Estrogen has well-documented neuroprotective effects in a variety of clinical and experimental disorders of the CNS, including autoimmune inflammation, traumatic injury, stroke, and neurodegenerative diseases. The beneficial effects of estrogens in CNS disorders include mitigation of clinical symptoms, as well as attenuation of histopathological signs of neurodegeneration and inflammation. The cellular mechanisms that underlie these CNS effects of estrogens are uncertain, because a number of different cell types express estrogen receptors in the peripheral immune system and the CNS. Here, we investigated the potential roles of two endogenous CNS cell types in estrogen-mediated neuroprotection. We selectively deleted estrogen receptor-α (ERα) from either neurons or astrocytes using well-characterized Cre-loxP systems for conditional gene knockout in mice, and studied the effects of these conditional gene deletions on ERα ligand-mediated neuroprotective effects in a wellcharacterized model of adoptive experimental autoimmune encephalomyelitis (EAE). We found that the pronounced and significant neuroprotective effects of systemic treatment with ERα ligand on clinical function, CNS inflammation, and axonal loss during EAE were completely prevented by conditional deletion of ERα from astrocytes, whereas conditional deletion of ERα from neurons had no significant effect. These findings show that signaling through ERα in astrocytes, but not through ERα in neurons, is essential for the beneficial effects of ERα ligand in EAE. Our findings reveal a unique cellular mechanism for estrogen-mediated CNS neuroprotective effects by signaling through astrocytes, and have implications for understanding the pathophysiology of sex hormone effects in diverse CNS disorders.multiple sclerosis | astrogliosis | conditional knockout T he female sex hormone, estrogen, is neuroprotective in many clinical and experimental CNS disorders, including autoimmune conditions such as multiple sclerosis (MS), neurodegenerative conditions such as Alzheimer's and Parkinson diseases, and traumatic injury and stroke (1-4). Estrogen treatment has been shown to ameliorate clinical disease and decrease neuropathology in these disease models (1-4). Pharmacological studies have suggested roles for different estrogen receptors, but the cell types that mediate neuroprotective effects of estrogen are not known for any experimental or clinical condition. Identifying cells that bear specific estrogen receptor subtypes and are essential for specific estrogen-mediated effects is fundamental to elucidating and therapeutically exploiting the mechanisms that underlie estrogen-mediated neuroprotection. Toward this end, we used a genetic loss-of-function strategy. We selectively deleted estrogen receptor-α (ERα) from two different CNS cell types, neurons and astrocytes, and then determined the effects of these conditional gene deletions on the ability of ERα-ligand treatment to ameliorate disease severity of experimental autoimmune encephalomyelitis (EAE) in mice.EAE i...

Decreasing the amplitude of the late component of the cardiac L-type Ca2+ channel current suppresses early afterdepolarizations, thereby decreasing the risk of arrhythmias.

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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.

Sickle cell disease (SCD) is a monogenic hemoglobinopathy associated with significant morbidity and mortality. Cardiopulmonary, vascular and sudden death are the reasons for the majority of young adult mortality in SCD. To better understand the clinical importance of multi‐level vascular dysfunction, in 2009 we assessed cardiac function including tricuspid regurgitant jet velocity (TRV), tissue velocity in systole(S′) and diastole (E′), inflammatory, rheologic and hemolytic biomarkers as predictors of mortality in patients with SCD. With up to 9 years of follow up, we determined survival in 95 children, adolescents and adults with SCD. Thirty‐eight patients (40%) were less than 21 years old at initial evaluation. Survival and Cox proportional‐hazards analysis were performed. There was 19% mortality in our cohort, with median age at death of 35 years. In the pediatric subset, there was 11% mortality during the follow up period. The causes of death included cardiovascular and pulmonary complications in addition to other end‐organ failure. On Cox proportional‐hazards analysis, our model predicts that a 0.1 m/s increase in TRV increases risk of mortality 3%, 1 cm/s increase in S′ results in a 91% increase, and 1 cm/s decrease in E′ results in a 43% increase in mortality. While excluding cardiac parameters, higher plasma free hemoglobin was significantly associated with risk of mortality (p=.049). In conclusion, elevated TRV and altered markers of cardiac systolic and diastolic function predict mortality in a cohort of adolescents and young adult patients with SCD. These predictors should be considered when counseling cardiovascular risk and therapeutic optimization at transition to adult providers.

Background: Sickle cell disease (SCD) is a genetically-inherited hemoglobinopathy where deoxygenated hemoglobin S polymerizes, leading to stiff red blood cells (RBC) and inefficient microcirculatory blood flow. Transfusion therapy acts as primary and secondary prevention of ischemic stroke in SCD. Whether blood transfusion alters the mechanical sensitivity of RBC to prolonged sub-hemolytic shear stress (shear) is unknown. We hypothesized that individuals with SCD undergoing chronic blood transfusion would have improved sensitivity to shear, compared with patients not on transfusion therapy. Methods and Materials: Blood suspensions from individuals with SCD not receiving (n = 15) and receiving (n = 15) chronic simple-transfusion were conditioned to shear (1, 4, 16, 32, 64 Pa) for various durations (1, 4, 16, 32, 64 s), and then deformability of RBC was immediately measured. Healthy young Controls (n = 15) were included for reference. A surface-mesh was interpolated using the data to determine the effect of blood transfusion on mechanical sensitivity of RBC. Results: There was impaired RBC deformability to prolonged supraphysiologic shear in both SCD groups; however, mechanical sensitivity actually improved in transfused patients when exposed to prolonged physiologic shear. Further, in the transfused SCD patients, the threshold above which subhemolytic damage occurs was similar to Control. Conclusion: We found that chronic transfusion therapy normalizes the mechanical sensitivity threshold above which RBC subhemolytic damage occurs following prolonged shear exposure in SCD. An important and novel finding in transfused SCD patients was the improvement in RBC deformability in response to prolonged shear exposure over the physiologic range.

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