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Abstract: TH-PO378

Activation of the Keap1/Nrf2 Pathway Increases GFR by Increasing Glomerular Effective Filtration Area Without Affecting the Afferent/Efferent Arteriole Ratio

Session Information

Category: Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)

  • 1800 Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)

Authors

  • Kidokoro, Kengo, Kawasaki Medical School, Kurashiki, Okayama, Japan
  • Nagasu, Hajime, Kawasaki Medical School, Kurashiki, Okayama, Japan
  • Satoh, Minoru, Kawasaki Medical School, Kurashiki, Okayama, Japan
  • Meyer, Colin John, Reata Pharmaceuticals, Irving, Texas, United States
  • Kashihara, Naoki, Kawasaki Medical School, Kurashiki, Okayama, Japan
Background

The Keap1/Nrf2 pathway regulates various cytoprotective, anti-inflammatory, and antioxidant genes. Nrf2 activator, Bardoxolone methyl (BARD), increases the estimated glomerular filtration rate (eGFR) in patients with diabetic kidney disease (DKD). Moreover, BARD improved renal function in DKD patients, as revealed through the assessment of inulin clearance, the gold standard for measuring the GFR. These findings indicate that the Keap1/Nrf2 pathway is largely involved in the regulation of the GFR; however, the precise underlying mechanisms are yet unclear. This study aimed to pharmacologically and genetically investigate the mechanisms underlying the regulation of the GFR by the Keap1/Nrf2 pathway via multiphoton microscope (MPM) imaging in vivo.

Methods

C57BL/6 (Control), Nrf2-knockout (Nrf2-KO), and Nrf2-activated Keap1-knockdown mice (Keap1-KD) were used herein and treated with the synthetic terpenoid RTA dh404 (RTA, 10 mg/kg/day by gavage) for 1 week. Single-nephron GFR (SNGFR), the diameter of the afferent/efferent arterioles and glomerular permeability were evaluated using MPM. Intracellular calcium in response to ATP and angiotensin II stimulation and the effect of RTA on [Ca2+]i were evaluated using Fluo 4 and Fura red in cultured mesangial cells and podocytes. Production of reactive oxygen species and nitric oxide (NO) availability were assessed using CellROX® Deep Red and diaminofluorescein-FM diacetate (DAF-FM DA) upon the exposure to these stimuli.

Results

SNGFR was significantly higher in Keap1-KD mice than in the control group (9.13±0.55 vs 4.40±0.39 nl/min, p<0.05). RTA administration increased the SNGFR in the control mice but not in Nrf2-KO mice (6.00±0.40 vs 4.66±0.35 nl/min, p<0.05). The glomerular afferent/efferent arteriole ratio was not altered significantly in all groups. RTA treatment did not affect the glomerular permeability of albumin and 40 kDa dextran. RTA treatment inhibited calcium influx into cultured podocytes and mesangial cells induced by angiotensin II or ATP, thereby affecting contractile responses. Oxidative stress and NO bioavailability were also ameliorated with upon RTA treatment.

Conclusion

The Keap1/Nrf2 pathway plays a pivotal role in regulating GFR and presumably mediates the effects of BARD on GFR.

Funding

  • Commercial Support