Deoxycholic Acid-Conjugated Polyethylenimine for Delivery of Heme Oxygenase-1 Gene in Rat Ischemic Stroke Model

New insight into gut microbiota and their metabolites in ischemic stroke: A promising therapeutic target

The gut-brain axis has been shown to play a vital role in the prognosis and recovery of ischemic stroke (IS), which is associated with gut microbiota dysfunction and changes in the gastrointestinal system and epithelial barrier integrity. In turn, gut microbiota and its derived metabolites can influence stroke outcomes. In this review, we first describe the relationship between IS (clinical and experimental IS) and the gut microbiota. Second, we summarize the role and specific mechanisms of microbiota-derived metabolites in IS. Further, we discuss the roles of natural medicines targeting the gut microbiota. Finally, the potential use of the gut microbiota and derived metabolites as a promising therapeutic opportunity for stroke prevention, diagnosis, and treatment is explored.

Circadian Factors in Stroke: A Clinician's Perspective

Stroke remains one of the leading causes of mortality and long-term and permanent disability worldwide despite technological innovations and developments in pharmacotherapy. In the last few decades, the growing data have evidenced the role of the circadian system in brain vulnerability to damage, the development and evolution of stroke, and short-term and long-term recovery. On the other hand, the stroke itself can affect the circadian system via direct injury of specific brain structures involved in circadian regulation (i.e., hypothalamus, retinohypothalamic tracts, etc.) and impairment of endogenous regulatory mechanisms, metabolic derangement, and a neurogenic inflammatory response in acute stroke. Moreover, the disruption of circadian rhythms can occur or exacerbate as a result of exogenous factors related to hospitalization itself, the conditions in the intensive care unit and the ward (light, noise, etc.), medication (sedatives and hypnotics), and loss of external factors entraining the circadian rhythms. In the acute phase of stroke, patients demonstrate abnormal circadian variations in circadian biomarkers (melatonin, cortisol), core body temperature, and rest-activity patterns. The approaches aimed at the restoration of disrupted circadian patterns include pharmacological (melatonin supplementation) and non-medication (bright light therapy, shifting feeding schedules, etc.) interventions; however, their effects on short- and long-term recovery after stroke are not well understood.

Novel hydrogel comprising non-ionic copolymer with various concentrations of pharmacologically active bile acids for cellular injectable gel

Deoxycholic acid (DCA) is a bile acid capable of forming micelles and modifying the properties of hydrogels. We incorporated DCA in sodium alginate (SA) and poloxamer 407 matrices creating novel DCA-copolymer hydrogel for therapeutic delivery. Hydrogels were assessed for common rheological properties. Biocompatibility and biological effect were examined on various cell lines. Cell viability was determent in normal and various hypoxic conditions, and full mitochondrial bioenergetic parameters were assessed in cell lines in order to illustrate hydrogel effects on survival, and cell metabolic profile within the hydrogels. Obtained data suggest that a low dose of DCA in permeable, biocompatible hydrogels can be beneficial for cells to combat hypoxic conditions.

Delivering the Promise of Gene Therapy with Nanomedicines in Treating Central Nervous System Diseases

Central Nervous System (CNS) diseases, such as Alzheimer's diseases (AD), Parkinson's Diseases (PD), brain tumors, Huntington's disease (HD), and stroke, still remain difficult to treat by the conventional molecular drugs. In recent years, various gene therapies have come into the spotlight as versatile therapeutics providing the potential to prevent and treat these diseases. Despite the significant progress that has undoubtedly been achieved in terms of the design and modification of genetic modulators with desired potency and minimized unwanted immune responses, the efficient and safe in vivo delivery of gene therapies still poses major translational challenges. Various non-viral nanomedicines have been recently explored to circumvent this limitation. In this review, an overview of gene therapies for CNS diseases is provided and describes recent advances in the development of nanomedicines, including their unique characteristics, chemical modifications, bioconjugations, and the specific applications that those nanomedicines are harnessed to deliver gene therapies.

Delivery of self-replicating messenger RNA into the brain for the treatment of ischemic stroke

Ischemic stroke is caused by the occlusion of cerebral arteries. In the ischemic stroke, ischemia-reperfusion injury increases the damage in the brain after reperfusion. In the previous study, heme oxygenase-1 (HO1) mRNA was delivered into the ischemic brain, showing that HO1-mRNA had higher therapeutic effect and less side-effect than HO1-plasmid (pHO1). However, mRNA is degraded faster than plasmid DNA reducing the duration of gene expression. In this study, self-replicating mRNA (Rep-mRNA) was developed using a replicon system from Venezuelan Equine Encephalitis virus to compensate this disadvantage of mRNA delivery. Deoxycholic acid-conjugated polyethylenimine (DA-PEI) was used as a carrier of the mRNA. The Rep-mRNA/DA-PEI complex had a size of around 90 nm and a zeta-potential of 33 mV. In the in vitro transfection assays, gene expression by the HO1-Rep-mRNA/DA-PEI complex persisted at least 14 days, while that by the HO1-mRNA/DA-PEI complex approached basal level at 3 days after transfection. Therapeutic effects of the HO1-Rep-mRNA/DA-PEI complexes were evaluated in the ischemic stroke animal models. The complexes were injected into the brain stereotaxically. HO1 expression by the HO1-Rep-mRNA/DA-PEI complex persisted at least 7 days after injection, but the pHO1/DA-PEI or HO1-mRNA/DA-PEI complex showed basal level of HO1-expression at 7 days after injection. Due to higher and longer expression of HO1, the apoptosis level and infarct size were decreased by the HO1-Rep-mRNA/DA-PEI complexes, compared with the pHO1/DA-PEI and HO1-mRNA/DA-PEI complex. These results suggest that HO1-Rep-mRNA/DA-PEI complex may have a potential as a long-lasting therapeutic system for the treatment of ischemic stroke.

Oxidative Stress in Ischemia/Reperfusion Injuries following Acute Ischemic Stroke

Recanalization therapy is increasingly used in the treatment of acute ischemic stroke. However, in about one third of these patients, recanalization is followed by ischemia/reperfusion injuries, and clinically to worsening of the neurological status. Much research has focused on unraveling the involved mechanisms in order to prevent or efficiently treat these injuries. What we know so far is that oxidative stress and mitochondrial dysfunction are significantly involved in the pathogenesis of ischemia/reperfusion injury. However, despite promising results obtained in experimental research, clinical studies trying to interfere with the oxidative pathways have mostly failed. The current article discusses the main mechanisms leading to ischemia/reperfusion injuries, such as mitochondrial dysfunction, excitotoxicity, and oxidative stress, and reviews the clinical trials with antioxidant molecules highlighting recent developments and future strategies.

Ischemic Stroke and Sleep: The Linking Genetic Factors

This review summarizes the available data about genetic factors which can link ischemic stroke and sleep. Sleep patterns (subjective and objective measures) are characterized by heritability and comprise up to 38-46%. According to Mendelian randomization analysis, genetic liability for short sleep duration and frequent insomnia symptoms is associated with ischemic stroke (predominantly of large artery subtype). The potential genetic links include variants of circadian genes, genes encoding components of neurotransmitter systems, common cardiovascular risk factors, as well as specific genetic factors related to certain sleep disorders.

The Role of Nanomaterials in Stroke Treatment: Targeting Oxidative Stress

Stroke has a high rate of morbidity and disability, which seriously endangers human health. In stroke, oxidative stress leads to further damage to the brain tissue. Therefore, treatment for oxidative stress is urgently needed. However, antioxidative drugs have demonstrated obvious protective effects in preclinical studies, but the clinical studies have not seen breakthroughs. Nanomaterials, with their characteristically small size, can be used to deliver drugs and have demonstrated excellent performance in treating various diseases. Additionally, some nanomaterials have shown potential in scavenging reactive oxygen species (ROS) in stroke according to the nature of nanomaterials. The drugs' delivery ability of nanomaterials has great significance for the clinical translation and application of antioxidants. It increases drug blood concentration and half-life and targets the ischemic brain to protect cells from oxidative stress-induced death. This review summarizes the characteristics and progress of nanomaterials in the application of antioxidant therapy in stroke, including ischemic stroke, hemorrhagic stroke, and neural regeneration. We also discuss the prospect of nanomaterials for the treatment of oxidative stress in stroke and the challenges in their application, such as the toxicity and the off-target effects of nanomaterials.

Messenger RNA/polymeric carrier nanoparticles for delivery of heme oxygenase-1 gene in the post-ischemic brain

Ischemic stroke is a cerebrovascular disease caused by narrowed cerebral arteries. Thrombolytic agents such as tissue-plasminogen activators have been used for recanalization of the blood supply into the ischemic region. However, ischemia-reperfusion damage continues to increase the infarction volume. In this study, heme oxygenase-1 (HO1)-mRNA was delivered into the brain, using a non-viral carrier. Various non-viral carriers such as polyethylenimine (25 kDa, PEI25k), lipofectamine, dexamethasone-conjugated PEI2k (Dexa-PEI2k), deoxycholic acid-conjugated PEI2k (DA-PEI2k), and R3V6 peptides were evaluated as carriers of mRNA into the brain. Gene delivery assays showed that DA-PEI2k and lipofectamine had a higher mRNA delivery efficiency than the other carriers in Neuro2A cells in vitro and a rat brain in vivo. Cytotoxicity assays showed that lipofectamine had higher toxicity than DA-PEI2k. Therefore, DA-PEI2k was used for delivery of HO1-mRNA. Unlike plasmid DNA (pDNA), mRNA is expressed in the cytosol without nuclear translocation. This suggests that mRNA may have higher gene expression than pDNA, since the nuclear location of pDNA is an inefficient step. Indeed, in in vitro transfection assays, HO1-mRNA/DA-PEI2k had higher gene expression than HO1-pDNA/DA-PEI2k without induction of a pro-inflammatory cytokine. The therapeutic effects of HO1-mRNA delivery using DA-PEI2k were evaluated in the middle cerebral artery occlusion animal model after local injection. HO1-mRNA delivery had higher gene expression than HO1-pDNA delivery 24 h after the local injection. In addition, HO1-mRNA delivery reduced the infarct size more efficiently than HO1-pDNA delivery. The results suggest that the delivery of mRNA using DA-PEI2k may be useful for gene therapy of ischemic stroke.

A self-assembled DNA-nanoparticle with a targeting peptide for hypoxia-inducible gene therapy of ischemic stroke

A self-assembled nanoparticle composed of hypoxia-specific anti-RAGE peptide (HSAP), heme oxygenase-1 plasmid (pHO1), and deoxycholate-conjugated polyethylenimine-2k (DP2k) was developed for ischemic stroke therapy. RAGE is over-expressed and induces inflammation in the ischemic brain. To inhibit RAGE-mediated signal transduction, HSAP was produced by recombinant DNA technology, based on the RAGE-binding domain of high mobility group box-1. Because of the specific binding to RAGE, the nanoparticle with HSAP (HSAP-NP) may have dual roles as a cytoprotective reagent and a specific ligand to RAGE for receptor-mediated transfection. As a cytoprotective reagent, the HSAP-NP reduced RAGE expression on the surface of the brain cells by inhibiting the positive feedback of RAGE-mediated signal transduction. As a result, inflammation, apoptosis, and reactive oxygen species were decreased in hypoxic cells. As a gene carrier, HSAP-NP showed a higher transfection efficiency than polyethylenimine-25k, DP2k, and Lipofectamine. Particularly, HSAP-NP enhanced gene delivery to hypoxic cells. In the stroke animal models, HSAP-NP reduced the levels of RAGE, inducible nitric oxide synthase, and inflammation. Additionally, HSAP-NP with pHO1 (HSAP-NP/pHO1) increased HO1 expression in the ischemic brain. Gene expression was higher in hypoxia-inducible factor-1α (HIF-1α)-positive cells than in HIF-1α-negative cells, suggesting that HSAP-NP delivered the genes to ischemic tissues more efficiently. Cell death and infarct volume in the stroke models were significantly decreased by HSAP-NP/pHO1 compared with HSAP alone or the DP2k/pHO1 complex. Therefore, HSAP-NP may be a useful gene and peptide therapy system for stroke therapy with dual functions of hypoxia-specific gene delivery and cytoprotective effects.

In vivo methods for acute modulation of gene expression in the central nervous system

Accurate and timely expression of specific genes guarantees the healthy development and function of the brain. Indeed, variations in the correct amount or timing of gene expression lead to improper development and/or pathological conditions. Almost forty years after the first successful gene transfection in in vitro cell cultures, it is currently possible to regulate gene expression in an area-specific manner at any step of central nervous system development and in adulthood in experimental animals in vivo, even overcoming the very poor accessibility of the brain. Here, we will review the diverse approaches for acute gene transfer in vivo, highlighting their advantages and disadvantages with respect to the efficiency and specificity of transfection as well as to brain accessibility. In particular, we will present well-established chemical, physical and virus-based approaches suitable for different animal models, pointing out their current and future possible applications in basic and translational research as well as in gene therapy.