Nonautonomous dynamics of acute cell injury.

Medical conditions due to acute cell injury, such as stroke and heart attack, are of tremendous impact and have attracted huge amounts of research effort. The biomedical research that seeks cures for these conditions has been dominated by a qualitative, inductive mind-set. Although the inductive approach has not been effective in developing medical treatments, it has amassed enough information to allow construction of quantitative, deductive models of acute cell injury.

Abstraction and Idealization in Biomedicine: The Nonautonomous Theory of Acute Cell Injury.

Neuroprotection seeks to halt cell death after brain ischemia and has been shown to be possible in laboratory studies. However, neuroprotection has not been successfully translated into clinical practice, despite voluminous research and controlled clinical trials. We suggested these failures may be due, at least in part, to the lack of a general theory of cell injury to guide research into specific injuries.

Disease of mRNA Regulation: Relevance for Ischemic Brain Injury.

In this mini-review we give an overview of the role of mRNA-binding proteins and their associated messenger ribonucleoprotein complexes (mRNPs) in several disease states, and bring this information to bear on the pathophysiology of brain ischemia. One conclusion reached is that mRNPs may play a causal role in proteotoxicity instead of being merely passive targets. Ischemia therapies targeting mRNPs have advantages over targeting single pathways, but the behavior of mRNPs needs to be considered in the design of therapies.

Regulation of mRNA following brain ischemia and reperfusion.

There is growing appreciation that mRNA regulation plays important roles in disease and injury. mRNA regulation and ribonomics occur in brain ischemia and reperfusion (I/R) following stroke and cardiac arrest and resuscitation. It was recognized over 40 years ago that translation arrest (TA) accompanies brain I/R and is now recognized as part of the intrinsic stress responses triggered in neurons.

Embryonic lethal abnormal vision proteins and adenine and uridine-rich element mRNAs after global cerebral ischemia and reperfusion in the rat.

Prolonged translation arrest correlates with delayed neuronal death of hippocampal CA1 neurons following global cerebral ischemia and reperfusion. Many previous studies investigated ribosome molecular biology, but mRNA regulatory mechanisms after brain ischemia have been less studied. Here we investigated the embryonic lethal abnormal vision/Hu isoforms HuR, HuB, HuC, and HuD, as well as expression of mRNAs containing adenine and rich uridine elements following global ischemia in rat brain.

Inductive and Deductive Approaches to Acute Cell Injury.

Many clinically relevant forms of acute injury, such as stroke, traumatic brain injury, and myocardial infarction, have resisted treatments to prevent cell death following injury. The clinical failures can be linked to the currently used inductive models based on biological specifics of the injury system. Here we contrast the application of inductive and deductive models of acute cell injury.

mRNA redistribution during permanent focal cerebral ischemia.

Translation arrest occurs in neurons following focal cerebral ischemia and is irreversible in penumbral neurons destined to die. Following global cerebral ischemia, mRNA is sequestered away from 40S ribosomal subunits as mRNA granules, precluding translation. Here, we investigated mRNA granule formation using fluorescence in situ histochemistry out to 8 h permanent focal cerebral ischemia using middle cerebral artery occlusion in Long Evans rats with and without diabetes.

HuR function and translational state analysis following global brain ischemia and reperfusion.

Prolonged translation arrest in post-ischemic hippocampal CA1 pyramidal neurons precludes translation of induced stress genes and directly correlates with cell death. We evaluated the regulation of mRNAs containing adenine- and uridine-rich elements (ARE) by assessing HuR protein and hsp70 mRNA nuclear translocation, HuR polysome binding, and translation state analysis of CA1 and CA3 at 8 h of reperfusion after 10 min of global cerebral ischemia. There was no difference between CA1 and CA3 at 8 h of reperfusion in nuclear or cytoplasmic HuR protein or hsp70 mRNA, or HuR polysome association, suggesting that neither mechanism contributed to post-ischemic outcome.

A program for solving the brain ischemia problem.

Our recently described nonlinear dynamical model of cell injury is here applied to the problems of brain ischemia and neuroprotection. We discuss measurement of global brain ischemia injury dynamics by time course analysis. Solutions to proposed experiments are simulated using hypothetical values for the model parameters.

A nonlinear dynamical theory of cell injury.

Multifactorial injuries, such as ischemia, trauma, etc., have proven stubbornly elusive to clinical therapeutics, in spite of the binary outcome of recovery or death. This may be due, in part, to the lack of formal approaches to cell injury.

Towards a dynamical network view of brain ischemia and reperfusion. Part I: background and preliminaries.

The general failure of neuroprotectants in clinical trials of ischemic stroke points to the possibility of a fundamental blind spot in the current conception of ischemic brain injury, the "ischemic cascade". This is the first in a series of four papers whose purpose is to work towards a revision of the concept of brain ischemia by applying network concepts to develop a bistable model of brain ischemia. This first paper sets the stage for developing the bistable model of brain ischemia.

Towards a dynamical network view of brain ischemia and reperfusion. Part IV: additional considerations.

The general failure of neuroprotectants in clinical trials of ischemic stroke points to the possibility of a fundamental blind spot in the current conception of ischemic brain injury, the "ischemic cascade". This is the fourth in a series of four papers whose purpose is to work towards a revision of the concept of brain ischemia by applying network concepts to develop a bistable model of brain ischemia. Here we consider additional issues to round out and close out this initial presentation of the bistable network view of brain ischemia.

Polyadenylated mRNA staining reveals distinct neuronal phenotypes following endothelin 1, focal brain ischemia, and global brain ischemia/ reperfusion.

Objectives: Most work on ischemia-induced neuronal death has revolved around the relative contributions of necrosis and apoptosis, but this work has not accounted for the role of ischemia-induced stress responses. An expanded view recognizes a competition between ischemia-induced damage mechanisms and stress responses in the genesis of ischemia-induced neuronal death. An important marker of post-ischemic stress responses is inhibition of neuronal protein synthesis, a morphological correlate of which is the compartmentalization of mRNA away from ribosomes in the form of cytoplasmic mRNA granules.

Texture analysis of poly-adenylated mRNA staining following global brain ischemia and reperfusion.

Texture analysis provides a means to quantify complex changes in microscope images. We previously showed that cytoplasmic poly-adenylated mRNAs form mRNA granules in post-ischemic neurons and that these granules correlated with protein synthesis inhibition and hence cell death. Here we utilized the texture analysis software MaZda to quantify mRNA granules in photomicrographs of the pyramidal cell layer of rat hippocampal region CA3 around 1h of reperfusion after 10min of normothermic global cerebral ischemia.

Towards a dynamical network view of brain ischemia and reperfusion. Part III: therapeutic implications.

The general failure of neuroprotectants in clinical trials of ischemic stroke points to the possibility of a fundamental blind spot in the current conception of ischemic brain injury, the "ischemic cascade". This is the third in a series of four papers whose purpose is to work towards a revision of the concept of brain ischemia by applying network concepts to develop a bistable model of brain ischemia. Here the bistable model of brain ischemia is compared to the ischemic cascade concept.

Towards a dynamical network view of brain ischemia and reperfusion. Part II: a post-ischemic neuronal state space.

The general failure of neuroprotectants in clinical trials of ischemic stroke points to the possibility of a fundamental blind spot in the current conception of ischemic brain injury, the "ischemic cascade". This is the second in a series of four papers whose purpose is to work towards a revision of the concept of brain ischemia by applying network concepts to develop a bistable model of brain ischemia. We here build the bistable network model of brain ischemia.

Translation arrest and ribonomics in post-ischemic brain: layers and layers of players.

A persistent translation arrest (TA) correlates precisely with the selective vulnerability of post-ischemic neurons. Mechanisms of post-ischemic TA that have been assessed include ribosome biochemistry, the link between TA and stress responses, and the inactivation of translational components via sequestration in subcellular structures. Each of these approaches provides a perspective on post-ischemic TA.

Hippocampal cellular stress responses after global brain ischemia and reperfusion.

Brain ischemia and reperfusion (I/R) induce neuronal intracellular stress responses, including the heat-shock response (HSR) and the unfolded protein response (UPR), but the roles of each in neuronal survival or death are not well understood. We assessed the relative expression of UPR (ATF4, CHOP, GRP78, XBP-1) and HSR-related (HSP70 and HSC70) mRNAs and proteins after brain I/R. We evaluated these in hippocampal CA1 and CA3 after normothermic, transient global forebrain ischemia and up to 42 h of reperfusion.

Brain endothelial HSP-70 stress response coincides with endothelial and pericyte death after brain trauma.

Objectives: Our objective was to characterize the heat shock response (HSR) in a model of traumatic brain injury (TBI) and to determine the association of HSR to cell death.

Methods: We used immunofluorescent detection of HSP-70 to characterize HSR and TUNEL labeling to determine the pattern of cell death.

Results: HSP-70 immunofluorescence revealed a steady increase from 4 to 48 hours following TBI, culminating in a ubiquitous expression with the capillary bed 48 hours post-TBI.

Irreversible translation arrest in the reperfused brain.

Irreversible translation arrest occurs in reperfused neurons that will die by delayed neuronal death. It is now recognized that suppression of protein synthesis is a general response of eukaryotic cells to exogenous stressors. Indeed, stress-induced translation arrest can be viewed as a component of cell stress responses, and consists of initiation, maintenance, and termination phases that work in concert with stress-induced transcriptional mechanisms.

PERK is activated differentially in peripheral organs following cardiac arrest and resuscitation.

Visceral organs display differential sensitivity to ischemia and reperfusion injury, but the cellular mechanisms underlying these differential responses are not completely understood. A significant response to ischemia identified in brain is stress to the endoplasmic reticulum (ER), as indicated by PKR-like endoplasmic reticulum eIF2alpha kinase (PERK)-mediated phosphorylation of eIF2alpha. To determine the generality of this response, we evaluated the PERK pathway in brain, GI tract, heart, liver, lung, kidney, pancreas and skeletal muscle following a clinically relevant, 10 min cardiac arrest-induced whole body ischemia and either 10 or 90 min reperfusion.

Renal ischemia and reperfusion activates the eIF 2 alpha kinase PERK.

Inhibition of protein synthesis occurs in the post-ischemic reperfused kidney but the molecular mechanism of renal translation arrest is unknown. Several pathways have been identified whereby cell stress inhibits translation initiation via phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF 2 alpha, phospho-form eIF 2 alpha(P)]. Here, we report a 20-fold increase in eIF 2 alpha(P) in kidney homogenates following 10 min of cardiac arrest-induced ischemia and 10 min reperfusion.

Cerebral ischemia and the unfolded protein response.

We review studies of endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) following cerebral ischemia and reperfusion (I/R). The UPR is a cell stress program activated when misfolded proteins accumulate in the ER lumen. UPR activation causes: (i) a PERK-mediated phosphorylation of eIF2alpha, inhibiting protein synthesis to prevent further accumulation of unfolded proteins in the ER and (ii) upregulation of genes coding for ER-resident enzymes and chaperones and others, via eIF2alpha(p), and ATF6 and IRE1 activation.

Acute and persistent protein synthesis inhibition following cerebral reperfusion.

Lack of recovery from protein synthesis inhibition (PSI) closely correlates with neuronal death following brain ischemia and reperfusion. It has therefore been suggested that understanding the mechanisms of PSI will shed light on the mechanisms of selective neuronal death following ischemia and reperfusion. It is now known that the PKR-like ER kinase (PERK)-mediated phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) causes translation inhibition at initial reperfusion.