In Vivo klotho Gene Delivery Protects against Endothelial Dysfunction in Multiple Risk Factor Syndrome

147

122

Klotho is a circulating protein, and Klotho deficiency disturbs endothelial integrity, but the molecular mechanism is not fully clarified. We report that vascular endothelium in Klotho-deficient mice showed hyperpermeability with increased apoptosis and down-regulation of vascular endothelial (VE)-cadherin because of an increase in VEGF-mediated internal calcium concentration ([Ca 2+ ]i) influx and hyperactivation of Ca 2+ -dependent proteases. Immunohistochemical analysis, the pull-down assay using Klotho-fixed agarose, and FRET confocal imaging confirmed that Klotho protein binds directly to VEGF receptor 2 (VEGFR-2) and endothelial, transient-receptor potential canonical Ca 2+ channel 1 (TRPC-1) and strengthens the association to promote their cointernalization. An in vitro mutagenesis study revealed that the second hydrolase domain of Klotho interacts with sixth and seventh Ig domains of VEGFR-2 and the third extracellular loop of TRPC-1. In Klotho-deficient endothelial cells, VEGF-mediated internalization of the VEGFR-2/TRPC-1 complex was impaired, and surface TRPC-1 expression increased 2.2-fold; these effects were reversed by supplementation of Klotho protein. VEGF-mediated elevation of [Ca 2+ ]i was sustained at higher levels in an extracellular Ca 2+ -dependent manner, and normalization of TRCP-1 expression restored the abnormal [Ca 2+ ]i handling. These findings provide evidence that Klotho protein is associated with VEGFR-2/TRPC-1 in causing cointernalization, thus regulating TRPC-1–mediated Ca 2+ entry to maintain endothelial integrity.

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Klotho is associated with VEGF receptor-2 and the transient receptor potential canonical-1 Ca ²⁺ channel to maintain endothelial integrity

Kusaba

Okigaki²,

Matui³

et al. 2010

147

122

“…The NO production may be aberrant in Kl Ϫ/Ϫ mice because they exhibit impaired vasodilation (15) and angiogenesis (16) with the loss of the protective effect of the Klotho protein on the cardiovascular system (17). Remarkably, in vivo Klotho gene delivery increases endothelial-derived NO production and abrogates cardiovascular complications in a rat model with multiple atherogenic risk factors (18). Human studies indicating NO deficiency contributing to cardiorenal vascular complications also emphasize the relevance of Klotho protein as a potential therapeutic agent (19).…”

Section: Discussionmentioning

confidence: 99%

Amelioration of progressive renal injury by genetic manipulation of Klotho gene

Haruna

Kashihara

Satoh

et al. 2007

224

212

Klotho, an antiaging gene with restricted organ distribution, is mainly expressed in the kidney tubules; the mutant mice have shortened life span, arteriosclerosis, anemia, and osteoporesis, features common to patients with chronic renal failure. Conceivably, the reduction of the Klotho gene expression may contribute to the development of kidney failure; alternatively, its overexpression may lead to the amelioration of renal injury in an ICR-derived glomerulonephritis (ICGN) mouse model with subtle immune complex-mediated disease. To address this issue, four different strains of mice were generated by cross-breeding: ICGN mice without the Klotho transgene (ICGN), ICGN mice with the Klotho transgene (ICGN/klTG), wild-type mice with the Klotho transgene (klTG), and wild-type mice without the Klotho transgene (control). At 40 weeks old, the survival rate was Ϸ30% in ICGN mice, and Ϸ70% in the ICGN/klTG group. This improvement was associated with dramatic improvement in renal functions, morphological lesions, and cytochrome c oxidase activity but a reduction in ␤-galactosidase activity (a senescence-associated protein), mitochondrial DNA fragmentation, superoxide anion generation, lipid peroxidation, and Bax protein expression and apoptosis. Interestingly, improvement was seen in both the tubular and glomerular compartments of the kidney, although Klotho is exclusively confined to the tubules, suggesting that its gene product has a remarkable renoprotective effect by potentially serving as a circulating hormone while mitigating the mitochondrial oxidative stress.aging ͉ glomerulonephritis ͉ oxidative stress ͉ tubular interstitial disease T he Klotho gene was originally identified by insertional mutagenesis, and it encodes a 130-kDa transmembrane protein that shares sequence homology with ␤-glucosidase (1). The gene is predominantly expressed in the kidney and, to a lesser extent, in the brain and reproductive and endocrine organs. Its deletion in mice (Kl Ϫ/Ϫ ) results in the development of a syndrome resembling human aging, including shortened life span, growth retardation, infertility, arteriosclerosis, skin and muscle atrophy, osteoporosis, and pulmonary emphysema (1). Conversely, overexpression of the Klotho gene extends the life span in mice (2). Although kl Ϫ/Ϫ mice do not show any overt renal abnormalities, the Klotho mRNA expression in the kidneys has been shown to be greatly reduced in patients with chronic renal failure (3). Notably, most of the features of Klotho gene-deleted mice are similar to those of the patients with chronic renal failure. In addition, Klotho gene expression has been found to be reduced in acute renal failure in ischemia-reperfusion injury murine models (4). These findings would imply that the reduction of Klotho protein may be relevant to the pathophysiology of renal failure. However, little is known concerning whether Klotho protein itself could exert an ameliorative effect on a diseased kidney to preserve its renal functions and thus could serve as a therapeutic target in various ...

“…Alternatively, klotho may contribute to or regulate signaling cascades with downstream targets that influence aging. Based on observations in klothodeficient mice, these targets may include factors involved in NO production and maintenance of proper endothelial function (4,5). These hypotheses remain to be tested in humans or mouse models of normal or accelerated aging.…”

Section: Discussionmentioning

confidence: 99%

“…These results suggest that klotho protein may protect the cardiovascular system through endothelium-derived NO production (4). Remarkably, in vivo klotho gene delivery can ameliorate vascular endothelial dysfunction, increase nitric oxide production, reduce elevated blood pressure, and prevent medial hypertrophy and perivascular fibrosis in a rat model with multiple atherogenic risk factors including hypertension, diabetes, obesity, and hyperlipidemia (5).…”

mentioning

confidence: 93%

Association of human aging with a functional variant of klotho

Arking¹,

Krebsová

Maçek

et al. 2002

452

340

Mice deficient in Klotho gene expression exhibit a syndrome resembling premature human aging. To determine whether variation in the human KLOTHO locus contributes to survival, we applied two newly characterized polymorphic microsatellite markers flanking the gene in a population-based association study. In a cohort chosen for its homogeneity, Bohemian Czechs, we demonstrated significant differences in selected marker allele frequencies between newborn and elderly individuals (P < 0.05). These results precipitated a search for functional variants of klotho. We identified an allele, termed KL-VS, containing six sequence variants in complete linkage disequilibrium, two of which result in amino acid substitutions F352V and C370S. Homozygous elderly individuals were underrepresented in three distinct populations: Bohemian Czechs, Baltimore Caucasians, and Baltimore African-Americans [combined odds ratio (OR) ‫؍‬ 2.59, P < 0.0023]. In a transient transfection assay, secreted levels of klotho harboring V352 are reduced 6-fold, whereas extracellular levels of the S370 form are increased 2.9-fold. The V352͞S370 double mutant exhibits an intermediate phenotype (1.6-fold increase), providing a rare example of intragenic complementation in cis by human single nucleotide polymorphisms. The remarkable conservation of F352 among homologous proteins suggests that it is functionally important. The corresponding substitution, F289V, in the closest human klotho paralog with a known substrate, cBGL1, completely eliminates its ability to cleave p-nitrophenyl-␤-D-glucoside. These results suggest that the KL-VS allele influences the trafficking and catalytic activity of klotho, and that variation in klotho function contributes to heterogeneity in the onset and severity of human age-related phenotypes.