(-)Epigallocatechin-3-gallate inhibits gelatinase activity of some bacterial isolates from ocular infection, and limits their invasion through gelatine.

The objective of this paper is to assess the gelatinase production by some ocular pathogenic bacterial strains, and evaluate the ability of (-)epigallocatechin-3-gallate (EGCg) to inhibit this gelatinase activity and thus limit bacterial invasion. The effect of EGCg on bacterial gelatinase activity was tested by classic zymography methods, while its effect on bacterial invasion was evaluated through the ability of growing bacteria to liquefy and thus penetrate a semisolid gelatine substrate. It was found that EGCg inhibits bacterial gelatinases with an IC(50) of about 0.2 mM, and limits invasion of gelatinase-positive bacteria at concentrations above 2 mM. These results show for the first time that EGCg, as well as having direct antibacterial activity, can also inhibit bacterial gelatinases, thus limiting their invasion on gelatine. Possible use of EGCg is thus suggested as an adjuvant in antibacterial chemotherapy.

In vivo toxicity of netilmicin and ofloxacin on intact and mechanically damaged eyes of rabbit.

PURPOSE: To evaluate the in vivo toxicity of netilmicin and ofloxacin using both normal and mechanically damaged eyes of rabbit. METHODS: Male albino New Zealand rabbits were given either 0.3% netilmicin, 0.3% ofloxacin, or 0.9% sodium chloride solution by topical instillation (50 microL) into the conjunctival sac 6 times daily for 5 days. In some animals a 6-mm-diameter epithelial wound was mechanically made to the center of the cornea. Ocular toxicity on normal eyes was evaluated by impression cytology of the conjunctiva, histology of the entire globes, and scanning electron microscopy (SEM) of the cornea. Analysis of toxicity and reepithelialization on wounded corneas was evaluated by SEM with observations being made 48 and 72 hours after induction of the wound. RESULTS: Cytologic, histopathologic, and SEM analyses of normal healthy eyes following netilmicin treatment revealed no signs of toxicity, whereas those treated with ofloxacin revealed alterations in the cornea (stromal swelling) and conjunctiva (infiltration of polymorphonuclear cells) with reduced goblet cell numbers. Wounded corneas treated with netilmicin exhibited normal morphology and reepithelialization, whereas the administration of ofloxacin resulted in disordered cellular organisation and slower rates of epithelial recovery. CONCLUSIONS: Netilmicin, an antibacterial aminoglycoside, is well tolerated even in an experimental wound-healing model where the integrity of the ocular surface is compromised, whereas ofloxacin, a fluoroquinolone, appears to provoke an inflammatory response in the normal eye and a clear alteration of reepithelialization in the wounded eye. These findings suggest that netilmicin may offer a superior toxicological profile in both normal eyes and clinical situations where the integrity of the ocular epithelium is suspect.

Capillary electrophoresis assay of netilmicin sulphate.

An effective method based on capillary electrophoresis (CE) for the determination of netilmicin sulphate in commercial ophthalmic formulations was developed and validated. The use of a polymer-coated capillary and a non-absorbing running buffer permitted the elution of netilmicin in cationic mode at pH 3.0 and with direct UV detection at lambda=195 nm. Since pre-treatment of the samples is not required, this procedure may be straightforwardly applied to the other aminoglycosides provided that their extinction coefficient is not too low.

Susceptibility of methicillin-resistant staphylococci to oregano essential oil, carvacrol and thymol.

The aim of this study was to evaluate the susceptibility of methicillin-susceptible and methicillin-resistant staphylococci (MSS, MRS) to oregano essential oil, carvacrol and thymol. The commercial aerial parts of Origanum vulgare L. were hydrodistilled and the essential oil analysed by gas- chromatography/electron impact mass spectrometry. The inhibition efficacy of this essence and its major components was assayed against 26 MSS and 21 MRS, using an agar dilution method. The methicillin resistance was thoroughly typed by Epsilometer test (E-test), polymerase chain reaction for mecA gene detection and PBP2' latex agglutination test. The results clearly demonstrated that the comparison between the susceptibility of MSS and MRS to oregano oil, carvacrol and thymol showed no significant differences (Fisher's exact test, P > 0.05). The best minimum inhibitory concentration values were reported for carvacrol (0.015-0.03%, v/v) followed by thymol (0.03-0.06%, v/v) and oregano oil (0.06-0.125%, v/v).

Differential expression of cyclooxygenase-1 and cyclooxygenase-2 in the cornea during wound healing.

Cyclooxygenases (COXs) are the key enzymes in the production of prostaglandins (PGs) and exist in two isoforms. Isoform 1 (COX-1) is constitutively expressed in most tissues, whereas cyclooxygenase-2 (COX-2) is rapidly induced by a variety of different stimuli. In this study, we have quantitatively analyzed mRNA expression of COX-1 and COX-2 and protein distribution during corneal reparative processes after wound. Total RNA was isolated from cornea samples of New Zealand rabbits that had been subjected to corneal wound by mechanical brush scraping. Quantification of RT-PCR results was made by using a DNA mimic approach. The localization and expression of the enzymes was studied by immunocytochemistry and Western blotting. In normal corneas COX-1 is expressed throughout the cornea in the whole tissue, while COX-2 is strongly expressed in stromal keratocytes. Following injury, COX-2 levels drastically increase and, at least in the epithelium, COX-2 becomes the predominant isoform of cyclooxygenases at an early stage of healing. Moreover, in the epithelium COX-2 is expressed predominantly by those cells close to the wound. These cells become migratory and move toward the injured area. In contrast, COX-1 levels remain unaffected in all corneal tissues. The system returns to the pre-injury state in about 24h. Thus, the expression of COX-2 in the corneal epithelium during wound repair is tightly regulated both temporally and spatially.

Interface properties of simplified tear-like fluids in relation to lipid and aqueous layers composition.

The Langmuir trough approach to the study of the physical properties of an in vitro system representing the natural tear lipid-aqueous interface gives useful information on the effect produced by changes of composition of both phases. We found that variations of the composition of the lipid mixture affect more strongly the characteristics of the film rather than changes in the aqueous phase composition. Therefore, future investigations should consider the possibility of searching for and optimising additions of lipid mixtures to the natural tear film. These novel mixtures should stabilise the lipid layer, and thus treat the evaporative Dry Eye Syndrome. More critical and worthy of further investigation is the effect of surface-active water-soluble components that can reduce and ultimately destroy the lipid film integrity and effectiveness. The beneficial effect of water-soluble components, either naturally occurring or artificially added, may be more precisely compared with possible side effects on the stability of the lipid tear layer. In any case, these side effects may be largely compensated by the presence of stability enhanced lipid composition. The present work may be considered as an introductory investigation that takes the physical-chemical approach into the realm of debated data about the tear film structure and properties. Refining the model we have adopted in the present work is certainly necessary. For instance, introducing into the model tear composition other components such as ceramides and cerebrosides will provide insight to their contribution to the packing structure. We may also couple different techniques such as measuring elastic and rheological properties of the films that may be relevant to its physiological behaviour.

Ocular permeability screening of dexamethasone esters through combined cellular and tissue systems.

Dexamethasone transport across ocular epithelium was evaluated by means of permeability studies on a series of ester prodrugs with the aim of identifying the most promising candidates for the treatment of the ocular surface. Organotypic conjunctival bovine epithelial cell cultures were assumed representative of an average ocular epithelium and used to describe the mechanism of permeation. Permeability coefficients were also determined in excised rabbit corneas set up and in vivo pharmacokinetic experiments. All dexamethasone esters permeated through the transcellular route and their permeability coefficient rose with the increase of the molecules lipophilicity until a maximum was reached in correspondence of dexamethasone butyrate (Log P = 3.95). It was found that esters hydrolysis occurring in various extent along the transport process, affected the overall permeability rate. There was evidence that the permeation process can be confined at the ocular epithelium layer if the ester is highly hydrophobic and not susceptible of fast hydrolysis.

Lactoferrin expression by bovine ocular surface epithelia: a primary cell culture model to study lactoferrin gene promoter activity.

Tear lactoferrin, mainly secreted by the lachrymal glands, exerts a protective effect on the ocular surface, and an abnormal decrease of its production may lead to an increased risk of infection and pathological alterations of ocular surface epithelia. In this study we analyzed whether corneal and conjunctival epithelia could be an additional source of tear lactoferrin, and whether conjunctival epithelial cells in culture could be a suitable model system to address regulation of lactoferrin gene expression. Real-time PCR and Western immunoblotting showed that in bovines lactoferrin is indeed produced by these epithelia, and that the human lactoferrin promoter can direct the expression of a CAT reporter gene, thus indicating that these cells are a true source of lactoferrin, and may be used in vitro to study the regulation of lactoferrin expression.

Surface-induced unfolding of human lactoferrin.

We have determined the structural conformations of human lactoferrin adsorbed at the air/water interface by neutron reflectivity (NR) and its solution structure by small angle neutron scattering (SANS). The neutron reflectivity measurements revealed a strong structural unfolding of the molecule when adsorbed at the interface from a pH 7 phosphate buffer solution (PBS with a total ionic strength at 4.5 mM) over a wide concentration range. Two distinct regions, a top dense layer of 15-20 angstroms on the air side and a bottom diffuse layer of some 50 angstroms into the aqueous subphase, characterized the unfolded interfacial layer. At a concentration around 1 g dm(-3), close to the physiological concentration of lactoferrin in biological fluids, the adsorbed amount was 5.5 x 10(-8) mol m(-2) in the absence of NaCl, but the addition of 0.3 M NaCl reduced protein adsorption to 3.5 x 10(-8) mol m(-2). Although the polypeptide distributions at the interface remained similar, quantitative analysis showed that the addition of NaCl reduced the layer thickness. Parallel measurements of lactoferrin adsorption in D2O instead of null reflecting water confirmed the unfolded structure at the interface. Furthermore, the D2O data indicated that the polypeptide in the top layer was predominantly protruded out of water, consistent with it being hydrophobic. In contrast, the scattering intensity profiles from SANS were well described by a cylindrical model with a diameter of 47 angstroms and a length of 105 angstroms in the presence of 0.3 M NaCl, indicating a retention of the globular framework in the bulk solution. In the absence of NaCl but with the same amount of phosphate buffer, the length of the cylinder increased to some 190 angstroms and the diameter remained constant. The length increase is indicative of changes in distance and orientation between the bilobal monomers due to the change in charge interactions. The results thus demonstrate that the surface structural unfolding was caused by the exposure of the protein molecule to the unsymmetrical energetic balance following surface adsorption.

Multilayer primary epithelial cell culture from bovine conjunctiva as a model for in vitro toxicity tests.

OBJECTIVE: The purpose of this study was to obtain a primary cell culture of bovine origin similar to the conjunctiva in terms of morphology and cell types, which could be of use for in vitro toxicity studies. METHODS: After separation from the stroma by enzymatic treatment, conjunctival epithelial cells were dissociated and plated onto collagen-coated Transwell filters (1.13 cm(2) area). One group of plates was maintained in immersion and another was cultured under air-lifted conditions. Anti-epithelial keratin antibodies (AE1/AE3, K4) and antidesmoplakin 1 and 2 were used to characterize the cells by indirect immunofluorescence. The cell layer was examined after histological processing of the Transwell filter. Ultrastructural analysis was carried out by scanning electron microscopy (SEM). The bioelectric parameters transepithelial electrical resistance (TEER), potential difference (PD), short circuit current and paracellular permeability profile of carboxyfluorescein were monitored as indices of the functional characteristics of these cultures. Cytotoxicity was evaluated on morphological and functional (TEER) grounds after treating the cultures with several test substances. RESULTS: Morphological studies showed pure and homogeneous cell cultures. In the SEM analysis, we observed contiguous polygonal cells with numerous short microvilli, a characteristic proportion of light, medium and dark cells and a sparse population of rounded PAS-positive cells, i.e. resembling goblet cells. Air-lifted cultures also showed a tissue-like cellular organization (8-9 layers). Immersion cultures reached a maximum TEER value of around 2.95 kOmega x cm(2) 7 days after plating while in air-lifted cultures TEER peaked up to 5.59 komega x cm(2) 11 days after plating. With regard to the use of bovine conjunctival epithelial cells (BCECs) for cytotoxicity screening, the system responded finely to the insults and yielded morphological and functional results in accordance with data obtained in vivo. CONCLUSIONS: BCECs reproduce cell morphology and differentiation of the original tissue and should prove a useful tool for initial studies of drug toxicity.

Epigallocatechin-gallate enhances the activity of tetracycline in staphylococci by inhibiting its efflux from bacterial cells.

Epigallocatechin-gallate (EGCg), the major catechin present in green tea extracts, has been shown to have several antibacterial activities, limiting bacterial growth and invasion and acting in synergy with beta-lactam antibiotics. In this article, we report that EGCg at doses half and below its calculated MIC of 100 microg/ml, is able to reverse tetracycline resistance in staphylococcal isolates expressing the specific efflux pump Tet(K) and appears to improve the MICs of tetracycline for susceptible staphylococcal isolates as well. The visible effect of EGCg is an increased accumulation of tetracycline inside bacterial cells. This effect is likely due to the inhibition of pump activity, and it is evident not only for Tet(K) pumps but also for efflux pumps of a different class [Tet(B)]. In summary, our data indicate that the observed dramatic enhancement by EGCg of tetracycline activity for resistant staphylococcal isolates is caused by impairment of tetracycline efflux pump activity and increased intracellular retention of the drug, suggesting a possible use of EGCg as an adjuvant in antibacterial therapy.