Beta3-Adrenergic Blockade Restores Erythropoietic Homeostasis in Anemia of Critical Illness

• Published in: Blood 2018-11, Vol.132 (Supplement 1), p.3615-3615
• Main Authors: Muthumalaiappan, Kuzhali, Hasan, Shirin, Kini, Ameet, Saini, Pravesh, Walczak, Julia, Baldea, Anthony J
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2018-99-112194

Introduction During anemia of critical illness such as burn injury, erythropoietin (Epo) resistance is accompanied by impaired bone marrow (BM) erythropoiesis. The non-selective β1, β2 -adrenergic receptor (AR) blocker propranolol was effective in mitigating MafB expression in multi potential progenitors and rescuing their erythrocyte commitment in burn patients. However, peripheral HGB levels did not reflect the effect of propranolol perhaps due to defective maturation of late erythroblasts, not regulated by propranolol. Subsequently, we reported that early commitment and late maturation stages are independently orchestrated via discrete β2- and β3-AR mechanisms respectively in the BM of mice with a parallel increase in blood HGB levels. Nonetheless, it is not clear whether commitment of progenitors or maturation of erythroblasts is essential to restore erythropoietic homeostasis after burn injury. In adult mice, the spleen serves as an extra medullary erythropoietic organ under hypoxia and also functions as a primary organ of erythropoietic homeostasis (Bozzini CE et al. Am J Physiol. 1970; 219(3):724). We examined in mice, erythropoietic responses to burn injury in two organs, the spleen and BM to understand the reciprocal relationship, if any, in erythropoiesis between the two adrenergically innervated organs in response to propranolol, and selective β2- and β3- AR blockers. As variation in the size of RBCs is an indication of ineffective maturation, we also evaluated coefficient of variation of RBC size (RDW) in peripheral blood from mice. To validate our animal studies, we also measured RBC parameters in human burn patients. Methods Animal study: B6D2F1 mice were randomized into 2 groups, 15% TBSA (total burn surface area) scald burn and sham burn. Burn mice were given β-AR blockers or saline either via Alzet pumps eight hours after injury or by daily injections. All treatments were terminated 24 hours before harvest. Animals were euthanized to obtain spleen, femurs and blood on post burn days (PBD) as specified in results. Single cell suspensions from spleen and BM were characterized for early erythroblasts (CD71+Ter119neg), orthochromatic erythroblasts (Ter119+CD71+Syto16+), reticulocytes (Ter119+CD71+Syto16neg), erythrocytes (Ter119+), and non-erythroid cells (Ter119neg CD71neg) by flow cytometry, and expressed as 103/106 total splenocytes or total BM cells. RDW was measured using HemaTrue analyzer. Human study: Retrospective analysis was done on