Sulforaphane inhibits multiple inflammasomes through an Nrf2-independent mechanism

Antitumor activity and expression profiles of genes induced by sulforaphane in human melanoma cells

Purpose

Human melanoma is a highly aggressive incurable cancer due to intrinsic cellular resistance to apoptosis, reprogramming, proliferation and survival during tumour progression. Sulforaphane (SFN), an isothiocyanate found in cruciferous vegetables, plays a role in carcinogenesis in many cancer types. However, the cytotoxic molecular mechanisms and gene expression profiles promoted by SFN in human melanoma remain unknown.

Methods

Three different cell lines were used: two human melanoma A375 and 501MEL and human epidermal melanocytes (HEMa). Cell viability and proliferation, cell cycle analysis, cell migration and invasion and protein expression and phosphorylation status of Akt and p53 upon SFN treatment were determined. RNA-seq of A375 was performed at different time points after SFN treatment.

Results

We demonstrated that SFN strongly decreased cell viability and proliferation, induced G₂/M cell cycle arrest, promoted apoptosis through the activation of caspases 3, 8, 9 and hampered migration and invasion abilities in the melanoma cell lines. Remarkably, HEMa cells were not affected by SFN treatment. Transcriptomic analysis revealed regulation of genes involved in response to stress, apoptosis/cell death and metabolic processes. SFN upregulated the expression of pro-apoptotic genes, such as p53, BAX, PUMA, FAS and MDM2; promoted cell cycle inhibition and growth arrest by upregulating EGR1, GADD45B, ATF3 and CDKN1A; and simultaneously acted as a potent inhibitor of genotoxicity by launching the stress-inducible protein network (HMOX1, HSPA1A, HSPA6, SOD1).

Conclusion

Overall, the data show that SFN cytotoxicity in melanoma derives from complex and concurrent mechanisms during carcinogenesis, which makes it a promising cancer prevention agent.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-017-1527-7) contains supplementary material, which is available to authorized users.

Chemopreventive effects of atractylenolide II on mammary tumorigenesis via activating Nrf2-ARE pathway

In the studies of chemoprevention, the Nrf2-ARE signaling pathway has received widespread attention due to its anti-inflammatory and anti-oxidation effects. Our previous study indicated that atractylenolide II, which is an active component of Atractylodes macrocephala Koidz, is a potential activator of Nrf2-ARE signaling pathway. In this study, we observed that atractylenolide II significantly increased Nrf2 expressing, nuclear translocation and the expression of its downstream detoxifying enzymes, thus decreasing 17β-Estradiol induced malignant transformation in MCF 10A cells, and we found that atractylenolide II acted through JNK/ERK-Nrf2-ARE pathway. Furthermore, atractylenolide II significantly reduced N-Nitroso-N-methylurea induced tumor incidence, multiplicity and volume, with activation of Nrf2-ARE pathway and decreased inflammation and oxidative stress in rat mammary tissue. Collectively, our results suggested that atractylenolide II could protect against mammary tumorigenesis both in vivo and in vitro via activating Nrf2-ARE signaling pathway, which supported atractylenolide II as a novel chemopreventive agent of breast cancer.

Activation of Nrf2 Signaling Augments Vesicular Stomatitis Virus Oncolysis via Autophagy-Driven Suppression of Antiviral Immunity

Oncolytic viruses (OVs) offer a promising therapeutic approach to treat multiple types of cancer. In this study, we show that the manipulation of the antioxidant network via transcription factor Nrf2 augments vesicular stomatitis virus Δ51 (VSVΔ51) replication and sensitizes cancer cells to viral oncolysis. Activation of Nrf2 signaling by the antioxidant compound sulforaphane (SFN) leads to enhanced VSVΔ51 spread in OV-resistant cancer cells and improves the therapeutic outcome in different murine syngeneic and xenograft tumor models. Chemoresistant A549 lung cancer cells that display constitutive dominant hyperactivation of Nrf2 signaling are particularly vulnerable to VSVΔ51 oncolysis. Mechanistically, enhanced Nrf2 signaling stimulated viral replication in cancer cells and disrupted the type I IFN response via increased autophagy. This study reveals a previously unappreciated role for Nrf2 in the regulation of autophagy and the innate antiviral response that complements the therapeutic potential of VSV-directed oncolysis against multiple types of OV-resistant or chemoresistant cancer.

Glucoraphanin Ameliorates Obesity and Insulin Resistance Through Adipose Tissue Browning and Reduction of Metabolic Endotoxemia in Mice

Low-grade sustained inflammation links obesity to insulin resistance and nonalcoholic fatty liver disease (NAFLD). However, therapeutic approaches to improve systemic energy balance and chronic inflammation in obesity are limited. Pharmacological activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) alleviates obesity and insulin resistance in mice; however, Nrf2 inducers are not clinically available owing to safety concerns. Thus, we examined whether dietary glucoraphanin, a stable precursor of the Nrf2 inducer sulforaphane, ameliorates systemic energy balance, chronic inflammation, insulin resistance, and NAFLD in high-fat diet (HFD)-fed mice. Glucoraphanin supplementation attenuated weight gain, decreased hepatic steatosis, and improved glucose tolerance and insulin sensitivity in HFD-fed wild-type mice but not in HFD-fed Nrf2 knockout mice. Compared with vehicle-treated controls, glucoraphanin-treated HFD-fed mice had lower plasma lipopolysaccharide levels and decreased relative abundance of the gram-negative bacteria family Desulfovibrionaceae in their gut microbiomes. In HFD-fed mice, glucoraphanin increased energy expenditure and the protein expression of uncoupling protein 1 (Ucp1) in inguinal and epididymal adipose depots. Additionally, in this group, glucoraphanin attenuated hepatic lipogenic gene expression, lipid peroxidation, classically activated M1-like macrophage accumulation, and inflammatory signaling pathways. By promoting fat browning, limiting metabolic endotoxemia-related chronic inflammation, and modulating redox stress, glucoraphanin may mitigate obesity, insulin resistance, and NAFLD.

Broccoli-Derived Nanoparticle Inhibits Mouse Colitis by Activating Dendritic Cell AMP-Activated Protein Kinase

The intestinal immune system is continuously exposed to massive amounts of nanoparticles derived from food. Whether nanoparticles from plants we eat daily have a role in maintaining intestinal immune homeostasis is poorly defined. Here, we present evidence supporting our hypothesis that edible nanoparticles regulate intestinal immune homeostasis by targeting dendritic cells (DCs). Using three mouse colitis models, our data show that orally given nanoparticles isolated from broccoli extracts protect mice against colitis. Broccoli-derived nanoparticle (BDN)-mediated activation of adenosine monophosphate-activated protein kinase (AMPK) in DCs plays a role in not only prevention of DC activation but also induction of tolerant DCs. Adoptively transferring DCs pre-pulsed with total BDN lipids, but not sulforaphane (SFN)-depleted BDN lipids, prevented DSS-induced colitis in C57BL/6 (B6) mice, supporting the role of BDN SFN in the induction of DC tolerance. Adoptively transferring AMPK^+/+, but not AMPK^-/-, DCs pre-pulsed with SFN prevented DSS-induced colitis in B6 mice, further supporting the DC AMPK role in SFN-mediated prevention of DSS-induced colitis. This finding could open new preventive or therapeutic avenues to address intestinal-related inflammatory diseases via activating AMPK.

Sulforaphane Protects Pancreatic Acinar Cell Injury by Modulating Nrf2-Mediated Oxidative Stress and NLRP3 Inflammatory Pathway

Acute pancreatitis (AP) is characterized by early activation of intra-acinar proteases followed by acinar cell death and inflammation. Cellular oxidative stress is a key mechanism underlying these pathological events. Sulforaphane (SFN) is a natural organosulfur antioxidant with undescribed effects on AP. Here we investigated modulatory effects of SFN on cellular oxidation and inflammation in AP. AP was induced by cerulean hyperstimulation in BALB/c mice. Treatment group received a single dose of 5 mg/kg SFN for 3 consecutive days before AP. We found that SFN administration attenuated pancreatic injury as evidenced by serum amylase, pancreatic edema, and myeloperoxidase, as well as by histological examination. SFN administration reverted AP-associated dysregulation of oxidative stress markers including pancreatic malondialdehyde and redox enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx). In acinar cells, SFN treatment upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) expression and Nrf2-regulated redox genes including quinoneoxidoreductase-1, heme oxidase-1, SOD1, and GPx1. In addition, SFN selectively suppressed cerulein-induced activation of the nucleotide-binding domain leucine-rich repeat containing family, pyrin domain-containing 3 (NLRP3) inflammasome, in parallel with reduced nuclear factor- (NF-) κB activation and modulated NF-κB-responsive cytokine expression. Together, our data suggested that SFN modulates Nrf2-mediated oxidative stress and NLRP3/NF-κB inflammatory pathways in acinar cells, thereby protecting against AP.

Sulforaphane induces neurovascular protection against a systemic inflammatory challenge via both Nrf2-dependent and independent pathways

Sepsis is often characterized by an acute brain inflammation and dysfunction, which is associated with increased morbidity and mortality worldwide. Preventing cerebral leukocyte recruitment may provide the key to halt progression of systemic inflammation to the brain. Here we investigated the influence of the anti-inflammatory and anti-oxidant compound, sulforaphane (SFN) on lipopolysaccharide (LPS)-induced cellular interactions in the brain. The inflammatory response elicited by LPS was blunted by SFN administration (5 and 50mg/kg i.p.) 24h prior to LPS treatment in WT animals, as visualized and quantified using intravital microscopy. This protective effect of SFN was lost in Nrf2-KO mice at the lower dose tested, however 50mg/kg SFN revealed a partial effect, suggesting SFN works in part independently of Nrf2 activity. In vitro, SFN reduced neutrophil recruitment to human brain endothelial cells via a down regulation of E-selectin and vascular cell adhesion molecule 1 (VCAM-1). Our data confirm a fundamental dose-dependent role of SFN in limiting cerebral inflammation. Furthermore, our data demonstrate that not only is Nrf2 in part essential in mediating these neuroprotective effects, but they occur via down-regulation of E-selectin and VCAM-1. In conclusion, SFN may provide a useful therapeutic drug to reduce cerebral inflammation in sepsis.

Hyperammonemia induces glial activation, neuroinflammation and alters neurotransmitter receptors in hippocampus, impairing spatial learning: reversal by sulforaphane

Background

Patients with liver cirrhosis and minimal hepatic encephalopathy (MHE) show mild cognitive impairment and spatial learning dysfunction. Hyperammonemia acts synergistically with inflammation to induce cognitive impairment in MHE. Hyperammonemia-induced neuroinflammation in hippocampus could contribute to spatial learning impairment in MHE. Two main aims of this work were: (1) to assess whether chronic hyperammonemia increases inflammatory factors in the hippocampus and if this is associated with microglia and/or astrocytes activation and (2) to assess whether hyperammonemia-induced neuroinflammation in the hippocampus is associated with altered membrane expression of glutamate and GABA receptors and spatial learning impairment. There are no specific treatments for cognitive alterations in patients with MHE. A third aim was to assess whether treatment with sulforaphane enhances endogenous the anti-inflammatory system, reduces neuroinflammation in the hippocampus of hyperammonemic rats, and restores spatial learning and if normalization of receptor membrane expression is associated with learning improvement.

Methods

We analyzed the following in control and hyperammonemic rats, treated or not with sulforaphane: (1) microglia and astrocytes activation by immunohistochemistry, (2) markers of pro-inflammatory (M1) (IL-1β, IL-6) and anti-inflammatory (M2) microglia (Arg1, YM-1) by Western blot, (3) membrane expression of GABA, AMPA, and NMDA receptors using the BS3 cross-linker, and (4) spatial learning using the radial maze.

Results

The results reported show that hyperammonemia induces astrocytes and microglia activation in the hippocampus, increasing pro-inflammatory cytokines IL-1β and IL-6. This is associated with altered membrane expression of AMPA, NMDA, and GABA receptors which would be responsible for altered neurotransmission and impairment of spatial learning in the radial maze. Treatment with sulforaphane promotes microglia differentiation from pro-inflammatory M1 to anti-inflammatory M2 phenotype and reduces activation of astrocytes in hyperammonemic rats. This reduces neuroinflammation, normalizes membrane expression of glutamate and GABA receptors, and restores spatial learning in hyperammonemic rats.

Conclusions

Hyperammonemia-induced neuroinflammation impairs glutamatergic and GABAergic neurotransmission by altering membrane expression of glutamate and GABA receptors, resulting in impaired spatial learning. Sulforaphane reverses all these effects. Treatment with sulforaphane could be useful to improve cognitive function in cirrhotic patients with minimal or clinical hepatic encephalopathy.

Nrf2 activators as potential modulators of injury in human kidney cells

Cisplatin is a chemotherapeutic agent used in the treatment of solid tumors, with clinical use often complicated by kidney toxicity. Nuclear factor (erythroid-derived-2)-like 2 (Nrf2) is a transcription factor involved in kidney protectant effects. The purpose of this study was to determine whether the Nrf2 activators oltipraz, sulforaphane, and oleanolic acid could protect human kidney cells against cisplatin-induced injury and to compare the protective effects between three Nrf2 activators. Human proximal tubule cells (hPTC) and human embryonic kidney 293 cells (HEK293) were exposed to cisplatin doses in the absence and presence of Nrf2 activators. Pre- and delayed-cisplatin and Nrf2 activator exposures were also assessed. Cell viability was enhanced with Nrf2 activator exposures, with differences detected between pre- and delayed-treatments. Both sulforaphane and oltipraz increased the expression of anti-oxidant genes GCLC and NQO1. These findings suggest potential human kidney protective benefits of Nrf2 activators with planned exposures to cisplatin.