Abstract
Purpose :
Age-related macular degeneration (AMD) is linked in part to genetic defects in complement system proteins as well as inflammatory markers of the innate immune system. Previously, our laboratory reported that AMD platelets have increased surface levels of complement component C3b at baseline and after platelet activation. In this study, we measured platelet levels of proteins from all three complement pathways as well as several innate immune proteins with associations to AMD.
Methods :
Whole blood was obtained from 13 pre-advanced AMD and 6 age-matched control subjects after receiving IRB approval and informed consent. Platelet-rich plasma was isolated by centrifugation and samples were prepared in buffer containing fibrin inhibitor Gly-Pro-Arg-Pro. Fluorescently-conjugated antibodies against complement proteins C1R, C3b, CFH, MASP-1/3, and Ficolin-2, as well as innate immune proteins Toll-like receptor 4 (TLR4) and TIMP-3, were measured at baseline and after activation with dual platelet agonists thrombin and convulxin (T/C) using a Beckman Coulter CytoFLEX S flow cytometer. Inhibitors of the TLR4 pathway resveratrol, quercetin, and curcumin were evaluated in combination (RQC) for their potential to reduce systemic vascular complement activation.
Results :
In AMD platelets, C1R (P=0.003), C3b (P=0.02), and innate immune receptor TLR4 (P=0.01) were significantly increased at baseline compared with controls. CFH, a negative regulator of complement activity, was decreased at baseline (P=0.04). Platelet activation with T/C increased surface levels of all measured proteins. Pre-treatment with RQC significantly inhibited the activation-induced increase in C1R (P=0.001), C3b (P=0.001), CFH (p=0.0001), MASP-1/3 (P=0.008), Ficolin-2 (P=0.0004), TLR4 (P=0.01), and TIMP-3 (P=0.0008).
Conclusions :
Systemic levels of complement and TLR4-associated innate immune system proteins are increased in AMD. Platelet complement and innate immune pathways may be a new target for AMD treatment.
This is a 2021 ARVO Annual Meeting abstract.