Activation of the renin-angiotensin system (RAS) plays an essential role in the pathogenesis of CKD and cardiovascular disease. However, current anti-RAS therapy only has limited efficacy, partly because of compensatory upregulation of renin expression. Therefore, a treatment strategy to simultaneously target multiple RAS genes is necessary to achieve greater efficacy. By bioinformatics analyses, we discovered that the promoter regions of all RAS genes contained putative T-cell factor (TCF)/lymphoid enhancer factor ( Extensive studies over the last several decades have established that activation of the renin-angiotensin system (RAS) plays an essential role in the pathogenesis of CKD and cardiovascular disease. 1-3 RAS consists of several key components, including angiotensinogen (AGT), renin, angiotensin-converting enzyme (ACE), angiotensin II type 1 receptor (AT1), and angiotensin II type 2 receptor (AT2). Many studies indicate that, after kidney injury, intrarenal RAS is markedly activated because of concurrent upregulation of multiple RAS genes. 4,5 RAS activation contributes to kidney and cardiovascular injury through a range of mechanisms. In addition to regulating BP and hemodynamics, 6,7 angiotensin II, the principal and active mediator of RAS, activates TGF-b1 and NF-kB signaling and directly promotes renal inflammation and fibrosis. 8-10 Studies using both genetic and pharmacologic approaches have confirmed the relevance and importance of RAS activation in the development and progression of CKD and cardiovascular disease. However, current anti-RAS therapy using ACE inhibitors (ACEIs) or angiotensin II receptor

Under pathologic conditions, renal tubular epithelial cells can undergo epithelial to mesenchymal transition (EMT), a phenotypic conversion that is believed to play a critical role in renal interstitial fibrogenesis. However, the underlying mechanism that governs this process remains largely unknown. Here we demonstrate that integrin-linked kinase (ILK) plays an important role in mediating tubular EMT induced by TGF-β1. TGF-β1 induced ILK expression in renal tubular epithelial cells in a time-and dose-dependent manner, which was dependent on intracellular Smad signaling. Forced expression of ILK in human kidney proximal tubular epithelial cells suppressed E-cadherin expression and induced fibronectin expression and its extracellular assembly. ILK also induced MMP-2 expression and promoted cell migration and invasion in Matrigel. Conversely, ectopic expression of a dominant-negative, kinase-dead form of ILK largely abrogated TGF-β1-initiated tubular cell phenotypic conversion. In vivo, ILK was markedly induced in renal tubular epithelia in mouse models of chronic renal diseases, and such induction was spatially and temporally correlated with tubular EMT. Moreover, inhibition of ILK expression by HGF was associated with blockade of tubular EMT and attenuation of renal fibrosis. These findings suggest that ILK is a critical mediator for tubular EMT and likely plays a crucial role in the pathogenesis of chronic renal fibrosis.

Integrin-linked kinase (ILK) is an intracellular serine/threonine protein kinase that regulates cell adhesion, survival, and epithelial-to-mesenchymal transition (EMT). In this study, we investigated the kinase activity of ILK during tubular EMT induced by TGF-␤1 and examined the therapeutic potential of an ILK inhibitor in obstructive nephropathy. TGF-␤1 induced a biphasic activation of ILK in renal tubular epithelial cells, with rapid activation starting at 5 min and the second wave of activation peaking at 24 h; the latter paralleled the induction of ILK protein expression. Pharmacologic inhibition of ILK with small-molecule inhibitor QLT-0267 abolished TGF-␤1-induced phosphorylation of Akt and glycogen synthase kinase-3␤, suppressed cyclin D1 expression, and largely restored the expression of E-cadherin and zonula occludens 1. Inhibition of ILK also blocked TGF-␤1-mediated induction of fibronectin, Snail1, plasminogen activator inhibitor 1, and matrix metalloproteinase 2. In a mouse model of obstructive nephropathy, administration of QLT-0267 inhibited ␤-catenin accumulation; suppressed Snail1, ␣-smooth muscle actin, fibronectin, vimentin, and type I and type III collagen expression; and reduced total tissue collagen content. Inhibition of ILK did not affect kidney structure or function in normal mice. These findings suggest that increased ILK activity mediates EMT and the progression of renal fibrosis. Pharmacologic inhibition of ILK signaling may hold therapeutic potential for fibrotic kidney diseases.

While highly active during development, Wnt/β-catenin signaling becomes quiescent in adult kidneys and reactivates during kidney injury (7-10). Activation of this signaling leads to a fibrotic response and promotes the progression of CKD via the upregulation of profibrotic mediators, such as fibronectin, the renin-angiotensin system, plasminogen activator inhibitor-1, and [11][12][13]. Induction of MMP-7 by Wnt/β-catenin is particularly interesting, because it is the most robust β-catenin downstream target, and its expression primarily occurs in renal tubules (14-16). As a secreted protein that can be detected in the urine, MMP-7 is an effective noninvasive urinary biomarker for activation of Wnt/β-catenin after kidney injury (16,17).In the current study, we evaluated kidney injury after chronic infusion of angiotensin II (Ang II) using conditional knockout mice with tubule-specific ablation of β-catenin (18). Interestingly, although the genetic mutation was restricted to renal tubules, we found that these mice had significant protection against glomerular injury and proteinuria, accompanied by a reduced MMP-7 expression. These results were replicated in an Adriamycin-induced proteinuria model. We further demonstrate that MMP-7 could degrade the slit diaphragm protein nephrin and impaired integrity of the glomerular filtration barrier. In vivo exposure of mice to elevated MMP-7 levels was sufficient to cause proteinuria, and global ablation of MMP-7 protected mice from Ang II-induced glomerular injury. Our findings illustrate that tubular injury promotes glomerular damage by β-catenin-driven release of MMP-7.