NQO1 modulates redox status and H2O2 levels in pancreatic β-cells. The study aimed to determine the role of NQO1 in β-cell health and metabolism. It was hypothesized that 1) NQO1 reduces oxidative stress in β-cells by lowering quinone-dependent H2O2 production and 2) NQO1 modulates the NAD(P)H-to-NAD(P)+ ratio in β-cells. Results showed that overexpressing NQO1 decreased menadione-dependent H2O2 production in INS-1 cells and isolated rodent islets, while NQO1 knockout increased H2O2 production. N

1. NQO1 modulates redox status and
H2O2 levels in pancreatic β-cells
Delaine Zayas-Bazán Burgos1 , Joshua Gray2,3, Emma Heart3
1University of Puerto Rico at Cayey
2U.S. Coast Guard Academy
3Marine Biology Laboratory

2. Pancreas: Islets of Langerhans
insulin
http://discovery.lifemapsc.com/in-vivo-development/pancreas/pancreatic-ducts

3. Glucose Metabolism is coupled to insulin
secretion in pancreatic β-cell

4. The role of NQO1 in metabolism
Detoxification enzyme
 NQO1 knock-out mice are
sensitive to oxidant stress
Joseph P et al (2007), Radjendirane V. (1998)
Intermediary metabolism
 NQO1 levels correlated with
fasting insulin levels
Palming J et al (2007)
 NQO1 knock-out mice have
metabolic defects
Gaikwad A et al (20o1)

5. NQO1 is cytosolic NAD(P)H-dependent Quinone
Oxidoreductase 1
Quinones are?
 Class of organic compound
 Exogenous
 Food: Thymoquinone
 Pollution: Athraquinone
 Endogenous Ubiquinone (CoQ10)
 Electron carrier
 Mitochondrial: known function
 All membranes including Plasma membrane
▫ PMET: Plasma Membrane Electron Transport

6. NQO1 metabolizes Quinones
Hydroquinone form
Semi-quinone form: reactive
NQO1 reduces H2O2 production by quinones: might be especially important
for β-cells, since they have a relatively low level of classical antioxidant
enzymes.

7. NQOI cytoprotection in β-cells
β-cells have relatively low levels of classical antioxidant
enzymes
 SOD : Superoxide dismutases 1,2 and 3
Why?
Oxidants are important for signaling in β-cell under
physiological situation
Pathological high doses of oxidants will harm β-cell
to greater extent than other cell types

8. NQO1 is a member of PMET
(Plasma Membrane Electron Transport)
Gray et al (2011)
Mediated by NQO1
Is the transfer of
electrons (reduced
equivalents)out of
the cell: PMET is
plasma membrane
analog of the
mitochondrial ETC
NQO1

9. Hypotheses to test:
Objective: to determine role of NQO1 in β-cell
health and metabolism.
Hypotheses:
 (1) NQO1 reduces oxidative stress in β-cells by
lowering quinone-dependent H2O2 production.
 (2) NQO1 modulates NAD(P)H-to-NAD(P)+ ratio in βcells.

10. Methods
INS-1 832/13 cells
• Over-expression of NQO1
▫ Adenovirus with NQO1
▫ NQO1 activity measured in
cell lysate by decrease in
absorbance of DCPIP
(dichlorophenolindophenol)
▫ Activity increased >10x
3.3E-10 ± 5.16E -12 5.6E-9 ± 1.96E-12
mol DCPIP//min
NQO1
(31KD)
Western blot of NQO1 protein in
lysates from INS-1 832/13 cells
(adapted from Gray et al 2011)

11. Effect of NQO1 over-expression on menadionedependent H2O2 production in INS-1 832/13 cells

12. Effect of NQO1 over-expression and knock-out (KO) on
menadione-dependent H2O2 production in isolated rodent islets
Over-expression
Knock-out

13. Hypotheses
Hypotheses:
 (1) NQO1 reduces oxidative stress in β-cells by
lowering quinone-dependent H2O2
production.
 (2) NQO1 modulates NAD(P)H-to-NAD(P)+
ratio in β-cells.
• NADH and NADPH are substrates for NQO1
• Gaikwad et al (2001): NQO1 has been show to
modulate redox ratios in fat and liver

14. NQO1 regulates NADH-to-NAD+ ratio
in INS-1 832/13 cells and rodent islets
INS-1 832/13
Rodent Islets

15. Conclusions
NQO1
▫ Protects β-cell from oxidant stress
▫ Modulates β-cell redox status by
lowering the NADH-to-NAD+ ratio:
effect on metabolism (GSIS)

16. Future Studies

17. Acknowledgments