Klotho modulates FGF23-mediated NO synthesis and oxidative stress in human coronary artery endothelial cells

Abstract

Chronic kidney disease (CKD) is a state of Klotho deficiency and excess of the phosphaturic hormone fibroblast growth factor 23 (FGF23). Both dysregulations were shown to be associated with endothelial dysfunction in humans, but direct vascular effects of FGF23 remain largely elusive. In vitro experiments were performed to assess the effects of FGF23 (10 ng/mL) in relation to its co-receptor Klotho on nitric oxide (NO) synthesis and reactive oxygen species (ROS) formation and detoxification in human coronary artery endothelial cells (HCAEC). Membrane-bound Klotho is expressed in HCAEC, and FGF23 increases the expression of the Klotho shedding protease ADAM17, and consequently the secretion of soluble Klotho. FGF23 activates FGF receptor 1 and stimulates NO release via Akt-dependent activation of endothelial NO synthase (eNOS). Both FGF receptor (FGFR)-dependent ROS formation via activation of NADPH oxidase 2 (Nox2) as well as ROS degradation via superoxide dismutase 2 (SOD2) and catalase (CAT) is stimulated by FGF23. Pre-incubation with a Klotho inhibitor blunts the FGF23-stimulated Akt-eNOS activation and NO synthesis, and decreases ROS degradation by blocking SOD2 and CAT enzymes, whereas FGF23-stimulated ROS synthesis via Nox2 is unaffected, resulting in low NO bioavailability and increased oxidative stress. Our data indicate that in the presence of Klotho, FGF23 induces NO release in HCAEC and its stimulating effects on ROS production are counterbalanced by increased ROS degradation. In states of Klotho deficiency, e.g., CKD, FGF23-mediated NO synthesis is blunted and ROS formation overrules ROS degradation. Thus, FGF23 excess may primarily promote oxidative stress and thus endothelial dysfunction.

Impaired Microcirculation in Children After Kidney Transplantation: Everolimus Versus Mycophenolate Based Immunosuppression Regimen

“…A recent in vitro study using cultured human coronary artery endothelial cells demonstrated that, in the presence of klotho, FGF23 induces NO release and its stimulating effects on oxidative stress are counterbalanced by increased reactive oxygen degradation [57]. This may at least partly explain the lack of association between endothelial function and FGF23 levels in the present study, as sklotho levels were normal in the majority of our patients.…”

Elevated serum fibroblast growth factor 23 levels as an indicator of lower extremity atherosclerotic disease in Chinese patients with type 2 diabetes mellitus

“…Basic research studies have demonstrated that FGF23 induces the onset and development of atherosclerosis through its effects on vascular calcification and endothelial dysfunction [7, 8]. Recently, clinical studies provided evidence supporting the relationship between increased circulating FGF23 levels and atherosclerotic cardiovascular disease [9, 10].…”

α-Klotho expression determines nitric oxide synthesis in response to FGF-23 in human aortic endothelial cells

“…Likewise, Richter et al . utilized coronary artery ECs to highlight that in states of α-Klotho deficiency, FGF-23 mediated NO production is attenuated, leading to an increase of reactive oxygen species (ROS) [22]. Two recent studies also showed that α-Klotho expression in human ECs declined under uremic status and with cell aging, which might account for vascular dysfunction under these conditions [23, 24].…”

“…As stated recently, Richter et al ., using human coronary artery ECs, also showed that NO production increases after FGF-23 treatment and this was dependent on the presence of α-Klotho [22]; however, their results suggest that these effects are due to the secretion of the soluble α-Klotho. In contrast, our study highlights that the addition of soluble α-Klotho to HAECs following α-Klotho knockdown was unable to rescue EC resistance to FGF-23.…”