Sex-specific Dry Eye Pathogenesis Correlates With Increased Activation of T cells and Decreased Resident PMN and Lipoxin Formation in Female Draining Lymph Nodes

Abstract

Purpose: The cause for the sex-specific prevalence of Dry Eye Disease (DED) in women is largely unknown. A protective and immune-regulatory lipid mediator circuit (lipoxin) is highly expressed in the ocular surface and markedly amplified by PMN. This lipid circuit is down regulated by estrogen and drives sex-specific differences in corneal wound healing and inflammatory responses. If the PMN-lipoxin circuit has a role in the pathogenesis of DED and lymphocyte activation in females is unknown. We investigated sex-specific difference in the pathogenesis of DED and regulation of the PMN-LXA4 circuit in the ocular surface and draining lymph nodes.

Methods: Male and female mice were subjected to the standard model of desiccating stress induced DED. Severity of DED was evaluated by Schirmer’s test and clinical fluorescence scoring. PMN and CD4+ T cells population were confirmed and quantified by using myeloperoxidase assay, fluorescence deconvolution microscopy and flow cytometry. Lipid mediator formation was quantified by LC/MS/MS-based lipidomics and gene expression quantified by qPCR.

Results: Female mice exhibited amplified Dry Eye severity compared to males. Both males and females had a significant population of tissue PMN in the limbus prior to inducing desiccating stress. In females that PMN population decreased by 56%, while CD4+ T cells increased by 42% after inducing DED. Compared to males, females had a striking phenotype of less neutrophils and more CD4+ T cells infiltration in the corneal limbus after inducing DED. This was paralleled by a marked depression of PMN in draining lymph nodes of females, while PMN in male lymph nodes increased 7.7 fold after inducing DED. The female phenotype correlated with a marked increase in CD4+ T cells in the draining lymph nodes and a marked reduction in endogenous formation of Lipoxin A4 in both the limbus and draining lymph nodes of female mice.

Conclusions: These results provide the first evidence that primary innate immune cells, PMN, and the LXA4 circuit are active in draining lymph nodes, suggesting a novel regulatory role. Desiccating stress induces a striking sex-specific regulation of PMN and the lipoxin circuit in in the limbus and draining lymph nodes that correlates with increased severity of DED and activation of T cells in females.

Keywords: 486 cornea: tears/tear film/dry eye • 555 immunomodulation/immunoregulation • 506 eicosanoids