Loss of clusterin expression worsens renal ischemia-reperfusion injury

Abstract

Prevention of ischemia-reperfusion injury (IRI) is a challenge in clinical care of the patients with kidney transplants or acute kidney injury, and understanding of the intrinsic mechanisms of resistance to injury in the kidney will lead to a novel therapy. Clusterin, a secreted glycoprotein, is an antiapoptotic protein in cancer cells. Our study is to investigate the role of clusterin in renal IRI. Renal IRI in mice was induced by clamping renal vein and artery for 45 or 50 min at 32 degrees C. Apoptosis of renal tubular epithelial cells (TECs) was determined by FACS analysis. Clusterin expression was examined by Western blot or immunohistochemistry. Here, we showed that clusterin protein was induced in TECs following IRI, and more tubules expressed clusterin in the kidneys following ischemia at higher temperatures. In human proximal TEC HKC-8 cultures, clusterin was upregulated by removal of serum and growth factors in medium and was downregulated by TNF-alpha-IFN-gamma mixture. The levels of clusterin were positively correlated with cell survival in these conditions. Knockdown or knockout of clusterin expression enhanced the sensitivity of TECs to apoptosis. In experimental models of renal IRI, deficiency in clusterin expression worsened the injury, as indicated by a significant increase in renal tissue damage with higher levels of serum creatinine and blood urea nitrogen and by a poorer recovery from the injury in clusterin-deficient mice compared with wild-type mice. Our data indicate that the reduction of inducible expression of clusterin results in an increase in TEC apoptosis in the cultures and renders mice susceptibility to IRI, implying a protective role of clusterin in kidney injury.

From Humans to Experimental Models: The Cytoprotective Role of Clusterin in the Kidney

“…In mice, CLU in normal tissues (heart and kidney) is present as a single protein band at approximately 40 kDa in Western blot analysis in our studies [24,55,56], while in cultured cells from these tissues two protein bands at approximately 60 kDa and 40 kDa are detected [24,55,56], suggesting that mouse CLU probably is also retrotranslocated to the cytosol following exposure to sub lethal stress in culture conditions. A variety of biological activities of intracellular sCLU or cytoplasmic CLU (cCLU) have been reported; it inhibits apoptosis by the interaction with BAX or GRP78 [54,57,58] or promotes cell survival by the activation of Akt and NF-κB pathway [48,59].…”

“…The phenotype of age-dependent glomerular injury in CLU KO mice clearly suggests the biological significance of CLU for tissue homeostasis of the kidney. Recently, we and others have demonstrated that following renal IRI or UUO, renal CLU expression is up-regulated [24,55,88], and the lack of CLU expression in the kidneys worsens IRI [24], impairs renal tissue repair after IRI [55] and accelerates renal fibrosis or increases the levels of plasminogen activator inhibitor (PAI)-1, type I collagen, and fibronectin in response to obstruction [88]. These results may suggest that upregulation of CLU during renal injury is a protective response that may prevent cell death during IRI, facilitate renal tubular cell proliferation for renal repair after IRI, and maintain renal tissue homeostasis against the development of renal fibrosis.…”

“…In tissue, upregulation of CLU expression (probably including nCLU) is associated with many pathophysiological processes, such as neuropathologies [15,16], heart disease [17], cancer [18][19][20], kidney transplant rejection, and kidney disease including glomerulonephritis [21,22]. In rodents, renal CLU is upregulated following a variety of insults, such as unilateral ureteral obstruction (UUO) and ischemia-reperfusion injury (IRI) [23,24], acute glycerol-induced renal failure, chronic vitamin E and selenium deficiency [25], lupus-like nephritis [26], and in resident glomerular cells exposed to complement-mediated injury [27]. The CLU expression in glomerular mesangial and epithelial cells, as well as renal proximal tubular epithelial cell (TEC) is increased in response to the stimulation of thrombin [28] and hypoxia in our unpublished observations.…”

Clusterin Reduces Cold Ischemia-Reperfusion Injury in Heart Transplantation Through Regulation of NF-kB Signaling and Bax/Bcl-xL Expression

“…In cultures of renal tubular epithelial cells, downregulation of clusterin expression results in an increase of proinflammatory cytokine-induced cell apoptosis. In a mouse model of renal I/R injury, the overexpression of clusterin is associated with a reduction of renal I/R injury and dysfunction of the kidneys and also contributes to the promotion of renal repair [23]. These results suggest that the local expression of clusterin may protect renal cells from cell death during kidney transplant rejection.…”

Oxidized high-density lipoprotein impairs the function of human renal proximal tubule epithelial cells through CD36

“…The exposure of renal tubular cells to oxidized HDL potently increased the generation of ROS and stimulated the production of pro-inflammatory factors, including TNF-α, MCP-1 and RANTES. These factors may contribute to the pathogenesis of cell injury, either by modulating the immune system or by directly promoting renal damage, eventually resulting in cell apoptosis and the inhibition of migration ability (3,27). Other factors, including TGF-β, also play an important role in the pathogenesis of inflammatory response during the course of chronic kidney damage.…”