Nrf2 Deficiency Exacerbates Oxidative Stress and Microvessel Susceptibility to Inflammation in Diabetic Rats
Authors: Xinghai Xia , LaPenna Kyle Brian , Zhang Yunpei , He Pingnian 
Published: June 2021

Our previous study demonstrated that microvessels of streptozotocin (STZ)‐induced diabetic rats have a moderate increase in basal permeability, but augmented responses to platelet activating factor, PAF. Increased reactive oxygen species (ROS) has been implicated to play an important role in diabetes‐associated microvascular dysfunction. Nrf2 (NF‐E2‐related factor 2) has been recognized as a master transcription factor regulating antioxidant defenses. However, its role in the regulation of diabetes‐associated microvascular dysfunction remains unknown. The objective of this study is to investigate the role of Nrf2 deficiency in microvessel permeability in normal and diabetic rats. Experiments were conducted in individually perfused mensenteric venules in wild type (WT) and Nrf2 knock out (Nrf2−/−) rats. Microvascular permeability was determined by measuring hydraulic conductivity (Lp) under basal conditions and after exposure to platelet activating factor (PAF). Plasma H2O2 was measured from fresh blood using peroxide assay kit. The oxidant stress‐caused endothelial cell damages were evaluated by immunostaining of the end‐product of lipid peroxidation, 4‐hydroxynonenal (HNE), in rat venules using confocal images. Results showed significantly elevated plasma H2O2 in both WT and Nrf2−/− diabetic rats compared to their normal controls. Nrf2−/− rats showed higher plasma H2O2 levels than WT rats under both normal (7.8 ± 0.6 vs 5.3 ± 0.5 μM, p = 0.005) and diabetic conditions (12.9 ± 1.2 vs 10.9 ± 0.7 μM, p = 0.2). Male rats in all groups showed higher levels of plasma H2O2 than female rats, but the gender differences were not statically significant. Similar results were observed in Lp measurements (all Lp values are the mean ± SE × 10−7cm/s/cmH2O). Compared to WT rats, Nrf2−/− rats showed significantly higher basal Lp (3.9 ± 0.3 vs 1.8 ± 0.2 p<0.0001) and Lp responses to PAF (18.0 ± 2.2 vs 31.4 ± 2.2, p=0.03) in both genders. Under diabetic conditions, NRF2−/− rats also showed higher Lp than WT rats. The mean basal Lp values of NRF2−/− and WT vessels were 5.7 ± 0.3 and 4.6 ± 0.4 (p = 0.04), and their peak Lp responses to PAF were 86.1 ± 7.4 and 63.2 ± 6.3 (p = 0.03). In all groups, male rats had higher Lp than female rats but only the WT male PAF response is significantly higher than that of female rats. Microvessels of Nrf2−/− rats also showed elevated HNE staining compared to WT rats. Most importantly, regression analysis showed a positive correlation between measured Lp values and the plasma H2O2 levels in all animal groups (R2 > 0.92). These results indicate that reduced Nrf2 and its downstream target genes elevate plasma ROS levels and exacerbate oxidative stress‐induced increases in microvessel susceptibility to inflammation in diabetes. This study provides direct evidence that NRF2‐dependent antioxidant defenses play an essential role in regulating plasma ROS levels and contribute to the maintenance of basal permeability and microvessel susceptibility to inflammation under diabetic conditions. The mechanisms revealed provide a better understanding of the pathogenesis of diabetes and benefits the discovery of new drug targets.

Support or Funding Information

Supported by HL130363, DK097391.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.