopamine and norepinephrine were also present in platelets, although in much lower amounts than serotonin. Despite the markedly increased serotonin concentration in the platelets of subjects with serotonin overproduction from carcinoid tumors, there was no alteration in the dopamine or norepinephrine concentration of their platelets.

Hereditary bleeding disorder due to a primary defect in platelet release reaction

A large family with a hereditary bleeding disorder was investigated. Easy bruising, epistaxis and menorrhagia were noted in seven members of three generations and at least one member in each generation was affected. Platelet function abnormalities were characterized by reduced 14C-serotonin release, absent second wave aggregation in response to ADP or epinephrine and reduced aggregation in response to collagen. Bleeding time was prolonged in three individuals and platelet factor 3 availability was abnormal in four. Platelet count, morphology, adhesiveness and clot retraction were normal in all. Platelet ADP and ATP as well as ATP to ADP ratio were normal. This family probably represents the first documented instance of hereditary platelet primary release disorder. To elucidate the pathogenetic mechanism, further functional studies were performed. No appreciable shape change, 14C-serotonin release of aggregation was observed when the propositus' platelets were stimulated with sodium arachidonate or a PGH2 analogue. By contrast, platelets responded normally to ionophore A23187, thrombin and ristocetin. The findings indicate that the hereditary primary release disorder is probably due to a reduced thromboxane A2 production secondary to thromboxane synthetase deficiency. Alternatively, it may be due to platelet membrane abnormalities which render platelets unresponsive to thromboxane A2.

Cryopreservation of platelets: an in-vitro comparison of four methods

Platelets were cryopreserved in four different cryoprotectives-two intracellular (dimethylsulphoxide, glycerol) and two extracellular (hydroxyethyl starch, dextran). The platelets were evaluated according to their yields, hypotonic shock response, and serotonin uptake, which are useful parameters for establishing optimum storage conditions. Hydroxyethyl starch and dextran were found to be poor cryoprotectives while 5% dimethylsulphoxide was the most suitable.

Storage pool disease: comparative fluorescence microscopical, cytochemical and biochemical studies on amine-storing organelles of human blood platelets

The platelet content of ATP, ADP, serotonin (5-HT), dopamine, noradrenaline and adrenaline as well as the net uptake of radiolabelled 5-HT and mepacrine were subnormal in six patients with Storage Pool Disease (SPD). Fewer amine-storing organelles were found by fluorescence microscopy with the fluorescent probe mepacrine and by electron microscopy with a cytochemical (uranaffin) reaction specific for 5'-phosphonucleotides. Both methods showed that SPD platelets have atypical organelles with a reduced capacity to store amines, 5'-phosphonucleotides and mepacrine. The changes were most marked in platelets of the two patients who also had oculocutaneous albinism.

Characterization of platelets from normal mink and mink with the Chediak-Higashi syndrome

Bleeding times of mink with the Chediak-Higashi (CH) syndrome was markedly prolonged. Platelet counts were normal but there was an impaired platelet aggregation response to collagen. The metabolic adenine nucleotide pool of platelets from normal and CH mink was labeled with 14C-adenine and the platelets were gel-filtered. Gel-filtered platelets (GFP) from CH mink contained only 37.9% of the adenosine triphosphate (ATP) and 9.6% of the adenosine diphosphate (ADP) found in normal platelets and the ATP/ADP ratio was similar to the 14C-ATP/14C-ADP ratio. Platelet content of Ca2+, Mg2+, and in particular 5-hydroxytryptamine was decreased. When GFP were incubated with thrombin to induce maximal secretion, only negligible amounts of ATP and ADP were released. The specific activity of the extracellular nucleotides approximated that within the platelet. These findings suggest that the stored nucleotide pool in CH platelets is virtually absent and that the abnormalities in platelet function may be due, in part, to the essential absence of secretable ADP and serotonin. The release of Ca2+ and Mg2+ by CH platelets was 56% and 27.8% of normal, respectively.

Platelet function in hairy-cell leukaemia

A quantitative study of various aspects of platelet function was carried out in eight patients with typical hairy-cell leukaemia (HCL). In at least two patients platelet aggregation was convincingly reduced to more than one aggregating agent (ADP, adrenaline, collagen, thrombin, and ristocetin). Granular storage capacity for {(14)C} 5-HT was reduced in five of the six patients tested. The two patients with definitely abnormal aggregation had the greatest reduction in granular storage pool and the longest bleeding times of those tested but, like the other patients, they did not have a clinical haemostatic defect. It was concluded that a granular storage pool defect (SPD) was at least partly responsible for aggregation abnormalities in HCL since the platelet release reaction in response to thrombin appeared to be normal. All our patients ran a chronic course uncomplicated by any of the factors known to predispose to a platelet SPD acquired in the circulation. Although in the one patient tested before and after splenectomy there was some improvement in platelet aggregation after operation, there was no clear general relationship between defective platelet function and either previous splenectomy or platelet count. Since a direct involvement of the megakaryocytic series in the underlying cell proliferation of HCL seems unlikely, it is concluded that the platelet defect can most reasonably be attributed to the production of abnormal platelets as a result of marrow fibrosis and/or infiltration by hairy cells.

Isolated deficiency of platelet procoagulant activity

This is a study of a 34 year old woman with a moderate to severe bleeding disorder in whom impaired platelet procoagulant activity (PPA) was found by several methods, including tests of factor 3 availability (PF-3a), prothrombin consumption and contact activation. No deficiencies of platelet adhesion, aggregation, secretion, metabolism or granule-bound substances were detectable. Under adequate platelet coverage, this woman underwent two surgical procedures without difficulty. These findings demonstrate the role of PPA in hemostasis and indicate that a defect in PPA can be an isolated occurrence. The abnormalities in PF-3a found in this patient could be due to the diminished number of factor V binding sites, resulting in impaired factor Xa binding, found in separate studies by Majerus et al.

Giant platelet granules in a child with the Chediak-Higashi syndrome

Previous ultrastructural investigation have not identified abnormal lysosomes in platelets obtained from humans or animals with the Chediak-Higashi Syndrome. We report here a patient whose megakaryocytes and platelets were found to contain giant granules when viewed by light and electron microscopy. The granules measured up to 1.5 micrometer in diameter, contained either homogeneous or heterogeneous material, were acid phosphatase positive, and were present in approximately 30% of bone marrow megakaryocytes and 5% of circulating platelets. A decrease was observed in serotonin containing dense granules, serotonin uptake and serotonin release as reported previously. Microtubules in platelets and megakaryocytes were intact and no other morphologic abnormalities were identified. No clinical evidence of bleeding was observed in this patient and platelet counts have been normal. The lack of giant platelet lysosomes in other reported cases of Chediak-Higashi Syndrome attests to significant heterogeneity in this disease with a spectrum of clinical and laboratory findings.

The ultrastructure of defective human platelets

Much of our current knowledge about the physiology of hemostasis has come from intensive study of platelets from patients with inherited and acquired bleeding disorders or an increased risk of thrombotic disease. Appreciation of the role of plasma proteins in platelet stickiness, of platelet surface membrane glyco-proteins in aggregation, of the substances stored in platelet organelles in cell-cell interaction, vascular injury and atherosclerosis, and of endoperoxides and thromboxanes in platelet intercellular communication have resulted largely from investigations on various types of defective platelets. While the techniques of physiology and biochemistry have generated critical details about abnormal platelets, electron microscopy and ultrastructural cytochemistry have provided an improved morphological framework in which to integrate the new discoveries. The present review has attempted to correlate physiological, biochemical and ultrastructural concepts as they relate to the current understanding of inherited platelet disorders.