Melatonin attenuates inflammatory response-induced brain edema in early brain injury following a subarachnoid hemorrhage: a possible role for the regulation of pro-inflammatory cytokines

Causal Relationships Between Gut Microbiota, Inflammatory Cells/Proteins, and Subarachnoid Hemorrhage: A Multi-omics Bidirectional Mendelian Randomization Study and Meta-analysis

Subarachnoid hemorrhage (SAH) is a neurological emergency that can lead to fatal outcomes. It occurs when bleeding happens in the subarachnoid space, a small gap between the arachnoid and pia mater. This condition results from the rupture of diseased or damaged blood vessels at the brain's base or surface. This study combined various omics approaches with Mendelian randomization analysis, including MR-IVW, MR Egger, MR weight median, and MR weight mode, to generate preliminary results. It also employed reverse Mendelian randomization, treating SAH as the exposure. Finally, a meta-analysis was conducted to summarize these findings. The study found positive correlations between SAH and both GBPA-Pyridoxal 5 phosphate biosynthesis I (OR=1.48, 95% CI, 1.04-2.12) and GBPA-glucose biosynthesis I (OR=0.68, 95% CI, 0.52-0.90). Increased levels of urokinase-type plasma activator were also associated with SAH (OR=1.17, 95% CI, 1.04-1.32). Associations were observed with SAH for CD80 on CD62L+ plasmacytoid dendritic cells, CD80 on plasmacytoid dendritic cells, CD123 on CD62L+ plasmacytoid dendritic cells, and SSC-A on plasmacytoid dendritic cells. This study, through Mendelian randomization and meta-analysis, established links between SAH and four inflammatory cells, one inflammatory protein, and two gut microbiota-related pathways. These findings suggest potential treatment targets for SAH, highlighting the importance of modulating gut microbiota and utilizing anti-inflammatory drugs in its management.

Netrin-1 Alleviates Early Brain Injury by Regulating Ferroptosis via the PPARγ/Nrf2/GPX4 Signaling Pathway Following Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a type of stroke with high morbidity and mortality. Netrin-1 (NTN-1) can alleviate early brain injury (EBI) following SAH by enhancing peroxisome proliferator-activated receptor gamma (PPARγ), which is an important transcriptional factor modulating lipid metabolism. Ferroptosis is a newly discovered type of cell death related to lipid metabolism. However, the specific function of ferroptosis in NTN-1-mediated neuroprotection following SAH is still unclear. This study aimed to evaluate the neuroprotective effects and the possible molecular basis of NTN-1 in SAH-induced EBI by modulating neuronal ferroptosis using the filament perforations model of SAH in mice and the hemin-stimulated neuron injury model in HT22 cells. NTN-1 or a vehicle was administered 2 h following SAH. We examined neuronal death, brain water content, neurological score, and mortality. NTN-1 treatment led to elevated survival probability, greater survival of neurons, and increased neurological score, indicating that NTN-1-inhibited ferroptosis ameliorated neuron death in vivo/in vitro in response to SAH. Furthermore, NTN-1 treatment enhanced the expression of PPARγ, nuclear factor erythroid 2-related factor 2 (Nrf2), and glutathione peroxidase 4 (GPX4), which are essential regulators of ferroptosis in EBI after SAH. The findings show that NTN-1 improves neurological outcomes in mice and protects neurons from death caused by neuronal ferroptosis. Furthermore, the mechanism underlying NTN-1 neuroprotection is correlated with the inhibition of ferroptosis, attenuating cell death via the PPARγ/Nrf2/GPX4 pathway and coenzyme Q10-ferroptosis suppressor protein 1 (CoQ10-FSP1) pathway.

Circulating inflammatory biomarkers and risk of intracranial aneurysm: a Mendelian randomization study

BACKGROUND

Intracranial aneurysm (IA) accounts for a substantial source of non-traumatic subarachnoid hemorrhage, with inflammation postulated as a potential factor in its pathogenesis. The present study aims at evaluating the association between circulating inflammatory cytokines and risk of IA under a bidirectional two-sample Mendelian randomization (MR) design.

METHODS

For primary analysis, summary statistics of inflammatory regulators was obtained from a genome-wide association study (GWAS) comprising 8293 Finnish participants. Summary data of IA were extracted from a GWAS which comprised 7495 cases and 71,934 controls in European descent. For targeted analysis, summary statistics were extracted from two proteomic studies, which recruit 3301 and 5368 European participants, respectively. Summary data of IA were acquired from FinnGen study with 5342 cases and 342,673 controls. We employed inverse variance weighted (IVW) method as main approach, with sensitivity analyses using weighted median, MR-Egger, and MR-PRESSO methods. Reverse MR analyses were conducted to minimize bias from reverse causality.

RESULTS

No causation of cytokines with IA subtypes was identified in both primary and targeted analysis after Bonferroni correction. In primary analysis, vascular endothelial growth factor (VEGF) and fibroblast growth factor basic (bFGF) levels were suggestively associated with aneurysmal subarachnoid hemorrhage (aSAH) [VEGF → aSAH: OR = 1.15, 95%CI  1.04-1.26, P = 0.005; bFGF → aSAH: OR = 0.62, 95% CI 0.42-0.92, P = 0.02]. Statistical significance failed to replicate in targeted analysis. Instead, suggestive protective effects for aSAH were identified in FGF-9 (FGF-9 → aSAH: OR = 0.74, 95% CI 0.62-0.89, P = 0.001) and FGF-16 (FGF-16 → aSAH: OR = 0.84, 95% CI 0.72-0.97, P = 0.017). Furthermore, reverse analyses identified suggestive effect of unruptured IA on RANTES, MIF, GRO-alpha, FGF-16, and FGF-19. Result remained robust after applying sensitivity tests.

CONCLUSIONS

No causality of inflammatory biomarkers on the risk of IA subtypes was identified. Future large-scale studies are in need to evaluate the temporal dynamics of cytokines in conjunction with IA.

Melatonin alleviates early brain injury by inhibiting the NRF2-mediated ferroptosis pathway after subarachnoid hemorrhage

Ferroptosis is a novel form of cell death that plays a critical role in the pathological and physiological processes of early brain injury following subarachnoid hemorrhage. Melatonin, as the most potent endogenous antioxidant, has shown strong protective effects against pathological changes following subarachnoid hemorrhage, but its impact on ferroptosis induced by subarachnoid hemorrhage remains unexplored. In our study, we established a subarachnoid hemorrhage model in male SD rats. We found that subarachnoid hemorrhage induced changes in ferroptosis-related indicators such as lipid peroxidation and iron metabolism, while intraperitoneal injection of melatonin (40 mg/kg) effectively ameliorated these changes to a certain degree. Moreover, in a subset of rats with subarachnoid hemorrhage who received pre-treatment via intravenous injection of the melatonin receptor antagonist Luzindole (1 mg/kg) and 4P-PDOT (1 mg/kg), we found that the protective effect of melatonin against subarachnoid hemorrhage includes inhibition of lipid peroxidation and reduction of iron accumulation depended on melatonin receptor 1B (MT2). Furthermore, our study demonstrated that melatonin inhibited neuronal ferroptosis by activating the NRF2 signaling pathway, as evidenced by in vivo inhibition of NRF2. In summary, melatonin acts through MT2 and activates NRF2 and downstream genes such as HO-1/NQO1 to inhibit ferroptosis in subarachnoid hemorrhage-induced neuronal injury, thereby improving neurological function in rats. These results suggest that melatonin is a promising therapeutic target for subarachnoid hemorrhage.

Melatonin intervention to prevent delirium in the intensive care units: a systematic review and meta-analysis of randomized controlled trials

Objective

To determine the preventive effect of melatonin on delirium in the intensive care units.

Methods

We conducted a systematic search of the PubMed, Cochrane Library, Science, Embase, and CNKI databases, with retrieval dates ranging from the databases' inception to September 2022. Controlled trials on melatonin and placebo for preventing delirium in the intensive care units were included. The meta-analysis was performed using Review Manager software (version 5.3) and Stata software (version 14.0).

Results

Six studies involving 2374 patients were included in the meta-analysis. The results of the meta-analysis showed that melatonin did not reduce the incidence of delirium in ICU patients (odds ratio [OR]: 0.71; 95% confidence interval [CI]: 0.46 to 1.12; p = 0.14). There was a strong hetero-geneity between the selected studies (I2 = 74%). Subgroup analysis results showed that melatonin reduced the incidence of delirium in cardiovascular care unit (CCU) patients (OR: 0.52; 95% CI: 0.37 to 0.73; p=0.0001), but did not in general intensive care unit (GICU) patients (OR: 1.14; 95% CI: 0.86 to 1.50; p=0.35). In terms of the secondary outcomes, there were no significant differences in all-cause mortality (OR: 0.85; 95% CI: 0.66 to 1.09; p=0.20), length of ICU stay (mean difference [MD]: 0.33; 95% CI: -0.53 to 1.18; p=0.45), or length of hospital stay (MD: 0.51; 95% CI: -1.17 to 2.19; p=0.55).

Conclusion

Melatonin reduced the incidence of delirium in CCU patients, but did not significantly reduce the incidence of delirium in GICU patients.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022367665.

Melatonin Ameliorates Apoptosis of A549 Cells Exposed to Chicken House PM2.5: A Novel Insight in Poultry Production

The particulate matter 2.5 (PM_2.5) from the chicken production system can cause lung injury and reduce productivity through prolonged breath as it attaches large amounts of harmful substances and microbes. Melatonin has acted to regulate physiological and metabolic disorders and improve growth performance during poultry production. This research would investigate the apoptosis caused by chicken house PM_2.5 on lung pulmonary epithelial cells and the protective action of melatonin. Here, the basal epithelial cells of human lung adenocarcinoma (A549 cells) were subjected to PM_2.5 from the broiler breeding house to investigate the apoptosis induced by PM_2.5 as well as the alleviation of melatonin. The apoptosis was aggravated by PM_2.5 (12.5 and 25 μg/mL) substantially, and the expression of Bcl-2, Bad, Bax, PERK, and CHOP increased dramatically after PM_2.5 treatment. Additionally, the up-regulation of cleaved caspase-9 and cleaved caspase-3 as well as endoplasmic reticulum stress (ERS)-related proteins, including ATF6 and CHOP, was observed due to PM_2.5 exposure. It is worth noting that melatonin could support A549 cells' survival, in which reduced expression of Bax, Bad, cleaved caspase-3, and cleaved caspase-9 appeared. Concurrently, the level of malondialdehyde (MDA) was down-regulated and enhanced the intracellular content of total superoxide dismutase (T-SOD) and catalase (CAT) after treatment by PM_2.5 together with melatonin. Collectively, our study underlined that melatonin exerted an anti-apoptotic action on A549 cells by strengthening their antioxidant capacity.

Matrine exerts its neuroprotective effects by modulating multiple neuronal pathways

Recent evidence suggests that misfolding, clumping, and accumulation of proteins in the brain may be common causes and pathogenic mechanism for several neurological illnesses. This causes neuronal structural deterioration and disruption of neural circuits. Research from various fields supports this idea, indicating that developing a single treatment for several severe conditions might be possible. Phytochemicals from medicinal plants play an essential part in maintaining the brain's chemical equilibrium by affecting the proximity of neurons. Matrine is a tetracyclo-quinolizidine alkaloid derived from the plant Sophora flavescens Aiton. Matrine has been shown to have a therapeutic effect on Multiple Sclerosis, Alzheimer's disease, and various other neurological disorders. Numerous studies have demonstrated that matrine protects neurons by altering multiple signalling pathways and crossing the blood-brain barrier. As a result, matrine may have therapeutic utility in the treatment of a variety of neurocomplications. This work aims to serve as a foundation for future clinical research by reviewing the current state of matrine as a neuroprotective agent and its potential therapeutic application in treating neurodegenerative and neuropsychiatric illnesses. Future research will answer many concerns and lead to fascinating discoveries that could impact other aspects of matrine.

Neuroprotective Effects of Piceatannol on Olfactory Bulb Injury after Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) accounts for 5% of all stroke cases and is responsible for significant permanent brain and neurological damage within the first few days. Loss of smell is one of those neurological disorders following olfactory bulb injury after SAH. Olfaction plays a critical role in several aspects of life. The primary underlying mechanism of olfactory bulb (OB) injury and loss of smell after SAH remains unknown. Piceatannol (PIC), a natural stilbene, possesses anti-inflammatory and anti-apoptotic effects against various diseases. In this study, we aimed to investigate the potential therapeutic effects of PIC on OB injury following SAH at molecular mechanism based on SIRT1, inflammatory (TNF-α, IL1-β, NF-κB, IL-6, TLR4), and apoptosis (p53, Bax, Bcl-2, caspase-3)-related gene expression markers and histopathology level; 27 male Wistar Albino rats were used in a pre-chiasmatic subarachnoid hemorrhage model. Animals were divided into groups (n = 9): SHAM, SAH, and PIC. Garcia's neurological examination, brain water content, RT-PCR, histopathology, and TUNEL analyses were performed in all experimental groups with OB samples. Our results indicated that PIC administration significantly suppressed inflammatory molecules (TNF-α, IL-6, IL1-β, TLR4, NF-κB, SIRT1) and apoptotic molecules (caspase-3, p53, Bax). We also evaluated edema levels and cell damage in OB injury after SAH. Ameliorative effects of PIC are also observed at the histopathology level. Garcia's neurological score test performed a neurological assessment. This study is the first to demonstrate the neuroprotective effects of PIC on OB injury after SAH. It suggests that PIC would be a potential therapeutic agent for alleviating OB injury after SAH.

Inflammation and immune cell abnormalities in intracranial aneurysm subarachnoid hemorrhage (SAH): Relevant signaling pathways and therapeutic strategies

Intracranial aneurysm subarachnoid hemorrhage (SAH) is a cerebrovascular disorder associated with high overall mortality. Currently, the underlying mechanisms of pathological reaction after aneurysm rupture are still unclear, especially in the immune microenvironment, inflammation, and relevant signaling pathways. SAH-induced immune cell population alteration, immune inflammatory signaling pathway activation, and active substance generation are associated with pro-inflammatory cytokines, immunosuppression, and brain injury. Crosstalk between immune disorders and hyperactivation of inflammatory signals aggravated the devastating consequences of brain injury and cerebral vasospasm and increased the risk of infection. In this review, we discussed the role of inflammation and immune cell responses in the occurrence and development of aneurysm SAH, as well as the most relevant immune inflammatory signaling pathways [PI3K/Akt, extracellular signal-regulated kinase (ERK), hypoxia-inducible factor-1α (HIF-1α), STAT, SIRT, mammalian target of rapamycin (mTOR), NLRP3, TLR4/nuclear factor-κB (NF-κB), and Keap1/nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/ARE cascades] and biomarkers in aneurysm SAH. In addition, we also summarized potential therapeutic drugs targeting the aneurysm SAH immune inflammatory responses, such as nimodipine, dexmedetomidine (DEX), fingolimod, and genomic variation-related aneurysm prophylactic agent sunitinib. The intervention of immune inflammatory responses and immune microenvironment significantly reduces the secondary brain injury, thereby improving the prognosis of patients admitted to SAH. Future studies should focus on exploring potential immune inflammatory mechanisms and developing additional therapeutic strategies for precise aneurysm SAH immune inflammatory regulation and genomic variants associated with aneurysm formation.

Melatonin as a Potential Neuroprotectant: Mechanisms in Subarachnoid Hemorrhage-Induced Early Brain Injury

Subarachnoid hemorrhage (SAH) is a common cerebrovascular disease with high mortality and disability rates. Despite progressive advances in drugs and surgical techniques, neurological dysfunction in surviving SAH patients have not improved significantly. Traditionally, vasospasm has been considered the main cause of death and disability following SAH, but anti-vasospasm therapy has not benefited clinical prognosis. Many studies have proposed that early brain injury (EBI) may be the primary factor influencing the prognosis of SAH. Melatonin is an indole hormone and is the main hormone secreted by the pineal gland, with low daytime secretion levels and high nighttime secretion levels. Melatonin produces a wide range of biological effects through the neuroimmune endocrine network, and participates in various physiological activities in the central nervous system, reproductive system, immune system, and digestive system. Numerous studies have reported that melatonin has extensive physiological and pharmacological effects such as anti-oxidative stress, anti-inflammation, maintaining circadian rhythm, and regulating cellular and humoral immunity. In recent years, more and more studies have been conducted to explore the molecular mechanism underlying melatonin-induced neuroprotection. The studies suggest beneficial effects in the recovery of intracerebral hemorrhage, cerebral ischemia-reperfusion injury, spinal cord injury, Alzheimer’s disease, Parkinson’s disease and meningitis through anti-inflammatory, antioxidant and anti-apoptotic mechanisms. This review summarizes the recent studies on the application and mechanism of melatonin in SAH.

2-Methoxyestradiol Alleviates Neuroinflammation and Brain Edema in Early Brain Injury After Subarachnoid Hemorrhage in Rats

Objective

Numerous studies have shown that neuroinflammation and brain edema play an important role in early brain injury (EBI) after subarachnoid hemorrhage (SAH). 2-Methoxyestradiol (2-ME) has been shown to have anti-inflammatory and anti-angiogenic effects. This study aimed to investigate the effects of 2-ME on neuroinflammation and brain edema after SAH and its underlying mechanism of action.

Methods

Rats were used to produce an endovascular puncture model of SAH. 2-ME or the control agent was injected intraperitoneally 1 h after SAH induction. At 24 h after surgery, the neurological score, SAH grading, brain water content, and blood–brain barrier (BBB) permeability were examined. The microglial activation level in the rat brain tissue was determined using immunofluorescence staining, whereas the cell apoptosis in the rat brain tissue was assessed using terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, the levels of Interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α were measured by enzyme linked immunosorbent assay, and the expression levels of ZO-1, occludin, hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and matrix metallopeptidase (MMP)-9 in the rat brain tissue were determined using western blotting.

Results

Twenty-four hours after SAH, brain water content, BBB permeability, microglial activation, and cell apoptosis were significantly increased, whereas neurological function deteriorated significantly in rats. Treatment with 2-ME significantly decreased brain water content, BBB permeability, microglial cell activation, and cell apoptosis and improved neurological dysfunction in rats. Treatment with 2-ME reduced the expression levels of inflammatory factors (IL-1β, IL-6, and TNF-α), which were significantly elevated 24 h after SAH. Treatment with 2-ME alleviated the disruption of tight junction proteins (ZO-1 and occludin), which significantly decreased 24 h after SAH. To further determine the mechanism of this protective effect, we found that 2-ME inhibited the expression of HIF-1α, MMP-9, and VEGF, which was associated with the inflammatory response to EBI and BBB disruption after SAH.

Conclusion

2-ME alleviated neuroinflammation and brain edema as well as improved neurological deficits after SAH in rats. The neuroprotective effect of 2-ME on EBI after SAH in rats may be related to the inhibition of neuroinflammation and brain edema.

The Novel Nrf2 Activator Omaveloxolone Regulates Microglia Phenotype and Ameliorates Secondary Brain Injury after Intracerebral Hemorrhage in Mice

The polarization of microglia is recognized as a crucial factor in reducing neuroinflammation and promoting hematoma clearance after intracerebral hemorrhage (ICH). Previous studies have revealed that redox components participate in the regulation of microglial polarization. Recently, the novel Nrf2 activator omaveloxolone (Omav) has been validated to improve neurological function in patients with neurodegenerative disorders by regulating antioxidant responses. In this study, we examined the efficacy of Omav in ICH. Omav significantly promoted Nrf2 nuclear accumulation and the expression of HO-1 and NQO1 in BV2 cells. In addition, both in vitro and in vivo experiments showed that Omav treatment inhibited M1-like activation and promoted the activation of the M2-like microglial phenotype. Omav inhibited OxyHb-induced ROS generation and preserved the function of mitochondria in BV2 cells. Intraperitoneal administration of Omav improved sensorimotor function in the ICH mouse model. Importantly, these effects were blocked by pretreatment with ML385, a selective inhibitor of Nrf2. Collectively, Omav modulated microglial polarization by activating Nrf2 and inhibiting ROS generation in ICH models, suggesting that it might be a promising drug candidate for the treatment of ICH.

COG133 Attenuates the Early Brain Injury Induced by Blood-Brain Barrier Disruption in Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a kind of severe hemorrhagic stroke, and early brain injury acted as one of the main causes of death and delayed neurological deficit in patients with subarachnoid hemorrhage. In this process, the function and structural integrity of the blood-brain barrier play an important role. In this study, we have observed whether the apolipoprotein E (apoE) mimetic peptide, COG133, can alleviate early brain injury after subarachnoid hemorrhage. For this purpose, an experimental subarachnoid hemorrhage model was constructed in mice and treated by intravenous injection of COG133 at a dosage of 1 mg/kg. Then, the function and integrity of the blood-brain barrier were detected, and the pyroptosis level of the neuron was determined. The results showed that COG133 could protect blood-brain barrier function and structure integrity, reduce early brain injury, and ameliorate neurological function after subarachnoid hemorrhage. In terms of molecular mechanism, COG133 inhibits blood-brain barrier destruction through the proinflammatory CypA-NF-κB-MMP9 pathway and reduces neuronal pyroptosis by inhibiting NLRP3 inflammasome activation. In conclusion, this study demonstrated that apoE-mimetic peptide, COG133, can play a neuroprotective role by protecting blood-brain barrier function and inhibiting brain cell pyroptosis to reduce early brain injury after subarachnoid hemorrhage.

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.

Inflammatory Cytokines are in Action: Brain Plasticity and Recovery after Brain Ischemia Due to Delayed Melatonin Administration

OBJECTIVES

Post-ischemic inflammation leads to apoptosis as an indirect cause of functional disabilities after the stroke. Melatonin may be a good candidate for the stroke recovery because of its anti-inflammatory effects. Therefore, we investigated the effect of melatonin on inflammation in the functional recovery of brain by evaluating ipsilesional and contralesional alterations.

MATERIALS AND METHODS

Melatonin (4 mg/kg/day) was intraperitoneally administered into the mice from the 3^rd to the 55^th day of the post-ischemia after 30 min of middle cerebral artery occlusion.

RESULTS

Melatonin produced a functional recovery by reducing the emigration of the circulatory leukocytes and the local microglial activation within the ischemic brain. Overall, the expression of the inflammation-related genes reduced upon melatonin treatment in the ischemic hemisphere. On the other hand, the expression level of the inflammatory cytokine genes raised in the contralateral hemisphere at the 55^th day of the post-ischemia. Furthermore, melatonin triggers an increase in the iNOS expression and a decrease in the nNOS expression in the ipsilateral hemisphere at the earlier times in the post-ischemic recovery. At the 55^th day of the post-ischemic recovery, melatonin administration enhanced the eNOS and nNOS protein expressions.

CONCLUSIONS

The present molecular, biological, and histological data have revealed broad anti-inflammatory effects of melatonin in both hemispheres with distinct temporal and spatial patterns at different phases of post-stroke recovery. These outcomes also established that melatonin act recruitment of contralesional rather than of ipsilesional.

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.

Profiling of T Cell Receptor β-Chain Complimentary Determining Regions 3 Repertoire in Subarachnoid Hemorrhage Patients Using High-Throughput Sequencing

Objective

The adaptive immune response following subarachnoid hemorrhage (SAH) is not well understood. We evaluated and compared the T cell receptor (TCR) immune repertoire of good-grade and poor-grade SAH patients to elucidate the T cell immunology after ictus.

Methods

Peripheral blood from six SAH patients was collected at two different times, admission and at the 7-day follow-up. Composition and variation of the TCR β-chain (TCRB) complimentary determining regions (CDR) 3 repertoire was examined using high-throughput sequencing; the analysis was based on sampling time and disease severity (good vs. poor-grade SAH).

Results

Clonality at admission and follow-up were 0.059 (0.037–0.038) and 0.027 (0.014–0.082) (median, 25th–75th percentile). Poor-grade SAH (0.025 [0.011–0.038]) was associated with significantly lower clonality than good-grade SAH (0.095 [0.079–0.101]). Poor-grade SAH patients had higher diversity scores than good-grade SAH patients. CDR length was shorter in good-grade SAH vs. poor-grade SAH. Differences in clonotype distribution were more prominent in TCRBV gene segments than TCRBJ segments. TCRBV19-01/TCRBJ02-04 and TCRBV28-01/TCRBJ02-04 were the most increased and the most decreased V-J pairs in the 7-day follow-up compared to admission in good-grade SAH. The most increased and decreased V-J pairs in poor-grade SAH patients were TCRBV28-01/TCRBJ02-06 and TCRBV30-01/TCRBJ02-04, respectively.

Conclusion

The TCRB repertoire is dynamic in nature following SAH. TCRB repertoire may facilitate our understanding of adaptive immune response according to SAH severity.

Protective effects of astaxanthin on lipopolysaccharide-induced inflammation in bovine endometrial epithelial cells†

Astaxanthin (AST), a natural antioxidant carotenoid, has been shown to exert anti-inflammatory effects. However, to our knowledge, no study has specifically addressed the potential protective effects of AST against bovine endometritis. The purpose of this study was to examine whether treatment with AST could protect endometrial epithelial cells against lipopolysaccharide (LPS)-induced inflammatory injury. Treatment of bovine endometrial (BEND) epithelial cell line with AST reduced LPS-induced production of interleukin-6 and tumor necrosis factor-alpha, increased the cellular activity of superoxide dismutase and catalase, decreased the proportion of apoptotic cells, and promoted the production of insulin-like growth factor and epithelial growth factor. The effects of AST were mediated through the downregulation of B-cell lymphoma 2 (Bcl-2) associated X, apoptosis regulator (Bax), and cleaved caspase-3 and through the upregulation of Bcl-2. Moreover, AST significantly increased the expression of the tight junction proteins (TJP) claudin, cadherin-1, and TJP1, which play an essential role in the maintenance of host endometrial defense barrier against pathogen infection. Collectively, these results demonstrated that treatment with AST protected against oxidative stress, prevented cell apoptosis, promoted BEND cells viability, and increased the production of growth factors, in addition to activating the endometrial defense barrier. Therefore, AST is a promising therapeutic agent for the prevention and treatment of endometritis. This finding is of utmost importance in the present times when the excessive use of antibiotics has resulted in the development of antibiotic-resistant bacteria.

Blood-brain barrier permeability imaging as a predictor for delayed cerebral ischaemia following subarachnoid haemorrhage. A narrative review

BACKGROUND

Aneurysmal subarachnoid haemorrhage is associated with significant morbidity and mortality due to the myriad of complications contributing to early brain injury and delayed cerebral ischaemia. There is increasing interest in the exploration of the association between blood-brain barrier integrity and risks of delayed cerebral ischaemia and poor outcomes. Despite recent advances in cerebral imaging, radiographic imaging of blood-brain barrier disruption, as a biomarker for outcome prediction, has not been adopted in clinical practice.

METHODS

We performed a narrative review by searching for articles describing molecular changes or radiological identification of changes in BBB permeability following subarachnoid haemorrhage (SAH) on MEDLINE. Preclinical studies were analysed if reported structural changes and clinical studies were included if they investigated for radiological markers of BBB disruption and its correlation with delayed cerebral ischaemia.

RESULTS

There is ample preclinical evidence to suggest that there are structural changes in BBB permeability following SAH. The available clinical literature has demonstrated correlations between permeability imaging and outcomes following aneurysmal subarachnoid haemorrhage (aSAH).

CONCLUSION

Radiological biomarkers offer a potential non-invasive prognostication tool and may also allow early identifications of patients who may be at risk of DCI.

Neutrophil Extracellular Traps may be a Potential Target for Treating Early Brain Injury in Subarachnoid Hemorrhage

Neuroinflammation is closely associated with poor prognosis in patients with subarachnoid hemorrhage (SAH). The purpose of this study was to investigate the role of neutrophil extracellular traps (NETs), which are important regulators of sterile inflammation, in SAH. In this study, markers of NET formation, quantified by the level of citrullinated histone H3 (CitH3), were significantly increased after SAH and correlated with SAH severity. CitH3 peaked at 12 h in peripheral blood and at 24 h in the brain. Administration of the peptidyl arginine deiminase 4 (PAD4) selective antagonist GSK484 substantially attenuated SAH-induced brain edema and neuronal injury. Moreover, the benefit of NET inhibition was also confirmed by DNAse I treatment and neutrophil depletion. Mechanistically, NETs markedly exacerbated microglial inflammation in vitro. NET formation aggravated neuroinflammation by promoting microglial activation and increased the levels of TNF-α, IL-1β, and IL-6, while inhibiting NETs demonstrated anti-inflammatory effects by decreasing the levels of these proinflammatory factors. Moreover, neurogenic pulmonary edema (NPE), a severe nonneurological complication after SAH, is associated with a high level of NET formation. However, GSK484 effectively inhibited the formation of NETs in the lungs of NPE mice, thereby preventing the diffusion of neutrophilic infiltration and attenuating the swelling of the alveolar interstitium. In conclusion, NETs promoted neuroinflammation after SAH, while pharmacological inhibition of PAD4-NETs could reduce the inflammatory damage caused by SAH. These results supported the idea that NETs might be potential therapeutic targets for SAH.

Inhibition of the NKCC1/NF-κB Signaling Pathway Decreases Inflammation and Improves Brain Edema and Nerve Cell Apoptosis in an SBI Rat Model

Surgical brain injury (SBI) triggers microglia to release numerous inflammatory factors, leading to brain edema and neurological dysfunction. Reducing neuroinflammation and protecting the blood-brain barrier (BBB) are key factors to improve the neurological function and prognosis after SBI. Na⁺-K⁺-Cl^– cotransporter 1 (NKCC1) and nuclear factor κB (NF-κB) have been implicated in the secretion of inflammatory cytokines by microglia in brain injury. This study aimed to establish the role of NKCC1 in inducing inflammation in SBI, as well as to determine whether NKCC1 controls the release of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) via phosphorylation of NF-κB in microglia, thus affecting BBB permeability and neuronal cell apoptosis. Male Sprague-Dawley (SD) rats were used to establish an SBI model. This study revealed that compared with the sham group, the expression levels of p-NKCC1, p-p65-NF-κB, and related inflammatory factor proteins in SBI model group significantly increased. After p-NKCC1 was inhibited, p-p65-NF-κB, IL-6, IL-1β, and TNF-α were downregulated, and nerve cell apoptosis and BBB permeability were significantly reduced. These findings suggest that the SBI-induced increase in p-NKCC1 exacerbates neuroinflammation, brain edema, and nerve function injury, which may be mediated by regulating the activity of p65-NF-κB that in turn influences the release of inflammatory factors.

Exosomal miR-155 from M1-polarized macrophages promotes EndoMT and impairs mitochondrial function via activating NF-κB signaling pathway in vascular endothelial cells after traumatic spinal cord injury

Pathologically, blood-spinal-cord-barrier (BSCB) disruption after spinal cord injury (SCI) leads to infiltration of numerous peripheral macrophages into injured areas and accumulation around newborn vessels. Among the leaked macrophages, M1-polarized macrophages are dominant and play a crucial role throughout the whole SCI process. The aim of our study was to investigate the effects of M1-polarized bone marrow-derived macrophages (M1-BMDMs) on vascular endothelial cells and their underlying mechanism. Microvascular endothelial cell line bEnd.3 cells were treated with conditioned medium or exosomes derived from M1-BMDMs, followed by evaluations of endothelial-to-mesenchymal transition (EndoMT) and mitochondrial function. After administration, we found conditioned medium or exosomes from M1-BMDMs significantly promoted EndoMT of vascular endothelial cells in vitro and in vivo, which aggravated BSCB disruption after SCI. In addition, significant dysfunction of mitochondria and accumulation of reactive oxygen species (ROS) were also detected. Furthermore, bioinformatics analysis demonstrated that miR-155 is upregulated in both M1-polarized macrophages and microglia. Experimentally, exosomal transfer of miR-155 participated in M1-BMDMs-induced EndoMT and mitochondrial ROS generation in bEnd.3 cells, and subsequently activated the NF-κB signaling pathway by targeting downstream suppressor of cytokine signaling 6 (SOCS6), and suppressing SOCS6-mediated p65 ubiquitination and degradation. Finally, a series of rescue assay further verified that exosomal miR155/SOCS6/p65 axis regulated the EndoMT process and mitochondrial function in vascular endothelial cells. In summary, our work revealed a potential mechanism describing the communications between macrophages and vascular endothelial cells after SCI which could benefit for future research and aid in the development of potential therapies for SCI.

The Potentials of Melatonin in the Prevention and Treatment of Bacterial Meningitis Disease

Bacterial meningitis (BM) is an acute infectious central nervous system (CNS) disease worldwide, occurring with 50% of the survivors left with a long-term serious sequela. Acute bacterial meningitis is more prevalent in resource-poor than resource-rich areas. The pathogenesis of BM involves complex mechanisms that are related to bacterial survival and multiplication in the bloodstream, increased permeability of blood-brain barrier (BBB), oxidative stress, and excessive inflammatory response in CNS. Considering drug-resistant bacteria increases the difficulty of meningitis treatment and the vaccine also has been limited to several serotypes, and the morbidity rate of BM still is very high. With recent development in neurology, there is promising progress for drug supplements of effectively preventing and treating BM. Several in vivo and in vitro studies have elaborated on understanding the significant mechanism of melatonin on BM. Melatonin is mainly secreted in the pineal gland and can cross the BBB. Melatonin and its metabolite have been reported as effective antioxidants and anti-inflammation, which are potentially useful as prevention and treatment therapy of BM. In bacterial meningitis, melatonin can play multiple protection effects in BM through various mechanisms, including immune response, antibacterial ability, the protection of BBB integrity, free radical scavenging, anti-inflammation, signaling pathways, and gut microbiome. This manuscript summarizes the major neuroprotective mechanisms of melatonin and explores the potential prevention and treatment approaches aimed at reducing morbidity and alleviating nerve injury of BM.

Resolvin D1 ameliorates Inflammation-Mediated Blood-Brain Barrier Disruption After Subarachnoid Hemorrhage in rats by Modulating A20 and NLRP3 Inflammasome

Inflammation is typically related to dysfunction of the blood-brain barrier (BBB) that leads to early brain injury (EBI) after subarachnoid hemorrhage (SAH). Resolvin D1 (RVD1), a lipid mediator derived from docosahexaenoic acid, possesses anti-inflammatory and neuroprotective properties. This study investigated the effects and mechanisms of RVD1 in SAH. A Sprague-Dawley rat model of SAH was established through endovascular perforation. RVD1was injected through the femoral vein at 1 and 12 h after SAH induction. To further explore the potential neuroprotective mechanism, a formyl peptide receptor two antagonist (WRW4) was intracerebroventricularly administered 1 h after SAH induction. The expression of endogenous RVD1 was decreased whereas A20 and NLRP3 levels were increased after SAH. An exogenous RVD1 administration increased RVD1 concentration in brain tissue, and improved neurological function, neuroinflammation, BBB disruption, and brain edema. RVD1 treatment upregulated the expression of A20, occludin, claudin-5, and zona occludens-1, as well as downregulated nuclear factor-κBp65, NLRP3, matrix metallopeptidase 9, and intercellular cell adhesion molecule-1 expression. Furthermore, RVD1 inhibited microglial activation and neutrophil infiltration and promoted neutrophil apoptosis. However, the neuroprotective effects of RVD1 were abolished by WRW4. In summary, our findings reveal that RVD1 provides beneficial effects against inflammation-triggered BBB dysfunction after SAH by modulating A20 and NLRP3 inflammasome.

Application Value of CTA in the Computer-Aided Diagnosis of Subarachnoid Hemorrhage of Different Origins

Subarachnoid hemorrhage (SAH) is difficult to detect because of its circulation through subarachnoid space, which leads to a high rate of missed diagnosis. Based on the above background, the purpose of this study is to study the application value of brain CT angiography (CTA) in computer-aided diagnosis of subarachnoid hemorrhage with a wide range of brain digital subtraction angiography as a gold standard. This paper collected images and related medical records of 111 patients with spontaneous subarachnoid hemorrhage receiving brain CTA and DSA examinations from February 2015 to November 2019 in the neurology department of our hospital. In contrast to the number, position, length, width, and neck width of the causative aneurysm detected by DSA, we evaluated the diagnostic results of CTA and evaluated whether there was statistical difference between the two detectives of intracranial aneurysms. The results showed that the area under ROC curve of subtraction CTA and conventional CTA was 1.000 and 0.818, respectively, which indicated that the former had better display effect on internal carotid aneurysm (AUC > 0.9), while the latter had medium value (0.7 < AUC ≤ 0.9), and the difference was statistically significant (z = 2.390, p=0.017).

Melatonin ameliorates microvessel abnormalities in the cerebral cortex and hippocampus in a rat model of Alzheimer's disease

Melatonin can attenuate cardiac microvascular ischemia/reperfusion injury, but it remains unclear whether melatonin can also ameliorate cerebral microvascular abnormalities. Rat models of Alzheimer’s disease were established by six intracerebroventricular injections of amyloid-beta 1–42, administered once every other day. Melatonin (30 mg/kg) was intraperitoneally administered for 13 successive days, with the first dose given 24 hours prior to the first administration of amyloid-beta 1–42. Melatonin ameliorated learning and memory impairments in the Morris water maze test, improved the morphology of microvessels in the cerebral cortex and hippocampus, increased microvessel density, alleviated pathological injuries of cerebral neurons, and decreased the expression of vascular endothelial growth factor and vascular endothelial growth factor receptors 1 and 2. These findings suggest that melatonin can improve microvessel abnormalities in the cerebral cortex and hippocampus by lowering the expression of vascular endothelial growth factor and its receptors, thereby improving the cognitive function of patients with Alzheimer’s disease. This study was approved by the Animal Care and Use Committee of Jinzhou Medical University, China (approval No. 2019015) on December 6, 2018.

Metabolomics Profiling and Diagnosis Biomarkers Searching for Drug-Induced Liver Injury Implicated to Polygonum multiflorum: A Cross-Sectional Cohort Study

Aim: The diagnosis of drug-induced liver injury (DILI) remains a challenge and the cases of Polygonum multiflorum Thunb. (PM) induced DILI (PM-DILI) have received much attention This study aimed to identify a simple and high-efficiency approach to PM-DILI diagnosis via metabolomics analysis.

Methods: Plasma metabolites in 13 PM-DILI patients were profiled by liquid chromatography along with high-resolution mass spectrometry. Meanwhile, the metabolic characteristics of the PM-DILI were compared with that of autoimmune hepatitis (AIH), hepatitis B (HBV), and healthy volunteers.

Results: Twenty-four metabolites were identified to present significantly different levels in PM-DILI patients compared with HBV and AIH groups. These metabolites were enriched into glucose, amino acids, and sphingolipids metabolisms. Among these essential metabolites, the ratios of P-cresol sulfate vs. phenylalanine and inosine vs. bilirubin were further selected using a stepwise decision tree to construct a classification model in order to differentiate PM-DILI from HBV and AIH. The model was highly effective with sensitivity of 92.3% and specificity of 88.9%.

Conclusions: This study presents an integrated view of the metabolic features of PM-DILI induced by herbal medicine, and the four-metabolite decision tree technique imparts a potent tool in clinical diagnosis.

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.

Atorvastatin reduces cerebral vasospasm and infarction after aneurysmal subarachnoid hemorrhage in elderly Chinese adults

We explored whether acute atorvastatin treatment would improve clinical outcomes and reduce the incidence of cerebral vasospasm after aneurysmal subarachnoid hemorrhage in elderly Chinese adults. Patients (60 to 90 years old) were admitted to intensive care units after surgery to clip or embolize their aneurysms. We assessed 592 patients and assigned 159 to receive atorvastatin (20 mg/day) and 158 to receive placebo once daily for up to 14 days. The primary outcome was the Glasgow outcome scale at 6 months, and secondary outcomes were cerebral vasospasm, 30-days all-cause mortality, cerebral infarction, and delayed ischemic neurological deficit. The incidence of postoperative cerebral vasospasm (39.3% vs 56%, P =0.004) and cerebral infarction (18.7% vs 27.3%, P=0.027) were significantly lower in the atorvastatin group. The study did not detect benefits in the use of atorvastatin for 6 months clinical outcome or 30-day all-cause mortality, but it suggests that atorvastatin together with nimodipine can reduce cerebral vasospasm and cerebral infarction after subarachnoid hemorrhage.

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.

Inflammatory Pathways Following Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is an acute cerebrovascular emergency resulting from the rupture of a brain aneurysm. Despite only accounting for 5% of all strokes, SAH imposes a significant health burden on society due to its relatively young age at onset. Those who survive the initial bleed are often afflicted with severe disabilities thought to result from delayed cerebral ischemia (DCI). Consequently, elucidating the underlying mechanistic pathways implicated in DCI development following SAH remains a priority. Neuroinflammation has recently been implicated as a promising new theory for the development of SAH complications. However, despite this interest, clinical trials have failed to provide consistent evidence for the use of anti-inflammatory agents in SAH patients. This may be explained by the complexity of SAH as a plethora of inflammatory pathways have been shown to be activated in the disease. By determining how these pathways may overlap and interact, we hope to better understand the developmental processes of SAH complications and how to prevent them. The goal of this review is to provide insight into the available evidence regarding the molecular pathways involved in the development of inflammation following SAH and how SAH complications may arise as a result of these inflammatory pathways.

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.

Tetramethylpyrazine Nitrone Reduces Oxidative Stress to Alleviate Cerebral Vasospasm in Experimental Subarachnoid Hemorrhage Models

Cerebral vasospasm is one of the deleterious complications after subarachnoid hemorrhage (SAH), leading to delayed cerebral ischemia and permanent neurological deficits or even death. Free radicals and oxidative stress are considered as crucial causes contributing to cerebral vasospasm and brain damage after SAH. Tetramethylpyrazine nitrone (TBN), a derivative of the clinically used anti-stroke drug tetramethylpyrazine armed with a powerful free radical scavenging nitrone moiety, has been reported to prevent brain damage from ischemic stroke. The present study aimed to investigate the effects of TBN on vasospasm and brain damage after SAH. Two experimental SAH models were used, a rat model by endovascular perforation and a rabbit model by intracisternal injection of autologous blood. The effects of TBN on SAH were evaluated assessing basilar artery spasm, neuronal apoptosis, and neurological deficits. TBN treatment significantly attenuated vasospasm, improved neurological behavior functions and reduced the number of apoptotic neurons in both the SAH rats and rabbits. Mechanistically, TBN suppressed the increase in 3-nitrotyrosine and 8-hydroxy-2-deoxyguanosine immuno-positive cells in the cortex of SAH rat brain. Western blot analyses indicated that TBN effectively reversed the altered expression of Bcl-2, Bax and cytochrome C, and up-regulated nuclear factor erythroid-derived 2-like 2 (Nrf2) and hemeoxygenase-1 (HO-1) protein expressions. In the in vitro studies, TBN inhibited H₂O₂-induced bEnd.3 cell apoptosis and reduced ROS generation. Additionally, TBN alleviated the contraction of rat basilar artery rings induced by H₂O₂ ex vivo. In conclusion, TBN ameliorated SAH-induced cerebral vasospasm and neuronal damage. These effects of TBN may be attributed to its anti-oxidative stress effect and up-regulation of Nrf2/HO-1.

Melatonin Affects Mitochondrial Fission/Fusion Dynamics in the Diabetic Retina

Mitochondrial fission and fusion are dependent on cellular nutritional states, and maintaining this dynamics is critical for the health of cells. Starvation triggers mitochondrial fusion to maintain bioenergetic efficiency, but during nutrient overloads (as with hyperglycemic conditions), fragmenting mitochondria is a way to store nutrients to avoid waste of energy. In addition to ATP production, mitochondria play an important role in buffering intracellular calcium (Ca2+). We found that in cultured 661W cells, a photoreceptor-derived cell line, hyperglycemic conditions triggered an increase of the expression of dynamin-related protein 1 (DRP1), a protein marker of mitochondrial fission, and a decrease of mitofusin 2 (MFN2), a protein for mitochondrial fusion. Further, these hyperglycemic cells also had decreased mitochondrial Ca2+ but increased cytosolic Ca2+. Treating these hyperglycemic cells with melatonin, a multifaceted antioxidant, averted hyperglycemia-altered mitochondrial fission-and-fusion dynamics and mitochondrial Ca2+ levels. To mimic how people most commonly take melatonin supplements, we gave melatonin to streptozotocin- (STZ-) induced type 1 diabetic mice by daily oral gavage and determined the effects of melatonin on diabetic eyes. We found that melatonin was not able to reverse the STZ-induced systemic hyperglycemic condition, but it prevented STZ-induced damage to the neural retina and retinal microvasculature. The beneficial effects of melatonin in the neural retina in part were through alleviating STZ-caused changes in mitochondrial dynamics and Ca2+ buffering.

Carnosic Acid Mitigates Early Brain Injury After Subarachnoid Hemorrhage: Possible Involvement of the SIRT1/p66shc Signaling Pathway

Carnosic acid (CA) has been reported to exhibit a variety of bioactivities including antioxidation, neuroprotection, and anti-inflammation; however, the impact of CA on subarachnoid hemorrhage (SAH) has never been elucidated. The current study was undertaken to explore the role of CA in early brain injury (EBI) secondary to SAH and the underlying mechanisms. Adult male Sprague-Dawley rats were perforated to mimic a clinical aneurysm with SAH. CA or vehicle was administered intravenously immediately after the SAH occurred. Mortality, SAH grade, neurologic function scores, brain water content, Evans blue extravasation, and the levels of reactive oxygen species (ROS) levels in the ipsilateral cortex were determined 24 h after the SAH occurred. Western blot, immunofluorescence, Fluoro-Jade C (FJC) and TUNEL staining were also performed. Our results showed that CA decreased ROS levels, alleviated brain edema and blood-brain barrier permeability, reduced neuronal cell death, and promoted neurologic function improvement. To probe into the potential mechanisms. We showed that CA increased SIRT1, MnSOD, and Bcl-2 expression, as well as decreased p66shc, Bax, and cleaved caspase-3 expression. Interestingly, sirtinol, a selective inhibitor of SIRT1, abolished the anti-apoptotic effects of CA. Taken together, these data revealed that CA has a neuroprotective role in EBI secondary to SAH. The potential mechanism may involve suppression of neuronal apoptosis through the SIRT1/p66shc signaling pathway. CA may provide a promising therapeutic regimen for management of SAH.

The Role of Oxidative Stress in Microvascular Disturbances after Experimental Subarachnoid Hemorrhage

Oxidative stress was shown to play a crucial role in the diverse pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Microcirculatory dysfunction is thought to be an important and fundamental pathological change in EBI. However, other than blood-brain barrier (BBB) disruption, the influence of oxidative stress on microvessels remains to be elucidated. The aim of this study was to investigate the role of oxidative stress on microcirculatory integrity in EBI. SAH was induced in male Sprague-Dawley rats using an endovascular perforation technique. A free radical scavenger, edaravone, was administered prophylactically by intraperitoneal injection. SAH grade, neurological score, brain water content, and BBB permeability were measured at 24 h after SAH induction. In addition, cortical samples taken at 24 h after SAH were analyzed to explore oxidative stress, microvascular mural cell apoptosis, microspasm, and microthrombosis. Edaravone treatment significantly ameliorated neurological deficits, brain edema, and BBB disruption. In addition, oxidative stress-induced modifications and subsequent apoptosis of microvascular endothelial cells and pericytes increased after SAH induction, while the administration of edaravone suppressed this. Consistent with apoptotic cell inhibition, microthromboses were also inhibited by edaravone administration. Oxidative stress plays a pivotal role in the induction of multiple pathological changes in microvessels in EBI. Antioxidants are potential candidates for the treatment of microvascular disturbances after SAH.

The multiple protective roles and molecular mechanisms of melatonin and its precursor N-acetylserotonin in targeting brain injury and liver damage and in maintaining bone health

Melatonin is a neurohormone associated with sleep and wakefulness and is mainly produced by the pineal gland. Numerous physiological functions of melatonin have been demonstrated including anti-inflammation, suppressing neoplastic growth, circadian and endocrine rhythm regulation, and its potent antioxidant activity as well as its role in regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others. In this review, we summarize the recent advances related to the multiple protective roles of melatonin receptor agonists, melatonin and N-acetylserotonin (NAS), in brain injury, liver damage, and bone health. Brain injury, including traumatic brain injury, ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, and newborn perinatal hypoxia-ischemia encephalopathy, is a major cause of mortality and disability. Liver disease causes serious public health problems and various factors including alcohol, chemical pollutants, and drugs induce hepatic damage. Osteoporosis is the most common bone disease in humans. Due in part to an aging population, both the cost of care of fracture patients and the annual fracture rate have increased steadily. Despite the discrepancy in the pathophysiological processes of these disorders, time frames and severity, they may share several common molecular mechanisms. Oxidative stress is considered to be a critical factor in these pathogeneses. We update the current state of knowledge related to the molecular processes, mainly including anti-oxidative stress, anti-apoptosis, autophagy dysfunction, and anti-inflammation as well as other properties of melatonin and NAS. Particularly, the abilities of melatonin and NAS to directly scavenge oxygen-centered radicals and toxic reactive oxygen species, and indirectly act through antioxidant enzymes are disscussed. In this review, we summarize the similarities and differences in the protection provided by melatonin and/or NAS in brain, liver and bone damage. We analyze the involvement of melatonin receptor 1A (MT1), melatonin receptor 1B (MT2), and melatonin receptor 1C (MT3) in the protection of melatonin and/or NAS. Additionally, we evaluate their potential clinical applications. The multiple mechanisms of action and multiple organ-targeted properties of melatonin and NAS may contribute to development of promising therapies for clinical trials.

Antioxidant Melatonin: Potential Functions in Improving Cerebral Autoregulation After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a subtype of stroke with high mortality and morbidity. Impaired cerebral autoregulation following SAH has been reported owing to effects on sympathetic control, endothelial function, myogenic response, and cerebral metabolism. Impaired cerebral autoregulation is associated with early brain injury, cerebral vasospasm/delayed cerebral ischemia, and SAH prognosis. However, few drugs have been reported to improve cerebral autoregulation after SAH. Melatonin is a powerful antioxidant that is effective (easily crosses the blood brain barrier) and safe (tolerated in large doses without toxicity). Theoretically, melatonin may impact the control mechanisms of cerebral autoregulation via antioxidative effects, protection of endothelial cell integrity, suppression of sympathetic nerve activity, increase in nitric oxide bioavailability, mediation of the myogenic response, and amelioration of hypoxemia. Furthermore, melatonin may have a comprehensive effect on cerebral autoregulation. This review discusses the potential effects of melatonin on cerebral autoregulation following SAH, in terms of the association between pharmacological activities and the mechanisms of cerebral autoregulation.

Brain endothelial cell junctions after cerebral hemorrhage: Changes, mechanisms and therapeutic targets

Vascular disruption is the underlying cause of cerebral hemorrhage, including intracerebral, subarachnoid and intraventricular hemorrhage. The disease etiology also involves cerebral hemorrhage-induced blood-brain barrier (BBB) disruption, which contributes an important component to brain injury after the initial cerebral hemorrhage. BBB loss drives vasogenic edema, allows leukocyte extravasation and may lead to the entry of potentially neurotoxic and vasoactive compounds into brain. This review summarizes current information on changes in brain endothelial junction proteins in response to cerebral hemorrhage (and clot-related factors), the mechanisms underlying junction modification and potential therapeutic targets to limit BBB disruption and, potentially, hemorrhage occurrence. It also addresses advances in the tools that are now available for assessing changes in junctions after cerebral hemorrhage and the potential importance of such junction changes. Recent studies suggest post-translational modification, conformational change and intracellular trafficking of junctional proteins may alter barrier properties. Understanding how cerebral hemorrhage alters BBB properties beyond changes in tight junction protein loss may provide important therapeutic insights to prevent BBB dysfunction and restore normal function.

Ameliorating mitochondrial dysfunction restores carbon ion-induced cognitive deficits via co-activation of NRF2 and PINK1 signaling pathway

Carbon ion therapy is a promising modality in radiotherapy to treat tumors, however, a potential risk of induction of late normal tissue damage should still be investigated and protected. The aim of the present study was to explore the long-term cognitive deficits provoked by a high-linear energy transfer (high-LET) carbon ions in mice by targeting to hippocampus which plays a crucial role in memory and learning. Our data showed that, one month after 4 Gy carbon ion exposure, carbon ion irradiation conspicuously resulted in the impaired cognitive performance, neurodegeneration and neuronal cell death, as well as the reduced mitochondrial integrity, the disrupted activities of tricarboxylic acid cycle flux and electron transport chain, and the depressed antioxidant defense system, consequently leading to a decline of ATP production and persistent oxidative damage in the hippocampus region. Mechanistically, we demonstrated the disruptions of mitochondrial homeostasis and redox balance typically characterized by the disordered mitochondrial dynamics, mitophagy and glutathione redox couple, which is closely associated with the inhibitions of PINK1 and NRF2 signaling pathway as the key regulators of molecular responses in the context of neurotoxicity and neurodegenerative disorders. Most importantly, we found that administration with melatonin as a mitochondria-targeted antioxidant promoted the PINK1 accumulation on the mitochondrial membrane, and augmented the NRF2 accumulation and translocation. Moreover, melatonin pronouncedly enhanced the molecular interplay between NRF2 and PINK1. Furthermore, in the mouse hippocampal neuronal cells, overexpression of NRF2/PINK1 strikingly protected the hippocampal neurons from carbon ion-elicited toxic insults. Thus, these data suggest that alleviation of the sustained mitochondrial dysfunction and oxidative stress through co-modulation of NRF2 and PINK1 may be in charge of restoration of the cognitive impairments in a mouse model of high-LET carbon ion irradiation.

Melatonin attenuated retinal neovascularization and neuroglial dysfunction by inhibition of HIF-1α-VEGF pathway in oxygen-induced retinopathy mice

Retinopathy of prematurity (ROP) is a retinopathy characterized by retinal neovascularization (RNV) occurring in preterm infants treated with high concentrations of oxygen and may lead to blindness in severe cases. Currently, anti-VEGF therapy is a major treatment for ROP, but it is costly and may cause serious complications. The previous study has demonstrated that melatonin exerted neuroprotective effect against retinal ganglion cell death induced by hypoxia in neonatal rats. However, whether melatonin is anti-angiogenic and neuroglial protective in the progression of ROP remains unknown. Thus, this study was to investigate the effect of melatonin on RNV and neuroglia in the retina of oxygen-induced retinopathy (OIR) mice. The results showed a reduction in retinal vascular leakage in OIR mice after melatonin treatment. Besides, the size of retinal neovascular and avascular areas, the number of preretinal neovascular cell nuclei, and the number of proliferative vascular endothelial cells within the neovascular area were significantly decreased in mice treated with melatonin. After oxygen-induced injury, the density of astrocytes was decreased, accompanied by morphologic and functional changes of astrocytes. Besides, retinal microglia were also activated. Meanwhile, the levels of inflammatory factors were elevated. However, these pathologic processes were all hindered by melatonin treatment. Furthermore, HIF-1α-VEGF pathway was activated in the retina of OIR mice, yet was suppressed in melatonin-treated OIR mice retinas. In conclusion, melatonin prevented pathologic neovascularization, protected neuroglial cells, and exerts anti-inflammation effect via inhibition of HIF-1α-VEGF pathway in OIR retinas, suggesting that melatonin could be a promising therapeutic agent for ROP.

Melatonin protects against blood-brain barrier damage by inhibiting the TLR4/ NF-κB signaling pathway after LPS treatment in neonatal rats

Hypoxic-ischemic and inflammatory (HII) induces the disruption of blood–brain barrier (BBB) which leads to inflammatory responses and neuronal cell death, resulting in brain secondary damage. Previous studies showed that melatonin produced potent neuroprotective effects in neonatal hypoxic-ischaemic models. However, the relationship between BBB disruption and melatonin in HII was still unclear. The present study therefore investigated the beneficial effects of melatonin on BBB after HII and the underlying mechanisms. HII animal model was conducted by receiving lipopolysaccharide followed by 90 min hypoxia-ischaemia in postnatal day 2 Sprague–Dawley rat pups. Melatonin was injected intraperitoneally 1 h before lipopolysaccharide injection and then once a day for 1 week to evaluate the long-term effects. In this study, we demonstrated that melatonin administration inhibited the disruption of BBB permeability and improved the white matter recovery in HII model rats. Melatonin significantly attenuated the degradation of junction proteins and the neuroprotective role was related to the inhibition of microglial toll-like receptor 4/ nuclear factor-kappa B signaling pathway both in vivo and in vitro. Taken together, our data demonstrated that therapeutic strategies targeting inflammation might be suitable for the therapy of preserving BBB integrity after HII.

Blood brain barrier (BBB)-disruption in intracortical silicon microelectrode implants

Chronically implanted microelectrodes in the neural tissue elicit inflammatory responses that are time varying and have been shown to depend on multiple factors. Among these factors, blood brain barrier (BBB)-disruption has been hypothesized as one of the dominant factors resulting in electrode failure. A series of events that includes BBB and cell-membrane disruption occurs during electrode implantation that triggers multiple biochemical cascades responsible for microglial and astroglial activation, hemorrhage, edema, and release of pro-inflammatory neurotoxic cytokines that causes neuronal degeneration and dysfunction. Typically, microwire arrays and silicon probes are inserted slowly into the neural tissue whereas the silicon Utah MEAs (UMEA) are inserted at a high speed using a pneumatic inserter. In this work, we report the sequelae of electrode-implant induced cortical injury at various acute time points in UMEAs implanted in the brain tissue by quantifying the expression profile for key genes mediating the inflammatory response and tight junction (TJ) and adherens junction (AJ) proteins that form the BBB and are critical to the functioning of the BBB. Our results indicated upregulation of most pro-inflammatory genes relative to naïve controls for all time points. Expression levels for the genes that form the TJ and AJ were downregulated suggestive of BBB-dysfunction. Moreover, there was no significant difference between stab and implant groups suggesting the effects of UMEA insertion-related trauma in the brain tissue. Our results provide an insight into the physiological events related to neuroinflammation and BBB-disruption occurring at acute time-points following insertion of UMEAs.

Docking studies for melatonin receptors

INTRODUCTION

Melatonin is a neurohormone that controls many relevant physiological processes beyond the control of circadian rhythms. Melatonin's actions are carried out by two main types of melatonin receptors; MT₁ and MT₂. These receptors are important, and not just because of the biological actions of its natural agonist; but also, because melatonin analogues can improve or antagonize their biological effect. Area covered: The following article describes the importance of melatonin as a biologically relevant molecule. It also defines the receptors for this substance, as well as the second messengers coupled to these receptors. Lastly, the article describes the amino acid residues involved in the docking process in both MT₁ and MT₂ melatonin receptors. Expert opinion: The biological actions of melatonin and their interpretations are becoming more relevant and therefore require the development of new pharmacological tools. Understanding the second messenger mechanisms involved in melatonin actions, as well as the characteristics of the docking of this molecule to MT₁ and MT₂ melatonin receptors, will permit the development of more selective agonists and antagonists which will help us to better understand this molecule as well to develop new therapeutic compounds.