Giovanni Scapagnini

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 Recent and unpublished data from our group revealed that low concentrations of epigallocatechin-3-gallate, the major green tea catechin, induces HO-1 by ARE/Nrf2 pathway in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.

New drug targets in depression: inflammatory, cell-mediated immune, oxidative and nitrosative stress, mitochondrial, antioxidant, and neuroprogressive pathways. And new drug candidates—Nrf2 activators and GSK-3 inhibitors

This paper reviews new drug targets in the treatment of depression and new drug candidates to treat depression. Depression is characterized by aberrations in six intertwined pathways: (1) inflammatory pathways as indicated by increased levels of proinflammatory cytokines, e.g. interleukin-1 (IL-1), IL-6, and tumour necrosis factor α. (2) Activation of cell-mediated immune pathways as indicated by an increased production of interferon γ and neopterin. (3) Increased reactive oxygen and nitrogen species and damage by oxidative and nitrosative stress (O&NS), including lipid peroxidation, damage to DNA, proteins and mitochondria. (4) Lowered levels of key antioxidants, such as coenzyme Q10, zinc, vitamin E, glutathione, and glutathione peroxidase. (5) Damage to mitochondria and mitochondrial DNA and reduced activity of respiratory chain enzymes and adenosine triphosphate production. (6) Neuroprogression, which is the progressive process of neurodegeneration, apoptosis, and reduced neurogenesis and neuronal plasticity, phenomena that are probably caused by inflammation and O&NS. Antidepressants tend to normalize the above six pathways. Targeting these pathways has the potential to yield antidepressant effects, e.g. using cytokine antagonists, minocycline, Cox-2 inhibitors, statins, acetylsalicylic acid, ketamine, ω3 poly-unsaturated fatty acids, antioxidants, and neurotrophic factors. These six pathways offer new, pathophysiologically guided drug targets suggesting that novel therapies could be developed that target these six pathways simultaneously. Both nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activators and glycogen synthase kinase-3 (GSK-3) inhibitors target the six above-mentioned pathways. GSK-3 inhibitors have antidepressant effects in animal models of depression. Nrf2 activators and GSK-3 inhibitors have the potential to be advanced to phase-2 clinical trials to examine whether they augment the efficacy of antidepressants or are useful as monotherapy.

Vitamin E and Neurodegenerative Disorders Associated with Oxidative Stress

Abstract Several neurodegenerative disorders are associated with oxidative stress that is manifested by lipid peroxidation, protein oxidation and other markers. Included in these disorders in which oxidative stress is thought to play an important role in their pathogenesis are Alzheimers disease (AD), Parkinsons disease (PD), amyotrophic lateral sclerosis (ALS), tardive dyskinesia, Huntingtons disease (HD), and multiple sclerosis. This review presents some of the chemistry of vitamin E as an antioxidant and summarizes studies in which vitamin E has been employed in these disorders and models thereof.

Curcumin, inflammation, ageing and age-related diseases

A Symposium regarding the Pathophysiology of Successful and Unsuccessful Ageing was held in Palermo, Italy between April 7 and 8th 2009. Here the lecture by Sikora with some input from the chairpersons Scapagnini and Barbagallo is summarized. Ageing is manifested by the decreasing health status and increasing probability to acquire age-related disease such as cancer, Alzheimers disease, atherosclerosis, metabolic disorders and others. They are likely caused by low grade inflammation driven by oxygen stress and manifested by the increased level of pro-inflammatory cytokines such as IL-1, IL-6 and TNF-α, encoded by genes activated by the transcription factor NF-κB. It is believed that ageing is plastic and can be slowed down by caloric restriction as well as by some nutraceuticals. Accordingly, slowing down ageing and postponing the onset of age-related diseases might be achieved by blocking the NF-κB-dependent inflammation. In this review we consider the possibility of the spice curcumin, a powerful antioxidant and anti-inflammatory agent possibly capable of improving the health status of the elderly.

Antioxidants as antidepressants: fact or fiction?

Depression is a medical condition with a complex biological pattern of aetiology, involving genetic and epigenetic factors, along with different environmental stressors. Recent evidence suggests that oxidative stress pro-cesses might play a relevant role in the pathogenic mechanism(s) underlying many major psychiatric disorders, including depression.Reactive oxygen and nitrogen species have been shown to modulate levels and activity of noradrenaline (norepinephrine), serotonin, dopamine and glutamate, the principal neurotransmitters involved in the neurobiology of depression. Major depression has been associated with lowered concentrations of several endogenous antioxidant compounds, such as vitamin E, zinc and coenzyme Q10, or enzymes, such as glutathione peroxidase, and with an impairment of the total antioxidant status. These observations introduce new potential targets for the development of therapeutic interventions based on antioxidant compounds.The present review focuses on the possible role of oxidative stress processes in the pathogenesis of depression. The therapeutic potential of antioxidant compounds as a co-adjuvant treatment to conventional antidepressants is discussed. For instance, N-acetyl-cysteine has been shown to have a signif-icant benefit on depressive symptoms in a randomized placebo-controlled trial. Additionally, curcumin, the yellow pigment of curry, has been shown to strongly interfere with neuronal redox homeostasis in the CNS and to possess antidepressant activity in various animal models of depression, also thanks to its ability to inhibit monoamine oxidases. There is an urgent need to develop better tolerated and more effective treatments for depressive disorders and several antioxidant treatments appear promising and deserve further study.

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 µM). 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 µM or EGCG 50 µM + zinc protoporphyrin IX 10 µM and then exposed for 2 hours to 50 mµ/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 µM EGCG, and its induction relates with the activation of Nrf2. Interestingly, pre-incubation (12 hours) with EGCG 50 µM 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.

Pleiotropic Protective Effects of Phytochemicals in Alzheimer's Disease

Alzheimers disease (AD) is a severe chronic neurodegenerative disorder of the brain characterised by progressive impairment in memory and cognition. In the past years an intense research has aimed at dissecting the molecular events of AD. However, there is not an exhaustive knowledge about AD pathogenesis and a limited number of therapeutic options are available to treat this neurodegenerative disease. Consequently, considering the heterogeneity of AD, therapeutic agents acting on multiple levels of the pathology are needed. Recent findings suggest that phytochemicals compounds with neuroprotective features may be an important resources in the discovery of drug candidates against AD. In this paper we will describe some polyphenols and we will discuss their potential role as neuroprotective agents. Specifically, curcumin, catechins, and resveratrol beyond their antioxidant activity are also involved in antiamyloidogenic and anti-inflammatory mechanisms. We will focus on specific molecular targets of these selected phytochemical compounds highlighting the correlations between their neuroprotective functions and their potential therapeutic value in AD.

Inflammation, Cytokines, Immune Response, Apolipoprotein E, Cholesterol, and Oxidative Stress in Alzheimer Disease: Therapeutic Implications

Alzheimer disease (AD) is a heterogeneous and progressive neurodegenerative disease, which in Western society mainly accounts for senile dementia. Today many countries have rising aging populations and are facing an increased prevalence of age-related diseases, such as AD, with increasing health-care costs. Understanding the pathophysiology process of AD plays a prominent role in new strategies for extending the health of the elderly population. Considering the future epidemic of AD, prevention and treatment are important goals of ongoing research. However, a better understanding of AD pathophysiology must be accomplished to make this objective feasible. In this paper, we review some hot topics concerning AD pathophysiology that have an important impact on therapeutic perspectives. Hence, we have focused our attention on inflammation, cytokines, immune response, apolipoprotein E (APOE), cholesterol, oxidative stress, as well as exploring the related therapeutic possibilities, i.e., nonsteroidal antiinflammatory drugs, cytokine blocking antibodies, immunotherapy, diet, and curcumin.

Neuroprotective effect of silibinin in diabetic mice.

Diabetes mellitus is associated with a higher oxidative stress and reduced activity of the antioxidant defense system in different brain regions. Results from numerous studies reported impaired cognitive and neurochemical function in diabetic patients and streptozotocin induced diabetic rodents. It is well established that polyphenols exert potent antioxidant and protective functions. Based on recent findings, one potential target for the antioxidant/antinflammatory properties of polyphenols is the heme oxygenase (HO)-1 pathway. Among various compounds tested silibinin, the main component of silymarin, has been shown to possess a strong antioxidant effect in various experimental models; however a study on the possible neuroprotective effect of this compound on the brain of diabetic animals is currently lacking. Therefore, we studied and measured in lean mice (db/m) and knock out mice for the leptin receptors mice (db/db) the effect of silibinin on HO-1 protein levels, non proteic thiol groups, isoprostanes and 8-OH deoxyguanosine (markers of lipid peroxidation and DNA damage, respectively) in different brain regions. Our results showed that HO-1 is differently expressed in various brain regions in db/db mice when compared to lean animals. Furthermore, silibinin provides DNA protection and reduces oxidative stress in a brain specific area, in part via the activation of the HO system. Silibinin may provide a valid tool to counteract oxidative stress in the diabetic status in the central nervous system under diabetic condition.

Post-transcriptional regulation of HSP70 expression following oxidative stress in SH-SY5Y cells: the potential involvement of the RNA-binding protein HuR.

Brain aging is associated with a progressive imbalance between intracellular concentration of Reactive Oxygen Species (ROS) and cells ability to activate defensive genes. Heat Shock Protein 70 (HSP70) has been shown to act as a fundamental defensive mechanism for neurons exposed to an oxidant challenge, and its expression decreases during senescence. In the present report we show that the RNA-binding protein ELAV/HuR can affect, post-transcriptionally, the fate of HSP70 mRNA following H(2)O(2)-mediated oxidative stress in SH-SY5Y human neuroblastoma cells. As a consequence of H(2)O(2) treatment (1mM for 30 minutes), HSP70 mRNA accumulates in the ribosomes associated to the cytoskeleton, where parallel Western blotting experiments reveal statistically significant increase for both HuR and HSP70 protein levels. We also confirm the capability of HuR to bind to HSP70 mRNA, and describe how the biological effect of this ELAV protein on the HSP70 mRNA could be due to a direct phosphorylation in serine/threonine residues of HuR itself by the early (10 minutes) H(2)O(2)-mediated activation of PKC alpha. Our findings shed light on the post-transcriptional regulation of HSP70 expression, suggesting the existence of a new molecular cascade -involving PKC/HuR/HSP70- that possibly represents an early event in the cellular response to H(2)O(2)-mediated oxidative stress in SH-SY5Y human neuroblastoma cells. The present results lead us to speculate that an impairment in this regulatory mechanism might directly contribute to the defective cellular response to oxidative stress, thus helping to dissect a potential tool useful to counteract some aspects associated to cerebral senescence.