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Humberto Hernandez, Rodrigo G. de Souza, Zhiyuan Yu, Robert A Britton, Cintia S De Paiva; Anti-inflammatory properties of butyrate on the ocular surface epithelium. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2818.
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© ARVO (1962-2015); The Authors (2016-present)
Dry eye is one of the most common ocular morbidities affecting millions of people in the US. The main risk factors include aging, female sex, hormonal changes, and low humidity environment. Dysbiosis, or microbial imbalance, has been associated with aging and dry eye and can be induced by oral antibiotic treatment. Butyrate is one of the short-chain fatty acids (SCFA) exclusively produced by certain members of the gut microbiota upon fermentation of dietary starches and fiber. Butyrate has been shown to have potent anti-inflammatory properties. The purpose of this study was two-fold: to investigate the expression of SCFA receptors and its transporter, sodium-coupled monocarboxylate transporter 1 (Slc5a8) and second, to investigate the anti-inflammatory properties of butyrate on the ocular surface epithelium.
The expression of butyrate receptors (GPR41, GPR43, and GPR109B) and transporter was investigated in cryosections from 8-week old C57BL/6 mice and primary explant cultures obtained from cornea and conjunctiva. Cultured conjunctival or corneal epithelial cells were pre-incubated with either sodium butyrate (0.5mM) or sodium 4-phenylbutyrate (PBA) for 2 hours before the addition of TNF-α (20ng/mL). Cells were lysed after 4 hours and expression of IL-1β, and NLRP3 was examined by real-time PCR. Bone marrow dendritic cells were stimulated with either LPS or TNF-α and NFκB phosphorylation levels was assessed using FACE assay.
Immunoreactivity of GPR41, GPR43, GPR109B receptors, and slc5a8 transporter was observed in cornea and conjunctiva from cryosections and cultured cells. TNF-α stimulation upregulated IL-1β (20.3±0.42 fold, P<0.0001) and NLRP3 (42.37±0.54 fold, P<0.0001) transcripts compared to non-stimulated control in cultured conjuctival cells. Butyrate treatment blunted TNF-α-induced upregulation of IL-1β and NLRP3 mRNA transcripts in conjunctival epithelial cells (2.11±2.6 and 5.27±1.7, respectively, P<0.0001 for both). Increased phosphorylated levels of NFκB were observed in bone marrow dendritic cells after TNF-α or LPS treatment while butyrate blocked this increase. Similar anti-inflammatory results were obtained with PBA in cultured corneal epithelial cells.
Our studies suggest that the ocular surface express the receptors and transporter for butyrate. Butyrate is a potent inhibitor of inflammatory stimuli. This indicates that SCFAs participate in ocular surface homeostasis.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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