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Kip M Connor, Saori Inafuku; The Alternative Complement System Mediates cell death in retinal ischemia reperfusion injury.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3945.
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© ARVO (1962-2015); The Authors (2016-present)
Ischemia reperfusion (IR) injury induces retinal cell death and contributes to visual impairment. It has been reported that the complement cascade plays a key role in IR injury in several systemic diseases. However, the involvement of the complement pathway in the retina has not been investigated. The aim of this study is to determine the role of the complement pathway in retinal IR injury.
C57BL/6, alternative pathway deficient mice (fb-/-) and mice deficient in the central mediator of the complement system (C3-/-) were used in a IR mouse model. Briefly, pupils were dilated with 1% tropicamide, and topical anesthesia (1 drop of proparacaine hydrochloride) was applied to cornea. The anterior chamber of the left eye was cannulated with a 30-gauge needle connected to a sterile saline reservoir elevated 140 cm. After 45 minutes of ischemia, the needle was withdrawn. Intraocular pressure (IOP) was measured 0, 15, 30 and 45 minutes after induction of ischemia, before and after the surgery using a TonoLab tonometer. Cell death was assessed by TUNEL staining in cross section and real-time PCR analysis was determined using validated probe sets for Crry, Cd46, Cd55 and Cd59.
In a retinal IR mouse model, mRNA expression of complement inhibitors, Crry, Cd55 and Cd59a was down-regulated following IR injury. The genetic deletion of complement components C3-/- or Fb-/-, resulted in a reduction of IR induced apoptosis (P<0.05 and P<0.01, respectively). Additionally, in human retinal endothelial cells (HRECs), complement inhibitors, Cd46, Cd55 and Cd59 were up-regulated, and complement mediated cell death was suppressed by shear stress.
In the current study, we demonstrated that the compliment inhibitors Crry, Cd55 and Cd59a were suppressed in the retina following IR injury. These inhibitors are regarded as critical negative regulators of the complement system due to their ability to modulate all three complement pathways. Crry and Cd55 inhibit the C3 convertase, whereas CD59 inhibits formation of the MAC. In the retinal IR mouse model, cell death in inner nuclear layer was suppressed in C3-/- mice compared to WT mice. Furthermore, a similar reduction in cell death was observed in Fb-/- mice. As factor B is exclusive to the alternative pathway, these results implicate the complement system, especially alternative pathway, in retinal cell death caused by IR injury.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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