Anantha Harijith

University of Illinois at Chicago, Chicago, Illinois, United States

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Publications (9)39.92 Total impact

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    ABSTRACT: Rationale: Lysocardiolipin acyltransferase (LYCAT), a cardiolipin-remodeling enzyme regulating the 18:2 linoleic acid pattern of mammalian mitochondrial cardiolipin, is necessary for maintaining normal mitochondrial function and vascular development. We hypothesized that modulation of LYCAT expression in lung epithelium regulates development of pulmonary fibrosis. Objectives: To define a role LYCAT in human and murine models pulmonary fibrosis. Methods: We analyzed the correlation of LYCAT expression in peripheral blood mononuclear cells (PBMCs) with the outcomes of pulmonary functions and overall survival, and used the murine models to establish the role of LYCAT in fibrogenesis. We studied the LYCAT action on cardiolipin remodeling, mitochondrial ROS generation, and apoptosis of alveolar epithelial cells under bleomycin challenge. Measurements and Main Results: LYCAT expression was significantly altered in PBMCs and lung tissues from IPF patients, which was confirmed in two preclinical murine models of IPF, bleomycin- and radiation-induced pulmonary fibrosis. LYCAT mRNA expression in PBMCs directly and significantly correlated with carbon monoxide diffusion capacity (DLCO), pulmonary function outcomes, and overall survival. In both bleomycin- and radiation-induced pulmonary fibrosis murine models, hLYCAT over-expression reduced several indices of lung fibrosis whereas, down-regulation of native LYCAT expression by siRNA accentuated fibrogenesis. In vitro studies demonstrated that LYCAT modulated bleomycin-induced cardiolipin remodeling, mitochondrial membrane potential, ROS generation, and apoptosis of alveolar epithelial cells, potential mechanisms of LYCAT-mediated lung protection. Conclusions: This study is the first to identify modulation of LYCAT expression in fibrotic lungs and offers a novel therapeutic approach for ameliorating lung inflammation and pulmonary fibrosis.
    Am J Respir Crit Care Med. 04/2014;
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    ABSTRACT: Rationale: Lysocardiolipin acyltransferase (LYCAT), a cardiolipin-remodeling enzyme regulating the 18:2 linoleic acid pattern of mammalian mitochondrial cardiolipin, is necessary for maintaining normal mitochondrial function and vascular development. We hypothesized that modulation of LYCAT expression in lung epithelium regulates development of pulmonary fibrosis. Objectives: To define a role LYCAT in human and murine models pulmonary fibrosis. Methods: We analyzed the correlation of LYCAT expression in peripheral blood mononuclear cells (PBMCs) with the outcomes of pulmonary functions and overall survival, and used the murine models to establish the role of LYCAT in fibrogenesis. We studied the LYCAT action on cardiolipin remodeling, mitochondrial ROS generation, and apoptosis of alveolar epithelial cells under bleomycin challenge. Measurements and Main Results: LYCAT expression was significantly altered in PBMCs and lung tissues from IPF patients, which was confirmed in two preclinical murine models of IPF, bleomycin- and radiation-induced pulmonary fibrosis. LYCAT mRNA expression in PBMCs directly and significantly correlated with carbon monoxide diffusion capacity (DLCO), pulmonary function outcomes, and overall survival. In both bleomycin- and radiation-induced pulmonary fibrosis murine models, hLYCAT over-expression reduced several indices of lung fibrosis whereas, down-regulation of native LYCAT expression by siRNA accentuated fibrogenesis. In vitro studies demonstrated that LYCAT modulated bleomycin-induced cardiolipin remodeling, mitochondrial membrane potential, ROS generation, and apoptosis of alveolar epithelial cells, potential mechanisms of LYCAT-mediated lung protection. Conclusions: This study is the first to identify modulation of LYCAT expression in fibrotic lungs and offers a novel therapeutic approach for ameliorating lung inflammation and pulmonary fibrosis.
    American Journal of Respiratory and Critical Care Medicine 04/2014; · 11.04 Impact Factor
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    ABSTRACT: Bronchopulmonary dysplasia of the premature newborn is characterized by lung injury, resulting in alveolar simplification and reduced pulmonary function. Exposure of neonatal mice to hyperoxia enhanced sphingosine-1-phosphate (S1P) levels in lung tissues; however, the role of increased S1P in the pathobiological characteristics of bronchopulmonary dysplasia has not been investigated. We hypothesized that an altered S1P signaling axis, in part, is responsible for neonatal lung injury leading to bronchopulmonary dysplasia. To validate this hypothesis, newborn wild-type, sphingosine kinase1(-/-) (Sphk1(-/-)), sphingosine kinase 2(-/-) (Sphk2(-/-)), and S1P lyase(+/-) (Sgpl1(+/-)) mice were exposed to hyperoxia (75%) from postnatal day 1 to 7. Sphk1(-/-), but not Sphk2(-/-) or Sgpl1(+/-), mice offered protection against hyperoxia-induced lung injury, with improved alveolarization and alveolar integrity compared with wild type. Furthermore, SphK1 deficiency attenuated hyperoxia-induced accumulation of IL-6 in bronchoalveolar lavage fluids and NADPH oxidase (NOX) 2 and NOX4 protein expression in lung tissue. In vitro experiments using human lung microvascular endothelial cells showed that exogenous S1P stimulated intracellular reactive oxygen species (ROS) generation, whereas SphK1 siRNA, or inhibitor against SphK1, attenuated hyperoxia-induced S1P generation. Knockdown of NOX2 and NOX4, using specific siRNA, reduced both basal and S1P-induced ROS formation. These results suggest an important role for SphK1-mediated S1P signaling-regulated ROS in the development of hyperoxia-induced lung injury in a murine neonatal model of bronchopulmonary dysplasia.
    American Journal Of Pathology 08/2013; · 4.60 Impact Factor
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    ABSTRACT: Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by alveolar epithelial cell injury, accumulation of fibroblasts/myofibroblasts and deposition of extracellular matrix proteins. Lysophosphatidic acid (LPA) signaling through its G protein-coupled receptors is critical for its various biological functions. Recently, LPA and LPA receptor 1 (LPA1) were implicated in lung fibrogenesis; however, the role of other LPA receptors in fibrosis is unclear. Here, we use the bleomycin induced pulmonary fibrosis model to investigate the roles of LPA2 in pulmonary fibrogenesis. In the current study, we found that LPA2 knockout (Lpar2-/-) mice were protected against bleomycin-induced lung injury, fibrosis and mortality compared to their wild type controls. Furthermore, LPA2 deficiency attenuated bleomycin-induced expression of fibronectin (FN), α-smooth muscle actin (α-SMA) and collagen in lung tissue, as well as levels of IL-6, transforming growth factor-β (TGF-β), and total protein in bronchoalveolar lavage (BAL) fluids. In human lung fibroblasts, knock down of LPA2 attenuated LPA-induced expression of TGF-β1, and differentiation of lung fibroblasts to myofibroblasts resulting in decreased expression of FN, α-SMA and collagen, as well as decreased activation of ERK1/2, Akt, Smad3 and p38 MAPK. Moreover, knock down of LPA2 with siRNA also mitigated TGF-β1-induced differentiation of lung fibroblasts. Additionally, LPA2 deficiency significantly attenuated bleomycin-induced apoptosis of alveolar and bronchial epithelial cells in the mouse lung. Together, our data indicated that knock-down of LPA2 attenuated bleomycin-induced lung injury and pulmonary fibrosis, and this may be related to inhibition of LPA induced expression of TGF-β and activation and differentiation of fibroblasts.
    American Journal of Respiratory Cell and Molecular Biology 06/2013; · 4.15 Impact Factor
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    ABSTRACT: Rationale: We noted a marked increase in cyclooxygenase 2 (Cox2) and activation of the ER stress pathway in newborn (NB) murine lung on exposure to hyperoxia and IFNγ. Objective: To evaluate Cox2-mediated ER stress pathway activation in hyperoxia-induced and IFNγ- mediated injury in developing lungs. Methods: In vivo genetic gain-of-function and genetic/chemical inhibition as well as in vitro loss-of-function genetic strategies. Measurements and Main Results: Hyperoxia-induced and IFNγ-mediated impaired alveolarization was rescued by Cox2 inhibition using celecoxib. Use of siRNA against the ER stress pathway mediator, C/EBP homologous protein or CHOP (also known as growth arrest and DNA-damage-inducible gene 153/GADD153), alleviated cell death in alveolar epithelial cells as well as hyperoxia-induced and IFNγ-mediated murine models of BPD. In addition, CHOP siRNA also restored alveolarization in the in vivo models. Furthermore, as evidence of clinical relevance, we show increased levels of Cox2 and ER stress pathway mediators in human lungs with BPD. Conclusions: Cox2, via CHOP, may significantly contribute to the final common pathway of hyperoxia-induced and IFNγ- mediated injury in developing lungs and human BPD.
    American Journal of Respiratory Cell and Molecular Biology 03/2013; · 4.15 Impact Factor
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    ABSTRACT: Coronins are a highly conserved family of actin binding proteins that regulate actin-dependent processes such as cell motility and endocytosis. We found that treatment of human pulmonary artery endothelial cells (HPAECs) with the bioactive lipid, sphingosine-1-phosphate (S1P) rapidly stimulates coronin 1B translocation to lamellipodia at the cell leading edge, which is required for S1P-induced chemotaxis. Further, S1P-induced chemotaxis of HPAECs was attenuated by pretreatment with small interfering RNA (siRNA) targeting coronin 1B (∼36%), PLD2 (∼45%) or Rac1 (∼50%) compared to scrambled siRNA controls. Down regulation PLD2 expression by siRNA also attenuated S1P-induced coronin 1B translocation to the leading edge of the cell periphery while PLD1 silencing had no effect. Also, S1P-induced coronin 1B redistribution to cell periphery and chemotaxis was attenuated by inhibition of Rac1 and over-expression of dominant negative PKC δ, ε and ζ isoforms in HPAECs. These results demonstrate that S1P activation of PLD2, PKC and Rac1 is part of the signaling cascade that regulates coronin 1B translocation to the cell periphery and the ensuing cell chemotaxis.
    PLoS ONE 01/2013; 8(5):e63007. · 3.53 Impact Factor
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    ABSTRACT: Supplemental oxygen is frequently prescribed. However, prolonged exposure to high concentrations of oxygen causes hyperoxic acute lung injury (HALI), which manifests as acute respiratory distress syndrome in adults and leads to bronchopulmonary dysplasia in newborns (NBs). Nitric oxide (NO), NO synthases (NOSs), and angiopoietin (Ang) 2 have been implicated in the pathogenesis of HALI. However, the mechanisms of the contributions of NOS/NO and the relationship(s) between NOS/NO and Ang2 have not been addressed. In addition, the relevance of these moieties in adults and NBs has not been evaluated. To address these issues, we compared the responses in hyperoxia of wild-type (NOS [+/+]) and NOS null (-/-) young adult and NB mice. When compared with NOS2(+/+) adult controls, NOS2(-/-) animals manifest exaggerated alveolar-capillary protein leak and premature death. These responses were associated with enhanced levels of structural cell death, enhanced expression of proapoptotic regulatory proteins, and Ang2. Importantly, silencing RNA knockdown of Ang2 decreased the levels of cell death and the expression of proapoptotic mediators. These effects were at least partially NOS2 specific, and were development dependent, because survival was similar in adult NOS3(+/+) and NOS3(-/-) mice and NB NOS2(+/+) and NOS2(-/-) mice, respectively. These studies demonstrate that NOS2 plays an important protective role in HALI in adult animals. They also demonstrate that this response is mediated, at least in part, by the ability of NOS2 to inhibit hyperoxia-induced Ang2 production and thereby decrease Ang2-induced tissue injury.
    American Journal of Respiratory Cell and Molecular Biology 01/2012; 46(5):668-76. · 4.15 Impact Factor
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    ABSTRACT: Supplemental oxygen is frequently prescribed. However, prolonged exposure to high concentrations of oxygen causes hyperoxic acute lung injury (HALI) which manifests as acute respiratory distress syndrome in adults and leads to bronchopulmonary dysplasia in newborns. Nitric oxide (NO), nitric oxide synthases (NOS) and Angiopoietin 2 (Ang2) have been implicated in the pathogenesis of HALI. However, the mechanisms of the contributions of NOS/NO and the relationship(s) between NOS/NO and Ang2 have not been addressed. In addition, the relevance of these moieties in adults and newborns has not been evaluated. To address these issues, we compared the responses in hyperoxia of wild type (NOS (+/+)) and NOS null (-/-) young adult and newborn mice. When compared to NOS2(+/+) adult controls, NOS2(-/-) animals manifest exaggerated alveolar-capillary protein leak and premature death. These responses were associated with enhanced levels of structural cell death, enhanced expression of pro-apoptotic regulatory proteins and Ang2. Importantly, siRNA knockdown of Ang2 decreased the levels of cell death, and the expression of pro-apoptotic mediators. These effects were at least partially NOS2-specific and were development dependent because survival was similar in adult NOS3(+/+), NOS3(-/-) mice and newborn NOS2(+/+) and NOS2(-/-) mice, respectively. These studies demonstrate that NOS2 plays an important protective role in HALI in adult animals. They also demonstrate that this response is mediated, at least in part, by the ability of NOS2 to inhibit hyperoxia-induced Ang2 production and thereby decrease Ang2-induced tissue injury.
    American Journal of Respiratory Cell and Molecular Biology 01/2012; · 4.15 Impact Factor
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    ABSTRACT: We noted a marked increase in IFNγ mRNA in newborn (NB) murine lungs after exposure to hyperoxia. We sought to evaluate the role of IFNγ in lung injury in newborns. Using a unique triple-transgenic (TTG), IFNγ-overexpressing, lung-targeted, externally regulatable NB murine model, we describe a lung phenotype of impaired alveolarization, resembling human bronchopulmonary dysplasia (BPD). IFNγ-mediated abnormal lung architecture was associated with increased cell death and the upregulation of cell death pathway mediators caspases 3, 6, 8, and 9, and angiopoietin 2. Moreover, an increase was evident in cathepsins B, H, K, L, and S, and in matrix metalloproteinases (MMPs) 2, 9, 12, and 14. The IFNγ-mediated abnormal lung architecture was found to be MMP9-dependent, as indicated by the rescue of the IFNγ-induced pulmonary phenotype and survival during hyperoxia with a concomitant partial deficiency of MMP9. This result was concomitant with a decrease in caspases 3, 6, 8, and 9 and angiopoietin 2, but an increase in the expression of angiopoietin 1. In addition, NB IFNγ TTG mice exhibited significantly decreased survival during hyperoxia, compared with littermate controls. Furthermore, as evidence of clinical relevance, we show increased concentrations of the downstream targets of IFNγ chemokine (C-X-C motif) ligands (CXCL10 and CXCL11) in baboon and human lungs with BPD. IFNγ and its downstream targets may contribute significantly to the final common pathway of hyperoxia-induced injury in the developing lung and in human BPD.
    American Journal of Respiratory Cell and Molecular Biology 01/2011; 44(5):621-30. · 4.15 Impact Factor