Biomarkers in Pulmonary Vascular Disease: Gauging Response to Therapy

Feline pulmonary hypertension: are we overlooking an important comorbidity?

Pulmonary hypertension (PH) is a potential complication in many disease states, yet it has been largely overlooked in feline medicine. Recently, increased awareness of potential underlying causes has led to a wider understanding of the disease process in humans, with a focus on tailoring therapy to include specific treatment of the underlying etiology. Most of these treatments are not yet available in veterinary medicine, but as they move from the human to the veterinary field, it would be beneficial to better understand the forms of PH encountered in different species. Recently, diagnosis and classification of PH in dogs has been the focus of an American College of Veterinary Internal Medicine consensus statement, yet this condition has received little attention in cats. It is therefore our intention to raise awareness of this condition in cats and to propose a classification system for the types of PH seen in feline patients. As new medications are developed for the treatment of PH, it is important to recognize which forms of PH are seen in feline patients and understand the etiology of the disease. There are many reports of PH (or suspected PH based on echocardiographic assessment) in cats. In this review, we highlight the large number of conditions, and different etiologies, that are associated with PH. Improving understanding of this condition will bring us closer to being able to investigate the benefits of potential new diagnostics and therapies as they become available.

Early diagnosis and targeted approaches to pulmonary vascular disease in bronchopulmonary dysplasia

Pulmonary hypertension has emerged as a life-threatening disease in preterm infants suffering from bronchopulmonary dysplasia (BPD). Its development is closely linked to respiratory disease, as vasculogenesis and alveologenesis are closely interconnected. Once clinically significant, BPD-associated pulmonary hypertension (BPD-PH) can be challenging to manage, due to poor reversibility and multiple comorbidities frequently associated. The pulmonary vascular disease process underlying BPD-PH is the result of multiple innate and acquired factors, and emerging evidence suggests that it progressively develops since birth and, in certain instances, may begin as early as fetal life. Therefore, early recognition and intervention are of great importance in order to improve long-term outcomes. Based on the most recent knowledge of BPD-PH pathophysiology, we review state-of-the-art screening and diagnostic imaging techniques currently available, their utility for clinicians, and their applicability and limitations in this specific population. We also discuss some biochemical markers studied in humans as a possible complement to imaging for the detection of pulmonary vascular disease at its early stages and the monitoring of its progression. In the second part, we review pharmacological agents currently available for BPD-PH treatment or under preclinical investigation, and discuss their applicability, as well as possible approaches for early-stage interventions in fetuses and neonates. IMPACT: BPD-associated PH is a complex disease involving genetic and epigenetic factors, as well as environmental exposures starting from fetal life. The value of combining multiple imaging and biochemical biomarkers is emerging, but requires larger, multicenter studies for validation and diffusion. Since "single-bullet" approaches have proven elusive so far, combined pharmacological regimen and cell-based therapies may represent important avenues for research leading to future cure and prevention.

Clinical efficacy, safety, tolerability, and survival outcome of long-term inhaled iloprost treatment in the management of pulmonary arterial hypertension: Data from prospective multicenter observational OPTION study

OBJECTIVE

To evaluate clinical efficacy, safety and tolerability of long-term inhaled iloprost treatment in the daily practice for the management of pulmonary arterial hypertension (PAH).

METHODS

A total of 115 patients with PAH on inhaled iloprost treatment were included. New York Heart Association (NYHA) functional class, brain natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, and 6-minute walk distance (6MWD) were recorded at baseline and at 3rd to 24th month visits. Safety and tolerability of iloprost treatment were also evaluated during follow-up, as were the survival, clinical worsening, and the related risk factors.

RESULTS

The treatment was associated with an increase in the percentage NYHA functional class II (from 0.0% at enrolment to 36.2% at 24th month visit) patients but no significant difference was noted in 6MWD values. Clinical worsening was observed in 63.5% patients, while survival rate was 69.6%. NT-proBNP levels were significantly higher in non-survivors than in survivors (p=0.042). Cox regression analysis revealed the association of female sex [odds ratio (OR)=0.318; 95% confidence interval (CI), 0.128-0.792; p=0.014] and scleroderma-related PAH (OR=0.347; 95% CI, 0.140-0.860; p=0.022) with significantly lower risk (3.14 fold and 2.88 fold, respectively) of mortality.

CONCLUSION

Our findings indicate favorable efficacy, safety, and tolerability of long-term iloprost treatment in the management of PAH, whereas improved NYHA functional class was not accompanied with a significant change in 6MWD values. Patient age was a risk factor for clinical worsening, while female sex, scleroderma subtype, and lower NT-proBNP levels were associated with significantly lower mortality risk.

The Nitric Oxide Pathway in Pulmonary Arterial Hypertension: Pathomechanism, Biomarkers and Drug Targets

The altered Nitric Oxide (NO) pathway in the pulmonary endothelium leads to increased vascular smooth muscle tone and vascular remodelling, and thus contributes to the development and progression of pulmonary arterial hypertension (PAH). The pulmonary NO signalling is abrogated by the decreased expression and dysfunction of the endothelial NO synthase (eNOS) and the accumulation of factors blocking eNOS functionality. The NO deficiency of the pulmonary vasculature can be assessed by detecting nitric oxide in the exhaled breath or measuring the degradation products of NO (nitrite, nitrate, S-nitrosothiol) in blood or urine. These non-invasive biomarkers might show the potential to correlate with changes in pulmonary haemodynamics and predict response to therapies. Current pharmacological therapies aim to stimulate pulmonary NO signalling by suppressing the degradation of NO (phosphodiesterase- 5 inhibitors) or increasing the formation of the endothelial cyclic guanosine monophosphate, which mediates the downstream effects of the pathway (soluble guanylate cyclase sensitizers). Recent data support that nitrite compounds and dietary supplements rich in nitrate might increase pulmonary NO availability and lessen vascular resistance. This review summarizes current knowledge on the involvement of the NO pathway in the pathomechanism of PAH, explores novel and easy-to-detect biomarkers of the pulmonary NO.

Biomarkers and indoor air quality: A translational research review

Introduction:

Air pollution is linked to mortality and morbidity. Since humans spend nearly all their time indoors, improving indoor air quality (IAQ) is a compelling approach to mitigate air pollutant exposure. To assess interventions, relying on clinical outcomes may require prolonged follow-up, which hinders feasibility. Thus, identifying biomarkers that respond to changes in IAQ may be useful to assess the effectiveness of interventions.

Methods:

We conducted a narrative review by searching several databases to identify studies published over the last decade that measured the response of blood, urine, and/or salivary biomarkers to variations (natural and intervention-induced) of changes in indoor air pollutant exposure.

Results:

Numerous studies reported on associations between IAQ exposures and biomarkers with heterogeneity across study designs and methods. This review summarizes the responses of 113 biomarkers described in 30 articles. The biomarkers which most frequently responded to variations in indoor air pollutant exposures were high sensitivity C-reactive protein (hsCRP), von Willebrand Factor (vWF), 8-hydroxy-2′-deoxyguanosine (8-OHdG), and 1-hydroxypyrene (1-OHP).

Conclusions:

This review will guide the selection of biomarkers for translational studies evaluating the impact of indoor air pollutants on human health.

Is There Value in Repeating Inhaled Nitric Oxide Vasoreactivity Tests in Patients with Pulmonary Arterial Hypertension?

BACKGROUND

In patients with pulmonary arterial hypertension (PAH), it remains unknown if the response to the acute pulmonary vasoreactivity test changes over time and determines prognosis.

METHODS

We included PAH patients who underwent two right heart catheterizations (RHC) with acute vasoreactivity challenge using inhaled nitric oxide (NO). The hemodynamic response was assessed by absolute or percentage change in mean pulmonary artery pressure (mPAP) or pulmonary vascular resistance (PVR).

RESULTS

We included 54 patients, age 51 ± 17 years, and 44 (82%) female. The median (IQR) time between the two RHC was 24.5 months (14.8-42 months). The percentage drop in mPAP was less pronounced in the second RHC (- 8.6 ± 8.1 versus - 12.3 ± 13.8 mmHg, p = 0.02). A total of 8 (14%) patients met criteria for a positive vasodilatory test during the first RHC but only 1 during the second. Patients with increased vasoreactivity at second RHC were more likely to receive (a) treatment with phosphodiesterase-5 inhibitors (PDE5-inh) at first RHC (56% versus 27%, p = 0.04) and (b) more PAH-specific medications by second RHC (2.3 ± 0.8 versus 1.8 ± 0.9, p = 0.03). Cox survival analysis showed that change in mPAP or PVR during vasodilatory challenge at or between the first and second RHC had no impact on survival.

CONCLUSIONS

Pulmonary vascular reactivity to inhaled NO might decrease over time; however, there is great variability among patients. The use of PDE5-inh at first RHC and number of PAH-specific treatments by the second RHC were associated with an improvement in pulmonary vasoreactivity over time.

Exploring clinical, echocardiographic and molecular biomarkers to predict bronchopulmonary dysplasia

Introduction

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease in childhood, related to prematurity, and the most common cause of pulmonary hypertension (PH) secondary to pulmonary disease in children. Moderate and severe BPD have a worse outcome and relate more frequently with PH. The prediction of moderate or severe BPD development in extremely premature newborns is vital to implement preventive strategies. Starting with the hypothesis that molecular biomarkers were better than clinical and echocardiographic factors, this study aims to explore the ability of clinical, echocardiographic and analytical variables to predict moderate or severe BPD in a cohort of extremely preterm infants.

Patients and methods

We designed a prospective longitudinal study, in which we followed a cohort of preterm newborns (gestational age <28 weeks and weight ≤ 1250 grams). In these newborns we recorded weekly clinical and echocardiographic variables as well as blood and tracheal aspirate samples, to analyze molecular biomarkers (IL-6, IL-1, IP10, uric acid, HGF, endothelin-1, VEGF, CCL5). Variables and samples were collected since birth up to week 36 (postmenstrual age), time-point at which the diagnosis of BPD is established.

Results

We included 50 patients with a median gestational age of 26 weeks (IQR 25–27) and weight of 871 g (SD 161,0) (range 590-1200g). Three patients were excluded due to an early death. Thirty-five patients (74.5%) developed BPD (mild n = 14, moderate n = 15, severe n = 6). We performed a logistic regression in order to identify risk factors for moderate or severe BPD. We compared two predictive models, one with two variables (mechanical ventilation and inter-ventricular septum flattening), and another-one with an additional molecular biomarker (ET-1).

Conclusions

The combination of clinical and echocardiographic variables is a valuable tool for determining the risk of BPD. We find the two variable model (mechanical ventilation and echocardiographic signs of PH) more practical for clinical and research purposes. Future research on BPD prediction should be oriented to explore the potential role of ET-1.

Diagnosis of pulmonary hypertension

A revised diagnostic algorithm provides guidelines for the diagnosis of patients with suspected pulmonary hypertension, both prior to and following referral to expert centres, and includes recommendations for expedited referral of high-risk or complicated patients and patients with confounding comorbidities. New recommendations for screening high-risk groups are given, and current diagnostic tools and emerging diagnostic technologies are reviewed.

Diagnosis of pulmonary hypertension

A revised diagnostic algorithm provides guidelines for the diagnosis of patients with suspected pulmonary hypertension, both prior to and following referral to expert centres, and includes recommendations for expedited referral of high-risk or complicated patients and patients with confounding comorbidities. New recommendations for screening high-risk groups are given, and current diagnostic tools and emerging diagnostic technologies are reviewed.