I. G. Alamo1, K. B. Kannan1, M. A. Smith1, P. A. Efron1, A. M. Mohr1 1University Of Florida,Surgery,Gainesville, FL, USA
Introduction: The cause of persistent injury-associated anemia is multifactorial and includes blood loss, impaired proliferation of erythroid progenitor cells, altered erythropoietin (EPO) response, dysregulation of iron homeostasis, and chronic inflammation/stress. Hepcidin plays a key role in iron homeostasis and has been shown to be regulated by anemia as well as inflammation and EPO is a main regulator of erythropoiesis induced by hypoxia. The relationship between these two factors in persistent injury-associated anemia has yet to be fully elucidated. Using a combined lung injury (LC)/hemorrhagic shock (HS)/chronic restraint stress (CS) model to produce persistent injury-associated anemia, the aim of this study was to investigate the regulation of hepcidin and EPO.
Methods: Male Sprague-Dawley rats (N=6-9 per group) were randomly assigned into one of the four groups of rodent models: naïve, CS alone, combined LCHS, or LCHS/CS. CS was performed using restraining cylinders every day for two hours following either LC or LCHS. During CS, rodents were exposed to 80-85 decibel alarms for two minutes every 30 minutes and rotated to prevent habituation. At day seven, blood, urine, bone marrow and lung tissue was harvested. Hemoglobin (Hgb), EPO, and hepcidin levels were assessed. Data presented as mean±SD in each group. *p<0.05 vs naive
Results: Compared to naïve rodents, plasma hepcidin levels were significantly decreased in CS, LCHS, and LCHS/CS groups (Figure). Similarly, urine hepcidin levels were significantly lower in CS, LCHS and LCHS/CS as compared to naïve (12±4*, 10±3*, 10±2* vs. 52±26 pg/mg protein). There was no change in bone marrow hepcidin mRNA levels in any group. In the LCHS/CS group, there was a significant 70% decrease in lung hepcidin mRNA level as compared to naive. Only LCHS/CS was associated with persistent anemia despite significant elevation of EPO (Figure). There was a strong inverse correlation between EPO and plasma hepcidin (Pearson R= -0.362, p<0.05).
Conclusion: Chronic stress, LCHS and LCHS/CS all significantly decrease plasma and urine hepcidin. Yet only LCHS/CS is associated with persistent anemia despite elevation of EPO. Although there is an inverse correlation between hepcidin and EPO in this model, anemia alone does not regulate hepcidin. The addition of chronic stress did not counteract hepcidin suppression. Further study of the mechanisms involved in injury-associated persistent anemia is warranted.
