Hypoxanthine Induces Neuroenergetic Impairment and Cell Death in Striatum of Young Adult Wistar Rats

Effect of Quinolinic Acid on Behavior, Morphology, and Expression of Inflammatory/oxidative Status in Rats' Striatum: Is Coenzyme Q10 a Good Protector?

Quinolinic acid (QUIN) is a toxic compound with pro-oxidant, pro-inflammatory, and pro-apoptotic actions found at high levels in the central nervous system (CNS) in several pathological conditions. Due to the toxicity of QUIN, it is important to evaluate strategies to protect against the damage caused by this metabolite in the brain. In this context, coenzyme Q10 (CoQ10) is a provitamin present in the mitochondria with a protective role in cells through several mechanisms of action. Based on these, the present study was aimed at evaluating the possible neuroprotective role of CoQ10 against damage caused by QUIN in the striatum of young Wistar rats. Twenty-one-day-old rats underwent a 10-day pretreatment with CoQ10 or saline (control) intraperitoneal injections and on the 30th day of life received QUIN intrastriatal or saline (control) administration. The animals were submitted to behavior tests or euthanized, and the striatum was dissected to neurochemical studies. Results showed that CoQ10 was able to prevent behavioral changes (the open field, object recognition, and pole test tasks) and neurochemical parameters (alteration in the gene expression of IL-1β, IL-6, SOD, and GPx, as well as in the immunocontent of cytoplasmic Nrf2 and nuclear p-Nf-κβ) caused by QUIN. These findings demonstrate the promising therapeutic effects of CoQ10 against QUIN toxicity.

Multi-omics analysis reveals neuroinflammation, activated glial signaling, and dysregulated synaptic signaling and metabolism in the hippocampus of aged mice

Aging is an intricate biological event that occurs in both vertebrates and invertebrates. During the aging process, the brain, a vulnerable organ, undergoes structural and functional alterations, resulting in behavioral changes. The hippocampus has long been known to be critically associated with cognitive impairment, dementia, and Alzheimer’s disease during aging; however, the underlying mechanisms remain largely unknown. In this study, we hypothesized that altered metabolic and gene expression profiles promote the aging process in the hippocampus. Behavioral tests showed that exploration, locomotion, learning, and memory activities were reduced in aged mice. Metabolomics analysis identified 69 differentially abundant metabolites and showed that the abundance of amino acids, lipids, and microbiota-derived metabolites (MDMs) was significantly altered in hippocampal tissue of aged animals. Furthermore, transcriptomic analysis identified 376 differentially expressed genes in the aged hippocampus. A total of 35 differentially abundant metabolites and 119 differentially expressed genes, constituting the top 200 correlations, were employed for the co-expression network. The multi-omics analysis showed that pathways related to inflammation, microglial activation, synapse, cell death, cellular/tissue homeostasis, and metabolism were dysregulated in the aging hippocampus. Our data revealed that metabolic perturbations and gene expression alterations in the aged hippocampus were possibly linked to their behavioral changes in aged mice; we also provide evidence that altered MDMs might mediate the interaction between gut and brain during the aging process.

The role of neuroimmune and inflammation in pediatric uremia-induced neuropathy

Uremic neuropathy in children encompasses a wide range of central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS), and psychological abnormalities, which is associated with progressive renal dysfunction. Clinically, the diagnosis of uremic neuropathy in children is often made retrospectively when symptoms improve after dialysis or transplantation, due to there is no defining signs or laboratory and imaging findings. These neurological disorders consequently result in increased morbidity and mortality among children population, making uremia an urgent public health problem worldwide. In this review, we discuss the epidemiology, potential mechanisms, possible treatments, and the shortcomings of current research of uremic neuropathy in children. Mechanistically, the uremic neuropathy may be caused by retention of uremic solutes, increased oxidative stress, neurotransmitter imbalance, and disturbance of the blood-brain barrier (BBB). Neuroimmune, including the change of inflammatory factors and immune cells, may also play a crucial role in the progression of uremic neuropathy. Different from the invasive treatment of dialysis and kidney transplantation, intervention in neuroimmune and targeted anti-inflammatory therapy may provide a new insight for the treatment of uremia.

Quinolinic Acid Impairs Redox Homeostasis, Bioenergetic, and Cell Signaling in Rat Striatum Slices: Prevention by Coenzyme Q10

Quinolinic acid (QUIN) is an important agonist of NMDA receptors that are found at high levels in cases of brain injury and neuroinflammation. Therefore, it is necessary to investigate neuroprotection strategies capable of neutralizing the effects of the QUIN on the brain. Coenzyme Q₁₀ (CoQ₁₀) is a provitamin that has an important antioxidant and anti-inflammatory action. This work aims to evaluate the possible neuroprotective effect of CoQ₁₀ against the toxicity caused by QUIN. Striatal slices from 30-day-old Wistar rats were preincubated with CoQ₁₀ 25-100 μM for 15 min; then, QUIN 100 μM was added to the incubation medium for 30 min. A dose-response curve was used to select the CoQ₁₀ concentration to be used in the study. Results showed that QUIN caused changes in the production of ROS, nitrite levels, activities of antioxidant enzymes, glutathione content, and damage to proteins and lipids. CoQ₁₀ was able to prevent the effects caused by QUIN, totally or partially, except for damage to proteins. QUIN also altered the activities of electron transport chain complexes and ATP levels, and CoQ₁₀ prevented totally and partially these effects, respectively. CoQ₁₀ prevented the increase in acetylcholinesterase activity, but not the decrease in the activity of Na⁺,K⁺-ATPase caused by QUIN. We also observed that QUIN caused changes in the total ERK and phospho-Akt content, and these effects were partially prevented by CoQ₁₀. These findings suggest that CoQ₁₀ may be a promising therapeutic alternative for neuroprotection against QUIN neurotoxicity.

Hippocampal Metabolite Profiles in Two Rat Models of Autism: NMR-Based Metabolomics Studies

Autism spectrum disorders (ASDs) are increasingly being diagnosed. Hypotheses link ASD to genetic, epigenetic, or environmental factors. The role of oxidative stress and the imbalance between excitatory and inhibitory neurotransmission in the pathogenesis of ASD has been suggested. Rats in which ASD symptoms are induced by valproate (VPA) or thalidomide (THAL) application in utero are useful models in ASD studies. Our study investigated whether rats in ASD models show changes in metabolite levels in the brain consistent with the hypothetical pathomechanisms of ASD. Female rats were fed one dose of 800 mg/kg VPA or 500 mg/kg THAL orally on the 11th day of gestation, and 1-month offspring were used for the experiments. Metabolic profiles from proton nuclear magnetic resonance spectroscopy of hydrophilic and hydrophobic extracts of rat hippocampi were subjected to OPLS-DA statistical analysis. Large differences between both models in the content of several metabolites in the rat hippocampus were noticed. The following metabolic pathways were identified as being disturbed in both ASD models: steroid hormone biosynthesis; fatty acid biosynthesis; the synthesis and degradation of ketone bodies; glycerophospholipid metabolism; cholesterol metabolism; purine metabolism; arginine and proline metabolism; valine, leucine, and isoleucine biosynthesis and degradation. These results indicate disorders of energy metabolism, altered structure of cell membranes, changes in neurotransmission, and the induction of oxidative stress in the hippocampus. Our data, consistent with hypotheses of ASD pathomechanisms, may be useful in future ASD studies, especially for the interpretation of the results of metabolomics analysis of body fluids in rat ASD models.

The transcriptome sequencing and functional analysis of eyestalk ganglions in Chinese mitten crab (Eriocheir sinensis) treated with different photoperiods

Photoperiod plays an important role in individual growth, development, and metabolism in crustaceans. The growth and reproduction of crabs are closely related to the photoperiod. However, as of yet, there are still no transcriptomic reports of eyestalk ganglions treated under different photoperiods in the Chinese mitten crab (Eriocheir sinensis), which is a benthonic crab with high commercial value in Asia. In this study, we collected the eyestalk ganglions of crabs that were reared under different photoperiods, including a control group (L: D = 12 h: 12 h, named CC), a constant light group (L: D = 24 h: 0 h, named LL) and a constant darkness group (L: D = 0 h: 24 h, named DD). RNA sequencing was performed on these tissues in order to examine the effects of different photoperiods. The total numbers of clean reads from the CC, LL and DD groups were 48,772,584 bp, 53,943,281 bp and 53,815,178 bp, respectively. After de novo assembly, 161,380 unigenes were obtained and were matched with different databases. The DEGs were significantly enriched in phototransduction and energy metabolism pathways. Results from RT-qPCR showed that TRP channel protein (TRP) in the phototransduction pathway had a significantly higher level of expression in LL and DD groups than in the CC group. We found that the downregulation of the pyruvate dehydrogenase complex (PDC) gene and the upregulation phosphoenolpyruvate carboxykinase (PPC) gene were involved in energy metabolism processes in LL or DD. In addition, we also found that the upregulation of the expression level of the genes Gαq, pyruvate kinase (PK), NADH peroxidase (NADH) and ATPase is involved in phototransduction and energy metabolism. These results may shed some light on the molecular mechanism underlying the effect of photoperiod in physiological activity of E. sinensis.

Emerging Role of Purine Metabolizing Enzymes in Brain Function and Tumors

The growing evidence of the involvement of purine compounds in signaling, of nucleotide imbalance in tumorigenesis, the discovery of purinosome and its regulation, cast new light on purine metabolism, indicating that well known biochemical pathways may still surprise. Adenosine deaminase is important not only to preserve functionality of immune system but also to ensure a correct development and function of central nervous system, probably because its activity regulates the extracellular concentration of adenosine and therefore its function in brain. A lot of work has been done on extracellular 5′-nucleotidase and its involvement in the purinergic signaling, but also intracellular nucleotidases, which regulate the purine nucleotide homeostasis, play unexpected roles, not only in tumorigenesis but also in brain function. Hypoxanthine guanine phosphoribosyl transferase (HPRT) appears to have a role in the purinosome formation and, therefore, in the regulation of purine synthesis rate during cell cycle with implications in brain development and tumors. The final product of purine catabolism, uric acid, also plays a recently highlighted novel role. In this review, we discuss the molecular mechanisms underlying the pathological manifestations of purine dysmetabolisms, focusing on the newly described/hypothesized roles of cytosolic 5′-nucleotidase II, adenosine kinase, adenosine deaminase, HPRT, and xanthine oxidase.

Kynurenic Acid Restores Nrf2 Levels and Prevents Quinolinic Acid-Induced Toxicity in Rat Striatal Slices

Kynurenic acid (KYNA) and quinolinic acid (QUIN) are metabolites produced in the degradation of tryptophan and have important neurological activities. KYNA/QUIN ratio changes are known to be associated with central nervous system disorders, such Alzheimer, Parkinson, and Huntington diseases. In the present study, we investigate the ability of KYNA in prevent the first events preceding QUIN-induced neurodegeneration in striatal slices of rat. We evaluated the protective effect of KYNA on oxidative status (reactive oxygen species production, antioxidant enzymes activities, lipid peroxidation, nitrite levels, protein and DNA damage, and iNOS immunocontent), mitochondrial function (mitochondrial mass, membrane potential, and respiratory chain enzymes), and Na⁺,K⁺-ATPase in striatal slices of rats treated with QUIN. Since QUIN alters the levels of Nrf2, we evaluated the influence of KYNA protection on this parameter. Striatal slices from 30-day-old Wistar rats were preincubated with KYNA (100 μM) for 15 min, followed by incubation with 100-μM QUIN for 30 min. Results showed that KYNA prevented the increase of ROS production caused by QUIN and restored antioxidant enzyme activities and the protein and lipid damage, as well as the Nrf2 levels. KYNA also prevented the effects of QUIN on mitochondrial mass and mitochondrial membrane potential, as well as the decrease in the activities of complex II, SDH, and Na⁺,K⁺-ATPase. We suggest that KYNA prevents changes in Nrf2 levels, oxidative imbalance, and mitochondrial dysfunction caused by QUIN in striatal slices. This study elucidates some of the protective effects of KYNA against the damage caused by QUIN toxicity.

A pharmacological screen for compounds that rescue the developmental lethality of a Drosophila ATM mutant

Ataxia-telangiectasia (A-T) is a neurodegenerative disease caused by mutation of the A-T mutated (ATM) gene. ATM encodes a protein kinase that is activated by DNA damage and phosphorylates many proteins, including those involved in DNA repair, cell cycle control, and apoptosis. Characteristic biological and molecular functions of ATM observed in mammals are conserved in Drosophila melanogaster. As an example, conditional loss-of-function ATM alleles in flies cause progressive neurodegeneration through activation of the innate immune response. However, unlike in mammals, null alleles of ATM in flies cause lethality during development. With the goals of understanding biological and molecular roles of ATM in a whole animal and identifying candidate therapeutics for A-T, we performed a screen of 2400 compounds, including FDA-approved drugs, natural products, and bioactive compounds, for modifiers of the developmental lethality caused by a temperature-sensitive ATM allele (ATM8) that has reduced kinase activity at non-permissive temperatures. Ten compounds reproducibly suppressed the developmental lethality of ATM8 flies, including Ronnel, which is an organophosphate. Ronnel and other suppressor compounds are known to cause mitochondrial dysfunction or to inhibit the enzyme acetylcholinesterase, which controls the levels of the neurotransmitter acetylcholine, suggesting that detrimental consequences of reduced ATM kinase activity can be rescued by inhibiting the function of mitochondria or increasing acetylcholine levels. We carried out further studies of Ronnel because, unlike the other compounds that suppressed the developmental lethality of homozygous ATM8 flies, Ronnel was toxic to the development of heterozygous ATM8 flies. Ronnel did not affect the innate immune response of ATM8 flies, and it further increased the already high levels of DNA damage in brains of ATM8 flies, but its effects were not harmful to the lifespan of rescued ATM8 flies. These results provide new leads for understanding the biological and molecular roles of ATM and for the treatment of A-T.

Chronic Mild Hyperhomocysteinemia Alters Inflammatory and Oxidative/Nitrative Status and Causes Protein/DNA Damage, as well as Ultrastructural Changes in Cerebral Cortex: Is Acetylsalicylic Acid Neuroprotective?

Homocysteine is a sulfur-containing amino acid derived from methionine metabolism. When plasma homocysteine levels exceed 10-15 μM, there is a condition known as hyperhomocysteinemia, which occur as a result of an inborn error of methionine metabolism or by non-genetic causes. Mild hyperhomocysteinemia is considered a risk factor for development of neurodegenerative diseases. The objective of the present study was to evaluate whether acetylsalicylic acid has neuroprotective role on the effect of homocysteine on inflammatory, oxidative/nitrative stress, and morphological parameters in cerebral cortex of rats subjected to chronic mild hyperhomocysteinemia. Wistar male rats received homocysteine (0.03 μmol/g of body weight) by subcutaneous injections twice a day and acetylsalicylic acid (25 mg/Kg of body weight) by intraperitoneal injections once a day from the 30th to the 60th postpartum day. Control rats received vehicle solution in the same volume. Results showed that rats subjected to chronic mild hyperhomocysteinemia significantly increased IL-1β, IL-6, and acetylcholinesterase activity and reduced nitrite levels. Homocysteine decreased catalase activity and immunocontent and superoxide dismutase activity, caused protein and DNA damage, and altered neurons ultrastructure. Acetylsalicylic acid totally prevented the effect of homocysteine on acetylcholinesterase activity and catalase activity and immunocontent, as well as the ultrastructural changes, and partially prevented alterations on IL-1β levels, superoxide dismutase activity, sulfhydryl content, and comet assay. Acetylsalicylic acid per se increased DNA damage index. In summary, our findings showed that chronic chemically induced model of mild hyperhomocysteinemia altered some parameters and acetylsalicylic acid administration seemed to be neuroprotective, at least in part, on neurotoxicity of homocysteine.