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Akira Takamiya, Masumi Takeda, Akitoshi Yoshida, Hiroshi Kiyama; Expression of Serine Protease Inhibitor 3 in Ocular Tissues in Endotoxin-Induced Uveitis in Rat. Invest. Ophthalmol. Vis. Sci. 2001;42(11):2427-2433.
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purpose. To ascribe the serine protease inhibitor 3 (SPI-3) as an ocular acute
inflammatory molecule and to clarify its producing cells in an
endotoxin-induced uveitis (EIU) model.
methods. Male Wistar rats were injected with lipopolysaccharide (LPS), and the
expression of SPI-3 mRNA in the ocular tissues was examined by in situ
hybridization (ISH) and Northern blot analysis. A combination of ISH
and immunohistochemistry (IHC) were performed to prove the
colocalization of SPI-3 mRNA and either glial fibrillary acidic protein
(GFAP) or OX-42. The expression of phosphorylated STAT3 (pSTAT3) was
demonstrated by IHC and Western blot after LPS injection. The
colocalization of SPI-3 mRNA and pSTAT3 was finally examined by the
double labeling of ISH and IHC.
results. After LPS injection, the expression of SPI-3 mRNA in ocular tissues was
quickly upregulated and reached a peak between 12 and 24 hours after
injection. An intense mRNA signal was observed in epithelial cells of
the iris and ciliary body and the innermost retinal layer. In the
retina, SPI-3 mRNA was colocalized with GFAP, demonstrating that the
cells expressing SPI-3 mRNA were astrocytes. After LPS treatment, SPI-3
mRNA and pSTAT3 were colocalized in retinal astrocytes, and pSTAT3
expression appeared slightly earlier than that of SPI-3 mRNA.
conclusions. Ocular inflammation induced the transient expression of SPI-3 mRNA in
retinal astrocytes and epithelial cells in the iris and ciliary body,
particularly during early phase of the inflammation. Simultaneously,
the activation of STAT3 (phosphorylation of STAT3) occurred slightly
earlier in astrocytes. This supports the previous in vitro results that
SPI-3 expression is induced in a STAT3-mediated manner. SPI-3 may have
some crucial roles in preventing some degenerative proteolysis, which
is induced by inflammatory stimuli.
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