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Elekes G, Csapó V, Szarka D, Szalay L, Korsós MM, Tálosi D, Török D, Tóth-Molnár E. The Role of Aquaporin 4 in Lacrimal Gland Ductal Fluid Secretion in Mice. Invest Ophthalmol Vis Sci 2024; 65:30. [PMID: 38771571 PMCID: PMC11114615 DOI: 10.1167/iovs.65.5.30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 05/04/2024] [Indexed: 05/22/2024] Open
Abstract
Purpose Earlier reports highlighted the predominant presence of aquaporin 4 (AQP4) in the duct cells of rabbit lacrimal glands (LGs). Whereas significant alterations in AQP4 mRNA levels have been observed in experimental dry eye and during pregnancy, the impact of AQP4 in LG ductal fluid production remains unclear. In our recent work, the role of AQP4 in LG ductal fluid secretion was investigated utilizing wild type (WT) and AQP4 knock out (KO) mice. Methods Tear production was assessed in both WT and KO animals. Immunostaining was used to identify AQP4 protein. Duct segments were harvested from LGs of WT and KO mice. Fluid secretion and filtration permeability (Pf) were quantified using video-microscopy. Ductal tear production, elicited by a cell-permeable cAMP analogue (8-bromo cAMP), carbachol, vasoactive intestinal peptide (VIP), and phenylephrine (PHE), were assessed in both WT and KO ducts. Results A higher expression of AQP4 protein was noted in the duct cells from WT mice when compared to acinar cells. Pf did not show notable alterations between WT and AQP4 KO ducts. Carbachol elicited comparable secretory responses in ducts from both WT and KO animals. However, 8-bromo cAMP, VIP, and PHE stimulation resulted in decreased secretion in ducts from AQP4 KO LGs. Conclusions Our findings underscore the functional relevance of AQP4 in the fluid production of mouse LG ducts. AQP4 seems to play different roles in fluid secretions elicited by different secretagogues. Specifically, cAMP-mediated, and adrenergic agonist-related secretions were reduced in AQP4 KO ducts.
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Affiliation(s)
- Gréta Elekes
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
| | - Virág Csapó
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
| | - Dóra Szarka
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
| | - László Szalay
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
| | | | - Dorottya Tálosi
- Albert Szent-Gyorgyi Medical School, University of Szeged, Szeged, Hungary
| | - Dénes Török
- Department of Anatomy, University of Szeged, Szeged, Hungary
| | - Edit Tóth-Molnár
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
- Faculty of Health Sciences and Social Studies, University of Szeged, Szeged, Hungary
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Nagase H, Shitara A, Ohno Y, Satoh K, Kashimata M. Loss of Cdc42 in Exocrine Acini Decreases Saliva Secretion but Increases Tear Secretion-A Potential Model of Exocrine Gland Senescence. Int J Mol Sci 2023; 24:17220. [PMID: 38139048 PMCID: PMC10743476 DOI: 10.3390/ijms242417220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 11/17/2023] [Accepted: 12/05/2023] [Indexed: 12/24/2023] Open
Abstract
Cdc42 is a small GTPase essential for the cell cycle, morphogenesis, and cell adhesion, and it is involved in the polarity of epithelial cells. However, the functional roles of Cdc42 in exocrine glands, such as the maintenance of acini and water secretion, are not yet well understood. In this study, we generated acinar-cell-specific Cdc42 conditional knockout (Cdc42cKO) mice to assess their maintenance of acinar cells and physiological functions in the salivary glands (SGs) and lacrimal glands (LGs). Our data revealed that the loss of Cdc42 altered the luminal structures to bulging structures and induced acinar cell apoptosis in both the parotid glands (PGs) and LGs of Cdc42cKO mice. Interestingly, saliva secretion in response to pilocarpine stimulation was decreased in the Cdc42cKO group, whereas tear secretion was increased. Consistent with the water secretion results, protein expression of the water channel AQP5 in acinar cells was also decreased in the PGs but conversely increased in the LGs. Moreover, the changes that increased AQP5 expression in LGs occurred in the acinar cells rather than the duct cells. The present study demonstrates that Cdc42 is involved in the structural and survival maintenance of acinar cells in SGs and LGs. On the other hand, depletion of Cdc42 caused the opposite physiological phenomena between PGs and LGs.
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Affiliation(s)
- Haruna Nagase
- Department of Pharmacology, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu 501-0296, Japan
| | - Akiko Shitara
- Department of Pharmacology, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu 501-0296, Japan
| | - Yuta Ohno
- Department of Pharmacology, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu 501-0296, Japan
| | - Keitaro Satoh
- Department of Pharmacology, Meikai University School of Dentistry, 1-1 Keyakidai, Sakado, Saitama 350-0283, Japan
| | - Masanori Kashimata
- Department of Pharmacology, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu 501-0296, Japan
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3
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Bai Y, Zhang K, Cao X, Chen P. Aquaporins in lacrimal glands and their role in dry eye disease. Exp Eye Res 2023; 236:109676. [PMID: 37827442 DOI: 10.1016/j.exer.2023.109676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 10/05/2023] [Accepted: 10/09/2023] [Indexed: 10/14/2023]
Abstract
Aging is the most important known risk factor for dry eye is aging, which is associated with changes in the structure and function of the lacrimal gland (LG) and characterized by atrophy, duct blocking lymphocyte infiltration, and reduced protein secretion. Aquaporins (AQP) have been proposed as a potential producer of exocrine gland fluids since exocrine secretion depends on the mobility of water. Therefore, the main topics of this review will be the expression, localization, and function of AQPs in LG. In addition, we review the mechanisms of fluid transport in exocrine gland fluid secretion and discuss the potential role of AQPs in dry eye.
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Affiliation(s)
- Ying Bai
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Kaier Zhang
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Xin Cao
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Peng Chen
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China; Clinical Laboratory, Qingdao Central Hospital, The Second Affiliated Hospital of Medical College of Qingdao University, Qingdao, 266042, Shandong Province, China.
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4
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Bai Y, Di G, Ge H, Li B, Zhang K, Zhang D, Wang D, Chen P. Regulation of Axon Guidance by Slit2 and Netrin-1 Signaling in the Lacrimal Gland of Aqp5 Knockout Mice. Invest Ophthalmol Vis Sci 2023; 64:27. [PMID: 37707834 PMCID: PMC10506685 DOI: 10.1167/iovs.64.12.27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 08/23/2023] [Indexed: 09/15/2023] Open
Abstract
Purpose Dry eye disease (DED) is multifactorial and associated with nerve abnormalities. We explored an Aquaporin 5 (AQP5)-deficiency-induced JunB activation mechanism, which causes abnormal lacrimal gland (LG) nerve distribution through Slit2 upregulation and Netrin-1 repression. Methods Aqp5 knockout (Aqp5-/-) and wild-type (Aqp5+/+) mice were studied. LGs were permeabilized and stained with neuronal class III β-tubulin, tyrosine hydroxylase (TH), vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP). Whole-mount images were acquired through tissue clearing and 3D fluorescence imaging. Mouse primary trigeminal ganglion (TG) neurons were treated with LG extracts and Netrin-1/Slit2 neutralizing antibody. Transcription factor (TF) prediction and chromatin immunoprecipitation-polymerase chain reaction (ChIP-PCR) experiments verified the JunB binding and regulatory effect on Netrin-1 and Slit2. Results Three-dimensional tissue and section immunofluorescence showed reduced LG nerves in Aqp5-/- mice, with sympathetic and sensory nerves significantly decreased. Netrin-1 was reduced and Slit2 increased in Aqp5-/- mice LGs. Aqp5+/+ mice LG tissue extracts (TEs) promoted Aqp5-/- TG neurons axon growth, but Netrin-1 neutralizing antibody (NAb) could inhibit that promotion. Aqp5-/- mice LG TEs inhibited Aqp5+/+ TG axon growth, but Slit2 NAb alleviated that inhibition. Furthermore, JunB, a Netrin-1 and Slit2 TF, could bind them and regulate their expression. SR11302, meanwhile, reversed the Netrin-1 and Slit2 shifts caused by AQP5 deficiency. Conclusions AQP5 deficiency causes LG nerve abnormalities. Persistent JunB activation, the common denominator for Netrin-1 suppression and Slit2 induction, was found in Aqp5-/- mice LG epithelial cells. This affected sensory and sympathetic nerve fibers' distribution in LGs. Our findings provide insights into preventing, reversing, and treating DED.
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Affiliation(s)
- Ying Bai
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Guohu Di
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, China
- Institute of Stem Cell Regeneration Medicine, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Huanhuan Ge
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Bin Li
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Kaier Zhang
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Di Zhang
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Dianqiang Wang
- Department of Ophthalmology, Qingdao Aier Eye Hospital, Qingdao, China
| | - Peng Chen
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, China
- Institute of Stem Cell Regeneration Medicine, School of Basic Medicine, Qingdao University, Qingdao, China
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5
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Zhang K, Di G, Bai Y, Liu A, Bian W, Chen P. Aquaporin 5 in the eye: Expression, function, and roles in ocular diseases. Exp Eye Res 2023; 233:109557. [PMID: 37380095 DOI: 10.1016/j.exer.2023.109557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 05/26/2023] [Accepted: 06/25/2023] [Indexed: 06/30/2023]
Abstract
As a water channel protein, aquaporin 5 (AQP5) is essential for the maintenance of the normal physiological functions of ocular tissues. This review provides an overview of the expression and function of AQP5 in the eye and discusses their role in related eye diseases. Although AQP5 plays a vital role in ocular functions, such as maintaining corneal and lens transparency, regulating water movement, and maintaining homeostasis, some of its functions in ocular tissues are still unclear. Based on the key role of AQP5 in eye function, this review suggests that in the future, eye diseases may be treated by regulating the expression of aquaporin.
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Affiliation(s)
- Kaier Zhang
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Guohu Di
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Ying Bai
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Anxu Liu
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Wenhan Bian
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China
| | - Peng Chen
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Qingdao University, Qingdao, 266071, Shandong Province, China; Clinical Laboratory, Qingdao Central Hospital, The Second Affiliated Hospital of Medical College of Qingdao University, Qingdao, 266042, Shandong Province, China.
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Kaushik R, Arya A, Kumar D, Goel A, Rout PK. Genetic studies of heat stress regulation in goat during hot climatic condition. J Therm Biol 2023; 113:103528. [PMID: 37055132 DOI: 10.1016/j.jtherbio.2023.103528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 02/13/2023] [Accepted: 02/22/2023] [Indexed: 04/15/2023]
Abstract
Various direct and indirect environmental constraints have an impact on livestock performance. The physiological parameters, such as rectal temperature, heart rate, and respiratory rate, are the primary indicators of thermal stress. Under a stressed environment temperature humidity index (THI) had established as a vital measurement to identify the thermal stress in livestock. THI in association with climatic variations can define the environmental effect as stressful or comfortable for livestock. Goats are small ruminants that adapt to a wide range of ecological variations due to their anatomical and physiological characteristics. However, the productivity of animals declines at the individual level during thermal stress. Stress tolerance can be determined through genetic studies associated with at the cellular level using physiological as well as molecular approaches. Information on genetic association with thermal stress in goats is scanty, this severely affects their survival and hence productivity of livestock. The ever-increasing demand for food across the globe needs deciphering novel molecular markers as well as stress indicators that play a vital role in livestock improvement. This review represents an analysis of current knowledge of phenotypic differences during thermal stress and signifies the importance of physiological responses and their association at the cellular level in goats. The regulation of vital genes associated with thermal stress such as Aquaporins (AQP 0, 1, 2, 4, 5, 6, 8), aquaglyceroporins (AQP3, 7, 9, and 10) and super-aquaporins (AQP 11, 12); BAX inhibitors such as PERK (PKR like ER kinase), IRE 1(inositol-requiring-1); Redox regulating genes such as NOX; Transport of Na+ and K+ such as ATPase (ATP1A1) and several heat shock proteins have been implicated in heat-stress related adaptations have been elucidated. As these changes have a significant impact on production performance as well as on livestock productivity. Such efforts may help in the development of molecular markers and will assist the breeders to develop heat-tolerant goats with improved productivity.
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Affiliation(s)
- Rakesh Kaushik
- Animal Genetics and Breeding Division, ICAR- Central Institute for Research on Goats, Makhdoom, Farah, Mathura, 281122, U.P, India; Department of Biotechnology, 17km Stone, NH-2, Mathura-Delhi Road Mathura, Chaumuhan, 281406, U.P, India.
| | - Aditya Arya
- ICMR-National Institute for Malaria Research, Dwarka Sector- 8, New Delhi, 110077, India
| | - Devendra Kumar
- Department of Biotechnology, Keral Verma Subharti College of Science, Swami Vivekanand Subharti University, Meerut, 250005, U.P, India
| | - Anjana Goel
- Department of Biotechnology, 17km Stone, NH-2, Mathura-Delhi Road Mathura, Chaumuhan, 281406, U.P, India
| | - P K Rout
- Animal Genetics and Breeding Division, ICAR- Central Institute for Research on Goats, Makhdoom, Farah, Mathura, 281122, U.P, India.
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7
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Involvement of aquaporin 5 in Sjögren's syndrome. Autoimmun Rev 2023; 22:103268. [PMID: 36621535 DOI: 10.1016/j.autrev.2023.103268] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 01/04/2023] [Indexed: 01/07/2023]
Abstract
Sjögren's syndrome (SS) is a chronic autoimmune disease with the pathological hallmark of lymphoplasmacytic infiltration of exocrine glands - more specifically salivary and lacrimal glands - resulting in a diminished production of tears and saliva (sicca syndrome). The pathophysiology underscoring the mechanisms of the sicca symptoms in SS has still yet to be unraveled but recent advances have identified a cardinal role of aquaporin-5 (AQP5) as a key player in saliva secretion as well as salivary gland epithelial cell dysregulation. AQP5 expression and localization are significantly altered in salivary glands from patients and mice models of the disease, shedding light on a putative mechanism accounting for diminished salivary flow. Furthermore, aberrant expression and localization of AQP5 protein partners, such as prolactin-inducible protein and ezrin, may account for altered AQP5 localization in salivary glands from patients suffering from SS and are considered as new players in SS development. This review provides an overview of the role of AQP5 in SS salivary gland epithelial cell dysregulation, focusing on its trafficking and protein-protein interactions.
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8
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Calamita G, Delporte C. Aquaporins in Glandular Secretion. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:225-249. [PMID: 36717498 DOI: 10.1007/978-981-19-7415-1_16] [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
Exocrine and endocrine glands deliver their secretory product, respectively, at the surface of the target organs or within the bloodstream. The release of their products has been shown to rely on secretory mechanisms often involving aquaporins (AQPs). This chapter will provide insight into the role of AQPs in secretory glands located within the gastrointestinal tract, including salivary glands, gastric glands, duodenal Brunner's glands, liver, gallbladder, intestinal goblets cells, and pancreas, as well and in other parts of the body, including airway submucosal glands, lacrimal glands, mammary glands, and eccrine sweat glands. The involvement of AQPs in both physiological and pathophysiological conditions will also be highlighted.
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Affiliation(s)
- Giuseppe Calamita
- Department of Biosciences, Biotechnologies and Environment, University of Bari "Aldo Moro", Bari, Italy
| | - Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Faculty of Medicine, Université Libre de Bruxelles, Brussels, Belgium.
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9
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Safonova TN, Pateyuk LS. [Features of water-electrolyte component of the tear fluid]. Vestn Oftalmol 2023; 139:106-113. [PMID: 36924522 DOI: 10.17116/oftalma2023139011106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
Tear production is a complex multi-step process that can be arbitrarily divided into three stages: «primary» secretion by the acinar cells of the main lacrimal glands, formation of «secondary» lacrimal fluid in the ducts of the main lacrimal glands, and «tertiary» modification of the tear composition in the conjunctival sac. This article highlights mechanisms of water and electrolytes secretion in the process of tear fluid production and describes the particularities of distribution of the membrane transport proteins in the lacrimal gland and the ocular surface.
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Affiliation(s)
- T N Safonova
- Krasnov Research Institute of Eye Diseases, Moscow, Russia
| | - L S Pateyuk
- Krasnov Research Institute of Eye Diseases, Moscow, Russia
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10
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Halliday LA, Wood JPM, Chidlow G, Casson RJ, Selva D, Sun MT. Establishing human lacrimal gland cultures from biopsy-sized tissue specimens. Eye (Lond) 2023; 37:62-68. [PMID: 35001090 PMCID: PMC9829670 DOI: 10.1038/s41433-021-01872-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 10/11/2021] [Accepted: 11/19/2021] [Indexed: 01/17/2023] Open
Abstract
OBJECTIVES To establish cultures of human lacrimal gland from patient-derived, biopsy-sized, tissue specimens. METHODS Tissue was obtained after surgical removal from patients without dry eye disease undergoing routine procedures. Samples were subjected to mechanical and enzymatic digestion and resulting cell suspensions were plated onto collagen-coated glass coverslips and grown for up to 21 days. Cultures were analysed by immunocytochemistry and light microscopy, and resultant cellular distributions were compared to those in sections of fixed human lacrimal gland tissue. RESULTS Dissociation of biopsy-sized pieces of human lacrimal gland and seeding onto coated surfaces allowed development of a mixed population of cells in vitro. Within 7-14 days, cellular aggregation was observed and by 21 days many cells had organised themselves into distinct three-dimensional complexes. Immunohistochemistry revealed a heterogeneous population of cells, including epithelial, myoepithelial, mesenchymal and progenitor cells. Some of the epithelia labelled positively for lysozyme and lactoferrin. CONCLUSIONS Collection and dissociation of biopsy-sized pieces of human lacrimal gland leads to a cellular preparation that can proliferate in vitro and organise into three-dimensional structures. This is the first report detailing that biopsy-collected specimens of human lacrimal gland can be used to establish cell cultures.
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Affiliation(s)
- Luke A Halliday
- Discipline of Ophthalmology & Visual Sciences, Level 7 Adelaide Health and Medical Sciences Building, University of Adelaide, North Terrace, Adelaide, SA, 5000, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, Port Road, Adelaide, SA, 5000, Australia
| | - John P M Wood
- Discipline of Ophthalmology & Visual Sciences, Level 7 Adelaide Health and Medical Sciences Building, University of Adelaide, North Terrace, Adelaide, SA, 5000, Australia.
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, Port Road, Adelaide, SA, 5000, Australia.
| | - Glyn Chidlow
- Discipline of Ophthalmology & Visual Sciences, Level 7 Adelaide Health and Medical Sciences Building, University of Adelaide, North Terrace, Adelaide, SA, 5000, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, Port Road, Adelaide, SA, 5000, Australia
| | - Robert J Casson
- Discipline of Ophthalmology & Visual Sciences, Level 7 Adelaide Health and Medical Sciences Building, University of Adelaide, North Terrace, Adelaide, SA, 5000, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, Port Road, Adelaide, SA, 5000, Australia
| | - Dinesh Selva
- Discipline of Ophthalmology & Visual Sciences, Level 7 Adelaide Health and Medical Sciences Building, University of Adelaide, North Terrace, Adelaide, SA, 5000, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, Port Road, Adelaide, SA, 5000, Australia
| | - Michelle T Sun
- Discipline of Ophthalmology & Visual Sciences, Level 7 Adelaide Health and Medical Sciences Building, University of Adelaide, North Terrace, Adelaide, SA, 5000, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, Port Road, Adelaide, SA, 5000, Australia
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11
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Wood JPM, Chidlow G, Halliday LA, Casson RJ, Selva D, Sun M. Histochemical Comparison of Human and Rat Lacrimal Glands: Implications for Bio-Engineering Studies. Transl Vis Sci Technol 2022; 11:10. [PMID: 36374486 PMCID: PMC9669807 DOI: 10.1167/tvst.11.11.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Purpose The purpose of this study was to determine whether rodent lacrimal glands (LGs) represent a suitable surrogate for human tissue in bio-engineering research, we undertook a meticulous histological and histochemical comparison of these two tissues. Methods Histological techniques and immunohistochemistry were used to compare the structure of adult human and rat LG tissues and the expression of key functional tissue elements. Results Compared with humans, the rat LG is comprised of much more densely packed acini which are devoid of an obvious central lumen. Myoepithelial, fibroblasts, dendritic cells, T cells, and putative progenitor cells are present in both tissues. However, human LG is replete with epithelium expressing cytokeratins 8 and 18, whereas rat LG epithelium does not express cytokeratin 8. Furthermore, human LG expresses aquaporins (AQPs) 1, 3, and 5, whereas rat LG expresses AQPs 1, 4, and 5. Additionally, mast cells were identified in the rat but not the human LGs and large numbers of plasma cells were detected in the human LGs but only limited numbers were present in the rat LGs. Conclusions The cellular composition of the human and rat LGs is similar, although there is a marked difference in the actual histo-architectural arrangement of the tissue. Further variances in the epithelial cytokeratin profile, in tissue expression of AQPs and in mast cell and plasma cell infiltration, may prove significant. Translational Relevance The rat LG can serve as a useful surrogate for the human equivalent, but there exist specific tissue differences meaning that caution must be observed when translating results to patients.
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Affiliation(s)
- John P. M. Wood
- Discipline of Ophthalmology & Visual Sciences, University of Adelaide, Adelaide South Australia, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, South Australia, Australia
| | - Glyn Chidlow
- Discipline of Ophthalmology & Visual Sciences, University of Adelaide, Adelaide South Australia, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, South Australia, Australia
| | - Luke A. Halliday
- Discipline of Ophthalmology & Visual Sciences, University of Adelaide, Adelaide South Australia, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, South Australia, Australia
| | - Robert J. Casson
- Discipline of Ophthalmology & Visual Sciences, University of Adelaide, Adelaide South Australia, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, South Australia, Australia
| | - Dinesh Selva
- Discipline of Ophthalmology & Visual Sciences, University of Adelaide, Adelaide South Australia, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, South Australia, Australia
| | - Michelle Sun
- Discipline of Ophthalmology & Visual Sciences, University of Adelaide, Adelaide South Australia, Australia
- South Australian Institute of Ophthalmology, Royal Adelaide Hospital, South Australia, Australia
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12
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Aquaporins 8 and 9 as Possible Markers for Adult Murine Lacrimal Gland Cells. BIOMED RESEARCH INTERNATIONAL 2021; 2021:6888494. [PMID: 34540996 PMCID: PMC8445729 DOI: 10.1155/2021/6888494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 08/10/2021] [Accepted: 08/25/2021] [Indexed: 11/17/2022]
Abstract
Aquaporins (AQPs) are proteins that selectively transport water across the cell membrane. Although AQPs play important roles in secretion in the lacrimal gland, the expression and localization of AQPs have not been clarified yet. In the current study, we investigated the expression pattern of AQP family members in the murine lacrimal gland during development. Lacrimal gland tissues were harvested from E13.5 and E17.5 murine embryos and from mice 8 weeks of age (adults). Corneal and conjunctival tissues from the latter served as controls. Total RNA was isolated and analyzed for the expression of AQP family members using qPCR. The localization of AQPs in the adult lacrimal gland in adult murine lacrimal glands was also analyzed. Expression of Aqp8 and Aqp9 mRNAs was detected in the adult lacrimal gland but not in the cornea, conjunctiva, or fetal lacrimal gland. AQP8 and AQP9 and α-SMA partially colocalized around the basal regions of the acinar unit. The levels of Aqp3 mRNAs and protein were much lower in the adult lacrimal gland but were readily detected in the adult cornea and conjunctiva. Our study suggests that AQP8 and AQP9 may serve as markers for adult murine lacrimal gland, ductal, and myoepithelial cells.
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Limaye A, Hall BE, Zhang L, Cho A, Prochazkova M, Zheng C, Walker M, Adewusi F, Burbelo PD, Sun ZJ, Ambudkar IS, Dolan JC, Schmidt BL, Kulkarni AB. Targeted TNF-α Overexpression Drives Salivary Gland Inflammation. J Dent Res 2019; 98:713-719. [PMID: 30958728 DOI: 10.1177/0022034519837240] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Chronic inflammation of the salivary glands from pathologic conditions such as Sjögren's syndrome can result in glandular destruction and hyposalivation. To understand which molecular factors may play a role in clinical cases of salivary gland hypofunction, we developed an aquaporin 5 (AQP5) Cre mouse line to produce genetic recombination predominantly within the acinar cells of the glands. We then bred these mice with the TNF-αglo transgenic line to develop a mouse model with salivary gland-specific overexpression of TNF-α; which replicates conditions seen in sialadenitis, an inflammation of the salivary glands resulting from infection or autoimmune disorders such as Sjögren's syndrome. The resulting AQP5-Cre/TNF-αglo mice display severe inflammation in the salivary glands with acinar cell atrophy, fibrosis, and dilation of the ducts. AQP5 expression was reduced in the salivary glands, while tight junction integrity appeared to be disrupted. The immune dysregulation in the salivary gland of these mice led to hyposalivation and masticatory dysfunction.
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Affiliation(s)
- A Limaye
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - B E Hall
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - L Zhang
- 2 Wuhan University, Wuhan, China
| | - A Cho
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - M Prochazkova
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - C Zheng
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - M Walker
- 3 School of Dentistry, Meharry Medical College, Nashville, TN, USA
| | - F Adewusi
- 4 School of Dental Medicine, University of Connecticut, Farmington, CT, USA
| | - P D Burbelo
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Z J Sun
- 2 Wuhan University, Wuhan, China
| | - I S Ambudkar
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - J C Dolan
- 5 School of Dentistry, New York University, New York, NY, USA
| | - B L Schmidt
- 5 School of Dentistry, New York University, New York, NY, USA
| | - A B Kulkarni
- 1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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Abstract
Aquaporins (AQPs ) are expressed in most exocrine and endocrine secretory glands. Consequently, summarizing the expression and functions of AQPs in secretory glands represents a daunting task considering the important number of glands present in the body, as well as the number of mammalian AQPs - thirteen. The roles played by AQPs in secretory processes have been investigated in many secretory glands. However, despite considerable research, additional studies are clearly needed to pursue our understanding of the role played by AQPs in secretory processes. This book chapter will focus on summarizing the current knowledge on AQPs expression and function in the gastrointestinal tract , including salivary glands, gastric glands, Duodenal Brunner's gland, liver and gallbladder, intestinal goblets cells, exocrine and endocrine pancreas, as well as few other secretory glands including airway submucosal glands, lacrimal glands, mammary glands and eccrine sweat glands.
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Affiliation(s)
- Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Faculty of Medicine, Université Libre de Bruxelles, Brussels, Belgium.
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Sisto M, Lorusso L, Ingravallo G, Nico B, Ribatti D, Ruggieri S, Lofrumento DD, Lisi S. Abnormal distribution of AQP4 in minor salivary glands of primary Sjögren’s syndrome patients. Autoimmunity 2017. [DOI: 10.1080/08916934.2017.1341495] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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
| | - Loredana Lorusso
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs (SMBNOS), Section of Human Anatomy and Histology, University of Bari “Aldo Moro”, Bari, Italy
| | - Giuseppe Ingravallo
- Department of Emergency and Organ Transplantation (DETO), Pathology Section, University of Bari “Aldo Moro”, Bari, Italy
| | - Beatrice Nico
- 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
- National Cancer Institute “Giovanni Paolo II”, Bari, Italy
| | - Simona Ruggieri
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs (SMBNOS), Section of Human Anatomy and Histology, University of Bari “Aldo Moro”, Bari, Italy
| | - Dario Domenico Lofrumento
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, 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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Ali M, Shah D, Pasha Z, Jassim SH, Jassim Jaboori A, Setabutr P, Aakalu VK. Evaluation of Accessory Lacrimal Gland in Muller's Muscle Conjunctival Resection Specimens for Precursor Cell Markers and Biological Markers of Dry Eye Disease. Curr Eye Res 2016; 42:491-497. [PMID: 27612554 DOI: 10.1080/02713683.2016.1214966] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
PURPOSE The accessory lacrimal glands (ALGs) are an understudied component of the tear functional unit, even though they are important in the development of dry eye syndrome (DES). To advance our understanding of aging changes, regenerative potential, and histologic correlates to human characteristics, we investigated human ALG tissue from surgical samples to determine the presence or absence of progenitor cell markers and lacrimal epithelial markers and to correlate marker expression to relevant patient characteristics. MATERIALS AND METHODS ALG tissues obtained from Muller's muscle conjunctival resection (MMCR) specimens were created using tissue microarrays (TMAs). Immunofluorescence staining of MMCR sections was performed using primary antibodies specific to cell protein markers. Cell marker localization in TMAs was then assessed by two blinded observers using a standardized scoring system. Patient characteristics including age, race, and status of ocular surface health were then compared against expression of stem cell markers. RESULTS Human ALG expressed a number of epithelial markers, and in particular, histatin-1 was well correlated with the expression of epithelial markers and was present in most acini. In addition, we noted the presence of precursor cell markers nestin, ABCG2, and CD90 in ALG tissue. There was a decrease in precursor cell marker expression with increasing age. Finally, we noted that a negative association was present between histatin-1 expression and DES. CONCLUSIONS Thus, we report for the first time that human ALG tissues contain precursor marker-positive cells and that this marker expression may decrease with increasing age. Moreover, histatin-1 expression may be decreased in DES. Future studies will be performed to use these cell markers to isolate and culture lacrimal epithelial cells from heterogeneous tissues, determine the relevance of histatin-1 expression to DES, and isolate candidate precursor cells from ALG tissue.
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Affiliation(s)
- Marwan Ali
- a Department of Ophthalmology and Visual Sciences , University of Illinois at Chicago , Chicago , IL , USA
| | - Dhara Shah
- a Department of Ophthalmology and Visual Sciences , University of Illinois at Chicago , Chicago , IL , USA
| | - Zeeshan Pasha
- a Department of Ophthalmology and Visual Sciences , University of Illinois at Chicago , Chicago , IL , USA
| | - Sarmad H Jassim
- a Department of Ophthalmology and Visual Sciences , University of Illinois at Chicago , Chicago , IL , USA
| | - Assraa Jassim Jaboori
- a Department of Ophthalmology and Visual Sciences , University of Illinois at Chicago , Chicago , IL , USA
| | - Pete Setabutr
- a Department of Ophthalmology and Visual Sciences , University of Illinois at Chicago , Chicago , IL , USA
| | - Vinay K Aakalu
- a Department of Ophthalmology and Visual Sciences , University of Illinois at Chicago , Chicago , IL , USA
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18
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Schey KL, Wang Z, L Wenke J, Qi Y. Aquaporins in the eye: expression, function, and roles in ocular disease. Biochim Biophys Acta Gen Subj 2013; 1840:1513-23. [PMID: 24184915 DOI: 10.1016/j.bbagen.2013.10.037] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 10/22/2013] [Accepted: 10/23/2013] [Indexed: 12/13/2022]
Abstract
BACKGROUND All thirteen known mammalian aquaporins have been detected in the eye. Moreover, aquaporins have been identified as playing essential roles in ocular functions ranging from maintenance of lens and corneal transparency to production of aqueous humor to maintenance of cellular homeostasis and regulation of signal transduction in the retina. SCOPE OF REVIEW This review summarizes the expression and known functions of ocular aquaporins and discusses their known and potential roles in ocular diseases. MAJOR CONCLUSIONS Aquaporins play essential roles in all ocular tissues. Remarkably, not all aquaporin function as a water permeable channel and the functions of many aquaporins in ocular tissues remain unknown. Given their vital roles in maintaining ocular function and their roles in disease, aquaporins represent potential targets for future therapeutic development. GENERAL SIGNIFICANCE Since aquaporins play key roles in ocular physiology, an understanding of these functions is important to improving ocular health and treating diseases of the eye. It is likely that future therapies for ocular diseases will rely on modulation of aquaporin expression and/or function. This article is part of a Special Issue entitled Aquaporins.
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Affiliation(s)
- Kevin L Schey
- Department of Biochemistry, Vanderbilt School of Medicine, Vanderbilt University, Nashville, TN 37232, USA.
| | - Zhen Wang
- Department of Biochemistry, Vanderbilt School of Medicine, Vanderbilt University, Nashville, TN 37232, USA
| | - Jamie L Wenke
- Department of Biochemistry, Vanderbilt School of Medicine, Vanderbilt University, Nashville, TN 37232, USA
| | - Ying Qi
- Department of Biochemistry, Vanderbilt School of Medicine, Vanderbilt University, Nashville, TN 37232, USA
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Terakado K, Yogo T, Kohara Y, Soeta S, Nezu Y, Harada Y, Hara Y, Amasaki H, Tagawa M. Marked depletion of the water-channel protein, AQP5, in the canine nictitating membrane glands might contribute to the development of KCS. Vet Pathol 2012; 50:664-7. [PMID: 23160543 DOI: 10.1177/0300985812467467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The objectives of this study were to investigate the normal histological localization of aquaporin (AQP) 5 protein in the lacrimal and nictitating membrane glands and to compare this localization in healthy and keratoconjunctivitis sicca (KCS) dogs. Lacrimal and nictitating membrane glands of 5 healthy Beagles and nictitating membrane glands of 5 KCS dogs (3 Beagles and 2 mongrel dogs: 0-13 years) were used for the present study. The owners of the KCS dogs did not consent to perform biopsies of the lacrimal glands. The localization and distribution of AQP5 protein were investigated by an immunohistochemical technique. In immunohistochemical staining, AQP5 was localized in the apical site of acinar epithelial and ductal epithelial cells from both the lacrimal and nictitating membrane glands in healthy dogs. However, AQP5 was not detected in the 5 KCS dogs. These results for immunohistochemical AQP5 localization might correlate with the deficiency in tear secretion found in KCS dogs.
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Affiliation(s)
- K Terakado
- Department of Veterinary Surgery, Nippon Veterinary and Life Science University, 1-7-1 Kyonancho Musashino, Tokyo 180-8602, Japan.
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20
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Dysfunction of lacrimal and salivary glands in Sjögren's syndrome: nonimmunologic injury in preinflammatory phase and mouse model. J Biomed Biotechnol 2011; 2011:407031. [PMID: 21660135 PMCID: PMC3110304 DOI: 10.1155/2011/407031] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 02/08/2011] [Accepted: 03/08/2011] [Indexed: 11/30/2022] Open
Abstract
Sjögren's syndrome (SjS) is a chronic autoimmune disorder characterized by dry eyes and dry mouth due to dacryoadenitis and sialoadenitis with SS-A/Ro and/or SS-B/La autoantibodies in genetically predisposed individuals. Destruction of lacrimal and salivary glands by autoimmune reactions may lead to clinical manifestation. However, the mechanisms behind the decreased volume of secretions in tears and saliva are complex and are not fully understood. Exocrine gland dysfunction may precede autoimmunity (acquired immunity) or represent a process independent from inflammation in the pathogenesis of SjS. The preceded functional and morphologic changes of those tissues by nonimmunologic injury before the development of inflammation at the sites of target organs have been implicated. This paper focuses on the several factors and components relating to glandular dysfunction and morphologic changes by nonimmunologic injury during the preinflammatory phase in mouse model, including the factors which link between innate immunity and adaptive immunity.
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21
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Ding C, Nandoskar P, Lu M, Thomas P, Trousdale MD, Wang Y. Changes of aquaporins in the lacrimal glands of a rabbit model of Sjögren's syndrome. Curr Eye Res 2011; 36:571-8. [PMID: 21524183 DOI: 10.3109/02713683.2011.574330] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AIMS To test the hypothesis that the expression of aquaporins (AQPs) 4 and 5 is altered in the lacrimal glands (LG) of rabbits with induced autoimmune dacryoadenitis (IAD). MATERIALS AND METHODS LGs were obtained from adult female rabbits with IAD, and age-matched female control rabbits. LGs were processed for laser capture microdissection (LCM), real time RT-PCR, Western blot, and immunofluorescence for the detection and quantification of protein and mRNAs of AQP4 and AQP5 in whole LGs, and purified acinar cells and duct cells from specific duct segments. RESULTS In rabbits with IAD, abundances of mRNAs for AQP4 and AQP5 from whole LGs were significantly lower than controls. Levels of mRNA for AQP4 were lower in most duct segments from rabbits with IAD. However, the mRNA abundance for AQP5 was significantly lower in acini from rabbits with IAD, while its abundance was higher in each duct segment. Western blot showed that the expression of AQP4 in LGs from rabbits with IAD was 36% more abundant than normal controls, whereas AQP5 was 72% less abundant. Immunofluorescence indicated that AQP4 immunoreactivity (AQP4-IR) was present on the basolateral membranes of acinar and ductal cells in control and diseased LGs, with ductal cells showing stronger AQP4-IR than acinar cells. AQP5-IR was found on apical and basolateral membranes of acinar cells, and showed a "mosaic" pattern, i.e., with some acini and/or acinar cells showing stronger AQP5-IR than others. Minimal AQP5-IR was detected in ductal cells from control animals, while its intensity was significantly increased in rabbits with IAD. CONCLUSIONS These data strongly support our hypothesis that expressions of AQPs are altered in rabbits with IAD, and that specific ductal segment play important roles in lacrimal secretion.
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Affiliation(s)
- Chuanqing Ding
- Department of Cell and Neurobiology, University of Southern California, Keck School of Medicine, Los Angeles, California 90089-9112, USA
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Schechter JE, Warren DW, Mircheff AK. A Lacrimal Gland is a Lacrimal Gland, But Rodent's and Rabbit's Are Not Human. Ocul Surf 2010; 8:111-34. [DOI: 10.1016/s1542-0124(12)70222-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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23
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Ruiz-Ederra J, Levin MH, Verkman AS. In situ fluorescence measurement of tear film [Na+], [K+], [Cl-], and pH in mice shows marked hypertonicity in aquaporin-5 deficiency. Invest Ophthalmol Vis Sci 2009; 50:2132-8. [PMID: 19136711 DOI: 10.1167/iovs.08-3033] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Tear film composition depends on water and ion transport across ocular surface epithelia and on fluid secretion by lacrimal glands. The purpose of this study was to establish in situ fluorescence methods to measure tear film ionic concentrations and pH in mice and to determine whether tear film composition is sensitive to deficiency of the major ocular surface aquaporin water channels. METHODS Tear film ionic concentrations and pH were measured in anesthetized mice by ratio imaging fluorescence microscopy after topical application of ion/pH-sensing, dual-wavelength fluorescent indicators. [Na(+)], [K(+)], and [Cl(-)] were measured with membrane-impermeant indicators developed by our laboratory, and pH was measured with bis(carboxyethyl)-carboxyfluorescein fluorescence-conjugated dextran. Measurements were performed on wild-type mice and on knockout mice lacking aquaporins AQP1, AQP3, and AQP5. RESULTS In wild-type mice, tear film [Na(+)] was 139 +/- 8 mM, [K(+)] was 48 +/- 1 mM, [Cl(-)] was 127 +/- 4 mM, and pH was 7.59 +/- 0.2 (SE; n = 5-8). pH did not differ significantly in the AQP knockout mice. [Na(+)] was increased by approximately twofold in AQP5 null mice (230 +/- 20 mM) and was greatly reduced after exposure of the ocular surface to a humidified atmosphere. [K(+)] was mildly reduced in AQP1 null mice. CONCLUSIONS These results establish an in situ optical methodology to measure tear film [Na(+)], [K(+)], [Cl(-)], and pH in living mice, without the need for fluid sampling. Tear film hypertonicity in AQP5 deficiency is likely caused by reduced transcorneal water secretion in response to evaporative water loss.
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Affiliation(s)
- Javier Ruiz-Ederra
- Department of Medicine and Physiology, Cardiovascular Research Institute, University of California, San Francisco, California 94143-0521, USA
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Abstract
The kidney is a model organ for transport physiology (Nielsen 1996). AQPs are well-characterized in mammalian kidneys, where they facilitate transepithelial water reabsorption. Most renal AQPs are expressed either in proximal tubule cells or in collecting duct principal cells, which are known as sites for water reabsorption. AQP1 is present in both apical and basolateral membranes of proximal tubules, and in descending limbs of Henle's loop where 70% of filtrated water is isoosmotically reabsorbed (King and Agre 1996). AQP2 is expressed in principal cells of the collecting duct; in response to vasopressin, AQP2 translocates from intracellular vesicles to the apical plasma membranes, thereby increasing water permeability to concentrate urine (Nielsen et al. 1993, 1995; Knepper 1997; Schrier 2006). AQP3 and AQP4 reside in the basolateral membranes of collecting duct principal cells, where they may provide the exit pathways for urine. AQP7, AQP8, and AQP11 are also present in the proximal tubules (Nielsen et al. 1998).A rat cDNA clone encoding AQP6 was isolated by PCR-based homologous cloning from a rat kidney cDNA library (Ma et al. 1993; Yasui et al. 1999). AQP6 has high sequence homology to AQP0, AQP2, and AQP5. A human AQP6 was also cloned (Ma et al. 1996). Interestingly, the genes encoding AQP2, AQP5, and AQP6 are mapped to chromosome band 12q13 as a family gene cluster at this locus (Ma et al. 1997). Nevertheless, AQP6 is distinct from AQP0, AQP2, and AQP5 in terms of function. Among the renal aquaporins mentioned above, AQP6 has a unique distribution and a distinct function.
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Affiliation(s)
- Masato Yasui
- Department of Pharmacology, Keio University School of Medicine, Tokyo, Japan.
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Abstract
The aquaporins (AQPs) are integral membrane proteins whose main function is to transport water across cell membranes in response to osmotic gradients. At the ocular surface, AQP1 is expressed in corneal endothelium, AQP3 and AQP5 in corneal epithelium, and AQP3 in conjunctival epithelium. AQPs are also expressed in lens fiber cells (AQP0), lens epithelium (AQP1), ciliary epithelium (AQP1, AQP4) and retinal Müller cells (AQP4). Mutations in AQP0 produce congenital cataracts in humans. Analysis of knockout mice lacking individual AQPs suggests their involvement in maintenance of corneal and lens transparency, corneal epithelial repair, intraocular pressure (IOP) regulation, retinal signal transduction and retinal swelling following injury. The mouse phenotype findings implicate AQPs as potential drug targets for therapy of elevated IOP and ocular disorders involving the cornea, lens and retina. However, much research remains in defining cell-level mechanisms for the ocular AQP functions, in establishing the relevance to human eye disease of conclusions from knockout mice, and in developing AQP-modulating drugs.
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Affiliation(s)
- A S Verkman
- Department of Medicine and Physiology, University of California, San Francisco, 1246 Health Sciences East Tower, San Francisco, CA 94143-0521, USA.
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