1808-LB: NIK-Mediated Microglia Polarization Induces Endothelial Dysfunction in Diabetic Retinopathy

Introduction & Objective: Chronic inflammation significantly contributes to endothelial dysfunction in diabetic retinopathy (DR). NIK, a central and specific signal component that regulates the activation of noncanonical NF-κB pathway, is overexpressed in inflammatory diseases, metabolic disorders, and cancer. Although some achievement have been made in the study of NIK, it is unknown whether NIK can participate in the progression of DR.

Methods: Mice fed a high-fat diet and injected with streptozotocin were induced to develop DR. At the same time, human microglial cells 3 (HMC3) and Human retina microvascular endothelial cells (hRMECs) were exposed to AGEs to mimic DR pathologies in vitro. B022 (a small-molecule inhibitor of NIK) was injected into DR mice and added into the cell culture medium to investigate the role of NIK in microglia polarization-induced endothelial dysfunction. To further explore the underlying mechanism, lentiviruses harboring a short hairpin RNA targeting NIK and an NIK overexpression were used to knock down and overexpress NIK, respectively.

Results: Compared with normal control, endothelial dysfunction, microglia M1/M2 polarization, and inflammatory factors they surged in both DR mice retinas and AGE-treated HMC3 cells or co-cultured model, according to HE staining, immunofluorescence, immunohistochemistry, TUNEL assay, vascular permeability assay, cell permeability assay, ELISA, RNA sequencing and western blotting. Moreover, NIK expression was higher in DR mice retinas and AGE-treated microglia. In the B022 treated mice or cells, endothelial dysfunction, M1/M2 polarization, and inflammatory microenvironment were improved. Manipulating NIK expression levels markedly regulated the non-classical NF-κB pathway and microglia polarization.

Conclusions: These results suggest that NIK maybe the potential target to treat diabetic retinopathy.