A retinoic acid receptor agonist Am80 rescues neurons, attenuates inflammatory reactions, and improves behavioral recovery after intracerebral hemorrhage in mice

Menaquinone-4 Alleviates Neurological Deficits Associated with Intracerebral Hemorrhage by Preserving Corticospinal Tract in Mice

Menaquinone-4 (MK-4) is an isoform of vitamin K2 that has been shown to exert various biological actions besides its functions in blood coagulation and bone metabolism. Here we examined the effect of MK-4 on a mouse model of intracerebral hemorrhage (ICH). Daily oral administration of 200 mg/kg MK-4 starting from 3 h after induction of ICH by intrastriatal collagenase injection significantly ameliorated neurological deficits. Unexpectedly, MK-4 produced no significant effects on various histopathological parameters, including the decrease of remaining neurons and the increase of infiltrating neutrophils within the hematoma, the increased accumulation of activated microglia/macrophages and astrocytes around the hematoma, as well as the injury volume and brain swelling by hematoma formation. In addition, ICH-induced increases in nitrosative/oxidative stress reflected by changes in the immunoreactivities against nitrotyrosine and heme oxygenase-1 as well as the contents of malondialdehyde and glutathione were not significantly affected by MK-4. In contrast, MK-4 alleviated axon tract injury in the internal capsule as revealed by neurofilament-H immunofluorescence. Enhanced preservation of the corticospinal tract by MK-4 was also confirmed by retrograde labeling of neurons in the primary motor cortex innervating the spinal cord. These results suggest that MK-4 produces therapeutic effect on ICH by protecting structural integrity of the corticospinal tract.

Nurr1 overexpression in the primary motor cortex alleviates motor dysfunction induced by intracerebral hemorrhage in the striatum in mice

Hemorrhage-induced injury of the corticospinal tract (CST) in the internal capsule (IC) causes severe neurological dysfunction in both human patients and rodent models of intracerebral hemorrhage (ICH). A nuclear receptor Nurr1 (NR4A2) is known to exert anti-inflammatory and neuroprotective effects in several neurological disorders. Previously we showed that Nurr1 ligands prevented CST injury and alleviated neurological deficits after ICH in mice. To prove direct effect of Nurr1 on CST integrity, we examined the effect of Nurr1 overexpression in neurons of the primary motor cortex on pathological consequences of ICH in mice. ICH was induced by intrastriatal injection of collagenase type VII, where hematoma invaded into IC. Neuron-specific overexpression of Nurr1 was induced by microinjection of synapsin I promoter-driven adeno-associated virus (AAV) vector into the primary motor cortex. Nurr1 overexpression significantly alleviated motor dysfunction but showed only modest effect on sensorimotor dysfunction after ICH. Nurr1 overexpression also preserved axonal structures in IC, while having no effect on hematoma-associated inflammatory events, oxidative stress, and neuronal death in the striatum after ICH. Immunostaining revealed that Nurr1 overexpression increased the expression of Ret tyrosine kinase and phosphorylation of Akt and ERK1/2 in neurons in the motor cortex. Moreover, administration of Nurr1 ligands 1,1-bis(3'-indolyl)-1-(p-chlorophenyl)methane or amodiaquine increased phosphorylation levels of Akt and ERK1/2 as well as expression of glial cell line-derived neurotrophic factor and Ret genes in the cerebral cortex. These results suggest that the therapeutic effect of Nurr1 on striatal ICH is attributable to the preservation of CST by acting on cortical neurons.

Acyclic retinoid peretinoin reduces hemorrhage-associated brain injury in vitro and in vivo

Peretinoin is an acyclic retinoid that stimulates retinoic acid receptors (NR1Bs) and produces therapeutic effects on hepatocellular cancer. We have previously shown that NR1B agonists such as Am80 and all trans-retinoic acid suppress pathogenic events in intracerebral hemorrhage. The present study addressed the actions of peretinoin and Am80 against cytotoxicity of a blood protease thrombin on cortico-striatal slice cultures obtained from neonatal rat brains. Application of 100 U/ml thrombin to the slice cultures for 72 h caused cell death in the cortical region and tissue shrinkage in the striatal region. Peretinoin (50 μM) and Am80 (1 μM) counteracted these cytotoxic effects of thrombin, and the effect of peretinoin and Am80 was blocked by LE540, an NR1B antagonist. A broad-spectrum kinase inhibitor K252a (3 μM) attenuated the cytoprotective effect of peretinoin in the cortical region, whereas a specific protein kinase A inhibitor KT5720 (1 μM) attenuated the protective effect of peretinoin in the cortical and the striatal regions. On the other hand, nuclear factor-κB (NF-κB) inhibitors such as pyrrolidine dithiocarbamate (50 μM) and Bay11-7082 (10 μM) prevented thrombin-induced shrinkage of the striatal region. Peretinoin and Am80 as well as Bay11-7082 blocked thrombin-induced nuclear translocation of NF-κB in striatal microglia and loss of striatal neurons. We also found that daily administration of peretinoin reduced histopathological injury and alleviated motor deficits in a mouse model of intracerebral hemorrhage. These results indicate that NR1B agonists including peretinoin may serve as a therapeutic option for hemorrhagic brain injury.

Retinoic acid signaling during priming licenses intestinal CD103+ CD8 TRM cell differentiation

CD8 tissue-resident memory T (TRM) cells provide frontline protection at barrier tissues; however, mechanisms regulating TRM cell development are not completely understood. Priming dictates the migration of effector T cells to the tissue, while factors in the tissue induce in situ TRM cell differentiation. Whether priming also regulates in situ TRM cell differentiation uncoupled from migration is unclear. Here, we demonstrate that T cell priming in the mesenteric lymph nodes (MLN) regulates CD103+ TRM cell differentiation in the intestine. In contrast, T cells primed in the spleen were impaired in the ability to differentiate into CD103+ TRM cells after entry into the intestine. MLN priming initiated a CD103+ TRM cell gene signature and licensed rapid CD103+ TRM cell differentiation in response to factors in the intestine. Licensing was regulated by retinoic acid signaling and primarily driven by factors other than CCR9 expression and CCR9-mediated gut homing. Thus, the MLN is specialized to promote intestinal CD103+ CD8 TRM cell development by licensing in situ differentiation.

Activation of the RARα Attenuated CSF Hypersecretion to Inhibit Hydrocephalus Development via Regulating the MAFB/MSR1 Pathway

Hydrocephalus has been observed in rats with spontaneous hypertension (SHRs). It has been demonstrated that activation of the oxidative stress related protein retinoic acid receptor alpha (RARα) has neuroprotective impacts. Our investigation aims to determine the potential role and mechanism of RARα in hydrocephalus. The RARα-specific agonist (Am80) and RARα inhibitor (AGN196996) were used to investigate the role of RARα in cerebrospinal fluid (CSF) secretion in the choroid plexus of SHRs. Evaluations of CSF secretion, ventricular volume, Western blotting, and immunofluorescent staining were performed. Hydrocephalus and CSF hypersecretion were identified in SHRs but not in Wistar-Kyoto rats, occurring at the age of 7 weeks. The RARα/MAFB/MSR1 pathway was also activated in SHRs. Therapy with Am80 beginning in week 5 decreased CSF hypersecretion, hydrocephalus development, and pathological changes in choroid plexus alterations by week 7. AGN196996 abolished the effect of Am80. In conclusion, activation of the RARα attenuated CSF hypersecretion to inhibit hydrocephalus development via regulating the MAFB/MSR1 pathway. RARα may act as a possible therapeutic target for hydrocephalus.

Identification of significant modules and hub genes involved in hepatic encephalopathy using WGCNA

BACKGROUND

Hepatic encephalopathy (HE) is a reversible syndrome of brain dysfunction caused by advanced liver disease. Weighted gene co-expression network analysis (WGCNA) could establish a robust co-expression network to identify the hub genes and underlying biological functions. This study was aimed to explore the potential therapeutic targets in HE by WGCNA.

RESULTS

The green and brown modules were found to be significantly associated with the development of HE. Functional enrichment analyses suggested the neuroinflammation, neuroimmune, extracellular matrix (ECM), and coagulation cascade were involved in HE. CYBB and FOXO1 were calculated as hub genes, which were upregulated in the HE patients. Tamibarotene and vitamin E were suggested as possible drug candidates to alleviate HE.

CONCLUSIONS

It is the first time to analyze transcriptomic data of HE by WGCNA. Our study not only promoted the current understanding of neuroinflammation in HE, but also provided the first evidence that CYBB and FOXO1 played pivotal roles in the pathogenesis of HE, which might be potential biomarkers and therapeutic targets. Tamibarotene might be a novel drug compound against HE.

A Nurr1 ligand C-DIM12 attenuates brain inflammation and improves functional recovery after intracerebral hemorrhage in mice

We have previously reported that amodiaquine, a compound that binds to the ligand-binding domain of a nuclear receptor Nurr1, attenuates inflammatory responses and neurological deficits after intracerebral hemorrhage (ICH) in mice. 1,1-Bis(3'-indolyl)-1-(p-chlorophenyl)methane (C-DIM12) is another Nurr1 ligand that recognizes a domain of Nurr1 different from the ligand-binding domain. In the present study, mice were treated daily with C-DIM12 (50 or 100 mg/kg, p.o.) or amodiaquine (40 mg/kg, i.p.), or twice daily with 1400 W (20 mg/kg, i.p.), an inducible nitric oxide synthase (iNOS) inhibitor, from 3 h after ICH induction by microinjection of collagenase into the striatum. C-DIM12 improved the recovery of neurological function and prevented neuron loss in the hematoma, while suppressed activation of microglia/macrophages and expression of inflammatory mediators interleukin-6 and CC chemokine ligand 2. In addition, C-DIM12 as well as amodiaquine preserved axonal structures in the internal capsule and axonal transport function. We also found that C-DIM12 and amodiaquine suppressed the increases of iNOS mRNA expression after ICH. Moreover, 1400 W improved neurological function and prevented neuron loss, activation of microglia/macrophages and axonal transport dysfunction. These results suggest that suppression of iNOS induction contributes to several features of the therapeutic effects of Nurr1 ligands.

High-Throughput mRNA Sequencing Reveals Potential Therapeutic Targets of Febuxostat in Secondary Injury After Intracerebral Hemorrhage

Febuxostat is a urate-lowering medication for the treatment of patients with gout. This study was performed to elucidate the effects and underlying mechanisms of febuxostat on neuronal injury induced by intracerebral hemorrhage (ICH) in mice. The results showed that the administration of febuxostat improved neurological severity scores and blood–brain barrier (BBB) permeability. Moreover, febuxostat attenuated neuronal cell death and cytokine levels compared with the ICH group. Next, we conducted a transcriptome analysis of the neuroprotective effects of febuxostat. The overlapping significant differentially expressed genes (DEGs) were identified. Gene ontology (GO) analysis revealed that the overlapping significant DEGs were most enriched in five items. The intersecting DEGs of the aforementioned five pathways were Wisp1, Wnt7b, Frzb, and Pitx2. In addition, GO terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways revealed that DEGs were mainly involved in the wnt signaling pathway. Furthermore, the expression of Wisp1 and Wnt7b in the perihematomal region at 72 h post-ICH was observed. The results showed that both Wisp1 and Wnt7b were increased in the ICH group and were decreased by the administration of febuxostat. Taken together, the study showed that febuxostat protected against secondary brain injury after ICH and the Wnt7b-Wisp1 pathway was closely related to neuroprotective effects.

Activation of RARα Receptor Attenuates Neuroinflammation After SAH via Promoting M1-to-M2 Phenotypic Polarization of Microglia and Regulating Mafb/Msr1/PI3K-Akt/NF-κB Pathway

Background and Purpose

Subarachnoid hemorrhage (SAH) is a life-threatening subtype of stroke with high rates of mortality. In the early stages of SAH, neuroinflammation is one of the important mechanisms leading to brain injury after SAH. In various central nervous system diseases, activation of RARα receptor has been proven to demonstrate neuroprotective effects. This study aimed to investigate the anti-inflammatory effects of RARα receptor activation after SAH.

Methods

Internal carotid artery puncture method used to established SAH model in Sprague-Dawley rats. The RARα specific agonist Am80 was injected intraperitoneally 1 hour after SAH. AGN196996 (specific RARα inhibitor), Msr1 siRNA and LY294002 (PI3K-Akt inhibitor) were administered via the lateral ventricle before SAH. Evaluation SAH grade, neurological function score, blood-brain barrier permeability. BV2 cells and SH-SY5Y cells were co-cultured and stimulated by oxyhemoglobin to establish an in vitro model of SAH. RT-PCR, Western blotting, and immunofluorescence staining were used to investigate pathway-related proteins, microglia activation and inflammatory response. Results: The expression of RARα, Mafb, and Msr1 increased in rat brain tissue after SAH. Activation of the RARα receptor with Am80 improved neurological deficits and attenuated brain edema, blood brain barrier permeability. Am80 increased the expression of Mafb and Msr1, and reduced neuroinflammation by enhancing the phosphorylation of Akt and by inhibiting the phosphorylation of NF-κB. AGN196996, Msr1 siRNA, and LY294002 reversed the therapeutic effects of Am80 by reducing the expression of Msr1 and the phosphorylation of Akt. In vitro model of SAH, Am80 promoted M1-to-M2 phenotypic polarization in microglia and suppressed the nuclear transcription of NF-κB.

Conclusion

Activation of the RARα receptor attenuated neuroinflammation by promoting M1-to-M2 phenotypic polarization in microglia and regulating the Mafb/Msr1/PI3K-Akt/NF-κB pathway. RARα might serve as a potential target for SAH therapy.

Hydroxychloroquine improves motor function and affords neuroprotection without inhibition of inflammation and autophagy in mice after intracerebral hemorrhage

We examined the effect of an immunomodulator hydroxychloroquine, also known as a Nurr1 ligand and an autophagy inhibitor, on a mouse model of intracerebral hemorrhage (ICH). Daily administration of hydroxychloroquine (100 mg/kg, i.p.) from 3 h after induction of ICH alleviated neurological deficits of mice, increased the number of surviving neurons in the hematoma and prevented fragmentation of axon structures in the internal capsule. Unexpectedly, hydroxychloroquine did not inhibit either upregulation of pro-inflammatory mediators or autophagic responses in the brain. Hence, hydroxychloroquine may produce therapeutic effects on ICH primarily via neuroprotection including preservation of the axon tract integrity.

Nuclear receptors of NR1 and NR4 subfamilies in the regulation of microglial functions and pathology

This review provides an overview of researches on the NR1 and NR4 nuclear receptors involved in the regulation of microglial functions. Nuclear receptors are attractive candidates for drug targets in the therapies of the central nervous system disorders, because the activation of these receptors is expected to regulate the functions and the phenotypes of microglia, by controlling the expression of specific gene subsets and also by regulating the cellular signaling mechanisms in a nongenomic manner. Several members of NR1 nuclear receptor subfamily have been examined for their ability to regulate microglial functions. For example, stimulation of vitamin D receptor inhibits the production of pro-inflammatory factors and increases the production of anti-inflammatory cytokines. Similar regulatory actions of nuclear receptor ligands on inflammation-related genes have also been reported for other NR1 members such as retinoic acid receptors, peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). In addition, stimulation of PPARγ and LXRs may also result in increased phagocytic activities of microglia. Consistent with these actions, the agonists at nuclear receptors of NR1 subfamily are shown to produce therapeutic effects on animal models of various neurological disorders such as experimental allergic encephalomyelitis, Alzheimer's disease, Parkinson's disease, and ischemic/hemorrhagic stroke. On the other hand, increasing lines of evidence suggest that the stimulation of NR4 subfamily members of nuclear receptors such as Nur77 and Nurr1 also regulates microglial functions and alleviates neuropathological events in several disease models. Further advancement of these research fields may prove novel therapeutic opportunities.

Ergosta-7,9(11),22-trien-3β-ol Alleviates Intracerebral Hemorrhage-Induced Brain Injury and BV-2 Microglial Activation

Intracerebral hemorrhage (ICH) is a devastating neurological disorder characterized by an exacerbation of neuroinflammation and neuronal injury, for which few effective therapies are available at present. Inhibition of excessive neuroglial activation has been reported to alleviate ICH-related brain injuries. In the present study, the anti-ICH activity and microglial mechanism of ergosta-7,9(11),22-trien-3β-ol (EK100), a bioactive ingredient from Asian medicinal herb Antrodia camphorate, were evaluated. Post-treatment of EK100 significantly attenuated neurobehavioral deficit and MRI-related brain lesion in the mice model of collagenase-induced ICH. Additionally, EK100 alleviated the inducible expression of cyclooxygenase (COX)-2 and the activity of matrix metalloproteinase (MMP)-9 in the ipsilateral brain regions. Consistently, it was shown that EK100 concentration-dependently inhibited the expression of COX-2 protein in Toll-like receptor (TLR)-4 activator lipopolysaccharide (LPS)-activated microglial BV-2 and primary microglial cells. Furthermore, the production of microglial prostaglandin E₂ and reactive oxygen species were attenuated by EK100. EK100 also attenuated the induction of astrocytic MMP-9 activation. Among several signaling pathways, EK100 significantly and concentration-dependently inhibited activation of c-Jun N-terminal kinase (JNK) MAPK in LPS-activated microglial BV-2 cells. Consistently, ipsilateral JNK activation was markedly inhibited by post-ICH-treated EK100 in vivo. In conclusion, EK100 exerted the inhibitory actions on microglial JNK activation, and attenuated brain COX-2 expression, MMP-9 activation, and brain injuries in the mice ICH model. Thus, EK100 may be proposed and employed as a potential therapeutic agent for ICH.

Different responses after intracerebral hemorrhage between young and early middle-aged mice

Although aging is a major risk factor for intracerebral hemorrhage (ICH), there are very few studies comparing ICH pathology between young and early middle-aged mice. In this study, 8-month old mice (early middle-aged mice) were compared against 2-month old mice (young mice) in neurological and histological changes after ICH induction, such as body weight, lesion volume, astrocytic responses, and motor and cognitive functions. At day 8 after ICH, there was no significant difference in lesion volume between the two groups, and both groups did not exhibit significant cognitive decline, as assessed by spontaneous alternative Y-maze test. On the other hand, 8-month old mice showed delayed recovery from body weight loss, along with reduced astrocytic activation. Interestingly, in the two motor function tests (beam-walking test and corner turn test), 8-month old mice exhibited lower scores only in the beam-walking test, suggesting a partial disturbance in motor recovery after ICH. These results suggest that age-related differences in ICH pathology may already start to appear in early middle-aged brains.

Nicotine promotes angiogenesis in mouse brain after intracerebral hemorrhage

Here we examined the effect of nicotine on angiogenesis in the brain after intracerebral hemorrhage (ICH), as angiogenesis is considered to provide beneficial effects on brain tissues during recovery from injury after stroke. Nicotine was administered to C57BL/6 mice suffering from collagenase-induced ICH in the striatum, either by inclusion in drinking water or by daily intraperitoneal injection. Nicotine administration by both routes enhanced angiogenesis within the hematoma-affected regions, as revealed by increased CD31-immunopositive area at 7 and 14 d after ICH. Double immunofluorescence histochemistry against CD31 and proliferating cell nuclear antigen revealed that nicotine increased the number of newly generated vascular endothelial cells within the hematoma. In spite of enhanced angiogenesis, nicotine did not worsen vascular permeability after ICH, as assessed by Evans Blue extravasation. These effects of nicotine were accompanied by an increased number of surviving neurons in the hematoma at 7 d after ICH. Unexpectedly, nicotine did not increase expression of vascular endothelial growth factor mRNA in the brain and did not enhance recruitment of endothelial progenitor cells from the bone marrow. These results suggest that nicotine enhances angiogenesis in the brain after ICH, via mechanisms distinct from those involved in its action on angiogenesis in peripheral tissues.

Laquinimod and 3,3'-diindolylemethane alleviate neuropathological events and neurological deficits in a mouse model of intracerebral hemorrhage

We examined the effects of compounds shown to activate aryl hydrocarbon receptor (AhR) signaling on a mouse model of intracerebral hemorrhage (ICH). Daily oral administration of laquinimod (25 mg/kg) or 3,3'-diindolylmethane (250 mg/kg) from 3 h after ICH induction improved motor functions, prevented the decrease of neurons within the hematoma, and attenuated activation of microglia/macrophages and astrocytes in the perihematomal region as well as infiltration of neutrophils into the hematoma. Elevated expression of AhR was detected in microglia and neutrophils, and both drugs inhibited upregulation of interleukin-6 and CXCL1. These results propose AhR as a therapeutic target for ICH.

Decreased Serum Retinoic Acid May Predict Poor Outcome in Ischemic Stroke Patients

BACKGROUND AND AIMS

Decreased serum retinoic acid (RA) levels have been shown to be linked with increased mortality in cardiovascular diseases. This study aimed to investigate the relationship between serum RA and 3-month functional outcome after ischemic stroke.

METHODS

Between January 2019 and September 2019, we prospectively recruited ischemic stroke patients within 24 hrs of symptom onset. Serum RA levels were measured for all patients at admission. The primary outcome was defined as poor functional outcome (modified Rankin Scale 3-6) at 90 days. The secondary outcome was defined as early neurological deterioration (END), which is considered as an increase of ≥1 point in motor power or total National Institutes of Health Stroke Scale score of ≥2 points within 7 days.

RESULTS

A total of 217 patients were included in the analysis. The median RA levels were 2.9 ng/mL. Ninety-four (43.3%) and 65 (30.0%) patients experienced 3-month poor outcome and END, respectively. After adjusted for potential confounders, decreased levels of serum RA were associated with a higher risk of poor outcome (P for trend = 0.001) and END (P for trend = 0.002). Adding RA quartile to the existing risk factors improved risk prediction for poor outcome [net reclassification improvement (NRI) = 42.6%, P = 0.001; integrated discrimination improvement (IDI) = 5.7%, P = 0.001] and END (NRI index = 45.4%, P = 0.001; IDI = 4.3%; P = 0.005).

CONCLUSION

Low serum RA levels at baseline were associated with poor prognosis at 90 days after ischemic stroke, suggesting that RA may be a potential prognostic biomarker for ischemic stroke.

Effect of Specific Retinoic Acid Receptor Agonists on Noise-Induced Hearing Loss

Noise is one of the most common causes of hearing loss in industrial countries. There are many studies about chemical agents to prevent noise-induced hearing loss (NIHL). However, there is no commercially available drug yet. Retinoic acid is an active metabolite of Vitamin A; it has an anti-apoptic role in NIHL. This study aims to verify the differences among selective agonists of retinoic acid receptors (RARs) in NIHL. All-trans retinoic acid (ATRA), AM80 (selective retinoic acid receptor α agonist), AC261066 (Selective retinoic acid receptor β1 agonist), and CD1530 (Selective retinoic acid λ agonist) were injected to 6–7 weeks old CJ5BL/6 mice before noise (110 dB for 3 h) exposure. In the auditory brainstem response test pre-, post 1, 3, and 7 days after noise exposure, not only ATRA but all kinds of selective RAR agonists showed protective effects in hearing threshold and wave I amplitude. Though there was no significant difference in the level of protective effects between agonists, α agonist showed the most prominent effect in preserving hearing function as well as outer hair cells after noise exposure. In conclusion, selective agonists of RAR demonstrate comparable protective effects against NIHL to retinoic acid. Given that these selective RAR agonists have less side effects than retinoic acid, they may be promising potential drugs against NIHL.

Transfusion of Resting Platelets Reduces Brain Hemorrhage After Intracerebral Hemorrhage and tPA-Induced Hemorrhage After Cerebral Ischemia

BACKGROUND

Exacerbated blood-brain barrier (BBB) damage is related with tissue plasminogen activator (tPA)-induced brain hemorrhage after stroke. Platelets have long been recognized as the cellular orchestrators of primary haemostasis. Recent studies have demonstrated further that platelets are required for supporting intact mature blood vessels and play a crucial role in maintaining vascular integrity during inflammation. Therefore, we sought to investigate whether platelets could reduce tPA-induced deterioration of cerebrovascular integrity and lead to less hemorrhagic transformation.

METHODS

Mice were subjected to models of collagenase-induced intracerebral hemorrhage (ICH) and transient middle cerebral artery (MCA) occlusion. After 2 h of MCA occlusion, tPA (10 mg/kg) was administered as an intravenous bolus injection of 1 mg/kg followed by a 9 mg/kg infusion for 30 min. Immediately after tPA treatment, mice were transfused with platelets. Hemorrhagic volume, infarct size, neurological deficit, tight junction and basal membrane damages, endothelial cell apoptosis, and extravascular accumulation of circulating dextran and IgG, and Evans blue were quantified at 24 h.

RESULTS

Platelet transfusion resulted in a significant decrease in hematoma volume after ICH. In mice after ischemia, tPA administration increased brain hemorrhage transformation and this was reversed by resting but not activated platelets. Consistent with this, we observed that tPA-induced brain hemorrhage was dramatically exacerbated in thrombocytopenic mice. Transfusion of resting platelets ameliorated tPA-induced loss of cerebrovascular integrity and reduced extravascular accumulation of circulating serum proteins and Evans blue, associated with improved neurological functions after ischemia. No changes were found for infarct volume. Inhibition of platelet receptor glycoprotein VI (GPVI) blunted the ability of platelets to attenuate tPA-induced BBB disruption and hemorrhage after ischemia.

CONCLUSION

Our findings demonstrate the importance of platelets in safeguarding BBB integrity and suggest that transfusion of resting platelets may be useful to improve the safety of tPA thrombolysis in ischemic stroke.

Lower serum retinoic acid level for prediction of higher risk of mortality in ischemic stroke

OBJECTIVE

To explore the association between serum retinoic acid (RA) level in patients with acute ischemic stroke (AIS) and mortality risk in the 6 months after admission.

METHODS

From January 2015 through December 2016, patients admitted to 3 stroke centers in China for first-ever AIS were screened. The primary endpoint was all-cause mortality or cardiovascular disease (CVD) mortality in the 6 months after admission. The significance of serum RA level, NIH Stroke Scale score, and established risk factors in predicting mortality were determined. The integrated discrimination improvement (IDI) and net reclassification improvement (NRI) statistics were applied in statistical analysis.

RESULTS

Of the 1,530 patients enrolled, 325 died within 6 months of admission, with an all-cause mortality of 21.2% and CVD-related mortality of 13.1%. In multivariable analysis, RA levels were expressed as quartiles with the clinical variables. The results of the second to fourth quartiles (Q2-Q4) were compared with the first quartile (Q1); RA levels showed prognostic significance, with decreased all-cause and CVD mortality of 55% and 63%, respectively. After RA was added to the existing risk factors, all-cause mortality could be better reclassified, in association with only the NRI statistic (p = 0.005); CVD mortality could be better reclassified with significance, in association with both the IDI and NRI statistics (p < 0.01).

CONCLUSIONS

Low circulating levels of RA were associated with increased risk of all-cause and CVD mortality in a cohort of patients with first-incidence AIS, indicating that RA level could be a predictor independent of established conventional risk factors.

A Nurr1 agonist amodiaquine attenuates inflammatory events and neurological deficits in a mouse model of intracerebral hemorrhage

Inflammatory responses are considered to play pivotal roles in the pathogenesis of intracerebral hemorrhage (ICH). Here we show that a nuclear receptor Nurr1 (NR4A2) was expressed prominently in microglia/macrophages and astrocytes in the perihematomal region in the striatum of mice after ICH. Daily administration of a Nurr1 agonist amodiaquine (40 mg/kg, i.p.) from 3 h after ICH induction diminished perihematomal activation of microglia/macrophages and astrocytes. Amodiaquine also suppressed ICH-induced mRNA expression of IL-1β, CCL2 and CXCL2, and ameliorated motor dysfunction of mice. These results suggest that Nurr1 serves a novel target for ICH therapy.

Intracerebral Hemorrhage as an Axonal Tract Injury Disorder with Inflammatory Reactions

Intracerebral hemorrhage (ICH) is a neurological disorder frequently accompanied by severe dysfunction. Critical pathogenic events leading to poor prognosis should be identified for the development of novel effective therapies for ICH. Here we focus on the injury of the axonal tract, particularly of the internal capsule, with reference to its contribution to ICH pathology and potential therapeutic interventions in addition to its cellular mechanisms. Studies on human ICH patients and rodent models of ICH suggest that invasion of hematoma into the internal capsule greatly worsens the severity of post-ICH symptoms. A blood-derived protease thrombin may play an important role in the acute phase of axonal tract injury in the internal capsule that includes compromised axonal transport and fragmentation of axonal structures. Several agents such as clioquinol, melatonin and Am80 (a retinoic acid receptor agonist) have been shown to produce therapeutic effects on rodent models of ICH associated with injury of the internal capsule. In the course of examinations on the effect of Am80, we obtained evidence for the involvement of CXCL2, a neutrophil chemotactic factor, in the pathogenesis of ICH. Accordingly, we also refer to the potential roles of infiltrating neutrophils and inflammatory responses in axonal tract injury and resultant neurological dysfunction in ICH.

Nicotinamide mononucleotide attenuates brain injury after intracerebral hemorrhage by activating Nrf2/HO-1 signaling pathway

Replenishment of NAD⁺ has been shown to protect against brain disorders such as amyotrophic lateral sclerosis and ischemic stroke. However, whether this intervention has therapeutic effects in intracerebral hemorrhage (ICH) is unknown. In this study, we sought to determine the potential therapeutic value of replenishment of NAD⁺ in ICH. In a collagenase-induced ICH (cICH) mouse model, nicotinamide mononucleotide (NMN), a key intermediate of nicotinamide adenine dinucleotide (NAD⁺) biosynthesis, was administrated at 30 minutes post cICH from tail vein to replenish NAD⁺. NMN treatment did not decrease hematoma volume and hemoglobin content. However, NMN treatment significantly reduced brain edema, brain cell death, oxidative stress, neuroinflammation, intercellular adhesion molecule-1 expression, microglia activation and neutrophil infiltration in brain hemorrhagic area. Mechanistically, NMN enhanced the expression of two cytoprotective proteins: heme oxygenase 1 (HO-1) and nuclear factor-like 2 (Nrf2). Moreover, NMN increased the nuclear translocation of Nrf2 for its activation. Finally, a prolonged NMN treatment for 7 days markedly promoted the recovery of body weight and neurological function. These results demonstrate that NMN treats brain injury in ICH by suppressing neuroinflammation/oxidative stress. The activation of Nrf2/HO-1 signaling pathway may contribute to the neuroprotection of NMN in ICH.

Palladium-mediated11C-carbonylations using aryl halides and cyanamide

A rapid, efficient and high-yielding synthesis of¹¹C-cyanobenzamides, including novel analogs of various drug molecules, is described.

Exogenous Modulation of Retinoic Acid Signaling Affects Adult RGC Survival in the Frog Visual System after Optic Nerve Injury

After lesions to the mammalian optic nerve, the great majority of retinal ganglion cells (RGCs) die before their axons have even had a chance to regenerate. Frog RGCs, on the other hand, suffer only an approximately 50% cell loss, and we have previously investigated the mechanisms by which the application of growth factors can increase their survival rate. Retinoic acid (RA) is a vitamin A-derived lipophilic molecule that plays major roles during development of the nervous system. The RA signaling pathway is also present in parts of the adult nervous system, and components of it are upregulated after injury in peripheral nerves but not in the CNS. Here we investigate whether RA signaling affects long-term RGC survival at 6 weeks after axotomy. Intraocular injection of all-trans retinoic acid (ATRA), the retinoic acid receptor (RAR) type-α agonist AM80, the RARβ agonist CD2314, or the RARγ agonist CD1530, returned axotomized RGC numbers to almost normal levels. On the other hand, inhibition of RA synthesis with disulfiram, or of RAR receptors with the pan-RAR antagonist Ro-41-5253, or the RARβ antagonist LE135E, greatly reduced the survival of the axotomized neurons. Axotomy elicited a strong activation of the MAPK, STAT3 and AKT pathways; this activation was prevented by disulfiram or by RAR antagonists. Finally, addition of exogenous ATRA stimulated the activation of the first two of these pathways. Future experiments will investigate whether these strong survival-promoting effects of RA are mediated via the upregulation of neurotrophins.

Toll-like receptor-4-mediated autophagy contributes to microglial activation and inflammatory injury in mouse models of intracerebral haemorrhage

AIMS

Much evidence demonstrates that Toll-like receptor-4 (TLR4)-mediated microglial activation is an important contributor to the inflammatory injury in intracerebral haemorrhage (ICH). However, the exact mechanism of TLR4-mediated microglial activation induced by ICH is not clear. In addition, microglial autophagy is involved other forms of nervous system injury. To explore the relationship between TLR4 and autophagy, we investigated the role of TLR4-mediated microglial autophagy and inflammation in ICH.

METHODS

We detected TLR4 expression, autophagy and inflammation of microglia treated with lysed erythrocytes in vitro, and observed the cerebral water content and neurological deficit of ICH mice [TLR4-/- and wild type (WT)] in vivo.

RESULTS

We found that lysed erythrocyte treated microglia (TLR4-/-) had reduced autophagy and inflammation compared with microglia (WT) in vitro. ICH mice (TLR4-/-) had reduced water content and neurological injury compared with ICH mice (WT). The autophagy inhibitor (3-methyladenine) decreased microglial activation and inflammatory injury due to lysed erythrocyte treatment, and improved the neurological function of ICH mice.

CONCLUSIONS

Taken together, these data suggested that TLR4 induced autophagy contributed to the microglial activation and inflammatory injury and might provide novel therapeutic interventions for ICH.

Axonal dysfunction in internal capsule is closely associated with early motor deficits after intracerebral hemorrhage in mice

Previously we showed that expansion of intracerebral hemorrhage (ICH) into the internal capsule greatly aggravated neurological symptoms in mice. Here we examined ICH-associated events in the internal capsule with relation to neurological dysfunction. Corticospinal axons labeled by biotinylated dextran amine exhibited fragmented appearance after ICH induced by local injection of collagenase into the internal capsule. Fragmentation of axonal structures was confirmed by neurofilament-H immunostaining, which was evident from 6h after induction of ICH. We also observed accumulation of amyloid precursor protein, which indicated compromised axonal transport, from 3h after induction of ICH. The early defect in axonal transport was accompanied by a robust decline in motor performance. Local application of an axonal transport inhibitor colchicine to the internal capsule induced a prompt decline in motor performance, suggesting that compromised axonal transport is closely associated with early neurological dysfunction in ICH. Arrest of axonal transport and fragmentation of axonal structures were also induced by local injection of thrombin, but not by thrombin receptor activator peptide-6, a protease-activated receptor-1 agonist. These results suggest that receptor-independent actions of thrombin mediate disruption of structure and function of axons by hemorrhage expansion into the internal capsule, which leads to severe neurological dysfunction.

Intracerebral hemorrhage in mouse models: therapeutic interventions and functional recovery

There has been strong pre-clinical research on mechanisms of initial cell death and tissue injury in intracerebral hemorrhage (ICH). This data has led to the evaluation of several therapeutics for neuroprotection or the mitigation of early tissue damage. Most of these studies have been done in the rat. Also, there has been little study of the mechanisms of tissue repair and recovery. This review examines the testing of candidate therapeutics in mouse models of ICH for their effect on tissue protection and repair. This review will help the readers compare it to the extensively researched rat model of ICH and thus enhance work that are pending in mouse model.

Suppression of CXCL2 upregulation underlies the therapeutic effect of the retinoid Am80 on intracerebral hemorrhage in mice

We previously demonstrated that a synthetic retinoic acid receptor agonist, Am80, attenuated intracerebral hemorrhage (ICH)-induced neuropathological changes and neurological dysfunction. Because inflammatory events are among the prominent features of ICH pathology that are affected by Am80, this study investigated the potential involvement of proinflammatory cytokines/chemokines in the effect of Am80 on ICH. ICH induced by collagenase injection into mouse striatum caused prominent upregulation of mRNAs for interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, CXCL1, CXCL2, and CCL3. We found that dexamethasone (DEX) and Am80 differently modulated the increase in expression of these cytokines/chemokines; TNF-α expression was attenuated only by DEX, whereas CXCL2 expression was attenuated only by Am80. Expression of IL-1β and IL-6 was inhibited both by DEX and Am80. Neurological assessments revealed that Am80, but not DEX, significantly alleviated motor dysfunction of mice after ICH. From these results, we suspected that CXCL2 might be critically involved in determining the extent of motor dysfunction. Indeed, magnetic resonance imaging-based classification of ICH in individual mice revealed that invasion of hematoma into the internal capsule, which has been shown to cause severe neurological disabilities, was associated with higher levels of CXCL2 expression than ICH without internal capsule invasion. Moreover, a CXCR1/2 antagonist reparixin ameliorated neurological deficits after ICH. Overall, suppression of CXCL2 expression may contribute to the beneficial effect of Am80 as a therapeutic agent for ICH, and interruption of CXCL2 signaling may provide a promising target for ICH therapy.

Fingolimod exerts neuroprotective effects in a mouse model of intracerebral hemorrhage

Recent studies have shown that fingolimod (FTY720) is neuroprotective in CNS injury models of cerebral ischemia and spinal cord injury. The purpose of the study was to examine the effect of fingolimod in a mouse model of intracerebral hemorrhage. ICH was produced in adult CD1 mice by injecting collagenase VII-S (0.5 µL, 0.06 U) into the basal ganglia. Fingolimod (or saline) was given 30 min after surgery and once daily for two days. Three days after intracerebral hemorrhage, brain edema, hematoma volume and the number of apoptotic cells were quantified. In another cohort of mice, brain atrophy was evaluated two weeks following intracerebral hemorrhage. Neurobehavioral tests were performed on the 3rd, the 7th and the 14th day. Fingolimod significantly decreased edema, apoptosis and brain atrophy. More importantly, fingolimod enhanced neurobehavioral recovery. Preliminary experiments showed no difference in the number of inflammatory (CD68-positive) cells between the two groups. In conclusion, fingolimod exerts protective effects in a mouse model of intracerebral hemorrhage; the mechanisms underlying these neuroprotective effects deserve further study.

Carvacrol alleviates cerebral edema by modulating AQP4 expression after intracerebral hemorrhage in mice

Carvacrol is a natural compound extracted from many plants of the family Lamiaceae. Previous studies have demonstrated that carvacrol has potential neuroprotective effects in central nervous system diseases such as Alzheimer's disease and cerebral ischemia. In this study, we investigated the preclinical effect of carvacrol on cerebral edema after intracerebral hemorrhage (ICH) using a bacterial collagenase-induced ICH mouse model. Mice were randomly divided into sham (n=43), vehicle-treated (n=51), and carvacrol-treated groups (n=101). In carvacrol-treated group, carvacrol was administrated to mice at 0h, 1h, or 3h after ICH induction. Carvacrol was injected intraperitoneally with single doses of 10, 25, 50, or 100mg/kg. Neurologic dysfunctions, brain water content, aquaporins (AQPs) mRNAs level and AQP4 protein expression in the perihematomal area were evaluated post ICH. Our results showed that carvacrol administration improved neurological deficits after day 3 following ICH (p<0.05). Carvacrol reduced cerebral edema and Evans Blue leakage at day 3 (p<0.05). We also found that carvacrol treatment decreased AQP4 mRNA in a dose-dependent manner at 24h. Furthermore, AQP4 protein expression in the perihematomal area was reduced by carvacrol significantly at day 3 after ICH (p<0.05). Our findings suggest that carvacrol may exert its protective effect on ICH injury by ameliorating AQP4-mediated cerebral edema.

MRI-based analysis of intracerebral hemorrhage in mice reveals relationship between hematoma expansion and the severity of symptoms

Intracerebral hemorrhage (ICH) is featured by poor prognosis such as high mortality rate and severe neurological dysfunction. In humans, several valuables including hematoma volume and ventricular expansion of hemorrhage are known to correlate with the extent of mortality and neurological dysfunction. However, relationship between hematoma conditions and the severity of symptoms in animal ICH models has not been clarified. Here we addressed this issue by using 7-tesla magnetic resonance imaging (MRI) on collagenase-induced ICH model in mice. We found that the mortality rate and the performance in behavioral tests did not correlate well with the volume of hematoma. In contrast, when hemorrhage invaded the internal capsule, mice exhibited high mortality and showed poor sensorimotor performance. High mortality rate and poor performance in behavioral tests were also observed when hemorrhage invaded the lateral ventricle, although worsened symptoms associated with ventricular hemorrhage were apparent only during early phase of the disease. These results clearly indicate that invasion of the internal capsule or the lateral ventricle by hematoma is a critical determinant of poor prognosis in experimental ICH model in mice as well as in human ICH patients. MRI assessment may be a powerful tool to refine investigations of pathogenic mechanisms and evaluations of drug effects in animal models of ICH.

Experimental high-altitude intracerebral hemorrhage in minipigs: histology, behavior, and intracranial pressure in a double-injection model

BACKGROUND

Specific pathophysiological mechanism in intracerebral hemorrhage (ICH) at high altitude is unclear, and at present, there is no relevant and suitable animal model.

METHODS

A hypobaric chamber was used to simulate an altitude of 4,000 m. Autologous arterial blood (3 ml) was slowly infused into the right basal ganglia of minipigs by a double-injection method for producing ICH.

RESULTS

The intracranial pressure and neurological score of the high-altitude group were significantly higher than those of the low-altitude (plain) group. The brain water contents and pathological lesions of perihematoma tissue were more severe in the high-altitude group.

CONCLUSIONS

The injury resulting from ICH at high altitude was more severe than that in the plain group. This model was able to produce controllable and reproducible hematomas and visible neurological deficits, which may be useful for future studies of the pathophysiology and functional rehabilitation of high-altitude ICH disease.

Retinoids in the treatment of glioma: a new perspective

Primary brain tumors are among the top ten causes of cancer-related deaths in the US. Malignant gliomas account for approximately 70% of the 22,500 new cases of malignant primary brain tumors diagnosed in adults each year and are associated with high morbidity and mortality. Despite optimal treatment, the prognosis for patients with gliomas remains poor. The use of retinoids (vitamin A and its congeners) in the treatment of certain tumors was originally based on the assumption that these conditions were associated with an underlying deficiency of vitamin A and that supplementation with pharmacological doses would correct the deficiency. Yet the results of retinoid treatment have been only modestly beneficial and usually short-lived. Studies also indicate that vitamin A excess and supplementation have pro-oxidant effects and are associated with increased risks of mortality from cancer and other diseases. The therapeutic role of vitamin A in cancer thus remains uncertain and a new perspective on the facts is needed. The modest and temporary benefits of retinoid treatment could result from a process of feedback inhibition, whereby exogenous retinoid temporarily inhibits the endogenous synthesis of these compounds. In fact, repeated and/or excessive exposure of the tissues to endogenous retinoic acid may contribute to carcinogenesis. Gliomas, in particular, may result from an imbalance in retinoid receptor expression initiated by environmental factors that increase the endogenous production of retinoic acid in glia. At the receptor level, it is proposed that this imbalance is characterized by excessive expression of retinoic acid receptor-α (RARα) and reduced expression of retinoic acid receptor-β (RARβ). This suggests a potential new treatment strategy for gliomas, possibly even at a late stage of the disease, ie, to combine the use of a RARα antagonist and a RARβ agonist. According to this hypothesis, the RARα antagonist would be expected to inhibit RARα-induced gliomas, while the RARβ agonist would suppress tumor growth and possibly contribute to the regeneration of normal glia.

Enhanced lithium-induced brain recovery following cranial irradiation is not impeded by inflammation

Radiation-induced brain injury occurs in many patients receiving cranial radiation therapy, and these deleterious effects are most profound in younger patients. Impaired neurocognitive functions in both humans and rodents are associated with inflammation, demyelination, and neural stem cell dysfunction. Here we evaluated the utility of lithium and a synthetic retinoid receptor agonist in reducing damage in a model of brain-focused irradiation in juvenile mice. We found that lithium stimulated brain progenitor cell proliferation and differentiation following cranial irradiation while also preventing oligodendrocyte loss in the dentate gyrus of juvenile mice. In response to inflammation induced by radiation, which may have encumbered the optimal reparative action of lithium, we used the anti-inflammatory synthetic retinoid Am80 that is in clinical use in the treatment of acute promyelocytic leukemia. Although Am80 reduced the number of cyclooxygenase-2-positive microglial cells following radiation treatment, it did not enhance lithium-induced neurogenesis recovery, and this alone was not significantly different from the effect of lithium on this proinflammatory response. Similarly, lithium was superior to Am80 in supporting the restoration of new doublecortin-positive neurons following irradiation. These data suggest that lithium is superior in its restorative effects to blocking inflammation alone, at least in the case of Am80. Because lithium has been in routine clinical practice for 60 years, these preclinical studies indicate that this drug might be beneficial in reducing post-therapy late effects in patients receiving cranial radiotherapy and that blocking inflammation in this context may not be as advantageous as previously suggested.

Acute effects of all-trans-retinoic acid in ischemic injury

All-trans-retinoic acid (ATRA) is a vitamin A derivative that is important in neuronal patterning, survival, and neurite outgrowth. Neuroprotective effects of ATRA in ischemia have been demonstrated but its effects on glial swelling are not known. We investigated the relatively acute effects of ATRA on cell swelling in ischemic injury and on key features hypothesized to contribute to cell swelling including increased reactive oxygen species/reactive nitrogen species (ROS/RNS), depolarization of the inner mitochondrial membrane potential (ΔΨm), and increased intracellular calcium ([Ca2+]i). C6 glial cultures were subjected to 5 hr oxygen-glucose deprivation (OGD). ATRA was added to separate groups after the end of OGD. OGD increased cell volume by 43%, determined at 90 min after the end of OGD, but this increase was significantly attenuated by ATRA. OGD induced an increase in ROS/RNS production in the whole cell and mitochondria, as assessed by the fluorescent dyes CM-H2DCFDA and MitoTracker CM-H2-XROS at the end of OGD. The increase in mitochondrial ROS, but not cellular ROS, was significantly attenuated by ATRA. OGD also induced a 67% decline in mitochondrial ΔΨm but this decline was significantly attenuated by ATRA. OGD-induced increase in [Ca2+]i was also significantly attenuated by ATRA. Taken together with our previous results where calcium channel blockers reduced cell swelling, the effects of ATRA in attenuating swelling are possibly mediated through its effects in regulating [Ca2+]i. Considering the paucity of agents in attenuating brain edema in ischemia, ATRA has the potential to reduce brain edema and associated neural damage in ischemic injury.