Untargeted metabolomics towards understanding molecular mechanisms of pulmonary arterial hypertension

Background

Pulmonary hypertension constitutes a rare disease characterized by a severe development and a high risk of premature death. One of its main clinical types is pulmonary arterial hypertension (PAH), in which the highest percentage of patients are affected by idiopathic PAH. The pathogenesis of this disease has not completely been discovered and elucidated so far, and non-specific clinical symptoms make the diagnosis of PAH a serious problem. Currently, PAH is confirmed with invasive examination based on right heart catheterization.

Purpose

The main aim of the study was to evaluate and compare both plasma and urine fingerprints of PAH patients and control group with the use of an untargeted metabolomics approach. The study also focused on correlation analysis between the observed metabolic changes and the clinical parameters to select specific indicators of PAH disease.

Methods

An untargeted metabolomics approach was applied to the plasma and urine samples with the use of gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ/MS) and advanced statistical tests were applied to evaluate the potential metabolic indicators of PAH. The PAH patients (n=40) and healthy controls (n=39) were matched for age, sex, BMI and included in the study. The obtained raw datasets were properly processed (data deconvolution, signal correction using QCSVR method and PQN normalization) and subsequently subjected to uni- and multivariate statistical tests (Student's t-test, Welch's test, U Mann-Whitney test, PCA and OPLS-DA). The identification of the statistically significant metabolites was performed using universal libraries, such as: Fiehn's and NIST11.

Results

The statistically significant metabolites (n=10 and 11 for urine and plasma samples, respectively)originate from various biochemical pathways associated with the carbohydrate, amino acid, lipid, fatty acid and pyrimidine metabolism. The metabolic changes observed in the urine samples of PAH patients (compared to the control group) included different concentrations in: threonic acid, hippuric acid, acetic acid, sorbitol, butanoic acid and propionic acid. The metabolic alterations in the plasma samples covered changes in the levels of valine, leucine, lactic acid, hydroxybutanoic acid, nonanoic acid, cholesterol and octadecanoic acid. Metabolites representing the highest correlation with mean pulmonary arterial pressure include, for instance: propionic acid (r=0.85), valine (r=0.75) and lactic acid (r=0.63)

Conclusions

The observed metabolic changes are related to various biological processes that are disturbed in the course of PAH, namely: proliferation of pulmonary vascular cells or the functions of cardiomyocytes and the right ventricle of the heart. The obtained results confirmed the potential of a metabolomics approach to uncover and explain the underlying molecular mechanisms of PAH.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Science and High Education of Poland

Identification of small-molecule inhibitors of USP2a

USP2a is a deubiquitinating protease that rescues its target proteins from destruction by the proteasome by reversing the process of protein ubiquitination. USP2a shows oncogenic properties in vivo and has been found to be a specific activator of cyclin D1. Many types of cancers are addicted to cyclin D1 expression. Targeting USP2a is a promising strategy for cancer therapy but little progress has been made in the field of inhibition of USP2a. Using NMR-based fragment screening and biophysical binding assays, we have discovered small molecules that bind to USP2a. Iterations of fragment combination and structure-driven design identified two 5-(2-thienyl)-3-isoxazoles as the inhibitors of the USP2a-ubiquitin protein-protein interaction. The affinity of these molecules for the catalytic domain of USP2a parallels their ability to interfere with USP2a binding to ubiquitin in vitro. Altogether, our results establish the 5-(2-thienyl)-3-isoxazole pharmacophore as an attractive starting point for lead optimization.

Association between concentration of melatonin, and lipoproteins, LPO, hsCRP, NTproBNP in chronic heart failure patients

The aim of the study was to examine concentrations and relationships between melatonin levels assessed at 0:200 hrs and 0:700 hrs, lipid hydroperoxide (LPO) assessed at 0:200 hrs and 0:700 hrs, and apolipoprotein (apo)AI, apoAII, apoB, high sensitivity C-reactive protein (hsCRP) and NT-proBNP, in 27 patients with chronic heart failure (CHF) (17 patients - with NYHA class II and 10 - with NYHA class III). In the study, Lipoproteins apoAI, apoAII, apoB, high sensitivity C-reactive protein (hsCRP) levels were determined by way of immunonephelometric methods, serum melatonin concentration was measured by using a competitive enzyme immunoassay technique, while serum LPO concentration was measured by using Cayman’s Lipid Hydroperoxide Assay Kit. In the study, CHF patients without acute inflammatory response demonstrated a decreased concentration of high density lipoprotein cholesterol (HDL-C), apoAI, apoAII levels, but an increased concentration of NT-proBNP, hsCRP and LPO at night, and LPO at daytime; however, the concentration of LPO at 0:700 was lower than at 0:200. Pearson’s correlation test and multiple ridge stepwise regression showed that melatonin administered at night exerts an effect on the composition of apoAI and apoAII of HDL particles, and induces decreased LPO at 0:700, but has no effect upon NT-proBNP levels in patients with NYHA class II. However, in patients with NYHA class III, melatonin administered at night induces an increase in the content of apoAII and apoAI, which further decreases hsCRP, and this, together with the administered melatonin, brings about daytime decreases in NT-proBNP and hsCRP levels. The results indicated that the content of apoAII and apoAI in HDL particles and melatonin demonstrate an anti-oxidative and anti-inflammatory effect, and together, have a cardio-protective effect on patients with advanced CHF. Hence, the results support melatonin being a cardio-protective agent. These relationships, however, need to be confirmed in further studies.

Degeneration of dopaminergic mesocortical neurons and activation of compensatory processes induced by a long-term paraquat administration in rats: implications for Parkinson's disease

A deficiency of the dopaminergic transmission in the mesocortical system has been suggested to contribute to cognitive disturbances in Parkinson's disease. Therefore, the aim of the present study was to examine whether the long-term administration of a commonly used herbicide, paraquat, which has already been found to induce a slowly progressing degeneration of the nigrostriatal neurons, influences mesocortical dopaminergic neurons in rats. Paraquat at a dose of 10 mg/kg i.p. was injected either acutely or once a week for 4, 8, 12 and 24 weeks. Acute treatment with this pesticide increased the level of homovanillic acid (HVA) and HVA/dopamine ratio in the prefrontal cortex. After 8 weeks of administration paraquat increased the number of stereologically counted tyrosine hydroxylase-immunoreactive (TH-ir) neurons and their staining intensity in the ventral tegmental area (VTA), which is a source of the mesocortical dopaminergic projection. At the same time, few TH-ir neurons appeared in different regions of the cerebral cortex: in the frontal, cingulate, retrosplenial and parietal cortices. Chronic paraquat administration did not influence the level of dopamine in the prefrontal cortex but increased the levels of its metabolites: 3,4-dihydroxyphenylacetic acid (after 8-12 weeks), HVA (after 4 and 12 weeks) and HVA/dopamine ratio (4 weeks). After 24 weeks this pesticide reduced the number of TH-ir neurons in the VTA by 42% and of the Nissl-stained neurons by 26%, and induced shrinkage of this structure by ca. 25%. Moreover, TH-ir neurons in the cortex were no more visible after such a long period of administration and levels of dopamine metabolites returned to control values. The present results suggest that the long-term paraquat administration destroys dopaminergic neurons of the VTA. However, compensatory activation of the VTA neurons and cortex overcomes progressing degeneration and maintains cortical dopaminergic transmission.

A slowly developing dysfunction of dopaminergic nigrostriatal neurons induced by long-term paraquat administration in rats: an animal model of preclinical stages of Parkinson's disease?

The aim of the present study was to examine the influence of the long-term paraquat administration on the dopaminergic nigrostriatal system in rats. Paraquat was injected at a dose of 10 mg/kg i.p. for 4-24 weeks. We found that this pesticide reduced the number of tyrosine hydroxylase-immunoreactive neurons of the substantia nigra; after the 4-week treatment the reduction (17%, nonsignificant) was confined to the rostrocentral region of this structure but, after 24 weeks, had spread along its whole length and was approximately 37%. Moreover, it induced a biphasic effect on dopaminergic transmission. First, levels of dopamine, its metabolites and turnover were elevated (4-8 weeks) in the caudate-putamen, then all these parameters returned to control values (12 weeks) and dropped by 25-30% after 24 weeks. The binding of [3H]GBR 12,935 to dopamine transporter in the caudate-putamen was decreased after 4-8 weeks, then returned to control values after 12 weeks but was again decreased after 24 weeks. Twenty-four-week paraquat administration also decreased the level of tyrosine hydroxylase (Western blot) in the caudate-putamen. In addition, paraquat activated serotonin and noradrenaline transmission during the first 12 weeks of treatment but no decreases in levels of these neurotransmitters were observed after 24 weeks. The above results seem to suggest that long-term paraquat administration produces a slowly progressing degeneration of nigrostriatal neurons, leading to delayed deficits in dopaminergic transmission, which may resemble early, presymptomatic, stages of Parkinson's disease.