Background and Aims Inflammation following intraventricular hemorrhage (IVH) has been shown to cause periventricular brain damage. Released free hemoglobin may be an early up-stream initiator of inflammation in the intraventricular space and cause damage to the choroid plexus. We aimed to evaluate release of free hemoglobin, the relationship to inflammation in the intraventricular space and effects on choroid plexus epithelium following IVH.
Methods IVH was induced in preterm rabbit pups. Intraventricular samples of cerebrospinal fluid (CSF) were obtained under guidance of high-frequency ultrasound at 24, 48 and 72h following IVH for measurement of free oxyhemoglobin (OxyHb), methemoglobin (MetHb) and TNFa. Analysis of gene expression (RT-PCR) for TNFa, IL-1b and heme-oxygenase-1 (HO-1) and immunostaining with electronmicroscopy (EM) was performed in choroid plexus obtained at 72h.
Results Intraventricular CSF concentrations of free OxyHb remained stable whereas those of MetHb and TNFa increased from 24 to 72 h. There was a highly positive correlation between concentrations of MetHb and TNFa in CSF at 72h (r= 0.98, p<0.0001). Levels of mRNA for HO-1, IL-1 b and TNF-a were up-regulated in choroid plexus following IVH as compared to controls (all p<0.01). EM showed choroid plexus epithelium with fragmented microvilli, apoptotic bodies, swollen mitochondria and increased epithelial expression of TNFa following IVH (fig. 1).
Conclusions Amount of released free Hb, subsequently auto-oxidised to MetHb determines degree of pro-inflammation in intraventricular CSF following IVH. This is associated with severe apoptosis in choroid plexus epithelium.