IRF-1 responsiveness to IFN-γ predicts different cancer immune phenotypes.

BACKGROUND: Several lines of evidence suggest a dichotomy between immune active and quiescent cancers, with the former associated with a good prognostic phenotype and better responsiveness to immunotherapy. Central to such dichotomy is the master regulator of the acute inflammatory process interferon regulatory factor (IRF)-1. However, it remains unknown whether the responsiveness of IRF-1 to cytokines is able to differentiate cancer immune phenotypes. METHODS: IRF-1 activation was measured in 15 melanoma cell lines at basal level and after treatment with IFN-γ, TNF-α and a combination of both. Microarray analysis was used to compare transcriptional patterns between cell lines characterised by high or low IRF-1 activation. RESULTS: We observed a strong positive correlation between IRF-1 activation at basal level and after IFN-γ and TNF-α treatment. Microarray demonstrated that three cell lines with low and three with high IRF-1 inducible translocation scores differed in the expression of 597 transcripts. Functional interpretation analysis showed mTOR and Wnt/ß-cathenin as the top downregulated pathways in the cell lines with low inducible IRF-1 activation, suggesting that a low IRF-1 inducibility recapitulates a cancer phenotype already described in literature characterised by poor prognosis. CONCLUSION: Our findings support the central role of IRF-1 in influencing different tumour phenotypes.

Lipid mediators in the rat retina: light exposure and trauma elicit leukotriene B4 release in vitro.

Light exposure not only elicits a visual response but may also alter functional and structural characteristics of the retina. Furthermore, light exposure can lead to reversible or irreversible lesions of photoreceptors and pigment epithelium. Previous studies in our laboratory have shown that light liberates arachidonic acid from retinal membrane phospholipids mainly by activating the phospholipase A2. In this study we show that light and trauma elicit the synthesis of leukotriene B4 in the isolated rat retina in vitro. Male albino rats were dark adapted for 36 h, isolated retinae were taken, incubated and exposed a) either to darkness or to 5,000 lux of cool white fluorescent light for 5, 10 or 15 min at 37 degrees C, b) either to darkness or to 5,000 lux of cool white fluorescent light for 15 min at 0 degrees C or c) either to darkness or to 5,000 lux of cool white fluorescent light for 15 min at 37 degrees C with a 5-lipoxygenase inhibitor (zileuton). Eicosanoids were extracted and leukotriene B4 levels were determined by radioimmunoassay. Removal of retinae and incubation in darkness caused a significant rise in leukotriene B4 levels with increasing incubation time. This rise was further augmented significantly after light exposure. The leukotriene B4 levels obtained when incubating the retinae either at 0 degree C or with the lipoxygenase inhibitor zileuton as well as the high specificity of the radioimmunoassay indicate that the light- and trauma-elicited synthesis of leukotriene B4 is mediated by activating the 5-lipoxygenase. Leukotriene B4 may be involved, at least in part, in the pathogenesis of retinal diseases including light damage. Curr. Eye Res. 14: 1001-1008, 1995.

[The 4-prism diopter base-in test in diagnosis of exophoria with asthenopia and compensation by accommodative convergence]. / Der 4-Prismendioptrien-Basis-innen-Test in der Diagnostik von Exophorien mit Asthenopie und Kompensation über die akkommodative Konvergenz.

About 30% of our patients suffering from purely binocular asthenopia showed lower binocular than monocular visual acuity. Cover test examination revealed exophoria at near fixation, which could be regarded to be physiological. Furthermore, the Pola test as well as Graefe's prism diplopia test showed no pathological findings. When given 4 prism base-in, a better binocular acuity was achieved and exophoria at for distance fixation was revealed. Often the prisms base-in had to be increased slowly and an operative treatment was indicated in 80%. The test is described in detail and examples from typical case studies are demonstrated. The importance of the test for understanding asthenopia in cases with heterophoria is discussed.

Light elicits the release of docosahexaenoic acid from membrane phospholipids in the rat retina in vitro.

Docosahexaenoic acid is the major polyunsaturated fatty acid in photoreceptor membrane phospholipids and is thought to be necessary for photoreceptor function. Docosahexaenoic acid may be metabolized to docosanoids or, by retroconversion, to eicosapentaenoic acid followed by lipoxygenation and synthesis of n-3 metabolites. In this study we investigated the time- and illuminance-dependent release of docosahexaenoic acid from photoreceptor phospholipids in the rat retina in vitro and the effects of the phospholipase A2 inhibitor, quinacrine, on this release. Isolated rat retinae were incubated in oxygenated Ringer-Bicarbonate-Glucose-Medium and labelled with [3H]docosahexaenoic acid for 180 min in darkness. The incorporation of [3H]docosahexaenoic acid into retinal phospholipids was monitored by thin-layer chromatography. The release of [3H]docosahexaenoic acid was determined under illuminances of 100, 500, 1000, 5000 and 10,000 lx for 10 min, illuminance durations of 0.25, 2, 5 and 10 min at 10,000 lx, and with the addition of 10 and 100 mumol quinacrine to the incubation medium at 10,000 lx for 10 min. Our results demonstrate a release of docosahexaenoic acid from retinal phospholipids that is finely tuned by light levels and exposure duration. The kinetics of the time dependent docosahexaenoic acid release and the effects of quinacrine suggest that this release is mediated in part by activation of phospholipase A2. The light-elicited docosahexaenoic acid release may serve as a protective measure against formation of prostaglandins by inhibiting cyclooxygenase and by promoting the synthesis of less potent leukotrienes of the 5-series via retroconversion to eicosapentaenoic acid and 5-lipoxygenation.

Light damage revisited: converging evidence, diverging views?

Are observations on ultraviolet (UV)- and visible light-induced ocular changes in animals relevant for human pathology? Different conclusions are drawn by different groups, depending on their perspective: while in the epidemiologist's view the evidence for those lesions is mostly limited or insufficient, laboratory scientists continually extend observations on radiation damage in animals. Consequently, there are diverging views on the necessity and specifications for eye protection. In this review, problems of epidemiological surveys and observations in humans and animal studies are discussed, and natural and artificial protection of the eye is outlined. The human and animal eye has an inherent potential for photochemical lesions due to chromophores including the visual pigments that are present at birth. Lifelong light exposure gives rise to additional absorbing molecules. With decreasing wavelengths of the electromagnetic spectrum the number of absorbing molecules rises; therefore, the likelihood of a photochemical reaction grows. As the spectral energy is augmented, more damage will occur. In our view, the knowledge gained from laboratory studies is a significant component of the total evidence from different fields-epidemiology, clinical observations, model studies and theoretical calculations-that UV radiation and short-wavelength visible light can cause acute and chronic changes in ocular structures. Such changes may comprise irreversible damage. Following recently issued recommendations of the major visual health organizations in the United States, protection against UV and blue light should be incorporated into the spectrum of safety considerations for sunglasses.

Lipofuscin in the retina: quantitative assay for an unprecedented autofluorescent compound (pyridinium bis-retinoid, A2-E) of ocular age pigment.

The pyridinium bis-retinoid, A2-E, has been discovered as one of the major autofluorescent components of retinal pigment epithelial lipofuscin. Due to its chemical characteristics, A2-E may contribute to cellular and molecular changes leading to age-related macular degeneration. Because A2-E is the first lipofuscin component that has been identified, purified, and its structure analysed, it represents an important marker molecule for studying lipofuscin formation under various conditions. In order to investigate the role of A2-E in ageing processes of the retinal pigment epithelium, we developed an HPLC assay for this compound using single wavelength UV-absorbance detection with continuous light emission. Standard A2-E was synthetized and purified by sequential TLC. In our assay, A2-E can be detected in amounts lower than 10 pmol. The assay has been applied to quantitative determination of A2-E amounts in albino rat eyes of different age groups. Our results demonstrate that there is a marked increase of A2-E levels in older animals. The method described is the first to allow quantification of this unusual retinoid from small amounts of biological samples.

[HPETE, an arachidonic acid metabolite, induces apoptosis in rat retina in vitro]. / HPETE, ein Arachidonsäure-Metabolit, induziert Apoptose in der Rattennetzhaut in vitro.

BACKGROUND: Apoptosis is a gene-regulated mode of cell death which gains increasing importance in retinal pathologies such as retinitis pigmentosa, retinal detachment and proliferative vitreoretinopathy. A better understanding of the regulation of apoptosis could imply the means to reduce photoreceptor cell death and thereby provide therapeutic strategies to influence the time course of retinal diseases. Previous studies in our laboratory demonstrated that light induces apoptosis in the rat retina in vivo as a function of light dose. In several cell systems, oxidative stress including oxygenated metabolites of arachidonic acid (AA) was found to evoke apoptosis. We have observed a light-elicited release of AA and the subsequent formation of its metabolites in the rat retina. Therefore, AA and its metabolites appeared to be suitable candidates for the induction of apoptosis during light exposure. MATERIALS AND METHODS: Isolated rat retinas were incubated for 60, 120 and 180 min, respectively, with and without the addition of 30 mumol 5S-hydroperoxyeicosatetraenoic acid (5-HPETE). Retinas were then processed for light- and electron microscopy and examined for the morphological signs of apoptosis. The rate of apoptosis in the outer nuclear layer was assessed quantitatively. RESULTS: 5S-HPETE induces apoptosis of photoreceptors in the rat retina in vitro. Quantitative analysis revealed a significant increase in the rate of apoptosis of 5S-HPETE-treated retinas when compared to untreated controls. CONCLUSION: Arachidonic acid metabolites released upon light exposure may represent messenger candidates for apoptosis in the retina.