Abstract
BackgroundThe objective of this study is to observe whether cyclosporine A (CsA) inhibits the expression of dectin-1 in human corneal epithelial cells infected with Aspergillus fumigatus (A. fumigatus) and to investigate the molecular mechanisms of the inhibition.MethodsImmortalized human corneal epithelial cells (HCECs) were pretreated with 1,25(OH)2D3 and VDR inhibitor for 1 h, and then they were pretreated with CsA for 12h. After these pretreatments, the HCECs were stimulated with A. fumigatus and curdlan respectively, and the expression of dectin-1 and proinflammatory cytokines (IL-1β and TNF-α) were detected by RT-PCR, western blot and ELISA.ResultsDectin-1 mRNA and dectin-1 protein expression increased when HCECs were stimulated with A. fumigatus or curdlan, and CsA inhibited the dectin-1 expression both in mRNA and protein levels specifically. Dectin-1 and proinflammatory cytokine expression levels were higher when HCECs were pretreated with VDR inhibitor and CsA compared to pretreatment with CsA alone, while dectin-1 and proinflammatory cytokine levels were lower when HCECs were pretreated with 1,25(OH)2D3 and CsA compared to pretreatment with CsA alone.ConclusionsThese data provide evidence that CsA can inhibit the expression of dectin-1 and proinflammatory cytokines through dectin-1 when HCECs are stimulated by A. fumigatus or curdlan. The active form of vitamin D, 1,25(OH)2D3, and VDR signaling pathway regulate the inhibition of CsA. The inhibition is enhanced by 1,25(OH)2D3, and the VDR inhibitor suppresses the inhibition.
Highlights
Fungal keratitis is a rare but severe infectious inflammation of the cornea that is still one of the main causes of corneal blindness and visual disability[1].It occurs more frequently in developing countries with significant agriculture-dependent populations[2], such as India, Ghana, Nepal and China
Dectin-1 mRNA and dectin-1 protein expression increased when human corneal epithelial cells (HCECs) were stimulated with A. fumigatus or curdlan, and cyclosporine A (CsA) inhibited the dectin-1 expression both in mRNA and protein levels
Dectin-1 and proinflammatory cytokine expression levels were higher when HCECs were pretreated with VDR inhibitor and CsA compared to pretreatment with CsA alone, while dectin-1 and proinflammatory cytokine levels were lower when HCECs were pretreated with 1,25(OH)2D3 and CsA compared to pretreatment with CsA alone
Summary
Fungal keratitis is a rare but severe infectious inflammation of the cornea that is still one of the main causes of corneal blindness and visual disability[1].It occurs more frequently in developing countries with significant agriculture-dependent populations[2], such as India, Ghana, Nepal and China. Fungal keratitis is relatively uncommon in developed countries [3]. Aspergillus fumigatus is known as one of the most common pathogens of fungal keratitis [4]. Pattern-recognition receptors (PRRs) that are expressed by innate immune cells recognize Aspergillus fumigatus. Dectin-1 is one such innate immune PRR, having a transmembrane protein that contains a single C-type lectin-like domain (CTLD) in the extracellular region and an immunoreceptortyrosine-based activation (ITAM)-like motif within its intracellular tail[5].Through the recognition of β-glucans, dectin-1 can bind to several fungal species[6] and induce a vast array of cellular effects, including actin-mediated phagocytosis, activation of therespiratory burst through production of reactive oxygen species, endocytosis, dendritic cell maturation and production of cytokines such as TNF-α,IL-1β,CXCL2 and GM-CSF[7,8]. The objective of this study is to observe whether cyclosporine A (CsA) inhibits the expression of dectin-1 in human corneal epithelial cells infected with Aspergillus fumigatus (A. fumigatus) and to investigate the molecular mechanisms of the inhibition
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