Reduction and Scavenging of Chemically Reactive Drug Metabolites by NAD(P)H:Quinone Oxidoreductase 1 and NRH:Quinone Oxidoreductase 2 and Variability in Hepatic Concentrations

Development of Nurr1 agonists from amodiaquine by scaffold hopping and fragment growing

The neuroprotective transcription factor nuclear receptor-related 1 (Nurr1) has shown great promise as a therapeutic target in Parkinson's and Alzheimer's disease as well as multiple sclerosis but high-quality chemical tools for pharmacological target validation of Nurr1 are rare. We have employed the weak Nurr1 modulator amodiaquine (AQ) and AQ-derived fragments as templates to design a new Nurr1 agonist chemotype by scaffold hopping and fragment growing strategies. Systematic structural optimization of this scaffold yielded Nurr1 agonists with nanomolar potency and binding affinity. Comprehensive in vitro profiling revealed efficient cellular target engagement and compliance with the highest probe criteria. In human midbrain organoids bearing a Parkinson-driving LRRK2 mutation, a novel Nurr1 agonist rescued tyrosine hydroxylase expression highlighting the potential of the new Nurr1 modulator chemotype as lead and as a chemical tool for biological studies.

Polymorphisms and Pharmacogenomics of NQO2: The Past and the Future

The flavoenzyme N-ribosyldihydronicotinamide (NRH):quinone oxidoreductase 2 (NQO2) catalyzes two-electron reductions of quinones. NQO2 contributes to the metabolism of biogenic and xenobiotic quinones, including a wide range of antitumor drugs, with both toxifying and detoxifying functions. Moreover, NQO2 activity can be inhibited by several compounds, including drugs and phytochemicals such as flavonoids. NQO2 may play important roles that go beyond quinone metabolism and include the regulation of oxidative stress, inflammation, and autophagy, with implications in carcinogenesis and neurodegeneration. NQO2 is a highly polymorphic gene with several allelic variants, including insertions (I), deletions (D) and single-nucleotide (SNP) polymorphisms located mainly in the promoter, but also in other regulatory regions and exons. This is the first systematic review of the literature reporting on NQO2 gene variants as risk factors in degenerative diseases or drug adverse effects. In particular, hypomorphic 29 bp I alleles have been linked to breast and other solid cancer susceptibility as well as to interindividual variability in response to chemotherapy. On the other hand, hypermorphic polymorphisms were associated with Parkinson's and Alzheimer's disease. The I and D promoter variants and other NQO2 polymorphisms may impact cognitive decline, alcoholism and toxicity of several nervous system drugs. Future studies are required to fill several gaps in NQO2 research.

Pan-cancer and single-cell analysis reveal the prognostic value and immune response of NQO1

Background: Overexpression of the NAD(P)H: Quinone Oxidoreductase 1 (NQOI) gene has been linked with tumor progression, aggressiveness, drug resistance, and poor patient prognosis. Most research has described the biological function of the NQO1 in certain types and limited samples, but a comprehensive understanding of the NQO1's function and clinical importance at the pan-cancer level is scarce. More research is needed to understand the role of NQO1 in tumor infiltration, and immune checkpoint inhibitors in various cancers are needed. Methods: The NQO1 expression data for 33 types of pan-cancer and their association with the prognosis, pathologic stage, gender, immune cell infiltration, the tumor mutation burden, microsatellite instability, immune checkpoints, enrichment pathways, and the half-maximal inhibitory concentration (IC50) were downloaded from public databases. Results: Our findings indicate that the NQO1 gene was significantly upregulated in most cancer types. The Cox regression analysis showed that overexpression of the NQO1 gene was related to poor OS in Glioma, uveal melanoma, head and neck squamous cell carcinoma, kidney renal papillary cell carcinoma, and adrenocortical carcinoma. NQO1 mRNA expression positively correlated with infiltrating immune cells and checkpoint molecule levels. The single-cell analysis revealed a potential relationship between the NQO1 mRNA expression levels and the infiltration of immune cells and stromal cells in bladder urothelial carcinoma, invasive breast carcinoma, and colorectal cancer. Conversely, a negative association was noted between various drugs (17-AAG, Lapatinib, Trametinib, PD-0325901) and the NQO1 mRNA expression levels. Conclusion: NQO1 expression was significantly associated with prognosis, immune infiltrates, and drug resistance in multiple cancer types. The inhibition of the NQO1-dependent signaling pathways may provide a promising strategy for developing new cancer-targeted therapies.

Defining NAD(P)(H) Catabolism

Dietary vitamin B3 components, such as nicotinamide and nicotinic acid, are precursors to the ubiquitous redox cofactor nicotinamide adenine dinucleotide (NAD⁺). NAD⁺ levels are thought to decline with age and disease. While the drivers of this decline remain under intense investigation, strategies have emerged seeking to functionally maintain NAD⁺ levels through supplementation with NAD⁺ biosynthetic intermediates. These include marketed products, such as nicotinamide riboside (NR) and its phosphorylated form (NMN). More recent developments have shown that NRH (the reduced form of NR) and its phosphorylated form NMNH also increases NAD⁺ levels upon administration, although they initially generate NADH (the reduced form of NAD⁺). Other means to increase the combined levels of NAD⁺ and NADH, NAD(H), include the inhibition of NAD⁺-consuming enzymes or activation of biosynthetic pathways. Multiple studies have shown that supplementation with an NAD(H) precursor changes the profile of NAD(H) catabolism. Yet, the pharmacological significance of NAD(H) catabolites is rarely considered although the distribution and abundance of these catabolites differ depending on the NAD(H) precursor used, the species in which the study is conducted, and the tissues used for the quantification. Significantly, some of these metabolites have emerged as biomarkers in physiological disorders and might not be innocuous. Herein, we review the known and emerging catabolites of the NAD(H) metabolome and highlight their biochemical and physiological function as well as key chemical and biochemical reactions leading to their formation. Furthermore, we emphasize the need for analytical methods that inform on the full NAD(H) metabolome since the relative abundance of NAD(H) catabolites informs how NAD(H) precursors are used, recycled, and eliminated.

Riboflavin compounds show NAD(P)H dependent quinone oxidoreductase-like quinone reducing activity

NAD(P)H-dependent quinone oxidoreductase (NQO) is an essential enzyme in living organisms and cells protecting them from oxidative stress. NQO reduces coenzyme Q (CoQ) using NAD(P)H as an electron donor. In the present study, we searched for coenzyme Q10 reducing activity from fractions of gel filtration-fractionated rat liver homogenate. In addition to the large-molecular-weight fraction containing NQO, CoQ10 reducing activity was also detected in a low-molecular-weight fraction. Furthermore, dicumarol, a conventional inhibitor of NQO1 (DT diaphorase), did not inhibit the reduction but quercetin did, suggesting that the activity was not due to NQO1. After further purification, the NADH-dependent CoQ10-reducing compound was identified as riboflavin. Riboflavin is an active substituent of other flavin compounds such as FAD and FMN. These flavin compounds also reduced not only CoQ homologues but also vitamin K homologues in the presence of NADH. The mechanism was speculated to work as follows: NADH reduces flavin compounds to the corresponding reduced forms, and subsequently, the reduced flavin compounds immediately reduce bio-quinones. Furthermore, the flavin-NADH system reduces CoQ10 bound with saposin B, which is believed to function as a CoQ transfer protein in vivo. This flavin-dependent CoQ10 reduction, therefore, may function in aqueous phases such as the cell cytosol and bodily fluids.

Interactions of Betel Quid Constituents with Drug Disposition Pathways: An Overview

Global estimates indicate that over 600 million individuals worldwide consume the areca (betel) nut in some form. Nonetheless, its consumption is associated with a myriad of oral and systemic ailments, such as precancerous oral lesions, oropharyngeal cancers, liver toxicity and hepatic carcinoma, cardiovascular distress, and addiction. Users commonly chew slivers of areca nut in a complex consumable preparation called betel quid (BQ). Consequently, the user is exposed to a wide array of chemicals with diverse pharmacokinetic behavior in the body. However, a comprehensive understanding of the metabolic pathways significant to BQ chemicals is lacking. Henceforth, we performed a literature search to identify prominent BQ constituents and examine each chemical's interplay with drug disposition proteins. In total, we uncovered over 20 major chemicals (e.g., arecoline, nicotine, menthol, quercetin, tannic acid) present in the BQ mixture that were substrates, inhibitors, and/or inducers of various phase I (e.g., CYP, FMO, hydrolases) and phase II (e.g., GST, UGT, SULT) drug metabolizing enzymes, along with several transporters (e.g., P-gp, BCRP, MRP). Altogether, over 80 potential interactivities were found. Utilizing this new information, we generated theoretical predictions of drug interactions precipitated by BQ consumption. Data suggests that BQ consumers are at risk for drug interactions (and possible adverse effects) when co-ingesting other substances (multiple therapeutic classes) with overlapping elimination mechanisms. Until now, prediction about interactions is not widely known among BQ consumers and their clinicians. Further research is necessary based on our speculations to elucidate the biological ramifications of specific BQ-induced interactions and to take measures that improve the health of BQ consumers.

Interactions of the antioxidant enzymes NAD(P)H: Quinone oxidoreductase 1 (NQO1) and NRH: Quinone oxidoreductase 2 (NQO2) with pharmacological agents, endogenous biochemicals and environmental contaminants

NAD(P)H

Quinone Oxidoreductase 1 (NQO1) is an antioxidant enzyme that catalyzes the two-electron reduction of several different classes of quinone-like compounds (quinones, quinone imines, nitroaromatics, and azo dyes). One-electron reduction of quinone or quinone-like metabolites is considered to generate semiquinones to initiate redox cycling that is responsible for the generation of reactive oxygen species and oxidative stress and may contribute to the initiation of adverse drug reactions and adverse health effects. On the other hand, the two-electron reduction of quinoid compounds appears important for drug activation (bioreductive activation) via chemical rearrangement or autoxidation. Two-electron reduction decreases quinone levels and opportunities for the generation of reactive species that can deplete intracellular thiol pools. Also, studies have shown that induction or depletion (knockout) of NQO1 were associated with decreased or increased susceptibilities to oxidative stress, respectively. Moreover, another member of the quinone reductase family, NRH: Quinone Oxidoreductase 2 (NQO2), has a significant functional and structural similarity with NQO1. The activity of both antioxidant enzymes, NQO1 and NQO2, becomes critically important when other detoxification pathways are exhausted. Therefore, this article summarizes the interactions of NQO1 and NQO2 with different pharmacological agents, endogenous biochemicals, and environmental contaminants that would be useful in the development of therapeutic approaches to reduce the adverse drug reactions as well as protection against quinone-induced oxidative damage. Also, future directions and areas of further study for NQO1 and NQO2 are discussed.

Association of NQO1Pro187Ser polymorphism with clinical outcomes and survival of lung cancer patients treated with platinum chemotherapy

Background: The study was carried out to evaluate the association of NQO1 P187S polymorphism in North Indian lung cancer (LC) patients. We determined the effect of this polymorphic variant on the survival of LC patients. Patients & methods/results: This case-control study comprised a total of 1100 subjects. The genotyping was carried out using PCR-RFLP and statistical analysis was carried out. The variant TT genotype exhibited 3.5-fold higher odds in subjects with stage III (p = 0.0006), fivefold higher odds of lymph-node invasion (p = 0.007) and an odd of <1 in case of metastasis (p = 0.0028). Patients possessing TT genotype and administered with paclitaxel, exhibited a poor survival (3.57 vs 12.20 months; hazard ratio = 7.95; p = 0.0098). Conclusion: These results suggest that NQO1 variant genotype was not found to modulate risk toward LC. However, the variant genotype was found to be strongly correlated with stage III LC, lymph node invasion and was found to be positively correlating with metastasis.

Activation of Nrf2 signaling pathway by natural and synthetic chalcones: a therapeutic road map for oxidative stress

Introduction:Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway plays a key role in diverse gene expressions responsible for protection against oxidative stress and xenobiotics. Chalcones with a common chemical scaffold of 1,3-diaryl-2- propen-1-one, are abundantly present in nature with a wide variety of pharmacological properties. This review will discuss the interactions of natural and synthetic chalcones with Nrf2 signaling.Areas covered:Chalcones are reportedly found to activate Nrf2 signaling pathway, expression of Nrf2-regulated antioxidant genes, induce cytoprotective proteins and upregulate multidrug resistance-associated proteins. Chalcones being soft electrophiles are less prone to hostile off-target effects and unlikely to induce carcinogenicity and mutagenicity. Furthermore, their low toxicity, structural diversity, feasibility in structural reorganization and the presence of α,β-unsaturated carbonyl group which makes them suitable drug candidates targeting Nrf2-dependent diseases.Expert opinion:Nrf2-Keap1 signaling pathway plays a central role in redox signaling. However, available therapeutic agents for Nrf2 activation have limited practical applications due to their associated risks, relatively low efficacy and bioavailability. The designing and fabrication of new chemical entities with chalcone scaffold-based Michael acceptor mechanism should be aimed as potential therapeutic Nrf2 activators to target oxidative stress and inflammation-mediated diseases such as atherosclerosis, Parkinson's disease and many more.

The Biochemical Pathways of Nicotinamide-Derived Pyridones

As catabolites of nicotinamide possess physiological relevance, pyridones are often included in metabolomics measurements and associated with pathological outcomes in acute kidney injury (AKI). Pyridones are oxidation products of nicotinamide, its methylated form, and its ribosylated form. While they are viewed as markers of over-oxidation, they are often wrongly reported or mislabeled. To address this, we provide a comprehensive characterization of these catabolites of vitamin B3, justify their nomenclature, and differentiate between the biochemical pathways that lead to their generation. Furthermore, we identify an enzymatic and a chemical process that accounts for the formation of the ribosylated form of these pyridones, known to be cytotoxic. Finally, we demonstrate that the ribosylated form of one of the pyridones, the 4-pyridone-3-carboxamide riboside (4PYR), causes HepG3 cells to die by autophagy; a process that occurs at concentrations that are comparable to physiological concentrations of this species in the plasma in AKI patients.

GSK3β is a key regulator of the ROS-dependent necrotic death induced by the quinone DMNQ

Signaling pathways controlling necrosis are still mysterious and debated. We applied a shRNA-based viability screen to identify critical elements of the necrotic response. We took advantage from a small molecule (G5) that makes covalent adducts with free thiols by Michael addition and elicits multiple stresses. In cells resistant to apoptosis, G5 triggers necrosis through the induction of protein unfolding, glutathione depletion, ER stress, proteasomal impairments, and cytoskeletal stress. The kinase GSK3β was isolated among the top hits of the screening. Using the quinone DMNQ, a ROS generator, we demonstrate that GSK3β is involved in the regulation of ROS-dependent necrosis. Our results have been validated using siRNA and by knocking-out GSK3β with the CRISPR/Cas9 technology. In response to DMNQ GSK3β is activated by serine 9 dephosphorylation, concomitantly to Akt inactivation. During the quinone-induced pro-necrotic stress, GSK3β gradually accumulates into the nucleus, before the collapse of the mitochondrial membrane potential. Accumulation of ROS in response to DMNQ is impaired by the absence of GSK3β. We provide evidence that the activities of the obligatory two-electrons reducing flavoenzymes, NQO1 (NAD(P)H quinone dehydrogenase 1) and NQO2 are required to suppress DMNQ-induced necrosis. In the absence of GSK3β the expression of NQO1 and NQO2 is dramatically increased, possibly because of an increased transcriptional activity of NRF2. In summary, GSK3β by blunting the anti-oxidant response and particularly NQO1 and NQO2 expression, favors the appearance of necrosis in response to ROS, as generated by the quinone DMNQ.

S29434, a Quinone Reductase 2 Inhibitor: Main Biochemical and Cellular Characterization

Quinone reductase 2 (QR2, E.C. 1.10.5.1) is an enzyme with a feature that has attracted attention for several decades: in standard conditions, instead of recognizing NAD(P)H as an electron donor, it recognizes putative metabolites of NADH, such as N-methyl- and N-ribosyl-dihydronicotinamide. QR2 has been particularly associated with reactive oxygen species and memory, strongly suggesting a link among QR2 (as a possible key element in pro-oxidation), autophagy, and neurodegeneration. In molecular and cellular pharmacology, understanding physiopathological associations can be difficult because of a lack of specific and powerful tools. Here, we present a thorough description of the potent, nanomolar inhibitor [2-(2-methoxy-5H-1,4b,9-triaza(indeno[2,1-a]inden-10-yl)ethyl]-2-furamide (S29434 or NMDPEF; IC₅₀ = 5-16 nM) of QR2 at different organizational levels. We provide full detailed syntheses, describe its cocrystallization with and behavior at QR2 on a millisecond timeline, show that it penetrates cell membranes and inhibits QR2-mediated reactive oxygen species (ROS) production within the 100 nM range, and describe its actions in several in vivo models and lack of actions in various ROS-producing systems. The inhibitor is fairly stable in vivo, penetrates cells, specifically inhibits QR2, and shows activities that suggest a key role for this enzyme in different pathologic conditions, including neurodegenerative diseases.