Inhibition of Integrin-Linked Kinase Attenuates Renal Interstitial Fibrosis

Abstract

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.

Involvement of matrix metalloproteinase-2 in the development of renal interstitial fibrosis in mouse obstructive nephropathy

“…[37][38][39] MMPs are involved in the regulation of cell-ECM interactions. 40 In addition, MMP-2 facilitates the production of active TGF-b1 protein, which is known as a key factor for EMT promotion.…”

tPA Is a Potent Mitogen for Renal Interstitial Fibroblasts

“…25 NRK-49F cells were treated with specific inhibitors of ILK and FAK, respectively. As shown in Figure 8A, treatment of NRK-49F cells with QLT-0267, a highly selective ILK inhibitor, 32 did not abolish the ERK1/2 activation induced by tPA. Similarly, blockade of ILK signaling by QLT-0267 did not abolish the tPA-induced c-fos, c-myc, PCNA, and cyclin D1 expression in NRK-49F cells ( Figure 8B).…”

“…31 The preparation of kidney tissue homogenates and Western blot analysis of protein expression were performed by using routine procedures as described previously. 32 …”

ILK (integrin-linked kinase)

“…Acquisition of invasive and migratory characteristics in cancer cells results primarily from adopting an EMT phenotype. Overexpression of ILK induces EMT in mammary epithelial cells (Somasiri et al, 2001) and targeting this signaling cascade is an effective strategy for the treatment of fibrotic kidney (Li et al, 2009), lung (Kavvadas et al, 2010) or bladder cancer (Matsui et al, 2011). ILK is a key intracellular mediator of TGFβ-1 induced EMT (Li et al, 2009) through a Snail and Slug mechanism (Serrano et al, 2013b).…”

“…Overexpression of ILK induces EMT in mammary epithelial cells (Somasiri et al, 2001) and targeting this signaling cascade is an effective strategy for the treatment of fibrotic kidney (Li et al, 2009), lung (Kavvadas et al, 2010) or bladder cancer (Matsui et al, 2011). ILK is a key intracellular mediator of TGFβ-1 induced EMT (Li et al, 2009) through a Snail and Slug mechanism (Serrano et al, 2013b). TGFβ-1 mediated EMT induces an interaction between ILK and Rictor and disruption of this interaction by silencing ILK or using ILK inhibitor molecule, QLT0267, blocks TGFβ-1 induced EMT and partially reverses the mesenchymal phenotype in breast cancer cell lines (Serrano et al, 2013b).…”