New insights into tetrahydrobiopterin pharmacodynamics from Pah, a mouse model for compound heterozygous tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency

Phenylketonuria (PKU), an autosomal recessive disease with phenylalanine hydroxylase (PAH) deficiency, was recently shown to be a protein misfolding disease with loss-of-function. It can be treated by oral application of the natural PAH cofactor tetrahydrobiopterin (BH₄) that acts as a pharmacological chaperone and rescues enzyme function in vivo. Here we identified Pah^enu1/2 bearing a mild and a severe mutation (V106A/F363S) as a new mouse model for compound heterozygous mild PKU. Although BH₄ treatment has become established in clinical routine, there is substantial lack of knowledge with regard to BH₄ pharmacodynamics and the effect of the genotype on the response to treatment with the natural cofactor. To address these questions we applied an elaborate methodological setup analyzing: (i) blood phenylalanine elimination, (ii) blood phenylalanine/tyrosine ratios, and (iii) kinetics of in vivo phenylalanine oxidation using ¹³C-phenylalanine breath tests. We compared pharmacodynamics in wild-type, Pah^enu1/1, and Pah^enu1/2 mice and observed crucial differences in terms of effect size as well as effect kinetics and dose response. Results from in vivo experiments were substantiated in vitro after overexpression of wild-type, V106A, and F263S in COS-7 cells. Pharmacokinetics did not differ between Pah^enu1/1 and Pah^enu1/2 indicating that the differences in pharmacodynamics were not induced by divergent pharmacokinetic behavior of BH₄. In conclusion, our findings show a significant impact of the genotype on the response to BH₄ in PAH deficient mice. This may lead to important consequences concerning the diagnostic and therapeutic management of patients with PAH deficiency underscoring the need for individualized procedures addressing pharmacodynamic aspects.     

脱氢穿心莲内酯辅助治疗对重度COPD急性加重期患者肺动脉高压血流动力学的影响

目的探讨脱氢穿心莲内酯辅助治疗对重度AECOPD患者肺动脉高压血流动力学的影响。方法 60例重度AECOPD患者(D级)随机平均分为脱氢穿心莲内酯(穿琥宁)+常规治疗组(干预组)和常规治疗组(对照组)。取30例健康体检患者作为空白组。分别测定0天和14天时患者动脉血气指标(PH、PO2和PCO2)、FEV1占预计值%和血浆ET-1和TXB2水平,并使用彩色多普勒超声心动图(CDE)测定射血分数(EF%)、平均肺动脉压(mPAP)、吸气相上腔静脉最大前向血流速度(VINS)、呼气相肺活量最大前向血流速度(VEXP)和VINS/VEXP比值。结果经14天治疗后患者动脉血气指标(PH、PO2和PCO2)、FEV1占预计值%、血浆ET-1和TXB2水平、EF%、mPAP、VINS、VEXP和VINS/VEXP比值均明显改善(均P>0.05),同时与对照组相比较干预组动脉血气指标(PH、PO2和PCO2)和FEV1占预计值%未见明显差异(均P>0.05),但血浆ET-1和TXB2水平、EF%、mPAP、VINS、VEXP和VINS/VEXP比值干预组改善更明显(均P<0.05)。同时该实验过程中干预组患者未出现与脱氢穿心莲内酯相关的严重不良反应。结论脱氢穿心莲内酯可通过调节血管内皮细胞功能降低肺循环压力改善AECOPD相关的肺动脉高压。该研究为脱氢穿心莲内酯应用于AECOPD相关的肺源性肺动脉高压和慢性肺源性心脏病的临床治疗奠定了基础。     

Riociguat for the treatment of pulmonary hypertension: a safety evaluation

ABSTRACT

Introduction: The development of pulmonary hypertension (PH) has multifactorial underlying pathophysiological causes and can be classified into five groups. While three different classes of therapeutic drugs are licensed for the treatment of pulmonary arterial hypertension (PAH, WHO group 1), specific medical therapies are lacking for other forms of PH, such as PH due to left heart disease. In 2013 riociguat, a first-in class soluble guanylate cyclase stimulator, has also become available for the treatment of PAH. Riociguat was further introduced as the first approved pharmacotherapy for the treatment of patients with chronic thromboembolic PH (WHO group 4, CTEPH). Despite these advances in therapeutic options for patients with PH, none of these agents have been approved for the treatment of PH due to left heart disease.

Areas covered: We aim to give an overview of the pathophysiology of PH, pharmacodynamics and pharmacokinetic properties, safety and efficacy of riociguat, including adverse events, contraindications and drug interactions.

Expert opinion: Considering the increasingly broad indications for riociguat in patients with PH, substantial knowledge of data and properties on safety and efficacy of riociguat are becoming more and more important for physicians prescribing riociguat to PH patients.     

Genotype–phenotype correlations analysis of mutations in the phenylalanine hydroxylase (PAH) gene

The aims of our research were to define the genotype–phenotype correlations of mutations in the phenylalanine hydroxylase (PAH) gene that cause phenylketonuria (PKU) among the Israeli population. The mutation spectrum of the PAH gene in PKU patients in Israel is described, along with a discussion on genotype–phenotype correlations. By using polymerase chain reaction/denaturing high-performance liquid chromatography (PCR/dHPLC) and DNA sequencing, we screened all exons of the PAH gene in 180 unrelated patients with four different PKU phenotypes [classic PKU, moderate PKU, mild PKU, and mild hyperphenylalaninemia (MHP)]. In 63.2% of patient genotypes, the metabolic phenotype could be predicted, though evidence is also found for both phenotypic inconsistencies among subjects with more than one type of mutation in the PAH gene. Data analysis revealed that about 25% of patients could participate in the future in (6R)-l-erythro-5, 6, 7, 8-tetrahydrobiopterin (BH₄) treatment trials according to their mutation genotypes. This study enables us to construct a national database in Israel that will serve as a valuable tool for genetic counseling and a prognostic evaluation of future cases of PKU.     

Tricuspid Regurgitation: Predicting the Need for Intervention,Procedural Success,and Recurrence of Disease

Interest in tricuspid valve pathology has rapidly expanded in response to reported poor clinical outcome for functional tricuspid regurgitation and the limited indications and options for treatment. In the past few years, different transcatheter technologies have emerged as alternatives to conventional surgery to serve this untreated high-risk population. In this review, the authors explore the indications for intervention in tricuspid regurgitation according to current guidelines, the published research to support the expansion of these indications including the role of transcatheter interventions, and the risk factors for therapy failure, which may help define the appropriate patient population for treatment.     

DNA repair as an emerging target for COPD-lung cancer overlap

Cigarette smoking is the leading cause of lung cancer and chronic obstructive pulmonary disease (COPD). Many of the detrimental effects of cigarette smoke have been attributed to the development of DNA damage, either directly from chemicals contained in cigarette smoke or as a product of cigarette smoke-induced inflammation and oxidative stress. In this review, we discuss the environmental, epidemiological, and physiological links between COPD and lung cancer and the likely role of DNA damage and repair in COPD and lung cancer development. We explore alterations in DNA damage repair by DNA repair proteins and pathways. We discuss emerging data supporting a key role for the DNA repair protein, xeroderma pigmentosum group C (XPC), in cigarette smoke-induced COPD and early lung cancer development. Understanding the interplay between cigarette smoke, DNA damage repair, COPD, and lung cancer may lead to prognostic tools and new, potentially targetable, pathways for lung cancer prevention and treatment.     

Oxidative stress and inflammatory effects in human lung epithelial A549 cells induced by phenanthrene,fluorene, and their binary mixture

Low molecular weight‐Polycyclic aromatic hydrocarbons (LMW‐PAHs) are ubiquitous environmental pollutants, which may contribute to respiratory diseases. However, studies of the relative mechanisms are limited. This study aimed to explore the effects of two LMW‐PAHs [phenanthrene (Phe) and fluorene (Flu)], separately and as binary PAH mixture on oxidative stress and inflammation in A549 cells. Cell viability was firstly detected at various concentrations (200‐800 μM) by Phe, Flu, and the mixture of Phe and Flu. ROS level, MDA content, SOD and CAT activities were then determined to evaluate oxidative damage. The protein and mRNA expressions of IL‐6, TNF‐α, TGF‐β, and the protein content of SP‐A were further determined to evaluate inflammation. Results showed that Phe, Flu, and their mixture triggered ROS generation and induced abnormal productions of MDA, SOD, and CAT. And the protein and mRNA expressions of TNF‐α and IL‐6 were increased by Phe, Flu, and their mixture, respectively. In addition, SP‐A was also increased by Phe and Flu, while it was decreased by their mixture at 600 μM. The results demonstrated that Phe, Flu, and their mixture could induce oxidative stress and subsequent inflammation in A549 cells, while combined inflammatory response was stronger than single actions.     

Endothelin inhibitors lower pulmonary vascular resistance and improve functional capacity in patients with Fontan circulation

Objectives

To evaluate the effects of endothelin inhibitors (ERAs) on hemodynamic and functional parameters in patients post-Fontan procedure with high pulmonary vascular resistance (PVR).

野百合碱性肺动脉高压大鼠右心功能分析

目的 研究肺动脉压力演变和右心室功能演变之间的关系。方法 将MCT诱导的4组肺动脉高压（pulmonary artery hypertension,PAH）模型组（每小组12只）,分别在第1、2、3、4周应用右心导管测量肺动脉压力,MRI右心功能动态检测,观察肺动脉压力和MRI参数演变关系。比较对照组、PAH模型组各组间的相关各参数差异。采用SPSS 17.0统计软件,应用Pearson相关性分析,评价右心室射血分数,右室舒张末期容积,右室收缩末期容积分别与平均肺动脉压的相关性,组间比较采用完全随机分组的t检验,P<0.05为差异有显著性。结果 注射野百合碱后1~4周,48只模型组大鼠的右心室射血分数、右心室舒张及收缩末期容积与平均肺动脉压有很好的相关性（分别为r_RVEF=-0.823,r_RVEDV=0.732,r_RVESV=0.803）。注射野百合碱前两周,野百合碱组大鼠的平均肺动脉压、右心室射血分数、右室舒张末期和收缩末期容积与对照组比较差异无显著性（P>0.05）。3~4周后,以上各参数与对照组比较差异有显著性（P<0.05）。结论 随着大鼠的肺动脉压增高,右心室射血分数逐渐降低,右心室舒张末期及收缩末期容积逐渐增加。对于大鼠慢性肺动脉高压模型的监测,MRI可以准确快速测量各项参数变化,右心室舒张末及收缩末期容积、射血分数等参数是提示肺动脉高压的敏感参数。     

Biomarker responses and PAH ratios in fish inhabiting an estuarine urban waterway

Many cities worldwide are established adjacent to estuaries and their catchments resulting in estuarine contamination due to intense anthropogenic activities. The aim of this study was to evaluate if fish living in an estuarine urban waterway were affected by contamination, via the measurement of a suite of biomarkers of fish health. Black bream (Acanthopagrus butcheri) were sampled in a small urban embayment and a suite of biomarkers of fish health measured. These were condition factor (CF), liver somatic index (LSI), gonadosomatic index (GSI), hepatic EROD activity, polycyclic aromatic hydrocarbon (PAH) biliary metabolites, serum sorbitol dehydrogenase (s‐SDH) and branchial enzymes cytochrome C oxidase (CCO), and lactate dehydrogenase (LDH) activities. The biomarkers of exposure EROD activity, and pyrene‐ and B(a)P‐type biliary metabolites confirmed current or recent exposure of the fish and that fish were metabolizing contaminants. Relative to a reference site, LSI was higher in fish collected in the urban inlet as was the metabolic enzyme LDH activity. CF, GSI, s‐SDH, CCO, and naphthalene‐type metabolites were at similar levels in the urban inlet relative to the reference site. PAH biliary metabolite ratios of high‐molecular‐weight to low‐molecular‐weight suggest that fish from the urban inlet were exposed to pyrogenic PAHs, likely from legacy contamination and road runoff entering the embayment. Similarly, the sediment PAH ratios and the freshness indices suggested legacy contamination of a pyrogenic source, likely originating from the adjacent historic gasworks site and a degree of contamination of petrogenic nature entering the inlet via storm water discharge. Biomarkers of exposure and effect confirmed that black bream collected in the Claisebrook Cove inlet, Western Australia, are currently exposed to contamination and are experiencing metabolic perturbations not observed in fish collected at a nearby reference site.