Influence of sickle cell disease on susceptibility to HIV infection.

People with sickle cell disease (SCD) are reported to have low rates of HIV infection, slower progression to AIDS and lower HIV-associated mortality compared to the general population. Mechanisms of potential resistance to HIV in SCD are incompletely understood. We retrospectively reviewed the Transfusion Safety Study to compare HIV status between people with SCD and other congenital anemias who were routinely exposed to blood products during the high-risk period before HIV screening implementation. Non-SCD congenital anemia diagnosis was associated with a higher risk of HIV acquisition compared to SCD (OR 13.1 95%CI 1.6-108.9). In addition, we prospectively enrolled 30 SCD cases and 30 non-SCD controls to investigate potential mechanisms of resistance to HIV in SCD. CCR5 and CCR7 expression was lower and CD4 expression was higher on CD4+ T cells from SCD cases compared to controls. Surface expression of CD4+ T cell CXCR4, CD38 and HLA-DR did not differ between the groups. SCD CD4+ T cells were not less susceptible to HIV infection than controls. Levels of multiple cytokines were elevated in the SCD plasma, but SCD plasma compared to control plasma did not inhibit HIV infection of target cells. In conclusion, our epidemiological data support people with SCD being resistant to HIV infection. Potential mechanisms include lower CD4+ T cell expression of CCR5 and CCR7, balanced by increased CD4 expression and cytokine levels, which did not result in in vitro resistance to HIV infection. Further study is needed to define the risk and pathophysiology of HIV in persons with SCD.

Evaluation of Mandible Fractures in Patients With Sickle Cell Anemia-A Nationwide Study.

PURPOSE: Sickle cell anemia is the most commonly inherited blood disorder in the United States. Despite its prevalence, clinicians know little about the extent of its impact on orofacial manifestations. MATERIALS AND METHODS: All patients with diagnoses of mandible fracture and sickle cell anemia admitted from 2004 through 2014 were identified using the National Inpatient Sample. Patient demographics, fracture regions, and complications were characterized by descriptive statistics. RESULTS: Fifty-one of 48,464 patients admitted for mandible fracture had sickle cell anemia. The mean age of the identified patients was 25 years (range, 4 to 58 yr). Of all admitted patients, mandible angle fracture was the most common (19%), followed by fracture of the body of the mandible. Seventy-five percent of cases reviewed were treated with open reduction and internal fixation. CONCLUSIONS: Most mandible fractures in patients with sickle cell anemia were located in the angle of the mandible. Complications were minimal and outcomes were satisfactory. Aseptic necrosis of the jaw was a frequent complication of mandible fracture in patients with sickle cell anemia. These results provide clinicians with a better understanding of the distribution and hospital course of patients with sickle cell anemia and facial fractures.

Beyond the definitions of the phenotypic complications of sickle cell disease: an update on management.

The sickle hemoglobin is an abnormal hemoglobin due to point mutation (GAG → GTG) in exon 1 of the ß globin gene resulting in the substitution of glutamic acid by valine at position 6 of the ß globin polypeptide chain. Although the molecular lesion is a single-point mutation, the sickle gene is pleiotropic in nature causing multiple phenotypic expressions that constitute the various complications of sickle cell disease in general and sickle cell anemia in particular. The disease itself is chronic in nature but many of its complications are acute such as the recurrent acute painful crises (its hallmark), acute chest syndrome, and priapism. These complications vary considerably among patients, in the same patient with time, among countries and with age and sex. To date, there is no well-established consensus among providers on the management of the complications of sickle cell disease due in part to lack of evidence and in part to differences in the experience of providers. It is the aim of this paper to review available current approaches to manage the major complications of sickle cell disease. We hope that this will establish another preliminary forum among providers that may eventually lead the way to better outcomes.

A potent oral P-selectin blocking agent improves microcirculatory blood flow and a marker of endothelial cell injury in patients with sickle cell disease.

Abnormal blood flow accounts for most of the clinical morbidity of sickle cell disease (SCD) [1,2]. Most notably, occlusion of flow in the microvasculature causes the acute pain crises [3] that are the commonest cause for patients with SCD to seek medical attention [4] and major determinants of their quality of life [5]. Based on evidence that endothelial P-selectin is central to the abnormal blood flow in SCD we provide results from four of our studies that are germane to microvascular blood flow in SCD. A proof-of-principle study established that doses of heparin lower than what are used for anticoagulation but sufficient to block P-selectin improved microvascular blood flow inpatients with SCD. An in vitro study showed that Pentosan Polysulfate Sodium (PPS) had greater P-selectin blocking activity than heparin. A Phase I clinical study demonstrated that a single oral dose of PPS increased microvascular blood flow in patients with SCD. A Phase II clinical study that was not completed documented that daily oral doses of PPS administered for 8 weeks lowered plasma levels of sVCAM-1 and tended to improve microvascular blood flow in patients with SCD. These data support the concept that P-selectin on the microvascular endothelium is critical to both acute vascular occlusion and chronically impaired microvascular blood flow in SCD. They also demonstrate that oral PPS is beneficial to microvascular sickle cell blood flow and has potential as an efficacious agent for long-term prophylactic therapy of SCD.

A pilot study of the short-term use of simvastatin in sickle cell disease: effects on markers of vascular dysfunction.

Sickle cell disease (SCD) is characterized by progressive vascular injury and its pathophysiology is strikingly similar to that of atherosclerosis. Statins decrease inflammation and improve endothelial function in cardiovascular disease, but their effect in SCD is not known. In this pilot study, we examined the safety and effect of short-term simvastatin on biomarkers of vascular dysfunction in SCD. We treated 26 SCD patients with simvastatin, 20 or 40 mg/d, for 21 d. Plasma nitric oxide metabolites (NOx), C-reactive protein (CRP), interleukin-6 (IL-6), vascular cell adhesion molecule-1 (VCAM-1), tissue factor (TF) and vascular endothelial growth factor (VEGF) were analyzed and responses to simvastatin were compared between the two treatment groups. Simvastatin increased NOx levels by 23% in the low-dose (P =0·01) and 106% in the moderate-dose (P =0·01) groups, and by 52% overall (P=0·0008). CRP decreased similarly in both dose groups and by 68% overall (P =0·02). Levels of IL-6 decreased by 50% (P=0·04) and 71% (P<0·05) in the low- and moderate-dose groups, respectively. Simvastatin had no effect on VEGF, VCAM1 or TF. Simvastatin was well-tolerated and safe. Our preliminary findings showing a dose-related effect of simvastatin on levels of NOx, CRP and IL-6 suggest a potential therapeutic role for simvastatin in SCD.

Erythrocyte glutamine depletion, altered redox environment, and pulmonary hypertension in sickle cell disease.

Erythrocyte glutathione depletion has been linked to hemolysis and oxidative stress. Glutamine plays an additional antioxidant role through preservation of intracellular nicotinamide adenine dinucleotide phosphate (NADPH) levels, required for glutathione recycling. Decreased nitric oxide (NO) bioavailability, which occurs in the setting of increased hemolysis and oxidative stress, contributes to the pathogenesis of pulmonary hypertension (PH) in sickle cell disease (SCD). We hypothesized that altered glutathione and glutamine metabolism play a role in this process. Total glutathione (and its precursors) and glutamine were assayed in plasma and erythrocytes of 40 SCD patients and 9 healthy volunteers. Erythrocyte total glutathione and glutamine levels were significantly lower in SCD patients than in healthy volunteers. Glutamine depletion was independently associated with PH, defined as a tricuspid regurgitant jet velocity (TRV) of at least 2.5 m/s. The ratio of erythrocyte glutamine:glutamate correlated inversely to TRV (r = -0.62, P < .001), plasma arginase concentration (r = -0.45, P = .002), and plasma-free hemoglobin level (r = -0.41, P = .01), linking erythrocyte glutamine depletion to dysregulation of the arginine-NO pathway and increased hemolytic rate. Decreased erythrocyte glutathione and glutamine levels contribute to alterations in the erythrocyte redox environment, which may compromise erythrocyte integrity, contribute to hemolysis, and play a role in the pathogenesis of PH of SCD.

Iron homeostasis during transfusional iron overload in beta-thalassemia and sickle cell disease: changes in iron regulatory protein, hepcidin, and ferritin expression.

Hypertransfusional (>8 transfusions/year) iron in liver biopsies collected immediately after transfusions in beta-thalassemia and sickle cell disease correlated with increased expression (RNA) for iron regulatory proteins 1 and 2 (3-, 9- to 11-fold) and hepcidin RNA: (5- to 8-fold) (each p <.01), while ferritin H and L RNA remained constant. A different H:L ferritin ratio in RNA (0.03) and protein (0.2-0.6) indicated disease-specific trends and suggests novel post-transcriptional effects. Increased iron regulatory proteins could stabilize the transferrin receptor mRNA and, thereby, iron uptake. Increased hepcidin, after correction of anemia by transfusion, likely reflects excess liver iron. Finally, the absence of a detectable change in ferritin mRNA indicates insufficient oxidative stress to significantly activate MARE/ARE promoters.

Morbidity and mortality in chronically transfused subjects with thalassemia and sickle cell disease: A report from the multi-center study of iron overload.

A natural history study was conducted in 142 Thalassemic (Thal), 199 transfused Sickle Cell Disease (Tx-SCD, n = 199), and 64 non-Tx-SCD subjects to describe the frequency of iron-related morbidity and mortality. Subjects recruited from 31 centers in the US, Canada or the UK were similar with respect to age (overall: 25 +/- 11 years, mean +/- SD) and gender (52% female). We found that Tx-SCD subjects were hospitalized more frequently compared with Thal or non-Tx-SCD (P < 0.001). Among those hospitalized, Tx-SCD adult subjects were more likely to be unemployed compared with Thal (RR = 1.6, 95% CI 1.0-2.5) or non-Tx-SCD (RR = 3.1, 95% CI 1.3-7.3). There was a positive relationship between the severity of iron overload, assessed by serum ferritin, and the frequency of hospitalizations (r= 0.20; P = 0.009). Twenty-three deaths were reported (6 Thal, 17 Tx-SCD) in 23.5 +/- 10 months of follow-up. Within the Tx-SCD group, those who died began transfusion (25.3 vs. 12.4 years, P < 0.001) and chelation therapy later (26.8 vs. 14.2 years, P = 0.01) compared with those who survived. The unadjusted death rate in Thal was lower (2.2/100 person years) compared with that in Tx-SCD (7.0/100 person years; RR = 0.38: 95% CI 0.12-0.99). However, no difference was observed when age at death was considered. Despite improvements in therapy, death rate in this contemporary sample of transfused adult subjects with Thal or SCD is 3 times greater than the general US population. Long term follow-up of this unique cohort of subjects will be helpful in further defining the relationship of chronic, heavy iron overload to morbidity and mortality.

Liver ferritin subunit ratios in neonatal hemochromatosis.

Neonatal hemochromatosis is an enigmatic disease. Little is known about iron metabolism in this disease, including the tissue concentration of ferritin or its H and L subunit ratio. The authors report the tissue iron, ferritin, and ferritin subunit content of a child who died at 5 weeks of neonatal hemochromatosis. The child was born at 29 weeks gestation to a mother with lupus, sickle cell trait, and gestational diabetes. The child's severe liver dysfunction led to the clinical diagnosis of neonatal hemochromatosis at 1 week of age. Despite aggressive support, including red cell transfusions and chelation, the child died of an intracranial hemorrhage. Autopsy showed liver fibrosis and iron staining characteristic of neonatal hemochromatosis. Autopsy liver tissue was compared to age-matched control tissue. Soluble protein was analyzed by the Bradford method. Soluble iron (over 90% of total iron) was analyzed by the o-phenanthroline complex. Tissue ferritin and human ferritin controls (Calzyme) were analyzed by Western blotting after SDS-PAGE, identified with sheep anti-human ferritin antibodies (The BindingSite) secondary antibody-fluorescence for detection, and quantified using the Molecular Dynamics Storm 840 phosphorimager and ImageQuant software. Protein, iron, and total ferritin were similar in the normal and neonatal hemochromatosis liver tissues. Ferritin subunits, however, showed an increased H/L-subunit ratio compared to an age-matched control. This first report of a marked increase in the ferritin H/L-subunit ratio may point to an underlying mechanism of disease in this enigmatic disorder.

Diseases of iron metabolism.

Diseases of iron metabolism are likely to be both more frequent than expected, and exhibit a wider range of clinic severity and effects. Some present without evidence of anemia. Unexplained diseases of end organs that are affected by iron (liver, heart, pancreas, kidney, adrenals, and cerebellum) should have an iron metabolism disorder considered. Review of the blood indices and serum iron and ferritin markers may alert the clinician to most disorders. Further research is likely to define the scope and approach to clinical diagnosis of the diseases of iron metabolism.