Alia Bazzy-Asaad

Prevalence and Risk Factors of Elevated Pulmonary Artery Pressures in Children With Sickle Cell Disease

OBJECTIVES. The objectives of this study were (1) to determine the prevalence and risk factors of elevated pulmonary artery pressures in children with homozygous SS or Sβ° thalassemia using Doppler echocardiography and (2) to determine a correlation between abnormal transcranial Doppler examinations and elevated pulmonary artery pressures. METHODS. Screening echocardiograms were prospectively performed during an annual comprehensive clinic visit on children who were older than 6 years and had homozygous SS or Sβ° thalassemia. Detailed history, examination, and laboratory tests were done, and transcranial Doppler examinations were obtained in children 2 to 14 years of age. Pulmonary hypertension was defined as pulmonary artery systolic pressure of at least 30 mmHg corresponding to a peak tricuspid regurgitant jet velocity of ≥2.5 m/second. Mild pulmonary hypertension was defined as tricuspid regurgitant jet velocity ≥2.5 to 2.9 m/second. Moderate pulmonary hypertension was defined as tricuspid regurgitant jet velocity ≥3 m/second. Patients with pulmonary stenosis or right outflow obstruction were excluded. Characteristics were compared between patients with mild, moderate, and no pulmonary hypertension using 1-way analysis of variance for continuous variable and Fishers exact test for categorical variables. RESULTS. Of the 75 patients who had homozygous SS/Sβ° thalassemia and were older than 6 years, echocardiograms were obtained for 62 (82.6%). Thirty percent (19 of 62) of patients had elevated tricuspid regurgitant jet velocity ≥2.5 m/second. One third of these patients had tricuspid regurgitant jet velocity ≥3 m/second. All patients with elevated tricuspid regurgitant jet velocity had SS disease. A high reticulocyte count, low oxygen saturation, and a high platelet count were significantly associated with elevated pulmonary artery pressures. There was no difference in age, gender, history of acute chest syndrome, hydroxyurea therapy, chronic blood transfusion, stroke, hemoglobin, and bilirubin between patients with and without elevated pulmonary artery pressures. A total of 47% patients with elevated tricuspid regurgitant jet velocity and 57% without elevated tricuspid regurgitant jet velocity had screening transcranial Doppler examinations. Transcranial Doppler examinations were normal for all patients. CONCLUSIONS. High pulmonary artery pressures do occur in children with sickle cell disease. Screening by echocardiography can lead to early detection and intervention that may potentially reverse this disease process. There was no correlation between elevated pulmonary artery pressures and abnormal transcranial Doppler examination in our study.

δ‐, but not µ‐, opioid receptor stabilizes K+ homeostasis by reducing Ca2+ influx in the cortex during acute hypoxia

Past work has shown that δ‐opioid receptor (DOR) activation by [D‐Ala2,D‐Leu5]‐enkephalin (DADLE) attenuated the disruption of K+ homeostasis induced by hypoxia or oxygen‐glucose deprivation (OGD) in the cortex, while naltrindole, a DOR antagonist blocked this effect, suggesting that DOR activity stabilizes K+ homeostasis in the cortex during hypoxic/ischemic stress. However, several important issues remain unclear regarding this new observation, especially the difference between DOR and other opioid receptors in the stabilization of K+ homeostasis and the underlying mechanism. In this study, we asked whether DOR is different from µ‐opioid receptors (MOR) in stabilizing K+ homeostasis and which membrane channel(s) is critically involved in the DOR effect. The main findings are that (1) similar to DADLE (10 µM), H‐Dmt‐Tic‐NH‐CH (CH2COOH)‐Bid (1–10 µM), a more specific and potent DOR agonist significantly attenuated anoxic K+ derangement in cortical slice; (2) [D‐Ala2, N‐Me‐Phe4, glycinol5]‐enkephalin (DAGO; 10 µM), a MOR agonist, did not produce any appreciable change in anoxic disruption of K+ homeostasis; (3) absence of Ca2+ greatly attenuated anoxic K+ derangement; (4) inhibition of Ca2+‐activated K+ (BK) channels with paxilline (10 µM) reduced anoxic K+ derangement; (5) DADLE (10 µM) could not further reduce anoxic K+ derangement in the Ca2+‐free perfused slices or in the presence of paxilline; and (6) glybenclamide (20 µM), a KATP channel blocker, decreased anoxia‐induced K+ derangement, but DADLE (10 µM) could further attenuate anoxic K+ derangement in the glybenclamide‐perfused slices. These data suggest that DOR, but not MOR, activation is protective against anoxic K+ derangement in the cortex, at least partially via an inhibition of hypoxia‐induced increase in Ca2+ entry‐BK channel activity. J. Cell. Physiol. 212: 60–67, 2007.

Sleep-Disordered Breathing in Children With Metabolic Syndrome: The Role of Leptin and Sympathetic Nervous System Activity and the Effect of Continuous Positive Airway Pressure

OBJECTIVE. The purpose of this work was to determine whether, in children with metabolic syndrome and sleep-disordered breathing, metabolic markers separate them from children with metabolic syndrome without sleep-disordered breathing and whether treatment of sleep-disordered breathing with continuous positive airway pressure is associated with an improvement in metabolic derangement. PATIENTS AND METHODS. Subjects aged 7 to 19 years old with metabolic syndrome and a positive validated sleep questionnaire were recruited. Subjects underwent overnight polysomnography, during which sympathetic nervous system activity was assessed via 8-hourly measurements of norepinephrine and epinephrine, together with leptin. The next morning, a fasting 3-hour oral glucose-tolerance test was performed to calculate whole-body insulin sensitivity. A fasting lipid panel interleukin 6, adiponectin, and C-reactive protein levels were also measured. Children with sleep-disordered breathing were placed on continuous positive airway pressure for 3 months and studied again. Sleep-disordered breathing and no sleep-disordered breathing groups were compared by using Fishers exact test and t test for independent samples with analysis of covariance to adjust for age and BMI. RESULTS. Of 34 children studied, 25 had sleep-disordered breathing (apnea-hypopnea index: >1.5). Mean hourly norepinephrine and leptin levels were higher in the group with sleep-disordered breathing compared with the group without sleep-disordered breathing (P < .005), with no difference in whole-body insulin sensitivity. Eleven subjects with sleep-disordered breathing completed 3 months of nightly continuous positive airway pressure treatment. In the follow-up study, mean hourly leptin levels were significantly lower than in the initial study, with no change in BMI z score or other measurements. CONCLUSION. Our findings support the hypothesis that sleep-disordered breathing in children with metabolic syndrome is associated with increased sympathetic nervous system activity and leptin levels but not worsening of insulin resistance. Treatment of sleep-disordered breathing with continuous positive airway pressure led to a significant decrease in leptin levels.

Longitudinal follow up of elevated pulmonary artery pressures in children with sickle cell disease

Elevated pulmonary artery pressures (PAP) occur in approximately 30% of children with sickle cell disease. In adults, pulmonary hypertension is significantly associated with mortality. There are no data on the long term significance in children. Nineteen children with SS/Sß0 thalassaemia had elevated PAP, defined as tricuspid regurgitant jet velocity (TRV) ≥2·5 m/s on screening echocardiograms. They were prospectively followed for 23 months (range 19–31 months). Patients with initial TRV ≥ 3 or TRV ≥ 2·5 m/s on repeat echocardiogram had cardiopulmonary evaluation and were offered treatment with hydroxyurea. Associated conditions like asthma and obstructive sleep apnea were treated. 18/19 patients had follow‐up echocardiograms. These showed normalization of TRV in 8 patients. Risk factors associated with persistent elevation were higher TRV on initial echocardiogram (P = 0·01), lower haemoglobin (P = 0·003) and lower oxygen saturation (P = 0·03). Five patients with persistently elevated PAP were treated with hydroxyurea. Mean right ventricular pressure dropped from 40·16 to 29·26 (P = 0·017) after 3–6 months and to 23·6 mmHg (P = 0·002) after 9–12 months on treatment. In conclusion (i) At borderline elevation of TRV there is intrapatient variability and echocardiograms should be repeated for confirmation. (ii) Elevated PAP are reversible in children with early detection and treatment with hydroxyurea.

Cortical δ-opioid receptors potentiate K+ homeostasis during anoxia and oxygen-glucose deprivation

Central neurons are extremely vulnerable to hypoxic/ischemic insult, which is a major cause of neurologic morbidity and mortality as a consequence of neuronal dysfunction and death. Our recent work has shown that δ-opioid receptor (DOR) is neuroprotective against hypoxic and excitotoxic stress, although the underlying mechanisms remain unclear. Because hypoxia/ischemia disrupts ionic homeostasis with an increase in extracellular K+, which plays a role in neuronal death, we asked whether DOR activation preserves K+ homeostasis during hypoxic/ischemic stress. To test this hypothesis, extracellular recordings with K+-sensitive microelectrodes were performed in mouse cortical slices under anoxia or oxygen–glucose deprivation (OGD). The main findings in this study are that (1) DOR activation with [D-Ala2, D-Leu5]-enkephalinamide attenuated the anoxia- and OGD-induced increase in extracellular K+ and decrease in DC potential in cortical slices; (2) DOR inhibition with naltrindole, a DOR antagonist, completely abolished the DOR-mediated prevention of increase in extracellular K+ and decrease in DC potential; (3) inhibition of protein kinase A (PKA) with N-(2-[p-bromocinnamylamino]-ethyl)-5-isoquinolinesulfonamide dihydrochloride had no effect on the DOR protection; and (4) inhibition of protein kinase C (PKC) with chelerythrine chloride reduced the DOR protection, whereas the PKC activator (phorbol 12-myristate 13-acetate) mimicked the effect of DOR activation on K+ homeostasis. These data suggest that activation of DOR protects the cortex against anoxia- or ODG-induced derangement of potassium homeostasis, and this protection occurs via a PKC-dependent and PKA-independent pathway. We conclude that an important aspect of DOR-mediated neuroprotection is its early action against derangement of K+ homeostasis during anoxia or ischemia.

Activation of DOR Attenuates Anoxic K+ Derangement via Inhibition of Na+ Entry in Mouse Cortex

We have recently found that in the mouse cortex, activation of delta-opioid receptor (DOR) attenuates the disruption of K(+) homeostasis induced by hypoxia or oxygen-glucose deprivation. This novel observation suggests that DOR may protect neurons from hypoxic/ischemic insults via the regulation of K(+) homeostasis because the disruption of K(+) homeostasis plays a critical role in neuronal injury under hypoxic/ischemic stress. The present study was performed to explore the ionic mechanism underlying the DOR-induced neuroprotection. Because anoxia causes Na(+) influx and thus stimulates K(+) leakage, we investigated whether DOR protects the cortex from anoxic K(+) derangement by targeting the Na(+)-based K(+) leakage. By using K(+)-sensitive microelectrodes in mouse cortical slices, we showed that 1) lowering Na(+) concentration and substituting with impermeable N-methyl-D-glucamine caused a concentration-dependent attenuation of anoxic K(+) derangement; 2) lowering Na(+) concentration by substituting with permeable Li(+) tended to potentiate the anoxic K(+) derangement; and 3) the DOR-induced protection against the anoxic K(+) responses was largely abolished by low-Na(+) perfusion irrespective of the substituted cation. We conclude that external Na(+) concentration greatly influences anoxic K(+) derangement and that DOR activation likely attenuates anoxic K(+) derangement induced by the Na(+)-activated mechanisms in the cortex.

A Role for Macrophage Migration Inhibitory Factor in the Neonatal Respiratory Distress Syndrome

Using a mouse model of neonatal respiratory distress syndrome (RDS), we demonstrate a central role for macrophage migration inhibitory factor (MIF) in lung maturation at the developmental stage when human neonates are most susceptible to RDS. We prematurely delivered mouse pups at embryonic day 18, during the early saccular stage of pulmonary development. Only 8% of the prematurely delivered pups genetically deficient in MIF survived 8 h vs 75% of wild-type controls (p < 0.001). This phenotype was corrected when pups of all genotypes were bred from dams heterozygote for MIF deficiency. Local production of MIF in the lung increased at embryonic day 18, continued until full-term at embryonic day 19.5, and decreased in adulthood, thus coinciding with this developmental window. The lungs of pups genetically deficient in MIF were less mature upon histological evaluation, and demonstrated lower levels of vascular endothelial growth factor and corticosterone – two factors that promote fetal lung maturation. In vitro studies support a role for MIF in surfactant production by pulmonary epithelial cells. In a cohort of human neonates with RDS, higher intrapulmonary MIF levels were associated with a lower likelihood of developing bronchopulmonary dysplasia, a sequelae of RDS (p < 0.03). This study demonstrates for the first time a role for MIF in lung maturation, and supports a protective role for MIF in newborn lung disease.

Predictors of Asthma-related Pediatric Emergency Department Visits and Hospitalizations

Objective. Asthma is a leading cause of emergency department visits and hospitalizations for children in the United States. As part of a larger study, the purpose of this analysis was to determine which variables were most effective at predicting subsequent pediatric asthma-related emergency department visits and hospitalizations. Methods. A retrospective, descriptive study was conducted. Subjects consisted of a convenience sample of 298 children admitted to a New England Childrens Hospital in 2006 with a primary diagnosis of asthma. Data from two hospital databases were collected for 12 months before and 12 months after the 2006 admission. Basic descriptive statistics were followed by chi-square tests to determine which variables were associated with emergency department visits and hospitalizations. Logistic regression analysis was used to determine which variables were significant predictors of asthma-related emergency department visits and hospitalizations. Results. Sixty-percent of all subjects were male. Ninety subjects experienced a total of 145 emergency department visits and 54 experienced a total of 70 hospitalizations. A previous emergency department visit was a significant predictor of both subsequent emergency department visits and subsequent hospitalizations. Age was also an independent risk factor for subsequent hospitalizations. In this sample, the risk of a hospitalization increased with each year increase in age. Conclusion. These findings support the importance of early identification of children with asthma so that appropriate asthma management can be instituted before an emergency department visit occurs. Furthermore, results suggest involving school-age and preadolescent children in the care of their asthma so that they can be equipped and encouraged to self-manage their own asthma.

Anisomycin protects cortical neurons from prolonged hypoxia with differential regulation of p38 and ERK

MAP kinase is associated with delta-opioid receptor (DOR) signaling and plays a role in cell survival/death. Since anisomycin may alter MAP kinase activity and affect neuronal survival, we investigated whether anisomycin alters neuronal response to hypoxic stress and DOR inhibition. The experiments were performed in cultured cortical neurons. MAP kinase activities were determined by immunoblotting and neuronal viability was assessed by LDH leakage and live/dead morphological study. DOR inhibition with naltrindole (10 microM) led to significant injury in normoxic neurons after 24 h of treatment and exacerbated hypoxia-induced injury. Along with the injury, either by hypoxia or naltrindole, phosphorylated p38 increased in a major way, while phosphorylated ERK and JNK had no significant change or slightly decreased. Anisomycin (50 ng/ml) prevented the increase in phosphorylated p38 immunoreactivity induced by naltrindole and reduced the neuronal injury. The results suggest that (1) MAP kinases are differentially involved in neuronal response to hypoxia and DOR inhibition in cortical neurons with phosphorylated p38 immunoreactivity being upregulated and (2) anisomycin attenuates the increase in phosphorylated p38 immunoreactivity and reduces neuronal injury induced by hypoxia and DOR inhibition.

DOR activation inhibits anoxic/ischemic Na+ influx through Na+ channels via PKC mechanisms in the cortex.

Activation of delta-opioid receptors (DOR) is neuroprotective against hypoxic/ischemic injury in the cortex, which is at least partially related to its action against hypoxic/ischemic disruption of ionic homeostasis that triggers neuronal injury. Na(+) influx through TTX-sensitive voltage-gated Na(+) channels may be a main mechanism for hypoxia-induced disruption of K(+) homeostasis, with DOR activation attenuating the disruption of ionic homeostasis by targeting voltage-gated Na(+) channels. In the present study we examined the role of DOR in the regulation of Na(+) influx in anoxia and simulated ischemia (oxygen-glucose deprivation) as well as the effect of DOR activation on the Na(+) influx induced by a Na(+) channel opener without anoxic/ischemic stress and explored a potential PKC mechanism underlying the DOR action. We directly measured extracellular Na(+) activity in mouse cortical slices with Na(+) selective electrodes and found that (1) anoxia-induced Na(+) influx occurred mainly through TTX-sensitive Na(+) channels; (2) DOR activation inhibited the anoxia/ischemia-induced Na(+) influx; (3) veratridine, a Na(+) channel opener, enhanced the anoxia-induced Na(+) influx; this could be attenuated by DOR activation; (4) DOR activation did not reduce the anoxia-induced Na(+) influx in the presence of chelerythrine, a broad-spectrum PKC blocker; and (5) DOR effects were blocked by PKCβII peptide inhibitor, and PKCθ pseudosubstrate inhibitor, respectively. We conclude that DOR activation inhibits anoxia-induced Na(+) influx through Na(+) channels via PKC (especially PKCβII and PKCθ isoforms) dependent mechanisms in the cortex.