Tissue iron staining revealed greater cortical iron accumulation in the kidneys of mice resuscitated with SRBCs, SRBCs combined with albumin and SRBCs combined with hemopexin than in the kidneys of mice transfused with FRBCs (Figure 6A and B).
Splenic iron content was greater in mice after resuscitation with SRBCs than in FRBC-transfused mice.
Taken together, these results indicate that haptoglobin co-transfusion prevented stored blood transfusion-associated renal iron uptake and led to increased weight and greater iron- accumulation in the spleens of mice.
Only transfusion of SRBCs and haptoglobin prevented SRBC-induced renal iron accumulation (Figure 6A and B).
In comparison to mice transfused with SRBCs alone, the spleens of mice resuscitated with SRBCs and haptoglobin contained more iron (Figure 6D).
Plasma hemoglobin scavenges nitric oxide and causes vasoconstriction, platelet aggregation and inflammation9,22–24.
Toxicity of free hemoglobin is also caused by the release of cell-free heme, which produces lipid peroxidation and mitochondrial damage and increases the production of reactive oxygen species.
Cell-free heme selectively triggers pro-inflammatory receptors such as TLR-4 and BACH-1, and activates proteasomes25.
The increase in hemopexin was associated with decreased plasma heme levels (Figure 3I).
These results demonstrate that transfusion with SRBCs and simultaneous infusion of exogenous hemopexin results in decreased levels of circulating cell-free heme.
The plasma hemoglobin levels at two and four hours after SRBC-transfusion were greater than the cell-free hemoglobin levels in the supernatant of the SRBCs before transfusion (Figure 1C, Supplemental Table I), providing evidence that hemolysis occurs in vivo during and after transfusion of SRBCs.
Hemoglobinuria was noted in mice resuscitated with SRBCs alone but not mice resuscitated with FRBCs or sham-treated mice (Figure 4A and B).
In mice resuscitated with SRBCs, plasma hemoglobin levels were greater than in mice resuscitated with FRBCs or in sham-treated mice at two, four, and 24 hours after transfusion (Figure 1C).
After resuscitation with SRBCs, only 58% of mice survived for 48 hours (SRBC vs. FRBC, P<0.05).
In animals resuscitated with SRBCs, plasma hemopexin levels significantly decreased from 147.1±11.4 mg/dl at baseline to 86.7±12.2 and 76.3±5. 4 mg/dl at two and four hours after resuscitation, respectively (p<0.05 for both, Figure 2A).
The increase in plasma haptoglobin levels from baseline to 48 hours after resuscitation was less in mice transfused with SRBCs compared to mice transfused with FRBCs (P<0.001).
Markers of renal damage, including kidney KIM-1 and NGAL mRNA levels, urinary KIM-1 protein levels, and plasma NGAL concentration, were greater in mice after resuscitation with SRBCs or SRBCs and albumin than in mice transfused with FRBCs (Figures 4C–F).
Kidney sections of mice resuscitated with SRBCs showed more cortical Ki-67 positive cells per 20× field (1.08 mm field diameter) than those of mice resuscitated with FRBCs (SRBC vs. FRBC: 156.2±10.4 vs. 56.4±4.7, p<0.01).
Liver damage, measured by plasma levels of alanine transaminase (ALT) and aspartate transaminase (AST) at 48 hours after resuscitation, was greater after resuscitation with SRBCs compared to resuscitation with FRBCs (Figure 6E and F).
In contrast, all of the mice survived after SRBC-transfusion and treatment with hemopexin (SRBC+Hx vs. SRBC+Alb, P=0.018). Similarly the survival rate of mice resuscitated with SRBCs and co-infusion of haptoglobin was 96% (SRBC+Hp vs. SRBC+Alb, P=0.030).
Tubular regeneration, an indirect marker of tubular injury, was assessed by quantification of the number of Ki-67-positive renal tubular cells at 48 hours after resuscitation and by measuring the level of Ki-67 mRNA in kidney tissue (Figures 5C–E).
Co-administration of haptoglobin with SRBCs results in a prolonged increase in plasma hemoglobin levels for more than 48 hours after transfusion.
Infusion of hemopexin together with SRBCs resulted in a 6.4-fold (95% CI [5.2 – 7.6]) increase in plasma hemopexin levels at four hours after transfusion (Figure 3D).
Resuscitation with SRBCs together with albumin did not alter plasma levels of hemoglobin, hemopexin, haptoglobin, or heme as compared to resuscitation with SRBCs alone (Figure 3C–E, I, Supplemental Material and Supplemental Figure II A–B).
The renal expression level of IL-6 was greater 48 hours after resuscitation with SRBCs alone, SRBC and albumin, and SRBCs and hemopexin when compared to resuscitation with FRBCs (Supplemental Figure VI D).
Mice that were resuscitated with SRBCs and albumin or SRBCs and hemopexin showed a marked increase in HO-1 expression when compared to mice resuscitated with FRBCs.
Hemoglobinuria was present in mice resuscitated with SRBCs combined with albumin or hemopexin but not in mice resuscitated with SRBCs combined with haptoglobin (Figure 4A and B).
Co-infusion of haptoglobin but not albumin or hemopexin prevented SRBC-induced hemoglobinuria and kidney injury at 48 hours after resuscitation from hemorrhagic shock.
However, kidney KIM-1 and NGAL mRNA levels, urinary KIM-1 protein levels and NGAL plasma concentrations in mice transfused with SRBCs and haptoglobin were lower than in mice transfused with SRBCs given a co-infusion of albumin (Figures 4C–F).
The number of Ki-67 positive cells in kidneys from mice that received SRBCs and haptoglobin was similar to the number of Ki-67 positive cells in kidneys from mice that received FRBCs..
Resuscitation with SRBCs and haptoglobin prevented the increase in SRBC-induced renal HO-1 expression (Figure 7F).
Without adjusting for multiple comparison testing, IL-6 expression was lower in kidneys of mice resuscitated with SRBCs and haptoglobin compared to mice resuscitated with SRBCs and albumin (P<0.05).
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If you find BEL Commons useful in your work, please consider citing: Hoyt, C. T., Domingo-Fernández, D., & Hofmann-Apitius, M. (2018). BEL Commons: an environment for exploration and analysis of networks encoded in Biological Expression Language. Database, 2018(3), 1–11.