NAD(P)H-dependent quinone oxidoreductase 1 (NQO1) and cytochrome P450 oxidoreductase (CYP450OR) differentially regulate menadione-mediated alterations in redox status, survival and metabolism in pancreatic β-cells

Abstract

NQO1 (NAD(P)H-quinone oxidoreductase 1) reduces quinones and xenobiotics to less-reactive compounds via 2-electron reduction, one feature responsible for the role of NQO1 in antioxidant defense in several tissues. In contrast, NADPH cytochrome P450 oxidoreductase (CYP450OR), catalyzes the 1-electron reduction of quinones and xenobiotics, resulting in enhanced superoxide formation. However, to date, the roles of NQO1 and CYP450OR in pancreatic β-cell metabolism under basal conditions and oxidant challenge have not been characterized. Using NQO1 inhibition, over-expression and knock out, we have demonstrated that, in addition to protection of β-cells from toxic concentrations of the redox cycling quinone menadione, NQO1 also regulates the basal level of reduced-to-oxidized nucleotides, suggesting other role(s) beside that of an antioxidant enzyme. In contrast, over-expression of NADPH cytochrome P450 oxidoreductase (CYP450OR) resulted in enhanced redox cycling activity and decreased cellular viability, consistent with the enhanced generation of superoxide and H2O2. Basal expression of NQO1 and CYP450OR was comparable in isolated islets and liver. However, NQO1, but not CYP450OR, was strongly induced in β-cells exposed to menadione. NQO1 and CYP450OR exhibited a reciprocal preference for reducing equivalents in β-cells: while CYP450OR preferentially utilized NADPH, NQO1 primarily utilized NADH. Together, these results demonstrate that NQO1 and CYP450OR reciprocally regulate oxidant metabolism in pancreatic β-cells.

Thymoquinone ameliorates diabetic phenotype in Diet-Induced Obesity mice via activation of SIRT-1-dependent pathways

“…However, non-physiologically high and toxic levels of quinones is known to generate excessive levels of reactive oxygen intermediates via quinone-dependent redox cycling, and this causes induction of the NAD(P)H-dependent Quinone Oxidoreductase 1 (NQO1). NQO1 is a phase 2 detoxification enzyme induced in response to oxidative stress, which expression is regulated by the Keap1/Nrf2/ARE pathway [ 10 , 37 ], and NQO1 alone has been show to regulate NADH/NAD + ratio [ 10 , 38 ]. To ascertain that applied doses of TQ were physiologically low and not inductive of NQO1 and/or oxidative stress, mRNA and protein levels of NQO1 were measured in liver and muscle.…”

“…TQ belongs to the family of quinones, naturally-derived compounds featuring a conjugated double bond system, which is responsible for their reactivity and intracellular process known as “redox cycling” [ 9 ]. Our laboratory has been instrumental in establishing the concept that re-oxidation of NADH back to NAD + via quinone-dependent redox cycling lowers cellular reductive poise and facilitates glucose and fatty acid oxidation, and is necessary for the overall health of the cells [ 9 , 10 ]. Our group has previously shown that TQ supports redox cycling in pancreatic β-cells, resulting in the reduction of NADH/NAD + ratio and normalization of defective glucose-stimulated insulin secretion (GSIS) under chronically elevated glucose via inhibition of acetyl CoA carboxylase (ACC) and enhanced oxidation of glucose and fatty acids [ 11 ].…”

Transcriptional profiling provides new insights into the role of nitric oxide in enhancing Ganoderma oregonense resistance to heat stress

“…The oxidative damage induced by HS is one of the main factors inhibiting mycelial growth and causing cell death 18 , 24 . Monooxygenases are enzymes that scavenge ROS in organisms by the concomitant oxidation of NAD(P)H 52 . Alcohol dehydrogenases catalyze the opposite reaction as part of fermentation to ensure a constant supply of NAD+ in bacteria, yeast, and plants 53 , 54 .…”

Pseudotime Ordering of Single Human β-Cells Reveals States of Insulin Production and Unfolded Protein Response

“…Antioxidant system genes involved in glutathione metabolism (CD44, GCLM, GSTP1, GLRX2, GLRX3, GPX1, GPX2, GPX3, GPX4, and SLC3A2), thioredoxin metabolism (PRDX1, PRDX2, PRDX6, TXN, TXNL1, and TXNRD1), quinone detoxification (NQO1), and iron storage (FTH1, FTL, and PCBP1) were also enriched in the INS lo UPR hi state and protect against ROS (Fig. 5) (34)(35)(36)(37).…”