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Our objective was to assess the effect of maternal intravenous immunoglobulin (IVIG) administration for severe red blood cell (RBC) alloimmunisation on fetal outcomes. This is a case-control study. Women with a history of severe early onset alloimmunisation resulting in fetal loss in a previous pregnancy and high anti-D or anti-K antibody titres received IVIG in a subsequent pregnancy. We assessed gestational age at first transfusion and fetal outcomes in the subsequent pregnancy and compared these with the outcomes in the previous pregnancy. The most responsible antibody was anti-D in 17 women and anti-K in two others, whilst seven had more than one antibody. In all, 19 women received IVIG in 22 pregnancies, two of which did not even need an intrauterine transfusion (IUT). For previous early losses despite transfusion, IVIG was associated with a relative increase in fetal haemoglobin between treated and untreated pregnancies of 36.5 g/L (95% confidence interval 19.8-53.2, p = 0.0013) and improved perinatal survival (eight of eight vs. none of six, p = 0.001). For previous losses at <20 weeks, it enabled first transfusion deferral in subsequent pregnancies to at least 19.9 weeks (mean 23.2 weeks). Overall, IVIG decreases the severity of haemolytic disease of the fetus and newborn and allows deferral of the first IUT to a safer gestation in severe early-onset RBC alloimmunisation and rarely may even avoid the need for IUT entirely.
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Eritroblastosis Fetal , Isoinmunización Rh , Embarazo , Recién Nacido , Humanos , Femenino , Inmunoglobulinas Intravenosas/uso terapéutico , Estudios de Casos y Controles , Eritrocitos , Anticuerpos , Transfusión de Sangre Intrauterina/métodos , Eritroblastosis Fetal/terapiaRESUMEN
Red blood cell (RBC) alloimmunisation with anti-D and anti-K comprise the majority of cases of fetal haemolytic disease requiring intrauterine red cell transfusion (IUT). Few studies have investigated which haematological parameters can predict adverse fetal or neonatal outcomes. The aim of the present study was to identify predictors of adverse outcome, including preterm birth, intrauterine fetal demise (IUFD), neonatal death (NND) and/or neonatal transfusion. We reviewed the records of all pregnancies alloimmunised with anti-K and anti-D, requiring IUT over 27 years at a quaternary fetal centre. We reviewed data for 128 pregnancies in 116 women undergoing 425 IUTs. The median gestational age (GA) at first IUT was significantly earlier for anti-K than for anti-D (24·3 vs. 28·7 weeks, P = 0·004). Women with anti-K required more IUTs than women with anti-D (3·84 vs. 3·12 mean IUTs, P = 0·036) and the fetal haemoglobin (Hb) at first IUT was significantly lower (51.0 vs. 70.5 g/l, P = 0·001). The mean estimated daily decrease in Hb did not differ between the two groups. A greater number of IUTs and a slower daily decrease in Hb (g/l/day) between first and second IUTs were predictive of a longer period in utero. Earlier GA at first IUT and a shorter interval from the first IUT until delivery predicted IUFD/NND. Earlier GA and lower Hb at first IUT significantly predicted need for phototherapy and/or blood product use in the neonate. In the anti-K group, a greater number of IUTs was required in women with a higher titre. Furthermore, the higher the titre, the earlier the GA at which an IUT was required in both groups. The rate of fall in fetal Hb between IUTs decreased, as the number of transfusions increased. Our present study identified pregnancies at considerable risk of an unfavourable outcome with anti-D and anti-K RBC alloimmunisation. Identifying such patients can guide pregnancy management, facilitates patient counselling, and can optimise resource use. Prospective studies can also incorporate these characteristics, in addition to laboratory markers, to further identify and improve the outcomes of these pregnancies.
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Anemia Hemolítica Autoinmune/terapia , Transfusión de Sangre Intrauterina/métodos , Eritrocitos/inmunología , Isoinmunización Rh/fisiopatología , Globulina Inmune rho(D)/metabolismo , Adulto , Femenino , Feto , Humanos , Embarazo , Estudios Retrospectivos , Resultado del TratamientoRESUMEN
Eltrombopag (ELT) is a thrombopoietin receptor agonist reported to decrease labile iron in leukemia cells. Here we examine the previously undescribed iron(III)-coordinating and cellular iron-mobilizing properties of ELT. We find a high binding constant for iron(III) (log ß2=35). Clinically achievable concentrations (1 µM) progressively mobilized cellular iron from hepatocyte, cardiomyocyte, and pancreatic cell lines, rapidly decreasing intracellular reactive oxygen species (ROS) and also restoring insulin secretion in pancreatic cells. Decrements in cellular ferritin paralleled total cellular iron removal, particularly in hepatocytes. Iron mobilization from cardiomyocytes exceeded that obtained with deferiprone, desferrioxamine, or deferasirox at similar iron-binding equivalents. When combined with these chelators, ELT enhanced cellular iron mobilization more than additive (synergistic) with deferasirox. Iron-binding speciation plots are consistent with ELT donating iron to deferasirox at clinically relevant concentrations. ELT scavenges iron citrate species faster than deferasirox, but rapidly donates the chelated iron to deferasirox, consistent with a shuttling mechanism. Shuttling is also suggested by enhanced cellular iron mobilization by ELT when combined with the otherwise ineffective extracellular hydroxypyridinone chelator, CP40. We conclude that ELT is a powerful iron chelator that decreases cellular iron and further enhances iron mobilization when combined with clinically available chelators.
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Benzoatos/farmacología , Espacio Extracelular/metabolismo , Hidrazinas/farmacología , Quelantes del Hierro/farmacología , Hierro/metabolismo , Pirazoles/farmacología , Animales , Benzoatos/química , Línea Celular Tumoral , Deferoxamina/farmacología , Ferritinas/metabolismo , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Humanos , Hidrazinas/química , Insulina/metabolismo , Secreción de Insulina , Células Secretoras de Insulina/metabolismo , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/metabolismo , Pirazoles/química , Piridonas/farmacología , Ratas , Especies Reactivas de Oxígeno/metabolismoAsunto(s)
Trastornos de Fallo de la Médula Ósea , Humanos , Embarazo , Femenino , Adulto , Resultado del Embarazo , Complicaciones Hematológicas del Embarazo/terapia , Enfermedades de la Médula Ósea , Anemia Aplásica/terapia , Recién Nacido , Hemoglobinuria Paroxística/terapia , Hemoglobinuria Paroxística/diagnósticoRESUMEN
INTRODUCTION: Laparoscopic myomectomy offers women many benefits over conventional open surgery, including an expedited recovery and return to employment. Our study evaluates the time taken for women to return to work after laparoscopic myomectomy and identifies factors prolonging recovery to > 8 weeks. MATERIAL AND METHODS: We prospectively evaluated 94 women undergoing laparoscopic myomectomy by a single surgeon between January 2012 and March 2015. Women had standardized preoperative counseling and completed a validated return to work questionnaire 3 months postoperatively via telephone, post or in clinic. RESULTS: In all, 71/94 (75.5%) women completed the questionnaire. Results were analyzed comparing women who returned to work in ≤ 8 weeks [43/71 (60.6%)] with those who returned > 8 weeks postoperatively [28/71 (39.4%)]. A higher proportion of Asian and Caucasian women returned to work in ≤ 8 weeks (24/29) compared with black African and Caribbean women (19/42) (p = 0.003). Mean number of fibroids removed (2.59 and 5.75, respectively) was the only significantly differing factor between the two groups (p = 0.004). There was a significant difference in body mass index (BMI) and time to return to normal activity between the ≤ 8-week and > 8-week groups (p = 0.027, p = 0.011, respectively). Logistic regression analysis demonstrated that BMI and time to return to normal activity were the only factors prolonging recovery to > 8 weeks (p = 0.039, p = 0.015, respectively). CONCLUSIONS: Time to return to normal activity and BMI significantly influenced the time taken for women to work after laparoscopic myomectomy. Further data would support clinicians in counseling women appropriately and optimizing their postoperative return to employment.
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Laparoscopía , Leiomioma , Obesidad/diagnóstico , Reinserción al Trabajo/estadística & datos numéricos , Miomectomía Uterina , Neoplasias Uterinas , Adulto , Índice de Masa Corporal , Femenino , Humanos , Laparoscopía/métodos , Laparoscopía/rehabilitación , Laparoscopía/estadística & datos numéricos , Leiomioma/etnología , Leiomioma/patología , Leiomioma/cirugía , Persona de Mediana Edad , Obesidad/epidemiología , Periodo Posoperatorio , Estudios Prospectivos , Factores de Tiempo , Reino Unido/epidemiología , Miomectomía Uterina/métodos , Miomectomía Uterina/rehabilitación , Miomectomía Uterina/estadística & datos numéricos , Neoplasias Uterinas/etnología , Neoplasias Uterinas/patología , Neoplasias Uterinas/cirugíaRESUMEN
We assessed the attitudes of UK Obstetrics and Gynaecology (O&G) trainees towards a caesarean delivery for maternal request (CDMR); and identified differences in attitude towards patients requesting CDMR and preferences for their own mode of delivery. An internet survey was constructed with questions covering trainees' personal preferences towards and experience of CDMR; attitudes to CDMR; and how they might treat patients making this request. From 02/2013 to 06/2013, the survey was sent electronically via email to all UK Deaneries to be forwarded to O&G trainees. Two hundred and forty O&G trainees participated; 78% female. 6/101 (6%) respondents had opted for CDMR in their first pregnancy. 28/131 (21%) would choose CDMR in their first pregnancy. Reasons for CDMR included concerns about pelvic floor/perineum, safety of the baby and convenience. 105/226 (46.4%) disagreed or strongly disagreed, and 67 (29.6%) agreed or strongly agreed with CDMR. 75/128 (58.6%) of respondents would grant CDMR to a patient; reasons included maternal choice, psychological concerns of the mother, perineal injury, pelvic floor. Our results are encouraging: positive attitudes of trainees towards vaginal delivery may help to reduce the rising caesarean rate. Impact Statement What is already known on this subject: Over the last 30 years, the rate of caesarean section in the UK has trebled and currently accounts for 25% of all deliveries. The rate of caesarean section in the UK has risen to 25% of all deliveries, incurring a financial burden and an excess clinical risk. With pressure to keep the caesarean rates low, understanding the attitudes and experience of obstetricians in training is important. What the results of this study add: Six percent of obstetric trainees, or their partners who had children had chosen a caesarean delivery for maternal request (CDMR), consistent with the population average. Twenty one percent of those who had not had children would choose CDMR. Both groups cited concerns over the pelvic floor as the predominant reason. Fifty nine percent of respondents would grant patients' request for CDMR. 29.6% of respondents agreed, and 46.4% disagreed with CDMR. Trainees' attitude to CDMR does not appear to be associated with whether or not they have had children, but does appear to be associated with whether they had experienced, or were planning to choose CDMR themselves in the future. What the implications are of these findings for clinical practice and/or further research: Training for obstetric trainees regarding the optimum way to manage patients' requests for, and clearer guidance on CDMR may be of benefit. It is important that obstetricians discuss the reasons behind such requests in order to individualise management.
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Actitud del Personal de Salud , Cesárea/estadística & datos numéricos , Procedimientos Quirúrgicos Electivos/psicología , Personal de Salud/psicología , Obstetricia/educación , Prioridad del Paciente/psicología , Adulto , Cesárea/efectos adversos , Parto Obstétrico/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Embarazo , Estudiantes de Medicina/psicología , Encuestas y CuestionariosRESUMEN
Cardiosiderosis is a leading cause of mortality in transfusion-dependent thalassemias. Plasma non-transferrin-bound iron and its redox-active component, labile plasma iron, are key sources of iron loading in cardiosiderosis. Risk factors were identified in 73 patients with or without cardiosiderosis. Soluble transferrin receptor-1 levels were significantly lower in patients with cardiosiderosis (odds ratio 21). This risk increased when transfusion-iron loading rates exceeded the erythroid transferrin uptake rate (derived from soluble transferrin receptor-1) by >0.21 mg/kg/day (odds ratio 48). Labile plasma iron was >3-fold higher when this uptake rate threshold was exceeded, but non-transferrin-bound iron and transferrin saturation were comparable. The risk of cardiosiderosis was decreased in patients with low liver iron, ferritin and labile plasma iron, or high bilirubin, reticulocyte counts or hepcidin. We hypothesized that high erythroid transferrin uptake rate decreases cardiosiderosis through increased erythroid re-generation of apotransferrin. To test this, iron uptake and intracellular reactive oxygen species were examined in HL-1 cardiomyocytes under conditions modeling transferrin effects on non-transferrin-bound iron speciation with ferric citrate. Intracellular iron and reactive oxygen species increased with ferric citrate concentrations especially when iron-to-citrate ratios exceeded 1:100, i.e. conditions favoring kinetically labile monoferric rather than oligomer species. Excess iron-binding equivalents of apotransferrin inhibited iron uptake and decreased both intracellular reactive oxygen species and labile plasma iron under conditions favoring monoferric species. In conclusion, high transferrin iron utilization, relative to the transfusion-iron load rate, decreases the risk of cardiosiderosis. A putative mechanism is the transient re-generation of apotransferrin by an active erythron, rapidly binding labile plasma iron-detectable ferric monocitrate species.
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Apoproteínas/sangre , Eritropoyesis , Hemosiderosis/etiología , Hierro/metabolismo , Miocardio/metabolismo , Talasemia/sangre , Talasemia/complicaciones , Adolescente , Adulto , Animales , Biomarcadores , Transfusión Sanguínea , Línea Celular , Niño , Preescolar , Ácido Cítrico/metabolismo , Estudios de Cohortes , Hemosiderosis/diagnóstico , Humanos , Lactante , Hierro/sangre , Ratones , Persona de Mediana Edad , Miocardio/patología , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/patología , Unión Proteica , Factores de Riesgo , Talasemia/terapia , Transferrina/metabolismo , Adulto JovenAsunto(s)
Infecciones por Coronavirus/congénito , Transmisión Vertical de Enfermedad Infecciosa , Neumonía Viral/congénito , Complicaciones Infecciosas del Embarazo , Adulto , Betacoronavirus , COVID-19 , Prueba de COVID-19 , Cesárea , Técnicas de Laboratorio Clínico , Infecciones por Coronavirus/diagnóstico , Infecciones por Coronavirus/transmisión , Femenino , Humanos , Recién Nacido , Masculino , Nasofaringe/virología , Pandemias , Placenta/patología , Placenta/virología , Neumonía Viral/diagnóstico , Neumonía Viral/transmisión , Embarazo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , SARS-CoV-2RESUMEN
BACKGROUND: The risk of venous thromboembolism (VTE) is 15 to 35-fold higher in the postpartum period compared to non-pregnant individuals. Clinical practice guidelines recommend the use of postpartum thromboprophylaxis with low molecular weight heparin (LMWH) for 6 weeks in individuals at high risk of developing VTE. However, a marked reduction in the risk of VTE risk occurs beyond the third week of the postpartum period. OBJECTIVE: We sought to characterize practice patterns of clinicians who manage postpartum individuals at high risk of VTE. METHODS: We conducted a cross-sectional study using a self-administered electronic questionnaire. The survey explored the use of postpartum thromboprophylaxis in high-risk individuals. Descriptive statistics were used to summarize survey responses. RESULTS: Of the 113 participants that responded to the initial invitation, 78 completed the survey (Europe (53.9 %); North America (23.2 %); Australia and New Zealand (19.0 %)). For individuals with a prior unprovoked or provoked deep venous thrombosis or pulmonary embolism, cerebral vein thrombosis and splanchnic vein thrombosis, 97.4 %, 93.5 %, 91.0 % and 88.5 % of the respondents recommended six weeks of postpartum thromboprophylaxis using LMWH, respectively. The recommendation for 6 weeks of thromboprophylaxis in patients with sickle cell disease and obstetric APS was comparatively lower (70.5 and 78.2 % respectively). Respondents with higher practice volumes and more years of experience in clinical practice were more likely to recommend a shorter duration of thromboprophylaxis. CONCLUSION: Our study highlights the variability in clinician recommendations and the acceptability of treatment durations for postpartum thromboprophylaxis in high-risk conditions. Prospective studies are needed to determine optimal duration and establish evidence-based management.
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ABSTRACT: Advancements in orally bioavailable iron chelators and MRI methods have improved life expectancy and reproductive potential in thalassemia major (TM) and thalassemia intermedia (TI). Pregnancy is associated with adverse maternal and neonatal outcomes, frequency of which has not been well delineated. This systematic review aims to provide risk estimates of maternal and fetal outcomes in TM and TI and explore pregnancy's impact on iron homeostasis. Fifteen studies (429 participants, 684 pregnancies) were included. Meta-analysis revealed a higher thrombosis risk in TI (3.7%) compared to TM (0.92%), unchanged from prepregnancy. Heart failure risks in the earlier years appeared similar (TM 1.6% vs TI 1.1%), and maternal mortality in TM was 3.7%, but with current management, these risks are rare. Gestational diabetes and pre-eclampsia occurred in 3.9% and 11.3% of TM pregnancies, respectively. Caesarean section rates were 83.9% in TM and 67% in TI. No significant difference in stillbirth, small for gestational age neonates, or preterm birth incidence between TM and TI was observed. In TM pregnancies, red cell requirements significantly increased (from 102 to 139 ml/kg/year, P = 0.001), and 70% of TI pregnancies required blood transfusions. As expected, increased transfusion alongside chelation cessation led to a significant increase in serum ferritin during pregnancy (TM by 1005 ng/mL; TI by 332 ng/mL, P < 0.0001). Deterioration in iron status was further reflected by an increase in liver iron concentration (from 4.6 to 11.9 mg/g dry weight, P < 0.0001), and myocardial T2-star (T2∗) magnetic resonance imaging decreased (from 36.2 ± 2.5 ms to 31.1 ms) during pregnancy. These findings emphasize the elevated maternal risk of iron-related cardiomyopathy during pregnancy and labor, stressing the importance of cardiac monitoring and postpartum chelation therapy resumption.
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Nacimiento Prematuro , Talasemia beta , Humanos , Recién Nacido , Embarazo , Femenino , Talasemia beta/complicaciones , Talasemia beta/terapia , Hierro , Resultado del Embarazo , CesáreaRESUMEN
BACKGROUND: The cumulative lifetime risk of ovarian cancer is 16-68% and 11-30% in female BRCA1 and BRCA2 gene alteration carriers, respectively. Risk-reducing bilateral salpingo-oophorectomy (RRSO) is the only proven way to reduce ovarian cancer mortality. We report a series of patients who underwent risk-reducing surgery at the time of planned obstetric-indicated cesarean delivery. CASES: This is a case series of four women carrying a pathogenic germline BRCA1 or BRCA2 gene alteration who underwent RRSO at the time of cesarean delivery between March 1, 2018, and March 31, 2022. All women were referred during pregnancy to the University College London Hospitals Familial Cancer Clinic for consideration of RRSO at the time of obstetric-indicated cesarean delivery. Women were considered eligible for RRSO if they had a proven pathogenic germline alteration, would have completed childbearing after the cesarean delivery, and were older than age 35 or 40 years with BRCA1 or BRCA2 alterations, respectively. Operating time, blood loss, transfusion requirements, length of hospital stay, complications, and ability to breastfeed were assessed and, where possible, compared with the institutional means for similar patients who underwent cesarean delivery only, to determine whether RRSO was associated with increased morbidity. Women were contacted 11-59 months postprocedure to assess satisfaction. The mean blood loss was 687 mL (range 400-1,000 mL), mean operating time was 68 minutes, mean length of hospital stay was 3 days, and mean change in hemoglobin was -1 g/dL. No patient required a transfusion, had internal organ damage, returned to the operating room, or was readmitted. One of two women with intact breast tissue successfully breastfed, and the other chose to bottle feed. The mean contemporaneous institutional blood loss for cesarean delivery was not significantly different at 681 mL for singleton pregnancies and 872 mL for twin pregnancies. All four women reported a high level of satisfaction with the combined procedure. CONCLUSION: Our results show that RRSO can be performed at the time of cesarean delivery with high patient satisfaction. This approach can be offered to appropriately counseled individuals, with the benefit of avoiding the need for two separate procedures, with potentially reduced patient morbidity and health care costs.
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Cesárea , Neoplasias Ováricas , Procedimientos Quirúrgicos Profilácticos , Salpingooforectomía , Adulto , Femenino , Humanos , Proteína BRCA1 , Proteína BRCA2 , Predisposición Genética a la Enfermedad , Mutación , Neoplasias Ováricas/genética , Neoplasias Ováricas/prevención & control , Salpingooforectomía/métodosRESUMEN
Eltrombopag (ELT) is a thrombopoietic agent approved for immune thrombocytopenia and also a potent iron chelator. Here we found that ELT exhibited dose-dependent opposing effects on in vitro megakaryopoiesis: low concentrations (≤6 µM, ELT6) stimulated megakaryopoiesis, but high concentrations (30 µM, ELT30) suppressed megakaryocyte (MK) differentiation and proliferation. The suppressive effects of ELT30 were reproduced by other iron chelators, supporting iron chelation as a likely mechanism. During MK differentiation, committed MK progenitors (CD34+/CD41+ and CD34-/CD41+ cells) were significantly more sensitive than undifferentiated progenitors (CD34+/CD41- cells) to the suppressive effects of ELT30, which resulted from both decreased proliferation and increased apoptosis. The antiproliferative effects of ELT30 were reversed by increased iron in the culture, as were the proapoptotic effects when exposure to ELT30 was short. Because committed MK progenitors exhibited the highest proliferative rate and the highest sensitivity to iron chelation, we tested whether their iron status influenced their response to ELT during rapid cell expansion. In these studies, iron deficiency reduced the proliferation of CD41+ cells in response to all ELT concentrations. Severe iron deficiency also reduced the number of MKs generated in response to high thrombopoietin concentrations by â¼50%, compared with iron-replete cultures. Our findings support the hypothesis that although iron deficiency can stimulate certain cells and steps in megakaryopoiesis, it can also limit the proliferation of committed MK progenitors, with severity of iron deficiency and degree of thrombopoietic stimulation influencing the ultimate output. Further studies are needed to clarify how megakaryopoiesis, iron deficiency, and ELT stimulation are clinically interrelated.
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Sangre Fetal , Células Progenitoras de Megacariocitos , Benzoatos , Diferenciación Celular , Hidrazinas , Hierro/farmacología , PirazolesRESUMEN
ß-thalassemia (ßT) is a genetic blood disorder causing profound and life threatening anemia. Current clinical management of ßT is a lifelong dependence on regular blood transfusions, a consequence of which is systemic iron overload leading to acute heart failure. Recent developments in gene and chelation therapy give hope of better prognosis for patients, but successful translation to clinical practice is hindered by the lack of thorough preclinical testing using representative animal models and clinically relevant quantitative biomarkers. Here we demonstrate a quantitative and non-invasive preclinical Magnetic Resonance Imaging (MRI) platform for the assessment of ßT in the γß0/γßA humanized mouse model of ßT. Changes in the quantitative MRI relaxation times as well as severe splenomegaly were observed in the heart, liver and spleen in ßT. These data showed high sensitivity to iron overload and a strong relationship between quantitative MRI relaxation times and hepatic iron content. Importantly these changes preceded the onset of iron overload cardiomyopathy, providing an early biomarker of disease progression. This work demonstrates that multiparametric MRI is a powerful tool for the assessment of preclinical ßT, providing sensitive and quantitative monitoring of tissue iron sequestration and cardiac dysfunction- parameters essential for the preclinical development of new therapeutics.
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Corazón/diagnóstico por imagen , Sobrecarga de Hierro/diagnóstico por imagen , Hígado/diagnóstico por imagen , Bazo/diagnóstico por imagen , Esplenomegalia/diagnóstico por imagen , Talasemia beta/diagnóstico por imagen , Animales , Cardiomiopatías/diagnóstico por imagen , Cardiomiopatías/metabolismo , Cardiomiopatías/patología , Modelos Animales de Enfermedad , Femenino , Corazón/fisiopatología , Humanos , Hierro/análisis , Hierro/metabolismo , Sobrecarga de Hierro/metabolismo , Sobrecarga de Hierro/patología , Hígado/metabolismo , Hígado/patología , Imagen por Resonancia Magnética/instrumentación , Imagen por Resonancia Magnética/métodos , Masculino , Ratones , Ratones Transgénicos , Bazo/metabolismo , Bazo/patología , Esplenomegalia/metabolismo , Esplenomegalia/patología , Talasemia beta/metabolismo , Talasemia beta/patologíaRESUMEN
Flavonoids are well-known antioxidants and free radical scavengers. Their metal-binding activity suggests that they could be effective protective agents in pathological conditions caused by both extracellular and intracellular oxidative stress linked to metal overload. Quercetin is both a permeant ligand via glucose transport proteins (GLUTs) and a high-affinity inhibitor of GLUT-mediated glucose transport. Chelatable "free iron" at micromolar concentrations in body fluids is a catalyst of hydroxyl radical (OH(â¢)) production from hydrogen peroxide. A number of flavonoids, e.g., quercetin, luteolin, chrysin, and 3,6-dihydroxyflavone, have been demonstrated to chelate intracellular iron and suppress OH(â¢) radical production in Madin Darby canine kidney cells. The most effective chelation comes from the flavonone B ring catechol found in both quercetin and luteolin. We show here that quercetin concentrations of <1µM can facilitate chelatable iron shuttling via GLUT1 in either direction across the cell membrane. These siderophoric effects are inhibited by raised quercetin concentrations (>1µM) or GLUT inhibitors, e.g., phloretin or cytochalasin B, and iron efflux is enhanced by impermeant extracellular iron chelators, either desferrioxamine or rutin. This iron shuttling property of quercetin might be usefully harnessed in chelotherapy of iron-overload conditions.
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Proteínas Facilitadoras del Transporte de la Glucosa/metabolismo , Quelantes del Hierro/farmacocinética , Quercetina/farmacocinética , Animales , Citocalasina B/farmacocinética , Citocalasina B/farmacología , Deferiprona , Deferoxamina/farmacocinética , Deferoxamina/farmacología , Perros , Piridonas/farmacocinética , Piridonas/farmacología , Transducción de Señal/efectos de los fármacos , Espectrometría de FluorescenciaRESUMEN
Duodenal cytochrome b (Dcytb) is a transmembrane oxidoreductase protein found in apical membranes of duodenal enterocytes, as well as human erythrocytes, with the capacity to transport electrons donated by cytosolic ascorbate to extracellular electron receptors such as Fe(III), dehydroascorbate, or molecular O(2). We have investigated the capacity of the flavonoid quercetin to act as an electron donor for Dcytb in a manner similar to that of ascorbate by observing the reduction of extracellular Fe(III) to Fe(II) in either Madin-Darby canine kidney (MDCK) cells overexpressing Dcytb (Dcytb(+)) or Dcytb-null MDCK cells. In Dcytb(+) cells there is a saturable increase in extracellular Fe(III) reduction in response to increasing intracellular quercetin concentrations (K(m)=6.53+/-1.57 microM), in addition to a small linear response, whereas in Dcytb-null cells there is only a small linear increase in extracellular Fe(III) reduction. No extracellular Fe(III) reduction occurs in Dcytb-null cells when the cells are preloaded with ascorbate. Flavonoids such as quercetin at their physiological concentrations can therefore function as modulators of ferric reductases, enhancing the import of Fe(II) and also providing extracellular reducing potential.