Lysine and arginine reduce the effects of cerebral ischemic insults and inhibit glutamate-induced neuronal activity in rats

Exploring the "gene-metabolite" network of ischemic stroke with blood stasis and toxin syndrome by integrated transcriptomics and metabolomics strategy

A research model combining a disease and syndrome can provide new ideas for the treatment of ischemic stroke. In the field of traditional Chinese medicine, blood stasis and toxin (BST) syndrome is considered an important syndrome seen in patients with ischemic stroke (IS). However, the biological basis of IS-BST syndrome is currently not well understood. Therefore, this study aimed to explore the biological mechanism of IS-BST syndrome. This study is divided into two parts: (1) establishment of an animal model of ischemic stroke disease and an animal model of BST syndrome in ischemic stroke; (2) use of omics methods to identify differentially expressed genes and metabolites in the models. We used middle cerebral artery occlusion (MCAO) surgery to establish the disease model, and utilized carrageenan combined with active dry yeast and MCAO surgery to construct the IS-BST syndrome model. Next, we used transcriptomics and metabolomics methods to explore the differential genes and metabolites in the disease model and IS-BST syndrome model. It is found that the IS-BST syndrome model exhibited more prominent characteristics of IS disease and syndrome features. Both the disease model and the IS-BST syndrome model share some common biological processes, such as thrombus formation, inflammatory response, purine metabolism, sphingolipid metabolism, and so on. Results of the "gene-metabolite" network revealed that the IS-BST syndrome model exhibited more pronounced features of complement-coagulation cascade reactions and amino acid metabolism disorders. Additionally, the "F2 (thrombin)-NMDAR/glutamate" pathway was coupled with the formation process of the blood stasis and toxin syndrome. This study reveals the intricate mechanism of IS-BST syndrome, offering a successful model for investigating the combination of disease and syndrome.

Urinary metabolic characterization of advanced tuberculous meningitis cases in a South African paediatric population

Tuberculous meningitis (TBM) is a severe form of tuberculosis with high neuro-morbidity and mortality, especially among the paediatric population (aged ≤12 years). Little is known of the associated metabolic changes. This study aimed to identify characteristic metabolic markers that differentiate severe cases of paediatric TBM from controls, through non-invasive urine collection. Urine samples selected for this study were from two paediatric groups. Group 1: controls (n = 44): children without meningitis, no neurological symptoms and from the same geographical region as group 2. Group 2: TBM cases (n = 13): collected from paediatric patients that were admitted to Tygerberg Hospital in South Africa on the suspicion of TBM, mostly severely ill; with a later confirmation of TBM. Untargeted 1H NMR-based metabolomics data of urine were generated, followed by statistical analyses via MetaboAnalyst (v5.0), and the identification of important metabolites. Twenty nine urinary metabolites were identified as characteristic of advanced TBM and categorized in terms of six dysregulated metabolic pathways: 1) upregulated tryptophan catabolism linked to an altered vitamin B metabolism; 2) perturbation of amino acid metabolism; 3) increased energy production-metabolic burst; 4) disrupted gut microbiota metabolism; 5) ketoacidosis; 6) increased nitrogen excretion. We also provide original biological insights into this biosignature of urinary metabolites that can be used to characterize paediatric TBM patients in a South African cohort.

Identification of a novel AIFM1 variant from a Chinese family with auditory neuropathy

Background: Auditory neuropathy (AN) is a specific type of hearing loss characterized by impaired language comprehension. Apoptosis inducing factor mitochondrion associated 1 (AIFM1) is the most common gene associated with late-onset AN. In this study, we aimed to screen the pathogenic variant of AIFM1 in a Chinese family with AN and to explore the molecular mechanism underlying the function of such variant in the development of AN.

Methods: One patient with AN and eight unaffected individuals from a Chinese family were enrolled in this study. A comprehensive clinical evaluation was performed on all participants. A targeted next-generation sequencing (NGS) analysis of a total of 406 known deafness genes was performed to screen the potential pathogenic variants in the proband. Sanger sequencing was used to confirm the variants identified in all participants. The pathogenicity of variant was predicted by bioinformatics analysis. Immunofluorescence and Western blot analyses were performed to evaluate the subcellular distribution and expression of the wild type (WT) and mutant AIFM1 proteins. Cell apoptosis was evaluated based on the TUNEL analyses.

Results: Based on the clinical evaluations, the proband in this family was diagnosed with AN. The results of NGS and Sanger sequencing showed that a novel missense mutation of AIFM1, i.e., c.1367A > G (p. D456G), was identified in this family. Bioinformatics analysis indicated that this variant was pathogenic. Functional analysis showed that in comparison with the WT, the mutation c.1367A > G of AIFM1 showed no effect on its subcellular localization and the ability to induce apoptosis, but changed its protein expression level.

Conclusion: A novel variant of AIFM1 was identified for the first time, which was probably the genetic cause of AN in a Chinese family with AN.

Zhilong Huoxue Tongyu Capsules' Effects on ischemic stroke: An assessment using fecal 16S rRNA gene sequencing and untargeted serum metabolomics

Zhilong Huoxue Tongyu capsule (ZHTC) is an effective traditional Chinese medicine compound for the treatment of ischemic stroke, which is widely used in clinical ischemic stroke patients. However, it is uncertain whether ZHTC affects ischemic stroke through gut microbiota and serum metabolites. In this study, a rat model of middle cerebral artery occlusion (MCAO) was prepared. By evaluating motor nerve function score, cerebral infarct size, brain tissue damage and intestinal barrier damage, it was found that ZHTC improved stroke-related symptoms in MCAO rats. Using 16S rRNA gene sequencing, fecal microbial transplantation (FMT), untargeted metabolomics, and spearman correlation analysis of gut microbiota and serum metabolites, we found that ZHTC can regulate the abundance of p_Firmicutes, p_Bacteroidota,p_Proteobacteria, g_Prevotella, and g_Lactobacillus, and regulated 23 differential metabolites. Spearman correlation analysis found that Arginine was positively correlated with p_Firmicutes, o_Clostridiales, c_Clostridia, and negatively correlated with p_Bacteroidetes, c_Bacteroidia,o_Bacteroidales; L-Lysine was negatively correlated with f_Christensenellaceae; L-methionine was positively correlated with o_Lactobacillales, f_Lactobacillaceae, and g_Lactobacillus. Altogether, this study shows for the first time that ZHTC can ameliorate ischemic stroke by modulating gut microbiota and metabolic disturbances. This lays the foundation for further revealing the causal relationship between ZHTC, gut dysbiosis, plasma metabolite levels and ischemic stroke, and provides a scientific explanation for the ameliorating effect of ZHTC on ischemic stroke.

Pilot Study on Acute Effects of Pharmacological Intraperitoneal L-Homoarginine on Homeostasis of Lysine and Other Amino Acids in a Rat Model of Isoprenaline-Induced Takotsubo Cardiomyopathy

L-Arginine:glycine amidinotransferase (AGAT) catalyzes the formation of L-homoarginine (hArg) and L-ornithine (Orn) from L-arginine (Arg) and L-lysine (Lys): Arg + Lys ↔ hArg + Orn; equilibrium constant K_hArg. AGAT also catalyzes the formation of guanidinoacetate (GAA) and Orn from Arg and glycine (Gly): Arg + Gly ↔ GAA + Orn; equilibrium constant K_GAA. In humans, pharmacological hArg is metabolized to Lys. Low circulating and low excretory concentrations of hArg are associated with worse outcomes and mortality in the renal and cardiovascular systems. The metabolism and pharmacology of hArg have been little investigated. In the present study, we investigated the effects of pharmacological hArg (i.p., 0, 20, 220, 440 mg/kg at time point 0 min) on amino acids homeostasis in a rat model of isoprenaline-induced takotsubo cardiomyopathy (i.p., 50 mg/kg at time point 15 min). We measured by gas chromatography-mass spectrometry free and proteinic amino acids, as well as the polyamines putrescine and spermidine in the heart, lung, kidney, and liver of ten rats sacrificed at various time points (range, 0 to 126 min). hArg administration resulted in multiple changes in the tissue contents of several free and proteinic amino acids, as well as in the putrescine-spermidine molar ratio, an indicator of polyamines catabolism. Our results suggest that Lys and Arg are major metabolites of pharmacological hArg. Kidneys and heart seem to play a major metabolic role for hArg. Circulating Lys does not change over time, yet there is a considerable interchange of free Lys between organs, notably kidney and heart, during the presence of isoprenaline in the rats (time range, 15 to 90 min). Antidromic changes were observed for K_hArg and K_GAA, notably in the heart in this time window. Our study shows for the first time that free hArg and sarcosine (N-methylglycine) are positively associated with each other. The acute effects of high-dosed hArg administration and isoprenaline on various amino acids and on AGAT-catalyzed reaction in the heart, lung, kidney, and liver are detailed and discussed.

Severe Spinal Cord Injury in Rats Induces Chronic Changes in the Spinal Cord and Cerebral Cortex Metabolism, Adjusted by Thiamine That Improves Locomotor Performance

Our study aims at developing knowledge-based strategies minimizing chronic changes in the brain after severe spinal cord injury (SCI). The SCI-induced long-term metabolic alterations and their reactivity to treatments shortly after the injury are characterized in rats. Eight weeks after severe SCI, significant mitochondrial lesions outside the injured area are demonstrated in the spinal cord and cerebral cortex. Among the six tested enzymes essential for the TCA cycle and amino acid metabolism, mitochondrial 2-oxoglutarate dehydrogenase complex (OGDHC) is the most affected one. SCI downregulates this complex by 90% in the spinal cord and 30% in the cerebral cortex. This is associated with the tissue-specific changes in other enzymes of the OGDHC network. Single administrations of a pro-activator (thiamine, or vitamin B1, 1.2 mmol/kg) or a synthetic pro-inhibitor (triethyl glutaryl phosphonate, TEGP, 0.02 mmol/kg) of OGDHC within 15–20 h after SCI are tested as protective strategies. The biochemical and physiological assessments 8 weeks after SCI reveal that thiamine, but not TEGP, alleviates the SCI-induced perturbations in the rat brain metabolism, accompanied by the decreased expression of (acetyl)p53, increased expression of sirtuin 5 and an 18% improvement in the locomotor recovery. Treatment of the non-operated rats with the OGDHC pro-inhibitor TEGP increases the p53 acetylation in the brain, approaching the brain metabolic profiles to those after SCI. Our data testify to an important contribution of the OGDHC regulation to the chronic consequences of SCI and their control by p53 and sirtuin 5.

L-Arginine Exerts Excellent Anti-Stress Effects on Stress-Induced Shortened Lifespan, Cognitive Decline and Depression

The anti-stress potential of dietary L-arginine (Arg) was assessed in psychosocially stress-loaded senescence-accelerated (SAMP10) mice. Although this strain of mouse is sensitive to stress, daily administration of Arg at 3 mg/kg significantly suppressed aging-related cognitive decline and behavioral depression at nine months of age and counteracted stress-induced shortened lifespan. To investigate the mechanism of the anti-stress effect of Arg in the brain, early changes in oxidative damage and gene expression levels were measured using SAMP10 mice that were stress-loaded for three days. Increased lipid peroxidation in the brains of stressed mice was significantly lowered by Arg intake. Several genes associated with oxidative stress response and neuronal excitotoxic cell death, including Nr4a1, Arc, and Cyr61, remarkably increased in response to psychosocial stress; however, their expression was significantly suppressed in mice that ingested Arg even under stress conditions. In contrast, the genes that maintain mitochondrial functions and neuronal survival, including Hba-a2 and Hbb-b2, were significantly increased in mice that ingested Arg. These results indicate that Arg reduces oxidative damage and enhances mitochondrial functions in the brain. We suggest that the daily intake of Arg plays important roles in reducing stress-induced brain damage and slowing aging.

The Role of Amino Acids in Neurotransmission and Fluorescent Tools for Their Detection

Neurotransmission between neurons, which can occur over the span of a few milliseconds, relies on the controlled release of small molecule neurotransmitters, many of which are amino acids. Fluorescence imaging provides the necessary speed to follow these events and has emerged as a powerful technique for investigating neurotransmission. In this review, we highlight some of the roles of the 20 canonical amino acids, GABA and β-alanine in neurotransmission. We also discuss available fluorescence-based probes for amino acids that have been shown to be compatible for live cell imaging, namely those based on synthetic dyes, nanostructures (quantum dots and nanotubes), and genetically encoded components. We aim to provide tool developers with information that may guide future engineering efforts and tool users with information regarding existing indicators to facilitate studies of amino acid dynamics.

Gelator length precisely tunes supramolecular hydrogel stiffness and neuronal phenotype in 3D culture

The brain is one of the softest tissues in the body with storage moduli (G') that range from hundreds to thousands of pascals (Pa) depending upon the anatomic region. Furthermore, pathological processes such as injury, aging and disease can cause subtle changes in the mechanical properties throughout the central nervous system. However, these changes in mechanical properties lie within an extremely narrow range of moduli and there is great interest in understanding their effect on neuron biology. We report here the design of supramolecular hydrogels based on anionic peptide amphiphile nanofibers using oligo-L-lysines of different molecular lengths to precisely tune gel stiffness over the range of interest and found that G' increases by 10.5 Pa for each additional lysine monomer in the oligo-L-lysine chain. We found that small changes in storage modulus on the order of 70 Pa significantly affect survival, neurite growth and tyrosine hydroxylase-positive population in dopaminergic neurons derived from induced pluripotent stem cells. The work reported here offers a strategy to tune mechanical stiffness of hydrogels for use in 3D neuronal cell cultures and transplantation matrices for neural regeneration.

Hypoxic Adaptation of Mitochondrial Metabolism in Rat Cerebellum Decreases in Pregnancy

Function of brain amino acids as neurotransmitters or their precursors implies changes in the amino acid levels and/or metabolism in response to physiological and environmental challenges. Modelling such challenges by pregnancy and/or hypoxia, we characterize the amino acid pool in the rat cerebellum, quantifying the levels and correlations of 15 amino acids and activity of 2-oxoglutarate dehydrogenase complex (OGDHC). The parameters are systemic indicators of metabolism because OGDHC limits the flux through mitochondrial TCA cycle, where amino acids are degraded and their precursors synthesized. Compared to non-pregnant state, pregnancy increases the cerebellar content of glutamate and tryptophan, decreasing interdependence between the quantified components of amino acid metabolism. In response to hypoxia, the dependence of cerebellar amino acid pool on OGDHC and the average levels of arginine, glutamate, lysine, methionine, serine, phenylalanine, and tryptophan increase in non-pregnant rats only. This is accompanied by a higher hypoxic resistance of the non-pregnant vs. pregnant rats, pointing to adaptive significance of the hypoxia-induced changes in the cerebellar amino acid metabolism. These adaptive mechanisms are not effective in the pregnancy-changed metabolic network. Thus, the cerebellar amino acid levels and OGDHC activity provide sensitive markers of the physiology-dependent organization of metabolic network and its stress adaptations.

Nutraceutical profile and evidence of alleviation of oxidative stress by Spirogyra porticalis (Muell.) Cleve inhabiting the high altitude Trans-Himalayan Region

The high altitude trans-Himalayan region indeed is hostile domain for survival. Algae inhabiting  this  hostile terrain have evolutionarily developed mechanisms to produce unique adaptogenic molecules against climatic stressors. The present study has focused on the high altitude alga Spirogyra porticalis (Muell.) Cleve- a filamentous Charophyte, and reports the estimation of amino acids (AAs), fatty acids (FAs), vitamins and their efficacy against oxidative stress. Reverse phase-HPLC, GC-FID and rapid resolution-LC/tandem mass spectrometry were used for analysis of AAs, FAs and vitamins. Analysis of the alga  revealed the presence of 19 AAs (239.51 ± 8.57 to 13102.40 ± 11.08 µg/g), dominated by alanine, proline and lysine. Enriched phenylalanine, cysteine-HCl and high lysine:arginine ratio could also have beneficial impact against hypoxia -induced cognitive impairment. A total of 9 FAs were detected (0.43 ± 0.00% to 34.76 ± 0.52%). Polyunsaturated and monounsaturated FAs were found to be dominant. The alga showed the presence of 8 vitamins within the range of 39.654 ± 3.198 to 5468.184 ± 106.859 µg/Kg, wherein Vitamin B₅, B₃ and B₂ were dominant. 600 µg/ml of methanolic extract showed recovery of GSH and trolox equivalent antioxidants in rat blood/hemolysate, while 400 µg/ml of extract showed revival in superoxide dismutase (SOD) activity. The present study concludes that the alga S. porticalis has immense potential to counter oxidative stress as a nutraceutical supplement.

Placenta-Derived Cells for Acute Brain Injury

Acute brain injury resulting from ischemic/hemorrhagic or traumatic damage is one of the leading causes of mortality and disability worldwide and is a significant burden to society. Neuroprotective options to counteract brain damage are very limited in stroke and traumatic brain injury (TBI). Given the multifaceted nature of acute brain injury and damage progression, several therapeutic targets may need to be addressed simultaneously to interfere with the evolution of the injury and improve the patient’s outcome. Stem cells are ideal candidates since they act on various mechanisms of protection and repair, improving structural and functional outcomes after experimental stroke or TBI. Stem cells isolated from placenta offer advantages due to their early embryonic origin, ease of procurement, and ethical acceptance. We analyzed the evidence for the beneficial effects of placenta-derived stem cells in acute brain injury, with the focus on experimental studies of TBI and stroke, the engineering strategies pursued to foster cell potential, and characterization of the bioactive molecules secreted by placental cells, known as their secretome, as an alternative cell-free strategy. Results from the clinical application of placenta-derived stem cells for acute brain injury and ongoing clinical trials are summarily discussed.

Amino Acid Biosignature in Plasma among Ischemic Stroke Subtypes

Ischemic stroke is a neurovascular disorder caused by reduced or blockage of blood flow to the brain, which may permanently affect motor and cognitive abilities. The diagnostic of stroke is performed using imaging technologies, clinical evaluation, and neuropsychological protocols, but no blood test is available yet. In this work, we analyzed amino acid concentrations in blood plasma from poststroke patients in order to identify differences that could characterize the stroke etiology. Plasma concentrations of sixteen amino acids from patients with chronic ischemic stroke (n = 73) and the control group (n = 16) were determined using gas chromatography coupled to mass spectrometry (GC-MS). The concentration data was processed by Partial Least Squares-Discriminant Analysis (PLS-DA) to classify patients with stroke and control. The amino acid analysis generated a first model able to discriminate ischemic stroke patients from control group. Proline was the most important amino acid for classification of the stroke samples in PLS-DA, followed by lysine, phenylalanine, leucine, and glycine, and while higher levels of methionine and alanine were mostly related to the control samples. The second model was able to discriminate the stroke subtypes like atherothrombotic etiology from cardioembolic and lacunar etiologies, with lysine, leucine, and cysteine plasmatic concentrations being the most important metabolites. Our results suggest an amino acid biosignature for patients with chronic stroke in plasma samples, which can be helpful in diagnosis, prognosis, and therapeutics of these patients.

Conditioned medium from amniotic cells protects striatal degeneration and ameliorates motor deficits in the R6/2 mouse model of Huntington's disease

Inflammation significantly impacts the progression of Huntington's disease (HD) and the mutant HTT protein determines a pro‐inflammatory activation of microglia. Mesenchymal stem/stromal cells (MSC) from the amniotic membrane (hAMSC), and their conditioned medium (CM‐hAMSC), have been shown to possess protective effects in vitro and in vivo in animal models of immune‐based disorders and of traumatic brain injury, which have been shown to be mediated by their immunomodulatory properties.

In this study, in the R6/2 mouse model for HD we demonstrate that mice treated with CM‐hAMSC display less severe signs of neurological dysfunction than saline‐treated ones. CM‐hAMSC treatment significantly delayed the development of the hind paw clasping response during tail suspension, reduced deficits in rotarod performance, and decreased locomotor activity in an open field test. The effects of CM‐hAMSC on neurological function were reflected in a significant amelioration in brain pathology, including reduction in striatal atrophy and the formation of striatal neuronal intranuclear inclusions. In addition, while no significant increase was found in the expression of BDNF levels after CM‐hAMSC treatment, a significant decrease of microglia activation and inducible nitric oxide synthase levels were observed. These results support the concept that CM‐hAMSC could act by modulating inflammatory cells, and more specifically microglia.

Method parameters' impact on mortality and variability in rat stroke experiments: a meta-analysis

Background

Even though more than 600 stroke treatments have been shown effective in preclinical studies, clinically proven treatment alternatives for cerebral infarction remain scarce. Amongst the reasons for the discrepancy may be methodological shortcomings, such as high mortality and outcome variability, in the preclinical studies. A common approach in animal stroke experiments is that A) focal cerebral ischemia is inflicted, B) some type of treatment is administered and C) the infarct sizes are assessed. However, within this paradigm, the researcher has to make numerous methodological decisions, including choosing rat strain and type of surgical procedure. Even though a few studies have attempted to address the questions experimentally, a lack of consensus regarding the optimal methodology remains.

Methods

We therefore meta-analyzed data from 502 control groups described in 346 articles to find out how rat strain, procedure for causing focal cerebral ischemia and the type of filament coating affected mortality and infarct size variability.

Results

The Wistar strain and intraluminal filament procedure using a silicone coated filament was found optimal in lowering infarct size variability. The direct and endothelin methods rendered lower mortality rate, whereas the embolus method increased it compared to the filament method.

Conclusions

The current article provides means for researchers to adjust their middle cerebral artery occlusion (MCAo) protocols to minimize infarct size variability and mortality.