Shinichiro Teranishi

Delayed Disruption of Barrier Function in Cultured Human Corneal Epithelial Cells Induced by Tumor Necrosis Factor-α in a Manner Dependent on NF-κB

PURPOSE The corneal epithelium provides a barrier that is both important for corneal homeostasis and dependent on tight junctions (TJs) between adjacent epithelial cells. The authors examined the effects of tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, on barrier function and the expression of TJ proteins in simian virus 40-transformed human corneal epithelial (HCE) cells. METHODS The barrier function of cultured HCE cells was evaluated by measurement of transepithelial electrical resistance (TER). The subcellular distribution of the TJ proteins zonula occludens-1 (ZO-1) and occludin and that of the p65 subunit of nuclear factor-kappaB (NF-kappaB) were determined by immunofluorescence staining. The expression of ZO-1 and occludin and the phosphorylation and degradation of the NF-kappaB inhibitory protein IkappaB-alpha were examined by immunoblot analysis. RESULTS TNF-alpha induced a decrease in the TER of HCE cells in a concentration- and time-dependent manner. It also induced the disappearance of ZO-1 from the interfaces of neighboring HCE cells without affecting the localization of occludin. The abundance of neither ZO-1 nor occludin was affected by TNF-alpha. TNF-alpha induced the phosphorylation and downregulation of IkappaB-alpha and the translocation of the p65 subunit of NF-kappaB to the nucleus. The NF-kappaB inhibitor curcumin blocked the effects of TNF-alpha on TER and the subcellular localization of ZO-1 at late phase. CONCLUSIONS TNF-alpha disrupted the barrier function of HCE cells, apparently by affecting the localization of ZO-1 at TJs in a manner dependent on NF-kappaB at late phase. This action of TNF-alpha may contribute to the loss of corneal epithelial barrier function associated with ocular inflammation.

Interleukin-1β-Induced Disruption of Barrier Function in Cultured Human Corneal Epithelial Cells

PURPOSE The barrier function of the corneal epithelium contributes to corneal homeostasis and is impaired by inflammation. Adherens junctions (AJs) and tight junctions (TJs) of the corneal epithelium are essential for cell adhesion and barrier function. We examined the effects of the proinflammatory cytokine interleukin (IL)-1beta on AJs and TJs as well as on barrier function in simian virus 40-transformed human corneal epithelial (HCE) cells. METHODS Barrier function was evaluated by measurement of transepithelial electrical resistance (TER). The subcellular distributions of the AJ proteins E-cadherin and beta-catenin, the TJ proteins ZO-1 and occludin, and the p65 subunit of nuclear factor (NF)-kappaB were determined by immunofluorescence staining. The expression of junctional proteins as well as the phosphorylation and degradation of the NF-kappaB-inhibitory protein IkappaB-alpha were examined by immunoblot analysis. RESULTS IL-1beta induced the disappearance of ZO-1 and occludin from the interfaces of neighboring HCE cells without affecting the localization of E-cadherin or beta-catenin. It also reduced the TER of HCE cells in a concentration- and time-dependent manner. The overall abundance of TJ and AJ proteins was not affected by IL-1beta. IL-1beta induced the phosphorylation and downregulation of IkappaB-alpha as well as the translocation of p65 to the nucleus. The NF-kappaB inhibitor curcumin blocked the effects of IL-1beta on both TER and the subcellular localization of ZO-1 and occludin. CONCLUSIONS IL-1beta induced the redistribution of ZO-1 and occludin from TJs of HCE cells and thereby disrupted the barrier function of these cells in a manner dependent on NF-kappaB. These effects of IL-1beta may contribute to the loss of corneal epithelial barrier function associated with ocular inflammation.

Detection of Subepithelial Fibrosis Associated with Corneal Stromal Edema by Second Harmonic Generation Imaging Microscopy

PURPOSE Human corneas with or without stromal edema were examined by second harmonic generation (SHG) imaging microscopy to characterize stromal collagen organization. METHODS Tissue buttons from 31 corneas with stromal edema and 8 normal corneas were fixed, and 3-mm(2) blocks were cut and stained with phalloidin, to visualize the cytoskeleton. The blocks were examined by SHG imaging with a laser confocal microscope and a mode-locked titanium:sapphire femtosecond laser. Samples were scanned to a depth of 150 microm from the surface of Bowmans layer, and SHG forward- and backscatter signals were collected. Phalloidin staining was detected by conventional laser confocal microscopy. The three-dimensional structure of the anterior segment of the cornea was reconstructed from stacked SHG images. RESULTS Three-dimensional reconstruction of SHG signals showed adherence of interwoven collagen lamellae in the anterior stroma to Bowmans layer in both normal and edematous corneas. Abnormal SHG signals at the level of Bowmans layer were observed in edematous corneas; three-dimensional images revealed that these signals were actually localized above Bowmans layer and were indicative of subepithelial fibrosis. Phalloidin staining showed transdifferentiation of stromal cells into fibroblastic cells in edematous corneas. The incidence of subepithelial fibrosis or of fibroblastic cells increased beginning 12 months after the onset of clinical stromal edema. CONCLUSIONS SHG imaging of the anterior segment of edematous corneas revealed a normal appearance of interwoven collagen lamellae in the anterior stroma. The development of subepithelial fibrosis beginning 12 months after the onset of edema suggests that stromal edema may be a progressive disease.

Role of Formation of an ERK-FAK-Paxillin Complex in Migration of Human Corneal Epithelial Cells during Wound Closure In Vitro

PURPOSE Migration of corneal epithelial cells is an important step in the corneal wound healing. The role of extracellular signal regulated kinase (ERK) for the regulation of cell migration during wound closure was examined. METHODS Scratch wounds were introduced into human corneal epithelial cells in the absence or presence of PD98059, an ERK signaling inhibitor. The phosphorylation and localization of ERK during wound closure were examined by immunoblot and immunofluorescence analyses. The tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin, as well as the association of FAK with paxillin and ERK, were evaluated by immunoprecipitation and immunoblot analysis. The effect of a mutant form of MEK1 on cell migration and proliferation was determined by transfection. RESULTS PD98059 inhibited cell migration in a concentration- and time-dependent manner. Wounding increased the phosphorylation of ERK as well as the tyrosine phosphorylation of FAK and paxillin in a manner sensitive to PD98059. Furthermore, wounding induced the formation of an ERK-FAK-paxillin complex and this effect as well as the wounding-induced formation of focal adhesions, membrane ruffles, and bundles of F-actin, were inhibited by PD98059. Phosphorylated ERK localized at the wound margin, and such localization was not observed in the presence of PD98059. Expression of dominant negative mutant form of MEK1 inhibited cell migration during wound closure without the effect of cell proliferation. CONCLUSIONS ERK regulates cell migration during wound healing in vitro by modulating the phosphorylation of FAK and paxillin and the consequent formation of focal adhesions. An ERK-FAK-paxillin signaling pathway may play an important role in corneal epithelial wound healing in vivo.

Role of JNK-Dependent Serine Phosphorylation of Paxillin in Migration of Corneal Epithelial Cells during Wound Closure

PURPOSE Migration of corneal epithelial cells plays an important role in healing of corneal epithelial wounds. The role of c-Jun NH(2)-terminal kinase (JNK), a member of the family of mitogen-activated protein kinases, in the intracellular signaling responsible for the migration of corneal epithelial cells during wound closure was examined. METHODS Scratch wounds were introduced into cultured monolayers of simian virus 40-transformed human corneal epithelial (HCE) cells in the absence or presence of the JNK inhibitor SP600125. The phosphorylation and localization of JNK and paxillin during wound closure were examined by immunoblot and immunofluorescence analyses. The effects of a small interfering RNA (siRNA) specific for JNK and of a mutant form of paxillin on HCE cell migration were determined by transfection. RESULTS SP600125 inhibited wound healing in a time- and concentration-dependent manner. Immunoblot analysis showed that wounding increased the phosphorylation of JNK and of paxillin on serine (Ser) 178 in a manner sensitive to SP600125. Immunofluorescence staining revealed that phosphorylated JNK colocalized with paxillin at focal adhesions formed by HCE cells at the wound margin and that SP600125 inhibited the formation of such adhesions. Expression of JNK siRNA or of a paxillin mutant in which Ser178 is replaced by alanine inhibited HCE cell migration during wound closure. CONCLUSIONS JNK regulates HCE cell migration by modulating the phosphorylation of paxillin and the consequent formation of focal adhesions. A JNK-paxillin signaling pathway may thus play an important role in corneal epithelial wound healing in vivo.

Protective effect of dexamethasone against hypoxia-induced disruption of barrier function in human corneal epithelial cells.

The corneal epithelium functions as a barrier to protect the cornea from external agents such as infectious organisms and toxins and thereby contributes to corneal homeostasis. The barrier function of epithelia is dependent on the formation of tight and adherens junctions between adjacent epithelial cells. We have previously shown that hypoxia disrupts the barrier function of cultured human corneal epithelial (HCE) cells by affecting tight junctions. We have now examined the effect of dexamethasone on this barrier disruption induced by hypoxia in HCE cells. Measurement of transepithelial electrical resistance revealed that the hypoxia-induced decrease in the barrier function of HCE cells was inhibited by dexamethasone in a concentration-dependent manner. The hypoxia-induced loss of the tight junction protein ZO-1 from the borders of adjacent HCE cells (as revealed by immunofluorescence analysis) as well as the hypoxia-induced down-regulation of ZO-1 expression (as revealed by immunoblot analysis) were also inhibited by dexamethasone, whereas this drug had no effect on the expression or distribution of the tight junction protein occludin or of the adherens junction proteins E-cadherin and β-catenin. Moreover, dexamethasone attenuated the reorganization of the actin cytoskeleton, the formation of focal adhesions, and the up-regulation of myosin light chain kinase expression induced by hypoxia in HCE cells. Our results thus suggest that dexamethasone protects corneal epithelial cells from the hypoxia-induced disruption of barrier function by maintaining the distribution and expression of ZO-1 as well as the organization of the actin cytoskeleton.

Protection of Human Corneal Epithelial Cells from Hypoxia-Induced Disruption of Barrier Function by Keratinocyte Growth Factor

PURPOSE The possible detrimental effect of hypoxia on the barrier function of corneal epithelial cells and whether keratinocyte growth factor (KGF) might protect against such an effect were investigated. METHODS Simian virus 40-transformed human corneal epithelial (HCE) cells were cultured for 4 days to allow the establishment of barrier function. They were then deprived of serum for 24 hours before exposure to 1% (hypoxia) or 21% (normoxia) oxygen for 24 hours. Barrier function was evaluated by measurement of transepithelial electrical resistance (TER). The localization of ZO-1 and occludin was determined by immunofluorescence microscopy, and the expression of these tight junctional proteins as well as the phosphorylation of the mitogen-activated protein kinases ERK, p38, and JNK were examined by immunoblot analysis. RESULTS Hypoxia induced a decrease in the TER of HCE cells compared with that of cells maintained under normoxia. The localization of ZO-1 at cell-cell borders was disrupted by hypoxia, whereas the distribution of occludin was not affected. Hypoxia also induced the downregulation of ZO-1 and a decrease in the phosphorylation of ERK without affecting the phosphorylation of p38 or JNK. All these effects of hypoxia were inhibited by KGF. The effects of KGF on TER and ZO-1 localization in cells exposed to hypoxia were inhibited by PD98059, an inhibitor of ERK signaling. Neither hypoxia nor KGF exhibited mitogenic or cytotoxic effects in HCE cells. CONCLUSIONS Hypoxia induces disruption of the barrier function of HCE cells by eliciting the redistribution and degradation of ZO-1, and this effect is inhibited by KGF in a manner dependent on ERK activation.

Protection of human corneal epithelial cells from hypoxia-induced disruption of barrier function by hepatocyte growth factor.

The barrier function of the corneal epithelium maintains corneal homeostasis and is mediated by tight junctions (TJs) and adherens junctions (AJs). It is also susceptible to disruption by hypoxia. We have now examined the effects of hypoxia on TJs and AJs as well as on barrier function in human corneal epithelial (HCE) cells. Moreover, we investigated whether such effects of hypoxia might be modulated by hepatocyte growth factor (HGF). The subcellular distribution of the TJ proteins ZO-1 and occludin, the AJ proteins E-cadherin and beta-catenin, and actin filaments was examined by fluorescence microscopy. The abundance of junctional proteins as well as of myosin light chain kinase (MLCK) was determined by immunoblot analysis. Barrier function was evaluated by measurement of transepithelial electrical resistance (TER). Hypoxia-induced both the disappearance of ZO-1 from the borders of neighboring HCE cells as well as the down-regulation of ZO-1 expression without affecting the distribution or abundance of occludin, E-cadherin, or beta-catenin. It also induced the formation of actin stress fibers, the up-regulation of MLCK expression, and a reduction in the TER of HCE cells. All these effects of hypoxia were inhibited by HGF. Neither hypoxia nor HGF exhibited a mitogenic or cytotoxic effect on HCE cells. HGF thus protects HCE cells from hypoxia-induced disruption of barrier function by maintaining the expression and distribution of ZO-1. Inhibition of the effects of hypoxia on the organization of the actin cytoskeleton might also contribute to this protective action of HGF.

Inhibition by All-Trans-Retinoic Acid of Transforming Growth Factor-β–Induced Collagen Gel Contraction Mediated by Human Tenon Fibroblasts

PURPOSE Excessive wound contraction can lead to scar formation in the conjunctiva. The effects of all-trans-retinoic acid (ATRA) on the contractility of human Tenon fibroblasts (HTFs) cultured in three-dimensional (3D) collagen gels were investigated. METHODS Human Tenon fibroblasts were cultured in 3D gels of type I collagen and in the absence or presence of TGF-β, ATRA, or various inhibitors. Collagen gel contraction was evaluated by measurement of gel diameter. Phosphorylation of various signaling molecules was examined by immunoblot analysis. The formation of actin stress fibers and focal adhesions was detected by laser confocal microscopy. RESULTS All-trans-retinoic acid inhibited TGF-β-induced collagen gel contraction mediated by HTFs in a concentration- and time-dependent manner. The TGF-β-induced phosphorylation of focal adhesion kinase (FAK) and formation of stress fibers and focal adhesions in HTFs were attenuated by ATRA. All-trans-retinoic acid also inhibited the TGF-β-induced phosphorylation of the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase (ERK), p38, and c-Jun NH2-terminal kinase (JNK) as well as that of c-Jun and Smad2/3. Furthermore, TGF-β-induced collagen gel contraction was blocked by inhibitors of ERK, p38, or JNK signaling. CONCLUSIONS All-trans-retinoic acid inhibited TGF-β-induced collagen gel contraction mediated by HTFs, most likely by attenuating the formation of actin stress fibers and focal adhesions as well as signaling by MAPKs, c-Jun, and Smads. All-trans-retinoic acid may therefore prove effective for inhibition of conjunctival scarring through attenuation of the contractility of Tenon fibroblasts.

Safety and Efficacy of Benzalkonium Chloride-optimized Tafluprost in Japanese Glaucoma Patients With Existing Superficial Punctate Keratitis.

Purpose:To evaluate the safety and efficacy of benzalkonium chloride (BAK)–optimized tafluprost (with a BAK concentration reduced from 0.01% to 0.001%) in glaucoma patients with existing superficial punctate keratitis (SPK). Patients and Methods:A prospective, multicenter, open-label study was designed to compare BAK-optimized tafluprost administered over 12 weeks relative to other preserved prostaglandin analogs previously administered in Japanese glaucoma patients. Thirty patients with SPK graded at <6 points by area density (AD) scoring in 1 eye were recruited. The primary outcome measure was change in AD score at 12 weeks after the switch in treatment compared with that at baseline. Secondary outcome measures included changes in tear film breakup time (TBUT), hyperemia score, and intraocular pressure (IOP). Four patients were excluded from analysis because of treatment discontinuation. Results:Mean AD score±SD decreased significantly from 3.4±0.9 to 1.8±1.8 after the switch (P<0.0001). Mean TBUT increased significantly from 6.3±3.3 to 8.0±4.2 seconds (P<0.01). Mean hyperemia score remained unchanged, whereas mean IOP decreased significantly from 15.6±2.6 to 14.4±2.0 mm Hg (P<0.01). For patients previously treated with BAK-preserved latanoprost (n=17) or bimatoprost (n=2), mean AD score decreased significantly from 3.4±0.9 to 1.8±1.8 (P<0.01) and mean TBUT increased significantly from 6.4±3.6 to 8.2±4.3 seconds (P<0.01); no such changes were apparent for patients previously treated with sofZia-preserved travoprost (n=7). Conclusions:BAK-optimized tafluprost is a treatment option to improve the condition of the ocular surface and to maintain IOP control in glaucoma patients with existing SPK who have been previously treated with other BAK-preserved prostaglandin analogs.