Activation of renal renin-angiotensin system in upstream stimulatory factor 2 transgenic mice

Abstract

S. Activation of renal renin-angiotensin system in upstream stimulatory factor 2 transgenic mice. Am J Physiol Renal Physiol 296: F257-F265, 2009. First published November 12, 2008 doi:10.1152/ajprenal.90493.2008.-Previously we demonstrated that upstream stimulatory factor 2 (USF2) transgenic (Tg) mice developed nephropathy including albuminuria and glomerular hypertrophy, accompanied by increased transforming growth factor (TGF)-␤ and fibronectin accumulation in the glomeruli. However, the mechanisms by which overexpression of USF2 induces kidney injury are unknown. USF has been shown to regulate renin expression. Moreover, the renin-angiotensin system (RAS) plays important roles in renal diseases. Therefore, in the present studies the effects of USF2 on the regulation of RAS in the kidney as well as in mesangial cells from USF2 (Tg) mice were examined. The role of USF2-mediated regulation of RAS in TGF-␤ production in mesangial cells was also determined. Our data demonstrate that USF2 (Tg) mice exhibit increased renin and angiotensin (ANG) II levels in the kidney. In contrast, renal expression of other components of RAS such as renin receptor, angiotensinogen, angiotensin-converting enzyme (ACE), ACE2, angiotensin type 1a (AT 1a) receptor, and AT 2 receptor was not altered in USF2 (Tg) mice. Similarly, mesangial cells isolated from USF2 (Tg) mice had increased renin and ANG II levels. Mesangial cells overexpressing USF2 also had increased TGF-␤ production, which was blocked by small interfering RNA-mediated renin gene knockdown or RAS blockade (enalapril or losartan). Collectively, these results suggest that USF2 promotes renal renin expression and stimulates ANG II generation, leading to activation of the intrarenal RAS. In addition, renin-dependent ANG II generation mediates the effect of USF2 on TGF-␤ production in mesangial cells, which may contribute to the development of nephropathy in USF2 (Tg) mice.transforming growth factor-␤ THE RENIN-ANGIOTENSIN SYSTEM (RAS) is a multistep enzymatic cascade to produce a family of angiotensin peptides that control blood pressure and fluid homeostasis. The components of the RAS, including angiotensinogen (AGT), renin, and angiotensin-converting enzyme (ACE), are present systemically for endocrine production of angiotensin (ANG) II. AGT, the only known precursor to ANG II, is constitutively secreted from hepatocytes as well as other cell types and generally is considered to be non-rate-limiting in the production of systemic ANG II (28). AGT is cleaved by the aspartyl protease renin to generate ANG I. For systemic production of ANG II, renin synthesis and release from juxtaglomerular (JG) cells of the afferent arteriole is the rate-limiting step. Hydrolysis of the COOH-terminal amino acids of ANG I by ACE results in the formation of ANG II, the primary peptide of the RAS with biological activity. A homolog of ACE, termed ACE2, has been recently discovered, which hydrolyzes ANG I to ANG(1-9) and ANG II to ANG(1-7) (8). ANG II exhibits the majority of its well-known phys...

Role of the USF1 transcription factor in diabetic kidney disease

“…The lack of TGF-␤1 gene stimulation in the USF1 Ϫ/Ϫ diabetic kidney likely contributes to the reduction of matrix gene expression of Stimulation of the RAS is a hallmark of diabetic kidney disease, and clinical studies have clearly demonstrated the benefits of inhibiting the RAS in diabetic nephropathy. Our study supports the accumulating evidence (13,26,37) that the key genes renin and angiotensinogen are likely the initial drivers of stimulating RAS activity in diabetic kidney disease. There was a Ͼ10-fold induction of angiotensinogen and a Ͼ4-fold induction of renin with diabetes.…”

“…Both genes were close to control levels in the diabetic USF1 Ϫ/Ϫ mice. These data are similar to what was found in the USF2 transgenic mouse as there was increased renin gene stimulation (26). It is therefore likely that USF1 and USF2 both contribute to stimulation of renin and may well act synergistically.…”

“…The USF2 Ϫ/Ϫ mice have a short life-span and thus cannot be studied with chronic diabetes. Overexpression of USF2 in transgenic mice leads to enhanced albuminuria in streptozotocin-induced diabetic mice by 6 mo of age (14) and is accompanied by enhanced thrombospondin, TGF-␤1, and renin gene expression (26). However, the role of USF1 has not been demonstrated in chronic diabetic kidney disease.…”

Post-transcriptional Up-regulation of Tsc-22 by Ybx1, a Target of miR-216a, Mediates TGF-β-induced Collagen Expression in Kidney Cells*

“…It should be noted that upstream stimulatory factors (USF1 and USF2) have been reported to be involved in TGF-␤ up-regulation by high glucose and diabetic conditions and associated with the pathogenesis of DN (13)(14)(15)56). USFs are also E-box-regulators and have a LZ motif, which is critical for homo-or heterodimerization (16).…”

High Glucose Upregulates Upstream Stimulatory Factor 2 in Human Renal Proximal Tubular Cells through Angiotensin II-Dependent Activation of CREB

“…After treatment, cells were harvested and total RNA was extracted using RNeasy mini kit, according to the manufacturer’s instructions (Qiagen, Valencia, Calif., USA). Total RNA was converted to cDNA with murine leukemia virus reverse transcriptase (Promega) and real-time PCR was performed to determine the changes in USF2 and the components of the RAS as described previously [18,21]. Primers were synthesized by Integrated DNA Technologies.…”