C-type natriuretic peptide attenuates renal osteodystrophy through inhibition of FGF-23/MAPK signaling.

Renal osteodystrophy (ROD) occurs as early as chronic kidney disease (CKD) stage 2 and seems ubiquitous in almost all pediatric patients with CKD stage 5. Fibroblast growth factor (FGF)-23, a bone-derived endocrine regulator of phosphate homeostasis, is overexpressed in CKD and disturbs osteoblast differentiation and matrix mineralization. In contrast, C-type natriuretic peptide (CNP) acts as a potent positive regulator of bone growth. In the present study, we infused CNP into uremic rats and observed whether CNP could attenuate ROD through the inhibition of FGF-23 cascades. In uremic rats, CNP administration significantly alleviated renal dysfunction, calcium phosphate metabolic disorders, hypovitaminosis D, secondary hyperparathyroidism, the decrease in bone turnover markers and retarded bone pathological progression. More importantly, within FGF-23/mitogen-activated protein kinase (MAPK) signaling, the fibroblast growth factor receptor-1, Klotho and alternative (STAT-1/phospho-STAT-1) elements were upregulated by CNP, whereas FGF-23, RAF-1/phospho-RAF-1, and downstream (ERK/phospho-ERK and P38/phospho-P38) elements were paradoxically underexpressed in bone tissue. Therefore, CNP exerts a therapeutic effect on ROD through inhibition of FGF-23/MAPK signaling at the RAF-1 level.

Fibroblast growth factor-23 may serve as a novel biomarker for renal osteodystrophy progression.

The purpose of the present study was to determine whether fibroblast growth factor (FGF)­23 could serve as a novel biomarker for renal osteodystrophy (ROD) progression. A rat model of ROD was induced by left nephrectomy plus intravenous injection of Adriamycin. Serum FGF­23 was determined using an enzyme­linked immunosorbent assay. Serum level and bone expression of FGF­23 were both significantly elevated in the ROD group at 24 h post­surgery. Serum FGF­23 was negatively correlated with calcium, phosphate, 25­hydroxyvitamin D, conventional bone biomarkers and bone collagen X. More importantly, serum FGF­23 was significantly associated with abnormalities in bone formation rate, osteoblasts, osteoclasts, trabecular volume thickness and osteoid volume. Therefore, FGF­23 may serve as a novel biomarker for ROD.

C-Type Natriuretic Peptide Dampens Fibroblast Growth Factor-23 Expression Through MAPK Signaling Pathway in Human Mesangial Cells.

C-type natriuretic peptide (CNP) is believed to be produced locally in the kidneys and possess several renoprotective properties. In contrast, fibroblast growth factor (FGF) -23 elevates in the early stage of chronic kidney disease and predicts its outcomes. Currently, several studies have demonstrated that CNP and FGF-23 act through a close pathway, and moreover, FGF-23/mitogen-activated protein kinase (MAPK) can be obviously suppressed by CNP. In the present study, human mesangial cells (MCs) were incubated in serum-containing medium in the absence or presence of CNP (0, 10 and 100 pM) for 24, 48 and 72 h, respectively. CNP administration significantly suppresses MCs proliferation in a time- and dose-dependent manner. As a down-stream signaling of CNP activation, the expressions of natriuretic peptide receptor (NPR)-B, cyclic guanosine monophosphate-dependent protein kinases II and NPR-C were obviously augmented, whereas neutral endopeptidase expression was significantly decreased after CNP treatment in MCs. FGF-23, FGF receptor-1 and RAF-1 experienced a pronounced down-regulation in MCs with different doses of CNP throughout the whole observational period. CNP may dampen FGF-23 expression via MAPK signaling pathway in MCs.

Receptor signaling and neutral endopeptidase are involved in the resistance of C-type natriuretic peptide to human mesangial proliferation and collagen-IV expression.

C-type natriuretic peptide (CNP) is regarded as a local, paracrine hormone to regulate vascular tone and cell proliferation. Although several in vivo studies have documented that CNP exerts the inhibitory effects on mesangial cells (MCs) proliferation and collagen production, a limited number of studies exist about the resistance of CNP to MCs proliferation in vitro. Besides, whether its receptor signaling and neutral endopeptidase (NEP) are involved remains unclear. In the present study, human MCs were incubated in serum-containing medium in the absence or presence of CNP (0, 10 and 100 pM) for 24, 48 and 72 hours, respectively. CNP administration significantly suppresses MCs proliferation and collagen-IV (Col-IV) expression in a time-dependent and dose-dependent manner. As a down-stream signal molecule of CNP activation, the expressions of natriuretic peptide receptor (NPR)-B, cyclic guanosine monophosphate-dependent protein kinases II and NPR-C were obviously augmented, whereas NEP expression was significantly decreased after CNP treatment. In conclusion, receptor signaling and NEP are involved in the resistance of CNP to human mesangial proliferation and Col-IV expression.

C-type natriuretic peptide suppresses mesangial proliferation and matrix expression via a MMPs/TIMPs-independent pathway in vitro.

C-type natriuretic peptide (CNP) acts mainly in a local, paracrine fashion to regulate vascular tone and cell proliferation. Although several in vivo studies have demonstrated that CNP exerts an inhibitory effect on mesangial matrix generation, a limited number of reports exist about the anti-extracellular matrix (ECM) accumulation effect of CNP and its underlying mechanisms in mesangial cells (MCs) in vitro. In this study, human MCs were incubated in serum-containing medium in the absence or presence of CNP (0, 10 and 100 pM) for 24, 48 and 72 h, respectively. CNP administration significantly suppresses MCs proliferation and collagen (Col)-IV expression in a time- and dose-dependent manner. In addition, the study presented herein was designed as a first demonstration of the regulative effects of CNP on the metabolisms of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in MCs in vitro, and found that: (1) CNP administration significantly decreased the secretion and expression of MMP-2 and MMP-9 in the cultured MCs; (2) the secretion and expression of TIMP-1 progressively elevated after treatment with CNP for 24 and 48 h, whereas declined at later time point; (3) CNP expression was negatively correlated with MMP-2 and MMP-9 expression; (4) the balance of MMPs/TIMPs was shifted toward the reduction in MMP-2 and MMP-9 activity and/or the increment in TIMP-1 expression, which could not account for the down-regulation of Col-IV expression in CNP-treated MCs. In conclusion, CNP suppresses mesangial proliferation and ECM expression via a MMPs/TIMPs-independent pathway in vitro.

TNF-α is superior to conventional inflammatory mediators in forecasting IVIG nonresponse and coronary arteritis in Chinese children with Kawasaki disease.

BACKGROUND: Tumor necrosis factor (TNF) -α is of inflammatory cytokines produced chiefly by activated monocyte/macrophages, and has been implicated in the pathogenesis of Kawasaki disease (KD). We elucidated the relationship of plasma TNF-α with conventional inflammatory mediators, clinical classification, intravenous immunoglobulin (IVIG) response and coronary arteritis in the course of KD. METHODS: Seventy Chinese children with KD were enrolled and divided into 6 subgroups, including complete KD, incomplete KD, IVIG-responsive KD, IVIG-nonresponsive KD, coronary artery (CA) -noninvolvement KD and CA-involvement KD. Blood samples were collected from all subjects at 24h pre- and 48h post-IVIG therapy, respectively. TNF-α, white blood cells counts (WBC), absolute neutrophil counts (ANC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and procalcitonin (PCT) were detected. RESULTS: Plasma TNF-α markedly increased in the acute phase of KD and was positively correlated with CRP and PCT, whereas remained high after IVIG therapy. TNF-α as well as conventional inflammatory mediators could not be used to differentiate the clinical classification of KD, but they may prove beneficial to heighten or reduce the suspicion of incomplete KD. Plasma TNF-α was significantly higher in both IVIG-nonresponsive patients and coronary arteritis patients, but no significant differences were observed in all the other inflammatory mediators. Moreover, plasma TNF-α was positively correlated with the internal diameter of CA. CONCLUSIONS: TNF-α is superior to conventional inflammatory mediators in forecasting IVIG nonresponse and coronary arteritis in Chinese children with KD.

Neutral endopeptidase and natriuretic peptide receptors participate in the regulation of C-type natriuretic peptide expression in renal interstitial fibrosis.

The initiation and progression of renal interstitial fibrosis (RIF) is a complicated process in which many factors may play an activate role. Among these factors, C-type natriuretic peptide (CNP) is an endothelium-derived hormone and acts in a local, paracrine fashion to regulate vascular smooth muscle tone and proliferation. In this study, we established a rat model of unilateral ureteral obstruction (UUO). CNP expression tends to be higher immediately after ligation and declined at later time points, occurring predominantly in tubular epithelial cells. A high-level CNP may contribute to the elevated expression of natriuretic peptide receptor (NPR)-B in the early phase of UUO. However, the sustained expression of NPR-C and neutral endopeptidase (NEP) observed throughout the study period (that is up to 3 months) helps to, at least partly, explain the subsequent decline of CNP. Thus, NEP and NPRs participate in the regulation of CNP expression in RIF.