N-terminally cleaved Bcl-x(L) mediates ischemia-induced neuronal death

Transient global ischemia in rats induces delayed death of hippocampal CA1 neurons. Early events include caspase activation, cleavage of anti-death Bcl-2 family proteins and large mitochondrial channel activity. However, whether these events have a causal role in ischemia-induced neuronal death is unclear. We found that the Bcl-2 and Bcl-xL inhibitor ABT-737, which enhances death of tumor cells, protected rats against neuronal death in a clinically relevant model of brain ischemia. Bcl-xL is prominently expressed in adult neurons and can be cleaved by caspases to generate a pro-death fragment, ΔN-Bcl-xL. We found that ABT-737 administered before or after ischemia inhibited ΔN-Bcl-xL–induced mitochondrial channel activity and neuronal death. To establish a causal role for ΔN-Bcl-xL, we generated knock-in mice expressing a caspase-resistant form of Bcl-xL. The knock-in mice exhibited markedly reduced mitochondrial channel activity and reduced vulnerability to ischemia-induced neuronal death. These findings suggest that truncated Bcl-xL could be a potentially important therapeutic target in ischemic brain injury

Towards a Physiology-Based Measure of Pain: Patterns of Human Brain Activity Distinguish Painful from Non-Painful Thermal Stimulation

Pain often exists in the absence of observable injury; therefore, the gold standard for pain assessment has long been self-report. Because the inability to verbally communicate can prevent effective pain management, research efforts have focused on the development of a tool that accurately assesses pain without depending on self-report. Those previous efforts have not proven successful at substituting self-report with a clinically valid, physiology-based measure of pain. Recent neuroimaging data suggest that functional magnetic resonance imaging (fMRI) and support vector machine (SVM) learning can be jointly used to accurately assess cognitive states. Therefore, we hypothesized that an SVM trained on fMRI data can assess pain in the absence of self-report. In fMRI experiments, 24 individuals were presented painful and nonpainful thermal stimuli. Using eight individuals, we trained a linear SVM to distinguish these stimuli using whole-brain patterns of activity. We assessed the performance of this trained SVM model by testing it on 16 individuals whose data were not used for training. The whole-brain SVM was 81% accurate at distinguishing painful from non-painful stimuli (p<0.0000001). Using distance from the SVM hyperplane as a confidence measure, accuracy was further increased to 84%, albeit at the expense of excluding 15% of the stimuli that were the most difficult to classify. Overall performance of the SVM was primarily affected by activity in pain-processing regions of the brain including the primary somatosensory cortex, secondary somatosensory cortex, insular cortex, primary motor cortex, and cingulate cortex. Region of interest (ROI) analyses revealed that whole-brain patterns of activity led to more accurate classification than localized activity from individual brain regions. Our findings demonstrate that fMRI with SVM learning can assess pain without requiring any communication from the person being tested. We outline tasks that should be completed to advance this approach toward use in clinical settings

N-terminally cleaved Bcl-xL mediates ischemia-induced neuronal death

Transient global ischemia in rats induces delayed death of hippocampal CA1 neurons. Early events include caspase activation, cleavage of anti-death Bcl-2 family proteins and large mitochondrial channel activity. However, a causal role of these events in ischemia-induced neuronal death is unclear. Unexpectedly, we found that the Bcl-2/Bcl-x(L) inhibitor ABT-737, which enhances death of tumor cells, protects rats against neuronal death in a clinically relevant model of brain ischemia. Bcl-x(L) is prominently expressed in adult neurons and can be cleaved by caspases to generate a pro-death fragment ΔN-Bcl-x(L). We found that ABT-737 administered before or after ischemia inhibited ΔN-Bcl-x(L)-induced mitochondrial channel activity and neuronal death. To establish a causal role for ΔN-Bcl-x(L), we generated knockin mice expressing caspase-resistant Bcl-x(L). The knockin mice exhibit strikingly reduced mitochondrial channel activity and reduced vulnerability to ischemia-induced neuronal death. These findings point to truncated Bcl-x(L) as a potentially important therapeutic target in ischemic brain injury