Small‐size platelet microparticles trigger platelet and monocyte functionality and modulate thrombogenesis via P‐selectin

This study aimed to examine the mechanisms of cellular activation by small‐size platelet microparticles (sPMP) and to present the performance of high‐resolution flow cytometry for the analysis of subcellular entities from different origins. Plasma counts of sPMP were analysed in coronary artery disease patients (n = 40) and healthy controls (n = 40). The effect of sPMP and platelet debris (PD) in pathophysiologically relevant doses on platelet and monocyte activation parameters and thrombogenesis was investigated via flow cytometry and thromboelastometry. New generation flow cytometry identifies differences in size, levels and surface molecules of sPMP derived in the absence of stimulus, thrombin activation and platelet disruption. Addition of sPMP resulted in platelet degranulation and P‐selectin redistribution to the membrane (P = 0·019) in a dose and time‐dependent manner. Blood clotting time decreased after addition of sPMP (P = 0·005), but was not affected by PD. Blocking P‐selectin (CD62P) in sPMP markedly reverted the effect on thrombus kinetics (P = 0·035). Exposure to sPMP stimulated monocyte expression of intercellular adhesion molecule‐1 (P < 0·03) and decreased monocyte interleukin‐6 receptor density (P < 0·01). These results implicate sPMP as a direct source of downstream platelet and monocyte activation. In pathological coronary artery disease conditions, higher levels of sPMP favour a prothrombotic state, partly through P‐selectin expression.     

Glucose‐6‐phosphate dehydrogenase deficiency in transfusion medicine: the unknown risks

The hallmark of glucose‐6‐phosphate dehydrogenase (G6PD) deficiency is red blood cell (RBC) destruction in response to oxidative stress. Patients requiring RBC transfusions may simultaneously receive oxidative medications or have concurrent infections, both of which can induce haemolysis in G6PD‐deficient RBCs. Although it is not routine practice to screen healthy blood donors for G6PD deficiency, case reports identified transfusion of G6PD‐deficient RBCs as causing haemolysis and other adverse events. In addition, some patient populations may be more at risk for complications associated with transfusions of G6PD‐deficient RBCs because they receive RBCs from donors who are more likely to have G6PD deficiency. This review discusses G6PD deficiency, its importance in transfusion medicine, changes in the RBC antioxidant system (of which G6PD is essential) during refrigerated storage and mechanisms of haemolysis. In addition, as yet unanswered questions that could be addressed by translational and clinical studies are identified and discussed.     

Rasburicase‐induced methemoglobinemia in two African–American female patients: an under‐recognized and continued problem

Rasburicase‐induced methemoglobinemia is a known adverse effect of patients administered rasburicase for tumor lysis syndrome who have concomitant glucose‐6‐phosphate dehydrogenase deficiency. This phenomenon has been described in multiple case reports but has been limited to male patients. We present the first case series illustrating this adverse effect in two female patients where morbidity and mortality associated with rasburicase‐induced methemoglobinemia were evident. Screening protocols at the reporting institutions were lacking. The prevalence of G6PD may be underestimated based on the epidemiology of sample subjects in previous studies of rasburicase. We argue that both male and female patients should be suspected of G6PD in this setting; however, more data on prevalence and cost‐effectiveness are needed on screening protocols for G6PD.     

Glucose‐6‐phosphate dehydrogenase deficiency: an unusual cause of acute jaundice after paracetamol overdose

Glucose‐6‐phosphate dehydrogenase (G6PD) deficiency is the commonest human enzyme defect causing haemolytic anaemia after exposure to specific triggers. Paracetamol‐induced haemolysis in G6PD deficiency is a rare complication and mostly reported in children. We report the first case (to the best of our knowledge) of acute jaundice without overt clinical features of a haemolytic crisis, in an otherwise healthy adult female following paracetamol overdose, due to previously undiagnosed G6PD deficiency. It is important that clinicians consider this condition when a patient presents following a paracetamol overdose with significant and disproportionate jaundice, without transaminitis or coagulopathy.     

Mediterranean glucose 6-phosphate dehydrogenase (G6PD) deficiency – Near normal decay of the mutant enzyme protein in circulating erythrocytes

Complete removal of leucocytes and platelets from erythrocytes and the development of a sensitized procedure for the assay of G6PD activity allowed the biochemical mechanisms of the Mediterranean variety of G6PD deficiency to be re-evaluated. Activity in the young erythrocytes from 9 G6PD-deficient subjects averaged 0.1% of the levels observed in the corresponding erythrocyte fraction from normal individuals: moreover, the decline of activity during aging of the G6PD-deficient erythrocytes was comparable with that observed for the normal enzyme. Mutant G6PD purified from granulocytes of a G6PD-deficient subject and entrapped within the corresponding erythrocytes was remarkably stable. Exposure of native erythrocytes to an oxidative stress (divicine plus ascorbate) resulted in a decrease of G6PD activity that was significantly more rapid and extensive in control than in G6PD-deficient cells. These results seem to exclude enhanced intracellular breakdown of the mutant protein within the circulating erythrocytes.     

Impact of glucose‐6‐phosphate dehydrogenase deficiency on sickle cell anaemia expression in infancy and early childhood: a prospective study

In patients with sickle cell anaemia (SCA), concomitant glucose‐6‐phosphate dehydrogenase (G6PD) deficiency is usually described as having no effect and only occasionally as increasing severity. We analysed sequential clinical and biological data for the first 42 months of life in SCA patients diagnosed by neonatal screening, including 27 G6PD‐deficient patients, who were matched on sex, age and parents' geographic origin to 81 randomly selected patients with normal G6PD activity. In the G6PD‐deficient group, steady‐state haemoglobin was lower (?6·2 g/l, 95% confidence interval (CI), [?10·1; ?2·3]) and reticulocyte count higher (247 × 10⁹/l, 95%CI, [97; 397]). The acute anaemic event rate was 3 times higher in the G6PD‐deficient group (P < 10^?3). A higher proportion of G6PD‐deficient patients required blood transfusion (20/27 [74%] vs. 37/81 [46%], P < 10^?3), for acute anaemic events, and also vaso‐occlusive and infectious events. No significant between‐group differences were found regarding the rates of vaso‐occlusive, infectious, or cerebrovascular events. G6PD deficiency in babies with SCA worsens anaemia and increases blood transfusion requirements in the first years of life. These effects decrease after 2 years of age, presumably as the decline in fetal haemoglobin levels leads to increased sickle cell haemolysis and younger red blood cells with higher G6PD activity.     

Red cell glucose-6-phosphate dehydrogenase status and pyruvate kinase activity in a Nigerian population

Glucose-6-phosphate dehydrogenase A- (G6PD A-) deficiency is a common enzymopathy in Africa that sporadically leads to manifest haemolytic anaemia. It is not exactly known how far the haematological status of individuals with either homozygous or heterozygous G6PD A- deficiency differs from that of individuals with normal G6PD activity. In a field study in Nigeria, we determined G6PD gene variants, the corresponding G6PD and pyruvate kinase (PK) activities, and basic haematological parameters in clinically healthy individuals, who were, in part, asymptomatically infected by malaria parasites. Red blood cell counts and haemoglobin levels were lower in G6PD A- deficient than in G6PD normal subjects. PK activities were higher in G6PD deficients, indicating a younger red cell population in these individuals. These findings suggest that G6PD A- deficiency is accompanied by chronic subclinical haemolysis. As a consequence, the reduced life span of red cells leads to an impaired diagnosis of G6PD heterozygosity when applying routine biochemical methods.     

Glyburide-induced acute haemolysis in a G6PD-deficient patient with NIDDM

In a 61-year-old man with glucose-6-phosphate dehydrogenase (G6PD) deficiency and poorly controlled non-insulin-dependent diabetes mellitus, an episode of acute haemolysis occurred after the administration of glyburide (glibenclamide). Erythrocyte fragmentation, with haemoglobin condensation zones next to clear zones, was observed on peripheral blood smears. Since autoimmune haemolysis was excluded on the basis of laboratory data, acute haemolysis was ascribed to G6PD deficiency.     

Malaria epidemiology, glucose 6-phosphate dehydrogenase deficiency and human settlement in the Vanuatu Archipelago

Vanuatu is located at the southeast margin of the malarious band extending from southeast Asia to eastern Melanesia. We analysed the malaria situation on different islands of Vanuatu, using passive case detection and malariometric survey data from 1985 to 1992, i.e. after the DDT residual programme ceased and before the impregnated bed-nets programme started on a larger scale. Malaria was mainly hypo-mesoendemic but with hyperendemic spots in certain years and on some islands. The transmission was generally more intense in the northern islands than in the south. In the late 1980s, annual parasite incidence per one thousand population (API) was around 180. The overall parasite rate was 11.9% with Plasmodium falciparum, P. vivax and P. malariae rate of 5.2, 6.7, and 0.1%, respectively. There was a seasonal fluctuation of P. falciparum incidence, whereas the P. vivax incidence was rather stable. Vivax malaria was confined to children less than 10 years old, while the prevalence of P. falciparum only changed moderately with age. The mean rate of glucose 6-phosphate dehydrogenase (G6PD) deficiency among male subjects was in 7.4% but with a wide variation of 0–14.3% on different islands. A positive rank-order correlation was found between malaria incidence and G6PD deficiency rate on the different islands. A reasonable hypothesis is that malaria was introduced to the islands with the first human settlement 4000 years ago, with a geographical malaria distribution similar to the present situation. Different malaria endemicities possibly then selected different prevalences of G6PD deficiency over many generations.     

Glucose-6-phosphate dehydrogenase (G6PD) iserlohn and G6PD regensburg: Two new severe enzyme defects in german families

Summary Two new inheritable variants of glucose-6-phosphate dehydrogenase have been found in two unrelated German families. Patients with one variant (G6PD Iserlohn, also referred to as G6PD I) suffered from intermittent hemolytic crises caused by fava beans; patients with the other variant (G6PD Regensburg, G6PD II) disclosed chronic nonspherocytic hemolytic anemia aggravated by drug treatment. Due to their unusual biochemical characteristics, the new variants were designated G6PD Iserlohn and G6PD Regensburg. Both variants showed a reduction of enzyme activity to about 6% of the normal in erythrocytes, normal electrophoretic mobility, increased affinity for glucose-6-phosphate, a reduced affinity for NADP and a pH optimum in the neutral region (7.0 and 7.5). G6PD Iserlohn had a decreased affinity for the inhibitor NADPH; G6PD Regensburg had a normal inhibitor constant. Deamino NADP was utilized at an increased rate by G6PD Regensburg. G6PD Iserlohn was thermostable, G6PD Regensburg mildly instable. G6PD activity in leukocytes was normal in G6PD Iserlohn and reduced to the same degree as in erythrocytets in G6PD Regensburg. The cause of the decreased activity of G6PD Iserlohn appears to be in vivo instability; in G6PD Regensburg further mechanisms might include reduced specific activity or reduced synthesis of the variant enzyme.     

PD‐1/PD‐L1 pathway and T‐cell exhaustion in chronic hepatitis virus infection

Summary. Dysfunctional virus‐specific T cells are a hallmark of many chronic viral infections. Recent studies have implicated the inhibitory PD‐1/PD‐L1 pathway with the functional impairment of T cells. In this respect, we will review the latest research on PD‐1/PD‐L1 pathway and T‐cell exhaustion in the context of human chronic hepatitis B and C virus infections. We will also discuss the therapeutic potential of PD‐1 blockade and how it may be enhanced through the modulation of other co‐stimulatory/inhibitory pathways.     

Bilirubin levels in the acute hemolytic crisis of G6PD deficiency are related to Gilbert's syndrome.

In this study we analyzed the effect of the (TA)7 polymorphism of the UGT1A gene associated with Gilbert's syndrome in G6PD-deficient subjects during an acute hemolytic crisis (fabic crisis). DNA from 44 subjects originating from the same geographic area in Sardinia was analyzed for the UGT1A promoter polymorphism. The increase of unconjugated bilirubin level during fabic crisis and its relationship with UGT1A polymorphism was evaluated. The UGT1A (TA)7 TATA box variant was found in 9/44 (21%) of the G6PD deficient subjects examined. The median value for unit of increase of bilirubin (mg/dl)/unit of decrease of hemoglobin (g/dl) was higher in variant homozygous than in heterozygous and normal subjects. These findings imply a contribution of the UGT1A polymorphism associated to Gilbert's syndrome to development of the hyperbilirubinemia in G6PD deficient subjects during acute hemolytic anemia.