Analysis of Ag-presenting cells in the conjunctiva during the development of experimental immune-mediated blepharoconjunctivitis

PURPOSE

The aim of this study was to investigate the phenotypes of antigen (Ag) presenting cells (APCs) in the conjunctiva during the development of experimental immune-mediated blepharoconjunctivitis (EC), which serves as a model for investigation of severe types of human allergic conjunctivitis.

METHODS

Brown Norway rats treated by ovalbumin (OVA) were used in this study. To confirm the restriction of MHC class II by OVA-specific T cells, monoclonal Abs against MHC class II were added to the conventional proliferation assay. To evaluate the MHC class II expression in the conjunctiva during the development of EC, an immunohistochemical analysis, either as the single or double staining, was performed. Conjunctival fibroblast cell lines were established from naive rats and the MHC class II expression was evaluated by flow cytometric analysis. To examine the roles of costimulatory molecules, OVA-specific T cells were stimulated with anti-TcR Ab and anti-CD28 Ab and then subjected for Western blotting to evaluate the ERK phosphorylation. Finally, in vivo expression of B7 molecules was examined immunohistochemically.

RESULTS

OVA-specific T cells recognized OVA in the context of MHC class II. MHC class II was expressed in conjunctival macrophages but not in fibroblasts. EC induction was accompanied by abundant infiltration of macrophages positive for MHC class II. MHC class II was also expressed in conjunctival epithelial cells by EC induction. Stimulation from CD28 was necessary for ERK phosphorylation. B7-2, but not B7-1, was expressed in the conjunctiva.

CONCLUSION

Conjunctival macrophages may represent a major source of APCs for the induction of EC in the conjunctiva.

Quantitative colocalization analysis of multicolor confocal immunofluorescence microscopy images: pushing pixels to explore biological phenomena

Quantitative colocalization analysis is an advanced digital imaging tool to examine antigens of interest in immunofluorescence images obtained using confocal microscopes. It employs specialized algorithms to estimate the degree of overlap of fluorescence signals and thus enables acquiring important new information not otherwise obtainable using qualitative approaches alone. As raw confocal images have high levels of background, they should be prepared to become suitable for reliable calculation of colocalization coefficients by correcting it. We provide concise theoretical basis of quantitative colocalization analysis, discuss its limitations, and describe proper use of the technique. The use of quantitative colocalization analysis is demonstrated by studying bile salt export pump and multidrug resistance associated protein 2 in the liver and major basic protein and platelet activating factor receptor antigens in conjunctiva. The review is focused on the applicability and correct interpretation of the results of colocalization coefficients calculations.

Ethanol consumption alters expression and colocalization of bile salt export pump and multidrug resistance protein 2 in the rat

Chronic ethanol consumption elicits detrimental changes of liver metabolism. By employing a 12-week-long feeding regimen, we investigated the effects of chronic ethanol consumption on the expression and localization of bile salt export pump (Bsep), a major canalicular exporter of bile salts, and multidrug resistance protein 2 (Mrp2), a canalicular organic anion transporter, in the rat liver. RT-PCR, confocal immunofluorescence microscopy, immunoblotting, and quantitative colocalization analysis were used to examine their gene and protein expression, and changes in the distribution of antigenic sites. Bsep mRNA was upregulated, while Mrp2 mRNA responded by downregulation. In agreement with mRNA, the expression of Bsep protein increased, while the expression of Mrp2 protein responded with a decrease, suggesting that the expression of both of them is transcriptionally regulated. Confocal immunofluorescence microscopy showed disruption of the colocalization of Bsep and Mrp2 proteins at the hepatocyte canalicular membrane and their relocation intracellularly. Quantitative colocalization analysis of Bsep and Mrp2 proteins revealed a steady decrease in the degree of colocalization and Mrp2 expression, indicating that although the properties of both transporters are affected, Mrp2 is altered more. These findings provide evidence that ethanol alters Bsep and Mrp2 canalicular transporters in the rat liver, at both the mRNA and protein levels. Mrp2 shows deeper involvement. Eight weeks appears to be a critical time point in this process.

Dynamics of PAF-induced conjunctivitis reveals differential expression of PAF receptor by macrophages and eosinophils in the rat

The action of platelet-activating factor (PAF) toward the PAF receptor (PAF-R) plays an important role in inflammation. We employed immunohistochemistry and quantitative confocal immunofluorescence microscopy to examine the dynamic changes of PAF-R expression in the conjunctiva in response to PAF-induced conjunctivitis in Brown Norway rats within the first 2 h after topical administration of PAF. Instillation of PAF caused an alteration in pattern of recruitment of macrophages and eosinophils into the conjunctiva, as was visualized by immunohistochemical staining for the antigens ED 1 and ED 2 (markers of macrophages) and MBP (a marker of eosinophils). An increase in the number of PAF-R positive cells was alos detected. Quantitative colocalization analysis revealed ther strongest rise in the degree of PAF-R expression by macrophages within the first 6 h, whereas their infiltration increased throughout the period of observation. However, eosinophils showed a high degree of PAF-R expression during all 24 h of the experiment, although they infiltrated strongly only within the first 2 h. Thus, for the first time, the use of quantitative colocalization analysis software developed by us has reveal intrinsic details of the interaction of PAF anf PAF-R in conjunctivitis, findings not otherwise obtainable by using qualitative approaches alone. Our results provide a theoretical basis for a definition of the proper time-frame in which to prevent and control the infiltration of macrophages and eosinophils into the conjunctiva.

Direct action of platelet activating factor (PAF) induces eosinophil accumulation and enhances expression of PAF receptors in conjunctivitis

PURPOSE

The goal of the present study was to investigate the role of platelet activating factor (PAF) and PAF receptor (PAF-R) in the recruitment of eosinophils into the conjunctiva in the course of PAF induced conjunctivitis. Eosinophils are important players in the immediate hypersensitivity reactions and in allergic conjunctivitis. PAF-R is expressed in many ocular tissues including conjunctival cells. Although it is known that PAF is one of the most potent chemotactic agents for the recruitment of eosinophils, factors responsible for it in conjunctivitis are not clear. Colocalization analysis has been employed to quantify the degree of colocalization of major basic protein (MBP) and PAF-R antigens in the course of PAF induced conjunctivitis.

METHODS

A 1% solution of PAF was applied in eye drops to male Brown Norway rats. Eyes were harvested with intact conjunctivas at different time points and examined using histology, immunohistochemistry, confocal immunofluorescence microscopy, and reverse transcription-polymerase chain reaction. PAF-R and MBP (a marker of eosinophils) antibodies have been used for immunohistochemical studies. Quantitative analysis of the colocalization of PAF-R and major basic protein (MBP) antigens was performed.

RESULTS

Instillation of PAF caused a time dependent recruitment of eosinophils. Eosinophils revealed PAF-R in the intact state. An influx of eosinophils into the conjunctiva was caused by the interaction of PAF with PAF-R and, possibly, with MBP antigen. PAF appeared to enhance the expression of PAF-R by eosinophils and to act toward the PAF-R directly, without chemokine mediation.

CONCLUSIONS

Quantitative colocalization analysis helped to determine that the recruitment of eosinophils in PAF induced conjunctivitis is accomplished via direct action of PAF toward the PAF-R. It also ensured an objective evaluation of the changes of the degree of colocalization of MBP and PAF-R antigens and the degree of PAF-R expression in dynamics, the findings not otherwise obtainable using qualitative approaches alone.

Experimental LPS-induced cholestasis alters subcellular distribution and affects colocalization of Mrp2 and Bsep proteins: A quantitative colocalization study

Quantitative colocalization analysis is a powerful tool for reliable estimation of the colocalization of antigens. We employed it to determine the changes of colocalization of multidrug resistance protein 2 (Mrp2) and bile salt export pump (Bsep) in confocal immunofluorescence microscopy images of rat liver following lipopolysaccharide (LPS) administration. Samples were taken 2, 24, 48 hours, and 1 week after LPS challenge. Pearson's correlation coefficient (PCC), an overlap coefficient according to Manders' (MOC), and overlap coefficients k1 and k2 were used to explore changes of the degree of colocalization. In intact animals, confocal microscopy showed tight colocalization of Mrp2 and Bsep proteins exclusively at the bile canaliculi. High degree of colocalization was confirmed quantitatively. Injection of LPS resulted in the appearance of fuzzy-looking areas of fluorescence of both proteins around bile canaliculi 2 and 24 hours after administration and relocation of Mrp2 protein to the basolateral domain of hepatocytes at 48 hours. By 1 week, canalicular localization was restored morphologically. Quantitative colocalization analysis of canalicular regions showed a steady decrease of the degree of colocalization of Mrp2 and Bsep up to 48 hours with the slight increase of its value by 1 week. These findings demonstrate that Mrp2, in contrast to Bsep, is partially and reversibly relocated from canalicular to basolateral domain of hepatocytes after LPS challenge.

Artificial tears inhibit the development of experimental immune-mediated blepharoconjunctivitis

PURPOSE

To investigate whether treatment with artificial tears inhibits the development of experimental immune-mediated blepharoconjunctivitis (EC).

METHODS

Brown Norway rats were immunized with ovalbumin (OVA) or ragweed (RW) emulsified in complete Freund's adjuvant. Fourteen days after immunization, the rats were challenged with the same antigen (Ag) in eye drops. Treated rats were administered artificial tears by eye drops immediately after, 15 min after, or 30 min after the Ag challenge. Treatment doses of 2, 4, or 8 drops per eye were evaluated. Twenty-four hours after the Ag challenge, the rats were killed and their eyes were harvested for histological studies.

RESULTS

Treatment with artificial tears immediately after and 15 min after challenge with partially insoluble RW Ag suppressed infiltration of inflammatory cells into the conjunctiva. Inhibition was not observed at any time following challenge with OVA Ag, which is a soluble protein. The treatment dose of artificial tears administered did not affect the extent of inhibition of EC following challenge with either Ag.

CONCLUSIONS

Treatment with artificial tears by eye drops inhibited the development of EC induced by the partially insoluble RW Ag when administered within 15 min of the Ag challenge.