Neuronal and Astrocyte Insulin-like Growth Factor-1 Signaling Differentially Modulates Ischemic Stroke Damage

Ischemic stroke is a leading cause of death and disability, as therapeutic options for mitigating the long-term deficits precipitated by the event remain limited. Acute administration of the neuroendocrine modulator insulin-like growth factor-1 (IGF-1) attenuates ischemic stroke damage in preclinical models, and clinical studies suggest IGF-1 can reduce the risk of stroke and improve overall outcomes. The cellular mechanism by which IGF-1 exerts this protection is poorly defined, as all cells within the neurovascular unit express the IGF-1 receptor. We hypothesize that the functional regulation of both neurons and astrocytes by IGF-1 is critical in minimizing damage in ischemic stroke. To test this, we utilized inducible astrocyte-specific or neuron-specific transgenic mouse models to selectively reduce IGF-1R in the adult mouse brain prior to photothrombotic stroke. Acute changes in blood brain barrier permeability, microglial activation, systemic inflammation, and biochemical composition of the brain were assessed 3 hours following photothrombosis, and significant protection was observed in mice deficient in neuronal and astrocytic IGF-1R. When the extent of tissue damage and sensorimotor dysfunction was assessed for 3 days following stroke, only the neurological deficit score continued to show improvements, and the extent of improvement was enhanced with additional IGF-1 supplementation. Overall, results indicate that neuronal and astrocytic IGF-1 signaling influences stroke damage but IGF-1 signaling within these individual cell types is not required for minimizing tissue damage or behavioral outcome.

Exosome therapies improve outcome in rodents with ischemic stroke; meta-analysis

OBJECTIVE

Exosome therapy has been theorized to be safer, more effective, and less cumbersome in replacing stem cell therapies for tissue repair and regeneration. There remains considerable uncertainty on whether exosome therapy is efficacious and safe for recovery from brain injury due to cerebral infarction. There is growing consensus that systematic reviews of data, from preclinical studies which yielded conflicting and confusing results, can provide valuable directions for novel therapeutic options for several clinical conditions. This study systematically evaluated the efficacy of exosome therapy in ischemic stroke in preclinical studies in rodent models.

METHODS

We reviewed existing literature on exosome therapy in rodent stroke models from various databases, and reviewed the interventional measures, and outcome measures systematically, with changes in the infarct volume and functional scores as outcome parameters. Seventeen homogeneous studies were found qualitatively acceptable for meta-analysis. The study used software RevMan 5.3 to conduct the meta-analysis (PROSPERO Register Number: CRD42022314138) RESULTS: Compared to placebo, exosomes treated ischemic stroke models showed significantly reduced brain infarct volume and improved functional recovery on days 7 and 28. Though there are no safety concerns reported in any preclinical studies, there is insufficient data to make robust conclusions on the therapy's safety.

INTERPRETATION

Therapy with subcellular exosomes is a promising treatment to be explored further in animal ischemic stroke models to arrive at robust conclusions for its safety and therapeutic dosage. This must precede Phase I and II- human randomized clinical trials to establish the safety and proof of concept of efficacy of exosome therapy in human ischemic stroke.

4-Trifluoromethyl-(E)-cinnamoyl]-L-4-F-phenylalanine acid exerts its effects on the prevention, post-therapeutic and prolongation of the thrombolytic window in ischemia-reperfusion rats through multiple mechanisms of action

Ischemic stroke is one of the leading causes of death and disability worldwide. The severe sequelae caused by ischemic thrombolysis and the narrow time window are now the main clinical challenges. Our previous study has reported 4-Trifluoromethyl-(E)-cinnamoyl]-L-4-F-phenylalanine Acid (AE-18) was a promising candidate for Parkinson's Disease. In this study, the preventive and therapeutic effects of AE-18 on focal cerebral ischemia-reperfusion injury and the mechanisms are explored. In oxygen glucose deprivation/reoxygenation (OGD/R)-induced well-differentiated PC12 cells model, AE-18 (10 or 20 μM) can significantly reduce nerve damage when administered before or after molding. In middle cerebral artery occlusion-reperfusion (MCAO/R) rat model, pre-modelling, or post-modelling administration of AE-18 (5 or 10 mg/kg) was effective in reducing neurological damage, decreasing infarct volume and improving motor disturbances. In addition, AE-18 (5 mg/kg) given by intravenous injection immediately after occlusion significantly reduce the infarct volume caused by reperfusion for different durations, indicating that AE-18 could extend the time window of thrombolytic therapy. Further studies demonstrate that AE-18 exerts the effects in the prevention, treatment, and prolongation of the time window of cerebral ischemic injury mainly through inhibiting excitotoxicity and improving BBB permeability, VEGF and BDNF. These results suggest that AE-18 is a good candidate for the treatment of ischemic stroke.

Preclinical animal studies in ischemic stroke: Challenges and some solutions

Despite the impressive efficacies demonstrated in preclinical research, hundreds of potentially neuroprotective drugs have failed to provide effective neuroprotection for ischemic stroke in human clinical trials. Lack of a powerful animal model for human ischemic stroke could be a major reason for the failure to develop successful neuroprotective drugs for ischemic stroke. This review recapitulates the available cerebral ischemia animal models, provides an anatomical comparison of the circle of Willis of each species, and describes the functional assessment tests used in these ischemic stroke models. The distinct differences between human ischemic stroke and experimental stroke in available animal models is explored. Innovative animal models more closely resembling human strokes, better techniques in functional outcome assessment and better experimental designs generating clearer and stronger evidence may help realise the development of truly neuroprotective drugs that will benefit human ischemic stroke patients. This may involve use of newer molecules or revisiting earlier studies with new experimental designs. Translation of any resultant successes may then be tested in human clinical trials with greater confidence and optimism.

Apoptosis regulation in the penumbra after ischemic stroke: expression of pro- and antiapoptotic proteins

Ischemic stroke is the leading cause of human disability and mortality in the world. The main problem in stroke therapy is the search of efficient neuroprotector capable to rescue neurons in the potentially salvageable transition zone (penumbra), which is expanding after brain damage. The data on molecular mechanisms of penumbra formation and expression of diverse signaling proteins in the penumbra during first 24 h after ischemic stroke are discussed. Two basic features of cell death regulation in the ischemic penumbra were observed: (1) both apoptotic and anti-apoptotic proteins are simultaneously over-expressed in the penumbra, so that the fate of individual cells is determined by the balance between these opposite tendencies. (2) Similtaneous and concerted up-regulation in the ischemic penumbra of proteins that execute apoptosis (caspases 3, 6, 7; Bcl-10, SMAC/DIABLO, AIF, PSR), signaling proteins that regulate different apoptosis pathways (p38, JNK, DYRK1A, neurotrophin receptor p75); transcription factors that control expression of various apoptosis regulation proteins (E2F1, p53, c-Myc, GADD153); and proteins, which are normally involved in diverse cellular functions, but stimulate apoptosis in specific situations (NMDAR2a, Par4, GAD65/67, caspase 11). Hence, diverse apoptosis initiation and regulation pathways are induced simultaneously in penumbra from very different initial positions. Similarly, various anti-apoptotic proteins (Bcl-x, p21/WAF-1, MDM2, p63, PKBα, ERK1, RAF1, ERK5, MAKAPK2, protein phosphatases 1α and MKP-1, estrogen and EGF receptors, calmodulin, CaMKII, CaMKIV) are upregulated. These data provide an integral view of neurodegeneration and neuroprotection in penumbra. Some discussed proteins may serve as potential targets for anti-stroke therapy.

Edaravone's free radical scavenging mechanisms of neuroprotection against cerebral ischemia: review of the literature

Free radicals and oxidative stress play key roles in cerebral ischemic pathogenesis and represent pharmacological targets for treatment. Edaravone (Edv), one of antioxidant agents that have been used in acute ischemic stroke in both clinical settings and animal experiments, exerts neuroprotective effect on ischemic injured brains. This review is aimed to elaborate the latest molecular mechanisms of the neuroprotection of Edv on cerebral ischemia and provide reasonable evidence in its clinical application. It is found that Edv has neuroprotective influence on cerebral ischemia, which is closely related to the facets of scavenging reactive oxygen species (ROS), hydroxyl radical (ċOH) and reactive nitrogen species (RNS). And it is a good antioxidant agent that can be safely used in the treatment of cerebral ischemia and chronic neurodegenerative disorders as well as other ischemia/reperfusion (I/R)-related diseases. The combination of Edv with thrombolytic therapy also can be applied in clinical settings and will be greatly beneficial to patients with stroke.