Leukemia virus long terminal repeat activates NFκB pathway by a TLR3-dependent mechanism

AbstractThe long terminal repeat (LTR) region of leukemia viruses plays a critical role in tissue tropism and pathogenic potential of the viruses. We have previously reported that U3-LTR from Moloney murine and feline leukemia viruses (Mo-MuLV and FeLV) upregulates specific cellular genes in trans in an integration-independent way. The U3-LTR region necessary for this action does not encode a protein but instead makes a specific RNA transcript. Because several cellular genes transactivated by the U3-LTR can also be activated by NFκB, and because the antiapoptotic and growth promoting activities of NFκB have been implicated in leukemogenesis, we investigated whether FeLV U3-LTR can activate NFκB signaling. Here, we demonstrate that FeLV U3-LTR indeed upregulates the NFκB signaling pathway via activation of Ras-Raf-IκB kinase (IKK) and degradation of IκB. LTR-mediated transcriptional activation of genes did not require new protein synthesis suggesting an active role of the LTR transcript in the process. Using Toll-like receptor (TLR) deficient HEK293 cells and PKR−/− mouse embryo fibroblasts, we further demonstrate that although dsRNA-activated protein kinase R (PKR) is not necessary, TLR3 is required for the activation of NFκB by the LTR. Our study thus demonstrates involvement of a TLR3-dependent but PKR-independent dsRNA-mediated signaling pathway for NFκB activation and thus provides a new mechanistic explanation of LTR-mediated cellular gene transactivation

Genetic determinants of haemolysis in sickle cell anaemia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97446/1/bjh12245.pd

A pilot study of a non-invasive oral nitrate stable isotopic method suggests that arginine and citrulline supplementation increases whole-body NO production in Tanzanian children with sickle cell disease.

BACKGROUND: Low bioavailability of nitric oxide (NO) is implicated in the pathophysiology of sickle cell disease (SCD). We designed a nested pilot study to be conducted within a clinical trial testing the effects of a daily ready-to-use supplementary food (RUSF) fortified with arginine (Arg) and citrulline (Citr) vs. non-fortified RUSF in children with SCD. The pilot study evaluated 1) the feasibility of a non-invasive stable isotope method to measure whole-body NO production and 2) whether Arg+Citr supplementation was associated with increased whole-body NO production. SUBJECTS: Twenty-nine children (70% male, 9-11years, weight 16.3-31.3 kg) with SCD. METHODS: Sixteen children received RUSF+Arg/Citr (Arg, 0.2  g/kg/day; Citr, 0.1  g/kg/day) in combination with daily chloroquine (50 mg) and thirteen received the base RUSF in combination with weekly chloroquine (150 mg). Plasma amino acids were assessed using ion-exchange elution (Biochrom-30, Biochrom, UK) and whole-body NO production was measured using a non-invasive stable isotopic method. RESULTS: The RUSF+Arg/Citr intervention increased plasma arginine (P = .02) and ornithine (P = .003) and decreased the ratio of asymmetric dimethylarginine to arginine (P = .01), compared to the base RUSF. A significant increase in whole-body NO production was observed in the RUSF-Arg/Citr group compared to baseline (weight-adjusted systemic NO synthesis 3.38 ± 2.29 μmol/kg/hr vs 2.35 ± 1.13 μmol/kg/hr, P = .04). No significant changes were detected in the base RUSF group (weight-adjusted systemic NO synthesis 2.64 ± 1.14 μmol/kg/hr vs 2.53 ± 1.12 μmol/kg/hr, P = .80). CONCLUSIONS: The non-invasive stable isotopic method was acceptable and the results provided supporting evidence that Arg/Citr supplementation may increase systemic NO synthesis in children with SCD

Genetic and molecular regulation of gamma globin gene expression in patients with sickle cell disease

Thesis (Ph.D.)--Boston UniversityPLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at [email protected]. Thank you.The variability of clinical severity in sickle cell anemia patients has been attributed in part to fetal hemoglobin (HbF) expression. Hereditary persistence of fetal hemoglobin (HPFH) describes benign disorders that are characterized by increased y-globin chain expression often with a reduction or absence of B-globin chain expression. HPFH can be due to naturally occurring deletions at the 3' end of the B-globin locus. Variable size deletions that remove alpha(HBO) and B(HBB) globin genes result in HPFH and alphaB-thalassemia. We examined clinical and hematology data in 28 patients with sickle hemoglobin (HbS)/HPFH. We found HbS/HPFH patients did not have anemia, and had slightly reduced mean corpuscular volume (MCV). Their age, hemoglobin and MCV were found to be correlated with HbF levels. These individuals were asymptomatic when compared to homozygous HbSS patients even with unusually high levels of HbF. Three major quantitative trait loci (QTL) significantly associated with HbF levels in individuals from different populations have been identified and include polymorphisms in the Gy-globin gene (HBG2) promoter, BCL 11A, and the HBS1 L-MYB intergenic region. We investigated polymorphisms in these QTL in a unique cohort of 20 African American patients with sickle cell anemia expressing HbF levels equal to or greater than 11%. We also found significant associations of HbF in 2 of the 3 major loci, BCL11A (rs766432) (P=0.05), and HBS1L-MYB intergenic region (rs9399137) (P= 0.02). A 3 basepair (bp) (TAG) deletion in high linkage disequilibrium with rs9399137 in the HBS1 L-MYB intergenic region might also account for high HbF expression. Two QTL influence HbF levels in African Americans with sickle cell anemia but together account for 20% of HbF variance [1]. Therefore to further explore possible causes of high HbF, we sequenced a 14.1 kilobases (kb) DNA fragment between Ay-globin gene (HBG1) and HBD in 15 high HbF and 15 low HbF patients. The DNA fragment houses the 7.2kb Corfu deletion that is associated with elevated HbF levels in the homozygous state and also contains binding sites for BCL11A. Thirty-eight single nucleotide polymorph isms (SNPs) were present in both groups of patients. Four SNPs had significantly higher major allele frequencies in the high HbF group (P<0.05) suggesting that polymorphisms in this area might contribute to elevated HbF levels in African American sickle cell anemia patients.2031-01-0

Endothelial function does not relate to haemoglobin or serum erythropoietin concentrations and these do not explain the gender difference in endothelial function in healthy middle-aged men and women

BackgroundHaemoglobin scavenges nitric oxide, and a previous study has shown a negative association between flow-mediated vasodilation (FMD), a measure of nitric oxide (NO)-dependent vasomotor function and haemoglobin concentrations [Hb]. Circulating erythropoietin (EPO) is also negatively associated with [Hb] and could influence availability of NO. The purpose of this study was to examine the association of FMD with [Hb] and EPO concentrations and to determine whether these contribute to the sex difference in FMD. FMD (by high-resolution ultrasound), [Hb], circulating immunoreactive EPO and cardiovascular risk factors were measured in 317 healthy middle-aged men and women (183 women, 33 premenopausal, mean age ± SD, 55 ± 6·8 years) participating in a dietary study.ResultsIn the whole mixed-sex group, FMD was negatively correlated with [Hb] (R = −0·23, P &lt; 0·001). However, in a multivariable model, incorporating sex and other confounding factors, FMD was independently negatively correlated only with age, male sex and systolic blood pressure: standardized regression coefficients −0·21 (P &lt; 0·01), −0·17 (P &lt; 0·05) and −0·20 (P &lt; 0·05) respectively and not with [Hb]. Similarly, when the analysis was restricted to men or to postmenopausal women, there was no significant relationship between FMD and Hb. There was no significant correlation between FMD and EPO on either univariate analysis in the whole group, in each sex, or in multivariate analysis.ConclusionThese results suggest that in healthy middle-aged subjects, FMD is not influenced by [Hb] or EPO and these do not contribute to the gender difference in FMD

Point-of-care end-tidal carbon monoxide reflects severity of hemolysis in sickle cell anemia

Carbon monoxide (CO) production from heme catabolism is increased with hemolysis. A portable end-tidal CO (ETCO) monitor was used to analyze breath samples in 16 children with sickle cell anemia (SCA, 5-14 years). Median (range) ETCO for SCA was 4.35 ppm (1.8-9.7) versus 0.80 ppm (0.2-2.3) for controls (P<0.001). ETCOc >2.1 ppm provided sensitivity and specificity of 93.8% (69.8-99.8%) for detecting SCA. ETCO correlated with reticulocytosis (P=0.015) and bilirubin (P=0.009), and was 32% lower in children receiving hydroxyurea (P=0.09). Point-of-care ETCO analysis may prove useful for non-invasive monitoring of hemolysis and as a screening test for SCA