Abstract
Purpose :
To characterize effects of attenuated retinoid X receptor alpha (RXRa) signaling by gene mutation (Pinkie strain) or chemical antagonist on phenotype and cytokine production by myeloid lineage cells and conjunctival goblet cell density.
Methods :
Conjunctival goblet cells (GC) were counted in PAS-stained sections and gene expression was evaluated by RNA sequencing, PCR, immunobead assay and immunostaining. Monocytes phenotype and cytokine production was measured by flow cytometry. Adoptively transferred cells were tracked in the conjunctiva and cervical lymph node (CLN) using a fluorescent violet tracer dye. Effects of Rxra antagonism with HX531 was evaluated in cultured bone marrow cells (BMDC) and a desiccating stress (DS) dry eye model.
Results :
CD11b+ monocyte lineage cells were the predominant population in the conjunctiva of the RXRa mutated Pinkie and WT C57BL/6 strains. The majority of adoptively transferred CD11b+ cells detected in the conjunctiva are Rxra+ suggesting retinoid responsiveness, while <5% of transferred CD11b+ cells in the CLN are Rxra+. A significantly increased number of MHCII-CD11b+Ly6C+cells population were noted in the Pinkie conjunctiva, and these were more efficient IL-12 and IFN-g producers than WT. Significantly reduced GC density in Pinkie was accompanied by upregulation of innate immunity, cytokine signaling and IFN-g signature genes detected by RNA seq and significantly higher IL-12 and IFN-g concentrations in tears. Treatment of LPS-stimulated BMDCs with HX531 significantly upregulated IL-12 and IFN-g production in vitro and reduced GC number after 10D of DS induced dry eye in C57BL/6.
Conclusions :
Attenuated Rxra+ signaling in Pinkie increases IL-12 and IFN-g expression by innate immature monocyte derived cells and increases IL-12 and IFN-g production by these cells in response to microbial and desiccating danger signals. IFN-g produced by these innate cells appears to promote conjunctival GC loss. RXRa signaling contributes to maintenance of immune tolerance and prevention of dry eye disease.
This is a 2020 ARVO Annual Meeting abstract.