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Aslesh T, Al-aghbari A, Yokota T. Assessing the Role of Aquaporin 4 in Skeletal Muscle Function. Int J Mol Sci 2023; 24:ijms24021489. [PMID: 36675000 PMCID: PMC9865462 DOI: 10.3390/ijms24021489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/09/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023] Open
Abstract
Water transport across the biological membranes is mediated by aquaporins (AQPs). AQP4 and AQP1 are the predominantly expressed AQPs in the skeletal muscle. Since the discovery of AQP4, several studies have highlighted reduced AQP4 levels in Duchenne muscular dystrophy (DMD) patients and mouse models, and other neuromuscular disorders (NMDs) such as sarcoglycanopathies and dysferlinopathies. AQP4 loss is attributed to the destabilizing dystrophin-associated protein complex (DAPC) in DMD leading to compromised water permeability in the skeletal muscle fibers. However, AQP4 knockout (KO) mice appear phenotypically normal. AQP4 ablation does not impair physical activity in mice but limits them from achieving the performance demonstrated by wild-type mice. AQP1 levels were found to be upregulated in DMD models and are thought to compensate for AQP4 loss. Several groups investigated the expression of other AQPs in the skeletal muscle; however, these findings remain controversial. In this review, we summarize the role of AQP4 with respect to skeletal muscle function and findings in NMDs as well as the implications from a clinical perspective.
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Affiliation(s)
- Tejal Aslesh
- Neuroscience and Mental Health Institute, Faculty of Medicine and Dentistry, University of Alberta, 116 St. and 85 Ave., Edmonton, AB T6G 2E1, Canada
| | - Ammar Al-aghbari
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, 116 St. and 85 Ave., Edmonton, AB T6G 2E1, Canada
| | - Toshifumi Yokota
- Neuroscience and Mental Health Institute, Faculty of Medicine and Dentistry, University of Alberta, 116 St. and 85 Ave., Edmonton, AB T6G 2E1, Canada
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, 116 St. and 85 Ave., Edmonton, AB T6G 2E1, Canada
- The Friends of Garret Cumming Research and Muscular Dystrophy Canada HM Toupin Neurological Science Research Chair, 8812 112 St., Edmonton, AB T6G 2H7, Canada
- Correspondence: ; Tel.: +1-(780)-492-1102
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2
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Wang Q, Li Y, Wu C, Wang T, Wu M. Aquaporin-1 inhibition exacerbates ischemia-reperfusion-induced lung injury in mouse. Am J Med Sci 2023; 365:84-92. [PMID: 36075463 DOI: 10.1016/j.amjms.2022.08.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Revised: 06/18/2022] [Accepted: 08/29/2022] [Indexed: 01/04/2023]
Abstract
BACKGROUND Ischemia-reperfusion injury (IRI), which involves severe inflammation and edema, is an inevitable feature of the lung transplantation process and leads to primary graft dysfunction (PGD). The activation of aquaporin 1 (AQP1) modulates fluid transport in the alveolar space. The current study investigated the role of AQP1 in ischemia-reperfusion (IR)-induced lung injury. METHODS A mouse model of lung IR was established by clamping the left lung hilar for 1 h and released for reperfusion for 24 h. The AQP1 inhibitor acetazolamide (AZA) was administered 3 days before lung ischemia with a dose of 100 mg/kg per day via gavage. Lung injury was evaluated using the ratio of wet-to-dry weight, peripheral bronchial epithelial thickness, degree of angioedema, acute lung injury score, neutrophil infiltration, and cytokine concentrations in bronchoalveolar lavage fluid. RESULTS Compared with sham treatment, ischemia with no reperfusion (IR 0h) and ischemia with reperfusion for 24 h (IR 24 h) significantly upregulated AQP1 expression, increased the wet/dry weight ratio, angioedema, neutrophil infiltration and cytokine production (interleukin -6 and tumor necrosis factor -α) and thickened the peripheral bronchial epithelium. AZA exacerbated inflammation and pulmonary edema. CONCLUSION AQP1 may exert a protective effect against IR-induced lung injury, which could be attributed to alleviating pulmonary edema and inflammation. AQP1 upregulation might be a potential application to alleviate lung IRI and decrease the incidence of PGD.
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Affiliation(s)
- Qi Wang
- Department of Thoracic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Yangfan Li
- Department of Thoracic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Chuanqiang Wu
- Department of Thoracic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China
| | - Tong Wang
- Department of Pharmacology, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Ming Wu
- Department of Thoracic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, China; Key Laboratory of The Diagnosis and Treatment of Severe Trauma and Burn of Zhejiang Province, Hangzhou, Zhejiang 310009, China.
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3
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Wang L, Wang J, Zhu X, Bai C, Song Y. Aquaporins in Respiratory System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:137-144. [PMID: 36717491 DOI: 10.1007/978-981-19-7415-1_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Aquaporins (AQPs) are water channel proteins facilitating fluid transport in alveolar space, airway humidification, pleural fluid absorption, and submucosal gland secretion. In this chapter, we mainly focus on the expression of four AQPs in the lungs, which include AQP1, AQP2, AQP4, and AQP5 in normal and disease status, and the experience of AQPs function from various model and transgenic mice were summarized in detail to improve our understanding of the role of AQPs in fluid balance of respiratory system. It has been suggested that AQPs play important roles in various physiology and pathophysiology conditions of different lung diseases. There still remains unclear the exact role of AQPs in lung diseases, and thus continuous efforts on elucidating the roles of AQPs in lung physiological and pathophysiological processes are warranted.
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Affiliation(s)
- Linlin Wang
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Jian Wang
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xiaodan Zhu
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Chunxue Bai
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Yuanlin Song
- Department of Pulmonary Medicine, Zhongshan Hospital, Fudan University, Shanghai, China.
- Shanghai Key Laboratory of Lung Inflammation and Injury, Shanghai, China.
- Shanghai Institute of Infectious Disease and Biosecurity, Shanghai, China.
- Shanghai Respiratory Research Institute, Shanghai, China.
- National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China.
- Jinshan Hospital of Fudan University, Shanghai, China.
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4
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Li X, Yang B. Non-Transport Functions of Aquaporins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:65-80. [PMID: 36717487 DOI: 10.1007/978-981-19-7415-1_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Although it has been more than 20 years since the first aquaporin was discovered, the specific functions of many aquaporins are still under investigation, because various mice lacking aquaporins have no significant phenotypes. And in many studies, the function of aquaporin is not directly related to its transport function. Therefore, this chapter will focus on some unexpected functions of aquaporins, such the decreased tumor angiogenesis in AQP1 knockout mice, and AQP1 promotes cell migration, possibly by accelerating the water transport in lamellipodia of migrating cells. AQP transports glycerol, and water regulates glycerol content in epidermis and fat, thereby regulating skin hydration/biosynthesis and fat metabolism. AQPs may also be involved in neural signal transduction, cell volume regulation, and organelle physiology. AQP1, AQP3, and AQP5 are also involved in cell proliferation. In addition, AQPs have also been reported to play roles in inflammation in various tissues and organs. The functions of these AQPs may not depend on the permeability of small molecules such as water and glycerol, suggesting AQPs may play more roles in different biological processes in the body.
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Affiliation(s)
- Xiaowei Li
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China
| | - Baoxue Yang
- School of Basic Medical Sciences, Peking University, Beijing, China.
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5
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Zong HF, Guo G, Liu J, Yang CZ, Bao LL. Influence of Alveolar Fluid on Aquaporins and Na+/K+-ATPase and Its Possible Theoretical or Clinical Significance. Am J Perinatol 2022; 29:1586-1595. [PMID: 33611784 DOI: 10.1055/s-0041-1724001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
OBJECTIVE Pulmonary edema is the most common pathophysiological change in pulmonary disease. Aquaporins (AQPs) and Na+/K+-ATPase play pivotal roles in alveolar fluid clearance. This study aimed to explore the influence of increased alveolar fluid on the absorption of lung fluid. STUDY DESIGN Eighty New Zealand rabbits were randomly divided into eight groups (n = 10 in each group), and models of different alveolar fluid contents were established by the infusion of different volumes of normal saline (NS) via the endotracheal tube. Five animals in each group were sacrificed immediately after infusion to determine the wet/dry ratio, while the remaining animals in each group were killed 4 hours later to determine the wet/dry ratio at 4 hours. Additionally, lung specimens were collected from each group, and quantitative real-time PCR (qRT-PCR), western blot, and immunohistochemical (IHC) analyses of AQPs and Na+/K+-ATPase were performed. RESULTS The qRT-PCR analysis and western blot studies showed markedly decreased mRNA and protein levels of AQP1 and Na+/K+-ATPase when the alveolar fluid volume was ≥6 mL/kg, and the mRNA level of AQP5 was significantly reduced when the alveolar fluid volume was ≥4 mL/kg. In addition, IHC analysis showed the same results. At 4 hours, the lung wet/dry ratio was significantly increased when the alveolar fluid volume was ≥6 mL/kg; however, compared with 0 hours after NS infusion, there was still a significant absorption of alveolar fluid for a period of 4 hours. CONCLUSION The results of this study suggest that increased alveolar fluid may induce the downregulation of the mRNA and protein expression of AQPs and Na+/K+-ATPase, which appear to affect alveolar fluid clearance in rabbit lungs. Early intervention is required to avoid excessive alveolar fluid accumulation. KEY POINTS · The expression levels of AQPs and Na+/K+--ATPase were significantly decreased as alveolar fluid increased.. · At 4 hours, wet/dry ratio was significantly increased when infusion volume was ≥ 6 mL/kg.. · Early intervention is required to avoid excessive alveolar fluid accumulation..
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Affiliation(s)
- Hai-Feng Zong
- Neonatal Intensive Care Unit, Southern Medical University, Affiliated Shenzhen Maternity & Child Healthcare Hospital, Shenzhen, China
- Department of Neonatology and NICU, Beijing Chaoyang District Maternal and Child Healthcare Hospital, Beijing, China
| | - Guo Guo
- Department of Neonatology and NICU, Beijing Chaoyang District Maternal and Child Healthcare Hospital, Beijing, China
- Department of Pediatrics, Medical School of Chinese PLA, Beijing, China
- Department of Neonatology, The Fifth Medical Center of the PLA General Hospital, Beijing, China
| | - Jing Liu
- Department of Neonatology and NICU, Beijing Chaoyang District Maternal and Child Healthcare Hospital, Beijing, China
| | - Chuan-Zhong Yang
- Neonatal Intensive Care Unit, Southern Medical University, Affiliated Shenzhen Maternity & Child Healthcare Hospital, Shenzhen, China
| | - Lin-Lin Bao
- Department of Dermatology, Shenzhen People's Hospital, Shenzhen, China
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6
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Keskinidou C, Vassiliou AG, Dimopoulou I, Kotanidou A, Orfanos SE. Mechanistic Understanding of Lung Inflammation: Recent Advances and Emerging Techniques. J Inflamm Res 2022; 15:3501-3546. [PMID: 35734098 PMCID: PMC9207257 DOI: 10.2147/jir.s282695] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 05/04/2022] [Indexed: 12/12/2022] Open
Abstract
Acute respiratory distress syndrome (ARDS) is a life-threatening lung injury characterized by an acute inflammatory response in the lung parenchyma. Hence, it is considered as the most appropriate clinical syndrome to study pathogenic mechanisms of lung inflammation. ARDS is associated with increased morbidity and mortality in the intensive care unit (ICU), while no effective pharmacological treatment exists. It is very important therefore to fully characterize the underlying pathobiology and the related mechanisms, in order to develop novel therapeutic approaches. In vivo and in vitro models are important pre-clinical tools in biological and medical research in the mechanistic and pathological understanding of the majority of diseases. In this review, we will present data from selected experimental models of lung injury/acute lung inflammation, which have been based on clinical disorders that can lead to the development of ARDS and related inflammatory lung processes in humans, including ventilation-induced lung injury (VILI), sepsis, ischemia/reperfusion, smoke, acid aspiration, radiation, transfusion-related acute lung injury (TRALI), influenza, Streptococcus (S.) pneumoniae and coronaviruses infection. Data from the corresponding clinical conditions will also be presented. The mechanisms related to lung inflammation that will be covered are oxidative stress, neutrophil extracellular traps, mitogen-activated protein kinase (MAPK) pathways, surfactant, and water and ion channels. Finally, we will present a brief overview of emerging techniques in the field of omics research that have been applied to ARDS research, encompassing genomics, transcriptomics, proteomics, and metabolomics, which may recognize factors to help stratify ICU patients at risk, predict their prognosis, and possibly, serve as more specific therapeutic targets.
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Affiliation(s)
- Chrysi Keskinidou
- First Department of Critical Care Medicine and Pulmonary Services, School of Medicine, National and Kapodistrian University of Athens, "Evangelismos" Hospital, Athens, Greece
| | - Alice G Vassiliou
- First Department of Critical Care Medicine and Pulmonary Services, School of Medicine, National and Kapodistrian University of Athens, "Evangelismos" Hospital, Athens, Greece
| | - Ioanna Dimopoulou
- First Department of Critical Care Medicine and Pulmonary Services, School of Medicine, National and Kapodistrian University of Athens, "Evangelismos" Hospital, Athens, Greece
| | - Anastasia Kotanidou
- First Department of Critical Care Medicine and Pulmonary Services, School of Medicine, National and Kapodistrian University of Athens, "Evangelismos" Hospital, Athens, Greece
| | - Stylianos E Orfanos
- First Department of Critical Care Medicine and Pulmonary Services, School of Medicine, National and Kapodistrian University of Athens, "Evangelismos" Hospital, Athens, Greece
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7
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Clarke-Bland CE, Bill RM, Devitt A. Emerging roles for AQP in mammalian extracellular vesicles. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183826. [PMID: 34843700 PMCID: PMC8755917 DOI: 10.1016/j.bbamem.2021.183826] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 11/18/2021] [Accepted: 11/19/2021] [Indexed: 12/13/2022]
Abstract
Recent research in the aquaporin (AQP) field has identified a role for diverse AQPs in extracellular vesicles (EV). Though still in its infancy, there is a growing body of knowledge in the area; AQPs in EV have been suggested as biomarkers for disease, as drug targets and show potential as therapeutics. To advance further in this field, AQPs in EV must be better understood. Here we summarize current knowledge of the presence and function of AQPs in EV and hypothesise their roles in health and disease.
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Affiliation(s)
| | - Roslyn M Bill
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Andrew Devitt
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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8
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Lin G, Chen L, Lin L, Lin H, Guo Z, Xu Y, Hu C, Fu J, Lin Q, Chen W, Zeng Y, Xu Y. Comprehensive Analysis of Aquaporin Superfamily in Lung Adenocarcinoma. Front Mol Biosci 2021; 8:736367. [PMID: 34708074 PMCID: PMC8542973 DOI: 10.3389/fmolb.2021.736367] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 08/25/2021] [Indexed: 12/25/2022] Open
Abstract
Background: Lung adenocarcinoma (LUAD) is the most predomintnt lung cancer subtype with increasing morbidity and mortality. Previous studies have shown that aquaporin (AQP) family genes were correlated with tumor progression and metastasis in several kinds of malignancies. However, their biological behaviors and prognostic values in LUAD have not been comprehensively elucidated. Methods: RNA sequencing and real-time reverse transcription PCR (RT-PCR) were used to assess AQP1/3/4/5 gene expressions in LUAD patients using GEPIA and UALCAN databases. And then Kaplan–Meier analysis, cBioPortal, Metascape, GeneMANIA, TISIDB, and TIMER were utilized to determine the prognostic value, mutation frequency, and immune cell infiltration of AQP family members in LUAD. Results: We found that AQP3 expression was significantly elevated and AQP1 expression was markedly reduced in LUAD patients, whereas the expression levels of AQP4 and AQP5 exhibited no significant changes. The Kaplan–Meier survival analysis indicated that the higher expressions of AQP1/4/5 were related to longer overall survival (OS). Of interest, AQP3 was significantly correlated with the clinical tumor stage and lower AQP3 expression showed favorable prognosis in stage I LUAD patients, which indicated that AQP3 may be a potential prognostic biomarker for patients. Through functional enrichment analysis, the functions of these four AQPs genes were mainly involved in the passive transport by aquaporins, water homeostasis, and protein tetramerization. Moreover, AQP1/3/4/5 expression was strongly associated with tumor-infiltrating lymphocytes (TILs) in LUAD. Conclusion: AQP3 can be used as a prognosis and survival biomarker for stage I LUAD. These findings may provide novel insights into developing molecular targeted therapies in LUAD.
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Affiliation(s)
- Guofu Lin
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China.,The Second Clinical College, Fujian Medical University, Fuzhou, China
| | - Luyang Chen
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China.,The Second Clinical College, Fujian Medical University, Fuzhou, China
| | - Lanlan Lin
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China.,The Second Clinical College, Fujian Medical University, Fuzhou, China
| | - Hai Lin
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China.,The Second Clinical College, Fujian Medical University, Fuzhou, China
| | - Zhifeng Guo
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China.,The Second Clinical College, Fujian Medical University, Fuzhou, China
| | - Yingxuan Xu
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China.,The Second Clinical College, Fujian Medical University, Fuzhou, China
| | - Chanchan Hu
- Department of Epidemiology and Health Statistics, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou, China
| | - Jinglan Fu
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China
| | - Qinhui Lin
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China
| | - Wenhan Chen
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China.,The Second Clinical College, Fujian Medical University, Fuzhou, China
| | - Yiming Zeng
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China
| | - Yuan Xu
- Department of Respiratory Pulmonary and Critical Care Medicine, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.,Respiratory Medicine Center of Fujian Province, Quanzhou, China
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9
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Weidenfeld S, Chupin C, Langner DI, Zetoun T, Rozowsky S, Kuebler WM. Sodium-coupled neutral amino acid transporter SNAT2 counteracts cardiogenic pulmonary edema by driving alveolar fluid clearance. Am J Physiol Lung Cell Mol Physiol 2021; 320:L486-L497. [PMID: 33439101 DOI: 10.1152/ajplung.00461.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The constant transport of ions across the alveolar epithelial barrier regulates alveolar fluid homeostasis. Dysregulation or inhibition of Na+ transport causes fluid accumulation in the distal airspaces resulting in impaired gas exchange and respiratory failure. Previous studies have primarily focused on the critical role of amiloride-sensitive epithelial sodium channel (ENaC) in alveolar fluid clearance (AFC), yet activation of ENaC failed to attenuate pulmonary edema in clinical trials. Since 40% of AFC is amiloride-insensitive, Na+ channels/transporters other than ENaC such as Na+-coupled neutral amino acid transporters (SNATs) may provide novel therapeutic targets. Here, we identified a key role for SNAT2 (SLC38A2) in AFC and pulmonary edema resolution. In isolated perfused mouse and rat lungs, pharmacological inhibition of SNATs by HgCl2 and α-methylaminoisobutyric acid (MeAIB) impaired AFC. Quantitative RT-PCR identified SNAT2 as the highest expressed System A transporter in pulmonary epithelial cells. Pharmacological inhibition or siRNA-mediated knockdown of SNAT2 reduced transport of l-alanine across pulmonary epithelial cells. Homozygous Slc38a2-/- mice were subviable and died shortly after birth with severe cyanosis. Isolated lungs of Slc38a2+/- mice developed higher wet-to-dry weight ratios (W/D) as compared to wild type (WT) in response to hydrostatic stress. Similarly, W/D ratios were increased in Slc38a2+/- mice as compared to controls in an acid-induced lung injury model. Our results identify SNAT2 as a functional transporter for Na+ and neutral amino acids in pulmonary epithelial cells with a relevant role in AFC and the resolution of lung edema. Activation of SNAT2 may provide a new therapeutic strategy to counteract and/or reverse pulmonary edema.
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Affiliation(s)
- Sarah Weidenfeld
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada.,Institute of Physiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Cécile Chupin
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
| | | | - Tamador Zetoun
- Institute of Physiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Simon Rozowsky
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Wolfgang M Kuebler
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Institute of Physiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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10
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Mariajoseph-Antony LF, Kannan A, Panneerselvam A, Loganathan C, Anbarasu K, Prahalathan C. Could aquaporin modulators be employed as prospective drugs for COVID-19 related pulmonary comorbidity? Med Hypotheses 2020; 143:110201. [PMID: 33017909 PMCID: PMC7430244 DOI: 10.1016/j.mehy.2020.110201] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 08/15/2020] [Indexed: 01/03/2023]
Abstract
COVID-19 initially an epidemic caused by SARS-CoV-2 has turned out to be a life- threatening global pandemic with increased morbidity and mortality. The presence of cytokine storm has been linked with the pathogenesis of severe lung injury as evinced in COVID-19. Aquaporins (AQPs) are molecular water channels, facilitating water transport across the cell membrane in response to osmotic gradients. Impairment in alveolar fluid clearance due to altered functional expression of respiratory AQPs highlight their pathophysiological significance in pulmonary edema associated respiratory illness. Therefore, we hypothesize that targeted modulation of AQPs in lungs in the intervening period of time, could diminish the dreadful effects of inflammation- induced comorbidity in COVID-19.
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Affiliation(s)
- Lezy Flora Mariajoseph-Antony
- Molecular Endocrinology Laboratory, Department of Biochemistry, Centre for Excellence in Life Sciences, Bharathidasan University, Tiruchirappalli 620 024, India
| | - Arun Kannan
- Molecular Endocrinology Laboratory, Department of Biochemistry, Centre for Excellence in Life Sciences, Bharathidasan University, Tiruchirappalli 620 024, India
| | - Antojenifer Panneerselvam
- Molecular Endocrinology Laboratory, Department of Biochemistry, Centre for Excellence in Life Sciences, Bharathidasan University, Tiruchirappalli 620 024, India
| | - Chithra Loganathan
- Molecular Endocrinology Laboratory, Department of Biochemistry, Centre for Excellence in Life Sciences, Bharathidasan University, Tiruchirappalli 620 024, India
| | - Kumarasamy Anbarasu
- Microbial Biotechnology Laboratory, Department of Marine Biotechnology, Bharathidasan University, Tiruchirappalli 620 024, India
| | - Chidambaram Prahalathan
- Molecular Endocrinology Laboratory, Department of Biochemistry, Centre for Excellence in Life Sciences, Bharathidasan University, Tiruchirappalli 620 024, India.
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11
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L-Glucose: Another Path to Cancer Cells. Cancers (Basel) 2020; 12:cancers12040850. [PMID: 32244695 PMCID: PMC7225996 DOI: 10.3390/cancers12040850] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 03/24/2020] [Accepted: 03/30/2020] [Indexed: 01/31/2023] Open
Abstract
Cancerous tumors comprise cells showing metabolic heterogeneity. Among numerous efforts to understand this property, little attention has been paid to the possibility that cancer cells take up and utilize otherwise unusable substrates as fuel. Here we discuss this issue by focusing on l-glucose, the mirror image isomer of naturally occurring d-glucose; l-glucose is an unmetabolizable sugar except in some bacteria. By combining relatively small fluorophores with l-glucose, we generated fluorescence-emitting l-glucose tracers (fLGs). To our surprise, 2-NBDLG, one of these fLGs, which we thought to be merely a control substrate for the fluorescent d-glucose tracer 2-NBDG, was specifically taken up into tumor cell aggregates (spheroids) that exhibited nuclear heterogeneity, a major cytological feature of malignancy in cancer diagnosis. Changes in mitochondrial activity were also associated with the spheroids taking up fLG. To better understand these phenomena, we review here the Warburg effect as well as key studies regarding glucose uptake. We also discuss tumor heterogeneity involving aberrant uptake of glucose and mitochondrial changes based on the data obtained by fLG. We then consider the use of fLGs as novel markers for visualization and characterization of malignant tumor cells.
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12
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Nielsen S. Aquaporin Water Channels in the Kidney: Localization and Regulation. Perit Dial Int 2020. [DOI: 10.1177/089686089601601s03] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Søren Nielsen
- Department of Cell Biology, Institute of Anatomy, University of Aarhus, Aarhus, Denmark
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13
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Affiliation(s)
| | - Raymond T. Krediet
- Renal Unit Academic Medical Center University of Amsterdam Amsterdam, the Netherlands
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14
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Sisto M, Ribatti D, Lisi S. Aquaporin water channels: New perspectives on the potential role in inflammation. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2019; 116:311-345. [PMID: 31036295 DOI: 10.1016/bs.apcsb.2018.11.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Aquaporins (AQPs) are a family of membrane water channel proteins that osmotically modulate water fluid homeostasis in several tissues; some of them also transport small solutes such as glycerol. At the cellular level, the AQPs regulate not only cell migration and transepithelial fluid transport across membranes, but also common events that are crucial for the inflammatory response. Emerging data reveal a new function of AQPs in the inflammatory process, as demonstrated by their dysregulation in a wide range of inflammatory diseases including edematous states, cancer, obesity, wound healing and several autoimmune diseases. This chapter summarizes the discoveries made so far about the structure and functions of the AQPs and provides updated information on the underlying mechanisms of AQPs in several human inflammatory diseases. The discovery of new functions for AQPs opens new vistas offering promise for the discovery of mechanisms and therapeutic opportunities in inflammatory disorders.
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Affiliation(s)
- Margherita Sisto
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs (SMBNOS), Section of Human Anatomy and Histology, University of Bari "Aldo Moro", Bari, Italy.
| | - Domenico Ribatti
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs (SMBNOS), Section of Human Anatomy and Histology, University of Bari "Aldo Moro", Bari, Italy
| | - Sabrina Lisi
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs (SMBNOS), Section of Human Anatomy and Histology, University of Bari "Aldo Moro", Bari, Italy
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15
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Wittekindt OH, Dietl P. Aquaporins in the lung. Pflugers Arch 2018; 471:519-532. [PMID: 30397774 PMCID: PMC6435619 DOI: 10.1007/s00424-018-2232-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 10/04/2018] [Accepted: 10/25/2018] [Indexed: 12/22/2022]
Abstract
The lung is the interface between air and blood where the exchange of oxygen and carbon dioxide occurs. The surface liquid that is directly exposed to the gaseous compartment covers both conducting airways and respiratory zone and forms the air-liquid interface. The barrier that separates this lining fluid of the airways and alveoli from the extracellular compartment is the pulmonary epithelium. The volume of the lining fluid must be kept in a range that guarantees an appropriate gas exchange and other functions, such as mucociliary clearance. It is generally accepted that this is maintained by balancing resorptive and secretory fluid transport across the pulmonary epithelium. Whereas osmosis is considered as the exclusive principle of fluid transport in the airways, filtration may contribute to alveolar fluid accumulation under pathologic conditions. Aquaporins (AQP) facilitate water flux across cell membranes, and as such, they provide a transcellular route for water transport across epithelia. However, their contribution to near-isosmolar fluid conditions in the lung still remains elusive. Herein, we discuss the role of AQPs in the lung with regard to fluid homeostasis across the respiratory epithelium.
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Affiliation(s)
- Oliver H Wittekindt
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
| | - Paul Dietl
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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16
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Vassiliou AG, Manitsopoulos N, Kardara M, Maniatis NA, Orfanos SE, Kotanidou A. Differential Expression of Aquaporins in Experimental Models of Acute Lung Injury. ACTA ACUST UNITED AC 2018; 31:885-894. [PMID: 28882955 DOI: 10.21873/invivo.11143] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 08/09/2017] [Accepted: 08/21/2017] [Indexed: 12/23/2022]
Abstract
AIM The mammalian lung expresses at least three aquaporin (AQP) water channels whose precise role in lung injury or inflammation is still controversial. MATERIALS AND METHODS Three murine models of lung inflammation and corresponding controls were used to evaluate the expression of Aqp1, Aqp4, Aqp5 and Aqp9: lipopolysaccharide (LPS)-induced lung injury; HCl-induced lung injury; and ventilation-induced lung injury (VILI). RESULTS All models yielded increased lung vascular permeability, and inflammatory cell infiltration in the broncho-alveolar lavage fluid; VILI additionally produced altered lung mechanics. Lung expression of Aqp4 decreased in the models that targeted primarily the alveolar epithelium, i.e. acid aspiration and mechanical ventilation, while Aqp5 expression decreased in the model that appeared to target both the capillary endothelium and alveolar epithelium, i.e. LPS. CONCLUSION Participation of aquaporins in the acute inflammatory process depends on localization and the type of lung injury.
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Affiliation(s)
- Alice G Vassiliou
- GP Livanos and M. Simou Laboratories, First Department of Critical Care Medicine & Pulmonary Services, Evangelismos Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Nikolaos Manitsopoulos
- GP Livanos and M. Simou Laboratories, First Department of Critical Care Medicine & Pulmonary Services, Evangelismos Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Matina Kardara
- GP Livanos and M. Simou Laboratories, First Department of Critical Care Medicine & Pulmonary Services, Evangelismos Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Nikolaos A Maniatis
- GP Livanos and M. Simou Laboratories, First Department of Critical Care Medicine & Pulmonary Services, Evangelismos Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece.,Second Department of Critical Care, Attikon Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Stylianos E Orfanos
- GP Livanos and M. Simou Laboratories, First Department of Critical Care Medicine & Pulmonary Services, Evangelismos Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece .,Second Department of Critical Care, Attikon Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Anastasia Kotanidou
- GP Livanos and M. Simou Laboratories, First Department of Critical Care Medicine & Pulmonary Services, Evangelismos Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece.,First Department of Critical Care Medicine & Pulmonary Services, National and Kapodistrian University of Athens Medical School, Evangelismos Hospital, Athens, Greece
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17
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Meli R, Pirozzi C, Pelagalli A. New Perspectives on the Potential Role of Aquaporins (AQPs) in the Physiology of Inflammation. Front Physiol 2018; 9:101. [PMID: 29503618 PMCID: PMC5820367 DOI: 10.3389/fphys.2018.00101] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 01/31/2018] [Indexed: 12/19/2022] Open
Abstract
Aquaporins (AQPs) are emerging, in the last few decades, as critical proteins regulating water fluid homeostasis in cells involved in inflammation. AQPs represent a family of ubiquitous membrane channels that regulate osmotically water flux in various tissues and sometimes the transport of small solutes, including glycerol. Extensive data indicate that AQPs, working as water channel proteins, regulate not only cell migration, but also common events essential for inflammatory response. The involvement of AQPs in several inflammatory processes, as demonstrated by their dysregulation both in human and animal diseases, identifies their new role in protection and response to different noxious stimuli, including bacterial infection. This contribution could represent a new key to clarify the dilemma of host-pathogen communications, and opens up new scenarios regarding the investigation of the modulation of specific AQPs, as target for new pharmacological therapies. This review provides updated information on the underlying mechanisms of AQPs in the regulation of inflammatory responses in mammals and discusses the broad spectrum of options that can be tailored for different diseases and their pharmacological treatment.
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Affiliation(s)
- Rosaria Meli
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Claudio Pirozzi
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Alessandra Pelagalli
- Department of Advanced Biomedical Sciences, University of Naples Federico II, Naples, Italy.,Institute of Biostructure and Bioimaging, National Research Council (CNR), Naples, Italy
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18
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Wang YI, Carmona C, Hickman JJ, Shuler ML. Multiorgan Microphysiological Systems for Drug Development: Strategies, Advances, and Challenges. Adv Healthc Mater 2018; 7:10.1002/adhm.201701000. [PMID: 29205920 PMCID: PMC5805562 DOI: 10.1002/adhm.201701000] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 09/18/2017] [Indexed: 12/19/2022]
Abstract
Traditional cell culture and animal models utilized for preclinical drug screening have led to high attrition rates of drug candidates in clinical trials due to their low predictive power for human response. Alternative models using human cells to build in vitro biomimetics of the human body with physiologically relevant organ-organ interactions hold great potential to act as "human surrogates" and provide more accurate prediction of drug effects in humans. This review is a comprehensive investigation into the development of tissue-engineered human cell-based microscale multiorgan models, or multiorgan microphysiological systems for drug testing. The evolution from traditional models to macro- and microscale multiorgan systems is discussed in regards to the rationale for recent global efforts in multiorgan microphysiological systems. Current advances in integrating cell culture and on-chip analytical technologies, as well as proof-of-concept applications for these multiorgan microsystems are discussed. Major challenges for the field, such as reproducibility and physiological relevance, are discussed with comparisons of the strengths and weaknesses of various systems to solve these challenges. Conclusions focus on the current development stage of multiorgan microphysiological systems and new trends in the field.
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Affiliation(s)
- Ying I Wang
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Carlos Carmona
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway Suite 400, Orlando, FL 32826, USA
| | - James J Hickman
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway Suite 400, Orlando, FL 32826, USA
- Hesperos, Inc., 3259 Progress Dr, Room 158, Orlando, FL 32826
| | - Michael L Shuler
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA
- Hesperos, Inc., 3259 Progress Dr, Room 158, Orlando, FL 32826
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
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19
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Aquaporins in Respiratory System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 969:115-122. [PMID: 28258569 DOI: 10.1007/978-94-024-1057-0_7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Aquaporins (AQPs ) are water channel proteins supposed to facilitating fluid transport in alveolar space, airway humidification, pleural fluid absorption, and submucosal gland secretion . In this chapter, we mainly focus on the expression of 4 AQPs in the lungs which include AQP1, AQP2 , AQP4 and AQP5 in normal and disease status, and the experience of AQPs function from various model and transgenic mice were summarized in detail to improve our understanding of the role of AQPs in fluid balance of respiratory system. It has been suggested that AQPs play important roles in various physiology and pathophysiology conditions of different lung diseases. There still remains unclear the exact role of AQPs in lung diseases, and thus continuous efforts on elucidating the roles of AQPs in lung physiological and pathophysilogical processes are warranted.
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20
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Schmidt H, Michel C, Braubach P, Fauler M, Neubauer D, Thompson KE, Frick M, Mizaikoff B, Dietl P, Wittekindt OH. Water Permeability Adjusts Resorption in Lung Epithelia to Increased Apical Surface Liquid Volumes. Am J Respir Cell Mol Biol 2017; 56:372-382. [DOI: 10.1165/rcmb.2016-0161oc] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Hanna Schmidt
- Institute of General Physiology, Ulm University, Ulm, Germany
| | | | - Peter Braubach
- Institute of Pathology, Medizinische Hochschule Hannover, Hannover, Germany
| | - Michael Fauler
- Institute of General Physiology, Ulm University, Ulm, Germany
| | - Daniel Neubauer
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, Ulm, Germany; and
| | - Kristin E. Thompson
- Institute of General Physiology, Ulm University, Ulm, Germany
- Institute de la Santé et de la Recherche Médicale, UMR_S938, Sorbonne Universités, Paris, France
| | - Manfred Frick
- Institute of General Physiology, Ulm University, Ulm, Germany
| | - Boris Mizaikoff
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, Ulm, Germany; and
| | - Paul Dietl
- Institute of General Physiology, Ulm University, Ulm, Germany
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21
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Xu C, Jiang L, Zou Y, Xing J, Sun H, Zhu B, Zhang H, Wang J, Zhang J. Involvement of water channel Aquaporin 5 in H 2S-induced pulmonary edema. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2017; 49:202-211. [PMID: 28088675 DOI: 10.1016/j.etap.2016.12.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 12/23/2016] [Accepted: 12/27/2016] [Indexed: 06/06/2023]
Abstract
Acute exposure to hydrogen sulfide (H2S) poses a significant threat to life, and the lung is one of the primary target organs of H2S. However, the mechanisms involved in H2S-induced acute pulmonary edema are poorly understood. This study aims to investigate the effects of H2S on the expression of water channel aquaporin 5 (AQP5) and to elucidate the signaling pathways involved in AQP5 regulation. In an in vivo study, C57BL6 mice were exposed to sub-lethal concentrations of inhaled H2S, and histological injury of the lungs and ultrastructure injury of the epithelial cells were evaluated. With real-time PCR and western blot assays, we found that H2S exposure contributed to a significant decrease in AQP5 expression both in murine lung tissue and the A549 cell line, and the ERK1/2 and p38 MAPK signaling pathways were demonstrated to be implicated in AQP5 regulation. Therefore, adjusting AQP5 protein levels could be considered a therapeutic strategy for the treatment of APE induced by H2S and other hazardous gases.
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Affiliation(s)
- Chunyang Xu
- Department of Emergency Medicine, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu, 210029, China
| | - Lei Jiang
- Department of Emergency Medicine, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu, 210029, China
| | - Yuxia Zou
- Key Lab of Modern Toxicology (NJMU), Ministry of Education. Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China
| | - Jingjing Xing
- Department of Emergency Medicine, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu, 210029, China
| | - Hao Sun
- Department of Emergency Medicine, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu, 210029, China
| | - Baoli Zhu
- Department of Occupational Disease Prophylactic-Therapeutic Institution, Jiangsu Provincial Center for Disease Prevention and Control, 122 Heban Cun, Nanjing, Jiangsu, 210028, China
| | - Hengdong Zhang
- Department of Occupational Disease Prophylactic-Therapeutic Institution, Jiangsu Provincial Center for Disease Prevention and Control, 122 Heban Cun, Nanjing, Jiangsu, 210028, China
| | - Jun Wang
- Key Lab of Modern Toxicology (NJMU), Ministry of Education. Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China.
| | - Jinsong Zhang
- Department of Emergency Medicine, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu, 210029, China.
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22
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Wittekindt OH. Tight junctions in pulmonary epithelia during lung inflammation. Pflugers Arch 2016; 469:135-147. [PMID: 27921210 PMCID: PMC5203840 DOI: 10.1007/s00424-016-1917-3] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 11/23/2016] [Accepted: 11/27/2016] [Indexed: 12/31/2022]
Abstract
Inflammatory lung diseases like asthma bronchiale, chronic obstructive pulmonary disease and allergic airway inflammation are widespread public diseases that constitute an enormous burden to the health systems. Mainly classified as inflammatory diseases, the treatment focuses on strategies interfering with local inflammatory responses by the immune system. Inflammatory lung diseases predispose patients to severe lung failures like alveolar oedema, respiratory distress syndrome and acute lung injury. These life-threatening syndromes are caused by increased permeability of the alveolar and airway epithelium and exudate formation. However, the mechanism underlying epithelium barrier breakdown in the lung during inflammation is elusive. This review emphasises the role of the tight junction of the airway epithelium as the predominating structure conferring epithelial tightness and preventing exudate formation and the impact of inflammatory perturbations on their function.
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Affiliation(s)
- Oliver H Wittekindt
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
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23
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Sharp K, Crampin E, Sneyd J. A spatial model of fluid recycling in the airways of the lung. J Theor Biol 2015; 382:198-215. [PMID: 26169010 DOI: 10.1016/j.jtbi.2015.06.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 06/26/2015] [Accepted: 06/30/2015] [Indexed: 12/11/2022]
Abstract
The genetic disease cystic fibrosis (CF) is a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and results in viscous mucus and impaired mucociliary clearance leading to chronic recurring pulmonary infections. Although extensive experimental research has been conducted over the last few decades, CF lung pathophysiology remains controversial. There are two competing explanations for the observed depletion of periciliary liquid (PCL) in CF lungs. The low volume hypothesis assumes fluid hyperabsorption through surface epithelia due to an over-active epithelial Na(+) channel (ENaC), and the low secretion hypothesis assumes inspissated mucins secreted from glands due to lack of serous fluid secreted from gland acini. We present a spatial mathematical model that reflects in vivo fluid recycling via submucosal gland (SMG) secretion, and absorption through surface epithelia. We then test the model in CF conditions by increasing ENaC open probability and decreasing SMG flux while simultaneously reducing CFTR open probability. Increasing ENaC activity only results in increased fluid absorption across surface epithelia, as seen in in vitro experiments. However, combining potential CF mechanisms results in markedly less fluid absorbed while providing the largest reduction in PCL volume, suggesting that a compromise in gland fluid secretion dominates over increased ENaC activity to decrease the amount of fluid transported transcellularly in CF lungs in vivo. Model results also indicate that a spatial model is necessary for an accurate calculation of total fluid transport, as the effects of spatial gradients can be severe, particularly in close proximity to the SMGs.
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Affiliation(s)
- Katie Sharp
- Department of Mathematics, University of Auckland, 23 Princes St, Auckland CBD, Auckland 1010, New Zealand.
| | - Edmund Crampin
- Department of Biomedical Engineering, Level 4, University of Melbourne, Parkville 3010, Victoria, Australia
| | - James Sneyd
- Department of Mathematics, University of Auckland, 23 Princes St, Auckland CBD, Auckland 1010, New Zealand
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24
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Nguyen T, Toussaint J, Xue Y, Raval C, Cancel L, Russell S, Shou Y, Sedes O, Sun Y, Yakobov R, Tarbell JM, Jan KM, Rumschitzki DS. Aquaporin-1 facilitates pressure-driven water flow across the aortic endothelium. Am J Physiol Heart Circ Physiol 2015; 308:H1051-64. [PMID: 25659484 PMCID: PMC4551120 DOI: 10.1152/ajpheart.00499.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 01/23/2015] [Indexed: 01/23/2023]
Abstract
Aquaporin-1, a ubiquitous water channel membrane protein, is a major contributor to cell membrane osmotic water permeability. Arteries are the physiological system where hydrostatic dominates osmotic pressure differences. In the present study, we show that the walls of large conduit arteries constitute the first example where hydrostatic pressure drives aquaporin-1-mediated transcellular/transendothelial flow. We studied cultured aortic endothelial cell monolayers and excised whole aortas of male Sprague-Dawley rats with intact and inhibited aquaporin-1 activity and with normal and knocked down aquaporin-1 expression. We subjected these systems to transmural hydrostatic pressure differences at zero osmotic pressure differences. Impaired aquaporin-1 endothelia consistently showed reduced engineering flow metrics (transendothelial water flux and hydraulic conductivity). In vitro experiments with tracers that only cross the endothelium paracellularly showed that changes in junctional transport cannot explain these reductions. Percent reductions in whole aortic wall hydraulic conductivity with either chemical blocking or knockdown of aquaporin-1 differed at low and high transmural pressures. This observation highlights how aquaporin-1 expression likely directly influences aortic wall mechanics by changing the critical transmural pressure at which its sparse subendothelial intima compresses. Such compression increases transwall flow resistance. Our endothelial and historic erythrocyte membrane aquaporin density estimates were consistent. In conclusion, aquaporin-1 significantly contributes to hydrostatic pressure-driven water transport across aortic endothelial monolayers, both in culture and in whole rat aortas. This transport, and parallel junctional flow, can dilute solutes that entered the wall paracellularly or through endothelial monolayer disruptions. Lower atherogenic precursor solute concentrations may slow their intimal entrainment kinetics.
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Affiliation(s)
- Tieuvi Nguyen
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Jimmy Toussaint
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Yan Xue
- Department of Chemical Engineering, City College of the City University of New York, New York, New York; Biology Department, City College and GSUC of The City College of New York, New York, New York; and
| | - Chirag Raval
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Limary Cancel
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Stewart Russell
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Yixin Shou
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Omer Sedes
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Yu Sun
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Roman Yakobov
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - John M Tarbell
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Kung-ming Jan
- Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York
| | - David S Rumschitzki
- Department of Chemical Engineering, City College of the City University of New York, New York, New York; Biology Department, City College and GSUC of The City College of New York, New York, New York; and Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York
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25
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Sun CY, Zhao YX, Zhong W, Liu DW, Chen YZ, Qin LL, Bai L, Liu D. The expression of aquaporins 1 and 5 in rat lung after thoracic irradiation. JOURNAL OF RADIATION RESEARCH 2014; 55:683-689. [PMID: 24570172 PMCID: PMC4100000 DOI: 10.1093/jrr/rru008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 01/28/2014] [Accepted: 01/28/2014] [Indexed: 06/03/2023]
Abstract
Radiation-induced lung toxicity (RILT), leading to radiation pneumonia or fibrosis, is a primary problem of radiation therapy. The pathogenesis of RILT remains unclear. In this study, we used a rat model of RILT to examine the expression of aquaporins (AQPs) after radiation injury. Sprague Dawley rats were given a single dose of 17 Gy (dose rate of 3.0 Gy/min) of X-irradiation to the thorax. Rats that survived acute pneumonitis (at 1-4 weeks) were evaluated weekly for the expression of AQP1 and AQP5 in the lung by immunohistochemical and reverse transcription polymerase chain reaction (RT-PCR) analyses. Immunohistochemical analysis showed that AQP1 protein was expressed in the capillary endothelium, and its level was significantly decreased after irradiation. AQP5 protein was expressed in the alveolar epithelium, and its level was increased between Days 7 and 14 after irradiation but decreased at Day 28, compared with the sham group. The RT-PCR results were consistent with the immunohistochemical analysis results. In summary, this study provides the first report of AQP1 and AQP5 expression in a model of radiation-induced pulmonary inflammation and edema. Decreased levels of AQP1 and AQP5 after irradiation suggest that these proteins play a role in the pathogenesis of RILT.
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Affiliation(s)
- Cheng-Ying Sun
- Department of Radiation Oncology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, China
| | - Yu-Xia Zhao
- Department of Radiation Oncology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, China
| | - Wen Zhong
- Department of Radiation Oncology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, China
| | - Da-Wei Liu
- Department of Radiation Oncology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, China
| | - Yan-Zhi Chen
- Department of Radiation Oncology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, China
| | - Li-Li Qin
- Department of Radiation Oncology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, China
| | - Lu Bai
- Department of Radiation Oncology, The First Affiliated Hospital of China Medical University, No. 155 Nanjing Street, Heping District, Shenyang 110001, China
| | - Dan Liu
- Department of Radiation Oncology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, China
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26
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Manicone AM. Role of the pulmonary epithelium and inflammatory signals in acute lung injury. Expert Rev Clin Immunol 2014. [DOI: 10.1586/1744666x.5.1.63] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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27
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Day RE, Kitchen P, Owen DS, Bland C, Marshall L, Conner AC, Bill RM, Conner MT. Human aquaporins: regulators of transcellular water flow. Biochim Biophys Acta Gen Subj 2013; 1840:1492-506. [PMID: 24090884 DOI: 10.1016/j.bbagen.2013.09.033] [Citation(s) in RCA: 181] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 09/19/2013] [Accepted: 09/23/2013] [Indexed: 02/06/2023]
Abstract
BACKGROUND Emerging evidence supports the view that (AQP) aquaporin water channels are regulators of transcellular water flow. Consistent with their expression in most tissues, AQPs are associated with diverse physiological and pathophysiological processes. SCOPE OF REVIEW AQP knockout studies suggest that the regulatory role of AQPs, rather than their action as passive channels, is their critical function. Transport through all AQPs occurs by a common passive mechanism, but their regulation and cellular distribution varies significantly depending on cell and tissue type; the role of AQPs in cell volume regulation (CVR) is particularly notable. This review examines the regulatory role of AQPs in transcellular water flow, especially in CVR. We focus on key systems of the human body, encompassing processes as diverse as urine concentration in the kidney to clearance of brain oedema. MAJOR CONCLUSIONS AQPs are crucial for the regulation of water homeostasis, providing selective pores for the rapid movement of water across diverse cell membranes and playing regulatory roles in CVR. Gating mechanisms have been proposed for human AQPs, but have only been reported for plant and microbial AQPs. Consequently, it is likely that the distribution and abundance of AQPs in a particular membrane is the determinant of membrane water permeability and a regulator of transcellular water flow. GENERAL SIGNIFICANCE Elucidating the mechanisms that regulate transcellular water flow will improve our understanding of the human body in health and disease. The central role of specific AQPs in regulating water homeostasis will provide routes to a range of novel therapies. This article is part of a Special Issue entitled Aquaporins.
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Affiliation(s)
- Rebecca E Day
- Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK
| | - Philip Kitchen
- Molecular Organisation and Assembly in Cells Doctoral Training Centre, University of Warwick, Coventry CV4 7AL, UK
| | - David S Owen
- Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK
| | - Charlotte Bland
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Lindsay Marshall
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alex C Conner
- School of Clinical and Experimental Medicine, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
| | - Roslyn M Bill
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
| | - Matthew T Conner
- Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
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Kooijman EE, Kuzenko SR, Gong D, Best MD, Folkesson HG. Phosphatidylinositol 4,5-bisphosphate stimulates alveolar epithelial fluid clearance in male and female adult rats. Am J Physiol Lung Cell Mol Physiol 2011; 301:L804-11. [PMID: 21873448 DOI: 10.1152/ajplung.00445.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cell membrane phospholipids, like phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)], can regulate epithelial Na channel (ENaC) activity. Gender differences in lung ENaC expression have also been demonstrated. However, the effects in vivo on alveolar fluid clearance are uncertain. Thus PI(4,5)P(2) effects on alveolar fluid clearance were studied in male and female rats. An isosmolar 5% albumin solution was intrapulmonary instilled; alveolar fluid clearance was studied for 1 h. Female rats had a 37 ± 19% higher baseline alveolar fluid clearance than male rats. Bilateral ovariectomy attenuated this gender difference. Compared with controls, PI(4,5)P(2) instillation (300 μM) increased alveolar fluid clearance by ∼93% in both genders. Amiloride or the specific αENaC small-interfering RNA inhibited baseline and PI(4,5)P(2)-stimulated alveolar fluid clearance in both genders, indicating a dependence on amiloride-sensitive pathways. The fraction of amiloride inhibition was greater in PI(4,5)P(2)-instilled rats (male: 64 ± 10%; female: 70 ± 11%) than in controls (male: 30 ± 6%; female: 44 ± 8%). PI(4,5)P(2) instillation lacked additional alveolar fluid clearance stimulation above that of terbutaline, nor did propranolol inhibit alveolar fluid clearance after PI(4,5)P(2) instillation, indicating that PI(4,5)P(2) stimulation was not secondary to endogenous β-adrenoceptor activation. PI(4,5)P(2) amine instillation resulted in an intermediate alveolar fluid clearance stimulation, suggesting that, to reach maximal alveolar fluid clearance stimulation, PI(4,5)P(2) must reside in cell membranes. In summary, PI(4,5)P(2) instillation upregulated in vivo alveolar fluid clearance similar to short-term β-adrenoceptor upregulation of alveolar fluid clearance. PI(4,5)P(2) stimulation was mediated partly by increased amiloride-sensitive Na transport. There exist important gender-related effects suggesting a female advantage that may have clinical implications for resolution of acute lung injury.
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Affiliation(s)
- Edgar E Kooijman
- Dept. of Biological Sciences, Kent State Univ., Kent, OH 44242, USA.
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O'Clock GD, Lee YW, Lee J, Warwick WJ. High-frequency and low-frequency chest compression: effects on lung water secretion, mucus transport, heart rate, and blood pressure using a trapezoidal source pressure waveform. IEEE Trans Biomed Eng 2011; 59:106-14. [PMID: 21775255 DOI: 10.1109/tbme.2011.2161608] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
High-frequency chest compression (HFCC), using an appropriate source (pump) waveform for frequencies at or above 3 Hz, can enhance pulmonary clearance for patients with cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). Using a trapezoidal HFCC source pressure waveform, secretion of water from epithelial tissue and transport of mucus through lung airways can be enhanced for patients with CF and COPD. At frequencies below 3 Hz, low-frequency chest compression (LFCC) appears to have a significant impact on the cardiovascular system. For a trapezoidal source pressure waveform at frequencies close to 1 Hz, LFCC produces amplitude or intensity variations in various components of the electrocardiogram time-domain waveform, produces changes at very low frequencies associated with the electrocardiogram frequency spectra (indicating enhanced parasympathetic nervous system activity), and promotes a form of heart rate synchronization. It appears that LFCC can also provide additional cardiovascular benefits by reducing peak and average systolic and diastolic blood pressure for patients with hypertension.
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Affiliation(s)
- George D O'Clock
- Defense of the Lungs Project, Pulmonary Disease/Critical Care, Department of Pediatrics, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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30
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Kun JF, de Carvalho EG. Novel therapeutic targets in Plasmodium falciparum: aquaglyceroporins. Expert Opin Ther Targets 2009; 13:385-94. [PMID: 19335062 DOI: 10.1517/14728220902817839] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Malaria is caused by the intracellular parasite Plasmodium falciparum. The constant need for novel malaria therapies is due to the development of resistance against existing drugs. OBJECTIVE To summarise attempts to investigate parasitic aquaporins as drug targets in malaria. METHODS Starting with a summary of the history of malaria we present aquaporin structure and function relationships. Potential interactions of inhibitors with plasmodial AQP (PfAQP) are discussed. PfAQP blockage is examined in the light of recent work on knock-out parasites. Since PfAQP is able to transport other small solutes the parasites are sensitive to other compounds which are harmless to the human host. RESULTS/CONCLUSIONS Total blockage of PfAQP may not lead to the death of the parasite but application of PfAQP as a vehicle for toxic substances may be a further pathway for research.
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Affiliation(s)
- Jürgen F Kun
- Department of Parasitology, Institute for Tropical Medicine, Tübingen, Germany.
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31
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Manicone AM. Role of the pulmonary epithelium and inflammatory signals in acute lung injury. Expert Rev Clin Immunol 2009; 5:63-75. [PMID: 19885383 PMCID: PMC2745180 DOI: 10.1586/177666x.5.1.63] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Acute lung injury (ALI) is a clinical disease marked by respiratory failure due to disruption of the epithelial and endothelial barrier, flooding of the alveolar compartment with protein-rich fluid and recruitment of neutrophils into the alveolar space. ALI affects approximately 200,000 patients annually in the USA and results in approximately 75,000 deaths. It is associated with prolonged mechanical ventilation, intensive medical care, high morbidity and mortality, and rising healthcare costs. Owing to its impact on public health, great strides have been made towards understanding the pathobiology of ALI to affect outcome. This review will focus on the role of the epithelial cell in the pathogenesis and resolution of ALI and the role of various inflammatory mediators in ALI.
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Affiliation(s)
- Anne M Manicone
- Center for Lung Biology, 815, Mercer Street, Box 358050, Seattle, WA 98115, USA,
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32
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Sumerkina VA, Popov GK, Voronova LV. In vitro study of the role of lenticular epithelial calcium channels and aquaporins in the development of cataract. Bull Exp Biol Med 2008; 145:184-7. [PMID: 19023964 DOI: 10.1007/s10517-008-0045-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of calcium and water channels (aquaporins) in the pathogenesis of cataract was studied in vitro. Aquaporin blockade caused opacity of the lens sooner than changes in calcium ion concentration in culture medium.
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33
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Kawedia JD, Jiang M, Kulkarni A, Waechter HE, Matlin KS, Pauletti GM, Menon AG. The protein kinase A pathway contributes to Hg2+-induced alterations in phosphorylation and subcellular distribution of occludin associated with increased tight junction permeability of salivary epithelial cell monolayers. J Pharmacol Exp Ther 2008; 326:829-37. [PMID: 18550693 PMCID: PMC2677297 DOI: 10.1124/jpet.107.135798] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Hg(2+) is commonly used as an inhibitor of many aquaporins during measurements of transcellular water transport. To investigate whether it could also act on the paracellular water transport pathway, we asked whether addition of Hg(2+) affected transport of radiolabeled probes through tight junctions of a salivary epithelial cell monolayer. Inclusion of 1 mM Hg(2+) decreased transepithelial electrical resistance by 8-fold and augmented mannitol and raffinose flux by 13-fold, which translated into an estimated 44% increase in pore radius at the tight junction. These Hg(2+)-induced effects could be partially blocked by the protein kinase A (PKA) inhibitor N-[2-((p-bromocinnamyl) amino) ethyl]-5-isoquinolinesulfonamide, 2HCl (H89), suggesting that both-PKA dependent and PKA-independent mechanisms contribute to tight junction regulation. Western blot analyses showed a 2-fold decrease in tight junction-associated occludin after Hg(2+) treatment and the presence of a novel hyperphosphorylated form of occludin in the cytoplasmic fraction. These findings were corroborated by confocal imaging. The results from this study reveal a novel contribution of the PKA pathway in Hg(2+)-induced regulation of tight junction permeability in the salivary epithelial barrier. Therapeutically, this could be explored for pharmacological intervention in the treatment of dry mouth, Sjögren's syndrome, and possibly other disorders of fluid transport.
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Affiliation(s)
- Jitesh D Kawedia
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0524, USA
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Upregulation of AQP3 and AQP5 induced by dexamethasone and ambroxol in A549 cells. Respir Physiol Neurobiol 2008; 161:111-8. [DOI: 10.1016/j.resp.2007.12.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Revised: 12/18/2007] [Accepted: 12/18/2007] [Indexed: 11/19/2022]
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35
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Verkman AS. Role of aquaporins in lung liquid physiology. Respir Physiol Neurobiol 2007; 159:324-30. [PMID: 17369110 PMCID: PMC3315286 DOI: 10.1016/j.resp.2007.02.012] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2006] [Revised: 02/08/2007] [Accepted: 02/09/2007] [Indexed: 12/21/2022]
Abstract
Aquaporins (AQPs) are small, integral membrane proteins that facilitate water transport across cell membranes in response to osmotic gradients. Water transport across epithelia and endothelia in the peripheral lung and airways occurs during airway hydration, alveolar fluid transport and submucosal gland secretion. Several AQPs are expressed in the lung and airways: AQP1 in microvascular endothelia, AQP3 and AQP4 in airway epithelia, and AQP5 in type I alveolar epithelial cells, submucosal gland acini, and a subset of airway epithelial cells. Phenotype analysis of transgenic knockout mice lacking AQPs has defined their roles in the lung and airways. AQP1 and AQP5 provide the principal route for osmotically driven water transport between airspace and capillary compartments; however, alveolar fluid clearance in the neonatal and adult lung is not affected by their deletion, nor is lung fluid accumulation in experimental models of lung injury. In the airways, though AQP3 and AQP4 facilitate osmotic water transport, their deletion does not impair airway hydration, regulation of airway surface liquid, or fluid absorption. In contrast to these negative findings, AQP5 deletion in submucosal glands reduced fluid secretion by >50%. The substantially slower fluid transport in the lung compared to renal and secretory epithelia probably accounts for the lack of functional significance of AQPs in the lung and airways. Recent data outside of the lung implicating the involvement of AQPs in cell migration and proliferation suggests possible new roles for lung AQPs to be explored.
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Affiliation(s)
- A S Verkman
- Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco, CA 94143-0521, USA.
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36
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McCoy E, Sontheimer H. Expression and function of water channels (aquaporins) in migrating malignant astrocytes. Glia 2007; 55:1034-43. [PMID: 17549682 PMCID: PMC2561225 DOI: 10.1002/glia.20524] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Aquaporins (AQP) constitute the principal pathway for water movement across biological membranes. Consequently, their expression and function is important for cell volume regulation. Glioma cells quickly adjust their cell volume in response to osmotic challenges or spontaneously as they invade into the narrow and tortuous extracellular spaces of the brain. These cell volume changes are likely to engage water movements across the cell membrane through AQP. AQP expression in glioma cells is poorly understood. In this study, we examined the expression of AQP in several commonly used human glioma cell lines (D54, D65, STTG1, U87, U251) and in numerous acute patient biopsies by PCR, Western blot, and immunocytochemistry and compared them to nonmalignant astrocytes and normal brain. All glioma patient biopsies expressed AQP1, AQP4 and some expressed AQP5. However, when isolated and grown as cell lines they lose all AQP proteins except a few cell lines that maintain expression of AQP1 (D65, U251, GBM62). Reintroducing either AQP1 or AQP4 stably into glioma cell lines allowed us to show that each AQP is sufficient to restore water permeability. Yet, only the presence of AQP1, but not AQP4, enhanced cell growth and migration, typical properties of gliomas, while AQP4 enhanced cell adhesion suggesting differential biological roles for AQP1 and AQP4 in glioma cell biology.
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Affiliation(s)
- Eric McCoy
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
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37
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Stockx EM, Pfister RE, Kyriakides MA, Brodecky V, Berger PJ. Expulsion of liquid from the fetal lung during labour in sheep. Respir Physiol Neurobiol 2007; 157:403-10. [PMID: 17368117 DOI: 10.1016/j.resp.2007.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 01/25/2007] [Accepted: 02/08/2007] [Indexed: 11/16/2022]
Abstract
Effective gas exchange after birth requires clearance of most of the liquid filling the lung during gestation. To date the focus has been on active Na(+) transport from lung lumen to interstitium, but Na(+) transport begins only close to delivery, making it an unlikely mechanism for clearing the bulk of fetal lung liquid. We hypothesised that fetal trunk muscle contractions, known to occur in labour, are involved in lung liquid clearance. We measured maternal uterine contractions, fetal tracheal flow directly and fetal electromyograms in thoracic and abdominal muscles. During labour in five fetal sheep, brief flow pulses were observed in the trachea, most of which expelled a small volume of lung liquid. Tracheal flow pulses were associated with fetal muscle contractions 89% of the time, which were associated on 91% of occasions with uterine contractions. Our results suggest that liquid contained in the fetal lung is cleared before and during labour as a result of fetal muscular effort, perhaps stimulated by uterine contractions.
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Affiliation(s)
- Elaine M Stockx
- Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, 246 Clayton Road, Clayton, Victoria 3168, Australia
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38
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Dobbs LG, Johnson MD. Alveolar epithelial transport in the adult lung. Respir Physiol Neurobiol 2007; 159:283-300. [PMID: 17689299 DOI: 10.1016/j.resp.2007.06.011] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 05/31/2007] [Accepted: 06/18/2007] [Indexed: 01/11/2023]
Abstract
The alveolar surface comprises >99% of the internal surface area of the lungs. At birth, the fetal lung rapidly converts from a state of net fluid secretion, which is necessary for normal fetal lung development, to a state in which there is a minimal amount of alveolar liquid. The alveolar surface epithelium facing the air compartment is composed of TI and TII cells. The morphometric characteristics of both cell types are fairly constant over a range of mammalian species varying in body weight by a factor of approximately 50,000. From the conservation of size and shape across species, one may infer that both TI and TII cells also have important conserved functions. The regulation of alveolar ion and liquid transport has been extensively investigated using a variety of experimental models, including whole animal, isolated lung, isolated cell, and cultured cell model systems, each with their inherent strengths and weaknesses. The results obtained with different model systems and a variety of different species point to both interesting parallels and some surprising differences. Sometimes it has been difficult to reconcile results obtained with different model systems. In this section, the primary focus will be on aspects of alveolar ion and liquid transport under normal physiologic conditions, emphasizing newer data and describing evolving paradigms of lung ion and fluid transport. We will highlight some of the unanswered questions, outline the similarities and differences in results obtained with different model systems, and describe some of the complex and interweaving regulatory networks.
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Affiliation(s)
- Leland G Dobbs
- Department of Medicine, University of California San Francisco, San Francisco, CA 94118, USA.
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39
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Levin MH, Sullivan S, Nielson D, Yang B, Finkbeiner WE, Verkman AS. Hypertonic saline therapy in cystic fibrosis: Evidence against the proposed mechanism involving aquaporins. J Biol Chem 2006; 281:25803-12. [PMID: 16829520 DOI: 10.1074/jbc.m604332200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent data indicate the clinical benefit of nebulized hypertonic saline in cystic fibrosis lung disease, with a proposed mechanism involving sustained increase in airway surface liquid volume. To account for the paradoxical observation that amiloride suppresses the beneficial effect of hypertonic saline, it has been previously concluded (Donaldson, S. H., Bennett, W. D., Zeman, K. L., Knowles, M. R., Tarran, R., and Boucher, R. C. (2006) N. Engl. J. Med. 354, 241-250) that amiloride-inhibitable aquaporin (AQP) water channels in airway epithelia modulate airway surface liquid volume. Here, we have characterized water permeability and amiloride effects in well differentiated, primary cultures of human airway epithelial cells, stably transfected Fisher rat thyroid epithelial cells expressing individual airway/lung AQPs, and perfused mouse lung. We found high transepithelial water permeability (P(f), 54 +/- 5 microm/s) in airway epithelial cells that was weakly temperature-dependent and inhibited by >90% by reduced pH in the basal membrane-facing solution. Reverse transcription-PCR and immunofluorescence suggested the involvement of AQPs 3, 4, and 5 in high airway water permeability. Experiments using several sensitive measurement methods indicated that amiloride does not inhibit water permeability in non-cystic fibrosis (non-CF) or CF airway epithelia, AQP-transfected Fisher rat thyroid cells, or intact lung. Our data provide evidence against the mechanism proposed by Donaldson et al. to account for the effects of amiloride and hypertonic saline in CF lung disease, indicating the need to identify alternate mechanisms.
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Affiliation(s)
- Marc H Levin
- Department of Medicine, University of California, San Francisco, California 94143-0521, USA
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40
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Maeda S, Ito H, Tanaka K, Hayakawa T, Seki M. Localization of aquaporin water channels in the airway of the musk shrew (Suncus murinus) and the rat. J Vet Med Sci 2006; 67:975-84. [PMID: 16276052 DOI: 10.1292/jvms.67.975] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aquaporins (AQPs) constitute a family of water channels that facilitate membrane water permeability in various tissues of animals. In this study, we compared the expression and localization of AQPs in the respiratory system of the musk shrew (Suncus murinus), which is an insectivore, and the rat by immunohistochemical methods. In both the musk shrew and the rat, AQP1 was expressed throughout the airway in endothelial cells of subepithelial blood vessels and in nasal submucosal fibroblasts. AQP3 and AQP4 were detected in neither the epithelium nor the subepithelial layer of the musk shrew airway, but were abundant in the rat airway epithelium. Musk shrew AQP5 was distributed in the superficial epithelial cells facing the airspaces and in submucosal glandular cells, but, unlike in the rat, not in lung alveolar cells. Additionally, the expression patterns of AQP4 and AQP5 of the musk shrew were partly similar to those of the human previously reported, absence of AQP4 and presence of AQP5 in the upper airway. The expression differences of AQPs between species in the airway indicate that the physiological importance of each AQP may be different in each species.
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Affiliation(s)
- Seishi Maeda
- Department of Anatomy, Hyogo College of Medicine, Nishinomiya, Japan
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41
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Bertorello AM, Sznajder JI. The dopamine paradox in lung and kidney epithelia: sharing the same target but operating different signaling networks. Am J Respir Cell Mol Biol 2005; 33:432-7. [PMID: 16234332 PMCID: PMC2715350 DOI: 10.1165/rcmb.2005-0297tr] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Stimulation of dopamine receptors in the lung or kidney epithelia has distinct and opposite effects on the function of Na,K-ATPase, which results in increased Na(+) absorption across the alveolar epithelium and increased sodium excretion via the kidney epithelium. In the lung, dopamine increases Na,K-ATPase by increasing cell basolateral surface expression of Na(+),K(+)-ATPase molecules, whereas in the kidney epithelia it decreases Na(+),K(+)-ATPase activity by removing active units from the plasma membrane by endocytosis. The opposite effects of dopamine over the same target (the Na(+),K(+)-ATPase) involve the activation of a distinct signaling network that it is target specific, and has a different spatial resolution. Understanding the specific signaling pathways involved in these actions of dopamine and their hierarchical organization may facilitate the drug discovery process that could lead to the design of new therapeutic approaches to clear lung edema in patients with acute lung injury and to decrease fluid overload during congestive heart failure and hypertension.
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Affiliation(s)
- Alejandro M Bertorello
- Department of Medicine, Atherosclerosis Research Unit, Membrane Signaling Networks, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
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Han X, Fink MP, Uchiyama T, Yang R, Delude RL. Increased iNOS activity is essential for pulmonary epithelial tight junction dysfunction in endotoxemic mice. Am J Physiol Lung Cell Mol Physiol 2004; 286:L259-67. [PMID: 12896879 DOI: 10.1152/ajplung.00187.2003] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
A murine endotoxemia model and cultured Calu-3 monolayers were used to test the hypothesis that excessive nitric oxide (NO) production secondary to induction of inducible NO synthase (iNOS) is a key factor leading to altered tight junction (TJ) protein expression and function in the pulmonary epithelium. C57Bl/6J mice were injected with either Escherichia coli 0111:B4 lipopolysaccharide (LPS; 2 mg/kg) or vehicle. Twelve hours later, leakage of FITC-dextran (M(r) 4 kDa; FD4) from blood into bronchoalveolar lavage fluid was significantly increased in endotoxemic but not control mice. This decrease in bronchoalveolar barrier function was associated with upregulation of iNOS protein expression and NF-kappaB activation in lung tissue. Expression of the TJ proteins, zonula occludens (ZO)-1, ZO-2, ZO-3, and occludin, as assessed by immunoblotting and/or immunofluorescence, decreased in lung after the injection of mice with LPS. Treatment of endotoxemic mice with an isoform-selective iNOS inhibitor [l-N(6)-(1-iminoethyl)lysine; l-NIL] ameliorated LPS-induced changes in TJ protein expression and preserved bronchoalveolar epithelial barrier function. Incubating Calu-3 bronchiolar epithelial monolayers with cytomix (a mixture of 1,000 U/ml IFN-gamma, 10 ng/ml TNF-alpha, and 1 ng/ml IL-1beta) increased permeability to FD4, but adding l-NIL prevented this effect. These results suggest that decreased expression and mistargeting of TJ proteins in lung after systemic inflammation may be NO dependent.
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Affiliation(s)
- Xiaonan Han
- Department of Critical Care Medicine, 616 Scaife Hall, 3550 Terrace St., Pittsburgh, PA 15261, USA
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Jiang J, Song Y, Bai C, Koller BH, Matthay MA, Verkman AS. Pleural surface fluorescence measurement of Na+ and Cl- transport across the air space-capillary barrier. J Appl Physiol (1985) 2003; 94:343-52. [PMID: 12391048 DOI: 10.1152/japplphysiol.00562.2002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We developed a pleural surface fluorescence method to measure Na(+) and Cl(-) transport in perfused mouse lungs. The air space was filled with aqueous fluid containing membrane-impermeant fluorescent indicators of Cl(-) (lucigenin) or Na(+) (Sodium Green). After instillation of a Cl(-)-free solution into the air space, an increase in perfusate Cl(-) concentration from 0 to 30 mM produced a decrease in surface lucigenin fluorescence (6.5%/min) corresponding to Cl(-) influx of 1.0 mM/min. Cl(-) influx was increased to 2.1 +/- 0.3 mM/min by forskolin, and the increase was inhibited by glibenclamide. cAMP-stimulated Cl(-) influx was decreased by 57% in CFTR null mice. After instillation of a Na(+)-free solution into the air space, an increase in perfusate Na(+) concentration from 0 to 30 mM gave increased Sodium Green fluorescence (Na(+) influx of 1.2 mM/min), which increased approximately fivefold after cAMP agonists. Cl(-) and Na(+) transport were not affected in lungs from mice lacking aquaporins AQP1 or AQP5. Our results establish a pleural surface fluorescence method to measure unidirectional Cl(-) and Na(+) flux in intact lung and provide evidence for cAMP-stimulated transcellular Cl(-) and Na(+) transport.
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Affiliation(s)
- Jinjun Jiang
- Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco, 94143 - 0521, USA
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Tsang KW, Leung JC, Tipoe GL, Leung R, Yan C, Ooi GC, Chan HH, Lam WK, Lai KN. Down-regulation of aquaporin 3 in bronchiectatic airways in vivo. Respir Med 2003; 97:59-64. [PMID: 12556012 DOI: 10.1053/rmed.2002.1413] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Bronchiectasis is characterized pathologically by permanent abnormal bronchial dilation, and clinically by chronic sputum production. Aquaporin 3 (AQP3), a recently described water channel that is also found in large airway cell membrane, could play a role in the pathogenesis and particularly that of bronchorrhea in bronchiectasis. However, little is known of its in vivo distribution and physiological role in human airways. We have, therefore, performed this quantitative immunohistochemistry study on endobronchial biopsies to evaluate the expression and clinical relevance of AQP3 in patients with idiopathic bronchiectasis (n = 25, 15 F, 64.3 +/- 11.5 years) and control subjects (n = 14, 5 F, 57.5 +/- 12.0 years). Quantitative image analysis was performed to evaluate the expression of AQP3 in the bronchial epithelial cells. Our results show that AQP3 was predominantly expressed in the basal cells of the epithelial layer in both groups. Expression of AQP3 was significantly reduced in the basal, but not columnar, epithelial cells in bronchiectasis compared with control airways (p = 0.02, 0.35). Only bronchiectatic patients with regular sputum production, but not their counterparts, had significant downregulation of epithelial AQP3 expression compared with control airways (p = 0.004, 0.24). Our findings suggest that AQP3 could have an important role in the pathogenesis of increased mucus production in bronchiectasis.
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Affiliation(s)
- K W Tsang
- University Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong SAR, China
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Borok Z, Verkman AS. Lung edema clearance: 20 years of progress: invited review: role of aquaporin water channels in fluid transport in lung and airways. J Appl Physiol (1985) 2002; 93:2199-206. [PMID: 12433939 DOI: 10.1152/japplphysiol.01171.2001] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Water transport across epithelial and endothelial barriers in bronchopulmonary tissues occurs during airway hydration, alveolar fluid transport, and submucosal gland secretion. Many of the tissues involved in these processes are highly water permeable and express aquaporin (AQP) water channels. AQP1 is expressed in microvascular endothelia throughout the lung and airways, AQP3 in epithelia in large airways, AQP4 in epithelia throughout the airways, and AQP5 in type I alveolar epithelial cells and submucosal gland acinar cells. The expression of some of these AQPs increases near the time of birth and is regulated by growth factors, inflammation, and osmotic stress. Transgenic mouse models of AQP deletion have provided information about their physiological role. In lung, AQP1 and AQP5 provide the principal route for osmotically driven water transport; however, alveolar fluid clearance in the neonatal and adult lung is not affected by AQP deletion nor is lung CO(2) transport or fluid accumulation in experimental models of lung injury. In the airways, AQP3 and AQP4 facilitate water transport; however, airway hydration, regulation of the airway surface liquid layer, and isosmolar fluid absorption are not impaired by AQP deletion. In contrast to these negative findings, AQP5 deletion in submucosal glands in upper airways reduced fluid secretion and increased protein content by greater than twofold. Thus, although AQPs play a major physiological role outside of the airways and lung, AQPs appear to be important mainly in airway submucosal gland function. The substantially slower rates of fluid transport in airways, pleura, and lung compared with renal and some secretory epithelia may account for the apparent lack of functional significance of AQPs at these sites. However, the possibility remains that AQPs may play a role in lung physiology under conditions of stress and/or injury not yet tested or in functions unrelated to transepithelial fluid transport.
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Affiliation(s)
- Zea Borok
- Will Rogers Institute Pulmonary Research Center, Department of Medicine, University of Southern California, Los Angeles 90033-3721, USA
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Matalon S, Lazrak A, Jain L, Eaton DC. Invited review: biophysical properties of sodium channels in lung alveolar epithelial cells. J Appl Physiol (1985) 2002; 93:1852-9. [PMID: 12381774 DOI: 10.1152/japplphysiol.01241.2001] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Amiloride-sensitive sodium channels in the lung play an important role in lung fluid balance. Particularly in the alveoli, sodium transport is closely regulated to maintain an appropriate fluid layer on the surface of the alveoli. Alveolar type II cells appear to play an important role in this sodium transport, with the role of alveolar type I cells being less clear. In alveolar type II cells, there are a variety of different amiloride-sensitive, sodium-permeable channels. This significant diversity appears to play a role in both normal lung physiology and in pathological states. In many epithelial tissues, amiloride-sensitive epithelial sodium channels (ENaC) are formed from three subunit proteins, designated alpha-, beta-, and gamma-ENaC. At least part of the diversity of sodium-permeable channels in lung arises from the assembling of different combinations of these subunits to form channels with different biophysical properties and different mechanisms for regulation. This leads to epithelial tissue in the lung, which has enormous flexibility to alter the magnitude and regulation of salt and water transport. In this review, we discuss the biophysical properties and occurrence of these various channels and some of the mechanisms for their regulation.
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Affiliation(s)
- Sadis Matalon
- Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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Matthay MA, Folkesson HG, Clerici C. Lung epithelial fluid transport and the resolution of pulmonary edema. Physiol Rev 2002; 82:569-600. [PMID: 12087129 DOI: 10.1152/physrev.00003.2002] [Citation(s) in RCA: 490] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The discovery of mechanisms that regulate salt and water transport by the alveolar and distal airway epithelium of the lung has generated new insights into the regulation of lung fluid balance under both normal and pathological conditions. There is convincing evidence that active sodium and chloride transporters are expressed in the distal lung epithelium and are responsible for the ability of the lung to remove alveolar fluid at the time of birth as well as in the mature lung when pathological conditions lead to the development of pulmonary edema. Currently, the best described molecular transporters are the epithelial sodium channel, the cystic fibrosis transmembrane conductance regulator, Na+-K+-ATPase, and several aquaporin water channels. Both catecholamine-dependent and -independent mechanisms can upregulate isosmolar fluid transport across the distal lung epithelium. Experimental and clinical studies have made it possible to examine the role of these transporters in the resolution of pulmonary edema.
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Affiliation(s)
- Michael A Matthay
- Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, California 94143-0624, USA.
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Sartori C, Matthay MA, Scherrer U. Transepithelial sodium and water transport in the lung. Major player and novel therapeutic target in pulmonary edema. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 502:315-38. [PMID: 11950147 DOI: 10.1007/978-1-4757-3401-0_21] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Active transepithelial transport of sodium from the airspaces to the lung interstitium is a primary mechanism driving alveolar fluid clearance. This mechanism depends on sodium uptake by amiloride-sensitive sodium channels on the apical membrane of alveolar type II cells followed by extrusion of sodium on the basolateral surface by the Na-K-ATPase. Injury to the alveolar epithelium can disrupt the integrity of the alveolar barrier or downregulate ion transport pathways thus reducing net alveolar fluid reabsorption, and enhancing the extent of alveolar edema. Endogenous catecholamines upregulate alveolar fluid clearance in several experimental models of acute lung injury, but this upregulation is short-term and often not sufficient to counterbalance alveolar flooding. There is new evidence, however, that pharmacological treatment with beta-adrenergic agonists and/or epithelial growth factors may induce a more sustained stimulation of alveolar fluid reabsorption and in turn facilitate recovery from experimental pulmonary edema. Similar results have been achieved experimentally by gene transfer enhancing the abundance of sodium transporters in the alveolar epithelium. Clinical studies show that impaired alveolar fluid transport mechanisms contribute to the development, severity and outcome of pulmonary edema in humans. Very recent data suggest that mechanisms that augment transepithelial sodium transport and enhance the clearance of alveolar edema may lead to more effective prevention or treatment for pulmonary edema and acute lung injury.
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Affiliation(s)
- C Sartori
- Department of Internal Medicine and Botnar Center of Clinical Research, CHUV, Lausanne, Switzerland
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Abstract
An understanding of the pathogenesis of ARDS is essential for choosing management strategies and developing new treatments. The key mediators involved in the inflammatory and fibroproliferative responses are reviewed and the mechanisms which regulate these responses are highlighted.
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Abstract
The aquaporins (AQP) are a family of homologous water channels expressed in many epithelial and endothelial cell types involved in fluid transport. AQP1 protein is strongly expressed in most microvascular endothelia outside of the brain, as well as in endothelial cells in cornea, intestinal lacteals, and other tissues. AQP4 is expressed in astroglial foot processes adjacent to endothelial cells in the central nervous system. Transgenic mice lacking aquaporins have been useful in defining their role in mammalian physiology. Mice lacking AQP1 manifest defective urinary concentrating ability, in part because of decreased water permeability in renal vasa recta microvessels. These mice also show a defect in dietary fat processing that may involve chylomicron absorption by intestinal lacteals, as well as defective active fluid transport across the corneal endothelium. AQP1 might also play a role in tumour angiogenesis and in renal microvessel structural adaptation. However, AQP1 in most endothelial tissues does not appear to have a physiological function despite its role in osmotically driven water transport. For example, mice lacking AQP1 have low alveolar-capillary water permeability but unimpaired lung fluid absorption, as well as unimpaired saliva and tear secretion, aqueous fluid outflow, and pleural and peritoneal fluid transport. In the central nervous system mice lacking AQP4 are partially protected from brain oedema in water intoxication and ischaemic models of brain injury. Therefore, although the role of aquaporins in epithelial fluid transport is in most cases well-understood, there remain many questions about the role of aquaporins in endothelial cell function. It is unclear why many leaky microvessels strongly express AQP1 without apparent functional significance. Improved understanding of aquaporin-endothelial biology may lead to novel therapies for human disease, such as pharmacological modulation of corneal fluid transport, renal fluid clearance and intestinal absorption.
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Affiliation(s)
- A S Verkman
- Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco 94143-0521, USA.
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