The role and therapeutic potential of heat shock proteins in haemorrhagic stroke

Targeting the neurovascular unit: Therapeutic potential of traditional Chinese medicine for the treatment of stroke

Stroke poses a significant global health challenge due to its elevated disability and mortality rates, particularly affecting developing nations like China. The neurovascular unit (NVU), a new concept encompassing neurons, brain microvascular endothelial cells, pericytes, astrocytes, microglia, and the extracellular matrix, has gained prominence in recent years. Traditional Chinese medicine (TCM), deeply rooted in Chinese history, employs a combination of acupuncture and herbal treatments, demonstrating significant efficacy across all stages of stroke, notably during recovery. The holistic approach of TCM aligns with the NVU's comprehensive view of treating stroke by addressing neurons, surrounding cells, and blood vessels collectively. This review examines the role of NVU in stroke and endeavors to elucidate the mechanisms through which traditional Chinese medicine exerts its anti-stroke effects within the NVU framework. The NVU contributes to neuroinflammation, immune infiltration, blood-brain barrier permeability, oxidative stress, and Ca2+ overload during stroke occurs. Additionally, TCM targeting the NVU facilitates nerve repair post-stroke through various pathways and approaches. Specific herbs, including panax notoginseng, ginseng, and borneol, alleviate brain injury by enhancing brain-derived neurotrophic factor expression and targeting astrocytes and microglia to yield anti-inflammatory and antioxidant effects. Acupuncture, another facet of TCM, promotes brain injury repair by augmenting cerebral blood flow and improving circulation. This exploration aims to assess the viability of stroke treatment by directing TCM interventions toward the NVU, thus paving the way for its broader clinical application.

Mesenchymal stem cell-derived extracellular vesicles mitigate neuronal damage from intracerebral hemorrhage by modulating ferroptosis

BACKGROUND

Hemorrhagic stroke is a devastating cerebrovascular event with a high rate of early mortality and long-term disability. The therapeutic potential of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) for neurological conditions, such as intracerebral hemorrhage (ICH), has garnered considerable interest, has garnered considerable interest, though their mechanisms of action remain poorly understood.

METHODS

EVs were isolated from human umbilical cord MSCs, and SPECT/CT was used to track the 99mTc-labeled EVs in a mouse model of ICH. A series of comprehensive evaluations, including magnetic resonance imaging (MRI), histological study, RNA sequencing (RNA-Seq), or miRNA microarray, were performed to investigate the therapeutic action and mechanisms of MSC-EVs in both cellular and animal models of ICH.

RESULTS

Our findings show that intravenous injection of MSC-EVs exhibits a marked affinity for the ICH-affected brain regions and cortical neurons. EV infusion alleviates the pathological changes observed in MRI due to ICH and reduces damage to ipsilateral cortical neurons. RNA-Seq analysis reveals that EV treatment modulates key pathways involved in the neuronal system and metal ion transport in mice subjected to ICH. These data were supported by the attenuation of neuronal ferroptosis in neurons treated with Hemin and in ICH mice following EV therapy. Additionally, miRNA microarray analysis depicted the EV-miRNAs targeting genes associated with ferroptosis, and miR-214-3p was identified as a regulator of neuronal ferroptosis in the ICH cellular model.

CONCLUSIONS

MSC-EVs offer neuroprotective effects against ICH-induced neuronal damage by modulating ferroptosis highlighting their therapeutic potential for combating neuronal ferroptosis in brain disorders.

Early and delayed blood-brain barrier permeability predicts delayed cerebral ischemia and outcomes following aneurysmal subarachnoid hemorrhage

OBJECTIVES

This study aimed to monitor blood-brain barrier permeability within 24 h and during the delayed cerebral ischemia (DCI) time window (DCITW) spanning 4-14 days after aneurysmal subarachnoid hemorrhage (aSAH) and to investigate its correlation with both DCI occurrence and outcomes at three months.

METHODS

A total of 128 patients were stratified based on the DCI occurrence and three-month modified Rankin scale scores. Comparison of Ktrans at admission (admission Ktrans) and during DCITW (DCITW Ktrans) was conducted between DCI and non-DCI groups, as well as between groups with good and poor outcomes. Changes in Ktrans were also analyzed. Multivariate logistic regression analysis was performed to identify independent predictors of DCI and poor outcomes.

RESULTS

Admission Ktrans (0.58 ± 0.18 vs 0.47 ± 0.12, p = 0.002) and DCITW Ktrans (0.54 ± 0.19 vs 0.41 ± 0.14, p < 0.001) were significantly higher in the DCI group compared with the non-DCI group. Although both were higher in the poor outcome group than the good outcome group, the difference was not statistically significant at admission (0.53 ± 0.18 vs 0.49 ± 0.14, p = 0.198). Ktrans in the non-DCI group (0.47 ± 0.12 vs 0.41 ± 0.14, p = 0.004) and good outcome group (0.49 ± 0.14 vs 0.41 ± 0.14, p < 0.001) decreased significantly from the admission to DCITW. Multivariate analysis identified DCITW Ktrans and admission Ktrans as independent predictors of poor outcomes (OR = 1.73, 95%CI: 1.24-2.43, p = 0.001) and DCI (OR = 1.75, 95%CI: 1.25-2.44, p = 0.001), respectively.

CONCLUSION

Elevated Ktrans at admission is associated with the occurrence of DCI. Continuous monitoring of Ktrans from admission to DCITW can accurately identify reversible and irreversible changes and can predict outcomes at 3 months.

CLINICAL RELEVANCE STATEMENT

Ktrans measured with CT perfusion is a valuable tool for predicting both delayed cerebral ischemia and three-month outcomes following aneurysmal subarachnoid hemorrhage. Monitoring changes in Ktrans from admission to time window of delayed cerebral ischemia can guide treatment and management decisions for aneurysmal subarachnoid hemorrhage patients.

KEY POINTS

• Ktrans measured at admission and during the delayed cerebral ischemia time window (4-14 days) holds distinct clinical significance following aneurysmal subarachnoid hemorrhage. • Admission Ktrans serves as a predictor for delayed cerebral ischemia, while continuous assessment of Ktrans from admission to the delayed cerebral ischemia time window can predict three-month outcomes. • Monitoring Ktrans at different stages improves instrumental in enhancing decision-making and treatment planning for patients with aneurysmal subarachnoid hemorrhage.

Anti-HMGB1 mAb Therapy Reduces Epidural Hematoma Injury

Epidural and subdural hematomas are commonly associated with traumatic brain injury. While surgical removal is the primary intervention for these hematomas, it is also critical to prevent and reduce complications such as post-traumatic epilepsy, which may result from inflammatory responses in the injured brain areas. In the present study, we observed that high mobility group box-1 (HMGB1) decreased in the injured brain area beneath the epidural hematoma (EDH) in rats, concurrent with elevated plasma levels of HMGB1. Anti-HMGB1 monoclonal antibody therapy strongly inhibited both HMGB1 release and the subsequent increase in plasma levels. Moreover, this treatment suppressed the up-regulation of inflammatory cytokines and related molecules such as interleukin-1-beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and inducible nitric oxide synthase (iNOS) in the injured areas. Our in vitro experiments using SH-SY5Y demonstrated that hematoma components-thrombin, heme, and ferrous ion- prompted HMGB1 translocation from the nuclei to the cytoplasm, a process inhibited by the addition of the anti-HMGB1 mAb. These findings suggest that anti-HMGB1 mAb treatment not only inhibits HMGB1 translocation but also curtails inflammation in injured areas, thereby protecting the neural tissue. Thus, anti-HMGB1 mAb therapy could serve as a complementary therapy for an EDH before/after surgery.

Metallic Nanocarriers for Therapeutic Peptides: Emerging Solutions Addressing the Delivery Challenges in Brain Ailments

Peptides and proteins have recently emerged as efficient therapeutic alternatives to conventional therapies. Although they emerged a few decades back, extensive exploration of various ailments or disorders began recently. The drawbacks of current chemotherapies and irradiation treatments, such as drug resistance and damage to healthy tissues, have enabled the rise of peptides in the quest for better prospects. The chemical tunability and smaller size make them easy to design selectively for target tissues. Other remarkable properties include antifungal, antiviral, anti-inflammatory, protection from hemorrhage stroke, and as therapeutic agents for gastric disorders and Alzheimer and Parkinson diseases. Despite these unmatched properties, their practical applicability is often hindered due to their weak susceptibility to enzymatic digestion, serum degradation, liver metabolism, kidney clearance, and immunogenic reactions. Several methods are adapted to increase the half-life of peptides, such as chemical modifications, fusing with Fc fragment, change in amino acid composition, and carrier-based delivery. Among these, nanocarrier-mediated encapsulation not only increases the half-life of the peptides in vivo but also aids in the targeted delivery. Despite its structural complexity, they also efficiently deliver therapeutic molecules across the blood-brain barrier. Here, in this review, we tried to emphasize the possible potentiality of metallic nanoparticles to be used as an efficient peptide delivery system against brain tumors and neurodegenerative disorders. SIGNIFICANCE STATEMENT: In this review, we have emphasized the various therapeutic applications of peptides/proteins, including antimicrobial, anticancer, anti-inflammatory, and neurodegenerative diseases. We also focused on these peptides' challenges under physiological conditions after administration. We highlighted the importance and potentiality of metallic nanocarriers in the ability to cross the blood-brain barrier, increasing the stability and half-life of peptides, their efficiency in targeting the delivery, and their diagnostic applications.

Hydrogen-rich medium ameliorates lipopolysaccharides-induced mitochondrial fission and dysfunction in human umbilical vein endothelial cells (HUVECs) via up-regulating HO-1 expression

BACKGROUND

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. It has been showed that the change of mitochondrial dynamics has been proved to be one of the main causes of death in patients with severe sepsis. And hydrogen has been proved to exert its protective effects against sepsis via heme oxygenase-1 (HO-1). This study was designed to demonstrate that whether the benefit effects of hydrogen can maintain the dynamic process of mitochondrial fusion/fission to mitigate human umbilical vein endothelial cells (HUVECs) injury exposed to endotoxin through HO-1.

METHODS

HUVECs cells cultured with medium which contained Lipopolysaccharides (LPS), Saline, hydrogen, Mdivi-1 (a dynamin-related protein 1 [Drp1] inhibitor) or zinc protoporphyrin IX (Znpp) (a HO-1 inhibitor) were also used in the research. Cell death and apoptosis were assessed using FITC annexin V and PI. Mitochondria were stained with Mitotracker orange and observed by confocal microscope. Oxygen consumption rate was assessed by seahorse xf24 extracellular analyzer. Mitochondrial membrane potential monitored by JC-1 dye. The expressions of Drp1 and HO-1 were tested by Western blot. The co-localization of Drp1 and mitochondria was determined by immunofluorescence.

RESULTS

LPS caused a decrease in ATP content, mitochondrial membrane potential, and maximal respiration rate. At the same time, increased expression of Drp1 were observed in LPS-stimulated HUVECs, concomitantly with excessive mitochondrial fission. We found that hydrogen-rich medium can increase ATP content, mitochondrial membrane potential and maximal respiration rate, and decrease the expression of Drp1 in LPS-treated HUVECs. Meanwhile, hydrogen can ameliorate excessive mitochondrial fission caused by LPS. Furthermore, hydrogen-rich medium had a similar effect to Mdivi-1, a mitochondrial fission blocker. Both of them rescued the up-regulation of Drp1 and mitochondrial fission induced by LPS, then normalized mitochondrial shape after LPS stimulation. But after Znpp pretreatment, HO-1 expression was inhibited and the protective effects of hydrogen were abrogated.

CONCLUSIONS

Hydrogen-rich medium can alleviate the LPS-induced mitochondrial fusion/fission and dysfunction in HUVECs via HO-1 up-regulation.

Glymphatic System: Emerging Therapeutic Target for Neurological Diseases

The newly discovered glymphatic system acts as pseudolymphatic vessels subserving brain waste clearance and is functionally dependent on astrocytic aquaporin-4 channels. The glymphatic system primarily functions during sleep as an interchange between cerebrospinal fluid and interstitial fluid, with cerebrospinal fluid flowing into the parenchyma via the perivascular spaces and then exchanging with interstitial fluid. The discovery of meningeal lymphatics helps refine the conceptual framework of glymphatic pathway, as certain waste products collected alongside perivascular spaces ultimately drain into the cervical lymph nodes via meningeal lymphatics, whose function regulates the functioning of the glymphatic system. The glymphatic and meningeal lymphatic systems are critical for the homeostasis of central nervous system, and their malfunctions complicate cerebral dysfunction and diseases. The present review will shed light on the structure, regulation, functions, and interrelationships of the glymphatic system and meningeal lymphatics. We will also expound on their impairments and corresponding targeted intervention in neurodegenerative diseases, traumatic brain injury, stroke, and infectious/autoimmune diseases, offering valuable references for future research.

Suberoylanilide hydroxamic acid suppresses axonal damage and neurological dysfunction after subarachnoid hemorrhage via the HDAC1/HSP70/TDP-43 axis

Increased focus has been placed on the role of histone deacetylase inhibitors as crucial players in subarachnoid hemorrhage (SAH) progression. Therefore, this study was designed to expand the understanding of SAH by exploring the downstream mechanism of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) in SAH. The expression of TDP-43 in patients with SAH and rat models of SAH was measured. Then, western blot analysis, immunofluorescence staining, and transmission electron microscope were used to investigate the in vitro effect of TDP-43 on a neuronal cell model of SAH established by oxyhemoglobin treatment. Immunofluorescence staining and coimmunoprecipitation assays were conducted to explore the relationship among histone deacetylase 1 (HDAC1), heat shock protein 70 (HSP70), and TDP-43. Furthermore, the in vivo effect of HDAC1 on SAH was investigated in rat models of SAH established by endovascular perforation. High expression of TDP-43 in the cerebrospinal fluid of patients with SAH and brain tissues of rat models of SAH was observed, and TDP-43 accumulation in the cytoplasm and the formation of inclusion bodies were responsible for axonal damage, abnormal nuclear membrane morphology, and apoptosis in neurons. TDP-43 degradation was promoted by the HDAC1 inhibitor SAHA via the acetylation of HSP70, alleviating SAH, and this effect was verified in vivo in rat models. In conclusion, SAHA relieved axonal damage and neurological dysfunction after SAH via the HSP70 acetylation-induced degradation of TDP-43, highlighting a novel therapeutic target for SAH.

Carbon Monoxide Protects Neural Stem Cells Against Iron Overload by Modulating the Crosstalk Between Nrf2 and NF-κB Signaling

Although accumulating evidences have demonstrated pro-survival effects of CO against various insults, the precise mechanism explaining how neural stem cells (NSCs) are protected by CO also remains largely unknown. Here we report CO pro-survival effect on NSCs against iron overload was comparable to that obtained with pharmacological inhibitors of reactive oxygen species (ROS). Its pro-survival effect was accompanied by the inhibition of ROS and subsequent inhibition of NF-κB which is mediated through nuclear factor erythroid 2-related factor 2 (Nrf2), in that activation of Nrf2 by CO inhibited ROS via up-regulation of NQO-1 while down-regulation of Nrf2 reversed the pro-survival effect of CO both in vitro and in vivo. CO-mediated preconditioning results in Nrf2 up-regulation and NF-κB inhibition, suggesting that these two pathways act in an inverse manner to maintain redox homeostasis. Our findings revealed CO preconditioning as a promising treatment strategy to improve efficacy of NSCs transplantation after hemorrhagic stroke.

The role of ferroptosis in acute lung injury

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a common disease with high morbidity and mortality, and its pathogenesis is believed to be related to oxidative stress, apoptosis, inflammation, and hypoxia. Ferroptosis is a type of nonapoptotic cell death characterized by iron-dependent lipid peroxide accumulation and is involved in many cellular physiological processes. Recent studies have confirmed that ferroptosis may be involved in the development of ALI. This review summarizes the most recent discoveries on the role of ferroptosis in ALI to provide new strategies for its prevention and treatment.

Hot head-out water immersion does not acutely alter dynamic cerebral autoregulation or cerebrovascular reactivity to hypercapnia

Recurring hot head-out water immersion (HOWI) enhances peripheral vascular function and cerebral blood velocity during non-immersion conditions. However, it is unknown if an acute bout of hot HOWI alters cerebrovascular function. Using two experimental studies, we tested the hypotheses that dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity (CVR) are improved during an acute bout of hot (HOT; 39 °C) vs. thermoneutral (TN; 35 °C) HOWI. Eighteen healthy participants (eight females) completed the dCA study, and 14 participants (6 females) completed the CVR study. Both studies consisted of two randomized (TNdCA vs. HOTdCA; TNCVR vs. HOTCVR) 45minute HOWI visits. Middle cerebral artery blood velocity (MCAvmean) was continuously recorded. dCA was assessed using a respiratory impedance device and analyzed via transfer gain and phase in the low-frequency band. CVR was assessed using stepped hypercapnia. Assessments were completed PRE and 30 minutes into HOWI. Values are reported as a change (Δ) from PRE (mean ± SD). There were no differences at PRE for either study. ΔMCAvmean was greater in TNdCA (TNdCA: 4 ± 4 vs. HOTdCA: -3 ± 5 cm/s; P < 0.01) and TNCVR (TNCVR: 5 ± 4 vs. HOTCVR: -1 ± 6 cm/s; P < 0.01) during HOWI. ΔGain was greater in HOTdCA during HOWI (TNdCA: -0.09 ± 0.15 vs. HOTdCA: 0.10 ± 0.17 cm/s/mmHg; P = 0.04). ΔPhase (P > 0.84) and ΔCVR (P > 0.94) were not different between conditions. These data indicate that hot and thermoneutral water immersion do not acutely alter cerebrovascular function in healthy, young adults.

Role of heat shock proteins in aging and chronic inflammatory diseases

Advanced age is associated with a decline in response to stress. This contributes to the establishment of chronic inflammation, one of the hallmarks of aging and age-related disease. Heat shock proteins (HSP) are determinants of life span, and their progressive malfunction leads to age-related pathology. To discuss the function of HSP on age-related chronic inflammation and illness. An updated review of literature and discussion of relevant work on the topic of HSP in normal aging and chronic inflammatory pathology was performed. HSP contribute to inflamm-aging. They also play a key role in age-associated pathology linked to chronic inflammation such as autoimmune disorders, neurological disease, cardiovascular disorder, and cancer. HSP may be targeted for control of their effects related to age and chronic inflammation. Research on HSP functions in age-linked chronic inflammatory disorders provides an opportunity to improve health span and delay age-related chronic disorders.

Neuroprotective and Angiogenesis Effects of Levetiracetam Following Ischemic Stroke in Rats

Objective: The present study explored whether levetiracetam (LEV) could protect against experimental brain ischemia and enhance angiogenesis in rats, and investigated the potential mechanisms in vivo and in vitro.

Methods: The middle cerebral artery was occluded for 60 min to induce middle cerebral artery occlusion (MCAO). The Morris water maze was used to measure cognitive ability. The rotation test was used to assess locomotor function. T2-weighted MRI was used to assess infarct volume. The neuronal cells in the cortex area were stained with cresyl purple. The anti-inflammatory effects of LEV on microglia were observed by immunohistochemistry. Enzyme-linked immunosorbent assays (ELISA) were used to measure the production of pro-inflammatory cytokines. Western blotting was used to detect the levels of heat shock protein 70 (HSP70), vascular endothelial growth factor (VEGF), and hypoxia-inducible factor-1α (HIF-1α) in extracts from the ischemic cortex. Flow cytometry was used to observe the effect of LEV on neuronal cell apoptosis.

Results: LEV treatment significantly increased the density of the surviving neurons in the cerebral cortex and reduced the infarct size (17.8 ± 3.3% vs. 12.9 ± 1.4%, p < 0.01) after MCAO. Concurrently, the time required to reach the platform for LEV-treated rats was shorter than that in the saline group on day 11 after MCAO (p < 0.01). LEV treatment prolonged the rotarod retention time on day 14 after MCAO (84.5 ± 6.7 s vs. 59.1 ± 6.2 s on day 14 compared with the saline-treated groups, p < 0.01). It also suppressed the activation of microglia and inhibited TNF-α and Il-1β in the ischemic brain (135.6 ± 5.2 pg/ml vs. 255.3 ± 12.5 pg/ml, 18.5 ± 1.3 pg/ml vs. 38.9 ± 2.3 pg/ml on day 14 compared with the saline-treated groups, p < 0.01). LEV treatment resulted in a significant increase in HIF-1α, VEGF, and HSP70 levels in extracts from the ischemic cerebral cortex. At the same time, LEV reduced neuronal cell cytotoxicity and apoptosis induced by an ischemic stroke (p < 0.01).

Conclusion: LEV treatment promoted angiogenesis and functional recovery after cerebral ischemia in rats. These effects seem to be mediated through anti-inflammatory and antiapoptotic activities, as well as inducing the expression of HSP70, VEGF, and HIF-1α.

Novel Technologies in Studying Brain Immune Response

Over the past few decades, the immune system, including both the adaptive and innate immune systems, proved to be essential and critical to brain damage and recovery in the pathogenesis of several diseases, opening a new avenue for developing new immunomodulatory therapies and novel treatments for many neurological diseases. However, due to the specificity and structural complexity of the central nervous system (CNS), and the limit of the related technologies, the biology of the immune response in the brain is still poorly understood. Here, we discuss the application of novel technologies in studying the brain immune response, including single-cell RNA analysis, cytometry by time-of-flight, and whole-genome transcriptomic and proteomic analysis. We believe that advancements in technology related to immune research will provide an optimistic future for brain repair.

The Updated Role of the Blood Brain Barrier in Subarachnoid Hemorrhage: From Basic and Clinical Studies

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke associated with high mortality and morbidity. The blood-brain-barrier (BBB) is a structure consisting primarily of cerebral microvascular endothelial cells, end feet of astrocytes, extracellular matrix, and pericytes. Post-SAH pathophysiology included early brain injury and delayed cerebral ischemia. BBB disruption was a critical mechanism of early brain injury and was associated with other pathophysiological events. These pathophysiological events may propel the development of secondary brain injury, known as delayed cerebral ischemia. Imaging advancements to measure BBB after SAH primarily focused on exploring innovative methods to predict clinical outcome, delayed cerebral ischemia, and delayed infarction related to delayed cerebral ischemia in acute periods. These predictions are based on detecting abnormal changes in BBB permeability. The parameters of BBB permeability are described by changes in computed tomography (CT) perfusion and magnetic resonance imaging (MRI). K_ep seems to be a stable and sensitive indicator in CT perfusion, whereas K^trans is a reliable parameter for dynamic contrast-enhanced MRI. Future prediction models that utilize both the volume of BBB disruption and stable parameters of BBB may be a promising direction to develop practical clinical tools. These tools could provide greater accuracy in predicting clinical outcome and risk of deterioration. Therapeutic interventional exploration targeting BBB disruption is also promising, considering the extended duration of post-SAH BBB disruption.

Osteopontin as a candidate of therapeutic application for the acute brain injury

Acute brain injury is the leading cause of human death and disability worldwide, which includes intracerebral haemorrhage, subarachnoid haemorrhage, cerebral ischaemia, traumatic brain injury and hypoxia‐ischaemia brain injury. Currently, clinical treatments for neurological dysfunction of acute brain injury have not been satisfactory. Osteopontin (OPN) is a complex adhesion protein and cytokine that interacts with multiple receptors including integrins and CD44 variants, exhibiting mostly neuroprotective roles and showing therapeutic potential for acute brain injury. OPN‐induced tissue remodelling and functional repair mainly rely on its positive roles in the coordination of pro‐inflammatory and anti‐inflammatory responses, blood‐brain barrier maintenance and anti‐apoptotic actions, as well as other mechanisms such as affecting the chemotaxis and proliferation of nerve cells. The blood OPN strongly parallel with the OPN induced in the brain and can be used as a novel biomarker of the susceptibility, severity and outcome of acute brain injury. In the present review, we summarized the molecular signalling mechanisms of OPN as well as its overall role in different kinds of acute brain injury.

Underlying Mechanisms and Potential Therapeutic Molecular Targets in Blood-Brain Barrier Disruption after Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a subtype of hemorrhagic stroke with significant morbidity and mortality. Aneurysmal bleeding causes elevated intracranial pressure, decreased cerebral blood flow, global cerebral ischemia, brain edema, blood component extravasation, and accumulation of breakdown products. These post-SAH injuries can disrupt the integrity and function of the blood-brain barrier (BBB), and brain tissues are directly exposed to the neurotoxic blood contents and immune cells, which leads to secondary brain injuries including inflammation and oxidative stress, and other cascades. Though the exact mechanisms are not fully clarified, multiple interconnected and/or independent signaling pathways have been reported to be involved in BBB disruption after SAH. In addition, alleviation of BBB disruption through various pathways or chemicals has a neuroprotective effect on SAH. Hence, BBB permeability plays an important role in the pathological course and outcomes of SAH. This review discusses the recent understandings of the underlying mechanisms and potential therapeutic targets in BBB disruption after SAH, emphasizing the dysfunction of tight junctions and endothelial cells in the development of BBB disruption. The emerging molecular targets, including toll-like receptor 4, netrin-1, lipocalin-2, tropomyosin-related kinase receptor B, and receptor tyrosine kinase ErbB4, are also summarized in detail. Finally, we discussed the emerging treatments for BBB disruption after SAH and put forward our perspectives on future research.

The role and therapeutic potential of heat shock proteins in haemorrhagic stroke

Heat shock proteins (HSPs) are induced after haemorrhagic stroke, which includes subarachnoid haemorrhage (SAH) and intracerebral haemorrhage (ICH). Most of these proteins function as neuroprotective molecules to protect cerebral neurons from haemorrhagic stroke and as markers to indicate cellular stress or damage. The most widely studied HSPs in SAH are HSP70, haeme oxygenase-1 (HO-1), HSP20 and HSP27. The subsequent pathophysiological changes following SAH can be divided into two stages: early brain injury and delayed cerebral ischaemia, both of which determine the outcome for patients. Because the mechanisms of HSPs in SAH are being revealed and experimental models in animals are continually maturing, new agents targeting HSPs with limited side effects have been suggested to provide therapeutic potential. For instance, some pharmaceutical agents can block neuronal apoptosis signals or dilate cerebral vessels by modulating HSPs. HO-1 and HSP70 are also critical topics for ICH research, which can be attributed to their involvement in pathophysiological mechanisms and therapeutic potential. However, the process of HO-1 metabolism can be toxic owing to iron overload and the activation of succedent pathways, for example, the Fenton reaction and oxidative damage; the overall effect of HO-1 in SAH and ICH tends to be protective and harmful, respectively, given the different pathophysiological changes in these two types of haemorrhagic stroke. In the present study, we focus on the current understanding of the role and therapeutic potential of HSPs involved in haemorrhagic stroke. Therefore, HSPs may be potential therapeutic targets, and new agents targeting HSPs are warranted.