Autophagy marker expression in Non-Sjögren and Sjögren syndrome dry eyes

Abstract

Purpose : Autophagy is a lysosome-mediated catabolic process that maintains cellular homeostasis through the degradation and recycling of cytoplasmic components and organelles. Recent data showed that enhanced autophagy was involved in the autoantibody redistribution in secretory epithelial cells in Sjögren syndrome (SS). We investigated autophagy markers (ATG5, LC3B) in tears and conjunctiva from non- SS and SS dry eyes (DE), and also analyzed their correlation with clinical features to determine whether autophagy dysregulation might be a key finding in SS DE.

Methods : Forty SS DE patients (78 eyes), 24 non-SS DE patients (48 eyes), and 16 normal healthy subjects (25 eyes) were included in the present study. Schirmer I test, tear film breakup time (TBUT), ocular surface staining (OSS) scores, and ocular surface disease index (OSDI) were assessed. ATG5, LC3BII/I conversion ratio in tears were analyzed by Western blot. Immunostaining and qPCR of ATG5 and LC3BII were also performed using conjunctival impression cytology. Additionally, two markers were observed in immunostained lacrimal glands of NOD/LtJ mice (SS animal model).

Results : SS DE showed lower values in Schirmer and TBUT and higher values in OSS staining scores compared to non-SS DE. ATG5 protein and LC3BII/I conversion ratio were significantly higher in SS DE than non-SS DE tears of patients and control. The levels of encoding ATG5 and LC3BII in the conjunctiva were also upregulated in SS DE than non-SS DE and control. The immunofluorescent staining of conjunctival impression cytology specimen showed a punctate staining pattern of ATG5 and LC3BII in SS DE, whereas the characteristic staining pattern was not observed in those of non-SS DE and control. Among clinical parameters, conjunctival staining scores were strongly correlated with ATG5 protein abundance in tears and ATG5 mRNA level in conjunctiva. After corticosteroid treatment in SS DE (32 eyes), ATG5 and LC3BII expression in tears and conjunctiva were significantly reduced.

Conclusions : Autophagy markers (ATG5 and LC3B) were upregulated in tears and conjunctiva. ATG5 expression was correlated with conjunctival staining scores in SS DE. Anti-inflammatory treatment induced downregulation of autophagy markers accompanied by improvement of clinical parameters in SS DE.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Fig 1. Protein abundance in tears

 

Fig 2. Immunostaining of conjunctival epithelium