Angiotensinogen (ANG) is the sole substrate of the renin-angiotensin system (RAS). Clinical studies have shown that RAS activation may lead to hypertension, a major cardiovascular and renal risk factor. To delineate the underlying mechanisms of hypertension-induced nephropathy, we generated transgenic mice that overexpress rat ANG (rANG) in the kidney to establish whether intrarenal RAS activation alone can evoke hypertension and kidney damage and whether RAS blockade can reverse these effects. Transgenic mice overexpressing renal rANG were generated by employing the kidney-specific, androgen-regulated protein promoter linked to rANG cDNA. This promoter targets rANG cDNA to renal proximal tubules and responds to androgen stimulation. Transgenic mice displayed kidney-specific expression of rANG, significantly increased blood pressure (BP) and albuminuria in comparison to non-transgenic littermates. Administration of losartan (an angiotensin II (type 1)-receptor antagonist) or perindopril (an angiotensin-converting enzyme inhibitor) reversed these abnormalities in transgenic animals. Renal injury was evident on examination of the kidneys in transgenic mice, and attenuated by losartan and perindopril treatment. We conclude that the overproduction of ANG alone in the kidney induces an increase in systemic BP, proteinuria, and renal injury. RAS blockers prevent these abnormalities. These data support the role of the intrarenal RAS in the development of hypertension and renal injury.

OBJECTIVE-The present study investigated the relationships between reactive oxygen species (ROS), interstitial fibrosis, and renal proximal tubular cell (RPTC) apoptosis in type 2 diabetic db/db mice and in db/db transgenic (Tg) mice overexpressing rat catalase (rCAT) in their RPTCs (db/db rCAT-Tg).RESEARCH DESIGN AND METHODS-Blood pressure, blood glucose, and albuminuria were monitored for up to 5 months. Kidneys were processed for histology and apoptosis studies (terminal transferase-mediated dUTP nick-end labeling or immunostaining for active caspase-3 and Bax). Real-time quantitative PCR assays were used to quantify angiotensinogen (ANG), p53, and Bax mRNA levels.RESULTS-db/db mice developed obesity, hyperglycemia, hypertension, and albuminuria. In contrast, db/db rCAT-Tg mice became obese and hyperglycemic but had normal blood pressure and attenuated albuminuria compared with db/db mice. Kidneys from db/db mice displayed progressive glomerular hypertrophy, glomerulosclerosis, interstitial fibrosis, and tubular apoptosis and increased expression of collagen type IV, Bax, and active caspase-3, as well as increased ROS production. These changes, except glomerular hypertrophy, were markedly attenuated in kidneys of db/db rCAT-Tg mice. Furthermore, ANG, p53, and Bax mRNA expression was increased in renal proximal tubules of db/db mice but not of db/db rCAT-Tg mice. D iabetes affects 5-10% of the world population. It is estimated that 30 -40% and 5-10% of patients with type 1 and type 2 diabetes, respectively, will eventually develop kidney failure or endstage renal disease (1). Diabetic nephropathy is now the most common cause of end-stage renal disease, accounting for 40 -50% (2). Diabetic nephropathy is associated with an increased risk of hypertension, myocardial infarction, stroke, and cardiovascular dysfunction (3). Multiple factors have been implicated in the pathogenesis of diabetic nephropathy, including hyperglycemia, hypertension, insulin resistance, and oxidative stress (4). However, the molecular mechanisms of action of these risk factors are incompletely understood. CONCLUSIONS-OurOxidative stress has long been implicated in the progression of diabetes complications. High glucose induces reactive oxygen species (ROS) generation, and ROS contribute to apoptosis in podocytes and mesangial and tubular cells (5-7). Ang II stimulates ROS generation via heightened NADPH oxidase activity in various renal cell types, whereas antioxidants provide renal protection in part by ameliorating oxidative stress (8 -11). Such data strongly indicate a link between ROS, renin-angiotensin system (RAS) activation, and renal cell apoptosis in diabetes.Recent studies have reported that 71% of glomeruli from proteinuric type 1 diabetic patients have glomerulo-tubular junction abnormalities, including atubular glomeruli, which may occur in 8 -17% of nephrons (12,13). Atubular glomeruli, glomeruli that are not connected to their proximal tubules as an end result of tubular atrophy, are characteristic of a variety of human kid...

We identified the far upstream element binding protein 1 (FBP1), an activator of transcription of the proto-oncogene c-myc, in a functional yeast survival screen for tumor-related antiapoptotic proteins and demonstrated strong overexpression of FBP1 in human hepato-cellular carcinoma (HCC). Knockdown of the protein in HCC cells resulted in increased sensitivity to apoptotic stimuli, reduced cell proliferation, and impaired tumor formation in a mouse xenograft transplantation model. Interestingly, analysis of gene regulation in these cells revealed that c-myc levels were not influenced by FBP1 in HCC cells. Instead, we identified the cell cycle inhibitor p21 as a direct target gene repressed by FBP1, and in addition, expression levels of the proapoptotic genes tumor necrosis factor α, tumor necrosis factor–related apoptosis-inducing ligand, Noxa, and Bik were elevated in the absence of FBP1. Conclusion Our data establish FBP1 as an important oncoprotein overexpressed in HCC that induces tumor propagation through direct or indirect repression of cell cycle inhibitors and proapoptotic target genes.

The intrarenal renin-angiotensin system (RAS) plays an important role in the progression of diabetic nephropathy. We have previously reported that mice overexpressing angiotensinogen in renal proximal tubular cells (RPTC) develop hypertension, albuminuria, and renal injury. Here, we investigated whether activation of the intrarenal RAS contributes to apoptosis of RPTC in diabetes. Induction of diabetes with streptozotocin in these transgenic mice led to significant increases in BP, albuminuria, RPTC apoptosis, and proapoptotic gene expression compared with diabetic nontransgenic littermates. Insulin and/or RAS blockers markedly attenuated these changes. Hydralazine prevented hypertension but not albuminuria, RPTC apoptosis, or proapoptotic gene expression. In vitro, high-glucose medium significantly increased apoptosis and caspase-3 activity in rat immortalized RPTC overexpressing angiotensinogen compared with control cells, and these changes were prevented by insulin and/or RAS blockers. In conclusion, intrarenal RAS activation and high glucose may act in concert to increase tubular apoptosis in diabetes, independent of systemic hypertension. Diabetic nephropathy (DN) is the leading cause of all ESRD in North America, accounting for 45% to 50% of all cases. 1,2 Intensive insulin therapy and chronic treatment with renin-angiotensin system (RAS) blockers are effective in retarding DN progression but do not provide a cure. [3][4][5] The local intrarenal RAS is well accepted. 6,7 Renal proximal tubular cells (RPTC) express all components of the RAS. 8 -10 Angiotensin II (Ang II) levels and RAS genes are elevated in the kidneys of diabetic rats and humans, 11-13 implying an important role for the intrarenal RAS in DN progression.Glomerular changes in DN first consist of hypertrophy and, later, thickening of the glomerular basement membrane, followed by expansion of the mesangial matrix and glomerulosclerosis. 14 -16 However, the gradual decline of renal function in later stages of DN is invariably associated with tubular atrophy and interstitial fibrosis, hallmarks of ESRD. 17,18 In fact, tubular atrophy and interstitial fibrosis are closely associated with loss of renal function and appear to be better predictors of renal disease progression than glomerular pathology. 15-18 Tubular atrophy in DN is incompletely understood, although apoptosis is a candidate mechanism. Indeed, apoptosis has been detected in RPTC of diabetic mouse, rat, and human kidneys. 19 -24