Cerebral ischaemia, or stroke, is a leading cause of death and disability worldwide. Ischaemic stroke, as a result of arterial occlusion, and subarachnoid haemorrhage (SAH), as a consequence of arterial rupture in the subarachnoid space, are major subtypes of stroke. Treatment options for both are limited, and many therapeutic strategies have failed. In ischaemic stroke, lack of evidence of brain penetration of treatments has been cited as a major weakness and contributing factor to failed clinical trials. In SAH, animal models do not always mimic key pathophysiological hallmarks of the disease, hindering development of new therapeutics. Inflammation is strongly associated with brain injury after cerebral ischaemia and inhibition of the pro-inflammatory cytokine interleukin-1 (IL-1) represents apossible therapeutic target. Therefore, the key objectives of this thesis were; (1) to improve preclinical data on a promising stroke treatment, interleukin-1 receptor antagonist (IL-1Ra), by investigating its pharmacokinetic profile and brain penetration in a rat model of ischaemic stroke, (2) to investigate the endovascular perforation model of SAH in rat, as a tool for the investigation of neuroprotectants, and (3) to examine the role of the inflammatory response in the SAH model and the effects of IL-1Ra.The neuroprotective effect, pharmacokinetic profile and brain penetration of IL-1Ra were assessed after a single subcutaneous (s.c.) dose (100mg/kg) in rats, after transient (90 min) middle cerebral artery occlusion (MCAo). A single s.c. dose of IL-1Ra reduced neuronal damage, resulted in sustained, high concentrations of IL-1Ra in plasma and cerebrospinal fluid and also penetrated brain tissue exclusively in areas of blood brain-barrier (BBB) breakdown. An endovascular perforation model of SAH in rat was investigated and produced widespread multifocal infarcts. In this model, administration of IL-1Ra (s.c.) reduced BBB breakdown, which correlated with injury at 48 h. IL-1_ was expressed in the brain early after SAH in areas associated with haem oxygenase-1 (HO-1) expression, indicating the presence of free haem. Stimulation of primary mouse mixed glial cells in vitro with haem induced expression and release of IL-1 alpha but not IL-1 beta. These data, after MCAo in rat, are the first to show that a single s.c. dose of IL-1Ra rapidly reaches salvageable brain tissue and is neuroprotective. This allows confidence that IL-1Ra is able to confer its protective actions both peripherally and centrally. After experimental SAH, we suggest that haem, a breakdown product of haemoglobin, released from lysed red blood cells in the subarachnoid space, acts as a danger associated molecular pattern (DAMP) driving IL-1- dependent inflammation. These data provide new insights into inflammation after SAH-induced brain injury and suggest IL-1Ra as a candidate treatment for the disease. Overall, these findings strengthen preclinical data supporting IL-1Ra as a neuroprotective therapy for ischaemic stroke, and identify SAH as a new indication for treatment with IL-1Ra.
|Date of Award||31 Dec 2011|
- The University of Manchester
|Supervisor||Nancy Rothwell (Supervisor) & Philippa Tyrrell (Supervisor)|
- Subarachnoid haemorrhage