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Ung L, Chodosh J. Foundational concepts in the biology of bacterial keratitis. Exp Eye Res 2021; 209:108647. [PMID: 34097906 PMCID: PMC8595513 DOI: 10.1016/j.exer.2021.108647] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 04/28/2021] [Accepted: 05/27/2021] [Indexed: 12/12/2022]
Abstract
Bacterial infections of the cornea, or bacterial keratitis (BK), are notorious for causing rapidly fulminant disease and permanent vision loss, even among treated patients. In the last sixty years, dramatic upward trajectories in the frequency of BK have been observed internationally, driven in large part by the commercialization of hydrogel contact lenses in the late 1960s. Despite this worsening burden of disease, current evidence-based therapies for BK - including broad-spectrum topical antibiotics and, if indicated, topical corticosteroids - fail to salvage vision in a substantial proportion of affected patients. Amid growing concerns of rapidly diminishing antibiotic utility, there has been renewed interest in urgently needed novel treatments that may improve clinical outcomes on an individual and public health level. Bridging the translational gap in the care of BK requires the identification of new therapeutic targets and rational treatment design, but neither of these aims can be achieved without understanding the complex biological processes that determine how bacterial corneal infections arise, progress, and resolve. In this chapter, we synthesize the current wealth of human and animal experimental data that now inform our understanding of basic BK pathophysiology, in context with modern concepts in ocular immunology and microbiology. By identifying the key molecular determinants of clinical disease, we explore how novel treatments can be developed and translated into routine patient care.
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Affiliation(s)
- Lawson Ung
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA; Infectious Disease Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA; Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, USA
| | - James Chodosh
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA; Infectious Disease Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA.
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Fleiszig SMJ, Kroken AR, Nieto V, Grosser MR, Wan SJ, Metruccio MME, Evans DJ. Contact lens-related corneal infection: Intrinsic resistance and its compromise. Prog Retin Eye Res 2019; 76:100804. [PMID: 31756497 DOI: 10.1016/j.preteyeres.2019.100804] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 11/05/2019] [Accepted: 11/12/2019] [Indexed: 12/20/2022]
Abstract
Contact lenses represent a widely utilized form of vision correction with more than 140 million wearers worldwide. Although generally well-tolerated, contact lenses can cause corneal infection (microbial keratitis), with an approximate annualized incidence ranging from ~2 to ~20 cases per 10,000 wearers, and sometimes resulting in permanent vision loss. Research suggests that the pathogenesis of contact lens-associated microbial keratitis is complex and multifactorial, likely requiring multiple conspiring factors that compromise the intrinsic resistance of a healthy cornea to infection. Here, we outline our perspective of the mechanisms by which contact lens wear sometimes renders the cornea susceptible to infection, focusing primarily on our own research efforts during the past three decades. This has included studies of host factors underlying the constitutive barrier function of the healthy cornea, its response to bacterial challenge when intrinsic resistance is not compromised, pathogen virulence mechanisms, and the effects of contact lens wear that alter the outcome of host-microbe interactions. For almost all of this work, we have utilized the bacterium Pseudomonas aeruginosa because it is the leading cause of lens-related microbial keratitis. While not yet common among corneal isolates, clinical isolates of P. aeruginosa have emerged that are resistant to virtually all currently available antibiotics, leading the United States CDC (Centers for Disease Control) to add P. aeruginosa to its list of most serious threats. Compounding this concern, the development of advanced contact lenses for biosensing and augmented reality, together with the escalating incidence of myopia, could portent an epidemic of vision-threatening corneal infections in the future. Thankfully, technological advances in genomics, proteomics, metabolomics and imaging combined with emerging models of contact lens-associated P. aeruginosa infection hold promise for solving the problem - and possibly life-threatening infections impacting other tissues.
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Affiliation(s)
- Suzanne M J Fleiszig
- School of Optometry, University of California, Berkeley, CA, USA; Graduate Group in Vision Science, University of California, Berkeley, CA, USA; Graduate Groups in Microbiology and Infectious Diseases & Immunity, University of California, Berkeley, CA, USA.
| | - Abby R Kroken
- School of Optometry, University of California, Berkeley, CA, USA
| | - Vincent Nieto
- School of Optometry, University of California, Berkeley, CA, USA
| | | | - Stephanie J Wan
- Graduate Group in Vision Science, University of California, Berkeley, CA, USA
| | | | - David J Evans
- School of Optometry, University of California, Berkeley, CA, USA; College of Pharmacy, Touro University California, Vallejo, CA, USA
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Onochie OE, Onyejose AJ, Rich CB, Trinkaus-Randall V. The Role of Hypoxia in Corneal Extracellular Matrix Deposition and Cell Motility. Anat Rec (Hoboken) 2019; 303:1703-1716. [PMID: 30861330 DOI: 10.1002/ar.24110] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 11/29/2018] [Accepted: 12/17/2018] [Indexed: 12/24/2022]
Abstract
The cornea is an excellent model tissue to study how cells adapt to periods of hypoxia as it is naturally exposed to diurnal fluxes in oxygen. It is avascular, transparent, and highly innervated. In certain pathologies, such as diabetes, limbal stem cell deficiency, or trauma, the cornea may be exposed to hypoxia for variable lengths of time. Due to its avascularity, the cornea requires atmospheric oxygen, and a reduction in oxygen availability can impair its physiology and function. We hypothesize that hypoxia alters membrane stiffness and the deposition of matrix proteins, leading to changes in cell migration, focal adhesion formation, and wound repair. Two systems-a 3D corneal organ culture model and polyacrylamide substrates of varying stiffness-were used to examine the response of corneal epithelium to normoxic and hypoxic environments. Exposure to hypoxia alters the deposition of the matrix proteins such as laminin and Type IV collagen. In addition, previous studies had shown a change in fibronectin after injury. Studies performed on matrix-coated acrylamide substrates ranging from 0.2 to 50 kPa revealed stiffness-dependent changes in cell morphology. The localization, number, and length of paxillin pY118- and vinculin pY1065-containing focal adhesions were different in wounded corneas and in human corneal epithelial cells incubated in hypoxic environments. Overall, these results demonstrate that low-oxygenated environments modify the composition of the extracellular matrix, basal lamina stiffness, and focal adhesion dynamics, leading to alterations in the function of the cornea. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Obianamma E Onochie
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts
| | - Anwuli J Onyejose
- Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts
| | - Celeste B Rich
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts
| | - Vickery Trinkaus-Randall
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts.,Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts
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Capasso D, Pepe MV, Rossello J, Lepanto P, Arias P, Salzman V, Kierbel A. Elimination of Pseudomonas aeruginosa through Efferocytosis upon Binding to Apoptotic Cells. PLoS Pathog 2016; 12:e1006068. [PMID: 27977793 PMCID: PMC5158079 DOI: 10.1371/journal.ppat.1006068] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 11/15/2016] [Indexed: 02/03/2023] Open
Abstract
For opportunistic pathogens such as Pseudomonas aeruginosa, the mucosal barrier represents a formidable challenge. Infections develop only in patients with altered epithelial barriers. Here, we showed that P. aeruginosa interacts with a polarized epithelium, adhering almost exclusively at sites of multi-cellular junctions. In these sites, numerous bacteria attach to an extruded apoptotic cell or apoptotic body. This dead cell tropism is independent of the type of cell death, as P. aeruginosa also binds to necrotic cells. We further showed that P. aeruginosa is internalized through efferocytosis, a process in which surrounding epithelial cells engulf and dispose of extruded apoptotic cells. Intracellularly, along with apoptotic cell debris, P. aeruginosa inhabits an efferocytic phagosome that acquires lysosomal features, and is finally killed. We propose that elimination of P. aeruginosa through efferocytosis is part of a host defense mechanism. Our findings could be relevant for the study of cystic fibrosis, which is characterized by an exacerbated number of apoptotic cells and ineffective efferocytosis. Pseudomonas aeruginosa is an opportunistic pathogen that infects vulnerable patients, such as those with cystic fibrosis or hospitalized in intensive care units. An advance towards understanding infections caused by P. aeruginosa would be to fully elucidate the mechanisms that operate in the bacteria-epithelial barrier interplay. Here, we showed that P. aeruginosa exhibits a remarkable tropism towards dead cells. As bacteria interact with a polarized epithelium, they attach and aggregate almost exclusively on apoptotic cells extruded from the epithelium, while the rest of the surface seems reluctant to bacterial adhesion. We further showed that P. aeruginosa is internalized by epithelial cells surrounding the infected apoptotic cell through efferocytosis, a process in which apoptotic cells are engulfed and disposed of by other cells. Bacteria are eliminated intracellularly. Our findings may help to understand why contexts such as cystic fibrosis, where apoptotic cells are unusually produced and efferocytosis fails, favor P. aeruginosa colonization.
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Affiliation(s)
- Darío Capasso
- Instituto de Investigaciones Biotecnológicas Dr. Rodolfo A. Ugalde (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (UNSAM-CONICET), San Martín, Buenos Aires, Argentina
| | - María Victoria Pepe
- Instituto de Investigaciones Biotecnológicas Dr. Rodolfo A. Ugalde (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (UNSAM-CONICET), San Martín, Buenos Aires, Argentina
| | | | | | - Paula Arias
- Instituto de Investigaciones Biotecnológicas Dr. Rodolfo A. Ugalde (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (UNSAM-CONICET), San Martín, Buenos Aires, Argentina
| | - Valentina Salzman
- Instituto de Investigaciones Biotecnológicas Dr. Rodolfo A. Ugalde (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (UNSAM-CONICET), San Martín, Buenos Aires, Argentina
| | - Arlinet Kierbel
- Instituto de Investigaciones Biotecnológicas Dr. Rodolfo A. Ugalde (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (UNSAM-CONICET), San Martín, Buenos Aires, Argentina
- * E-mail:
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Wei C, Zhu M, Petroll WM, Robertson DM. Pseudomonas aeruginosa infectious keratitis in a high oxygen transmissible rigid contact lens rabbit model. Invest Ophthalmol Vis Sci 2014; 55:5890-9. [PMID: 25125601 PMCID: PMC4168740 DOI: 10.1167/iovs.14-14235] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 08/02/2014] [Indexed: 12/20/2022] Open
Abstract
PURPOSE To establish a rabbit model of infectious Pseudomonas aeruginosa keratitis using ultrahigh oxygen transmissible rigid lenses and characterize the frequency and severity of infection when compared to a non-oxygen transmissible lens material. METHODS Rabbits were fit with rigid lenses composed of ultrahigh and non-oxygen transmissible materials. Prior to wear, lenses were inoculated with an invasive corneal isolate of P. aeruginosa stably conjugated to green fluorescent protein (GFP). Corneas were examined before and after lens wear using a modified Heidelberg Rostock Tomograph in vivo confocal microscope. Viable bacteria adherent to unworn and worn lenses were assessed by standard plate counts. The presence of P. aeruginosa-GFP and myeloperoxidase-labeled neutrophils in infected corneal tissue was evaluated using laser scanning confocal microscopy. RESULTS The frequency and severity of infectious keratitis was significantly greater with inoculated ultrahigh oxygen transmissible lenses. Infection severity was associated with increasing neutrophil infiltration and in severe cases, corneal melting. In vivo confocal microscopic analysis of control corneas following lens wear confirmed that hypoxic lens wear was associated with mechanical surface damage, whereas no ocular surface damage was evident in the high-oxygen lens group. CONCLUSIONS These data indicate that in the absence of adequate tear clearance, the presence of P. aeruginosa trapped under the lens overrides the protective effects of oxygen on surface epithelial cells. These findings also suggest that alternative pathophysiological mechanisms exist whereby changes under the lens in the absence of frank hypoxic damage result in P. aeruginosa infection in the otherwise healthy corneal epithelium.
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Affiliation(s)
- Cynthia Wei
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Meifang Zhu
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - W Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Danielle M Robertson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
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Abstract
Microbial keratitis is a sight-threatening complication associated with contact lenses. The introduction of silicone hydrogel lens materials with increased oxygen transmission to the ocular surface has not significantly altered the incidence of microbial keratitis. These data suggest that alternate, or additional, predisposing factors involving lens wear must be addressed to reduce or eliminate these infections. The contact lens can provide a surface for microbial growth in situ and can also influence ocular surface homeostasis through effects on the tear fluid and corneal epithelium. Thus, it is intuitive that future contact lens materials could make a significant contribution to preventing microbial keratitis. Design of the "right" material to prevent microbial keratitis requires understanding the effects of current materials on bacterial virulence in the cornea and on ocular surface innate defenses. Current knowledge in each of these areas will be presented with a discussion of future directions needed to understand the influence of lens material on the pathogenesis of microbial keratitis.
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Peng H, Katsnelson J, Yang W, Brown MA, Lavker RM. FIH-1/c-kit signaling: a novel contributor to corneal epithelial glycogen metabolism. Invest Ophthalmol Vis Sci 2013; 54:2781-6. [PMID: 23548624 DOI: 10.1167/iovs.12-11512] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
PURPOSE Corneal epithelial cells have large stores of glycogen, which serve as their primary energy source. Recently, we demonstrated that factor-inhibiting hypoxia-inducible factor 1 (FIH-1) diminished glycogen stores in vitro and in vivo, working through the Akt/Glycogen Synthase Kinase (GSK)-3β pathway. In this study we investigated the relationship between FIH-1 and c-kit as it pertains to limbal and corneal epithelial glycogen stores. METHODS Limbal and corneal epithelia from wild-type FIH-1(-/-) and Kit(W/Wv) mice were stained with periodic acid Schiff (PAS) to detect glycogen. RNA samples prepared from laser-capture microdissected populations of limbal epithelium were subjected to real-time quantitative PCR to determine c-kit ligand expression. Submerged cultures of primary human corneal epithelial keratinocytes (HCEKs) transduced with FIH-1 were treated with c-kit ligand to establish further a FIH-1/c-kit interaction via Western analysis. Akt phosphorylation was assessed by Western blotting. RESULTS The limbal epithelial cells of FIH-1 null mice had an increase in glycogen levels as well as increased c-kit ligand mRNA compared with wild-type controls. Consistent with a FIH-1/c-kit association, the diminished Akt signaling observed in FIH-1-overexpressing HCEKs could be restored by the addition of c-kit ligand. Interestingly, Akt signaling and glycogen content of the corneal epithelium were significantly decreased in c-kit mutant mice. CONCLUSIONS c-Kit signaling has been shown to affect glucose metabolism via the Akt/GSK-3β pathway. An inverse relationship between FIH-1 and c-kit signaling pathways accounts, in part, for differences in glycogen content between corneal and limbal epithelial cells.
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Affiliation(s)
- Han Peng
- Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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Robertson DM. The effects of silicone hydrogel lens wear on the corneal epithelium and risk for microbial keratitis. Eye Contact Lens 2013; 39:67-72. [PMID: 23266590 PMCID: PMC3587121 DOI: 10.1097/icl.0b013e31827c5b73] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Previous studies using animal models and human clinical trials have demonstrated that the use of low-oxygen-transmissible contact lens materials produce corneal epithelial surface damage resulting in increased Pseudomonas aeruginosa (PA) adhesion and raft-mediated internalization into surface corneal epithelial cells. These findings led to the testable clinical predictions that (1) microbial keratitis (MK) risk is expected to be the greatest during the first 6 months of wear; (2) there is no difference between 6 and 30 night extended wear; and (3) that wear of hyperoxygen-transmissible lenses would reduce the reported incidence of infection. Subsequent epidemiologic studies have confirmed the first two predictions; however, increased oxygen transmissibility with silicone hydrogel (SiHy) lens wear has not altered the overall incidence of MK. In this review, more recent clinical and basic studies that investigate epithelial alterations and bacterial adhesion to corneal epithelial cells after the wear of SiHy lenses with and without concomitant exposure to chemically preserved multipurpose solutions (MPS) will be examined. The collective results of these studies demonstrate that even in the absence of lens-related hypoxia, MPS induce ocular surface changes during SiHy lens wear that are associated with a pathophysiologic increase in PA adherence and internalization in the corneal epithelium, and therefore, predict a greater risk for PA-MK. In addition, new data supporting an interactive role for inflammation in facilitating PA adherence and internalization in the corneal epithelium will also be discussed.
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Affiliation(s)
- Danielle M Robertson
- Department of Ophthalmology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA.
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Peng H, Hamanaka RB, Katsnelson J, Hao LL, Yang W, Chandel NS, Lavker RM. MicroRNA-31 targets FIH-1 to positively regulate corneal epithelial glycogen metabolism. FASEB J 2012; 26:3140-7. [PMID: 22532441 DOI: 10.1096/fj.11-198515] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Corneal epithelium relies on abundant glycogen stores as its primary energy source. MicroRNA-31 (miR-31), a corneal epithelial-preferred miRNA, negatively regulates factor inhibiting hypoxia-inducible factor-1 (FIH-1). Since HIF-1α is involved in anaerobic energy production, we investigated the role that miR-31 and FIH-1 play in regulating corneal epithelial glycogen. We used antagomirs (antago) to reduce the level of miR-31 in primary human corneal epithelial keratinocytes (HCEKs), and a miR-31-resistant FIH-1 to increase FIH-1 levels. Antago-31 raised FIH-1 levels and significantly reduced glycogen stores in HCEKs compared to irrelevant-antago treatment. Similarly, HCEKs retrovirally transduced with a miR-31-resistant FIH-1 had markedly reduced glycogen levels compared with empty vector controls. In addition, we observed no change in a HIF-1α reporter or known genes downstream of HIF-1α indicating that the action of FIH-1 and miR-31 on glycogen is HIF-1α-independent. An enzyme-dead FIH-1 mutation failed to restore glycogen stores, indicating that FIH-1 negatively regulates glycogen in a hydroxylase-independent manner. FIH-1 overexpression in HCEKs decreased AKT signaling, activated GSK-3β, and inactivated glycogen synthase. Treatment of FIH-1-transduced HCEKs with either a myristolated Akt or a GSK-3β inhibitor restored glycogen stores, confirming the direct involvement of Akt/GSK-3β signaling. Silencing FIH-1 in HCEKs reversed the observed changes in Akt-signaling. Glycogen regulation in a HIF-1α-independent manner is a novel function for FIH-1 and provides new insight into how the corneal epithelium regulates its energy requirements.
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Affiliation(s)
- Han Peng
- Department of Dermatology, The Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Pan H, Wu X. Hypoxia attenuates inflammatory mediators production induced by Acanthamoeba via Toll-like receptor 4 signaling in human corneal epithelial cells. Biochem Biophys Res Commun 2012; 420:685-91. [PMID: 22450324 DOI: 10.1016/j.bbrc.2012.03.069] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 03/10/2012] [Indexed: 10/28/2022]
Abstract
Acanthamoeba keratitis (AK) is a vision-threatening corneal infection that is intimately associated with contact lens use which leads to hypoxic conditions on the corneal surface. However, the effect of hypoxia on the Acanthamoeba-induced host inflammatory response of corneal epithelial cells has not been studied. In the present study, we investigated the effect of hypoxia on the Acanthamoeba-induced production of inflammatory mediators interleukin-8 (IL-8) and interferon-β (IFN-β) in human corneal epithelial cells and then evaluated its effects on the Toll-like receptor 4 (TLR4) signaling, including TLR4 and myeloid differentiation primary response gene (88) (MyD88) expression as well as the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and extracellular signal-regulated kinases 1/2 (ERK1/2). We then studied the effect of hypoxia on a TLR4-specific inflammatory response triggered by the TLR4 ligand lipopolysaccharide (LPS). Our data showed that hypoxia significantly decreased the production of IL-8 and IFN-β. Furthermore, hypoxia attenuated Acanthamoeba-triggered TLR4 expression as well as the activation of NF-κB and ERK1/2, indicating that hypoxia abated Acanthamoeba-induced inflammatory responses by affecting TLR4 signaling. Hypoxia also inhibited LPS-induced IL-6 and IL-8 secretion, myeloid differentiation primary response gene (88) MyD88 expression and NF-κB activation, confirming that hypoxia suppressed the LPS-induced inflammatory response by affecting TLR4 signaling. In conclusion, our results demonstrated that hypoxia attenuated the host immune and inflammatory response against Acanthamoeba infection by suppressing TLR4 signaling, indicating that hypoxia might impair the host cell's ability to eliminate the Acanthamoeba invasion and that hypoxia could enhance cell susceptibility to Acanthamoeba infection. These results may explain why contact lens use is one of the most prominent risk factors for AK.
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Affiliation(s)
- Hong Pan
- Department of Ophthalmology, Qilu Hospital, Shandong University, 107#, Wenhua Xi Road, Jinan 250012, PR China
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Byfield FJ, Kowalski M, Cruz K, Leszczyńska K, Namiot A, Savage PB, Bucki R, Janmey PA. Cathelicidin LL-37 Increases Lung Epithelial Cell Stiffness, Decreases Transepithelial Permeability, and Prevents Epithelial Invasion byPseudomonas aeruginosa. THE JOURNAL OF IMMUNOLOGY 2011; 187:6402-9. [DOI: 10.4049/jimmunol.1102185] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Effects of multipurpose contact lens care solutions and their ingredients on membrane-associated mucins of human corneal epithelial cells. Eye Contact Lens 2011; 36:361-6. [PMID: 21060261 DOI: 10.1097/icl.0b013e3181faa43e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE Membrane-associated mucins play an important role for protecting epithelial cells at the ocular surface from microbial invasion. The purpose of this study was to determine whether multipurpose solutions (MPSs) for contact lens care and their ingredients alter the expression of membrane-associated mucins in human corneal epithelial (HCE-T) cells. METHODS SV40-immortalized HCE-T cells were cultured in Dulbecco's modified Eagle medium/F12 medium with 5% fetal bovine serum to confluence and were then exposed to 10% dilutions of five different MPSs, or to their representative ingredients, 0.1% macrogolglycerol hydroxystearate, 0.1% poloxamer, 0.1% poloxamine, 1 and 5 ppm polyhexamethylene biguanide, or 0.05% and 0.1% boric acid for 24 hr. Quantitative real-time polymerase chain reaction was used to investigate the gene expression of MUC1, MUC4, and MUC16. Immunofluorescence staining of MUC16 protein on the surface of the HCE-T cells exposed to 10% diluted MPSs for 24 hr or undiluted MPSs for 30 min was observed by laser confocal scanning microscopy followed by quantitative image analysis. RESULTS Three MPSs containing boric acid significantly reduced gene expressions of MUC1 from 20.2% to 56.7% (P<0.01). Gene expressions of MUC4 and MUC16 were also reduced by these MPSs; however, there were no significant differences. Among ingredients, 0.1% boric acid significantly reduced gene expressions of MUC1 and MUC16 by 7.4% and 18.9%, respectively (P<0.01). Immunofluorescence microscopy also demonstrated that in undiluted form, three MPSs containing boric acid significantly reduced the expression of MUC16 protein. CONCLUSIONS The MPSs containing boric acid downregulate membrane-associated mucins as compared with MPSs that do not contain boric acid. There may be some subtle membrane or other interactions between ingredients in lens-care solutions that adversely alter corneal cell mucins.
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Abstract
PURPOSE To identify the pathophysiological changes produced by contact lens wear that predispose the cornea to infection and search for prospective modifiable risk factors that could reduce the incidence of this critical complication in millions of patients worldwide. METHODS Significant experimental and clinical publications are reviewed, and the results of ongoing studies are presented. RESULTS Pseudomonas aeruginosa (PA) is the most common pathogen causing lens-related infectious keratitis over 3 decades. Contact lens wear can increase the risk of infection by increasing surface cell PA binding, thereby promoting invasion between broken tight junctions and initiating direct intracellular invasion mediated by lens-induced membrane lipid rafts. Prevention of upregulation of specific surface-binding receptors for PA with concomitant increase in infection risk is a zero damage game where independent interactions among lens type, mode of wear, oxygen transmissibility, polymer, and toxic effects of associated care solutions ideally should collectively produce no increased ability for PA to attach and/or to invade, thus minimizing the risk for lens-associated infections. The specific hypothesis tested is, "no increased epithelial surface damage... no increased PA binding or invasion... no increased risk for infection." Testing of this new paradigm has been performed in vitro and in animal and human clinical trials and correlated clinically with relative risk results from robust current epidemiological studies. Results to date clearly support the use of lens-related increases in PA binding (bench) as a noninvasive clinical predictor of risk for lens-related infection in subsequent large-scale population studies (bedside). Currently, results suggest that use of common commercial multipurpose lens care solutions with soft lenses may alone significantly increase infection risk by enhancing lens-related PA binding as compared with use of nonpreserved solutions (hydrogen peroxide). Clinical testing also shows that only peroxide solutions show significant disinfection capability against amoebic cysts. Further case-control studies to examine relative risk for infection by lens type and lens care solution are urgently needed. CONCLUSIONS Millions of patients are dependent on contact lenses for vision worldwide; over 3 decades, lens use has increased, although risk for lens-related infection has remained stubbornly unchanged. Unfortunately, recent introduction of a new generation of hyper-oxygen transmissible lenses used with traditional multipurpose lens care solutions has not lowered overall risks for lens-related infections; however, similar lenses used with nonpreserved care solutions (peroxide) recently demonstrated no significant increases in PA binding in a 1-year clinical trial. Collectively, these findings along with the urgent need for amoebic cysticidal disinfection have led to a current recommendation to patients to use nonpreserved (hydrogen peroxide) care solutions in soft lens wear.
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Abstract
Sight-threatening microbial keratitis associated with contact lens wear remains a serious concern for patients, eye-care practitioners, and the contact lens industry. Several decades of research and some major advances in lens and solution technology have not resulted in a decline in disease incidence. Here, we offer a perspective on the complex pathogenesis of microbial keratitis, the factors that have prevented a better understanding of this disease, and new approaches being used to tackle this important clinical problem.
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Sosne G, Qiu P, Kurpakus-Wheater M, Matthew H. Thymosin β4 and corneal wound healing: visions of the future. Ann N Y Acad Sci 2010; 1194:190-8. [PMID: 20536468 DOI: 10.1111/j.1749-6632.2010.05472.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Gabriel Sosne
- Department of Ophthalmology and Anatomy, Wayne State University School of Medicine, Kresge Eye Institute, Detroit, Michigan, USA.
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Tam C, Mun JJ, Evans DJ, Fleiszig SMJ. The impact of inoculation parameters on the pathogenesis of contact lens-related infectious keratitis. Invest Ophthalmol Vis Sci 2010; 51:3100-6. [PMID: 20130275 DOI: 10.1167/iovs.09-4593] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
PURPOSE Contact lens wear predisposes to Pseudomonas aeruginosa keratitis, but the mechanisms involved remain unclear. An in vivo model was used to study lens inoculation conditions enabling disease. METHODS Custom-made hydrogel contact lenses were fitted to rats after incubation in P. aeruginosa approximately 10(11) cfu/mL (3 hours) or approximately 10(3) cfu/mL (24 hours). Another group was inadvertently inoculated with a suction pen previously used with high inocula, but rinsed in ethanol and stored dry (6 months). Some corneas were tissue paper-blotted to cause fluorescein staining before lens fitting. Contralateral eyes were untreated. Twenty-four hours after disease detection, lenses were transferred to naive rats or examined by confocal microscopy before homogenization to quantify viable bacteria. After lens removal, corneas were washed to collect nonadherent bacteria and were analyzed by immunohistochemistry. RESULTS All eyes challenged with unworn contaminated lenses developed keratitis after approximately 7 to 10 days. Disease delay and severity were unaffected by inoculum parameters or tissue blotting but occurred sooner with lenses transferred from infected eyes ( approximately 2 days). Worn lenses and corneal washes contained infecting bacteria. Posterior, not anterior, lens surfaces harbored P. aeruginosa biofilms that penetrated the lens matrix. Diseased corneas showed an infiltration of phagocytes and T-lymphocytes. CONCLUSIONS P. aeruginosa induces keratitis in this lens-wearing model after a single inoculation. Delayed disease onset was interesting considering the greater keratitis risk during extended wear. Infection did not require the disruption of corneal barrier function before lens wear and occurred without exposure to lens care solutions. The data suggest that keratitis involves biofilm formation or other bacterial adaptations in vivo.
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Affiliation(s)
- Connie Tam
- School of Optometry, University of California, Berkeley, California 94720-2020, USA
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Protection of human corneal epithelial cells from hypoxia-induced disruption of barrier function by hepatocyte growth factor. Exp Eye Res 2010; 90:337-43. [DOI: 10.1016/j.exer.2009.11.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 10/30/2009] [Accepted: 11/18/2009] [Indexed: 11/19/2022]
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Effects of Multipurpose Contact-Lens Care Solutions on Adhesion of Pseudomonas aeruginosa to Corneal Epithelial Cells. Eye Contact Lens 2009; 35:98-104. [DOI: 10.1097/icl.0b013e31819a67fd] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Alarcon I, Evans DJ, Fleiszig SMJ. The role of twitching motility in Pseudomonas aeruginosa exit from and translocation of corneal epithelial cells. Invest Ophthalmol Vis Sci 2009; 50:2237-44. [PMID: 19136693 DOI: 10.1167/iovs.08-2785] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The authors have shown that twitching motility, a pilus-mediated form of bacterial surface movement, is required for Pseudomonas aeruginosa virulence in a murine model of keratitis. To study the role of twitching motility in virulence, Pseudomonas traversal of multilayered corneal epithelia in vitro was investigated. METHODS Translocation of multilayered corneal epithelia was investigated with the invasive strain PAK and isogenic twitching motility mutants. Rabbit corneal epithelial cells were grown to multilayers with filters and inoculated on their apical surfaces with 10(6) colony-forming unit bacteria, and translocating bacteria were quantified by viable counts of the basal chamber. Transepithelial resistance (TER) was recorded. Cellular exit of P. aeruginosa after invasion was quantified with modified gentamicin survival assays, and the role of apoptosis in exit was explored. RESULTS PAK translocated the epithelia as early as 1 hour after infection, and by 8 hours apical and basal numbers of bacteria were similar. Bacterial translocation did not reduce TER. Each twitching motility mutant (pilU, pilT with pili, pilA lacking pili) was defective in translocation (>2 log reduction vs. PAK; P < 0.005). All twitching mutants were competent for cell invasion but defective in cellular exit, accumulating intracellularly to numbers exceeding those of PAK. Inhibiting apoptosis reduced the cellular exit of PAK. CONCLUSIONS These results show that twitching motility enables P. aeruginosa to translocate corneal epithelial layers and suggest that it contributes to epithelial cell exit by a mechanism involving apoptosis. The relationship between these in vitro findings and the role of twitching motility in P. aeruginosa virulence in vivo remains to be determined.
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Affiliation(s)
- Irania Alarcon
- Program in Microbiology, University of California, Berkeley, California, USA
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Robertson DM, Cavanagh HD. The Clinical and Cellular Basis of Contact Lens-related Corneal Infections: A Review. Clin Ophthalmol 2008; 2:907-917. [PMID: 19277209 PMCID: PMC2652884 DOI: 10.2147/opth.s3249] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Microbial keratitis (MK) is the most visually devastating complication associated
with contact lens wear. Pseudomonas aeruginosa (PA) is highly
invasive in the corneal epithelium and is responsible for more than half of the
reported cases of contact lens-related MK. To protect against
Pseudomonas-mediated MK, the corneal epithelium has evolved
overlapping defense mechanisms that function to protect the ocular surface from
microbial invasion. Research has shown that contact lens wear disrupts these
protective mechanisms through breakdown of normal homeostatic surface renewal as
well as damaging the corneal surface, exposing underlying cell membrane
receptors that bind and internalize PA through the formation of lipid rafts.
Human clinical trials have shown that initial adherence of PA with resulting
increased risk for microbial infection is mediated in part by contact lens
oxygen transmissibility. Recently, chemical preserved multipurpose solutions
(MPS) have been implicated in increasing PA adherence to corneal epithelial
cells, in addition to inducing significant levels of toxic staining when used in
conjunction with specific silicone hydrogel lenses. This review summarizes what
is currently known about the relationship between contact lenses, the corneal
epithelium, MPS, and infection.
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Affiliation(s)
- Danielle M Robertson
- Department of Ophthalmology The University of Texas Southwestern Medical Center, Dallas, TX, USA
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Rabbit Models of Contact Lens–Associated Corneal Hypoxia: A Review of the Literature. Eye Contact Lens 2008; 34:160-5. [DOI: 10.1097/icl.0b013e31815788d7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Angus AA, Lee AA, Augustin DK, Lee EJ, Evans DJ, Fleiszig SMJ. Pseudomonas aeruginosa induces membrane blebs in epithelial cells, which are utilized as a niche for intracellular replication and motility. Infect Immun 2008; 76:1992-2001. [PMID: 18316391 PMCID: PMC2346716 DOI: 10.1128/iai.01221-07] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Revised: 10/10/2007] [Accepted: 02/14/2008] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is known to invade epithelial cells during infection and in vitro. However, little is known of bacterial or epithelial factors modulating P. aeruginosa intracellular survival or replication after invasion, except that it requires a complete lipopolysaccharide core. In this study, real-time video microscopy revealed that invasive P. aeruginosa isolates induced the formation of membrane blebs in multiple epithelial cell types and that these were then exploited for intracellular replication and rapid real-time motility. Further studies revealed that the type three secretion system (T3SS) of P. aeruginosa was required for blebbing. Mutants lacking either the entire T3SS or specific T3SS components were instead localized to intracellular perinuclear vacuoles. Most T3SS mutants that trafficked to perinuclear vacuoles gradually lost intracellular viability, and vacuoles containing those bacteria were labeled by the late endosomal marker lysosome-associated marker protein 3 (LAMP-3). Interestingly, mutants deficient only in the T3SS translocon structure survived and replicated within the vacuoles that did not label with LAMP-3. Taken together, these data suggest two novel roles of the P. aeruginosa T3SS in enabling bacterial intracellular survival: translocon-dependent formation of membrane blebs, which form a host cell niche for bacterial growth and motility, and effector-dependent bacterial survival and replication within intracellular perinuclear vacuoles.
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Affiliation(s)
- Annette A Angus
- School of Optometry, University of California, Berkeley, CA 94720, USA
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Zaidi T, Bajmoczi M, Zaidi T, Golan DE, Pier GB. Disruption of CFTR-dependent lipid rafts reduces bacterial levels and corneal disease in a murine model of Pseudomonas aeruginosa keratitis. Invest Ophthalmol Vis Sci 2008; 49:1000-9. [PMID: 18326723 DOI: 10.1167/iovs.07-0993] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
PURPOSE Pseudomonas aeruginosa enters corneal epithelial cells in vitro via membrane microdomains or lipid rafts. Bacterial entry, mediated by the cystic fibrosis transmembrane conductance regulator (CFTR), promotes infection and disease. This study was conducted to determine whether P. aeruginosa and CFTR are colocalized to rafts in isogenic corneal cells expressing wild-type (WT) or mutant DeltaF508-CFTR and whether disruption of the rafts both in vitro and in vivo affects the bacterial levels and the course of the disease. METHODS Transformed human corneal epithelial cells from a patient homozygous for DeltaF508-CFTR, and the same cells corrected with WT-CFTR, were exposed to six isolates of P. aeruginosa-three invasive and three cytotoxic strains-in the presence of beta-cyclodextrin (CD), which disrupts rafts. Association and cellular uptake of the invasive strains were measured, as was lactate dehydrogenase release induced by the cytotoxic strains. Scratch-injured mouse eyes were infected with the six P. aeruginosa strains, and the effect of prophylactic or therapeutic administration of CD on bacterial levels and disease was evaluated. RESULTS P. aeruginosa and CFTR were colocalized with lipid rafts in cells with WT-CFTR, and CD treatment of these cells disrupted bacterial association, internalization, and cytotoxic effects. Cells expressing DeltaF508-CFTR were marginally affected by CD. Prophylactic and therapeutic topical application of CD ameliorated corneal disease and reduced the bacterial count in the eye. CONCLUSIONS P. aeruginosa enters human corneal epithelial cells via lipid rafts containing CFTR, and disruption of raft-mediated uptake of this organism by CD protects against disease and reduces bacterial levels in the mouse model of keratitis.
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Affiliation(s)
- Tanweer Zaidi
- Channing Laboratory and Hematology Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Abstract
PURPOSE OF REVIEW Infectious keratitis is a medical emergency. Improper management can lead to marked loss of vision. This review identifies recent trends in the study of infectious keratitis. RECENT FINDINGS A multicountry outbreak of Fusarium keratitis emphasizes that contact lens wear is a major risk factor for infectious keratitis. Acanthamoeba and fungal keratitis are the most expensive forms of infectious keratitis to treat. Noninvasive methods and molecular techniques have improved diagnosis of infectious keratitis. Fortified topical antibiotics and fluoroquinolones are still the mainstay of bacterial keratitis therapy. Voriconazole and new routes of administration of conventional antifungals appear promising for fungal keratitis. Antivirals and amelioration of host inflammatory response are promising for viral keratitis; the host response is also crucial in pathogenesis of Pseudomonas aeruginosa keratitis. Trauma-induced bacterial and fungal keratitis and contact lens-associated keratitis are preventable entities. SUMMARY Improved modalities of diagnosis and treatment have improved the outcome of infectious keratitis, but therapy of acanthamoebal, fungal and P. aeruginosa keratitis is still a challenge. Effective strategies must neutralize potential risk factors and counter host response overactivity without impairing killing of infecting microorganisms. Trauma-induced bacterial and fungal keratitis can be prevented.
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Robertson DM, Petroll WM, Jester JV, Cavanagh HD. Current concepts: contact lens related Pseudomonas keratitis. Cont Lens Anterior Eye 2006; 30:94-107. [PMID: 17084658 DOI: 10.1016/j.clae.2006.10.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 10/10/2006] [Accepted: 10/10/2006] [Indexed: 11/19/2022]
Abstract
Despite the development of silicone hydrogel lenses, Pseudomonas aeruginosa (PA) continues to be the leading cause of contact lens related microbial keratitis. Understanding the pathogenesis of PA-mediated corneal infection is critical to the development of new prevention and treatment strategies. Recently intracellular invasion of surface corneal epithelial cells by PA has been revisited as an important element in the infection process. This review identifies the mechanisms involved, and examines the roles of the lens, hypoxia alone, PA stain, cystic fibrosis transmembrane receptor protein (CFTR), and membrane lipid rafts in mediating intracellular invasion in both in vitro and in vivo conditions. Non-toxic blockade of raft formation in vitro or in vivo effectively abrogates PA internalization and may represent a unique, new strategy to prevent or ameliorate lens-related PA microbial keratitis.
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Affiliation(s)
- Danielle M Robertson
- Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9057, USA
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