Lactoferrin in human ocular tissues

Effectiveness of Single-Dose Oral Pilocarpine Administration in Patients with Sjögren's Syndrome

In this study, we evaluated the effectiveness of a single-dose oral pilocarpine administration on tear film (TF), as well as dry eye and dry mouth symptoms, in 53 eyes of 27 Sjögren syndrome (SS) patients who were experiencing dry mouth. To evaluate the changes in tear volume, a digital video-meniscometer was used to measure the radius of the lower central tear meniscus curvature (R, mm) of each eye at prior to the administration of 5 mg oral pilocarpine, and at 15 (R:(15)), 30 (R:(30)), and 60 (R:(60)) minutes after administration. The fluorescein breakup time (FBUT, seconds) and ocular and oral dryness symptoms were evaluated before and at 60 min after administration using a visual analogue scale (VAS, mm). A significant increase in R was observed at 15 and 30 min after administration compared to that at prior to administration. FBUT showed significant improvement at 60 min after administration, and the VAS score for ocular and oral dryness symptoms was found to have decreased significantly at 60 min after administration. A single-dose administration of 5 mg oral pilocarpine had a beneficial effect on TF, as well as on ocular and oral dryness symptoms, in patients with SS.

How Can We Best Diagnose Severity Levels of Dry Eye Disease: Current Perspectives

Dry eye disease (DED) is a common ocular condition, but the diagnosis relative to other ocular conditions and the evaluation of severity of the condition has often been difficult. This challenge can be due to clinical signs and symptoms not always correlating with each other. An understanding of the various components which create the condition, as well as the diagnostic measures used to evaluate these components, is useful to the clinician working with DED patients. This review paper will discuss traditional diagnostic options, diagnostic imaging, and Advanced Point of Care testing capabilities to determine the severity level of dry eye disease more adequately.

Biomedical Applications of Lactoferrin on the Ocular Surface

Lactoferrin (LF) is a first-line defense protein with a pleiotropic functional pattern that includes anti-inflammatory, immunomodulatory, antiviral, antibacterial, and antitumoral properties. Remarkably, this iron-binding glycoprotein promotes iron retention, restricting free radical production and avoiding oxidative damage and inflammation. On the ocular surface, LF is released from corneal epithelial cells and lacrimal glands, representing a significant percentage of the total tear fluid proteins. Due to its multifunctionality, the availability of LF may be limited in several ocular disorders. Consequently, to reinforce the action of this highly beneficial glycoprotein on the ocular surface, LF has been proposed for the treatment of different conditions such as dry eye, keratoconus, conjunctivitis, and viral or bacterial ocular infections, among others. In this review, we outline the structure and the biological functions of LF, its relevant role at the ocular surface, its implication in LF-related ocular surface disorders, and its potential for biomedical applications.

Analysis and comparison of tear protein profiles in dogs using different tear collection methods

BACKGROUND

Tear proteomic analysis has become an important tool in medical and veterinary research. The tear collection method could influence the tear protein profile. This study aims to evaluate the protein profiles of dog tears collected using microcapillary tubes (MT), Schirmer tear strips (ST), and ophthalmic sponges (OS).

METHODS

The tear samples were collected using MT, ST, and OS. Tear protein profiles were analyzed using two-dimensional electrophoresis (2-DE) and the different protein spots' expression was compared. Fourteen protein spots were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Tear protein concentrations ranged from 2.80 to 4.03 μg/μL, with no statistically significant differences among collection methods. Protein expression in each collection method differed in terms of both the number and intensity of the spots. There were 249, 327, and 330 protein spots found from tears collected with MT, ST, and OS, respectively. The proteins albumin, haptoglobin, and lactoferrin identified from OS were found to have higher spot intensities than other methods of collection. The use of MT demonstrated the downregulation of nine proteins.

CONCLUSIONS

The recent study supported that tear protein analysis is affected by different tear collection methods. Although ST is commonly used for tear collection, it provides insufficient information to study particular tear proteins.

Host Defense Peptides at the Ocular Surface: Roles in Health and Major Diseases, and Therapeutic Potentials

Sight is arguably the most important sense in human. Being constantly exposed to the environmental stress, irritants and pathogens, the ocular surface – a specialized functional and anatomical unit composed of tear film, conjunctival and corneal epithelium, lacrimal glands, meibomian glands, and nasolacrimal drainage apparatus – serves as a crucial front-line defense of the eye. Host defense peptides (HDPs), also known as antimicrobial peptides, are evolutionarily conserved molecular components of innate immunity that are found in all classes of life. Since the first discovery of lysozyme in 1922, a wide range of HDPs have been identified at the ocular surface. In addition to their antimicrobial activity, HDPs are increasingly recognized for their wide array of biological functions, including anti-biofilm, immunomodulation, wound healing, and anti-cancer properties. In this review, we provide an updated review on: (1) spectrum and expression of HDPs at the ocular surface; (2) participation of HDPs in ocular surface diseases/conditions such as infectious keratitis, conjunctivitis, dry eye disease, keratoconus, allergic eye disease, rosacea keratitis, and post-ocular surgery; (3) HDPs that are currently in the development pipeline for treatment of ocular diseases and infections; and (4) future potential of HDP-based clinical pharmacotherapy for ocular diseases.

Tear Proteomics of Children and Young Adult Soft Contact Lens, Orthokeratology and Spectacle Wearers - A Pilot Study

PURPOSE

Contact lens complications occur more often in older teenagers and young adults compared to children. This study explored differences in tear proteomics between children and young adults wearing soft contact lens (SCL), orthokeratology or spectacles for >3 years.

METHODS

Twelve children and 12 sex- and correction-matched young adults were enrolled. Tears were collected via Schirmer strips for tear proteomic analysis using mass spectrometry. Proteome Discoverer was used for protein identification. Label-Free Quantitation was generated using Scaffold software; Fisher's Exact tests were used to compare proteins by age and correction groups. Generalized linear models were used to assess differences in overall protein levels by age and correction groups. A secondary analysis of proteins presented in >50% of samples of each group was conducted using the R/Bioconductor limma package.

RESULTS

There were 385 proteins present only in young adults while 183 were unique in children. There were 528 unique proteins to SCL, 96 to orthokeratology and 149 to spectacle wearers. Based on Fisher's Exact analyses, 126 proteins were higher in young adults than children (all P < 0.048). Forty-seven protein levels were higher in SCL compared to orthokeratology (all P < 0.01), 33 protein levels were higher in SCL compared to spectacles (all P < 0.01), 15 protein levels were higher in orthokeratology compared to spectacle wearers (all P < 0.01). Based on generalized linear models, young adults had higher overall protein levels than children (P = 0.001), SCL had higher protein levels than spectacle wearers (P < 0.001) but no differences were found between orthokeratology and spectacle wearers (P = 0.79). Based on the secondary analysis, only Antileukoproteinase was higher in the young adult orthokeratology group compared to other groups (P < 0.01).

CONCLUSIONS

Tear protein type and abundance differ by age and correction. Further research is needed to understand the effects of contact lens correction in children and young adults on the tear proteome.

The Protective Effect of an Eye Wash Solution on the Ocular Surface Damage Induced by Airborne Carbon Black Exposure

PURPOSE

To investigate the effects of an eye wash solution on the ocular surface damage induced by airborne carbon black (CB) exposure.

METHODS

Sprague-Dawley rats were exposed to ambient CB for 5 days. During the 5 days, a commercial eye wash solution (Eyebon-W) was used for irrigation twice daily on CB-exposed rat eyes; normal saline was used as the vehicle control. Lactic dehydrogenase (LDH) activity and matrix metallopeptidase (MMP)-9, histamine, and lactoferrin levels were measured in tears. The expression of inflammatory cytokines in the anterior segment of the eyeball was measured by Western blot analysis.

RESULTS

The ocular surface staining scores, tear LDH activity, tear MMP-9, histamine, and lactoferrin concentrations, and the expression of interleukin-4 and interferon-γ in the eye were significantly increased in the CB group versus the normal control group. When compared with CB group, the Eyebon-W eye wash treatment significantly reversed these elevations induced by CB, including ocular staining scores, tear LDH activity, histamine and MMP-9 concentrations in the tear fluid, and the expression of interleukin-4 in the eye. On the other hand, saline irrigation only reduced the concentrations of histamine and MMP-9 in tear fluid and the expression of interferon-γ in the eye.

CONCLUSIONS

Both Eyebon-W eye wash treatment and saline irrigation reversed CB-induced ocular surface injury, but the efficacy of Eyebon-W was more significant than that of the saline solution when compared with CB group. The use of an eye wash solution seems to play a protective role for the ocular surface when exposed to airborne particulate matter.

Tear Lactoferrin and Features of Ocular Allergy in Different Severities of Meibomian Gland Dysfunction

SIGNIFICANCE

Meibomian gland dysfunction, but not atrophy, was associated with lower tear lactoferrin concentration, greater dry eye, and allergic symptoms, indicating greater inflammation and discomfort in patients with lower meibomian gland expressibility.

PURPOSE

Meibomian gland dysfunction can potentially damage adjacent palpebral structures, which may induce inflammation in accessory lacrimal glands and affect lactoferrin secretion. This study aimed to examine the relationships between the severity of meibomian gland dysfunction with tear lactoferrin, conjunctival cell morphology, and clinical features of ocular allergy.

METHODS

Forty subjects were divided into two groups based on the severity of meibomian gland plugging and expressibility and secondarily based on its atrophy. Dry eye and allergy questionnaires; slit-lamp examination, including lid telangiectasia; and meibography were performed. Tear lactoferrin concentration was measured using TearScan 270 MicroAssay. Impression cytology was performed on the upper palpebral conjunctiva, and goblet cell density and epithelial squamous metaplasia were quantified.

RESULTS

Twenty-two subjects with meibomian gland dysfunction were categorized into severely obstructed group (case), whereas 19 subjects had minimal/no obstruction (comparison). Lower lactoferrin (1.3 ± 0.4 vs. 1.7 ± 0.4 mg/mL, P = .007), greater dry eye (7 [1 to 10] vs. 2 [0 to 5], P = .03), and allergy symptoms (9 [4 to 23] vs. 6 [0 to 9], P = .05) were found in the cases compared with the comparisons. There were no differences in conjunctival cell morphology between groups. The plugging score was correlated with lactoferrin concentration (ρ = -0.43, P = .006), dry eye (ρ = 0.36, P = .02), and allergic symptoms (ρ = 0.33, P = .04). Greater lid margin telangiectasia was associated with meibomian gland obstruction, but not atrophy.

CONCLUSIONS

Meibomian gland activity/dysfunction, but not atrophy, may be associated with increased inflammation on the ocular surface. The inflammation may be sufficient to reduce tear lactoferrin production from damage to accessory lacrimal glands and/or meibomian gland and result in increased symptoms.

Increased Cathepsin S activity associated with decreased protease inhibitory capacity contributes to altered tear proteins in Sjögren's Syndrome patients

Cathepsin S (CTSS) activity is elevated in Sjögren's Syndrome (SS) patient tears. Here we tested whether protease inhibition and cystatin C (Cys C) levels are reduced in SS tears, which could lead to enhanced CTSS-driven degradation of tear proteins. CTSS activity against Cys C, LF and sIgA was tested in SS or healthy control tears. Tears from 156 female subjects (33, SS; 33, rheumatoid arthritis; 31, other autoimmune diseases; 35, non-autoimmune dry eye (DE); 24, healthy controls) were analyzed for CTSS activity and Cys C, LF, and sIgA levels. Cys C and LF showed enhanced degradation in SS tears supplemented with recombinant CTSS, but not supplemented healthy control tears. CTSS activity was significantly increased, while Cys C, LF and sIgA levels were significantly decreased, in SS tears compared to other groups. While tear CTSS activity remained the strongest discriminator of SS in autoimmune populations, combining LF and CTSS improved discrimination of SS beyond CTSS in DE patients. Reductions in Cys C and other endogenous proteases may enhance CTSS activity in SS tears. Tear CTSS activity is reconfirmed as a putative biomarker of SS in an independent patient cohort while combined LF and CTSS measurements may distinguish SS from DE patients.

Ocular Mucosal Immunity

Mucosal immunity defends the ocular surface against antigenic challenge and microbial invasion. The principal effector site is the lacrimal gland, where immunoglobulin A (IgA) antibodies are produced. Nasal-associated lymphoid tissue and posterior cervical lymph nodes function as major inductive sites for tear IgA responses. Neural connections and systemic hormones maintain the integrity and function of the ocular surface. Neuroenzyme activities in the lacrimal gland are influenced by ocular infections, leading to reduced expression of acetylcholine and modulation of receptors on acinar cells and on plasma cells, thereby decreasing fluid and immunoglobulin secretion. T lymphocyte-dependent responses result in production of interleukin-4 in lacrimal glands, thereby influencing cholinergic enzyme activity affecting immune processes and lacrimal physiology. Furthermore, neuropeptides released into lymphoid structures or inflamed tissues are chemotactic for antigen-presenting cells and affect their interactions with T cells. Thus, in developing therapeutic approaches for treating dry-eye conditions and vaccination strategies to elicit protective ocular mucosal immune responses, the entire lacrimal functional unit should be considered.

Evaluation of dry eye

Dry eye is a common yet complex condition. Intrinsic and extrinsic factors can cause dysfunction of the lids, lacrimal glands, meibomian glands, ocular surface cells, or neural network. These problems would ultimately be expressed at the tear film-ocular surface interface. The manifestations of these problems are experienced as symptoms such as grittiness, discomfort, burning sensation, hyperemia, and secondary epiphora in some cases. Accurate investigation of dry eye is crucial to correct management of the condition. Techniques can be classed according to their investigation of tear production, tear stability, and surface damage (including histological tests). The application, validity, reliability, compatibility, protocols, and indications for these are important. The use of a diagnostic algorithm may lead to more accurate diagnosis and management. The lack of correlation between signs and symptoms seems to favor tear film osmolarity, an objective biomarker, as the best current clue to correct diagnosis.

Dietary lactoferrin alleviates age-related lacrimal gland dysfunction in mice

Background

Decrease in lacrimal gland secretory function is related to age-induced dry eye disease. Lactoferrin, the main glycoprotein component of tears, has multiple functions, including anti-inflammatory effects and the promotion of cell growth. We investigated how oral administration of lactoferrin affects age-related lacrimal dysfunction.

Methods and Findings

Twelve-month-old male C57BL/6Cr Slc mice were randomly divided into a control fed group and an oral lactoferrin treatment group. Tear function was measured at a 6-month time-point. After euthanasia, the lacrimal glands were subjected to histological examination with 8-hydroxy-2′-deoxyguanosine (8-OHdG) antibodies, and serum concentrations of 8-OHdG and hexanoyl-lysine adduct (HEL) were evaluated. Additionally, monocyte chemotactic protein-1(MCP-1) and tumor necrosis factor-α (TNF-α) gene expression levels were determined by real-time PCR. The volume of tear secretion was significantly larger in the treated group than in the control. Lactoferrin administration reduced inflammatory cell infiltration and the MCP-1 and TNF-α expression levels. Serum concentrations of 8-OHdG and HEL in the lactoferrin group were lower than those in the control group and were associated with attenuated 8-OHdG immunostaining of the lacrimal glands.

Conclusion

Oral lactoferrin administration preserves lacrimal gland function in aged mice by attenuating oxidative damage and suppressing subsequent gland inflammation.

Immunolocalization of lactoferrin in healthy and inflamed gingival tissues

BACKGROUND

It has been reported that lactoferrin prevents biofilm formation and exerts antimicrobial activity. The aim of the present study was to evaluate the cellular source of lactoferrin in healthy and inflamed gingiva.

METHODS

Lactoferrin synthesis was examined in relation to disease manifestation in biopsies of the marginal gingiva by immunohistochemistry. The expression of lactoferrin in cell cultures was studied by immunocytochemistry and reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Healthy gingiva demonstrated no immunoreactivity to lactoferrin in epithelial and connective tissue cells. In inflamed specimens, lactoferrin staining was related to inflammatory cells. These results were confirmed by cell cultures of keratinocytes that did not show any immunoreactivity against lactoferrin. No mRNA message for lactoferrin was detected by RT-PCR in keratinocytes.

CONCLUSIONS

These data provide evidence that lactoferrin is not synthesized in healthy gingival tissues. Therefore, elevated lactoferrin levels in the crevicular fluid of inflamed tissues originate from invading cells of the inflammatory reaction.

Laboratory findings in tear fluid analysis

The tear film, composed of the lipid, aqueous and mucin layers, has many functions including defending the ocular surface. The tear film covering the ocular surface presents a mechanical and antimicrobial barrier and ensures an optical refractive surface. The lipid component originates from the meibomian glands of the tarsus and forms the superficial layer of the tear film. The aqueous component contains electrolytes, water, and a large variety of proteins, peptides and glycoproteins, and is primarily secreted by the lacrimal gland. Mucins are glycoproteins expressed by epithelial tissues of mucous surfaces. They protect tissues by functioning as antioxidants, providing lubrication, and inhibiting bacterial adherence. Quantitatively and qualitatively, its composition must be maintained within the fairly narrow limits to maintain a healthy and functional visual system. Abnormalities of the tear film, affecting the constituents or the volume, can rapidly result in serious dysfunction of the eyelids and conjunctiva and ultimately affect the transparency of the cornea. Many ocular surface tests have been developed for the clinical diagnosis of dry eye syndromes. This paper provides an overview on laboratory methods for the analysis of the tear film. Understanding the components of the tear film will aid in the treatment of dry eye syndromes and the ocular surface diseases.

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.

Apocrine Glands in the Eyelid of Primates Contribute to the Ocular Host Defense

Apocrine glands of Moll are regular components of primate eyelids. We studied the distribution and localization of these glands in three different primate species, the common marmoset, the rhesus monkey, and the hamadryas baboon. In addition, we tested the primate glands of Moll with antibodies against antimicrobial proteins, cytoskeletal proteins and the androgen receptor. The glands of Moll differ in abundance and distribution in different monkeys. In the common marmoset, a representative of the New World monkeys, Platyrrhini, the apocrine glands are frequently found at the lid margin and in the overlying epidermis of the lid. In the rhesus monkey and the hamadryas baboon, representatives of Old World monkeys, Catarrhini, apocrine glands are rarer and located predominantly at the margin of the lid. The immunohistochemical analysis indicates the presence of a variety of antimicrobial proteins, e.g. lysozyme, beta-defensin-2, adrenomedullin, lactoferrin, and IgA, in these glands. Interestingly, there are basically no androgen receptors in the nuclei of apocrine glands at the lid margin in all three monkey species. In the common marmoset, however, androgen receptors are found in apocrine glands of the overlying epidermis of the lid. We speculate that the glands of Moll are derived from apocrine glands as found in the skin of the entire body in New World monkeys which developed at the lid margins of higher primates and humans into specialized glands secreting agents of host defense in the eye.

Abnormal protein profiles in tears with dry eye syndrome

PURPOSE

To verify the hypothesis that protein concentrations, such as lactoferrin, epidermal growth factor (EGF), and aquaporin 5 (AQP5), in tears are abnormal in patients with dry eye.

DESIGN

Prospective case-control study.

METHODS

One hundred three dry eye patients were divided into three groups: dry eye not associated with the Sjögren syndrome (non-SS; n = 71), Sjögren syndrome (SS; n = 23), and Stevens-Johnson syndrome (SJS; n = 9). Sixteen normal control subjects were also checked. The concentrations of lactoerrin, EGF, and AQP5 were measured by enzyme-linked immunosorbent assay.

RESULTS

The concentration of lactoferrin was significantly decreased in tears of non-SS (P =.0001), SS (P =.00005), and SJS (P =.0006) patients compared with control subjects. The concentration of EGF was significantly decreased in non-SS (P =.0005), SS (P =.00002), and SJS (P =.0001) patients compared with control subjects. The concentration of AQP5 was significantly increased in tears of only SS patients (P =.01) compared with control subjects and increased in tears of only SS patients compared with non-SS patients (P =.007).

CONCLUSIONS

The decrease in both lactoferrin and EGF was found not only in SS patients but also in non-SS patients, indicating that tear components in dry eyes differ in their quantity and quality. Quantification of AQP5 increased only in SS patients, suggesting that AQP5 protein leaks into the tears when acinar cells of the lacrimal gland are damaged by lymphocytic infiltration.

Evaluation of lysozyme and lactoferrin in lacrimal and other ocular glands of bison and cattle and in tears of bison

OBJECTIVE

To evaluate lactoferrin and lysozyme content in various ocular glands of bison and cattle and in tears of bison.

SAMPLE POPULATION

Tissues of ocular glands obtained from 15 bison and 15 cattle and tears collected from 38 bison.

PROCEDURE

Immunohistochemical analysis was used to detect lysozyme and lactoferrin in formalin-fixed, paraffin-embedded sections of the ocular glands. Protein gel electrophoresis was used to analyze ocular glands and pooled bison tears by use of a tris-glycine gel and SDS-PAGE. Western blotting was used to detect lactoferrin and lysozyme.

RESULTS

Immunohistochemical staining for lactoferrin was evident in the lacrimal gland and gland of the third eyelid in cattle and bison and the deep gland of the third eyelid (Harder's gland) in cattle. Equivocal staining for lactoferrin was seen for the Harder's gland in bison. An 80-kd band (lactoferrin) was detected via electrophoresis and western blots in the lacrimal gland and gland of the third eyelid in cattle and bison, Harder's glands of cattle, and bison tears. An inconsistent band was seen in Harder's glands of bison. Lysozyme was not detected in the lacrimal gland of cattle or bison with the use of immunohistochemical analysis or western blots. Western blots of bison tears did not reveal lysozyme.

CONCLUSIONS AND CLINICAL RELEVANCE

Distribution of lactoferrin and a lack of lysozyme are similar in the lacrimal gland of cattle and bison. Differences in other tear components may be responsible for variability in the susceptibility to infectious corneal diseases that exists between bison and cattle.

Detection of lysozyme in llama, sheep, and cattle tears

OBJECTIVE

To determine whether the tears of llamas, sheep, and cattle contain lysozyme and compare lysozyme concentrations in tears among these species.

ANIMALS

40 llamas, 5 sheep, and 36 cattle.

PROCEDURE

Electrophoresis, western blot immunoassay for lysozyme, a spectrophotometric assay to detect tear lysozyme by its ability to lyse a suspension of Micrococcus lysodeiticus, and a microtiter plate colorometric assay were performed.

RESULTS

A 13.6-kd protein band was detected by use of electrophoresis and western blot immunoassay in llama and sheep tears but not cattle tears. Results of spectrophotometric assay suggested that llama and sheep tears had high concentrations of lysozyme, whereas cattle tears had low concentrations. Results of the microtiter plate colorometric assay suggested that llama tears had high concentrations of lysozyme, whereas concentrations in sheep and cattle tears were lower.

CONCLUSIONS AND CLINICAL RELEVANCE

Lysozyme concentrations in tears may vary among species and this variability may contribute to differing susceptibilities to ocular diseases such as infectious keratoconjunctivitis.

Comparison of tear proteins of llamas and cattle

OBJECTIVE

To analyze and compare contents of the preocular tear films of llamas and cattle.

ANIMALS

40 llamas and 35 cattle.

PROCEDURE

Tear pH was determined by use of a pH meter. Total protein concentration was determined by use of 2 microtiter methods. Tear proteins were separated by use of electrophoresis and molecular weights of bands were calculated. Western blot immunoassay was used to detect IgA, lactoferrin, transferrin, ceruloplasmin, alpha1-antitrypsin, alpha1-amylase, and alpha2-macroglobulin. Enzyme electrophoresis was used to detect proteases.

RESULTS

The pH of llama and cattle tears were 8.05 +/- 0.01 and 8.10 +/- 0.01, respectively. For results of both methods, total protein concentration of llama tears was significantly greater than that of cattle tears. Molecular weights of tear protein bands were similar within and between the 2 species, although llama tears had a distinct 13.6-kd band that was not detected in cattle. Lactoferrin, IgA, transferrin, ceruloplasmin, alpha1-antitrypsin, alpha1-amylase, alpha2-macroglobulin, and proteases were detected in both species.

CONCLUSIONS AND CLINICAL RELEVANCE

Llama tears have significantly greater total protein concentration than cattle tears, whereas pH is similar between species. Because little variation was detected within species for the number and molecular weight of protein bands, pooling of tears for analysis is justified. Results suggest that lactoferrin, ceruloplasmin, transferrin, alpha1-antitrypsin, alpha2-macroglobulin, alpha1-amylase, and IgA are present in the tears of llamas and cattle.

Lactoferrin protects against UV-B irradiation-induced corneal epithelial damage in rats

PURPOSE

Lactoferrin supplementation suppresses ultraviolet light B (UV-B)-induced oxidation of cultures of human corneal epithelial cells. To investigate the protective effect of lactoferrin containing eyedrops against UV-B-induced corneal damage in vivo, we examined lactoferrin efficacy in a rat UV-B keratitis model.

METHODS

Sprague-Dawley rats were irradiated with >10 kJ/m2 after anesthetization, and then corneal epithelial defect was observed at 24 h postirradiation. The pre- or postapplication of vehicle or lactoferrin-containing eyedrops was performed, and then corneal epithelial damage was scored based on fluorescein staining.

RESULTS

Posttreatment with lactoferrin did not inhibit the extent of corneal damage and did not affect wound healing. However, pretreatment by topical application of lactoferrin suppressed development of a corneal epithelial defect induced by UV-B irradiation in rats.

CONCLUSION

These results suggest that the presence of lactoferrin in human tear fluid may inhibit UV-induced corneal epithelial damage.

Decreased tear lactoferrin concentration in patients with chronic hepatitis C

BACKGROUND/AIMS

Decreased tear volume in patients with chronic hepatitis C has been reported in the literature. Lactoferrin is abundantly present in human tears, the main source of which is the acini of the lacrimal glands. In this study tear lactoferrin levels were measured to investigate the dry eye condition of patients with chronic hepatitis C.

METHODS

Lactoferrin in tears/fluid was measured by a radial immunodiffusion assay in 42 patients with chronic hepatitis C. The rate of lacrimal secretion was determined by the cotton thread test. Rose bengal staining of the ocular surface was also performed.

RESULTS

Only three patients out of 42 complained of dry eye sensation and, in 31 patients, six showed positive results on the rose bengal staining test of the ocular surface. The lactoferrin concentration of tear fluid in the chronic hepatitis C group (1.42 (SD 0.56) mg/ml) was significantly lower than in the control group (1.90 (0.62) mg/ml; p <0.00048). The cotton thread test results in the chronic hepatitis C group (12.9 (5. 5) mm) were significantly lower than in the control group (17.9 (5. 3) mm; p<0.00048). Also, in the chronic hepatitis C group, tear lactoferrin concentration correlated with the results of the cotton thread test (r = 0.35, p<0.05).

CONCLUSION

Chronic hepatitis C patients showed both decreased tear volume, and decreased tear lactoferrin concentration. These findings suggest that there may be dysfunction of the lacrimal glands in patients with chronic hepatitis C, which may account for the mild dry eye.

Tear lactoferrin concentration during postoperative ocular inflammation in cataract surgery

Tear lactoferrin concentration was measured by ELISA technique and followed in 30 patients undergoing cataract surgery. On the first day following surgery, there was a significant decrease in tear lactoferrin concentration followed by a gradual return to the initial values during the postoperative observation period of 7 days. There was an inverse linear relationship between tear lactoferrin concentration and the tear secretion rate measured by a modified Schirmer I test (1 min) suggesting a constant lactoferrin secretion by the tear glands. Since lactoferrin has known antibacterial and anti-inflammatory effects, the results may contribute to further understanding of the microbial vulnerability or resistance of the eye following surgical procedures.

Tear lactoferrin levels and ocular bacterial flora in HIV positive patients

Keratoconjunctivitis Sicca(4) has recently been reported to occur at a greater rate in HIV-positive symptomatic patients. We looked at HIV positive asymptomatic patients, compared to age matched HIV negative patients to study external ocular resistant factors, namely lactoferrin levels in tears, bacterial flora in lid margins, conjunctiva and tears, and evidence of dry eyes using a Schirmer test and tear osmolarity. Eighteen eyes of nine HIV positive patients and eighteen eyes of HIV negative controls were studied. Results showed markedly decreased lactoferrin levels in HIV positive asymptomatic patients with a mean of 85.8 mgs/dcl compared to HIV negative patients with a mean 156 mgs/dcl (P < 0.01). There were increased numbers of colonies of bacterial flora on the lids of HIV positive asymptomatic patients with an average colony count 4.1 colonies/patient compared to 1.5 colonies/patients in the control group (P < 0.025). Seventy eight percent of the study group had bacterial growth compared to 33% in the control group. The tear osmolarity in both groups had no significant difference; mean in HIV positive being 312 mosml/litre; mean in control 306 mosml/litre. The Schirmer test also showed no significant difference, with the mean in HIV positive patients being 11 mm wetting, and in control patients being 12.7 mm wetting. Therefore, despite no symptomatic or clinical evidence of dry eyes, asymptomatic HIV-positive patients had markedly decreased levels of lactoferrin in tears and increased colony counts of bacterial flora in the lids.

Filtration and local synthesis of lacrimal proteins in acquired immunodeficiency syndrome

In AIDS the onset of the ocular dry syndrome, characterized by lacrimal hyposecretion and deterioration of the corneal and conjunctival epithelium, generally accompanies the clinical aggravation of immunodepression. The study of serum and lacrimal proteins contributes to our knowledge of the pathophysiology of this syndrome. The lacrimal clearance of albumin indicates changes in the permeability of the haemato-lacrimal and conjunctival barrier. Lacrimal monomeric IgA and IgG are mainly of plasmatic origin, while polymeric IgA and IgM are synthesized in situ. The concentrations of these analytes thus reflect ocular humoral immune status. They show a strong humoral protein response in patients with cytomegalovirus retinitis. Lacrimal concentrations of lactoferrin and lysozyme were found to be significantly decreased in AIDS patients with ocular dryness, reflecting a decrease in the secretory activity of the lacrimal gland. Moreover, ocular lympho-plasmocyte infiltration was observed in several patients, with an increase in lacrimal beta 2-microglobulin concentrations. These various lacrimal proteins could be good markers of the ocular dry syndrome in AIDS.

Immunohistochemical demonstration of epidermal growth factor in the lacrimal and submandibular glands of rats

The extraorbital and intraorbital lacrimal glands, the Harderian glands, and the submandibular glands of five rats were excised after ethanol perfusion under general anesthesia. Indirect immunohistochemistry with antibodies specific to epidermal growth factor (EGF) was performed. EGF-like immunofluorescence (EGF-LI) was shown to be present both in the lacrimal glands (extra- and intraorbital) and in the submaxillary gland. In the lacrimal glands the specific immunoreaction appeared within the lumen of the acini and the cells of the tubular ducts close to the acini. Only faint EGF-LI was observed within the acinar cells. The submandibular glands showed intense EGF-LI only in the cells of the granular convoluted tubules. The Harderian gland did not show any EGF-LI. The results strongly support the idea that the lacrimal gland is a source of EGF in tear fluid (TF). Diseases of the lacrimal gland therefore may lead to decreased concentrations of EGF in tears. This may account in part for the pathophysiology of tear deficiency syndromes and may serve as the basis of a new rationale for the external application of EGF.

Localization of lactoferrin in the male reproductive tract

The immunohistochemical localization of lactoferrin in the normal human prostate, seminal vesicle, vas deferens, epididymis and testis was studied using the peroxidase-antiperoxidase method at the light and electron microscopical level. Lactoferrin immunoreactivity was localized in the glandular epithelial cells and granulocytes in the prostate and seminal vesicle. In the prostate, lactoferrin showed an uneven distribution; some of the glands contained exclusively positive cells and others were completely lactoferrin negative, while the rest contained scattered positive cells. The seminal vesicles were divided into three segments, and their lactoferrin content varied significantly although it was always epithelial. The ductus deferens, epididymis and testis contained no lactoferrin. In conclusion, lactoferrin was found in the prostate and seminal vesicles, but not in the testis.

The concentration of lactoferrin in tears during post-operative ocular inflammation

Tear concentration of lactoferrin (LF) was measured by an ELISA technique and followed in 25 patients undergoing cataract surgery. The pre-operative concentration of LF in tears was 773 +/- 60 micrograms/ml (+/- SE) (range: 407-1514 micrograms/ml). On the first day following surgery, there was a significant decrease in tear LF concentration to 377 +/- 45 micrograms/ml followed by a gradual return to the initial value during a post-operative observation period of twelve days. There was an inverse linear relationship between the LF concentration and the tear secretion rate measured by a modified Schirmer I test (1 min) suggesting a constant LF secretion rate by the tear glands. The contribution of LF from neutrophils to the tear fluid seems to be of minor importance. Since LF has known antibacterial and anti-inflammatory effects, our results may contribute to a further understanding of the microbial vulnerability or resistance of the eye following surgical procedures.

Influence of secretagogues on volume and protein pattern in rabbit lacrimal fluid

After certain tear proteins had been found to be markers of duct cell activity in the rabbit lacrimal gland, different secretagogues were tested to increase volume and protein secretion. Carbamyl-choline and the peptides eledoisin and vasoactive intestinal peptide (VIP) stimulated volume flux as well as secretion of the marker proteins indicating duct cell activation. Beta-adrenergic stimulation also increased secretion of a further tear protein. This might indicate that water is secreted by the duct cells. These are stimulated by the secretagogues mentioned above. Beta-adrenergic stimulation might in addition activate the acinar cell system.

Normal tear protein profiles and age-related changes

The specific and non-specific tear proteins have been analysed by means of the ELISA technique to establish the normal and age-related values. There is a linear and related decline of lysozyme and lactoferrin with age, and a similar but unrelated reduction in tear volume. IgA levels gradually decline, while caeruloplasmin and IgG both increase after the fifth decade. The results suggest that tear IgG and caeruloplasmin are probably transudates from the serum, that IgA is secreted independently of tear volume, and that lysozyme and lactoferrin are secreted at the same site but independently of tear volume.

The relations between tear fluid concentrations of lysozyme, tear-specific prealbumin and lactoferrin

A degeneration of the tear gland leads to reduced lysozyme concentrations in the tear fluid. Tear lysozyme concentrations are generally determined by enzymatic methods. Lysozyme determination by radial immunodiffusion has some advantages above the enzymatic assays, and laboratory facilities are not required. The enzymatic properties of lysozyme that favoured its choice as a parameter for tear gland function, influenced to some extent the results of the radial immunodiffusion assay. Therefore we looked among the proteins originating from the lacrimal gland for alternative parameters of tear gland function. In 94 tear samples obtained from a heterogeneous group, ranging from persons with normal lacrimal gland function to severe kerato-conjunctivitis sicca patients, a high degree of correlation was found between lysozyme concentration and that of lactoferrin as well as tear-specific prealbumin. This indicates that the latter two proteins can be used as alternatives for lysozyme in tear gland function tests.

Lactoferrin levels in normal human tears

Using commercially available reagents we developed an enzyme-linked immunosorbent assay to measure lactoferrin in normal human tears. Tears obtained from 38 normal human subjects contained a mean lactoferrin content of 2.2 mg/ml (g/l). No differences in the mean level of lactoferrin were found when tears were collected by either Schirmer tear strips or by glass capillaries after short tear gas stimulation. Tear lactoferrin levels were not influenced by age or sex of the subjects investigated in this study. We found that lactoferrin represents approximately 25% by weight of the total tear proteins.

Plasma lactoferrin levels in pregnancy and cystic fibrosis

Plasma lactoferrin levels were determined by radioimmunoassay for the different weeks of normal pregnancy, in normal healthy adults and in children with and without cystic fibrosis. The lactoferrin levels were higher in pregnancy than in both male and female normal adults and showed a slight progressive increase up to week 29 and thereafter remained high. Five our of seven children with cystic fibrosis had markedly raised plasma lactoferrin levels from six to 16 times higher than the mean of a control group of children.

The questionably dry eye

This paper is concerned with the recognition of the dry eye when the clinical diagnosis is in doubt and other external eye diseases may be present. Papillary conjunctivitis is common to the dry eye as well as other pathological conditions and confuses the diagnosis. We have correlated the factors involved in the assessment for dryness. We have shown that particulate matter in the unstained tear film is associated with low tear lysozyme concentration. Tear flow and tear lysozyme are not necessarily interrelated, but a low lysozyme concentration (tear lysozyme ratio < 1.0) is associated with keratoconjunctivitis sicca. The Schirmer I test can produce false positive results, and we have suggested a modification to overcome this. This modified test will detect the eye with severely depleted lysozyme secretion, but it is unreliable for detecting the eye with moderately depleted secretion. We find that its lowest normal limit should be considered as 6 mm.