Autophagy activation is associated with neuroprotection against apoptosis via a mitochondrial pathway in a rat model of subarachnoid hemorrhage

Dopamine-D2-agonist targets mitochondrial dysfunction via diminishing Drp1 mediated fission and normalizing PGC1-α/SIRT3 pathways in a rodent model of Subarachnoid Haemorrhage

The adverse impact of disturbmitochondrialbiogenesis onearly brain injury (EBI) following subarachnoid haemorrhage (SAH) has been broadly recognized and is closely associated with oxidative stress and neuronal apoptosis. Previous studies have indicated the therapeutic potential of Ropinirole, a dopamine D2 agonist, in Ischemic Stroke. However, there is a lack of evidence regarding the ability of Ropinirole to enhance mitochondrial biogenesis and quality control after subarachnoid haemorrhage. The objective of this study is to investigate the effects of Ropinirole specific doses (10 & 20 mg/kg b. wt.) on mitochondria dysfunction in endovascular perforation SAH model in male Wistar rat. An endovascular perforation model was established using male Wistar rats that had sustained SAH injury. After the SAH injury, SAH grading on blood clot, Nissl staining, and neurobehavioral assessment were used to determine the severity. ROS and MMP, which are indicators of oxidative stress, were examined using flow cytometry. The findings demonstrated that the use of Ropinirole improved neurobehavioral outcomes, decreased brain edema, and reduced oxidative stress and mitochondrial based apoptosis. Further research showed that, Ropinirole therapy inhibit Drp1-mediated fission by accelerating the activity of fusion protein Mfn2/OPA1 along with regulating the translocation of PGC1-α and SIRT3 through restricting cytochrome C inside mitochondria to maintain mitochondrial metabolism. Ropinirole exerted neuroprotective effects by improving mitochondrial activity in a PGC1-α/SIRT3-dependent way via regulating Drp1 mediated fission. The effective treatment for SAH-induced EBI may involve increasing biogenesis and inhibiting excessive mitochondrial fission with Ropinirole.

Sirtuins as Potential Targets for Neuroprotection: Mechanisms of Early Brain Injury Induced by Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a prevalent cerebrovascular disease with significant global mortality and morbidity rates. Despite advancements in pharmacological and surgical approaches, the quality of life for SAH survivors has not shown substantial improvement. Traditionally, vasospasm has been considered a primary contributor to death and disability following SAH, but anti-vasospastic therapies have not demonstrated significant benefits for SAH patients' prognosis. Emerging studies suggest that early brain injury (EBI) may play a crucial role in influencing SAH prognosis. Sirtuins (SIRTs), a group of NAD + -dependent deacylases comprising seven mammalian family members (SIRT1 to SIRT7), have been found to be involved in neural tissue development, plasticity, and aging. They also exhibit vital functions in various central nervous system (CNS) processes, including cognition, pain perception, mood, behavior, sleep, and circadian rhythms. Extensive research has uncovered the multifaceted roles of SIRTs in CNS disorders, offering insights into potential markers for pathological processes and promising therapeutic targets (such as SIRT1 activators and SIRT2 inhibitors). In this article, we provide an overview of recent research progress on the application of SIRTs in subarachnoid hemorrhage and explore their underlying mechanisms of action.

Transcription factor EB (TFEB) promotes autophagy in early brain injury after subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH) has high mortality. Early brain injury (EBI) is responsible for unfavorable outcomes for patients with SAH. The protective involvement of autophagy in hemorrhagic stroke has been proposed. The transcription factor EB (TFEB) can increase autophagic flux by promoting autophagosome formation and autophagosome-lysosome fusion, and dysregulation of TFEB activity might induce the development of several diseases. However, the biological functions of TFEB in EBI after SAH remain unknown. We established an animal model of SAH by the modified endovascular perforation method. Expression of TFEB and autophagy required genes was measured by western blotting and immunofluorescence staining. SAH grading, brain water content and neurobehavioral functions were evaluated at 24 h post-SAH. Neuronal apoptosis in cerebral cortex was assessed by TUNEL staining and Fluoro Jade B staining. TFEB was downregulated in SAH rats, and its overexpression reduced brain edema and ameliorated neurological deficits of SAH rats. Additionally, the neuronal apoptosis induced by SAH was inhibited by TFEB overexpression. Moreover, TFEB overexpression promoted autophagy after SAH. TFEB overexpression promotes autophagy to inhibit neuronal apoptosis, brain edema and neurological deficits post-SAH.

Secukinumab Ameliorates Oxidative Damage Induced by Subarachnoid Hemorrhage

OBJECTIVE

This study aimed to investigate the histological and biochemical neuroprotective effects of secukinumab (SEC) on brain damage induced by subarachnoid hemorrhage (SAH) in male Wistar Albino rats.

METHODS

Forty male Wistar Albino rats were randomly divided into 4 groups of equal size: control, SEC, SAH, and SAH + SEC. SAH was induced the SAH and SAH + SEC groups by injecting autologous blood collected from the hearts of the rats into the subarachnoid space via the foramen magnum. SEC was administered intraperitoneally once a week to the SEC and SAH + SEC groups after the surgical procedure. On the 14th day of surgery, the rats were sacrificed and their cerebral tissues were collected for biochemical analysis and histopathological examination.

RESULTS

SAH led to changes in oxidative stress parameters by increasing malondialdehyde levels and decreasing superoxide dismutase, glutathione, catalase, and glutathione peroxidase levels. Histopathologically, cerebral tissues in the SAH groups showed alterations such as congestion and cell infiltration. Treatment with SEC significantly reduced malondialdehyde levels and increased superoxide dismutase, glutathione, catalase, and glutathione peroxidase levels. SEC also decreased histopathological alterations in brain tissues.

CONCLUSIONS

This study revealed that SEC (3 mg/kg) therapeutically influenced oxidative and histopathological changes in blood parameters and brain tissues caused by experimental SAH. SEC helps reduce brain damage in rats with SAH and possesses antioxidant and neuroprotective properties. Further advanced studies are needed to prove its potential benefits for humans.

Ferroptosis in early brain injury after subarachnoid hemorrhage: review of literature

Spontaneous subarachnoid hemorrhage (SAH), mainly caused by ruptured intracranial aneurysms, is a serious acute cerebrovascular disease. Early brain injury (EBI) is all brain injury occurring within 72 h after SAH, mainly including increased intracranial pressure, decreased cerebral blood flow, disruption of the blood-brain barrier, brain edema, oxidative stress, and neuroinflammation. It activates cell death pathways, leading to neuronal and glial cell death, and is significantly associated with poor prognosis. Ferroptosis is characterized by iron-dependent accumulation of lipid peroxides and is involved in the process of neuron and glial cell death in early brain injury. This paper reviews the research progress of ferroptosis in early brain injury after subarachnoid hemorrhage and provides new ideas for future research.

Gut Microbiota in Autophagy Regulation: New Therapeutic Perspective in Neurodegeneration

Gut microbiota and the brain are related via a complex bidirectional interconnective network. Thus, intestinal homeostasis is a crucial factor for the brain, as it can control the environment of the central nervous system and play a significant role in disease progression. The link between neuropsychological behavior or neurodegeneration and gut dysbiosis is well established, but many involved pathways remain unknown. Accumulating studies showed that metabolites derived from gut microbiota are involved in the autophagy activation of various organs, including the brain, one of the major pathways of the protein clearance system that is essential for protein aggregate clearance. On the other hand, some metabolites are evidenced to disrupt the autophagy process, which can be a modulator of neurodegeneration. However, the detailed mechanism of autophagy regulation by gut microbiota remains elusive, and little research only focused on that. Here we tried to evaluate the crosstalk between gut microbiota metabolites and impaired autophagy of the central nervous system in neurodegeneration and the key to future research regarding gut dysbiosis and compromised autophagy in neurodegenerative diseases.

Orexin-A exerts neuroprotective effect in experimental intracerebral hemorrhage by suppressing autophagy via OXR1-mediated ERK/mTOR signaling pathway

Background

Orexin-A (OXA) is a polypeptide produced in the hypothalamus, which binds to specific receptors and exerts multiple physiological effects. Autophagy plays a vital role in early brain injury (EBI) after intracerebral hemorrhage (ICH). However, the relationship between OXA and autophagy after ICH has not been confirmed.

Methods

In this study, the protective role of OXA was investigated in a model of hemin-induced injury in PC12 cells and blood-injection ICH model in rats, and its potential molecular mechanism was clarified. Neurobehavioral tests, brain water content, and pathologic morphology were assessed after ICH. Cell survival rate was determined using Cell Counting Kit-8 (CCK-8), while apoptosis was detected using flow cytometry. The autophagy protein LC3 that was originally identified as microtubule-associated protein 1 light 3 was evaluated by immunohistochemistry. The ultrastructural changes of cells following ICH were observed by transmission electron microscopy. Western blotting was performed to determine the expression levels of LC3, p62/SQSTM1 (p62), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK_1/2), total extracellular signal-regulated kinase 1/2 (t-ERK_1/2), mammalian target of rapamycin (mTOR), and phosphorylated mammalian target of rapamycin (p-mTOR).

Results

OXA treatment significantly improved neurofunctional outcomes, reduced brain edema, and alleviated neuronal apoptosis. OXA administration upregulated p-mTOR and p62, while it downregulated p-ERK_1/2 and LC3; this effect was reversed by the orexin receptor 1 (OXR1) antagonist SB-334867.

Conclusions

This study demonstrates that OXA suppresses autophagy via the OXR1-mediated ERK/mTOR signaling pathway to exert neuroprotective effects, and it might provide a novel therapeutic approach in patients suffering from ICH.

FDA-Approved Kinase Inhibitors in Preclinical and Clinical Trials for Neurological Disorders

Cancers and neurological disorders are two major types of diseases. We previously developed a new concept termed "Aberrant Cell Cycle Diseases" (ACCD), revealing that these two diseases share a common mechanism of aberrant cell cycle re-entry. The aberrant cell cycle re-entry is manifested as kinase/oncogene activation and tumor suppressor inactivation, which are hallmarks of both tumor growth in cancers and neuronal death in neurological disorders. Therefore, some cancer therapies (e.g., kinase inhibition, tumor suppressor elevation) can be leveraged for neurological treatments. The United States Food and Drug Administration (US FDA) has so far approved 74 kinase inhibitors, with numerous other kinase inhibitors in clinical trials, mostly for the treatment of cancers. In contrast, there are dire unmet needs of FDA-approved drugs for neurological treatments, such as Alzheimer's disease (AD), intracerebral hemorrhage (ICH), ischemic stroke (IS), traumatic brain injury (TBI), and others. In this review, we list these 74 FDA-approved kinase-targeted drugs and identify those that have been reported in preclinical and/or clinical trials for neurological disorders, with a purpose of discussing the feasibility and applicability of leveraging these cancer drugs (FDA-approved kinase inhibitors) for neurological treatments.

Elevated Level of Cerebrospinal Fluid Pyruvate Dehydrogenase Kinase 4 Is a Predictive Biomarker of Clinical Outcome after Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a central nervous system disease with high mortality and morbidity. Some independent factors valuable for prognosis prediction in patients with SAH are still lacking. In our earlier study, we found that PDK4 exerts a protective effect after SAH, primarily by reducing oxidative stress and neuronal death via the ROS/ASK1/p38 signaling pathway. Therefore, we investigated the changes in the level of pyruvate dehydrogenase kinase 4 (PDK4) in patients after subarachnoid hemorrhage (SAH) and analyzed the value of the cerebrospinal fluid (CSF) PDK4 level in predicting the prognoses of patients with SAH after interventional embolization surgery. Some knee arthritis subjects who needed surgery were recruited as a control group. The results showed that PDK4 expression was elevated in the CSF of SAH patients compared with that of controls. PDK4 levels in CSF (OR = 4.525; 95% CI: 1.135-18.038; p = 0.032), time to surgery (OR = 0.795; 95% CI: 0.646-0.977; p = 0.029), and initial GCS scores (OR = 2.758; 95% CI: 0.177-43.106; p = 0.469) were independent prognostic risk factors for SAH patients after surgery. The receiver operating characteristic (ROC) curve showed PDK4 levels in CSF had a higher predictive value. Thus, PDK4 in CSF could be an independent prognostic risk factor for SAH patients after surgery. PDK4 has the potential to serve as a new therapeutic target and biomarker for use in the diagnosis of SAH severity and the prediction of recovery.

Case report: Stereotactic body radiation therapy with 12 Gy for silencing refractory ventricular tachycardia

BACKGROUND

Encouraging results have been reported for the treatment of ventricular tachycardia (VT) with stereotactic body radiation therapy (SBRT) with 25 Gy. SBRT with 12 Gy for refractory VT was designed to reduce long-term cardiac toxicity.

METHODS

Stereotactic body radiation therapy-VT simulation, planning, and treatment were performed using standard techniques. A patient was treated with a marginal dose of 12 Gy in a single fraction to the planning target volume (PTV). The goal was for at least ≥ 95% of the PTV to be covered by at least 95% of 12 Gy radiation.

RESULTS

From April 2021 through June 2022, a patient with refractory VT underwent treatment. The volume for PTV was 65.8 cm3. The mean radiation dose administered to the heart (the heart volume excluding the PTV) was 2.2 Gy. No acute or late toxicity was observed after SBRT. Six months after SBRT, the patient experienced new monomorphic right ventricular outflow tract (RVOT) VT. Interestingly, the substrate of the left ventricular basal to middle posteroseptal wall before SBRT was turned into scar zones with a local voltage < 0.5 mV. Catheter ablation to treat RVOT VT was performed, and the situation remains stable to date.

CONCLUSION

This study reports the first patient with refractory VT successfully treated with 12.0 Gy SBRT, suggesting that 12 Gy is a potential dose to treat refractory VT. Further investigations and enrollment of more patients are warranted to assess the long-term efficacy and side effects of this treatment.

Regulation of DAPK1 by Natural Products: An Important Target in Treatment of Stroke

Stroke is a sudden neurological disorder that occurs due to impaired blood flow to an area of the brain. Stroke can be caused by the blockage or rupture of a blood vessel in the brain, called ischemic stroke and hemorrhagic stroke, respectively. Stroke is more common in men than women. Atrial fibrillation, hypertension, kidney disease, high cholesterol and lipids, genetic predisposition, inactivity, poor nutrition, diabetes mellitus, family history and smoking are factors that increase the risk of stroke. Restoring blood flow by repositioning blocked arteries using thrombolytic agents or endovascular therapy are the most effective treatments for stroke. However, restoring circulation after thrombolysis can cause fatal edema or intracranial hemorrhage, and worsen brain damage in a process known as ischemia-reperfusion injury. Therefore, there is a pressing need to find and develop more effective treatments for stroke. In the past, the first choice of treatment was based on natural compounds. Natural compounds are able to reduce the symptoms and reduce various diseases including stroke that attract the attention of the pharmaceutical industry. Nowadays, as a result of the numerous studies carried out in the field of herbal medicine, many useful and valuable effects of plants have been identified. The death-associated protein kinase (DAPK) family is one of the vital families of serine/threonine kinases involved in the regulation of some biological functions in human cells. DAPK1 is the most studied kinase within the DAPKs family as it is involved in neuronal and recovery processes. Dysregulation of DAPK1 in the brain is involved in the developing neurological diseases such as stroke. Natural products can function in a variety of ways, including reducing cerebral edema, reducing brain endothelial cell death, and inhibiting TNFα and interleukin-1β (IL-1β) through regulating the DAPK1 signal against stroke. Due to the role of DAPK1 in neurological disorders, the aim of this article was to investigate the role of DAPK1 in stroke and its modulation by natural compounds.

New Mechanisms and Targets of Subarachnoid Hemorrhage: A Focus on Mitochondria

Spontaneous subarachnoid hemorrhage (SAH) accounts for 5-10% of all strokes and is a subtype of hemorrhagic stroke that places a heavy burden on health care. Despite great progress in surgical clipping and endovascular treatment for ruptured aneurysms, cerebral vasospasm (CVS) and delayed cerebral ischemia (DCI) threaten the long-term outcomes of patients with SAH. Moreover, there are limited drugs available to reduce the risk of DCI and adverse outcomes in SAH patients. New insight suggests that early brain injury (EBI), which occurs within 72 h after the onset of SAH, may lay the foundation for further DCI development and poor outcomes. The mechanisms of EBI mainly include excitotoxicity, oxidative stress, neuroinflammation, blood-brain barrier (BBB) destruction, and cellular death. Mitochondria are a double-membrane organelle, and they play an important role in energy production, cell growth, differentiation, apoptosis, and survival. Mitochondrial dysfunction, which can lead to mitochondrial membrane potential (Δψm) collapse, overproduction of reactive oxygen species (ROS), release of apoptogenic proteins, disorders of mitochondrial dynamics, and activation of mitochondria-related inflammation, is considered a novel mechanism of EBI related to DCI as well as post-SAH outcomes. In addition, mitophagy is activated after SAH. In this review, we discuss the latest perspectives on the role of mitochondria in EBI and DCI after SAH. We emphasize the potential of mitochondria as therapeutic targets and summarize the promising therapeutic strategies targeting mitochondria for SAH.

The role of autophagy and apoptosis in early brain injury after subarachnoid hemorrhage: an updated review

Subarachnoid hemorrhage (SAH) is a worldwide devastating type of stroke with high mortality and morbidity. Accumulating evidence show early brain injury (EBI) as the leading cause of mortality after SAH. The pathological processes involved in EBI include decreased cerebral blood flow, increased intracranial pressure, vasospasm, and disruption of the blood-brain barrier. In addition, neuroinflammation, oxidative stress, apoptosis, and autophagy have also been proposed to contribute to EBI. Among the various processes involved in EBI, neuronal apoptosis has been proven to be a key factor contributing to the poor prognosis of SAH patients. Meanwhile, as another important catabolic process maintaining the cellular and tissue homeostasis, autophagy has been shown to be neuroprotective after SAH. Studies have shown that enhancing autophagy reduced apoptosis, whereas inhibiting autophagy aggravate neuronal apoptosis after SAH. The physiological substrates and mechanisms of neuronal autophagy and apoptosis by which defects in neuronal function are largely unknown. In this review, we summarize and discuss the role of autophagy and apoptosis after SAH and contribute to further study for investigation of the means to control the balance between them.

HMGB1/TLR4 induces autophagy and promotes neuroinflammation after intracerebral hemorrhage

BACKGROUND AND PURPOSE

Intracerebral hemorrhage (ICH) causes autophagy as well as inflammation; the latter is known to involve the high-mobility group box 1 protein (HMGB1)/Toll-like receptor 4 (TLR4) axis. Here we investigated whether this axis may help mediate both the autophagy and inflammation associated with ICH.

METHODS

ICH was induced by injecting autologous blood into Sprague-Dawley rats, followed in some cases by intracerebroventricular injection of short interfering RNA (siRNA) against HMGB1 or TLR4 at 6 h after ICH induction or by intraperitoneal injection of the autophagy inhibitor 3-methyladenine (3-MA) or autophagy activator rapamycin at 6, 24, and 48 h after ICH induction. Western blotting, immunohistochemistry or immunofluorescence was used to assess levels of HMGB1/TLR4 signaling pathway proteins as well as markers of autophagy (LC3B, Beclin1, Atg5) or inflammation (IL-1 beta, TNF-α). Numbers of apoptotic cells were determined using TUNEL staining. Changes in levels of these proteins were correlated with neurological deficits measured using the modified Neurological Severity Score.

RESULTS

ICH caused HMGB1 to translocate from the nucleus into the cytoplasm, and it up-regulated expression of TLR4 and myeloid differentiation factor 88 (MyD88), and induced neurological deficits. Administering siRNA against HMGB1 or TLR4 reversed this up-regulation. Levels of markers of autophagy (LC3B, Beclin1, Atg5) or inflammation (IL-1 beta, TNF-α) were significantly higher 72 h after ICH than at baseline, as were the numbers of TUNEL-positive cells. Administering siRNA against HMGB1 or TLR4 markedly alleviated inflammation, and autophagy, apoptosis, and neurological deficits. Similarly, administering autophagy inhibitor 3-MA alleviated inflammation, apoptosis, and neurological deficits. Conversely, autophagy activator rapamycin exacerbated these effects of ICH.

CONCLUSIONS

During the acute phase of ICH, the HMGB1/TLR4/MyD88 axis acts via autophagy to promote inflammation.

Astaxanthin Modulates Autophagy, Apoptosis, and Neuronal Oxidative Stress in a Rat Model of Compression Spinal Cord Injury

The effects of astaxanthin (AST) were evaluated on oxidative mediators, neuronal apoptosis, and autophagy in functional motor recovery after spinal cord injury (SCI). Rats were divided into three groups of sham, SCI + DMSO (dimethyl sulfoxide), and SCI + AST. Rats in the sham group only underwent a laminectomy at thoracic 8-9. While, the SCI + DMSO and SCI + AST groups had a compression SCI with an aneurysm clip. Then, this groups received an intrathecal (i.t.) injection of 5% DMSO and AST (10 μl of 0.005 mg/kg), respectively. The rat motor functions were assessed weekly until the 28th day using a combined behavioral score (CBS). Total antioxidant capacity (TAC), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were measured in spinal tissue to evaluate oxidative stress-related parameters. Besides, autophagy-related proteins (P62, LC3B, and Beclin1) and apoptosis-associated proteins (Bax and Bcl2) were determined using western blotting on the 1st and 7th days after surgery. Hematoxylin-eosin and Fluoro-Jade B staining were performed to detect the histological alterations and neuronal degeneration. As the result, treatment with AST potentially attenuated rat CBS scores (p < 0.001) towards a better motor performance. AST significantly reduced the spinal level of oxidative stress by increasing TAC, SOD, and GPx, while decreasing MDA (p < 0.001). Furthermore, AST treatment remarkably upregulated expression of LC3B (p < 0.001), and Beclin1 (p < 0.05) in the spinal cord, but downregulated P62 (p < 0.05) and the Bax/Bcl2 ratio (p < 0.001). Consequently, AST reduced SCI-induced histological alterations and neuronal degeneration (p < 0.001). In conclusion, AST can improve motor function after SCI by reducing oxidative stress/apoptosis and increasing neuronal autophagy.

Activation of Cholinergic Anti-Inflammatory Pathway Ameliorates Cerebral and Cardiac Dysfunction After Intracerebral Hemorrhage Through Autophagy

Background

Intracerebral hemorrhage (ICH) is the devastating subtype of stroke with cardiovascular complications, resulting in high rates of mortality and morbidity with the release of inflammatory factors. Previous studies have demonstrated that activation of α7nAChR can reduce immune and inflammation-related diseases by triggering the cholinergic anti-inflammatory pathway (CAIP). α7nAChR mediates protection from nervous system inflammation through AMPK-mTOR-p70S6K-associated autophagy. Therefore, the purpose of this study is to explore whether the activation of α7nAChR improves cerebral and cardiac dysfunction after ICH through autophagy.

Methods

Male C57BL/6 mice were randomly divided into five groups (1): Control + saline (2), ICH+ saline (3), ICH + PNU-282987 (4), ICH+ PNU-282987 + MLA (5), ICH + PNU-282987 + 3-MA. The neurological function was evaluated at multiple time points. Brain water content was measured at 3 days after ICH to assess the severity of brain edema. PCR, immunofluorescence staining, and Western Blot were performed at 7 days after ICH to detect inflammation and autophagy. Picro-Sirius Red staining was measured at 30 days after ICH to evaluate myocardial fibrosis, echocardiography was performed at 3 and 30 days to measure cardiac function.

Results

Our results indicated that the PNU-282987 reduced inflammatory factors (MCP-1, IL-1β, MMP-9, TNF-α, HMGB1, TLR2), promoted the polarization of macrophage/microglia into anti-inflammatory subtypes(CD206), repaired blood-brain barrier injury (ZO-1, Claudin-5, Occludin), alleviated acute brain edema and then recovered neurological dysfunction. Echocardiography and PSR indicated that activation of α7nAChR ameliorated cardiac dysfunction. Western Blot showed that activation of α7nAChR increased autophagy protein (LC3, Beclin) and decreased P62. It demonstrated that the activation of α7nAChR promotes autophagy and then recovers brain and heart function after ICH.

Conclusions

In conclusion, PNU-282987 promoted the cerebral and cardiac functional outcomes after ICH in mice through activated α7nAChR, which may be attributable to promoting autophagy and then reducing inflammatory reactions after ICH.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

PDK4 Decrease Neuronal Apoptosis via Inhibiting ROS-ASK1/P38 Pathway in Early Brain Injury After Subarachnoid Hemorrhage

Aims: Metabolic disorders may play key roles in oxidative stress and neuronal apoptosis in response to early brain injury (EBI) after subarachnoid hemorrhage (SAH). Pyruvate dehydrogenase (PDH) is related to oxidative stress in EBI, and its activity obviously decreases after SAH. We discovered that only pyruvate dehydrogenase kinase 4 (PDK4) expression was obviously increased among the four PDK isozymes after SAH in preliminary experiments. Therefore, we attempted to investigate the effects and corresponding mechanisms of PDK4 on oxidative stress after SAH. Results: First, we confirmed that PDK4 overexpression promoted PDH phosphorylation, inhibited PDH activity, and changed cell metabolism after SAH. A small interfering RNA (siRNA) targeting PDK4, a lentiviral PDK4 overexpression vector, and dichloroacetic acid (DCA) were used to regulate the expression and activity of PDK4. The siRNA decreased PDH phosphorylation, promoted reactive oxygen species (ROS) production, activated the apoptosis signal-regulating kinase 1 (ASK1)/P38 pathway, and induced neuronal apoptosis. The lentivirus further attenuated PDH activity, oxidative stress, and neuronal apoptosis. DCA inhibited the activity of PDK4, but increased the expression of PDK4 due to a feedback mechanism. Inactivated PDK4 did not effectively suppress PDH activity, which increased ROS production, activated the ASK1/P38 pathway, and led to neuronal apoptosis. Innovation: This study provides new insights into the potential antioxidant and antiapoptotic effects of the PDK4-PDH axis on EBI after SAH. Conclusions: The early overexpression of PDK4 after SAH may attenuate neuronal apoptosis by reducing oxidative stress via the ROS/ASK1/P38 pathway. PDK4 may be a new potential therapeutic target to ameliorate EBI after SAH. Antioxid. Redox Signal. 36, 505-524.

Acetyl CoA synthase 2 potentiates ATG5-induced autophagy against neuronal apoptosis after subarachnoid hemorrhage

ATG5-induced autophagy is triggered in the early stages after SAH, which plays a vital role in subarachnoid hemorrhage (SAH). Acyl-CoA synthetase short-chain family 2 (ACSS2) is not just involved in energy metabolism but also binds to TEFB to form a complex translocated to related autophagy genes to regulate the expression of autophagy-related genes. However, the contribution of ACSS2 to the activation of autophagy in early brain injury (EBI) after SAH has barely been discussed. The purpose of this study was to investigate the alterations of ACSS2 and its neuroprotective effects following SAH. We first evaluated the expression of ACSS2 at different time points (6, 12, 24, and 72 h after SAH) in vivo and primary cortical neurons stimulated by oxyhemoglobin (OxyHb). Subsequently, adeno-associated virus and lentivirus were used to regulate ACSS2 expression to investigate the effect of ACSS2 after SAH. The results showed that the ACSS2 level decreased significantly in the early stages of SAH and was minimized at 24 h post-SAH. After artificial intervention to overexpress ACSS2, ATG5-induced autophagy was further enhanced in EBI after SAH, and neuronal apoptosis was alleviated to protect brain injury. In addition, brain edema and neurological function scores were improved. These results suggest that ACSS2 plays an important role in the neuroprotection against EBI after SAH by increasing ATG5-induce autophagy and inhibiting apoptosis.

Anticachectic regulator analysis reveals Perp-dependent antitumorigenic properties of 3-methyladenine in pancreatic cancer

Approximately 80% of pancreatic cancer patients suffer from cachexia, and one-third die due to cachexia-related complications such as respiratory failure and cardiac arrest. Although there has been considerable research into cachexia mechanisms and interventions, there are, to date, no FDA-approved therapies. A major contributing factor for the lack of therapy options could be the failure of animal models to accurately recapitulate the human condition. In this study, we generated an aged model of pancreatic cancer cachexia to compare cachexia progression in young versus aged tumor-bearing mice. Comparative skeletal muscle transcriptome analyses identified 3-methyladenine (3-MA) as a candidate antiwasting compound. In vitro analyses confirmed antiwasting capacity, while in vivo analysis revealed potent antitumor effects. Transcriptome analyses of 3-MA-treated tumor cells implicated Perp as a 3-MA target gene. We subsequently (a) observed significantly higher expression of Perp in cancer cell lines compared with control cells, (b) noted a survival disadvantage associated with elevated Perp, and (c) found that 3-MA-associated Perp reduction inhibited tumor cell growth. Finally, we have provided in vivo evidence that survival benefits conferred by 3-MA administration are independent of its effect on tumor progression. Taken together, we report a mechanism linking 3-MA to Perp inhibition, and we further implicate Perp as a tumor-promoting factor in pancreatic cancer.

Scalp Acupuncture Attenuates Brain Damage After Intracerebral Hemorrhage Through Enhanced Mitophagy and Reduced Apoptosis in Rats

To study the effect of scalp acupuncture (SA) on the mitophagy signaling pathway in the caudate nucleus of Sprague-Dawley rats following intracerebral hemorrhage (ICH). An ICH model was established by injecting autologous arterial blood into the caudate nucleus in 200 male Sprague-Dawley rats, which were divided into five groups: sham, ICH, 3-methyladenine group (3-MA, 30 mg/kg), SA, and SA+3-MA. Animals were analyzed at 6 and 24 h as well as at 3 and 7 days. Composite neurological scale score was significantly higher in the SA group than in the ICH group. Transmission electron microscopy showed less structural damage and more autophagic vacuoles within brain in the SA group than in the ICH group. SA group showed higher levels of Beclin1, Parkin, PINK1, NIX protein, and a lower level of Caspase-9 in brain tissue. These animals consequently showed less neural cell apoptosis. Compared with the SA group, however, the neural function score and levels of mitophagy protein in the SA+3-MA group were decreased, neural cell apoptosis was increased with more severe structural damage, which suggested that 3-MA may antagonize the protective effect of SA on brain in rats with ICH. SA may mitigate the neurologic impairment after ICH by enhancing mitophagy and reducing apoptosis.

P-Glycoprotein Aggravates Blood Brain Barrier Dysfunction in Experimental Ischemic Stroke by Inhibiting Endothelial Autophagy

P-glycoprotein (P-gp) is expressed on brain microvessel endothelial cells of blood-brain barrier (BBB) and elevated after cerebral ischemia. In this study, we explored the influence and potential mechanisms of P-gp on BBB function in experimental ischemic stroke in vivo and in vitro. Middle cerebral artery occlusion/reperfusion (MCAO/R) was created in mice. Oxygen-glucose deprivation/reoxygenation (OGD/R) was performed in brain microvascular vessel-derived endothelial cells (bEnd.3) to mimic ischemia/reperfusion injury in vitro. P-gp-specific siRNA and pharmacological inhibitor cyclosporine A were used to inhibit P-gp, whereas pcDNA3.1 was utilized to overexpress P-gp. Twenty-four hours after reperfusion, acute ischemic stroke outcome, BBB integrity and permeability, autophagic proteins and relative signaling pathways were evaluated. P-gp levels were markedly elevated in mouse brain and endothelial cells following MCAO/R and OGD/R, respectively. P-gp siRNA silencing or pharmacologically inhibiting (cyclosporine A) reduced infarct volume and brain edema, attenuated brain pathology, and improved neurological behavior in association with attenuated accumulation of neutrophils and macrophages, reduced expression levels of inflammatory cytokines (TNF-α and IL-1β), matrix metalloproteinases (MMP-2 and MMP-9) and adhesion molecules (ICAM-1 and VCAM-1). P-gp silence also counteracted BBB leakage, restored the expressions of tight junction proteins (Claudin-5, Occludin and ZO-1), activated autophagic proteins (upregulated LC3-II/LC3-I and Beclin 1, and downregulated P62), and diminished Akt/mTOR signal activity in mice following MCAO/R. In the endothelial cell OGD/R assay, P-gp silence downregulated the expressions of inflammatory cytokines and adhesion molecules, inhibited leukocytes adhesion and migration, increased tight junction protein levels, and activated autophagy, all were reversible by forceful P-gp expression. Additionally, treatment with an autophagy inhibitor (3-methyladenine) abolished protections against ischemic stroke and tight junction proteins reduction followed by P-gp silence. In conclusion, increased P-gp expression after ischemic injury resulted in BBB dysfunction and hyperpermeability by suppressing Akt/mTOR-induced endothelial autophagy.

An Update on Antioxidative Stress Therapy Research for Early Brain Injury After Subarachnoid Hemorrhage

The main reasons for disability and death in aneurysmal subarachnoid hemorrhage (aSAH) may be early brain injury (EBI) and delayed cerebral ischemia (DCI). Despite studies reporting and progressing when DCI is well-treated clinically, the prognosis is not well-improved. According to the present situation, we regard EBI as the main target of future studies, and one of the key phenotype-oxidative stresses may be called for attention in EBI after laboratory subarachnoid hemorrhage (SAH). We summarized the research progress and updated the literature that has been published about the relationship between experimental and clinical SAH-induced EBI and oxidative stress (OS) in PubMed from January 2016 to June 2021. Many signaling pathways are related to the mechanism of OS in EBI after SAH. Several antioxidative stress drugs were studied and showed a protective response against EBI after SAH. The systematical study of antioxidative stress in EBI after laboratory and clinical SAH may supply us with new therapies about SAH.

Effect of Sertoli Cell Transplant and Rapamycin Pretreatment on Middle Cerebral Artery Occlusion-Induced Brain Ischemia in a Rat Model

OBJECTIVES

Stroke exacts a heavy toll on death and disability worldwide. In animal studies, cell transplant has shown a positive effect by inducing neurogenesis, angiogenesis, and modulating inflammation. Cell transplant therapy could provide researchers with new strategies for treating stroke. The mechanistic target of rapamycin is a central signaling pathway for coordination and control; the administration of rapamycin, a key modulator of this pathway, could be a new therapeutic approach in neurological disorders.

MATERIALS AND METHODS

Adult rats were grouped into 5 main groups: control, sham, rapamycin receiving, Sertoli cell receiving, and rapamycin plus Sertoli cell receiving groups. Sertoli cells were taken from another rat tissue and injected into the right striatum region. After 5 days, ischemic induction was performed, and rapamycin injection (300 mg/kg) was performed 1 hour before surgery. After 24 hours, some regions of the brain, including the cortex, striatum, and piriform cortex-amygdala, were isolated for evaluation.

RESULTS

Our results showed that infarct volume, brain edema, and blood-brain barrier permeability assessments were significantly reduced in some areas of the brain in rats that received rapamycin plus Sertoli cells compared with results shown in the control group.

CONCLUSIONS

Pretreatment with Sertoli cell transplant plus rapamycin injection may enhance neural survival during ischemia through increased glial cell-derived neurotrophic factor and vascular endothelial growth factor, inhibiting the mechanistic target of rapamycin pathway and increasing autophagy performance.

Ferritinophagy is Involved in Experimental Subarachnoid Hemorrhage-Induced Neuronal Ferroptosis

Ferroptosis is a novel form of regulated cell death involved in the pathophysiological process of experimental subarachnoid hemorrhage (SAH), but how neuronal ferroptosis occurs remains unknown. In this study, we report that SAH-induced ferroptosis is macroautophagy/autophagy dependent because the inhibition of autophagy by knocking out autophagy-related gene 5 (ATG5) apparently mitigated SAH-induced ferroptosis. We created an experimental SAH model in Sprague-Dawley rats to determine the possible mechanism. We found that SAH can trigger neuronal ferroptosis, as evidenced by the disruption of iron homeostasis, elevation of intracellular lipid peroxidation (LPO) and decreased expression of ferroptosis-protective proteins. Then, we inhibited autophagy by ATG5 gene knockout, showing that autophagy inhibition can reduce the intracellular iron level and LPO, improve the expression of ferroptosis-protective proteins, and subsequently alleviate SAH-induced cell death. Additionally, autophagy inhibition also attenuated SAH prognostic indicators, such as brain edema, blood-brain barrier permeability, and neurological deficits. These findings not only present an opinion that SAH triggers neuronal ferroptosis via activation of ferritinophagy but also indicate that regulating ferritinophagy and maintaining iron homeostasis could provide clues for the prevention of early brain injury.

Efficacy of Melatonin in Animal Models of Subarachnoid Hemorrhage: A Systematic Review and Stratified Meta-Analysis

Background and Purpose: Subarachnoid hemorrhage (SAH) is a severe disease characterized by sudden headache, loss of consciousness, or focal neurological deficits. Melatonin has been reported as a potential neuroprotective agent of SAH. It provides protective effects through the anti-inflammatory effects or the autophagy pathway. Our systematic review aims to evaluate the efficacy of melatonin administration on experimental SAH animals and offer support for the future clinical trial design of the melatonin treatment following SAH.

Methods: The following online databases were searched for experimentally controlled studies of the effect of melatonin on SAH models: PubMed, Web of Knowledge, Embase, and China National Knowledge Infrastructure (all until March 2021). The melatonin effect on the brain water content (BWC) and neurological score (NS) were compared between the treatment and control groups using the standardized mean difference (SMD).

Results: Our literature identified 160 possible articles, and most of them were excluded due to duplication (n = 69) and failure to meet the inclusion criteria (n = 56). After screening the remaining 35 articles in detail, we excluded half of them because of no relevant outcome measures (n = 16), no relevant interventions (n = 3), review articles (n = 1), duplicated publications (n = 1), and studies on humans or cells (n = 2). Finally, this systematic review contained 12 studies between 2008 and 2018. All studies were written in English except for one study in Chinese, and all of them showed the effect of melatonin on BWC and NS in SAH models.

Conclusion: Our research shows that melatonin can significantly improve the behavior and pathological results of SAH animal models. However, due to the small number of studies included in this meta-analysis, the experimental design and experimental method limitations should be considered when interpreting the results. Significant clinical and animal studies are still required to evaluate whether melatonin can be used in the adjuvant treatment of clinical SAH patients.

Targeting autophagy in disease: established and new strategies

Macroautophagy/autophagy is an evolutionarily conserved pathway responsible for clearing cytosolic aggregated proteins, damaged organelles or invading microorganisms. Dysfunctional autophagy leads to pathological accumulation of the cargo, which has been linked to a range of human diseases, including neurodegenerative diseases, infectious and autoimmune diseases and various forms of cancer. Cumulative work in animal models, application of genetic tools and pharmacologically active compounds, has suggested the potential therapeutic value of autophagy modulation in disease, as diverse as Huntington, Salmonella infection, or pancreatic cancer. Autophagy activation versus inhibition strategies are being explored, while the role of autophagy in pathophysiology is being studied in parallel. However, the progress of preclinical and clinical development of autophagy modulators has been greatly hampered by the paucity of selective pharmacological agents and biomarkers to dissect their precise impact on various forms of autophagy and cellular responses. Here, we summarize established and new strategies in autophagy-related drug discovery and indicate a path toward establishing a more efficient discovery of autophagy-selective pharmacological agents. With this knowledge at hand, modern concepts for therapeutic exploitation of autophagy might become more plausible.

Abbreviations: ALS: amyotrophic lateral sclerosis; AMPK: AMP-activated protein kinase; ATG: autophagy-related gene; AUTAC: autophagy-targeting chimera; CNS: central nervous system; CQ: chloroquine; GABARAP: gamma-aminobutyric acid type A receptor-associated protein; HCQ: hydroxychloroquine; LYTAC: lysosome targeting chimera; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; NDD: neurodegenerative disease; PDAC: pancreatic ductal adenocarcinoma; PE: phosphatidylethanolamine; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol 3-phosphate; PROTAC: proteolysis-targeting chimera; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; SQSTM1/p62: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1.

Electroacupuncture at GV20‑GB7 regulates mitophagy to protect against neurological deficits following intracerebral hemorrhage via inhibition of apoptosis

The acupuncture penetrating line of Baihui (GV20) to Qubin (GB7) spans the parietal, frontal and temporal lobes. The present study aimed to elucidate the mechanism by which electroacupuncture (EA) at GV20‑GB7 regulates mitophagy in intracerebral hemorrhage (ICH) and whether it serves a neuroprotective role. A whole blood‑induced ICH model was used. Mitophagy‑regulating proteins, including BCL/adenovirus E1B 19 kDa‑interacting protein 3 (BNIP3), PTEN‑induced putative kinase 1 (PINK1), Parkin and apoptosis‑associated proteins were detected by western blotting; autophagy following ICH was evaluated by immunofluorescent techniques; morphological characteristics of mitophagy were observed using transmission electron microscopy; and TUNEL assay was performed to determine the number of apoptotic cells. Immunohistochemistry was used to detect p53 expression. The protective role of EA (GV20‑GB7) via enhanced mitophagy and suppressed apoptosis in ICH was further confirmed by decreased modified neurological severity score. The results showed that EA (GV20‑GB7) treatment upregulated mitochondrial autophagy following ICH and inhibited apoptotic cell death. The mechanism underlying EA (GV20‑GB7) treatment may involve inhibition of p53, an overlapping protein of autophagy and apoptosis. EA (GV20‑GB7) treatment decreased neurobehavioral deficits following ICH but pretreatment with 3‑methyladenine counteracted the beneficial effects of EA (GV20‑GB7) treatment. In conclusion, EA (GV20‑GB7) improved recovery from ICH by regulating the balance between mitophagy and apoptosis.

Perspectives on the development of first-in-class protein degraders

Targeted protein degradation is a broad and expanding field aimed at the modulation of protein homeostasis. A focus of this field has been directed toward molecules that hijack the ubiquitin proteasome system with heterobifunctional ligands that recruit a target protein to an E3 ligase to facilitate polyubiquitination and subsequent degradation by the 26S proteasome. Despite the success of these chimeras toward a number of clinically relevant targets, the ultimate breadth and scope of this approach remains uncertain. Here we highlight recent advances in assays and tools available to evaluate targeted protein degradation, including and beyond the study of E3-targeted chimeric ligands. We note several challenges associated with degrader development and discuss various approaches to expanding the protein homeostasis toolbox.

MerTK inhibits the activation of the NLRP3 inflammasome after subarachnoid hemorrhage by inducing autophagy

The NLR family pyrin domain-containing 3 (NLRP3) multiprotein complex is associated with neuroinflammation and poor prognosis after subarachnoid hemorrhage (SAH). Accumulating evidence shows that Mer tyrosine kinase (MerTK) alleviates inflammatory responses via a negative feedback mechanism. However, the contribution and function of MerTK in SAH remain to be determined. In this study, we explored the role of MerTK during microglial NLRP3 inflammasome activation and evaluated its contribution to the outcome of SAH in mice. Activating MerTK with growth arrest-specific 6 (Gas6) alleviated brain edema, neuronal degeneration and neurological deficits after SAH by regulating neuroinflammation. Gas6 did not change the mRNA levels of Nlrp3 or Casp1 but decreased the protein expression of NLRP3, cleaved caspase1 (p20), interleukin-1β and interleukin-18. Furthermore, Gas6 increased the expression of Beclin1, the ratio of LC3-II/LC3-I and the level of autophagic flux. Inhibiting autophagy with 3-MA reversed the inhibition of NLRP3 inflammasome activation and diminished the neuroprotective effects of Gas6. Thus, MerTK activation may exert protective effects by limiting neuroinflammation and promoting neurological recovery after SAH via autophagy induction.

MICAL1 (molecule interacting with CasL 1) protects oligodendrocyte cells from oxidative injury through regulating apoptosis, autophagy in spinal cord injury

Molecule's mechanism of action interacting with CasL 1 (MICAL1) in spinal cord injury (SCI) is unclear. This study aimed to detect the function of MICAL1 in SCI. Western blot was used to analyze the change of MICAL1 in vivo. Immunofluorescence staining was used to detect the location of MICAL1 expression. Oligodendrocyte cells were treated with H₂O₂ to induce oxidative injury. Subsequently, siRNA transfection was performed to decrease MICAL1 expression in oligodendrocyte cells. Then, the effects of MICAL1 on oxidative stress, apoptosis, and autophagy were assessed. We found that silencing of MICAL1 could significantly reduce the levels of the nuclear factor erythroid 2-related factor 2 (Nrf2), increase the expression of pro-apoptotic factors (Bax and C-caspase 3), decrease the levels of anti-apoptotic factor (Bcl-2) and pro-autophagy factors (Beclin1 and LC3B). Therefore, MICAL1 is a potential target gene for SCI clinical therapy.

Mitochondria: Novel Mechanisms and Therapeutic Targets for Secondary Brain Injury After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a destructive form of stroke that often results in death or disability. However, the survivors usually experience sequelae of neurological impairments and psychiatric disorders, which affect their daily functionality and working capacity. The recent MISTIE III and STICH II trials have confirmed that early surgical clearance of hematomas does not improve the prognosis of survivors of ICH, so it is vital to find the intervention target of secondary brain injury (SBI) after ICH. Mitochondrial dysfunction, which may be induced by oxidative stress, neuroinflammation, and autophagy, among others, is considered to be a novel pathological mechanism of ICH. Moreover, mitochondria play an important role in promoting neuronal survival and improving neurological function after a hemorrhagic stroke. This review summarizes the mitochondrial mechanism involved in cell death, reactive oxygen species (ROS) production, inflammatory activation, blood–brain barrier (BBB) disruption, and brain edema underlying ICH. We emphasize the potential of mitochondrial protection as a potential therapeutic target for SBI after stroke and provide valuable insight into clinical strategies.

[Autophagy activation attenuates the neurotoxicity of local anaesthetics by decreasing caspase-3 activity in rats]

BACKGROUND AND OBJECTIVES

The mechanisms by which local anaesthetics cause neurotoxicity are very complicated. Apoptosis and autophagy are highly coordinated mechanisms that maintain cellular homeostasis against stress. Studies have shown that autophagy activation serves as a protective mechanism in vitro. However, whether it also plays the same role in vivo is unclear. The aim of this study was to explore the role of autophagy in local anaesthetic-induced neurotoxicity and to elucidate the mechanism of neurotoxicity in an intrathecally injected rat model.

METHODS

Eighteen healthy adult male Sprague-Dawley rats were randomly divided into three groups. Before receiving an intrathecal injection of 1% bupivacaine, each rat received an intraperitoneal injection of vehicle or rapamycin (1 mg.kg^-1) once a day for 3 days. The pathological changes were examined by Haematoxylin and Eosin (HE) staining. Apoptosis was analysed by TdT-mediated dUTP Nick-End Labelling (TUNEL) staining. Caspase-3, Beclin1 and LC3 expression was examined by Immunohistochemical (IHC) staining. Beclin1 and LC3 expression and the LC3-II/LC3-I ratio were detected by western blot analysis.

RESULTS

After bupivacaine was injected intrathecally, pathological damage occurred in spinal cord neurons, and the levels of apoptosis and caspase-3 increased. Enhancement of autophagy with rapamycin markedly alleviated the pathological changes and decreased the levels of apoptosis and caspase-3 while increasing the expression of LC3 and Beclin1 and the ratio of LC3-II to LC3-I.

CONCLUSIONS

Enhancement of autophagy decreases caspase-3-dependent apoptosis and improves neuronal survival in vivo. Activation of autophagy may be a potential therapeutic strategy for local anaesthetic-induced neurotoxicity.

Hamartin: An Endogenous Neuroprotective Molecule Induced by Hypoxic Preconditioning

Hypoxic/ischemic preconditioning (HPC/IPC) is an innate neuroprotective mechanism in which a number of endogenous molecules are known to be involved. Tuberous sclerosis complex 1 (TSC1), also known as hamartin, is thought to be one such molecule. It is also known that hamartin is involved as a target in the rapamycin (mTOR) signaling pathway, which functions to integrate a variety of environmental triggers in order to exert control over cellular metabolism and homeostasis. Understanding the role of hamartin in ischemic/hypoxic neuroprotection will provide a novel target for the treatment of hypoxic-ischemic disease. Therefore, the proposed molecular mechanisms of this neuroprotective role and its preconditions are reviewed in this paper, with emphases on the mTOR pathway and the relationship between the expression of hamartin and DNA methylation.

[Autophagy activation attenuates the neurotoxicity of local anaesthetics by decreasing caspase-3 activity in rats]

BACKGROUND AND OBJECTIVES

The mechanisms by which local anesthetics cause neurotoxicity are very complicated. Apoptosis and autophagy are highly coordinated mechanisms that maintain cellular homeostasis against stress. Studies have shown that autophagy activation serves as a protective mechanism in vitro. However, whether it also plays the same role in vivo is unclear. The aim of this study was to explore the role of autophagy in local anesthetic-induced neurotoxicity and to elucidate the mechanism of neurotoxicity in an intrathecally injected rat model.

METHODS

Eighteen healthy adult male Sprague-Dawley rats were randomly divided into three groups. Before receiving an intrathecal injection of 1% bupivacaine, each rat received an intraperitoneal injection of vehicle or rapamycin (1 mg.kg^-1) once a day for 3 days. The pathological changes were examined by Haematoxylin and Eosin (HE) staining. Apoptosis was analysed by TdT-mediated dUTP Nick-End Labelling (TUNEL) staining. Caspase-3, Beclin1 and LC3 expression was examined by Immunohistochemical (IHC) staining. Beclin1 and LC3 expression and the LC3-II/LC3-I ratio were detected by western blot analysis.

RESULTS

After bupivacaine was injected intrathecally, pathological damage occurred in spinal cord neurons, and the levels of apoptosis and caspase-3 increased. Enhancement of autophagy with rapamycin markedly alleviated the pathological changes and decreased the levels of apoptosis and caspase-3 while increasing the expression of LC3 and Beclin1 and the ratio of LC3-II to LC3-I.

CONCLUSIONS

Enhancement of autophagy decreases caspase-3-dependent apoptosis and improves neuronal survivalin vivo. Activation of autophagy may be a potential therapeutic strategy for local anaesthetic-induced neurotoxicity.

Autophagy and Hemorrhagic Stroke

Hemorrhagic stroke includes cerebral hemorrhage and subarachnoid hemorrhage. An increasing number of studies have found that autophagy also occurs in brain tissues after cerebral hemorrhage and subarachnoid hemorrhage. The potential role of selective autophagy in the clinical treatment of hemorrhagic stroke has been recognized, but a consensus on the exact effect and function of autophagy has not been reached, and the mechanism needs to be further studied. In this chapter, the mechanism of brain injury after cerebral hemorrhage and subarachnoid hemorrhage is briefly introduced, and changes in the autophagy pathway and the role of autophagy in the process of brain injury are discussed.

The Glycoprotein and Nucleocapsid Protein of Hantaviruses Manipulate Autophagy Flux to Restrain Host Innate Immune Responses

Hantavirus infection, which causes severe zoonotic diseases with high mortality in humans, has become a global public health concern. Here, we demonstrate that Hantaan virus (HTNV), the prevalent prototype of the hantavirus in Asia, can restrain innate immune responses by manipulating host autophagy flux. HTNV induces complete mitophagy at the early stage of infection but incomplete autophagy at the late stage, and these responses involve the viral glycoprotein (Gn) and nucleocapsid protein (NP), respectively. Gn translocates to mitochondria and interacts with TUFM, recruiting LC3B and promoting mitophagy. Gn-induced mitophagy inhibits type I interferon (IFN) responses by degrading MAVS. Additionally, we found that NP competes with Gn for binding to LC3B, which inhibits Gn-mediated autophagosome formation, and interacts with SNAP29, which prevents autophagosome-lysosome fusion. Thus, NP disturbs the autophagic degradation of Gn. These findings highlight how hantaviruses repurpose host autophagy and evade innate immune responses for their life cycle and pathogenesis.

HMGB1-Mediated Neuroinflammatory Responses in Brain Injuries: Potential Mechanisms and Therapeutic Opportunities

Brain injuries are devastating conditions, representing a global cause of mortality and morbidity, with no effective treatment to date. Increased evidence supports the role of neuroinflammation in driving several forms of brain injuries. High mobility group box 1 (HMGB1) protein is a pro-inflammatory-like cytokine with an initiator role in neuroinflammation that has been implicated in Traumatic brain injury (TBI) as well as in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Herein, we discuss the implication of HMGB1-induced neuroinflammatory responses in these brain injuries, mediated through binding to the receptor for advanced glycation end products (RAGE), toll-like receptor4 (TLR4) and other inflammatory mediators. Moreover, we provide evidence on the biomarker potential of HMGB1 and the significance of its nucleocytoplasmic translocation during brain injuries along with the promising neuroprotective effects observed upon HMGB1 inhibition/neutralization in TBI and EBI induced by SAH. Overall, this review addresses the current advances on neuroinflammation driven by HMGB1 in brain injuries indicating a future treatment opportunity that may overcome current therapeutic gaps.

Inhibition of mTOR Alleviates Early Brain Injury After Subarachnoid Hemorrhage Via Relieving Excessive Mitochondrial Fission

The mammalian target of rapamycin (mTOR) was reported to regulate cell autophagy and outcomes of several neurological diseases. Mitochondria, which serve as critical organelles in neurons. are also involved in the pathology of neurological diseases. However, the role of mTOR in mitochondrial morphology has not been clarified especially in subarachnoid hemorrhage (SAH). In this study, we established SAH models both in vivo and in vitro. Rapamycin and 3-methyl adenine (3-MA) were then administered to alter mTOR activity. Post-SAH assessment included SAH grading, neurological evaluation, blood-brain barrier (BBB) permeability, brain water content, mitochondrial membrane potential (MMP), mitochondrial morphology, ATP content, cell viability, cytotoxicity, and expression of proteins related to apoptosis and mitochondrial fission. The results showed that (1) neurological deficits, BBB permeability, and brain edema were increased after SAH and that cell viability was exacerbated in brain tissue. (2) Excessive mitochondrial fission was evident based on changes in mitochondrial morphology, while MMP and ATP content were decreased in neurons after SAH. (3) Administration of rapamycin improved the excessive mitochondrial fission and restored mitochondrial function, which subsequently reduced apoptosis. (4) 3-MA showed an adverse effect on mitochondria and aggravated excessive mitochondrial fission and dysfunction in SAH. Neurological deficits and neuronal viability were also exacerbated following the administration of 3-MA. Therefore, our study suggests that mTOR inhibition has neuroprotective effects against neuronal injury after SAH via alleviating excessive mitochondrial fission.

Mitochondrial Degeneration and Autophagy Associated With Delayed Effects of Radiation in the Mouse Brain

Mitochondria are linked with various radiation responses, including mitophagy, genomic instability, apoptosis, and the bystander effect. Mitochondria play an important role in preserving cellular homeostasis during stress responses, and dysfunction in mitochondrial contributes to aging, carcinogenesis and neurologic diseases. In this study, we have investigated the mitochondrial degeneration and autophagy in the hippocampal region of brains from mice administered with BBT-059, a long-acting interleukin-11 analog, or its formulation buffer 24 h prior to irradiation at different radiation doses collected at 6 and 12 months post-irradiation. The results demonstrated a higher number of degenerating mitochondria in 12 Gy BBT-059 treated mice after 6 months and 11.5 Gy BBT-059 treated mice after 12 months as compared to the age-matched naïve (non-irradiated control animals). Apg5l, Lc3b and Sqstm1 markers were used to analyze the autophagy in the brain, however only the Sqstm1 marker exhibited significantly reduced expression after 12 months in 11.5 Gy BBT-059 treated mice as compared to naïve. Immunohistochemistry (IHC) results of Bcl2 also demonstrated a decrease in expression after 12 months in 11.5 Gy BBT-059 treated mice as compared to other groups. In conclusion, our results demonstrated that higher doses of ionizing radiation (IR) can cause persistent upregulation of mitochondrial degeneration. Reduced levels of Sqstm1 and Bcl2 can lead to intensive autophagy which can lead to degradation of cellular structure.

An early neuroprotective effect of atorvastatin against subarachnoid hemorrhage

Atorvastatin has been shown to reduce early brain edema and neuronal death after subarachnoid hemorrhage, but its mechanism is not clear. In this study, rat models of subarachnoid hemorrhage were established by autologous blood injection in the cisterna magna. Rat models were intragastrically administered 20 mg/kg atorvastatin 24 hours before subarachnoid hemorrhage, 12 and 36 hours after subarachnoid hemorrhage. Compared with the controls, atorvastatin treatment demonstrated that at 72 hours after subarachnoid hemorrhage, neurological function had clearly improved; brain edema was remarkably relieved; cell apoptosis was markedly reduced in the cerebral cortex of rats; the number of autophagy-related protein Beclin-1-positive cells and the expression levels of Beclin-1 and LC3 were increased compared with subarachnoid hemorrhage only. The ultrastructural damage of neurons in the temporal lobe was also noticeably alleviated. The similarities between the effects of atorvastatin and rapamycin were seen in all the measured outcomes of subarachnoid hemorrhage. However, these were contrary to the results of 3-methyladenine injection, which inhibits the signaling pathway of autophagy. These findings indicate that atorvastatin plays an early neuroprotective role in subarachnoid hemorrhage by activating autophagy. The experimental protocol was approved by the Animal Ethics Committee of Anhui Medical University, China (904 Hospital of Joint Logistic Support Force of PLA; approval No. YXLL-2017-09) on February 22, 2017.

Elucidating the novel biomarker and therapeutic potentials of High-mobility group box 1 in Subarachnoid hemorrhage: A review

Subarachnoid hemorrhage (SAH) frequently arises after an aneurysm in a cerebral artery ruptures, resulting into bleeding as well as clot formation. High-mobility group box 1 (HMGB1) is an extremely preserved, universal protein secreted in the nuclei of all cell varieties. This review explores the biomarker as well as therapeutic potentials of HMBG1 in SAH especially during the occurrence of cerebral vasospasms. Plasma HMGB1 levels have proven to be very useful prognosticators of effective outcome as well as death after SAH. Correspondingly, higher HMGB1 levels in the cerebrospinal fluid (CSF) of SAH patients correlated well with poor outcome; signifying that, CSF level of HMGB1 is a novel predictor of outcome following SAH. Nonetheless, the degree of angiographic vasospasm does not always correlate with the degree of neurological deficits in SAH patients. HMGB1 stimulated cerebral vasospasm, augmented gene as well as protein secretory levels of receptor for advance glycation end product (RAGE) in neurons following SAH; which means that, silencing HMGB1 during SAH could be of therapeutic value. Compounds like resveratrol, glycyrrhizin, rhinacanthin, purpurogallin, 4′-O-β-D-Glucosyl-5-O-Methylvisamminol (4OGOMV) as well as receptor-interacting serine/threonine-protein kinase 3 (RIPK3) gene are capable of interacting with HMGB1 resulting in therapeutic benefits following SAH.

Rapamycin protects against early brain injury independent of cerebral blood flow changes in a mouse model of subarachnoid haemorrhage

We evaluated the neuroprotective role of rapamycin, a mammalian target of rapamycin (mTOR) kinase inhibitor, in cerebral ischaemia and locomotor function in a mouse model of subarachnoid haemorrhage (SAH). Pretreatment with rapamycin, an mTOR kinase inhibitor, resulted in better recovery from cerebral hypoxia early after SAH than control (P < .05), while the values of peak flow velocity in the middle cerebral artery did not change significantly (P > .05). Average distance travelled and the ratio of central-area distance/total travelled distance determined by open-field test after day 14 was significantly higher in mice pretreated with rapamycin than in control mice (P < .05). Inhibition of the mTOR pathway could be protective against post-SAH early brain injury, ameliorating brain tissue hypoxia and locomotor hypoactivity.

The Neuroprotective Effects of Necrostatin-1 on Subarachnoid Hemorrhage in Rats Are Possibly Mediated by Preventing Blood-Brain Barrier Disruption and RIP3-Mediated Necroptosis

Despite the substantial efforts to elucidate the role of early brain injury in subarachnoid hemorrhage (SAH), an effective pharmaceutical therapy for patients with SAH continues to be unavailable. This study aims to reveal the role of necroptosis after SAH, and explore whether the disruption of the blood-brain barrier (BBB) and RIP3-mediated necroptosis following SAH in a rat SAH model are altered by necrostatin-1 via its selective inhibition of receptor-interacting protein kinase 1 (RIP1). Sixty-five rats were used in the experiments. The SAH model was established using endovascular perforation. Necrostatin-1 was intracerebroventricularly injected 1 h before SAH induction. The neuroprotective effects of necrostatin-1 were evaluated with multiple methods such as magnetic resonance imaging (MRI) scanning, immunohistochemistry, propidium iodide (PI) labeling, and western blotting. Pretreatment with necrostatin-1 attenuated brain swelling and reduced the lesion volume on T2 sequence and ventricular volume on MRI 72 h after SAH induction. Albumin leakage and the degradation of tight junction proteins were also ameliorated by necrostatin-1 administration. In addition, necrostatin-1 decreased the number of PI-positive cells in the basal cortex, reduced the levels of the RIP3 and MLKL proteins, and inhibited the production of the pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. Based on the findings from the present study, the selective RIP1 inhibitor necrostatin-1 functioned as a neuroprotective agent after SAH by attenuating brain swelling and BBB disruption. Moreover, the necrostatin-1 pretreatment prevented SAH-induced necroptosis by suppressing the activity of the RIP3/MLKL signaling pathway. These results will provide insights into new drugs and pharmacological targets to manage SAH, which are worth further study.

Osteopontin-Enhanced Autophagy Attenuates Early Brain Injury via FAK-ERK Pathway and Improves Long-Term Outcome after Subarachnoid Hemorrhage in Rats

Osteopontin (OPN) enhances autophagy, reduces apoptosis, and attenuates early brain injury (EBI) after a subarachnoid hemorrhage (SAH). A total of 87 Sprague–Dawley rats were subjected to sham or SAH operations to further investigate the signaling pathway involved in osteopontin-enhanced autophagy during EBI, and the potential effect of recombinant OPN (rOPN) administration to improve long-term outcomes after SAH. Rats were randomly divided into five groups: Sham, SAH + Vehicle (PBS, phosphate-buffered saline), SAH + rOPN (5 μg/rat recombinant OPN), SAH + rOPN + Fib-14 (30 mg/kg of focal adhesion kinase (FAK) inhibitor-14), and SAH + rOPN + DMSO (dimethyl sulfoxide). Short-term and long-term neurobehavior tests were performed, followed by a collection of brain samples for assessment of autophagy markers in neurons, pathway proteins expression, and delayed hippocampal injury. Western blot, double immunofluorescence staining, Nissl staining, and Fluoro-Jade C staining assay were used. Results showed that rOPN administration increased autophagy in neurons and improved neurobehavior in a rat model of SAH. With the administration of FAK inhibitor-14 (Fib-14), neurobehavioral improvement and autophagy enhancement induced by rOPN were abolished, and there were consistent changes in the phosphorylation level of ERK1/2. In addition, early administration of rOPN in rat SAH models improved long-term neurobehavior results, possibly by alleviating hippocampal injury. These results suggest that FAK–ERK signaling may be involved in OPN-enhanced autophagy in the EBI phase after SAH. Early administration of rOPN may be a preventive and therapeutic strategy against delayed brain injury after SAH.

Osteopontin attenuates early brain injury through regulating autophagy-apoptosis interaction after subarachnoid hemorrhage in rats

Aim

To determine the effect of osteopontin (OPN) on autophagy and autophagy‐apoptosis interactions after SAH.

Methods

The endovascular perforation model of SAH or sham surgery was performed in a total of 86 Sprague‐Dawley male rats. The temporal expressions of endogenous OPN and autophagy‐related proteins (Beclin 1, ATG5, LC3 II to I ratio) were measured in sham and SAH rats at different time points (3, 6, 12, 24, and 72 hours). Rats were randomly divided into three groups: Sham, SAH + Vehicle (PBS, phosphate‐buffered saline), and SAH + rOPN (5 μg/rat recombinant OPN). Neurobehavioral tests were performed 24 hours after SAH, followed by the collection of brain samples for assessment of autophagy and apoptosis proteins. These tests assessed whether an autophagy‐apoptosis relationship existed on the histological level in the brain.

Results

Endogenous OPN and autophagy‐related proteins all increased after SAH. rOPN administration improved neurological dysfunction, increased the expression of autophagy‐related proteins (Beclin 1, ATG5, LC3 II to I ratio) and antiapoptotic protein Bcl‐2, while decreasing the expression of proapoptotic proteins (cleaved Caspase‐3 and Bax). rOPN also regulated autophagy‐apoptosis interactions 24 hours after SAH.

Conclusion

rOPN attenuates early brain injury and inhibits neuronal apoptosis by activating autophagy and regulating autophagy‐apoptosis interactions.