Calcium channel blocker nilvadipine,but not diltiazem,inhibits ocular inflammation in endotoxin-induced uveitis

Purpose  

Calcium channel blockers (CCBs), widely used for hypertensive patients, have recently been shown to inhibit atherosclerosis by their antioxidative action. The aim of the present study was to examine whether the CCBs nilvadipine and diltiazem reduce ocular inflammation in endotoxin-induced uveitis (EIU).     

Suppressive effects of histamine H1 receptor antagonist diphenhydramine on the leukocyte infiltration during endotoxin-induced uveitis.

Histamine has been shown to play an important role in the step of leukocyte rolling, the initial step to leukocyte infiltration into an inflamed region. We investigated the roles of histamine in the leukocyte recruitment during endotoxin-induced uveitis (EIU) in vivo using acridine orange digital fluorography. An injection of histamine into the vitreous cavity of a Lewis rat induced leukocyte rolling along the major retinal veins. In other experiments, EIU was induced in Lewis rats by footpad injection of lipopolysaccharide (LPS). Leukocyte rolling was also observed in the retinal veins of EIU rats. To block the histamine H1 receptor, diphenhydramine (DPH) was administered intraperitoneally 15 min before the LPS injection. DPH significantly inhibited leukocyte rolling along the major retinal veins of EIU rats, suppressing leukocyte infiltration into the vitreous cavity. The vasodilation in EIU was also significantly suppressed with DPH. Moreover, leukocyte infiltration into aqueous humor was significantly suppressed in DPH-treated rats. Although the inhibitory effects of DPH was less obvious at later time points, addition of DPH every 12 hr showed prolonged anti-inflammatory effects up to 48 hr after LPS injection. In contrast, protein leakage into the aqueous humor was not suppressed as much as leukocyte infiltration with DPH. These results suggest that histamine would play a pivotal role in leukocyte recruitment during EIU in rats. Blocking the histamine H1 receptor might help to prevent or minimize leukocyte infiltration in uveitis.     

Inhibition of leukocyte sticking and infiltration, but not rolling, by antibodies to ICAM-1 and LFA-1 in murine endotoxin-induced uveitis

PURPOSE: Cell-adhesion molecules are critical elements in intravascular rolling and sticking of leukocytes during acute inflammation. In this process, selectins are thought to be involved in initial adhesion and rolling, and integrin-Ig superfamily interactions are believed primarily to mediate stronger adhesion and transendothelial migration. This study clarifies the role of two adhesion molecules, intercellular adhesion molecule (ICAM)-1 and leukocyte functional antigen (LFA)-1, in endotoxin-induced uveitis (EIU). METHODS: Intravital microscopy was used to record the movement and location of leukocytes in the irises of mice with uveitis induced by intravitreal injection of 250 ng Escherichia coli endotoxin. Each mouse concurrently received an intraperitoneal injection of monoclonal neutralizing antibodies for ICAM-1, LFA-1, or both or control irrelevant antibodies. RESULTS: Mice treated with endotoxin and control antibodies had an inflammatory response that was clearly present at the 6- and 24-hour time points and was mostly resolved by 48 hours. Mice that received anti-ICAM-1 or anti-LFA-1 had significantly fewer cells infiltrating their irises at 6 and 24 hours. Detailed analysis of the 6-hour time point recordings revealed that neither anti-ICAM-1 nor anti-LFA-1 significantly reduced the number of leukocytes rolling on venule endothelial surfaces, but the treatments reduced the number of firmly adherent cells. CONCLUSIONS: These data confirm previous reports that ICAM-1 and LFA-1 are important mediators of EIU. The dynamic in vivo images clearly support the hypothesis that integrin-mediated cell adhesion is more critical for the firm adhesion of sticking cells than for leukocyte rolling.     

The effect of chlorpromazine on endotoxin-induced uveitis in the Lewis rat.

Chlorpromazine (CPZ) has been used extensively in the treatment of psychiatric disorders, and has recently been shown to possess systemic anti-inflammatory properties as well. To investigate the potential effects of CPZ on ocular inflammation, we evaluated its action on endotoxin-induced uveitis (EIU) in Lewis rats. At three different dosage levels, CPZ produced highly significant reductions in the mean aqueous aspirate inflammatory cell counts and histological inflammatory scores as compared to controls treated with vehicle only. Analysis of aqueous fluid demonstrated a similar decrease in protein concentration and phospholipase A2 (PLA-2) activity in the treated animals. The ability of CPZ to inhibit the development of EIU may be related to its properties as a calcium channel blocker and inhibitor of the enzyme phospholipase A2.     

Cortical area V4 is critical for certain texture discriminations, but this effect is not dependent on attention

This study examined the question of which features of a complex grouping discrimination make it vulnerable to permanent elimination by V4 lesions. We first verified that the line element grouping discrimination, which we previously reported to be devastated by V4 lesions, was similarly affected in the monkeys of this study. The permanence of the deficit was established by mapping its visual field distribution and then testing this discrimination for an extended period at a locus on the border of the deficit. Also, a staircase procedure was used to provide the monkey with within session instruction in the grouping discrimination, but this did not improve V4 lesion performance. Grouping was then compared with several discriminations that shared some features with it, but which were found not to be permanently eliminated by V4 lesions. This comparison suggested that grouping (rather than segmentation or response to a single element) was one feature that made the discrimination vulnerable, a second was the similarity in shape of the texture elements to be grouped. Finally, we tested visual crowding, a property of peripheral vision that is thought to reflect neuronal interactions early in visual cortex, possibly in area V1, and found no effect of V4 lesions. A control experiment with human observers tested whether the elimination of grouping by V4 lesions might be due to an alteration of attention, but found no evidence to support this hypothesis. These results show that severe disruption of texture discriminations by V4 lesions depends on both the nature of the discrimination and the type of texture elements involved, but does not necessarily involve the disruption of attention.     

Functional binocular vision is not dependent on visual experience in the praying mantis.

In vertebrates, it has been shown that binocular visual experience is necessary to develop normal spatial vision. We have investigated whether this is also true for an invertebrate, the praying mantis. The praying mantis is a predatory insect in which prey localization involves the use of binocular disparities. We raised mantids which had one eye occluded throughout development and tested monocular visual fixation and binocular distance estimation in the adult animals. The results revealed that both fixation and prey catching behavior were normally functional in the monocularly reared animals. Thus we conclude that, in mantids, binocular vision is based on a fixed mode of development.     

Susceptibility to endotoxin induced uveitis is not reduced in mice deficient in BLT1, the high affinity leukotriene B4 receptor

AIM: To investigate the role of arachidonic acid derived chemotactic factor, LTB(4), in the development of endotoxin induced uveitis (EIU), using mice deficient in the BLT1 gene which encodes the high affinity LTB(4) receptor. METHODS: BLT1 gene deficient and wild type BALB/c mice were injected intravitreally with Escherichia coli 055:B5 lipopolysaccharide (250 ng/2 microl). Number of leukocytes invading the anterior chamber 24 hours later were counted on tissue cross sections. RESULTS: In all mice, EIU was characterised by a polymorphonuclear and mononuclear cell infiltrate. Numbers of infiltrating cells did not differ significantly between control and BLT1 gene knockout mice. CONCLUSION: Chemotactic factors other than LTB(4) are primarily responsible for leukocyte migration into the eye during murine EIU.     

Class I disparate corneal grafts enjoy afferent but not efferent blockade of the immune response.

Class I antigens are normally expressed on cells in all three layers of the cornea. In congenic rats that differ only at the single Class I locus RT1 A, central orthotopic corneal grafts were rejected 18% of the time with a mean survival time (MST) of 11.5 days. Pre-immunized recipients always rejected Class I disparate corneal grafts (100%, MST = 13.3 days). Surprisingly, the presence of donor Langerhans cells in the cornea at the time of grafting did not increase the rejection of grafts (20%, MST = 14.0 days). To determine if long term surviving grafts enjoyed immune priviledged in the form of efferent blockade, the recipients were challenged with skin grafts 4 to 6 weeks following corneal transplantation. All of the corneal grafts underwent rejection (100%, MST = 14.7 days). A number of important conclusions may be drawn from these studies. A single Class I mismatch is a weak barrier to successful engraftment of corneal grafts. However if the recipient has previously been exposed to donor antigens, a single Class I disparity is sufficient to provoke rejection of all subsequent corneal grafts. The susceptibility of long term surviving grafts to rejection induced by skin grafts indicates the orthotopic corneal grafts are antigenic but not immunogenic.     

The continuous Wagon Wheel Illusion depends on, but is not identical to neuronal adaptation

The occurrence of perceived reversed motion while observers view a continuous, periodically moving stimulus (a bistable phenomenon coined the "continuous Wagon Wheel Illusion" or "c-WWI") has been taken as evidence that some aspects of motion perception rely on discrete sampling of visual information. Alternative accounts rely on the possibility of a motion aftereffect that may become visible even while the adapting stimulus is present. Here I show that motion adaptation might be necessary, but is not sufficient to explain the illusion. When local adaptation is prevented by slowly drifting the moving wheel across the retina, the c-WWI illusion tends to decrease, as do other bistable percepts (e.g. binocular rivalry). However, the strength of the c-WWI and that of adaptation (as measured by either the static or flicker motion aftereffects) are not directly related: although the c-WWI decreases with increasing eccentricity, the aftereffects actually intensify concurrently. A similar dissociation can be induced by manipulating stimulus contrast. This indicates that the c-WWI may be enabled by, but is not equivalent to, local motion adaptation - and that other factors such as discrete sampling may be involved in its generation.     

Melanin in the trabecular meshwork is associated with age, POAG but not Latanoprost treatment. A masked morphometric study

We wished to conduct a light and electron microscopic investigation of pigmentation within the trabecular meshwork of normals and primary open angle glaucoma (POAG) patients. In particular we wished to get a precise determination of whether there was a relationship between pigmentation and age. In addition we wanted to know if there was a difference between normals and POAGs and whether trabecular meshwork hyperpigmentation was associated with topical latanoprost medication. A total of 25 sham trabeculectomies conducted on post mortem donor eyes provided the age-matched normals and there were 62 trabeculectomy specimens from POAG patients. These were masked and the meshwork subjected to qualitative and quantitative morphological investigation. Light and electron microscopy confirmed that most of the trabecular meshwork melanin was phagocytosed and within meshwork cells. The granules were measured and found to be of the large iris epithelial type. Light microscopic morphometric analysis showed that the number of meshwork cell profiles that contained melanin increased both in normals and POAGs with age. However there was nearly three times more pigmented meshwork cells in the POAGs than the normals. The POAGs were divided into three groups of (1) minimal or no medication prior to surgery, (2) maximal medical therapy and (3) maximum medical therapy including latanoprost (12 specimens). All groups were significantly greater that the normals but of the three it was the maximal medical therapy group (without latanoprost) that had the highest pigmentation. We concluded that pigmentation of the meshwork is age-related and it is elevated in POAG by mechanisms unknown. The melanin accumulation seems to be partly due to the disease process, partly as a consequence of chronic antiglaucoma medication but interestingly not due to latanoprost even in patients where there is iris darkening (four specimens).     

Selective suppression of pathologic, but not physiologic, retinal neovascularization by blocking the angiotensin II type 1 receptor

PURPOSE: To investigate the anti-inflammatory and anti-angiogenic effects of telmisartan, an angiotensin II type 1 receptor (AT1-R) antagonist, on ischemia-induced retinal neovascularization. METHODS: C57BL/6 neonatal mice were reared in an 80% concentration of oxygen from postnatal day (P)7 to P12, followed by room-air breathing until P17, to induce ischemia-initiated retinal neovascularization (i.e., a murine model of ischemic retinopathy). Tissue localization of AT1-R was examined by immunohistochemistry for murine retinal wholemounts and human fibrovascular tissues excised at vitrectomy for proliferative diabetic retinopathy. Animals received intraperitoneal injection of telmisartan or vehicle. A concanavalin A lectin perfusion-labeling technique was used to evaluate the areas of physiological and pathologic retinal new vessels and the number of leukocytes adhering to the vasculature. Retinal mRNA and protein levels of intercellular adhesion molecule (ICAM)-1, vascular endothelial growth factor receptor (VEGFR)-1, and VEGFR-2 were examined by RT-PCR and ELISA. RESULTS: Vessels in human fibrovascular tissues and the murine retinas were positive for AT1-R. Pathologic (P < 0.01), but not physiologic (P > 0.05), retinal neovascularization was significantly suppressed in telmisartan-treated mice compared with vehicle-treated animals. The number of adherent leukocytes (P < 0.01) was also significantly reduced, together with retinal ICAM-1 levels (P < 0.01) in the telmisartan-treated group compared with the control group. No significant difference was detected in retinal VEGFR-2 levels between the two groups, whereas retinal VEGFR-1 levels in the telmisartan-treated group were significantly (P < 0.05) lower than in the vehicle-treated group. CONCLUSIONS: The present findings suggest that the AT1-R signaling blockade leads to the selective suppression of pathologic, but not physiological, retinal neovascularization through the inhibition of the inflammatory processes related to pathologic neovascularization.     

Effects of spatial frequency bands on perceptual decision: it is not the stimuli but the comparison

Observers performed three between- and two within-category perceptual decisions with hybrid stimuli comprising low and high spatial frequency (SF) images. We manipulated (a) attention to, and (b) congruency of information in the two SF bands. Processing difficulty of the different SF bands varied across different categorization tasks: house-flower, face-house, and valence decisions were easier when based on high SF bands, while flower-face and gender categorizations were easier when based on low SF bands. Larger interference also arose from response relevant distracters that were presented in the "preferred" SF range of the task. Low SF effects were facilitated by short exposure durations. The results demonstrate that decisions are affected by an interaction of task and SF range and that the information from the non-attended SF range interfered at the decision level. A further analysis revealed that overall differences in the statistics of image features, in particular differences of orientation information between two categories, were associated with decision difficulty. We concluded that the advantage of using information from one SF range over another depends on the specific task requirements that built on the differences of the statistical properties between the compared categories.     

Exertion of the suppressive effects of IFN-gamma on experimental immune mediated blepharoconjunctivitis in Brown Norway rats during the induction phase but not the effector phase

BACKGROUND/AIMS: Interferon gamma (IFN-gamma) knockout mice exhibit severe allergic conjunctivitis (AC), indicating that IFN-gamma regulates the development of AC. The authors examined whether this inhibitory effect of IFN-gamma is exerted during the induction or effector phase of experimental AC. METHODS: Experimental immune mediated blepharoconjunctivitis (EC) was induced in Brown Norway (BN) rats, using ovalbumin (OVA) as the antigen. To investigate the role of IFN-gamma in the induction phase, EC was induced by active immunisation and IFN-gamma (10 micro g/time, total 70 micro g), or phosphate buffered saline (PBS) as a control, was injected intraperitoneally every other day from the day of immunisation. The rats were challenged with OVA eye drops 13 days after immunisation, and 24 hours later, the eyes were harvested for histology. To examine the effects of IFN-gamma in the effector phase, OVA specific T cells were transferred into syngeneic rats and IFN-gamma (10 micro g/time, total 50 micro g) or PBS was injected each day after the transfer until induction of EC 4 days later with an OVA challenge. To investigate the role of endogenous IFN-gamma during the effector phase, an anti-IFN-gamma monoclonal antibody (3 mg/time) was injected on days 3 and 4. RESULTS: Injection of IFN-gamma into actively immunised rats suppressed eosinophilic infiltration but not infiltration of mononuclear cells. In contrast, neither IFN-gamma nor anti-IFN-gamma affected EC in passively immunised rats. CONCLUSION: IFN-gamma is a suppressive cytokine for the development of EC and exerts this suppressive effect during the induction phase.     

The requirement for pertussis to induce EAU is strain-dependent: B10.RIII, but not B10.A mice, develop EAU and Th1 responses to IRBP without pertussis treatment.

PURPOSE: Experimental autoimmune uveoretinitis (EAU) in mice is an important model for elucidating basic mechanisms in autoimmune eye disease. The need for pertussis toxin (PTX) as an additional adjuvant to elicit EAU has limited the usefulness of this model in some types of studies by introducing a pleiotropic factor with confounding effects on the immune response. METHODS: In the present study the authors examined the ability of B10.RIII mice, the most susceptible strain known so far, to develop EAU in response to the retinal antigen, interphotoreceptor retinoid-binding protein (IRBP), and to a major uveitogenic epitope of IRBP, peptide (p)161-180, in the absence of PTX treatment. RESULTS: The data indicate that high disease scores in response to IRBP and p161-180 were found in B10.RIII mice, without the need for PTX as part of the immunization protocol. Unlike the B10.A strain in which appreciable disease did not develop without PTX, B10.RIII mice mounted a high IFN-gamma response to IRBP in the absence of PTX treatment. Interestingly, and unlike the effect with IRBP, in vitro recall response to p161-180 was low in IFN-gamma, despite good EAU scores. CONCLUSIONS: The data indicate that an important mechanism through which PTX facilitates induction of cell-mediated autoimmunity is by promoting a Th1 polarization of the immune response. The propensity of B10.RIII mice to mount a more polarized Th1 response to IRBP than other strains may contribute to their ability to develop EAU without pertussis adjuvant. Nevertheless, the induction of EAU by p161-180 in the context of a relatively limited IFN-gamma production indicates that non-Th1- and Th-related mechanisms are likely to act in concert to determine the outcome of disease.     

Effect of TNF, IL-1, and IL-6 on the proliferation of human Tenon's capsule fibroblasts in tissue culture.

Trabeculectomy is a commonly performed procedure for primary open angle glaucoma and is successful in the majority of cases. However, certain factors including aphakia, previous surgery, secondary glaucomas, ethnic origin, and the long term use of topical antiglaucoma medications may be associated with a reduced success rate. The mechanism (or mechanisms) which influence clinical outcome following trabeculectomy remain elusive. Alterations in the composition of the conjunctiva or aqueous humour may be partly responsible for this effect, and this could be mediated by cytokines. In this study we found that tumour necrosis factor (TNF), and interleukin 1 (IL-1) were capable of stimulating the proliferation of Tenon's capsule fibroblasts in tissue culture. Interleukin 6 (IL-6) did not appear to have any effect. The relevance of this to wound healing following trabeculectomy is discussed.     

The circadian component of spinule dynamics in teleost retinal horizontal cells is dependent on the dopaminergic system.

During the light phase of a light/dark cycle, dendrites of teleost cone horizontal cells display numerous finger-like projections, called spinules, which are formed at dawn and degraded at dusk, and are thought to be involved in chromatic feedback processes. We have studied the oscillations of these spinules during a normal light/dark cycle and during 48 h of constant darkness in two groups of strongly rhythmic, diurnal fish, Aequidens pulcher. In one group the retinal dopaminergic system had been destroyed by the application of 6-OHDA, while in the other (control) group, the dopaminergic system was intact. In control fish, oscillations of spinule numbers were observed under both normal and constant dark conditions, indicating the presence of a robust circadian rhythm. However, spinule dynamics were severely affected by the absence of retinal dopamine. During the normal light phase, the number of spinules in 6-OHDA injected retinae was strongly reduced, and throughout continual darkness, spinule formation was almost completely suppressed. These results indicate that dopamine is essential for both light-evoked and circadian spinule formation; furthermore, we conclude that there is no circadian oscillator within horizontal cells controlling the formation of spinules.