Abstract
Purpose: :
Thrombospondin-1 (TSP-1) deficient mice develop ocular surface inflammation as seen in autoimmune Sjögren’s syndrome, which follows lacrimal gland dysfunction and inflammation detectable as early as 8 wks of age. In this study we investigate the temporal relationship of conjunctival inflammation in TSP-1null mice and determine its correlation with the oxidative stress related damage in the tissue.
Methods: :
Lacrimal gland (LG) and conjunctiva tissues were harvested from WT (C57BL/6) and TSP-1null male mice at ages 6, 8 and 21 wks. Tissue lysates from 6 and 8 wks old mice were assessed for the levels of oxidative stress associated cellular damage related markers such as lipid peroxidation end product thiobarbituric acid reacting substances (TBARS), advanced oxidation protein product (AOPP) and total oxidant species (TOS) using biochemical assays. Expression of inflammatory cytokines IFN-γ, TNF-α, IL-1β, IL-6 and IL-17 in conjunctiva was determined by real-time PCR analysis of total RNA isolated from all the tissues collected.
Results: :
Significantly elevated levels of TOS were detectable in both conjunctiva and LG tissue harvested from 6 wks old TSP-1null mice as compared to the age-matched WT control tissues. However at this age, significant increase in TBARS and AOPP was detectable only in the conjuctiva, but not in LGs, harvested from TSP-1null mice compared to control tissues. Significantly increased expression of IFN-γ, IL-6 and IL-17 cytokines was detectable in conjunctiva harvested from 6 weeks old TSP-1null mice while expression of TNF-α and IL-β remained unaltered compared to control tissues. At the age of 8 wks all the tested oxidative stress related marker levels were significantly elevated in conjunctiva as well as LGs from TSP-1null mice. Also, a significantly increased expression of all the tested inflammatory cytokines was detectable in conjunctiva harvested from 21 wks old TSP-1null mice.
Conclusions: :
Conjunctiva deficient in TSP-1 is more vulnerable to oxidative stress related cellular damage as compared to lacrimal gland. Such cellular damage coincides with the appearance of inflammatory cytokines. Therefore oxidative stress related markers might serve as early biomarkers for the detection of conjunctival inflammation.
Keywords: inflammation • conjunctiva • oxidation/oxidative or free radical damage