Abstract P086: Superoxide but Not Hydrogen Peroxide Increases Nuclear Translocation of Transcription Factor Sp3 and AT1 Receptor Expression in the Renal Cells

Age-associated oxidative stress causes up-regulation of renal AT1 receptor function (AT1R) and hypertension in aging Fischer Brown Norway (FBN) rats. Here we studied the mechanism of up-regulation of renal AT1R, and further tested superoxide Vs hydrogen peroxide (H2O2) specificity in this phenomenon. We found that transcription factor Sp3 plasmid increased (Control vs Sp3: 0.1165 ± 0.01 vs 0.3810 ± 0.03) while Sp3 siRNA decreased (Control siRNA vs Sp3 siRNA: 1.11 ± 0.25 vs 0.64 ± 0.06) the levels of AT1 receptor protein in human kidney (HK2) cells. Whereas transcription factor NF-kB p-65 plasmid did not affect AT1 receptor protein levels in these cells (Control vs NF-kB: 0.25 ± 0.025 vs 0.31 ± 0.035). DDC, a superoxide prodrug, but not H 2 O 2 treatments increased nuclear levels of Sp3 and NF-kB proteins in HK2 cells [(Control vs DDC, vs H 2 O 2, vs H 2 O 2 + tempol): Sp3 (0.50 ± 0.08 vs 1.28 ± 0.21 vs 0.68 ± 0.14 vs 1.04 ± 0.30 densities); NF-kB (0.4025 ± 0.13 vs 1.808 ± 0.54 vs 0.4950 ± 0.15 vs 0.6375 vs ± 0.18 densities)]. Tempol treatment, a superoxide scavenger, attenuated DDC-mediated nuclear accumulation of Sp3 (DDC vs DDC + tempol: 1.28 ± 0.21 vs 0.52 ± 0.12 densities) and NF-kB (DDC vs DDC + tempol: 1.808 ± .54 vs 0.43 ± 0.18 densities]. In addition, DDC but not H 2 O 2 increased AT1 receptor mRNA expression, measured by RT-qPCR [(Control vs DDC, vs H 2 O 2 ): (1.000 ± 0.0 vs 3.323 ± 0.79, vs 1.218 ± 0.49)]. This effect was attenuated by tempol treatment [(DDC vs DDC + tempol) (3.323 ± 0.79 vs 0.7225 ± 0.16 densities)]. Similarly, DDC treatment increased AT1 receptor protein expression that was attenuated by tempol treatment, measured by immunoblotting [(Control vs DDC vs DDC + Tempol) (0.3535 ± 0.99 vs 0.9975 ± 0.19 vs 0.3250 ± 0.02 densities)]. These results suggest that superoxide but not H 2 O 2 regulates both Sp-3 and NF-kB in the renal cells. However, it is Sp3 but not NF-kB that up-regulates renal AT1 receptor expression. Taken together, this phenomenon may represent a mechanism for hypertension in aging FBNs.