Role of lactoferrin in the tear film

The surface of the eye provides an inert barrier against infection. Through its unique combination of antimicrobial action and anti-inflammatory activities lactoferrin (Lf) in the tear film plays an important role in the maintenance of ocular health. In order to maintain clarity the eye must provide immunological defense without immunopathology. Along with physical barriers, soluble plasma factors and other proteins such as lysozyme, Lf produced by the acinar cells of the lacrimal gland serves a number of roles in defense for this purpose. Lf in tears provides antimicrobial efficacy by binding free iron thus reducing the availability of iron necessary for microbial growth and survival as well as pathogenesis. Lf has been shown to inhibit biofilm formation and thus may play a role in protecting contact lens surfaces from colonization. Virus particles' entry into epithelial cells is inhibited by Lf while an excess of Lf in tear film is thought to limit the opportunistic Lf-mediated bridging of adenovirus and host cell that occurs in other tissues. Lf dampens the classical complement activation pathway by binding to markers of inflammation and immune activation while pathogen-associated molecular patterns such as lipopolysaccharide (LPS) are targeted by Lf for removal through tears and hydrodynamic flushing. This review focuses on the role of Lf in human tear film and its contribution to ocular health during contact lens wear.     

Toll-like receptors and corneal innate immunity

The ocular surface is constantly exposed to a wide array of microorganisms. The ability of the cornea to recognize pathogens as foreign and eliminate them is critical to retain its transparency, hence preservation of sight. In the eye, as in other parts of the body, the early response against invading pathogens is provided by innate immunity. Corneal innate immune system uses a series of pattern recognition receptors to detect the presence of pathogens thus allowing for rapid host defense responses to invading microbes. A key component of such receptors is the "Toll-like receptors" (TLRs), which have come to occupy the center stage in innate immunity against invading pathogens. An increasing number of studies have shown that TLRs are expressed by a variety of tissues and cells of the eye and play an important role in ocular defense against microbial infection. Here in this review we summarize the current knowledge about TLR expression in human eye with main emphasis on the cornea, and discuss the future directions of the field.     

A relatively small change in sodium chloride concentration has a strong effect on adhesion of ocular bacteria to contact lenses

Adhesion of bacteria to hydrogel lenses is thought to be an initial step of ocular colonization allowing evasion of normal host defences. The salt concentration of media is an important parameter controlling microbial adhesion. Salinity varies from 0·97% NaCl equivalents in the open eye to 0·89% in the closed eye state. In this study, the effect of sodium chloride in the concentration range of 0·8–1·0% (w/v) NaCl on adhesion of ocular bacteria to soft contact lenses was investigated using a static adhesion assay. Pseudomonas aeruginosa was found to adhere to lenses in significantly greater amounts than Serratia marcescens, Flavobacterium meningosepticum, Stenotrophomonas maltophilia and Staphylococcus intermedius . Increasing NaCl from 0·8% to 1·0% (w/v) increased adhesion of all bacteria tested. This adhesion was strong since the organisms could not be removed by washing in low ionic buffer. Adhesion of these organisms did not correlate with their cell surface properties as determined by bacterial adhesion to hydrocarbons (BATH) and retention on sepharose columns.     

Benefit of Bi-Ocular Visual Stimulation for Postural Control in Children with Strabismus

Vision is important for postural control as is shown by the Romberg quotient (RQ): with eyes closed, postural instability increases relative to eyes open (RQ = 2). Yet while fixating at far distance, postural stability is similar with eyes open and eyes closed (RQ = 1). Postural stability can be better with both eyes viewing than one eye, but such effect is not consistent among healthy subjects. The first goal of the study is to test the RQ as a function of distance for children with convergent versus divergent strabismus. The second goal is to test whether vision from two eyes relative to vision from one eye provides better postural stability. Thirteen children with divergent strabismus and eleven with convergent strabismus participated in this study. Posturtography was done with the Techno concept device. Experiment 1, four conditions: fixation at 40 cm and at 200 cm both with eyes open and eyes covered (evaluation of RQ). Experiment 2, six conditions: fixation at 40 cm and at 200 cm, with both eyes viewing or under monocular vision (dominant and non-dominant eye). For convergent strabismus, the groups mean value of RQ was 1.3 at near and 0.94 at far distance; for divergent, it was 1.06 at near and 1.68 at far. For all children, the surface of body sway was significantly smaller under both eyes viewing than monocular viewing (either eye). Increased RQ value at near for convergent and at far for divergent strabismus is attributed to the influence of the default strabismus angle and to better use of ocular motor signals. Vision with the two eyes improves postural control for both viewing distances and for both types of strabismus. Such benefit can be due to complementary mechanisms: larger visual field, better quality of fixation and vergence angle due to the use of visual inputs from both eyes.     

Lipoxins in the eye and their role in wound healing

The eye must contain highly evolved programs to limit inflammation and promote wound healing as an errant response can lead to blindness. However, pathways that protect the delicate visual axis and account for its atypical inflammatory responses remain to be clearly defined. Hence, research efforts have been initiated to elucidate the role of the anti-inflammatory LXA4 circuits in the eye. LXA4 is formed in healthy and injured corneas and both its receptor and 12/15-lipoxygenase are predominantly expressed in epithelial cells. An essential role for LXA4 in preserving ocular function is supported by 12/15-LOX deficient mice that exhibit a phenotype of impaired wound healing and LXA4 formation. A novel epithelial bioaction role for LXA4 has been uncovered in the cornea as topical LXA4 promotes wound healing and limits the sequelae of injury. These emerging studies indicate that the LXA4 circuit may hold a fundamental role in maintaining an ocular environment that actively restricts inflammation while promoting wound healing.     

Recognition of commensal microflora by toll-like receptors is required for intestinal homeostasis

Toll-like receptors (TLRs) play a crucial role in host defense against microbial infection. The microbial ligands recognized by TLRs are not unique to pathogens, however, and are produced by both pathogenic and commensal microorganisms. It is thought that an inflammatory response to commensal bacteria is avoided due to sequestration of microflora by surface epithelia. Here, we show that commensal bacteria are recognized by TLRs under normal steady-state conditions, and this interaction plays a crucial role in the maintenance of intestinal epithelial homeostasis. Furthermore, we find that activation of TLRs by commensal microflora is critical for the protection against gut injury and associated mortality. These findings reveal a novel function of TLRs-control of intestinal epithelial homeostasis and protection from injury-and provide a new perspective on the evolution of host-microbial interactions.     

Video-oculography in Mice

Eye movements are very important in order to track an object or to stabilize an image on the retina during movement. Animals without a fovea, such as the mouse, have a limited capacity to lock their eyes onto a target. In contrast to these target directed eye movements, compensatory ocular eye movements are easily elicited in afoveate animals^1,2,3,4. Compensatory ocular movements are generated by processing vestibular and optokinetic information into a command signal that will drive the eye muscles. The processing of the vestibular and optokinetic information can be investigated separately and together, allowing the specification of a deficit in the oculomotor system. The oculomotor system can be tested by evoking an optokinetic reflex (OKR), vestibulo-ocular reflex (VOR) or a visually-enhanced vestibulo-ocular reflex (VVOR). The OKR is a reflex movement that compensates for "full-field" image movements on the retina, whereas the VOR is a reflex eye movement that compensates head movements. The VVOR is a reflex eye movement that uses both vestibular as well as optokinetic information to make the appropriate compensation. The cerebellum monitors and is able to adjust these compensatory eye movements. Therefore, oculography is a very powerful tool to investigate brain-behavior relationship under normal as well as under pathological conditions (f.e. of vestibular, ocular and/or cerebellar origin).Testing the oculomotor system, as a behavioral paradigm, is interesting for several reasons. First, the oculomotor system is a well understood neural system⁵. Second, the oculomotor system is relative simple⁶; the amount of possible eye movement is limited by its ball-in-socket architecture ("single joint") and the three pairs of extra-ocular muscles⁷. Third, the behavioral output and sensory input can easily be measured, which makes this a highly accessible system for quantitative analysis⁸. Many behavioral tests lack this high level of quantitative power. And finally, both performance as well as plasticity of the oculomotor system can be tested, allowing research on learning and memory processes⁹.Genetically modified mice are nowadays widely available and they form an important source for the exploration of brain functions at various levels¹⁰. In addition, they can be used as models to mimic human diseases. Applying oculography on normal, pharmacologically-treated or genetically modified mice is a powerful research tool to explore the underlying physiology of motor behaviors under normal and pathological conditions. Here, we describe how to measure video-oculography in mice⁸.     

The role of bacterial biofilms in ocular infections

There is increasing evidence that bacterial biofilms play a role in a variety of ocular infections. Bacterial growth is characterized as a biofilm when bacteria attach to a surface and/or to each other. This is distinguished from a planktonic or free-living mode of bacterial growth where these interactions are not present. Biofilm formation is a genetically controlled process in the life cycle of bacteria resulting in numerous changes in the cellular physiology of the organism, often including increased antibiotic resistance compared to growth under planktonic conditions. The presence of bacterial biofilms has been demonstrated on many medical devices including intravenous catheters, as well as materials relevant to the eye such as contact lenses, scleral buckles, suture material, and intraocular lenses. Many ocular infections often occur when such prosthetic devices come in contact with or are implanted in the eye. For instance, 56% of corneal ulcers in the United States are associated with contact lens wear. Bacterial biofilms may participate in ocular infections by allowing bacteria to persist on abiotic surfaces that come in contact with, or are implanted in the eye, and by direct biofilm formation on the biotic surfaces of the eye. An understanding of the role of bacterial biofilm formation in ocular infections may aid in the development of future antimicrobial strategies in ophthalmology. We review the current literature and concepts relating to biofilm formation and infections of the eye.     

Human optokinetic responses under quasi-open and closed loop conditions

The human optokinetic response to a horizontally moving striped pattern surrounding the subject was investigated under quasi-open and closed loop conditions. Open loop conditions were produced by the addition of an external signal from measured slow phase eye velocity to stripe velocity. A comparison of open and closed loop responses to step and sinusoidal changes of stripe velocity indicates that the central nervous system controlling slow phase optokinetic following can be described as a simple first order lag (Ka/(s+a)) where K is 4.7 and the time constant, 1/a, is 1.25 s.     

Conformational dynamics of wild-type Lys-48-linked diubiquitin in solution

Proteasomal degradation is mediated through modification of target proteins by Lys-48-linked polyubiquitin (polyUb) chain, which interacts with several binding partners in this pathway through hydrophobic surfaces on individual Ub units. However, the previously reported crystal structures of Lys-48-linked diUb exhibit a closed conformation with sequestered hydrophobic surfaces. NMR studies on mutated Lys-48-linked diUb indicated a pH-dependent conformational equilibrium between closed and open states with the predominance of the former under neutral conditions (90% at pH 6.8). To address the question of how Ub-binding proteins can efficiently access the sequestered hydrophobic surfaces of Ub chains, we revisited the conformational dynamics of Lys-48-linked diUb in solution using wild-type diUb and cyclic forms of diUb in which the Ub units are connected through two Lys-48-mediated isopeptide bonds. Our newly determined crystal structure of wild-type diUb showed an open conformation, whereas NMR analyses of cyclic Lys-48-linked diUb in solution revealed that its structure resembled the closed conformation observed in previous crystal structures. Comparison of a chemical shift of wild-type diUb with that of monomeric Ub and cyclic diUb, which mimic the open and closed states, respectively, with regard to the exposure of hydrophobic surfaces to the solvent indicates that wild-type Lys-48-linked diUb in solution predominantly exhibits the open conformation (75% at pH 7.0), which becomes more populated upon lowering pH. The intrinsic properties of Lys-48-linked Ub chains to adopt the open conformation may be advantageous for interacting with Ub-binding proteins.     

Disifin (Sodium tosylchloramide) and Toll-like receptors (TLRs): evolving importance in health and diseases

Disifin has emerged as a unique and very effective agent used in disinfection of wounds, disinfection of surfaces, materials and water, and other substances contaminated with almost every type of pathogenic microorganism ranging from viruses, bacteria, fungi and yeast, and, very possibly, protozoan parasites, as well. The major active component of Disifin is tosylchloramide sodium (chloramine T). However, the mechanism by which Disifin suppresses the activities of pathogenic microbial agents remains enigmatic. The molecular mechanisms, and the receptors and the signal transducing pathways responsible for the biological effects of Disifin are largely unknown. Despite considerable advances, enormous investigative efforts and large resources invested in the research on infectious diseases, microbial infection still remains a public health problem in many parts of the world. The exact nature of the pathogenic agents responsible for many infectious diseases, and the nature of the receptors mediating the associated inflammatory events are incompletely understood. Recent advances in understanding the molecular basis for mammalian host immune responses to microbial invasion suggest that the first line of defense against microbes is the recognition of pathogen-associated molecular patterns (PAMPs) by a family of transmembrane pattern-recognizing and signal transducing receptor proteins called Toll-like receptors (TLRs). The TLR family plays an instructive role in innate immune responses against microbial pathogens, as well as the subsequent induction of adaptive immune responses. TLRs mediate recognition and inflammatory responses to a wide range of microbial products and are crucial for effective host defense by eradication of the invading pathogens. Now, recent updates demonstrated the ability of Disifin-derived products, Disifin-Animal and Disifin-Pressant to effectively suppress the progression and activities of Chikungunya fever and that of avian influenza A virus [A/cardialis/Germany/72, H7N1: the agent of a highly pathogenic avian influenza (HPAI)] infection, respectively. Overall, the above findings led me to suggest that Disifin and TLRs may mechanistically overlap in the processes of executing their functions against pathogenic microbial organisms. Thus, elucidating and better understanding of the molecular underpinnings responsible for the biochemical effects of Disifin-products, and the nature and mode of the interaction(s) of Disifin with TLRs in the process of exerting their biological effects may open a novel dimension in the research of infectious diseases, which may provide novel therapeutic targets for the prevention and treatment of a wide range of infectious diseases.     

Ocular disease in patients with ANCA-positive vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-positive vasculitis—the term recently applied to Wegener's granulomatosis—is a rare multi-system inflammation characterized by necrotizing granulomas and vasculitis. We investigated the ocular manifestations of this disease in a group of patients drawn from five inflammatory eye disease clinics across the United States. Of 8,562 persons with ocular inflammation, 59 individuals were diagnosed with ANCA-positive vasculitis; 35 males and 21 females, aged 16 to 96 years, were included in this study. Ocular diagnoses were scleritis (75.0%), uveitis (17.9%), and other ocular inflammatory conditions (33.9%) including peripheral ulcerative keratitis and orbital pseudotumor. Mean duration of ocular disease was 4.6 years. Oral corticosteroids and other systemic immunosuppressive agents were used by 85.7% and 78.5% of patients, respectively. Over time, patients with ANCA-positive vasculitis experienced 2.75-fold higher mortality than other patients with inflammatory eye disease.     

The host selects mucosal and luminal associations of coevolved gut microorganisms: a novel concept

Along the human gastrointestinal tract, microorganisms are confronted with multiple barriers. Besides selective physical conditions, the epithelium is regularly replaced and covered with a protective mucus layer trapping immune molecules. Recent insights into host defense strategies show that the host selects the intestinal microbiota, particularly the mucosa-associated microbial community. In this context, humans coevolved with thousands of intestinal microbial species that have adapted to provide host benefits, while avoiding pathogenic behavior that might destabilize their host interaction. While mucosal microorganisms would be crucial for immunological priming, luminal microorganisms would be important for nutrient digestion. Further, we propose that the intestinal microorganisms also coevolved with each other, leading to coherently organized, resilient microbial associations. During disturbances, functionally redundant members become more abundant and are crucial for preserving community functionality. The outside of the mucus layer, where host defense molecules are more diluted, could serve as an environment where microorganisms are protected from disturbances in the lumen and from where they can recolonize the lumen after perturbations. This might explain the remarkable temporal stability of microbial communities. Finally, commensals that become renegade or a decreased exposure to essential coevolved microorganisms may cause particular health problems such as inflammatory bowel diseases, obesity or allergies.     

Neutrophil cell signaling in infection: role of phosphatidylinositide 3-kinase

Neutrophils play a pivotal role in the innate immune response to microbial pathogens. They are uniquely suited to this role by virtue of specialized antimicrobial capabilities that include the capacity to sense minute amounts of microbial products and inflammatory mediators, to move to the site of infection, and finally to bind, internalize and kill the pathogens. To optimize host defense capabilities while minimizing damage to host tissues ('collateral damage'), these microbicidal responses must be tightly regulated. Additionally, neutrophils clear inflammatory debris, a process that is necessary for restoration of the native architecture and function of the tissue. This review highlights some recent advances in our knowledge of cell signaling as it pertains to neutrophil function, with specific emphasis on the role of the phosphatidylinositide 3-kinase in antimicrobial function.     

Toll-like receptor 4-mediated signaling by epithelial surfaces: necessity or threat?

Recent data suggest that the lipopolysaccharide receptor Toll-like receptor (TLR) 4 is expressed by epithelial cells and might play a role in the mucosal host defense against Gram-negative bacteria. However, since many body surfaces are colonized by the physiological microflora, activation of epithelial TLRs must be tightly controlled to avoid unintended stimulation and mucosal inflammation. The present review summarizes the current understanding of TLR4-mediated recognition and addresses specific questions on microbial recognition on mucosal surfaces, with particular emphasis on the gastrointestinal and urinary tract.     

抗生素与抗菌药物协同作用防控生物膜的研究进展

生物膜(Biofilm)是指微生物为适应周围环境,黏附于介质表面并被其自身分泌的胞外基质包裹而形成的一种复杂的、高度异质的聚合结构。生物膜对宿主防御和药物具有很强的抵御能力,使用单一药物防治往往效果不显著,而利用协同作用将不同抗菌药物的优势联合起来用于生物膜的防控则优势明显。重点阐述了抗生素与抗生素、抗生素与中药、抗生素与噬菌体、抗生素与酶的协同作用研究,以期为生物膜的防控提供新思路。     

Retinal Muller glia initiate innate response to infectious stimuli via toll-like receptor signaling

Ocular surgeries and trauma predispose the eye to develop infectious endophthalmitis, which often leads to vision loss. The mechanisms of initiation of innate defense in this disease are not well understood but are presumed to involve retinal glial cells. We hypothesize that retinal Muller glia can recognize and respond to invading pathogens via TLRs, which are key regulators of the innate immune system. Using the mouse retinal sections, human retinal Muller cell line (MIO-M1), and primary mouse retinal Muller cells, we show that they express known human TLR1-10, adaptor molecules MyD88, TRIF, TRAM, and TRAF6, and co-receptors MD2 and CD14. Consistent with the gene expression, protein levels were also detected for the TLRs. Moreover, stimulation of the Muller glia with TLR 2, 3, 4, 5, 7 and 9 agonists resulted in an increased TLR expression as assayed by Western blot and flow cytometry. Furthermore, TLR agonists or live pathogen (S. aureus, P. aeruginosa, & C. albicans)-challenged Muller glia produced significantly higher levels of inflammatory mediators (TNF-α, IL-1β, IL-6 and IL-8), concomitantly with the activation of NF-κB, p38 and Erk signaling. This data suggests that Muller glia directly contributes to retinal innate defense by recognizing microbial patterns under infectious conditions; such as those in endophthalmitis.     

Mini-review: microbial problems in paper production

Paper mills are open systems, which provide favorable conditions for microbial growth. Microbial contamination can cause substantial economic losses, including the deterioration of raw materials, interference with production processes by breakdowns and lowering product quality, and eventually, problems in wastewater treatment. Damage is caused by acidification, attack on raw materials, the formation of odorous products, discoloration of pigments, and the formation of methane and hydrogen, thereby producing potentially explosive conditions. Population analyses have revealed that a wide variety of microorganisms are involved, but there appear to be no typical strains associated with paper mills. Current trends in process engineering, such as chlorine-free bleaching, processing at neutral pH, closed cycles, and the use of recycled paper also favor microbial growth and biofilm (slime) formation. A fundamental problem associated with slimes is the extensive matrix of extracellular polymeric substances, which is composed of a large variety of highly hydrated polysaccharides, proteins, nucleic acids, and lipids. No ‘silver bullet’ against biofouling can be expected, and effective countermeasures have to be based on holistic approaches.