Chronic Treatment of Ascorbic Acid Leads to Age-Dependent Neuroprotection against Oxidative Injury in Hippocampal Slice Cultures

NXP031 restores memory function by dual effects degrading Aβ accumulation and facilitating antioxidant pathway in Alzheimer's disease models

Alzheimer's disease (AD) is a representative neurodegenerative disease that is characterized by the overaccumulation of amyloid beta (Aβ) proteins. Since AD is accompanied by excessive oxidative stress, which aggravates neurological pathologies, the use of antioxidants has been considered to prevent disease development. NXP031, a combination of vitamin C (VitC) and an optimized aptamer that binds to VitC and stabilizes the reactivity of VitC, was designed. This study aimed to evaluate the effects of NXP031 on AD pathology, including Aβ accumulation, Aβ-induced oxidative stress, neuronal damage, and neuroinflammation. When NXP031 was administered to 5xFAD transgenic mice, NXP031 exerted a strong inhibitory action on Aβ accumulation, superior to that of VitC, by inducing an increase in Aβ-degrading endopeptidase expression. NXP031 diminished lipid peroxidation levels, activated Nrf2-mediated antioxidant pathways, and suppressed overactivated neuroinflammation. An in vitro study using Neuro2a cells revealed that NXP031 protects the cells against oxidative stress by regulating the MAPK signaling pathway-mediated apoptosis. Additionally, the neuroprotective effects of NXP031 were confirmed in a dose-dependent manner when administered to intrahippocampal Aβ-injected mice, as NXP031 attenuated memory decline, neuronal apoptosis, synaptic degeneration, and excessive glial activation, and reduced NOX-2 expression in the hippocampus. Taken together, NXP031 reduced the Aβ burden by regulating Aβ-degeneration and attenuated memory impairment, neuronal death, synaptic degeneration, and neuroinflammation induced by Aβ toxicity. These results suggest the potential of NXP031 as a therapeutic agent for AD.

Effects of natural reduced water on cognitive functions in older adults: A RCT study

Oxidative stress and diabetes increase the risk of cognitive decline and dementia. Natural reduced water contains active hydrogen (hydrogen radicals), eliminates reactive oxygen species, and has antidiabetic effects. However, whether natural reduced water affects human cognitive function is unknown. Therefore, we implemented a double-blind intervention experiment in which participants consumed 1 L of natural reduced water or tap water daily for 6 months. The participants were healthy older adults living in Japan. The intervention group showed significant improvements in cognitive functions of attention function (p < 0.01) and short-term memory (p < 0.05). These results indicate that the continuous intake of natural reduced water improves several cognitive functions.

Role of Nanoparticle-Conjugates and Nanotheranostics in Abrogating Oxidative Stress and Ameliorating Neuroinflammation

Oxidative stress is a deteriorating condition that arises due to an imbalance between the reactive oxygen species and the antioxidant system or defense of the body. The key reasons for the development of such conditions are malfunctioning of various cell organelles, such as mitochondria, endoplasmic reticulum, and Golgi complex, as well as physical and mental disturbances. The nervous system has a relatively high utilization of oxygen, thus making it particularly vulnerable to oxidative stress, which eventually leads to neuronal atrophy and death. This advances the development of neuroinflammation and neurodegeneration-associated disorders such as Alzheimer's disease, Parkinson's disease, epilepsy, dementia, and other memory disorders. It is imperative to treat such conditions as early as possible before they worsen and progress to irreversible damage. Oxidative damage can be negated by two mechanisms: improving the cellular defense system or providing exogenous antioxidants. Natural antioxidants can normally handle such oxidative stress, but they have limited efficacy. The valuable features of nanoparticles and/or nanomaterials, in combination with antioxidant features, offer innovative nanotheranostic tools as potential therapeutic modalities. Hence, this review aims to represent novel therapeutic approaches like utilizing nanoparticles with antioxidant properties and nanotheranostics as delivery systems for potential therapeutic applications in various neuroinflammation- and neurodegeneration-associated disease conditions.

Construction of a Brain-specific SLC23A2 Gene Knockout Mice Model

Vitamin C (VC) is a key antioxidant of the Central Nervous System (CNS) and SLC23A2 (SVCT2) is the only transporter that actively transports VC into the brain. While the existing animal models of VC deficiency are in the whole body, the essential role of VC in brain development remains elusive. In our study presented here, the CRISPR/Cas9 technology was applied for the construction of a C57BL/6J-SLC23A2 em1(flox)Smoc mouse model, which was crossed with the Glial fibrillary acidic protein-driven Cre Recombinase (GFAP-Cre) genotype mice to generate a conditional knockout model of SLC23A2(SVCT2) gene in mice brain (GFAP-Cre;SLC23A2 flox/flox) after generations of crossbreeding. Our results showed that the expression of SVCT2 in GFAP-Cre;SLC23A2 flox/flox (Cre;svct2 f/f) mice brain was significantly decreased, and consistently, the expression of Neuronal nuclei antigen (NeuN), Glial fibrillary acidic protein (GFAP), calbindin-28k, brain-derived neurotrophic factor (BDNF) was down-regulated but Ionized calcium binding adapter molecule 1 (Iba-1) was up-regulated in Cre;svct2 f/f mice brain tissues. On the other hand, the levels of Glutathione, Reduced (GSH), myeloperoxidase (MDA), 8-isoprostane, tumor necrosis factor-α (TNF-α) and interleukin-6(IL-6) were significantly increased, but the levels of VC in brain tissue of the model group were decreased in Cre;svct2 f/f mice brain tissues, indicating the protective effect of VC against oxidative stress and inflammation during pregnancy. Thus, the conditional knockout of the SLC23A2 gene in the brain of mouse was successfully established by the CRISPR/Cas9 technology in our study, providing an effective animal model for studying the role of VC in fetal brain development.

Antioxidant Therapy in Oxidative Stress-Induced Neurodegenerative Diseases: Role of Nanoparticle-Based Drug Delivery Systems in Clinical Translation

Free radicals are formed as a part of normal metabolic activities but are neutralized by the endogenous antioxidants present in cells/tissue, thus maintaining the redox balance. This redox balance is disrupted in certain neuropathophysiological conditions, causing oxidative stress, which is implicated in several progressive neurodegenerative diseases. Following neuronal injury, secondary injury progression is also caused by excessive production of free radicals. Highly reactive free radicals, mainly the reactive oxygen species (ROS) and reactive nitrogen species (RNS), damage the cell membrane, proteins, and DNA, which triggers a self-propagating inflammatory cascade of degenerative events. Dysfunctional mitochondria under oxidative stress conditions are considered a key mediator in progressive neurodegeneration. Exogenous delivery of antioxidants holds promise to alleviate oxidative stress to regain the redox balance. In this regard, natural and synthetic antioxidants have been evaluated. Despite promising results in preclinical studies, clinical translation of antioxidants as a therapy to treat neurodegenerative diseases remains elusive. The issues could be their low bioavailability, instability, limited transport to the target tissue, and/or poor antioxidant capacity, requiring repeated and high dosing, which cannot be administered to humans because of dose-limiting toxicity. Our laboratory is investigating nanoparticle-mediated delivery of antioxidant enzymes to address some of the above issues. Apart from being endogenous, the main advantage of antioxidant enzymes is their catalytic mechanism of action; hence, they are significantly more effective at lower doses in detoxifying the deleterious effects of free radicals than nonenzymatic antioxidants. This review provides a comprehensive analysis of the potential of antioxidant therapy, challenges in their clinical translation, and the role nanoparticles/drug delivery systems could play in addressing these challenges.

Dietary total antioxidant capacity and mortality outcomes: the Singapore Chinese Health Study

PURPOSE

To evaluate the relations of dietary total antioxidant capacity (DTAC) with mortality outcomes in a Chinese population.

METHODS

The study included 62,063 participants from the Singapore Chinese Health Study. The participants were 45-74 years at baseline (1993-1998) when dietary data were collected with a validated 165-item food frequency questionnaire. The DTAC was derived using two widely adopted scores of integrated dietary consumption of antioxidant nutrients, i.e., the Comprehensive Dietary Antioxidant Index (CDAI) and Vitamin C Equivalent Antioxidant Capacity (VCEAC). We used Cox proportional hazard model to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations with adjustment for potential confounders.

RESULTS

During 1,212,318 person-years of follow-up, 23,397 deaths [cardiovascular diseases (CVD): 7523; respiratory diseases: 4696; and cancer: 7713] occurred. In multivariable models, the HR (95% CI) comparing participants in the highest vs. lowest quartile of CDAI was 0.85 (0.82, 0.88) for all-cause mortality, 0.82 (0.76, 0.88) for CVD mortality, 0.76 (0.70, 0.83) for respiratory disease mortality (all P-trend < 0.001), and 0.94 (0.88, 1.00) for cancer mortality (P-trend = 0.16). Similar associations were found with the VCEAC index. Higher intakes of the DTAC components, i.e., vitamin C, vitamin E, carotenoids, and flavonoids, were all associated with lower mortality risk.

CONCLUSION

Diet with a higher antioxidant capacity in midlife was associated with a lower risk of all-cause, cardiovascular and respiratory disease mortality in the Singapore Chinese population, supporting the public health recommendation of consuming more plant-based foods that are rich in antioxidant nutrients.

Crosstalk between Neuron and Glial Cells in Oxidative Injury and Neuroprotection

To counteract oxidative stress and associated brain diseases, antioxidant systems rescue neuronal cells from oxidative stress by neutralizing reactive oxygen species and preserving gene regulation. It is necessary to understand the communication and interactions between brain cells, including neurons, astrocytes and microglia, to understand oxidative stress and antioxidant mechanisms. Here, the role of glia in the protection of neurons against oxidative injury and glia–neuron crosstalk to maintain antioxidant defense mechanisms and brain protection are reviewed. The first part of this review focuses on the role of glia in the morphological and physiological changes required for brain homeostasis under oxidative stress and antioxidant defense mechanisms. The second part focuses on the essential crosstalk between neurons and glia for redox balance in the brain for protection against oxidative stress.

Oxidative Stress and Cognitive Decline: The Neuroprotective Role of Natural Antioxidants

Free- radicals (Oxygen and Nitrogen species) are formed in mitochondria during the oxidative phosphorylation. Their high reactivity, due to not-engaged electrons, leads to an increase of the oxidative stress. This condition affects above all the brain, that usually needs a large oxygen amount and in which there is the major possibility to accumulate "Reacting Species." Antioxidant molecules are fundamental in limiting free-radical damage, in particular in the central nervous system: the oxidative stress, in fact, seems to worsen the course of neurodegenerative diseases. The aim of this review is to sum up natural antioxidant molecules with the greatest neuroprotective properties against free radical genesis, understanding their relationship with the Central Nervous System.