Enhanced hydrogen peroxide and renin release in primary cultures of juxtaglomerular (JG) cells from diabetic mice
Mendez M. Enhanced hydrogen peroxide and renin release in primary cultures of juxtaglomerular (JG) cells from diabetic mice. FASEB Journal 2018; 32(1 Suppl):721.15.
Diabetes mellitus and its complications represent an increasing burden for healthcare. A large fraction of patients with diabetes mellitus develops diabetic nephropathy. The Akita mice strain is one of the few mouse models of diabetes mellitus that shows features of the human disease including hypertension and kidney damage. Previous reports have shown increased levels of reactive oxygen species in the kidneys of Akita mice. We previously showed that hydrogen peroxide is a potent stimuli for renin release from the juxtaglomerular cells, increasing plasma renin and blood pressure in mice. Thus, we hypothesized that hydrogen peroxide levels are higher in JG cells from Akita mice leading to increased renin release in this strain. Using Western Blot, we found that the NADPH oxidase isoforms NOX1 and NOX4 are expressed, but only NOX1 being upregulated in primary JG cells isolated from Akita mice, compared to JG cells from the control (C57) strain (C57=100%. Akita/NOX1= 147%±10; n=4; p<0.05). Confocal imaging showed the expression of NOX1 and NOX4 in JG cells where they both co-localized with renin immunolabeling in renin-containing granules. In addition, the expression of Catalase, which scavenges H202, was reduced in JG cells from diabetic Akita mice (C57=100%; Akita= 72%±7.2 of C57; n=4; p<0.05). We measured H202 levels by transducing JG cells with the fluorescent protein sensor Hyper under control of the renin1 promoter. We found that JG cells isolated from Akita mice had higher baseline levels of H202 (C57= 100, Akita=117±7%, p<0.05). Since we previously found that H202 stimulates renin release, we studied whether JG cells from Akita mice had higher total renin activity or release. For this, we measured baseline renin release to the media during 2 hours from primary JG cells cultured from Akita or control mice. JG cells were then lysed and total renin content measured. We found that in the absence of any stimuli, JG cells from Akita mice had ~2 fold higher renin release (C57= 100%, Akita=219.2±26%; p<0.04, n=6). We did not observe a significant difference in total renin content between strains. Transduction of replicate plates with adenovirus encoding Catalase (AD-Cat) decreased baseline renin release by 35±8% (p<0.05) in JG cells from Akita mice whereas it did not affect renin release in control JG cells. We conclude that renin cells from diabetic Akita mice have higher endogenous H202 leading to increased renin release. The NADPH isoform NOX1 is enhanced in Akita mice and may be responsible for higher levels of H202 and renin release from JG cells. Our data suggest that direct stimulation of renin release by H202 could be potentially be involved in renal damage in diabetes mellitus.