Inflammatory-promoting roles of thymic stromal lymphopoietin and interleukin-4 in allergic conjunctivitis mice

Background

Researches showed that thymic stromal lymphopoietin (TSLP) is an interleukin-17-like inflammatory factor and plays important roles in the pathogenesis and development of allergic diseases.However, the study whether TSLP plays roles in allergic conjunctivitis is rare.

Objective

This study was to investigate the expression change of TSLP and IL-4 in ocular surface tissue and cervical lymph node in the mice with allergic conjunctivitis induced by artemisia annua, a common plant in China, and to explore the role of TSLP and IL-4 in the pathogenesis and development of allergic conjunctivitis.

Methods

Twenty female BALB/c mice aged 6-8 weeks were randomized into normal control group and model group.Antigen solution was prepared using 400 μl extracting solution of artemisia annua pollen with 400 μl antigen solvent.The mouse models of allergic conjunctivitis were established by injection of 50 μl antigen solution in footpad followed by ocular topical administration of extracting solution once a day from day 10 to 12 after injection, and no any intervention was given in the normal control group.The mice were sacrificed and eyeballs were obtained 13 days after modeling, and corneal epithelium, conjunctiva and cervical lymph nodes were harvested for the detection of TSLP mRNA and IL-4 mRNA by real-time PCR.Immunochemistry was employed to assay the expression of TSLP and IL-4 proteins in corneal, conjunctival and subconjunctival tissues.

Results

Ocular inflammatory signs appeared 0.5 hours after ocular topical administration of extracting solution, including eyelid edema, conjunctival congestion, tears, scratching eyelids, etc.The symptoms lasted for 6-24 hours, with the model successful rate 80%.Real-time PCR indicated that the expression of IL-4 was absent in corneal epithelium in both model group and normal control group.The relative expression levels of TSLP mRNA in the corneal epithelium, conjunctiva and cervical lymph nodes in the model group were more (1.63±0.20) times, (2.71±0.48) times and (1.48±0.05) times than the normal control group, showing significant differences between the two groups (t=4.44, 14.16, 5.01, all at P<0.05). Compared with the normal control group, the relative expression levels of IL-4 mRNA in the model group increased (2.94±0.39) times and (1.74±0.09) times, with significant differences between the two groups (t=9.92, 14.54, both at P<0.05). Immunochemistry assay showed that the expression of TSLP protein in the corneal and conjunctival epithelial cells were enhanced in the model group compared with the normal control group.In addition, an intensive expression of IL-4 protein was seen in subconjunctival tissue in the model group, while the expression of IL-4 was absent in the normal control group.

Conclusions

TSLP is mainly expressed in the cornea, conjunctiva and cervical lymph nodes of the mice with allergic conjunctivitis, suggesting that TSLP promotes the inflammatory process of cornea and conjunctiva; IL-4 is mainly expressed in conjunctiva, showing IL-4 participates in conjunctival inflammatory process.TSLP and IL-4 play synergistic roles in promoting the inflammatory process of ocular surface in the mice with allergic conjunctivitis, which may be new therapeutic targets.

Conjunctivitis, allergic/immunology; Allergens/adverse effects; Thymic stromal lymphopoietin; Interleukin-4; Epithelial cells, eye; Disease models, animal; Mice, inbred BALB/c