Brain iron overload following intracranial haemorrhage

Intracranial haemorrhages,including intracerebral haemorrhage(ICH),intraventricular haemorrhage(IVH)and subarachnoid haemorrhage(SAH),are leading causes of morbidity and mortality worldwide.In addition,haemorrhage contributes to tissue damage in traumatic brain injury(TBI).To date,efforts to treat the long-term consequences of cerebral haemorrhage have been unsatisfactory.Incident rates and mortality have not showed significant improvement in recent years.In terms of secondary damage following haemorrhage,it is becoming increasingly apparent that blood components are of integral importance,with haemoglobin-derived iron playing a major role.However,the damage caused by iron is complex and varied,and therefore,increased investigation into the mechanisms by which iron causes brain injury is required.As ICH,IVH,SAH and TBI are related,this review will discuss the role of iron in each,so that similarities in injury pathologies can be more easily identified.It summarises important components of normal brain iron homeostasis and analyses the existing evidence on iron-related brain injury mechanisms.It further discusses treatment options of particular promise.

Role of lipocalin 2 in intraventricular haemoglobin-induced brain injury

Objective:Our recent studies have shown that blood components,including haemoglobin and iron,contribute to hydrocephalus development and brain injury after intraventricular haemorrhage(IVH).The current study investigated the role of lipocalin 2(LCN2),a protein involved in iron handling,in the ventricular dilation and neuroinflammation caused by brain injury in a mouse model of IVH.Design:Female wild-type(WT)C57BL/6 mice and LCN2-deficient(LCN2^(−/−))mice had an intraventricular injection of haemoglobin,and control mice received an equivalent amount of saline.MRI was performed presurgery and postsurgery to measure ventricular volume and the brains were used for either immunohistochemistry or western blot.Results:Ventricular dilation was observed in WT mice at 24 h after haemoglobin(25 mg/mL,20µL)injection(12.5±2.4 vs 8.6±1.5 mm^(3) in the control,p<0.01).Western blotting showed that LCN2 was significantly upregulated in the periventricular area(p<0.01).LCN2 was mainly expressed in astrocytes,whereas the LCN2 receptor was detected in astrocytes,microglia/macrophages and neurons.Haemoglobin-induced ventricle dilation and glia activation were less in LCN2^(−/−)mice(p<0.01).Injection of high-dose haemoglobin(50 mg/mL)resulted in lower mortality in LCN2^(−/−)mice(27%vs 86%in WT;p<0.05).Conclusions:Intraventricular haemoglobin caused LCN2 upregulation and ventricular dilation.Haemoglobin resulted in lower mortality and less ventricular dilation in LCN2^(−/−)mice.These results suggest that LCN2 has a role in haemoglobin-induced brain injury and may be a therapeutic target for IVH.