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Hemoglobin induces inflammation after preterm intraventricular hemorrhage by methemoglobin formation.

Gram M, Sveinsdottir S, Ruscher K, Hansson SR, Cinthio M, Akerström B, Ley D - J Neuroinflammation (2013)

Bottom Line: Also, the mRNA expression of TNFα, IL-1β, and Toll-like receptor-4 and TNFα protein levels were significantly increased in periventricular tissue at 72 hours, which was accompanied by extensive astrocyte activation (that is, glial fibrillary acidic protein (GFAP)staining).Thus, the formation of metHb might be a crucial initial event in the development of brain damage following preterm IVH.Accordingly, removal, scavenging, or neutralization of Hb could present a therapeutic opportunity and plausible approach to decreasing the damage in the immature brain following preterm IVH.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Infection Medicine, Lund University, S-221 84 Lund, Sweden. magnus.gram@med.lu.se

ABSTRACT

Background: Cerebral intraventricular hemorrhage (IVH) is a major cause of severe neurodevelopmental impairment in preterm infants. To date, no therapy is available that prevents infants from developing serious neurological disability following IVH. Thus, to develop treatment strategies for IVH, it is essential to characterize the initial sequence of molecular events that leads to brain damage. In this study, we investigated extracellular hemoglobin (Hb) as a causal initiator of inflammation in preterm IVH.

Methods: Using a preterm rabbit pup model, we investigated the molecular mechanisms and events following IVH. We also characterized the concentrations of cell-free Hb metabolites and pro-inflammatory mediators in the cerebrospinal fluid (CSF) of preterm human infants and rabbit pups. Finally, Hb metabolites were evaluated as causal initiators of inflammation in primary rabbit astrocyte cell cultures.

Results: Following IVH in preterm rabbit pups, the intraventricular CSF concentration of cell-free methemoglobin (metHb) increased from 24 to 72 hours and was strongly correlated with the concentration of TNFα at 72 hours (r2 = 0.896, P <0.001). Also, the mRNA expression of TNFα, IL-1β, and Toll-like receptor-4 and TNFα protein levels were significantly increased in periventricular tissue at 72 hours, which was accompanied by extensive astrocyte activation (that is, glial fibrillary acidic protein (GFAP)staining). Furthermore, exposure of primary rabbit astrocyte cell cultures to metHb caused a dose-dependent increase in TNFα mRNA and protein levels, which was not observed following exposure to oxyhemoglobin (oxyHb) or hemin. Finally, a positive correlation (r2 = 0.237, P <0.03) between metHb and TNFα concentrations was observed in the CSF of preterm human infants following IVH.

Conclusions: Following preterm IVH, increased metHb formation in the intraventricular space induces expression of pro-inflammatory cytokines. Thus, the formation of metHb might be a crucial initial event in the development of brain damage following preterm IVH. Accordingly, removal, scavenging, or neutralization of Hb could present a therapeutic opportunity and plausible approach to decreasing the damage in the immature brain following preterm IVH.

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Hb metabolites and TNFα in CSF from preterm infants following IVH. Levels of metHb and TNFα from CSF obtained in serial samples from four preterm infants with IVH were determined as described in the Methods section. The correlation between TNFα and metHb was determined by linear regression analysis (r2 = 0.237, P = 0.01). CSF, cerebrospinal fluid; Hb, hemoglobin; IVH, intraventricular hemorrhage; metHb, methemoglobin.
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Figure 9: Hb metabolites and TNFα in CSF from preterm infants following IVH. Levels of metHb and TNFα from CSF obtained in serial samples from four preterm infants with IVH were determined as described in the Methods section. The correlation between TNFα and metHb was determined by linear regression analysis (r2 = 0.237, P = 0.01). CSF, cerebrospinal fluid; Hb, hemoglobin; IVH, intraventricular hemorrhage; metHb, methemoglobin.

Mentions: Following IVH, serial CSF samples from four preterm infants were collected (as described above), and the concentrations of cell-free oxyHb, metHb and TNFα were determined. A positive correlation was observed between concentrations of metHb and TNFα (r2 = 0.237, P = 0.01) (Figure 9), but no significant correlation was identified between those of oxyHb and TNFα (r2 = 0.01, P = 0.7) (not shown).


Hemoglobin induces inflammation after preterm intraventricular hemorrhage by methemoglobin formation.

Gram M, Sveinsdottir S, Ruscher K, Hansson SR, Cinthio M, Akerström B, Ley D - J Neuroinflammation (2013)

Hb metabolites and TNFα in CSF from preterm infants following IVH. Levels of metHb and TNFα from CSF obtained in serial samples from four preterm infants with IVH were determined as described in the Methods section. The correlation between TNFα and metHb was determined by linear regression analysis (r2 = 0.237, P = 0.01). CSF, cerebrospinal fluid; Hb, hemoglobin; IVH, intraventricular hemorrhage; metHb, methemoglobin.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750409&req=5

Figure 9: Hb metabolites and TNFα in CSF from preterm infants following IVH. Levels of metHb and TNFα from CSF obtained in serial samples from four preterm infants with IVH were determined as described in the Methods section. The correlation between TNFα and metHb was determined by linear regression analysis (r2 = 0.237, P = 0.01). CSF, cerebrospinal fluid; Hb, hemoglobin; IVH, intraventricular hemorrhage; metHb, methemoglobin.
Mentions: Following IVH, serial CSF samples from four preterm infants were collected (as described above), and the concentrations of cell-free oxyHb, metHb and TNFα were determined. A positive correlation was observed between concentrations of metHb and TNFα (r2 = 0.237, P = 0.01) (Figure 9), but no significant correlation was identified between those of oxyHb and TNFα (r2 = 0.01, P = 0.7) (not shown).

Bottom Line: Also, the mRNA expression of TNFα, IL-1β, and Toll-like receptor-4 and TNFα protein levels were significantly increased in periventricular tissue at 72 hours, which was accompanied by extensive astrocyte activation (that is, glial fibrillary acidic protein (GFAP)staining).Thus, the formation of metHb might be a crucial initial event in the development of brain damage following preterm IVH.Accordingly, removal, scavenging, or neutralization of Hb could present a therapeutic opportunity and plausible approach to decreasing the damage in the immature brain following preterm IVH.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Infection Medicine, Lund University, S-221 84 Lund, Sweden. magnus.gram@med.lu.se

ABSTRACT

Background: Cerebral intraventricular hemorrhage (IVH) is a major cause of severe neurodevelopmental impairment in preterm infants. To date, no therapy is available that prevents infants from developing serious neurological disability following IVH. Thus, to develop treatment strategies for IVH, it is essential to characterize the initial sequence of molecular events that leads to brain damage. In this study, we investigated extracellular hemoglobin (Hb) as a causal initiator of inflammation in preterm IVH.

Methods: Using a preterm rabbit pup model, we investigated the molecular mechanisms and events following IVH. We also characterized the concentrations of cell-free Hb metabolites and pro-inflammatory mediators in the cerebrospinal fluid (CSF) of preterm human infants and rabbit pups. Finally, Hb metabolites were evaluated as causal initiators of inflammation in primary rabbit astrocyte cell cultures.

Results: Following IVH in preterm rabbit pups, the intraventricular CSF concentration of cell-free methemoglobin (metHb) increased from 24 to 72 hours and was strongly correlated with the concentration of TNFα at 72 hours (r2 = 0.896, P <0.001). Also, the mRNA expression of TNFα, IL-1β, and Toll-like receptor-4 and TNFα protein levels were significantly increased in periventricular tissue at 72 hours, which was accompanied by extensive astrocyte activation (that is, glial fibrillary acidic protein (GFAP)staining). Furthermore, exposure of primary rabbit astrocyte cell cultures to metHb caused a dose-dependent increase in TNFα mRNA and protein levels, which was not observed following exposure to oxyhemoglobin (oxyHb) or hemin. Finally, a positive correlation (r2 = 0.237, P <0.03) between metHb and TNFα concentrations was observed in the CSF of preterm human infants following IVH.

Conclusions: Following preterm IVH, increased metHb formation in the intraventricular space induces expression of pro-inflammatory cytokines. Thus, the formation of metHb might be a crucial initial event in the development of brain damage following preterm IVH. Accordingly, removal, scavenging, or neutralization of Hb could present a therapeutic opportunity and plausible approach to decreasing the damage in the immature brain following preterm IVH.

Show MeSH
Related in: MedlinePlus