Interleukin-6 in the pathogenesis of posterior capsule opacification and the potential role for interleukin-6 inhibition in the future of cataract surgery

Posterior capsule pacification (PCO) is a debilitating and relatively common complication of cataract surgery despite modern medical and surgical advances. The pathophysiology of this condition has largely been attributed to peptide mediators, such as transforming growth factor-beta (TGF beta), epidermal growth factor (EGF) and matrix metalloproteinases (MMPs), with the inhibition of these and other related molecules showing promising results. Studies have also shown that the levels of interleukin-6 are elevated in the eyes following cataract surgery and in various ocular inflammatory disorders that predispose to PCO development. This review proposes, utilizing ocular and extra-ocular disease models, several potential pathways through which IL-6 may modulate the activity of TGF beta, EGF, MMP-2/-9 and immune cells to promote PCO. Among the IL-6-mediated pathways discussed are the transactivation of EGF receptor, the up-regulation of TGF beta and MMP-2/-9, and the loss of ocular immune privilege through trans-signaling, down-regulation of T-regulatory cells (Tregs) and up-regulation of Th17 cells. After establishing both the potential role of ocular IL-6 in the development of PCO and the apparent upstream activity of IL-6 in relation to the known mediators of PCO, the author hypothesizes that intraoperative anti-IL-6 therapy may be of great benefit in reducing all parameters of PCO pathogenesis. This review also provides a strong basis for carrying out multiple experimental studies with IL-6 inhibitors to further elucidate the specific pathways by which IL-6 may promote PCO as well as to better determine what role inflammation may play in this disease process. (C) 2013 Elsevier Ltd. All rights reserved.