Techniques for Intracranial Stereotaxic Injections of Adeno-Associated Viral Vectors in Adult Mice

D-allose Inhibits TLR4/PI3K/AKT Signaling to Attenuate Neuroinflammation and Neuronal Apoptosis by Inhibiting Gal-3 Following Ischemic Stroke

BACKGROUND

Ischemic stroke (IS) occurs when a blood vessel supplying the brain becomes obstructed, resulting in cerebral ischemia. This type of stroke accounts for approximately 87% of all strokes. Globally, IS leads to high mortality and poor prognosis and is associated with neuroinflammation and neuronal apoptosis. D-allose is a bio-substrate of glucose that is widely expressed in many plants. Our previous study showed that D-allose exerted neuroprotective effects against acute cerebral ischemic/reperfusion (I/R) injury by reducing neuroinflammation. Here, we aimed to clarify the beneficial effects D-allose in suppressing IS-induced neuroinflammation damage, cytotoxicity, neuronal apoptosis and neurological deficits and the underlying mechanism in vitro and in vivo.

METHODS

In vivo, an I/R model was induced by middle cerebral artery occlusion and reperfusion (MCAO/R) in C57BL/6 N mice, and D-allose was given by intraperitoneal injection within 5 min after reperfusion. In vitro, mouse hippocampal neuronal cells (HT-22) with oxygen-glucose deprivation and reperfusion (OGD/R) were established as a cell model of IS. Neurological scores, some cytokines, cytotoxicity and apoptosis in the brain and cell lines were measured. Moreover, Gal-3 short hairpin RNAs, lentiviruses and adeno-associated viruses were used to modulate Gal-3 expression in neurons in vitro and in vivo to reveal the molecular mechanism.

RESULTS

D-allose alleviated cytotoxicity, including cell viability, LDH release and apoptosis, in HT-22 cells after OGD/R, which also alleviated brain injury, as indicated by lesion volume, brain edema, neuronal apoptosis, and neurological functional deficits, in a mouse model of I/R. Moreover, D-allose decreased the release of inflammatory factors, such as IL-1β, IL-6 and TNF-α. Furthermore, the expression of Gal-3 was increased by I/R in wild-type mice and HT-22 cells, and this factor further bound to TLR4, as confirmed by three-dimensional structure prediction and Co-IP. Silencing the Gal-3 gene with shRNAs decreased the activation of TLR4 signaling and alleviated IS-induced neuroinflammation, apoptosis and brain injury. Importantly, the loss of Gal-3 enhanced the D-allose-mediated protection against I/R-induced HT-22 cell injury, inflammatory insults and apoptosis, whereas activation of TLR4 by the selective agonist LPS increased the degree of neuronal injury and abolished the protective effects of D-allose.

CONCLUSIONS

In summary, D-allose plays a crucial role in inhibiting inflammation after IS by suppressing Gal-3/TLR4/PI3K/AKT signaling pathway in vitro and in vivo.

Effects of low-intensity ultrasound opening the blood-brain barrier on Alzheimer's disease-a mini review

Due to the complex pathological mechanisms of Alzheimer's disease (AD), its treatment remains a challenge. One of the major difficulties in treating AD is the difficulty for drugs to cross the blood-brain barrier (BBB). Low-intensity ultrasound (LIUS) is a novel type of ultrasound with neuromodulation function. It has been widely reported that LIUS combined with intravenous injection of microbubbles (MB) can effectively, safely, and reversibly open the BBB to achieve non-invasive targeted drug delivery. However, many studies have reported that LIUS combined with MB-mediated BBB opening (LIUS + MB-BBBO) can improve pathological deposition and cognitive impairment in AD patients and mice without delivering additional drugs. This article reviews the relevant research studies on LIUS + MB-BBBO in the treatment of AD, analyzes its potential mechanisms, and summarizes relevant ultrasound parameters.

Cell primitive-based biomimetic nanomaterials for Alzheimer's disease targeting and therapy

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, which is not just confined to the older population. Although developments have been made in AD treatment, various limitations remain to be addressed. These are partly contributed by biological hurdles, such as the blood-brain barrier and peripheral side effects, as well as by lack of carriers that can efficiently deliver the therapeutics to the brain while preserving their therapeutic efficacy. The increasing AD prevalence and the unavailability of effective treatments have encouraged researchers to develop improved, convenient, and affordable therapies. Functional materials based on primitive cells and nanotechnology are emerging as attractive therapeutics in AD treatment. Cell primitives possess distinct biological functions, including long-term circulation, lesion site targeting, and immune suppression. This review summarizes the challenges in the delivery of AD drugs and recent advances in cell primitive-based materials for AD treatment. Various cell primitives, such as cells, extracellular vesicles, and cell membranes, are presented together with their distinctive biological functions and construction strategies. Moreover, future research directions are discussed on the basis of foreseeable challenges and perspectives.

Activity-dependent labeling and manipulation of fentanyl-recruited striatal ensembles using ArcTRAP approach

Understanding the memory substrates underlying substance abuse requires the permanent tagging and manipulation of drug-recruited neural ensembles. Here, we present a protocol for activity-dependent labeling and chemogenetic manipulation of fentanyl-activated striatal ensembles using the ArcTRAP approach. We outline the necessary steps to breed ArcTRAP mice, prepare drugs and reagents, conduct behavioral training, and perform tagging and manipulation. This approach can be adapted to investigate drug-recruited ensembles in other brain regions, providing a versatile tool for exploring the neural mechanisms underlying addiction. For complete details on the use and execution of this protocol, please refer to Wang et al.1.

Loading Intracranial Drug-Eluting Reservoirs Across the Blood-Brain Barrier With Focused Ultrasound

OBJECTIVE

Efficient, sustained and long-term delivery of therapeutics to the brain remains an important challenge to treatment of diseases such as brain cancer, stroke and neurodegenerative disease. Focused ultrasound can assist movement of drugs into the brain, but frequent and long-term use has remained impractical. Single-use intracranial drug-eluting depots show promise but are limited for the treatment of chronic diseases as they cannot be refilled non-invasively. Refillable drug-eluting depots could serve as a long-term solution, but refilling is hindered by the blood-brain barrier (BBB), which prevents drug refills from accessing the brain. In this article, we describe how focused ultrasound enables non-invasive loading of intracranial drug depots in mice.

METHODS

Female CD-1 mice (n = 6) were intracranially injected with click-reactive and fluorescent molecules that are capable of anchoring in the brain. After healing, animals were treated with high-intensity focused ultrasound and microbubbles to temporarily increase the permeability of the blood-brain barrier and deliver dibenzocyclooctyne (DBCO)-Cy7. The mice were perfused, and the brains were imaged via ex vivo fluorescence imaging.

RESULTS

Fluorescence imaging indicated small molecule refills are captured by intracranial depots as long as 4 wk after administration and are retained for up to 4 wk based on fluorescence imaging. Efficient loading was dependent on both focused ultrasound and the presence of refillable depots in the brain as absence of either prevented intracranial loading.

CONCLUSION

The ability to target and retain small molecules at predetermined intracranial sites with pinpoint accuracy provides opportunities to continuously deliver drugs to the brain over weeks and months without excessive BBB opening and with minimal off-target side effects.

Overexpressing lnc240 Rescues Learning and Memory Dysfunction in Hepatic Encephalopathy Through miR-1264-5p/MEF2C Axis

Hepatic encephalopathy (HE) is a nervous system disease caused by severe liver diseases and different degrees of learning and memory dysfunction. Long non-coding RNA (lncRNA) is highly expressed in the brain and plays important roles in central nervous system diseases like Alzheimer's disease. In the present work, we found that the expression of lnc240 in the hippocampus of HE mice was significantly downregulated, but its pathogenesis in HE has not been clarified. This study aimed to explore the effects of lnc240 on the cognitive function of HE. The expression of lnc240, miR-1264-5p, and MEF2C was analyzed with RNA-seq and further determined by qRT-PCR in HE mouse. Double luciferase reporter gene testing confirmed the relationship between lnc240, MEF2C, and miR-1264-5p. The functional role of lnc240 and MEF2C in vitro and in vivo was evaluated by qRT-PCR, western blot analysis, immunofluorescence staining, Golgi staining, electrophysiology, and Morris water maze. The expression of lnc240 was decreased in HE mice. The overexpression of lnc240 could significantly downregulate miR-1264-5p and upregulate MEF2C, also increasing the amplitude and frequency of mEPSC in primary cultured hippocampal neurons. The overexpression of miR-1264-5p reversed the effect of lnc240 on MEF2C. Moreover, in vivo experiments have shown that the overexpression of lnc240 could improve HE mice's spatial learning and memory functions. Golgi staining suggested that overexpression of lnc240 could increase the density and maturity of dendritic spines in hippocampal neurons of HE mice. Lnc240 can regulate the expression of MEF2C through miR-1264-5p and regulate the synaptic plasticity of hippocampal neurons, thereby saving the learning and memory dysfunction in HE mice, suggesting that lnc240 might be a potential therapeutic target for the treatment of HE.

Ultrasound-mediated blood-brain barrier opening: An effective drug delivery system for theranostics of brain diseases

Blood-brain barrier (BBB) remains a significant obstacle to drug therapy for brain diseases. Focused ultrasound (FUS) combined with microbubbles (MBs) can locally and transiently open the BBB, providing a potential strategy for drug delivery across the BBB into the brain. Nowadays, taking advantage of this technology, many therapeutic agents, such as antibodies, growth factors, and nanomedicine formulations, are intensively investigated across the BBB into specific brain regions for the treatment of various brain diseases. Several preliminary clinical trials also have demonstrated its safety and good tolerance in patients. This review gives an overview of the basic mechanisms, ultrasound contrast agents, evaluation or monitoring methods, and medical applications of FUS-mediated BBB opening in glioblastoma, Alzheimer's disease, and Parkinson's disease.

Two-photon calcium imaging of neuronal activity

In vivo two-photon calcium imaging (2PCI) is a technique used for recording neuronal activity in the intact brain. It is based on the principle that, when neurons fire action potentials, intracellular calcium levels rise, which can be detected using fluorescent molecules that bind to calcium. This Primer is designed for scientists who are considering embarking on experiments with 2PCI. We provide the reader with a background on the basic concepts behind calcium imaging and on the reasons why 2PCI is an increasingly powerful and versatile technique in neuroscience. The Primer explains the different steps involved in experiments with 2PCI, provides examples of what ideal preparations should look like and explains how data are analysed. We also discuss some of the current limitations of the technique, and the types of solutions to circumvent them. Finally, we conclude by anticipating what the future of 2PCI might look like, emphasizing some of the analysis pipelines that are being developed and international efforts for data sharing.

Single-Cell Quantification of Triple-AAV Vector Genomes Coexpressed in Neurons

Adeno-associated viruses (AAVs) are one of the most widely used types of viral vectors for research and gene therapy. AAV vectors are safe, have a low immunogenic profile, and provide efficient and long-term transgene expression in a variety of tissues and organs targeted by a specific serotype. Despite these unique features, therapeutic applications, as well as basic research studies, of AAVs have been limited by their packaging capacity of less than 5 kb. Multiple strategies have been explored to deliver large genes. One strategy is to split large transgenes into two or three fragments and package them into separate AAV capsids, generating dual or triple AAV vectors. Combining the fragments potentially allows reconstitution of an mRNA transcript containing the complete sequence of transgene in the same cell. The success of AAVs as vectors for the delivery of large or multiple genes depends directly on the efficiency of co-transduction. Here, we describe a method to measure the efficacy of codelivery, quantifying the number of AAV vectors per cell. We detail how to calculate the average number of incoming AAV genomes in neurons, given the distribution of cell fluorescence across in vitro and in vivo experimental models. To validate the method, we simulated a triple AAV strategy using three fluorescent-protein-encoding genes. We provide a general protocol for constructing plasmids and producing and purifying AAV vectors. We also include a protocol for triple AAV vector co-transduction in primary neuronal cultures and mouse brain. The method can be applied to multiple organs and tissues for the treatment of disorders caused by mutations in multiple or large genes. These protocols will be useful for researchers working to develop and improve new gene delivery technologies. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Construction of AAV plasmids and production of AAVs Basic Protocol 2: AAV transduction of primary superior cervical ganglia (SCG) neuronal cultures Basic Protocol 3: Mouse surgery, AAV injection, and tissue collection and processing Basic Protocol 4: Image analysis and AAV genome quantification.

Toxicity after AAV delivery of RNAi expression constructs into nonhuman primate brain

RNA interference (RNAi) for spinocerebellar ataxia type 1 can prevent and reverse behavioral deficits and neuropathological readouts in mouse models, with safety and benefit lasting over many months. The RNAi trigger, expressed from adeno-associated virus vectors (AAV.miS1), also corrected misregulated microRNAs (miRNA) such as miR150. Subsequently, we showed that the delivery method was scalable, and that AAV.miS1 was safe in short-term pilot nonhuman primate (NHP) studies. To advance the technology to patients, investigational new drug (IND)-enabling studies in NHPs were initiated. After AAV.miS1 delivery to deep cerebellar nuclei, we unexpectedly observed cerebellar toxicity. Both small-RNA-seq and studies using AAVs devoid of miRNAs showed that this was not a result of saturation of the endogenous miRNA processing machinery. RNA-seq together with sequencing of the AAV product showed that, despite limited amounts of cross-packaged material, there was substantial inverted terminal repeat (ITR) promoter activity that correlated with neuropathologies. ITR promoter activity was reduced by altering the miS1 expression context. The surprising contrast between our rodent and NHP findings highlight the need for extended safety studies in multiple species when assessing new therapeutics for human application.

Deficiency of ROS-Activated TRPM2 Channel Protects Neurons from Cerebral Ischemia-Reperfusion Injury through Upregulating Autophagy

Cerebral ischemia-reperfusion (I-R) transiently increased autophagy by producing excessively reactive oxygen species (ROS); on the other hand, activated autophagy would remove ROS-damaged mitochondria and proteins, which led to cell survival. However, the regulation mechanism of autophagy activity during cerebral I-R is still unclear. In this study, we found that deficiency of the TRPM2 channel which is a ROS sensor significantly decreased I-R-induced neuronal damage. I-R transiently increased autophagy activity both in vitro and in vivo. More importantly, TRPM2 deficiency decreased I-R-induced neurological deficit score and infarct volume. Interestingly, our results indicated that TRPM2 deficiency could further activate AMPK rather than Beclin1 activity, suggesting that TRPM2 inhibits autophagy by regulating the AMPK/mTOR pathway in I-R. In conclusion, our study reveals that ROS-activated TRPM2 inhibits autophagy by downregulating the AMPK/mTOR pathway, which results in neuronal death induced by cerebral I-R, further supporting that TRPM2 might be a potential drug target for cerebral ischemic injury therapy.

HSV-1 H129-Derived Anterograde Neural Circuit Tracers: Improvements, Production, and Applications

Anterograde viral tracers are powerful and essential tools for dissecting the output targets of a brain region of interest. They have been developed from herpes simplex virus 1 (HSV-1) strain H129 (H129), and have been successfully applied to map diverse neural circuits. Initially, the anterograde polysynaptic tracer H129-G4 was used by many groups. We then developed the first monosynaptic tracer, H129-dTK-tdT, which was highly successful, yet improvements are needed. Now, by inserting another tdTomato expression cassette into the H129-dTK-tdT genome, we have created H129-dTK-T2, an updated version of H129-dTK-tdT that has improved labeling intensity. To help scientists produce and apply our H129-derived viral tracers, here we provide the protocol describing our detailed and standardized procedures. Commonly-encountered technical problems and their solutions are also discussed in detail. Broadly, the dissemination of this protocol will greatly support scientists to apply these viral tracers on a large scale.

Effect of Sox10 on remyelination of the hippocampus in cuprizone-induced demyelinated mice

OBJECTIVE

The low number of oligodendrocytes (OLs) in the hippocampus of patients with schizophrenia suggests that hippocampal demyelination is changed in this condition. Sox10 is expressed throughout OL development. The effect of Sox10 on myelin regeneration is unknown. This study aimed to analyze changes in Sox10 expression in the hippocampus and its regulatory role in hippocampal myelin regeneration in a mouse model of demyelination.

METHODS

Mice were fed 0.2% cuprizone (CPZ) for six weeks to establish the acute demyelinating model (CPZ mice). Behavioral changes of these mice were assessed via open field and tail suspension tests. The ultrastructure of the myelin sheaths in the hippocampus was observed by transmission electron microscopy. The expression levels of myelin sheath-related proteins and the transcription factor Sox10 were detected via immunohistochemistry and Western blots. Furthermore, Sox10-overexpressing adeno-associated virus was injected into the hippocampus after establishing the demyelinating model to investigate effects of Sox10 on remyelination.

RESULTS

CPZ mice showed abnormal behavioral changes, a large number of pathological changes in the myelin sheaths, and significantly reduced protein expression of the myelin sheath markers myelin basic protein and proteolipid protein. This confirmed that the demyelinating model was successfully established. Meanwhile, the protein expression of the oligodendrocyte precursor cell marker neural/glial antigen 2 (NG2) increased, whereas Sox10 expression decreased. After Sox10 overexpression in the hippocampus, the abnormal behavior was improved, the ultrastructure of the myelin sheaths was restored, and the expression of myelin sheath protein was reversed. NG2 expression was upregulated.

CONCLUSION

Overexpression of Sox10 promotes hippocampal remyelination after CPZ-induced acute demyelination.