Lung epithelial barrier function and wound healing are decreased by IL-4 and IL-13 and enhanced by IFN-gamma

To understand theeffects of cytokines on epithelial cells in asthma, we haveinvestigated the effects of interleukin (IL)-4, IL-13, and interferon(IFN)- on barrier function and wound healing in Calu-3 human lungepithelial cells. IL-4 and IL-13 treatment of Calu-3 cells grown onTranswell filters resulted in a 70-75% decrease in barrierfunction as assessed by electrophysiological and[¹⁴C]mannitol flux measurements. In contrast, IFN-enhanced barrier function threefold using these same parameters. Cellstreated concurrently with IFN- and IL-4 or IL-13 showed an initialdecline in barrier function that was reversed within 2 days, resulting in barrier levels comparable to control cells. Analysis of the tightjunction-associated proteins ZO-1 and occludin showed that IL-4 andIL-13 significantly reduced ZO-1 expression and modestly decreasedoccludin expression compared with controls. IFN-, quite unexpectedlygiven its enhancing effect on barrier function, reduced expression ofZO-1 and occludin to almost undetectable levels compared with controls.In wound-healing assays of cells grown on collagen I, IL-4 and IL-13decreased migration, whereas IFN- treatment enhanced migration,compared with control cells. Addition of IFN-, in combination withIL-4 or IL-13, restored migration of cells to control levels. Migrationdifferences observed between the various cytokine treatments wascorrelated with expression of the collagen I-binding₂₁-integrin at the leading edge of cellsat the wound front; ₂₁-integrinexpression was decreased in IFN--treated cells compared withcontrols, whereas it was highest in IL-4- and IL-13-treated cells.These results demonstrate that IL-4 and IL-13 diminish the capacity ofCalu-3 cells to maintain barrier function and repair wounds, whereasIFN- promotes epithelial restitution by enhancing barrier functionand wound healing.

     

Development and organization of polarity-specific segregation of primary vestibular afferent fibers in mice

A striking feature of vestibular hair cells is the polarized arrangement of their stereocilia as the basis for their directional sensitivity. In mammals, each of the vestibular end organs is characterized by a distinct distribution of these polarized cells. We utilized the technique of post-fixation transganglionic neuronal tracing with fluorescent lipid soluble dyes in embryonic and postnatal mice to investigate whether these polarity characteristics correlate with the pattern of connections between the endorgans and their central targets; the vestibular nuclei and cerebellum. We found that the cerebellar and brainstem projections develop independently from each other and have a non-overlapping distribution of neurons and afferents from E11.5 on. In addition, we show that the vestibular fibers projecting to the cerebellum originate preferentially from the lateral half of the utricular macula and the medial half of the saccular macula. In contrast, the brainstem vestibular afferents originate primarily from the medial half of the utricular macula and the lateral half of the saccular macula. This indicates that the line of hair cell polarity reversal within the striola region segregates almost mutually exclusive central projections. A possible interpretation of this feature is that this macular organization provides an inhibitory side-loop through the cerebellum to produce synergistic tuning effects in the vestibular nuclei. The canal cristae project to the brainstem vestibular nuclei and cerebellum, but the projection to the vestibulocerebellum originates preferentially from the superior half of each of the cristae. The reason for this pattern is not clear, but it may compensate for unequal activation of crista hair cells or may be an evolutionary atavism reflecting a different polarity organization in ancestral vertebrate ears.     

Methionine limitation results in increased hepatic FAS activity, higher liver 18:1 to 18:0 fatty acid ratio and hepatic TAG accumulation in Atlantic salmon, Salmo salar

The current experiment aimed to study whether interactions with lipid metabolism possibly might explain the relative increased liver weight obtained in fish fed sub-optimal methionine levels. A basal diet based on a blend of plant proteins which is low in methionine (1.6 g Met/16 g N) was compared to a methionine adequate diet (2.2 g Met/16 g N) prepared by adding dl-methionine (2.4 g/kg) to the basal diet in the expense of wheat grain. Fish oil was used as the lipid source. The diets were balanced in all nutrients except methionine. The diets were fed to Atlantic salmon (500 g BW) for a period of 3 months. Feed intake did not differ, rendering the intake of all nutrients except methionine equal. Fish fed the low methionine diet had an increased liver size relative to body weight, indicating fat deposition in the liver. Fish given the sub-optimal methionine diet showed about six times higher fatty acid synthase (FAS) activity as compared to the fish fed the adequate methionine diet, indicating a higher de novo lipogenesis. A significant rise in the liver 18:1 to 18:0 fatty acid ratios also supported storage of lipids over fatty acid oxidation. Indeed, methionine limitation resulted in significantly higher TAG concentrations in the liver. Sub-optimal dietary methionine also resulted in lower hepatic taurine concentrations and the total bile acids concentrations were reduced in faeces and tended to be reduced in plasma. Taken together, our data show that salmon fed sub-optimal methionine levels had increased relative liver weight and developed signs commonly described in the early stage of non-alcoholic fatty liver disease in rodent models (increased FAS activity, changed fatty acid ratios and TAG accumulation).