Ethyl ferulate, a lipophilic polyphenol, induces HO-1 and protects rat neurons against oxidative stress

Sex hormonal regulation and hormesis in aging and longevity: role of vitagenes

Aging process is accompanied by hormonal changes characterized by an imbalance between catabolic hormones, such as cortisol and thyroid hormones which remain stable and hormones with anabolic effects (testosterone, insulin like growth factor-1 (IGF-1) and dehydroepiandrosterone sulphate (DHEAS), that decrease with age. Deficiencies in multiple anabolic hormones have been shown to predict health status and longevity in older persons.Unlike female menopause, which is accompanied by an abrupt and permanent cessation of ovarian function (both folliculogenesis and estradiol production), male aging does not result in either cessation of testosterone production nor infertility. Although the circulating serum testosterone concentration does decline with aging, in most men this decrease is small, resulting in levels that are generally within the normal range. Hormone therapy (HT) trials have caused both apprehension and confusion about the overall risks and benefits associated with HT treatment. Stress-response hormesis from a molecular genetic perspective corresponds to the induction by stressors of an adaptive, defensive response, particularly through alteration of gene expression. Increased longevity can be associated with greater resistance to a range of stressors. During aging, a gradual decline in potency of the heat shock response occur and this may prevent repair of protein damage. Conversely, thermal stress or pharmacological agents capable of inducing stress responses, by promoting increased expression of heat-shock proteins, confer protection against denaturation of proteins and restoration of proteome function. If induction of stress resistance increases life span and hormesis induces stress resistance, hormesis most likely result in increased life span. Hormesis describes an adaptive response to continuous cellular stresses, representing a phenomenon where exposure to a mild stressor confers resistance to subsequent, otherwise harmful, conditions of increased stress. This biphasic dose-response relationship, displaying low-dose stimulation and a high-dose inhibition, as adaptive response to detrimental lifestyle factors determines the extent of protection from progression to metabolic diseases such as diabetes and more in general to hormonal dysregulation and age-related pathologies. Integrated responses exist to detect and control diverse forms of stress. This is accomplished by a complex network of the so-called longevity assurance processes, which are composed of several genes termed vitagenes. Vitagenes encode for heat shock proteins (Hsps), thioredoxin and sirtuin protein systems. Nutritional antioxidants, have recently been demonstrated to be neuroprotective through the activation of hormetic pathways under control of Vitagene protein network. Here we focus on possible signaling mechanisms involved in the activation of vitagenes resulting in enhanced defense against functional defects leading to degeneration and cell death with consequent impact on longevity processes.

Altered expression pattern of Nrf2/HO-1 axis during accelerated-senescence in HIV-1 transgenic rat

Chronic oxidative stress plays a central role in the pathogenesis of many diseases, including HIV-1 associated disorders. Concomitantly with the decline of endogenous antioxidant systems, it was reported that HIV-1-related proteins increase the production of radical species in cells and tissues that are not directly infected by the virus. In the context of HIV-1 infection, the role of Nrf2, a key transcription factor that contributes to the maintenance of cellular redox homeostasis, remains largely uncharacterized. One of the major stress-responsive player regulated by Nrf2 is the antioxidant enzyme HO-1. The Nrf2/HO-1 axis constitutes a crucial cell survival mechanism to counteract oxidative stress and inflammation. The present study aims to investigate the age-related patterns of Nrf2 and HO-1 in different brain regions and tissues of HIV-1 transgenic rat. Since HIV-1 induces an accelerated aging and the redox imbalance may actively promote senescence, we also evaluated the senescence phenotype-switching by quantifying levels of β-galactosidase activity. Our results showed changes in gene expression, with different trends depending on the brain regions and tissues examined. However, compared to age-matched controls, we observed in HIV-1 transgenic rats a significant reduction in the protein levels of Nrf2 and HO-1, suggesting a weakening in the protection exerted by Nrf2/HO-1 system. Moreover, we show that senescence occurs more rapidly in HIV-1 transgenic rats than in control animals. To our knowledge this is the first in vivo report showing the involvement of Nrf2/HO-1 pathway in a rat model of HIV-1.

Ethyl ferulate, a component with anti-inflammatory properties for emulsion-based creams

Ethyl ferulate (FAEE) has been widely studied due to its beneficial heath properties and, when incorporated in creams, shows a high sun protection capacity. Here we aimed to compare FAEE and its precursor, ferulic acid (FA), as free radical scavengers, inhibitors of oxidants produced by leukocytes and the alterations in rheological properties when incorporated in emulsion based creams. The cell-free antiradical capacity of FAEE was decreased compared to FA. However, FAEE was more effective regarding the scavenging of reactive oxygen species produced by activated leukocytes. Stress and frequency sweep tests showed that the formulations are more elastic than viscous. The viscoelastic features of the formulations were confirmed in the creep and recovery assay and showed that the FAEE formulation was less susceptive to deformation. Liberation experiments showed that the rate of FAEE release from the emulsion was slower compared to FA. In conclusion, FAEE is more effective than FA as a potential inhibitor of oxidative damage produced by oxidants generated by leukocytes. The rheological alterations caused by the addition of FAEE are indicative of lower spreadability, which could be useful for formulations used in restricted areas of the skin.

Brain iron homeostasis: from molecular mechanisms to clinical significance and therapeutic opportunities

Iron has emerged as a significant cause of neurotoxicity in several neurodegenerative conditions, including Alzheimer's disease (AD), Parkinson's disease (PD), sporadic Creutzfeldt-Jakob disease (sCJD), and others. In some cases, the underlying cause of iron mis-metabolism is known, while in others, our understanding is, at best, incomplete. Recent evidence implicating key proteins involved in the pathogenesis of AD, PD, and sCJD in cellular iron metabolism suggests that imbalance of brain iron homeostasis associated with these disorders is a direct consequence of disease pathogenesis. A complete understanding of the molecular events leading to this phenotype is lacking partly because of the complex regulation of iron homeostasis within the brain. Since systemic organs and the brain share several iron regulatory mechanisms and iron-modulating proteins, dysfunction of a specific pathway or selective absence of iron-modulating protein(s) in systemic organs has provided important insights into the maintenance of iron homeostasis within the brain. Here, we review recent information on the regulation of iron uptake and utilization in systemic organs and within the complex environment of the brain, with particular emphasis on the underlying mechanisms leading to brain iron mis-metabolism in specific neurodegenerative conditions. Mouse models that have been instrumental in understanding systemic and brain disorders associated with iron mis-metabolism are also described, followed by current therapeutic strategies which are aimed at restoring brain iron homeostasis in different neurodegenerative conditions. We conclude by highlighting important gaps in our understanding of brain iron metabolism and mis-metabolism, particularly in the context of neurodegenerative disorders.

The Janus face of the heme oxygenase/biliverdin reductase system in Alzheimer disease: it's time for reconciliation

Alzheimer disease (AD) is the most common form of dementia among the elderly and is characterized by progressive loss of memory and cognition. These clinical features are due in part to the increase of reactive oxygen and nitrogen species that mediate neurotoxic effects. The up-regulation of the heme oxygenase-1/biliverdin reductase-A (HO-1/BVR-A) system is one of the earlier events in the adaptive response to stress. HO-1/BVR-A reduces the intracellular levels of pro-oxidant heme and generates equimolar amounts of the free radical scavengers biliverdin-IX alpha (BV)/bilirubin-IX alpha (BR) as well as the pleiotropic gaseous neuromodulator carbon monoxide (CO) and ferrous iron. Two main and opposite hypotheses for a role of the HO-1/BVR-A system in AD propose that this system mediates neurotoxic and neuroprotective effects, respectively. This apparent controversy was mainly due to the fact that for over about 20years HO-1 was the only player on which all the analyses were focused, excluding the other important and essential component of the entire system, BVR. Following studies from the Butterfield laboratory that reported alterations in BVR activity along with decreased phosphorylation and increased oxidative/nitrosative post-translational modifications in the brain of subjects with AD and amnestic mild cognitive impairment (MCI) subjects, a debate was opened on the real pathophysiological and clinical significance of BVR-A. In this paper we provide a review of the main discoveries about the HO/BVR system in AD and MCI, and propose a mechanism that reconciles these two hypotheses noted above of neurotoxic and the neuroprotective aspects of this important stress responsive system.

Oxidative/nitrosative stress and antidepressants: targets for novel antidepressants

The brain is an organ predisposed to oxidative/nitrosative stress. This is especially true in the case of aging as well as several neurodegenerative diseases. Under such circumstances, a decline in the normal antioxidant defense mechanisms leads to an increase in the vulnerability of the brain to the deleterious effects of oxidative damage. Highly reactive oxygen/nitrogen species damage lipids, proteins, and mitochondrial and neuronal genes. Unless antioxidant defenses react appropriately to damage inflicted by radicals, neurons may experience microalteration, microdysfunction, and degeneration. We reviewed how oxidative and nitrosative stresses contribute to the pathogenesis of depressive disorders and reviewed the clinical implications of various antioxidants as future targets for antidepressant treatment.

Ferulic acid improves cardiovascular and kidney structure and function in hypertensive rats

Ferulic acid is a simple phenolic acid commonly present in cereals. In this study, changes in heart and kidney structure and function were measured in young N(ω)-nitro-L-arginine methyl ester (L-NAME)-treated Wistar rats and 10-month-old spontaneously hypertensive rats (SHR) alone and after chronic treatment with ferulic acid (FA; 50 mg·kg⁻¹·d⁻¹; n = 6-10; *P < 0.05). Systolic blood pressures were increased after L-NAME treatment (control 125 ± 2 mm Hg, L-NAME 205 ± 6* mm Hg after 8 weeks) and in SHR (250 ± 2 mm Hg; WKY 149 ± 4 mm Hg). Hypertensive rats developed left ventricular hypertrophy, increased ventricular diastolic stiffness (κ; Wistar, 21.4 ± 1.6; L-NAME, 30.1 ± 0.9*; WKYs, 24.1 ± 0.9; SHR 29.5 ± 0.7) and fibrosis of heart and kidneys. Treatment with ferulic acid reduced systolic blood pressure (L-NAME + FA, 157 ± 4*; SHR + FA 214 ± 8* mm Hg), reduced left ventricular diastolic stiffness (L-NAME + FA, 25.2 ± 0.5*; SHR + FA 26.3 ± 0.5*) and attenuated inflammatory cell infiltration, ferric iron accumulation, and collagen deposition in left ventricles and kidneys. Ferulic acid improved both endothelium-dependent relaxation in isolated thoracic aortic rings and antioxidant status by increasing superoxide dismutase and catalase activity in the heart and kidneys. FA decreased plasma liver enzyme activities and plasma creatinine concentrations. Thus, FA improved the structure and function of the heart, blood vessels, liver, and kidneys in hypertensive rats.

Resveratrol protects C6 astrocyte cell line against hydrogen peroxide-induced oxidative stress through heme oxygenase 1

Resveratrol, a polyphenol presents in grapes and wine, displays antioxidant and anti-inflammatory properties and cytoprotective effect in brain pathologies associated to oxidative stress and neurodegeneration. In previous work, we demonstrated that resveratrol exerts neuroglial modulation, improving glial functions, mainly related to glutamate metabolism. Astrocytes are a major class of glial cells and regulate neurotransmitter systems, synaptic processing, energy metabolism and defense against oxidative stress. This study sought to determine the protective effect of resveratrol against hydrogen peroxide (H₂O₂)-induced cytotoxicity in C6 astrocyte cell line, an astrocytic lineage, on neurochemical parameters and their cellular and biochemical mechanisms. H₂O₂ exposure increased oxidative-nitrosative stress, iNOS expression, cytokine proinflammatory release (TNFα levels) and mitochondrial membrane potential dysfunction and decreased antioxidant defenses, such as SOD, CAT and creatine kinase activity. Resveratrol strongly prevented C6 cells from H₂O₂-induced toxicity by modulating glial, oxidative and inflammatory responses. Resveratrol per se increased heme oxygenase 1 (HO1) expression and extracellular GSH content. In addition, HO1 signaling pathway is involved in the protective effect of resveratrol against H₂O₂-induced oxidative damage in astroglial cells. Taken together, these results show that resveratrol represents an important mechanism for protection of glial cells against oxidative stress.

Desipramine protects neuronal cell death and induces heme oxygenase-1 expression in Mes23.5 dopaminergic neurons

BACKGROUND

Desipramine is known principally as a tricyclic antidepressant drug used to promote recovery of depressed patients. It has also been used in a number of other psychiatric and medical conditions. The present study is the first to investigate the neuroprotective effect of desipramine.

METHODOLOGY/PRINCIPAL FINDINGS

Mes23.5 dopaminergic cells were used to examine neuroprotective effect of desipramine. Western blot, reverse transcription-PCR, MTT assay, siRNA transfection and electrophoretic mobility shift assay (EMSA) were carried out to assess the effects of desipramine. Desipramine induces endogenous anti-oxidative enzyme, heme oxygenase-1 (HO-1) protein and mRNA expression in concentration- and time-dependent manners. A different type of antidepressant SSRI (selective serotonin reuptake inhibitor), fluoxetine also shows similar effects of desipramine on HO-1 expression. Moreover, desipramine induces HO-1 expression through activation of ERK and JNK signaling pathways. Desipramine also increases NF-E2-related factor-2 (Nrf2) accumulation in the nucleus and enhances Nrf2-DNA binding activity. Moreover, desipramine-mediated increase of HO-1 expression is reduced by transfection with siRNA against Nrf2. On the other hand, pretreatment of desipramine protects neuronal cells against rotenone- and 6-hydroxydopamine (6-OHDA)-induced neuronal death. Furthermore, inhibition of HO-1 activity by a HO-1 pharmacological inhibitor, ZnPP IX, attenuates the neuroprotective effect of desipramine. Otherwise, activation of HO-1 activity by HO-1 activator and inducer protect 6-OHDA-induced neuronal death.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that desipramine-increased HO-1 expression is mediated by Nrf2 activation through the ERK and JNK signaling pathways. Our results also suggest that desipramine provides a novel effect of neuroprotection, and neurodegenerative process might play an important role in depression disorder.

Effect of Treatment with Cyanidin-3-O-β-D-Glucoside on Rat Ischemic/Reperfusion Brain Damage

This study investigated the effect of cyanidin-3-O-β-glucoside on an experimental model of partial/transient cerebral ischemia in the rats in order to verify the effectiveness of both pre- and posttreatments. Cyanidin-3-O-β-glucoside-pretreated rats were injected with 10 mg/Kg i.p. 1 h before the induction of cerebral ischemia; in posttreated rats, the same dosage was injected during reperfusion (30 min after restoring blood flow). Cerebral ischemia was induced by bilateral clamping of common carotid arteries for 20 min. Ischemic rats were sacrificed immediately after 20 min ischemia; postischemic reperfused animals were sacrificed after 3 or 24 h of restoring blood flow. Results showed that treatment with cyanidin increased the levels of nonproteic thiol groups after 24 h of postischemic reperfusion, significantly reduced the lipid hydroperoxides, and increased the expression of heme oxygenase and γ-glutamyl cysteine synthase; a significant reduction in the expression of neuronal and inducible nitric oxide synthases and the equally significant increase in the endothelial isoform were observed. Significant modifications were also detected in enzymes involved in metabolism of endogenous inhibitors of nitric oxide. Most of the effects were observed with both pre- and posttreatments with cyanidin-3-O-β-glucoside suggesting a role of anthocyanin in both prevention and treatment of postischemic reperfusion brain damage.

Ayurvedic medicinal plants for Alzheimer's disease: a review

Alzheimer's disease is an age-associated, irreversible, progressive neurodegenerative disease that is characterized by severe memory loss, unusual behavior, personality changes, and a decline in cognitive function. No cure for Alzheimer's exists, and the drugs currently available to treat the disease have limited effectiveness. It is believed that therapeutic intervention that could postpone the onset or progression of Alzheimer's disease would dramatically reduce the number of cases in the next 50 years. Ayurvedic medicinal plants have been the single most productive source of leads for the development of drugs, and over a hundred new products are already in clinical development. Indeed, several scientific studies have described the use of various Ayurvedic medicinal plants and their constituents for treatment of Alzheimer's disease. Although the exact mechanism of their action is still not clear, phytochemical studies of the different parts of the plants have shown the presence of many valuable compounds, such as lignans, flavonoids, tannins, polyphenols, triterpenes, sterols, and alkaloids, that show a wide spectrum of pharmacological activities, including anti-inflammatory, anti-amyloidogenic, anti-cholinesterase, hypolipidemic, and antioxidant effects. This review gathers research on various medicinal plants that have shown promise in reversing the Alzheimer's disease pathology. The report summarizes information concerning the phytochemistry, biological, and cellular activities and clinical applications of these various plants in order to provide sufficient baseline information that could be used in drug discovery campaigns and development process, thereby providing new functional leads for Alzheimer's disease.

Dietary polyphenols as modulators of brain functions: biological actions and molecular mechanisms underpinning their beneficial effects

Accumulating evidence suggests that diet and lifestyle can play an important role in delaying the onset or halting the progression of age-related health disorders and to improve cognitive function. In particular, polyphenols have been reported to exert their neuroprotective actions through the potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation, and the potential to promote memory, learning, and cognitive function. Despite significant advances in our understanding of the biology of polyphenols, they are still mistakenly regarded as simply acting as antioxidants. However, recent evidence suggests that their beneficial effects involve decreases in oxidative/inflammatory stress signaling, increases in protective signaling and neurohormetic effects leading to the expression of genes that encode antioxidant enzymes, phase-2 enzymes, neurotrophic factors, and cytoprotective proteins. Specific examples of such pathways include the sirtuin-FoxO pathway, the NF-κB pathway, and the Nrf-2/ARE pathway. Together, these processes act to maintain brain homeostasis and play important roles in neuronal stress adaptation and thus polyphenols have the potential to prevent the progression of neurodegenerative pathologies.

Small molecule modulators of Keap1-Nrf2-ARE pathway as potential preventive and therapeutic agents

Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elements (ARE) pathway represents one of the most important cellular defense mechanisms against oxidative stress and xenobiotic damage. Activation of Nrf2 signaling induces the transcriptional regulation of ARE-dependent expression of various detoxifying and antioxidant defense enzymes and proteins. Keap1-Nrf2-ARE signaling has become an attractive target for the prevention and treatment of oxidative stress-related diseases and conditions including cancer, neurodegenerative, cardiovascular, metabolic, and inflammatory diseases. Over the last few decades, numerous Nrf2 inducers have been developed and some of them are currently undergoing clinical trials. Recently, overactivation of Nrf2 has been implicated in cancer progression as well as in drug resistance to cancer chemotherapy. Thus, Nrf2 inhibitors could potentially be used to improve the effectiveness of cancer therapy. Herein, we review the signaling mechanism of Keap1-Nrf2-ARE pathway, its disease relevance, and currently known classes of small molecule modulators. We also discuss several aspects of Keap1-Nrf2 interaction, Nrf2-based peptide inhibitor design, and the screening assays currently used for the discovery of direct inhibitors of Keap1-Nrf2 interaction.

Modulation of experimental herpes encephalitis-associated neurotoxicity through sulforaphane treatment

Reactive oxygen species (ROS) produced by brain-infiltrating macrophages and neutrophils, as well as resident microglia, are pivotal to pathogen clearance during viral brain infection. However, unchecked free radical generation is also responsible for damage to and cytotoxicity of critical host tissue bystander to primary infection. These unwanted effects of excessive ROS are combated by local cellular production of antioxidant enzymes, including heme oxygenase-1 (HO-1) and glutathione peroxidase 1 (Gpx1). In this study, we showed that experimental murine herpes encephalitis triggered robust ROS production, as well as an opposing upregulation of the antioxidants HO-1 and Gpx1. This antioxidant response was insufficient to prevent tissue damage, neurotoxicity, and mortality associated with viral brain infection. Previous studies corroborate our data supporting astrocytes as the major antioxidant producer in brain cell cultures exposed to HSV-1 stimulated microglia. We hypothesized that stimulating opposing antioxidative responses in astrocytes, as well as neurons, would mitigate the effects of ROS-mediated neurotoxicity both in vitro and during viral brain infection in vivo. Here, we demonstrate that the addition of sulforaphane, a potent stimulator of antioxidant responses, enhanced HO-1 and Gpx1 expression in astrocytes through the activation of nuclear factor-E2-related factor 2 (Nrf2). Additionally, sulforaphane treatment was found to be effective in reducing neurotoxicity associated with HSV-stimulated microglial ROS production. Finally, intraperitoneal injections of sulforaphane into mice during active HSV infection reduced neuroinflammation via a decrease in brain-infiltrating leukocytes, macrophage- and neutrophil-produced ROS, and MHCII-positive, activated microglia. These data support a key role for astrocyte-produced antioxidants in modulating oxidative stress and neuronal damage in response to viral infection.

Alkyl esters of hydroxycinnamic acids with improved antioxidant activity and lipophilicity protect PC12 cells against oxidative stress

Hydroxycinnamic acids (HCAs) are phenolic compounds present in dietary plants, which possess considerable antioxidant activity. In order to increase the lipophilicity of HCAs, with the aim of improving their cellular absorption and expansion of their use in lipophilic media, methyl, ethyl, propyl and butyl esters of caffeic acid and ferulic acid have been synthesized. All caffeate esters had a slightly lower DPPH IC(50) (13.5-14.5 μM) and higher ferric reducing antioxidant power (FRAP) values (1490-1588 mM quercetin/mole [mMQ/mole]) compared to caffeic acid (16.6 μM and 1398 mMQ/mole, respectively) in antioxidant assays. In contrast, ferulate esters were less active in DPPH (56.3-74.7 μM) and FRAP assays (193-262 mMQ/mole) compared to ferulic acid (44.6 μM and 324 mMQ/mole, respectively). Redox properties of HCAs were in line with their antioxidant capacities, so that compounds with higher antioxidant activities had lower oxidation potentials. Measurement of partition coefficients disclosed the higher lipophilicity of the esters compared to parent compounds. All esters of caffeic acid significantly inhibited hydrogen peroxide-induced neuronal PC12 cell death assessed by MTT assay at 5 and 25 μM. However, caffeic acid, ferulic acid and ferulate esters were not able to protect the cells. In conclusion, these findings suggest that alkyl esterification of some HCAs augments their antioxidant properties as well as their lipophilicity and as a consequence, improves their cell protective activity against oxidative stress. These compounds could have useful applications in conditions where oxidative stress plays a pathogenic role.

Ferulic acid ethyl ester as a potential therapy in neurodegenerative disorders

Oxidative stress is involved in the onset, progression and pathogenesis of a number of diseases including neurodegenerative diseases. It is critical to develop a pharmacological approach to combat oxidative stress which may reduce the risk of diseases and help in promoting healthy life. In an attempt to reduce the side effects associated with allopathic medicines a number of studies are now focusing on developing treatment regimens from naturally occurring plant products. In this review, the protective role of ferulic acid (4-hydroxy-3-methoxycinnamic acid) (FA), a naturally occurring antioxidant compound found in fruit, some vegetables, and grains, and its ethyl ester derivative are discussed with respect to neurodegeneration. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Modulation of Nrf2/ARE pathway by food polyphenols: a nutritional neuroprotective strategy for cognitive and neurodegenerative disorders

In recent years, there has been a growing interest, supported by a large number of experimental and epidemiological studies, for the beneficial effects of some phenolic substances, contained in commonly used spices and herbs, in preventing various age-related pathologic conditions, ranging from cancer to neurodegenerative diseases. Although the exact mechanisms by which polyphenols promote these effects remain to be elucidated, several reports have shown their ability to stimulate a general xenobiotic response in the target cells, activating multiple defense genes. Data from our and other laboratories have previously demonstrated that curcumin, the yellow pigment of curry, strongly induces heme-oxygenase-1 (HO-1) expression and activity in different brain cells via the activation of heterodimers of NF-E2-related factors 2 (Nrf2)/antioxidant responsive element (ARE) pathway. Many studies clearly demonstrate that activation ofNrf2 target genes, and particularly HO-1, in astrocytes and neurons is strongly protective against inflammation, oxidative damage, and cell death. In the central nervous system, the HO system has been reported to be very active, and its modulation seems to play a crucial role in the pathogenesis of neurodegenerative disorders. Recent and unpublished data from our group revealed that low concentrations of epigallocatechin-3-gallate, the major green tea catechin, induces HO-1 by ARE/Nrf2 pathway in hippocampal neurons, and by this induction, it is able to protect neurons against different models of oxidative damages. Furthermore, we have demonstrated that other phenolics, such as caffeic acid phenethyl ester and ethyl ferulate, are also able to protect neurons via HO-1 induction. These studies identify a novel class of compounds that could be used for therapeutic purposes as preventive agents against cognitive decline.

Cellular stress responses, the hormesis paradigm, and vitagenes: novel targets for therapeutic intervention in neurodegenerative disorders

Despite the capacity of chaperones and other homeostatic components to restore folding equilibrium, cells appear poorly adapted for chronic oxidative stress that increases in cancer and in metabolic and neurodegenerative diseases. Modulation of endogenous cellular defense mechanisms represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. This article introduces the concept of hormesis and its applications to the field of neuroprotection. It is argued that the hormetic dose response provides the central underpinning of neuroprotective responses, providing a framework for explaining the common quantitative features of their dose-response relationships, their mechanistic foundations, and their relationship to the concept of biological plasticity, as well as providing a key insight for improving the accuracy of the therapeutic dose of pharmaceutical agents within the highly heterogeneous human population. This article describes in mechanistic detail how hormetic dose responses are mediated for endogenous cellular defense pathways, including sirtuin and Nrf2 and related pathways that integrate adaptive stress responses in the prevention of neurodegenerative diseases. Particular attention is given to the emerging role of nitric oxide, carbon monoxide, and hydrogen sulfide gases in hormetic-based neuroprotection and their relationship to membrane radical dynamics and mitochondrial redox signaling.

The major green tea polyphenol, (-)-epigallocatechin-3-gallate, induces heme oxygenase in rat neurons and acts as an effective neuroprotective agent against oxidative stress

BACKGROUND

Oxidative stress induced by hyperglycemia is a key factor in the pathogenesis of diabetic complications, such as neuropathy. Recently, green tea catechins have received much attention, as they can facilitate a number of antioxidative mechanisms and improve glycemic control.

OBJECTIVE

The aim of this study was to investigate the cytoprotective effects of (-)-epigallocatechin-3-gallate (EGCG) against oxidative stress damage in a cell line of rat neurons. The role of heme oxygenase 1 (HO-1) induction by EGCG and the transcriptional mechanisms involved were also evaluated.

METHODS

Immortalized rat neurons (H 19-7) were exposed to various concentrations of EGCG (10-200 microM). After treatments (6 or 24 hours), cells were harvested for the determination of heme oxygenase activity, mRNA levels, and protein expression. Nuclear levels of Nrf2, a transcriptional factor involved in HO-1 activation, were also measured. Neurons were pretreated for 12 hours with EGCG 50 microM or EGCG 50 microM + zinc protoporphyrin IX 10 microM and then exposed for 2 hours to 50 mmicro/mL glucose-oxidase before cell viability was determined.

RESULTS

In cultured neurons, elevated expression of HO-1 mRNA and protein were detected after 6 hours of incubation with 25-100 microM EGCG, and its induction relates with the activation of Nrf2. Interestingly, pre-incubation (12 hours) with EGCG 50 microM resulted in an enhanced cellular resistance to glucose oxidase-mediated oxidative damage; this cytoprotective effect was considerably attenuated by zinc protoporphyrin IX, an inhibitor of heme oxygenase activity.

CONCLUSIONS

In this study, we demonstrated that EGCG, the major green tea catechin, induced HO-1 expression in cultured neurons, possibly by activation of the transcription factor Nrf2, and by this mechanism was able to protect against oxidative stress-induced cell death.

Structure-activity relationships in the cytoprotective effect of caffeic acid phenethyl ester (CAPE) and fluorinated derivatives: effects on heme oxygenase-1 induction and antioxidant activities

To determine the relationship between catechol ring modifications and the activity of caffeic acid phenethyl ester (CAPE) as a cytoprotective agent, six catechol ring-fluorinated CAPE derivatives were evaluated for their cytoprotective abilities, as well as for their antioxidant and heme oxygenase-1 (HO-1) inducing capacity in a human umbilical vein endothelial cell (HUVEC) model of oxidant stress. To ascertain the involvement of HO-1 induction in the cytoprotective effects of CAPE analogues, their ability to induce HO-1 at 20microM was determined by reverse transcriptase polymerase chain reaction, western blotting and the use of HO-1 inhibitor tin protoporphyrin IX. There was significant induction of HO-1 by CAPE derivatives. Inhibition of HO-1 enzymatic activity resulted in reduced cytoprotection. Modification of the catechol ring of CAPE by introduction of fluorine at various positions resulted in dramatic changes in cytoprotective activity. The maintenance of at least one hydroxyl group on the CAPE catechol ring and the phenethyl ester portion was required for HO-1 induction. CAPE and its derivatives were screened for their ability to scavenge intracellular reactive oxygen species generated in HUVECs by measuring 5-(and-6)-chlormethyl-2', 7'-dichlorodihydrofluorescein diacetate oxidation. The maintenance of 3, 4-dihydroxyl groups on the catechol ring was required for antioxidant activity, but antioxidant activity did not guarantee cytoprotection. Methylation or replacement of one hydroxyl group on the catechol ring of CAPE, however, provided both pro-oxidant and cytoprotective activities. These results indicate that the induction of HO-1 plays a more important role in the cytoprotective activity of CAPE derivatives than their direct antioxidant activity.

Up-regulation of Nrf2-mediated heme oxygenase-1 expression by eckol, a phlorotannin compound, through activation of Erk and PI3K/Akt

The aim of the present study was to examine the cytoprotective effect of eckol, a phlorotannin found in Ecklonia cava and to elucidate underlying mechanisms. Heme oxygenase-1 (HO-1) is an important antioxidant enzyme that plays a role in cytoprotection against oxidative stress. Eckol-induced HO-1 expression both at the level of mRNA and protein in Chinese hamster lung fibroblast (V79-4) cells, resulting in increased HO-1 activity. The transcription factor NF-E2-related factor 2 (Nrf2) is a critical regulator of HO-1, achieved by binding to the antioxidant response element (ARE). Eckol treatment resulted in the enhanced level of phosphorylated form, nuclear translocation, ARE-binding, and transcriptional activity of Nrf2. Extracellular regulated kinase (Erk) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB, Akt) contributed to ARE-driven HO-1 expression. Eckol activated both Erk and Akt, and treatments with U0126 (an Erk kinase inhibitor), LY294002 (a PI3K inhibitor), specific Erk1 siRNA, and Akt siRNA suppressed the eckol-induced activation of Nrf2, resulting in a decrease in HO-1 expression. ZnPP (a HO-1 inhibitor), HO-1 siRNA, and Nrf2 siRNA markedly abolished the cytoprotective effect of eckol against hydrogen peroxide-induced cell damage. Likewise, U0126 and LY294002 inhibited the eckol-induced cytoprotective effect against oxidative cell damage. These studies demonstrate that eckol attenuates oxidative stress by activating Nrf2-mediated HO-1 induction via Erk and PI3K/Akt signaling.

Vitagenes, cellular stress response, and acetylcarnitine: relevance to hormesis

Modulation of endogenous cellular defense mechanisms via the stress response signaling represents an innovative approach to therapeutic intervention in diseases causing chronic damage, such as neurodegeneration and cancer. Protein thiols play a key role in redox sensing, and regulation of cellular redox state is crucial mediator of multiple metabolic, signaling, and transcriptional processes. Maintenance of optimal long-term health conditions is accomplished by a complex network of longevity assurance processes that are controlled by vitagenes, a group of genes involved in preserving cellular homeostasis during stressful conditions. Vitagenes encode for heat shock proteins (Hsp) Hsp32, Hsp70, the thioredoxin, and the sirtuin protein systems. Dietary antioxidants, such as polyphenols and L-carnitine/acetyl-L-carnitine, have recently been demonstrated to be neuroprotective through the activation of hormetic pathways, including vitagenes. The hormetic dose-response, challenges long-standing beliefs about the nature of the dose-response in a low dose zone, having the potential to affect significantly the design of pre-clinical studies and clinical trials as well as strategies for optimal patient dosing in the treatment of numerous diseases. Given the broad cytoprotective properties of the heat shock response, there is now strong interest in discovering and developing pharmacological agents capable of inducing these responses. In this review we discuss the most current and up-to-date understanding of the possible signaling mechanisms by which acetylcarnitine by activating vitagenes can differentially modulate signal transduction cascades inducing apoptosis/cell death in abnormal cancer cells but at the same time enhancing defensive enzymes to protect against carcinogenesis and neurodegeneration in normal cells. (c) 2009 International Union of Biochemistry and Molecular Biology, Inc.

Redox regulation of cellular stress response by ferulic acid ethyl ester in human dermal fibroblasts: role of vitagenes

Skin is one of the main targets for reactive oxygen species; thus, reactive oxygen species-induced damage and protein and lipid modifications occur, and skin can undergo a wide array of diseases, from photosensitivity to cancer. In this study, human dermal fibroblasts exposed to hydrogen peroxide (0-1000 micromol/L) exhibited a marked increase in both protein carbonyls and 4-hydroxy-2-nonenal, which are indices of protein and lipid oxidation, respectively. An amount of 25 micromol/L ferulic acid ethyl ester, a well-known nutritional antioxidant, significantly counteracted both protein and lipid oxidation and reduced the loss in cell viability elicited by 500 micromol/L of hydrogen peroxide. A common way for cells to react to oxidative stress is up-regulation of vitagenes. To the vitagene family belong the heat shock proteins heme oxygenase-1 and heat shock protein-70, which are involved in the cellular defense against oxidative stress by different mechanisms. The administration of 25 micromol/L ferulic acid ethyl ester significantly decreased hydrogen peroxide-induced protein and lipid oxidation. Dermal fibroblasts exposed to 25 micromol/L ferulic acid ethyl ester in the presence of 500 micromol/L hydrogen peroxide showed an increased level of both heme oxygenase-1 and heat shock protein-70 compared with dermal fibroblasts treated with hydrogen peroxide alone. These findings provide evidence for the protective role of vitagenes in free radical-induced skin damage and highlight the potential protective use of nutritional antioxidants, such as ferulic acid and its derivatives.

Regulation of haeme oxygenase-1 for treatment of neuroinflammation and brain disorders

Injury to the CNS elicits a host defense reaction that utilizes astrocytes, microglia, neurons and oligodendrocytes. Neuroinflammation is a major host defense mechanism designed to restore normal structure and function after CNS insult, but like other forms of inflammation, chronic neuroinflammation may contribute to pathogenesis. The inducible haeme oxygenase isoform, haeme oxygenase-1 (HO-1), is a phase 2 enzyme upregulated in response to electrophilic xenobiotics, oxidative stress, cellular injury and disease. There is emerging evidence that HO-1 expression helps mediate the resolution of inflammation, including neuroinflammation. Whether this is solely because of the catabolism of haeme or includes additional mechanisms is unclear. This review provides a brief background on the molecular biology and biochemistry of haeme oxygenases and the actions of haeme, bilirubin, iron and carbon monoxide in the CNS. It then presents our current state of knowledge regarding HO-1 expression in the CNS, regulation of HO-1 induction in neural cells and discusses the prospect of pharmacological manipulation of HO-1 as therapy for CNS disorders. Because of recognized species and cellular differences in HO-1 regulation, a major objective of this review is to draw attention to areas where gaps exist in the experimental record regarding regulation of HO-1 in neural cells. The results indicate the HO-1 system to be an important therapeutic target in CNS disorders, but our understanding of HO-1 expression in human neural cells is severely lacking.

Alzheimer's disease: new diagnostic and therapeutic tools

On March 19, 2008 a Symposium on Pathophysiology of Ageing and Age-Related diseases was held in Palermo, Italy. Here, the lectures of M. Racchi on History and future perspectives of Alzheimer Biomarkers and of G. Scapagnini on Cellular Stress Response and Brain Ageing are summarized. Alzheimer's disease (AD) is a heterogeneous and progressive neurodegenerative disease, which in Western society mainly accounts for clinica dementia. AD prevention is an important goal of ongoing research. Two objectives must be accomplished to make prevention feasible: i) individuals at high risk of AD need to be identified before the earliest symptoms become evident, by which time extensive neurodegeneration has already occurred and intervention to prevent the disease is likely to be less successful and ii) safe and effective interventions need to be developed that lead to a decrease in expression of this pathology. On the whole, data here reviewed strongly suggest that the measurement of conformationally altered p53 in blood cells has a high ability to discriminate AD cases from normal ageing, Parkinson's disease and other dementias. On the other hand, available data on the involvement of curcumin in restoring cellular homeostasis and rebalancing redox equilibrium, suggest that curcumin might be a useful adjunct in the treatment of neurodegenerative illnesses characterized by inflammation, such as AD.

Pharmacologic induction of heme oxygenase-1

Heme oxygenase-1 (HO-1) is a cytoprotective protein whose expression is consistently associated with therapeutic benefits in a number of pathologic conditions such as atherosclerotic vascular disease and inflammation. Although the expression of HO-1 in most tissues is low, a large number of clinical and experimental pharmacologic compounds have been demonstrated to induce HO-1. This induction is suggested to be at least partially responsible for the perceived therapeutic efficacy of these compounds. The increase in HO-1 expression in response to these compounds is the result of a complex regulatory network involving many signaling pathways and transcription factors. Understanding both the pathways by which HO-1 is induced and the mechanism through which the enzyme exerts its beneficial effects may facilitate the development of novel drugs.

Oxidative stress: A bridge between Down's syndrome and Alzheimer's disease

Besides the genetic, biochemical and neuropathological analogies between Down's syndrome (DS) and Alzheimer's disease (AD), there is ample evidence of the involvement of oxidative stress (OS) in the pathogenesis of both disorders. The present paper reviews the publications on DS and AD in the past 10 years in light of the "gene dosage" and "two-hit" hypotheses, with regard to the alterations caused by OS in both the central nervous system and the periphery, and the main pipeline of antioxidant therapeutic strategies. OS occurs decades prior to the signature pathology and manifests as lipid, protein and DNA oxidation, and mitochondrial abnormalities. In clinical settings, the assessment of OS has traditionally been hampered by the use of assays that suffer from inherent problems related to specificity and/or sensitivity, which explains some of the conflicting results presented in this work. For DS, no scientifically proven diet or drug is yet available, and AD trials have not provided a satisfactory approach for the prevention of and therapy against OS, although most of them still need evidence-based confirmation. In the future, a balanced up-regulation of endogenous antioxidants, together with multiple exogenous antioxidant supplementation, may be expected to be one of the most promising treatment methods.

Ferulic Acid: therapeutic potential through its antioxidant property

There has been considerable public and scientific interest in the use of phytochemicals derived from dietary components to combat human diseases. They are naturally occurring substances found in plants. Ferulic acid (FA) is a phytochemical commonly found in fruits and vegetables such as tomatoes, sweet corn and rice bran. It arises from metabolism of phenylalanine and tyrosine by Shikimate pathway in plants. It exhibits a wide range of therapeutic effects against various diseases like cancer, diabetes, cardiovascular and neurodegenerative. A wide spectrum of beneficial activity for human health has been advocated for this phenolic compound, at least in part, because of its strong antioxidant activity. FA, a phenolic compound is a strong membrane antioxidant and known to positively affect human health. FA is an effective scavenger of free radicals and it has been approved in certain countries as food additive to prevent lipid peroxidation. It effectively scavenges superoxide anion radical and inhibits the lipid peroxidation. It possesses antioxidant property by virtue of its phenolic hydroxyl group in its structure. The hydroxy and phenoxy groups of FA donate electrons to quench the free radicals. The phenolic radical in turn forms a quinone methide intermediate, which is excreted via the bile. The past few decades have been devoted to intense research on antioxidant property of FA. So, the present review deals with the mechanism of antioxidant property of FA and its possible role in therapeutic usage against various diseases.

Curcumin attenuates the kainic acid-induced hippocampal cell death in the mice

Kainic acid (KA) induced oxidative stress is associated with hippocampal cell death. Recent studies suggest that curcumin, a potent antioxidant, may provide protection for KA-induced oxidative stress. We investigated the effects of curcumin treatment on hippocampal reactive astrocytes in mice with KA-induced seizures. Eighteen hours after curcumin treatment, mice were treated with KA (30 mg/kg, i.p.), and then sacrificed after a further 48 h. Using cresyl violet staining and TUNEL analysis, histological evaluation revealed cell death in the KA-treated hippocampus. However, marked cell death was not observed in mice treated with curcumin. In addition, curcumin treatment reduced the KA-induced immunoreactivity of caspase-3. Similarly, immunoreactivity analyses indicated that KA causes upregulation of hippocampal GFAP, eNOS, and HO-1 levels, all of which were reduced in animals those received the curcumin treatment. Our findings indicate that curcumin is a potent inhibitor of reactive astrocyte expression and thus, prevents hippocampal cell death. These results also support its potential for use in the treatment of neurodegenerative diseases.

Brazilian plants with possible action on the central nervous system: a study of historical sources from the 16th to 19th century

Brazil is a country rich in biodiversity, endemism, and cultural diversity, inhabited by different types of population. European expeditions and the migratory processes that began in the 16th century greatly contributed both to cultural diversity and to Brazilian popular therapeutics, and produced the first records on medicinal plants in Brazil. This study comprises a bibliographical survey of historic books found in Sao Paulo libraries (16th through 19th centuries) on medicinal plants exerting effects on the central nervous system (CNS). Thirty-four plants native to Brazil were selected from the reading of the books. Of these 34 plants, 13 were also recorded in ethnopharmacological studies among modern Brazilian communities and 16 have been studied phytochemically. Only eight have been the object of pharmacological studies, six of these, recently, with a request for a patent. Results showed that most of the species recorded in this study have been reported as medicinal for centuries, but have never been the object of pharmacological investigation down to the present time. Such results provide ideas for a selection of these species as potentially bioactive to be included in future pharmacological studies.

Redox regulation of cellular stress response in aging and neurodegenerative disorders: role of vitagenes

Reduced expression and/or activity of antioxidant proteins lead to oxidative stress, accelerated aging and neurodegeneration. However, while excess reactive oxygen species (ROS) are toxic, regulated ROS play an important role in cell signaling. Perturbation of redox status, mutations favoring protein misfolding, altered glyc(osyl)ation, overloading of the product of polyunsaturated fatty acid peroxidation (hydroxynonenals, HNE) or cholesterol oxidation, can disrupt redox homeostasis. Collectively or individually these effects may impose stress and lead to accumulation of unfolded or misfolded proteins in brain cells. Alzheimer's (AD), Parkinson's and Huntington's disease, amyotrophic lateral sclerosis and Friedreich's ataxia are major neurological disorders associated with production of abnormally aggregated proteins and, as such, belong to the so-called "protein conformational diseases". The pathogenic aggregation of proteins in non-native conformation is generally associated with metabolic derangements and excessive production of ROS. The "unfolded protein response" has evolved to prevent accumulation of unfolded or misfolded proteins. Recent discoveries of the mechanisms of cellular stress signaling have led to new insights into the diverse processes that are regulated by cellular stress responses. The brain detects and overcomes oxidative stress by a complex network of "longevity assurance processes" integrated to the expression of genes termed vitagenes. Heat-shock proteins are highly conserved and facilitate correct protein folding. Heme oxygenase-1, an inducible and redox-regulated enzyme, has having an important role in cellular antioxidant defense. An emerging concept is neuroprotection afforded by heme oxygenase by its heme degrading activity and tissue-specific antioxidant effects, due to its products carbon monoxide and biliverdin, which is then reduced by biliverdin reductase in bilirubin. There is increasing interest in dietary compounds that can inhibit, retard or reverse the steps leading to neurodegeneration in AD. Specifically any dietary components that inhibit inappropriate inflammation, AbetaP oligomerization and consequent increased apoptosis are of particular interest, with respect to a chronic inflammatory response, brain injury and beta-amyloid associated pathology. Curcumin and ferulic acid, the first from the curry spice turmeric and the second a major constituent of fruit and vegetables, are candidates in this regard. Not only do these compounds serve as antioxidants but, in addition, they are strong inducers of the heat-shock response. Food supplementation with curcumin and ferulic acid are therefore being considered as a novel nutritional approach to reduce oxidative damage and amyloid pathology in AD. We review here some of the emerging concepts of pathways to neurodegeneration and how these may be overcome by a nutritional approach.

Oxidative stress and therapeutic approaches in HIV dementia

Despite the rapidly increasing incidence of HIV infection worldwide and the increasing prevalence of HIVassociated cognitive impairment, even in patients adequately treated with antiretroviral therapy, currently no effective treatment exists for HIV dementia. A broad range of studies using either brain or cerebrospinal fluid (CSF) tissues from well-characterized patients with HIV dementia, animal models, and in vitro studies from several laboratories using HIV-infected cells or HIV proteins provide overwhelming evidence for oxidative stress in mediating neuronal injury in this patient population. These studies also suggest that patients with apolipoprotein E (ApoE) 4 allele are more susceptible to such oxidative damage. In this review, we provide a critical analysis of these studies, including the few clinical trials that have used antioxidants to treat HIV dementia. We also discuss several novel agents with potent antioxidative properties and provide a rationale for combination antioxidant and neuroprotective therapy.

In vivo protective effects of ferulic acid ethyl ester against amyloid-beta peptide 1-42-induced oxidative stress

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the deposition of amyloid-beta peptide (Abeta), a peptide that as both oligomers and fibrils is believed to play a central role in the development and progress of AD by inducing oxidative stress in brain. Therefore, treatment with antioxidants might, in principle, prevent propagation of tissue damage and neurological dysfunction. The aim of the present study was to investigate the in vivo protective effect of the antioxidant compound ferulic acid ethyl ester (FAEE) against Abeta-induced oxidative damage on isolated synaptosomes. Gerbils were injected intraperitoneally (i.p.) with FAEE or with dimethylsulfoxide, and synaptosomes were isolated from the brain. Synaptosomes isolated from FAEE-injected gerbils and then treated ex vivo with Abeta(1-42) showed a significant decrease in oxidative stress parameters: reactive oxygen species levels, protein oxidation (protein carbonyl and 3-nitrotyrosine levels), and lipid peroxidation (4-hydroxy-2-nonenal levels). Consistent with these results, both FAEE and Abeta(1-42) increased levels of antioxidant defense systems, evidenced by increased levels of heme oxygenase 1 and heat shock protein 72. FAEE led to decreased levels of inducible nitric oxide synthase. These results are discussed with potential therapeutic implications of FAEE, a brain accessible, multifunctional antioxidant compound, for AD involving modulation of free radicals generated by Abeta.

Curcumin activates defensive genes and protects neurons against oxidative stress

Spices and herbs often contain active phenolic substances endowed with potent antioxidative properties. We had previously shown that curcumin, the yellow pigment in curry, strongly induced HO-1 expression and activity in rat astrocytes. In the CNS, HO-1 has been reported to operate as a fundamental defensive mechanism for neurons exposed to an oxidant challenge. Treatment of astrocytes with curcumin upregulated expression of HO-1 protein at both cytoplasmic and nuclear levels, as shown by immunofluorescence analysis under laser-scanning confocal microscopy. A significant expression of quinone reductase and glutathione S transferase, two members of phase II detoxification enzymes, was found in astrocytes exposed to 5-15 microM curcumin. Moreover, the effects of curcumin on HO-1 activity were explored in cultured hippocampal neurons. Elevated expression of HO-1 mRNA and protein were detected after 6 h incubation with 5-25 microM curcumin. Higher concentrations of curcumin (50-100 microM) caused a substantial cytotoxic effect with no change in HO-1 protein expression. Interestingly, pre-incubation (18 h) with curcumin resulted in an enhanced cellular resistance to glucose oxidase-mediated oxidative damage; this cytoprotective effect was considerably attenuated by zinc protoporphyrin IX, an inhibitor of heme oxygenase activity. This study gives additional support to the possible use of curcumin as a dietary preventive agent against oxidative stress-related diseases.

Redox regulation of heat shock protein expression by signaling involving nitric oxide and carbon monoxide: relevance to brain aging, neurodegenerative disorders, and longevity

Increased free radical generation and decreased efficiency of the reparative/degradative mechanisms both primarily contribute to age-related elevation in the level of oxidative stress and brain damage. Excess formation of reactive oxygen and nitrogen species can cause proteasomal dysfunction and protein overloading. The major neurodegenerative diseases are all associated with the presence of abnormal proteins. Different integrated responses exist in the brain to detect oxidative stress which is controlled by several genes termed vitagenes, including the heat shock protein (HSP) system. Of the various HSPs, heme oxygenase-I (HO-1), by generating the vasoactive molecule carbon monoxide and the potent antioxidant bilirubin, could represent a protective system potentially active against brain oxidative injury. The HO-1 gene is redox regulated and its expression is modulated by redox active compounds, including nutritional antioxidants. Given the broad cytoprotective properties of the heat shock response, there is now strong interest in discovering and developing pharmacological agents capable of inducing the heat shock response. These findings have opened up new neuroprotective strategies, as molecules inducing this defense mechanism can be a therapeutic target to minimize the deleterious consequences associated with accumulation of conformationally aberrant proteins to oxidative stress, such as in neurodegenerative disorders and brain aging, with resulting prolongation of a healthy life span.

Redox modulation of heat shock protein expression by acetylcarnitine in aging brain: relationship to antioxidant status and mitochondrial function

There is significant evidence to show that aging is characterized by a stochastic accumulation of molecular damage and by a progressive failure of maintenance and repair processes. Protective mechanisms exist in the brain which are controlled by vitagenes and include members of the heat shock system, heme oxygenase-I, and Hsp70 as critical determinants of brain stress tolerance. Given the broad cytoprotective properties of the heat shock response, molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. Acetyl-L-carnitine is proposed as a therapeutic agent for several neurodegenerative disorders, and the present study reports that treatment for 4 months of senescent rats with acetyl-L-carnitine induces heme oxygenase-1 as well as Hsp70 and SOD-2. This effect was associated with upregulation of GSH levels, prevention of age-related changes in mitochondrial respiratory chain complex expression, and decrease in protein carbonyls and HNE formation. We hypothesize that maintenance or recovery of the activity of vitagenes may delay the aging process and decrease the risk of age-related diseases. Particularly, modulation of endogenous cellular defense mechanisms via acetyl-L-carnitine may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration.

Protective effect of ferulic acid on γ-radiation-induced micronuclei, dicentric aberration and lipid peroxidation in human lymphocytes

In this study we examined radioprotective effect of ferulic acid (FA) on gamma radiation-induced dicentric aberration and lipid peroxidation with reference to alterations in cellular antioxidant status in cultured lymphocytes. To establish most effective protective support we used three different concentrations of FA (1, 5 and 10 microg/ml) and three different doses of gamma-radiation (1, 2 and 4 Gy). Treatment of lymphocytes with FA alone (at 10 microg/ml) gave no significant change in micronuclei (MN), dicentric aberration (DC), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) or glutathione peroxidase (GPx) activities when compared with normal lymphocytes; irradiation at 1, 2 and 4 Gy increased the MN and DC frequencies in a dose-dependent manner. Treatment with FA for 30 min before radiation exposure resulted in a significant decline of MN and DC yields as FA concentration increased. Compared to 1 Gy exposure alone, the extent to which FA (1 microg/ml) reduced the MN and DC yields was 75% and 50%, respectively. With 4 Gy irradiation, FA (10 microg/ml) decreased 45% MN and 25% DC frequencies. FA-pretreated lymphocytes (1, 5 and 10 microg/ml) showed progressively decreased TBARS levels after irradiation. Irradiation (1, 2 and 4 Gy) significantly decreased GSH levels, SOD, CAT and GPx activities in a dose-dependent manner. Pretreatment with 10 microg/ml of FA significantly (p<0.05) prevented the decreases in the radiation-induced GSH, SOD, CAT and GPx activities. These findings suggest potential use and benefit of FA as a radioprotector.

1,2,3,4,6-penta-O-galloyl-β-D-glucose up-regulates heme oxygenase-1 expression by stimulating Nrf2 nuclear translocation in an extracellular signal-regulated kinase-dependent manner in HepG2 cells

AIM: To examine the potency of 1,2,3,4,6-penta-O-galloyl-β-D-glucose (PGG) as a hepatic heme oxygenase-1 (HO-1) inducer and its regulation in HepG2 cells.

METHODS: Expression of HO-1 and NF-E2-related factor 2 (Nrf2) and activation of mitogen-activated protein (MAP) kinases were analyzed by Western blot, immunofluorescence assay, and flow cytometry. Transfections of HO-1 gene, small interfering RNAs for HO-1 and Nrf2, and dominant-negative gene for MAP/extracellular signal-regulated kinase (ERK) were carried out to dissect the signaling pathways leading to HO-1 expression in HepG 2 cells.

RESULTS: PGG up-regulated HO-1 expression and this expression conferred cytoprotection against oxidative injury induced by t-butyl hydroperoxide. Moreover, PGG induced Nrf2 nuclear translocation, which was found to be an upstream step of PGG-induced HO-1 expression, and ERK activation, of which pathway was involved in PGG-induced Nrf2 nuclear translocation, HO-1 expression and cytoprotection.

CONCLUSION: PGG up-regulates HO-1 expression by stimulating Nrf2 nuclear translocation in an ERK-dependent manner, and HO-1 expression by PGG may serve as one of the important mechanisms for its hepatoprotective effects.