In Vivo klotho Gene Transfer Ameliorates Angiotensin II-Induced Renal Damage

Abstract

Abstract-The klotho gene, originally identified by insertional mutagenesis in mice, suppresses the expression of multiple aging-associated phenotypes. This gene is predominantly expressed in the kidney. Recent studies have shown that expression of renal klotho gene is regulated in animal models of metabolic diseases and in humans with chronic renal failure. However, little is known about the mechanisms and the physiological relevance of the regulation of the expression of the klotho gene in the kidney in some diseased conditions. In the present study, we first investigated the role of angiotensin II in the regulation of renal klotho gene expression. Long-term infusion of angiotensin II downregulated renal klotho gene expression at both the mRNA and protein levels. This angiotensin II-induced renal klotho downregulation was an angiotensin type 1 receptor-dependent but pressor-independent event. Adenovirus harboring mouse klotho gene (ad-klotho, 3.3ϫ10 10 plaque forming units) was also intravenously administered immediately before starting angiotensin II infusion in some rats. This resulted in a robust induction of Klotho protein in the liver at day 4, which was still detectable 14 days after the gene transfer. T he klotho gene, identified by insertional mutagenesis in mice, is a suppressor of the expression of multiple aging phenotypes similar to age-related diseases in humans, such as arteriosclerosis, osteoporosis, infertility, pulmonary emphysema, and short lifespan. 1 Interestingly, expression of klotho mRNA in the kidney can be only faintly detected in the prenatal rat, and it is markedly augmented after 4 days of age. 2 Although the klotho gene has a role in phenotypic alterations in various organs, expression of klotho mRNA is predominantly observed in the kidney, 1 suggesting that the Klotho protein or its metabolites may function as humoral factors. Recent studies have shown that expression of renal klotho gene is regulated in animals 2 and in humans 3 in some diseased conditions. At present, however, the mechanism regulating klotho gene expression is poorly understood.In the present study, we have investigated the role of angiotensin (Ang) II in the regulation of renal klotho gene expression. In addition, to clarify the possible physiological role of the klotho gene in the Ang II-infused rats, exogenous klotho gene was delivered into Ang II-infused rats, and functional and histological changes in the kidney were analyzed. Methods Animal ModelsThe experiments were performed in accordance with the guidelines and practices established by the Animal Center for Biomedical Research, University of Tokyo, Faculty of Medicine. The rat Ang II hypertension model was induced in male Sprague-Dawley rats (Nippon Bio-Supply Center, Tokyo, Japan) by the continuous infusion of [Val 5 ]-Ang II (Sigma) at a dose of 0.7 mg/kg per day via an osmotic minipump (Alza) as described previously. 4 In some experiments, the selective angiotensin type 1 receptor antagonist losartan (25 mg/kg per day; a gift from Merck, Rahway, NJ) ...

Klotho Deficiency Causes Vascular Calcification in Chronic Kidney Disease

“…Klotho overexpression lessens progression of CKD, improves Pi metabolism, and protects the vasculature from calcification. Previous studies showed that overexpressing Klotho by viral-based gene transfer 34 or genetic manipulation 33 attenuated progressive renal injury, but the Klotho status and systemic complications of CKD were not studied. Because Klotho is present in multiple body fluids, 25,27,36,57 the restoration of Klotho clearly exerts multiple systemic effects in addition to renoprotection.…”

“…Renal Klotho mRNA is lower in a five-sixths nephrectomy model of CKD and in human nephrectomy samples from end-stage sclerotic kidneys. 30 -32 A modest amelioration of proteinuria and renal function was observed when Klotho was overexpressed genetically in a chronic glomerulonephritis model 33 or via viral delivery in a chronic angiotension II 34 and a spontaneous hypertension model. 35 We will test three hypotheses: (1) CKD is a state of Klotho deficiency; (2) low Klotho is an early marker of CKD; and (3) Klotho deficiency contributes to VC and Klotho replacement ameliorates CKD via multiple mechanisms.…”

Blood Pressure, Proteinuria, and Phosphate as Risk Factors for Progressive Kidney Disease: A Hypothesis

“…Of note, restoration of klotho by gene transfer improves angiotensin II-induced proteinuria. 70 As this discussion attests, the FGF-23/klotho system is strongly connected with the RAAS (Fig 1). Abnormal activation of the systemic and local RAAS is found commonly in patients with CKD and deeply influences medium-to long-term control of both blood pressure and proteinuria.…”

“…87,88 Inflammation and oxidative stress are linked inseparably and represent major mediators of CKD progression and the associated cardiovascular complications. 62,70,81,89 …”

Research Advances on the Genetic Mechanism of Diabetic Nephropathy

“…There is no doubt that this system has a pivotal role in the development of DN. Previous research has shown that renal creatinine clearance increased and urinary protein excretion decreased after the Klotho gene was injected into the body of rats with continuous ATII infusion [15]. In conclusion, in diabetic nephropathy, the activation of RAAS inhibits the expression of the Klotho protein in the kidney and the Klotho gene can induce renal damage by inhibiting RAAS.…”