Standardization of Stroke Perfusion CT for Reperfusion Therapy

Imaging Acute Stroke: From One-Size-Fit-All to Biomarkers

In acute stroke management, time window has been rigidly used as a guide for decades and the reperfusion treatment is only available in the first few limited hours. Recently, imaging-based selection of patients has successfully expanded the treatment window out to 16 and even 24 h in the DEFUSE 3 and DAWN trials, respectively. Recent guidelines recommend the use of imaging techniques to guide therapeutic decision-making and expanded eligibility in acute ischemic stroke. A tissue window is proposed to replace the time window and serve as the surrogate marker for potentially salvageable tissue. This article reviews the evolution of time window, addresses the advantage of a tissue window in precision medicine for ischemic stroke, and discusses both the established and emerging techniques of neuroimaging and their roles in defining a tissue window. We also emphasize the metabolic imaging and molecular imaging of brain pathophysiology, and highlight its potential in patient selection and treatment response prediction in ischemic stroke.

Applications and development of permeability imaging in ischemic stroke

Brain permeability imaging techniques are specific for the assessment of blood-brain barrier integrity. The present review article primarily focuses on the application of permeability imaging in cases of ischemic stroke. The permeability maps may be used to predict future hemorrhagic transformation in patients following acute ischemic stroke, that have been treated with tissue plasminogen activator (tPA) or recanalization therapy. The permeability imaging would help make the clinical decision to administer tPA following acute ischemic stroke or not, which is not only due to the current 3-4.5 h time window. Additionally, permeability imaging may also be used to evaluate the collateral circulation in the perfusion and permeability of the ischemic area of the brain.

Chrysophanol inhibits endoplasmic reticulum stress in cerebral ischemia and reperfusion mice

Endoplasmic reticulum (ER) stress plays a critical role in mediating ischemia/reperfusion (I/R) damage in the brain. Our previous study showed that Chrysophanol (CHR) alleviated cerebral ischemic injury in mice and nuclear factor-κB (NF-κB) involved in its neuroprotective effect, but the precise mechanism remains not fully understood. The present study investigated the effect of CHR treatment on I/R-induced ER stress. Mice were subjected to middle cerebral artery occlusion (MCAO) for 45min and received either vehicle or CHR (0.1mg/kg) for 14 days after reperfusion. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) was used to detect apoptotic cells in penumbral tissue. The expression of ER stress-related factors including glucose-regulated protein 78 (GRP78), phosphorylated eukaryotic initiation factor 2α (p-eIF2α), CCAAT-enhancer-binding protein homologous protein (CHOP), and caspase-12 as well as inhibitory κB-α (IκB-α), the inhibitor of NF-κB, was assessed. Our results demonstrated that CHR treatment reduced MCAO-induced upregulation of GRP78, p-eIF2α, CHOP, and caspase-12 in the ischemic brain. Moreover, the TUNEL-positive neuronal cells, which were colocalized with CHOP and caspase-12, decreased in response to CHR treatment, indicating that CHR protects against I/R injury by inhibiting ER stress-associated neuronal apoptosis. In addition, CHR reversed the decrease in IκB-α level induced by MCAO, which was attributed at least in part to the attenuation of translational inhibition induced by eIF2α phosphorylation, indicating that CHR exerts anti-inflammatory effects following I/R by inhibiting ER stress response. These results suggest that attenuation of ER stress may be involved in the mechanisms of neuroprotective effects of CHR.

Reduction of zinc accumulation in mitochondria contributes to decreased cerebral ischemic injury by normobaric hyperoxia treatment in an experimental stroke model

Cerebral ischemia interrupts oxygen supply to the affected tissues. Our previous studies have reported that normobaric hyperoxia (NBO) can maintain interstitial partial pressure of oxygen (pO2) in the penumbra of ischemic stroke rats at the physiological level, thus affording significant neuroprotection. However, the mechanisms that are responsible for the penumbra rescue by NBO treatment are not fully understood. Recent studies have shown that zinc, an important mediator of intracellular and intercellular neuronal signaling, accumulates in neurons and leads to ischemic neuronal injury. In this study, we investigate whether NBO could regulate zinc accumulation in the penumbra and prevent mitochondrial damage in penumbral tissue using a transient cerebral ischemic rat model. Our results showed that NBO significantly reduced zinc-staining positive cells and zinc-staining intensity in penumbral tissues, but not in the ischemic core. Moreover, ischemia-induced zinc accumulation in mitochondria, isolated from penumbral tissues, was greatly attenuated by NBO or a zinc-specific chelator, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN). NBO or TPEN administration stabilized the mitochondrial membrane potential in the penumbra after cerebral ischemia. Finally, ischemia-induced cytochrome c release from mitochondria in penumbral tissues was significantly reduced by NBO or TPEN treatment. These findings demonstrate a novel mechanism for NBO's neuroprotection, especially to penumbral tissues, providing further evidence for the potential clinical benefit of NBO for acute ischemic stroke.