Splenic iron decreases without change in volume or liver parameters during luspatercept therapy.

Splenic iron decreased whereas liver iron was stable during luspatercept therapy in some individuals with thalassemia. This suggests a reduction of ineffective erythropoiesis changes the organ distribution of iron and demonstrates that liver iron concentration alone may not accurately reflect total body iron content. This article describes data from subjects enrolled in BELIEVE (NCT02604433) and BEYOND (NCT03342404).

Decreased erythrocyte aggregation in Glenn and Fontan: univentricular circulation as a rheologic disease model.

BACKGROUND: In the Fontan palliation for single ventricle heart disease (SVHD), pulmonary blood flow is non-pulsatile/passive, low velocity, and low shear, making viscous power loss a critical determinant of cardiac output. The rheologic properties of blood in SVHD patients are essential for understanding and modulating their limited cardiac output and they have not been systematically studied. We hypothesize that viscosity is decreased in single ventricle circulation. METHODS: We evaluated whole blood viscosity, red blood cell (RBC) aggregation, and RBC deformability to evaluate changes in healthy children and SVHD patients. We altered suspending media to understand cellular and plasma differences contributing to rheologic differences. RESULTS: Whole blood viscosity was similar between SVHD and healthy at their native hematocrits, while viscosity was lower at equivalent hematocrits for SVHD patients. RBC deformability is increased, and RBC aggregation is decreased in SVHD patients. Suspending SVHD RBCs in healthy plasma resulted in increased RBC aggregation and suspending healthy RBCs in SVHD plasma resulted in lower RBC aggregation. CONCLUSIONS: Hematocrit corrected blood viscosity is lower in SVHD vs. healthy due to decreased RBC aggregation and higher RBC deformability, a viscous adaptation of blood in patients whose cardiac output is dependent on minimizing viscous power loss. IMPACT: Patients with single ventricle circulation have decreased red blood cell aggregation and increased red blood cell deformability, both of which result in a decrease in blood viscosity across a large shear rate range. Since the unique Fontan circulation has very low-shear and low velocity flow in the pulmonary arteries, blood viscosity plays an increased role in vascular resistance, therefore this work is the first to describe a novel mechanism to target pulmonary vascular resistance as a modifiable risk factor. This is a novel, modifiable risk factor in this patient population.

Black Sexual Minority Men's Experiences in MPowerment Interventions: Implications for HIV Prevention.

BACKGROUND: Black sexual minority men (BSMM) are disproportionately vulnerable to HIV acquisition; the MPowerment model is one community-based framework for preventing HIV in this population. It focuses on developing a supportive network of peers to promote health messaging, reduce stigma, and improve resilience. While these interventions have demonstrated general success, there are important challenges related to race, sexuality, and internalized stigma. Our study aimed to explore these experiences among BSMM in MPowerment models focused on HIV prevention. METHOD: We conducted 24 qualitative interviews of BSMM attending HIV prevention-related MPowerment events in the greater D.C. Metropolitan area. In-depth interviews were conducted via phone, and interviews were analyzed using thematic analysis. RESULTS: We identified four themes from the transcript analysis process: Black queer intersectional social support and community, HIV-related information and destigmatization, social status, and sexuality. Within each of these themes, we identified relationships with overall HIV prevention messaging, including barriers to PrEP use. Barriers related to social status were especially prevalent and described as unique to the D.C. metropolitan area. CONCLUSION: Overall, MPowerment event spaces provide a forum for BSMM to feel safe and supported while gaining important HIV-related knowledge and prevention access. Challenges related to social status and destigmatization of sexuality are important considerations in designing and implementing this model, especially related to PrEP promotion.

Management of luspatercept therapy in patients with transfusion-dependent ß-thalassaemia.

Patients with transfusion-dependent ß-thalassaemia require lifelong, regular red blood cell transfusions for survival; however, frequent blood transfusions are associated with an increased risk of iron overload, transfusion-transmitted disease and alloimmunization, as well as reduced quality of life. Luspatercept, an erythroid maturation agent that promotes late-stage erythroid maturation independently of erythropoietin, has demonstrated efficacy in reducing transfusion burden in patients with transfusion-dependent ß-thalassaemia. In this review, we discuss treatment initiation, ongoing evaluation, dose adjustment and management of adverse events in transfusion-dependent patients with ß-thalassaemia receiving luspatercept, and we provide guidance on how to determine whether patients are deriving clinical benefit.

A Phase 3 Trial of Luspatercept in Patients with Transfusion-Dependent ß-Thalassemia.

BACKGROUND: Patients with transfusion-dependent ß-thalassemia need regular red-cell transfusions. Luspatercept, a recombinant fusion protein that binds to select transforming growth factor ß superfamily ligands, may enhance erythroid maturation and reduce the transfusion burden (the total number of red-cell units transfused) in such patients. METHODS: In this randomized, double-blind, phase 3 trial, we assigned, in a 2:1 ratio, adults with transfusion-dependent ß-thalassemia to receive best supportive care plus luspatercept (at a dose of 1.00 to 1.25 mg per kilogram of body weight) or placebo for at least 48 weeks. The primary end point was the percentage of patients who had a reduction in the transfusion burden of at least 33% from baseline during weeks 13 through 24 plus a reduction of at least 2 red-cell units over this 12-week interval. Other efficacy end points included reductions in the transfusion burden during any 12-week interval and results of iron studies. RESULTS: A total of 224 patients were assigned to the luspatercept group and 112 to the placebo group. Luspatercept or placebo was administered for a median of approximately 64 weeks in both groups. The percentage of patients who had a reduction in the transfusion burden of at least 33% from baseline during weeks 13 through 24 plus a reduction of at least 2 red-cell units over this 12-week interval was significantly greater in the luspatercept group than in the placebo group (21.4% vs. 4.5%, P<0.001). During any 12-week interval, the percentage of patients who had a reduction in transfusion burden of at least 33% was greater in the luspatercept group than in the placebo group (70.5% vs. 29.5%), as was the percentage of those who had a reduction of at least 50% (40.2% vs. 6.3%). The least-squares mean difference between the groups in serum ferritin levels at week 48 was -348 µg per liter (95% confidence interval, -517 to -179) in favor of luspatercept. Adverse events of transient bone pain, arthralgia, dizziness, hypertension, and hyperuricemia were more common with luspatercept than placebo. CONCLUSIONS: The percentage of patients with transfusion-dependent ß-thalassemia who had a reduction in transfusion burden was significantly greater in the luspatercept group than in the placebo group, and few adverse events led to the discontinuation of treatment. (Funded by Celgene and Acceleron Pharma; BELIEVE ClinicalTrials.gov number, NCT02604433; EudraCT number, 2015-003224-31.).

Understanding the Unique Barriers and Facilitators that Affect Men's Initiation and Retention in HIV Care: A Qualitative Study to Inform Interventions for Men Across the Treatment Cascade in Malawi.

Men in sub-Saharan Africa are underrepresented in antiretroviral therapy (ART) programs. Our secondary analysis of 40 in-depth interviews with Malawian men living with HIV examined barriers and facilitators for ART initiation versus retention. Interviewees included men who never initiated or initiated ART late (initiation respondents, n = 19); and men who initiated ART but were late for an appointment (retention respondents, n = 21). Transcribed interviews were coded using deductive and inductive coding techniques and analyzed using constant comparison methods. Long wait times, frequent facility visits, and insufficient in-clinic privacy were barriers for initiation and retention. Poor knowledge of ART was primarily a barrier for initiation; unexpected travel was a barrier for retention. Key facilitators for initiation and retention included previous positive experiences with health facilities. Having examples of successful men using ART primarily facilitated initiation; support from spouses and male peers facilitated retention. Results may inform interventions to increase men's engagement in ART services.

Triple Benefit: Impact of an Integrated Early Childhood Development and PMTCT Intervention on ART Outcomes Among Mothers Living with HIV and Infants in Malawi-An Endline Evaluation.

We conducted a programmatic, observational cohort study with mother-infant pairs (MIPs) enrolled in prevention-of-mother-to-child-transmission (PMTCT) programs in Malawi to assess the feasibility and potential HIV-related benefits of integrating Early Childhood Development (ECD) services into PMTCT programs. Six health facilities were included in the intervention. We offered ECD counseling from the WHO/UNICEF Care for Child Development package in PMTCT waiting spaces while MIPs waited for PMTCT and broader treatment consultations. Primary outcomes were mothers' retention in HIV care at 12 months and infant HIV testing at 6 weeks and 12 months after birth. Routine facility-level data from six comparison health facilities were collected as an adhoc standard of care comparison and used to calculate the cost of delivering the intervention. A total of 607 MIPs were enrolled in the integrated ECD-PMTCT intervention between June 2018 and December 2019. The average age of MIPs was 30 years and 7 weeks respectively. We found that 86% of mothers attended ≥ 5 of the 8 ECD sessions over the course of 12 months; 88% of intervention mothers were retained in PMTCT versus 59% of mothers in comparison health facilities, and 96% of intervention infants were tested for HIV by six weeks compared to 66% of infants in comparison health facilities. Costing data demonstrated the financial feasibility of integrating ECD and PMTCT programs in government health facilities in Malawi. Integrating ECD into PMTCT programs was feasible, acceptable, resulted in better programmatic outcomes for both mothers and infants. Further investigation is required to determine optimal delivery design for scale-up.

Sexual Risk among Pregnant Women at Risk of HIV Infection in Cape Town, South Africa: What Does Alcohol Have to Do with It?

This study examines baseline associations between alcohol use and HIV sexual risk among a cohort of HIV-uninfected pregnant women (n = 1201) residing in a high HIV burdened community in Cape Town, South Africa. Alcohol use was measured using a modified version of the Alcohol Use Disorder Identification Test (AUDIT). HIV sexual risk was measured through a composite variable of four risk factors: diagnosis with a STI, self-report of > 1 recent sex partners, partner HIV serostatus (unknown or HIV+) and condomless sex at last sex. Any past year alcohol use prior to pregnancy was reported by half of participants (50%); 6.0% reported alcohol use during pregnancy. Alcohol use prior to pregnancy was associated with increased odds of being at high risk of HIV (aOR = 1.33, 95% CI 1.05-1.68, for 2 risks and aOR = 1.47, 95% CI 0.95-2.27 for 3 risks). In addition to reducing alcohol use, several other strategies to address HIV sexual risk were identified. Evidence-based interventions to address alcohol use and other HIV sexual risk behaviors during pregnancy in South Africa are desperately needed. Qualitative work exploring individual and community level drivers of alcohol use among pregnant and breastfeeding women in this setting could support development of a culturally tailored intervention to address these issues in this population.

Consensus definition of essential, optimal, and suggested components of a pediatric sickle cell disease center.

Sickle cell disease (SCD) requires coordinated, specialized medical care for optimal outcomes. There are no United States (US) guidelines that define a pediatric comprehensive SCD program. We report a modified Delphi consensus-seeking process to determine essential, optimal, and suggested elements of a comprehensive pediatric SCD center. Nineteen pediatric SCD specialists participated from the US. Consensus was predefined as 2/3 agreement on each element's categorization. Twenty-six elements were considered essential (required for guideline-based SCD care), 10 were optimal (recommended but not required), and five were suggested. This work lays the foundation for a formal recognition process of pediatric comprehensive SCD centers.

Progressive vasoconstriction with sequential thermal stimulation indicates vascular dysautonomia in sickle cell disease.

Persons with sickle cell disease (SCD) exhibit subjective hypersensitivity to cold and heat perception in experimental settings, and triggers such as cold exposure are known to precipitate vaso-occlusive crises by still unclear mechanisms. Decreased microvascular blood flow (MBF) increases the likelihood of vaso-occlusion by increasing entrapment of sickled red blood cells in the microvasculature. Because those with SCD have dysautonomia, we anticipated that thermal exposure would induce autonomic hypersensitivity of their microvasculature with an increased propensity toward vasoconstriction. We exposed 17 patients with SCD and 16 control participants to a sequence of predetermined threshold temperatures for cold and heat detection and cold and heat pain via a thermode placed on the right hand. MBF was measured on the contralateral hand by photoplethysmography, and cardiac autonomic balance was assessed by determining heart rate variability. Thermal stimuli at both detection and pain thresholds caused a significant decrease in MBF in the contralateral hand within seconds of stimulus application, with patients with SCD showing significantly stronger vasoconstriction (P = .019). Furthermore, patients with SCD showed a greater progressive decrease in blood flow than did the controls, with poor recovery between episodes of thermal stimulation (P = .042). They had faster vasoconstriction than the controls (P = .033), especially with cold detection stimulus. Individuals with higher anxiety also experienced more rapid vasoconstriction (P = .007). Augmented vasoconstriction responses and progressive decreases in perfusion with repeated thermal stimulation in SCD are indicative of autonomic hypersensitivity in the microvasculature. These effects are likely to increase red cell entrapment in response to clinical triggers such as cold or stress, which have been associated with vaso-occlusive crises in SCD.

Effects of B1+ Heterogeneity on Spin Echo-Based Liver Iron Estimates.

BACKGROUND: Liver iron concentration (LIC) measured by MRI has become the clinical reference standard for managing iron overload in chronically transfused patients. Transverse relaxivity (R2 or R2* ) measurements are converted to LIC units using empirically derived calibration curves. HYPOTHESIS: That flip angle (FA) error due to B1+ spatial heterogeneity causes significant LIC quantitation error. B1+ scale (b1 , [FAactual /FAspecified ]) variation is a major problem at 3 T which could reduce the accuracy of transverse relaxivity measurements. STUDY TYPE: Prospective. POPULATION: Forty-seven subjects with chronic transfusional iron overload undergoing clinically indicated LIC assessment. FIELD STRENGTH/SEQUENCE: 5 T/3 T dual-repetition time B1+ mapping sequence ASSESSMENT: We quantified the average/standard deviation b1 in the right and left lobes of the liver from B1+ maps acquired at 1.5 T and 3 T. The impact of b1 variation on spin echo LIC estimates was determined using a Monte Carlo model. STATISTICAL TESTS: Mean, median, and standard deviation in whole liver and right and left lobes; two-sided t-test between whole-liver b1 means. RESULTS: Average b1 within the liver was 99.3% ± 12.3% at 1.5 T versus 69.6% ± 14.6% at 3 T and was independent of iron burden (P < 0.05). Monte Carlo simulations demonstrated that b1 systematically increased R2 estimates at lower LIC (<~25 mg/g at 1.5 T, <~15 mg/g at 3 T) but flattened or even inverted the R2 -LIC relationship at higher LIC (≥~25 mg/g to 1.5 T, ≥~15 mg/g to 3 T); changes in the R2 -LIC relationship were symmetric with respect to over and under excitation and were similar at 1.5 T and 3 T (for the same R2 value). The R2* -LIC relationship was independent of b1 . CONCLUSION: Spin echo R2 measurement of LIC at 3 T is error-prone without correction for b1 errors. The impact of b1 error on current 1.5 T spin echo-based techniques for LIC quantification is large enough to introduce measurable intersubject variability but the in vivo effect size needs a dedicated validation study. TECHNICAL EFFICACY STAGE: 2.

Maternal PrEP Use in HIV-Uninfected Pregnant Women in South Africa: Role of Stigma in PrEP Initiation, Retention and Adherence.

Pregnant women in sub-Saharan Africa are at high risk of HIV acquisition and require effective methods to prevent HIV. In a cohort of pregnant women offered Pre-exposure prophylaxis (PrEP), we evaluate the relationship between internalized and anticipated stigma and PrEP initiation at first antenatal visit, 3-month continuation and adherence using multivariable logistic regression. High internalized and anticipated PrEP stigma are associated with lower PrEP care initiation at first antenatal visit (aOR internalized stigma = 0.06; 95% CI = 0.03-0.11 and aOR anticipated stigma = 0.55; 95% CI = 0.31-1.00) compared to women with low reported stigma, after controlling for covariates. Women whose partners have not been tested for HIV or whose serostatus remains unknown have 1.6-times odds of PrEP retention at 3-months compared to women whose partners have been tested (aOR = 1.60; 95% CI = 1.02-2.52) after adjusting for covariates. PrEP counseling and maternal PrEP interventions must consider individual- and relational-level interventions to overcome anticipated PrEP stigma and other barriers to PrEP initiation and adherence.

Barriers to Oral HIV Pre-exposure Prophylaxis (PrEP) Adherence Among Pregnant and Post-partum Women from Cape Town, South Africa.

Cisgender women, particularly pregnant and postpartum women in Eastern and Southern Africa, face an unacceptably high risk of HIV acquisition. Oral pre-exposure prophylaxis (PrEP) is an effective HIV prevention intervention that can reduce HIV acquisition and vertical transmission. In this qualitative study, we interviewed 21 postpartum women from Cape Town, South Africa who initiated PrEP during pregnancy and who self-reported low PrEP adherence or missed > 1 PrEP follow-up collection. We identified multiple overlapping barriers to PrEP continuation and/or adherence. Individual factors included forgetting to take PrEP daily, being away from home when PrEP should be taken, anticipated stigma and limited disclosure of PrEP use. Women also reported pill-related factors such as side effects and having to take PrEP in addition to other tablets during pregnancy and the postpartum period. Facility-related barriers included logistics around PrEP collection especially when not in antenatal care, as well as transport and financial barriers.

Stepped care to optimize pre-exposure prophylaxis (PrEP) effectiveness in pregnant and postpartum women (SCOPE-PP) in South Africa: a randomized control trial.

BACKGROUND: HIV incidence among pregnant and postpartum women remains high in South Africa. Pre-exposure prophylaxis (PrEP) use remains suboptimal in this population, particularly during the postpartum period when women's engagement with routine clinic visits outside PrEP decreases. Key barriers to sustained PrEP use include the need for ongoing contact with the health facility and suboptimal counseling around effective PrEP use. METHODS: Stepped Care to Optimize PrEP Effectiveness in Pregnant and Postpartum women (SCOPE-PP), is a two-stepped unblinded, individually randomized controlled trial (RCT) that aims to optimize peripartum and postpartum PrEP use by providing a stepped package of evidence-based interventions. We will enroll 650 pregnant women (> 25 weeks pregnant) who access PrEP at a busy antenatal clinic in Cape Town at the time of recruitment and follow them for 15 months. We will enroll and individually randomize pregnant women > 16 years who are not living with HIV who are either on PrEP or interested in starting PrEP during pregnancy. In step 1, we will evaluate the impact of enhanced adherence counselling and biofeedback (using urine tenofovir tests for biofeedback) and rapid PrEP collection (to reduce time required) on PrEP use in early peripartum compared to standard of care (SOC) (n = 325 per arm). The primary outcome is PrEP persistence per urine tenofovir levels and dried blood spots of tenofovir diphosphate (TFV-DP) after 6-months. The second step will enroll and individually randomize participants from Step 1 who discontinue taking PrEP or have poor persistence in Step 1 but want to continue PrEP. Step 2 will test the impact of enhanced counseling and biofeedback plus rapid PrEP collection compared to community PrEP delivery with HIV self-testing on PrEP use (n = up to 325 postpartum women). The primary outcome is PrEP continuation and persistence 6-months following second randomization (~ 9-months postpartum). Finally, we will estimate the cost effectiveness of SCOPE-PP vs. SOC per primary outcomes and disability-adjusted life-years (DALYs) averted in both Step 1 and 2 using micro-costing with trial- and model-based economic evaluation. DISCUSSION: This study will provide novel insights into optimal strategies for delivering PrEP to peripartum and postpartum women in this high-incidence setting. TRIAL REGISTRATION: NCT05322629 : Date of registration: April 12, 2022.

Kidney iron deposition by R2* is associated with haemolysis and urinary iron.

Kidney iron deposition measured by R2* (magnetic resonance imaging) MRI is posited to result from tubular reabsorption of filtered haemoglobin due to intravascular haemolysis. In chronically transfused sickle cell disease (SCD), R2* is elevated and positively correlated with lactate dehydrogenase (LDH). To account for contributions to renal iron from systemic iron overload, we evaluated kidney R2*, urinary iron and haemolysis markers in 62 non-transfused SCD patients. On multivariate analysis, kidney R2* was associated with urinary iron and LDH (R2  = 0·55, P < 0·0001). Our study confirms that kidney R2* is associated with intravascular haemolysis and raises important questions regarding the role of iron in SCD nephropathy.

Calibration of T2 oximetry MRI for subjects with sickle cell disease.

PURPOSE: Cerebral T2 oximetry is a non-invasive imaging method to measure blood T2 and cerebral venous oxygenation. Measured T2 values are converted to oximetry estimates using carefully validated and potentially disease-specific calibrations. In sickle cell disease, red blood cells have abnormal cell shape and membrane properties that alter T2 oximetry calibration relationships in clinically meaningful ways. Previous in vitro works by two independent groups established potentially competing calibration models. METHODS: This study analyzed pooled datasets from these two studies to establish a unified and more robust sickle-specific calibration to serve as a reference standard in the field. RESULTS: Even though the combined calibration did not demonstrate statistical superiority compared to previous models, the calibration was unbiased compared to blood-gas co-oximetry and yielded limits of agreement of (-10.1%, 11.6%) in non-transfused subjects with sickle cell disease. In transfused patients, this study proposed a simple correction method based on individual hemoglobin S percentage that demonstrated reduced bias in saturation measurement compared to previous uncorrected sickle calibrations. CONCLUSION: The combined calibration is based on a larger range of hematocrit, providing greater confidence in the hematocrit-dependent model parameters, and yielded unbiased estimates to blood-gas co-oximetry measurements from both sites. Additionally, this work also demonstrated the need to correct for transfusion in T2 oximetry measurements for hyper-transfused sickle cell disease patients and proposes a correction method based on patient-specific hemoglobin S concentration.

Reduced global cerebral oxygen metabolic rate in sickle cell disease and chronic anemias.

Anemia is the most common blood disorder in the world. In patients with chronic anemia, such as sickle cell disease or major thalassemia, cerebral blood flow increases to compensate for decreased oxygen content. However, the effects of chronic anemia on oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2 ) are less well understood. In this study, we examined 47 sickle-cell anemia subjects (age 21.7 ± 7.1, female 45%), 27 non-sickle anemic subjects (age 25.0 ± 10.4, female 52%) and 44 healthy controls (age 26.4 ± 10.6, female 71%) using MRI metrics of brain oxygenation and flow. Phase contrast MRI was used to measure resting cerebral blood flow, while T2 -relaxation-under-spin-tagging (TRUST) MRI with disease appropriate calibrations were used to measure OEF and CMRO2 . We observed that patients with sickle cell disease and other chronic anemias have decreased OEF and CMRO2 (respectively 27.4 ± 4.1% and 3.39 ± 0.71 ml O2 /100 g/min in sickle cell disease, 30.8 ± 5.2% and 3.53 ± 0.64 ml O2 /100 g/min in other anemias) compared to controls (36.7 ± 6.0% and 4.00 ± 0.65 ml O2 /100 g/min). Impaired CMRO2 was proportional to the degree of anemia severity. We further demonstrate striking concordance of the present work with pooled historical data from patients having broad etiologies for their anemia. The reduced cerebral oxygen extraction and metabolism are consistent with emerging data demonstrating increased non-nutritive flow, or physiological shunting, in sickle cell disease patients.

Nocturnal peripheral vasoconstriction predicts the frequency of severe acute pain episodes in children with sickle cell disease.

The basic model of SCD physiology states that vaso-occlusion occurs when hemoglobin S-containing red blood cells (RBC) undergo sickling before they escape the capillary into a larger vessel. We have shown that mental stress, pain and cold, and events reported by patients to trigger SCD vaso-occlusive crisis (VOC), cause rapid and significant decrease in blood flow, reducing the likelihood that RBC could transit the microvasculature before sickling occurs. However, the critical link between decrease in microvascular blood flow and the incidence of future sickle VOC has never been established experimentally in humans. Using data from centrally adjudicated, overnight polysomnograms (PSG), previously collected in a prospective multi-center cohort sleep study, we analyzed the beat-to-beat amplitudes of vasoconstriction reported by the fingertip photoplethysmogram in 212 children and adolescents with SCD and developed an algorithm that detects vasoconstriction events and quantifies the magnitude (Mvasoc ), duration, and frequency of vasoconstriction that reflect the individual's inherent peripheral vasoreactivity. The propensity to vasoconstrict, quantified by median Mvasoc , predicted the incidence rate of post-PSG severe acute vaso-occlusive pain events (P = .006) after accounting for age and hemoglobin. Indices of sleep-disordered breathing contributed to median Mvasoc but did not predict future pain rate. Median Mvasoc was not associated with vaso-occlusive pain events that occurred prior to each PSG. These results show that SCD individuals with high inherent propensity to vasoconstrict have more frequent severe acute pain events. Our empirical findings are consistent with the fundamental SCD hypothesis that decreased microvascular flow promotes microvascular occlusion.

Loss of alpha-globin genes in human subjects is associated with improved nitric oxide-mediated vascular perfusion.

Alpha thalassemia is a hemoglobinopathy due to decreased production of the α-globin protein from loss of up to four α-globin genes, with one or two missing in the trait phenotype. Individuals with sickle cell disease who co-inherit the loss of one or two α-globin genes have been known to have reduced risk of morbid outcomes, but the underlying mechanism is unknown. While α-globin gene deletions affect sickle red cell deformability, the α-globin genes and protein are also present in the endothelial wall of human arterioles and participate in nitric oxide scavenging during vasoconstriction. Decreased production of α-globin due to α-thalassemia trait may thereby limit nitric oxide scavenging and promote vasodilation. To evaluate this potential mechanism, we performed flow-mediated dilation and microvascular post-occlusive reactive hyperemia in 27 human subjects (15 missing one or two α-globin genes and 12 healthy controls). Flow-mediated dilation was significantly higher in subjects with α-trait after controlling for age (P = .0357), but microvascular perfusion was not different between groups. As none of the subjects had anemia or hemolysis, the improvement in vascular function could be attributed to the difference in α-globin gene status. This may explain the beneficial effect of α-globin gene loss in sickle cell disease and suggests that α-globin gene status may play a role in other vascular diseases.