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Ahmad D, Linares I, Pietropaoli A, Waugh RE, McGrath JL. Sided Stimulation of Endothelial Cells Modulates Neutrophil Trafficking in an In Vitro Sepsis Model. Adv Healthc Mater 2024:e2304338. [PMID: 38547536 DOI: 10.1002/adhm.202304338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 03/22/2024] [Indexed: 04/09/2024]
Abstract
While the role of dysregulated polymorphonuclear leukocyte (PMN) transmigration in septic mediated tissue damage is well documented, strategies to mitigate aberrant transmigration across endothelium have yet to yield viable therapeutics. Recently, microphysiological systems (MPS) have emerged as novel in vitro mimetics that facilitate the development of human models of disease. With this advancement, aspects of endothelial physiology that are difficult to assess with other models can be directly probed. In this study, the role of endothelial cell (EC) apicobasal polarity on leukocyte trafficking response is evaluated with the µSiM-MVM (microphysiological system enabled by a silicon membrane - microvascular mimetic). Here, ECs are stimulated either apically or basally with a cytokine cocktail to model a septic-like challenge before introducing healthy donor PMNs into the device. Basally oriented stimulation generated a stronger PMN transmigratory response versus apical stimulation. Importantly, healthy PMNs are unable to migrate towards a bacterial peptide chemoattractant when ECs are apically stimulated, which mimics the attenuated PMN chemotaxis seen in sepsis. Escalating the apical inflammatory stimulus by a factor of five is necessary to elicit high PMN transmigration levels across endothelium. These results demonstrate that EC apicobasal polarity modulates PMN transmigratory behavior and provides insight into the mechanisms underlying sepsis.
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Affiliation(s)
- Danial Ahmad
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - Isabelle Linares
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - Anthony Pietropaoli
- Department of Medicine, Pulmonary Diseases and Critical Care at the University of Rochester, Rochester, NY, 14627, USA
| | - Richard E Waugh
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - James L McGrath
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
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2
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Coavoy-Sanchez SA, da Costa Marques LA, Costa SKP, Muscara MN. Role of Gasotransmitters in Inflammatory Edema. Antioxid Redox Signal 2024; 40:272-291. [PMID: 36974358 DOI: 10.1089/ars.2022.0089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Significance: Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are, to date, the identified members of the gasotransmitter family, which consists of gaseous signaling molecules that play central roles in the regulation of a wide variety of physiological and pathophysiological processes, including inflammatory edema. Recent Advances: Recent studies show the potential anti-inflammatory and antiedematogenic effects of NO-, CO-, and H2S-donors in vivo. In general, it has been observed that the therapeutical effects of NO-donors are more relevant when administered at low doses at the onset of the inflammatory process. Regarding CO-donors, their antiedematogenic effects are mainly associated with inhibition of proinflammatory mediators (such as inducible NO synthase [iNOS]-derived NO), and the observed protective effects of H2S-donors seem to be mediated by reducing some proinflammatory enzyme activities. Critical Issues: The most recent investigations focus on the interactions among the gasotransmitters under different pathophysiological conditions. However, the biochemical/pharmacological nature of these interactions is neither general nor fully understood, although specifically dependent on the site where the inflammatory edema occurs. Future Directions: Considering the nature of the involved mechanisms, a deeper knowledge of the interactions among the gasotransmitters is mandatory. In addition, the development of new pharmacological tools, either donors or synthesis inhibitors of the three gasotransmitters, will certainly aid the basic investigations and open new strategies for the therapeutic treatment of inflammatory edema. Antioxid. Redox Signal. 40, 272-291.
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Affiliation(s)
| | | | - Soraia Katia Pereira Costa
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
| | - Marcelo Nicolas Muscara
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
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3
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Aguilar G, Koning T, Ehrenfeld P, Sánchez FA. Role of NO and S-nitrosylation in the Expression of Endothelial Adhesion Proteins That Regulate Leukocyte and Tumor Cell Adhesion. Front Physiol 2020; 11:595526. [PMID: 33281627 PMCID: PMC7691576 DOI: 10.3389/fphys.2020.595526] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 10/20/2020] [Indexed: 12/11/2022] Open
Abstract
Leukocyte recruitment is one of the most important cellular responses to tissue damage. Leukocyte extravasation is exquisitely regulated by mechanisms of selective leukocyte-endothelium recognition through adhesion proteins in the endothelial cell surface that recognize specific integrins in the activated leukocytes. A similar mechanism is used by tumor cells during metastasis to extravasate and form a secondary tumor. Nitric oxide (NO) has been classically described as an anti-inflammatory molecule that inhibits leukocyte adhesion. However, the evidence available shows also a positive role of NO in leukocyte adhesion. These apparent discrepancies might be explained by the different NO concentrations reached during the inflammatory response, which are highly modulated by the expression of different nitric oxide synthases, along the inflammatory response and by changes in their subcellular locations.
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Affiliation(s)
- Gaynor Aguilar
- Instituto de Inmunología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile
| | - Tania Koning
- Instituto de Inmunología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile
| | - Pamela Ehrenfeld
- Instituto de Anatomía, Histología y Patología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile.,Centro Interdisciplinario de Estudios del Sistema Nervioso, Universidad Austral de Chile, Valdivia, Chile
| | - Fabiola A Sánchez
- Instituto de Inmunología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile.,Centro Interdisciplinario de Estudios del Sistema Nervioso, Universidad Austral de Chile, Valdivia, Chile
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4
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Wang L, Mehta S, Ahmed Y, Wallace S, Pape MC, Gill SE. Differential Mechanisms of Septic Human Pulmonary Microvascular Endothelial Cell Barrier Dysfunction Depending on the Presence of Neutrophils. Front Immunol 2018; 9:1743. [PMID: 30116240 PMCID: PMC6082932 DOI: 10.3389/fimmu.2018.01743] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 07/16/2018] [Indexed: 01/06/2023] Open
Abstract
Sepsis is characterized by injury of pulmonary microvascular endothelial cells (PMVEC) leading to barrier dysfunction. Multiple mechanisms promote septic PMVEC barrier dysfunction, including interaction with circulating leukocytes and PMVEC apoptotic death. Our previous work demonstrated a strong correlation between septic neutrophil (PMN)-dependent PMVEC apoptosis and pulmonary microvascular albumin leak in septic mice in vivo; however, this remains uncertain in human PMVEC. Thus, we hypothesize that human PMVEC apoptosis is required for loss of PMVEC barrier function under septic conditions in vitro. To assess this hypothesis, human PMVECs cultured alone or in coculture with PMN were stimulated with PBS or cytomix (equimolar interferon γ, tumor necrosis factor α, and interleukin 1β) in the absence or presence of a pan-caspase inhibitor, Q-VD, or specific caspase inhibitors. PMVEC barrier function was assessed by transendothelial electrical resistance (TEER), as well as fluoroisothiocyanate-labeled dextran and Evans blue-labeled albumin flux across PMVEC monolayers. PMVEC apoptosis was identified by (1) loss of cell membrane polarity (Annexin V), (2) caspase activation (FLICA), and (3) DNA fragmentation [terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)]. Septic stimulation of human PMVECs cultured alone resulted in loss of barrier function (decreased TEER and increased macromolecular flux) associated with increased apoptosis (increased Annexin V, FLICA, and TUNEL staining). In addition, treatment of septic PMVEC cultured alone with Q-VD decreased PMVEC apoptosis and prevented septic PMVEC barrier dysfunction. In septic PMN-PMVEC cocultures, there was greater trans-PMVEC macromolecular flux (both dextran and albumin) vs. PMVEC cultured alone. PMN presence also augmented septic PMVEC caspase activation (FLICA staining) vs. PMVEC cultured alone but did not affect septic PMVEC apoptosis. Importantly, pan-caspase inhibition (Q-VD treatment) completely attenuated septic PMN-dependent PMVEC barrier dysfunction. Moreover, inhibition of caspase 3, 8, or 9 in PMN-PMVEC cocultures also reduced septic PMVEC barrier dysfunction whereas inhibition of caspase 1 had no effect. Our data demonstrate that human PMVEC barrier dysfunction under septic conditions in vitro (cytomix stimulation) is clearly caspase-dependent, but the mechanism differs depending on the presence of PMN. In isolated PMVEC, apoptosis contributes to septic barrier dysfunction, whereas PMN presence enhances caspase-dependent septic PMVEC barrier dysfunction independently of PMVEC apoptosis.
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Affiliation(s)
- Lefeng Wang
- Centre for Critical Illness Research, Lawson Health Research Institute, London, ON, Canada.,Department of Medicine, Western University, London, ON, Canada
| | - Sanjay Mehta
- Centre for Critical Illness Research, Lawson Health Research Institute, London, ON, Canada.,Department of Medicine, Western University, London, ON, Canada.,Division of Respirology, Western University, London, ON, Canada
| | - Yousuf Ahmed
- Centre for Critical Illness Research, Lawson Health Research Institute, London, ON, Canada.,Department of Medicine, Western University, London, ON, Canada
| | - Shelby Wallace
- Department of Physiology and Pharmacology, Western University, London, ON, Canada
| | - M Cynthia Pape
- Centre for Critical Illness Research, Lawson Health Research Institute, London, ON, Canada.,Department of Medicine, Western University, London, ON, Canada
| | - Sean E Gill
- Centre for Critical Illness Research, Lawson Health Research Institute, London, ON, Canada.,Department of Medicine, Western University, London, ON, Canada.,Division of Respirology, Western University, London, ON, Canada.,Department of Physiology and Pharmacology, Western University, London, ON, Canada
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5
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Li JT, Wang WQ, Wang L, Liu NN, Zhao YL, Zhu XS, Liu QQ, Gao CF, Yang AG, Jia LT. Subanesthetic isoflurane relieves zymosan-induced neutrophil inflammatory response by targeting NMDA glutamate receptor and Toll-like receptor 2 signaling. Oncotarget 2017; 7:31772-89. [PMID: 27144523 PMCID: PMC5077975 DOI: 10.18632/oncotarget.9091] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 04/18/2016] [Indexed: 01/13/2023] Open
Abstract
Neutrophil release of NO/ONOO− induces endothelial cell barrier dysfunction in inflammatory acute lung injury (ALI). Previous studies using zymosan-triggered inflammation and ALI model revealed that zymosan promotes inducible NO synthase (iNOS) expression in neutrophils, and that isoflurane inhibits zymosan-induced oxidative stress and iNOS biosynthesis. However, the underlying mechanisms remain largely unknown. We found here that in zymosan-primed neutrophils, iNOS is transcriptionally activated by NF-κB, whose nuclear translocation is triggered by excessive reactive oxygen species (ROS) and consequently activated p38 MAPK. ROS production is attributed to zymosan-initiated Toll-like receptor 2 (TLR2) signaling, in which the adaptor MyD88 recruits and activates c-Src, and c-Src activates NADPH oxidase to generate ROS. Subanesthetic isoflurane counteracts the aforementioned zymosan-induced signaling by targeting N-methyl-D-aspartic acid (NMDA) glutamate receptor and thereby suppressing calcium influx and c-Src activation. Whereas iNOS accelerates NO/ONOO− production in neutrophils which eventually promote protein leak from pulmonary microvascular endothelial cells (PMVEC), isoflurane reduced NO/ONOO− release from zymosan-treated neutrophils, and thus relieves trans- PMVEC protein leak. This study provides novel insights into the roles of neutrophils and the underlying mechanisms in zymosan-induced ALI, and has implications for the therapeutic potential of subanesthetic isoflurane in attenuating inflammatory responses causing lung endothelial cell damage.
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Affiliation(s)
- Jun-Tang Li
- Centre of Inflammation and Cancer Research, 150th Central Hospital of PLA, Luoyang, Henan, China.,State Key Laboratory of Cancer Biology, Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China.,State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Wei-Qi Wang
- State Key Laboratory of Military Stomatology, Department of Oral and Maxillofacial Surgery, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | | | - Ning-Ning Liu
- Centre of Inflammation and Cancer Research, 150th Central Hospital of PLA, Luoyang, Henan, China
| | - Ya-Li Zhao
- Centre of Inflammation and Cancer Research, 150th Central Hospital of PLA, Luoyang, Henan, China
| | - Xiao-Shan Zhu
- Centre of Inflammation and Cancer Research, 150th Central Hospital of PLA, Luoyang, Henan, China
| | - Qin-Qin Liu
- Centre of Inflammation and Cancer Research, 150th Central Hospital of PLA, Luoyang, Henan, China
| | - Chun-Fang Gao
- Centre of Inflammation and Cancer Research, 150th Central Hospital of PLA, Luoyang, Henan, China
| | - An-Gang Yang
- State Key Laboratory of Cancer Biology, Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Lin-Tao Jia
- State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, Shaanxi, China
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6
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Inhibition of Murine Pulmonary Microvascular Endothelial Cell Apoptosis Promotes Recovery of Barrier Function under Septic Conditions. Mediators Inflamm 2017; 2017:3415380. [PMID: 28250575 PMCID: PMC5303866 DOI: 10.1155/2017/3415380] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/25/2016] [Accepted: 12/20/2016] [Indexed: 12/13/2022] Open
Abstract
Sepsis is characterized by injury of the pulmonary microvasculature and the pulmonary microvascular endothelial cells (PMVEC), leading to barrier dysfunction and acute respiratory distress syndrome (ARDS). Our recent work identified a strong correlation between PMVEC apoptosis and microvascular leak in septic mice in vivo, but the specific role of apoptosis in septic PMVEC barrier dysfunction remains unclear. Thus, we hypothesize that PMVEC apoptosis is likely required for PMVEC barrier dysfunction under septic conditions in vitro. Septic stimulation (mixture of tumour necrosis factor α, interleukin 1β, and interferon γ [cytomix]) of isolated murine PMVEC resulted in a significant loss of barrier function as early as 4 h after stimulation, which persisted until 24 h. PMVEC apoptosis, as reflected by caspase activation, DNA fragmentation, and loss of membrane polarity, was first apparent at 8 h after cytomix. Pretreatment of PMVEC with the pan-caspase inhibitor Q-VD significantly decreased septic PMVEC apoptosis and was associated with reestablishment of PMVEC barrier function at 16 and 24 h after stimulation but had no effect on septic PMVEC barrier dysfunction over the first 8 h. Collectively, our data suggest that early septic murine PMVEC barrier dysfunction driven by proinflammatory cytokines is not mediated through apoptosis, but PMVEC apoptosis contributes to late septic PMVEC barrier dysfunction.
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7
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Arpino V, Mehta S, Wang L, Bird R, Rohan M, Pape C, Gill SE. Tissue inhibitor of metalloproteinases 3-dependent microvascular endothelial cell barrier function is disrupted under septic conditions. Am J Physiol Heart Circ Physiol 2016; 310:H1455-67. [PMID: 26993226 DOI: 10.1152/ajpheart.00796.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 03/13/2016] [Indexed: 11/22/2022]
Abstract
Sepsis is associated with dysfunction of microvascular endothelial cells (MVEC) leading to tissue edema and multiple organ dysfunction. Metalloproteinases can regulate MVEC function through processing of cell surface proteins, and tissue inhibitor of metalloproteinases 3 (TIMP3) regulates metalloproteinase activity in the lung following injury. We hypothesize that TIMP3 promotes normal pulmonary MVEC barrier function through inhibition of metalloproteinase activity. Naive Timp3(-/-) mice had significantly higher basal pulmonary microvascular Evans blue (EB) dye-labeled albumin leak vs. wild-type (WT) mice. Additionally, cecal-ligation/perforation (CLP)-induced sepsis significantly increased pulmonary microvascular EB-labeled albumin leak in WT but not Timp3(-/-) mice. Similarly, PBS-treated isolated MVEC monolayers from Timp3(-/-) mice displayed permeability barrier dysfunction vs. WT MVEC, evidenced by lower transendothelial electrical resistance and greater trans-MVEC flux of fluorescein-dextran and EB-albumin. Cytomix (equimolar interferon γ, tumor necrosis factor α, and interleukin 1β) treatment of WT MVEC induced significant barrier dysfunction (by all three methods), and was associated with a time-dependent decrease in TIMP3 mRNA and protein levels. Additionally, basal Timp3(-/-) MVEC barrier dysfunction was associated with disrupted MVEC surface VE-cadherin localization, and both barrier dysfunction and VE-cadherin localization were rescued by treatment with GM6001, a synthetic metalloproteinase inhibitor. TIMP3 promotes normal MVEC barrier function, at least partially, through inhibition of metalloproteinase-dependent disruption of adherens junctions, and septic downregulation of TIMP3 may contribute to septic MVEC barrier dysfunction.
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Affiliation(s)
- Valerie Arpino
- Centre for Critical Illness Research, Lawson Health Research Institute, London, Ontario, Canada; Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Sanjay Mehta
- Centre for Critical Illness Research, Lawson Health Research Institute, London, Ontario, Canada; Division of Respirology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; and
| | - Lefeng Wang
- Centre for Critical Illness Research, Lawson Health Research Institute, London, Ontario, Canada; Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; and
| | - Ryan Bird
- Centre for Critical Illness Research, Lawson Health Research Institute, London, Ontario, Canada; Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; and
| | - Marta Rohan
- Centre for Critical Illness Research, Lawson Health Research Institute, London, Ontario, Canada
| | - Cynthia Pape
- Centre for Critical Illness Research, Lawson Health Research Institute, London, Ontario, Canada; Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; and
| | - Sean E Gill
- Centre for Critical Illness Research, Lawson Health Research Institute, London, Ontario, Canada; Division of Respirology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; and Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
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8
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Khakpour S, Wilhelmsen K, Hellman J. Vascular endothelial cell Toll-like receptor pathways in sepsis. Innate Immun 2015; 21:827-46. [DOI: 10.1177/1753425915606525] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 08/11/2015] [Indexed: 12/20/2022] Open
Abstract
The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.
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Affiliation(s)
- Samira Khakpour
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA, USA
- Biomedical Sciences and Immunology Programs, University of California, San Francisco, CA, USA
| | - Kevin Wilhelmsen
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA, USA
| | - Judith Hellman
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA, USA
- Biomedical Sciences and Immunology Programs, University of California, San Francisco, CA, USA
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9
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Gill SE, Rohan M, Mehta S. Role of pulmonary microvascular endothelial cell apoptosis in murine sepsis-induced lung injury in vivo. Respir Res 2015; 16:109. [PMID: 26376777 PMCID: PMC4574190 DOI: 10.1186/s12931-015-0266-7] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 08/24/2015] [Indexed: 02/07/2023] Open
Abstract
Background Sepsis remains a common and serious condition with significant morbidity and mortality due to multiple organ dysfunction, especially acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Sepsis-induced ALI is characterized by injury and dysfunction of the pulmonary microvasculature and pulmonary microvascular endothelial cells (PMVEC), resulting in enhanced pulmonary microvascular sequestration and pulmonary infiltration of polymorphonuclear leukocytes (PMN) as well as disruption of the normal alveolo-capillary permeability barrier with leak of albumin-rich edema fluid into pulmonary interstitium and alveoli. The role of PMVEC death and specifically apoptosis in septic pulmonary microvascular dysfunction in vivo has not been established. Methods In a murine cecal ligation/perforation (CLP) model of sepsis, we quantified and correlated time-dependent changes in pulmonary microvascular Evans blue (EB)-labeled albumin permeability with (1) PMVEC death (propidium iodide [PI]-staining) by both fluorescent intravital videomicroscopy (IVVM) and histology, and (2) PMVEC apoptosis using histologic fluorescent microscopic assessment of a panel of 3 markers: cell surface phosphatidylserine (detected by Annexin V binding), caspase activation (detected by FLIVO labeling), and DNA fragmentation (TUNEL labeling). Results Compared to sham mice, CLP-sepsis resulted in pulmonary microvascular barrier dysfunction, quantified by increased EB-albumin leak, and PMVEC death (PI+ staining) as early as 2 h and more marked by 4 h after CLP. Septic PMVEC also exhibited increased presence of all 3 markers of apoptosis (Annexin V+, FLIVO+, TUNEL+) as early as 30 mins – 1 h after CLP-sepsis, which all similarly increased markedly until 4 h. The time-dependent changes in septic pulmonary microvascular albumin-permeability barrier dysfunction were highly correlated with PMVEC death (PI+; r = 0.976, p < 0.01) and PMVEC apoptosis (FLIVO+; r = 0.991, p < 0.01). Treatment with the pan-caspase inhibitor Q-VD prior to CLP reduced PMVEC death/apoptosis and attenuated septic pulmonary microvascular dysfunction, including both albumin-permeability barrier dysfunction and pulmonary microvascular PMN sequestration (p < 0.05). Septic PMVEC apoptosis and pulmonary microvascular dysfunction were also abrogated following CLP-sepsis in mice deficient in iNOS (Nos2−/−) or NADPH oxidase (p47phox−/− or gp91phox−/−) and in wild-type mice treated with the NADPH oxidase inhibitor, apocynin. Conclusions Septic murine pulmonary microvascular dysfunction in vivo is due to PMVEC death, which is mediated through caspase-dependent apoptosis and iNOS/NADPH-oxidase dependent signaling.
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Affiliation(s)
- Sean E Gill
- Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, ON, Canada.,Division of Respirology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.,Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Marta Rohan
- Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, ON, Canada
| | - Sanjay Mehta
- Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, ON, Canada. .,Division of Respirology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. .,Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. .,Division of Respirology, E6.204, London Health Sciences Center - Victoria Hospital, 800 Commissioners Road East, London, ON, N6A 5W9, Canada.
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10
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Gill SE, Taneja R, Rohan M, Wang L, Mehta S. Pulmonary microvascular albumin leak is associated with endothelial cell death in murine sepsis-induced lung injury in vivo. PLoS One 2014; 9:e88501. [PMID: 24516666 PMCID: PMC3917898 DOI: 10.1371/journal.pone.0088501] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 01/10/2014] [Indexed: 11/19/2022] Open
Abstract
Sepsis is a systemic inflammatory response that targets multiple components of the cardiovascular system including the microvasculature. Microvascular endothelial cells (MVEC) are central to normal microvascular function, including maintenance of the microvascular permeability barrier. Microvascular/MVEC dysfunction during sepsis is associated with barrier dysfunction, resulting in the leak of protein-rich edema fluid into organs, especially the lung. The specific role of MVEC apoptosis in septic microvascular/MVEC dysfunction in vivo remains to be determined. To examine pulmonary MVEC death in vivo under septic conditions, we used a murine cecal ligation/perforation (CLP) model of sepsis and identified non-viable pulmonary cells with propidium iodide (PI) by intravital videomicroscopy (IVVM), and confirmed this by histology. Septic pulmonary microvascular Evans blue (EB)-labeled albumin leak was associated with an increased number of PI-positive cells, which were confirmed to be predominantly MVEC based on specific labeling with three markers, anti-CD31 (PECAM), anti-CD34, and lectin binding. Furthermore, this septic death of pulmonary MVEC was markedly attenuated by cyclophosphamide-mediated depletion of neutrophils (PMN) or use of an anti-CD18 antibody developed for immunohistochemistry but shown to block CD18-dependent signaling. Additionally, septic pulmonary MVEC death was iNOS-dependent as mice lacking iNOS had markedly fewer PI-positive MVEC. Septic PI-positive pulmonary cell death was confirmed to be due to apoptosis by three independent markers: caspase activation by FLIVO, translocation of phosphatidylserine to the cell surface by Annexin V binding, and DNA fragmentation by TUNEL. Collectively, these findings indicate that septic pulmonary MVEC death, putatively apoptosis, is a result of leukocyte activation and iNOS-dependent signaling, and in turn, may contribute to pulmonary microvascular barrier dysfunction and albumin hyper-permeability during sepsis.
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Affiliation(s)
- Sean E. Gill
- Pulmonary Inflammation, Injury, and Repair Lab (PIIRL), Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Division of Respirology, Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Ravi Taneja
- Pulmonary Inflammation, Injury, and Repair Lab (PIIRL), Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Department of Critical Care Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
- Department of Anesthesia and Perioperative Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Marta Rohan
- Pulmonary Inflammation, Injury, and Repair Lab (PIIRL), Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
| | - Lefeng Wang
- Pulmonary Inflammation, Injury, and Repair Lab (PIIRL), Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
| | - Sanjay Mehta
- Pulmonary Inflammation, Injury, and Repair Lab (PIIRL), Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Division of Respirology, Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
- * E-mail:
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11
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Wang L, Taneja R, Wang W, Yao LJ, Veldhuizen RAW, Gill SE, Fortin D, Inculet R, Malthaner R, Mehta S. Human alveolar epithelial cells attenuate pulmonary microvascular endothelial cell permeability under septic conditions. PLoS One 2013; 8:e55311. [PMID: 23393568 PMCID: PMC3564849 DOI: 10.1371/journal.pone.0055311] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 12/21/2012] [Indexed: 01/11/2023] Open
Abstract
Acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), are characterised by high-protein pulmonary edema and severe hypoxaemic respiratory failure due to increased permeability of pulmonary microvascular endothelial cells (PMVEC). Alveolar epithelial cells (AEC) contribute importantly to normal alveolar function, and AEC dysfunction in ALI/ARDS is associated with worse outcomes. We hypothesized that AEC can modulate human PMVEC barrier function, and investigated the effects of AEC presence on human PMVEC barrier under septic conditions in vitro. PMVEC isolated from human lung were treated in vitro with septic stimulation (lipopolysaccharide [LPS], a mixture of clinically-relevant cytokines [cytomix], or plasma from patients with severe sepsis), and the trans-PMVEC leak of Evans Blue dye-labeled albumin assessed. PMVEC septic responses were compared in the presence/absence of co-cultured A549 epithelial cell line or primary human AEC. Septic stimulation with LPS, cytomix, or septic plasma induced marked PMVEC hyper-permeability (10.2±1.8, 8.9±2.2, and 3.7±0.2 fold-increase vs. control, respectively, p<0.01 for all). The presence of A549 cells or primary human AEC in a non-contact co-culture model attenuated septic PMVEC hyper-permeability by 39±4% to 100±3%, depending on the septic stimulation (p<0.05). Septic PMVEC hyper-permeability was also attenuated following treatment with culture medium conditioned by previous incubation with either naïve or cytomix-treated A549 cells (p<0.05), and this protective effect of A549 cell-conditioned medium was both heat-stable and transferable following lipid extraction. Cytomix-stimulated PMN-dependent PMVEC hyper-permeability and trans-PMVEC PMN migration were also inhibited in the presence of A549 cells or A549 cell-conditioned medium (p<0.05). Human AEC appear to protect human PMVEC barrier function under septic conditions in vitro, through release of a soluble mediator(s), which are at least partly lipid in nature. This study suggests a scientific and potential clinical therapeutic importance of epithelial-endothelial cross talk in maintaining alveolar integrity in ALI/ARDS.
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Affiliation(s)
- Lefeng Wang
- Centre for Critical Illness Research, Division of Respirology, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Department of Medicine, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Ravi Taneja
- Centre for Critical Illness Research, Division of Respirology, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Department of Anesthesia, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
- Department of Critical Care Medicine, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Wei Wang
- Centre for Critical Illness Research, Division of Respirology, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Department of Medicine, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Li-Juan Yao
- Centre for Critical Illness Research, Division of Respirology, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
| | - Ruud A. W. Veldhuizen
- Centre for Critical Illness Research, Division of Respirology, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Department of Medicine, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Sean E. Gill
- Centre for Critical Illness Research, Division of Respirology, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Department of Medicine, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Dalilah Fortin
- Department of Critical Care Medicine, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
- Department of Thoracic Surgery, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Richard Inculet
- Department of Thoracic Surgery, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Richard Malthaner
- Department of Thoracic Surgery, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Sanjay Mehta
- Centre for Critical Illness Research, Division of Respirology, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada
- Department of Medicine, Schulich Faculty of Medicine and Dentistry, Western University, London, Ontario, Canada
- * E-mail:
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Hossain M, Qadri SM, Liu L. Inhibition of nitric oxide synthesis enhances leukocyte rolling and adhesion in human microvasculature. JOURNAL OF INFLAMMATION-LONDON 2012; 9:28. [PMID: 22812684 PMCID: PMC3414823 DOI: 10.1186/1476-9255-9-28] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/19/2012] [Indexed: 02/08/2023]
Abstract
Background Nitric oxide (NO) is a multifunctional signaling molecule that regulates important cellular events in inflammation including leukocyte recruitment. Previous studies have shown that pharmacological inhibition of NO synthesis induces leukocyte recruitment in various in vitro and animal models. However, it is not known whether NO modulation has similar effects on leukocyte-endothelial cell interactions within the human microvasculature. The present study explored the effect of systemic L-NAME treatment on leukocyte recruitment in the SCID-hu mouse model. Methods Human skin xenografts were transplanted in SCID mice to study human leukocyte dynamics in human vasculature. Early events of human leukocyte recruitment in human vasculature were studied using intravital microscopy. NO synthesis was pharmacologically inhibited using NG-nitro-L-arginine methyl ester (L-NAME). Immunohistochemical analysis was performed to elucidate E-selectin expression in human xenograft skin. Human neutrophil-endothelial cell interactions were also studied in an in vitro flow chamber assay system. P- and E-selectin expression on cultured human umbilical vein endothelial cells (HUVECs) was measured using ELISA. Platelet-activating factor (PAF) synthesis was detected using a TLC-based assay. Results L-NAME treatment significantly enhanced the rolling and adhesion of human leukocytes to the human vasculature. Functional blocking of P- and E-selectins significantly inhibited rolling but not adhesion induced by inhibition of NO synthesis. Systemic L-NAME treatment enhanced E-selectin expression in human xenograft skin. L-NAME treatment significantly enhanced P- and E-selectin expression on HUVECs. L-NAME treatment did not significantly modify neutrophil rolling or adhesion to HUVECs indicating that L-NAME−induced subtle P- and E-selectin expression was insufficient to elicit dynamic neutrophil-HUVEC interactions in vitro. Moreover, synthesis of endothelial-derived PAF was not significantly modified by L-NAME treatment. These results point to the accelerated leukocyte recruitment in human vasculature following suppression of NO synthesis, effects that are mediated by P- and E-selectins. The findings are, however, not supported by the in vitro data. Conclusion Inhibition of endogenous NO triggers early events of human leukocyte recruitment in human vasculature, involving complex cellular or molecular mechanisms in addition to P- and E-selectin-mediated leukocyte rolling.
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Affiliation(s)
- Mokarram Hossain
- Department of Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK, S7N 5E5, Canada.
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13
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Specific Role of Neutrophil Inducible Nitric Oxide Synthase in Murine Sepsis-Induced Lung Injury In Vivo. Shock 2012; 37:539-47. [DOI: 10.1097/shk.0b013e31824dcb5a] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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14
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Takabe W, Warabi E, Noguchi N. Anti-atherogenic effect of laminar shear stress via Nrf2 activation. Antioxid Redox Signal 2011; 15:1415-26. [PMID: 21126170 DOI: 10.1089/ars.2010.3433] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Fluid shear stress plays a critical role in the regulation of vascular biology and its pathology, such as atherosclerosis, via modulation of redox balance. Both pro-atherogenic (either oscillatory or turbulent, nonunidirectional) shear stress and anti-atherogenic (either steady or pulsatile, unidirectional laminar) shear stress stimulate production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) that are involved in signal transduction of gene expression. Nonunidirectional shear stress induces pro-atherogenic genes encoding adhesion molecules and chemokines in a manner dependent on production of both superoxide and nitric oxide. Steady or pulsatile laminar shear stress induces expression of genes encoding cytoprotective enzymes for glutathione biosynthesis and detoxification, which are regulated by the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). We show that pulsatile laminar shear stress (PLSS)-induced expression of adhesion molecules and chemokines was enhanced in human umbilical vein endothelial cells (HUVEC) treated with Nrf2 siRNA and arterial endothelial cells isolated from Nrf2 knockout mice. Hence, we propose the hypothesis that PLSS maintains the endothelium in an anti-atherogenic state via intracellular antioxidant levels increased as a result of Nrf2 activation, thereby preventing excess ROS/RNS production required for pro-atherogenic gene expression.
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Affiliation(s)
- Wakako Takabe
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
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Shah SK, Jimenez F, Walker PA, Xue H, Feeley TD, Uray KS, Norbury KC, Stewart RH, Laine GA, Cox CS. Peritoneal fluid: a potential mechanism of systemic neutrophil priming in experimental intra-abdominal sepsis. Am J Surg 2011; 203:211-6. [PMID: 21679918 DOI: 10.1016/j.amjsurg.2010.12.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 12/03/2010] [Accepted: 12/03/2010] [Indexed: 11/25/2022]
Abstract
BACKGROUND Recent studies suggest that peritoneal fluid (PF) may be an important mediator of inflammation. The aim of this study was to test the hypothesis that PF may drive systemic inflammation in intra-abdominal sepsis by representing a priming agent for neutrophils. METHODS PF was collected 12 hours after the initiation of intra-abdominal sepsis in swine. Naive human neutrophils were primed with PF before treatment with N-formyl-Met-Leu-Phe or phorbol 12-myristate 13-acetate to elucidate receptor-dependent and receptor-independent mechanisms of neutrophil activation. Flow cytometry was used to quantify neutrophil surface adhesion marker expression of integrins and selectins and superoxide anion production. Additionally, proinflammatory cytokines were quantified in PF. RESULTS PF primed neutrophils via receptor-dependent and receptor-independent mechanisms. There were significant increases in the proinflammatory cytokines interleukin-6 and tumor necrosis factor-α in PF correlating with the development of intra-abdominal sepsis. CONCLUSIONS PF represents a priming agent for naive polymorphonuclear cells in intra-abdominal sepsis. This may be secondary to increased levels of proinflammatory cytokines. Strategies to reduce the amount of PF may decrease the systemic inflammatory response by reducing a priming agent for neutrophils.
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Affiliation(s)
- Shinil K Shah
- Departments of Pediatric Surgery and Surgery, University of Texas Medical School at Houston, USA
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L-arginine enhances nitrative stress and exacerbates tumor necrosis factor-alpha toxicity to human endothelial cells in culture: prevention by propofol. J Cardiovasc Pharmacol 2010; 55:358-67. [PMID: 20125033 DOI: 10.1097/fjc.0b013e3181d265a3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Supplementation of L-arginine, a nitric oxide precursor, during the late phase of myocardial ischemia/reperfusion increases myocyte apoptosis and exacerbates myocardial injury, but the underlying mechanism is unclear. During myocardial ischemia/reperfusion, apoptosis of endothelial cells precedes that of cardiomyocyte. Tumor necrosis factor-alpha (TNF) production is increased during myocardial ischemia/reperfusion, which may exacerbate myocardial injury by inducing endothelial cell apoptosis. We postulated that L-arginine may exacerbate TNF-induced endothelial cell apoptosis by enhancing peroxynitrite-mediated nitrative stress. Cultured human umbilical vein endothelial cells were either not treated (control) or treated with TNF alone or with TNF in the presence of L-arginine, the nonselective nitric oxide synthase inhibitor N (omega)-nitro-L-arginine (L-NNA), propofol (an anesthetic that scavenges peroxynitrite), or L-arginine plus propofol, respectively, for 24 hours. TNF increased intracellular superoxide and hydrogen peroxide production accompanied by increases of inducible nitric oxide synthase (iNOS) protein expression and nitric oxide production. This was accompanied by increased protein expression of nitrotyrosine, a fingerprint of peroxynitrite and an index of nitrative stress, and increased endothelial cell apoptosis. L-arginine did not enhance TNF-induced increases of superoxide and peroxynitrite production but further increased TNF-induced increase of nitrotyrosine production and exacerbated TNF-mediated cell apoptosis. L-NNA and propofol, respectively, reduced TNF-induced nitrative stress and attenuated TNF cellular toxicity. The L-arginine-mediated enhancement of nitrative stress and TNF toxicity was attenuated by propofol. Thus, under pathological conditions associated with increased TNF production, L-arginine supplementation may further exacerbate TNF cellular toxicity by enhancing nitrative stress.
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Shah SK, Jimenez F, Walker PA, Aroom KR, Xue H, Feeley TD, Uray KS, Norbury KC, Stewart RH, Laine GA, Cox CS. A novel mechanism for neutrophil priming in trauma: potential role of peritoneal fluid. Surgery 2010; 148:263-70. [PMID: 20466401 DOI: 10.1016/j.surg.2010.03.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Accepted: 03/25/2010] [Indexed: 12/24/2022]
Abstract
BACKGROUND We sought to determine the effect of peritoneal fluid from a novel animal model of abdominal compartment syndrome (ACS) on the proinflammatory status of polymorphonuclear leukocytes (PMNs) and monocytes. We hypothesize that peritoneal fluid is a potential priming and/or activating agent for PMNs/monocytes. METHODS ACS was induced in female Yorkshire swine, and peritoneal fluid was collected at the time of decompressive laparotomy. Naïve PMNs/monocytes were primed and/or activated with peritoneal fluid, phosphatidylcholine (PAF) plus peritoneal fluid, peritoneal fluid plus n-formyl-met-leu-phe (fMLP), and peritoneal fluid plus phorbol 12-myristate 13-acetate (PMA). Activation was determined by surface marker expression of integrins (CD11b an CD18) and selectins (CD62L). Additionally, proinflammatory cytokines in peritoneal fluid were analyzed. RESULTS Peritoneal fluid did not activate PMNs but increased CD11b expression on monocytes. When used as a primer for fMLP- or PMA-induced activation, peritoneal fluid significantly increased CD11b and CD18 expression on PMNs and monocytes. Peritoneal fluid collected at 6 and 12 h post decompressive laparotomy had similar effects. Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) levels were increased in peritoneal fluid. CONCLUSION Peritoneal fluid represents a primer for PMNs/monocytes and seems to act through receptor-dependent and receptor-independent pathways. Strategies to reduce the amount of peritoneal fluid may decrease the locoregional and systemic inflammatory response by reducing priming and activation of neutrophils/monocytes.
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Affiliation(s)
- Shinil K Shah
- Department of Pediatric Surgery, University of Texas Medical School at Houston, Houston, TX 77030, USA
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