Tomotaka Nakayama

A new nonsense mutation of SMAD8 associated with pulmonary arterial hypertension

Background: Pulmonary arterial hypertension (PAH) is a progressive disorder characterised by raised pulmonary artery pressures with pathological changes in small pulmonary arteries. Previous studies have shown that approximately 70% of familial PAH and also 11–40% of idiopathic PAH (IPAH) cases have mutations in the bone morphogenetic protein receptor type II (BMPR2) gene. In addition, mutations in the activin receptor-like kinase 1 (ALK1) gene have been reported in PAH patients. Since both the BMPR2 and ALK1 belonging to the transforming growth factor (TGF)-β superfamily are known to predispose to PAH, mutations in other genes of the TGF-β/BMP signalling pathways may also predispose to PAH. Methods: We screened for mutations in ENDOGLIN(ENG), SMAD1, SMAD2, SMAD3, SMAD4, SMAD5, SMAD6 and SMAD8 genes, which are involved in the TGF-β/BMP signallings, in 23 patients with IPAH who had no mutations in BMPR2 or ALK1. Results: A nonsense mutation in SMAD8 designated c.606 C>A, p.C202X was identified in one patient. The father of this patient was also identified as having the same mutation. Functional analysis showed the truncated form of the SMAD8 C202X protein was not phosphorylated by constitutively active ALK3 and ALK1. The SMAD8 mutant was also unable to interact with SMAD4. The response to BMP was analysed using promoter-reporter activities with SMAD4 and/or ca-ALK3. The transcriptional activation of the SMAD8 mutant was inefficient compared with the SMAD8 wild type. Conclusion: We describe the first mutation in SMAD8 in a patient with IPAH. Our findings suggest the involvement of SMAD8 in the pathogenesis of PAH.

Tissue Doppler Imaging Predicts Adverse Outcome in Children with Idiopathic Pulmonary Arterial Hypertension

OBJECTIVE To evaluate the clinical utility of tissue Doppler imaging (TDI) in assessment of disease severity and prognostic value in children with idiopathic pulmonary arterial hypertension (PAH). STUDY DESIGN A prospective study was performed to evaluate TDI velocities (systolic myocardial velocity, early diastolic myocardial relaxation velocity [Em], late diastolic myocardial velocity associated with atrial contraction), brain natriuretic peptide, New York Heart Association (NYHA) functional class, and hemodynamics in 51 children (mean age; 11.6 years) with idiopathic PAH. Fifty-one healthy children with comparable demographics served as controls. RESULTS Em, Em/late diastolic myocardial velocity associated with atrial contraction ratio, and systolic myocardial velocity at mitral annulus, septum, and tricuspid annulus in PAH were significantly reduced compared with controls. Tricuspid Em had significant inverse correlations with plasma brain natriuretic peptide levels (r = -0.60, P < .001), right ventricular end-diastolic pressure (r = -0.79, P < .001), and mean pulmonary arterial pressure (r = -0.67, P < .001). Statistically significant differences were observed in tricuspid Em between NYHA functional class II vs combined III and IV (mean and SD; 11.9 ± 4.2 cm/s vs 8.2 ± 3.6 cm/s, respectively, P = .002). Cumulative event-free survival rate was significantly lower when tricuspid Em was ≤8 cm/s (log-rank test, P < .001) CONCLUSIONS Tricuspid Em velocity correlated with NYHA functional class as disease severity and may serve as a useful prognostic marker in children with idiopathic PAH. The present study is the initial report to evaluate TDI velocities against midterm outcome variables in a relatively large pediatric PAH population.

Outcomes of childhood pulmonary arterial hypertension in BMPR2 and ALK1 mutation carriers

Mutations in the bone morphogenetic protein receptor type 2 (BMPR2) gene and the activin receptor-like kinase 1 (ALK1) gene have been reported in heritable pulmonary arterial hypertension (HPAH) and idiopathic pulmonary arterial hypertension (IPAH). However, the relation between clinical characteristics and each gene mutation in IPAH and HPAH is still unclear, especially in childhood. The aim of this study was to determine, in a retrospective study, the influence and clinical outcomes of gene mutations in childhood IPAH and HPAH. Fifty-four patients with IPAH or HPAH whose onset of disease was at <16 years of age were included. Functional characteristics, hemodynamic parameters, and clinical outcomes were compared in BMPR2 and ALK1 mutation carriers and noncarriers. Overall 5-year survival for all patients was 76%. Eighteen BMPR2 mutation carriers and 7 ALK1 mutation carriers were detected in the 54 patients with childhood IPAH or HPAH. Five-year survival was lower in BMPR2 mutation carriers than mutation noncarriers (55% vs 90%, hazard ratio 12.54, p = 0.0003). ALK1 mutation carriers also had a tendency to have worse outcome than mutation noncarriers (5-year survival rate 64%, hazard ratio 5.14, p = 0.1205). In conclusion, patients with childhood IPAH or HPAH with BMPR2 mutation have the poorest clinical outcomes. ALK1 mutation carriers tended to have worse outcomes than mutation noncarriers. It is important to consider aggressive treatment for BMPR2 or ALK1 mutation carriers.

Pharmacokinetics of Bosentan in Routinely Treated Japanese Pediatric Patients with Pulmonary Arterial Hypertension

We evaluated the pharmacokinetics of routinely administered bosentan in 46 Japanese pediatric patients with pulmonary arterial hypertension. Plasma samples were taken twice at times corresponding to the peak and trough concentrations following repetitive oral administration. The population pharmacokinetic parameters of bosentan were estimated by use of the NONMEM program, in which a one-compartment model with repetitive bolus dosing was parameterized in terms of the oral clearance (CL/F) and elimination rate constant (k). Polymorphisms of CYP3A5, SLCO1B1, SLCO1B3, and SLCO2B1 had no significant effect on the disposition of bosentan. In addition, the pharmacokinetics of bosentan was not altered by heart failure or coadministration of sildenafil. In contrast, weight (WT)-normalized values of CL/F were correlated negatively with age (AGE). The final population mean values of CL/F and k were estimated to be 0.409 · (1 - 0.0377 · (AGE - 3.81)) · WT L/h and 0.175 h(-1), respectively.

Mutations of NOTCH3 in childhood pulmonary arterial hypertension

Mutations of BMPR2 and other TGF‐β superfamily genes have been reported in pulmonary arterial hypertension (PAH). However, 60–90% of idiopathic PAH cases have no mutations in these genes. Recently, the expression of NOTCH3 was shown to be increased in the pulmonary artery smooth muscle cells of PAH patients. We sought to investigate NOTCH3 and its target genes in PAH patients and clarify the role of NOTCH3 signaling. We screened for mutations in NOTCH3, HES1, and HES5 in 41 PAH patients who had no mutations in BMPR2, ALK1, endoglin, SMAD1/4/8, BMPR1B, or Caveolin‐1. Two novel missense mutations (c.2519 G>A p.G840E, c.2698 A>C p.T900P) in NOTCH3 were identified in two PAH patients. We performed functional analysis using stable cell lines expressing either wild‐type or mutant NOTCH3. The protein‐folding chaperone GRP78/BiP was colocalized with wild‐type NOTCH3 in the endoplasmic reticulum, whereas the majority of GRP78/BiP was translocated into the nuclei of cells expressing mutant NOTCH3. Cell proliferation and viability were higher for cells expressing mutant NOTCH3 than for those expressing wild‐type NOTCH3. We identified novel NOTCH3 mutations in PAH patients and revealed that these mutations were involved in cell proliferation and viability. NOTCH3 mutants induced an impairment in NOTCH3‐HES5 signaling. The results may contribute to the elucidation of PAH pathogenesis.

Clinical characteristics of aseptic meningitis induced by intravenous immunoglobulin in patients with Kawasaki disease

BackgroundAseptic meningitis is a serious adverse reaction to intravenous immunoglobulin (IVIG) therapy. We studied the clinical characteristics of patients with acute Kawasaki disease (KD) who developed IVIG-induced aseptic meningitis.MethodsA retrospective analysis of the medical records of patients with KD who developed aseptic meningitis after IVIG treatment was performed.ResultsDuring the 10-year period from 2000 through 2009, among a total of 384 patients with Kawasaki disease, 4 (3 females and 1 male; age range, 19-120 months) developed aseptic meningitis after IVIG. All 4 developed aseptic meningitis within 48 hours (range, 25-40 hours) of initiation of IVIG. The analyses of cerebrospinal fluid (CSF) revealed elevated white blood cell counts (22-1,248/μL) in all 4 patients; a predominance of polynuclear cells (65%-89%) was noted in 3. The CSF protein level was elevated in only 1 patient (59 mg/dL), and the glucose levels were normal in all 4 patients. Two patients were treated with intravenous methylprednisolone; the other 2 children were observed carefully without any special therapy. All patients recovered without neurological complications.ConclusionsIn our patients with Kawasaki disease, aseptic meningitis induced by IVIG occurred within 48 hours after initiation of IVIG, resolved within a few days, and resulted in no neurological complications, even in patients who did not receive medical treatment.

Sildenafil reduces pulmonary vascular resistance in single ventricular physiology

BACKGROUND High pulmonary vascular resistance (PVR) may be a risk factor for early and late mortality in both Glen shunt and Fontan operation patients. Furthermore, PVR may increase long after the Fontan operation. Whether pulmonary vasodilators such as phosphodiesterase 5 inhibitors can decrease PVR in patients with single ventricular physiology remains undetermined. METHODS AND RESULTS This was a prospective, multicenter study. Patients with single ventricular physiology who have a PVR index higher than 2.5 Wood units·㎡ (WU) were enrolled. Cardiac catheterization was performed before and after administration of sildenafil in all patients. After the Fontan operation, a six minute walk test (6MWT) was also performed. A total of 42 patients were enrolled. PVR was significantly decreased in each stage of single ventricular physiology after sildenafil administration: from 4.3±1.5WU to 2.1±0.6WU (p<0.01) in patients before a Glenn shunt, from 3.2±0.5WU to 1.6±0.6WU (p<0.001) in patients after a Glenn shunt, and from 3.9±1.7WU to 2.3±0.8WU (p<0.001) in patients after Fontan. In patients after Fontan, the 6MWT increased from 416±74m to 485±72m (p<0.01), and NYHA functional class improved significantly (p<0.05) after sildenafil administration. No major side effects were observed in any patients. CONCLUSIONS Sildenafil reduced PVR in patients with single ventricle physiology. Sildenafil increased exercise capacity and improved NYHA functional class in patients after a Fontan operation. This implies that pulmonary vasodilation is a potential therapeutic target in selected patients with elevated PVR with single ventricle physiology. Long-term clinical significance warrants further study.

Pulmonary Arterial Capacitance Index Is a Strong Predictor for Adverse Outcome in Children with Idiopathic and Heritable Pulmonary Arterial Hypertension

Objectives To evaluate the clinical utility of pulmonary artery capacitance index (PACi) in the assessment of disease severity and prognostic value in children with idiopathic and heritable pulmonary arterial hypertension (PAH). Study Design PACi is defined as the ratio of stroke volume index over pulmonary pulse pressure. A retrospective study was performed to compare PACi, brain natriuretic peptide (BNP), 6‐minute walk distance, New York Heart association (NYHA) functional class, and adverse outcomes (hospitalization due to heart failure, lung transplantation, and cardiac mortality) in 72 Japanese children (10 ± 3.6 years) with idiopathic and heritable PAH. Results PACi had significant correlations with pulmonary vascular resistance index (r =−0.73, P < .0001), BNP levels (r = −0.40, P = .0008), and 6‐minute walk distance (r = 0.57, P < .05). Statistically significant differences in PACi were observed between NYHA functional class II vs combined III and IV (median; 1.1 vs 0.6 mL/mm Hg/m2, respectively, P < .05). There were 25 of 72 (35%) children who had an adverse event including initiation of hospitalization due to heart failure, lung transplantation, and death. Cumulative event‐free survival rate was significantly lower when PACi was <0.85 mL/mm Hg/m2 (log‐rank test, P < .0001). Conclusions PACi correlated with BNP and NYHA functional class and may serve as a strong prognostic marker in children with idiopathic and heritable PAH.

Efficacy and safety of an orally administered selective prostacyclin receptor agonist, selexipag, in Japanese patients with pulmonary arterial hypertension

BACKGROUND Selexipag is an orally available prostacyclin receptor (IP receptor) agonist with a non-prostanoid structure. In this open-label Phase II trial, the efficacy and safety of selexipag in Japanese patients with pulmonary arterial hypertension (PAH) is examined.Methods and Results:Selexipag was administered at 200 μg twice daily and titrated up to 1,600 μg by increments of 200 μg in 37 subjects to reach the individual maximum tolerated dose. At 16 weeks, in 33 patients comprising the per-protocol set, the pulmonary vascular resistance (PVR; primary endpoint) decreased from 683.2±237.3 to 560.3±238.7 dyn·s/cm5(P<0.0001). For the secondary endpoint, the 6-min walk distance (6MWD) increased from 445.0±102.2 to 459.1±112.8 m (P=0.0324); World Health Organization functional class improved in 4 patients (12.1%), and was maintained in 29 patients (87.9%). A decrease in PVR was also shown in patients treated with selexipag, on top of a phosphodiesterase inhibitor and endothelin receptor antagonist. Most of the commonly reported adverse events were consistent with those reported for other PGI2formulations. Thirty-four patients attained the individual maximum tolerated dose (maintenance dose). CONCLUSIONS The efficacy and tolerability of selexipag in Japanese PAH patients was confirmed by improvement in pulmonary hemodynamics, exercise capacity, symptoms. Selexipag is an efficacious treatment option for Japanese PAH patients. (Trial registration: JAPIC Clinical Trials Information [JapicCTI-111532].).

Clinical Impact of Main Pulmonary Artery Dilatation on Outcome in Pediatric Idiopathic and Heritable Pulmonary Arterial Hypertension

BACKGROUND Few studies have investigated the clinical impact of pulmonary artery (PA) dilatation on outcomes in pediatric pulmonary arterial hypertension (PAH).Methods and Results:This study investigated the clinical outcomes of idiopathic or heritable PAH in 66 children aged <18 years at diagnosis. Main PA/thorax (MPA/T) ratio was measured on chest radiography in PAH patients. Patients were divided into 2 groups based on MPA/T ratio, and compared with a control group of 166 age- and gender-matched healthy children. Group A had higher MPA/T ratio than normal, and group B had normal MPA/T ratio. Composite outcomes included cardiac death, lung transplantation, and hospitalization due to heart failure. Group A consisted of 27 patients and group B, 39 patients. At diagnosis, group A had significantly higher brain natriuretic peptide (BNP), cardiothoracic ratio, PA pressure, and pulmonary vascular resistance index compared with group B. The number of patients with New York Heart Association (NYHA) functional class III and IV was significantly higher in group A than in group B. Cumulative event-free survival rate was significantly lower in group A. CONCLUSIONS MPA dilatation correlated with BNP, NYHA functional class, and hemodynamics with regard to disease severity, and may be a potential prognostic factor in pediatric idiopathic and heritable PAH.