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Jingwen Huang, Wenru Su, Xiaoqing Chen, Xiaokang Cheng, Ye Dai, Longhui Han, Dan Liang; Doxycycline Attenuates Endotoxin-Induced Uveitis by Prostaglandin E2-EP4 Signaling. Invest. Ophthalmol. Vis. Sci. 2015;56(11):6686-6693. doi: 10.1167/iovs.15-17045.
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© ARVO (1962-2015); The Authors (2016-present)
We explored the anti-inflammatory effects of doxycycline in experimental uveitis and the underlying mechanisms.
Rats with endotoxin-induced uveitis (EIU) received doxycycline (1.5 mg/kg) or the control vehicle via intraperitoneal injection. Clinical scores were graded under a slit lamp. Rat peritoneal macrophages were used in vitro to further explore the anti-inflammatory mechanisms of doxycycline. The levels of nitric oxide (NO), TNF-α, IL-1β, prostaglandin E2 (PGE2), cyclooxygenase (COX)-2, I kappa B-α (IκB-α), inducible nitric oxide synthase (iNOS), Akt, caspase-3, and nuclear factor-kappa B (NF-κB) were analyzed.
Treatment with doxycycline dramatically reduced the clinical scores of EIU (P < 0.001), with significant decreases in inflammatory cell infiltration, protein concentrations, and the production of NO, TNF-α, and IL-1β in the aqueous humor (AqH). In vitro, doxycycline significantly inhibited the production of NO, IL-1β, and TNF-α in peritoneal macrophages by modulating the PI3K/Akt/IκB-α/NF-κB pathway. Importantly, we found that doxycycline significantly enhanced COX2 expression and PGE2 production both in vivo and in vitro. More importantly, blockade of the EP4 receptor of PGE2 significantly reversed the doxycycline-mediated inhibition of macrophages and the PI3K/Akt pathway in vitro. Furthermore, simultaneous injection of an EP4 antagonist and doxycycline significantly blocked the doxycycline-mediated attenuation of EIU.
Doxycycline can ameliorate EIU, and PGE2-EP4 signaling is essential for the anti-inflammatory effects of doxycycline in vitro and in vivo.
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