Microbiota Metabolites and Immune Regulation Affect Ischemic Stroke Occurrence, Development, and Prognosis

The gut microbiota are not only related to the development and occurrence of digestive system disease, but also have a bidirectional relationship with nervous system diseases via the microbiota-gut-brain axis. At present, correlations between the gut microbiota and neurological diseases, including stroke, are one of the focuses of investigation and attention in the medical community. Ischemic stroke (IS) is a cerebrovascular disease accompanied by focal neurological deficit or central nervous system injury or death. In this review, we summarize the contemporary latest research on correlations between the gut microbiota and IS. Additionally, we discuss the mechanisms of gut microbiota implicated in IS and related to metabolite production and immune regulation. Moreover, the factors of gut microbiota that affecting IS occurrence, and research implicating the gut microbiota as potential therapeutic targets for IS, are highlighted. Our review highlights the evidential relationships and connections between the gut microbiota and IS pathogenesis and prognosis.

Aberrant branched-chain amino acid accumulation along the microbiota-gut-brain axis: Crucial targets affecting the occurrence and treatment of ischaemic stroke

BACKGROUND AND PURPOSE

Although increasing evidence illustrated that the bidirectional communication between the brain and the gut is closely related to the occurrence of various complex diseases. Limited effort has been made to explore the influence of intestinal flora on the risk of ischaemic stroke. The present study aims to identify microbiota and specialized microbiota metabolites related to the occurrence and treatment of ischaemic stroke.

EXPERIMENTAL APPROACH

The role of microbiota in the occurrence and the treatment of ischaemic stroke was evaluated on ischaemia/reperfusion (I/R), pseudo-germ-free and faecal transplantation animals. The target microbiota and specialized metabolites were identified by comparing their distribution in flora and metabolomic profiles in ischaemic stroke patients and animals with compared with healthy controls. The effects and mechanisms involved of the targeted metabolites in ischaemic stroke were explored in ischaemia/reperfusion rats, hypoxia/reoxygenation PC12 cells and LPS-induced inflammatory BV2 cells.

KEY RESULTS

Both ischaemic stroke patients and I/R rats had significant accumulation of branched-chain amino acids, which were closely associated with gut microflora dysbiosis and the development of ischaemic stroke. Lactobacillus helveticus (L.hel) and Lactobacillus brevis (L.bre) are identified as the microbiota most affected by ischaemia/reperfusion modelling and treatment. L.hel and L.bre colonization exhibited significant neuroprotective activity and could greatly alleviate the accumulation of branched-chain amino acids. In addition, branched-chain amino acid (BCAA) accumulation was shown to exacerbate microglia-induced neuroinflammation by activating AKT/STAT3/NF-κB signalling.

CONCLUSION AND IMPLICATIONS

Our findings demonstrated the crucial role of intestinal flora and microbiota metabolites in the occurrence and treatment of ischaemic stroke.

Interventional strategies for ischemic stroke based on the modulation of the gut microbiota

The microbiota-gut-brain axis connects the brain and the gut in a bidirectional manner. The organism's homeostasis is disrupted during an ischemic stroke (IS). Cerebral ischemia affects the intestinal flora and microbiota metabolites. Microbiome dysbiosis, on the other hand, exacerbates the severity of IS outcomes by inducing systemic inflammation. Some studies have recently provided novel insights into the pathogenesis, efficacy, prognosis, and treatment-related adverse events of the gut microbiome in IS. In this review, we discussed the view that the gut microbiome is of clinical value in personalized therapeutic regimens for IS. Based on recent non-clinical and clinical studies on stroke, we discussed new therapeutic strategies that might be developed by modulating gut bacterial flora. These strategies include dietary intervention, fecal microbiota transplantation, probiotics, antibiotics, traditional Chinese medication, and gut-derived stem cell transplantation. Although the gut microbiota-targeted intervention is optimistic, some issues need to be addressed before clinical translation. These issues include a deeper understanding of the potential underlying mechanisms, conducting larger longitudinal cohort studies on the gut microbiome and host responses with multiple layers of data, developing standardized protocols for conducting and reporting clinical analyses, and performing a clinical assessment of multiple large-scale IS cohorts. In this review, we presented certain opportunities and challenges that might be considered for developing effective strategies by manipulating the gut microbiome to improve the treatment and prevention of ischemic stroke.

Progress on traditional Chinese medicine in treatment of ischemic stroke via the gut-brain axis

Ischemic stroke is a common issue that severely affects the human health. Between the central nervous system and the enteric system, the " Gut-Brain " axis, the bidirectional connection involved in the neuro-immuno-endocrine network, is crucial for the occurrence and development of ischemic stroke. Ischemic stroke can lead to change in the gut microbiota and gastrointestinal hormones, which will then reversely affect the disease development. Traditional Chinese Medicine (TCM) has unique advantages with reference to the treatment for ischemic stroke. The latest research revealed that a significant portion of medicines and prescriptions of TCM exert their therapeutic effects by improving the gut microbiota and regulating the secretion of gastrointestinal hormones. The present review summarized the Chinese medicines that play a therapeutic role in cerebral ischemia through regulating the "Gut-Brain" axis and described the corresponding mechanisms. This study attempts to provide reference for clinical selection of Chinese medicines and helps better understand the relevant mechanisms of action.

Involvement of Intestinal Microbiota in Adult Neurogenesis and the Expression of Brain-Derived Neurotrophic Factor

Growing evidence suggests a possible involvement of the intestinal microbiota in generating new neurons, but a detailed breakdown of the microbiota composition is lacking. In this report, we systematically reviewed preclinical rodent reports addressing the connection between the composition of the intestinal microbiota and neurogenesis and neurogenesis-affecting neurotrophins in the hippocampus. Various changes in bacterial composition from low taxonomic resolution at the phylum level to high taxonomic resolution at the species level were identified. As for neurogenesis, studies predominantly used doublecortin (DCX) as a marker of newly formed neurons or bromodeoxyuridine (BrdU) as a marker of proliferation. Brain-derived neurotrophic factor (BDNF) was the only neurotrophin found researched in relation to the intestinal microbiota. Phylum Actinobacteria, genus Bifidobacterium and genus Lactobacillus found the strongest positive. In contrast, phylum Firmicutes, phylum Bacteroidetes, and family Enterobacteriaceae, as well as germ-free status, showed the strongest negative correlation towards neurogenesis or BDNF mRNA expression. Age, short-chain fatty acids (SCFA), obesity, and chronic stress were recurring topics in all studies identified. Overall, these findings add to the existing evidence of a connection between microbiota and processes in the brain. To better understand this interaction, further investigation based on analyses of higher taxonomic resolution and clinical studies would be a gain to the matter.

Probiotic as a Potential Gut Microbiome Modifier for Stroke Treatment: A Systematic Scoping Review of In Vitro and In Vivo Studies

BACKGROUND

Pharmacologic and non-pharmacologic treatments for stroke are essential but can be costly or harmful, whereas probiotics are a promising alternative. This scoping review aimed to synthesize the in vitro and in vivo evidence of probiotics on stroke-related neurological, biochemical, and histochemical outcomes.

METHODS

A systematic review was conducted in PubMed, Embase, and Cochrane Central Register of Clinical Trials (CENTRAL) up to 7 May 2021. Titles and abstracts were screened and assessed by two independent reviewers. The initial screening criteria aimed to include studies using probiotics, prebiotics, and symbiotics both in vitro and in vivo for the prevention and/or treatment of stroke.

RESULTS

Of 6293 articles, 4990 passed the initial screen after excluding duplication articles, of which 36 theme-related full texts were assessed and 13 were included in this review. No in vitro studies passed the criteria to be included in this review. Probiotics can ameliorate neurological deficits and show their anti-inflammation and anti-oxidative properties. Decreased loss of cerebral volume and inhibition of neuronal apoptosis were revealed in histopathological evidence.

CONCLUSIONS

There are potential cognitive benefits of probiotic supplementation, especially among animal models, on decreasing cerebral volume, increasing neurological score, and decreasing the inflammatory response. However, further investigation is needed to validate these conclusions in various populations.

Global analysis of qualitative and quantitative metabolism of Notoginsenoside R1 in rat liver-brain-gut axis based on LC-IT-TOF/MS combing mMDF strategy

BACKGROUND

The metabolism study of active components for traditional Chinese medicine (TCM) in target organs is conducive to clarify the authentic active ingredients. Notoginsenoside R1 (NG-R1), one of the bioactive components of Panax notoginsenoside (PNS), is commonly acknowledged as the characteristic marker of PNS. However, the metabolism of NG-R1 in target organs has not been clarified yet due to the lack of robust technique and approach.

PURPOSE

The present study aimed to develop a reliable and efficient strategy and technology for revealing the qualitative and quantitative metabolism of active components of TCMs in target organs, and to clarify the biotransformation of NG-R1 in liver-brain-intestinal axis.

METHODS

The metabolic transformation of NG-R1 in the brain gut axis was investigated in the in vitro incubation system of fresh rat brain, liver homogenate, and intestinal flora. To quickly lock the target metabolites, we set the mass defect filter (MDF) in different ranges to screen metabolites with different molecular weight (MW). This strategy was defined as multi-stage MDF (mMDF). In addition, we performed relative quantitative analysis on all metabolites according to the peak area acquired by LC-IT-TOF/MS to overcome the challenge that metabolites are difficult to be quantified due to the lack of standards.

RESULTS

When MDF was set at 0.50 to 0.65 to screen metabolites with MW of 900 to 1200 Da, 6 novel metabolites were quickly found, and then identified as glucuronic acid binding, oxidation, dehydrogenation, methylation and hydrogenation products according to their LC and MS characteristics. When setting MDF at 0.42 - 0.52, 6 metabolites with MW of 600 to 900 Da were effectively screened and identified as Rg1, NG-R2, Rh1, Rg1+CH₂+2H and Rg1+CH₂. To screen the metabolites with MW of 300 to 600 Da, MDF was set at 0.25 - 0.42, and 4 novel metabolites were screened rapidly. The results of quantitative metabolism suggested that intestinal flora was the main metabolic site of NG-R1 in rat, and more than 60% of NG-R1 was converted to Rg1 by deglycosylation in the intestinal flora.

CONCLUSION

The mMDF strategy can significantly improve the research efficiency of qualitative metabolism of saponins. Although NG-R1 could be transformed into a variety of metabolites in rat liver and brain homogenate, it still existed mainly in prototype form. In the rat flora, NG-R1 mainly existed in the form of deglycosylated metabolite Rg1.

Notoginsenoside R1 Promotes Migration, Adhesin, Spreading, and Osteogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stromal Cells

Cellular activities, such as attachment, spreading, proliferation, migration, and differentiation are indispensable for the success of bone tissue engineering. Mesenchymal stromal cells (MSCs) are the key precursor cells to regenerate bone. Bioactive compounds from natural products had shown bone regenerative potential. Notoginsenoside R1 (NGR1) is a primary bioactive natural compound that regulates various biological activities, including cardiovascular protection, neuro-protection, and anti-cancer effects. However, the effect of NGR1 on migration, adhesion, spreading, and osteogenic differentiation of MSCs required for bone tissue engineering application has not been tested properly. In this study, we aimed to analyze the effect of NGR1 on the cellular activities of MSCs. Since human adipose-derived stromal cells (hASCs) are commonly used MSCs for bone tissue engineering, we used hASCs as a model of MSCs. The optimal concentration of 0.05 μg/mL NGR1 was biocompatible and promoted migration and osteogenic differentiation of hASCs. Pro-angiogenic factor VEGF expression was upregulated in NGR1-treated hASCs. NGR1 enhanced the adhesion and spreading of hASCs on the bio-inert glass surface. NGR1 robustly promoted hASCs adhesion and survival in 3D-printed TCP scaffold both in vitro and in vivo. NGR1 mitigated LPS-induced expression of inflammatory markers IL-1β, IL-6, and TNF-α in hASCs as well as inhibited the RANKL/OPG expression ratio. In conclusion, the biocompatible NGR1 promoted the migration, adhesion, spreading, osteogenic differentiation, and anti-inflammatory properties of hASCs.

Aging Microbiota-Gut-Brain Axis in Stroke Risk and Outcome

The microbiota-gut-brain-axis (MGBA) is a bidirectional communication network between gut microbes and their host. Many environmental and host-related factors affect the gut microbiota. Dysbiosis is defined as compositional and functional alterations of the gut microbiota that contribute to the pathogenesis, progression and treatment responses to disease. Dysbiosis occurs when perturbations of microbiota composition and function exceed the ability of microbiota and its host to restore a symbiotic state. Dysbiosis leads to dysfunctional signaling of the MGBA, which regulates the development and the function of the host's immune, metabolic, and nervous systems. Dysbiosis-induced dysfunction of the MGBA is seen with aging and stroke, and is linked to the development of common stroke risk factors such as obesity, diabetes, and atherosclerosis. Changes in the gut microbiota are also seen in response to stroke, and may impair recovery after injury. This review will begin with an overview of the tools used to study the MGBA with a discussion on limitations and potential experimental confounders. Relevant MGBA components are introduced and summarized for a better understanding of age-related changes in MGBA signaling and its dysfunction after stroke. We will then focus on the relationship between the MGBA and aging, highlighting that all components of the MGBA undergo age-related alterations that can be influenced by or even driven by the gut microbiota. In the final section, the current clinical and preclinical evidence for the role of MGBA signaling in the development of stroke risk factors such as obesity, diabetes, hypertension, and frailty are summarized, as well as microbiota changes with stroke in experimental and clinical populations. We conclude by describing the current understanding of microbiota-based therapies for stroke including the use of pre-/pro-biotics and supplementations with bacterial metabolites. Ongoing progress in this new frontier of biomedical sciences will lead to an improved understanding of the MGBA's impact on human health and disease.

Exogenous glutathione exerts a therapeutic effect in ischemic stroke rats by interacting with intrastriatal dopamine

We previously showed that oral administration of exogenous glutathione (GSH) exerted a direct and/or indirect therapeutic effect on ischemic stroke rats, but the underlying mechanisms remain elusive. In the current study, we conducted a quantitative proteomic analysis to explore the pathways mediating the therapeutic effect of GSH in cerebral ischemia/reperfusion (I/R) model rats. Rats were subjected to middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion. The rats were treated with GSH (250 mg/kg, ig) or levodopa (L-dopa, 100 mg/kg, ig) plus carbidopa (10 mg/kg, ig). Neurologic deficits were assessed, and the rats were sacrificed at 24 h after cerebral I/R surgery to measure brain infarct sizes. We conducted a proteomic analysis of the lesion side striatum samples and found that tyrosine metabolism and dopaminergic synapse were involved in the occurrence of cerebral stroke and the therapeutic effect of GSH. Western blot assay revealed that tyrosine hydroxylase (TH) mediated the occurrence of I/R-induced ischemic stroke and the therapeutic effect of GSH. We analyzed the regulation of GSH on endogenous small molecule metabolites and showed that exogenous GSH had the most significant effect on intrastriatal dopamine (DA) in I/R model rats by promoting its synthesis and inhibiting its degradation. To further explore whether DA-related alterations were potential targets of GSH, we investigated the therapeutic effect of DA accumulation on ischemic brain injury. The combined administration of the precursor drugs of DA (L-dopa and carbidopa) significantly ameliorated neurological deficits, reduced infarct size, and oxidative stress, and decreased pro-inflammatory cytokines levels in the striatum of I/R injury rats. More interestingly, exogenous L-dopa/carbidopa could also greatly enhance the exposure of intracerebral GSH by upregulating GSH synthetases and enhancing homocysteine (HCY) levels in the striatum. Thus, administration of exogenous GSH exerts a therapeutic effect on ischemic stroke by increasing intrastriatal DA, and the accumulated DA can, in turn, enhance the exposure of GSH and its related substances, thus promoting the therapeutic effect of GSH.

Could the Gut Microbiota Serve as a Therapeutic Target in Ischemic Stroke?

The brain-gut axis is a relatively recent discovery of a two-way regulation system between the gut and brain, suggesting that the gut microbiota may be a promising targeted prevention and treatment strategy for patients with a high risk of acute cerebral ischemia/reperfusion injury. There are many risk factors for ischemic stroke, and many studies have shown that the gut microbiota affects the absorption and metabolism of the body, as well as the risk factors of stroke, such as blood pressure, blood glucose, blood lipids, and atherosclerosis, either directly or indirectly. Furthermore, the gut microbiota can affect the occurrence and prognosis of ischemic stroke by regulating risk factors or immune responses. Therefore, this study aimed to collect evidence of the interaction between gut microbiota and ischemic stroke, summarize the interaction mechanism between the two, and explore the gut microbiota as a new targeted prevention and treatment strategy for patients with high ischemic risk.

Neuroprotective Effects of Medicinal Plants in Cerebral Hypoxia and Anoxia: A Systematic Review

Background:

Hypoxia and anoxia are dangerous and sometimes irreversible complications in the central nervous system (CNS), which in some cases lead to death.

Objective:

The aim of this review was to investigate the neuroprotective effects of medicinal plants in cerebral hypoxia and anoxia.

Methods:

The word hypox*, in combination with some herbal terms such as medicinal plant, phyto* and herb*, was used to search for relevant publications indexed in the Institute for Scientific Information (ISI) and PubMed from 2000-2019.

Results:

Certain medicinal plants and herbal derivatives can exert their protective effects in several ways. The most important mechanisms are the inhibition of inducible nitric oxide synthase (iNOS), production of NO, inhibition of both hypoxia-inducible factor 1α and tumor necrosis factor-alpha activation, and reduction of extracellular glutamate, N-Methyl-D-aspartic and intracellular Ca (2+). In addition, they have an antioxidant activity and can adjust the expression of genes related to oxidant generation or antioxidant capacity. These plants can also inhibit lipid peroxidation, up-regulate superoxide dismutase activity and inhibit the content of malondialdehyde and lactate dehydrogenase. Moreover, they also have protective effects against cytotoxicity through down-regulation of the proteins that causes apoptosis, anti-excitatory activity, inhibition of apoptosis signaling pathway, reduction of pro-apoptotic proteins, and endoplasmic reticulum stress that causes apoptosis during hypoxia, increasing anti-apoptotic protein, inhibition of protein tyrosine kinase activation, decreasing proteases activity and DNA fragmentation, and upregulation of mitochondrial cytochrome oxidase.

Conclusion:

The results indicated that medicinal plants and their compounds mainly exert their neuroprotective effects in hypoxia via regulating proteins that are related to antioxidant, anti-apoptosis and anti-inflammatory activities.

Focus on Notoginsenoside R1 in Metabolism and Prevention Against Human Diseases

Notoginsenoside (NG)-R1 is one of the main bioactive compounds from Panax notoginseng (PN) root, which is well known in the prescription for mediating the micro-circulatory hemostasis in human. In this article, we mainly discuss NG-R1 in metabolism and the biological activities, including cardiovascular protection, neuro-protection, anti-diabetes, liver protection, gastrointestinal protection, lung protection, bone metabolism regulation, renal protection, and anti-cancer. The metabolites produced by deglycosylation of NG-R1 exhibit higher permeability and bioavailability. It has been extensively verified that NG-R1 may ameliorate ischemia-reperfusion (IR)-induced injury in cardiovascular and neuronal systems mainly by upregulating the activity of estrogen receptor α-dependent phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) and nuclear factor erythroid-2-related factor 2 (NRF2) pathways and downregulating nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. However, no specific targets for NG-R1 have been identified. Expectedly, NG-R1 has been used as a main bioactive compound in many Traditional Chinese Medicines clinically, such as Xuesaitong, Naodesheng, XueShuanTong, ShenMai, and QSYQ. These suggest that NG-R1 exhibits a significant potency in drug development.

The Roles of GABA in Ischemia-Reperfusion Injury in the Central Nervous System and Peripheral Organs

Ischemia-reperfusion (I/R) injury is a common pathological process, which may lead to dysfunctions and failures of multiple organs. A flawless medical way of endogenous therapeutic target can illuminate accurate clinical applications. γ-Aminobutyric acid (GABA) has been known as a marker in I/R injury of the central nervous system (mainly in the brain) for a long time, and it may play a vital role in the occurrence of I/R injury. It has been observed that throughout cerebral I/R, levels, syntheses, releases, metabolisms, receptors, and transmissions of GABA undergo complex pathological variations. Scientists have investigated the GABAergic enhancers for attenuating cerebral I/R injury; however, discussions on existing problems and mechanisms of available drugs were seldom carried out so far. Therefore, this review would summarize the process of pathological variations in the GABA system under cerebral I/R injury and will cover corresponding probable issues and mechanisms in using GABA-related drugs to illuminate the concern about clinical illness for accurately preventing cerebral I/R injury. In addition, the study will summarize the increasing GABA signals that can prevent I/R injuries occurring in peripheral organs, and the roles of GABA were also discussed correspondingly.

Systematically identifying the hepatoprotective ingredients of schisandra lignan extract from pharmacokinetic and pharmacodynamic perspectives

BACKGROUND

Herbal medicines (HMs) have been proven to be productive sources of leads for the development of drugs. To date approximately 150 lignans have been identified from Schisandra sphenanthera. Hepatoprotective activity is a well-known characteristic of schisandra lignans, yet the authentic types of active lignans are still not well known.

PURPOSE

The present study aimed to develop a reliable and efficient strategy for identifying the hepatoprotective ingredients of schisandra lignan extract (SLE).

METHODS

SLEs were prepared by extracting Schisandra sphenanthera powder using 10%, 50% and 90% ethanol (w/w 1:10) combining 5-fold volume of ethyl acetate. The schisandra lignans in SLEs were qualitatively analyzed based on liquid chromatography hybrid ion trap time-of-flight mass spectrometry (LCMS-IT-TOF). Preparative liquid chromatography (PLC) was used to collect ingredient fractions. The hepatoprotective activity of schisandra lignans was systematically investigated on in vivo and in vitro models.

RESULTS

The SLE extracted by 50% ethanol and 5-fold volume of ethyl acetate (50%SLE) had the highest lignan content and exhibited significantly stronger hepatoprotective activity than other SLEs (P <  0.01). The hepatoprotective effect of 50%SLE mainly attributed to the SLE segment which collected from 12 to 22 min by PLC. Schisantherin A (Sth A) was confirmed as the most promising hepatoprotective drug in Schisandra sphenanthera due to high content in crude materials, high exposure level in vivo and high efficiency on APAP-induced hepatotoxicity.

CONCLUSION

The hepatoprotective ingredients of SLEs were systematically investigated based on the presently developed approach, and Sth A was identified as the optimum hepatoprotective candidate in Schisandra sphenanthera.

Ginsenoside Rb1 exerts neuroprotective effects through regulation of Lactobacillus helveticus abundance and GABAA receptor expression

Background

Ginsenoside Rb1 (Rb1), one of the most abundant protopanaxadiol-type ginsenosides, exerts excellent neuroprotective effects even though it has low intracephalic exposure.

Purpose

The present study aimed to elucidate the apparent contradiction between the pharmacokinetics and pharmacodynamics of Rb1 by studying the mechanisms underlying neuroprotective effects of Rb1 based on regulation of microflora.

Methods

A pseudo germ-free (PGF) rat model was established, and neuroprotective effects of Rb1 were compared between conventional and PGF rats. The relative abundances of common probiotics were quantified to reveal the authentic probiotics that dominate in the neuroprotection of Rb1. The expressions of the gamma-aminobutyric acid (GABA) receptors, including GABAA receptors (α2, β2, and γ2) and GABAB receptors (1b and 2), in the normal, ischemia/reperfusion (I/R), and I/R+Rb1 rat hippocampus and striatum were assessed to reveal the neuroprotective mechanism of Rb1.

Results

The results showed that microbiota plays a key role in neuroprotection of Rb1. The relative abundance of Lactobacillus helveticus (Lac.H) increased 15.26 fold after pretreatment with Rb1. I/R surgery induced effects on infarct size, neurological deficit score, and proinflammatory cytokines (IL-1β, IL-6, and TNF-α) were prevented by colonizing the rat gastrointestinal tract with Lac.H (1 × 10⁹ CFU) by gavage 15 d before I/R surgery. Both Rb1 and Lac.H upregulated expression of GABA receptors in I/R rats. Coadministration of a GABA_A receptor antagonist significantly attenuated neuroprotective effects of Rb1 and Lac.H.

Conclusion

In sum, Rb1 exerts neuroprotective effects by regulating Lac.H and GABA receptors rather than through direct distribution to the target sites.