Influence of different erythrocyte storage times on the macrophage response in haemorrhagic shock mice.

Objective: To investigate the characteristics of the macrophage response to transfusion of erythrocytes kept at different storage times in the mouse model of haemorrhagic shock.

Methods: Erythrocytes were isolated from mice and stored for 7, 21 or 35 days and samples injected intravenously into haemorrhagic shock mice. Changes in macrophages, inflammatory cytokines and T cell differentiation were assessed using flow cytometry or enzyme-linked immunosorbent assay (ELISA). In a second experiment, haemorrhagic shock mice were injected with 21D-erythrocytes and the expression of nuclear factor erythroid 2 p45-related factor 2 (Nrf2), arginine -1 (Arg-1) and inducible nitrous oxide (iNOS) determined.

Results: The proportion of M1-polarized macrophages was greatest in the 21D group while M2 macrophages tended to increase with the erythrocyte storage time. Levels of inflammatory cytokines and T helper 1 (Th1) cells increased in proportion to erythrocytes storage time. Most regulatory T cells (Treg) were found at 21D. Arg-1 expression was significantly increased in a group that received an heme oxygenase 1 (HO-1) agonist and significantly decreased in a group that received an HO-1 inhibitor but there were no differences in the expression of iNOS or Nrf2.

Conclusion: 21D storage time may be an important time point for erythrocyte storage and immunity response and Arg-1 may have a role in the macrophage response to erythrocyte infusion.