Aspergillus fumigatus activate human corneal epithelial cells via Toll-like receptor 2 and 4
Author:
Gao JL, Wu XY.
Date: 24 November 2006
Abstract:
OBJECTIVE: To determine Toll-like receptors (TLR) 2 and TLR4 expression in human corneal epithelial tissue and cell line (THCE), and its activation by aspergillus fumigatus (AF) in inflammatory response. METHODS: The expression of TLR2 and TLR4 protein in human corneal epithelial tissue and THCE was detected by Western blot and immunocytochemistry. THCE was challenged with AF mycelium fragment (5 x 10(6)/ml) and supernatant extract agent (equivalent to bovine serum albumin 10 microg/ml). IL-8 and TNF-alpha in THCE supernatant were detected by ELISA at 1, 2, 4 and 8 h post stimulation. The protein of IkappaBalpha in THCE cells was assayed by Western blot at 30 min, 1 h and 2 h after treatment. Antibody blocking test was utilized to evaluate the effect on IL-8 and TNF-alpha expression of THCE by blocking TLR2 and (or) TLR4 before challenge with AF agent. RESULTS: TLR2 and TLR4 protein were expressed in human corneal epithelial tissue and THCE. The IL-8 and TNF-alpha level in THCE supernatant was elevated at 1 h, increased to (64.71 +/- 5.15) pg/ml and (32.46 +/- 3.28) pg/ml (AF mycelium challenge group), (94.94 +/- 11.92) pg/ml and (48.70 +/- 3.32) pg/ml (AF supernatant challenge group) 8 h post-challenged, which was 3.0 times and 2.5 times, 4.5 times and 3.5 times to that of control group respectively (P < 0.01). The activity of IkappaBalpha in THCE cells was decreased to 10.31 +/- 1.30 (gray scale value) and 8.15 +/- 2.37 at 30 min after challenged with AF mycelium or supernatant extract agent compared to 51.57 +/- 5.58 and 49.23 +/- 3.49 of control group (P < 0.01), and was reverted at 2 h. The secretion of IL-8 and TNF-alpha was partly inhibited by blocking TLR2 or TLR4 (P < 0.05), obviously inhibited by blocking TLR2 and TLR4 (50% and 40% compared to that of control group) (P < 0.01) when challenged with AF mycelium. And that was markedly inhibited by blocking TLR4 or blocking TLR2 and TLR4 when challenged with AF supernatant (P < 0.01). The secretion of IL-8 and TNF-alpha was not inhibited by blocking TLR2 when challenged with AF supernatant (P > 0.05). CONCLUSIONS: AF agent may induce human corneal epithelial cells express inflammatory cytokines via TLR-NF-kappaB pathway. TLR2 and TLR4 possibly mediate the recognition to AF mycelium, and TLR4 may dominate the recognition to AF supernatant agent.
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