Neuroscience and hormesis: overview and general findings

Current advances and future trends of hormesis in disease

Hormesis, an adaptive response, occurs when exposure to low doses of a stressor potentially induces a stimulatory effect, while higher doses may inhibit it. This phenomenon is widely observed across various organisms and stressors, significantly advancing our understanding and inspiring further exploration of the beneficial effects of toxins at doses both below and beyond traditional thresholds. This has profound implications for promoting biological regulation at the cellular level and enhancing adaptability throughout the biosphere. Therefore, conducting bibliometric analysis in this field is crucial for accurately analyzing and summarizing its current research status. The results of the bibliometric analysis reveal a steady increase in the number of publications in this field over the years. The United States emerges as the leading country in both publication and citation numbers, with the journal Dose-Response publishing the highest number of papers in this area. Calabrese E.J. is a prominent person with significant contributions and influence among authors. Through keyword co-occurrence and trend analysis, current hotspots in this field are identified, primarily focusing on the relationship between hormesis, oxidative stress, and aging. Analysis of highly cited references predicts that future research trends may center around the relationship between hormesis and stress at different doses, as well as exploring the mechanisms and applications of hormesis. In conclusion, this review aims to visually represent hormesis-related research through bibliometric methods, uncovering emerging patterns and areas of focus within the field. It provides a summary of the current research status and forecasts trends in hormesis-related research.

Modulation in growth, oxidative stress, photosynthesis, and morphology reveals higher toxicity of alpha-cypermethrin than chlorpyrifos towards a non-target green alga at high doses

Considering the frequent detection of pesticides in the aquatic environment, the ecotoxicological effects of Chlorpyrifos (CHP), an organophosphate, and alpha-cypermethrin (ACM), a pyrethroid, on freshwater microalgae were compared for the first time in this study. High concentrations of both CHP and ACM significantly suppressed the growth of test microalga Graesiella emersonii (p < 0.05). The 96-h EC50 of CHP and ACM were 54.42 mg L-1 and 29.40 mg L-1, respectively. Sub-inhibitory doses of both pesticides increased ROS formation in a concentration-dependent manner, which was accompanied by changes in antioxidant enzymes activities, lipid peroxidation, and variations in photosynthetic pigment concentration. Furthermore, both pesticides influenced photosystem II performance, oxygen-evolving complex efficiency and, intracellular ATP levels. Scanning electron microscopy analysis revealed that high concentrations of both CHP and ACM caused considerable morphological changes in the microalga. In comparison, CHP was more toxic than ACM at low concentrations, whereas ACM was more toxic at high concentrations.

Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies

Aging accompanied by several age-related complications, is a multifaceted inevitable biological progression involving various genetic, environmental, and lifestyle factors. The major factor in this process is oxidative stress, caused by an abundance of reactive oxygen species (ROS) generated in the mitochondria and endoplasmic reticulum (ER). ROS and RNS pose a threat by disrupting signaling mechanisms and causing oxidative damage to cellular components. This oxidative stress affects both the ER and mitochondria, causing proteopathies (abnormal protein aggregation), initiation of unfolded protein response, mitochondrial dysfunction, abnormal cellular senescence, ultimately leading to inflammaging (chronic inflammation associated with aging) and, in rare cases, metastasis. RONS during oxidative stress dysregulate multiple metabolic pathways like NF-κB, MAPK, Nrf-2/Keap-1/ARE and PI3K/Akt which may lead to inappropriate cell death through apoptosis and necrosis. Inflammaging contributes to the development of inflammatory and degenerative diseases such as neurodegenerative diseases, diabetes, cardiovascular disease, chronic kidney disease, and retinopathy. The body's antioxidant systems, sirtuins, autophagy, apoptosis, and biogenesis play a role in maintaining homeostasis, but they have limitations and cannot achieve an ideal state of balance. Certain interventions, such as calorie restriction, intermittent fasting, dietary habits, and regular exercise, have shown beneficial effects in counteracting the aging process. In addition, interventions like senotherapy (targeting senescent cells) and sirtuin-activating compounds (STACs) enhance autophagy and apoptosis for efficient removal of damaged oxidative products and organelles. Further, STACs enhance biogenesis for the regeneration of required organelles to maintain homeostasis. This review article explores the various aspects of oxidative damage, the associated complications, and potential strategies to mitigate these effects.

Indole Alkaloids of Rauvolfia ligustrina and Their Anxiolytic Effects in Adult Zebrafish

Rauvolfia species are well known as producers of bioactive monoterpene indole alkaloids, which exhibit a broad spectrum of biological activities. A new vobasine-sarpagan-type bisindole alkaloid (1: ) along with six known monomeric indoles (2, 3/4, 5: , and 6/7: ) were isolated from the ethanol extract of the roots of Rauvolfia ligustrina. The structure of the new compound was elucidated by interpretation of their spectroscopic data (1D and 2D NMR and HRESIMS) and comparison with published data for analog compounds. The cytotoxicity of the isolated compounds was screened in a zebrafish (Danio rerio) model. The possible GABAergic (diazepam as the positive control) and serotoninergic (fluoxetine as the positive control) mechanisms of action in adult zebrafish were also evaluated. No compounds were cytotoxic. Compound 2: and the epimers 3: /4: and 6: /7: showed a mechanism action by GABAA, while compound 1: showed a mechanism action by a serotonin receptor (anxiolytic activity). Molecular docking studies showed that compounds 2: and 5: have a greater affinity by the GABAA receptor when compared with diazepam, whereas 1: showed the best affinity for the 5HT2AR channel when compared to risperidone.

Many Paths to Alzheimer's Disease: A Unifying Hypothesis Integrating Biological, Chemical, and Physical Risk Factors

Sporadic Alzheimer's disease (AD) is a complex, multifactorial disease. We should therefore expect to find many factors involved in its causation. The known neuropathology seen at autopsy in patients dying with AD is not consistently seen in all patients with AD and is sometimes seen in patients without dementia. This suggests that patients follow different paths to AD, with different people having slightly different combinations of predisposing physical, chemical and biologic risk factors, and varying neuropathology. This review summarizes what is known of the biologic and chemical predisposing factors and features in AD. We postulate that, underlying the neuropathology of AD is a progressive failure of neurons, with advancing age or other morbidity, to rid themselves of entropy, i.e., the disordered state resulting from brain metabolism. Understanding the diverse causes of AD may allow the development of new therapies targeted at blocking the paths that lead to dementia in each subset of patients.

Low-to-moderate level of perceived stress strengthens working memory: Testing the hormesis hypothesis through neural activation

The negative impact of stress on neurocognitive functioning is extensively documented by empirical research. However, emerging reports suggest that stress may also confer positive neurocognitive effects. This hypothesis has been advanced by the hormesis model of psychosocial stress, in which low-moderate levels of stress are expected to result in neurocognitive benefits, such as improved working memory (WM), a central executive function. We tested the hormesis hypothesis, purporting an inverted U-shaped relation between stress and neurocognitive performance, in a large sample of young adults from the Human Connectome Project (n = 1000, Mage = 28.74, SD = 3.67, 54.3% female). In particular, we investigated whether neural response during a WM challenge is a potential intermediary through which low-moderate levels of stress confer beneficial effects on WM performance. Further, we tested whether the association between low-moderate prolonged stress and WM-related neural function was stronger in contexts with more psychosocial resources. Findings showed that low-moderate levels of perceived stress were associated with elevated WM-related neural activation, resulting in more optimal WM behavioral performance (α *β = -0.02, p = .046). The strength of this association tapered off at high-stress levels. Finally, we found that the benefit of low-moderate stress was stronger among individuals with access to higher levels of psychosocial resources (β = -0.06, p = .021). By drawing attention to the dose-dependent, nonlinear relation between stress and WM, this study highlights emerging evidence of a process by which mild stress induces neurocognitive benefits, and the psychosocial context under which benefits are most likely to manifest.

Neurohormetic phytochemicals in the pathogenesis of neurodegenerative diseases

The world population is progressively ageing, assuming an enormous social and health challenge. As the world ages, neurodegenerative diseases are on the rise. Regarding the progressive nature of these diseases, none of the neurodegenerative diseases are curable at date, and the existing treatments can only help relieve the symptoms or slow the progression. Recently, hormesis has increased attention in the treatment of age-related neurodegenerative diseases. The concept of hormesis refers to a biphasic dose-response phenomenon, where low levels of the drug or stress exert protective of beneficial effects and high doses deleterious or toxic effects. Neurohormesis, as the adaptive aspect of hormetic dose responses in neurons, has been shown to slow the onset of neurodegenerative diseases and reduce the damages caused by aging, stroke, and traumatic brain injury. Hormesis was also observed to modulate anxiety, stress, pain, and the severity of seizure. Thus, neurohormesis can be considered as a potentially innovative approach in the treatment of neurodegenerative and other neurologic disorders. Herbal medicinal products and supplements are often considered health resources with many applications. The hormesis phenomenon in medicinal plants is valuable and several studies have shown that hormetic mechanisms of bioactive compounds can prevent or ameliorate the neurodegenerative pathogenesis in animal models of Alzheimer’s and Parkinson’s diseases. Moreover, the hormesis activity of phytochemicals has been evaluated in other neurological disorders such as Autism and Huntington’s disease. In this review, the neurohormetic dose–response concept and the possible underlying neuroprotection mechanisms are discussed. Different neurohormetic phytochemicals used for the better management of neurodegenerative diseases, the rationale for using them, and the key findings of their studies are also reviewed.

Is perceived stress linked to enhanced cognitive functioning and reduced risk for psychopathology? Testing the hormesis hypothesis

Extensive research documents the impact of psychosocial stress on risk for the development of psychiatric symptoms across one's lifespan. Further, evidence exists that cognitive functioning mediates this link. However, a growing body of research suggests that limited stress can result in cognitive benefits that may contribute to resilience. The hypothesis that low-to-moderate levels of stress are linked to more adaptive outcomes has been referred to as hormesis. Using a sample of young adults from the Human Connectome Project (N = 1,206, 54.4% female, M_age = 28.84), the present study aims to test the hormetic effect between low-to-moderate perceived stress and psychopathological symptoms (internalizing and externalizing symptoms), as well as to cross-sectionally explore the intermediate role of cognitive functioning in this effect. Results showed cognitive functioning as a potential intermediating mechanism underlying the curvilinear associations between perceived stress and externalizing, but not internalizing, behaviors. This study provides preliminary support for the benefits of limited stress to the process of human resilience.

Hormesis and insects: Effects and interactions in agroecosystems

Insects in agroecosystems contend with many stressors - e.g., chemicals, heat, nutrient deprivation - that are often encountered at low levels. Exposure to mild stress is now well known to induce hormetic (stimulatory) effects in insects, with implications for insect management, and ecological structure and function in agroecosystems. In this review, we examine the major ecological niches insects occupy or guilds to which they belong in agroecosystems and how hormesis can manifest within and across these groups. The mechanistic underpinnings of hormesis in insects are starting to become established, explaining the many phenotypic hormetic responses observed in insect reproduction, development, and behavior. Whereas potential effects on insect populations are well supported in laboratory experiments, field-based hypothesis-driven research on hormesis is greatly lacking. Furthermore, because most ecological paradigms are founded within the context of communities, entomological agroecologists interested in hormesis need to 'level up' and test hypotheses that explore effects on species interactions, and community structure and functioning. Embedded in this charge is to continue experimentation on herbivorous pest species while shifting more focus towards insect natural enemies, pollinators, and detritivores - guilds that play crucial roles in highly functioning agroecosystems that have been understudied in hormesis research. Important areas for future insect agroecology research on hormesis are discussed.

PLGA-Based Curcumin Delivery System: An Interesting Therapeutic Approach in the Treatment of Alzheimer's Disease

Progressive degeneration and dysfunction of the nervous system because of oxidative stress, aggregations of misfolded proteins, and neuroinflammation are the key pathological features of neurodegenerative diseases. Alzheimer's disease is a chronic neurodegenerative disorder driven by uncontrolled extracellular deposition of β-amyloid (Aβ) in the amyloid plaques and intracellular accumulation of hyperphosphorylated tau protein. Curcumin is a hydrophobic polyphenol with noticeable neuroprotective and anti-inflammatory effects that can cross the blood-brain barrier. Therefore, it is widely studied for the alleviation of inflammatory and neurological disorders. However, the clinical application of curcumin is limited due to its low aqueous solubility and bioavailability. Recently, nano-based curcumin delivery systems are developed to overcome these limitations effectively. This review article discusses the effects and potential mechanisms of curcumin-loaded PLGA nanoparticles in Alzheimer's disease.

Poststroke dendritic arbor regrowth requires the actin nucleator Cobl

Ischemic stroke is a major cause of death and long-term disability. We demonstrate that middle cerebral artery occlusion (MCAO) in mice leads to a strong decline in dendritic arborization of penumbral neurons. These defects were subsequently repaired by an ipsilateral recovery process requiring the actin nucleator Cobl. Ischemic stroke and excitotoxicity, caused by calpain-mediated proteolysis, significantly reduced Cobl levels. In an apparently unique manner among excitotoxicity-affected proteins, this Cobl decline was rapidly restored by increased mRNA expression and Cobl then played a pivotal role in poststroke dendritic arbor repair in peri-infarct areas. In Cobl knockout (KO) mice, the dendritic repair window determined to span day 2 to 4 poststroke in wild-type (WT) strikingly passed without any dendritic regrowth. Instead, Cobl KO penumbral neurons of the primary motor cortex continued to show the dendritic impairments caused by stroke. Our results thereby highlight a powerful poststroke recovery process and identified causal molecular mechanisms critical during poststroke repair.

Ischemic stroke is a major cause of death and long-term disability. This study reveals that, in mice, stroke-induced damage to dendritic arborization in the area around an infarct is rapidly repaired via dendritic regrowth; this plasticity requires the actin nucleator Cobl.

Brain health promotion: Tactics within a strategic approach based upon valid, yet evolving scientific evidence

There is growing interest in finding ways to enhance longevity and the quality of life. This paper summarizes a vast scientific literature over the past two decades that has suggested approaches to enhancing biological resilience - and particularly neurological function - via hormetic and preconditioning processes. The employment of hormesis and preconditioning has been shown to protect biological systems from many of the effects of aging, both by sustaining structural and functional integrity, and by affording relative protection against certain types of diseases. The paper confronts the challenges - and opportunities - for society when considering possible practical use of evolving evidence about the mechanisms, processes and effects of these biological phenomena.

Hormesis: Transforming disciplines that rely on the dose response

This article tells the story of hormesis from its conceptual and experimental origins, its dismissal by the scientific and medical communities in the first half of the 20th century, and its rediscovery over the past several decades to be a fundamental evolutionary adaptive strategy. The upregulation of hormetic adaptive mechanisms has the capacity to decelerate the onset and reduce the severity of a broad spectrum of common age-related health, behavioral, and performance decrements and debilitating diseases, thereby significantly enhancing the human health span. Incorporation of hormetic-based lifestyle options within the human population would have profoundly positive impacts on the public health, significantly reducing health care costs.

The Role of Poly-Herbal Extract in Sodium Chloride-Induced Oxidative Stress and Hyperlipidemia in Male Wistar Rats

Consistent consumption of high salt diet (HSD) has been associated with increased cellular generation of free radicals, which has been implicated in the derangement of some vital organs and etiology of cardiovascular disorders. This study was designed to investigate the combined effect of some commonly employed medicinal plants on serum lipid profile and antioxidant status of aorta, kidney, and liver of high salt diet-fed animals. Out of the total fifty male Wistar rats obtained, fifteen were used for acute toxicity study, while the remaining thirty-five were divided into 5 groups of 7 animals each. Group 1 and 2 animals were fed normal rat chow (NRC) and 16% high salt diet (HSD) only, respectively. Animals in groups 3, 4 and 5 were fed 16% HSD with 800, 400, and 200 mg/kg bw poly-herbal extract (PHE), respectively, once for 28 consecutive days. Serum low-density lipoprotein (LDL), triacylglycerol (TG), total cholesterol (TC) and high-density lipoprotein (HDL), malondialdehyde, nitric oxide, catalase, superoxide dismutase, glutathione peroxidase, glutathione concentration, and activities were assessed in the aorta, kidney, and liver. Poly-herbal extract (p < 0.05) significantly reduced malondialdehyde and nitric oxide concentrations and also increased antioxidant enzymes and glutathione activity. Elevated serum TG, TC, LDL, and TC content in HSD-fed animals were significantly (p < 0.05) reduced to normal in PHE-treated rats while HDL was significantly elevated (p < 0.05) in a concentration-dependent manner in PHE treated animals. Feeding with PHE attenuated high-salt diet imposed derangement in serum lipid profile and antioxidant status in the organs of the experimental rats.

Demonstrated hormetic mechanisms putatively subserve riluzole-induced effects in neuroprotection against amyotrophic lateral sclerosis (ALS): Implications for research and clinical practice

This paper provides evidence to support that riluzole, an FDA-approved treatment for amyotrophic lateral sclerosis (ALS), like many neuroprotective agents, displays and exerts hormetic biphasic dose responses. These findings have important implications for the experimental study and clinical treatment of ALS.

Bi-phasic dose response in the preclinical and clinical developments of sigma-1 receptor ligands for the treatment of neurodegenerative disorders

Introduction: The sigma-1 receptor (S1R) is attracting much attention for disease-modifying therapies in neurodegenerative diseases. It is a conserved protein, present in plasma and endoplasmic reticulum (ER) membranes and enriched in mitochondria-associated ER membranes (MAMs). It modulates ER-mitochondria Ca2+ transfer and ER stress pathways. Mitochondrial and MAM dysfunctions contribute to neurodegenerative processes in diseases such as Alzheimer, Parkinson, Huntington or Amyotrophic Lateral Sclerosis. Interestingly, the S1R can be activated by small druggable molecules and accumulating preclinical data suggest that S1R agonists are effective protectants in these neurodegenerative diseases.Area covered: In this review, we will present the data showing the high therapeutic potential of S1R drugs for the treatment of neurodegenerative diseases, focusing on pridopidine as a potent and selective S1R agonist under clinical development. Of particular interest is the bi-phasic (bell-shaped) dose-response effect, representing a common feature of all S1R agonists and described in numerous preclinical models in vitro, in vivo and in clinical trials.Expert opinion: S1R agonists modulate inter-organelles communication altered in neurodegenerative diseases and activate intracellular survival pathways. Research will continue growing in the future. The particular cellular nature of this chaperone protein must be better understood to facilitate the clinical developement of promising molecules.

Hormesis Mediates Acquired Resilience: Using Plant-Derived Chemicals to Enhance Health

This review provides an assessment of hormesis, a highly conserved evolutionary dose-response adaptive strategy that leads to the development of acquired resilience within well-defined temporal windows. The hormetic-based acquired resilience has a central role in affecting healthy aging, slowing the onset and progression of numerous neurodegenerative and other age-related diseases, and reducing risks and damage due to heart attacks, stroke, and other serious conditions of public health and medical importance. The review provides the historical foundations of hormesis, its dose-response features, its capacity for generalization across biological models and endpoints measured, and its mechanistic foundations. The review also provides a focus on the adaptive features of hormesis, i.e., its capacity to upregulate acquired resilience and how this can be mediated by numerous plant-derived extracts, such as curcumin, ginseng, Ginkgo biloba, resveratrol, and green tea, that induce a broad spectrum of chemopreventive effects via hormesis.

Putative hormetic mechanisms and effects of atypical antipsychotic agents: Implications for study design and clinical psychopharmacotherapeutics

This paper addresses a novel putative mechanism by which atypical antipsychotic agents induce clinically significant neuroprotective effects that may be viable in the treatment of schizophrenia - and perhaps other neuropsychiatric disorders. Based upon experimental studies with multiple in vitro models (i.e., PC 12 cells, NSC-34 hybrid cells, SH-SY5Y cells, the immune cell line U-937) and several rodent in vivo models, six atypical antipsychotic drugs, within direct experimental comparisons and/or preconditioning protocol studies with six different stressor/toxic agents (i.e. rotenone, hydrogen peroxide, MPP+, serum withdrawal, beta-amyloid, and corticosterone) were demonstrated to induce neuroprotective effects with consistently hormetic dose response patterns. These findings suggest that some of the reported neuroprotective effects of atypical human antipsychotic agents are likely to be mediated by hormetic mechanisms. These findings may have important implications for both experimental study design and clinical therapeutics.

Effects of glyphosate on germination, photosynthesis and chloroplast morphology in tomato

The adverse effects of glyphosate herbicide on plants are well recognised, however, potential hormetic effects have not been well studied. This study aimed to use tomato as a model organism to explore the potential hormetic effects of glyphosate in water (0-30 mg L-1) and in compost soil (0-30 mg kg-1). The growth-promoting effects of glyphosate at concentrations of 0.03-1 mg L-1 in water or 0.03-1 mg kg-1 in compost were demonstrated in tomato for the first time. These hormetic effects were manifest as increased hypocotyl and radicle growth of seedlings germinated on paper towel soaked in glyphosate solution and also in crops which had been sprayed with glyphosate. Increased rates of photosynthesis (up to 2-fold) were observed in 4-week old crops when seeds were sown in compost amended with glyphosate and also when leaves were sprayed with glyphosate. The examination of chloroplast morphology using transmission electron microscopy revealed that the hormetic effects were associated with elongation of chloroplasts, possibly due to lateral expansion of thylakoid grana.

Hormesis: A potential strategic approach to the treatment of neurodegenerative disease

This review describes neuroprotective effects mediated by pre- and post-conditioning-induced processes that act via the quantitative features of the hormetic dose response. These lead to the development of acquired resilience that can protect neuronal systems from endogenous and exogenous stresses and insult. Particular attention is directed to issues of dose optimization, inter-individual variation, and potential ways to further study and employ hormetic-based preconditioning approaches in medical and public health efforts to treat and prevent neurodegenerative disease.

Does Green Tea Induce Hormesis?

Green tea, and its principal constituent (-)-epigallocatechin-3-gallate (EGCG), are commonly shown to induce biphasic concentration/dose responses in a broad range of cell types, including non-tumor cells, and tumor cell lines. The most active area of research dealt with an assessment of neural cells with application to neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease cell models, often using preconditioning experimental protocols. The general findings demonstrate EGCG-induced hormetic effects resulting in an enhanced acquired resilience within an adaptive and temporally dependent homeodynamic framework. The biphasic dose responses displayed the typical quantitative features of the hormetic dose response with respect to the amplitude and width of the stimulatory response. These findings provide further evidence for the general occurrence of hormetic dose responses with such responses being independent of the biological model, end point, inducing agent, and mechanism. The biphasic nature of these responses has important implications since it suggests optimal dose ranges for end points of public health and therapeutic applications. These findings indicate the need to assess the entire dose-response continuum in order to better define the nature of the dose response, especially in the low-dose zone where such exposures are common in human populations.

One Step Ahead-Attention Control Capabilities at Baseline Are Associated With the Effectiveness of the Attention Training Technique

BACKGROUND

Attentional control has been observed to play an important role in affective disorders by impacting information processing, the ability to exert top-down control in response to distracting stimuli, and by affecting emotional regulation. Prior studies demonstrated an association between attentional control and response to psychotherapy, thereby identifying attentional control as an interesting prognostic pre-treatment factor. Improving attentional control and flexibility is a cornerstone in metacognitive therapy (MCT), which is trained by the use of the Attentional Training Technique (ATT). However, as of yet, it remains unclear if pre-treatment attentional control is related to the effect of ATT.

METHODS

An aggregated sample of 139 healthy participants [study 1: 85 participants, mean age 23.7 years, previously published (Barth et al., 2019); study 2: 54 participants, mean age 33.7 years, not previously published] performed an attentional performance test battery before and after applying ATT. Before ATT was administered, attentional control was measured using a well-established self-report instrument, i.e., the Attentional Control Scale (ACS; Derryberry and Reed, 2002). ATT was given in 2, 4, or 15 doses and compared to sham ATT. The test battery comprised a selection of established neurocognitive tasks: emotional dot probe, Stroop, 2-back, and dichotic listening.

RESULTS

Sham ATT showed no interaction with ACS score on performance outcome in all tests. At four doses of ATT, ACS score was associated with training response, i.e., subjects with high self-reported attentional control before training showed the largest improvements post-training (all P-values <0.05; see Figure 3). At 2 and 15 doses of ATT, the ACS score was unrelated to training response.

CONCLUSION

This is a first attempt in understanding the optimal dosage in which ATT should be administered dependent on the individual characteristics of each subject pre-training. The current data suggest self-reported attentional control pre-training as a marker to determine an optimal individual ATT training profile. Future studies should investigate if other domains of metacognitions also interact with training outcome and evaluate the extent to which this relationship transfers to clinical samples. If successful, assessing attentional control prior to treatment in clinical samples could be of use regarding personalized therapy plans and treatment outcome.

Central Sympathetic Nervous System Effects on Cognitive-Motor Performance

Abstract. The intriguing interplay between acute stress physiology and cognitive processes has long been noted. However, while stress-induced release of glucocorticoids has repeatedly been shown to impact brain mechanisms underlying cognition and memory, less experimental research addressed the effects of stress-induced central sympathetic nervous system (SNS) activation on cognitive performance. Moreover, despite the long-standing notion that the way performance is modulated by arousal may crucially depend on task complexity, mechanistic research demonstrating a direct, causal influence of altered SNS activity is scarce. Twelve healthy men participated in a placebo-controlled, pharmacologic dose–response study involving three within-subject assessments (1-week intervals). Subjective and objective indices of SNS activity as well as reaction time (RT) in three different tasks varying in cognitive demand (simple RT, choice RT, and verbal RT in complex mental arithmetic) were assessed during modulation of central SNS tone by intravenous infusions of dexmedetomidine (alpha2-agonist), yohimbine (alpha2-antagonist), and placebo. Cognitive performance was negatively affected by alpha2-agonism in all task conditions. By contrast, administration of yohimbine improved simple RT, while diminishing complex RT, supporting the assumption of a nonlinear way of action depending on task characteristics. Our results highlight the consequences of central (noradrenergic) SNS activation for cognitive-motor performance in RT tasks of varying complexity.

A source of exogenous oxidative stress improves oxidative status and favors pheomelanin synthesis in zebra finches

Some organisms can modulate gene expression to trigger physiological responses that help adapt to environmental stress. The synthesis of the pigment pheomelanin in melanocytes seems to be one of these responses, as it may contribute to cellular homeostasis. We experimentally induced environmental oxidative stress in male zebra finches Taeniopygia guttata by the administration of the herbicide diquat dibromide during feather growth to test if the expression of genes involved in pheomelanin synthesis shows epigenetic lability. As pheomelanin synthesis implies decreasing the availability of the main cellular antioxidant (glutathione), it is expected to cause oxidative stress unless a protective mechanism limits pheomelanin synthesis and thus favors the antioxidant capacity. However, diquat exposure did not only improve the antioxidant capacity of birds, but also upregulated the expression of a gene (AGRP) that promotes pheomelanin synthesis in feather melanocytes, leading to the development of darker plumage coloration. No changes in the expression of other genes involved in pheomelanin synthesis (Slc7a11, Slc45a2, MC1R, ASIP and CTNS) were detected. DNA methylation levels only changed in MC1R, suggesting that epigenetic modifications other than changes in methylation may regulate AGRP expression lability. Our results suggest that exogenous oxidative stress induced a hormetic response that enhanced the oxidative status of birds and, consequently, promoted pheomelanin-based pigmentation, supporting the idea that birds adjust pheomelanin synthesis to their oxidative stress conditions.

Stimulating hair growth via hormesis: Experimental foundations and clinical implications

Numerous agents (approximately 90) are shown to stimulate hair growth in cellular and animal models in a hormetic-like biphasic dose response manner. These hormetic dose responses occur within the framework of direct stimulatory responses as well as in preconditioning experimental protocols. These findings have important implications for experimental and clinical investigations with respect to study design strategies, dose selection and dose spacing along with sample size and statistical power issues. These findings further reflect the general occurrence of hormetic dose responses within the biological and biomedical literature that consistently appear to be independent of biological model, level of biological organization (i.e., cell, organ, and organism), endpoint, inducing agent, potency of the inducing agent, and mechanism.

Considerations for the Use of Polyphenols as Therapies in Neurodegenerative Diseases

Over the last two decades, the increase in the incidence of neurodegenerative diseases due to the increasingly ageing population has resulted in a major social and economic burden. At present, a large body of literature supports the potential use of functional nutrients, which exhibit potential neuroprotective properties to mitigate these diseases. Among the most studied dietary molecules, polyphenols stand out because of their multiple and often overlapping reported modes of action. However, ambiguity still exists as to the significance of their influence on human health. This review discusses the characteristics and functions of polyphenols that shape their potential therapeutic actions in neurodegenerative diseases while the less-explored gaps in knowledge of these nutrients will also be highlighted.

Redox Homeostasis and Natural Dietary Compounds: Focusing on Antioxidants of Rice (Oryza sativa L.)

Redox homeostasis may be defined as the dynamic equilibrium between electrophiles and nucleophiles to maintain the optimum redox steady state. This mechanism involves complex reactions, including nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, activated by oxidative stress in order to restore the redox balance. The ability to maintain the optimal redox homeostasis is fundamental for preserving physiological functions and preventing phenotypic shift toward pathological conditions. Here, we reviewed mechanisms involved in redox homeostasis and how certain natural compounds regulate the nucleophilic tone. In addition, we focused on the antioxidant properties of rice and particularly on its bioactive compound, γ-oryzanol. It is well known that γ-oryzanol exerts a variety of beneficial effects mediated by its antioxidant properties. Recently, γ-oryzanol was also found as a Nrf2 inducer, resulting in nucleophilic tone regulation and making rice a para-hormetic food.

Simulation as a means to develop firefighters as emergency care professionals

Objective. The aim of this study was to evaluate the simulated emergency care performed by firefighters and their perception of simulation as an educational method. Methods. This study had a mixed method with both a quantitative and a qualitative approach. Data were collected by simulation assessment, a questionnaire and written comments. Descriptive analysis was conducted on the quantitative data whereas a qualitative content analysis was conducted on the qualitative data. Finally, a contingent analysis was used where a synthesis configured both the quantitative and the qualitative results into a narrative result. Results. The cognitive workload that firefighters face during simulated emergency care is crucial for learning. In this study, the severity and complexity of the scenarios provided were higher than expected by the firefighters. Clearly stated conditions for the simulation and constructive feedback were considered positive for learning. Patient actors induced realism in the scenario, increasing the experience of stress, in comparison to a manikin. Conclusion. Simulation in a realistic on-scene environment increases firefighters' cognitive ability to critically analyze problems and manage emergency care. Simulation of emergency care developed the firefighters as professionals.

Hormetic approaches to the treatment of Parkinson's disease: Perspectives and possibilities

Age-related changes in the brain reflect a dynamic interaction of genetic, epigenetic, phenotypic, and environmental factors that can be temporally restricted or more longitudinally present throughout the lifespan. Fundamental to these mechanisms is the capacity for physiological adaptation through modulation of diverse molecular and biochemical signaling occurring from the intracellular to the network-systemic level throughout the brain. A number of agents that affect the onset and progression of Parkinson's disease (PD)-like effects in experimental models exhibit temporal features, and mechanisms of hormetic dose responses. These findings have particular significance since the hormetic dose response describes the amplitude and range of potential therapeutic effects, thereby affecting the design and conduct of studies of interventions against PD (and other neurodegenerative diseases), and may also be important to a broader consideration of hormetic processes in resilient adaptive responses that might afford protection against the onset and/or progression of PD and related disorders.

Dominant and opponent relations in cortical function: An EEG study of exam performance and stress

This paper analyzes the opponent dynamics of human motivational and affective processes, as conceptualized by RS Solomon, from the position of AA Ukhtomsky's neurophysiological principle of the dominant and its applications in the field of human electroencephalographic analysis. As an experimental model, we investigate the dynamics of cortical activity in students submitting university final course oral examinations in naturalistic settings, and show that successful performance in these settings depends on the presence of specific types of cortical activation patterns, involving high indices of left-hemispheric and frontal cortical dominance, whereas the lack thereof predicts poor performance on the task, and seems to be associated with difficulties in the executive regulation of cognitive (intellectual) and motivational processes in these highly demanding and stressful conditions. Based on such knowledge, improved educational and therapeutic interventions can be suggested which take into account individual variability in the neurocognitive mechanisms underlying adaptation to motivationally and intellectually challenging, stressful tasks, such as oral university exams. Some implications of this research for opponent-process theory and its closer integration into current neuroscience research on acquired motivations are discussed.

Hormesis as a mechanistic approach to understanding herbal treatments in traditional Chinese medicine

Traditional Chinese medicine (TCM) has been long practiced and is becoming ever more widely recognized as providing curative and/or healing treatments for a number of diseases and physiological conditions. This paper posits that herbal medicines used in TCM treatments may act through hormetic dose-response mechanisms. It is proposed that the stimulatory (i.e., low dose) and inhibitory (i.e., high dose) components of the hormetic dose response correspond to respective "regulating" and "curing" aspects of TCM herbal treatments. Specifically, the "regulating" functions promote adaptive or preventive responses, while "curing" treatments alleviate the clinical symptoms. Patterns of hormetic responses are described, and the applicability of these processes to herbal medicines of TCM are explicated. It is noted that a research agenda aimed at elucidating these mechanisms and patterns would be expansive and complex. However, we argue its value, in that hormesis may afford something akin to a Rosetta Stone with which to interpret, translate, and explain TCM herbology in ways that are aligned with biomedical perspectives that could enable a more integrative approach to medicine.

Human Factors and Neurophysiological Metrics in Air Traffic Control: A Critical Review

This paper provides a focused and organized review of the research progress on neurophysiological indicators, also called "neurometrics," to show how they can effectively address some of the most important human factors (HFs) needs in the air traffic management (ATM) field. In order to better understand and highlight available opportunities of such neuroscientific applications, state of the art on the most involved HFs and related cognitive processes (e.g., mental workload and cognitive training) are presented together with examples of possible applications in current and future ATM scenarios. Furthermore, this paper will discuss the potential enhancements that further research and development activities could bring to the efficiency and safety of the ATM service.

Berberine protects against 6-OHDA-induced neurotoxicity in PC12 cells and zebrafish through hormetic mechanisms involving PI3K/AKT/Bcl-2 and Nrf2/HO-1 pathways

Berberine (BBR) is a renowned natural compound that exhibits potent neuroprotective activities. However, the cellular and molecular mechanisms are still unclear. Hormesis is an adaptive mechanism generally activated by mild oxidative stress to protect the cells from further damage. Many phytochemicals have been shown to induce hormesis. This study aims to investigate whether the neuroprotective activity of BBR is mediated by hormesis and the related signaling pathways in 6-OHDA-induced PC12 cells and zebrafish neurotoxic models. Our results demonstrated that BBR induced a typical hormetic response in PC12 cells, i.e. low dose BBR significantly increased the cell viability, while high dose BBR inhibited the cell viability. Moreover, low dose BBR protected the PC12 cells from 6-OHDA-induced cytotoxicity and apoptosis, whereas relatively high dose BBR did not show neuroprotective activity. The hormetic and neuroprotective effects of BBR were confirmed to be mediated by up-regulated PI3K/AKT/Bcl-2 cell survival and Nrf2/HO-1 antioxidative signaling pathways. In addition, low dose BBR markedly mitigated the 6-OHDA-induced dopaminergic neuron loss and behavior movement deficiency in zebrafish, while high dose BBR only slightly exhibited neuroprotective activities. These results strongly suggested that the neuroprotection of BBR were attributable to the hormetic mechanisms via activating cell survival and antioxidative signaling pathways.

The role of hormesis in the functional performance and protection of neural systems

This paper addresses how hormesis, a biphasic dose response, can protect and affect performance of neural systems. Particular attention is directed to the potential role of hormesis in mitigating age-related neurodegenerative diseases, genetically based neurological diseases, as well as stroke, traumatic brain injury, seizure, and stress-related conditions. The hormetic dose response is of particular significance since it mediates the magnitude and range of neuroprotective processes. Consideration of hormetic dose-response concepts can also enhance the quality of study designs, including sample size/statistical power strategies, selection of treatment groups, dose spacing, and temporal/repeat measures’ features.

Hormetic effect of panaxatriol saponins confers neuroprotection in PC12 cells and zebrafish through PI3K/AKT/mTOR and AMPK/SIRT1/FOXO3 pathways

Hormesis is an adaptive response of living organisms to a moderate stress. However, its biomedical implication and molecular mechanisms remain to be intensively investigated. Panaxatriol saponins (PTS) is the major bioactive components extracted from Panax notoginseng, a widely used herbal medicine for cerebrovascular diseases. This study aims to examine the hormetic and neuroprotective effects of PTS in PC12 cells and zebrafish Parkinson's disease (PD) models. Our results demonstrated that PTS stimulated PC12 cell growth by about 30% at low doses, while PTS at high doses inhibited cell growth, which is a typical hormetic effect. Moreover, we found that low dose PTS pretreatment significantly attenuated 6-OHDA-induced cytotoxicity and up-regulated PI3K/AKT/mTOR cell proliferation pathway and AMPK/SIRT1/FOXO3 cell survival pathway in PC12 cells. These results strongly suggested that neuroprotective effects of PTS may be attributable to the hormetic effect induced by PTS through activating adaptive response-related signaling pathways. Notably, low dose PTS could significantly prevent the 6-OHDA-induced dopaminergic neuron loss and improve the behavior movement deficiency in zebrafish, whereas relative high dose PTS exhibited neural toxicity, further supporting the hormetic and neuroprotective effects of PTS. This study indicates that PTS may have the potential in the development of future therapeutic medicines for PD.

Inflammasomes, hormesis, and antioxidants in neuroinflammation: Role of NRLP3 in Alzheimer disease

Alzheimer disease (AD) is a progressive neurodegenerative disorder leading to cognitive decline, neuropsychiatric symptoms, disability, caregiver burden, and premature death. It represents the most prevalent cause of dementia, and its incidence rates exponentially increase with increasing age. The number of Americans living with AD is rapidly increasing. An estimated 5.4 million Americans of all ages have AD in 2016. One in nine people aged 65 and older has AD, and by midcentury, someone in the United States will develop the disease every 33 sec. It is now accepted that neuroinflammation is a common feature of neurological disease. Inflammasomes, which are a multiprotein complex part of the innate immune system, induce inflammation in response to various stimuli, such as pathogens and stress. Inflammasomes activate proinflammatory caspases, such as caspase-1, leading to the activation of the proinflammatory cytokines interleukin (IL)-1b, IL-18, and IL-33, which promote neuroinflammation and brain pathologies. The nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing-3 (NLRP3) inflammasome is the best characterized in neurodegenerative diseases, in particular AD. Recent research suggests that NLRP3 could possibly be used in targeted therapies to alleviate neuroinflammation. Modulation of endogenous cellular defense mechanisms may be an innovative approach to therapeutic intervention in AD and other disorders associated with neuroinflammation and neurodegeneration. Herein, we introduce the hormetic dose-response concept and present possible mechanisms and applications to neuroprotection. We summarize the mechanisms involved in activation of the NLRP3 inflammasome and its role in neuroinflammation. We also address and propose the potential therapeutic utility of the nutritional antioxidants sulforaphane and hydroxytyrosol against particular signs and symptoms of AD. © 2016 Wiley Periodicals, Inc.

Adaptive Automation Triggered by EEG-Based Mental Workload Index: A Passive Brain-Computer Interface Application in Realistic Air Traffic Control Environment

Adaptive Automation (AA) is a promising approach to keep the task workload demand within appropriate levels in order to avoid both the under- and over-load conditions, hence enhancing the overall performance and safety of the human-machine system. The main issue on the use of AA is how to trigger the AA solutions without affecting the operative task. In this regard, passive Brain-Computer Interface (pBCI) systems are a good candidate to activate automation, since they are able to gather information about the covert behavior (e.g., mental workload) of a subject by analyzing its neurophysiological signals (i.e., brain activity), and without interfering with the ongoing operational activity. We proposed a pBCI system able to trigger AA solutions integrated in a realistic Air Traffic Management (ATM) research simulator developed and hosted at ENAC (École Nationale de l'Aviation Civile of Toulouse, France). Twelve Air Traffic Controller (ATCO) students have been involved in the experiment and they have been asked to perform ATM scenarios with and without the support of the AA solutions. Results demonstrated the effectiveness of the proposed pBCI system, since it enabled the AA mostly during the high-demanding conditions (i.e., overload situations) inducing a reduction of the mental workload under which the ATCOs were operating. On the contrary, as desired, the AA was not activated when workload level was under the threshold, to prevent too low demanding conditions that could bring the operator's workload level toward potentially dangerous conditions of underload.

Major pathogenic mechanisms in vascular dementia: Roles of cellular stress response and hormesis in neuroprotection

Vascular dementia (VaD), considered the second most common cause of cognitive impairment after Alzheimer disease in the elderly, involves the impairment of memory and cognitive function as a consequence of cerebrovascular disease. Chronic cerebral hypoperfusion is a common pathophysiological condition frequently occurring in VaD. It is generally associated with neurovascular degeneration, in which neuronal damage and blood-brain barrier alterations coexist and evoke beta-amyloid-induced oxidative and nitrosative stress, mitochondrial dysfunction, and inflammasome- promoted neuroinflammation, which contribute to and exacerbate the course of disease. Vascular cognitive impairment comprises a heterogeneous group of cognitive disorders of various severity and types that share a presumed vascular etiology. The present study reviews major pathogenic factors involved in VaD, highlighting the relevance of cerebrocellular stress and hormetic responses to neurovascular insult, and addresses these mechanisms as potentially viable and valuable as foci of novel neuroprotective methods to mitigate or prevent VaD. © 2016 Wiley Periodicals, Inc.

Does Chronic Unpredictable Stress during Adolescence Affect Spatial Cognition in Adulthood?

Spatial abilities allow animals to retain and cognitively manipulate information about their spatial environment and are dependent upon neural structures that mature during adolescence. Exposure to stress in adolescence is thought to disrupt neural maturation, possibly compromising cognitive processes later in life. We examined whether exposure to chronic unpredictable stress in adolescence affects spatial ability in late adulthood. We evaluated spatial learning, reference and working memory, as well as long-term retention of visuospatial cues using a radial arm water maze. We found that stress in adolescence decreased the rate of improvement in spatial learning in adulthood. However, we found no overall performance impairments in adult reference memory, working memory, or retention caused by adolescent-stress. Together, these findings suggest that adolescent-stress may alter the strategy used to solve spatial challenges, resulting in performance that is more consistent but is not refined by incorporating available spatial information. Interestingly, we also found that adolescent-stressed rats showed a shorter latency to begin the water maze task when re-exposed to the maze after an overnight delay compared with control rats. This suggests that adolescent exposure to reoccurring stressors may prepare animals for subsequent reoccurring challenges. Overall, our results show that stress in adolescence does not affect all cognitive processes, but may affect cognition in a context-dependent manner.

HORMESIS: A Fundamental Concept with Widespread Biological and Biomedical Applications

Hormesis is a biphasic dose response with specific quantitative features for the amplitude and width of the stimulation. It is highly generalizable and independent of biological model, endpoint, inducing agent, level of biological organization and mechanism. Hormesis may be induced via a direct stimulation or by overcompensation to a disruption of homeostasis. The induction of hormesis by low-level stressor agents not only rapidly upregulates adaptive processes to repair damage but also protects the adapted system from damage due to a subsequent challenging dose (toxic) within a definable temporal window. The striking consistency of the amplitude of hormetic response suggests that hormesis provides a quantitative description of biological plasticity. Knowledge of hormesis has particular potential biomedical significance with respect to slowing or retarding both normal aging processes and the progression of severe neurological diseases.