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- Agyemang, Alex Adusei, et al.
(författare)
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Cell-free oxidized hemoglobin drives reactive oxygen species production and pro-inflammation in an immature primary rat mixed glial cell culture
- 2021
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Ingår i: Journal of Neuroinflammation. - : Springer Science and Business Media LLC. - 1742-2094. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Germinal matrix intraventricular hemorrhage (GM-IVH) is associated with deposition of redox active cell-free hemoglobin (Hb), derived from hemorrhagic cerebrospinal fluid (CSF), in the cerebrum and cerebellum. In a recent study, using a preterm rabbit pup model of IVH, intraventricularly administered haptoglobin (Hp), a cell-free Hb scavenger, partially reversed the damaging effects observed following IVH. Together, this suggests that cell-free Hb is central in the pathophysiology of the injury to the immature brain following GM-IVH. An increased understanding of the causal pathways and metabolites involved in eliciting the damaging response following hemorrhage is essential for the continued development and implementation of neuroprotective treatments of GM-IVH in preterm infant.METHODS: We exposed immature primary rat mixed glial cells to hemorrhagic CSF obtained from preterm human infants with IVH (containing a mixture of Hb-metabolites) or to a range of pure Hb-metabolites, incl. oxidized Hb (mainly metHb with iron in Fe3+), oxyHb (mainly Fe2+), or low equivalents of heme, with or without co-administration with human Hp (a mixture of isotype 2-2/2-1). Following exposure, cellular response, reactive oxygen species (ROS) generation, secretion and expression of pro-inflammatory cytokines and oxidative markers were evaluated.RESULTS: Exposure of the glial cells to hemorrhagic CSF as well as oxidized Hb, but not oxyHb, resulted in a significantly increased rate of ROS production that positively correlated with the rate of production of pro-inflammatory and oxidative markers. Congruently, exposure to oxidized Hb caused a disintegration of the polygonal cytoskeletal structure of the glial cells in addition to upregulation of F-actin proteins in microglial cells. Co-administration of Hp partially reversed the damaging response of hemorrhagic CSF and oxidized Hb.CONCLUSION: Exposure of mixed glial cells to oxidized Hb initiates a pro-inflammatory and oxidative response with cytoskeletal disintegration. Early administration of Hp, aiming to minimize the spontaneous autoxidation of cell-free oxyHb and liberation of heme, may provide a therapeutic benefit in preterm infant with GM-IVH.
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| 2. |
- Jungner, Åsa, et al.
(författare)
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Cardiopulmonary bypass in the newborn: effects of circulatory cell-free hemoglobin and hyperoxia evaluated in a novel rat pup model
- 2017
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Ingår i: Intensive Care Medicine Experimental. - : Springer Science and Business Media LLC. - 2197-425X. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Infants with congenital heart defects (CHD) are at risk for white matter brain injury. This novel rat pup model characterizes the systemic effects of intravasal cell-free hemoglobin and hyperoxia, hypothesizing that immature endogenous scavenging systems relate to increased vulnerability to conditions present during cardiopulmonary bypass (CPB).Methods: Plasma pharmacokinetics of cell-free human hemoglobin (Hb) was determined after intraperitoneal (i.p.) administration in postnatal day 6 (P6) rat pups. Cell-free hemoglobin degradation, scavenger- and oxidative stress responses in altered oxygen environments were evaluated in P6 rat pups exposed to i.p. cell-free Hb or vehicle and subjected to hyperoxia or normoxia for 24 h. Plasma and liver were analyzed for free heme, haptoglobin, hemopexin, heme-oxygenase 1, and 8-OHdG at 3–120 h post-injection. Baseline scavenging properties were evaluated in P0-P12 rat pups.Results: Cell-free Hb displayed peak plasma concentrations of 3.6 ± 0.5 mg/mL (mean ± SD) at 3 h post-administration. Animals exposed to cell-free Hb demonstrated a 30-fold increase in plasma haptoglobin and a decrease in plasma hemopexin to 1/6 of concentrations observed in pups exposed to vehicle. Exposure to cell-free Hb and hyperoxia mediated increased plasma concentrations of free heme (72.7 ± 19.5 μM, mean ± SD) compared to exposure to cell-free Hb and normoxia (49.3 ± 13.1 μM) at 3 h, and an elevated hepatic mRNA expression of heme-oxygenase 1. mRNA expression of haptoglobin and hemopexin was increased in animals exposed to hemoglobin with a mitigated response in pups exposed to hemoglobin and hyperoxia. Animals exposed to hyperoxia displayed an increase in hepatic transcription of scavenger proteins at 24 h. Combined exposure to cell-free Hb and hyperoxia mediated an increased DNA- oxidation at 6 h, whereas all insults conveyed a decrease in DNA-oxidation at 120 h.Conclusions: In this study, we present a novel rat pup model with scavenging characteristics and brain maturation similar to newborns with CHD. We have confirmed a distinct scavenger response after exposure to systemic cell-free hemoglobin. We have indications of an accelerated metabolism of cell-free Hb and of an altered transcription of scavenger proteins in a hyperoxic environment. We believe that this model will prove valuable in future delineation of inflammatory and oxidative end-organ damage following CPB.
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| 3. |
- Jungner, Åsa, et al.
(författare)
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White Matter Brain Development after Exposure to Circulating Cell-Free Hemoglobin and Hyperoxia in a Rat Pup Model
- 2020
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Ingår i: Developmental Neuroscience. - : S. Karger AG. - 0378-5866 .- 1421-9859. ; 41:3-4, s. 234-246
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Tidskriftsartikel (refereegranskat)abstract
- Neonates born with critical congenital heart defects are at risk of diffuse white matter injuries and neurodevelopmental impairments. This study aimed to determine the impact of circulating cell-free hemoglobin and hyperoxia, both present during cardiopulmonary bypass circulation, on white matter brain development. Postnatal day 6 rat pups were injected intraperitoneally with cell-free Hb or vehicle and exposed to hyperoxia (fiO2 = 0.8) or normoxia (fiO2 = 0.21) for 24 h. We evaluated apoptosis, myelination, and oligodendrocyte maturation with immunohistochemistry, gene and protein analyses, and in vivo diffusion tensor magnetic resonance imaging (MRI). Consistent with previous studies, we found an increase in apoptosis of oligodendrocytes as determined by TUNEL+ staining in Olig2+ cells in white matter, cortex, thalamus, and hippocampus following exposure to hyperoxia with no additional effect of cell-free Hb. A transient increase in the mRNA expression of intercellular adhesion molecule 1 at 6 h was observed following combined exposure to cell-free Hb and hyperoxia. No indications of oligodendrocyte maturational delay or hypomyelination were observed after either insult, delivered separately or combined, as determined by immunohistochemistry, Western blot, and diffusion tensor MRI. In our model, exposure to circulatory cell-free Hb, with or without concomitant hyperoxia, did not significantly alter brain white matter development.
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