ALBERT

Description: Introduction: Sickle cell disease (SCD), an inherited blood disorder, is characterized by episodes of painful vaso-occlusive crises (VOC). Peripheral vasoconstriction may contribute to VOC by prolonging the transit time of red blood cells through the microvasculature. We recently demonstrated that heat-induced pain produces stronger vasoconstriction in SCD subjects versus controls, suggesting abnormal autonomic regulation of regional blood flow in SCD. Thus, although pain is generally thought to be a consequence of VOC, it is possible that pain itself may trigger a cascade of events that leads to large-scale VOC by promoting regional peripheral vasoconstriction. Objective: To determine if the underlying functional mechanisms of the vasoconstriction response to heat-induced pain in SCD differ from normal controls. Experimental Protocols: 22 SCD and 23 control (healthy and sickle cell trait) subjects were recruited at Children's Hospital of Los Angeles. Quasi-periodic pulses of pain were delivered on the right forearm using TSA-II neuro analyzer heating thermode. Electrocardiogram, respiration, continuous blood pressure and photoplethysmogram (PPG) were recorded. Both blood pressure and PPG were measured on the ring finger and thumb on the contralateral hand. Reductions in PPG amplitude were taken to represent vasoconstriction. Analysis: A mathematical model was applied to the data to extract the key parameters relating the thermal (pain) pulses, blood pressure and respiration to vasoconstriction. The model enabled the vasoconstriction response to pain to be decomposed into: 1) a neurogenic component, measuring the direct effect of the thermal pain pulse on vasoconstriction; 2) a local vascular component, relating fluctuations in blood pressure, induced by pain, to vasoconstriction; 3) a neurogenic-vascular interaction component, reflecting the modulation of the vascular component by the pain stimulus; and 4) a respiratory coupling component. Results: The model predicted stronger vasoconstriction responses to heat pain in SCD than controls (p = 0.002), consistent with the previous results reported by Khaleel et al. (Blood 126 (23):67, 2015). The pattern of the neurogenic response in both groups was similar but stronger in SCD (Fig 1a). The time-course of the local vascular component was quite pronounced in SCD (Fig 1b) - increases in blood pressure promoted stronger and more rapid vasoconstriction in SCD relative to controls. The neurogenic-vascular interaction (not shown) caused further peripheral vasoconstriction in SCD, but tended to reduce vasoconstriction in controls. The respiratory contribution was small in both groups. Discussion & Conclusions: Heat-induced pain produces peripheral vasoconstriction via direct autonomic nervous system activation, as well as indirectly through the local vascular response to pain-triggered blood pressure fluctuations. The complex dynamics of the vasoconstriction response can only be understood by application of a mathematical model incorporating several relevant simultaneously measured and frequently sampled physiological signals. The stronger neurogenic response in SCD suggests elevated sympathetic activity compared to controls. The local vascular component in the SCD subjects exhibits a higher reactivity to increases in local blood pressure that promotes vasoconstriction, consistent with underlying endothelial dysfunction. The contribution of neurogenic-vascular interaction derived from the model likely represents the degree to which sympathetic overactivity leads to vascular dysfunction in SCD. These results suggest that dysautonomia and its interaction with peripheral vascular dysregulation participate in the genesis of vaso-occlusive crisis. Figure 1 (a) average neurogenic response (% change from baseline) to a heat pain pulse (20 °C, 10-sec long) in SCD (N = 22) and controls (N = 23); (b) average vascular response (% change from baseline) to a blood pressure pulse induced by pain (10 mmHg, 10-sec long) in SCD and controls. Figure 1. (a) average neurogenic response (% change from baseline) to a heat pain pulse (20 °C, 10-sec long) in SCD (N = 22) and controls (N = 23); (b) average vascular response (% change from baseline) to a blood pressure pulse induced by pain (10 mmHg, 10-sec long) in SCD and controls. Disclosures Wood: Biomed Informatics: Consultancy; AMAG: Consultancy; Vifor: Consultancy; Ionis Pharmaceuticals: Consultancy; Vifor: Consultancy; World Care Clinical: Consultancy; Celgene: Consultancy; Biomed Informatics: Consultancy; AMAG: Consultancy; Apopharma: Consultancy; Apopharma: Consultancy; World Care Clinical: Consultancy; Celgene: Consultancy; Ionis Pharmaceuticals: Consultancy.

Description: Introduction: Although routine tissue iron monitoring using magnetic resonance imaging (MRI) has become a standard clinical management of both transfusion dependent and non-transfusion dependent thalassemias (TDT & NTDT) in several developed countries since this module can provide a better organ-directed iron measurement and related to clinical outcome including morbidity and mortality secondary to iron overload (IOL). However, accessibility of this monitoring remains limited in several developing countries including Thailand, where thalassemia and hemoglobinopathies are highly prevalent. Earlier in 2016, we have demonstrated that although not so perfectly crafted, a cross-sectional measurement of serum ferritin (SF) can be used for determination of IOL as a predictive marker; in NTDT, MRI for liver iron concentration (LIC) should be performed in those with SF 〉300 ug/L and for TDT, the SF cut off of 〉2,500 and 〉3,500 ug/L are useful to predict patients with severe LIC (〉15 mgFe/g dw) and cardiac siderosis (T2*〈 20 ms) (Ekwattanakit S. et.al., EHA 2016). In this study, we performed a further analysis to evaluate whether a serial measurement of SF and its trend can provide a better prediction. Objectives: To evaluate the clinical utility of serial SF trend compared with a cross-sectional SF cut-off for early detection of IOL in a real-life practice in thalassemic patients in order to select the most vulnerable patients for further MRI evaluation in a resource limited setting. Methods: In this prospective study, total 968 standard MRI for LIC and cardiac T2*were performed at Siriraj hospital during 2009-2014 and paired clinical data including serial SF measurements were collected from 301 thalassemia patients; NTDT (N=76; 109 LIC and 95 cardiac T2* results) and TDT (N=155; 478 LIC and 474 cardiac T2*). In addition, 71 patients were NTDT with regular blood transfusion later on in their life, mainly Hb E/β thalassemia (218 LIC and 210 cardiac T2*). These patients were evaluated for IOL using SF every 4-12 weeks during their follow up. Median follow up time was 96 months. Receiver operating characteristic (ROC) analysis was performed using different SF cut-off levels (1000, 1500 and 2000ug/L) and percentage of serial SF measurements that above each these cut-off levels (50 and 75%) during different durations before MRI (1, 2, or 3 years priori) for predicting liver IOL (LIC 〉5 in NTDT and severe liver siderosis; LIC 〉 15 mgFe/g dw) and cardiac IOL (T2*1000 ug/L over 75% of serial measurements in 1-year period prior to MRI can predict LIC 〉 5 mgFe/g dw with the AUC of 0.59 with PPV 86.7% and NPV 51.1% and serial SF 〉1500 ug/l over 50% of measurement in a year prior predict LIC 〉15 mgFe/g dw (AUC of 0.72, PPV 75% and NPV 89.7%). Only 1 NTDT had cardiac IO. These newly identified criteria do not provide a more sensitive predictor of LIC results than our previous SF cut-off. In TDT population, the majority of patients were HbE/β thal (78%) and cardiac iron overload was detected mainly in patients older than 15 yrs (81/83; 97.6%). The best predictor for LIC〉15 mgFe/g dw was SF 〉2000 ug/L over 75% of serial measurement durations in 3-year period (AUC 0.778, PPV 50.8%, NPV 95.5%). However this cut-off during 1 year priori also provided a similar prediction (AUC 0.769, PPV 51%, NPV 93.6%). This cut-off value also provided the best prediction for cardiac T2* 〈 20 ms in all age group (AUC 0.754, PPV 31.5%, NPV 97.4%) and a higher sensitivity and specificity when it was applied in patients 〉15 yrs of age (AUC 0.764, PPV 41.9%, NPV 96.3%). In NTDT with regular transfusion, all cardiac IOL (N=19) occurred after 15 years of age and again the same criteria was the good predictive cut-off for cardiac IO (AUC 0.788, PPV 19%, NPV 100%) and severe LIC 〉15 mgFe/g dw (AUC 0.728, PPV 52.8%, NPV 87.3%). Conclusions: In a resource limited setting for MRI evaluation, a serial measurement of SF and its values in thalassemic patients who received regular blood transfusion above the cut-off of 2000 ug/L over 75% of measurement in one year priori could be used as a predictive marker for selecting the most vulnerable TDT for MRI evaluation since this criteria is strongly associated with severe liver (LIC 〉 15 mgFe/g dw) and cardiac siderosis (T2*

Description: Abstract 1523 Poster Board I-546 Sickle cell anemia (SCA) is a genetic disorder characterized by recurring episodes of vaso-occlusive crisis (VOC) that can lead to hospitalization or sudden death. Hypoxia is an accepted trigger of sickling and degrees of nighttime hypoxia correlate with strokes and frequency of VOC. To better understand the mechanism of events leading to VOC, we simulated the occurrence of nocturnal hypoxia in SCA patients by administration of five breaths of 100% nitrogen. Tidal volume (Vt), arterial oxygen saturation, electrocardiogram (ECG), and microvascular perfusion (PU) by Laser-Doppler were continuously recorded. We had anticipated a drop in PU after each controlled episode of hypoxia. However, we observed multiple prominent drops in PU in SCA subjects (n=8) that were not as clearly evident in controls (CTL; n=9), and found no direct relationship between hypoxia and change in PU (p = NS). As deep breaths or sighs can trigger reflex peripheral vasoconstriction, we examined Vt respiratory tracings obtained simultaneously and observed that PU drops frequently followed sighs (see Figure) in SCA subjects, but rarely in CTL. A statistical algorithm was used to find all sighs and vasoconstrictive events (PU drops) during each 40-minute experimental session. PU drops were associated with sighs in 7 of 8 SCA patients and in 4 of 9 CTL subjects (P 〈 0.001, Poisson regression analysis). Five CTL and 1 SCA subjects had infrequent sighs and no association between sighs and PU drops. The likelihood ratio of sigh-associated PU drops was significantly higher in SCA than CTL subjects (median = 59.9 % vs. 〈 1 % for SCA vs. CTL, P = 0.008, rank-sum test) whereas the frequency of sighs was not significantly different between the two groups (median = 2.2 % vs. 1.3 % for SCA vs. CTL, P = 0.16, rank-sum test), indicating that SCA patients are much more likely to have sigh-associated peripheral vasoconstriction. Since the sigh-vasoconstrictor response is controlled by the autonomic nervous system (ANS), we measured heart rate variability (HRV) which is an accepted index of sympathetic/parasympathetic balance. These studies showed substantial reduction of parasympathetic modulation of HRV during hypoxia in SCA but not in CTL subjects (p 〈 0.01), indicating a marked abnormality of the ANS in SCA. In overview, the likelihood of coupling between spontaneous sighs and subsequent vasoconstrictive events (PU drops) is much higher in SCA patients than in CTL. Thus, we speculate that a drop in perfusion secondary to increased neural coupling between the lung and vasculature may be an initiating event in VOC. Hypoxia may secondarily promote VOC by altering ANS sensitivity and increasing the probability that a sigh will in turn lead to reflex peripheral vasoconstriction. In a background of HbS, transient decreases in perfusion may prolong red cell residence time in the microvasculature, leading to HbS polymerization, sickling and vascular occlusion. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4244 Introduction: Long-term storage iron (hemosiderin) is insoluble and not directly accessible to iron chelation. Ascorbate is a potent facilitator of redox cycling and facilitates the mobilization of cellular iron stores in patients chelated with deferoxamine. Ascorbate deficiency is quite common in thalassemia major and may create a phenotype of relative chelator refractoriness. However, the synergistic role of ascorbate supplementation has never been demonstrated for other chelators, including the oral chelator deferasirox. Ascorbate can be freely synthesized in many animals, making them unsuitable models to address this question. The osteodystrophic syndrome (ODS) rat is a spontaneous mutant lacking L-gulono-gamma-lactone oxidase, the initial enzyme in ascorbate synthesis. Iron loading and chelation have never been performed in ODS rats, so we report a pilot study aimed at optimizing organ iron loading and clearance. Methods: Twenty-six 8-week old male ODS rats were maintained vitamin C replete by supplying ascorbate in the chow or drinking water. Fourteen animals were iron loaded using a combination of 0.4% TMH ferrocene and 3% carbonyl iron in standard rodent chow. Twelve animals were loaded with iron dextran (200 mg/kg/week) by subcutaneous injection. To characterize loading kinetics, two animals were analyzed at five, ten, and twelve weeks of oral iron loading as well as five and ten weeks of iron dextran injections. Sixteen animals were iron loaded for ten weeks (half enterally, half parenterally) and transitioned into the chelation arm. Iron chelation was performed with oral deferasirox at 75 mg/kg/dose, once daily five times per week. Chelation was administered for six and twelve weeks in six animals, divided equally between parenteral and enteral iron loading; sham chelation was given to the remaining four animals. Following euthanasia, H&E and iron staining were performed and tissue iron was quantified by atomic absorption. Results: Parenteral iron loading was well tolerated and yielded liver iron concentration (LIC) values of approximately 3 and 4.5 mg/g wet weight (∼11-16.8 mg/g dry weight) at five and ten weeks, respectively. Iron loading was predominantly reticuloendothelial, with little parenchymal redistribution. Spontaneous iron loss after 12 weeks of iron chelation was modest at 1.3% per week. In contrast, oral iron loading with the combination of TMH-ferrocene and carbonyl iron was poorly tolerated. Animals developed severe diarrhea and required fluid replacement and frequent dose reductions. These GI disturbances gradually lessened over a period of four weeks and animals received approximately 80% of the targeted iron dose. LIC values were lower at five weeks (2.2 mg/g ww) but nearly equivalent by 10 weeks (4.2 mg/g ww). Iron was entirely parenchymal, with little reticuloendothelial deposition. Spontaneous iron losses after 12 weeks of iron chelation were strikingly higher than for parenteral iron loading, measuring 4.7% per week. Iron chelation with deferasirox was well tolerated in both groups. Iron chelation was less efficient in iron dextran loaded animals. LIC was 3.1 ± 0.7 mg/g ww compared with 3.8 ± 0.2 mg/g ww in sham chelated animals, p=0.25. In contrast, deferasirox treatment nearly completely cleared liver iron in TMH treated animals 0.4 ± 0.1 mg/g ww vs 1.5 ± 0.04 mg/g ww, p = 0.001, with most of the residual iron located primarily in reticuloendothelial store on histologic analysis. Discussion: Iron loading in the ODS rat can be performed with either iron dextran or TMH-ferrocene but the characteristics of iron staining, spontaneous iron loss, and chelator accessibility are completely different. Iron dextran loads the reticuloendothelial system. Iron redistribution to parenchymal tissues is sluggish, based upon the low spontaneous iron elimination rate and modest response to deferasirox therapy (1.5% per week). In contrast, TMH produced exclusively parenchymal loading, high spontaneous iron losses (4.7% per week) and more vigorous response to chelation (6.3% per week). Subsequent studies will determine whether the degree of ascorbate sufficiency modulates deferasirox efficacy in animals with primarily reticuloendothelial iron loading. Disclosures: Nick: Novartis: Employment. Wood:Novartis: Research Funding; Ferrokin Biosciences: Consultancy.

Description: Introduction: Deferasirox (ICL670) is a novel tridentate oral iron chelator currently being evaluated for the treatment of transfusional iron overload. Phase III clinical trials have demonstrated that once-daily ICL670 (20 mg/kg) is equally effective at controlling liver iron concentration as standard deferoxamine therapy (40 mg/kg/day, 5 days per week). While ICL670’s long serum half-life should offer good protection against cardiac iron accumulation, little is known regarding its ability to remove stored cardiac iron. Therefore, we compared the relative efficacy of ICL670, deferiprone (L1), and deferoxamine (DFO) in removing cardiac iron from iron-loaded gerbils. Methods: 37 8–10 week old female gerbils underwent ten weekly iron dextran injections of 200 mg/kg/D, followed by a 13 day equilibration period. Five animals were then sacrificed to determine pre-chelation iron burdens. Chelation was initiated in 3 groups of 8 animals (ICL670 100 mg/kg/D po QD, L1 375 mg/kg/D po divided TID, DFO 200 mg/kg/D sub Q divided BID) five days per week and maintained for 12 weeks. The remaining 8 animals received sham chelation. All animals underwent ECG and treadmill assessment at baseline, following iron loading, and after completing chelation therapy. Animals were sacrificed for liver and heart iron measurement (Mayo Medical Laboratory) and semiquantitative histology. Hearts were evaluated for iron loading/distribution, tissue fibrosis, and myocyte hypertrophy, while livers were scored for iron loading/distribution and fibrosis. Results: Chelator-independent iron excretion and redistribution was evident, unlike in humans. Cardiac and liver iron contents fell 30.4% and 23.2%, respectively, with sham chelation; all subsequent chelator comparisons are reported with respect to the sham-chelated animals. ICL670 reduced cardiac iron content 20.5%. There were no changes in cardiac weight, myocyte hypertrophy, fibrosis, or wet-to-dry weight ratio. ICL670 treatment reduced liver iron content 51%. Iron elimination was greatest in hepatocytes with no detectable Kupfer-cell iron clearance. L1 produced comparable reductions in cardiac iron content (18.6%). Wet weight cardiac iron concentration fell nearly 30% but this was offset by greater cardiac mass (16.5% increase). Histologic analysis demonstrated decreased iron staining but increased myocyte hypertrophy. L1 decreased liver iron content 24.9%. Wet weight liver iron concentration fell 43.8% but was offset by a 30% increase in liver weight and water content. Iron elimination was balanced between Kupfer cells and hepatocytes. DFO did not reduce biochemically-assayed cardiac or liver iron content, although it improved histologic iron scores in both organs. Hearts from DFO treated animals were enlarged and had greater fibrosis. Cardiac and liver iron contents were closely correlated (r = 0.66), but ICL670 animals had lower hepatic iron contents for any given cardiac iron content. Iron loading broadened QRS duration by 10.6%; this effect was antagonized by both L1 and ICL670 therapy. PR, QRS, and QTc interval were weakly correlated with cardiac and liver iron contents. Treadmill exercise time was independent of chelation therapy. Conclusion: ICL670 and L1 were equally effective in removing stored cardiac iron in a gerbil animal model but ICL670 removed more hepatic iron for a given cardiac iron burden.

Description: Vitamin D deficiency is epidemic in the United States and is associated with decreased calcium absorption and metabolism, leading to bone loss, muscle weakness, and impaired pancreatic function. Many thalassemia major patients, as a result of decreases sunlight exposure and increased metabolic demand, are vitamin D deficient. We hypothesized that vitamin D deficiency might be associated with cardiac siderosis and impaired cardiac function through its modulation of calcium signaling in these patients. Methods: Permission for review of medical records was obtained from the Committee on Clinical Investigation at Children’s Hospital Los Angeles. We compared vitamin D25-0H and D1-25 levels in our thalassemia major patients with cardiac R2* (1/T2*) and left ventricular ejection fraction (LVEF) from the patient’s most recent cardiac MRI. Time difference between the exams was 2.8 ± 3.3 months with a range of 0.2 to 9.4 months. Other parameters recorded included age, gender, ferritin, liver iron (by MRI) and transferrin saturation. Univariate and multivariate regression was performed using JMP 5.1 (SAS, Cary, NC). Results: Twenty four patients had records suitable for review. There were 11 women and 13 men with a mean age of 14.7 ± 7.6 years [1.4 – 25.8]. Population was moderately iron overloaded with ferritin values of 2089 ± 1920 ng/ml [246 – 8230], liver iron 13.7 ± 11.4 mg/g dry wt [2–39.5], cardiac R2* 65 ± 61 Hz [19.8 – 229], and transferrin saturation 84 ± 18% [36%–106%]. Vitamin D25-OH levels were markedly depressed, 17.1 ± 8.5 pg/ml [1–33], with 13/24 values below the lower limit of 20 ng/ml. Surprisingly, vitamin D1-25OH levels were normal or elevated in all patients, 59.9 ± 19.5 pg/ml [32–103] with four patients exceeding the upper limit of normal of 71 pg/ml. There was no correlation between D25-0H and D1-25OH levels. D25-OH levels (but not D1-25OH levels) fell sharply with age (r2 = 0.48) and were negatively associated with liver iron (r2 = 0.20). Figures 1 and 2 demonstrated cardiac R2* and LVEF as functions of D25-OH levels. Cardiac R2* was log-linearly correlated with D25-OH level (r2 = 0.44, p=0.0001; levels below 13 ng/ml were associated with severe cardiac iron loading. Multivariate analysis of D25-OH, D1-25, HIC, ferritin, age, and transferrin saturation demonstrated that D25-0H and ferritin are the sole predictors of abnormal cardiac R2*, accounting for 38% and 5% of the variability respectively. LVEF was also negatively related to D25-OH levels (r2 = 0.35, p = 0.002). In multivariate analysis, vitamin D250H and vitamin D1-25OH levels accounted for 50% of the LVEF variability, independent of cardiac R2*. Conclusion Vitamin D deficiency is common in thalassemia major patients and strongly associated with cardiac iron uptake and ventricular dysfunction. Figure Figure Figure Figure