Beclin 1 Haploinsufficiency Ameliorates High-Fat Diet-Induced Myocardial Injury via Inhibiting Alternative Mitophagy

Aims: Mitochondrial homeostasis is essential for maintaining redox balance. Besides canonical autophagy, Rab9-dependent alternative autophagy is a crucial mechanism in metabolic cardiomyopathy. Here, we aim to investigate the role of alternative mitophagy and Beclin 1 haploinsufficiency (Beclin 1+/-) in high-fat diet (HFD)-induced metabolic cardiomyopathy. Results: Twenty-four-week HFD impaired glucose tolerance and cardiomyocyte contraction in wild-type mice, both of which were rescued in Beclin 1+/- mice. Beclin 1 haploinsufficiency had little effect on the conventional autophagy mediators (ATG5, LC3 II/LC3 I) but further upregulated Rab9 expression, a marker of alternative autophagy, in response to HFD challenge. Furthermore, either the inhibition of alternative autophagy or Beclin 1 haploinsufficiency abolished palmitic acid (PA)-induced cardiomyocyte contractile anomalies. In vitro, PA overactivated mitophagy, resulting in decreased mitochondrial content in H9C2 cells. These aberrations were alleviated in cells deficient in alternative autophagy but not in cells deficient in conventional autophagy. Mechanistically, HFD promoted reactive oxygen species (ROS) production, activated Rab9-dependent alternative mitophagy, and inhibited mitochondrial biosynthesis. Beclin 1+/- rescued HFD-induced ROS overflow, mitochondrial biogenesis impairment, and prevented Rab9 translocation from the cytoplasm to the mitochondria, thereby inhibiting Rab9-mediated mitophagy overactivation. Innovation: For the first time, this study suggests that prolonged alternative mitophagy exacerbates chronic HFD-induced cardiac dysfunction and supports the protective role of Beclin 1 haploinsufficiency in metabolic cardiomyopathy. This provides additional evidence for a target-based pharmacological intervention. Conclusion: Beclin 1 haploinsufficiency protects against HFD-induced cardiac dysfunction by inhibiting Rab9-dependent alternative mitophagy and ROS production, while promoting mitochondrial biogenesis. Modulating Beclin 1 expression holds promise in preventing chronic HFD-related cardiomyopathy.

Impact of Epicardial Adipose Tissue on Right Cardiac Function and Prognosis in Pulmonary Arterial Hypertension

BACKGROUND

Although epicardial adipose tissue (EAT) is linked to effects on survival in left-sided heart failure, the association between EAT and right-sided heart failure caused by pulmonary arterial hypertension (PAH) remains unknown.

RESEARCH QUESTION

What are the potential impacts of EAT volume (EATV) on right ventricular function, biomarkers of myocardial injury, and long-term prognosis in patients with PAH?.

STUDY DESIGN AND METHODS

A total of 135 age- and BMI-matched patients with PAH and 49 control subjects were included in this study. EATV was quantified by using cardiac magnetic resonance and was related to clinical correlates, N-terminal pro-brain natriuretic peptide, and cardiac function. Levels of EATV associated with the risk of clinical worsening were evaluated on a continuous scale (restricted cubic splines) and by previously defined centile categories with Cox proportional hazards regression models and Kaplan-Meier survival estimates.

RESULTS

Compared with the control subjects, patients with PAH had a lower EATV (ln [EATV], 3.2 ± 0.8 mL vs 3.5 ± 0.7 mL; P = .034). The association of EATV with right ventricular end-diastolic volume (Pnonlinear = .001), right ventricular end-diastolic volume index (P < .001), right ventricular cardiac output (P = .003), N-terminal pro-brain natriuretic peptide (P = .030), and the risk of clinical worsening (P = .014) was U shaped. Compared with individuals with middle-level EATV, multivariable-adjusted hazard ratio for clinical worsening was 6.0 (95% CI, 1.3-27.8) for the individuals with low-level EATV and 6.8 (95% CI, 1.5-30.2) for high-level EATV in patients with PAH.

INTERPRETATION

Patients with PAH had a decreased EATV compared with control subjects. EATV exhibited a U-shaped association with right ventricular function and biomarkers of myocardial injury in patients with PAH. Low and high levels of EATV might reduce long-term event-free survival in patients with PAH.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry; No. ChiCTR2100049804; www.chictr.org.cn.

Pulmonary veno-occlusive disease in Sjogren's syndrome: a case report

BACKGROUND

Pulmonary arterial hypertension (PAH) associated with connective tissue disease (CTD) belongs to Group 1 pulmonary hypertension. Pulmonary veno-occlusive disease (PVOD), which is characterized by venous system aberrations, has been previously reported in CTD-PAH; however, it has rarely been observed in Sjogren's syndrome (SS).

CASE PRESENTATION

Our 28-year-old female patient was admitted to the hospital with recurrent shortness of breath even after minimal physical activity. Her chest high-resolution CT scan demonstrated pulmonary artery dilatation and bilateral ground-glass nodules. A subsequent right heart catheterization confirmed pulmonary hypertension because her mean pulmonary arterial pressure was 62 mmHg. Our inquisitive genomic assessment identified a novel EIF2AK4 mutation at c.1021 C > T (p. Gln341*), the dominant causal gene of PVOD. Histological examination demonstrated stenosis and occlusions in the pulmonary veins. Because she presented with features such as dry eyes and Raynaud's phenomenon, we performed a biopsy on the labial salivary gland, which confirmed SS. Her treatment regimen included PAH-targeted therapies (tadalafil and macitentan) in combination with hydroxychloroquine. Although she was hospitalized several times due to acute exacerbation of PAH, her disease progression was under control, and she did not demonstrate any signs of pulmonary edema even after a three-year treatment period.

CONCLUSION

Here, we report the case of an SS-PAH patient with PVOD who carried a novel biallelic EIF2AK4 mutation, and PAH-targeted therapies were well tolerated by our patient.

Thromboxane-Prostanoid Receptor Signaling Drives Persistent Fibroblast Activation in Pulmonary Fibrosis

Rationale: Although persistent fibroblast activation is a hallmark of idiopathic pulmonary fibrosis (IPF), mechanisms regulating persistent fibroblast activation in the lungs have not been fully elucidated. Objectives: On the basis of our observation that lung fibroblasts express TBXA2R (thromboxane-prostanoid receptor) during fibrosis, we investigated the role of TBXA2R signaling in fibrotic remodeling. Methods: We identified TBXA2R expression in lungs of patients with IPF and mice and studied primary mouse and human lung fibroblasts to determine the impact of TBXA2R signaling on fibroblast activation. We used TBXA2R-deficient mice and small-molecule inhibitors to investigate TBXA2R signaling in preclinical lung fibrosis models. Measurements and Main Results: TBXA2R expression was upregulated in fibroblasts in the lungs of patients with IPF and in mouse lungs during experimental lung fibrosis. Genetic deletion of TBXA2R, but not inhibition of thromboxane synthase, protected mice from bleomycin-induced lung fibrosis, thereby suggesting that an alternative ligand activates profibrotic TBXA2R signaling. In contrast to thromboxane, F2-isoprostanes, which are nonenzymatic products of arachidonic acid induced by reactive oxygen species, were persistently elevated during fibrosis. F2-isoprostanes induced TBXA2R signaling in fibroblasts and mediated a myofibroblast activation profile due, at least in part, to potentiation of TGF-β (transforming growth factor-β) signaling. In vivo treatment with the TBXA2R antagonist ifetroban reduced profibrotic signaling in the lungs, protected mice from lung fibrosis in three preclinical models (bleomycin, Hermansky-Pudlak mice, and radiation-induced fibrosis), and markedly enhanced fibrotic resolution after bleomycin treatment. Conclusions: TBXA2R links oxidative stress to fibroblast activation during lung fibrosis. TBXA2R antagonists could have utility in treating pulmonary fibrosis.

Association of cardiac injury with hypertension in hospitalized patients with COVID-19 in China

Outbreak of global pandemic Coronavirus disease 2019 (COVID-19) has so far caused countless morbidity and mortality. However, a detailed report on the impact of COVID-19 on hypertension (HTN) and ensuing cardiac injury is unknown. Herein, we have evaluated the association between HTN and cardiac injury in 388 COVID-19 (47.5 ± 15.2 years) including 75 HTN and 313 normotension. Demographic data, cardiac injury markers, other laboratory findings, and comorbidity details were collected and analyzed. Compared to patients without HTN, hypertensive-COVID-19 patients were older, exhibited higher C-reactive protein (CRP), erythrocyte sedimentation rate, and comorbidities such as diabetes, coronary heart disease, cerebrovascular disease and chronic kidney disease. Further, these hypertensive-COVID-19 patients presented more severe disease with longer hospitalization time, and a concomitant higher rate of bilateral pneumonia, electrolyte disorder, hypoproteinemia and acute respiratory distress syndrome. In addition, cardiac injury markers such as creatine kinase (CK), myoglobin, lactic dehydrogenase (LDH), and N-terminal pro brain natriuretic peptide were significantly increased in these patients. Correlation analysis revealed that systolic blood pressure correlated significantly with the levels of CK, and LDH. Further, HTN was associated with increased LDH and CK-MB in COVID- 19 after adjusting essential variables. We also noticed that patients with elevated either high sensitivity-CRP or CRP demonstrated a significant high level of LDH along with a moderate increase in CK (p = 0.07) and CK-MB (p = 0.09). Our investigation suggested that hypertensive patients presented higher risk of cardiac injury and severe disease phenotype in COVID-19, effectively control blood pressure in HTN patients might improve the prognosis of COVID-19 patients.

Overexpression of Msx1 in Mouse Lung Leads to Loss of Pulmonary Vessels Following Vascular Hypoxic Injury

Pulmonary arterial hypertension (PAH) is a progressive lung disease caused by thickening of the pulmonary arterial wall and luminal obliteration of the small peripheral arteries leading to increase in vascular resistance which elevates pulmonary artery pressure that eventually causes right heart failure and death. We have previously shown that transcription factor Msx1 (mainly expressed during embryogenesis) is strongly upregulated in transformed lymphocytes obtained from PAH patients, especially IPAH. Under pathological conditions, Msx1 overexpression can cause cell dedifferentiation or cell apoptosis. We hypothesized that Msx1 overexpression contributes to loss of small pulmonary vessels in PAH. In IPAH lung, MSX1 protein localization was strikingly increased in muscularized remodeled pulmonary vessels, whereas it was undetectable in control pulmonary arteries. We developed a transgenic mouse model overexpressing MSX1 (MSX1^OE) by about 4-fold and exposed these mice to normoxic, sugen hypoxic (3 weeks) or hyperoxic (100% 02 for 3 weeks) conditions. Under normoxic conditions, compared to controls, MSX1^OE mice demonstrated a 30-fold and 2-fold increase in lung Msx1 mRNA and protein expression, respectively. There was a significant retinal capillary dropout (p < 0.01) in MSX1^OE mice, which was increased further (p < 0.03) with sugen hypoxia. At baseline, the number of pulmonary vessels in MSX1^OE mice was similar to controls. In sugen-hypoxia-treated MSX1^OE mice, the number of small (0-25 uM) and medium (25-50 uM) size muscularized vessels increased approximately 2-fold (p < 0.01) compared to baseline controls; however, they were strikingly lower (p < 0.001) in number than in sugen-hypoxia-treated control mice. In MSX1^OE mouse lung, 104 genes were upregulated and 67 genes were downregulated compared to controls. Similarly, in PVECs, 156 genes were upregulated and 320 genes were downregulated from siRNA to MSX1^OE, and in PVSMCs, 65 genes were upregulated and 321 genes were downregulated from siRNA to MSX1^OE (with control in the middle). Many of the statistically significant GO groups associated with MSX1 expression in lung, PVECs, and PVSMCs were similar, and were involved in cell cycle, cytoskeletal and macromolecule organization, and programmed cell death. Overexpression of MSX1 suppresses many cell-cycle-related genes in PVSMCs but induces them in PVECs. In conclusion, overexpression of Msx1 leads to loss of pulmonary vessels, which is exacerbated by sugen hypoxia, and functional consequences of Msx1 overexpression are cell-dependent.

KCNK3 Mutation Causes Altered Immune Function in Pulmonary Arterial Hypertension Patients and Mouse Models

Loss of function KCNK3 mutation is one of the gene variants driving hereditary pulmonary arterial hypertension (PAH). KCNK3 is expressed in several cell and tissue types on both membrane and endoplasmic reticulum and potentially plays a role in multiple pathological process associated with PAH. However, the role of various stressors driving the susceptibility of KCNK3 mutation to PAH is unknown. Hence, we exposed kcnk3^fl/fl animals to hypoxia, metabolic diet and low dose lipopolysaccharide (LPS) and performed molecular characterization of their tissue. We also used tissue samples from KCNK3 patients (skin fibroblast derived inducible pluripotent stem cells, blood, lungs, peripheral blood mononuclear cells) and performed microarray, immunohistochemistry (IHC) and mass cytometry time of flight (CyTOF) experiments. Although a hypoxic insult did not alter vascular tone in kcnk3^fl/fl mice, RNASeq study of these lungs implied that inflammatory and metabolic factors were altered, and the follow-up diet study demonstrated a dysregulation of bone marrow cells in kcnk3^fl/fl mice. Finally, a low dose LPS study clearly showed that inflammation could be a possible second hit driving PAH in kcnk3^fl/fl mice. Multiplex, IHC and CyTOF immunophenotyping studies on human samples confirmed the mouse data and strongly indicated that cell mediated, and innate immune responses may drive PAH susceptibility in these patients. In conclusion, loss of function KCNK3 mutation alters various physiological processes from vascular tone to metabolic diet through inflammation. Our data suggests that altered circulating immune cells may drive PAH susceptibility in patients with KCNK3 mutation.

Expression of a Human Caveolin-1 Mutation in Mice Drives Inflammatory and Metabolic Defect-Associated Pulmonary Arterial Hypertension

Background: In 2012, mutations in Cav1 were found to be the driving mutation in several cases of heritable pulmonary arterial hypertension (PAH). These mutations replaced the last 21 amino acids of Cav1 with a novel 22-amino-acid sequence. Because previously only Cav1 knockouts had been studied in the context of PAH, examining the in vivo effects of this novel mutation holds promise for new understanding of the role of Cav1 in disease etiology.

Methods: The new 22 amino acids created by the human mutation were knocked into the native mouse Cav1 locus. The mice underwent hemodynamic, energy balance, and inflammatory measurements, both at baseline and after being stressed with either a metabolic or an inflammatory challenge [low-dose lipopolysaccharide (LPS)]. To metabolically challenge the mice, they were injected with streptozotocin (STZ) and fed a high-fat diet for 12 weeks.

Results: Very little mutant protein was found in vivo (roughly 2% of wild-type by mass spectrometry), probably because of degradation after failure to traffic from the endoplasmic reticulum. The homozygous mutants developed a mild, low-penetrance PAH similar to that described previously in knockouts, and neither baseline nor metabolic nor inflammatory stress resulted in pressures above normal in heterozygous animals. The homozygous mutants had increased lean mass and worsened oral glucose tolerance, as previously described in knockouts. Novel findings include the preservation of Cav2 and accessory proteins in the liver and the kidney, while they are lost with homozygous Cav1 mutation in the lungs. We also found that the homozygous mutants had a significantly lower tolerance to voluntary spontaneous exercise than the wild-type mice, with the heterozygous mice at an intermediate level. The mutants also had higher circulating monocytes, with both heterozygous and homozygous animals having higher pulmonary MCP1 and MCP5 proteins. The heterozygous animals also lost weight at an LPS challenge level at which the wild-type mice continued to gain weight.

Conclusions: The Cav1 mutation identified in human patients in 2012 is molecularly similar to a knockout of Cav1. It results in not only metabolic deficiencies and mild pulmonary hypertension, as expected, but also an inflammatory phenotype and reduced spontaneous exercise.

Rapid disease progress in a PVOD patient carrying a novel EIF2AK4 mutation: a case report

Background

Pulmonary veno-occlusive disease (PVOD) and pulmonary arterial hypertension (PAH) share an overlapping disease phenotype. Hence it is necessary to distinguish them.

Case presentation

Our 14-year-old female patient admitted with progressive shortness of breath, dizziness, and fatigue even after minimal physical activity was clinically suspected for PAH, based on her previous history. Her chest computed tomography artery reported the presence of PVOD triad features - subpleural thickened septal lines, ground-glass nodules/opacities and mediastinal lymphadenopathy. Because of her weak physical stature, a lung biopsy was not performed; however, the genetic testing identified a novel heterozygous EIF2AK4 mutation at c.4833_4836dup (p.Q1613Kfs*10) - the dominant susceptible factor driving PVOD. Combination of genetic testing and computed tomography artery facilitated us to distinguish PVOD from PAH. Her disease symptoms advanced aggressively so that she died even before the lung transplantation, which was less than 6 months from the onset of disease symptoms.

Conclusion

This case report highlights that novel EIF2AK4 mutation at [c.4833_4836dup (p.Q1613Kfs*10)] would predict an aggressive phenotype of PVOD. Hence, we conclude that a genetic test identifying EIF2AK4 mutation would serve as a tool for the early diagnosis of PVOD, circumventing lung biopsy.

Complementary Embryonic and Adult Cell Populations Enhance Myocardial Repair in Rat Myocardial Injury Model

We compared the functional outcome of Isl-1+ cardiac progenitors, CD90+ bone marrow-derived progenitor cells, and the combination of the two in a rat myocardial infarction (MI) model. Isl-1+ cells were isolated from embryonic day 12.5 (E12.5) rat hearts and expanded in vitro. Thy-1+/CD90+ cells were isolated from the bone marrow of adult Sprague-Dawley rats by immunomagnetic cell sorting. Six-week-old female Sprague-Dawley rats underwent permanent left anterior descending (LAD) coronary artery ligation and received intramyocardial injection of either saline, Isl-1+ cells, CD90+ cells, or a combination of Isl-1+ and CD90+ cells, at the time of infarction. Cells were delivered transepicardially to the peri-infarct zone. Left ventricular function was assessed by transthoracic echocardiography at 1- and 4-week post-MI and by Millar catheterization (-dP/dt and +dP/dt) at 4-week post-MI. Fluorescence in situ hybridization (Isl-1+cells) and monochrystalline iron oxide nanoparticles labeling (MION; CD90+ cells) were performed to assess biodistribution of transplanted cells. Only the combination of cells demonstrated a significant improvement of cardiac function as assessed by anterior wall contractility, dP/dt (max), and dP/dt (min), compared to Isl-1+ or CD90+ cell monotherapies. In the combination cell group, viable cells were detected at week 4 when anterior wall motion was completely restored. In conclusion, the combination of Isl-1+ cardiac progenitors and adult bone marrow-derived CD90+ cells shows prolonged and robust myocardial tissue repair and provides support for the use of complementary cell populations to enhance myocardial repair.

Ubiquitin chains: a new way of screening for regulatory differences in pulmonary hypertension

Protein ubiquitination serves many regulatory functions; in addition to degradation, ubiquitination has roles in intracellular trafficking, cell cycle, innate immunity, and more. Using mass spectrometry, it is possible to assess the ubiquitination state of every protein simultaneously. In this issue, Wade et al. have for the first time done just that in a hypoxic mouse model of pulmonary hypertension (PH). New techniques drive new discoveries; their work is important not just because they have found new ways to intervene in known PH-related pathways but have found regulation of proteins not previously associated with disease.

A potential therapeutic role for angiotensin-converting enzyme 2 in human pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a deadly disease with no cure. Alternate conversion of angiotensin II (AngII) to angiotensin-(1-7) (Ang-(1-7)) by angiotensin-converting enzyme 2 (ACE2) resulting in Mas receptor (Mas1) activation improves rodent models of PAH. Effects of recombinant human (rh) ACE2 in human PAH are unknown. Our objective was to determine the effects of rhACE2 in PAH.We defined the molecular effects of Mas1 activation using porcine pulmonary arteries, measured AngII/Ang-(1-7) levels in human PAH and conducted a phase IIa, open-label pilot study of a single infusion of rhACE2 (GSK2586881, 0.2 or 0.4 mg·kg^-1 intravenously).Superoxide dismutase 2 (SOD2) and inflammatory gene expression were identified as markers of Mas1 activation. After confirming reduced plasma ACE2 activity in human PAH, five patients were enrolled in the trial. GSK2586881 was well tolerated with significant improvement in cardiac output and pulmonary vascular resistance. GSK2586881 infusion was associated with reduced plasma markers of inflammation within 2-4 h and increased SOD2 plasma protein at 2 weeks.PAH is characterised by reduced ACE2 activity. Augmentation of ACE2 in a pilot study was well tolerated, associated with improved pulmonary haemodynamics and reduced markers of oxidant and inflammatory mediators. Targeting this pathway may be beneficial in human PAH.

Involvement of Neuroinflammation in the Pathogenesis of Monocrotaline-Induced Pulmonary Hypertension

Pulmonary hypertension (PH) is a devastating disease and its successful treatment remains to be accomplished despite recent advances in pharmacotherapy. It has been proposed that PH be considered as a systemic disease, rather than primarily a disease of the pulmonary vasculature. Consequently, an investigation of the intricate interplay between multiple organs such as brain, vasculature, and lung in PH could lead to the identification of new targets for its therapy. However, little is known about this interplay. This study was undertaken to examine the concept that altered autonomic-pulmonary communication is important in PH pathophysiology. Therefore, we hypothesize that activation of microglial cells in the paraventricular nucleus of hypothalamus and neuroinflammation is associated with increased sympathetic drive and pulmonary pathophysiology contributing to PH. We utilized the monocrotaline rat model for PH and intracerebroventricular administration of minocycline for inhibition of microglial cells activation to investigate this hypothesis. Hemodynamic, echocardiographic, histological, immunohistochemical, and confocal microscopic techniques assessed cardiac and pulmonary function and microglial cells. Monocrotaline treatment caused cardiac and pulmonary pathophysiology associated with PH. There were also increased activated microglial cells and mRNA for proinflammatory cytokines (IL [interleukin]-1β, IL-6, and TNF [tumor necrosis factor]-α) in the paraventricular nucleus. Furthermore, increased sympathetic drive and plasma norepinephrine were observed in rats with PH. Intracerebroventricular infusion of minocycline inhibited all these parameters and significantly attenuated PH. These observations implicate a dysfunctional autonomic-lung communication in the development and progression of PH providing new therapeutic targets, such as neuroinflammation, for PH therapy.

rhACE2 Therapy Modifies Bleomycin-Induced Pulmonary Hypertension via Rescue of Vascular Remodeling

Background: Pulmonary hypertension (PH) is a progressive cardiovascular disease, characterized by endothelial and smooth muscle dysfunction and vascular remodeling, followed by right heart failure. Group III PH develops secondarily to chronic lung disease such as idiopathic pulmonary fibrosis (IPF), and both hastens and predicts mortality despite of all known pharmacological interventions. Thus, there is urgent need for development of newer treatment strategies. Objective: Angiotensin converting enzyme 2 (ACE2), a member of the renin angiotensin family, is therapeutically beneficial in animal models of pulmonary vascular diseases and is currently in human clinical trials for primary PH. Although previous studies suggest that administration of ACE2 prevents PH secondary to bleomycin-induced murine IPF, it is unknown whether ACE2 can reverse or treat existing disease. Therefore, in the present study, we tested the efficacy of ACE2 in arresting the progression of group 3 PH. Methods: To establish pulmonary fibrosis, we administered 0.018 U/g bleomycin 2x/week for 4 weeks in adult FVB/N mice, and sacrificed 5 weeks following the first injection. ACE2 or vehicle was administered via osmotic pump for the final 2 weeks, beginning 3 weeks after bleomycin. Echocardiography and hemodynamic assessment was performed prior to sacrifice and tissue collection. Results: Administration of bleomycin significantly increased lung collagen expression, pulmonary vascular remodeling, and pulmonary arterial pressure, and led to mild right ventricular hypertrophy. Acute treatment with ACE2 significantly attenuated vascular remodeling and increased pulmonary SOD2 expression without measurable effects on pulmonary fibrosis. This was associated with nonsignificant positive effects on pulmonary arterial pressure and cardiac function. Conclusion: Collectively, our findings enumerate that ACE2 treatment improved pulmonary vascular muscularization following bleomycin exposure, concomitant with increased SOD2 expression. Although it may not alter the pulmonary disease course of IPF, ACE2 could be an effective therapeutic strategy for the treatment of group 3 PH.

The Selective Angiotensin II Type 2 Receptor Agonist, Compound 21, Attenuates the Progression of Lung Fibrosis and Pulmonary Hypertension in an Experimental Model of Bleomycin-Induced Lung Injury

Idiopathic Pulmonary Fibrosis (IPF) is a chronic lung disease characterized by scar formation and respiratory insufficiency, which progressively leads to death. Pulmonary hypertension (PH) is a common complication of IPF that negatively impacts clinical outcomes, and has been classified as Group III PH. Despite scientific advances, the dismal prognosis of IPF and associated PH remains unchanged, necessitating the search for novel therapeutic strategies. Accumulating evidence suggests that stimulation of the angiotensin II type 2 (AT₂) receptor confers protection against a host of diseases. In this study, we investigated the therapeutic potential of Compound 21 (C21), a selective AT₂ receptor agonist in the bleomycin model of lung injury. A single intra-tracheal administration of bleomycin (2.5 mg/kg) to 8-week old male Sprague Dawley rats resulted in lung fibrosis and PH. Two experimental protocols were followed: C21 was administered (0.03 mg/kg/day, ip) either immediately (prevention protocol, BCP) or after 3 days (treatment protocol, BCT) of bleomycin-instillation. Echocardiography, hemodynamic, and Fulton's index assessments were performed after 2 weeks of bleomycin-instillation. Lung tissue was processed for gene expression, hydroxyproline content (a marker of collagen deposition), and histological analysis. C21 treatment prevented as well as attenuated the progression of lung fibrosis, and accompanying PH. The beneficial effects of C21 were associated with decreased infiltration of macrophages in the lungs, reduced lung inflammation and diminished pulmonary collagen accumulation. Further, C21 treatment also improved pulmonary pressure, reduced muscularization of the pulmonary vessels and normalized cardiac function in both the experimental protocols. However, there were no major differences in any of the outcomes measured from the two experimental protocols. Collectively, our findings indicate that stimulation of the AT₂ receptor by C21 attenuates bleomycin-induced lung injury and associated cardiopulmonary pathology, which needs to be further explored as a promising approach for the clinical treatment of IPF and Group III PH.

Isolation and characterization of endothelial-to-mesenchymal transition cells in pulmonary arterial hypertension

Endothelial-to-mesenchymal transition (EndMT) is a process in which endothelial cells lose polarity and cell-to cell contacts, and undergo a dramatic remodeling of the cytoskeleton. It has been implicated in initiation and progression of pulmonary arterial hypertension (PAH). However, the characteristics of cells which have undergone EndMT cells in vivo have not been reported and so remain unclear. To study this, sugen5416 and hypoxia (SuHx)-induced PAH was established in Cdh5-Cre/Gt(ROSA)26Sor^{tm4(ACTB-tdTomato,EGFP)Luo}/J double transgenic mice, in which GFP was stably expressed in pan-endothelial cells. After 3 wk of SuHx, flow cytometry and immunohistochemistry demonstrated CD144-negative and GFP-positive cells (complete EndMT cells) possessed higher proliferative and migratory activity compared with other mesenchymal cells. While CD144-positive and α-smooth muscle actin (α-SMA)-positive cells (partial EndMT cells) continued to express endothelial progenitor cell markers, complete EndMT cells were Sca-1-rich mesenchymal cells with high proliferative and migratory ability. When transferred in fibronectin-coated chamber slides containing smooth muscle media, α-SMA robustly expressed in these cells compared with cEndMT cells that were grown in maintenance media. Demonstrating additional paracrine effects, conditioned medium from isolated complete EndMT cells induced enhanced mesenchymal proliferation and migration and increased angiogenesis compared with conditioned medium from resident mesenchymal cells. Overall, these findings show that EndMT cells could contribute to the pathogenesis of PAH both directly, by transformation into smooth muscle-like cells with higher proliferative and migratory potency, and indirectly, through paracrine effects on vascular intimal and medial proliferation.

Therapeutic potential of adipose stem cell-derived conditioned medium against pulmonary hypertension and lung fibrosis

BACKGROUND AND PURPOSE

Pulmonary hypertension (PH) and pulmonary fibrosis (PF) are life threatening cardiopulmonary diseases. Existing pharmacological interventions have failed to improve clinical outcomes or reduce disease-associated mortality. Emerging evidence suggests that stem cells offer an effective treatment approach against various pathological conditions. It has been proposed that their beneficial actions may be mediated via secretion of paracrine factors. Herein, we evaluated the therapeutic potential of conditioned media (CM) from adipose stem cells (ASCs) against experimental models of PH and PF.

EXPERIMENTAL APPROACH

Monocrotaline (MCT) or bleomycin (Bleo) was injected into male Sprague-Dawley rats to induce PH or PF respectively. A subset of MCT and Bleo animals were treated with ASCs or CM. Echocardiographic and haemodynamic measurements were performed at the end of the study. Lung and heart tissues were harvested for RNA, protein and histological measurements.

KEY RESULTS

CM treatment attenuated MCT-induced PH by improving pulmonary blood flow and inhibiting cardiac remodelling. Further, histological studies revealed that right ventricular fibrosis, pulmonary vessel wall thickness and pericyte distribution were significantly decreased by CM administration. Likewise, CM therapy arrested the progression of PF in the Bleo model by reducing collagen deposition. Elevated expression of markers associated with tissue remodelling and inflammation were significantly reduced in both PF and PH lungs. Similar results were obtained with ASCs administration.

CONCLUSIONS AND IMPLICATIONS

Our study indicates that CM treatment is as effective as ASCs in treating PH and PF. These beneficial effects of CM may provide an innovative approach to treat cardiopulmonary disorders.

Stem cell therapy restores viscoelastic properties of myocardium in rat model of hypertension

Extensive remodeling of the myocardium is seen in a variety of cardiovascular diseases, including systemic hypertension. Stem cell therapy has been proposed to improve the clinical outcomes of hypertension, and we hypothesized that changes in mechanical properties of the myocardium would accompany the progression of disease and the results of treatment conditions. Using spontaneously hypertensive rats (SHR) as a model of hypertension, we treated 13-week-old hypertensive rats with a single injection of adipose-derived stem cells (ADSC) isolated from a normotensive control. We indented the isolated ventricles of control, untreated sham-injected SHR, and ADSC-treated SHR hearts with a custom cantilever-based system and fit the resulting data to a standard linear solid model. SHR animals had higher blood pressure (198.4±25.9mmHg) and lower ejection fraction (69.9±4.2%) than age-matched control animals (109.0±1.6mmHg, 88.2±1.3%), and increased viscoelastic properties accompanied these clinical changes (right ventricle effective stiffness, SHR: 21.97±5.10kPa, Control: 13.14±3.48kPa). ADSC-treated animals saw improvement in clinical parameters compared to the untreated SHR group, which was also accompanied by a significant restoration of viscoelastic properties of the myocardium (ACSD-treated SHR: 9.77±6.96kPa).

Abstract 028: ACE2 Activator, Diminazene, Rebalances Gut Microbial Dysbiosis and Attenuates Pulmonary Hypertension

Introduction: Our previous studies have established that increasing the levels of pulmonary Angiotensin converting enzyme2 (ACE2) either by genetic overexpression or by a small molecule activator, Diminazene aceturate (DIZE) provides protection against lung injury. In view of the mounting evidence of the involvement of the gut microbiota in inflammatory, metabolic and neurological diseases, we proposed the following hypothesis: gut dysfunction and microbial dysbiosis is associated with pulmonary hypertension (PH) and that the cardiopulmonary beneficial effect of DIZE is mediated, in part, by its influence on the gut microbial composition.

Methods: PH was induced in male Sprague Dawley rats by a single injection of monocrotaline (MCT; 50mg/Kg s.c). A subset of MCT rats was treated daily with DIZE (15mg/Kg/day s.c) for 4-weeks, after which hemodynamic parameters were measured and fecal samples collected for bacterial 16S ribosomal DNA analysis. In addition, colon samples were isolated to determine tissue stiffness by ex vivo atomic force microscopy.

Results: MCT administration resulted in the development of PH as evidenced by increase in right ventricular systolic pressure (RVSP - Control: 30+2; MCT: 93+10 mmHg; p<0.05), which was associated with significant decreases in gut microbial richness (37%), diversity (22%), and evenness (16%). Furthermore, we observed a significant reduction in acetate- and butyrate-producing, and increases in lactate-producing bacterial population in PH animals. Elastic modulus and viscosity of the colon were increased by 61% and 86% respectively in MCT animals as compared with controls, indicating greater tissue stiffness (Elastic modulus - Control: 7.33+1.66; MCT: 11.84+3.41 kPa; Viscosity - Control: 145+19; MCT: 270+36 kPa*s; p<0.05). However, chronic treatment with DIZE attenuated all these parameters (RVSP - MCT+DIZE: 52+9 mmHg; Elastic modulus - MCT+DIZE: 8.97+3.84 kPa; Viscosity - MCT+DIZE: 180+77 kPa*s; p<0.05)

Conclusions: These observations demonstrate for the first time that a) gut microbial dysbiosis is associated with MCT-induced PH; b) DIZE attenuates PH pathophysiology and significantly rebalances dysbiosis. They suggest that the gut microbiota could be a potential target for PH therapy.

Selective activation of angiotensin AT2 receptors attenuates progression of pulmonary hypertension and inhibits cardiopulmonary fibrosis

BACKGROUND AND PURPOSE

Pulmonary hypertension (PH) is a devastating disease characterized by increased pulmonary arterial pressure, which progressively leads to right-heart failure and death. A dys-regulated renin angiotensin system (RAS) has been implicated in the development and progression of PH. However, the role of the angiotensin AT2 receptor in PH has not been fully elucidated. We have taken advantage of a recently identified non-peptide AT2 receptor agonist, Compound 21 (C21), to investigate its effects on the well-established monocrotaline (MCT) rat model of PH.

EXPERIMENTAL APPROACH

A single s.c. injection of MCT (50 mg·kg(-1) ) was used to induce PH in 8-week-old male Sprague Dawley rats. After 2 weeks of MCT administration, a subset of animals began receiving either 0.03 mg·kg(-1) C21, 3 mg·kg(-1) PD-123319 or 0.5 mg·kg(-1) A779 for an additional 2 weeks, after which right ventricular haemodynamic parameters were measured and tissues were collected for gene expression and histological analyses.

KEY RESULTS

Initiation of C21 treatment significantly attenuated much of the pathophysiology associated with MCT-induced PH. Most notably, C21 reversed pulmonary fibrosis and prevented right ventricular fibrosis. These beneficial effects were associated with improvement in right heart function, decreased pulmonary vessel wall thickness, reduced pro-inflammatory cytokines and favourable modulation of the lung RAS. Conversely, co-administration of the AT2 receptor antagonist, PD-123319, or the Mas antagonist, A779, abolished the protective actions of C21.

CONCLUSIONS AND IMPLICATIONS

Taken together, our results suggest that the AT2 receptor agonist, C21, may hold promise for patients with PH.

Oral delivery of Angiotensin-converting enzyme 2 and Angiotensin-(1-7) bioencapsulated in plant cells attenuates pulmonary hypertension

Emerging evidences indicate that diminished activity of the vasoprotective axis of the renin-angiotensin system, constituting angiotensin-converting enzyme 2 (ACE2) and its enzymatic product, angiotensin-(1-7) [Ang-(1-7)] contribute to the pathogenesis of pulmonary hypertension (PH). However, long-term repetitive delivery of ACE2 or Ang-(1-7) would require enhanced protein stability and ease of administration to improve patient compliance. Chloroplast expression of therapeutic proteins enables their bioencapsulation within plant cells to protect against gastric enzymatic degradation and facilitates long-term storage at room temperature. Besides, fusion to a transmucosal carrier helps effective systemic absorption from the intestine on oral delivery. We hypothesized that bioencapsulating ACE2 or Ang-(1-7) fused to the cholera nontoxin B subunit would enable development of an oral delivery system that is effective in treating PH. PH was induced in male Sprague Dawley rats by monocrotaline administration. Subset of animals was simultaneously treated with bioencapsulaed ACE2 or Ang-(1-7) (prevention protocol). In a separate set of experiments, drug treatment was initiated after 2 weeks of PH induction (reversal protocol). Oral feeding of rats with bioencapsulated ACE2 or Ang-(1-7) prevented the development of monocrotaline-induced PH and improved associated cardiopulmonary pathophysiology. Furthermore, in the reversal protocol, oral ACE2 or Ang-(1-7) treatment significantly arrested disease progression, along with improvement in right heart function, and decrease in pulmonary vessel wall thickness. In addition, a combination therapy with ACE2 and Ang-(1-7) augmented the beneficial effects against monocrotaline-induced lung injury. Our study provides proof-of-concept for a novel low-cost oral ACE2 or Ang-(1-7) delivery system using transplastomic technology for pulmonary disease therapeutics.

Abstract 039: Oral Delivery of Angiotensin Converting Enzyme2 and Angiotensin-(1-7) Bioencapsulated in Plant Cells Attenuates Pulmonary Hypertension

Rationale: Emerging evidences indicate that diminished activity of the vasoprotective axis of the renin-angiotensin system, constituting angiotensin converting enzyme2 (ACE2) and its enzymatic product, angiotensin-(1-7) [Ang-(1-7)] contribute to the pathogenesis of pulmonary hypertension (PH). However, long-term repetitive delivery of ACE2 or Ang-(1-7) would require enhanced protein stability and ease of administration to improve patient compliance.

Objective: To develop a low-cost oral delivery system for ACE2 and Ang-(1-7), and demonstrate their therapeutic efficacy in an experimental model of PH.

Methods: We have taken advantage of transplastomic technology, which enables chloroplasts to generate high levels of therapeutic proteins within plant leaves. Transplastomic plants expressing ACE2 or Ang-(1-7) were created using biolistic delivery of chloroplast vectors. Male rats were given a single subcutaneous injection of monocrotaline (MCT, 50mg/Kg) to induce PH. Oral gavage of the frozen powdered leaves (500mg in phosphate buffered saline) expressing either ACE2 or Ang-(1-7) was performed twice daily for 4-weeks in MCT rats.

Results: MCT injected rats exhibited marked increase in right ventricular systolic pressure (RVSP; Control: 33±1mmHg; MCT: 89±4mmHg),signifying development of PH, which was associated with right ventricular hypertrophy (RVH; Control: 0.28±0.01; MCT: 0.63±0.03).However, oral feeding of MCT rats with bioencapsulated ACE2 or Ang-(1-7) showed significant decreases in RVSP (MCT+ACE2: 55±8mmHg, MCT+Ang-(1-7): 62±7mmHg ) and RVH (MCT+ACE2: 0.39±0.05, MCT+Ang-(1-7): 0.4±0.03). Similarly, echocardiography data revealed significant improvement in right heart function, along with enhanced pulmonary blood flow in MCT animals fed with ACE2 or Ang-(1-7). Furthermore, histological studies revealed considerable reduction in right ventricular fibrosis and pulmonary vessel wall thickness in ACE2 or Ang-(1-7) fed animals.These protective effects were associated with decreased inflammation.

Conclusion: Our study provides the first proof-of-concept for a novel low-cost oral ACE2 and Ang-(1-7) delivery system, using transplastomic technology that has significant clinical implications for treating PH.

Abstract 060: Adipose Derived Stem Cell (ADSC) Therapy Prevents The Progression Of Hypertension And Improves Cardiac Functions

Despite major advances in pharmacological and interventional therapies, 30% of hypertensive patients do not achieve their blood pressure (BP) target and have apparent treatment resistant hypertension (TRH). Thus, innovative strategies are urgently needed for the control of TRH considering its prevalence and deleterious complications. The objective of the current study was to evaluate effects of ADSC on BP in spontaneously hypertensive rats (SHR). The rational for using ADSC is that they have multipotent differentiation capacities and potent anti-inflammatory effects. Moreover, autologous ADSC are an attractive therapeutic option for clinical trials based on availability, less invasive isolation procedure, and safety in several hundred patient studies. ADSC were isolated from inguinal adipose tissue of a normotensive WKY rat, characterized using flow cytometry (CD44 + ,CD90 + ,CD34 - and CD45 - ), and their differentiation ability to adipocyte was confirmed by Oil Red “O” staining. Basal systolic BP for SHR at 13 week age was 191.6 ± 5.6 mmHg measured by a tail-cuff method. SHR animals were then randomly assigned to control and ADSC-treated groups. ADSC (5х10 6 cells/animal) was intravenously administered through jugular vein into treated SHR. Three weeks after treatment, left ventricular function was assessed using echocardiography and direct BP was measured using a Millar catheter. The SHR control exhibited 82% increase in systolic BP (198.4 ± 25.9 vs WKY: 109.0 ± 1.6, mmHg) and 14% elevation in ventricular mass (3.3 ± 0.2 vs WKY: 2.9 ± 0.1, g/kg). Furthermore, the SHR control demonstrated 42% increase in deceleration time of mitral valve (58.1 ± 6.0 vs WKY: 40.8 ± 2.3; ms) and 21% decrease in ejection fraction (69.9 ± 4.2 vs WKY: 88.2 ± 1.3, %). Single injection of ADSC resulted in a 28% decrease in systolic BP (142.5 ± 25.8mmHg), 18% reduction in ventricular mass (2.7 ± 0.3g/kg), 36% decrease in deceleration time of mitral valve (36.9 ± 16.3ms), and 17% increase in ejection fraction (80.0 ± 3.4%). Collectively, our data demonstrate that ADSC arrested the progression of hypertension and associated left ventricular dysfunction in the hypertensive animals. It warrants additional study on ADSC intervention as a potential alternative treatment for hypertension.

Abstract 609: Potential Role Of Adipose Derived Stem Cells In Attenuating Pulmonary Hypertension

Pulmonary hypertension (PH) is a devastating cardiopulmonary

disorder, which often results in right heart failure. In spite of recent

advancements in the pharmacotherapy of pulmonary hypertension, the mortality

rate has not been significantly reduced. Recently stem cell therapy has gained

more attention for the treatment of cardiopulmonary diseases. Despite the

promising results shown by bone marrow derived stem cells in attenuating right heart

failure in PH, it remains a highly invasive and laborious procedure. On the contrary, adipose derived stem cell

(ADSC) presents a less complicated option. Therefore, we proposed to use ADSC in

attenuating the progression of PH. Monocrotaline

(MCT) at a 50 mg/kg dose was injected to eight-week old male Sprague-Dawley

rats to induce PH. Four weeks post MCT injection; animals developed PH with

elevated right ventricular systolic pressure (RVSP, Control: 28.65±0.40; MCT:

78.06±6.4 mmHg; n=6-8), and right ventricular hypertrophy (RVH, Control;

0.22±0.005; MCT: 0.48±0.054 [ratio, AU]; n=6-8). ADSC (isolated from inguinal fat of healthy male

rat) were characterized using flow cytometry (CD44 + , CD90 + ,

CD34 - and CD45 - ) and their differentiation to adipocyte

was confirmed by Oil Red O staining. ADSCs

(1x10 6 ; passage 2-4) were injected through the jugular vein, 14 days

post MCT injection. After 2 weeks following

ADSC therapy, RVSP (MCT+ADSC: 55.67±8.99 mmHg; n=6-8) and RVH (MCT+ADSC:

0.32±0.062 [AU]; n=6-8) was significantly reduced. Moreover, the elevated right ventricular end

diastolic pressure (RVEDP) and ±dP/dT associated with PH were attenuated

significantly in ADSC treated MCT animals. An additional group of animals received only

the ADSC conditioned media (CM) from 1x10 6 cells. After 2 weeks of CM administration, RVSP

(MCT+CM: 42.11±4.66 mmHg; n=5) and RVH (MCT+CM: 0.29±0.020 [AU]; n=5) was

significantly reduced. Further, the RVEDP

and ± dP/dT were also significantly reduced in CM treated MCT animals. Collectively, either ADSC or conditioned media

alone can attenuate the progression of PH, which suggest that paracrine-like substances

may be responsible for the beneficial effects observed and may be considered as

a potential therapeutic alternative for the treatment of right heart failure.

Diminazene attenuates pulmonary hypertension and improves angiogenic progenitor cell functions in experimental models

RATIONALE

Studies have demonstrated that angiotensin-converting enzyme 2 (ACE2) plays a protective role against lung diseases, including pulmonary hypertension (PH). Recently, an antitrypanosomal drug, diminazene aceturate (DIZE), was shown to exert an "off-target" effect of enhancing the enzymatic activity of ACE2 in vitro.

OBJECTIVES

To evaluate the pharmacological actions of DIZE in experimental models of PH.

METHODS

PH was induced in male Sprague Dawley rats by monocrotaline, hypoxia, or bleomycin challenge. Subsets of animals were simultaneously treated with DIZE. In a separate set of experiments, DIZE was administered after 3 weeks of PH induction to determine whether the drug could reverse PH.

MEASUREMENTS AND MAIN RESULTS

DIZE treatment significantly prevented the development of PH in all of the animal models studied. The protective effects were associated with an increase in the vasoprotective axis of the lung renin-angiotensin system, decreased inflammatory cytokines, improved pulmonary vasoreactivity, and enhanced cardiac function. These beneficial effects were abolished by C-16, an ACE2 inhibitor. Initiation of DIZE treatment after the induction of PH arrested disease progression. Endothelial dysfunction represents a hallmark of PH pathophysiology, and growing evidence suggests that bone marrow-derived angiogenic progenitor cells contribute to endothelial homeostasis. We observed that angiogenic progenitor cells derived from the bone marrow of monocrotaline-challenged rats were dysfunctional and were repaired by DIZE treatment. Likewise, angiogenic progenitor cells isolated from patients with PH exhibited diminished migratory capacity toward the key chemoattractant stromal-derived factor 1α, which was corrected by in vitro DIZE treatment.

CONCLUSIONS

Our results identify a therapeutic potential of DIZE in PH therapy.