Topical retinoic acid induces corneal strengthening by upregulating transglutaminase 2 in murine cornea.

Transglutaminase 2 (TG2) is the most abundant crosslinking enzyme in murine and human cornea, while retinoids are well-known inducers of TG2 expression. This study aims to determine if the retinoic acid supplementation can increase corneal stiffness by crosslinking through upregulating the corneal TG2 expression. The right eyes of C57BL/6 mice were treated with 2 × 10-2M retinol palmitate (VApal) eyedrops or control eyedrops and hold for 30 min, once a day for 28 consecutive days. The WB and qPCR results showed increased expression of TG2 in murine cornea with the prolongation of VApal eyedrop application. After 28 days of VApal eyedrop treatment, the increased TG2 were found catalytically active and distributed in corneal epithelium and stroma as detected by 5-(biotinamido) pentylamine (5-BP) incorporation method and immunofluorescence staining. The transmission electron microscope image revealed that VApal treated cornea manifested with increased collagen density in anterior and middle layer of stroma. The higher elastic module was found among VApal treated cornea by nano-indentation test. In cultured corneal epithelial cells and keratocytes, all-trans retinoid acid (ATRA) treatment increased the content of TG2 in cell lysis and in culture medium. These results indicate that retinoic acid induce the reinforcement of the cornea by TG2 mediated crosslinking via increasing the TG2 expression in corneal epithelium and keratocyte. As TG2 was found to be less in the cornea of keratoconus patients in several RNA-sequencing studies, retinoic acid could serve as a non-invasive prevention method for keratoconus progression.

LCAT, ApoD, and ApoA1 Expression and Review of Cholesterol Deposition in the Cornea.

Lecithin:cholesterol acyltransferase (LCAT) is an enzyme secreted by the liver and circulates with high-density lipoprotein (HDL) in the blood. The enzyme esterifies plasma cholesterol and increases the capacity of HDL to carry and potentially remove cholesterol from tissues. Cholesterol accumulates within the extracellular connective tissue matrix of the cornea stroma in individuals with genetic deficiency of LCAT. LCAT can be activated by apolipoproteins (Apo) including ApoD and ApoA1. ApoA1 also mediates cellular synthesis of HDL. This study examined the expression of LCAT by epithelial cells, keratocytes, and endothelial cells, the cell types that comprise from anterior to posterior the three layers of the cornea. LCAT and ApoD were immunolocalized to all three cell types within the cornea, while ApoA1 was immunolocalized to keratocytes and endothelium but not epithelium. In situ hybridization was used to detect LCAT, ApoD, and ApoA1 mRNA to learn what cell types within the cornea synthesize these proteins. No corneal cells showed mRNA for ApoA1. Keratocytes and endothelium both showed ApoD mRNA, but epithelium did not. Epithelium and endothelium both showed LCAT mRNA, but despite the presence of LCAT protein in keratocytes, keratocytes did not show LCAT mRNA. RNA sequencing analysis of serum-cultured dedifferentiated keratocytes (commonly referred to as corneal stromal fibroblasts) revealed the presence of both LCAT and ApoD (but not ApoA1) mRNA, which was accompanied by their respective proteins detected by immunolabeling of the cultured keratocytes and Western blot analysis of keratocyte lysates. The results indicate that keratocytes in vivo show both ApoA1 and LCAT proteins, but do not synthesize these proteins. Rather, keratocytes in vivo must take up ApoA1 and LCAT from the corneal interstitial tissue fluid.

Modulation of Corneal FAK/PI3K/Akt Signaling Expression and of Metalloproteinase-2 and Metalloproteinase-9 during the Development of Herpes Simplex Keratitis.

To observe the expression of MMP-2 and MMP-9 and of the FAK/PI3K/Akt signaling pathway in HSK. Fifty BALB/c mice were infected to establish the model and killed on days 0, 2, 7, 14, and 28. The cornea samples were prepared, respectively. Slit lamp examination, immunofluorescence staining, reverse transcription PCR, and Western blot were used to detect the index. After HSV-1 infection, different degrees of epithelial or stromal damage and corneal opacity were observed. Immunofluorescence staining showed that the expressions of MMP-2 and MMP-9 at different levels of corneal tissue were observed on the 0d, 2d, 7d, 14d, and 28d. Compared with 0d, the relative expression levels of MMP-2 and MMP-9 mRNA at 2d, 7d, 14d, and 28d were significantly increased (all P< 0.05). Compared with 14d, the relative expression of MMP-2 and MMP-9 mRNA decreased on the 2d, 7d, and 28d (all P< 0.05). Western blot showed that the protein expressions of p-FAK, p-PI3K, p-Akt, MMP-2, and MMP-9 at 2d, 14d, and 28d were all significantly higher than 0d (all P< 0.05). At 14 d, the expressions of p-FAK, p-PI3K, p-Akt, and MMP-2 were significantly higher than those at 2d, 7d, and 28d (all P< 0.05). The protein expression of FAK, PI3K, and Akt in corneal of mice in each time period had no significant (all P> 0.05). These data suggest that FAK/PI3K/Akt signaling pathway and MMP-2 and MMP-9 may be involved in the development of HSK.

Innovative corneal active storage machine for long-term eye banking.

Optimal ex vivo corneal storage in eye banks is crucial to increase both the number of corneas suitable for graft and their intrinsic quality, mainly the number of viable endothelial cells, which dictates graft survival in recipients. With both passive storage methods used worldwide (short-term cold storage in the United States, long-term organ culture in Europe), significant endothelial cell loss is inevitable. Here we show that, with an active storage machine, also called a bioreactor, which restores 2 fundamental physiological parameters, intraocular pressure and medium renewal, endothelial cell survival is improved by 23% compared with organ culture after 4 weeks' storage. Also observed in the bioreactor is a 4-fold higher expression of Na+ /K+ ATPase, which supports one of the major endothelial cell pumping functions. In addition, corneas remain thin and transparent, so they are suitable for surgery at any time. This new active eye banking method may help to reduce the severe global scarcity of donor corneas.

Cyclooxygenase-2 expression in the eyes of cats with and without uveitis.

OBJECTIVE To characterize the distribution and intensity of cyclooxygenase (COX)-2 expression in the eyes of cats with and without uveitis and to determine whether COX-2 expression is correlated with severity of inflammation. SAMPLES Archived ocular tissue specimens from 51 cats with and 10 cats without ocular disease. PROCEDURES Specimens from only 1 eye were evaluated for each cat. Specimens were stained with H&E stain or immunohistochemical stain for detection of COX-2 and reviewed. For each eye, the type, severity, and distribution of inflammation and the distribution and intensity of COX-2 expression were determined for the uvea and other ocular tissues. Correlation between COX-2 expression and inflammation severity was also assessed. RESULTS COX-2 was not expressed in any nondiseased eye. Of the 51 diseased eyes, 20 had histologic evidence of lymphocytic-plasmacytic uveitis, 13 had neutrophilic uveitis, 11 had diffuse iris melanoma with uveitis, and 7 had diffuse iris melanoma without uveitis. Of the 44 eyes with uveitis, COX-2 was detected in the uvea of 16, including 11 eyes with lymphocytic-plasmacytic uveitis, 4 with neutrophilic uveitis, and 1 with diffuse iris melanoma-induced uveitis. Inflammation was severe, moderate, or mild in 10, 5, and 1 of those eyes, respectively. Cyclooxygenase-2 was detected in the cornea of 21 eyes with uveitis and 1 eye with diffuse iris melanoma without uveitis. Uveitis severity was positively correlated with COX-2 expression in both the uvea and cornea. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that COX-2 is an inflammatory mediator in feline uveitis but not diffuse iris melanoma.

The presence of kynurenine aminotransferases in the human cornea: Evidence from bioinformatics analysis of gene expression and immunohistochemical staining.

PURPOSE: Kynurenine aminotransferases (KATs) catalyze the synthesis of kynurenic acid (KYNA), a compound of significant biological activity. The aim of this study is to investigate the presence and distribution of KAT immunoreactivity in the healthy human cornea. METHODS: Data on gene expression in human eye structures were extracted from public microarray experiments using Genevestigator software. Immunohistochemistry was conducted using polyclonal antibodies against KAT I, II, and III on sections of eight enucleated eyes from patients with choroidal melanoma. RESULTS: Bioinformatics analysis showed that all four KAT isoforms were actively transcribed in the cornea and the conjunctiva. Immunohistochemical analysis revealed the presence of KAT I, II, and III in all examined corneal sections. The corneal endothelium showed the strongest reactivity for all three KAT isoforms. There was a slight positive staining of the corneal stroma for KAT I and II. KAT III immunoreactivity was found only in the stroma of the limbal region. In the corneal epithelium, the expression of all three KAT isoforms showed a specific pattern of the stain with fine squatter granules throughout the cytoplasm. This reactivity was more pronounced in the basal cell layers. The intermediate cell layers showed only faint immunoreactivity, and occasionally, there was no staining. KAT I, II, and III were also present in the adjacent limbal conjunctiva. CONCLUSIONS: The results indicate that kynurenine can be metabolized to KYNA in the corneal epithelium, stroma, and endothelium.

Bicarbonate-sensing soluble adenylyl cyclase is present in the cell cytoplasm and nucleus of multiple shark tissues.

The enzyme soluble adenylyl cyclase (sAC) is directly stimulated by bicarbonate (HCO3-) to produce the signaling molecule cyclic adenosine monophosphate (cAMP). Because sAC and sAC-related enzymes are found throughout phyla from cyanobacteria to mammals and they regulate cell physiology in response to internal and external changes in pH, CO2, and HCO3-, sAC is deemed an evolutionarily conserved acid-base sensor. Previously, sAC has been reported in dogfish shark and round ray gill cells, where they sense and counteract blood alkalosis by regulating the activity of V-type H+- ATPase. Here, we report the presence of sAC protein in gill, rectal gland, cornea, intestine, white muscle, and heart of leopard shark Triakis semifasciata Co-expression of sAC with transmembrane adenylyl cyclases supports the presence of cAMP signaling microdomains. Furthermore, immunohistochemistry on tissue sections, and western blots and cAMP-activity assays on nucleus-enriched fractions demonstrate the presence of sAC protein in and around nuclei. These results suggest that sAC modulates multiple physiological processes in shark cells, including nuclear functions.

Expression of glutathione transferases in corneal cell lines, corneal tissues and a human cornea construct.

Glutathione transferase (GST) expression and activity were examined in a three-dimensional human cornea construct and were compared to those of excised animal corneas. The objective of this study was to characterize phase II enzyme expression in the cornea construct with respect to its utility as an alternative to animal cornea models. The expression of the GSTO1-1 and GSTP1-1 enzymes was investigated using immunofluorescence staining and western blotting. The level of total glutathione transferase activity was determined using 1-chloro-2,4- dinitrobenzene as the substrate. Furthermore, the levels of GSTO1-1 and GSTP1-1 activity were examined using S-(4-nitrophenacyl)glutathione and ethacrynic acid, respectively, as the specific substrates. The expression and activity levels of these enzymes were examined in the epithelium, stroma and endothelium, the three main cellular layers of the cornea. In summary, the investigated enzymes were detected at both the protein and functional levels in the cornea construct and the excised animal corneas. However, the enzymatic activity levels of the human cornea construct were lower than those of the animal corneas.

Expression of SIRT1 and oxidative stress in diabetic dry eye.

OBJECTIVE: To explore the expression of SIRT1 with oxidative stress and observe physiological and pathological changes in the corneas as well as the association between SIRT1 and oxidative stress of diabetic dry eyes in mice. METHOD: Forty-eight C57BL/6Jdb/db mice at eight weeks of age were divided randomly into two groups: the diabetic dry eye group and the diabetic group. An additional forty-eight C57BL/6J mice at eight weeks of age were divided randomly into two groups: the dry eye group and the control group. Every mouse in the dry eye groups (diabetic and normal) was injected with scopolamine hydrobromide three times daily, combined with low humidity to establish a dry eye model. After the intervention, phenol red cotton string tests and corneal fluorescein staining were performed. In addition, HE staining and immunofluorescence were done. Expression of SIRT1 in the cornea was examined by real-time PCR and Western Blot and expression of FOXO3 and MnSOD proteins was detected by Western Blot. RESULTS: At one, four, and eight weeks post intervention, all of the groups except the controls showed significant decreases in tear production and increases in the corneal fluorescein stain (P<0.05 vs control). Between the experimental groups, the diabetic dry eye group had the least tear production and the highest corneal fluorescein stain score (P<0.05). As the disease progressed, all of the experimental groups showed obviously pathological changes in HE staining, particularly the diabetic dry eye group. In the 1(st) and 4(th) week, the expression of SIRT1, FOXO3, and MnSOD were significantly higher in the diabetic DE and DM groups but lower in the DE group compared to the controls (P<0.05). In the 8(th) week, the expression of SIRT1, FOXO3, and MnSOD was significantly down-regulated in the diabetic DE group and the DM group (P<0.05). Immunofluorescence showed similar results. CONCLUSION: In the condition of diabetic dry eye, tear production declined markedly coupled with seriously wounded corneal epithelium. Oxidative stress in the cornea was enhanced significantly and the expression of SIRT1 was decreased.

Osmoprotectants suppress the production and activity of matrix metalloproteinases induced by hyperosmolarity in primary human corneal epithelial cells.

PURPOSE: Hyperosmolarity has been recognized as a proinflammatory stress in the pathogenesis of dry eye disease. This study investigated the suppressive effect of osmoprotectants (L-carnitine, erythritol, and betaine) on the production and activity of matrix metalloproteinases (MMPs) in primary human corneal epithelial cells (HCECs) exposed to hyperosmotic stress. METHODS: Primary HCECs were established from fresh donor limbal tissue explants. The cultures in iso-osmolar medium (312 mOsM) were switched to hyperosmotic media with or without prior incubation with different concentrations of L-carnitine, erythritol, or betaine (2, 10, or 20 mM). The mRNA expression of the MMPs was determined with reverse transcription and quantitative real-time PCR (RT-qPCR). Protein production and activity were evaluated with immunofluorescent staining and gelatin zymography. RESULTS: Hyperosmotic media (400, 450, or 500 mOsM) significantly stimulated mRNA expression of collagenase MMP-13, gelatinases MMP-9 and MMP-2, stromelysin MMP-3, and matrilysin MMP-7, mostly in an osmolarity-dependent fashion. The stimulated mRNA expression and protein production of these MMPs were significantly but differentially suppressed by L-carnitine, erythritol, or betaine, as evaluated with RT-qPCR and immunofluorescent staining. Interestingly, these osmoprotectants not only suppressed production but also inhibited activation of MMP-9 and MMP-2, as evaluated with gelatin zymography. CONCLUSIONS: Our findings for the first time demonstrate that osmoprotectants, L-carnitine, erythritol, and betaine, suppress the gene expression, protein production, and enzymatic activity of MMPs in HCECs exposed to hyperosmotic stress. L-carnitine appears to have the broadest and strongest suppressive effect on these MMPs. These osmoprotectants may have potential effects in protecting ocular surface epithelia from MMP-mediated disorders in dry eye disease.

Epigallocatechin gallate eye drops protect against ultraviolet B-induced corneal oxidative damage in mice.

PURPOSE: Ultraviolet B (UVB) radiation from sunlight is a known risk factor for human corneal injury. The aim of the present study was to investigate the protective effects of green tea polyphenol epigallocatechin gallate (EGCG) on UVB radiation-induced corneal oxidative damage in male imprinting control region (ICR) mice. METHODS: Corneal oxidative damage was induced by exposure to UVB radiation at 560 µW/cm(2). The animals received 0%, 0.1%, and 0.01% EGCG eye drops at a 5 mg/ml dose, twice daily for 8 days. Corneal surface damage was graded according to smoothness and the extent of lissamine green staining. Corneal glutathione (GSH), thiobarbituric acid-reactive substances (TBARS), and protein carbonyl levels, as well as superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px), and glutathione reductase (GSH-Rd) activity in the cornea, were measured to monitor corneal injury. RESULTS: UVB radiation caused significant damage to the corneas, including apparent corneal ulceration and severe epithelial exfoliation, leading to a decrease in SOD, catalase, GSH-Px, GSH-Rd, and GSH activity in the cornea. However, the corneal TBARS and protein carbonyls increased compared with the control group. Treatment with EGCG eye drops significantly (p<0.05) ameliorated corneal damage, increased SOD, catalase, GSH-Px, GSH-Rd, and GSH activity, and decreased the TBARS and protein carbonyls in the corneas compared with the UVB-treated group. CONCLUSIONS: EGCG eye drops exhibit potent protective effects on UVB radiation-induced corneal oxidative damage in mice, likely due to the increase in antioxidant defense system activity and the inhibition of lipid peroxidation and protein oxidation.

Lack of association between VAP-1/SSAO activity and corneal neovascularization in a rabbit model.

The aim of this study is to determine the efficacy of a potent and specific vascular adhesive protein-1/semicarbazide-sensitive amine oxidase (VAP-1/SSAO) inhibitor, LJP 1207, as a potential antiangiogenic and anti-inflammatory agent in the therapy of corneal neovascularization. Corneal neovascularization was induced with intrastromal suturing in rabbits (n = 20). Topical treatment with VAP-1/SSAO inhibitor LJP 1207 (n = 5, 4 times a day), bevacizumab (n = 5, daily), their combination (n = 5) and vehicle only (n = 5, 4 times a day) were applied postoperatively for 2 weeks. The development and extent of corneal neovascularization were evaluated by digital image analysis. At the end of the observation period, the level of corneal and serum VAP-1/SSAO activity was measured fluorometrically and radiochemically. The corneal VAP-1/SSAO activity was significantly elevated in the suture-challenged vehicle-treated group (3,075 ± 1,009 pmol/mg/h) as compared to unoperated controls (464.2 ± 135 pmol/mg/h, p < 0.001). Treatment with LJP 1207 resulted in slower early phase neovascularization compared to vehicle-treated animals (not significant). At days 7-14, there was no significant difference in the extent of corneal neovascularization between inhibitor- and vehicle-treated corneas, even though inhibitor treatment caused a normalization of corneal VAP-1/SSAO activity (885 ± 452 pmol/mg/h). Our results demonstrate that the significant elevation of VAP-1/SSAO activity due to corneal injury can be prevented with VAP-1/SSAO inhibitor LJP 1207 treatment. However, normalization of VAP-1/SSAO activity in this model does not prevent the development of corneal neovascularization.

Inhibition of multiple pathogenic pathways by histone deacetylase inhibitor SAHA in a corneal alkali-burn injury model.

Neovascularization (NV) in the cornea is a major cause of vision impairment and corneal blindness. Hemangiogenesis and lymphangiogenesis induced by inflammation underlie the pathogenesis of corneal NV. The current mainstay treatment, corticosteroid, treats the inflammation associated with corneal NV, but is not satisfactory due to such side effects as cataract and the increase in intraocular pressure. It is imperative to develop a novel therapy that specifically targets the hemangiogenesis, lymphangiogenesis, and inflammation pathways underlying corneal NV. Histone deacetylase inhibitors (HDACi) have been in clinical trials for cancer and other diseases. In particular, HDACi suberoylanilide hydroxamic acid (SAHA, vorinostat, Zolinza) has been approved by the FDA for the treatment of cutaneous T-cell lymphoma. The functional mechanism of SAHA in cancer and especially in corneal NV remains unclear. Here, we show that topical application of SAHA inhibits neovascularization in an alkali-burn corneal injury model. Mechanistically, SAHA inhibits corneal NV by repressing hemangiogenesis, inflammation pathways, and previously overlooked lymphangiogenesis. Topical SAHA is well tolerated on the ocular surface. In addition, the potency of SAHA in corneal NV appears to be comparable to the current steroid therapy. SAHA may possess promising therapeutic potential in alkali-burn corneal injury and other inflammatory neovascularization disorders.

[Effect of flavin adenine dinucleotide on ultraviolet B induced damage in cultured human corneal epithelial cells].

This study evaluated the effects of flavin adenine dinucleotide (FAD) on ultraviolet B (UV-B)-induced damage in cultured human corneal epithelial (HCE-T) cells. The cultured HCE-T cells were treated with 0.003125-0.05% FAD before exposure to 80 mJ/cm2 UV-B. Cell viability was measured 24 h after UV-B irradiation using the MTS assay. Reactive oxygen species (ROS) were detected 30 min after UV-B irradiation using 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester. Apoptosis was evaluated 4 h after UV-B irradiation in the caspase-3/7 activity assay. UV-B irradiation reduced cell viability and stimulated ROS production and caspase-3/7 activity in HCE-T cells. Pretreatment of UV-B irradiated HCE-T cells with FAD significantly attenuated cell viability reduction and inhibited the stimulation of both ROS production and caspase-3/7 activity due to UV-B exposure compared with those with vehicle (0% FAD). These results clarified that FAD inhibits ROS-mediated apoptosis by UV-B irradiation in HCE-T cells and suggest that FAD may be effective as a radical scavenger in UV-B-induced corneal damage.

[Cross-linking in an artificial human cornea via induction of tissue transglutaminases]. / Vernetzung einer humanen künstlichen Hornhaut durch Induktion von Tissue-Transglutaminasen.

PURPOSE: In recent years many three-dimensional cornea models have been developed. However, they show poor collagen stability in the stroma. Transglutaminases (Tgases) are calcium-dependent proteins which play an important role in cross-linking of the corneal stroma. The purpose of this study was to find out whether it is possible to induce in vitro cross-linking of the stroma in an artificial hemicornea model with the help of Tgases. MATERIALS AND METHODS: For the construction of the hemicornea, human SV40 adenovector corneal epithelial cells (HCE) and human SV40 adenovector corneal keratocytes (HCK) were cultivated. Confluent HCK cells were treated for 24 h with transforming growth factor beta (TGFb) 1, 2 and 3 at different concentrations as well as with other growth factors and the treated cells were compared to untreated cultivated cells. The quantification of the expression of the Tgases by HCKs was examined with the use of real time PCR, Western blot imaging and immunochemistry. RESULTS: All concentrations of TGFbs used resulted in a significant increase of Tgase-mRNA, Tgase protein level and Tgase activity. The Tgases remained unaffected after treatment with other growth factors in comparison to untreated control cells. Treatment of the hemicornea with TGFb2 showed a very strong contraction and haze in comparison to the untreated hemicornea. CONCLUSION: It has been shown for the first time that TGFb induces a strong expression of Tgases in HCK cells. This effect caused an undesired contraction and haze of the human hemicornea model. Further research is necessary in order to find out whether the induction of Tgases in the HCK cells can be regulated without losing stability of the constructed hemicornea.

mRNA expression of metabolic enzymes in human cornea, corneal cell lines, and hemicornea constructs.

PURPOSE: Drugs from ophthalmic formulations are mainly absorbed into the eye via the corneal route. However, little is known about drug metabolism during the transcorneal passage. The objective of this study was to determine the mRNA expression of phase I and II isoenzymes in human corneal epithelial tissue, corneal cell lines, and a tissue-engineered cornea equivalent (a hemicornea construct) as in vitro model for drug absorption studies. METHODS: The reverse transcription polymerase chain reaction was used to profile the mRNA expression of 10 cytochrome P450 enzymes (CYP) and seven phase II enzymes in the three human corneal cell lines and the hemicornea construct. The human corneal epithelial cell line (HCE-T), human corneal keratocyte cell line (HCK-Ca) and human corneal endothelial cell line (HENC) were used. Human liver tissue, human corneal epithelium from donor corneas, and the human colon adenocarcinoma cell line Caco-2 were also investigated. RESULTS: All the phase I and II mRNAs were expressed in the human liver tissue. The Caco-2 cell line showed an expression pattern similar to the liver tissue, although the signals for CYP1A2 and CYP3A4 were absent. In the case of the donor human corneal epithelium, all the detected phase I mRNAs had lower levels than did the liver tissue. By contrast, the phase II mRNA expression pattern was heterogeneous to the liver tissue. The expression patterns in the three human corneal cell lines were comparable, although the signals for a few phase I enzymes and N-acetyltransferase (NAT2) mRNAs were only detectable in the HCE-T. In the hemicornea construct, all the investigated phase I and II mRNA (except for CYP1A2, CYP2B6, CYP2C19, and NAT2) were expressed. CONCLUSIONS: Overall, the mRNA expressions of the tested phase I and phase II enzymes in the hemicornea construct and the three corneal cell lines correlated well with the expression patterns of the ex vivo human corneal epithelium.

Phospholipase C/Protein Kinase C pathway is essential for corneal re-epithelialization induced by Ap(4)A.

PURPOSE: We have previously demonstrated the importance of P2Y(2) receptors in the corneal re-epithelialization effect triggered by diadenosine tetraphosphate (Ap(4)A). In addition, we have also shown the ERK1/2 and ROCK-I activation in Ap(4)A-wound repair response. Phospholipase C/Protein Kinase C (PLC/PKC) pathway activation has been suggested as a molecular mechanism of growth factors-modulated corneal cell migration and P2Y(2) agonists. Hence, the aim of this study is to investigate the role of PLC/PKC cascade in the modification of re-epithelialization rate triggered by Ap(4)A in an established corneal epithelial cell line (Statens Seruminstitut rabbit cornea [SIRC] cells). METHODS: In wounded confluent SIRC cell monolayers and in the presence or absence of Ap(4)A 100 µM, a group of PLC/PKC inhibitors (U73122 3 µM, Staurosporine 1 nM and Bisindolylmaleimide-I 10 µM) and activator (PDBU 1 µM) were assayed and the migration rate was evaluated. Also, the activation of ERK1/2 and ROCK-I was examined by Western blot assay after treatment with or without Ap(4)A, U73122, Staurosporine, Bisindolylmaleimide-I and PDBU. RESULTS: Pre-treatment of wounded SIRC cells with PLC/PKC inhibitors significantly diminished the Ap(4)A-stimulated cell migration rate. Furthermore, PLC/PKC inhibitors also reduced ERK1/2 phosphorylation and ROCK-I activation triggered by Ap(4)A. CONCLUSIONS: The present study shows the involvement of PLC/PKC pathway in the activation of ERK1/2 and ROCK-I downstream signal transduction pathways stimulated by Ap(4)A/P2Y(2) receptor during corneal epithelial wound repair.

Functional analyses of the bone marrow kinase in the X chromosome in vascular endothelial growth factor-induced lymphangiogenesis.

OBJECTIVE: The goal of this study was to investigate the novel hypothesis that bone marrow kinase in the X chromosome (Bmx), an established inflammatory mediator of pathological angiogenesis, promotes lymphangiogenesis. METHODS AND RESULTS: We have recently demonstrated a critical role for Bmx in inflammatory angiogenesis. However, the role of Bmx in lymphangiogenesis has not been investigated. Here, we show that in wild-type mice, Bmx is upregulated in lymphatic vessels in response to vascular endothelial growth factor (VEGF). In comparison with wild-type mice, Bmx-deficient mice mount weaker lymphangiogenic responses to VEGF-A and VEGF-C in 2 mouse models. In vitro, Bmx is expressed in cultured human dermal microvascular lymphatic endothelial cells. Furthermore, pharmacological inhibition and short interfering RNA mediated silencing of Bmx reduces VEGF-A and VEGF-C-induced signaling and lymphatic endothelial cell tube formation. Mechanistically, we demonstrated that Bmx differentially regulates VEGFR-2 and VEGFR-3 receptor signaling pathways: Bmx associates with and directly regulates VEGFR-2 activation, whereas Bmx associates with VEGFR-3 and regulates downstream signaling without an effect on the receptor autophosphorylation. CONCLUSIONS: Our in vivo and in vitro results provide the first insight into the mechanism by which Bmx mediates VEGF-dependent lymphangiogenic signaling.

MMP-7 knock-in corneal fibroblast cell lines secrete MMP-7 with proteolytic activity towards collagen XVIII.

PURPOSE: To determine whether matrix metalloproteinase-7 (MMP-7) that is stably overexpressed by mouse corneal fibroblast cell lines exhibits proteolytic activity against the NC1 fragment of collagen XVIII. METHODS: Corneal fibroblasts isolated from MMP-7 knockout (7ko) mice were subjected to SV40 T-antigen immortalization and stably transfected with a bicistronic retroviral vector encoding green fluorescence protein and active MMP-7. The resulting MMP-7 knock-in fibroblasts (7ko-MMP-7 cells) were isolated and enriched by fluorescence activated cell sorting (FACS). Culture media samples from 7ko and 7ko-MMP-7 cells were then incubated with the recombinant NC1 fragment of collagen XVIII, and NC1 degradation was monitored by immunoblotting. RESULTS: Immunoblot analysis revealed that MMP-7 was present in lysates and culture media from 7ko-MMP-7 fibroblasts, but not media from immortalized 7ko fibroblasts. Importantly, lower amounts of the NC1 fragment were present in in vitro enzymatic reaction mixtures containing concentrated 7ko-MMP-7 media than in those containing concentrated 7ko media. CONCLUSION: Immortalized fibroblasts stably transfected with MMP-7 secrete active MMP-7 with proteolytic activity towards the NC1 fragment of collagen XVIII.

Urokinase down-regulation by aprotinin in rabbit corneal cells after photorefractive keratectomy.

PURPOSE: To examine the effect of aprotinin eye drops on urokinase-type plasminogen activator (uPA) gene expression in rabbit corneal cells during wound healing after photorefractive keratectomy (PRK). METHODS: Both eyes of 22 rabbits were subjected to PRK. One eye of each rabbit was treated with antibiotic eye drops five times while the contralateral eye was treated at the same time with antibiotic eye drops and a serine protease inhibitor. The animals were sacrificed at different time frames, and 2-4 rabbits were used for each time point. Half of each cornea was used for the determination of the amount of uPA mRNA after reverse transcription and real-time quantitative polymerase chain reaction, while frozen sections were prepared from the other halves for in situ zymography to detect uPA activity. RESULTS: The level of uPA mRNA in corneal cells was markedly increased in corneal samples obtained hours after PRK. The time-dependent up-regulation of uPA mRNA was strongly dependent on the diameter of the area from which the epithelial cells were removed before the surgery. Independently of the time scale of uPA up-regulation, application of eye drops containing aprotinin significantly diminished the uPA expression. In situ zymography confirmed that aprotinin has also decreased overall uPA activity. CONCLUSIONS: Aprotinin down-regulates uPA gene expression in corneal cells during the wound-healing phase after PRK.