Oxidative stress response and Nrf2 signaling in aging

Protein kinase Cδ knockout mice are protected from cocaine-induced hepatotoxicity

We investigated whether protein kinase Cδ (PKCδ) mediates cocaine-induced hepatotoxicity in mice. Cocaine treatment (60 mg/kg, i.p.) significantly increased cleaved PKCδ expression in the liver of wild-type (WT) mice, and led to significant increases in oxidative parameters (i.e., reactive oxygen species, 4-hydroxylnonenal and protein carbonyl). These cocaine-induced oxidative burdens were attenuated by pharmacological (i.e., rottlerin) or genetic depletion of PKCδ. We also demonstrated that treatment with cocaine resulted in significant increases in nuclear factor erythroid-2-related factor 2 (Nrf-2) nuclear translocation and increased Nrf-2 DNA-binding activity in wild-type (WT) mice. These increases were more pronounced in the rottlerin-treated WT or PKCδ knockout mice than in the saline-treated WT mice. Although cocaine treatment increased Nrf-2 nuclear translocation, DNA binding activity, and γ-glutamyl cysteine ligases (i.e., GCLc and GCLm) mRNA expressions, while it reduced the glutathione level and GSH/GSSG ratio. These decreases were attenuated by PKCδ depletion. Cocaine treatment significantly increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the serum of WT mice signifying the hepatic damage. These increases were also attenuated by PKCδ depletion. In addition, cocaine-induced hepatic degeneration in WT mice was evident 1 d post-cocaine. At that time, cocaine treatment decreased Bcl-2 and Bcl-xL levels, and increased Bax, cytosolic cytochrome c, and cleaved caspase-3 levels. Pharmacological or genetic depletion of PKCδ significantly ameliorated the pro-apoptotic properties and hepatic degeneration. Therefore, our results suggest that inhibition of PKCδ, as well as activation of Nrf-2, is important for protecting against hepatotoxicity induced by cocaine.

Sonodynamic therapy induces oxidative stress, DNA damage and apoptosis in glioma cells

Malignant glioma remains one of the most challenging diseases to treat because of the invasive growth of glioma cells and the existence of the blood-brain barrier (BBB), which blocks drug delivery to the brain. New strategies are urgently needed to overcome these shortcomings and improve the outcomes. Ultrasound represents a promising noninvasive and reversible BBB opening approach and the related sonodynamic therapy (SDT) is rapidly emerging. This study aims to explore the ultrasound parameters for BBB opening and the cell killing effect of SDT in human glioma U373 cells by using a recently reported sonosensitizer, sinoporphyrin sodium (DVDMS). The in vitro BBB model indicated that SDT caused a time-dependent permeability increase, which peaked at 2 h post treatment and then recovered gradually. The results of toxicology tests showed significant U373 cell viability loss and apoptosis increase after DVDMS-SDT, accompanied by enhanced cleaved-caspase-3 level and DNA fragmentation, in which reactive oxygen species (ROS) were a major triggering intermediate during DVDMS-SDT. Furthermore, DVDMS-SDT produced DNA damage and the underlying mechanisms were evaluated, in order to provide a fundamental basis for DVDMS-SDT application in glioma therapy. The findings indicated that the DNA molecules could be temporarily regulated by SDT and DNA double-strand breaks (DSBs), which increased the difficulty of cellular self-repair, thus aggravating cell apoptosis and inhibiting glioma cell invasive growth. Therefore, this study supports the use of SDT as an alternative approach for glioma therapy.

The Synergy of Aging and LPS Exposure in a Mouse Model of Parkinson's Disease

Aging is an inevitable physiological challenge occurring in organisms over time, and is also the most important risk factor of neurodegenerative diseases. In this study, we observed cellular and molecular changes of different age mice and LPS-induced Parkinson disease (PD) model. The results showed that behavioral performance and dopaminergic (DA) neurons were declined, accompanied by increased expression of pro-inflammatory factors (TLR2, p-NF-kB-p65, IL-1β and TNF-α), as well as pro-oxidative stress factor gp91phox in aged mice compared with young mice. Aging exaggerated inflammatory M1 microglia, and destroyed the balance between oxidation and anti-oxidation. The intranasal LPS instillation induced PD model in both young and aged mice. The poor behavioral performance and the loss of DA neurons as well as TLR2, p-NF-kB-p65, IL-1β, TNF-α, iNOS and gp91phox were further aggravated in LPS-aged mice. Interestingly, the expression of Nrf2 and HO-1 was up-regulated by LPS only in young LPS-PD mice, but not in aged mice. The results indicate that the synergy of aging process and LPS exposure may prominently aggravate the DA neurons loss caused by more serious neuroinflammation and oxidative stress in the brain.

A distinct class of antioxidant response elements is consistently activated in tumors with NRF2 mutations

NRF2 is a redox-responsive transcription factor that regulates expression of cytoprotective genes via its interaction with DNA sequences known as antioxidant response elements (AREs). NRF2 activity is induced by oxidative stress, but oxidative stress is not the only context in which NRF2 can be activated. Mutations that disrupt the interaction between NRF2 and KEAP1, an inhibitor of NRF2, lead to NRF2 hyperactivation and promote oncogenesis. The mechanisms underlying NRF2's oncogenic properties remain unclear, but likely involve aberrant expression of select NRF2 target genes. We tested this possibility using an integrative genomics approach to get a precise view of the direct NRF2 target genes dysregulated in tumors with NRF2 hyperactivating mutations. This approach revealed a core set of 32 direct NRF2 targets that are consistently upregulated in NRF2 hyperactivated tumors. This set of NRF2 "cancer target genes" includes canonical redox-related NRF2 targets, as well as target genes that have not been previously linked to NRF2 activation. Importantly, NRF2-driven upregulation of this gene set is largely independent of the organ system where the tumor developed. One key distinguishing feature of these NRF2 cancer target genes is that they are regulated by high affinity AREs that fall within genomic regions possessing a ubiquitously permissive chromatin signature. This implies that these NRF2 cancer target genes are responsive to oncogenic NRF2 in most tissues because they lack the regulatory constraints that restrict expression of most other NRF2 target genes. This NRF2 cancer target gene set also serves as a reliable proxy for NRF2 activity, and high NRF2 activity is associated with significant decreases in survival in multiple cancer types. Overall, the pervasive upregulation of these NRF2 cancer targets across multiple cancers, and their association with negative outcomes, suggests that these will be central to dissecting the functional implications of NRF2 hyperactivation in several cancer contexts.

Cx26 partial loss causes accelerated presbycusis by redox imbalance and dysregulation of Nfr2 pathway

Mutations in GJB2, the gene that encodes connexin 26 (Cx26), are the most common cause of sensorineural hearing impairment. The truncating variant 35delG, which determines a complete loss of Cx26 protein function, is the prevalent GJB2 mutation in several populations. Here, we generated and analyzed Gjb2+/- mice as a model of heterozygous human carriers of 35delG. Compared to control mice, auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) worsened over time more rapidly in Gjb2+/- mice, indicating they were affected by accelerated age-related hearing loss (ARHL), or presbycusis. We linked causally the auditory phenotype of Gjb2+/- mice to apoptosis and oxidative damage in the cochlear duct, reduced release of glutathione from connexin hemichannels, decreased nutrient delivery to the sensory epithelium via cochlear gap junctions and deregulated expression of genes that are under transcriptional control of the nuclear factor erythroid 2-related factor 2 (Nrf2), a pivotal regulator of tolerance to redox stress. Moreover, a statistically significant genome-wide association with two genes (PRKCE and TGFB1) related to the Nrf2 pathway (p-value < 4 × 10-2) was detected in a very large cohort of 4091 individuals, originating from Europe, Caucasus and Central Asia, with hearing phenotype (including 1076 presbycusis patients and 1290 healthy matched controls). We conclude that (i) elements of the Nrf2 pathway are essential for hearing maintenance and (ii) their dysfunction may play an important role in the etiopathogenesis of human presbycusis.

Oxidative stress and mitochondrial dysfunction contributes to postoperative cognitive dysfunction in elderly rats

Postoperative cognitive dysfunction (POCD) is defined by cognitive impairment determined by neuropsychological tests from before to after surgery. Several mechanisms have been proposed in this bidirectional communication between the immune system and the brain after surgery. We aimed at understanding the mechanisms underlying POCD elderly rats in an experimental tibial fracture model. Elderly male Wistar rats were subjected to tibial fracture (TF) model. Control (sham) and fracture (TF) groups were followed to determine nitrite/nitrate concentration; oxidative damage to lipids and proteins; the activity of antioxidant enzymes (superoxide dismutase-SOD and catalase-CAT), mitochondrial respiratory chain enzymes, and creatine kinase (CK); and BDNF levels in the hippocampus and prefrontal cortex (at 24 h and at seven days) and cognitive function through habituation to the open field task and novel object recognition task (only at seven days). TF group presented increased concentration of nitrite/nitrate, hippocampal lipid peroxidation at seven days, protein oxidative damage in the prefrontal cortex and hippocampus at 24 h, decreased antioxidant activity in both structures on the first postoperative day and compromised function of the mitochondrial respiratory chain complexes as well as the CK enzyme. In addition, the levels of BDNF were reduced and memory function was impaired in the TF group. In conclusion, elderly rats submitted to an experimental model of tibial fracture displayed memory impairment accompanied by an increase in oxidative stress, mitochondrial dysfunction and reduced neurotrophin level.

Targeting Crosstalk between Nrf-2, NF-κB and Androgen Receptor Signaling in Prostate Cancer

Oxidative stress, inflammation and androgen receptor (AR) signaling play a pivotal role in the initiation, development and progression of prostate cancer (PCa). Numerous papers in the literature have documented the interconnection between oxidative stress and inflammation; and how antioxidants can combat the inflammation. It has been shown in the literature that both oxidative stress and inflammation regulate AR, the key receptor involved in the transition of PCa to castration resistant prostate cancer (CRPC). In this review, we discuss about the importance of targeting Nrf-2-antioxidant signaling, NF-κB inflammatory response and AR signaling in PCa. Finally, we discuss about the crosstalk between these three critical pathways as well as how the anti-inflammatory antioxidant phytochemicals like sulforaphane (SFN) and curcumin (CUR), which can also target AR, can be ideal candidates in the chemoprevention of PCa.

[Antioxidant and anti-inflammatory modulation of exercise during aging]

Aging is characterised by a gradual loss of the functional reserve. This, along with the fostering of sedentary habits and the increase in risk factors, causes a deterioration of antioxidant defences and an increase of the circulatory levels of inflammatory and oxidative markers, boosting a low-rate chronic inflammation, defined as inflamm-aging. This phenomenon is present in the aetiopathology of chronic diseases, as well as in cognitive deterioration cases associated with aging. The objective of this review is to describe the modulation of antioxidant and anti-inflammatory effects of physical exercise of moderate intensity and volume in the elderly. Evidence of its effectiveness as a non-pharmacological resource is presented, which decreases some deleterious effects of aging. This is mainly due to its neuroprotective action, the increase in circulating anti-inflammatory markers, and the improvement of antioxidant defence derived from its practice.

Activation of Nrf2 signaling by salvianolic acid C attenuates NF‑κB mediated inflammatory response both in vivo and in vitro

Neurodegenerative diseases are closely related to neuroinflammation. Drugs targeting inflammation have been proved to be effective in many animal models. Salvianolic acid C (SalC) is a compound isolated from Salvia miltiorrhiza Bunge, a plant with reported effects of inhibiting inflammation. However, the anti-inflammation effects and biological mechanisms of SalC on LPS-stimulated neuroinflammation remain unknown. The aim of this paper was to study its protective effects and its anti-inflammation mechanisms. LPS was used both in vivo and in vitro to induce neuroinflammation in SD rats and microglia cells. MTT assay was carried out to detect cell viability. The levels of TNF‑α, IL‑1β, IL‑6, IL‑10 and PGE₂ were detected by ELISA method. The expressions of p‑AMPK, p‑NF‑κB p65, p‑IκBα, Nrf2, HO‑1 and NQO1 proteins were examined by Western blot analysis. The nuclear translocation of NF‑κB p65 was studied by immunofluorescence assay. The specific Nrf2 siRNA was used to clarify the interaction between Nrf2 and NF‑κB p65. The AMPK inhibitor Compound C was used study the upstream protein of Nrf2. Results showed that LPS induced the overexpression of inflammatory cytokines and mediated the phosphorylation and nuclear translocation of NF‑κB p65 in rat brains and microglia cells. SalC reversed the inflammatory response induced by LPS and inhibited the NF‑κB activation. SalC also upregulated the expression of p‑AMPK, Nrf2, HO‑1 and NQO1. But the anti-inflammation and NF‑κB inhibition effects of SalC were attenuated by transfection with specific Nrf2 siRNA or interference with the potent AMPK inhibitor Compound C. In conclusion, SalC inhibited LPS-induced inflammatory response and NF‑κB activation through the activation of AMPK/Nrf2 signaling both in vivo and in vitro.

Dr. Jekyll and Mr. Hyde: Oxidizable phenol-generated reactive oxygen species enhance sulforaphane's antioxidant response element activation, even as they suppress Nrf2 protein accumulation

The transcription factor Nrf2 is a master regulator of antioxidant and cytoprotective genes, binding to antioxidant response elements (AREs) in their promoter regions. Due to the therapeutic role of the Nrf2/ARE system in oxidative homeostasis, its activation has been investigated in many pre-clinical and clinical trials for common chronic diseases. One of the most promising Nrf2 activators is sulforaphane, the subject of over 50 clinical trials. In this work, we examine the effect of reactive oxygen species (ROS) on sulforaphane's Nrf2/ARE activation in the non-tumorigenic keratinocyte cell line HaCaT, with the non-arylating oxidizable phenol, 2,5-di-tert-butylhydroquinone (dtBHQ), as the source of ROS. We find that, in combination with 2.5 µM sulforaphane, dtBHQ markedly enhances ARE-regulated gene expression, including expression of the cytoprotective proteins aldo-keto reductase family 1 member C1 (AKR1C1) and heme oxygenase-1 (HO-1). Additionally, sulforaphane's therapeutic window is widened by 12.5 µM dtBHQ. Our data suggest that H₂O₂ generated by dtBHQ oxidation is responsible for these effects, as shown by inclusion of catalase and by co-treatment with sulforaphane and H₂O₂. While sulforaphane treatment causes Nrf2 protein to accumulate as expected, interestingly, dtBHQ and H₂O₂ appear to act on targets downstream of Nrf2 protein accumulation to enhance sulforaphane's ARE-regulated gene expression. Inclusion of dtBHQ or H₂O₂ with sulforaphane does not increase Nrf2 protein levels, and catalase has little effect on Nrf2 protein levels in the presence of sulforaphane and dtBHQ. Surprisingly, dtBHQ suppresses Nrf2 protein synthesis. Inclusion of a superoxide dismutase mimetic with sulforaphane and dtBHQ partly rescues Nrf2 suppression and significantly further increases sulforaphane's efficacy for ARE-reporter expression. Thus, there is a "Dr. Jekyll and Mr. Hyde" effect of ROS: ROS enhance sulforaphane's ARE-regulated gene expression even as they also inhibit Nrf2 protein synthesis. This unexpected finding reveals the degree to which targets in the ARE pathway downstream of Nrf2 protein accumulation contribute to gene expression. The results presented here provide a model system for significant enhancement of sulforaphane's potency with small molecule co-treatment.

A novel and compact review on the role of oxidative stress in female reproduction

In recent years, the study of oxidative stress (OS) has become increasingly popular. In particular, the role of OS on female fertility is very important and has been focused on closely. The occurrence of OS is due to the excessive production of reactive oxygen species (ROS). ROS are a double-edged sword; they not only play an important role as secondary messengers in many intracellular signaling cascades, but they also exert indispensable effects on pathological processes involving the female genital tract. ROS and antioxidants join in the regulation of reproductive processes in both animals and humans. Imbalances between pro-oxidants and antioxidants could lead to a number of female reproductive diseases. This review focuses on the mechanism of OS and a series of female reproductive processes, explaining the role of OS in female reproduction and female reproductive diseases caused by OS, including polycystic ovary syndrome (PCOS), endometriosis, preeclampsia and so on. Many signaling pathways involved in female reproduction, including the Keap1-Nrf2, NF-κB, FOXO and MAPK pathways, which are affected by OS, are described, providing new ideas for the mechanism of reproductive diseases.

Adaptive homeostasis and the free radical theory of ageing

The Free Radical Theory of Ageing, was first proposed by Denham Harman in the mid-1950's, based largely on work conducted by Rebeca Gerschman and Daniel Gilbert. At its core, the Free Radical Theory of Ageing posits that free radical and related oxidants, from the environment and internal metabolism, cause damage to cellular constituents that, over time, result in an accumulation of structural and functional problems. Several variations on the original concept have been advanced over the past six decades, including the suggestion of a central role for mitochondria-derived reactive species, and the proposal of an age-related decline in the effectiveness of protein, lipid, and DNA repair systems. Such innovations have helped the Free Radical Theory of Aging to achieve widespread popularity. Nevertheless, an ever-growing number of apparent 'exceptions' to the Theory have seriously undermined its acceptance. In part, we suggest, this has resulted from a rather simplistic experimental approach of knocking-out, knocking-down, knocking-in, or overexpressing antioxidant-related genes to determine effects on lifespan. In some cases such experiments have yielded results that appear to support the Free Radical Theory of Aging, but there are just as many published papers that appear to contradict the Theory. We suggest that free radicals and related oxidants are but one subset of stressors with which all life forms must cope over their lifespans. Adaptive Homeostasis is the mechanism by which organisms dynamically expand or contract the homeostatic range of stress defense and repair systems, employing a veritable armory of signal transduction pathways (such as the Keap1-Nrf2 system) to generate a complex profile of inducible and enzymatic protection that best fits the particular need. Viewed as a component of Adaptive Homeostasis, the Free Radical Theory of Aging appears both viable and robust.

Expression and localization of nuclear factor erythroid 2-related factor 2 in the ovarian tissues of mice at different ages

The aim of the present study was to investigate the expression and localization of nuclear factor erythroid 2-related factor 2 (Nrf2) in the ovaries of mice in different age groups, and to explore the association between Nrf2 and premature ovarian aging. The present study identified the localization of Nrf2 protein by performing immunohistochemical assay of ovarian tissues obtained from mice in different age groups. The mRNA expression levels of Nrf2 were detected via reverse transcription-quantitative polymerase chain reaction, while the expression levels of Nrf2 protein and apoptosis-associated proteins, including Caspase3 and B-cell lymphoma 2 (Bcl-2), were evaluated by western blot analysis. The results revealed that Nrf2 protein was mainly localized in granulosa cells, as well as in the secondary follicles and antral follicles of oocytes. Nrf2 expression levels were significantly lower in mice aged 4 days compared with 12-week-old mice (P<0.05), and the level of Nrf2 was lower in mice aged 40 weeks compared with those aged 12 weeks (P<0.05). In addition, the expression of the apoptosis protein Caspase3 in the ovarian tissue of mice aged 3, 8 and 12 weeks remained markedly greater when compared with those aged 4 days and 40 weeks. Bcl-2, an anti-apoptotic protein, was also significantly expressed in the ovarian tissues of juvenile (4-day-old) mice when compared with mice aged >40 weeks (P<0.05). In conclusion, Nrf2 was highly expressed in the ovarian tissues of mice of childbearing age (8–12 weeks old) and may possibly be involved in ovarian regulatory functions. The results indicated that Nrf2 expression and localization may have important implications in the prevention of ovarian aging.

Heme Oxygenase 1 in the Nervous System: Does It Favor Neuronal Cell Survival or Induce Neurodegeneration?

Heme oxygenase 1 (HO-1) up-regulation is recognized as a pivotal mechanism of cell adaptation to stress. Under control of different transcription factors but with a prominent role played by Nrf2, HO-1 induction is crucial also in nervous system response to damage. However, several lines of evidence have highlighted that HO-1 expression is associated to neuronal damage and neurodegeneration especially in Alzheimer’s and Parkinson’s diseases. In this review, we summarize the current literature regarding the role of HO-1 in nervous system pointing out different molecular mechanisms possibly responsible for HO-1 up-regulation in nervous system homeostasis and neurodegeneration.

Dysregulation of Mesenchymal Stromal Cell Antioxidant Responses in Progressive Multiple Sclerosis

The potential of autologous cell-based therapies including those using multipotent mesenchymal stromal cells (MSCs) is being investigated for multiple sclerosis (MS) and other neurological conditions. However, the phenotype of MSC in neurological diseases has not been fully characterized. We have previously shown that MSC isolated from patients with progressive MS (MS-MSC) have reduced expansion potential, premature senescence, and reduced neuroprotective potential in vitro. In view of the role of antioxidants in ageing and neuroprotection, we examined the antioxidant capacity of MS-MSC demonstrating that MS-MSC secretion of antioxidants superoxide dismutase 1 (SOD1) and glutathione S-transferase P (GSTP) is reduced and correlates negatively with the duration of progressive phase of MS. We confirmed reduced expression of SOD1 and GSTP by MS-MSC along with reduced activity of SOD and GST and, to examine the antioxidant capacity of MS-MSC under conditions of nitrosative stress, we established an in vitro cell survival assay using nitric oxide-induced cell death. MS-MSC displayed differential susceptibility to nitrosative stress with accelerated senescence and greater decline in expression of SOD1 and GSTP in keeping with reduced expression of master regulators of antioxidant responses nuclear factor erythroid 2-related factor 2 and peroxisome proliferator-activated receptor gamma coactivator 1-α. Our results are compatible with dysregulation of antioxidant responses in MS-MSC and have significant implications for development of autologous MSC-based therapies for MS, optimization of which may require that these functional deficits are reversed. Furthermore, improved understanding of the underlying mechanisms may yield novel insights into MS pathophysiology and biomarker identification. Stem Cells Translational Medicine 2018;7:748-758.

Genetic reduction of Nrf2 exacerbates cognitive deficits in a mouse model of Alzheimer's disease

Aging is the major risk factor for several neurodegenerative diseases, including Alzheimer's disease (AD). However, the mechanisms by which aging contributes to neurodegeneration remain elusive. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a transcription factor that regulates expression of a vast number of genes by binding to the antioxidant response element. Nrf2 levels decrease as a function of age, and reduced Nrf2 levels have been reported in postmortem human brains and animal models of AD. Nevertheless, it is still unknown whether Nrf2 plays a role in the cognitive deficits associated with AD. To address this question, we used a genetic approach to remove the Nrf2 gene from APP/PS1 mice, a widely used animal model of AD. We found that the lack of Nrf2 significantly exacerbates cognitive deficits in APP/PS1, without altering gross motor function. Specifically, we found an exacerbation of deficits in spatial learning and memory, as well as in working and associative memory. Different brain regions control these behavioral tests, indicating that the lack of Nrf2 has a global effect on brain function. The changes in cognition were linked to an increase in Aβ and interferon-gamma (IFNγ) levels, and microgliosis. The changes in IFNγ levels are noteworthy as previously published evidence indicates that IFNγ can increase microglia activation and induce Aβ production. Our data suggest a clear link between Nrf2 and AD-mediated cognitive decline and further strengthen the connection between Nrf2 and AD.

β-glucan Salecan Improves Exercise Performance and Displays Anti-Fatigue Effects through Regulating Energy Metabolism and Oxidative Stress in Mice

Fatigue induced by prolonged exercise not only leads to the decrease of exercise capacity, but also might be the cause of many diseases. In consideration of the side effects of pharmacological drugs, dietary supplements seem to be a better choice to ameliorate exercise-induced fatigue. The present study aimed to investigate the anti-fatigue effect of Salecan, a novel water-soluble β-glucan, during exercise and explore the underlying mechanisms. Male Institute of Cancer Research (ICR) mice were divided into five groups, including the Rest group and the other four Swim-groups treated with Salecan at 0, 25, 50, and 100 mg/kg/day for four weeks. Salecan treatment markedly increased the exhaustive swimming time of mice in the forced swimming test. Exercise fatigue and injury-related biochemical biomarkers including lactate, blood urea nitrogen (BUN), creatinine kinase (CK), alanine transaminase (ALT), and aspartate transaminase (AST) were ameliorated by Salecan. Salecan reversed the decreased serum glucose levels and glycogen contents caused by exercise. In addition, Salecan improved oxidative stress induced by exercise through regulating Nrf2/HO–1/Trx signaling pathway. Thus, the beneficial effects of Salecan against fatigue may be due to its positive effects on energy metabolism and antioxidation defence. Our results suggest that Salecan could be a novel potential candidate for anti-fatigue dietary supplements.

MicroRNAs mediate the senescence-associated decline of NRF2 in endothelial cells

Oxidative stress predisposes to several aging-associated diseases, such as cardiovascular diseases and cancer. In aging, increase in the production of reactive oxygen species is typically accompanied with a decline in adaptive stress responses to oxidative stress. The decline is primarily due to a decrease in antioxidant production. Nuclear factor E2-Related Factor 2 (NRF2) is a key transcription factor regulating oxidative and electrophilic stress responses, but it has also been shown to play a role in the regulation of cell metabolism. NRF2 expression declines in aging, but the mechanisms remain unclear. In this study, we show that microRNAs (miRNAs) that are abundant in old endothelial cells decrease NRF2 expression by direct targeting of NRF2 mRNA. The effect is reversed by miRNA inhibition. The senescence-associated downregulation of NRF2 decreases endothelial glycolytic activity and stress tolerance both of which are restored after reinstating NRF2. Manipulation of the senescence-associated miRNA levels affects the glycolytic activity and stress tolerance consistently with the NRF2 results. We conclude that senescence-associated miRNAs are involved in the decline of NRF2 expression, thus contributing to the repression of adaptive responses during cell senescence.

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A post-transcriptional mechanism for NRF2 downregulation in aging is proposed.

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The mechanism implicates senescence-associated miRNA alterations in NRF2 decline.

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Inhibition of senescence-associated miRNA function increases NRF2 expression in old cells.

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Upregulation of NRF2 increases cell viability.

Aging attenuates redox adaptive homeostasis and proteostasis in female mice exposed to traffic-derived nanoparticles ('vehicular smog')

Environmental toxicants are catalysts for protein damage, aggregation, and the aging process. Fortunately, evolution selected adaptive homeostasis as a system to mitigate such damage by expanding the normal capacity to cope with toxic stresses. Little is known about the subcellular degradative responses to proteins oxidatively damaged by air pollution. To better understand the impact of environmental toxicants upon the adaptive homeostatic response, female C57BL/6 mice were exposed for 10 weeks to filtered air or reaerosolized vehicular-derived nano-scale particulate matter (nPM), at which point tissues from young (6 month) and middle-aged (21 month) mice were studied. We found significant increases of proteolytic capacity in lung, liver, and heart. Up to two-fold increases were seen in the 20S Proteasome, the Immunoproteasome, the mitochondrial Lon protease, and NF-E2-related factor 2 (Nrf2), a major transcriptional factor for these and other stress-responsive genes. The responses were equivalent in all organs, despite the indirect input of inhaled particles to heart and liver which are downstream of lung. To our knowledge, this is the first exploration of proteostatic responses to oxidative damage by air pollution. Although, middle-aged mice had higher basal levels, their Nrf2-responsive-genes exhibited no response to nanoparticulate exposure. We also found a parallel age-associated rise in the Nrf2 transcriptional inhibitors, Bach1 and c-Myc which appear to attenuate adaptive responses in older mammals, possibly explaining the 'age-ceiling effect.' This report extends prior findings in male mice by demonstrating the involvement of proteolytic responses to traffic-related air pollution in lung, liver, and heart of female mice, with an age-dependent loss of adaptive homeostasis.

The Role of Nrf2 in the Response to Normal Tissue Radiation Injury

The transcription factor Nrf2 is an important modulator of antioxidant and drug metabolism, carbohydrate and lipid metabolism, as well as heme and iron metabolism. Regulation of Nrf2 expression occurs transcriptionally and post-transcriptionally. Post-transcriptional regulation entails ubiquitination followed by proteasome-dependent degradation. Additionally, Nrf2-mediated gene expression is subject to negative regulation by ATF3, Bach1 and cMyc. Nrf2-mediated gene expression is an important regulator of a cell's response to radiation. Although a majority of studies have shown that Nrf2 deficient cells are radiosensitized and Nrf2 over expression confers radioresistance, Nrf2's role in mediating the radiation response of crypt cells is controversial. The Nrf2 activator CDDO attenuates radiation-mediated crypt injury, whereas intestinal crypts in Nrf2 null mice are radiation resistant. Further investigation is needed in order to define the relationship between Nrf2 and radiation sensitivity in Lgr5+ and Bmi1+ cells that regulate regeneration of crypt stem cells. In hematopoietic compartments Nrf2 promotes the survival of irradiated osteoblasts that support long-term hematopoietic stem cell (LT-HSC) niches. Loss of Nrf2 in LT-HSCs increases stem cell intrinsic radiosensitivity, with the consequence of lowering the LD50₃₀. An Nrf2 deficiency drives LT-HSCs from a quiescent to a proliferative state. This results in hematopoietic exhaustion and reduced engraftment after myoablative irradiation. The question of whether induction of Nrf2 in LT-HSC enhances hematopoietic reconstitution after bone marrow transplantation is not yet resolved. Irradiation of the lung induces pulmonary pneumonitis and fibrosis. Loss of Nrf2 promotes TGF-β/Smad signaling that induces ATF3 suppression of Nrf2-mediated target gene expression. This, in turn, results in elevated reactive oxygen species (ROS) and isolevuglandin adduction of protein that impairs collagen degradation, and may contribute to radiation-induced chronic cell injury. Loss of Nrf2 impairs ΔNp63 stem/progenitor cell mobilization after irradiation, while promoting alveolar type 2 cell epithelial-mesenchymal transitions into myofibroblasts. These studies identify Nrf2 as an important factor in the radiation response of normal tissue.

Nrf2 inhibits oxaliplatin-induced peripheral neuropathy via protection of mitochondrial function

Oxaliplatin-induced peripheral neuropathy (OIPN) is a severe, dose-limiting toxicity associated with cancer chemotherapy. The efficacy of antioxidant administration in OIPN is debatable, as the promising preliminary results obtained with a number of antioxidants have not been confirmed in larger clinical trials. Besides its antioxidant activity, the transcription factor, nuclear factor-erythroid 2 (NF-E2) p45-related factor 2 (Nrf2) plays a crucial role in the maintenance of mitochondrial homeostasis, and mitochondrial dysfunction is a key contributor to OIPN. Here, we have investigated the protective properties of Nrf2 in OIPN. Nrf2^-/- mice displayed severe mechanical allodynia and cold sensitivity and thus experienced increased peripheral nervous system injury compared to Nrf2^+/+ mice. Furthermore, Nrf2 knockout aggravated oxaliplatin-induced reactive oxygen species production, decreased the mitochondrial membrane potential, led to abnormal intracellular calcium levels, and induced cytochrome c-related apoptosis and overexpression of the TRP protein family. Sulforaphane-induced activation of the Nrf2 signaling pathway alleviated morphological alterations, mitochondrial dysfunction in dorsal root ganglion neurons, and nociceptive sensations in mice. Our findings reveal that Nrf2 may play a critical role in ameliorating OIPN, through protection of mitochondrial function by alleviating oxidative stress and inhibiting TRP protein family expression. This suggests that pharmacological or therapeutic activation of Nrf2 may be used to prevent or slow down the progression of OIPN.

To adapt or not to adapt: Consequences of declining Adaptive Homeostasis and Proteostasis with age

Many consequences of ageing can be broadly attributed to the inability to maintain homeostasis. Multiple markers of ageing have been identified, including loss of protein homeostasis, increased inflammation, and declining metabolism. Although much effort has been focused on characterization of the ageing phenotype, much less is understood about the underlying causes of ageing. To address this gap, we outline the age-associated consequences of dysregulation of 'Adaptive Homeostasis' and its proposed contributing role as an accelerator of the ageing phenotype. Adaptive Homeostasis is a phenomenon, shared across cells and tissues of both simple and complex organisms, that enables the transient plastic expansion or contraction of the homeostatic range to modulate stress-protective systems (such as the Proteasome, the Immunoproteasome, and the Lon protease) in response to varying internal and external environments. The age-related rise in the baseline of stress-protective systems and the inability to increase beyond a physiological ceiling is likely a contributor to the reduction and loss of Adaptive Homeostasis. We propose that dysregulation of Adaptive Homeostasis in the final third of lifespan is a significant factor in the ageing process, while successful maintenance of Adaptive Homeostasis below a physiological ceiling results in extended longevity.

Cardiovascular Adaptive Homeostasis in Exercise

Adaptive Homeostasis has been defined as, "The transient expansion or contraction of the homeostatic range in response to exposure to sub-toxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events." (Davies, 2016). I propose that one of the most significant examples of adaptive homeostasis may be the adaptation of the cardiovascular system to exercise training. In particular, endurance type training involves the generation of increased levels of free radicals such as ubisemiquinone, superoxide, nitric oxide, and other (non-radical) reactive oxygen species such as hydrogen peroxide (H2O2), in a repetitive manner, typically several times per week. As long as the training intensity and duration are sub-maximal and not exhaustive these reactive species do not cause damage, but rather activate signal transduction pathways to induce mitochondrial biogenesis-the foundation of increased exercise endurance. Particularly important are the NFκB and Nrf2 signal transduction pathways which respond to reactive oxygen and nitrogen species generated during exercise. As with other examples of adaptive homeostasis the effects are transient, lasting only as long as the training is maintained. Unfortunately, the ability to adapt to exercise training declines with age, perhaps as a result of impaired Nrf2 and NFκB signaling, as does adaptive homeostasis capacity in general. Since this is an Hypothesis/Theory Paper and not a review, I have not tried to provide a comprehensive discussion of all the literature relating to exercise adaptation and the cardiovascular system. Rather, I have attempted to develop the Hypothesis or Theory that adaptive homeostasis is the foundation for adaptation of the cardiovascular system to exercise training, largely based on work from my own laboratory, that of close collaborators, and that of key contributors over a period of almost 40 years.

Acetylcholinesterase Inhibition and Antioxidant Activity of N-trans-Caffeoyldopamine and N-trans-Feruloyldopamine

Phenolic acids and their derivatives found in nature are well-known for their potential biological activity. In this study, two amides derived from trans-caffeic/ferulic acid and dopamine were synthesized and characterized by Fourier-transform infrared spectroscopy (FTIR), mass spectrometry, proton and carbon-13 nuclear magnetic resonance spectroscopy. The compounds were tested for the inhibition of acetylcholinesterase (AChE) from Electrophorus electricus and for antioxidant activity by scavenging 2,2-diphenyl-1-pycrylhydrazyl free radical (DPPH^•) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS^•+), reducing ferric ions, and ferrous ions chelation. N-trans-Feruloyldopamine displayed the highest inhibitory effect on AChE with half-maximal inhibitory concentration (IC₅₀) values of 8.52 μM. In addition, an in silico study was done to determine the most favorable AChE cluster with the synthesized compounds. Further, these clusters were investigated for binding positions at the lowest free binding energy. Both synthesized hydroxycinnamates were found to be better antioxidants than the parent acids in in vitro tests applied. N-trans-Caffeoyldopamine showed the best antioxidant activity in the three tested methods—against non-biological stable free radicals IC₅₀ 5.95 μM for DPPH^•, 0.24 μM for the ABTS^•+ method, and for reducing power (ascorbic acid equivalent (AAE) 822.45 μmol/mmol)—while for chelation activity against Fe²⁺ ions N-trans-feruloyldopamine had slightly better antioxidant activity (IC₅₀ 3.17 mM).

Erythropoietin suppresses D-galactose-induced aging of rats via the PI3K/Akt/Nrf2-ARE pathway

EPO (erythropoietin) is a hormone-like substance with a putative role in hematopoietic regulation. Current research suggests that it exerts a neuroprotective effect by enhancing the activity of antioxidant enzymes. Our previous studies in vitro have confirmed that EPO can delay senescence of cultured neurons by activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and the phosphoinositide-3-kinase (PI3K)/AKT pathway. Thus we set out to further substantiate the mechanism in vivo. A rat model of aging was induced by continuous subcutaneous injection of 5% D-galactose for 6 weeks. Starting at the 7th week, physiological saline or EPO was administered twice daily. LY294002, an inhibitor of the PI3K/AKT pathway, was also given to one of the groups. Improvement of learning and memory abilities were observed in the EPO intervention group. Raised levels of Cu-Zn SOD protein were detected by immunohistochemical staining and Western blot after using EPO, together with increased expression of PI3K/AKT pathway proteins. Concomitantly, there was an increase in expression of Nrf2 mRNA and a decrease in expression of Keap1 mRNA by qRT-PCR. All these effects were not found in the group injected with LY294002. We conclude that EPO can suppress aging by reducing oxidative stress. The proposed mechanism is an upregulation of the PI3K/Akt/Nrf2-ARE pathway and thus maintenance of expression and activation of antioxidant enzymes in aging rats.

Nitrated fatty acids in cardiovascular diseases

Cardiovascular disease (CVD) is the leading cause of death and accounts for one third of disease-related mortality worldwide. Dysregulated redox mechanisms, in particular the formation of reactive oxygen species (ROS) play a pivotal pathogenetic role in CVD. Nitro-fatty acids (NO2-FAs) are electrophilic molecules which have a NO2-group bound to one of their olefinic carbons. They are endogenously formed by the reaction of reactive nitrogen species with unsaturated fatty acids. Basal levels of NO2-FAs are in the low nanomolar range and higher concentrations can be encountered under acidic (stomach) and inflammatory (e.g. ischemia/reperfusion) conditions. Dietary intake of polyunsaturated fatty acids in combination with nitrites raises circulating NO2-FAs to a clinically relevant level in mice. NO2-FAs undergo reversible covalent binding to cysteine residues and by virtue of these posttranslational protein modifications act as potent anti-inflammatory signaling mediators via modulation of various critical pathways like nuclear factor E2-related factor 2 (Nrf2)- and peroxisome proliferator-activated receptor γ (PPARγ) activation, nuclear factor-kappa B (NF-κB) inhibition and hem oxygenase-1 (HO-1)- and heat shock protein (HSP) induction. In this review article, we summarize recent findings about the effects and underlying molecular mechanisms of NO2-FAs from a variety of pre-clinical cardiovascular disease models. The described findings suggest the potential of NO2-FAs to emerge as therapeutic agents with a broad range of potential clinical applications for CVD.

Protein aggregates and proteostasis in aging: Amylin and β-cell function

The ubiquitin-proteasomal-system (UPS) and the autophagy-lysosomal-system (ALS) are both highly susceptible for disturbances leading to the accumulation of cellular damage. A decline of protein degradation during aging results in the formation of oxidatively damaged and aggregated proteins finally resulting in failure of cellular functionality. Besides protein aggregation in response to oxidative damage, amyloids are a different type of protein aggregates able to distract proteostasis and interfere with cellular functionality. Amyloids are clearly linked to the pathogenesis of age-related degenerative diseases such as Alzheimer's disease. Human amylin is one of the peptides forming fibrils in β-sheet conformation finally leading to amyloid formation. In contrast to rodent amylin, human amylin is prone to form amyloidogenic aggregates, proposed to play a role in the pathogenesis of Type 2 Diabetes by impairing β-cell functionality. Since aggregates such as lipofuscin and β-amyloid are known to impair proteostasis, it is likely to assume similar effects for human amylin. In this review, we focus on the effects of IAPP on UPS and ALS and their role in amylin degradation, since both systems play a crucial role in maintaining proteome balance thereby influencing, at least in part, cellular fate and aging.

Cytoprotective effects of diosmetin against hydrogen peroxide-induced L02 cell oxidative damage via activation of the Nrf2-ARE signaling pathway

Oxidative stress is considered a crucial mediator in the pathogenesis of various liver diseases. The flavone diosmetin has been reported to exhibit antioxidant activities; however, the hepatoprotective effects of diosmetin against oxidative stress, and the underlying molecular mechanisms, remain unknown. The present study aimed to investigate the potential hepatoprotective effects of diosmetin on hydrogen peroxide (H2O2)‑induced oxidative damage in L02 cells and attempted to evaluate the role of the nuclear factor erythroid 2‑related factor 2 (Nrf2)/antioxidant response element pathway in this process. L02 cells were divided into groups: Control (DMSO, diosmetin), H2O2, Trolox or tertiary butylhydroquinone and diosmetin (different doses). Protective effects in L02 cells were determined by CCK‑8, cell apoptosis and lactate dehydrogenase leakage assays. Flow cytometry and inverted fluorescence microscope were used to measure the intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). Protein expression levels were of Nrf2, heme oxygenase‑1 (HO‑1) and NAD(P)H quinone oxidoreductase‑1 (NQO1) were determined by western blotting and mRNA levels were determined by reverse transcription‑quantitative polymerase chain reaction. The results revealed that H2O2 induced notable injury to L02 cells, as demonstrated by decreased cell viability, increased lactate dehydrogenase release, apoptotic rate and intracellular ROS production, and by the loss of MMP. Conversely, diosmetin (20‑40 µM) significantly reversed the damaging effects of H2O2, which indicated that diosmetin may exhibit potent hepatoprotective potential against H2O2‑induced oxidative damage. Furthermore, pretreatment with diosmetin elevated mRNA and protein expression levels of Nrf2, HO‑1 and NQO1. The present study is the first, to the best of our knowledge, to demonstrate that activation of the Nrf2/NQO1‑HO‑1 signaling pathway maybe involved in the cytoprotective effects of diosmetin against oxidative stress. Therefore, diosmetin may be considered a promising therapeutic agent for the treatment of various liver diseases associated with oxidative stress.

Selective cytotoxicity of the herbal substance acteoside against tumor cells and its mechanistic insights

Natural products are characterized by extreme structural diversity and thus they offer a unique source for the identification of novel anti-tumor agents. Herein, we report that the herbal substance acteoside being isolated by advanced phytochemical methods from Lippia citriodora leaves showed enhanced cytotoxicity against metastatic tumor cells; acted in synergy with various cytotoxic agents and it sensitized chemoresistant cancer cells. Acteoside was not toxic in physiological cellular contexts, while it increased oxidative load, affected the activity of proteostatic modules and suppressed matrix metalloproteinases in tumor cell lines. Intraperitoneal or oral (via drinking water) administration of acteoside in a melanoma mouse model upregulated antioxidant responses in the tumors; yet, only intraperitoneal delivery suppressed tumor growth and induced anti-tumor-reactive immune responses. Mass-spectrometry identification/quantitation analyses revealed that intraperitoneal delivery of acteoside resulted in significantly higher, vs. oral administration, concentration of the compound in the plasma and tumors of treated mice, suggesting that its in vivo anti-tumor effect depends on the route of administration and the achieved concentration in the tumor. Finally, molecular modeling studies and enzymatic activity assays showed that acteoside inhibits protein kinase C. Conclusively, acteoside holds promise as a chemical scaffold for the development of novel anti-tumor agents.

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Acteoside was not toxic in physiological cellular or tissue contexts.

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This natural compound modulated antioxidant responses and proteostatic modules.

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Acteoside showed in vitro and in vivo selective cytotoxicity against tumor cells.

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IP administration of acteoside in a mouse tumor model activated immune responses.

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Acteoside inhibited Protein Kinase C.

SC79 protects dopaminergic neurons from oxidative stress

Oxidative stress could lead to dopaminergic neuronal cell death. SC79 is a novel, selective and highly-efficient Akt activator. The current study tested its effect in dopaminergic neurons with oxidative stress. In both SH-SY5Y cells and primary murine dopaminergic neurons, pre-treatment with SC79 largely inhibited hydrogen peroxide (H2O2)-induced cell viability reduction, apoptosis and necrosis. SC79 activated Akt in the neuronal cells, which was required for its neuroprotection against H2O2. Inhibition of Akt activation (by MK-2206 or AT7867) or expression (by targeted short hairpin RNA) largely attenuated SC79-induced neuroprotection. Further, CRISPR-Cas9-mediated Akt1 knockout in SH-SY5Y cells abolished SC79-induced neuroprotective function against H2O2. Reversely, forced activation of Akt by the constitutively-active Akt1 mimicked SC79-induced anti-H2O2 activity. Together, we conclude that activation of Akt by SC79 protects dopaminergic neurons from H2O2.

Natural Dietary Pigments: Potential Mediators against Hepatic Damage Induced by Over-The-Counter Non-Steroidal Anti-Inflammatory and Analgesic Drugs

Over-the-counter (OTC) analgesics are among the most widely prescribed and purchased drugs around the world. Most analgesics, including non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen, are metabolized in the liver. The hepatocytes are responsible for drug metabolism and detoxification. Cytochrome P450 enzymes are phase I enzymes expressed mainly in hepatocytes and they account for ≈75% of the metabolism of clinically used drugs and other xenobiotics. These metabolic reactions eliminate potentially toxic compounds but, paradoxically, also result in the generation of toxic or carcinogenic metabolites. Cumulative or overdoses of OTC analgesic drugs can induce acute liver failure (ALF) either directly or indirectly after their biotransformation. ALF is the result of massive death of hepatocytes induced by oxidative stress. There is an increased interest in the use of natural dietary products as nutritional supplements and/or medications to prevent or cure many diseases. The therapeutic activity of natural products may be associated with their antioxidant capacity, although additional mechanisms may also play a role (e.g., anti-inflammatory actions). Dietary antioxidants such as flavonoids, betalains and carotenoids play a preventive role against OTC analgesics-induced ALF. In this review, we will summarize the pathobiology of OTC analgesic-induced ALF and the use of natural pigments in its prevention and therapy.

Sexual Dimorphism and Aging Differentially Regulate Adaptive Homeostasis

External and internal stimuli cause modifications to gene and biochemical pathways. In turn, demonstrating that biological systems continuously make short-term adaptations both to set-points, and to the range of "normal" capacity, due to mild conditional changes, or to subtoxic, nondamaging levels of chemical agents. This is termed as "Adaptive Homeostasis," defined with the following: "The transient expansion or contraction of the homeostatic range in response to exposure to sub-toxic, nondamaging, signaling molecules or events, or the removal or cessation of such molecules or events." Research from several laboratories, including our own, found that adaptive homeostasis declines with age in organisms as diverse as worms, flies, and mammals, and decreases with senescence in mammalian cell cultures. We suggest that diminishing adaptive homeostasis may play a causal role as a factor responsible for the aging phenotype. Furthermore, although studies of humans, animals, and model organisms are often limited to a single sex, and cell culture studies may even be conducted with lines whose donor's sex was unknown, studies reveal distinct sexual dimorphism in adaptive homeostasis. Interestingly, although young males and females may exhibit dramatic differences in adaptive capacities and/or preferences, these distinctions are lost with age as adaptive homeostasis patterns converge.

Conjugated linoleic acid prevents age-dependent neurodegeneration in a mouse model of neuropsychiatric lupus via the activation of an adaptive response

Oxidative stress is a key mediator of autoimmune/neurodegenerative disorders. The antioxidant/anti-inflammatory effect of a synthetic conjugated linoleic acid (CLA) mixture in MRL/MpJ-Fas lpr mice (MRL/lpr), an animal model of neuropsychiatric lupus, was previously associated with the improvement of nuclear factor-E2-related factor 2 (Nrf2) defenses in the spleen and liver. However, little is known about the neuroprotective ability of a CLA mixture. This study investigated the age-dependent progression of oxidative stress and the hyperactivation of redox-sensitive compensatory pathways (macroautophagy, Nrf2) in old/diseased MRL/lpr mice brains and examines the effect produced by dietary CLA supplementation. Disrupted redox homeostasis was evidenced in the blood, liver, and brain of 21- to 22-week-old MRL/lpr (Old) mice compared with 8- to 10-week-old MRL/lpr (Young) animals. This alteration was associated with significant hyperactivation of compensatory mechanisms (macroautophagy, Nrf2, and astrocyte activation) in the brains of Old mice. Five-week daily supplementation with CLA (650 mg/kg-1 body weight) of 16-week-old (CLA+Old) mice diminished all the pathological hallmarks at a level comparable to Young mice or healthy controls (BALB/c). Such data demonstrated that MRL/lpr mice can serve as a valuable model for the evaluation of the effectiveness of neuroprotective drugs. Notably, the preventive effect provided by CLA supplementation against age-associated neuronal damage and hyperactivation of compensatory mechanisms suggests that the activation of an adaptive response is at least in part accountable for its neuroprotective ability.

Redox Regulation of Homeostasis and Proteostasis in Peroxisomes

Peroxisomes are highly dynamic intracellular organelles involved in a variety of metabolic functions essential for the metabolism of long-chain fatty acids, d-amino acids, and many polyamines. A byproduct of peroxisomal metabolism is the generation, and subsequent detoxification, of reactive oxygen and nitrogen species, particularly hydrogen peroxide (H2O2). Because of its relatively low reactivity (as a mild oxidant), H2O2 has a comparatively long intracellular half-life and a high diffusion rate, all of which makes H2O2 an efficient signaling molecule. Peroxisomes also have intricate connections to mitochondria, and both organelles appear to play important roles in regulating redox signaling pathways. Peroxisomal proteins are also subject to oxidative modification and inactivation by the reactive oxygen and nitrogen species they generate, but the peroxisomal LonP2 protease can selectively remove such oxidatively damaged proteins, thus prolonging the useful lifespan of the organelle. Peroxisomal homeostasis must adapt to the metabolic state of the cell, by a combination of peroxisome proliferation, the removal of excess or badly damaged organelles by autophagy (pexophagy), as well as by processes of peroxisome inheritance and motility. More recently the tumor suppressors ataxia telangiectasia mutate (ATM) and tuberous sclerosis complex (TSC), which regulate mTORC1 signaling, have been found to regulate pexophagy in response to variable levels of certain reactive oxygen and nitrogen species. It is now clear that any significant loss of peroxisome homeostasis can have devastating physiological consequences. Peroxisome dysregulation has been implicated in several metabolic diseases, and increasing evidence highlights the important role of diminished peroxisomal functions in aging processes.

Targeting NRF2 for Improved Skin Barrier Function and Photoprotection: Focus on the Achiote-Derived Apocarotenoid Bixin

The transcription factor NRF2 (nuclear factor-E2-related factor 2) orchestrates major cellular defense mechanisms including phase-II detoxification, inflammatory signaling, DNA repair, and antioxidant response. Recent studies strongly suggest a protective role of NRF2-mediated gene expression in the suppression of cutaneous photodamage induced by solar UV (ultraviolet) radiation. The apocarotenoid bixin, a Food and Drug Administration (FDA)-approved natural food colorant (referred to as 'annatto') originates from the seeds of the achiote tree native to tropical America, consumed by humans since ancient times. Use of achiote preparations for skin protection against environmental insult and for enhanced wound healing has long been documented. We have recently reported that (i) bixin is a potent canonical activator of the NRF2-dependent cytoprotective response in human skin keratinocytes; that (ii) systemic administration of bixin activates NRF2 with protective effects against solar UV-induced skin damage; and that (iii) bixin-induced suppression of photodamage is observable in Nrf2+/+ but not in Nrf2-/- SKH-1 mice confirming the NRF2-dependence of bixin-induced antioxidant and anti-inflammatory effects. In addition, bixin displays molecular activities as sacrificial antioxidant, excited state quencher, PPAR (peroxisome proliferator-activated receptor) α/γ agonist, and TLR (Toll-like receptor) 4/NFκB (nuclear factor kappa-light-chain-enhancer of activated B cells) antagonist, all of which might be relevant to the enhancement of skin barrier function and environmental stress protection. Potential skin photoprotection and photochemoprevention benefits provided by topical application or dietary consumption of this ethno-pharmacologically validated phytochemical originating from the Americas deserves further preclinical and clinical examination.

Isoprostanes as markers for muscle aging in older athletes

Introduction

Production of isoprostanes (IsoPs) is enhanced after acute, intense, and prolonged exercise, in untrained subjects. This effect is greater in older subjects. The present study aims to delineate the profile of acute-exercise-induced IsoPs levels in young and older endurance-trained subjects.

Methods

All included subjects were male, young (n = 6; 29 yrs ± 5.7) or older (n = 6; 63.7 yrs ± 2.3), and competitors. The kinetics of F₂-IsoPs in blood-sera was assessed at rest, for the maximal aerobic exercise power (MAP) corresponding to the cardio-respiratory fitness index and after a 30-min recovery period.

Results

No significant time effect on F₂-IsoPs kinetics was identified in young subjects. However, in older athletes, F₂-IsoPs blood-concentrations at the MAP were higher than at rest, whereas these blood-concentrations did not differ between rest and after the 30-min recovery period.

Conclusion

Because plasma glutathione (GSH) promotes the formation of some F₂-IsoPs, we suggest that the surprising decrease in F₂-IsoPs levels in older subjects would be caused by decreased GSH under major ROS production in older subjects. We argue that the assessment F₂-IsoPs in plasma as biomarkers of the aging process should be challenged by exercise to improve the assessment of the functional response against reactive oxygen species in older subjects.

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Acute exercise promotes an increase in F₂-IsoPs plasma level in older athletes.

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The F₂-IsoPs plasma level significantly decreased after recovery in older athletes.

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This kinetic of F₂-IsoPs could reflect a decrease of glutathione (GSH).

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Oxidative stress status determination should be challenged by exercise.

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Assessment of F₂-IsoPs plasma level should be paired to GSH assessment.

Nrf2 mediates the expression of BAG3 and autophagy cargo adaptor proteins and tau clearance in an age-dependent manner

During aging, decreased efficiency of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activation and autophagic processes in the brain may be a contributing factor in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease. Therefore, we analyzed the expression of Bcl-2-associated athanogene 3, a cochaperone that mediates autophagy, and the autophagy adaptors NBR1, NDP52, and sequestosome 1/p62 in the brains of 4-, 8-, and 12-month-old wild-type and Nrf2 knockout (-/-) mice. We also analyzed the levels of total tau and phospho-tau species. There were minimal differences in the expression of autophagy-related genes or tau species in 4-month-old animals; however, by 12 months, all of these autophagy-associated genes were expressed at significantly lower levels in the Nrf2 (-/-) mice. The decreases in the autophagy-associated genes were accompanied by significantly elevated levels of phospho-tau species in the 12-month-old Nrf2 (-/-) brains. These findings indicate that Nrf2 regulation of autophagy-related genes likely plays a greater role in mediating the clearance of tau as an organism ages.

Temporal changes in glutathione biosynthesis during the lipopolysaccharide-induced inflammatory response of THP-1 macrophages

How macrophages maintain redox homeostasis in the inflammatory process, in which a large amount of oxidants are produced, remains elusive. In this study, we investigated the temporal changes in the intracellular glutathione (GSH), the master antioxidant, and the expression of glutamate cysteine ligase (GCL), the rate-limiting enzyme for GSH biosynthesis, in the inflammatory response of human macrophages (THP1 cells) to lipopolysaccharide. Intracellular GSH concentration was decreased significantly in the early phase (~6h) of LPS exposure, and then gradually went back to the basal level in the late phase (9-24h). The expression level of the catalytic subunit of GCL (GCLC) followed a similar pattern of change as GSH: its mRNA and protein levels were reduced in the early phase and then back to basal level in the late phase. In contrast, the expression of the modifier subunit of GCL (GCLM) was significantly increased in the phase of LPS exposure. Activation Nrf2, the transcription factor involved in the induction of both GCLC and GCLM, occurred at as early as 3h after LPS exposure; whereas the activation of NF-κB occurred at as early as 30min. Inhibition of NF-κB signaling with SN50 prevented the decrease of GCLC and inhibited Nrf2 activation in response to LPS. These data demonstrate time-dependent changes in the expression of GCL and Nrf2 signaling during the inflammatory response, and that the regulation of GCLC and GCLM might be through different pathways in this process.

Curcumin revitalizes Amyloid beta (25-35)-induced and organophosphate pesticides pestered neurotoxicity in SH-SY5Y and IMR-32 cells via activation of APE1 and Nrf2

Amyloid beta (Aβ) peptide deposition is the primary cause of neurodegeneration in Alzheimer's disease (AD) pathogenesis. Several reports point towards the role of pesticides in the AD pathogenesis, especially organophosphate pesticides (OPPs). Monocrotophos (MCP) and Chlorpyrifos (CP) are the most widely used OPPs. In this study, the role of MCP and CP in augmenting the Aβ-induced oxidative stress associated with the neurodegeneration in AD has been assessed in human neuroblastoma IMR-32 and SH-SY5Y cell lines. From the cell survival assay, it was observed that MCP and CP reduced cell survival both dose- and time-dependently. Nitro blue tetrazolium (NBT) based assay for determination of intracellular reactive oxygen species (ROS) demonstrated that Aβ(25-35), MCP or CP produce significant oxidative stress alone or synergistically in IMR-32 and SH-SY5Y cells, while pretreatment of curcumin reduced ROS levels significantly in all treatment combinations. In this study, we also demonstrate that treatment of Aβ(25-35) and MCP upregulated inducible nitric oxide synthase (iNOS/NOS2) whereas, no change was observed in neuronal nitric oxide synthase (nNOS/NOS1), but down-regulation of the nuclear factor erythroid 2-related factor 2 (Nrf2) level was observed. While curcumin pretreatment resulted in upregulation of iNOS and Nrf2 proteins. Also, the expression of key DNA repair enzymes APE1, DNA polymerase beta (Pol β), and PARP1 were found to be downregulated upon treatment with MCP, Aβ(25-35) and their combinations at 24 h and 48 h time points. In this study, pretreatment of curcumin to the SH-SY5Y cells enhanced the expression of DNA repair enzymes APE1, pol β, and PARP1 enzymes to counter the oxidative DNA base damage via base excision repair (BER) pathway, and also activated the antioxidant element (ARE) via Nrf2 upregulation. Furthermore, the immunofluorescent confocal imaging studies in SH-SY5Y and IMR-32 cells treated with Aβ(25-35) and MCP-mediated oxidative stress and their combinations at different time periods suggesting for cross-talk between the two proteins APE1 and Nrf2. The APE1's association with Nrf2 might be associated with the redox function of APE1 that might be directly regulating the ARE-mediated neuronal survival mechanisms.

Transcriptome profiling analysis of senescent gingival fibroblasts in response to Fusobacterium nucleatum infection

Periodontal disease is caused by dental plaque biofilms. Fusobacterium nucleatum is an important periodontal pathogen involved in the development of bacterial complexity in dental plaque biofilms. Human gingival fibroblasts (GFs) act as the first line of defense against oral microorganisms and locally orchestrate immune responses by triggering the production of reactive oxygen species and pro-inflammatory cytokines (IL-6 and IL-8). The frequency and severity of periodontal diseases is known to increase in elderly subjects. However, despite several studies exploring the effects of aging in periodontal disease, the underlying mechanisms through which aging affects the interaction between F. nucleatum and human GFs remain unclear. To identify genes affected by infection, aging, or both, we performed an RNA-Seq analysis using GFs isolated from a single healthy donor that were passaged for a short period of time (P4) 'young GFs' or for longer period of time (P22) 'old GFs', and infected or not with F. nucleatum. Comparing F. nucleatum-infected and uninfected GF(P4) cells the differentially expressed genes (DEGs) were involved in host defense mechanisms (i.e., immune responses and defense responses), whereas comparing F. nucleatum-infected and uninfected GF(P22) cells the DEGs were involved in cell maintenance (i.e., TGF-β signaling, skeletal development). Most DEGs in F. nucleatum-infected GF(P22) cells were downregulated (85%) and were significantly associated with host defense responses such as inflammatory responses, when compared to the DEGs in F. nucleatum-infected GF(P4) cells. Five genes (GADD45b, KLF10, CSRNP1, ID1, and TM4SF1) were upregulated in response to F. nucleatum infection; however, this effect was only seen in GF(P22) cells. The genes identified here appear to interact with each other in a network associated with free radical scavenging, cell cycle, and cancer; therefore, they could be potential candidates involved in the aged GF's response to F. nucleatum infection. Further studies are needed to confirm these observations.

Curcumin elevates sirtuin level but does not postpone in vitro senescence of human cells building the vasculature

It is believed that curcumin, a component of the turmeric that belongs to hormetins, possesses anti-aging propensity. This property of curcumin can be partially explained by its influence on the level of sirtuins. Previously, we have shown that relatively high (2.5-10 µM) doses of curcumin induce senescence of cancer cells and cells building the vasculature. In the present study we examined whether curcumin at low doses (0.1 and 1 µM) is able to delay cell senescence and upregulate the level of sirtuins in human cells building the vasculature, namely vascular smooth muscle (VSMC) and endothelial (EC) cells. To this end we used cells senescing in a replicative and premature manner. We showed that low doses of curcumin in case of VSMC neither postponed the replicative senescence nor protected from premature senescence induced by doxorubicin. Moreover, curcumin slightly accelerated replicative senescence of EC. Despite some fluctuations, a clear increasing tendency in the level of sirtuins was observed in curcumin-treated young, senescing or already senescent cells. Sirtuin activation could be caused by the activation of AMPK resulting from superoxide elevation and ATP reduction. Our results show that curcumin at low doses can increase the level of sirtuins without delaying senescence of VSMC.

'Molecular habituation' as a potential mechanism of gradual homeostatic loss with age

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Constitutive signals indicate homeostatic dysregulation but their effect on signal transduction remains largely unexplored.

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A theoretical approach is undertaken to examine how oxidative stress may affect redox signal transduction.

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Constitutive signals can result in a ‘molecular habituation’ effect that interferes with information transmission.

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The robustness of such a theoretical observation to the underlying methodology hints at the generality of this principle.

The ability of reactive oxygen species (ROS) to cause molecular damage has meant that chronic oxidative stress has been mostly studied from the point of view of being a source of toxicity to the cell. However, the known duality of ROS molecules as both damaging agents and cellular redox signals implies another perspective in the study of sustained oxidative stress. This is a perspective of studying oxidative stress as a constitutive signal within the cell. In this work, we adopt a theoretical perspective as an exploratory and explanatory approach to examine how chronic oxidative stress can interfere with signal processing by redox signalling pathways in the cell. We report that constitutive signals can give rise to a ‘molecular habituation’ effect that can prime for a gradual loss of biological function. This is because a constitutive signal in the environment has the potential to reduce the responsiveness of a signalling pathway through the prolonged activation of negative regulators. Additionally, we demonstrate how this phenomenon is likely to occur in different signalling pathways exposed to persistent signals and furthermore at different levels of biological organisation.

Reduced mitochondrial mass and function add to age-related susceptibility toward diet-induced fatty liver in C57BL/6J mice

Nonalcoholic fatty liver disease (NAFLD) is a major health burden in the aging society with an urging medical need for a better understanding of the underlying mechanisms. Mitochondrial fatty acid oxidation and mitochondrial‐derived reactive oxygen species (ROS) are considered critical in the development of hepatic steatosis, the hallmark of NAFLD. Our study addressed in C57BL/6J mice the effect of high fat diet feeding and age on liver mitochondria at an early stage of NAFLD development. We therefore analyzed functional characteristics of hepatic mitochondria and associated alterations in the mitochondrial proteome in response to high fat feeding in adolescent, young adult, and middle‐aged mice. Susceptibility to diet‐induced obesity increased with age. Young adult and middle‐aged mice developed fatty liver, but not adolescent mice. Fat accumulation was negatively correlated with an age‐related reduction in mitochondrial mass and aggravated by a reduced capacity of fatty acid oxidation in high fat‐fed mice. Irrespective of age, high fat diet increased ROS production in hepatic mitochondria associated with a balanced nuclear factor erythroid‐derived 2 like 2 (NFE2L2) dependent antioxidative response, most likely triggered by reduced tethering of NFE2L2 to mitochondrial phosphoglycerate mutase 5. Age indirectly influenced mitochondrial function by reducing mitochondrial mass, thus exacerbating diet‐induced fat accumulation. Therefore, consideration of age in metabolic studies must be emphasized.

Diminished stress resistance and defective adaptive homeostasis in age-related diseases

Adaptive homeostasis is defined as the transient expansion or contraction of the homeostatic range following exposure to subtoxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events (Mol. Aspects Med. (2016) 49, 1-7). Adaptive homeostasis allows us to transiently adapt (and then de-adapt) to fluctuating levels of internal and external stressors. The ability to cope with transient changes in internal and external environmental stress, however, diminishes with age. Declining adaptive homeostasis may make older people more susceptible to many diseases. Chronic oxidative stress and defective protein homeostasis (proteostasis) are two major factors associated with the etiology of age-related disorders. In the present paper, we review the contribution of impaired responses to oxidative stress and defective adaptive homeostasis in the development of age-associated diseases.

Ghrelin rescues skeletal muscle catabolic profile in the R6/2 mouse model of Huntington's disease

Accumulating evidence suggests altered energy metabolism as a key feature in Huntington’s disease (HD) pathology. Hyper-catabolism, including weight loss and muscle atrophy, is seen in HD patients and HD mouse models. Metabolic hormones are key players, not only in energy metabolism, but also in neurodegenerative processes. Ghrelin, a gut peptide-hormone, plays an important role in regulating energy metabolism, stimulating appetite, and affects brain function and increases neuronal survival. The R6/2 mouse model of HD has previously been shown to exhibit progressive weight loss, dysregulated glucose metabolism, skeletal muscle atrophy and altered body composition. In this study, we targeted energy metabolism in R6/2 mice using ghrelin administration, with the primary aim to delay weight loss and reduce muscle atrophy. We also evaluated glucose metabolism and behaviour. We here demonstrate that ghrelin administration (subcutaneous 150 μg/kg daily injections) for 4 weeks, reversed the catabolic gene expression profile (increased expression of Caspase 8, Traf-5 and Creb1) seen in R6/2 mouse skeletal muscle. Skeletal muscle morphology was also improved with ghrelin, and importantly, ghrelin administration normalized behavioural deficits in R6/2 mice. Taken together, our findings encourage further studies targeting metabolism in HD.