Neuroprotection by Exogenous and Endogenous Neuregulin-1 in Mouse Models of Focal Ischemic Stroke

Single nuclei RNA-seq reveals a medium spiny neuron glutamate excitotoxicity signature prior to the onset of neuronal death in an ovine Huntington's disease model

Huntington's disease (HD) is a neurodegenerative genetic disorder caused by an expansion in the CAG repeat tract of the huntingtin (HTT) gene resulting in behavioural, cognitive, and motor defects. Current knowledge of disease pathogenesis remains incomplete, and no disease course-modifying interventions are in clinical use. We have previously reported the development and characterisation of the OVT73 transgenic sheep model of HD. The 73 polyglutamine repeat is somatically stable and therefore likely captures a prodromal phase of the disease with an absence of motor symptomatology even at 5-years of age and no detectable striatal cell loss. To better understand the disease-initiating events we have undertaken a single nuclei transcriptome study of the striatum of an extensively studied cohort of 5-year-old OVT73 HD sheep and age matched wild-type controls. We have identified transcriptional upregulation of genes encoding N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors in medium spiny neurons, the cell type preferentially lost early in HD. Further, we observed an upregulation of astrocytic glutamate uptake transporters and medium spiny neuron GABAA receptors, which may maintain glutamate homeostasis. Taken together, these observations support the glutamate excitotoxicity hypothesis as an early neurodegeneration cascade-initiating process but the threshold of toxicity may be regulated by several protective mechanisms. Addressing this biochemical defect early may prevent neuronal loss and avoid the more complex secondary consequences precipitated by cell death.

Alteration of N6-methyladenosine modification profiles in the neutrophilic RNAs following ischemic stroke

BACKGROUND

N6-methyladenosine (m6A) is one of the most extensive RNA methylation modifications in eukaryotes and participates in the pathogenesis of numerous diseases including ischemic stroke. Peripheral blood neutrophils are forerunners after ischemic brain injury and exert crucial functions. This study aims to explore the transcriptional profiles of m6A modification in neutrophils of patients with ischemic stroke.

RESULTS

We found that the expression levels of m6A regulators FTO and YTHDC1 were notably decreased in the neutrophils following ischemic stroke, and FTO expression was negatively correlated with neutrophil counts and neutrophil-to-lymphocyte ratio (NLR). The m6A mRNA&lncRNA epigenetic transcriptome microarray identified 416 significantly upregulated and 500 significantly downregulated mRNA peaks in neutrophils of ischemic stroke patients. Moreover, 48 mRNAs and 18 lncRNAs were hypermethylated, and 115 mRNAs and 29 lncRNAs were hypomethylated after cerebral ischemia. Gene ontology (GO) analysis identified that these m6A-modified mRNAs were primarily enriched in calcium ion transport, long-term synaptic potentiation, and base-excision repair. The signaling pathways involved were EGFR tyrosine kinase inhibitor resistance, ErbB, and base excision repair signaling pathway. MeRIP-qPCR validation results showed that NRG1 and GDPD1 were significantly hypermethylated, and LIG1, CHRND, lncRNA RP11-442J17.2, and lncRNA RP11-600P1.2 were significantly hypomethylated after cerebral ischemia. Moreover, the expression levels of major m6A regulators Mettl3, Fto, Ythdf1, and Ythdf3 were obviously declined in the brain and leukocytes of post-stroke mouse models.

CONCLUSION

This study explored the RNA m6A methylation pattern in the neutrophils of ischemic stroke patients, indicating that it is an intervention target of epigenetic regulation in ischemic stroke.

The case for neuregulin-1 as a clinical treatment for stroke

Ischemic stroke is the leading cause of serious long-term disability and the 5th leading cause of death in the United States. Revascularization of the occluded cerebral artery, either by thrombolysis or endovascular thrombectomy, is the only effective, clinically-approved stroke therapy. Several potentially neuroprotective agents, including glutamate antagonists, anti-inflammatory compounds and free radical scavenging agents were shown to be effective neuroprotectants in preclinical animal models of brain ischemia. However, these compounds did not demonstrate efficacy in clinical trials with human patients following stroke. Proposed reasons for the translational failure include an insufficient understanding on the cellular and molecular pathophysiology of ischemic stroke, lack of alignment between preclinical and clinical studies and inappropriate design of clinical trials based on the preclinical findings. Therefore, novel neuroprotective treatments must be developed based on a clearer understanding of the complex spatiotemporal mechanisms of ischemic stroke and with proper clinical trial design based on the preclinical findings from specific animal models of stroke. We and others have demonstrated the clinical potential for neuregulin-1 (NRG-1) in preclinical stroke studies. NRG-1 significantly reduced ischemia-induced neuronal death, neuroinflammation and oxidative stress in rodent stroke models with a therapeutic window of >13 h. Clinically, NRG-1 was shown to be safe in human patients and improved cardiac function in multisite phase II studies for heart failure. This review summarizes previous stroke clinical candidates and provides evidence that NRG-1 represents a novel, safe, neuroprotective strategy that has potential therapeutic value in treating individuals after acute ischemic stroke.

Neuregulin 1 as a potential biomarker for disease progression in moyamoya disease: A case-control study in Chinese population

OBJECTIVE

Moyamoya disease (MMD) is a rare and progressive stenosis of cerebral arteries characterized by abnormally proliferative vasculopathy. Current studies have demonstrated that Neuregulin 1 (NRG1) plays a key role in angiogenesis-related disorders. Thus, the aim of our study is to investigate the serum NRG1 levels and their clinical correlations in MMD patients.

METHODS

In this study, thirty adult patients with MMD and age-gender matched healthy controls were enrolled from our hospital between July 2020 and April 2022. Peripheral blood samples were collected at baseline, and clinical data were obtained from the electronic medical record system. Serum NRG1 concentrations were measured by enzyme-linked immunosorbent assay. Sanger sequencing was applied to detect the RNF213 p.R4810K mutation.

RESULTS

The serum NRG1 levels were significantly higher in MMD patients compared to controls (14.48 ± 10.81 vs.7.54 ± 6.35mmol/L, p < 0.001). No statistical difference in baseline clinical characteristics was found between both groups. Correlation analyses showed that NRG1 levels were positively associated with Suzuki staging (r = 0.4137, p = 0.023) while not related to other clinical features (reduced cerebral blood flow, posterior cerebral artery involvement, bilateral or unilateral steno-occlusive changes). Furthermore, subgroup analysis revealed that MMD patients with the RNF213 p.R4810K mutation presented with significantly higher NRG1 levels than those without the mutation (9.60 ± 0.929 vs. 25.89 ± 4.338 mmol/L, p = 0.001).

CONCLUSIONS

Our study suggests that increased serum NRG1 levels may constitute a characteristic feature of MMD, indicating a potential positive correlation with disease progression and the presence of the RNF213 mutation. This positions NRG1 as a potentially crucial target for further studies aimed at comprehending the pathogenesis of MMD.

Effect of thymosin β4 on lipopolysaccharide‑stimulated brain microvascular endothelial cell remodeling: A possible role in blood‑brain barrier injury

War veterans, in particular, are more prone to mental illness as they are more likely to have encountered multiple traumatic brain injuries (TBIs) whilst serving on active duty in war zone areas. A TBI is known to cause mortality or serious neurological disabilities among survivors and elicits a number of pathological processes, including neuroinflammation and blood brain barrier (BBB) disruption, leading to secondary brain damage and subsequent impairment of the neurovascular unit. Although several drugs exhibit promising effects for TBI, the repertoire of currently available therapeutic strategies remains limited. Thymosin 4 (Tβ4) is a 43-amino acid G-acting sequestering peptide that confers neuroprotective potential in TBI models. However, its role in BBB function remains unclear. Further research into the mechanism of BBB disruption induced by TBI and its specific role in neurovascular pathophysiology is necessary. In the present study, the protective effects of Tβ4 in lipopolysaccharide (LPS)-stimulated gene expression of several tight junction proteins, inflammatory genes, apoptotic genes, and adhesion genes in human brain microvascular endothelial cells (hBMVECs), one of the pivotal cell types in the BBB, were reported. The results suggested that pretreatment with Tβ4 reversed the LPS-induced damage of BBB components in hBMVECs. Furthermore, these results identified neuregulin 1 as a possible target for Tβ4. Therefore, it is proposed that Tβ4-mediated cellular signaling in hBMVEC may be vital for understanding the association between the BBB and TBI pathophysiology, which warrants further investigation.

Neuregulin-1/PI3K signaling effects on oligodendrocyte proliferation, remyelination and behaviors deficit in a male mouse model of ischemic stroke

In this study, we investigated the effect of neuregulin-1 (NRG1) on demyelination and neurological function in an ischemic stroke model, and further explored its neuroprotective mechanisms. Adult male ICR mice underwent photothrombotic ischemia surgery and were injected with NRG1 beginning 30 min after ischemia. Cylinder and grid walking tests were performed to evaluate the forepaw function. In addition, the effect of NRG1 on neuronal damage/death (Cresyl violet, CV), neuronal nuclei (NeuN), nestin, doublecortin (DCX), myelin basic protein (MBP), non-phosphorylated neurofilaments (SMI-32), adenomatous polyposis coli (APC), erythroblastic leukemia viral oncogene homolog (ErbB) 2, 4 and serine-threonine protein kinase (Akt) in cortex were evaluated using immunohistochemistry, immunofluorescence and western blot. The cylinder and grid walking tests exposed that treatment of NRG1 observably regained the forepaw function. NRG1 treatment reduced cerebral infarction, restored forepaw function, promoted proliferation and differentiation of neuron and increased oligodendrogliogenesis. The neuroprotective effect of NRG1 is involved in its activation of PI3K/Akt signaling pathway via ErbB2, as shown by the suppression of the effect of NRG1 by the PI3K inhibitor LY294002. Our results demonstrate that NRG1 is effective in ameliorating the both acute phase neuroprotection and long-term neurological functions via resumption of neuronal proliferation and differentiation and oligodendrogliogenesis in a male mouse model of ischemic stroke.

Neuregulin-1 reverses anxiety-like behavior and social behavior deficits induced by unilateral micro-injection of CoCl2 into the ventral hippocampus (vHPC)

Neuregulin-1 (NRG1) is an epidermal growth factor family member with essential roles in the developing and adult nervous systems. In recent years, establishing evidence has collectively suggested that NRG1 is a new modulator of central nervous system (CNS) injury and disease, with multifaceted roles in neuroprotection, remyelination, neuroinflammation, and other repair mechanisms. NRG1 signaling exerts its effects via the tyrosine kinase receptors ErbB2-ErbB4. The NRG1/ErbB network in CNS pathology and repair has evolved, primarily in recent years. In the present study, we demonstrated that a unilateral microinjection of CoCl₂ into the ventral hippocampus (vHPC) induced hypoxic insult and led to anxiety-related behaviors and deficit sociability in mice. NRG1 treatment significantly alleviated the CoCl₂-induced increase of hypoxic-related molecules and behavioral abnormalities. Furthermore, NRG1 reduced the CoCl₂-induced neuroinflammation and neuronal deficits in the vHPC or primary hippocampal neurons in mice. Collectively, these results suggest that NRG1 ameliorates hypoxia by alleviating synaptic deficits and behavioral abnormalities of the CoCl₂-induced vHPC hypoxic model.

Astragaloside VI Ameliorates Post-Stroke Depression via Upregulating the NRG-1-Mediated MEK/ERK Pathway

BACKGROUND

Post-stroke depression (PSD) has been identified as one of the most commonly occurring complications attributed to stroke. Astragaloside VI (AsVI), which is an active Radix Astragali (AR)-derived compound, has been reported to be a potential drug for post-stroke therapy, but its effects on PSD and the underlying mechanisms remain uncovered.

METHODS

In this study, healthy male SD rats underwent a middle cerebral artery occlusion (MCAO) stroke model. To create a PSD model, these rats were then kept in isolated houses and subjected to chronic unpredictable mild stress. The rats were examined every five days for a series of behavioral tests of depression. The antidepressant properties of AsVI were also investigated in vitro in a corticosterone (CORT)-induced major depression model using a CCK-8 assay. The release of neurotransmitters dopamine (DA)/5-hydroxytryptamine (5-HT) was measured using HPLC. The expression of the neurotrophic factor Neuregulin 1 (NRG-1) in rat brain tissues was detected by immunostaining. The protein expression of NRG-1, p-MEK1, and p-ERK1/2 was analyzed utilizing western blotting.

RESULTS

AsVI treatment significantly reduced depression-like behaviors in PSD rats and attenuated the CORT-induced apoptotic cell death in neuronal PC-12 cells. Besides, AsVI treatment remarkably prevented the decrease of the levels of DA and 5-HT in the PSD rat brains and in CORT-induced PC-12 cells. Furthermore, AsVI treatment upregulated the NRG-1-mediated MEK/ERK pathway, which is associated with the improvement of PSD.

CONCLUSIONS

These findings suggest that AsVI could improve PSD at least partially by upregulating NRG-1-mediated MEK/ERK pathway. AsVI could be a novel therapeutic option for treating PSD.

Spatial Analysis of Neural Cell Proteomic Profiles Following Ischemic Stroke in Mice Using High-Plex Digital Spatial Profiling

Stroke is ranked as the fifth leading cause of death and the leading cause of adult disability in the USA. The progression of neuronal damage after stroke is recognized to be a complex integration of glia, neurons, and the surrounding extracellular matrix, therefore potential treatments must target the detrimental effects created by these interactions. In this study, we examined the spatial cellular and neuroinflammatory mechanisms occurring early after ischemic stroke utilizing Nanostring Digital Spatial Profiling (DSP) technology. Male C57bl/6 mice were subjected to photothrombotic middle cerebral artery occlusion (MCAO) and sacrificed at 3 days post-ischemia. Spatial distinction of the ipsilateral hemisphere was studied according to the regions of interest: the ischemic core, peri-infarct tissues, and peri-infarct normal tissue (PiNT) in comparison to the contralateral hemisphere. We demonstrated that the ipsilateral hemisphere initiates distinct spatial regulatory proteomic profiles with DSP technology that can be identified consistently with the immunohistochemical markers, FJB, GFAP, and Iba-1. The core border profile demonstrated an induction of neuronal death, apoptosis, autophagy, immunoreactivity, and early degenerative proteins. Most notably, the core border resulted in a decrease of the neuronal proteins Map2 and NeuN; an increase in the autophagy proteins BAG3 and CTSD; an increase in the microglial and peripheral immune invasion proteins Iba1, CD45, CD11b, and CD39; and an increase in the neurodegenerative proteins BACE1, APP, amyloid β 1-42, ApoE, and hyperphosphorylated tau protein S-199. The peri-infarct region demonstrated increased astrocytic, immunoreactivity, apoptotic, and neurodegenerative proteomic profiles, with an increase in BAG3, GFAP, and hyperphosphorylated tau protein S-199. The PiNT region displayed minimal changes compared to the contralateral cortex with only an increase in GFAP. In this study, we showed that mechanisms known to be associated with stroke, such as apoptosis and inflammation, occur in distinct spatial domains of the injured brain following ischemia. We also demonstrated the dysregulation of specific autophagic pathways that may lead to neurodegeneration in peri-infarct brain tissues. Taken together, these data suggest that identifying post-ischemic mechanisms occurring in a spatiotemporal manner may lead to more precise targets for successful therapeutic interventions to treat stroke.

Regulation of NRG-1-ErbB4 signaling and neuroprotection by exogenous neuregulin-1 in a mouse model of epilepsy

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. Dysregulation of glutamate transporters has been a common finding across animal models of epilepsy and in patients with TLE. In this study, we investigate NRG-1/ErbB4 signaling in epileptogenesis and the neuroprotective effects of NRG-1 treatment in a mouse model of temporal lobe epilepsy. Using immunohistochemistry, we report the first evidence for NRG-1/ErbB4-dependent selective upregulation of glutamate transporter EAAC1 and bihemispheric neuroprotection by exogeneous NRG-1 in the intrahippocampal kainic acid (IHKA) model of TLE. Our findings provide evidence that dysregulation of glutamate transporter EAAC1 contributes to the development of epilepsy and can be therapeutically targeted to reduce neuronal death following IHKA-induced status epilepticus (SE).

Availability of neuregulin-1beta1 protects neurons in spinal cord injury and against glutamate toxicity through caspase dependent and independent mechanisms

Spinal cord injury (SCI) causes sensorimotor and autonomic impairment that partly reflects extensive, permanent loss of neurons at the epicenter and penumbra of the injury. Strategies aimed at enhancing neuronal protection are critical to attenuate neurodegeneration and improve neurological recovery after SCI. In rat SCI, we previously uncovered that the tissue levels of neuregulin-1beta 1 (Nrg-1β1) are acutely and persistently downregulated in the injured spinal cord. Nrg-1β1 is well-known for its critical roles in the development, maintenance and physiology of neurons and glia in the developing and adult spinal cord. However, despite this pivotal role, Nrg-1β1 specific effects and mechanisms of action on neuronal injury remain largely unknown in SCI. In the present study, using a clinically-relevant model of compressive/contusive SCI in rats and an in vitro model of glutamate toxicity in primary neurons, we demonstrate Nrg-1β1 provides early neuroprotection through attenuation of reactive oxygen species, lipid peroxidation, necrosis and apoptosis in acute and subacute stages of SCI. Mechanistically, availability of Nrg-1β1 following glutamate challenge protects neurons from caspase-dependent and independent cell death that is mediated by modulation of mitochondria associated apoptotic cascades and MAP kinase and AKT signaling pathways. Altogether, our work provides novel insights into the role and mechanisms of Nrg-1β1 in neuronal injury after SCI and introduces its potential as a new neuroprotective target for this debilitating neurological condition.

Elevated neuregulin-1β levels correlate with plasma biomarkers of cerebral injury and high stroke risk in children with sickle cell anemia

Stroke, or cerebral infarction, is one of the most serious complications of sickle cell anemia (SCA) in childhood, potentially leading to impaired development and life-long physical and cognitive disabilities. About one in ten children with SCA are at risk for developing overt stroke and an additional 25% may develop silent cerebral infarcts. This is largely due to underlying cerebral injury caused by chronic cerebral ischemia and vascular insult associated with SCA. We previously identified two elevated markers of cerebral injury, plasma brain-derived neurotropic factor (BDNF) and platelet-derived growth factor (PDGF)-AA, in children with SCA and high stroke risk. The objective of this study was to investigate whether neuregulin-1β (NRG-1), an endogenous neuroprotective polypeptide may also be elevated in children with SCA. Neuregulin-1β is involved in the preservation of blood brain barrier integrity and brain microvascular cell viability and is cytoprotective in conditions of heme-induced injury and ischemia. Since elevated plasma heme and ischemia are signature characteristics of SCA, we hypothesized that NRG-1 would be elevated in children with SCA, and that NRG-1 levels would also correlate with our biomarkers of cerebral injury. Plasma NRG-1, BDNF and PDGF-AA levels were measured in children with SCA and healthy Controls. Plasma NRG-1 was found to be nearly five-fold higher in those children with SCA compared to Controls. Neuregulin-1β was also positively correlated with both BDNF and PDGF-AA concentrations, but was not associated with degree of anemia, suggesting that NRG-1 production may be an endogenous response to subclinical cerebral ischemia in SCA warranting further exploration.

The Endocrine Disruptor Bisphenol A (BPA) Affects the Enteric Neurons Immunoreactive to Neuregulin 1 (NRG1) in the Enteric Nervous System of the Porcine Large Intestine

The enteric nervous system (ENS), located in the wall of the gastrointestinal (GI) tract, is characterized by complex organization and a high degree of neurochemical diversity of neurons. One of the less known active neuronal substances found in the enteric neurons is neuregulin 1 (NRG1), a factor known to be involved in the assurance of normal development of the nervous system. During the study, made up using the double immunofluorescence technique, the presence of NRG1 in the ENS of the selected segment of porcine large intestine (caecum, ascending and descending colon) was observed in physiological conditions, as well as under the impact of low and high doses of bisphenol A (BPA) which is commonly used in the production of plastics. In control animals in all types of the enteric plexuses, the percentage of NRG1-positive neurons oscillated around 20% of all neurons. The administration of BPA caused an increase in the number of NRG1-positive neurons in all types of the enteric plexuses and in all segments of the large intestine studied. The most visible changes were noted in the inner submucous plexus of the ascending colon, where in animals treated with high doses of BPA, the percentage of NRG1-positive neurons amounted to above 45% of all neuronal cells. The mechanisms of observed changes are not entirely clear, but probably result from neurotoxic, neurodegenerative and/or proinflammatory activity of BPA and are protective and adaptive in nature.

Targeting the NF-κB pathway for therapy of ischemic stroke

Ischemic strokes occur when a major cerebral artery or its branches are occluded, resulting in activation of inflammatory processes that cause secondary tissue injury, breakdown of the blood–brain barrier, edema or hemorrhage. Treatments that inhibit inflammatory processes may thus be highly beneficial. A key regulator of the inflammatory process is the nuclear factor kappa B (NF-κB) pathway. In its active form, NF-κB regulates expression of proinflammatory and proapoptotic genes. The molecules that interact with NF-κB, and the subunits that compose NF-κB itself, represent therapeutic targets that can be modulated to decrease inflammation. This review focuses on our current understanding of the NF-κB pathway and the potential benefits of inhibiting NF-κB in ischemia-reperfusion injury of the brain.

Impact of High Salt Diet on Cerebral Vascular Function and Stroke in Tff3-/-/C57BL/6N Knockout and WT (C57BL/6N) Control Mice

High salt (HS) dietary intake leads to impaired vascular endothelium-dependent responses to various physiological stimuli, some of which are mediated by arachidonic acid (AA) metabolites. Transgenic Tff3^−/− gene knockout mice (Tff3^−/−/C57BL/6N) have changes in lipid metabolism which may affect vascular function and outcomes of stroke. We aimed to study the effects of one week of HS diet (4% NaCl) on vascular function and stroke induced by transient occlusion of middle cerebral artery in Tff3^−/− and wild type (WT/C57BL/6N) mice. Flow-induced dilation (FID) of carotid artery was reduced in WT-HS mice, but not affected in Tff3^−/−-HS mice. Nitric oxide (NO) mediated FID. NO production was decreased with HS diet. On the contrary, acetylcholine-induced dilation was significantly decreased in Tff3^−/− mice on both diets and WT-HS mice. HS intake and Tff3 gene depletion affected the structural components of the vessels. Proteomic analysis revealed a significant effect of Tff3 gene deficiency on HS diet-induced changes in neuronal structural proteins and acute innate immune response proteins’ expression and Tff3 depletion, but HS diet did not increase the stroke volume, which is related to proteome modification and upregulation of genes involved mainly in cellular antioxidative defense. In conclusion, Tff3 depletion seems to partially impair vascular function and worsen the outcomes of stroke, which is moderately affected by HS diet.