Inhibition of Anaplerosis Attenuated Vascular Proliferation in Pulmonary Arterial Hypertension

Vascular remodeling is considered a key event in the pathogenesis of pulmonary arterial hypertension (PAH). However, mechanisms of gaining the proliferative phenotype by pulmonary vascular cells are still unresolved. Due to well-established pyruvate dehydrogenase (PDH) deficiency in PAH pathogenesis, we hypothesized that the activation of another branch of pyruvate metabolism, anaplerosis, via pyruvate carboxylase (PC) could be a key contributor to the metabolic reprogramming of the vasculature. In sugen/hypoxic PAH rats, vascular proliferation was found to be accompanied by increased activation of Akt signaling, which upregulated membrane Glut4 translocation and caused upregulation of hexokinase and pyruvate kinase-2, and an overall increase in the glycolytic flux. Decreased PDH activity and upregulation of PC shuttled more pyruvate to oxaloacetate. This results in the anaplerotic reprogramming of lung vascular cells and their subsequent proliferation. Treatment of sugen/hypoxia rats with the PC inhibitor, phenylacetic acid 20 mg/kg, starting after one week from disease induction, significantly attenuated right ventricular systolic pressure, Fulton index, and pulmonary vascular cell proliferation. PC inhibition reduced the glycolytic shift by attenuating Akt-signaling, glycolysis, and restored mitochondrial pyruvate oxidation. Our findings suggest that targeting PC mediated anaplerosis is a potential therapeutic intervention for the resolution of vascular remodeling in PAH.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Early progression of pulmonary hypertension in the monocrotaline model in males is associated with increased lung permeability

Background The mechanisms involved in pulmonary hypertension (PH) development in patients and pre-clinical models are poorly understood. PH has a well-established sex dimorphism in patients with increased frequency of PH in females, and more severe disease with poor survival prognosis in males. Previously, we found that heme signaling plays an essential role in the development phase of the Sugen/Hypoxia (SU/Hx) model. This study is focused on the elucidation of sex differences in mechanisms of PH development related to heme action at the early stage of the monocrotaline (MCT) PH model. Methods Rats received MCT injection (60 mg/kg, i.p.) and followed for 14 days to investigate early disease changes. Hemodynamic parameters were recorded at the end of the study; plasma, lung homogenates, and nuclear fractions were used for the evaluation of protein levels. Results Our data indicate that on day 14, rats did not show any significant increase in the Fulton index due to the early disease phase. However, the right ventricular systolic pressure was significantly increased in male rats, while female rats showed only a trend. Interestingly, only males demonstrated an increased lung-to-bodyweight ratio that indicated lung edema. Indeed, lung histology confirmed severe perivascular edema in males. Previously, we have reported that the increased perivascular edema in SU/Hx model correlated with intravascular hemolysis and activated heme signaling. Here, we found that elevated free hemoglobin levels and perivascular edema were increased, specifically in males showing more rapid progress of PH. A high level of heme carrier protein 1 (HCP-1), which is involved in heme uptake from the bloodstream into the cells, was also found elevated in the lungs of males. The upregulation of heme oxygenase in males indicated increased intracellular heme catabolism. Increased heme signaling resulted in the activation of heme-mediated barrier-disruptive mechanisms. Thus, hemolysis in males can be responsible for increased permeability of the lungs and early disease development. Conclusions Our study indicates the importance of barrier-disruptive mechanisms as an earlier event in the induction of pulmonary hypertension. Importantly, males are more susceptible to hemolysis and develop PH earlier than females.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Antioxidant-Conjugated Peptide Attenuated Metabolic Reprogramming in Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a chronic cardiopulmonary disorder instigated by pulmonary vascular cell proliferation. Activation of Akt was previously reported to promote vascular remodeling. Also, the irreversible nitration of Y350 residue in Akt results in its activation. NitroAkt was increased in PAH patients and the SU5416/Hypoxia (SU/Hx) PAH model. This study investigated whether the prevention of Akt nitration in PAH by Akt targeted nitroxide-conjugated peptide (NP) could reverse vascular remodeling and metabolic reprogramming. Treatment of the SU/Hx model with NP significantly decreased nitration of Akt in lungs, attenuated right ventricle (RV) hypertrophy, and reduced RV systolic pressure. In the PAH model, Akt-nitration induces glycolysis by activation of the glucose transporter Glut4 and lactate dehydrogenase-A (LDHA). Decreased G6PD and increased GSK3 beta in SU/Hx additionally shunted intracellular glucose via glycolysis. The increased glycolytic rate upregulated anaplerosis due to activation of pyruvate carboxylase in a nitroAkt-dependent manner. NP treatment resolved glycolytic switch and activated collateral pentose phosphate and glycogenesis pathways. Prevention of Akt-nitration significantly controlled pyruvate in oxidative phosphorylation by decreasing lactate and increasing pyruvate dehydrogenases activities. Histopathological studies showed significantly reduced pulmonary vascular proliferation. Based on our current observation, preventing Akt-nitration by using an Akt-targeted nitroxide-conjugated peptide could be a useful treatment option for controlling vascular proliferation in PAH.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Acquirement of the autonomic nervous system modulation evaluated by heart rate variability in medaka (Oryzias latipes).

Small teleosts have recently been established as models of human diseases. However, measuring heart rate by electrocardiography is highly invasive for small fish and not widely used. The physiological nature and function of vertebrate autonomic nervous system (ANS) modulation of the heart has traditionally been investigated in larvae, transparent but with an immature ANS, or in anesthetized adults, whose ANS activity may possibly be disturbed under anesthesia. Here, we defined the frequency characteristics of heart rate variability (HRV) modulated by the ANS from observations of heart movement in high-speed movie images and changes in ANS regulation under environmental stimulation in unanesthetized adult medaka (Oryzias latipes). The HRV was significantly reduced by atropine (1 mM) in the 0.25-0.65 Hz and by propranolol (100 μM) at 0.65-1.25 Hz range, suggesting that HRV in adult medaka is modulated by both the parasympathetic and sympathetic nervous systems within these frequency ranges. Such modulations of HRV by the ANS in adult medaka were remarkably suppressed under anesthesia and continuous exposure to light suppressed HRV only in the 0.25-0.65 Hz range, indicating parasympathetic withdrawal. Furthermore, pre-hatching embryos did not show HRV and the power of HRV developed as fish grew. These results strongly suggest that ANS modulation of the heart in adult medaka is frequency-dependent phenomenon, and that the impact of long-term environmental stimuli on ANS activities, in addition to development of ANS activities, can be precisely evaluated in medaka using the presented method

<i>TBX1</i> Mutation Identified by Exome Sequencing in a Japanese Family with 22q11.2 Deletion Syndrome-Like Craniofacial Features and Hypocalcemia

<div><p>Background</p><p>Although <i>TBX1</i> mutations have been identified in patients with 22q11.2 deletion syndrome (22q11.2DS)-like phenotypes including characteristic craniofacial features, cardiovascular anomalies, hypoparathyroidism, and thymic hypoplasia, the frequency of <i>TBX1</i> mutations remains rare in deletion-negative patients. Thus, it would be reasonable to perform a comprehensive genetic analysis in deletion-negative patients with 22q11.2DS-like phenotypes.</p><p>Methodology/Principal Findings</p><p>We studied three subjects with craniofacial features and hypocalcemia (group 1), two subjects with craniofacial features alone (group 2), and three subjects with normal phenotype within a single Japanese family. Fluorescence <i>in situ</i> hybridization analysis excluded chromosome 22q11.2 deletion, and genomewide array comparative genomic hybridization analysis revealed no copy number change specific to group 1 or groups 1+2. However, exome sequencing identified a heterozygous <i>TBX1</i> frameshift mutation (c.1253delA, p.Y418fsX459) specific to groups 1+2, as well as six missense variants and two in-frame microdeletions specific to groups 1+2 and two missense variants specific to group 1. The <i>TBX1</i> mutation resided at exon 9C and was predicted to produce a non-functional truncated protein missing the nuclear localization signal and most of the transactivation domain.</p><p>Conclusions/Significance</p><p>Clinical features in groups 1+2 are well explained by the <i>TBX1</i> mutation, while the clinical effects of the remaining variants are largely unknown. Thus, the results exemplify the usefulness of exome sequencing in the identification of disease-causing mutations in familial disorders. Furthermore, the results, in conjunction with the previous data, imply that <i>TBX1</i> isoform C is the biologically essential variant and that <i>TBX1</i> mutations are associated with a wide phenotypic spectrum, including most of 22q11.2DS phenotypes.</p></div

The pedigree of this family.

<p>Facial features of subjects III-5 and III-7 are shown.</p

Clinical findings of the family members.

<p>Individuals correspond to those shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091598#pone-0091598-g001" target="_blank">Fig. 1</a>.</p><p>i-phosphate: inorganic phosphate; SD: standard deviation; F: female; M: male; and N.E.: not examined.</p>a<p>Reference values: calcium, 9.0–11.0 mg/dL in infants and 8.8–10.2 mg/dL in adults; inorganic phosphate, 4.8–7.5 mg/dL in infants and 2.5–4.5 mg/dL in adults, and intact PTH, 10–65 pg/dL in infants and 14–55 pg/dL in adults.</p><p>Conversion factor to the SI unit: 0.25 for calcium (mmol/L), 0.32 for inorganic phosphate (mmol/L), and 0.106 for intact PTH (pmol/L).</p>b<p>Examined by echocardiography, chest roentgenography, and/or electrocardiography.</p>c<p>Examined by computed tomography.</p>d<p>Received velopharyngeal closure.</p>e<p>On treatment with vitamin D.</p>f<p>Repeated otitis media only.</p>g<p>Received speech therapy.</p>h<p>Required hearing aids.</p>i<p>At the time of diagnosis (11 years of age), serum TSH was <0.01 mIU/L, free T₃ 33.1 pg/mL [51.0 pmol/L], free T₄ 5.11 ng/dL [65.8 nmol/L], and TSH receptor antibody 1284% [normal range <1.9%].</p

FISH and array CGH analyses in the proband (III-5).

<p><b>A.</b> FISH analysis. Two signals are shown for both <i>HIRA</i> at 22q11.2 (red signals indicated by arrows) and <i>ARSA</i> at 22q13 (green signals indicated by arrowheads). <b>B.</b> Array CGH analysis. No copy number change is found for chromosome 10 carrying the second DiGeorge region and chromosome 22 harboring the DGS/VCFS critical region, as well as other chromosomes (not shown). Black, red, and green dots denote signals indicative of the normal, the increased (>+0.5), and the decreased (<−0.8) copy numbers, respectively. Although several red and green signals are seen, there is no portion associated with ≥3 consecutive red or green signals.</p