Brain Ischemia and Nonlinear Dynamics

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DESCRIPTION (provided by applicant): Human brain ischemia and reperfusion (I/R) occurs clinically following stroke and cardiac arrest. Over 100 stroke and cardiac arrest clinical trials f neuroprotection have completely failed. This spectacular failure suggests there may be something fundamentally wrong with the current understanding of brain I/R. The current model of I/R injury, the "ischemic cascade", is a list of intracellular pathways induced in neurons by I/. We suggest that the failure of this viewpoint may rest in the assumption that a linear sequence of molecular changes causes outcome. We offer a novel, alternative, systems biology view of cell injury that posits all injury-induced changes in the cell contribute causally to outcome. Causality is not due to the action of linear pathways but to a nonlinear network of interactions. The theory is expressed by nonlinear ordinary differential equations. We seek to operationalize this theory by assessing means of measuring the differential equation variables. We propose the theory variables can be obtained from proteomic and transcriptomic data treated as quantitative deviations in the total amount of molecular damage and molecular stress responses from the control state. We propose to measure these distances in two classes of neurons, CA1 and CA3, using a well-studied model of global brain I/R in the rat.