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Xiaoyu Jiang, Sharon A. McClellan, Ronald P. Barrett, Elizabeth A. Berger, Yunfan Zhang, Linda D. Hazlett; Vasoactive Intestinal Peptide Regulates Toll-like Receptors in the Infected Cornea. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6130.
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© ARVO (1962-2015); The Authors (2016-present)
Toll-like receptors (TLRs) are able to recognize microbial pathogens and to trigger the earliest immune response leading to inflammation. Therefore, the purpose of this study was to examine how vasoactive intestinal peptide (VIP) regulates TLR during bacterial keratitis.
C57BL/6 mice were injected with VIP and mRNA, protein levels and immunostaining for various TLRs were done. Mice also were injected with siRNA for AC7 to determine if VIP effects were cAMP dependent. In vitro studies with Langerhans cells were also performed.
PCR array and real-time RT-PCR demonstrated several pro-inflammatory TLRs (Chuk, IRAK1, 2, TLR1, 3, 4, 6, 8, 9 and TRAF6) were down-regulated, while anti-inflammatory TLRs (SIGIRR and ST2) were upregulated after VIP vs PBS treatment. ELISA data showed that phosphorylated Chuk was downregulated and ST2 was upregulated; while Western blot showed SIGIRR was upregulated, all confirming the mRNA data. Immunostaining for TLR4 revealed its reduction after VIP treatment, also confirmatory of the mRNA data. To determine whether the mechanism of VIP regulation was cAMP dependent or not, AC7 siRNA (blocks cAMP) was injected into B6 mice plus or minus VIP. TLR1, TRAF6 and ST2 were cAMP dependent, while Chuk, IRAK1, 2, TLR3, 4, 8, 9 and SIGIRR were not. In vitro VIP also down-regulated mRNA expression of several pro-inflammatory TLRs in endotoxin stimulated Langerhans (XS52) cells.
Collectively, the data provide evidence that VIP regulates both pro and anti-inflammatory TLRs and that this regulation is both cAMP dependent and independent.
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