Abstract
Purpose: :
Innate immunity has been implicated to play a role in ischemia-reperfusion injury in the brain and heart. We previously showed the protective effect of neuroglobin overexpression in transgenic mice with retinal ischemia-reperfusion injury. Here, we investigated the role of innate immunity in retinal ischemia-reperfusion injury and the protective mechanism of neuroglobin through innate immune response.
Methods: :
Retinal ischemia was induced in wild type (WT) and in transgenic mice overexpressing neuroglobin (Ngb+/+) by cannulating the anterior chamber of the left eye and maintaining the intraocular pressure at 110mmHg for 60 minutes. The untreated fellow eye was used as control. The animals were euthanized at day 7 of reperfusion and the eyes were subjected to immunohistochemical analysis to detect retinal thickness and localization of neuroglobin. A second group of experimental and control eyes was processed for Western blot analysis and a PCR array to analyze gene expression related to innate immunity.
Results: :
Overexpression of neuroglobin in transgenic mice was confirmed by immunohistochemistry and Western blot analysis. Retinal ganglion cell damage was significantly reduced in the Ngb+/+ mice compared to WT mice with ischemia. This was further confirmed by Western blot analysis with decreased expression of activated-caspase 3 and cytochrome c. Toll-like receptors and their signaling pathway genes were upregulated in both WT and Ngb+/+ mice with ischemia compared to controls. But some genes related to NFkb (csf3, IFN-gamma, IL2, Nfkbil1, IL12a and Tnfaip3) were downregulated in the Ngb+/+ mice with ischemia compared to the WT mice. Other genes (IFNb1, IL10, IL1b and IL6) were upregulated in the transgenic mice compared to the WT mice.
Conclusions: :
The above results suggest that innate immune response is activated in both WT and Ngb+/+ mice during ischemia-reperfusion in the retina .However, there is a protective effect in the Ngb+/+ mice against apoptosis and the mechanism of this neuroprotective effect appears to act downstream on the NFkb signaling pathway of the innate immune response.
Keywords: ischemia • neuroprotection • transgenics/knock-outs