Antagonists of the system L neutral amino acid transporter (LAT) promote endothelial adhesivity of human red blood cells.
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The system L neutral amino acid transporter (LAT; LAT1, LAT2, LAT3, or LAT4) has multiple functions in human biology, including the cellular import of S-nitrosothiols (SNOs), biologically active derivatives of nitric oxide (NO). SNO formation by haemoglobin within red blood cells (RBC) has been studied, but the conduit whereby a SNO leaves the RBC remains unidentified. Here we hypothesised that SNO export by RBCs may also depend on LAT activity, and investigated the role of RBC LAT in modulating SNO-sensitive RBC-endothelial cell (EC) adhesion. We used multiple pharmacologic inhibitors of LAT in vitro and in vivo to test the role of LAT in SNO export from RBCs and in thereby modulating RBC-EC adhesion. Inhibition of human RBC LAT by type-1-specific or nonspecific LAT antagonists increased RBC-endothelial adhesivity in vitro, and LAT inhibitors tended to increase post-transfusion RBC sequestration in the lung and decreased oxygenation in vivo. A LAT1-specific inhibitor attenuated SNO export from RBCs, and we demonstrated LAT1 in RBC membranes and LAT1 mRNA in reticulocytes. The proadhesive effects of inhibiting LAT1 could be overcome by supplemental L-CSNO (S-nitroso-L-cysteine), but not D-CSNO or L-Cys, and suggest a basal anti-adhesive role for stereospecific intercellular SNO transport. This study reveals for the first time a novel role of LAT1 in the export of SNOs from RBCs to prevent their adhesion to ECs. The findings have implications for the mechanisms of intercellular SNO signalling, and for thrombosis, sickle cell disease, and post-storage RBC transfusion, when RBC adhesivity is increased.
Published Version (Please cite this version)
Dosier, Laura Beth Mann, Vikram J Premkumar, Hongmei Zhu, Izzet Akosman, Michael F Wempe and Timothy J McMahon (2017). Antagonists of the system L neutral amino acid transporter (LAT) promote endothelial adhesivity of human red blood cells. Thrombosis and haemostasis, 117(7). pp. 1402–1411. 10.1160/TH16-05-0373 Retrieved from https://hdl.handle.net/10161/19095.
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My research focuses on abnormal breathing in sleep including central sleep apnea, obstructive sleep apnea, snoring, and abnormal sleep in children with complex medical conditions.
In my practice, I focus on pediatric diseases of the lungs and sleep. I think that it is important to collaborate with primary care providers and families to create individualized care plans for each of my patients.
The McMahon Lab at Duke University and Durham VA Medical Center is investigating novel roles of the red blood cell (RBC) in the circulation. The regulated release of the vasodilator SNO (a form of NO, nitric oxide) by RBCs within the respiratory cycle in mammals optimizes nutrient delivery at multiple levels, especially in the lung (gas exchange) and the peripheral microcirculation (O2 transport to tissues). Deficiency of RBC SNO bioactivity (as in human RBCs banked for transfusion), for example, appears to contribute to the serious lung and circulatory problems associated with RBC transfusion in some settings. We have also demonstrated benefit in the use of treatments that exploit RBCs as a vehicle for delivery of SNOs, in both human patients and in model animals.
RBCs also release ATP in response to stimuli including deformation and hypoxia, and the exported ATP also participates in the maintenance of a healthy circulation, according to mechanisms that we are now unraveling.
We use basic and translational approaches to understand the molecular mechanisms by which these RBC-derived signals effect circulatory changes in human health and disease, particularly in the lung. Disease states driving this research include acute and chronic lung diseases such as sepsis (severe infection, such as COVID-19), transfusion-related respiratory problems, sickle cell disease, and pulmonary hypertension of adults and newborns.
Funding: VA and NIH.
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