Non-traumatic intracerebral hemorrhage (ICH) is a major public health problem that lacks specific therapy. We present several lines of evidence suggesting that plasmalemma permeability and necrosis contribute to cell death after collagenase induced ICH in mice. Following ICH, plasmalemma permeability to propidium iodide (PI) is a key feature of cellular injury and death;plasmalemma permeability after ICH is reduced by 50% in mice deficient in TNF alpha and Fas receptor;necrotic-like cell death, assessed by EM, histological, and biochemical criteria occurs after ICH;and PI+ cells are reduced after ICH by RIPK3 knockout (a key molecule governing programmed necrosis). These preliminary findings strongly suggest that necroptosis (initiated by TNF/Fas and mediated by RIPK1 and RIPK3) contribute to cell death, and perhaps neurological dysfunction, after ICH. Necrostatins are small molecule inhibitors of RIPK1 that inhibit necroptosis in cells and protect against cell death and functional deficits in brain trauma and ischemic stroke models. Kollidon VA64 is a FDA approved formulary component in pill manufacture that reseals injured cells after CCI and ICH in vivo. VA64 administration reduces blood brain barrier damage, brain edema, cell death, and motor dysfunction after CCI, and reseals injured cells and reduces BBB damage after collagenase ICH in mice. Using mouse collagenase and autologous blood ICH models, we propose 3 specific aims to test the central hypotheses that (1) plasmalemma damage is a marker and mediator of cell death after ICH, and (2) that programmed necrosis contributes to cell death and functional outcome after ICH.
Aim 1 will use pulse labeling experiments to follow the fate of injured cells in vivo and test the hypothesis that loss of plasmalemma integrity is a biomarker of fatal cellular injury after ICH;
Aim 2 will test the hypothesis that VA64 restores plasmalemma integrity, reduces secondary injury and rescues injured brain cells from death after ICH;
Aim 3 will test the hypothesis that necroptosis induces loss of plasmalemma integrity and cell death after ICH, using RIPK3 knockout mice and necrostatins, and a translational approach using necrostatins plus VA64. Completion of these Aims will establish necrosis as central to ICH, and may establish VA64 and necrostatins as novel therapies for ICH.
The proposed work could impact public health in the short term by developing at least two new treatments for patients with intracerebral hemorrhage. In the long term, elucidation of a new biomarker for fatal cell injury may speed development of other pharmacological agents for humans with intracerebral hemorrhage.