Purpose To investigate the expression of PPARγ, TNF-a and IL-1β in the conjunctiva and the relationship between inflammatory cytokine and PPAR-γ in the pathogenesis of the experimental induced dry eye.
Methods Dry eye was induced in 6-week-old female C57 mice by subcutaneous injections of scopolamine hydrobromide and combined with a desiccated environment. After the treatment on day1,3,5,10,12,15,20, tear production, cornea fluorescent stain, conjunctiva goblet cell were observed and the expression of PPAR-γ, TNF-α and IL-1β mRNA were measured by Realtime PCR. Western blotting was used for examine PPAR-γ protein in conjunctiva tissue. TNF-α and IL-1β in both conjunctiva tissue and tear-wash fluid were determined by ELISA assay.
Results The experimental induced dry eye mice showed significant decrease in aqueous tear production (P<0.001) and goblet cell number (p<0.01) compared with control group since treated for 1 day. Realtime PCR showed the expression of PPAR-γ in the conjunctiva of the dry eye mice decreased significantly with time( p<0.01 since day1, P<0.001since day 5), and the Western blotting assay of PPAR-γ confirmed this finding. The expression of IL-1β mRNA up-regulated in all the dry eye groups except group day 15 (P<0.001) and TNF-α expression increased in group day 5,day 10 and day 12 (p<0.05 vs control). The TNF-α concentration in conjunctiva tissue increased in all the dry eye groups (p<0.01 vs control ), and tear-wash fluid TNF-α concentration increased in group day 1,3,5,12,15,20 (p<0.001 vs control). The IL-1β concentration in conjunctiva tissue increased in group day 3,5,10,15,20 (p<0.01 vs control ), and tear-wash fluid IL-1β concentration increased in group day 1,3,5,12,15,20 (p<0.001 vs control).
Conclusion The experimental induced dry eye mouse model represented the similar manifestation of dry eye in human. The expression of PPAR-γ in the conjunctiva of the mice was down regulated with increased TNF-a and IL-1β. Decreased PPAR-γ expression might play a role in the development of the disease.