Danchen Wu - Academia.edu (original) (raw)

Papers by Danchen Wu

Research paper thumbnail of Oxygen-sensing in the Lung is Regulated by Mitochondrial Complex I Ndufs2: Role of Mitochondria-derived Hydrogen Peroxide in Hypoxic Pulmonary Vasoconstriction

Free Radical Biology and Medicine, Nov 1, 2017

Research paper thumbnail of Germline and Somatic Mutations in DNA Methyltransferase 3A (DNMT3A) Predispose to Pulmonary Arterial Hypertension (PAH) in Humans and Mice: Implications for Associated PAH

Research paper thumbnail of Electron Leak From the Mitochondrial Electron Transport Chain Complex I at Site I <sub>Q</sub> Is Crucial for Oxygen Sensing in Rabbit and Human Ductus Arteriosus

Journal of the American Heart Association, Jul 4, 2023

Background As partial pressure of oxygen (pO 2 ) rises with the first breath, the ductus arterios... more Background As partial pressure of oxygen (pO 2 ) rises with the first breath, the ductus arteriosus (DA) constricts, diverting blood flow to the pulmonary circulation. The DA's O 2 sensor resides within smooth muscle cells. The DA smooth muscle cells’ mitochondrial electron transport chain (ETC) produces reactive oxygen species (ROS) in proportion to oxygen tension, causing vasoconstriction by regulating redox‐sensitive ion channels and enzymes. To identify which ETC complex contributes most to DA O 2 sensing and determine whether ROS mediate O 2 sensing independent of metabolism, we used electron leak suppressors, S1QEL (suppressor of site I Q electron leak) and S3QEL (suppressor of site III Qo electron leak), which decrease ROS production by inhibiting electron leak from quinone sites I Q and III Qo , respectively. Methods and Results The effects of S1QEL, S3QEL, and ETC inhibitors (rotenone and antimycin A) on DA tone, mitochondrial metabolism, O 2 ‐induced changes in intracellular calcium, and ROS were studied in rabbit DA rings, and human and rabbit DA smooth muscle cells. S1QEL's effects on DA patency were assessed in rabbit kits, using micro computed tomography. In DA rings, S1QEL, but not S3QEL, reversed O 2 ‐induced constriction ( P =0.0034) without reducing phenylephrine‐induced constriction. S1QEL did not inhibit mitochondrial metabolism or ETC‐I activity. In human DA smooth muscle cells, S1QEL and rotenone inhibited O 2 ‐induced increases in intracellular calcium ( P =0.02 and 0.001, respectively), a surrogate for DA constriction. S1QEL inhibited O 2 ‐induced ROS generation ( P =0.02). In vivo, S1QEL prevented O 2 ‐induced DA closure ( P &lt;0.0001). Conclusions S1QEL, but not S3QEL, inhibited O 2 ‐induced rises in ROS and DA constriction ex vivo and in vivo. DA O 2 sensing relies on pO 2 ‐dependent changes in electron leak at site I Q in ETC‐I, independent of metabolism. S1QEL offers a therapeutic means to maintain DA patency.

Research paper thumbnail of Mitochondria in the Pulmonary Vasculature in Health and Disease: Oxygen‐Sensing, Metabolism, and Dynamics

Comprehensive Physiology, Mar 12, 2020

Research paper thumbnail of Novel Dynamin-Related Protein 1 GTPase Inhibitor Prevents Myocardial Ischemia-Reperfusion Injury

Research paper thumbnail of Oxygen-sensing in the Lung is Regulated by Mitochondrial Complex I Ndufs2: Role of Mitochondria-derived Hydrogen Peroxide in Hypoxic Pulmonary Vasoconstriction

Free Radical Biology and Medicine, Nov 1, 2017

Research paper thumbnail of Abstract 10715: Therapeutic Efficacy of Drpitor1a, a Novel Dynamin-Related Protein 1 (DRP1) Inhibitor, in Preclinical Pulmonary Arterial Hypertension

Circulation

Introduction: Dynamin-related protein 1 (DRP1) is a large GTPase that mediates mitotic fission (t... more Introduction: Dynamin-related protein 1 (DRP1) is a large GTPase that mediates mitotic fission (the division of mitochondria which is coordinated with mitosis, ensuring equitable distribution of mitochondria to daughter cells). In pulmonary arterial hypertension (PAH) pulmonary artery smooth muscle cells (PASMC), mitotic fission, and DRP1 activity are increased, contributing to its hyperproliferative phenotype. We investigated the therapeutic efficacy of Drpitor1a, a novel, small molecule, Drp1 GTPase inhibitor, in a rat PAH model. Methods: A single dose of monocrotaline (MCT, 60mg/kg, SC) or PBS was injected to female Sprague-Dawley rats on day 0 (n=20 for MCT and n=15 for PBS). On day 14, the development of PAH was confirmed by echocardiography and the rats were randomized for treatments. An indwelling catheter was implanted through the left jugular vein on day 15. Drpitor1a (1mg/kg) or normal saline (NS) was administered by IV every 48 hours from day 17 to day 27. Right ventricul...

Research paper thumbnail of Acquired disorders of mitochondrial metabolism and dynamics in pulmonary arterial hypertension

Frontiers in Cell and Developmental Biology, Feb 2, 2023

Pulmonary arterial hypertension (PAH) is an orphan disease of the cardiopulmonary unit that refle... more Pulmonary arterial hypertension (PAH) is an orphan disease of the cardiopulmonary unit that reflects an obstructive pulmonary vasculopathy and presents with hypertrophy, inflammation, fibrosis, and ultimately failure of the right ventricle (RVF). Despite treatment using pulmonary hypertension (PH)-targeted therapies, persistent functional impairment reduces the quality of life for people with PAH and death from RVF occurs in approximately 40% of patients within 5 years of diagnosis. PH-targeted therapeutics are primarily vasodilators and none, alone or in combination, are curative. This highlights a need to therapeutically explore molecular targets in other pathways that are involved in the pathogenesis of PAH. Several candidate pathways in PAH involve acquired mitochondrial dysfunction. These mitochondrial disorders include: 1) a shift in metabolism related to increased expression of pyruvate dehydrogenase kinase and pyruvate kinase, which together increase uncoupled glycolysis (Warburg metabolism); 2) disruption of oxygen-sensing related to increased expression of hypoxia-inducible factor 1α, resulting in a state of pseudohypoxia; 3) altered mitochondrial calcium homeostasis related to impaired function of the mitochondrial calcium uniporter complex, which elevates cytosolic calcium and reduces intramitochondrial calcium; and 4) abnormal mitochondrial dynamics related to increased expression of dynamin-related protein 1 and its binding partners, such as mitochondrial dynamics proteins of 49 kDa and 51 kDa, and depressed expression of mitofusin 2, resulting in increased mitotic fission. These acquired mitochondrial abnormalities increase proliferation and impair apoptosis in most pulmonary vascular cells (including endothelial cells, smooth muscle cells and fibroblasts). In the RV, Warburg metabolism and induction of glutaminolysis impairs bioenergetics and promotes hypokinesis, hypertrophy, and fibrosis. This review will explore our current knowledge of the causes and consequences of disordered mitochondrial function in PAH. KEYWORDS pyruvate dehydrogenase kinase (PDK), hypoxia-inducible factor 1-alpha (HIF-1α), dynaminrelated protein 1 (DRP1), mitochondrial calcium uniporter complex (MCUC), pyruvate kinase (PK), Warburg metabolism

Research paper thumbnail of SARS-CoV-2 mitochondriopathy in COVID-19 pneumonia exacerbates hypoxemia

Redox Biology

RationaleSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 pneumonia. ... more RationaleSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 pneumonia. We hypothesize that SARS-CoV-2 causes alveolar injury and hypoxemia by damaging mitochondria in airway epithelial cells (AEC) and pulmonary artery smooth muscle cells (PASMC), triggering apoptosis and bioenergetic impairment, and impairing hypoxic pulmonary vasoconstriction (HPV), respectively.ObjectivesWe examined the effects of: A) human betacoronaviruses, SARS-CoV-2 and HCoV-OC43, and individual SARS-CoV-2 proteins on apoptosis, mitochondrial fission, and bioenergetics in AEC; and B) SARS-CoV-2 proteins and mouse hepatitis virus (MHV-1) infection on HPV.MethodsWe used transcriptomic data to identify temporal changes in mitochondrial-relevant gene ontology (GO) pathways post-SARS-CoV-2 infection. We also transduced AECs with SARS-CoV-2 proteins (M, Nsp7 or Nsp9) and determined effects on mitochondrial permeability transition pore (mPTP) activity, relative membrane potential, apoptosis, mitochondrial fission, and oxygen consumption rates (OCR). In human PASMC, we assessed the effects of SARS-CoV-2 proteins on hypoxic increases in cytosolic calcium, an HPV proxy. In MHV-1 pneumonia, we assessed HPV via cardiac catheterization and apoptosis using the TUNEL assay.ResultsSARS-CoV-2 regulated mitochondrial apoptosis, mitochondrial membrane permeabilization and electron transport chain (ETC) GO pathways within 2 hours of infection. SARS-CoV-2 downregulated ETC Complex I and ATP synthase genes, and upregulated apoptosis-inducing genes. SARS-CoV-2 and HCoV-OC43 upregulated and activated dynamin-related protein 1 (Drp1) and increased mitochondrial fission. SARS-CoV-2 and transduced SARS-CoV-2 proteins increased apoptosis inducing factor (AIF) expression and activated caspase 7, resulting in apoptosis. Coronaviruses also reduced OCR, decreased ETC Complex I activity and lowered ATP levels in AEC. M protein transduction also increased mPTP opening. In human PASMC, M and Nsp9 proteins inhibited HPV. In MHV-1 pneumonia, infected AEC displayed apoptosis and HPV was suppressed. BAY K8644, a calcium channel agonist, increased HPV and improved SpO2.ConclusionsCoronaviruses, including SARS-CoV-2, cause AEC apoptosis, mitochondrial fission, and bioenergetic impairment. SARS-CoV-2 also suppresses HPV by targeting mitochondria. This mitochondriopathy is replicated by transduction with SARS-CoV-2 proteins, indicating a mechanistic role for viral-host mitochondrial protein interactions. Mitochondriopathy is a conserved feature of coronaviral pneumonia that may exacerbate hypoxemia and constitutes a therapeutic target.

Research paper thumbnail of Mitochondrial fission links ECM mechanotransduction to metabolic redox homeostasis and metastatic chemotherapy resistance

Nature Cell Biology, 2022

Metastatic breast cancer cells disseminate to organs with a soft microenvironment. Whether and ho... more Metastatic breast cancer cells disseminate to organs with a soft microenvironment. Whether and how the mechanical properties of the local tissue influence their response to treatment remains unclear. Here we found that a soft extracellular matrix empowers redox homeostasis. Cells cultured on a soft extracellular matrix display increased peri-mitochondrial F-actin, promoted by Spire1C and Arp2/3 nucleation factors, and increased DRP1- and MIEF1/2-dependent mitochondrial fission. Changes in mitochondrial dynamics lead to increased production of mitochondrial reactive oxygen species and activate the NRF2 antioxidant transcriptional response, including increased cystine uptake and glutathione metabolism. This retrograde response endows cells with resistance to oxidative stress and reactive oxygen species-dependent chemotherapy drugs. This is relevant in a mouse model of metastatic breast cancer cells dormant in the lung soft tissue, where inhibition of DRP1 and NRF2 restored cisplatin sensitivity and prevented disseminated cancer-cell awakening. We propose that targeting this mitochondrial dynamics- and redox-based mechanotransduction pathway could open avenues to prevent metastatic relapse.

Research paper thumbnail of Mitochondria in the Pulmonary Vasculature in Health and Disease: Oxygen‐Sensing, Metabolism, and Dynamics

Comprehensive Physiology, 2020

Research paper thumbnail of PINK1‐induced phosphorylation of mitofusin 2 at serine 442 causes its proteasomal degradation and promotes cell proliferation in lung cancer and pulmonary arterial hypertension

The FASEB Journal, 2021

Impaired mitochondrial fusion, due in part to decreased mitofusin 2 (Mfn2) expression, contribute... more Impaired mitochondrial fusion, due in part to decreased mitofusin 2 (Mfn2) expression, contributes to unrestricted cell proliferation and apoptosis-resistance in hyperproliferative diseases like pulmonary arterial hypertension (PAH) and non-small cell lung cancer (NSCLC). We hypothesized that Mfn2 levels are reduced due to increased proteasomal degradation of Mfn2 triggered by its phosphorylation at serine 442 (S442) and investigated the potential kinase mediators. Mfn2 expression was decreased and Mfn2 S442 phosphorylation was increased in pulmonary artery smooth muscle cells from PAH patients and in NSCLC cells. Mfn2 phosphorylation was mediated by PINK1 and protein kinase A (PKA), although only PINK1 expression was increased in these diseases. We designed a S442 phosphorylation deficient Mfn2 construct (PD-Mfn2) and a S442 constitutively phosphorylated Mfn2 construct (CP-Mfn2). The effects of these modified Mfn2 constructs on Mfn2 expression and biological function were compared with those of the wildtype Mfn2 construct (WT-Mfn2). WT-Mfn2 increased Mfn2 expression and mitochondrial fusion in both PAH and NSCLC cells resulting in increased apoptosis and decreased cell proliferation. Compared to WT-Mfn2, PD-Mfn2 caused greater Mfn2 expression, suppression of proliferation, apoptosis induction and cell cycle arrest. Conversely, CP-Mfn2 caused only a small increase in Mfn2 expression and did not restore mitochondrial fusion, inhibit cell proliferation or induce apoptosis. Silencing PINK1 or PKA, or proteasome blockade using MG132, increased Mfn2 expression, enhanced mitochondrial fusion and induced apoptosis. In a xenotransplantation NSCLC model, PD-Mfn2 gene therapy caused greater tumor regression than did therapy with WT-Mfn2. Mfn2 deficiency in PAH and NSCLC reflects proteasomal degradation triggered by Mfn2-S442 phosphorylation by PINK1 and/or PKA. Inhibiting Mfn2 phosphorylation has potential therapeutic benefit in PAH and lung cancer.

Research paper thumbnail of Excess Protein O-GlcNAcylation Links Metabolic Derangements to Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

International Journal of Molecular Sciences, 2020

The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosa... more The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosamine, which, when added to serines or threonines, modulates protein function through protein O-GlcNAcylation. Glutamine-fructose-6-phosphate amidotransferase (GFAT) regulates HBP flux, and AMP-kinase phosphorylation of GFAT blunts GFAT activity and O-GlcNAcylation. While numerous studies demonstrate increased right ventricle (RV) glucose uptake in pulmonary arterial hypertension (PAH), the relationship between O-GlcNAcylation and RV function in PAH is unexplored. Therefore, we examined how colchicine-mediated AMP-kinase activation altered HBP intermediates, O-GlcNAcylation, mitochondrial function, and RV function in pulmonary artery-banded (PAB) and monocrotaline (MCT) rats. AMPK activation induced GFAT phosphorylation and reduced HBP intermediates and O-GlcNAcylation in MCT but not PAB rats. Reduced O-GlcNAcylation partially restored the RV metabolic signature and improved RV function i...

Research paper thumbnail of Oxygen sensing, mitochondrial biology and experimental therapeutics for pulmonary hypertension and cancer

Free Radical Biology and Medicine, 2021

The homeostatic oxygen sensing system (HOSS) optimizes systemic oxygen delivery. Specialized tiss... more The homeostatic oxygen sensing system (HOSS) optimizes systemic oxygen delivery. Specialized tissues utilize a conserved mitochondrial sensor, often involving NDUFS2 in complex I of the mitochondrial electron transport chain, as a site of pO2-responsive production of reactive oxygen species (ROS). These ROS are converted to a diffusible signaling molecule, hydrogen peroxide (H2O2), by superoxide dismutase (SOD2). H2O2 exits the mitochondria and regulates ion channels and enzymes, altering plasma membrane potential, intracellular Ca2+ and Ca2+-sensitization and controlling acute, adaptive, responses to hypoxia that involve changes in ventilation, vascular tone and neurotransmitter release. Subversion of this O2-sensing pathway creates a pseudohypoxic state that promotes disease progression in pulmonary arterial hypertension (PAH) and cancer. Pseudohypoxia is a state in which biochemical changes, normally associated with hypoxia, occur despite normal pO2. Epigenetic silencing of SOD2 by DNA methylation alters H2O2 production, activating hypoxia-inducible factor 1α, thereby disrupting mitochondrial metabolism and dynamics, accelerating cell proliferation and inhibiting apoptosis. Other epigenetic mechanisms, including dysregulation of microRNAs (miR), increase pyruvate dehydrogenase kinase and pyruvate kinase muscle isoform 2 expression in both diseases, favoring uncoupled aerobic glycolysis. This Warburg metabolic shift also accelerates cell proliferation and impairs apoptosis. Disordered mitochondrial dynamics, usually increased mitotic fission and impaired fusion, promotes disease progression in PAH and cancer. Epigenetic upregulation of dynamin-related protein 1 (Drp1) and its binding partners, MiD49 and MiD51, contributes to the pathogenesis of PAH and cancer. Finally, dysregulation of intramitochondrial Ca2+, resulting from impaired mitochondrial calcium uniporter complex (MCUC) function, links abnormal mitochondrial metabolism and dynamics. MiR-mediated decreases in MCUC function reduce intramitochondrial Ca2+, promoting Warburg metabolism, whilst increasing cytosolic Ca2+, promoting fission. Epigenetically disordered mitochondrial O2-sensing, metabolism, dynamics, and Ca2+ homeostasis offer new therapeutic targets for PAH and cancer. Promoting glucose oxidation, restoring the fission/fusion balance, and restoring mitochondrial calcium regulation are promising experimental therapeutic strategies.

Research paper thumbnail of An epigenetic increase in mitochondrial fission by MiD49 and MiD51 regulates the cell cycle in cancer: Diagnostic and therapeutic implications

Research paper thumbnail of Epigenetic Metabolic Reprogramming of Right Ventricular Fibroblasts in Pulmonary Arterial Hypertension

Circulation Research, 2020

Rationale: Right ventricular (RV) fibrosis in pulmonary arterial hypertension contributes to RV f... more Rationale: Right ventricular (RV) fibrosis in pulmonary arterial hypertension contributes to RV failure. While RV fibrosis reflects changes in the function of resident RV fibroblasts (RVfib), these cells are understudied. Objective: Examine the role of mitochondrial metabolism of RVfib in RV fibrosis in human and experimental pulmonary arterial hypertension. Methods and Results: Male Sprague-Dawley rats received monocrotaline (MCT; 60 mg/kg) or saline. Drinking water containing no supplement or the PDK (pyruvate dehydrogenase kinase) inhibitor dichloroacetate was started 7 days post-MCT. At week 4, treadmill testing, echocardiography, and right heart catheterization were performed. The effects of PDK activation on mitochondrial dynamics and metabolism, RVfib proliferation, and collagen production were studied in RVfib in cell culture. Epigenetic mechanisms for persistence of the profibrotic RVfib phenotype in culture were evaluated. PDK expression was also studied in the RVfib of pa...

Research paper thumbnail of Identification of novel dynamin‐related protein 1 (Drp1) GTPase inhibitors: Therapeutic potential of Drpitor1 and Drpitor1a in cancer and cardiac ischemia‐reperfusion injury

Research paper thumbnail of Clinical value of non-coding RNAs in cardiovascular, pulmonary, and muscle diseases

American Journal of Physiology-Cell Physiology, 2019

Although a majority of the mammalian genome is transcribed to RNA, mounting evidence indicates th... more Although a majority of the mammalian genome is transcribed to RNA, mounting evidence indicates that only a minor proportion of these transcriptional products are actually translated into proteins. Since the discovery of the first non-coding RNA (ncRNA) in the 1980s, the field has gone on to recognize ncRNAs as important molecular regulators of RNA activity and protein function, knowledge of which has stimulated the expansion of a scientific field that quests to understand the role of ncRNAs in cellular physiology, tissue homeostasis, and human disease. Although our knowledge of these molecules has significantly improved over the years, we have limited understanding of their precise functions, protein interacting partners, and tissue-specific activities. Adding to this complexity, it remains unknown exactly how many ncRNAs there are in existence. The increased use of high-throughput transcriptomics techniques has rapidly expanded the list of ncRNAs, which now includes classical ncRNA...

Research paper thumbnail of Ndufs2, a Core Subunit of Mitochondrial Complex I, Is Essential for Acute Oxygen-Sensing and Hypoxic Pulmonary Vasoconstriction

Circulation Research, 2019

Rationale: Hypoxic pulmonary vasoconstriction (HPV) optimizes systemic oxygen delivery by matchin... more Rationale: Hypoxic pulmonary vasoconstriction (HPV) optimizes systemic oxygen delivery by matching ventilation to perfusion. HPV is intrinsic to pulmonary artery smooth muscle cells (PASMCs). Hypoxia dilates systemic arteries, including renal arteries. Hypoxia is sensed by changes in mitochondrial-derived reactive oxygen species, notably hydrogen peroxide (H 2 O 2 ) ([H 2 O 2 ] mito ). Decreases in [H 2 O 2 ] mito elevate pulmonary vascular tone by increasing intracellular calcium ([Ca 2+ ] i ) through reduction-oxidation regulation of ion channels. Although HPV is mimicked by the Complex I inhibitor, rotenone, the molecular identity of the O 2 sensor is unknown. Objective: To determine the role of Ndufs2 (NADH [nicotinamide adenine dinucleotide] dehydrogenase [ubiquinone] iron-sulfur protein 2), Complex I’s rotenone binding site, in pulmonary vascular oxygen-sensing. Methods and Results: Mitochondria-conditioned media from pulmonary and renal mitochondria isolated from normoxic and...

Research paper thumbnail of Epigenetic Dysregulation of the Dynamin-Related Protein 1 Binding Partners MiD49 and MiD51 Increases Mitotic Mitochondrial Fission and Promotes Pulmonary Arterial Hypertension

Circulation, 2018

Background:Mitotic fission is increased in pulmonary arterial hypertension (PAH), a hyperprolifer... more Background:Mitotic fission is increased in pulmonary arterial hypertension (PAH), a hyperproliferative, apoptosis-resistant disease. The fission mediator dynamin-related protein 1 (Drp1) must complex with adaptor proteins to cause fission. Drp1-induced fission has been therapeutically targeted in experimental PAH. Here, we examine the role of 2 recently discovered, poorly understood Drp1 adapter proteins, mitochondrial dynamics protein of 49 and 51 kDa (MiD49 and MiD51), in normal vascular cells and explore their dysregulation in PAH.Methods:Immunoblots of pulmonary artery smooth muscle cells (control, n=6; PAH, n=8) and immunohistochemistry of lung sections (control, n=6; PAH, n=6) were used to assess the expression of MiD49 and MiD51. The effects of manipulating MiDs on cell proliferation, cell cycle, and apoptosis were assessed in human and rodent PAH pulmonary artery smooth muscle cells with flow cytometry. Mitochondrial fission was studied by confocal imaging. A microRNA (miR) ...

Research paper thumbnail of Oxygen-sensing in the Lung is Regulated by Mitochondrial Complex I Ndufs2: Role of Mitochondria-derived Hydrogen Peroxide in Hypoxic Pulmonary Vasoconstriction

Free Radical Biology and Medicine, Nov 1, 2017

Research paper thumbnail of Germline and Somatic Mutations in DNA Methyltransferase 3A (DNMT3A) Predispose to Pulmonary Arterial Hypertension (PAH) in Humans and Mice: Implications for Associated PAH

Research paper thumbnail of Electron Leak From the Mitochondrial Electron Transport Chain Complex I at Site I <sub>Q</sub> Is Crucial for Oxygen Sensing in Rabbit and Human Ductus Arteriosus

Journal of the American Heart Association, Jul 4, 2023

Background As partial pressure of oxygen (pO 2 ) rises with the first breath, the ductus arterios... more Background As partial pressure of oxygen (pO 2 ) rises with the first breath, the ductus arteriosus (DA) constricts, diverting blood flow to the pulmonary circulation. The DA's O 2 sensor resides within smooth muscle cells. The DA smooth muscle cells’ mitochondrial electron transport chain (ETC) produces reactive oxygen species (ROS) in proportion to oxygen tension, causing vasoconstriction by regulating redox‐sensitive ion channels and enzymes. To identify which ETC complex contributes most to DA O 2 sensing and determine whether ROS mediate O 2 sensing independent of metabolism, we used electron leak suppressors, S1QEL (suppressor of site I Q electron leak) and S3QEL (suppressor of site III Qo electron leak), which decrease ROS production by inhibiting electron leak from quinone sites I Q and III Qo , respectively. Methods and Results The effects of S1QEL, S3QEL, and ETC inhibitors (rotenone and antimycin A) on DA tone, mitochondrial metabolism, O 2 ‐induced changes in intracellular calcium, and ROS were studied in rabbit DA rings, and human and rabbit DA smooth muscle cells. S1QEL's effects on DA patency were assessed in rabbit kits, using micro computed tomography. In DA rings, S1QEL, but not S3QEL, reversed O 2 ‐induced constriction ( P =0.0034) without reducing phenylephrine‐induced constriction. S1QEL did not inhibit mitochondrial metabolism or ETC‐I activity. In human DA smooth muscle cells, S1QEL and rotenone inhibited O 2 ‐induced increases in intracellular calcium ( P =0.02 and 0.001, respectively), a surrogate for DA constriction. S1QEL inhibited O 2 ‐induced ROS generation ( P =0.02). In vivo, S1QEL prevented O 2 ‐induced DA closure ( P &lt;0.0001). Conclusions S1QEL, but not S3QEL, inhibited O 2 ‐induced rises in ROS and DA constriction ex vivo and in vivo. DA O 2 sensing relies on pO 2 ‐dependent changes in electron leak at site I Q in ETC‐I, independent of metabolism. S1QEL offers a therapeutic means to maintain DA patency.

Research paper thumbnail of Mitochondria in the Pulmonary Vasculature in Health and Disease: Oxygen‐Sensing, Metabolism, and Dynamics

Comprehensive Physiology, Mar 12, 2020

Research paper thumbnail of Novel Dynamin-Related Protein 1 GTPase Inhibitor Prevents Myocardial Ischemia-Reperfusion Injury

Research paper thumbnail of Oxygen-sensing in the Lung is Regulated by Mitochondrial Complex I Ndufs2: Role of Mitochondria-derived Hydrogen Peroxide in Hypoxic Pulmonary Vasoconstriction

Free Radical Biology and Medicine, Nov 1, 2017

Research paper thumbnail of Abstract 10715: Therapeutic Efficacy of Drpitor1a, a Novel Dynamin-Related Protein 1 (DRP1) Inhibitor, in Preclinical Pulmonary Arterial Hypertension

Circulation

Introduction: Dynamin-related protein 1 (DRP1) is a large GTPase that mediates mitotic fission (t... more Introduction: Dynamin-related protein 1 (DRP1) is a large GTPase that mediates mitotic fission (the division of mitochondria which is coordinated with mitosis, ensuring equitable distribution of mitochondria to daughter cells). In pulmonary arterial hypertension (PAH) pulmonary artery smooth muscle cells (PASMC), mitotic fission, and DRP1 activity are increased, contributing to its hyperproliferative phenotype. We investigated the therapeutic efficacy of Drpitor1a, a novel, small molecule, Drp1 GTPase inhibitor, in a rat PAH model. Methods: A single dose of monocrotaline (MCT, 60mg/kg, SC) or PBS was injected to female Sprague-Dawley rats on day 0 (n=20 for MCT and n=15 for PBS). On day 14, the development of PAH was confirmed by echocardiography and the rats were randomized for treatments. An indwelling catheter was implanted through the left jugular vein on day 15. Drpitor1a (1mg/kg) or normal saline (NS) was administered by IV every 48 hours from day 17 to day 27. Right ventricul...

Research paper thumbnail of Acquired disorders of mitochondrial metabolism and dynamics in pulmonary arterial hypertension

Frontiers in Cell and Developmental Biology, Feb 2, 2023

Pulmonary arterial hypertension (PAH) is an orphan disease of the cardiopulmonary unit that refle... more Pulmonary arterial hypertension (PAH) is an orphan disease of the cardiopulmonary unit that reflects an obstructive pulmonary vasculopathy and presents with hypertrophy, inflammation, fibrosis, and ultimately failure of the right ventricle (RVF). Despite treatment using pulmonary hypertension (PH)-targeted therapies, persistent functional impairment reduces the quality of life for people with PAH and death from RVF occurs in approximately 40% of patients within 5 years of diagnosis. PH-targeted therapeutics are primarily vasodilators and none, alone or in combination, are curative. This highlights a need to therapeutically explore molecular targets in other pathways that are involved in the pathogenesis of PAH. Several candidate pathways in PAH involve acquired mitochondrial dysfunction. These mitochondrial disorders include: 1) a shift in metabolism related to increased expression of pyruvate dehydrogenase kinase and pyruvate kinase, which together increase uncoupled glycolysis (Warburg metabolism); 2) disruption of oxygen-sensing related to increased expression of hypoxia-inducible factor 1α, resulting in a state of pseudohypoxia; 3) altered mitochondrial calcium homeostasis related to impaired function of the mitochondrial calcium uniporter complex, which elevates cytosolic calcium and reduces intramitochondrial calcium; and 4) abnormal mitochondrial dynamics related to increased expression of dynamin-related protein 1 and its binding partners, such as mitochondrial dynamics proteins of 49 kDa and 51 kDa, and depressed expression of mitofusin 2, resulting in increased mitotic fission. These acquired mitochondrial abnormalities increase proliferation and impair apoptosis in most pulmonary vascular cells (including endothelial cells, smooth muscle cells and fibroblasts). In the RV, Warburg metabolism and induction of glutaminolysis impairs bioenergetics and promotes hypokinesis, hypertrophy, and fibrosis. This review will explore our current knowledge of the causes and consequences of disordered mitochondrial function in PAH. KEYWORDS pyruvate dehydrogenase kinase (PDK), hypoxia-inducible factor 1-alpha (HIF-1α), dynaminrelated protein 1 (DRP1), mitochondrial calcium uniporter complex (MCUC), pyruvate kinase (PK), Warburg metabolism

Research paper thumbnail of SARS-CoV-2 mitochondriopathy in COVID-19 pneumonia exacerbates hypoxemia

Redox Biology

RationaleSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 pneumonia. ... more RationaleSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 pneumonia. We hypothesize that SARS-CoV-2 causes alveolar injury and hypoxemia by damaging mitochondria in airway epithelial cells (AEC) and pulmonary artery smooth muscle cells (PASMC), triggering apoptosis and bioenergetic impairment, and impairing hypoxic pulmonary vasoconstriction (HPV), respectively.ObjectivesWe examined the effects of: A) human betacoronaviruses, SARS-CoV-2 and HCoV-OC43, and individual SARS-CoV-2 proteins on apoptosis, mitochondrial fission, and bioenergetics in AEC; and B) SARS-CoV-2 proteins and mouse hepatitis virus (MHV-1) infection on HPV.MethodsWe used transcriptomic data to identify temporal changes in mitochondrial-relevant gene ontology (GO) pathways post-SARS-CoV-2 infection. We also transduced AECs with SARS-CoV-2 proteins (M, Nsp7 or Nsp9) and determined effects on mitochondrial permeability transition pore (mPTP) activity, relative membrane potential, apoptosis, mitochondrial fission, and oxygen consumption rates (OCR). In human PASMC, we assessed the effects of SARS-CoV-2 proteins on hypoxic increases in cytosolic calcium, an HPV proxy. In MHV-1 pneumonia, we assessed HPV via cardiac catheterization and apoptosis using the TUNEL assay.ResultsSARS-CoV-2 regulated mitochondrial apoptosis, mitochondrial membrane permeabilization and electron transport chain (ETC) GO pathways within 2 hours of infection. SARS-CoV-2 downregulated ETC Complex I and ATP synthase genes, and upregulated apoptosis-inducing genes. SARS-CoV-2 and HCoV-OC43 upregulated and activated dynamin-related protein 1 (Drp1) and increased mitochondrial fission. SARS-CoV-2 and transduced SARS-CoV-2 proteins increased apoptosis inducing factor (AIF) expression and activated caspase 7, resulting in apoptosis. Coronaviruses also reduced OCR, decreased ETC Complex I activity and lowered ATP levels in AEC. M protein transduction also increased mPTP opening. In human PASMC, M and Nsp9 proteins inhibited HPV. In MHV-1 pneumonia, infected AEC displayed apoptosis and HPV was suppressed. BAY K8644, a calcium channel agonist, increased HPV and improved SpO2.ConclusionsCoronaviruses, including SARS-CoV-2, cause AEC apoptosis, mitochondrial fission, and bioenergetic impairment. SARS-CoV-2 also suppresses HPV by targeting mitochondria. This mitochondriopathy is replicated by transduction with SARS-CoV-2 proteins, indicating a mechanistic role for viral-host mitochondrial protein interactions. Mitochondriopathy is a conserved feature of coronaviral pneumonia that may exacerbate hypoxemia and constitutes a therapeutic target.

Research paper thumbnail of Mitochondrial fission links ECM mechanotransduction to metabolic redox homeostasis and metastatic chemotherapy resistance

Nature Cell Biology, 2022

Metastatic breast cancer cells disseminate to organs with a soft microenvironment. Whether and ho... more Metastatic breast cancer cells disseminate to organs with a soft microenvironment. Whether and how the mechanical properties of the local tissue influence their response to treatment remains unclear. Here we found that a soft extracellular matrix empowers redox homeostasis. Cells cultured on a soft extracellular matrix display increased peri-mitochondrial F-actin, promoted by Spire1C and Arp2/3 nucleation factors, and increased DRP1- and MIEF1/2-dependent mitochondrial fission. Changes in mitochondrial dynamics lead to increased production of mitochondrial reactive oxygen species and activate the NRF2 antioxidant transcriptional response, including increased cystine uptake and glutathione metabolism. This retrograde response endows cells with resistance to oxidative stress and reactive oxygen species-dependent chemotherapy drugs. This is relevant in a mouse model of metastatic breast cancer cells dormant in the lung soft tissue, where inhibition of DRP1 and NRF2 restored cisplatin sensitivity and prevented disseminated cancer-cell awakening. We propose that targeting this mitochondrial dynamics- and redox-based mechanotransduction pathway could open avenues to prevent metastatic relapse.

Research paper thumbnail of Mitochondria in the Pulmonary Vasculature in Health and Disease: Oxygen‐Sensing, Metabolism, and Dynamics

Comprehensive Physiology, 2020

Research paper thumbnail of PINK1‐induced phosphorylation of mitofusin 2 at serine 442 causes its proteasomal degradation and promotes cell proliferation in lung cancer and pulmonary arterial hypertension

The FASEB Journal, 2021

Impaired mitochondrial fusion, due in part to decreased mitofusin 2 (Mfn2) expression, contribute... more Impaired mitochondrial fusion, due in part to decreased mitofusin 2 (Mfn2) expression, contributes to unrestricted cell proliferation and apoptosis-resistance in hyperproliferative diseases like pulmonary arterial hypertension (PAH) and non-small cell lung cancer (NSCLC). We hypothesized that Mfn2 levels are reduced due to increased proteasomal degradation of Mfn2 triggered by its phosphorylation at serine 442 (S442) and investigated the potential kinase mediators. Mfn2 expression was decreased and Mfn2 S442 phosphorylation was increased in pulmonary artery smooth muscle cells from PAH patients and in NSCLC cells. Mfn2 phosphorylation was mediated by PINK1 and protein kinase A (PKA), although only PINK1 expression was increased in these diseases. We designed a S442 phosphorylation deficient Mfn2 construct (PD-Mfn2) and a S442 constitutively phosphorylated Mfn2 construct (CP-Mfn2). The effects of these modified Mfn2 constructs on Mfn2 expression and biological function were compared with those of the wildtype Mfn2 construct (WT-Mfn2). WT-Mfn2 increased Mfn2 expression and mitochondrial fusion in both PAH and NSCLC cells resulting in increased apoptosis and decreased cell proliferation. Compared to WT-Mfn2, PD-Mfn2 caused greater Mfn2 expression, suppression of proliferation, apoptosis induction and cell cycle arrest. Conversely, CP-Mfn2 caused only a small increase in Mfn2 expression and did not restore mitochondrial fusion, inhibit cell proliferation or induce apoptosis. Silencing PINK1 or PKA, or proteasome blockade using MG132, increased Mfn2 expression, enhanced mitochondrial fusion and induced apoptosis. In a xenotransplantation NSCLC model, PD-Mfn2 gene therapy caused greater tumor regression than did therapy with WT-Mfn2. Mfn2 deficiency in PAH and NSCLC reflects proteasomal degradation triggered by Mfn2-S442 phosphorylation by PINK1 and/or PKA. Inhibiting Mfn2 phosphorylation has potential therapeutic benefit in PAH and lung cancer.

Research paper thumbnail of Excess Protein O-GlcNAcylation Links Metabolic Derangements to Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

International Journal of Molecular Sciences, 2020

The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosa... more The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosamine, which, when added to serines or threonines, modulates protein function through protein O-GlcNAcylation. Glutamine-fructose-6-phosphate amidotransferase (GFAT) regulates HBP flux, and AMP-kinase phosphorylation of GFAT blunts GFAT activity and O-GlcNAcylation. While numerous studies demonstrate increased right ventricle (RV) glucose uptake in pulmonary arterial hypertension (PAH), the relationship between O-GlcNAcylation and RV function in PAH is unexplored. Therefore, we examined how colchicine-mediated AMP-kinase activation altered HBP intermediates, O-GlcNAcylation, mitochondrial function, and RV function in pulmonary artery-banded (PAB) and monocrotaline (MCT) rats. AMPK activation induced GFAT phosphorylation and reduced HBP intermediates and O-GlcNAcylation in MCT but not PAB rats. Reduced O-GlcNAcylation partially restored the RV metabolic signature and improved RV function i...

Research paper thumbnail of Oxygen sensing, mitochondrial biology and experimental therapeutics for pulmonary hypertension and cancer

Free Radical Biology and Medicine, 2021

The homeostatic oxygen sensing system (HOSS) optimizes systemic oxygen delivery. Specialized tiss... more The homeostatic oxygen sensing system (HOSS) optimizes systemic oxygen delivery. Specialized tissues utilize a conserved mitochondrial sensor, often involving NDUFS2 in complex I of the mitochondrial electron transport chain, as a site of pO2-responsive production of reactive oxygen species (ROS). These ROS are converted to a diffusible signaling molecule, hydrogen peroxide (H2O2), by superoxide dismutase (SOD2). H2O2 exits the mitochondria and regulates ion channels and enzymes, altering plasma membrane potential, intracellular Ca2+ and Ca2+-sensitization and controlling acute, adaptive, responses to hypoxia that involve changes in ventilation, vascular tone and neurotransmitter release. Subversion of this O2-sensing pathway creates a pseudohypoxic state that promotes disease progression in pulmonary arterial hypertension (PAH) and cancer. Pseudohypoxia is a state in which biochemical changes, normally associated with hypoxia, occur despite normal pO2. Epigenetic silencing of SOD2 by DNA methylation alters H2O2 production, activating hypoxia-inducible factor 1α, thereby disrupting mitochondrial metabolism and dynamics, accelerating cell proliferation and inhibiting apoptosis. Other epigenetic mechanisms, including dysregulation of microRNAs (miR), increase pyruvate dehydrogenase kinase and pyruvate kinase muscle isoform 2 expression in both diseases, favoring uncoupled aerobic glycolysis. This Warburg metabolic shift also accelerates cell proliferation and impairs apoptosis. Disordered mitochondrial dynamics, usually increased mitotic fission and impaired fusion, promotes disease progression in PAH and cancer. Epigenetic upregulation of dynamin-related protein 1 (Drp1) and its binding partners, MiD49 and MiD51, contributes to the pathogenesis of PAH and cancer. Finally, dysregulation of intramitochondrial Ca2+, resulting from impaired mitochondrial calcium uniporter complex (MCUC) function, links abnormal mitochondrial metabolism and dynamics. MiR-mediated decreases in MCUC function reduce intramitochondrial Ca2+, promoting Warburg metabolism, whilst increasing cytosolic Ca2+, promoting fission. Epigenetically disordered mitochondrial O2-sensing, metabolism, dynamics, and Ca2+ homeostasis offer new therapeutic targets for PAH and cancer. Promoting glucose oxidation, restoring the fission/fusion balance, and restoring mitochondrial calcium regulation are promising experimental therapeutic strategies.

Research paper thumbnail of An epigenetic increase in mitochondrial fission by MiD49 and MiD51 regulates the cell cycle in cancer: Diagnostic and therapeutic implications

Research paper thumbnail of Epigenetic Metabolic Reprogramming of Right Ventricular Fibroblasts in Pulmonary Arterial Hypertension

Circulation Research, 2020

Rationale: Right ventricular (RV) fibrosis in pulmonary arterial hypertension contributes to RV f... more Rationale: Right ventricular (RV) fibrosis in pulmonary arterial hypertension contributes to RV failure. While RV fibrosis reflects changes in the function of resident RV fibroblasts (RVfib), these cells are understudied. Objective: Examine the role of mitochondrial metabolism of RVfib in RV fibrosis in human and experimental pulmonary arterial hypertension. Methods and Results: Male Sprague-Dawley rats received monocrotaline (MCT; 60 mg/kg) or saline. Drinking water containing no supplement or the PDK (pyruvate dehydrogenase kinase) inhibitor dichloroacetate was started 7 days post-MCT. At week 4, treadmill testing, echocardiography, and right heart catheterization were performed. The effects of PDK activation on mitochondrial dynamics and metabolism, RVfib proliferation, and collagen production were studied in RVfib in cell culture. Epigenetic mechanisms for persistence of the profibrotic RVfib phenotype in culture were evaluated. PDK expression was also studied in the RVfib of pa...

Research paper thumbnail of Identification of novel dynamin‐related protein 1 (Drp1) GTPase inhibitors: Therapeutic potential of Drpitor1 and Drpitor1a in cancer and cardiac ischemia‐reperfusion injury

Research paper thumbnail of Clinical value of non-coding RNAs in cardiovascular, pulmonary, and muscle diseases

American Journal of Physiology-Cell Physiology, 2019

Although a majority of the mammalian genome is transcribed to RNA, mounting evidence indicates th... more Although a majority of the mammalian genome is transcribed to RNA, mounting evidence indicates that only a minor proportion of these transcriptional products are actually translated into proteins. Since the discovery of the first non-coding RNA (ncRNA) in the 1980s, the field has gone on to recognize ncRNAs as important molecular regulators of RNA activity and protein function, knowledge of which has stimulated the expansion of a scientific field that quests to understand the role of ncRNAs in cellular physiology, tissue homeostasis, and human disease. Although our knowledge of these molecules has significantly improved over the years, we have limited understanding of their precise functions, protein interacting partners, and tissue-specific activities. Adding to this complexity, it remains unknown exactly how many ncRNAs there are in existence. The increased use of high-throughput transcriptomics techniques has rapidly expanded the list of ncRNAs, which now includes classical ncRNA...

Research paper thumbnail of Ndufs2, a Core Subunit of Mitochondrial Complex I, Is Essential for Acute Oxygen-Sensing and Hypoxic Pulmonary Vasoconstriction

Circulation Research, 2019

Rationale: Hypoxic pulmonary vasoconstriction (HPV) optimizes systemic oxygen delivery by matchin... more Rationale: Hypoxic pulmonary vasoconstriction (HPV) optimizes systemic oxygen delivery by matching ventilation to perfusion. HPV is intrinsic to pulmonary artery smooth muscle cells (PASMCs). Hypoxia dilates systemic arteries, including renal arteries. Hypoxia is sensed by changes in mitochondrial-derived reactive oxygen species, notably hydrogen peroxide (H 2 O 2 ) ([H 2 O 2 ] mito ). Decreases in [H 2 O 2 ] mito elevate pulmonary vascular tone by increasing intracellular calcium ([Ca 2+ ] i ) through reduction-oxidation regulation of ion channels. Although HPV is mimicked by the Complex I inhibitor, rotenone, the molecular identity of the O 2 sensor is unknown. Objective: To determine the role of Ndufs2 (NADH [nicotinamide adenine dinucleotide] dehydrogenase [ubiquinone] iron-sulfur protein 2), Complex I’s rotenone binding site, in pulmonary vascular oxygen-sensing. Methods and Results: Mitochondria-conditioned media from pulmonary and renal mitochondria isolated from normoxic and...

Research paper thumbnail of Epigenetic Dysregulation of the Dynamin-Related Protein 1 Binding Partners MiD49 and MiD51 Increases Mitotic Mitochondrial Fission and Promotes Pulmonary Arterial Hypertension

Circulation, 2018

Background:Mitotic fission is increased in pulmonary arterial hypertension (PAH), a hyperprolifer... more Background:Mitotic fission is increased in pulmonary arterial hypertension (PAH), a hyperproliferative, apoptosis-resistant disease. The fission mediator dynamin-related protein 1 (Drp1) must complex with adaptor proteins to cause fission. Drp1-induced fission has been therapeutically targeted in experimental PAH. Here, we examine the role of 2 recently discovered, poorly understood Drp1 adapter proteins, mitochondrial dynamics protein of 49 and 51 kDa (MiD49 and MiD51), in normal vascular cells and explore their dysregulation in PAH.Methods:Immunoblots of pulmonary artery smooth muscle cells (control, n=6; PAH, n=8) and immunohistochemistry of lung sections (control, n=6; PAH, n=6) were used to assess the expression of MiD49 and MiD51. The effects of manipulating MiDs on cell proliferation, cell cycle, and apoptosis were assessed in human and rodent PAH pulmonary artery smooth muscle cells with flow cytometry. Mitochondrial fission was studied by confocal imaging. A microRNA (miR) ...