Cytokine and Chemokine Induction Using Cell Wall Component and Toxin Derived from Gram-Positive Bacteria in the Rat Middle Ear

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Abstract
Lipoteichoic acid (LTA) is one of the components present within the cell wall layer of most gram-positive bacteria. It plays an important role in the initiation and progression of bacterial infection. In this study, we performed a rat middle ear and nasal perfusion with LTA purified from two different gram-positive bacterial species. Using ELISA and RT-PCR, the production and mRNA expression of rat chemokine, GRO/CINC-1, proinflammatory cytokine, TNF-alpha, in rat middle ear lavage and mucosa were investigated. GRO/CINC-1 in middle ear lavage was produced by stimulation of LTA in a time-dependent fashion; however, TNF-alpha production into the lavage was not detectable using ELISA assay. The mRNA expressions of GRO/CINC-1 and TNF-alpha in the middle ear mucosa were both induced after LTA and exotoxin exposures. The expression of IL-10 mRNA was also induced after 6 h of LTA and exotoxin exposures. The profile of the production of GRO/CINC-1 and TNF-alpha in rat nasal lavage was similar to that in the middle ear; however, the mRNA expressions of GRO/CINC-1, TNF-alpha and IL-10 in the nasal mucosa were different from those in the middle ear mucosa. These results suggest that the cell wall component and exotoxin of gram-positive bacteria can induce several cytokines in vivo and play an important role in the initiation of the inflammatory cascade in the middle ear.