Inhibition of mitochondrial fission prevents hypoxia-induced metabolic shift and cellular proliferation of pulmonary arterial smooth muscle cells

Mitochondrial dynamics in pulmonary disease: Implications for the potential therapeutics

Mitochondria are dynamic organelles that continuously undergo fusion/fission to maintain normal cell physiological activities and energy metabolism. When mitochondrial dynamics is unbalanced, mitochondrial homeostasis is broken, thus damaging mitochondrial function. Accumulating evidence demonstrates that impairment in mitochondrial dynamics leads to lung tissue injury and pulmonary disease progression in a variety of disease models, including inflammatory responses, apoptosis, and barrier breakdown, and that the role of mitochondrial dynamics varies among pulmonary diseases. These findings suggest that modulation of mitochondrial dynamics may be considered as a valid therapeutic strategy in pulmonary diseases. In this review, we discuss the current evidence on the role of mitochondrial dynamics in pulmonary diseases, with a particular focus on its underlying mechanisms in the development of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), asthma, pulmonary fibrosis (PF), pulmonary arterial hypertension (PAH), lung cancer and bronchopulmonary dysplasia (BPD), and outline effective drugs targeting mitochondrial dynamics-related proteins, highlighting the great potential of targeting mitochondrial dynamics in the treatment of pulmonary disease.

STAT3 phosphorylation at Tyr705 affects DRP1 (dynamin-related protein 1) controlled-mitochondrial fission during the development of apoptotic-resistance in pulmonary arterial endothelial cells

BACKGROUND

The apoptosis-resistant pulmonary arterial endothelial cells (PAECs) are known to be major players in the pulmonary remodeling of pulmonary arterial hypertension (PAH) and exhibit an abnormal metabolic profile with mitochondrial dysfunction. Mitochondrial fission has been shown to regulate the apoptosis of several cell types, but this is largely unexplored in the PAECs.

OBJECTIVE

The roles of mitochondrial fission control by Dynamin related protein-1 (DRP1) in the development of PAECs apoptosis suppression were investigated in present study and the potential mechanisms behind this were furtherly explored.

METHODS

The mitochondrial morphology was investigated in PAECs from PAH rats with the pulmonary plexiform lesions, and the relations of it with DRP1 expression and apoptosis were furtherly identified in apoptosis-resistant PAECs induced by hypoxia. PAECs were isolated from rats with severe PAH and from normal subjects, the apoptotic-resistant PAECs were induced by hypoxia. DRP1 gene knockdown was achieved via DRP1-siRNA, DRP1 and STAT3 phosphorylation were blocked using its inhibitors, respectively. Apoptosis was analyzed by flow cytometry, and mitochondrial morphology was investigated by transmission electron microscope and confocal microscopy.

RESULTS

The PAECs isolated from PAH rats with the pulmonary plexiform-like lesions and displayed lower apoptotic rate with increased DRP1 expression and mitochondrial fragmentation. In addition, similar observations were achieved in apoptosis-resistant PAECs induced by hypoxia. Targeting DRP1 using siRNA and pharmacologic blockade prevented the mitochondrial fission and subsequent apoptotic resistance in PAECs under hypoxia. Mechanistically, STAT3 phosphorylation at Tyr705 was shown to be activated in both PAH and hypoxia-treated PAECs, leading to the regulation of DRP1 expression. Of importance, targeting STAT3Tyr705 phosphorylation prevented DRP1 disruption on apoptosis in PAECs under hypoxia.

CONCLUSIONS

These data indicated that STAT3 phosphorylation at Tyr705 impacted DRP1-controlled mitochondrial fission during the development of apoptosis-resistance in PAECs, suggesting mitochondrial dynamics may represent a therapeutic target for PAH.

Multifaceted role of dynamin-related protein 1 in cardiovascular disease: From mitochondrial fission to therapeutic interventions

Mitochondria are central to cellular energy production and metabolic regulation, particularly in cardiomyocytes. These organelles constantly undergo cycles of fusion and fission, orchestrated by key proteins like Dynamin-related Protein 1 (Drp-1). This review focuses on the intricate roles of Drp-1 in regulating mitochondrial dynamics, its implications in cardiovascular health, and particularly in myocardial infarction. Drp-1 is not merely a mediator of mitochondrial fission; it also plays pivotal roles in autophagy, mitophagy, apoptosis, and necrosis in cardiac cells. This multifaceted functionality is often modulated through various post-translational alterations, and Drp-1's interaction with intracellular calcium (Ca2 + ) adds another layer of complexity. We also explore the pathological consequences of Drp-1 dysregulation, including increased reactive oxygen species (ROS) production and endothelial dysfunction. Furthermore, this review delves into the potential therapeutic interventions targeting Drp-1 to modulate mitochondrial dynamics and improve cardiovascular outcomes. We highlight recent findings on the interaction between Drp-1 and sirtuin-3 and suggest that understanding this interaction may open new avenues for therapeutically modulating endothelial cells, fibroblasts, and cardiomyocytes. As the cardiovascular system increasingly becomes the focal point of aging and chronic disease research, understanding the nuances of Drp-1's functionality can lead to innovative therapeutic approaches.

Effects of mitochondrial dysfunction on cellular function: Role in atherosclerosis

Atherosclerosis, an immunoinflammatory disease of medium and large arteries, is associated with life-threatening clinical events, such as acute coronary syndromes and stroke. Chronic inflammation and impaired lipoprotein metabolism are considered to be among the leading causes of atherosclerosis, while numerous risk factors, including arterial hypertension, diabetes mellitus, obesity, and aging, can contribute to the development of the disease. In recent years, emerging evidence has underlined the key role of mitochondrial dysfunction in the pathogenesis of atherosclerosis. Mitochondrial dysfunction is believed to result in an increase in reactive oxygen species, leading to oxidative stress, chronic inflammation, and intracellular lipid deposition, all of which can contribute to the pathogenesis of atherosclerosis. Critical cells, including endothelial cells, vascular smooth muscle cells, and macrophages, play an important role in atherosclerosis. Mitochondrial function is also involved in maintaining the normal function of these cells. To better understand the relationship between mitochondrial dysfunction and atherosclerosis, this review summarizes the findings of recent studies and discusses the role of mitochondrial dysfunction in the risk factors and critical cells of atherosclerosis. FACTS: OPEN QUESTIONS.

SIRT1 regulates mitochondrial fission to alleviate high altitude hypoxia inducedcardiac dysfunction in rats via the PGC-1α-DRP1/FIS1/MFF pathway

High-altitude exposure has been linked to cardiac dysfunction. Silent information regulator factor 2-related enzyme 1 (sirtuin 1, SIRT1), a nicotinamide adenine dinucleotide-dependent deacetylase, plays a crucial role in regulating numerous cardiovascular diseases. However, the relationship between SIRT1 and cardiac dysfunction induced by hypobaric hypoxia (HH) remains unexplored. This study aims to assess the impact of SIRT1 on HH-induced cardiac dysfunction and delve into the underlying mechanisms, both in vivo and in vitro. In this study, we have demonstrated that exposure to HH results in cardiomyocyte injury, along with the downregulation of SIRT1 and mitochondrial dysfunction. Upregulating SIRT1 significantly inhibits mitochondrial fission, improves mitochondrial function, reduces cardiomyocyte injury, and consequently enhances cardiac function in HH-exposed rats. Additionally, HH exposure triggers aberrant expression of mitochondrial fission-regulated proteins, with a decrease in PPARγ coactivator 1 alpha (PGC-1α) and mitochondrial fission factor (MFF) and an increase in mitochondrial fission 1 (FIS1) and dynamin-related protein 1 (DRP1), all of which are mitigated by SIRT1 upregulation. Furthermore, inhibiting PGC-1α diminishes the positive effects of SIRT1 regulation on the expression of DRP1, MFF, and FIS1, as well as mitochondrial fission. These findings demonstrate that SIRT1 alleviates HHinduced cardiac dysfunction by preventing mitochondrial fission through the PGC-1α-DRP1/FIS1/MFF pathway.

Fatty Oil of Descurainia Sophia Nanoparticles Improve Monocrotaline-Induced Pulmonary Hypertension in Rats Through PLC/IP3R/Ca2+ Signaling Pathway

Purpose

Fatty oil of Descurainia Sophia (OIL) has poor stability and low solubility, which limits its pharmacological effects. We hypothesized that fatty oil nanoparticles (OIL-NPs) could overcome this limitation. The protective effect of OIL-NPs against monocrotaline-induced lung injury in rats was studied.

Methods

We prepared OIL-NPs by wrapping fatty oil with polylactic-polyglycolide nanoparticles (PLGA-NPs) and conducted in vivo and in vitro experiments to explore its anti-pulmonary hypertension (PH) effect. In vitro, we induced malignant proliferation of pulmonary artery smooth muscle cells (RPASMC) using anoxic chambers, and studied the effects of OIL-NPs on the malignant proliferation of RPASMC cells and phospholipase C (PLC)/inositol triphosphate receptor (IP3R)/Ca2+ signal pathways. In vivo, we used small animal echocardiography, flow cytometry, immunohistochemistry, western blotting (WB), polymerase chain reaction (PCR) and metabolomics to explore the effects of OIL-NPs on the heart and lung pathological damage and PLC/IP3R/Ca2+ signal pathway of pulmonary hypertension rats.

Results

We prepared fatty into OIL-NPs. In vitro, OIL-NPs could improve the mitochondrial function and inhibit the malignant proliferation of RPASMC cells by inhibiting the PLC/IP3R/Ca2+signal pathway. In vivo, OIL-NPs could reduce the pulmonary artery pressure of rats and alleviate the pathological injury and inflammatory reaction of heart and lung by inhibiting the PLC/IP3R/Ca2+ signal pathway.

Conclusion

OIL-NPs have anti-pulmonary hypertension effect, and the mechanism may be related to the inhibition of PLC/IP3R/Ca2+signal pathway.

Pressure stress delays cyclooxygenase-2 expression induced by interleukin-1β in cultured human pulmonary artery smooth muscle cells

Introduction

Pulmonary artery smooth muscle cells (PASMCs) play an important role in the sequence of events leading to the formation of pulmonary hypertension (PH). However, little is known about the direct effects of high pressure on the function and intercellular signaling pathways of PASMCs. The aim of this study was to evaluate the effect of pressure stress that simulates PH on interleukin (IL)-1β- or angiotensin II-induced cyclooxygenase-2 (COX-2) expression in cultured human PASMCs.

Methods

Either 20 or 60 mmHg atmospheric pressure was applied to PASMCs by a pressure-loading apparatus. Protein expression and phosphorylation were analyzed by western blotting. mRNA expression was analyzed by quantitative real-time reverse transcription-polymerase chain reaction.

Results

IL-1β-induced COX-2 protein expression peaked at 6 h in non-pressurized cells, whereas COX-2 expression was delayed, peaking at 12 h, in 20 and 60 mmHg pressurized cells. Both pressures also delayed the time to peak COX-2 mRNA expression induced by IL-1β. In addition, pressure stress delayed the time to peak mitogen-activated protein kinase (MAPK) phosphorylation induced by IL-1β. In contrast, angiotensin II-induced transient COX-2 mRNA expression and MAPK phosphorylation were not affected by pressure stress.

Conclusion

These results suggest that pressure stress delays IL-1β-induced COX-2 expression via the delayed activation of MAPKs in PASMCs, and the effects of pressure stress differ according to the bioactive substance being stimulated. Our results demonstrate that the application of pressure stress to PASMCs directly alters cell function, which may provide a basic insight into our understanding of the pathogenesis of PH.

Role of Mitochondrial Dynamics in Heart Diseases

Mitochondrial dynamics, including fission and fusion processes, are essential for heart health. Mitochondria, the powerhouses of cells, maintain their integrity through continuous cycles of biogenesis, fission, fusion, and degradation. Mitochondria are relatively immobile in the adult heart, but their morphological changes due to mitochondrial morphology factors are critical for cellular functions such as energy production, organelle integrity, and stress response. Mitochondrial fusion proteins, particularly Mfn1/2 and Opa1, play multiple roles beyond their pro-fusion effects, such as endoplasmic reticulum tethering, mitophagy, cristae remodeling, and apoptosis regulation. On the other hand, the fission process, regulated by proteins such as Drp1, Fis1, Mff and MiD49/51, is essential to eliminate damaged mitochondria via mitophagy and to ensure proper cell division. In the cardiac system, dysregulation of mitochondrial dynamics has been shown to cause cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and various cardiac diseases, including metabolic and inherited cardiomyopathies. In addition, mitochondrial dysfunction associated with oxidative stress has been implicated in atherosclerosis, hypertension and pulmonary hypertension. Therefore, understanding and regulating mitochondrial dynamics is a promising therapeutic tool in cardiac diseases. This review summarizes the role of mitochondrial morphology in heart diseases for each mitochondrial morphology regulatory gene, and their potential as therapeutic targets to heart diseases.

Mitochondria in hypoxic pulmonary hypertension, roles and the potential targets

Mitochondria are the centrol hub for cellular energy metabolisms. They regulate fuel metabolism by oxygen levels, participate in physiological signaling pathways, and act as oxygen sensors. Once oxygen deprived, the fuel utilizations can be switched from mitochondrial oxidative phosphorylation to glycolysis for ATP production. Notably, mitochondria can also adapt to hypoxia by making various functional and phenotypes changes to meet the demanding of oxygen levels. Hypoxic pulmonary hypertension is a life-threatening disease, but its exact pathgenesis mechanism is still unclear and there is no effective treatment available until now. Ample of evidence indicated that mitochondria play key factor in the development of hypoxic pulmonary hypertension. By hypoxia-inducible factors, multiple cells sense and transmit hypoxia signals, which then control the expression of various metabolic genes. This activation of hypoxia-inducible factors considered associations with crosstalk between hypoxia and altered mitochondrial metabolism, which plays an important role in the development of hypoxic pulmonary hypertension. Here, we review the molecular mechanisms of how hypoxia affects mitochondrial function, including mitochondrial biosynthesis, reactive oxygen homeostasis, and mitochondrial dynamics, to explore the potential of improving mitochondrial function as a strategy for treating hypoxic pulmonary hypertension.

Hypoxia-reprogramed megamitochondrion contacts and engulfs lysosome to mediate mitochondrial self-digestion

Mitochondria are the key organelles for sensing oxygen, which is consumed by oxidative phosphorylation to generate ATP. Lysosomes contain hydrolytic enzymes that degrade misfolded proteins and damaged organelles to maintain cellular homeostasis. Mitochondria physically and functionally interact with lysosomes to regulate cellular metabolism. However, the mode and biological functions of mitochondria-lysosome communication remain largely unknown. Here, we show that hypoxia remodels normal tubular mitochondria into megamitochondria by inducing broad inter-mitochondria contacts and subsequent fusion. Importantly, under hypoxia, mitochondria-lysosome contacts are promoted, and certain lysosomes are engulfed by megamitochondria, in a process we term megamitochondria engulfing lysosome (MMEL). Both megamitochondria and mature lysosomes are required for MMEL. Moreover, the STX17-SNAP29-VAMP7 complex contributes to mitochondria-lysosome contacts and MMEL under hypoxia. Intriguingly, MMEL mediates a mode of mitochondrial degradation, which we termed mitochondrial self-digestion (MSD). Moreover, MSD increases mitochondrial ROS production. Our results reveal a mode of crosstalk between mitochondria and lysosomes and uncover an additional pathway for mitochondrial degradation.

Targeting Mitochondrial Metabolic Dysfunction in Pulmonary Hypertension: Toward New Therapeutic Approaches?

Pulmonary arterial hypertension (PAH) is a rare disease characterized by pulmonary vascular remodeling leading to right heart failure and death. To date, despite the three therapeutic approaches targeting the three major endothelial dysfunction pathways based on the prostacyclin, nitric oxide/cyclic guanosine monophosphate, and endothelin pathways, PAH remains a serious disease. As such, new targets and therapeutic agents are needed. Mitochondrial metabolic dysfunction is one of the mechanisms involved in PAH pathogenesis in part through the induction of a Warburg metabolic state of enhanced glycolysis but also through the upregulation of glutaminolysis, tricarboxylic cycle and electron transport chain dysfunction, dysregulation of fatty acid oxidation or mitochondrial dynamics alterations. The aim of this review is to shed light on the main mitochondrial metabolic pathways involved in PAH and to provide an update on the resulting interesting potential therapeutic perspectives.

Nitric oxide augments signaling for contraction in hypoxic pulmonary arterial smooth muscle—Implications for hypoxic pulmonary hypertension

Introduction: Hypoxic persistent pulmonary hypertension in the newborn (PPHN) is usually treated with oxygen and inhaled nitric oxide (NO), both pulmonary arterial relaxants. But treatment failure with NO occurs in 25% of cases. We previously demonstrated that 72 h exposure to hypoxia, modeling PPHN, sensitized pulmonary artery smooth muscle cells (PASMC) to the contractile agonist thromboxane and inhibited relaxant adenylyl cyclase (AC) activity.

Methods: In this study, we examined the effects of sodium nitroprusside (SNP), as NO donor, on the thromboxane-mediated contraction and NO-independent relaxation pathways and on reactive oxygen species (ROS) accumulation in PASMC. In addition, we examined the effect of the peroxynitrite scavenger 5,10,15,20-Tetrakis (4-sulfonatophenyl)porphyrinato Iron (III) (FeTPPS) on these processes.

Results: Exposure of PASMC to 72 h hypoxia increased total intracellular ROS compared to normoxic control cells and this was mitigated by treatment of cells with either SNP or FeTPPS. Total protein nitrosylation was increased in hypoxic PASMC compared to controls. Both normoxic and hypoxic cells treated with SNP exhibited increased total protein nitrosylation and intracellular nitrite; this was reduced by treatment with FeTPPS. While cell viability and mitochondrial number were unchanged by hypoxia, mitochondrial activity was decreased compared to controls; addition of FeTPPS did not alter this. Basal and maximal mitochondrial metabolism and ATP turnover were reduced in hypoxic PASMC compared to controls. Hypoxic PASMC had higher basal Ca2+, and a heightened peak Ca2+ response to thromboxane challenge compared to controls. Addition of SNP further elevated the peak Ca2+ response, while addition of FeTPPS brought peak Ca2+ response down to control levels. AC mediated relaxation was impaired in hypoxic PASMC compared to controls but was normalized following treatment with FeTPPS. Addition of SNP inhibited adenylyl cyclase activity in both normoxic and hypoxic PASMC. Moreover, addition of the Ca2+ chelator BAPTA improved AC activity, but the effect was minimal.

Discussion: We conclude that NO independently augments contraction and inhibits relaxation pathways in hypoxic PASMC, in part by a mechanism involving nitrogen radical formation and protein nitrosylation. These observations may partially explain impaired effectiveness of NO when treating hypoxic pulmonary hypertension.

Preliminary screening of biomarkers in HAPE based on quasi-targeted metabolomics

High altitude pulmonary edema (HAPE) is a serious threat to the physical and mental health of people who quickly enter high plateaus, deserves more attention and in-depth research. In our study, through the detection of various physiological indexes and other phenotypes in a HAPE rat model, the HAPE group showed a significant decrease in oxygen partial pressure and oxygen saturation, and a significant increase in pulmonary artery pressure and lung tissue water content. The lung histomorphology showed characteristics such as pulmonary interstitial thickening and inflammatory cell infiltration. We applied quasi-targeted metabolomics to compare and analyze the components of metabolites in arterial–veinous blood in control rats and HAPE rats. Using kyoto Encyclopedia of Genes Genomes (KEGG) enrichment analysis and two machine algorithms, we speculate that after hypoxic stress and comparing arterial blood and venous blood products in rats, the metabolites were richer, indicating that normal physiological activities, such as metabolism and pulmonary circulationhad a greater impact after hypoxic stress; D-mannoseDOWN, oxidized glutathioneDOWN, glutathione disulfideDOWN, and dehydrocholic acidDOWN in arterial blood play key roles in predicting the occurrence of HAPE; in venous blood, L-leucineDOWN, L-thyroxineDOWN, and cis-4-hydroxy- D-prolineDOWN may have key roles, which can be considered biomarkers of HAPE. This result provides a new perspective for the further diagnosis and treatment of plateau disease and lays a strong foundation for further research.

Effects of Trimetazidine on Right Ventricular Function and Ventricular Remodeling in Patients with Pulmonary Artery Hypertension: A Randomised Controlled Trial

BACKGROUND

Pulmonary artery hypertension (PAH) is a chronic and progressive disease. Although current therapy has improved the disease prognosis, PAH has a poor survival rate. The key feature leading to disease progression and death is right ventricular (RV) failure.

METHODS AND RESULTS

We assessed the role of trimetazidine, a fatty acid beta-oxidation (FAO) inhibitor, in right ventricular function, remodeling, and functional class in PAH patients, with a placebo-controlled double-blind, case-crossover trial. Twenty-seven PAH subjects were enrolled, randomized, and assigned to trimetazidine or placebo for three months and then reallocated to the other study arm. The primary endpoint was RV morphology and function change after three months of treatment. Secondary endpoints were the change in exercise capacity assessed by a 6 min walk test after three months of treatment and the change in pro-BNP and Galectin-3 plasma levels after three months. Trimetazidine use was safe and well-tolerated. After three months of treatment, patients in the trimetazidine group showed a small but significant reduction of RV diastolic area, and a substantial increase in the 6 min walk distance (418 vs. 438 mt, p = 0.023), without significant changes in biomarkers.

CONCLUSIONS

A short course of trimetazidine is safe and well-tolerated on PAH patients, and it is associated with significant increases in the 6MWT and minor but significant improvement in RV remodeling. The therapeutic potential of this drug should be evaluated in larger clinical trials.

The evolutionarily conserved hif-1/bnip3 pathway promotes mitophagy and mitochondrial fission in crustacean testes during hypoxia

The hypoxia-inducible factor 1 (HIF-1) cascade is an ancient and strongly evolutionarily conserved signaling pathway that is involved in the hypoxic responses of most metazoans. Despite immense advances in the understanding of the HIF-1-mediated regulation of hypoxic responses in mammals, the contribution of the hif-1 cascade in the hypoxic adaptation of nonmodel invertebrates remains unclear. In this study, we used the oriental river prawn Macrobrachium nipponense for investigating the roles of hif-1-regulated mitophagy in crustacean testes under hypoxic conditions. We identified that the Bcl-2/adenovirus E1B 19-kDa interacting protein (bnip3) functions as a regulator of mitophagy in M. nipponense and demonstrated that hif-1α activates bnip3 by binding to the bnip3 promoter. Hif-1α knockdown suppressed the expression of multiple mitophagy-related genes, and prawns with hif-1α knockdown exhibited higher mortality under hypoxic conditions. We observed that the levels of BNIP3 were induced under hypoxic conditions and detected that bnip3 knockdown inhibited the mitochondrial translocation of dynamin-related protein 1 (drp1), which is associated with mitochondrial fission. Notably, bnip3 knockdown inhibited hypoxia-induced mitophagy and aggravated the deleterious effects of hypoxia-induced reactive oxygen species (ROS) production and apoptosis. The experimental studies demonstrated that hypoxia induced mitochondrial fission in M. nipponense via drp1. Altogether, the study elucidated the mechanism underlying hif-1/bnip3-mediated mitochondrial fission and mitophagy and demonstrated that this pathway protects crustaceans against ROS production and apoptosis induced by acute hypoxia.

Arterial remodeling: the role of mitochondrial metabolism in vascular smooth muscle cells

Arterial remodeling is a common pathological basis of cardiovascular diseases such as atherosclerosis, vascular restenosis, hypertension, pulmonary hypertension, aortic dissection, and aneurysm. Vascular smooth muscle cells (VSMCs) are not only the main cellular components in the middle layer of the arterial wall but also the main cells involved in arterial remodeling. Dedifferentiated VSMCs lose their contractile properties and are converted to a synthetic, secretory, proliferative, and migratory phenotype, playing key roles in the pathogenesis of arterial remodeling. As mitochondria are the main site of biological oxidation and energy transformation in eukaryotic cells, mitochondrial numbers and function are very important in maintaining the metabolic processes in VSMCs. Mitochondrial dysfunction and oxidative stress are novel triggers of the phenotypic transformation of VSMCs, leading to the onset and development of arterial remodeling. Therefore, pharmacological measures that alleviate mitochondrial dysfunction reverse arterial remodeling by ameliorating VSMCs metabolic dysfunction and phenotypic transformation, providing new options for the treatment of cardiovascular diseases related to arterial remodeling. This review summarizes the relationship between mitochondrial dysfunction and cardiovascular diseases associated with arterial remodeling and then discusses the potential mechanism by which mitochondrial dysfunction participates in pathological arterial remodeling. Furthermore, maintaining or improving mitochondrial function may be a new intervention strategy to prevent the progression of arterial remodeling.

Mitochondrial dysfunction in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by the increased pulmonary vascular resistance due to pulmonary vasoconstriction and vascular remodeling. PAH has high disability, high mortality and poor prognosis, which is becoming a more common global health issue. There is currently no drug that can permanently cure PAH patients. The pathogenesis of PAH is still not fully elucidated. However, the role of metabolic theory in the pathogenesis of PAH is becoming clearer, especially mitochondrial metabolism. With the deepening of mitochondrial researches in recent years, more and more studies have shown that the occurrence and development of PAH are closely related to mitochondrial dysfunction, including the tricarboxylic acid cycle, redox homeostasis, enhanced glycolysis, and increased reactive oxygen species production, calcium dysregulation, mitophagy, etc. This review will further elucidate the relationship between mitochondrial metabolism and pulmonary vasoconstriction and pulmonary vascular remodeling. It might be possible to explore more comprehensive and specific treatment strategies for PAH by understanding these mitochondrial metabolic mechanisms.

The Therapeutic Strategies Targeting Mitochondrial Metabolism in Cardiovascular Disease

Cardiovascular disease (CVD) is a group of systemic disorders threatening human health with complex pathogenesis, among which mitochondrial energy metabolism reprogramming has a critical role. Mitochondria are cell organelles that fuel the energy essential for biochemical reactions and maintain normal physiological functions of the body. Mitochondrial metabolic disorders are extensively involved in the progression of CVD, especially for energy-demanding organs such as the heart. Therefore, elucidating the role of mitochondrial metabolism in the progression of CVD is of great significance to further understand the pathogenesis of CVD and explore preventive and therapeutic methods. In this review, we discuss the major factors of mitochondrial metabolism and their potential roles in the prevention and treatment of CVD. The current application of mitochondria-targeted therapeutic agents in the treatment of CVD and advances in mitochondria-targeted gene therapy technologies are also overviewed.

Flow pattern-dependent mitochondrial dynamics regulates the metabolic profile and inflammatory state of endothelial cells

Endothelial mitochondria play a pivotal role in maintaining endothelial cell (EC) homeostasis through constantly altering their size, shape, and intracellular localization. Studies show that the disruption of the basal mitochondrial network in EC, forming excess fragmented mitochondria, implicates cardiovascular disease. However, cellular consequences underlying the morphological changes in the endothelial mitochondria under distinctively different, but physiologically occurring, flow patterns (i.e., unidirectional flow [UF] versus disturbed flow [DF]) are largely unknown. The purpose of this study was to investigate the effect of different flow patterns on mitochondrial morphology and its implications in EC phenotypes. We show that mitochondrial fragmentation is increased at DF-exposed vessel regions, where elongated mitochondria are predominant in the endothelium of UF-exposed regions. DF increased dynamin-related protein 1 (Drp1), mitochondrial reactive oxygen species (mtROS), hypoxia-inducible factor 1, glycolysis, and EC activation. Inhibition of Drp1 significantly attenuated these phenotypes. Carotid artery ligation and microfluidics experiments further validate that the significant induction of mitochondrial fragmentation was associated with EC activation in a Drp1-dependent manner. Contrarily, UF in vitro or voluntary exercise in vivo significantly decreased mitochondrial fragmentation and enhanced fatty acid uptake and OXPHOS. Our data suggest that flow patterns profoundly change mitochondrial fusion/fission events, and this change contributes to the determination of proinflammatory and metabolic states of ECs.

Inhibitors of Mitochondrial Dynamics Mediated by Dynamin-Related Protein 1 in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a chronic, lethal pulmonary disease characterized by pulmonary vascular remodeling. It leads to malignant results, such as rupture of pulmonary arterial dissection, dyspnea, right heart failure, and even death. Previous studies have confirmed that one of the main pathological changes of this disease is abnormal mitochondrial dynamics, which include mitochondrial fission, fusion, and autophagy that keep a dynamic balance under certain physiological state. Dynamin-related protein 1 (Drp1), the key molecule in mitochondrial fission, mediates mitochondrial fission while also affecting mitochondrial fusion and autophagy through numerous pathways. There are various abnormalities of Drp1 in PAH pathophysiology, including Drp1 overexpression and activation as well as an upregulation of its outer mitochondrial membrane ligands. These aberrant alterations will eventually induce the development of PAH. With the process of recent studies, the structure and function of Drp1 have been gradually revealed. Meanwhile, inhibitors targeting this pathway have also been discovered. This review aims to shed more light on the mechanism of Drp1 and its inhibitors in the abnormal mitochondrial dynamics of PAH. Furthermore, it seeks to provide more novel insights to clinical therapy.

Cell death regulation by MAMs: from molecular mechanisms to therapeutic implications in cardiovascular diseases

The endoplasmic reticulum (ER) and mitochondria are interconnected intracellular organelles with vital roles in the regulation of cell signaling and function. While the ER participates in a number of biological processes including lipid biosynthesis, Ca²⁺ storage and protein folding and processing, mitochondria are highly dynamic organelles governing ATP synthesis, free radical production, innate immunity and apoptosis. Interplay between the ER and mitochondria plays a crucial role in regulating energy metabolism and cell fate control under stress. The mitochondria-associated membranes (MAMs) denote physical contact sites between ER and mitochondria that mediate bidirectional communications between the two organelles. Although Ca²⁺ transport from ER to mitochondria is vital for mitochondrial homeostasis and energy metabolism, unrestrained Ca²⁺ transfer may result in mitochondrial Ca²⁺ overload, mitochondrial damage and cell death. Here we summarize the roles of MAMs in cell physiology and its impact in pathological conditions with a focus on cardiovascular disease. The possibility of manipulating ER-mitochondria contacts as potential therapeutic approaches is also discussed.

Current Understanding of the Pivotal Role of Mitochondrial Dynamics in Cardiovascular Diseases and Senescence

The heart is dependent on ATP production in mitochondria, which is closely associated with cardiovascular disease because of the oxidative stress produced by mitochondria. Mitochondria are highly dynamic organelles that constantly change their morphology to elongated (fusion) or small and spherical (fission). These mitochondrial dynamics are regulated by various small GTPases, Drp1, Fis1, Mitofusin, and Opa1. Mitochondrial fission and fusion are essential to maintain a balance between mitochondrial biogenesis and mitochondrial turnover. Recent studies have demonstrated that mitochondrial dynamics play a crucial role in the development of cardiovascular diseases and senescence. Disruptions in mitochondrial dynamics affect mitochondrial dysfunction and cardiomyocyte survival leading to cardiac ischemia/reperfusion injury, cardiomyopathy, and heart failure. Mitochondrial dynamics and reactive oxygen species production have been associated with endothelial dysfunction, which in turn causes the development of atherosclerosis, hypertension, and even pulmonary hypertension, including pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Here, we review the association between cardiovascular diseases and mitochondrial dynamics, which may represent a potential therapeutic target.

Comparative analysis of long noncoding RNA and mRNA expression provides insights into adaptation to hypoxia in Tibetan sheep

Tibetan sheep have lived on the Qinghai-Tibetan Plateau for thousands of years and have good adaptability to the hypoxic environment and strong disease resistance. However, the molecular mechanism by which Tibetan sheep adapt to this extreme environment, especially the role of genetic regulation, is still unknown. Emerging evidence suggests that long noncoding RNAs (lncRNAs) participate in the regulation of a diverse range of biological processes. To explore the potential lncRNAs involved in the adaptation to high-altitude hypoxia of Tibetan sheep, we analysed the expression profile of lncRNAs and mRNAs in the liver and lung tissues of sheep using comparative transcriptome analysis between four Tibetan sheep populations (high altitude) and one Hu sheep population (low altitude). The results showed a total of 7848 differentially expressed (DE) lncRNA transcripts, and 22,971 DE mRNA transcripts were detected by pairwise comparison. The expression patterns of selected mRNAs and lncRNAs were validated by qRT-PCR, and the results correlated well with the transcriptome data. Moreover, the functional annotation analysis based on the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases showed that DE mRNAs and the target genes of the lncRNAs were significantly enriched in organ morphogenesis, response to stimulus, haem binding, the immune system, arginine and proline metabolism, and fatty acid biosynthesis. The prediction of mRNA–mRNA and lncRNA–mRNA interaction networks further revealed transcripts potentially involved in adaptation to high-altitude hypoxia, and the hub genes DDX24, PDCD11, EIF4A3, NDUFA11, SART1, PRPF8 and TCONS_00306477, TCONS_00306029, TCONS_00139593, TCONS_00293272, and TCONS_00313398 were selected. Additionally, a set of target genes, PIK3R1, IGF1R, FZD6, IFNB2, ATF3, MB, CYP2B4, PSMD13, and TGFB1, were also identified as candidate genes associated with high-altitude hypoxia adaptation. In conclusion, a collection of novel expressed lncRNAs, a set of target genes and biological pathways known to be relevant for altitude adaptation were identified by comparative transcriptome analysis between Tibetan sheep and Hu sheep. Our results are the first to identify the characterization and expression profile of lncRNAs between Tibetan sheep and Hu sheep and provide insights into the genetic regulation mechanisms by which Tibetan sheep adapt to high-altitude hypoxic environments.

1,8-cineole Ameliorates Right Ventricle Dysfunction Associated With Pulmonary Arterial Hypertension by Restoring Connexin 43 and Mitochondrial Homeostasis

For the first time, the present study unravels a cardiospecific therapeutic approach for Pulmonary Arterial Hypertension (PAH), a disease with a very poor prognosis and high mortality rates due to right ventricle dysfunction. We first established a new in vitro model of high-pressure-induced hypertrophy that closely resembles heart defects associated with PAH and validated our in vitro findings on a preclinical in vivo model of monocrotaline (MCT)-induced PAH. Our results showed the in vitro antihypertrophic effect of 1,8-cineole, a monoterpene widely found in several essential oils. Also, a decrease in RV hypertrophy and fibrosis, and an improvement in heart function in vivo was observed, when 1,8-cineole was applied topically. Furthermore, 1,8-cineole restored gap junction protein connexin43 distribution at the intercalated discs and mitochondrial functionality, suggesting it may act by preserving cardiac cell-to-cell communication and bioenergetics. Overall, our results point out a promising therapeutic compound that can be easily applied topically, thus paving the way for the development of effective cardiac-specific therapies to greatly improve PAH outcomes.

Signal Transduction during Metabolic and Inflammatory Reprogramming in Pulmonary Vascular Remodeling

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by (mal)adaptive remodeling of the pulmonary vasculature, which is associated with inflammation, fibrosis, thrombosis, and neovascularization. Vascular remodeling in PAH is associated with cellular metabolic and inflammatory reprogramming that induce profound endothelial and smooth muscle cell phenotypic changes. Multiple signaling pathways and regulatory loops act on metabolic and inflammatory mediators which influence cellular behavior and trigger pulmonary vascular remodeling in vivo. This review discusses the role of bioenergetic and inflammatory impairments in PAH development.

Mitochondrial Metabolism, Redox, and Calcium Homeostasis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by elevated pulmonary arterial pressure due to increased pulmonary vascular resistance, secondary to sustained pulmonary vasoconstriction and excessive obliterative pulmonary vascular remodeling. Work over the last decade has led to the identification of a critical role for metabolic reprogramming in the PAH pathogenesis. It is becoming clear that in addition to its role in ATP generation, the mitochondrion is an important organelle that regulates complex and integrative metabolic- and signal transduction pathways. This review focuses on mitochondrial metabolism alterations that occur in deranged pulmonary vessels and the right ventricle, including abnormalities in glycolysis and glucose oxidation, fatty acid oxidation, glutaminolysis, redox homeostasis, as well as iron and calcium metabolism. Further understanding of these mitochondrial metabolic mechanisms could provide viable therapeutic approaches for PAH patients.

Dichotomy in hypoxia-induced mitochondrial fission in placental mesenchymal cells during development and preeclampsia: consequences for trophoblast mitochondrial homeostasis

Dynamic changes in physiologic oxygen are required for proper placenta development; yet, when low-oxygen levels persist, placental development is halted, culminating in preeclampsia (PE), a serious complication of pregnancy. Considering mitochondria’s function is intimately linked to oxygen changes, we investigated the impact of oxygen on mitochondrial dynamics in placental mesenchymal stromal cells (pMSCs) that are vital for proper placental development. Transmission electron microscopy, proximity ligation assays for mitochondrial VDAC1 and endoplasmic reticulum IP3R, and immunoanalyses of p-DRP1 and OPA1, demonstrate that low-oxygen conditions in early 1st trimester and PE promote mitochondrial fission in pMSCs. Increased mitochondrial fission of mesenchymal cells was confirmed in whole PE placental tissue sections. Inhibition of DRP1 oligomerization with MDiVi-1 shows that low oxygen-induced mitochondrial fission is a direct consequence of DRP1 activation, likely via HIF1. Mitophagy, a downstream event prompted by mitochondrial fission, is a prominent outcome in PE, but not 1st trimester pMSCs. We also investigated whether mesenchymal–epithelial interactions affect mitochondrial dynamics of trophoblasts in PE placentae. Exposure of trophoblastic JEG3 cells to exosomes of preeclamptic pMSCs caused heightened mitochondrial fission in the cells via a sphingomyelin-dependent mechanism that was restored by MDiVi-1. Our data uncovered dichotomous regulation of mitochondrial fission and health in human placental mesenchymal cells under physiologic and pathologic hypoxic conditions and its impact on neighboring trophoblast cells.

The MFF-SIRT1/3 axis, regulated by miR-340-5p, restores mitochondrial homeostasis of hypoxia-induced pulmonary artery smooth muscle cells

Mitochondrial dynamics and quality control play a central role in the maintenance of the proliferation-apoptosis balance, which is closely related to the progression of pulmonary arterial hypertension (PAH). However, the exact mechanism of this balance remains unknown. Pulmonary artery smooth muscle cells (PASMCs) were cultured in hypoxia condition for constructing a PAH model in vitro. The expression of genes and proteins were determined by qRT-PCR and western bolt assays. Cell proliferation-apoptosis balance were tested by MTT, EdU and TUNEL assays. The mitochondrial functions were assessed by flow cytometry, JC-1, Mito tracker red staining, and corresponding kits. Besides, the molecular interaction was validated by dual-luciferase reporter assay. MFF was overexpressed in hypoxia-treated PAMSCs. Knockdown of MFF significantly repressed the excessive proliferation but enhanced cell apoptosis in hypoxia-treated PAMSCs. Moreover, MFF silencing improved mitochondrial function of hypoxia-treated PAMSCs by increasing ATP production and decreasing ROS release and mitochondrial fission. Mechanistically, MFF was a directly target of miR-340-5p, and could negatively regulate SIRT1/3 expression. Subsequently, functional rescue assays showed that the biological effects of MFF in hypoxia-treated PAMSCs were negatively regulated by miR-340-5p and depended on the regulation on SIRT1/3 pathway. These results provided evidences that miR-340-5p regulated MFF-SIRT1/3 axis to improve mitochondrial homeostasis and proliferation-apoptosis imbalance of hypoxia-treated PAMSCs, which provided a theoretical basis for the prevention and treatment of PAH.

Role of mitochondrial dynamics and mitophagy of vascular smooth muscle cell proliferation and migration in progression of atherosclerosis

Vascular smooth muscle cell (VSMC) proliferation and migration are critical events that contribute to the pathogenesis of vascular diseases such as atherosclerosis, restenosis, and hypertension. Recent findings have revealed that VSMC phenotype switching is associated with metabolic switch, which is related to the role of mitochondria. Mitochondrial dynamics are directly associated with mitochondrial function and cellular homeostasis. Interestingly, it has been suggested that mitochondrial dynamics and mitophagy play crucial roles in the regulation of VSMC proliferation and migration through various mechanisms. Especially, dynamin-related protein-1 and mitofusion-2 are two main molecules that play a key role in regulating mitochondrial dynamics to induce VSMC proliferation and migration. Therefore, this review describes the function and role of mitochondrial dynamics and mitophagy in VSMC homeostasis as well as the underlying mechanisms. This will provide insight into the development of innovative approaches to treat atherosclerosis.

miR‑205‑3p promotes lung cancer progression by targeting APBB2

Non-small cell lung cancer (NSCLC), a leading cause of cancer-associated mortality, has resulted in low survival rates and a high mortality worldwide. Accumulating evidence has suggested that microRNAs (miRs) play critical roles in the regulation of cancer progression and the present study aimed to explore the underlying mechanism of miR-205 in NSCLC. Reverse transcription-quantitative PCR was performed, which determined that miR-205 expression was upregulated in NSCLC, and the present study detected the upregulation of miR-205-3p in a number of NSCLC cell lines and NSCLC tissues. In addition, the mediation of amyloid β precursor protein-binding family B member 2 (APBB2) by miR-205-3p was demonstrated. Moreover, miR-205-3p was predicted to directly target the 3′untranslated region of APBB2, which was confirmed using a dual-luciferase reporter assay. It was found that lentivirus mediated-APBB2 knockdown could promote cellular viability and suppress apoptosis in NSCLC cells, as determined via MTT, TUNEL and flow cytometry assays. Thus, the current findings highlighted the potential promotive impact of miR-205-3p on NSCLC processes and may provide theoretical evidence for miR-205-3p as a potential clinical gene therapy target.

Novel molecular insights and public omics data in pulmonary hypertension

Pulmonary hypertension is a rare disease with high morbidity and mortality which mainly affects women of reproductive age. Despite recent advances in understanding the pathogenesis of pulmonary hypertension, the high heterogeneity in the presentation of the disease among different patients makes it difficult to make an accurate diagnosis and to apply this knowledge to effective treatments. Therefore, new studies are required to focus on translational and personalized medicine to overcome the lack of specificity and efficacy of current management. Here, we review the majority of public databases storing 'omics' data of pulmonary hypertension studies, from animal models to human patients. Moreover, we review some of the new molecular mechanisms involved in the pathogenesis of pulmonary hypertension, including non-coding RNAs and the application of 'omics' data to understand this pathology, hoping that these new approaches will provide insights to guide the way to personalized diagnosis and treatment.

HIGD‑1B inhibits hypoxia‑induced mitochondrial fragmentation by regulating OPA1 cleavage in cardiomyocytes

The dynamic regulation of mitochondrial morphology is key for eukaryotic cells to manage physiological challenges. Therefore, it is important to understand the molecular basis of mitochondrial dynamic regulation. The aim of the present study was to explore the role of HIG1 hypoxia inducible domain family member 1B (HIGD‑1B) in hypoxia‑induced mitochondrial fragmentation. Protein expression was determined via western blotting. Immunofluorescence assays were performed to detect the subcellular location of HIGD‑1B. Cell Counting Kit‑8 assays and flow cytometry were carried out to measure cell viability and apoptosis, respectively. Protein interactions were evaluated by co‑immunoprecipitation. In the present study, it was found that HIGD‑1B serves a role in cell survival by maintaining the integrity of the mitochondria under hypoxic conditions. Knockdown of HIGD‑1B promoted mitochondrial fragmentation, while overexpression of HIGD‑1B increased survival by preventing activation of caspase‑3 and ‑9. HIGD‑1B expression was associated with cell viability and apoptosis in cardiomyocytes. Furthermore, HIGD‑1B delayed the cleavage process of optic atrophy 1 (OPA1) and stabilized mitochondrial morphology by interacting with OPA1. Collectively, the results from the present study identified a role for HIGD‑1B as an inhibitor of the mitochondrial fission in cardiomyocytes.

Role of Interleukin-6 in Vascular Health and Disease

IL-6 is usually described as a pleiotropic cytokine produced in response to tissue injury or infection. As a pro-inflammatory cytokine, IL-6 activates innate and adaptative immune responses. IL-6 is released in the innate immune response by leukocytes as well as stromal cells upon pattern recognition receptor activation. IL-6 then recruits immune cells and triggers B and T cell response. Dysregulated IL-6 activity is associated with pathologies involving chronic inflammation and autoimmunity, including atherosclerosis. However, IL-6 is also produced and released under beneficial conditions, such as exercise, where IL-6 is associated with the anti-inflammatory and metabolic effects coupled with physical adaptation to intense training. Exercise-associated IL-6 acts on adipose tissue to induce lipogenesis and on arteries to induce adaptative vascular remodeling. These divergent actions could be explained by complex signaling networks. Classical IL-6 signaling involves a membrane-bound IL-6 receptor and glycoprotein 130 (gp130), while trans-signaling relies on a soluble version of IL-6R (sIL-6R) and membrane-bound gp130. Trans-signaling, but not the classical pathway, is regulated by soluble gp130. In this review, we discuss the similarities and differences in IL-6 cytokine and myokine signaling to explain the differential and opposite effects of this protein during inflammation and exercise, with a special focus on the vascular system.

Hypoxia induces pulmonary artery smooth muscle dysfunction through mitochondrial fragmentation-mediated endoplasmic reticulum stress

Pulmonary arterial hypertension (PAH) is characterized by pulmonary artery smooth muscle cell (PASMC) dysfunction. However, the underlying mechanisms of PASMC dysfunction remain largely unknown. Here, we show that mitochondrial fragmentation contributes to PASMC dysfunction through enhancement of endoplasmic reticulum (ER) stress. PASMC dysfunction accompanied by mitochondrial fragmentation and ER stress was observed in the pulmonary arteries of hypoxia-induced rats with PAH, as well as isolated PASMCs under hypoxia. Treatment with Mdivi-1 inhibited mitochondrial fragmentation and ER stress and improved PASMC function in isolated PASMCs under hypoxia, while Drp1 overexpression increased mitochondrial fragmentation and ER stress, impairing PASMC function in isolated PASMCs under normoxia. However, inhibition of ER stress using ER stress inhibitors showed a negligible effect on mitochondrial morphology but improved PASMC function during hypoxia. Additionally, we found that mitochondrial fragmentation-promoted ER stress was dependent on mitochondrial reactive oxygen species. Furthermore, inhibition of mitochondrial fragmentation using Mdivi-1 attenuated mitochondrial fragmentation and ER stress in hypoxic PASMCs and improved the pulmonary artery smooth muscle function in hypoxic rats. These results suggest that hypoxia induces pulmonary artery smooth muscle dysfunction through mitochondrial fragmentation-mediated ER stress and that mitochondrial morphology is a potential target for treatment of hypoxia-induced pulmonary artery smooth muscle dysfunction.

Deletion of Bmal1 Impairs Pancreatic β-Cell Function via Mitochondrial Signaling Pathway

Several studies have demonstrated that brain and muscle Arnt-like protein-1 (Bmal1) acts as a core clock gene for maintaining normal cell function, including hepatocytes and cardiomyocytes. Loss of Bmal1 is associated with type 2 diabetes due to pancreatic β-cell failure. However, little information is available about its role and mechanism in pancreatic β-cell. To address this, we investigated the consequences of Bmal1 inhibition in an insulinoma cell line (INS-1) by using small interfering RNA (siRNA). We observed that knockout of Bmal1 impaired glucose-stimulated insulin secretion in β-cell. Meanwhile, the depletion of Bmal1 in β-cell caused an adverse change in mitochondrial membrane potential and mitochondrial architecture. Deletion of Bmal1 attenuated mRNA and protein expression of mitofusin 1 (Mfn1) and mitofusin 2 (Mfn2) and enhanced the expression of fission 1 (Fis1). In summary, the deletion of Bmal1 impaired β-cell function may be via the mitochondrial signaling pathway in INS-1 cells.

The Role and Regulation of Pulmonary Artery Smooth Muscle Cells in Pulmonary Hypertension

Pulmonary hypertension (PH) is one of the most devastating cardiovascular diseases worldwide and it draws much attention from numerous scientists. As an indispensable part of pulmonary artery, smooth muscle cells are worthy of being carefully investigated. To elucidate the pathogenesis of PH, several theories focusing on pulmonary artery smooth muscle cells (PASMC), such as hyperproliferation, resistance to apoptosis, and cancer theory, have been proposed and widely studied. Here, we tried to summarize the studies, concentrating on the role of PASMC in the development of PH, feasible molecular basis to intervene, and potential treatment to PH.

Angiotensin-(1-9) prevents vascular remodeling by decreasing vascular smooth muscle cell dedifferentiation through a FoxO1-dependent mechanism

The renin-angiotensin system, one of the main regulators of vascular function, controls vasoconstriction, inflammation and vascular remodeling. Antagonistic actions of the counter-regulatory renin-angiotensin system, which include vasodilation, anti-proliferative, anti-inflammatory and anti-remodeling effects, have also been described. However, little is known about the direct effects of angiotensin-(1-9), a peptide of the counter-regulatory renin-angiotensin system, on vascular smooth muscle cells. Here, we studied the anti-vascular remodeling effects of angiotensin-(1-9), with special focus on the control of vascular smooth muscle cell phenotype. Angiotensin-(1-9) decreased blood pressure and aorta media thickness in spontaneously hypertensive rats. Reduction of media thickness was associated with decreased vascular smooth muscle cell proliferation. In the A7r5 VSMC cell line and in primary cultures of rat aorta smooth muscle cells, angiotensin-(1-9) did not modify basal proliferation. However, angiotensin-(1-9) inhibited proliferation, migration and contractile protein decrease induced by platelet derived growth factor-BB. Moreover, angiotensin-(1-9) reduced Akt and FoxO1 phosphorylation at 30 min, followed by an increase of total FoxO1 protein content. Angiotensin-(1-9) effects were blocked by the AT2R antagonist PD123319, Akt-Myr overexpression and FoxO1 siRNA. These data suggest that angiotensin-(1-9) inhibits vascular smooth muscle cell dedifferentiation by an AT2R/Akt/FoxO1-dependent mechanism.

New perspectives on the role of Drp1 isoforms in regulating mitochondrial pathophysiology

Mitochondria are dynamic organelles constantly undergoing fusion and fission. A concerted balance between the process of mitochondrial fusion and fission is required to maintain cellular health under different physiological conditions. Mutation and dysregulation of Drp1, the major driver of mitochondrial fission, has been associated with various neurological, oncological and cardiovascular disorders. Moreover, when subjected to pathological insults, mitochondria often undergo excessive fission, generating fragmented and dysfunctional mitochondria leading to cell death. Therefore, manipulating mitochondrial fission by targeting Drp1 has been an appealing therapeutic approach for cytoprotection. However, studies have been inconsistent. Studies employing Drp1 constructs representing alternate Drp1 isoforms, have demonstrated differing impacts of these isoforms on mitochondrial fission and cell death. Furthermore, there are distinct expression patterns of Drp1 isoforms in different tissues, suggesting idiosyncratic engagement in specific cellular functions. In this review, we will discuss these inherent variations among human Drp1 isoforms and how they could affect Drp1-mediated mitochondrial fission and cell death.

Rats with a Human Mutation of NFU1 Develop Pulmonary Hypertension

NFU1 is a mitochondrial protein that is involved in the biosynthesis of iron-sulfur clusters, and its genetic modification is associated with disorders of mitochondrial energy metabolism. Patients with autosomal-recessive inheritance of the NFU1 mutation G208C have reduced activity of the respiratory chain Complex II and decreased levels of lipoic-acid-dependent enzymes, and develop pulmonary arterial hypertension (PAH) in ∼70% of cases. We investigated whether rats with a human mutation in NFU1 are also predisposed to PAH development. A point mutation in rat NFU1^G206C (human G208C) was introduced through CRISPR/Cas9 genome editing. Hemodynamic data, tissue samples, and fresh mitochondria were collected and analyzed. NFU1^G206C rats showed increased right ventricular pressure, right ventricular hypertrophy, and high levels of pulmonary artery remodeling. Computed tomography and angiography of the pulmonary vasculature indicated severe angioobliterative changes in NFU1^G206C rats. Importantly, the penetrance of the PAH phenotype was found to be more prevalent in females than in males, replicating the established sex difference among patients with PAH. Male and female homozygote rats exhibited decreased expression and activity of mitochondrial Complex II, and markedly decreased pyruvate dehydrogenase activity and lipoate binding. The limited development of PAH in males correlated with the preserved levels of oligomeric NFU1, increased expression of ISCU (an alternative branch of the iron-sulfur assembly system), and increased complex IV activity. Thus, the male sex has additional plasticity to overcome the iron-sulfur cluster deficiency. Our work describes a novel, humanized rat model of NFU1 deficiency that showed mitochondrial dysfunction similar to that observed in patients and developed PAH with the same sex dimorphism.

Mitochondrial division inhibitor (mdivi-1) decreases oxidative metabolism in cancer

Background

Previous studies suggested that mdivi-1 (mitochondrial division inhibitor), a putative inhibitor of dynamin-related protein (DRP1), decreased cancer cell proliferation through inducing mitochondrial fusion and altering oxygen consumption. However, the metabolic reprogramming underlying the DRP1 inhibition is still unclear in cancer cells.

Methods

To better understand the metabolic effect of DRP1 inhibition, [U-¹³C]glucose isotope tracing was employed to assess mdivi-1 effects in several cancer cell lines, DRP1-WT (wild-type) and DRP1-KO (knockout) H460 lung cancer cells and mouse embryonic fibroblasts (MEFs).

Results

Mitochondrial staining confirmed that mdivi-1 treatment and DRP1 deficiency induced mitochondrial fusion. Surprisingly, metabolic isotope tracing found that mdivi-1 decreased mitochondrial oxidative metabolism in the lung cancer cell lines H460, A549 and the colon cancer cell line HCT116. [U-¹³C]glucose tracing studies also showed that the TCA cycle intermediates had significantly lower enrichment in mdivi-1-treated cells. In comparison, DRP1-WT and DRP1-KO H460 cells had similar oxidative metabolism, which was decreased by mdivi-1 treatment. Furthermore, mdivi-1-mediated effects on oxidative metabolism were independent of mitochondrial fusion.

Conclusions

Our data suggest that, in cancer cells, mdivi-1, a putative inhibitor of DRP1, decreases oxidative metabolism to impair cell proliferation.

Comprehensive transcriptomic profiling reveals SOX7 as an early regulator of angiogenesis in hypoxic human endothelial cells

Endothelial cells (ECs) lining the vasculature of vertebrates respond to low oxygen (hypoxia) by maintaining vascular homeostasis and initiating adaptive growth of new vasculature through angiogenesis. Previous studies have uncovered the molecular underpinnings of the hypoxic response in ECs; however, there is a need for comprehensive temporal analysis of the transcriptome during hypoxia. Here, we sought to investigate the early transcriptional programs of hypoxic ECs by using RNA-Seq of primary cultured human umbilical vein ECs exposed to progressively increasing severity and duration of hypoxia. We observed that hypoxia modulates the expression levels of approximately one-third of the EC transcriptome. Intriguingly, expression of the gene encoding the developmental transcription factor SOX7 (SRY-box transcription factor 7) rapidly and transiently increased during hypoxia. Transcriptomic and functional analyses of ECs following SOX7 depletion established its critical role in regulating hypoxia-induced angiogenesis. We also observed that depletion of the hypoxia-inducible factor (HIF) genes, HIF1A (encoding HIF-1α) and endothelial PAS domain protein 1 (EPAS1 encoding HIF-2α), inhibited both distinct and overlapping transcriptional programs. Our results indicated a role for HIF-1α in down-regulating mitochondrial metabolism while concomitantly up-regulating glycolytic genes, whereas HIF-2α primarily up-regulated the angiogenesis transcriptional program. These results identify the concentration and time dependence of the endothelial transcriptomic response to hypoxia and an early key role for SOX7 in mediating angiogenesis.

Mesenchymal stromal cell-derived exosomes improve mitochondrial health in pulmonary arterial hypertension

Secreted exosomes are bioactive particles that elicit profound responses in target cells. Using targeted metabolomics and global microarray analysis, we identified a role of exosomes in promoting mitochondrial function in the context of pulmonary arterial hypertension (PAH). Whereas chronic hypoxia results in a glycolytic shift in pulmonary artery smooth muscle cells (PASMCs), exosomes restore energy balance and improve O₂ consumption. These results were confirmed in a hypoxia-induced mouse model and a semaxanib/hypoxia rat model of PAH wherein exosomes improved the mitochondrial dysfunction associated with disease. Importantly, exosome exposure increased PASMC expression of pyruvate dehydrogenase (PDH) and glutamate dehydrogenase 1 (GLUD1), linking exosome treatment to the TCA cycle. Furthermore, we show that although prolonged hypoxia induced sirtuin 4 expression, an upstream inhibitor of both GLUD1 and PDH, exosomes reduced its expression. These data provide direct evidence of an exosome-mediated improvement in mitochondrial function and contribute new insights into the therapeutic potential of exosomes in PAH.

Mitochondrial metabolism in pulmonary hypertension: beyond mountains there are mountains

Pulmonary hypertension (PH) is a heterogeneous and fatal disease of the lung vasculature, where metabolic and mitochondrial dysfunction may drive pathogenesis. Similar to the Warburg effect in cancer, a shift from mitochondrial oxidation to glycolysis occurs in diseased pulmonary vessels and the right ventricle. However, appreciation of metabolic events in PH beyond the Warburg effect is only just emerging. This Review discusses molecular, translational, and clinical concepts centered on the mitochondria and highlights promising, controversial, and challenging areas of investigation. If we can move beyond the "mountains" of obstacles in this field and elucidate these fundamental tenets of pulmonary vascular metabolism, such work has the potential to usher in much-needed diagnostic and therapeutic approaches for the mitochondrial and metabolic management of PH.

Metabolic dysfunction in pulmonary hypertension: from basic science to clinical practice

Pulmonary hypertension (PH) is an often-fatal vascular disease of unclear molecular origins. The pulmonary vascular remodelling which occurs in PH is characterised by elevated vasomotor tone and a pro-proliferative state, ultimately leading to right ventricular dysfunction and heart failure. Guided in many respects by prior evidence from cancer biology, recent investigations have identified metabolic aberrations as crucial components of the disease process in both the pulmonary vessels and the right ventricle. Given the need for improved diagnostic and therapeutic options for PH, the development or repurposing of metabolic tracers and medications could provide an effective avenue for preventing or even reversing disease progression. In this review, we describe the metabolic mechanisms that are known to be dysregulated in PH; we explore the advancing diagnostic testing and imaging modalities that are being developed to improve diagnostic capability for this disease; and we discuss emerging drugs for PH which target these metabolic pathways.

Understanding metabolic pathways in PH provides opportunities for improved diagnostic and therapeutic optionshttp://ow.ly/pFQb30guez6