Broccoli as a Nrf2 ActivatorEat your broccoli! How many times did you hear that as a kid?
Well, it turns out that perhaps what was initially based on a "housewife's tale" and probably by those who had no idea what Nrf2 actually is were actually right on the mark. Latest scientific research validated the powerful impact that broccoli has as a Nrf2 activator. Below are the latest 15 studies published on Pubmed. Don't forget now, "eat your broccoli".
Glucoraphanin: a broccoli sprout extract that ameliorates obesity-induced inflammation and insulin resistance
Obesity is a low-grade sustained inflammatory state that causes oxidative stress in different metabolic tissues, which leads to insulin resistance and nonalcoholic fatty liver disease (NAFLD). Particularly, obesity-induced metabolic endotoxemia plays an important role in the pathogenesis of insulin resistance and inflammation. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key regulator of antioxidant signaling that serves as a primary cellular defense against the cytotoxic effects of oxidative stress. Pharmacological stimulation of Nrf2 mitigates obesity and insulin resistance in mice; however, Nrf2 activators are not clinically available due to biosafety concerns. A recent study demonstrated that glucoraphanin, a precursor of the Nrf2 activator sulforaphane, ameliorates obesity by enhancing energy expenditure and browning of white adipose tissue, and attenuates obesity-related inflammation and insulin resistance by polarizing M2 macrophages and reducing metabolic endotoxemia. Thus, this review focuses on the efficiency and safety of glucoraphanin in alleviating obesity, insulin resistance, and NAFLD.
Sulforaphane Promotes Mitochondrial Protection in SH-SY5Y Cells Exposed to Hydrogen Peroxide by an Nrf2-Dependent Mechanism
Sulforaphane (SFN; CHNOS) is an isothiocyanate found in cruciferous vegetables, such as broccoli, kale, and radish. SFN exhibits antioxidant, anti-apoptotic, anti-tumor, and anti-inflammatory activities in different cell types. However, it was not previously demonstrated whether and how this natural compound would exert mitochondrial protection experimentally. Therefore, we investigated here the effects of a pretreatment (for 30 min) with SFN at 5 μM on mitochondria obtained from human neuroblastoma SH-SY5Y cells exposed to hydrogen peroxide (HO) at 300 μM for 24 h. We found that SFN prevented loss of viability in HO-treated SH-SY5Y cells. Furthermore, SFN decreased lipid peroxidation, protein carbonylation, and protein nitration in mitochondrial membranes of HO-exposed cells. Importantly, SFN enhanced the levels of both cellular and mitochondrial glutathione (GSH). SFN also suppressed the HO-mediated inhibition of mitochondrial components involved in the maintenance of the bioenergetics state, such as aconitase, α-ketoglutarate dehydrogenase, and succinate dehydrogenase, as well as complexes I and V. Consequently, SFN prevented the decline induced by HO on the levels of ATP in SH-SY5Y cells. Silencing of the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor by using small interfering RNA (siRNA) abolished the mitochondrial and cellular protection elicited by SFN. Therefore, SFN abrogated the HO-induced mitochondrial impairment by an Nrf2-dependent manner.
Broccoli Sprout Extract Alleviates Alcohol-Induced Oxidative Stress and Endoplasmic Reticulum Stress in C57BL/6 Mice
The potential efficacy of sulforaphane in protecting alcohol-induced hepatic injury in vivo and its underlying mechanism were investigated. Male C57BL/6 mice were orally administrated with broccoli sprout extract (BSE) containing sulforaphane [7.6, 25.2, and 50.4 mg/kg of body weight (bw)] once a day for 14 days. At the 13th day, mice were challenged with alcohol (5 g/kg of bw) every 12 h for 3 times, which increased malondialdehyde (MDA) levels (4.44 ± 1.24 nmol/mg of protein, p < 0.01) in the liver. Our results showed that low-, medium-, and high-dose BSE markedly reversed the decrease of antioxidant capacity through enhancing glutathione (GSH) (2.07 ± 0.31 mg/g of protein, p < 0.05; 2.31 ± 0.32 mg/g of protein, p < 0.01; and 2.46 ± 0.21 mg/g of protein, p < 0.01), superoxide dismutase (SOD) (483.20 ± 62.76 units/mg of protein; 500.81 ± 49.82 units/mg of protein, p < 0.05; and 605.00 ± < 64.32 units/mg of protein, p < 0.01), glutathione peroxidase (GSH-Px) (318 ± 60.74 units/mg of protein; 400.67 ± 72.47 units/mg of protein, p < 0.01; and 394.72 ± 62.97 units/mg of protein, p < 0.01), and glutathione S-transferase (GST) (31.84 ± 6.34 units/mg of protein, p < 0.05; 30.34 ± 6.40 units/mg of protein, p < 0.05; and 38.08 ± 7.05 units/mg of protein, p < 0.01) in the liver. The protective actions are also associated activation of phase 2 enzymes via nuclear erythoriod-2-related factor 2 (Nrf2). The endoplasmic reticulum (ER)-stress-specific proteins, such as glucose-regulated protein 78 (GRP78), activating transcription factor 6, and protein kinase RNA (PKR)-like ER kinase (PERK), were also significantly attenuated by BSE. These results indicate that BSE protects the liver against alcohol challenge via upregulating antioxidant capacity and downregulating ER stress.
Nrf2 targeting by sulforaphane: A potential therapy for cancer treatment
In the past decades, extensive studies have reported the potential chemopreventive activity of sulforaphane, an isothiocyanate derived from glucoraphanin, occurring in large amounts in Brassica genus plants. Sulforaphane was found to be active against several forms of cancer. A growing body of data shows that sulforaphane acts against cancer at different levels, from development to progression, through pleiotropic effects. In this review, we discuss the available experimental and clinical data on the potential therapeutic role of sulforaphane against cancer. Its effects range from the protection of cells from DNA damage to the modulation of the cell cycle via pro-apoptotic, anti-angiogenesis and anti-metastasis activities. At molecular level, sulforaphane modulates cellular homeostasis via the activation of the transcription factor Nrf2. Although data from clinical studies are limited, sulforaphane remains a good candidate in the adjuvant therapy based on natural molecules against several types of cancer.
Contribution of NRF2 in Gastrointestinal Protection From Oxidative Injury
The human gastrointestinal tract is exposed to a variety of toxic agents, such as Helicobacter pylori (H.pylori), nonsteroidal anti-inflammatory drugs (NSAIDs), gastric acid, enteric pathogenic bacteria, excessive auto immune reactions, and chronic mental stresses. These stressors generate free radicals within the gastrointestinal tissues, causing chronic inflammatory diseases, ulcers, cancers, and functional disturbances. Recent studies have demonstrated that some natural food compounds upregulate the nuclear factor erythroid 2-related factor 2-mediated antioxidant system, ameliorating or preventing these disorders. We have previously shown that dietary intake of sulforaphane-rich broccoli sprouts, ameliorates gastric inflammation induced by H. pylori, prevents NSAIDs-induced small intestinal injury, and improve functional constipation. There have been many other compounds, which enhance the nuclear factor erythroid 2-related factor 2-mediated antioxidant system, sufficient evidence for their clinical efficacy has not yet been provided. In addition, we have to pay attention to some reports, which have shown that excessive stimulation of nuclear factor erythroid 2-related factor 2 enhance chemoresistance and facilitates growth of cancer cells.
Comparison of Adaptive Neuroprotective Mechanisms of Sulforaphane and its Interconversion Product Erucin in in Vitro and in Vivo Models of Parkinson's Disease
Several studies suggest that an increase of glutathione (GSH) through activation of the transcriptional nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in the dopaminergic neurons may be a promising neuroprotective strategy in Parkinson's disease (PD). Among Nrf2 activators, isothiocyanate sulforaphane (SFN), derived from precursor glucosinolate present in Brassica vegetables, has gained attention as a potential neuroprotective compound. Bioavailability studies also suggest the contribution of SFN metabolites, including erucin (ERN), to the neuroprotective effects of SFN. Therefore, we compared the in vitro neuroprotective effects of SFN and ERN at the same dose level (5 μM) and oxidative treatment with 6-hydroxydopamine (6-OHDA) in SH-SY5Y cells. The pretreatment of SH-SY5Y cells with SFN recorded a higher (p < 0.05) active nuclear Nrf2 protein (12.0 ± 0.4 vs 8.0 ± 0.2 fold increase), mRNA Nrf2 (2.0 ± 0.3 vs 1.4 ± 0.1 fold increase), total GSH (384.0 ± 9.0 vs 256.0 ± 8.0 μM) levels, and resistance to neuronal apoptosis elicited by 6-OHDA compared to ERN. By contrast, the simultaneous treatment of SH-SY5Y cells with either SFN or ERN and 6-OHDA recorded similar neuroprotective effects with both the isothiocyanates (Nrf2 protein 2.2 ± 0.2 vs 2.1 ± 0.1 and mRNA Nrf2 2.1 ± 0.3 vs 1.9 ± 0.2 fold increase; total GSH 384.0 ± 4.8 vs 352.0 ± 6.4 μM). Finally, in vitro finding was confirmed in a 6-OHDA-PD mouse model. The metabolic oxidation of ERN to SFN could account for their similar neuroprotective effects in vivo, raising the possibility of using vegetables containing a precursor of ERN for systemic antioxidant benefits in a similar manner to SFN.
KEAP1 and Done? Targeting the NRF2 Pathway with Sulforaphane
Since the re-discovery of sulforaphane in 1992 and the recognition of the bioactivity of this phytochemical, many studies have examined its mode of action in cells, animals and humans. Broccoli, especially as young sprouts, is a rich source of sulforaphane and broccoli-based preparations are now used in clinical studies probing efficacy in health preservation and disease mitigation. Many putative cellular targets are affected by sulforaphane although only one, KEAP1-NRF2 signaling, can be considered a validated target at this time. The transcription factor NRF2 is a master regulator of cell survival responses to endogenous and exogenous stressors.
Brassica-Derived Plant Bioactives as Modulators of Chemopreventive and Inflammatory Signaling Pathways
A high consumption of vegetables belonging to the family has been related to a lower incidence of chronic diseases including different kinds of cancer. These beneficial effects of, e.g., broccoli, cabbage or rocket (arugula) intake have been mainly dedicated to the sulfur-containing glucosinolates (GLSs)-secondary plant compounds nearly exclusively present in and in particular to their bioactive breakdown products including isothiocyanates (ITCs). Overall, the current literature indicate that selected -derived ITCs exhibit health-promoting effects in vitro, as well as in laboratory mice in vivo. Some studies suggest anti-carcinogenic and anti-inflammatory properties for ITCs which may be communicated through an activation of the redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) that controls the expression of antioxidant and phase II enzymes. Furthermore, it has been shown that ITCs are able to significantly ameliorate a severe inflammatory phenotype in colitic mice in vivo. As there are studies available suggesting an epigenetic mode of action for -derived phytochemicals, the conduction of further studies would be recommendable to investigate if the beneficial effects of these compounds also persist during an irregular consumption pattern.
Sulforaphane reduces hepatic glucose production and improves glucose control in patients with type 2 diabetes
A potentially useful approach for drug discovery is to connect gene expression profiles of disease-affected tissues ("disease signatures") to drug signatures, but it remains to be shown whether it can be used to identify clinically relevant treatment options. We analyzed coexpression networks and genetic data to identify a disease signature for type 2 diabetes in liver tissue. By interrogating a library of 3800 drug signatures, we identified sulforaphane as a compound that may reverse the disease signature. Sulforaphane suppressed glucose production from hepatic cells by nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2) and decreased expression of key enzymes in gluconeogenesis. Moreover, sulforaphane reversed the disease signature in the livers from diabetic animals and attenuated exaggerated glucose production and glucose intolerance by a magnitude similar to that of metformin. Finally, sulforaphane, provided as concentrated broccoli sprout extract, reduced fasting blood glucose and glycated hemoglobin (HbA1c) in obese patients with dysregulated type 2 diabetes.
Prophylactic effects of sulforaphane on depression-like behavior and dendritic changes in mice after inflammation
Inflammation plays a role in the pathophysiology of depression. Sulforaphane (SFN), an isothiocyanate compound derived from broccoli, is a potent activator of the NF-E2-related factor-2 (Nrf2), which plays a role in inflammation. In this study, we examined whether the prevention effects of SFN in lipopolysaccharide (LPS) induced depression-like behavior in mice. Pretreatment with SFN significantly blocked an increase in the serum tumor necrosis factor-α (TNF-α) level and an increase in microglial activation of brain regions after a single administration of LPS (0.5 mg/kg). Furthermore, SFN significantly potentiated increased serum levels of IL-10 after LPS administration. In the tail-suspension test and forced swimming test, SFN significantly attenuated an increase of the immobility time after LPS administration. In addition, SFN significantly recovered to control levels for LPS-induced alterations in the proteins such as brain-derived neurotrophic factor, postsynaptic density protein 95 and AMPA receptor 1 (GluA1) and dendritic spine density in the brain regions. Finally, dietary intake of 0.1% glucoraphanin (a glucosinolate precursor of SFN) food during the juvenile and adolescence could prevent the onset of LPS-induced depression-like behaviors and dendritic spine changes in the brain regions at adulthood. In conclusion, these findings suggest that dietary intake of SFN-rich broccoli sprout has prophylactic effects on inflammation-related depressive symptoms. Therefore, supplementation of SFN-rich broccoli sprout could be prophylactic vegetable to prevent or minimize the relapse by inflammation in the remission state of depressed patients.
A proof-of-concept clinical study examining the NRF2 activator sulforaphane against neutrophilic airway inflammation
Sulforaphane (SFN), a naturally occurring isothiocyanate found in cruciferous vegetables, is implicated as a possible therapy for airway inflammation via induction of the transcription factor NF-E2-related factor 2 (NRF2). In this proof-of-concept clinical study, we show that supplementation of SFN with broccoli sprout homogenate in healthy human subjects did not induce expression of antioxidant genes or protect against neutrophilic airway inflammation in an ozone-exposure model. Therefore, dietary sulforaphane supplementation is not a promising candidate for larger scale clinical trials targeting airway inflammation.
Broccoli sprout extract prevents diabetic cardiomyopathy via Nrf2 activation in db/db T2DM mice
To develop a clinic-relevant protocol for systemic up-regulation of NFE2-related factor 2 (Nrf2) to prevent diabetic cardiomyopathy (DCM), male db/db and age-matched wild-type (WT) mice were given sulforaphane (SFN, an Nrf2 activator) and its natural source, broccoli sprout extract (BSE) by gavage every other day for 3 months, with four groups: vehicle (0.1 ml/10 g), BSE-low dose (estimated SFN availability at 0.5 mg/kg), BSE-high dose (estimated SFN availability at 1.0 mg/kg), and SFN (0.5 mg/kg). Cardiac function and pathological changes (hypertrophy, fibrosis, inflammation and oxidative damage) were assessed by echocardiography and histopathological examination along with Western blot and real-time PCR, respectively. Both BSE and SFN significantly prevented diabetes-induced cardiac dysfunction, hypertrophy and fibrosis. Mechanistically, BSE, like SFN, significantly up-regulated Nrf2 transcriptional activity, evidenced by the increased Nrf2 nuclear accumulation and its downstream gene expression. This resulted in a significant prevention of cardiac oxidative damage and inflammation. For all these preventive effects, BSE at high dose provided a similar effect as did SFN. These results indicated that BSE at high dose prevents DCM in a manner congruent with SFN treatment. Therefore, it suggests that BSE could potentially be used as a natural and safe treatment against DCM via Nrf2 activation.
Lack of Effect of Oral Sulforaphane Administration on Nrf2 Expression in COPD: A Randomized, Double-Blind, Placebo Controlled Trial
COPD patients have high pulmonary and systemic oxidative stress that correlates with severity of disease. Sulforaphane has been shown to induce expression of antioxidant genes via activation of a transcription factor, nuclear factor erythroid-2 related factor 2 (Nrf2).
Sulforaphane Protects against Brain Diseases: Roles of Cytoprotective Enzymes
Sulforaphane (SFN) is a kind of isothiocyanate derived from broccoli and other cruciferous vegetables. Because of its roles of antioxidant, anti-inflammatory, and anti-tumor through multiple targets and various mechanisms, SFN has drawn broad attention of the researchers. One of the most important target of SFN is nuclear factor erythroid 2 related factor 2 (Nrf2), wildly known for its ability to regulate the expression of a series of cytoprotective enzymes with antioxidative, prosurvival, and detoxification effects. Multiple researches have shown that SFN protects against central nervous system diseases through Nrf2pathway. In this article, we list SFN contents in common cruciferous vegetables, and summarize recent advances in the protective effects of SFN against acute brain injuries and neurodegenerative diseases through activating Nrf2 signaling pathway.
Correction: Lack of Effect of Oral Sulforaphane Administration on Nrf2 Expression in COPD: A Randomized, Double-Blind, Placebo Controlled Trial
[This corrects the article DOI: 10.1371/journal.pone.0163716.].