Mechanisms of oxidative stress resistance in the brain: Lessons learned from hypoxia tolerant extremophilic vertebrates

The Untapped Potential of Comparative Biology in Aging Research: Insights From the Extraordinary-Long-Lived Naked Mole-Rat

The search for solutions to the vagaries of aging has, historically, been akin to searching at night in the bright light under street lamps by utilizing the few preexisting and well-established animal model systems. Throughout my career as a comparative biologist, I have ventured into the darkness across 4 continents and studied over 150 different animal species, many of which have evolved remarkable adaptations to survive on the harsh and rugged fitness landscape that exists outside of the laboratory setting. In this Fellows Forum, I will discuss the main focus of my research for the last 25 years and dig deeply into the biology of the preternaturally long-lived naked mole-rat that makes it an ideal model system for the characterization of successful strategies to combat aging.

Superoxide dismutase and neurological disorders

Superoxide dismutase (SOD) is a common antioxidant enzyme found majorly in living cells. The main physiological role of SOD is detoxification and maintain the redox balance, acts as a first line of defence against Reactive nitrogen species (RNS), Reactive oxygen species (ROS), and other such potentially hazardous molecules. SOD catalyses the conversion of superoxide anion free radicals (O 2 -.) into molecular oxygen (O 2) and hydrogen peroxide (H 2O 2) in the cells. Superoxide dismutases (SODs) are expressed in neurons and glial cells throughout the CNS both intracellularly and extracellularly. Endogenous oxidative stress (OS) linked with enlarged production of reactive oxygen metabolites (ROMs), inflammation, deregulation of redox balance, mitochondrial dysfunction and bioenergetic crisis are found to be prerequisite for neuronal loss in neurological diseases. Clinical and genetic studies indicate a direct correlation between mutations in SOD gene and neurodegenerative diseases, like Amyotrophic Lateral Sclerosis (ALS), Huntington's disease (HD), Parkinson's Disease (PD) and Alzheimer's Disease (AD). Therefore, inhibitors of OS are considered as an optimistic approach to prevent neuronal loss. SOD mimetics like Metalloporphyrin Mn (II)-cyclic polyamines, Nitroxides and Mn (III)- Salen complexes are designed and used as therapeutic extensively in the treatment of neurological disorders. SODs and SOD mimetics are promising future therapeutics in the field of various diseases with OS-mediated pathology.

CACNA1B protects naked mole-rat hippocampal neuron from apoptosis via altering the subcellular localization of Nrf2 after 60Co irradiation

Although radiotherapy is the most effective treatment modality for brain tumors, it always injures the central nervous system, leading to potential sequelae such as cognitive dysfunction. Radiation induces molecular, cellular, and functional changes in neuronal and glial cells. The hippocampus plays a critical role in learning and memory; therefore, concerns about radiation-induced injury are widespread. Multiple studies have focused on this complex problem, but the results have not been fully elucidated. Naked mole rat brains were irradiated with 60Co at a dose of 10 Gy. On 7 days, 14 days, and 28 days after irradiation, hippocampi in the control groups were obtained for next-generation sequencing. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were subsequently performed. Venn diagrams revealed 580 differentially expressed genes (DEGs) that were common at different times after irradiation. GO and KEGG analyses revealed that the 580 common DEGs were enriched in molecular transducer activity. In particular, CACNA1B mediated regulatory effects after irradiation. CACNA1B expression increased significantly after irradiation. Downregulation of CACNA1B led to a reduction in apoptosis and reactive oxygen species levels in hippocampal neurons. This was due to the interaction between CACNA1B and Nrf2, which disturbed the normal nuclear localization of Nrf2. In addition, CACNA1B downregulation led to a decrease in the cognitive functions of naked mole rats. These findings reveal the pivotal role of CACNA1B in regulating radiation-induced brain injury and will lead to the development of a novel strategy to prevent brain injury after irradiation.

The entrancing role of dietary polyphenols against the most frequent aging-associated diseases

Aging, a fundamental physiological process influenced by innumerable biological and genetic pathways, is an important driving factor for several aging-associated disorders like diabetes mellitus, osteoporosis, cancer, and neurodegenerative diseases including Alzheimer's and Parkinson's diseases. In the modern era, the several mechanisms associated with aging have been deeply studied. Treatment and therapeutics for age-related diseases have also made considerable advances; however, for the effective and long-lasting treatment, nutritional therapy particularly including dietary polyphenols from the natural origin are endorsed. These dietary polyphenols (e.g., apigenin, baicalin, curcumin, epigallocatechin gallate, kaempferol, quercetin, resveratrol, and theaflavin), and many other phytochemicals target certain molecular, genetic mechanisms. The most common pathways of age-associated diseases are mitogen-activated protein kinase, reactive oxygen species production, nuclear factor kappa light chain enhancer of activated B cells signaling pathways, metal chelation, c-Jun N-terminal kinase, and inflammation. Polyphenols slow down the course of aging and help in combatting age-linked disorders. This exemplified in the form of clinical trials on specific dietary polyphenols in various aging-associated diseases. With this context in mind, this review reveals the new insights to slow down the aging process, and consequently reduce some classic diseases associated with age such as aforementioned, and targeting age-associated diseases by the activities of dietary polyphenols of natural origin.

A narrative review of the effects of dexamethasone on traumatic brain injury in clinical and animal studies: focusing on inflammation

Traumatic brain injury (TBI) is a type of brain injury resulting from a sudden physical force to the head. TBI can range from mild, such as a concussion, to severe, which might result in long-term complications or even death. The initial impact or primary injury to the brain is followed by neuroinflammation, excitotoxicity, and oxidative stress, which are the hallmarks of the secondary injury phase, that can further damage the brain tissue. Dexamethasone (DXM) has neuroprotective effects. It reduces neuroinflammation, a critical factor in secondary injury-associated neuronal damage. DXM can also suppress the microglia activation and infiltrated macrophages, which are responsible for producing pro-inflammatory cytokines that contribute to neuroinflammation. Considering the outcomes of this research, some of the effects of DXM on TBI include: (1) DXM-loaded hydrogels reduce apoptosis, neuroinflammation, and lesion volume and improves neuronal cell survival and motor performance, (2) DXM treatment elevates the levels of Ndufs2, Gria3, MAOB, and Ndufv2 in the hippocampus following TBI, (3) DXM decreases the quantity of circulating endothelial progenitor cells, (4) DXM reduces the expression of IL1, (5) DXM suppresses the infiltration of RhoA + cells into primary lesions of TBI and (6) DXM treatment led to an increase in fractional anisotropy values and a decrease in apparent diffusion coefficient values, indicating improved white matter integrity. According to the study, the findings show that DXM treatment has neuroprotective effects in TBI. This indicates that DXM is a promising therapeutic approach to treating TBI.

Role of Oxidative Stress in Metabolic Reprogramming of Brain Cancer

Brain cancer is known as one of the deadliest cancers globally. One of the causative factors is the imbalance between oxidative and antioxidant activities in the body, which is referred to as oxidative stress (OS). As part of regular metabolism, oxygen is reduced by electrons, resulting in the creation of numerous reactive oxygen species (ROS). Inflammation is intricately associated with the generation of OS, leading to the increased production and accumulation of reactive oxygen and nitrogen species (RONS). Glioma stands out as one of the most common malignant tumors affecting the central nervous system (CNS), characterized by changes in the redox balance. Brain cancer cells exhibit inherent resistance to most conventional treatments, primarily due to the distinctive tumor microenvironment. Oxidative stress (OS) plays a crucial role in the development of various brain-related malignancies, such as glioblastoma multiforme (GBM) and medulloblastoma, where OS significantly disrupts the normal homeostasis of the brain. In this review, we provide in-depth descriptions of prospective targets and therapeutics, along with an assessment of OS and its impact on brain cancer metabolism. We also discuss targeted therapies.

Molecular mechanisms underlying cyclophosphamide-induced cognitive impairment and strategies for neuroprotection in preclinical models

Cyclophosphamide has drastically enhanced the expectancy and quality of life of cancer patients. However, it is accompanied by diverse neurological complications which are considered a dose-limiting adverse effect. Neurotoxicity caused by cyclophosphamide can manifest in numerous manners including anxiety, depression, motor dysfunction and cognitive deficits. This review article offers an overview on cyclophosphamide-induced neurotoxicity, providing a unified point of view on the possible underlying molecular mechanisms including oxidative brain damage, neuroinflammation, apoptotic neuronal cell death as well as disruption of the balance of brain neurotransmitters and neurotrophic factors. Besides, this review sheds light on the promising protective agents that have been investigated using preclinical animal models as well as their biological targets and protection mechanisms. Despite promising results in experimental models, none of these agents has been studied in clinical trials. Thus, there is lack of evidence to advocate the use of any neuroprotective agent in the clinical setting. Furthermore, none of the protective agents has been evaluated for its effect on the anticancer activity of cyclophosphamide in tumor-bearing animals. Therefore, there is a great necessity for adequate well-designed clinical studies for evaluation of the therapeutic values of these candidates. Conclusively, this review summarizes the molecular mechanisms accounting for cyclophosphamide-induced neurotoxicity together with the potential protective strategies seeking for downgrading this neurological complication, thus enhancing the quality of life and well-being of cancer patients treated with cyclophosphamide.

Oxidative Stress and Antioxidant Defense in the Brain of Bat Species with Different Feeding Habits

Assessing the levels of oxidative stress markers and antioxidant enzymes in the brain is crucial in evaluating its antioxidant capacity and understanding the influence of various dietary patterns on brain well-being. This study aimed to investigate the antioxidant status and oxidative damage in the brain of bat species with different feeding habits to gain insights into their protective mechanisms against oxidative stress and their interspecific variation. The levels of oxidative damage markers and the activities of antioxidants were measured in the brain of four bat species with different feeding habits, namely insectivorous, frugivorous, nectarivorous, and hematophagous. Insectivorous bats showed higher levels of SOD and fumarase compared to the other groups, while hematophagous bats showed lower levels of these enzymes. On the other hand, the activities of glutathione peroxidase and glutathione S-transferase were higher in hematophagous bats and lower in insectivorous bats. The carbonyl groups and malondialdehyde levels were lower in frugivores, while they were similar in the other feeding guilds. Nitrite and nitrate levels were higher in the hematophagous group and relatively lower in all other groups. The GSSG/GSH ratio was higher in the hematophagous group and lower in frugivores. Overall, our results indicate that the levels of oxidative stress markers and the activities of antioxidant enzymes in the brain vary significantly among bat species with different feeding habitats. The findings suggest that the antioxidant status of the brain is influenced by diet and feeding habits.

Sericin improves memory and sociability impairments evoked by transient global cerebral ischemia through suppression of hippocampal oxidative stress, inflammation, and apoptosis

Sericin (Ser) is a natural neuroactive macromolecule with diverse pharmacological properties, and our previous findings have shown its neuroprotective potentials. This study aimed to investigate the therapeutic potential of Ser on cognitive dysfunction induced by transient global cerebral ischemia/reperfusion (tGI/R) and its mechanism of action. The tGI/R was induced in BALB/c mice by bilateral occlusion of the common carotid arteries for two 5 min followed by a 10-min reperfusion period. After 24 h, mice were treated with normal saline or different doses of Ser (100, 200, and 300 mg/kg) for 10 days. Cognitive performances were assessed using the Barnes maze and social interaction tasks. Oxidative stress markers including superoxide dismutase (SOD), glutathione peroxidase (GPx), total antioxidant capacity (TAC), and malondialdehyde (MDA) as well as pro-inflammatory cytokines (interleukin (IL)-6 and tumor necrosis factor-alpha) and anti-inflammatory cytokine (IL-10) were assessed in the hippocampus. Markers of apoptosis (pro- and cleaved caspase-9 and 3, Bax, and Bcl-2) were assessed by Western blotting. Besides, transferase-mediated dUTP nick end-labeling assay was used to detect apoptotic cell death. We show here that Ser administration improved tGI/R-induced cognitive deficits, enhanced the activity of SOD and GPx, increased TAC levels, while reduced MDA levels. Notably, Ser decreased neuronal apoptotic cell death in the hippocampal dentate gyrus (DG) region, accompanied by suppression of neuroinflammation, downregulation of pro-apoptotic proteins (caspase-9, caspases-3, and Bax), and upregulation of anti-apoptotic protein, Bcl-2. Taken together, Ser administration protected hippocampal neurons from apoptotic cell death by impeding oxidative stress and inflammatory responses and, in turn, improved cognitive function in the tGI/R mice.

Mechanisms of Mitochondrial Oxidative Stress in Brain Injury: From Pathophysiology to Therapeutics

Mitochondrial oxidative stress has been implicated in various forms of brain injury, both traumatic and non-traumatic. Due to its oxidative demand, the brain is intimately dependent on its mitochondrial functioning. However, there remains appreciable heterogeneity in the development of these injuries regarding ROS and their effect on the sequelae. These include traumatic insults such as TBIs and intracranial hemorrhaging secondary to this. In a different vein, such injuries may be attributed to other etiologies such as infection, neoplasm, or spontaneous hemorrhage (strokes, aneurysms). Clinically, the manner of treatment may also be adjusted in relation to each injury and its unique progression in the context of ROS. In the current review, then, the authors highlight the role of mitochondrial ROS in various forms of brain injury, emphasizing both the collective and unique elements of each form. Lastly, these narratives are met with the current therapeutic landscape and the role of emerging therapies in treating reactive oxygen species in brain injuries.

The Protective Effects of Policosanol on Learning and Memory Impairments in a Male Rat Model of Alzheimer's Disease

Alzheimer's disease (AD), the most common form of dementia, is characterized by a progressive decline in cognitive performance and memory formation. The present study was designed to investigate the effect of policosanol (PCO) on cognitive function, oxidative-antioxidative status, and amyloid-beta (Aβ) plaque formation in an AD rat model induced by intracerebroventricular (ICV) injection of Aβ_1-40. Healthy adult male Wistar rats were randomly divided into seven groups: control, sham (5 μL, ICV injection of phosphate-buffered saline), AD model (5 μL, ICV injection of Aβ), acacia gum (50 mg/kg, 8 weeks, gavage), PCO (50 mg/kg, 8 weeks, gavage), AD + acacia gum (50 mg/kg, 8 weeks, gavage), and AD + PCO (50 mg/kg, 8 weeks, gavage). During the ninth and tenth weeks of the study, the cognitive function of the rats was assessed by commonly used behavioral paradigms. Subsequently, oxidative-antioxidative status was examined in the serum. Moreover, compact Aβ plaques were detected by Congo red staining. The results showed that injection of Aβ impaired recognition memory in the novel object recognition test, reduced the spatial cognitive ability in the Morris water maze, and alleviated retention and recall capability in the passive avoidance task. Additionally, injection of Aβ resulted in increased total oxidant status, decreased total antioxidant capacity, and enhanced Aβ plaque formation in the rats. Intriguingly, PCO treatment improved all the above-mentioned neuropathological changes in the Aβ-induced AD rats. The results suggest that PCO improves Aβ-induced cognitive decline, possibly through modulation of oxidative-antioxidative status and inhibition of Aβ plaque formation.

Fipronil impairs the GABAergic brain responses of Nile Tilapia during the transition from normoxia to acute hypoxia

γ-aminobutyric acid (GABA) is one of the main neurotransmitters involved in the adaptation processes against the damage that hypoxia can cause to the brain. Due to its antagonist action on GABA receptors, the insecticide fipronil can turn the fish more susceptible to the negative effects of hypoxia. This study aimed to understand better if fipronil affects these GABAergic responses of Tilapia ahead to hypoxia. Oreochromis Niloticus (Nile Tilapia) were exposed for 3 and 8 h to fipronil (0.0, 0.1, and 0.5 µg.L^-1 ) under normoxia (dissolved O₂  > 6 mg.L^-1 ) and moderate hypoxia (dissolved O₂  < 2 mg.L^-1 ) conditions. Briefly, hypoxia caused opposite effects on the gene transcription of the evaluated ionotropic and metabotropic GABA receptors. Unexpectedly, we obtained reduced HIF1A mRNA and brain GABA levels, mostly in the first 3 h of the experiment, for the hypoxic group compared with the normoxia one. Besides that, we also demonstrated that the insecticide fipronil impairs the brain GABAergic signaling of a hypoxia-tolerant fish during the transition from a normoxic to an acute hypoxic state. Thus, these results predict the relevant impact on the brain metabolic adaptations of fishes exposed to such stressful conditions in an aquatic environment, as well as the effects of fipronil in the GABAergic responses to hypoxia, which in turn may have ecological and physiological significance to hypoxia-tolerant fishes exposed to this insecticide.

Therapeutic effects of growth hormone in a rat model of total sleep deprivation: Evaluating behavioral, hormonal, biochemical and electrophysiological parameters

OBJECTIVE

Total sleep deprivation (TSD) causes several harmful changes in the brain, including memory impairment, increased stress and depression levels, as well as reduced antioxidant activity. Growth hormone (GH) has been shown to boost antioxidant levels while improving memory and depression. The present study was conducted to explain the possible effects of exogenous GH against behavioral and biochemical disorders caused by TSD and the possible mechanisms involved.

MAIN METHODS

To induce TSD, rats were housed in homemade special cages equipped with stainless steel wire conductors to induce general and inconsistent TSD. They received a mild repetitive electric shock to their paws every 10 min for 21 days. GH (1 ml/kg, sc) was administered to rats during induction of TSD for 21 days. Memory retrieval, anxiety, depression-like behaviors, pain behaviors, antioxidant activity, hippocampal level of BDNF, and simultaneously brain electrical activity were measured at scheduled times after TSD.

KEY FINDINGS

The results showed that GH treatment improved memory (p < 0.001) in the PAT test of rats exposed to TSD. These beneficial effects were associated with lowering the level of anxiety and depression-like behavior (p < 0.001), rising the pain threshold (p < 0.01), increasing the activity of antioxidants (p < 0.01), hippocampal BDNF (p < 0.001), and regular brain electrical activity.

SIGNIFICANCE

Our findings show that GH plays a key role in modulating memory, anxiety and depression behaviors, as well as reducing oxidative stress and improve hippocampal single-unit activity in the brain during TSD.

Active Nrf2 signaling flexibly regulates HO-1 and NQO-1 in hypoxic Gansu Zokor (Eospalax cansus)

Gansu zokor (Eospalax cansus) is a typical subterranean rodent species with resistance to ambient hypoxia. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling plays a key role in regulating redox homeostasis. However, little is known about the regulation of Nrf2 signaling in Gansu zokor. We exposed Gansu zokors and SD rats to chronic hypoxia (44 h at 10.5% O₂) or acute hypoxia (6 h at 6.5% O₂) andmeasured the activities of heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 (NQO-1)，gene expression of HO-1, NQO-1, Nrf2, Kelch-like ECH-associated protein-1 (KEAP1), and β-transducin repeat-containing protein (β-TRCP) in the brain and liver. We found that Gansu zokor increased the NQO-1 protein content and activity, HO-1 protein content in the brain, and increased HO-1 activity and mRNA level, NQO-1 activity and protein content in the liver by up regulating Nrf2 gene expression under chronic hypoxia. Although acute hypoxia enhanced the expression of Nrf2 gene, only the level of HO-1 mRNA in the liver increased. Besides, the HO-1 and NQO-1 genes in the brain, HO-1 genes and NQO-1 mRNA in the Gansu zokor liver were significantly higher than those in SD rats under normoxia. Negative regulators of Nrf2 signaling were tissue specific: KEAP1 protein decreased in the brain, and β-TRCP decreased in the liver. The Nrf2 signaling and expression of downstream antioxidant enzymes were different under different oxygen concentrations, reflecting the flexible characteristics of Gansu zokor to deal with the hypoxic environment.

Mitochondrial DNA Repair in Neurodegenerative Diseases and Ageing

Mitochondria are the only organelles, along with the nucleus, that have their own DNA. Mitochondrial DNA (mtDNA) is a double-stranded circular molecule of ~16.5 kbp that can exist in multiple copies within the organelle. Both strands are translated and encode for 22 tRNAs, 2 rRNAs, and 13 proteins. mtDNA molecules are anchored to the inner mitochondrial membrane and, in association with proteins, form a structure called nucleoid, which exerts a structural and protective function. Indeed, mitochondria have evolved mechanisms necessary to protect their DNA from chemical and physical lesions such as DNA repair pathways similar to those present in the nucleus. However, there are mitochondria-specific mechanisms such as rapid mtDNA turnover, fission, fusion, and mitophagy. Nevertheless, mtDNA mutations may be abundant in somatic tissue due mainly to the proximity of the mtDNA to the oxidative phosphorylation (OXPHOS) system and, consequently, to the reactive oxygen species (ROS) formed during ATP production. In this review, we summarise the most common types of mtDNA lesions and mitochondria repair mechanisms. The second part of the review focuses on the physiological role of mtDNA damage in ageing and the effect of mtDNA mutations in neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. Considering the central role of mitochondria in maintaining cellular homeostasis, the analysis of mitochondrial function is a central point for developing personalised medicine.

Antioxidant and non-specific immune defenses in partially freeze-tolerant Xizang plateau frogs, Nanorana parkeri

The Xizang plateau frog Nanorana parkeri can tolerate brief and partial freezing of their body. To determine the significant role of antioxidant defense and non-specific immune defense in freezing survival of this species, we assayed parameters of oxidative damage, antioxidant defense and non-specific immune enzymes during freezing exposure (-2 °C for 12 h) in five organs (heart, brain, liver, kidney, and skeletal muscle). The results showed that freezing led to a significant rise in the content of malondialdehyde (MDA) and carbonyl groups (CG) in brain, liver and kidney tissues. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) increased significantly in brain and liver tissues with an augmentation of total antioxidant capacity (T-AOC). Apparent increments in muscle SOD activity and liver GST activity were also observed during freezing exposure. Vitamin C content significantly decreased in liver and kidney but a significant increase occurred in brain. Activities of non-specific immune enzymes, acid phosphatase (ACP) and alkaline phosphatase (AKP), were also assessed. ACP activity was significantly reduced in all five tissues tested whereas AKP activity decreased significantly in four tissues but rose in brain. In summary, freezing is accompanied by oxidative stress in the high-altitude frog, N. parkeri, as documented by increases in the content of MDA and CG in tissues. Freezing exposure also induced tissue-specific changes in the antioxidant defenses showing that activation of antioxidant systems is a part of the survival strategy of this in a high-altitude frog during freezing. Such up-regulation of antioxidant enzymes suggests a particularly important role for them in the liver and brain, serving as an anticipatory mechanism to deal with the ROS challenge during freeze/thaw episodes. Our findings contribute to extending the current understanding of the mechanisms of freeze tolerance in high-altitude frogs.

Fucoidan Modulated Oxidative Stress and Caspase-3 mRNA Expression Induced by Sulfoxaflor in the Brain of Mice

The current study aimed to investigate the role of fucoidan in the oxidative and apoptotic effects of sulfoxaflor, a neonicotinoid sulfoximine insecticide, in the brain of Swiss albino mice (Mus musculus). Sulfoxaflor and fucoidan were administered to mice at doses of 15 mg/kg/day (1/50 oral LD50) and 50 mg/kg/day, respectively, by oral gavage for 24 h or 7 days. The tGSH, TBARS and protein levels, and GPx, GR, and GST enzyme activities were determined by spectrophotometric methods. Caspase-3 gene expression level was determined by RT-PCR. Data analysis showed that brains of sulfoxaflor-treated mice exhibited higher TBARS levels; GPx, GR, and GST enzyme activities; and caspase-3 expression levels, as well as lower levels of tGSH. Co-administration of fucoidan and sulfoxaflor reduced the TBARS levels, increased tGSH levels, and increased GPx, GR, and GST enzyme activities. Fucoidan also decreased the sulfoxaflor-induced up-regulation of caspase-3 mRNA expression. Results of the present study showed that sulfoxaflor caused oxidative stress by inducing lipid peroxidation and altering GSH-dependent antioxidants in the brain of mice. In addition, sulfoxaflor may trigger apoptotic cell death shown by the up-regulation of caspase-3. Fucoidan treatment modulated all the aforementioned alterations in the brain of mice. It was concluded that fucoidan might have antioxidant effects that support the GSH-dependent antioxidant system and can play a modulator role in oxidative stress and caspase-3 expression in the brain of sulfoxaflor treated-mice.

Hypoxia Tolerant Species: The Wisdom of Nature Translated into Targets for Stroke Therapy

Human neurons rapidly die after ischemia and current therapies for stroke management are limited to restoration of blood flow to prevent further brain damage. Thrombolytics and mechanical thrombectomy are the available reperfusion treatments, but most of the patients remain untreated. Neuroprotective therapies focused on treating the pathogenic cascade of the disease have widely failed. However, many animal species demonstrate that neurons can survive the lack of oxygen for extended periods of time. Here, we reviewed the physiological and molecular pathways inherent to tolerant species that have been described to contribute to hypoxia tolerance. Among them, Foxo3 and Eif5A were reported to mediate anoxic survival in Drosophila and Caenorhabditis elegans, respectively, and those results were confirmed in experimental models of stroke. In humans however, the multiple mechanisms involved in brain cell death after a stroke causes translation difficulties to arise making necessary a timely and coordinated control of the pathological changes. We propose here that, if we were able to plagiarize such natural hypoxia tolerance through drugs combined in a pharmacological cocktail it would open new therapeutic opportunities for stroke and likely, for other hypoxic conditions.

Subacute silica nanoparticle exposure induced oxidative stress and inflammation in rat hippocampus combined with disruption of cholinergic system and behavioral functions

Increasing environmental exposure to silica nanoparticles (SiNPs) and limited neurotoxicity studies pose a challenge for safety evaluation and management of these materials. This study aimed to explore the adverse effects and underlying mechanisms of subacute exposure to SiNPs by the intraperitoneal route on hippocampus function in rats. Data showed that SiNPs induced a significant increase in oxidative/nitrosative stress markers including reactive oxygen species (ROS), malondialdehyde (MDA), protein oxidation (PCO) and nitrite (NO) production accompanied by reduced antioxidant enzyme activity (catalase, superoxide dismutase, and glutathione peroxidase) and decreased glutathione (GSH). Phenotypically, SiNPs exhibited spatial learning and memory impairment in the Morris water maze (MWM) test, a decrease of the discrimination index in the novel object recognition test (NORT) and higher anxiety-like behavior. SiNPs affected the cholinergic system as reflected by reduced acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity. In addition, SiNPs significantly increased mRNA expression level of genes related to inflammation (TNF-α, IL-1β, IL-6, and COX-2) and decreased mRNA expression level of genes related to cholinergic system including choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT), AChE, muscarinic acetylcholine receptor M1 (m1AChR) and nicotinic acetylcholine receptors (nAChR). Histopathological results further showed an alteration in the hippocampus of treated animals associated with marked vacuolation in different hippocampus areas. These findings provide new insights into the molecular mechanism of SiNPs-induced hippocampal alterations leading to impairment of cognitive and behavioral functions, and implicating oxidative stress and inflammation in the hippocampus, as well as disruption of cholinergic system.

The effect of long-term cold acclimation on redox state and antioxidant defense in the high-altitude frog, Nanorana pleskei

Cold hardiness is a key determinant of the distribution and abundance of ectothermic animals, and thermal acclimation can strongly influence stress tolerance phenotypes. However, the effect of cold acclimation on oxidative stress and antioxidant defenses is still not well understood. Here, we investigated the effects of long-term cold exposure (30 days at 4 °C in darkness versus 30 days at 20 °C in natural light) on the redox state and antioxidant defenses of the high-altitude frog, Nanorana pleskei, indigenous to the Tibetan plateau. We found that cold acclimation, under conditions mimicking winter, led to a significant increase in the ratio of oxidized glutathione (GSSG) to its reduced form (GSH) in liver and skeletal muscle tissues, suggesting that cold exposure induced oxidative stress in this species. Furthermore, malondialdehyde (MDA) contents were significantly augmented in heart, liver and muscle, indicating cold-related oxidative damage in these tissues. In the brain, GST activity, total antioxidant capacity (T-AOC), and vitamin C content showed a significant reduction after cold acclimation. In liver, an apparent decrease was also observed in the activities of SOD and GST, as well as T-AOC, whereas CAT and GPX activities showed a prominent increase in cold-acclimated groups. In kidney, there was a significant decrease in most antioxidant enzyme activities except for SOD and GST activity. In skeletal muscle, the activity of SOD, CAT, GR as well as T-AOC significantly decreased but GPX activity showed a significant increase in cold-acclimated frogs. These findings indicate that, in general, cold acclimation induces a suppression of the antioxidant defense system. Overall, our present study systematically describes the responses of antioxidant defenses to long-term cold acclimation and these findings contribute to extending the current understanding of the mechanisms of cold tolerance in high-altitude frogs.

Protective effects of vitamin D on neurophysiologic alterations in brain aging: role of brain-derived neurotrophic factor (BDNF)

Background/aim: Vitamin D has been hypothesized to be main regulator of the aging rate, alongside evidences support its role in neuroprotection. However, data about the protective role of vitamin D against neurophysiologic alterations associated with brain aging is limited. This study investigated the possible protective effects that vitamin D has on brain-derived neurotrophic factor (BDNF), cholinergic function, oxidative stress and apoptosis in aging rat brain.Methods: Male Wister albino rats aged 5 months (young), 12 months (middle aged) and 24 months (old) (n = 20 each) were used. Each age group subdivided to either vitamin D3 supplementation (500 IU/kg/day orally for 5 weeks) or no supplementation (control) group (n = 10 each). Serum 25-hydroxyvitamin D [25(OH)D], brain BDNF and malondialdehyde levels and activities of acetylcholinesterase (AChE), antioxidant enzymes (glutathione reductase, glutathione peroxidase and superoxide dismutase) and caspase-3 were quantified.Results: Vitamin D supplementation significantly mitigated the observed aging-related reduction in brain BDNF level and activities of AChE and antioxidant enzymes and elevation in malondialdehyde level and caspase-3 activity compared to control groups. Brain BDNF level correlated positively with serum 25(OH) D level and brain AChE activity and negatively with brain malondialdehyde level and caspase-3 activity in supplemented groups.Conclusion: Restoring vitamin D levels may, therefore, represent a useful strategy for healthy brain aging. Augmenting brain BDNF seems to be a key mechanism through which vitamin D counteracts age-related brain dysfunction.

High fat diet and its effects on cognitive health: alterations of neuronal and vascular components of brain

It has been well recognized that intake of diets rich in saturated fats could result in development of metabolic disorders such as type 2 diabetes mellitus, obesity and cardiovascular diseases. Recent studies have suggested that intake of high fat diet (HFD) is also associated with cognitive dysfunction. Various preclinical studies have demonstrated the impact of short and long term HFD feeding on the biochemical and behavioural alterations. This review summarizes studies and the protocols used to assess the impacts of HFD feeding on cognitive performance in rodents. Further, it discuss the key mechanisms that are altered by HFD feeding, such as, insulin resistance, oxidative stress, neuro-inflammation, transcriptional dysregulation and loss of synaptic plasticity. Along with these, HFD feeding also alters the vascular components of brain such as loss of BBB integrity and reduced cerebral blood flow. It is highly possible that these factors are responsible for the development of cognitive deficits as a result of HFD feeding.

AC/DC magnetic device for safe medical use of potentially harmful magnetic nanocarriers

Continuing our previous research work on a drug delivery system based on combined AC/DC magnetic fields, we have developed a prototype AC/DC magnetic syringe device for stimulation of drug release from drug carriers, with the options of injecting/removing drug carriers. The porous Fe₃O₄ carrier, in a dose-dependent manner, causes acute oxidative damage and reduces the viability of differentiated SH-SY5Y human neuroblastoma cells, indicating the necessity for its removal once it reaches the therapeutic concentration at the target tissue. The working mechanism of the device consists of three simple steps. First, direct injection of the drug adsorbed on the surface of a carrier via a needle inserted into the targeted area. The second step is stimulation of drug release using a combination of AC magnetic field (a coil magnetised needle with AC current) and permanent magnets (DC magnetic lens outside of the body), and the third step is removal of the drug carriers from the injected area after the completion of drug release by magnetising the tip of the needle with DC current. Removing the drug carriers allows us to avoid possible acute and long term side effects of the drug carriers in the patient's body, as well as any potential response of the body to the drug carriers.

Histopathological study on neuroapoptotic alterations induced by etomidate in rat hippocampus

In human, there is substantial neurogenesis in the hippocampus that is implicated in memory formation and learning. These new-born neurons can be affected by neuropathological conditions. Anesthesia and surgical procedures are associated with postoperative cognitive changes particularly, impaired memory and learning. Therefore, the aim of this study was to evaluate the possible neurodegenerative effects of etomidate in rat hippocampus. Thirty male Wistar rats weighing 250 ± 30 g were randomly divided into 3 groups: 1) Etomidate group; four times 20 mg intraperitoneal injection with 1-h intervals, 2) Control group; the equal volume of normal saline, and 3) Normal group; without any intervention. 6 h after the last injection, the brains were removed and processed according to routine histological methods. TUNEL assay and toluidine blue staining were performed to evaluate neuro-histopathological changes in different regions of hippocampus. Our results showed that the number of TUNEL positive cells and dark neurons (DNs) in etomidate group were significantly higher in the CA1, CA2, CA3, and dentate gyrus (DG) of hippocampus compared with the control and normal groups (p < 0.05). While, there was no significant difference between the various regions of hippocampus in control and normal groups. Our findings showed that etomidate can increase apoptotic cells and dark neurons induction in different regions of hippocampus mainly in DG.

Molecular mechanisms in Alzheimer's disease and the impact of physical exercise with advancements in therapeutic approaches

Alzheimer's disease (AD) is one of the most common, severe neurodegenerative brain disorder characterized by the accumulation of amyloid-beta plaques, neurofibrillary tangles in the brain causing neural disintegration, synaptic dysfunction, and neuronal death leading to dementia. Although many US-FDA-approved drugs like Donepezil, Rivastigmine, Galantamine are available in the market, their consumption reduces only the symptoms of the disease but fails in potency to cure the disease. This disease affects many individuals with aging. Combating the disease tends to be very expensive. This review focuses on biochemical mechanisms in the neuron both at normal and AD state with relevance to the tau hypothesis, amyloid hypothesis, the risk factors influencing dementia, oxidative stress, and neuroinflammation altogether integrated with neurodegeneration. A brief survey is carried out on available biomarkers in the diagnosis of the disease, drugs used for the treatment, and the challenges in approaching therapeutic targets in inhibiting the disease pathologies. This review conjointly assesses the demerits with the inefficiency of drugs to reach targets, their side effects, and toxicity. Optimistically, this review directs on the advantageous strategies in using nanotechnology-based drug delivery systems to cross the blood-brain barrier for improving the efficacy of drugs combined with a novel neuronal stem cell therapy approach. Determinately, this review aims at the natural, non-therapeutic healing impact of physical exercise on different model organisms and the effect of safe neuromodulation treatments using repetitive Transcranial Magnetic Stimulation (rTMS), transcranial Electrical Stimulation (tES) in humans to control the disease pathologies prominent in enhancing the synaptic function.

Plant Polyphenols as Neuroprotective Agents in Parkinson's Disease Targeting Oxidative Stress

Parkinson's disease (PD) is the second most prevalent progressive neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the human midbrain. Various ongoing research studies are competing to understand the pathology of PD and elucidate the mechanisms underlying neurodegeneration. Current pharmacological treatments primarily focused on improving dopamine metabolism in PD patients, despite the side effects of long-term usage. In recent years, it is recognized that oxidative stress-mediated pathways lead to neurodegeneration in the brain, which is associated with the pathophysiology of PD. The importance of oxidative stress is often less emphasized when developing potential therapeutic approaches. Natural plant antioxidants have been shown to mediate the oxidative stress-induced effects in PD, which has gained considerable attention in both in vitro and in vivo studies. Yet, clinical trials on natural polyphenol compounds are limited, restricting the potential use of these compounds as an alternative treatment for PD. Therefore, this review provides an understanding of the oxidative stress-induced effects in PD by elucidating the underlying events contributing to oxidative stress and explore the potential use of polyphenols in improving the oxidative status in PD. Preclinical findings have supported the potential of polyphenols in providing neuroprotection against oxidative stress-induced toxicity in PD. However, limiting factors, such as safety and bioavailability of polyphenols, warrant further investigations so as to make them the potential target for clinical applications in the treatment and management of PD.

Traumatic brain injury-induced cerebral microbleeds in the elderly

Traumatic brain injury (TBI) was shown to lead to the development of cerebral microbleeds (CMBs), which are associated with long term cognitive decline and gait disturbances in patients. The elderly is one of the most vulnerable parts of the population to suffer TBI. Importantly, ageing is known to exacerbate microvascular fragility and to promote the formation of CMBs. In this overview, the effect of ageing is discussed on the development and characteristics of TBI-related CMBs, with special emphasis on CMBs associated with mild TBI. Four cases of TBI-related CMBs are described to illustrate the concept that ageing exacerbates the deleterious microvascular effects of TBI and that similar brain trauma may induce more CMBs in old patients than in young ones. Recommendations are made for future prospective studies to establish the mechanistic effects of ageing on the formation of CMBs after TBI, and to determine long-term consequences of CMBs on clinically relevant outcome measures including cognitive performance, gait and balance function.

Norwogonin attenuates hypoxia-induced oxidative stress and apoptosis in PC12 cells

Background

Norwogonin is a natural flavone with three phenolic hydroxyl groups in skeletal structure and has excellent antioxidant activity. However, the neuroprotective effect of norwogonin remains unclear. Here, we investigated the protective capacity of norwogonin against oxidative damage elicited by hypoxia in PC12 cells.

Methods

The cell viability and apoptosis were examined by MTT assay and Annexin V-FITC/PI staining, respectively. Reactive oxygen species (ROS) content was measured using DCFH-DA assay. Lactate dehydrogenase (LDH), malondialdehyde (MDA) and antioxidant enzyme levels were determined using commercial kits. The expression of related genes and proteins was measured by real-time quantitative PCR and Western blotting, respectively.

Results

We found that norwogonin alleviated hypoxia-induced injury in PC12 cells by increasing the cell viability, reducing LDH release, and ameliorating the changes of cell morphology. Norwogonin also acted as an antioxidant by scavenging ROS, reducing MDA production, maintaining the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and decreasing the expression levels of HIF-1α and VEGF. In addition, norwogonin prevented cell apoptosis via inhibiting the expression levels of caspase-3, cytochrome c and Bax, while increasing the expression levels of Bcl-2 and the ratio of Bcl-2/Bax.

Conclusions

Norwogonin attenuates hypoxia-induced injury in PC12 cells by quenching ROS, maintaining the activities of antioxidant enzymes, and inhibiting mitochondrial apoptosis pathway.

Mitohormesis; Potential implications in neurodegenerative diseases

Mitochondrial dysfunction is known to be associated with neurodegenerative diseases (NDDs), which is a major burden on the society. Therefore, understanding the regulation of mitochondrial dysfunctions and its implication in neurodegeneration has been major goal for exploiting these mechanisms to rescue neuronal death. The crosstalk between mitochondria and nucleus is important for different neuronal functions including axonal branching, energy homeostasis, neuroinflammation and neuronal survival. The decreased mitochondria capacity during progressive neurodegeneration leads to the altered OXPHOS activity and generation of ROS. The ROS levels in narrow physiological range can reprogram nuclear gene expression to enhance the cellular survival by phenomenon called mitohormesis. Here, we have systematically reviewed the existing reports of mitochondrial dysfunctions causing altered ROS levels in NDDs. We further discussed the role of ROS in regulating mitohormesis and emphasized the importance of mitohormesis in neuronal homeostasis. The emerging role of mitohormesis highlights its importance in future studies on intracellular ROS mediated rescue of mitochondrial dysfunction along with other prevailing mechanisms to alleviate neurodegeneration.

Maternal Spirulina supplementation during pregnancy and lactation partially prevents oxidative stress, glial activation and neuronal damage in protein malnourished F1 progeny

Protein malnutrition (PMN) is a global health issue but most prevalent in Africa and Asia. It exerts detrimental effect on structural and physiological aspects of hippocampal circuitry. Despite accumulating evidence for PMN induced changes in nervous system, relatively very little is known about how maternal nutritional supplementation during malnutrition affects glial cells and neurons. Herein, we aimed to investigate the effects of maternal Spirulina supplementation against PMN induced oxidative stress, reactive gliosis and neuronal damage in hippocampus of F1 progeny. Three months old healthy Sprague Dawley females (n = 24) were shifted to normoprotein (NC; 20% protein) and low protein (LP; 8% protein) diets 15 days before conception. The NC and LP group females were subdivided into two groups according to Spirulina supplementation (400 mg/kg/b.wt. orally throughout gestation and lactation period): normal control with Spirulina (NC SPI) and low protein with Spirulina supplemented group (LP SPI). F1 progeny born were used in present study. Thus, building on earlier results of ameliorated neurobehavioral and cognitive abilities in Spirulina supplemented protein deprived rats, the present study incorporates neurochemical and morphometric analysis of glial cells and neurons and revealed that maternal Spirulina consumption partially prevented the PMN associated neuropathological alterations in terms of attenuated oxidative brain damage, reduced reactive gliosis and apoptotic cell population, improved dendritic branch complexity with few damaged neurons and enhanced mushroom shaped spine density. The results suggest that cellular changes in hippocampus after PMN are partially restored after maternal Spirulina supplementation and one could envision intervention approaches using Spirulina against malnutrition.

Exploring the Expression of Cardiac Regulators in a Vertebrate Extremophile: The Cichlid Fish Oreochromis (Alcolapia) alcalica

Although it is widely accepted that the cellular and molecular mechanisms of vertebrate cardiac development are evolutionarily conserved, this is on the basis of data from only a few model organisms suited to laboratory studies. Here, we investigate gene expression during cardiac development in the extremophile, non-model fish species, Oreochromis (Alcolapia) alcalica. We first characterise the early development of O. alcalica and observe extensive vascularisation across the yolk prior to hatching. We further investigate heart development by identifying and cloning O. alcalica orthologues of conserved cardiac transcription factors gata4, tbx5, and mef2c for analysis by in situ hybridisation. Expression of these three key cardiac developmental regulators also reveals other aspects of O. alcalica development, as these genes are expressed in developing blood, limb, eyes, and muscle, as well as the heart. Our data support the notion that O. alcalica is a direct-developing vertebrate that shares the highly conserved molecular regulation of the vertebrate body plan. However, the expression of gata4 in O. alcalica reveals interesting differences in the development of the circulatory system distinct from that of the well-studied zebrafish. Understanding the development of O. alcalica embryos is an important step towards providing a model for future research into the adaptation to extreme conditions; this is particularly relevant given that anthropogenic-driven climate change will likely result in more freshwater organisms being exposed to less favourable conditions.

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.

Protective effect of Mucuna pruriens against arsenic-induced liver and kidney dysfunction and neurobehavioral alterations in rats

BACKGROUND AND AIM

Intoxication of arsenic in rats is known to result in neurological effects as well as liver and kidney dysfunction. Mucuna pruriens has been identified for its medicinal properties. The aim of the study was to investigate the protective effect of aqueous seed extract of M. pruriens on sodium arsenite-induced memory impairment, liver, and kidney functions in rats.

MATERIALS AND METHODS

The experiment was divided into short-term treatment (45 days) and long-term treatment (90 days), with each group divided into nine sub-groups consisting of six animals each. Sub-groups 1 and 2 served as normal, and N-acetylcysteine (NAC) controls, respectively. Sub-groups 3-9 received sodium arsenite in drinking water (50 mg/L). In addition, sub-group 4 received NAC (210 mg/kg b.wt) orally once daily, sub-groups 5-7 received aqueous seed extract of M. pruriens (350 mg/kg b.wt, 530 mg/kg b.wt, and 700 mg/kg b.wt) orally once daily and sub-groups 8 and 9 received a combination of NAC and aqueous seed extract of M. pruriens (350 mg/kg b.wt and 530 mg/kg b.wt) orally once daily. Following the treatment, the blood was drawn retro-orbitally to assess the liver (serum alanine transaminase [ALT], serum aspartate transaminase, and serum alkaline phosphatase) and kidney (serum urea and serum creatinine) functions. Learning and memory were assessed by passive avoidance test. Animals were sacrificed by an overdose of ketamine, and their Nissl stained hippocampal sections were analyzed for alterations in neural cell numbers in CA1 and CA3 regions.

RESULTS

In the short-term treatment, groups administered with M. pruriens 530 mg/kg b.wt alone and combination of NAC + M. pruriens 350 mg/kg b.wt exhibited a significant improvement in memory retention, less severe neurodegeneration, and decrease in serum ALT levels. In long-term treatment, groups administered with M. pruriens 700 mg/kg b.wt alone and combination of NAC+M. pruriens 350 mg/kg b.wt, respectively, showed better memory retention, decreased neural deficits, and reduced levels of kidney and liver enzymes.

CONCLUSION

The seed extract of M. pruriens showed significant enhancement in memory and learning. The number of surviving neurons in the CA1 and CA3 regions also increased on treatment with M. pruriens. Serum ALT, serum urea, and serum creatinine levels showed significant improvement on long-term treatment with M. pruriens.

Therapeutic Potential of Dihydropyridine Calcium Channel Blockers on Oxidative Injury Caused by Organophosphates in Cortex and Cerebellum: An In Vivo Study

This study was designed to investigate the effects of amlodipine (AM), a dihydropyridine calcium channel blocker, on the oxidative damage induced by diazinon (DZN) in the rat cortex and cerebellum. Forty-two rats were randomly divided into six groups. The rats were treated intraperitoneally with normal saline (group 1), AM (9 mg/kg; group 2), DZN (32 mg/kg; group 3) and different doses of AM (3, 6, and 9 mg/kg; groups 4, 5, and 6, respectively) with DZN. After 14 days, the cerebellum and cortex tissues were removed for biochemical and histological experiments. DZN significantly decreased acetylcholinesterase activity (AChE; 57%, p < 0.001 and 39.1%, p < 0.05), depleted total antioxidant capacity (TAC; 46.2%, p < 0.01 and 44.7%, p < 0.05), and increased lactate dehydrogenase activity (LDH; 96%, p < 0.001 and 202%, p < 0.001), nitric oxide (NO; 130%, p < 0.001 and 74.4%, p < 0.001), and lipid peroxidation levels (LPO; 35.6%, p < 0.001 and 128.7%, p < 0.001), in the cerebellum and cortex tissues, respectively. In addition, DZN induced structural alterations in the cerebellum and cortex. Following AM administration, a remarkable improvement was observed in LDH activity and some of the oxidative markers, such as NO and LPO; however, no significant changes were found in AChE activity when the DZN group was compared with the AM-treated groups. This study suggests that AM may prevent DZN-induced neurotoxicity via improvement of the oxidative/antioxidant balance in the cerebellum and cortex tissues.

The brains of six African mole-rat species show divergent responses to hypoxia

Mole-rats are champions of self-preservation, with increased longevity compared with other rodents their size, strong antioxidant capabilities and specialized defenses against endogenous oxidative stress. However, how the brains of these subterranean mammals handle acute in vivo hypoxia is poorly understood. This study is the first to examine the molecular response to low oxygen in six different species of hypoxia-tolerant mole-rats from sub-Saharan Africa. Protein carbonylation, a known marker of DNA damage (hydroxy-2'-deoxyguanosine), and antioxidant capacity did not change following hypoxia but HIF-1 protein levels increased significantly in the brains of two species. Nearly 30 miRNAs known to play roles in hypoxia tolerance were differentially regulated in a species-specific manner. The miRNAs exhibiting the strongest response to low oxygen stress inhibit apoptosis and regulate neuroinflammation, likely providing neuroprotection. A principal component analysis (PCA) using a subset of the molecular targets assessed herein revealed differences between control and hypoxic groups for two solitary species (Georychus capensis and Bathyergus suillus), which are ecologically adapted to a normoxic environment, suggesting a heightened sensitivity to hypoxia relative to species that may experience hypoxia more regularly in nature. By contrast, all molecular data were included in the PCA to detect a difference between control and hypoxic populations of eusocial Heterocephalus glaber, indicating they may require many lower-fold changes in signaling pathways to adapt to low oxygen settings. Finally, none of the Cryptomys hottentotus subspecies showed a statistical difference between control and hypoxic groups, presumably due to hypoxia tolerance derived from environmental pressures associated with a subterranean and social lifestyle.

Surgery/Anesthesia disturbs mitochondrial fission/fusion dynamics in the brain of aged mice with postoperative delirium

Postoperative delirium (POD) is a common complication following surgery and anesthesia (Surgery/Anesthesia). Mitochondrial dysfunction, which is demonstrated by energy deficits and excessively activated oxidative stress, has been reported to contribute to POD. The dynamic balance between mitochondrial fusion and fission processes is critical in regulating mitochondrial function. However, the impact of Surgery/Anesthesia on mitochondrial fusion/fission dynamics remains unclear. Here, we evaluate the effects of laparotomy under 1.4% isoflurane anesthesia for 2 hours on mitochondrial fission/fusion dynamics in the brain of aged mice. Mice in Surgery/Anesthesia group showed unbalanced fission/fusion dynamics, with decreased DISC1 expression and increased expression of Drp1 and Mfn2 in the mitochondrial fraction, leading to excessive mitochondrial fission and disturbed mitochondrial morphogenesis in the hippocampus and prefrontal cortex. In addition, surgical mice presented mitochondrial dysfunction, demonstrated by abnormally activated oxidative stress (increased ROS level, decreased SOD level) and energy deficits (decreased levels of ATP and MMP). Surgery/Anesthesia also decreased the expression of neuronal/synaptic plasticity-related proteins such as PSD-95 and BDNF. Furthermore, Surgery/Anesthesia induced delirium-like behavior in aged mice. In conclusion, Surgery/Anesthesia disturbed mitochondrial fission/fusion dynamics and then impaired mitochondrial function in the brain of aged mice; these effects may be involved in the underlying mechanism of POD.

The interplay between redox signalling and proteostasis in neurodegeneration: In vivo effects of a mitochondria-targeted antioxidant in Huntington's disease mice

Abnormal protein homeostasis (proteostasis), dysfunctional mitochondria, and aberrant redox signalling are often associated in neurodegenerative disorders, such as Huntington's (HD), Alzheimer's and Parkinson's diseases. It remains incompletely understood, however, how changes in redox signalling affect proteostasis mechanisms, including protein degradation pathways and unfolded protein responses (UPR). Here we address this open question by investigating the interplay between redox signalling and proteostasis in a mouse model of HD, and by examining the in vivo effects of the mitochondria-targeted antioxidant MitoQ. We performed behavioural tests in wild-type and R6/2 HD mice, examined markers of oxidative stress, UPR activation, and the status of key protein degradation pathways in brain and peripheral tissues. We show that R6/2 mice present widespread markers of oxidative stress, with tissue-specific changes in proteostasis that were more pronounced in the brain and muscle than in the liver. R6/2 mice presented increased levels of cytosolic and mitochondrial chaperones, particularly in muscle, indicating UPR activation. Treatment with MitoQ significantly ameliorated fine motor control of R6/2 mice, and reduced markers of oxidative damage in muscle. Additionally, MitoQ attenuated overactive autophagy induction in the R6/2 muscle, which has been associated with muscle wasting. Treatment with MitoQ did not alter autophagy markers in the brain, in agreement with its low brain bioavailability, which limits the risk of impairing neuronal protein clearance mechanisms. This study supports the hypotheses that abnormal redox signalling in muscle contributes to altered proteostasis and motor impairment in HD, and that redox interventions can improve muscle performance, highlighting the importance of peripheral therapeutics in HD.

The untapped potential of reptile biodiversity for understanding how and why animals age

1. The field of comparative aging biology has greatly expanded in the past 20 years. Longitudinal studies of populations of reptiles with a range of maximum lifespans have accumulated and been analyzed for evidence of mortality senescence and reproductive decline. While not as well represented in studies of amniote senescence, reptiles have been the subjects of many recent demographic and mechanistic studies of the biology of aging. 2. We review recent literature on reptile demographic senescence, mechanisms of senescence, and identify unanswered questions. Given the ecophysiological and demographic diversity of reptiles, what is the expected range of reptile senescence rates? Are known mechanisms of aging in reptiles consistent with canonical hallmarks of aging in model systems? What are the knowledge gaps in our understanding of reptile aging? 3. We find ample evidence of increasing mortality with advancing age in many reptiles. Testudines stand out as slower aging than other orders, but data on crocodilians and tuatara are sparse. Sex-specific analyses are generally not available. Studies of female reproduction suggest that reptiles are less likely to have reproductive decline with advancing age than mammals. 4. Reptiles share many physiological and molecular pathways of aging with mammals, birds, and laboratory model organisms. Adaptations related to stress physiology coupled with reptilian ectothermy suggest novel comparisons and contrasts that can be made with canonical aging phenotypes in mammals. These include stem cell and regeneration biology, homeostatic mechanisms, IIS/TOR signaling, and DNA repair. 5. To overcome challenges to the study of reptile aging, we recommend extending and expanding long-term monitoring of reptile populations, developing reptile cell lines to aid cellular biology, conducting more comparative studies of reptile morphology and physiology sampled along relevant life-history axes, and sequencing more reptile genomes for comparative genomics. Given the diversity of reptile life histories and adaptations, achieving these directives will likely greatly benefit all aging biology.

Brain oxidative damage in murine models of neonatal hypoxia/ischemia and reoxygenation

The brain is one of the main organs affected by hypoxia and reoxygenation in the neonatal period and one of the most vulnerable to oxidative stress. Hypoxia/ischemia and reoxygenation leads to impairment of neurogenesis, disruption of cortical migration, mitochondrial damage and neuroinflammation. The extent of the injury depends on the clinical manifestation in the affected regions. Preterm newborns are highly vulnerable, and they exhibit severe clinical manifestations such as intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP) and diffuse white matter injury (DWMI) among others. In the neonatal period, the accumulation of high levels of reactive oxygen species exacerbated by the immature antioxidant defense systems in represents cellular threats that, if they exceed or bypass physiological counteracting mechanisms, are responsible of significant neuronal damage. Several experimental models in mice mimic the consequences of perinatal asphyxia and the use of oxygen in the reanimation process that produce brain injury. The aim of this review is to highlight brain damage associated with oxidative stress in different murine models of hypoxia/ischemia and reoxygenation.

Therapeutic effects of chrysin in a rat model of traumatic brain injury: A behavioral, biochemical, and histological study

AIMS

Oxidative stress and apoptosis have major roles in the progression of traumatic brain injury (TBI)-associated motor and cognitive deficits. The present study was aimed to elucidate the putative effects of chrysin, a natural flavonoid compound, against TBI-induced motor and cognitive dysfunctions and possible involved mechanisms.

MAIN METHODS

Chrysin (25, 50 or 100 mg/kg) was orally administered to rats starting immediately following TBI induction by Marmarou's weight-drop technique and continuously for 3 or 14 days. Neurological functions, motor coordination, learning and memory performances, histological changes, cell apoptosis, expression of pro- and anti-apoptotic proteins, and oxidative status were assayed at scheduled time points after experimental TBI.

KEY FINDINGS

The results indicated that treatment with chrysin improved learning and memory disabilities in passive avoidance task, and ameliorated motor coordination impairment in rotarod test after TBI. These beneficial effects were accompanied by increased the concentrations of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH), decreased malondialdehyde (MDA) content, prevented neuronal loss, diminished apoptotic index, elevated the expression of anti-apoptotic Bcl-2 protein, and reduced the expression of pro-apoptotic Bax protein in the cerebral cortex and hippocampus tissues.

SIGNIFICANCE

Our findings suggest that both anti-oxidative and anti-apoptotic properties of chrysin (especially in the dose of 100 mg/kg) are possible mechanisms that improve cognitive/motor deficits and prevent neuronal cell death after TBI.

Eventual analysis of global cerebral ischemia-reperfusion injury in rat brain: a paradigm of a shift in stress and its influence on cognitive functions

Cognitive issues in stroke arise as a result of reperfusion of a clogged artery, which is reported to exacerbate the injury in the brain leading to oxidative stress. Through the present work, we try to understand the regional variations across brain regions mainly cortex and striatum associated with the progression of ischemia-reperfusion injury (IRI). In a rat model of IRI, the influence of varying ischemia and reperfusion times on the biochemical phases across the brain regions were monitored. IRI resulted in the blood-brain barrier disruption and developed mild areas of risk. The brain's tolerance towards IRI indicated a progressive trend in the injury and apoptosis from ischemia to reperfusion that was supported by the activities of plasma lactate dehydrogenase and tissue caspase-3. Cognitive impairment in these rats was an implication of cellular oxidative stress (higher lipid peroxidation and lower antioxidant enzyme activity) that persisted by 24-h reperfusion. The oxidative stress was prominent in the cortex than the striatum and was supported by the lower ATP level. Upregulated Mn-SOD expression leading to a preserved mitochondria in the striatum could be attributed to the regional protection. Overall, a progression of IRI was observed from striatum to cortex leading to 5-day cognitive decline.

Caloric restriction and redox homeostasis in various regions of aging male rat brain: Is caloric restriction still worth trying even after early-adulthood?: Redox homeostasis and caloric restriction in brain

Despite recent studies have shown that caloric restriction (CR) could improve some functional loss associated with brain aging, the biochemical effects of CR on brain aging are still not well understood on a quantifiable biochemical basis, including whether CR could be protective when started around middle adulthood, when age-related neurodegenerative diseases are thought to set in. Therefore, in the light of more than ever aging societies and increasing neurodegenerative diseases, we aimed to test the biochemical effects of CR on redox homeostasis in different parts of male Sprague-Dawley rat brain by using the biomarkers we consistently validated in our previous work (TOS, PCO, AOPP, AGEs, sRAGE, P-SH, LHPs, 4-HNE, TAS, Cu, Zn-SOD). Our results indicate that oxidative stress biomarkers are lower in CR group, implying a more favorable redox status that has been previously shown to be correlated with better neural function. PRACTICAL APPLICATIONS: We report that the beneficial effects of caloric restriction (CR) on various brain tissues result in significant improvements in biochemical markers, even though CR is not started in early adulthood. Hence, our select age group provides a sound redox status-related neurochemical understanding for many recent CR studies, where a functional loss was detected at this age.

Protective role of l-glutamic acid and l-cysteine in mitigation the chlorpyrifos-induced oxidative stress in rats

Exposure to the organophosphorus insecticide chlorpyrifos (CPF) can lead to oxidative stress. The aim of this work was to investigate and compare the protective effects of amino acids (l-glutamic acid (l-Glu) and l-cysteine (L-Cys) alone or in combination) for the purpose of suppression and mitigation of CPF-induced oxidative stress in rats. Rats were divided into five groups: CPF, CPF/L-Glu, CPF/L-Glu and l-Cys, CPF/L-Cys, control. The level of GSH and the activities of glutathione-related enzymes were determined. The content of lipid peroxidation products was also monitored. The obtained results suggest that level of GSH and activity of GSH-related enzymes was significantly inhibited by CPF. l-Glu and l-Cys were able to prevent CPF-induced oxidative stress. In rats treated with amino acids, we observed less significant or no changes in studied parameters. It was established that the above-mentioned amino acids, administered alone and in their combination, can mitigate and suppress CPF-induced oxidative stress. The most significant mitigation effect was found in rats treated with l-Glu only.

An effort toward molecular biology of food deprivation induced food hoarding in gonadectomized NMRI mouse model: focus on neural oxidative status

Background

Environmental uncertainty, such as food deprivation, may alter internal milieu of nervous system through various mechanisms. In combination with circumstances of stress or aging, high consumption of unsaturated fatty acids and oxygen can make neural tissues sensitive to oxidative stress (OS). For adult rats, diminished level of gonadal steroid hormones accelerates OS and may result in special behavioral manifestations. This study was aimed to partially answer the question whether OS mediates trade-off between food hoarding and food intake (fat hoarding) in environmental uncertainty (e.g., fluctuations in food resource) within gonadectomized mouse model in the presence of food deprivation-induced food hoarding behavior.

Results

Hoarding behavior was not uniformly expressed in all male mice that exposed to food deprivation. Extended phenotypes including hoarder and non-hoarder mice stored higher and lower amounts of food respectively as compared to that of low-hoarder mice (normal phenotype) after food deprivation. Results showed that neural oxidative status was not changed in the presence of hoarding behavior in gonadectomized mice regardless of tissue type, however, glutathione levels of brain tissues were increased in the presence of hoarding behavior. Decreased superoxide dismutase activity in brain and spinal cord tissues and increased malondialdehyde in brain tissues of gonadectomized mice were also seen.

Conclusions

Although, food deprivation-induced hoarding behavior is a strategic response to food shortage in mice, it did not induce the same amount of hoarding across all colony mates. Hoarding behavior, in this case, is a response to the environmental uncertainty of food shortage, therefore is not an abnormal behavior. Hoarding behavior induced neural OS with regard to an increase in brain glutathione levels but failed to show other markers of neural OS. Decreased superoxide dismutase activity in brain and spinal cord tissues and increased malondialdehyde levels in brain tissues of gonadectomized mice could be a hallmark of debilitated antioxidative defense and more lipid peroxidation due to reduced amount of gonadal steroid hormones during aging.

Naked mole-rat acid-sensing ion channel 3 forms nonfunctional homomers, but functional heteromers

Acid-sensing ion channels (ASICs) form both homotrimeric and heterotrimeric ion channels that are activated by extracellular protons and are involved in a wide range of physiological and pathophysiological processes, including pain and anxiety. ASIC proteins can form both homotrimeric and heterotrimeric ion channels. The ASIC3 subunit has been shown to be of particular importance in the peripheral nervous system with pharmacological and genetic manipulations demonstrating a role in pain. Naked mole-rats, despite having functional ASICs, are insensitive to acid as a noxious stimulus and show diminished avoidance of acidic fumes, ammonia, and carbon dioxide. Here we cloned naked mole-rat ASIC3 (nmrASIC3) and used a cell-surface biotinylation assay to demonstrate that it traffics to the plasma membrane, but using whole-cell patch clamp electrophysiology we observed that nmrASIC3 is insensitive to both protons and the non-proton ASIC3 agonist 2-guanidine-4-methylquinazoline. However, in line with previous reports of ASIC3 mRNA expression in dorsal root ganglia neurons, we found that the ASIC3 antagonist APETx2 reversibly inhibits ASIC-like currents in naked mole-rat dorsal root ganglia neurons. We further show that like the proton-insensitive ASIC2b and ASIC4, nmrASIC3 forms functional, proton-sensitive heteromers with other ASIC subunits. An amino acid alignment of ASIC3s between 9 relevant rodent species and human identified unique sequence differences that might underlie the proton insensitivity of nmrASIC3. However, introducing nmrASIC3 differences into rat ASIC3 (rASIC3) produced only minor differences in channel function, and replacing the nmrASIC3 sequence with that of rASIC3 did not produce a proton-sensitive ion channel. Our observation that nmrASIC3 forms nonfunctional homomers may reflect a further adaptation of the naked mole-rat to living in an environment with high-carbon dioxide levels.