scholarly journals Changes in the immune system in depression and dementia: causal or coincidental effects?

2006 ◽  
Vol 8 (2) ◽  
pp. 163-174 ◽  
Keyword(s):  
Neurotrophic Factors ◽  
Kynurenic Acid ◽  
Neuronal Damage ◽  
Later Life ◽  
Epidemiological Studies ◽  
Kynurenine Pathway ◽  
Pathological Changes ◽  
Induced Apoptosis ◽  
Inflammatory Changes ◽  
The Brain

Epidemiological studies show that there is a correlation between chronic depression and the likelihood of dementia in later life. There is evidence that inflammatory changes in the brain are pathological features of both depression and dementia. This suggests that an increase in inflammation-induced apoptosis, together with a reduction in the synthesis of neurotrophic factors caused by a rise in brain glucocorticoids, may play a role in the pathology of these disorders. A reduction in the neuroprotective components of the kynurenine pathway such as kynurenic acid, and an increase in the neurodegenerative components, 3-hydroxykynurenine and quinolinic acid, contribute to the pathological changes. Such changes are postulated to cause neuronal damage, and thereby predispose chronically depressed patients to dementia.

scholarly journals Extracellular Vesicles in Alzheimer’s and Parkinson’s Disease: Small Entities with Large Consequences

Cells ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 2485
Author(s):  
Charysse Vandendriessche ◽  
Arnout Bruggeman ◽  
Caroline Van Cauwenberghe ◽  
Roosmarijn E. Vandenbroucke
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Disease Progression ◽  
Extracellular Vesicles ◽  
Neurodegenerative Disorders ◽  
Neuronal Damage ◽  
Protein Aggregates ◽  
Pathological Changes ◽  
Associated Proteins ◽  
The Brain

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are incurable, devastating neurodegenerative disorders characterized by the formation and spreading of protein aggregates throughout the brain. Although the exact spreading mechanism is not completely understood, extracellular vesicles (EVs) have been proposed as potential contributors. Indeed, EVs have emerged as potential carriers of disease-associated proteins and are therefore thought to play an important role in disease progression, although some beneficial functions have also been attributed to them. EVs can be isolated from a variety of sources, including biofluids, and the analysis of their content can provide a snapshot of ongoing pathological changes in the brain. This underlines their potential as biomarker candidates which is of specific relevance in AD and PD where symptoms only arise after considerable and irreversible neuronal damage has already occurred. In this review, we discuss the known beneficial and detrimental functions of EVs in AD and PD and we highlight their promising potential to be used as biomarkers in both diseases.

scholarly journals Effects of Sleep Deprivation on the Tryptophan Metabolism

2020 ◽  
Vol 13 ◽  
pp. 117864692097090
Author(s):  
Abid Bhat ◽  
Ananda Staats Pires ◽  
Vanessa Tan ◽  
Saravana Babu Chidambaram ◽  
Gilles J Guillemin
Keyword(s):  
Sleep Deprivation ◽  
Kynurenic Acid ◽  
Second Messengers ◽  
Sleep Time ◽  
Kynurenine Pathway ◽  
Tryptophan Metabolism ◽  
Cellular Functions ◽  
Intracellular Second Messengers ◽  
The Impact ◽  
The Brain

Sleep has a regulatory role in maintaining metabolic homeostasis and cellular functions. Inadequate sleep time and sleep disorders have become more prevalent in the modern lifestyle. Fragmentation of sleep pattern alters critical intracellular second messengers and neurotransmitters which have key functions in brain development and behavioral functions. Tryptophan metabolism has also been found to get altered in SD and it is linked to various neurodegenerative diseases. The kynurenine pathway is a major regulator of the immune response. Adequate sleep alleviates neuroinflammation and facilitates the cellular clearance of metabolic toxins produced within the brain, while sleep deprivation activates the enzymatic degradation of tryptophan via the kynurenine pathway, which results in an increased accumulation of neurotoxic metabolites. SD causes increased production and accumulation of kynurenic acid in various regions of the brain. Higher levels of kynurenic acid have been found to trigger apoptosis, leads to cognitive decline, and inhibit neurogenesis. This review aims to link the impact of sleep deprivation on tryptophan metabolism and associated complication in the brain.

Role of Tryptophan-kynurenine Pathway in Depression: Psychopathological Aspect

2009 ◽  
Vol 24 (S1) ◽  
pp. 1-1
Author(s):  
A.-M. Myint
Keyword(s):  
Kynurenic Acid ◽  
Excitatory Amino Acid ◽  
Kynurenine Pathway ◽  
Response To Treatment ◽  
Excitatory Amino Acid Receptors ◽  
Amino Acid Receptors ◽  
Tryptophan Catabolism ◽  
Ifn Γ ◽  
The Brain

It was reported that cytokines such as IFN-γ reduce the synthesis of 5-HT by stimulating the activity of indoleamine 2,3 dioxygenase (IDO) enzyme which degrades tryptophan to kynurenine. Kynurenine is further metabolized to kynurenic acid (KYNA), 3-hydroxykynurenine (3OHK) and quinolinic acid (QA) by kynurenine aminotransferase (KAT), kynurenine 3-monooxygenase (KMO) and kynureninase. Both KMO and kynureninase are also shown to be activated by IFNγ. The 3OHK is neurotoxic apoptotic while QA is the excitotoxic N-methyl-D-aspartate (NMDA) receptor agonist. Conversely KYNA is an antagonist of all three ionotropic excitatory amino acid receptors and considered neuroprotective. In the brain, tryptophan catabolism occurs in the astrocytes and. The astrocytes are shown to produce mainly KYNA whereas microglia and macrophages produced mainly 3OHK and QA. The astrocytes have been demonstrated to metabolise the QA produced by the neighbouring microglia.Tryptophan breakdown has been found to be increased but KYNA, the neuroprotective metabolite is decreased in both blood and cerebrospinal fluid of the patients with major depression compared to healthy controls. Moreover, the ratio between KYNA and 3OHK showed significant correlation with response to treatment. These findings lead to the hypothesis an imbalance neuroprotection-neurodegener-ation in terms of kynurenine metabolites and their immunological and biochemical interactions in the brain might further induce the apoptosis of the neuroprotective astrocytes and the vulnerability to stress is thereby enhanced.

Kynurenic acid in brain function and dysfunction

2020 ◽  
pp. 323-332
Author(s):  
Robert Schwarcz ◽  
Sophie Erhardt
Keyword(s):  
Kynurenic Acid ◽  
Kynurenine Pathway ◽  
Psychotic Symptoms ◽  
Gabaergic Neurotransmission ◽  
Novel Approach ◽  
Healthy Control ◽  
Amino Acid Tryptophan ◽  
Persons With Schizophrenia ◽  
And Function ◽  
The Brain

The essential amino acid tryptophan is degraded primarily by the kynurenine pathway, a cascade of enzymatic steps leading to the generation of several neuroactive compounds. Of those, kynurenic acid (KYNA), an antagonist at N-methyl-D-aspartate (NMDA) and alpha7-nicotinic receptors, has gained much attention in schizophrenia research. The concentrations of both KYNA and its precursor, kynurenine, have been repeatedly found significantly elevated both in the postmortem cerebral cortex and in the cerebrospinal fluid of schizophrenia persons as compared to healthy control subjects. Studies in experimental animals have demonstrated that KYNA tightly controls dopaminergic, cholinergic, glutamatergic, and GABAergic neurotransmission, and elevated brain levels appear related to psychotic symptoms and cognitive impairments. The kyurenine pathway is highly inducible by immune activation, and studies have shown that the pro-inflammatory cytokines interleukin (IL)-1β‎ and IL-6 are elevated in schizophrenia and stimulate the production of KYNA. Another mechanism that may account for the abnormally high central kynurenine and KYNA levels seen in schizophrenia might be the observed reduced expression and activity of the enzyme kynurenine 3-monooxygenase (KMO), shunting the synthesis of kynurenine toward KYNA. In line with these studies and concepts, preclinical results suggest that inhibition of kynurenine aminotransferase (KAT) II, by reducing the synthesis and function of KYNA in the brain, offers a novel approach to ameliorate psychosis and to improve cognitive performance in persons with schizophrenia.

scholarly journals Experimental Pneumococcal Meningitis: Impaired Clearance of Bacteria from the Blood Due to Increased Apoptosis in the Spleen in Bcl-2-Deficient Mice

2004 ◽  
Vol 72 (6) ◽  
pp. 3113-3119 ◽  
Author(s):  
Andreas Wellmer ◽  
Matthias von Mering ◽  
Annette Spreer ◽  
Ricarda Diem ◽  
Helmut Eiffert ◽  
...  
Keyword(s):  
Pneumococcal Meningitis ◽  
Neuronal Damage ◽  
Hippocampal Formation ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Clinical Score ◽  
Tight Rope ◽  
Induced Apoptosis ◽  
The Brain ◽  
Deficient Mice

ABSTRACT Necrotic and apoptotic neuronal cell death can be found in pneumococcal meningitis. We investigated the role of Bcl-2 as an antiapoptotic gene product in pneumococcal meningitis using Bcl-2 knockout (Bcl-2−/−) mice. By using a model of pneumococcal meningitis induced by intracerebral infection, Bcl-2-deficient mice and control littermates were assessed by clinical score and a tight rope test at 0, 12, 24, 32, and 36 h after infection. Then mice were sacrificed, the bacterial titers in blood, spleen, and cerebellar homogenates were determined, and the brain and spleen were evaluated histologically. The Bcl-2-deficient mice developed more severe clinical illness, and there were significant differences in the clinical score at 24, 32, and 36 h and in the tight rope test at 12 and 32 h. The bacterial titers in the blood were greater in Bcl-2-deficient mice than in the controls (7.46 ± 1.93 log CFU/ml versus 5.16 ± 0.96 log CFU/ml [mean ± standard deviation]; P < 0.01). Neuronal damage was most prominent in the hippocampal formation, but there were no significant differences between groups. In situ tailing revealed only a few apoptotic neurons in the brain. In the spleen, however, there were significantly more apoptotic leukocytes in Bcl-2-deficient mice than in controls (5,148 ± 3,406 leukocytes/mm2 versus 1,070 ± 395 leukocytes/mm2; P < 0.005). Bcl-2 appears to counteract sepsis-induced apoptosis of splenic lymphocytes, thereby enhancing clearance of bacteria from the blood.

Will caloric restriction and folate protect against AD and PD?

Neurology ◽  
2003 ◽  
Vol 60 (4) ◽  
pp. 690-695 ◽  
Author(s):  
Mark P. Mattson
Keyword(s):  
Folic Acid ◽  
Dietary Restriction ◽  
Neurodegenerative Disorders ◽  
Neurotrophic Factors ◽  
Animal Studies ◽  
Neuronal Damage ◽  
Epidemiologic Studies ◽  
Beneficial Effects ◽  
The Brain ◽  
High Calorie

Recent epidemiologic studies of different sample populations have suggested that the risk of AD and PD may be increased in individuals with high-calorie diets and in those with increased homocysteine levels. Dietary restriction and supplementation with folic acid can reduce neuronal damage and improve behavioral outcome in mouse models of AD and PD. Animal studies have shown that the beneficial effects of dietary restriction result, in part, from increased production of neurotrophic factors and cytoprotective protein chaperones in neurons. By keeping homocysteine levels low, folic acid can protect cerebral vessels and can prevent the accumulation of DNA damage in neurons caused by oxidative stress and facilitated by homocysteine. Although further studies are required in humans, the emerging data suggest that high-calorie diets and elevated homocysteine levels may render the brain vulnerable to neurodegenerative disorders.

scholarly journals Natural Molecules and Neuroprotection: Kynurenic Acid, Pantethine and α-Lipoic Acid

2021 ◽  
Vol 22 (1) ◽  
pp. 403
Author(s):  
Fanni Tóth ◽  
Edina Katalin Cseh ◽  
László Vécsei
Keyword(s):  
Neurodegenerative Diseases ◽  
Lipoic Acid ◽  
Kynurenic Acid ◽  
Biological Activities ◽  
Neuroprotective Effect ◽  
Structural Diversity ◽  
Kynurenine Pathway ◽  
Glutamate Excitotoxicity ◽  
Neuroprotective Agents ◽  
Starting Point

The incidence of neurodegenerative diseases has increased greatly worldwide due to the rise in life expectancy. In spite of notable development in the understanding of these disorders, there has been limited success in the development of neuroprotective agents that can slow the progression of the disease and prevent neuronal death. Some natural products and molecules are very promising neuroprotective agents because of their structural diversity and wide variety of biological activities. In addition to their neuroprotective effect, they are known for their antioxidant, anti-inflammatory and antiapoptotic effects and often serve as a starting point for drug discovery. In this review, the following natural molecules are discussed: firstly, kynurenic acid, the main neuroprotective agent formed via the kynurenine pathway of tryptophan metabolism, as it is known mainly for its role in glutamate excitotoxicity, secondly, the dietary supplement pantethine, that is many sided, well tolerated and safe, and the third molecule, α-lipoic acid is a universal antioxidant. As a conclusion, because of their beneficial properties, these molecules are potential candidates for neuroprotective therapies suitable in managing neurodegenerative diseases.

scholarly journals Langat virus encephalitis in mice II. The effect of irradiation

1968 ◽  
Vol 66 (3) ◽  
pp. 355-364 ◽  
Author(s):  
H. E. Webb ◽  
D. G. D. Wight ◽  
G. Wiernik ◽  
G. S. Platt ◽  
C. E. G. Smith
Keyword(s):  
Technical Assistance ◽  
Neuronal Damage ◽  
Preceding Paper ◽  
Virus Multiplication ◽  
Whole Body ◽  
Virus Concentration ◽  
Langat Virus ◽  
The Central Nervous System ◽  
Intraperitoneal Infection ◽  
Inflammatory Changes

Summary1. Irradiation in a whole body dose of 200 rads or more increased the sensitivity of mice to intraperitoneal infection with Langat virus so that the LD 50 was increased to about the intracerebral LD 50.2. In mice given 500 rads before infection: (a) viraemia was prolonged by about 5 days; (b) the IgM response was depressed; (c) the IgG response was delayed by about 3 days and depressed in titre; (d) virus concentration in the brain rose continuously until death on about the tenth day while in the controls it reached a peak on the fifth day then subsided; (e) histological changes in the CNS were delayed and minimal even at death; (f) irradiated mice died with little evidence of paralysis while the controls died with severe paralysis.3. In irradiated mice, protection was observed when antibody was administered on the third day following infection. Antibody given on the 3 days after infection to control mice aggravated the disease.4. The results in this and the preceding paper are discussed in relation to the pathogenesis of encephalitis. It is concluded that neuronal damage is caused both by virus multiplication in neurones and by damage superimposed by inflammatory changes with associated oedema and hypoxia. The inflammatory changes appear to be due to an allergic reaction to virus-antibody complexes formed in the circulation and in the central nervous system.We are grateful to Miss S. J. Illavia, B.Sc., and Miss G. E. Fairbairn for their skilled technical assistance; to the Department of Radiotherapy at St Thomas's Hospital for providing time and staff to help with the irradiation experiments; and to Mr S. Peto of the Microbiological Research Establishment for statistical advice.This work was made possible by a generous grant from the Wellcome Trust and the Endowment Funds of St Thomas's Hospital.

scholarly journals The Kynurenic Acid Analog SZR72 Enhances Neuronal Activity after Asphyxia but Is Not Neuroprotective in a Translational Model of Neonatal Hypoxic Ischemic Encephalopathy

2021 ◽  
Vol 22 (9) ◽  
pp. 4822
Author(s):  
Viktória Kovács ◽  
Gábor Remzső ◽  
Tímea Körmöczi ◽  
Róbert Berkecz ◽  
Valéria Tóth-Szűki ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Kynurenic Acid ◽  
Neuronal Damage ◽  
Brain Regions ◽  
Hypoxic Ischemic Encephalopathy ◽  
Hippocampal Field ◽  
Power Spectral ◽  
Density Values ◽  
Ischemic Encephalopathy

Hypoxic–ischemic encephalopathy (HIE) remains to be a major cause of long-term neurodevelopmental deficits in term neonates. Hypothermia offers partial neuroprotection warranting research for additional therapies. Kynurenic acid (KYNA), an endogenous product of tryptophan metabolism, was previously shown to be beneficial in rat HIE models. We sought to determine if the KYNA analog SZR72 would afford neuroprotection in piglets. After severe asphyxia (pHa = 6.83 ± 0.02, ΔBE = −17.6 ± 1.2 mmol/L, mean ± SEM), anesthetized piglets were assigned to vehicle-treated (VEH), SZR72-treated (SZR72), or hypothermia-treated (HT) groups (n = 6, 6, 6; Tcore = 38.5, 38.5, 33.5 °C, respectively). Compared to VEH, serum KYNA levels were elevated, recovery of EEG was faster, and EEG power spectral density values were higher at 24 h in the SZR72 group. However, instantaneous entropy indicating EEG signal complexity, depression of the visual evoked potential (VEP), and the significant neuronal damage observed in the neocortex, the putamen, and the CA1 hippocampal field were similar in these groups. In the caudate nucleus and the CA3 hippocampal field, neuronal damage was even more severe in the SZR72 group. The HT group showed the best preservation of EEG complexity, VEP, and neuronal integrity in all examined brain regions. In summary, SZR72 appears to enhance neuronal activity after asphyxia but does not ameliorate early neuronal damage in this HIE model.

scholarly journals Power Failure of Mitochondria and Oxidative Stress in Neurodegeneration and Its Computational Models

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 229
Author(s):  
JunHyuk Woo ◽  
Hyesun Cho ◽  
YunHee Seol ◽  
Soon Ho Kim ◽  
Chanhyeok Park ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Dysfunction ◽  
Computational Models ◽  
Neuronal Damage ◽  
Living Organism ◽  
The Body ◽  
Mitochondrial Functions ◽  
A Cell ◽  
The Brain ◽  
And Oxidative Stress

The brain needs more energy than other organs in the body. Mitochondria are the generator of vital power in the living organism. Not only do mitochondria sense signals from the outside of a cell, but they also orchestrate the cascade of subcellular events by supplying adenosine-5′-triphosphate (ATP), the biochemical energy. It is known that impaired mitochondrial function and oxidative stress contribute or lead to neuronal damage and degeneration of the brain. This mini-review focuses on addressing how mitochondrial dysfunction and oxidative stress are associated with the pathogenesis of neurodegenerative disorders including Alzheimer’s disease, amyotrophic lateral sclerosis, Huntington’s disease, and Parkinson’s disease. In addition, we discuss state-of-the-art computational models of mitochondrial functions in relation to oxidative stress and neurodegeneration. Together, a better understanding of brain disease-specific mitochondrial dysfunction and oxidative stress can pave the way to developing antioxidant therapeutic strategies to ameliorate neuronal activity and prevent neurodegeneration.

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