Friend or Foe: Xenobiotic Activation of Nrf2 in Disease Control and Cardioprotection

Glucosinolates in cancer prevention and treatment: experimental and clinical evidence

Glucosinolates are naturally occurring β-d-thioglucosides that mainly exist in the Brassicaceae family. The enzyme myrosinase hydrolyzes glucosinolates to form isothiocyanates, which are chemical protectors. Phenethyl isothiocyanate, sulforaphane, and benzyl isothiocyanate are potential isothiocyanate with efficient anti-cancer effects as a protective or treatment agent. Glucosinolate metabolites exert the cancer-preventive activity through different mechanisms, including induction of the Nrf2 transcription factor, inhibition of expression of tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β), induction of apoptosis through inhibiting phase I enzymes and inducting phase II enzymes, interruption of caspase pathways, STAT1/STAT2, inhibition of sulfotransferases. Moreover, glucosinolates and their metabolites are effective in cancer treatment by inhibiting angiogenesis, upregulating natural killers, increasing expression of p53, p21, caspase 3 and 9, and modulating NF-κB. Despite the mentioned cancer-preventing effects, some isothiocyanates can increase the risk of tumors. So, further studies are needed to obtain an accurate and effective dose for each glucosinolates to treat different types of tumors.

MK-886 protects against cardiac ischaemia/reperfusion injury by activating proteasome-Keap1-NRF2 signalling

Oxidative stress is considered a key factor contributing to the initiation and development of cardiac injury following ischaemia‒reperfusion (I/R). Arachidonate 5-lipoxygenase (ALOX5) is a rate-limiting enzyme for leukotriene biosynthesis. MK-886 is an inhibitor of ALOX5 that exhibits anti-inflammatory and antioxidant activities. However, the significance of MK-886 in preventing I/R-mediated cardiac injury and the underlying mechanism remain unclear. Cardiac I/R model was produced by ligation/release of the left anterior descending artery. MK-886 (20 mg/kg) was administered intraperitoneally into mice at 1 and 24 h before I/R. Our results indicated that MK-886 treatment significantly attenuated I/R-mediated cardiac contractile dysfunction and decreased the infarct area, myocyte apoptosis, and oxidative stress accompanied with reduction of Kelch-like ECH-associated protein 1 (keap1) and upregulation of nuclear factor erythroid 2-related factor 2 (NRF2). Conversely, administration of the proteasome inhibitor epoxomicin and NRF2 inhibitor ML385 greatly abrogated MK-886-mediated cardioprotection after I/R injury. Mechanistically, MK-886 enhanced the expression of the immunoproteasome subunit β5i, which interacted with keap1 and enhanced its degradation, leading to activation of the NRF2-dependent antioxidant response and improvement of mitochondrial fusion-fission balance in the I/R-treated heart. In summary, our present findings indicated that MK-886 could protect the heart against I/R injury and highlight that MK-886 may represent a promising therapeutic candidate for preventing ischaemic disease.

Immunomodulatory actions of a kynurenine-derived endogenous electrophile

The up-regulation of kynurenine metabolism induces immunomodulatory responses via incompletely understood mechanisms. We report that increases in cellular and systemic kynurenine levels yield the electrophilic derivative kynurenine-carboxyketoalkene (Kyn-CKA), as evidenced by the accumulation of thiol conjugates and saturated metabolites. Kyn-CKA induces NFE2 like bZIP transcription factor 2- and aryl hydrocarbon receptor-regulated genes and inhibits nuclear factor κB- and NLR family pyrin domain containing 3-dependent proinflammatory signaling. Sickle cell disease (SCD) is a hereditary hemolytic condition characterized by basal inflammation and recurrent vaso-occlusive crises. Both transgenic SCD mice and patients with SCD exhibit increased kynurenine and Kyn-CKA metabolite levels. Plasma hemin and kynurenine concentrations are positively correlated, indicating that Kyn-CKA synthesis in SCD is up-regulated during pathogenic vascular stress. Administration of Kyn-CKA abrogated pulmonary microvasculature occlusion in SCD mice, an important factor in lung injury development. These findings demonstrate that the up-regulation of kynurenine synthesis and its metabolism to Kyn-CKA is an adaptive response that attenuates inflammation and protects tissues.

Targeting CAR and Nrf2 improves cyclophosphamide bioactivation while reducing doxorubicin-induced cardiotoxicity in triple-negative breast cancer treatment

Cyclophosphamide (CPA) and doxorubicin (DOX) are key components of chemotherapy for triple-negative breast cancer (TNBC), although suboptimal outcomes are commonly associated with drug resistance and/or intolerable side effects. Through an approach combining high-throughput screening and chemical modification, we developed CN06 as a dual activator of the constitutive androstane receptor (CAR) and nuclear factor erythroid 2-related factor 2 (Nrf2). CN06 enhances CAR-induced bioactivation of CPA (a prodrug) by provoking hepatic expression of CYP2B6, while repressing DOX-induced cytotoxicity in cardiomyocytes in vitro via stimulating Nrf2-antioxidant signaling. Utilizing a multicellular coculture model incorporating human primary hepatocytes, TNBC cells, and cardiomyocytes, we show that CN06 increased CPA/DOX-mediated TNBC cell death via CAR-dependent CYP2B6 induction and subsequent conversion of CPA to its active metabolite 4-hydroxy-CPA, while protecting against DOX-induced cardiotoxicity by selectively activating Nrf2-antioxidant signaling in cardiomyocytes but not in TNBC cells. Furthermore, CN06 preserves the viability and function of human iPSC-derived cardiomyocytes by modulating antioxidant defenses, decreasing apoptosis, and enhancing the kinetics of contraction and relaxation. Collectively, our findings identify CAR and Nrf2 as potentially novel combined therapeutic targets whereby CN06 holds the potential to improve the efficacy/toxicity ratio of CPA/DOX-containing chemotherapy.

The role of non-coding RNAs in ferroptosis regulation

Ferroptosis is a newly recognized form of cell death that is distinct from apoptosis, necrosis, autophagy in morphology, biochemistry, and heredity. The basic process of ferroptosis involves disordered permeability of plasma membrane, which is caused by abnormal accumulation of lipids and reactive oxygen species (ROS). The regulatory mechanism of ferroptosis is important due to its involvement in tumor progression, neurotoxicity, neurodegenerative diseases, acute renal failure, and ischemia-reperfusion injury. Recent studies have shown that in ferroptosis metabolism, non-coding RNAs (ncRNAs) can interfere with multiple signaling pathways at both the pre-transcriptional and post-transcriptional levels. Despite great progress, current research on the mechanism of ncRNAs and ferroptosis remains insufficient. This review provides an overview of the main mechanisms and targets of ferroptosis and focuses on the mechanisms of non-coding RNA regulation. Analyzing the deficiencies in current research may provide ideas for future studies to investigate.