epiglucan and Keratitis

Indoleamine 2,3-dioxygenase (IDO), which is mainly expressed in activated dendritic cells, is known as a regulator of immune responses. However, the role of IDO in immune responses against fungal corneal infection has not been investigated. To evaluate the regulatory mechanisms of IDO in fungal inflammation, we resorted to human corneal epithelial cells (HCECs), known as the first barrier of cornea against pathogenic microorganisms. We found that IDO was significantly up-regulated in corneal epithelium infected with Aspergillus fumigatus (A. fumigatus) and HCECs incubated with spores of A. fumigatus. Furthermore, IDO inhibitor (1-methyltryptophan, 1-MT) enhanced inflammatory cytokines IL-1β and IL-6 expression which were up-regulated by A. fumigatus spores infection. Dectin-1, as one of the important C-type lectin receptors, can identify β-glucan, and mediate fungal innate immune responses. In the present study, pre-treatment with curdlan, a Dectin-1 agonist, further enhanced IDO expression compared with A. fumigatus stimulation. While laminarin, the Dectin-1 specific inhibitor, partially inhibited IDO expression stimulated by A. fumigatus. Further studies demonstrated inhibition of IDO activity amplified the expressions of inflammatory cytokines IL-1β and IL-6 induced by activation of Dectin-1. These results suggested that IDO was involved in the immune responses of fungal keratitis. The activation of Dectin-1 may contribute to A. fumigatus spores-induced up-regulation of IDO.

Topics: Animals; Aspergillus fumigatus; beta-Glucans; Cytokines; Disease Models, Animal; Epithelium, Corneal; Female; Gene Expression; Humans; Indoleamine-Pyrrole 2,3,-Dioxygenase; Inflammation Mediators; Keratitis; Lectins, C-Type; Mice; RNA, Messenger

Aspergillus species are a major worldwide cause of corneal ulcers, resulting in visual impairment and blindness in immunocompetent individuals. To enhance our understanding of the pathogenesis of Aspergillus keratitis, we developed a murine model in which red fluorescent protein (RFP)-expressing A. fumigatus (Af293.1RFP) conidia are injected into the corneal stroma, and disease progression and fungal survival are tracked over time. Using Mafia mice in which c-fms expressing macrophages and dendritic cells can be induced to undergo apoptosis, we demonstrated that the presence of resident corneal macrophages is essential for production of IL-1beta and CXCL1/KC, and for recruitment of neutrophils and mononuclear cells into the corneal stroma. We found that beta-glucan was highly expressed on germinating conidia and hyphae in the cornea stroma, and that both Dectin-1 and phospho-Syk were up-regulated in infected corneas. Additionally, we show that infected Dectin-1(-/-) corneas have impaired IL-1beta and CXCL1/KC production, resulting in diminished cellular infiltration and fungal clearance compared with control mice, especially during infection with clinical isolates expressing high beta-glucan. In contrast to Dectin 1(-/-) mice, cellular infiltration into infected TLR2(-/-), TLR4(-/-), and MD-2(-/-) mice corneas was unimpaired, indicating no role for these receptors in cell recruitment; however, fungal killing was significantly reduced in TLR4(-/-) mice, but not TLR2(-/-) or MD-2(-/-) mice. We also found that TRIF(-/-) and TIRAP(-/-) mice exhibited no fungal-killing defects, but that MyD88(-/-) and IL-1R1(-/-) mice were unable to regulate fungal growth. In conclusion, these data are consistent with a model in which beta-glucan on A.fumigatus germinating conidia activates Dectin-1 on corneal macrophages to produce IL-1beta, and CXCL1, which together with IL-1R1/MyD88-dependent activation, results in recruitment of neutrophils to the corneal stroma and TLR4-dependent fungal killing.

Topics: Animals; Aspergillus fumigatus; beta-Glucans; Chemokine CXCL1; Corneal Stroma; Interleukin-1beta; Intracellular Signaling Peptides and Proteins; Keratitis; Lectins, C-Type; Macrophages; Membrane Proteins; Mice; Nerve Tissue Proteins; Protein-Tyrosine Kinases; Syk Kinase; Toll-Like Receptor 4

Increased concentration of (1,3)-beta-D-glucan, one of the major components of fungal cell walls, is detected in the serum of systemic fungal infection. In our study, the concentration of (1,3)-beta-D-glucan was measured in the tear fluid of patients with mycotic keratitis.. Tear fluid was collected from patients with fungal keratitis (n = 4) and bacterial corneal ulcers (n = 4) with or without corneal scraping. In addition, tear fluid was collected from patients without corneal diseases.. The concentration of (1,3)-beta-D-glucan in tear fluid collected without corneal scraping was 4.0 +/- 3.5, 5.8 +/- 2.6, 184 +/- 128 pg/ml in the control, bacterial corneal ulcer, and mycotic keratitis samples respectively. The concentration of (1,3)-beta-D-glucan in tear fluid collected after scraping the corneal lesions with a tip of glass capillary was 4.4 +/- 1.3, 8.2 +/- 5.2 and >1,000 pg/ml in the control, bacterial ulcer, and mycotic keratitis samples respectively.. A significant increase in (1,3)-beta-D-glucan was detected in tear samples from patients with mycotic keratitis. Measuring the concentration of (1,3)-beta-D-glucan in tear fluid might be helpful in the diagnosis of mycotic keratitis.

Topics: beta-Glucans; Corneal Ulcer; Eye Infections, Bacterial; Eye Infections, Fungal; Humans; Keratitis; Osmolar Concentration; Proteoglycans; Tears