Background
NF-E2-related factor 2 (Nrf2), a master regulator of the oxidative stress response, plays an important role in influencing the severity of the renal injury. However, non-invasive biomarkers to detect the Nrf2 activation in the kidney have yet to be elucidated. We focused on urine exosomes as a source of non-invasive biomarkers. Exosomes are released from all renal epithelial cells, and contain nucleic acids, proteins, and lipids. In this study, in order to search biomarkers for the Nrf2 activation, we employed bardoxolone methyl (BARD), a Nrf2 activator, and analyzed RNA in urine exosomes.
Methods
Male Sprague-Dawley rats were divided into two groups: the vehicle and BARD groups (10 mg/kg). Urine samples were collected for 6 hours after BARD administration, and exosomes were isolated from the urine using the polymer precipitation method. The kidneys were collected at 6 hours after the dosing. RNAs were extracted from urine exosomes and kidneys, and examined by microarray analysis. The urine exosomes were also analyzed by next generation sequencing.
Results
Among the RNAs in the kidney and urine exosomes, the expressions of eight mRNAs and one miRNA were commonly altered after the treatment with BARD. Next-generation sequencing showed that BARD altered only the expression level of pirin mRNA among RNAs mentioned above.
Conclusion
These results suggest that pirin mRNA in urine exosomes might be a useful biomarker to detect the renal activation of Nrf2.